Science.gov

Sample records for adjustable mechanical properties

  1. 3D printed auxetic forms on knitted fabrics for adjustable permeability and mechanical properties

    NASA Astrophysics Data System (ADS)

    Grimmelsmann, N.; Meissner, H.; Ehrmann, A.

    2016-07-01

    The 3D printing technology can be applied into manufacturing primary shaping diverse products, from models dealing as examples for future products that will be produced with another technique, to useful objects. Since 3D printing is nowadays significantly slower than other possibilities to manufacture items, such as die casting, it is often used for small parts that are produced in small numbers or for products that cannot be created in another way. Combinations of 3D printing with other objects, adding novel functionalities to them, are thus favourable to a complete primary shaping process. Textile fabrics belong to the objects whose mechanical and other properties can notably be modified by adding 3D printed forms. This article mainly reports on a new possibility to change the permeability of textile fabrics by 3D printing auxetic forms, e.g. for utilising them in textile filters. In addition, auxetic forms 3D printed on knitted fabrics can bring about mechanical properties that are conducive to tensile constructions.

  2. Kinematic synthesis of adjustable robotic mechanisms

    NASA Astrophysics Data System (ADS)

    Chuenchom, Thatchai

    1993-01-01

    Conventional hard automation, such as a linkage-based or a cam-driven system, provides high speed capability and repeatability but not the flexibility required in many industrial applications. The conventional mechanisms, that are typically single-degree-of-freedom systems, are being increasingly replaced by multi-degree-of-freedom multi-actuators driven by logic controllers. Although this new trend in sophistication provides greatly enhanced flexibility, there are many instances where the flexibility needs are exaggerated and the associated complexity is unnecessary. Traditional mechanism-based hard automation, on the other hand, neither can fulfill multi-task requirements nor are cost-effective mainly due to lack of methods and tools to design-in flexibility. This dissertation attempts to bridge this technological gap by developing Adjustable Robotic Mechanisms (ARM's) or 'programmable mechanisms' as a middle ground between high speed hard automation and expensive serial jointed-arm robots. This research introduces the concept of adjustable robotic mechanisms towards cost-effective manufacturing automation. A generalized analytical synthesis technique has been developed to support the computational design of ARM's that lays the theoretical foundation for synthesis of adjustable mechanisms. The synthesis method developed in this dissertation, called generalized adjustable dyad and triad synthesis, advances the well-known Burmester theory in kinematics to a new level. While this method provides planar solutions, a novel patented scheme is utilized for converting prescribed three-dimensional motion specifications into sets of planar projections. This provides an analytical and a computational tool for designing adjustable mechanisms that satisfy multiple sets of three-dimensional motion specifications. Several design issues were addressed, including adjustable parameter identification, branching defect, and mechanical errors. An efficient mathematical scheme for

  3. On feedback and stable price adjustment mechanisms

    NASA Astrophysics Data System (ADS)

    Fernandez-Anaya, Guillermo; Alvarez-Ramirez, Jose; Ibarra-Valdez, Carlos

    2007-04-01

    Given an excess demand function of an economy, say Z(p), a stable price adjustment mechanism (SPAM) guarantees convergence of solution path p(t,p0) to an equilibrium peq solution of Z(p)=0. Besides, all equilibrium points of Z(p) are asymptotically stable. Some SPAMs have been proposed, including Newton and transpose Jacobian methods. Despite this powerful stability property of SPAMs, their acceptation in the economics community has been limited by a lack of interpretation. This paper focuses on this issue. Specifically, feedback control theory is used to link SPAMs and price dynamics models with control inputs, which match the economically intuitive Walrasian Hypothesis (i.e., prices change with excess demand sign). Under mild conditions, it is shown the existence of a feedback function that transforms the price dynamics into a desired SPAM. Hence, a SPAM is interpreted as a fundamental (e.g., Walrasian) price dynamics under the action of a feedback function aimed to stabilize the equilibrium set of the excess demand function.

  4. Defense mechanisms and psychological adjustment in childhood.

    PubMed

    Sandstrom, Marlene J; Cramer, Phebe

    2003-08-01

    The association between maturity of defense use and psychological functioning was assessed in a group of 95 elementary school children. Defense mechanisms were measured using a valid and reliable storytelling task, and psychological adjustment was assessed through a combination of parent and self-report questionnaires. Correlational analyses indicated that children who relied on the developmentally immature defense of denial reported higher levels of self-rated social anxiety and depression and received higher ratings of parent-reported internalizing and externalizing behavior problems. However, children who made use of the developmentally mature defense of identification exhibited higher scores on perceived competence in social, academic, conduct, athletic, and global domains. Significantly, there was no relationship between children's use of denial and their level of perceived competence or between children's use of identification and their degree of maladjustment.

  5. A membrane-type acoustic metamaterial with adjustable acoustic properties

    NASA Astrophysics Data System (ADS)

    Langfeldt, F.; Riecken, J.; Gleine, W.; von Estorff, O.

    2016-07-01

    A new realization of a membrane-type acoustic metamaterial (MAM) with adjustable sound transmission properties is presented. The proposed design distinguishes itself from other realizations by a stacked arrangement of two MAMs which is inflated using pressurized air. The static pressurization leads to large nonlinear deformations and, consequently, geometrical stiffening of the MAMs which is exploited to adjust the eigenmodes and sound transmission loss of the structure. A theoretical analysis of the proposed inflatable MAM design using numerical and analytical models is performed in order to identify two important mechanisms, namely the shifting of the eigenfrequencies and modal residuals due to the pressurization, responsible for the transmission loss adjustment. Analytical formulas are provided for predicting the eigenmode shifting and normal incidence sound transmission loss of inflated single and double MAMs using the concept of effective mass. The investigations are concluded with results from a test sample measurement inside an impedance tube, which confirm the theoretical predictions.

  6. 47 CFR 69.731 - Low-end adjustment mechanism.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 3 2010-10-01 2010-10-01 false Low-end adjustment mechanism. 69.731 Section 69.731 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER SERVICES (CONTINUED) ACCESS CHARGES Pricing Flexibility § 69.731 Low-end adjustment mechanism. (a) Any price cap LEC...

  7. Mechanical Properties of Polymers.

    ERIC Educational Resources Information Center

    Aklonis, J. J.

    1981-01-01

    Mechanical properties (stress-strain relationships) of polymers are reviewed, taking into account both time and temperature factors. Topics include modulus-temperature behavior of polymers, time dependence, time-temperature correspondence, and mechanical models. (JN)

  8. Mechanism For Adjustment Of Commutation Of Brushless Motor

    NASA Technical Reports Server (NTRS)

    Schaefer, Richard E.

    1995-01-01

    Mechanism enables adjustment of angular position of set of Hall-effect devices that sense instantaneous shaft angle of brushless dc motor. Outputs of sensors fed to commutation circuitry. Measurement of shaft angle essential for commutation; that is, application of voltage to stator windings must be synchronized with shaft angle. To obtain correct angle measurement for commutation, Hall-effect angle sensors positioned at proper reference angle. The present mechanism accelerates adjustment procedure and makes it possible to obtain more accurate indication of minimum-current position because it provides for adjustment while motor running.

  9. Mechanical properties of viruses.

    PubMed

    de Pablo, Pedro J; Mateu, Mauricio G

    2013-01-01

    Structural biology techniques have greatly contributed to unveil the relationships between structure, properties and functions of viruses. In recent years, classic structural approaches are being complemented by single-molecule techniques such as atomic force microscopy and optical tweezers to study physical properties and functions of viral particles that are not accessible to classic structural techniques. Among these features are mechanical properties such as stiffness, intrinsic elasticity, tensile strength and material fatigue. The field of virus mechanics is contributing to materials science by investigating some physical parameters of "soft" biological matter and biological nano-objects. Virus mechanics studies are also starting to unveil the biological implications of physical properties of viruses. Growing evidence indicate that viruses are subjected to internal and external forces, and that they may have adapted to withstand and even use those forces. This chapter describes what is known on the mechanical properties of virus particles, their structural determinants, and possible biological implications, of which several examples are provided.

  10. Novel biodegradable calcium phosphate/polymer composite coating with adjustable mechanical properties formed by hydrothermal process for corrosion protection of magnesium substrate.

    PubMed

    Kaabi Falahieh Asl, Sara; Nemeth, Sandor; Tan, Ming Jen

    2016-11-01

    Ceramic type coatings on metallic implants, such as calcium phosphate (Ca-P), are generally stiff and brittle, potentially leading to the early failure of the bone-implant interface. To reduce material brittleness, polyacrylic acid and carboxymethyl cellulose were used in this study to deposit two types of novel Ca-P/polymer composite coatings on AZ31 magnesium alloy using a one-step hydrothermal process. X-ray diffraction and scanning electron microscopy showed that the deposited Ca-P crystal phase and morphology could be controlled by the type and concentration of polymer used. Incorporation of polymer in the Ca-P coatings reduced the coating elastic modulus bringing it close to that of magnesium and that of human bone. Nanoindentation test results revealed significantly decreased cracking tendency with the incorporation of polymer in the Ca-P coating. Apart from mechanical improvements, the protective composite layers had also enhanced the corrosion resistance of the substrate by a factor of 1000 which is sufficient for implant application. Cell proliferation studies indicated that the composite coatings induced better cell attachment compared with the purely inorganic Ca-P coating, confirming that the obtained composite materials could be promising candidates for surface protection of magnesium for implant application with the multiple functions of corrosion protection, interfacial stress reduction, and cell attachment/cell growth promotion. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 1643-1657, 2016.

  11. Psychometric properties of the index of relocation adjustment.

    PubMed

    Bekhet, Abir K; Zauszniewski, Jaclene A

    2014-06-01

    More and more American older adults are relocating to retirement communities, and they experience challenges in adjusting to new surroundings that may increase their depression and mortality. An instrument not previously tested in the United States, the Index of Relocation Adjustment (IRA), may help in early identification of poor relocation adjustment. This study examined the psychometric properties of the IRA using secondary data from a convenience sample of 104 older adults who relocated to 6 retirement communities in Northeast Ohio. Cronbach's alpha was .86. The IRA was correlated with measures of positive cognitions (r = .48, p < .01) and relocation controllability (r = -.62, p < .01), suggesting construct validity. Results indicated a single factor reflecting relocation adjustment with loadings for all items ranging from .62 to .83. The IRA is potentially useful as a screening measure for early detection of poor adjustment among relocated older adults.

  12. 47 CFR 69.731 - Low-end adjustment mechanism.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...) ACCESS CHARGES Pricing Flexibility § 69.731 Low-end adjustment mechanism. (a) Any price cap LEC obtaining Phase I or Phase II pricing flexibility for any service in any MSA in its service region, or for the non... affiliate of any price cap LEC obtaining Phase I or Phase II pricing flexibility for any service in any...

  13. 47 CFR 69.731 - Low-end adjustment mechanism.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ...) ACCESS CHARGES Pricing Flexibility § 69.731 Low-end adjustment mechanism. (a) Any price cap LEC obtaining Phase I or Phase II pricing flexibility for any service in any MSA in its service region, or for the non... affiliate of any price cap LEC obtaining Phase I or Phase II pricing flexibility for any service in any...

  14. 47 CFR 69.731 - Low-end adjustment mechanism.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ...) ACCESS CHARGES Pricing Flexibility § 69.731 Low-end adjustment mechanism. (a) Any price cap LEC obtaining Phase I or Phase II pricing flexibility for any service in any MSA in its service region, or for the non... affiliate of any price cap LEC obtaining Phase I or Phase II pricing flexibility for any service in any...

  15. 47 CFR 69.731 - Low-end adjustment mechanism.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...) ACCESS CHARGES Pricing Flexibility § 69.731 Low-end adjustment mechanism. (a) Any price cap LEC obtaining Phase I or Phase II pricing flexibility for any service in any MSA in its service region, or for the non... affiliate of any price cap LEC obtaining Phase I or Phase II pricing flexibility for any service in any...

  16. Defense mechanisms in adolescent conduct disorder and adjustment reaction.

    PubMed

    Cramer, Phebe; Kelly, Francis D

    2004-02-01

    The use of defense mechanisms by male and female adolescents with a diagnosis of conduct disorder was compared with the defense use of adolescents with a diagnosis of adjustment reaction. Because conduct disorder has been shown to be associated with a developmental lag in several areas of psychological functioning, we expected that these adolescents would show immaturity in the use of defenses. This expectation was confirmed. As compared with adjustment reaction, conduct disordered youths were more likely to use the immature defense of denial and less likely to use the mature defense of identification.

  17. An impossibility theorem for price-adjustment mechanisms

    PubMed Central

    Papadimitriou, Christos H.; Yannakakis, Mihalis

    2010-01-01

    We show that there is no discrete-time price-adjustment mechanism (any process that at each period looks at the history of prices and excess demands and updates the prices) such that for any market (a set of goods and consumers with endowments and strictly concave utilities) the price-adjustment mechanism will achieve excess demands that are at most an ϵ fraction of the total supply within a number of periods that is polynomial in the number of goods and . This holds even if one restricts markets so that excess demand functions are differentiable with derivatives bounded by a small constant. For the convergence time to the actual price equilibrium, we show by a different method a stronger result: Even in the case of three goods with a unique price equilibrium, there is no function of ϵ that bounds the number of periods needed by a price-adjustment mechanism to arrive at a set of prices that is ϵ-close to the equilibrium. PMID:20133833

  18. Mechanical Properties of Cells

    NASA Technical Reports Server (NTRS)

    Bradley, Robert; Becerril, Joseph; Jeevarajan, Anthony

    2007-01-01

    Many physiologic and pathologic processes alter the biomechanical properties of the tissue they affect, and these changes may be manifest at the single cell level. The normal and abnormal mechanical properties of a given cell type can be established with the aid of an atomic force microscope (AFM), nonetheless, consistency in the area of the tip has been a mayor limitation of using the AFM for quantitative measurements of mechanical properties. This project attempts to overcome this limitation by using materials with a known elastic modulus, which resembles the one of the cell, to create force-deformation curves to calculate the area of indentation by means of Hooke s Law (sigma = E(epsilon)), which states that stress (sigma) is proportional to the strain (epsilon) where the constant of proportionality, E, is called the Young s modulus, also referred as the elastic modulus. Hook s Law can be rearranged to find the area of indentation (Area= Force/ E(epsilon)), where the indentation force is defined by the means of the added mass spring calibration method.

  19. Mechanical Properties of Aerogels

    NASA Technical Reports Server (NTRS)

    Parmenter, Kelly E.; Milstein, Frederick

    1995-01-01

    Aerogels are extremely low density solids that are characterized by a high porosity and pore sizes on the order of nanometers. Their low thermal conductivity and sometimes transparent appearance make them desirable for applications such as insulation in cryogenic vessels and between double paned glass in solar architecture. An understanding of the mechanical properties of aerogels is necessary before aerogels can be used in load bearing applications. In the present study, the mechanical behavior of various types of fiber-reinforced silica aerogels was investigated with hardness, compression, tension and shear tests. Particular attention was paid to the effects of processing parameters, testing conditions, storage environment, and age on the aerogels' mechanical response. The results indicate that the addition of fibers to the aerogel matrix generally resulted in softer, weaker materials with smaller elastic moduli. Furthermore, the testing environment significantly affected compression results. Tests in ethanol show an appreciable amount of scatter, and are not consistent with results for tests in air. In fact, the compression specimens appeared to crack and begin to dissolve upon exposure to the ethanol solution. This is consistent with the inherent hydrophobic nature of these aerogels. In addition, the aging process affected the aerogels' mechanical behavior by increasing their compressive strength and elastic moduli while decreasing their strain at fracture. However, desiccation of the specimens did not appreciably affect the mechanical properties, even though it reduced the aerogel density by removing trapped moisture. Finally, tension and shear test results indicate that the shear strength of the aerogels exceeds the tensile strength. This is consistent with the response of brittle materials. Future work should concentrate on mechanical testing at cryogenic temperatures, and should involve more extensive tensile tests. Moreover, before the mechanical response

  20. Demographic mechanisms of inbreeding adjustment through extra-pair reproduction

    PubMed Central

    Reid, Jane M; Duthie, A Bradley; Wolak, Matthew E; Arcese, Peter; van de Pol, Martijn

    2015-01-01

    One hypothesis explaining extra-pair reproduction is that socially monogamous females mate with extra-pair males to adjust the coefficient of inbreeding (f) of extra-pair offspring (EPO) relative to that of within-pair offspring (WPO) they would produce with their socially paired male. Such adjustment of offspring f requires non-random extra-pair reproduction with respect to relatedness, which is in turn often assumed to require some mechanism of explicit pre-copulatory or post-copulatory kin discrimination. We propose three demographic processes that could potentially cause mean f to differ between individual females’ EPO and WPO given random extra-pair reproduction with available males without necessarily requiring explicit kin discrimination. Specifically, such a difference could arise if social pairings formed non-randomly with respect to relatedness or persisted non-randomly with respect to relatedness, or if the distribution of relatedness between females and their sets of potential mates changed during the period through which social pairings persisted. We used comprehensive pedigree and pairing data from free-living song sparrows (Melospiza melodia) to quantify these three processes and hence investigate how individual females could adjust mean offspring f through instantaneously random extra-pair reproduction. Female song sparrows tended to form social pairings with unrelated or distantly related males slightly less frequently than expected given random pairing within the defined set of available males. Furthermore, social pairings between more closely related mates tended to be more likely to persist across years than social pairings between less closely related mates. However, these effects were small and the mean relatedness between females and their sets of potential extra-pair males did not change substantially across the years through which social pairings persisted. Our framework and analyses illustrate how demographic and social structuring

  1. Demographic mechanisms of inbreeding adjustment through extra-pair reproduction.

    PubMed

    Reid, Jane M; Duthie, A Bradley; Wolak, Matthew E; Arcese, Peter

    2015-07-01

    One hypothesis explaining extra-pair reproduction is that socially monogamous females mate with extra-pair males to adjust the coefficient of inbreeding (f) of extra-pair offspring (EPO) relative to that of within-pair offspring (WPO) they would produce with their socially paired male. Such adjustment of offspring f requires non-random extra-pair reproduction with respect to relatedness, which is in turn often assumed to require some mechanism of explicit pre-copulatory or post-copulatory kin discrimination. We propose three demographic processes that could potentially cause mean f to differ between individual females' EPO and WPO given random extra-pair reproduction with available males without necessarily requiring explicit kin discrimination. Specifically, such a difference could arise if social pairings formed non-randomly with respect to relatedness or persisted non-randomly with respect to relatedness, or if the distribution of relatedness between females and their sets of potential mates changed during the period through which social pairings persisted. We used comprehensive pedigree and pairing data from free-living song sparrows (Melospiza melodia) to quantify these three processes and hence investigate how individual females could adjust mean offspring f through instantaneously random extra-pair reproduction. Female song sparrows tended to form social pairings with unrelated or distantly related males slightly less frequently than expected given random pairing within the defined set of available males. Furthermore, social pairings between more closely related mates tended to be more likely to persist across years than social pairings between less closely related mates. However, these effects were small and the mean relatedness between females and their sets of potential extra-pair males did not change substantially across the years through which social pairings persisted. Our framework and analyses illustrate how demographic and social structuring within

  2. A Boresight Adjustment Mechanism for use on Laser Altimeters

    NASA Technical Reports Server (NTRS)

    Hakun, Claef; Budinoff, Jason; Brown, Gary; Parong, Fil; Morell, Armando

    2004-01-01

    This paper describes the development of the Boresight Adjustment Mechanism (BAM) for the Geoscience Laser Altimeter System (GLAS) Instrument. The BAM was developed late in the integration and test phase of the GLAS instrument flight program. Thermal vacuum tests of the GLAS instrument indicated that the instrument boresight alignment stability over temperature may be marginal. To reduce the risk that GLAS may not be able to meet the boresight alignment requirements, an intensive effort was started to develop a BAM. Observatory-level testing and further evaluation of the boresight alignment data indicated that sufficient margin could be obtained utilizing existing instrument resources and therefore the BAM was never integrated onto the GLAS Instrument. However, the BAM was designed fabricated and fully qualified over a 4 month timeframe to be capable of precisely steering (< 1 arcsec over 300 arcsec) the output of three independent lasers to ensure the alignment between the transmit and receive paths of the GLAS instrument. The short timeline for the development of the mechanism resulted in several interesting design solutions. This paper discusses the requirement definition, design, and testing processes of the BAM development effort, how the design was affected by the extremely tight development schedule, and the lessons learned throughout the process.

  3. Mechanical Properties of MEMS Materials

    DTIC Science & Technology

    2004-03-01

    thermal strain for polysilicon (data points) compared with bulk silicon (Thermophysical Properties of Matter, Volume 13, Y. S. Touloukian , Editor...AFRL-IF-RS-TR-2004-76 Final Technical Report March 2004 MECHANICAL PROPERTIES OF MEMS MATERIALS Johns Hopkins University...TITLE AND SUBTITLE MECHANICAL PROPERTIES OF MEMS MATERIALS 6. AUTHOR(S) W. N. Sharpe, Jr., K. J. Hemker - Dept of Mechanical Engineering R. L

  4. Generating apparatus with an adjustable speed change mechanism

    SciTech Connect

    Kaneyuki, K.

    1987-03-17

    A generating apparatus is described comprising: a charging generator having a rotating input shaft; a rotating input body adapted to be connected to a motor so as to be rotated thereby, the rotating input body comprising a cylindrical body surrounding the input shaft; an adjustable speed change mechanism comprising a planetary cone reduction gear housed within the rotating input body and operatively associated with the rotating input body and the input shaft of the charging generator so as to transmit rotational force from the rotating input body to the input shaft. The planetary cone reduction gear comprises: a cone support ring mounted on the input shaft and adapted to rotate with respect thereto, a plurality of planetary cones having stems which are rotatably mounted on the cone support ring, the axis of each of the planetary cones being disposed such that a line which is parallel to the input shaft can be drawn from the vertex of each cone to its base along its top surface, a stationary guide ring which surrounds the input shaft and frictionally engages the peripheral surfaces of the stems of the planetary cones, a speed change ring surrounding the input shaft and having an inner surface frictionally engaging the top surfaces of the planetary cones. The speed change ring is supported by the rotating input body so as to rotate together with the input body and adapted to move in the axial direction of the input body with respect thereto.

  5. Study on Posture Adjusting System of Spacecraft Based on Stewart Mechanism

    NASA Astrophysics Data System (ADS)

    Gao, Feng; Feng, Wei; Dai, Wei-Bing; Yi, Wang-Min; Liu, Guang-Tong; Zheng, Sheng-Yu

    In this paper, the design principles of adjusting parallel mechanisms is introduced, including mechanical subsystem, control sub-system and software sub-system. According to the design principles, key technologies for system of adjusting parallel mechanisms are analyzed. Finally, design specifications for system of adjusting parallel mechanisms are proposed based on requirement of spacecraft integration and it can apply to cabin docking, solar array panel docking and camera docking.

  6. Apparatus for a compact adjustable passive compliant mechanism

    DOEpatents

    Salisbury, Curt Michael

    2015-03-17

    Various technologies described herein pertain to an adjustable compliance apparatus. The adjustable compliance apparatus includes a shaft, a sleeve element, and a torsion spring. The sleeve element includes a bore there through, where the shaft is positioned through the bore of the sleeve element. Further, the torsion spring includes a plurality of coils, where the shaft is positioned through the plurality of coils. Moreover, the sleeve element is slidable in an axial direction along the shaft between the torsion spring and the shaft. Accordingly, compliance of the adjustable compliance apparatus is adjustable based on a number of the plurality of coils in contact with the sleeve element as positioned along the shaft within the torsion spring.

  7. Mechanical Properties of Axons

    NASA Astrophysics Data System (ADS)

    Bernal, Roberto; Pullarkat, Pramod A.; Melo, Francisco

    2007-07-01

    The mechanical response of PC12 neurites under tension is investigated using a microneedle technique. Elastic response, viscoelastic relaxation, and active contraction are observed. The mechanical model proposed by Dennerll et al. [J. Cell Biol. 109, 3073 (1989).JCLBA30021-952510.1083/jcb.109.6.3073], which involves three mechanical devices—a stiff spring κ coupled with a Voigt element that includes a less stiff spring k and a dashpot γ—has been improved by adding a new element to describe the main features of the contraction of axons. This element, which represents the action of molecular motors, acts in parallel with viscous forces defining a global tension response of axons T against elongation rates δ˙k. Under certain conditions, axons show a transition from a viscoelastic elongation to active contraction, suggesting the presence of a negative elongation rate sensitivity in the curve T vs δ˙k.

  8. 26 CFR 1.743-1 - Optional adjustment to basis of partnership property.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 26 Internal Revenue 8 2014-04-01 2014-04-01 false Optional adjustment to basis of partnership... (CONTINUED) INCOME TAX (CONTINUED) INCOME TAXES (CONTINUED) Transfers of Interests in A Partnership § 1.743-1 Optional adjustment to basis of partnership property. (a) Generally. The basis of partnership property...

  9. 26 CFR 1.743-1 - Optional adjustment to basis of partnership property.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 26 Internal Revenue 8 2012-04-01 2012-04-01 false Optional adjustment to basis of partnership... (CONTINUED) INCOME TAX (CONTINUED) INCOME TAXES (CONTINUED) Transfers of Interests in A Partnership § 1.743-1 Optional adjustment to basis of partnership property. (a) Generally. The basis of partnership property...

  10. 26 CFR 1.743-1 - Optional adjustment to basis of partnership property.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 26 Internal Revenue 8 2013-04-01 2013-04-01 false Optional adjustment to basis of partnership... (CONTINUED) INCOME TAX (CONTINUED) INCOME TAXES (CONTINUED) Transfers of Interests in A Partnership § 1.743-1 Optional adjustment to basis of partnership property. (a) Generally. The basis of partnership property...

  11. [Neurally adjusted ventilatory assist: a revolution of mechanical ventilation?].

    PubMed

    Piquilloud, Lise; Jolliet, Philippe; Tassaux, Didier

    2010-12-15

    Neurally adjusted ventilatory assist or NAVA is a new assisted ventilatory mode which, in comparison with pressure support, leads to improved patient-ventilator synchrony and a more variable ventilatory pattern. It also improves arterial oxygenation. With NAVA, the electrical activity of the diaphragm is recorded through a nasogastric tube equipped with electrodes. This electrical activity is then used to pilot the ventilator. With NAVA, the patient's respiratory pattern controls the ventilator's timing of triggering and cycling as well as the magnitude of pressurization, which is proportional to inspiratory demand. The effect of NAVA on patient outcome remains to be determined through well-designed prospective studies.

  12. Mechanical properties of graphene papers

    NASA Astrophysics Data System (ADS)

    Liu, Yilun; Xie, Bo; Zhang, Zhong; Zheng, Quanshui; Xu, Zhiping

    2012-04-01

    Graphene-based paper materials attract particular interests recently owing to their outstanding properties, the key of which is their layer-by-layer hierarchical structures similar to many biological materials such as bone, teeth and nacre, combining intralayer strong sp2 bonds and interlayer crosslinks for efficient load transfer. Here we firstly study the mechanical properties of various interlayer and intralayer crosslinks through first-principles calculations, and then perform continuum model analysis for the overall mechanical properties of graphene-based paper materials. We find that there is a characteristic length scale l0, defined as √{Dh0/4G}, where D is the stiffness of the graphene sheet, h0 and G are height of interlayer crosslink and shear modulus respectively. When the size of the graphene sheets exceeds 3l0, the tension-shear (TS) chain model, which is widely used for nanocomposites, fails to predict the overall mechanical properties of the graphene-based papers. Instead we proposed here a deformable tension-shear (DTS) model by considering elastic deformation of graphene sheets, also the interlayer and intralayer crosslinks. The DTS is then applied to predict the mechanical properties of graphene papers under tensile loading. According to the results we thus obtain, optimal design strategies are proposed for graphene papers with ultrahigh stiffness, strength and toughness.

  13. A Disequilibrium Adjustment Mechanism for CPE Macroeconometric Models: Initial Testing on SOVMOD.

    DTIC Science & Technology

    1979-02-01

    062 1H0 SRI INTERNATIONAL ARLINGTON VA STRATEGIC STUDIES CENTER F/ T 5/3 DISEQUILIBRIUM ADJUSTMENT MECHANISM FOR CPE MACROECOAI0AIETRIC -E (U) FEB...wC) u Approved for Review Distribution: 0 Richard B. Foster, Director Strategic Studies Center Approved for public release; distribution unlimited...describes work on the model aimed at facilitating the integration of a disequilibrium adjustment mechanism into the macroeconometric model. The

  14. Regulatory properties of ADP glucose pyrophosphorylase are required for adjustment of leaf starch synthesis in different photoperiods.

    PubMed

    Mugford, Sam T; Fernandez, Olivier; Brinton, Jemima; Flis, Anna; Krohn, Nicole; Encke, Beatrice; Feil, Regina; Sulpice, Ronan; Lunn, John E; Stitt, Mark; Smith, Alison M

    2014-12-01

    Arabidopsis (Arabidopsis thaliana) leaves synthesize starch faster in short days than in long days, but the mechanism that adjusts the rate of starch synthesis to daylength is unknown. To understand this mechanism, we first investigated whether adjustment occurs in mutants lacking components of the circadian clock or clock output pathways. Most mutants adjusted starch synthesis to daylength, but adjustment was compromised in plants lacking the GIGANTEA or FLAVIN-BINDING, KELCH REPEAT, F BOX1 components of the photoperiod-signaling pathway involved in flowering. We then examined whether the properties of the starch synthesis enzyme adenosine 5'-diphosphate-glucose pyrophosphorylase (AGPase) are important for adjustment of starch synthesis to daylength. Modulation of AGPase activity is known to bring about short-term adjustments of photosynthate partitioning between starch and sucrose (Suc) synthesis. We found that adjustment of starch synthesis to daylength was compromised in plants expressing a deregulated bacterial AGPase in place of the endogenous AGPase and in plants containing mutant forms of the endogenous AGPase with altered allosteric regulatory properties. We suggest that the rate of starch synthesis is in part determined by growth rate at the end of the preceding night. If growth at night is low, as in short days, there is a delay before growth recovers during the next day, leading to accumulation of Suc and stimulation of starch synthesis via activation of AGPase. If growth at night is fast, photosynthate is used for growth at the start of the day, Suc does not accumulate, and starch synthesis is not up-regulated.

  15. Woven TPS Mechanical Property Evaluation

    NASA Technical Reports Server (NTRS)

    Gonzales, Gregory Lewis; Kao, David Jan-Woei; Stackpoole, Margaret M.

    2013-01-01

    Woven Thermal Protection Systems (WTPS) is a relatively new program funded by the Office of the Chief Technologist (OCT). The WTPS approach to producing TPS architectures uses precisely engineered 3-D weaving techniques that allow tailoring material characteristics needed to meet specific mission requirements. A series of mechanical tests were performed to evaluate performance of different weave types, and get a better understanding of failure modes expected in these three-dimensional architectures. These properties will aid in material down selection and guide selection of the appropriate WTPS for a potential mission.

  16. Mechanical Properties of Niobium Cavities

    SciTech Connect

    Ciovati, Gianluigi; Dhakal, Pashupati; Matalevich, Joseph R.; Myneni, Ganapati Rao

    2015-09-01

    The mechanical stability of bulk Nb cavity is an important aspect to be considered in relation to cavity material, geometry and treatments. Mechanical properties of Nb are typically obtained from uniaxial tensile tests of small samples. In this contribution we report the results of measurements of the resonant frequency and local strain along the contour of single-cell cavities made of ingot and fine-grain Nb of different purity subjected to increasing uniform differential pressure, up to 6 atm. Measurements have been done on cavities subjected to different heat treatments. Good agreement between finite element analysis simulations and experimental data in the elastic regime was obtained with a single set of values of Young’s modulus and Poisson’s ratio. The experimental results indicate that the yield strength of medium-purity ingot Nb cavities is higher than that of fine-grain, high-purity Nb.

  17. Mechanical Properties of Viral Capsids

    NASA Astrophysics Data System (ADS)

    Zandi, Roya; Reguera, David

    2005-03-01

    Viral genomes, whether they involve RNA or DNA molecules, are invariably protected by a rigid, single-protein-thick, shell referred to as ``capsid.'' Viral capsids are known to tolerate wide ranges of pH and salt conditions and to withstand internal pressures as high as 100 atms. We study the mechanical properties of viral capsids, calling explicit attention to the inhomogeneity of the shells that is inherent in their being discrete/polyhedral rather than continuous/spherical. We analyze the distribution of stress in these capsids due to isotropic internal pressure (arising, for instance, from genome confinement and/or osmotic activity), and compare the results with appropriate generalizations of classical elasticity theory. We also examine the competing mechanisms for viral shell failure, e.g., in-plane crack formation vs radial bursting. The biological consequences of the special stabilities and stress distributions of viral capsids are also discussed.

  18. Mechanical properties of metal dihydrides

    SciTech Connect

    Schultz, Peter A.; Snow, Clark S.

    2016-02-04

    First-principles calculations are used to characterize the bulk elastic properties of cubic and tetragonal phase metal dihydrides, $\\text{M}{{\\text{H}}_{2}}$ {$\\text{M}$ = Sc, Y, Ti, Zr, Hf, lanthanides} to gain insight into the mechanical properties that govern the aging behavior of rare-earth di-tritides as the constituent 3H, tritium, decays into 3He. As tritium decays, helium is inserted in the lattice, the helium migrates and collects into bubbles, that then can ultimately create sufficient internal pressure to rupture the material. The elastic properties of the materials are needed to construct effective mesoscale models of the process of bubble growth and fracture. Dihydrides of the scandium column and most of the rare-earths crystalize into a cubic phase, while dihydrides from the next column, Ti, Zr, and Hf, distort instead into the tetragonal phase, indicating incipient instabilities in the phase and potentially significant changes in elastic properties. We report the computed elastic properties of these dihydrides, and also investigate the off-stoichiometric phases as He or vacancies accumulate. As helium builds up in the cubic phase, the shear moduli greatly soften, converting to the tetragonal phase. Conversely, the tetragonal phases convert very quickly to cubic with the removal of H from the lattice, while the cubic phases show little change with removal of H. Finally, the source and magnitude of the numerical and physical uncertainties in the modeling are analyzed and quantified to establish the level of confidence that can be placed in the computational results, and this quantified confidence is used to justify using the results to augment and even supplant experimental measurements.

  19. Mechanical properties of metal dihydrides

    DOE PAGES

    Schultz, Peter A.; Snow, Clark S.

    2016-02-04

    First-principles calculations are used to characterize the bulk elastic properties of cubic and tetragonal phase metal dihydrides,more » $$\\text{M}{{\\text{H}}_{2}}$$ {$$\\text{M}$$ = Sc, Y, Ti, Zr, Hf, lanthanides} to gain insight into the mechanical properties that govern the aging behavior of rare-earth di-tritides as the constituent 3H, tritium, decays into 3He. As tritium decays, helium is inserted in the lattice, the helium migrates and collects into bubbles, that then can ultimately create sufficient internal pressure to rupture the material. The elastic properties of the materials are needed to construct effective mesoscale models of the process of bubble growth and fracture. Dihydrides of the scandium column and most of the rare-earths crystalize into a cubic phase, while dihydrides from the next column, Ti, Zr, and Hf, distort instead into the tetragonal phase, indicating incipient instabilities in the phase and potentially significant changes in elastic properties. We report the computed elastic properties of these dihydrides, and also investigate the off-stoichiometric phases as He or vacancies accumulate. As helium builds up in the cubic phase, the shear moduli greatly soften, converting to the tetragonal phase. Conversely, the tetragonal phases convert very quickly to cubic with the removal of H from the lattice, while the cubic phases show little change with removal of H. Finally, the source and magnitude of the numerical and physical uncertainties in the modeling are analyzed and quantified to establish the level of confidence that can be placed in the computational results, and this quantified confidence is used to justify using the results to augment and even supplant experimental measurements.« less

  20. 26 CFR 1.734-1 - Optional adjustment to basis of undistributed partnership property.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... partnership property. 1.734-1 Section 1.734-1 Internal Revenue INTERNAL REVENUE SERVICE, DEPARTMENT OF THE TREASURY (CONTINUED) INCOME TAX (CONTINUED) INCOME TAXES (CONTINUED) Distributions by A Partnership § 1.734-1 Optional adjustment to basis of undistributed partnership property. (a) General rule....

  1. 26 CFR 1.734-1 - Optional adjustment to basis of undistributed partnership property.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... partnership property. 1.734-1 Section 1.734-1 Internal Revenue INTERNAL REVENUE SERVICE, DEPARTMENT OF THE TREASURY (CONTINUED) INCOME TAX (CONTINUED) INCOME TAXES (CONTINUED) Distributions by A Partnership § 1.734-1 Optional adjustment to basis of undistributed partnership property. (a) General rule....

  2. 26 CFR 1.743-1 - Optional adjustment to basis of partnership property.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... a result of the transfer of an interest in a partnership by sale or exchange or on the death of a... partnership property) is in effect with respect to the partnership. Whether or not the election provided in section 754 is in effect, the basis of partnership property is not adjusted as the result of...

  3. Mechanical Properties of Nanocrystal Supercrystals

    SciTech Connect

    Tam, Enrico; Podsiadlo, Paul; Shevchenko, Elena; Ogletree, D. Frank; Delplancke-Ogletree, Marie-Paule; Ashby, Paul D.

    2009-12-30

    Colloidal nanocrystals attract significant interest due to their potential applications in electronic, magnetic, and optical devices. Nanocrystal supercrystals (NCSCs) are particularly appealing for their well ordered structure and homogeneity. The interactions between organic ligands that passivate the inorganic nanocrystal cores critically influence their self-organization into supercrystals, By investigating the mechanical properties of supercrystals, we can directly characterize the particle-particle interactions in a well-defined geometry, and gain insight into both the self-assembly process and the potential applications of nanocrystal supercrystals. Here we report nanoindentation studies of well ordered lead-sulfide (Pbs) nanocrystal supercrystals. Their modulus and hardness were found to be similar to soft polymers at 1.7 GPa and 70 MPa respectively and the fractures toughness was 39 KPa/m1/2, revealing the extremely brittle nature of these materials.

  4. Mechanical Properties of Primary Cilia

    NASA Astrophysics Data System (ADS)

    Battle, Christopher; Schmidt, Christoph F.

    2013-03-01

    Recent studies have shown that the primary cilium, long thought to be a vestigial cellular appendage with no function, is involved in a multitude of sensory functions. One example, interesting from both a biophysical and medical standpoint, is the primary cilium of kidney epithelial cells, which acts as a mechanosensitive flow sensor. Genetic defects in ciliary function can cause, e.g., polycystic kidney disease (PKD). The material properties of these non-motile, microtubule-based 9 +0 cilia, and the way they are anchored to the cell cytoskeleton, are important to know if one wants to understand the mechano-electrochemical response of these cells, which is mediated by their cilia. We have probed the mechanical properties, boundary conditions, and dynamics of the cilia of MDCK cells using optical traps and DIC/fluorescence microscopy. We found evidence for both elastic relaxation of the cilia themselves after bending and for compliance in the intracellular anchoring structures. Angular and positional fluctuations of the cilia reflect both thermal excitations and cellular driving forces.

  5. Photopatterning the mechanical properties of polydimethylsiloxane films

    NASA Astrophysics Data System (ADS)

    Cotton, D. P. J.; Popel, A.; Graz, I. M.; Lacour, S. P.

    2011-03-01

    Silicone rubber films with graded and localized mechanical properties are prepared using two-part polydimethylsiloxane (PDMS) elastomer, photoinhibitor compounds and conventional photolithography. First the un-cross-linked PDMS is mixed with benzophenone. The resulting positive photosensitive material is then exposed through a mask to UV light from a conventional mask aligner. Cross-linking of the UV exposed elastomer is inhibited, leading to softer regions than the surrounding unexposed matrix. By empirically fitting the nonlinear, hyperelastic Mooney-Rivlin model to experimentally measured stress-strain curves we determine the equivalent tensile modulus (E) of the rubber film. We show the PDMS tensile modulus can then be adjusted in the 0.65-2.9 MPa range by decreasing the UV exposure dose (from 24 000 to 0 mJ cm-2). Further, using a patterned UV mask, we can locally define differential regions of tensile modulus within a single PDMS rubber film. We demonstrate that "hard islands" (E ≈ 2.9 MPa) of 100 μm minimum diameter can be patterned within a 100-μm-thick, single "soft" PDMS rubber membrane (E ≈ 0.65 MPa) cured at 150 °C for 24 h. Thin gold film conductors patterned directly onto the photopatterned PDMS are stretchable and withstand uniaxial cycling to tens of percent strain. The mechanically "pixellated" PDMS rubber film provides an improved substrate with built-in strain relief for stretchable electronics.

  6. A simple auxetic tubular structure with tuneable mechanical properties

    NASA Astrophysics Data System (ADS)

    Ren, Xin; Shen, Jianhu; Ghaedizadeh, Arash; Tian, Hongqi; Xie, Yi Min

    2016-06-01

    Auxetic materials and structures are increasingly used in various fields because of their unusual properties. Auxetic tubular structures have been fabricated and studied due to their potential to be adopted as oesophageal stents where only tensile auxetic performance is required. However, studies on compressive mechanical properties of auxetic tubular structures are limited in the current literature. In this paper, we developed a simple tubular structure which exhibits auxetic behaviour in both compression and tension. This was achieved by extending a design concept recently proposed by the authors for generating 3D metallic auxetic metamaterials. Both compressive and tensile mechanical properties of the auxetic tubular structure were investigated. It was found that the methodology for generating 3D auxetic metamaterials could be effectively used to create auxetic tubular structures as well. By properly adjusting certain parameters, the mechanical properties of the designed auxetic tubular structure could be easily tuned.

  7. Mechanically-Adjustable and Electrically-Gated Single-Molecule Transistors

    NASA Astrophysics Data System (ADS)

    Champagne, Alexandre

    2006-03-01

    We describe the fabrication and characterization of single-molecule transistors whose properties can be tuned in two independent ways to achieve systematic measurements of electron transport. The spacing between the source and drain electrodes can be adjusted with better than 1 pm stability using the mechanical breakjunction technique -- the electrodes are freely suspended above a flexible substrate, and their spacing can be varied by bending the substrate. In the same devices, we are also able to apply a gate voltage to the molecule. This is done by employing lithographic techniques to suspend the breakjunction only 40 nm above the substrate surface and using the substrate as an electrostatic back gate. With the independent in-situ variations provided by these two experimental ``knobs'', we are able to achieve a more detailed characterization of electron transport through the molecule than is possible with either technique separately. To demonstrate the device capabilities, we have studied transport through single C60 molecules at low temperature. We observe Coulomb blockaded transport and can resolve discrete energy levels of the molecule. We are able to mechanically tune the spacing between the electrodes (over a range of 5 å) to modulate the lead-molecule coupling, and we can electrostatically tune the energy levels on the molecule by up to 160 meV using the gate electrode. We will also present data of Kondo transport in single [Co(tpy-SH)2]^2+ molecules. We are able to vary the strength of the Kondo resonance in these devices by changing the spacing between the source and drain electrodes.

  8. Modeling and Control of the Redundant Parallel Adjustment Mechanism on a Deployable Antenna Panel

    PubMed Central

    Tian, Lili; Bao, Hong; Wang, Meng; Duan, Xuechao

    2016-01-01

    With the aim of developing multiple input and multiple output (MIMO) coupling systems with a redundant parallel adjustment mechanism on the deployable antenna panel, a structural control integrated design methodology is proposed in this paper. Firstly, the modal information from the finite element model of the structure of the antenna panel is extracted, and then the mathematical model is established with the Hamilton principle; Secondly, the discrete Linear Quadratic Regulator (LQR) controller is added to the model in order to control the actuators and adjust the shape of the panel. Finally, the engineering practicality of the modeling and control method based on finite element analysis simulation is verified. PMID:27706076

  9. Modeling and Control of the Redundant Parallel Adjustment Mechanism on a Deployable Antenna Panel.

    PubMed

    Tian, Lili; Bao, Hong; Wang, Meng; Duan, Xuechao

    2016-10-01

    With the aim of developing multiple input and multiple output (MIMO) coupling systems with a redundant parallel adjustment mechanism on the deployable antenna panel, a structural control integrated design methodology is proposed in this paper. Firstly, the modal information from the finite element model of the structure of the antenna panel is extracted, and then the mathematical model is established with the Hamilton principle; Secondly, the discrete Linear Quadratic Regulator (LQR) controller is added to the model in order to control the actuators and adjust the shape of the panel. Finally, the engineering practicality of the modeling and control method based on finite element analysis simulation is verified.

  10. Adaptively Adjusted Event-Triggering Mechanism on Fault Detection for Networked Control Systems.

    PubMed

    Wang, Yu-Long; Lim, Cheng-Chew; Shi, Peng

    2016-12-08

    This paper studies the problem of adaptively adjusted event-triggering mechanism-based fault detection for a class of discrete-time networked control system (NCS) with applications to aircraft dynamics. By taking into account the fault occurrence detection progress and the fault occurrence probability, and introducing an adaptively adjusted event-triggering parameter, a novel event-triggering mechanism is proposed to achieve the efficient utilization of the communication network bandwidth. Both the sensor-to-control station and the control station-to-actuator network-induced delays are taken into account. The event-triggered sensor and the event-triggered control station are utilized simultaneously to establish new network-based closed-loop models for the NCS subject to faults. Based on the established models, the event-triggered simultaneous design of fault detection filter (FDF) and controller is presented. A new algorithm for handling the adaptively adjusted event-triggering parameter is proposed. Performance analysis verifies the effectiveness of the adaptively adjusted event-triggering mechanism, and the simultaneous design of FDF and controller.

  11. Mechanical properties of warped membranes

    NASA Astrophysics Data System (ADS)

    Kosmrlj, Andrej; Xiao, Kechao; Weaver, James C.; Vlassak, Joost J.; Nelson, David R.

    2014-03-01

    We explore how a frozen background metric affects the mechanical properties of solid planar membranes at zero temperature. Our focus is a special class of ``warped membranes'' with a preferred random height profile characterized by random Gaussian variables h(q) in Fourier space with zero mean and variance < | h(q) | 2 > q-m . Using statistical physics tools to treat this quenched random disorder, we find that in the linear response regime, similar to thermally fluctuating polymerized membranes, an increasing scale-dependent effective bending rigidity, while the Young and the shear moduli are reduced. Compared to flat plates of the same thickness t, the bending rigidity of warped membranes is increased by a factor hv / t while the in-plane elastic moduli are reduced by t /hv , where hv =√{< | h(x) | 2 > } describes the frozen height fluctuations. Interestingly, hv is system size dependent for warped membranes characterized with m > 2 . Numerical results show good agreement with theoretical predictions, which are now being tested experimentally, where warped membranes are prepared with 3D printers.

  12. Research on mechanical properties of corn stalk

    NASA Astrophysics Data System (ADS)

    Zhang, Kaifei; He, Yujing; Zhang, Hongmei; Li, He

    2017-03-01

    Many domestic scholars have studied on straw utilization from lodging resistance, by breeding agricultural experts to optimization parameters, which selected by agricultural mechanical experts and efficient utilization after the harvest crush. Therefore, the study of the mechanical properties of corn stalks has great prospects. It can provide the basis for the design of agricultural machinery and comprehensive utilization of straw that study the relationship between the properties of the corn stalk and the mechanical properties. In this paper, the radial compression and bending mechanical properties of corn stalk was conducted by universal material testing machine, which contributes to the increase of corn crop and provides basis for the development of equipment.

  13. Mechanisms for force adjustments to unpredictable frictional changes at individual digits during two-fingered manipulation.

    PubMed

    Birznieks, I; Burstedt, M K; Edin, B B; Johansson, R S

    1998-10-01

    Previous studies on adaptation of fingertip forces to local friction at individual digit-object interfaces largely focused on static phases of manipulative tasks in which humans could rely on anticipatory control based on the friction in previous trials. Here we instead analyze mechanisms underlying this adaptation after unpredictable changes in local friction between consecutive trials. With the tips of the right index and middle fingers or the right and left index fingers, subjects restrained a manipulandum whose horizontal contact surfaces were located side by side. At unpredictable moments a tangential force was applied to the contact surfaces in the distal direction at 16 N/s to a plateau at 4 N. The subjects were free to use any combination of normal and tangential forces at the two fingers, but the sum of the tangential forces had to counterbalance the imposed load. The contact surface of the right index finger was fine-grained sandpaper, whereas that of the cooperating finger was changed between sandpaper and the more slippery rayon. The load increase automatically triggered normal force responses at both fingers. When a finger contacted rayon, subjects allowed slips to occur at this finger during the load force increase instead of elevating the normal force. These slips accounted for a partitioning of the load force between the digits that resulted in an adequate adjustment of the normal:tangential force ratios to the local friction at each digit. This mechanism required a fine control of the normal forces. Although the normal force at the more slippery surface had to be comparatively low to allow slippage, the normal forces applied by the nonslipping digit at the same time had to be high enough to prevent loss of the manipulandum. The frictional changes influenced the normal forces applied before the load ramp as well as the size of the triggered normal force responses similarly at both fingers, that is, with rayon at one contact surface the normal forces

  14. Enhancement of mechanical properties of 123 superconductors

    DOEpatents

    Balachandran, Uthamalingam

    1995-01-01

    A composition and method of preparing YBa.sub.2 Cu.sub.3 O.sub.7-x superconductor. Addition of tin oxide containing compounds to YBCO superconductors results in substantial improvement of fracture toughness and other mechanical properties without affect on T.sub.c. About 5-20% additions give rise to substantially improved mechanical properties.

  15. Enhancement of mechanical properties of 123 superconductors

    DOEpatents

    Balachandran, U.

    1995-04-25

    A composition and method are disclosed of preparing YBa{sub 2}Cu{sub 3}O{sub 7{minus}x} superconductor. Addition of tin oxide containing compounds to YBCO superconductors results in substantial improvement of fracture toughness and other mechanical properties without affect on T{sub c}. About 5-20% additions give rise to substantially improved mechanical properties.

  16. Determining the Mechanical Properties of Lattice Block Structures

    NASA Technical Reports Server (NTRS)

    Wilmoth, Nathan

    2013-01-01

    Lattice block structures and shape memory alloys possess several traits ideal for solving intriguing new engineering problems in industries such as aerospace, military, and transportation. Recent testing at the NASA Glenn Research Center has investigated the material properties of lattice block structures cast from a conventional aerospace titanium alloy as well as lattice block structures cast from nickel-titanium shape memory alloy. The lattice block structures for both materials were sectioned into smaller subelements for tension and compression testing. The results from the cast conventional titanium material showed that the expected mechanical properties were maintained. The shape memory alloy material was found to be extremely brittle from the casting process and only compression testing was completed. Future shape memory alloy lattice block structures will utilize an adjusted material composition that will provide a better quality casting. The testing effort resulted in baseline mechanical property data from the conventional titanium material for comparison to shape memory alloy materials once suitable castings are available.

  17. Mechanical property characterization of intraply hybrid composites

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.; Lark, R. F.; Sinclair, J. H.

    1979-01-01

    An investigation of the mechanical properties of intraply hybrids made from graphite fiber/epoxy matrix hybridized with secondary S-glass or Kevlar 49 fiber composites is presented. The specimen stress-strain behavior was determined, showing that mechanical properties of intraply hybrid composites can be measured with available methods such as the ten-degree off-axis test for intralaminar shear, and conventional tests for tensile, flexure, and Izod impact properties. The results also showed that combinations of high modulus graphite/S-glass/epoxy matrix composites exist which yield intraply hybrid laminates with the best 'balanced' properties, and that the translation efficiency of mechanical properties from the constituent composites to intraply hybrids may be assessed with a simple equation.

  18. Mechanical deformation mechanisms and properties of amyloid fibrils.

    PubMed

    Choi, Bumjoon; Yoon, Gwonchan; Lee, Sang Woo; Eom, Kilho

    2015-01-14

    Amyloid fibrils have recently received attention due to their remarkable mechanical properties, which are highly correlated with their biological functions. We have studied the mechanical deformation mechanisms and properties of amyloid fibrils as a function of their length scales by using atomistic simulations. It is shown that the length of amyloid fibrils plays a role in their deformation and fracture mechanisms in such a way that the competition between shear and bending deformations is highly dependent on the fibril length, and that as the fibril length increases, so does the bending strength of the fibril while its shear strength decreases. The dependence of rupture force for amyloid fibrils on their length is elucidated using the Bell model, which suggests that the rupture force of the fibril is determined from the hydrogen bond rupture mechanism that critically depends on the fibril length. We have measured the toughness of amyloid fibrils, which is shown to depend on the fibril length. In particular, the toughness of the fibril with its length of ∼3 nm is estimated to be ∼30 kcal mol(-1) nm(-3), comparable to that of a spider silk crystal with its length of ∼2 nm. Moreover, we have shown the important effect of the pulling rate on the mechanical deformation mechanisms and properties of amyloid fibril. It is found that as the pulling rate increases, so does the contribution of the shear effect to the elastic deformation of the amyloid fibril with its length of <10 nm. However, we found that the deformation mechanism of the amyloid fibril with its length of >15 nm is almost independent of the pulling rate. Our study sheds light on the role of the length scale of amyloid fibrils and the pulling rate in their mechanical behaviors and properties, which may provide insights into how the excellent mechanical properties of protein fibrils can be determined.

  19. Mechanical properties of low tantalum alloys

    NASA Technical Reports Server (NTRS)

    Kortovich, C. S.

    1982-01-01

    The mechanical property behavior of equiaxed cast B-1900 + Hf alloy as a function of tantalum content was studied. Tensile and stress rupture characterization was conducted on cast to size test bars containing tantalum at the 4.3% (standard level), 2.2% and 0% levels. Casting parameters were selected to duplicate conditions used to prepare test specimens for master metal heat qualification. The mechanical property results as well as results of microstructural/phase analysis of failed test bars are presented.

  20. Mechanical Properties of Infrared Transmitting Materials

    DTIC Science & Technology

    1978-01-01

    72-0170, 1972. Touloukian , Y. S., Ed., "Thermophysical Properties of Matter" series. A Comprehensive Compilation of Data by the Thermophysical...Research Projects Agency, 675 North Randolph Street, Arlington, VA 22203-2114. DARPA ltr, 20 Mar 1980 RIA-78-0291 2 01010695 2 Iviecnanica Properties of...336 2. GOVT ACCESSION NO 3. RECIPIENT’S CATALOG NUMBER 4. TITLE (end Subtitle) Mechanical Properties of Infrared Transmitting Materials 5

  1. Portable mass spectrometer with one or more mechanically adjustable electrostatic sectors and a mechanically adjustable magnetic sector all mounted in a vacuum chamber

    DOEpatents

    Andresen, B.D.; Eckels, J.D.; Kimmons, J.F.; Martin, W.H.; Myers, D.W.; Keville, R.F.

    1992-10-06

    A portable mass spectrometer is described having one or more electrostatic focusing sectors and a magnetic focusing sector, all of which are positioned inside a vacuum chamber, and all of which may be adjusted via adjustment means accessible from outside the vacuum chamber. Mounting of the magnetic sector entirely within the vacuum chamber permits smaller magnets to be used, thus permitting reductions in both weight and bulk. 13 figs.

  2. Portable mass spectrometer with one or more mechanically adjustable electrostatic sectors and a mechanically adjustable magnetic sector all mounted in a vacuum chamber

    DOEpatents

    Andresen, Brian D.; Eckels, Joel D.; Kimmons, James F.; Martin, Walter H.; Myers, David W.; Keville, Robert F.

    1992-01-01

    A portable mass spectrometer is described having one or more electrostatic focusing sectors and a magnetic focusing sector, all of which are positioned inside a vacuum chamber, and all of which may be adjusted via adjustment means accessible from outside the vacuum chamber. Mounting of the magnetic sector entirely within the vacuum chamber permits smaller magnets to be used, thus permitting reductions in both weight and bulk.

  3. Tuning the properties of polymer bulk heterojunction solar cells by adjusting fullerene size to control intercalation.

    PubMed

    Cates, Nichole C; Gysel, Roman; Beiley, Zach; Miller, Chad E; Toney, Michael F; Heeney, Martin; McCulloch, Iain; McGehee, Michael D

    2009-12-01

    We demonstrate that intercalation of fullerene derivatives between the side chains of conjugated polymers can be controlled by adjusting the fullerene size and compare the properties of intercalated and nonintercalated poly(2,5-bis(3-hexadecylthiophen-2-yl)thieno[3,2-b]thiophene (pBTTT):fullerene blends. The intercalated blends, which exhibit optimal solar-cell performance at 1:4 polymer:fullerene by weight, have better photoluminescence quenching and lower absorption than the nonintercalated blends, which optimize at 1:1. Understanding how intercalation affects performance will enable more effective design of polymer:fullerene solar cells.

  4. Physical and mechanical properties of stony meteorites

    NASA Astrophysics Data System (ADS)

    Slyuta, E. N.

    2017-01-01

    The method for experimental research of physical and mechanical properties of stony meteorites is considered. Experimental data on the physical and mechanical properties of samples of three ordinary chondrites are reported. Ordinary chondrites are characterized by a well-defined three-dimensional (spatial) anisotropy of physical and mechanical properties, when a compression strength in one of the directions significantly exceeds that in the other two directions. A measured compression strength of ordinary chondrites is in the range from 105 to 203 MPa, while a tensile strength is in the range from 18 to 31 MPa. As follows from the available published data on the strength of carbonaceous chondrites, they are drastically different in properties from ordinary chondrites. The observed critical aerodynamic loads do not exceed a measured tensile strength value of ordinary chondrites, which is actually the upper limit restricting the maximum aerodynamic load for ordinary chondrites.

  5. Assessment of net lost revenue adjustment mechanisms for utility DSM programs

    SciTech Connect

    Baxter, L.W.

    1995-01-01

    Utility shareholders can lose money on demand-side management (DSM) investments between rate cases. Several industry analysts argue that the revenues lost from utility DSM programs are an important financial disincentive to utility DSM investment. A key utility regulatory reform undertaken since 1989 allows utilities to recover the lost revenues incurred through successful operation of DSM programs. Explicitly defined net lost revenue adjustment (NLRA) mechanisms are states` preferred approach to lost revenue recovery from DSM programs. This report examines the experiences states and utilities are having with the NLRA approach. The report has three objectives. First, we determine whether NLRA is a feasible and successful approach to removing the lost-revenue disincentive to utility operation of DSM programs. Second, we identify the conditions linked to successful implementation of NLRA mechanisms in different states and assess whether NLRA has changed utility investment behavior. Third, we suggest improvements to NLRA mechanisms. We first identify states with NLRA mechanisms where utilities are recovering lost revenues from DSM programs. We interview staff at regulatory agencies in all these states and utility staff in four states. These interviews focus on the status of NLRA, implementation issues, DSM measurement issues, and NLRA results. We also analyze regulatory agency orders on NLRA, as well as associated testimony, reports, and utility lost revenue recovery filings. Finally, we use qualitative and quantitative indicators to assess NLRA`s effectiveness. Contrary to the concerns raised by some industry analysts, our results indicate NLRA is a feasible approach to the lost-revenue disincentive.

  6. Designed biomaterials to mimic the mechanical properties of muscles.

    PubMed

    Lv, Shanshan; Dudek, Daniel M; Cao, Yi; Balamurali, M M; Gosline, John; Li, Hongbin

    2010-05-06

    The passive elasticity of muscle is largely governed by the I-band part of the giant muscle protein titin, a complex molecular spring composed of a series of individually folded immunoglobulin-like domains as well as largely unstructured unique sequences. These mechanical elements have distinct mechanical properties, and when combined, they provide the desired passive elastic properties of muscle, which are a unique combination of strength, extensibility and resilience. Single-molecule atomic force microscopy (AFM) studies demonstrated that the macroscopic behaviour of titin in intact myofibrils can be reconstituted by combining the mechanical properties of these mechanical elements measured at the single-molecule level. Here we report artificial elastomeric proteins that mimic the molecular architecture of titin through the combination of well-characterized protein domains GB1 and resilin. We show that these artificial elastomeric proteins can be photochemically crosslinked and cast into solid biomaterials. These biomaterials behave as rubber-like materials showing high resilience at low strain and as shock-absorber-like materials at high strain by effectively dissipating energy. These properties are comparable to the passive elastic properties of muscles within the physiological range of sarcomere length and so these materials represent a new muscle-mimetic biomaterial. The mechanical properties of these biomaterials can be fine-tuned by adjusting the composition of the elastomeric proteins, providing the opportunity to develop biomaterials that are mimetic of different types of muscles. We anticipate that these biomaterials will find applications in tissue engineering as scaffold and matrix for artificial muscles.

  7. Quadriceps Muscle Mechanical Simulator for Training of Vastus Medialis Obliquus and Vastus Lateralis Obliquus Mechanical Properties

    PubMed Central

    Irmak, Rafet; Irmak, Ahsen; Biçer, Gökhan

    2014-01-01

    Objectives: In classical anatomy quadriceps muscle has four heads. Clinical studies have demostrated 6 heads of this muscle. These heads were demostrated seperately not only by their functional properties,but also by innervation and kinesiological properties. In our previous study we have developed and demostrated electrophysiological properties of vastus medialis obliquus by an electronic patient simulator. The purpose of this study is to develop a mechanical simulator which can be used to demostrate mechanical properties of 6 heads of quadriceps muscle and the screw home mechanism. Methods: Quadriceps femoris muscle has 6 heads: rectus femoris, vastus intermedius, vastus medialis obliquus, vastus medialis longus, vastus lateralis obliquus and vastus lateralis longus. The fundamental mechanical properties of each head is seperated by insersio and angle of pull. Main design principle was to demostrate all heads with insersio and angle of pull properties. Second design principle was to demostrate the screw-home mechanism which is the result of difference in articular surfaces of medial and lateral of condyles of femur. Results: Final design of the simulator consists of three planes for demostration of angle of pull and pulling forces (patellar plane, proximal and distal planes) of each heads. On each plane channels were graved as origo and insersio for demostration of angle of pull. Distal plane was movable for demostration of pulling forces in different angels of knee flexion and extention. Also proximal plane was adjustable to demostrate different sitting and standing positions. Srew home mechanism was demostrated by specially designed hingle mechanism. Left and right side hingle mechanisms have different radii as femoral condyles and this difference can cause rotation in terminal extension as in the screw home mechanism. Conclusion: Vastus medialis obliquus, vastus lateralis obliquus and screw-home mechanism have clinical significance. We were not able to find

  8. Mechanical Properties of Crystalline Silicon Carbide Nanowires.

    PubMed

    Zhang, Huan; Ding, Weiqiang; Aidun, Daryush K

    2015-02-01

    In this paper, the mechanical properties of crystalline silicon carbide nanowires, synthesized with a catalyst-free chemical vapor deposition method, were characterized with nanoscale tensile testing and mechanical resonance testing methods inside a scanning electron microscope. Tensile testing of individual silicon carbide nanowire was performed to determine the tensile properties of the material including the tensile strength, failure strain and Young's modulus. The silicon carbide nanowires were also excited to mechanical resonance in the scanning electron microscope vacuum chamber using mechanical excitation and electrical excitation methods, and the corresponding resonance frequencies were used to determine the Young's modulus of the material according to the simple beam theory. The Young's modulus values from tensile tests were in good agreement with the ones obtained from the mechanical resonance tests.

  9. Distinct mechanisms mediate speed-accuracy adjustments in cortico-subthalamic networks

    PubMed Central

    Herz, Damian M; Tan, Huiling; Brittain, John-Stuart; Fischer, Petra; Cheeran, Binith; Green, Alexander L; FitzGerald, James; Aziz, Tipu Z; Ashkan, Keyoumars; Little, Simon; Foltynie, Thomas; Limousin, Patricia; Zrinzo, Ludvic; Bogacz, Rafal; Brown, Peter

    2017-01-01

    Optimal decision-making requires balancing fast but error-prone and more accurate but slower decisions through adjustments of decision thresholds. Here, we demonstrate two distinct correlates of such speed-accuracy adjustments by recording subthalamic nucleus (STN) activity and electroencephalography in 11 Parkinson’s disease patients during a perceptual decision-making task; STN low-frequency oscillatory (LFO) activity (2–8 Hz), coupled to activity at prefrontal electrode Fz, and STN beta activity (13–30 Hz) coupled to electrodes C3/C4 close to motor cortex. These two correlates differed not only in their cortical topography and spectral characteristics but also in the relative timing of recruitment and in their precise relationship with decision thresholds. Increases of STN LFO power preceding the response predicted increased thresholds only after accuracy instructions, while cue-induced reductions of STN beta power decreased thresholds irrespective of instructions. These findings indicate that distinct neural mechanisms determine whether a decision will be made in haste or with caution. DOI: http://dx.doi.org/10.7554/eLife.21481.001 PMID:28137358

  10. Developmental sexual dimorphism and the evolution of mechanisms for adjustment of sex ratios in mammals.

    PubMed

    Cameron, Elissa Z; Edwards, Amy M; Parsley, Laura M

    2017-02-01

    Sex allocation theory predicts biased offspring sex ratios in relation to local conditions if they would maximize parental lifetime reproductive return. In mammals, the extent of the birth sex bias is often unpredictable and inconsistent, leading some to question its evolutionary significance. For facultative adjustment of sex ratios to occur, males and females would need to be detectably different from an early developmental stage, but classic sexual dimorphism arises from hormonal influences after gonadal development. Recent advances in our understanding of early, pregonadal sexual dimorphism, however, indicate high levels of dimorphism in gene expression, caused by chromosomal rather than hormonal differences. Here, we discuss how such dimorphism would interact with and link previously hypothesized mechanisms for sex-ratio adjustment. These differences between males and females are sufficient for offspring sex both to be detectable to parents and to provide selectable cues for biasing sex ratios from the earliest stages. We suggest ways in which future research could use the advances in our understanding of sexually dimorphic developmental physiology to test the evolutionary significance of sex allocation in mammals. Such an approach would advance our understanding of sex allocation and could be applied to other taxa.

  11. Assessing mechanical properties from cone indentation hardness

    NASA Astrophysics Data System (ADS)

    Dicarlo, Anthony Albert

    This dissertation investigates methods for assessing the mechanical properties of materials using hardness values obtained from cone indentations. A broad range of isotropic metallic materials was simulated using finite element analysis. In particular, the elastic and plastic bulk properties, which define the stress-strain behavior of materials that exhibit power law hardening, are studied. Other investigators have found that the Young's modulus, E, can be determined from the unloading data of a cone indentation. Therefore, the remaining properties of interest, in this study, are the yield strength, Y, and the work hardening exponent, n. Atkins and Tabor have conducted pioneering work in the area of determining the stress-strain behavior of a metallic material from cone indentation experiments. This work has been re-visited in this study using computational models implementing an expanded range of mechanical properties. Consequently, discrepancies in this prediction method were uncovered when the mechanical properties were outside of the original range studied. As a result, two new prediction methods have been developed using the data collected from the finite element simulations in conjunction with a regression technique. The first method correlates the non-dimensional hardness values, H/E, collected from five cone indentations to the non-dimensional mechanical properties, Y/E and n. The second method is similar in principle, but uses two hardness values as opposed to five. The yield strength can be estimated with a priori knowledge of E. Both of these methods are compared to the method developed by Atkins and Tabor. Although the majority of the work mentioned is focused on the macro-scale, bulk mechanical properties, there is some investigation of meso-scale cone indentations. At the meso-scale, the number of geometric dislocations is significant enough to noticeably increase the strength of a material. This length scale effect is studied for various angled cone

  12. Biomolecular motor modulates mechanical property of microtubule.

    PubMed

    Kabir, Arif Md Rashedul; Inoue, Daisuke; Hamano, Yoshimi; Mayama, Hiroyuki; Sada, Kazuki; Kakugo, Akira

    2014-05-12

    The microtubule (MT) is the stiffest cytoskeletal filamentous protein that takes part in a wide range of cellular activities where its mechanical property plays a crucially significant role. How a single biological entity plays multiple roles in cell has been a mystery for long time. Over the recent years, it has been known that modulation of the mechanical property of MT by different cellular agents is the key to performing manifold in vivo activities by MT. Studying the mechanical property of MT thus has been a prerequisite in understanding how MT plays such diversified in vivo roles. However, the anisotropic structure of MT has been an impediment in obtaining a precise description of the mechanical property of MT along its longitudinal and lateral directions that requires employment of distinct experimental approach and has not been demonstrated yet. In this work, we have developed an experimental system that enabled us to investigate the effect of tensile stress on MT. By using our newly developed system, (1) we have determined the Young's modulus of MT considering its deformation under applied tensile stress and (2) a new role of MT associated motor protein kinesin in modulating the mechanical property of MT was revealed for the first time. Decrease in Young's modulus of MT with the increase in interaction with kinesin suggests that kinesin has a softening effect on MT and thereby can modulate the rigidity of MT. This work will be an aid in understanding the modulation of mechanical property of MTs by MT associated proteins and might also help obtain a clear insight of the endurance and mechanical instability of MTs under applied stress.

  13. DNA origami compliant nanostructures with tunable mechanical properties.

    PubMed

    Zhou, Lifeng; Marras, Alexander E; Su, Hai-Jun; Castro, Carlos E

    2014-01-28

    DNA origami enables fabrication of precise nanostructures by programming the self-assembly of DNA. While this approach has been used to make a variety of complex 2D and 3D objects, the mechanical functionality of these structures is limited due to their rigid nature. We explore the fabrication of deformable, or compliant, objects to establish a framework for mechanically functional nanostructures. This compliant design approach is used in macroscopic engineering to make devices including sensors, actuators, and robots. We build compliant nanostructures by utilizing the entropic elasticity of single-stranded DNA (ssDNA) to locally bend bundles of double-stranded DNA into bent geometries whose curvature and mechanical properties can be tuned by controlling the length of ssDNA strands. We demonstrate an ability to achieve a wide range of geometries by adjusting a few strands in the nanostructure design. We further developed a mechanical model to predict both geometry and mechanical properties of our compliant nanostructures that agrees well with experiments. Our results provide a basis for the design of mechanically functional DNA origami devices and materials.

  14. Mechanical properties of nanoparticles: basics and applications

    NASA Astrophysics Data System (ADS)

    Guo, Dan; Xie, Guoxin; Luo, Jianbin

    2014-01-01

    The special mechanical properties of nanoparticles allow for novel applications in many fields, e.g., surface engineering, tribology and nanomanufacturing/nanofabrication. In this review, the basic physics of the relevant interfacial forces to nanoparticles and the main measuring techniques are briefly introduced first. Then, the theories and important results of the mechanical properties between nanoparticles or the nanoparticles acting on a surface, e.g., hardness, elastic modulus, adhesion and friction, as well as movement laws are surveyed. Afterwards, several of the main applications of nanoparticles as a result of their special mechanical properties, including lubricant additives, nanoparticles in nanomanufacturing and nanoparticle reinforced composite coating, are introduced. A brief summary and the future outlook are also given in the final part.

  15. Physical and mechanical properties of hemp seed

    NASA Astrophysics Data System (ADS)

    Taheri-Garavand, A.; Nassiri, A.; Gharibzahedi, S.

    2012-04-01

    The current study was conducted to investigate the effect of moisture content on the post-harvest physical and mechanical properties of hemp seed in the range of 5.39 to 27.12% d.b. Results showed that the effect of moisture content on the most physical properties of the grain was significant (P<0.05). The results of mechanical tests demonstrated that the effect of loading rate on the mechanical properties of hemp seed was not significant. However, the moisture content effect on rupture force and energy was significant (P<0.01). The lowest value of rupture force was obtained at the highest loading rate (3mm min-1)and in the moisture content of 27.12% d.b. Moreover, the interaction effects of loading rate and moisture content on the rupture force and energy of hemp seed were significant (P<0.05).

  16. Mechanical properties of septal cartilage homografts

    SciTech Connect

    Glasgold, M.J.; Kato, Y.P.; Christiansen, D.; Hauge, J.A.; Glasgold, A.I.; Silver, F.H.

    1988-10-01

    The compressive mechanical properties of untreated and chemically and physically treated nasal septum homografts were determined. Mechanical properties of control, saline-, thimerosal (Merthiolate)- and Alcide-treated specimens were similar. At high strains, the stiffness of treated cartilage ranged from 12.8 to 22.5 MPa and was unaffected by storage time. In comparison, irradiated and freeze-dried nasal septum exhibited stiffnesses of 35 and 37.5 MPa, respectively, after approximately 1 month of storage. These values of stiffness were significantly different from controls at a 0.95 confidence level. On the basis of these results, it was concluded that Alcide and Merthiolate treatment did not alter the compressive mechanical properties of cartilage and that a combination of these treatments may adequately sterilize and preserve nasal septum homografts.

  17. Mechanical Properties of Ingot Nb Cavities

    SciTech Connect

    Ciovati, Gianluigi; Dhakal, Pashupati; Kneisel, Peter; Mammosser, John; Matalevich, Joseph; Rao Myneni, Ganapati

    2014-07-01

    This contribution presents the results of measurements of the resonant frequency and of strain along the contour of a single-cell cavity made of ingot Nb subjected to increasing uniform differential pressure, up to 6 atm. The data were used to infer mechanical properties of this material after cavity fabrication, by comparison with the results from simulation calculations done with ANSYS. The objective is to provide useful information about the mechanical properties of ingot Nb cavities which can be used in the design phase of SRF cavities intended to be built with this material.

  18. Stainless Steel Microstructure and Mechanical Properties Evaluation

    SciTech Connect

    Switzner, Nathan T

    2010-06-01

    A nitrogen strengthened 21-6-9 stainless steel plate was spinformed into hemispherical test shapes. A battery of laboratory tests was used to characterize the hemispheres. The laboratory tests show that near the pole (axis) of a spinformed hemisphere the yield strength is the lowest because this area endures the least “cold-work” strengthening, i.e., the least deformation. The characterization indicated that stress-relief annealing spinformed stainless steel hemispheres does not degrade mechanical properties. Stress-relief annealing reduces residual stresses while maintaining relatively high mechanical properties. Full annealing completely eliminates residual stresses, but reduces yield strength by about 30%.

  19. Mechanical properties of polygonal carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Huang, Ling; Cao, Dapeng

    2012-08-01

    A group of polygonal carbon nanotubes (P-CNTs) have been designed and their mechanical behavior was investigated by classical molecular dynamics simulations. The research aimed at exploring the effects of structure, temperature, and strain rate on the mechanical properties. The results indicate that the Young's modulus of P-CNTs is lower than those of circumcircle carbon nanotubes (C-CNT). Moreover, with an increase in the number of sides to the polygons, the Young's modulus increases and is much closer to that of C-CNT. The effects of temperature and strain rate on the mechanical properties of P-CNTs show that the higher temperature and slower strain rate result in a lower critical strain and weaker tensile strength. In addition, it was found that the critical strains of P-CNTs are dependent on the tube size. Finally, we used the transition-state theory model to predict the critical strain of P-CNTs at given experimental conditions. It is expected that this work could provide feasible means to manipulate the mechanical properties of novel P-CNTs and facilitate the mechanical application of nanostructures as potential electronic devices.A group of polygonal carbon nanotubes (P-CNTs) have been designed and their mechanical behavior was investigated by classical molecular dynamics simulations. The research aimed at exploring the effects of structure, temperature, and strain rate on the mechanical properties. The results indicate that the Young's modulus of P-CNTs is lower than those of circumcircle carbon nanotubes (C-CNT). Moreover, with an increase in the number of sides to the polygons, the Young's modulus increases and is much closer to that of C-CNT. The effects of temperature and strain rate on the mechanical properties of P-CNTs show that the higher temperature and slower strain rate result in a lower critical strain and weaker tensile strength. In addition, it was found that the critical strains of P-CNTs are dependent on the tube size. Finally, we used the

  20. Laminar Tendon Composites with Enhanced Mechanical Properties

    PubMed Central

    Alberti, Kyle A.; Sun, Jeong-Yun; Illeperuma, Widusha R.; Suo, Zhigang; Xu, Qiaobing

    2015-01-01

    Purpose A strong isotropic material that is both biocompatible and biodegradable is desired for many biomedical applications, including rotator cuff repair, tendon and ligament repair, vascular grafting, among others. Recently, we developed a technique, called “bioskiving” to create novel 2D and 3D constructs from decellularized tendon, using a combination of mechanical sectioning, and layered stacking and rolling. The unidirectionally aligned collagen nanofibers (derived from sections of decellularized tendon) offer good mechanical properties to the constructs compared with those fabricated from reconstituted collagen. Methods In this paper, we studied the effect that several variables have on the mechanical properties of structures fabricated from tendon slices, including crosslinking density and the orientation in which the fibers are stacked. Results We observed that following stacking and crosslinking, the strength of the constructs is significantly improved, with crosslinked sections having an ultimate tens ile strength over 20 times greater than non-crosslinked samples, and a modulus nearly 50 times higher. The mechanism of the mechanical failure mode of the tendon constructs with or without crosslinking was also investigated. Conclusions The strength and fiber organization, combined with the ability to introduce transversely isotropic mechanical properties makes the laminar tendon composites a biocompatiable material that may find future use in a number of biomedical and tissue engineering applications. PMID:25691802

  1. Probing cell mechanical properties with microfluidic devices

    NASA Astrophysics Data System (ADS)

    Rowat, Amy

    2012-02-01

    Exploiting flow on the micron-scale is emerging as a method to probe cell mechanical properties with 10-1000x advances in throughput over existing technologies. The mechanical properties of cells and the cell nucleus are implicated in a wide range of biological contexts: for example, the ability of white blood cells to deform is central to immune response; and malignant cells show decreased stiffness compared to benign cells. We recently developed a microfluidic device to probe cell and nucleus mechanical properties: cells are forced to deform through a narrow constrictions in response to an applied pressure; flowing cells through a series of constrictions enables us to probe the ability of hundreds of cells to deform and relax during flow. By tuning the constriction width so it is narrower than the width of the cell nucleus, we can specifically probe the effects of nuclear physical properties on whole cell deformability. We show that the nucleus is the rate-limiting step in cell passage: inducing a change in its shape to a multilobed structure results in cells that transit more quickly; increased levels of lamin A, a nuclear protein that is key for nuclear shape and mechanical stability, impairs the passage of cells through constrictions. We are currently developing a new class of microfluidic devices to simultaneously probe the deformability of hundreds of cell samples in parallel. Using the same soft lithography techniques, membranes are fabricated to have well-defined pore distribution, width, length, and tortuosity. We design the membranes to interface with a multiwell plate, enabling simultaneous measurement of hundreds of different samples. Given the wide spectrum of diseases where altered cell and nucleus mechanical properties are implicated, such a platform has great potential, for example, to screen cells based on their mechanical phenotype against a library of drugs.

  2. Mechanical Properties of Unsaturated Polyester / Montmorillonite Composites

    DTIC Science & Technology

    2001-11-01

    Montmorillonite Composites DISTRIBUTION: Approved for public release, distribution unlimited This paper is part of the following report: TITLE: Nanophase and...Mechanical Properties of Unsaturated Polyester / Montmorillonite Composites A. Baran Inceoglu and Ulku Yilmazer Middle East Technical University, Chemical...analysed the nature of the curing agent on structure. Kornmann, Berglund and Giannelis [8] studied nanocomposites based on montmorillonite modified

  3. Improvement of mechanical properties of glass substrates

    NASA Astrophysics Data System (ADS)

    Karbay, Ismail Hakki Cengizhan; Budakoglu, Refika; Zayim, Esra Ozkan

    2015-12-01

    This paper aims to enhance the mechanical and optical properties of glass substrates with thin films by the sol-gel method. TiO2-SiO2 binary system and Ta2O5 were deposited on glass substrates with high transparency. Ring-on-ring flexure and scratch tests were the main mechanical characterization tests. Herein, we report that the thin films can be used to enhance the mechanical properties of the glass substrates efficiently and effectively. TiO2-SiO2 binary system shows more than two times and Ta2O5 thin films show nearly three times better ultimate strength in the ring-on-ring flexure test. Besides, Ta2O5 thin film samples show superior scratch resistance. Additionally, the finite element method was also used to check the conformity in the application of mechanical properties of composite materials. It is also worth noting that, the finite element method can be used to accurately analyze the mechanical stability of composite materials. The use of the finite element method can reduce the total number of experimental trials without losing reliability.

  4. Mechanical Properties of Doubly Stabilized Microtubule Filaments

    PubMed Central

    Hawkins, Taviare L.; Sept, David; Mogessie, Binyam; Straube, Anne; Ross, Jennifer L.

    2013-01-01

    Microtubules are cytoskeletal filaments responsible for cell morphology and intracellular organization. Their dynamical and mechanical properties are regulated through the nucleotide state of the tubulin dimers and the binding of drugs and/or microtubule-associated proteins. Interestingly, microtubule-stabilizing factors have differential effects on microtubule mechanics, but whether stabilizers have cumulative effects on mechanics or whether one effect dominates another is not clear. This is especially important for the chemotherapeutic drug Taxol, an important anticancer agent and the only known stabilizer that reduces the rigidity of microtubules. First, we ask whether Taxol will combine additively with another stabilizer or whether one stabilizer will dominate another. We call microtubules in the presence of Taxol and another stabilizer, doubly stabilized. Second, since Taxol is often added to a number of cell types for therapeutic purposes, it is important from a biomedical perspective to understand how Taxol added to these systems affects the mechanical properties in treated cells. To address these questions, we use the method of freely fluctuating filaments with our recently developed analysis technique of bootstrapping to determine the distribution of persistence lengths of a large population of microtubules treated with different stabilizers, including Taxol, guanosine-5′ [(α, β)-methyleno] triphosphate, guanosine-5′-O-(3-thiotriphosphate), tau, and MAP4. We find that combinations of these stabilizers have novel effects on the mechanical properties of microtubules. PMID:23561528

  5. Mechanical properties of doubly stabilized microtubule filaments.

    PubMed

    Hawkins, Taviare L; Sept, David; Mogessie, Binyam; Straube, Anne; Ross, Jennifer L

    2013-04-02

    Microtubules are cytoskeletal filaments responsible for cell morphology and intracellular organization. Their dynamical and mechanical properties are regulated through the nucleotide state of the tubulin dimers and the binding of drugs and/or microtubule-associated proteins. Interestingly, microtubule-stabilizing factors have differential effects on microtubule mechanics, but whether stabilizers have cumulative effects on mechanics or whether one effect dominates another is not clear. This is especially important for the chemotherapeutic drug Taxol, an important anticancer agent and the only known stabilizer that reduces the rigidity of microtubules. First, we ask whether Taxol will combine additively with another stabilizer or whether one stabilizer will dominate another. We call microtubules in the presence of Taxol and another stabilizer, doubly stabilized. Second, since Taxol is often added to a number of cell types for therapeutic purposes, it is important from a biomedical perspective to understand how Taxol added to these systems affects the mechanical properties in treated cells. To address these questions, we use the method of freely fluctuating filaments with our recently developed analysis technique of bootstrapping to determine the distribution of persistence lengths of a large population of microtubules treated with different stabilizers, including Taxol, guanosine-5' [(α, β)-methyleno] triphosphate, guanosine-5'-O-(3-thiotriphosphate), tau, and MAP4. We find that combinations of these stabilizers have novel effects on the mechanical properties of microtubules.

  6. Isotropic microscale mechanical properties of coral skeletons

    PubMed Central

    Pasquini, Luca; Molinari, Alan; Fantazzini, Paola; Dauphen, Yannicke; Cuif, Jean-Pierre; Levy, Oren; Dubinsky, Zvy; Caroselli, Erik; Prada, Fiorella; Goffredo, Stefano; Di Giosia, Matteo; Reggi, Michela; Falini, Giuseppe

    2015-01-01

    Scleractinian corals are a major source of biogenic calcium carbonate, yet the relationship between their skeletal microstructure and mechanical properties has been scarcely studied. In this work, the skeletons of two coral species: solitary Balanophyllia europaea and colonial Stylophora pistillata, were investigated by nanoindentation. The hardness HIT and Young's modulus EIT were determined from the analysis of several load–depth data on two perpendicular sections of the skeletons: longitudinal (parallel to the main growth axis) and transverse. Within the experimental and statistical uncertainty, the average values of the mechanical parameters are independent on the section's orientation. The hydration state of the skeletons did not affect the mechanical properties. The measured values, EIT in the 76–77 GPa range, and HIT in the 4.9–5.1 GPa range, are close to the ones expected for polycrystalline pure aragonite. Notably, a small difference in HIT is observed between the species. Different from corals, single-crystal aragonite and the nacreous layer of the seashell Atrina rigida exhibit clearly orientation-dependent mechanical properties. The homogeneous and isotropic mechanical behaviour of the coral skeletons at the microscale is correlated with the microstructure, observed by electron microscopy and atomic force microscopy, and with the X-ray diffraction patterns of the longitudinal and transverse sections. PMID:25977958

  7. Mechanical Properties of Polymer Nano-composites

    NASA Astrophysics Data System (ADS)

    Srivastava, Iti

    Thermoset polymer composites are increasingly important in high-performance engineering industries due to their light-weight and high specific strength, finding cutting-edge applications such as aircraft fuselage material and automobile parts. Epoxy is the most widely employed thermoset polymer, but is brittle due to extensive cross-linking and notch sensitivity, necessitating mechanical property studies especially fracture toughness and fatigue resistance, to ameliorate the low crack resistance. Towards this end, various nano and micro fillers have been used with epoxy to form composite materials. Particularly for nano-fillers, the 1-100 nm scale dimensions lead to fascinating mechanical properties, oftentimes proving superior to the epoxy matrix. The chemical nature, topology, mechanical properties and geometry of the nano-fillers have a profound influence on nano-composite behavior and hence are studied in the context of enhancing properties and understanding reinforcement mechanisms in polymer matrix nano-composites. Using carbon nanotubes (CNTs) as polymer filler, uniquely results in both increased stiffness as well as toughness, leading to extensive research on their applications. Though CNTs-polymer nano-composites offer better mechanical properties, at high stress amplitude their fatigue resistance is lost. In this work covalent functionalization of CNTs has been found to have a profound impact on mechanical properties of the CNT-epoxy nano-composite. Amine treated CNTs were found to give rise to effective fatigue resistance throughout the whole range of stress intensity factor, in addition to significantly enhancing fracture toughness, ductility, Young's modulus and average hardness of the nano-composite by factors of 57%, 60%, 30% and 45% respectively over the matrix as a result of diminished localized cross-linking. Graphene, a one-atom-thick sheet of atoms is a carbon allotrope, which has garnered significant attention of the scientific community and is

  8. Food mechanical properties and dietary ecology.

    PubMed

    Berthaume, Michael A

    2016-01-01

    Interdisciplinary research has benefitted the fields of anthropology and engineering for decades: a classic example being the application of material science to the field of feeding biomechanics. However, after decades of research, discordances have developed in how mechanical properties are defined, measured, calculated, and used due to disharmonies between and within fields. This is highlighted by "toughness," or energy release rate, the comparison of incomparable tests (i.e., the scissors and wedge tests), and the comparison of incomparable metrics (i.e., the stress and displacement-limited indices). Furthermore, while material scientists report on a myriad of mechanical properties, it is common for feeding biomechanics studies to report on just one (energy release rate) or two (energy release rate and Young's modulus), which may or may not be the most appropriate for understanding feeding mechanics. Here, I review portions of materials science important to feeding biomechanists, discussing some of the basic assumptions, tests, and measurements. Next, I provide an overview of what is mechanically important during feeding, and discuss the application of mechanical property tests to feeding biomechanics. I also explain how 1) toughness measures gathered with the scissors, wedge, razor, and/or punch and die tests on non-linearly elastic brittle materials are not mechanical properties, 2) scissors and wedge tests are not comparable and 3) the stress and displacement-limited indices are not comparable. Finally, I discuss what data gathered thus far can be best used for, and discuss the future of the field, urging researchers to challenge underlying assumptions in currently used methods to gain a better understanding between primate masticatory morphology and diet.

  9. Correlation of Cell and Substrate Mechanical Properties

    NASA Astrophysics Data System (ADS)

    Setton, Tedhar; Levine, Joshua; Levine, Joseph; Guan, E.; Collazo, Lourdes; Ge, Shouren; Entcheva, Emilia; Rafailovich, Miriam

    2003-03-01

    The mechanical properties of neonatal rat ventricular fibroblasts plated onto elastomer surfaces were studied in vitro and correlated to the mechanical response of the substrate. In order to differentiate the response of the cells to mechanical as opposed to mechanical modifications in their environment, only the rheological properties of the substrates were modified. In the case of entangled polymers this can be accomplished either by varying the molecular weight or the thickness of polymer films spun cast onto rigid supports. Scanning lateral force microscopy, which has been shown to be an effective technique for measuring relative modulii of surfaces(1) was used to track the mechanical response of the substrates as a function of processing procedures, molecular weight, both in liquid, air, and following fibronectin incubation. The response of the living cells was then compared to that of the underlying substrate. The samples were then stained and the distribution of actin correlated to the mechanical response. 1. S. Ge et al. Phys. Rev. Lett. 11, (2000)2340

  10. Microstructure and Mechanical Properties of Porous Mullite

    NASA Astrophysics Data System (ADS)

    Hsiung, Chwan-Hai Harold

    Mullite (3 Al2O3 : 2 SiO2) is a technologically important ceramic due to its thermal stability, corrosion resistance, and mechanical robustness. One variant, porous acicular mullite (ACM), has a unique needle-like microstructure and is the material platform for The Dow Chemical Company's diesel particulate filter AERIFY(TM). The investigation described herein focuses on the microstructure-mechanical property relationships in acicular mullites as well as those with traditional porous microstructures with the goal of illuminating the critical factors in determining their modulus, strength, and toughness. Mullites with traditional pore morphologies were made to serve as references via slipcasting of a kaolinite-alumina-starch slurry. The starch was burned out to leave behind a pore network, and the calcined body was then reaction-sintered at 1600C to form mullite. The samples had porosities of approximately 60%. Pore size and shape were altered by using different starch templates, and pore size was found to influence the stiffness and toughness. The ACM microstructure was varied along three parameters: total porosity, pore size, and needle size. Total porosity was found to dominate the mechanical behavior of ACM, while increases in needle and pore size increased the toughness at lower porosities. ACM was found to have much improved (˜130%) mechanical properties relative to its non-acicular counterpart at the same porosity. A second set of investigations studied the role of the intergranular glassy phase which wets the needle intersections of ACM. Removal of the glassy phase via an HF etch reduced the mechanical properties by ˜30%, highlighting the intergranular phase's importance to the enhanced mechanical properties of ACM. The composition of the glassy phase was altered by doping the ACM precursor with magnesium and neodymium. Magnesium doping resulted in ACM with greatly reduced fracture strength and toughness. Studies showed that the mechanical properties of the

  11. Mechanical Properties of Fe-Ni Meteorites

    NASA Astrophysics Data System (ADS)

    Roberta, Mulford; El Dasher, B.

    2010-10-01

    Iron-nickel meteorites exhibit a unique lamellar microstructure, Widmanstatten patterns, consisting of small regions with steep-iron-nickel composition gradients.1,2 The microstructure arises as a result of extremely slow cooling in a planetary core or other large mass. Mechanical properties of these structures have been investigated using microindentation, x-ray fluorescence, and EBSD. Observation of local mechanical properties in these highly structured materials supplements bulk measurements, which can exhibit large variation in dynamic properties, even within a single sample. 3 Accurate mechanical properties for meteorites may enable better modeling of planetary cores, the likely origin of these objects. Appropriate values for strength are important in impact and crater modeling and in understanding the consequences of observed impacts on planetary crusts. Previous studies of the mechanical properties of a typical iron-nickel meteorite, a Diablo Canyon specimen, indicated that the strength of the composite was higher by almost an order of magnitude than values obtained from laboratory-prepared specimens.4 This was ascribed to the extreme work-hardening evident in the EBSD measurements. This particular specimen exhibited only residual Widmanstatten structures, and may have been heated and deformed during its traverse of the atmosphere. Additional specimens from the Canyon Diablo fall (type IAB, coarse octahedrite) and examples from the Muonionalusta meteorite and Gibeon fall ( both IVA, fine octahedrite), have been examined to establish a range of error on the previously measured yield, to determine the extent to which deformation upon re-entry contributes to yield, and to establish the degree to which the strength varies as a function of microstructure. 1. A. Christiansen, et.al., Physica Scripta, 29 94-96 (1984.) 2. Goldstein and Ogilvie, Geochim Cosmochim Acta, 29 893-925 (1965.) 3. M. D. Furnish, M.B. Boslough, G.T. Gray II, and J.L. Remo, Int. J. Impact Eng

  12. Elastic proteins: biological roles and mechanical properties.

    PubMed Central

    Gosline, John; Lillie, Margo; Carrington, Emily; Guerette, Paul; Ortlepp, Christine; Savage, Ken

    2002-01-01

    The term 'elastic protein' applies to many structural proteins with diverse functions and mechanical properties so there is room for confusion about its meaning. Elastic implies the property of elasticity, or the ability to deform reversibly without loss of energy; so elastic proteins should have high resilience. Another meaning for elastic is 'stretchy', or the ability to be deformed to large strains with little force. Thus, elastic proteins should have low stiffness. The combination of high resilience, large strains and low stiffness is characteristic of rubber-like proteins (e.g. resilin and elastin) that function in the storage of elastic-strain energy. Other elastic proteins play very different roles and have very different properties. Collagen fibres provide exceptional energy storage capacity but are not very stretchy. Mussel byssus threads and spider dragline silks are also elastic proteins because, in spite of their considerable strength and stiffness, they are remarkably stretchy. The combination of strength and extensibility, together with low resilience, gives these materials an impressive resistance to fracture (i.e. toughness), a property that allows mussels to survive crashing waves and spiders to build exquisite aerial filters. Given this range of properties and functions, it is probable that elastic proteins will provide a wealth of chemical structures and elastic mechanisms that can be exploited in novel structural materials through biotechnology. PMID:11911769

  13. Mechanical properties of crosslinked polymer coatings

    NASA Technical Reports Server (NTRS)

    Csernica, Jeffrey

    1994-01-01

    The objectives of this experiment are to: fabricate and test thin films to explore relations between a polymer's structure and its mechanical properties; expose students to testing methods for hardness and impact energy that are simple to perform and which have results that are easy to comprehend; show importance of polymer properties in materials that students frequently encounter; illustrate a system which displays a tradeoff between strength and impact resistance, the combination of which would need to be optimized for a particular application; and to expose students to coatings technology and testing.

  14. Punishment Mechanism with Self-Adjusting Rules in Spatial Voluntary Public Goods Games

    NASA Astrophysics Data System (ADS)

    Wu, Zhong-Wei; Xu, Zhao-Jin; Zhang, Lian-Zhong

    2014-11-01

    The phenomena of cooperation in animal and human society are ubiquitous, but the selfish outcome that no player contributes to the public good will lead to the “tragedy of the commons”. The recent research shows that high punishment can improve the cooperation of the population. In this paper, we introduce a punishment mechanism into spatial voluntary public goods games with every individual only knowing his own payoff in each round. Using the self-adjusting rules, we find that the different cost for punishment can lead to different effects on the voluntary public goods games. Especially, when the cost for punishment is decreased, a higher contribution region will appear in the case of low r value. It means even for the low r value, individuals can form the contributing groups in large quantities to produce a more efficient outcome than that in moderate r value. In addition, we also find the players' memory can have effects on the average outcome of the population.

  15. Mechanical properties of intra-ocular lenses

    NASA Astrophysics Data System (ADS)

    Ehrmann, Klaus; Kim, Eon; Parel, Jean-Marie

    2008-02-01

    Cataract surgery usually involves the replacement of the natural crystalline lens with a rigid or foldable intraocular lens to restore clear vision for the patient. While great efforts have been placed on optimising the shape and optical characteristics of IOLs, little is know about the mechanical properties of these devices and how they interact with the capsular bag once implanted. Mechanical properties measurements were performed on 8 of the most commonly implanted IOLs using a custom build micro tensometer. Measurement data will be presented for the stiffness of the haptic elements, the buckling resistance of foldable IOLs, the dynamic behaviour of the different lens materials and the axial compressibility. The biggest difference between the lens types was found between one-piece and 3-piece lenses with respect to the flexibility of the haptic elements

  16. Advanced mechanical properties of graphene paper

    NASA Astrophysics Data System (ADS)

    Ranjbartoreh, Ali R.; Wang, Bei; Shen, Xiaoping; Wang, Guoxiu

    2011-01-01

    Graphene paper (GP) has been prepared by flow-directed assembly of graphene nanosheets. The mechanical properties of as-prepared GPs were investigated by tensile, indentation, and bending tests. Heat treated GPs demonstrate superior hardness, ten times that of synthetic graphite, and two times that of carbon steel; besides, their yielding strength is significantly higher than that of carbon steel. GPs show extremely high modulus of elasticity during bending test; in the range of a few terapascal. The high strength and stiffness of GP is ascribed to the interlocking-tile microstructure of individual graphene nanosheets in the paper. These outstanding mechanical properties of GPs could lead to a wide range of engineering applications.

  17. Rhenium Mechanical Properties and Joining Technology

    NASA Technical Reports Server (NTRS)

    Reed, Brian D.; Biaglow, James A.

    1996-01-01

    Iridium-coated rhenium (Ir/Re) provides thermal margin for high performance and long life radiation cooled rockets. Two issues that have arisen in the development of flight Ir/Re engines are the sparsity of rhenium (Re) mechanical property data (particularly at high temperatures) required for engineering design, and the inability to directly electron beam weld Re chambers to C103 nozzle skirts. To address these issues, a Re mechanical property database is being established and techniques for creating Re/C103 transition joints are being investigated. This paper discusses the tensile testing results of powder metallurgy Re samples at temperatures from 1370 to 2090 C. Also discussed is the evaluation of Re/C103 transition pieces joined by both, explosive and diffusion bonding. Finally, the evaluation of full size Re transition pieces, joined by inertia welding, as well as explosive and diffusion bonding, is detailed.

  18. Mechanical properties of functionalized carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Zhang, Z. Q.; Liu, B.; Chen, Y. L.; Jiang, H.; Hwang, K. C.; Huang, Y.

    2008-10-01

    Carbon nanotubes (CNTs) used to reinforce polymer matrix composites are functionalized to form covalent bonds with the polymer in order to enhance the CNT/polymer interfaces. These bonds destroy the perfect atomic structures of a CNT and degrade its mechanical properties. We use atomistic simulations to study the effect of hydrogenization on the mechanical properties of single-wall carbon nanotubes. The elastic modulus of CNTs gradually decreases with the increasing functionalization (percentage of C-H bonds). However, both the strength and ductility drop sharply at a small percentage of functionalization, reflecting their sensitivity to C-H bonds. The cluster C-H bonds forming two rings leads to a significant reduction in the strength and ductility. The effect of carbonization has essentially the same effect as hydrogenization.

  19. 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

  20. Mechanical Properties of Palm Fiber Mattress

    NASA Astrophysics Data System (ADS)

    Li, Yu-Qian; Wu, Jia-Yu; Gu, Hao-Wei; Chen, Zong-Yong; Shi, Xiao-Bing; Liao, Ting-Mao; An, Cheng; Yuan, Hong; Liu, Ren-Huai

    2016-05-01

    Palm fiber mattress is increasingly accepted by many families. This study aims at evaluating the mechanical properties of palm fiber mattress. Two experiments were conduct to investigate the Young's modulus of palm fiber mattress in three directions. In addition, finite element models were established to characterize palm fiber mattress under uniform distributed pressure. Finally, results from finite element analysis are presented to illustrate that the thick mattress will stick with human body curve perfectly, which can support vertebral column effectively.

  1. Mechanical property characterization of intraply hybrid composites

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.; Lark, R. F.; Sinclair, J. H.

    1979-01-01

    An investigation was conducted to characterize the mechanical properties of intraply hybrids made from graphite fiber/epoxy matrix (primary composites) hybridized with varying amounts of secondary composites made from S-glass or Kevlar 49 fibers. The tests were conducted using thin laminates having the same thickness. The specimens for these tests were instrumented with strain gages to determine stress-strain behavior. Significant results are included.

  2. Compositional Determinants of Mechanical Properties of Enamel

    PubMed Central

    Baldassarri, M.; Margolis, H.C.; Beniash, E.

    2008-01-01

    Dental enamel is comprised primarily of carbonated apatite, with less than 1% w/w organic matter and 4-5% w/w water. To determine the influence of each component on the microhardness and fracture toughness of rat incisor enamel, we mechanically tested specimens in which water and organic matrix were selectively removed. Tests were performed in mid-sagittal and transverse orientations to assess the effect of the structural organization on enamel micromechanical properties. While removal of organic matrix resulted in up to a 23% increase in microhardness, and as much as a 46% decrease in fracture toughness, water had a significantly lesser effect on these properties. Moreover, removal of organic matrix dramatically weakened the dentino-enamel junction (DEJ). Analysis of our data also showed that the structural organization of enamel affects its micromechanical properties. We anticipate that these findings will help guide the development of bio-inspired nanostructured materials for mineralized tissue repair and regeneration. PMID:18573984

  3. Determinants of the mechanical properties of bones

    NASA Technical Reports Server (NTRS)

    Martin, R. B.

    1991-01-01

    The mechanical properties of bones are governed by the same principles as those of man-made load-bearing structures, but the organism is able to adapt its bone structure to changes in skeletal loading. In this overview of the determinants of the strength and stiffness of bone, a continuum approach has been taken, in which the behavior of a macroscopic structure depends on its shape and size, and on the mechanical properties of the material within. The latter are assumed to depend on the composition (porosity and mineralization) and organization (trabecular or cortical bone architecture, collagen fiber orientation, fatigue damage) of the bone. The effects of each of these factors are reviewed. Also, the possible means of non-invasively estimating the strength or other mechanical properties of a bone are reviewed, including quantitative computed tomography, photon absorptiometry, and ultrasonic measurements. The best estimates of strength have been obtained with photon absorptiometry and computed tomography, which at best are capable of accounting for 90% of the strength variability in a simple in vitro test, but results from different laboratories have been highly variable.

  4. Database of Mechanical Properties of Textile Composites

    NASA Technical Reports Server (NTRS)

    Delbrey, Jerry

    1996-01-01

    This report describes the approach followed to develop a database for mechanical properties of textile composites. The data in this database is assembled from NASA Advanced Composites Technology (ACT) programs and from data in the public domain. This database meets the data documentation requirements of MIL-HDBK-17, Section 8.1.2, which describes in detail the type and amount of information needed to completely document composite material properties. The database focuses on mechanical properties of textile composite. Properties are available for a range of parameters such as direction, fiber architecture, materials, environmental condition, and failure mode. The composite materials in the database contain innovative textile architectures such as the braided, woven, and knitted materials evaluated under the NASA ACT programs. In summary, the database contains results for approximately 3500 coupon level tests, for ten different fiber/resin combinations, and seven different textile architectures. It also includes a limited amount of prepreg tape composites data from ACT programs where side-by-side comparisons were made.

  5. Wild capuchin monkeys adjust stone tools according to changing nut properties.

    PubMed

    Luncz, Lydia V; Falótico, Tiago; Pascual-Garrido, Alejandra; Corat, Clara; Mosley, Hannah; Haslam, Michael

    2016-09-14

    Animals foraging in their natural environments need to be proficient at recognizing and responding to changes in food targets that affect accessibility or pose a risk. Wild bearded capuchin monkeys (Sapajus libidinosus) use stone tools to access a variety of nut species, including otherwise inaccessible foods. This study tests whether wild capuchins from Serra da Capivara National Park in Brazil adjust their tool selection when processing cashew (Anacardium spp.) nuts. During the ripening process of cashew nuts, the amount of caustic defensive substance in the nut mesocarp decreases. We conducted field experiments to test whether capuchins adapt their stone hammer selection to changing properties of the target nut, using stones of different weights and two maturation stages of cashew nuts. The results show that although fresh nuts are easier to crack, capuchin monkeys used larger stone tools to open them, which may help the monkeys avoid contact with the caustic hazard in fresh nuts. We demonstrate that capuchin monkeys are actively able to distinguish between the maturation stages within one nut species, and to adapt their foraging behaviour accordingly.

  6. Wild capuchin monkeys adjust stone tools according to changing nut properties

    PubMed Central

    Luncz, Lydia V.; Falótico, Tiago; Pascual-Garrido, Alejandra; Corat, Clara; Mosley, Hannah; Haslam, Michael

    2016-01-01

    Animals foraging in their natural environments need to be proficient at recognizing and responding to changes in food targets that affect accessibility or pose a risk. Wild bearded capuchin monkeys (Sapajus libidinosus) use stone tools to access a variety of nut species, including otherwise inaccessible foods. This study tests whether wild capuchins from Serra da Capivara National Park in Brazil adjust their tool selection when processing cashew (Anacardium spp.) nuts. During the ripening process of cashew nuts, the amount of caustic defensive substance in the nut mesocarp decreases. We conducted field experiments to test whether capuchins adapt their stone hammer selection to changing properties of the target nut, using stones of different weights and two maturation stages of cashew nuts. The results show that although fresh nuts are easier to crack, capuchin monkeys used larger stone tools to open them, which may help the monkeys avoid contact with the caustic hazard in fresh nuts. We demonstrate that capuchin monkeys are actively able to distinguish between the maturation stages within one nut species, and to adapt their foraging behaviour accordingly. PMID:27624672

  7. Melt-processable hydrophobic acrylonitrile-based copolymer systems with adjustable elastic properties designed for biomedical applications.

    PubMed

    Cui, J; Trescher, K; Kratz, K; Jung, F; Hiebl, B; Lendlein, A

    2010-01-01

    (AN-co-nBA) biomaterials were sterilized with ethylene oxide and tested for cytotoxicity in direct contact tests with L929 cells according to the EN DIN ISO standard 10993-5. All tested samples exhibited non-toxic effects on the functional integrity of the cell membrane and the mitochondrial activity. However, the morphology of the cells on the samples was different from that observed on polystyrene as control, indicating slightly cytotoxic effects according to the evaluation guide of the US Pharmacopeial Convention. Thus, the melt-processable, hydrophobic P(AN-co-nBA) copolymers with adjustable mechanical properties are promising candidates for in vitro investigations of tissue growth kinetics.

  8. Machining as a mechanical property test revisited

    NASA Astrophysics Data System (ADS)

    Smith, David L.

    There is much need for data on mechanical behavior of metals at high strains and strain rates. This need is dictated by modeling of processes like forming and machining, wherein the material in the deformation zone is subjected to severe deformation conditions atypical of conventional material property tests such as tension and torsion. Accurate flow stress data is an essential input for robust prediction of process outputs. Similar requirements arise from applications in high speed ballistic penetration and design of materials for armor. Since the deformation zone in cutting of metals is characterized by unique and extreme combinations of strain, strain rate and temperature, an opportunity exists for using plane-strain cutting as a mechanical property test for measuring flow properties of metals. The feasibility of using plane-strain cutting to measure flow properties of metals is revisited in the light of recent data showing controllability of the deformation conditions in chip formation by systematic variation of process input parameters. A method is outlined as to how the deformation conditions can be varied by changing the process parameters. The method is applied to cutting of commercially pure copper (FCC), iron (BCC) and zinc (HCP). Forces and chip geometries are measured, in conjunction with particle image velocimetry characterization of the deformation using high speed image sequences. The flow stresses are estimated from these measurements. The measured flow stress and its dependence on strain are shown to agree well with prior measurements of these parameters using conventional tests, and flow stress inferred from hardness characterization. The method is also demonstrated to be able to measure properties of metals that recrystallize at room temperature (zinc), wherein quasi-static tests predict much lower strength. Sources of variability and uncertainty in the application of this measurement technique are discussed. Future work in the context of further

  9. Fabrication of drug-loaded anti-infective guided tissue regeneration membrane with adjustable biodegradation property.

    PubMed

    Xue, Jiajia; Shi, Rui; Niu, Yuzhao; Gong, Min; Coates, Phil; Crawford, Aileen; Chen, Dafu; Tian, Wei; Zhang, Liqun

    2015-11-01

    For guided tissue regeneration (GTR) membrane, synchronization of the membrane biodegradation rate and tissue regeneration rate is important. Besides, the major reason for GTR membrane failure in clinical application is infection which can be prevented by loading anti-bacterial drug. To realize the consistency in membrane degradation rate and tissue regeneration rate of the anti-infective membrane, we developed metronidazole-loaded electrospun poly(ɛ-caprolactone)-gelatin nanofiber membranes with different poly(ɛ-caprolactone)/gelatin ratios (95:5, 90:10, 80:20, 70:30, 60:40, and 50:50). Homogeneous nanofibers were successfully fabricated. The mechanical strength of the membranes increased with the poly(ɛ-caprolactone) content, while the hydrophilicity decreased. The controlled and sustained release of metronidazole from all the membranes prevented the colonization of anaerobic bacteria. At all poly(ɛ-caprolactone)/gelatin ratios, all the membranes presented good biocompatibility while the increase of gelatin content resulted in enhanced cell adhesion and proliferation. Subcutaneous implantation in rabbits for 8 months demonstrated that all the membranes showed good biocompatibility without infection. Both in vitro and in vivo results showed that the biodegradation rate of the membranes was accelerated with the increase of gelatin content. The biodegradation rate and biocompatibility of the membranes can be adjusted by changing the PCL/gelatin ratio. The optimal membrane can be chosen based on the patient and tissue type to realize the synchronization of membrane degradation with tissue regeneration for the best treatment effect.

  10. Design of monoliths through their mechanical properties.

    PubMed

    Podgornik, Aleš; Savnik, Aleš; Jančar, Janez; Krajnc, Nika Lendero

    2014-03-14

    Chromatographic monoliths have several interesting properties making them attractive supports for analytics but also for purification, especially of large biomolecules and bioassemblies. Although many of monolith features were thoroughly investigated, there is no data available to predict how monolith mechanical properties affect its chromatographic performance. In this work, we investigated the effect of porosity, pore size and chemical modification on methacrylate monolith compression modulus. While a linear correlation between pore size and compression modulus was found, the effect of porosity was highly exponential. Through these correlations it was concluded that chemical modification affects monolith porosity without changing the monolith skeleton integrity. Mathematical model to describe the change of monolith permeability as a function of monolith compression modulus was derived and successfully validated for monoliths of different geometries and pore sizes. It enables the prediction of pressure drop increase due to monolith compressibility for any monolith structural characteristics, such as geometry, porosity, pore size or mobile phase properties like viscosity or flow rate, based solely on the data of compression modulus and structural data of non-compressed monolith. Furthermore, it enables simple determination of monolith pore size at which monolith compressibility is the smallest and the most robust performance is expected. Data of monolith compression modulus in combination with developed mathematical model can therefore be used for the prediction of monolith permeability during its implementation but also to accelerate the design of novel chromatographic monoliths with desired hydrodynamic properties for particular application.

  11. PICA Variants with Improved Mechanical Properties

    NASA Technical Reports Server (NTRS)

    Thornton, Jeremy; Ghandehari, Ehson M.; Fan, Wenhong; Stackpoole, Margaret; Chavez-Garcia, Jose

    2011-01-01

    Phenolic Impregnated Carbon Ablator (PICA) is a member of the family of Lightweight Ceramic Ablators (LCAs) and was developed at NASA Ames Research Center as a thermal protection system (TPS) material for the Stardust mission probe that entered the Earth s atmosphere faster than any other probe or vehicle to date. PICA, carbon fiberform base and phenolic polymer, shows excellent thermal insulative properties at heating rates from about 250 W/sq cm to 1000 W/sq cm. The density of standard PICA - 0.26 g/cu cm to 0.28 g/cu cm - can be changed by changing the concentration of the phenolic resin. By adding polymers to the phenolic resin before curing it is possible to significantly improve the mechanical properties of PICA without significantly increasing the density.

  12. Design and mechanical properties of insect cuticle.

    PubMed

    Vincent, Julian F V; Wegst, Ulrike G K

    2004-07-01

    Since nearly all adult insects fly, the cuticle has to provide a very efficient and lightweight skeleton. Information is available about the mechanical properties of cuticle-Young's modulus of resilin is about 1 MPa, of soft cuticles about 1 kPa to 50 MPa, of sclerotised cuticles 1-20 GPa; Vicker's Hardness of sclerotised cuticle ranges between 25 and 80 kgf mm(-2); density is 1-1.3 kg m(-3)-and one of its components, chitin nanofibres, the Young's modulus of which is more than 150 GPa. Experiments based on fracture mechanics have not been performed although the layered structure probably provides some toughening. The structural performance of wings and legs has been measured, but our understanding of the importance of buckling is lacking: it can stiffen the structure (by elastic postbuckling in wings, for example) or be a failure mode. We know nothing of fatigue properties (yet, for instance, the insect wing must undergo millions of cycles, flexing or buckling on each cycle). The remarkable mechanical performance and efficiency of cuticle can be analysed and compared with those of other materials using material property charts and material indices. Presented in this paper are four: Young's modulus-density (stiffness per unit weight), specific Young's modulus-specific strength (elastic hinges, elastic energy storage per unit weight), toughness-Young's modulus (fracture resistance under various loading conditions), and hardness (wear resistance). In conjunction with a structural analysis of cuticle these charts help to understand the relevance of microstructure (fibre orientation effects in tendons, joints and sense organs, for example) and shape (including surface structure) of this fibrous composite for a given function. With modern techniques for analysis of structure and material, and emphasis on nanocomposites and self-assembly, insect cuticle should be the archetype for composites at all levels of scale.

  13. 26 CFR 1.734-1 - Optional adjustment to basis of undistributed partnership property.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... of the partner's entire interest in the partnership, the adjusted basis of the remaining partnership... distributee partner, or (ii) The excess of the adjusted basis to the partnership immediately before the... the distributee partner. See § 1.460-4(k)(2)(iv)(D) for a rule determining the partnership's basis...

  14. 26 CFR 1.743-1 - Optional adjustment to basis of partnership property.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... gift to T3 of fifty percent of T2's interest in PRS. At the time of the transfer, T2 has a $200 basis adjustment under section 743(b). T2 is treated as transferring $100 of the basis adjustment to T3 with...

  15. Synergistic effect of adjustments of elastic stockings to maintain reduction in leg volume after mechanical lymph drainage.

    PubMed

    de Godoy, José Maria Pereira; Lopes Pinto, Renata; Pereira de Godoy, Ana Carolina; de Fátima Guerreiro Godoy, Maria

    2014-01-01

    The objective of the present study was to evaluate the effect of elastic compression stockings on volumetric variations of lymphedematous limbs between mechanical lymph drainage sessions. Eleven patients with Grade II leg lymphedema, regardless of etiology, were evaluated in a randomized clinical trial. The ages ranged from 47 to 83 years old with a mean of 62.4 years. Participants were submitted to mechanical lymph drainage (RAGodoy) associated with adjusted and unadjusted knee-high elastic compression stockings (20/30 Venosan). The effect of these stockings on the maintenance of volumetric reductions between sessions of lymph drainage was assessed. In all, 33 evaluations were carried out, 18 of patients using well-adjusted stockings and 15 with badly-adjusted stockings. The differences in volumes were significant (unpaired t-test; P-value < 0.0001). Adjusting the compression provided by elastic stockings according to the size of the leg has a synergistic effect in reducing volume during mechanical lymph drainage.

  16. Linking properties to microstructure through multiresolution mechanics

    NASA Astrophysics Data System (ADS)

    McVeigh, Cahal James

    The macroscale mechanical and physical properties of materials are inherently linked to the underlying microstructure. Traditional continuum mechanics theories have focused on approximating the heterogeneous microstructure as a continuum, which is conducive to a partial differential equation mathematical description. Although this makes large scale simulation of material much more efficient than modeling the detailed microstructure, the relationship between microstructure and macroscale properties becomes unclear. In order to perform computational materials design, material models must clearly relate the key underlying microstructural parameters (cause) to macroscale properties (effect). In this thesis, microstructure evolution and instability events are related to macroscale mechanical properties through a new multiresolution continuum analysis approach. The multiresolution nature of this theory allows prediction of the evolving magnitude and scale of deformation as a direct function of the changing microstructure. This is achieved via a two-pronged approach: (a) Constitutive models which track evolving microstructure are developed and calibrated to direct numerical simulations (DNS) of the microstructure. (b) The conventional homogenized continuum equations of motion are extended via a virtual power approach to include extra coupled microscale stresses and stress couples which are active at each characteristic length scale within the microstructure. The multiresolution approach is applied to model the fracture toughness of a cemented carbide, failure of a steel alloy under quasi-static loading conditions and the initiation and velocity of adiabatic shear bands under high speed dynamic loading. In each case the multiresolution analysis predicts the important scale effects which control the macroscale material response. The strain fields predicted in the multiresolution continuum analyses compare well to those observed in direct numerical simulations of the

  17. Mechanical properties of low dimensional materials

    NASA Astrophysics Data System (ADS)

    Saini, Deepika

    Recent advances in low dimensional materials (LDMs) have paved the way for unprecedented technological advancements. The drive to reduce the dimensions of electronics has compelled researchers to devise newer techniques to not only synthesize novel materials, but also tailor their properties. Although micro and nanomaterials have shown phenomenal electronic properties, their mechanical robustness and a thorough understanding of their structure-property relationship are critical for their use in practical applications. However, the challenges in probing these mechanical properties dramatically increase as their dimensions shrink, rendering the commonly used techniques inadequate. This dissertation focuses on developing techniques for accurate determination of elastic modulus of LDMs and their mechanical responses under tensile and shear stresses. Fibers with micron-sized diameters continuously undergo tensile and shear deformations through many phases of their processing and applications. Significant attention has been given to their tensile response and their structure-tensile properties relations are well understood, but the same cannot be said about their shear responses or the structure-shear properties. This is partly due to the lack of appropriate instruments that are capable of performing direct shear measurements. In an attempt to fill this void, this dissertation describes the design of an inexpensive tabletop instrument, referred to as the twister, which can measure the shear modulus (G) and other longitudinal shear properties of micron-sized individual fibers. An automated system applies a pre-determined twist to the fiber sample and measures the resulting torque using a sensitive optical detector. The accuracy of the instrument was verified by measuring G for high purity copper and tungsten fibers. Two industrially important fibers, IM7 carbon fiber and KevlarRTM 119, were found to have G = 17 and 2.4 GPa, respectively. In addition to measuring the shear

  18. Passive mechanical properties of ovine rumen tissue

    NASA Astrophysics Data System (ADS)

    Waite, Stephen J.; Cater, John E.; Walker, Cameron G.; Amirapu, Satya; Waghorn, Garry C.; Suresh, Vinod

    2016-05-01

    Mechanical and structural properties of ovine rumen tissue have been determined using uniaxial tensile testing of tissue from four animals at five rumen locations and two orientations. Animal and orientation did not have a significant effect on the stress-strain response, but there was a significant difference between rumen locations. Histological studies showed two orthogonal muscle layers in all regions except the reticulum, which has a more isotropic structure. A quasi-linear viscoelastic model was fitted to the relaxation stage for each region. Model predictions of the ramp stage had RMS errors of 13-24% and were within the range of the experimental data.

  19. Mechanical properties of phosphorene nanoribbons and oxides

    SciTech Connect

    Hao, Feng; Chen, Xi

    2015-12-21

    Mechanical properties of phosphorene nanoribbons and oxides are investigated by using density functional theory. It is found that the ideal strength of nanoribbon decreases in comparison with that of 2D phosphorene. The Young's modulus of armchair nanoribbon has a remarkable size effect because of the edge relaxations. The analysis of the stress-strain relation indicates that, owing to chemisorbed oxygen atoms, the ideal strength and Young's modulus of 2D phosphorene oxide are greatly reduced along the zigzag direction, especially upon high oxidation ratios. In addition, strain and oxidation have significant impacts on phonon dispersion.

  20. Physical and Mechanical Properties of Glass--Reinforced Plastics,

    DTIC Science & Technology

    REINFORCED PLASTICS , REVIEWS), GLASS TEXTILES, MECHANICAL PROPERTIES, ELECTRICAL PROPERTIES, SILICONE PLASTICS , POLYESTER PLASTICS , PHENOLIC... PLASTICS , EPOXY RESINS, TEST METHODS, NONDESTRUCTIVE TESTING, FIRE RESISTANT MATERIALS, POLYVINYL CHLORIDE, USSR

  1. Braiding Simulation and Prediction of Mechanical Properties

    NASA Astrophysics Data System (ADS)

    Pickett, Anthony K.; Sirtautas, Justas; Erber, Andreas

    2009-12-01

    Rotary braiding is a cost effective method to manufacture near net shaped preforms that generally have a closed section and may have an arbitrary shape if braiding is performed over a shaped mandrel. The reinforcement architecture can be varied by the number and spacing of active bobbins, and by the speeds used to ‘take-up’ the braid and move the circumferential bobbins. Analytical methods are available that can reliably predict yarn paths and the final braid meso-structure for simple regular sections, and further analytical methods have been proposed to estimate composite braid elastic mechanical properties. A full simulation chain using the explicit Finite Element (FE) technique is presented for composite braid manufacture and mechanical stiffness prediction of the final composite. First simulation of the braiding process provides detailed information on yarns paths and braid meso-structure, from which Representative Volume Elements (RVE) of the braid may be constructed for analysis of stiffness properties. The techniques are general and can be applied to any braid geometry. A specific problem of meshing the yarn structure and interspersed resin volumes is overcome using conventional solid elements for the yarns and Smooth Particle Hydrodynamics for the resin, with link element to join the two constituents. Details of the background theory, braid simulation methods, meso- model analysis and validation again analytical and test measurements are presented.

  2. Mechanical properties of 3D ceramic nanolattices

    NASA Astrophysics Data System (ADS)

    Meza, Lucas

    Developments in advanced nanoscale fabrication techniques have allowed for the creation of 3-dimensional hierarchical structural meta-materials that can be designed with arbitrary geometry. These structures can be made on length scales spanning multiple orders of magnitude, from tens of nanometers to hundreds of microns. The smallest features are controllable on length scales where materials have been shown to exhibit size effects in their mechanical properties. Combining novel nanoscale mechanical properties with a 3-dimensional architecture enables the creation of new classes of materials with tunable and unprecedented mechanical properties. We present the fabrication and mechanical deformation of hollow tube alumina nanolattices that were fabricated using two-photon lithography direct laser writing (DLW), atomic layer deposition (ALD), and oxygen plasma etching. Nanolattices were designed in a number of different geometries including octet-truss, octahedron, and 3D Kagome. Additionally, a number of structural parameters were varied including tube wall thickness (t) , tube major axis (a) , and unit cell size (L) . The resulting nanolattices had a range of densities from ρ = 4 to 250 mg/cm3. Uniaxial compression and cyclic loading tests were performed on the nanolattices to obtain the yield strength and modulus. In these tests, a marked change in the deformation response was observed when the wall thickness was reduced below 20nm; thick-walled nanolattices (t>20nm) underwent catastrophic, brittle failure, which transitioned to a gradual, ductile-like deformation as wall thickness was reduced. Thick-walled nanolattices also exhibited no recovery after compression, while thin-walled structures demonstrated notable recovery, with some recovering by 98% after compression to 50% strain and by 80% when compressed to 90% strain. Across all geometries, unit cell sizes, and wall thicknesses, we found a consistent power law relation between strength and modulus with

  3. Mechanical properties of the beetle elytron, a biological composite material

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We determined the relationship between composition and mechanical properties of elytral (modified forewing) cuticle of the beetles Tribolium castaneum and Tenebrio molitor. Elytra of both species have similar mechanical properties at comparable stages of maturation (tanning). Shortly after adult ecl...

  4. Denial and External Locus of Control as Mechanisms of Adjustment in Chronic Medical Illness

    ERIC Educational Resources Information Center

    Goldstein, Alan M.

    1976-01-01

    Adjustment of patients with a serious medical condition to psychological stress accompanying their disorder was investigated. Long-term hemodialysis patients (N=22) and 24 patients in recovery stages of minor medical problems were experimental and control subjects. A significant relationship was found between denial and external locus of control…

  5. Mechanical properties of icosahedral virus capsids

    NASA Astrophysics Data System (ADS)

    Vliegenthart, G. A.; Gompper, G.

    2007-12-01

    Virus capsids are self-assembled protein shells in the size range of 10 to 100 nanometers. The shells of DNA-viruses have to sustain large internal pressures while encapsulating and protecting the viral DNA. We employ computer simulations to study the mechanical properties of crystalline shells with icosahedral symmetry that serve as a model for virus capsids. The shells are positioned on a substrate and deformed by a uni-axial force excerted by a small bead. We predict the elastic response for small deformations, and the buckling transitions at large deformations. Both are found to depend strongly on the number N of elementary building blocks (capsomers), and the Föppl-von Kármán number γ which characterizes the relative importance of shear and bending elasticity.

  6. Mechanical properties of high-strength concrete

    NASA Astrophysics Data System (ADS)

    Mokhtarzadeh, Alireza

    This report summarizes an experimental program conducted to investigate production techniques and mechanical properties of high strength concrete in general and to provide recommendations for using these concretes in manufacturing precast/prestressed bridge girders. Test variables included total amount and composition of cementitious material (portland cement, fly ash, and silica fume), type and brand of cement, type of silica fume (dry densified and slurry), type and brand of high-range water-reducing admixture, type of aggregate, aggregate gradation, maximum aggregate size, and curing. Tests were conducted to determine the effects of these variables on changes in compressive strength and modulus of elasticity over time, splitting tensile strength, modulus of rupture, creep, shrinkage, and absorption potential (as an indirect indicator of permeability). Also investigated were the effects of test parameters such as mold size, mold material, and end condition. Over 6,300 specimens were cast from approximately 140 mixes over a period of 3 years.

  7. Valve timing adjusting mechanism for internal combustion engine for adjusting timing of intake valve and/or exhaust valve corresponding to engine operating conditions

    SciTech Connect

    Akassaka, A.; Suga, S.; Sawada, T.

    1989-03-14

    A valve timing adjusting mechanism for an internal combustion engine is described, comprising: a camshaft carrying a cam for driving one of an intake valve and an exhaust valve, the camshaft having a section formed with first helical gear teeth; a cam pulley engaging a timing belt driven by the engine for rotation in synchronism with engine revolution, the cam pulley having second helical gear teeth; a ring gear having inner and outer helical gear teeth engageable with the first and second gear teeth of the camshaft and the cam pulley; first means for defining an enclosed chamber facing one planar face of the ring gear and connected with a fluid pressure source to receive pressurized fluid therefrom; a spring means associated with the other planar face of the ring gear for exerting an initial biasing force on the ring gear in opposition to the force due to the pressure on the ring gear from the enclosed chamber; and second means for controlling the fluid pressure introduced into the enclosed chamber in accordance with engine operating conditions so as to shift the ring gear between two positions.

  8. A poly(glycerol sebacate)-coated mesoporous bioactive glass scaffold with adjustable mechanical strength, degradation rate, controlled-release and cell behavior for bone tissue engineering.

    PubMed

    Lin, Dan; Yang, Kai; Tang, Wei; Liu, Yutong; Yuan, Yuan; Liu, Changsheng

    2015-07-01

    Various requirements in the field of tissue engineering have motivated the development of three-dimensional scaffold with adjustable physicochemical properties and biological functions. A series of multiparameter-adjustable mesoporous bioactive glass (MBG) scaffolds with uncrosslinked poly(glycerol sebacate) (PGS) coating was prepared in this article. MBG scaffold was prepared by a modified F127/PU co-templating process and then PGS was coated by a simple adsorption and lyophilization process. Through controlling macropore parameters and PGS coating amount, the mechanical strength, degradation rate, controlled-release and cell behavior of the composite scaffold could be modulated in a wide range. PGS coating successfully endowed MBG scaffold with improved toughness and adjustable mechanical strength covering the bearing range of trabecular bone (2-12MPa). Multilevel degradation rate of the scaffold and controlled-release rate of protein from mesopore could be achieved, with little impact on the protein activity owing to an "ultralow-solvent" coating and "nano-cavity entrapment" immobilization method. In vitro studies indicated that PGS coating promoted cell attachment and proliferation in a dose-dependent manner, without affecting the osteogenic induction capacity of MBG substrate. These results first provide strong evidence that uncrosslinked PGS might also yield extraordinary achievements in traditional MBG scaffold. With the multiparameter adjustability, the composite MBG/PGS scaffolds would have a hopeful prospect in bone tissue engineering. The design considerations and coating method of this study can also be extended to other ceramic-based artificial scaffolds and are expected to provide new thoughts on development of future tissue engineering materials.

  9. Mechanical properties of nanocrystalline diamond films

    NASA Astrophysics Data System (ADS)

    Shen, Z. H.; Hess, P.; Huang, J. P.; Lin, Y. C.; Chen, K. H.; Chen, L. C.; Lin, S. T.

    2006-06-01

    Nanocrystalline diamond (NCD) films with thicknesses in the range of 0.12-1.5 μm were deposited on silicon substrates in CH4/H2/O2 gas mixtures by microwave plasma-enhanced chemical vapor deposition. The morphology and structure of these NCD films were analyzed by field-emission scanning electron microscopy, x-ray diffraction (XRD), and ultraviolet-Raman spectroscopy. The lower limit of the grain size in the NCD films was estimated to be 10 nm from the XRD measurements. These grains are embedded in a columnar-type structure. The elastic and mechanical properties of the NCD films were determined by measuring the dispersion of laser-induced surface acoustic waves. The densities were in the range of 3.41+/-0.11 g/cm3 and Young's moduli varied between 674+/-34 and 953+/-48 GPa, depending on the growth time and deposition conditions. It is concluded that oxygen may have a significant positive effect on the elastic properties of NCD films. The growth rate decreases sharply for an oxygen content in the source gas in excess of about 4%.

  10. Mechanical properties of semiconductors and their alloys

    NASA Astrophysics Data System (ADS)

    Sher, A.; Berding, M. A.; Paxton, A. T.; Krishnamurthy, S.; Chen, A.-B.

    1992-02-01

    A wide range of subjects have been treated in this contract. We have devoted time to the development and applications of two first principles computational methods: one, the full-potential linear muffin tin orbital (FP-LMTO) method is somewhat mature and highly accurate, while the other, linear combination of atomic orbitals (LCAO), is less accurate but more flexible and is easily incorporated into the other calculations we have in place, e.g., surface Green's function methods and CPA. Tight binding has also been used. These methods have been applied to solve a host of mechanical-property problems including elastic constants, cleavage energies, sublimation energies, interactions between surface atoms relating to their surface order-disorder state and growth theory, surface segregation, bulk order-disorder theory and phase stability, the effect of dislocations on electronic transport and electro-optic properties of semiconductors, the Ni-Al intermetallic phase diagram, planar fault energies in L12 alloys, high-performance structural metal alloy design, and a contribution to understanding the Jones theory of metal alloying. Many of these subjects have been brought to publishable conclusions. Whenever possible, we have presented our detailed results in the form of preprints and reprints, with only brief summaries of the work given here. In instances where the research is incomplete, we have given somewhat longer expositions.

  11. Mechanical properties of nanostructure of biological materials

    NASA Astrophysics Data System (ADS)

    Ji, Baohua; Gao, Huajian

    2004-09-01

    Natural biological materials such as bone, teeth and nacre are nanocomposites of protein and mineral with superior strength. It is quite a marvel that nature produces hard and tough materials out of protein as soft as human skin and mineral as brittle as classroom chalk. What are the secrets of nature? Can we learn from this to produce bio-inspired materials in the laboratory? These questions have motivated us to investigate the mechanics of protein-mineral nanocomposite structure. Large aspect ratios and a staggered alignment of mineral platelets are found to be the key factors contributing to the large stiffness of biomaterials. A tension-shear chain (TSC) model of biological nanostructure reveals that the strength of biomaterials hinges upon optimizing the tensile strength of the mineral crystals. As the size of the mineral crystals is reduced to nanoscale, they become insensitive to flaws with strength approaching the theoretical strength of atomic bonds. The optimized tensile strength of mineral crystals thus allows a large amount of fracture energy to be dissipated in protein via shear deformation and consequently enhances the fracture toughness of biocomposites. We derive viscoelastic properties of the protein-mineral nanostructure and show that the toughness of biocomposite can be further enhanced by the viscoelastic properties of protein.

  12. Biodegradable compounds: Rheological, mechanical and thermal properties

    NASA Astrophysics Data System (ADS)

    Nobile, Maria Rossella; Lucia, G.; Santella, M.; Malinconico, M.; Cerruti, P.; Pantani, R.

    2015-12-01

    Recently great attention from industry has been focused on biodegradable polyesters derived from renewable resources. In particular, PLA has attracted great interest due to its high strength and high modulus and a good biocompatibility, however its brittleness and low heat distortion temperature (HDT) restrict its wide application. On the other hand, Poly(butylene succinate) (PBS) is a biodegradable polymer with a low tensile modulus but characterized by a high flexibility, excellent impact strength, good thermal and chemical resistance. In this work the two aliphatic biodegradable polyesters PBS and PLA were selected with the aim to obtain a biodegradable material for the industry of plastic cups and plates. PBS was also blended with a thermoplastic starch. Talc was also added to the compounds because of its low cost and its effectiveness in increasing the modulus and the HDT of polymers. The compounds were obtained by melt compounding in a single screw extruder and the rheological, mechanical and thermal properties were investigated. The properties of the two compounds were compared and it was found that the values of the tensile modulus and elongation at break measured for the PBS/PLA/Talc compound make it interesting for the production of disposable plates and cups. In terms of thermal resistance the compounds have HDTs high enough to contain hot food or beverages. The PLA/PBS/Talc compound can be, then, considered as biodegradable substitute for polystyrene for the production of disposable plates and cups for hot food and beverages.

  13. Mechanical properties of DNA-like polymers

    PubMed Central

    Peters, Justin P.; Yelgaonkar, Shweta P.; Srivatsan, Seergazhi G.; Tor, Yitzhak; James Maher, L.

    2013-01-01

    The molecular structure of the DNA double helix has been known for 60 years, but we remain surprisingly ignorant of the balance of forces that determine its mechanical properties. The DNA double helix is among the stiffest of all biopolymers, but neither theory nor experiment has provided a coherent understanding of the relative roles of attractive base stacking forces and repulsive electrostatic forces creating this stiffness. To gain insight, we have created a family of double-helical DNA-like polymers where one of the four normal bases is replaced with various cationic, anionic or neutral analogs. We apply DNA ligase-catalyzed cyclization kinetics experiments to measure the bending and twisting flexibilities of these polymers under low salt conditions. Interestingly, we show that these modifications alter DNA bending stiffness by only 20%, but have much stronger (5-fold) effects on twist flexibility. We suggest that rather than modifying DNA stiffness through a mechanism easily interpretable as electrostatic, the more dominant effect of neutral and charged base modifications is their ability to drive transitions to helical conformations different from canonical B-form DNA. PMID:24013560

  14. Trabecular Bone Mechanical Properties and Fractal Dimension

    NASA Technical Reports Server (NTRS)

    Hogan, Harry A.

    1996-01-01

    Countermeasures for reducing bone loss and muscle atrophy due to extended exposure to the microgravity environment of space are continuing to be developed and improved. An important component of this effort is finite element modeling of the lower extremity and spinal column. These models will permit analysis and evaluation specific to each individual and thereby provide more efficient and effective exercise protocols. Inflight countermeasures and post-flight rehabilitation can then be customized and targeted on a case-by-case basis. Recent Summer Faculty Fellowship participants have focused upon finite element mesh generation, muscle force estimation, and fractal calculations of trabecular bone microstructure. Methods have been developed for generating the three-dimensional geometry of the femur from serial section magnetic resonance images (MRI). The use of MRI as an imaging modality avoids excessive exposure to radiation associated with X-ray based methods. These images can also detect trabecular bone microstructure and architecture. The goal of the current research is to determine the degree to which the fractal dimension of trabecular architecture can be used to predict the mechanical properties of trabecular bone tissue. The elastic modulus and the ultimate strength (or strain) can then be estimated from non-invasive, non-radiating imaging and incorporated into the finite element models to more accurately represent the bone tissue of each individual of interest. Trabecular bone specimens from the proximal tibia are being studied in this first phase of the work. Detailed protocols and procedures have been developed for carrying test specimens through all of the steps of a multi-faceted test program. The test program begins with MRI and X-ray imaging of the whole bones before excising a smaller workpiece from the proximal tibia region. High resolution MRI scans are then made and the piece further cut into slabs (roughly 1 cm thick). The slabs are X-rayed again

  15. Comparison of the Properties of Regression and Categorical Risk-Adjustment Models

    PubMed Central

    Averill, Richard F.; Muldoon, John H.; Hughes, John S.

    2016-01-01

    Clinical risk-adjustment, the ability to standardize the comparison of individuals with different health needs, is based upon 2 main alternative approaches: regression models and clinical categorical models. In this article, we examine the impact of the differences in the way these models are constructed on end user applications. PMID:26945302

  16. Mechanical properties of thermal protection system materials.

    SciTech Connect

    Hardy, Robert Douglas; Bronowski, David R.; Lee, Moo Yul; Hofer, John H.

    2005-06-01

    An experimental study was conducted to measure the mechanical properties of the Thermal Protection System (TPS) materials used for the Space Shuttle. Three types of TPS materials (LI-900, LI-2200, and FRCI-12) were tested in 'in-plane' and 'out-of-plane' orientations. Four types of quasi-static mechanical tests (uniaxial tension, uniaxial compression, uniaxial strain, and shear) were performed under low (10{sup -4} to 10{sup -3}/s) and intermediate (1 to 10/s) strain rate conditions. In addition, split Hopkinson pressure bar tests were conducted to obtain the strength of the materials under a relatively higher strain rate ({approx}10{sup 2} to 10{sup 3}/s) condition. In general, TPS materials have higher strength and higher Young's modulus when tested in 'in-plane' than in 'through-the-thickness' orientation under compressive (unconfined and confined) and tensile stress conditions. In both stress conditions, the strength of the material increases as the strain rate increases. The rate of increase in LI-900 is relatively small compared to those for the other two TPS materials tested in this study. But, the Young's modulus appears to be insensitive to the different strain rates applied. The FRCI-12 material, designed to replace the heavier LI-2200, showed higher strengths under tensile and shear stress conditions. But, under a compressive stress condition, LI-2200 showed higher strength than FRCI-12. As far as the modulus is concerned, LI-2200 has higher Young's modulus both in compression and in tension. The shear modulus of FRCI-12 and LI-2200 fell in the same range.

  17. Mechanical Properties of Nuclear Fuel Surrogates using Picosecond Laser Ultrasonics

    SciTech Connect

    David Hurley; Marat Khafizov; Farhad Farzbod; Eric Burgett

    2013-05-01

    Detailed understanding between microstructure evolution and mechanical properties is important for designing new high burnup nuclear fuels. In this presentation we discuss the use of picosecond ultrasonics to measure localize changes in mechanical properties of fuel surrogates. We develop measurement techniques that can be applied to investigate heterogeneous elastic properties caused by localize changes in chemistry, grain microstructure caused by recrystallization, and mechanical properties of small samples prepared using focused ion beam sample preparation. Emphasis is placed on understanding the relationship between microstructure and mechanical properties

  18. 26 CFR 1.734-1 - Optional adjustment to basis of undistributed partnership property.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... the basis of partnership property as the result of a distribution of property to a partner, unless the... and a distribution of partnership property is made, whether or not in liquidation of the partner's... partner. See § 1.460-4(k)(2)(iv)(D) for a rule determining the partnership's basis in a long-term...

  19. Fluid Mechanical Properties of Silkworm Fibroin Solutions

    NASA Astrophysics Data System (ADS)

    Matsumoto, Akira

    2005-11-01

    The aqueous solution behavior of silk fibroin is of interest due to the assembly and processing of this protein related to the spinning of protein fibers that exhibit remarkable mechanical properties. To gain insight into the origins of this functional feature, it is desired to determine how the protein behaves under a range of solution conditions. Pure fibroin at different concentrations in water was studied for surface tension, as a measure of surfactancy. In addition, shear induced changes on these solutions in terms of structure and morphology was also determined. Fibroin solutions exhibited shear rate-sensitive viscosity changes and precipitated at a critical shear rate where a dramatic increase of 75-150% of the initial value was observed along with a decrease in viscosity. In surface tension measurements, critical micelle concentrations were in the range of 3-4% w/v. The influence of additional factors, such as sericin protein, divalent and monovalent cations, and pH on the solution behavior in relation to structural and morphological features will also be described.

  20. Mechanical properties of lattice grid composites

    NASA Astrophysics Data System (ADS)

    Fan, Hualin; Fang, Daining; Jin, Fengnian

    2008-08-01

    An equivalent continuum method only considering the stretching deformation of struts was used to study the in-plane stiffness and strength of planar lattice grid composite materials. The initial yield equations of lattices were deduced. Initial yield surfaces were depicted separately in different 3D and 2D stress spaces. The failure envelope is a polyhedron in 3D spaces and a polygon in 2D spaces. Each plane or line of the failure envelope is corresponding to the yield or buckling of a typical bar row. For lattices with more than three bar rows, subsequent yield of the other bar row after initial yield made the lattice achieve greater limit strength. The importance of the buckling strength of the grids was strengthened while the grids were relative sparse. The integration model of the method was used to study the nonlinear mechanical properties of strain hardening grids. It was shown that the integration equation could accurately model the complete stress-strain curves of the grids within small deformations.

  1. Mechanical Properties of the Upper Airway

    PubMed Central

    Strohl, Kingman P.; Butler, James P.; Malhotra, Atul

    2013-01-01

    The importance of the upper airway (nose, pharynx, and larynx) in health and in the pathogenesis of sleep apnea, asthma, and other airway diseases, discussed elsewhere in the Comprehensive Physiology series, prompts this review of the biomechanical properties and functional aspects of the upper airway. There is a literature based on anatomic or structural descriptions in static circumstances, albeit studied in limited numbers of individuals in both health and disease. As for dynamic features, the literature is limited to studies of pressure and flow through all or parts of the upper airway and to the effects of muscle activation on such features; however, the links between structure and function through airway size, shape, and compliance remain a topic that is completely open for investigation, particularly through analyses using concepts of fluid and structural mechanics. Throughout are included both historically seminal references, as well as those serving as signposts or updated reviews. This article should be considered a resource for concepts needed for the application of biomechanical models of upper airway physiology, applicable to understanding the pathophysiology of disease and anticipated results of treatment interventions. PMID:23723026

  2. The social adjustment scale-self-report: psychometric properties for older adults.

    PubMed

    Zweig, Richard A; Turkel, Elihu

    2007-12-01

    To assess the reliability and validity of the Social Adjustment Scale-Self-Report for older adults, 129 community dwelling elderly ranging in age from 63 to 87 years (M=72.3 yr., SD=5.0) were surveyed using a modified version of the scale. The average internal consistency of subscales was satisfactory (mean coefficient alpha=.62). Overall social functioning impairment (total score) was associated with measures of depression (Beck Depression Inventory, r =.58) and global psychiatric symptoms (Brief Symptom Inventory, r = .55). Older adults scored higher on Marital role, Family Unit role, and overall social functioning impairment compared to mixed-age adults assessed in previous research, and higher on marital role impairment but similarly on overall social functioning when compared with a mixed-age sample from primary care. The modified Social Adjustment Scale-Self-Report has acceptable psychometric characteristics for research use with older adults, and select subscales may account for findings of age-related differences.

  3. Epigenetic Mechanisms and Microbiota as a Toolbox for Plant Phenotypic Adjustment to Environment

    PubMed Central

    Vannier, Nathan; Mony, Cendrine; Bittebière, Anne-Kristel; Vandenkoornhuyse, Philippe

    2015-01-01

    The classic understanding of organisms focuses on genes as the main source of species evolution and diversification. The recent concept of genetic accommodation questions this gene centric view by emphasizing the importance of phenotypic plasticity on evolutionary trajectories. Recent discoveries on epigenetics and symbiotic microbiota demonstrated their deep impact on plant survival, adaptation and evolution thus suggesting a novel comprehension of the plant phenotype. In addition, interplays between these two phenomena controlling plant plasticity can be suggested. Because epigenetic and plant-associated (micro-) organisms are both key sources of phenotypic variation allowing environmental adjustments, we argue that they must be considered in terms of evolution. This ‘non-conventional’ set of mediators of phenotypic variation can be seen as a toolbox for plant adaptation to environment over short, medium and long time-scales. PMID:26779191

  4. Cell Mechanosensitivity: Mechanical Properties and Interaction with Gravitational Field

    PubMed Central

    Ogneva, I. V.

    2013-01-01

    This paper addressed the possible mechanisms of primary reception of a mechanical stimulus by different cells. Data concerning the stiffness of muscle and nonmuscle cells as measured by atomic force microscopy are provided. The changes in the mechanical properties of cells that occur under changed external mechanical tension are presented, and the initial stages of mechanical signal transduction are considered. The possible mechanism of perception of different external mechanical signals by cells is suggested. PMID:23509748

  5. An adjustable slit mechanism for a fiber-fed multi-object spectrograph

    NASA Astrophysics Data System (ADS)

    Bailey, John I.; Mateo, Mario L.; Bagish, Alan P.; Crane, Jeffrey D.; Slater, Colin T.

    2012-09-01

    Fiber-fed multi-object spectrographs have greatly enhanced the spectroscopic capabilities of the world's premiere telescopes, but their flexibility has typically been limited by a fixed effective slit size that constrains the available resolving power. We present a novel mechanism that, for the first time, equips a fiber-fed spectrograph with multiple discreet slits of different widths. In this paper, we detail the mechanical design of our variable slit mechanism, which is capable of positioning any one of six slits in front of the fibers immediately prior to injection into the spectrograph's optical train. Further, we present the details of related systems necessary to achieve closed loop positioning of the slit mechanism given that no encoder is used. We also briefly discuss our use of open source and open hardware projects in the design. Finally, we describe the control system we have implemented for this subsystem.

  6. Auxetic oesophageal stents: structure and mechanical properties.

    PubMed

    Ali, Murtaza Najabat; Busfield, James J C; Rehman, Ihtesham U

    2014-02-01

    Oesophageal cancer is the ninth leading cause of malignant cancer death and its prognosis remains poor, ranking as the sixth most frequent cause of death in the world. This research work aims to adopt an Auxetic (rotating-squares) geometry device, that had previously been examined theoretically and analysed by Grima and Evans (J Mater Sci Lett 19(17):1563-1565, 2000), to produce a novel Auxetic oesophageal stent and stent-grafts relevant to the palliative treatment of oesophageal cancer and also for the prevention of dysphagia. This paper discusses the manufacture of a small diameter Auxetic oesophageal stent and stent-graft. The oral deployment of such an Auxetic stent would be simplest if a commercial balloon dilatational catheter was used as this obviates the need for an expensive dedicated delivery system. A novel manufacturing route was employed in this research to develop both Auxetic films and Auxetic oesophageal stents, which ranged from conventional subtractive techniques to a new additive manufacturing method. Polyurethane was selected as a material for the fabrication of Auxetic films and Auxetic oesophageal stents because of its good biocompatibility and non-toxicological properties. The Auxetic films were later used for the fabrication of seamed Auxetic oesophageal stents. The flexible polyurethane tubular grafts were also attached to the inner luminal side of the seamless Auxetic oesophageal stents, in order to prevent tumour in-growth. Scanning electron microscopy was used to conduct surface morphology study by using different Auxetic specimens developed from different conventional and new additive manufacturing techniques. Tensile testing of the Auxetic films was performed to characterise their mechanical properties. The stent expansion tests of the Auxetic stents were done to analyse the longitudinal extension and radial expansion of the Auxetic stent at a range of radial pressures applied by the balloon catheter, and to also identify the pressure

  7. Microstructure, mechanical properties, bio-corrosion properties and antibacterial properties of Ti-Ag sintered alloys.

    PubMed

    Chen, Mian; Zhang, Erlin; Zhang, Lan

    2016-05-01

    In this research, Ag element was selected as an antibacterial agent to develop an antibacterial Ti-Ag alloy by a powder metallurgy. The microstructure, phase constitution, mechanical properties, corrosion resistance and antibacterial properties of the Ti-Ag sintered alloys have been systematically studied by X-ray diffraction (XRD), scanning electron microscope (SEM), compressive test, electrochemical measurements and antibacterial test. The effects of the Ag powder size and the Ag content on the antibacterial property and mechanical property as well as the anticorrosion property have been investigated. The microstructure results have shown that Ti-Ag phase, residual pure Ag and Ti were the mainly phases in Ti-Ag(S75) sintered alloy while Ti2Ag was synthesized in Ti-Ag(S10) sintered alloy. The mechanical test indicated that Ti-Ag sintered alloy showed a much higher hardness and the compressive yield strength than cp-Ti but the mechanical properties were slightly reduced with the increase of Ag content. Electrochemical results showed that Ag powder size had a significant effect on the corrosion resistance of Ti-Ag sintered alloy. Ag content increased the corrosion resistance in a dose dependent way under a homogeneous microstructure. Antibacterial tests have demonstrated that antibacterial Ti-Ag alloy was successfully prepared. It was also shown that the Ag powder particle size and the Ag content influenced the antibacterial activity seriously. The reduction in the Ag powder size was benefit to the improvement in the antibacterial property and the Ag content has to be at least 3wt.% in order to obtain a strong and stable antibacterial activity against Staphylococcus aureus bacteria. The bacterial mechanism was thought to be related to the Ti2Ag and its distribution.

  8. Mechanical Properties of Several Magnesium and Aluminum Composites

    DTIC Science & Technology

    1992-12-01

    34AD-A262 481 ARMY RESEARCH LABORATORY Mechanical Properties of Several Magnesium and Aluminum Composites Nikos Tsangarakis and Barmac Taleghani ARL...ESJEI L .PwmOM N.ajmns Mechanical Properties of Several Magnesium and Aluminum Composites 2.AUIwORU Nikos Tsangarakis and Barmac Taleghani 7. PERONUMMN...Several composites of magnesiumn and aluminum alloys were tested In order to assess and evaluate their mechanical properties . The magnesium alloys were

  9. Disruptive coloration in cuttlefish: a visual perception mechanism that regulates ontogenetic adjustment of skin patterning.

    PubMed

    Barbosa, Alexandra; Mäthger, Lydia M; Chubb, Charles; Florio, Christopher; Chiao, Chuan-Chin; Hanlon, Roger T

    2007-04-01

    Among the changeable camouflage patterns of cuttlefish, disruptive patterning is shown in response to certain features of light objects in the visual background. However, whether animals show disruptive patterns is dependent not only on object size but also on their body size. Here, we tested whether cuttlefish (Sepia officinalis) are able to match their disruptive body patterning with increasing size of background objects as they grow from hatchling to adult size (0.7 to 19.6 cm mantle length; factor of 28). Specifically, do cuttlefish have a single ;visual sampling rule' that scales accurately during ontogeny? For each of seven size classes of cuttlefish, we created black and white checkerboards whose check sizes corresponded to 4, 12, 40, 120, 400 and 1200% of the area of the cuttlefish's White square, which is a neurophysiologically controlled component of the skin. Disruptive body patterns were evoked when, regardless of animal size, the check size measured either 40 or 120% of the area of the cuttlefish's White square, thus demonstrating a remarkable ontogenetic conformity to a single visual sampling rule. Cuttlefish have no known visual feedback loop with which to adjust their skin patterns. Since the area of a cuttlefish's White square skin component is a function of body size, our results indicate that cuttlefish are solving a visual scaling problem of camouflage presumably without visual confirmation of the size of their own skin component.

  10. Adjustable Nonlinear Mechanism System for Wideband Energy Harvesting in Rotational Circumstances

    NASA Astrophysics Data System (ADS)

    Zhang, Y.; Nakano, K.; Zheng, R.; Cartmell, M. P.

    2016-09-01

    Nonlinear energy harvesters have already been exhibited to draw energy from ambient vibration owing to their particular dynamic characteristics, and are feasible to desirable responses for broadband excitations of bistable and monostable systems. This study proposes an energy harvester for rotational applications, in which a cantilever beam pasted piezoelectric film and magnets with the same polarity are comprised as a nonlinear vibrating system. As the rotationally angular velocity gradually increases, the tensile stress to the cantilever beam is also self-adjusted with the increscent centrifugal force, causing the potential barriers of bistable type become shallow, so that the cantilever beam has the ability to maintain the high energy orbit motion from bistable hardening type to monostable hardening behavior. From the implemented results, the valid bandwidth of angular frequency can be improved from 26 rad/s - 132 rad/s to 15 rad/s - 215 rad/s, under the case of the effect of centrifugal force on nonlinear vibrating behavior. It demonstrates that the centrifugal force can significantly promote the performance of nonlinear energy harvesters.

  11. Timing matters: tuning the mechanics of a muscle-tendon unit by adjusting stimulation phase during cyclic contractions.

    PubMed

    Sawicki, Gregory S; Robertson, Benjamin D; Azizi, Emanuel; Roberts, Thomas J

    2015-10-01

    A growing body of research on the mechanics and energetics of terrestrial locomotion has demonstrated that elastic elements acting in series with contracting muscle are critical components of sustained, stable and efficient gait. Far fewer studies have examined how the nervous system modulates muscle-tendon interaction dynamics to optimize 'tuning' or meet varying locomotor demands. To explore the fundamental neuromechanical rules that govern the interactions between series elastic elements (SEEs) and contractile elements (CEs) within a compliant muscle-tendon unit (MTU), we used a novel work loop approach that included implanted sonomicrometry crystals along muscle fascicles. This enabled us to decouple CE and SEE length trajectories when cyclic strain patterns were applied to an isolated plantaris MTU from the bullfrog (Lithobates catesbeianus). Using this approach, we demonstrate that the onset timing of muscle stimulation (i.e. stimulation phase) that involves a symmetrical MTU stretch-shorten cycle during active force production results in net zero mechanical power output, and maximal decoupling of CE and MTU length trajectories. We found it difficult to 'tune' the muscle-tendon system for strut-like isometric force production by adjusting stimulation phase only, as the zero power output condition involved significant positive and negative mechanical work by the CE. A simple neural mechanism - adjusting muscle stimulation phase - could shift an MTU from performing net zero to net positive (energy producing) or net negative (energy absorbing) mechanical work under conditions of changing locomotor demand. Finally, we show that modifications to the classical work loop paradigm better represent in vivo muscle-tendon function during locomotion.

  12. Timing matters: tuning the mechanics of a muscle–tendon unit by adjusting stimulation phase during cyclic contractions

    PubMed Central

    Sawicki, Gregory S.; Robertson, Benjamin D.; Azizi, Emanuel; Roberts, Thomas J.

    2015-01-01

    ABSTRACT A growing body of research on the mechanics and energetics of terrestrial locomotion has demonstrated that elastic elements acting in series with contracting muscle are critical components of sustained, stable and efficient gait. Far fewer studies have examined how the nervous system modulates muscle–tendon interaction dynamics to optimize ‘tuning’ or meet varying locomotor demands. To explore the fundamental neuromechanical rules that govern the interactions between series elastic elements (SEEs) and contractile elements (CEs) within a compliant muscle–tendon unit (MTU), we used a novel work loop approach that included implanted sonomicrometry crystals along muscle fascicles. This enabled us to decouple CE and SEE length trajectories when cyclic strain patterns were applied to an isolated plantaris MTU from the bullfrog (Lithobates catesbeianus). Using this approach, we demonstrate that the onset timing of muscle stimulation (i.e. stimulation phase) that involves a symmetrical MTU stretch–shorten cycle during active force production results in net zero mechanical power output, and maximal decoupling of CE and MTU length trajectories. We found it difficult to ‘tune’ the muscle–tendon system for strut-like isometric force production by adjusting stimulation phase only, as the zero power output condition involved significant positive and negative mechanical work by the CE. A simple neural mechanismadjusting muscle stimulation phase – could shift an MTU from performing net zero to net positive (energy producing) or net negative (energy absorbing) mechanical work under conditions of changing locomotor demand. Finally, we show that modifications to the classical work loop paradigm better represent in vivo muscle–tendon function during locomotion. PMID:26232413

  13. Potential Mechanization in the Flue-Cured Tobacco Industry--with Emphasis on Human Resource Adjustment.

    ERIC Educational Resources Information Center

    McElroy, Robert C.; And Others

    Large numbers of people are still employed in production, marketing, and processing of flue-cured tobacco in eight agricultural subregions in five southeastern states. Mechanization and new technology which is being introduced could result in substantial economic and social problems unless new economic opportunities are developed. However,…

  14. Adjoint methods for adjusting three-dimensional atmosphere and surface properties to fit multi-angle/multi-pixel polarimetric measurements

    NASA Astrophysics Data System (ADS)

    Martin, William; Cairns, Brian; Bal, Guillaume

    2014-09-01

    This paper derives an efficient procedure for using the three-dimensional (3D) vector radiative transfer equation (VRTE) to adjust atmosphere and surface properties and improve their fit with multi-angle/multi-pixel radiometric and polarimetric measurements of scattered sunlight. The proposed adjoint method uses the 3D VRTE to compute the measurement misfit function and the adjoint 3D VRTE to compute its gradient with respect to all unknown parameters. In the remote sensing problems of interest, the scalar-valued misfit function quantifies agreement with data as a function of atmosphere and surface properties, and its gradient guides the search through this parameter space. Remote sensing of the atmosphere and surface in a three-dimensional region may require thousands of unknown parameters and millions of data points. Many approaches would require calls to the 3D VRTE solver in proportion to the number of unknown parameters or measurements. To avoid this issue of scale, we focus on computing the gradient of the misfit function as an alternative to the Jacobian of the measurement operator. The resulting adjoint method provides a way to adjust 3D atmosphere and surface properties with only two calls to the 3D VRTE solver for each spectral channel, regardless of the number of retrieval parameters, measurement view angles or pixels. This gives a procedure for adjusting atmosphere and surface parameters that will scale to the large problems of 3D remote sensing. For certain types of multi-angle/multi-pixel polarimetric measurements, this encourages the development of a new class of three-dimensional retrieval algorithms with more flexible parametrizations of spatial heterogeneity, less reliance on data screening procedures, and improved coverage in terms of the resolved physical processes in the Earth's atmosphere.

  15. Mechanical properties of non-woven glass fiber geopolymer composites

    NASA Astrophysics Data System (ADS)

    Rieger, D.; Kadlec, J.; Pola, M.; Kovářík, T.; Franče, P.

    2017-02-01

    This experimental research focuses on mechanical properties of non-woven glass fabric composites bound by geopolymeric matrix. This study investigates the effect of different matrix composition and amount of granular filler on the mechanical properties of final composites. Matrix was selected as a metakaolin based geopolymer hardened by different amount of potassium silicate activator. The ceramic granular filler was added into the matrix for investigation of its impact on mechanical properties and workability. Prepared pastes were incorporated into the non-woven fabrics by hand roller and final composites were stacked layer by layer to final thickness. The early age hardening of prepared pastes were monitored by small amplitude dynamic rheology approach and after 28 days of hardening the mechanical properties were examined. The electron microscopy was used for detail description of microstructural properties. The imaging methods revealed good wettability of glass fibers by geopolymeric matrix and results of mechanical properties indicate usability of these materials for constructional applications.

  16. Neural Mechanisms of Post-error Adjustments of Decision Policy in Parietal Cortex.

    PubMed

    Purcell, Braden A; Kiani, Roozbeh

    2016-02-03

    Humans often slow down after mistakes (post-error slowing [PES]), but the neural mechanism and adaptive role of PES remain controversial. We studied changes in the neural mechanisms of decision making after errors in humans and monkeys that performed a motion direction discrimination task. We found that PES is mediated by two factors: a reduction in sensitivity to sensory information and an increase in the decision bound. Both effects are implemented through dynamic changes in the decision-making process. Neuronal responses in the monkey lateral intraparietal area revealed that bound changes are implemented by decreasing an evidence-independent urgency signal. They also revealed a reduction in the rate of evidence accumulation, reflecting reduced sensitivity. These changes in the bound and sensitivity provide a quantitative account of choices and response times. We suggest that PES reflects an adaptive increase of decision bound in anticipation of maladaptive reductions in sensitivity to incoming evidence.

  17. Mechanical properties determination of AM components

    NASA Astrophysics Data System (ADS)

    Dzugan, J.; Sibr, M.; Konopík, P.; Procházka, R.; Rund, M.

    2017-02-01

    Characterisation of engineering materials and components is a crucial part for design and save service life utilization. Due to components processing technologies and exploitation conditions local properties can significantly vary from location to location over larger components as well as over small material volumes with gradual material changes such as welds, coatings or additively manufactured parts. The current paper is dealing with local properties characterisation for additively manufacture (AM) components by micro tensile test (M-TT). Components produced by additive manufacturing techniques yield properties variation in dependence of the considered location within the component regarding to direction in relation to deposition process. Properties vary over the thickness, length, angle or contacts with the supporting structures necessary for a successful components production by additive manufacturing techniques. The properties differences are mainly related to varying heating/reheating and cooling conditions at various locations of usually very complex parts produced mainly by these technologies. The standard testing procedures fail to characterize such local properties of complex shaped objects due to large size requirements on specimens. Therefore, new techniques have to be established for such detailed local characterizations. Results of miniaturized tensile tests application for local properties and orientations are shown here.

  18. Calcium-linked adjustment of myocardial metabolism to changing mechanical demands in the isolated rat heart.

    PubMed

    Rubányi, G; Kovách, A G

    1980-01-01

    Isolated rat hearts perfused by the modified Langendorff technique were used to study the effects of changes in perfusate calcium concentration (Cap2+) on left ventricular mechanical performance, O2-consumption, NADH-fluorescence and lactate release in the presence of glucose or pyruvate as the sole exogenous substrate. Stepwise elevation of Ca2+ from 0.31 to 7.8 mM resulted in a continuous increase of contractile activity and O2-consumption independent of the substrate present. Redox changes similar to State 3 to 4 transition (NAD+ reduction) were observed when mechanical activity was reduced by perfusing the hearts with 0.65 or 0.31 mM Cap2+, which was also substrate independent. At high Cap2+ (2.6--7.8 mM) increase of contractile activity and O2-consumption was accompanied by Cap2+ dependent NAD+ reduction in the presence of glucose. Inhibition of glycolisis by pyruvate reversed the direction of NADH response (NADH oxidation following Cap2+ elevation). Myocardial lactate relealse was increased by elevation of Cap2+ from 1.3 to 5.2 mM in the presence of glucose, but this effect was significantly inhibited in the pyruvate perfused hearts. It is concluded that NADH signal originates from both the cytosolic and mitochondrial NADH compartment. The direction of NAD+/NADH redox state changes following Cap2+ elevation is grately influenced by the substrate preferentially consumed by the heart. The data suggest that calcium increases the availability of reducing equivalents to the respiratory chain thereby ensuring adequate supply of ATP when myocardial mechanical demands are changing.

  19. Tailoring of mechanical properties of a side sill part made of martensitic stainless steel by press hardening

    NASA Astrophysics Data System (ADS)

    Meza-García, Enrique; Rautenstrauch, Anja; Kräusel, Verena; Landgrebe, Dirk

    2016-10-01

    The present work deals with a technological study to integrate the 1.4034 martensitic stainless steel sheet alloy in the conventional press hardening process. Based on preliminary work, side sill demonstrators with tailored mechanical properties were manufactured by press hardening under conventional process parameters. The resulting microstructure and mechanical properties of the produced parts were characterized. The tailoring of the mechanical properties consists of the development of two sections with completely different mechanical properties in a single part. To achieve this, a half of the blank was insulated with a refractory during austenitization treatment. This avoided the heating of the insulated side until the austenitization temperature. Therefore, only the non-insulated side was hardened by quenching. Moreover, depending on the austenitization temperature the resulting mechanical properties can be adjusted.

  20. Tomato fruit carotenoid biosynthesis is adjusted to actual ripening progression by a light-dependent mechanism.

    PubMed

    Llorente, Briardo; D'Andrea, Lucio; Ruiz-Sola, M Aguila; Botterweg, Esther; Pulido, Pablo; Andilla, Jordi; Loza-Alvarez, Pablo; Rodriguez-Concepcion, Manuel

    2016-01-01

    Carotenoids are isoprenoid compounds that are essential for plants to protect the photosynthetic apparatus against excess light. They also function as health-promoting natural pigments that provide colors to ripe fruit, promoting seed dispersal by animals. Work in Arabidopsis thaliana unveiled that transcription factors of the phytochrome-interacting factor (PIF) family regulate carotenoid gene expression in response to environmental signals (i.e. light and temperature), including those created when sunlight reflects from or passes though nearby vegetation or canopy (referred to as shade). Here we show that PIFs use a virtually identical mechanism to modulate carotenoid biosynthesis during fruit ripening in tomato (Solanum lycopersicum). However, instead of integrating environmental information, PIF-mediated signaling pathways appear to fulfill a completely new function in the fruit. As tomatoes ripen, they turn from green to red due to chlorophyll breakdown and carotenoid accumulation. When sunlight passes through the flesh of green fruit, a self-shading effect within the tissue maintains high levels of PIFs that directly repress the master gene of the fruit carotenoid pathway, preventing undue production of carotenoids. This effect is attenuated as chlorophyll degrades, causing degradation of PIF proteins and boosting carotenoid biosynthesis as ripening progresses. Thus, shade signaling components may have been co-opted in tomato fruit to provide information on the actual stage of ripening (based on the pigment profile of the fruit at each moment) and thus finely coordinate fruit color change. We show how this mechanism may be manipulated to obtain carotenoid-enriched fruits.

  1. Mechanical Properties of Degraded PMR-15 Resin

    NASA Technical Reports Server (NTRS)

    Tsuji, Luis C.; McManus, Hugh L.; Bowles, Kenneth J.

    1998-01-01

    Thermo-oxidative aging produces a non-uniform degradation state in PMR-15 resin. A surface layer, usually attributed to oxidative degradation, forms. This surface layer has different properties from the inner material. A set of material tests was designed to separate the properties of the oxidized surface layer from the properties of interior material. Test specimens were aged at 316 C in either air or nitrogen, for durations of up to 800 hours. The thickness of the oxidized surface layer in air aged specimens, and the shrinkage and Coefficient of Thermal Expansion (CTE) of nitrogen aged specimens were measured directly. Four-point-bend tests were performed to determine modulus of both the oxidized surface layer and the interior material. Bimaterial strip specimens consisting of oxidized surface material and unoxidized interior material were constructed and used to determine surface layer shrinkage and CTE. Results confirm that the surface layer and core materials have substantially different properties.

  2. Wave-Mechanical Properties of Stationary States.

    ERIC Educational Resources Information Center

    Holden, Alan

    This monograph is a review of the quantum mechanical concepts presented in two other monographs, "The Nature of Atoms" and "Bonds Between Atoms," by the same author. It is assumed the reader is familiar with these ideas. The monograph sketches only those aspects of quantum mechanics that are of most direct use in picturing and calculating the…

  3. Mechanical properties of a polyamide 6-reinforced PTFE composite

    NASA Astrophysics Data System (ADS)

    Li, J.

    2009-05-01

    Polytetrafluoroethylene (PTFE) blends with polyamide 6 (PA6) in various ratios were prepared in a corotating twin-screw extruder, where PTFE acted as a polymer matrix and PA6 as a disperse phase, and the morphology and mechanical properties of the blends were investigated by using SEM. With increasing content of PA6 in the blends, their flexural properties improved. The interfacial adhesion promoted the creation of an interphase between the PTFE and PA6 and led to improved mechanical properties of the material. The mechanical properties of the blends were optimum at 30 vol.% PA6.

  4. Mechanical properties of UV irradiated rat tail tendon (RTT) collagen.

    PubMed

    Sionkowska, Alina; Wess, Tim

    2004-04-01

    The mechanical properties of RTT collagen tendon before and after UV irradiation have been investigated by mechanical testing (Instron). Air-dried tendon were submitted to treatment with UV irradiation (wavelength 254 nm) for different time intervals. The changes in such mechanical properties as breaking strength and percentage elongation have been investigated. The results have shown, that the mechanical properties of the tendon were greatly affected by time of UV irradiation. Ultimate tensile strength and ultimate percentage elongation decreased after UV irradiation of the tendon. Increasing UV irradiation leads to a decrease in Young's modulus of the tendon.

  5. Mechanical and physical properties of plasma-sprayed stabilized zirconia

    NASA Technical Reports Server (NTRS)

    Siemers, P. A.; Mehan, R. L.

    1983-01-01

    Physical and mechanical properties were determined for plasma-sprayed MgO- or Y2O3-stabilized ZrO2 thermal barrier coatings. Properties were determined for the ceramic coating in both the freestanding condition and as-bonded to a metal substrate. The properties of the NiCrAlY bond coating were also investigated.

  6. Electronic, thermal and mechanical properties of carbon nanotubes.

    PubMed

    Dresselhaus, M S; Dresselhaus, G; Charlier, J C; Hernández, E

    2004-10-15

    A review of the electronic, thermal and mechanical properties of nanotubes is presented, with particular reference to properties that differ from those of the bulk counterparts and to potential applications that might result from the special structure and properties of nanotubes. Both experimental and theoretical aspects of these topics are reviewed.

  7. Mechanical Properties of Degraded PMR-15 Resin

    NASA Technical Reports Server (NTRS)

    Tsuji, Luis C.

    2000-01-01

    Thermo-oxidative aging produces a nonuniform degradation state in PMR-15 resin. A surface layer, usually attributed to oxidative degradation, forms. This surface layer has different properties from the inner material. A set of material tests was designed to separate the properties of the oxidized surface layer from the properties of interior material. Test specimens were aged at 316 C in either air or nitrogen, for durations of up to 800 hr. The thickness of the oxidized surface layer in air aged specimens, and the shrinkage and coefficient of thermal expansion (CTE) of nitrogen aged specimens were measured directly. The nitrogen-aged specimens were assumed to have the same properties as the interior material in the air-aged specimens. Four-point-bend tests were performed to determine modulus of both the oxidized surface layer and the interior material. Bimaterial strip specimens consisting of oxidized surface material and unoxidized interior material were constructed and used to determine surface layer shrinkage and CTE. Results confirm that the surface layer and core materials have substantially different properties.

  8. Mechanical properties of natural cartilage and tissue-engineered constructs.

    PubMed

    Little, Christopher James; Bawolin, Nahshon Kenneth; Chen, Xiongbiao

    2011-08-01

    There has been much research over the past two decades with the aim of engineering cartilage constructs for repairing or restoring damaged cartilage. To engineer healthy neocartilage, the constructs must have mechanical properties matching those of native cartilage as well as appropriate for the loading conditions of the joint. This article discusses the mechanical behavior of native cartilage and surveys different types of tensile, compressive, and shear tests with their limitations. It also comprehensively reviews recent work and achievements in developing the mathematical models representing the mechanical properties of both native and engineered cartilage. Different methods for enhancing the mechanical properties of engineered cartilage are also discussed, including scaffold design, mechanical stimulation, and chemical stimulation. This article concludes with recommendations for future research aimed at achieving engineered cartilage with mechanical properties matching those found in native cartilage.

  9. How divergence mechanisms influence disassortative mixing property in biology

    NASA Astrophysics Data System (ADS)

    Xu, Chunsui; Liu, Zengrong; Wang, Ruiqi

    2010-02-01

    The duplication-divergence mechanism of network growth has been widely investigated, especially in gene and protein networks. Both the duplication and divergence have a key role in biological network evolution. However, the relative roles of these mechanisms in the influence of disassortative property in protein interaction networks remain to be clarified. It has been shown that duplication can indeed make protein networks evolve towards disassortative networks. To make the relationship between the disassortative property and the duplication-divergence mechanism more clear, we further discuss how the divergence mechanism influences the disassortative property. We tested four different divergence mechanisms, i.e., node deletion, edge deletion, edge addition, and edge rewiring to study their effects on disassortative property. Our study highlights the crucial roles of different divergence evolution mechanisms.

  10. Molecular mechanism of prostate cancer cell apoptosis induced by busulfan via adjustment of androgen receptor phosphatization

    PubMed Central

    Liu, Jun; Jiang, Guojun; Yang, Aiping; Yang, Guohui; Yang, Wenjuan; Fang, Yi

    2016-01-01

    Objective: To probe killing effect of busulfan to prostate cancer cell without androgen and the influence of androgen receptor phosphatization and analyze its molecular mechanism. Methods: prostate cancer cell line 22RV1, LAPC4 and LNCaP treated with busulfan under androgen-free condition underwent CCK-8 examination to probe killing ability of the medicine. Flow cytometry was used to check the influence of busulfan on apoptosis rate of prostate cancer cell line LAPC4. Expression level of androgen receptor (AR), Src and Ack1 and change in phosphatization of AR after busulfan treatment were measured by RT-PCR and Western blotting. Finally, influence o proliferation ability and apoptosis of LAPC4 were measured using EGF-busulfan co-processing. Results: Significant dose-dependency was observed as killing ability rises with higher busulfan concentration (p<0.05). Significant improvement in prostate cancer cell inhibition ability of busulfan was also observed with prolonging of time (p<0.05). Then we discovered, as indicated by flow cytometry, that busulfan inhibits prostate cancer cell LAPC4 proliferation by strengthening its apoptosis (p<0.05), which showed significant dose- and time-dependency. Detection of AR expression and phosphatization level showed no significant influence on mRNA and protein expression level of AR made by busulfan. However, decline of phosphatization level at AR Y534 site was positively related to busulfan treatment time. Busulfan was found to be inhibitory to Src kinase induced by EGF and level of resulting AR phosphatization in our further probe into the mechanism of busulfan influence on phosphatization level at AR Y534 site. Nude mice experiment indicated that busulfan was inhibitory to protein expression of AR downstream target gene prostate specific antigen (PSA) and human tissue kallikrein2 (hk-2), thus inhibited in vivo tumorigenic ability of prostate cancer cells. Conclusion: Busulfan was significantly inhibitory to prostate cancer cell

  11. Development of a Fiber Laser with Independently Adjustable Properties for Optical Resolution Photoacoustic Microscopy.

    PubMed

    Aytac-Kipergil, Esra; Demirkiran, Aytac; Uluc, Nasire; Yavas, Seydi; Kayikcioglu, Tunc; Salman, Sarper; Karamuk, Sohret Gorkem; Ilday, Fatih Omer; Unlu, Mehmet Burcin

    2016-12-08

    Photoacoustic imaging is based on the detection of generated acoustic waves through thermal expansion of tissue illuminated by short laser pulses. Fiber lasers as an excitation source for photoacoustic imaging have recently been preferred for their high repetition frequencies. Here, we report a unique fiber laser developed specifically for multiwavelength photoacoustic microscopy system. The laser is custom-made for maximum flexibility in adjustment of its parameters; pulse duration (5-10 ns), pulse energy (up to 10 μJ) and repetition frequency (up to 1 MHz) independently from each other and covers a broad spectral region from 450 to 1100 nm and also can emit wavelengths of 532, 355, and 266 nm. The laser system consists of a master oscillator power amplifier, seeding two stages; supercontinuum and harmonic generation units. The laser is outstanding since the oscillator, amplifier and supercontinuum generation parts are all-fiber integrated with custom-developed electronics and software. To demonstrate the feasibility of the system, the images of several elements of standardized resolution test chart are acquired at multiple wavelengths. The lateral resolution of optical resolution photoacoustic microscopy system is determined as 2.68 μm. The developed system may pave the way for spectroscopic photoacoustic microscopy applications via widely tunable fiber laser technologies.

  12. Development of a Fiber Laser with Independently Adjustable Properties for Optical Resolution Photoacoustic Microscopy

    PubMed Central

    Aytac-Kipergil, Esra; Demirkiran, Aytac; Uluc, Nasire; Yavas, Seydi; Kayikcioglu, Tunc; Salman, Sarper; Karamuk, Sohret Gorkem; Ilday, Fatih Omer; Unlu, Mehmet Burcin

    2016-01-01

    Photoacoustic imaging is based on the detection of generated acoustic waves through thermal expansion of tissue illuminated by short laser pulses. Fiber lasers as an excitation source for photoacoustic imaging have recently been preferred for their high repetition frequencies. Here, we report a unique fiber laser developed specifically for multiwavelength photoacoustic microscopy system. The laser is custom-made for maximum flexibility in adjustment of its parameters; pulse duration (5–10 ns), pulse energy (up to 10 μJ) and repetition frequency (up to 1 MHz) independently from each other and covers a broad spectral region from 450 to 1100 nm and also can emit wavelengths of 532, 355, and 266 nm. The laser system consists of a master oscillator power amplifier, seeding two stages; supercontinuum and harmonic generation units. The laser is outstanding since the oscillator, amplifier and supercontinuum generation parts are all-fiber integrated with custom-developed electronics and software. To demonstrate the feasibility of the system, the images of several elements of standardized resolution test chart are acquired at multiple wavelengths. The lateral resolution of optical resolution photoacoustic microscopy system is determined as 2.68 μm. The developed system may pave the way for spectroscopic photoacoustic microscopy applications via widely tunable fiber laser technologies. PMID:27929049

  13. Development of a Fiber Laser with Independently Adjustable Properties for Optical Resolution Photoacoustic Microscopy

    NASA Astrophysics Data System (ADS)

    Aytac-Kipergil, Esra; Demirkiran, Aytac; Uluc, Nasire; Yavas, Seydi; Kayikcioglu, Tunc; Salman, Sarper; Karamuk, Sohret Gorkem; Ilday, Fatih Omer; Unlu, Mehmet Burcin

    2016-12-01

    Photoacoustic imaging is based on the detection of generated acoustic waves through thermal expansion of tissue illuminated by short laser pulses. Fiber lasers as an excitation source for photoacoustic imaging have recently been preferred for their high repetition frequencies. Here, we report a unique fiber laser developed specifically for multiwavelength photoacoustic microscopy system. The laser is custom-made for maximum flexibility in adjustment of its parameters; pulse duration (5–10 ns), pulse energy (up to 10 μJ) and repetition frequency (up to 1 MHz) independently from each other and covers a broad spectral region from 450 to 1100 nm and also can emit wavelengths of 532, 355, and 266 nm. The laser system consists of a master oscillator power amplifier, seeding two stages; supercontinuum and harmonic generation units. The laser is outstanding since the oscillator, amplifier and supercontinuum generation parts are all-fiber integrated with custom-developed electronics and software. To demonstrate the feasibility of the system, the images of several elements of standardized resolution test chart are acquired at multiple wavelengths. The lateral resolution of optical resolution photoacoustic microscopy system is determined as 2.68 μm. The developed system may pave the way for spectroscopic photoacoustic microscopy applications via widely tunable fiber laser technologies.

  14. Lunar soil properties and soil mechanics

    NASA Technical Reports Server (NTRS)

    Mitchell, J. K.; Houston, W. N.

    1974-01-01

    The long-range objectives were to develop methods of experimentation and analysis for the determination of the physical properties and engineering behavior of lunar surface materials under in situ environmental conditions. Data for this purpose were obtained from on-site manned investigations, orbiting and softlanded spacecraft, and terrestrial simulation studies. Knowledge of lunar surface material properties are reported for the development of models for several types of lunar studies and for the investigation of lunar processes. The results have direct engineering application for manned missions to the moon.

  15. Photoresponsive Polysaccharide-Based Hydrogels with Tunable Mechanical Properties for Cartilage Tissue Engineering.

    PubMed

    Giammanco, Giuseppe E; Carrion, Bita; Coleman, Rhima M; Ostrowski, Alexis D

    2016-06-15

    Photoresponsive hydrogels were obtained by coordination of alginate-acrylamide hybrid gels (AlgAam) with ferric ions. The photochemistry of Fe(III)-alginate was used to tune the chemical composition, mechanical properties, and microstructure of the materials upon visible light irradiation. The photochemical treatment also induced changes in the swelling properties and transport mechanism in the gels due to the changes in material composition and microstructure. The AlgAam gels were biocompatible and could easily be dried and rehydrated with no change in mechanical properties. These gels showed promise as scaffolds for cartilage tissue engineering, where the photochemical treatment could be used to tune the properties of the material and ultimately change the growth and extracellular matrix production of chondrogenic cells. ATDC5 cells cultured on the hydrogels showed a greater than 2-fold increase in the production of sulfated glycosaminoglycans (sGAG) in the gels irradiated for 90 min compared to the dark controls. Our method provides a simple photochemical tool to postsynthetically control and adjust the chemical and mechanical environment in these gels, as well as the pore microstructure and transport properties. By changing these properties, we could easily access different levels of performance of these materials as substrates for tissue engineering.

  16. An analysis of the dynamic avalanche mechanism of an improved FCE diode with a deep p+ adjusting region

    NASA Astrophysics Data System (ADS)

    Cailin, Wang; Lei, Zhang

    2015-04-01

    An improved field charge extraction (FCE) diode with a deep p+ adjusting region at the cathode side is studied. The reverse recovery mechanism and electric field gradient are thoroughly analyzed and validated using ISE simulation results. The results show that, based on the premise of ensuring the static characteristics, the improved FCE diode can clearly improve the softness and effectively suppress the peak electric field of the nn- junction at the cathode side during reverse recovery, and thus has a high dynamic avalanche capability compared with conventional FCE diodes. Project supported by the Doctoral Program of Higher Education of China (RFDP) (No. 20136118110004), and the National Natural Science Foundation of China (Nos. 51077110, 51477137).

  17. Mechanical Properties of Normal and Diseased Cerebrovascular System

    PubMed Central

    Ebrahimi, Ali P.

    2009-01-01

    Background: Blood vessel mechanics has traditionally been of interest to researchers and clinicians. Changes in mechanical properties of arteries have been associated with various diseases. Objective: To provide a comprehensive review directed towards understanding the basic biomechanical properties of cerebral arteries under normal and diseased conditions. Methods: Literature review supplemented by personal knowledge. Results: The mechanical properties of vascular tissue may depend on several factors including macromolecular volume fraction, molecular orientation, and volume or number of cells such as smooth muscle cells. Mechanical properties of a blood vessel have been characterized using different methods such as in vitro tensile testing, non-invasive ultrasound examination, and mathematical models. Experiments are complicated by the variation in properties and content of materials that make up the vessel wall and more challenging as the size of the vessel of interest decreases. Therapeutic interventions aiming to alter the mechanical response are either pharmaceutical: including calcium channel blockers, angiotensin converting enzyme inhibitors (ACEI), angiotensin receptor blockers (ARB), and β-blockers; or, mechanical interventions such as angioplasty, stent placement, mechanical thrombectomy, or embolization procedures. Conclusion: It is apparent from the literature that macromolecular and cellular mechanics of blood vessels are not fully understood. Therefore, further studies are necessary to better understand contribution of these mechanisms to the overall mechanics of the vascular tissue. PMID:22518247

  18. Physical and mechanical properties of icebergs

    SciTech Connect

    Gammon, P.H.; Bobby, W.; Gagnon, R.E.; Russell, W.E.

    1983-05-01

    Physical and mechanical characteristics of iceberg ice were studied from samples collected near the shores of eastern Newfoundland. Although the physical characteristics show considerable diversity, iceberg ice has some common features and is generally porous, lacks significant concentrations of dissolved materials, contains internal cracks and has an irregular interlocking grain structure. A review of mechanical testing of ice was carried out and an experimental setup was devised to reduce effects of improper contact between specimen and loading apparatus. Uniaxial compressive strength for iceberg ice was determined and compared with that for lake ice. The strength of iceberg ice was higher than that of lake ice but Young's Modulus for lake ice was higher.

  19. Cost per QALY (Quality-Adjusted Life Year) and Lifetime Cost of Prolonged Mechanical Ventilation in Taiwan

    PubMed Central

    Hung, Mei-Chuan; Lu, Hsin-Ming; Chen, Likwang; Lin, Ming-Shian; Chen, Cheng-Ren; Yu, Chong-Jen; Wang, Jung-Der

    2012-01-01

    Introduction Patients who require prolonged mechanical ventilation (PMV) are increasing and producing financial burdens worldwide. This study determines the cost per QALY (quality-adjusted life year), out-of-pocket expenses, and lifetime costs for PMV patients stratified by underlying diseases and cognition levels. Methods A nationwide sample of 50,481 patients with continual mechanical ventilation for more than 21 days was collected during 1997–2007. After stratifying the patients according to specific diagnoses, a latent class analysis (LCA) was performed to categorise PMV patients with multiple co-morbidities into several homogeneous groups. The survival functions were estimated for individual groups using the Kaplan-Meier method and extrapolated to 300 months through a semi-parametric method. The survival functions were adjusted using an EQ-5D utility value derived from a convenience sample of 142 PMV patients to estimate quality-adjusted life expectancies (QALE). Another convenience sample of 165 patients was used to estimate the out-of-pocket expenses. The lifetime expenditures paid by the single-payer National Health Insurance (NHI) system and patients' families were estimated by multiplying average monthly expenditures by the survival probabilities and summing the values over lifetime. Results PMV therapy costs more than 100,000 U.S. dollars (USD) per QALY for all patients with poor cognition. For patients with partial cognition, PMV therapy costs less than 56,000 USD per QALY for those with liver cirrhosis, intracranial or spinal cord injuries, and 57,000–69,000 USD for patients with multiple co-morbidities under age of 65. The average lifetime cost of PMV was usually below 56,000 USD. The out-of-pocket expenses were often more than one-third of the total cost of treatment. Conclusions PMV treatment for patients with poor cognition would cost more than 5 times Taiwan's GDP (gross domestic products), or less cost-effective. The out-of-pocket expenses

  20. Differences in Mechanical Properties of the Human and Monkey Tibia

    NASA Technical Reports Server (NTRS)

    Arnaud, Sara B.; Hutchinson, T. M.; Bakulin, A. V.; Rahkmanov, A. S.; Steele, C. R.; Hargens, Alan R. (Technical Monitor)

    1996-01-01

    A method which uses an instrument that detects the response of a long bone to a vibratory stimulus to quantify mechanical properties non-invasively was revised and validated for use in the tibia. Stored data from healthy men was reanalyzed and compared with values from non-human primates. The analysis uses the relationship K(sub b) = 48 EI/L(sup 3) where K(sub b) is the lateral stiffness of a beam with force applied midspan, E is the elastic modulus, I the geometric moment of inertia and L, the limb length. Values for stiffness (EI, Nm(sup2)), the Euler buckling load (P(sub cr) = EI (pi/L)(sup 2)), and bone sufficiency (S) which represents the axial load the bone can support, adjusted to BW (S=P(sub cr)/BW) were obtained. The interest precision of the method in relaxed men, 5.8%, and in sedated male monkeys, 4.3%, was based on repeated measures in the same subjects at 1 month intervals. The R tibias of 40 men, aged 38.6 +/- 7.3 yrs with BW 78.9 +/- 7.9 kg, showed average (+/- SD) L to be 35 +/- 2 cm, EI 222 +/- 71 Nm(sup 2), P(sub cr) 18.1 +/- 4.9 kN, and S 23.4 +/- 5.7 N. The R tibias of 24 Rhesus monkeys ranging in age from 2-12 years, BW 4.9 +/- 3 kg, showed L to be 14.7 +/- 1.9 cm, EI 6.0 +/- 4.8 Nm(sup 2), P(sub cr) 2.51 +/- 1.2 kN and S 57.3 N. These measurements indicate that the tibia of a terrestrial non-human primate, M. mulatta, has higher load carrying capacity for the level of body weights in the species than the human bone.

  1. Supramolecular Polymer Nanocomposites - Improvement of Mechanical Properties

    NASA Astrophysics Data System (ADS)

    Hinricher, Jesse; Neikirk, Colin; Priestley, Rodney

    2015-03-01

    Supramolecular polymers differ from traditional polymers in that their repeat units are connected by hydrogen bonds that can reversibly break and form under various stimuli. They can be more easily recycled than conventional materials, and their highly temperature dependent viscosities result in reduced energy consumption and processing costs. Furthermore, judicious selection of supramolecular polymer architecture and functionality allows the design of advanced materials including shape memory and self-healing materials. Supramolecular polymers have yet to see widespread use because they can't support much weight due to their inherent mechanical weakness. In order to address this issue, the mechanical strength of supramolecular polymer nanocomposites based on ureidopyrmidinone (UPy) telechelic poly(caprolactone) doped with surface activated silica nanoparticles was investigated by tensile testing and dynamic mechanical analysis. The effects of varying amounts and types of nanofiller surface functionality were investigated to glean insight into the contributions of filler-filler and filler-matrix interactions to mechanical reinforcement in supramolecular polymer nanocomposites. MRSEC NSF DMR 0819860 (PI: Prof. N. Phuan Ong) REU Site Grant: NSF DMR-1156422 (PI: Prof. Mikko Haataja)

  2. Composite propellant technology research: Mechanical property characterization

    NASA Technical Reports Server (NTRS)

    Bower, Mark V.

    1991-01-01

    Proof for the existence of a single Poisson's ratio function in isotropic linear viscoelastic materials is presented. An in-depth discussion is given of three dimensional viscoelastic material properties and their relationships to linear isotropic and orthotropic viscoelastic materials. A discussion of the alternate invariant definition as used by Abaqus and how it relates to the form used by Dr. S. Peng is presented.

  3. Axially adjustable magnetic properties in arrays of multilayered Ni/Cu nanowires with variable segment sizes

    NASA Astrophysics Data System (ADS)

    Shirazi Tehrani, A.; Almasi Kashi, M.; Ramazani, A.; Montazer, A. H.

    2016-07-01

    Arrays of multilayered Ni/Cu nanowires (NWs) with variable segment sizes were fabricated into anodic aluminum oxide templates using a pulsed electrodeposition method in a single bath for designated potential pulse times. Increasing the pulse time between 0.125 and 2 s in the electrodeposition of Ni enabled the formation of segments with thicknesses ranging from 25 to 280 nm and 10-110 nm in 42 and 65 nm diameter NWs, respectively, leading to disk-shaped, rod-shaped and/or near wire-shaped geometries. Using hysteresis loop measurements at room temperature, the axial and perpendicular magnetic properties were investigated. Regardless of the segment geometry, the axial coercivity and squareness significantly increased with increasing Ni segment thickness, in agreement with a decrease in calculated demagnetizing factors along the NW length. On the contrary, the perpendicular magnetic properties were found to be independent of the pulse times, indicating a competition between the intrawire interactions and the shape demagnetizing field.

  4. Manufacturing and mechanical properties of calcium phosphate biomaterials

    NASA Astrophysics Data System (ADS)

    Laasri, S.; Taha, M.; Hlil, E. K.; Laghzizil, A.; Hajjaji, A.

    2012-10-01

    In this study, the influence of powder manufacturing and sintering temperature on densification, microstructure and mechanical properties of dense β-tricalcium phosphate (β-TCP) bioceramic has been studied. Densification results show that the β-TCP can be sintered at 1160 °C for 3 hours to have good density and high performance mechanic properties (Vickers hardness, toughness and Young's modulus). X-ray diffraction and SEM microscopy are used to check the microstructure changes during the sintering temperature. The used processing of β-TCP ceramic improved its densification, microstructure homogeneity and mechanical properties.

  5. Elastic properties and mechanical tension of graphene

    NASA Astrophysics Data System (ADS)

    Ramírez, R.; Herrero, C. P.

    2017-01-01

    Room-temperature simulations of graphene have been performed as a function of the mechanical tension of the layer. Finite-size effects are accurately reproduced by an acoustic dispersion law for the out-of-plane vibrations that, in the long-wave limit, behaves as ρ ω2=σ k2+κ k4 . The fluctuation tension σ is finite (˜0.1 N/m) even when the external mechanical tension vanishes. Transverse vibrations imply a duplicity in the definition of the elastic constants of the layer, as observables related to the real area of the surface may differ from those related to the in-plane projected area. This duplicity explains the variability of experimental data on the Young modulus of graphene based on electron spectroscopy, interferometric profilometry, and indentation experiments.

  6. Adjustable Reeds For Weaving

    NASA Technical Reports Server (NTRS)

    Farley, Gary L.

    1994-01-01

    Local characteristics of fabrics varied to suit special applications. Adjustable reed machinery proposed for use in weaving fabrics in various net shapes, widths, yarn spacings, and yarn angles. Locations of edges of fabric and configuration of warp and filling yarns varied along fabric to obtain specified properties. In machinery, reed wires mounted in groups on sliders, mounted on lengthwise rails in reed frame. Mechanisms incorporated to move sliders lengthwise, parallel to warp yarns, by sliding them along rails; move sliders crosswise by translating reed frame rails perpendicular to warp yarns; and crosswise by spreading reed rails within group. Profile of reed wires in group on each slider changed.

  7. Mechanical properties of intermediate filament proteins

    PubMed Central

    Charrier, Elisabeth E.; Janmey, Paul A.

    2016-01-01

    Purified intermediate filament proteins can be reassembled in vitro to produce polymers closely resembling those found in cells, and these filament form viscoelastic gels. The crosslinks holding IFs together in the network include specific bonds between polypeptides extending from the filament surface and ionic interactions mediated by divalent cations. IF networks exhibit striking non-linear elasticity with stiffness, as quantified by shear modulus, increasing an order of magnitude as the networks are deformed to large stains resembling those that soft tissues undergo in vivo. Individual Ifs can be stretched to more than 2 or 3 times their resting length without breaking. At least ten different rheometric methods have been used to quantify the viscoelasticity of IF networks over a wide range of timescales and strain magnitudes. The mechanical roles of different classes of IF on mesenchymal and epithelial cells in culture have also been studied by an even wider range of microrheological methods. These studies have documented the effects on cell mechanics when IFs are genetically or pharmacologically disrupted or when normal or mutant IF proteins are exogenously expressed in cells. Consistent with in vitro rheology, the mechanical role of IFs is more apparent as cells are subjected to larger and more frequent deformations. PMID:26795466

  8. Mechanical properties of alumina porcelain during heating

    NASA Astrophysics Data System (ADS)

    Šín, Peter; Podoba, Rudolf; ŠtubÅa, Igor; Trník, Anton

    2014-11-01

    The mechanical strength and Young's modulus of green alumina porcelain (50 wt. % of kaolin, 25 wt. % of Al2O3, and 25 wt. % of feldspar) were measured during heating up to 900 °C and 1100 °C, respectively. To this end, we used the three point-bending method and modulated force thermomechanical analysis (mf-TMA). The loss liberation - of the physically bound water (20 - 250 °C) strengthens the sample and Young's modulus increases its values significantly. The dehydroxylation that takes place in the range of 400 - 650 °C causes a slight decrease in Young's modulus. On the other hand, the mechanical strength slightly increases in this temperature range, although it has a sudden drop at 420 °C. Beyond the dehydroxylation range, above 650 °C, both Young's modulus and mechanical strength increase. Above 950 °C, a sharp increase of Young's modulus is caused by the solid-state sintering and the new structure created by the high-temperature reactions in metakaolinite.

  9. The mechanical and strength properties of diamond.

    PubMed

    Field, J E

    2012-12-01

    Diamond is an exciting material with many outstanding properties; see, for example Field J E (ed) 1979 The Properties of Diamond (London: Academic) and Field J E (ed) 1992 The Properties of Natural and Synthetic Diamond (London: Academic). It is pre-eminent as a gemstone, an industrial tool and as a material for solid state research. Since natural diamonds grew deep below the Earth's surface before their ejection to mineable levels, they also contain valuable information for geologists. The key to many of diamond's properties is the rigidity of its structure which explains, for example, its exceptional hardness and its high thermal conductivity. Since 1953, it has been possible to grow synthetic diamond. Before then, it was effectively only possible to have natural diamond, with a small number of these found in the vicinity of meteorite impacts. Techniques are now available to grow gem quality synthetic diamonds greater than 1 carat (0.2 g) using high temperatures and pressures (HTHP) similar to those found in nature. However, the costs are high, and the largest commercially available industrial diamonds are about 0.01 carat in weight or about 1 mm in linear dimension. The bulk of synthetic diamonds used industrially are 600 µm or less. Over 75% of diamond used for industrial purposes today is synthetic material. In recent years, there have been two significant developments. The first is the production of composites based on diamond; these materials have a significantly greater toughness than diamond while still maintaining very high hardness and reasonable thermal conductivity. The second is the production at low pressures by metastable growth using chemical vapour deposition techniques. Deposition onto non-diamond substrates was first demonstrated by Spitsyn et al 1981 J. Cryst. Growth 52 219-26 and confirmed by Matsumoto et al 1982 Japan J. Appl. Phys. 21 L183-5. These developments have added further to the versatility of diamond. Two other groups of

  10. The mechanical and strength properties of diamond

    NASA Astrophysics Data System (ADS)

    Field, J. E.

    2012-12-01

    Diamond is an exciting material with many outstanding properties; see, for example Field J E (ed) 1979 The Properties of Diamond (London: Academic) and Field J E (ed) 1992 The Properties of Natural and Synthetic Diamond (London: Academic). It is pre-eminent as a gemstone, an industrial tool and as a material for solid state research. Since natural diamonds grew deep below the Earth's surface before their ejection to mineable levels, they also contain valuable information for geologists. The key to many of diamond's properties is the rigidity of its structure which explains, for example, its exceptional hardness and its high thermal conductivity. Since 1953, it has been possible to grow synthetic diamond. Before then, it was effectively only possible to have natural diamond, with a small number of these found in the vicinity of meteorite impacts. Techniques are now available to grow gem quality synthetic diamonds greater than 1 carat (0.2 g) using high temperatures and pressures (HTHP) similar to those found in nature. However, the costs are high, and the largest commercially available industrial diamonds are about 0.01 carat in weight or about 1 mm in linear dimension. The bulk of synthetic diamonds used industrially are 600 µm or less. Over 75% of diamond used for industrial purposes today is synthetic material. In recent years, there have been two significant developments. The first is the production of composites based on diamond; these materials have a significantly greater toughness than diamond while still maintaining very high hardness and reasonable thermal conductivity. The second is the production at low pressures by metastable growth using chemical vapour deposition techniques. Deposition onto non-diamond substrates was first demonstrated by Spitsyn et al 1981 J. Cryst. Growth 52 219-26 and confirmed by Matsumoto et al 1982 Japan J. Appl. Phys. 21 L183-5. These developments have added further to the versatility of diamond. Two other groups of materials

  11. Mechanical property characterization of polymeric composites reinforced by continuous microfibers

    NASA Astrophysics Data System (ADS)

    Zubayar, Ali

    Innumerable experimental works have been conducted to study the effect of polymerization on the potential properties of the composites. Experimental techniques are employed to understand the effects of various fibers, their volume fractions and matrix properties in polymer composites. However, these experiments require fabrication of various composites which are time consuming and cost prohibitive. Advances in computational micromechanics allow us to study the various polymer based composites by using finite element simulations. The mechanical properties of continuous fiber composite strands are directional. In traditional continuous fiber laminated composites, all fibers lie in the same plane. This provides very desirable increases in the in-plane mechanical properties, but little in the transverse mechanical properties. The effect of different fiber/matrix combinations with various orientations is also available. Overall mechanical properties of different micro continuous fiber reinforced composites with orthogonal geometry are still unavailable in the contemporary research field. In this research, the mechanical properties of advanced polymeric composite reinforced by continuous micro fiber will be characterized based on analytical investigation and FE computational modeling. Initially, we have chosen IM7/PEEK, Carbon Fiber/Nylon 6, and Carbon Fiber/Epoxy as three different case study materials for analysis. To obtain the equivalent properties of the micro-hetero structures, a concept of micro-scale representative volume elements (RVEs) is introduced. Five types of micro scale RVEs (3 square and 2 hexagonal) containing a continuous micro fiber in the polymer matrix were designed. Uniaxial tensile, lateral expansion and transverse shear tests on each RVE were designed and conducted by the finite element computer modeling software ANSYS. The formulae based on elasticity theory were derived for extracting the equivalent mechanical properties (Young's moduli, shear

  12. Mechanical Properties of Austenitic Stainless Steel Made by Additive Manufacturing

    PubMed Central

    Luecke, William E; Slotwinski, John A

    2014-01-01

    Using uniaxial tensile and hardness testing, we evaluated the variability and anisotropy of the mechanical properties of an austenitic stainless steel, UNS S17400, manufactured by an additive process, selective laser melting. Like wrought materials, the mechanical properties depend on the orientation introduced by the processing. The recommended stress-relief heat treatment increases the tensile strength, reduces the yield strength, and decreases the extent of the discontinuous yielding. The mechanical properties, assessed by hardness, are very uniform across the build plate, but the stress-relief heat treatment introduced a small non-uniformity that had no correlation to position on the build plate. Analysis of the mechanical property behavior resulted in four conclusions. (1) The within-build and build-to-build tensile properties of the UNS S17400 stainless steel are less repeatable than mature engineering structural alloys, but similar to other structural alloys made by additive manufacturing. (2) The anisotropy of the mechanical properties of the UNS S17400 material of this study is larger than that of mature structural alloys, but is similar to other structural alloys made by additive manufacturing. (3) The tensile mechanical properties of the UNS S17400 material fabricated by selective laser melting are very different from those of wrought, heat-treated 17-4PH stainless steel. (4) The large discontinuous yielding strain in all tests resulted from the formation and propagation of Lüders bands. PMID:26601037

  13. Mechanical Properties of Austenitic Stainless Steel Made by Additive Manufacturing.

    PubMed

    Luecke, William E; Slotwinski, John A

    2014-01-01

    Using uniaxial tensile and hardness testing, we evaluated the variability and anisotropy of the mechanical properties of an austenitic stainless steel, UNS S17400, manufactured by an additive process, selective laser melting. Like wrought materials, the mechanical properties depend on the orientation introduced by the processing. The recommended stress-relief heat treatment increases the tensile strength, reduces the yield strength, and decreases the extent of the discontinuous yielding. The mechanical properties, assessed by hardness, are very uniform across the build plate, but the stress-relief heat treatment introduced a small non-uniformity that had no correlation to position on the build plate. Analysis of the mechanical property behavior resulted in four conclusions. (1) The within-build and build-to-build tensile properties of the UNS S17400 stainless steel are less repeatable than mature engineering structural alloys, but similar to other structural alloys made by additive manufacturing. (2) The anisotropy of the mechanical properties of the UNS S17400 material of this study is larger than that of mature structural alloys, but is similar to other structural alloys made by additive manufacturing. (3) The tensile mechanical properties of the UNS S17400 material fabricated by selective laser melting are very different from those of wrought, heat-treated 17-4PH stainless steel. (4) The large discontinuous yielding strain in all tests resulted from the formation and propagation of Lüders bands.

  14. Quantifying tissue mechanical properties using photoplethysmography

    SciTech Connect

    Akl, Tony; Wilson, Mark A.; Ericson, Milton Nance; Cote, Gerard L.

    2014-01-01

    Photoplethysmography (PPG) is a non-invasive optical method that can be used to detect blood volume changes in the microvascular bed of tissue. The PPG signal comprises two components; a pulsatile waveform (AC) attributed to changes in the interrogated blood volume with each heartbeat, and a slowly varying baseline (DC) combining low frequency fluctuations mainly due to respiration and sympathetic nervous system activity. In this report, we investigate the AC pulsatile waveform of the PPG pulse for ultimate use in extracting information regarding the biomechanical properties of tissue and vasculature. By analyzing the rise time of the pulse in the diastole period, we show that PPG is capable of measuring changes in the Young s Modulus of tissue mimicking phantoms with a resolution of 4 KPa in the range of 12 to 61 KPa. In addition, the shape of the pulse can potentially be used to diagnose vascular complications by differentiating upstream from downstream complications. A Windkessel model was used to model changes in the biomechanical properties of the circulation and to test the proposed concept. The modeling data confirmed the response seen in vitro and showed the same trends in the PPG rise and fall times with changes in compliance and vascular resistance.

  15. Porosity and mechanical properties of zirconium ceramics

    SciTech Connect

    Kalatur, Ekaterina Narikovich, Anton; Buyakova, Svetlana E-mail: kulkov@ispms.tsc.ru; Kulkov, Sergey E-mail: kulkov@ispms.tsc.ru

    2014-11-14

    The article studies the porous ceramics consisting of ultra-fine ZrO{sub 2} powders. The porosity of ceramic samples varied from 15% to 80%. The structure of the ceramic materials had a cellular configuration. The distinctive feature of all experimentally obtained strain diagrams is their nonlinearity at low deformations characterized by the parabolic law. It was shown that the observed nonlinear elasticity for low deformations shown in strain diagrams is due to the mechanical instability of cellular elements of the ceramic framework.

  16. Influence of initial flaws on the mechanical properties of nacre.

    PubMed

    Anup, S

    2015-06-01

    Nacre is a bio-composite made up of hard mineral and soft protein, and has excellent mechanical properties. This paper examines the effect of naturally occurring defects (initial flaws) in nacre on its mechanical properties such as toughness and strength. A random fuse model is developed incorporating initial flaws. Numerical simulations show that initial flaws affect different mechanical properties at different rates. The variation in the experimentally obtained mechanical properties of nacre reported in the literature is shown to be due to initial flaws. The stress in the mineral and protein increases due to initial flaws, but by different amounts. The results obtained in this study are useful for gaining insight into the failure of nacre and development of nacre-inspired composites.

  17. Tailoring of mechanical properties of hydroformed aluminum tubes

    SciTech Connect

    Hong, Sung-tae; Lavender, Curt A.

    2007-07-06

    Tailoring of the mechanical properties of hydroformed aluminum 6063-T4 tubes to those of aluminum 6063-T6 was performed by heat treatment. Quasi-static tensile tests and a SEM analysis were conducted to evaluate the change of the mechanical properties. The experimental results of the hydroformed tubes in T4 condition (before the heat treatment) show significant variations of the mechanical properties along the length due to the different extents of work hardening by hydroforming. The experimental results of the hydroformed tubes in T6 condition (after the heat treatment) show that the precipitation hardening successfully removed the effects of the non-uniform work hardening and resulted in the uniform mechanical properties in the tube.

  18. Mechanical properties of plastics predetermined by empirical method

    NASA Technical Reports Server (NTRS)

    Lohr, J. J.; Parker, J. A.

    1964-01-01

    To predetermine the mechanical properties of rigid plastics as a function of plasticizer content and composition, a set of equations has been empirically derived. These relate strain rate, yield stress, temperature, and weight fraction of the plasticizer.

  19. Modified Polypropylene with Improved Physical-Mechanical Properties

    NASA Astrophysics Data System (ADS)

    Chervakov, D. O.; Bashtanyk, P. I.; Burmistr, M. V.

    2015-03-01

    The use of mixtures of benzoyl peroxide and polysiloxane polyol compounds as polypropylene modifiers is suggested. It is established that, in such a way, its physical-mechanical properties can be changed purposefully.

  20. Characterising Mechanical Properties of Braided and Woven Textile Composite Beams

    NASA Astrophysics Data System (ADS)

    Dauda, Benjamin; Oyadiji, S. Olutunde; Potluri, Prasad

    2009-02-01

    The focus of this paper is on the manufacture of textile composite beams and on the determination of their mechanical properties. This includes investigating the effects of fibre orientation on the mechanical properties of braided and woven textile composites. Composites were manufactured from nominally identical constituents and identical consolidation processes, leaving as the only variables, variations caused by the different fibre architecture of the preform. The repeatability and, hence, reliability of this approach is demonstrated. Results obtained show that fibre architecture affects composite strength and extensibility. Composites with woven preforms are practically linear up to catastrophic failure while composites with braided preforms exhibit non-linearity prior to failure. Also the mechanical properties of the textile composite beams were determined. Results show that by tailoring the braid angle and pick density of braided and woven composite performs, the mechanical properties of the composite beams can be controlled to suit end-use requirement.

  1. Primate dietary ecology in the context of food mechanical properties.

    PubMed

    Coiner-Collier, Susan; Scott, Robert S; Chalk-Wilayto, Janine; Cheyne, Susan M; Constantino, Paul; Dominy, Nathaniel J; Elgart, Alison A; Glowacka, Halszka; Loyola, Laura C; Ossi-Lupo, Kerry; Raguet-Schofield, Melissa; Talebi, Mauricio G; Sala, Enrico A; Sieradzy, Pawel; Taylor, Andrea B; Vinyard, Christopher J; Wright, Barth W; Yamashita, Nayuta; Lucas, Peter W; Vogel, Erin R

    2016-09-01

    Substantial variation exists in the mechanical properties of foods consumed by primate species. This variation is known to influence food selection and ingestion among non-human primates, yet no large-scale comparative study has examined the relationships between food mechanical properties and feeding strategies. Here, we present comparative data on the Young's modulus and fracture toughness of natural foods in the diets of 31 primate species. We use these data to examine the relationships between food mechanical properties and dietary quality, body mass, and feeding time. We also examine the relationship between food mechanical properties and categorical concepts of diet that are often used to infer food mechanical properties. We found that traditional dietary categories, such as folivory and frugivory, did not faithfully track food mechanical properties. Additionally, our estimate of dietary quality was not significantly correlated with either toughness or Young's modulus. We found a complex relationship among food mechanical properties, body mass, and feeding time, with a potential interaction between median toughness and body mass. The relationship between mean toughness and feeding time is straightforward: feeding time increases as toughness increases. However, when considering median toughness, the relationship with feeding time may depend upon body mass, such that smaller primates increase their feeding time in response to an increase in median dietary toughness, whereas larger primates may feed for shorter periods of time as toughness increases. Our results emphasize the need for additional studies quantifying the mechanical and chemical properties of primate diets so that they may be meaningfully compared to research on feeding behavior and jaw morphology.

  2. Processing effects on the mechanical properties of tungsten heavy alloys

    NASA Technical Reports Server (NTRS)

    Kishi, Toshihito; German, R. M.

    1990-01-01

    Tungsten heavy alloys exhibit significant mechanical property sensitivities to the fabrication variables. These sensitivities are illustrated in this examination of vacuum sintering and the effects of composition, sintering temperature, and sintering time on the mechanical properties of tungsten heavy alloys. Measurements were conducted to assess the density, strength, hardness, and elongation dependencies. A detrimental aspect of vacuum sintering is matrix phase evaporation, although vacuum sintering does eliminate the need for postsintering heat treatments.

  3. Microstructure and mechanical properties of neoprene montmorillonite nanocomposites

    NASA Astrophysics Data System (ADS)

    Yeh, Meng-Heng; Hwang, Weng-Sing; Cheng, Lin-Ri

    2007-03-01

    To investigate the microstructure and mechanical properties of neoprene-montmorillonite nanocomposite, three modified montmorillonite are used. An X-ray diffractometer is used to measure the corresponding change in d-spacing. Scanning electron microscopy is employed to investigate the morphology of the various composites. Transmission electron microscopy is employed to investigate the composite of montmorillonite and neoprene. The results indicate that the addition of montmorillonite enhances the mechanical properties of neoprene significantly.

  4. Mechanical properties of henequen fibre/epoxy resin composites

    NASA Astrophysics Data System (ADS)

    Gonzalez-Murillo, C.; Ansell, M. P.

    2009-07-01

    By using surface-treated and untreated henequen fibres and an epoxy resin, composites were made by compression moulding, and their mechanical properties and failure modes were determined experimentally in tension, bending, and impact loading. The results obtained show that the treatment of fibre surface does not improve the bond between the fibres and the resin matrix, and the general mechanical properties of the composites are similar.

  5. Effective elastic mechanical properties of single layer graphene sheets.

    PubMed

    Scarpa, F; Adhikari, S; Srikantha Phani, A

    2009-02-11

    The elastic moduli of single layer graphene sheet (SLGS) have been a subject of intensive research in recent years. Calculations of these effective properties range from molecular dynamic simulations to use of structural mechanical models. On the basis of mathematical models and calculation methods, several different results have been obtained and these are available in the literature. Existing mechanical models employ Euler-Bernoulli beams rigidly jointed to the lattice atoms. In this paper we propose truss-type analytical models and an approach based on cellular material mechanics theory to describe the in-plane linear elastic properties of the single layer graphene sheets. In the cellular material model, the C-C bonds are represented by equivalent mechanical beams having full stretching, hinging, bending and deep shear beam deformation mechanisms. Closed form expressions for Young's modulus, the shear modulus and Poisson's ratio for the graphene sheets are derived in terms of the equivalent mechanical C-C bond properties. The models presented provide not only quantitative information about the mechanical properties of SLGS, but also insight into the equivalent mechanical deformation mechanisms when the SLGS undergoes small strain uniaxial and pure shear loading. The analytical and numerical results from finite element simulations show good agreement with existing numerical values in the open literature. A peculiar marked auxetic behaviour for the C-C bonds is identified for single graphene sheets under pure shear loading.

  6. Mechanical properties of hydroxyapatite/mica composite.

    PubMed

    Nordström, E G; Herø, H; Jørgensen, R B

    1994-01-01

    Bend specimens of the inorganic synthetic materials hydroxyapatite (HA) and a composite of hydroxyapatite/muscovite mica have been prepared and tested mechanically. Sintering followed by hot isostatic pressing (HIP) without encapsulation gave an increased strength for HA alone, but no significant increase in strength compared with sintering alone for HA/mica composites. The bend strength of the HA/mica composite was inferior to that of HA alone, the reason being inadequate bonding between HA and mica. HIP in glass capsules and an increased cold compaction pressure tended to improve the bend strength of the composite. Corrosion in tris for 7 d did not affect the bend strength of the investigated materials significantly.

  7. Mechanical properties of rare earth stannate pyrochlores

    NASA Astrophysics Data System (ADS)

    Feng, J.; Xiao, B.; Qu, Z. X.; Zhou, R.; Pan, W.

    2011-11-01

    The RE2Sn2O7 series compounds (RE = La, Nb, Sm, Gd, Er, Yb) with a pyrochlore structure are prepared by co-precipitation method. The bulk, shear, Young's moduli, B/G, and Poisson's ratios are calculated using density functional theory and also measured by ultrasonic resonance method. The theoretical values of lattice constants and mechanical moduli are smaller than experimental results. The electronic structures of RE2Sn2O7 are analogous to RE2Zr2O7. La2Sn2O7 exhibits stronger ionic bonds than others. The covalent interactions are slightly enhanced in the heavy rare earth stannate pyrochlores. The Vickers harnesses of RE2Sn2O7 are measured experimentally, which are smaller than theoretical predictions.

  8. The perivascular environment along the vertebral artery governs segment-specific structural and mechanical properties.

    PubMed

    Zhou, Boran; Alshareef, Mohammed; Prim, David; Collins, Michael; Kempner, Michael; Hartstone-Rose, Adam; Eberth, John F; Rachev, Alexander; Shazly, Tarek

    2016-11-01

    The vertebral arteries (VAs) are anatomically divided into four segments (V1-V4), which cumulatively transport blood flow through neck and ultimately form the posterior circulation of the brain. The vital physiological function of these conduit vessels depends on their geometry, composition and mechanical properties, all of which may vary among the defined arterial segments. Despite their significant role in blood circulation and susceptibility to injury, few studies have focused on characterizing the mechanical properties of VAs, and none have investigated the potential for segmental variation that could arise due to distinct perivascular environments. In this study, we compare the passive mechanical response of the central, juxtaposed arterial segments of porcine VAs (V2 and V3) via inflation-extension mechanical testing. Obtained experimental data and histological measures of arterial wall composition were used to adjust parameters of structure-motivated constitutive models that quantify the passive mechanical properties of each arterial segment and enable prediction of wall stress distributions under physiologic loads and boundary conditions. Our findings reveal significant segmental differences in the arterial wall geometry and structure. Nevertheless, similar wall stress distributions are predicted in these neighboring arterial segments if calculations account for their specific perivascular environments. These findings allow speculation that segmental differences in wall structure and geometry are a consequence of a previously introduced principle of optimal operation of arteries, which ensures effective bearing of physiological load and a favorable mechanical environment for mechanosensitive vascular smooth muscle cells.

  9. Analgesic Drugs Alter Connective Tissue Remodeling and Mechanical Properties

    PubMed Central

    Carroll, Chad C.

    2015-01-01

    Exercising individuals commonly consume analgesics but these medications alter tendon and skeletal muscle connective tissue properties, possibly limiting a person from realizing the full benefits of exercise training. I detail the novel hypothesis that analgesic medications alter connective tissue structure and mechanical properties by modifying fibroblast production of growth factors and matrix enzymes, which are responsible for extracellular matrix remodeling. PMID:26509485

  10. Analgesic Drugs Alter Connective Tissue Remodeling and Mechanical Properties.

    PubMed

    Carroll, Chad C

    2016-01-01

    Exercising individuals commonly consume analgesics, but these medications alter tendon and skeletal muscle connective tissue properties, possibly limiting a person from realizing the full benefits of exercise training. I detail the novel hypothesis that analgesic medications alter connective tissue structure and mechanical properties by modifying fibroblast production of growth factors and matrix enzymes, which are responsible for extracellular matrix remodeling.

  11. Mechanical properties of Inconel 617 and 618

    SciTech Connect

    McCoy, H E; King, J F

    1985-02-01

    Inconel 617 and 618 were evaluated for application in high-temperature gas-cooled reactors (HTGRs). Techniques were developed for making sound welds, and tests were performed on base and weld metals. Specimens of both materials were aged to 20,000 h to evaluate thermal stability. Short-term tensile tests on alloy 617 showed that aging severely reduced the strain at fracture at both ambient and elevated temperatures. The impact energy at ambient temperature was severely degraded by aging. Creep tests showed that fracture occurred at 593 through 704{sup 0}C after only 1 to 2% strain, and higher strains were noted at higher temperatures. There was no detectable difference between the creep behavior in air and that in HTGR helium environments. Inconel alloy 618 had excellent stability during aging. Fracture strains in short-term tensile tests and impact energies in impact tests remained high after aging. The creep properties of alloy 618 were equivalent in air and in HTGR helium. Both alloys were carburized during creep testing in HTGR helium, and the rate of carburization became rather high at 760{sup 0}C and higher temperatures. 49 figures, 20 tables.

  12. Adjustment of surface chemical and physical properties with functionalized polymers to control cell adhesion

    NASA Astrophysics Data System (ADS)

    Zhou, Zhaoli

    Cell-surface interaction is crucial in many cellular functions such as movement, growth, differentiation, proliferation and survival. In the present work, we have developed several strategies to design and prepare synthetic polymeric materials with selected cues to control cell attachment. To promote neuronal cell adhesion on the surfaces, biocompatible, non-adhesive PEG-based materials were modified with neurotransmitter acetylcholine functionalities to produce hydrogels with a range of porous structures, swollen states, and mechanical strengths. Mice hippocampal cells cultured on the hydrogels showed differences in number, length of processes and exhibited different survival rates, thereby highlighting the importance of chemical composition and structure in biomaterials. Similar strategies were used to prepare polymer brushes to assess how topographical cues influence neuronal cell behaviors. The brushes were prepared using the "grown from" method through surface-initiated atom transfer radical polymerization (SI-ATRP) reactions and further patterned via UV photolithography. Protein absorption tests and hippocampal neuronal cell culture of the brush patterns showed that both protein and neuronal cells can adhere to the patterns and therefore can be guided by the patterns at certain length scales. We also prepared functional polymers to discourage attachment of undesirable cells on the surfaces. For example, we synthesized PEG-perfluorinated alkyl amphiphilic surfactants to modify polystyrene-block-poly(ethylene-ran-butylene)- block-polyisoprene (SEBI or K3) triblock copolymers for marine antifouling/fouling release surface coatings. Initial results showed that the polymer coated surfaces can facilitate removal of Ulva sporelings on the surfaces. In addition, we prepared both bioactive and dual functional biopassive/bioactive antimicrobial coatings based on SEBI polymers. Incubating the polymer coated surfaces with gram-positive bacteria (S. aureus), gram

  13. Porosity and mechanical properties of zirconium ceramics

    NASA Astrophysics Data System (ADS)

    Buyakova, S.; Sablina, T.; Kulkov, S.

    2015-11-01

    Has been studied a porous ceramics obtained from ultra-fine powders. Porous ceramic ZrO2(MgO), ZrO2(Y2O3) powder was prepared by pressing and subsequent sintering of compacts homologous temperatures ranging from 0.63 to 0.56 during the isothermal holding duration of 1 to 5 hours. The porosity of ceramic samples was from 15 to 80%. The structure of the ceramic materials produced from plasma-sprayed ZrO2 powder was represented as a system of cell and rod structure elements. Cellular structure formed by stacking hollow powder particles can be easily seen at the images of fracture surfaces of obtained ceramics. There were three types of pores in ceramics: large cellular hollow spaces, small interparticle pores which are not filled with powder particles and the smallest pores in the shells of cells. The cells generally did not have regular shapes. The size of the interior of the cells many times exceeded the thickness of the walls which was a single-layer packing of ZrO2 grains. A distinctive feature of all deformation diagrams obtained in the experiment was their nonlinearity at low deformations which was described by the parabolic law. It was shown that the observed nonlinear elasticity for low deformation on deformation diagrams is due to mechanical instability of the cellular elements in the ceramic carcass.

  14. Mechanical Properties of Nanoscopic Lipid Domains

    SciTech Connect

    Nickels, Jonathan D.; Cheng, Xiaolin; Mostofian, Barmak; Stanley, Christopher; Lindner, Benjamin; Heberle, Frederick A.; Perticaroli, Stefania; Feygenson, Mikhail; Egami, Takeshi; Standaert, Robert F.; Smith, Jeremy C.; Myles, Dean A. A.; Ohl, Michael; Katsaras, John

    2015-09-28

    We found that the lipid raft hypothesis presents insight into how the cell membrane organizes proteins and lipids to accomplish its many vital functions. Yet basic questions remain about the physical mechanisms that lead to the formation, stability, and size of lipid rafts. Thus, much interest has been generated in the study of systems that contain similar lateral heterogeneities, or domains. In the current work we present an experimental approach that is capable of isolating the bending moduli of lipid domains. This is accomplished using neutron scattering and its unique sensitivity to the isotopes of hydrogen. Combining contrast matching approaches with inelastic neutron scattering, we isolate the bending modulus of ~13 nm diameter domains residing in 60 nm unilamellar vesicles, whose lipid composition mimics the mammalian plasma membrane outer leaflet. Importantly, the bending modulus of the nanoscopic domains differs from the modulus of the continuous phase surrounding them. Moreover, from additional structural measurements and all-atom simulations, we also determine that nanoscopic domains are in-register across the bilayer leaflets. Taken together, these results inform a number of theoretical models of domain/raft formation and highlight the fact that mismatches in bending modulus must be accounted for when explaining the emergence of lateral heterogeneities in lipid systems and biological membranes.

  15. Mechanical Properties of Nanoscopic Lipid Domains

    DOE PAGES

    Nickels, Jonathan D.; Cheng, Xiaolin; Mostofian, Barmak; ...

    2015-09-28

    We found that the lipid raft hypothesis presents insight into how the cell membrane organizes proteins and lipids to accomplish its many vital functions. Yet basic questions remain about the physical mechanisms that lead to the formation, stability, and size of lipid rafts. Thus, much interest has been generated in the study of systems that contain similar lateral heterogeneities, or domains. In the current work we present an experimental approach that is capable of isolating the bending moduli of lipid domains. This is accomplished using neutron scattering and its unique sensitivity to the isotopes of hydrogen. Combining contrast matching approachesmore » with inelastic neutron scattering, we isolate the bending modulus of ~13 nm diameter domains residing in 60 nm unilamellar vesicles, whose lipid composition mimics the mammalian plasma membrane outer leaflet. Importantly, the bending modulus of the nanoscopic domains differs from the modulus of the continuous phase surrounding them. Moreover, from additional structural measurements and all-atom simulations, we also determine that nanoscopic domains are in-register across the bilayer leaflets. Taken together, these results inform a number of theoretical models of domain/raft formation and highlight the fact that mismatches in bending modulus must be accounted for when explaining the emergence of lateral heterogeneities in lipid systems and biological membranes.« less

  16. Porosity and mechanical properties of zirconium ceramics

    SciTech Connect

    Buyakova, S. Kulkov, S.; Sablina, T.

    2015-11-17

    Has been studied a porous ceramics obtained from ultra-fine powders. Porous ceramic ZrO{sub 2}(MgO), ZrO{sub 2}(Y{sub 2}O{sub 3}) powder was prepared by pressing and subsequent sintering of compacts homologous temperatures ranging from 0.63 to 0.56 during the isothermal holding duration of 1 to 5 hours. The porosity of ceramic samples was from 15 to 80%. The structure of the ceramic materials produced from plasma-sprayed ZrO{sub 2} powder was represented as a system of cell and rod structure elements. Cellular structure formed by stacking hollow powder particles can be easily seen at the images of fracture surfaces of obtained ceramics. There were three types of pores in ceramics: large cellular hollow spaces, small interparticle pores which are not filled with powder particles and the smallest pores in the shells of cells. The cells generally did not have regular shapes. The size of the interior of the cells many times exceeded the thickness of the walls which was a single-layer packing of ZrO{sub 2} grains. A distinctive feature of all deformation diagrams obtained in the experiment was their nonlinearity at low deformations which was described by the parabolic law. It was shown that the observed nonlinear elasticity for low deformation on deformation diagrams is due to mechanical instability of the cellular elements in the ceramic carcass.

  17. Mechanical properties of lanthanum and yttrium chromites

    SciTech Connect

    Paulik, S.W.; Armstrong, T.R.

    1996-12-31

    In an operating high-temperature (1000{degrees}C) solid oxide fuel cell (SOFC), the interconnect separates the fuel (P(O{sub 2}){approx}10{sup -16} atm) and the oxidant (P(O2){approx}10{sup 0.2} atm), while being electrically conductive and connecting the cells in series. Such severe atmospheric and thermal demands greatly reduce the number of viable candidate materials. Only two materials, acceptor substituted lanthanum chromite and yttrium chromite, meet these severe requirements. In acceptor substituted chromites (Sr{sup 2+} or Ca{sup 2+} for La{sup 3+}), charge compensation is primarily electronic in oxidizing conditions (through the formation of Cr{sup 4+}). Under reducing conditions, ionic charge compensation becomes significant as the lattice becomes oxygen deficient. The formation of oxygen vacancies is accompanied by the reduction of Cr{sup 4+} ions to Cr{sup 3+} and a resultant lattice expansion. The lattice expansion observed in large chemical potential gradients is not desirable and has been found to result in greatly reduced mechanical strength.

  18. Fluid mechanical properties of flames in enclosures

    SciTech Connect

    Rotman, D.A.; Pindera, M.Z.; Oppenheim, A.K.

    1988-07-01

    In an enclosure where the reacting medium is initially at rest, the flame first generates a flowfield that then gets stretched, i.e., its front is pulled along the surface by the flowfield in which it then finds itself residing. A methodology developed for numerical modeling of such fields is described. Of key significance in this respect is the zero Mach number model/endash/a reasonable idealization in view of the relatively high temperature, and hence sound speed, that exists, concomitantly with a comparatively low particle velocity, in the confinement of a combustion chamber. According to this model, the density gradient in the field is nullified, while across the flame front it approaches infinity. One has thus two regimes: one of the unburned medium and the other of the burned gas, each of spatially uniform density, separated by a flame front interface. The latter is endowed with four properties, of which the first two are purely kinematic and the others dynamic in nature, namely: 1) it is advected at the local velocity of flow; 2) it self-advances at the normal burning speed, the eigenvalue of the system; 3) it acts as the velocity source due to the exothermicity of the combustion process; and 4) it acts as the vorticity source due to the baroclinic effect generated by the pressure gradient along its surface and the density gradient across it. A solution obtained for a flame propagating in an oblong rectangular enclosure demonstrates that the latter has a significant influence upon the formation of the well known tulip shape. 12 refs., 4 figs.

  19. Mechanical properties of dental investment materials.

    PubMed

    Low, D; Swain, M V

    2000-07-01

    Measurement of the elastic modulus (E) of investment materials has been difficult because of their low strength. However, these values are essential for engineering simulation and there are many methods available to assess the elasticity of materials. The present study compared two different methods with one of the methods being non-destructive in nature and can be used for specimens prepared for other tests. Two different types of investment materials were selected, gypsum-and phosphate-bonded. Method 1 is a traditional three-point bending test. Twelve rectangular bars with dimension of (70 x 9 x 3 mm) were prepared and placed on supports 56.8 mm apart. The test was conducted at a cross-head speed of 1 mm/min by use of a universal testing machine. The load applied to the test specimen and the corresponding deflection were measured until the specimen fractured. The E value was calculated from a linear part of the stress-strain plot. Method 2 is an ultra micro-indentation system to determine near surface properties of materials with nanometer resolution. The measurement procedure was programmed such that the specimens were indented with an initial contact force of 5 mN then followed by a maximum force of 500 mN. Measurement consisted of 10 indentations conducted with a spherical stainless steel indenter (R = 250 microm) that were equally spaced (500 microm). The E value rose asymptotically with depth of penetration and would approach the three-point bending test value at approximately four time's maximum contact depth for both materials. Both methods are practical ways of measuring the E of investment materials.

  20. Characterization of the mechanical properties of HL-1 cardiomyocytes with high throughput magnetic tweezers

    SciTech Connect

    Chen, La; Maybeck, Vanessa; Offenhäusser, Andreas; Krause, Hans-Joachim

    2015-08-03

    We characterized the mechanical properties of cardiomyocyte-like HL-1 cells using our recently developed multi-pole magnetic tweezers. With the optimized design, both high force and high throughput are achieved at the same time. Force up to 100 pN can be applied on a 1 μm diameter superparamagnetic bead in a workspace with 60 μm radius, which is encircled symmetrically by 3 sharp magnetic tips. By adjusting the coil currents, both the strength and direction of force can be controlled. The result shows that both viscosity and shear elastic modulus of HL-1 cells exhibit an approximately log-normal distribution. The cells became stiffer as they matured, consistent with a transition from proliferating cells to contractile muscle tissue. Moreover, the mechanical properties of HL-1 cells show high heterogeneity, which agrees well with their physiological structure.

  1. Dynamic monitoring of cell mechanical properties using profile microindentation

    PubMed Central

    Guillou, L.; Babataheri, A.; Puech, P.-H.; Barakat, A. I.; Husson, J.

    2016-01-01

    We have developed a simple and relatively inexpensive system to visualize adherent cells in profile while measuring their mechanical properties using microindentation. The setup allows simultaneous control of cell microenvironment by introducing a micropipette for the delivery of soluble factors or other cell types. We validate this technique against atomic force microscopy measurements and, as a proof of concept, measure the viscoelastic properties of vascular endothelial cells in terms of an apparent stiffness and a dimensionless parameter that describes stress relaxation. Furthermore, we use this technique to monitor the time evolution of these mechanical properties as the cells’ actin is depolymerized using cytochalasin-D. PMID:26857265

  2. Mechanical Properties of Continuous Fiber Reinforced Zirconium Diboride Matrix Composites

    NASA Technical Reports Server (NTRS)

    Stuffle, Kevin; Creegan, Peter; Nowell, Steven; Bull, Jeffrey D.; Rasky, Daniel J. (Technical Monitor)

    1995-01-01

    Continuous fiber reinforced zirconium diboride matrix composites, SCS-9a-(RBSiCZrB2)matrix, are being developed for leading edge, rocket nozzle and turbine engine applications. Recently, the composite materials have been characterized for tensile properties to 1250 C, the highest temperature tested. The tensile properties are fiber dominated as the matrix is microcracked on fabrication, but favorable failure characteristic are observed. Compression and shear mechanical testing results will be reported if completed. The effects of fiber volume fraction and matrix density on mechanical properties will be discussed. The target applications of the materials will be discussed. Specific testing being performed towards qualification for these applications will be included.

  3. Biodegradability and mechanical properties of poly-([beta]-hyroxybutyrate-Co-[beta]-hydroxyvalerate)-starch blends

    SciTech Connect

    Ramsay, B.A.; Langlade, V.; Carreau, P.J.; Ramsay, J.A. )

    1993-04-01

    PHAs, biodegradable thermoplastics, are a promising option to synthetic resins such as polyethylene, in combination with starch, to produce biodegradable plastics. This paper describes the mechanical properties and biodegradability of blends of wheat starch and P(HB-co-HV). The results indicate that the addition of starch to P(HB-co-HV) not only reduces the cost but also leads to a completely biodegradable material whose degradation can be tailored by adjusting the starch/PHA ratio. 15 refs., 3 figs., 1 tab.

  4. Mechanical and biological properties of keratose biomaterials.

    PubMed

    de Guzman, Roche C; Merrill, Michelle R; Richter, Jillian R; Hamzi, Rawad I; Greengauz-Roberts, Olga K; Van Dyke, Mark E

    2011-11-01

    The oxidized form of extractable human hair keratin proteins, commonly referred to as keratose, is gaining interest as a biomaterial for multiple tissue engineering studies including those directed toward peripheral nerve, spinal cord, skin, and bone regeneration. Unlike its disulfide cross-linked counterpart, kerateine, keratose does not possess a covalently cross-linked network structure and consequently displays substantially different characteristics. In order to understand its mode(s) of action and potential for clinical translatability, detailed characterization of the composition, physical properties, and biological responses of keratose biomaterials are needed. Keratose was obtained from end-cut human hair fibers by peracetic acid treatment, followed by base extraction, and subsequent dialysis. Analysis of lyophilized keratose powder determined that it contains 99% proteins by mass with amino acid content similar to human hair cortex. Metallic elements were also found in minute quantities. Protein oxidation led to disulfide bond cleavage and drastic reduction of free thiols due to conversion of sulfhydryl to sulfonic acid, chain fragmentation, and amino acid modifications. Mass spectrometry identified the major protein constituents as a heterogeneous mixture of 15 hair keratins (type I: K31-35 and K37-39, and type II: K81-86) with small amounts of epithelial keratins which exist in monomeric, dimeric, multimeric, and even degraded forms. Re-hydration with PBS enabled molecular assembly into an elastic solid-like hydrogel. Highly-porous scaffolds formed by lyophilization of the gel had the compression behavior of a cellular foam material and reverted back to gel upon wetting. Cytotoxicity assays showed that the EC50 for various cell lines were attained at 8-10 mg/mL keratose, indicating the non-toxic nature of the material. Implantation in mouse subcutaneous tissue pockets demonstrated that keratose resorption follows a rectangular hyperbolic regression

  5. Maintaining dimensions and mechanical properties of ionically crosslinked alginate hydrogel scaffolds in vitro.

    PubMed

    Kuo, Catherine K; Ma, Peter X

    2008-03-15

    Ionically crosslinked alginate hydrogels are attractive scaffolds because of their biocompatibility and mild gelation reaction that allows for gentle cell incorporation. However, the instability of ionically crosslinked hydrogels in an aqueous environment is a challenge that limits their application. This report presents a novel method to control the dimensions and mechanical properties of ionically crosslinked hydrogels via control of the ionic concentration of the medium. Homogeneous calcium-alginate gels were incubated in physiological saline baths adjusted to specific calcium ion concentrations. Swelling and shrinking occurred at low and high ionic concentrations of the medium, respectively, while an "optimal" intermediate calcium ion concentration of the medium was found to maintain original size and shape of the hydrogel. This optimal calcium ion concentration was found to be a function of crosslinking density and polymer concentration of the hydrogel and chemical composition of the alginate. The effects of optimal and high calcium ion concentrations of the medium on swelling behavior, calcium content, dry weight, and mechanical properties of the immersed hydrogels were investigated. It was found that the resulting hydrogel composition and mechanical properties depended on not only the calcium concentration of the medium, but also the crosslinking density and polymer concentration of the gel. In an 8-week experiment, controlled dimensions and mechanical properties of alginate gels in an aqueous environment were demonstrated. This new technique significantly enhances the potential of alginate hydrogels for tissue engineering and other biomedical applications.

  6. Mechanical Properties of Isotactic Polypropylene Modified with Thermoplastic Potato Starch

    NASA Astrophysics Data System (ADS)

    Knitter, M.; Dobrzyńska-Mizera, M.

    2015-05-01

    In this paper selected mechanical properties of isotactic polypropylene (iPP) modified with potato starch have been presented. Thermoplastic starch (TPS) used as a modifier in the study was produced from potato starch modified with glycerol. Isotactic polypropylene/thermoplastic potato starch composites (iPP/TPS) that contained 10, 30, 50 wt.% of modified starch were examined using dynamic mechanical-thermal analysis, static tensile, Brinell hardness, and Charpy impact test. The studies indicated a distinct influence of a filler content on the mechanical properties of composites in comparison with non-modified polypropylene.

  7. Mechanical properties of carbon nanotube/polymer composites

    NASA Astrophysics Data System (ADS)

    Arash, B.; Wang, Q.; Varadan, V. K.

    2014-10-01

    The remarkable mechanical properties of carbon nanotubes, such as high elastic modulus and tensile strength, make them the most ideal and promising reinforcements in substantially enhancing the mechanical properties of resulting polymer/carbon nanotube composites. It is acknowledged that the mechanical properties of the composites are significantly influenced by interfacial interactions between nanotubes and polymer matrices. The current challenge of the application of nanotubes in the composites is hence to determine the mechanical properties of the interfacial region, which is critical for improving and manufacturing the nanocomposites. In this work, a new method for evaluating the elastic properties of the interfacial region is developed by examining the fracture behavior of carbon nanotube reinforced poly (methyl methacrylate) (PMMA) matrix composites under tension using molecular dynamics simulations. The effects of the aspect ratio of carbon nanotube reinforcements on the elastic properties, i.e. Young's modulus and yield strength, of the interfacial region and the nanotube/polymer composites are investigated. The feasibility of a three-phase micromechanical model in predicting the elastic properties of the nanocomposites is also developed based on the understanding of the interfacial region.

  8. Mechanical properties of carbon nanotube/polymer composites

    PubMed Central

    Arash, B.; Wang, Q.; Varadan, V. K.

    2014-01-01

    The remarkable mechanical properties of carbon nanotubes, such as high elastic modulus and tensile strength, make them the most ideal and promising reinforcements in substantially enhancing the mechanical properties of resulting polymer/carbon nanotube composites. It is acknowledged that the mechanical properties of the composites are significantly influenced by interfacial interactions between nanotubes and polymer matrices. The current challenge of the application of nanotubes in the composites is hence to determine the mechanical properties of the interfacial region, which is critical for improving and manufacturing the nanocomposites. In this work, a new method for evaluating the elastic properties of the interfacial region is developed by examining the fracture behavior of carbon nanotube reinforced poly (methyl methacrylate) (PMMA) matrix composites under tension using molecular dynamics simulations. The effects of the aspect ratio of carbon nanotube reinforcements on the elastic properties, i.e. Young's modulus and yield strength, of the interfacial region and the nanotube/polymer composites are investigated. The feasibility of a three-phase micromechanical model in predicting the elastic properties of the nanocomposites is also developed based on the understanding of the interfacial region. PMID:25270167

  9. Mechanical properties of carbon nanotubes and their polymer nanocomposites.

    PubMed

    Miyagawa, Hiroaki; Misra, Manjusri; Mohanty, Amar K

    2005-10-01

    More than 10 years have passed since carbon nanotubes (CNT) have been found during observations by transmission electron microscopy (TEM). Since then, one of the major applications of the CNT is the reinforcements of plastics in processing composite materials, because it was found by experiments that CNT possessed splendid mechanical properties. Various experimental methods are conducted in order to understand the mechanical properties of varieties of CNT and CNT-based composite materials. The systematized data of the past research results of CNT and their nanocomposites are extremely useful to improve processing and design criteria for new nanocomposites in further studies. Before the CNT observations, vapor grown carbon fibers (VGCF) were already utilized for composite applications, although there have been only few experimental data about the mechanical properties of VGCF. The structure of VGCF is similar to that of multi-wall carbon nanotubes (MWCNT), and the major benefit of VGCF is less commercial price. Therefore, this review article overviews the experimental results regarding the various mechanical properties of CNT, VGCF, and their polymer nanocomposites. The experimental methods and results to measure the elastic modulus and strength of CNT and VGCF are first discussed in this article. Secondly, the different surface chemical modifications for CNT and VGCF are reviewed, because the surface chemical modifications play an important role for polymer nanocomposite processing and properties. Thirdly, fracture and fatigue properties of CNT/polymer nanocomposites are reviewed, since these properties are important, especially when these new nanocomposite materials are applied for structural applications.

  10. Lithophysal Rock Mass Mechanical Properties of the Repository Host Horizon

    SciTech Connect

    D. Rigby

    2004-11-10

    The purpose of this calculation is to develop estimates of key mechanical properties for the lithophysal rock masses of the Topopah Spring Tuff (Tpt) within the repository host horizon, including their uncertainties and spatial variability. The mechanical properties to be characterized include an elastic parameter, Young's modulus, and a strength parameter, uniaxial compressive strength. Since lithophysal porosity is used as a surrogate property to develop the distributions of the mechanical properties, an estimate of the distribution of lithophysal porosity is also developed. The resulting characterizations of rock parameters are important for supporting the subsurface design, developing the preclosure safety analysis, and assessing the postclosure performance of the repository (e.g., drift degradation and modeling of rockfall impacts on engineered barrier system components).

  11. Mechanical Properties and Durability of "Waterless Concrete"

    NASA Technical Reports Server (NTRS)

    Toutanji, Houssam; Grugel, Richard N.

    2008-01-01

    Waterless concrete consists of molten elementary sulfur and aggregate. The aggregates in lunar environment will be lunar rocks and soil. Sulfur is present on the Moon in Troilite soil (FeS) and by oxidation soil iron and sulfur can be produced. Iron can be used to reinforce the sulfur concrete. Sulfur concrete specimens were cycled between liquid nitrogen (approximately 191 C) and room temperature (approximately 21 C) to simulate exposure to a lunar environment. Cycled and control specimens were subsequently tested in compression at room temperatures (approximately 21 C) and approximately 101 C. Test results showed that due to temperature cycling, compressive strength of cycled specimens was 20% of those non-cycled. Microscopic examination of the fracture surfaces from the cycled samples showed clear de-bonding of the sulfur from the aggregate material whereas it was seen well bonded in those non-cycled. This reduction in strength can be attributed to the large differences in thermal coefficients of expansion of the materials constituting the concrete which promoted cracking. Similar sulfur concrete mixtures were strengthened with short and long glass fibers. The glass fibers from lunar regolith simulant was melted in a 25 cc Pt-Rh crucible in a Sybron Thermoline high temperature MoSi2 furnace at melting temperatures of 1450 to 1600 C for times of 30 min to 1 hour. Glass fibers were cast from the melt into graphite crucibles and were annealed for a couple of hours at 600 C. Glass fibers and small rods were pulled from the melt. The glass melt wets the ceramic rod and long continuous glass fibers were easily hand drawn. The glass fibers were immediately coated with a protective polymer to maintain the mechanical strength. The glass fibers were used to reinforce sulfur concrete plated to improve the flexural strength of the sulfur concrete. Prisms beams strengthened with glass fibers were tested in 4-point bending test. Beams strengthened with glass fiber showed to

  12. Mechanical Properties Comparing Composite Fiber Length to Amalgam

    PubMed Central

    Petersen, Richard C.; Liu, Perng-Ru

    2016-01-01

    Photocure fiber-reinforced composites (FRCs) with varying chopped quartz-fiber lengths were incorporated into a dental photocure zirconia-silicate particulate-filled composite (PFC) for mechanical test comparisons with a popular commercial spherical-particle amalgam. FRC lengths included 0.5-mm, 1.0 mm, 2.0 mm, and 3.0 mm all at a constant 28.2 volume percent. Four-point fully articulated fixtures were used according to American Standards Test Methods with sample dimensions of 2×2×50 mm3 across a 40 mm span to provide sufficient Euler flexural bending and prevent top-load compressive shear error. Mechanical properties for flexural strength, modulus, yield strength, resilience, work of fracture, critical strain energy release, critical stress intensity factor, and strain were obtained for comparison. Fiber length subsequently correlated with increasing all mechanical properties, p < 1.1×10−5. Although the modulus was significantly statistically higher for amalgam than all composites, all FRCs and even the PFC had higher values than amalgam for all other mechanical properties. Because amalgams provide increased longevity during clinical use compared to the standard PFCs, modulus would appear to be a mechanical property that might sufficiently reduce margin interlaminar shear stress and strain-related microcracking that could reduce failure rates. Also, since FRCs were tested with all mechanical properties that statistically significantly increased over the PFC, new avenues for future development could be provided toward surpassing amalgam in clinical longevity. PMID:27642629

  13. Bioinspired design of nanostructured elastomers with cross-linked soft matrix grafting on the oriented rigid nanofibers to mimic mechanical properties of human skin.

    PubMed

    Wang, Zhongkai; Jiang, Feng; Zhang, Yaqiong; You, Yezi; Wang, Zhigang; Guan, Zhibin

    2015-01-27

    Human skin exhibits highly nonlinear elastic properties that are essential to its physiological functions. It is soft at low strain but stiff at high strain, thereby protecting internal organs and tissues from mechanical trauma. However, to date, the development of materials to mimic the unique mechanical properties of human skin is still a great challenge. Here we report a bioinspired design of nanostructured elastomers combining two abundant plant-based biopolymers, stiff cellulose and elastic polyisoprene (natural rubber), to mimic the mechanical properties of human skin. The nanostructured elastomers show highly nonlinear mechanical properties closely mimicking that of human skin. Importantly, the mechanical properties of these nanostructured elastomers can be tuned by adjusting cellulose content, providing the opportunity to synthesize materials that mimic the mechanical properties of different types of skins. Given the simplicity, efficiency, and tunability, this design may provide a promising strategy for creating artificial skin for both general mechanical and biomedical applications.

  14. Coupling mechanisms in inductive discharges with RF substrate bias driven at consecutive harmonics with adjustable relative phase

    NASA Astrophysics Data System (ADS)

    Steinberger, Thomas; Berger, Birk; Schulze, Julian; Schuengel, Edmund; Koepke, Mark

    2016-09-01

    Hybrid combinations of inductive and capacitive RF discharges are commonly used for plasma etching because the inductive coupling ensures a high plasma density, while the capacitive coupling allows the control of the ion bombardment energy at the substrate. We experimentally study the coupling mechanisms between the two driving-voltage sources in such a plasma driven inductively at 13.56 MHz and capacitively at 27.12 MHz in argon and neon at low pressure. We find that the resulting DC self-bias can be controlled via the Electrical Asymmetry Effect by adjusting the relative phase between the two driving harmonics in the E-mode. Langmuir probe measurements and Phase Resolved Optical Emission Spectroscopy (PROES) reveal that the addition of the applied RF-bias in the plasma acts as a catalyst for the transition between E- and H-mode. PROES measurements generally show that the electron power absorption dynamics are affected by the relative phase between the two driving voltage waveforms and by the ratio of the inductive to the capacitive driving powers. Finally, the ion flux-energy distribution function is measured at the RF-powered electrode and found also to be affected by coupling effects.

  15. Mechanics of intraply hybrid composites - Properties, analysis and design

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.; Sinclair, J. H.

    1979-01-01

    A mechanics theory is developed for predicting the physical thermal, hygral and mechanical properties (including various strengths) of unidirectional intraply hybrid composites (UIHC) based on unidirectional properties of the constituent composites. Procedures are described which can use this theory in conjunction with composite mechanics computer codes and general purpose structural analysis finite element programs for the analysis/design of structural components made from intraply hybrid angleplied laminates (IHAL). Comparisons with limited data show that this theory predicts mechanical properties of UIHC and flexural stiffnesses of IHAL which are in good agreement with experimental data. The theory developed herein makes it possible to design and optimize structural components from IHAL based on a large class of available constituent fibers.

  16. Processing, texture and mechanical properties of sintered silicon carbide

    NASA Technical Reports Server (NTRS)

    Landfermann, H.; Hausner, H.

    1988-01-01

    With regard to its favorable properties, in particular those shown at high temperatures, silicon carbide is of great interest for applications related to the construction of engines and turbines. Thus, silicon carbide could replace heat-resisting alloys with the objective to achieve a further increase in operational temperature. The present investigation is concerned with approaches which can provide silicon carbide material with suitable properties for the intended applications, taking into account the relations between characteristics of the raw material, material composition, sinter conditions, and results of the sintering process. The effects of density and texture formation on the mechanical properties are studied. It is found that a dense material with a fine-grained microstructure provides optimal mechanical properties, while any deviation from this ideal condition can lead to a considerable deterioration with respect to the material properties.

  17. Mechanical properties of jennite: A theoretical and experimental study

    SciTech Connect

    Moon, Juhyuk; Yoon, Seyoon; Monteiro, Paulo J.M.

    2015-05-15

    The objective of this study is to determine the mechanical properties of jennite. To date, several hypotheses have been proposed to predict the structural properties of jennite. For the first time as reported herein, the isothermal bulk modulus of jennite was measured experimentally. Synchrotron-based high-pressure x-ray diffraction experiments were performed to observe the variation of lattice parameters under pressure. First-principles calculations were applied to compare with the experimental results and predict additional structural properties. Accurately measured isothermal bulk modulus herein (K{sub 0} = 64(2) GPa) and the statistical assessment on experimental and theoretical results suggest reliable mechanical properties of shear and Young's modulus, Poisson's ratio, and elastic tensor coefficients. Determination of these fundamental structural properties is the first step toward greater understanding of calcium–silicate–hydrate, as well as provides a sound foundation for forthcoming atomic level simulations.

  18. Mechanical properties that influence antimicrobial peptide activity in lipid membranes.

    PubMed

    Marín-Medina, Nathaly; Ramírez, Diego Alejandro; Trier, Steve; Leidy, Chad

    2016-12-01

    Antimicrobial peptides are small amphiphilic proteins found in animals and plants as essential components of the innate immune system and whose function is to control bacterial infectious activity. In order to accomplish their function, antimicrobial peptides use different mechanisms of action which have been deeply studied in view of their potential exploitation to treat antibiotic-resistant bacterial infections. One of the main mechanisms of action of these peptides is the disruption of the bacterial membrane through pore formation, which, in some cases, takes place via a monomer to oligomer cooperative transition. Previous studies have shown that lipid composition, and the presence of exogenous components, such as cholesterol in model membranes or carotenoids in bacteria, can affect the potency of distinct antimicrobial peptides. At the same time, considering the membrane as a two-dimensional material, it has been shown that membrane composition defines its mechanical properties which might be relevant in many membrane-related processes. Nevertheless, the correlation between the mechanical properties of the membrane and antimicrobial peptide potency has not been considered according to the importance it deserves. The relevance of these mechanical properties in membrane deformation due to peptide insertion is reviewed here for different types of pores in order to elucidate if indeed membrane composition affects antimicrobial peptide activity by modulation of the mechanical properties of the membrane. This would also provide a better understanding of the mechanisms used by bacteria to overcome antimicrobial peptide activity.

  19. Improvement of mechanical properties by additive assisted laser sintering of PEEK

    SciTech Connect

    Kroh, M. Bonten, C.; Eyerer, P.

    2014-05-15

    The additive assisted laser sintering was recently developed at IKT: A carbon black (CB) additive is used to adjust the polymer's laser absorption behavior with the aim to improve the interconnection of sintered powder layers. In this paper a parameter study, Polyetheretherketone (PEEK) samples were prepared with different contents of carbon black and were laser sintered with varying thermal treatment. The samples were mechanically tested and investigated by optical light and transmission electron microscopy. An influence on the morphology at the border areas of particles and intersections of laser sintered layers was found. Depending on the viscosity of the raw material and CB content, different shapes of lamellae were observed. These (trans-) crystalline or polymorph structures, respectively, influence the thermal and mechanical behavior of the virgin PEEK. Moreover, the thermal treatment during the sintering process caused an improvement of mechanical properties like tensile strength and elongation at break.

  20. Structural properties for determining mechanisms of toxic action

    SciTech Connect

    Bradbury, S.P.; Lipnick, R.L.

    1989-01-01

    The results of a workshop co-sponsored by EPA through the Health and Environmental Review Division, Office of Toxic Substances and the Environmental Research Laboratory-Duluth, of the Office of Research and Development are briefly summarized as an introduction to a series of manuscripts dealing with the structural properties of chemicals that determine their toxic mechanisms. Results of the workshop are intended to be incorporated in an expert system to predict mechanisms from chemical structure and aid in predictive toxicology applications in the Agency. The goal of the workshop was to review current understanding of fundamental mechanisms, and develop an initial knowledge base on chemical features and properties from which toxic mechanisms could be predicted from structure. Areas addressed included general anesthesia, or narcosis, oxidative phosphorylation uncoupling, electrophile and free-radical reactivity, and a variety of pesticide-based mechanisms.

  1. Metal Additive Manufacturing: A Review of Mechanical Properties

    NASA Astrophysics Data System (ADS)

    Lewandowski, John J.; Seifi, Mohsen

    2016-07-01

    This article reviews published data on the mechanical properties of additively manufactured metallic materials. The additive manufacturing techniques utilized to generate samples covered in this review include powder bed fusion (e.g., EBM, SLM, DMLS) and directed energy deposition (e.g., LENS, EBF3). Although only a limited number of metallic alloy systems are currently available for additive manufacturing (e.g., Ti-6Al-4V, TiAl, stainless steel, Inconel 625/718, and Al-Si-10Mg), the bulk of the published mechanical properties information has been generated on Ti-6Al-4V. However, summary tables for published mechanical properties and/or key figures are included for each of the alloys listed above, grouped by the additive technique used to generate the data. Published values for mechanical properties obtained from hardness, tension/compression, fracture toughness, fatigue crack growth, and high cycle fatigue are included for as-built, heat-treated, and/or HIP conditions, when available. The effects of test orientation/build direction on properties, when available, are also provided, along with discussion of the potential source(s) (e.g., texture, microstructure changes, defects) of anisotropy in properties. Recommendations for additional work are also provided.

  2. Mechanical properties of basement membrane in health and disease.

    PubMed

    Miller, R Tyler

    2017-01-01

    Physical properties are differentiated characteristics of tissues that are essential to their function. For example, the function of bone depends on its rigidity, and the function of skin depends on its elasticity. The aggregate physical properties of tissues are determined by a collaborative relationship between their cells and matrix and are the product of genetic programs, circulating chemical signals, physical signals, and age. The mechanical properties of matrix and basement membranes in biologic systems are difficult to understand in detail because of their complexity and technical limitations of measurements. Matrix may contain fibrillary collagens, network collagens, other fibrillar proteins such as elastin, fibronectin, and laminins, proteoglycans, and can be a reservoir for growth factors. In each tissue and in different regions of the same tissue, matrix composition can vary. The goal of measuring the mechanical properties of matrix is to understand the physical environment experienced by specific cell types to be able to control cell behavior in vivo and for tissue engineering. At this time, such precise analysis is not possible. The general elastic properties of tissues are now better characterized, and model systems using limited numbers of matrix constituents permit improved understanding of the physical behavior of matrix and its effects on cells. This review will describe model systems for understanding problems of matrix elasticity, focus on a relatively new aspect of matrix mechanics, strain-stiffening, and the interactions of cells with matrix to produce overall tissue mechanical properties.

  3. The fracture properties and toughening mechanisms of bone and dentin

    NASA Astrophysics Data System (ADS)

    Koester, Kurt John

    The mechanical properties of bone and dentin and in particular their fracture properties, are the subject of intense research. The relevance of these properties is increasing as our population ages and fracture incidence impacts the lives of a greater portion of the population. A robust framework is needed to understand the fracture properties of bone and dentin to guide researchers as they attempt to characterize the effects of aging, disease, and pharmaceutical treatments on the properties of these mineralized tissues. In the present work, this framework is provided and applied to human bone, human dentin, and animal bone. In situ electron microscopy was also used to identify the salient toughening mechanisms in bone and dentin. It was found that bone and dentin are extrinsically toughened materials and consequently their fracture properties are best characterized utilizing a crack-growth resistance approach. A description of the different mechanical measurements commonly employed when using small animal models (rats and mice) to evaluate the influence of drug therapies on bone fragility is provided. A study where these properties were measured for a large population of wild-type rats and mice was also conducted. Given my findings, it was determined that for the most complete understanding of small animal bone it was necessary to measure strength and toughness. Strength measurements probe the flaw distribution and toughness measurements to evaluate the resistance to facture in the presence of a single dominant worst-case flaw.

  4. Mechanical, Thermal and Dynamic Mechanical Properties of PP/GF/xGnP Nanocomposites

    NASA Astrophysics Data System (ADS)

    Ashenai Ghasemi, F.; Ghorbani, A.; Ghasemi, I.

    2017-03-01

    The mechanical, thermal, and dynamic mechanical properties of ternary nanocomposites based on polypropylene, short glass fibers, and exfoliated graphene nanoplatelets were studied. To investigate the mechanical properties, uniaxial tensile and Charpy impact tests were carried out. To study the crystallinity of the compositions, a DSC test was performed. A dynamic mechanical analysis was used to characterize the storage modulus and loss factor (tan δ). The morphology of the composites was studied by a scanning electron microscope (SEM). The results obtained are presented in tables and graphics.

  5. Microstructural influences on the mechanical properties of solder

    SciTech Connect

    Morris, J.W. Jr.; Goldstein, J.L.F.; Mei, Z.

    1993-04-01

    Intent of this book is to review analytic methods for predicting behavior of solder joints, based on continuum mechanics. The solder is treated as a continuous, homogeneous body, or composite of such bodies, whose mechanical behavior is uniform and governed by simple constitutive equations. The microstructure of a solder joint influences its mechanical properties in 3 ways: it governs deformation and failure; common solders deform inhomogeneously; and common solders are microstructurally unstable. The variety of microstructures often found in solder joints are briefly reviewed, and some of the ways are discussed in which the microstructure influences the common types of high-temperature mechanical behavior. 25 figs, 40 refs.

  6. Bioinspired Reductionistic Peptide Engineering for Exceptional Mechanical Properties.

    PubMed

    Avinash, M B; Raut, Devaraj; Mishra, Manish Kumar; Ramamurty, Upadrasta; Govindaraju, T

    2015-11-03

    A simple solution-processing and self-assembly approach that exploits the synergistic interactions between multiple hydrogen bonded networks and aromatic interactions was utilized to synthesize molecular crystals of cyclic dipeptides (CDPs), whose molecular weights (~0.2 kDa) are nearly three orders of magnitude smaller than that of natural structural proteins (50-300 kDa). Mechanical properties of these materials, measured using the nanoindentation technique, indicate that the stiffness and strength are comparable and sometimes better than those of natural fibres. The measured mechanical responses were rationalized by recourse to the crystallographic structural analysis and intermolecular interactions in the self-assembled single crystals. With this work we highlight the significance of developing small molecule based bioinspired design strategies to emulate biomechanical properties. A particular advantage of the successfully demonstrated reductionistic strategy of the present work is its amenability for realistic industrial scale manufacturing of designer biomaterials with desired mechanical properties.

  7. Bioinspired Reductionistic Peptide Engineering for Exceptional Mechanical Properties

    PubMed Central

    Avinash, M. B.; Raut, Devaraj; Mishra, Manish Kumar; Ramamurty, Upadrasta; Govindaraju, T.

    2015-01-01

    A simple solution-processing and self-assembly approach that exploits the synergistic interactions between multiple hydrogen bonded networks and aromatic interactions was utilized to synthesize molecular crystals of cyclic dipeptides (CDPs), whose molecular weights (~0.2 kDa) are nearly three orders of magnitude smaller than that of natural structural proteins (50–300 kDa). Mechanical properties of these materials, measured using the nanoindentation technique, indicate that the stiffness and strength are comparable and sometimes better than those of natural fibres. The measured mechanical responses were rationalized by recourse to the crystallographic structural analysis and intermolecular interactions in the self-assembled single crystals. With this work we highlight the significance of developing small molecule based bioinspired design strategies to emulate biomechanical properties. A particular advantage of the successfully demonstrated reductionistic strategy of the present work is its amenability for realistic industrial scale manufacturing of designer biomaterials with desired mechanical properties. PMID:26525957

  8. Passive and active mechanical properties of biotemplated ceramics revisited.

    PubMed

    Van Opdenbosch, Daniel; Fritz-Popovski, Gerhard; Plank, Johann; Zollfrank, Cordt; Paris, Oskar

    2016-10-13

    Living nature and human technology apply different principles to create hard, strong and tough materials. In this review, we compare and discuss prominent aspects of these alternative strategies, and demonstrate for selected examples that nanoscale-precision biotemplating is able to produce uncommon mechanical properties as well as actuating behavior, resembling to some extent the properties of the original natural templates. We present and discuss mechanical testing data showing for the first time that nanometer-precision biotemplating can lead to porous ceramic materials with deformation characteristics commonly associated with either biological or highly advanced technical materials. We also review recent findings on the relation between hierarchical structuring and humidity-induced directional motion. Finally, we discuss to which extent the observed behavior is in agreement with previous results and theories on the mechanical properties of multiscale hierarchical materials, as well as studies of highly disperse technical materials, together with an outlook for further lines of investigation.

  9. Bioinspired Reductionistic Peptide Engineering for Exceptional Mechanical Properties

    NASA Astrophysics Data System (ADS)

    Avinash, M. B.; Raut, Devaraj; Mishra, Manish Kumar; Ramamurty, Upadrasta; Govindaraju, T.

    2015-11-01

    A simple solution-processing and self-assembly approach that exploits the synergistic interactions between multiple hydrogen bonded networks and aromatic interactions was utilized to synthesize molecular crystals of cyclic dipeptides (CDPs), whose molecular weights (~0.2 kDa) are nearly three orders of magnitude smaller than that of natural structural proteins (50-300 kDa). Mechanical properties of these materials, measured using the nanoindentation technique, indicate that the stiffness and strength are comparable and sometimes better than those of natural fibres. The measured mechanical responses were rationalized by recourse to the crystallographic structural analysis and intermolecular interactions in the self-assembled single crystals. With this work we highlight the significance of developing small molecule based bioinspired design strategies to emulate biomechanical properties. A particular advantage of the successfully demonstrated reductionistic strategy of the present work is its amenability for realistic industrial scale manufacturing of designer biomaterials with desired mechanical properties.

  10. Build-in Electric Field Induced Mechanical Property Change

    NASA Astrophysics Data System (ADS)

    Chien, Te-Yu; Liu, Jian; Yost, Andrew J.; Chakhalian, Jacques; Freeland, John W.; Guisinger, Nathan P.

    Mechanical properties describe how materials respond to external stress. Microscopically, many intrinsic and extrinsic factors, such as bond length and strength (intrinsic) and grain boundaries (extrinsic), may affect the mechanical property of the materials. In this study, we observed a change of fracturing behavior of Nb-doped SrTiO3 in a Schottky barrier near the interfaces with metallic LaNiO3 films. Through cross-sectional scanning tunneling microscopy and spectroscopy (XSTM/S) experiments and theoretical analysis, the observed fractured topography could be explained by the change of the bond length caused alternation of mechanical property inside the Schottky barrier. Same model could also explain the widely observed dielectric dead layer for SrTiO3 in contact with metal electrodes.

  11. Method of predicting mechanical properties of decayed wood

    DOEpatents

    Kelley, Stephen S.

    2003-07-15

    A method for determining the mechanical properties of decayed wood that has been exposed to wood decay microorganisms, comprising: a) illuminating a surface of decayed wood that has been exposed to wood decay microorganisms with wavelengths from visible and near infrared (VIS-NIR) spectra; b) analyzing the surface of the decayed wood using a spectrometric method, the method generating a first spectral data of wavelengths in VIS-NIR spectra region; and c) using a multivariate analysis to predict mechanical properties of decayed wood by comparing the first spectral data with a calibration model, the calibration model comprising a second spectrometric method of spectral data of wavelengths in VIS-NIR spectra obtained from a reference decay wood, the second spectral data being correlated with a known mechanical property analytical result obtained from the reference decayed wood.

  12. Mechanical properties and fiber type composition of chronically inactive muscles

    NASA Technical Reports Server (NTRS)

    Roy, R. R.; Zhong, H.; Monti, R. J.; Vallance, K. A.; Kim, J. A.; Edgerton, V. R.

    2000-01-01

    A role for neuromuscular activity in the maintenance of skeletal muscle properties has been well established. However, the role of activity-independent factors is more difficult to evaluate. We have used the spinal cord isolation model to study the effects of chronic inactivity on the mechanical properties of the hindlimb musculature in cats and rats. This model maintains the connectivity between the motoneurons and the muscle fibers they innervate, but the muscle unit is electrically "silent". Consequently, the measured muscle properties are activity-independent and thus the advantage of using this model is that it provides a baseline level (zero activity) from which regulatory factors that affect muscle cell homeostasis can be defined. In the present paper, we will present a brief review of our findings using the spinal cord isolation model related to muscle mechanical and fiber type properties.

  13. A review of the literature pertaining to the efficacy, safety, educational requirements, uses and usage of mechanical adjusting devices

    PubMed Central

    Taylor, Shane H; Arnold, Nicole D; Biggs, Lesley; Colloca, Christopher J; Mierau, Dale R; Symons, Bruce P; Triano, John J

    2004-01-01

    Over the past decade, mechanical adjusting devices (MADs) were a major source of debate within the Chiropractors’ Association of Saskatchewan (CAS). Since Saskatchewan was the only jurisdiction in North America to prohibit the use of MADs, the CAS established a committee in 2001 to review the literature on MADs. The committee evaluated the literature on the efficacy, safety, and uses of moving stylus instruments within chiropractic practice, and the educational requirements for chiropractic practice. Following the rating criteria for the evaluation of evidence, as outlined in the Clinical Guidelines for Chiropractic Practice in Canada (1994), the committee reviewed 55 articles – all of which pertained to the Activator. Of the 55 articles, 13 were eliminated from the final study. Of the 42 remaining articles, 6 were rated as class 1 evidence; 11 were rated as class 2 evidence and 25 were rated as class 3 evidence. In this article – the first in a series of two – the background and the methods utilized by the MAD committee’s activities are described, as well as the results for the review of the literature on efficacy. Of the 21 articles related to efficacy, five were identified as Class 1 evidence; 4 were identified as Class 2 evidence; and 12 were identified as Class 3. Overall, the committee reached consensus that the MAD procedures using the Activator were as effective as manual (HVLA) procedures in producing clinical benefit and biological change. A minority report was also written, arguing that there was not enough evidence to support or refute the efficacy of MADs. PMID:17549220

  14. The relationships between deformation mechanisms and mechanical properties of additively manufactured porous biomaterials.

    PubMed

    Kadkhodapour, J; Montazerian, H; Darabi, A Ch; Zargarian, A; Schmauder, S

    2016-09-16

    Modulating deformation mechanism through manipulating morphological parameters of scaffold internal pore architecture provides potential to tailor the overall mechanical properties under physiological loadings. Whereas cells sense local strains, cell differentiation is also impressed by the elastic deformations. In this paper, structure-property relations were developed for Ti6-Al-4V scaffolds designed based on triply periodic minimal surfaces. 10mm cubic scaffolds composed of 5×5×5 unit cells formed of F-RD (bending dominated) and I-WP (stretching dominated) architectures were additively manufactured at different volume fractions and subjected to compressive tests. The first stages of deformation for stretching dominated structure, was accompanied by bilateral layer-by-layer failure of unit cells owing to the buckling of micro-struts, while for bending dominated structure, namely F-RD, global shearing bands appeared since the shearing failure of struts in the internal architecture. Promoted mechanical properties were found for stretching dominated structure since the global orientation of struts were parallel to loading direction while inclination of struts diminished specific properties for bending dominated structure. Moreover, elastic-plastic deformation was computationally studied by applying Johnson-Cook damage model to the voxel-based models in FE analysis. Scaling analysis was performed for mechanical properties with respect to the relative density thereby failure mechanism was correlated to the constants of power law describing mechanical properties.

  15. Controlling Mechanical Properties of Bis-leucine Oxalyl Amide Gels

    NASA Astrophysics Data System (ADS)

    Chang, William; Carvajal, Daniel; Shull, Kenneth

    2011-03-01

    is-leucine oxalyl amide is a low molecular weight gelator capable of gelling polar and organic solvents. A fundamental understanding of self-assembled systems can lead to new methods in drug delivery and the design of new soft material systems. An important feature of self-assembled systems are the intermolecular forces between solvent and gelator molecule; by changing the environment the gel is in, the mechanical properties also change. In this project two variables were considered: the degree of neutralization present for the gelator molecule from neutral to completely ionized, and the concentration of the gelator molecule, from 1 weight percent to 8 weight percent in 1-butanol. Mechanical properties were studied using displacement controlled indentation techniques and temperature sweep rheometry. It has been found that properties such as the storage modulus, gelation temperature and maximum stress allowed increase with bis-leucine oxalyl amide concentration. The results from this study establish a 3-d contour map between the gelator concentration, the gelator degree of ionization and mechanical properties such as storage modulus and maximum stress allowed. The intermolecular forces between the bis-leucine low molecular weight gelator and 1-butanol govern the mechanical properties of the gel system, and understanding these interactions will be key to rationally designed self-assembled systems.

  16. Investigation of mechanical properties of cryogenically treated music wire

    NASA Astrophysics Data System (ADS)

    Heptonstall, A.; Waller, M.; Robertson, N. A.

    2015-08-01

    It has been reported that treating music wire (high carbon steel wire) by cooling to cryogenic temperatures can enhance its mechanical properties with particular reference to those properties important for musical performance. We use such wire for suspending many of the optics in Advanced LIGO, the upgrade to LIGO—the Laser Interferometric Gravitational-Wave Observatory. Two properties that particularly interest us are mechanical loss and breaking strength. A decrease in mechanical loss would directly reduce the thermal noise associated with the suspension, thus enhancing the noise performance of mirror suspensions within the detector. An increase in strength could allow thinner wire to be safely used, which would enhance the dilution factor of the suspension, again leading to lower suspension thermal noise. In this article, we describe the results of an investigation into some of the mechanical properties of music wire, comparing untreated wire with the same wire which has been cryogenically treated. For the samples we studied, we conclude that there is no significant difference in the properties of interest for application in gravitational wave detectors.

  17. Transient dynamic mechanical properties of resilin-based elastomeric hydrogels

    PubMed Central

    Li, Linqing; Kiick, Kristi L.

    2014-01-01

    The outstanding high-frequency properties of emerging resilin-like polypeptides (RLPs) have motivated their development for vocal fold tissue regeneration and other applications. Recombinant RLP hydrogels show efficient gelation, tunable mechanical properties, and display excellent extensibility, but little has been reported about their transient mechanical properties. In this manuscript, we describe the transient mechanical behavior of new RLP hydrogels investigated via both sinusoidal oscillatory shear deformation and uniaxial tensile testing. Oscillatory stress relaxation and creep experiments confirm that RLP-based hydrogels display significantly reduced stress relaxation and improved strain recovery compared to PEG-based control hydrogels. Uniaxial tensile testing confirms the negligible hysteresis, reversible elasticity and superior resilience (up to 98%) of hydrated RLP hydrogels, with Young's modulus values that compare favorably with those previously reported for resilin and that mimic the tensile properties of the vocal fold ligament at low strain (<15%). These studies expand our understanding of the properties of these RLP materials under a variety of conditions, and confirm the unique applicability, for mechanically demanding tissue engineering applications, of a range of RLP hydrogels. PMID:24809044

  18. Mechanical Properties and Fractography of Electroslag Remelted 300M Steel.

    DTIC Science & Technology

    1983-03-01

    the minimum requirements. Charpy impact energy values shown in Table 3 varied from a high of 22 ft-lb for the L-T orientation to 9 ft-lb for the S-L...specimen orientations are shown in Figures la and lb. 3 ’ab 4. MECHANICAL PROPERTIES OF 300M AND 4340 STEELS Impact emp. Orien- i.?% Y.S. U.T.S. Eon...AMMRC TR 83-13 IAD II MECHANICAL PROPERTIES AND FRACTOGRAPHY OF ELECTROSLAG REMELTED 300M STEEL 0 f ALBERT A. ANCTIL METALS RESEARCH DIVISION March

  19. Mechanical properties of carbon fiber composites for applications in space

    NASA Astrophysics Data System (ADS)

    Hana, P.; Inneman, A.; Daniel, V.; Sieger, L.; Petru, M.

    2015-01-01

    This article describes method of measurement mechanical properties of carbon fiber composites in space. New material structures are specifically designed for use on space satellites. Composite structures will be exposed to cosmic radiation in Earth orbit on board of a '2U CubeSat' satellite. Piezoelectric ceramic sensors are used for detection mechanical vibrations of composite test strip. A great deal of attention is paid to signal processing using 8-bit microcontroler. Fast Fourier Transformation is used. Fundamental harmonic frequencies and damping from on-board measurements will serve as the input data for terrestrial data processing. The other step of elaboration data is creation of the physical model for evaluating mechanical properties of Carbon composite - Piezoelectric ceramic system. Evaluation of anisotropic mechanical properties of piezoelectric ceramics is an interesting secondary outcome of the investigation. Extreme changes in temperature and the effect of cosmic rays will affect the mechanical properties and durability of the material used for the external construction of satellites. Comparative terrestrial measurements will be performed.

  20. Characterization of High Temperature Mechanical Properties Using Laser Ultrasound

    SciTech Connect

    David Hurley; Stephen Reese; Farhad Farzbod; Rory Kennedy

    2012-05-01

    Mechanical properties are controlled to a large degree by defect structures such as dislocations and grain boundaries. These microstructural features involve a perturbation of the perfect crystal lattice (i.e. strain fields). Viewed in this context, high frequency strain waves (i.e. ultrasound) provide a natural choice to study microstructure mediated mechanical properties. In this presentation we use laser ultrasound to probe mechanical properties of materials. This approach utilizes lasers to excite and detect ultrasonic waves, and as a consequence has unique advantages over other methods—it is noncontacting, requires no couplant or invasive sample preparation (other than that used in metallurgical analysis), and has the demonstrated capability to probe microstructure on a micron scale. Laser techniques are highly reproducible enabling sophisticated, microstructurally informed data analysis. Since light is being used for generation and detection of the ultrasonic wave, the specimen being examined is not mechanically coupled to the transducer. As a result, laser ultrasound can be carried out remotely, an especially attractive characteristic for in situ measurements in severe environments. Several examples involving laser ultrasound to measure mechanical properties in high temperature environments will be presented. Emphasis will be place on understanding the role of grain microstructure.

  1. Mechanical and Electrical Properties of Cryo-worked Cu

    NASA Astrophysics Data System (ADS)

    Bettinali, Livio; Tosti, Silvano; Pizzuto, Aldo

    2014-01-01

    For manufacturing the magnets of fusion machines pure copper of both high mechanical resistance and electrical conductivity is required. Though high purity copper guarantees high electrical conductivity, its mechanical properties may be not suitable for the applications in tokamaks. In this view, a new procedure developed for obtaining high purity copper with excellent mechanical strength is described in this work. Samples of oxygen free copper (OFC) have been worked by pressing in liquid nitrogen (77 K). It has been verified that the mechanical properties of the worked metal are strongly dependent on the strain rate. Very low strain rates permitted to attain values of tensile yield strength (550 MPa) significantly higher than those obtained by traditional cold-working at room temperature (450 MPa). The electrical conductivity of the cryo-worked Cu decreases with the tensile yield strength even though the hardest samples of tensile yield strength of 550 MPa exhibit still acceptable values of conductivity (about 94 % IACS at room temperature).

  2. Influence of intraocular pressure on geometrical properties of a linear model of the eyeball: Effect of optical self-adjustment

    NASA Astrophysics Data System (ADS)

    Asejczyk-Widlicka, M.; Srodka, D. W.; Kasprzak, H.; Iskander, D. R.

    In general, visual acuity does not change with variations in intraocular pressure. Experiments in vitro as well as our clinical findings lead us to hypothesise that the eyeball could possess certain mechanical properties enabling it to automatically produce a sharp image on the retina despite variations in intraocular pressure. Previously reported simple biomechanical models of the eye did not confirm this hypothesis. Here, we propose a generalised mechanical model of the eyeball in which we include an appropriate limbus ring that mimics the ciliary body and the iris. The Finite Element Method is used to model the eyeball and to test its behaviour. A set of geometrical and material parameters has been determined for the model so that the postulated function of the eye is preserved. Numerical simulations have confirmed the hypothesis. The anatomically justified inclusion of the limbus ring in the proposed model of the eyeball makes it more realistic than those previously reported.

  3. Surface Effects on the Mechanical Properties of Si-nanorods

    NASA Astrophysics Data System (ADS)

    Wu, Shi-Yu; Liu, Shudun; Jayanthi, C. S.; Zhang, Zhenyu

    2000-03-01

    Mechanical properties of Si-nanorods of various sizes are studied using an order(N) non-orthogonal tight-binding molecular dynamics [1]. As the size of the nanorod decreases, we find an evolution in the surface reconstruction pattern and change in the structural and elastic properties. In particular, we examine how the surface effects modify and eventually lead to the break down of the scaling behavior of the elastic properties of Si-nanorods. [1] C.S. Jayanthi, S.Y. Wu, J. Cocks, N.S. Luo, Z.L. Xie, M. Menon and G. Yang, Phys. Rev. B57, 3799(1998).

  4. Mechanical And Thermal Properties Of Optical Materials - A Review

    NASA Astrophysics Data System (ADS)

    Ballard, Stanley S.

    1980-02-01

    In selecting an optical material, the instrument designer's first consideration is optical properties, especially transmission region but also homogeneity, freedom from birefringence, perhaps refractive index and dispersion. Next in his hierarchy are the other physical properties: mechanical, thermal, and chemical (solubility, for example). In this review article, the several properties are listed, and data sources are given. No single compilation or handbook contains all the desired data, so many references are quoted. This review covers materials useful in the ultraviolet and esuecially the infrared spectral regions; it does not include the standard glasses used in the visible region.

  5. Modified Gellan Gum hydrogels with tunable physical and mechanical properties

    PubMed Central

    Coutinho, Daniela F.; Sant, Shilpa; Shin, Hyeongho; Oliveira, João T.; Gomes, Manuela E.; Neves, Nuno M.; Khademhosseini, Ali; Reis, Rui L.

    2010-01-01

    Gellan Gum (GG) has been recently proposed for tissue engineering applications. GG hydrogels are produced by physical crosslinking methods induced by temperature variation or by the presence of divalent cations. However, physical crosslinking methods may yield hydrogels that become weaker in physiological conditions due to the exchange of divalent cations by monovalent ones. Hence, this work presents a new class of GG hydrogels crosslinkable by both physical and chemical mechanisms. Methacrylate groups were incorporated in the GG chain, leading to the production of a methacrylated gellan gum (MeGG) hydrogel with highly tunable physical and mechanical properties. The chemical modification was confirmed by proton nuclear magnetic resonance (1H-NMR) and Fourier transform infrared spectroscopy (FTIR-ATR). The mechanical properties of the developed hydrogel networks, with Young’s modulus values between 0.15 and 148 kPa, showed to be tuned by the different crosslinking mechanisms used. The in vitro swelling kinetics and hydrolytic degradation rate was dependent on the crosslinking mechanisms used to form the hydrogels. Three-dimensional (3D) encapsulation of NIH-3T3 fibroblast cells in MeGG networks demonstrated in vitro biocompatibility confirmed by high cell survival. Given the highly tunable mechanical and degradation properties of MeGG, it may be applicable for a wide range of tissue engineering approaches. PMID:20663552

  6. Characterization of mechanical and biochemical properties of developing embryonic tendon

    PubMed Central

    Marturano, Joseph E.; Arena, Jeffrey D.; Schiller, Zachary A.; Georgakoudi, Irene; Kuo, Catherine K.

    2013-01-01

    Tendons have uniquely high tensile strength, critical to their function to transfer force from muscle to bone. When injured, their innate healing response results in aberrant matrix organization and functional properties. Efforts to regenerate tendon are challenged by limited understanding of its normal development. Consequently, there are few known markers to assess tendon formation and parameters to design tissue engineering scaffolds. We profiled mechanical and biological properties of embryonic tendon and demonstrated functional properties of developing tendon are not wholly reflected by protein expression and tissue morphology. Using force volume-atomic force microscopy, we found that nano- and microscale tendon elastic moduli increase nonlinearly and become increasingly spatially heterogeneous during embryonic development. When we analyzed potential biochemical contributors to modulus, we found statistically significant but weak correlation between elastic modulus and collagen content, and no correlation with DNA or glycosaminoglycan content, indicating there are additional contributors to mechanical properties. To investigate collagen cross-linking as a potential contributor, we inhibited lysyl oxidase-mediated collagen cross-linking, which significantly reduced tendon elastic modulus without affecting collagen morphology or DNA, glycosaminoglycan, and collagen content. This suggests that lysyl oxidase-mediated cross-linking plays a significant role in the development of embryonic tendon functional properties and demonstrates that changes in cross-links alter mechanical properties without affecting matrix content and organization. Taken together, these data demonstrate the importance of functional markers to assess tendon development and provide a profile of tenogenic mechanical properties that may be implemented in tissue engineering scaffold design to mechanoregulate new tendon regeneration. PMID:23576745

  7. 26 CFR 1.754-1 - Time and manner of making election to adjust basis of partnership property.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 26 Internal Revenue 8 2010-04-01 2010-04-01 false Time and manner of making election to adjust..., Subchapter K, Chapter 1 of the Code § 1.754-1 Time and manner of making election to adjust basis of... sections 734(b) and 743(b) if it files an election in accordance with the rules set forth in paragraph...

  8. Relationship of the optical absorption and scattering properties with mechanical and structural properties of apple tissue

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Optical absorption and scattering properties of fruit change with the physiological and biochemical activities in the tissue during ripening and postharvest storage. But it has not been well understood on how these changes are related to the structural and mechanical properties of fruit. This resear...

  9. Mechanical properties of tricalcium phosphate-alumina composites

    NASA Astrophysics Data System (ADS)

    Sakka, S.; Ben Ayed, F.; Bouaziz, J.

    2012-02-01

    Tricalcium phosphate and alumina powder were mixed in order to elaborate biphasic ceramics composites. This study deals to produce bioceramics composites sintered at various temperatures for differents times. The characterization of samples, before and after the sintering process was investigated, using X-Ray diffraction, scanning electronic microscopy, 31P and 27Al nuclear magnetic resonance and differential thermal analysis. Mechanical properties of biphasic composites were studied using Brazilian test. The tricalcium phosphate - 75 wt% alumina composites mechanical resistance increased with sintered temperature. The mechanical resistance reach it's optimum value (8.6 MPa) at 1550°C for two hours.

  10. Interspecific comparison of the mechanical properties of mussel byssus.

    PubMed

    Brazee, Shanna L; Carrington, Emily

    2006-12-01

    Byssally tethered mussels are found in a variety of habitats, including rocky intertidal, salt marsh, subtidal, and hydrothermal vents. One key to the survival of mussels in these communities is a secure attachment, achieved by the production of byssal threads. Although many studies have detailed the unique biomechanical properties of byssal threads, only a few prevalent species have been examined. This study assesses the variation in the mechanical properties of byssus in a broad range of mussel species from diverse environments, including intertidal and subtidal Mytilus edulis, Modiolus modiolus, Geukensia demissa, Bathymodiolus thermophilus, and Dreissena polymorpha. A tensometer was used to measure quasi-static and dynamic mechanical properties of individual threads, and several aspects of morphology were quantified. The results indicate that thread mechanical properties vary among mussel species, and several novel properties were observed. For example, of the species examined, D. polymorpha threads were the strongest, stiffest, least resilient, and fastest to recover after partial deformation. Threads of M. modiolus were characterized by the presence of two distinct yield regions prior to tensile failure. This comparative study not only provides insight into the ecological limitations and evolution of mussels, but also suggests new models for the design of novel biomimetic polymers.

  11. Physical and mechanical properties of the lunar soil (a review)

    NASA Astrophysics Data System (ADS)

    Slyuta, E. N.

    2014-09-01

    We review the data on the physical and mechanical properties of the lunar soil that were acquired in the direct investigations on the lunar surface carried out in the manned and automatic missions and in the laboratory examination of the lunar samples returned to the Earth. In justice to the American manned program Apollo, we show that a large volume of the data on the properties of the lunar soil was also obtained in the Soviet automatic program Lunokhod and with the automatic space stations Luna-16, -20, and -24 that returned the lunar soil samples to the Earth. We consider all of the main physical and mechanical properties of the lunar soil, such as the granulometric composition, density and porosity, cohesion and adhesion, angle of internal friction, shear strength of loose soil, deformation characteristics (the deformation modulus and Poisson ratio), compressibility, and the bearing capacity, and show the change of some properties versus the depth. In most cases, the analytical dependence of the main parameters is presented, which is required in developing reliable engineering models of the lunar soil. The main physical and mechanical properties are listed in the summarizing table, and the currently available models and simulants of the lunar soil are reviewed.

  12. Nonmetallic impurities improve mechanical properties of vapor-deposited tungsten

    NASA Technical Reports Server (NTRS)

    Chin, J.; Weinberg, A. F.; Lindgren, J. R.

    1972-01-01

    Mechanical properties of vapor deposited tungsten are improved by selective incorporation of various nonmetallic impurities. Addition of trace quantities of carbon, nitrogen, or oxygen can significantly increase both low and high temperature yield strength without greatly affecting ductile-to-brittle transition temperature.

  13. Variations in the mechanical properties of Alouatta palliata molar enamel.

    PubMed

    Darnell, Laura A; Teaford, Mark F; Livi, Kenneth J T; Weihs, Timothy P

    2010-01-01

    Teeth have provided insights into many topics including primate diet, paleobiology, and evolution, due to the fact that they are largely composed of inorganic materials and may remain intact long after an animal is deceased. Previous studies have reported that the mechanical properties, chemistry, and microstructure of human enamel vary with location. This study uses nanoindentation to map out the mechanical properties of Alouatta palliata molar enamel on an axial cross-section of an unworn permanent third molar, a worn permanent first molar, and a worn deciduous first molar. Variations were then correlated with changes in microstructure and chemistry using scanning electron microscopy and electron microprobe techniques. The hardness and Young's modulus varied with location throughout the cross-sections from the occlusal surface to the dentin-enamel junction (DEJ), from the buccal to lingual sides, and also from one tooth to another. These changes in mechanical properties correlated with changes in the organic content of the tooth, which was shown to increase from approximately 6% near the occlusal surface to approximately 20% just before the DEJ. Compared to human enamel, the Alouatta enamel showed similar microstructures, chemical constituents, and magnitudes of mechanical properties, but showed less variation in hardness and Young's modulus, despite the very different diet of this species.

  14. Sterilizing elastomeric chains without losing mechanical properties. Is it possible?

    PubMed Central

    Pithon, Matheus Melo; Ferraz, Caio Souza; Rosa, Francine Cristina Silva; Rosa, Luciano Pereira

    2015-01-01

    OBJECTIVE: To investigate the effects of different sterilization/disinfection methods on the mechanical properties of orthodontic elastomeric chains. METHODS: Segments of elastomeric chains with 5 links each were sent for sterilization by cobalt 60 (Co60) (20 KGy) gamma ray technology. After the procedure, the elastomeric chains were contaminated with clinical samples of Streptococcus mutans. Subsequently, the elastomeric chains were submitted to sterilization/disinfection tests carried out by means of different methods, forming six study groups, as follows: Group 1 (control - without contamination), Group 2 (70°GL alcohol), Group 3 (autoclave), Group 4 (ultraviolet), Group 5 (peracetic acid) and Group 6 (glutaraldehyde). After sterilization/disinfection, the effectiveness of these methods, by Colony forming units per mL (CFU/mL), and the mechanical properties of the material were assessed. Student's t-test was used to assess the number of CFUs while ANOVA and Tukey's test were used to assess elastic strength. RESULTS: Ultraviolet treatment was not completely effective for sterilization. No loss of mechanical properties occurred with the use of the different sterilization methods (p > 0.05). CONCLUSION: Biological control of elastomeric chains does not affect their mechanical properties. PMID:26154462

  15. A biodegradable polymer nanocomposite: Mechanical and barrier properties

    NASA Astrophysics Data System (ADS)

    Lilichenko, N.; Maksimov, R. D.; Zicans, J.; Merijs Meri, R.; Plume, E.

    2008-01-01

    The preparation of an environmentally friendly nanocomposite based on plasticized potato starch and unmodified montmorillonite clay is described. Data on the influence of montmorillonite concentration on the mechanical properties of the materials obtained are reported. The effective elastic constants of the nanocomposites are calculated. The calculation results are compared with experimental data. The influence of montmorillonite content on the moisture permeability is also investigated.

  16. Barrier and Mechanical Properties of Starch-Clay Nanocomposite Films

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The poor barrier and mechanical properties of biopolymer-based food packaging can potentially be enhanced by the use of layered silicates (nanoclay) to produce nanocomposites. In this study, starch-clay nano-composites were synthesized by a melt extrusion method. Natural (MMT) and organically modifi...

  17. Mechanical shear and tensile properties of selected biomass stems

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Lignocellulosic biomass, such as big bluestem, corn stalk, intermediate wheat grass and switchgrass stem are abundant and dominant species in the Midwest region of US. There is a need to understand the mechanical properties for these crops for better handling and processing of the biomass feedstocks...

  18. Thermal treatment and mechanical properties of aluminum-2021

    NASA Technical Reports Server (NTRS)

    Brennecke, M. W.

    1970-01-01

    Mechanical properties, after thermal treatments, are summarized for sheet and plate of copper-rich, high-strength, heat-treatable aluminum-2021. The alloy is quench sensitive, quench rate and variations in aging affect corrosion behavior. Aging effects on yield strength, tensile strength, and elongation of sheet and plate are compared.

  19. Mechanical and physical properties of modern boron fibers

    NASA Technical Reports Server (NTRS)

    Dicarlo, J. A.

    1978-01-01

    The results of accurate measurements of the modern boron fiber's Young's modulus, flexural modulus, shear modulus, and Poisson's ratio are reported. Physical property data concerning fiber density, thermal expansion, and resistance obtained during the course of the mechanical studies are also given.

  20. Processing dependence of mechanical properties of metallic glass nanowires

    SciTech Connect

    Zhang, Qi; Li, Mo; Li, Qi-Kai

    2015-02-16

    Compared to their crystalline counterparts, nanowires made of metallic glass have not only superb properties but also remarkable processing ability. They can be processed easily and cheaply like plastics via a wide range of methods. To date, the underlying mechanisms of how these different processing routes affect the wires' properties as well as the atomic structure remains largely unknown. Here, by using atomistic modeling, we show that different processing methods can greatly influence the mechanical properties. The nanowires made via focused ion beam milling and embossing exhibit higher strength but localized plastic deformation, whereas that made by casting from liquid shows excellent ductility with homogeneous deformation but reduced strength. The different responses are reflected sensitively in the underlying atomic structure and packing density, some of which have been observed experimentally. The presence of the gradient of alloy concentration and surface effect will be discussed.

  1. A review of mechanical and electromechanical properties of piezoelectric nanowires.

    PubMed

    Espinosa, Horacio D; Bernal, Rodrigo A; Minary-Jolandan, Majid

    2012-09-04

    Piezoelectric nanowires are promising building blocks in nanoelectronic, sensing, actuation and nanogenerator systems. In spite of great progress in synthesis methods, quantitative mechanical and electromechanical characterization of these nanostructures is still limited. In this article, the state-of-the art in experimental and computational studies of mechanical and electromechanical properties of piezoelectric nanowires is reviewed with an emphasis on size effects. The review covers existing characterization and analysis methods and summarizes data reported in the literature. It also provides an assessment of research needs and opportunities. Throughout the discussion, the importance of coupling experimental and computational studies is highlighted. This is crucial for obtaining unambiguous size effects of nanowire properties, which truly reflect the effect of scaling rather than a particular synthesis route. We show that such a combined approach is critical to establish synthesis-structure-property relations that will pave the way for optimal usage of piezoelectric nanowires.

  2. 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).

  3. Mechanical property determination of high conductivity metals and alloys

    NASA Technical Reports Server (NTRS)

    Harrod, D. L.; Vandergrift, E.; France, L.

    1973-01-01

    Pertinent mechanical properties of three high conductivity metals and alloys; namely, vacuum hot pressed grade S-200E beryllium, OFHC copper and beryllium-copper alloy no. 10 were determined. These materials were selected based on their possible use in rocket thrust chamber and nozzle hardware. They were procured in a form and condition similar to that which might be ordered for actual hardware fabrication. The mechanical properties measured include (1) tension and compression stress strain curves at constant strain rate (2) tensile and compressive creep, (3) tensile and compressive stress-relaxation behavior and (4) elastic properties. Tests were conducted over the temperature range of from 75 F to 1600 F. The resulting data is presented in both graphical and tabular form.

  4. Influence of mechanical activation of steel powder on its properties

    NASA Astrophysics Data System (ADS)

    Vaulina, O. Yu; Darenskaia, E. A.; Myachin, Y. V.; Vasilyeva, I. E.; Kulkov, S. N.

    2017-02-01

    It has been studied properties of stainless steel based powders after mechanical activation using planetary ball milling technique. It have been shown that after one minute mechanical activation porosity of sintered steel is less than 5%, which is less than the porosity of the sintered steel powder without mechanical activation. The sample without activation has austenite state, which changes after activation toaustenite and ferrite mixtures. X-ray analysis confirmed that the mechanical activation leads to a change in the phase state of the samples: the samples without activation of the FCC structure (γ-Fe), after activation - FCC (γ-Fe) and BCC (α-Fe). The hardness increases at increasing activation time from 800 MPa for the sample without mechanical activation to 1250 MPa for the sample with the activation time of 10 minutes.

  5. Brillouin microspectroscopy of nanostructured biomaterials: photonics assisted tailoring mechanical properties

    NASA Astrophysics Data System (ADS)

    Meng, Zhaokai; Jaiswal, Manish K.; Chitrakar, Chandani; Thakur, Teena; Gaharwar, Akhilesh K.; Yakovlev, Vladislav V.

    2016-03-01

    Developing new biomaterials is essential for the next-generation of materials for bioenergy, bioelectronics, basic biology, medical diagnostics, cancer research, and regenerative medicine. Specifically, recent progress in nanotechnology has stimulated the development of multifunctional biomaterials for tissue engineering applications. The physical properties of nanocomposite biomaterials, including elasticity and viscosity, play key roles in controlling cell fate, which underlines therapeutic success. Conventional mechanical tests, including uniaxial compression and tension, dynamic mechanical analysis and shear rheology, require mechanical forces to be directly exerted onto the sample and therefore may not be suitable for in situ measurements or continuous monitoring of mechanical stiffness. In this study, we employ spontaneous Brillouin spectroscopy as a viscoelasticity-specific probing technique. We utilized a Brillouin spectrometer to characterize biomaterial's microscopic elasticity and correlated those with conventional mechanical tests (e.g., rheology).

  6. Do Non-Collagenous Proteins Affect Skeletal Mechanical Properties?

    PubMed Central

    Morgan, Stacyann; Poundarik, Atharva A.; Vashishth, Deepak

    2015-01-01

    The remarkable mechanical behavior of bone is attributed to its complex nanocomposite structure that, in addition to mineral and collagen, comprises a variety of non-collagenous matrix proteins or NCPs. Traditionally, NCPs have been studied as signaling molecules in biological processes including bone formation, resorption and turnover. Limited attention has been given to their role in determining the mechanical properties of bone. Recent studies have highlighted that NCPs can indeed be lost or modified with aging, diseases and drug therapies. Homozygous and heterozygous mice models of key NCP provide a useful approach to determine the impact of NCPs on bone morphology as well as matrix quality, and to carry out detailed mechanical analysis for elucidating the pathway by which NCPs can affect the mechanical properties of bone. In this article, we present a systematic analysis of a large cohort of NCPs on bone’s structural and material hierarchy, and identify three principal pathways by which they determine bone’s mechanical properties. These pathways include alterations of bone morphological parameters crucial for bone’s structural competency, bone quality changes in key matrix parameters (mineral and collagen), and a direct role as load bearing structural proteins. PMID:26048282

  7. Porcine bladder acellular matrix (ACM): protein expression, mechanical properties.

    PubMed

    Farhat, Walid A; Chen, Jun; Haig, Jennifer; Antoon, Roula; Litman, Jessica; Sherman, Christopher; Derwin, Kathleen; Yeger, Herman

    2008-06-01

    Experimentally, porcine bladder acellular matrix (ACM) that mimics extracellular matrix has excellent potential as a bladder substitute. Herein we investigated the spatial localization and expression of different key cellular and extracellular proteins in the ACM; furthermore, we evaluated the inherent mechanical properties of the resultant ACM prior to implantation. Using a proprietary decellularization method, the DNA contents in both ACM and normal bladder were measured; in addition we used immunohistochemistry and western blots to quantify and localize the different cellular and extracellular components, and finally the mechanical testing was performed using a uniaxial mechanical testing machine. The mean DNA content in the ACM was significantly lower in the ACM compared to the bladder. Furthermore, the immunohistochemical and western blot analyses showed that collagen I and IV were preserved in the ACM, but possibly denatured collagen III in the ACM. Furthermore, elastin, laminin and fibronectin were mildly reduced in the ACM. Although the ACM did not exhibit nucleated cells, residual cellular components (actin, myosin, vimentin and others) were still present. There was, on the other hand, no significant difference in the mean stiffness between the ACM and the bladder. Although our decellularization method is effective in removing nuclear material from the bladder while maintaining its inherent mechanical properties, further work is mandatory to determine whether these residual DNA and cellular remnants would lead to any immune reaction, or if the mechanical properties of the ACM are preserved upon implantation and cellularization.

  8. Mechanical Properties of Non-Accreting Neutron Star Crusts

    NASA Astrophysics Data System (ADS)

    Hoffman, Kelsey L.; Heyl, J. S.

    2013-01-01

    The mechanical properties of a neutron star crust, such as breaking strain and shear modulus, have implications for the detection of gravitational waves from a neutron star as well as bursts from Soft Gamma-ray Repeaters (SGRs). These properties are calculated here for three different crustal compositions for a non-accreting neutron star that results from three different cooling histories, as well as for a pure iron crust. A simple shear is simulated using molecular dynamics to the crustal compositions by deforming the simulation box. The breaking strain and shear modulus are found to be similar in the four cases, with a breaking strain of ˜0.1 and a shear modulus of ˜1030 dyne cm-2 at a density of ρ = 1014g cm-3 for simulations with an initially perfect BCC lattice. With these crustal properties and the observed properties of PSR J2124-3358 the predicted strain amplitude of gravitational waves for a maximally deformed crust is found to be greater than the observational upper limits from LIGO. This suggests that the neutron star crust in this case may not be maximally deformed or it may not have a perfect BCC lattice structure. The implications of the calculated crustal properties of bursts from SGRs are also explored. The mechanical properties found for a perfect BCC lattice structure find that crustal events alone can not be ruled out for triggering the energy in SGR bursts.

  9. Mechanical properties of non-accreting neutron star crusts

    NASA Astrophysics Data System (ADS)

    Hoffman, Kelsey; Heyl, Jeremy

    2012-11-01

    The mechanical properties of a neutron star crust, such as breaking strain and shear modulus, have implications for the detection of gravitational waves from a neutron star as well as bursts from soft Gamma-ray repeaters (SGRs). These properties are calculated here for three different crustal compositions for a non-accreting neutron star that results from three different cooling histories, as well as for a pure iron crust. A simple shear is simulated using molecular dynamics to the crustal compositions by deforming the simulation box. The breaking strain and shear modulus are found to be similar in the four cases, with a breaking strain of ˜0.1 and a shear modulus of ˜1030 dyne cm-2 at a density of ρ = 1014 g cm-3 for simulations with an initially perfect body-centred cubic (BCC) lattice. With these crustal properties and the observed properties of PSR J2124-3358, the predicted strain amplitude of gravitational waves for a maximally deformed crust is found to be greater than the observational upper limits from LIGO. This suggests that the neutron star crust in this case may not be maximally deformed or it may not have a perfect BCC lattice structure. The implications of the calculated crustal properties of bursts from SGRs are also explored. The mechanical properties found for a perfect BCC lattice structure find that crustal events alone cannot be ruled out for triggering the energy in SGR bursts.

  10. Hydrothermal-hydrolysis synthesis and photocatalytic properties of nano-TiO2 with an adjustable crystalline structure.

    PubMed

    Zhang, Jinghuan; Xiao, Xin; Nan, Junmin

    2010-04-15

    Tri-phase (anatase, rutile, and brookite), bi-phase (anatase and rutile), and mono-phase (rutile) TiO(2) nanomaterials with different morphologies were successively synthesized using a hydrothermal-hydrolysis method and adjusting the Ti(4+)/Ti(3+) molar ratio in a precursor solution. The properties of the fabricated nanomaterials were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), photocatalytic reaction, and other techniques. It has been shown that TiO(2) nanorods can be obtained by increasing the Ti(4+)/Ti(3+) molar ratio in a precursor solution from 1:0 to 0.3:0.7. TiO(2) nanoparticles are formed if the Ti(3+) fraction in the solution is further increased. The selective synthesis of TiO(2) nanomaterials is explained by a decrease in the reaction rate and by changes in acidity with increasing Ti(3+) content. The tri-phase nanorods and bi-phase nanoparticles synthesized with Ti(4+)/Ti(3+) molar ratios from 1:0 to 0.8:0.2 and 0.2:0.8 to 0:1, respectively, have a higher degradation ability with respect to methylene blue aqueous solutions under UV irradiation at ambient temperature compared to purely rutile TiO(2) nanorods synthesized with Ti(4+)/Ti(3+) molar ratios from 0.7:0.3 to 0.3:0.7. The high photocatalytic activity of the multi-phase TiO(2) samples is primarily attributed to their larger band gap and suppressed recombination of photo-generated electron-hole pairs.

  11. Optical and mechanical properties of single-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Marcus, Matthew S.

    The experiments presented in this thesis provide insight into the optical and mechanical properties of carbon nanotubes. In the process of studying the properties of carbon nanotube structures we also discovered some interesting features of intermittent contact atomic force microscopy. Phase data from non-contact AFM reveals in-plane material properties . In the process of characterizing carbon nanotubes with an intermittent contact AFM (ICAFM), we discovered something quite interesting: ICAFM is sensitive to in-plane properties. We found that phase contrast in ICAFM reveals in-plane mechanical properties of the poly-di-acetylene films. Our measurements are possible because, during ICAFM, the cantilever tip oscillates not just perpendicular but also parallel to the sample surface along the long axis of the cantilever. Understanding photo-induced conductivity changes in carbon nanotubes . The basic process for using a nanotube as a photo-detector involves using light to change the conductivity of the nanotube, typically measured as a change in current. We review the different mechanisms for how light changes the conductivity of a nanotube, and then focus on a photo-gating mechanism. In a photo-gating mechanism, light interacts with the nanotube's environment changing the conductivity of the nanotube. Thermally driven oscillations play a significant role in chemical vapor deposition growth. The elevated temperatures during the CVD growth thermally drive nanotube oscillations with amplitudes on the order of 80nm. Nanotubes suspended a small distance above the substrate will often oscillate with an amplitude as large as the suspension height and interact with the substrate. The large binding energy between the nanotube and the substrate causes the nanotube to become stuck: the nanotube is no longer suspended. Using data from CVD growths on our suspended structures we are able to extract a Young's modulus value for our nanotubes which both validates the thermally driven

  12. Ultrasonic evaluation of the physical and mechanical properties of granites.

    PubMed

    Vasconcelos, G; Lourenço, P B; Alves, C A S; Pamplona, J

    2008-09-01

    Masonry is the oldest building material that survived until today, being used all over the world and being present in the most impressive historical structures as an evidence of spirit of enterprise of ancient cultures. Conservation, rehabilitation and strengthening of the built heritage and protection of human lives are clear demands of modern societies. In this process, the use of nondestructive methods has become much common in the diagnosis of structural integrity of masonry elements. With respect to the evaluation of the stone condition, the ultrasonic pulse velocity is a simple and economical tool. Thus, the central issue of the present paper concerns the evaluation of the suitability of the ultrasonic pulse velocity method for describing the mechanical and physical properties of granites (range size between 0.1-4.0 mm and 0.3-16.5 mm) and for the assessment of its weathering state. The mechanical properties encompass the compressive and tensile strength and modulus of elasticity, and the physical properties include the density and porosity. For this purpose, measurements of the longitudinal ultrasonic pulse velocity with distinct natural frequency of the transducers were carried out on specimens with different size and shape. A discussion of the factors that induce variations on the ultrasonic velocity is also provided. Additionally, statistical correlations between ultrasonic pulse velocity and mechanical and physical properties of granites are presented and discussed. The major output of the work is the confirmation that ultrasonic pulse velocity can be effectively used as a simple and economical nondestructive method for a preliminary prediction of mechanical and physical properties, as well as a tool for the assessment of the weathering changes of granites that occur during the serviceable life. This is of much interest due to the usual difficulties in removing specimens for mechanical characterization.

  13. Sintering time and atmosphere influences on the microstructure and mechanical properties of tungsten heavy alloys

    NASA Technical Reports Server (NTRS)

    German, R. M.; Bose, A.; Mani, S. S.

    1992-01-01

    The present paper traces the microstructure and mechanical property variations vs sintering time under conditions where the atmosphere was adjusted to suppress pore generation. Attention is given to tracing the mechanical property links to the grain size under optimized sintering conditions. The optimal cycle is used to sinter two heavy alloy compositions (88 and 95 wt pct W) for times up to 600 minutes at 1480 C. The 88-pct-W samples slumped, but the 95-pct-W samples were fully densified and suitable for tensile testing. At long sintering times, the tungsten grains flattened and the tungsten contiguity decreased, indicating a transition to low-energy configurations for the solid-liquid interfaces. The cube of the mean grain size varied linearly with the isothermal sintering time. This allowed the determination of grain size effects on mechanical properties, showing a decreasing yield strength with increasing time in agreement with the Hall-Petch behavior. The tensile strength and elongation were highest for sintering times from 30 to 90 min, reflecting a minimum in the residual porosity.

  14. An Introduction to the Mechanical Properties of Ceramics

    NASA Astrophysics Data System (ADS)

    Green, David J.

    1998-09-01

    Over the past twenty-five years ceramics have become key materials in the development of many new technologies as scientists have been able to design these materials with new structures and properties. An understanding of the factors that influence their mechanical behavior and reliability is essential. This book will introduce the reader to current concepts in the field. It contains problems and exercises to help readers develop their skills. This is a comprehensive introduction to the mechanical properties of ceramics, and is designed primarily as a textbook for advanced undergraduates in materials science and engineering. It will also be of value as a supplementary text for more general courses and to industrial scientists and engineers involved in the development of ceramic-based products, materials selection and mechanical design.

  15. Chirality-Mediated Mechanical and Structural Properties of Oligopeptide Hydrogels

    SciTech Connect

    Taraban, Marc B.; Feng, Yue; Hammouda, Boualem; Hyland, Laura L.; Yu, Y. Bruce

    2012-10-29

    The origin and the effects of homochirality in the biological world continuously stimulate numerous hypotheses and much debate. This work attempts to look at the biohomochirality issue from a different angle - the mechanical properties of the bulk biomaterial and their relation to nanoscale structures. Using a pair of oppositely charged peptides that co-assemble into hydrogels, we systematically investigated the effect of chirality on the mechanical properties of these hydrogels through different combinations of syndiotactic and isotactic peptides. It was found that homochirality confers mechanical advantage, resulting in a higher elastic modulus and strain yield value. Yet, heterochirality confers kinetic advantage, resulting in faster gelation. Structurally, both homochiral and heterochiral hydrogels are made of fibers interconnected by lappet-like webs, but the homochiral peptide fibers are thicker and denser. These results highlight the possible role of biohomochirality in the evolution and/or natural selection of biomaterials.

  16. Mechanical Properties of Nanotextured Titanium Orthopedic Screws for Clinical Applications.

    PubMed

    Descamps, Stephane; Awitor, Komla O; Raspal, Vincent; Johnson, Matthew B; Bokalawela, Roshan S P; Larson, Preston R; Doiron, Curtis F

    2013-06-01

    In this work, we modified the topography of commercial titanium orthopedic screws using electrochemical anodization in a 0.4 wt% hydrofluoric acid solution to produce titanium dioxide nanotube layers. The morphology of the nanotube layers were characterized using scanning electron microscopy. The mechanical properties of the nanotube layers were investigated by screwing and unscrewing an anodized screw into several different types of human bone while the torsional force applied to the screwdriver was measured using a torque screwdriver. The range of torsional force applied to the screwdriver was between 5 and [Formula: see text]. Independent assessment of the mechanical properties of the same surfaces was performed on simple anodized titanium foils using a triboindenter. Results showed that the fabricated nanotube layers can resist mechanical stresses close to those found in clinical situations.

  17. Nano-palpation AFM and its quantitative mechanical property mapping.

    PubMed

    Nakajima, Ken; Ito, Makiko; Wang, Dong; Liu, Hao; Nguyen, Hung Kim; Liang, Xiaobin; Kumagai, Akemi; Fujinami, So

    2014-06-01

    We review nano-palpation atomic force microscopy, which offers quantitative mechanical property mapping especially for soft materials. The method measures force-deformation curves on the surfaces of soft materials. The emphasis is placed on how both Hertzian and Derjaguin-Muller-Toporov contact mechanics fail to reproduce the experimental curves and, alternatively, how the Johnson-Kendall-Roberts model does. We also describe the force-volume technique for obtaining a two-dimensional map of mechanical properties, such as the elastic modulus and adhesive energy, based on the above-mentioned analysis. Finally, we conclude with several counterpart measurements, which describe the viscoelastic nature of soft materials, and give examples, including vulcanized isoprene rubber and the current status of ISO standardization.

  18. Mechanical Properties of Iron Alumininides Intermetallic Alloy with Molybdenum Addition

    SciTech Connect

    Zuhailawati, H.; Fauzi, M. N. A.

    2010-03-11

    In this work, FeAl-based alloys with and without molybdenum addition were fabricated by sintering of mechanically alloyed powders in order to investigate the effect of molybdenum on iron aluminide mechanical properties. Bulk samples were prepared by mechanical alloying for 4 hours, pressing at 360 MPa and sintering at 1000 deg. C for 2 hours. The specimens were tested in compression at room temperature using Instron machine. The phase identification and microstructure of the consolidated material was examined by x-ray diffraction and scanning electron microscope correspondingly. Results show that 2.5 wt%Mo addition significantly increased the ultimate stress and ultimate strain in compressive mode due to solid solution hardening. However, the addition of Mo more than 2.5 wt% was accompanied by a reduction in both properties caused by the presence of Mo-rich precipitate particles.

  19. Mechanical Properties of Materials with Nanometer Scale Microstructures

    SciTech Connect

    William D. Nix

    2004-10-31

    We have been engaged in research on the mechanical properties of materials with nanometer-scale microstructural dimensions. Our attention has been focused on studying the mechanical properties of thin films and interfaces and very small volumes of material. Because the dimensions of thin film samples are small (typically 1 mm in thickness, or less), specialized mechanical testing techniques based on nanoindentation, microbeam bending and dynamic vibration of micromachined structures have been developed and used. Here we report briefly on some of the results we have obtained over the past three years. We also give a summary of all of the dissertations, talks and publications completed on this grant during the past 15 years.

  20. Developing a Procedure for the Characterization of Mechanical Properties of Collagen Gels

    NASA Astrophysics Data System (ADS)

    Chambers, Christopher; Lovelady, Heather; Matthews, Garrett

    2011-03-01

    The characterization of bulk mechanical properties of type I collagen gels is critical to understanding the role of collagen in the extracellular matrix (ECM), and developing biocompatible devices for use in the human body. Understanding the mechanical properties of the gel state of collagen can lead to the ability to adjust these properties for multiple uses. Here, we examined the Young's modulus of the synthesized gels. This project used a microrheological approach to discover these properties. Gels were first formed using a known process and magnetic microspheres were embedded in the gel prior to formation. An optical microscope was fitted with a magnetic chamber used to drive the embedded beads in two modes, an oscillatory motion and a pulse motion. Tracking software was modified and used to analyze the motion of the beads recorded with a CCD camera on the microscope. These techniques should be sufficient to obtain a reliable value for the Young's modulus of collagen gels, as well as other similar materials. This work was supported by NSF REU program (award No DMR-1004873).

  1. A Flexure-Based Mechanism for Precision Adjustment of National Ignition Facility Target Shrouds in Three Rotational Degrees of Freedom

    DOE PAGES

    Boehm, K. -J.; Gibson, C. R.; Hollaway, J. R.; ...

    2016-09-01

    This study presents the design of a flexure-based mount allowing adjustment in three rotational degrees of freedom (DOFs) through high-precision set-screw actuators. The requirements of the application called for small but controlled angular adjustments for mounting a cantilevered beam. The proposed design is based on an array of parallel beams to provide sufficiently high stiffness in the translational directions while allowing angular adjustment through the actuators. A simplified physical model in combination with standard beam theory was applied to estimate the deflection profile and maximum stresses in the beams. A finite element model was built to calculate the stresses andmore » beam profiles for scenarios in which the flexure is simultaneously actuated in more than one DOF.« less

  2. A Flexure-Based Mechanism for Precision Adjustment of National Ignition Facility Target Shrouds in Three Rotational Degrees of Freedom

    SciTech Connect

    Boehm, K. -J.; Gibson, C. R.; Hollaway, J. R.; Espinoza-Loza, F.

    2016-09-01

    This study presents the design of a flexure-based mount allowing adjustment in three rotational degrees of freedom (DOFs) through high-precision set-screw actuators. The requirements of the application called for small but controlled angular adjustments for mounting a cantilevered beam. The proposed design is based on an array of parallel beams to provide sufficiently high stiffness in the translational directions while allowing angular adjustment through the actuators. A simplified physical model in combination with standard beam theory was applied to estimate the deflection profile and maximum stresses in the beams. A finite element model was built to calculate the stresses and beam profiles for scenarios in which the flexure is simultaneously actuated in more than one DOF.

  3. Mechanical Properties of the TiAl IRIS Alloy

    NASA Astrophysics Data System (ADS)

    Voisin, Thomas; Monchoux, Jean-Philippe; Thomas, Marc; Deshayes, Christophe; Couret, Alain

    2016-12-01

    This paper presents a study of the mechanical properties at room and high temperature of the boron and tungsten containing IRIS alloy (Ti-48Al-2W-0.08B at. pct). This alloy was densified by Spark Plasma Sintering (SPS). The resultant microstructure consists of small lamellar colonies surrounded by γ regions containing B2 precipitates. Tensile tests are performed from room temperature to 1273 K (1000 °C). Creep properties are determined at 973 K (700 °C)/300 MPa, 1023 K (750 °C)/120 MPa, and 1023 K (750 °C)/200 MPa. The tensile strength and the creep resistance at high temperature are found to be very high compared to the data reported in the current literature while a plastic elongation of 1.6 pct is preserved at room temperature. A grain size dependence of both ductility and strength is highlighted at room temperature. The deformation mechanisms are studied by post-mortem analyses on deformed samples and by in situ straining experiments, both performed in a transmission electron microscope. In particular, a low mobility of non-screw segments of dislocations at room temperature and the activation of a mixed-climb mechanism during creep have been identified. The mechanical properties of this IRIS alloy processed by SPS are compared to those of other TiAl alloys developed for high-temperature structural applications as well as to those of similar tungsten containing alloys obtained by more conventional processing techniques. Finally, the relationships between mechanical properties and microstructural features together with the elementary deformation mechanisms are discussed.

  4. Structures and Mechanical Properties of Natural and Synthetic Diamonds

    NASA Technical Reports Server (NTRS)

    Miyoshi, Kazuhisa

    1998-01-01

    A revolution in the diamond technology is in progress, as the low-pressure process becomes an industrial reality. It will soon be possible to take advantage of the demanding properties of diamond to develop a myriad of new applications, particularly for self-lubricating, wear-resistant, and superhard coatings. The production of large diamond films or sheets at low cost, a distinct possibility in the not-too-distant future, may drastically change tribology technology, particularly regarding solid lubricants and lubricating materials and systems. This paper reviews the structures and properties of natural and synthetic diamonds to gain a better understanding of the tribological properties of diamond and related materials. Atomic and crystal structure, impurities, mechanical properties, and indentation hardness of diamond are described.

  5. Multi-modality gellan gum-based tissue-mimicking phantom with targeted mechanical, electrical, and thermal properties

    NASA Astrophysics Data System (ADS)

    Chen, Roland K.; Shih, A. J.

    2013-08-01

    This study develops a new class of gellan gum-based tissue-mimicking phantom material and a model to predict and control the elastic modulus, thermal conductivity, and electrical conductivity by adjusting the mass fractions of gellan gum, propylene glycol, and sodium chloride, respectively. One of the advantages of gellan gum is its gelling efficiency allowing highly regulable mechanical properties (elastic modulus, toughness, etc). An experiment was performed on 16 gellan gum-based tissue-mimicking phantoms and a regression model was fit to quantitatively predict three material properties (elastic modulus, thermal conductivity, and electrical conductivity) based on the phantom material's composition. Based on these material properties and the regression model developed, tissue-mimicking phantoms of porcine spinal cord and liver were formulated. These gellan gum tissue-mimicking phantoms have the mechanical, thermal, and electrical properties approximately equivalent to those of the spinal cord and the liver.

  6. Mechanical properties of Municipal Solid Waste by SDMT

    SciTech Connect

    Castelli, Francesco; Maugeri, Michele

    2014-02-15

    Highlights: • The adoption of the SDMT for the measurements of MSW properties is proposed. • A comparison between SDMT results and laboratory tests was carried out. • A good reliability has been found in deriving waste properties by SDMT. • Results seems to be promising for the friction angle and Young’s modulus evaluation. - Abstract: In the paper the results of a geotechnical investigation carried on Municipal Solid Waste (MSW) materials retrieved from the “Cozzo Vuturo” landfill in the Enna area (Sicily, Italy) are reported and analyzed. Mechanical properties were determined both by in situ and laboratory large-scale one dimensional compression tests. While among in situ tests, Dilatomer Marchetti Tests (DMT) is used widely in measuring soil properties, the adoption of the DMT for the measurements of MSW properties has not often been documented in literature. To validate its applicability for the estimation of MSW properties, a comparison between the seismic dilatometer (SDMT) results and the waste properties evaluated by laboratory tests was carried out. Parameters for “fresh” and “degraded waste” have been evaluated. These preliminary results seems to be promising as concerns the assessment of the friction angle of waste and the evaluation of the S-wave in terms of shear wave velocity. Further studies are certainly required to obtain more representative values of the elastic parameters according to the SDMT measurements.

  7. Mechanical Properties of Nanostructured Materials Determined Through Molecular Modeling Techniques

    NASA Technical Reports Server (NTRS)

    Clancy, Thomas C.; Gates, Thomas S.

    2005-01-01

    The potential for gains in material properties over conventional materials has motivated an effort to develop novel nanostructured materials for aerospace applications. These novel materials typically consist of a polymer matrix reinforced with particles on the nanometer length scale. In this study, molecular modeling is used to construct fully atomistic models of a carbon nanotube embedded in an epoxy polymer matrix. Functionalization of the nanotube which consists of the introduction of direct chemical bonding between the polymer matrix and the nanotube, hence providing a load transfer mechanism, is systematically varied. The relative effectiveness of functionalization in a nanostructured material may depend on a variety of factors related to the details of the chemical bonding and the polymer structure at the nanotube-polymer interface. The objective of this modeling is to determine what influence the details of functionalization of the carbon nanotube with the polymer matrix has on the resulting mechanical properties. By considering a range of degree of functionalization, the structure-property relationships of these materials is examined and mechanical properties of these models are calculated using standard techniques.

  8. Mechanical Properties in a Bamboo Fiber/PBS Biodegradable Composite

    NASA Astrophysics Data System (ADS)

    Ogihara, Shinji; Okada, Akihisa; Kobayashi, Satoshi

    In recent years, biodegradable plastics which have low effect on environment have been developed. However, many of them have lower mechanical properties than conventional engineering plastics. Reinforcing them with a natural fiber is one of reinforcing methods without a loss of their biodegradability. In the present study, we use a bamboo fiber as the reinforcement and polybutylenesuccinate (PBS) as the matrix. We fabricate long fiber unidirectional composites and cross-ply laminate with different fiber weight fractions (10, 20, 30, 40 and 50wt%). We conduct tensile tests to evaluate the mechanical properties of these composites. In addition, we measure bamboo fiber strength distribution. We discuss the experimentally-obtained properties based on the mechanical properties of the constituent materials. Young's modulus and tensile strength in unidirectional composite and cross-ply laminate increase with increasing fiber weight fraction. However, the strain at fracture showed decreasing tendency. Young's modulus in fiber and fiber transverse directions are predictable by the rules of mixture. Tensile strength in fiber direction is lower than Curtin's prediction of strength which considers distribution of fiber strength. Young's modulus in cross-ply laminate is predictable by the laminate theory. However, analytical prediction of Poisson's ratio in cross-ply laminate by the laminate theory is lower than the experimental results.

  9. Mechanical properties and microstructure of centrifugally cast alloy 718

    NASA Astrophysics Data System (ADS)

    Michel, D. J.; Smith, H. H.

    1985-07-01

    The relationship between the microstructure and mechanical properties of alloy 718 was investigated for two discs centrifugally cast at 50 and 200 rpm and given a duplex age heat treatment. The results of mechanical property tests at temperatures from 426 to 649 °C showed that the tensile yield and ultimate strength levels of both castings were similar. However, the creep-rupture properties were considerably enhanced for the casting produced at 200 rpm. Comparison of the radial and transverse creep properties of each disc indicated that creep life was generally independent of orientation, but ductility was greatest for specimens oriented transverse to the radial direction of the casting. Fatigue crack propagation performance was not greatly influenced by orientation or mold speed parameters and was comparable to wrought alloy 718 when compared on the basis of stress intensity factor range. The centrifugal casting process was found to produce a homogeneous microstructure free of porosity but with the expected segregation of solute alloying elements to Laves and carbide phases. The effect of the as-cast microstructure on the mechanical behavior and the potential influence of hot isostatic pressing to improve the microstructure are discussed.

  10. Evolution of mechanical properties in ErT2 films.

    SciTech Connect

    Browning, James Frederick; Bond, Gillian Mary; Knapp, James Arthur

    2010-04-01

    The mechanical properties of rare earth tritide films evolve as tritium decays into {sup 3}He, which forms bubbles that influence long-term film stability in applications such as neutron generators. Ultralow load nanoindentation, combined with finite-element modeling to separate the mechanical properties of the thin films from their substrates, has been used to follow the mechanical properties of model ErT{sub 2} films as they aged. The size of the growing {sup 3}He bubbles was followed with transmission electron microscopy, while ion beam analysis was used to monitor total T and {sup 3}He content. The observed behavior is divided into two regimes: a substantial increase in layer hardness but elasticity changed little over {approx}18 months, followed by a decrease in elastic stiffness and a modest decease in hardness over the final 24 months. We show that the evolution of properties is explained by a combination of dislocation pinning by the bubbles, elastic softening as the bubbles occupy an increasing fraction of the material, and details of bubble growth modes.

  11. Mechanical properties of several iron-nickel meteorites

    SciTech Connect

    Mulford, Roberta N; El - Dasher, Bassem

    2011-01-06

    Iron-nickel meteorites exhibit a unique lamellar microstructure, consisting of small regions with steep-iron-nickel composition gradients. The microstructure arises as a result of slow cooling in a planetary core or other large mass. The microstructure is further influenced by variable concentrations of other elements such as phosphorous which may have influenced cooling and phase separation. Mechanical properties of these composite structures have been investigated using Vickers and spherical indentation, x-ray fluorescence, and EBSD. Direct observation of mechanical properties in these highly structured materials provides a valuable supplement to bulk measurements, which frequently exhibit large variation in dynamic properties, even within a single sample. Previous studies of the mechanical properties of a typical iron-nickel meteorite, a Diablo Canyon specimen, indicated that the strength of the composite was higher by almost an order of magnitude than values obtained from laboratory-prepared specimens. This was ascribed to the extreme work-hardening evident in the EBSD measurements. Additional specimens from the Canyon Diablo fall (type IAB, coarse octahedrite) and several fine octahedrite meteorites, from the Muonionalusta meteorite (IVA) and Gibeon fall (IVA), have been examined to establish a range of error on the previously measured yield, to determine the extent to which deformation upon reentry contributes to yield, and to establish the degree to which the strength varies as a function of microstructure.

  12. Mechanical properties of high-temperature brazed titanium materials

    SciTech Connect

    Lugscheider, E.; Broich, U.

    1995-05-01

    The mechanical properties of commercial titanium CPTi and Ti-Al6-V4 joints, brazed with Ti-based filler metals in the system Ti(Zr)-Cu-Ni-(Pd) are evaluated by tensile test at various temperatures, as well as by fatigue test at room temperature. The influence of the microstructure in the brazing zone on the mechanical properties of the joints was assessed by conducting metallographic analysis. A vacuum furnace and an induction heating furnace were used for the production of the metallographic and tensile samples. The results from the mechanical and metallographic investigations revealed a strong dependence of the tensile strength of the titanium joints on the microstructure of the brazing zone. The presence of the brittle intermetallic Ti-Cu and Ti-Ni phases in the brazing zone leads to the weakening of the joint. However, for the formation of these intermetallic phases can be avoided by using adequate brazing process parameters and by optimizing the joint clearance. In that case, it is possible to fabricate titanium joints with Ti-based filler metals that have excellent mechanical properties comparable to those of the base metal.

  13. Loops determine the mechanical properties of mitotic chromosomes

    NASA Astrophysics Data System (ADS)

    Zhang, Yang; Heermann, Dieter W.

    2013-03-01

    In mitosis, chromosomes undergo a condensation into highly compacted, rod-like objects. Many models have been put forward for the higher-order organization of mitotic chromosomes including radial loop and hierarchical folding models. Additionally, mechanical properties of mitotic chromosomes under different conditions were measured. However, the internal organization of mitotic chromosomes still remains unclear. Here we present a polymer model for mitotic chromosomes and show how chromatin loops play a major role for their mechanical properties. The key assumption of the model is the ability of the chromatin fibre to dynamically form loops with the help of binding proteins. Our results show that looping leads to a tight compaction and significantly increases the bending rigidity of chromosomes. Moreover, our qualitative prediction of the force elongation behaviour is close to experimental findings. This indicates that the internal structure of mitotic chromosomes is based on self-organization of the chromatin fibre. We also demonstrate how number and size of loops have a strong influence on the mechanical properties. We suggest that changes in the mechanical characteristics of chromosomes can be explained by an altered internal loop structure. YZ gratefully appreciates funding by the German National Academic Foundation (Studienstiftung des deutschen Volkes) and support by the Heidelberg Graduate School for Mathematical and Computational Methods in the Sciences (HGS MathComp).

  14. Woven glass fabric reinforced laminates based on polyolefin wastes: Thermal, mechanical and dynamic-mechanical properties

    NASA Astrophysics Data System (ADS)

    Russo, Pietro; Acierno, Domenico; Simeoli, Giorgio; Lopresto, Valentina

    2014-05-01

    Potentialities of polyolefin wastes in place of virgin polypropylene to produce composite laminates have been investigated. Plaques reinforced with a woven glass fabric were prepared by film-stacking technique and systematically analyzed in terms of thermal, mechanical and dynamic-mechanical properties. In case of PP matrices, the use of a typical compatibilizer to improve the adhesion at the interface has been considered. Thermal properties emphasized the chemical nature of plastic wastes. About mechanical properties, static tests showed an increase of flexural parameters for compatibilized systems due to the coupling effect between grafted maleic anhydride and silane groups on the surface of the glass fabric. These effects, maximized for composites based on car bumper wastes, is perfectly reflected in terms of storage modulus and damping ability of products as determined by single-cantilever bending dynamic tests.

  15. Mechanical properties of normal versus cancerous breast cells

    PubMed Central

    Smelser, Amanda M.; Macosko, Jed C.; O’Dell, Adam P.; Smyre, Scott; Bonin, Keith

    2016-01-01

    A cell’s mechanical properties are important in determining its adhesion, migration, and response to the mechanical properties of its microenvironment and may help explain behavioral differences between normal and cancerous cells. Using fluorescently labeled peroxisomes as microrheological probes, the interior mechanical properties of normal breast cells were compared to a metastatic breast cell line, MDA-MB-231. To estimate the mechanical properties of cell cytoplasms from the motions of their peroxisomes, it was necessary to reduce the contribution of active cytoskeletal motions to peroxisome motion. This was done by treating the cells with blebbistatin, to inhibit myosin II, or with sodium azide and 2-deoxy-D-glucose, to reduce intracellular ATP. Using either treatment, the peroxisomes exhibited normal diffusion or subdiffusion, and their mean squared displacements (MSDs) showed that the MDA-MB-231 cells were significantly softer than normal cells. For these two cell types, peroxisome MSDs in treated and untreated cells converged at high frequencies, indicating that cytoskeletal structure was not altered by the drug treatment. The MSDs from ATP-depleted cells were analyzed by the generalized Stokes–Einstein relation to estimate the interior viscoelastic modulus G* and its components, the elastic shear modulus G′ and viscous shear modulus G″, at angular frequencies between 0.126 and 628rad/s. These moduli are the material coefficients that enter into stress–strain relations and relaxation times in quantitative mechanical models such as the poroelastic model of the interior regions of cancerous and non-cancerous cells. PMID:25929519

  16. Mechanical and tribological properties of ion beam-processed surfaces

    SciTech Connect

    Kodali, Padma

    1998-01-01

    The intent of this work was to broaden the applications of well-established surface modification techniques and to elucidate the various wear mechanisms that occur in sliding contact of ion-beam processed surfaces. The investigation included characterization and evaluation of coatings and modified surfaces synthesized by three surface engineering methods; namely, beam-line ion implantation, plasma-source ion implantation, and DC magnetron sputtering. Correlation among measured properties such as surface hardness, fracture toughness, and wear behavior was also examined. This dissertation focused on the following areas of research: (1) investigating the mechanical and tribological properties of mixed implantation of carbon and nitrogen into single crystal silicon by beam-line implantation; (2) characterizing the mechanical and tribological properties of diamond-like carbon (DLC) coatings processed by plasma source ion implantation; and (3) developing and evaluating metastable boron-carbon-nitrogen (BCN) compound coatings for mechanical and tribological properties. The surface hardness of a mixed carbon-nitrogen implant sample improved significantly compared to the unimplanted sample. However, the enhancement in the wear factor of this sample was found to be less significant than carbon-implanted samples. The presence of nitrogen might be responsible for the degraded wear behavior since nitrogen-implantation alone resulted in no improvement in the wear factor. DLC coatings have low friction, low wear factor, and high hardness. The fracture toughness of DLC coatings has been estimated for the first time. The wear mechanism in DLC coatings investigated with a ruby slider under a contact stress of 1 GPa was determined to be plastic deformation. The preliminary data on metastable BCN compound coatings indicated high friction, low wear factor, and high hardness.

  17. The mechanical and tribological properties of UHMWPE loaded ALN after mechanical activation for joint replacements.

    PubMed

    Gong, Kemeng; Qu, Shuxin; Liu, Yumei; Wang, Jing; Zhang, Yongchao; Jiang, Chongxi; Shen, Ru

    2016-08-01

    Ultra-high molecular weight polyethylene (UHMWPE) loaded with alendronate sodium (ALN) has tremendous potential as an orthopeadic biomaterial for joint replacements. However, poor mechanical and tribological properties of UHMWPE-ALN are still obstacle for further application. The purpose of this study was to investigate the effect and mechanism of mechanical activation on mechanical and tribological properties of 1wt% ALN-loaded UHMWPE (UHMWPE-ALN-ma). In this study, tensile test, small punch test and reciprocating sliding wear test were applied to characterize the mechanical and tribological properties of UHMWPE-ALN-ma. Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and Fourier transform infrared spectroscopy (FTIR) were employed to characterize UHMWPE-ALN-ma. Tensile test and small punch test showed that Young׳s modulus, tensile strength and work-to-failure (WTF) of UHMWPE-ALN-ma increased significantly compared to those of UHMWPE-ALN. The friction coefficients and wear factors of UHMWPE-ALN-ma both decreased significantly compared to those of UHMWPE-ALN. Mechanical activation obviously reduced type 1 (void) and type 2 (the disconnected and dislocated machining marks) fusion defects of UHMWPE-ALN-ma, which were revealed by SEM images of freeze fracture surfaces after etching and lateral surfaces of specimens after extension to fracture, respectively. It was attributed to peeled-off layers and chain scission of molecular chains of UHMWPE particles after mechanical activation, which were revealed by SEM images and FTIR spectra of UHMWPE-ALN-ma and UHMWPE-ALN, respectively. Moreover, EDS spectra revealed the more homogeneous distribution of ALN in UHMWPE-ALN-ma compared to that of UHMWPE-ALN. The present results showed that mechanical activation was a potential strategy to improve mechanical and tribological properties of UHMWPE-ALN-ma as an orthopeadic biomaterial for joint replacements.

  18. Micro-mechanical properties of bio-materials

    NASA Astrophysics Data System (ADS)

    Zakiev, V.; Markovsky, A.; Aznakayev, E.; Zakiev, I.; Gursky, E.

    2005-09-01

    Investigation of physical-mechanical characteristics of stomatologic materials (ceramics for crowns, silver amalgam, cements and materials on a polymeric basis) properties by the modern methods and correspondence their physical-mechanical properties to the physical-mechanical properties of native teeth is represented. The universal device "Micron-Gamma" is built for this purpose. This device allows investigate the physical-mechanical characteristics of stomatologic materials (an elastic modulus, micro-hardness, destruction energy, resistance to scratching) by the methods of continuous indentation, scanning and pricking. A new effective method as well as its device application for the investigation of surface layers of materials and their physical-mechanical properties by means of the constant indenting of an indenter is realized. This method is based on the automatic registration of loading (P) on the indenter with the simultaneous measurement of its indentation depth (h). The results of investigations are presented on a loading diagram P=f(h) and as a digital imaging on the PC. This diagram allows get not only more diverse characteristics in the real time regime but also gives new information about the stomatologic material properties. Therefore, we can to investigate the wide range of the physical-mechanical properties of stomatologic materials. "Micron-alpha" is digital detection device for light imaging applications. It enables to detect the very low material surface relief heights and restoration of surface micro topography by a sequence data processing of interferential data of partially coherent light also. "Micron-alpha" allows: to build 2D and 3D imaging of a material surface; to estimate the quantitatively characteristics of a material surface; to observe the imaging interferential pictures both in the white and in the monochromatic light; to carry out the investigation of blood cells, microbes and biological macromolecules profiles. The method allows

  19. Brain Mechanical Property Measurement Using MRE with Intrinsic Activation

    PubMed Central

    Pattison, Adam J.; McGarry, Matthew D.; Perreard, Irina M.; Swienckowski, Jessica G.; Eskey, Clifford J.; Lollis, S. Scott; Paulsen, Keith D.

    2013-01-01

    Problem Addressed Many pathologies alter the mechanical properties of tissue. Magnetic resonance elastography (MRE) has been developed to noninvasively characterize these quantities in vivo. Typically, small vibrations are induced in the tissue of interest with an external mechanical actuator. The resulting displacements are measured with phase contrast sequences and are then used to estimate the underlying mechanical property distribution. Several MRE studies have quantified brain tissue properties. However, the cranium and meninges, especially the dura, are very effective at damping externally applied vibrations from penetrating deeply into the brain. Here, we report a method, termed ‘intrinsic activation’, that eliminates the requirement for external vibrations by measuring the motion generated by natural blood vessel pulsation. Methodology A retrospectively gated phase contrast MR angiography sequence was used to record the tissue velocity at eight phases of the cardiac cycle. The velocities were numerically integrated via the Fourier transform to produce the harmonic displacements at each position within the brain. The displacements were then reconstructed into images of the shear modulus based on both linear elastic and poroelastic models. Results, Significance and Potential Impact The mechanical properties produced fall within the range of brain tissue estimates reported in the literature and, equally important, the technique yielded highly reproducible results. The mean shear modulus was 8.1 kPa for linear elastic reconstructions and 2.4 kPa for poroelastic reconstructions where fluid pressure carries a portion of the stress. Gross structures of the brain were visualized, particularly in the poroelastic reconstructions. Intra-subject variability was significantly less than the inter-subject variability in a study of 6 asymptomatic individuals. Further, larger changes in mechanical properties were observed in individuals when examined over time than when

  20. Structural and mechanical properties of mandibular condylar bone.

    PubMed

    van Eijden, T M G J; van der Helm, P N; van Ruijven, L J; Mulder, L

    2006-01-01

    The trabecular bone of the mandibular condyle is structurally anisotropic and heterogeneous. We hypothesized that its apparent elastic moduli are also anisotropic and heterogeneous, and depend on trabecular density and orientation. Eleven condyles were scanned with a micro-CT system. Volumes of interest were selected for the construction of finite element models. We simulated compressive and shear tests to determine the principal mechanical directions and the apparent elastic moduli. Compressive moduli were relatively large in directions acting in the sagittal plane, and small in the mediolateral direction. The degree of mechanical anisotropy ranged from 4.7 to 10.8. Shear moduli were largest in the sagittal plane and smallest in the transverse plane. The magnitudes of the moduli varied with the condylar region and were proportional to the bone volume fraction. Furthermore, principal mechanical direction correlated significantly with principal structural direction. It was concluded that variation in trabecular structure coincides with variation in apparent mechanical properties.

  1. Enzymatic treatment of mechanical pulp fibers for improving papermaking properties.

    PubMed

    Wong, K K; Richardson, J D; Mansfield, S D

    2000-01-01

    Three enzyme preparations (crude cellulase, laccase, and proteinase) were evaluated for their potential to improve the papermaking properties of mechanical pulp. After treating a long fibre-rich fraction of the pulp with enzyme, the fibres were recombined with untreated fines for handsheet making and testing. None of the enzymes altered the retention of fines or the consolidation of the furnish mix during handsheet formation. All three enzymes increased tensile stiffness index, which is a measure of the initial resistance of the handsheets to strain. Only the laccase preparation, an enzyme that modifies pulp lignin, consistently increased fibre bonding to enhance other strength properties of the handsheets.

  2. Constitutive Modeling of the Mechanical Properties of Optical Fibers

    NASA Technical Reports Server (NTRS)

    Moeti, L.; Moghazy, S.; Veazie, D.; Cuddihy, E.

    1998-01-01

    Micromechanical modeling of the composite mechanical properties of optical fibers was conducted. Good agreement was obtained between the values of Young's modulus obtained by micromechanics modeling and those determined experimentally for a single mode optical fiber where the wave guide and the jacket are physically coupled. The modeling was also attempted on a polarization-maintaining optical fiber (PANDA) where the wave guide and the jacket are physically decoupled, and found not to applicable since the modeling required perfect bonding at the interface. The modeling utilized constituent physical properties such as the Young's modulus, Poisson's ratio, and shear modulus to establish bounds on the macroscopic behavior of the fiber.

  3. Imaging and mechanical property measurements of kerogen via nanoindentation

    NASA Astrophysics Data System (ADS)

    Zeszotarski, Jonathan C.; Chromik, Richard R.; Vinci, Richard P.; Messmer, Marie C.; Michels, Raymond; Larsen, John W.

    2004-10-01

    Most analyses of kerogens rely on samples that have been isolated by dissolving the rock matrix. The properties of the kerogen before and after such isolation may be different and all sample orientation information is lost. We report a method of measuring kerogen mechanical properties in the rock matrix without isolation. An atomic force microscope (AFM) based nanoindenter is used to measure the hardness and reduced modulus of the kerogen within Woodford shale. The same instrument also provides useful images of polished rock sections on a submicrometer scale. Measurements were carried out both parallel and perpendicular to the bedding plane.

  4. Review of research on the mechanical properties of the human tooth

    PubMed Central

    Zhang, Ya-Rong; Du, Wen; Zhou, Xue-Dong; Yu, Hai-Yang

    2014-01-01

    ‘Bronze teeth' reflect the mechanical properties of natural teeth to a certain extent. Their mechanical properties resemble those of a tough metal, and the gradient of these properties lies in the direction from outside to inside. These attributes confer human teeth with effective mastication ability. Understanding the various mechanical properties of human teeth and dental materials is the basis for the development of restorative materials. In this study, the elastic properties, dynamic mechanical properties (visco-elasticity) and fracture mechanical properties of enamel and dentin were reviewed to provide a more thorough understanding of the mechanical properties of human teeth. PMID:24743065

  5. Electrical and dielectric properties of bovine trabecular bone--relationships with mechanical properties and mineral density.

    PubMed

    Sierpowska, J; Töyräs, J; Hakulinen, M A; Saarakkala, S; Jurvelin, J S; Lappalainen, R

    2003-03-21

    Interrelationships of trabecular bone electrical and dielectric properties with mechanical characteristics and density are poorly known. While electrical stimulation is used for healing fractures, better understanding of these relations has clinical importance. Furthermore, earlier studies have suggested that bone electrical and dielectric properties depend on the bone density and could, therefore, be used to predict bone strength. To clarify these issues, volumetric bone mineral density (BMDvol), electrical and dielectric as well as mechanical properties were determined from 40 cylindrical plugs of bovine trabecular bone. Phase angle, relative permittivity, loss factor and conductivity of wet bovine trabecular bone were correlated with Young's modulus, yield stress, ultimate strength, resilience and BMDvol. The reproducibility of in vitro electrical and dielectric measurements was excellent (standardized coefficient of variation less than 1%, for all parameters), especially at frequencies higher than 1 kHz. Correlations of electrical and dielectric parameters with the bone mechanical properties or density were frequency-dependent. The relative permittivity showed the strongest linear correlations with mechanical parameters (r > 0.547, p < 0.01, n = 40, at 50 kHz) and with BMDvol (r = 0.866, p < 0.01, n = 40, at 50 kHz). In general, linear correlations between relative permittivity and mechanical properties or BMDvol were highest at frequencies over 6 kHz. In addition, a significant site-dependent variation of electrical and dielectric characteristics, mechanical properties and BMDvol was revealed in bovine femur (p < 0.05, Kruskall-Wallis H-test). Based on the present results, we conclude that the measurement of electrical and dielectric properties provides quantitative information that is related to bone quantity and quality.

  6. Evaluation of the compressive mechanical properties of endoluminal metal stents.

    PubMed

    Schrader, S C; Beyar, R

    1998-06-01

    The mechanical properties of metal stents are important parameters in the consideration of stent design, matched to resist arterial recoil and vascular spasm. The purpose of this study was to develop a system for a standardized quantitative evaluation of the mechanical characteristics of various coronary stents. Several types of stents were compressed by external hydrostatic pressure. The stent diameter was assessed by placing a pair of small ultrasonic sono-crystals on the stent. From pressure-strain diagrams the ultimate strength and radial stiffness for each stent were determined. For all stents, except the MICRO-II and the Wiktor stent, the diameter decreased homogeneously until an ultimate compressive strength was exceeded, causing an abrupt collapse. Expanded to 3 mm, the mechanical behavior of the beStent, the Crown and the Palmaz-Schatz stent (PS153-series) were comparable. The spiral articulated Palmaz-Schatz stent showed twice the strength (1.26 atm) of the PS-153 (0.65 atm). The NIR stent yielded a maximum strength of 1.05 atm. The MICRO-II and the Wiktor stent did not collapse abruptly but rather showed a continuous decline of diameter with increasing external pressure. The Cardiocoil stent behaved in a fully elastic manner and showed the largest radial stiffness. Difference in mechanical properties between stents were documented using a new device specifically developed for that purpose. These mechanical stent parameters may have important clinical implications.

  7. Metallurgical Mechanisms Controlling Mechanical Properties of Aluminum Alloy 2219 Produced By Electron Beam Freeform Fabrication

    NASA Technical Reports Server (NTRS)

    Domack, Marcia S.; Taminger, Karen M. B.; Begley, Matthew

    2006-01-01

    The electron beam freeform fabrication (EBF3) layer-additive manufacturing process has been developed to directly fabricate complex geometry components. EBF3 introduces metal wire into a molten pool created on the surface of a substrate by a focused electron beam. Part geometry is achieved by translating the substrate with respect to the beam to build the part one layer at a time. Tensile properties have been demonstrated for electron beam deposited aluminum and titanium alloys that are comparable to wrought products, although the microstructures of the deposits exhibit features more typical of cast material. Understanding the metallurgical mechanisms controlling mechanical properties is essential to maximizing application of the EBF3 process. In the current study, mechanical properties and resulting microstructures were examined for aluminum alloy 2219 fabricated over a range of EBF3 process variables. Material performance was evaluated based on tensile properties and results were compared with properties of Al 2219 wrought products. Unique microstructures were observed within the deposited layers and at interlayer boundaries, which varied within the deposit height due to microstructural evolution associated with the complex thermal history experienced during subsequent layer deposition. Microstructures exhibited irregularly shaped grains, typically with interior dendritic structures, which were described based on overall grain size, morphology, distribution, and dendrite spacing, and were correlated with deposition parameters. Fracture features were compared with microstructural elements to define fracture paths and aid in definition of basic processing-microstructure-property correlations.

  8. Crosstalk between focal adhesions and material mechanical properties governs cell mechanics and functions.

    PubMed

    Fusco, Sabato; Panzetta, Valeria; Embrione, Valerio; Netti, Paolo A

    2015-09-01

    Mechanical properties of materials strongly influence cell fate and functions. Focal adhesions are involved in the extremely important processes of mechanosensing and mechanotransduction. To address the relationship between the mechanical properties of cell substrates, focal adhesion/cytoskeleton assembly and cell functions, we investigated the behavior of NIH/3T3 cells over a wide range of stiffness (3-1000kPa) using two of the most common synthetic polymers for cell cultures: polyacrylamide and polydimethylsiloxane. An overlapping stiffness region was created between them to compare focal adhesion characteristics and cell functions, taking into account their different time-dependent behavior. Indeed, from a rheological point of view, polyacrylamide behaves like a strong gel (elastically), whereas polydimethylsiloxane like a viscoelastic solid. First, focal adhesion characteristics and dynamics were addressed in terms of material stiffness, then cell spreading area, migration rate and cell mechanical properties were correlated with focal adhesion size and assembly. Focal adhesion size was found to increase in the whole range of stiffness and to be in agreement in the overlapping rigidity region for the investigated materials. Cell mechanics directly correlated with focal adhesion lengths, whereas migration rate followed an inverse correlation. Cell spreading correlated with the substrate stiffness on polyacrylamide hydrogel, while no specific trend was found on polydimethylsiloxane. Substrate mechanics can be considered as a key physical cue that regulates focal adhesion assembly, which in turn governs important cellular properties and functions.

  9. Simulated Hail Ice Mechanical Properties and Failure Mechanism at Quasi-Static Strain Rates

    NASA Astrophysics Data System (ADS)

    Swift, Jonathan M.

    Hail is a significant threat to aircraft both on the ground and in the air. Aeronautical engineers are interested in better understanding the properties of hail to improve the safety of new aircraft. However, the failure mechanism and mechanical properties of hail, as opposed to clear ice, are not well understood. A literature review identifies basic mechanical properties of ice and a failure mechanism based upon the state of stress within an ice sphere is proposed. To better understand the properties of Simulated Hail Ice (SHI), several tests were conducted using both clear and cotton fiber reinforced ice. Pictures were taken to show the internal crystal structure of SHI. SHI crush tests were conducted to identify the overall force-displacement trends at various quasi-static strain rates. High speed photography was also used to visually track the failure mechanism of spherical SHI. Compression tests were done to measure the compression strength of SHI and results were compared to literature data. Fracture toughness tests were conducted to identify the crack resistance of SHI. Results from testing clear ice samples were successfully compared to previously published literature data to instill confidence in the testing methods. The methods were subsequently used to test and characterize the cotton fiber reinforced ice.

  10. Stretchable polyurethane sponge reinforced magnetorheological material with enhanced mechanical properties

    NASA Astrophysics Data System (ADS)

    Ge, Lin; Xuan, Shouhu; Liao, Guojiang; Yin, Tiantian; Gong, Xinglong

    2015-03-01

    A stretchable magnetorheological material (SMRM) consisting of micro-meter carbonyl iron (CI) particles, low cross-linking polyurethane (PU) polymer and porous PU sponge has been developed. Due to the presence of the PU sponge, the high-performance MR material can be reversibly stretched or bent, just as MR elastomers. When the CI content increases to 80 wt%, the magnetic induced modulus of the MR material can reach as high as 7.34 MPa and the corresponding relative MR effect increases to 820%. A possible strengthening mechanism of the SMRM was proposed. The attractive mechanical properties make the SMRM a promising candidate for future high-performance devices.

  11. Failure criterion for materials with spatially correlated mechanical properties.

    PubMed

    Faillettaz, J; Or, D

    2015-03-01

    The role of spatially correlated mechanical elements in the failure behavior of heterogeneous materials represented by fiber bundle models (FBMs) was evaluated systematically for different load redistribution rules. Increasing the range of spatial correlation for FBMs with local load sharing is marked by a transition from ductilelike failure characteristics into brittlelike failure. The study identified a global failure criterion based on macroscopic properties (external load and cumulative damage) that is independent of spatial correlation or load redistribution rules. This general metric could be applied to assess the mechanical stability of complex and heterogeneous systems and thus provide an important component for early warning of a class of geophysical ruptures.

  12. Structure and mechanical properties of liquid crystalline filaments

    SciTech Connect

    Eremin, Alexey; Nemes, Alexandru; Stannarius, Ralf; Schulz, Mario; Nadasi, Hajnalka; Weissflog, Wolfgang

    2005-03-01

    The formation of stable freely suspended filaments is an interesting peculiarity of some liquid crystal phases. So far, little is known about their structure and stability. Similarly to free-standing smectic films, an internal molecular structure of the mesophase stabilizes these macroscopically well-ordered objects with length to diameter ratios of 10{sup 3} and above. In this paper, we report observations of smectic liquid crystal fibers formed by bent-shaped molecules in different mesophases. Our study, employing several experimental techniques, focuses on mechanical and structural aspects of fiber formation such as internal structure, stability, and mechanical and optical properties.

  13. Effective mechanical properties of hexagonal boron nitride nanosheets.

    PubMed

    Boldrin, L; Scarpa, F; Chowdhury, R; Adhikari, S

    2011-12-16

    We propose an analytical formulation to extract from energy equivalence principles the equivalent thickness and in-plane mechanical properties (tensile and shear rigidity, and Poisson's ratio) of hexagonal boron nitride (h-BN) nanosheets. The model developed provides not only very good agreement with existing data available in the open literature from experimental, density functional theory (DFT) and molecular dynamics (MD) simulations, but also highlights the specific deformation mechanisms existing in boron nitride sheets, and their difference with carbon-based graphitic systems.

  14. Dynamic Mechanical Properties of Natural Rubber/Polyaniline Composites

    NASA Astrophysics Data System (ADS)

    Najidha, S.; Predeep, P.; Saxena, N. S.

    2008-04-01

    The Dynamic Mechanical properties of polymer composite containing Natural Rubber (NR) as the matrix and polyaniline as filler has been studied. The composites were prepared by mechanical mixing in a roll mill and vulcanized in a hot press. The dynamic modulus such as tanδ, storage modulus and loss modulus of the composite were evaluated. The glass transition (Tg) temperature of the Natural Rubber phase in the composite was shifted to lower temperature indicating that the polyaniline content strongly affects the behavior of the composite. Addition of polyaniline lowered the crosslinking degree, but produced a reinforcing effect in the elastomer.

  15. Prediction of Mechanical Properties of Polymers With Various Force Fields

    NASA Technical Reports Server (NTRS)

    Odegard, Gregory M.; Clancy, Thomas C.; Gates, Thomas S.

    2005-01-01

    The effect of force field type on the predicted elastic properties of a polyimide is examined using a multiscale modeling technique. Molecular Dynamics simulations are used to predict the atomic structure and elastic properties of the polymer by subjecting a representative volume element of the material to bulk and shear finite deformations. The elastic properties of the polyimide are determined using three force fields: AMBER, OPLS-AA, and MM3. The predicted values of Young s modulus and shear modulus of the polyimide are compared with experimental values. The results indicate that the mechanical properties of the polyimide predicted with the OPLS-AA force field most closely matched those from experiment. The results also indicate that while the complexity of the force field does not have a significant effect on the accuracy of predicted properties, small differences in the force constants and the functional form of individual terms in the force fields determine the accuracy of the force field in predicting the elastic properties of the polyimide.

  16. Quantitative ultrasonic evaluation of mechanical properties of engineering materials

    NASA Technical Reports Server (NTRS)

    Vary, A.

    1978-01-01

    Current progress in the application of ultrasonic techniques to nondestructive measurement of mechanical strength properties of engineering materials is reviewed. Even where conventional NDE techniques have shown that a part is free of overt defects, advanced NDE techniques should be available to confirm the material properties assumed in the part's design. There are many instances where metallic, composite, or ceramic parts may be free of critical defects while still being susceptible to failure under design loads due to inadequate or degraded mechanical strength. This must be considered in any failure prevention scheme that relies on fracture analysis. This review will discuss the availability of ultrasonic methods that can be applied to actual parts to assess their potential susceptibility to failure under design conditions.

  17. A Review of the Mechanical Properties of Concrete Containing Biofillers

    NASA Astrophysics Data System (ADS)

    Ezdiani Mohamad, Mazizah; Mahmood, Ali A.; Min, Alicia Yik Yee; Khalid, Nur Hafizah A.

    2016-11-01

    Sustainable construction is a rapidly increasing research area. Investigators of all backgrounds are using industrial and agro wastes to replace Portland cement in concrete to reduce greenhouse emissions and the corresponding decline in general health. Many types of wastes have been used as cement replacements in concrete including: fly ash, slag and rice husk ash in addition to others. This study investigates the possibility of producing a sustainable approach to construction through the partial replacement of concrete using biofillers. This will be achieved by studying the physical and mechanical properties of two widely available biological wastes in Malaysia; eggshell and palm oil fuel ash (POFA). The mechanical properties tests that were studied and compared are the compression, tensile and flexural tests.

  18. On the mechanical properties of selenite glass nanocomposites

    NASA Astrophysics Data System (ADS)

    Bar, Arun Kr.; Kundu, Ranadip; Roy, Debasish; Bhattacharya, Sanjib

    2016-05-01

    In this paper the room temperature micro-hardness of selenite glass-nanocomposites has been measured using a Vickers and Knoop micro hardness tester where the applied load varies from 0.01N to 0.98 N. A significant indentation size effect was observed for each sample at relatively low indentation test loads. The classical Meyer's law and the proportional specimen resistance model were used to analyze the micro-hardness behavior. It was found that the selenite glass-nanocomposite becomes harder with increasing CuI composition and the work hardening coefficient and mechanical properties like Young modulus, E, were also calculated. Our results open the way for the preparation, application and investigation of significant mechanical properties of new type of glass-nanocomposites.

  19. Computer simulations of the mechanical properties of metals.

    PubMed

    Schiøtz, J; Vegge, T

    1999-01-01

    Atomic-scale computer simulations can be used to gain a better understanding of the mechanical properties of materials. In this paper we demonstrate how this can be done in the case of nanocrystalline copper, and give a brief overview of how simulations may be extended to larger length scales. Nanocrystline metals are metals with grain sizes in the nanometre range, they have a number of technologically interesting properties such as much increased hardness and yield strength. Our simulations show that the deformation mechanisms are different in these materials than in coarse-grained materials. The main deformation is occurring in the grain boundaries, and only little dislocation activity is seen inside the grains. This leads to a hardening of the material as the grain size is increased, and the volume fraction of grain boundaries is decreased.

  20. Ultrasound Study of the Mechanical Properties of the Arterial Wall

    NASA Astrophysics Data System (ADS)

    Bernal Restrepo, Miguel

    Arterial elasticity has become an important predictor of cardiovascular diseases and mortality in the past few of decades. Several in vivo and ex vivo techniques have been developed to characterize the elastic properties of vessels. In vivo approaches, even though have shown correlation of diseases and mortality with arterial elasticity in population studies, are not widely used as a clinical tool for the diagnosis and follow up of patients. Ex vivo techniques have focused their efforts on studying the mechanical properties of the arterial tissue in different axes. These techniques are usually destructive testing methods which can not be applied in an in vivo setting. In this work we present two different approaches to the characterization of the mechanical properties of arterial wall. One of the methodologies presented here uses piezoelectric elements attached to the arterial wall to measure the strain and the stresses in two directions (circumferential and longitudinal) as the arteries are pressurized. The second part of this works focuses on a technique that uses ultrasound radiation force to generate mechanical waves in the arterial wall. These waves are measured and analyzed in the frequency domain to determine the different modes of propagation and from there, estimate the material properties of the wall tissue. This technique has a high temporal resolution which will allow the dynamic study of the elastic and viscous properties throughout the heart cycle. At the same time the method posses a high spatial resolution allowing the characterization of different vascular segments within the arterial tree. We are currently working on the implementation of this methodology in a clinical system for the translation into a clinical setting.

  1. Mechanical properties of polymeric composites with carbon dioxide particles

    NASA Astrophysics Data System (ADS)

    Moskalyuk, O. A.; Samsonov, A. M.; Semenova, I. V.; Smirnova, V. E.; Yudin, V. E.

    2017-02-01

    Nanocomposites consisting of a polymethylmethacrylate or polystyrene matrix with embedded silicon dioxide nanoparticles surface-modified by silazanes have been prepared by melting technology. The influence of particles on viscoelastic properties of the nanocomposites has been studied using dynamic mechanical analysis. It has been revealed that the addition of 20 wt % of SiO2 raises the flexural modulus of the nanocomposites by 30%.

  2. ORMOSIL thin films: tuning mechanical properties via a nanochemistry approach.

    PubMed

    Palmisano, Giovanni; Le Bourhis, Eric; Ciriminna, Rosaria; Tranchida, Davide; Pagliaro, Mario

    2006-12-19

    The mechanical properties (hardness and elastic modulus) of organically modified silicate thin films can be finely tuned by varying the degree of alkylation and thus the fraction of six- and four-membered siloxane rings in the organosilica matrix. This opens the way to large tunability of parameters that are of crucial practical importance for films that are finding increasing application in numerous fields ranging from microelectronics to chemical sensing.

  3. Mechanical and thermophysical properties of hot-pressed SYNROC B

    SciTech Connect

    Hoenig, C.L.; Newkirk, H.W.; Otto, R.A.; Brady, R.L.; Brown, A.E.; Ulrich, A.R.; Lum, R.C.

    1981-05-06

    The optimal SYNROC compositons for use with commercial waste are reviewed. Large amounts of powder (about 2.5 kg) were prepared by convention al ceramic operations to test the SYNROC concept on a processing scale. Samples, 15.2 cm in diameter, were hot pressed in graphite, and representative samples were cut for microstructural evaluations. Measured mechanical and thermophysical properties did not vary significantly as a function of sample location and were typical of titanate ceramic materials.

  4. High Strain Rate Mechanical Properties of Glassy Polymers

    DTIC Science & Technology

    2012-07-25

    Force Materiel Command  United States Air Force  Eglin Air Force Base AFRL-RW-EG-TP-2012-008 High Strain Rate...TITLE AND SUBTITLE High Strain Rate Mechanical Properties of Glassy Polymers 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT...1990s, a range of experimental data has been generated describing the response of glassy polymers to high strain rate loading in compression. More

  5. Nondestructive measurement of esophageal biaxial mechanical properties utilizing sonometry

    NASA Astrophysics Data System (ADS)

    Aho, Johnathon M.; Qiang, Bo; Wigle, Dennis A.; Tschumperlin, Daniel J.; Urban, Matthew W.

    2016-07-01

    Malignant esophageal pathology typically requires resection of the esophagus and reconstruction to restore foregut continuity. Reconstruction options are limited and morbid. The esophagus represents a useful target for tissue engineering strategies based on relative simplicity in comparison to other organs. The ideal tissue engineered conduit would have sufficient and ideally matched mechanical tolerances to native esophageal tissue. Current methods for mechanical testing of esophageal tissues both in vivo and ex vivo are typically destructive, alter tissue conformation, ignore anisotropy, or are not able to be performed in fluid media. The aim of this study was to investigate biomechanical properties of swine esophageal tissues through nondestructive testing utilizing sonometry ex vivo. This method allows for biomechanical determination of tissue properties, particularly longitudinal and circumferential moduli and strain energy functions. The relative contribution of mucosal-submucosal layers and muscular layers are compared to composite esophagi. Swine thoracic esophageal tissues (n  =  15) were tested by pressure loading using a continuous pressure pump system to generate stress. Preconditioning of tissue was performed by pressure loading with the pump system and pre-straining the tissue to in vivo length before data was recorded. Sonometry using piezocrystals was utilized to determine longitudinal and circumferential strain on five composite esophagi. Similarly, five mucosa-submucosal and five muscular layers from thoracic esophagi were tested independently. This work on esophageal tissues is consistent with reported uniaxial and biaxial mechanical testing and reported results using strain energy theory and also provides high resolution displacements, preserves native architectural structure and allows assessment of biomechanical properties in fluid media. This method may be of use to characterize mechanical properties of tissue engineered esophageal

  6. Mechanical properties of D0 Run IIB silicon detector staves

    SciTech Connect

    Lanfranco, Giobatta; Fast, James; /Fermilab

    2001-06-01

    A proposed stave design for the D0 Run IIb silicon tracker outer layers featuring central cooling channels and a composite shell mechanical structure is evaluated for self-deflection and deflection due to external loads. This paper contains an introduction to the stave structure, a section devoted to composite lamina and laminate properties and finally a section discussing the beam deflections expected for assembled staves using these laminates.

  7. Interface Characteristics and the Mechanical Properties of Metal Matrix Composites.

    DTIC Science & Technology

    1987-09-28

    oxide were identified to most probably be y - A120 3 or the MgAI20 4 type spinel. Details are given in Appendix K. Summary -. The research reported ...Zecas aT Austit. INTERFACE CHARACTERISTICS AND THE MECHANICAL PROPERTIES OF METAL MATRIX COMPOSITES UTCMSE-87-3 Office of Naval Research Technical Report ...THIS PAGE (When Date Entered) READ INSTRUCTIONSREPORT DOCUMENTATION PAGE I RE COSPLETIOR~BEFORE MPLETING FORM VI REPORT NUMBER 2. GOVT ACCESSION NO., 3

  8. Effect of Preheating on the Mechanical Properties of Resin Composites

    PubMed Central

    Uctasli, Mine Betül; Arisu, Hacer Deniz; Lasilla, Lippo VJ; Valittu, Pekka K.

    2008-01-01

    Objectives The purpose of this study was to compare the flexural strength and modulus of two commercial resin composites, at room temperature and 40, 45 and 50°C prior to light polymerization with standard and step-cure protocols. Methods One nanohybrid (Grandio, VOCO, Cuxhaven, Germany), and microhybrid composite resin (Filtek Z250, 3M ESPE, St. Paul, MN, USA) were used. The materials were inserted into rectangular moulds at room temperature or preheated to a temperature of 40, 45 or 50°C and cured with standard or step-cure protocols with high intensity halogen (Elipar Highlight, 3M-ESPE, St. Paul, MN, USA). Ten specimens were prepared for each preheating and light curing protocol. A three-point bending test was performed using a universal testing machine at a crosshead speed of 1 mm/min. The data were analyzed by one-way analysis of variance and Tukey’s post hoc tests (P<.05) to examine the effect of curing protocol and preheating. Pearson’s correlation test was used to determine the correlation between tested mechanical properties and preheating. Results There were no statistically significant difference between tested mechanical properties of the materials, curing protocols and temperature of the materials. No significant correlation was found between preheating and tested mechanical properties. Conclusions The mechanical properties of the tested materials did not changed by preheating so the tested materials could be preheated because of the other potential clinical advantages like more adaptation to the cavity walls. PMID:19212532

  9. The mechanical properties of density graded hemp/polyethylene composites

    NASA Astrophysics Data System (ADS)

    Dauvegis, Raphaël; Rodrigue, Denis

    2015-05-01

    In this work, the production and mechanical characterization of density graded biocomposites based on high density polyethylene and hemp fibres was performed. The effect of coupling agent addition (maleated polyethylene) and hemp content (0-30%) was studied to determine the effect of hemp distribution (graded content) inside the composite (uniform, linear, V and Λ). Tensile and flexural properties are reported to compare the structures, especially in terms of their stress-strain behaviors under tensile loading.

  10. A comparison of mechanical properties of some foams and honeycombs

    NASA Technical Reports Server (NTRS)

    Bhat, Balakrishna T.; Wang, T. G.

    1990-01-01

    A comparative study is conducted of the mechanical properties of foam-core and honeycomb-core sandwich panels, using a normalizing procedure based on common properties of cellular solids and related properties of dense solids. Seven different honeycombs and closed-foam cells are discussed; of these, three are commercial Al alloy honeycombs, one is an Al-alloy foam, and two are polymeric foams. It is concluded that ideal, closed-cell foams may furnish compressive strengths which while isotropic can be fully comparable to the compressive strengths of honeycombs in the thickness direction. The shear strength of ideal closed-cell foams may be superior to the shear strength of honeycombs.

  11. Conductive magnetorheological elastomer: fatigue dependent impedance-mechanic coupling properties

    NASA Astrophysics Data System (ADS)

    Wang, Yu; Xuan, Shouhu; Ge, Lin; Wen, Qianqian; Gong, Xinglong

    2017-01-01

    This work investigated the relationship between the impedance properties and dynamic mechanical properties of magnetorheological elastomers (MREs) under fatigue loading. The storage modulus and the impedance properties of MREs were highly influenced by the pressure and magnetic field. Under the same experimental condition, the two characteristics exhibited similar fatigue dependent change trends. When pressure was smaller than 10 N, the capacitance of MRE could be divided into four sections with the increase of the cyclic numbers. The relative equivalent circuit model was established to fit the experimental results of the impedance spectra. Each parameter of circuit element reflected the change of fatigue loading, relative microstructure of MRE, MRE-electrode interface layer, respectively. Based on the above analysis, the real-time and nondestructive impedance method was demonstrated to be high potential on detecting the fatigue of the MRE device.

  12. Rubber-toughened cyanate composites - Properties and toughening mechanism

    NASA Technical Reports Server (NTRS)

    Yang, P. C.; Woo, E. P.; Laman, S. A.; Jakubowski, J. J.; Pickelman, D. M.; Sue, H. J.

    1991-01-01

    Earlier work by Young et al. (1990) has shown that Dow experimental cyanate ester resin XU71787.02 is readily toughenable by rubber. A particularly effective rubber for this purpose is an experimental core-shell rubber which toughens the polymer by inducing shear yielding. This paper describes an investigation into the toughening mechanism in the corresponding carbon-fiber composite systems and the effect of fibers on composite properties. Resin-fiber interfacial shear strengths have been successfully correlated to the compressive strengths after impact and other key properties of composites based on rubber-toughened cyanate and several carbon fibers. The differences in the properties are explained by the difference in the functioning of the rubber particles during the fracture process.

  13. High-Mn steel weldment mechanical properties at 4 K

    SciTech Connect

    Chan, J.W.; Sunwoo, A.J.; Morris, J.W. Jr.

    1988-06-01

    Advanced high-field superconducting magnets of the next generation of magnetic confinement fusion devices will require structural alloys with high yield strength and high toughness at cryogenic temperatures. Commercially available alloys used in the current generation of magnets, such as 300 series stainless steels, do not have the required properties. N-strengthened, high-Mn alloys meet base plate requirements in the as-rolled condition. However, the property changes associated with weld microstructural and chemical changes in these alloys have not been well characterized. In this work welding induced cryogenic mechanical property changes of an 18Mn-16Cr-5Ni-0.2N alloy are correlated with as-solidified weld microstructures and chemistries. 30 refs., 12 figs., 3 tabs.

  14. Protocol dependence of mechanical properties in granular systems.

    PubMed

    Inagaki, S; Otsuki, M; Sasa, S

    2011-11-01

    We study the protocol dependence of the mechanical properties of granular media by means of computer simulations. We control a protocol of realizing disk packings in a systematic manner. In 2D, by keeping material properties of the constituents identical, we carry out compaction with various strain rates. The disk packings exhibit the strain rate dependence of the critical packing fraction above which the pressure becomes non-zero. The observed behavior contrasts with the well-studied jamming transitions for frictionless disk packings. We also observe that the elastic moduli of the disk packings depend on the strain rate logarithmically. Our results suggest that there exists a time-dependent state variable to describe macroscopic material properties of disk packings, which depend on its protocol.

  15. Structure and mechanical properties of Octopus vulgaris suckers

    PubMed Central

    Tramacere, Francesca; Kovalev, Alexander; Kleinteich, Thomas; Gorb, Stanislav N.; Mazzolai, Barbara

    2014-01-01

    In this study, we investigate the morphology and mechanical features of Octopus vulgaris suckers, which may serve as a model for the creation of a new generation of attachment devices. Octopus suckers attach to a wide range of substrates in wet conditions, including rough surfaces. This amazing feature is made possible by the sucker's tissues, which are pliable to the substrate profile. Previous studies have described a peculiar internal structure that plays a fundamental role in the attachment and detachment processes of the sucker. In this work, we present a mechanical characterization of the tissues involved in the attachment process, which was performed using microindentation tests. We evaluated the elasticity modulus and viscoelastic parameters of the natural tissues (E ∼ 10 kPa) and measured the mechanical properties of some artificial materials that have previously been used in soft robotics. Such a comparison of biological prototypes and artificial material that mimics octopus-sucker tissue is crucial for the design of innovative artificial suction cups for use in wet environments. We conclude that the properties of the common elastomers that are generally used in soft robotics are quite dissimilar to the properties of biological suckers. PMID:24284894

  16. Relationships between supercontraction and mechanical properties of spider silk.

    PubMed

    Liu, Yi; Shao, Zhengzhong; Vollrath, Fritz

    2005-12-01

    Typical spider dragline silk tends to outperform other natural fibres and most man-made filaments. However, even small changes in spinning conditions can have large effects on the mechanical properties of a silk fibre as well as on its water uptake. Absorbed water leads to significant shrinkage in an unrestrained dragline fibre and reversibly converts the material into a rubber. This process is known as supercontraction and may be a functional adaptation for the silk's role in the spider's web. Supercontraction is thought to be controlled by specific motifs in the silk proteins and to be induced by the entropy-driven recoiling of molecular chains. In analogy, in man-made fibres thermal shrinkage induces changes in mechanical properties attributable to the entropy-driven disorientation of 'unfrozen' molecular chains (as in polyethylene terephthalate) or the 'broken' intermolecular hydrogen bonds (as in nylons). Here we show for Nephila major-ampullate silk how in a biological fibre the spinning conditions affect the interplay between shrinkage and mechanical characteristics. This interaction reveals design principles linking the exceptional properties of silk to its molecular orientation.

  17. [Mechanical properties of wiredrawn Ag-Pd-Cu alloys].

    PubMed

    Hasegawa, T; Miyagawa, Y; Nakamura, K

    1989-01-01

    Nine experimental Ag-Pd-Cu ternary alloys, containing 20-30 wt% Pd and 10-20 wt% Cu, were cast into rods 4.5 mm in diameter using an original vacuum/argon-pressure oxide-free casting technique. Test samples 2.0 mm in diameter were made from the rods by wire-drawing. After softening and hardening heat treatments, mechanical properties (modulus of elasticity, elastic limit, proof stress, tensile strength, elongation, and Vickers hardness) of the samples were measured to analyze the effects of composition and fifteen sets of correlations between the mechanical properties on the condition that few internal casting defects existed. After softening heat treatment, values of hardness and strength increased with increasing Cu and Pd contents, while they increased approximately with increasing Pd content after hardening heat treatment. After softening and hardening heat treatments, tensile strength ranged from 44.4 to 60.7 and from 68.1 to 89.1 kgf/mm2, respectively. Values of elongation were more than 10% even after hardening heat treatment. Fourteen out of fifteen correlation coefficients (r) were statistically significant (p less than 0.01). One of the regression lines derived was as follows. Tensile strength (kgf/mm2) = 9.1 +/- 0.305 Hv (r = 0.990) Moreover, the mechanical properties observed in this investigation were compared with those of ordinarily cast samples with the same compositions.

  18. Multi-axial mechanical properties of human trabecular bone.

    PubMed

    Rincón-Kohli, Liliana; Zysset, Philippe K

    2009-06-01

    In the context of osteoporosis, evaluation of bone fracture risk and improved design of epiphyseal bone implants rely on accurate knowledge of the mechanical properties of trabecular bone. A multi-axial loading chamber was designed, built and applied to explore the compressive multi-axial yield and strength properties of human trabecular bone from different anatomical locations. A thorough experimental protocol was elaborated for extraction of cylindrical bone samples, assessment of their morphology by micro-computed tomography and application of different mechanical tests: torsion, uni-axial traction, uni-axial compression and multi-axial compression. A total of 128 bone samples were processed through the protocol and subjected to one of the mechanical tests up to yield and failure. The elastic data were analyzed using a tensorial fabric-elasticity relationship, while the yield and strength data were analyzed with fabric-based, conewise generalized Hill criteria. For each loading mode and more importantly for the combined results, strong relationships were demonstrated between volume fraction, fabric and the elastic, yield and strength properties of human trabecular bone. Despite the reviewed limitations, the obtained results will help improve the simulation of the damage behavior of human bones and bone-implant systems using the finite element method.

  19. Bulk Mechanical Properties of Single Walled Carbon Nanotube Electrodes

    NASA Astrophysics Data System (ADS)

    Giarra, Matthew; Landi, Brian; Cress, Cory; Raffaelle, Ryne

    2007-03-01

    The unique properties of single walled carbon nanotubes (SWNTs) make them especially well suited for use as electrodes in power devices such as lithium ion batteries, hydrogen fuel cells, solar cells, and supercapacitors. The performances of such devices are expected to be influenced, at least in part, by the mechanical properties of the SWNTs used in composites or in stand alone ``papers.'' Therefore, the elastic moduli and ultimate tensile strengths of SWNT papers were measured as functions of temperature, SWNT purity, SWNT length, and SWNT bundling. The SWNTs used to produce the papers were synthesized in an alexandrite laser vaporization reactor at 1100^oC and purified using conventional acid-reflux conditions. Characterization of the SWNTs was performed using SEM, BET, TGA, and optical and Raman spectroscopy. The purified material was filtered and dried to yield papers of bundled SWNTs which were analyzed using dynamic mechanical analysis (DMA). It was observed that the mechanical properties of acid-refluxed SWNT papers were significantly improved by controlled thermal oxidation and strain-hardening. Elastic moduli of SWNT papers were measured between 3 and 6 GPa. Ultimate (breaking) tensile stresses were measured between 45 and 90 MPa at 1-3% strain. These results and their implications in regard to potential applications in power devices will be discussed.

  20. Reconstruction of Sedimentary Rock Based on MechanicalProperties

    SciTech Connect

    Jin, Guodong; Patzek, Tad W.; Silin, Dmitry B.

    2004-05-04

    We describe a general, physics-based approach to numericalreconstruction of the geometrical structure and mechanical properties ofnatural sedimentary rock in 3D. Our procedure consists of three mainsteps: sedimentation, compaction, and diagenesis, followed by theverification of rock mechanical properties. The dynamic geologicprocesses of grain sedimentation and compaction are simulated by solvinga dimensionless form of Newton's equations of motion for an ensemble ofgrains. The diagenetic rock transformation is modeled using a cementationalgorithm, which accounts for the effect of rock grain size on therelative rate of cement overgrowth. Our emphasis is on unconsolidatedsand and sandstone. The main input parameters are the grain sizedistribution, the final rock porosity, the type and amount of cement andclay minerals, and grain mechanical properties: the inter-grain frictioncoefficient, the cement strength, and the grain stiffness moduli. We usea simulated 2D Fontainebleau sandstone to obtain the grain mechanicalproperties. This Fontainebleau sandstone is also used to study theinitiation, growth, and coalescence of micro-cracks under increasingvertical stress. The box fractal dimension of the micro-crackdistribution, and its variation with the applied stress areestimated.

  1. Mechanical Properties of a Primary Cilium Measured by Resonant Oscillation

    NASA Astrophysics Data System (ADS)

    Resnick, Andrew

    Primary cilia are ubiquitous mammalian cellular substructures implicated in an ever-increasing number of regulatory pathways. The well-established `ciliary hypothesis' states that physical bending of the cilium (for example, due to fluid flow) initiates signaling cascades, yet the mechanical properties of the cilium remain incompletely measured, resulting in confusion regarding the biological significance of flow-induced ciliary mechanotransduction. In this work we measure the mechanical properties of a primary cilium by using an optical trap to induce resonant oscillation of the structure. Our data indicate 1), the primary cilium is not a simple cantilevered beam, 2), the base of the cilium may be modeled as a nonlinear rotatory spring, the linear spring constant `k' of the cilium base calculated to be (4.6 +/- 0.62)*10-12 N/rad and nonlinear spring constant ` α' to be (-1 +/- 0.34) *10-10 N/rad2 , and 3) the ciliary base may be an essential regulator of mechanotransduction signalling. Our method is also particularly suited to measure mechanical properties of nodal cilia, stereocilia, and motile cilia, anatomically similar structures with very different physiological functions.

  2. Relationships between supercontraction and mechanical properties of spider silk

    NASA Astrophysics Data System (ADS)

    Liu, Yi; Shao, Zhengzhong; Vollrath, Fritz

    2005-12-01

    Typical spider dragline silk tends to outperform other natural fibres and most man-made filaments. However, even small changes in spinning conditions can have large effects on the mechanical properties of a silk fibre as well as on its water uptake. Absorbed water leads to significant shrinkage in an unrestrained dragline fibre and reversibly converts the material into a rubber. This process is known as supercontraction and may be a functional adaptation for the silk's role in the spider's web. Supercontraction is thought to be controlled by specific motifs in the silk proteins and to be induced by the entropy-driven recoiling of molecular chains. In analogy, in man-made fibres thermal shrinkage induces changes in mechanical properties attributable to the entropy-driven disorientation of `unfrozen' molecular chains (as in polyethylene terephthalate) or the `broken' intermolecular hydrogen bonds (as in nylons). Here we show for Nephila major-ampullate silk how in a biological fibre the spinning conditions affect the interplay between shrinkage and mechanical characteristics. This interaction reveals design principles linking the exceptional properties of silk to its molecular orientation.

  3. Structure and mechanical properties of Octopus vulgaris suckers.

    PubMed

    Tramacere, Francesca; Kovalev, Alexander; Kleinteich, Thomas; Gorb, Stanislav N; Mazzolai, Barbara

    2014-02-06

    In this study, we investigate the morphology and mechanical features of Octopus vulgaris suckers, which may serve as a model for the creation of a new generation of attachment devices. Octopus suckers attach to a wide range of substrates in wet conditions, including rough surfaces. This amazing feature is made possible by the sucker's tissues, which are pliable to the substrate profile. Previous studies have described a peculiar internal structure that plays a fundamental role in the attachment and detachment processes of the sucker. In this work, we present a mechanical characterization of the tissues involved in the attachment process, which was performed using microindentation tests. We evaluated the elasticity modulus and viscoelastic parameters of the natural tissues (E ∼ 10 kPa) and measured the mechanical properties of some artificial materials that have previously been used in soft robotics. Such a comparison of biological prototypes and artificial material that mimics octopus-sucker tissue is crucial for the design of innovative artificial suction cups for use in wet environments. We conclude that the properties of the common elastomers that are generally used in soft robotics are quite dissimilar to the properties of biological suckers.

  4. Novel F-releasing Composite with Improved Mechanical Properties

    PubMed Central

    Ling, L.; Xu, X.; Choi, G.-Y.; Billodeaux, D.; Guo, G.; Diwan, R.M.

    2009-01-01

    In recent years, the authors have been developing novel fluoride-releasing dental composites containing ternary zirconium fluoride chelates. The aim of this study was to improve the physical and mechanical properties of these composites by improving the formulation of the monomers and photoinitiators. The hypothesis was that reduction of hydrophilic monomers and improvement of the photoinitiators could reduce water sorption and significantly increase the mechanical properties of the composite. The degree of conversion of the composites containing different compositions of photoinitiators was studied by Fourier transform near-infrared spectroscopy (FT-NIR). Ten experimental composites containing different compositions of ethoxylated bisphenol-A dimethacrylate (EBPADMA), 1,6-hexanediol dimethacrylate (HDDMA), triethylene glycol dimethacrylate (TEGDMA), and 2,2-bis[4-(2-hydroxy-3-methacryloyloxypropoxy)phenyl]-propane (BisGMA) were tested for flexural strength, viscosity, and water sorption. The experimental composite containing 20% synthesized fluoride-releasing monomer, 30% BisGMA, 30% EBPADMA, and 20% HDDMA showed significantly higher fluoride release and recharge, but physical and mechanical properties similar to those of the control composite containing 40% BisGMA, 40% EBPADMA, and 20% HDDMA. PMID:19131323

  5. Enhanced mechanical properties of nanocomposites at low graphene content.

    PubMed

    Rafiee, Mohammad A; Rafiee, Javad; Wang, Zhou; Song, Huaihe; Yu, Zhong-Zhen; Koratkar, Nikhil

    2009-12-22

    In this study, the mechanical properties of epoxy nanocomposites with graphene platelets, single-walled carbon nanotubes, and multi-walled carbon nanotube additives were compared at a nanofiller weight fraction of 0.1 +/- 0.002%. The mechanical properties measured were the Young's modulus, ultimate tensile strength, fracture toughness, fracture energy, and the material's resistance to fatigue crack propagation. The results indicate that graphene platelets significantly out-perform carbon nanotube additives. The Young's modulus of the graphene nanocomposite was approximately 31% greater than the pristine epoxy as compared to approximately 3% increase for single-walled carbon nanotubes. The tensile strength of the baseline epoxy was enhanced by approximately 40% with graphene platelets compared to approximately 14% improvement for multi-walled carbon nanotubes. The mode I fracture toughness of the nanocomposite with graphene platelets showed approximately 53% increase over the epoxy compared to approximately 20% improvement for multi-walled carbon nanotubes. The fatigue resistance results also showed significantly different trends. While the fatigue suppression response of nanotube/epoxy composites degrades dramatically as the stress intensity factor amplitude is increased, the reverse effect is seen for graphene-based nanocomposites. The superiority of graphene platelets over carbon nanotubes in terms of mechanical properties enhancement may be related to their high specific surface area, enhanced nanofiller-matrix adhesion/interlocking arising from their wrinkled (rough) surface, as well as the two-dimensional (planar) geometry of graphene platelets.

  6. Mechanical Properties of Calcium Fluoride-Based Composite Materials

    PubMed Central

    Kleczewska, Joanna; Pryliński, Mariusz; Podlewska, Magdalena; Sokołowski, Jerzy; Łapińska, Barbara

    2016-01-01

    Aim of the study was to evaluate mechanical properties of light-curing composite materials modified with the addition of calcium fluoride. The study used one experimental light-curing composite material (ECM) and one commercially available flowable light-curing composite material (FA) that were modified with 0.5–5.0 wt% anhydrous calcium fluoride. Morphology of the samples and uniformity of CaF2 distribution were analyzed using Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). Mechanical properties were tested after 24-hour storage of specimens in dry or wet conditions. Stored dry ECM enriched with 0.5–1.0 wt% CaF2 showed higher tensile strength values, while water storage of all modified ECM specimens decreased their tensile strength. The highest Vickers hardness tested after dry storage was observed for 2.5 wt% CaF2 content in ECM. The addition of 2.0–5.0 wt% CaF2 to FA caused significant decrease in tensile strength after dry storage and overall tensile strength decrease of modified FA specimens after water storage. The content of 2.0 wt% CaF2 in FA resulted in the highest Vickers hardness tested after wet storage. Commercially available composite material (FA), unmodified with fluoride addition, demonstrated overall significantly higher mechanical properties. PMID:28004001

  7. Hierarchically structured ZnO/petal hybrid composites with tuned optoelectronic and mechanical properties.

    PubMed

    Park, Cheolmin; So, Hye-Mi; Jeong, Hyeon Jun; Jeong, Mun Seok; Pippel, Eckhard; Chang, Won Seok; Lee, Seung-Mo

    2014-09-24

    Impressive biophotonic functions of flora in Mother Nature are often attributed to the optical diffraction occurring on hierarchically structured surfaces. The petals, displaying vivid colors, have diverse surface structures. The shapes of those structures alter significantly depending on the part of the petal, and they adjust the intensity of the reflected color and the light absorbance. Here, we added semiconducting properties to those intriguing optical functions arising from the unique surface structures. By means of atomic layer deposition (ALD), we conformally deposited a ZnO layer on the yellow rose petal, which has hierarchical surface structures and exhibits peculiar light absorbance behaviors. The resulting ZnO/petal composites revealed unique optoelectronic characteristics by synergetic effects between the biophotonic structures and inherent semiconducting properties. From several control experiments, we identified that the biophotonic hierarchical structures give rise to strong modulation of the light absorbance. We found that ZnO/petal exhibits superior mechanical stability to the raw petal likely due to the Zn infiltration into the petal. The design inspired by floral creatures with photonic structures and manufactured in the form of composite with mechanical stability and distinctive optoelectronic properties is believed to offer a new paradigm for the preparation of bioinspired photonic devices.

  8. Spec Rekindled-A Simple Torque Correction Mechanics for Transposed Teeth in Conjunction with Pre-adjusted Edgewise Appliance System

    PubMed Central

    Singh, Harpreet; Thakkar, Surbhi

    2016-01-01

    Complete transposition of teeth is a rather rare phenomenon. After correction of transposed and malaligned lateral incisor and canine, attainment of appropriate individual antagonistic tooth torque is indispensable, which many orthodontists consider to be a herculean task. Here, a novel method is proposed which demonstrates the use of Spec reverse torquing auxillary as an effective adjunctive aid in conjunction with pre-adjusted edgewise brackets. PMID:28209017

  9. Spec Rekindled-A Simple Torque Correction Mechanics for Transposed Teeth in Conjunction with Pre-adjusted Edgewise Appliance System.

    PubMed

    Singh, Harpreet; Maurya, Raj Kumar; Thakkar, Surbhi

    2016-12-01

    Complete transposition of teeth is a rather rare phenomenon. After correction of transposed and malaligned lateral incisor and canine, attainment of appropriate individual antagonistic tooth torque is indispensable, which many orthodontists consider to be a herculean task. Here, a novel method is proposed which demonstrates the use of Spec reverse torquing auxillary as an effective adjunctive aid in conjunction with pre-adjusted edgewise brackets.

  10. Mechanical properties of several magnesium and aluminum composites. Final report

    SciTech Connect

    Tsangarakis, N.; Taleghani, B.

    1992-12-01

    Several composites of magnesium and aluminum alloys were tested in order to assess and evaluate their mechanical properties. The magnesium alloys were AZ91 C, ZE41 A, and commercially pure magnesium, reinforced with 40% by volume continuous graphite fiber. The tensile properties of these composites were not superior to those of unreinforced magnesium and estimates of their fracture toughness were low. The matrices of the aluminum composites were 2124-T6, 6061-T4, 2124-T4, and 2219-T4. The reinforcements were either particulate or whiskers of silicon carbide or boron carbide and their volume content was 15% to 30%. The aluminum composites which were reinforced with silicon carbide particulate exhibited improved yield and ultimate tensile stresses, as well as tensile elastic modulus over the unreinforced aluminum alloys. The 2124-T4/B4C/25p composite exhibited the highest ultimate tensile strength which was 511 MPa. The composite which was reinforced with whiskers of silicon carbide exhibited an endurance limit which was 20% higher than that of the matrix alloy. The compressive properties and fracture toughness of some of these aluminum composites were not improved over those of the unreinforced matrix alloy.... Composites, Mechanical properties.

  11. Measurement of the Mechanical Properties of Intact Collagen Fibrils

    NASA Astrophysics Data System (ADS)

    Mercedes, H.; Heim, A.; Matthews, W. G.; Koob, T.

    2006-03-01

    Motivated by the genetic disorder Ehlers-Danlos syndrome (EDS), in which proper collagen synthesis is interrupted, we are investigating the structural and mechanical properties of collagen fibrils. The fibrous glycoprotein collagen is the most abundant protein found in the human body and plays a key role in the extracellular matrix of the connective tissue, the properties of which are altered in EDS. We have selected as our model system the collagen fibrils of the sea cucumber dermis, a naturally mutable tissue. This system allows us to work with native fibrils which have their proteoglycan complement intact, something that is not possible with reconstituted mammalian collagen fibrils. Using atomic force microscopy, we measure, as a function of the concentration of divalent cations, the fibril diameter, its response to force loading, and the changes in its rigidity. Through these experiments, we will shed light on the mechanisms which control the properties of the sea cucumber dermis and hope to help explain the altered connective tissue extracellular matrix properties associated with EDS.

  12. Hierarchical graphene nanoribbon assemblies feature unique electronic and mechanical properties

    NASA Astrophysics Data System (ADS)

    Xu, Zhiping; Buehler, Markus J.

    2009-09-01

    Graphene nanoribbons present intriguing electronic properties due to their characteristic size and edge shape, and have been suggested for a wide range of applications from electronics to electromechanical systems. To bridge the scales from their nanostructural geometry—the key for their unique properties—to the requirements critical for large-scale electronics and device applications, here we propose a de novo hierarchical material assembled from functionalized graphene nanoribbons stabilized through hydrogen bonds, mimicking the structure of beta-sheet proteins. By investigating their mechanical and electronic properties through first principles calculations, we demonstrate that hierarchical graphene nanoribbons not only preserve the unique electronic properties of individual graphene nanoribbons in the bulk, but are also energetically and mechanically stable. Specifically, we find that the energy gap of the bulk material shrinks as the width of the constituting graphene nanoribbons increases. The tuning of bulk material properties through controlling the nanostructure enables the synthesis of a broader class of biomimetic multifunctional mechanomutable and electromutable nanomaterials for electromechanical applications.

  13. Poly(amido-amine)-based hydrogels with tailored mechanical properties and degradation rates for tissue engineering.

    PubMed

    Martello, Federico; Tocchio, Alessandro; Tamplenizza, Margherita; Gerges, Irini; Pistis, Valentina; Recenti, Rossella; Bortolin, Monica; Del Fabbro, Massimo; Argentiere, Simona; Milani, Paolo; Lenardi, Cristina

    2014-03-01

    Poly(amido-amine) (PAA) hydrogels containing the 2,2-bisacrylamidoacetic acid-4-amminobutyl guanidine monomeric unit have a known ability to enhance cellular adhesion by interacting with the arginin-glycin-aspartic acid (RGD)-binding αVβ3 integrin, expressed by a wide number of cell types. Scientific interest in this class of materials has traditionally been hampered by their poor mechanical properties and restricted range of degradation rate. Here we present the design of novel biocompatible, RGD-mimic PAA-based hydrogels with wide and tunable degradation rates as well as improved mechanical and biological properties for biomedical applications. This is achieved by radical polymerization of acrylamide-terminated PAA oligomers in both the presence and absence of 2-hydroxyethylmethacrylate. The degradation rate is found to be precisely tunable by adjusting the PAA oligomer molecular weight and acrylic co-monomer concentration in the starting reaction mixture. Cell adhesion and proliferation tests on Madin-Darby canine kidney epithelial cells show that PAA-based hydrogels have the capacity to promote cell adhesion up to 200% compared to the control. Mechanical tests show higher compressive strength of acrylic chain containing hydrogels compared to traditional PAA hydrogels.

  14. Mechanical properties and failure behavior of phosphorene with grain boundaries

    NASA Astrophysics Data System (ADS)

    Sorkin, V.; Zhang, Y. W.

    2017-02-01

    Using the density-functional tight-binding method, we studied the effect of grain boundaries on the mechanical properties and failure behavior of phosphorene. We found that the high-angle tilt boundaries with a higher density of (5∣7) defect pairs (oriented along the armchair direction) are stronger than the low-angle tilt boundaries with a lower defect density, and similarly the high-angle boundaries with a higher density of (4∣8) defect pairs (oriented along the zigzag direction) are stronger than the low-angle boundaries with a lower defect density. The failure is due to the rupture of the most pre-strained bonds in the heptagons of the (5∣7) defect pair or octagons of the (4∣8) pairs. The high-angle grain boundaries are better at accommodating the pre-strained bonds in heptagon and octagon defects, leading to a higher failure stress and strain. The results cannot be described by a Griffith-type fracture mechanics criterion, since this does not take into account the bond pre-stretching. Interestingly, these anomalous mechanical and failure characteristics of tilt grain boundaries in phosphorene are also shared by graphene and hexagonal boron nitride, signifying that they may be universal for 2D materials. The findings revealed here may be useful in tuning the mechanical properties of phosphorene via defect engineering for specific applications.

  15. Anomalous magnetic properties of mechanically milled cobalt oxide nanoparticles.

    PubMed

    Mishra, S R; Dubenko, I; Losby, J; Ghosh, l K; Khan, M; Ali, N

    2005-12-01

    Defect induced magnetic properties of CoO nanoparticles produced via mechanical ball milling have been assessed by detailed magnetic measurements. A progressive decrease in the particle size and a concomitant increase in the induced strain have been observed with the milling times. The mechanically milled nanoparticles of CoO exhibit anomalous magnetic properties such as FM hysteresis when compared with the unmilled CoO sample. The presence of weak ferromagnetism, with a highest value of magnetization of 0.532 emu/g at 10 K in the 100 h milled sample, is attributed to the uncompensated surface spins resulting from induced surface defects via mechanical milling. The ZFC coercive force, measured at 10 K, increases with milling time reaching a maximum value of 1066 Oe for the 100 h milled sample. The temperature dependent field-cooled (FC) and zero-field-cooled (ZFC) magnetic measurements indicate a presence of an exchange bias field arising from uncompensated moments generated by mechanical strain and the antiferromagnetic (AFM) core. The exchange bias field measured at 10 K reaches a value 210 Oe for the 50 h milled sample and decreases upon prolonged milling. The exchange bias field vanishes at a temperature approximately 200 K, a temperature much lower than the Neel temperature of CoO (TN approximately 291 K). The observed anomalous magnetic behavior of CoO could be interpreted in terms of the exchanged bias FM-AFM model.

  16. Mechanical properties of tricalcium phosphate-fluorapatite-alumina composites

    NASA Astrophysics Data System (ADS)

    Bouslama, N.; Ben Ayed, F.; Bouaziz, J.

    2009-11-01

    This study deals to produce tricalcium phosphate - fluorapatite composites sintering at various temperatures (1300∘ C, 1350∘ C and 1400∘ C) and with different alumina additives amounts (2.5 wt%, 5 wt%, 7.5 wt%, 10 wt% and 20 wt%). The characterization of samples before and after sintering was investigated, using X-ray diffraction, infrared spectroscopy, scanning electronic microscopy and by analysis using 31P and 27Al nuclear magnetic resonance. Mechanical properties have been measured by Brazilian test. The evolution of composite rupture strength was studied as a function of sintering temperature. The effect of sintering on the mechanical properties was measured with the change in composition and microstructure of the composite. The mechanical resistances of composites were increased with the temperatures and with concentrations of alumina. At 1350∘ C, the mechanical resistance reaches its maximum value with 5 wt% Al2O3 (13.6 MPa) whereas the optimum density is about 90% with 2.5 wt% Al2O3.

  17. Length-dependent mechanical properties of gold nanowires

    PubMed Central

    Han, Jing; Fang, Liang; Sun, Jiapeng; Han, Ying; Sun, Kun

    2012-01-01

    The well-known “size effect” is not only related to the diameter but also to the length of the small volume materials. It is unfortunate that the length effect on the mechanical behavior of nanowires is rarely explored in contrast to the intensive studies of the diameter effect. The present paper pays attention to the length-dependent mechanical properties of 〈111〉-oriented single crystal gold nanowires employing the large-scale molecular dynamics simulation. It is discovered that the ultrashort Au nanowires exhibit a new deformation and failure regime-high elongation and high strength. The constrained dislocation nucleation and transient dislocation slipping are observed as the dominant mechanism for such unique combination of high strength and high elongation. A mechanical model based on image force theory is developed to provide an insight to dislocation nucleation and capture the yield strength and nucleation site of first partial dislocation indicated by simulation results. Increasing the length of the nanowires, the ductile-to-brittle transition is confirmed. And the new explanation is suggested in the predict model of this transition. Inspired by the superior properties, a new approach to strengthen and toughen nanowires-hard/soft/hard sandwich structured nanowires is suggested. A preliminary evidence from the molecular dynamics simulation corroborates the present opinion. PMID:23284186

  18. Mechanical Properties of Mineralized Collagen Fibrils As Influenced By Demineralization

    SciTech Connect

    Balooch, M.; Habelitz, S.; Kinney, J.H.; Marshall, S.J.; Marshall, G.W.

    2009-05-11

    Dentin and bone derive their mechanical properties from a complex arrangement of collagen type-I fibrils reinforced with nanocrystalline apatite mineral in extra- and intrafibrillar compartments. While mechanical properties have been determined for the bulk of the mineralized tissue, information on the mechanics of the individual fibril is limited. Here, atomic force microscopy was used on individual collagen fibrils to study structural and mechanical changes during acid etching. The characteristic 67 nm periodicity of gap zones was not observed on the mineralized fibril, but became apparent and increasingly pronounced with continuous demineralization. AFM-nanoindentation showed a decrease in modulus from 1.5 GPa to 50 MPa during acid etching of individual collagen fibrils and revealed that the modulus profile followed the axial periodicity. The nanomechanical data, Raman spectroscopy and SAXS support the hypothesis that intrafibrillar mineral etches at a substantially slower rate than the extrafibrillar mineral. These findings are relevant for understanding the biomechanics and design principles of calcified tissues derived from collagen matrices.

  19. Equivalent mechanical properties of textile monolayers from discrete asymptotic homogenization

    NASA Astrophysics Data System (ADS)

    Goda, Ibrahim; Assidi, Mohamed; Ganghoffer, Jean-François

    2013-12-01

    The determination of the effective mechanical moduli of textiles from mechanical measurements is usually difficult due to their discrete architecture, which makes micromechanical analyses a relevant alternative to access those properties. Micropolar continuum models describing the effective mechanical behavior of woven fabric monolayers are constructed from the homogenization of an identified repetitive pattern of the textile within a representative unit cell. The interwoven yarns within the textile are represented as a network of trusses connected by nodes at their crossover points. These trusses have extensional and bending rigidities to allow for yarn stretching and flexion, and a transverse shear deformation is additionally considered. Interactions between yarns at the crossover points are captured by beam segments connecting the nodes. The woven fabric is modeled after homogenization as an anisotropic planar continuum with two preferred material directions in the mean plane of the textile. Based on the developed methodology, the effective mechanical properties of plain weave and twill are evaluated, including their bending moduli and characteristic flexural lengths. A satisfactory agreement is obtained between the effective moduli obtained by homogenization and numerical values obtained by finite element simulations performed over periodic unit cells.

  20. Mechanical Properties of Type IV Pili in P. Aeruginosa

    NASA Astrophysics Data System (ADS)

    Lu, Shun; Touhami, Ahmed; Scheurwater, Edie; Harvey, Hanjeong; Burrows, Lori; Dutcher, John

    2009-03-01

    Type IV pili (Tfp) are thin flexible protein filaments that extend from the cell membrane of bacteria such as Pseudomonas aeruginosa and Neisseria gonorrhoeae. The mechanical properties of Tfp are of great importance since they allow bacteria to interact with and colonize various surfaces. In the present study, we have used atomic force microscopy (AFM) for both imaging and pulling on Tfp from P. aeruginosa (PAO1) and from its PilA, PilT, and FliC mutants. A single pilus filament was mechanically stretched and the resulting force-extension profiles were fitted using the worm-like-chain (WLC) model. The statistical distributions obtained for contour length, persistence length, and number of pili per bacteria pole, were used to evaluate the mechanical properties of a single pilus and the biogenesis functions of different proteins (PilA, PilT) involved in its assembly and disassembly. Importantly, the persistence length value of ˜ 1 μm measured in the present study, which is consistent with the curvature of the pili observed in our AFM images, is significantly lower than the value of 5 μm reported earlier by Skerker et al. (1). Our results shed new light on the role of mechanical forces that mediate bacteria-surface interactions and biofilm formation. 1- J.M. Skerker and H.C. Berg, Proc. Natl. Acad. Sci. USA, 98, 6901-6904 (2001).

  1. Mechanical and thermal properties of nanoparticle filled epoxy nanocomposites

    NASA Astrophysics Data System (ADS)

    Zhao, Su

    2007-12-01

    One of the potential advantages of nanoparticle filled thermosets is the unique combination of mechanical properties that can be obtained. There have been several reports of improved ductility and toughness in brittle thermoset polymers due to the addition of equiaxed nanoparticles. The mechanisms leading to these improvements, however, are poorly understood. In the present study, a model system of nanoscale alumina filled bisphenol A based epoxy with two interface conditions was used to highlight the mechanisms leading to significant improvements in ductility, toughness, modulus and fatigue crack propagation resistance. It was found that the interfacial condition is critical to controlling the mechanical properties of the nanocomposites. Well-bonded APTES-Al 2O3 (3-aminopropyltriethoxysilane treated alumina) nanoparticle filled epoxy nanocomposites showed significant improvements in tensile ductility (max 39%), fracture toughness (max 26%) and fatigue crack propagation resistance, while exhibiting an increase in modulus and maintained strength. Poorly-bonded NT-Al2O3 (non-treated) nanoparticle filled epoxy nanocomposites only showed improvements in fatigue crack propagation resistance and modulus. Fracture morphology and theoretical predictions were used to study the mechanisms. The key mechanism, that significantly improved the ductility or tensile toughness of the treated nanocomposites and distinguished the treated nanocomposites from the untreated nanocomposites, is crack deflection. Crack deflection occurred much more for the well-bonded nanocomposites due to the stronger particle/matrix adhesion. Furthermore, it was found that crack deflection, interfacial debonding and particle pull-out were critical for composites with a weak interface, but that a stronger interface lead to additional mechanisms of further crack deflection, plastic deformation, microcracking and as a result a further improvement in mechanical properties. In addition, higher thermal

  2. Mechanical properties testing and results for thermal barrier coatings

    NASA Technical Reports Server (NTRS)

    Cruse, Thomas A.; Johnsen, B. P.; Nagy, Andrew

    1995-01-01

    The paper reports on several years of mechanical testing of thermal barrier coatings. The test results were generated to support the development of durability models for the coatings in heat engine applications. The test data that are reviewed include modulus, static strength, and fatigue strength data. The test methods and results are discussed, along with the significant difficulties inherent in mechanical testing of thermal barrier coating materials. The materials include 7 percent wt. and 8 percent wt. yttria, partially stabilized zirconia as well as a cermet material. Both low pressure plasma spray and electron-beam physical vapor deposited coatings were tested. The data indicate the basic trends in the mechanical properties of the coatings over a wide range of isothermal conditions. Some of the trends are correlated with material density.

  3. AFM Manipulation of Viruses: Substrate Interactions and Mechanical Properties

    NASA Astrophysics Data System (ADS)

    Falvo, M. R.; Superfine, R.; Washburn, S.; Finch, M.; Taylor, R. M.; Chi, V.; Brooks, F. P.; Ferrari, F.; Samulski, R.

    1996-03-01

    Using an AFM tip as a manipulation tool, we have translated, rotated, and dissected individual Tobacco Mosaic Virus (TMV) and Adenovirus particles. We have implemented a teleoperation system which allows manual control of the relative tip-sample position while also allowing conventional AFM operation for imaging resulting structure. Using simple tip trajectories to bend the rod-shaped TMV, we observed a variety of resulting structures and mechanical failures. The distributed adhesive interaction between the virus and the sample surface, as well as the local tip-virus interaction affect the distortion in the shape of the virus. Experiments were performed in air as well as in liquid on graphite and Si substrates. The in-liquid experiments allow tuning of the environmental conditions, including osmolarity and pH, which are known to profoundly affect the virus structure. A continuum mechanical model relating mechanical properties to observations provides insight into the constraints for successful nondestructive manipulation.

  4. Size Dependent Mechanical Properties of Monolayer Densely Arranged Polystyrene Nanospheres.

    PubMed

    Huang, Peng; Zhang, Lijing; Yan, Qingfeng; Guo, Dan; Xie, Guoxin

    2016-12-13

    In contrast to macroscopic materials, the mechanical properties of polymer nanospheres show fascinating scientific and application values. However, the experimental measurements of individual nanospheres and quantitative analysis of theoretical mechanisms remain less well performed and understood. We provide a highly efficient and accurate method with monolayer densely arranged honeycomb polystyrene (PS) nanospheres for the quantitatively mechanical characterization of individual nanospheres on the basis of atomic force microscopy (AFM) nanoindentation. The efficiency is improved by 1-2 orders, and the accuracy is also enhanced almost by half-order. The elastic modulus measured in the experiments increases with decreasing radius to the smallest nanospheres (25-35 nm in radius). A core-shell model is introduced to predict the size dependent elasticity of PS nanospheres, and the theoretical prediction agrees reasonably well with the experimental results and also shows a peak modulus value.

  5. Manipulation of individual viruses: friction and mechanical properties.

    PubMed Central

    Falvo, M R; Washburn, S; Superfine, R; Finch, M; Brooks, F P; Chi, V; Taylor, R M

    1997-01-01

    We present our results on the manipulation of individual viruses using an advanced interface for atomic force microscopes (AFMs). We show that the viruses can be dissected, rotated, and translated with great facility. We interpret the behavior of tobacco mosaic virus with a mechanical model that makes explicit the competition between sample-substrate lateral friction and the flexural rigidity of the manipulated object. The manipulation behavior of tobacco mosaic virus on graphite is shown to be consistent with values of lateral friction observed on similar interfaces and the flexural rigidity expected for macromolecular assemblies. The ability to manipulate individual samples broadens the scope of possible studies by providing a means for positioning samples at specific binding sites or predefined measuring devices. The mechanical model provides a framework for interpreting quantitative measurements of virus binding and mechanical properties and for understanding the constraints on the successful, nondestructive AFM manipulation of delicate samples. Images FIGURE 1 FIGURE 2 FIGURE 3 FIGURE 5 PMID:9138585

  6. Spherical agglomerates of lactose with enhanced mechanical properties.

    PubMed

    Lamešić, Dejan; Planinšek, Odon; Lavrič, Zoran; Ilić, Ilija

    2017-01-10

    The aim of this study was to prepare spherical agglomerates of lactose and to evaluate their physicochemical properties, flow properties, particle friability and compaction properties, and to compare them to commercially available types of lactose for direct compression (spray-dried, granulated and anhydrous β-lactose). Porous spherical agglomerates of α-lactose monohydrate with radially arranged prism-like primary particles were prepared exhibiting a high specific surface area. All types of lactose analysed had passable or better flow properties, except for anhydrous β-lactose, which had poor flowability. Particle friability was more pronounced in larger granulated lactose particles; however, particle structure was retained in all samples analysed. The mechanical properties of spherical agglomerates of lactose, in terms of compressibility, established with Walker analysis, and compactibility, established with a compactibility profile, were found to be superior to any commercially available types of lactose. Higher compactibility of spherical agglomerates of lactose is ascribed to significantly higher particle surface area due to a unique internal structure with higher susceptibility to fragmentation.

  7. Mechanical and hydraulic properties of rocks related to induced seismicity

    USGS Publications Warehouse

    Witherspoon, P.A.; Gale, J.E.

    1977-01-01

    Witherspoon, P.A. and Gale, J.E., 1977. Mechanical and hydraulic properties of rocks related to induced seismicity. Eng. Geol., 11(1): 23-55. The mechanical and hydraulic properties of fractured rocks are considered with regard to the role they play in induced seismicity. In many cases, the mechanical properties of fractures determine the stability of a rock mass. The problems of sampling and testing these rock discontinuities and interpreting their non-linear behavior are reviewed. Stick slip has been proposed as the failure mechanism in earthquake events. Because of the complex interactions that are inherent in the mechanical behavior of fractured rocks, there seems to be no simple way to combine the deformation characteristics of several sets of fractures when there are significant perturbations of existing conditions. Thus, the more important fractures must be treated as individual components in the rock mass. In considering the hydraulic properties, it has been customary to treat a fracture as a parallel-plate conduit and a number of mathematical models of fracture systems have adopted this approach. Non-steady flow in fractured systems has usually been based on a two-porosity model, which assumes the primary (intergranular) porosity contributes only to storage and the secondary (fracture) porosity contributes only to the overall conductivity. Using such a model, it has been found that the time required to achieve quasi-steady state flow in a fractured reservoir is one or two orders of magnitude greater than it is in a homogeneous system. In essentially all of this work, the assumption has generally been made that the fractures are rigid. However, it is clear from a review of the mechanical and hydraulic properties that not only are fractures easily deformed but they constitute the main flow paths in many rock masses. This means that one must consider the interaction of mechanical and hydraulic effects. A considerable amount of laboratory and field data is now

  8. An Experimental Investigation of Shale Mechanical Properties Through Drained and Undrained Test Mechanisms

    NASA Astrophysics Data System (ADS)

    Islam, Md. Aminul; Skalle, Paal

    2013-11-01

    Shale mechanical properties are evaluated from laboratory tests after a complex workflow that covers tasks from sampling to testing. Due to the heterogeneous nature of shale, it is common to obtain inconsistent test results when evaluating the mechanical properties. In practice, this variation creates errors in numerical modeling when test results differ significantly, even when samples are from a similar core specimen. This is because the fundamental models are based on the supplied test data and a gap is, therefore, always observed during calibration. Thus, the overall goal of this study was to provide additional insight regarding the organization of the non-linear model input parameters in borehole simulations and to assist other researchers involved in the rock physics-related research fields. To achieve this goal, the following parallel activities were carried out: (1) perform triaxial testing with different sample orientations, i.e., 0°, 45°, 60°, and 90°, including the Brazilian test and CT scans, to obtain a reasonably accurate description of the anisotropic properties of shale; (2) apply an accurate interpretative method to evaluate the elastic moduli of shale; (3) evaluate and quantify the mechanical properties of shale by accounting for the beddings plane, variable confinement pressures, drained and undrained test mechanisms, and cyclic versus monotonic test effects. The experimental results indicate that shale has a significant level of heterogeneity. Postfailure analysis confirmed that the failure plane coincides nicely with the weak bedding plane. The drained Poisson’s ratios were, on average, 40 % or lower than the undrained rates. The drained Young’s modulus was approximately 48 % that of the undrained value. These mechanical properties were significantly impacted by the bedding plane orientation. Based on the Brazilian test, the predicted tensile strength perpendicular to the bedding plane was 12 % lower than the value obtained using the

  9. Size effects on mechanical and thermal properties of thin films

    NASA Astrophysics Data System (ADS)

    Alam, Md Tarekul

    Materials, from electronic to structural, exhibit properties that are sensitive to their composition and internal microstructures such as grain and precipitate sizes, crystalline phases, defects and dopants. Therefore, the research trend has been to obtain fundamental understanding in processing-structure-properties to develop new materials or new functionalities for engineering applications. The advent of nanotechnology has opened a new dimension to this research area because when material size is reduced to nanoscale, properties change significantly from the bulk values. This phenomenon expands the problem to 'size-processing-structure-propertiesfunctionalities'. The reinvigorated research for the last few decades has established size dependency of the material properties such as thermal conductivity, Young's modulus and yield strength, electrical resistivity, photo-conductance etc. It is generally accepted that classical physical laws can be used to scale down the properties up to 25-50 nm length-scale, below which their significant deviation or even breakdown occur. This dissertation probes the size effect from a different perspective by asking the question, if nanoscale size influences one physical domain, why it would not influence the coupling between two or more domains? Or in other words, if both mechanical and thermal properties are different at the nanoscale, can mechanical strain influence thermal conductivity? The hypothesis of size induced multi-domain coupling is therefore the foundation of this dissertation. It is catalyzed by the only few computational studies available in the literature while experimental validations have been non-existent owing to experimental challenges. The objective of this research is to validate this hypothesis, which will open a novel avenue to tune properties and functionalities of materials with the size induced multi-domain coupling. Single domain characterization itself is difficult at the nanoscale due to specimen

  10. Morphology, orientation, and mechanical properties of gelatin films

    SciTech Connect

    Blanton, T.N.; Tsou, A.H.

    1996-12-31

    Gelatin is a polypeptide derived from degradation and disorganization of collagen fibers and is the primary binder in photographic emulsions. Gelatin provides the mechanical integrity and strength to the photographic emulsion allowing for packaging, handling, and photofinishing operations. Gelatin films generated from aqueous-solution casting can exist in a semicrystalline or an amorphous state. When a gelatin solution is cooled below its helix-coil transition temperature, partial renaturation of gelatin to form triple helices can occur. The degree of renaturation in a coated film is dependent upon the drying temperature and the drying rate. During the drying process, gelatin crystals can be formed by lateral association of the triple helices through a mechanism of nucleation and growth of a fringed micelle structure. X-ray scattering techniques have been utilized to examine the morphology and orientation of gelatin films. Based on X-ray diffraction data, it is observed that aggregates of triple-helix rods lie parallel to the film plane but are symmetrically distributed within the film plane. Since a material`s physical and mechanical properties are related to its structure, it is necessary to understand and to characterize the morphological development in gelatin film formation. In this study, an X-ray diffractometer and pole figure goniometer were utilized to examine the structural development and orientation anisotropy in solid-state gelatin films. Also, in this study, the in-plane mechanical properties of a gelatin film were determined from a uniaxial tensile test, and the gelatin film properties in the thickness direction were extracted from an indentation test based on the finite element analysis of the indentation results using a viscoelastic material model.

  11. Mechanical properties of lunar regolith and lunar soil simulant

    NASA Technical Reports Server (NTRS)

    Perkins, Steven W.

    1989-01-01

    Through the Surveyor 3 and 7, and Apollo 11-17 missions a knowledge of the mechanical properties of Lunar regolith were gained. These properties, including material cohesion, friction, in-situ density, grain-size distribution and shape, and porosity, were determined by indirect means of trenching, penetration, and vane shear testing. Several of these properties were shown to be significantly different from those of terrestrial soils, such as an interlocking cohesion and tensile strength formed in the absence of moisture and particle cementation. To characterize the strength and deformation properties of Lunar regolith experiments have been conducted on a lunar soil simulant at various initial densities, fabric arrangements, and composition. These experiments included conventional triaxial compression and extension, direct tension, and combined tension-shear. Experiments have been conducted at low levels of effective confining stress. External conditions such as membrane induced confining stresses, end platten friction and material self weight have been shown to have a dramatic effect on the strength properties at low levels of confining stress. The solution has been to treat these external conditions and the specimen as a full-fledged boundary value problem rather than the idealized elemental cube of mechanics. Centrifuge modeling allows for the study of Lunar soil-structure interaction problems. In recent years centrifuge modeling has become an important tool for modeling processes that are dominated by gravity and for verifying analysis procedures and studying deformation and failure modes. Centrifuge modeling is well established for terrestrial enginering and applies equally as well to Lunar engineering. A brief review of the experiments is presented in graphic and outline form.

  12. DNA motion capture reveals the mechanical properties of DNA at the mesoscale.

    PubMed

    Price, Allen C; Pilkiewicz, Kevin R; Graham, Thomas G W; Song, Dan; Eaves, Joel D; Loparo, Joseph J

    2015-05-19

    Single-molecule studies probing the end-to-end extension of long DNAs have established that the mechanical properties of DNA are well described by a wormlike chain force law, a polymer model where persistence length is the only adjustable parameter. We present a DNA motion-capture technique in which DNA molecules are labeled with fluorescent quantum dots at specific sites along the DNA contour and their positions are imaged. Tracking these positions in time allows us to characterize how segments within a long DNA are extended by flow and how fluctuations within the molecule are correlated. Utilizing a linear response theory of small fluctuations, we extract elastic forces for the different, ∼2-μm-long segments along the DNA backbone. We find that the average force-extension behavior of the segments can be well described by a wormlike chain force law with an anomalously small persistence length.

  13. Mechanical properties of granular materials: A variational approach to grain-scale simulations

    SciTech Connect

    Holtzman, R.; Silin, D.B.; Patzek, T.W.

    2009-01-15

    The mechanical properties of cohesionless granular materials are evaluated from grain-scale simulations. A three-dimensional pack of spherical grains is loaded by incremental displacements of its boundaries. The deformation is described as a sequence of equilibrium configurations. Each configuration is characterized by a minimum of the total potential energy. This minimum is computed using a modification of the conjugate gradient algorithm. Our simulations capture the nonlinear, path-dependent behavior of granular materials observed in experiments. Micromechanical analysis provides valuable insight into phenomena such as hysteresis, strain hardening and stress-induced anisotropy. Estimates of the effective bulk modulus, obtained with no adjustment of material parameters, are in agreement with published experimental data. The model is applied to evaluate the effects of hydrate dissociation in marine sediments. Weakening of the sediment is quantified as a reduction in the effective elastic moduli.

  14. The mechanical properties of human ribs in young adult.

    PubMed

    Pezowicz, Celina; Głowacki, Maciej

    2012-01-01

    A good understanding of thoracic biomechanics is important for complete examination and control of chest behaviour under conditions of physiological and pathological work, and under the impact of external forces leading to traumatic loading of the chest. The purpose of the study was to analyse the mechanical properties of human ribs obtained from individuals under the age of 25 with scoliosis deformation and to correlate them with geometric properties of ribs. Thirty three fragments of ribs (9th to 12th) were tested in three-point bending. Rib fragments were collected intraoperatively from female patients treated for scoliosis in the thoracic, thoracolumbar, and lumbar spine. The results were used to determine the maximum failure force, stiffness, and Young's modulus. A significant relationship was found between the age and elastic modulus of the ribs. The analysis was carried out for two age groups, i.e., between the ages of 10 and 15 and between the ages of 16 and 22, and statistically significant differences were obtained for Young's modulus (p = 0.0001) amounting to, respectively, 2.79 ± 1.34 GPa for the first group and 7.44 ± 2.85 GPa for the second group. The results show a significant impact of age on the mechanical properties of ribs.

  15. Enhancing the Mechanical Properties of Single-Crystal CVD Diamond

    SciTech Connect

    Liang, Q.; Yan, C; Meng, Y; Lai, J; Krasnicki, S; Mao, H; Hemley, R

    2009-01-01

    Approaches for enhancing the strength and toughness of single-crystal diamond produced by chemical vapor deposition (CVD) at high growth rates are described. CVD processes used to grow single-crystal diamond in high density plasmas were modified to incorporate boron and nitrogen. Semi-quantitative studies of mechanical properties were carried out using Vickers indentation techniques. The introduction of boron in single-crystal CVD diamond can significantly enhance the fracture toughness of this material without sacrificing its high hardness ({approx}78 GPa). Growth conditions were varied to investigate its effect on boron incorporation and optical properties by means of photoluminescence, infrared, and ultraviolet-visible absorption spectroscopy. Boron can be readily incorporated into single-crystal diamond by the methods used, but with nitrogen addition, the incorporation of boron was hindered. The spectroscopic measurements indicate that nitrogen and boron coexist in the diamond structure, which helps explain the origin of the enhanced fracture toughness of this material. Further, low pressure/high temperature annealing can enhance the intrinsic hardness of single-crystal CVD diamond by a factor of two without appreciable loss in fracture toughness. This doping and post-growth treatment of diamond may lead to new technological applications that require enhanced mechanical properties of diamond.

  16. Mimicking the mechanical properties of the cell cortex by the self-assembly of an actin cortex in vesicles

    NASA Astrophysics Data System (ADS)

    Luo, Tianzhi; Srivastava, Vasudha; Ren, Yixin; Robinson, Douglas N.

    2014-04-01

    The composite of the actin cytoskeleton and plasma membrane plays important roles in many biological events. Here, we employed the emulsion method to synthesize artificial cells with biomimetic actin cortex in vesicles and characterized their mechanical properties. We demonstrated that the emulsion method provides the flexibility to adjust the lipid composition and protein concentrations in artificial cells to achieve the desired size distribution, internal microstructure, and mechanical properties. Moreover, comparison of the cortical elasticity measured for reconstituted artificial cells to that of real cells, including those manipulated using genetic depletion and pharmacological inhibition, strongly supports that actin cytoskeletal proteins are dominant over lipid molecules in cortical mechanics. Our study indicates that the assembly of biological systems in artificial cells with purified cellular components provides a powerful way to answer biological questions.

  17. Measurement of Mechanical Properties of Cantilever Shaped Materials

    PubMed Central

    Finot, Eric; Passian, Ali; Thundat, Thomas

    2008-01-01

    Microcantilevers were first introduced as imaging probes in Atomic Force Microscopy (AFM) due to their extremely high sensitivity in measuring surface forces. The versatility of these probes, however, allows the sensing and measurement of a host of mechanical properties of various materials. Sensor parameters such as resonance frequency, quality factor, amplitude of vibration and bending due to a differential stress can all be simultaneously determined for a cantilever. When measuring the mechanical properties of materials, identifying and discerning the most influential parameters responsible for the observed changes in the cantilever response are important. We will, therefore, discuss the effects of various force fields such as those induced by mass loading, residual stress, internal friction of the material, and other changes in the mechanical properties of the microcantilevers. Methods to measure variations in temperature, pressure, or molecular adsorption of water molecules are also discussed. Often these effects occur simultaneously, increasing the number of parameters that need to be concurrently measured to ensure the reliability of the sensors. We therefore systematically investigate the geometric and environmental effects on cantilever measurements including the chemical nature of the underlying interactions. To address the geometric effects we have considered cantilevers with a rectangular or circular cross section. The chemical nature is addressed by using cantilevers fabricated with metals and/or dielectrics. Selective chemical etching, swelling or changes in Young's modulus of the surface were investigated by means of polymeric and inorganic coatings. Finally to address the effect of the environment in which the cantilever operates, the Knudsen number was determined to characterize the molecule-cantilever collisions. Also bimaterial cantilevers with high thermal sensitivity were used to discern the effect of temperature variations. When appropriate

  18. 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

  19. Mechanical properties of the beetle elytron, a biological composite material.

    PubMed

    Lomakin, Joseph; Huber, Patricia A; Eichler, Christian; Arakane, Yasuyuki; Kramer, Karl J; Beeman, Richard W; Kanost, Michael R; Gehrke, Stevin H

    2011-02-14

    We determined the relationship between composition and mechanical properties of elytra (modified forewings that are composed primarily of highly sclerotized dorsal and less sclerotized ventral cuticles) from the beetles Tribolium castaneum (red flour beetle) and Tenebrio molitor (yellow mealworm). Elytra of both species have similar mechanical properties at comparable stages of maturation (tanning). Shortly after adult eclosion, the elytron of Tenebrio is ductile and soft with a Young's modulus (E) of 44 ± 8 MPa, but it becomes brittle and stiff with an E of 2400 ± 1100 MPa when fully tanned. With increasing tanning, dynamic elastic moduli (E') increase nearly 20-fold, whereas the frequency dependence of E' diminishes. These results support the hypothesis that cuticle tanning involves cross-linking of components, while drying to minimize plasticization has a lesser impact on cuticular stiffening and frequency dependence. Suppression of the tanning enzymes laccase-2 (TcLac2) or aspartate 1-decarboxylase (TcADC) in Tribolium altered mechanical characteristics consistent with hypotheses that (1) ADC suppression favors formation of melanic pigment with a decrease in protein cross-linking and (2) Lac2 suppression reduces both cuticular pigmentation and protein cross-linking.

  20. Mechanical properties of borophene films: a reactive molecular dynamics investigation

    NASA Astrophysics Data System (ADS)

    Quy Le, Minh; Mortazavi, Bohayra; Rabczuk, Timon

    2016-11-01

    The most recent experimental advances could provide ways for the fabrication of several atomic thick and planar forms of boron atoms. For the first time, we explore the mechanical properties of five types of boron films with various vacancy ratios ranging from 0.1-0.15, using molecular dynamics simulations with ReaxFF force field. It is found that the Young’s modulus and tensile strength decrease with increasing the temperature. We found that boron sheets exhibit an anisotropic mechanical response due to the different arrangement of atoms along the armchair and zigzag directions. At room temperature, 2D Young’s modulus and fracture stress of these five sheets appear in the range 63-136 N m-1 and 12-19 N m-1, respectively. In addition, the strains at tensile strength are in the ranges of 9%-14%, 11%-19%, and 10%-16% at 1, 300, and 600 K, respectively. This investigation not only reveals the remarkable stiffness of 2D boron, but establishes relations between the mechanical properties of the boron sheets to the loading direction, temperature and atomic structures.

  1. Mechanical Property of HVOF Inconel 718 Coating for Aeronautic Repair

    NASA Astrophysics Data System (ADS)

    Lyphout, Christophe; Fasth, Angelica; Nylen, Per

    2014-02-01

    The module of elasticity is one of the most important mechanical properties defining the strength of a material which is a prerequisite to design a component from its early stage of conception to its field of application. When a material is to be thermally sprayed, mechanical properties of the deposited layers differ from the bulk material, mainly due to the anisotropy of the highly textured coating microstructure. The mechanical response of the deposited layers significantly influences the overall performance of the coated component. It is, therefore, of importance to evaluate the effective module of elasticity of the coating. Conventional experimental methods such as microindentation, nanoindentation and four-point bending tests have been investigated and their results vary significantly, mainly due to inhomogeneous characteristics of the coating microstructure. Synchrotron radiation coupled with a tensile test rig has been proposed as an alternative method to determine the coating anisotropic elastic behavior dependence on crystallographic orientations. The investigation was performed on Inconel 718 (IN718) HVOF coatings sprayed on IN718 substrates. Combining these experimental techniques yield a deeper understanding of the nature of the HVOF coating Young's modulus and thus a tool for Design Practice for repair applications.

  2. Study on Thermal and Mechanical Properties of EPDM Insulation

    NASA Astrophysics Data System (ADS)

    Zhang, Zhong-Shui; Xu, Jin-Sheng; Chen, Xiong; Jiang, Jing

    As the most common insulation material of solid rocket motors, thermal and mechanical properties of ethylene propylene diene monomer (EPDM) composite are inspected in the study. Referring to the results of thermogravimetric analysis (TGA), composition and morphology of EPDM composite in different thermal degradation degree are investigated by scanning electron microscope (SEM) to inspect the mechanism of thermal insulation. Mechanical properties of EPDM composite in the state of pyrolysis are investigated by uniaxial tensile tests. At the state of initial pyrolysis, composite belongs to the category of hyperelastic-viscoelastic material. The tendency of tensile strength increased and elongation decreased with increasing of heating temperature. Composite behaves as the linear rule at the state of late pyrolysis, which belongs to the category of bittle. The elasticity modulus of curves are almost the same while the heating temperature ranges from 200°C to 300°C, and then gradually go down. The tensile strength of pyrolytic material reach the highest at the heating temperature of 300°C, and the virgin material has the largest elongation.

  3. Mechanical properties for irradiated face-centred cubic nanocrystalline metals.

    PubMed

    Xiao, X Z; Song, D K; Chu, H J; Xue, J M; Duan, H L

    2015-05-08

    In this paper, a self-consistent plasticity theory is proposed to model the mechanical behaviours of irradiated face-centred cubic nanocrystalline metals. At the grain level, a tensorial crystal model with both irradiation and grain size effects is applied for the grain interior (GI), whereas both grain boundary (GB) sliding with irradiation effect and GB diffusion are considered in modelling the behaviours of GBs. The elastic-viscoplastic self-consistent method with considering grain size distribution is developed to transit the microscopic behaviour of individual grains to the macroscopic properties of nanocrystals (NCs). The proposed theory is applied to model the mechanical properties of irradiated NC copper, and the feasibility and efficiency have been validated by comparing with experimental data. Numerical results show that: (i) irradiation-induced defects can lead to irradiation hardening in the GIs, but the hardening effect decreases with the grain size due to the increasing absorption of defects by GBs. Meanwhile, the absorbed defects would make the GBs softer than the unirradiated case. (ii) There exists a critical grain size for irradiated NC metals, which separates the grain size into the irradiation hardening dominant region (above the critical size) and irradiation softening dominant region (below the critical size). (iii) The distribution of grain size has a significant influence on the mechanical behaviours of both irradiated and unirradiated NCs. The proposed model can offer a valid theoretical foundation to study the irradiation effect on NC materials.

  4. Metallurgical Mechanisms Controlling Mechanical Properties of Aluminum Alloy 2219 Produced by Electron Beam Freeform Fabrication

    NASA Technical Reports Server (NTRS)

    Domack, Marcia S.; Tainger, Karen M.

    2006-01-01

    The electron beam freeform fabrication (EBF3) layer-additive manufacturing process has been developed to directly fabricate complex geometry components. EBF3 introduces metal wire into a molten pool created on the surface of a substrate by a focused electron beam. Part geometry is achieved by translating the substrate with respect to the beam to build the part one layer at a time. Tensile properties demonstrated for electron beam deposited aluminum and titanium alloys are comparable to wrought products, although the microstructures of the deposits exhibit cast features. Understanding the metallurgical mechanisms controlling mechanical properties is essential to maximizing application of the EBF3 process. Tensile mechanical properties and microstructures were examined for aluminum alloy 2219 fabricated over a range of EBF3 process variables. Unique microstructures were observed within the deposited layers and at interlayer boundaries, which varied within the deposit height due to microstructural evolution associated with the complex thermal history experienced during subsequent layer deposition. Microstructures exhibited irregularly shaped grains with interior dendritic structures, described based on overall grain size, morphology, distribution, and dendrite spacing, and were correlated with deposition parameters. Fracture features were compared with microstructural elements to define fracture paths and aid in definition of basic processing-microstructure-property correlations.

  5. Design of an adaptive-passive dynamic vibration absorber composed of a string-mass system equipped with negative stiffness tension adjusting mechanism

    NASA Astrophysics Data System (ADS)

    Acar, M. A.; Yilmaz, C.

    2013-01-01

    In this study, a new adaptive-passive dynamic vibration absorber design is discussed. The proposed design is composed of a string under variable tension with a central mass attachment as an undamped dynamic vibration absorber (DVA), a negative stiffness mechanism as a string tension adjustment aid and a tuning controller to make it adaptive. The dependency of the natural frequencies of this system on the string tension is determined analytically and verified using the finite element method. It is analytically shown that with the help of a negative stiffness element, the tuning force requirement is almost zero throughout the whole operation range. A string tension adjustment algorithm is proposed, which tunes the DVA system depending on the magnitude and frequency of the most dominant component of the vibration signal. Finally, a prototype of the system is built and a series of experiments are conducted on the prototype that validate the analytical and numerical calculations.

  6. [Eco-physiological responses and related adjustment mechanisms of Artemisia ordosica and Caragana korshinskii under different configuration modes to precipitation variation].

    PubMed

    Zhou, Hai-Yan; Wang, Ying-Jue; Fan, Fan; Fan, Heng-Wen

    2013-01-01

    This paper studied the community characteristics of two sand-fixing plants (Artemisia ordosica and Caragana korshinskii) under different configuration modes (1 m x 1 m and 2 m x 2 m) in the Shapotou region of Northwest China as well as the water relation, gas exchange, and their adjustment mechanisms of the plants under natural and artificial precipitation conditions. With the variation of soil water content, the physiological water consumption and growth characteristics of A. ordosica differed from those of C. korshinskii. A. ordosica presented obvious fluctuation in the stomatal conductance, water potential, transpiration rate, photosynthetic rate, and rapid growth, and had higher water consumption than C. korshinskii. However, the variations of the above-mentioned indices of C. korshinskii were relatively slow and more constant. The C. korshinskii had a lower photosynthetic rate but a very high accumulated biomass over years than A. ordosica. The response procedures and adjustment mechanisms of the two plants under water stress differed, with a water-conserving mechanism for A. ordosica and a water-saving mechanism for C. korshinskii. In extremely drought years, the C. korshinskii had stronger capabilities of water-saving and stress tolerance than A. ordosica. It was suggested that the selection of sand-fixing plants should have a view to the benefits in water saving and sand fixation, and also, to the stability of sand-fixing forest.

  7. Mechanical Properties of ZnSe for the FEANICS Module

    NASA Technical Reports Server (NTRS)

    Salem, Jon

    2006-01-01

    Mechanical and physical properties of ZnSe windows to be used with the FEANICS (Flow Enclosure Accommodating Novel Investigations in Combustion of Solids) experiments were measured in order to determine design allowables. In addition, the literature on crack growth properties was summarized. The average Young's modulus, Poisson's ratio, equibiaxial fracture strength, flaw size, grain size, Knoop hardness, Vicker's hardness, and branching constant were 74.3 +/- 0.1 GPa, 0.31, 57.8 +/- 6.5 MPa, 21 4 mm, 43 +/- 9 micron, 0.97 +/- 0.02 GPa, 0.97 +/- 0.02 GPa, and 1.0 +/- 0.1 MPam(exp 0.5), respectively. The properties of current ZnSe made by chemical vapor deposition are in good agreement with those measured in the 1970's. The hardness of CVD ZnSe windows is about one twentieth of the sapphire window being replaced, and about one-sixth of that of window glass. Thus the ZnSe window must be handled with great care. The large grain size relative to the inherent crack size implies the need to use single crystal crack growth properties in the design process. In order to determine the local failure stresses in one of the test specimens, a solution for the stresses between the support ring and the edge of a circular plate load between concentric rings was derived.

  8. Chiropractic Adjustment

    MedlinePlus

    ... structural alignment and improve your body's physical function. Low back pain, neck pain and headache are the most common ... treated. Chiropractic adjustment can be effective in treating low back pain, although much of the research done shows only ...

  9. Adjustment disorder

    MedlinePlus

    ... from other people Skipped heartbeats and other physical complaints Trembling or twitching To have adjustment disorder, you ... ADAM Health Solutions. About MedlinePlus Site Map FAQs Customer Support Get email updates Subscribe to RSS Follow ...

  10. Low-temperature mechanical properties of glass/epoxy laminates

    NASA Astrophysics Data System (ADS)

    Reed, R. P.; Madhukar, M.; Thaicharoenporn, B.; Martovetsky, N. N.

    2014-01-01

    Selected mechanical properties of glass/epoxy laminate candidates for use in the electrical turn and ground insulation of the ITER Central solenoid (CS) modules were measured. Short-beam shear and flexural tests have been conducted on various E-glass cloth weaves/epoxy laminates at 295 and 77 K. Types of glass weave include 1581, 7500, 7781, and 38050, which represent both satin and plain weaves. The epoxy, planned for use for vacuum-pressure impregnation of the CS module, consists of an anhydride-cured bisphenol F resin system. Inter-laminar shear strength, flexural elastic modulus, and flexural strength have been measured. The data indicate that these properties are dependent on the volume percent of glass. Short-beam shear strength was measured as a function of the span-to-thickness ratio for all laminates at 77 K. Comprehensive fractography was conducted to obtain the failure mode of each short-beam shear test sample.

  11. Mechanical properties of biological specimens explored by atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Kasas, S.; Longo, G.; Dietler, G.

    2013-04-01

    The atomic force microscope is a widely used surface scanning apparatus capable of reconstructing at a nanometric scale resolution the 3D morphology of biological samples. Due to its unique sensitivity, it is now increasingly used as a force sensor, to characterize the mechanical properties of specimens with a similar lateral resolution. This unique capability has produced, in the last years, a vast increase in the number of groups that have exploited the versatility and sensitivity of the instrument to explore the nanomechanics of various samples in the fields of biology, microbiology and medicine. In this review we outline the state of the art in this field, reporting the most interesting recent works involving the exploration of the nanomechanical properties of various biological samples.

  12. Low-temperature mechanical properties of glass/epoxy laminates

    SciTech Connect

    Reed, R. P.; Madhukar, M.; Thaicharoenporn, B.; Martovetsky, N. N.

    2014-01-27

    Selected mechanical properties of glass/epoxy laminate candidates for use in the electrical turn and ground insulation of the ITER Central solenoid (CS) modules were measured. Short-beam shear and flexural tests have been conducted on various E-glass cloth weaves/epoxy laminates at 295 and 77 K. Types of glass weave include 1581, 7500, 7781, and 38050, which represent both satin and plain weaves. The epoxy, planned for use for vacuum-pressure impregnation of the CS module, consists of an anhydride-cured bisphenol F resin system. Inter-laminar shear strength, flexural elastic modulus, and flexural strength have been measured. The data indicate that these properties are dependent on the volume percent of glass. Short-beam shear strength was measured as a function of the span-to-thickness ratio for all laminates at 77 K. Comprehensive fractography was conducted to obtain the failure mode of each short-beam shear test sample.

  13. Evaluation of the mechanical and architectural properties of glenoid bone.

    PubMed

    Mimar, Raghad; Limb, David; Hall, Richard M

    2008-01-01

    Successful glenoid fixation in shoulder arthroplasty is partly dependent on the properties of the underlying bone. Therefore, mapping of the glenoid surface and locating the bone with the highest quality, in terms of mechanical properties and morphology, is a key requirement in ensuring effective fixation. To this end, an investigation was undertaken to study the relationship between indentation behavior and the quality of the glenoid bone. Nineteen embalmed glenoids were obtained from human cadavers (mean age at death, 82 years). Each specimen was tested using a cylindrical indentor at 11 predetermined points to investigate load-displacement behavior. Microcomputed tomography analysis was performed to ascertain the bone volume (BV)/total volume (TV) fraction of the trabecular bone and the subchondral thickness. Statistical analysis showed that both strength and modulus varied with indentation position. Significant relationships were found between either strength or modulus and BV/TV or subchondral thickness, although the explained variance was relatively low.

  14. Estimation of mechanical properties of nanomaterials using artificial intelligence methods

    NASA Astrophysics Data System (ADS)

    Vijayaraghavan, V.; Garg, A.; Wong, C. H.; Tai, K.

    2014-09-01

    Computational modeling tools such as molecular dynamics (MD), ab initio, finite element modeling or continuum mechanics models have been extensively applied to study the properties of carbon nanotubes (CNTs) based on given input variables such as temperature, geometry and defects. Artificial intelligence techniques can be used to further complement the application of numerical methods in characterizing the properties of CNTs. In this paper, we have introduced the application of multi-gene genetic programming (MGGP) and support vector regression to formulate the mathematical relationship between the compressive strength of CNTs and input variables such as temperature and diameter. The predictions of compressive strength of CNTs made by these models are compared to those generated using MD simulations. The results indicate that MGGP method can be deployed as a powerful method for predicting the compressive strength of the carbon nanotubes.

  15. Thermodynamics and statistical mechanics. [thermodynamic properties of gases

    NASA Technical Reports Server (NTRS)

    1976-01-01

    The basic thermodynamic properties of gases are reviewed and the relations between them are derived from the first and second laws. The elements of statistical mechanics are then formulated and the partition function is derived. The classical form of the partition function is used to obtain the Maxwell-Boltzmann distribution of kinetic energies in the gas phase and the equipartition of energy theorem is given in its most general form. The thermodynamic properties are all derived as functions of the partition function. Quantum statistics are reviewed briefly and the differences between the Boltzmann distribution function for classical particles and the Fermi-Dirac and Bose-Einstein distributions for quantum particles are discussed.

  16. Mechanical properties of nacre and highly mineralized bone.

    PubMed

    Currey, J D; Zioupos, P; Davies, P; Casino, A

    2001-01-07

    We compared the mechanical properties of 'ordinary' bovine bone, the highly mineralized bone of the rostrum of the whale Mesoplodon densirostris, and mother of pearl (nacre) of the pearl oyster Pinctada margaritifera. The rostrum and the nacre are similar in having very little organic material. However, the rostral bone is much weaker and more brittle than nacre, which in these properties is close to ordinary bone. The ability of nacre to outperform rostral bone is the result of its extremely well-ordered microstructure, with organic material forming a nearly continuous jacket round all the tiny aragonite plates, a design well adapted to produce toughness. In contrast, in the rostrum the organic material, mainly collagen, is poorly organized and discontinuous, allowing the mineral to join up to form, in effect, a brittle stony material.

  17. Matrix-dominated mechanical properties of a fiber composite lamina

    SciTech Connect

    Lyon, R.E.; Schumann, D.L.; DeTeresa, S.J.

    1992-05-18

    Matrix-dominated mechanical properties of unidirectional fiber composite laminae were determined from hoop-wound tube specimens and cylindrical rods fabricated from both wet-filament winding and prepreg material systems. Longitudinal shear modulus and strength as well as transverse Young's modulus, transverse tensile strength, and transverse compressive strength were obtained from a thin-walled tube specimen using a new fixturing design. Lamina properties are presented for several carbon fiber/epoxy composite materials. Longitudinal shear moduli were measured for both tubes and rods in torsion. Results obtained in the linear-elastic regimes above and below the glass transition temperature (Tg) of the matrix phase were compared with micromechanics predictions. Although agreement between predicted and measured shear moduli was reasonable below Tg, large discrepancies were observed when the matrix phase was elastomeric.

  18. Matrix-dominated mechanical properties of a fiber composite lamina

    SciTech Connect

    Lyon, R.E.; Schumann, D.L.; DeTeresa, S.J.

    1992-05-18

    Matrix-dominated mechanical properties of unidirectional fiber composite laminae were determined from hoop-wound tube specimens and cylindrical rods fabricated from both wet-filament winding and prepreg material systems. Longitudinal shear modulus and strength as well as transverse Young`s modulus, transverse tensile strength, and transverse compressive strength were obtained from a thin-walled tube specimen using a new fixturing design. Lamina properties are presented for several carbon fiber/epoxy composite materials. Longitudinal shear moduli were measured for both tubes and rods in torsion. Results obtained in the linear-elastic regimes above and below the glass transition temperature (Tg) of the matrix phase were compared with micromechanics predictions. Although agreement between predicted and measured shear moduli was reasonable below Tg, large discrepancies were observed when the matrix phase was elastomeric.

  19. Mechanical properties of nacre and highly mineralized bone.

    PubMed Central

    Currey, J D; Zioupos, P; Davies, P; Casino, A

    2001-01-01

    We compared the mechanical properties of 'ordinary' bovine bone, the highly mineralized bone of the rostrum of the whale Mesoplodon densirostris, and mother of pearl (nacre) of the pearl oyster Pinctada margaritifera. The rostrum and the nacre are similar in having very little organic material. However, the rostral bone is much weaker and more brittle than nacre, which in these properties is close to ordinary bone. The ability of nacre to outperform rostral bone is the result of its extremely well-ordered microstructure, with organic material forming a nearly continuous jacket round all the tiny aragonite plates, a design well adapted to produce toughness. In contrast, in the rostrum the organic material, mainly collagen, is poorly organized and discontinuous, allowing the mineral to join up to form, in effect, a brittle stony material. PMID:12123292

  20. Mechanical properties of a biodegradable bone regeneration scaffold

    NASA Technical Reports Server (NTRS)

    Porter, B. D.; Oldham, J. B.; He, S. L.; Zobitz, M. E.; Payne, R. G.; An, K. N.; Currier, B. L.; Mikos, A. G.; Yaszemski, M. J.

    2000-01-01

    Poly (Propylene Fumarate) (PPF), a novel, bulk erosion, biodegradable polymer, has been shown to have osteoconductive effects in vivo when used as a bone regeneration scaffold (Peter, S. J., Suggs, L. J., Yaszemski, M. J., Engel, P. S., and Mikos, A. J., 1999, J. Biomater. Sci. Polym. Ed., 10, pp. 363-373). The material properties of the polymer allow it to be injected into irregularly shaped voids in vivo and provide mechanical stability as well as function as a bone regeneration scaffold. We fabricated a series of biomaterial composites, comprised of varying quantities of PPF, NaCl and beta-tricalcium phosphate (beta-TCP), into the shape of right circular cylinders and tested the mechanical properties in four-point bending and compression. The mean modulus of elasticity in compression (Ec) was 1204.2 MPa (SD 32.2) and the mean modulus of elasticity in bending (Eb) was 1274.7 MPa (SD 125.7). All of the moduli were on the order of magnitude of trabecular bone. Changing the level of NaCl from 20 to 40 percent, by mass, did not decrease Ec and Eb significantly, but did decrease bending and compressive strength significantly. Increasing the beta-TCP from 0.25 g/g PPF to 0.5 g/g PPF increased all of the measured mechanical properties of PPF/NVP composites. These results indicate that this biodegradable polymer composite is an attractive candidate for use as a replacement scaffold for trabecular bone.

  1. Mechanical properties of a biodegradable bone regeneration scaffold.

    PubMed

    Porter, B D; Oldham, J B; He, S L; Zobitz, M E; Payne, R G; An, K N; Currier, B L; Mikos, A G; Yaszemski, M J

    2000-06-01

    Poly (Propylene Fumarate) (PPF), a novel, bulk erosion, biodegradable polymer, has been shown to have osteoconductive effects in vivo when used as a bone regeneration scaffold (Peter, S. J., Suggs, L. J., Yaszemski, M. J., Engel, P. S., and Mikos, A. J., 1999, J. Biomater. Sci. Polym. Ed., 10, pp. 363-373). The material properties of the polymer allow it to be injected into irregularly shaped voids in vivo and provide mechanical stability as well as function as a bone regeneration scaffold. We fabricated a series of biomaterial composites, comprised of varying quantities of PPF, NaCl and beta-tricalcium phosphate (beta-TCP), into the shape of right circular cylinders and tested the mechanical properties in four-point bending and compression. The mean modulus of elasticity in compression (Ec) was 1204.2 MPa (SD 32.2) and the mean modulus of elasticity in bending (Eb) was 1274.7 MPa (SD 125.7). All of the moduli were on the order of magnitude of trabecular bone. Changing the level of NaCl from 20 to 40 percent, by mass, did not decrease Ec and Eb significantly, but did decrease bending and compressive strength significantly. Increasing the beta-TCP from 0.25 g/g PPF to 0.5 g/g PPF increased all of the measured mechanical properties of PPF/NVP composites. These results indicate that this biodegradable polymer composite is an attractive candidate for use as a replacement scaffold for trabecular bone.

  2. Thermal and mechanical treatments for nickel and some nickel-base alloys: Effects on mechanical properties

    NASA Technical Reports Server (NTRS)

    Hall, A. M.; Beuhring, V. F.

    1972-01-01

    This report deals with heat treating and working nickel and nickel-base alloys, and with the effects of these operations on the mechanical properties of the materials. The subjects covered are annealing, solution treating, stress relieving, stress equalizing, age hardening, hot working, cold working, combinations of working and heat treating (often referred to as thermomechanical treating), and properties of the materials at various temperatures. The equipment and procedures used in working the materials are discussed, along with the common problems that may be encountered and the precautions and corrective measures that are available.

  3. Scanning Probe Evaluation of Electronic, Mechanical and Structural Material Properties

    NASA Astrophysics Data System (ADS)

    Virwani, Kumar

    2011-03-01

    We present atomic force microscopy (AFM) studies of a range of properties from three different classes of materials: mixed ionic electronic conductors, low-k dielectrics, and polymer-coated magnetic nanoparticles. (1) Mixed ionic electronic conductors are being investigated as novel diodes to drive phase-change memory elements. Their current-voltage characteristics are measured with direct-current and pulsed-mode conductive AFM (C-AFM). The challenges to reliability of the C-AFM method include the electrical integrity of the probe, the sample and the contacts, and the minimization of path capacitance. The role of C-AFM in the optimization of these electro-active materials will be presented. (2) Low dielectric constant (low-k) materials are used in microprocessors as interlayer insulators, a role directly affected by their mechanical performance. The mechanical properties of nanoporous silicate low-k thin films are investigated in a comparative study of nanomechanics measured by AFM and by traditional nanoindentation. Both methods are still undergoing refinement as reliable analytical tools for determining nanomechanical properties. We will focus on AFM, the faster of the two methods, and its developmental challenges of probe shape, cantilever force constant, machine compliance and calibration standards. (3) Magnetic nanoparticles are being explored for their use in patterned media for magnetic storage. Current methods for visualizing the core-shell structure of polymer-coated magnetic nanoparticles include dye-staining the polymer shell to provide contrast in transmission electron microscopy. AFM-based fast force-volume measurements provide direct visualization of the hard metal oxide core within the soft polymer shell based on structural property differences. In particular, the monitoring of adhesion and deformation between the AFM tip and the nanoparticle, particle-by-particle, provides a reliable qualitative tool to visualize core-shell contrast without the use

  4. Mechanical properties of several Fe-Ni meteorites

    SciTech Connect

    Mulford, Roberta N; El - Dasher, Bassem

    2010-10-28

    The strength and elastic constants of meteorites are of increasing interest as predictions of meteorite impacts on earth come within the realm of possibility. In addition, meteorite impacts on extraterrestrial bodies provide an excellent sampling tool for evaluation of planetary compositions and properties. Fe-Ni meteorites provide a well-defined group of materials of fairly uniform composition. Iron-nickel meteorites exhibit a unique lamellar microstructure, a Widmanstatten structure, consisting of small regions with steep-iron-nickel composition gradients. This microstructure is found in the Fe-Ni system only in meteorites, and is believed to arise as a result of slow cooling in a planetary core or other large mass. Meteorites with compositions consisting of between 5 and 17% nickel in iron are termed 'octahedrite,' and further characterized according to the width of the Ni-poor kamacite bands; 'fine,' (0.2-0.5 mm) 'medium,' (0.5-1.3 mm) and 'coarse,' (1.5-3.3 mm). Many meteorites have inclusions and structures indicating that the material has been shocked at some point early in its evolution. Several Iron-nickel meteorites have been examined using Vickers and spherical indentation, x-ray fluorescence, and EBSD. Direct observation of mechanical properties in these highly structured materials provides a valuable supplement to bulk measurements, which frequently exhibit large variation in dynamic properties, even within a single sample. Previous studies of the mechanical properties of a typical iron-nickel meteorite, a Diablo Canyon specimen, indicated that the strength of the composite was higher by almost an order of magnitude than values obtained from laboratory-prepared specimens. Additional meteorite specimens have been examined to establish a range of error on the previously measured yield, to determine the extent to which deformation upon re-entry contributes to yield, and to establish the degree to which the strength varies as a function of microstructure.

  5. Genetic and environmental modification of the mechanical properties of wood

    NASA Astrophysics Data System (ADS)

    Sederoff, R.; Allona, I.; Whetten, R.

    1996-02-01

    Wood is one of the nation's leading raw materials and is used for a wide variety of products, either directly as wood, or as derived materials in pulp and paper. Wood is a biological material and evolved to provide mechanical support and water transport to the early plants that conquered the land. Wood is a tissue that results from the differentiation and programmed cell death of cells that derive from a tissue known as the vascular cambium. The vascular cambium is a thin cylinder of undifferentiated tissue in plant stems and roots that gives rise to several different cell types. Cells that differentiate on the internal side of the cambium form xylem, a tissue composed in major part, of long thin cells that die leaving a network of interconnected cell walls that serve to transport water and to provide mechanical support for the woody plant. The shape and chemical composition of the cells in xylem are well suited for these functions. The structure of cells in xylem determines the mechanical properties of the wood because of the strength derived from the reinforced matrix of the wall. The hydrophobic phenolic surface of the inside of the cell walls is essential to maintain surface tension upon which water transport is based and to resist decay caused by microorganisms. The properties of wood derived from the function of xylem also determine its structural and chemical properties as wood and paper products. Therefore, the physical and chemical properties of wood and paper products also depend on the morphology and composition of the cells from which they are derived. Wood (xylem cell walls) is an anisotropic material, a composite of lignocellulose. It is a matrix of cellulose microfibrils, complexed with hemicelluloses, (carbohydrate polymers which contain sugars other than glucose, both pentoses and hexoses), embedded together in a phenolic matrix of lignin. The high tensile strength of wood in the longitudinal direction, is due to the structure of cellulose and the

  6. How Molecular Structure Affects Mechanical Properties of an Advanced Polymer

    NASA Technical Reports Server (NTRS)

    Nicholson, Lee M.; Whitley, Karen S.; Gates, Thomas S.; Hinkley, Jeffrey A.

    2000-01-01

    density was performed over a range of temperatures below the glass transition temperature. The physical characterization, elastic properties and notched tensile strength all as a function of molecular weight and test temperature were determined. For the uncrosslinked SI material, it was shown that notched tensile strength is a strong function of both temperature and molecular weight, whereas stiffness is only a strong function of temperature. For the crosslinked PETI-SI material, it was shown that the effect of crosslinking significantly enhances the mechanical performance of the low molecular weight material; comparable to that exhibited by the high molecular weight material.

  7. Mechanical properties of oxide dispersion strengthened (ODS) molybdenum alloys

    SciTech Connect

    Bianco, R.; Buckman, R.W. Jr.

    1998-03-01

    Oxide dispersion strengthened molybdenum, Mo-ODS, developed by a proprietary powder metallurgy process, exhibits a creep rupture life at 0.65T{sub m} (1,600 C) of three to five orders of magnitude greater than unalloyed molybdenum, while maintaining ductile fracture behavior at temperatures significantly below room temperature. In comparison, the creep rupture life of the Mo-50Re solid solution strengthened alloy at 1,600 C is only an order of magnitude greater than unalloyed molybdenum. The results of microstructural characterization and thermal stability and mechanical property testing are discussed.

  8. Mechanical Properties of Oil Palm Empty Fruit Bunch Fiber

    NASA Astrophysics Data System (ADS)

    Gunawan, Fergyanto E.; Homma, Hiroomi; Brodjonegoro, Satryo S.; Hudin, Afzer Bin Baseri; Zainuddin, Aryanti Binti

    In tropical countries such as Indonesia and Malaysia, the empty fruit bunches are wastes of the oil palm industry. The wastes are abundantly available and has reached a level that severely threats the environment. Therefore, it is a great need to find useful applications of those waste materials; but firstly, the mechanical properties of the EFB fiber should be quantified. In this work, a small tensile test machine is manufactured, and the tensile test is performed on the EFB fibers. The results show that the strength of the EFB fiber is strongly affected by the fiber diameter; however, the fiber strength is relatively low in comparison to other natural fibers.

  9. Investigation into mechanical properties of bone and its main constituents

    NASA Astrophysics Data System (ADS)

    Evdokimenko, Ekaterina

    Bone is a hierarchically structured natural composite material, consisting of organic phase (type-I collagen), inorganic phase (hydroxyapatite), and water. Studies of the two main bone constituents, utilizing controlled demineralization and deproteinization, can shed light on mineral-collagen interaction which makes bone such a unique biological material. This knowledge is necessary for computational analysis of bone structure to identify preferential sites in the collagen matrix and mineral network that degrade more easily. The main goal of this work is to develop a comprehensive picture of mechanical properties of bone and its main constituents. Following the Introduction, Chapter 2 presents an investigation of microstructure and compressive mechanical properties of bovine femur cortical bone carried out on completely demineralized, completely deproteinized, and untreated bone samples in three anatomical directions. Anisotropic nature of bone was clearly identified in all cases. Extra levels of porosity along with microstructural differences for the three directions were found to be the main sources of the anisotropy. In Chapter 3, a new theoretical model of cortical and trabecular bone as composite materials with hierarchical structure spanning from nanometer (collagen-mineral) level to millimeter (bone) level was developed. Compression testing was performed on untreated, demineralized, and deproteinized cortical and trabecular bovine femur bone samples to verify the model. The experimental data were compared with theoretical predictions; excellent agreement was found between the theory and experiments for all bone phases. Optical microscopy, scanning electron microscopy, and micro-computed tomography techniques were applied to characterize the structure of the samples at multiple length scales and provide further inputs for the modeling. Chapter 4 presents a comparative study of mechanical properties, microstructure, and porosity of mature and young bovine

  10. Electronic, mechanical and dielectric properties of silicane under tensile strain

    NASA Astrophysics Data System (ADS)

    Jamdagni, Pooja; Kumar, Ashok; Sharma, Munish; Thakur, Anil; Ahluwalia, P. K.

    2015-05-01

    The electronic, mechanical and dielectric properties of fully hydrogenated silicene i.e. silicane in stable configuration are studied by means of density functional theory based calculations. The band gap of silicane monolayer can be flexibly reduced to zero when subjected to bi-axial tensile strain, leading to semi-conducting to metallic transition, whereas the static dielectric constant for in-plane polarization increases monotonically with increasing strain. Also the EEL function show the red shift in resonance peak with tensile strain. Our results offer useful insight for the application of silicane monolayer in nano-optical and electronics devices.

  11. Electronic, mechanical and dielectric properties of silicane under tensile strain

    SciTech Connect

    Jamdagni, Pooja Sharma, Munish; Ahluwalia, P. K.; Kumar, Ashok; Thakur, Anil

    2015-05-15

    The electronic, mechanical and dielectric properties of fully hydrogenated silicene i.e. silicane in stable configuration are studied by means of density functional theory based calculations. The band gap of silicane monolayer can be flexibly reduced to zero when subjected to bi-axial tensile strain, leading to semi-conducting to metallic transition, whereas the static dielectric constant for in-plane polarization increases monotonically with increasing strain. Also the EEL function show the red shift in resonance peak with tensile strain. Our results offer useful insight for the application of silicane monolayer in nano-optical and electronics devices.

  12. Optical imaging predicts mechanical properties during decellularization of cardiac tissue.

    PubMed

    Merna, Nick; Robertson, Claire; La, Anh; George, Steven C

    2013-10-01

    Decellularization of xenogeneic hearts offers an acellular, naturally occurring, 3D scaffold that may aid in the development of an engineered human heart tissue. However, decellularization impacts the structural and mechanical properties of the extracellular matrix (ECM), which can strongly influence a cell response during recellularization. We hypothesized that multiphoton microscopy (MPM), combined with image correlation spectroscopy (ICS), could be used to characterize the structural and mechanical properties of the decellularized cardiac matrix in a noninvasive and nondestructive fashion. Whole porcine hearts were decellularized for 7 days by four different solutions of Trypsin and/or Triton. The compressive modulus of the cardiac ECM decreased to < 20% of that of the native tissue in three of the four conditions (range 2-8 kPa); the modulus increased by -150% (range 125-150 kPa) in tissues treated with Triton only. The collagen and elastin content decreased steadily over time for all four decellularization conditions. The ICS amplitude of second harmonic generation (SHG, ASHG) collagen images increased in three of the four decellularization conditions characterized by a decrease in fiber density; the ICS amplitude was approximately constant in tissues treated with Triton only. The ICS ratio (R(SHG), skew) of collagen images increased significantly in the two conditions characterized by a loss of collagen crimping or undulations. The ICS ratio of two-photon fluorescence (TPF, R(TPF)) elastin images decreased in three of the four conditions, but increased significantly in Triton-only treated tissue characterized by retention of densely packed elastin fibers. There were strong linear relationships between both the log of A(SHG) (R(2) = 0.86) and R(TPF) (R(2) = 0.92) with the compressive modulus. Using these variables, a linear model predicts the compressive modulus: E=73.9 × Log(A(SHG))+70.1 × R(TPF) - 131 (R(2) = 0.94). This suggests that the collagen

  13. Nanometer scale mechanical properties of Au(111) thin films

    SciTech Connect

    Salmeron, M.; Folch, A.; Neubauer, G.

    1992-11-01

    The mechanical properties of gold films of (111) orientation were studied as a function of load when contacted by a single asperity Pt-Rh alloy tip. The interaction forces were measured in the direction perpendicular to the surface. The contribution of various types of forces (van der Waals, capillarity from contaminants, and metallic adhesion) in the process of contact was determined. We investigated the elastic and plastic response of the gold film as a function of applied load by examination of the contact area in subsequent imaging with STM and AFM.

  14. Magnetic properties of metastable Fe Pd alloys by mechanical alloying

    NASA Astrophysics Data System (ADS)

    Yabe, Hiromasa; O'Handley, Robert C.; Kuji, Toshiro

    2007-03-01

    Metastable Fe-Pd powder samples with various Pd content were synthesized by mechanical alloying. Their fundamental properties, i.e., structure, magnetization and coercive fore are discussed. The saturation magnetizations of the metastable Fe-Pd powders gradually decreases with increasing Pd content. The coercive forces observed in as-milled samples are all less than 40 Oe. However, some of the heat-treated samples, notably, Pd content around 55 at% with L1 0 structure, shows Hc up to 1589 Oe.

  15. The Effects of Mechanical Transparency on Adjustment to a Complex Visuomotor Transformation at Early and Late Working Age

    ERIC Educational Resources Information Center

    Heuer, Herbert; Hegele, Mathias

    2010-01-01

    Mechanical tools are transparent in the sense that their input-output relations can be derived from their perceptible characteristics. Modern technology creates more and more tools that lack mechanical transparency, such as in the control of the position of a cursor by means of a computer mouse or some other input device. We inquired whether an…

  16. Structural and mechanical properties of Laponite-PEG hybrid films.

    PubMed

    Shikinaka, Kazuhiro; Aizawa, Kazuto; Murakami, Yoshihiko; Osada, Yoshihito; Tokita, Masatoshi; Watanabe, Junji; Shigehara, Kiyotaka

    2012-03-01

    Inorganic/organic hybrids were obtained by the sol-gel type organic modification reaction of Laponite sidewalls with poly(ethylene glycol) (PEG) bearing alkoxysiloxy terminal functionality. By casting an aqueous dispersion of the hybrid, the flexible and transparent hybrid films were obtained. Regardless of the inorganic/organic component ratio, the hybrid film had the ordered structure of Laponite in-plane flat arrays. The mechanical strength of hybrid films was drastically improved by the presence of cross-linking among alkoxysilyl functionalities of PEG terminals and the absence of PEG crystallines. Hybrid films, especially those that consisted of PEG with short chain, showed good mechanical properties that originate from quasi-homogeneous dispersion of components due to anchoring of PEG terminal to Laponite sidewall and interaction of PEG to Laponite surface.

  17. Hydrodynamic interaction induced mechanical properties of SGF reinforced polyethersulfone

    NASA Astrophysics Data System (ADS)

    Munirathnamma, L. M.; Ningaraju, S.; Kumar, K. V. Aneesh; Ravikumar, H. B.

    2016-05-01

    In order to explore the effect of short glass fiber (SGF) reinforcement on the mechanical properties of Polyethersulfone (PES), short glass fibers of different proportion (10 - 40 wt %) are reinforced into PES matrix. The free volume distribution of SGFR-PES composites derived from CONTIN-PALS2 program exhibits the narrow full width at half maximum (FWHM). This is attributed to the improved adhesion resulted by the hydrodynamic interaction between the polymeric chains of PES matrix and SGF. The hydrodynamic interaction parameter (h) decreases as a function of SGF wt% and becomes more negative for 40 wt% SGFR-PES composites suggest the generation of excess friction at the interface. This improves the adhesion between the polymeric chains of PES matrix and SGF and hence the mechanical strength of the SGFR-PES composites.

  18. Mechanical properties of polyimide coated optical fibers at elevated temperatures

    NASA Astrophysics Data System (ADS)

    Huang, Lei; Dyer, Robert S.; Lago, Ralph J.; Stolov, Andrei A.; Li, Jie

    2016-03-01

    High temperature mechanical strength and reliability of optical fibers have become important subjects as optical fibers are increasingly used for harsher environments. Theories and models of fiber mechanical properties established for traditional telecommunications applications may need to be validated for applications at elevated temperatures. In this paper, we describe the test setup for high temperature tensile strength of fiber and report initial results of dynamic tensile strength of polyimide coated optical fiber at 300 and 350ºC for different heating time intervals. The results are compared with room temperature strength data, data available in the literature, and our earlier work on thermogravimetric analysis (TGA) weight loss of the polyimide coating and the observations on surface morphology at elevated temperatures. Interesting observations are discussed and possible explanations are proposed.

  19. Measurement of Anisotropic Mechanical Properties of the Tectorial Membrane

    NASA Astrophysics Data System (ADS)

    Gavara, N.; Chadwick, R. S.

    2009-02-01

    The tectorial membrane (TM) in the cochlea is an anisotropic tissue with a key role in hearing. The TM's structural andmechanical anisotropy is provided by oriented collagen bundles about 1 micron thick. Here we report the three elastic moduli that characterize the TM, as well as the novel technique used to measure the mechanical properties of an anisotropic material. We have measured mechanical anisotropy by combining Atomic Force Microscopy (AFM) and optical tracking of microspheres. The surface Green's tensor for an incompressible anisotropic material was then used to compute the elastic moduli from imposed forces and the resulting surface deformations. Our results suggest a critical role of TM's strong anisotropy by enhancing the cochlear amplifier.

  20. Mechanical properties and biocompatibility of plasma-nitrided laser-cut 316L cardiovascular stents.

    PubMed

    Arslan, Erdem; Iğdil, Mustafa C; Yazici, Hilal; Tamerler, Candan; Bermek, Hakan; Trabzon, Levent

    2008-05-01

    The effect of surface modification of laser-cut 316L cardiovascular stents by low-T plasma nitriding was evaluated in terms of mechanical properties and biocompatibility of the stents. The plasma nitriding was performed at 400, 450 or 500 degrees C using various ratios of nitrogen-hydrogen gas mixtures. The flexibility and radial strength were measured in crimped and expanded state of the stents, respectively. The mechanical properties could be adjusted and improved by plasma nitriding conducted at temperatures lower than 450 degrees C and/or nitrogen content less than 10% in the treatment gas. An osteoblast cell culture model system was utilized to investigate the effect of plasma nitriding of the stents on the biological response towards the stents, using biological criteria such as cell viability, alkaline phosphatase and nitric oxide production. In terms of cell viability and alkaline phosphatase production, the plasma nitriding procedure did not appear to negatively affect the biocompatibility of the 316L steel stents. However, in terms of nitric oxide production that was slightly increased in the presence of the plasma-nitrided stents, an indirect improvement in the biocompatibility could possibly be expected.

  1. Bioinspired composites from cross-linked galactoglucomannan and microfibrillated cellulose: Thermal, mechanical and oxygen barrier properties.

    PubMed

    Oinonen, Petri; Krawczyk, Holger; Ek, Monica; Henriksson, Gunnar; Moriana, Rosana

    2016-01-20

    In this study, new wood-inspired films were developed from microfibrillated cellulose and galactoglucomannan-lignin networks isolated from chemothermomechanical pulping side streams and cross-linked using laccase enzymes. To the best of our knowledge, this is the first time that cross-linked galactoglucomannan-lignin networks have been used for the potential development of composite films inspired by woody-cell wall formation. Their capability as polymeric matrices was assessed based on thermal, structural, mechanical and oxygen permeability analyses. The addition of different amounts of microfibrillated cellulose as a reinforcing agent and glycerol as a plasticizer on the film performances was evaluated. In general, an increase in microfibrillated cellulose resulted in a film with better thermal, mechanical and oxygen barrier performance. However, the presence of glycerol decreased the thermal stability, stiffness and oxygen barrier properties of the films but improved their elongation. Therefore, depending on the application, the film properties can be tailored by adjusting the amounts of reinforcing agent and plasticizer in the film formulation.

  2. Contractile and Mechanical Properties of Epithelia with Perturbed Actomyosin Dynamics

    PubMed Central

    Fischer, Sabine C.; Blanchard, Guy B.; Duque, Julia; Adams, Richard J.; Arias, Alfonso Martinez; Guest, Simon D.; Gorfinkiel, Nicole

    2014-01-01

    Mechanics has an important role during morphogenesis, both in the generation of forces driving cell shape changes and in determining the effective material properties of cells and tissues. Drosophila dorsal closure has emerged as a reference model system for investigating the interplay between tissue mechanics and cellular activity. During dorsal closure, the amnioserosa generates one of the major forces that drive closure through the apical contraction of its constituent cells. We combined quantitation of live data, genetic and mechanical perturbation and cell biology, to investigate how mechanical properties and contraction rate emerge from cytoskeletal activity. We found that a decrease in Myosin phosphorylation induces a fluidization of amnioserosa cells which become more compliant. Conversely, an increase in Myosin phosphorylation and an increase in actin linear polymerization induce a solidification of cells. Contrary to expectation, these two perturbations have an opposite effect on the strain rate of cells during DC. While an increase in actin polymerization increases the contraction rate of amnioserosa cells, an increase in Myosin phosphorylation gives rise to cells that contract very slowly. The quantification of how the perturbation induced by laser ablation decays throughout the tissue revealed that the tissue in these two mutant backgrounds reacts very differently. We suggest that the differences in the strain rate of cells in situations where Myosin activity or actin polymerization is increased arise from changes in how the contractile forces are transmitted and coordinated across the tissue through ECadherin-mediated adhesion. Altogether, our results show that there is an optimal level of Myosin activity to generate efficient contraction and suggest that the architecture of the actin cytoskeleton and the dynamics of adhesion complexes are important parameters for the emergence of coordinated activity throughout the tissue. PMID:24759936

  3. 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

  4. Effects of Zoledronate and Mechanical Loading during Simulated Weightlessness on Bone Structure and Mechanical Properties

    NASA Technical Reports Server (NTRS)

    Scott, R. T.; Nalavadi, M. O.; Shirazi-Fard, Y.; Castillo, A. B.; Alwood, J. S.

    2016-01-01

    Space flight modulates bone remodeling to favor bone resorption. Current countermeasures include an anti-resorptive drug class, bisphosphonates (BP), and high-force loading regimens. Does the combination of anti-resorptives and high-force exercise during weightlessness have negative effects on the mechanical and structural properties of bone? In this study, we implemented an integrated model to mimic mechanical strain of exercise via cyclical loading (CL) in mice treated with the BP Zoledronate (ZOL) combined with hindlimb unloading (HU). Our working hypothesis is that CL combined with ZOL in the HU model induces additive structural and mechanical changes. Thirty-two C57BL6 mice (male,16 weeks old, n8group) were exposed to 3 weeks of either HU or normal ambulation (NA). Cohorts of mice received one subcutaneous injection of ZOL (45gkg), or saline vehicle, prior to experiment. The right tibia was axially loaded in vivo, 60xday to 9N in compression, repeated 3xweek during HU. During the application of compression, secant stiffness (SEC), a linear estimate of slope of the force displacement curve from rest (0.5N) to max load (9.0N), was calculated for each cycle once per week. Ex vivo CT was conducted on all subjects. For ex vivo mechanical properties, non-CL left femurs underwent 3-point bending. In the proximal tibial metaphysis, HU decreased, CL increased, and ZOL increased the cancellous bone volume to total volume ratio by -26, +21, and +33, respectively. Similar trends held for trabecular thickness and number. Ex vivo left femur mechanical properties revealed HU decreased stiffness (-37),and ZOL mitigated the HU stiffness losses (+78). Data on the ex vivo Ultimate Force followed similar trends. After 3 weeks, HU decreased in vivo SEC (-16). The combination of CL+HU appeared additive in bone structure and mechanical properties. However, when HU + CL + ZOL were combined, ZOL had no additional effect (p0.05) on in vivo SEC. Structural data followed this trend with

  5. Properties and mechanisms of olfactory learning and memory.

    PubMed

    Tong, Michelle T; Peace, Shane T; Cleland, Thomas A

    2014-01-01

    Memories are dynamic physical phenomena with psychometric forms as well as characteristic timescales. Most of our understanding of the cellular mechanisms underlying the neurophysiology of memory, however, derives from one-trial learning paradigms that, while powerful, do not fully embody the gradual, representational, and statistical aspects of cumulative learning. The early olfactory system-particularly olfactory bulb-comprises a reasonably well-understood and experimentally accessible neuronal network with intrinsic plasticity that underlies both one-trial (adult aversive, neonatal) and cumulative (adult appetitive) odor learning. These olfactory circuits employ many of the same molecular and structural mechanisms of memory as, for example, hippocampal circuits following inhibitory avoidance conditioning, but the temporal sequences of post-conditioning molecular events are likely to differ owing to the need to incorporate new information from ongoing learning events into the evolving memory trace. Moreover, the shapes of acquired odor representations, and their gradual transformation over the course of cumulative learning, also can be directly measured, adding an additional representational dimension to the traditional metrics of memory strength and persistence. In this review, we describe some established molecular and structural mechanisms of memory with a focus on the timecourses of post-conditioning molecular processes. We describe the properties of odor learning intrinsic to the olfactory bulb and review the utility of the olfactory system of adult rodents as a memory system in which to study the cellular mechanisms of cumulative learning.

  6. Mechanical properties of monocrystalline and polycrystalline monolayer black phosphorus

    NASA Astrophysics Data System (ADS)

    Cao, Pinqiang; Wu, Jianyang; Zhang, Zhisen; Ning, Fulong

    2017-01-01

    The mechanical properties of monocrystalline and polycrystalline monolayer black phosphorus (MBP) are systematically investigated using classic molecular dynamic simulations. For monocrystalline MBP, it is found that the shear strain rate, sample dimensions, temperature, atomic vacancies and applied statistical ensemble affect the shear behaviour. The wrinkled morphology is closely connected with the direction of the in-plane shear, dimensions of the samples, and applied ensembles. Particularly, small samples subjected to loading/unloading of the shear deformation along the armchair direction demonstrate a clear mechanical hysteresis loop. For polycrystalline MBP, the maximum shear stress as a function of the average grain size follows an inverse pseudo Hall-Petch type relationship under an isothermal-isobaric (NPT) ensemble, whereas under a canonical (NVT) ensemble, the maximum shear stress of polycrystalline MBP exhibits a ‘flipped’ behaviour. Furthermore, polycrystalline MBP subjected to uniaxial tension also exhibits a strongly grain size-dependent mechanical response, and it can fail by brittle intergranular and transgranular fractures because of its weaker grain boundary structures and the direction-dependent edge energy, respectively. These findings provide useful insight into the mechanical design of BP for nanoelectronic devices.

  7. Dynamic thermo-mechanical properties of various flowable resin composites

    PubMed Central

    Balthazard, Rémy; Vincent, Marin; Dahoun, Abdessellam; Mortier, Eric

    2016-01-01

    Background This study compared the storage modulus (E’), the loss modulus (E’’) and the loss tangent (tan δ) of various flowable resin composites. Material and Methods Grandio Flow (GRF), GrandioSo Heavy Flow (GHF), Filtek Supreme XTE (XTE) and Filtek Bulk Fill (BUL) flowable resins and Clinpro Sealant (CLI) ultra-flowable pit and fissure sealant resin were used. 25 samples were tested using a dynamical mechanical thermal analysis system in bending mode. Measurements were taken within a temperature range of 10 to 55°C. The results were statistically analyzed using mixed-effect and repeated-measure analysis of variance followed by paired multiple comparisons. Results For all the materials, the E’ values decrease with temperature, whereas the tan δ values increase. Irrespective of the temperature, GHF and GRF present E’ and E’’ values significantly higher than all the other materials and CLI presents values significantly lower than all the other materials. Observation of the values for all the materials reveals a linear progression of the tan δ values with temperature. Conclusions A variation in temperature within a physiological range generates modifications in mechanical properties without damaging the material, however. Filler content in volume terms appears to be the crucial parameter in the mechanical behavior of tested materials. Key words:Dynamic mechanical thermal analysis, elastic modulus, filler content, flowable resin composites, loss modulus, loss tangent. PMID:27957266

  8. Experimental evaluation of stent retrievers’ mechanical properties and effectiveness

    PubMed Central

    Machi, Paolo; Jourdan, Franck; Ambard, Dominique; Reynaud, Cedric; Lobotesis, Kyriakos; Sanchez, Mathieu; Bonafé, Alain; Costalat, Vincent

    2017-01-01

    Background Five randomized controlled trials recently appeared in the literature demonstrating that early mechanical thrombectomy in patients with acute ischemic stroke is significantly related to an improved outcome. Stent retrievers are accepted as the most effective devices for intracranial thrombectomy. Objective To analyze the mechanical properties of stent retrievers, their behavior during retrieval, and interaction with different clots and to identify device features that might correlate with the effectiveness of thrombus removal. Materials and methods All stent retrievers available in France up to June 2015 were evaluated by mechanical and functional tests aimed at investigating the variation of their radial force and their behavior during retrieval. Devices were also tested during in vitro thrombectomies using white and red experimental thrombi produced with human blood. Functional tests and in vitro thrombectomies were conducted using a rigid 3D printed vascular model. Results Mechanical tests showed a variation in radial force during retrieval for each stent. A constant radial force during retrieval was related to continuous cohesion over the vessel wall and a higher rate of clot removal efficacy. All stent retrievers failed when interacting with white large thrombi (diameter ≥6 mm). Conclusions None of the tested devices were effective in removing white clots of large diameter (≥6 mm). Constant radial force during retrieval allows constant cohesion to the vessel wall and pressure over the clot; such features allow for a higher rate of clot removal. PMID:27016318

  9. Decoupling Mechanical and Ion Transport Properties in Polymer Electrolyte Membranes

    NASA Astrophysics Data System (ADS)

    McIntosh, Lucas D.

    Polymer electrolytes are mixtures of a polar polymer and salt, in which the polymer replaces small molecule solvents and provides a dielectric medium so that ions can dissociate and migrate under the influence of an external electric field. Beginning in the 1970s, research in polymer electrolytes has been primarily motivated by their promise to advance electrochemical energy storage and conversion devices, such as lithium ion batteries, flexible organic solar cells, and anhydrous fuel cells. In particular, polymer electrolyte membranes (PEMs) can improve both safety and energy density by eliminating small molecule, volatile solvents and enabling an all-solid-state design of electrochemical cells. The outstanding challenge in the field of polymer electrolytes is to maximize ionic conductivity while simultaneously addressing orthogonal mechanical properties, such as modulus, fracture toughness, or high temperature creep resistance. The crux of the challenge is that flexible, polar polymers best-suited for polymer electrolytes (e.g., poly(ethylene oxide)) offer little in the way of mechanical robustness. Similarly, polymers typically associated with superior mechanical performance (e.g., poly(methyl methacrylate)) slow ion transport due to their glassy polymer matrix. The design strategy is therefore to employ structured electrolytes that exhibit distinct conducting and mechanically robust phases on length scales of tens of nanometers. This thesis reports a remarkably simple, yet versatile synthetic strategy---termed polymerization-induced phase separation, or PIPS---to prepare PEMs exhibiting an unprecedented combination of both high conductivity and high modulus. This performance is enabled by co-continuous, isotropic networks of poly(ethylene oxide)/ionic liquid and highly crosslinked polystyrene. A suite of in situ, time-resolved experiments were performed to investigate the mechanism by which this network morphology forms, and it appears to be tied to the

  10. Digital holography for mechanical vibration measurements in rigid body displacement: elimination of the latter by means of a variable focal length adjustment

    NASA Astrophysics Data System (ADS)

    Pérez-López, Carlos; Mendoza Santoyo, Fernando; Gutiérrez Hernández, David Asael; Muñoz Solis, Silvino

    2008-06-01

    We present our investigation on the separation of mechanical vibrations from rigid body displacements. Pairs of digital holograms acquired between two consecutive time intervals from this type of events produce phase maps that contain both the vibration and rigid body motion information, or even further fully decorrelated phase maps after computer processing. In order to compensate for body displacements, a conjugate object-image experimental arrangement for digital holography is used to measure the mechanical vibrations in a rectangular flat plate. This is achieved by including an extra lens with variable focal length adjustments in front of the typical lens-aperture combination used in the optical head of a digital holographic set up. Out of plane data is obtained from a framed metal plate subjected to a known modal vibration that is also allowed to move perpendicularly to its surface. We will demonstrate that due to the power adjustment of the added lens the angular phase change in the digital hologram from the known object motion allows the separation of the vibration mode at the image plane. The proposed lens addition into a new optical head arrangement in digital holography combined with an a priori knowledge of the rigid body displacement is able to accurately separate the mechanical vibrations making it a promising method in experiments performed under noisy environments. This research suggests the inclusion of adaptive lenses to control the effective focal length when there is a need to separate two distinctive motion types, i.e., vibration from rigid body motion.

  11. Neuro-mechanical adjustments to shod versus barefoot treadmill runs in the acute and delayed stretch-shortening cycle recovery phases.

    PubMed

    Morio, Cedric; Sevrez, Violaine; Chavet, Pascale; Berton, Eric; Nicol, Caroline

    2016-01-01

    In habitually shod recreational runners, we studied the combined influence of footwear and stretch-shortening cycle (SSC) fatigue on treadmill running pattern, paying special attention to neuro-mechanical adjustments in the acute and 2-day delayed recovery periods. The SSC exercise consisted of a series of 25 sub-maximal rebounds on a sledge apparatus repeated until exhaustion. The acute and delayed functional fatigue effects were quantified in a maximal drop jump test. The neuro-mechanical adjustments to fatigue were examined during two submaximal treadmill run tests of 3 min performed either barefoot or with shoes on. Surface electromyographic (EMG) activities, tibial accelerations and kinematics of the right lower limb were recorded during the first and last 15 s of each run. The main result was that neuro-mechanical differences between the shod and barefoot running patterns, classically reported in the absence of fatigue, persisted in the fatigued state. However, in the delayed recovery phase, rearfoot eversion was found to significantly increase in the shod condition. This specific footwear effect is considered as a potential risk factor of overuse injuries in longer runs. Therefore, specific care should be addressed in the delayed recovery phase of SSC fatigue and the use of motion control shoes could be of interest.

  12. Hybrid polyurea elastomers with enzymatic degradation and tunable mechanical properties.

    PubMed

    Sears, Nicholas A; Pena-Galea, Geraldine; Cereceres, Stacy N; Cosgriff-Hernandez, Elizabeth

    2016-01-01

    Herein, we report on the synthesis and characterization of enzymatically labile polyureas for use as a tissue-engineered ligament scaffold. Polyureas were selected due to their excellent tensile properties, fatigue resistance, and highly tunable nature. Incorporation of a collagenase-sensitive peptide into the backbone of the polyurea provided a means to confer cell-responsive degradation to the synthetic polymer. Chemical, morphological, and mechanical testing were used to confirm incorporation of the peptide and characterize polyurea films. Notably, the incorporation of the peptide resulted in an increase in modulus, elongation, and tensile strength. This was attributed to an increase in phase mixing and an increase in hydrogen bonding between the hard and soft segments. Candidate polyureas with varying levels of collagen-mimetic peptide (0%, 10%, 20%) were then subjected to degradation in collagenase media or buffer at 37°C over 4 weeks. Statistically significant decreases in strength and elongation were observed in polyureas with 20% peptide content after collagenase treatment, whereas specimens in phosphate-buffered saline showed no statistically significant difference. These observations confirmed that enzyme-specific degradation was conferred to the polyurea. Overall, these polyureas hold great promise as a material for ligament reconstruction due to the promising mechanical properties and potential for cell-mediated degradation.

  13. Mechanical and structural property analysis of bacterial cellulose composites.

    PubMed

    Dayal, Manmeet Singh; Catchmark, Jeffrey M

    2016-06-25

    Bacterial cellulose (BC) exhibits unique properties including high mechanical strength and high crystallinity. Improvement in the mechanical properties of BC is sought for many applications ranging from food to structural composites to biomedical materials. In this study, different additives including carboxymethyl cellulose (CMC), pectin, gelatin, cornstarch, and corn steep liquor were included in the fermentation media to alter the BC produced. Three different concentrations (1%, 3% and 5%) were chosen for each of the additives, with no additive (0%) as the control. The produced BC was then analyzed to determine tensile and compression modulus. Amongst the tested additives, BC produced in media containing 3% (w/v) pectin had the maximum compressive modulus (142kPa), and BC produced in media containing 1% (w/v) gelatin exhibited the maximum tensile modulus (21MPa). Structural characteristics of BC and BC-additive composites were compared using X-Ray diffraction (XRD). The crystal size and crystallinity of BC was reduced when grown in the presence of CMC and gelatin while pectin only decreased the crystallite size. This suggested that CMC and gelatin may be incorporated into the BC fibril structure. The field emission scanning electron microscopy (FESEM) images showed the increased micro-fibril aggregation in BC pellicles grown in the presence of additives to the culture media.

  14. Dynamic mechanical and swelling properties of maleated hyaluronic acid hydrogels.

    PubMed

    Lin, Hai; Liu, Jun; Zhang, Kai; Fan, Yujiang; Zhang, Xingdong

    2015-06-05

    A series of maleated hyaluronan (MaHA) are developed by modification with maleic anhydride. The degrees of substitution (DS) of MaHA vary between 7% and 75%. The DS of MaHA is both higher and wider than methacrylated HA derivatives (MeHA) reported in the literature. MaHA hydrogels are then prepared by photopolymerization and their dynamic mechanical and swelling properties of the hydrogels are investigated. The results showed that MaHA hydrogels with moderate DS (25%, 50% and 65%) have higher storage modulus and lower equilibrium swelling ratios than those with either low or high DS (7%, 15% and 75%). Theoretical analyses also suggest a similar pattern among hydrogels with different DS. The results confirm that the increased cross-linking density enhances the strength of hydrogels. Meanwhile, the hydrophilicity of introduced groups during modification and the degree of incomplete crosslinking reaction might have negative impact on the mechanical and swelling properties of MaHA hydrogels.

  15. Directionally Solidified Biopolymer Scaffolds: Mechanical Properties and Endothelial Cell Responses

    PubMed Central

    Meghri, Nichols W.; Donius, Amalie E.; Riblett, Benjamin W.; Martin, Elizabeth J.; Clyne, Alisa Morss; Wegst, Ulrike G.K.

    2011-01-01

    Vascularization is a primary challenge in tissue engineering. To achieve it in a tissue scaffold, an environment with the appropriate structural, mechanical, and biochemical cues must be provided enabling endothelial cells to direct blood vessel growth. While biochemical stimuli such as growth factors can be added through the scaffold material, the culture medium, or both, a well-designed tissue engineering scaffold is required to provide the necessary local structural and mechanical cues. As chitosan is a well-known carrier for biochemical stimuli, the focus of this study was on structure-property correlations, to evaluate the effects of composition and processing conditions on the three-dimensional architecture and properties of freeze-cast scaffolds; to establish whether freeze-cast scaffolds are promising candidates as constructs promoting vascularization; and to conduct initial tissue culture studies with endothelial cells on flat substrates of identical compositions as those of the scaffolds to test whether these are biocompatible and promote cell attachment and proliferation. PMID:21544225

  16. Directionally solidified biopolymer scaffolds: Mechanical properties and endothelial cell responses

    NASA Astrophysics Data System (ADS)

    Meghri, Nicholas W.; Donius, Amalie E.; Riblett, Benjamin W.; Martin, Elizabeth J.; Clyne, Alisa Morss; Wegst, Ulrike G. K.

    2010-07-01

    Vascularization is a primary challenge in tissue engineering. To achieve it in a tissue scaffold, an environment with the appropriate structural, mechanical, and biochemical cues must be provided enabling endothelial cells to direct blood vessel growth. While biochemical stimuli such as growth factors can be added through the scaffold material, the culture medium, or both, a well-designed tissue engineering scaffold is required to provide the necessary local structural and mechanical cues. As chitosan is a well-known carrier for biochemical stimuli, the focus of this study was on structure-property correlations, to evaluate the effects of composition and processing conditions on the three-dimensional architecture and properties of freeze-cast scaffolds; to establish whether freeze-east scaffolds are promising candidates as constructs promoting vascularization; and to conduct initial tissue culture studies with endothelial cells on flat substrates of identical compositions as those of the scaffolds to test whether these are biocompatible and promote cell attachment and proliferation.

  17. Directionally Solidified Biopolymer Scaffolds: Mechanical Properties and Endothelial Cell Responses.

    PubMed

    Meghri, Nichols W; Donius, Amalie E; Riblett, Benjamin W; Martin, Elizabeth J; Clyne, Alisa Morss; Wegst, Ulrike G K

    2010-07-01

    Vascularization is a primary challenge in tissue engineering. To achieve it in a tissue scaffold, an environment with the appropriate structural, mechanical, and biochemical cues must be provided enabling endothelial cells to direct blood vessel growth. While biochemical stimuli such as growth factors can be added through the scaffold material, the culture medium, or both, a well-designed tissue engineering scaffold is required to provide the necessary local structural and mechanical cues. As chitosan is a well-known carrier for biochemical stimuli, the focus of this study was on structure-property correlations, to evaluate the effects of composition and processing conditions on the three-dimensional architecture and properties of freeze-cast scaffolds; to establish whether freeze-cast scaffolds are promising candidates as constructs promoting vascularization; and to conduct initial tissue culture studies with endothelial cells on flat substrates of identical compositions as those of the scaffolds to test whether these are biocompatible and promote cell attachment and proliferation.

  18. Mechanical and thermal properties variant of polymer optical fibers

    NASA Astrophysics Data System (ADS)

    Waalib-Singh, Nirmal K.; Sceats, Mark

    2004-09-01

    Building on recent work, this paper describes the viscoelastic behavior of microstructured polymer optical fiber (MPOF). Previously published fixed frequency dynamic mechanical and thermal properties of the two types of POFs; a commercial, C-type and MPOF fiber prototype B are compared here with multi-frequency data. As expected of viscoelastic materials, results reveal a rate dependent behavior of the fibers where storage modulus (E') increases with frequency at each temperature and the glass transition (Tg) shifts to higher temperatures. A lack of a clear (Tg) and least amount of separation between low- and high-temperature transitions at different frequencies in the C fiber clearly indicate the speciality of the fiber; it exhibits extensive elongation or rather strain-softening beyond the draw-temperature-under-load (DrTUL), which is a highly desired property for optimized hot-drawing. Strain-hardening as exhibited by the MPOF B is a brought-forward effect of the mechanical and thermal histories from its macroscopic deformation during preform structuring and fiber-forming. Polymer entanglements that cause an increase in storage modulus and 'resistive' contraction from 60 to 105°C are most likely to be networked in an orderly manner. Demonstrated again in both types of fiber, DrTUL is critical for load bearing drawing.

  19. Effect of collagen on the mechanical properties of hydroxyapatite coatings.

    PubMed

    Ou, Keng-Liang; Chung, Ren-Jei; Tsai, Fu-Yi; Liang, Pei-Yu; Huang, Shih-Wei; Chang, Shou-Yi

    2011-05-01

    In this study, the mechanical properties of bioactive coatings on Ti6Al4V substrates were investigated using instrumented nanoindentation. The aim was to observe the differences in the mechanical properties before and after immersion in collagen solution. The hydroxyapatite coatings were prepared through two processes: self-assembly in simulated body fluid and a hydrothermal method. Sintered hydroxyapatite disks were used as controls. The test samples were then incubated in a dilute collagen solution for 24 hours to produce composite coatings. The materials were investigated using XRD, SEM and nanoindentation. The results showed that the grain sizes of the hydroxyapatite coatings formed using two processes were 1 μm and 10 μm, respectively. The Young's modulus of the pure hydroxyapatite, the disk and the coatings, was 3.6 GPa. After collagen incubation treatment, the composites had a Young's modulus of 7.5 GPa. The results also showed that the strengthening phenomena of collagen were more obvious for homogeneous and small-grain hydroxyapatite coatings. These results suggest that there are similarities between these HAp/collagen composited and natural composite materials, such as teeth and bones.

  20. Mechanical properties of niobium radio-frequency cavities

    DOE PAGES

    Ciovati, Gianluigi; Dhakal, Pashupati; Matalevich, Joseph R.; ...

    2015-07-02

    Radio-frequency cavities made of bulk niobium are one of the components used in modern particle accelerators. The mechanical stability is an important aspect of cavity design, which typically relies on finite-element analysis simulations using material properties from tensile tests on sample. This contribution presents the results of strain and resonant frequency measurements as a function of a uniform pressure up to 722 kPa, applied to single-cell niobium cavities with different crystallographic structure, purity and treatments. In addition, burst tests of high-purity multi-cell cavities with different crystallographic structure have been conducted up to the tensile strength of the material. Finite-element analysismore » of the single-cell cavity geometry is in good agreement with the observed behavior in the elastic regime assuming a Young's modulus value of 88.5 GPa and a Poisson's ratio of 0.4, regardless of crystallographic structure, purity or treatment. However, the measured yield strength and tensile strength depend on crystallographic structure, material purity and treatment. In particular, the results from this study show that the mechanical properties of niobium cavities with large crystals are comparable to those of cavities made of fine-grain niobium.« less

  1. Mechanical properties of niobium radio-frequency cavities

    SciTech Connect

    Ciovati, Gianluigi; Dhakal, Pashupati; Matalevich, Joseph R.; Myneni, Ganapati Rao; Schmidt, A.; Iversen, J.; Matheisen, A.; Singer, W.

    2015-07-02

    Radio-frequency cavities made of bulk niobium are one of the components used in modern particle accelerators. The mechanical stability is an important aspect of cavity design, which typically relies on finite-element analysis simulations using material properties from tensile tests on sample. This contribution presents the results of strain and resonant frequency measurements as a function of a uniform pressure up to 722 kPa, applied to single-cell niobium cavities with different crystallographic structure, purity and treatments. In addition, burst tests of high-purity multi-cell cavities with different crystallographic structure have been conducted up to the tensile strength of the material. Finite-element analysis of the single-cell cavity geometry is in good agreement with the observed behavior in the elastic regime assuming a Young's modulus value of 88.5 GPa and a Poisson's ratio of 0.4, regardless of crystallographic structure, purity or treatment. However, the measured yield strength and tensile strength depend on crystallographic structure, material purity and treatment. In particular, the results from this study show that the mechanical properties of niobium cavities with large crystals are comparable to those of cavities made of fine-grain niobium.

  2. Mechanical properties of continuously spun fibers of carbon nanotubes.

    PubMed

    Motta, Marcelo; Li, Ya-Li; Kinloch, Ian; Windle, Alan

    2005-08-01

    We report on the mechanical properties of fibers consisting of pure carbon nanotube fibers directly spun from an aerogel formed during synthesis by chemical vapor deposition. The continuous withdrawal of product from the gas phase imparts a high commercial potential to the process, either for the production of particularly strong fibers or for the economic production of bulk quantities of carbon nanotubes. Tensile tests were performed on fibers produced from the dissociation of three different hydrocarbons, namely, ethanol, ethylene glycol, and hexane, with a range of iron (catalyst) concentrations. The conditions were chosen to lie within the range known to enable satisfactory continuous spinning, the iron concentration being varied within this range. Increasing proportions of single wall nanotubes were found as the iron concentration was decreased, conditions which also produced fibers of best strength and stiffness. The maximum tensile strength obtained was 1.46 GPa (equivalent to 0.70 N/tex assuming a density of 2.1 g/cm(3)). The experiments indicate that significant improvements in the mechanical properties can be accomplished by optimizing the process conditions.

  3. Electronic and Mechanical Properties of Hydrogenated Irradiated and Amorphous Graphene

    NASA Astrophysics Data System (ADS)

    Weerasinghe, Asanka; Ramasubramaniam, Ashwin; Maroudas, Dimitrios

    Defect engineering and chemical functionalization of graphene are promising routes for fabrication of carbon nanostructures and 2D metamaterials with unique properties and function. Here, we use hydrogenation of irradiated, including irradiation-induced amorphous, graphene as a means of studying chemical functionalization effects on its electronic structure and mechanical response. We use molecular-dynamics simulations based on a reliable bond-order potential to prepare the hydrogenated configurations and carry out dynamic deformation tests at constant strain rate and temperature. Our mechanical tests show that hydrogenation does not affect the ultimate tensile strength (UTS) of the irradiated graphene sheet if the hydrogenated C atoms remain sp2-hybridized; however, upon inducing sp3 hybridization of these C atoms, UTS decreases by about 10 GPa. Furthermore, the fracture strain of the irradiated structure decreases by up to 30% upon hydrogenation independent of the hybridization type. We also report results for the electronic structure of hydrogenated configurations based on a density-functional tight-binding approach and assess the potential for tuning the electronic properties of these defective, functionalized graphenes.

  4. Nanostructured Block Copolymer Solutions and Composites: Mechanical and Structural Properties

    NASA Astrophysics Data System (ADS)

    Walker, Lynn

    2015-03-01

    Self-assembled block copolymer templates are used to control the nanoscale structure of materials that would not otherwise order in solution. In this work, we have developed a technique to use close-packed cubic and cylindrical mesophases of a thermoreversible block copolymer (PEO-PPO-PEO) to impart spatial order on dispersed nanoparticles. The thermoreversible nature of the template allows for the dispersion of particles synthesized outside the template. This feature extends the applicability of this templating method to many particle-polymer systems, including proteins, and also permits a systematic evaluation of the impact of design parameters on the structure and mechanical properties of the nanocomposites. The criteria for forming co-crystals have been characterized using small-angle scatting and the mechanical properties of these soft crystals determined. Numerous crystal structures have been reported for the block copolymer system and we have taken advantage of several to generate soft co-crystals. The result of this templating is spatially ordered nanoparticle arrays embedded within the block copolymer nanostructure. These soft materials can be shear aligned into crystals with long range order and this shear alignment is discussed. Finally, the dynamics of nanoparticles within the nanostructured material are characterized with fluorescence recovery after photobleaching (FRAP). The applications and general behavior of these nanostructured hydrogels are outlined.

  5. Hybrid polyurea elastomers with enzymatic degradation and tunable mechanical properties

    PubMed Central

    Sears, Nicholas A; Pena-Galea, Geraldine; Cereceres, Stacy N; Cosgriff-Hernandez, Elizabeth

    2016-01-01

    Herein, we report on the synthesis and characterization of enzymatically labile polyureas for use as a tissue-engineered ligament scaffold. Polyureas were selected due to their excellent tensile properties, fatigue resistance, and highly tunable nature. Incorporation of a collagenase-sensitive peptide into the backbone of the polyurea provided a means to confer cell-responsive degradation to the synthetic polymer. Chemical, morphological, and mechanical testing were used to confirm incorporation of the peptide and characterize polyurea films. Notably, the incorporation of the peptide resulted in an increase in modulus, elongation, and tensile strength. This was attributed to an increase in phase mixing and an increase in hydrogen bonding between the hard and soft segments. Candidate polyureas with varying levels of collagen-mimetic peptide (0%, 10%, 20%) were then subjected to degradation in collagenase media or buffer at 37°C over 4 weeks. Statistically significant decreases in strength and elongation were observed in polyureas with 20% peptide content after collagenase treatment, whereas specimens in phosphate-buffered saline showed no statistically significant difference. These observations confirmed that enzyme-specific degradation was conferred to the polyurea. Overall, these polyureas hold great promise as a material for ligament reconstruction due to the promising mechanical properties and potential for cell-mediated degradation. PMID:27994846

  6. Biodegradable HEMA-based hydrogels with enhanced mechanical properties.

    PubMed

    Moghadam, Mohamadreza Nassajian; Pioletti, Dominique P

    2016-08-01

    Hydrogels are widely used in the biomedical field. Their main purposes are either to deliver biological active agents or to temporarily fill a defect until they degrade and are followed by new host tissue formation. However, for this latter application, biodegradable hydrogels are usually not capable to sustain any significant load. The development of biodegradable hydrogels presenting load-bearing capabilities would open new possibilities to utilize this class of material in the biomedical field. In this work, an original formulation of biodegradable photo-crosslinked hydrogels based on hydroxyethyl methacrylate (HEMA) is presented. The hydrogels consist of short-length poly(2-hydroxyethyl methacrylate) (PHEMA) chains in a star shape structure, obtained by introducing a tetra-functional chain transfer agent in the backbone of the hydrogels. They are cross-linked with a biodegradable N,O-dimethacryloyl hydroxylamine (DMHA) molecule sensitive to hydrolytic cleavage. We characterized the degradation properties of these hydrogels submitted to mechanical loadings. We showed that the developed hydrogels undergo long-term degradation and specially meet the two essential requirements of a biodegradable hydrogel suitable for load bearing applications: enhanced mechanical properties and low molecular weight degradation products. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 1161-1169, 2016.

  7. Mechanical properties of sand, silt, and clay containing tetrahydrofuran hydrate

    NASA Astrophysics Data System (ADS)

    Yun, T. S.; Santamarina, J. C.; Ruppel, C.

    2007-04-01

    The mechanical behavior of hydrate-bearing sediments subjected to large strains has relevance for the stability of the seafloor and submarine slopes, drilling and coring operations, and the analysis of certain small-strain properties of these sediments (for example, seismic velocities). This study reports on the results of comprehensive axial compression triaxial tests conducted at up to 1 MPa confining pressure on sand, crushed silt, precipitated silt, and clay specimens with closely controlled concentrations of synthetic hydrate. The results show that the stress-strain behavior of hydrate-bearing sediments is a complex function of particle size, confining pressure, and hydrate concentration. The mechanical properties of hydrate-bearing sediments at low hydrate concentration (probably < 40% of pore space) appear to be determined by stress-dependent soil stiffness and strength. At high hydrate concentrations (>50% of pore space), the behavior becomes more independent of stress because the hydrates control both stiffness and strength and possibly the dilative tendency of sediments by effectively increasing interparticle coordination, cementing particles together, and filling the pore space. The cementation contribution to the shear strength of hydrate-bearing sediments decreases with increasing specific surface of soil minerals. The lower the effective confining stress, the greater the impact of hydrate formation on normalized strength.

  8. Measurement of Mechanical Properties of Soft Tissue with Ultrasound Vibrometry

    NASA Astrophysics Data System (ADS)

    Nenadich, I.; Bernal, M.; Greenleaf, J. F.

    The cardiovascular diseases atherosclerosis, coronary artery disease, hypertension and heart failure have been related to stiffening of vessels and myocardium. Noninvasive measurements of mechanical properties of cardiovascular tissue would facilitate detection and treatment of disease in early stages, thus reducing mortality and possibly reducing cost of treatment. While techniques capable of measuring tissue elasticity have been reported, the knowledge of both elasticity and viscosity is necessary to fully characterize mechanical properties of soft tissues. In this article, we summarize the Shearwave Dispersion Ultrasound Vibrometry (SDUV) method developed by our group and report on advances made in characterizing stiffness of large vessels and myocardium. The method uses radiation forceFadiation force to excite shear waves in soft tissue and pulse echo ultrasound to measure the motion. The speed of propagation of shear waves at different frequencies is used to generate dispersions curves for excised porcine left-ventricular free-wall myocardium and carotid arteries. An antisymmetric Lamb wave model was fitted to the LV myocardium dispersion curves to obtain elasticity and viscosity moduli. The results suggest that the speed of shear wave propagation in four orthogonal directions on the surface of the excised myocardium is similar. These studies show that the SDUV method has potential for clinical application in noninvasive quantification of elasticity and viscosity of vessels and myocardium.

  9. Mechanical properties of some polymer materials used for tooth positioners.

    PubMed

    Collett, A R; Cook, W D; West, V C

    1994-10-01

    The chemical composition, thermal behaviour and mechanical properties of three tooth positioner materials, Urethane P1 (P1), White Rubber (WR) and Elastocryl (EL) were investigated. Infra-red spectrophotometry indicated the P1 polyurethane material to be of the polyether type, and EL to be a blend of poly(ethyl methacrylate) and poly(methyl methacrylate) while WR appeared to be filled cis-poly (isoprene) (natural rubber). The glass transition temperature (Tg) for EL was determined as approximately 10 degrees C, and for both P1 and WR the Tg was less than -50 degrees C. The stress relaxation behaviour was assessed in compression by measuring the stress variation with time. The results for all three materials conformed to the superelastic theory of rubber elasticity. EL exhibited both a more rapid rate and higher degree of stress relaxation than did P1 and WR. Recovery from deformation was assessed by compressing cylinders for given periods of time and then measuring the level of reduced residual strain of the material with time. All three materials exhibited significant residual strain (epsilon(t)) over 'clinically relevant' time periods, and the reduced residual strain (epsilon(t)/epsilon(O)) following deformation was greater for EL than P1 or WR. There was some indication that the three materials have some permanent set following deformation. It was concluded that, in considering desirable mechanical properties of tooth positioner materials, EL is the least suitable of the three examined, with none of the materials being ideal.

  10. Mechanical and Electrical Properties of Aluminum/Epoxy Nanocomposites

    NASA Astrophysics Data System (ADS)

    Dong, Lina; Zhou, Wenying; Sui, Xuezhen; Wang, Zijun; Cai, Huiwu; Wu, Peng; Zhang, Yating; Zhou, Anning

    2016-11-01

    Surface-modified self-passivated aluminum (Al) nanoparticles were used for reinforcing epoxy (EP) resin, and the curing behavior, mechanical and electrical properties of the Al/EP nanocomposites were investigated. The incorporation of Al nanoparticles into EP significantly decreases the cure reaction enthalpy of the nancomposites, and the apparent activation energy of Al/EP systems is 64.96 kJ/mol. The coefficient of thermal expansion of the nanocomposites decreases with increasing the Al loading due to the strong interaction between the Al and the EP matrix. The storage modulus of the nanocomposites increases continuously with Al content, whereas, the glass transition temperature declines slightly. With increasing the Al content, the tensile modulus, flexural modulus and compressive modulus of the nanocomposites increase continuously compared with the neat one. The mechanical properties are improved by Al nanoparticles at low Al contents. The best overall dielectric and electrical performance are achieved about at 1 wt.% of Al concentration. The enhanced dielectric breakdown strength is mainly related to the insulating alumina shell on the surface of core Al and the strong interfacial interactions.

  11. Acousto-mechanical and thermal properties of clotted blood.

    PubMed

    Nahirnyak, Volodymyr M; Yoon, Suk Wang; Holland, Christy K

    2006-06-01

    The efficacy of ultrasound-assisted thrombolysis as an adjunct treatment of ischemic stroke is being widely investigated. To determine the role of ultrasound hyperthermia in the process of blood clot disruption, the acousto-mechanical and thermal properties of clotted blood were measured in vitro, namely, density, speed of sound, frequency-dependent attenuation, specific heat, and thermal conductivity. The amplitude coefficient of attenuation of the clots was determined for 120 kHz, 1.0 MHz, and 3.5 MHz ultrasound at room temperature (20 +/- 2 degrees C). The attenuation coefficient ranged from 0.10 to 0.30 Np/cm in porcine clots and from 0.09 to 0.23 Np/cm in human clots. The experimentally determined values of specific heat and thermal conductivity for porcine clotted blood are (3.2 +/- 0.5) x 10(3) J/kg x K and 0.55 +/- 0.13 W/m x K, respectively, and for human clotted blood are (3.5 +/- 0.8) x 10(3) J/kg x K and 0.59 +/- 0.11 W/m x K, respectively. Measurements of the acousto-mechanical and thermal properties of clotted blood can be helpful in theoretical modeling of ultrasound hyperthermia in ultrasound-assisted thrombolysis and other high-intensity focused ultrasound applications.

  12. Mechanical properties of sand, silt, and clay containing tetrahydrofuran hydrate

    USGS Publications Warehouse

    Yun, T.S.; Santamarina, C.J.; Ruppel, C.

    2007-01-01

    The mechanical behavior of hydrate-bearing sediments subjected to large strains has relevance for the stability of the seafloor and submarine slopes, drilling and coring operations, and the analysis of certain small-strain properties of these sediments (for example, seismic velocities). This study reports on the results of comprehensive axial compression triaxial tests conducted at up to 1 MPa confining pressure on sand, crushed silt, precipitated silt, and clay specimens with closely controlled concentrations of synthetic hydrate. The results show that the stress-strain behavior of hydrate-bearing sediments is a complex function of particle size, confining pressure, and hydrate concentration. The mechanical properties of hydrate-bearing sediments at low hydrate concentration (probably 50% of pore space), the behavior becomes more independent of stress because the hydrates control both stiffness and strength and possibly the dilative tendency of sediments by effectively increasing interparticle coordination, cementing particles together, and filling the pore space. The cementation contribution to the shear strength of hydrate-bearing sediments decreases with increasing specific surface of soil minerals. The lower the effective confining stress, the greater the impact of hydrate formation on normalized strength.

  13. Mechanical properties of bimetallic one-dimensional structures

    NASA Astrophysics Data System (ADS)

    Smelova, Ekaterina M.; Sitnikov, Ivan I.; Zelensky, Vladimir S.; Tsysar, Kseniya M.; Andreev, Valery G.; Vdovin, Vladimir A.; Saletsky, Alexander M.

    2016-12-01

    Mechanical properties of freestanding Au-Mn nanowires and Au-Mn nanowire on a Cu (110) substrate are studied with ab initio theoretical approach. The calculations were carried out using the software package Vienna Ab-initio Simulation Package (VASP), which is based on the density functional theory (DFT). It was shown that the breaking force (0.45nN) as well as the interatomic distance at a breaking point in bimetallic nanowire (3.0 Å) are higher than in one component Au wire (0.4 nN and 2.6Å respectively). Relative elongation of 15 % results in a fracture of bimetallic nanowire. We studied the mechanical response of the nanojunction in a form of three-atomic Au chain aligned vertically between two pyramidal gold electrodes and demonstrated that the breaking of nanocontact depends only the interaction between Au atoms in the chain and dependents slightly on the structure and properties of the atomic structure of the electrodes.

  14. Microstructures and mechanical properties of sputtered Cu/Cr multilayers

    SciTech Connect

    Misra, A.; Kung, H.; Mitchell, T.E.; Jervis, T.R.; Nastasi, M.

    1998-03-01

    The microstructures and mechanical properties of Cu/Cr multilayers prepared by sputtering onto {l_brace}100{r_brace} Si substrates at room temperature are presented. The films exhibit columnar grain microstructures with nanoscale grain sizes. The interfaces are planar and abrupt with no intermixing, as expected from the phase diagram. The multilayers tend to adopt a Kurdjumov-Sachs (KS) orientation relationship: {l_brace}110{r_brace}Cr // {l_brace}111{r_brace}Cu, <111>Cr // <110>Cu. The hardness of the multilayered structures, as measured by nanoindentation, increase with decreasing layer thickness for layer thicknesses ranging from 200 nm to 50 nm, whereas for lower thicknesses the hardness of the multilayers is independent of the layer thickness. Dislocation-based models are used to interpret the variation of hardness with layer periodicity. The possible effects of factors such as grain size within the layers, density and composition of films and residual stress in the multilayers are highlighted. Comparisons are made to the mechanical properties of sputtered polycrystalline Cu/Nb multilayers which, like Cu/Cr, exhibit sharp fcc/bcc interfaces with no intermixing and a KS orientation relationship, but have a small shear modulus mismatch.

  15. Mechanical Properties of Gels; Stress from Confined Fluids

    SciTech Connect

    George W. Scherer

    2009-12-01

    Abstract for Grant DE-FG02-97ER45642 Period: 1997-2002 Mechanical Properties of Gels 2002-2008 Stress from Confined Fluids Principal investigator: Prof. George W. Scherer Dept. Civil & Env. Eng./PRISM Eng. Quad. E-319 Princeton, NJ 08544 USA Recipient organization: Trustees of Princeton University 4 New South Princeton, NJ 08544 USA Abstract: The initial stage of this project, entitled Mechanical Properties of Gels, was dedicated to characterizing and explaining the properties of inorganic gels. Such materials, made by sol-gel processing, are of interest for fabrication of films, fibers, optical devices, advanced insulation and other uses. However, their poor mechanical properties are an impediment in some applications, so understanding the origin of these properties could lead to enhanced performance. Novel experimental methods were developed and applied to measure the stiffness and permeability of gels and aerogels. Numerical simulations were developed to reproduce the growth process of the gels, resulting in structures whose mechanical properties matched the measurements. The models showed that the gels are formed by the growth of relatively robust clusters of molecules that are joined by tenuous links whose compliance compromises the stiffness of the structure. Therefore, synthetic methods that enhance the links could significantly increase the rigidity of such gels. The next stage of the project focused on Stress from Confined Fluids. The first problem of interest was the enhanced thermal expansion coefficient of water that we measured in the nanometric pores of cement paste. This could have a deleterious effect on the resistance of concrete to rapid heating in fires, because the excessive thermal expansion of water in the pores of the concrete could lead to spalling and collapse. A series of experiments demonstrated that the expansion of water increases as the pore size decreases. To explain this behavior, we undertook a collaboration with Prof. Stephen

  16. Ultrasonic evaluations of Achilles tendon mechanical properties poststroke

    PubMed Central

    Zhao, Heng; Ren, Yupeng; Wu, Yi-Ning; Liu, Shu Q.; Zhang, Li-Qun

    2009-01-01

    Spasticity, contracture, and muscle weakness are commonly observed poststroke in muscles crossing the ankle. However, it is not clear how biomechanical properties of the Achilles tendon change poststroke, which may affect functions of the impaired muscles directly. Biomechanical properties of the Achilles tendon, including the length and cross-sectional area, in the impaired and unimpaired sides of 10 hemiparetic stroke survivors were evaluated using ultrasonography. Elongation of the Achilles tendon during controlled isometric ramp-and-hold and ramping up then down contractions was determined using a block-matching method. Biomechanical changes in stiffness, Young's modulus, and hysteresis of the Achilles tendon poststroke were investigated by comparing the impaired and unimpaired sides of the 10 patients. The impaired side showed increased tendon length (6%; P = 0.04), decreased stiffness (43%; P < 0.001), decreased Young's modulus (38%; P = 0.005), and increased mechanical hysteresis (1.9 times higher; P < 0.001) compared with the unimpaired side, suggesting Achilles tendon adaptations to muscle spasticity, contracture, and/or disuse poststroke. In vivo quantitative characterizations of the tendon biomechanical properties may help us better understand changes of the calf muscle-tendon unit as a whole and facilitate development of more effective treatments. PMID:19118156

  17. Energetic Particle Synthesis of Metastable Layers for Superior Mechanical Properties

    SciTech Connect

    Follstaedt, D.M.; Knapp, J.A.; Myers, S.M.; Dugger, M.T.; Friedmann, T.A.; Sullivan, J.P.; Monteiro, O.R.; Ager, J.W. III; Brown, I.G.; Christenson, T.

    1998-01-01

    Energetic particle methods have been used to synthesize two metastable layers with superior mechanical properties: amorphous Ni implanted with overlapping Ti and C, and amorphous diamond-like carbon (DLC) formed by vacuum-arc deposition or pulsed laser deposition. Elastic modulus, yield stress and hardness were reliably determined for both materials by fitting finite-element simulations to the observed layer/substrate responses during nanoindentation. Both materials show exceptional properties, i.e., the yield stress of amorphous Ni(Ti,C) exceeds that of hardened steels and other metallic glasses, and the hardness of DLC (up to 88 GPa) approaches that of crystalline diamond (approx. 100 GPa). Tribological performance of the layers during unlubricated sliding contact appears favorable for treating Ni-based micro-electromechanical systems: stick-slip adhesion to Ni is eliminated, giving a low coefficient of friction (approx. 0.3-0.2) and greatly reduced wear. We discuss how energetic particle synthesis is critical to forming these phases and manipulating their properties for optimum performance.

  18. The mechanical properties of phase separated protein droplets

    NASA Astrophysics Data System (ADS)

    Jawerth, Louise; Ijavi, Mahdiye; Patel, Avinash; Saha, Shambaditya; Jülicher, Frank; Hyman, Anthony

    In vivo, numerous proteins associate into liquid compartments by de-mixing from the surrounding solution, similar to oil molecules in water. Many of these proteins and their corresponding liquid compartments play a crucial role in important biological processes, for instance germ line specification in C. elegans or in neurodegenerative diseases such as Amyotrophic lateral sclerosis (ALS). However, despite their importance, very little is known about the physical properties of the resulting droplets as well as the physical mechanisms that control their phase separation from solution. To gain a deeper understanding of these aspects, we study a few such proteins in vitro. When these proteins are purified and added to a physiological buffer, they phase separate into droplets ranging in size from a few to tens of microns with liquid-like behavior similar to their physiological counterparts. By attaching small beads to the surface of the droplets, we can deform the droplets by manipulating the beads directly using optical tweezers. By measuring the force required to deform the droplets we determine their surface tension, elasticity and viscosity as well as the frequency response of these properties. We also measure these properties using passive micro-rheology.

  19. Mechanical and thermal properties of bulk ZrB2

    NASA Astrophysics Data System (ADS)

    Nakamori, Fumihiro; Ohishi, Yuji; Muta, Hiroaki; Kurosaki, Ken; Fukumoto, Ken-ichi; Yamanaka, Shinsuke

    2015-12-01

    ZrB2 appears to have formed in the fuel debris at the Fukushima Daiichi nuclear disaster site, through the reaction between Zircaloy cladding materials and the control rod material B4C. Since ZrB2 has a high melting point of 3518 K, the ceramic has been widely studied as a heat-resistant material. Although various studies on the thermochemical and thermophysical properties have been performed for ZrB2, significant differences exist in the data, possibly due to impurities or the porosity within the studied samples. In the present study, we have prepared a ZrB2 bulk sample with 93.1% theoretical density by sintering ZrB2 powder. On this sample, we have comprehensively examined the thermal and mechanical properties of ZrB2 by the measurement of specific heat, ultrasonic sound velocities, thermal diffusivity, and thermal expansion. Vickers hardness and fracture toughness were also measured and found to be 13-23 GPa and 1.8-2.8 MPa m0.5, respectively. The relationships between these properties were carefully examined in the present study.

  20. Antibacterial properties and mechanisms of gold-silver nanocages

    NASA Astrophysics Data System (ADS)

    Wang, Yulan; Wan, Jiangshan; Miron, Richard J.; Zhao, Yanbin; Zhang, Yufeng

    2016-05-01

    Despite the number of antibiotics used in routine clinical practice, bacterial infections continue to be one of the most important challenges faced in humans. The main concerns arise from the continuing emergence of antibiotic-resistant bacteria and the difficulties faced with the pharmaceutical development of new antibiotics. Thus, advancements in the avenue of novel antibacterial agents are essential. In this study, gold (Au) was combined with silver (Ag), a well-known antibacterial material, to form silver nanoparticles producing a gold-silver alloy structure with hollow interiors and porous walls (gold-silver nanocage). This novel material was promising in antibacterial applications due to its better biocompatibility than Ag nanoparticles, potential in photothermal effects and drug delivery ability. The gold-silver nanocage was then tested for its antibacterial properties and the mechanism involved leading to its antibacterial properties. This study confirms that this novel gold-silver nanocage has broad-spectrum antibacterial properties exerting its effects through the destruction of the cell membrane, production of reactive oxygen species (ROS) and induction of cell apoptosis. Therefore, we introduce a novel gold-silver nanocage that serves as a potential nanocarrier for the future delivery of antibiotics.

  1. Ultrasonic evaluations of Achilles tendon mechanical properties poststroke.

    PubMed

    Zhao, Heng; Ren, Yupeng; Wu, Yi-Ning; Liu, Shu Q; Zhang, Li-Qun

    2009-03-01

    Spasticity, contracture, and muscle weakness are commonly observed poststroke in muscles crossing the ankle. However, it is not clear how biomechanical properties of the Achilles tendon change poststroke, which may affect functions of the impaired muscles directly. Biomechanical properties of the Achilles tendon, including the length and cross-sectional area, in the impaired and unimpaired sides of 10 hemiparetic stroke survivors were evaluated using ultrasonography. Elongation of the Achilles tendon during controlled isometric ramp-and-hold and ramping up then down contractions was determined using a block-matching method. Biomechanical changes in stiffness, Young's modulus, and hysteresis of the Achilles tendon poststroke were investigated by comparing the impaired and unimpaired sides of the 10 patients. The impaired side showed increased tendon length (6%; P = 0.04), decreased stiffness (43%; P < 0.001), decreased Young's modulus (38%; P = 0.005), and increased mechanical hysteresis (1.9 times higher; P < 0.001) compared with the unimpaired side, suggesting Achilles tendon adaptations to muscle spasticity, contracture, and/or disuse poststroke. In vivo quantitative characterizations of the tendon biomechanical properties may help us better understand changes of the calf muscle-tendon unit as a whole and facilitate development of more effective treatments.

  2. Microstructure and Mechanical Properties of Composite Actin Networks

    NASA Astrophysics Data System (ADS)

    Gardel, Margaret; Shin, Jennifer; Mahadevan, L.; Matsudaira, Paul; Weitz, D. A.

    2003-03-01

    There exits a family of actin-binding proteins (ABPs) and each protein has a distinct function for bundling, networking, gelating, capping, or simply binding to actin. Whether actin serves as a structural or motile component, its mechanical properties are determined by its degree and kinds of association with different ABPs and these properties are often closely related to its functional needs. For instance, in a cell actin is highly crosslinked with multiple ABPs (fimbrin, alpha-actinin, etc.) to generate thrust and strength for locomotion. In the acrosomal reaction of horseshoe crab sperm, actin exists as a bundle of preassembled filaments crosslinked with scruin to form a rigid structure to penetrate into an egg without yielding. We study the effects three different ABPs (scruin,fimbrin and alpha-actinin) have on the rheology and microstructure of actin networks using multiparticle tracking, imaging, and bulk rheology. From these experiments we can deduce how an evolving microstructure affects the bulk rheological properties and the role different concentrations and kinds of ABPs have in these changes.

  3. Designing the Structure of Carbon Fibers for Optimal Mechanical Properties

    SciTech Connect

    Ozcan, Soydan; Vautard, Frederic; Naskar, Amit K

    2014-01-01

    Carbon fiber manufacturing follows generic processing steps: formation of thermoplastic fibers, stabilization, and carbonization. The final structures and end properties of the carbon fiber can differ significantly depending on the precursor chemistry and the associated processing sciences. Polyacrylonitrile (PAN) and mesophase pitch are the predominant precursors used in the production of carbon fibers. PAN-based carbon fibers consist of nanocrystalline graphitic domains typically 1.5 5 nm in size surrounded by amorphous carbon; in contrast, pitch-based carbon fibers are 10 50 nm crystallites with the graphitic (002) planes mostly aligned parallel to the fiber axis. It has been seen that the skin core structure of PAN-based carbon fibers plays a significant role in their mechanical properties. Designing a more homogenous carbon fiber microstructure by controlling the starting polymer and process parameters results in a different set of tensile strengths and elastic moduli. In this study the microstructural defect distribution (0.1 200 nm), measured by small-angle X-ray scattering, was shown to be directly related to the tensile strength of the carbon fibers. Here the formation of carbon structures from various polymer precursors is reviewed. Such a comprehensive understanding offers the opportunity to design carbon fiber microstructures with improved properties and to ultimately create new types of carbon fibers from alternative precursors at reduced cost.

  4. Improving the mechanical properties of nano-hydroxyapatite

    NASA Astrophysics Data System (ADS)

    Khanal, Suraj Prasad

    Hydroxyapatite (HAp) is an ideal bioactive material that is used in orthopedics. Chemical composition and crystal structure properties of HAp are similar to the natural bone hence it promotes bone growth. However, its mechanical properties of synthetic HAp are not sufficient for major load-bearing bone replacement. The potential of improving the mechanical properties of synthetic hydroxyapatite (HAp) by incorporating carboxyl functionalized single walled carbon nanotubes (CfSWCNT) and polymerized epsilon-caprolactam (nylon) is studied. The fracture toughness, tensile strength, Young's modulus, stiffness and fracture energy were studied for a series of HAp samples with CfSWCNT concentrations varying from 0 to 1.5 wt. % without, and with nylon addition. X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Differential Scanning Calorimetry (DSC) were used to characterize the samples. The fracture toughness and tensile test was performed under the standard protocol of ASTM D5045 and ASTM D638-02a respectively. Reproducible maximum values of (3.60 +/- 0.3) MPa.m1/2 for fracture toughness and 65.38 MPa for tensile strength were measured for samples containing 1 wt. % CfSWCNT and nylon. The Young's modulus, stiffness and fracture energy of the samples are 10.65 GPa, 1482.12 N/mm, and 644 J/m2 respectively. These values are comparable to those of the cortical bone. Further increase of the CfSWCNT content results to a decreased fracture toughness and tensile strength and formation of a secondary phase.

  5. Mechanical Properties for Fracture Analysis of Mild Steel Storage Tasks

    SciTech Connect

    Sindelar, R.L.

    1999-03-03

    Mechanical properties of 1950's vintage, A285 Grade B carbon steels have been compiled for elastic-plastic fracture mechanics analysis of storage tanks (Lam and Sindelar, 1999). The properties are from standard Charpy V-notch (CVN), 0.4T planform Compact Tension (C(T)), and Tensile (T) specimens machined from archival steel from large water piping. The piping and storage tanks were constructed in the 1950s from semi-killed, hot-rolled carbon steel plate specified as A285 Grade B. Evaluation of potential aging mechanisms at both service conditions shows no loss in fracture resistance of the steel in either case.Site and literature data show that the A285, Grade B steel, at and above approximately 70 degrees Fahrenheit, is in the upper transition to upper shelf region for absorbed energy and is not subject to cleavage cracking or a brittle fracture mode. Furthermore, the tank sidewalls are 1/2 or 5/8-inch thick, and therefore, the J-resistance (JR) curve that characterizes material resistance to stable crack extension under elastic-plastic deformation best defines the material fracture toughness. The JR curves for several heats of A285, Grade B steel tested at 40 degrees Fahrenheit, a temperature near the average ductile-to-brittle (DBTT) transition temperature (CVN {at} 15 ft-lb), are presented. This data is applicable to evaluate flaw stability of the storage tanks that are operated above 70 degrees Fahrenheit since, even at 40 degrees Fahrenheit, crack advance is observed to proceed by ductile tearing.

  6. Electronic, optical, mechanical and thermoelectric properties of graphene

    NASA Astrophysics Data System (ADS)

    Muley, Sarang Vilas

    Graphene, a two-dimensional allotrope of graphite with sp2 bonded carbon atoms, is arranged in honeycomb structure. Its quasi one-dimensional form is graphene nanoribbon (GNR). Graphene related materials have been found to display excellent electronic, chemical, mechanical properties along with uniquely high thermal conductivity, electrical conductivity and high optical transparency. With excellent electrical characteristics such as high carrier transport properties, quantum Hall effect at room temperature and unusual magnetic properties, graphene has applications in optoelectronic devices. Electronically, graphene is a zero bandgap semiconductor making it essential to tailor its structure for obtaining specific band structure. Narrow GNRs are known to open up bandgap and found to exhibit variations for different chiralities i.e., armchair and zigzag. Doping graphene, with p- or n- type elements, is shown to exhibit bandgap in contrast to pristine graphene. In this study, optical properties including dielectric functions, absorption coefficient, transmittance, and reflectance, as a function of wavelength and incident energy, are studied. Refractive index and extinction coefficient of pristine graphene are presented. A key optical property in the infrared region, emissivity, is studied as a function of wavelength for various multilayered configurations having graphene as one of the constituent layers. Application of such a structure is in the fabrication of a Hot Electron Bolometer (a sensor that operates on the basis of temperature-dependent electrical resistance). Graphene is found to have very high elastic modulus and intrinsic strength. Nanoindentation of graphene sheet is simulated to study the force versus displacement curves. Effects of variation of diameter of indenter, speed of indentation and number of layers of graphene on the mechanical properties are presented. Shrinking size of electronic devices has led to an acute need for thermal management. This

  7. Fundamental Studies of Assembly and Mechanical Properties of Lipid Bilayer Membranes and Unilamellar Vesicles

    NASA Astrophysics Data System (ADS)

    Wang, Xi

    This dissertation work focuses on: (i) obtaining a phospholipid bilayer membrane (LBM)/conducting electrode system with low defect density and optimized rigidity; (ii) investigating vesicle stability and mechanical properties. LBM is a simplified yet representative cell membrane model. LBMs assembled on conductive surfaces can probe protein-LBM interactions activities electrochemically. Sterically stabilized vesicles could be used as cell models or for drug delivery. The main challenges for LBM assembly on gold are vesicles do not spontaneously rupture to form LBMs on gold and the roughness of the gold substrate has considerable influence on molecular film defect density. In this study, 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) vesicles were functionalized with 1,2-distearoyl-sn-glycero-3-phosphoethanolamine- N-poly(ethylene glycol)-2000-N-[3-(2-pyridyldithio)propionate] (DSPE-PEG-PDP) to yield stable LBMs on gold without surface modification. A template-stripping method was used to obtain atomically flat and pristine gold surfaces. The critical force to initiate vesicle rupture decreases with increasing DSPE-PEG-PDP concentration, indicating that gold-thiolate bonding between DSPE-PEG-PDP and gold substrates promotes LBM formation. Mechanical properties of LBMs and vesicles were investigated as a function of DSPE-PEG-PDP concentration via Atomic Force Microscopy. The elastic moduli of LBMs were determined with DSPE-PEG-PDP concentration ranging from 0mol% to 24mol% and were found to depend on PEG chain conformation. Incorporating DSPE-PEG-PDP molecules with PEG in mushroom conformation results in a decrease of LBM rigidity, while incorporating PEG in brush conformation leads to LBM stiffening. Contrarily, mechanical properties of functionalized vesicles did not vary significantly by varying DSPE-PEG-PDP concentration. LBM with tunable rigidity by adjusting DSPE-PEG-PDP concentration provides a versatile cell membrane model for studying protein or

  8. Mechanical properties of materials at micro/nano scales

    NASA Astrophysics Data System (ADS)

    Xu, Wei-Hua

    Mechanical properties of materials in small dimensions, including the depth-dependent hardness at the nano/micrometer scales, and the mechanical characterization of thin films and nanotubes, are reported. The surface effect on the depth-dependent nano/microhardness was studied and an apparent surface stress was introduced to represent the energy dissipated per unit area of a solid surface. A plastic bearing ratio model was proposed for the nanoindentation of rough surfaces. The energy dissipation occurring at the indented surface is among the factors that cause the Indentation Size Effect (ISE) at the micro/nanometer scales. Furthermore, an elastic-plastic bearing ratio model was developed for nanoindentation of rough surfaces with a flat indenter tip. The theoretical predictions agree with the experimental results and finite element simulations, from which the elastic constant and the surface hardness were extracted. The surface hardness exhibits an inverse ISE due to the interaction of asperities. The nanoindentation tests on Highly Oriented Pyrolytic Graphite (HOPG) may lead to the formation of carbon tubes, which are rolled up by the delaminated graphite layers. The nanoindentation loading-unloading curves reveal single pop-in and multiple pop-in phenomena, which is induced by fracture of the graphite layers and/or by delamination between the layers. From the load at pop-in, the fracture strength of the layers and/or the bonding strength between the layers can be estimated by the elastic field model for Hertzian contact including sliding friction for transverse isotropy. Two novel methods were developed to estimate the mechanical properties of films, including the Raman spectra method for the estimation of residual stresses in thin ferroelectric films and the microbridge testing method for the mechanical characterization of trilayer thin films. Mechanical characterization was also carried out on Tobacco Mosaic Virus (TMV) nanotubes with each being comprised of

  9. Mechanical and Thermal Properties of Praseodymium Monopnictides: AN Ultrasonic Study

    NASA Astrophysics Data System (ADS)

    Bhalla, Vyoma; Kumar, Raj; Tripathy, Chinmayee; Singh, Devraj

    2013-09-01

    We have computed ultrasonic attenuation, acoustic coupling constants and ultrasonic velocities of praseodymium monopnictides PrX(X: N, P, As, Sb and Bi) along the <100>, <110>, <111> in the temperature range 100-500 K using higher order elastic constants. The higher order elastic constants are evaluated using Coulomb and Born-Mayer potential with two basic parameters viz. nearest-neighbor distance and hardness parameter in the temperature range of 0-500 K. Several other mechanical and thermal parameters like bulk modulus, shear modulus, Young's modulus, Poisson ratio, anisotropic ratio, tetragonal moduli, Breazeale's nonlinearity parameter and Debye temperature are also calculated. In the present study, the fracture/toughness (B/G) ratio is less than 1.75 which implies that PrX compounds are brittle in nature at room temperature. The chosen material fulfilled Born criterion of mechanical stability. We also found the deviation of Cauchy's relation at higher temperatures. PrN is most stable material as it has highest valued higher order elastic constants as well as the ultrasonic velocity. Further, the lattice thermal conductivity using modified approach of Slack and Berman is determined at room temperature. The ultrasonic attenuation due to phonon-phonon interaction and thermoelastic relaxation mechanisms have been computed using modified Mason's approach. The results with other well-known physical properties are useful for industrial applications.

  10. Mechanical properties of spindle poles are symmetrically balanced

    PubMed Central

    Suzuki, Kazuya; Itabashi, Takeshi; Ishiwata, Shin’ichi

    2017-01-01

    The metaphase spindle is organized for accurate chromosome segregation. One of the fundamental features of the spindle across the species is its symmetrical shape; the spindle consists of two polar arrays of microtubules at both ends. Although it has been suggested that the formation of the bipolar shape requires force balance coordination by molecular motors, i.e., kinesins and dyneins, quantitative analysis for the pole mechanics has not been conducted. Here, we demonstrate that it is not only the shape but also the stiffness and microtubule density of the pairs of pole regions are symmetrically balanced in single spindles self-assembled in Xenopus egg extracts. We found that the inhibition of dynein functions dramatically reduced the stiffness and microtubule density in the pole region. By contrast, the inhibition of one of the kinesins, Eg5, which is the antagonistic motor protein of dynein, increased the value of these parameters. Moreover, the inhibition of both dynein and Eg5 recovered these parameter values to those of non-treated spindle poles. We also found that, when one pole structure was held widened with the use of two glass microneedles, the opposite pole structure spontaneously widened, resulting in the formation of the barrel-like shaped spindle. The values of stiffness and microtubule density in the manipulated pole region decreased, following the spontaneous decrement of those in the paired unmanipulated pole region. These results suggest that the spindle possesses a mechanism to dynamically maintain its symmetry in mechanical properties.

  11. Mechanical properties of the lungs during acclimatization to altitude.

    PubMed

    Gautier, H; Peslin, R; Grassino, A; Milic-Emili, J; Hannhart, B; Powell, E; Miserocchi, G; Bonora, M; Fischer, J T

    1982-06-01

    Mechanical properties of the lung were studied in nine healthy lowlanders during a 6-day sojourn at an altitude of 3,457 m. In comparison to sea-level values, it was found at altitude that 1) lung volumes measured by plethysmography including total lung capacity, vital capacity, and functional residual capacity (FRC) presented small changes not exceeding 300 ml; 2) static and dynamic lung compliances were not modified but static pressure-volume curves of lungs were shifted progressively to the left (the decrease in lung elastic recoil averaged about 2 cmH2O on days 4-6); and 3) maximal midexpiratory flow, forced expiratory volume in 1 s, and maximal expiratory and inspiratory flows were increased and, conversely, airways and pulmonary flow resistances were decreased on most days at altitude. The unchanged FRC in the face of a decreased lung recoil may be explained by an increase in thoracic blood volume at altitude, but other possible mechanisms are discussed. The decrease in resistances and increase in maximal flows may be partly explained by the decreased air density at altitude, but another contributing factor such as a bronchodilatation is also suggested. It is proposed that changes in lung mechanics at altitude may account for some of the changes in the pattern of breathing and mouth occlusion pressure (P0.1) observed during acclimatization of lowlanders to altitude.

  12. Effects of Microwave Radiation on Selected Mechanical Properties of Silk

    NASA Astrophysics Data System (ADS)

    Reed, Emily Jane

    Impressive mechanical properties have served to peak interest in silk as an engineering material. In addition, the ease with which silk can be altered through processing has led to its use in various biomaterial applications. As the uses of silk branch into new territory, it is imperative (and inevitable) to discover the boundary conditions beyond which silk no longer performs as expected. These boundary conditions include factors as familiar as temperature and humidity, but may also include other less familiar contributions, such as exposure to different types of radiation. The inherent variations in mechanical properties of silk, as well as its sensitivity to moisture, suggest that in an engineering context silk is best suited for use in composite materials; that way, silk can be shielded from ambient moisture fluctuations, and the surrounding matrix allows efficient load transfer from weaker fibers to stronger ones. One such application is to use silk as a reinforcing fiber in epoxy composites. When used in this way, there are several instances in which exposure to microwave radiation is likely (for example, as a means of speeding epoxy cure rates), the effects of which remain mostly unstudied. It will be the purpose of this dissertation to determine whether selected mechanical properties of B. mori cocoon silk are affected by exposure to microwave radiation, under specified temperature and humidity conditions. Results of our analyses are directly applicable wherever exposure of silk to microwave radiation is possible, including in fiber reinforced epoxy composites (the entire composite may be microwaved to speed epoxy cure time), or when silk is used as a component in the material used to construct the radome of an aircraft (RADAR units use frequencies in the microwave range of the electromagnetic spectrum), or when microwave energy is used to sterilize biomaterials (such as cell scaffolds) made of silk. In general, we find that microwave exposure does not

  13. 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

  14. Optimization of the mechanical properties and water-vapor transmission properties of free films of hydroxypropylmethylcellulose.

    PubMed

    Nagarsenker, M S; Hegde, D D

    1999-01-01

    Free films of hydroxypropylmethylcellulose were prepared by a spraying technique. Methocel E5 and Methocel E15 were used in varying proportions in the preparation of films. The free films were studied for their mechanical properties and moisture permeability characteristics. A 2(2) factorial design was used to quantitate the effect of each polymer on the tensile strength and permeability constant of the films.

  15. Adjoint Methods for Adjusting Three-Dimensional Atmosphere and Surface Properties to Fit Multi-Angle Multi-Pixel Polarimetric Measurements

    NASA Technical Reports Server (NTRS)

    Martin, William G.; Cairns, Brian; Bal, Guillaume

    2014-01-01

    This paper derives an efficient procedure for using the three-dimensional (3D) vector radiative transfer equation (VRTE) to adjust atmosphere and surface properties and improve their fit with multi-angle/multi-pixel radiometric and polarimetric measurements of scattered sunlight. The proposed adjoint method uses the 3D VRTE to compute the measurement misfit function and the adjoint 3D VRTE to compute its gradient with respect to all unknown parameters. In the remote sensing problems of interest, the scalar-valued misfit function quantifies agreement with data as a function of atmosphere and surface properties, and its gradient guides the search through this parameter space. Remote sensing of the atmosphere and surface in a three-dimensional region may require thousands of unknown parameters and millions of data points. Many approaches would require calls to the 3D VRTE solver in proportion to the number of unknown parameters or measurements. To avoid this issue of scale, we focus on computing the gradient of the misfit function as an alternative to the Jacobian of the measurement operator. The resulting adjoint method provides a way to adjust 3D atmosphere and surface properties with only two calls to the 3D VRTE solver for each spectral channel, regardless of the number of retrieval parameters, measurement view angles or pixels. This gives a procedure for adjusting atmosphere and surface parameters that will scale to the large problems of 3D remote sensing. For certain types of multi-angle/multi-pixel polarimetric measurements, this encourages the development of a new class of three-dimensional retrieval algorithms with more flexible parametrizations of spatial heterogeneity, less reliance on data screening procedures, and improved coverage in terms of the resolved physical processes in the Earth?s atmosphere.

  16. Phsyical and Mechanical Properties of Fiber-Glass Reinforced Plastics (A Collection of Articles),

    DTIC Science & Technology

    REINFORCED PLASTICS , MECHANICAL PROPERTIES), LAMINATED PLASTICS , GLASS TEXTILES, TEST METHODS, SILICONE PLASTICS , POLYESTER PLASTICS , PHENOLIC... PLASTICS , EPOXY RESINS, POLYVINYL CHLORIDE, STYRENE PLASTICS , POLYAMIDE PLASTICS , TENSILE PROPERTIES, COMPRESSIVE PROPERTIES, SHEAR STRESSES, NONDESTRUCTIVE TESTING, ULTRANSONIC RADIATION, FIRE RESISTANT MATERIALS, USSR

  17. Mechanism of the electrophoretic assembly of cadmium selenide nanocrystal films and their mechanical properties

    NASA Astrophysics Data System (ADS)

    Jia, Shengguo

    This thesis consists of two closely related experimental studies of electrophoretically deposited CdSe nanocrystal films. In the first part of this thesis, the charging of CdSe nanocrystal in non-aqueous solvent and the mechanism of electrophoretic deposition (EPD) are discussed from the point of view of the influence of the nanocrystal surface. Our experiments show that the charge of these nanocrystals originates from the surface defects of the nanocrystal. EPD leads to equally thick films of CdSe nanocrystals on both positive and negative electrodes due to the deposition of equal numbers of negatively and positively charged nanocrystals, even though their concentrations are not equal in solution. The deposition stops when the charged nanocrystals with lower concentration are depleted. The second part of this thesis focuses on the mechanical and optical properties of these electrophoretically deposited CdSe nanocrystal films. Approaches to measure and analyze the mechanical parameters and fracture properties of electrophoretically deposited CdSe nanocrystal films are described in this part. The values of the elastic modulus of electrophoretically deposited CdSe nanocrystal films composed of 3.2 nm diameter nanocrystals measured by Raman microprobe scattering (˜9.7 GPa) and nanoindentation (˜10 GPa) match each other. The mechanical response of nanocrystal films suggests polymeric features that are attributable to the organic ligand on the nanocrystal cores. After nanocrystal cross-linking and partial ligand removal, the nanocrystal films exhibit more features of granularity. The fracture, strain, and stress of electrophoretically deposited CdSe nanocrystal films are studied as a function of the film thickness, nanocrystal size, and drying method. In addition to Raman microprobe scattering, optical methods such as photoluminescence, high-spatial resolution infrared spectroscopy, and ellipsometry are used to investigate the properties of these electrophoretically

  18. Investigation of mechanical properties of pavement through electromagnetic techniques

    NASA Astrophysics Data System (ADS)

    Benedetto, Andrea; Tosti, Fabio; D'Amico, Fabrizio

    2014-05-01

    Ground-penetrating radar (GPR) is considered as one of the most flexible geophysical tools that can be effectively and efficiently used in many different applications. In the field of pavement engineering, GPR can cover a wide range of uses, spanning from physical to geometrical inspections of pavements. Traditionally, such inferred information are integrated with mechanical measurements from other traditional (e.g. plate bearing test) or non-destructive (e.g. falling weight deflectometer) techniques, thereby resulting, respectively, in time-consuming and low-significant measurements, or in a high use of technological resources. In this regard, the new challenge of retrieving mechanical properties of road pavements and materials from electromagnetic measurements could represent a further step towards a greater saving of economic resources. As far as concerns unpaved and bound layers it is well-known that strength and deformation properties are mostly affected, respectively, by inter-particle friction and cohesion of soil particles and aggregates, and by bitumen adhesion, whose variability is expressed by the Young modulus of elasticity. In that respect, by assuming a relationship between electromagnetic response (e.g. signal amplitudes) and bulk density of materials, a reasonable correlation between mechanical and electric properties of substructure is therefore expected. In such framework, a pulse GPR system with ground-coupled antennae, 600 MHz and 1600 MHz centre frequencies was used over a 4-m×30-m test site composed by a flexible pavement structure. The horizontal sampling resolution amounted to 2.4×10-2 m. A square regular grid mesh of 836 nodes with a 0.40-m spacing between the GPR acquisition tracks was surveyed. Accordingly, a light falling weight deflectometer (LFWD) was used for measuring the elastic modulus of pavement at each node. The setup of such instrument consisted of a 10-kg falling mass and a 100-mm loading plate so that the influence domain

  19. Localized Mechanical Properties of Friction Stir Processed Sensitized 5456-H116 Al

    DTIC Science & Technology

    2013-04-01

    FSP is applied to a sensitized 5456-H116 aluminum plate and the resulting microstructure is linked to local mechanical properties (0.2% yield...have negatively affected the mechanical properties 15. SUBJECT TERMS Aluminum Alloys, Friction Stir Processing, Sensitization, Mechanical Testing... aluminum 5456-H116 (wt. %) ..............................................3 Table 2. Bulk base material properties for H116, O, and sensitized H116

  20. Mechanical Property Analysis in the Retracted Pin-Tool (RPT) Region of Friction Stir Welded (FSW) Aluminum Lithium 2195

    NASA Technical Reports Server (NTRS)

    Ding, R. Jeffrey; Oelgoetz, Peter A.

    1999-01-01

    The "Auto-Adjustable Pin Tool for Friction Stir Welding", was developed at The Marshall Space Flight Center to address process deficiencies unique to the FSW process. The auto-adjustable pin tool, also called the retractable pin-tool (R.PT) automatically withdraws the welding probe of the pin-tool into the pin-tool's shoulder. The primary function of the auto-adjustable pin-tool is to allow for keyhole closeout, necessary for circumferential welding and localized weld repair, and, automated pin-length adjustment for the welding of tapered material thickness. An overview of the RPT hardware is presented. The paper follows with studies conducted using the RPT. The RPT was used to simulate two capabilities; welding tapered material thickness and closing out the keyhole in a circumferential weld. The retracted pin-tool regions in aluminum- lithium 2195 friction stir weldments were studied through mechanical property testing and metallurgical sectioning. Correlation's can be =de between retractable pin-tool programmed parameters, process parameters, microstructure, and resulting weld quality.