Test method for mechanical properties of implantable catheters according to DIN 10555-3.

PubMed

Busch, J D; Schröder, H; Sellenschloh, K; Adam, G; Ittrich, H; Huber, G

2018-06-01

To enable causal analysis of port catheter failure, this study aimed to develop an experimental setup for uniaxial tensile tests that addresses the specific requirements of highly elastic medical catheters; and to quantify parameters of the catheters' mechanical competence with respect to effects of artificial aging. Segments of 6F-polyurethane catheters were tested in their native status, after chemical and after mechanical aging. Tension experiments were performed with a rate of 220 mm/min until catheter failure. Material behavior was analyzed based on load cell measurements of the universal test system and an additional optical distance registration. The Young's modulus, the ultimate stress and the ultimate strain were determined. Chemical aging significantly decreased Young's modulus (84%; p = 0.001) and ultimate stress (83%; p < 0.001), whereas mechanical aged samples demonstrated similar results for the Young's modulus (p = 0.772) and a non-significant rise of ultimate stress (13%; p = 0.128). Ultimate strain did not differ significantly regardless of the pretreatment. The results proof reliability, reproducibility and sensitivity to quantify artificial aging induced variations and also promise to detect deviations in material features caused by long-term clinical usage of catheters. Copyright © 2018 Elsevier Ltd. All rights reserved.

Pulsed laser ablation and incubation of nickel, iron and tungsten in liquids and air

NASA Astrophysics Data System (ADS)

Lasemi, N.; Pacher, U.; Zhigilei, L. V.; Bomatí-Miguel, O.; Lahoz, R.; Kautek, W.

2018-03-01

Incubation effects in the nanosecond laser ablation of metals exhibit a strong dependence on the thermal and mechanical properties of both the target material and the background gas or liquid. The incubation in air is controlled mainly by thermal properties such as the heat of vaporization. In liquid, the correlation of the incubation and the ultimate tensile stress of the metals suggests that incubation may be related to the mechanical impact on the solid material by the cavitation bubble collapse, causing accumulation of voids and cracks in the subsurface region of the ablation craters. At high ultimate tensile stress, however, the low sensitivity to the environment suggests that the mechanical impact is likely to play a negligible role in the incubation. Finally, the correlation between the incubation and the carbon content of alcoholic liquids may be explained by an absorptivity increase of the cavity surfaces due to carbonaceous deposits generated by laser-induced pyrolysis, or by the mechanical impact of long-living bubbles at higher dynamic viscosity of liquids.

Incorporation of a Decorin Biomimetic Enhances the Mechanical Properties of Electrochemically Aligned Collagen Threads

PubMed Central

Kishore, Vipuil; Paderi, John E.; Akkus, Anna; Smith, Katie M.; Balachandran, Dave; Beaudoin, Stephen; Panitch, Alyssa; Akkus, Ozan

2011-01-01

Orientational anisotropy of collagen molecules is integral for the mechanical strength of collagen-rich tissues. We have previously reported a novel methodology to synthesize highly oriented electrochemically aligned collagen (ELAC) threads with mechanical properties converging upon those of native tendon. Decorin, a small leucine rich proteoglycan (SLRP), binds to fibrillar collagen and has been suggested to enhance the mechanical properties of tendon. Based on the structure of natural decorin, we have previously designed and synthesized a peptidoglycan (DS-SILY) that mimics decorin both structurally and functionally. In this study, we investigated the effect of the incorporation of DS-SILY on the mechanical properties and structural organization of ELAC threads. The results indicated that the addition of DS-SILY at a molar ratio of 30:1 (Collagen:DS-SILY) significantly enhanced the ultimate stress and ultimate strain of the ELAC threads. Furthermore, differential scanning calorimetry revealed that the addition of DS-SILY at a molar ratio of 30:1 resulted in a more thermally stable collagen structure. However, addition of DS-SILY at a higher concentration (10:1 Collagen:DS-SILY) yielded weaker threads with mechanical properties comparable to collagen control threads. Transmission emission microscopy revealed that the addition of DS-SILY at a higher concentration (10:1) resulted in pronounced aggregation of collagen fibrils. More importantly, these aggregates were not aligned along the long axis of the ELAC thereby compromising on the overall tensile properties of the material. We conclude that incorporation of an optimal amount of DS-SILY is a promising approach to synthesize mechanically competent collagen based biomaterials for tendon tissue engineering applications. PMID:21356334

Mechanical properties of a nitrogen-bearing austenitic steel during static and cycle deformation

NASA Astrophysics Data System (ADS)

Blinov, E. V.; Terent'ev, V. F.; Prosvirnin, D. V.

2016-09-01

The mechanical properties of a nitrogen-bearing corrosion-resistant austenitic steel containing 0.311% nitrogen have been studied during static and cyclic deformation. It is found that the steel having an ultimate strength of 930 MPa exhibits a plasticity of 33%. The endurance limit under repeated tension at 106 loading cycles is 400 MPa. The propagation of a fatigue crack at low and high amplitudes of cyclic deformation follows a ductile fracture mechanism with the presence of fatigue grooves.

Effects of extrusion and heat treatment on the mechanical properties and biocorrosion behaviors of a Mg-Nd-Zn-Zr alloy.

PubMed

Zhang, Xiaobo; Yuan, Guangyin; Mao, Lin; Niu, Jialin; Fu, Penghuai; Ding, Wenjiang

2012-03-01

Mechanical properties at room temperature and biocorrosion behaviors in simulated body fluid (SBF) at 37 °C of a new type of patented Mg-3Nd-0.2Zn-0.4Zr (hereafter, denoted as JDBM) alloy prepared at different extrusion temperatures, as well as heat treatment, were studied. The mechanical properties of this magnesium alloy at room temperature were improved significantly after extrusion and heat treatment compared to an as-cast alloy. The results of mechanical properties show that the yield strength (YS) decreases with increasing extrusion temperature. The tensile elongation decreases a little while the ultimate tensile strength (UTS) has no obvious difference. The yield strength and ultimate tensile strength were improved clearly after heat treatment at 200 °C for 10 h compared with that at the extrusion state, which can be mainly contributed to the precipitation strengthening. The biocorrosion behaviors of the JDBM alloy were studied using immersion tests and electrochemical tests. The results reveal that the extruded JDBM alloy and the aging treatment on the extruded alloy show much better biocorrosion resistance than that at solid solution state (T4 treatment), and the JDBM exhibited favorable uniform corrosion mode in SBF. Copyright © 2011 Elsevier Ltd. All rights reserved.

Effects of Fiber Content on Mechanical Properties of CVD SiC Fiber-Reinforced Strontium Aluminosilicate Glass-Ceramic Composites

NASA Technical Reports Server (NTRS)

Bansal, Narottam P.

1996-01-01

Unidirectional CVD SiC(f)(SCS-6) fiber-reinforced strontium aluminosilicate (SAS) glass-ceramic matrix composites containing various volume fractions, approximately 16 to 40 volume %, of fibers were fabricated by hot pressing at 1400 C for 2 h under 27.6 MPa. Monoclinic celsian, SrAl2Si2O8, was the only crystalline phase formed, with complete absence of the undesired hexacelsian phase, in the matrix. Room temperature mechanical properties were measured in 3-point flexure. The matrix microcracking stress and the ultimate strength increased with increase in fiber volume fraction, reached maximum values for V(sub f) approximately equal to 0.35, and degraded at higher fiber loadings. This degradation in mechanical properties is related to the change in failure mode, from tensile at lower V(sub f) to interlaminar shear at higher fiber contents. The extent of fiber loading did not have noticeable effect on either fiber-matrix debonding stress, or frictional sliding stress at the interface. The applicability of micromechanical models in predicting the mechanical properties of the composites was also examined. The currently available theoretical models do not appear to be useful in predicting the values of the first matrix cracking stress, and the ultimate strength of the SCS-6/SAS composites.

Effect of ion irradiation on the surface, structural and mechanical properties of brass

NASA Astrophysics Data System (ADS)

Ahmad, Shahbaz; Bashir, Shazia; Ali, Nisar; Umm-i-Kalsoom; Yousaf, Daniel; Faizan-ul-Haq; Naeem, Athar; Ahmad, Riaz; Khlaeeq-ur-Rahman, M.

2014-04-01

Modifications to the surface, structural and mechanical properties of brass after ion irradiation have been investigated. Brass targets were bombarded by carbon ions of 2 MeV energy from a Pelletron linear accelerator for various fluences ranging from 56 × 1012 to 26 × 1013 ions/cm2. A scanning electron microscope and X-ray diffractometer were utilized to analyze the surface morphology and crystallographic structure respectively. To explore the mechanical properties e.g., yield stress, ultimate tensile strength and microhardness of irradiated brass, an universal tensile testing machine and Vickers microhardness tester were used. Scanning electron microscopy results revealed an irregular and randomly distributed sputter morphology for a lower ion fluence. With increasing ion fluence, the incoherently shaped structures were transformed into dendritic structures. Nano/micro sized craters and voids, along with the appearance of pits, were observed at the maximum ion fluence. From X-ray diffraction results, no new phases were observed to be formed in the brass upon irradiation. However, a change in the peak intensity and higher and lower angle shifting were observed, which represents the generation of ion-induced defects and stresses. Analyses confirmed modifications in the mechanical properties of irradiated brass. The yield stress, ultimate tensile strength and hardness initially decreased and then increased with increasing ion fluence. The changes in the mechanical properties of irradiated brass are well correlated with surface and crystallographic modifications and are attributed to the generation, augmentation, recombination and annihilation of the ion-induced defects.

Low temperature mechanical properties, fractographic and metallographic evaluation of several alloy steels

NASA Technical Reports Server (NTRS)

Montano, J. W.

1973-01-01

The mechanical properties are presented of alloy steels, 4130, 4140, 4340, 6150, and 8740. Test specimens were manufactured from approximately 1.00 inch (2.54 cm) diameter bar stock which had been heat treated to two different hardness levels. The following mechanical tests were performed at temperatures of 80 F (+26.7 C), 0 F (-17.8 C), -100 F (-73 C), and -200 F (-129 C): (1) tensile test (Ultimate, yield, modulus, elongation, and reduction of area), (2) notched tensile test, (3) charpy V-notched impact test (impact energy), and (4) double shear strength test (ultimate and yield). The test data indicate excellent tensile strength, notched/unnotched tensile ratios, ductility, impact, and shear properties at all test temperatures, except at -200 F (-129 C) where the impact strength of the higher strength group of alloy steels, 4130 (Rc-37) and 4140 (Rc-44) decreased to approximately 9 ft. lbs. (12 joules) and 6 ft. lbs. (8 joules), respectively. Chemical, metallographic, and fractographic analyses were also performed to evaluate microstructure, microhardness and the effect of decrease in temperature on the ductile to brittle failure transition.

Effect of ZnO nanoparticles to mechanical properties of thixoformed Mg-Al-Zn alloy

NASA Astrophysics Data System (ADS)

Kusharjanto; Soepriyanto, Syoni; Ardian Korda, Akhmad; Adi Dwiwanto, Supono

2018-03-01

Magnesium alloys are lightweight metallic materials with low mechanical properties. Therefore, in order to meet the requirements in various industrial sector applications such as automotive, aerospace and electronic frame, improvement strength and ductility is required. The purpose of this research is to investigate the effect of adding ZnO nanoparticles to changes in microstructure, hardness, mechanical properties regarding with yield and ultimate strength. In this research, the molten Mg-Al-Zn alloy is added ZnO nanoparticles with a various range of 0, 1; 3 and 5 wt% and then cooling in the room temperature. Futhermore, Mg-Al-Zn-ZnO is heated at a temperature of 530 °C (in the semi-solid temperature range 470 °C–595 °C or 53% solid fraction) and then thixoforming process is performed. The characterization results of the thixoforming product show that, the microstructure is globular in shape with maximum hardness value of 107.14 VHN, the yield strength of 214.87 MPa, and the ultimate tensile strength of 311.25 MPa in 5 wt% ZnO nanoparticles.

Development and validation of a canine radius replica for mechanical testing of orthopedic implants.

PubMed

Little, Jeffrey P; Horn, Timothy J; Marcellin-Little, Denis J; Harrysson, Ola L A; West, Harvey A

2012-01-01

To design and fabricate fiberglass-reinforced composite (FRC) replicas of a canine radius and compare their mechanical properties with those of radii from dog cadavers. Replicas based on 3 FRC formulations with 33%, 50%, or 60% short-length discontinuous fiberglass by weight (7 replicas/group) and 5 radii from large (> 30-kg) dog cadavers. Bones and FRC replicas underwent nondestructive mechanical testing including 4-point bending, axial loading, and torsion and destructive testing to failure during 4-point bending. Axial, internal and external torsional, and bending stiffnesses were calculated. Axial pullout loads for bone screws placed in the replicas and cadaveric radii were also assessed. Axial, internal and external torsional, and 4-point bending stiffnesses of FRC replicas increased significantly with increasing fiberglass content. The 4-point bending stiffness of 33% and 50% FRC replicas and axial and internal torsional stiffnesses of 33% FRC replicas were equivalent to the cadaveric bone stiffnesses. Ultimate 4-point bending loads did not differ significantly between FRC replicas and bones. Ultimate screw pullout loads did not differ significantly between 33% or 50% FRC replicas and bones. Mechanical property variability (coefficient of variation) of cadaveric radii was approximately 2 to 19 times that of FRC replicas, depending on loading protocols. Within the range of properties tested, FRC replicas had mechanical properties equivalent to and mechanical property variability less than those of radii from dog cadavers. Results indicated that FRC replicas may be a useful alternative to cadaveric bones for biomechanical testing of canine bone constructs.

Distribution of chloride, pH, resistivity, and sulfate levels in backfill for mechanically-stabilized earth walls and implications for corrosion testing.

DOT National Transportation Integrated Search

2015-05-01

The ultimate goals of this research were to improve quality, speed completion, and reduce risk in mechanically-stabilized : earth (MSE) wall projects. Research objectives were to assure (1) that variability in the corrosion properties of soil (pH, : ...

Bootstrap calculation of ultimate strength temperature maxima for neutron irradiated ferritic/martensitic steels

NASA Astrophysics Data System (ADS)

Obraztsov, S. M.; Konobeev, Yu. V.; Birzhevoy, G. A.; Rachkov, V. I.

2006-12-01

The dependence of mechanical properties of ferritic/martensitic (F/M) steels on irradiation temperature is of interest because these steels are used as structural materials for fast, fusion reactors and accelerator driven systems. Experimental data demonstrating temperature peaks in physical and mechanical properties of neutron irradiated pure iron, nickel, vanadium, and austenitic stainless steels are available in the literature. A lack of such an information for F/M steels forces one to apply a computational mathematical-statistical modeling methods. The bootstrap procedure is one of such methods that allows us to obtain the necessary statistical characteristics using only a sample of limited size. In the present work this procedure is used for modeling the frequency distribution histograms of ultimate strength temperature peaks in pure iron and Russian F/M steels EP-450 and EP-823. Results of fitting the sums of Lorentz or Gauss functions to the calculated distributions are presented. It is concluded that there are two temperature (at 360 and 390 °C) peaks of the ultimate strength in EP-450 steel and single peak at 390 °C in EP-823.

Effect of alkaline treatment on mechanical properties of kenaf fiber reinforced polyester composites

NASA Astrophysics Data System (ADS)

Reddy, Bijjam Ramgopal; Dhoria, Sneha H.

2018-04-01

This paper focuses on the study of the effect of chemical treatment on mechanical properties such as tensile, flexural and impact properties of kenaf fiber reinforced polyester composites. Adhesion between the fiber and polymer is one of factors affecting the mechanical properties of composites. In order to increase the adhesion, the fibers are chemically treated with 5% of sodium hydroxide (NaOH) solution. The composite specimens are prepared in both untreated and treated forms of kenaf fibers with five levels of fiber volume fractions. The specimens are prepared according to ASTM standards. Mechanical tests such as tensile, flexural and impact are conducted to determine ultimate tensile strength, bending strength and impact strength of composites. The effect of change in volume fraction on the mechanical properties of the composites is studied for both untreated (raw) and chemically treated kenaf fibers. It has been found that the composites made of chemically treated fibers have good mechanical properties compared to untreated fibers.

High Temperature Tensile Properties of Unidirectional Hi-Nicalon/Celsian Composites In Air

NASA Technical Reports Server (NTRS)

Gyekenyesi, John Z.; Bansal, Narottam P.

2000-01-01

High temperature tensile properties of unidirectional BN/SiC-coated Hi-Nicalon SiC fiber reinforced celsian matrix composites have been measured from room temperature to 1200 C (2190 F) in air. Young's modulus, the first matrix cracking stress, and the ultimate strength decreased from room temperature to 1200 C (2190 F). The applicability of various micromechanical models, in predicting room temperature values of various mechanical properties for this CMC, has also been investigated. The simple rule of mixtures produced an accurate estimate of the primary composite modulus. The first matrix cracking stress estimated from ACK theory was in good agreement with the experimental value. The modified fiber bundle failure theory of Evans gave a good estimate of the ultimate strength.

The effect of a simple annealing heat treatment on the mechanical properties of cold-sprayed aluminum

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hall, Aaron Christopher; Roemer, Timothy John; Hirschfeld, Deidre A.

2004-11-01

Cold spray, a new member of the thermal spray process family, can be used to prepare dense, thick metal coatings. It has tremendous potential as a spray-forming process. However, it is well known that significant cold work occurs during the cold spray deposition process. This cold work results in hard coatings but relatively brittle bulk deposits. This work investigates the mechanical properties of cold-sprayed aluminum and the effect of annealing on those properties. Cold spray coatings approximately 1 cm thick were prepared using three different feedstock powders: Valimet H-10; Valimet H-20; and Brodmann Flomaster. ASTM E8 tensile specimens were machinedmore » from these coatings and tested using standard tensile testing procedures. Each material was tested in two conditions: as-sprayed; and after a 300 C, 22 h air anneal. The as-sprayed material showed high ultimate strength and low ductility, with <1% elongation. The annealed samples showed a reduction in ultimate strength but a dramatic increase in ductility, with up to 10% elongation. The annealed samples exhibited mechanical properties that were similar to those of wrought 1100 H14 aluminum. Microstructural examination and fractography clearly showed a change in fracture mechanism between the as-sprayed and annealed materials. These results indicate good potential for cold spray as a bulk-forming process.« less

The effect of a simple annealing heat treatement on the mechanical properties of cold-sprayed aluminium.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hall, Aaron Christopher; Roemer, Timothy John; Hirschfeld, Deidre A.

2005-08-01

Cold spray, a new member of the thermal spray process family, can be used to prepare dense, thick metal coatings. It has tremendous potential as a spray-forming process. However, it is well known that significant cold work occurs during the cold spray deposition process. This cold work results in hard coatings but relatively brittle bulk deposits. This work investigates the mechanical properties of cold-sprayed aluminum and the effect of annealing on those properties. Cold spray coatings approximately 1 cm thick were prepared using three different feedstock powders: Valimet H-10: Valimet H-20: and Brodmann Flomaster. ASTM E8 tensile specimens were machinedmore » from these coatings and tested using standard tensile testing procedures. Each material was tested in two conditions: as-sprayed; and after a 300 C, 22h air anneal. The as-sprayed material showed high ultimate strength and low ductility, with <1% elongation. The annealed samples showed a reduction in ultimate strength but a dramatic increase in ductility, with up to 10% elongation. The annealed samples exhibited mechanical properties that were similar to those of wrought 1100 H14 aluminum. Microstructural examination and fractography clearly showed a change in fracture mechanism between the as-sprayed and annealed materials. These results indicate good potential for cold spray as a bulkforming process.« less

Quantitative US Elastography Can Be Used to Quantify Mechanical and Histologic Tendon Healing in a Rabbit Model of Achilles Tendon Transection.

PubMed

Yamamoto, Yohei; Yamaguchi, Satoshi; Sasho, Takahisa; Fukawa, Taisuke; Akatsu, Yorikazu; Akagi, Ryuichiro; Yamaguchi, Tadashi; Takahashi, Kenji; Nagashima, Kengo; Takahashi, Kazuhisa

2017-05-01

Purpose To determine the time-dependent change in strain ratios (SRs) at the healing site of an Achilles tendon rupture in a rabbit model of tendon transection and to assess the correlation between SRs and the mechanical and histologic properties of the healing tissue. Materials and Methods Experimental methods were approved by the institutional animal care and use committee. The Achilles tendons of 24 New Zealand white rabbits (48 limbs) were surgically transected. The SRs of Achilles tendons were calculated by using compression-based quantitative ultrasonographic elastography measurements obtained 2, 4, 8, and 12 weeks after transection. After in vivo elastography, the left Achilles tendon was harvested for mechanical testing of ultimate load, ultimate stress, elastic modulus, and linear stiffness, and the right tendons were harvested for tissue histologic analysis with the Bonar scale. Time-dependent changes in SRs, mechanical parameters, and Bonar scale scores were evaluated by using repeated-measures analysis of variance. The correlation between SRs and each measured variable was evaluated by using the Spearman rank correlation coefficient. Results Mean SRs and Bonar scale values decreased as a function of time after transection, whereas mechanical parameters increased (P < .001). SR correlated with ultimate stress (ρ = 0.68, P <.001,) elastic modulus (ρ = 0.74, P <.001), and the Bonar scale (ρ = 0.87, P <.001). Conclusion Quantitative elastography could be a useful method with which to evaluate mechanical and histologic properties of the healing tendon. © RSNA, 2017 Online supplemental material is available for this article.

Effects of Casting Size on Microstructure and Mechanical Properties of Spheroidal and Compacted Graphite Cast Irons: Experimental Results and Comparison with International Standards

NASA Astrophysics Data System (ADS)

Ceschini, L.; Morri, Alessandro; Morri, Andrea

2017-05-01

The aim of this research was to investigate the effects of casting size (10-210 mm) on the microstructure and mechanical properties of spheroidal (SGI) and compacted (CGI) graphite cast irons. A comparison of the experimental mechanical data with those specified by ISO standards is presented and discussed. The study highlighted that the microstructure and mechanical properties of SGI (also known as ductile or nodular cast iron) are more sensitive to casting size than CGI (also known as vermicular graphite cast irons). In particular, in both types of cast iron, hardness, yield strength and ultimate tensile strength decreased, with increasing casting size, by 27% in SGI and 17% in CGI. Elongation to failure showed, instead, an opposite trend, decreasing from 5 to 3% in CGI, while increasing from 5 to 11% in SGI. These results were related to different microstructures, the ferritic fraction being more sensitive to the casting size in SGI than CGI. Degeneration of spheroidal graphite was observed at casting size above 120 mm. The microstructural similarities between degenerated SGI and CGI suggested the proposal of a unified empirical constitutional law relating the most important microstructural parameters to the ultimate tensile strength. An outstanding result was also the finding that standard specifications underestimated the mechanical properties of both cast irons (in particular SGI) and, moreover, did not take into account their variation with casting size, at thicknesses over 60 mm.

The Cryogenic Properties of Several Aluminum-Beryllium Alloys and a Beryllium Oxide Material

NASA Technical Reports Server (NTRS)

Gamwell, Wayne R.; McGill, Preston B.

2003-01-01

Performance related mechanical properties for two aluminum-beryllium (Al-Be) alloys and one beryllium-oxide (BeO) material were developed at cryogenic temperatures. Basic mechanical properties (Le., ultimate tensile strength, yield strength, percent elongation, and elastic modulus were obtained for the aluminum-beryllium alloy, AlBeMetl62 at cryogenic [-195.5"C (-320 F) and -252.8"C (-423"F)I temperatures. Basic mechanical properties for the Be0 material were obtained at cyrogenic [- 252.8"C (-423"F)] temperatures. Fracture properties were obtained for the investment cast alloy Beralcast 363 at cryogenic [-252.8"C (-423"F)] temperatures. The AlBeMetl62 material was extruded, the Be0 material was hot isostatic pressing (HIP) consolidated, and the Beralcast 363 material was investment cast.

Detergent-enzymatic decellularization of swine blood vessels: insight on mechanical properties for vascular tissue engineering.

PubMed

Pellegata, Alessandro F; Asnaghi, M Adelaide; Stefani, Ilaria; Maestroni, Anna; Maestroni, Silvia; Dominioni, Tommaso; Zonta, Sandro; Zerbini, Gianpaolo; Mantero, Sara

2013-01-01

Small caliber vessels substitutes still remain an unmet clinical need; few autologous substitutes are available, while synthetic grafts show insufficient patency in the long term. Decellularization is the complete removal of all cellular and nuclear matters from a tissue while leaving a preserved extracellular matrix representing a promising tool for the generation of acellular scaffolds for tissue engineering, already used for various tissues with positive outcomes. The aim of this work is to investigate the effect of a detergent-enzymatic decellularization protocol on swine arteries in terms of cell removal, extracellular matrix preservation, and mechanical properties. Furthermore, the effect of storage at -80°C on the mechanical properties of the tissue is evaluated. Swine arteries were harvested, frozen, and decellularized; histological analysis revealed complete cell removal and preserved extracellular matrix. Furthermore, the residual DNA content in decellularized tissues was far low compared to native one. Mechanical testings were performed on native, defrozen, and decellularized tissues; no statistically significant differences were reported for Young's modulus, ultimate stress, compliance, burst pressure, and suture retention strength, while ultimate strain and stress relaxation of decellularized vessels were significantly different from the native ones. Considering the overall results, the process was confirmed to be suitable for the generation of acellular scaffolds for vascular tissue engineering.

The Cryogenic Tensile Properties of an Extruded Aluminum-Beryllium Alloy

NASA Technical Reports Server (NTRS)

Gamwell, W. R.

2002-01-01

Basic mechanical properties; i.e., ultimate tensile strength, yield strength, percent elongation, and elastic modulus, were obtained for the aluminum-beryllium alloy, AlBeMet162, at cryogenic (-195.5 C (-320 F) and -252.8 C (-423 F)) temperatures. The material evaluated was purchased to the requirements of SAE-AMS7912, "Aluminum-Beryllium Alloy, Extrusions."

Carbon fiber reinforced root canal posts. Mechanical and cytotoxic properties.

PubMed

Torbjörner, A; Karlsson, S; Syverud, M; Hensten-Pettersen, A

1996-01-01

The aim of this study was to compare the mechanical properties of a prefabricated root canal post made of carbon fiber reinforced composites (CFRC) with metal posts and to assess the cytotoxic effects elicited. Flexural modulus and ultimate flexural strength was determined by 3 point loading after CRFC posts had been stored either dry or in water. The bending test was carried out with and without preceding thermocycling of the CFRC posts. The cytotoxicity was evaluated by an agar overlay method after dry and wet storage. The values of flexural modulus and ultimate flexural strength were for dry stored CFRC post 82 +/- 6 GPa and 1154 +/- 65 MPa respectively. The flexural values decreased significantly after water storage and after thermocycling. No cytotoxic effects were observed adjacent to any CFRC post. Although fiber reinforced composites may have the potential to replace metals in many clinical situations, additional research is needed to ensure a satisfying life-span.

Comparison of the biomechanical properties of rottweiler and racing greyhound cranial cruciate ligaments.

PubMed

Wingfield, C; Amis, A A; Stead, A C; Law, H T

2000-07-01

An in vitro study of rottweiler and racing greyhound cranial cruciate ligaments revealed that the rottweiler ligaments had a significantly greater cross-sectional area at their distal attachments. Mechanical testing showed that the ultimate load related to body mass was significantly higher in the extended racing greyhound stifle during cranial tibial loading to failure, as were linear stiffness, tensile strength and tangent modulus. During ligament axis loading to failure, the only significant difference in structural and mechanical properties recorded between the two breeds was a greater ultimate strain for the greyhound ligament with the stifle joint flexed. Energy absorbed by the ligament complex at failure during cranial tibial loading was twice that for ligament axis loading for both breeds. The clinical significance is that the rottweiler cranial cruciate ligament is more vulnerable to damage as it requires half the load per unit body mass that the greyhound requires to cause a rupture.

Effect of heat treatment on microstructure and mechanical properties of Mg-4Y-1.6Nd-1Sm-0.5Zr alloy

NASA Astrophysics Data System (ADS)

Jia, Guilong; Guo, Erjun; Feng, Yicheng; Wang, Liping; Wang, Changliang

2018-03-01

Microstructure and mechanical properties of Mg-4Y-1.6Nd-1Sm-0.5Zr alloy during heat treatments were investigated, while the room-temperature tensile fractographs were observed and analyzed. The results show that the eutectic phases almost dissolve into the matrix after being solutionized at 525 °C for 8 h. The ultimate tensile strength, yield strength and elongation reach 300 MPa, 219 MPa, 6.5% respectively after being under-aged at 200 °C for 16 h. The ultimate tensile strength and yield strength of the alloy decrease gradually, while the elongation increases gradually with increasing the test temperatures. The room-temperature tensile fracture modes of the as-cast alloy, solutionized alloy, aged alloy are mixed fracture of transgranular and intergranular, transgranular cleavage fracture, transgranular fracture, respectively.

[Mechanical behavior of the subchondral bone in the experimentally induced osteoarthritis].

PubMed

Miyanaga, Y

1979-06-01

In order to evaluate the role of the subchondral bone (cancellous bone) in the development and progression of the joint degeneration, osteoarthritis of the knee joint was produced experimentally in the rabbits and viscoelasticity and strength of the subchondral bone from the femoral medial condyle have been investigated along with the pathological, histological study of the joint. The viscoelastic spectrometer and the Instron type testing machine were used. As the first change after operation, osteophyte formation around the joint margin has been observed before the initiation of the degeneration of articular cartilage and there is a possibility that mechanical properties of subchondral bone such as high deformability and low elasticity to the mechanism of osteophyte formation. Subchondral bone softening with marked increase of ultimate strain and phase lag, marked decrease of compressive elastic modulus and ultimate stress precedes or occurs concurrently with the degeneration of the articular cartilage. These facts indicate the relationship between the mechanical properties of the subchondral bone and joint degeneration. Once the joint degeneration starts, degeneration continues progressively while the subchondral bone tends to become brittle. These changes may be considered as a kind of functional adaptation to the damage or denudation of articular cartilage. It is postulated that some architectural changes of the subchondral bone may provide alterations of the mechanical properties. Biomechanical roles of the subchondral bone is suggested as one of the factors in the joint degeneration.

Towards the feasibility of using ultrasound to determine mechanical properties of tissues in a bioreactor.

PubMed

Mansour, Joseph M; Gu, Di-Win Marine; Chung, Chen-Yuan; Heebner, Joseph; Althans, Jake; Abdalian, Sarah; Schluchter, Mark D; Liu, Yiying; Welter, Jean F

2014-10-01

Our ultimate goal is to non-destructively evaluate mechanical properties of tissue-engineered (TE) cartilage using ultrasound (US). We used agarose gels as surrogates for TE cartilage. Previously, we showed that mechanical properties measured using conventional methods were related to those measured using US, which suggested a way to non-destructively predict mechanical properties of samples with known volume fractions. In this study, we sought to determine whether the mechanical properties of samples, with unknown volume fractions could be predicted by US. Aggregate moduli were calculated for hydrogels as a function of SOS, based on concentration and density using a poroelastic model. The data were used to train a statistical model, which we then used to predict volume fractions and mechanical properties of unknown samples. Young's and storage moduli were measured mechanically. The statistical model generally predicted the Young's moduli in compression to within <10% of their mechanically measured value. We defined positive linear correlations between the aggregate modulus predicted from US and both the storage and Young's moduli determined from mechanical tests. Mechanical properties of hydrogels with unknown volume fractions can be predicted successfully from US measurements. This method has the potential to predict mechanical properties of TE cartilage non-destructively in a bioreactor.

Towards the feasibility of using ultrasound to determine mechanical properties of tissues in a bioreactor

PubMed Central

Mansour, Joseph M.; Gu, Di-Win Marine; Chung, Chen-Yuan; Heebner, Joseph; Althans, Jake; Abdalian, Sarah; Schluchter, Mark D.; Liu, Yiying; Welter, Jean F.

2016-01-01

Introduction Our ultimate goal is to non-destructively evaluate mechanical properties of tissue-engineered (TE) cartilage using ultrasound (US). We used agarose gels as surrogates for TE cartilage. Previously, we showed that mechanical properties measured using conventional methods were related to those measured using US, which suggested a way to non-destructively predict mechanical properties of samples with known volume fractions. In this study, we sought to determine whether the mechanical properties of samples, with unknown volume fractions could be predicted by US. Methods Aggregate moduli were calculated for hydrogels as a function of SOS, based on concentration and density using a poroelastic model. The data were used to train a statistical model, which we then used to predict volume fractions and mechanical properties of unknown samples. Young's and storage moduli were measured mechanically. Results The statistical model generally predicted the Young's moduli in compression to within < 10% of their mechanically measured value. We defined positive linear correlations between the aggregate modulus predicted from US and both the storage and Young's moduli determined from mechanical tests. Conclusions Mechanical properties of hydrogels with unknown volume fractions can be predicted successfully from US measurements. This method has the potential to predict mechanical properties of TE cartilage non-destructively in a bioreactor. PMID:25092421

High Mechanical Property of Laminated Electromechanical Sensors by Carbonized Nanolignocellulose/Graphene Composites.

PubMed

Chen, Yipeng; Sheng, Chengmin; Dang, Baokang; Qian, Temeng; Jin, Chunde; Sun, Qingfeng

2018-02-28

Although widely used in nanocomposites, the effect of embedding graphene in carbonized nanolignocellulose substrates is less clear. We added graphene to a carbonized nanolignocellulose to change its mechanical and electromechanical properties. Here, the laminated carbonized nanolignocellulose/graphene composites were fabricated by carbonizing the nanolignocellulose/graphene composites prepared through mechanochemistry and flow-directed assembly process. The resulting composites exhibit excellent mechanical property with the ultimate bending strength of 25.6 ± 4.2 MPa. It is observed reversible electrical resistance change in these composites with strain, which is associated with the tunneling conduction model. This type of high-strength conductive composite has great potential applications in load-bearing electromechanical sensors.

Solid impingement erosion mechanisms and characterization of erosion resistance of ductile metals

NASA Technical Reports Server (NTRS)

Rao, V. P.; Buckley, D. H.

1982-01-01

Experimental results pertaining to spherical glass bead and angular crushed glass particle impingement are presented. A concept of energy adsorption to explain the failure of material is proposed. The erosion characteristics of several pure metals were correlated with the proposed energy parameters and with other properties. Correlations of erosion and material properties were also carried out with these materials to study the effect of the angle of impingement. Analyses of extensive erosion data indicate that surface energy, strain energy, melting point, bulk modulus, hardness, ultimate resilience, atomic volume and product of linear coefficient of thermal expansion, bulk modulus, and temperature rise required for melting, and ultimate resilience, and hardness exhibit the best correlations. It appears that both energy and thermal properties contribute to the total erosion.

Engineering and design properties of thallium-doped sodium iodide and selected properties of sodium-doped cesium iodide

NASA Technical Reports Server (NTRS)

Forrest, K.; Haehner, C.; Heslin, T.; Magida, M.; Uber, J.; Freiman, S.; Hicho, G.; Polvani, R.

1984-01-01

Mechanical and thermal properties, not available in the literature but necessary to structural design, using thallium doped sodium iodide and sodium doped cesium iodide were determined to be coefficient of linear thermal expansion, thermal conductivity, thermal shock resistance, heat capacity, elastic constants, ultimate strengths, creep, hardness, susceptibility to subcritical crack growth, and ingot variation of strength. These properties were measured for single and polycrystalline materials at room temperature.

Investigation on mechanical properties of basalt composite fabrics (experiment study)

NASA Astrophysics Data System (ADS)

Talebi Mazraehshahi, H.; Zamani, H.

2010-06-01

To fully appreciate the role and application of composite materials to structures, correct understanding of mechanical behaviors required for selection of optimum material. Fabric reinforced composites are composed of a matrix that is reinforced with pliable fabric, glass fabric is most popular reinforcement for different application specially in aircraft structure, although other fabric material are also used. At this study new fabric material called basalt with epoxy resin introduced and mechanical behaviors of this material investigated from view point of testing. For this study two type of fabric with different thickness used. Comparison between this composite reinforcement with popular reinforcement as carbon, glass, kevlar performed. To determine mechanical properties of epoxy based basalt fabric following test procedure performed : 1). Tensile testing according to ASTM D3039 in 0° and 90° direction to find ultimate strength in tension and shear, modulus of elasticity, elangation and ultimate strain. 2). Compression testing according to EN 2850 ultimate compression strength and maximum deformation under compression loading. 3). Shear testing according to ASTM D3518-94 to find in plane shear response of polymer matrix composites materials. 4). Predict flexural properties of sandwich construction which manufactured from basalt facing with PVC foam core according to ASTM C393-94. Material strength properties must be based on enough tests of material to meet the test procedure specifications [1]. For this reason six specimens were manufactured for testing and the tests were performed on them using an INSTRON machine model 5582. In the study, the effect of percent of resin in basalt reinforced composite was investigated. Also the weights of the ballast based composites with different percent of resin were measured with conventional composites. As the weight is an important parameter in aerospace industry when the designer wants to replace one material with another, the effect of weight must be considered. Weight measurement showed that the replacement of glass fabric reinforcement with basalt fabric has little effect on weight. Investigation also shows that mechanical behavior of basalt fabric is higher than glass fabric. This is due to the excellent mechanical properties of the ballast fabric such as Young modulus and strength in compare with the glass fabric. Figure1 shows the samples which used for tensile testing in warp direction.

Mechanical tensile testing of titanium 15-3-3-3 and Kevlar 49 at cryogenic temperatures

NASA Astrophysics Data System (ADS)

James, B. L.; Martinez, R. M.; Shirron, P.; Tuttle, J.; Galassi, N. M.; McGuinness, D. S.; Puckett, D.; Francis, J. J.; Flom, Y.

2012-06-01

Titanium 15-3-3-3 and Kevlar 49 are highly desired materials for structural components in cryogenic applications due to their low thermal conductivity at low temperatures. Previous tests have indicated that titanium 15-3-3-3 becomes increasingly brittle as the temperature decreases. Furthermore, little is known regarding the mechanical properties of Kevlar 49 at low temperatures, most specifically its Young's modulus. This testing investigates the mechanical properties of both materials at cryogenic temperatures through cryogenic mechanical tensile testing to failure. The elongation, ultimate tensile strength, yield strength, and break strength of both materials are provided and analyzed here.

Mechanical Tensile Testing of Titanium 15-3-3-3 and Kevlar 49 at Cryogenic Temperatures

NASA Technical Reports Server (NTRS)

James, Bryan L.; Martinez, Raul M.; Shirron, Peter; Tuttle, Jim; Galassi, Nicholas M.; Mcguinness, Daniel S.; Puckett, David; Francis, John J.; Flom, Yury

2011-01-01

Titanium 15-3-3-3 and Kevlar 49 are highly desired materials for structural components in cryogenic applications due to their low thennal conductivity at low temperatures. Previous tests have indicated that titanium 15-3-3-3 becomes increasingly brittle as the temperature decreases. Furthermore, little is known regarding the mechanical properties of Kevlar 49 at low temperatures, most specifically its Young's modulus. This testing investigates the mechanical properties of both materials at cryogenic temperatures through cryogenic mechanical tensile testing to failure. The elongation, ultimate tensile strength, yield strength, and break strength of both materials are provided and analyzed here.

Heritability of Lumbar Trabecular Bone Mechanical Properties in Baboons

PubMed Central

Havill, L.M.; Allen, M.R.; Bredbenner, T.L.; Burr, D.B.; Nicolella, D.P.; Turner, C.H.; Warren, D.M.; Mahaney, M.C.

2010-01-01

Genetic effects on mechanical properties have been demonstrated in rodents, but not confirmed in primates. Our aim was to quantify the proportion of variation in vertebral trabecular bone mechanical properties that is due to the effects of genes. L3 vertebrae were collected from 110 females and 46 male baboons (6–32 years old) from a single extended pedigree. Cranio-caudally oriented trabecular bone cores were scanned with microCT then tested in monotonic compression to determine apparent ultimate stress, modulus, and toughness. Age and sex effects and heritability (h2) were assessed using maximum likelihood-based variance components methods. Additive effects of genes on residual trait variance were significant for ultimate stress (h2=0.58), toughness (h2=0.64), and BV/TV (h2=0.55). When BV/TV was accounted for, the residual variance in ultimate stress accounted for by the additive effects of genes was no longer significant. Toughness, however, showed evidence of a non-BV/TV-related genetic effect. Overall, maximum stress and modulus show strong genetic effects that are nearly entirely due to bone volume. Toughness shows strong genetic effects related to bone volume and shows additional genetic effects (accounting for 10% of the total trait variance) that are independent of bone volume. These results support continued use of bone volume as a focal trait to identify genes related to skeletal fragility, but also show that other focal traits related to toughness and variation in the organic component of bone matrix will enhance our ability to find additional genes that are particularly relevant to fatigue-related fractures. PMID:19900599

A “fullerene-carbon nanotube” structure with tunable mechanical properties

NASA Astrophysics Data System (ADS)

Ji, W. M.; Zhang, L. W.; Liew, K. M.

2018-03-01

Carbon-based nanostructures have drawn tremendous research interest and become promising building blocks for the new generation of smart sensors and devices. Utilizing a bottom-up strategy, the chemical interconnecting sp 3 covalent bond between carbon building blocks is an efficient way to enhance its Young's modulus and ductility. The formation of sp 3 covalent bond, however, inevitably degrades its ultimate tensile strength caused by stress concentration at the junction. By performing a molecular dynamics simulation of tensile deformation for a fullerene-carbon nanotube (FCNT) structure, we propose a tunable strategy in which fullerenes with various angle energy absorption capacities are utilized as building blocks to tune their ductile behavior, while still maintaining a good ultimate tensile strength of the carbon building blocks. A higher ultimate tensile strength is revealed with the reduction of stress concentration at the junction. A brittle-to-ductile transition during the tensile deformation is detected through the structural modification. The development of ductile behavior is attributed to the improvement of energy propagation ability during the fracture initiation, in which the released energy from bonds fracture is mitigated properly, leading to the further development of mechanical properties.

Torsional and axial compressive properties of tibiotarsal bones of red-tailed hawks (Buteo jamaicensis).

PubMed

Kerrigan, Shannon M; Kapatkin, Amy S; Garcia, Tanya C; Robinson, Duane A; Guzman, David Sanchez-Migallon; Stover, Susan M

2018-04-01

OBJECTIVE To describe the torsional and axial compressive properties of tibiotarsal bones of red-tailed hawks (Buteo jamaicensis). SAMPLE 16 cadaveric tibiotarsal bones from 8 red-tailed hawks. PROCEDURES 1 tibiotarsal bone from each bird was randomly assigned to be tested in torsion, and the contralateral bone was tested in axial compression. Intact bones were monotonically loaded in either torsion (n = 8) or axial compression (8) to failure. Mechanical variables were derived from load-deformation curves. Fracture configurations were described. Effects of sex, limb side, and bone dimensions on mechanical properties were assessed with a mixed-model ANOVA. Correlations between equivalent torsional and compressive properties were determined. RESULTS Limb side and bone dimensions were not associated with any mechanical property. During compression tests, mean ultimate cumulative energy and postyield energy for female bones were significantly greater than those for male bones. All 8 bones developed a spiral diaphyseal fracture and a metaphyseal fissure or fracture during torsional tests. During compression tests, all bones developed a crushed metaphysis and a fissure or comminuted fracture of the diaphysis. Positive correlations were apparent between most yield and ultimate torsional and compressive properties. CONCLUSIONS AND CLINICAL RELEVANCE The torsional and axial compressive properties of tibiotarsal bones described in this study can be used as a reference for investigations into fixation methods for tibiotarsal fractures in red-tailed hawks. Although the comminuted and spiral diaphyseal fractures induced in this study were consistent with those observed in clinical practice, the metaphyseal disruption observed was not and warrants further research.

Evaluation of the interfacial bond properties between carbon phenolic and glass phenolic composites

NASA Technical Reports Server (NTRS)

Jordan, K.; Clinton, R.; Jeelani, S.

1991-01-01

The effects of moisture and surface finish on the mechanical and physical properties of the interfacial bond between carbon/phenolic (C/P) and glass/phenolic (G/P) composite materials have been studied. Test results indicate that moisture substantially degrades the integrity of the interfacial bond between C/P and G/P materials. The apparent effect of the autoclave curing of the C/P material reduces the ultimate interlaminar shear length of the C/P material by 20 percent compared to the hydroclave curing of the C/P material. The variation in applied surface finishes is found to have no appreciable effect on the ultimate interlaminar shear strength of the interface in the wet laminate.

Microstructure and mechanical properties of a hot-extruded Al-based composite reinforced with core-shell-structured Ti/Al3Ti

NASA Astrophysics Data System (ADS)

Zhang, Li; Wu, Bao-lin; Liu, Yu-lin

2017-12-01

An Al-based composite reinforced with core-shell-structured Ti/Al3Ti was fabricated through a powder metallurgy route followed by hot extrusion and was found to exhibit promising mechanical properties. The ultimate tensile strength and elongation of the composite sintered at 620°C for 5 h and extruded at a mass ratio of 12.75:1 reached 304 MPa and 14%, respectively, and its compressive deformation reached 60%. The promising mechanical properties are due to the core-shell-structured reinforcement, which is mainly composed of Al3Ti and Ti and is bonded strongly with the Al matrix, and to the reduced crack sensitivity of Al3Ti. The refined grains after hot extrusion also contribute to the mechanical properties of this composite. The mechanical properties might be further improved through regulating the relative thickness of Al-Ti intermetallics and Ti metal layers by adjusting the sintering time and the subsequent extrusion process.

Effects of thermomechanical treatments on the microstructures and mechanical properties of GTA-welded AZ31B magnesium alloy

NASA Astrophysics Data System (ADS)

Chu, Ya-jie; Chen, Jian; Li, Xiao-quan; Wu, Shen-qing; Yang, Zong-hui

2012-10-01

Thermomechanical treatments were carried out to improve the properties of AZ31B joints prepared by gas tungsten arc welding. The microstructures of the joints were studied by optical microscopy and scanning electron microscopy with energy-dispersive spectrometry. Tensile tests and hardness tests were performed to investigate the effects of thermomechanical treatments on the mechanical properties of the joints. It is found that the thermomechanical-treated joints show superior mechanical properties against the as-welded joints, and their ultimate tensile strength can reach more than 92% of the base material. This mainly attributes to the formation of fine equiaxed grains in the fusion zone. After thermomechanical treatments the dendrites are transformed to fine spherical grains, and the dendritic segregation can be effectively eliminated.

Mechanical Properties of Organized Microcomposites Fabricated by Interference Lithography

NASA Astrophysics Data System (ADS)

Singamaneni, Srikanth; Chang, Sehoon; Jang, Ji-Hyun; Davis, Whitney; Thomas, Edwin; Tsukruk, Vladimir

2009-03-01

We demonstrate that organized, porous, polymer microstructures with continuous open nanoscale pores and sub-micron spacings obtained via interference lithography can be successfully utilized in a highly non-traditional field of ordered microcomposites. Organized microcomposite structures are fabricated by employing two independent strategies, namely, capillary infiltration and in situ polymerization of the rubbery component into the porous glassy microframes. The mechanical properties and ultimate fracture behavior of the single and bicomponent microframes are investigated at different length scales. The ordered single and bi-component microstructures with high degree of control over the microscopic organization of the polymeric phases result in excellent mechanical properties. Combining hard and soft polymer components provides multifunctional materials and coatings with synergetic properties and is frequently utilized for design of advanced polymeric composites.

Effect of thermal history on mechanical properties of polyetheretherketone below the glass transition temperature

NASA Technical Reports Server (NTRS)

Cebe, Peggy; Chung, Shirley Y.; Hong, Su-Don

1987-01-01

The effect of thermal history on the tensile properties of polyetheretherketone neat resin films was investigated at different test temperatures (125, 25, and -100) using four samples: fast-quenched amorphous (Q); quenched, then crystallized at 180 C (C180); slowly cooled (for about 16 h) from the melt (SC); and air-cooled (2-3 h) from the melt (AC). It was found that thermal history significantly affects the tensile properties of the material below the glass transition. Fast quenched amorphous films were most tough, could be drawn to greatest strain before rupture, and undergo densification during necking; at the test temperature of -100 C, these films had the best ultimate mechanical properties. At higher temperatures, the semicrystalline films AC and C180 had properties that compared favorably with the Q films. The SC films exhibited poor mechanical properties at all test temperatures.

Effect of modifications in mineralized collagen fibril and extra-fibrillar matrix material properties on submicroscale mechanical behavior of cortical bone.

PubMed

Wang, Yaohui; Ural, Ani

2018-06-01

A key length scale of interest in assessing the fracture resistance of bone is the submicroscale which is composed of mineralized collagen fibrils (MCF) and extra-fibrillar matrix (EFM). Although the processes through which the submicroscale constituents of bone contribute to the fracture resistance in bone have been identified, the extent of the modifications in submicroscale mechanical response due to the changes in individual properties of MCFs and EFM has not been determined. As a result, this study aims to quantify the influence of individual MCF and EFM material property modifications on the mechanical behavior (elastic modulus, ultimate strength, and resistance to failure) of bone at the submicroscale using a novel finite element modeling approach that incorporate 3D networks of MCFs with three different orientations as well as explicit representation of EFM. The models were evaluated under tensile loading in transverse (representing MCF separation) and longitudinal (representing MCF rupture) directions. The results showed that the apparent elastic modulus at the submicroscale under both loading directions for all orientations was only affected by the change in the elastic modulus of MCFs. MCF separation and rupture strengths were mainly dependent on the ultimate strength of EFM and MCFs, respectively, with minimal influence of other material properties. The extent of damage during MCF separation increased with increasing ultimate strength of EFM and decreased with increasing fracture energy of EFM with minimal contribution from elastic modulus of MCFs. For MCF rupture, there was an almost one-to-one linear relationship between the percent change in fracture energy of MCFs and the percent change in the apparent submicroscale fracture energy. The ultimate strength and elastic modulus of MCFs had moderate to limited influence on the MCF rupture fracture energy. The results of this study quantified the extent of changes that may be seen in the energy dissipation processes during MCF rupture and separation relative to the changes in the individual constituents of the tissue. This new knowledge significantly contributes to improving the understanding of how the material property alterations at the submicroscale that can occur due to diseases, age-related changes, and treatments affect the fracture processes at larger length scales. Copyright © 2018 Elsevier Ltd. All rights reserved.

Direct in situ observation of ZnO nucleation and growth via transmission X-ray microscopy

NASA Astrophysics Data System (ADS)

Tay, S. E. R.; Goode, A. E.; Nelson Weker, J.; Cruickshank, A. A.; Heutz, S.; Porter, A. E.; Ryan, M. P.; Toney, M. F.

2016-01-01

The nucleation and growth of a nanostructure controls its size and morphology, and ultimately its functional properties. Hence it is crucial to investigate growth mechanisms under relevant growth conditions at the nanometer length scale. Here we image the nucleation and growth of electrodeposited ZnO nanostructures in situ, using a transmission X-ray microscope and specially designed electrochemical cell. We show that this imaging technique leads to new insights into the nucleation and growth mechanisms in electrodeposited ZnO including direct, in situ observations of instantaneous versus delayed nucleation.The nucleation and growth of a nanostructure controls its size and morphology, and ultimately its functional properties. Hence it is crucial to investigate growth mechanisms under relevant growth conditions at the nanometer length scale. Here we image the nucleation and growth of electrodeposited ZnO nanostructures in situ, using a transmission X-ray microscope and specially designed electrochemical cell. We show that this imaging technique leads to new insights into the nucleation and growth mechanisms in electrodeposited ZnO including direct, in situ observations of instantaneous versus delayed nucleation. Electronic supplementary information (ESI) available: Methods and videos of nanoparticle growth. See DOI: 10.1039/c5nr07019h

Microstructures and mechanical properties of Ti5553 alloy processed by high-pressure torsion

NASA Astrophysics Data System (ADS)

Jiang, B. Z.; Emura, S.; Tsuchiya, K.

2014-08-01

In the present research, the effects of high-pressure torsion (HPT) processing on the microstructure and mechanical properties of Ti-5Al-5Mo-5V-3Cr (Ti5553) alloy were studied. HPT processing produced a white etching layer (WEL) in the middle section of the cross-section and numerous shear bands in the surface region of the cross-section. And the thickness of the WEL increased with increasing the HPT revolutions. TEM observation of the WEL revealed an ultrafine-grained structure with high degree of lattice distortions. The mechanical properties measurements showed that the hardness and ultimate tensile strength increased by HPT processing, accompanied with a decrease in the elongation to failure. It is considered that the mechanical properties of HPT processed Ti5553 alloy are mostly dominated by the shear banded region and the WEL where have the finest grain size and high density of dislocations.

First-principles investigation of mechanical properties of silicene, germanene and stanene

NASA Astrophysics Data System (ADS)

Mortazavi, Bohayra; Rahaman, Obaidur; Makaremi, Meysam; Dianat, Arezoo; Cuniberti, Gianaurelio; Rabczuk, Timon

2017-03-01

Two-dimensional allotropes of group-IV substrates including silicene, germanene and stanene have recently attracted considerable attention in nanodevice fabrication industry. These materials involving the buckled structure have been experimentally fabricated lately. In this study, first-principles density functional theory calculations were utilized to investigate the mechanical properties of single-layer and free-standing silicene, germanene and stanene. Uniaxial tensile and compressive simulations were carried out to probe and compare stress-strain properties; such as the Young's modulus, Poisson's ratio and ultimate strength. We evaluated the chirality effect on the mechanical response and bond structure of the 2D substrates. Our first-principles simulations suggest that in all studied samples application of uniaxial loading can alter the electronic nature of the buckled structures into the metallic character. Our investigation provides a general but also useful viewpoint with respect to the mechanical properties of silicene, germanene and stanene.

High-Power Diode Laser-Treated 13Cr4Ni Stainless Steel for Hydro Turbines

NASA Astrophysics Data System (ADS)

Mann, B. S.

2014-06-01

The cast martensitic chromium nickel stainless steels such as 13Cr4Ni, 16Cr5Ni, and 17Cr4Ni PH have found wide application in hydro turbines. These steels have adequate corrosion resistance with good mechanical properties because of chromium content of more than 12%. The 13Cr4Ni stainless steel is most widely used among these steels; however, lacks silt, cavitation, and water impingement erosion resistances (SER, CER, and WIER). This article deals with characterizing 13Cr4Ni stainless steel for silt, cavitation, and water impingement erosion; and studying its improved SER, CER, and WIER behavior after high-power diode laser (HPDL) surface treatment. The WIER and CER have improved significantly after laser treatment, whereas there is a marginal improvement in SER. The main reason for improved WIER and CER is due to its increased surface hardness and formation of fine-grained microstructure after HPDL surface treatment. CER and WIER of HPDL-treated 13Cr4Ni stainless steel samples have been evaluated as per ASTM G32-2003 and ASTM G73-1978, respectively; and these were correlated with microstructure and mechanical properties such as ultimate tensile strength, modified ultimate resilience, and microhardness. The erosion damage mechanism, compared on the basis of scanning electron micrographs and mechanical properties, is discussed and reported in this article.

Fabrication of Carbon Nanofibers/A356 Nanocomposites by High-Intensity Ultrasonic Processing

NASA Astrophysics Data System (ADS)

Wu, Qing-Jie; Yan, Hong

2018-03-01

A356 alloy reinforced with carbon nanofibers (CNFs) was fabricated by high-intensity ultrasonic vibration processing. The microstructure and mechanical properties were investigated. The distribution of CNFs became more and more uniform with the increase of ultrasonic power, and the mechanical properties of nanocomposites were significantly enhanced accordingly. The yield strength (YS), ultimate tensile strength (UTS), and microhardness of the nanocomposite increased by 38.3, 21.9, and 43.2 pct, respectively, at a CNF content of 0.9 wt pct compared with the matrix without CNF addition. The improvement in mechanical properties was the effect of CNFs on the thermal expansion mismatch strengthening of the nanocomposite, the grain refinement of the nanocomposite, and the load transfer from the matrix to the nanofibers.

Fabrication of Carbon Nanofibers/A356 Nanocomposites by High-Intensity Ultrasonic Processing

NASA Astrophysics Data System (ADS)

Wu, Qing-Jie; Yan, Hong

2018-06-01

A356 alloy reinforced with carbon nanofibers (CNFs) was fabricated by high-intensity ultrasonic vibration processing. The microstructure and mechanical properties were investigated. The distribution of CNFs became more and more uniform with the increase of ultrasonic power, and the mechanical properties of nanocomposites were significantly enhanced accordingly. The yield strength (YS), ultimate tensile strength (UTS), and microhardness of the nanocomposite increased by 38.3, 21.9, and 43.2 pct, respectively, at a CNF content of 0.9 wt pct compared with the matrix without CNF addition. The improvement in mechanical properties was the effect of CNFs on the thermal expansion mismatch strengthening of the nanocomposite, the grain refinement of the nanocomposite, and the load transfer from the matrix to the nanofibers.

An Investigation of Physico-Mechanical Properties of Ultrafine-Grained Magnesium Alloys Subjected to Severe Plastic Deformation

NASA Astrophysics Data System (ADS)

Kozulyn, A. A.; Skripnyak, V. A.; Krasnoveikin, V. A.; Skripnyak, V. V.; Karavatskii, A. K.

2015-01-01

The results of investigations of physico-mechanical properties of specimens made from the structural Mg-based alloy (Russian grade Ma2-1) in its coarse-grained and ultrafine-grained states after SPD processing are presented. To form the ultrafine-grained structure, use was made of the method of orthogonal equal-channel angular pressing. After four passes through the die, a simultaneous increase was achieved in microhardness, yield strength, ultimate tensile strength and elongation to failure under conditions of uniaxial tensile loading.

Combined Intercritical Annealing and Q&P Processing of Medium Mn Steel

NASA Astrophysics Data System (ADS)

De Cooman, Bruno C.; Lee, Seon Jong; Shin, Sunmi; Seo, Eun Jung; Speer, John G.

2017-01-01

The microstructure and mechanical properties of intercritically annealed medium Mn steel are dependent on the selection of the intercritical annealing (IA) temperature. While the yield strength (YS) decreases with increasing IA temperature, the ultimate tensile strength increases with increasing IA temperature. Strain aging phenomena, both static and dynamic, are also often observed. The present contribution shows that, by combining IA with the quench and partitioning processing of the intercritical austenite, it is possible to obtain non-aging mechanical properties which combine a high YS with an ultra-high tensile strength. These properties are particularly suitable for automotive parts related to passenger safety.

Optimizing concrete mix designs to produce cost effective paving mixes.

DOT National Transportation Integrated Search

2009-09-01

This research is designed to determine the effect of the mechanically activated fly ash on fresh : concrete properties and the ultimate strength of the hardened concrete. Six types of fly ash that are : locally available in the state of Oklahoma were...

Enhanced mechanical properties of epoxy nanocomposites by mixing noncovalently functionalized boron nitride nanoflakes.

PubMed

Lee, Dongju; Song, Sung Ho; Hwang, Jaewon; Jin, Sung Hwan; Park, Kwang Hyun; Kim, Bo Hyun; Hong, Soon Hyung; Jeon, Seokwoo

2013-08-12

The influence of surface modifications on the mechanical properties of epoxy-hexagonal boron nitride nanoflake (BNNF) nanocomposites is investigated. Homogeneous distributions of boron nitride nanoflakes in a polymer matrix, preserving intrinsic material properties of boron nitride nanoflakes, is the key to successful composite applications. Here, a method is suggested to obtain noncovalently functionalized BNNFs with 1-pyrenebutyric acid (PBA) molecules and to synthesize epoxy-BNNF nanocomposites with enhanced mechanical properties. The incorporation of noncovalently functionalized BNNFs into epoxy resin yields an elastic modulus of 3.34 GPa, and 71.9 MPa ultimate tensile strength at 0.3 wt%. The toughening enhancement is as high as 107% compared to the value of neat epoxy. The creep strain and the creep compliance of the noncovalently functionalized BNNF nanocomposite is significantly less than the neat epoxy and the nonfunctionalized BNNF nanocomposite. Noncovalent functionalization of BNNFs is effective to increase mechanical properties by strong affinity between the fillers and the matrix. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The polymethyl methacrylate cervical cage for treatment of cervical disk disease Part III. Biomechanical properties.

PubMed

Chen, Jyi-Feng; Lee, Shih-Tseng

2006-10-01

In a previous article, we used the PMMA cervical cage in the treatment of single-level cervical disk disease and the preliminary clinical results were satisfactory. However, the mechanical properties of the PMMA cage were not clear. Therefore, we designed a comparative in vitro biomechanical study to determine the mechanical properties of the PMMA cage. The PMMA cervical cage and the Solis PEEK cervical cage were compressed in a materials testing machine to determine the mechanical properties. The compressive yield strength of the PMMA cage (7030 +/- 637 N) was less than that of the Solis polymer cervical cage (8100 +/- 572 N). The ultimate compressive strength of the PMMA cage (8160 +/- 724 N) was less than that of the Solis cage (9100 +/- 634 N). The stiffness of the PMMA cervical cage (8106 +/- 817 N/mm) was greater than that of the Solis cage (6486 +/- 530 N/mm). The elastic modulus of the PMMA cage (623 +/- 57 MPa) was greater than that of the Solis cage (510 +/- 42 MPa). The elongation of PMMA cage (43.5 +/- 5.7%) was larger than that of the Solis cage (36.1 +/- 4.3%). Although the compressive yield strength and ultimate compressive strength of the PMMA cervical cage were less than those of the Solis polymer cage, the mechanical properties are better than those of the cervical vertebral body. The PMMA cage is strong and safe for use as a spacer for cervical interbody fusion. Compared with other cage materials, the PMMA cage has many advantages and no obvious failings at present. However, the PMMA cervical cage warrants further long-term clinical study.

Electronic properties and mechanical strength of β-phosphorene nano-ribbons

DOE Office of Scientific and Technical Information (OSTI.GOV)

Swaroop, Ram; Bhatia, Pradeep; Kumar, Ashok, E-mail: ashok@cup.ac.in

We have performed first principles calculations to find out the effect of mechanical strain on the electronic properties of zig-zag edged nano ribbons of β-phosphorene. It is found that electronic band-gap get opened-up to 2.61 eV by passivation of the edges of ribbons. Similarly, the mechanical strength is found to be increase from 1.75 GPa to 2.65 GPa on going from unpassivated nano ribbons to passivated ones along with the 2% increase in ultimate tensile strain. The band-gap value of passivated ribbon gets decreased to 0.43 eV on applying strain up to which the ribbon does not break. These tunable properties ofmore » β-phospherene with passivation with H-atom and applying mechanical strain offer its use in tunable nano electronics.« less

Relationship between tendon stiffness and failure: a metaanalysis

PubMed Central

LaCroix, Andrew S.; Duenwald-Kuehl, Sarah E.; Lakes, Roderic S.

2013-01-01

Tendon is a highly specialized, hierarchical tissue designed to transfer forces from muscle to bone; complex viscoelastic and anisotropic behaviors have been extensively characterized for specific subsets of tendons. Reported mechanical data consistently show a pseudoelastic, stress-vs.-strain behavior with a linear slope after an initial toe region. Many studies report a linear, elastic modulus, or Young's modulus (hereafter called elastic modulus) and ultimate stress for their tendon specimens. Individually, these studies are unable to provide a broader, interstudy understanding of tendon mechanical behavior. Herein we present a metaanalysis of pooled mechanical data from a representative sample of tendons from different species. These data include healthy tendons and those altered by injury and healing, genetic modification, allograft preparation, mechanical environment, and age. Fifty studies were selected and analyzed. Despite a wide range of mechanical properties between and within species, elastic modulus and ultimate stress are highly correlated (R2 = 0.785), suggesting that tendon failure is highly strain-dependent. Furthermore, this relationship was observed to be predictable over controlled ranges of elastic moduli, as would be typical of any individual species. With the knowledge gained through this metaanalysis, noninvasive tools could measure elastic modulus in vivo and reasonably predict ultimate stress (or structural compromise) for diseased or injured tendon. PMID:23599401

Effects of Vacancy Concentration and Temperature on Mechanical Properties of Single-Crystal γ-TiAl Based on Molecular Dynamics Simulation

NASA Astrophysics Data System (ADS)

Ruicheng, Feng; Hui, Cao; Haiyan, Li; Zhiyuan, Rui; Changfeng, Yan

2018-01-01

Molecular dynamics simulation is used to analyze tensile strength and elastic modulus under different temperatures and vacancy concentrations. The effects of temperature and vacancy concentration on the mechanical properties of γ-TiAl alloy are investigated. The results show that the ultimate stress, ultimate strain and elastic modulus decrease nonlinearly with increasing temperature and vacancy concentration. As the temperature increases, the plastic of material is reinforced. The influence of temperature on strength and elastic modulus is larger than that of vacancy concentration. The evolution process of vacancy could be observed clearly. Furthermore, vacancies with different concentrations develop into voids first as a function of external forces or other factors, micro cracks evolve from those voids, those micro cracks then converge to a macro crack, and fracture will finally occur. The vacancy evolution process cannot be observed clearly owing to the thermal motion of atoms at high temperature. In addition, potential energy is affected by both temperature and vacancy concentration.

Microstructure and mechanical behavior of porous Ti-6Al-4V parts obtained by selective laser melting.

PubMed

Sallica-Leva, E; Jardini, A L; Fogagnolo, J B

2013-10-01

Rapid prototyping allows titanium porous parts with mechanical properties close to that of bone tissue to be obtained. In this article, porous parts of the Ti-6Al-4V alloy with three levels of porosity were obtained by selective laser melting with two different energy inputs. Thermal treatments were performed to determine the influence of the microstructure on the mechanical properties. The porous parts were characterized by both optical and scanning electron microscopy. The effective modulus, yield and ultimate compressive strength were determined by compressive tests. The martensitic α' microstructure was observed in all of the as-processed parts. The struts resulting from the processing conditions investigated were thinner than those defined by CAD models, and consequently, larger pores and a higher experimental porosity were achieved. The use of the high-energy input parameters produced parts with higher oxygen and nitrogen content, their struts that were even thinner and contained a homogeneous porosity distribution. Greater mechanical properties for a given relative density were obtained using the high-energy input parameters. The as-quenched martensitic parts showed yield and ultimate compressive strengths similar to the as-processed parts, and these were greater than those observed for the fully annealed samples that had the lamellar microstructure of the equilibrium α+β phases. The effective modulus was not significantly influenced by the thermal treatments. A comparison between these results and those of porous parts with similar geometry obtained by selective electron beam melting shows that the use of a laser allows parts with higher mechanical properties for a given relative density to be obtained. Copyright © 2013 Elsevier Ltd. All rights reserved.

Effect of flame retardants on the properties of monolithic and foamed polyurethanes at low temperatures

NASA Astrophysics Data System (ADS)

Yakushin, V. A.; Stirna, U. K.; Zhmud', N. P.

1999-09-01

The dependence of physical and mechanical properties of monolithic and foamed rigid polyurethanes on the content of flame retardants was investigated at 293 and 98 K. The character of the influence of the content of trichloroethyl phosphate on the ultimate tensile elongation and the coefficient of linear thermal expansion for monolithic and foamed polyurethanes at a temperature of 98 K was established.

Mechanical properties and flexure behaviour of lightweight foamed concrete incorporating coir fibre

NASA Astrophysics Data System (ADS)

Mohamad, Noridah; Afif Iman, Muhamad; Othuman Mydin, M. A.; Samad, A. A. A.; Rosli, J. A.; Noorwirdawati, A.

2018-04-01

This paper presents an experimental investigation on the mechanical properties and flexural behaviour of lightweight foamed concrete (LFC) with added coir fibre as filler. The compressive strength (Pt), tensile strength (Ft), modulus of elasticity (E), ultimate load and crack pattern of the foamed concrete were determined. The coir fibre was added to the foamed concrete mixture at 0.1%, 0.2% and 0.3% of the total weight of cement. Effects of various percentage of coir fibre used on foam concrete’s mechanical and properties and flexural behaviour were studied and analysed. It was found that the increase percentage of fibre resulted in increase in compressive strength, tensile strength and modulus of elasticity of LFC mixture. LFC with added coir of 0.3% experienced the smallest crack propagation.

Post-print UV curing method for improving the mechanical properties of prototypes derived from two-photon lithography [A post-print UV curing method for improving the mechanical properties of prototypes derived from two-photon polymerization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oakdale, James S.; Ye, Jianchao; Smith, William L.

Here, two photon polymerization (TPP) is a precise, reliable, and increasingly popular technique for rapid prototyping of micro-scale parts with sub-micron resolution. The materials of choice underlying this process are predominately acrylic resins cross-linked via free-radical polymerization. Due to the nature of the printing process, the derived parts are only partially cured and the corresponding mechanical properties, i.e. modulus and ultimate strength, are lower than if the material were cross-linked to the maximum extent. Herein, post-print curing via UV-driven radical generation, is demonstrated to increase the overall degree of cross-linking of low density, TPP-derived structures.

Post-print UV curing method for improving the mechanical properties of prototypes derived from two-photon lithography [A post-print UV curing method for improving the mechanical properties of prototypes derived from two-photon polymerization

DOE PAGES

Oakdale, James S.; Ye, Jianchao; Smith, William L.; ...

2016-11-28

Here, two photon polymerization (TPP) is a precise, reliable, and increasingly popular technique for rapid prototyping of micro-scale parts with sub-micron resolution. The materials of choice underlying this process are predominately acrylic resins cross-linked via free-radical polymerization. Due to the nature of the printing process, the derived parts are only partially cured and the corresponding mechanical properties, i.e. modulus and ultimate strength, are lower than if the material were cross-linked to the maximum extent. Herein, post-print curing via UV-driven radical generation, is demonstrated to increase the overall degree of cross-linking of low density, TPP-derived structures.

The Effect of Temperature and Rotational Speed on Structure and Mechanical Properties of Cast Cu Base Alloy (Cu-Al-Si-Fe) Welded by Semisolid Stir Joining Method

NASA Astrophysics Data System (ADS)

Ferasat, Keyvan; Aashuri, Hossein; Kokabi, Amir Hossein; Shafizadeh, Mahdi; Nikzad, Siamak

2015-12-01

Semisolid stir joining has been under deliberation as a possible method for joining of copper alloys. In this study, the effect of temperature and rotational speed of stirrer on macrostructure evaluation and mechanical properties of samples were investigated. Optical microscopy and X-ray diffraction were performed for macro and microstructural analysis. A uniform micro-hardness profile was attained by semisolid stir joining method. The ultimate shear strength and bending strength of welded samples were improved in comparison with the cast sample. There is also lower area porosity in welded samples than the cast metal. The mechanical properties were improved by increasing temperature and rotational speed of the joining process.

Tensile properties of a morphologically split supraspinatus tendon.

PubMed

Matsuhashi, Tomoya; Hooke, Alexander W; Zhao, Kristin D; Goto, Akira; Sperling, John W; Steinmann, Scott P; An, Kai-Nan

2014-07-01

The supraspinatus tendon consists morphologically of two sub-regions, anterior and posterior. The anterior sub-region is thick and tubular while the posterior is thin and strap-like. The purpose of this study was to compare the structural and mechanical properties of the anterior and posterior sub-regions of the supraspinatus tendon. The supraspinatus tendons from seven human cadaveric shoulders were morphologically divided into the anterior and posterior sub-regions. Length, width, and thickness were measured. A servo-hydraulic testing machine (MTS Systems Corporation, Minneapolis, MN) was used for tensile testing. The maximal load at failure, modulus of elasticity and ultimate tendon stress were calculated. Repeated measures were used for statistical comparisons. The mean anterior tendon cross-sectional area was 47.3 mm(2) and the posterior was 32.1 mm(2) . Failure occurred most often at the insertion site: anterior (5/7) and posterior (6/7). All parameters of the anterior sub-region were significantly greater than those of the posterior sub-region. The moduli of elasticity at the insertion site were 592.4 MPa in the anterior sub-region and 217.7 MPa in the posterior (P = 0.01). The ultimate failure loads were 779.2 N in the anterior sub-region and 335.6 N in the posterior (P = 0.003). The ultimate stresses were 22.1 MPa in the anterior sub-region and 11.6 MPa in the posterior (P = 0.008). We recognized that the anterior and posterior sub-regions of the SSP tendon have significantly different mechanical properties. In a future study, we need to evaluate how best to repair an SSP tendon considering these region-specific properties. Copyright © 2013 Wiley Periodicals, Inc.

Temperature effects on the mechanical properties of annealed and HERF 304L stainless steel.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Antoun, Bonnie R.

2004-11-01

The effect of temperature on the tensile properties of annealed 304L stainless steel and HERF 304L stainless steel forgings was determined by completing experiments over the moderate range of -40 F to 160 F. Temperature effects were more significant in the annealed material than the HERF material. The tensile yield strength of the annealed material at -40 F averaged twenty two percent above the room temperature value and at 160 F averaged thirteen percent below. The tensile yield strength for the three different geometry HERF forgings at -40 F and 160 F changed less than ten percent from room temperature.more » The ultimate tensile strength was more temperature dependent than the yield strength. The annealed material averaged thirty six percent above and fourteen percent below the room temperature ultimate strength at -40 F and 160 F, respectively. The HERF forgings exhibited similar, slightly lower changes in ultimate strength with temperature. For completeness and illustrative purposes, the stress-strain curves are included for each of the tensile experiments conducted. The results of this study prompted a continuation study to determine tensile property changes of welded 304L stainless steel material with temperature, documented separately.« less

ZM-21 magnesium alloy corrosion properties and cryogenic to elevated temperature mechanical properties

NASA Technical Reports Server (NTRS)

Montana, J. W.; Nelson, E. E.

1972-01-01

The mechanical properties of bare ZM-21 magnesium alloy flat tensile specimens were determined for test temperatures of +400 F, +300 F, +200 F, +80 F, 0 F, -100 F, -200 F, and -320 F. The ultimate tensile and yield strengths of the material increased with decreasing temperature with a corresponding reduction in elongation values. Stress corrosion tests performed under: (1) MSFC atmospheric conditions; (2) 95% relative humidity; and (3) submerged in 100 ppm chloride solution for 8 weeks indicated that the alloy is not susceptible to stress corrosion. The corrosion tests indicated that the material is susceptible to attack by crevice corrosion in high humidity and chemical type attack by chloride solution. Atmospheric conditions at MSFC did not produce any adverse effects on the material, probably due to the rapid formation of a protective oxide coating. In both the mechanical properties and the stress corrosion evaluations the test specimens which were cut transverse to the rolling direction had superior properties when compared to the longitudinal properties.

Innate Immunity and Biomaterials at the Nexus: Friends or Foes.

PubMed

Christo, Susan N; Diener, Kerrilyn R; Bachhuka, Akash; Vasilev, Krasimir; Hayball, John D

2015-01-01

Biomaterial implants are an established part of medical practice, encompassing a broad range of devices that widely differ in function and structural composition. However, one common property amongst biomaterials is the induction of the foreign body response: an acute sterile inflammatory reaction which overlaps with tissue vascularisation and remodelling and ultimately fibrotic encapsulation of the biomaterial to prevent further interaction with host tissue. Severity and clinical manifestation of the biomaterial-induced foreign body response are different for each biomaterial, with cases of incompatibility often associated with loss of function. However, unravelling the mechanisms that progress to the formation of the fibrotic capsule highlights the tightly intertwined nature of immunological responses to a seemingly noncanonical "antigen." In this review, we detail the pathways associated with the foreign body response and describe possible mechanisms of immune involvement that can be targeted. We also discuss methods of modulating the immune response by altering the physiochemical surface properties of the biomaterial prior to implantation. Developments in these areas are reliant on reproducible and effective animal models and may allow a "combined" immunomodulatory approach of adapting surface properties of biomaterials, as well as treating key immune pathways to ultimately reduce the negative consequences of biomaterial implantation.

Effects of alloying element on weld characterization of laser-arc hybrid welding of pure copper

NASA Astrophysics Data System (ADS)

Hao, Kangda; Gong, Mengcheng; Xie, Yong; Gao, Ming; Zeng, Xiaoyan

2018-06-01

Effects of alloying elements of Si and Sn on weld characterizations of laser-arc hybrid welded pure copper (Cu) with thickness of 2 mm was studied in detail by using different wires. The weld microstructure was analyzed, and the mechanical properties (micro-hardness and tensile property), conductivity and corrosion resistance were tested. The results showed that the alloying elements benefit the growth of column grains within weld fusion zone (FZ), increase the ultimate tensile strength (UTS) of the FZ and weld corrosion resistance, and decrease weld conductivity. The mechanisms were discussed according to the results.

Mechanical properties of Fe -10Ni -7Mn martensitic steel subjected to severe plastic deformation via cold rolling and wire drawing

NASA Astrophysics Data System (ADS)

Ghasemi-Nanesa, H.; Nili-Ahmadabadi, M.; Shirazi, H.

2010-07-01

Fe-Ni-Mn martensitic steels are one of the major groups of ultra-high strength steels that have good mechanical properties and ductility in as annealed condition but they suffer from severe inter-granular embitterment after aging. In this paper, the effect of heavy shaped cold rolling and wire drawing on the mechanical properties of Fe-Ni-Mn steel was investigated. This process could provide a large strain deformation in this alloy. The total strain was epsilon ~7. Aging behavior and tensile properties of Fe-10Ni-7Mn were studied after aging at 753 K. The results showed that the ultimate tensile strength and ductility after cold rolling, wire drawing and aging increased up to 2540 MPa and 7.1 %, respectively, while the conventional steels show a premature fracture stress of 830 MPa with about zero ductility after aging.

Development of biodegradable materials; balancing degradability and performance

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mayer, J.M.; Allen, A.L.; Dell, P.A.

1993-12-31

The development of biodegradable materials suitable for packaging must take into consideration various performance criteria such as mechanical and barrier properties, as well as rate of biodegradability in given environments. Individual or blended biopolymer films were obtained commercially or blown into film in the laboratory and tested for tensile strength, ultimate elongation and oxygen barrier. These films were then subjected to accelerated marine biodegradation tests as well as simulated marine respirometry. Starch/ethylene vinyl alcohol films exhibited good mechanical and excellent oxygen barrier properties, but were very slow to biodegrade in the simulated and excellent oxygen barrier properties, but were verymore » slow to biodegrade in the simulated marine environment. Polyhydroxyalkanoates had good mechanical properties, average oxygen barrier and good biodegradability. Data indicate that performance and biodegradability of packaging can be tailored to needs by combining individual biopolymers in different proportions in blends and laminates.« less

Moisture effect on mechanical properties of polymeric composite materials

NASA Astrophysics Data System (ADS)

Airale, A. G.; Carello, M.; Ferraris, A.; Sisca, L.

2016-05-01

The influence of moisture on the mechanical properties of fibre-reinforced polymer matrix composites (PMCs) was investigated. Four materials had been take into account considering: both 2×2-Twill woven carbon fibre or glass fibre, thermosetting matrix (Epoxy Resin) or thermoplastic matrix (Polyphenylene Sulfide). The specimens were submitted for 1800 hours to a hygrothermic test to evaluate moisture absorption on the basis of the Fick's law and finally tested to verify the mechanical properties (ultimate tensile strength). The results showed that the absorbed moisture decreases those properties of composites which were dominated by the matrix or the interface, while was not detectable the influence of water on the considered fibre. An important result is that the diffusion coefficient is highest for glass/PPS and lowest for carbon/epoxy composite material. The results give useful suggestions for the design of vehicle components that are exposed to environmental conditions (rain, snow and humidity).

The Impact of Halloysite on the Thermo-Mechanical Properties of Polymer Composites.

PubMed

Gaaz, Tayser Sumer; Sulong, Abu Bakar; Kadhum, Abdul Amir H; Al-Amiery, Ahmed A; Nassir, Mohamed H; Jaaz, Ahed Hameed

2017-05-20

Nanotubular clay minerals, composed of aluminosilicate naturally structured in layers known as halloysite nanotubes (HNTs), have a significant reinforcing impact on polymer matrixes. HNTs have broad applications in biomedical applications, the medicine sector, implant alloys with corrosion protection and manipulated transportation of medicines. In polymer engineering, different research studies utilize HNTs that exhibit a beneficial enhancement in the properties of polymer-based nanocomposites. The dispersion of HNTs is improved as a result of pre-treating HNTs with acids. The HNTs' percentage additive up to 7% shows the highest improvement of tensile strength. The degradation of the polymer can be also significantly improved by doping a low percentage of HNTs. Both the mechanical and thermal properties of polymers were remarkably improved when mixed with HNTs. The effects of HNTs on the mechanical and thermal properties of polymers, such as ultimate strength, elastic modulus, impact strength and thermal stability, are emphasized in this study.

Experimental studies on mechanical properties of T6 treated Al25Mg2Si2Cu4Fe alloy

NASA Astrophysics Data System (ADS)

Sondur, D. G.; Mallapur, D. G.; Udupa, K. Rajendra

2018-04-01

Effect of T6 treatment on the mechanical properties of Al25Mg2Si2Cu4Fe alloy was evaluated by conducting mechanical tests on test pieces using universal testing machine. Increase in the mechanical properties such as ultimate tensile strength, hardness and % elongation was observed. Microstructure characterization revealed the modification in the size and shapes of the precipitates formed during the homogenization process. This modification increases the anisotropy of the microstructure and the stresses in the as cast structure. The increase in the hardness of T6 treated alloy is due to the partial recrystallization, fragmentation and redistribution of primary Mg2Si phase, precipitation of fine θ, Q phases. The high volume fractions of uniformly dispersed hard β-particles greatly increase the flow stress and provide an appreciable impediment to plastic deformation. Thus increasing the hardness of the alloy.

Effect of Age and Exercise on the Viscoelastic Properties of Rat Tail Tendon

PubMed Central

LaCroix, Andrew S.; Duenwald-Kuehl, Sarah E.; Brickson, Stacey; Akins, Tiffany L.; Diffee, Gary; Aiken, Judd; Vanderby, Ray; Lakes, Roderic S.

2013-01-01

Tendon mechanical properties are thought to degrade during aging but improve with exercise. A remaining question is whether exercise in aged animals provides sufficient regenerative, systemic stimulus to restore younger mechanical behaviors. Herein we address that question with tail tendons from aged and exercised rats, which would be subject to systemic effects but not direct loading from the exercise regimen. Twenty-four month old rats underwent one of three treadmill exercise training protocols for 12 months: sedentary (walking at 0° incline for 5 min/day), moderate (running at 0° incline for 30 min/day), or high (running at 4° incline for 30 min/day). A group of 9 month old rats were used to provide an adult control, while a group of 3 month old rats provided a young control. Tendons were harvested at sacrifice and mechanically tested. Results show significant age-dependent differences in modulus, ultimate stress, relaxation rate, and percent relaxation. Relaxation rate was strain-dependent, consistent with nonlinear superposition or Schapery models but not with quasilinear viscoelasticity (QLV). Trends in exercise data suggest that with exercise, tendons assume the elastic character of younger rats (lower elastic modulus and ultimate stress). PMID:23549897

Tendon material properties vary and are interdependent among turkey hindlimb muscles

PubMed Central

Matson, Andrew; Konow, Nicolai; Miller, Samuel; Konow, Pernille P.; Roberts, Thomas J.

2012-01-01

SUMMARY The material properties of a tendon affect its ability to store and return elastic energy, resist damage, provide mechanical feedback and amplify or attenuate muscle power. While the structural properties of a tendon are known to respond to a variety of stimuli, the extent to which material properties vary among individual muscles remains unclear. We studied the tendons of six different muscles in the hindlimb of Eastern wild turkeys to determine whether there was variation in elastic modulus, ultimate tensile strength and resilience. A hydraulic testing machine was used to measure tendon force during quasi-static lengthening, and a stress–strain curve was constructed. There was substantial variation in tendon material properties among different muscles. Average elastic modulus differed significantly between some tendons, and values for the six different tendons varied nearly twofold, from 829±140 to 1479±106 MPa. Tendons were stretched to failure, and the stress at failure, or ultimate tensile stress, was taken as a lower-limit estimate of tendon strength. Breaking tests for four of the tendons revealed significant variation in ultimate tensile stress, ranging from 66.83±14.34 to 112.37±9.39 MPa. Resilience, or the fraction of energy returned in cyclic length changes was generally high, and one of the four tendons tested was significantly different in resilience from the other tendons (range: 90.65±0.83 to 94.02±0.71%). An analysis of correlation between material properties revealed a positive relationship between ultimate tensile strength and elastic modulus (r2=0.79). Specifically, stiffer tendons were stronger, and we suggest that this correlation results from a constrained value of breaking strain, which did not vary significantly among tendons. This finding suggests an interdependence of material properties that may have a structural basis and may explain some adaptive responses observed in studies of tendon plasticity. PMID:22771746

Tendon material properties vary and are interdependent among turkey hindlimb muscles.

PubMed

Matson, Andrew; Konow, Nicolai; Miller, Samuel; Konow, Pernille P; Roberts, Thomas J

2012-10-15

The material properties of a tendon affect its ability to store and return elastic energy, resist damage, provide mechanical feedback and amplify or attenuate muscle power. While the structural properties of a tendon are known to respond to a variety of stimuli, the extent to which material properties vary among individual muscles remains unclear. We studied the tendons of six different muscles in the hindlimb of Eastern wild turkeys to determine whether there was variation in elastic modulus, ultimate tensile strength and resilience. A hydraulic testing machine was used to measure tendon force during quasi-static lengthening, and a stress-strain curve was constructed. There was substantial variation in tendon material properties among different muscles. Average elastic modulus differed significantly between some tendons, and values for the six different tendons varied nearly twofold, from 829±140 to 1479±106 MPa. Tendons were stretched to failure, and the stress at failure, or ultimate tensile stress, was taken as a lower-limit estimate of tendon strength. Breaking tests for four of the tendons revealed significant variation in ultimate tensile stress, ranging from 66.83±14.34 to 112.37±9.39 MPa. Resilience, or the fraction of energy returned in cyclic length changes was generally high, and one of the four tendons tested was significantly different in resilience from the other tendons (range: 90.65±0.83 to 94.02±0.71%). An analysis of correlation between material properties revealed a positive relationship between ultimate tensile strength and elastic modulus (r(2)=0.79). Specifically, stiffer tendons were stronger, and we suggest that this correlation results from a constrained value of breaking strain, which did not vary significantly among tendons. This finding suggests an interdependence of material properties that may have a structural basis and may explain some adaptive responses observed in studies of tendon plasticity.

Rheological and mechanical properties of polypropylene prepared with multi-walled carbon nanotube masterbatch.

PubMed

Shim, Young-Sun; Park, Soo-Jin

2012-07-01

In this study, the effects of polypropylene-grafted maleic-anhydride-treated multi-walled carbon nanotubes (PP-MWNTs) on the viscoelastic behaviors and mechanical properties of a polypropylene-(PP)-based composite system were examined. The PP-MWNT/PP composites were prepared via melt mixing with a 3:1 ratio of PP-g-MA and acid-treated MWNTs at 220 degrees C. The surface characteristics of the PP-MWNTs were confirmed via Fourier transform infrared (FTIR) spectroscopy and transmission electron microscopy (TEM). The viscoelastic behavior and mechanical properties of the PP-MWNT/PP composites were confirmed using a rheometer and an ultimate testing machine (UTM). The storage and loss moduli increased with increasing PP-MWNT content. The critical intensity stress factor (K(IC)) of the PP-MWNT/PP composites at high filler loading was also higher than that of the MWNT/PP composites. In conclusion, the viscoelastic behavior and mechanical properties of MWNT/PP can be improved by grafting MWNTs to PP-g-MA.

Cellulose whiskers versus microfibrils: influence of the nature of the nanoparticle and its surface functionalization on the thermal and mechanical properties of nanocomposites.

PubMed

Siqueira, Gilberto; Bras, Julien; Dufresne, Alain

2009-02-09

In the present work, nanowhiskers and microfibrillated cellulose (MFC) both extracted from sisal were used to reinforce polycaprolactone (PCL). We report the influence of the nanoparticle's nature on the mechanical and thermal properties of the ensuing nanocomposites. The surface of both the nanoparticles was chemically modified to improve their compatibilization with the polymeric matrix. N-Octadecyl isocyanate (C18H37NCO) was used as the grafting agent. PCL nanocomposite films reinforced with sisal whiskers or MFC (raw or chemically modified) were prepared by film casting. The thermal behavior (Tg, Tm, Tc, and degree of crystallinity) and the mechanical properties of the nanocomposites in both the linear and the nonlinear range were determined using differential scanning calorimetry (DSC), dynamical mechanical analysis (DMA), and tensile tests, respectively. Significant differences were reported according to the nature of the nanoparticle and amount of nanofillers used as reinforcement. It was also proved that the chemical treatment clearly improves the ultimate properties of the nanocomposites.

Phase transition induced strain in ZnO under high pressure

DOE PAGES

Yan, Xiaozhi; Dong, Haini; Li, Yanchun; ...

2016-05-13

Under high pressure, the phase transition mechanism and mechanical property of material are supposed to be largely associated with the transformation induced elastic strain. However, the experimental evidences for such strain are scanty. The elastic and plastic properties of ZnO, a leading material for applications in chemical sensor, catalyst, and optical thin coatings, were determined using in situ high pressure synchrotron axial and radial x-ray diffraction. The abnormal elastic behaviors of selected lattice planes of ZnO during phase transition revealed the existence of internal elastic strain, which arise from the lattice misfit between wurtzite and rocksalt phase. Furthermore, the strengthmore » decrease of ZnO during phase transition under non-hydrostatic pressure was observed and could be attributed to such internal elastic strain, unveiling the relationship between pressure induced internal strain and mechanical property of material. Ultimately, these findings are of fundamental importance to understanding the mechanism of phase transition and the properties of materials under pressure.« less

Mechanical properties of composite materials

NASA Technical Reports Server (NTRS)

Thornton, H. Richard; Cornwell, L. R.

1993-01-01

A composite material incorporates high strength, high modulus fibers in a matrix (polymer, metal, or ceramic). The fibers may be oriented in a manner to give varying in-plane properties (longitudinal, transverse-stress, strain, and modulus of elasticity). The lay-up of the composite laminates is such that a center line of symmetry and no bending moment exist through the thickness. The laminates are tabbed, with either aluminum or fiberglass, and are ready for tensile testing. The determination of the tensile properties of resin matrix composites, reinforced by continuous fibers, is outlined in ASTM standard D 3039, Tensile Properties of Oriented Fiber Composites. The tabbed flat tensile coupons are placed into the grips of a tensile machine and load-deformation curves plotted. The load-deformation data are translated into stress-strain curves for determination of mechanical properties (ultimate tensile strength and modulus of elasticity).

Development of Duplex Stainless Steels by Field-Assisted Hot Pressing: Influence of the Particle Size and Morphology of the Powders on the Final Mechanical Properties

NASA Astrophysics Data System (ADS)

García-Junceda, A.; Rincón, M.; Torralba, J. M.

2018-01-01

The feasibility of processing duplex stainless steels with promising properties using a powder metallurgical route, including the consolidation by field-assisted hot pressing, is assessed in this investigation. The influence of the particle size and morphology of the raw austenitic and ferritic powders on the final microstructure and properties is also evaluated for an austenitic content of 60 wt pct. In addition, the properties of a new microconstituent generated between the initial constituents are analyzed. The maximum sintered density (98.9 pct) and the best mechanical behavior, in terms of elastic modulus, nanohardness, yield strength, ultimate tensile strength, and ductility, are reached by the duplex stainless steel processed with austenitic and ferritic gas atomized stainless steel powders.

Thrust chamber life prediction. Volume 1: Mechanical and physical properties of high performance rocket nozzle materials

NASA Technical Reports Server (NTRS)

Esposito, J. J.; Zabora, R. F.

1975-01-01

Pertinent mechanical and physical properties of six high conductivity metals were determined. The metals included Amzirc, NARloy Z, oxygen free pure copper, electroformed copper, fine silver, and electroformed nickel. Selection of these materials was based on their possible use in high performance reusable rocket nozzles. The typical room temperature properties determined for each material included tensile ultimate strength, tensile yield strength, elongation, reduction of area, modulus of elasticity, Poisson's ratio, density, specific heat, thermal conductivity, and coefficient of thermal expansion. Typical static tensile stress-strain curves, cyclic stress-strain curves, and low-cycle fatigue life curves are shown. Properties versus temperature are presented in graphical form for temperatures from 27.6K (-410 F) to 810.9K (1000 F).

Acellularization-Induced Changes in Tensile Properties Are Organ Specific - An In-Vitro Mechanical and Structural Analysis of Porcine Soft Tissues

PubMed Central

Aust, Gabriela; Boldt, Andreas; Fritsch, Sebastian; Keil, Isabel; Koch, Holger; Möbius, Robert; Scheidt, Holger A.; Wagner, Martin F. X.; Hammer, Niels

2016-01-01

Introduction Though xenogeneic acellular scaffolds are frequently used for surgical reconstruction, knowledge of their mechanical properties is lacking. This study compared the mechanical, histological and ultrastructural properties of various native and acellular specimens. Materials and Methods Porcine esophagi, ureters and skin were tested mechanically in a native or acellular condition, focusing on the elastic modulus, ultimate tensile stress and maximum strain. The testing protocol for soft tissues was standardized, including the adaption of the tissue’s water content and partial plastination to minimize material slippage as well as templates for normed sample dimensions and precise cross-section measurements. The native and acellular tissues were compared at the microscopic and ultrastructural level with a focus on type I collagens. Results Increased elastic modulus and ultimate tensile stress values were quantified in acellular esophagi and ureters compared to the native condition. In contrast, these values were strongly decreased in the skin after acellularization. Acellularization-related decreases in maximum strain were found in all tissues. Type I collagens were well-preserved in these samples; however, clotting and a loss of cross-linking type I collagens was observed ultrastructurally. Elastins and fibronectins were preserved in the esophagi and ureters. A loss of the epidermal layer and decreased fibronectin content was present in the skin. Discussion Acellularization induces changes in the tensile properties of soft tissues. Some of these changes appear to be organ specific. Loss of cross-linking type I collagen may indicate increased mechanical strength due to decreasing transverse forces acting upon the scaffolds, whereas fibronectin loss may be related to decreased load-bearing capacity. Potentially, the alterations in tissue mechanics are linked to organ function and to the interplay of cells and the extracellular matrix, which is different in hollow organs when compared to skin. PMID:26960134

High-density carbon nanotube buckypapers with superior transport and mechanical properties.

PubMed

Zhang, Ling; Zhang, Guang; Liu, Changhong; Fan, Shoushan

2012-09-12

High-density buckypapers were obtained by using well-aligned carbon nanotube arrays. The density of the buckypapers was as high as 1.39 g cm(-3), which is close to the ultimate density of ideal buckypapers. Then we measured the transport and mechanical properties of the buckypapers. Our results demonstrated that its electrical and thermal conductivities could be almost linearly improved by increasing its density. In particular, its superior thermal conductivity is nearly twice that of common metals, which enables it a lightweight and more efficient heat-transfer materials. The Young's modulus of the buckypapers could reach a magnitude over 2 GPa, which is greatly improved compared with previous reported results. In view of this, our work provided a simple and convenient method to prepare high-density buckypapers with excellent transport and mechanical properties.

The interrelation between mechanical properties, corrosion resistance and microstructure of Pb-Sn casting alloys for lead-acid battery components

NASA Astrophysics Data System (ADS)

Peixoto, Leandro C.; Osório, Wislei R.; Garcia, Amauri

It is well known that there is a strong influence of thermal processing variables on the solidification structure and as a direct consequence on the casting final properties. The morphological microstructural parameters such as grain size and cellular or dendritic spacings will depend on the heat transfer conditions imposed by the metal/mould system. There is a need to improve the understanding of the interrelation between the microstructure, mechanical properties and corrosion resistance of dilute Pb-Sn casting alloys which are widely used in the manufacture of battery components. The present study has established correlations between cellular microstructure, ultimate tensile strength and corrosion resistance of Pb-1 wt% Sn and Pb-2.5 wt% Sn alloys by providing a combined plot of these properties as a function of cell spacing. It was found that a compromise between good corrosion resistance and good mechanical properties can be attained by choosing an appropriate cell spacing range.

Clean Cast Steel Technology: Effect of Micro-porosity on Tensile and Charpy Properties of Four Cast Steels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Griffin, John, A.; Bates, Charles, E.

2005-09-19

The effect of these large shrink cavities on mechanical properties could be easily calculated using well established engineering formulas. Over the years, increases in computational and metallurgical resources have allowed the modeler to improve accuracy and increase the complexity of numerical predictors. An accurate prediction of micro-porosity, not observable using conventional radiographic techniques, and an engineering understanding of the effect on mechanical properties would give a designer confidence in using a more efficient casting design and a lower safety factor. This will give castings an additional design advantage. The goal of this project is to provide current and future modelers/designersmore » with a tensile and Charpy property dataset for validation of micro-porosity predictors. The response of ultimate strength, elongation, and reduction in area to micro-porosity was very similar in all four alloys. Ultimate strength was largely unaffected by tensile fracture surface porosity until values of about 25% were reached and decreased linearly with increasing values. Elongation and reduction in area decreased sharply after less than 5% fracture surface porosity. Niyama values of about 0.7 were produced sound material and acceptable tensile properties. Ultrasonic velocities of 0.233 in/usec and higher produced acceptable tensile properties. Metallographic examination revealed a ratio of 4-6 to 1 in fracture surface porosity to metallographic porosity. Charpy impact properties were largely unaffected by the microporosity concentrations examined in this study and did not correlate to either Niyama values, fracture surface porosity, or metallographic porosity.« less

Investigation of mechanical properties for open cellular structure CoCrMo alloy fabricated by selective laser melting process

NASA Astrophysics Data System (ADS)

Azidin, A.; Taib, Z. A. M.; Harun, W. S. W.; Che Ghani, S. A.; Faisae, M. F.; Omar, M. A.; Ramli, H.

2015-12-01

Orthodontic implants have been a major focus through mechanical and biological performance in advance to fabricate shape of complex anatomical. Designing the part with a complex mechanism is one of the challenging process and addition to achieve the balance and desired mechanical performance brought to the right manufacture technique to fabricate. Metal additive manufacturing (MAM) is brought forward to the newest fabrication technology in this field. In this study, selective laser melting (SLM) process was utilized on a medical grade cobalt-chrome molybdenum (CoCrMo) alloy. The work has focused on mechanical properties of the CoCrMo open cellular structures samples with 60%, 70%, and 80% designed volume porosity that could potentially emulate the properties of human bone. It was observed that hardness values decreased as the soaking time increases except for bottom face. For compression test, 60% designed volume porosity demonstrated highest ultimate compressive strength compared to 70% and 80%.

Environmental and strain rate effects on graphite/epoxy composites. Final Report; M.S. Thesis, 1987

NASA Technical Reports Server (NTRS)

Peimandis, Konstantinos

1991-01-01

The hygrothermal characterization of unidirectional graphite/epoxy composites over a range of strain rates was investigated. Special techniques developed for such hygrothermal characterization are also described. The mechanical properties of the composite material were obtained and analyzed by means of a time-temperature-moisture superposition principle. The results show the following: (1) the embedded gage technique was thoroughly examined and found to be appropriate for both hygrothermal expansion and mechanical strain measurements; (2) all transverse properties were found to decrease with increasing temperature and moisture content; and (3) ultimate transverse properties were found to increase with strain rate at low temperatures but follow an opposite trend at high temperatures compared to dry specimens.

Effect of Heat Index on Microstructure and Mechanical Behavior of Friction Stir Processed AZ31

NASA Astrophysics Data System (ADS)

Yuan, Wei; Mishra, Rajiv S.

Friction stir processing modifies the micro structure and properties of metals through intense plastic deformation. The frictional heat input affects the microstructure evolution and resulting mechanical properties. 2 mm thick commercial AZ31B-H24 Mg alloy was friction stir processed under various process parameter combinations to investigate the effect of heat index on micro structure and properties. Recrystallized grain structure in the nugget region was observed for all processing conditions with decrease in hardness. Results indicate a reduced tensile yield strength and ultimate tensile strength compared to the as-received material in H-temper, but with an improved hardening capacity. The strain hardening behavior of friction stir processed material is discussed.

A Carbon Nanotube Cable for a Space Elevator

ERIC Educational Resources Information Center

Bochnícek, Zdenek

2013-01-01

In this paper the mechanical properties of carbon nanotubes are discussed in connection with the possibility to use them for the construction of a space elevator. From the fundamental information about the structure of a carbon nanotube and the chemical bond between carbon atoms, Young's modulus and the ultimate tensile strength are…

Effect of particle Alignment on mechanical properties of neat cellulose nanocrystal films

Treesearch

Alexander B. Reising; Robert J. Moon; Jeffrey P. Youngblood

2012-01-01

Shear-based film casting methods were used to cast neat films from wood-based cellulose nanocrystal (CNC) suspensions. The degree of CNC alignment in dried films was characterized using the Hermans order parameter (S), and the film elastic modulus (E), ultimate tensile strength (σf ), elongation at failure (εf...

Microstructure and Mechanical Property of 12Cr Oxide Dispersion Strengthened Steel

NASA Astrophysics Data System (ADS)

Xu, Haijian; Lu, Zheng; Jia, Chunyan; Gao, Hao; Liu, Chunming

2016-03-01

Nanostructured oxide dispersion strengthened (ODS) steels with nominal compositions (wt%): Fe-12Cr-2W-0.3Ti-0.3Y2O3 were produced by mechanical alloying and hot isostatic pressing. The microstructure was characterized by means of electron microscopy (EBSD, TEM and HRTEM) and the hardness and the tensile properties at different temperatures were measured. The results showed that the ultimate tensile strength of the fabricated 12Cr-ODS steel reached nearly 1,100 MPa at room temperature and maintained around 340 MPa at 700°C. Nano-oxide particles with size ranging from several nm to 30 nm and the number density was 3.6 × 1020/m3 were observed by TEM. Following heat treatment, including normalizing at 1,100°C for 1 h and tempering at 750°C for 2 h, the average grain size was a little decreased. The number of nano-oxide particles increased and the number density was 8.9 × 1020/m3. Specimens showed much higher ductility and there was a slight increase of ultimate tensile strength and Vickers hardness at the same time.

Biomimetic Hybridization of Kevlar into Silk Fibroin: Nanofibrous Strategy for Improved Mechanic Properties of Flexible Composites and Filtration Membranes.

PubMed

Lv, Lili; Han, Xiangsheng; Zong, Lu; Li, Mingjie; You, Jun; Wu, Xiaochen; Li, Chaoxu

2017-08-22

Silk, one of the strongest natural biopolymers, was hybridized with Kevlar, one of the strongest synthetic polymers, through a biomimetic nanofibrous strategy. Regenerated silk materials have outstanding properties in transparency, biocompatibility, biodegradability and sustainability, and promising applications as diverse as in pharmaceutics, electronics, photonic devices and membranes. To compete with super mechanic properties of their natural counterpart, regenerated silk materials have been hybridized with inorganic fillers such as graphene and carbon nanotubes, but frequently lose essential mechanic flexibility. Inspired by the nanofibrous strategy of natural biomaterials (e.g., silk fibers, hemp and byssal threads of mussels) for fantastic mechanic properties, Kevlar was integrated in regenerated silk materials by combining nanometric fibrillation with proper hydrothermal treatments. The resultant hybrid films showed an ultimate stress and Young's modulus two times as high as those of pure regenerated SF films. This is not only because of the reinforcing effect of Kevlar nanofibrils, but also because of the increasing content of silk β-sheets. When introducing Kevlar nanofibrils into the membranes of silk nanofibrils assembled by regenerated silk fibroin, the improved mechanic properties further enabled potential applications as pressure-driven nanofiltration membranes and flexible substrates of electronic devices.

The effect of sterilization on mechanical properties of soft tissue allografts.

PubMed

Conrad, Bryan P; Rappé, Matthew; Horodyski, MaryBeth; Farmer, Kevin W; Indelicato, Peter A

2013-09-01

One major concern regarding soft tissue allograft use in surgical procedures is the risk of disease transmission. Current techniques of tissue sterilization, such as irradiation have been shown to adversely affect the mechanical properties of soft tissues. Grafts processed using Biocleanse processing (a proprietary technique developed by Regeneration Technologies to sterilize human tissues) will have better biomechanical characteristics than tissues that have been irradiated. Fifteen pairs of cadaveric Achilles tendon allografts were obtained and separated into three groups of 10 each. Three treatment groups were: Biocleanse, Irradiated, and Control (untreated). Each specimen was tested to determine the biomechanical properties of the tissue. Specimens were cyclically preloaded and then loaded to failure in tension. During testing, load, displacement, and optical strain data were captured. Following testing, the cross sectional area of the tendons was determined. Tendons in the control group were found to have a higher extrinsic stiffness (slope of the load-deformation curve, p = .005), have a higher ultimate stress (force/cross sectional area, p = .006) and higher ultimate failure load (p = .003) than irradiated grafts. Biocleanse grafts were also found to be stiffer than irradiated grafts (p = .014) yet were not found to be statistically different from either irradiated or non-irradiated grafts in terms of load to failure. Biocleanse processing seems to be a viable alternative to irradiation for Achilles tendon allografts sterilization in terms of their biomechanical properties.

High performance aluminum–cerium alloys for high-temperature applications

DOE PAGES

Sims, Zachary C.; Rios, Orlando R.; Weiss, David; ...

2017-08-01

Light-weight high-temperature alloys are important to the transportation industry where weight, cost, and operating temperature are major factors in the design of energy efficient vehicles. Aluminum alloys fill this gap economically but lack high-temperature mechanical performance. Alloying aluminum with cerium creates a highly castable alloy, compatible with traditional aluminum alloy additions, that exhibits dramatically improved high-temperature performance. These compositions display a room temperature ultimate tensile strength of 400 MPa and yield strength of 320 MPa, with 80% mechanical property retention at 240 °C. A mechanism is identified that addresses the mechanical property stability of the Al-alloys to at least 300more » °C and their microstructural stability to above 500 °C which may enable applications without the need for heat treatment. Lastly, neutron diffraction under load provides insight into the unusual mechanisms driving the mechanical strength.« less

Formulation/cure technology for ultrahigh molecular weight silphenylene-siloxane polymers

NASA Technical Reports Server (NTRS)

Hundley, N. H.; Patterson, W. J.

1985-01-01

Molecular weights above one million were achieved for methylvinylsilphenylene-siloxane terpolymers using a two-stage polymerization technique which was successfully scaled up to 200 grams. The resulting polymer was vulcanized by two different formulations and compared to an identically formulated commercial methylvinyl silicone on the basis of ultimate strength, Young's modulus, percent elongation at failure, and tear strength. Relative thermal/oxidative stabilities of the elastomers were assessed by gradient and isothermal thermogravimetric analyses performed in both air and nitrogen. The experimental elastomer exhibited enhanced thermal/oxidative stability and possed equivalent or superior mechanical properties. The effect of variations in prepolymer molecular weight on mechanical properties was also investigated.

A multilevel approach to modeling of porous bioceramics

NASA Astrophysics Data System (ADS)

Mikushina, Valentina A.; Sidorenko, Yury N.

2015-10-01

The paper is devoted to discussion of multiscale models of heterogeneous materials using principles. The specificity of approach considered is the using of geometrical model of composites representative volume, which must be generated with taking the materials reinforcement structure into account. In framework of such model may be considered different physical processes which have influence on the effective mechanical properties of composite, in particular, the process of damage accumulation. It is shown that such approach can be used to prediction the value of composite macroscopic ultimate strength. As an example discussed the particular problem of the study the mechanical properties of biocomposite representing porous ceramics matrix filled with cortical bones tissue.

Study on Mechanical Properties of Barite Concrete under Impact Load

NASA Astrophysics Data System (ADS)

Chen, Z. F.; Cheng, K.; Wu, D.; Gan, Y. C.; Tao, Q. W.

2018-03-01

In order to research the mechanical properties of Barite concrete under impact load, a group of concrete compression tests was carried out under the impact load by using the drop test machine. A high-speed camera was used to record the failure process of the specimen during the impact process. The test results show that:with the increase of drop height, the loading rate, the peak load, the strain under peak load, the strain rate and the dynamic increase factor (DIF) all increase gradually. The ultimate tensile strain is close to each other, and the time of impact force decreases significantly, showing significant strain rate effect.

A Novel Preparation Method of SiC Reinforced Aluminum Composite Through Vertical Rotatory Furnace

NASA Astrophysics Data System (ADS)

Nassar, Amal Ebrahim; Nassar, Eman Ebrahim; Younis, Mona Ahmed

2018-04-01

The aluminum composite was prepared successfully by stirring using internal blade installed inside a vertical rotatory furnace. Pure aluminum was used as matrix and silicon carbide particles with 10 weight percentage as reinforcement. To evaluate the efficiency of the suggested stirrer, the microstructure of the samples was analyzed using scanning electron microscope, image analyzer software available with optical microscope and energy dispersive X-ray spectroscopy analysis. Furthermore, mechanical properties were studied by measuring ultimate and yield strength, wear resistance, hardness and porosity. It was found that the particle distribution was enhanced and consequently improved the mechanical properties of the composite.

New Soft Tissue Implants Using Organic Elastomers

NASA Astrophysics Data System (ADS)

Ku, David N.

Typical biomaterials are stiff, difficult to manufacture, and not initially developed for medical implants. A new biomaterial is proposed that is similar to human soft tissue. The biomaterial provides mechanical properties similar to soft tissue in its mechanical and physical properties. Characterization is performed for modulus of elasticity, ultimate strength and wear resistance. The material further exhibits excellent biocompatibility with little toxicity and low inflammation. The material can be molded into a variety of anatomic shapes for use as a cartilage replacement, heart valve, and reconstructive implant for trauma victims. The biomaterial may be suitable for several biodevices of the future aimed at soft-tissue replacements.

Computational studies of physical properties of Nb-Si based alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ouyang, Lizhi

2015-04-16

The overall goal is to provide physical properties data supplementing experiments for thermodynamic modeling and other simulations such as phase filed simulation for microstructure and continuum simulations for mechanical properties. These predictive computational modeling and simulations may yield insights that can be used to guide materials design, processing, and manufacture. Ultimately, they may lead to usable Nb-Si based alloy which could play an important role in current plight towards greener energy. The main objectives of the proposed projects are: (1) developing a first principles method based supercell approach for calculating thermodynamic and mechanic properties of ordered crystals and disordered latticesmore » including solid solution; (2) application of the supercell approach to Nb-Si base alloy to compute physical properties data that can be used for thermodynamic modeling and other simulations to guide the optimal design of Nb-Si based alloy.« less

Fabrication of elastomeric silk fibers.

PubMed

Bradner, Sarah A; Partlow, Benjamin P; Cebe, Peggy; Omenetto, Fiorenzo G; Kaplan, David L

2017-09-01

Methods to generate fibers from hydrogels, with control over mechanical properties, fiber diameter, and crystallinity, while retaining cytocompatibility and degradability, would expand options for biomaterials. Here, we exploited features of silk fibroin protein for the formation of tunable silk hydrogel fibers. The biological, chemical, and morphological features inherent to silk were combined with elastomeric properties gained through enzymatic crosslinking of the protein. Postprocessing via methanol and autoclaving provided tunable control of fiber features. Mechanical, optical, and chemical analyses demonstrated control of fiber properties by exploiting the physical cross-links, and generating double network hydrogels consisting of chemical and physical cross-links. Structure and chemical analyses revealed crystallinity from 30 to 50%, modulus from 0.5 to 4 MPa, and ultimate strength 1-5 MPa depending on the processing method. Fabrication and postprocessing combined provided fibers with extensibility from 100 to 400% ultimate strain. Fibers strained to 100% exhibited fourth order birefringence, revealing macroscopic orientation driven by chain mobility. The physical cross-links were influenced in part by the drying rate of fabricated materials, where bound water, packing density, and microstructural homogeneity influenced cross-linking efficiency. The ability to generate robust and versatile hydrogel microfibers is desirable for bottom-up assembly of biological tissues and for broader biomaterial applications. © 2017 Wiley Periodicals, Inc.

Innate Immunity and Biomaterials at the Nexus: Friends or Foes

PubMed Central

Christo, Susan N.; Diener, Kerrilyn R.; Bachhuka, Akash; Vasilev, Krasimir; Hayball, John D.

2015-01-01

Biomaterial implants are an established part of medical practice, encompassing a broad range of devices that widely differ in function and structural composition. However, one common property amongst biomaterials is the induction of the foreign body response: an acute sterile inflammatory reaction which overlaps with tissue vascularisation and remodelling and ultimately fibrotic encapsulation of the biomaterial to prevent further interaction with host tissue. Severity and clinical manifestation of the biomaterial-induced foreign body response are different for each biomaterial, with cases of incompatibility often associated with loss of function. However, unravelling the mechanisms that progress to the formation of the fibrotic capsule highlights the tightly intertwined nature of immunological responses to a seemingly noncanonical “antigen.” In this review, we detail the pathways associated with the foreign body response and describe possible mechanisms of immune involvement that can be targeted. We also discuss methods of modulating the immune response by altering the physiochemical surface properties of the biomaterial prior to implantation. Developments in these areas are reliant on reproducible and effective animal models and may allow a “combined” immunomodulatory approach of adapting surface properties of biomaterials, as well as treating key immune pathways to ultimately reduce the negative consequences of biomaterial implantation. PMID:26247017

Influence of High Pulsed Magnetic Field on the Dislocations and Mechanical Properties of Al2O3/Al Composites

NASA Astrophysics Data System (ADS)

Cheng, Jiang-feng; Li, Gui-rong; Wang, Hong-ming; Li, Pei-si; Li, Chao-qun

2018-03-01

At T6 state, Al-Zn-Mg-Cu aluminum matrix composites reinforced with Al2O3 particles generated in situ were subjected to high pulsed magnetic fields at different magnetic induction intensities ( B = 2, 3 and 4 T). The results show that the dislocation densities in the treated samples increased with increasing B, and the magnetoplastic effect was determined to be the primary cause. The effect of the magnetic field is believed to alter the spin state of free electrons between dislocations and obstacles from the singlet state (associated with high bonding energy) to the triplet state (low bonding energy). The maximum ultimate tensile strength of 532 MPa was obtained at B = 4 T with 30 pulses, which was 20.7% higher than that of the initial sample, primarily because of dislocation strengthening. At B = 2 T, the elongation was at its maximum of 9.3%, representing an increase of 12% compared with the initial sample, while the associated ultimate tensile strength (447 MPa) was still higher than that of the untreated sample (440 MPa). The relationship between mechanical properties and microstructure was analyzed, and the improved properties observed in this work are explained by the transition of the electron spin state and the piling up of dislocations.

Evaluating Changes in Tendon Crimp with Fatigue Loading as an ex vivo Structural Assessment of Tendon Damage

PubMed Central

Freedman, Benjamin R.; Zuskov, Andrey; Sarver, Joseph J.; Buckley, Mark R.; Soslowsky, Louis J.

2015-01-01

The complex structure of tendons relates to their mechanical properties. Previous research has associated the waviness of collagen fibers (crimp) during quasi-static tensile loading to tensile mechanics, but less is known about the role of fatigue loading on crimp properties. In this study (IACUC approved), mouse patellar tendons were fatigue loaded while an integrated plane polariscope simultaneously assessed crimp properties. We demonstrate a novel structural mechanism whereby tendon crimp amplitude and frequency are altered with fatigue loading. In particular, fatigue loading increased the crimp amplitude across the tendon width and length, and these structural alterations were shown to be both region and load dependent. The change in crimp amplitude was strongly correlated to mechanical tissue laxity (defined as the ratio of displacement and gauge length relative to the first cycle of fatigue loading assessed at constant load throughout testing), at all loads and regions evaluated. Together, this study highlights the role of fatigue loading on tendon crimp properties as a function of load applied and region evaluated, and offers an additional structural mechanism for mechanical alterations that may lead to ultimate tendon failure. PMID:25773654

Elevated-Temperature Mechanical Properties of Lead-Free Sn-0.7Cu- xSiC Nanocomposite Solders

NASA Astrophysics Data System (ADS)

Mohammadi, A.; Mahmudi, R.

2018-02-01

Mechanical properties of Sn-0.7 wt.%Cu lead-free solder alloy reinforced with 0 vol.%, 1 vol.%, 2 vol.%, and 3 vol.% 100-nm SiC particles have been assessed using the shear punch testing technique in the temperature range from 25°C to 125°C. The composite materials were fabricated by the powder metallurgy route by blending, compacting, sintering, and finally extrusion. The 2 vol.% SiC-containing composite showed superior mechanical properties. In all conditions, the shear strength was adversely affected by increasing test temperature, and the 2 vol.% SiC-containing composite showed superior mechanical properties. Depending on the test temperature, the shear yield stress and ultimate shear strength increased, respectively, by 3 MPa to 4 MPa and 4 MPa to 5.5 MPa, in the composite materials. The strength enhancement was mostly attributed to the Orowan particle strengthening mechanism due to the SiC nanoparticles, and to a lesser extent to the coefficient of thermal expansion mismatch between the particles and matrix in the composite solder. A modified shear lag model was used to predict the total strengthening achieved by particle addition, based on the contribution of each of the above mechanisms.

Thermo-mechanical treatment of low-cost alloy Ti-4.5Al-6.9Cr-2.3Mn and microstructure and mechanical characteristics

NASA Astrophysics Data System (ADS)

Chen, Guangyao; Kang, Juyun; Wang, Shusen; Wang, Shihua; Lu, Xionggang; Li, Chonghe

2018-04-01

In this study, the thermo-mechanical treatment process for low-cost Ti-4.5Al-6.9Cr-2.3Mn alloy were designed on the basis of assessment of Ti-Al-Cr-Mn thermodynamic system. The microstructure and mechanical properties of Ti-4.5Al-6.9Cr-2.3Mn forging and sheet were investigated by using the OM, SEM and universal tensile testing machine. The results show that both the forging and sheet were consisted of α + β phase, which is consistent with the expectation, and no element Cr and Mn existed in the grain boundaries of the sheet after quenching, and the C14 laves phase was not detected. The average ultimate tensile strength (σ b), 0.2% proof strength (σ 0.2) and elongation (EI) of alloy sheet after quenching can reach 1059 MPa, 1051 MPa and 24.6 Pct., respectively. Moreover, the average ultimate tensile strength of Ti-4.5Al-6.9Cr-2.3Mn forgings can reach 1599 MPa and the average elongation can reach 11.2 Pct., and a more excellent property of Ti-4.5Al-6.9Cr-2.3Mn forging is achieved than that of TC4 forging. It provides a theoretical support for further developing this low-cost alloy.

Changes in the physical and mechanical properties of Al-Mg alloy processed by severe plastic deformation

NASA Astrophysics Data System (ADS)

Krasnoveikin, V. A.; Kozulin, A. A.; Skripnyak, V. A.; Moskvichev, E. N.; Borodulin, D. A.

2017-12-01

This paper presents the results of studies into the effect of severe plastic deformation on the microstructure, physical and mechanical properties of coarse-grained Al-Mg alloy 1560 in the as-received state with an average grain size of 50 µm. Severe plastic deformation is performed by four-pass equal channel angular pressing (ECAP), which results in the formation of an ultrafine-grained structure with an average grain size of 3 µm in the alloy. Analysis of experimental data revealed that the physical and mechanical properties change significantly after severe plastic deformation. The microhardness of the ECAPed alloy increases by 50%, tensile yield strength by 80%, and ultimate strength by 44% in comparison with these parameters in the as-received state. The constants of approximating functions have been determined for the experimental stress-strain curves of the alloy specimens in the as-received and ECAPed states.

Topological structure and mechanics of glassy polymer networks.

PubMed

Elder, Robert M; Sirk, Timothy W

2017-11-22

The influence of chain-level network architecture (i.e., topology) on mechanics was explored for unentangled polymer networks using a blend of coarse-grained molecular simulations and graph-theoretic concepts. A simple extension of the Watts-Strogatz model is proposed to control the graph properties of the network such that the corresponding physical properties can be studied with simulations. The architecture of polymer networks assembled with a dynamic curing approach were compared with the extended Watts-Strogatz model, and found to agree surprisingly well. The final cured structures of the dynamically-assembled networks were nearly an intermediate between lattice and random connections due to restrictions imposed by the finite length of the chains. Further, the uni-axial stress response, character of the bond breaking, and non-affine displacements of fully-cured glassy networks were analyzed as a function of the degree of disorder in the network architecture. It is shown that the architecture strongly affects the network stability, flow stress, onset of bond breaking, and ultimate stress while leaving the modulus and yield point nearly unchanged. The results show that internal restrictions imposed by the network architecture alter the chain-level response through changes to the crosslink dynamics in the flow regime and through the degree of coordinated chain failure at the ultimate stress. The properties considered here are shown to be sensitive to even incremental changes to the architecture and, therefore, the overall network architecture, beyond simple defects, is predicted to be a meaningful physical parameter in the mechanics of glassy polymer networks.

Influence of γ-irradiation and temperature on the mechanical properties of EPDM cable insulation

NASA Astrophysics Data System (ADS)

Šarac, T.; Quiévy, N.; Gusarov, A.; Konstantinović, M. J.

2016-08-01

The mechanical properties of EPDM polymers, degraded as a result of extensive thermal and radiochemical aging treatment, are studied. The focus is given to dose rate effects in polymer insulation materials extracted from industrial cables in use in Belgian nuclear power plants. All studied mechanical characteristics such as the ultimate tensile stress, the Young's modulus, and the total elongation (or elongation at break) are found to be strongly affected by the irradiation dose. The ultimate tensile stress and Young's modulus are clearly exhibiting the dose rate effect, which originated from oxidation mediated interplay of polymer cross-linking and chain scission processes. The change of crossover between these two processes is found to be gradual, without critical dose rate or temperature values. On the contrary, the total elongation is observed not to be sensitive neither to irradiation temperature nor to the dose rate. Both cross-linking and chain scission seem to affect the total elongation in a similar way by reducing the average polymers chain length. This idea is confirmed by the model which shows that all total elongation data as a function of irradiation time can be reproduced by varying a single parameter, the pre-exponential factor of the irradiation rate constant.

Matrix density effects on the mechanical properties of SiC fiber-reinforced silicon nitride matrix properties

NASA Technical Reports Server (NTRS)

Bhatt, Ramakrishna T.; Kiser, Lames D.

1990-01-01

The room temperature mechanical properties were measured for SiC fiber reinforced reaction-bonded silicon nitride composites (SiC/RBSN) of different densities. The composites consisted of approx. 30 vol percent uniaxially aligned 142 micron diameter SiC fibers (Textron SCS-6) in a reaction-bonded Si3N4 matrix. The composite density was varied by changing the consolidation pressure during RBSN processing and by hot isostatically pressing the SiC/RBSN composites. Results indicate that as the consolidation pressure was increased from 27 to 138 MPa, the average pore size of the nitrided composites decreased from 0.04 to 0.02 microns and the composite density increased from 2.07 to 2.45 gm/cc. Nonetheless, these improvements resulted in only small increases in the first matrix cracking stress, primary elastic modulus, and ultimate tensile strength values of the composites. In contrast, HIP consolidation of SiC/RBSN resulted in a fully dense material whose first matrix cracking stress and elastic modulus were approx. 15 and 50 percent higher, respectively, and ultimate tensile strength values were approx. 40 percent lower than those for unHIPed SiC/RBSN composites. The modulus behavior for all specimens can be explained by simple rule-of-mixture theory. Also, the loss in ultimate strength for the HIPed composites appears to be related to a degradation in fiber strength at the HIP temperature. However, the density effect on matrix fracture strength was much less than would be expected based on typical monolithic Si3N4 behavior, suggesting that composite theory is indeed operating. Possible practical implications of these observations are discussed.

Biocomposites from abaca strands and polypropylene. Part I: Evaluation of the tensile properties.

PubMed

Vilaseca, Fabiola; Valadez-Gonzalez, Alex; Herrera-Franco, Pedro J; Pèlach, M Angels; López, Joan Pere; Mutjé, Pere

2010-01-01

In this paper, abaca strands were used as reinforcement of polypropylene matrix and their tensile mechanical properties were studied. It was found relevant increments on the tensile properties of the abaca strand-PP composites despite the lack of good adhesion at fiber-matrix interface. Afterwards, it was stated the influence of using maleated polypropylene (MAPP) as compatibilizer to promote the interaction between abaca strands and polypropylene. The intrinsic mechanical properties of the reinforcement were evaluated and used for modeling both the tensile strength and elastic modulus of the composites. For these cases, the compatibility factor for the ultimate tensile strength was deduced from the modified rule of mixtures. Additionally, the experimental fiber orientation coefficient was measured, allowing determining the interfacial shear strengths of the composites and the critical fiber length of the abaca strand reinforcement. The mechanical improvement was compared to that obtained for fiberglass-reinforced PP composites and evaluated under an economical and technical point of view.

The Mechanics of Long Bone Fractures.

DTIC Science & Technology

1981-01-31

r = .99) between wet density and ultimate bending strength for 37 specimens of human femoral bone. Evans (1973) studied embalmed human tibial...Work 2 2.2 Methods 6 2.2.1 Torsional Loading 6 2.2.2 The Effects of Combined Loading 10 2.2.3 Cancellous Bone Effects 11 2.3 Results 11 2.3.1...PROPERTIES 21 3.1 Previous Work 22 3.2 Methods 26 3.2.1 Cross Sectional Property Software 26 3.2.2 CT Scanning Procedure 28 3.2.3 Linear Dependency of

CAD/CAM milled complete removable dental prostheses: An in vitro evaluation of biocompatibility, mechanical properties, and surface roughness.

PubMed

Srinivasan, Murali; Gjengedal, Harald; Cattani-Lorente, Maria; Moussa, Mira; Durual, Stéphane; Schimmel, Martin; Müller, Frauke

2018-03-06

This study compared the biocompatibility, mechanical properties, and surface roughness of a pre-polymerized polymethyl methacrylate (PMMA) resin for CAD/CAM complete removable dental prostheses (CRDPs) and a traditional heat-polymerized PMMA resin. Two groups of resin substrates [Control (RC): conventional PMMA; Test (RA): CAD/CAM PMMA] were fabricated. Human primary osteoblasts and mouse embryonic-fibroblasts were cultured for biocompatibility assays. Mechanical properties and surface roughness were compared. ANOVA revealed no difference between the resin groups in the biocompatibility assays. RA demonstrated a higher elastic modulus (p=0.002), young's modulus (p=0.002), plastic energy (p=0.002), ultimate strength (p=0.0004), yield point (p=0.016), strain at yield point (p=0.037), and toughness (p<0.0001); while RC displayed a higher elastic energy (p<0.0001). Laser profilometry concluded a rougher surface profile (p<0.0001) for RA. This study concluded that the tested CAD/CAM resin was equally biocompatible and presented with improved mechanical properties than the traditional heat-polymerized PMMA resin used in the fabrication of CRDPs.

Failure Analysis in Platelet Molded Composite Systems

NASA Astrophysics Data System (ADS)

Kravchenko, Sergii G.

Long-fiber discontinuous composite systems in the form of chopped prepreg tapes provide an advanced, structural grade, molding compound allowing for fabrication of complex three-dimensional components. Understanding of process-structure-property relationship is essential for application of prerpeg platelet molded components, especially because of their possible irregular disordered heterogeneous morphology. Herein, a structure-property relationship was analyzed in the composite systems of many platelets. Regular and irregular morphologies were considered. Platelet-based systems with more ordered morphology possess superior mechanical performance. While regular morphologies allow for a careful inspection of failure mechanisms derived from the morphological characteristics, irregular morphologies are representative of the composite architectures resulting from uncontrolled deposition and molding with chopped prerpegs. Progressive failure analysis (PFA) was used to study the damaged deformation up to ultimate failure in a platelet-based composite system. Computational damage mechanics approaches were utilized to conduct the PFA. The developed computational models granted understanding of how the composite structure details, meaning the platelet geometry and system morphology (geometrical arrangement and orientation distribution of platelets), define the effective mechanical properties of a platelet-molded composite system, its stiffness, strength and variability in properties.

Mechanical Properties Analysis of 4340 Steel Specimen Heat Treated in Oven and Quenching in Three Different Fluids

NASA Astrophysics Data System (ADS)

Fakir, Rachid; Barka, Noureddine; Brousseau, Jean

2018-03-01

This paper proposes a statistical approach to analyze the mechanical properties of a standard test specimen, of cylindrical geometry and in steel 4340, with a diameter of 6 mm, heat-treated and quenched in three different fluids. Samples were evaluated in standard tensile test to access their characteristic quantities: hardness, modulus of elasticity, yield strength, tensile strength and ultimate deformation. The proposed approach is gradually being built (a) by a presentation of the experimental device, (b) a presentation of the experimental plan and the results of the mechanical tests, (c) anova analysis of variance and a representation of the output responses using the RSM response surface method, and (d) an analysis of the results and discussion. The feasibility and effectiveness of the proposed approach leads to a precise and reliable model capable of predicting the variation of mechanical properties, depending on the tempering temperature, the tempering time and the cooling capacity of the quenching medium.

Microstructure Evolution and Mechanical Properties of Al-TiB2/TiC In Situ Aluminum-Based Composites during Accumulative Roll Bonding (ARB) Process

PubMed Central

Nie, Jinfeng; Wang, Fang; Li, Yusheng; Cao, Yang; Liu, Xiangfa; Zhao, Yonghao; Zhu, Yuntian

2017-01-01

In this study, a kind of Al-TiB2/TiC in situ composite was successfully prepared using the melt reaction method and the accumulative roll-bonding (ARB) technique. The microstructure evolution of the composites with different deformation treatments was characterized using field emission scanning electron microscopy (FESEM) and a transmission electron microscope (TEM). The mechanical properties of the Al-TiB2/TiC in situ composite were also studied with tensile and microhardness tests. It was found that the distribution of reinforcement particles becomes more homogenous with an increasing ARB cycle. Meanwhile, the mechanical properties showed great improvement during the ARB process. The ultimate tensile strength (UTS) and microhardness of the composites were increased to 173.1 MPa and 63.3 Hv after two ARB cycles, respectively. Furthermore, the strengthening mechanism of the composite was analyzed based on its fracture morphologies. PMID:28772467

A comparative study of sliding wear of nonmetallic dental restorative materials with emphasis on micromechanical wear mechanisms.

PubMed

Dupriez, Nataliya Deyneka; von Koeckritz, Ann-Kristin; Kunzelmann, Karl-Heinz

2015-05-01

The purpose of this study is to investigate the in vitro tribological behavior of modern nonmetallic restorative materials. Specimen prepared of IPS e.max Press lithium disilicate glass ceramic, IPS Empress Esthetic leucite-reinforced glass ceramic, Everest ZS Blanks yttria-stabilized zirconia and Lava Ultimate composite were subjected to wear using a wear machine designed to simulate occlusal loads. The wear of the investigated materials and antagonists were evaluated by a three-dimensional surface scanner. The quantitative wear test results were used to compare and rank the materials. Specimens were divided into two groups with steatite and alumina antagonists. For each antagonist material an analysis of variance was applied. As a post hoc test of the significant differences, Tukey's honest significant difference test was used. With steatite antagonist: wear of zirconia < wear of leucite-reinforced ceramic < wear of lithium disilicate ceramic < wear of Lava Ultimate composite. No significant wear difference was found for steatite antagonist. The wear of IPS e.max Press and Lava Ultimate against hard alumina was found to be twice lower as compared to their wear when opposing to steatite. The differences were associated with materials mechanical properties (hardness and fracture toughness) and with materials microstructure. Wear mechanisms are discussed. © 2014 Wiley Periodicals, Inc.

Alterations in biomechanical properties and microstructure of colon wall in early-stage experimental colitis.

PubMed

Gong, Xiaohui; Xu, Xiaojuan; Lin, Sisi; Cheng, Yu; Tong, Jianhua; Li, Yongyu

2017-08-01

The aim of the current study was to investigate the effects of early-stage dextran sodium sulfate (DSS)-induced mouse colitis on the biomechanical properties and microstructure of colon walls. In the present study, colitis was induced in 8-week-old mice by the oral administration of DSS, and then 10 control and 10 experimental colitis samples were harvested. Uniaxial tensile tests were performed to measure the ultimate tensile strength and ultimate stretches of colon tissues. In addition, histological investigations were performed to characterize changes in the microstructure of the colon wall following treatment. The results revealed that the ultimate tensile stresses were 232±33 and 183±25 kPa for the control and DSS groups, respectively (P=0.001). Ultimate stretches at rupture for the control and DSS groups were 1.43±0.04 and 1.51±0.06, respectively (P=0.006). However, there was no statistically significant difference in tissue stiffness between the two groups. Histological analysis demonstrated high numbers of inflammatory cells infiltrated into the stroma in the DSS group, leading to significant submucosa edema. Hyperplasia was also identified in the DSS-treated submucosa, causing a disorganized microstructure within the colon wall. Furthermore, a large number of collagen fibers in the DSS-treated muscular layer were disrupted, and fiber bundles were thinner when compared with the control group. In conclusion, early-stage experimental colitis alters the mechanical properties and microstructural characteristics of the colon walls, further contributing to tissue remodeling in the pathological process.

Laser irradiation effects on the surface, structural and mechanical properties of Al-Cu alloy 2024

NASA Astrophysics Data System (ADS)

Yousaf, Daniel; Bashir, Shazia; Akram, Mahreen; kalsoom, Umm-i.-; Ali, Nisar

2014-02-01

Laser irradiation effects on surface, structural and mechanical properties of Al-Cu-Mg alloy (Al-Cu alloy 2024) have been investigated. The specimens were irradiated for various fluences ranging from 3.8 to 5.5 J/cm2 using an Excimer (KrF) laser (248 nm, 18 ns, 30 Hz) under vacuum environment. The surface and structural modifications of the irradiated targets have been investigated by scanning electron microscope (SEM) and X-ray diffractometer (XRD), respectively. SEM analysis reveals the formation of micro-sized craters along the growth of periodic surface structures (ripples) at their peripheries. The size of the craters initially increases and then decreases by increasing the laser fluence. XRD analysis shows an anomalous trend in the peak intensity and crystallite size of the specimen irradiated for various fluences. A universal tensile testing machine and Vickers microhardness tester were employed in order to investigate the mechanical properties of the irradiated targets. The changes in yield strength, ultimate tensile strength and microhardness were found to be anomalous with increasing laser fluences. The changes in the surface and structural properties of Al-Cu alloy 2024 after laser irradiation have been associated with the changes in mechanical properties.

From Computational Photobiology to the Design of Vibrationally Coherent Molecular Devices and Motors

NASA Astrophysics Data System (ADS)

Olivucci, Massimo

2014-03-01

In the past multi-configurational quantum chemical computations coupled with molecular mechanics force fields have been employed to investigate spectroscopic, thermal and photochemical properties of visual pigments. Here we show how the same computational technology can nowadays be used to design, characterize and ultimately, prepare light-driven molecular switches which mimics the photophysics of the visual pigment bovine rhodopsin (Rh). When embedded in the protein cavity the chromophore of Rh undergoes an ultrafast and coherent photoisomerization. In order to design a synthetic chromophore displaying similar properties in common solvents, we recently focused on indanylidene-pyrroline (NAIP) systems. We found that these systems display light-induced ground state coherent vibrational motion similar to the one detected in Rh. Semi-classical trajectories provide a mechanistic description of the structural changes associated to the observed coherent motion which is shown to be ultimately due to periodic changes in the π-conjugation.

Indirect and direct tensile behavior of Devonian oil shales

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chong, K.P.; Chen, J.L.; Dana, G.F.

1984-03-01

Ultimate indirect tensile strengths of Devonian oil shales across the bedding planes is a mechanical property parameter important to predicting how oil shale will break. This is particularly important to in-situ fragmentation. The Split Cylinder Test was used to determine the indirect tensile strengths between the bedding planes. Test specimens, cored perpendicular to the bedding planes, representing oil shales of different oil yields taken from Silver Point Quad in DeKalb County, Tennessee and Friendship in Scioto County, Ohio, were subjected to the Split Cylinder Test. Linear regression equations relating ultimate tensile strength across the bedding planes to volume percent ofmore » organic matter in the rock were developed from the test data. In addition, direct tensile strengths were obtained between the bedding planes for the Tennessee oil shales. This property is important for the design of horizontal fractures in oil shales. Typical results were presented.« less

Study of high performance alloy electroforming

NASA Technical Reports Server (NTRS)

Malone, G. A.

1984-01-01

The first series of heat treated nickel manganese alloys are tested for mechanical properties at temperatures of 148.9 C (300 F) and 260 C (500 F). All material receives the same heat treatment in order to provide a common basis for comparison of results. Mechanical property performance improves with increasing manganese content in the alloy. Although all manganese bearing alloy is significantly superior to conventional electroformed nickel, samples containing over 3000 ppm manganese display outstanding ultimate and yield strengths while maintaining reasonably satisfactory ductility. Alloy containing over 6000 ppm of manganese is very competitive to Inconel 718 (mill annealed and age hardened) at all temperatures of interest, although ductility is not as great in the electrodeposited counterpart.

Influence of Ionizing Radiation on the Mechanical Properties of a Wood-Plastic Composite

NASA Astrophysics Data System (ADS)

Palm, Andrew; Smith, Jennifer; Driscoll, Mark; Smith, Leonard; Larsen, L. Scott

The focus of this study was to examine the potential benefits of irradiating polyethylene (PE)-based wood-plastic composites (WPCs) in order to enhance the mechanical properties of the WPC. The PE-based WPCs were irradiated, post extrusion, at dose levels of 0, 50, 100, 150, 200, and 250 kGy with an electron beam (EB). The irradiated WPCs were then evaluated using a third point bending test (ASTM D4761) along with scanning electron microscopy (SEM). It was found that ultimate strength and modulus of elasticity (MOE) increased with increasing dose level. Examination of the fracture surfaces of polyethylene revealed a distinct difference in failure between irradiated and non-irradiated surfaces.

Method of forming biaxially textured alloy substrates and devices thereon

DOEpatents

Goyal, Amit; Specht, Eliot D.; Kroeger, Donald M.; Paranthaman, Mariappan

2000-01-01

Specific alloys, in particular Ni-based alloys, that can be biaxially textured, with a well-developed, single component texture are disclosed. These alloys have a significantly reduced Curie point, which is very desirable from the point of view of superconductivity applications. The biaxially textured alloy substrates also possess greatly enhanced mechanical properties (yield strength, ultimate tensile strength) which are essential for most applications, in particular, superconductors. A method is disclosed for producing complex multicomponent alloys which have the ideal physical properties for specific applications, such as lattice parameter, degree of magnetism and mechanical strength, and which cannot be in textured form. In addition, a method for making ultra thin biaxially textured substrates with complex compositions is disclosed.

Pore network properties of sandstones in a fault damage zone

NASA Astrophysics Data System (ADS)

Bossennec, Claire; Géraud, Yves; Moretti, Isabelle; Mattioni, Luca; Stemmelen, Didier

2018-05-01

The understanding of fluid flow in faulted sandstones is based on a wide range of techniques. These depend on the multi-method determination of petrological and structural features, porous network properties and both spatial and temporal variations and interactions of these features. The question of the multi-parameter analysis on fluid flow controlling properties is addressed for an outcrop damage zone in the hanging wall of a normal fault zone on the western border of the Upper Rhine Graben, affecting the Buntsandstein Group (Early Triassic). Diagenetic processes may alter the original pore type and geometry in fractured and faulted sandstones. Therefore, these may control the ultimate porosity and permeability of the damage zone. The classical model of evolution of hydraulic properties with distance from the major fault core is nuanced here. The hydraulic behavior of the rock media is better described by a pluri-scale model including: 1) The grain scale, where the hydraulic properties are controlled by sedimentary features, the distance from the fracture, and the impact of diagenetic processes. These result in the ultimate porous network characteristics observed. 2) A larger scale, where the structural position and characteristics (density, connectivity) of the fracture corridors are strongly correlated with both geo-mechanical and hydraulic properties within the damage zone.

The effects of Nitinol phases on corrosion and fatigue behavior

NASA Astrophysics Data System (ADS)

Denton, Melissa

The purpose of these studies was to provide a detailed understanding of Nitinol phases and their effects on corrosion and fatigue life. The two primary phases, austenite and martensite, were carefully evaluated with respect to material geometry, corrosion behavior, wear, and fatigue life. Material characterization was performed using several techniques that include metallography, scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), x-ray photoelectron spectrum (XPS), and Auger electron spectroscopy (AES). Uniaxial tensile tests were conducted to determine the mechanical properties such as elongation, ultimate tensile strength, modulus, transformation strain, and plateau stress. In addition, accelerated wear testing and four point bend fatigue testing were completed to study the fatigue life and durability of the material. The corrosion of Nitinol was found to be dependent on various surface conditions. Electrochemical corrosion behavior of each phase was investigated using cyclic potentiodyamic polarization testing. The corrosion response of electropolished Nitinol was found to be acceptable, even after durability testing. Stress-induced martensite had a lower breakdown potential due to a rougher surface morphology, while thermally induced martensite and austenite performed similarly well. The surface conditioning also had a significant effect on Nitinol mechanical properties. Electropolishing provided a smooth mirror finish that reduced localized texture and enhanced the ductility of the material. Quasi-static mechanical properties can be good indicators of fatigue life, but further fatigue testing revealed that phase transformations had an important role as well. The governing mechanisms for the fatigue life of Nitinol were determined to be both martesitic phase transformations and surface defects. A new ultimate dislocation strain model was proposed based on specific accelerated step-strain testing.

Structure-Composition-Property Relationships in Polymeric Amorphous Calcium Phosphate-Based Dental Composites †

PubMed Central

O’Donnell, Justin N.R.; Schumacher, Gary E.; Antonucci, Joseph M.; Skrtic, Drago

2009-01-01

Our studies of amorphous calcium phosphate (ACP)-based materials over the last decade have yielded bioactive polymeric composites capable of protecting teeth from demineralization or even regenerating lost tooth mineral. The anti-cariogenic/re-mineralizing potential of these ACP composites originates from their propensity, when exposed to the oral environment, to release in a sustained manner sufficient levels of mineral-forming calcium and phosphate ions to promote formation of stable apatitic tooth mineral. However, the less than optimal ACP filler/resin matrix cohesion, excessive polymerization shrinkage and water sorption of these experimental materials can adversely affect their physicochemical and mechanical properties, and, ultimately, limit their lifespan. This study demonstrates the effects of chemical structure and composition of the methacrylate monomers used to form the matrix phase of composites on degree of vinyl conversion (DVC) and water sorption of both copolymers and composites and the release of mineral ions from the composites. Modification of ACP surface via introducing cations and/or polymers ab initio during filler synthesis failed to yield mechanically improved composites. However, moderate improvement in composite’s mechanical stability without compromising its remineralization potential was achieved by silanization and/or milling of ACP filler. Using ethoxylated bisphenol A dimethacrylate or urethane dimethacrylate as base monomers and adding moderate amounts of hydrophilic 2-hydroxyethyl methacrylate or its isomer ethyl-α-hydroxymethacrylate appears to be a promising route to maximize the remineralizing ability of the filler while maintaining high DVC. Exploration of the structure/composition/property relationships of ACP fillers and polymer matrices is complex but essential for achieving a better understanding of the fundamental mechanisms that govern dissolution/re-precipitation of bioactive ACP fillers, and, ultimately, the suitability of the composites for clinical evaluation. PMID:21966588

Relationship between mechanical properties of one-step self-etch adhesives and water sorption.

PubMed

Hosaka, Keiichi; Nakajima, Masatoshi; Takahashi, Masahiro; Itoh, Shima; Ikeda, Masaomi; Tagami, Junji; Pashley, David H

2010-04-01

The purpose of this study was to evaluate the relationship between changes in the modulus of elasticity and ultimate tensile strength of one-step self-etch adhesives, and their degree of water sorption. Five one-step self-etch adhesives, Xeno IV (Dentsply Caulk), G Bond (GC Corp.), Clearfil S3 Bond (Kuraray Medical Inc.), Bond Force (Tokuyama Dental Corp.), and One-Up Bond F Plus (Tokuyama Dental Corp.) were used. Ten dumbelled-shaped polymers of each adhesive were used to obtain the modulus of elasticity by the three-point flexural bending test and the ultimate tensile strength by microtensile testing. The modulus of elasticity and the ultimate tensile strength were measured in both dry and wet conditions before/after immersion in water for 24h. Water sorption was measured, using a modification of the ISO-4049 standard. Each result of the modulus of elasticity and ultimate tensile strength was statistically analyzed using a two-way ANOVA and the result of water sorption was statistically analyzed using a one-way ANOVA. Regression analyses were used to determine the correlations between the modulus of elasticity and the ultimate tensile strength in dry or wet states, and also the percent decrease in these properties before/after immersion of water vs. water sorption. In the dry state, the moduli of elasticity of the five adhesive polymers varied from 948 to 1530 MPa, while the ultimate tensile strengths varied from 24.4 to 61.5 MPa. The wet specimens gave much lower moduli of elasticity (from 584 to 1073 MPa) and ultimate tensile strengths (from 16.5 to 35.0 MPa). Water sorption varied from 32.1 to 105.8 g mm(-3). The moduli of elasticity and ultimate tensile strengths of the adhesives fell significantly after water-storage. Water sorption depended on the constituents of the adhesive systems. The percent decreases in the ultimate tensile strengths of the adhesives were related to water sorption, while the percent reductions in the moduli of elasticity of the adhesives were not related to water sorption. Copyright (c) 2009 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

The effect of altered lignin composition on mechanical properties of CINNAMYL ALCOHOL DEHYDROGENASE (CAD) deficient poplars.

PubMed

Özparpucu, Merve; Gierlinger, Notburga; Burgert, Ingo; Van Acker, Rebecca; Vanholme, Ruben; Boerjan, Wout; Pilate, Gilles; Déjardin, Annabelle; Rüggeberg, Markus

2018-04-01

CAD-deficient poplars enabled studying the influence of altered lignin composition on mechanical properties. Severe alterations in lignin composition did not influence the mechanical properties. Wood represents a hierarchical fiber-composite material with excellent mechanical properties. Despite its wide use and versatility, its mechanical behavior has not been entirely understood. It has especially been challenging to unravel the mechanical function of the cell wall matrix. Lignin engineering has been a useful tool to increase the knowledge on the mechanical function of lignin as it allows for modifications of lignin content and composition and the subsequent studying of the mechanical properties of these transgenics. Hereby, in most cases, both lignin composition and content are altered and the specific influence of lignin composition has hardly been revealed. Here, we have performed a comprehensive micromechanical, structural, and spectroscopic analysis on xylem strips of transgenic poplar plants, which are downregulated for cinnamyl alcohol dehydrogenase (CAD) by a hairpin-RNA-mediated silencing approach. All parameters were evaluated on the same samples. Raman microscopy revealed that the lignin of the hpCAD poplars was significantly enriched in aldehydes and reduced in the (relative) amount of G-units. FTIR spectra indicated pronounced changes in lignin composition, whereas lignin content was not significantly changed between WT and the hpCAD poplars. Microfibril angles were in the range of 18°-24° and were not significantly different between WT and transgenics. No significant changes were observed in mechanical properties, such as tensile stiffness, ultimate stress, and yield stress. The specific findings on hpCAD poplar allowed studying the specific influence of lignin composition on mechanics. It can be concluded that the changes in lignin composition in hpCAD poplars did not affect the micromechanical tensile properties.

Protein mechanics: from single molecules to functional biomaterials.

PubMed

Li, Hongbin; Cao, Yi

2010-10-19

Elastomeric proteins act as the essential functional units in a wide variety of biomechanical machinery and serve as the basic building blocks for biological materials that exhibit superb mechanical properties. These proteins provide the desired elasticity, mechanical strength, resilience, and toughness within these materials. Understanding the mechanical properties of elastomeric protein-based biomaterials is a multiscale problem spanning from the atomistic/molecular level to the macroscopic level. Uncovering the design principles of individual elastomeric building blocks is critical both for the scientific understanding of multiscale mechanics of biomaterials and for the rational engineering of novel biomaterials with desirable mechanical properties. The development of single-molecule force spectroscopy techniques has provided methods for characterizing mechanical properties of elastomeric proteins one molecule at a time. Single-molecule atomic force microscopy (AFM) is uniquely suited to this purpose. Molecular dynamic simulations, protein engineering techniques, and single-molecule AFM study have collectively revealed tremendous insights into the molecular design of single elastomeric proteins, which can guide the design and engineering of elastomeric proteins with tailored mechanical properties. Researchers are focusing experimental efforts toward engineering artificial elastomeric proteins with mechanical properties that mimic or even surpass those of natural elastomeric proteins. In this Account, we summarize our recent experimental efforts to engineer novel artificial elastomeric proteins and develop general and rational methodologies to tune the nanomechanical properties of elastomeric proteins at the single-molecule level. We focus on general design principles used for enhancing the mechanical stability of proteins. These principles include the development of metal-chelation-based general methodology, strategies to control the unfolding hierarchy of multidomain elastomeric proteins, and the design of novel elastomeric proteins that exhibit stimuli-responsive mechanical properties. Moving forward, we are now exploring the use of these artificial elastomeric proteins as building blocks of protein-based biomaterials. Ultimately, we would like to rationally tailor mechanical properties of elastomeric protein-based materials by programming the molecular sequence, and thus nanomechanical properties, of elastomeric proteins at the single-molecule level. This step would help bridge the gap between single protein mechanics and material biomechanics, revealing how the mechanical properties of individual elastomeric proteins are translated into the properties of macroscopic materials.

Effect of thermomechanical treatment on the microstructure, phase composition, and mechanical properties of Al-Cu-Mn-Mg-Zr alloy

NASA Astrophysics Data System (ADS)

Zuiko, I. S.; Gazizov, M. R.; Kaibyshev, R. O.

2016-09-01

The effect of the thermomechanical treatment on the microstructure, phase composition, and mechanical properties of heat-treatable AA2519 aluminum alloy (according to the classification of the Aluminum Association) has been considered. After solid-solution treatment, quenching, and artificial aging (T6 treatment) at 180°C for the peak strength, the yield stress, ultimate tensile strength, and elongation to failure are ~300 MPa, 435 MPa, and 21.7%, respectively. It has been shown that treatments that include intermediate plastic deformations with degrees of 7 and 15% (T87 and T815 treatments, respectively) have a significant effect on the phase composition and morphology of strengthening particles precipitated during peak aging T8X type, where X is pre-strain percent, treatments initiate the precipitation of significant amounts of particles of the θ'- and Ω-phases. After T6 treatment, predominantly homogeneously distributed particles of θ″-phase have been observed. Changes in the microstructure and phase composition of the AA2519 alloy, which are caused by intermediate deformation, lead to a significant increase in the yield stress and ultimate tensile strength (by ~40 and ~8%, respectively), whereas the plasticity decreases by 40-50%.

The effect of ageing on the mechanical properties of the silk of the bridge spider Larinioides cornutus (Clerck, 1757)

NASA Astrophysics Data System (ADS)

Lepore, Emiliano; Isaia, Marco; Mammola, Stefano; Pugno, Nicola

2016-05-01

Spider silk is regarded as one of the best natural polymer fibers especially in terms of low density, high tensile strength and high elongation until breaking. Since only a few bio-engineering studies have been focused on spider silk ageing, we conducted nano-tensile tests on the vertical naturally spun silk fibers of the bridge spider Larinioides cornutus (Clerck, 1757) (Arachnida, Araneae) to evaluate changes in the mechanical properties of the silk (ultimate stress and strain, Young’s modulus, toughness) over time. We studied the natural process of silk ageing at different time intervals from spinning (20 seconds up to one month), comparing silk fibers spun from adult spiders collected in the field. Data were analyzed using Linear Mixed Models. We detected a positive trend versus time for the Young’s modulus, indicating that aged silks are stiffer and possibly less effective in catching prey. Moreover, we observed a negative trend for the ultimate strain versus time, attesting a general decrement of the resistance force. These trends are interpreted as being due to the drying of the silk protein chains and the reorientation among the fibers.

A Theoretical Analysis of the Effect of the Hydrogenation of Graphene to Graphane on Its Mechanical Properties

NASA Astrophysics Data System (ADS)

Peng, Q.; Liang, Chao; Ji, Wei; de, Suvranu

2013-03-01

We investigated the mechanical properties of graphene and graphane using first-principles calculations based on density-functional theory. A conventional unitcell containing a hexagonal ring made of carbon atoms was chosen to capture the finite wave vector ``soft modes'', which affect the the fourth and fifth elastic constants considerably. Graphane has about 2/3 ultimate strengths in all three tested deformation modes - armchair, zigzag, and biaxial- compared to graphene. However, graphane has larger ultimate strains in zigzag deformation, and smaller in armchair deformation. We obtained the second, third, fourth, and fifth order elastic constants for a rigorous continuum description of the elastic response. Graphane has a relatively low in-plane stiffness of 240 N/m which is about 2/3 of that of graphene, and a very small Poisson ratio of 0.078, 44% of that of graphene. The pressure dependence of the second order elastic constants were predicted from the third order elastic constants. The Poisson's ratio monotonically decreases with increasing pressure. Acknowledge the financial support from DTRA Grant # BRBAA08-C-2-0130, the U.S. NRCFDP # NRC-38-08-950, and U.S. DOE NEUP Grant #DE-NE0000325.

Mechanical properties of silicon in subsurface damage layer from nano-grinding studied by atomistic simulation

NASA Astrophysics Data System (ADS)

Zhang, Zhiwei; Chen, Pei; Qin, Fei; An, Tong; Yu, Huiping

2018-05-01

Ultra-thin silicon wafer is highly demanded by semi-conductor industry. During wafer thinning process, the grinding technology will inevitably induce damage to the surface and subsurface of silicon wafer. To understand the mechanism of subsurface damage (SSD) layer formation and mechanical properties of SSD layer, atomistic simulation is the effective tool to perform the study, since the SSD layer is in the scale of nanometer and hardly to be separated from underneath undamaged silicon. This paper is devoted to understand the formation of SSD layer, and the difference between mechanical properties of damaged silicon in SSD layer and ideal silicon. With the atomistic model, the nano-grinding process could be performed between a silicon workpiece and diamond tool under different grinding speed. To reach a thinnest SSD layer, nano-grinding speed will be optimized in the range of 50-400 m/s. Mechanical properties of six damaged silicon workpieces with different depths of cut will be studied. The SSD layer from each workpiece will be isolated, and a quasi-static tensile test is simulated to perform on the isolated SSD layer. The obtained stress-strain curve is an illustration of overall mechanical properties of SSD layer. By comparing the stress-strain curves of damaged silicon and ideal silicon, a degradation of Young's modulus, ultimate tensile strength (UTS), and strain at fracture is observed.

Ropivacaine alters the mechanical properties of hamstring tendons: In vitro controlled mechanical testing of tendons from living donors.

PubMed

Ollivier, M; Sbihi, J; Sbihi, A; Pithioux, M; Parratte, S; Argenson, J-N

2017-11-01

Intraarticular or periarticular injection of ropivacaine (RI) is an element of current knee surgery practices. The goal of this study was to determine the effects of RI on the mechanical properties of hamstring tendons. We hypothesized that RI would have a detrimental effect on the mechanical properties of periarticular soft tissues METHODS: A tensile test to failure was performed on 120 hamstring tendon segments harvested during ACL reconstruction surgery in 120 patients. Two sets of tensile tests were done. The first evaluated the effect of RI itself on the mechanical properties of tendons: 30 samples were soaked for 1hour in a 2% RI solution and compared to 30 samples soaked in a saline solution (control group). The second evaluated the effect of RI concentration on the mechanical properties of hamstring tendons: 30 samples were soaked for 1hour in a 2% RI solution and 30 samples were soaked in a 7.5% RI solution. In the first test, 29 samples from each group were analyzed as two samples (one in each group) failed at the grip interface. The specimens exposed to 2% RI had lower ultimate tensile strength (Δ=4.4MPa, P=0.001), strain energy (Δ=13MPa, P=0.001) and Young's modulus (Δ=1.6MPa, P=0.02) than the specimens in the control group. There was no significant difference in the strain at failure between groups (Δ=5%, P=0.3). In the second test, one specimen from the 7.5% RI group failed during the preloading and was excluded. There was no significant difference in terms of the load at failure and ultimate tensile stress (Δ=0.45MPa, P=0.6) and strain energy (Δ=0.49MPa, P=0.49) between the two groups. There were significant differences in terms of elongation at failure (Δ=28%, P=0.0003) and Young's modulus (Δ=2.6MPa, P=0.005), with the specimens exposed to 7.5% RI undergoing greater deformation and having a lower Young's modulus. While local RI injections are widely performed in clinical practice, the results of this in vitro study point to short-term alterations of the mechanical properties of hamstring tendons. If these results hold in vivo, this could lead to weakness of the soft tissues exposed to this product, particularly the tendons and ligaments around the injection area. Experimental study. Level 1. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

Mechanical properties of SiC fiber-reinforced reaction-bonded Si3N4 composites

NASA Technical Reports Server (NTRS)

Bhatt, R. T.

1985-01-01

The room temperature mechanical and physical properties of silicon carbide fiber reinforced reaction-bonded silicon nitride composites (SiC/RBSN) have been evaluated. The composites contained 23 and 40 volume fraction of aligned 140 micro m diameter chemically vapor deposited SiC fibers. Preliminary results for composite tensile and bend strengths and fracture strain indicate that the composites displayed excellent properties when compared with unreinforced RBSN of comparable porosity. Fiber volume fraction showed little influence on matrix first cracking strain but did influence the stressed required for matrix first cracking and for ultimate composite fracture strength. It is suggested that by reducing matrix porosity and by increasing the volume fraction of the large diameter SiC fiber, it should be possible to further improve the composite stress at which the matrix first cracks.

Microstructure and Tensile/Corrosion Properties Relationships of Directionally Solidified Al-Cu-Ni Alloys

NASA Astrophysics Data System (ADS)

Rodrigues, Adilson V.; Lima, Thiago S.; Vida, Talita A.; Brito, Crystopher; Garcia, Amauri; Cheung, Noé

2018-03-01

Al-Cu-Ni alloys are of scientific and technological interest due to high strength/high temperature applications, based on the reinforcement originated from the interaction between the Al-rich phase and intermetallic composites. The nature, morphology, size, volume fraction and dispersion of IMCs particles throughout the Al-rich matrix are important factors determining the resulting mechanical and chemical properties. The present work aims to evaluate the effect of the addition of 1wt%Ni into Al-5wt%Cu and Al-15wt%Cu alloys on the solidification rate, macrosegregation, microstructure features and the interrelations of such characteristics on tensile and corrosion properties. A directional solidification technique is used permitting a wide range of microstructural scales to be examined. Experimental growth laws relating the primary and secondary dendritic spacings to growth rate and solidification cooling rate are proposed, and Hall-Petch type equations are derived relating the ultimate tensile strength and elongation to the primary dendritic spacing. Considering a compromise between ultimate tensile strength and corrosion resistance of the examined alloys samples from both alloys castings it is shown that the samples having more refined microstructures are associated with the highest values of such properties.

Effects of LDEF flight exposure on selected polymer matrix resin composite materials

NASA Technical Reports Server (NTRS)

Slemp, Wayne S.; Young, Philip R.; Witte, William G., Jr.; Shen, James Y.

1991-01-01

The characterization of selected graphite fiber reinforced epoxy and polysulfone matrix resin composites which received exposure to the LEO environment on the LDEF is reported. The changes in mechanical properties of ultimate tensile strength and tensile modulus for exposed flight specimens are compared to the three sets of control specimens. Marked changes in surface appearance are discussed, and resin loss is reported. The chemical characterization including IR, thermal, and selected solution property measurements showed that the molecular structure of the polymeric matrix had not changed significantly in response to this exposure.

Effect of processing on Polymer/Composite structure and properties

NASA Technical Reports Server (NTRS)

1982-01-01

Advances in the vitality and economic health of the field of polymer forecasting are discussed. A consistent and rational point of view which considers processing as a participant in the underlying triad of relationships which comprise materials science and engineering is outlined. This triad includes processing as it influences material structure, and ultimately properties. Methods in processing structure properties, polymer science and engineering, polymer chemistry and synthesis, structure and modification and optimization through processing, and methods of melt flow modeling in processing structure property relations of polymer were developed. Mechanical properties of composites are considered, and biomedical materials research to include polymer processing effects are studied. An analysis of the design technology of advances graphite/epoxy composites is also reported.

Reduced mechanical load decreases the density, stiffness, and strength of cancellous bone of the mandibular condyle.

PubMed

Giesen, E B W; Ding, M; Dalstra, M; van Eijden, T M G J

2003-05-01

To investigate the influence of decreased mechanical loading on the density and mechanical properties of the cancellous bone of the human mandibular condyle. Destructive compressive mechanical tests were performed on cancellous bone specimens.Background. Reduced masticatory function in edentate people leads to a reduction of forces acting on the mandible. As bone reacts to its mechanical environment a change in its material properties can be expected. Cylindrical bone specimens were obtained from dentate and edentate embalmed cadavers. Mechanical parameters were determined in the axial and in the transverse directions. Subsequently, density parameters were determined according to a method based on Archimedes' principle. The apparent density and volume fraction of the bone were about 18% lower in the edentate group; no age-related effect on density was found. The decrease of bone in the edentate group was associated with a lower stiffness and strength (about 22% and 28%, respectively). The ultimate strain, however, did not differ between the two groups. Both groups had similar mechanical anisotropy; in axial loading the bone was stiffer and stronger than in transverse loading. Reduced mechanical load had affected the density and herewith the mechanical properties of condylar cancellous bone, but not its anisotropy. The change in material properties of the cancellous bone after loss of teeth indicate that the mandibular condyle is sensitive for changes in its mechanical environment. Therefore, changes in mechanical loading of the condyle have to be accounted for in surgical procedures of the mandible.

Retention Strength of PMMA/UDMA-Based Crowns Bonded to Dentin: Impact of Different Coupling Agents for Pretreatment

PubMed Central

Stawarczyk, Bogna; Teuss, Simona; Eichberger, Marlis; Roos, Malgorzata; Keul, Christine

2015-01-01

Computer aided design/computer aided manufacturing (CAD/CAM) polymers for long-term dental restorations benefit from enhanced mechanical properties. However, the quantification of their bonding properties on teeth is lacking. Therefore, the aim of this study was to determine the retention strength (RS) of differently pretreated new developed polymethylmethacrylate/urethanedimethacrylate-based CAD/CAM polymer bonded on dentin. In summary, 120 human caries-free molars were prepared, and polymeric crowns were milled and pretreated (n = 20): visio.link (VL), Scotchbond Universal (SU), Monobond Plus/Heliobond (MH), Margin Bond (MB), Margin Bond mixed with acetone (1:1) (MBA) or not pretreated (CG). Half of the specimens were cemented using Variolink II and the other half with RelyX Ultimate. Specimens were stored for 24 h in distilled water and thermal cycled (5000 ×, 5 °C/55 °C). The retention load was measured and failure types were defined. RS was calculated and analyzed using both two- and one-way ANOVA with a post-hoc Scheffé-test, unpaired t-test, Kaplan–Meier with Breslow–Gehan test and chi-squared test (p < 0.05). Crowns bonded using RelyX Ultimate showed higher RS than those bonded using Variolink II. The pretreatment showed no impact on the RS. However, survival analysis within Variolink II found an impact of pretreatment. The median RS for MH was the lowest and statistically different from MB, MBA and CG. For Variolink II MH had the poorest survival as the estimated cumulative failure function of the debonded crown increased very quickly with increasing TBS. Within the RelyX Ultimate groups, no significant differences were determined. The newly developed CAD/CAM polymer showed the highest bonding properties after cementation using RelyX Ultimate. PMID:28793651

Improving the particle distribution and mechanical properties of friction-stir-welded composites by using a smooth pin tool

NASA Astrophysics Data System (ADS)

Liu, Huijie; Hu, Yanying; Zhao, Yunqiang; Fujii, Hidetoshi

2017-09-01

Friction stir welding (FSW) is a very promising technique for joining particle-reinforced aluminum-matrix composites (PRAMCs), but with increase in the volume fraction of reinforcing particles, their distribution in welds becomes inhomogeneous. This leads to an inconsistent deformation of welds and their destruction at low stresses. In order to improve the weld microstructure, a smooth pin tool was used for the friction stir welding of AC4A + 30 vol.% SiC particle-reinforced aluminum-matrix composites. The present work describes the effect of welding parameters on the characteristics of particle distribution and the mechanical properties of welds. The ultimate strength of weld reached, 309 MPa, was almost 190% of that of the basic material. The mechanism of SiC particle conglomeration is clearly illustrated by means of schematic illustrations.

Investigation of Mechanical Properties and Fracture Simulation of Solution-Treated AA 5754

NASA Astrophysics Data System (ADS)

Kumar, Pankaj; Singh, Akhilendra

2017-10-01

In this work, mechanical properties and fracture toughness of as-received and solution-treated aluminum alloy 5754 (AA 5754) are experimentally evaluated. Solution heat treatment of the alloy is performed at 530 °C for 2 h, and then, quenching is done in water. Yield strength, ultimate tensile strength, impact toughness, hardness, fatigue life, brittle fracture toughness (K_{Ic} ) and ductile fracture toughness (J_{Ic} ) are evaluated for as-received and solution-treated alloy. Extended finite element method has been used for the simulation of tensile and fracture behavior of material. Heaviside function and asymptotic crack tip enrichment functions are used for modelling of the crack in the geometry. Ramberg-Osgood material model coupled with fracture energy is used to simulate the crack propagation. Fracture surfaces obtained from various mechanical tests are characterized by scanning electron microscopy.

Channeling Polyolefin Molecular Structure - Bulk Property Correlation Strategies for Industrial Applicability

NASA Astrophysics Data System (ADS)

Hule, Rohan; Thurman, Derek; Doufas, Antonios

Polyolefins occupy a significant volume of the polymer products portfolio in commodity and high value applications. Quantifying and optimizing structure-property relationships enables growth in new markets. It is well recognized that coupling lab-based, comprehensive methodologies with bulk properties of interest to industrial environments offer the greatest potential of technology advancement, ultimately leading to commercial success. It is imperative to recognize the existing gap of knowledge translation between lab measurements and industrial-scale operability. This study highlights experimental HDPEs synthesized from dual, single-site, co-supported catalysts that exhibit enhanced solid-state properties such as stiffness, impact and ESCR surpassing conventional trends. Commercial resins across distinct sub-families were included as well. Commonality amongst these resins is bimodality and broad MW distribution with well-defined splits and spreads. Investigations on commercially relevant parameters such as melt strength, melt elasticity and shear thinning established excellent performance for experimental bimodals, corroborating potential benefits compared to commercial HDPEs. To summarize, the effort highlights well-recognized pathways such as improvements in mechanical and melt properties that can be attributed to apposite tuning of polymer chain architecture and MW distribution with implications across myriad markets. Ultimately, this may serve as a pathway for producing innovative products that deliver business success and growth.

A mechanical property and stress corrosion evaluation of Custom 455 stainless steel alloy

NASA Technical Reports Server (NTRS)

Montano, J. W.

1972-01-01

The mechanical and stress corrosion properties are presented of vacuum melted Custom 455 stainless steel alloy bar (1.0-inch diameter) and sheet (0.083-inch thick) material aged at 950 F, 1000 F, and 1050 F. Low temperature mechanical properties were determined at temperatures of 80 F, 0 F, -100 F, and -200 F. For all three aging treatments, the ultimate tensile and 0.2 percent offset yield strengths increased with decreasing test temperatures while the elongation held fairly constant down to -100 F and decreased at -200 F. Reduction in Area decreased moderately with decreasing temperature for the longitudinal round (0.250-inch diameter) specimens. Notched tensile strength and charpy V-notched impact strength decreased with decreasing test temperature. For all three aging treatments, no failures were observed in the unstressed specimens or the specimens stressed to 50, 75, and 100 percent of their yield strengths for 180 days of alternate immersion testing in a 3.5 percent NaCl solution. As indicated by the results of tensile tests performed after alternate immersion testing, the mechanical properties of Custom 455 alloy were not affected by stress or exposure under the conditions of the evaluation.

Influence of Powder Bed Preheating on Microstructure and Mechanical Properties of H13 Tool Steel SLM Parts

NASA Astrophysics Data System (ADS)

Mertens, R.; Vrancken, B.; Holmstock, N.; Kinds, Y.; Kruth, J.-P.; Van Humbeeck, J.

Powder bed preheating is a promising development in selective laser melting (SLM), mainly applied to avoid large thermal stresses in the material. This study analyses the effect of in-process preheating on microstructure, mechanical properties and residual stresses during SLM of H13 tool steel. Sample parts are produced without any preheating and are compared to the corresponding parts made with preheating at 100°, 200°, 300°, and 400°C. Interestingly, internal stresses at the top surface of the parts evolve from compressive (-324MPa) without preheating to tensile stresses (371MPa) with preheating at 400°C. Nevertheless, application of powder bed preheating results in a more homogeneous microstructure with better mechanical properties compared to H13 SLM parts produced without preheating. The fine bainitic microstructure leads to hardness values of 650-700Hv and ultimate tensile strength of 1965MPa, which are comparable to or even better than those of conventionally made and heat treated H13 tool steel.

Effects of aging treatment and heat input on the microstructures and mechanical properties of TIG-welded 6061-T6 alloy joints

NASA Astrophysics Data System (ADS)

Peng, Dong; Shen, Jun; Tang, Qin; Wu, Cui-ping; Zhou, Yan-bing

2013-03-01

Aging treatment and various heat input conditions were adopted to investigate the microstructural evolution and mechanical properties of TIG welded 6061-T6 alloy joints by microstructural observations, microhardness tests, and tensile tests. With an increase in heat input, the width of the heat-affected zone (HAZ) increases and grains in the fusion zone (FZ) coarsen. Moreover, the hardness of the HAZ decreases, whereas that of the FZ decreases initially and then increases with an increase in heat input. Low heat input results in the low ultimate tensile strength of the welded joints due to the presence of partial penetrations and pores in the welded joints. After a simple artificial aging treatment at 175°C for 8 h, the microstructure of the welded joints changes slightly. The mechanical properties of the welded joints enhance significantly after the aging process as few precipitates distribute in the welded seam.

Mechanical characterization and structural analysis of recycled fiber-reinforced-polymer resin-transfer-molded beams

NASA Astrophysics Data System (ADS)

Tan, Eugene Wie Loon

1999-09-01

The present investigation was focussed on the mechanical characterization and structural analysis of resin-transfer-molded beams containing recycled fiber-reinforced polymers. The beams were structurally reinforced with continuous unidirectional glass fibers. The reinforcing filler materials consisted entirely of recycled fiber-reinforced polymer wastes (trim and overspray). The principal resin was a 100-percent dicyclo-pentadiene unsaturated polyester specially formulated with very low viscosity for resin transfer molding. Variations of the resin transfer molding technique were employed to produce specimens for material characterization. The basic materials that constituted the structural beams, continuous-glass-fiber-reinforced, recycled-trim-filled and recycled-overspray-filled unsaturated polyesters, were fully characterized in axial and transverse compression and tension, and inplane and interlaminar shear, to ascertain their strengths, ultimate strains, elastic moduli and Poisson's ratios. Experimentally determined mechanical properties of the recycled-trim-filled and recycled-overspray-filled materials from the present investigation were superior to those of unsaturated polyester polymer concretes and Portland cement concretes. Mechanical testing and finite element analyses of flexure (1 x 1 x 20 in) and beam (2 x 4 x 40 in) specimens were conducted. These structurally-reinforced specimens were tested and analyzed in four-point, third-point flexure to determine their ultimate loads, maximum fiber stresses and mid-span deflections. The experimentally determined load capacities of these specimens were compared to those of equivalent steel-reinforced Portland cement concrete beams computed using reinforced concrete theory. Mechanics of materials beam theory was utilized to predict the ultimate loads and mid-span deflections of the flexure and beam specimens. However, these predictions proved to be severely inadequate. Finite element (fracture propagation) analyses of the flexure and beam specimens were also performed. These progressive failure analyses more closely approximated flexural behavior under actual testing conditions by reducing the elastic moduli of elements that were considered to have partially or totally failed. Individual element failures were predicted using the maximum stress, Tsai-Hill and Tsai-Wu failure criteria. Excellent predictions of flexural behavior were attributed to the progressive failure analyses combined with an appropriate failure criterion, and the reliable input material properties that were generated.

Method of forming biaxially textured alloy substrates and devices thereon

DOEpatents

Goyal, Amit; Specht, Eliot D.; Kroeger, Donald M.; Paranthaman, Mariappan

1999-01-01

Specific alloys, in particular Ni-based alloys, that can be biaxially textured, with a well-developed, single component texture are disclosed. These alloys have a significantly reduced Curie point, which is very desirable from the point of view of superconductivity applications. The biaxially textured alloy substrates also possess greatly enhanced mechanical properties (yield strength, ultimate tensile strength) which are essential for most applications, in particular, superconductors. A method is disclosed for producing complex multicomponent alloys which have the ideal physical properties for specific applications, such as lattice parameter, degree of magnetism and mechanical strength, and which cannot be fabricated in textured form. In addition, a method for making ultra thin biaxially textured substrates with complex compositions is disclosed.

Spectral (optical) and mechanical responses of fresh and cryopreserved issued arteries

NASA Astrophysics Data System (ADS)

Pery, Emilie; Blondel, Walter C.; Goebel, Jean-Christophe; Didelon, Jacques; Guillemin, Francois

2005-04-01

Cryopreservation is the only method for conserving blood vessels as future allografts with biological immunity controls. Although it affects vessels mechanical structure, no biomechanical integrity simple test is available today. Biological tissues optical properties characterization by spectroscopic methods is of interest due to their types or natures variations. Collected data complementarity contributes to "photodiagnosis" applicative prospects (cancer, vascular...). Pig carotid artery rings were tested after excision and after one month cryopreservation. An uniaxial mechanical testing device was used for ring stretching, and elongation and axial forces measurement. Circumferential large strains and stresses were calculated. Simultaneously, each artery ring optical characteristics was measured using fibered autofluorescence and elastic scattering spectrometers. Mechanical results showed nonlinear strain/stress curves and large deformations in good agreement with other referenced works. Significant differences (p<0.05) between fresh and cryopreserved rings mechanical properties were noticed. Elastic scattering spectra intensity variations were well correlated with artery mechanical properties. The standardized autofluorescence spectra were more clearly correlated with anatomo-histological changes due to cryopreservation, providing rather accurate differentiation between fresh and cryopreserved samples. This study offers a new perspective to detect changes of cryopreserved arterial samples mechanical properties. Coupling mechanical tests (uniaxial traction of arterial rings) and optical spectroscopic measurements (autofluorescence, elastic scattering) is the driving point: it allows correlating mechanical modifications and spectral variations of artery rings before and after cryopreservation. Ultimately, this new approach could help developping a device allowing non-invasive, atraumatic and contactless optical examinations of arterial graft to assess its mechanical state before reimplantation.

Preserving Cellulose Structure: Delignified Wood Fibers for Paper Structures of High Strength and Transparency.

PubMed

Yang, Xuan; Berthold, Fredrik; Berglund, Lars A

2018-05-23

To expand the use of renewable materials, paper products with superior mechanical and optical properties are needed. Although beating, bleaching, and additives are known to improve industrially produced Kraft pulp papers, properties are limited by the quality of the fibers. While the use of nanocellulose has been shown to significantly increase paper properties, the current cost associated with their production has limited their industrial relevance. Here, using a simple mild peracetic acid (PAA) delignification process on spruce, we produce hemicellulose-rich holocellulose fibers (28.8 wt %) with high intrinsic strength (1200 MPa for fibers with microfibrillar angle smaller than 10°). We show that PAA treatment causes less cellulose/hemicellulose degradation and better preserves cellulose nanostructure in comparison to conventional Kraft pulping. High-density holocellulose papers with superior mechanical properties (Young's modulus of 18 GPa and ultimate strength of 195 MPa) are manufactured using a water-based hot-pressing process, without the use of beating or additives. We propose that the preserved hemicelluloses act as "glue" in the interfiber region, improving both mechanical and optical properties of papers. Holocellulose fibers may be affordable and applicable candidates for making special paper/composites where high mechanical performance and/or optical transmittance are of interest.

High temperature tensile behavior and microstructure of Al-SiC nanocomposite fabricated by mechanical milling and hot extrusion technique

NASA Astrophysics Data System (ADS)

Soltani, Mohammadreza; Atrian, Amir

2018-02-01

This paper investigates the high-temperature tensile behavior of Al-SiC nanocomposite reinforced with 0, 1.5, and 3 vol% SiC nano particles. To fabricate the samples, SiC nano reinforcements and aluminum (Al) powders were milled using an attritor milling and then were cold pressed and hot extruded at 500 °C. Afterward, mechanical and microstructural characteristics were studied in different temperatures. To this end, tensile and compressive tests, micro-hardness test, microscopic examinations, and XRD analysis were performed. The results showed significant improvement of mechanical properties of Al-SiC nanocomposite in room temperature including 40% of ultimate tensile strength (UTS), 36% of ultimate compressive strength (UCS), and 44% of micro-hardness. Moreover, performing tensile tests at elevated temperatures (up to 270 °C) decreased the tensile strength by about 53%, 46%, and 45% for Al-0 vol% SiC, Al-1.5 vol% SiC, and Al-3 vol% SiC, respectively. This temperature rise also enhanced the elongation by about 11% and 133% for non-reinforced Al and Al-3 vol% SiC, respectively.

Materials as stem cell regulators

PubMed Central

Murphy, William L.; McDevitt, Todd C.; Engler, Adam J.

2014-01-01

The stem cell/material interface is a complex, dynamic microenvironment in which the cell and the material cooperatively dictate one another's fate: the cell by remodelling its surroundings, and the material through its inherent properties (such as adhesivity, stiffness, nanostructure or degradability). Stem cells in contact with materials are able to sense their properties, integrate cues via signal propagation and ultimately translate parallel signalling information into cell fate decisions. However, discovering the mechanisms by which stem cells respond to inherent material characteristics is challenging because of the highly complex, multicomponent signalling milieu present in the stem cell environment. In this Review, we discuss recent evidence that shows that inherent material properties may be engineered to dictate stem cell fate decisions, and overview a subset of the operative signal transduction mechanisms that have begun to emerge. Further developments in stem cell engineering and mechanotransduction are poised to have substantial implications for stem cell biology and regenerative medicine. PMID:24845994

Microstructural evolution and mechanical properties of a low alloy high strength Ni-Cr-Mo-V steel during heat treatment process

NASA Astrophysics Data System (ADS)

Wu, C.; Han, S.

2018-05-01

In order to obtain an optimal heat treatment for a low alloy high strength Ni-Cr-Mo-V steel, the microstructural evolution and mechanical properties of the material were studied. For this purpose, a series of quenching and temper experiments were carried out. The results showed that the effects of tempering temperature, time, original microstructure on the microstructural evolution and final properties were significant. The martensite can be completely transformed into the tempered lath structure. The width and length of the lath became wider and shorter, respectively with increasing temperature and time. The amount and size of the precipitates increased with temperature and time. The yield strength (YS), ultimate tensile strength (UTS) and hardness decreased with temperature and time, but the reduction in area (Z), elongation (E) and impact toughness displayed an opposite trend, which was related to the morphological evolution of the lath tempered structure.

A new type of smart basalt fiber-reinforced polymer bars as both reinforcements and sensors for civil engineering application

NASA Astrophysics Data System (ADS)

Tang, Yongsheng; Wu, Zhishen; Yang, Caiqian; Wu, Gang; Shen, Sheng

2010-11-01

In this paper, a new type of smart basalt fiber-reinforced polymer (BFRP) bar is developed and their sensing performance is investigated by using the Brillouin scattering-based distributed fiber optic sensing technique. The industrial manufacturing process is first addressed, followed by an experimental study on the strain, temperature and fundamental mechanical properties of the BFRP bars. The results confirm the superior sensing properties, in particular the measuring accuracy, repeatability and linearity through comparing with bare optical fibers. Results on the mechanical properties show stable elastic modulus and high ultimate strength. Therefore, the smart BFRP bar has potential applications for long-term structural health monitoring (SHM) as embedded sensors as well as strengthening and upgrading structures. Moreover the coefficient of thermal expansion for smart BFRP bars is similar to the value for concrete.

An investigation of the effect of processing conditions on the lamellar and spherulitic morphology of polyhydroxyalkanoates

NASA Astrophysics Data System (ADS)

Xie, Yuping; Akpalu, Yvonne A.

2007-03-01

Polyhydroxyalkanoates (PHAs) have recently attracted much interest because of their biodegradability and biocompatibility. Since the ultimate properties of polymers can be controlled by processing conditions, particularly cooling rates, the systematic and thorough understanding of the effects of cooling rates on the final morphology and the resulting mechanical properties of PHAs is necessary and important. In this presentation, the lamellar (tens of nanometers), fibrillar (several hundred nanometers) and spherulitic (˜μm) morphologies of poly (3-hydroxybutyric acid) (PHB) and the copolymer poly (3-hydroxybutyric acid-co-3-hydroxyvaleric acid) (PHBV) crystallized under different cooling rates were studied using small angle X-ray scattering, ultra small angle X-ray scattering, and polarized optical microscopy, respectively. The morphology was observed to depend strongly on cooling rate. The influence of cooling rate on the morphology and mechanical properties such as toughness, tensile strength and overall stress-strain behavior will be discussed.

Characterization of polymer composites during autoclave manufacturing by Fourier transform Raman spectroscopy

NASA Astrophysics Data System (ADS)

Farquharson, Stuart; Smith, Wayne W.; Rigas, Elias J.; Granville, Dana

2001-02-01

12 The superior engineering properties of fiber reinforced polymer matrix composites, primarily the high strength-to- weight ratio, make them suitable to applications ranging from sporting goods to aircraft components (e.g. helicopter blades). Unfortunately, consistent fabrication of components with desired mechanical properties has proven difficult, and has led to high production costs. This is largely due to the inability to monitor and control polymer cure, loosely defined as the process of polymer chain extension and cross- linking. Even with stringent process control, slight variations in the pre-polymer formulations (e.g. prepreg) can influence reaction rates, reaction mechanisms, and ultimately, product properties. In an effort to optimize the performance of thermoset composite, we have integrated fiber optic probes between the plies of laminates and monitored cure by Raman spectroscopy, with the eventual goal of process control. Here we present real-time measurements of two high performance aerospace companies cured within an industrial autoclave.

Mechanical properties in crumple-formed paper derived materials subjected to compression.

PubMed

Hanaor, D A H; Flores Johnson, E A; Wang, S; Quach, S; Dela-Torre, K N; Gan, Y; Shen, L

2017-06-01

The crumpling of precursor materials to form dense three dimensional geometries offers an attractive route towards the utilisation of minor-value waste materials. Crumple-forming results in a mesostructured system in which mechanical properties of the material are governed by complex cross-scale deformation mechanisms. Here we investigate the physical and mechanical properties of dense compacted structures fabricated by the confined uniaxial compression of a cellulose tissue to yield crumpled mesostructuring. A total of 25 specimens of various densities were tested under compression. Crumple formed specimens exhibited densities in the range 0.8-1.3 g cm -3 , and showed high strength to weight characteristics, achieving ultimate compressive strength values of up to 200 MPa under both quasi-static and high strain rate loading conditions and deformation energy that compares well to engineering materials of similar density. The materials fabricated in this work and their mechanical attributes demonstrate the potential of crumple-forming approaches in the fabrication of novel energy-absorbing materials from low-cost precursors such as recycled paper. Stiffness and toughness of the materials exhibit density dependence suggesting this forming technique further allows controllable impact energy dissipation rates in dynamic applications.

Mechanical behavior of monocrystalline aluminum-lithium alloy at low temperatures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Z.G.; Liu, W.; Xu, Y.B.

1994-12-01

Investigations have indicated that at low temperature aluminum- lithium alloys display improved toughness and an improved strength-toughness relationship. The yield strength, ultimate tensile strength, elongation and the fracture toughness increase with decreasing temperatures. Several mechanisms have been proposed to explain this most striking feature. Webster claimed that low melting point impurities, such as sodium and potassium, are responsible for the improvement of mechanical properties in Al-Li alloys at low temperatures. However, Venkateswara Rao et al. indicated that the increased delamination at low temperatures can increase the degree of in-plane crack deflection, resulting in toughening of the alloys. On the basismore » of their own results, Xu and coworker pointed out that the improvement of tensile and fatigue properties at liquid nitrogen temperatures is also presumably attributable to the delamination. Therefore, the mechanisms responsible for the variation in mechanical properties with temperature are not currently well-understood. In order to elucidate the real situation, single crystals of a binary aluminum-lithium alloy were adopted in the present study. This paper is devoted to the description of the behavior of the load-displacement curves and the associated slip traces on the sample surfaces.« less

Electro-mechanical characterization of structural supercapacitors

NASA Astrophysics Data System (ADS)

Gallagher, T.; LaMaster, D.; Ciocanel, C.; Browder, C.

2012-04-01

The paper presents electrical and mechanical properties of structural supercapacitors and discusses limitations associated with the approach taken for the electrical properties evaluation. The structural supercapacitors characterized in this work had the electrodes made of carbon fiber weave, separator made of several cellulose based products, and the solid electrolyte made as PEGDGE based polymer blend. The reported electrical properties include capacitance and leakage resistance; the former was measured using cyclic voltammetry. Mechanical properties have been evaluated thorough tensile and three point bending tests performed on structural supercapacitor coupons. The results indicate that the separator material plays an important role on the electrical as well as mechanical properties of the structural capacitor, and that Celgard 3501 used as separator leads to most benefits for both mechanical and electrical properties. Specific capacitance and leakage resistance as high as 1.4kF/m3 and 380kΩ, respectively, were achieved. Two types of solid polymer electrolytes were used in fabrication, with one leading to higher and more consistent leakage resistance values at the expense of a slight decrease in specific capacitance when compared to the other SPE formulation. The ultimate tensile strength and modulus of elasticity of the developed power storage composite were evaluated at 466MPa and 18.9MPa, respectively. These values are 58% and 69% of the tensile strength and modulus of elasticity values measured for a single layer composite material made with the same type of carbon fiber and with a West System 105 epoxy instead of solid polymer electrolyte.

Impact of pregnancy and vaginal delivery on the passive and active mechanics of the rat vagina.

PubMed

Feola, Andrew; Moalli, Pamela; Alperin, Marianna; Duerr, Robbie; Gandley, Robin E; Abramowitch, Steven

2011-01-01

Remodeling of vaginal extracellular matrix and smooth muscle likely plays a critical role in reducing the risk of maternal injury during vaginal delivery by altering the mechanical properties to increase distension and reduce stress. Long-Evans rats were divided into five groups to examine the passive mechanical and active contractile properties throughout pregnancy and postpartum: virgin (n=17), mid-pregnant (Day 14-16, n=12), late-pregnant (Day 20-22, n=14), immediate postpartum (0-2 h after delivery, n=14), and 4 week postpartum (n=15). Longitudinal sections of vaginal tissue were loaded to failure uniaxially for passive mechanical or active contractile properties were examined. For passive mechanics, the tangent modulus decreased 45% by mid-pregnancy and immediately postpartum (p<0.001). The ultimate strain continuously increased up to 43% higher than virgin animals (p=0.007) in the immediate postpartum group. For active mechanics, the maximal contractile force was 36-56% lower through immediate postpartum animals, and was significantly more sensitive to K+ throughout pregnancy and postpartum (p=0.003). The changes observed in the passive and active properties of the rat vagina are consistent with what would be expected from a tissue that is remodeling to maximize its ability to distend at the time of vaginal delivery to facilitate passage of the fetus with minimal injury.

Investigation on the modification behavior of A356.2 alloy with Yb-La composite modifier

NASA Astrophysics Data System (ADS)

Zhang, Shaochen; Leng, Jinfeng; Wang, Zhibin; Wang, Qi; Shao, Yuewen; Teng, Xinying

2018-01-01

In this work, an investigation was conducted to evaluate the influence of the Yb + La addition on the microstructures and mechanical properties of A356.2 alloy. The results show that the the grain size was refined and morphological structure of Si changed from needle-like to fine spheroidal particle by adding Yb + La. The eutectic temperature decreased from 589 °C to 581 °C and the freezing range of primary α-Al become wider after adding Yb + La. The mechanical properties showed great improvement after T6 heat treatment. The ultimate tensile strength and microhardness of the composites were increased to 279.0 MPa and 99.2 HB after T6 heat treatment which increased by 28.2% and 47.3%, respectively. The fracture mechanism was analyzed using the scanning electron microscopy and proved to be a transgranular/intergranular fracture modes.

Graphene nanoplatelets induced heterogeneous bimodal structural magnesium matrix composites with enhanced mechanical properties

PubMed Central

Xiang, Shulin; Wang, Xiaojun; Gupta, Manoj; Wu, Kun; Hu, Xiaoshi; Zheng, Mingyi

2016-01-01

In this work, graphene nanoplatelets (GNPs) reinforced magnesium (Mg) matrix composites were synthesised using the multi-step dispersion route. Well-dispersed but inhomogeneously distributed GNPs were obtained in the matrix. Compared with the monolithic alloy, the nanocomposites exhibited dramatically enhanced Young’s modulus, yield strength and ultimate tensile strength and relatively high plasticity, which mainly attributed to the significant heterogeneous laminated microstructure induced by the addition of GNPs. With increasing of the concentration of GNPs, mechanical properties of the composites were gradually improved. Especially, the strengthening efficiency of all the composites exceeded 100%, which was significantly higher than that of carbon nanotubes reinforced Mg matrix composites. The grain refinement and load transfer provided by the two-dimensional and wrinkled surface structure of GNPs were the dominated strengthening mechanisms of the composites. This investigation develops a new method for incorporating GNPs in metals for fabricating high-performance composites. PMID:27941839

Graphene nanoplatelets induced heterogeneous bimodal structural magnesium matrix composites with enhanced mechanical properties

NASA Astrophysics Data System (ADS)

Xiang, Shulin; Wang, Xiaojun; Gupta, Manoj; Wu, Kun; Hu, Xiaoshi; Zheng, Mingyi

2016-12-01

In this work, graphene nanoplatelets (GNPs) reinforced magnesium (Mg) matrix composites were synthesised using the multi-step dispersion route. Well-dispersed but inhomogeneously distributed GNPs were obtained in the matrix. Compared with the monolithic alloy, the nanocomposites exhibited dramatically enhanced Young’s modulus, yield strength and ultimate tensile strength and relatively high plasticity, which mainly attributed to the significant heterogeneous laminated microstructure induced by the addition of GNPs. With increasing of the concentration of GNPs, mechanical properties of the composites were gradually improved. Especially, the strengthening efficiency of all the composites exceeded 100%, which was significantly higher than that of carbon nanotubes reinforced Mg matrix composites. The grain refinement and load transfer provided by the two-dimensional and wrinkled surface structure of GNPs were the dominated strengthening mechanisms of the composites. This investigation develops a new method for incorporating GNPs in metals for fabricating high-performance composites.

Effect of Atmospheric Corrosion on the Mechanical Properties of SAE 1020 Structural Steel.

PubMed

Martínez, Carola; Briones, Francisco; Villarroel, María; Vera, Rosa

2018-04-11

Resistance to atmospheric corrosion in different environments located in Chile and the corrosion's effect on the mechanical properties of SAE 1020 steel were studied. Atmospheric corrosivity categories at each station under study were determined. These categories were C2, for Laja; C3 and C4, for the Arica and Antarctic stations, respectively; and the most aggressive, C5 and higher at Quintero. These specific environments significantly influenced the mechanical responses of steel exposed for 36 months. Rupture elongation, the modulus of toughness, ultimate tensile strength, and hardness of the material all decreased as a function of environmental atmospheric aggressiveness. Lowered ductility is the result of the increased corrosion rate due to the high deposition of chlorides. This is due to the morphology of material degradation, which consequently occurs as pores, microstrains, and other defects that promote early rupture of the steel.

Effect of Atmospheric Corrosion on the Mechanical Properties of SAE 1020 Structural Steel

PubMed Central

Briones, Francisco; Villarroel, María; Vera, Rosa

2018-01-01

Resistance to atmospheric corrosion in different environments located in Chile and the corrosion’s effect on the mechanical properties of SAE 1020 steel were studied. Atmospheric corrosivity categories at each station under study were determined. These categories were C2, for Laja; C3 and C4, for the Arica and Antarctic stations, respectively; and the most aggressive, C5 and higher at Quintero. These specific environments significantly influenced the mechanical responses of steel exposed for 36 months. Rupture elongation, the modulus of toughness, ultimate tensile strength, and hardness of the material all decreased as a function of environmental atmospheric aggressiveness. Lowered ductility is the result of the increased corrosion rate due to the high deposition of chlorides. This is due to the morphology of material degradation, which consequently occurs as pores, microstrains, and other defects that promote early rupture of the steel. PMID:29641490

Enhanced micro-vibration sensitive high-damping capacity and mechanical strength achieved in Al matrix composites reinforced with garnet-like lithium electrolyte

NASA Astrophysics Data System (ADS)

Wang, Xian-Ping; Zhang, Yi; Xia, Yu; Jiang, Wei-Bing; Liu, Hui; Liu, Wang; Gao, Yun-Xia; Zhang, Tao; Fang, Qian-Feng

2017-03-01

A novel micro-vibration sensitive-type high-damping Al matrix composites reinforced with Li7- x La3Zr2- x Nb x O12 (LLZNO, x = 0.25) was designed and prepared using an advanced spark plasma sintering (SPS) technique. The damping capacity and mechanical properties of LLZNO/Al composites (LLZNO content: 0-40 wt.%) were found to be greatly improved by the LLZNO addition. The maximum damping capacity and the ultimate tensile strength (UTS) of LLZNO/Al composite can be respectively up to 0.033 and 101.2 MPa in the case of 20 wt.% LLZNO addition. The enhancement of damping and mechanical properties of the composites was ascribed to the intrinsic high-damping capacity and strengthening effects of hard LLZNO particulate. This investigation provides a new insight to sensitively suppress micro-vibration of payloads in the aerospace environment.

Effect of adsorbed/intercalated anionic dyes into the mechanical properties of PVA: layered zinc hydroxide nitrate nanocomposites.

PubMed

Marangoni, Rafael; Mikowski, Alexandre; Wypych, Fernando

2010-11-15

Zinc hydroxide nitrate (ZHN) was adsorbed with anions of blue dyes (Chicago sky blue, CSB; Evans blue, EB; and Niagara blue, NB) and intercalated with anions of orange dyes (Orange G, OG; Orange II, OII; methyl orange, MO). Transparent, homogeneous and colored nanocomposite films were obtained by casting after dispersing the pigments (dye-intercalated/adsorbed into LHSs) into commercial poly(vinyl alcohol) (PVA). The films were characterized by XRD, UV-Vis spectroscopy, and mechanical testing. The mechanical properties of the PVA compounded with the dye-intercalated/adsorbed ZHN were evaluated, and reasonable increases in Young's modulus and ultimate tensile strength were observed, depending on the amount and choice of layered filler. These results demonstrate the possibility of using a new class of layered hydroxide salts intercalated and adsorbed with anionic dyes to prepare multifunctional polymer nanocomposite materials. Copyright © 2010 Elsevier Inc. All rights reserved.

Hardening Potential of an Al-Cu-Li Friction Stir Weld

NASA Astrophysics Data System (ADS)

Ivanov, Rosen; Boselli, Julien; Denzer, Diana; Larouche, Daniel; Gauvin, Raynald; Brochu, Mathieu

The evolution of the microstructure during friction stir welding of a third generation AA2199 Al-Li alloy has been described and related to the mechanical properties of welds. The coupling of electron microscopy and micro-hardness have helped generate an understanding of the relationship between grain structure, precipitate density and morphology behind the observed changes in mechanical properties during post weld artificial ageing. The ability of welds to recover hardness and strength during post weld heat treatment was linked to the limited formation of large scale precipitates which act as sinks for alloying elements. Welds obtained with high tool rotation speed (within parameters studied) showed ultimate tensile strength levels of about 93% of the base metal, an elongation of 6% at fracture, and hardness values ranging between 120-140 HV in the stir zone, thermo-mechanically affected zone, and heat affected zone upon post weld heat treatment.

Interlaboratory round robin study on axial tensile properties of SiC-SiC CMC tubular test specimens [Interlaboratory round robin study on axial tensile properties of SiC/SiC tubes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Singh, Gyanender P.; Gonczy, Steve T.; Deck, Christian P.

An interlaboratory round robin study was conducted on the tensile strength of SiC–SiC ceramic matrix composite (CMC) tubular test specimens at room temperature with the objective of expanding the database of mechanical properties of nuclear grade SiC–SiC and establishing the precision and bias statement for standard test method ASTM C1773. The mechanical properties statistics from the round robin study and the precision statistics and precision statement are presented herein. The data show reasonable consistency across the laboratories, indicating that the current C1773–13 ASTM standard is adequate for testing ceramic fiber reinforced ceramic matrix composite tubular test specimen. Furthermore, it wasmore » found that the distribution of ultimate tensile strength data was best described with a two–parameter Weibull distribution, while a lognormal distribution provided a good description of the distribution of proportional limit stress data.« less

Interlaboratory round robin study on axial tensile properties of SiC-SiC CMC tubular test specimens [Interlaboratory round robin study on axial tensile properties of SiC/SiC tubes

DOE PAGES

Singh, Gyanender P.; Gonczy, Steve T.; Deck, Christian P.; ...

2018-04-19

An interlaboratory round robin study was conducted on the tensile strength of SiC–SiC ceramic matrix composite (CMC) tubular test specimens at room temperature with the objective of expanding the database of mechanical properties of nuclear grade SiC–SiC and establishing the precision and bias statement for standard test method ASTM C1773. The mechanical properties statistics from the round robin study and the precision statistics and precision statement are presented herein. The data show reasonable consistency across the laboratories, indicating that the current C1773–13 ASTM standard is adequate for testing ceramic fiber reinforced ceramic matrix composite tubular test specimen. Furthermore, it wasmore » found that the distribution of ultimate tensile strength data was best described with a two–parameter Weibull distribution, while a lognormal distribution provided a good description of the distribution of proportional limit stress data.« less

Mechanical Properties and Fracture Behaviors of GTA-Additive Manufactured 2219-Al After an Especial Heat Treatment

NASA Astrophysics Data System (ADS)

Bai, J. Y.; Fan, C. L.; Lin, S. B.; Yang, C. L.; Dong, B. L.

2017-04-01

2219-Al parts were produced by gas tungsten arc-additive manufacturing and sequentially processed by an especial heat treatment. In order to investigate the effects of heat treatment on its mechanical properties, multiple tests were conducted. Hardness tests were carried out on part scale and layer scale along with tensile tests which were performed on welding and building directions. Results show that compared to conventional casting + T6 2219-Al, the current deposit + T6 2219-Al exhibits satisfying properties with regard to strength but unsatisfying results in plasticity. Additionally, anisotropy is significant. Fractures were observed and the cracks' propagating paths in both directional specimens are described. The effects of heat treatment on the cracks' initiation and propagation were also investigated. Ultimately, a revised formula was developed to calculate the strength of the deposit + T6 2219-Al. The aforementioned formula, which takes into consideration the belt-like porosities-distributing feature, can scientifically describe the anisotropic properties in the material.

Mechanical Characterization and Material Modeling of Diabetic Aortas in a Rabbit Model.

PubMed

Tong, Jianhua; Yang, F; Li, X; Xu, X; Wang, G X

2018-03-01

Diabetes has been recognized as a major risk factor to cause macrovascular diseases and plays a key role in aortic wall remodeling. However, the effects of diabetes on elastic properties of aortas remain largely unknown and quantitative mechanical data are lacking. Thirty adult rabbits (1.6-2.2 kg) were collected and the type 1 diabetic rabbit model was induced by injection of alloxan. A total of 15 control and 15 diabetic rabbit (abdominal) aortas were harvested. Uniaxial and biaxial tensile tests were performed to measure ultimate tensile strength and to characterize biaxial mechanical behaviors of the aortas. A material model was fitted to the biaxial experimental data to obtain constitutive parameters. Histological and mass fraction analyses were performed to investigate the underlying microstructure and dry weight percentages of elastin and collagen in the control and the diabetic aortas. No statistically significant difference was found in ultimate tensile strength between the control and the diabetic aortas. Regarding biaxial mechanical responses, the diabetic aortas exhibited significantly lower extensibility and significantly higher tissue stiffness than the control aortas. Notably, tissue stiffening occurred in both circumferential and axial directions for the diabetic aortas; however, mechanical anisotropy does not change significantly. The material model was able to fit biaxial experimental data very well. Histology showed that a number of isolated foam cells were embedded in the diabetic aortas and hyperplasia of collagen was identified. The dry weight percentages of collagen within the diabetic aortas increased significantly as compared to the control aortas, whereas no significant change was found for that of elastin. Our data suggest that the diabetes impairs elastic properties and alters microstructure of the aortas and consequently, these changes may further contribute to complex aortic wall remodeling.

Surface Characterization Techniques: An Overview

NASA Technical Reports Server (NTRS)

Miyoshi, Kazuhisa

2002-01-01

To understand the benefits that surface modifications provide, and ultimately to devise better ones, it is necessary to study the physical, mechanical, and chemical changes they cause. This chapter surveys classical and leading-edge developments in surface structure and property characterization methodologies. The primary emphases are on the use of these techniques as they relate to surface modifications, thin films and coatings, and tribological engineering surfaces and on the implications rather than the instrumentation.

Evaluation of five CAD/CAM materials by microstructural characterization and mechanical tests: a comparative in vitro study.

PubMed

Sonmez, Nesrin; Gultekin, Pinar; Turp, Volkan; Akgungor, Gokhan; Sen, Deniz; Mijiritsky, Eitan

2018-01-08

Polymer infiltrated ceramics and nano-ceramic resins are the new restorative materials which have been developed in order to enhance the adverse properties of glass-matrix ceramics and resin composites. The aim of the present in vitro study was to evaluate the characteristics of various CAD/CAM materials through mechanical, microstructural, and SEM analysis. Five test groups (n = 22) were formed by using the indicated CAD/CAM blocks: VITA Enamic (VITA Zahnfabrik), Lava Ultimate (3 M ESPE), IPS e.max CAD (Ivoclar Vivadent), IPS Empress CAD (Ivoclar Vivadent), and VITA Mark II (VITA Zahnfabrik). Two specimens from each test group were used for XRD and EDS analysis. Remaining samples were divided into two subgroups (n = 10). One subgroup specimens were thermocycled (5 °C to 55 °C, 30s, 10,000 cycles) whereas the other were not. All of the specimens were evaluated in terms of flexural strength, Vickers hardness, and fracture toughness. Results were statistically analyzed using two-way ANOVA, one-way ANOVA, Tukey's HSD, and Student's t tests (α = .05). Fractured specimens were evaluated using SEM. The highest Vickers microhardness value was found for VITA Mark II (p < .001), however flexural strength and fracture toughness results were lowest conversely (p < .05). IPS e.max CAD was found to have the highest flexural strength (p < .001). Fracture toughness of IPS e.max CAD was also higher than other tested block materials (p < .001). Lava Ultimate and VITA Enamic's mechanical properties were affected negatively from thermocycling (p < .05). Microhardness, flexural strength, and fracture toughness values of Lava Ultimate and VITA Enamic were found to be similar to VITA Mark II and IPS Empress CAD groups. It should be realised that simulated aging process seem to affect ceramic-polymer composite materials more significantly than glass ceramics.

Functional Materials from Polymeric Ionic Liquids

NASA Astrophysics Data System (ADS)

Segalman, Rachel; Sanoja, Gabriel; Michenfelder-Schauser, Nicole; Mitragotri, Samir; Seshadri, Ram

Ionic liquids (IL's) have been suggested for applications as diverse as solubilizing cellulose, antimicrobial treatments, and electrolytes in batteries due to their molten salt properties. A polymeric cation (such as imidazolium) is an excellent host for any associated anion. As a result, polymerized ionic liquids are not just solid counterparts to IL's, but are shown to be vectors for the inclusion of a wide variety of functionalities ranging from multi-valent ions to magnetic anions. Moreover, PIL block copolymers allow orthogonal control over mechanical and morphological properties, ultimately leading to a conceptual framework for processable, tunable, multifunctional materials.

Mechanical properties of a Gum-type Ti-Nb-Zr-Fe-O alloy

NASA Astrophysics Data System (ADS)

Nocivin, Anna; Cinca, Ion; Raducanu, Doina; Cojocaru, Vasile Danut; Popovici, Ion Alexandru

2017-08-01

A new Gum-type alloy (Ti-Nb-Zr-Fe-O) in which Fe is used instead of Ta was subjected to a particular thermomechanical processing scheme to assess whether its mechanical characteristics (fine β-grains with high strength and low modulus) render it suitable as a biomedical implant material. After a homogenization treatment followed by cold-rolling with 50% reduction, the specimens were subjected to one of three different recrystallization treatments at 1073, 1173, and 1273 K. The structural and mechanical properties of all of the treated specimens were analyzed. The mechanical characterization included tensile tests, microhardness determinations, and fractography by scanning electron microscopy. The possible deformation mechanisms were discussed using the \\overline {Bo} - \\overline {Md} diagram. By correlating all of the experimental results, we concluded that the most promising processing variant corresponds to recrystallization at 1073 K, which can provide suitable mechanical characteristics for this type of alloys: high yield and ultimate tensile strengths (1038 and 1083 MPa, respectively), a low modulus of elasticity (62 GPa), and fine crystalline grain size (approximately 50 μm).

The Structure and Mechanical Properties of High-Strength Bulk Ultrafine-Grained Cobalt Prepared Using High-Energy Ball Milling in Combination with Spark Plasma Sintering

PubMed Central

Marek, Ivo; Vojtěch, Dalibor; Michalcová, Alena; Kubatík, Tomáš František

2016-01-01

In this study, bulk ultrafine-grained and micro-crystalline cobalt was prepared using a combination of high-energy ball milling and subsequent spark plasma sintering. The average grain sizes of the ultrafine-grained and micro-crystalline materials were 200 nm and 1 μm, respectively. Mechanical properties such as the compressive yield strength, the ultimate compressive strength, the maximum compressive deformation and the Vickers hardness were studied and compared with those of a coarse-grained as-cast cobalt reference sample. The bulk ultrafine-grained sample showed an ultra-high compressive yield strength that was greater than 1 GPa, which is discussed with respect to the preparation technique and a structural investigation. PMID:28773514

Thermal-mechanical properties of epoxy-impregnated Bi-2212/Ag composite

DOE PAGES

Li, Pei; Wang, Yang; Fermi National Accelerator Lab.; ...

2014-11-26

In this study, knowledge of the thermal-mechanical properties of epoxy/superconductor/insulation composite is important for designing, fabricating, and operating epoxy impregnated high field superconducting magnets near their ultimate potentials. We report measurements of the modulus of elasticity, Poisson's ratio, and the coefficient of thermal contraction of epoxy-impregnated composite made from the state-of-the-art powder-in-tube multifilamentary Ag/Bi 2Sr 2CaCu 2O x round wire at room temperature and cryogenic temperatures. Stress-strain curves of samples made from single-strand and Rutherford cables were tested under both monotonic and cyclic compressive loads, with single strands insulated using a thin TiO 2 insulation coating and the Rutherford cablemore » insulated with a braided ceramic sleeve.« less

Valorisation of chicken feathers: Characterisation of chemical properties.

PubMed

Tesfaye, Tamrat; Sithole, Bruce; Ramjugernath, Deresh; Chunilall, Viren

2017-10-01

The characterisation of the chemical properties of the whole chicken feather and its fractions (barb and rachis), was undertaken to identify opportunities for valorizing this waste product. The authors have described the physical, morphological, mechanical, electrical and thermal properties of the chicken feathers and related them to potential valorisation routes of the waste. However, identification of their chemical properties is necessary to complete a comprehensive description of chicken feather fractions. Hence, the chicken feathers were thoroughly characterised by proximate and ultimate analyses, elemental composition, spectroscopic analyses, durability in different solvents, burning test, and hydrophobicity. The proximate analysis of chicken feathers revealed the following compositions: crude lipid (0.83%), crude fibre (2.15%), crude protein (82.36%), ash (1.49%), NFE (1.02%) and moisture content (12.33%) whereas the ultimate analyses showed: carbon (64.47%), nitrogen (10.41%), oxygen (22.34%), and sulphur (2.64%). FTIR analysis revealed that the chicken feather fractions contain amide and carboxylic groups indicative of proteinious functional groups; XRD showed a crystallinity index of 22. Durability and burning tests confirmed that feathers behaved similarly to animal fibre. This reveals that chicken feather can be a valuable raw material in textile, plastic, cosmetics, pharmaceuticals, biomedical and bioenergy industries. Copyright © 2017 Elsevier Ltd. All rights reserved.

Effect of Terminal Modification on the Molecular Assembly and Mechanical Properties of Protein-Based Block Copolymers.

PubMed

Jacobsen, Matthew M; Tokareva, Olena S; Ebrahimi, Davoud; Huang, Wenwen; Ling, Shengjie; Dinjaski, Nina; Li, David; Simon, Marc; Staii, Cristian; Buehler, Markus J; Kaplan, David L; Wong, Joyce Y

2017-09-01

Accurate prediction and validation of the assembly of bioinspired peptide sequences into fibers with defined mechanical characteristics would aid significantly in designing and creating materials with desired properties. This process may also be utilized to provide insight into how the molecular architecture of many natural protein fibers is assembled. In this work, computational modeling and experimentation are used in tandem to determine how peptide terminal modification affects a fiber-forming core domain. Modeling shows that increased terminal molecular weight and hydrophilicity improve peptide chain alignment under shearing conditions and promote consolidation of semicrystalline domains. Mechanical analysis shows acute improvements to strength and elasticity, but significantly reduced extensibility and overall toughness. These results highlight an important entropic function that terminal domains of fiber-forming peptides exhibit as chain alignment promoters, which ultimately has notable consequences on the mechanical behavior of the final fiber products. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A molecular dynamics study of the role of molecular water on the structure and mechanics of amorphous geopolymer binders.

PubMed

Sadat, Mohammad Rafat; Bringuier, Stefan; Asaduzzaman, Abu; Muralidharan, Krishna; Zhang, Lianyang

2016-10-07

In this paper, molecular dynamics simulations are used to study the effect of molecular water and composition (Si/Al ratio) on the structure and mechanical properties of fully polymerized amorphous sodium aluminosilicate geopolymer binders. The X-ray pair distribution function for the simulated geopolymer binder phase showed good agreement with the experimentally determined structure in terms of bond lengths of the various atomic pairs. The elastic constants and ultimate tensile strength of the geopolymer binders were calculated as a function of water content and Si/Al ratio; while increasing the Si/Al ratio from one to three led to an increase in the respective values of the elastic stiffness and tensile strength, for a given Si/Al ratio, increasing the water content decreased the stiffness and strength of the binder phase. An atomic-scale analysis showed a direct correlation between water content and diffusion of alkali ions, resulting in the weakening of the AlO 4 tetrahedral structure due to the migration of charge balancing alkali ions away from the tetrahedra, ultimately leading to failure. In the presence of water molecules, the diffusion behavior of alkali cations was found to be particularly anomalous, showing dynamic heterogeneity. This paper, for the first time, proves the efficacy of atomistic simulations for understanding the effect of water in geopolymer binders and can thus serve as a useful design tool for optimizing composition of geopolymers with improved mechanical properties.

Effect of Strain Rate on Mechanical Properties of Wrought Sintered Tungsten at Temperatures above 2500 F

NASA Technical Reports Server (NTRS)

Sikora, Paul F.; Hall, Robert W.

1961-01-01

Specimens of wrought sintered commercially pure tungsten were made from 1/8-inch swaged rods. All the specimens were recrystallized at 4050 F for 1 hour prior to testing at temperatures from 2500 to 4000 F at various strain rates from 0.002 to 20 inches per inch per minute. Results showed that, at a constant temperature, increasing the strain rate increased the ultimate tensile strength significantly. The effects of both strain rate and temperature on the ultimate tensile strength of tungsten may be correlated by the linear parameter method of Manson and Haferd and may be used to predict the ultimate tensile strength at higher temperatures, 4500 and 5000 F. As previously reported, ductility, as measured by reduction of area in a tensile test, decreases with increasing temperature above about 3000 F. Increasing the strain rate at temperatures above 3000 F increases the ductility. Fractures are generally transgranular at the higher strain rates and intergranular at the lower strain rates.

Mechanical design of mussel byssus: material yield enhances attachment strength

PubMed

Bell; Gosline

1996-01-01

The competitive dominance of mussels in the wave-swept rocky intertidal zone is in part due to their ability to maintain a secure attachment. Mussels are tethered to the substratum by a byssus composed of numerous extracellular, collagenous threads secreted by the foot. Each byssal thread has three serially arranged parts: a corrugated proximal region, a smooth distal region and an adhesive plaque. This study examines the material and structural properties of the byssal threads of three mussel species: Mytilus californianus, M. trossulus, and M. galloprovincialis. Tensile tests in general reveal similar material properties among species: the proximal region has a lower initial modulus, a lower ultimate stress and a higher ultimate strain than the distal region. The distal region also yields at a stress well below its ultimate value. In whole thread tests, the proximal region and adhesive plaque are common sites of structural failure and are closely matched in strength, while the distal region appears to be excessively strong. We propose that the high strength of the distal region is the byproduct of a material designed to yield and extend before structural failure occurs. Experimental and theoretical evidence is presented suggesting that thread yield and extensibility provide two important mechanisms for increasing the overall attachment strength of the mussel: (1) the reorientation of threads towards the direction of applied load, and (2) the 'recruitment' of more threads into tension and the consequent distribution of applied load over a larger cross-sectional area, thereby reducing the stress on each thread. This distal region yield behavior is most striking for M. californianus and may be a key to its success in extreme wave-swept environments.

Matrix density effects on the mechanical properties of SiC/RBSN composites

NASA Technical Reports Server (NTRS)

Bhatt, Ramakrishna T.; Kiser, James D.

1990-01-01

The room temperature mechanical properties were measured for SiC fiber reinforced reaction-bonded silicon nitride composites (SiC/RBSN) of different densities. The composites consisted of approx. 30 vol percent uniaxially aligned 142 micron diameter SiC fibers (Textron SCS-6) in a reaction-bonded Si3N4 matrix. The composite density was varied by changing the consolidation pressure during RBSN processing and by hot isostatically pressing the SiC/RBSN composites. Results indicate that as the consolidation pressure was increased from 27 to 138 MPa, the average pore size of the nitrided composites decreased from 0.04 to 0.02 microns and the composite density increased from 2.07 to 2.45 gm/cc. Nonetheless, these improvements resulted in only small increases in the first matrix cracking stress, primary elastic modulus, and ultimate tensile strength values of the composites. In contrast, HIP consolidation of SiC/RBSN resulted in a fully dense material whose first matrix cracking stress and elastic modulus were approx. 15 and 50 percent higher, respectively, and ultimate tensile strength values were approx. 40 percent lower than those for unHIPed SiC/RBSN composites. The modulus behavior for all specimens can be explained by simple rule-of-mixture theory. Also, the loss in ultimate strength for the HIPed composites appears to be related to a degradation in fiber strength at the HIP temperature. However, the density effect on matrix fracture strength was much less than would be expected based on typical monolithic Si3N4 behavior, suggesting that composite theory is indeed operating. Possible practical implications of these observations are discussed.

Interrelationships Between Morphometric, Densitometric, and Mechanical Properties of Teeth in 5-Month-Old Polish Merino Sheep.

PubMed

Tatara, Marcin R; Szabelska, Anna; Krupski, Witold; Tymczyna, Barbara; Łuszczewska-Sierakowska, Iwona; Bieniaś, Jarosław; Ostapiuk, Monika

2018-06-01

Interrelationships between morphological, densitometric, and mechanical properties of deciduous mandibular teeth (incisors, canine, second premolar) were investigated. To perform morphometric, densitometric, and mechanical analyses, teeth were obtained from 5-month-old sheep. Measurements of mean volumetric tooth mineral density and total tooth volume were performed using quantitative computed tomography. Microcomputed tomography was used to measure total enamel volume, volumetric enamel mineral density, total dentin volume, and volumetric dentin mineral density. Maximum elastic strength and ultimate force of teeth were determined using 3-point bending and compression tests. Pearson correlation coefficients were determined between all investigated variables. Mutual dependence was observed between morphological and mechanical properties of the investigated teeth. The highest number of positive correlations of the investigated parameters was stated in first incisor indicating its superior predictive value of tooth quality and masticatory organ function in sheep. Positive correlations of the volumetric dentin mineral density in second premolar with final body weight may indicate predictive value of this parameter in relation with growth rate in sheep. Evaluation of deciduous tooth properties may prove helpful for breeding selection and further reproduction of sheep possessing favorable traits of teeth and better masticatory organ function, leading to improved performance and economic efficiency of the flock.

The FP7 ULTimateCO2 project: a study of the long term fate of CO2

NASA Astrophysics Data System (ADS)

Audigane, Pascal; Waldmann, Svenja; Pearce, Jonathan; Dimier, Alain; Le Gallo, Yann; Frykman, Peter; Maurand, Nicolas; Gherardi, Fabrizio; Yalamas, Thierry; Cremer, Holger; Spiers, Chris; Nussbaum, Christophe

2014-05-01

The objectives of the European FP7 ULTimateCO2 project are to study specific processes that could influence the long-term fate of geologically stored CO2, mainly: the trapping mechanisms occurring in the storage reservoir, the influence of fluid-rock interactions on mechanical integrity of caprock and well vicinity, and also the modifications induced at the regional scale (brine displacement, fault reactivation, hydrogeology changes...). A comprehensive approach combining laboratory experiments, numerical modeling and natural analogue studies is developed to assess all the processes mentioned above. A collection of data has been generated from natural and industrial (oil industry) analogues on the fluid flow and mechanical properties, structure, and mineralogy of faults and fractures that could affect the long-term storage capacity of underground CO2 storage sites. To address geochemical trapping at reservoir scale, an experimental approach is developed using sandstone core materials in batch reactive mode with CO2 and impurities at reservoir pressure and temperature conditions. Three inter-related lines of laboratory experiments investigate the long-term evolution of the mechanical properties and sealing integrity of fractured and faulted caprocks using Opalinus clay of Mont Terri Gallery (Switzerland), an analogue for caprock well investigated in the past for nuclear waste disposal purpose. To evaluate the interactions between CO2 (and formation fluid) and the well environment (formation, cement, casing) and to assess the consequences of these interactions on the transport properties of well materials, a 1 to 1 scale experiment has been set in the Mont Terri Gallery Opalinus clay to reproduce classical well objects (cemented annulus, casing and cement plug) perforating caprock formations. An extensive program of numerical modeling is also developed to calibrate, to reproduce and to extrapolate the experimental results at longer time scales including uncertainty assessment methods. www.ultimateco2.eu

Effect of Holding Pressure on Microstructure and Mechanical Properties of A356 Aluminum Alloy

NASA Astrophysics Data System (ADS)

Wu, Xiaoyan; Zhang, Huarui; Ma, Zhen; Jia, Lina; Zhang, Hu

2018-02-01

In this study, the effect of holding pressure on microstructure and mechanical properties of low-pressure die cast A356 aluminum alloy was investigated. The results showed that the application of high holding pressure (300 kPa) generated castings with denser structure and superior mechanical properties. By increasing the holding pressure up to 300 kPa, the size of secondary dendrite arm spacing greatly reduced by 22.7% at the cooling rate of 1°C/s and decreased by 12.8% at 10°C/s. The Feret's diameter and aspect ratio of eutectic silicon particles decreased by 8.4 and 5.1% at the cooling rate of 1°C/s and decreased by 9.3 and 6.4% at 10°C/s, respectively. Meanwhile, the density of A356 aluminum alloy increased to 2.678 g/cm3 and the area fraction of porosity decreased to 0.035%. Thus, tensile properties of A356 aluminum alloy obtained at high holding pressure were enhanced, especially the ductility. All these could be associated with the better filling capability and faster cooling rate caused by high holding pressure. In the analytical range of experimental conditions, the correlation of mechanical properties with process parameters was established by statistical models to predict the ultimate tensile strength and elongation of low-pressure die cast A356 aluminum alloy.

Evolution of the structure and mechanical properties of sheets of the Al-4.7Mg-0.32Mn-0.21Sc-0.09Zr alloy due to deformation accumulated upon rolling

NASA Astrophysics Data System (ADS)

Zolotorevskiy, V. S.; Dobrojinskaja, R. I.; Cheverikin, V. V.; Khamnagdaeva, E. A.; Pozdniakov, A. V.; Levchenko, V. S.; Besogonova, E. S.

2016-11-01

The mechanical properties and microstructure of sheets of an Al-4.7Mg-0.32Mn-0.21Sc-0.09Zr alloy deformed and annealed after rolling have been investigated. The total accumulated true strain was ɛf = 3.33-5.63, and the true strain at room temperature and at 200 °C was ɛc = 0.25-2.3. The strength properties of the sheets (yield stress σ0.2 = 495 MPa and ultimate tensile strength σu = 525 MPa) in the deformed state were greater than those after equal-channel angular pressing (ECAP) deformation. The mechanical properties of the deformed sheets after annealing depended on the size of subgrains inside the deformed grains bands with high-angle grain boundaries (HABs). With the increase in the annealing temperature from 150 to 300°C, the subgrain size increased from 80 to 300 nm. The relative elongation δ in the as-cast state and after annealing at 200-250°C (δ = 40-50%) was higher than that after annealing at 300-370°C (δ = 24-29%).

Evaluation of the Elastic Properties of Thirteen Silicone Interocclusal Recording Materials

PubMed Central

Zietek, Marek

2016-01-01

Background. Addition silicones are popular as dental impression materials and are used in bite registration procedures. Objective. This study aimed to compare the postsetting elasticities and other mechanical properties of thirteen addition silicone interocclusal recording materials. Materials and Methods. The following materials were investigated: Colorbite D, Futar D, Genie Bite, Jet Blue Bite fast, Memoreg 2, O-Bite, Occlufast Rock, Omni-Bite Plus, Regidur i, Registrado X-tra, Regofix transparent, StoneBite, and Variotime Bite. Thirty specimens of each material were tested. The elasticities and strengths of the materials were measured with a universal testing machine, and computer software was used to determine the E-moduli, ultimate tensile strengths, and ultimate elongations of the specimens. Results. The results were subjected to statistical analysis using the Kruskal-Wallis test (p ≤ 0.05). The statistics revealed that the mean E-modulus values varied significantly across the materials (p = 0.000) and were highest for the StoneBite and Registrado X-tra and lowest for the Regofix transparent. The ultimate tensile strengths were highest for the Regofix transparent and Registrado X-tra (p = 0.000) and lowest for the Jet Blue Bite fast and Memoreg 2 (p = 0.000). The elongation percentages at the point of breaking varied significantly across the materials (p = 0.000); the lowest value was observed for the StoneBite, whereas the Regofix transparent nearly doubled original length. Conclusions. The authors concluded that materials with the high E-moduli and great ultimate tensile strengths may be most useful clinically. Registrado X-tra and StoneBite best met these criteria. PMID:27747239

Plasma-modified graphene nanoplatelets and multiwalled carbon nanotubes as fillers for advanced rubber composites

NASA Astrophysics Data System (ADS)

Sicinski, M.; Gozdek, T.; Bielinski, D. M.; Szymanowski, H.; Kleczewska, J.; Piatkowska, A.

2015-07-01

In modern rubber industry, there still is a room for new fillers, which can improve the mechanical properties of the composites, or introduce a new function to the material. Modern fillers like carbon nanotubes or graphene nanoplatelets (GnP), are increasingly applied in advanced polymer composites technology. However, it might be hard to obtain a well dispersed system for such systems. The polymer matrix often exhibits higher surface free energy (SFE) level with the filler, which can cause problems with polymer-filler interphase adhesion. Filler particles are not wet properly by the polymer, and thus are easier to agglomerate. As a consequence, improvement in the mechanical properties is lower than expected. In this work, multi-walled carbon nanotubes (MWCNT) and GnP surface were modified with low-temperature plasma. Attempts were made to graft some functionalizing species on plasma-activated filler surface. The analysis of virgin and modified fillers’ SFE was carried out. MWCNT and GnP rubber composites were produced, and ultimately, their morphology and mechanical properties were studied.

Electron beam detection of a Nanotube Scanning Force Microscope.

PubMed

Siria, Alessandro; Niguès, Antoine

2017-09-14

Atomic Force Microscopy (AFM) allows to probe matter at atomic scale by measuring the perturbation of a nanomechanical oscillator induced by near-field interaction forces. The quest to improve sensitivity and resolution of AFM forced the introduction of a new class of resonators with dimensions at the nanometer scale. In this context, nanotubes are the ultimate mechanical oscillators because of their one dimensional nature, small mass and almost perfect crystallinity. Coupled to the possibility of functionalisation, these properties make them the perfect candidates as ultra sensitive, on-demand force sensors. However their dimensions make the measurement of the mechanical properties a challenging task in particular when working in cavity free geometry at ambient temperature. By using a focused electron beam, we show that the mechanical response of nanotubes can be quantitatively measured while approaching to a surface sample. By coupling electron beam detection of individual nanotubes with a custom AFM we image the surface topography of a sample by continuously measuring the mechanical properties of the nanoresonators. The combination of very small size and mass together with the high resolution of the electron beam detection method offers unprecedented opportunities for the development of a new class of nanotube-based scanning force microscopy.

Characterization of fine abrasive particles for optical fabrication

NASA Astrophysics Data System (ADS)

Funkenbusch, Paul D.; Zhou, Y. Y.; Takahashi, Toshio; Quesnel, David J.; Lambropoulos, John C.

1995-08-01

Material removal during fine grinding operations is accomplished primarily by the action of individual abrasive particles on the glass surface. The mechanical properties of the abrasive are therefore important. Unfortunately it is difficult to directly measure the mechanical response of abrasives once they reach the scale of approximately 10 microns. As a result mechanical properties of fine abrasives are sometimes characterized in terms of an empirical `friability', based on the response of the abrasive to crushing by a metal ball in a vial. In this paper we report on modeling/experiments designed to more precisely quantify the mechanical properties of fine abrasives and ultimately to relate them to the conditions experienced by bound particles during grinding. Experiments have been performed on various types and sizes of diamond abrasives. The response of the particles is a strong function of the loading conditions and can be tracked by changing the testing parameters. Diamond size is also found to play a critical role, with finer diamonds less susceptible to fracture. A micromechanical model from the literature is employed estimate the forces likely to be seen during testing. We are also developing dynamic models to better predict the forces experienced during `friability' testing as a function of the testing parameters.

Tensile, Creep, and Fatigue Behaviors of 3D-Printed Acrylonitrile Butadiene Styrene

NASA Astrophysics Data System (ADS)

Zhang, Hanyin; Cai, Linlin; Golub, Michael; Zhang, Yi; Yang, Xuehui; Schlarman, Kate; Zhang, Jing

2018-01-01

Acrylonitrile butadiene styrene (ABS) is a widely used thermoplastics in 3D printing. However, there is a lack of thorough investigation of the mechanical properties of 3D-printed ABS components, including orientation-dependent tensile strength and creep fatigue properties. In this work, a systematic characterization is conducted on the mechanical properties of 3D-printed ABS components. Specifically, the effect of printing orientation on the tensile and creep properties is investigated. The results show that, in tensile tests, the 0° printing orientation has the highest Young's modulus of 1.81 GPa, and ultimate strength of 224 MPa. In the creep test, the 90° printing orientation has the lowest k value of 0.2 in the plastics creep model, suggesting 90° is the most creep resistant direction. In the fatigue test, the average cycle number under load of 30 N is 3796 cycles. The average cycle number decreases to 128 cycles when the load is 60 N. Using the Paris law, with an estimated crack size of 0.75 mm, and stress intensity factor is varied from 352 to 700 N√ m, the derived fatigue crack growth rate is 0.0341 mm/cycle. This study provides important mechanical property data that is useful for applying 3D-printed ABS in engineering applications.

A Comparison of the Quasi-static Mechanical and Nonlinear Viscoelastic Properties of the Human Semitendinosus and Gracilis Tendons

PubMed Central

Abramowitch, Steven D.; Zhang, Xiaoyan; Curran, Molly; Kilger, Robert

2010-01-01

Background Over fifty-percent of anterior cruciate ligament reconstructions are performed using semitendinosus and gracilis tendon autografts. Despite their increased use, there remains little quantitative data on their mechanical behavior. Therefore, the objective of this study was to investigate the quasi-static mechanical and nonlinear viscoelastic properties of human semitendinosus and gracilis tendons, as well as the variation of these properties along their length. Methods Specimens were subjected to a series of uniaxial tensile tests: one-hour static stress-relaxation test, 30-cycle cyclic stress-relaxation test and load to failure test. To describe the nonlinear viscoelastic behavior, the quasi-linear viscoelastic theory was utilized to model data from the static stress relaxation experiment. Findings The constants describing the viscoelastic behavior were similar between the proximal and distal halves of the gracilis tendon. The proximal half of the semitendinosus tendon, however, had a greater viscous response than its distal half, which was also significantly higher than the proximal gracilis tendon. In terms of the quasi-static mechanical properties, the properties were similar between the proximal and distal halves of the semitendinosus tendon. However, the distal gracilis tendon showed a significantly higher tangent modulus and ultimate stress compared to its proximal half, which was also significantly higher than the distal semitendinosus tendon. Interpretation The results of this study demonstrate differences between the semitendinosus and gracilis tendons in terms of their quasi-static mechanical and nonlinear viscoelastic properties. These results are important for establishing surgical preconditioning protocols and graft selection. PMID:20092917

High Temperature Mechanical Characterization of Ceramic Matrix Composites

NASA Technical Reports Server (NTRS)

Gyekenyesi, John Z.

1998-01-01

A high temperature mechanical characterization laboratory has been assembled at NASA Lewis Research Center. One contribution of this work is to test ceramic matrix composite specimens in tension in environmental extremes. Two high temperature tensile testing systems were assembled. The systems were assembled based on the performance and experience of other laboratories and meeting projected service conditions for the materials in question. The systems use frames with an electric actuator and a center screw. A PC based data acquisition and analysis system is used to collect and analyze the data. Mechanical extensometers are used to measure specimen strain. Thermocouples, placed near the specimen, are used to measure the specimen gage section temperature. The system for testing in air has a resistance element furnace with molybdenum disilicide elements and pneumatic grips with water cooling attached to hydraulic alignment devices. The system for testing in an inert gas has a graphite resistance element furnace in a chamber with rigidly mounted, water cooled, hydraulically actuated grips. Unidirectional SiC fiber reinforced reaction bonded Si3N4 and triaxially woven, two dimensional, SiC fiber reinforced enhanced SiC composites were tested in unidirectional tension. Theories for predicting the Young's modulus, modulus near the ultimate strength, first matrix cracking stress, and ultimate strength were applied and evaluated for suitability in predicting the mechanical behavior of SiC/RBSN and enhanced SiC/SiC composites. The SiC/RBSN composite exhibited pseudo tough behavior (increased area under the stress/strain curve) from 22 C to 1500 C. The rule of mixtures provides a good estimate of the Young's modulus of the SiC/RBSN composite using the constituent properties from room temperature to 1440 C for short term static tensile tests in air or nitrogen. The rule of mixtures significantly overestimates the secondary modulus near the ultimate strength. The ACK theory provides the best approximation of the first matrix cracking stress when residual stresses are ignored. The theory of Cao and Thouless, based on Weibull statistics, gave the best prediction for the composite ultimate strength. The enhanced SiC/SiC composite exhibited nonlinear stress/strain behavior from 24 C to 1370 C in air with increased ultimate strain when compared to monolithic SiC. The theory of Yang and Chou with the assumption of a frictional fiber/matrix interface provided the best estimate of the Young's modulus. The theory of Cao and Thouless gave the best estimate for the ultimate strength.

Mechanical properties of contemporary composite resins and their interrelations.

PubMed

Thomaidis, Socratis; Kakaboura, Afrodite; Mueller, Wolf Dieter; Zinelis, Spiros

2013-08-01

To characterize a spectrum of mechanical properties of four representative types of modern dental resin composites and to investigate possible interrelations. Four composite resins were used, a microhybrid (Filtek Z-250), a nanofill (Filtek Ultimate), a nanohybrid (Majesty Posterior) and an ormocer (Admira). The mechanical properties investigated were Flexural Modulus and Flexural Strength (three point bending), Brinell Hardness, Impact Strength, mode I and mode II fracture toughness employing SENB and Brazilian tests and Work of Fracture. Fractographic analysis was carried out in an SEM to determine the origin of fracture for specimens subjected to SENB, Brazilian and Impact Strength testing. The results were statistically analyzed employing ANOVA and Tukey post hoc test (a=0.05) while Pearson correlation was applied among the mechanical properties. Significant differences were found between the mechanical properties of materials tested apart from mode I fracture toughness measured by Brazilian test. The latter significantly underestimated the mode I fracture toughness due to analytical limitations and thus its validity is questionable. Fractography revealed that the origin of fracture is located at notches for fracture toughness tests and contact surface with pendulum for Impact Strength testing. Pearson analysis illustrated a strong correlation between modulus of elasticity and hardness (r=0.87) and a weak negative correlation between Work of Fracture and Flexural Modulus (r=-0.46) and Work of Fracture and Hardness (r=-0.44). Weak correlations were also allocated between Flexural Modulus and Flexural Strength (r=0.40), Flexural Strength and Hardness (r=0.39), and Impact Strength and Hardness (r=0.40). Since the four types of dental resin composite tested exhibited large differences among their mechanical properties differences in their clinical performance is also anticipated. Copyright © 2013 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

The Effects of Carbon Nanotubes on the Mechanical and Wear Properties of AZ31 Alloy

PubMed Central

Zhou, Mingyang; Qu, Xiaoni; Ren, Lingbao; Fan, Lingling; Zhang, Yuwenxi; Guo, Yangyang; Quan, Gaofeng; Liu, Bin; Sun, Hao

2017-01-01

Carbon nanotube (CNT)-reinforced AZ31 matrix nanocomposites were successfully fabricated using a powder metallurgy method followed by hot extrusion. The influence of CNTs on microstructures, mechanical properties, and wear properties were systematically investigated by optical microscope (OM), scanning electron microscope (SEM), X-ray diffraction (XRD), hardness test, tensile test, and wear test. The results revealed that the nanocomposites showed a slightly smaller grain size compared with the matrix and uniform distribution that CNTs could achieve at proper content. As a result, the addition of CNTs could weaken basal plane texture. However, the yield strength and ultimate tensile strength of the composites were enhanced as the amount of CNTs increased up to 2.0 wt. %, reaching maximum values of 241 MPa (+28.2%) and 297 MPa (+6.1%), respectively. The load transfer mechanism, Orowan mechanism, and thermal mismatch mechanism played important roles in the enhancement of the yield strength, and several classical models were employed to predict the theoretical values. The effect of CNT content on the friction coefficient and weight loss of the nanocomposites was also studied. The relationships between the amount of CNTs, the friction coefficient, and weight loss could be described by the exponential decay model and the Boltzmann model, respectively. PMID:29207543

Reference point indentation is insufficient for detecting alterations in traditional mechanical properties of bone under common experimental conditions.

PubMed

Krege, John B; Aref, Mohammad W; McNerny, Erin; Wallace, Joseph M; Organ, Jason M; Allen, Matthew R

2016-06-01

Reference point indentation (RPI) was developed as a novel method to assess mechanical properties of bone in vivo, yet it remains unclear what aspects of bone dictate changes/differences in RPI-based parameters. The main RPI parameter, indentation distance increase (IDI), has been proposed to be inversely related to the ability of bone to form/tolerate damage. The goal of this work was to explore the relationshipre-intervention RPI measurebetween RPI parameters and traditional mechanical properties under varying experimental conditions (drying and ashing bones to increase brittleness, demineralizing bones and soaking in raloxifene to decrease brittleness). Beams were machined from cadaveric bone, pre-tested with RPI, subjected to experimental manipulation, post-tested with RPI, and then subjected to four-point bending to failure. Drying and ashing significantly reduced RPI's IDI, as well as ultimate load (UL), and energy absorption measured from bending tests. Demineralization increased IDI with minimal change to bending properties. Ex vivo soaking in raloxifene had no effect on IDI but tended to enhance post-yield behavior at the structural level. These data challenge the paradigm of an inverse relationship between IDI and bone toughness, both through correlation analyses and in the individual experiments where divergent patterns of altered IDI and mechanical properties were noted. Based on these results, we conclude that RPI measurements alone, as compared to bending tests, are insufficient to reach conclusions regarding mechanical properties of bone. This proves problematic for the potential clinical use of RPI measurements in determining fracture risk for a single patient, as it is not currently clear that there is an IDI, or even a trend of IDI, that can determine clinically relevant changes in tissue properties that may contribute to whole bone fracture resistance. Copyright © 2016 Elsevier Inc. All rights reserved.

Reference point indentation is insufficient for detecting alterations in traditional mechanical properties of bone under common experimental conditions

PubMed Central

Krege, John B.; Aref, Mohammad W.; McNerny, Erin; Wallace, Joseph M.; Organ, Jason M.; Allen, Matthew R.

2016-01-01

Reference point indentation (RPI) was developed as a novel method to assess mechanical properties of bone in vivo, yet it remains unclear what aspects of bone dictate changes/differences in RPI-based parameters. The main RPI parameter, indentation distance increase (IDI), has been proposed to be inversely related to the ability of bone to form/tolerate damage. The goal of this work was to explore the relationship between RPI parameters and traditional mechanical properties under varying experimental conditions (drying and ashing bones to increase brittleness, demineralizing bones and soaking in raloxifene to decrease brittleness). Beams were machined from cadaveric bone, pre-tested with RPI, subjected to experimental manipulation, post-tested with RPI, and then subjected to four-point bending to failure. Drying and ashing significantly reduced RPI’s IDI, as well as ultimate load (UL), and energy absorption measured from bending tests. Demineralization increased IDI with minimal change to bending properties. Ex vivo soaking in raloxifene had no effect on IDI but tended to enhance post-yield behavior at the structural level. These data challenge the paradigm of an inverse relationship between IDI and bone toughness, both through correlation analyses and in the individual experiments where divergent patterns of altered IDI and mechanical properties were noted. Based on these results, we conclude that RPI measurements alone, as compared to bending tests, are insufficient to reach conclusions regarding mechanical properties of bone. This proves problematic for the potential clinical use of RPI measurements in determining fracture risk for a single patient, as it is not currently clear that there is an IDI, or even a trend of IDI, that can determine clinically relevant changes in tissue properties that may contribute to whole bone fracture resistance. PMID:27072518

Effect of TiC nano-particles on the mechanical properties of an Al-5Cu alloy after various heat treatments

NASA Astrophysics Data System (ADS)

Zhang, Qingquan; Zhang, Wei; Tian, Weisi; Zhao, Qinglong

2017-12-01

In this paper, the effects of TiC nano-particles on the mechanical properties of Al-5Cu alloy were investigated. Adding TiC nano-particles can effectively refine grain size and secondary dendritic arm. The ultimate tensile strength, yield strength and elongation of the Al-5Cu alloy in each of the three states (i.e. as-cast, solid-solution state and T6 state) were also improved by adding TiC nano-particles. Moreover, the elastic-plastic plane-strain fracture toughness (K J) and work of fracture ( wof) of Al-5Cu containing TiC were significantly higher than those of Al-5Cu without TiC after aging for 10 h. The addition of TiC nano-particles also led to finer and denser ‧ precipitates.

Effects of Changing Hot Rolling Direction on Microstructure, Texture and Mechanical Properties of Cu-2.7Be Sheets

NASA Astrophysics Data System (ADS)

Zhu, Daibo; Liu, Chuming; Yu, Haijun; Han, Tan

2018-03-01

A hot rolling scheme (cross-rolling and unidirectional rolling) was adopted to process Cu-2.7Be sheets used as multiplier dynodes in photomultiplier. The effects of changing rolling direction on microstructure, texture and mechanical properties were studied by a combination of XRD, EBSD and TEM. It was found that higher copper-type texture and lower brass texture intensity were obtained in the ultimately cross-rolling (CR) sheet compared with the unidirectional rolling (UR) sheet.The EBSD results indicated that the grain orientation from mainly < {101} > for UR sample turns to random for CR sample. Great enhancements in YS and UTS after unidirectional rolling were attributed to the massive and polygonal γ precipitates. The CR sample exhibited lower anisotropy, because of the increase of S and γ precipitates with spherical and tiny shape.

Hybrid MoS2/h-BN Nanofillers As Synergic Heat Dissipation and Reinforcement Additives in Epoxy Nanocomposites.

PubMed

Ribeiro, Hélio; Trigueiro, João Paulo C; Silva, Wellington M; Woellner, Cristiano F; Owuor, Peter S; Cristian Chipara, Alin; Lopes, Magnovaldo C; Tiwary, Chandra S; Pedrotti, Jairo J; Villegas Salvatierra, Rodrigo; Tour, James M; Chopra, Nitin; Odeh, Ihab N; Silva, Glaura G; Ajayan, Pulickel M

2017-09-26

Two-dimensional (2D) nanomaterials as molybdenum disulfide (MoS 2 ), hexagonal boron nitride (h-BN), and their hybrid (MoS 2 /h-BN) were employed as fillers to improve the physical properties of epoxy composites. Nanocomposites were produced in different concentrations and studied in their microstructure, mechanical and thermal properties. The hybrid 2D mixture imparted efficient reinforcement to the epoxy leading to increases of up to 95% in tensile strength, 60% in ultimate strain, and 58% in Young's modulus. Moreover, an enhancement of 203% in thermal conductivity was achieved for the hybrid composite as compared to the pure polymer. The incorporation of MoS 2 /h-BN mixture nanofillers in epoxy resulted in nanocomposites with multifunctional characteristics for applications that require high mechanical and thermal performance.

Microstructure and Mechanical Property Change During FSW and GTAW of Al6061 Alloy

NASA Astrophysics Data System (ADS)

Fahimpour, V.; Sadrnezhaad, S. K.; Karimzadeh, F.

2013-05-01

The variation of morphology and mechanical properties of Al6061 automotive aluminum alloy due to friction stir welding (FSW) and gas tungsten arc welding (GTAW) was investigated by optical metallography, scanning electron microscopy, microhardness measurement, X-ray diffraction, tensile testing, and fractography. The center-line dendrite emergence and microhardness reduction in the heat-affected zone were observed in the GTAW process. Although similar microhardness reduction with respect to the base metal was observed in the FSW samples, higher HVs were obtained for the FSW rather than the GTAW process at almost all heat-affected locations. Ultimate tensile strengths of the FSW and the GTAW samples in the transverse direction were ~0.57 and ~0.35 of the base metal, respectively. Post-weld aging improved the strength, but reduced the ductility of the welding.

TRIP effect in austenitic-martensitic VNS9-Sh steel at various strain rates

NASA Astrophysics Data System (ADS)

Terent'ev, V. F.; Slizov, A. K.; Prosvirnin, D. V.

2016-10-01

The mechanical properties of austenitic-martensitic VNS9-Sh (23Kh15N5AM3-Sh) steel are studied at a static strain rate from 4.1 × 10-5 to 17 × 10-3 s-1 (0.05-20 mm/min). It is found that, as the strain rate increases, the ultimate tensile strength decreases and the physical yield strength remains unchanged (≈1400 MPa). As the strain rate increases, the yield plateau remains almost unchanged and the relative elongation decreases continuously. Because of high microplastic deformation, the conventional yield strength is lower than the physical yield strength over the entire strain rate range under study. The influence of the TRIP effect on the changes in the mechanical properties of VNS9-Sh steel at various strain rates is discussed.

Strain-induced phase transition and electron spin-polarization in graphene spirals

PubMed Central

Zhang, Xiaoming; Zhao, Mingwen

2014-01-01

Spin-polarized triangular graphene nanoflakes (t-GNFs) serve as ideal building blocks for the long-desired ferromagnetic graphene superlattices, but they are always assembled to planar structures which reduce its mechanical properties. Here, by joining t-GNFs in a spiral way, we propose one-dimensional graphene spirals (GSs) with superior mechanical properties and tunable electronic structures. We demonstrate theoretically the unique features of electron motion in the spiral lattice by means of first-principles calculations combined with a simple Hubbard model. Within a linear elastic deformation range, the GSs are nonmagnetic metals. When the axial tensile strain exceeds an ultimate strain, however, they convert to magnetic semiconductors with stable ferromagnetic ordering along the edges. Such strain-induced phase transition and tunable electron spin-polarization revealed in the GSs open a new avenue for spintronics devices. PMID:25027550

Strain-induced phase transition and electron spin-polarization in graphene spirals.

PubMed

Zhang, Xiaoming; Zhao, Mingwen

2014-07-16

Spin-polarized triangular graphene nanoflakes (t-GNFs) serve as ideal building blocks for the long-desired ferromagnetic graphene superlattices, but they are always assembled to planar structures which reduce its mechanical properties. Here, by joining t-GNFs in a spiral way, we propose one-dimensional graphene spirals (GSs) with superior mechanical properties and tunable electronic structures. We demonstrate theoretically the unique features of electron motion in the spiral lattice by means of first-principles calculations combined with a simple Hubbard model. Within a linear elastic deformation range, the GSs are nonmagnetic metals. When the axial tensile strain exceeds an ultimate strain, however, they convert to magnetic semiconductors with stable ferromagnetic ordering along the edges. Such strain-induced phase transition and tunable electron spin-polarization revealed in the GSs open a new avenue for spintronics devices.

Tensile Deformation Temperature Impact on Microstructure and Mechanical Properties of AISI 316LN Austenitic Stainless Steel

NASA Astrophysics Data System (ADS)

Xiong, Yi; He, Tiantian; Lu, Yan; Ren, Fengzhang; Volinsky, Alex A.; Cao, Wei

2018-03-01

Uniaxial tensile tests were conducted on AISI 316LN austenitic stainless steel from - 40 to 300 °C at a rate of 0.5 mm/min. Microstructure and mechanical properties of the deformed steel were investigated by optical, scanning and transmission electron microscopies, x-ray diffraction, and microhardness testing. The yield strength, ultimate tensile strength, elongation, and microhardness increase with the decrease in the test temperature. The tensile fracture morphology has the dimple rupture feature after low-temperature deformations and turns to a mixture of transgranular fracture and dimple fracture after high-temperature ones. The dominating deformation microstructure evolves from dislocation tangle/slip bands to large deformation twins/slip bands with temperature decrease. The deformation-induced martensite transformation can only be realized at low temperature, and its quantity increases with the decrease in the temperature.

Investigation into the energy-absorbing properties of multilayered circular thin-walled tube

NASA Astrophysics Data System (ADS)

Qi, Aidong; Liu, Chuanhua; Hu, Gongli; Gu, Hongjun

2002-05-01

With the rise in collision accident and the increase in requirement for resistance of blastproof structures in recent years, people attach much importance to the research and application of energy-absorbing device. In this paper the author calculates the specific strength, the specific hardness and ultimate internal force of a circular thin-walled tube by theoretic calculations, discusses the feasibility of using circular thin-walled tube as an energy-absorbing element, analyzes the energy-absorbing properties and the energy-absorbing mechanism through the energy-absorbing experiments using various materials and forms of arrangement, reaches the conclusion that the load-bearing capacity and energy-absorbing properties of multilayered tubes are superior to that of single tube, and puts forward the concept of 'grading tube'.

Stiff and tough: a comparative study on the tensile properties of shark skin.

PubMed

Creager, Shelby B; Porter, Marianne E

2018-02-01

In sharks, the skin is a biological composite with mineralized denticles embedded within a collagenous matrix. Swimming performance is enhanced by the dermal denticles on the skin, which have drag reducing properties produced by regional morphological variations and changes in density along the body. We used mechanical testing to quantify the effect of embedded mineralized denticles on the quasi-static tensile properties of shark skin to failure in four coastal species. We investigated regional differences in denticle density and skin properties by dissecting skin from the underlying fascia and muscle at 10 anatomical landmarks. Hourglass-shaped skin samples were extracted in the cranial to caudal orientation. Denticle density was quantified and varied significantly among both regions and species. We observed the greatest denticle densities in the cranial region of the body for the bonnethead, scalloped hammerhead, and bull sharks. Skin samples were then tested in tension until failure, stress strain curves were generated, and mechanical properties calculated. We found significant species and region effects for all three tensile mechanical properties. We report the greatest ultimate tensile strength, stiffness, and toughness near the cranial and lateral regions of the body for all 4 of the coastal species. We also report that denticle density increases with skin stiffness but decreases with toughness. Copyright © 2017 Elsevier GmbH. All rights reserved.

Multiscale mechanisms of nutritionally induced property variation in spider silks.

PubMed

Blamires, Sean J; Nobbs, Madeleine; Martens, Penny J; Tso, I-Min; Chuang, Wei-Tsung; Chang, Chung-Kai; Sheu, Hwo-Shuenn

2018-01-01

Variability in spider major ampullate (MA) silk properties at different scales has proven difficult to determine and remains an obstacle to the development of synthetic fibers mimicking MA silk performance. A multitude of techniques may be used to measure multiscale aspects of silk properties. Here we fed five species of Araneoid spider solutions that either contained protein or were protein deprived and performed silk tensile tests, small and wide-angle X-ray scattering (SAXS/WAXS), amino acid composition analyses, and silk gene expression analyses, to resolve persistent questions about how nutrient deprivation induces variations in MA silk mechanical properties across scales. Our analyses found that the properties of each spider's silk varied differently in response to variations in their protein intake. We found changes in the crystalline and non-crystalline nanostructures to play specific roles in inducing the property variations we found. Across treatment MaSp expression patterns differed in each of the five species. We found that in most species MaSp expression and amino acid composition variations did not conform with our predictions based on a traditional MaSp expression model. In general, changes to the silk's alanine and proline compositions influenced the alignment of the proteins within the silk's amorphous region, which influenced silk extensibility and toughness. Variations in structural alignment in the crystalline and non-crystalline regions influenced ultimate strength independent of genetic expression. Our study provides the deepest insights thus far into the mechanisms of how MA silk properties vary from gene expression to nanostructure formations to fiber mechanics. Such knowledge is imperative for promoting the production of synthetic silk fibers.

Collagen hydrogels incorporated with surface-aminated mesoporous nanobioactive glass: Improvement of physicochemical stability and mechanical properties is effective for hard tissue engineering.

PubMed

El-Fiqi, Ahmed; Lee, Jae Ho; Lee, Eun-Jung; Kim, Hae-Won

2013-12-01

Collagen (Col) hydrogels have poor physicochemical and mechanical properties and are susceptible to substantial shrinkage during cell culture, which limits their potential applications in hard tissue engineering. Here, we developed novel nanocomposite hydrogels made of collagen and mesoporous bioactive glass nanoparticles (mBGns) with surface amination, and addressed the effects of mBGn addition (Col:mBG = 2:1, 1:1 and 1:2) and its surface amination on the physicochemical and mechanical properties of the hydrogels. The amination of mBGn was shown to enable chemical bonding with collagen molecules. As a result, the nanocomposite hydrogels exhibited a significantly improved physicochemical and mechanical stability. The hydrolytic and enzymatic degradation of the Col-mBGn hydrogels were slowed down due to the incorporation of mBGn and its surface amination. The mechanical properties of the hydrogels, specifically the resistance to loading as well as the stiffness, significantly increased with the addition of mBGn and its aminated form, as assessed by a dynamic mechanical analysis. Mesenchymal stem cells cultivated within the Col-mBGn hydrogels were highly viable, with enhanced cytoskeletal extensions, due to the addition of surface aminated mBGn. While the Col hydrogel showed extensive shrinkage (down to ∼20% of initial size) during a few days of culture, the shrinkage of the mBGn-added hydrogel was substantially reduced, and the aminated mBGn-added hydrogel had no observable shrinkage over 21 days. Results demonstrated the effective roles of aminated mBGn in significantly improving the physicochemical and mechanical properties of Col hydrogel, which are ultimately favorable for applications in stem cell culture for bone tissue engineering. Copyright © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Nano/micro/meso scale interactions in mechanics of pharmaceutical solid dosage forms

NASA Astrophysics Data System (ADS)

Akseli, Ilgaz

Oral administration in form tablets has been the most common method for delivering drug to the human systemic blood circulation accurately and reproducibly due to its established manufacturing methods and reliability as well as cost. The mechanical criteria for a successful powder-to-tablet processing are good flowability, compressibility and compactibility that are closely related to the mechanical and adhesion properties of the particles and particle strength. In this thesis, air-coupled acoustic and ultrasonic techniques are presented and demonstrated as noncontact and nondestructive methods for physical (mechanical) integrity monitoring and mechanical characterization of tablets. A testing and characterization experimental platform for defect detection, coating thickness and mechanical property determination of tablets was also developed. The presented air-coupled technique was based on the analysis of the transient vibrational responses of a tablet in both temporal and spectral domains. The contact ultrasonic technique was based on the analysis of the propagation speed of an acoustic pulse launched into a tablet and its reflection from the coat-core interface of the tablet. In defect monitoring, the ultimate objective is to separate defective tablets from nominal ones. In the case of characterization, to extract the coating layer thicknesses and mechanical properties of the tablets from a subset of the measured resonance frequencies, an iterative computational procedure was demonstrated. In the compaction monitoring experiments, an instrumented punch and a cylindrical die were employed to extract the elasticity properties of tablets during compaction. To study the effect of compaction kinetics on tablet properties and defect, finite element analyses of single layer and bilayer tablets were performed. A noncontact work-of-adhesion technique was also demonstrated to determine the work-of-adhesion of pharmaceutical powder particles.

Atomic-scale to Meso-scale Simulation Studies of Thermal Ageing and Irradiation Effects in Fe- Cr Alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stanley, Eugene; Liu, Li

In this project, we target at three primary objectives: (1) Molecular Dynamics (MD) code development for Fe-Cr alloys, which can be utilized to provide thermodynamic and kinetic properties as inputs in mesoscale Phase Field (PF) simulations; (2) validation and implementation of the MD code to explain thermal ageing and radiation damage; and (3) an integrated modeling platform for MD and PF simulations. These two simulation tools, MD and PF, will ultimately be merged to understand and quantify the kinetics and mechanisms of microstructure and property evolution of Fe-Cr alloys under various thermal and irradiation environments

Bending-induced folding, an actuation mechanism for plant reconfiguration.

NASA Astrophysics Data System (ADS)

Terwagne, Denis; Segers, JéRéMy; trioS. lab-Soft Structures; Surfaces Lab Team

Inspired by the sophisticated mechanism of the opening and closing of the ice seed plant valves (Aizoaceae), we present a simple model experiment of this mechanism based on an origami folding. By imposing a curvature to one of the plate connected to a fold designed along a curved path, we actuate its opening and closing. The imposed curvature induces inner mechanical constraints that give us a precise control of the deflection angle, which ultimately leads the fold to close completely. In this talk, we will present an analysis and characterization of this mechanism as a function of the geometrical and mechanical parameters of the system. From these insights, we will show how to build origami pliers with tunable mechanical properties. Possible out comings that might arise in various fields, ranging from deployable engineered structure to soft robotics and medical devices, are discussed. DT and JS thank the Belgian national science foundation F.R.S-FNRS for funding.

Experimental Study on Basic Mechanical Properties of BFRP Bars

NASA Astrophysics Data System (ADS)

Fan, Xiaochun; Xu, Ting; Zhou, Zhengrong; Zhou, Xun

2017-10-01

Basalt Fiber Reinforced Polymer (BFRP) bars have the advantages of corrosion resistance, high strength, light weight, good dielectric properties, and they are new type of green reinforced alternative material. In order to determine the mechanical properties of BFRP bars, the tensile strength of basalt fiber bars was necessary to be studied. The diameters of the basalt fiber bars were compared by means of uniaxial tensile test in this article. Then the stress-strain curve can be drawn out. The results show that the stress - strain curve of BFRP bars present straight line relation, and there is no sign before failure; there is no yield platform on the stress-strain curve of BFRP bars, which are typical brittle material;the tensile strength of BFRP bars is about 3 times higher than that of ordinary steel bars. and the elastic modulus is about 1/5 of that of ordinary steel; the ultimate tensile strength of BFRP bars varies little with the increase of diameter, but there exist some differences in modulus values.

Effect of Multi-Pass Friction Stir Processing on Mechanical Properties for AA2024/Al2O3 Nanocomposites

PubMed Central

2017-01-01

In the present work, an aluminum metal matrix reinforced with (Al2O3) nanoparticles was fabricated as a surface composite sheet using friction stir processing (FSP). The effects of processing parameters on mechanical properties, hardness, and microstructure grain were investigated. The results revealed that multi-pass FSP causes a homogeneous distribution and good dispersion of Al2O3 in the metal matrix, and consequently an increase in the hardness of the matrix composites. A finer grain is observed in the microstructure examination in specimens subjected to second and third passes of FSP. The improvement in the grain refinement is 80% compared to base metal. The processing parameters, particularly rotational tool speed and pass number in FSP, have a major effect on strength properties and surface hardness. The ultimate tensile strength (UTS) and the average hardness are improved by 25% and 46%, respectively, due to presence of reinforcement Al2O3 nanoparticles. PMID:28885575

Effect of tulle on the mechanical properties of a maxillofacial silicone elastomer.

PubMed

Gunay, Yumushan; Kurtoglu, Cem; Atay, Arzu; Karayazgan, Banu; Gurbuz, Cihan Cem

2008-11-01

The purpose of this research was to investigate if physical properties could be improved by incorporating a tulle reinforcement material into a maxillofacial silicone elastomer. A-2186 silicone elastomer was used in this study. The study group consisted of 20 elastomer specimens incorporated with tulle and fabricated in dumbbell-shaped silicone patterns using ASTM D412 and D624 standards. The control group consisted of 20 elastomer specimens fabricated without tulle. Tensile strength, ultimate elongation, and tear strength of all specimens were measured and analyzed. Statistical analyses were performed using Mann-Whitney U test with a statistical significance at 95% confidence level. It was found that the tensile and tear strengths of tulle-incorporated maxillofacial silicone elastomer were higher than those without tulle incorporation (p < 0.05). Therefore, findings of this study suggested that tulle successfully reinforced a maxillofacial silicone elastomer by providing it with better mechanical properties and augmented strength--especially for the delicate edges of maxillofacial prostheses.

The effect of annealing temperature on the properties of powder metallurgy processed Ti-35Nb-2Zr-0.5O alloy.

PubMed

Málek, Jaroslav; Hnilica, František; Veselý, Jaroslav; Smola, Bohumil; Medlín, Rostislav

2017-11-01

Ti-35Nb-2Zr-0.5O (wt%) alloy was prepared via a powder metallurgy process (cold isostatic pressing of blended elemental powders and subsequent sintering) with the primary aim of using it as a material for bio-applications. Sintered specimens were swaged and subsequently the influence of annealing temperature on the mechanical and structural properties was studied. Specimens were annealed at 800, 850, 900, 950, and 1000°C for 0.5h and water quenched. Significant changes in microstructure (i.e. precipitate dissolution or grain coarsening) were observed in relation to increasing annealing temperature. In correlation with those changes, the mechanical properties were also studied. The ultimate tensile strength increased from 925MPa (specimen annealed at 800°C) to 990MPa (900°C). Also the elongation increased from ~ 13% (800°C) to more than 20% (900, 950, and 1000°C). Copyright © 2017 Elsevier Ltd. All rights reserved.

Dopamine-Mediated Sclerotization of Regenerated Chitin in Ionic Liquid.

PubMed

Oh, Dongyeop X; Shin, Sara; Lim, Chanoong; Hwang, Dong Soo

2013-09-06

Chitin is a promising structural material for biomedical applications, due to its many advantageous properties and abundance in nature. However, its usage and development in the biomedical field have been stagnant, because of chitin's poor mechanical properties in wet conditions and the difficulties in transforming it into an applicable form. To overcome these challenges, we created a novel biomimetic chitin composite. This regenerated chitin, prepared with ionic liquid, showed improved mechanical properties in wet conditions by mimicking insect cuticle and squid beak sclerotization, i.e. , catechol-meditated cross-linking. By ionic liquid-based heat treatment, dopamine oxidation produced melanin-like compounds and dopamine-meditated cross-links without any solvent evaporation and oxidant utilization. The dopamine-meditated sclerotization increased the ultimate tensile strength (UTS) of the regenerated chitin by 2.52-fold, measured after six weeks of phosphate-buffered saline (PBS) submersion. In addition, the linear swelling ratio (LSR) of the chitin film was reduced by about 22%. This strategy raises a possibility of using regenerated chitin as an artificial hard tissue in wet conditions.

Study of high performance alloy electroforming

NASA Technical Reports Server (NTRS)

Malone, G. A.

1985-01-01

More panels electroformed with intentional variations of pulse plating parameters are being made. Pulse plating frequency was noted to have a significant effect regarding mechanical properties. The use of a high pulse frequency (assuming fixed duty cycles) results in an increase in ductility and a decrease in ultimate and yield strengths. Electroforming to intermediate frequencies is being done to obtain the best possible combination of ductility and strength. Results of some tests from high frequency specimens are tabulated.

Effects of ion irradiation on the mechanical properties of several polymers

NASA Astrophysics Data System (ADS)

Sasuga, Tsuneo; Kawanishi, Shunichi; Nishii, Masanobu; Seguchi, Tadao; Kohno, Isao

The effects of high-energy ion irradiation (8 MeV protons, 30 MeV He 2+, 80 MeV C 4+, and N 4+) on the tensile properties of polymers were studied under conditions in which ions should pass completely through the specimen and the results were compared with 2 MeV electron irradiation effects. Experiments were carried out on polymers having various constituents and molecular structures, i.e. eight aliphatic polymers and four aromatic polymers. In the aliphatic polymers studied (PE, PP, PVdF, ETFE, EVA, nylon-6, EPDM, and PE-TPE), there was scarcely any difference in the dose dependence of the tensile strength and ultimate elongation between proton and electron irradiation. In aromatic polymers (PET, PES, U-PS, and U-polymer), however, the decrements in the tensile strength and ultimate elongation vs proton dose were less than those for electron irradiation. In heavy-ion irradiation, the radiation damage of PE (an aliphatic polymer) decreased with increase of LET, but no obvious LET effects were observed in PES (an aromatic polymer).

Effects of MgO modified β-TCP nanoparticles on the microstructure and properties of β-TCP/Mg-Zn-Zr composites.

PubMed

Zheng, H R; Li, Z; You, C; Liu, D B; Chen, M F

2017-03-01

The mechanical properties and corrosion resistance of magnesium alloy composites were improved by the addition of MgO surface modified tricalcium phosphate ceramic nanoparticles (m-β-TCP). Mg-3Zn-0.8Zr composites with unmodified (MZZT) and modified (MZZMT) nanoparticles were produced by high shear mixing technology. Effects of MgO m-β-TCP nanoparticles on the microstructure, mechanical properties, electrochemical corrosion properties and cytocompatibility of Mg-Zn-Zr/β-TCP composites were investigated. After hot extrusion deformation and dynamic recrystallization, the grain size of MZZMT was the half size of MZZT and the distribution of m-β-TCP particles in the matrix was more uniform than β-TCP particles. The yield tensile strength (YTS), ultimate tensile strength (UTS), and corrosion potential (Ecorr) of MZZMT were higher than MZZT; the corrosion current density (I corr ) of MZZMT was lower than MZZT. Cell proliferation of co-cultured MZZMT and MZZT composite samples were roughly the same and the cell number at each time point is higher for MZZMT than for MZZT samples.

[Design and fabrication of the custom-made titanium condyle by selective laser melting technology].

PubMed

Chen, Jianyu; Luo, Chongdai; Zhang, Chunyu; Zhang, Gong; Qiu, Weiqian; Zhang, Zhiguang

2014-10-01

To design and fabricate the custom-made titanium mandibular condyle by the reverse engineering technology combined with selective laser melting (SLM) technology and to explore the mechanical properties of the SLM-processed samples and the application of the custom-made condyle in the temporomandibular joint (TMJ) reconstruction. The three-dimensional model of the mandibular condyle was obtained from a series of CT databases. The custom-made condyle model was designed by the reverse engineering software. The mandibular condyle was made of titanium powder with a particle size of 20-65 µm as the basic material and the processing was carried out in an argon atmosphere by the SLM machine. The yield strength, ultimate strength, bending strength, hardness, surface morphology and roughness were tested and analyzed. The finite element analysis (FEA) was used to analyze the stress distribution. The complex geometry and the surface of the custom-made condyle can be reproduced precisely by the SLM. The mechanical results showed that the yield strength, ultimate strength, bending strength and hardness were (559±14) MPa, (659±32) MPa, (1 067±42) MPa, and (212±4)HV, respectively. The surface roughness was reduced by sandblast treatment. The custom-made titanium condyle can be fabricated by SLM technology which is time-saving and highly digitized. The mechanical properties of the SLM sample can meet the requirements of surgical implant material in the clinic. The possibility of fabricating custom-made titanium mandibular condyle combined with the FEA opens new interesting perspectives for TMJ reconstruction.

Elastomeric and soft conducting microwires for implantable neural interfaces

PubMed Central

Kolarcik, Christi L.; Luebben, Silvia D.; Sapp, Shawn A.; Hanner, Jenna; Snyder, Noah; Kozai, Takashi D.Y.; Chang, Emily; Nabity, James A.; Nabity, Shawn T.; Lagenaur, Carl F.; Cui, X. Tracy

2015-01-01

Current designs for microelectrodes used for interfacing with the nervous system elicit a characteristic inflammatory response that leads to scar tissue encapsulation, electrical insulation of the electrode from the tissue and ultimately failure. Traditionally, relatively stiff materials like tungsten and silicon are employed which have mechanical properties several orders of magnitude different from neural tissue. This mechanical mismatch is thought to be a major cause of chronic inflammation and degeneration around the device. In an effort to minimize the disparity between neural interface devices and the brain, novel soft electrodes consisting of elastomers and intrinsically conducting polymers were fabricated. The physical, mechanical and electrochemical properties of these materials were extensively characterized to identify the formulations with the optimal combination of parameters including Young’s modulus, elongation at break, ultimate tensile strength, conductivity, impedance and surface charge injection. Our final electrode has a Young’s modulus of 974 kPa which is five orders of magnitude lower than tungsten and significantly lower than other polymer-based neural electrode materials. In vitro cell culture experiments demonstrated the favorable interaction between these soft materials and neurons, astrocytes and microglia, with higher neuronal attachment and a two-fold reduction in inflammatory microglia attachment on soft devices compared to stiff controls. Surface immobilization of neuronal adhesion proteins on these microwires further improved the cellular response. Finally, in vivo electrophysiology demonstrated the functionality of the elastomeric electrodes in recording single unit activity in the rodent visual cortex. The results presented provide initial evidence in support of the use of soft materials in neural interface applications. PMID:25993261

Effect of Friction Stir Process Parameters on the Mechanical and Thermal Behavior of 5754-H111 Aluminum Plates.

PubMed

Serio, Livia Maria; Palumbo, Davide; De Filippis, Luigi Alberto Ciro; Galietti, Umberto; Ludovico, Antonio Domenico

2016-02-23

A study of the Friction Stir Welding (FSW) process was carried out in order to evaluate the influence of process parameters on the mechanical properties of aluminum plates (AA5754-H111). The process was monitored during each test by means of infrared cameras in order to correlate temperature information with eventual changes of the mechanical properties of joints. In particular, two process parameters were considered for tests: the welding tool rotation speed and the welding tool traverse speed. The quality of joints was evaluated by means of destructive and non-destructive tests. In this regard, the presence of defects and the ultimate tensile strength (UTS) were investigated for each combination of the process parameters. A statistical analysis was carried out to assess the correlation between the thermal behavior of joints and the process parameters, also proving the capability of Infrared Thermography for on-line monitoring of the quality of joints.

Effect of Friction Stir Process Parameters on the Mechanical and Thermal Behavior of 5754-H111 Aluminum Plates

PubMed Central

Serio, Livia Maria; Palumbo, Davide; De Filippis, Luigi Alberto Ciro; Galietti, Umberto; Ludovico, Antonio Domenico

2016-01-01

A study of the Friction Stir Welding (FSW) process was carried out in order to evaluate the influence of process parameters on the mechanical properties of aluminum plates (AA5754-H111). The process was monitored during each test by means of infrared cameras in order to correlate temperature information with eventual changes of the mechanical properties of joints. In particular, two process parameters were considered for tests: the welding tool rotation speed and the welding tool traverse speed. The quality of joints was evaluated by means of destructive and non-destructive tests. In this regard, the presence of defects and the ultimate tensile strength (UTS) were investigated for each combination of the process parameters. A statistical analysis was carried out to assess the correlation between the thermal behavior of joints and the process parameters, also proving the capability of Infrared Thermography for on-line monitoring of the quality of joints. PMID:28773246

Effect of Nb Content on Mechanical Behavior and Structural Properties of W/(Zr55Cu30Al10Ni5)100- x Nb x Composite

NASA Astrophysics Data System (ADS)

Mahmoodan, Morteza; Gholamipour, Reza; Mirdamadi, Shamseddin; Nategh, Said

2017-05-01

In the present study, (Zr55Cu30Al10Ni5)100- x Nb( x=0,1,2,3) bulk metallic glass matrix/tungsten wire composites were fabricated by infiltration process. Structural studies were investigated by scanning electron microscopy and X-ray diffraction method. Also, mechanical behaviors of the materials were analyzed using quasi-static compressive tests. Results indicated that the best mechanical properties i.e., 2105 MPa compressive ultimate strength and 28 pct plastic strain before failure, were achieved in the composite sample with X = 2. It was also found that adding Nb to the matrix modified interface structure in W fiber/(Zr55Cu30Al10Ni5)98Nb2 since the stable diffusion band formation acts as a functionally graded layer. Finally, the observation of multiple shear bands formation in the matrix could confirm the excellent plastic deformation behavior of the composite.

Microstructure and mechanical properties of Al/Cu/Mg laminated composite sheets produced by the ARB proces

NASA Astrophysics Data System (ADS)

Rahmatabadi, Davood; Tayyebi, Moslem; Hashemi, Ramin; Faraji, Ghader

2018-05-01

In the present study, an Al/Cu/Mg multi-layered composite was produced by accumulative roll bonding (ARB) through seven passes, and its microstructure and mechanical properties were evaluated. The microstructure investigations show that plastic instability occurred in both the copper and magnesium reinforcements in the primary sandwich. In addition, a composite with a perfectly uniform distribution of copper and magnesium reinforcing layers was produced during the last pass. By increasing the number of ARB cycles, the microhardness of the layers including aluminum, copper, and magnesium was significantly increased. The ultimate tensile strength of the sandwich was enhanced continually and reached a maximum value of 355.5 MPa. This strength value was about 3.2, 2, and 2.1 times higher than the initial strength values for the aluminum, copper, and magnesium sheets, respectively. Investigation of tensile fracture surfaces during the ARB process indicated that the fracture mechanism changed to shear ductile at the seventh pass.

Strengthening Mechanisms in Thermomechanically Processed NbTi-Microalloyed Steel

NASA Astrophysics Data System (ADS)

Kostryzhev, Andrii G.; Marenych, Olexandra O.; Killmore, Chris R.; Pereloma, Elena V.

2015-08-01

The effect of deformation temperature on microstructure and mechanical properties was investigated for thermomechanically processed NbTi-microalloyed steel with ferrite-pearlite microstructure. With a decrease in the finish deformation temperature at 1348 K to 1098 K (1075 °C to 825 °C) temperature range, the ambient temperature yield stress did not vary significantly, work hardening rate decreased, ultimate tensile strength decreased, and elongation to failure increased. These variations in mechanical properties were correlated to the variations in microstructural parameters (such as ferrite grain size, solid solution concentrations, precipitate number density and dislocation density). Calculations based on the measured microstructural parameters suggested the grain refinement, solid solution strengthening, precipitation strengthening, and work hardening contributed up to 32 pct, up to 48 pct, up to 25 pct, and less than 3 pct to the yield stress, respectively. With a decrease in the finish deformation temperature, both the grain size strengthening and solid solution strengthening increased, the precipitation strengthening decreased, and the work hardening contribution did not vary significantly.

Phase separated microstructure and dynamics of polyurethane elastomers under strain

NASA Astrophysics Data System (ADS)

Iacob, Ciprian; Padsalgikar, Ajay; Runt, James

The molecular mobility of polyurethane elastomers is of the utmost importance in establishing physical properties for uses ranging from automotive tires and shoe soles to more sophisticated aerospace and biomedical applications. In many of these applications, chain dynamics as well as mechanical properties under external stresses/strains are critical for determining ultimate performance. In order to develop a more complete understanding of their mechanical response, we explored the effect of uniaxial strain on the phase separated microstructure and molecular dynamics of the elastomers. We utilize X-ray scattering to investigate soft segment and hard domain orientation, and broadband dielectric spectroscopy for interrogation of the dynamics. Uniaxial deformation is found to significantly perturb the phase-separated microstructure and chain orientation, and results in a considerable slowing down of the dynamics of the elastomers. Attenuated total reflectance Fourier transform infrared spectroscopy measurements of the polyurethanes under uniaxial deformation are also employed and the results are quantitatively correlated with mechanical tensile tests and the degree of phase separation from small-angle X-ray scattering measurements.

Advanced performance of small diaphragm vacuum pumps through the use of mechatronics

NASA Astrophysics Data System (ADS)

Lachenmann, R.; Dirscherl, J.

Oil-free diaphragm vacuum pumps have proven to be the best way in vacuum generation for the chemical laboratory and they also find increasing use as backing pumps for modern wide-range turbo molecular pumps. The majority of vacuum pumps in practical use pump only a rather small percentage of their lifetime at full gas load. A pump backing a turbo molecular pump does not have to pump a significant gas load when the high-vacuum pump is running at ultimate vacuum pressure. Also, for a vacuum distillation the vacuum pump has to operate at full speed only at the beginning to lower the pressure inside the system to a vacuum level where evaporation starts. In a rather leak-tight system the distillation process continues by evaporating from the hot liquid and condensing at the cold condenser without the need of a mechanical vacuum pump. Rotational speed controlled diaphragm pumps are now available through progress in mechatronics and offer high pumping speed capability for fast pump-down cycles and precise pressure control for distillations. At low gas load the rotational speed can be reduced, improving maintenance intervals, power consumption, noise, vibration and - surprisingly - also ultimate pressure. The different behaviour in pumping speed and ultimate pressure of rotational speed controlled diaphragm pumps in comparison to constant-speed pumps is related to the mechanical properties of the valves and gas dynamics .

Mechanical suitability of glycerol-preserved human dura mater for construction of prosthetic cardiac valves.

PubMed

McGarvey, K A; Lee, J M; Boughner, D R

1984-03-01

We have examined the tensile viscoelastic properties of fresh and glycerol-preserved human dura mater, and correlated the results with structural information from the scanning electron microscope. The interwoven laminar structure of dura produces rather high flexural stiffness, while the crossed-fibrillar laminae produce planar mechanical isotropy. Glycerol storage shifts the stress-strain curve to lower strain, reduces stress relaxation and creep, and lowers the ultimate tensile strength and strain at fracture. These changes may be due to glyceraldehyde crosslinking, or to increased interfibrillar friction. The latter hypothesis suggests that glycerol storage may reduce the fatigue lifetime of the tissue.

Molecular mechanism of Danshensu on platelet antiaggregation

NASA Astrophysics Data System (ADS)

Yu, Chen; Geng, Feng; Fan, Hua-Ying; Luan, Hai-Yun; Liu, Yue; Ji, Kai; Fu, Feng-Hua

2018-04-01

In this study, we detected the effect of Danshensu on PARs-PLCβsignaling pathway to elucidate molecular mechanism of Danshensu on platelet anti-aggregation. Our results demonstrate that Danshensu is able to decrease the levels of IP3, Ca2+ and AA secretion, which indicate that Danshensu may involve in PARs-PLCβ signaling pathways. Molecular docking study shows that Danshesu has similar polar interactions with PAR1 receptors as BMS200261 at the same position. The findings from our study enable a better understanding of Danshensu biological properties, which could ultimately lead to the development of multi-target antiplatelet natural medicine for the treatment and/or prevention of some thrombotic diseases.

Structure and mechanical properties of a high-carbon steel subjected to severe deformation

NASA Astrophysics Data System (ADS)

Gorkunov, E. S.; Zadvorkin, S. M.; Goruleva, L. S.; Makarov, A. V.; Pecherkina, N. L.

2017-10-01

The structure and mechanical properties of a high-carbon eutectic steel subjected to the cold plastic deformation by hydrostatic extrusion in a wide range of true strain have been studied. Using scanning and transmission electron microscopy, it has been shown that the formation of cellular, fragmented, and submicrocrystalline structures occurs in the ferritic constituent of the pearlite structure of the steel upon extrusion. This is a consequence of the occurrence of dynamic recovery and continuous dynamic and post-dynamic recrystallization, which cause a decrease in the density of free dislocations at the true strain of more than 1.62. The partial dissolution of the carbide phase is also observed. It has been found that, at a true strain of up to 0.81, the strength properties of the investigated steel are determined mainly by subgrain, dislocation, and precipitation mechanisms of the strengthening; in the deformation range of 0.81-1.62, the role of the grainboundary strengthening increases. At strains above 1.62, grain-boundary strengthening is a prevailing mechanism in the formation of the level of strength properties of the extruded U8A steel. The ultimate tensile strength and yield stress over the entire strain range only uniquely correlate with the density of highangle boundaries; the dependences of the strength characteristics on other structural parameters are not monotonic.

The Effect of UVC Irradiation on the Mechanical Properties of Chitosan Membrane in Sterilization Process

NASA Astrophysics Data System (ADS)

Rupiasih, N. N.; Sumadiyasa, M.; Putra, I. K.

2018-04-01

The present study, we report about the effect of UVC irradiation on the mechanical properties of chitosan membrane in the sterilization process. The membrane used was chitosan membrane 2% which prepared by a casting method using chitosan as matrix and acetic acid 1% as a solvent. The UVC source used was germicidal ultraviolet (UVG) which widely used for sterilization purposes. Variation doses were done by the varying time of irradiation, e.g. 5 min, 15 min, 30 min, and 60 min. Those samples are named as S1, S2, S3, and S4, respectively. Chitosan membrane before irradiation namely S0 also used for comparative study. The effect of UVC irradiation on the mechanical properties of membranes has been examined by different techniques including FTIR, DMA, and the water uptake capability. The results showed that ultimate tensile strength (UTS) and moduli of elasticity (E) were increased by increasing the irradiation time. From FTIR analysis obtained that no new molecules were formed in irradiated membranes. The water uptakes capability of the membranes after irradiation was smaller compared with before irradiation, and among the irradiated membranes, the water uptake capabilities were increased by increasing the exposure time. These observations suggested that more care should be taken during the sterilization process and outdoor used of the membrane. The other side, the UVC irradiation can improve the mechanical properties of the membranes.

Influence of multiple-passes on microstructure and mechanical properties of Al-Mg/SiC surface composites fabricated via underwater friction stir processing

NASA Astrophysics Data System (ADS)

Srivastava, Manu; Rathee, Sandeep; Maheshwari, Sachin; Siddiquee, Arshad Noor

2018-06-01

Friction stir processing (FSP) is a relatively newly developed solid-state process involving surface modifications for fabricating metal matrix surface composites. Obtaining metal matrix nano-composites with uniform dispersion of reinforcement particles via FSP route is an intricate task to accomplish. In this work, AA5059/SiC nano surface composites (SCs) were developed. Effect of multiple FSP passes and SiC addition on microstructure and mechanical properties of fabricated SCs during underwater condition was investigated. Results reflected that the average microhardness value of base metal (BM) increases from 85 Hv to 159 Hv in stir zone of four pass underwater friction stir processed (FSPed) SC. Highest ultimate tensile strength (UTS) achieved during four pass FSPed sample was 377 MPa that is higher than UTS of BM (321 MPa) and four pass FSPed sample developed at ambient air FSP conditions (347 MPa). An appreciably narrower heat affected zone is obtained owing to fast cooling and reduced heat conduction during underwater FSP, amounting to higher UTS as compared to BM and SC at ambient conditions. Thus, it can be concluded that surrounding medium and number of FSP passes have significant impact on mechanical properties of fabricated SCs. Analysis of microstructures and distribution of SiC particles in fabricated SCs were studied by optical microscope and FESEM respectively and found in good corroboration with the mechanical properties.

Effects of crosslinking on the mechanical properties, drug release and cytocompatibility of protein polymers.

PubMed

Martinez, Adam W; Caves, Jeffrey M; Ravi, Swathi; Li, Wehnsheng; Chaikof, Elliot L

2014-01-01

Recombinant elastin-like protein polymers are increasingly being investigated as component materials of a variety of implantable medical devices. This is chiefly a result of their favorable biological properties and the ability to tailor their physical and mechanical properties. In this report, we explore the potential of modulating the water content, mechanical properties, and drug release profiles of protein films through the selection of different crosslinking schemes and processing strategies. We find that the selection of crosslinking scheme and processing strategy has a significant influence on all aspects of protein polymer films. Significantly, utilization of a confined, fixed volume, as well as vapor-phase crosslinking strategies, decreased protein polymer equilibrium water content. Specifically, as compared to uncrosslinked protein gels, water content was reduced for genipin (15.5%), glutaraldehyde (GTA, 24.5%), GTA vapor crosslinking (31.6%), disulfide (SS, 18.2%) and SS vapor crosslinking (25.5%) (P<0.05). Distinct crosslinking strategies modulated protein polymer stiffness, strain at failure and ultimate tensile strength (UTS). In all cases, vapor-phase crosslinking produced the stiffest films with the highest UTS. Moreover, both confined, fixed volume and vapor-phase approaches influenced drug delivery rates, resulting in decreased initial drug burst and release rates as compared to solution phase crosslinking. Tailored crosslinking strategies provide an important option for modulating the physical, mechanical and drug delivery properties of protein polymers. Copyright © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Size-dependent fracture behavior of silver nanowires.

PubMed

Cao, Ke; Han, Ying; Zhang, Hongti; Gao, Libo; Yang, Hongwei; Chen, Jialin; Li, Yuxiu; Lu, Yang

2018-07-20

Silver (Ag) nanowires have great potential to be used in the flexible electronics industry for their applications in flexible, transparent conductors due to high conductivity and light reflectivity. Those applications always involve mechanical loading and deformations, which requires an in-depth understanding of their mechanical behavior and performance under loadings. However, current understanding on the mechanical properties of Ag nanowires is limited, especially on their size-dependent fracture behavior. In this work, mechanical properties of Ag nanowires with diameters ranging from 50 to 300 nm were systematically studied by in situ TEM tensile testing for the first time. The size effect was clearly found, with the increasing of the diameter of Ag nanowires, the ultimate tensile stress decreased. More importantly, the fracture behavior of Ag nanowire was studied and a brittle-to-ductile transition in fracture behavior was observed at the diameters around 100 nm which could be attributed to the dislocation activities within the geometry confinement. This work could give insights for understanding nanosized Ag wires and the design of Ag nanowire-based flexible devices and touchable panels.

Size-dependent fracture behavior of silver nanowires

NASA Astrophysics Data System (ADS)

Cao, Ke; Han, Ying; Zhang, Hongti; Gao, Libo; Yang, Hongwei; Chen, Jialin; Li, Yuxiu; Lu, Yang

2018-07-01

Silver (Ag) nanowires have great potential to be used in the flexible electronics industry for their applications in flexible, transparent conductors due to high conductivity and light reflectivity. Those applications always involve mechanical loading and deformations, which requires an in-depth understanding of their mechanical behavior and performance under loadings. However, current understanding on the mechanical properties of Ag nanowires is limited, especially on their size-dependent fracture behavior. In this work, mechanical properties of Ag nanowires with diameters ranging from 50 to 300 nm were systematically studied by in situ TEM tensile testing for the first time. The size effect was clearly found, with the increasing of the diameter of Ag nanowires, the ultimate tensile stress decreased. More importantly, the fracture behavior of Ag nanowire was studied and a brittle-to-ductile transition in fracture behavior was observed at the diameters around 100 nm which could be attributed to the dislocation activities within the geometry confinement. This work could give insights for understanding nanosized Ag wires and the design of Ag nanowire-based flexible devices and touchable panels.

The effect of scandium addition on microstructure and mechanical properties of Al–Si–Mg alloy: A multi-refinement modifier

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, Cong, E-mail: xucong55555@gmail.com; Xiao, Wenlong, E-mail: wlxiao@buaa.edu.cn; Hanada, Shuji

2015-12-15

Effect of scandium (Sc) additions on the microstructure, mechanical properties and fracture behavior of Al–Si–Mg casting alloy (F357) were systematically investigated. It was found that Sc addition caused a multi-refining efficiency on the microstructure of as-cast F357 alloy, including refinement of grains and secondary dendrite arm spacing (SDAS), modification of eutectic Si and harmless disposal of β-Al{sub 5}FeSi phase. Subsequent T6 heat treatment had further induced the complete spheroidization of eutectic Si and precipitation of fine secondary Al{sub 3}Sc dispersoids in the Sc modified alloys. Thus the mechanical properties, especially the ductility, were significantly enhanced by the addition of Scmore » combined with the heat treatment. The highest ultimate tensile strength, yield strength and elongation were achieved in 0.8 wt.% Sc modified F357 alloy combined with T6 heat treatment. Furthermore, fractographic examinations indicated that the ductile fracture mechanism served as a dominate role in the modified alloys due to the formation of fine, deep and uniformly distributed dimples. - Highlights: • Detailed characterization of the multi-refining microstructure of Sc modified F357 alloy was performed. • The multi-refinement was proposed to refine grain and SDAS, modify eutectic Si and β-phase. • Sc modifier combined with T6 treatment is effective in improving tensile properties. • Modification of eutectic Si in F357 alloy with Sc is consistent with the IIT mechanism.« less

Dynamic Tensile Loading Improves the Functional Properties of Mesenchymal Stem Cell-Laden Nanofiber-Based Fibrocartilage

PubMed Central

Baker, Brendon M.; Shah, Roshan P.; Huang, Alice H.

2011-01-01

Fibrocartilaginous tissues such as the meniscus serve critical load-bearing roles, relying on arrays of collagen fibers to resist tensile loads experienced with normal activity. As these structures are frequently injured and possess limited healing capacity, there exists great demand for tissue-engineered replacements. Toward recreating the structural features of these anisotropic tissues in vitro, we employ scaffolds composed of co-aligned nanofibers that direct mesenchymal stem cell (MSC) orientation and the formation of organized extracellular matrix (ECM). Concomitant with ECM synthesis, the mechanical properties of constructs increase with free-swelling culture, but ultimately failed to achieve equivalence with meniscal fibrocartilage. As mechanical forces are essential to the development and maintenance of musculoskeletal tissues, this work examined the effect of cyclic tensile loading on MSC-laden nanofibrous constructs. We hypothesized that loading would modulate the transcriptional behavior of MSCs, spur the deposition of ECM, and lead to enhancements in construct mechanical properties compared to free-swelling controls. Fiber-aligned scaffolds were seeded with MSCs and dynamically loaded daily in tension or maintained as nonloaded controls for 4 weeks. With mechanical stimulation, fibrous gene expression increased, collagen deposition increased, and the tensile modulus increased by 16% relative to controls. These results show that dynamic tensile loading enhances the maturation of MSC-laden aligned nanofibrous constructs, suggesting that recapitulation of the structural and mechanical environment of load-bearing tissues results in increases in functional properties that can be exploited for tissue engineering applications. PMID:21247342

Dynamic tensile loading improves the functional properties of mesenchymal stem cell-laden nanofiber-based fibrocartilage.

PubMed

Baker, Brendon M; Shah, Roshan P; Huang, Alice H; Mauck, Robert L

2011-05-01

Fibrocartilaginous tissues such as the meniscus serve critical load-bearing roles, relying on arrays of collagen fibers to resist tensile loads experienced with normal activity. As these structures are frequently injured and possess limited healing capacity, there exists great demand for tissue-engineered replacements. Toward recreating the structural features of these anisotropic tissues in vitro, we employ scaffolds composed of co-aligned nanofibers that direct mesenchymal stem cell (MSC) orientation and the formation of organized extracellular matrix (ECM). Concomitant with ECM synthesis, the mechanical properties of constructs increase with free-swelling culture, but ultimately failed to achieve equivalence with meniscal fibrocartilage. As mechanical forces are essential to the development and maintenance of musculoskeletal tissues, this work examined the effect of cyclic tensile loading on MSC-laden nanofibrous constructs. We hypothesized that loading would modulate the transcriptional behavior of MSCs, spur the deposition of ECM, and lead to enhancements in construct mechanical properties compared to free-swelling controls. Fiber-aligned scaffolds were seeded with MSCs and dynamically loaded daily in tension or maintained as nonloaded controls for 4 weeks. With mechanical stimulation, fibrous gene expression increased, collagen deposition increased, and the tensile modulus increased by 16% relative to controls. These results show that dynamic tensile loading enhances the maturation of MSC-laden aligned nanofibrous constructs, suggesting that recapitulation of the structural and mechanical environment of load-bearing tissues results in increases in functional properties that can be exploited for tissue engineering applications.

Mechanical properties of single electrospun drug-encapsulated nanofibres

PubMed Central

Chew, Sing Yian; Hufnagel, Todd C; Lim, Chwee Teck; Leong, Kam W

2008-01-01

The mechanical and structural properties of a surface play an important role in determining the morphology of attached cells, and ultimately their cellular functions. As such, mechanical and structural integrity are important design parameters for a tissue scaffold. Electrospun fibrous meshes are widely used in tissue engineering. When in contact with electrospun scaffolds, cells see the individual micro- or nanofibres as their immediate microenvironment. In this study, tensile testing of single electrospun nanofibres composed of poly(ε-caprolactone) (PCL), and its copolymer, poly(caprolactone-co-ethyl ethylene phosphate) (PCLEEP), revealed a size effect in the Young's modulus, E, and tensile strength, σT. Both strength and stiffness increase as the fibre diameter decreases from bulk (∼5 μm) into the nanometre region (200–300 nm). In particular, E and σT of individual PCL nanofibres were at least two-fold and an order of magnitude higher than that of PCL film, respectively. PCL films were observed to have more pronounced crystallographic texture than the nanofibres; however no difference in crystalline fraction, perfection, or texture was detected among the various fibres. When drugs were encapsulated into single PCLEEP fibres, mechanical properties were enhanced with 1–20 wt% of loaded retinoic acid, but weakened by 10–20 wt% of encapsulated bovine serum albumin. This understanding of the effect of size and drug and protein encapsulation on the mechanical properties of electrospun fibres may help in the optimization of tissue scaffold design that combines biochemical and biomechanical cues for tissue regeneration. PMID:19079553

Mechanical properties of organic semiconductors for mechanically stable and intrinsically stretchable solar cells (Conference Presentation)

NASA Astrophysics Data System (ADS)

Lipomi, Darren J.

2016-09-01

This presentation describes my group's efforts to understand the molecular and microstructural basis for the mechanical properties of organic semiconductors for organic photovoltaic (OPV) devices. Our work is motivated by two goals. The first goal is to mitigate mechanical forms of degradation of printed modules during roll-to-roll fabrication, installation, and environmental forces—i.e., wind, rain, snow, and thermal expansion and contraction. Mechanical stability is a prerequisite for inexpensive processing on flexible substrates: to encapsulate devices in glass is to surrender this advantage. The second goal is to enable the next generation of ultra-flexible and stretchable solar cells for collapsible, portable, and wearable applications, and as low-cost sources of energy—"solar tarps"—for disaster relief and for the developing world. It may seem that organic semiconductors, due to their carbon framework, are already sufficiently compliant for these applications. We have found, however, that the mechanical properties (stiffness and brittleness) occupy a wide range of values, and can be difficult to predict from molecular structure alone. We are developing an experimental and theoretical framework for how one can combine favorable charge-transport properties and mechanical compliance in organic semiconductor films. In particular, we have explored the roles of the backbone, alkyl side chain, microstructural order, the glass transition, molecular packing with fullerenes, plasticizing effects of additives, extent of separation of [60]PCBM and [70]PCBM, structural randomness in low-bandgap polymers, and reinforcement by encapsulation, on the mechanical compliance. We are exploring the applicability of semi-empirical "back-of-the-envelope" models, along with multi-scale molecular dynamics simulations, with the ultimate goal of designing electroactive organic materials whose mechanical properties can be dialed-in. We have used the insights we have developed to demonstrate several new applications for OPV that demand extreme compliance, including biaxial stretching and conformal bonding of whole devices to hemispheres, and devices with ultrathin encapsulation mounted on human skin that survive significant cyclic mechanical deformation in the outdoor environment.

Water Droplet Erosion Behavior of High-Power Diode Laser Treated 17Cr4Ni PH Stainless Steel

NASA Astrophysics Data System (ADS)

Mann, B. S.

2014-05-01

This article deals with water droplet erosion (WDE) behavior of high-power diode laser (HPDL) treated 17Cr4Ni PH stainless steel. After HPDL treatment, the water droplet erosion resistance (WDER) of 17Cr4Ni PH stainless steel has not improved. The main reason is the surface hardness, which has not improved after HPDL treatment though the microstructure has become much finer. On the other hand, precipitation hardening of the alloy at 490°C for 3 h has resulted in improved WDER more than twice. This is because of its increased microhardness and improved modified ultimate resilience (MUR), and formation of fine grained microstructure. The WDER has been correlated with MUR, a single mechanical property, based upon microhardness, ultimate tensile strength, and Young's modulus. WDERs of HPDL treated, untreated, and precipitation hardened 17Cr4Ni PH stainless steel samples were determined using a WDE test facility as per ASTM G73-1978. The WDE damage mechanism, compared on the basis of MUR and scanning electron micrographs, is discussed and reported in this article.

Facile Fabrication of Multifunctional Aramid Nanofiber Films by Spin Coating

NASA Astrophysics Data System (ADS)

Lyu, Jing; Liu, Lehao; Zhao, Xing; Shang, Yudong; Zhao, Tingkai; Li, Tiehu

2016-11-01

Polymer matrices with excellent mechanical properties, thermal stability and other features are highly demanded for the effective utilization within nanocomposites. Here, we fabricate free-standing aramid nanofiber films via spin coating of an aramid nanofiber/dimethyl sulfoxide solution. Compared with traditional film fabrication methods, this process is time-saving and also able to easily tune the thickness of the films. The resultant films show greatly improved stretchability than that of Kevlar threads and relatively high mechanical strength. Typically, these films with a thickness of 5.5 µm show an ultimate strength of 182 MPa with an ultimate tensile strain of 10.5%. We also apply a finite element modeling to simulate the strain and strength distributions of the films under uniaxial tension, and the results of the simulation are in accordance with the experimental data. Furthermore, the aramid nanofiber films exhibit outstanding thermostability (decomposition at 550 °C under N2 atmosphere and 500 °C in air) and chemical inertness, which would endure acid and alkali. The simple method demonstrated here provides an important way to prepare high-performance aramid nanofiber films for designing new composite systems.

Neural network modeling of conditions of destruction of wood plank based on measurements

NASA Astrophysics Data System (ADS)

Filkin, V.; Kaverzneva, T.; Lazovskaya, T.; Lukinskiy, E.; Petrov, A.; Stolyarov, O.; Tarkhov, D.

2016-11-01

The paper deals with the possibility of predicting the ultimate load breaking timber sample based on the loading force dependence on the deflection before destruction. Prediction of mechanical properties of wood is handicapped by complex anisotropic structures. The anisotropic nature of the material and, in a great measure, the random nature of wood grain local features defining moment of destruction lead to a significant dependence of the required load on the individual characteristics of a particular bar. The ultimate load is sought as a function of the coefficients of the neural network approximation of the loading force dependence on the deflection. For this purpose, a number of experiments on timber sample loading until the destruction is conducted. Modeling of the conditions of material destruction may provide the required safety control in building industry.

Kant and the nature of matter: Mechanics, chemistry, and the life sciences.

PubMed

Gaukroger, Stephen

2016-08-01

Kant believed that the ultimate processes that regulate the behavior of material bodies can be characterized exclusively in terms of mechanics. In 1790, turning his attention to the life sciences, he raised a potential problem for his mechanically-based account, namely that many of the operations described in the life sciences seemed to operate teleologically. He argued that the life sciences do indeed require us to think in teleological terms, but that this is a fact about us, not about the processes themselves. Nevertheless, even were we to concede his account of the life sciences, this would not secure the credentials of mechanics as a general theory of matter. Hardly any material properties studied in the second half of the eighteenth century were, or could have been, conceived in mechanical terms. Kant's concern with teleology is tangential to the problems facing a general matter theory grounded in mechanics, for the most pressing issues have nothing to do with teleology. They derive rather from a lack of any connection between mechanical forces and material properties. This is evident in chemistry, which Kant dismisses as being unscientific on the grounds that it cannot be formulated in mechanical terms. Copyright © 2016 Elsevier Ltd. All rights reserved.

Fabrication of low-cost beta-type Ti-Mn alloys for biomedical applications by metal injection molding process and their mechanical properties.

PubMed

Santos, Pedro Fernandes; Niinomi, Mitsuo; Liu, Huihong; Cho, Ken; Nakai, Masaaki; Itoh, Yoshinori; Narushima, Takayuki; Ikeda, Masahiko

2016-06-01

Titanium and its alloys are suitable for biomedical applications owing to their good mechanical properties and biocompatibility. Beta-type Ti-Mn alloys (8-17 mass% Mn) were fabricated by metal injection molding (MIM) as a potential low cost material for use in biomedical applications. The microstructures and mechanical properties of the alloys were evaluated. For up to 13 mass% Mn, the tensile strength (1162-938MPa) and hardness (308-294HV) of the MIM fabricated alloys are comparable to those of Ti-Mn alloys fabricated by cold crucible levitation melting. Ti-9Mn exhibits the best balance of ultimate tensile strength (1046MPa) and elongation (4.7%) among the tested alloys, and has a Young's modulus of 89GPa. The observed low elongation of the alloys is attributed to the combined effects of high oxygen content, with the presence of interconnected pores and titanium carbides, the formation of which is due to carbon pickup during the debinding process. The elongation and tensile strength of the alloys decrease with increasing Mn content. The Ti-Mn alloys show good compressive properties, with Ti-17Mn showing a compressive 0.2% proof stress of 1034MPa, and a compressive strain of 50%. Copyright © 2016 Elsevier Ltd. All rights reserved.

Handbook of Analytical Methods for Textile Composites

NASA Technical Reports Server (NTRS)

Cox, Brian N.; Flanagan, Gerry

1997-01-01

The purpose of this handbook is to introduce models and computer codes for predicting the properties of textile composites. The handbook includes several models for predicting the stress-strain response all the way to ultimate failure; methods for assessing work of fracture and notch sensitivity; and design rules for avoiding certain critical mechanisms of failure, such as delamination, by proper textile design. The following textiles received some treatment: 2D woven, braided, and knitted/stitched laminates and 3D interlock weaves, and braids.

Benefits of Intercritical Annealing in Quenching and Partitioning Steel

NASA Astrophysics Data System (ADS)

Wang, X.; Liu, L.; Liu, R. D.; Huang, M. X.

2018-03-01

Compared to the quenching and partitioning (Q&P) steel produced by full austenization annealing, the Q&P steel produced by the intercritical annealing shows a similar ultimate tensile stress but a larger tensile ductility. This property is attributable to the higher volume fraction and the better mechanical stability of the retained austenite after the intercritical annealing. Moreover, intercritical annealing produces more ferrite and fewer martensite phases in the microstructure, making an additional contribution to a higher work hardening rate and therefore a better tensile ductility.

Unraveling the Age Hardening Response in U-Nb Alloys

DOE PAGES

Hackenberg, Robert Errol; Hemphill, Geralyn M. Sewald; Forsyth, Robert Thomas; ...

2016-11-15

Complicating factors that have stymied understanding of uranium-niobium’s aging response are briefly reviewed, including (1) niobium inhomogeneity, (2) machining damage effects on tensile properties, (3) early-time transients of ductility increase, and (4) the variety of phase transformations. A simple Logistic-Arrhenius model was applied to predict yield and ultimate tensile strengths and tensile elongation of U-4Nb as a function of thermal age. Lastly, fits to each model yielded an apparent activation energy that was compared with phase transformation mechanisms.

Microstructure and Mechanical Properties of Narrow Gap Laser-Arc Hybrid Welded 40 mm Thick Mild Steel.

PubMed

Zhang, Chen; Li, Geng; Gao, Ming; Zeng, XiaoYan

2017-01-26

Both laser-arc hybrid welding and narrow gap welding have potential for the fabrication of thick sections, but their combination has been seldom studied. In this research, 40 mm thick mild steel was welded by narrow gap laser-arc hybrid welding. A weld with smooth layer transition, free of visible defects, was obtained by nine passes at a 6 mm width narrow gap. The lower part of the weld has the lowest mechanical properties because of the lowest amount of acicular ferrite, but its ultimate tensile strength and impact absorbing energy is still 49% and 60% higher than those of base metal, respectively. The microhardness deviation of all filler layers along weld thickness direction is no more than 15 HV 0.2 , indicating that no temper softening appeared during multiple heat cycles. The results provide an alternative technique for improving the efficiency and quality of welding thick sections.

Stress Corrosion Cracking of Basalt/Epoxy Composites under Bending Loading

NASA Astrophysics Data System (ADS)

Shokrieh, Mahmood M.; Memar, Mahdi

2010-04-01

The purpose of this research is to study the stress corrosion behavior of basalt/epoxy composites under bending loading and submerged in 5% sulfuric acid corrosive medium. There are limited numbers of research in durability of fiber reinforced polymer composites. Moreover, studies on basalt fibers and its composites are very limited. In this research, mechanical property degradation of basalt/epoxy composites under bending loading and submerged in acidic corrosive medium is investigated. Three states of stress, equal to 30%, 50% and 70% of the ultimate strength of composites, are applied on samples. High stress states are applied to the samples to accelerate the testing procedure. Mechanical properties degradation consists of bending strength, bending modulus of elasticity and fracture energy of samples are examined. Also, a normalized strength degradation model for stress corrosion condition is presented. Finally, microscopic images of broken cross sections of samples are examined.

Microstructure and Mechanical Properties of Narrow Gap Laser-Arc Hybrid Welded 40 mm Thick Mild Steel

PubMed Central

Zhang, Chen; Li, Geng; Gao, Ming; Zeng, XiaoYan

2017-01-01

Both laser-arc hybrid welding and narrow gap welding have potential for the fabrication of thick sections, but their combination has been seldom studied. In this research, 40 mm thick mild steel was welded by narrow gap laser-arc hybrid welding. A weld with smooth layer transition, free of visible defects, was obtained by nine passes at a 6 mm width narrow gap. The lower part of the weld has the lowest mechanical properties because of the lowest amount of acicular ferrite, but its ultimate tensile strength and impact absorbing energy is still 49% and 60% higher than those of base metal, respectively. The microhardness deviation of all filler layers along weld thickness direction is no more than 15 HV0.2, indicating that no temper softening appeared during multiple heat cycles. The results provide an alternative technique for improving the efficiency and quality of welding thick sections. PMID:28772469

Antioxidant Properties of Probiotic Bacteria.

PubMed

Wang, Yang; Wu, Yanping; Wang, Yuanyuan; Xu, Han; Mei, Xiaoqiang; Yu, Dongyou; Wang, Yibing; Li, Weifen

2017-05-19

Oxidative stress defines a condition in which the prooxidant-antioxidant balance in the cell is disturbed, resulting in DNA hydroxylation, protein denaturation, lipid peroxidation, and apoptosis, ultimately compromising cells' viability. Probiotics have been known for many beneficial health effects, and the consumption of probiotics alone or in food shows that strain-specific probiotics can present antioxidant activity and reduce damages caused by oxidation. However, the oxidation-resistant ability of probiotics, especially the underling mechanisms, is not properly understood. In this view, there is interest to figure out the antioxidant property of probiotics and summarize the mode of action of probiotic bacteria in antioxidation. Therefore, in the present paper, the antioxidant mechanisms of probiotics have been reviewed in terms of their ability to improve the antioxidant system and their ability to decrease radical generation. Since in recent years, oxidative stress has been associated with an altered gut microbiota, the effects of probiotics on intestinal flora composition are also elaborated.

Extrusion of xylans extracted from corn cobs into biodegradable polymeric materials.

PubMed

Bahcegul, Erinc; Akinalan, Busra; Toraman, Hilal E; Erdemir, Duygu; Ozkan, Necati; Bakir, Ufuk

2013-12-01

Solvent casting technique, which comprises multiple energy demanding steps including the dissolution of a polymer in a solvent followed by the evaporation of the solvent from the polymer solution, is currently the main technique for the production of xylan based polymeric materials. The present study shows that sufficient water content renders arabinoglucuronoxylan (AGX) polymers extrudable, enabling the production of AGX based polymeric materials in a single step via extrusion, which is economically advantageous to solvent casting process for mass production. AGX polymers with water content of 27% were found to yield extrudates at an extrusion temperature of 90°C. The extruded strips showed very good mechanical properties with an ultimate tensile strength of 76 ± 6 MPa and elongation at break value of 35 ± 8%, which were superior to the mechanical properties of the strips obtained from polylactic acid. Copyright © 2013 Elsevier Ltd. All rights reserved.

Microstructure and mechanical properties of quenched and tempered 300M steel

NASA Technical Reports Server (NTRS)

Youngblood, J. L.; Raghavan, M.

1978-01-01

Type 300M steel, which is being used for the landing gear on the space shuttle orbiter, was subjected to a wide range of quenched and tempered heat treatments. The plane-strain fracture toughness and the tensile ultimate and yield strengths were evaluated. Cryogenic mechanical properties were obtained for conventionally heat-treated steel. The microstructure of all heat-treated test coupons was studied both optically and by transmission electron microscopy. Fracture surfaces were studied by means of scanning electron microscopy. Results indicate that substantial improvement in toughness with no loss in strength can be accomplished in quenched and tempered steel by austenitizing at 1255 K or higher. Low fracture toughness in conventionally austenitized 300M steel (1144 K) appears to be caused by undissolved precipitates, seen both in the submicrostructure and on the fracture surface, which promote failure by quasi-cleavage. The precipitates appeared to dissolve in the range 1200 to 1255 K.

Antioxidant Properties of Probiotic Bacteria

PubMed Central

Wang, Yang; Wu, Yanping; Wang, Yuanyuan; Xu, Han; Mei, Xiaoqiang; Yu, Dongyou; Wang, Yibing; Li, Weifen

2017-01-01

Oxidative stress defines a condition in which the prooxidant–antioxidant balance in the cell is disturbed, resulting in DNA hydroxylation, protein denaturation, lipid peroxidation, and apoptosis, ultimately compromising cells’ viability. Probiotics have been known for many beneficial health effects, and the consumption of probiotics alone or in food shows that strain-specific probiotics can present antioxidant activity and reduce damages caused by oxidation. However, the oxidation-resistant ability of probiotics, especially the underling mechanisms, is not properly understood. In this view, there is interest to figure out the antioxidant property of probiotics and summarize the mode of action of probiotic bacteria in antioxidation. Therefore, in the present paper, the antioxidant mechanisms of probiotics have been reviewed in terms of their ability to improve the antioxidant system and their ability to decrease radical generation. Since in recent years, oxidative stress has been associated with an altered gut microbiota, the effects of probiotics on intestinal flora composition are also elaborated. PMID:28534820

Mechanical Properties of Lightweight Porous Magnesium Processed Through Powder Metallurgy

NASA Astrophysics Data System (ADS)

Zou, Ning; Li, Qizhen

2018-02-01

Porous magnesium (Mg) samples with various overall porosities (28.4 ± 1.8%, 35.5 ± 2.5%, 45.4 ± 1.9%, and 62.4 ± 2.2%) were processed through powder metallurgy and characterized to study their mechanical properties. Different porosities were obtained by utilizing different mass fractions of space holder camphene. Camphene was removed by sublimation before sintering and contributed to processing porous Mg with high purity and small average pore size. The average pore size increased from 5.2 µm to 15.1 µm with increase of the porosity from 28.4 ± 1.8% to 62.4 ± 2.2%. Compressive strain-stress data showed that the strain hardening rate, yield strength, and ultimate compressive strength decreased with increase of the porosity. The theoretical yield strength of porous Mg obtained using the Gibson-Ashby model agreed with experimental data.

Fiber laser welding of nickel based superalloy Inconel 625

NASA Astrophysics Data System (ADS)

Janicki, Damian M.

2013-01-01

The paper describes the application of single mode high power fiber laser (HPFL) for the welding of nickel based superalloy Inconel 625. Butt joints of Inconel 625 sheets 0,8 mm thick were laser welded without an additional material. The influence of laser welding parameters on weld quality and mechanical properties of test joints was studied. The quality and mechanical properties of the joints were determined by means of tensile and bending tests, and micro hardness tests, and also metallographic examinations. The results showed that a proper selection of laser welding parameters provides non-porous, fully-penetrated welds with the aspect ratio up to 2.0. The minimum heat input required to achieve full penetration butt welded joints with no defect was found to be 6 J/mm. The yield strength and ultimate tensile strength of the joints are essentially equivalent to that for the base material.

The correlation between elongation at break and thermal decomposition of aged EPDM cable polymer

NASA Astrophysics Data System (ADS)

Šarac, T.; Devaux, J.; Quiévy, N.; Gusarov, A.; Konstantinović, M. J.

2017-03-01

The effect of simultaneous thermal and gamma irradiation ageing on the mechanical and physicochemical properties of industrial EPDM was investigated. Accelerated ageing, covering a wide range of dose rates, doses and temperatures, was preformed in stagnant air on EPDM polymer samples extracted from the cables in use in the Belgian nuclear power plants. The mechanical properties, ultimate tensile stress and elongation at break, are found to exhibit the strong dependence on the dose, ageing temperature and dose rate. The thermal decomposition of aged polymer is observed to be the dose dependent when thermogravimetry test is performed under air atmosphere. No dose dependence is observed when thermal decomposition is performed under nitrogen atmosphere. The thermal decomposition rates are found to fully mimic the reduction of elongation at break for all dose rates and ageing temperatures. This effect is argued to be the result of thermal and radiation mediated oxidation degradation process.

Mechanisms Underlying Development of Visual Maps and Receptive Fields

PubMed Central

Huberman, Andrew D.; Feller, Marla B.; Chapman, Barbara

2008-01-01

Patterns of synaptic connections in the visual system are remarkably precise. These connections dictate the receptive field properties of individual visual neurons and ultimately determine the quality of visual perception. Spontaneous neural activity is necessary for the development of various receptive field properties and visual feature maps. In recent years, attention has shifted to understanding the mechanisms by which spontaneous activity in the developing retina, lateral geniculate nucleus, and visual cortex instruct the axonal and dendritic refinements that give rise to orderly connections in the visual system. Axon guidance cues and a growing list of other molecules, including immune system factors, have also recently been implicated in visual circuit wiring. A major goal now is to determine how these molecules cooperate with spontaneous and visually evoked activity to give rise to the circuits underlying precise receptive field tuning and orderly visual maps. PMID:18558864

Characterization of Ni-Cr alloys using different casting techniques and molds.

PubMed

Chen, Wen-Cheng; Teng, Fu-Yuan; Hung, Chun-Cheng

2014-02-01

This study differentiated the mechanical properties of nickel-chromium (Ni-Cr) alloys under various casting techniques (different casting molds and casting atmospheres). These techniques were sampled by a sand mold using a centrifugal machine in ambient air (group I) and electromagnetic induction in an automatic argon castimatic casting machine (group II). The specimen casting used a graphite mold by a castimatic casting machine (group III). The characteristics of the Ni-Cr alloys, yield and ultimate tensile strength, bending modulus, microhardness, diffraction phase, grindability, ability to spring back, as well as ground microstructure and pattern under different casting conditions were evaluated. The group III specimens exhibited the highest values in terms of strength, modulus, hardness, and grindability at a grind rate of 500 rpm. Moreover, group III alloys exhibited smaller grain sizes, higher ability to spring back, and greater ductility than those casted by sand investment (groups I and II). The main factor, "casting mold," significantly influenced all mechanical properties. The graphite mold casting of the Ni-Cr dental alloys in a controlled atmosphere argon casting system provided an excellent combination of high mechanical properties and good ability to spring back, and preserved the ductile properties for application in Ni-Cr porcelain-fused system. The results can offer recommendations to assist a prosthetic technician in selecting the appropriate casting techniques to obtain the desired alloy properties. Copyright © 2013 Elsevier B.V. All rights reserved.

Effect of vacancies on the mechanical properties of phosphorene nanotubes.

PubMed

Sorkin, V; Zhang, Y W

2018-06-08

Using density functional tight-binding method, we studied the mechanical properties, deformation and failure of armchair (AC) and zigzag (ZZ) phosphorene nanotubes (PNTs) with monovacancies and divacancies subjected to uniaxial tensile strain. We found that divacancies in AC PNTs and monovacancies in ZZ PNTs possess the lowest vacancy formation energy, which decreases with the tube diameter in AC PNTs and increases in ZZ PNTs. The Young's modulus is reduced, while the radial and thickness Poisson's ratios are increased by hosted vacancies. In defective AC PNTs, deformation involves fracture of the intra-pucker bonds and formation of the new inter-pucker bonds at a critical strain, and the most stretched bonds around the vacancy rupture first, triggering a sequence of the structural transformations terminated by the ultimate failure. The critical strain of AC PNTs is reduced significantly by hosted vacancies, whereas their effect on the critical stress is relatively weaker. Defective ZZ PNTs fail in a brittle-like manner once the most stretched bonds around a vacancy rupture, and vacancies are able to significantly reduce the failure strain but only moderately reduce the failure stress of ZZ PNTs. The understandings revealed here on the mechanical properties and the deformation and failure mechanisms of PNTs provide useful guidelines for their design and fabrication as building blocks in nanodevices.

Effect of vacancies on the mechanical properties of phosphorene nanotubes

NASA Astrophysics Data System (ADS)

Sorkin, V.; Zhang, Y. W.

2018-06-01

Using density functional tight-binding method, we studied the mechanical properties, deformation and failure of armchair (AC) and zigzag (ZZ) phosphorene nanotubes (PNTs) with monovacancies and divacancies subjected to uniaxial tensile strain. We found that divacancies in AC PNTs and monovacancies in ZZ PNTs possess the lowest vacancy formation energy, which decreases with the tube diameter in AC PNTs and increases in ZZ PNTs. The Young’s modulus is reduced, while the radial and thickness Poisson’s ratios are increased by hosted vacancies. In defective AC PNTs, deformation involves fracture of the intra-pucker bonds and formation of the new inter-pucker bonds at a critical strain, and the most stretched bonds around the vacancy rupture first, triggering a sequence of the structural transformations terminated by the ultimate failure. The critical strain of AC PNTs is reduced significantly by hosted vacancies, whereas their effect on the critical stress is relatively weaker. Defective ZZ PNTs fail in a brittle-like manner once the most stretched bonds around a vacancy rupture, and vacancies are able to significantly reduce the failure strain but only moderately reduce the failure stress of ZZ PNTs. The understandings revealed here on the mechanical properties and the deformation and failure mechanisms of PNTs provide useful guidelines for their design and fabrication as building blocks in nanodevices.

Microstructure-Mechanical Property Relationships for a Fe/Mn/Cr Rock Bolt Reinforcing Steel

NASA Astrophysics Data System (ADS)

Panigrahi, B. K.

2010-08-01

The influence of low chromium additions to a 0.25C-1.5Mn semikilled steel on microstructure, and tensile and impact behaviors of high strength rock bolt reinforcing bars has been investigated. Although chromium imparted adequate tensile properties at ambient temperature (yield stress: 624 MPa; ultimate tensile stress: 819 MPa; elongation: 12.5%) by forming transformation products such as tempered martensite, lower and upper bainite, and small amounts of acicular ferrite, it increased the ductile-to-brittle transition temperature due to coarser upper bainite in the core region of bar having larger unit crack paths. The synthesized steel is considered to be effective in realizing the desired tensile properties, and suitable for application in rock bolt, as well as other reinforced concrete structures.

Multi-Objective Optimization of Friction Stir Welding Process Parameters of AA6061-T6 and AA7075-T6 Using a Biogeography Based Optimization Algorithm

PubMed Central

Tamjidy, Mehran; Baharudin, B. T. Hang Tuah; Paslar, Shahla; Matori, Khamirul Amin; Sulaiman, Shamsuddin; Fadaeifard, Firouz

2017-01-01

The development of Friction Stir Welding (FSW) has provided an alternative approach for producing high-quality welds, in a fast and reliable manner. This study focuses on the mechanical properties of the dissimilar friction stir welding of AA6061-T6 and AA7075-T6 aluminum alloys. The FSW process parameters such as tool rotational speed, tool traverse speed, tilt angle, and tool offset influence the mechanical properties of the friction stir welded joints significantly. A mathematical regression model is developed to determine the empirical relationship between the FSW process parameters and mechanical properties, and the results are validated. In order to obtain the optimal values of process parameters that simultaneously optimize the ultimate tensile strength, elongation, and minimum hardness in the heat affected zone (HAZ), a metaheuristic, multi objective algorithm based on biogeography based optimization is proposed. The Pareto optimal frontiers for triple and dual objective functions are obtained and the best optimal solution is selected through using two different decision making techniques, technique for order of preference by similarity to ideal solution (TOPSIS) and Shannon’s entropy. PMID:28772893

Effect of Si on Fe-rich intermetallic formation and mechanical properties of heat-treated Al–Cu–Mn–Fe alloys

NASA Astrophysics Data System (ADS)

Zhao, Yuliang; Zhang, Weiwen; Yang, Chao; Zhang, Datong; Wang, Zhi

2018-04-01

The effect of Si on Fe-rich intermetallics formation and mechanical properties of heat-treated squeeze cast Al-5.0Cu-0.6Mn-0.7Fe alloy was investigated. Our results show that increasing Si content promotes the formation of Al15(FeMn)3(SiCu)2 (${\\alpha}$-Fe), and varying the morphology of T (Al20Cu3Mn2) where the size decreases and the amount increases. The major reason is that Si promotes heterogeneous nucleation of the intermetallics leading to finer precipitates. Si addition significantly enhances ultimate tensile strength and yield strength of the alloys. The strengthening effect is mainly owing to the dispersoid strengthening by increasing volume fraction of T phase and less harmful ${\\alpha}$-Fe with a compact structure, which make the cracks more difficult to initiate and propagation during tensile test. The squeeze cast Al-5.0Cu-0.6Mn-0.7Fe alloy with 1.1% Si shows significantly improved mechanical properties than the alloy without Si addition, which has tensile strength of 386 MPa, yield strength of 280 MPa and elongation of 8.6%.

Mechanical Characteristics, In Vitro Degradation, Cytotoxicity, and Antibacterial Evaluation of Zn-4.0Ag Alloy as a Biodegradable Material

PubMed Central

Li, Ping; Schille, Christine; Schweizer, Ernst; Rupp, Frank; Heiss, Alexander; Legner, Claudia; Klotz, Ulrich E.; Geis-Gerstorfer, Jürgen

2018-01-01

Zn-based biodegradable metallic materials have been regarded as new potential biomaterials for use as biodegradable implants, mainly because of the ideal degradation rate compared with those of Mg-based alloys and Fe-based alloys. In this study, we developed and investigated a novel Zn-4 wt % Ag alloy as a potential biodegradable metal. A thermomechanical treatment was applied to refine the microstructure and, consequently, to improve the mechanical properties, compared to pure Zn. The yield strength (YS), ultimate tensile strength (UTS) and elongation of the Zn-4Ag alloy are 157 MPa, 261 MPa, and 37%, respectively. The corrosion rate of Zn-4Ag calculated from released Zn ions in DMEM extracts is approximately 0.75 ± 0.16 μg cm–2 day–1, which is higher than that of pure Zn. In vitro cytotoxicity tests showed that the Zn-4Ag alloy exhibits acceptable toxicity to L929 and Saos-2 cells, and could effectively inhibit initial bacteria adhesion. This study shows that the Zn-4Ag exhibits excellent mechanical properties, predictable degradation behavior, acceptable biocompatibility, and effective antibacterial properties, which make it a candidate biodegradable material. PMID:29518938

Production of Poly(ε-Caprolactone)/Hydroxyapatite Composite Scaffolds with a Tailored Macro/Micro-Porous Structure, High Mechanical Properties, and Excellent Bioactivity

PubMed Central

Kim, Jong-Woo; Shin, Kwan-Ha; Koh, Young-Hag; Hah, Min Jin; Moon, Jiyoung; Kim, Hyoun-Ee

2017-01-01

We produced poro-us poly(ε-caprolactone) (PCL)/hydroxyapatite (HA) composite scaffolds for bone regeneration, which can have a tailored macro/micro-porous structure with high mechanical properties and excellent in vitro bioactivity using non-solvent-induced phase separation (NIPS)-based 3D plotting. This innovative 3D plotting technique can create highly microporous PCL/HA composite filaments by inducing unique phase separation in PCL/HA solutions through the non-solvent-solvent exchange phenomenon. The PCL/HA composite scaffolds produced with various HA contents (0 wt %, 10 wt %, 15 wt %, and 20 wt %) showed that PCL/HA composite struts with highly microporous structures were well constructed in a controlled periodic pattern. Similar levels of overall porosity (~78 vol %) and pore size (~248 µm) were observed for all the PCL/HA composite scaffolds, which would be highly beneficial to bone tissue regeneration. Mechanical properties, such as ultimate tensile strength and compressive yield strength, increased with an increase in HA content. In addition, incorporating bioactive HA particles into the PCL polymer led to remarkable enhancements in in vitro apatite-forming ability. PMID:28937605

Antimicrobial acrylic materials with in situ generated silver nanoparticles.

PubMed

Oei, James D; Zhao, William W; Chu, Lianrui; DeSilva, Mauris N; Ghimire, Abishek; Rawls, H Ralph; Whang, Kyumin

2012-02-01

Polymethyl methacrylate (PMMA) is widely used to treat traumatic head injuries (cranioplasty) and orthopedic injuries (bone cement), but there is a problem with implant-centered infections. With organisms such as Acinetobacter baumannii and methicillin-resistant staphylococcus aureus developing resistance to antibiotics, there is a need for novel antimicrobial delivery mechanisms without risk of developing resistant organisms. To develop a novel antimicrobial implant material by generating silver nanoparticles (AgNP) in situ in PMMA. All PMMA samples with AgNP's (AgNP-PMMA) released Ag(+) ions in vitro for over 28 days. In vitro antimicrobial assays revealed that these samples (even samples with the slowest release rate) inhibited 99.9% of bacteria against four different strains of bacteria. Long-term antimicrobial assay showed a continued antibacterial effect past 28 days. Some AgNP-loaded PMMA groups had comparable Durometer-D hardness (a measure of degree of cure) and modulus to control PMMA, but all experimental groups had slightly lower ultimate transverse strengths. AgNP-PMMA demonstrated a tremendously broad-spectrum and long-intermediate-term antimicrobial effect with comparable mechanical properties to control PMMA. Current efforts are focused on further improving mechanical properties by reducing AgNP loading and assessing fatigue properties. Copyright © 2011 Wiley Periodicals, Inc.

Correlation between structure and compressive strength in a reticulated glass-reinforced hydroxyapatite foam.

PubMed

Callcut, S; Knowles, J C

2002-05-01

Glass-reinforced hydroxyapatite (HA) foams were produced using reticulated foam technology using a polyurethane template with two different pore size distributions. The mechanical properties were evaluated and the structure analyzed through density measurements, image analysis, X-ray diffraction (XRD) and scanning electron microscopy (SEM). For the mechanical properties, the use of a glass significantly improved the ultimate compressive strength (UCS) as did the use of a second coating. All the samples tested showed the classic three regions characteristic of an elastic brittle foam. From the density measurements, after application of a correction to compensate for the closed porosity, the bulk and apparent density showed a 1 : 1 correlation. When relative bulk density was plotted against UCS, a non-linear relationship was found characteristic of an isotropic open celled material. It was found by image analysis that the pore size distribution did not change and there was no degradation of the macrostructure when replicating the ceramic from the initial polyurethane template during processing. However, the pore size distributions did shift to a lower size by about 0.5 mm due to the firing process. The ceramic foams were found to exhibit mechanical properties typical of isotropic open cellular foams.

Effect of in-situ formed Al3Ti particles on the microstructure and mechanical properties of 6061 Al alloy

NASA Astrophysics Data System (ADS)

Gupta, Rahul; Chaudhari, G. P.; Daniel, B. S. S.

2018-03-01

In this study, in situ Titanium-tri-aluminide (Al3Ti) particles reinforced Al 6061 alloy matrix composites were fabricated by the reaction of potassium hexafluorotitanate (K2TiF6) inorganic salt with molten Al 6061 alloy via liquid metallurgy route. The development of in-situ Al3Ti particles and their effects on the mechanical properties such as yield strength (YS), ductility, ultimate tensile strength (UTS) and hardness, and microstructure of Al 6061 alloy were studied. It was observed from the results that in-situ formed Al3Ti particles were blocky in morphology whose average size was around 2.6 ± 1.1 μm. Microstructure studies showed that grain size of Al matrix was reduced due to the nucleating effect of Al3Ti particles. It was observed from the mechanical properties analysis that when the volume fraction of Al3Ti particles was increased, the hardness, UTS and YS of the composites were also increased as compared to that of Al 6061 alloy. An improvement in ductility was observed with the dispersion of Al3Ti particles in base alloy which is contrary to many other composites.

Selective laser melting of high-performance pure tungsten: parameter design, densification behavior and mechanical properties

PubMed Central

Zhou, Kesong; Ma, Wenyou; Attard, Bonnie; Zhang, Panpan; Kuang, Tongchun

2018-01-01

Abstract Selective laser melting (SLM) additive manufacturing of pure tungsten encounters nearly all intractable difficulties of SLM metals fields due to its intrinsic properties. The key factors, including powder characteristics, layer thickness, and laser parameters of SLM high density tungsten are elucidated and discussed in detail. The main parameters were designed from theoretical calculations prior to the SLM process and experimentally optimized. Pure tungsten products with a density of 19.01 g/cm3 (98.50% theoretical density) were produced using SLM with the optimized processing parameters. A high density microstructure is formed without significant balling or macrocracks. The formation mechanisms for pores and the densification behaviors are systematically elucidated. Electron backscattered diffraction analysis confirms that the columnar grains stretch across several layers and parallel to the maximum temperature gradient, which can ensure good bonding between the layers. The mechanical properties of the SLM-produced tungsten are comparable to that produced by the conventional fabrication methods, with hardness values exceeding 460 HV0.05 and an ultimate compressive strength of about 1 GPa. This finding offers new potential applications of refractory metals in additive manufacturing. PMID:29707073

Mechanical Properties of Friction Stir Welds in A12195-T8

NASA Technical Reports Server (NTRS)

Kinchen, David G.; Li, Zhixian; Adams, Glynn P.

1999-01-01

An extensive study of the mechanical properties of friction stir welded Al-Li 2195 has been conducted by Lockheed Martin Michoud Space Systems under contract to NASA. The study was part of a development program in which weld parameters were defined for using FSW to assemble large-scale aluminum cryogenic tanks. In excess of 300 feet of 0.320 in. gage plate material was welded and tested. The tests include room temperature and cryogenic temperature tensile tests and surface crack tension (SCT) tests, nondestructive evaluation, metallurgical studies, and photostress analysis. The results of the testing demonstrated improved mechanical properties with FSW as compared to typical fusion welding processes. Increases in ultimate tensile strength, cryogenic enhancement and elongation were observed with the tensile test results. Increased fracture toughness was observed with the SCT results. Nondestructive evaluations were conducted on all welded Joints. No volumetric defects were indicated. Surface indications on the root side of the welds did not significantly affect weld strength. The results of the nondestructive evaluations were confirmed via metallurgical studies. Photostress analysis revealed strain concentrations in multi-pass and heat-repaired FSW's. Details of the tests and results are presented.

Multi-Objective Optimization of Friction Stir Welding Process Parameters of AA6061-T6 and AA7075-T6 Using a Biogeography Based Optimization Algorithm.

PubMed

Tamjidy, Mehran; Baharudin, B T Hang Tuah; Paslar, Shahla; Matori, Khamirul Amin; Sulaiman, Shamsuddin; Fadaeifard, Firouz

2017-05-15

The development of Friction Stir Welding (FSW) has provided an alternative approach for producing high-quality welds, in a fast and reliable manner. This study focuses on the mechanical properties of the dissimilar friction stir welding of AA6061-T6 and AA7075-T6 aluminum alloys. The FSW process parameters such as tool rotational speed, tool traverse speed, tilt angle, and tool offset influence the mechanical properties of the friction stir welded joints significantly. A mathematical regression model is developed to determine the empirical relationship between the FSW process parameters and mechanical properties, and the results are validated. In order to obtain the optimal values of process parameters that simultaneously optimize the ultimate tensile strength, elongation, and minimum hardness in the heat affected zone (HAZ), a metaheuristic, multi objective algorithm based on biogeography based optimization is proposed. The Pareto optimal frontiers for triple and dual objective functions are obtained and the best optimal solution is selected through using two different decision making techniques, technique for order of preference by similarity to ideal solution (TOPSIS) and Shannon's entropy.

Effect of weld line positions on the tensile deformation of two-component metal injection moulding

NASA Astrophysics Data System (ADS)

Manonukul, Anchalee; Songkuea, Sukrit; Moonchaleanporn, Pongporn; Tange, Makiko

2017-12-01

Knowledge of the mechanical properties of two-component parts is critical for engineering functionally graded components. In this study, mono- and two-component tensile test specimens were metal injection moulded. Three different weld line positions were generated in the two-component specimens. Linear shrinkage of the two-component specimens was greater than that of the mono-component specimens because the incompatibility of sintering shrinkage of both materials causes biaxial stresses and enhances sintering. The mechanical properties of 316L stainless steel were affected by the addition of a coloured pigment used to identify the weld line position after injection moulding. For the two-component specimens, the yield stress and ultimate tensile stress were similar to those of 316L stainless steel. Because 316L and 630 (also known as 17-4PH) stainless steels were well-sintered at the interface, the mechanical properties of the weaker material (316L stainless steel) were dominant. However, the elongations of the two-component specimens were lower than those of the mono-component specimens. An interfacial zone with a microstructure that differed from those of the mono-material specimens was observed; its different microstructure was attributed to the gradual diffusion of nickel and copper.

Selective laser melting of high-performance pure tungsten: parameter design, densification behavior and mechanical properties.

PubMed

Tan, Chaolin; Zhou, Kesong; Ma, Wenyou; Attard, Bonnie; Zhang, Panpan; Kuang, Tongchun

2018-01-01

Selective laser melting (SLM) additive manufacturing of pure tungsten encounters nearly all intractable difficulties of SLM metals fields due to its intrinsic properties. The key factors, including powder characteristics, layer thickness, and laser parameters of SLM high density tungsten are elucidated and discussed in detail. The main parameters were designed from theoretical calculations prior to the SLM process and experimentally optimized. Pure tungsten products with a density of 19.01 g/cm 3 (98.50% theoretical density) were produced using SLM with the optimized processing parameters. A high density microstructure is formed without significant balling or macrocracks. The formation mechanisms for pores and the densification behaviors are systematically elucidated. Electron backscattered diffraction analysis confirms that the columnar grains stretch across several layers and parallel to the maximum temperature gradient, which can ensure good bonding between the layers. The mechanical properties of the SLM-produced tungsten are comparable to that produced by the conventional fabrication methods, with hardness values exceeding 460 HV 0.05 and an ultimate compressive strength of about 1 GPa. This finding offers new potential applications of refractory metals in additive manufacturing.

Correlation between mechanical properties and retained austenite characteristics in a low-carbon medium manganese alloyed steel plate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Jun, E-mail: cjer19841011@163.com; Lv, Mengyang; Tang, Shuai

2015-08-15

The effects of retained austenite characteristics on tensile properties and low-temperature impact toughness have been investigated by means of transmission electron microscopy and X-ray diffraction. It was found that only part of austenite phase formed during heat treating was left at room temperature. Moreover, the film-like retained austenite is displayed between bcc-martensite laths after heat treating at 600 °C, while the block-form retained austenite with thin hcp-martensite laths is observed after heat treating at 650 °C. It has been demonstrated that the film-like retained austenite possesses relatively high thermal and mechanical stability, and it can greatly improve low-temperature impact toughness,more » but its contribution to strain hardening capacity is limited. However, the block-form retained austenite can greatly enhance ultimate tensile strength and strain hardening capacity, but its contribution to low-temperature impact toughness is poor. - Highlights: • Correlation between retained austenite and impact toughness was elucidated. • The impact toughness is related to mechanical stability of retained austenite. • The effect of retained austenite on tensile and impact properties is inconsistent.« less

The Effects of Antimony Addition on the Microstructural, Mechanical, and Thermal Properties of Sn-3.0Ag-0.5Cu Solder Alloy

NASA Astrophysics Data System (ADS)

Sungkhaphaitoon, Phairote; Plookphol, Thawatchai

2018-02-01

In this study, we investigated the effects produced by the addition of antimony (Sb) to Sn-3.0Ag-0.5Cu-based solder alloys. Our focus was the alloys' microstructural, mechanical, and thermal properties. We evaluated the effects by means of scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), differential scanning calorimetry (DSC), and a universal testing machine (UTM). The results showed that a part of the Sb was dissolved in the Sn matrix phase, and the remaining one participated in the formation of intermetallic compounds (IMCs) of Ag3(Sn,Sb) and Cu6(Sn,Sb)5. In the alloy containing the highest wt pct Sb, the added component resulted in the formation of SnSb compound and small particle pinning of Ag3(Sn,Sb) along the grain boundary of the IMCs. Our tests of the Sn-3.0Ag-0.5Cu solder alloys' mechanical properties showed that the effects produced by the addition of Sb varied as a function of the wt pct Sb content. The ultimate tensile strength (UTS) increased from 29.21 to a maximum value of 40.44 MPa, but the pct elongation (pct EL) decreased from 48.0 to a minimum 25.43 pct. Principally, the alloys containing Sb had higher UTS and lower pct EL than Sb-free solder alloys due to the strengthening effects of solid solution and second-phase dispersion. Thermal analysis showed that the alloys containing Sb had a slightly higher melting point and that the addition amount ranging from 0.5 to 3.0 wt pct Sb did not significantly change the solidus and liquidus temperatures compared with the Sb-free solder alloys. Thus, the optimal concentration of Sb in the alloys was 3.0 wt pct because the microstructure and the ultimate tensile strength of the SAC305 solder alloys were improved.

Mechanics of Platelet-Matrix Composites across Scales: Theory, Multiscale Modeling, and 3D Fabrication

NASA Astrophysics Data System (ADS)

Sakhavand, Navid

Many natural and biomimetic composites - such as nacre, silk and clay-polymer - exhibit a remarkable balance of strength, toughness, and/or stiffness, which call for a universal measure to quantify this outstanding feature given the platelet-matrix structure and material characteristics of the constituents. Analogously, there is an urgent need to quantify the mechanics of emerging electronic and photonic systems such as stacked heterostructures, which are composed of strong in-plane bonding networks but weak interplanar bonding matrices. In this regard, development of a universal composition-structure-property map for natural platelet-matrix composites, and stacked heterostructures opens up new doors for designing materials with superior mechanical performance. In this dissertation, a multiscale bottom-up approach is adopted to analyze and predict the mechanical properties of platelet-matrix composites. Design guidelines are provided by developing universally valid (across different length scales) diagrams for science-based engineering of numerous natural and synthetic platelet-matrix composites and stacked heterostructures while significantly broadening the spectrum of strategies for fabricating new composites with specific and optimized mechanical properties. First, molecular dynamics simulations are utilized to unravel the fundamental underlying physics and chemistry of the binding nature at the atomic-level interface of organic-inorganic composites. Polymer-cementitious composites are considered as case studies to understand bonding mechanism at the nanoscale and open up new venues for potential mechanical enhancement at the macro-scale. Next, sophisticated mathematical derivations based on elasticity and plasticity theories are presented to describe pre-crack (intrinsic) mechanical performance of platelet-matrix composites at the microscale. These derivations lead to developing a unified framework to construct series of universal composition-structure-property maps that decode the interplay between various geometries and inherent material features, encapsulated in a few dimensionless parameters. Finally, after crack mechanical properties (extrinsic) of platelet-matrix composites until ultimate failure of the material at the macroscale is investigated via combinatorial finite element simulations. The effect of different composition-structure-property parameters on mechanical properties synergies are depicted via 2D and 3D maps. 3D-printed specimens are fabricated and tested against the theoretical prediction. The combination of the presented diagrams and guidelines paves the path toward platelet-matrix composites and stacked-heterostructures with superior and optimized mechanical properties.

Multiscale mechanisms of nutritionally induced property variation in spider silks

PubMed Central

Nobbs, Madeleine; Martens, Penny J.; Tso, I-Min; Chuang, Wei-Tsung; Chang, Chung-Kai; Sheu, Hwo-Shuenn

2018-01-01

Variability in spider major ampullate (MA) silk properties at different scales has proven difficult to determine and remains an obstacle to the development of synthetic fibers mimicking MA silk performance. A multitude of techniques may be used to measure multiscale aspects of silk properties. Here we fed five species of Araneoid spider solutions that either contained protein or were protein deprived and performed silk tensile tests, small and wide-angle X-ray scattering (SAXS/WAXS), amino acid composition analyses, and silk gene expression analyses, to resolve persistent questions about how nutrient deprivation induces variations in MA silk mechanical properties across scales. Our analyses found that the properties of each spider’s silk varied differently in response to variations in their protein intake. We found changes in the crystalline and non-crystalline nanostructures to play specific roles in inducing the property variations we found. Across treatment MaSp expression patterns differed in each of the five species. We found that in most species MaSp expression and amino acid composition variations did not conform with our predictions based on a traditional MaSp expression model. In general, changes to the silk’s alanine and proline compositions influenced the alignment of the proteins within the silk’s amorphous region, which influenced silk extensibility and toughness. Variations in structural alignment in the crystalline and non-crystalline regions influenced ultimate strength independent of genetic expression. Our study provides the deepest insights thus far into the mechanisms of how MA silk properties vary from gene expression to nanostructure formations to fiber mechanics. Such knowledge is imperative for promoting the production of synthetic silk fibers. PMID:29390013

Effects of LDEF flight exposure on selected polymer matrix resin composite materials

NASA Technical Reports Server (NTRS)

Slemp, Wayne S.; Young, Philip R.; Witte, William G., Jr.; Shen, James Y.

1992-01-01

The characterization of selected graphite fiber reinforced epoxy (934 and 5208) and polysulfone (P1700) matrix resin composites materials which received over five years and nine months of exposure to the low earth orbit (LEO) environment in experiment AO134 on the Long Duration Exposure Facility is reported. The changes in mechanical properties of ultimate tensile strength and tensile modulus for exposed flight specimens are compared to the three sets of control specimens. Marked changes in surface appearance are discussed, and resin loss is reported. The chemical characterization including infrared, thermal, and selected solution property measurements showed that the molecular structure of the polymetric matrix had not changed significantly in response to this exposure.

[Effect of sterilisation with formaldehyde, gamma irradiation and ethylene oxide on the properties of polyethylene joint replacement components].

PubMed

Fulín, P; Pokorný, D; Slouf, M; Vacková, T; Dybal, J; Sosna, A

2014-01-01

Each method of sterilisation has some effect on the structure and properties of UHMWPE and thus also on joint replacement longevity. This study was designed to compare, using objective methods of measurement, several kinds of sterilisation and to recommend the one which has the best prospect for making joint replacements last longer. Two groups of UHMWPE samples were tested. Group 1 included virgin GUR 1020 polyethylene, non-modified and non-sterilised (Meditech, Germany). Group 2 comprised of three sets of samples sterilised with formaldehyde, gamma irradiation and ethylene oxide, respectively. In both groups, physicochemical properties were assessed by infrared spectroscopy (IR), and the oxidation (OI) and trans-vinyl (VI) indices, which show the degree of oxidation of a material, were determined. Free-radical concentrations were measured by the method of electron spin resonance (ESR). The mechanical properties of each sample were studied using small punch tests (SPT) and testing microhardness (MH). Any change in mechanical properties can affect, to various degrees, the quality and longevity of a prosthetic joint. The samples sterilised by gamma irradiation showed higher values of both the OI (0.37) and the VI index (0.038) than the other samples (OI, 0.02 to 0.05 and VI, 0). Also, the free-radical concentration was detectable only in the gamma-sterilised sample. Values obtained for mechanical properties were as follows: peak load in the range of 58.48 N (gamma irradiation) to 59.60 N (ethylene oxide); ultimate load in the range of 46.69 N (gamma irradiation) to 57.50 N (ethylene oxide); ultimate displacement in the range of 4.29 mm (gamma irradiation) to 4.58 mm (virgin polyethylene and formaldehyde); and work to failure in the range of 185.18 mJ (gamma irradiation) to 205.89 mJ (virgin polyethylene). Microhardness values were obtained in the following ranges: 41.2 to 44.6 MPa (virgin polyethylene); 40.2 to 44.1 MPa (formaldehyde); 46.1 to 49.3 MPa (gamma irradiation); and 40.3 to 44.2 MPa (ethylene oxide). The samples sterilised with formaldehyde and ethylene oxide have mechanical properties very similar to virgin polyethylene, they are not damaged by oxidation and do not contain free radicals. Owing to these characteristics, the immediate and long-term oxidation stability of the three samples is higher. The sample sterilised by gamma irradiation showed the presence of free radicals and immediate and long-term oxidative degradation. This results in the deterioration of mechanical properties and the growth of crystallinity due to enhanced oxidation and leads to higher polyethylene microhardness. Sterilisation with gamma irradiation results in oxidative degradation and mechanical property deterioration, which is one of the potential risks of a shorter life span of joint replacements. The use of ethylene oxide or formaldehyde does not change polymer properties nor has any effect on oxidation of materials. Therefore, a longer life expectancy of the joint replacements sterilised with ethylene oxide can be expected. The life span of their joint replacements is a key issue for the patients. Prosthetic joint loosening is painful and the patient often requires re-implantation. A higher number of re-implantations is associated with higher costs for the institution involved and, consequently, for the whole health care system. Although this study basically deals with chemical issues, it informs the surgeon of the latest developments leading to the improvement of implanted materials, which can increase the life expectancy of joint replacements and patients' satisfaction.

Bone characteristics of late-term embryonic and hatchling broilers: bone development under extreme growth rate.

PubMed

Yair, R; Uni, Z; Shahar, R

2012-10-01

The development of broilers is an extreme example of rapid growth, increasing in weight from 40 g at hatch to 2,000 g 5 to 6 wk later. Such rapid growth requires a correspondingly fast development of the skeleton. Bone development is a genetically programmed process that is modified by epigenetic factors, mainly muscle-induced stresses and strains. In this study, we describe the temporal changes in bone morphology and material properties during the prehatch period [embryonic day (E) 14, E17, E19, E21] and posthatch d 3 and 7. The bones were examined for their weight, length, ash content, mechanical properties, and cortical structure. We show that the cross-sectional shape of the tibia and femur changes during the examination period from circular to elliptical. Additionally, the changes in bone properties are time-dependent and nonuniform: from E14 to E17 and from d 3 to 7, fast bone growth was noted, with major increases in both mechanical properties (stiffness, ultimate load, and energy to fracture) and geometric properties (cross-sectional area and thickness, medullary area, and moment of inertia). On the other hand, during the last days of incubation, most mechanical and geometric properties remain unchanged or even decrease. The reasons for this finding may relate to the hatching process but also to mineral shortage during the last days of incubation. This study leads to better understanding of bone development in ovo and posthatch in fast-growing broilers.

Gap Analysis of Material Properties Data for Ferritic/Martensitic HT-9 Steel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brown, Neil R.; Serrano De Caro, Magdalena; Rodriguez, Edward A.

2012-08-28

The US Department of Energy (DOE), Office of Nuclear Energy (NE), is supporting the development of an ASME Code Case for adoption of 12Cr-1Mo-VW ferritic/martensitic (F/M) steel, commonly known as HT-9, primarily for use in elevated temperature design of liquid-metal fast reactors (LMFR) and components. In 2011, Los Alamos National Laboratory (LANL) nuclear engineering staff began assisting in the development of a small modular reactor (SMR) design concept, previously known as the Hyperion Module, now called the Gen4 Module. LANL staff immediately proposed HT-9 for the reactor vessel and components, as well as fuel clad and ducting, due to itsmore » superior thermal qualities. Although the ASME material Code Case, for adoption of HT-9 as an approved elevated temperature material for LMFR service, is the ultimate goal of this project, there are several key deliverables that must first be successfully accomplished. The most important key deliverable is the research, accumulation, and documentation of specific material parameters; physical, mechanical, and environmental, which becomes the basis for an ASME Code Case. Time-independent tensile and ductility data and time-dependent creep and creep-rupture behavior are some of the material properties required for a successful ASME Code case. Although this report provides a cursory review of the available data, a much more comprehensive study of open-source data would be necessary. This report serves three purposes: (a) provides a list of already existing material data information that could ultimately be made available to the ASME Code, (b) determines the HT-9 material properties data missing from available sources that would be required and (c) estimates the necessary material testing required to close the gap. Ultimately, the gap analysis demonstrates that certain material properties testing will be required to fulfill the necessary information package for an ASME Code Case.« less

Continuous quantum measurement and the quantum to classical transition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bhattacharya, Tanmoy; Habib, Salman; Jacobs, Kurt

2003-04-01

While ultimately they are described by quantum mechanics, macroscopic mechanical systems are nevertheless observed to follow the trajectories predicted by classical mechanics. Hence, in the regime defining macroscopic physics, the trajectories of the correct classical motion must emerge from quantum mechanics, a process referred to as the quantum to classical transition. Extending previous work [Bhattacharya, Habib, and Jacobs, Phys. Rev. Lett. 85, 4852 (2000)], here we elucidate this transition in some detail, showing that once the measurement processes that affect all macroscopic systems are taken into account, quantum mechanics indeed predicts the emergence of classical motion. We derive inequalities thatmore » describe the parameter regime in which classical motion is obtained, and provide numerical examples. We also demonstrate two further important properties of the classical limit: first, that multiple observers all agree on the motion of an object, and second, that classical statistical inference may be used to correctly track the classical motion.« less

Thermomechanical Formation–Structure–Property Relationships in Photopolymerized Copper-Catalyzed Azide–Alkyne (CuAAC) Networks

PubMed Central

Baranek, Austin; Song, Han Byul; McBride, Mathew; Finnegan, Patricia; Bowman, Christopher N.

2016-01-01

Bulk photopolymerization of a library of synthesized multifunctional azides and alkynes was carried out toward developing structure–property relationships for CuAAC-based polymer networks. Multifunctional azides and alkynes were formulated with a copper catalyst and a photoinitiator, cured, and analyzed for their mechanical properties. Material properties such as the glass transition temperatures (Tg) show a strong dependence on monomer structure with Tg values ranging from 41 to 90 °C for the series of CuAAC monomers synthesized in this study. Compared to the triazoles, analogous thioether-based polymer networks exhibit a 45–49 °C lower Tg whereas analogous monomers composed of ethers in place of carbamates exhibit a 40 °C lower Tg. Here, the formation of the triazole moiety during the polymerization represents a critical component in dictating the material properties of the ultimate polymer network where material properties such as the rubbery modulus, cross-link density, and Tg all exhibit strong dependence on polymerization conversion, monomer composition, and structure postgelation. PMID:27867223

Heat Treatment Effects on the Tensile Properties and Microstructures of a SiC/RBSN Composite in Nitrogen

NASA Technical Reports Server (NTRS)

Bhatt, R. T.

1995-01-01

The room-temperature tensile properties and constituent microstructures of a unidirectionally reinforced SiC/reaction bonded silicon nitride (RBSN) composite have been investigated after heat treatments at 1400, 1600, or 1800 C in nitrogen for up to 100 hr. The composite consisted of approximately 24 vol% of aligned 140 micron diameter, continuous length, chemically vapor deposited SiC fibers in an approximately 40% porous silicon nitride matrix. The composites heat treated at 1400 C for up to 100 hr showed elastic modulus, first matrix cracking strength, and ultimate tensile strength values similar to those of the as-fabricated composites, but those heat treated for 1 hr beyond this temperature displayed losses in all three properties. Recrystallization of the SiC fibers, reaction between the carbon-rich interface coating on the fibers and the RBSN matrix, and dissociation of the RBSN matrix are the reasons for the loss of mechanical properties.

Mechanical properties of untreated and alkaline treated fibers from zalacca midrib wastes

NASA Astrophysics Data System (ADS)

Raharjo, Wahyu Purwo; Soenoko, Rudy; Purnowidodo, Anindito; Choiron, Mochammad Agus; Triyono

2016-03-01

The environmental concern has been raised due to the abundance of waste from synthetic materials which cannot be biodegraded after their life-time. It provides opportunity to exploit natural resources which are neglected. For example, midrib wastes from zalacca plants after cutting are able to utilize as composite reinforcement. The aim of this research was to characterize the mechanical properties of zalacca midrib fibers. As other ones, zalacca midrib fibers consisted of cellulose, hemicellulose and lignin, which their compositions were 42.54, 34.35 and 28.01 % respectively. To raise their cellulose content, the zalacca fibers were alkaline treated by immersion in the sodium hydroxide for 2 hours and rinsing in the distilled water. The concentration of sodium hydroxide was varied 1 and 5%. To investigate the influence of alkaline treatment, the mechanical testing and morphological analysis was performed. The tensile testing was done to obtain ultimate strength, elastic modulus and strain to fracture. The surface morphology of fibers was observed by SEM. The average ultimate tensile strength of zalacca fibers ranged from 182.12 MPa (untreated) to 417.94 MPa (5%NaOH treated). The diameter measurement showed that the alkaline treatment reduce the average fiber diameters due to the decline of the hemicellulose and lignin content as fiber matrix. This caused the increase of the tensile strength and elastic modulus due to the reduction of diameters as divider meanwhile the cellulose content as structural supporter of the fibers was relatively constant. From the SEM analysis, it was shown that the alkaline treatment reduced the fiber matrix so that its surface morphology became rougher due to the microfibrils appearance.

Comparative characterization of a novel cad-cam polymer-infiltrated-ceramic-network

PubMed Central

Pascual, Agustín; Camps, Isabel; Grau-Benitez, María

2015-01-01

Background The field of dental ceramics for CAD-CAM is enriched with a new innovative material composition having a porous three-dimensional structure of feldspathic ceramic infiltrated with acrylic resins.The aim of this study is to determine the mechanical properties of Polymer-Infiltrated-Ceramic-Network (PICN) and compare its performance with other ceramics and a nano-ceramic resin available for CAD-CAM systems. Material and Methods In this study a total of five different materials for CAD-CAM were investigated. A polymer-infiltrated ceramic (Vita Enamic), a nano-ceramic resin (Lava Ultimate), a feldspathic ceramic (Mark II), a lithium disilicate ceramic (IPS-e max CAD) and finally a Leucite based ceramic (Empress - CAD). From CAD-CAM blocks, 120 bars (30 for each material cited above) were cut to measure the flexural strength with a three-point-bending test. Strain at failure, fracture stress and Weibull modulus was calculated. Vickers hardness of each material was also measured. Results IPS-EMAX presents mechanical properties significantly better from the other materials studied. Its strain at failure, flexural strength and hardness exhibited significantly higher values in comparison with the others. VITA ENAMIC and LAVA ULTIMATE stand out as the next most resistant materials. Conclusions The flexural strength, elastic modulus similar to a tooth as well as having less hardness than ceramics make PICN materials an option to consider as a restorative material. Key words:Ceramic infiltrated with resin, CAD-CAM, Weibull modulus, flexural strength, micro hardness. PMID:26535096

Development of the mechanical properties of engineered skin substitutes after grafting to full-thickness wounds.

PubMed

Sander, Edward A; Lynch, Kaari A; Boyce, Steven T

2014-05-01

Engineered skin substitutes (ESSs) have been reported to close full-thickness burn wounds but are subject to loss from mechanical shear due to their deficiencies in tensile strength and elasticity. Hypothetically, if the mechanical properties of ESS matched those of native skin, losses due to shear or fracture could be reduced. To consider modifications of the composition of ESS to improve homology with native skin, biomechanical analyses of the current composition of ESS were performed. ESSs consist of a degradable biopolymer scaffold of type I collagen and chondroitin-sulfate (CGS) that is populated sequentially with cultured human dermal fibroblasts (hF) and epidermal keratinocytes (hK). In the current study, the hydrated biopolymer scaffold (CGS), the scaffold populated with hF dermal skin substitute (DSS), or the complete ESS were evaluated mechanically for linear stiffness (N/mm), ultimate tensile load at failure (N), maximum extension at failure (mm), and energy absorbed up to the point of failure (N-mm). These biomechanical end points were also used to evaluate ESS at six weeks after grafting to full-thickness skin wounds in athymic mice and compared to murine autograft or excised murine skin. The data showed statistically significant differences (p <0.05) between ESS in vitro and after grafting for all four structural properties. Grafted ESS differed statistically from murine autograft with respect to maximum extension at failure, and from intact murine skin with respect to linear stiffness and maximum extension. These results demonstrate rapid changes in mechanical properties of ESS after grafting that are comparable to murine autograft. These values provide instruction for improvement of the biomechanical properties of ESS in vitro that may reduce clinical morbidity from graft loss.

The effect of re-ageing on a novel thermomechanical treatment for improving the mechanical properties of AA2139 aerospace aluminium alloys

NASA Astrophysics Data System (ADS)

Ragkousis, A.; Bakare, F.; Babalola, M. I.

2017-11-01

This study presents the effects of a novel thermomechanical treatment on the mechanical properties of the AA2139 aerospace aluminium alloys. The novel treatment, which is comprised of a combination of under-aging, cold-rolling, and re-aging, was successfully employed by Wang et al (2014 Mater. Sci. Eng. A 607 313-7) to enhance the mechanical and microstructure properties of 6000 series aluminium alloys. The influence of under-ageing and re-aging parameters of the treatment on the AA2139 properties has been examined by tensile and hardness testing, differential scanning calorimetry, and thermoelectric power measurements. It was determined that a higher temperature under-ageing, combined with lower temperature and long duration re-ageing resulted in the most attractive mechanical properties, which significantly exceeded those of other traditional treatments. More specifically, a 175 °C/1.5 h under-ageing treatment, followed by a cold rolling reduction of 75% and a 110 °C/96 h re-ageing resulted in a yield strength of 554 MPa, an ultimate tensile strength of 618 MPa, and an elongation of 7.5%, far exceeding the strength requirements and 5% acceptable elongation for applications in the aerospace industry. These results, in conjunction with the results of the parallel study focusing on the effects of the cold-rolling component of the treatment (Bakare et al 2017 Mater. Res. Express 4) further reinforce the position that the treatment employed is superior to conventional ones for the 2139 alloy.

Ultimate force and stiffness of 2-piece zirconium dioxide implants with screw-retained monolithic lithium-disilicate reconstructions.

PubMed

Joda, Tim; Voumard, Benjamin; Zysset, Philippe K; Brägger, Urs; Ferrari, Marco

2018-04-01

The aims were to analyze stiffness, ultimate force, and failure modes of a 2-piece zirconium dioxide (ZrO 2 ) implant system. Eleven 2-piece ZrO 2 implants, each mounted with ZrO 2 abutments plus bonded monolithic lithium disilicate (LS 2 ) restorations, were grouped for 3.3mm (A) and 4.1mm (B) diameter samples. Quasi-static load was monotonically applied under a standardized test set-up (loading configuration according to DIN ISO 14801). The ultimate force was defined as the maximum force that implants are able to carry out until fracture; stiffness was measured as the maximum slope during loading. An unpaired t-test was performed between group A and B for ultimate force and stiffness (p<0.05). Force-displacement curves revealed statistically homogenous inner-group results for all samples. Failure modes showed characteristic fractures at the neck configuration of the implants independent of the diameter. Mean stiffness was 1099N/mm (±192) for group A, and significantly lower compared to group B with 1630N/mm (±274) (p<0.01); whereas mean ultimate force was 348N (±53) for group A, and significantly increased for group B with 684N (±29) (p<0.0001). The examined 2-piece ZrO 2 implant system mounted to LS 2 -restorations seems to be a stable unit under in-vitro conditions with mechanical properties compared to loading capacity of physiological force. The metal-free implant reconstructions demonstrated high stiffness and ultimate force under quasi-static load for single tooth replacement under consideration of the dental indication of narrow and standard diameter implants. Copyright © 2017 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.

Correlations Between Bone Mechanical Properties and Bone Composition Parameters in Mouse Models of Dominant and Recessive Osteogenesis Imperfecta and the Response to Anti-TGF-β Treatment.

PubMed

Bi, Xiaohong; Grafe, Ingo; Ding, Hao; Flores, Rene; Munivez, Elda; Jiang, Ming Ming; Dawson, Brian; Lee, Brendan; Ambrose, Catherine G

2017-02-01

Osteogenesis imperfecta (OI) is a group of genetic disorders characterized by brittle bones that are prone to fracture. Although previous studies in animal models investigated the mechanical properties and material composition of OI bone, little work has been conducted to statistically correlate these parameters to identify key compositional contributors to the impaired bone mechanical behaviors in OI. Further, although increased TGF-β signaling has been demonstrated as a contributing mechanism to the bone pathology in OI models, the relationship between mechanical properties and bone composition after anti-TGF-β treatment in OI has not been studied. Here, we performed follow-up analyses of femurs collected in an earlier study from OI mice with and without anti-TGF-β treatment from both recessive (Crtap -/- ) and dominant (Col1a2 +/P.G610C ) OI mouse models and WT mice. Mechanical properties were determined using three-point bending tests and evaluated for statistical correlation with molecular composition in bone tissue assessed by Raman spectroscopy. Statistical regression analysis was conducted to determine significant compositional determinants of mechanical integrity. Interestingly, we found differences in the relationships between bone composition and mechanical properties and in the response to anti-TGF-β treatment. Femurs of both OI models exhibited increased brittleness, which was associated with reduced collagen content and carbonate substitution. In the Col1a2 +/P.G610C femurs, reduced hydroxyapatite crystallinity was also found to be associated with increased brittleness, and increased mineral-to-collagen ratio was correlated with increased ultimate strength, elastic modulus, and bone brittleness. In both models of OI, regression analysis demonstrated that collagen content was an important predictor of the increased brittleness. In summary, this work provides new insights into the relationships between bone composition and material properties in models of OI, identifies key bone compositional parameters that correlate with the impaired mechanical integrity of OI bone, and explores the effects of anti-TGF-β treatment on bone-quality parameters in these models. © 2016 American Society for Bone and Mineral Research. © 2016 American Society for Bone and Mineral Research.

Surface orientation effects on bending properties of surgical mesh are independent of tensile properties.

PubMed

Simon, David D; Andrews, Sharon M; Robinson-Zeigler, Rebecca; Valdes, Thelma; Woods, Terry O

2018-02-01

Current mechanical testing of surgical mesh focuses primarily on tensile properties even though implanted devices are not subjected to pure tensile loads. Our objective was to determine the flexural (bending) properties of surgical mesh and determine if they correlate with mesh tensile properties. The flexural rigidity values of 11 different surgical mesh designs were determined along three textile directions (machine, cross-machine, and 45° to machine; n = 5 for each) using ASTM D1388-14 while tracking surface orientation. Tensile testing was also performed on the same specimens using ASTM D882-12. Linear regressions were performed to compare mesh flexural rigidity to mesh thickness, areal mass density, filament diameter, ultimate tensile strength, and maximum extension. Of 33 mesh specimen groups, 30 had significant differences in flexural rigidity values when comparing surface orientations (top and bottom). Flexural rigidity and mesh tensile properties also varied with textile direction (machine and cross-machine). There was no strong correlation between the flexural and tensile properties, with mesh thickness having the best overall correlation with flexural rigidity. Currently, surface orientation is not indicated on marketed surgical mesh, and a single mesh may behave differently depending on the direction of loading. The lack of correlation between flexural stiffness and tensile properties indicates the need to examine mesh bending stiffness to provide a more comprehensive understanding of surgical mesh mechanical behaviors. Further investigation is needed to determine if these flexural properties result in the surgical mesh behaving mechanically different depending on implantation direction. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 854-862, 2018. © 2017 Wiley Periodicals, Inc.

An evaluation of the interfacial bond properties between carbon phenolic and glass phenolic composites

NASA Technical Reports Server (NTRS)

Jordan, Kelvin; Clinton, Raymond; Jeelani, Shaik

1989-01-01

The effects of moisture and surface finish on the mechanical and physical properties of the interfacial bond between the carbon/phenolic (C/P) and glass/phenolic (G/P) composite materials are presented. Four flat panel laminates were fabricated using the C/P and G/P materials. Of the four laminates, one panel was fabricated in which the C/P and G/P materials were cured simultaneously. It was identified as the cocure. The remaining laminates were processed with an initial simultaneous cure of the three C/P billets. Two surface finishes, one on each half, were applied to the top surface. Prior to the application and cure of the G/P material to the machined surface of the three C/P panels, each was subjected to the specific environmental conditioning. Types of conditioning included: (1) nominal fabrication environment, (2) a prescribed drying cycle, and (3) a total immersion in water at 160 F. Physical property tests were performed on specimens removed from the C/P materials of each laminate for determination of the specific gravity, residual volatiles and and resin content. Comparisons of results with shuttle solid rocket motor (SRM) nozzle material specifications verified that the materials used in fabricating the laminates met acceptance criteria and were representative of SRM nozzle materials. Mechanical property tests were performed at room temperature on specimens removed from the G/P, the C/P and the interface between the two materials for each laminate. The double-notched shear strength test was used to determine the ultimate interlaminar shear strength. Results indicate no appreciable difference in the C/P material of the four laminates with the exception of the cocure laminate, where 20 percent reduction in the strength was observed. The most significant effect and the ultimate strength was significantly reduced in the wet material. No appreciable variation was noted between the surface finishes in the wet laminate.

The microstructure and tensile properties of nitrogen containing vacuum atomized Alloy 690

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fuchs, G.E.; Hayden, S.Z.

1991-02-01

The mechanical properties and microstructure of a heat of nitrogen containing vacuum atomized A690 have been characterized. Although wrought A690 exhibits extensive grain growth during solution annealing heat treatments, only limited grain growth was observed in P/M690N{sub 2}. The presence of the nitrogen in the P/M690N{sub 2} resulted in the formation of a fine dispersion of Ti(C,N) which limited grain growth during elevated temperature exposures. The yield and ultimate tensile strength of the P/M690N{sub 2} was significantly greater than wrought A690 and elevated temperature exposures did not greatly affect the properties of the P/M690N{sub 2}. Although the P/M690N{sub 2} didmore » exhibit appreciably higher strengths than wrought A690, the ductility was not adversely affected. In general, the resulting microstructure and, hence, mechanical properties of the P/M690N{sub 2} were very stable, uniform, and reproducible, even after long-term elevated temperature exposures of up to 24 hours at 1100{degree}C. 14 refs., 5 figs., 1 tab.« less

Non-Hookean Mechanics of Crystalline Membranes

NASA Astrophysics Data System (ADS)

Nicholl, Ryan J. T.

The goal of the thesis is to explore the effect of crumpling on the mechanics of graphene--the ultimate thin membrane. The effect due to crumpling on the mechanical response of 2D materials is almost universally ignored in prior experiments. This is because the most widely used measurement schemes require high and non-uniform applied stress that suppresses crumpling. Experiments that do probe the interplay between crumpling and graphene mechanics remain highly challenging. To measure the mechanical effects of crumpling we need to develop a new measurement scheme which can apply low and uniform stress, allow non-invasive topography measurements, and be applicable at cryogenic temperatures. The motivating questions of this thesis are the following: • How does out-of plane crumpling affect the mechanical constants of 2D materials? • How do we implement measurement techniques sensitive to crumpling? • Can we identify sources of crumpling and distinguish between static and dynamic crumpling? • Can we tune the mechanical properties of 2D materials by controlling crumpling?

Modification of the Structure of Low-Carbon Pipe Steel by Helical Rolling, and the Increase in Its Strength and Cold Resistance

NASA Astrophysics Data System (ADS)

Derevyagina, L. S.; Gordienko, A. I.; Pochivalov, Yu. I.; Smirnova, A. S.

2018-01-01

The paper reports the investigation results on the microstructure and mechanical properties of low-carbon pipe steel after helical rolling. The processing of the steel leads to the refinement of ferritic grains from 12 (for the coarse-grained state) to 5 μm, to the strengthening of ferrite by carbide particles, a decrease in the total fraction of perlite grains, a more uniform alternation of ferrite and perlite, and the formation of regions with bainitic structure. The mechanical properties of the steel have been determined in the conditions of static and dynamic loading in the range of test temperatures from +20 to-70°C. As a result of processing, the ultimate tensile strength increases (from 650 to 770 MPa at a rolling temperature from 920°C) and the viscoplastic properties at negative temperatures are improved significantly. The ductile-brittle transition temperature of the rolled steel decreases from-32 to-55°C and the impact toughness at the test temperature-40°C increases eight times compared to the initial state of the steel.

A hydrogel pericardial patch.

PubMed

Allder, M A; Guilbeau, E J; Brandon, T A; Walker, A S; Koeneman, J B; Fisk, R L

1990-01-01

Patients undergoing repeat cardiac operations are higher operative risks than those undergoing an initial cardiac procedure because adhesion formation can occur if the native pericardium is not closed. A unique composite patch that may be used to augment the pericardial tissue when primary closure is not possible has been developed. The patch is made of a hydrogel, poly (2-hydroxyethyl methacrylate), reinforced with an ethylene tetrafluoroethylene (ETFE) mesh. The mesh provides the needed mechanical properties, whereas the patch's surface properties are comparable to the hydrogel. Two types of patches were fabricated: one with the mesh weave at a perpendicular orientation and one at 45 degrees to the principle loading direction. The patches were mechanically tested and compared with canine pericardium. Ultimate tensile strength of the patches is not significantly different from canine pericardium (p less than 0.05), are the patch suture strength is nearly twice that of canine pericardium. The perpendicular patch is stiffer than canine pericardium, whereas the 45 degree patch is not (p less than 0.05). The 45 degree patch shows considerable promise as a pericardial substitute because it closely matches the properties native canine pericardium.

The structure and mechanical properties of parts elaborated by direct laser deposition 316L stainless steel powder obtained in various ways

NASA Astrophysics Data System (ADS)

Loginova, I. S.; Solonin, A. N.; Prosviryakov, A. S.; Adisa, S. B.; Khalil, A. M.; Bykovskiy, D. P.; Petrovskiy, V. N.

2017-12-01

In this work the morphology, the size and the chemical composition of the powders of steel 316L received by the two methods was studied: fusion dispersion by a gas stream and reduction of metal chlorides with the subsequent plasma atomization of the received powder particles. The powder particles received by the first method have a spherical shape (aspect ratio 1,0-1,2) with an average size of 77 μm and are characterized by the absence of internal porosity. Particles of the powder received by the second method also have a spherical shape and faultless structure, however, their chemical composition may vary in different particles. The average size of particles is 32 μm. Though the obtained powders had different properties, the experimental samples received by DLD technology demonstrated by equally high durability (Ultimate strength is 623±5 and of 623±18 MPa respectively) and plasticity (38 and 41% respectively). It is established that mechanical properties of DLD samples increase for 7-10% after treatment of the surface.

Mechanical property degradation of high crystalline SiC fiber–reinforced SiC matrix composite neutron irradiated to ~100 displacements per atom

DOE PAGES

Koyanagi, Takaaki; Nozawa, Takashi; Katoh, Yutai; ...

2017-12-20

For the development of silicon carbide (SiC) materials for next-generation nuclear structural applications, degradation of material properties under intense neutron irradiation is a critical feasibility issue. This paper evaluated the mechanical properties and microstructure of a chemical vapor infiltrated SiC matrix composite, reinforced with a multi-layer SiC/pyrolytic carbon–coated Hi-Nicalon TM Type S SiC fiber, following neutron irradiation at 319 and 629 °C to ~100 displacements per atom. Both the proportional limit stress and ultimate flexural strength were significantly degraded as a result of irradiation at both temperatures. After irradiation at 319 °C, the quasi-ductile fracture behavior of the nonirradiated compositemore » became brittle, a result that was explained by a loss of functionality of the fiber/matrix interface associated with the disappearance of the interphase due to irradiation. Finally, the specimens irradiated at 629 °C showed increased apparent failure strain because the fiber/matrix interphase was weakened by irradiation-induced partial debonding.« less

Dopamine-Mediated Sclerotization of Regenerated Chitin in Ionic Liquid

PubMed Central

Oh, Dongyeop X.; Shin, Sara; Lim, Chanoong; Hwang, Dong Soo

2013-01-01

Chitin is a promising structural material for biomedical applications, due to its many advantageous properties and abundance in nature. However, its usage and development in the biomedical field have been stagnant, because of chitin’s poor mechanical properties in wet conditions and the difficulties in transforming it into an applicable form. To overcome these challenges, we created a novel biomimetic chitin composite. This regenerated chitin, prepared with ionic liquid, showed improved mechanical properties in wet conditions by mimicking insect cuticle and squid beak sclerotization, i.e., catechol-meditated cross-linking. By ionic liquid-based heat treatment, dopamine oxidation produced melanin-like compounds and dopamine-meditated cross-links without any solvent evaporation and oxidant utilization. The dopamine-meditated sclerotization increased the ultimate tensile strength (UTS) of the regenerated chitin by 2.52-fold, measured after six weeks of phosphate-buffered saline (PBS) submersion. In addition, the linear swelling ratio (LSR) of the chitin film was reduced by about 22%. This strategy raises a possibility of using regenerated chitin as an artificial hard tissue in wet conditions. PMID:28788308

Mechanical property degradation of high crystalline SiC fiber–reinforced SiC matrix composite neutron irradiated to ~100 displacements per atom

DOE Office of Scientific and Technical Information (OSTI.GOV)

Koyanagi, Takaaki; Nozawa, Takashi; Katoh, Yutai

For the development of silicon carbide (SiC) materials for next-generation nuclear structural applications, degradation of material properties under intense neutron irradiation is a critical feasibility issue. This paper evaluated the mechanical properties and microstructure of a chemical vapor infiltrated SiC matrix composite, reinforced with a multi-layer SiC/pyrolytic carbon–coated Hi-Nicalon TM Type S SiC fiber, following neutron irradiation at 319 and 629 °C to ~100 displacements per atom. Both the proportional limit stress and ultimate flexural strength were significantly degraded as a result of irradiation at both temperatures. After irradiation at 319 °C, the quasi-ductile fracture behavior of the nonirradiated compositemore » became brittle, a result that was explained by a loss of functionality of the fiber/matrix interface associated with the disappearance of the interphase due to irradiation. Finally, the specimens irradiated at 629 °C showed increased apparent failure strain because the fiber/matrix interphase was weakened by irradiation-induced partial debonding.« less

Long-term influence of physical aging processes in epoxy matrix composites

NASA Technical Reports Server (NTRS)

Kong, E. S. W.

1981-01-01

Selected mechanical properties of (plus or minus 45 degree sub 4s) graphite/epoxy composites were found to be affected by sub T sub g annealing. Postcured specimens of Thornel 300 graphite/Narmco 5208 epoxy were sub T sub G annealed at 413 K (140 C) for ca. 10 to the first through 10 to the fifth powers min., with a prior quenching from above T sub g. The ultimate tensile strength, strain-to-break, and toughness of the composite were found to decrease as a function of sub T sub g annealing time. The time-dependent change in properties can be explained on the basis of physical aging which is related to free volume changes in the non-equilibrium glassy state of network epoxies. The results imply possible changes in composite properties with service time.

Stainless steel valves with enhanced performance through microstructure optimization

NASA Astrophysics Data System (ADS)

Barani, A. A.; Boukhattam, M.; Haggeney, M.; Güler, S.

2017-08-01

Compressor valves are made of hardened and tempered martensitic steels. The main design criterion for the material selection is the fatigue performance of the material under bending loads. In some cases impact loads and corrosive atmospheres additionally act on the part. For the first time, the microstructure of the most commonly used stainless steel and its influence on the properties relevant for flapper valves is presented and described in this paper. It is demonstrated how the tensile properties of a martensitic stainless steel can be enhanced by tailoring the microstructure. Electron back scatter diffraction method is carried out to explain the changes in monotonic mechanical properties. Through a modified heat treatment the martensite microstructure is refined resulting in an increase of yield and ultimate tensile strength and at the same time a significant increase of elongation.

Mechanical performance of PPy helix tube microactuator

NASA Astrophysics Data System (ADS)

Bahrami Samani, Mehrdad; Spinks, Geoffrey M.; Cook, Christopher

2004-02-01

Conducting polymer actuators with favourable properties such as linearity, high power density and compliance are of increasing demand in micro applications. These materials generate forces over two times larger than produced by mammalian skeletal muscles. They operate to convert electro chemical energy to mechanical stress and strain. On the other hand, the application of conducting polymers is limited by the lack of a full description of the relation between four essential parameters: stress, strain, voltage and current. In this paper, polypyrrole helix tube micro actuator mechanical characteristics are investigated. The electrolyte is propylene carbonate and the dopant is TBA. PF6. The experiments are both in isotonic and isometric conditions and the input parameters are both electrical and mechanical. A dual mode force and length control and potentiostat / galvanostat are utilized for this purpose. Ultimately, the viscoelastic behaviour of the actuator is presented in this paper by a standard stress relaxation test. The effect of electrical stimulus on mechanical parameters is also explored by cyclic voltametry at different scan rates to obtain the best understanding of the actuation mechanism. The results demonstrate that the linear viscoelastic model, which performed well on conducting polymer film actuators, has to be modified to explain the mechanical behaviour of PPy helix tube fibre micro actuators. Secondly, the changes in mechanical properties of PPy need to be considered when modelling electromechanical behaviour.

The Stress Corrosion Resistance and the Cryogenic Temperature Mechanical Behavior of 18-3 Mn (Nitronic 33) Stainless Steel Parent and Welded Material

NASA Technical Reports Server (NTRS)

Montano, J. W.

1976-01-01

The ambient and cryogenic temperature mechanical properties and the ambient temperature stress corrosion results of 18-3 Mn (Nitronic 33)stainless steel, longitudinal and transverse, as received and as welded (TIG) material specimens manufactured from 0.063 inch thick sheet material, were described. The tensile test results indicate an increase in ultimate tensile and yield strengths with decreasing temperature. The elongation remained fairly constant to -200 F, but below that temperature the elongation decreased to less than 6.0% at liquid hydrogen temperature. The notched tensile strength (NTS) for the parent metal increased with decreasing temperature to liquid nitrogen temperature. Below -320 F the NTS decreased rapidly. The notched/unnotched (N/U) tensile ratio of the parent material specimens remained above 0.9 from ambient to -200 F, and decreased to approximately 0.65 and 0.62, respectively, for the longitudinal and transverse directions at liquid hydrogen temperature. After 180 days of testing, only those specimens exposed to the salt spray indicated pitting and some degradation of mechanical properties.

Effect of prolonged isothermal heat treatment on the mechanical behavior of advanced NANOBAIN steel

NASA Astrophysics Data System (ADS)

Avishan, Behzad

2017-09-01

The microstructural evolution and consequent changes in strength and ductility of advanced NANOBAIN steel during prolonged isothermal heat-treatment stages were investigated. The microstructure and mechanical properties of nanostructured bainite were not expected to be influenced by extending the heat-treatment time beyond the optimum value because of the autotempering phenomenon and high tempering resistance. However, experimental results indicated that the microstructure was thermodynamically unstable and that prolonged austempering resulted in carbon depletion from high-carbon retained austenite and carbide precipitations. Therefore, austenite became thermally less stable and partially transformed into martensite during cooling to room temperature. Prolonged austempering did not lead to the typical tempering sequence of bainite, and the sizes of the microstructural constituents were independent of the extended heat-treatment times. This independence, in turn, resulted in almost constant ultimate tensile strength values. However, microstructural variations enhanced the yield strength and the hardness of the material at extended isothermal heat-treatment stages. Finally, although microstructural changes decreased the total elongation and impact toughness, considerable combinations of mechanical properties could still be achieved.

Comparison of the Effects of Tool Geometry for Friction Stir Welding Thin Sheet Aluminum Alloys for Aerospace Applications

NASA Technical Reports Server (NTRS)

Merry, Josh; Takeshita, Jennifer; Tweedy, Bryan; Burford, Dwight

2006-01-01

In this presentation, the results of a recent study on the effect of pin tool design for friction stir welding thin sheets (0.040") of aluminum alloys 2024 and 7075 are provided. The objective of this study was to investigate and document the effect of tool shoulder and pin diameter, as well as the presence of pin flutes, on the resultant microstructure and mechanical properties at both room temperature and cryogenic temperature. Specifically, the comparison between three tools will include: FSW process load analysis (tool forces required to fabricate the welds), Static Mechanical Properties (ultimate tensile strength, yield strength, and elongation), and Process window documenting the range of parameters that can be used with the three pin tools investigated. All samples were naturally aged for a period greater than 10 days. Prior research has shown 7075 may require post weld heat treatment. Therefore, an additional pair of room temperature and cryogenic temperature samples was post-weld aged to the 7075-T7 condition prior to mechanical testing.

Hypervelocity penetration against mechanical properties of target materials

NASA Astrophysics Data System (ADS)

Kamarudin, Khairul Hasni; Abdullah, Mohamad Faizal; Zaidi, Ahmad Mujahid Ahmad; Nor, Norazman M.; Ismail, Ariffin; Yusof, Mohammed Alias; Hilmi, Ahmad Humaizi

2018-02-01

This paper study the mechanical properties behavior of metal plates against hypervelocity penetration caused by shaped charge. Five different materials were used as target specimen fabricated from welded stacks of material plates, namely Rolled Homogeneous Armor (RHA), Hardox-500, mild steel, aluminum and brass. Specimens had undergone an initial monolithic test consist of tensile tests and microstructure observations, followed by series of hydrodynamics penetration blast tests using shape charge mechanism. Results from blast test shows that the least penetrated specimen is RHA (58mm) followed by Hardox-500 (92 mm), mild steel (110 mm), Brass (155 mm) and aluminum 238 mm). Comparing these with the specimen yield strength from the tensile test results shows that Hardox-500 has higher yield strength (Sy) followed by RHA, mild steel, brass and aluminum, which are 1370 MPa, 1320 MPa, 280,221 respectively, which are not inversely proportional to the penetration. However, the ultimate tensile strength (Sut) where the RHA were the highest followed by Hardox-500, mild steel, brass and aluminum, were inversely proportional with the depth of penetration. The penetration results also show consistence relation with energy absorption.

Development of Testing Methodologies for the Mechanical Properties of MEMS

NASA Technical Reports Server (NTRS)

Ekwaro-Osire, Stephen

2003-01-01

This effort is to investigate and design testing strategies to determine the mechanical properties of MicroElectroMechanical Systems (MEMS) as well as investigate the development of a MEMS Probabilistic Design Methodology (PDM). One item of potential interest is the design of a test for the Weibull size effect in pressure membranes. The Weibull size effect is a consequence of a stochastic strength response predicted from the Weibull distribution. Confirming that MEMS strength is controlled by the Weibull distribution will enable the development of a probabilistic design methodology for MEMS - similar to the GRC developed CARES/Life program for bulk ceramics. However, the primary area of investigation will most likely be analysis and modeling of material interfaces for strength as well as developing a strategy to handle stress singularities at sharp corners, filets, and material interfaces. This will be a continuation of the previous years work. The ultimate objective of this effort is to further develop and verify the ability of the Ceramics Analysis and Reliability Evaluation of Structures Life (CARES/Life) code to predict the time-dependent reliability of MEMS structures subjected to multiple transient loads.

Production, microstructure and mechanical properties of two different austenitic ODS steels

NASA Astrophysics Data System (ADS)

Gräning, T.; Rieth, M.; Hoffmann, J.; Möslang, A.

2017-04-01

This article is to summarize and examine processing parameters of novel developed austenitic oxide dispersed strengthened (ODS) steels. Comparing hot-rolled and extruded conditions after the same degree of deformation after and before annealing, are just some examples to give insights into the complex processing of austenitic ODS steels. One of the major drawbacks of the material is the more sophisticated production process. Due to a ductile matrix material with an increased stickiness during milling, a two-step milling procedure with the use of ZrO2 milling balls was applied to raise the production yield and to use the abrasion of the ZrO2 as an additional element to facilitate the formation of nano-sized precipitates. To get a better understanding how the different powder particle sizes after milling affect final properties, sieving was applied and revealed a serious effect in terms of precipitate size, distribution and mechanical properties. Grain sizes in relation to the precipitate size, annealing time and processing parameters were determined and compared to the mechanical properties. Hardness and tensile test have pointed out, that the precipitate size and number are more important in respect to the ultimate tensile strength than the grain size and that in this study hot-rolled material exhibited the better properties. The investigation of the microstructure illustrated the stability of precipitates during annealing at 1100 °C for 40 h. These heat treatments also led to a consistent grain size, due to the pinning effect of the grain boundaries, caused by precipitates.

Lessons from (patho)physiological tissue stiffness and their implications for drug screening, drug delivery and regenerative medicine.

PubMed

Chen, Wen Li Kelly; Simmons, Craig A

2011-04-30

Diseased tissues are noted for their compromised mechanical properties, which contribute to organ failure; regeneration entails restoration of tissue structure and thereby functions. Thus, the physical signature of a tissue is closely associated with its biological function. In this review, we consider a mechanics-centric view of disease and regeneration by drawing parallels between in vivo tissue-level observations and corroborative cellular evidence in vitro to demonstrate the importance of the mechanical stiffness of the extracellular matrix in these processes. This is not intended to devalue the importance of biochemical signaling; in fact, as we discuss, many mechanical stiffness-driven processes not only require cooperation with biochemical cues, but they ultimately converge at common signaling cascades to influence cell and tissue function in an integrative manner. The study of how physical and biochemical signals collectively modulate cell function not only brings forth a more holistic understanding of cell (patho)biology, but it also creates opportunities to control material properties to improve culture platforms for research and drug screening and aid in the rationale design of biomaterials for molecular therapy and tissue engineering applications. Copyright © 2011 Elsevier B.V. All rights reserved.

Optimization of BI test parameters to investigate mechanical properties of Grade 92 steel

NASA Astrophysics Data System (ADS)

Barbadikar, Dipika R.; Vincent, S.; Ballal, Atul R.; Peshwe, Dilip R.; Mathew, M. D.

2018-04-01

The ball indentation (BI) testing is used to evaluate the tensile properties of materials namely yield strength, strength coefficient, ultimate tensile strength, and strain hardening exponent. The properties evaluated depend on a number of BI test parameters. These parameters include the material constants like yield slope (YS), constraint factor (CF), yield offset parameter (YOP). Number of loading/unloading cycles, preload, indenter size and depth of penetration of indenter also affects the properties. In present investigation the effect of these parameters on the stress-strain curve of normalized and tempered Grade 92 steel is evaluated. Grade 92 is a candidate material for power plant application over austenitic stainless steel and derives its strength from M23C6, MX precipitates and high dislocation density. CF, YS and YOP changed the strength properties considerably. Indenter size effect resulted in higher strength for smaller indenter. It is suggested to use larger indenter diameter and higher number of loading cycles for GRADE 92 steel to get best results using BI technique.

Effects of Laser Energies on Wear and Tensile Properties of Biomimetic 7075 Aluminum Alloy

NASA Astrophysics Data System (ADS)

Yuan, Yuhuan; Zhang, Peng; Zhao, Guoping; Gao, Yang; Tao, Lixi; Chen, Heng; Zhang, Jianlong; Zhou, Hong

2018-03-01

Inspired by the non-smooth surface of certain animals, a biomimetic coupling unit with various sizes, microstructure, and hardness was prepared on the surface of 7075 aluminum alloy. Following experimental studies were conducted to investigate the wear and tensile properties with various laser energy inputs. The results demonstrated that the non-smooth surface with biomimetic coupling units had a positive effect on both the wear resistance and tensile property of 7075 aluminum alloy. In addition, the sample with the unit fabricated by the laser energy of 420.1 J/cm2 exhibited the most significant improvement on the wear and tensile properties owing to the minimum grain size and the highest microhardness. Also, the weight loss of the sample was one-third of the untreated one's, and the yield strength, the ultimate tensile strength, and the elongation improved by 20, 20, and 34% respectively. Moreover, the mechanisms of wear and tensile properties improvement were also analyzed.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cole, K.C.; Noel, D.; Hechler, J.-J.

Samples of Narmco Rigidite 5208/WC3000 carbon-epoxy composite prepreg were exposed to ambient temperature and 50 percent relative humidity for different periods up to 66 days. The aging has a significant effect on prepreg physical properties such as tack, volatiles content, and gel time. A set of four-ply laminates made from aged prepreg was subjected to tensile testing, ultrasonic inspection, and optothermal inspection. No relationship could be discerned between laminate properties and prepreg aging time. However, variations in panel homogeneity were observed, and these correlated with thermal diffusivity and tensile modulus measurements, but not with ultimate tensile strength or elongation. Amore » set of six-ply laminates was used to measure compressive properties, interlaminar shear strength, and physical properties. These panels also showed variations in porosity, again unrelated to aging, but in addition, the fiber-resin ratio was observed to decrease with aging time. Both factors were found to affect mechanical properties. The implications concerning the importance of monitoring the aging by physicochemical methods are discussed. 30 refs.« less

Effect of Chemical and Physical Properties on the In Vitro Degradation of 3D Printed High Resolution Poly(propylene fumarate) Scaffolds.

PubMed

Walker, Jason M; Bodamer, Emily; Krebs, Olivia; Luo, Yuanyuan; Kleinfehn, Alex; Becker, Matthew L; Dean, David

2017-04-10

Two distinct molecular masses of poly(propylene fumarate) (PPF) are combined with an additive manufacturing process to fabricate highly complex scaffolds possessing controlled chemical properties and porous architecture. Scaffolds were manufactured with two polymer molecular masses and two architecture styles. Degradation was assessed in an accelerated in vitro environment. The purpose of the degradation study is not to model or mimic in vivo degradation, but to efficiently compare the effect of modulating scaffold properties. This is the first study addressing degradation of chain-growth synthesized PPF, a process that allows for considerably more control over molecular mass distribution. It demonstrates that, with greater process control, not only is scaffold fabrication reproducible, but the mechanical properties and degradation kinetics can be tailored by altering the physical properties of the scaffold. This is a clear step forward in using PPF to address unmet medical needs while meeting regulatory demands and ultimately obtaining clinical relevancy.

Variation of mechanical properties and oxidation with radiation dose and source in highly crosslinked remelted UHMWPE.

PubMed

Fung, Mitchell; Bowsher, John G; Van Citters, Douglas W

2018-06-01

Ultra-high molecular weight polyethylene (UHMWPE) is the current gold standard for bearing materials used in total joint arthroplasty. High-dose radiation is commonly used to crosslink UHMWPE, thereby improving its wear resistance. A subsequent remelting step eliminates trapped residual free radicals to promote oxidative stability on the shelf, and to prevent material degradation over the long term. Assessment of clinically retrieved, highly crosslinked UHMWPE devices shows signs of unanticipated oxidation occurring in vivo, despite the absence of free radicals prior to implantation. These findings warrant further investigation into possible factors impacting this phenomenon along with its clinical implications. The overall objective of this work is to quantify the influence of irradiation dose and source on UHMWPE's oxidative stability, along with the effects of oxidation on the ultimate mechanical properties, including strength, ductility, and toughness. The results showed a strong positive correlation between maximum oxidation and initial transvinylene content. Critical oxidation levels in the context of mechanical property loss were determined for e-beam and gamma treatments at various radiation doses. Further, it was shown that critical oxidation was more dependent on radiation dose and less dependent on source. If in vivo oxidation persists in these devices, this can potentially lead to mechanical failure (e.g. fatigue damage) as observed in terminally gamma-sterilized devices. Copyright © 2018 Elsevier Ltd. All rights reserved.

Precipitation and ultimate pH effect on chemical and gelation properties of protein prepared by isoelectric solubilization/precipitation process from pale, soft, exudative (PSE)-like chicken breast meat1.

PubMed

Zhao, X; Xing, T; Chen, X; Han, M-Y; Li, X; Xu, X-L; Zhou, G-H

2017-05-01

Pale, soft, exudative (PSE)-like chicken breast is considered deteriorated raw material in the poultry meat industry that has inferior processing ability. The chemical and gelation properties of PSE-like chicken breast meat paste were studied. These pastes were prepared by the pH adjustment method and protein isolation using the isoelectric solubilization/precipitation (ISP) process from PSE-like chicken meat. The ISP-isolated samples were solubilized at pH 11.0 and recovered at pH 5.5 and 6.2. The ultimate pH of the ISP-isolated protein and meat paste was adjusted to 6.2 and 7.0. The ultimate pH in this article referred to the final pH of the extracted protein and meat paste. Higher reactive sulfhydryl content and surface hydrophobicity were found in the precipitation at pH 6.2 than at pH 5.5. However, various ultimate pH values showed no significant influence on the surface hydrophobicity. The hardness of gel, as measured by textural profile analysis, was improved using 6.2 as the precipitation pH compared with pH 5.5. The viscoelastic modulus (G΄) of gel pastes prior to the thermal gelation was higher with ISP treatment. However, lower G΄ was seen after thermal gelation compared with the control. Dynamic rheological measurement demonstrated a different gel-forming mechanism for protein precipitated at pH values of 5.5 and 6.2 compared with the meat paste. The cooking loss showed that the recovered protein failed to form a gel with good water-retention capacity unless the ultimate pH was adjusted to 7.0. Gels made from protein extracted by the ISP method had higher yellowness and lower redness values, probably due to protein denaturation. Precipitation at pH 6.2 formed a harder gel with lower water-retention ability than that at pH 5.5, and this result was possibly due to higher surface hydrophobicity and S-S bridge formation. Overall, network characteristics of ISP-treated protein gels were strongly dependent on precipitation pH and ultimate pH. © 2016 Poultry Science Association Inc.

Inducing Propulsion of Colloidal Dimers by Breaking the Symmetry in Electrohydrodynamic Flow.

PubMed

Ma, Fuduo; Yang, Xingfu; Zhao, Hui; Wu, Ning

2015-11-13

We show that dielectric colloidal dimers with broken symmetry in geometry, composition, or interfacial charges can all propel in directions that are perpendicular to the applied ac electric field. The asymmetry in particle properties ultimately results in an unbalanced electrohydrodynamic flow on two sides of the particles. Consistent with scaling laws, the propulsion direction, speed, and orientation of dimers can be conveniently tuned by frequency. The new propulsion mechanism revealed here is important for building colloidal motors and studying collective behavior of active matter.

Radar cross section studies

NASA Technical Reports Server (NTRS)

Burnside, W. D.; Dominek, A. K.; Gupta, I. J.; Newman, E. H.; Pathak, P. H.; Peters, L., Jr.

1987-01-01

The ultimate goal is to generate experimental techniques and computer codes of rather general capability that would enable the aerospace industry to evaluate the scattering properties of aerodynamic shapes. Another goal involves developing an understanding of scattering mechanisms so that modification of the vehicular structure could be introduced within constraints set by aerodynamics. The development of indoor scattering measurement systems with special attention given to the compact range is another goal. There has been considerable progress in advancing state-of-the-art scattering measurements and control and analysis of the electromagnetic scattering from general targets.

Design and fabrication of a micron scale free-standing specimen for uniaxial micro-tensile tests

NASA Astrophysics Data System (ADS)

Tang, Jun; Wang, Hong; Li, Shi Chen; Liu, Rui; Mao, Sheng Ping; Li, Xue Ping; Zhang, Cong Chun; Ding, Guifu

2009-10-01

This paper presents a novel design and fabrication of test chips with a nickel free-standing specimen for the micro uniaxial tensile test. To fabricate test chips on the quartz substrate significantly reduces the fabrication time, minimizes the number of steps and eliminates the effect of the wet anisotropic etching process on mechanical properties. The test chip can be gripped tightly to the test machine and aligned accurately in the pulling direction; furthermore, the approximately straight design of the specimen rather than the traditional dog-bone structure enables the strain be directly measured by a displacement sensor. Both finite-element method (FEM) analysis and experimental results indicate the reliability of the new design. The test chip can also be extended to other materials. The experimental measured Young's modulus of a thin nickel film and the ultimate tensile strength are approximately 94.5 Gpa and 1.76 Gpa, respectively. The results were substantially supported by the experiment on larger gauge specimens by a commercial dynamic mechanical analysis (DMA) instrument. These specimens were electroplated under the same conditions. The low Young's modulus and the high ultimate tensile strength might be explained by the fine grain in the electroplated structure.

Failure models for textile composites

NASA Technical Reports Server (NTRS)

Cox, Brian

1995-01-01

The goals of this investigation were to: (1) identify mechanisms of failure and determine how the architecture of reinforcing fibers in 3D woven composites controlled stiffness, strength, strain to failure, work of fracture, notch sensitivity, and fatigue life; and (2) to model composite stiffness, strength, and fatigue life. A total of 11 different angle and orthogonal interlock woven composites were examined. Composite properties depended on the weave architecture, the tow size, and the spatial distributions and strength of geometrical flaws. Simple models were developed for elastic properties, strength, and fatigue life. A more complicated stochastic model, called the 'Binary Model,' was developed for damage tolerance and ultimate failure. These 3D woven composites possessed an extraordinary combination of strength, damage tolerance, and notch insensitivity.

Fundamental investigation of the tribological and mechanical responses of materials and nanostructures

NASA Astrophysics Data System (ADS)

Bucholz, Eric W.

In the field of tribology, the ability to predict, and ultimately control, frictional performance is of critical importance for the optimization of tribological systems. As such, understanding the specific mechanisms involved in the lubrication processes for different materials is a fundamental step in tribological system design. In this work, a combination of computational and experimental methods that include classical molecular dynamics (MD) simulations, atomic force microscopy (AFM) experiments, and multivariate statistical analyses provides fundamental insight into the tribological and mechanical properties of carbon-based and inorganic nanostructures, lamellar materials, and inorganic ceramic compounds. One class of materials of modern interest for tribological applications is nanoparticles, which can be employed either as solid lubricating films or as lubricant additives. In experimental systems, however, it is often challenging to attain the in situ observation of tribological interfaces necessary to identify the atomic-level mechanisms involved during lubrication and response to mechanical deformation. Here, classical MD simulations establish the mechanisms occurring during the friction and compression of several types of nanoparticles including carbon nano-onions, amorphous carbon nanoparticles, and inorganic fullerene-like MoS2 nanoparticles. Specifically, the effect of a nanoparticle's structural properties on the lubrication mechanisms of rolling, sliding, and lamellar exfoliation is indicated; the findings quantify the relative impact of each mechanism on the tribological and mechanical properties of these nanoparticles. Beyond identifying the lubrication mechanisms of known lubricating materials, the continual advancement of modern technology necessitates the identification of new candidate materials for use in tribological applications. To this effect, atomic-scale AFM friction experiments on the aluminosilicate mineral pyrophyllite demonstrate that pyrophyllite provides a low friction coefficient and low shear stresses as well as a high threshold to interfacial wear; this suggests the potential for use of pyrophyllite as a lubricious material under specific conditions. Also, a robust and accurate model for estimating the friction coefficients of inorganic ceramic materials that is based on the fundamental relationships between material properties is presented, which was developed using multivariate data mining algorithms. These findings provide the tribological community with a new means of quickly identifying candidate materials that may provide specific frictional properties for desired applications.

An investigation of electrochemomechanical actuation of conductive Polyacrylonitrile (PAN) nanofiber composites

NASA Astrophysics Data System (ADS)

Gonzalez, Mark A.; Walter, Wayne W.

2014-03-01

A polymer-based nanofiber composite actuator designed for contractile actuation was fabricated by electrospinning, stimulated by electrolysis, and characterized by electrochemical and mechanical testing to address performance limitations and understand the activation processing effects on actuation performance. Currently, Electroactive polymers (EAPs) have provided uses in sensory and actuation technology, but have either low force output or expand rather than contract, falling short in capturing the natural kinetics and mechanics of muscle needed to provide breakthroughs in the bio-medical and robotic fields. In this study, activated Polyacrylonitrile (PAN) fibers have demonstrated biomimetic functionalities similar to the sarcomere contraction responsible for muscle function. Activated PAN has also been shown to contract and expand by electrolysis when in close vicinity to the anode and cathode, respectively. PAN nanofibers (~500 nm) especially show faster response to changes in environmental pH and improved mechanical properties compared to larger diameter fibers. Tensile testing was conducted to examine changes in mechanical properties between annealing and hydrolysis processing. Voltage driven transient effects of localized pH were examined to address pHdefined actuation thresholds of PAN fibers. Electrochemical contraction rates of the PAN/Graphite composite actuator demonstrated up to 25%/min. Strains of 58.8%, ultimate stresses up to 77.1 MPa, and moduli of 0.21 MPa were achieved with pure PAN nanofiber mats, surpassing mechanical properties of natural muscles. Further improvements, however, to contraction rates and Young's moduli were found essential to capture the function and performance of skeletal muscles appropriately.

Microstructure examination of Fe-14Cr ODS ferritic steels produced through different processing routes

NASA Astrophysics Data System (ADS)

Oksiuta, Z.; Hosemann, P.; Vogel, S. C.; Baluc, N.

2014-08-01

Various thermo-mechanical treatments were applied to refine and homogenise grain size and improve mechanical properties of hot-isostatically pressed (HIP) 14%Cr ODS ferritic steel. The grain size was reduced, improving mechanical properties, tensile strength and Charpy impact, however bimodal-like distribution was also observed. As a result, larger, frequently elongated grains with size above 1 μm and refined, equiaxed grains with a diameter ranging from 250 to 500 nm. Neutron diffraction measurements revealed that for HIP followed by hydrostatic extrusion material the strongest fiber texture was observed oriented parallel to the extrusion direction. In comparison with hot rolling and hot pressing methods, this material exhibited promising mechanical properties: the ultimate tensile strength of 1350 MPa, yield strength of 1280 MPa, total elongation of 21.7% and Charpy impact energy of 5.8 J. Inferior Charpy impact energy of ∼3.0 J was measured for HIP and hot rolled material, emphasising that parameters of this manufacturing process still have to be optimised. As an alternative manufacturing route, due to the uniform microstructure and simplicity of the process, hot pressing might be a promising method for production of smaller parts of ODS ferritic steels. Besides, the ductile-to-brittle transition temperature of all thermo-mechanically treated materials, in comparison with as-HIPped ODS steel, was improved by more than 50%, the transition temperature ranging from 50 to 70 °C (323 and 343 K) remains still unsatisfactory.

Mechanical Properties and Microstructure Investigation of Lead Free Solder

NASA Technical Reports Server (NTRS)

Wang, Qing; Gail, William F.; Johnson, R. Wayne; Strickland, Mark; Blanche, Jim

2005-01-01

While the electronics industry appears to be focusing on Sn-Ag-Cu as the alloy of choice for lead free electronics assembly, ,the exact composition varies by geographic region, supplier and user. Add to that dissolved copper and silver from the printed circuit board traces and surface finish, and there can be significant variation in the final solder joint composition. A systematic study of the mechanical and microstructural properties of Sn-Ag-Cu alloys with Ag varying from 2wt% to 4wt% and Cu varying from 0.5wt% to lSwt%, was undertaken in this research study. Different sample preparation techniques (water quenched, oil quenched and water quenched followed by reflow) were explored and the resulting microstructure compared to that of a typical reflowed lead free chip scale package (CSP) solder joint. Tensile properties (modulus, 0.2% yield strength and the ultimate tensile strength) and creep behavior of selected alloy compositions (Sn-4Ag-1 X u , Sn-4Ag-OSCu, Sn- 2Ag-1 X u , Sn-2Ag-OSCu, Sn-3.5Ag-O.SCu) were determined for three conditions: as- cast; aged for 100 hours at 125OC; and aged for 250 hours at 125OC. There was no significant difference in Young's Modulus as a function of alloy composition. After an initial decrease in modulus after 100 hours at 125"C, there was an insignificant change with further aging. The distribution of 0.2% strain yield stress and ultimate tensile strength as a function of alloy composition was more significant and decreased with aging time and temperature. The microstructures of these alloys were examined using light and scanning electron microscopy (LM and SEM) respectively and SEM based energy dispersive x-ray spectroscopy (EDS). Fracture surface and cross-section analysis were performed on the specimens after creep testing. The creep testing results and the effect of high temperature aging on mechanical properties is presented for the oil quenched samples. In general the microstructure of oil quenched specimen exhibited a eutectic region of Sn with moderately dispersed Ag3Sn intermetallic, surrounded by a dendritic Sn-rich phase. The SEM images of the fracture surface indicated the presence of a tough shear surface at the initial cavity break area and a break line in the middle of specimen along the failure direction. A hyperbolic-sine creep model was adopted and used to fit the creep experiment data. The effect on the mechanical properties by adding the quaternary element bismuth to the Sn-3.5Ag-0.8Cu alloy was measured and compared with the mechanical properties of the ternary alloys. The results of this research study provide necessary data for the modeling of solder joint reliability for a range of Sn-Ag-Cu compositions and a baseline for evaluating the effects of subsequent quaternary additions.

Influence of Sc on microstructure and mechanical properties of Al-Si-Mg-Cu-Zr alloy

NASA Astrophysics Data System (ADS)

Li, Yukun; Du, Xiaodong; Zhang, Ya; Zhang, Zhen; Fu, Junwei; Zhou, Shi'ang; Wu, Yucheng

2018-02-01

In the present study, the effects of Mg, Cu, Sc and Zr combined additions on the microstructure and mechanical properties of hypoeutectic Al-Si cast alloy were systematically investigated. Characterization techniques such as optical microscopy (OM), scanning electron microscope (SEM), energy dispersive spectrometer (EDS), electron back-scatter diffraction (EBSD), atomic force microscopy (AFM), transmission electron microscope (TEM), Brinell hardness tester and universal testing machine were employed to analyze the microstructure and mechanical properties. The results showed that Sc served as modifier on the microstructure of Al-3Si-0.45Mg-0.45Cu-0.2Zr alloys, including modification of eutectic Si and grains. Extraordinarily, grain refinement was found to be related to the primary particles, which exhibited a close orientation to matrix. After T6 heat treatment, the grain structures were composed of nano-scaled secondary Al3(Sc, Zr) precipitates and spherical eutectic Si. Combined with T6 heat treatment, the highest hardness, yield strength, ultimate tensile strength and elongation were achieved in 0.56 wt.% Sc-modified alloy. Interestingly, the strength and ductility had a similar tendency. This paper demonstrated that combined additions of Mg, Cu, Sc and Zr could significantly improve the microstructure and performance of the hypoeutectic Al-Si cast alloy.

High-Strength Konjac Glucomannan/Silver Nanowires Composite Films with Antibacterial Properties

PubMed Central

Lei, Jia; Zhou, Lei; Tang, Yongjian; Luo, Yong; Duan, Tao; Zhu, Wenkun

2017-01-01

Robust, high-strength and environmentally friendly antibacterial composite films were prepared by simply blending konjac glucomannan (KGM) and silver nanowires (Ag NWs) in an aqueous system. The samples were then characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), thermal gravimetric analysis, mechanical property tests, Fourier transform infrared spectra (FT-IR), X-ray photoelectron spectroscopy (XPS) and antimicrobial tests. The results showed that there was a high ratio of Ag NWs uniformly distributed in the composite films, which was vital for mechanical reinforcement and stable antibacterial properties. The enhanced thermal stability and mechanical intensity increased, while the elongation at break was reduced with an increase in the amount of Ag NWs found in the composite films. When the percentage of Ag NWs in the composite films reached 5%, the tensile strength was 148.21 MPa, Young’s modulus was 13.79 GPa and the ultimate strain was 25.28%. Antibacterial tests showed that the KGM films had no antibacterial effect. After the addition of Ag NWs, the composite films had an obvious inhibitory effect on bacteria, with the uniform dispersion of Ag NWs promoting the antibacterial effect to a certain degree. These results indicated that these composite films would have a potential application in the fields of environmentally friendly packaging or medicine. PMID:28772883

Histo-mechanical properties of the swine cardinal and uterosacral ligaments.

PubMed

Tan, Ting; Davis, Frances M; Gruber, Daniel D; Massengill, Jason C; Robertson, John L; De Vita, Raffaella

2015-02-01

The focus of this study was to determine the structural and mechanical properties of two major ligaments that support the uterus, cervix, and vagina: the cardinal ligament (CL) and the uterosacral ligament (USL). The adult swine was selected as animal model. Histological analysis was performed on longitudinal and cross sections of CL and USL specimens using Masson׳s trichrome and Verhoeff-van Giesson staining methods. Scanning electron microscopy was employed to visualize the through-thickness organization of the collagen fibers. Quasi-static uniaxial tests were conducted on specimens that were harvested from the CL/USL complex of a single swine. Dense connective tissue with a high content of elastin and collagen fibers was observed in the USL. Loose connective tissue with a considerable amount of smooth muscle cells and ground substance was detected in both the CL and USL. Collagen fibers, smooth muscle cells, blood vessels, and nerve fibers were arranged primarily in the plane of the ligaments. The USL was significantly stronger than the CL with higher ultimate stress and tangent modulus of the linear region of the stress-strain curve. Knowledge about the mechanical properties of the CL and USL will aid in the design of novel mesh materials, stretching routines, and surgical procedures for pelvic floor disorders. Copyright © 2014 Elsevier Ltd. All rights reserved.

Mechanical Properties and Microstructure of TIG and FSW Joints of a New Al-Mg-Mn-Sc-Zr Alloy

NASA Astrophysics Data System (ADS)

Xu, Guofu; Qian, Jian; Xiao, Dan; Deng, Ying; Lu, Liying; Yin, Zhimin

2016-04-01

A new Al-5.8%Mg-0.4%Mn-0.25%Sc-0.10%Zr (wt.%) alloy was successfully welded by tungsten inert gas (TIG) and friction stir welding (FSW) techniques, respectively. The mechanical properties and microstructure of the welded joints were investigated by microhardness measurements, tensile tests, and microscopy methods. The results show that the ultimate tensile strength, yield strength, and elongation to failure are 358, 234 MPa, and 27.6% for TIG welded joint, and 376, 245 MPa and 31.9% for FSW joint, respectively, showing high strength and superior ductility. The TIG welded joint fails in the heat-affected zone and the fracture of FSW joint is located in stirred zone. Al-Mg-Mn-Sc-Zr alloy is characterized by lots of dislocation tangles and secondary coherent Al3(Sc,Zr) particles. The superior mechanical properties of the TIG and FSW joints are mainly derived from the Orowan strengthening and grain boundary strengthening caused by secondary coherent Al3(Sc,Zr) nano-particles (20-40 nm). For new Al-Mg-Mn-Sc-Zr alloy, the positive effect from secondary Al3(Sc, Zr) particles in the base metal can be better preserved in FSW joint than in TIG welded joint.

The European FP7 ULTimateCO2 project: A comprehensive approach to study the long term fate of CO2 geological storage sites

NASA Astrophysics Data System (ADS)

Audigane, P.; Brown, S.; Dimier, A.; Pearce, J.; Frykman, P.; Maurand, N.; Le Gallo, Y.; Spiers, C. J.; Cremer, H.; Rutters, H.; Yalamas, T.

2013-12-01

The European FP7 ULTimateCO2 project aims at significantly advance our knowledge of specific processes that could influence the long-term fate of geologically stored CO2: i) trapping mechanisms, ii) fluid-rock interactions and effects on mechanical integrity of fractured caprock and faulted systems and iii) leakage due to mechanical and chemical damage in the well vicinity, iv) brine displacement and fluid mixing at regional scale. A realistic framework is ensured through collaboration with two demonstration sites in deep saline sandstone formations: the onshore former NER300 West Lorraine candidate in France (ArcelorMittal GeoLorraine) and the offshore EEPR Don Valley (former Hatfield) site in UK operated by National Grid. Static earth models have been generated at reservoir and basin scale to evaluate both trapping mechanisms and fluid displacement at short (injection) and long (post injection) time scales. Geochemical trapping and reservoir behaviour is addressed through experimental approaches using sandstone core materials in batch reactive mode with CO2 and impurities at reservoir pressure and temperature conditions and through geochemical simulations. Collection of data has been generated from natural and industrial (oil industry) analogues on the fluid flow and mechanical properties, structure, and mineralogy of faults and fractures that could affect the long-term storage capacity of underground CO2 storage sites. Three inter-related lines of laboratory experiments investigate the long-term evolution of the mechanical properties and sealing integrity of fractured and faulted caprocks using Opalinus clay of Mont Terri Gallery (Switzerland) (OPA), an analogue for caprock well investigated in the past for nuclear waste disposal purpose: - Characterization of elastic parameters in intact samples by measuring strain during an axial experiment, - A recording of hydraulic fracture flow properties by loading and shearing samples in order to create a 'realistic' fracture, followed by a gas injection in the fracture plan, - An assessment of temperature influences on carbonate and water content which affect carbonate bearing fault gouge using shear experiments at 20C and 120C on simulated fault gouges prepared by crushed OPA samples. To evaluate the interactions between CO2 (and formation fluids) and the well environment (formation, cement, casing) and to assess the consequences of these interactions on the transport properties of well materials, a 1:1 scale experiment has been set in the OPA to reproduce classical well objects (cemented annulus, casing and cement plug) perforating caprock formations (OPA). Innovative probabilistic modelling tools are also under development in order to build robust calibration methods for uncertainty management of the simulated long term scenarios.

Effect of fiber orientation of collagen-based electrospun meshes on human fibroblasts for ligament tissue engineering applications.

PubMed

Full, Sean Michael; Delman, Connor; Gluck, Jessica M; Abdmaulen, Raushan; Shemin, Richard J; Heydarkhan-Hagvall, Sepideh

2015-01-01

Within the past two decades polylactic-co-glycolic acid (PLGA) has gained considerable attention as a biocompatible and biodegradable polymer that is suitable for tissue engineering and regenerative medicine. In this present study, we have investigated the potential of PLGA, collagen I (ColI), and polyurethane (PU) scaffolds for ligament tissue regeneration. Two different ratios of PLGA (50:50 and 85:15) were used to determine the effects on mechanical tensile properties and cell adhesion. The Young's modulus, tensile stress at yield, and ultimate tensile strain of PLGA(50:50)-ColI-PU scaffolds demonstrated similar tensile properties to that of ligaments found in the knee. Whereas, scaffolds composed of PLGA(85:15)-ColI-PU had lower tensile properties than that of ligaments. Furthermore, we investigated the effect of fiber orientation on mechanical properties and our results indicate that aligned fiber scaffolds demonstrate higher tensile properties than scaffolds with random fiber orientation. Also, human fibroblasts attached and proliferated with no need for additional surface modifications to the presented electrospun scaffolds in both categories. Collectively, our investigation demonstrates the effectiveness of electrospun PLGA scaffolds as a suitable candidate for regenerative medicine, capable of being manipulated and combined with other polymers to create three-dimensional microenvironments with adjustable tensile properties to mimic native tissues. © 2014 Wiley Periodicals, Inc.

High-Temperature Mechanical Properties of the P/M Extruded Mg -SiCp Composites

NASA Astrophysics Data System (ADS)

Labib, F.; Mahmudi, R.; Ghasemi, H. M.

2018-03-01

In the present study, pure magnesium reinforced with 0, 5, 10 and 15 vol.% SiC particulates was successfully prepared by powder metallurgy technique before being hot extruded. The average 14 μm grain size of the composite specimens remained almost unchanged after addition of SiC particles, while their dimensional stability was improved because of the reduction in the coefficient of thermal expansion (CTE) from 28.6 × 10-6 K-1 in pure Mg to 27.3, 25.3 and 23.4 × 10-6 K-1 in the Mg-5% SiC, Mg-10% SiC and Mg-15% SiC composites, respectively. Mechanical properties of the specimens were investigated in the temperature range of 298-498 K, implementing shear punch testing and hot hardness techniques. Depending on the test temperature, addition of SiC particles to the pure Mg matrix increased shear yield stress and ultimate shear strength of the materials by 5-25 and 6-23 MPa, respectively. The shear strength improvement was mainly attributed to the CTE mismatch strengthening mechanism (9.5-25.5 MPa), and to a lesser extent (1-4.5 MPa), to the load transfer mechanism. Finally, using the modified Clyne model, the contribution of different strengthening mechanisms to the total shear strength improvement in the composites was evaluated.

Effect of electrospun nanofibers on flexural properties of fiberglass composites

NASA Astrophysics Data System (ADS)

White, Fatima T.

In the present study, sintered electrospun TEOS nanofibers were interleaved in S2 fiberglass woven fabric layers, and composite panels were fabricated using the heated vacuum assisted resin transfer molding (H-VARTM) process. Cured panels were water jet cut to obtain the flexural test coupons. Flexural coupons were then tested using ASTM D7264 standard. The mechanical properties such as flexural strength, ultimate flexural failure strains, flexural modulus, and fiber volume fraction were measured. The S-2 fiberglass composite with the sintered TEOS electrospun nanofibers displayed lower flexural stiffness and strength as compared to the composites that were fabricated using S-2 fiberglass composite without the TEOS electrospun nanofibers. The present study also indicated that the composites fabricated with sintered TEOS electrospun nanofibers have larger failure strains as compared to the ones that were fabricated without the presence of electrospun nanofibers. The study indicates that the nanoengineered composites have better energy absorbing mechanism under flexural loading as compared to conventional fiberglass composites without presence of nanofibers.

Mechanical properties of as-cast and heat-treated ZA-27 alloy/short glass fiber composites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sharma, S.C.; Girish, B.M.; Satish, B.M.

1998-02-01

This paper reports on the mechanical properties of as-cast and heat-treated ZA-27 alloy composites reinforced with glass fibers from 1 to 5 wt%. The composites were fabricated using the Compocasting method, in which short glass fibers were introduced into the vortex created in the molten alloy through an impeller rotated at 500 rpm. The molten mass was thoroughly stirred and poured into permanent molds and squeezed under pressure. The specimens were heat treated at 320 C for 1, 2, 3, and 4 h. The tests on the as-cast composites revealed that as the glass content in the composites was increased,more » the ultimate tensile strength (UTS), compressive strength, and hardness of the composite increased, while the ductility and impact strength were decreased. Heat treatment was found to improve significantly the ductility, compressive strength, and impact strength, while the hardness and UTS were reduced. This paper discusses the behavior of these composites.« less

Development of COPVS for High pressure, In-Space, Cryogenic Fuel Storage

NASA Technical Reports Server (NTRS)

DeLay, Tom; Schneider, Judy; Dyess, Mark; Hastings, Chad; Noorda, Ryan; Noorda, Jared; Patterson, James

2008-01-01

Polymeric composite overwrapped pressure vessels (COPVs) provide an attractive material system to support developing commercial launch business and alternate fuel ventures. However to be able to design with these materials, the mechanical behavior of the materials must be understood with regards to processing, performance, damage tolerance, and environment. For the storage of cryogenic propellants, it is important to evaluate the materials performance and impact damage resistance at cryogenic temperatures in order to minimize weight and to ensure safety and reliability. To evaluate the ultimate performance, various polymeric COPV's have been statically burst tested at cryogenic conditions before and after exposure to irradiation. Materials selected for these COPVs were based on the measured mechanical properties of candidate resin systems and fibers that were also tested at cryogenic conditions before and after exposure to irradiation. The correlation of COPV burst pressures with the constituent material properties has proven to be a valuable screening method for selection of suitable candidate materials with resistance to material degradation due to exposure to temperature and radiation.

Anisotropic Responses of Mechanical and Thermal Processed Cast Al-Si-Mg-Cu Alloy

NASA Astrophysics Data System (ADS)

Adeosun, S. O.; Akpan, E. I.; Balogun, S. A.; Onoyemi, O. K.

2015-05-01

The effects of ambient directional rolling and heat treatments on ultimate tensile strength (UTS), hardness (HD), percent elongation (PE), and impact energy (IE) on Al-Si-Mg-Cu alloy casting with reference to inclination to rolling direction are discussed in this article. The results show that rolled and quenched (CQ) sample possess superior UTS and HD to as-cast and those of rolled and aged samples (CA). Improved IE resistance with ductility is shown by both CQ and CA samples. However, these mechanical properties are enhanced as changes in the test sample direction moved away from rolling direction for all heat-treated samples. The CQ samples displayed highest tensile strength (108 MPa) and PE (19.8%) in the 90° direction.

Two-dimensional nanostructured Y{sub 2}O{sub 3} particles for viscosity modification

DOE Office of Scientific and Technical Information (OSTI.GOV)

He, Xingliang; Xiao, Huaping; Liang, Hong, E-mail: hliang@tamu.edu

Nanoparticle additives have been shown to improve the mechanical and transport phenomena of various liquids; however, little has been done to try and explain the rheological modifications provided from such modifications from a theoretical standpoint. Here, we report a non-Einstein-like reduction of viscosity of mineral oil with the utilization of yttrium oxide nanosheet additives. Experimental results, coupled with generalized smoothed-particle hydrodynamics simulations, provide insight into the mechanism behind this reduction of fluid shear stress. The ordered inclination of these two-dimensional nanoparticle additives markedly improves the lubricating properties of the mineral oil, ultimately reducing the friction, and providing a way inmore » designing and understanding next generation of lubricants.« less

Structure and mechanical properties of coatings fabricated by nonvacuum electron beam cladding of Ti-Ta-Zr powder mixtures

NASA Astrophysics Data System (ADS)

Samoylenko, Vitaliy V.; Lenivtseva, Olga G.; Polyakov, Igor A.; Laptev, Ilya S.

2015-10-01

In this paper structural investigations and mechanical tests of Ti-Ta-Zr coatings obtained on surfaces of cp-titanium workpieces were carried out. It was found that the coatings had a dendrite structure; investigations at high-power magnifications revealed a platelet structure. An increase of tantalum concentration led to refinement of structural components. The microhardness level of all coatings, excepting a specimen with the maximum tantalum content, was 370 HV. The microhardness of this coating reached 400 HV. The ultimate tensile strength of cladded layers varied from 697 to 947 MPa. Adhesion tests showed that bimetallic composites were characterized by high bond strength of cladded layers to the substrate, which exceeded cp-titanium strength characteristics.

Determination of mechanical properties of some glass fiber reinforced plastics suitable to Wind Turbine Blade construction

NASA Astrophysics Data System (ADS)

Steigmann, R.; Savin, A.; Goanta, V.; Barsanescu, P. D.; Leitoiu, B.; Iftimie, N.; Stanciu, M. D.; Curtu, I.

2016-08-01

The control of wind turbine's components is very rigorous, while the tower and gearbox have more possibility for revision and repairing, the rotor blades, once they are deteriorated, the defects can rapidly propagate, producing failure, and the damages can affect large regions around the wind turbine. This paper presents the test results, performed on glass fiber reinforced plastics (GFRP) suitable to construction of wind turbine blades (WTB). The Young modulus, shear modulus, Poisson's ratio, ultimate stress have been determined using tensile and shear tests. Using Dynamical Mechanical Analysis (DMA), the activation energy for transitions that appear in polyester matrix as well as the complex elastic modulus can be determined, function of temperature.

Data of the properties of rebar steel brands in Lagos, Nigerian market used in reinforced concrete applications.

PubMed

Joshua, Opeyemi; Olusola, Kolapo O; Oyeyemi, Kehinde D; Ogunde, Ayodeji O; Amusan, Lekan M; Nduka, David O; Abuka-Joshua, Joyce

2018-04-01

The data presented herein are compilations of the research summary of "Assessment of the Quality of Steel Reinforcement Bars Available in Nigerian Market" (Joshua et al., 2013) [1]. This data article provides information on the properties and cost of steel rebars used in reinforced concrete in Lagos, Nigeria. The data is based on the properties of 12 mm rebar brands which are the most used steel diameter in construction and they include actual diameters, yield strengths, ultimate strengths, ultimate/yield strength ratio, ductility and the cost of each brand. This data also contains the limiting standard properties of the highlighted properties in this data.

Scaling Effects in Perovskite Ferroelectrics: Fundamental Limits and Process-Structure-Property Relations

DOE PAGES

Ihlefeld, Jon F.; Harris, David T.; Keech, Ryan; ...

2016-07-05

Ferroelectric materials are well-suited for a variety of applications because they can offer a combination of high performance and scaled integration. Examples of note include piezoelectrics to transform between electrical and mechanical energies, capacitors used to store charge, electro-optic devices, and non-volatile memory storage. Accordingly, they are widely used as sensors, actuators, energy storage, and memory components, ultrasonic devices, and in consumer electronics products. Because these functional properties arise from a non-centrosymmetric crystal structure with spontaneous strain and a permanent electric dipole, the properties depend upon physical and electrical boundary conditions, and consequently, physical dimension. The change of properties withmore » decreasing physical dimension is commonly referred to as a size effect. In thin films, size effects are widely observed, while in bulk ceramics, changes in properties from the values of large-grained specimens is most notable in samples with grain sizes below several microns. It is important to note that ferroelectricity typically persists to length scales of about 10 nm, but below this point is often absent. Despite the stability of ferroelectricity for dimensions greater than ~10 nm, the dielectric and piezoelectric coefficients of scaled ferroelectrics are suppressed relative to their bulk counterparts, in some cases by changes up to 80%. The loss of extrinsic contributions (domain and phase boundary motion) to the electromechanical response accounts for much of this suppression. In this article the current understanding of the underlying mechanisms for this behavior in perovskite ferroelectrics are reviewed. We focus on the intrinsic limits of ferroelectric response, the roles of electrical and mechanical boundary conditions, grain size and thickness effects, and extraneous effects related to processing. Ultimately, in many cases, multiple mechanisms combine to produce the observed scaling effects.« less

Laminate behavior for SiC fiber-reinforced reaction-bonded silicon nitride matrix composites

NASA Technical Reports Server (NTRS)

Rhatt, R. T.; Phillips, R. E.

1988-01-01

The room temperature mechanical properties of SiC fiber reinforced reaction-bonded silicon nitride matrix composite laminates (SiC/RBSN) have been measured. The laminates contained approx 30 volume fraction of aligned 142-micron diameter SiC fiber in a porous RBSN matrix. Three types of laminate studied were unidirectional: (1) (0) sub 8, (2) (10) sub 8, and (3) (45) sub 8, and (90) sub 8; cross plied laminates (0 sub 2/90 sub 2); and angle plied laminates: (+45 sub 2/-45 sub 2). Each laminate contained eight fiber plies. Results of the unidirectionally reinforced composites tested at various angles to the reinforcement direction indicate large anisotropy in in-plane properties. In addition, strength properties of these composites along the fiber direction were independent of specimen gage length and were unaffected by notches normal to the fiber direction. Splitting parallel to the fiber at the notch tip appears to be the dominant crack blunting mechanism responsible for notch insensitive behavior of these composites. In-plane properties of the composites can be improved by 2-D laminate construction. Mechanical property results for (0 sub 2/90 sub 2)sub s and (+45/-45 sub 2) sub s laminates showed that their matrix failure strains were similar to that for (0) sub 8 laminates, but their primary elastic moduli, matrix cracking strengths, and ultimate composite strengths were lower. The elastic properties of unidirectional, cross-ply, and angle-ply composites can be predicted from modified constitutive equations and laminate theory. Further improvements in laminate properties may be achieved by reducing the matrix porosity and by optimizing the bond strength between the SiC fiber and RBSN matrix.

Laminate behavior for SiC fiber-reinforced reaction-bonded silicon nitride matrix composites

NASA Technical Reports Server (NTRS)

Bhatt, Ramakrishna T.; Phillips, Ronald E.

1990-01-01

The room temperature mechanical properties of SiC fiber reinforced reaction-bonded silicon nitride matrix composite laminates (SiC/RBSN) have been measured. The laminates contained approx 30 volume fraction of aligned 142-micron diameter SiC fiber in a porous RBSN matrix. Three types of laminate studied were unidirectional: (1) (0) sub 8, (2) (10) sub 8, and (3) (45) sub 8, and (90) sub 8; cross plied laminates (0 sub 2/90 sub 2); and angle plied laminates: (+45 sub 2/-45 sub 2). Each laminate contained eight fiber plies. Results of the unidirectionally reinforced composites tested at various angles to the reinforcement direction indicate large anisotropy in in-plane properties. In addition, strength properties of these composites along the fiber direction were independent of specimen gage length and were unaffected by notches normal to the fiber direction. Splitting parallel to the fiber at the notch tip appears to be the dominant crack blunting mechanism responsible for notch insensitive behavior of these composites. In-plane properties of the composites can be improved by 2-D laminate construction. Mechanical property results for (0 sub 2/90 sub 2) sub s and (+45/-45 sub 2) sub s laminates showed that their matrix failure strains were similar to that for (0) sub 8 laminates, but their primary elastic moduli, matrix cracking strengths, and ultimate composite strengths were lower. The elastic properties of unidirectional, cross-ply, and angle-ply composites can be predicted from modified constitutive equations and laminate theory. Further improvements in laminate properties may be achieved by reducing the matrix porosity and by optimizing the bond strength between the SiC fiber and RBSN matrix.

Age Effects on Hypocotyl Mechanics.

PubMed

Saxe, Friederike; Weichold, Susann; Reinecke, Antje; Lisec, Jan; Döring, Anett; Neumetzler, Lutz; Burgert, Ingo; Eder, Michaela

2016-01-01

Numerous studies deal with composition and molecular processes involved in primary cell wall formation and alteration in Arabidopsis. However, it still remains difficult to assess the relation between physiological properties and mechanical function at the cell wall level. The thin and fragile structure of primary cell walls and their large biological variability, partly related to structural changes during growth, make mechanical experiments challenging. Since, to the best of our knowledge, there is no reliable data in the literature about how the properties of the fully elongated zone of hypocotyls change with age. We studied in a series of experiments on two different seed batches the tensile properties the region below the growth zone of 4 to 7 day old etiolated Arabidopsis hypocotyls. Additionally, we analysed geometrical parameters, hypocotyl density and cellulose content as individual traits and their relation to tissue mechanics. No significant differences of the mechanical parameters of the non-growing region between 5-7 day old plants could be found whereas in 4 day old plants both tensile stiffness and ultimate tensile stress were significantly lower than in the older plants. Furthermore hypocotyl diameters and densities remain almost the same for 5, 6 and 7 day old seedlings. Naturally, hypocotyl lengths increase with age. The evaluation whether the choice-age or length-influences the mechanical properties showed that both are equally applicable sampling parameters. Additionally, our detailed study allows for the estimation of biological variability, connections between mechanics and hypocotyl age could be established and complement the knowledge on biochemistry and genetics affecting primary plant cell wall growth. The application of two different micromechanical devices for testing living Arabidopsis hypocotyls allows for emphasizing and discussing experimental limitations and for presenting a wide range of possibilities to address current and future questions related to plant cell wall mechanics, synthesis and growth in combination with molecular biology methodologies.

Mechanical properties and internal fit of 4 CAD-CAM block materials.

PubMed

Goujat, Alexis; Abouelleil, Hazem; Colon, Pierre; Jeannin, Christophe; Pradelle, Nelly; Seux, Dominique; Grosgogeat, Brigitte

2018-03-01

Recent polymer-based computer-assisted design and computer-assisted manufacturing (CAD-CAM) materials have been commercialized for inlay restorations, a polymer-infiltrated ceramic-network (PICN) and composite resin nanoceramics. Little independent evidence regarding their mechanical properties exists. Internal adaptation is an important factor for the clinical success and longevity of a restoration, and data concerning this parameter for inlays made with these blocks are scarce. The purpose of this in vitro study was to evaluate and compare the mechanical properties (flexural strength, flexural modulus, Vickers hardness, fracture toughness) and the internal adaptation of these recent polymer-based blocks with a lithium disilicate glass-ceramic block. The materials tested in this study were a PICN material (Vita Enamic), 2 composite resin nanoceramics (Lava Ultimate; 3M ESPE and Cerasmart; GCDental Products), and a lithium disilicate glass-ceramic (IPS e.max CAD). Mechanical properties were evaluated according to ISO norm DIS 6872:2013. Bar-shaped specimens (18×3×3 mm) were prepared and submitted to a 3-point bend test using a universal testing machine at a cross-head speed of 0.5 mm/min. In addition, identical cavities were prepared in 60 human mandibular extracted molars (n=15) and optically scanned to receive mesioocclusodistal inlays milled with the 4 materials tested in a CEREC Inlab milling machine. The replica technique and a stereomicroscope (×20) were used to measure the internal fit of the inlays at 9 preselected locations. All data were statistically analyzed using 1-way ANOVA and the post hoc Tukey multiple comparison or Games-Howell test (α=.05). The mean flexural strength of the tested blocks ranged from 148.7 ±9.5 MPa (Vita Enamic) to 216.5 ±28.3 MPa (Cerasmart). The mean flexural modulus ranged from 23.3 ±6.4 GPa (Vita Enamic) to 52.8 ±10.5 GPa (IPS e.max CAD). The mean Vickers hardness ranged from 0.66 ±0.02 GPa (Cerasmart) to 5.98 ±0.69 GPa (IPS e.max CAD). The mean fracture toughness ranged from 1.2 ±0.17 MPa.m 1/2 (Cerasmart) to 1.8 ±0.29 MPa.m 1/2 (IPS e.max CAD). The values for internal discrepancy ranged from 119 ±55 μm to 234 ±51 μm. The mean internal discrepancy was significantly higher for Lava Ultimate (P<.05) than IPS e.max CAD and Cerasmart but not for Vita Enamic. The factor ''material'' was statistically significant in relation to the mechanical properties evaluated in this study (P<.05). The Pearson correlation was negative between the flexural strength results and the internal discrepancy of the materials tested (R 2 =0.941; P<.05). The mechanical properties of the CAD-CAM block materials tested were within the acceptable range for fabrication of single restorations according to the ISO standard for ceramics (ISO 6872:2008). IPS e.max CAD and Cerasmart were observed to have superior flexural strength and better internal fit. Copyright © 2017 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

Microstructures, mechanical properties, and degradation behaviors of heat-treated Mg-Sr alloys as potential biodegradable implant materials.

PubMed

Wang, Yuxiang; Tie, Di; Guan, Renguo; Wang, Ning; Shang, Yingqiu; Cui, Tong; Li, Junqiao

2018-01-01

In previous studies, Mg-Sr alloys exhibited great biocompatibility with regard to test animals, and enhanced peri-implant bone formation. The objective of the present study was to investigate the effects of heat treatments on the mechanical and corrosion properties of Mg-Sr alloys. Various heat-treated Mg-xSr (x = 0.5, 1, and 2wt%, nominal composition) alloys were prepared using homogenization and aging treatments. Mechanical tests were performed at room temperature on the as-cast, homogenized, and peak-aged alloys. As the Sr content increased, the volume fraction of Mg 17 Sr 2 phases within the as-cast alloys increased; in addition, the mechanical strength of the alloys initially increased and subsequently decreased, while the ductility decreased. Following the homogenization treatment, the mechanical strength of the alloys decreased, and the ductility increased. Nano-sized Mg 17 Sr 2 phases were re-precipitated during the aging treatment. The age-hardening response at 160°C was enhanced as the Sr content increased. Following the aging treatment, there was an increase in the mechanical strength of the alloys; however, there was a slight reduction in the ductility. Immersion tests were conducted at 37°C for 360h, using Hank's buffered salt solution (HBSS), to study the degradation behavior of the alloys. As the Sr content of the Mg-Sr alloys increased, the corrosion rate (CR) increased owing to the galvanic effect. The homogenization treatment consequently reduced the CR dramatically, and the aging treatment had a slight effect on the CR. The peak-aged Mg-1Sr (wt%) alloy exhibited the best combination of properties. The tensile yield strength (TYS), ultimate tensile strength (UTS), elongation, compressive yield strength (CYS), ultimate compressive strength (UCS), compressibility, and CR of the as-cast Mg-1Sr (wt%) alloy were 56.0MPa, 92.67MPa, 1.27%, 171.4MPa, 243.6MPa, 22.3%, and 1.76mm/year, respectively. The respective results obtained for the peak-aged Mg-1Sr (wt%) alloys were 69.7MPa, 135.6MPa, 3.22%, 183.1MPa, 273.6MPa, 27.6%, and 1.33mm/year. Following immersion in HBSS, the primary corrosion products of the peak-aged Mg-1Sr (wt%) alloy were Mg(OH) 2 , MgO, MgCO 3 , Mg 3 (PO 4 ) 2 , MgHPO 4 , and Mg(H 2 PO 4 ) 2 , which enhanced the corrosion resistance by forming a composite corrosion film. Copyright © 2017 Elsevier Ltd. All rights reserved.

Ultrafine-Grained Plates of Al-Mg-Si Alloy Obtained by Incremental Equal Channel Angular Pressing: Microstructure and Mechanical Properties

NASA Astrophysics Data System (ADS)

Lipinska, Marta; Chrominski, Witold; Olejnik, Lech; Golinski, Jacek; Rosochowski, Andrzej; Lewandowska, Malgorzata

2017-10-01

In this study, an Al-Mg-Si alloy was processed using via incremental equal channel angular pressing (I-ECAP) in order to obtain homogenous, ultrafine-grained plates with low anisotropy of the mechanical properties. This was the first attempt to process an Al-Mg-Si alloy using this technique. Samples in the form of 3 mm-thick square plates were subjected to I-ECAP with the 90 deg rotation around the axis normal to the surface of the plate between passes. Samples were investigated first in their initial state, then after a single pass of I-ECAP, and finally after four such passes. Analyses of the microstructure and mechanical properties demonstrated that the I-ECAP method can be successfully applied in Al-Mg-Si alloys. The average grain size decreased from 15 to 19 µm in the initial state to below 1 µm after four I-ECAP passes. The fraction of high-angle grain boundaries in the sample subjected to four I-ECAP passes lay within 53 to 57 pct depending on the examined plane. The mechanism of grain refinement in Al-Mg-Si alloy was found to be distinctly different from that in pure aluminum with the grain rotation being more prominent than the grain subdivision, which was attributed to lower stacking fault energy and the reduced mobility of dislocations in the alloy. The ultimate tensile strength increased more than twice, whereas the yield strength was more than threefold. Additionally, the plates processed by I-ECAP exhibited low anisotropy of mechanical properties (in plane and across the thickness) in comparison to other SPD processing methods, which makes them attractive for further processing and applications.

Synthesis, mechanical properties and corrosion behavior of powder metallurgy processed Fe/Mg2Si composites for biodegradable implant applications.

PubMed

Sikora-Jasinska, M; Paternoster, C; Mostaed, E; Tolouei, R; Casati, R; Vedani, M; Mantovani, D

2017-12-01

Recently, Fe and Fe-based alloys have shown their potential as degradable materials for biomedical applications. Nevertheless, the slow corrosion rate limits their performance in certain situations. The shift to iron matrix composites represents a possible approach, not only to improve the mechanical properties, but also to accelerate and tune the corrosion rate in a physiological environment. In this work, Fe-based composites reinforced by Mg 2 Si particles were proposed. The initial powders were prepared by different combinations of mixing and milling processes, and finally consolidated by hot rolling. The influence of the microstructure on mechanical properties and corrosion behavior of Fe/Mg 2 Si was investigated. Scanning electron microscopy and X-ray diffraction were used for the assessment of the composite structure. Tensile and hardness tests were performed to characterize the mechanical properties. Potentiodynamic and static corrosion tests were carried out to investigate the corrosion behavior in a pseudo-physiological environment. Samples with smaller Mg 2 Si particles showed a more homogenous distribution of the reinforcement. Yield and ultimate tensile strength increased when compared to those of pure Fe (from 400MPa and 416MPa to 523MPa and 630MPa, respectively). Electrochemical measurements and immersion tests indicated that the addition of Mg 2 Si could increase the corrosion rate of Fe even twice (from 0.14 to 0.28mm·year -1 ). It was found that the preparation method of the initial composite powders played a major role in the corrosion process as well as in the corrosion mechanism of the final composite. Copyright © 2017 Elsevier B.V. All rights reserved.

[The effects of different welding wires on the mechanical properties of laser welding joints].

PubMed

Huang, Qing-feng; Zhang, Jian-zhong; Jiang, Wei-dong; Li, Quan; Yu, Jin-xing

2006-08-01

To evaluate the mechanical properties and microstructure of laser-welded joints with different welding wires for clinical use of welding wire. The standard tensile test and three-point bending test rods were made from Co-Cr and Ni-Cr alloy, and were laser-welded with different welding wire (commercially welding wire and casting wire). Then the tensile rods were tested for the ultimate tensile strength (UTS), and the bending rods for the ultimate bending strength (UBS). The results was analyzed by one-way ANOVA. The tensile fracture surface were examined by scanning electron microscopy (SEM). Metallurgical analysis were also performed on polished longitudinal sectioned samples. For Co-Cr alloy, the UTS of casting wire group and commercially welding wire group was respectively (606.40+/-82.53)MPa and (693.61+/-47.68)MPa; the UBS was respectively (997.95+/-88.89)MPa and (1160.76+/-91.59)MPa. ANOVA showed a significant difference of UTS and UBS between the two groups at the 0.05 level (P<0.05). For Ni-Cr alloy, the UTS of casting wire group and commercially welding wire group was respectively (558.14+/-46.75)MPa and (582.32+/-35.43)MPa; the UBS was respectively (1084.75+/-46.02)MPa and (1078.29+/-36.25)MPa. There was no significant difference between the two groups (P>0.05). SEM and metallurgical examination showed the welded zone exhibiting more cracks in the casting wire group than in the commercially welding wire group. It would be advisable to work with commercially welding wire for the joints that need better strength.

Soybean-oil-based waterborne polyurethane dispersions: effects of polyol functionality and hard segment content on properties.

PubMed

Lu, Yongshang; Larock, Richard C

2008-11-01

The environmentally friendly vegetable-oil-based waterborne polyurethane dispersions with very promising properties have been successfully synthesized without difficulty from a series of methoxylated soybean oil polyols (MSOLs) with different hydroxyl functionalities ranging from 2.4 to as high as 4.0. The resulting soybean-oil-based waterborne polyurethane (SPU) dispersions exhibit a uniform particle size, which increases from about 12 to 130 nm diameter with an increase in the OH functionality of the MSOL from 2.4 to 4.0 and decreases with increasing content of the hard segments. The structure and thermophysical and mechanical properties of the resulting SPU films, which contain 50-60 wt % MSOL as renewable resources, have been studied by Fourier transform infrared spectroscopy, differential scanning calorimetry, dynamic mechanical analysis, thermogravimetric analysis, transmission electron microscopy, and mechanical testing. The experimental results reveal that the functionality of the MSOLs and the hard segment content play a key role in controlling the structure and the thermophysical and mechanical properties of the SPU films. These novel films exhibit tensile stress-strain behavior ranging from elastomeric polymers to rigid plastics and possess Young's moduli ranging from 8 to 720 MPa, ultimate tensile strengths ranging from 4.2 to 21.5 MPa, and percent elongation at break values ranging from 16 to 280%. This work has addressed concerns regarding gelation and higher cross-linking caused by the high functionality of vegetable-oil-based polyols. This article reports novel environmentally friendly biobased SPU materials with promising applications as decorative and protective coatings.

Impact of parity on ewe vaginal mechanical properties relative to the nonhuman primate and rodent.

PubMed

Knight, Katrina M; Moalli, Pamela A; Nolfi, Alexis; Palcsey, Stacy; Barone, William R; Abramowitch, Steven D

2016-08-01

Parity is the leading risk factor for the development of pelvic organ prolapse. To assess the impact of pregnancy and delivery on vaginal tissue, researchers commonly use nonhuman primate (NHP) and rodent models. The purpose of this study was to evaluate the ewe as an alternative model by investigating the impact of parity on the ewe vaginal mechanical properties and collagen structure. Mechanical properties of 15 nulliparous and parous ewe vaginas were determined via uniaxial tensile tests. Collagen content was determined by hydroxyproline assay and collagen fiber thickness was analyzed using picrosirius red staining. Outcome measures were compared using Independent samples t or Mann-Whitney U tests. ANOVA (Gabriel's pairwise post-hoc test) or the Welch Alternative for the F-ratio (Games Howell post-hoc test) was used to compare data with previously published NHP and rodent data. Vaginal tissue from the nulliparous ewe had a higher tangent modulus and tensile strength compared with the parous ewe (p < 0.025). The parous ewe vagina elongated 42 % more than the nulliparous ewe vagina (p = 0.015). No significant differences were observed in collagen structure among ewe vaginas. The tangent modulus of the nulliparous ewe vagina was not different from that of the NHP or rodent (p = 0.290). Additionally, the tangent moduli of the parous ewe and NHP vaginas did not differ (p = 0.773). Parity has a negative impact on the mechanical properties of the ewe vagina, as also observed in the NHP. The ewe may serve as an alternative model for studying parity and ultimately prolapse development.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smedskjaer, Morten M., E-mail: mos@bio.aau.dk; Bauchy, Mathieu; Mauro, John C.

The properties of glass are determined not only by temperature, pressure, and composition, but also by their complete thermal and pressure histories. Here, we show that glasses of identical composition produced through thermal annealing and through quenching from elevated pressure can result in samples with identical density and mean interatomic distances, yet different bond angle distributions, medium-range structures, and, thus, macroscopic properties. We demonstrate that hardness is higher when the density increase is obtained through thermal annealing rather than through pressure-quenching. Molecular dynamics simulations reveal that this arises because pressure-quenching has a larger effect on medium-range order, while annealing hasmore » a larger effect on short-range structures (sharper bond angle distribution), which ultimately determine hardness according to bond constraint theory. Our work could open a new avenue towards industrially useful glasses that are identical in terms of composition and density, but with differences in thermodynamic, mechanical, and rheological properties due to unique structural characteristics.« less

Advancing Renewable Materials by Light and X-ray Scattering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Akpalu, Yvonne A

With the ultimate goal to design PHA polymer nanocomposites with tailored properties, we have completed systematic study of the influence of cooling rate [Xie et al, J. Appl. Poly. Sci., 2008] and nanofiller [Xie et al, Polymer 2009] characteristics on model bionanocomposites. Structure-property relationships for a model bionanocomposites system were investigated. These results yielded new fundamental knowledge that supports the discovery of cost-effective manufacturing technologies for a family of promising polyhydroxyalkanoates (PHAs) polyesters, with the potential to replace polyethylene and polypropylene (see Noda letter). Our results show that simple two-phase composite models do not account for the data. Although improvementmore » of the mechanical properties (stiffness/modulus and toughness) must be due to alteration of the matrix by the nanoparticle filler, the observed improvement was not caused by the change of crystallinity or spherulitic morphology. Instead, improvement depends on the molecular weight of the polymer matrix and unknown filler-matrix interactions.« less

Advance of Mechanically Controllable Break Junction for Molecular Electronics.

PubMed

Wang, Lu; Wang, Ling; Zhang, Lei; Xiang, Dong

2017-06-01

Molecular electronics stands for the ultimate size of functional elements, keeping up with an unstoppable trend over the past few decades. As a vital component of molecular electronics, single molecular junctions have attracted significant attention from research groups all over the world. Due to its pronounced superiority, the mechanically controllable break junctions (MCBJ) technique has been widely applied to characterize the dynamic performance of single molecular junctions. This review presents a system analysis for single-molecule junctions and offers an overview of four test-beds for single-molecule junctions, thus offering more insight into the mechanisms of electron transport. We mainly focus on the development of state-of-the-art mechanically controlled break junctions. The three-terminal gated MCBJ approaches are introduced to manipulate the electron transport of molecules, and MCBJs are combined with characterization techniques. Additionally, applications of MCBJs and remarkable properties of single molecules are addressed. Finally, the challenges and perspective for the mechanically controllable break junctions technique are provided.

Fabrication and Analysis of the Wear Properties of Hot-Pressed Al-Si/SiCp + Al-Si-Cu-Mg Metal Matrix Composite

NASA Astrophysics Data System (ADS)

Bang, Jeongil; Oak, Jeong-Jung; Park, Yong Ho

2016-01-01

The aim of this study was to characterize microstructures and mechanical properties of aluminum metal matrix composites (MMC's) prepared by powder metallurgy method. Consolidation of mixed powder with gas atomized Al-Si/SiCp powder and Al-14Si-2.5Cu-0.5Mg powder by hot pressing was classified according to sintering temperature and sintering time. Sintering condition was optimized using tensile properties of sintered specimens. Ultimate tensile strength of the optimized sintered specimen was 228 MPa with an elongation of 5.3% in longitudinal direction. In addition, wear properties and behaviors of the sintered aluminum-based MMC's were analyzed in accordance with vertical load and linear speed. As the linear speed and vertical load of the wear increased, change of the wear behavior occurred in order of oxidation of Al-Si matrix, formation of C-rich layer, Fe-alloying to matrix, and melting of the specimen

High-temperature Tensile Properties and Creep Life Assessment of 25Cr35NiNb Micro-alloyed Steel

NASA Astrophysics Data System (ADS)

Ghatak, Amitava; Robi, P. S.

2016-05-01

Reformer tubes in petrochemical industries are exposed to high temperatures and gas pressure for prolonged period. Exposure of these tubes at severe operating conditions results in change in the microstructure and degradation of mechanical properties which may lead to premature failure. The present work highlights the high-temperature tensile properties and remaining creep life prediction using Larson-Miller parametric technique of service exposed 25Cr35NiNb micro-alloyed reformer tube. Young's modulus, yield strength, and ultimate tensile strength of the steel are lower than the virgin material and decreases with the increase in temperature. Ductility continuously increases with the increase in temperature up to 1000 °C. Strain hardening exponent increases up to 600 °C, beyond which it starts decreasing. The tensile properties are discussed with reference to microstructure and fractographs. Based on Larson-Miller technique, a creep life of at least 8.3 years is predicted for the service exposed material at 800 °C and 5 MPa.

Manipulating the structure and mechanical properties of thermoplastic polyurethane/polycaprolactone hybrid small diameter vascular scaffolds fabricated via electrospinning using an assembled rotating collector.

PubMed

Mi, Hao-Yang; Jing, Xin; Yu, Emily; Wang, Xiaofeng; Li, Qian; Turng, Lih-Sheng

2018-02-01

The success of blood vessel transplants with vascular scaffolds (VSs) highly depends on their structure and mechanical properties. The fabrication of small diameter vascular scaffolds (SDVSs) mimicking the properties of native blood vessels has been a challenge. Herein, we propose a facile method to fabricate thermoplastic polyurethane (TPU)/polycaprolactone (PCL) hybrid SDVSs via electrospinning using a modified rotating collector. By varying the ratio between the TPU and the PCL, and changing the electrospinning volume, SDVSs with a wavy configuration and different properties could be obtained. Detailed investigation revealed that certain TPU/PCL hybrid SDVSs closely resembled the mechanical behaviors of blood vessels due to the presence of a wavy region and the combination of flexible TPU and rigid PCL, which mimicked the properties of elastin and collagen in blood vessels. The fabricated TPU/PCL SDVSs achieved lumen diameters of 1-3mm, wall thicknesses of 100-570µm, circumferential moduli of 1-6MPa, ultimate strengths of 2-8MPa, over 250% elongation-at-break values, toe regions of 5.3-9.4%, high recoverability, and compliances close to those of human veins. Moreover, these TPU/PCL SDVSs possessed sufficient suture retention strength and burst pressure to fulfill transplantation requirements and maintain normal blood flow. Human endothelial cell culture revealed good biocompatibility of the scaffolds, and cells were able to grow on the inner surface of the tubular scaffolds, indicating promising prospects for use as tissue-engineered vascular grafts. Copyright © 2017 Elsevier Ltd. All rights reserved.

Raloxifene reduces skeletal fractures in an animal model of osteogenesis imperfecta.

PubMed

Berman, Alycia G; Wallace, Joseph M; Bart, Zachary R; Allen, Matthew R

2016-01-01

Osteogenesis imperfecta (OI) is a genetic disease of Type I collagen and collagen-associated pathways that results in brittle bone behavior characterized by fracture and reduced mechanical properties. Based on previous work in our laboratory showing that raloxifene (RAL) can significantly improve bone mechanical properties through non-cellular mechanisms, we hypothesized that raloxifene would improve the mechanical properties of OI bone. In experiment 1, tibiae from female wild type (WT) and homozygous oim mice were subjected to in vitro soaking in RAL followed by mechanical tests. RAL soaking resulted in significantly higher post-yield displacement (+75% in WT, +472% in oim; p<0.004), with no effect on ultimate load or stiffness, in both WT and oim animals. In experiment 2, eight-week old WT and oim male mice were treated for eight weeks with saline vehicle (VEH) or RAL. Endpoint measures included assessment of in vivo skeletal fractures, bone density/geometry and mechanical properties. In vivo skeletal fractures of the femora, assessed by micro CT imaging, were significantly lower in oim-RAL (20%) compared to oim-VEH (48%, p=0.047). RAL led to significantly higher DXA-based BMD (p<0.01) and CT-based trabecular BV/TV in both WT and oim animals compared to those treated with VEH. Fracture toughness of the femora was lower in oim mice compared to WT and improved with RAL in both genotypes. These results suggest that raloxifene reduces the incidence of fracture in this mouse model of oim. Furthermore, they suggest that raloxifene's effects may be the result of both cellular (increased bone mass) and non-cellular (presumably changes in hydration) mechanisms, raising the possibility of using raloxifene, or related compounds, as a new approach for treating bone fragility associated with OI. Copyright © 2016 International Society of Matrix Biology. Published by Elsevier B.V. All rights reserved.

Effect of β-hydroxy-β-methylbutyrate (HMB) administration on volumetric bone mineral density, and morphometric and mechanical properties of tibia in male turkeys.

PubMed

Tatara, M R

2009-12-01

This study was performed to investigate the effects of β-hydroxy-β-methylbutyrate (HMB) administration on skeletal system properties in turkeys. Thirty-two males were randomly divided into two groups at the age of 35 days of life. The first group included control turkeys (n = 16) treated with placebo, while the second group of birds (HMB group; n = 16) was administered orally with calcium salt of HMB during the last 15 weeks of life. The turkeys were sacrificed at the age of 20 weeks and tibia was isolated for analysis of bone geometrical parameters, volumetric bone mineral density (vBMD) and mechanical properties. Furthermore, assessment of free amino acid concentrations in plasma was performed. The results showed a 6.3% increase of vBMD of tibia in response to HMB treatment (p < 0.01). Cross-sectional area, second moment of inertia, maximum elastic strength and ultimate strength of tibia were significantly increased in HMB-treated turkeys by 21.3%, 49.0%, 27.2% and 28.3%, respectively (p ≤ 0.01). β-hydroxy-β-methylbutyrate administration increased plasma concentrations of proline,glutamate, leucine, isoleucine, valine, alanine, aspartate, phenylalanine and cysteic acid (p < 0.05). These results indicate that long-term administration of HMB improves vBMD, and geometrical and mechanical properties of skeletal system in turkeys, and that these effects are associated with improved plasma amino acid concentrations.

Investigation of fabrication and environmental effects on bioceramic bone scaffolds

NASA Astrophysics Data System (ADS)

Vivanco Morales, Juan Francisco

2011-12-01

Bioactive ceramic materials like tricalcium phosphates (TCP) have been emerging as viable material alternatives to the current therapies of bone scaffolding to target fracture healing and osteoporosis. Once scaffolds are implanted at the defect site they should provide mechanical and biological functions, ultimately serving to facilitate with surrounding native tissue. Optimal osteogenic signal expression and subsequent differentiation of cells seeded on the scaffold in both in vivo and in vitro conditions is known to be influenced by scaffold properties and biomechanical environmental conditions. Thus, the objective of this research was to investigate the effect of fabrication and environmental variables on the properties of bioceramic scaffolds for bone tissue engineering applications. Specifically, the effect of sintering temperature in the range of 950°C -1150°C of a cost-effective on a large scale manufacturing process, on the physical and mechanical properties of bioceramic bone scaffolds, was investigated. In addition, the effect of a controlled environment was investigated by implementing a bioreactor and bone loading system to study the response of ex vivo trabecular bone to compressive load while perfused with culture medium. Collectively, this thesis demonstrates that: (1) the sintering temperature to fabricate bioceramic scaffolds can be tuned to structural properties, and (2) the use of a controlled mechanical and biochemical environment can enhance bone tissue development. These findings support the development of clinically successful bioceramic scaffolds that may stimulate bone regeneration and scaffold integration while providing structural integrity.

Influence of Cu Addition on the Structure, Mechanical and Corrosion Properties of Cast Mg-2%Zn Alloy

NASA Astrophysics Data System (ADS)

Lotfpour, M.; Emamy, M.; Dehghanian, C.; Tavighi, K.

2017-05-01

Effects of different concentrations of Cu on the structure, mechanical and corrosion properties of Mg-2%Zn alloy were studied by the use of x-ray diffraction, optical microscopy, scanning electron microscopy, energy dispersive spectroscopy, standard tensile testing, polarization and electrochemical impedance spectroscopy (EIS) measurements. The average grain size of the alloy decreased from above 1000 μm to about 200 μm with 5 wt.% Cu addition in as-cast condition. Microstructural studies revealed that Mg-2Zn- xCu alloys matrix typically consists of primary α-Mg and MgZnCu and Mg(Zn,Cu)2 intermetallics which are mainly found at the grain boundaries. The results obtained from mechanical testing ascertained that Cu addition increased the hardness values significantly. Although the addition of 0.5 wt.% Cu improved the ultimate tensile strength and elongation values, more Cu addition (i.e., 5 wt.%) weakened the tensile properties of the alloy by introducing semi-continuous network of brittle intermetallic phases. Based on polarization test results, it can be concluded that Cu eliminates a protective film on Mg-2%Zn alloy surface. Among Mg-2%Zn- x%Cu alloys, the one containing 0.1 wt.% Cu exhibited the best anti-corrosion property. However, further Cu addition increased the volume fraction of intermetallics culminating in corrosion rate enhancement due to the galvanic couple effect. EIS and microstructural analysis also confirmed the polarization results.

Experimental and numerical investigation on cladding of corrosion-erosion resistant materials by a high power direct diode laser

NASA Astrophysics Data System (ADS)

Farahmand, Parisa

In oil and gas industry, soil particles, crude oil, natural gas, particle-laden liquids, and seawater can carry various highly aggressive elements, which accelerate the material degradation of component surfaces by combination of slurry erosion, corrosion, and wear mechanisms. This material degradation results into the loss of mechanical properties such as strength, ductility, and impact strength; leading to detachment, delamination, cracking, and ultimately premature failure of components. Since the failure of high valued equipment needs considerable cost and time to be repaired or replaced, minimizing the tribological failure of equipment under aggressive environment has been gaining increased interest. It is widely recognized that effective management of degradation mechanisms will contribute towards the optimization of maintenance, monitoring, and inspection costs. The hardfacing techniques have been widely used to enhance the resistance of surfaces against degradation mechanisms. Applying a surface coating improves wear and corrosion resistance and ensures reliability and long-term performance of coated parts. A protective layer or barrier on the components avoids the direct mechanical and chemical contacts of tool surfaces with process media and will reduce the material loss and ultimately its failure. Laser cladding as an advanced hardfacing technique has been widely used for industrial applications in order to develop a protective coating with desired material properties. During the laser cladding, coating material is fused into the base material by means of a laser beam in order to rebuild a damaged part's surface or to enhance its surface function. In the hardfacing techniques such as atmospheric plasma spraying (APS), high velocity oxygen-fuel (HVOF), and laser cladding, mixing of coating materials with underneath surface has to be minimized in order to utilize the properties of the coating material most effectively. In this regard, laser cladding offers advantages due to creating coating layers with superior properties in terms of purity, homogeneity, low dilution, hardness, bonding, and microstructure. In the development of modern materials for hardfacing applications, the functionality is often improved by combining materials with different properties into composites. Metal Matrix Composite (MMC) coating is a composite material with two constituent parts, i.e., matrix and the reinforcement. This class of composites are addressing improved mechanical properties such as stiffness, strength, toughness, and tribological and chemical resistance. Fabrication of MMCs is to achieve a combination of properties not achievable by any of the materials acting alone. MMCs have attracted significant attention for decades due to their combination of wear-resistivity, corrosion-resistivity, thermal, electrical and magnetic properties. Presently, there is a strong emphasis on the development of advanced functional coatings for corrosion, erosion, and wear protection for different industrial applications. In this research, a laser cladding system equipped with a high power direct diode laser associated with gas driven metal powder delivery system was used to develop advanced MMC coatings. The high power direct diode laser used in this study offers wider beam spot, shorter wavelength and uniform power distribution. These properties make the cladding set-up ideal for coating due to fewer cladding tracks, lower operation cost, higher laser absorption, and improved coating qualities. In order to prevent crack propagation, porosity, and uniform dispersion of carbides in MMC coating, cladding procedure was assisted by an induction heater as a second heat source. The developed defect free MMC coatings were combined with nano-size particles of WC, rare earth (RE) element (La2O3), and Mo as a refractory metal to enhance mechanical properties, chemical composition, and subsequently improve the tribological performance of the coatings. The resistance of developed MMC coatings were examined under highly accelerated slurry erosion, corrosion, and wear as the most frequently encountered failure modes of mechanical components. The microstructure, mechanical properties, and the level of induced residual stress on the coating after cladding procedure are closely related to cladding process variables. Study about the effect of processing parameters on clad quality and experienced thermal history and thermally-induced stress evolution requires both theoretical and experimental understanding of the associated physical phenomena. Numerical modeling offers a cost-efficient way to better understand the related complex physics in laser cladding process. It helps to reveal the effects and significance of each processing parameters on the desired characteristics of clad parts. Successful numerical simulation can provide unique insight into complex laser cladding process, efficiently calculate the complex procedure, and help to obtain coating parts with quality integrity. Therefore, current study develops a three-dimensional (3D) transient and uncoupled thermo-elastic-plastic model to study thermal history, molten pool evolution, thermally induced residual stress, and the effect of utilizing an induction heater as a second heat source on the mechanical properties and microstructural properties of final cladded coating.

Rheological Properties of Cross-Linked Hyaluronan–Gelatin Hydrogels for Tissue Engineering

PubMed Central

Vanderhooft, Janssen L.; Alcoutlabi, Mataz; Magda, Jules J.; Prestwich, Glenn D.

2009-01-01

Hydrogels that mimic the natural extracellular matrix (ECM) are used in three-dimensional cell culture, cell therapy, and tissue engineering. A semi-synthetic ECM based on cross-linked hyaluronana offers experimental control of both composition and gel stiffness. The mechanical properties of the ECM in part determine the ultimate cell phenotype. We now describe a rheological study of synthetic ECM hydrogels with storage shear moduli that span three orders of magnitude, from 11 to 3 500 Pa, a range important for engineering of soft tissues. The concentration of the chemically modified HA and the cross-linking density were the main determinants of gel stiffness. Increase in the ratio of thiol-modified gelatin reduced gel stiffness by diluting the effective concentration of the HA component. PMID:18839402

Epoxy thermoset networks derived from vegetable oils and their blends

NASA Astrophysics Data System (ADS)

Ryu, Chang; Ravalli, Matthew

2015-03-01

Epoxidized vegetable oils (EVOs), such as epoxidized soybean oil and linseed oils were prepared by the partial oxidation of the unsaturated double bonds in vegetable oils and used as monomers for preparing epoxy thermoset materials based on the cationic polymerization. These EVOs have been used to prepare epoxy thermosets of different network densities by cationic polymerization using onium salt catalyst. The crosslinked epoxy thermosets provide an ideal platform to study the structure-property-relationships of networked polymers. In particular, rheological studies on the epoxidized vegetable oil thermosets have been performed to measure the molecular weights between crosslinks (Mx) in the epoxy thermosets and to ultimately elucidate the role of functionality of epoxy groups in EVO on the mechanical and thermophysical properties of the epoxy thermoset materials. NSF DMR POLYMERS 1308617.

Comparison of candidate scaffolds for tissue engineering for stress urinary incontinence and pelvic organ prolapse repair.

PubMed

Mangera, Altaf; Bullock, Anthony J; Roman, Sabiniano; Chapple, Christopher R; MacNeil, Sheila

2013-09-01

To identify candidate materials which have sufficient potential to be taken forward for an in vivo tissue-engineering approach to restoring the tissue structure of the pelvic floor in women with stress urinary incontinence (SUI) or pelvic organ prolapse (POP). Oral mucosal fibroblasts were seeded onto seven different scaffold materials, AlloDerm ( LifeCell Corp., Branchburg, NJ, USA), cadaveric dermis, porcine dermis, polypropylene, sheep forestomach, porcine small intestinal submucosa (SIS) and thermoannealed poly(L) lactic acid (PLA) under both free and restrained conditions. The scaffolds were assessed for: cell attachment using AlamarBlue and 4,6-diamidino-2-phenylindole (DAPI); contraction using serial photographs; and extracellular matrix production using Sirius red staining, immunostaining and scanning electron microscopy. Finally the biomechanical properties of all the scaffolds were assessed. Of the seven, there were two biodegradable scaffolds, synthetic PLA and natural SIS, which supported good cell attachment and proliferation. Immunostaining confirmed the presence of collagen I, III and elastin which was highest in SIS and PLA. The mechanical properties of PLA were closest to native tissue with an ultimate tensile strength of 0.72 ± 0.18 MPa, ultimate tensile strain 0.53 ± 0.16 and Young's modulus 4.5 ± 2.9 MPa. Scaffold restraint did not have a significant impact on the above properties in the best scaffolds. These data support both PLA and SIS as good candidate materials for use in making a tissue-engineered repair material for SUI or POP. © 2013 BJU International.

Strain rate dependent orthotropic properties of pristine and impulsively loaded porcine temporomandibular joint disk.

PubMed

Beatty, M W; Bruno, M J; Iwasaki, L R; Nickel, J C

2001-10-01

The purpose of this study was to characterize the tensile stress-strain behavior of the porcine temporomandibular joint (TMJ) disk with respect to collagen orientation and strain rate dependency. The apparent elastic modulus, ultimate tensile strength, and strain at maximum stress were measured at three elongation rates (0.5, 50, and 500 mm/min) for dumbbell-shaped samples oriented along either anteroposterior or mediolateral axes of the disks. In order to study the effects of impact-induced fissuring on the mechanical behavior, the same properties were measured along each orientation at an elongation rate of 500 mm/min for disks subjected to impulsive loads of 0.5 N. s. The results suggested a strongly orthotropic nature to the healthy pristine disk. The values for the apparent modulus and ultimate strength were 10-fold higher along the anteroposterior axis (p < or = 0.01), which represented the primary orientation of the collagen fibers. Strain rate dependency was evident for loading along the anteroposterior axis but not along the mediolateral axis. No significant differences in any property were noted between pristine and impulsively loaded disks for either orientation (p > 0.05). The results demonstrated the importance of choosing an orthotropic model for the TMJ disk to conduct finite element modeling, to develop failure criteria, and to construct tissue-engineered replacements. Impact-induced fissuring requires further study to determine if the TMJ disk is orthotropic with respect to fatigue.

Investigation of Mechanical Properties and Interfacial Mechanics of Crystalline Nanomaterials

NASA Astrophysics Data System (ADS)

Qin, Qingquan

Nanowires (NWs) and nanotubes (NTs) are critical building blocks of nanotechnologies. The operation and reliability of these nanomaterials based devices depend on their mechanical properties of the nanomaterials, which is therefore important to accurately measure the mechanical properties. Besides, the NW--substrate interfaces also play a critical role in both mechanical reliability and electrical performance of these nanodevices, especially when the size of the NW is small. In this thesis, we focus on the mechanical properties and interface mechanics of three important one dimensional (1D) nanomaterials: ZnO NWs, Ag NWs and Si NWs. For the size effect study, this thesis presents a systematic experimental investigation on the elastic and failure properties of ZnO NWs under different loading modes: tension and buckling. Both tensile modulus (from tension) and bending modulus (from buckling) were found to increase as the NW diameter decreased from 80 to 20 nm. The elastic modulus also shows loading mode dependent; the bending modulus increases more rapidly than the tensile modulus. The tension experiments showed that fracture strain and strength of ZnO NWs increase as the NW diameter decrease. A resonance testing setup was developed to measure elastic modulus of ZnO NWs to confirm the loading mode dependent effect. A systematic study was conducted on the effect of clamping on resonance frequency and thus measured Young's modulus of NWs via a combined experiment and simulation approach. A simple scaling law was provided as guidelines for future designs to accurate measure elastic modulus of a cantilevered NW using the resonance method. This thesis reports the first quantitative measurement of a full spectrum of mechanical properties of five-fold twinned Ag NWs including Young's modulus, yield strength and ultimate tensile strength. In situ tensile testing of Ag NWs with diameters between 34 and 130 nm was carried out inside a SEM. Young's modulus, yield strength and ultimate tensile strength were found to all increased as the NW diameter decreased. For the temperature effect study, a brief review on brittle-to-ductile transition (BDT) of silicon (Si) is presented. BDT temperature shows decreasing trend as size of the sample decrease. However, controversial results have been reported in terms of brittle or ductile behaviors for Si NWs at room temperature. A microelectromechanical systems (MEMS) thermal actuator (ETA) was designed to test NW without involving external heating. To circumvent undesired heating of the end effector, heat sink beams that can be co-fabricated with the thermal actuator were introduced. A combined modeling and experimental study was conducted to access the effect of such heat sink beams. Temperature distribution was measured and simulated using Raman scattering and multiphysics finite element method, respectively. Our results demonstrated that heat sink beams are effective in reducing the temperature of the thermal actuator. To get elevated temperature in a controllable fashion, a comb drive actuator was designed with separating actuation and heating mechanisms. Multiphysics finite element analysis (coupled electrical-thermal-mechanical) was used to optimize structure design and minimize undesired thermal loading/unloading. A Si NW with diameter of 50 nm was tested on the device under different temperatures. Stress strain curves at different temperatures revealed that plastic deformation occurs at temperature of 55 °C. For interfacial mechanics, we report an experimental study on the friction between Ag and ZnO NW tips (ends) and a gold substrate. An innovative experimental method based on column buckling theory was developed for the friction measurements. Direct measurements of the static friction force and interfacial shear strength between Si NWs and poly(dimethylsiloxane) (PDMS) is reported. The static friction and shear strength were found to increase rapidly and then decrease with the increasing ultraviolet/ozone (UVO) treatment of PDMS.

Effect of load eccentricity and substructure deformation on ultimate strength of shuttle orbiter thermal protection system

NASA Technical Reports Server (NTRS)

Sawyer, J. W.

1981-01-01

The effect of load eccentricity and substructure deformation on the ultimate strength and stress displacement properties of the shuttle orbiter thermal protection system (TPS) was determined. The LI-900 Reusable Surface Insulation (RSI) tiles mounted on the .41 cm thick Strain Isolator Pad (SIP) were investigated. Substructure deformations reduce the ultimate strength of the SIP/tile TPS and increase the scatter in the ultimate strength data. Substructure deformations that occur unsymmetric to the tile can cause the tile to rotate when subjected to a uniform applied load. Load eccentricity reduces SIP/tile TPS ultimate strength and causes tile rotation.

Effects of SiO2 nano-particles on tribological and mechanical properties of aluminum matrix composites by different dispersion methods

NASA Astrophysics Data System (ADS)

Azadi, Mahboobeh; Zolfaghari, Mehrdad; Rezanezhad, Saeid; Azadi, Mohammad

2018-05-01

This study has been presented with mechanical properties of aluminum matrix composites, reinforced by SiO2 nano-particles. The stir casting method was employed to produce various aluminum matrix composites. Different composites by varying the SiO2 nano-particle content (including 0.5 and 1 weight percents) and two dispersion methods (including ball-milling and pre-heating) were made. Then, the density, the hardness, the compression strength, the wear resistance and the microstructure of nano-composites have been studied in this research. Besides, the distribution of nano-particles in the aluminum matrix for all composites has been also evaluated by the field emission scanning electron microscopy (FESEM). Obtained results showed that the density, the elongation and the ultimate compressive strength of various nano-composites decreased by the presence of SiO2 nano-particles; however, the hardness, the wear resistance, the yield strength and the elastic modulus of composites increased by auditioning of nano-particles to the aluminum alloy. FESEM images indicated better wetting of the SiO2 reinforcement in the aluminum matrix, prepared by the pre-heating dispersion method, comparing to ball-milling. When SiO2 nano-particles were added to the aluminum alloy, the morphology of the Si phase and intermetallic phases changed, which enhanced mechanical properties. In addition, the wear mechanism plus the friction coefficient value were changed for various nano-composites with respect to the aluminum alloy.

Robust and Elastic Polymer Membranes with Tunable Properties for Gas Separation

DOE PAGES

Cao, Peng -Fei; Li, Bingrui; Hong, Tao; ...

2017-07-17

Here, polymer membranes with the capability to process a massive volume of gas are especially attractive for practical applications of gas separation. Although much effort has been devoted to develop novel polymer membranes with increased selectivity, the overall gas-separation performance and lifetime of membrane are still negatively affected by the weak mechanical performance, low plasticization resistance and poor physical aging tolerance. Recently, elastic polymer membranes with tunable mechanical properties have been attracting significant attentions due to their tremendous potential applications. Herein, we report a series of urethanerich PDMS-based polymer networks (U-PDMS-NW) with improved mechanical performance for gas separation. The cross-linkmore » density of U-PDMS-NWs is tailored by varying the molecular weight ( M n) of PDMS. The U-PDMS-NWs show up to 400% elongation and tunable Young’s modulus (1.3–122.2 MPa), ultimate tensile strength (1.1–14.3 MPa), and toughness (0.7–24.9 MJ/m 3). All of the U-PDMS-NWs exhibit salient gas-separation performance with excellent thermal resistance and aging tolerance, high gas permeability (>100 Barrer), and tunable gas selectivity (up to α[ P CO2/ P N2] ≈ 41 and α[ P CO2/ P CH4] ≈ 16). With well-controlled mechanical properties and gas-separation performance, these U-PDMS-NW can be used as a polymermembrane platform not only for gas separation but also for other applications such as microfluidic channels and stretchable electronic devices.« less

Structure, mechanical property and corrosion behaviors of (HA+β-TCP)/Mg-5Sn composite with interpenetrating networks.

PubMed

Wang, X; Li, J T; Xie, M Y; Qu, L J; Zhang, P; Li, X L

2015-11-01

In this paper, a novel (Hydroxyapatite+β-tricalcium phosphate)/Mg-5Sn ((HA+β-TCP)/Mg-5Sn) composite with interpenetrating networks was fabricated by infiltrating Mg-5Sn alloy into porous HA+β-TCP using suction casting technique. The structure, mechanical property and corrosion behaviors of the composite have been evaluated by means of scanning electron microscopy (SEM), X-ray diffraction (XRD), mechanical testing, electrochemical and immersion test. It is shown that the molten Mg-5Sn alloy has infiltrated not only into the pores but also into the struts of the HA+β-TCP scaffold to forming a compact composite. The microstructure observation also shows that the Mg alloy contacts to the HA+β-TCP closely, and no reaction layer can be found between Mg-5Sn alloy and scaffold. The ultimate compressive strength of the composite is as high as 176MPa, which is about four fifths of the strength of the Mg-5Sn bulk alloy. The electrochemical and immersion tests indicate that the corrosion resistance of the composite is better than that of the Mg-5Sn bulk alloy. The corrosion products on the composite surface are mainly Mg(OH)2, Ca3(PO4)2 and HA. Appropriate mechanical and corrosion properties of the (HA+β-TCP)/Mg-5Sn composite indicate its possibility for new bone tissue implant materials. Copyright © 2015 Elsevier B.V. All rights reserved.

Hot pressing titanium metal matrix composites reinforced with graphene nanoplatelets through an in-situ reactive method

NASA Astrophysics Data System (ADS)

Mu, X. N.; Zhang, H. M.; Cai, H. N.; Fan, Q. B.; Wu, Y.; Fu, Z. J.; Wang, Q. X.

2017-05-01

This study proposed an in-situ reactive method that uses graphene as a reinforcement to fabricate titanium metal matrix composites (TiMMCs) through powder metallurgy processing route. The volume fraction of graphene nanoplatelets was 1.8%vol, and the pure titanium was used as a matrix. The Archimedes density, hardness, microstructure and mechanical properties of specimens were compared under different ball milling times (20 min and 2.5 h) and hot pressing temperatures (900°C, 1150°C, and 1300°C,). The ultimate tensile strength of 630 MPa, which demonstrated a 27.3% increase compared with pure Ti, was achieved under a ball milling time of 20 min. Elongation increased with increasing temperature. When the ball milling time and hot pressing temperature were increased to 2.5 h and 1300 °C, respectively, the ultimate tensile strength of the composites reached 750 MPa, showing an increase of 51.5% compared with pure Ti.

Evaluation of Fiber Reinforced Cement Using Digital Image Correlation

PubMed Central

Melenka, Garrett W.; Carey, Jason P.

2015-01-01

The effect of short fiber reinforcements on the mechanical properties of cement has been examined using a splitting tensile – digital image correlation (DIC) measurement method. Three short fiber reinforcement materials have been used in this study: fiberglass, nylon, and polypropylene. The method outlined provides a simple experimental setup that can be used to evaluate the ultimate tensile strength of brittle materials as well as measure the full field strain across the surface of the splitting tensile test cylindrical specimen. Since the DIC measurement technique is a contact free measurement this method can be used to assess sample failure. PMID:26039590

Total Longitudinal Moment Calculation and Reliability Analysis of Yacht Structures

NASA Astrophysics Data System (ADS)

Zhi, Wenzheng; Lin, Shaofen

In order to check the reliability of the yacht in FRP (Fiber Reinforce Plastic) materials, in this paper, the vertical force and the calculation method of the overall longitudinal bending moment on yacht was analyzed. Specially, this paper focuses on the impact of speed on the still water bending moment on yacht. Then considering the mechanical properties of the cap type stiffeners in composite materials, the ultimate bearing capacity of the yacht has been worked out, finally the reliability of the yacht was calculated with using response surface methodology. The result can be used in yacht design and yacht driving.

Quantum crystallography: A perspective.

PubMed

Massa, Lou; Matta, Chérif F

2018-06-30

Extraction of the complete quantum mechanics from X-ray scattering data is the ultimate goal of quantum crystallography. This article delivers a perspective for that possibility. It is desirable to have a method for the conversion of X-ray diffraction data into an electron density that reflects the antisymmetry of an N-electron wave function. A formalism for this was developed early on for the determination of a constrained idempotent one-body density matrix. The formalism ensures pure-state N-representability in the single determinant sense. Applications to crystals show that quantum mechanical density matrices of large molecules can be extracted from X-ray scattering data by implementing a fragmentation method termed the kernel energy method (KEM). It is shown how KEM can be used within the context of quantum crystallography to derive quantum mechanical properties of biological molecules (with low data-to-parameters ratio). © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

Microstructural and mechanical evolutions during the forging step of the COBAPRESS, a casting/forging process

NASA Astrophysics Data System (ADS)

Perrier, Frédéric; Desrayaud, Christophe; Bouvier, Véronique

Aluminum casting/forging processes are used to produce parts for the automotive industry. In this study, we examined the influence of the forging step on the microstructure and the mechanical properties of an A356 aluminum alloy modified with strontium. Firstly, a design of samples which allows us to test mechanically the alloy before and after forging was created. A finite element analysis with the ABAQUS software predicts a maximum of strain in the core of the specimens. Observations with the EBSD technique confirm a more intense sub-structuration of the dendrite cells in this zone. Yield strength, ultimate tensile strength, elongation and fatigue lives were then improved for the casting/forging samples compared to the only cast specimens. The closure of the porosities and the improvement of the surface quality during the forging step enhance also the fatigue resistance of the samples.

Mechanical Deformation Behavior of Sn-Ag-Cu Solders with Minor Addition of 0.05 wt.% Ni

NASA Astrophysics Data System (ADS)

Hammad, A. E.; El-Taher, A. M.

2014-11-01

The aim of the present work is to develop a comparative evaluation of the microstructural and mechanical deformation behavior of Sn-Ag-Cu (SAC) solders with the minor addition of 0.05 wt.% Ni. Test results showed that, by adding 0.05Ni element into SAC solders, generated mainly small rod-shaped (Cu,Ni)6Sn5 intermetallic compounds (IMCs) inside the β-Sn phase. Moreover, increasing the Ag content and adding Ni could result in the change of the shape and size of the IMC precipitate. Hence, a significant improvement is observed in the mechanical properties of SAC solders with increasing Ag content and Ni addition. On the other hand, the tensile results of Ni-doped SAC solders showed that both the yield stress and ultimate tensile strengths decrease with increasing temperature and with decreasing strain rate. This behavior was attributed to the competing effects of work hardening and dynamic recovery processes. The Sn-2.0Ag-0.5Cu-0.05Ni solder displayed the highest mechanical properties due to the formation of hard (Cu,Ni)6Sn5 IMCs. Based on the obtained stress exponents and activation energies, it is suggested that the dominant deformation mechanism in SAC (205)-, SAC (0505)- and SAC (0505)-0.05Ni solders is pipe diffusion, and lattice self-diffusion in SAC (205)-0.05Ni solder. In view of these results, the Sn-2.0Ag-0.5Cu-0.05Ni alloy is a more reliable solder alloy with improved properties compared with other solder alloys tested in the present work.

Structure, mechanical characteristics and in vitro degradation, cytotoxicity, genotoxicity and mutagenicity of novel biodegradable Zn-Mg alloys.

PubMed

Kubásek, J; Vojtěch, D; Jablonská, E; Pospíšilová, I; Lipov, J; Ruml, T

2016-01-01

Zn-(0-1.6)Mg (in wt.%) alloys were prepared by hot extrusion at 300 °C. The structure, mechanical properties and in vitro biocompatibility of the alloys were investigated. The hot-extruded magnesium-based WE43 alloy was used as a control. Mechanical properties were evaluated by hardness, compressive and tensile testing. The cytotoxicity, genotoxicity (comet assay) and mutagenicity (Ames test) of the alloy extracts and ZnCl2 solutions were evaluated with the use of murine fibroblasts L929 and human osteosarcoma cell line U-2 OS. The microstructure of the Zn alloys consisted of recrystallized Zn grains of 12 μm in size and fine Mg2Zn11 particles arranged parallel to the hot extrusion direction. Mechanical tests revealed that the hardness and strength increased with increasing Mg concentration. The Zn-0.8 Mg alloys showed the best combination of tensile mechanical properties (tensile yield strength of 203 MPa, ultimate tensile strength of 301 MPa and elongation of 15%). At higher Mg concentrations the plasticity of Zn-Mg alloys was deteriorated. Cytotoxicity tests with alloy extracts and ZnCl2 solutions proved the maximum safe Zn(2+) concentrations of 120 μM and 80 μM for the U-2 OS and L929 cell lines, respectively. Ames test with extracts of alloys indicated that the extracts were not mutagenic. The comet assay demonstrated that 1-day extracts of alloys were not genotoxic for U-2 OS and L929 cell lines after 1-day incubation. Copyright © 2015 Elsevier B.V. All rights reserved.

Failure and fatigue characteristics of adhesive athletic tape.

PubMed

Bragg, Richard W; Macmahon, John M; Overom, Erin K; Yerby, Scott A; Matheson, Gordon O; Carter, Dennis R; Andriacchi, Thomas P

2002-03-01

Athletic tape has been commonly reported to lose much of its structural support after 20 min of exercise. Although many studies have addressed the functional performance characteristics of athletic tape, its mechanical properties are poorly understood. This study examines the failure and fatigue properties of several commonly used athletic tapes. A Web-based survey of professional sports trainers was used to select the following three tapes for the study: Zonas (Johnson & Johnson), Leukotape (Beiersdorf), and Jaylastic (Jaybird & Mais). Using a hydraulic material testing system (MTS), eight samples of each tape were compared in three different mechanical tests: load-to-failure, fatigue testing under load control, and fatigue testing under displacement control. Differences in tape microstructure were used to interpret the results of the mechanical tests. Significant differences (P < 0.001) in failure load, elongation at failure, and stiffness were found from failure tests. Significant differences were also found (P < 0.001) in fatigue behavior under both modes of control. As a representative example, in one normalized displacement control fatigue test after 20 min of cycling, 21% (Zonas), 29% (Leukotape), and 57% (Jaylastic) of the mechanical support was lost. After cycling, all tapes loaded to failure showed increased stiffness (P < 0.001), indicating significant energy absorption during cycling. Observed differences in the tapes' microstructure were qualitatively consistent with the measured differences in their mechanical properties. In understanding the shortcomings of currently available tapes, the results of these tests can now be used as benchmarks with which to compare and develop future tape designs. Ultimately, these improved tapes should reduce ankle injuries among athletes.

Mechanical Behavior of Stainless Steel Fiber-Reinforced Composites Exposed to Accelerated Corrosion

PubMed Central

O’Brien, Caitlin; McBride, Amanda; E. Zaghi, Arash; Burke, Kelly A.; Hill, Alex

2017-01-01

Recent advancements in metal fibers have introduced a promising new type of stainless steel fiber with high stiffness, high failure strain, and a thickness < 100 μm (<0.00394 in.) that can be utilized in a steel fiber-reinforced polymer. However, stainless steel is known to be susceptible to pitting corrosion. The main goal of this study is to compare the impact of corrosion on the mechanical properties of steel fiber-reinforced composites with those of conventional types of stainless steel. By providing experimental evidences, this study may promote the application of steel fiber-reinforced composite as a viable alternative to conventional metals. Samples of steel fiber-reinforced polymer and four different types of stainless steel were subjected to 144 and 288 h of corrosion in ferric chloride solution to simulate accelerated corrosion conditions. The weight losses due to corrosion were recorded. The corroded and control samples were tested under monotonic tensile loading to measure the ultimate stresses and strains. The effect of corrosion on the mechanical properties of the different materials was evaluated. The digital image correlation (DIC) technique was used to investigate the failure mechanism of the corrosion-damaged specimens. Overall, steel fiber-reinforced composites had the greatest corrosion resistance. PMID:28773132

Thermo-mechanical behavior and structure of melt blown shape-memory polyurethane nonwovens.

PubMed

Safranski, David L; Boothby, Jennifer M; Kelly, Cambre N; Beatty, Kyle; Lakhera, Nishant; Frick, Carl P; Lin, Angela; Guldberg, Robert E; Griffis, Jack C

2016-09-01

New processing methods for shape-memory polymers allow for tailoring material properties for numerous applications. Shape-memory nonwovens have been previously electrospun, but melt blow processing has yet to be evaluated. In order to determine the process parameters affecting shape-memory behavior, this study examined the effect of air pressure and collector speed on the mechanical behavior and shape-recovery of shape-memory polyurethane nonwovens. Mechanical behavior was measured by dynamic mechanical analysis and tensile testing, and shape-recovery was measured by unconstrained and constrained recovery. Microstructure changes throughout the shape-memory cycle were also investigated by micro-computed tomography. It was found that increasing collector speed increases elastic modulus, ultimate strength and recovery stress of the nonwoven, but collector speed does not affect the failure strain or unconstrained recovery. Increasing air pressure decreases the failure strain and increases rubbery modulus and unconstrained recovery, but air pressure does not influence recovery stress. It was also found that during the shape-memory cycle, the connectivity density of the fibers upon recovery does not fully return to the initial values, accounting for the incomplete shape-recovery seen in shape-memory nonwovens. With these parameter to property relationships identified, shape-memory nonwovens can be more easily manufactured and tailored for specific applications. Copyright © 2016 Elsevier Ltd. All rights reserved.

Acoustic emission from trabecular bone during mechanical testing: the effect of osteoporosis and osteoarthritis.

PubMed

Leichter, I; Bivas, A; Margulies, J Y; Roman, I; Simkin, A

1990-01-01

This study examines the relation between the nature of acoustic emission signals emitted from cancellous bone under compression and the mechanical properties of the tissue. The examined bone specimens were taken from 12 normal, 31 osteoporotic and six osteoarthritic femoral heads. The mechanical behaviour of the osteoporotic bone specimens was found to be significantly different from that of the normal specimens both in the pre-yield and post-yield ranges. In the osteoarthritic bones only the elastic behaviour was significantly different. The rates of acoustic events before yield and beyond it were found to be significantly higher both in the osteoporotic and osteoarthritic bone specimens. The average peak amplitude of the signals was also significantly higher in the diseased bones. Stepwise regression analysis showed that a combination of the acoustic emission parameters could significantly predict some mechanical properties of the bone. The energy absorbed during compression and the ultimate compressive stress of the specimens could be estimated from the rate of pre-yield acoustic events, the average amplitude of the signals and the rate of post-yield events. However, the explanation power of the acoustic emission parameters was only moderate. The nature of acoustic emission signals was thus demonstrated to be a potential tool for assessing bone quality.

Self-Healing Proton-Exchange Membranes Composed of Nafion-Poly(vinyl alcohol) Complexes for Durable Direct Methanol Fuel Cells.

PubMed

Li, Yixuan; Liang, Liang; Liu, Changpeng; Li, Yang; Xing, Wei; Sun, Junqi

2018-04-30

Proton-exchange membranes (PEMs) that can heal mechanical damage to restore original functions are important for the fabrication of durable and reliable direct methanol fuel cells (DMFCs). The fabrication of healable PEMs that exhibit satisfactory mechanical stability, enhanced proton conductivity, and suppressed methanol permeability via hydrogen-bonding complexation between Nafion and poly(vinyl alcohol) (PVA) followed by postmodification with 4-carboxybenzaldehyde (CBA) molecules is presented. Compared with pure Nafion, the CBA/Nafion-PVA membranes exhibit enhanced mechanical properties with an ultimate tensile strength of ≈20.3 MPa and strain of ≈380%. The CBA/Nafion-PVA membrane shows a proton conductivity of 0.11 S cm -1 at 80 °C, which is 1.2-fold higher than that of a Nafion membrane. The incorporated PVA gives the CBA/Nafion-PVA membranes excellent proton conductivity and methanol resistance. The resulting CBA/Nafion-PVA membranes are capable of healing mechanical damage of several tens of micrometers in size and restoring their original proton conductivity and methanol resistance under the working conditions of DMFCs. The healing property originates from the reversibility of hydrogen-bonding interactions between Nafion and CBA-modified PVA and the high chain mobility of Nafion and CBA-modified PVA. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effects of tissue mechanical properties on susceptibility to histotripsy-induced tissue damage

NASA Astrophysics Data System (ADS)

Vlaisavljevich, Eli; Kim, Yohan; Owens, Gabe; Roberts, William; Cain, Charles; Xu, Zhen

2014-01-01

Histotripsy is a non-invasive tissue ablation method capable of fractionating tissue by controlling acoustic cavitation. To determine the fractionation susceptibility of various tissues, we investigated histotripsy-induced damage on tissue phantoms and ex vivo tissues with different mechanical strengths. A histotripsy bubble cloud was formed at tissue phantom surfaces using 5-cycle long ultrasound pulses with peak negative pressure of 18 MPa and PRFs of 10, 100, and 1000 Hz. Results showed significantly smaller lesions were generated in tissue phantoms of higher mechanical strength. Histotripsy was also applied to 43 different ex vivo porcine tissues with a wide range of mechanical properties. Gross morphology demonstrated stronger tissues with higher ultimate stress, higher density, and lower water content were more resistant to histotripsy damage in comparison to weaker tissues. Based on these results, a self-limiting vessel-sparing treatment strategy was developed in an attempt to preserve major vessels while fractionating the surrounding target tissue. This strategy was tested in porcine liver in vivo. After treatment, major hepatic blood vessels and bile ducts remained intact within a completely fractionated liver volume. These results identify varying susceptibilities of tissues to histotripsy therapy and provide a rational basis to optimize histotripsy parameters for treatment of specific tissues.

Comparison of completely knotless and hybrid double-row fixation systems: a biomechanical study.

PubMed

Chu, Thomas; McDonald, Erik; Tufaga, Michael; Kandemir, Utku; Buckley, Jenni; Ma, C Benjamin

2011-04-01

The purpose of this study was to compare the biomechanical performance of a completely knotless double-row repair system (SutureCross Knotless Anatomic Fixation System; KFx Medical, Carlsbad, CA) with 2 commonly used hybrid double-row repair (medial knot-tying, lateral knotless) systems (Bio-Corkscrew/PushLock [Arthrex, Naples, FL] and Spiralok/Versalok [DePuy Mitek, Raynham, MA]). Fourteen pairs of fresh-frozen cadaveric shoulders were harvested, the supraspinatus tendons were isolated, and full-thickness supraspinatus tears were created. One of each pair was repaired with the completely knotless system, and the contralateral side was repaired with either of the hybrid systems. The repairs were then subjected to cyclic loading followed by load to failure. Conditioning elongation, peak-to-peak elongation, ultimate load, and mechanism of failure were recorded and compared by use of paired t tests. Seven additional shoulders were tested to determine the effect of refrigeration storage on the completely knotless system by use of the same mechanical testing protocol. For the completely knotless repair group, 11 of 14 paired specimens failed during the cyclic loading period. Only 1 of 14 hybrid repair systems had failures during cyclic loading, and both hybrid repair systems had statistically lower conditioning elongation than the completely knotless repair group. The mean ultimate load of the SutureCross group was 166 ± 87 N, which was significantly lower than that in the Corkscrew/PushLock (310 ± 82 N) and Spiralok/Versalok (337 ± 44 N) groups. There was an effect of refrigeration storage on the peak-to-peak elongation and stiffness of the SutureCross group; however, there was no difference in ultimate tensile load or conditioning elongation. The completely knotless repair system has lower time-zero biomechanical properties than the other 2 hybrid systems. The SutureCross system has lower time-zero biomechanical properties when compared with other hybrid repair systems. Clinical outcome studies are needed to determine the significance. Copyright © 2011 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.

Microstructure Evolution during Dissimilar Friction Stir Welding of AA7003-T4 and AA6060-T4.

PubMed

Dong, Jialiang; Zhang, Datong; Zhang, Weiwen; Zhang, Wen; Qiu, Cheng

2018-02-27

In this work, the dissimilar joint of AA7003-T4 and 6060-T4 alloy has been produced by friction stir welding (FSW). The microstructure was examined by optical microscope (OM), electron back scattered diffraction (EBSD), transmission electron microscopy (TEM), and the mechanical properties of the joint were investigated. It is demonstrated that sound dissimilar joint can be produced through FSW. In the nugget; precipitations dissolve into the matrix and η' reprecipitate subsequently; and the elongated aluminum grains are replaced by fine and equiaxed grains due to dynamic recrystallization (DRX). In the heat affected zone (HAZ), coarse β' and η precipitates are formed and the aluminum grains are coarser as compared to the base materials. In the thermo-mechanical affected zone (TMAZ), equiaxed and elongated grains coexist due to incomplete DRX. The ultimate tensile strength of the dissimilar joint is 159.2 MPa and its elongation is 10.4%. The weak area exists in the HAZ of 6060 alloy, which is placed in the retreating side during FSW. The correlations between the microstucture and mechanical properties of the dissimilar joint are discussed.

Microstructure Evolution during Dissimilar Friction Stir Welding of AA7003-T4 and AA6060-T4

PubMed Central

Dong, Jialiang; Zhang, Datong; Zhang, Weiwen; Zhang, Wen; Qiu, Cheng

2018-01-01

In this work, the dissimilar joint of AA7003-T4 and 6060-T4 alloy has been produced by friction stir welding (FSW). The microstructure was examined by optical microscope (OM), electron back scattered diffraction (EBSD), transmission electron microscopy (TEM), and the mechanical properties of the joint were investigated. It is demonstrated that sound dissimilar joint can be produced through FSW. In the nugget; precipitations dissolve into the matrix and η′ reprecipitate subsequently; and the elongated aluminum grains are replaced by fine and equiaxed grains due to dynamic recrystallization (DRX). In the heat affected zone (HAZ), coarse β′ and η precipitates are formed and the aluminum grains are coarser as compared to the base materials. In the thermo-mechanical affected zone (TMAZ), equiaxed and elongated grains coexist due to incomplete DRX. The ultimate tensile strength of the dissimilar joint is 159.2 MPa and its elongation is 10.4%. The weak area exists in the HAZ of 6060 alloy, which is placed in the retreating side during FSW. The correlations between the microstucture and mechanical properties of the dissimilar joint are discussed. PMID:29495463

Pectin-chitosan-PVA nanofibrous scaffold made by electrospinning and its potential use as a skin tissue scaffold.

PubMed

Lin, Hsin-Yi; Chen, Hsin-Hung; Chang, Shih-Hsin; Ni, Tsung-Sheng

2013-01-01

Scaffolds made of chitosan nanofibers are often too mechanically weak for their application and often their manufacturing processes involve the use of harmful and flammable organic solvents. In the attempt to improve the mechanical properties of nanofibrous scaffolds made of chitosan without the use of harmful chemicals, pectin, an anionic polymer was blended with chitosan, a cationic polymer, to form a polyelectrolyte complex and electrospun into nanofibers for the first time. The electrospun chitosan-pectin scaffolds, when compared to electrospun chitosan scaffolds, had a 58% larger diameter, a 21% higher Young's modulus, a 162% larger strain at break, and a 104% higher ultimate tensile strength. Compared to the chitosan scaffolds, the chitosan-pectin scaffolds' swelling ratios decreased by 55% after 60 min in a saline solution and more quickly released the preloaded tetracycline HCl. The L929 fibroblast cells proliferated slightly slower on the chitosan-pectin scaffolds than on the chitosan scaffolds. Nonetheless, cells on both materials deposited similar levels of extracellular type I collagen on a per DNA basis. In conclusion, a novel chitosan-pectin nanofibrous scaffold with superior mechanical properties than a chitosan nanofibrous scaffold was successfully made without the use of harmful solvents.

Microstructure and Mechanical Properties of Ultrafine-Grained Al-6061 Prepared Using Intermittent Ultrasonic-Assisted Equal-Channel Angular Pressing

NASA Astrophysics Data System (ADS)

Lu, Jianxun; Wu, Xiaoyu; Wu, Zhaozhi; Liu, Zhiyuan; Guo, Dengji; Lou, Yan; Ruan, Shuangchen

2017-10-01

Equal-channel angular pressing (ECAP) is an efficient technique to achieve grain refinement in a wide range of materials. However, the extrusion process requires an excessive extrusion force, the microstructure of ECAPed specimens scatters heterogeneously because of considerable fragmentation of the structure and strain heterogeneity, and the resultant ultrafine grains exhibit poor thermal stability. The intermittent ultrasonic-assisted ECAP (IU-ECAP) approach was proposed to address these issues. In this work, ECAP and IU-ECAP were applied to produce ultrafine-grained Al-6061 alloys, and the differences in their mechanical properties, microstructural characteristics, and thermal stability were investigated. Mechanical testing demonstrated that the necessary extrusion force for IU-ECAP was significantly reduced; even more, the microhardness and ultimate tensile strength were strengthened. In addition, the IU-ECAPed Al alloy exhibited a smaller grain size with a more homogeneous microstructure. X-ray diffraction analysis indicated that the intensities of the textures were weakened using IU-ECAP, and a more homogeneous microstructure and larger dislocation densities were obtained. Investigation of the thermal stability revealed that the ultrafine-grained materials produced using IU-ECAP recrystallized at higher temperature or after longer time; the materials thus exhibited improved thermal stability.

Does artificial aging affect mechanical properties of CAD/CAM composite materials.

PubMed

Egilmez, Ferhan; Ergun, Gulfem; Cekic-Nagas, Isil; Vallittu, Pekka K; Lassila, Lippo V J

2018-01-01

The purpose of this study was to determine the flexural strength and Weibull characteristics of different CAD/CAM materials after different in vitro aging conditions. The specimens were randomly assigned to one of the six in vitro aging conditions: (1) water storage (37°C, 3 weeks), (2) boiling water (24h), (3) hydrochloric acid exposure (pH: 1.2, 24h), (4) autoclave treatment (134°C, 200kPa, 12h), (5) thermal cycling (5000 times, 5-55°C), (6) cyclic loading (100N, 50,000 cycles). No treatment was applied to the specimens in control group. Three-point bending test was used for the calculation of flexural strength. The reliability of the strength was assessed by Weibull distribution. Surface roughness and topography was examined by coherence scanning interferometry. Evaluated parameters were compared using the Kruskall-Wallis or Mann-Whitney U test. Water storage, autoclave treatment and thermal cycling significantly decreased the flexural strength of all materials (p<0.05), whereas HCl exposure or cyclic loading did not affect the properties (p>0.05). Weibull moduli of Cerasmart™ and Lava™ Ultimate were similar with control. Vita Enamic ® exhibited similar Weibull moduli in all aging groups except the HCl treated group (p>0.05). R a values of Cerasmart™ and Lava™ Ultimate were in the range of 0.053-0.088μm in the aged groups. However R a results of Vita Enamic ® were larger than 0.2μm. Flexural strength of newly developed restorative CAD/CAM materials was significantly decreased by artificial aging. Cyclic loading or HCl exposure does not affect to the flexural strength and structural reliability of Cerasmart™ and Lava™ Ultimate. Copyright © 2017 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.

Scanning-electron-microscopy observations and mechanical characteristics of ion-beam-sputtered surgical implant alloys

NASA Technical Reports Server (NTRS)

Weigand, A. J.; Meyer, M. L.; Ling, J. S.

1977-01-01

An electron bombardment ion thruster was used as an ion source to sputter the surfaces of orthopedic prosthetic metals. Scanning electron microscopy photomicrographs were made of each ion beam textured surface. The effect of ion texturing an implant surface on its bond to bone cement was investigated. A Co-Cr-W alloy and surgical stainless steel were used as representative hard tissue implant materials to determine effects of ion texturing on bulk mechanical properties. Work was done to determine the effect of substrate temperature on the development of an ion textured surface microstructure. Results indicate that the ultimate strength of the bulk materials is unchanged by ion texturing and that the microstructure will develop more rapidly if the substrate is heated prior to ion texturing.

A strong and stretchable self-healing film with self-activated pressure sensitivity for potential artificial skin applications

PubMed Central

Hou, Chengyi; Huang, Tao; Wang, Hongzhi; Yu, Hao; Zhang, Qinghong; Li, Yaogang

2013-01-01

Artificial skin, which mimics the functions of natural skin, will be very important in the future for robots used by humans in daily life. However, combining skin's pressure sensitivity and mechanical self-healing properties in a man-made material remains a challenging task. Here, we show that graphene and polymers can be integrated into a thin film which mimics both the mechanical self-healing and pressure sensitivity behavior of natural skin without any external power supply. Its ultimate strain and tensile strength are even two and ten times larger than the corresponding values of human skin, respectively. It also demonstrates highly stable sensitivity to a very light touch (0.02 kPa), even in bending or stretching states. PMID:24190511

High Temperature Mechanical Characterization and Analysis of Al2O3 /Al2O3 Composition

NASA Technical Reports Server (NTRS)

Gyekenyesi, John Z.; Jaskowiak, Martha H.

1999-01-01

Sixteen ply unidirectional zirconia coated single crystal Al2O3 fiber reinforced polycrystalline Al2O3 was tested in uniaxial tension at temperatures to 1400 C in air. Fiber volume fractions ranged from 26 to 31%. The matrix has primarily open porosity of approximately 40%. Theories for predicting the Young's modulus, first matrix cracking stress, and ultimate strength were applied and evaluated for suitability in predicting the mechanical behavior of Al2O3/Al2O3 composites. The composite exhibited pseudo tough behavior (increased area under the stress/strain curve relative to monolithic alumina) from 22 to 1400 C. The rule-of-mixtures provides a good estimate of the Young's modulus of the composite using the constituent properties from room temperature to approximately 1200 C for short term static tensile tests in air. The ACK theory provides the best approximation of the first matrix cracking stress while accounting for residual stresses at room temperature. Difficulties in determining the fiber/matrix interfacial shear stress at high temperatures prevented the accurate prediction of the first matrix cracking stress above room temperature. The theory of Cao and Thouless, based on Weibull statistics, gave the best prediction for the composite ultimate tensile strength.

Influence of biocorrosion on microstructure and mechanical properties of deformed Mg-Y-Er-Zn biomaterial containing 18R-LPSO phase.

PubMed

Leng, Zhe; Zhang, Jinghuai; Yin, Tingting; Zhang, Li; Guo, Xuying; Peng, Qiuming; Zhang, Milin; Wu, Ruizhi

2013-12-01

The microstructure and mechanical properties of as-extruded Mg-8Y-1Er-2Zn (wt%) alloy containing long period stacking ordered (LPSO) phase are comparatively investigated before and after corrosion in a simulated body fluid (SBF) at 37°C. The as-extruded alloy consists of a long strip-like 18R-LPSO phase and some fine lamellae grains formed by primary recrystallization during the extrusion process. The hydrogen evolution volume per day fluctuates between 0.21 and 0.32ml/cm(2) in the immersion test for 240h, and the corresponding corrosion rate is calculated as 0.568mm/y. The corrosion product is determined as Mg(OH)2, whilst a Ca(H2PO4)2 compound is also observed on the surface of the samples. The corrosion site preferentially occurs at the interface between LPSO phase and Mg matrix. Before immersing, the tensile yield strength (TYS), ultimate tensile strength (UTS) and elongation of the alloy are 275MPa, 359MPa, and 19%, respectively. More attractively, these mechanical properties can be maintained even after immersing in SBF for 240h (TYS, UTS and elongation are 216MPa, 286MPa and 6.8%, respectively) because of the existence of high anti-corrosion LPSO phase. © 2013 Elsevier Ltd. All rights reserved.

Effect of Zn Concentration on the Microstructure and Mechanical Properties of Al-Mg-Si-Zn Alloys Processed by Gravity Die Casting

NASA Astrophysics Data System (ADS)

Li, Longfei; Ji, Shouxun; Zhu, Qiang; Wang, Yun; Dong, Xixi; Yang, Wenchao; Midson, Stephen; Kang, Yonglin

2018-06-01

The microstructure and mechanical properties of Al-8.1Mg-2.6Si-(0.08 to 4.62)Zn alloys (in wt pct) have been investigated by the permanent mold casting process. X-ray diffraction analysis shows that the τ-Mg32(Al, Zn)49 phase forms when the Zn content is 1.01 wt pct. With higher Zn contents of 2.37 and 3.59 wt pct, the η-MgZn2 and τ-Mg32(Al, Zn)49 phases precipitate in the microstructure, and the η-MgZn2 phase forms when the Zn content is 4.62 wt pct. Metallurgical analysis shows that the η-MgZn2 and τ-Mg32(Al, Zn)49 phases strengthen the Al-8.1Mg-2.6Si-(0.08 to 4.62)Zn alloys. After solutionizing at 510 °C for 180 minutes and aging at 180 °C for 90 minutes, the η'-MgZn2 phase precipitates in the α-Al matrix, which significantly enhances the mechanical properties. Addition of 3.59 wt pct Zn to the Al-8.1Mg-2.6Si alloy with heat treatment increases the yield strength from 96 to 280 MPa, increases the ultimate tensile strength from 267 to 310 MPa, and decreases the elongation from 9.97 to 1.74 pct.

Effect of the incorporation of chitosan on the physico-chemical, mechanical properties and biological activity on a mixture of polycaprolactone and polyurethanes obtained from castor oil.

PubMed

Arévalo, Fabian; Uscategui, Yomaira L; Diaz, Luis; Cobo, Martha; Valero, Manuel F

2016-11-01

In the present study, polyurethane materials were obtained from castor oil, polycaprolactone and isophorone diisocyanate by incorporating different concentrations of chitosan (0.5, 1.0 and 2.0% w/w) as an additive to improve the mechanical properties and the biological activity of polyurethanes. The polyurethanes were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, stress/strain fracture tests and swelling analysis, and the hydrophilic character of the surface was determined by contact angle trials. The objectives of the study were to evaluate the effect of the incorporation of chitosan on the changes of the physico-chemical and mechanical properties and the in vitro biological activity of the polyurethanes. It was found that the incorporation of chitosan enhances the ultimate tensile strength of the polyurethanes and does not affect the strain at fracture in polyurethanes with 5% w/w of polycaprolactone and concentrations of chitosan ranging from 0 to 2% w/w. In addition, PCL5-Q-PU formulations and their degradation products did not affect cell viability of L929 mouse fibroblast and 3T3, respectively. Polyurethane formulations showed antibacterial activities against Staphylococcus aureus and Escherichia coli bacteria. The results of this study have highlighted the potential biomedical application of this polyurethanes related to soft and cardiovascular tissues. © The Author(s) 2016.

Metallurgical and mechanical properties of laser welded high strength low alloy steel

PubMed Central

Oyyaravelu, Ramachandran; Kuppan, Palaniyandi; Arivazhagan, Natarajan

2016-01-01

The study aimed at investigating the microstructure and mechanical properties of Neodymium-Doped Yttrium Aluminum Garnet (Nd:YAG) laser welded high strength low alloy (HSLA) SA516 grade 70 boiler steel. The weld joint for a 4 mm thick plate was successfully produced using minimum laser power of 2 kW by employing a single pass without any weld preheat treatment. The micrographs revealed the presence of martensite phase in the weld fusion zone which could be due to faster cooling rate of the laser weldment. A good correlation was found between the microstructural features of the weld joints and their mechanical properties. The highest hardness was found to be in the fusion zone of cap region due to formation of martensite and also enrichment of carbon. The hardness results also showed a narrow soft zone at the heat affected zone (HAZ) adjacent to the weld interface, which has no effect on the weld tensile strength. The yield strength and ultimate tensile strength of the welded joints were 338 MPa and 549 MPa, respectively, which were higher than the candidate metal. These tensile results suggested that the laser welding process had improved the weld strength even without any weld preheat treatment and also the fractography of the tensile fractured samples showed the ductile mode of failure. PMID:27222751

Multiaxial mechanical response and constitutive modeling of esophageal tissues: Impact on esophageal tissue engineering.

PubMed

Sommer, Gerhard; Schriefl, Andreas; Zeindlinger, Georg; Katzensteiner, Andreas; Ainödhofer, Herwig; Saxena, Amulya; Holzapfel, Gerhard A

2013-12-01

Congenital defects of the esophagus are relatively frequent, with 1 out of 2500 babies suffering from such a defect. A new method of treatment by implanting tissue engineered esophagi into newborns is currently being developed and tested using ovine esophagi. For the reconstruction of the biological function of native tissues with engineered esophagi, their cellular structure as well as their mechanical properties must be considered. Since very limited mechanical and structural data for the esophagus are available, the aim of this study was to investigate the multiaxial mechanical behavior of the ovine esophagus and the underlying microstructure. Therefore, uniaxial tensile, biaxial tensile and extension-inflation tests on esophagi were performed. The underlying microstructure was examined in stained histological sections through standard optical microscopy techniques. Moreover, the uniaxial ultimate tensile strength and residual deformations of the tissue were determined. Both the mucosa-submucosa and the muscle layers showed nonlinear and anisotropic mechanical behavior during uniaxial, biaxial and inflation testing. Cyclical inflation of the intact esophageal tube caused marked softening of the passive esophagi in the circumferential direction. The rupture strength of the mucosa-submucosa layer was much higher than that of the muscle layer. Overall, the ovine esophagus showed a heterogeneous and anisotropic behavior with different mechanical properties for the individual layers. The intact and layer-specific multiaxial properties were characterized using a well-known three-dimensional microstructurally based strain-energy function. This novel and complete set of data serves the basis for a better understanding of tissue remodeling in diseased esophagi and can be used to perform computer simulations of surgical interventions or medical-device applications. Copyright © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Multi-scale mechanical response of freeze-dried collagen scaffolds for tissue engineering applications.

PubMed

Offeddu, Giovanni S; Ashworth, Jennifer C; Cameron, Ruth E; Oyen, Michelle L

2015-02-01

Tissue engineering has grown in the past two decades as a promising solution to unresolved clinical problems such as osteoarthritis. The mechanical response of tissue engineering scaffolds is one of the factors determining their use in applications such as cartilage and bone repair. The relationship between the structural and intrinsic mechanical properties of the scaffolds was the object of this study, with the ultimate aim of understanding the stiffness of the substrate that adhered cells experience, and its link to the bulk mechanical properties. Freeze-dried type I collagen porous scaffolds made with varying slurry concentrations and pore sizes were tested in a viscoelastic framework by macroindentation. Membranes made up of stacks of pore walls were indented using colloidal probe atomic force microscopy. It was found that the bulk scaffold mechanical response varied with collagen concentration in the slurry consistent with previous studies on these materials. Hydration of the scaffolds resulted in a more compliant response, yet lesser viscoelastic relaxation. Indentation of the membranes suggested that the material making up the pore walls remains unchanged between conditions, so that the stiffness of the scaffolds at the scale of seeded cells is unchanged; rather, it is suggested that thicker pore walls or more of these result in the increased moduli for the greater slurry concentration conditions. Copyright © 2014 The Authors. Published by Elsevier Ltd.. All rights reserved.

Comparative study of pulsed Nd:YAG laser welding of AISI 304 and AISI 316 stainless steels

NASA Astrophysics Data System (ADS)

Kumar, Nikhil; Mukherjee, Manidipto; Bandyopadhyay, Asish

2017-02-01

Laser welding is a potentially useful technique for joining two pieces of similar or dissimilar materials with high precision. In the present work, comparative studies on laser welding of similar metal of AISI 304SS and AISI 316SS have been conducted forming butt joints. A robotic control 600 W pulsed Nd:YAG laser source has been used for welding purpose. The effects of laser power, scanning speed and pulse width on the ultimate tensile strength and weld width have been investigated using the empirical models developed by RSM. The results of ANOVA indicate that the developed models predict the responses adequately within the limits of input parameters. 3-D response surface and contour plots have been developed to find out the combined effects of input parameters on responses. Furthermore, microstructural analysis as well as hardness and tensile behavior of the selected weld of 304SS and 316SS have been carried out to understand the metallurgical and mechanical behavior of the weld. The selection criteria are based on the maximum and minimum strength achieved by the respective weld. It has been observed that the current pulsation, base metal composition and variation in heat input have significant influence on controlling the microstructural constituents (i.e. phase fraction, grain size etc.). The result suggests that the low energy input pulsation generally produce fine grain structure and improved mechanical properties than the high energy input pulsation irrespective of base material composition. However, among the base materials, 304SS depict better microstructural and mechanical properties than the 316SS for a given parametric condition. Finally, desirability function analysis has been applied for multi-objective optimization for maximization of ultimate tensile strength and minimization of weld width simultaneously. Confirmatory tests have been conducted at optimum parametric conditions to validate the optimization techniques.

Mapping of compositional properties of coal using isometric log-ratio transformation and sequential Gaussian simulation - A comparative study for spatial ultimate analyses data.

PubMed

Karacan, C Özgen; Olea, Ricardo A

2018-03-01

Chemical properties of coal largely determine coal handling, processing, beneficiation methods, and design of coal-fired power plants. Furthermore, these properties impact coal strength, coal blending during mining, as well as coal's gas content, which is important for mining safety. In order for these processes and quantitative predictions to be successful, safer, and economically feasible, it is important to determine and map chemical properties of coals accurately in order to infer these properties prior to mining. Ultimate analysis quantifies principal chemical elements in coal. These elements are C, H, N, S, O, and, depending on the basis, ash, and/or moisture. The basis for the data is determined by the condition of the sample at the time of analysis, with an "as-received" basis being the closest to sampling conditions and thus to the in-situ conditions of the coal. The parts determined or calculated as the result of ultimate analyses are compositions, reported in weight percent, and pose the challenges of statistical analyses of compositional data. The treatment of parts using proper compositional methods may be even more important in mapping them, as most mapping methods carry uncertainty due to partial sampling as well. In this work, we map the ultimate analyses parts of the Springfield coal from an Indiana section of the Illinois basin, USA, using sequential Gaussian simulation of isometric log-ratio transformed compositions. We compare the results with those of direct simulations of compositional parts. We also compare the implications of these approaches in calculating other properties using correlations to identify the differences and consequences. Although the study here is for coal, the methods described in the paper are applicable to any situation involving compositional data and its mapping.

Combining flagelliform and dragline spider silk motifs to produce tunable synthetic biopolymer fibers.

PubMed

Teulé, Florence; Addison, Bennett; Cooper, Alyssa R; Ayon, Joel; Henning, Robert W; Benmore, Chris J; Holland, Gregory P; Yarger, Jeffery L; Lewis, Randolph V

2012-06-01

The two Flag/MaSp 2 silk proteins produced recombinantly were based on the basic consensus repeat of the dragline silk spidroin 2 protein (MaSp 2) from the Nephila clavipes orb weaving spider. However, the proline-containing pentapeptides juxtaposed to the polyalanine segments resembled those found in the flagelliform silk protein (Flag) composing the web spiral: (GPGGX(1) GPGGX(2))(2) with X(1) /X(2) = A/A or Y/S. Fibers were formed from protein films in aqueous solutions or extruded from resolubilized protein dopes in organic conditions when the Flag motif was (GPGGX(1) GPGGX(2))(2) with X(1) /X(2) = Y/S or A/A, respectively. Post-fiber processing involved similar drawing ratios (2-2.5×) before or after water-treatment. Structural (ssNMR and XRD) and morphological (SEM) changes in the fibers were compared to the mechanical properties of the fibers at each step. Nuclear magnetic resonance indicated that the fraction of β-sheet nanocrystals in the polyalanine regions formed upon extrusion, increased during stretching, and was maximized after water-treatment. X-ray diffraction showed that nanocrystallite orientation parallel to the fiber axis increased the ultimate strength and initial stiffness of the fibers. Water furthered nanocrystal orientation and three-dimensional growth while plasticizing the amorphous regions, thus producing tougher fibers due to increased extensibility. These fibers were highly hygroscopic and had similar internal network organization, thus similar range of mechanical properties that depended on their diameters. The overall structure of the consensus repeat of the silk-like protein dictated the mechanical properties of the fibers while protein molecular weight limited these same properties. Subtle structural motif re-design impacted protein self-assembly mechanisms and requirements for fiber formation. Copyright © 2011 Wiley Periodicals, Inc.

Combining flagelliform and dragline spider silk motifs to produce tunable synthetic biopolymer fibers

PubMed Central

Teulé, Florence; Addison, Bennett; Cooper, Alyssa R.; Ayon, Joel; Henning, Robert W.; Benmore, Chris J.; Holland, Gregory P.; Yarger, Jeffery L.; Lewis, Randolph V.

2012-01-01

The two Flag/MaSp 2 silk proteins produced recombinantly were based on the basic consensus repeat of the dragline silk spidroin 2 protein (MaSp 2) from the Nephila clavipes orb weaving spider. However, the proline-containing pentaptides juxtaposed to the polyalanine segments resembled those found in the flagelliform silk protein (Flag) composing the web spiral: (GPGGX1 GPGGX2)2 with X1/X2=A/A or Y/S. Fibers were formed from protein films in aqueous solutions or extruded from resolubilized protein dopes in organic conditions when the Flag motif was (GPGGX1 GPGGX2)2 with X1/X2 = Y/S or A/A, respectively. Post fiber processing involved similar drawing ratios (2–2.5×) before or after water-treatment. Structural (ssNMR and XRD) and morphological (SEM) changes in the fibers were compared to the mechanical properties of the fibers at each step. NMR indicated that the fraction of β-sheet nanocrystals in the polyalanine regions formed upon extrusion, increased during stretching, and was maximized after water-treatment. XRD showed that nanocrystallite orientation parallel to the fiber axis increased the ultimate strength and initial stiffness of the fibers. Water furthered nanocrystal orientation and three-dimensional growth while plasticizing the amorphous regions, thus producing tougher fibers due to increased extensibility. These fibers were highly hygroscopic and had similar internal network organization, thus similar range of mechanical properties that depended on their diameters. The overall structure of the consensus repeat of the silk-like protein dictated the mechanical properties of the fibers while protein molecular weight limited these same properties. Subtle structural motif redesign impacted protein self-assembly mechanisms and requirements for fiber formation. PMID:22012252

Study on mechanical properties and damage behaviors of Kevlar fiber reinforced epoxy composites by digital image correlation technique under optical microscope

NASA Astrophysics Data System (ADS)

Gao, Xiang; Shao, Wenquan; Ji, Hongwei

2010-10-01

Kevlar fiber-reinforced epoxy (KFRE) composites are widely used in the fields of aerospace, weapon, shipping, and civil industry, due to their outstanding capabilities. In this paper, mechanical properties and damage behaviors of KFRE laminate (02/902) were tested and studied under tension condition. To precisely measure the tensile mechanical properties of the material and investigate its micro-scale damage evolution, a micro-image measuring system with in-situ tensile device was designed. The measuring system, by which the in-situ tensile test can be carried out and surface morphology evolution of the tensile specimen can be visually monitored and recorded during the process of loading, includes an ultra-long working distance zoom microscope and a in-situ tensile loading device. In this study, a digital image correlation method (DICM) was used to calculate the deformation of the tensile specimen under different load levels according to the temporal series images captured by an optical microscope and CCD camera. Then, the elastic modulus and Poisson's ratio of the KFRE was obtained accordingly. The damage progresses of the KFRE laminates were analyzed. Experimental results indicated that: (1) the KFRE laminate (02/902) is almost elastic, its failure mode is brittle tensile fracture.(2) Mechanical properties parameters of the material are as follows: elastic modulus is 14- 16GPa, and tensile ultimate stress is 450-480 Mpa respectively. (3) The damage evolution of the material is that cracks appear in epoxy matrix firstly, then, with the increasing of the tensile loading, matrix cracks add up and extend along a 45° angle direction with tensile load. Furthermore, decohesion between matrix and fibers as well as delamination occurs. Eventually, fibers break and the material is damaged.

In vivo degradation of polyethylene liners after gamma sterilization in air.

PubMed

Kurtz, Steven M; Rimnac, Clare M; Hozack, William J; Turner, Joseph; Marcolongo, Michele; Goldberg, Victor M; Kraay, Matthew J; Edidin, Avram A

2005-04-01

Ultra-high molecular weight polyethylene degrades during storage in air following gamma sterilization, but the extent of in vivo degradation remains unclear. The purpose of this study was to quantify the extent to which the mechanical properties and oxidation of conventional polyethylene acetabular liners treated with gamma sterilization in air change in vivo. Fourteen modular cementless acetabular liners were revised at an average of 10.3 years (range, 5.9 to 13.5 years) after implantation. All liners, which had been machined from GUR 415 resin, had been gamma-sterilized in air; the average shelf life was 0.3 year (range, 0.0 to 0.8 year). After removal, the components were expeditiously frozen to minimize ex vivo changes to the polyethylene prior to characterization. The average duration between freezing and testing was 0.6 year. Mechanical properties and oxidation were measured with use of the small-punch test and Fourier transform infrared spectroscopy, respectively, in the loaded and unloaded regions of the liners. There was substantial regional variation in the mechanical properties and oxidation of the retrieved liners. The ultimate load was observed to vary by >90% near the surface. On the average, the rim and the unloaded bearing showed evidence of severe oxidation near the surface after long-term in vivo aging, but these trends were not typically observed on the loaded bearing surface or near the backside of the liners. The mechanical properties of polyethylene that has been gamma-sterilized in air may decrease substantially in vivo, depending on the location in the liner. The most severe oxidation was observed at the rim, suggesting that the femoral head inhibits access of oxygen-containing body fluids to the bearing surface. This is perhaps why in vivo oxidation has not been associated with clinical performance to date.

Impact of parity on ewe vaginal mechanical properties relative to the nonhuman primate and rodent

PubMed Central

Knight, Katrina M.; Moalli, Pamela A.; Nolfi, Alexis; Palcsey, Stacy; Barone, William R.

2016-01-01

Introduction and hypothesis Parity is the leading risk factor for the development of pelvic organ prolapse. To assess the impact of pregnancy and delivery on vaginal tissue, researchers commonly use nonhuman primate (NHP) and rodent models. The purpose of this study was to evaluate the ewe as an alternative model by investigating the impact of parity on the ewe vaginal mechanical properties and collagen structure. Methods Mechanical properties of 15 nulliparous and parous ewe vaginas were determined via uniaxial tensile tests. Collagen content was determined by hydroxyproline assay and collagen fiber thickness was analyzed using picrosirius red staining. Outcome measures were compared using Independent samples t or Mann–Whitney U tests. ANOVA (Gabriel’s pairwise post-hoc test) or the Welch Alternative for the F-ratio (Games Howell post-hoc test) was used to compare data with previously published NHP and rodent data. Results Vaginal tissue from the nulliparous ewe had a higher tangent modulus and tensile strength compared with the parous ewe (p < 0.025). The parous ewe vagina elongated 42 % more than the nulliparous ewe vagina (p = 0.015). No significant differences were observed in collagen structure among ewe vaginas. The tangent modulus of the nulliparous ewe vagina was not different from that of the NHP or rodent (p = 0.290). Additionally, the tangent moduli of the parous ewe and NHP vaginas did not differ (p = 0.773). Conclusions Parity has a negative impact on the mechanical properties of the ewe vagina, as also observed in the NHP. The ewe may serve as an alternative model for studying parity and ultimately prolapse development. PMID:26872644

Comparative study on the mechanical and microstructural characterisation of AA 7075 nano and hybrid nanocomposites produced by stir and squeeze casting.

PubMed

Kannan, C; Ramanujam, R

2017-07-01

In this research work, a comparative evaluation on the mechanical and microstructural characteristics of aluminium based single and hybrid reinforced nanocomposites was carried out. The manufacture of a single reinforced nanocomposite was conducted with the distribution of 2 wt.% nano alumina particles (avg. particle size 30-50 nm) in the molten aluminium alloy of grade AA 7075; while the hybrid reinforced nanocomposites were produced with of 4 wt.% silicon carbide (avg. particle size 5-10 µm) and 2 wt.%, 4 wt.% nano alumina particles. Three numbers of single reinforced nanocomposites were manufactured through stir casting with reinforcements preheated to different temperatures viz. 400 °C, 500 °C, and 600 °C. The stir cast procedure was extended to fabricate two hybrid reinforced nanocomposites with reinforcements preheated to 500 °C prior to their inclusion. A single reinforced nanocomposite was also developed by squeeze casting with a pressure of 101 MPa. Mechanical and physical properties such as density, hardness, ultimate tensile strength, and impact strength were evaluated on all the developed composites. The microstructural observation was carried out using optical and scanning electron microscopy. On comparison with base alloy, an improvement of 63.7% and 81.1% in brinell hardness was observed for single and hybrid reinforced nanocomposites respectively. About 16% higher ultimate tensile strength was noticed with the squeeze cast single reinforced nanocomposite over the stir cast.

Study on Microstructure and Mechanical Properties of Al-Li Based Alloys Processed by Extrusion.

PubMed

Kim, Yong-Ho; Yoo, Hyo-Sang; Jung, Chang-Gi; Son, Hyeon-Taek

2018-03-01

Aluminum and its alloys, due to their low density, high specific strength and high corrosion resistance amongst various structural materials, are used in a wide range of industrial applications for different aqueous solutions. In the present study, we studied effects of Ce addition on microstructure and mechanical properties of Al-2Li-1Cu-0.8Mg-0.1Zr alloys. The melt was held at 780 °C for 20 min and poured into a mold. And as-cast Al alloys were hot-extruded into a plate that was 4 mm in thickness with a reduction ratio of 14:1. The extruded plates were held at 540 °C for 4 hr in water quenching to solution treatment them. As-extruded Al-2Li-1Cu-0.8Mg-0.1Zr-xCe (x = 0.3, 0.6, 0.9 and 1.2 wt.%) alloys are composed of Al, AlLi, AlCuLi and Al11Ce3 phases. By increasing the Ce content from 0 to 1.2 wt.%, the Al11Ce3 phase is increased, after solution treatment the AlLi and AlCuLi phases are decreased. With increasing Ce addition from 0 to 1.2 wt.%, the average grain size of the as-extruded Al alloys were decreased slightly from 100.7, 113.74, 84.3, 74.7 and 61.7 μm and ultimate tensile strength was decreased slightly from 267.59, 264.92, 237.40, 220.93 and 207.83 MPa at room temperature. After solution treatment, ultimate tensile strength was measured with 205.13, 198.12, 195.50, 198.27 and 208.01 MPa at room temperature.

Cryogenic Properties of Aluminum Beryllium and Beryllium Materials

NASA Technical Reports Server (NTRS)

Gamwell, Wayne R.; McGill, Preston B.

2003-01-01

Ultimate tensile strength, yield strength, and elongation were obtained for the aluminum-beryllium alloy, AlBeMetl62 (38%Al-62%Be), at cryogenic (-195.5 C (-320 F) and (-252.8 C) (-423 F)) temperatures, and for an optical grade beryllium, O-30H (99%Be), at -252.8 C. AlBeMetl62 material was purchased to the requirements of SAE-AMS7912, "Aluminum-Beryllium Alloy, Extrusions." O-30H material was purchased to the requirements of Brush Wellman Inc. specification O-30H Optical Grade Beryllium. The ultimate tensile and yield strengths for extruded AlBeMetl62 material increased with decreasing temperature, and the percent elongation decreased with decreasing temperature. Design properties for the ultimate tensile strength, yield strength, and percent elongation for extruded AlBeMetl62 were generated. It was not possible to distinguish a difference in the room and cryogenic ultimate strength for the hot isostatically pressed (HIP'ed) O-30H material. The O30H elongation decreased with decreasing temperature.

Static behavior and the effects of thermal cycling in hybrid laminates

NASA Technical Reports Server (NTRS)

Liber, T. M.; Daniel, I. M.; Chamis, C. C.

1977-01-01

Static stiffness, strength and ultimate strain after thermal cycling were investigated for graphite/Kevlar 49/epoxy and graphite/S-glass/epoxy angle-ply laminates. Tensile stress-strain curves to failure and uniaxial tensile properties were determined, and theoretical predictions of modulus, Poisson's ratio and ultimate strain, based on linear lamination theory, constituent ply properties and measured strength, were made. No significant influence on tensile stress properties due to stacking sequence variations was observed. In general, specimens containing two 0-degree Kevlar or S-glass plies were found to behave linearly to failure, while specimens containing 4 0-degree Kevlar or S-glass plies showed some nonlinear behavior.

Prediction of nonlinear optical properties of organic materials. General theoretical considerations

NASA Technical Reports Server (NTRS)

Cardelino, B.; Moore, C.; Zutaut, S.

1993-01-01

The prediction of nonlinear optical properties of organic materials is geared to assist materials scientists in the selection of good candidate molecules. A brief summary of the quantum mechanical methods used for estimating hyperpolarizabilities will be presented. The advantages and limitations of each technique will be discussed. Particular attention will be given to the finite-field method for calculating first and second order hyperpolarizabilities, since this method is better suited for large molecules. Corrections for dynamic fields and bulk effects will be discussed in detail, focusing on solvent effects, conformational isomerization, core effects, dispersion, and hydrogen bonding. Several results will be compared with data obtained from third-harmonic-generation (THG) and dc-induced second harmonic generation (EFISH) measurements. These comparisons will demonstrate the qualitative ability of the method to predict the relative strengths of hyperpolarizabilities of a class of compounds. The future application of molecular mechanics, as well as other techniques, in the study of bulk properties and solid state defects will be addressed. The relationship between large values for nonlinear optical properties and large conjugation lengths is well known, and is particularly important for third-order processes. For this reason, the materials with the largest observed nonresonant third-order properties are conjugated polymers. An example of this type of polymer is polydiacetylene. One of the problems in dealing with polydiacetylene is that substituents which may enhance its nonlinear properties may ultimately prevent it from polymerizing. A model which attempts to predict the likelihood of solid-state polymerization is considered, along with the implications of the assumptions that are used. Calculations of the third-order optical properties and their relationship to first-order properties and energy gaps will be discussed. The relationship between monomeric and polymeric third-order optical properties will also be considered.

Effect of solute atoms on dislocation motion in Mg: An electronic structure perspective

PubMed Central

Tsuru, T.; Chrzan, D. C.

2015-01-01

Solution strengthening is a well-known approach to tailoring the mechanical properties of structural alloys. Ultimately, the properties of the dislocation/solute interaction are rooted in the electronic structure of the alloy. Accordingly, we compute the electronic structure associated with, and the energy barriers to dislocation cross-slip. The energy barriers so obtained can be used in the development of multiscale models for dislocation mediated plasticity. The computed electronic structure can be used to identify substitutional solutes likely to interact strongly with the dislocation. Using the example of a-type screw dislocations in Mg, we compute accurately the Peierls barrier to prismatic plane slip and argue that Y, Ca, Ti, and Zr should interact strongly with the studied dislocation, and thereby decrease the dislocation slip anisotropy in the alloy. PMID:25740411

Bioinspired Design: Magnetic Freeze Casting

NASA Astrophysics Data System (ADS)

Porter, Michael Martin

Nature is the ultimate experimental scientist, having billions of years of evolution to design, test, and adapt a variety of multifunctional systems for a plethora of diverse applications. Next-generation materials that draw inspiration from the structure-property-function relationships of natural biological materials have led to many high-performance structural materials with hybrid, hierarchical architectures that fit form to function. In this dissertation, a novel materials processing method, magnetic freeze casting, is introduced to develop porous scaffolds and hybrid composites with micro-architectures that emulate bone, abalone nacre, and other hard biological materials. This method uses ice as a template to form ceramic-based materials with continuously, interconnected microstructures and magnetic fields to control the alignment of these structures in multiple directions. The resulting materials have anisotropic properties with enhanced mechanical performance that have potential applications as bone implants or lightweight structural composites, among others.

Effect of rolling on the high temperature tensile and stress-rupture properties of tungsten fiber-superalloy composites

NASA Technical Reports Server (NTRS)

Petrasek, D. W.

1974-01-01

An investigation was conducted to determine the effects of mechanical working on the 1093 C (2000 F) tensile and stress-rupture strength of tungsten alloy/superalloy composites. Hot pressed composites containing either conventional tungsten lamp filament wire or tungsten-1% ThO2 wire and a nickel base alloy matrix were hot rolled at 1093 C (2000 F). The hot pressed and rolled composite specimens were then tested in tension and stress-rupture at 1093 C (2000 F). Rolling decreased the degree of fiber-matrix reaction as a function of time of exposure at 1093 C (2000 F). The stress-rupture properties of the rolled composites were superior to hot pressed composites containing equivalent diameter fibers. Rolling did not appreciably affect the 1093 C (2000 F) ultimate tensile strength of the composites.

A chondroitinase-ABC and TGF-β1 treatment regimen for enhancing the mechanical properties of tissue-engineered fibrocartilage.

PubMed

MacBarb, Regina F; Makris, Eleftherios A; Hu, Jerry C; Athanasiou, Kyriacos A

2013-01-01

The development of functionally equivalent fibrocartilage remains elusive despite efforts to engineer tissues such as knee meniscus, intervertebral disc and temporomandibular joint disc. Attempts to engineer these structures often fail to create tissues with mechanical properties on a par with native tissue, resulting in constructs unsuitable for clinical applications. The objective of this study was to engineer a spectrum of biomimetic fibrocartilages representative of the distinct functional properties found in native tissues. Using the self-assembly process, different co-cultures of meniscus cells and articular chondrocytes were seeded into agarose wells and treated with the catabolic agent chondroitinase-ABC (C-ABC) and the anabolic agent transforming growth factor-β1 (TGF-β1) via a two-factor (cell ratio and bioactive treatment), full factorial study design. Application of both C-ABC and TGF-β1 resulted in a beneficial or positive increase in the collagen content of treated constructs compared to controls. Significant increases in both the collagen density and fiber diameter were also seen with this treatment, increasing these values by 32 and 15%, respectively, over control values. Mechanical testing found the combined bioactive treatment to synergistically increase the Young's modulus and ultimate tensile strength of the engineered fibrocartilages compared to controls, with values reaching the lower spectrum of those found in native tissues. Together, these data demonstrate that C-ABC and TGF-β1 interact to develop a denser collagen matrix better able to withstand tensile loading. This study highlights a way to optimize the tensile properties of engineered fibrocartilage using a biochemical and a biophysical agent together to create distinct fibrocartilages with functional properties mimicking those of native tissue. Copyright © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

A chondroitinase-ABC and TGF-β1 treatment regimen for enhancing the mechanical properties of tissue engineered fibrocartilage

PubMed Central

MacBarb, Regina F.; Makris, Eleftherios A.; Hu, Jerry C.; Athanasiou, Kyriacos A.

2012-01-01

The development of functionally equivalent fibrocartilage remains elusive despite efforts to engineer tissues such as the knee menisci, intervertebral disc, and TMJ disc. Attempts to engineer these structures often fail to create tissues with mechanical properties on par with native tissue, resulting in constructs unsuitable for clinical applications. The objective of this study was to engineer a spectrum of biomimetic fibrocartilages representative of the distinct functional properties found in native tissues. Using the self-assembly process, different co-cultures of meniscus cells (MCs) and articular chondrocytes (ACs) were seeded into agarose wells and treated with the catabolic agent chondroitinase-ABC (C-ABC) and the anabolic agent transforming growth factor-β1 (TGF-β1) via a two-factor (cell ratio and bioactive treatment), full factorial study design. Application of both C-ABC and TGF-β1 resulted in a beneficial or positive increase in the collagen content of treated constructs compared to controls. Significant increases in both the collagen density and fiber diameter were also seen with this treatment, increasing these values 32% and 15%, respectively, over control values. Mechanical testing found the combined bioactive treatment to synergistically increase the Young’s modulus and ultimate tensile strength of the engineered fibrocartilages compared to controls, with values reaching the lower spectrum of those found in native tissues. Together, these data demonstrate that C-ABC and TGF-β1 interact to develop a denser collagen matrix better able to withstand tensile loading. This study highlights a way to optimize the tensile properties of engineered fibrocartilage using a biochemical and biophysical agent together to create distinct fibrocartilages with functional properties mimicking those of native tissue. PMID:23041782

Natural and Synthetic Biohydrogels Design, Characterization, Network Structure Imaging and Modeling

NASA Astrophysics Data System (ADS)

Marmorat, Clement

Biocompatible hydrogels can be derived from materials that are naturally obtained, such as proteins or polysaccharides, or synthetic, such as poloxamers. In order to be classified as biocompatible, these water-swollen networks can not trigger a toxic response once introduced into a biological or physiological environment and, therefore, must be immunoneutral. Hyaluronic acid hydrogels can be great candidates for tissue engineering applications as long as the cross-linking chemistry and process does not affect the biocompatibility of the natural protein matrix. Thermoreversible hydrogels have the advantage of undergoing a sol/gel phase transition at specific temperatures. Thus, they are excellent candidates for biomedical applications such as drug delivery systems, wound healing coatings or cellular scaffolds. Although these hydrogels can be used in their natural form without further modification or chemical alteration, the original protein or polymer matrix is often strengthened by the use of a crosslinking agent to achieve a specific set of properties. In the case of gelatin fibril formation at low temperatures or the micellization of triblock copolymers in solution with temperature increase, the natural phase transition is modified when crosslinkers are introduced to alter the biohydrogels properties and, ultimately, disturb the system's equilibrium. By using spectroscopy techniques, rheology and cryo-imaging we investigated several biocompatible polymeric networks in their natural form as well as their engineered structures to better understand the mechanisms of gelation and artificial internal re-organization of the networks. Natural and synthetic biohydrogels were designed and their mechanical properties were characterized before imaging. Models that better describe the relationship between network configuration and resulting mechanical properties showed great agreement with experimental mesh size observations. Finally, a novel set of hybrid gels was developed and exhibited outstanding thermomechanical properties.

Influence of Li₂Sb Additions on Microstructure and Mechanical Properties of Al-20Mg₂Si Alloy.

PubMed

Yu, Hong-Chen; Wang, Hui-Yuan; Chen, Lei; Zha, Min; Wang, Cheng; Li, Chao; Jiang, Qi-Chuan

2016-03-29

It is found that Li₂Sb compound can act as the nucleus of primary Mg₂Si during solidification, by which the particle size of primary Mg₂Si decreased from ~300 to ~15-25 μm. Owing to the synergistic effect of the Li₂Sb nucleus and adsorption-poisoning of Li atoms, the effect of complex modification of Li-Sb on primary Mg₂Si was better than that of single modification of Li or Sb. When Li-Sb content increased from 0 to 0.2 and further to 0.5 wt.%, coarse dendrite changed to defective truncated octahedron and finally to perfect truncated octahedral shape. With the addition of Li and Sb, ultimate compression strength (UCS) of Al-20Mg₂Si alloys increased from ~283 to ~341 MPa and the yield strength (YS) at 0.2% offset increased from ~112 to ~179 MPa while almost no change was seen in the uniform elongation. Our study offers a simple method to control the morphology and size of primary Mg₂Si, which will inspire developing new Al-Mg-Si alloys with improved mechanical properties.

Effects of Complex Modification by Sr-Sb on the Microstructures and Mechanical Properties of Al-18 wt % Mg₂Si-4.5Cu Alloys.

PubMed

Sun, Youhong; Ma, Shaoming; Wang, Huiyuan; Chen, Lei; Gao, Ke; Ma, Yinlong; Liu, Baochang

2016-03-04

This research was carried out to investigate the influence of Sr-Sb on the microstructures and mechanical properties of Al-18 wt % Mg₂Si-4.5Cu alloys. After the addition of 0.2 wt % Sr-Sb, the morphologies of primary Mg₂Si transformed from equiaxed dendrite to cube in as-cast alloys and the average size of primary Mg₂Si decreased from ~50 to ~20 μm. The shape of eutectic Mg₂Si changed from Chinese script to short rod. After extrusion and T6 heat treatment, the ultimate tensile strength of modified alloy at room temperature (RT) and 100 °C increased respectively from 229 to 288 MPa, and from 231 to 272 MPa. The elongation-to-failure only slightly improved from 2.9% to 3.8% and from 3.3% to 3.7% at RT and 100 °C, respectively. The tensile fracture surface revealed a transition from brittle fracture to ductile fracture after modifying by 0.2 wt % Sr-Sb.

Grain Refinement of Al-Si-Fe-Cu-Zn-Mn Based Alloy by Al-Ti-B Alloy and Its Effect on Mechanical Properties.

PubMed

Yoo, Hyo-Sang; Kim, Yong-Ho; Jung, Chang-Gi; Lee, Sang-Chan; Lee, Seong-Hee; Son, Hyeon-Taek

2018-03-01

We investigated the effects of Al-5.0wt%Ti-1.0wt%B addition on the microstructure and mechanical properties of the as-extruded Al-0.15wt%Si-0.2wt%Fe-0.3wt%Cu-0.15wt%Zn-0.9wt%Mn based alloys. The Aluminum alloy melt was held at 800 °C and then poured into a mould at 200 °C. Aluminum alloys were hot-extruded into a rod that was 12 mm in thickness with a reduction ratio of 38:1. AlTiB addition to Al-0.15Si-0.2Fe-0.3Cu-0.15Zn-0.9Mn based alloys resulted in the formation of Al3Ti and TiB2 intermetallic compounds and grain refinement. With increasing of addition AlTiB, ultimate tensile strength increased from 93.38 to 99.02 to 100.01 MPa. The tensile strength of the as-extruded alloys was improved due to the formation of intermetallic compounds and grain refinement.

Effects of Complex Modification by Sr–Sb on the Microstructures and Mechanical Properties of Al–18 wt % Mg2Si–4.5Cu Alloys

PubMed Central

Sun, Youhong; Ma, Shaoming; Wang, Huiyuan; Chen, Lei; Gao, Ke; Ma, Yinlong; Liu, Baochang

2016-01-01

This research was carried out to investigate the influence of Sr–Sb on the microstructures and mechanical properties of Al–18 wt % Mg2Si–4.5Cu alloys. After the addition of 0.2 wt % Sr–Sb, the morphologies of primary Mg2Si transformed from equiaxed dendrite to cube in as-cast alloys and the average size of primary Mg2Si decreased from ~50 to ~20 μm. The shape of eutectic Mg2Si changed from Chinese script to short rod. After extrusion and T6 heat treatment, the ultimate tensile strength of modified alloy at room temperature (RT) and 100 °C increased respectively from 229 to 288 MPa, and from 231 to 272 MPa. The elongation-to-failure only slightly improved from 2.9% to 3.8% and from 3.3% to 3.7% at RT and 100 °C, respectively. The tensile fracture surface revealed a transition from brittle fracture to ductile fracture after modifying by 0.2 wt % Sr–Sb. PMID:28773282

The Influence of Friction Stir Weld Tool Form and Welding Parameters on Weld Structure and Properties: Nugget Bulge in Self-Reacting Friction Stir Welds

NASA Technical Reports Server (NTRS)

Schneider, Judy; Nunes, Arthur C., Jr.; Brendel, Michael S.

2010-01-01

Although friction stir welding (FSW) was patented in 1991, process development has been based upon trial and error and the literature still exhibits little understanding of the mechanisms determining weld structure and properties. New concepts emerging from a better understanding of these mechanisms enhance the ability of FSW engineers to think about the FSW process in new ways, inevitably leading to advances in the technology. A kinematic approach in which the FSW flow process is decomposed into several simple flow components has been found to explain the basic structural features of FSW welds and to relate them to tool geometry and process parameters. Using this modelling approach, this study reports on a correlation between the features of the weld nugget, process parameters, weld tool geometry, and weld strength. This correlation presents a way to select process parameters for a given tool geometry so as to optimize weld strength. It also provides clues that may ultimately explain why the weld strength varies within the sample population.

Effect of solidification parameters on mechanical properties of directionally solidified Al-Rich Al-Cu alloys

NASA Astrophysics Data System (ADS)

Çadırlı, Emin

2013-05-01

Al(100-x)-Cux alloys (x=3 wt%, 6 wt%, 15 wt%, 24 wt% and 33 wt%) were prepared using metals of 99.99% high purity in vacuum atmosphere. These alloys were directionally solidified under steady-state conditions by using a Bridgman-type directional solidification furnace. Solidification parameters (G, V and ), microstructure parameters (λ1, λ2 and λE) and mechanical properties (HV, σ) of the Al-Cu alloys were measured. Microstructure parameters were expressed as functions of solidification parameters by using a linear regression analysis. The dependency of HV, σ on the cooling rate, microstructure parameters and composition were determined. According to experimental results, the microhardness and ultimate tensile strength of the solidified samples was increased by increasing the cooling rate and Cu content, but decreased with increasing microstructure parameters. The microscopic fracture surfaces of the different samples were observed using scanning electron microscopy. Fractographic analysis of the tensile fracture surfaces showed that the type of fracture significantly changed from ductile to brittle depending on the composition.

Mechanical properties and corrosion behavior of Mg-Gd-Ca-Zr alloys for medical applications.

PubMed

Shi, Ling-Ling; Huang, Yuanding; Yang, Lei; Feyerabend, Frank; Mendis, Chamini; Willumeit, Regine; Ulrich Kainer, Karl; Hort, Norbert

2015-07-01

Magnesium alloys are promising candidates for biomedical applications. In this work, influences of composition and heat treatment on the microstructure, the mechanical properties and the corrosion behavior of Mg-Gd-Ca-Zr alloys as potential biomedical implant candidates were investigated. Mg5Gd phase was observed at the grain boundaries of Mg-10Gd-xCa-0.5Zr (x=0, 0.3, 1.2wt%) alloys. Increase in the Ca content led to the formation of additional Mg2Ca phase. The Ca additions increased both the compressive and the tensile yield strengths, but reduced the ductility and the corrosion resistance in cell culture medium. After solution heat treatment, the Mg5Gd particles dissolved in the Mg matrix. The compressive strength decreased, while the corrosion resistance improved in the solution treated alloys. After ageing at 200°C, metastable β' phase formed on prismatic planes and a new type of basal precipitates have been observed, which improved the compressive and tensile ultimate strength, but decreased the ductility. Copyright © 2015 Elsevier Ltd. All rights reserved.

Effect of Solidification Behavior on Microstructures and Mechanical Properties of Ni-Cr-Fe Superalloy Investment Casting

PubMed Central

Kang, Maodong; Wang, Jun; Gao, Haiyan; Han, Yanfeng; Wang, Guoxiang; He, Shuxian

2017-01-01

The effect of solidification behavior on the microstructures and mechanical properties of Ni-Cr-Fe superalloy investment casting is given. Metallographic and image analysis have been used to quantitatively examine the microstructures’ evolution. For the parts with the thickness of 3 mm and 24 mm, the volume fraction and maximum equivalent radius of the Laves phase increases from 0.3% to 1.2%, from 11.7 μm to 23.4 μm, respectively. Meanwhile, the volume fraction and maximum equivalent radius of carbides increase from 0.3% to 0.5%, from 8.1 μm to 9.9 μm, respectively. In addition, the volume fraction of microporosity increases from 0.3% to 2.7%. As a result, the ultimate tensile strength is reduced from 1125.5 MPa to 820.9 MPa, the elongation from 13.3% to 7.7%, and the quality index from 1294.2 MPa to 954.0 MPa, respectively. A typical brittle fracture is observed on the tensile fracture. As the cooling rate decreases, the microstructures become coarser. PMID:28772611

Study of the SCC Behavior of 7075 Aluminum Alloy After One-Step Aging at 163 °C

NASA Astrophysics Data System (ADS)

Silva, G.; Rivolta, B.; Gerosa, R.; Derudi, U.

2013-01-01

For the past many years, 7075 aluminum alloys have been widely used especially in those applications for which high mechanical performances are required. It is well known that the alloy in the T6 condition is characterized by the highest ultimate and yield strengths, but, at the same time, by poor stress corrosion cracking (SCC) resistance. For this reason, in the aeronautic applications, new heat treatments have been introduced to produce T7X conditions, which are characterized by lower mechanical strength, but very good SCC behavior, when compared with the T6 condition. The aim of this study is to study the tensile properties and the SCC behavior of 7075 thick plates when submitted to a single-step aging by varying the aging times. The tests were carried out according to the standards and the data obtained from the SCC tests were analyzed quantitatively using an image analysis software. The results show that, when compared with the T7X conditions, the single-step aging performed in the laboratory can produce acceptable tensile and SCC properties.

Damage prediction of 7025 aluminum alloy during equal-channel angular pressing

NASA Astrophysics Data System (ADS)

Ebrahimi, M.; Attarilar, Sh.; Gode, C.; Djavanroodi, F.

2014-10-01

Equal-channel angular pressing (ECAP) is a prominent technique that imposes severe plastic deformation into materials to enhance their mechanical properties. In this research, experimental and numerical approaches were utilized to investigate the mechanical properties, strain behavior, and damage prediction of ECAPed 7025 aluminum alloy in various conditions, such as die channel angle, outer corner angle, and friction coefficient. Experimental results indicate that, after the first pass, the yield strength, ultimate tensile strength, and hardness magnitude are improved by approximately 95%, 28%, and 48.5%, respectively, compared with the annealed state, mainly due to grain refinement during the deformation. Finite element analysis shows that the influence of die channel angle is more important than that of outer corner angle or friction coefficient on both the strain behavior and the damage prediction. Also, surface cracks are the main cause of damage during the ECAP process for every die channel angle except for 90°; however, the cracks initiated from the neighborhood of the central regions are the possible cause of damage in the ECAPed sample with the die channel angle of 90°.

Effect of tensile pre-strain at different orientation on martensitic transformation and mechanical properties of 316L stainless steel

NASA Astrophysics Data System (ADS)

Wibowo, F.; Zulfi, F. R.; Korda, A. A.

2017-01-01

Deformation induced martensite was studied in 316L stainless steel through tensile pre-strain deformation in the rolling direction (RD) and perpendicular to the rolling direction (LT) at various %pre-strain. The experiment was carried out at various given %pre-strain, which were 0%, 4.6%, 12%, 17.4%, and 25.2% for the RD, whereas for LT were 0%, 4.6%, 12%, 18%, and 26% for LT. Changes in the microstructure and mechanical properties were observed using optical microscope, tensile testing, hardness testing, and X-ray diffraction (XRD) analysis. The experimental results showed that the volume fraction of martensite was increased as the %pre-strain increased. In the same level of deformation by tensile pre-strain, the volume of martensite for RD was higher than that with LT direction. The ultimate tensile strength (UTS), yield strength (YS), and hardness of the steel were increased proportionally with the increases in %pre-strain, while the value of elongation and toughness were decreased with the increases in %pre-strain.

Disentangled solid state and metastable polymer melt; a solvent free route to high-modulus high-strength tapes and films of UHMWPE

NASA Astrophysics Data System (ADS)

Rastogi, Sanjay

2013-03-01

Ultra High Molecular Weight Polyethylene (UHMWPE) having average molar mass greater than a million g/mol is an engineering polymer. Due to its light-weight, high abrasion resistance and biocompatibility it is used for demanding applications such as body armour, prostheses etc. At present, because of its high melt viscosity to achieve the uniaxial/biaxial properties in the form of fibers/films the polymer is processed via solution route where nearly 95wt% of the solvent is used to process 5wt% of the polymer. In past several attempts have been made to process the polymer without using any solvent. However, compared to the solvent processing route the achieved mechanical properties were rather poor. Here we show that by controlled synthesis it is feasible to obtain UHMWPE that could be processed free of solvent to make uniaxial tapes and biaxial films, having unprecedented mechanical properties, exceeding that of the solution spun fibers. We address some of the fundamental aspects of chemistry, physics, rheology and processing for the development of desired morphological features to achieve the ultimate mechanical properties in tapes and films. The paper will also address the metastable melt state obtained on melting of the disentangled crystals and its implication on rheology in linear and nonlinear viscoelastic region. Solid state NMR studies will be applied to establish disentangled state in solid state to the polymerisation conditions. References: Macromolecules 2011, 44(14), 5558-5568; Nature Materials 2005, 4, 635-641; Phys Rev Lett 2006, 96(21), 218303-218205. The authors acknowledge financial support by the Dutch Polymer Institute.

Magnetic susceptibility, artifact volume in MRI, and tensile properties of swaged Zr-Ag composites for biomedical applications.

PubMed

Imai, Haruki; Tanaka, Yoji; Nomura, Naoyuki; Doi, Hisashi; Tsutsumi, Yusuke; Ono, Takashi; Hanawa, Takao

2017-02-01

Zr-Ag composites were fabricated to decrease the magnetic susceptibility by compensating for the magnetic susceptibility of their components. The Zr-Ag composites with a different Zr-Ag ratio were swaged, and their magnetic susceptibility, artifact volume, and mechanical properties were evaluated by magnetic balance, three-dimensional (3-D) artifact rendering, and a tensile test, respectively. These properties were correlated with the volume fraction of Ag using the linear rule of mixture. We successfully obtained the swaged Zr-Ag composites up to the reduction ratio of 96% for Zr-4, 16, 36, 64Ag and 86% for Zr-81Ag. However, the volume fraction of Ag after swaging tended to be lower than that before swaging, especially for Ag-rich Zr-Ag composites. The magnetic susceptibility of the composites linearly decreased with the increasing volume fraction of Ag. No artifact could be estimated with the Ag volume fraction in the range from 93.7% to 95.4% in three conditions. Young's modulus, ultimate tensile strength (UTS), and 0.2% yield strength of Zr-Ag composites showed slightly lower values compared to the estimated values using a linear rule of mixture. The decrease in magnetic susceptibility of Zr and Ag by alloying or combining would contribute to the decrease of the Ag fraction, leading to the improvement of mechanical properties. Copyright © 2016 Elsevier Ltd. All rights reserved.

Recent advances in understanding the reinforcing ability and mechanism of carbon nanotubes in ceramic matrix composites.

PubMed

Estili, Mehdi; Sakka, Yoshio

2014-12-01

Since the discovery of carbon nanotubes (CNTs), commonly referred to as ultimate reinforcement, the main purpose for fabricating CNT-ceramic matrix composites has been mainly to improve the fracture toughness and strength of the ceramic matrix materials. However, there have been many studies reporting marginal improvements or even the degradation of mechanical properties. On the other hand, those studies claiming noticeable toughening measured using indentation, which is an indirect/unreliable characterization method, have not demonstrated the responsible mechanisms applicable to the nanoscale, flexible CNTs; instead, those studies proposed those classical methods applicable to microscale fiber/whisker reinforced ceramics without showing any convincing evidence of load transfer to the CNTs. Therefore, the ability of CNTs to directly improve the macroscopic mechanical properties of structural ceramics has been strongly questioned and debated in the last ten years. In order to properly discuss the reinforcing ability (and possible mechanisms) of CNTs in a ceramic host material, there are three fundamental questions to our knowledge at both the nanoscale and macroscale levels that need to be addressed: (1) does the intrinsic load-bearing ability of CNTs change when embedded in a ceramic host matrix?; (2) when there is an intimate atomic-level interface without any chemical reaction with the matrix, could one expect any load transfer to the CNTs along with effective load bearing by them during crack propagation?; and (3) considering their nanometer-scale dimensions, flexibility and radial softness, are the CNTs able to improve the mechanical properties of the host ceramic matrix at the macroscale when individually, intimately and uniformly dispersed? If so, how? Also, what is the effect of CNT concentration in such a defect-free composite system? Here, we briefly review the recent studies addressing the above fundamental questions. In particular, we discuss the new reinforcing mechanism at the nanoscale responsible for unprecedented, simultaneous mechanical improvements and highlight the scalable processing method enabling the fabrication of defect-free CNT-concentered ceramics and CNT-graded composites with unprecedented properties. Finally, possible future directions will be briefly presented.

Recent advances in understanding the reinforcing ability and mechanism of carbon nanotubes in ceramic matrix composites

PubMed Central

Estili, Mehdi; Sakka, Yoshio

2014-01-01

Since the discovery of carbon nanotubes (CNTs), commonly referred to as ultimate reinforcement, the main purpose for fabricating CNT–ceramic matrix composites has been mainly to improve the fracture toughness and strength of the ceramic matrix materials. However, there have been many studies reporting marginal improvements or even the degradation of mechanical properties. On the other hand, those studies claiming noticeable toughening measured using indentation, which is an indirect/unreliable characterization method, have not demonstrated the responsible mechanisms applicable to the nanoscale, flexible CNTs; instead, those studies proposed those classical methods applicable to microscale fiber/whisker reinforced ceramics without showing any convincing evidence of load transfer to the CNTs. Therefore, the ability of CNTs to directly improve the macroscopic mechanical properties of structural ceramics has been strongly questioned and debated in the last ten years. In order to properly discuss the reinforcing ability (and possible mechanisms) of CNTs in a ceramic host material, there are three fundamental questions to our knowledge at both the nanoscale and macroscale levels that need to be addressed: (1) does the intrinsic load-bearing ability of CNTs change when embedded in a ceramic host matrix?; (2) when there is an intimate atomic-level interface without any chemical reaction with the matrix, could one expect any load transfer to the CNTs along with effective load bearing by them during crack propagation?; and (3) considering their nanometer-scale dimensions, flexibility and radial softness, are the CNTs able to improve the mechanical properties of the host ceramic matrix at the macroscale when individually, intimately and uniformly dispersed? If so, how? Also, what is the effect of CNT concentration in such a defect-free composite system? Here, we briefly review the recent studies addressing the above fundamental questions. In particular, we discuss the new reinforcing mechanism at the nanoscale responsible for unprecedented, simultaneous mechanical improvements and highlight the scalable processing method enabling the fabrication of defect-free CNT-concentered ceramics and CNT-graded composites with unprecedented properties. Finally, possible future directions will be briefly presented. PMID:27877730

Mechanical performance and parameter sensitivity analysis of 3D braided composites joints.

PubMed

Wu, Yue; Nan, Bo; Chen, Liang

2014-01-01

3D braided composite joints are the important components in CFRP truss, which have significant influence on the reliability and lightweight of structures. To investigate the mechanical performance of 3D braided composite joints, a numerical method based on the microscopic mechanics is put forward, the modeling technologies, including the material constants selection, element type, grid size, and the boundary conditions, are discussed in detail. Secondly, a method for determination of ultimate bearing capacity is established, which can consider the strength failure. Finally, the effect of load parameters, geometric parameters, and process parameters on the ultimate bearing capacity of joints is analyzed by the global sensitivity analysis method. The results show that the main pipe diameter thickness ratio γ, the main pipe diameter D, and the braided angle α are sensitive to the ultimate bearing capacity N.

Mechanical tensile properties of the anterolateral ligament.

PubMed

Zens, Martin; Feucht, Matthias J; Ruhhammer, Johannes; Bernstein, Anke; Mayr, Hermann O; Südkamp, Norbert P; Woias, Peter; Niemeyer, Philipp

2015-12-01

In a noticeable percentage of patients anterolateral rotational instabilities (ALRI) remain after an isolated ACL reconstruction. Those instabilities may occur due to an insufficiently directed damage of anterolateral structures that is often associated with ACL ruptures. Recent publications describe an anatomical structure, termed the anterolateral ligament (ALL), and suggest that this ligament plays a significant role in the pathogenesis of ALRI of the knee joint. However, only limited knowledge about the biomechanical characteristics and tensile properties of the anterolateral ligament exists. The anterolateral ligament was dissected in four fresh-frozen human cadaveric specimens and all surrounding tissue removed. The initial length of the anterolateral ligament was measured using a digital caliper. Tensile tests with load to failure were performed using a materials testing machine. The explanted anterolateral ligaments were histologically examined to measure the cross-sectional area. The mean ultimate load to failure of the anterolateral ligament was 49.90 N (± 14.62 N) and the mean ultimate strain was 35.96% (± 4.47%). The mean length of the ligament was 33.08 mm (± 2.24) and the mean cross-sectional area was 1.54 m m (2) (± 0.48 m m (2)). Including the areal measurements the maximum tension was calculated to be 32.78 [Formula: see text] (± 4.04 [Formula: see text]). The anterolateral ligament is an anatomical structure with tensile properties that are considerably weaker compared to other peripheral structures of the knee. Knowledge of the anterolateral ligament's tensile strengths may help to better understand its function and with graft choices for reconstruction procedures.

EBSD characterization of low temperature deformation mechanisms in modern alloys

NASA Astrophysics Data System (ADS)

Kozmel, Thomas S., II

For structural applications, grain refinement has been shown to enhance mechanical properties such as strength, fatigue resistance, and fracture toughness. Through control of the thermos-mechanical processing parameters, dynamic recrystallization mechanisms were used to produce microstructures consisting of sub-micron grains in 9310 steel, 4140 steel, and Ti-6Al-4V. In both 9310 and 4140 steel, the distribution of carbides throughout the microstructure affected the ability of the material to dynamically recrystallize and determined the size of the dynamically recrystallized grains. Processing the materials at lower temperatures and higher strain rates resulted in finer dynamically recrystallized grains. Microstructural process models that can be used to estimate the resulting microstructure based on the processing parameters were developed for both 9310 and 4140 steel. Heat treatment studies performed on 9310 steel showed that the sub-micron grain size obtained during deformation could not be retained due to the low equilibrium volume fraction of carbides. Commercially available aluminum alloys were investigated to explain their high strain rate deformation behavior. Alloys such as 2139, 2519, 5083, and 7039 exhibit strain softening after an ultimate strength is reached, followed by a rapid degradation of mechanical properties after a critical strain level has been reached. Microstructural analysis showed that the formation of shear bands typically preceded this rapid degradation in properties. Shear band boundary misorientations increased as a function of equivalent strain in all cases. Precipitation behavior was found to greatly influence the microstructural response of the alloys. Additionally, precipitation strengthened alloys were found to exhibit similar flow stress behavior, whereas solid solution strengthened alloys exhibited lower flow stresses but higher ductility during dynamic loading. Schmid factor maps demonstrated that shear band formation behavior was influenced by texturing in these alloys.

Multiscale structure and damage tolerance of coconut shells.

PubMed

Gludovatz, B; Walsh, F; Zimmermann, E A; Naleway, S E; Ritchie, R O; Kruzic, J J

2017-12-01

We investigated the endocarp of the fruit of Cocos nucifera (i.e., the inner coconut shell), examining the structure across multiple length scales through advanced characterization techniques and in situ testing of mechanical properties. Like many biological materials, the coconut shell possesses a hierarchical structure with distinct features at different length scales that depend on orientation and age. Aged coconut was found to have a significantly stronger (ultimate tensile strength, UTS = 48.5MPa), stiffer (Young's modulus, E = 1.92GPa), and tougher (fracture resistance (R-curve) peak of K J = 3.2MPa m 1/2 ) endocarp than the younger fruit for loading in the latitudinal orientation. While the mechanical properties of coconut shell were observed to improve with age, they also become more anisotropic: the young coconut shell had the same strength (17MPa) and modulus (0.64GPa) values and similar R-curves for both longitudinal and latitudinal loading configurations, whereas the old coconut had 82% higher strength for loading in the latitudinal orientation, and >50% higher crack growth toughness for cracking on the latitudinal plane. Structural aspects affecting the mechanical properties across multiple length scales with aging were identified as improved load transfer to the cellulose crystalline nanostructure (identified by synchrotron x-ray diffraction) and sclerification of the endocarp, the latter of which included closing of the cell lumens and lignification of the cell walls. The structural changes gave a denser and mechanically superior micro and nanostructure to the old coconut shell. Additionally, the development of anisotropy was attributed to the formation of an anisotropic open channel structure throughout the shell of the old coconut that affected both crack initiation during uniaxial tensile tests and the toughening mechanisms of crack trapping and deflection during crack propagation. Copyright © 2017 Elsevier Ltd. All rights reserved.

Densification behavior and mechanical properties of nanocrystalline TiC reinforced 316L stainless steel composite parts fabricated by selective laser melting

NASA Astrophysics Data System (ADS)

Zhao, Shuming; Shen, Xianfeng; Yang, Jialin; Teng, Wenhua; Wang, Yingying

2018-07-01

Metal matrix composite parts produced using selective laser melting have superior mechanical properties to those produced using traditional powder metallurgy. In this study, nanocrystalline TiC reinforced 316L stainless steel composite parts were fabricated using selective laser melting, and the effects of the TiC mass fraction, particle size, and processing parameters on the relative density, microhardness, and mechanical properties of the TiC/316L composites were investigated. The results show that the relative density of the fabricated parts is related to the laser power and exposure time, and increases when these parameters are increased. The greater the mass fraction of nano-TiC added, the more severe the degree of spheroidization and the lower the density of the resulting material. The microhardness of the 316L stainless steel parts is enhanced by the nano-TiC particles, and increases with increasing nano-TiC mass fraction. The tensile strength is improved with longer exposure time and with the addition of 2 wt% nano-TiC particles. Compared with pure 316L, the microhardness of the TiC/316L composite parts fabricated with 2 wt% 40 nm TiC enhanced from HV0.3 = 219.1 to 277.6, and the ultimate tensile strength significantly increased from 627.5 to 748.6 MPa. The strengthening mechanism of TiC particles is the refinement of the grain size of the 316L matrix, and the greater amount of TiC particles added, the better the grain refinement of 316L.

An Investigation of Electrochemomechanical Actuation of Conductive Polyacrylonitrile (PAN) Nanofiber Composites

NASA Astrophysics Data System (ADS)

Gonzalez, Mark A.

A polymer-based nanofiber composite actuator designed for linear actuation was fabricated by electrospinning, actuated by electrolysis, and characterized by electrical and mechanical testing to address performance limitations and understand the activation processing effects on actuation performance. Currently, Electroactive polymers (EAPs) have provided uses in sensory and actuation technology, but have either low force output or expand rather than contract, falling short in capturing the natural motion and function of muscle desperately needed to provide breakthroughs in the bio-medical and robotic fields. Previous research has shown activated Polyacrylonitrile (PAN) fibers having biomimetic functionalities similar to the sarcomere contraction responsible for muscle function. Activated PAN is also known to contract and expand by electrolysis when in close vicinity to the anode and cathode, respectively. PAN nanofibers especially show faster response to changes in environmental pH and improved mechanical properties over larger diameter fibers. Conductive additives were introduced to the electrospinning solution and activated in an attempt to create composite PAN nanofiber gel actuators with improved conductivity and eliminate the need of stiff electrodes. Tensile testing was conducted to examine changes in mechanical properties between annealing and hydrolysis processing. Introducing conductive additives did not show a significant increase in conductivity and created unusable samples, requiring alternative electrode materials. Electrochemical contraction rates up to 25%/ min were achieved. Strains of 58.8%, ultimate stresses up to 77.1 MPa, and moduli of 0.21 MPa were achieved with pure PAN nanofiber mats, surpassing mechanical properties of natural muscles. Improvements to contraction rates and young's moduli are necessary to capture the function and performance of skeletal muscles properly.

EXTRACTION OF FRACTURE-MECHANICS AND TRANSMISSION-ELECTRON-MICROSCOPY SAMPLES FROM TRITIUM-EXPOSED RESERVOIRS USING ELECTRIC-DISCHARGE MACHINING

DOE Office of Scientific and Technical Information (OSTI.GOV)

Morgan, M; Ken Imrich, K; Michael Tosten, M

2006-08-31

The Enhanced Surveillance Campaign is funding a program to investigate tritium aging effects on the structural properties of tritium reservoir steels. The program is designed to investigate how the structural properties of reservoir steels change during tritium service and to examine the role of microstructure and reservoir manufacturing on tritium compatibility. New surveillance tests are also being developed that can better gauge the long-term effects of tritium and its radioactive decay product, helium-3, on the properties of reservoir steels. In order to conduct these investigations, three types of samples are needed from returned reservoirs: tensile, fracture mechanics, and transmission-electron microscopymore » (TEM). An earlier report demonstrated how the electric-discharge machining (EDM) technique can be used for cutting tensile samples from serial sections of a 3T reservoir and how yield strength, ultimate strength and elongation could be measured from those samples. In this report, EDM was used successfully to section sub-sized fracture-mechanics samples from the inner and outer walls of a 3T reservoir and TEM samples from serial sections of a 1M reservoir. This report fulfills the requirements for the FY06 Level 3 milestone, TSR 15.1 ''Cut Fracture-Mechanics Samples from Tritium-Exposed Reservoir'' and TSR 15.2 ''Cut Transmission-electron-microscopy foils from Tritium-Exposed Reservoir'' for the Enhance Surveillance Campaign (ESC). This was in support of ESC L2-1870 Milestone-''Provide aging and lifetime assessments of selected components and materials for multiple enduring stockpile systems''.« less

Biomechanical properties of an advanced new carbon/flax/epoxy composite material for bone plate applications.

PubMed

Bagheri, Zahra S; El Sawi, Ihab; Schemitsch, Emil H; Zdero, Rad; Bougherara, Habiba

2013-04-01

This work is part of an ongoing program to develop a new carbon fiber/flax/epoxy (CF/flax/epoxy) hybrid composite material for use as an orthopaedic long bone fracture plate, instead of a metal plate. The purpose of this study was to evaluate the mechanical properties of this new novel composite material. The composite material had a "sandwich structure", in which two thin sheets of CF/epoxy were attached to each outer surface of the flax/epoxy core, which resulted in a unique structure compared to other composite plates for bone plate applications. Mechanical properties were determined using tension, three-point bending, and Rockwell hardness tests. Also, scanning electron microscopy (SEM) was used to characterize the failure mechanism of specimens in tension and three-point bending tests. The results of mechanical tests revealed a considerably high ultimate strength in both tension (399.8MPa) and flexural loading (510.6MPa), with a higher elastic modulus in bending tests (57.4GPa) compared to tension tests (41.7GPa). The composite material experienced brittle catastrophic failure in both tension and bending tests. The SEM images, consistent with brittle failure, showed mostly fiber breakage and fiber pull-out at the fractured surfaces with perfect bonding at carbon fibers and flax plies. Compared to clinically-used orthopaedic metal plates, current CF/flax/epoxy results were closer to human cortical bone, making the material a potential candidate for use in long bone fracture fixation. Copyright © 2013 Elsevier Ltd. All rights reserved.

Preparation and characterization of collagen/hydroxypropyl methylcellulose (HPMC) blend film.

PubMed

Ding, Cuicui; Zhang, Min; Li, Guoying

2015-03-30

This study aimed to prepare and characterize the collagen/HPMC blend film (1/1). Thermogravimetric analysis and differential scanning calorimetry were used to investigate the thermal properties of the film. Both thermal decomposition temperature and denaturation temperature of the blend film were higher than those of the collagen film due to the intermolecular hydrogen bonding interaction between collagen and HPMC, which was demonstrated by Fourier transform infrared spectroscopy. Additionally, the morphologies, mechanical properties and hydrophilicity of films were examined. The blend film exhibited a more homogeneous and compact structure compared with that of the collagen film, as observed from scanning electron microscopy and atomic force microscopy. The tensile strength, ultimate elongation and hydrophilicity of the blend film were superior to those of the pure collagen film. Furthermore, the introduction of polyethylene glycol 1500 had almost no influence on the thermal properties of the blend film but obviously improved its stretch-ability and smoothness. Copyright © 2014 Elsevier Ltd. All rights reserved.

The effect of texture and grain size on improving the mechanical properties of Mg-Al-Zn alloys by friction stir processing.

PubMed

Peng, Jinhua; Zhang, Zhen; Liu, Zhao; Li, Yaozu; Guo, Peng; Zhou, Wei; Wu, Yucheng

2018-03-08

Friction stir processing (FSP) was used to achieve grain refinement on Mg-Al-Zn alloys, which also brought in significant texture modification. The different micro-texture characteristics were found to cause irregular micro-hardness distribution in FSPed region. The effects of texture and grain size were investigated by comparative analyses with strongly textured rolling sheet. Grain refinement improved both strength and elongation in condition of a basal texture while such led to an increment in yield stress and a drop in elongation and ultimate stress when the basal texture was modified by FSP.

Utilization of multiwalled boron nitride nanotubes for the reinforcement of lightweight aluminum ribbons

PubMed Central

2013-01-01

Multiwalled boron nitride nanotubes (BNNTs) have very attractive mechanical and thermal properties, e.g., elasticity, tensile strength, and high resistance to oxidation, and may be considered as ideal reinforcing agents in lightweight metal matrix composites. Herein, for the first time, Al-BNNT ribbons with various BNNT contents (up to 3 wt.%) were fabricated via melt spinning in an argon atmosphere. BNNTs were randomly dispersed within a microcrystalline Al matrix under ribbon casting and led to more than doubling of room-temperature ultimate tensile strength of the composites compared to pure Al ribbons produced at the similar conditions. PMID:23279813

A Fast and Effective Pyridine-Free Method for the Determination of Hydroxyl Value of Hydroxyl-Terminated Polybutadiene and Other Hydroxy Compounds

NASA Astrophysics Data System (ADS)

Alex, Ancy Smitha; Kumar, Vijendra; Sekkar, V.; Bandyopadhyay, G. G.

2017-07-01

Hydroxyl-terminated polybutadiene (HTPB) is the workhorse propellant binder for launch vehicle and missile applications. Accurate determination of the hydroxyl value (OHV) of HTPB is crucial for tailoring the ultimate mechanical and ballistic properties of the propellant derived. This article describes a fast and effective methodology free of pyridine based on acetic anhydride, N-methyl imidazole, and toluene for the determination of OHV of nonpolar polymers like HTPB and other hydroxyl compounds. This method gives accurate and reproducible results comparable to standard methods and is superior to existing methods in terms of user friendliness, efficiency, and time requirement.

A Hypothesis on Biological Protection from Space Radiation Through the Use of Therapeutic Gases

NASA Technical Reports Server (NTRS)

Schoenfeld, Michael

2011-01-01

This slide presentation proposes a hypothesis to use therapeutic gases in space to enhance the biological protection for astronauts from space radiation. The fundamental role in how radiation causes biological damage appears to be radiolysis, the dissociation of water by radiation. A chain of events appears to cause molecular and biological transformations that ultimately manifest into medical diseases. The hypothesis of this work is that applying medical gases may increase resistance to radiation, by possessing the chemical properties that effectively improve the radical scavenging and enhance bond repair and to induce biological processes which enhance and support natural resistance and repair mechanisms.

Nanotechnology-Driven Therapeutic Interventions in Wound Healing: Potential Uses and Applications

PubMed Central

2017-01-01

The chronic nature and associated complications of nonhealing wounds have led to the emergence of nanotechnology-based therapies that aim at facilitating the healing process and ultimately repairing the injured tissue. A number of engineered nanotechnologies have been proposed demonstrating unique properties and multiple functions that address specific problems associated with wound repair mechanisms. In this outlook, we highlight the most recently developed nanotechnology-based therapeutic agents and assess the viability and efficacy of each treatment, with emphasis on chronic cutaneous wounds. Herein we explore the unmet needs and future directions of current technologies, while discussing promising strategies that can advance the wound-healing field. PMID:28386594

The Brittleness and Chemical Stability of Optimized Geopolymer Composites

PubMed Central

Steinerova, Michaela; Matulova, Lenka; Vermach, Pavel; Kotas, Jindrich

2017-01-01

Geopolymers are known as high strength and durable construction materials but have a brittle fracture. In practice, this results in a sudden collapse at ultimate load, without any chance of preventing the breakdown of parts or of withstanding the stress for some time. Glass fiber usage as a total anisotropic shape acting as a compact structure component should hinder the fracture mechanism. The optimized compositions in this study led to a significant reinforcement, especially in the case of flexural strength, but also in terms of the compressive strength and notch toughness. The positive and negative influence of the fibers on the complex composite properties provided chemical stability. PMID:28772756

The Brittleness and Chemical Stability of Optimized Geopolymer Composites.

PubMed

Steinerova, Michaela; Matulova, Lenka; Vermach, Pavel; Kotas, Jindrich

2017-04-09

Geopolymers are known as high strength and durable construction materials but have a brittle fracture. In practice, this results in a sudden collapse at ultimate load, without any chance of preventing the breakdown of parts or of withstanding the stress for some time. Glass fiber usage as a total anisotropic shape acting as a compact structure component should hinder the fracture mechanism. The optimized compositions in this study led to a significant reinforcement, especially in the case of flexural strength, but also in terms of the compressive strength and notch toughness. The positive and negative influence of the fibers on the complex composite properties provided chemical stability.

Mechanical Behaviour of 304 Austenitic Stainless Steel Processed by Room Temperature Rolling

NASA Astrophysics Data System (ADS)

Singh, Rahul; Goel, Sunkulp; Verma, Raviraj; Jayaganthan, R.; Kumar, Abhishek

2018-03-01

To study the effect of room temperature rolling on mechanical properties of 304 Austenitic Stainless Steel, the as received 304 ASS was rolled at room temperature for different percentage of plastic deformation (i.e. 30, 50, 70 and 90 %). Microstructural study, tensile and hardness tests were performed in accordance with ASTM standards to study the effect of rolling. The ultimate tensile strength (UTS) and hardness of a rolled specimen have enhanced with rolling. The UTS has increased from 693 MPa (as received) to 1700 MPa (after 90% deformation). The improvement in UTS of processed samples is due to combined effect of grain refinement and stress induced martensitic phase transformation. The hardness values also increases from 206 VHN (as received) to 499 VHN (after 90% deformation). Magnetic measurements were also conducted to confirm the formation of martensitic phase.

The Effect of Poly (Glycerol Sebacate) Incorporation within Hybrid Chitin-Lignin Sol-Gel Nanofibrous Scaffolds.

PubMed

Abudula, Tuerdimaimaiti; Gzara, Lassaad; Simonetti, Giovanna; Alshahrie, Ahmed; Salah, Numan; Morganti, Pierfrancesco; Chianese, Angelo; Fallahi, Afsoon; Tamayol, Ali; Bencherif, Sidi A; Memic, Adnan

2018-03-19

Chitin and lignin primarily accumulate as bio-waste resulting from byproducts of crustacean crusts and plant biomass. Recently, their use has been proposed for diverse and unique bioengineering applications, amongst others. However, their weak mechanical properties need to be improved in order to facilitate their industrial utilization. In this paper, we fabricated hybrid fibers composed of a chitin-lignin (CL)-based sol-gel mixture and elastomeric poly (glycerol sebacate) (PGS) using a standard electrospinning approach. Obtained results showed that PGS could be coherently blended with the sol-gel mixture to form a nanofibrous scaffold exhibiting remarkable mechanical performance and improved antibacterial and antifungal activity. The developed hybrid fibers showed promising potential in advanced biomedical applications such as wound care products. Ultimately, recycling these sustainable biopolymers and other bio-wastes alike could propel a "greener" economy.

Structural and elastoplastic properties of β -Ga2O3 films grown on hybrid SiC/Si substrates

NASA Astrophysics Data System (ADS)

Osipov, A. V.; Grashchenko, A. S.; Kukushkin, S. A.; Nikolaev, V. I.; Osipova, E. V.; Pechnikov, A. I.; Soshnikov, I. P.

2018-04-01

Structural and mechanical properties of gallium oxide films grown on (001), (011) and (111) silicon substrates with a buffer layer of silicon carbide are studied. The buffer layer was fabricated by the atom substitution method, i.e., one silicon atom per unit cell in the substrate was substituted by a carbon atom by chemical reaction with carbon monoxide. The surface and bulk structure properties of gallium oxide films have been studied by atomic-force microscopy and scanning electron microscopy. The nanoindentation method was used to investigate the elastoplastic characteristics of gallium oxide, and also to determine the elastic recovery parameter of the films under study. The ultimate tensile strength, hardness, elastic stiffness constants, elastic compliance constants, Young's modulus, linear compressibility, shear modulus, Poisson's ratio and other characteristics of gallium oxide have been calculated by quantum chemistry methods based on the PBESOL functional. It is shown that all these properties of gallium oxide are essentially anisotropic. The calculated values are compared with experimental data. We conclude that a change in the silicon orientation leads to a significant reorientation of gallium oxide.

The effect of pre-straining and pre-ageing on a novel thermomechanical treatment for improving the mechanical properties of AA2139 aerospace aluminium alloys

NASA Astrophysics Data System (ADS)

Bakare, F.; Alsubhi, Y.; Ragkousis, A.; Ebomwonyi, O.; Damisa, J.; Okunzuwa, S.

2017-07-01

The novel thermomechanical treatment employed by Wang Z et al (2014 Mater. Sci. Eng. A 607 313-7) in enhancing the mechanical and microstructure properties of 6000 series aluminium alloys has been replicated for AA2139 aerospace aluminium alloys. The novel route which involves under-ageing, cold-rolling reductions and re-ageing at a fixed temperature has been carried out focusing on the effect of pre-straining and pre-ageing on the alloy properties. The influence of varying cold-rolling reductions and pre-ageing has been examined by tensile testing, hardness testing, differential scanning calorimetry, thermoelectric power measurements and scanning electron microscope (SEM). Further analyses were conducted with DSC and TEP measurements to check for precipitation sequence and solute retention respectively. On comparing the hardness and strength of the non pre-aged to the pre-aged samples, there is a remarkable increase in the hardness and strength of the aerospace alloy showing the huge influence of both pre-ageing and pre-straining stage of the novel thermomechanical treatment as observed in the 6000 series alloy, albeit at a higher rate. The treatments that exhibited the most promising mechanical properties (hardness, yield and ultimate tensile strength, elongation to failure) were found to be at a pre-ageing temperature of 175 °C for 1.5 h, 40% cold-rolling and re-ageing at 150 °C. The material was found to have yield strength of 590 MPa and 8.1% uniform elongation, which is well above the 5% acceptable value for structural applications and with strength levels adaptable for aerospace industries. The presence of higher volume fraction of well dispersed precipitates observed in the SEM further shows that intermediate cold-rolling reductions combines well with pre-ageing to give the best mechanical properties in this alloy.

Influence of Lanthanum on Solidification, Microstructure, and Mechanical Properties of Eutectic Al-Si Piston Alloy

NASA Astrophysics Data System (ADS)

Ahmad, R.; Asmael, M. B. A.

2016-07-01

The effects of Lanthanum (La) concentration on the solidification parameters of the α-Al, Al-Si, and Al-Cu phases and on the microstructure, tensile, and hardness properties of eutectic Al-Si-Cu-Mg alloy were systematically investigated. The solidification parameters were examined using computer-aided cooling curve thermal analysis (CA-CCTA). The cooling curve and microstructure analysis showed that La altered the Si structure. The nucleation and growth temperatures of eutectic Si decreased when 0.3 wt.% La was added, and a high depression temperature was obtained with 1.0 wt.% La. High amounts of La considerably modified the Si structure and decreased the area and aspect ratio by 69.9 and 51%, respectively. The thermal analysis result recorded a faster freezing time with the La addition and a 36% alteration in the secondary dendrite arm spacing. Two secondary or ternary La-rich intermetallic phases were formed with needle- and plate-like structures. Furthermore, the mechanical properties were investigated by hardness and tensile tests with different La concentrations. The addition of small amounts of La (0.1 wt.%) significantly improved the ultimate tensile strength and quality index of the Al-Si-Cu-Mg alloy. In addition, the hardness value of Al-11Si-Cu increased by 7-8% with the increasing amount of La added.

Mechanical properties of highly defective graphene: from brittle rupture to ductile fracture.

PubMed

Xu, Lanqing; Wei, Ning; Zheng, Yongping

2013-12-20

Defects are generally believed to deteriorate the superlative performance of graphene-based devices but may also be useful when carefully engineered to tailor the local properties and achieve new functionalities. Central to most defect-associated applications is the defect coverage and arrangement. In this work, we investigate, by molecular dynamics simulations, the mechanical properties and fracture dynamics of graphene sheets with randomly distributed vacancies or Stone-Wales defects under tensile deformations over a wide defect coverage range. With defects presented, an sp-sp(2) bonding network and an sp-sp(2)-sp(3) bonding network are observed in vacancy-defected and Stone-Wales-defected graphene, respectively. The ultimate strength degrades gradually with increasing defect coverage and saturates in the high-ratio regime, whereas the fracture strain presents an unusual descending-saturating-improving trend. In the dense vacancy defect situation, the fracture becomes more plastic and super-ductility is observed. Further fracture dynamics analysis reveals that the crack trapping by sp-sp(2) and sp-sp(2)-sp(3) rings and the crack-tip blunting account for the ductile fracture, whereas geometric rearrangement on the entire sheet for vacancy defects and geometric rearrangement on the specific defect sites for Stone-Wales defects account for their distinctive rules of the evolution of the fracture strain.

Microstructure and Mechanical Properties of Laser Solid Formed Ti-6Al-4V Alloy Under Dynamic Shear Loading

NASA Astrophysics Data System (ADS)

Zhou, Ping; Guo, Wei-Guo; Su, Yu; Wang, Jianjun; Lin, Xin; Huang, Weidong

2017-07-01

To investigate the mechanical properties of the Ti-6Al-4V alloy fabricated by laser solid forming technology, both static and dynamic shear tests were conducted on hat-shaped specimens by a servohydraulic testing machine and an enhanced split Hopkinson pressure bar system, over a temperature range of 173-573 K. The microstructure of both the original and deformed specimens was characterized by optical microscopy and scanning electron microscopy. The results show that: (1) the anisotropy of shear properties is not significant regardless of the visible stratification and the prior- β grains that grow epitaxially along the depositing direction; (2) the ultimate shear strength of this material is lower than that of those Ti-6Al-4V alloys fabricated by forging and extrusion; (3) the adiabatic shear bands of approximately 25.6-36.4 μm in width can develop at all selected temperatures during the dynamic shear deformation; and (4) the observed microstructure and measured microhardness indicate that the grains become refined in adiabatic shear band. Estimation of the temperature rise shows that the temperature in shear band exceeds the recrystallization temperature. The process of rotational dynamic recrystallization is considered to be the cause of the grain refinement in shear band.

Oxygen Release Induced Chemomechanical Breakdown of Layered Cathode Materials

DOE PAGES

Mu, Linqin; Lin, Ruoqian; Xu, Rong; ...

2018-04-18

Chemical and mechanical properties interplay on the nanometric scale and collectively govern the functionalities of battery materials. Understanding the relationship between the two can inform the design of battery materials with optimal chemomechanical properties for long-life lithium batteries. Herein, we report a mechanism of nanoscale mechanical breakdown in layered oxide cathode materials, originating from oxygen release at high states of charge under thermal abuse conditions. Here, we observe that the mechanical breakdown of charged Li 1-xNi 0.4Mn 0.4Co 0.2O 2 materials proceeds via a two-step pathway involving intergranular and intragranular crack formation. Owing to the oxygen release, sporadic phase transformationsmore » from the layered structure to the spinel and/or rocksalt structures introduce local stress, which initiates microcracks along grain boundaries and ultimately leads to the detachment of primary particles; i.e., intergranular crack formation. Furthermore, intragranular cracks (pores and exfoliations) form, likely due to the accumulation of oxygen vacancies and continuous phase transformations at the surfaces of primary particles. Finally, finite element modeling confirms our experimental observation that the crack formation is attributable to formation of oxygen vacancies, oxygen release, and phase transformations. This study is designed to directly observe the chemomechanical behavior of layered oxide cathode materials and provides a chemical basis for strengthening primary and secondary particles by stabilizing the oxygen anions in the lattice.« less

Oxygen Release Induced Chemomechanical Breakdown of Layered Cathode Materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mu, Linqin; Lin, Ruoqian; Xu, Rong

Chemical and mechanical properties interplay on the nanometric scale and collectively govern the functionalities of battery materials. Understanding the relationship between the two can inform the design of battery materials with optimal chemomechanical properties for long-life lithium batteries. Herein, we report a mechanism of nanoscale mechanical breakdown in layered oxide cathode materials, originating from oxygen release at high states of charge under thermal abuse conditions. Here, we observe that the mechanical breakdown of charged Li 1-xNi 0.4Mn 0.4Co 0.2O 2 materials proceeds via a two-step pathway involving intergranular and intragranular crack formation. Owing to the oxygen release, sporadic phase transformationsmore » from the layered structure to the spinel and/or rocksalt structures introduce local stress, which initiates microcracks along grain boundaries and ultimately leads to the detachment of primary particles; i.e., intergranular crack formation. Furthermore, intragranular cracks (pores and exfoliations) form, likely due to the accumulation of oxygen vacancies and continuous phase transformations at the surfaces of primary particles. Finally, finite element modeling confirms our experimental observation that the crack formation is attributable to formation of oxygen vacancies, oxygen release, and phase transformations. This study is designed to directly observe the chemomechanical behavior of layered oxide cathode materials and provides a chemical basis for strengthening primary and secondary particles by stabilizing the oxygen anions in the lattice.« less

Influence of interfacial shear strength on the mechanical properties of SiC fiber reinforced reaction-bonded silicon nitride matrix composites

NASA Technical Reports Server (NTRS)

Bhatt, Ramakrishna T.

1990-01-01

The influence of fiber/matrix interface microstructure and interfacial shear strength on the mechanical properties of a fiber-reinforced ceramic composite was evaluated. The composite consisted of approximately 30 vol percent uniaxially aligned 142 microns diameter SiC fibers (Textron SCS-6) in a reaction-bonded Si3N4 matrix (SiC/RBSN). The interface microstructure was varied by controlling the composite fabrication conditions and by heat treating the composite in an oxidizing environment. Interfacial shear strength was determined by the matrix crack spacing method. The results of microstructural examination indicate that the carbon-rich coating provided with the as-produced SiC fibers was stable in composites fabricated at 1200 C in a nitrogen or in a nitrogen plus 4 percent hydrogen mixture for 40 hr. However this coating degraded in composites fabricated at 1350 C in N2 + 4 percent H2 for 40 and 72 hr and also in composites heat treated in an oxidizing environment at 600 C for 100 hr after fabrication at 1200 C in a nitrogen. It was determined that degradation occurred by carbon removal which in turn had a strong influence on interfacial shear strength and other mechanical properties. Specifically, as the carbon coating was removed, the composite interfacial shear strength, primary elastic modulus, first matrix cracking stress, and ultimate tensile strength decreased, but the first matrix cracking strain remained nearly the same.

Effect of Al–5Ti–C Master Alloy on the Microstructure and Mechanical Properties of Hypereutectic Al–20%Si Alloy

PubMed Central

Ding, Wanwu; Xia, Tiandong; Zhao, Wenjun; Xu, Yangtao

2014-01-01

Al–5Ti–C master alloy was prepared and used to modify hypereutectic Al–20%Si alloy. The microstructure evolution and mechanical properties of hypereutectic Al–20%Si alloy with Al–5Ti–C master alloy additions (0, 0.4, 0.6, 1.0, 1.6 and 2.0 wt%) were investigated. The results show that, Al–5Ti–C master alloy (0.6 wt%, 10 min) can significantly refine both eutectic and primary Si of hypereutectic Al–20%Si alloy. The morphology of the primary Si crystals was significantly refined from a coarse polygonal and star-like shape to a fine polyhedral shape and the grain size of the primary Si was refined from roughly 90–120 μm to 20–50 μm. The eutectic Si phases were modified from a coarse platelet-like/needle-like structure to a fine fibrous structure with discrete particles. The Al–5Ti–C master alloy (0.6 wt%, 30 min) still has a good refinement effect. The ultimate tensile strength (UTS), elongation (El) and Brinell hardness (HB) of Al–20%Si alloy modified by the Al–5Ti–C master alloy (0.6 wt%, 10 min) increased by roughly 65%, 70% and 51%, respectively, due to decreasing the size and changing the morphology on the primary and eutectic Si crystals. The change in mechanical properties corresponds to evolution of the microstructure. PMID:28788509

Study on the Microstructure, Mechanical Properties and Corrosion Behavior of Mg-Zn-Ca Alloy Wire for Biomaterial Application

NASA Astrophysics Data System (ADS)

Zheng, Maobo; Xu, Guangquan; Liu, Debao; Zhao, Yue; Ning, Baoqun; Chen, Minfang

2018-03-01

Due to their excellent biocompatibility and biodegradability, magnesium alloy wires have attracted much attention for biomaterial applications including orthopedic K-wires and sutures in wound closure. In this study, Mg-3Zn-0.2Ca alloy wires were prepared by cold drawing combined with proper intermediate annealing process. Microstructures, texture, mechanical properties and corrosion behavior of Mg-3Zn-0.2Ca alloy wire in a simulated body fluid were investigated. The results showed that the secondary phase and average grain size of the Mg-3Zn-0.2Ca alloy were refined in comparison with the as-extruded alloy and a strong (0002)<10-10>//DD basal fiber texture system was formed after multi-pass cold drawing. After the annealing, most of the basal planes were tilted to the drawing direction (DD) by about 35°, presenting the characteristics of random texture, and the texture intensity decreased. The as-annealed wire shows good mechanical properties with the ultimate tensile strength (UTS), yield strength (YS) and elongation of 253 ± 8.5 MPa, 212 ± 11.3 MPa and 9.2 ± 0.9%, respectively. Electrochemical and hydrogen evolution measurements showed that the corrosion resistance of the Mg-3Zn-0.2Ca alloy wire was improved after the annealing. The immersion test indicated that the Mg-3Zn-0.2Ca wire exhibited uniform corrosion behavior during the initial period of immersion, but then exhibited local corrosion behavior.

Variation of the uniaxial tensile behavior of ultrafine-grained pure aluminum after cyclic pre-deformation

NASA Astrophysics Data System (ADS)

Yan, Ying; Chen, Li-jia; Zhang, Guo-qiang; Han, Dong; Li, Xiao-wu

2018-06-01

To explore the influence of cyclic pre-deformation on the mechanical behavior of ultrafine-grained (UFG) materials with a high stacking fault energy (SFE), UFG Al processed by equal-channel angular pressing (ECAP) was selected as a target material and its tensile behavior at different pre-cyclic levels D ( D = N i / N f, where N i and N f are the applied cycles and fatigue life at a constant stress amplitude of 50 MPa, respectively) along with the corresponding microstructures and deformation features were systematically studied. The cyclic pre-deformation treatment on the ECAPed UFG Al led to a decrease in flow stress, and a stress quasi-plateau stage was observed after yielding for all of the different-state UFG Al samples. The yield strength σ YS, ultimate tensile strength σ UTS, and uniform strain ɛ exhibited a strong dependence on D when D ≤ 20%; however, when D was in the range from 20% to 50%, no obvious change in mechanical properties was observed. The micro-mechanism for the effect of cyclic pre-deformation on the tensile properties of the ECAPed UFG Al was revealed and compared with that of ECAPed UFG Cu through the observations of deformation features and microstructures.

Mechanical behavior and failure mechanisms of Li-ion battery separators

DOE PAGES

Kalnaus, Sergiy; Wang, Yanli; Turner, John A.

2017-03-09

We determine and compare anisotropic mechanical properties for three types of commercially available Li-ion battery separators: Celgard 2325, Celgard PP2075 dry-processed polymer separators, and DreamWeaver Gold 40 non-woven separator. Significant amount of anisotropy of properties was determined, with the Young's modulus being different by up to a factor of 5 and ultimate strength being different by a factor of 10 between orthogonal directions within a polymer separator layer. Strain rate sensitivity was investigated by applying strain rates ranging from 1•10 -4 s -1 to 0.1 s -1. Significant strengthening was observed and the strain rate strengthening coefficients were determined formore » both elastic modulus and yield stress in case of polymer separators. Digital image correlation technique was used to measure and map the strains over the specimen's gage section. A significant strain concentration in bands running perpendicular to the tensile axis was observed in polymer separator samples oriented in transverse direction. Such localized necking allows for extremely high strains close to 300% to develop in the material. Furthermore, the failure mode was remarkably different for all three types of separators which adds additional variable in safe design of Li-ion batteries for prevention of internal short circuits.« less

Self-lubricating Al-WS2 composites for efficient and greener tribological parts.

PubMed

Niste, Vlad Bogdan; Ratoi, Monica; Tanaka, Hiroyoshi; Xu, Fang; Zhu, Yanqiu; Sugimura, Joichi

2017-11-07

Due to their mechanical and physical properties, aluminium alloys possess wide potential in the automotive industry, particularly in hot reciprocating applications such as pistons for diesel and petrol engines. WS 2 particle-reinforced composites could bring further improvements by reducing friction and wear between moving parts. Reducing friction improves efficiency by lowering energy/fuel use, ultimately leading to lower greenhouse gas emissions, while antiwear properties can prolong component life. This study compares for the first time the tribological performance of powder metallurgy-consolidated Al composites reinforced with either IF- or 2H-WS 2 particles, so as to elucidate their mechanism of action in test conditions similar to those encountered in engine applications. The composites were tested in lubricated reciprocating contacts against AISI52100 steel balls and the impact of WS 2 could be seen at both 25 and 100 °C. The reduced friction and wear at ambient temperature is due to the predominantly physical mechanism of action of WS 2 , while the best antiwear performance is measured at elevated (standard operating engine) temperatures that promote the chemical reaction of WS 2 with the aluminium matrix. The investigation focused on studying the wear tracks/scars and the tribofilms generated on the composite and ball with optical profilometry, SEM, XPS and Auger spectroscopy.

Development of a High-Strength Ultrafine-Grained Ferritic Steel Nanocomposite

NASA Astrophysics Data System (ADS)

Rahmanifard, Roohollah; Farhangi, Hasan; Novinrooz, Abdul Javad; Moniri, Samira

2013-02-01

This article describes the microstructural and mechanical properties of 12YWT oxide-dispersion-strengthened (ODS)-ferritic steel nanocomposite. According to the annealing results obtained from X-ray diffraction line profile analysis on mechanically alloyed powders milled for 80 hours, the hot extrusion at 1123 K (850 °C) resulted in a nearly equiaxed ultrafine structure with an ultimate tensile strength of 1470 MPa, yield strength of 1390 MPa, and total elongation of 13 pct at room temperature comparable with high-strength 14YWT ODS steel. Maximum total elongation was found at 973 K (600 °C) where fractography of the tensile specimen showed a fully ductile dimple feature compared with the splitting cracks and very fine dimpled structure observed at room temperature. The presence of very small particles on the wall of dimples at 1073 K (800 °C) with nearly chemical composition of the matrix alloy was attributed to the activation of the boundaries decohesion mechanism as a result of diffusion of solute atoms. The results of Charpy impact test also indicated significant improvement of transition temperature with respect to predecessor 12YWT because of the decreased grain size and more homogeneity of grain size distribution. Hence, this alloy represented a good compromise between the strength and Charpy impact properties.

Improving the fracture toughness and the strength of epoxy using nanomaterials--a review of the current status.

PubMed

Domun, N; Hadavinia, H; Zhang, T; Sainsbury, T; Liaghat, G H; Vahid, S

2015-06-21

The incorporation of nanomaterials in the polymer matrix is considered to be a highly effective technique to improve the mechanical properties of resins. In this paper the effects of the addition of different nanoparticles such as single-walled CNT (SWCNT), double-walled CNT (DWCNT), multi-walled CNT (MWCNT), graphene, nanoclay and nanosilica on fracture toughness, strength and stiffness of the epoxy matrix have been reviewed. The Young's modulus (E), ultimate tensile strength (UTS), mode I (GIC) and mode II (GIIC) fracture toughness of the various nanocomposites at different nanoparticle loadings are compared. The review shows that, depending on the type of nanoparticles, the integration of the nanoparticles has a substantial effect on mode I and mode II fracture toughness, strength and stiffness. The critical factors such as maintaining a homogeneous dispersion and good adhesion between the matrix and the nanoparticles are highlighted. The effect of surface functionalization, its relevancy and toughening mechanism are also scrutinized and discussed. A large variety of data comprised of the mechanical properties of nanomaterial toughened composites reported to date has thus been compiled to facilitate the evolution of this emerging field, and the results are presented in maps showing the effect of nanoparticle loading on mode I fracture toughness, stiffness and strength.

Dual Function of Glucosamine in Gelatin/Hyaluronic Acid Cryogel to Modulate Scaffold Mechanical Properties and to Maintain Chondrogenic Phenotype for Cartilage Tissue Engineering.

PubMed

Chen, Chih-Hao; Kuo, Chang-Yi; Wang, Yan-Jie; Chen, Jyh-Ping

2016-11-23

Glucosamine (GlcN) fulfills many of the requirements as an ideal component in scaffolds used in cartilage tissue engineering. The incorporation of GlcN in a gelatin/hyaluronic acid (GH) cryogel scaffold could provide biological cues in maintaining the phenotype of chondrocytes. Nonetheless, substituting gelatin with GlcN may also decrease the crosslinking density and modulate the mechanical properties of the cryogel scaffold, which may be beneficial as physical cues for chondrocytes in the scaffold. Thus, we prepared cryogel scaffolds containing 9% GlcN (GH-GlcN9) and 16% GlcN (GH-GlcN16) by carbodiimide-mediated crosslinking reactions at -16 °C. The crosslinking density and the mechanical properties of the cryogel matrix could be tuned by adjusting the content of GlcN used during cryogel preparation. In general, incorporation of GlcN did not influence scaffold pore size and ultimate compressive strain but increased porosity. The GH-GlcN16 cryogel showed the highest swelling ratio and degradation rate in hyaluronidase and collagenase solutions. On the contrary, the Young's modulus, storage modulus, ultimate compressive stress, energy dissipation level, and rate of stress relaxation decreased by increasing the GlcN content in the cryogel. The release of GlcN from the scaffolds in the culture medium of chondrocytes could be sustained for 21 days for GH-GlcN16 in contrast to only 7 days for GH-GlcN9. In vitro cell culture experiments using rabbit articular chondrocytes revealed that GlcN incorporation affected cell proliferation, morphology, and maintenance of chondrogenic phenotype. Overall, GH-GlcN16 showed the best performance in maintaining chondrogenic phenotype with reduced cell proliferation rate but enhanced glycosaminoglycans (GAGs) and type II collagen (COL II) secretion. Quantitative real-time polymerase chain reaction also showed time-dependent up-regulation of cartilage-specific marker genes (COL II, aggrecan and Sox9) for GH-GlcN16. Implantation of chondrocytes/GH-GlcN16 constructs into full-thickness articular cartilage defects of rabbits could regenerate neocartilage with positive staining for GAGs and COL II. The GH-GlcN16 cryogel will be suitable as a scaffold for the treatment of articular cartilage defects.

Layer-by-layer assembly of nanostructured composites: Mechanics and applications

NASA Astrophysics Data System (ADS)

Podsiadlo, Paul

The development of efficient methods for preparation of nanometer-sized materials and our evolving ability to manipulate the nanoscale objects have brought about a scientific and technological revolution called: nanotechnology. This revolution has been especially driven by discovery of unique nanoscale properties of the nanomaterials which are governed by their inherent size. Today, the total societal impact of nanotechnology is expected to be greater than the combined influences that the silicon integrated circuit, medical imaging, computer-aided engineering, and man-made polymers have had in the last century. Many nanomaterials were also found to possess exceptional mechanical properties. This led to tremendous interest into developing composite materials by exploiting the mechanical properties of these building blocks. In spite of a tremendous volume of work done in the field, preparation of such nanocomposites (NCs) has proven to be elusive due to inability of traditional "top-down" fabrication approaches to effectively harness properties of the nano-scale building blocks. This thesis focuses on preparation of organic/inorganic and solely organic NCs via a bottom-up nano-manufacturing approach called the layer-by-layer (LBL) assembly. Two natural and inexpensive nanoscale building blocks are explored: nanosheets of Na+-montmorillonite clay (MTM) and rod-shaped nanocrystals of cellulose (CNRs). In the first part of the thesis, we present results from systematic study of mechanics of MTM-based NCs. Different compositions are explored with a goal of understanding the nanoscale mechanics. Ultimately, development of a transparent composite with record-high strength and stiffness is presented. In the second part, we present results from LBL assembly of the CNRs. We demonstrate feasibility of assembly and mechanical properties of the resulting films. We also demonstrate preparation of LBL films with anti- reflective properties from tunicate (a sea animal) CNRs. In the final part, we show preparation of high toughness and hierarchically organized NCs using two concepts: "exponential" LBL (e-LBL) assembly and charged polyurethanes. We show preparation of novel e-LBL structures and highly flexible LBL multilayers. We also demonstrate preparation of macro-scale composites from hierarchical, post-assembly consolidation of LBL sheets. This last result represents a potential paradigm change in the practice of LBL assembly by enabling transformation of the thin-films into macro-scale structures.

Otto LaPorte Lecture: Ultimate Rayleigh-Bénard and Taylor-Couette turbulence

NASA Astrophysics Data System (ADS)

Lohse, Detlef

2017-11-01

Rayleigh-Bénard flow - the flow in a box heated from below and cooled from above - and Taylor-Couette flow - the flow between two coaxial co- or counter-rotating cylinders - are the two paradigmatic systems in physics of fluids and many new concepts have been tested with them. They are mathematically well defined, namely by the Navier-Stokes equations and the respective boundary conditions, and share many features. While the low Reynolds number regime (i.e., weakly driven systems) has been very well explored in the '80s and '90s of the last century, in the fully turbulent regime major research activity only developed in the last two decades. In this talk we will first briefly review this recent progress in our understanding of fully developed Rayleigh-Bénard (RB) and Taylor-Couette (TC) turbulence, from the experimental, theoretical, and numerical point of view. We will explain the parameter dependences of the global transport properties of the flow and the local flow organisation, including velocity profiles and boundary layers, which are closely connected to the global properties. Next, we will discuss transitions between different (turbulent) flow states. We will in particular focus on the so-called ultimate regime, in which the boundary layer has become turbulent, and which therefore has enhanced transport properties. In the mechanical driven TC flow this ultimate regime can also be achieved in our high-performance numerical simulations, showing excellent agreement with our experiments on the Twente Turbulent Taylor-Couette (T3 C) facility. In the last part of the talk we will discuss RB and TC turbulence with rough walls. There the results can be expressed in terms of the skin-friction factor, revealing analogy to turbulent flow in rough pipes. Finally, we will present our results on RB and TC flow with bubbles, focusing on bubbly drag reduction and its origin. This is joint work with many colleagues over the years, and I in particular would like to name Chao Sun, Roberto Verzicco, Siegfried Grossmann, Richard Stevens, Erwin van der Poel, Rodolfo Ostilla-Monico, Xiaojue Zhu, Dennis van Gils, Sander Huisman, Ruben Verschoof, and Gert-Wim Bruggert.

Uniaxial Tensile Properties of Atherosclerotic Carotid Artery After Mobilization of Pushing on Qiao-Gong: A Safety Study Using an Animal Model of Carotid Atherosclerosis.

PubMed

Qi, Ji; Zhang, Shaoqun; Zhang, Lei; Ping, Ruiyue; Ping, Kaike; Ye, Da; Shen, Honggui; Chen, Yili; Li, Yikai

2018-02-01

This study aimed to preliminarily explore the effects of the soft tissue mobilization of pushing on Qiao-Gong (MPQ) on biomechanical properties of the carotid artery using an animal model of carotid atherosclerosis (CAS). Fifty rabbits were randomly divided into 4 groups: animals with CAS treated with MPQ (CAS-MPQ [n = 15]); animals with CAS treated without MPQ (CAS [n = 15]); normal animals treated with MPQ (normal-MPQ [n = 10]); and a blank control group (n = 10). The MPQ procedure consisted of soft tissue mobilization of the Qiao-Gong acupoint on the front edge of the sternocleidomastoid muscle applied from top to bottom, by flat pushing with the thumb repeatedly for 20 times. Disease in the CAS models was induced by carotid artery balloon injury combined with a high-fat diet for 12 weeks. At the end of modeling, carotid color Doppler ultrasonography examination was performed to confirm which animal models were successfully induced with CAS, excluding model rabbits without typical CAS at the same time. Then, MPQ was applied on rabbits in the CAS-MPQ and the normal-MPQ groups for 3 weeks. By contrast, rabbits in the other 2 groups were fed normally without MPQ. Uniaxial failure tests were later performed on carotid arteries in all 4 groups, and at the end of the study, a 2-way factorial analysis of variance of the results was conducted. (1) At the end of modeling, 10 rabbits in the CAS-MPQ group and 9 in the CAS group were included with typical carotid atherosclerotic characteristics. (2) Young's elastic modulus of the rabbit carotid artery increased more significantly in the CAS-MPQ group than the CAS group. (3) Compared with normal rabbit carotid arteries, atherosclerotic carotid arteries had lower levels of ultimate stress and ultimate strain but higher levels of ultimate load. The uniaxial tensile mechanical properties of the rabbit atherosclerotic carotid artery were impaired after MPQ. Copyright © 2018. Published by Elsevier Inc.

Size effects on elasticity, yielding, and fracture of silver nanowires: In situ experiments

NASA Astrophysics Data System (ADS)

Zhu, Yong; Qin, Qingquan; Xu, Feng; Fan, Fengru; Ding, Yong; Zhang, Tim; Wiley, Benjamin J.; Wang, Zhong Lin

2012-01-01

This paper reports the quantitative measurement of a full spectrum of mechanical properties of fivefold twinned silver (Ag) nanowires (NWs), including Young's modulus, yield strength, and ultimate tensile strength. In-situ tensile testing of Ag NWs with diameters between 34 and 130 nm was carried out inside a scanning electron microscope (SEM). Young's modulus, yield strength, and ultimate tensile strength all increased as the NW diameter decreased. The maximum yield strength in our tests was found to be 2.64 GPa, which is about 50 times the bulk value and close to the theoretical value of Ag in the 110 orientation. The size effect in the yield strength is mainly due to the stiffening size effect in the Young's modulus. Yield strain scales reasonably well with the NW surface area, which reveals that yielding of Ag NWs is due to dislocation nucleation from surface sources. Pronounced strain hardening was observed for most NWs in our study. The strain hardening, which has not previously been reported for NWs, is mainly attributed to the presence of internal twin boundaries.

Tensile Property of ANSI 304 Stainless Steel Weldments Subjected to Cavitation Erosion Based on Treatment of Laser Shock Processing.

PubMed

Zhang, Lei; Liu, Yue-Hua; Luo, Kai-Yu; Zhang, Yong-Kang; Zhao, Yong; Huang, Jian-Yun; Wu, Xu-Dong; Zhou, Chuang

2018-05-16

Tensile property was one important index of mechanical properties of ANSI 304 stainless steel laser weldments subjected to cavitation erosion (CE). Laser shock processing (LSP) was utilized to strengthen the CE resistance, and the tensile property and fracture morphology were analyzed through three replicated experiment times. Results showed tensile process of treated weldments was composed of elastic deformation, plastic deformation, and fracture. The elastic limit, elastic modulus, elongation, area reduction, and ultimate tensile strength of tensile sample after CE were higher in view of LSP. In the fracture surface, the fiber zone, radiation zone and shear lip zone were generated, and those were more obvious through LSP. The number and size of pores in the fracture surface were smaller, and the fracture surface was smoother and more uniform. The dimples were elongated along the unified direction due to effects of LSP, and the elongated direction was in agreement with the crack propagation direction. Their distribution and shape were uniform with deeper depth. It could be reflected that the tensile property was improved by LSP and the CE resistance was also enhanced.

Tensile Property of ANSI 304 Stainless Steel Weldments Subjected to Cavitation Erosion Based on Treatment of Laser Shock Processing

PubMed Central

Zhang, Lei; Liu, Yue-Hua; Luo, Kai-Yu; Zhang, Yong-Kang; Zhao, Yong; Huang, Jian-Yun; Wu, Xu-Dong; Zhou, Chuang

2018-01-01

Tensile property was one important index of mechanical properties of ANSI 304 stainless steel laser weldments subjected to cavitation erosion (CE). Laser shock processing (LSP) was utilized to strengthen the CE resistance, and the tensile property and fracture morphology were analyzed through three replicated experiment times. Results showed tensile process of treated weldments was composed of elastic deformation, plastic deformation, and fracture. The elastic limit, elastic modulus, elongation, area reduction, and ultimate tensile strength of tensile sample after CE were higher in view of LSP. In the fracture surface, the fiber zone, radiation zone and shear lip zone were generated, and those were more obvious through LSP. The number and size of pores in the fracture surface were smaller, and the fracture surface was smoother and more uniform. The dimples were elongated along the unified direction due to effects of LSP, and the elongated direction was in agreement with the crack propagation direction. Their distribution and shape were uniform with deeper depth. It could be reflected that the tensile property was improved by LSP and the CE resistance was also enhanced. PMID:29772661

Assessment of the ``cross-bridge''-induced interaction of red blood cells by optical trapping combined with microfluidics

NASA Astrophysics Data System (ADS)

Lee, Kisung; Wagner, Christian; Priezzhev, Alexander V.

2017-09-01

Red blood cell (RBC) aggregation is an intrinsic property of the blood that has a direct effect on the blood viscosity and circulation. Nevertheless, the mechanism behind the RBC aggregation has not been confirmed and is still under investigation with two major hypotheses, known as "depletion layer" and "cross-bridging." We aim to ultimately understand the mechanism of the RBC aggregation and clarify both models. To measure the cell interaction in vitro in different suspensions (including plasma, isotonic solution of fibrinogen, isotonic solution of fibrinogen with albumin, and phosphate buffer saline) while moving the aggregate from one solution to another, an approach combining optical trapping and microfluidics has been applied. The study reveals evidence that RBC aggregation in plasma is at least partly due to the cross-bridging mechanism. The cell interaction strength measured in the final solution was found to be significantly changed depending on the initial solution where the aggregate was formed.

Effects of helium implantation on the tensile properties and microstructure of Ni₇₃P₂₇ metallic glass nanostructures

DOE PAGES

Liontas, Rachel; Gu, X. Wendy; Fu, Engang; ...

2014-09-10

We report fabrication and nanomechanical tension experiments on as-fabricated and helium-implanted ~130 nm diameter Ni₇₃P₂₇ metallic glass nano-cylinders. The nano-cylinders were fabricated by a templated electroplating process and implanted with He⁺ at energies of 50, 100, 150, and 200 keV to create a uniform helium concentration of ~3 at. % throughout the nano-cylinders. Transmission electron microscopy (TEM) imaging and through-focus analysis reveal that the specimens contained ~2 nm helium bubbles distributed uniformly throughout the nano-cylinder volume. In-situ tensile experiments indicate that helium-implanted specimens exhibit enhanced ductility as evidenced by a 2-fold increase in plastic strain over as-fabricated specimens, with nomore » sacrifice in yield and ultimate tensile strengths. This improvement in mechanical properties suggests that metallic glasses may actually exhibit a favorable response to high levels of helium implantation.« less