A Critical Assessment of Cyclic Softening and Hardening Behavior in a Near- α Titanium Alloy During Thermomechanical Fatigue

NASA Astrophysics Data System (ADS)

Prasad, Kartik; Sarkar, Rajdeep; Rao, K. Bhanu Sankara; Sundararaman, M.

2016-10-01

Thermomechanical fatigue behavior of Ti-alloy Timetal 834 has been studied at two temperature intervals viz. 573 K to 723 K (300 °C to 450 °C) and 723 K to 873 K (450 °C to 600 °C) under mechanical strain-controlled cycling. Among the temperatures studied, the alloy exhibited initial cyclic softening followed by cyclic hardening at 723 K (450 °C) in the temperature interval of 573 K to 723 K (300 °C to 450 °C). However, continuous cyclic hardening was observed at 723 K (450 °C) in 723 K to 873 K (450 °C to 600 °C). At 573 K (300 °C) and 873 K (600 °C), cyclic softening was observed in the cyclic stress response curves in both the temperature intervals. The dislocation substructure was observed to be planar in both the modes of TMF loading. Based on TEM microstructures and few unconventional fatigue tests, the observed cyclic hardening is attributed to dynamic strain aging. The reduced fatigue life at 723 K to 873 K (450 °C to 600 °C) under OP-TMF loading was attributed to the combined effect of cyclic hardening (leading to early strain localization and crack initiation), oxidation, and development of tensile mean stresses.

Analysis of hardening behavior of sheet metals by a new simple shear test method taking into account the Bauschinger effect

NASA Astrophysics Data System (ADS)

Bang, Sungsik; Rickhey, Felix; Kim, Minsoo; Lee, Hyungyil; Kim, Naksoo

2013-12-01

In this study we establish a process to predict hardening behavior considering the Bauschinger effect for zircaloy-4 sheets. When a metal is compressed after tension in forming, the yield strength decreases. For this reason, the Bauschinger effect should be considered in FE simulations of spring-back. We suggested a suitable specimen size and a method for determining the optimum tightening torque for simple shear tests. Shear stress-strain curves are obtained for five materials. We developed a method to convert the shear load-displacement curve to the effective stress-strain curve with FEA. We simulated the simple shear forward/reverse test using the combined isotropic/kinematic hardening model. We also investigated the change of the load-displacement curve by varying the hardening coefficients. We determined the hardening coefficients so that they follow the hardening behavior of zircaloy-4 in experiments.

Age hardening and creep resistance of cast Al–Cu alloy modified by praseodymium

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

Bai, Zhihao; Qiu, Feng; Wu, Xiaoxue

The effects of praseodymium on age hardening behavior and creep resistance of cast Al–Cu alloy were investigated. The results indicated that praseodymium facilitated the formation of the θ′ precipitates during the age process and improved the hardness of the Al–Cu alloy. Besides, praseodymium resulted in the formation of the Al{sub 11}Pr{sub 3} phase in the grain boundaries and among the dendrites of the modified alloy. Because of the good thermal stability of Al{sub 11}Pr{sub 3} phase, it inhibits grain boundary migration and dislocation movement during the creep process, which contributes to the improvement in the creep resistance of the modifiedmore » alloy at elevated temperatures. - Highlights: • Pr addition enhances the hardness and creep resistance of the Al–Cu alloy. • Pr addition facilitates the formation of the θ′ precipitates. • Pr addition results in the formation of the Al11Pr3 phase in the Al–Cu alloy.« less

Experimental analysis of the sheet metal forming behavior of newly developed press hardening steels

NASA Astrophysics Data System (ADS)

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

2018-05-01

The aim of this work was the characterization of the newly developed press hardening sheet alloys 1800 PHS and 2000 PHS developed by SSAB with regard to their hot forming behavior on the basis of the experimental determination of relevant mechanical and technological properties. For this purpose conventional and non-conventional sheet metal testing methods were used. To determine the friction coefficient, the strip drawing test was applied, while the deep drawing cup test was used to determine the maximum draw depth. Finally, a V-bending test was carried out to evaluate the springback behavior of the investigated alloys by varying the blank temperature and quenching media. This work provides a technological guideline for the production of press hardened sheet parts made of these investigated sheet metals.

Group precipitation and age hardening of nanostructured Fe-based alloys with ultra-high strengths

DOE PAGES

Jiao, Z. B.; Luan, J. H.; Miller, M. K.; ...

2016-02-19

The precipitation of nanoparticles plays a key role in determining the properties of many structural materials, and the understanding of their formation and stabilization mechanisms has been a long standing interest in the material field. However, the critical issues involving the group precipitation of various nanoparticles and their cooperative hardening mechanism remain elusive in the newly discovered Fe-based alloys with nanostructures. Here we quantitatively elucidate the nucleation mechanism, evolution kinetics and hardening effects of the group-precipitated nanoparticles in the Fe-Cu-Ni-Al-based alloys by atom probe tomography together with both first-principles and thermodynamic calculations. Our results provide the compelling evidence for twomore » interesting but complex group precipitation pathways of nanoparticles, i.e., the Cu-rich and NiAl-based precipitations. Lastly, the co-existence of the two precipitation pathways plays a key role in age hardening kinetics and ultimately enhances the hardening response, as compared to the single particle type of strengthening, therefore providing an effective new approach for strengthening materials for structural applications.« less

Group precipitation and age hardening of nanostructured Fe-based alloys with ultra-high strengths

PubMed Central

Jiao, Z. B.; Luan, J. H.; Miller, M. K.; Yu, C. Y.; Liu, C. T.

2016-01-01

The precipitation of nanoparticles plays a key role in determining the properties of many structural materials, and the understanding of their formation and stabilization mechanisms has been a long standing interest in the material field. However, the critical issues involving the group precipitation of various nanoparticles and their cooperative hardening mechanism remain elusive in the newly discovered Fe-based alloys with nanostructures. Here we quantitatively elucidate the nucleation mechanism, evolution kinetics and hardening effects of the group-precipitated nanoparticles in the Fe-Cu-Ni-Al-based alloys by atom probe tomography together with both first-principles and thermodynamic calculations. Our results provide the compelling evidence for two interesting but complex group precipitation pathways of nanoparticles, i.e., the Cu-rich and NiAl-based precipitations. The co-existence of the two precipitation pathways plays a key role in age hardening kinetics and ultimately enhances the hardening response, as compared to the single particle type of strengthening, therefore providing an effective new approach for strengthening materials for structural applications. PMID:26892834

Identifying Deformation and Strain Hardening Behaviors of Nanoscale Metallic Multilayers Through Nano-wear Testing

DOE PAGES

Economy, David Ross; Mara, Nathan A.; Schoeppner, R.; ...

2016-01-13

In complex loading conditions (e.g. sliding contact), mechanical properties, such as strain hardening and initial hardness, will dictate the long-term performance of materials systems. With this in mind, the strain hardening behaviors of Cu/Nb nanoscale metallic multilayer systems were examined by performing nanoindentation tests within nanoscratch wear boxes and undeformed, as-deposited regions. Both the architecture and substrate influence were examined by utilizing three different individual layer thicknesses (2, 20, and 100 nm) and two total film thicknesses (1 and 10 μm). After nano-wear deformation, multilayer systems with thinner layers showed less volume loss as measured by laser scanning microscopy. Additionally,more » the hardness of the deformed regions significantly rose with respect to the as-deposited measurements, which further increased with greater wear loads. Strain hardening exponents for multilayers with thinner layers (2 and 20 nm, n ≈ 0.018 and n ≈ 0.022 respectively) were less than was determined for 100 nm systems (n ≈ 0.041). These results suggest that singledislocation based deformation mechanisms observed for the thinner systems limit the extent of achievable strain hardening. This conclusion indicates that impacts of both architecture strengthening and strain hardening must be considered to accurately predict multilayer performance during sliding contact across varying length scales.« less

Effect of Ag and Cu Contents on the Age Hardning Behavior of Al-Zn-Mg Alloys

NASA Astrophysics Data System (ADS)

Watanabe, Katsumi; Kawabata, Tokimasa; Ikeno, Susumu; Yoshida, Tomoo; Murakami, Satoshi; Matsuda, Kenji

Al-Zn-Mg alloy has been known as one of the aluminum alloys with the good age-hardening ability and the high strength among commercial aluminum alloys. The mechanical property of the limited ductility, however, is required to further improvement. In this work, three alloys, which were added Cu or Ag into the Al-Zn-Mg-Si alloy, were prepared to compare the effect of the additional elements on the aging behavior. The content of Ag and Cu were 0.2 at.% and 0.2at.%, respectively. The age-hardening behavior and microstructures of those alloys were investigated by hardness measurement, high resolution transmission electron microscope (HRTEM) and selected area electron diffraction (SAED) technique. Ag or Cu added alloy showed higher peak hardness than Ag or Cu free alloy. According to addition of Ag or Cu, the number density of the precipitates increased than Ag or Cu free alloy.

Work Hardening Behavior of 1020 Steel During Cold-Beating Simulation

NASA Astrophysics Data System (ADS)

CUI, Fengkui; LING, Yuanfei; XUE, Jinxue; LIU, Jia; LIU, Yuhui; LI, Yan

2017-03-01

The present research of cold-beating formation mainly focused on roller design and manufacture, kinematics, constitutive relation, metal flow law, thermo-mechanical coupling, surface micro-topography and microstructure evolution. However, the research on surface quality and performance of workpieces in the process of cold-beating is rare. Cold-beating simulation experiment of 1020 steel is conducted at room temperature and strain rates ranging from 2000 to 4000 s-1 base on the law of plastic forming. According to the experimental data, the model of strain hardening of 1020 steel is established, Scanning Electron Microscopy(SEM) is conducted, the mechanism of the work hardening of 1020 steel is clarified by analyzing microstructure variation of 1020 steel. It is found that the strain rate hardening effect of 1020 steel is stronger than the softening effect induced by increasing temperatures, the process of simulation cold-beating cause the grain shape of 1020 steel significant change and microstructure elongate significantly to form a fibrous tissue parallel to the direction of deformation, the higher strain rate, the more obvious grain refinement and the more hardening effect. Additionally, the change law of the work hardening rate is investigated, the relationship between dislocation density and strain, the relationship between work hardening rate and dislocation density is obtained. Results show that the change trend of the work hardening rate of 1020 steel is divided into two stages, the work hardening rate decreases dramatically in the first stage and slowly decreases in the second stage, finally tending toward zero. Dislocation density increases with increasing strain and strain rate, work hardening rate decreases with increasing dislocation density. The research results provide the basis for solving the problem of improving the surface quality and performance of workpieces under cold-beating formation of 1020 steel.

Strain Hardening of Hadfield Manganese Steel

NASA Astrophysics Data System (ADS)

Adler, P. H.; Olson, G. B.; Owen, W. S.

1986-10-01

The plastic flow behavior of Hadfield manganese steel in uniaxial tension and compression is shown to be greatly influenced by transformation plasticity phenomena. Changes in the stress-strain (σ-ɛ) curves with temperature correlate with the observed extent of deformation twinning, consistent with a softening effect of twinning as a deformation mechanism and a hardening effect of the twinned microstructure. The combined effects give upward curvature to the σ-ɛ curve over extensive ranges of plastic strain. A higher strain hardening in compression compared with tension appears to be consistent with the observed texture development. The composition dependence of stacking fault energy computed using a thermodynamic model suggests that the Hadfield composition is optimum for a maximum rate of deformation twinning. Comparisons of the Hadfield steel with a Co-33Ni alloy exhibiting similar twinning kinetics, and an Fe-21Ni-lC alloy deforming by slip indicate no unusual strain hardening at low strains where deformation is controlled by slip, but an unusual amount of structural hardening associated with the twin formation in the Hadfield steel. A possible mechanism of anomalous twin hardening is discussed in terms of modified twinning behavior (pseudotwinning) in nonrandom solid solutions.

Influence of preliminary deformation on the hardening effect upon aging of Al-Cu-Li alloys

NASA Astrophysics Data System (ADS)

Betsofen, S. Ya.; Ashmarin, A. A.; Knyazev, M. I.; Dolgova, M. I.

2016-09-01

The influence of preliminary deformation upon rolling of wedge specimens on the mechanical properties and the structural phase state of Al-Cu-Li alloys are studied by X-ray diffraction and hardness measurements. Strong dependence of the hardening effect upon aging on the reduction upon rolling has been revealed. Deformation weakly influences the hardness and significantly increases the hardening upon aging. Herewith, the hardening effect is nearly absent at the minimum deformation ratio of 1% and increases with its increase. It is demonstrated that the content of T1 phase increases from 2 to 4% in the range of a preliminary deformation ratio of 6-10% and the content of δ' phase is 17% at a deformation ratio in the range 1‒6% and increases to 18-19% at a deformation ratio of 6-10%. The δ' phase in an alloy contains <20% nanocrystalline particles with 6-20 nm in size, and the remaining part consists of amorphous particles (as detected by X-ray diffraction) <5 nm in size, which precipitate coherently from the matrix and have the same orientation as the nanocrystalline particles and the solid solution.

Weldable, age hardenable, austenitic stainless steel

DOEpatents

Brooks, J.A.; Krenzer, R.W.

1975-07-22

An age hardenable, austenitic stainless steel having superior weldability properties as well as resistance to degradation of properties in a hydrogen atmosphere is described. It has a composition of from about 24.0 to about 34.0 weight percent (w/o) nickel, from about 13.5 to about 16.0 w/o chromium, from about 1.9 to about 2.3 w/o titanium, from about 1.0 to about 1.5 w/ o molybdenum, from about 0.01 to about 0.05 w/o carbon, from about 0 to about 0.25 w/o manganese, from about 0 to about 0.01 w/o phosphorous and preferably about 0.005 w/o maximum, from about 0 to about 0.010 w/o sulfur and preferably about 0.005 w/o maximum, from about 0 to about 0.25 w/o silicon, from about 0.1 to about 0.35 w/o aluminum, from about 0.10 to about 0.50 w/o vanadium, from about 0 to about 0.0015 w/o boron, and the balance essentially iron. (auth)

Decomposition pathways in age hardening of Ti-Al-N films

NASA Astrophysics Data System (ADS)

Rachbauer, R.; Massl, S.; Stergar, E.; Holec, D.; Kiener, D.; Keckes, J.; Patscheider, J.; Stiefel, M.; Leitner, H.; Mayrhofer, P. H.

2011-07-01

The ability to increase the thermal stability of protective coatings under work load gives rise to scientific and industrial interest in age hardening of complex nitride coating systems such as ceramic-like Ti1-xAlxN. However, the decomposition pathway of these systems from single-phase cubic to the thermodynamically stable binary nitrides (cubic TiN and wurtzite AlN), which are essential for age hardening, are not yet fully understood. In particular, the role of decomposition kinetics still requires more detailed investigation. In the present work, the combined effect of annealing time and temperature upon the nano-structural development of Ti0.46Al0.54N thin films is studied, with a thermal exposure of either 1 min or 120 min in 100 °C steps from 500 °C to 1400 °C. The impact of chemical changes at the atomic scale on the development of micro-strain and mechanical properties is studied by post-annealing investigations using X-ray diffraction, nanoindentation, 3D-atom probe tomography and high-resolution transmission electron microscopy. The results clearly demonstrate that the spinodal decomposition process, triggering the increase of micro-strain and hardness, although taking place throughout the entire volume, is enhanced at high diffusivity paths such as grain or column boundaries and followed within the grains. Ab initio calculations further show that the early stages of wurtzite AlN precipitation are connected with increased strain formation, which is in excellent agreement with experimental observations.

Materials science. Modeling strain hardening the hard way.

PubMed

Gumbsch, Peter

2003-09-26

The plastic deformation of metals results in strain hardening, that is, an increase in the stress with increasing strain. Materials engineers can provide a simple approximate description of such deformation and hardening behavior. In his perspective, Gumbsch discusses work by Madec et al. who have undertaken the formidable task of computing the physical basis for the development of strain hardening by individually following the fate of all the dislocations involved. Their simulations show that the collinear dislocation interaction makes a substantial contribution to strain hardening. It is likely that such simulations will play an important role in guiding the development of future engineering descriptions of deformation and hardening.

Effect of Cold Rolling on Age Hardening in Excess Mg-Type Al-Mg-Si Alloys Including Some Minor Elements

NASA Astrophysics Data System (ADS)

Ogawa, Yurie; Matsuda, Kenji; Kawabata, Tokimasa; Uetani, Yasuhiro; Ikeno, Susumu

It has been known that transition metals improve the mechanical property of Al-Mg-Si alloy. The thermo-mechanical treatment is also effective to improve the strength of Al-Mg-Si alloy. In this work, the aging behavior of deformed excess Mg-type Al-Mg-Si alloy including Ag,Cu,Pt was investigated by hardness test and TEM observation. The value of the maximum hardness increased and the aging time to the maximum hardness became shorter by increasing the amount of the deformation. The age-hardening ability (ΔHV) was decreased with increasing amount of the deformation. The effect of additional element on AHV was also similar to the result of the deformation described above. Comparing the value of the maximum hardness for the alloys aged at 423-523 K, the ex. Mg-Cu alloy was the highest, the ex. Mg-Ag alloy was middle, and the ex. Mg and ex. Mg-Pt alloys were the lowest because of total amounts of added elements.

Influence of Austenitizing Parameters on Mechanical Behavior of Press Hardened Steels

NASA Astrophysics Data System (ADS)

Golem, Lindsay

Recent increases in the Corporate Average Fuel Economy standard have led to an increased focus on lightweight materials for use in vehicle architectures. In particular, press hardened steels (PHS) have been identified as suitable materials to reduce vehicle mass while maintaining or possibly improving vehicle crash performance. A fundamental understanding of the mechanical behavior of PHS with respect to changes in processing conditions is critical to their proper use. In this work, 22MnB5 Al-Si coated blanks were austenitized at several different times and temperatures to produce a range of prior austenite grain sizes. Mechanical behavior was evaluated using smooth sided tensile testing, double edge notch tensile testing, and free bend testing. Metrics, such as notch tensile strength, notch strength ratio, and notch displacement, which is based on the fracture mechanics parameter crack tip opening displacement, were derived from double edge notch tensile testing to assess material notch sensitivity and toughness as a function of processing conditions. Additionally, bend angle at maximum load, post uniform bending slope, and energy for fracture were measured using free bend testing to provide another means for evaluating mechanical behavior. Increasing the austenitizing temperature and hold time resulted in an increase in the measured prior austenite grain size; however, elevated austenitizing temperatures also increased the thickness of the coating interdiffusion layer. In the coated material, tensile strength decreased with increasing prior austenite grain size for both notched and smooth sided tensile samples, but minimal difference was observed in the strain to failure results. Notch displacement, bend angle at maximum load, and energy for fracture during free bend testing all decreased with increasing prior austenite grain size in the coated PHS and also showed a significant drop in measured behavior for the 1025 °C for 30 minutes austenitizing condition

Mechanism of work hardening in Hadfield manganese steel

NASA Astrophysics Data System (ADS)

Dastur, Y. N.; Leslie, W. C.

1981-05-01

When Hadfield manganese steel in the single-phase austenitic condition was strained in tension, in the temperature range - 25 to 300 °C, it exhibited jerky (serrated) flow, a negative (inverse) strain-rate dependence of flow stress and high work hardening, characteristic of dynamic strain aging. The strain rate-temperature regime of jerky flow was determined and the apparent activation energies for the appearance and disappearance of serrations were found to be 104 kJ/mol and 146 kJ/mol, respectively. The high work hardening cannot be a result of mechanical twinning because at -50 °C numerous twins were produced, but the work hardening was low and no twins were formed above 225 °C even though work hardening was high. The work hardening decreased above 300 °C because of the cessation of dynamic strain aging and increased again above 400 °C because of precipitation of carbides. An apparent activation energy of 138 kJ/mol was measured for static strain aging between 300 and 400 °C, corresponding closely to the activation energies for the disapperance of serrations and for the volume diffusion of carbon in Hadfield steel. Evidence from the present study, together with the known effect of manganese on the activity of carbon in austenite and previous internal friction studies of high-manganese steels, lead to the conclusion that dynamic strain aging, brought about by the reorientation of carbon members of C-Mn couples in the cores of dislocations, is the principal cause of rapid work hardening in Hadfield steel.

Effects of alloying on aging and hardening processes of steel with 20% nickel

NASA Technical Reports Server (NTRS)

Bogachev, I. N.; Zvigintsev, N. V.; Maslakova, T. M.

1981-01-01

Measurements of hardness, thermal emf, and electrical resistance were used to study the effects of Co, Mo, Ti and Al contents on aging and hardening processes in Fe 20%Ni steel. It is shown that the effects of these alloying elements differ substantially. Anomalies which arise in the temperature dependence of physical properties due to the presence of cobalt and molybdenum are reduced by the inclusion of titanium and aluminum (and vice versa).

Precipitation and Hardening in Magnesium Alloys

NASA Astrophysics Data System (ADS)

Nie, Jian-Feng

2012-11-01

Magnesium alloys have received an increasing interest in the past 12 years for potential applications in the automotive, aircraft, aerospace, and electronic industries. Many of these alloys are strong because of solid-state precipitates that are produced by an age-hardening process. Although some strength improvements of existing magnesium alloys have been made and some novel alloys with improved strength have been developed, the strength level that has been achieved so far is still substantially lower than that obtained in counterpart aluminum alloys. Further improvements in the alloy strength require a better understanding of the structure, morphology, orientation of precipitates, effects of precipitate morphology, and orientation on the strengthening and microstructural factors that are important in controlling the nucleation and growth of these precipitates. In this review, precipitation in most precipitation-hardenable magnesium alloys is reviewed, and its relationship with strengthening is examined. It is demonstrated that the precipitation phenomena in these alloys, especially in the very early stage of the precipitation process, are still far from being well understood, and many fundamental issues remain unsolved even after some extensive and concerted efforts made in the past 12 years. The challenges associated with precipitation hardening and age hardening are identified and discussed, and guidelines are outlined for the rational design and development of higher strength, and ultimately ultrahigh strength, magnesium alloys via precipitation hardening.

The effects of solution treatment on the mechanical properties of age-hardened A-286 bar stock at elevated and cryogenic temperature

NASA Technical Reports Server (NTRS)

Montano, J. W.

1972-01-01

The mechanical properties are presented of solution treated and age hardened A-286 corrosion resistant steel bar stock. Material solution treated at 899 C or 982 C, each followed by an age hardening treatment of 718 C, was evaluated. Test specimens manufactured from 1.50 inch (3.81 cm) diameter bar stock were tested at temperatures from +649 C to -253 C. The test data indicated excellent tensile, yield, elongation and reduction-in-area properties at all testing temperatures for both solution treated and aged materials. Cryogenic temperature notched tensile, impact, and shear tests indicated excellent notch strength, ductility, and shear values. There was very little difference in the mechanical properties of the two solution treated and aged materials. The only exception was that the 962 C solution treated and aged material had superior stress rupture properties at 649 C.

Effect of heat treatment on mechanical properties of age-hardenable gold alloy at intraoral temperature.

PubMed

Watanabe, I; Watanabe, E; Cai, Z; Okabe, T; Atsuta, M

2001-09-01

The aim of this study was to investigate the effect of various heat treatments on the mechanical properties of gold alloys capable of age-hardening at intraoral temperature. Dumbbell-shaped patterns (ISO 6871) were cast with three gold alloys (Sofard; NC Type-IV; Aurum Cast, NihombashiTokuriki Co.). The Sofard alloy is age-hardenable at intraoral temperature. The castings underwent various heat treatments [as-cast (AC); solution treatment (ST); high-temperature aging (HA); intraoral aging (IA)]. After these heat treatments, ultimate tensile strength (UTS), 0.2% offset yield strength (YS), and elongation (EL) were measured at a strain rate of 1.7x10(-4)/s. Fracture surfaces of the specimens after tensile testing were observed using SEM. Vickers hardness was also measured after heat treating. After IA, the hardness values of the Sofard alloy increased and reached values similar to the hardness of the Sofard specimens aged at high temperature (HA). The hardness values of the NC Type-IV and Aurum Cast specimens slightly increased after IA, but did not reach the values of the specimens after HA. All the Sofard, NC Type-IV and Aurum Cast specimens showed significantly (P<0.05) greater hardness values after HA, compared with the values after any other heat treatments (AC, ST and IA). The UTS and YS of the specimens indicated a tendency similar to the results obtained for hardness. The Sofard specimens with ST showed the greatest elongation compared to the corresponding NC Type-IV and Aurum Cast specimens. However, the elongation of the Sofard specimens was abruptly reduced after intraoral aging. Intraoral aging significantly improved the mechanical properties and hardness of the Sofard alloy.

Effect of Plate Hardening Behavior on the Deformation of Stainless Steel Metal Bellows

NASA Astrophysics Data System (ADS)

Hao, Zengliang; Luo, Shuyi; Zhao, He; Zhang, Chunxiang; Luo, Junting

2017-11-01

Tensile tests of original plate samples from three types of stainless steel metal bellows were performed at room temperature. The constitutive equations for the three hardening curves were obtained and fitted. The analysis results of the microstructure and fracture morphology of the tensile specimens show that the grain size of the plate with a high logarithmic-exponential hardening rate is uneven and the dimple of the shear fracture is elongated into an ellipse. By contrast, the grain size of the plate with a relatively low linear hardening rate is even and the dimple of the fracture is uniformly equiaxial. Finite element simulations of the hydraulic bulging and repeated limit bending deformation of the metal bellows of the three types of materials were also conducted. The repeated limit bending deformation process was tested experimentally. Although the effect of the hardening exponent on the residual stress of the metal bellows after hydraulic bulging is minimal, this exponent considerably influences the repeated limit bending deformation of the metal bellows after subsequent use. The trough hardening phenomenon is serious in the repeated limit bending process. Moreover, when the hardening exponent of the original plate is high, the resistance to bending fracture at the trough area is poor.

Influence of Secondary Cyclic Hardening on the Low Cycle Fatigue Behavior of Nitrogen Alloyed 316LN Stainless Steel

NASA Astrophysics Data System (ADS)

Prasad Reddy, G. V.; Sandhya, R.; Mathew, M. D.; Sankaran, S.

2013-12-01

In this article, the occurrence of secondary cyclic hardening (SCH) and its effect on high-temperature cyclic deformation and fatigue life of 316LN Stainless steel are presented. SCH is found to result from planar slip mode of deformation and enhance the degree of hardening over and above that resulted from dynamic strain aging. The occurrence of SCH is strongly governed by the applied strain amplitude, test temperature, and the nitrogen content in the 316LN SS. Under certain test conditions, SCH is noticed to decrease the low cycle fatigue life with the increasing nitrogen content.

Method and apparatus for welding precipitation hardenable materials

DOEpatents

Murray, Jr., Holt; Harris, Ian D.; Ratka, John O.; Spiegelberg, William D.

1994-01-01

A method for welding together members consisting of precipitation age hardened materials includes the steps of selecting a weld filler material that has substantially the same composition as the materials being joined, and an age hardening characteristic temperature age threshold below that of the aging kinetic temperature range of the materials being joined, whereby after welding the members together, the resulting weld and heat affected zone (HAZ) are heat treated at a temperature below that of the kinetic temperature range of the materials joined, for obtaining substantially the same mechanical characteristics for the weld and HAZ, as for the parent material of the members joined.

Method and apparatus for welding precipitation hardenable materials

DOEpatents

Murray, H. Jr.; Harris, I.D.; Ratka, J.O.; Spiegelberg, W.D.

1994-06-28

A method for welding together members consisting of precipitation age hardened materials includes the steps of selecting a weld filler material that has substantially the same composition as the materials being joined, and an age hardening characteristic temperature age threshold below that of the aging kinetic temperature range of the materials being joined, whereby after welding the members together, the resulting weld and heat affected zone (HAZ) are heat treated at a temperature below that of the kinetic temperature range of the materials joined, for obtaining substantially the same mechanical characteristics for the weld and HAZ, as for the parent material of the members joined. 5 figures.

An Anisotropic Hardening Model for Springback Prediction

NASA Astrophysics Data System (ADS)

Zeng, Danielle; Xia, Z. Cedric

2005-08-01

As more Advanced High-Strength Steels (AHSS) are heavily used for automotive body structures and closures panels, accurate springback prediction for these components becomes more challenging because of their rapid hardening characteristics and ability to sustain even higher stresses. In this paper, a modified Mroz hardening model is proposed to capture realistic Bauschinger effect at reverse loading, such as when material passes through die radii or drawbead during sheet metal forming process. This model accounts for material anisotropic yield surface and nonlinear isotropic/kinematic hardening behavior. Material tension/compression test data are used to accurately represent Bauschinger effect. The effectiveness of the model is demonstrated by comparison of numerical and experimental springback results for a DP600 straight U-channel test.

Two Back Stress Hardening Models in Rate Independent Rigid Plastic Deformation

NASA Astrophysics Data System (ADS)

Yun, Su-Jin

In the present work, the constitutive relations based on the combination of two back stresses are developed using the Armstrong-Frederick, Phillips and Ziegler’s type hardening rules. Various evolutions of the kinematic hardening parameter can be obtained by means of a simple combination of back stress rate using the rule of mixtures. Thus, a wide range of plastic deformation behavior can be depicted depending on the dominant back stress evolution. The ultimate back stress is also determined for the present combined kinematic hardening models. Since a kinematic hardening rule is assumed in the finite deformation regime, the stress rate is co-rotated with respect to the spin of substructure obtained by incorporating the plastic spin concept. A comparison of the various co-rotational rates is also included. Assuming rigid plasticity, the continuum body consists of the elastic deformation zone and the plastic deformation zone to form a hybrid finite element formulation. Then, the plastic deformation behavior is investigated under various loading conditions with an assumption of the J2 deformation theory. The plastic deformation localization turns out to be strongly dependent on the description of back stress evolution and its associated hardening parameters. The analysis for the shear deformation with fixed boundaries is carried out to examine the deformation localization behavior and the evolution of state variables.

Significant contribution of stacking faults to the strain hardening behavior of Cu-15%Al alloy with different grain sizes.

PubMed

Tian, Y Z; Zhao, L J; Chen, S; Shibata, A; Zhang, Z F; Tsuji, N

2015-11-19

It is commonly accepted that twinning can induce an increase of strain-hardening rate during the tensile process of face-centered cubic (FCC) metals and alloys with low stacking fault energy (SFE). In this study, we explored the grain size effect on the strain-hardening behavior of a Cu-15 at.%Al alloy with low SFE. Instead of twinning, we detected a significant contribution of stacking faults (SFs) irrespective of the grain size even in the initial stage of tensile process. In contrast, twinning was more sensitive to the grain size, and the onset of deformation twins might be postponed to a higher strain with increasing the grain size. In the Cu-15 at.%Al alloy with a mean grain size of 47 μm, there was a stage where the strain-hardening rate increases with strain, and this was mainly induced by the SFs instead of twinning. Thus in parallel with the TWIP effect, we proposed that SFs also contribute significantly to the plasticity of FCC alloys with low SFE.

Significant contribution of stacking faults to the strain hardening behavior of Cu-15%Al alloy with different grain sizes

PubMed Central

Tian, Y. Z.; Zhao, L. J.; Chen, S.; Shibata, A.; Zhang, Z. F.; Tsuji, N.

2015-01-01

It is commonly accepted that twinning can induce an increase of strain-hardening rate during the tensile process of face-centered cubic (FCC) metals and alloys with low stacking fault energy (SFE). In this study, we explored the grain size effect on the strain-hardening behavior of a Cu-15 at.%Al alloy with low SFE. Instead of twinning, we detected a significant contribution of stacking faults (SFs) irrespective of the grain size even in the initial stage of tensile process. In contrast, twinning was more sensitive to the grain size, and the onset of deformation twins might be postponed to a higher strain with increasing the grain size. In the Cu-15 at.%Al alloy with a mean grain size of 47 μm, there was a stage where the strain-hardening rate increases with strain, and this was mainly induced by the SFs instead of twinning. Thus in parallel with the TWIP effect, we proposed that SFs also contribute significantly to the plasticity of FCC alloys with low SFE. PMID:26582568

Effects of quench rate and natural ageing on the age hardening behaviour of aluminium alloy AA6060

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

Strobel, Katharina, E-mail: katharina.strobel@aol.com; Lay, Matthew D.H., E-mail: mlay@fbrice.com; Easton, Mark A., E-mail: mark.easton@rmit.edu.au

Quench sensitivity in Al–Mg–Si alloys has been largely attributed to the solute loss at the heterogeneous nucleation sites, primarily dispersoids, during slow cooling after extrusion. As such, the number density of dispersoids, the solute type and concentration are considered to be the key variables for the quench sensitivity. In this study, quench sensitivity and the influence of natural ageing in a lean Al–Mg–Si alloy, AA6060, which contains few dispersoids, have been investigated by hardness measurement, thermal analysis, transmission electron microscopy (TEM) and positron annihilation lifetime spectroscopy (PALS). It is shown that the quench sensitivity in this alloy is associated withmore » the degree of supersaturation of vacancies after cooling. Due to vacancy annihilation and clustering during natural ageing, the quench sensitivity is more pronounced after a short natural ageing time (30 min) compared to a longer natural ageing time (24 h). Therefore, prolonged natural ageing not only leads to an increase in hardness, but can also have a positive effect on the quench sensitivity of lean Al–Mg–Si alloys. - Highlights: • Significant quench sensitivity observed in AA6060 alloy after 30 min natural ageing • Prolonged natural ageing increased hardness and reduced QS. • Low dispersoid density leads to insignificant QS from non-hardening precipitates. • Vacancy supersaturation identified as a contributor to QS.« less

Statistical thermodynamics of strain hardening in polycrystalline solids

DOE PAGES

Langer, James S.

2015-09-18

This paper starts with a systematic rederivation of the statistical thermodynamic equations of motion for dislocation-mediated plasticity proposed in 2010 by Langer, Bouchbinder, and Lookman. The paper then uses that theory to explain the anomalous rate-hardening behavior reported in 1988 by Follansbee and Kocks and to explore the relation between hardening rate and grain size reported in 1995 by Meyers et al. A central theme is the need for physics-based, nonequilibrium analyses in developing predictive theories of the strength of polycrystalline materials.

Dissolution Kinetics of Spheroidal-Shaped Precipitates in Age-Hardenable Aluminum Alloys

NASA Astrophysics Data System (ADS)

Anjabin, Nozar; Salehi, Majid Seyed

2018-05-01

As a first attempt, a mathematical model is proposed to predict the dissolution kinetics of non-spherical secondary phase precipitates during solution heat treatment of age-hardenable aluminum alloys. The model uses general spheroidal geometry to describe the dissolution process of the alloys containing needle/disc-shaped particles with different size distributions in a finite matrix. It is found that as the aspect ratio deviates from unity, the dissolution rate is accelerated. Also, the dissolution rate of the particles in the alloy containing the particle size distribution is lower than that of mono-sized particles system. The modeling results for dissolution of θ' precipitates in an Al-Cu alloy are compared with experiments, and a good agreement was found between the modeling and the experimental results. The proposed model can be applied to different isothermal and non-isothermal annealing conditions.

Steels with controlled hardenability for induction hardening

NASA Astrophysics Data System (ADS)

Shepelyakovskii, K. Z.

1980-07-01

Steels of the CH and LH type developed in the Soviet Union permit the use of a new method of induction hardening — bulk-surface hardening — and efficient utilization of the high-strength conditions (σb = 230-250 kgf/mm2). These steels make it possible to improve the structural strength, operating characteristics, service life, and reliability of critical heavily loaded machine parts. At the same time, CH steels make it possible to reduce by a factor of 2-3 the quantity of alloying elements, reduce the electrical energy for heat treatment, and completely exclude the cost of quenching oil for heat treatment in automatic equipment with high labor productivity, while retaining good working conditions. All this leads to substantial savings in production and operation. For example, when transmission gears (cylindrical and conical) are manufactured from LH steels the annual savings amount to more than 700,000 rubles at two automobile plants. Machine parts of CH steels — half axles and bearings in railway cars —have saved respectively six and four million rubles annually. The introduction of controlled-hardenability steels for induction hardening is a necessary condition for technological progress in machine construction and metallurgy.

Characterization and Strain-Hardening Behavior of Friction Stir-Welded Ferritic Stainless Steel

NASA Astrophysics Data System (ADS)

Sharma, Gaurav; Dwivedi, Dheerendra Kumar; Jain, Pramod Kumar

2017-12-01

In this study, friction stir-welded joint of 3-mm-thick plates of 409 ferritic stainless steel (FSS) was characterized in light of microstructure, x-ray diffraction analysis, hardness, tensile strength, ductility, corrosion and work hardening properties. The FSW joint made of ferritic stainless steel comprises of three distinct regions including the base metal. In stir zone highly refined ferrite grains with martensite and some carbide precipitates at the grain boundaries were observed. X-ray diffraction analysis also revealed precipitation of Cr23C6 and martensite formation in heat-affected zone and stir zone. In tensile testing of the transverse weld samples, the failure eventuated within the gauge length of the specimen from the base metal region having tensile properties overmatched to the as-received base metal. The tensile strength and elongation of the longitudinal (all weld) sample were found to be 1014 MPa and 9.47%, respectively. However, in potentiodynamic polarization test, the corrosion current density of the stir zone was highest among all the three zones. The strain-hardening exponent for base metal, transverse and longitudinal (all weld) weld samples was calculated using various equations. Both the transverse and longitudinal weld samples exhibited higher strain-hardening exponents as compared to the as-received base metal. In Kocks-Mecking plots for the base metal and weld samples at least two stages of strain hardening were observed.

Yield Behavior of Solution Treated and Aged Ti-6Al-4V

NASA Technical Reports Server (NTRS)

Ring, Andrew J.; Baker, Eric H.; Salem, Jonathan A.; Thesken, John C.

2014-01-01

Post yield uniaxial tension-compression tests were run on a solution treated and aged (STA), titanium 6-percent aluminum 4-percent vanadium (Ti-6Al-4V) alloy to determine the yield behavior on load reversal. The material exhibits plastic behavior almost immediately on load reversal implying a strong Bauschinger effect. The resultant stress-strain data was compared to a 1D mechanics model and a finite element model used to design a composite overwrapped pressure vessel (COPV). Although the models and experimental data compare well for the initial loading and unloading in the tensile regime, agreement is lost in the compressive regime due to the Bauschinger effect and the assumption of perfect plasticity. The test data presented here are being used to develop more accurate cyclic hardening constitutive models for future finite element design analysis of COPVs.

Influence of Cooling Condition on the Performance of Grinding Hardened Layer in Grind-hardening

NASA Astrophysics Data System (ADS)

Wang, G. C.; Chen, J.; Xu, G. Y.; Li, X.

2018-02-01

45# steel was grinded and hardened on a surface grinding machine to study the effect of three different cooling media, including emulsion, dry air and liquid nitrogen, on the microstructure and properties of the hardened layer. The results show that the microstructure of material surface hardened with emulsion is pearlite and no hardened layer. The surface roughness is small and the residual stress is compressive stress. With cooling condition of liquid nitrogen and dry air, the specimen surface are hardened, the organization is martensite, the surface roughness is also not changed, but high hardness of hardened layer and surface compressive stress were obtained when grinding using liquid nitrogen. The deeper hardened layer grinded with dry air was obtained and surface residual stress is tensile stress. This study provides an experimental basis for choosing the appropriate cooling mode to effectively control the performance of grinding hardened layer.

Evaluation of Solute Clusters Associated with Bake-Hardening Response in Isothermal Aged Al-Mg-Si Alloys Using a Three-Dimensional Atom Probe

NASA Astrophysics Data System (ADS)

Aruga, Yasuhiro; Kozuka, Masaya; Takaki, Yasuo; Sato, Tatsuo

2014-12-01

Temporal changes in the number density, size distribution, and chemical composition of clusters formed during natural aging at room temperature and pre-aging at 363 K (90 °C) in an Al-0.62Mg-0.93Si (mass pct) alloy were evaluated using atom probe tomography. More than 10 million atoms were examined in the cluster analysis, in which about 1000 clusters were obtained for each material after various aging treatments. The statistically proven records show that both number density and the average radius of clusters in pre-aged materials are larger than in naturally aged materials. It was revealed that the fraction of clusters with a low Mg/Si ratio after natural aging for a short time is higher than with other aging treatments, regardless of cluster size. This indicates that Si-rich clusters form more easily after short-period natural aging, and that Mg atoms can diffuse into the clusters or possibly form another type of Mg-Si cluster after prolonged natural aging. The formation of large clusters with a uniform Mg/Si ratio is encouraged by pre-aging. It can be concluded that an increase of small clusters with various Mg/Si ratios does not promote the bake-hardening (BH) response, whereas large clusters with a uniform Mg/Si ratio play an important role in hardening during the BH treatment at 443 K (170 °C).

Comparison of linear and square superposition hardening models for the surface nanoindentation of ion-irradiated materials

NASA Astrophysics Data System (ADS)

Xiao, Xiazi; Yu, Long

2018-05-01

Linear and square superposition hardening models are compared for the surface nanoindentation of ion-irradiated materials. Hardening mechanisms of both dislocations and defects within the plasticity affected region (PAR) are considered. Four sets of experimental data for ion-irradiated materials are adopted to compare with theoretical results of the two hardening models. It is indicated that both models describe experimental data equally well when the PAR is within the irradiated layer; whereas, when the PAR is beyond the irradiated region, the square superposition hardening model performs better. Therefore, the square superposition model is recommended to characterize the hardening behavior of ion-irradiated materials.

TEM Studies of Boron-Modified 17Cr-7Ni Precipitation-Hardenable Stainless Steel via Rapid Solidification Route

NASA Astrophysics Data System (ADS)

Gupta, Ankur; Bhargava, A. K.; Tewari, R.; Tiwari, A. N.

2013-09-01

Commercial grade 17Cr-7Ni precipitation-hardenable stainless steel has been modified by adding boron in the range 0.45 to 1.8 wt pct and using the chill block melt-spinning technique of rapid solidification (RS). Application of RS has been found to increase the solid solubility of boron and hardness of 17Cr-7Ni precipitation-hardenable stainless steel. The hardness of the boron-modified rapidly solidified alloys has been found to increase up to ~280 pct after isochronal aging to peak hardness. A TEM study has been carried out to understand the aging behavior. The presence of M23(B,C)6 and M2(B,C) borocarbides and epsilon-carbide in the matrix of austenite and ferrite with a change in heat treatment temperature has been observed. A new equation for Creq is also developed which includes the boron factor on ferrite phase stability. The study also emphasizes that aluminum only takes part in ferrite phase stabilization and remains in the solution.

Ageing behaviour of an Fe-20Ni-1.8Mn-1.6Ti-0.59Al (wt%) maraging alloy: clustering, precipitation and hardening

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

Pereloma, E.V.; Shekhter, A.; Miller, M.K.

2004-11-08

Changes in the solute distribution as well as the evolution of precipitation, microstructure and mechanical properties have been studied in an experimental maraging Fe-20Ni-1.8Mn-1.5Ti-0.59Al (wt%) alloy during ageing at 550 deg C. An initial hardening reaction within 5 s is reported, which is remarkable in terms of extent and rapidity. This strengthening was caused by the formation of complex multi-component atomic co-clusters containing primarily Ni-Ti-Al as well as some Mn. This cluster strengthened condition produced the optimum toughness observed throughout the ageing sequence. After 60 s ageing, the appearance of discrete precipitation of needle-shaped {eta}-Ni{sub 3}Ti particles was associated withmore » a second rise in hardness towards an eventual peak at 600 s. This precipitation hardening was accompanied by an increase in tensile strength and a decrease in ductility. A reverse transformation of martensite to austenite occurs progressively during ageing and this contributes to the initial and secondary softening.« less

Influence of Microstructural and Load Wave Form Control on Fatigue Crack Growth behavior of Precipitation Hardening Stainless Steels

DTIC Science & Technology

1976-07-01

heating to temperatures below the Acl precipitates a copper -rich phase within the martensite increasing hardness and strength. The stress relieving effect...experimental approach varied the heat treatment of two precipitation hardening martensitic alloys , 17-4 PH1 and 15-b PH. Fatigue-crack growth data was...hardenable by precipitation hardening. Alloys that do harden by this mechanism have only one thing in common, this is, a decreasing solubility for one phase

Microstructure and Mechanical Behavior of 17-4 Precipitation Hardenable Steel Processed by Selective Laser Melting

NASA Astrophysics Data System (ADS)

Rafi, H. Khalid; Pal, Deepankar; Patil, Nachiket; Starr, Thomas L.; Stucker, Brent E.

2014-12-01

The mechanical behavior and the microstructural evolution of 17-4 precipitation hardenable (PH) stainless steel processed using selective laser melting have been studied. Test coupons were produced from 17-4 PH stainless steel powder in argon and nitrogen atmospheres. Characterization studies were carried out using mechanical testing, optical microscopy, scanning electron microscopy, and x-ray diffraction. The results show that post-process heat treatment is required to obtain typically desired tensile properties. Columnar grains of smaller diameters (<2 µm) emerged within the melt pool with a mixture of martensite and retained austenite phases. It was found that the phase content of the samples is greatly influenced by the powder chemistry, processing environment, and grain diameter.

Development of Press Hardening Steel with High Resistance to Hydrogen Embrittlement

NASA Astrophysics Data System (ADS)

Bian, Jian; Mohrbacher, Hardy; Lu, Hongzhou; Wang, Wenjun

Press hardening has become the state-of-art technology in the car body manufacturing to enhance safety standard and to reduce CO2 emission of new vehicles. However the delayed cracking due to hydrogen embrittlement remains to be a critical issue. Generally press hardening steel is susceptible to hydrogen embrittlement due to ultra-high strength and martensitic microstructure. The hydrogen charging tests clearly demonstrate that only a few ppm of diffusible hydrogen is sufficient to cause such embrittlement. Currently the hydrogen embrittlement cannot be detected in the press hardened components and the embitteled components could collapse in the crash situation with fatal consequences arisen through dramatic loss in both strength and ductility. This paper introduces a new metallurgical solution to increase the resistance to hydrogen embrittlement of conventional press hardening steel based on 22MnB5 by Nb microalloying. In the hydrogen embrittlement and permeation tests the impact of Nb microalloying on the hydrogen embrittlement behavior was investigated under different hydrogen charging conditions and constant load. The test results revealed that Nb addition increases the resistance to hydrogen embrittlement due to reduced hydrogen diffusivity. The focus of this paper is to investigate the precipitation behavior of microalloying elements by using TEM and STEM and to find out the mechanisms leading to higher performance against hydrogen embrittlement of Nb alloyed steels.

Surface Fatigue Resistance with Induction Hardening

NASA Technical Reports Server (NTRS)

Townsend, Dennis; Turza, Alan; Chapman, Mike

1996-01-01

Induction hardening has been used for some years to harden the surface and improve the strength and service life of gears and other components. Many applications that employ induction hardening require a relatively long time to finish the hardening process and controlling the hardness of the surface layer and its depth often was a problem. Other surface hardening methods, ie., carbonizing, take a very long time and tend to cause deformations of the toothing, whose elimination requires supplementary finishing work. In double-frequency induction hardening, one uses a low frequency for the preheating of the toothed wheel and a much higher frequency for the purpose of rapidly heating the surface by way of surface hardening.

The effect of matrix microstructure on cyclic response and fatigue behavior of particle- reinforced 2219 aluminum: Part I. room temperature behavior

NASA Astrophysics Data System (ADS)

Vyletel, G. M.; Allison, J. E.; van Aken, D. C.

1995-12-01

The low-cycle and high-cycle fatigue behavior and cyclic response of naturally aged and overaged 2219/TiC/15p and unreinforced 2219 Al were investigated using plastic strain-controlled and stress-controlled testing. In addition, the influence of grain size on the particle-reinforced materials was examined. In both reinforced and unreinforced materials, the naturally aged conditions were cyclically unstable, exhibiting an initial hardening behavior followed by an extended region of cyclic stability and ultimately a softening region. The overaged reinforced material was cyclically stable for the plastic strains examined, while the overaged unreinforced material exhibited cyclic hardening at plastic strains greater than 2.5 × 10-4. Decreasing grain size of particle-reinforced materials modestly increased the cyclic flow stress of both naturally aged and overaged materials. Reinforced and unreinforced materials exhibited similar fatigue life behaviors; however, the reinforced and unreinforced naturally aged materials had superior fatigue lives in comparison to the overaged materials. Grain size had no effect on the fatigue life behavior of the particle-reinforced materials. The fatigue lives were strongly influenced by the presence of clusters of TiC particles and exogenous Al3Ti intermetallics.

Effect of Aging Temperature on Corrosion Behavior of Sintered 17-4 PH Stainless Steel in Dilute Sulfuric Acid Solution

NASA Astrophysics Data System (ADS)

Szewczyk-Nykiel, Aneta; Kazior, Jan

2017-07-01

The general corrosion behavior of sintered 17-4 PH stainless steel processed under different processing conditions in dilute sulfuric acid solution at 25 °C was studied by open-circuit potential measurement and potentiodynamic polarization technique. The corrosion resistance was evaluated based on electrochemical parameters, such as polarization resistance, corrosion potential, corrosion current density as well as corrosion rate. The results showed that the precipitation-hardening treatment could significantly improve the corrosion resistance of the sintered 17-4 PH stainless steel in studied environment. As far as the influence of aging temperature on corrosion behavior of the sintered 17-4 PH stainless steel is concerned, polarization resistance and corrosion rate are reduced with increasing aging temperature from 480 up to 500 °C regardless of the temperature of solution treatment. It can be concluded that the highest corrosion resistance in 0.5 M H2SO4 solution exhibits 17-4 PH after solution treatment at 1040 °C followed by aging at 480 °C.

Hardening [Chapter 12

Treesearch

Douglass F. Jacobs; Thomas D. Landis

2009-01-01

To promote survival and growth following outplanting, nursery stock must undergo proper hardening. Without proper hardening, plants do not store well over winter and are likely to grow poorly or die on the outplanting site. It is important to understand that native plant nurseries are different from traditional horticultural systems in that native plants must endure an...

System-Level Radiation Hardening

NASA Technical Reports Server (NTRS)

Ladbury, Ray

2014-01-01

Although system-level radiation hardening can enable the use of high-performance components and enhance the capabilities of a spacecraft, hardening techniques can be costly and can compromise the very performance designers sought from the high-performance components. Moreover, such techniques often result in a complicated design, especially if several complex commercial microcircuits are used, each posing its own hardening challenges. The latter risk is particularly acute for Commercial-Off-The-Shelf components since high-performance parts (e.g. double-data-rate synchronous dynamic random access memories - DDR SDRAMs) may require other high-performance commercial parts (e.g. processors) to support their operation. For these reasons, it is essential that system-level radiation hardening be a coordinated effort, from setting requirements through testing up to and including validation.

Model Identification and FE Simulations: Effect of Different Yield Loci and Hardening Laws in Sheet Forming

NASA Astrophysics Data System (ADS)

Flores, P.; Duchêne, L.; Lelotte, T.; Bouffioux, C.; El Houdaigui, F.; Van Bael, A.; He, S.; Duflou, J.; Habraken, A. M.

2005-08-01

The bi-axial experimental equipment developed by Flores enables to perform Baushinger shear tests and successive or simultaneous simple shear tests and plane-strain tests. Such experiments and classical tensile tests investigate the material behavior in order to identify the yield locus and the hardening models. With tests performed on two steel grades, the methods applied to identify classical yield surfaces such as Hill or Hosford ones as well as isotropic Swift type hardening or kinematic Armstrong-Frederick hardening models are explained. Comparison with the Taylor-Bishop-Hill yield locus is also provided. The effect of both yield locus and hardening model choice will be presented for two applications: Single Point Incremental Forming (SPIF) and a cup deep drawing.

Production and Precipitation Hardening of Beta-Type Ti-35Nb-10Cu Alloy Foam for Implant Applications

NASA Astrophysics Data System (ADS)

Mutlu, Ilven; Yeniyol, Sinem; Oktay, Enver

2016-04-01

In this study, beta-type Ti-35Nb-10Cu alloy foams were produced by powder metallurgy method for dental implant applications. 35% Nb was added to stabilize the beta-Ti phase with low Young's modulus. Cu addition enhanced sinterability and gave precipitation hardening capacity to the alloy. Sintered specimens were precipitation hardened in order to enhance the mechanical properties. Electrochemical corrosion behavior of the specimens was examined by electrochemical impedance spectroscopy in artificial saliva. Electrochemical impedance spectroscopy results indicated that the oxide film on the surface of foam is a bi-layer structure consisting of outer porous layer and inner barrier layer. Impedance values of barrier layer were higher than porous layer. Corrosion resistance of specimens decreased at high fluoride concentrations and at low pH of artificial saliva. Corrosion resistance of alloys was slightly decreased with aging. Mechanical properties, microstructure, and surface roughness of the specimens were also examined.

Effect of reinforcing particle type on morphology and age-hardening behavior of Al–4.5 wt.% Cu based nanocomposites synthesized through mechanical milling

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

Mostaed, A., E-mail: alimostaed@yahoo.com; Saghafian, H.; Mostaed, E.

2013-02-15

The effects of reinforcing particle type (SiC and TiC) on morphology and precipitation hardening behavior of Al–4.5%Cu based nanocomposites synthesized via mechanical milling were investigated in the current work. In order to study the microstructure and morphology of mechanically milled powder, X-ray diffraction technique, scanning electron microscopy and high resolution transmission electron microscopy were utilized. Results revealed that at the early stages of mechanical milling, when reinforcing particles are polycrystal, the alloying process is enhanced more in the case of using the TiC particles as reinforcement. But, at the final stages of mechanical milling, when reinforcing particles are single crystal,more » the alloying process is enhanced more in the case of using the SiC ones. Transmission electron microscopy results demonstrated that Al–4.5 wt.%Cu based nanocomposite powders were synthesized and confirmed that the mutual diffusion of aluminum and copper occurs through the interfacial plane of (200). The hardness results showed that not only does introducing 4 vol.% of reinforcing particles (SiC or TiC) considerably decrease the porosity of the bulk composite samples, but also it approximately doubles the hardness of Al–4.5 wt.%Cu alloy (53.4 HB). Finally, apart from TEM and scanning electron microscopy observation which are localized, a decline in hardness in the TiC and SiC contained samples, respectively, after 1.5 and 2 h aging time at 473 K proves the fact that the size of SiC particles is smaller than the size of the TiC ones. - Highlights: ► HRTEM results show mutual diffusion of Al and Cu occurs through the (200) planes. ► TiC particles enhance alloying process more than the SiC ones at the early stages of MM. ► SiC particles enhance alloying process more than the TiC ones at the final stages of MM.« less

Nanoparticle amount, and not size, determines chain alignment and nonlinear hardening in polymer nanocomposites

PubMed Central

Varol, H. Samet; Meng, Fanlong; Hosseinkhani, Babak; Malm, Christian; Bonn, Daniel; Bonn, Mischa; Zaccone, Alessio

2017-01-01

Polymer nanocomposites—materials in which a polymer matrix is blended with nanoparticles (or fillers)—strengthen under sufficiently large strains. Such strain hardening is critical to their function, especially for materials that bear large cyclic loads such as car tires or bearing sealants. Although the reinforcement (i.e., the increase in the linear elasticity) by the addition of filler particles is phenomenologically understood, considerably less is known about strain hardening (the nonlinear elasticity). Here, we elucidate the molecular origin of strain hardening using uniaxial tensile loading, microspectroscopy of polymer chain alignment, and theory. The strain-hardening behavior and chain alignment are found to depend on the volume fraction, but not on the size of nanofillers. This contrasts with reinforcement, which depends on both volume fraction and size of nanofillers, potentially allowing linear and nonlinear elasticity of nanocomposites to be tuned independently. PMID:28377517

Strain hardening and fracture behavior during tension of directionally solidified high-nitrogen austenitic steel

NASA Astrophysics Data System (ADS)

Maier, Galina; Astafurova, Elena; Melnikov, Eugene; Moskvina, Valentina; Galchenko, Nina

2017-12-01

The effect of grain orientation relative to tensile load on the strain hardening behavior and fracture mechanism of directionally solidified high-nitrogen steel Fe-20Cr-22Mn-1.5V-0.2C-0.6N (in wt %) was studied. The tensile samples oriented along the longitudinal direction of columnar grains demonstrated the improved mechanical properties compared to specimens with the transversal directions of columnar grains: the values of tensile strength and strain-to-fracture were as high as 1080 MPa and 22%, respectively, for tension along the columnar grains and 870 MPa and 11%, respectively, for the tension transversal to the columnar grains. The change in the grain orientation relative to the tensile load varies a fracture mode of the steel. The fraction of the transgranular fracture was higher in the samples with longitudinal directions of the columnar grains compared to the transversal ones.

Processing, Microstructures and Properties of a Dual Phase Precipitation-Hardening PM Stainless Steel

NASA Astrophysics Data System (ADS)

Schade, Christopher

To improve the mechanical properties of PM stainless steels in comparison with their wrought counterparts, a PM stainless steel alloy was developed which combines a dual-phase microstructure with precipitation-hardening. The use of a mixed microstructure of martensite and ferrite results in an alloy with a combination of the optimum properties of each phase, namely strength and ductility. The use of precipitation hardening via the addition of copper results in additional strength and hardness. A range of compositions was studied in combination with various sintering conditions to determine the optimal thermal processing to achieve the desired microstructure. The microstructure could be varied from predominately ferrite to one containing a high percentage of martensite by additions of copper and a variation of the sintering temperature before rapid cooling. Mechanical properties (transverse rupture strength (TRS), yield strength, tensile strength, ductility and impact toughness) were measured as a function of the v/o ferrite in the microstructure. A dual phase alloy with the optimal combination of properties served as the base for introducing precipitation hardening. Copper was added to the base alloy at various levels and its effect on the microstructure and mechanical properties was quantified. Processing at various sintering temperatures led to a range of microstructures; dilatometry was used utilized to monitor and understand the transformations and the formation of the two phases. The aging process was studied as a function of temperature and time by measuring TRS, yield strength, tensile strength, ductility, impact toughness and apparent hardness. It was determined that optimum aging was achieved at 538°C for 1h. Aging at slightly lower temperatures led to the formation of carbides, which contributed to reduced hardness and tensile strength. As expected, at the peak aging temperature, an increase in yield strength and ultimate tensile strength as well as

Extracting material response from simple mechanical tests on hardening-softening-hardening viscoplastic solids

NASA Astrophysics Data System (ADS)

Mohan, Nisha

Uniaxial Compression of Vertically Aligned Carbon Nanotubes," J. Mech.Phys. Solids, 59, pp. 2227--2237, Erratum 60, 1753-1756 (2012)], the property space exploration was advanced to three types of simple mechanical tests: 1) uniaxial compression, 2) uniaxial tension, and 3) nanoindentation with a conical and a flat-punch tip. The simulations attempt to explain some of the salient features in experimental data, like 1) The initial linear elastic response. 2) One or more nonlinear instabilities, yielding, and hardening. The model-inherent relationships between the material properties and the overall stress-strain behavior were validated against the available experimental data. The material properties include the gradient in stiffness along the height, plastic and elastic compressibility, and hardening. Each of these tests was evaluated in terms of their efficiency in extracting material properties. The uniaxial simulation results proved to be a combination of structural and material influences. Out of all deformation paths, flat-punch indentation proved to be superior since it is the most sensitive in capturing the material properties.

Contact allergy to epoxy hardeners.

PubMed

Aalto-Korte, Kristiina; Suuronen, Katri; Kuuliala, Outi; Henriks-Eckerman, Maj-Len; Jolanki, Riitta

2014-09-01

Diglycidylether of bisphenol A resin is the most important sensitizer in epoxy systems, but a minority of patients develop concomitant or solitary contact allergy to epoxy hardeners. At the Finnish Institute of Occupational Health, several in-house test substances of epoxy hardeners have been tested in a special epoxy compound patch test series. To analyse the frequency and clinical relevance of allergic reactions to different epoxy hardeners. Test files (January 1991 to March 2013) were screened for contact allergy to different epoxy hardeners, and the clinical records of patients with allergic reactions were analysed for occupation, concomitant allergic reactions, and exposure. The most commonly positive epoxy hardeners were m-xylylenediamine (n = 24), 2,4,6-tris-(dimethylaminomethyl)phenol (tris-DMP; n = 14), isophorone-diamine (n = 12), and diethylenetriamine (n = 9). Trimethylhexamethylenediamine (n = 7), tetraethylenepentamine (n = 4), and triethylenetetramine (n = 2) elicited some reactions, although most patients were found to have no specific exposure. Allergic reactions to hexamethylenetetramine, dimethylaminopropylamine and ethylenediamine dihydrochloride were not related to epoxy products. Tris-DMP is an important sensitizer in epoxy hardeners, and should be included in the patch test series of epoxy chemicals. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Effect of temper rolling on the bake-hardening behavior of low carbon steel

NASA Astrophysics Data System (ADS)

Kuang, Chun-fu; Zhang, Shen-gen; Li, Jun; Wang, Jian; Li, Pei

2015-01-01

In a typical process, low carbon steel was annealed at two different temperatures (660°C and 750°C), and then was temper rolled to improve the mechanical properties. Pre-straining and baking treatments were subsequently carried out to measure the bake-hardening (BH) values. The influences of annealing temperature and temper rolling on the BH behavior of the steel were investigated. The results indicated that the microstructure evolution during temper rolling was related to carbon atoms and dislocations. After an apparent increase, the BH value of the steel significantly decreased when the temper rolling reduction was increased from 0% to 5%. This was attributed to the increase in solute carbon concentration and dislocation density. The maximum BH values of the steel annealed at 660°C and 750°C were 80 MPa and 89 MPa at the reductions of 3% and 4%, respectively. Moreover, increasing the annealing temperature from 660 to 750°C resulted in an obvious increase in the BH value due to carbide dissolution.

Properties and Commercial Application of Manual Plasma Hardening

NASA Astrophysics Data System (ADS)

Korotkov, V. A.

2016-11-01

A new method and a device for plasma hardening of various parts are considered. Installation of the new device does not require too much investment (the active mechanical productions are appropriate for its accommodation) and special choice of personnel (welders train to use it without difficulty). Plasma hardening does not deform and worsen the smoothness of the surface, which makes it possible to employ many hardened parts without finishing mechanical treatment required after bulk or induction hardening. The hardened layer (about 1 mm) produced by plasma hardening exhibits better wear resistance than after bulk hardening with tempering, which prolongs the service life of the parts.

Kinematic hardening of a porous limestone

NASA Astrophysics Data System (ADS)

Cheatham, J. B.; Allen, M. B.; Celle, C. C.

1984-10-01

A concept for a kinematic hardening yield surface in stress space for Cordova Cream limestone (Austin Chalk) developed by Celle and Cheatham (1981) has been improved using Ziegler's modification of Prager's hardening rule (Ziegler, 1959). Data to date agree with the formulated concepts. It is shown how kinematic hardening can be used to approximate the yield surface for a wide range of stress states past the initial yield surface. The particular difficulty of identifying the yield surface under conditions of unloading or extension is noted. A yield condition and hardening rule which account for the strain induced anisotropy in Cordova Cream Limestone were developed. Although the actual yield surface appears to involve some change of size and shape, it is concluded that true kinematic hardening provides a basis for engineering calculations.

Simulation of irradiation hardening of Zircaloy within plate-type dispersion nuclear fuel elements

NASA Astrophysics Data System (ADS)

Jiang, Yijie; Wang, Qiming; Cui, Yi; Huo, Yongzhong; Ding, Shurong

2011-06-01

Within plate-type dispersion nuclear fuel elements, the metal matrix and cladding attacked continuously by fast neutrons undergo irradiation hardening, which might have remarkable effects upon the mechanical behaviors within fuel elements. In this paper, with the irradiation hardening effect of metal materials mainly considered together with irradiation growth effect of the cladding, the three-dimensional large-deformation constitutive relations for the metal matrix and cladding are developed. The method of virtual temperature increase in the previous studies is further developed to model the irradiation swelling of fuel particles; the method of anisotropic thermal expansion is introduced to model irradiation growth of the cladding; and a method of multi-step-temperature loading is proposed to simulate the coupling features of irradiation-induced swelling of the fuel particles together with irradiation growth of the cladding. Above all, based on the developed relationship between irradiation growth at certain burnup and the loaded virtual temperatures, with considering that certain burnup corresponds to certain fast neutron fluence, the time-dependent constitutive relation due to irradiation hardening effect is replaced by the virtual-temperature-dependent one which is introduced into the commercial software to simulate the irradiation hardening effects of the matrix and cladding. Numerical simulations of the irradiation-induced mechanical behaviors are implemented with the finite element method in consideration of the micro-structure of the fuel meat. The obtained results indicate that when the irradiation hardening effects are introduced into the constitutive relations of the metal matrix and cladding: (1) higher maximum Mises stresses for certain burnup at the matrix exist with the equivalent plastic strains remaining almost the same at lower burnups; (2) the maximum Mises stresses for certain burnup at the cladding are enhanced while the maximum equivalent

Radiation Hardened Electronics for Extreme Environments

NASA Technical Reports Server (NTRS)

Keys, Andrew S.; Watson, Michael D.

2007-01-01

The Radiation Hardened Electronics for Space Environments (RHESE) project consists of a series of tasks designed to develop and mature a broad spectrum of radiation hardened and low temperature electronics technologies. Three approaches are being taken to address radiation hardening: improved material hardness, design techniques to improve radiation tolerance, and software methods to improve radiation tolerance. Within these approaches various technology products are being addressed including Field Programmable Gate Arrays (FPGA), Field Programmable Analog Arrays (FPAA), MEMS Serial Processors, Reconfigurable Processors, and Parallel Processors. In addition to radiation hardening, low temperature extremes are addressed with a focus on material and design approaches.

Cyclic hardening behavior of extruded ZK60 magnesium alloy with different grain sizes

NASA Astrophysics Data System (ADS)

Zhang, Lixin; Zhang, Wencong; Chen, Wenzhen; Wang, Wenke

2018-04-01

Montonic and fully reversed strain-controlled cyclic deformation experiments were conducted on extruded ZK60 magnesium alloy with two different grain sizes in ambient air. Results revealed that the hardening rates of the ZK60 magnesium alloy rods with fine grain and coarse grain in the monotonic deformation and the fully reversed strain-controlled cyclic deformation were opposite along the extrusion direction. Electron Backscatter Diffration analysis revealed that fine grains were more easily rotated than coarse grains under the cyclic deformation. Under the twinning and detwinning process of the cyclic deformation at a large strain amplitude, the coarse grained ZK60 magnesium alloys were more prone to tension twinning {10-12}<10-11> and more residual twins were observed. Texture hardening of coarse grained magnesium alloy was more obvious in cyclic defromation than fine-grained magnesium alloy.

Early age strength increase of fly ash blended cement by a ternary hardening accelerating admixture

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

Hoang, Kien; Justnes, Harald; SINTEF Building and Infrastructure

The applicability of a combination of sodium thiocyanate (NaSCN), diethanolamine (DEA) and glycerol (Gly) with small dosages as a ternary hardening accelerating admixture for fly ash blended cement (OPC-FA) was studied. The ternary admixture induced higher early and later age mortar strength at both low (5 °C) and normal (20 °C) temperature. Despite used in lower dosage the ternary admixture led to higher strength of the investigated OPC-FA system than other chemicals (e.g. sodium sulfate). Results obtained from isothermal calorimetry, thermogravimetric analysis (TGA) and X-ray diffraction (XRD) showed that the ternary admixture accelerated the cement hydration and increased the amountmore » of AFm (notably calcium hemicarboaluminate hydrate) in the hydration products. A synergistic effect between the three components of the accelerator on the hydration of OPC-FA system was observed.« less

X-Ray Diffraction Profile Analysis for Characterizing Isothermal Aging Behavior of M250 Grade Maraging Steel

NASA Astrophysics Data System (ADS)

Mahadevan, S.; Jayakumar, T.; Rao, B. P. C.; Kumar, Anish; Rajkumar, K. V.; Raj, Baldev

2008-08-01

X-ray diffraction (XRD) studies were carried out to characterize aging behavior of M250 grade maraging steel samples subjected to isothermal aging at 755 K for varying durations of 0.25, 1, 3, 10, 40, 70, and 100 hours. Earlier studies had shown typical features of precipitation hardening, wherein the hardness increased to a peak value due to precipitation of intermetallics and decreased upon further aging (overaging) due to reversion of martensite to austenite. Intermetallic precipitates, while coherent, are expected to increase the microstrain in the matrix. Hence, an attempt has been made in the present study to understand the microstructural changes in these samples using XRD line profile analysis. The anisotropic broadening with diffraction angle observed in the simple Williamson Hall (WH) plot has been addressed using the modified WH (mWH) approach, which takes into account the contrast caused by dislocations on line profiles, leading to new scaling factors in the WH plot. The normalized mean square strain and crystallite size estimated from mWH have been used to infer early precipitation and to characterize aging behavior. The normalized mean square strain has been used to determine the Avrami exponent in the Johnson Mehl Avrami (JMA) equation, which deals with the kinetics of precipitation. The Avrami exponent thus determined has matched well with values found by other methods, as reported in literature.

Press-hardening of zinc coated steel - characterization of a new material for a new process

NASA Astrophysics Data System (ADS)

Kurz, T.; Larour, P.; Lackner, J.; Steck, T.; Jesner, G.

2016-11-01

Press-hardening of zinc-coated PHS has been limited to the indirect process until a pre-cooling step was introduced before the hot forming to prevent liquid metal embrittlement. Even though that's only a minor change in the process itself it does not only eliminate LME, but increases also the demands on the base material especially in terms of hardenability or phase transformations at temperatures below 700 °C in general. This paper deals with the characterization of a modified zinc-coated material for press-hardening with pre-cooling that assures a robust process. The pre-cooling step itself and especially the transfer of the blank in the hot-forming die is more demanding than the standard 22MnB5 can stand to ensure full hardenability. Therefore the transformation behavior of the modified material is shown in CCT and TTT diagrams. Of the same importance are the changed hot forming temperature and flow curves for material at lower temperatures than typically used in direct hot forming. The resulting mechanical properties after hardening from tensile testing and bending tests are shown in detail. Finally some results from side impact crash tests and correlations of the findings with mechanical properties such as fracture elongation, tensile strength, VDA238 bending angle at maximum force as well as postuniform bending slope are given as well. Fracture elongation is shown to be of little help for damage prediction in side impact crash. Tensile strength and VDA bending properties enable however some accurate prediction of the PHS final damage behavior in bending dominated side impact load case.

Influence of Yield Stress Determination in Anisotropic Hardening Model on Springback Prediction in Dual-Phase Steel

NASA Astrophysics Data System (ADS)

Lee, J.; Bong, H. J.; Ha, J.; Choi, J.; Barlat, F.; Lee, M.-G.

2018-05-01

In this study, a numerical sensitivity analysis of the springback prediction was performed using advanced strain hardening models. In particular, the springback in U-draw bending for dual-phase 780 steel sheets was investigated while focusing on the effect of the initial yield stress determined from the cyclic loading tests. The anisotropic hardening models could reproduce the flow stress behavior under the non-proportional loading condition for the considered parametric cases. However, various identification schemes for determining the yield stress of the anisotropic hardening models significantly influenced the springback prediction. The deviations from the measured springback varied from 4% to 13.5% depending on the identification method.

Dynamic strain aging behavior of 10Cr steel under low cycle fatigue at 650°C

NASA Astrophysics Data System (ADS)

Mishnev, Roman; Dudova, Nadezhda; Kaibyshev, Rustam

2017-12-01

The low cycle fatigue behavior of a 10Cr-2W-0.7Mo-3Co-NbV steel with 80 ppm of B additions was studied at elevated temperatures of 600 and 650°C. The steel after normalizing and tempering at 770°C was tested under fully reversed tension-compression loading with the total strain amplitude controlled from ±0.2 to ±1.0% at temperatures of 600 and 650°C. It was revealed that the steel exhibits a positive temperature dependence of both the cyclic strain hardening exponent n' and the cyclic strength coefficient K ' during cyclic loading at 650°C. It was suggested that dynamic strain aging causes fatigue resistance degradation through facilitating microcrack initiation.

Precipitation of T1 and θ′ Phase in Al-4Cu-1Li-0.25Mn During Age Hardening: Microstructural Investigation and Phase-Field Simulation

PubMed Central

Häusler, Ines; Schwarze, Christian; Bilal, Muhammad Umer; Valencia Ramirez, Daniela; Hetaba, Walid; Darvishi Kamachali, Reza; Skrotzki, Birgit

2017-01-01

Experimental and phase field studies of age hardening response of a high purity Al-4Cu-1Li-0.25Mn-alloy (mass %) during isothermal aging are conducted. In the experiments, two hardening phases are identified: the tetragonal θ′ (Al2Cu) phase and the hexagonal T1 (Al2CuLi) phase. Both are plate shaped and of nm size. They are analyzed with respect to the development of their size, number density and volume fraction during aging by applying different analysis techniques in TEM in combination with quantitative microstructural analysis. 3D phase-field simulations of formation and growth of θ′ phase are performed in which the full interfacial, chemical and elastic energy contributions are taken into account. 2D simulations of T1 phase are also investigated using multi-component diffusion without elasticity. This is a first step toward a complex phase-field study of T1 phase in the ternary alloy. The comparison between experimental and simulated data shows similar trends. The still unsaturated volume fraction indicates that the precipitates are in the growth stage and that the coarsening/ripening stage has not yet been reached. PMID:28772481

a Calorimetric Study of the Precipitation Hardening Mechanisms in AN Al-Cu-Mg-Si Alloy

NASA Astrophysics Data System (ADS)

Hayoune, Abdelali

2013-08-01

The precipitation phenomena and the related hardening in an Al-Cu-Mg-Si alloy were studied by calorimetry, X-ray diffraction analysis and microhardness measurements. The main calorimetric peaks were identified to be due to β‧‧, θ‧ and Q‧ phases precipitation. The hardening during aging at room temperature and 160°C, was respectively, explained by atomic clusters and GP zones formation and by GP zones and β‧‧/θ‧ phases coprecipitation. Although the mechanical properties variation during aging at 200°C is simple, the corresponding microstructural evolution is complex: on the basis of the DSC results, the increasing of microhardness values, is mainly due to the coprecipitation of GP zones and β‧‧/θ‧ phases, however, the maximum hardening is explained by the coexistence of β‧‧/θ‧ and θ‧‧ phases. Another important conclusion is that during aging at 160°C and 200°C, the θ‧ phase is essentially developed from GP zones.

Aging behavior of an in-situ TiB{sub 2}/Al-Cu-Li-x matrix composite

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

Shen, Yanwei; Hong, Tianran; Geng, Jiwei

Transmission electron microscopy, differential scanning calorimetry and hardness tests have been performed on an in-situ TiB{sub 2}/Al-3.3Cu-1.0Li-0.60Mg-0.40Ag-0.14Zr-0.13Si composite to study its aging behavior at 175 °C. A cubic phase suspected to be the σ (Al{sub 5}Cu{sub 6}Mg{sub 2}) phase or its variant is precipitated at all aging stages studied, and this phase is not typically observed in the Al-Cu-Li alloys. The primary hardening (aging for 3 h) phases consist of δ′ (Al{sub 3}Li), β′ (Al{sub 3}Zr) and the cubic phase. After aging for 18 h, all precipitates including T{sub 1} (Al{sub 2}CuLi), S (Al{sub 2}CuMg), θ′ (Al{sub 2}Cu), δ′, β′more » and the cubic phase have appeared, and the formation of T{sub 1} and S results in a rapid increase in hardness. With prolonging of aging time, the apparent coarsening of T{sub 1} and S results in a decline in hardness. - Highlights: •The aging behavior of an in-situ TiB{sub 2}/Al-Cu-Li-x composite was studied. •A cubic phase suspected to be σ (Al{sub 5}Cu{sub 6}Mg{sub 2}) or its variant was precipitated. •The hardness change was dominated by the evolution of T{sub 1} (Al{sub 2}CuLi) and S (Al{sub 2}CuMg).« less

The role of twinning deformation on the hardening response of polycrystalline magnesium from discrete dislocation dynamics simulations

DOE PAGES

Fan, Haidong; Aubry, Sylvie; Arsenlis, Athanasios; ...

2015-04-13

The mechanical response of micro-twinned polycrystalline magnesium was studied through three-dimensional discrete dislocation dynamics (DDD). A systematic interaction model between dislocations and (1012) tension twin boundaries (TBs) was proposed and introduced into the DDD framework. In addition, a nominal grain boundary (GB) model agreeing with experimental results was also introduced to mimic the GB’s barrier effect. The current simulation results show that TBs act as a strong obstacle to gliding dislocations, which contributes significantly to the hardening behavior of magnesium. On the other hand, the deformation accommodated by twinning plays a softening role. Therefore, the concave shape of the Mgmore » stress-strain curve results from the competition between dislocation-TB induced hardening and twinning deformation induced softening. At low strain levels, twinning deformation induced softening dominates and a decreasing hardening rate is observed in Stage-I. In Stage-II, both the hardening and softening effects decline, but twinning deformation induced softening declines faster, which leads to an increasing hardening rate.« less

Laser Surface Hardening of Groove Edges

NASA Astrophysics Data System (ADS)

Hussain, A.; Hamdani, A. H.; Akhter, R.; Aslam, M.

2013-06-01

Surface hardening of groove-edges made of 3Cr13 Stainless Steel has been carried out using 500 W CO2 laser with a rectangular beam of 2.5×3 mm2. The processing speed was varied from 150-500 mm/min. It was seen that the hardened depth increases with increase in laser interaction time. A maximum hardened depth of around 1mm was achieved. The microhardness of the transformed zone was 2.5 times the hardness of base metal. The XRD's and microstructural analysis were also reported.

Microstructures, Mechanical Properties, and Strain Hardening Behavior of an Ultrahigh Strength Dual Phase Steel Developed by Intercritical Annealing of Cold-Rolled Ferrite/Martensite

NASA Astrophysics Data System (ADS)

Mazaheri, Y.; Kermanpur, A.; Najafizadeh, A.

2015-07-01

A dual phase (DP) steel was produced by a new process utilizing an uncommon cold-rolling and subsequent intercritical annealing of a martensite-ferrite duplex starting structure. Ultrafine grained DP steels with an average grain size of about 2 μm and chain-networked martensite islands were achieved by short intercritical annealing of the 80 pct cold-rolled duplex microstructure. The strength of the low carbon steel with the new DP microstructure was reached about 1300 MPa (140 pct higher than that of the as-received state, e.g., 540 MPa), without loss of ductility. Tensile testing revealed good strength-elongation balance for the new DP steels (UTS × UE ≈ 11,000 to 15,000 MPa pct) in comparison with the previous works and commercially used high strength DP steels. Two strain hardening stages with comparable exponents were observed in the Holloman analysis of all DP steels. The variations of hardness, strength, elongation, and strain hardening behavior of the specimens with thermomechanical parameters were correlated to microstructural features.

Over-Aging Effect on Fracture Toughness of Beryllium Copper Alloy C17200

NASA Astrophysics Data System (ADS)

Jen, Kei-Peng; Xu, Liqun; Hylinski, Steven; Gildersleeve, Nate

2008-10-01

This study experimentally increased the fracture toughness of Beryllium Copper (CuBe) UNS C17200 alloy using three different age hardening processes. At the same time, the micro- and macro-fracture behavior of this alloy were comprehensively studied. ASTM E399 fracture toughness, tensile, and Charpy impact tests were conducted for all three heat-treated rods. The fracture surfaces were examined under both an optical microscope and a scanning electron microscope to investigate the failure mechanisms. Multiple test orientations were considered to explore isotropy. Increasing the temperature and duration at which age hardening was performed increased fracture toughness while decreasing ultimate tensile strength. The maximum fracture toughness was reached on the most overaged specimen, while retaining a serviceable tensile strength. The specimen test data allowed a relationship to be established among Charpy impact toughness, fracture toughness, and yield strength. Analysis of fracture behavior revealed an interesting relationship between fracture toughness and pre-cracking fatigue propagation rate.

Microstructure-property relationships and constitutive response of plastically graded case hardened steels

NASA Astrophysics Data System (ADS)

Klecka, Michael A.

. The average plastic strain induced by an indent is shown to be an effective measure of the representative plastic strain, which is used in order to relate hardness to yield strength in both virgin and plastically deformed materials. It is shown that the two carburized steels contain gradients in yield strength, but constant strain hardening exponent with depth. The resulting model of material behavior is used to characterize the influence of specific gradients in material properties on the surface indentation behavior under increasing indentation loads. It is also shown that the response of the material is not greatly influenced by strain hardening exponent, while a gradient in strain hardening ability only has minimal impact. Gradients in elastic properties are also shown to have negligible influence for a fixed gradient in hardness. The depth of subsurface plastic deformation is shown to increase with sharper gradients in hardness, but is not altered by gradients in elastic properties. The proposed approach is not specific to case hardened materials and can be used to determine the subsurface hardness gradient for any graded material.

7 CFR 58.622 - Hardening and storage rooms.

Code of Federal Regulations, 2013 CFR

2013-01-01

... 7 Agriculture 3 2013-01-01 2013-01-01 false Hardening and storage rooms. 58.622 Section 58.622....622 Hardening and storage rooms. Hardening and storage rooms for frozen desserts shall be constructed... insure adequate storage temperature (−10° or lower). Air shall be circulated to maintain uniform...

7 CFR 58.622 - Hardening and storage rooms.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 7 Agriculture 3 2011-01-01 2011-01-01 false Hardening and storage rooms. 58.622 Section 58.622....622 Hardening and storage rooms. Hardening and storage rooms for frozen desserts shall be constructed... insure adequate storage temperature (−10° or lower). Air shall be circulated to maintain uniform...

7 CFR 58.622 - Hardening and storage rooms.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 7 Agriculture 3 2010-01-01 2010-01-01 false Hardening and storage rooms. 58.622 Section 58.622....622 Hardening and storage rooms. Hardening and storage rooms for frozen desserts shall be constructed... insure adequate storage temperature (−10° or lower). Air shall be circulated to maintain uniform...

Structural heredity influence upon principles of strain wave hardening

NASA Astrophysics Data System (ADS)

Kiricheck, A. V.; Barinov, S. V.; Yashin, A. V.

2017-02-01

It was established experimentally that by penetration of a strain wave through material hardened not only the technological modes of processing, but also a technological heredity - the direction of the fibers of the original macrostructure have an influence upon the diagram of microhardness. By penetration of the strain wave along fibers, the degree of hardening the material is less, however, a product is hardened throughout its entire section mainly along fibers. In the direction of the strain waves across fibers of the original structure of material, the degree of material hardening is much higher, the depth of the hardened layer with the degree of hardening not less than 50% makes at least 3 mm. It was found that under certain conditions the strain wave can completely change the original structure of the material. Thus, a heterogeneously hardened structure characterized by the interchange of harder and more viscous areas is formed, which is beneficial for assurance of high operational properties of material.

Theoretical Study of the Oxidation Behavior of Precipitation Hardening Steel

NASA Astrophysics Data System (ADS)

Pistofidis, N.; Vourlias, G.; Psyllaki, P.; Chrissafis, K.

2010-01-01

The oxidation of precipitation hardening (PH) steels is a rather unexplored area. In the present work an attempt is made is made to estimate the kinetics of a PH steel. For this purpose specimens of the material under examination were isothermally heated at 850, 900 and 950° C for 15 hr. Kinetics was based on TGA results. During heating a thick scale is formed on the substrate surface, which is composed by different oxides. The layer close to the substrate is compact and as a result it impedes corrosion. The mathematical analysis of the collected data shows that the change of the mass of the substrate per unit area versus time is described by a parabolic law.

A constitutive model accounting for strain ageing effects on work-hardening. Application to a C-Mn steel

NASA Astrophysics Data System (ADS)

Ren, Sicong; Mazière, Matthieu; Forest, Samuel; Morgeneyer, Thilo F.; Rousselier, Gilles

2017-12-01

One of the most successful models for describing the Portevin-Le Chatelier effect in engineering applications is the Kubin-Estrin-McCormick model (KEMC). In the present work, the influence of dynamic strain ageing on dynamic recovery due to dislocation annihilation is introduced in order to improve the KEMC model. This modification accounts for additional strain hardening rate due to limited dislocation annihilation by the diffusion of solute atoms and dislocation pinning at low strain rate and/or high temperature. The parameters associated with this novel formulation are identified based on tensile tests for a C-Mn steel at seven temperatures ranging from 20 °C to 350 °C. The validity of the model and the improvement compared to existing models are tested using 2D and 3D finite element simulations of the Portevin-Le Chatelier effect in tension.

Behavioral biomarkers of aging: illustration of a multivariate approach for detecting age-related behavioral changes.

PubMed

Markowska, A L; Breckler, S J

1999-12-01

The goal of the current project is to develop a multivariate statistical strategy for the formation of behavioral indices of performance and, further, to apply this strategy to establish the relationship between age and important characteristics of performance. The strategy was to begin with a large set of measures that span a broad range of behaviors. The behavioral effects of the following variables were examined: Age (4, 12, 24, and 30 months), genotype [Fischer 344 and a hybrid (F1) of Fischer 344 and Brown Norway (F344xBN)], gender (Fischer 344 males and Fischer 344 females), long-term diet (ad lib diet or dietary restriction beginning at 4 months of age), and short-term diet (ad lib diet or dietary restriction during testing). The behavioral measures were grouped into conceptually related indicators. The indicators within a set were submitted to a principal component analysis to help identify the summary indices of performance, which were formed with the assumption that these component scores would offer more reliable and valid measures of relevant aspects of behavioral performance than would individual measures taken alone. In summary, this approach has made a number of important contributions. It has provided sensitive and selective measures of performance that indicated contributions of all variables: psychological process, age, genotype, gender, long-term and short-term diet and has increased the sensitivity of behavioral measures to age-related behavioral impairment. It has also improved task-manageability by decreasing the number of meaningful variables without losing important information, consequently providing a simplification of the pattern of changes.

High-Performance, Radiation-Hardened Electronics for Space Environments

NASA Technical Reports Server (NTRS)

Keys, Andrew S.; Watson, Michael D.; Frazier, Donald O.; Adams, James H.; Johnson, Michael A.; Kolawa, Elizabeth A.

2007-01-01

The Radiation Hardened Electronics for Space Environments (RHESE) project endeavors to advance the current state-of-the-art in high-performance, radiation-hardened electronics and processors, ensuring successful performance of space systems required to operate within extreme radiation and temperature environments. Because RHESE is a project within the Exploration Technology Development Program (ETDP), RHESE's primary customers will be the human and robotic missions being developed by NASA's Exploration Systems Mission Directorate (ESMD) in partial fulfillment of the Vision for Space Exploration. Benefits are also anticipated for NASA's science missions to planetary and deep-space destinations. As a technology development effort, RHESE provides a broad-scoped, full spectrum of approaches to environmentally harden space electronics, including new materials, advanced design processes, reconfigurable hardware techniques, and software modeling of the radiation environment. The RHESE sub-project tasks are: SelfReconfigurable Electronics for Extreme Environments, Radiation Effects Predictive Modeling, Radiation Hardened Memory, Single Event Effects (SEE) Immune Reconfigurable Field Programmable Gate Array (FPGA) (SIRF), Radiation Hardening by Software, Radiation Hardened High Performance Processors (HPP), Reconfigurable Computing, Low Temperature Tolerant MEMS by Design, and Silicon-Germanium (SiGe) Integrated Electronics for Extreme Environments. These nine sub-project tasks are managed by technical leads as located across five different NASA field centers, including Ames Research Center, Goddard Space Flight Center, the Jet Propulsion Laboratory, Langley Research Center, and Marshall Space Flight Center. The overall RHESE integrated project management responsibility resides with NASA's Marshall Space Flight Center (MSFC). Initial technology development emphasis within RHESE focuses on the hardening of Field Programmable Gate Arrays (FPGA)s and Field Programmable Analog

A tale of two mechanisms. Strain-softening versus strain-hardening in single crystals under small stressed volumes

DOE PAGES

Bei, Hongbin; Xia, Yuzhi; Barabash, Rozaliya; ...

2015-08-10

Pre-straining defect-free single crystals will introduce heterogeneous dislocation nucleation sources that reduce the measured strength from the theoretical value, while pre-straining bulk samples will lead to strain hardening. Their competition is investigated by nanoindentation pop-in tests on variously pre-strained Mo single crystals with several indenter radii (~micrometer). Pre-straining primarily shifts deformation mechanism from homogeneous dislocation nucleation to a stochastic behavior, while strain hardening plays a secondary role, as summarized in a master plot of pop-in strength versus normalized indenter radius.

X-ray Diffraction Investigation of Annealing Behavior of Peened Surface Deformation Layer on Precipitation Hardening Stainless Steel

NASA Astrophysics Data System (ADS)

Huang, Junjie; Wang, Zhou; Gan, Jin; Yang, Ying; Huang, Feng; Wu, Gang; Meng, Qingshuai

2018-05-01

In order to investigate the recrystallization behavior of peened surface deformation layer of precipitation hardening stainless steel, a classic x-ray diffraction line profile analysis, Voigt method, was carried out on peened 17-4PH with different isothermal annealing temperatures. The activation energy of domain boundary migration ( Q a) and the activation energy of microstrain relaxation ( Q b) were calculated by regression analysis in different annealing temperature conditions. The results show that the value of Q a decreases with annealing temperature increasing, which is due to the influence of precipitation (ɛ-Cu) size on the movements of grain and subgrain boundaries. The maximum growth rate of ɛ-Cu particles occurs during 400 to 500 °C interval. Compared with growth behavior of domain size, microstrain relaxation behavior is less sensitive to precipitation particle size. The effects of annealing temperature and time on dislocation density are both significant when annealing temperature is lower than 500 °C. However, the effect of annealing temperature on dislocation density becomes insignificant when annealing temperature is higher than 500 °C. 300 °C annealing temperature only leads to the microstrain relaxation but nearly cannot lead to the domain size growth even if prolonging annealing time. Microstructure enhancement effect still exists in plastic deformation layer when 300 °C annealing temperature lasts for 60 min but nearly disappears when 600 °C annealing temperature lasts for 20 min.

X-ray Diffraction Investigation of Annealing Behavior of Peened Surface Deformation Layer on Precipitation Hardening Stainless Steel

NASA Astrophysics Data System (ADS)

Huang, Junjie; Wang, Zhou; Gan, Jin; Yang, Ying; Huang, Feng; Wu, Gang; Meng, Qingshuai

2018-04-01

In order to investigate the recrystallization behavior of peened surface deformation layer of precipitation hardening stainless steel, a classic x-ray diffraction line profile analysis, Voigt method, was carried out on peened 17-4PH with different isothermal annealing temperatures. The activation energy of domain boundary migration (Q a) and the activation energy of microstrain relaxation (Q b) were calculated by regression analysis in different annealing temperature conditions. The results show that the value of Q a decreases with annealing temperature increasing, which is due to the influence of precipitation (ɛ-Cu) size on the movements of grain and subgrain boundaries. The maximum growth rate of ɛ-Cu particles occurs during 400 to 500 °C interval. Compared with growth behavior of domain size, microstrain relaxation behavior is less sensitive to precipitation particle size. The effects of annealing temperature and time on dislocation density are both significant when annealing temperature is lower than 500 °C. However, the effect of annealing temperature on dislocation density becomes insignificant when annealing temperature is higher than 500 °C. 300 °C annealing temperature only leads to the microstrain relaxation but nearly cannot lead to the domain size growth even if prolonging annealing time. Microstructure enhancement effect still exists in plastic deformation layer when 300 °C annealing temperature lasts for 60 min but nearly disappears when 600 °C annealing temperature lasts for 20 min.

Radiation Hardened DDR2 SDRAM Solution

NASA Astrophysics Data System (ADS)

Wang, Pierre-Xiao; Sellier, Charles

2016-08-01

The Radiation Hardened (RH) DDR2 SDRAM Solution is a User's Friendly, Plug-and-Play and Radiation Hardened DDR2 solution, which includes the radiation tolerant stacking DDR2 modules and a radiation intelligent memory controller (RIMC) IP core. It provides a high speed radiation hardened by design DRAM solution suitable for all space applications such as commercial or scientific geo-stationary missions, earth observation, navigation, manned space vehicles and deep space scientific exploration. The DDR2 module has been guaranteed with SEL immune and TID > 100Krad(Si), on the other hand the RIMC IP core provides a full protection against the DDR2 radiation effects such as SEFI and SEU.

The development of high strength corrosion resistant precipitation hardening cast steels

NASA Astrophysics Data System (ADS)

Abrahams, Rachel A.

Precipitation Hardened Cast Stainless Steels (PHCSS) are a corrosion resistant class of materials which derive their properties from secondary aging after a normalizing heat treatment step. While PHCSS materials are available in austenitic and semi-austenitic forms, the martensitic PHCSS are most widely used due to a combination of high strength, good toughness, and corrosion resistance. If higher strength levels can be achieved in these alloys, these materials can be used as a lower-cost alternative to titanium for high specific strength applications where corrosion resistance is a factor. Although wrought precipitation hardened materials have been in use and specified for more than half a century, the specification and use of PHCSS has only been recent. The effects of composition and processing on performance have received little attention in the cast steel literature. The work presented in these investigations is concerned with the experimental study and modeling of microstructural development in cast martensitic precipitation hardened steels at high strength levels. Particular attention is focused on improving the performance of the high strength CB7Cu alloy by control of detrimental secondary phases, notably delta ferrite and retained austenite, which is detrimental to strength, but potentially beneficial in terms of fracture and impact toughness. The relationship between age processing and mechanical properties is also investigated, and a new age hardening model based on simultaneous precipitation hardening and tempering has been modified for use with these steels. Because the CB7Cu system has limited strength even with improved processing, a higher strength prototype Fe-Ni-Cr-Mo-Ti system has been designed and adapted for use in casting. This prototype is expected to develop high strengths matching or exceed that of cast Ti-6Al-4V alloys. Traditional multicomponent constitution phase diagrams widely used for phase estimation in conventional stainless steels

Thermal relaxation behavior of residual stress in laser hardened 17-4PH steel after shot peening treatment

NASA Astrophysics Data System (ADS)

Wang, Zhou; Chen, Yanhua; Jiang, Chuanhai

2011-09-01

In order to investigate the residual stress relaxations of shot peened layer, isothermal annealing treatments were carried out on tempered and laser hardened 17-4PH steel after shot peening with different temperatures from 300 °C to 600 °C. The results showed that the residual stresses were relaxed in the whole deformation layer especially under higher temperature. The maximum rates of stress relaxation took place at the initial stage of annealing process in all conditions. The relaxation process during isothermal annealing could be described by Zener-Wert-Avrami function. The thermal stability of residual stress in tempered 17-4PH was higher than that in laser hardened 17-4PH as well as that in α-iron, which was due to the pinning effects of ɛ-Cu precipitates on the dislocation movement. As massive ɛ-Cu precipitates formed in the temperature about 480 °C, the activation enthalpies for stress relaxation in laser hardened 17-4PH were the same as that in tempered 17-4PH in the conditions of isothermal annealing temperatures of 500 °C and 600 °C.

Nano Precipitation and Hardening of Die-Quenched 6061 Aluminum Alloy.

PubMed

Utsunomiya, Hiroshi; Tada, Koki; Matsumoto, Ryo; Watanabe, Katsumi; Matsuda, Kenji

2018-03-01

Die quenching is applied to an age-hardenable aluminium alloys to obtain super-saturated solid solution. The application is advantageous because it can reduce number of manufacturing processes, and may increase strength by strain aging. If die quenching is realized in forging as well as sheet forming, it may widen industrial applicability further. In this study, Al-Mg-Si alloy AA6061 8 mm-thick billets were reduced 50% in height without cracks by die-quench forging. Supersaturated solid solution was successfully obtained. The die-quenched specimen shows higher hardness with nano precipitates at shorter aging time than the conventional water-quenched specimen.

The effect of aluminum on the work hardening and wear resistance of hadfield manganese steel

NASA Astrophysics Data System (ADS)

Zuidema, B. K.; Subramanyam, D. K.; Leslie, W. C.

1987-09-01

A study has been made of the work-hardening and wear resistance of aluminum-modified Hadfield manganese steels ranging in composition from 1.00 to 1.75 Pct carbon and from 0.0 to 4.0 Pct aluminum. Aluminum additions reduced carbon activity and diffusivity in austenites of Hadfield’s composition, increasing the metastable solubility of carbon in Hadfield steel. Aluminum additions inhibited mechanical twinning and, by inference, increased the stacking fault energy of austenite. Increasing carbon in solution in austenite expanded the temperature range over which dynamic strain aging and rapid work hardening occurred. Simultaneous aluminum additions and increased carbon content increased the work-hardening rate and high-stress abrasion resistance of Hadfield steel, but there was an optimum aluminum content beyond which both declined. Maximum work-hardening rate was exhibited by an alloy containing nominally 1.75 Pct C, 13.5 Pct Mn, and 1.3 Pct Al. Improved high-stress abrasion resistance was also found in an alloy containing nominally 1.00 Pct C, 13.5 Pct Mn, and 4.0 Pct Al.

7 CFR 58.641 - Hardening and storage.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 7 Agriculture 3 2011-01-01 2011-01-01 false Hardening and storage. 58.641 Section 58.641 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Standards... Procedures § 58.641 Hardening and storage. Immediately after the semifrozen product is placed in its intended...

7 CFR 58.641 - Hardening and storage.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 7 Agriculture 3 2010-01-01 2010-01-01 false Hardening and storage. 58.641 Section 58.641 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Standards... Procedures § 58.641 Hardening and storage. Immediately after the semifrozen product is placed in its intended...

7 CFR 58.641 - Hardening and storage.

Code of Federal Regulations, 2013 CFR

2013-01-01

... 7 Agriculture 3 2013-01-01 2013-01-01 false Hardening and storage. 58.641 Section 58.641 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Standards... Procedures § 58.641 Hardening and storage. Immediately after the semifrozen product is placed in its intended...

Beam hardening and partial beam hardening of the bowtie filter: Effects on dosimetric applications in CT

NASA Astrophysics Data System (ADS)

Lopez-Rendon, X.; Zhang, G.; Bosmans, H.; Oyen, R.; Zanca, F.

2014-03-01

Purpose: To estimate the consequences on dosimetric applications when a CT bowtie filter is modeled by means of full beam hardening versus partial beam hardening. Method: A model of source and filtration for a CT scanner as developed by Turner et. al. [1] was implemented. Specific exposures were measured with the stationary CT X-ray tube in order to assess the equivalent thickness of Al of the bowtie filter as a function of the fan angle. Using these thicknesses, the primary beam attenuation factors were calculated from the energy dependent photon mass attenuation coefficients and used to include beam hardening in the spectrum. This was compared to a potentially less computationally intensive approach, which accounts only partially for beam hardening, by giving the photon spectrum a global (energy independent) fan angle specific weighting factor. Percentage differences between the two methods were quantified by calculating the dose in air after passing several water equivalent thicknesses representative for patients having different BMI. Specifically, the maximum water equivalent thickness of the lateral and anterior-posterior dimension and of the corresponding (half) effective diameter were assessed. Results: The largest percentage differences were found for the thickest part of the bowtie filter and they increased with patient size. For a normal size patient they ranged from 5.5% at half effective diameter to 16.1% for the lateral dimension; for the most obese patient they ranged from 7.7% to 19.3%, respectively. For a complete simulation of one rotation of the x-ray tube, the proposed method was 12% faster than the complete simulation of the bowtie filter. Conclusion: The need for simulating the beam hardening of the bow tie filter in Monte Carlo platforms for CT dosimetry will depend on the required accuracy.

Modification of Grange-Kiefer Approach for Determination of Hardenability in Eutectoid Steel

NASA Astrophysics Data System (ADS)

Sushanthi, Neethi; Maity, Joydeep

2014-12-01

In this research work, an independent mathematical modeling approach has been adopted for determination of the hardenability of steels. In this model, at first, cooling curves were generated by solving transient heat transfer equation through discretization with pure explicit finite difference scheme coupled with MATLAB-based programming considering variable thermo-physical properties of 1080 steel. Thereafter, a new fundamental approach is proposed for obtaining CCT noses as a function of volume fraction transformed through modification of Grange-Kiefer approach. The cooling curves were solved against 50 pct transformation nose of CCT diagram in order to predict hardening behavior of 1080 steel in terms of hardenability parameters (Grossmann critical diameter, D C; and ideal critical diameter, D I) and the variation of the unhardened core diameter ( D u) to diameter of steel bar ( D) ratio with diameter of the steel bar ( D). The experiments were also performed to ascertain actual D C value of 1080 steel for still water quenching. The D C value obtained by the developed model was found to match the experimental D C value with only 3 pct deviation. Therefore, the model developed in the present work can be used for direct determination of D I, D C and D u without resorting to any rigorous experimentation.

Rapid surface hardening and enhanced tribological performance of 4140 steel by friction stir processing

DOE PAGES

Lorenzo-Martin, Cinta; Ajayi, Oyelayo O.

2015-06-06

Tribological performance of steel materials can be substantially enhanced by various thermal surface hardening processes. For relatively low-carbon steel alloys, case carburization is often used to improve surface performance and durability. If the carbon content of steel is high enough (>0.4%), thermal treatments such as induction, flame, laser, etc. can produce adequate surface hardening without the need for surface compositional change. This paper presents an experimental study of the use of friction stir processing (FSP) as a means to hardened surface layer in AISI 4140 steel. The impacts of this surface hardening process on the friction and wear performance weremore » evaluated under both dry and lubricated contact conditions in reciprocating sliding. FSP produced the same level of hardening and superior tribological performance when compared to conventional thermal treatment, using only 10% of the energy and without the need for quenching treatments. With FSP surface hardness of about 7.8 GPa (62 Rc) was achieved while water quenching conventional heat treatment produced about 7.5 GPa (61 Rc) hardness. Microstructural analysis showed that both FSP and conventional heat treatment produced martensite. Although the friction behavior for FSP treated surfaces and the conventional heat treatment were about the same, the wear in FSP processed surfaces was reduced by almost 2× that of conventional heat treated surfaces. Furthermore, the superior performance is attributed to the observed grain refinement accompanying the FSP treatment in addition to the formation of martensite. As it relates to tribological performance, this study shows FSP to be an effective, highly energy efficient, and environmental friendly (green) alternative to conventional heat treatment for steel.« less

An improved Armstrong-Frederick-Type Plasticity Model for Stable Cyclic Stress-Strain Responses Considering Nonproportional Hardening

NASA Astrophysics Data System (ADS)

Li, Jing; Zhang, Zhong-ping; Li, Chun-wang

2018-03-01

This paper modified an Armstrong-Frederick-type plasticity model for investigating the stable cyclic deformation behavior of metallic materials with different sensitivity to nonproportional loadings. In the modified model, the nonproportionality factor and nonproportional cyclic hardening coefficient coupled with the Jiang-Sehitoglu incremental plasticity model were used to estimate the stable stress-strain responses of the two materials (1045HR steel and 304 stainless steel) under various tension-torsion strain paths. A new equation was proposed to calculate the nonproportionality factor on the basis of the minimum normal strain range. Procedures to determine the minimum normal strain range were presented for general multiaxial loadings. Then, the modified model requires only the cyclic strain hardening exponent and cyclic strength coefficient to determine the material constants. It is convenient for predicting the stable stress-strain responses of materials in engineering application. Comparisons showed that the modified model can reflect the effect of nonproportional cyclic hardening well.

Microscopic Origin of Strain Hardening in Methane Hydrate

PubMed Central

Jia, Jihui; Liang, Yunfeng; Tsuji, Takeshi; Murata, Sumihiko; Matsuoka, Toshifumi

2016-01-01

It has been reported for a long time that methane hydrate presents strain hardening, whereas the strength of normal ice weakens with increasing strain after an ultimate strength. However, the microscopic origin of these differences is not known. Here, we investigated the mechanical characteristics of methane hydrate and normal ice by compressive deformation test using molecular dynamics simulations. It is shown that methane hydrate exhibits strain hardening only if the hydrate is confined to a certain finite cross-sectional area that is normal to the compression direction. For normal ice, it does not present strain hardening under the same conditions. We show that hydrate guest methane molecules exhibit no long-distance diffusion when confined to a finite-size area. They appear to serve as non-deformable units that prevent hydrate structure failure, and thus are responsible for the strain-hardening phenomenon. PMID:27009239

Effect of Microstructural Evolution and Hardening in Subsurface on Wear Behavior of Mg-3Al-1Zn Alloy

NASA Astrophysics Data System (ADS)

Liang, C.; Li, C.; An, J.; Yu, M.; Hu, Y. C.; Lin, W. H.; Liu, F.; Ding, Y. H.

2013-12-01

Dry sliding tests were performed on as-cast AZ31 alloy using a pin-on-disc configuration. Coefficient of friction and wear rate were measured within a load range of 5-360 N at a sliding velocity of 0.785 m/s. Worn surface morphologies were examined using scanning electron microscopy. Five wear mechanisms, namely abrasion, oxidation, delamination, thermal softening, and melting, have been observed. Surface hardness, subsurface plastic strain, worn surface temperature, and cross-sectional optical microscopy were used to characterize hardness change, plastic deformation, and the microstructure evolution in subsurface. The results illustrate the correlation between the wear behavior and evolution of microstructure and hardness in subsurface, and reveal that in the load range of 5-120 N, surface oxidation and hardening originating from large plastic deformation play an important role in maintaining the mild wear, and softening originating from dynamic recrystallization in subsurface and surface melting are responsible for the severe wear in the load range of 120-360 N.

Effect of heat treatments on machinability of gold alloy with age-hardenability at intraoral temperature.

PubMed

Watanabe, I; Baba, N; Watanabe, E; Atsuta, M; Okabe, T

2004-01-01

This study investigated the effect of heat treatment on the machinability of heat-treated cast gold alloy with age-hardenability at intraoral temperature using a handpiece engine with SiC wheels and an air-turbine handpiece with carbide burs and diamond points. Cast gold alloy specimens underwent various heat treatments [As-cast (AC); Solution treatment (ST); High-temperature aging (HA), Intraoral aging (IA)] before machinability testing. The machinability test was conducted at a constant machining force of 0.784N. The three circumferential speeds used for the handpiece engine were 500, 1,000 and 1,500 m/min. The machinability index (M-index) was determined as the amount of metal removed by machining (volume loss, mm(3)). The results were analyzed by ANOVA and Scheffé's test. When an air-turbine handpiece was used, there was no difference in the M-index of the gold alloy among the heat treatments. The air-turbine carbide burs showed significantly (p<0.05) higher M-indexes than the diamond points after any heat treatments. With the SiC wheels, increasing the circumferential speed increased the M-index values for each heat treatment. The specimens heat-treated with AC, HA and IA had similar M-indexes at the lower speeds (500 and 1,000 m/min). The ST specimens exhibited the lowest M-index at the lower speeds. However, at the highest speed (1,500 m/min), there were no significant differences in the M-indexes among the heat treatments except for HA, which showed the highest M-index. There was no effect of heat treatment on the machinability of the gold alloy using the air-turbine handpiece. The heat treatments had a small effect on the M-index of the gold alloy machined with a SiC wheel for a handpiece engine.

Technology Developments in Radiation-Hardened Electronics for Space Environments

NASA Technical Reports Server (NTRS)

Keys, Andrew S.; Howell, Joe T.

2008-01-01

The Radiation Hardened Electronics for Space Environments (RHESE) project consists of a series of tasks designed to develop and mature a broad spectrum of radiation hardened and low temperature electronics technologies. Three approaches are being taken to address radiation hardening: improved material hardness, design techniques to improve radiation tolerance, and software methods to improve radiation tolerance. Within these approaches various technology products are being addressed including Field Programmable Gate Arrays (FPGA), Field Programmable Analog Arrays (FPAA), MEMS, Serial Processors, Reconfigurable Processors, and Parallel Processors. In addition to radiation hardening, low temperature extremes are addressed with a focus on material and design approaches. System level applications for the RHESE technology products are discussed.

Behavior analysis and the study of human aging

PubMed Central

Derenne, Adam; Baron, Alan

2002-01-01

As the population of older adults continues to rise, psychologists along with other behavioral and social scientists have shown increasing interest in this age group. Although behavior analysts have contributed to research on aging, the focus has been on applications that remedy age-related deficits, rather than a concern with aging as a developmental process. In particular, there has been little interest in the central theoretical questions that have guided gerontologists. How does behavior change with advancing years, and what are the sources of those changes? We consider the possibility that this neglect reflects the long-standing commitment of behavior analysts to variables that can be experimentally manipulated, a requirement that excludes the key variable—age itself. We review the options available to researchers and present strategies that minimize deviations from the traditional features of behavior-analytic designs. Our comments are predicated on the view that aging issues within contemporary society are far too important for behavior analysts to ignore. PMID:22478383

Radiation-Hardened Electronics for the Space Environment

NASA Technical Reports Server (NTRS)

Keys, Andrew S.; Watson, Michael D.

2007-01-01

RHESE covers a broad range of technology areas and products. - Radiation Hardened Electronics - High Performance Processing - Reconfigurable Computing - Radiation Environmental Effects Modeling - Low Temperature Radiation Hardened Electronics. RHESE has aligned with currently defined customer needs. RHESE is leveraging/advancing SOA space electronics, not duplicating. - Awareness of radiation-related activities through out government and industry allow advancement rather than duplication of capabilities.

Mechanical stress modified ferroelectric aging behavior

NASA Astrophysics Data System (ADS)

Xu, Tingting; Kan, Yi; Jin, Yaming; Sun, Hui; Du, Yingchao; Wu, Xiumei; Bo, Huifeng; Cai, Wei; Huang, Fengzhen; Lu, Xiaomei; Zhu, Jinsong

2013-05-01

Mechanical stress effect on aging behavior of Bi3.25La0.75Ti3O12 (BLT) and PbZr0.53Ti0.47O3 (PZT) films was investigated. It is found that the remnant polarization decreases with time while the coercive field increases in stress-free BLT films. For unconfined PZT films, both the remnant polarization and the coercive field decrease as time elapses. The applied tensile stress weakens the aging of remnant polarization of BLT films but strengthens the aging of coercive field, while the applied tensile stress possesses opposite effect. In contrary, the applied compressive stress simultaneously improves the aging behavior of both remnant polarization and coercive field of PZT films. Mechanical-stress-induced variation of domain wall mobility in different materials was suggested as the possible origin of these observations. This work indicates that the aging behavior modification using stress could be realized, and it is helpful for promoting the reliability of ferroelectric films for industrial applications.

Decline in Radiation Hardened Microcircuit Infrastructure

NASA Technical Reports Server (NTRS)

LaBel, Kenneth A.

2015-01-01

Two areas of radiation hardened microcircuit infrastructure will be discussed: 1) The availability and performance of radiation hardened microcircuits, and, and 2) The access to radiation test facilities primarily for proton single event effects (SEE) testing. Other areas not discussed, but are a concern include: The challenge for maintaining radiation effects tool access for assurance purposes, and, the access to radiation test facilities primarily for heavy ion single event effects (SEE) testing. Status and implications will be discussed for each area.

Twinning-induced plasticity (TWIP) and work hardening in Ti-based metallic glass matrix composites.

PubMed

Fan, J; Qiao, J W; Wang, Z H; Rao, W; Kang, G Z

2017-05-12

The present study demonstrates that Ti-based metallic glass matrix composites (MGMCs) with a normal composition of Ti 43 Zr 32 Ni 6 Ta 5 Be 14 containing ductile dendrites dispersed in the glass matrix has been developed, and deformation mechanisms about the tensile property have been investigated by focusing on twinning-induced plasticity (TWIP) effect. The Ti-based MGMC has excellent tensile properties and pronounced tensile work-hardening capacity, with a yield strength of 1100 MPa and homogeneous elongation of 4%. The distinguished strain hardening is ascribed to the formation of deformation twinning within the dendrites. Twinning generated in the dendrites works as an obstacle for the rapid propagation of shear bands, and then, the localized necking is avoided, which ensures the ductility of such kinds of composites. Besides, a finite-element model (FEM) has been established to explain the TWIP effect which brings out a work-hardening behavior in the present MGMC instead of a localized strain concentration. According to the plasticity theory of traditional crystal materials and some new alloys, TWIP effect is mainly controlled by stacking fault energy (SFE), which has been analyzed intensively in the present MGMC.

Surface hardening of titanium alloys with melting depth controlled by heat sink

DOEpatents

Oden, Laurance L.; Turner, Paul C.

1995-01-01

A process for forming a hard surface coating on titanium alloys includes providing a piece of material containing titanium having at least a portion of one surface to be hardened. The piece having a portion of a surface to be hardened is contacted on the backside by a suitable heat sink such that the melting depth of said surface to be hardened may be controlled. A hardening material is then deposited as a slurry. Alternate methods of deposition include flame, arc, or plasma spraying, electrodeposition, vapor deposition, or any other deposition method known by those skilled in the art. The surface to be hardened is then selectively melted to the desired depth, dependent on the desired coating thickness, such that a molten pool is formed of the piece surface and the deposited hardening material. Upon cooling a hardened surface is formed.

Age Related Changes in Preventive Health Behavior.

ERIC Educational Resources Information Center

Leventhal, Elaine A.; And Others

Health behavior may be influenced by age, beliefs, and symptomatology. To examine age-related health beliefs and behaviors with respect to six diseases (the common cold, colon-rectal cancer, lung cancer, heart attack, high blood pressure, and senility), 396 adults (196 males, 200 females) divided into three age groups completed a questionnaire…

Research on SEU hardening of heterogeneous Dual-Core SoC

NASA Astrophysics Data System (ADS)

Huang, Kun; Hu, Keliu; Deng, Jun; Zhang, Tao

2017-08-01

The implementation of Single-Event Upsets (SEU) hardening has various schemes. However, some of them require a lot of human, material and financial resources. This paper proposes an easy scheme on SEU hardening for Heterogeneous Dual-core SoC (HD SoC) which contains three techniques. First, the automatic Triple Modular Redundancy (TMR) technique is adopted to harden the register heaps of the processor and the instruction-fetching module. Second, Hamming codes are used to harden the random access memory (RAM). Last, a software signature technique is applied to check the programs which are running on CPU. The scheme need not to consume additional resources, and has little influence on the performance of CPU. These technologies are very mature, easy to implement and needs low cost. According to the simulation result, the scheme can satisfy the basic demand of SEU-hardening.

Phase Transformation and Aging Behavior of Al0.5CoCrFeNiSi0.2 High-Entropy Alloy

NASA Astrophysics Data System (ADS)

Zhang, C.; Wu, G. F.; Dai, P. Q.

2015-05-01

An Al0.5CoCrFeNiSi0.2 high-entropy alloy was prepared by vacuum arc melting. The alloy was aged from 700 to 1100 °C. The effects of aging on the phase transformation and mechanical performances were explored. The as-cast alloy showed a dendritic (DR) microstructure. The DR region was an Fe,Cr-rich FCC phase, while the interdendritic (ID) region was a spinodal structure composed of Fe,Cr-rich BCC (A2) and Ni,Al-rich BCC (B2) phases. At aging temperatures between 700 and 900 °C, the Fe,Cr-rich BCC (A2) phase in the ID region transformed into σ and Fe,Cr-rich FCC phases. Meanwhile, some Ni,Al-rich FCC phase particles precipitated from the DR region. During aging at 1100 °C, the DR microstructure disappeared, and a microstructure composed of Fe,Cr-rich FCC and Ni,Al-rich BCC (B2) phases both possessing a lamellar shape was developed. The alloy exhibited evident hardening and lower tensile strain when the aging temperature was lower than 1000 °C, which was mainly attributed to the generation of the σ phase in the ID region. However, a contrasting behavior was observed when the aging temperature was higher than 1000 °C, which was attributed to the redissolution of the σ phase and the microstructure coarsening.

"Deviance Proneness" and Adolescent Smoking 1980 versus 2001: Has There Been a "Hardening" of Adolescent Smoking?

ERIC Educational Resources Information Center

Chassin, Laurie; Presson, Clark; Morgan-Lopez, Antonio; Sherman, Steven J.

2007-01-01

In a midwestern community sample, we tested for evidence of "hardening" of adolescent cigarette smoking between 1980 and 2001 by comparing adolescent smokers and nonsmokers at these two times on measures indicative of "deviance proneness" in Jessor and Jessor's [Jessor, R., & Jessor, S. L. (1977). "Problem behavior and psychosocial development: A…

Radiation-hardened backside-illuminated 512 x 512 charge-coupled device

NASA Astrophysics Data System (ADS)

Bates, Philip A.; Levine, Peter A.; Sauer, Donald J.; Hsueh, Fu-Lung; Shallcross, Frank V.; Smeltzer, Ronald K.; Meray, Grazyna M.; Taylor, Gordon C.; Tower, John R.

1995-04-01

A four-port 512 X 512 charge coupled device (CCD) imager hardened against proton displacement damage and total dose degradation has been fabricated and tested. The device is based upon an established thinned, backside illuminated, triple polysilicon, buried channel CCD process technology. The technology includes buried blooming drains. A three step approach has been taken to hardening the device. The first phase addressed hardening against proton displacement damage. The second phase addressed hardening against both proton displacement damage and total dose degradation. The third phase addresses final optimization of the design. Test results from the first and second phase efforts are presented. Plans for the third phase are discussed.

Reverse-Martensitic Hardening of Austenitic Stainless Steel upon Up-quenching

NASA Astrophysics Data System (ADS)

Sato, Kiminori; Guo, Defeng; Li, Xiaohong; Zhang, Xiangyi

2016-08-01

Reverse-martensitic transformation utilizing up-quenching was demonstrated for austenitic stainless steel. Up-quenching was done following the stress-induced phase modification to martensite and then enrichment of the body-centered-cubic ferrite. Transmission-electron-microscopy observation and Vickers hardness test revealed that the reverse-martensitic transformation yields quench hardening owing to an introduction of highly-concentrated dislocation. It is furthermore found that Cr precipitation on grain boundaries caused by isothermal aging is largely suppressed in the present approach.

Effect of Prestrain on Precipitation Behaviors of Ti-2.5Cu Alloy

NASA Astrophysics Data System (ADS)

Lincai, Zhang; Xiaoming, Ding; Wei, Ye; Man, Zhang; Zhenya, Song

2018-04-01

As a special hardenable α titanium alloy, Ti-2.5 Cu alloy was a candidate material for high temperature components requiring high strength and plasticity. The effect of prestrain on the precipitation behaviors was investigated in the present study. Tensile tests show that elongation up to 22 % can be obtained after solid solution (SS) treatment. Thereafter, prestrain in tension with 5 %, 10 %, 15 % and 20 % was carried out for the SS samples and then duplex aging was applied. Transmitting electron microscopy (TEM) investigations show that larger Ti2Cu particles were observed in the prestrained condition than free aging one, as prestrain significantly speeds up the precipitation kinetics. The strength firstly increases and then decreases for the prestrained samples after duplex aging, where the competition between precipitation hardening and recovery softening should be responsible. With the consideration of SS, precipitation and recovery, a strength model for duplex aging combined with prestrain was established, which is in well agreement with experiments. Present study may provide a promising way to obtain the strength of deformed hcp materials in industry application.

Caffeine delays oocyte aging and maintains the quality of aged oocytes safely in mouse.

PubMed

Zhang, Xia; Liu, Xiaoyan; Chen, Li; Wu, Dan-Ya; Nie, Zheng-Wen; Gao, Ying-Ying; Miao, Yi-Liang

2017-03-28

Caffeine, as an oocyte aging inhibitor, was used in many different species to control or delay oocyte aging. However, the safety of caffeine and developmental competence of aged oocytes inhibited by caffeine has not been studied systematically. So we detected the spindle morphology, distribution of cortical granules, zona pellucida hardening and pronucleus formation to assess oocyte quality of caffeine treated oocytes. We found that aged oocytes treated by caffeine maintained weak susceptibility to activating stimuli and regained normal competent after aged further 6 hr. Caffeine maintained the spindle morphology, changed cortical granules distribution of aged oocytes and could not prevent zona pellucida hardening. Furthermore, caffeine increased pronucleus formation of aged oocytes and decreased fragmentation after fertilization. These results suggested that caffeine could maintain the quality of aged oocytes safely in mouse.

Hardening fertilization and nutrient loading of conifer seedlings

Treesearch

R. Kasten Dumroese

2003-01-01

Continuing to fertilize bareroot and container seedlings during the hardening process (from cessation of height growth until lifting) can improve seedling viability. The process of fertilizing during hardening has many names, but in the last decade a new term, nutrient loading, has come into use. The process of nutrient loading seedlings leads to luxury consumption...

Mechanical properties of friction stir welded Al alloys with different hardening mechanisms

NASA Astrophysics Data System (ADS)

Lim, Sunggon; Kim, Sangshik; Lee, Chang-Gil; Kim, Sung Joon

2005-04-01

The mechanical properties of precipitation hardened Al 6061-T651 and Al 7075-T6 and strain hardened Al 5083-H32, friction stir welded with various welding parameters, were examined in the present study. 4 mm thick Al 6061-T651, Al 7075-T6, and Al 5083-H32 alloy plates were used for friction stir welding (FSW) with rotating speed varied from 1000 to 2500 rpm (rotation per minute) and welding speed ranging from 0.1 to 0.4 mpm (m/min). Each alloy displayed slightly different trends with respect to the effect of different welding parameters on the tensile properties of the FSWed Al alloys. The tensile elongation of FSWed Al 6061-T651 and Al 7075-T6 tended to increase greatly, while the tensile strength decreased marginally, with increasing welding speed and/or decreasing rotating speed. The tensile strength and the tensile elongation of Al 6061-T651 decreased from 135 to 154 MPa and 10.6 to 17.0%, respectively, with increasing welding speed from 0.1 to 0.4 mpm at a rotating speed of 1,600 rpm. Unlike the age-hardened Al 6061-T651 and Al 7075-T6, the strain-hardened Al 5083-H32 showed no notable change in tensile property with varying welding parameters. The change in the strength level with different welding parameters for each alloy was not as significant as the variation in tensile elongation. It was believed that the tensile elongation of FSWed Al alloys with varying welding parameters was mainly determined by the coarse particle clustering. With respect to the change in tensile strength during friction stir welding, it is hypothesized that two competing mechanisms, recovery by friction and heat and strain hardening by plastic flow in the weld zone offset the effects of different welding parameters on the tensile strength level of FSWed Al alloys.

Scintillation-Hardened GPS Receiver

NASA Technical Reports Server (NTRS)

Stephens, Donald R.

2015-01-01

CommLargo, Inc., has developed a scintillation-hardened Global Positioning System (GPS) receiver that improves reliability for low-orbit missions and complies with NASA's Space Telecommunications Radio System (STRS) architecture standards. A software-defined radio (SDR) implementation allows a single hardware element to function as either a conventional radio or as a GPS receiver, providing backup and redundancy for platforms such as the International Space Station (ISS) and high-value remote sensing platforms. The innovation's flexible SDR implementation reduces cost, weight, and power requirements. Scintillation hardening improves mission reliability and variability. In Phase I, CommLargo refactored an open-source GPS software package with Kalman filter-based tracking loops to improve performance during scintillation and also demonstrated improved navigation during a geomagnetic storm. In Phase II, the company generated a new field-programmable gate array (FPGA)-based GPS waveform to demonstrate on NASA's Space Communication and Navigation (SCaN) test bed.

Emotion identification and aging: Behavioral and neural age-related changes.

PubMed

Gonçalves, Ana R; Fernandes, Carina; Pasion, Rita; Ferreira-Santos, Fernando; Barbosa, Fernando; Marques-Teixeira, João

2018-05-01

Aging is known to alter the processing of facial expressions of emotion (FEE), however the impact of this alteration is less clear. Additionally, there is little information about the temporal dynamics of the neural processing of facial affect. We examined behavioral and neural age-related changes in the identification of FEE using event-related potentials. Furthermore, we analyze the relationship between behavioral/neural responses and neuropsychological functioning. To this purpose, 30 younger adults, 29 middle-aged adults and 26 older adults identified FEE. The behavioral results showed a similar performance between groups. The neural results showed no significant differences between groups for the P100 component and an increased N170 amplitude in the older group. Furthermore, a pattern of asymmetric activation was evident in the N170 component. Results also suggest deficits in facial feature decoding abilities, reflected by a reduced N250 amplitude in older adults. Neuropsychological functioning predicts P100 modulation, but does not seem to influence emotion identification ability. The findings suggest the existence of a compensatory function that would explain the age-equivalent performance in emotion identification. The study may help future research addressing behavioral and neural processes involved on processing of FEE in neurodegenerative conditions. Copyright © 2018 International Federation of Clinical Neurophysiology. Published by Elsevier B.V. All rights reserved.

Work-hardening behaviour of Mg single crystals oriented for basal slip

NASA Astrophysics Data System (ADS)

Bhattacharya, B.; Niewczas, M.

2011-06-01

Work-hardening behaviour of Mg single crystals oriented for basal slip was studied by means of tensile tests carried out at 4, 78 and 295 K. The crystals show critical resolved shear stress values (CRSS) for a {0001} ? basal slip system in the range 1-1.5 MPa. The samples exhibit two-stage work hardening characteristics consisting of a long easy glide stage and a stage of rapid hardening terminated by failure. The onset of the plastic flow up to the point of fracture is accompanied by a low work-hardening rate in the range 5 × 10-5-5 × 10-4 µ, corresponding to the hardening rate in Stage I of copper single crystals. The analysis of thermally activated glide parameters suggests that forest interactions are rate-controlling processes. The very low value of the activation distance found at 4 K, ∼0.047 b, is attributed to zero-point energy effects. The failure of crystals occurs well before their hardening capacity is exhausted by mechanisms which are characteristic of deformation temperature.

Process design of press hardening with gradient material property influence

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

Neugebauer, R.; Professorship for Machine Tools and Forming Technology, TU Chemnitz; Schieck, F.

Press hardening is currently used in the production of automotive structures that require very high strength and controlled deformation during crash tests. Press hardening can achieve significant reductions of sheet thickness at constant strength and is therefore a promising technology for the production of lightweight and energy-efficient automobiles. The manganese-boron steel 22MnB5 have been implemented in sheet press hardening owing to their excellent hot formability, high hardenability, and good temperability even at low cooling rates. However, press-hardened components have shown poor ductility and cracking at relatively small strains. A possible solution to this problem is a selective increase of steelmore » sheet ductility by press hardening process design in areas where the component is required to deform plastically during crash tests. To this end, process designers require information about microstructure and mechanical properties as a function of the wide spectrum of cooling rates and sequences and austenitizing treatment conditions that can be encountered in production environments. In the present work, a Continuous Cooling Transformation (CCT) diagram with corresponding material properties of sheet steel 22MnB5 was determined for a wide spectrum of cooling rates. Heating and cooling programs were conducted in a quenching dilatometer. Motivated by the importance of residual elasticity in crash test performance, this property was measured using a micro-bending test and the results were integrated into the CCT diagrams to complement the hardness testing results. This information is essential for the process design of press hardening of sheet components with gradient material properties.« less

Process design of press hardening with gradient material property influence

NASA Astrophysics Data System (ADS)

Neugebauer, R.; Schieck, F.; Rautenstrauch, A.

2011-05-01

Press hardening is currently used in the production of automotive structures that require very high strength and controlled deformation during crash tests. Press hardening can achieve significant reductions of sheet thickness at constant strength and is therefore a promising technology for the production of lightweight and energy-efficient automobiles. The manganese-boron steel 22MnB5 have been implemented in sheet press hardening owing to their excellent hot formability, high hardenability, and good temperability even at low cooling rates. However, press-hardened components have shown poor ductility and cracking at relatively small strains. A possible solution to this problem is a selective increase of steel sheet ductility by press hardening process design in areas where the component is required to deform plastically during crash tests. To this end, process designers require information about microstructure and mechanical properties as a function of the wide spectrum of cooling rates and sequences and austenitizing treatment conditions that can be encountered in production environments. In the present work, a Continuous Cooling Transformation (CCT) diagram with corresponding material properties of sheet steel 22MnB5 was determined for a wide spectrum of cooling rates. Heating and cooling programs were conducted in a quenching dilatometer. Motivated by the importance of residual elasticity in crash test performance, this property was measured using a micro-bending test and the results were integrated into the CCT diagrams to complement the hardness testing results. This information is essential for the process design of press hardening of sheet components with gradient material properties.

Effect of ferrite transformation on the tensile and stress corrosion properties of type 316 L stainless steel weld metal thermally aged at 873 K

NASA Astrophysics Data System (ADS)

Shaikh, H.; Khatak, H. S.; Seshadri, S. K.; Gnanamoorthy, J. B.; Rodriguez, P.

1995-07-01

This article deals with the effect of the microstructural changes, due to transformation of delta ferrite, on the associated variations that take place in the tensile and stress corrosion properties of type 316 L stainless steel weld deposits when subjected to postweld heat treatment at 873 K for prolonged periods (up to 2000 hours). On aging for short durations (up to 20 hours), carbide/ carbonitride was the dominant transformation product, whereas sigma phase was dominant at longer aging times. The changes in the tensile and stress corrosion behavior of the aged weld metal have been attributed to the two competitive processes of matrix softening and hardening. Yield strength (YS) was found to depend predominantly on matrix softening only, while sig-nificant changes in the ultimate tensile strength (UTS) and the work-hardening exponent, n, occurred due to matrix hardening. Ductility and stress corrosion properties were considerably affected by both factors. Fractographic observations on the weld metal tested for stress-corrosion cracking (SCC) indicated a combination of transgranular cracking of the austenite and interface cracking.

Laser Transformation Hardening of Firing Zone Cutout Cams.

DTIC Science & Technology

1981-06-01

bath nitriding to case harden firing zone cutout cams for the Mk 10 Guided Missile Launcher System (GMLS). These cams, machined of 4340 steel ...salt bath nitriding to case harden firing zone cutout cams for the Mk 10 Guided Missile Launcher System (GMLS). These cams, machined of 4340 steel ...Patterns ........ ................ 8 9 Laser Beam Step Pattern ...... .................. .. 10 10 Hardness Profile, 4340 Steel

Radiation-hardened MRAM-based LUT for non-volatile FPGA soft error mitigation with multi-node upset tolerance

NASA Astrophysics Data System (ADS)

Zand, Ramtin; DeMara, Ronald F.

2017-12-01

In this paper, we have developed a radiation-hardened non-volatile lookup table (LUT) circuit utilizing spin Hall effect (SHE)-magnetic random access memory (MRAM) devices. The design is motivated by modeling the effect of radiation particles striking hybrid complementary metal oxide semiconductor/spin based circuits, and the resistive behavior of SHE-MRAM devices via established and precise physics equations. The models developed are leveraged in the SPICE circuit simulator to verify the functionality of the proposed design. The proposed hardening technique is based on using feedback transistors, as well as increasing the radiation capacity of the sensitive nodes. Simulation results show that our proposed LUT circuit can achieve multiple node upset (MNU) tolerance with more than 38% and 60% power-delay product improvement as well as 26% and 50% reduction in device count compared to the previous energy-efficient radiation-hardened LUT designs. Finally, we have performed a process variation analysis showing that the MNU immunity of our proposed circuit is realized at the cost of increased susceptibility to transistor and MRAM variations compared to an unprotected LUT design.

Role of Slip Mode on Stress Corrosion Cracking Behavior

NASA Astrophysics Data System (ADS)

Vasudevan, A. K.; Sadananda, K.

2011-02-01

In this article, we examine the effect of aging treatment and the role of planarity of slip on stress corrosion cracking (SCC) behavior in precipitation-hardened alloys. With aging, the slip mode can change from a planar slip in the underage (UA) to a wavy slip in the overage (OA) region. This, in turn, results in sharpening the crack tip in the UA compared to blunting in the OA condition. We propose that the planar slip enhances the stress concentration effects by making the alloys more susceptible to SCC. In addition, the planarity of slip enhances plateau velocities, reduces thresholds for SCC, and reduces component life. We show that the effect of slip planarity is somewhat similar to the effects of mechanically induced stress concentrations such as due to the presence of sharp notches. Aging treatment also causes variations in the matrix and grain boundary (GB) microstructures, along with typical mechanical and SCC properties. These properties include yield stress, work hardening rate, fracture toughness K IC , thresholds K Iscc, and steady-state plateau velocity ( da/ dt). The SCC data for a wide range of ductile alloys including 7050, 7075, 5083, 5456 Al, MAR M steels, and solid solution copper-base alloys are collected from the literature. Our assertion is that slip mode and the resulting stress concentration are important factors in SCC behavior. This is further supported by similar observations in many other systems including some steels, Al alloys, and Cu alloys.

Effect of shot peening on the microstructure of laser hardened 17-4PH

NASA Astrophysics Data System (ADS)

Wang, Zhou; Jiang, Chuanhai; Gan, Xiaoyan; Chen, Yanhua

2010-12-01

In order to investigate the influence of shot peening on microstructure of laser hardened steel and clarify how much influence of initial microstructure induced by laser hardening treatment on final microstructure of laser hardened steel after shot peening treatment, measurements of retained austenite, measurements of microhardness and microstructural analysis were carried out on three typical areas including laser hardened area, transitional area and matrix area of laser hardened 17-4PH steel. The results showed that shot peening was an efficient cold working method to eliminate the retained austenite on the surface of laser hardened samples. The surface hardness increased dramatically when shot peening treatments were carried out. The analyses of microstructure of laser hardened 17-4PH after shot peening treatment were carried out in matrix area and laser hardened area via Voigt method. With the increasing peening intensity, the influence depth of shot peening on hardness and microstructure increased but the surface hardness and microstructure did not change when certain peening intensity was reached. Influence depth of shot peening on hardness was larger than influence depth of shot peening on microstructure due to the kinetic energy loss along the depth during shot peening treatment. From the microstructural result, it can be shown that the shot peening treatment can influence the domain size and microstrain of treated samples but laser hardening treatment can only influence the microstrain of treated samples.

Strength computation of forged parts taking into account strain hardening and damage

NASA Astrophysics Data System (ADS)

Cristescu, Michel L.

2004-06-01

Modern non-linear simulation software, such as FORGE 3 (registered trade mark of TRANSVALOR), are able to compute the residual stresses, the strain hardening and the damage during the forging process. A thermally dependent elasto-visco-plastic law is used to simulate the behavior of the material of the hot forged piece. A modified Lemaitre law coupled with elasticiy, plasticity and thermic is used to simulate the damage. After the simulation of the different steps of the forging process, the part is cooled and then virtually machined, in order to obtain the finished part. An elastic computation is then performed to equilibrate the residual stresses, so that we obtain the true geometry of the finished part after machining. The response of the part to the loadings it will sustain during it's life is then computed, taking into account the residual stresses, the strain hardening and the damage that occur during forging. This process is illustrated by the forging, virtual machining and stress analysis of an aluminium wheel hub.

Radiation Hardened Electronics for Space Environments (RHESE)

NASA Technical Reports Server (NTRS)

Keys, Andrew S.; Adams, James H.; Frazier, Donald O.; Patrick, Marshall C.; Watson, Michael D.; Johnson, Michael A.; Cressler, John D.; Kolawa, Elizabeth A.

2007-01-01

Radiation Environmental Modeling is crucial to proper predictive modeling and electronic response to the radiation environment. When compared to on-orbit data, CREME96 has been shown to be inaccurate in predicting the radiation environment. The NEDD bases much of its radiation environment data on CREME96 output. Close coordination and partnership with DoD radiation-hardened efforts will result in leveraged - not duplicated or independently developed - technology capabilities of: a) Radiation-hardened, reconfigurable FPGA-based electronics; and b) High Performance Processors (NOT duplication or independent development).

The effects of interstitial content and annealing on the flow and fracture behavior on polycrystalline beta-NiAl

NASA Technical Reports Server (NTRS)

Weaver, M. L.; Levit, V.; Kaufman, M. J.; Noebe, R. D.

1994-01-01

The strain behavior of three polycrystalline NiAl alloys has been investigated at temperatures between 300 and 1200 K. Yield stress plateaus, yield stress transients upon a ten-fold increase in strain rate, work hardening peaks, and dips in the strain rate sensitivity (SRS) have been observed between 700 and 800 K. These observations are indicative of dynamic strain aging (DSA) and are discussed in terms of conventional strain aging theories.

Design and characterization of cellulose nanocrystal-enhanced epoxy hardeners

Treesearch

Shane X. Peng; Robert J. Moon; Jeffrey P. Youngblood

2014-01-01

Cellulose nanocrystals (CNCs) are renewable, sustainable, and abundant nanomaterial widely used as reinforcing fillers in the field of polymer nanocomposites. In this study, two-part epoxy systems with CNC-enhanced hardeners were fabricated. Three types of hardeners, Jeffamine D400 (JD400), diethylenetriamine (DETA), and (±)-trans-1,2- diaminocyclohexane (DACH), were...

Effect of preheating on fatigue resistance of gears in spin induction coil hardening process

NASA Astrophysics Data System (ADS)

Kumar, Pawan; Aggarwal, M. L.

2018-02-01

Spin hardening inductors are typically used for fine-sized teeth gear geometry. With the proper selection of several design parameters, only the gear teeth can be case surface hardened without affecting the other surface of gear. Preheating may be done to reach an adapted high austenitizing temperature in the root circle to avoid overheating of the tooth tip during final heating. The effect of preheating of gear on control of compressive residual stresses and case hardening has been experimentally discussed in this paper. Present work is about analysing single frequency mode, preheat hardening treatment and compressive residual stresses field for hardening process of spur gear using spin hardening inductors.

Analysis of the regimes in the scanner-based laser hardening process

NASA Astrophysics Data System (ADS)

Martínez, S.; Lamikiz, A.; Ukar, E.; Calleja, A.; Arrizubieta, J. A.; Lopez de Lacalle, L. N.

2017-03-01

Laser hardening is becoming a consolidated process in different industrial sectors such as the automotive industry or in the die and mold industry. The key to ensure the success in this process is to control the surface temperature and the hardened layer thickness. Furthermore, the development of reliable scanners, based on moving optics for guiding high power lasers at extremely fast speeds allows the rapid motion of laser spots, resulting on tailored shapes of swept areas by the laser. If a scanner is used to sweep a determined area, the laser energy density distribution can be adapted by varying parameters such us the scanning speed or laser power inside this area. Despite its advantages in terms of versatility, the use of scanners for the laser hardening process has not yet been introduced in the thermal hardening industry because of the difficulty of the temperature control and possible non-homogeneous hardness thickness layers. In the present work the laser hardening process with scanning optics applied to AISI 1045 steel has been studied, with special emphasis on the influence of the scanning speed and the results derived from its variation, the evolution of the hardened layer thickness and different strategies for the control of the process temperature. For this purpose, the hardened material has been studied by measuring microhardness at different points and the shape of the hardened layer has also been evaluated. All tests have been performed using an experimental setup designed to keep a nominal temperature value using a closed-loop control. The tests results show two different regimes depending on the scanning speed and feed rate values. The experimental results conclusions have been validated by means of thermal simulations at different conditions.

Age and Employee Green Behaviors: A Meta-Analysis

PubMed Central

Wiernik, Brenton M.; Dilchert, Stephan; Ones, Deniz S.

2016-01-01

Recent economic and societal developments have led to an increasing emphasis on organizational environmental performance. At the same time, demographic trends are resulting in increasingly aging labor forces in many industrialized nations. Commonly held stereotypes suggest that older workers are less likely to be environmentally responsible than younger workers. To evaluate the degree to which such age differences are present, we meta-analyzed 132 independent correlations and 336 d-values based on 4676 professional workers from 22 samples in 11 countries. Contrary to popular stereotypes, age showed small positive relationships with pro-environmental behaviors, suggesting that older adults engaged in these workplace behaviors slightly more frequently. Relationships with age appeared to be linear for overall, Conserving, Avoiding Harm, and Taking Initiative pro-environmental behaviors, but non-linear trends were observed for Transforming and Influencing Others behaviors. PMID:26973550

[Knowledge of Emotion Regulation Strategies, Problem Behavior, and Prosocial Behavior in Preschool Age].

PubMed

Gust, Nicole; Koglin, Ute; Petermann, Franz

2015-01-01

The present study examines the relation between knowledge of emotion regulation strategies and social behavior in preschoolers. Knowledge of emotion regulation strategies of 210 children (mean age 55 months) was assessed. Teachers rated children's social behavior with SDQ. Linear regression analysis examined how knowledge of emotion regulation strategies influenced social behavior of children. Significant effects of gender on SDQ scales "prosocial behavior", "hyperactivity", "behavior problems", and SDQ total problem scale were identified. Age was a significant predictor of SDQ scales "prosocial behavior", "hyperactivity", "problems with peers" and SDQ total problem scale. Knowledge of emotion regulation strategies predicted SDQ total problem scores. Results suggest that deficits in knowledge of emotion regulation strategies are linked with increased problem behavior.

Malnutrition at Age 3 Years and Externalizing Behavior Problems at Ages 8, 11, and 17 Years

PubMed Central

Liu, Jianghong; Raine, Adrian; Venables, Peter H.; Mednick, Sarnoff A.

2006-01-01

Objective Poor nutrition is thought to predispose to externalizing behavior problems, but to date there appear to have been no prospective longitudinal studies testing this hypothesis. This study assessed whether 1) poor nutrition at age 3 years predisposes to antisocial behavior at ages 8, 11, and 17 years, 2) such relationships are independent of psychosocial adversity, and 3) IQ mediates the relationship between nutrition and externalizing behavior problems. Method The participants were drawn from a birth cohort (N=1,795) in whom signs of malnutrition were assessed at age 3 years, cognitive measures were assessed at ages 3 and 11 years, and antisocial, aggressive, and hyperactive behavior was assessed at ages 8, 11, and 17 years. Results In relation to comparison subjects (N=1,206), the children with malnutrition signs at age 3 years (N=353) were more aggressive or hyperactive at age 8 years, had more externalizing problems at age 11, and had greater conduct disorder and excessive motor activity at age 17. The results were independent of psychosocial adversity and were not moderated by gender. There was a dose-response relationship between degree of malnutrition and degree of externalizing behavior at ages 8 and 17. Low IQ mediated the link between malnutrition and externalizing behavior at ages 8 and 11. Conclusions These results indicate that malnutrition predisposes to neurocognitive deficits, which in turn predispose to persistent externalizing behavior problems throughout childhood and adolescence. The findings suggest that reducing early malnutrition may help reduce later antisocial and aggressive behavior. PMID:15514400

Age-related changes in behavior in C57BL/6J mice from young adulthood to middle age.

PubMed

Shoji, Hirotaka; Takao, Keizo; Hattori, Satoko; Miyakawa, Tsuyoshi

2016-01-28

Aging is considered to be associated with progressive changes in the brain and its associated sensory, motor, and cognitive functions. A large number of studies comparing young and aged animals have reported differences in various behaviors between age-cohorts, indicating behavioral dysfunctions related to aging. However, relatively little is known about behavioral changes from young adulthood to middle age, and the effect of age on behavior during the early stages of life remains to be understood. In order to investigate age-related changes in the behaviors of mice from young adulthood to middle age, we performed a large-scale analysis of the behavioral data obtained from our behavioral test battery involving 1739 C57BL/6J wild-type mice at 2-12 months of age. Significant behavioral differences between age groups (2-3-, 4-5-, 6-7-, and 8-12-month-old groups) were found in all the behavioral tests, including the light/dark transition, open field, elevated plus maze, rotarod, social interaction, prepulse inhibition, Porsolt forced swim, tail suspension, Barnes maze, and fear conditioning tests, except for the hot plate test. Compared with the 2-3-month-old group, the 4-5- and 6-7-month-old groups exhibited decreased locomotor activity to novel environments, motor function, acoustic startle response, social behavior, and depression-related behavior, increased prepulse inhibition, and deficits in spatial and cued fear memory. For most behaviors, the 8-12-month-old group showed similar but more pronounced changes in most of these behaviors compared with the younger age groups. Older groups exhibited increased anxiety-like behavior in the light/dark transition test whereas those groups showed seemingly decreased anxiety-like behavior measured by the elevated plus maze test. The large-scale analysis of behavioral data from our battery of behavioral tests indicated age-related changes in a wide range of behaviors from young adulthood to middle age in C57BL/6J mice, though

Child Sexual Behaviors in School Context: Age and Gender Differences.

PubMed

Miragoli, Sarah; Camisasca, Elena; Di Blasio, Paola

2017-01-01

The main purpose of the study was to explore the child sexual behaviors that Italian teachers have observed in the school context. A representative sample of 227 children, from 5 to 10 years old, was rated by their teachers through the Child Sexual Behavior Inventory. Frequencies of sexual behaviors among children aged 5 to 6, 7 to 8, and 9 to 10 are presented. Younger children showed a broader range of sexual behaviors that decrease with the growing age, such as males in comparison to females. Moreover, findings showed that child sexual behavior is not only related to age and gender but also to family characteristics. These results suggested that child sexual behaviors reported by teachers through the Child Sexual Behavior Inventory may provide useful information about the development of children's sexuality. The knowledge of age appropriate sexual behaviors can help teachers discern normal sexual behaviors from problematic sexual behaviors.

RETRACTED ARTICLE: Precipitation behavior of B2-ordered aluminide

NASA Astrophysics Data System (ADS)

Han, Chang-Suk

2006-12-01

Fine dispersion of disordered phases is obtained in Ni-Al-Cr and Fe-Al-Co temary systems. A transmission electron microscope investigation has been performed on the precipitation of α-Cr in B2-ordered β-NiAl with different stoichiometry and α-Fe in B2-FeAl(Co) compound. Precipitation behavior and hardening were investigated by measuring the hardness variation. The hardness of NiAl and FeAl increases appreciably with the fine precipitation of α-Cr and α-Fe, and over-age softening occurs after prolonged aging. In the case of B2-NiAl(Cr), perfect lattice coherency is maintained at the interfaces between the α-Cr particles and the matrix during the initial stage of aging. After prolonged aging, a loss of coherency occurs by the attraction of matrix dislocations to the particle/matrix interface, followed by climbing around the particles. On the other hand, in the case of B2-FeAl(Co), the disordered α-Fe phase is present as a precipitate in the B2-FeAl(Co) matrix and has a cubic-cubic orientation with the matrix. At the early aging periods, prismatic dislocation loops formed in the B2-FeAl(Co) matrix. B2-FeAl(Co) matrix is typically hardened by the precipitation of α-Fe.

Effect of cutting parameters on strain hardening of nickel–titanium shape memory alloy

NASA Astrophysics Data System (ADS)

Wang, Guijie; Liu, Zhanqiang; Ai, Xing; Huang, Weimin; Niu, Jintao

2018-07-01

Nickel–titanium shape memory alloy (SMA) has been widely used as implant materials due to its good biocompatibility, shape memory property and super-elasticity. However, the severe strain hardening is a main challenge due to cutting force and temperature caused by machining. An orthogonal experiment of nickel–titanium SMA with different milling parameters conditions was conducted in this paper. On the one hand, the effect of cutting parameters on work hardening is obtained. It is found that the cutting speed has the most important effect on work hardening. The depth of machining induced layer and the degree of hardening become smaller with the increase of cutting speed when the cutting speed is less than 200 m min‑1 and then get larger with further increase of cutting speed. The relative intensity of diffraction peak increases as the cutting speed increase. In addition, all of the depth of machining induced layer, the degree of hardening and the relative intensity of diffraction peak increase when the feed rate increases. On the other hand, it is found that the depth of machining induced layer is closely related with the degree of hardening and phase transition. The higher the content of austenite in the machined surface is, the higher the degree of hardening will be. The depth of the machining induced layer increases with the degree of hardening increasing.

Skin hardening effect in patients with polymorphic light eruption: comparison of UVB hardening in hospital with a novel home UV-hardening device.

PubMed

Franken, S M; Genders, R E; de Gruijl, F R; Rustemeyer, T; Pavel, S

2013-01-01

An effective prophylactic treatment of patients with polymorphic light eruption (PLE) consists of repeated low, gradually increasing exposures to UVB radiation. This so-called UV(B) hardening induces better tolerance of the skin to sunlight. SunshowerMedical company (Amsterdam) has developed an UV (B) source that can be used during taking shower. The low UV fluence of this apparatus makes it an interesting device for UV hardening. In a group of PLE patients, we compared the effectiveness of the irradiation with SunshowerMedical at home with that of the UVB treatment in the hospital. The PLE patients were randomized for one of the treatments. The hospital treatment consisted of irradiations with broad-band UVB (Waldmann 85/UV21 lamps) twice a week during 6 weeks. The home UV-device was used each day with the maximal irradiation time of 6 min. The outcome assessment was based on the information obtained from patients' dermatological quality of life (DLQI) questionnaires, the ability of both phototherapies to reduce the provocation reaction and from the patients' evaluation of the long-term benefits of their phototherapies. Sixteen patients completed treatment with SunshowerMedical and thirteen completed treatment in hospital. Both types of phototherapy were effective. There was a highly significant improvement in DLQI with either treatment. In most cases, the hardening reduced or even completely suppressed clinical UV provocation of PLE. The patients using SunshowerMedical at home were, however, much more content with the treatment procedure than the patients visiting the dermatological units. Both treatments were equally effective in the induction of skin tolerance to sunlight in PLE patients. However, the home treatment was much better accepted than the treatment in the hospital. © 2011 The Authors. Journal of the European Academy of Dermatology and Venereology © 2011 European Academy of Dermatology and Venereology.

Impulse Excitation Internal Friction Study of Dislocation and Point Defect Interactions in Ultra-Low Carbon Bake-Hardenable Steel

NASA Astrophysics Data System (ADS)

Jung, Il-Chan; Kang, Deok-Gu; De Cooman, Bruno C.

2014-04-01

The simultaneous presence of interstitial solutes and dislocations in an ultra-low carbon bake-hardenable steel gives rise to two characteristic peaks in the internal friction (IF) spectrum: the dislocation-enhanced Snoek peak and the Snoek-Kê-Köster peak. These IF peaks were used to study the dislocation structure developed by the pre-straining and the static strain aging effect of C during the bake-hardening process. A Ti-stabilized interstitial-free steel was used to ascertain the absence of a γ-peak in the IF spectrum of the deformed ultra-low carbon steel. The analysis of the IF data shows clearly that the bake-hardening effect in ultra-low carbon steel is entirely due to atmosphere formation, with the dislocation segment length being the main parameter affecting the IF peak amplitude. Recovery annealing experiments showed that the rearrangement of the dislocation structure lead to the elimination of the C atmosphere.

Generation Mechanism of Work Hardened Surface Layer in Metal Cutting

NASA Astrophysics Data System (ADS)

Hikiji, Rikio; Kondo, Eiji; Kawagoishi, Norio; Arai, Minoru

Finish machining used to be carried out in grinding, but it is being replaced by cutting with very small undeformed chip thickness. In ultra precision process, the effects of the cutting conditions and the complicated factors on the machined surface integrity are the serious problems. In this research, work hardened surface layer was dealt with as an evaluation of the machined surface integrity and the effect of the mechanical factors on work hardening was investigated experimentally in orthogonal cutting. As a result, it was found that work hardened surface layer was affected not only by the shear angle varied under the cutting conditions and the thrust force of cutting resistance, but also by the thrust force acting point, the coefficient of the thrust force and the compressive stress equivalent to the bulk hardness. Furthermore, these mechanical factors acting on the depth of the work hardened surface layer were investigated with the calculation model.

Strengthening of Cu–Ni–Si alloy using high-pressure torsion and aging

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

Lee, Seungwon, E-mail: chominamlsw@gmail.com; WPI, International Institute for Carbon-Neutral Energy Research; Matsunaga, Hirotaka

2014-04-01

An age-hardenable Cu–2.9%Ni–0.6%Si alloy was subjected to high-pressure torsion. Aging behavior was investigated in terms of hardness, electrical conductivity and microstructural features. Transmission electron microscopy showed that the grain size is refined to ∼ 150 nm and the Vickers microhardness was significantly increased through the HPT processing. Aging treatment of the HPT-processed alloy led to a further increase in the hardness. Electrical conductivity is also improved with the aging treatment. It was confirmed that the simultaneous strengthening by grain refinement and fine precipitation is achieved while maintaining high electrical conductivity. Three dimensional atom probe analysis including high-resolution transmission electron microscopymore » revealed that nanosized precipitates having compositions of a metastable Cu{sub 3}Ni{sub 5}Si{sub 2} phase and a stable NiSi phase were formed in the Cu matrix by aging of the HPT-processed samples and these particles are responsible for the additional increase in strength after the HPT processing. - Highlights: • Grain refinement is achieved in Corson alloy the size of ∼150nm by HPT. • Aging at 300°C after HPT leads to further increase in the mechanical property. • Electrical conductivity reaches 40% IACS after aging for 100 h. • 3D-APT revealed the formation of nanosized-precipitates during aging treatment. • Simultaneous hardening in both grain refinement and precipitation is achieved.« less

Segmentation-free empirical beam hardening correction for CT.

PubMed

Schüller, Sören; Sawall, Stefan; Stannigel, Kai; Hülsbusch, Markus; Ulrici, Johannes; Hell, Erich; Kachelrieß, Marc

2015-02-01

The polychromatic nature of the x-ray beams and their effects on the reconstructed image are often disregarded during standard image reconstruction. This leads to cupping and beam hardening artifacts inside the reconstructed volume. To correct for a general cupping, methods like water precorrection exist. They correct the hardening of the spectrum during the penetration of the measured object only for the major tissue class. In contrast, more complex artifacts like streaks between dense objects need other techniques of correction. If using only the information of one single energy scan, there are two types of corrections. The first one is a physical approach. Thereby, artifacts can be reproduced and corrected within the original reconstruction by using assumptions in a polychromatic forward projector. These assumptions could be the used spectrum, the detector response, the physical attenuation and scatter properties of the intersected materials. A second method is an empirical approach, which does not rely on much prior knowledge. This so-called empirical beam hardening correction (EBHC) and the previously mentioned physical-based technique are both relying on a segmentation of the present tissues inside the patient. The difficulty thereby is that beam hardening by itself, scatter, and other effects, which diminish the image quality also disturb the correct tissue classification and thereby reduce the accuracy of the two known classes of correction techniques. The herein proposed method works similar to the empirical beam hardening correction but does not require a tissue segmentation and therefore shows improvements on image data, which are highly degraded by noise and artifacts. Furthermore, the new algorithm is designed in a way that no additional calibration or parameter fitting is needed. To overcome the segmentation of tissues, the authors propose a histogram deformation of their primary reconstructed CT image. This step is essential for the proposed

Segmentation-free empirical beam hardening correction for CT

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

Schüller, Sören; Sawall, Stefan; Stannigel, Kai

2015-02-15

Purpose: The polychromatic nature of the x-ray beams and their effects on the reconstructed image are often disregarded during standard image reconstruction. This leads to cupping and beam hardening artifacts inside the reconstructed volume. To correct for a general cupping, methods like water precorrection exist. They correct the hardening of the spectrum during the penetration of the measured object only for the major tissue class. In contrast, more complex artifacts like streaks between dense objects need other techniques of correction. If using only the information of one single energy scan, there are two types of corrections. The first one ismore » a physical approach. Thereby, artifacts can be reproduced and corrected within the original reconstruction by using assumptions in a polychromatic forward projector. These assumptions could be the used spectrum, the detector response, the physical attenuation and scatter properties of the intersected materials. A second method is an empirical approach, which does not rely on much prior knowledge. This so-called empirical beam hardening correction (EBHC) and the previously mentioned physical-based technique are both relying on a segmentation of the present tissues inside the patient. The difficulty thereby is that beam hardening by itself, scatter, and other effects, which diminish the image quality also disturb the correct tissue classification and thereby reduce the accuracy of the two known classes of correction techniques. The herein proposed method works similar to the empirical beam hardening correction but does not require a tissue segmentation and therefore shows improvements on image data, which are highly degraded by noise and artifacts. Furthermore, the new algorithm is designed in a way that no additional calibration or parameter fitting is needed. Methods: To overcome the segmentation of tissues, the authors propose a histogram deformation of their primary reconstructed CT image. This step is essential

Alloy solution hardening with solute pairs

DOEpatents

Mitchell, John W.

1976-08-24

Solution hardened alloys are formed by using at least two solutes which form associated solute pairs in the solvent metal lattice. Copper containing equal atomic percentages of aluminum and palladium is an example.

Influence of Thermal Aging on Tensile and Low Cycle Fatigue Behavior of Type 316LN Austenitic Stainless Steel Weld Joint

NASA Astrophysics Data System (ADS)

Suresh Kumar, T.; Nagesha, A.; Ganesh Kumar, J.; Parameswaran, P.; Sandhya, R.

2018-05-01

Influence of short-term thermal aging on the low-cycle fatigue (LCF) behavior of 316LN austenitic stainless steel weld joint with 0.07 wt pct N has been investigated. Prior thermal exposure was found to improve the fatigue life compared with the as-welded condition. Besides, the treatment also imparted a softening effect on the weld metal, leading to an increase in the ductility of the weld joint which had a bearing on the cyclic stress response. The degree of cyclic hardening was seen to increase after aging. Automated ball-indentation (ABI) technique was employed toward understanding the mechanical properties of individual zones across the weld joint. It was observed that the base metal takes most of the applied cyclic strain during LCF deformation in the as-welded condition. In the aged condition, however, the weld also participates in the cyclic deformation. The beneficial effect of thermal aging on cyclic life is attributed to a reduction in the severity of the metallurgical notch leading to a restoration of ductility of the weld region. The transformation of δ-ferrite to σ-phase during the aging treatment was found to influence the location of crack initiation. Fatigue cracks were found to initiate in the base metal region of the joint in most of the testing conditions. However, embrittlement in the weld metal caused a shift in the point of crack initiation with increasing strain amplitude under LCF.

Helium-induced hardening effect in polycrystalline tungsten

NASA Astrophysics Data System (ADS)

Kong, Fanhang; Qu, Miao; Yan, Sha; Zhang, Ailin; Peng, Shixiang; Xue, Jianming; Wang, Yugang

2017-09-01

In this paper, helium induced hardening effect of tungsten was investigated. 50 keV He2+ ions at fluences vary from 5 × 1015 cm-2 to 5 × 1017 cm-2 were implanted into polycrystalline tungsten at RT to create helium bubble-rich layers near the surface. The microstructure and mechanical properties of the irradiated specimens were studied by TEM and nano-indentor. Helium bubble rich layers are formed in near surface region, and the layers become thicker with the rise of fluences. Helium bubbles in the area of helium concentration peak are found to grow up, while the bubble density is almost unchanged. Obvious hardening effect is induced by helium implantation in tungsten. Micro hardness increases rapidly with the fluence firstly, and more slowly when the fluence is above 5 × 1016 cm-2. The hardening effect of tungsten can be attributed to helium bubbles, which is found to be in agreement with the Bacon-Orowan stress formula. The growing diameter is the major factor rather than helium bubbles density (voids distance) in the process of helium implantation at fluences below 5 × 1017 cm-2.

An adolescent age group approach to examining youth risk behaviors.

PubMed

Oman, Roy F; McLeroy, Kenneth R; Vesely, Sara; Aspy, Cheryl B; Smith, David W; Penn, David A

2002-01-01

To investigate relationships among youth risk behaviors and demographic factors using an adolescent age group approach. Cross-sectional data from a randomly selected population. Risk behaviors were compared within specific demographic factors and by adolescent age groups. Racially diverse, inner-city neighborhoods in two midwestern cities. Teenagers (n = 1350) and parents (n = 1350) of the teenagers. Truancy; arrested/picked up by police; weapon carrying; fighting; sexual intercourse; tobacco, alcohol, and other drug use; demographic factors; and family structure. Youth mean age was 15.4 (+/- 1.7) years and 52% were female; racial/ethnic characteristics were 47% White, 22% Black, 19% Hispanic, and 10% Native American. Parents' mean age was 42.2 (+/- 8.4) years and 81% were female. chi 2 analyses indicated numerous significant (p < .05) youth risk behavior differences within the demographic factors and that many of the differences varied by adolescent age group. For example, risk behavior differences within racial/ethnic groups were most profound in the middle and older age groups, whereas risk behavior differences within parent income, education levels, and family structure were most apparent in the younger age groups. Of the demographic factors, family structure was most frequently associated with the risk behaviors. The results generally suggest that the relationships among risk behaviors and demographic factors vary within the adolescent age groups included in this study. The results will be useful for developing age-appropriate prevention programs for youth who fit the profile for these risk behaviors. The study protocol also includes specific sampling methods that may be useful for future studies that intend to collect data from difficult-to-reach populations.

Modeling spray/puddle dissolution processes for deep-ultraviolet acid-hardened resists

NASA Astrophysics Data System (ADS)

Hutchinson, John M.; Das, Siddhartha; Qian, Qi-De; Gaw, Henry T.

1993-10-01

A study of the dissolution behavior of acid-hardened resists (AHR) was undertaken for spray and spray/puddle development processes. The Site Services DSM-100 end-point detection system is used to measure both spray and puddle dissolution data for a commercially available deep-ultraviolet AHR resist, Shipley SNR-248. The DSM allows in situ measurement of dissolution rate on the wafer chuck and hence allows parameter extraction for modeling spray and puddle processes. The dissolution data for spray and puddle processes was collected across a range of exposure dose and postexposure bake temperature. The development recipe was varied to decouple the contribution of the spray and puddle modes to the overall dissolution characteristics. The mechanisms involved in spray versus puddle dissolution and the impact of spray versus puddle dissolution on process performance metrics has been investigated. We used the effective-dose-modeling approach and the measurement capability of the DSM-100 and developed a lumped parameter model for acid-hardened resists that incorporates the effects of exposure, postexposure bake temperature and time, and development condition. The PARMEX photoresist-modeling program is used to determine parameters for the spray and for the puddle process. The lumped parameter AHR model developed showed good agreement with experimental data.

Microstructural changes and strain hardening effects in abrasive contacts at different relative velocities and temperatures

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

Rojacz, H., E-mail: rojacz@ac2t.at

2016-08-15

Strain hardening is commonly used to reach the full potential of materials and can be beneficial in tribological contacts. 2-body abrasive wear was simulated in a scratch test, aimed at strain hardening effects in various steels. Different working conditions were examined at various temperatures and velocities. Strain hardening effects and microstructural changes were analysed with high resolution scanning electron microscopy (HRSEM), electron backscatter diffraction (EBSD), micro hardness measurements and nanoindentation. Statistical analysing was performed quantifying the influence of different parameters on microstructures. Results show a crucial influence of temperature and velocity on the strain hardening in tribological contacts. Increased velocitymore » leads to higher deformed microstructures and higher increased surface hardness at a lower depth of the deformed zones at all materials investigated. An optimised surface hardness can be achieved knowing the influence of velocity (strain rate) and temperature for a “tailor-made” surface hardening in tribological systems aimed at increased wear resistance. - Highlights: •Hardening mechanisms and their intensity in tribological contacts are dependent on relative velocity and temperature. •Beneficial surface hardened zones are formed at certain running-in conditions; the scientific background is presented here. •Ferritic-pearlitic steels strain hardens via grain size reduction and decreasing interlamellar distances in pearlite. •Austenitic steels show excellent surface hardening (120% hardness increase) by twinning and martensitic transformation. •Ferritic steels with hard phases harden in the ferrite phase as per Hall-Petch equation and degree of deformation.« less

Birth Order and Maladaptive Behavior in School-Aged Children.

ERIC Educational Resources Information Center

Carmichael, Karla D.

Drawing on Alfred Adler's theories on the effect of birth order on maladaptive behavior in children, this study focused on the relationship between birth order and the referral to counseling of school-aged children with maladaptive disorder. School-aged children (N=217) with academic or behavioral problems, ages 5 to 18, were referred to the staff…

Cognitive Delay and Behavior Problems Prior to School Age

PubMed Central

Palta, Mari; Kotelchuck, Milton; Poehlmann, Julie; Witt, Whitney P.

2014-01-01

OBJECTIVE: To investigate the relationship between cognitive delay (CD) and behavior problems between ages 9 months and 5 years, while adjusting for covariates related to CD. METHODS: Data were from 4 waves of the Early Childhood Longitudinal Study, Birth Cohort (n = 8000). Children were classified as typically developing (TD) or as having resolved, newly developed, or persistent CD between 9 and 24 months, based on scores from the Bayley Short Form-Research Edition below or above the 10th percentile. Child behavior was measured by using the Infant/Toddler Symptom Checklist (ages 9 and 24 months) and the Preschool and Kindergarten Behavior Scales (ages 4 and 5 years); children in the top 10th percentile were considered to have a behavior problem. Hierarchical linear modeling estimated the effect of CD status on children’s behavioral trajectories, adjusted for confounders. RESULTS: CD resolved for 80.3% of children between 9 and 24 months. Behavior problems at 24 months were detected in 19.3%, 21.8%, and 35.5% of children with resolved, newly developed, and persistent CD, respectively, versus 13.0% of TD children. Behavior problems increased among children with CD over time, and more so among children with persistent CD. By age 5, children with persistent CD had behavior scores moderately (0.59 SD) higher than TD children. CONCLUSIONS: Behavior problems among children with CD are slightly higher at 9 months, clearly evident by 24 months, and increase as children move toward school age. Efforts to promote the earliest identification, evaluation, and service referral may be necessary to improve outcomes for these children. PMID:25113290

Assessment of the microstructure and torsional fatigue performance of an induction hardened vanadium microalloyed medium-carbon steel

NASA Astrophysics Data System (ADS)

Rothleutner, Lee M.

Vanadium microalloying of medium-carbon bar steels is a common practice in industry for a number of hot rolled as well as forged and controlled-cooled components. However, use of vanadium microalloyed steels has expanded into applications beyond their originally designed controlled-cooled processing scheme. Applications such as transmission shafts often require additional heat-treatments such as quench and tempering and/or induction hardening to meet packaging or performance requirements. As a result, there is uncertainty regarding the influence of vanadium on the properties of heat-treated components, specifically the effect of rapid heat-treating such as induction hardening. In the current study, the microstructural evolution and torsional fatigue behavior of induction hardened 1045 and 10V45 (0.08 wt pct V) steels were examined. Torsional fatigue specimens specifically designed for this research were machined from the as-received, hot rolled bars and induction hardened using both scanning (96 kHz/72 kW) and single-shot (31 kHz/128 kW) methods. Four conditions were evaluated, three scan hardened to 25, 32, and 44 pct nominal effective case depths and one single-shot hardened to 44 pct. Torsional fatigue tests were conducted at a stress ratio of 0.1 and shear stress amplitudes of 550, 600, and 650 MPa. Physical simulations using the thermal profiles from select induction hardened conditions were conducted in the GleebleRTM 3500 to augment microstructural analysis of torsional fatigue specimens. Thermal profiles were calculated by a collaborating private company using electro-thermal finite element analysis. Residual stresses were evaluated for all conditions using a strain gage hole drilling technique. The results showed that vanadium microalloying has an influence on the microstructure in the highest hardness region of the induction-hardened case as well as the total case region. Vanadium microalloyed conditions consistently exhibited a greater amount of non

Predictors of Intrusive Sexual Behaviors in Preschool-Aged Children.

PubMed

Smith, Tyler J; Lindsey, Rebecca A; Bohora, Som; Silovsky, Jane F

2018-04-10

Intrusive sexual behaviors (ISBs) are a specific type of problematic sexual behavior characterized by the invasive nature of the acts (e.g., touching others' private parts, attempting intercourse; Friedrich, 1997). The limited amount of research on ISBs has focused on sexual abuse history as the primary predictor. However, Friedrich, Davies, Feher, and Wright (2003) found that ISBs in children up to age 12 were related to four broad conceptual factors: (a) exposure to sexual content, (b) exposure to violent behavior, (c) family adversity, and (d) child vulnerabilities. The current study sought to replicate Friedrich's study using a clinical sample of 217 preschool-aged children (ages two to six). Results supported variables from within the child vulnerabilities construct (externalizing behaviors, β EXT  = 0.032, p = 0.001), post-traumatic stress disorder (PTSD) criteria met (β PTSD  = 0.177, p = 0.02), and an inverse relationship with age (β AGE  = -0.206, p = 0.024). These results highlight the importance of considering childhood behavioral patterns and reactivity to traumatic events as correlates of ISBs in young children.

Comparison of air void content measurements in fresh versus hardened concretes.

DOT National Transportation Integrated Search

1990-01-01

This study compares the air content of freshly mixed and hardened concretes. At the fresh stage, pressure meters (Types A and B) and a volumetric meter were used to determine the air content. At the hardened stage, the air content was calculated usin...

Physico-chemical studies of hardened cement paste structure with micro-reinforcing fibers

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

Steshenko, Aleksei, E-mail: steshenko.alexey@gmail.com; Kudyakov, Aleksander; Konusheva, Viktoriya

The results of physico-chemical studies of modified hardened cement paste with micro-reinforcing fibers are given in this article. The goal was to study the reasons of the increase of strength properties of modified hardened cement paste by the method of X-ray diffraction and electron microscopy. It is shown that the use of mineral fibers in the production of cement based material has positive effect on its properties. The study found out that the increase in the strength of the hardened cement paste with micro-reinforcing fibers is due to the increase of the rate of hydration of cement without a significantmore » change in the phase composition in comparison with hardened cement paste without additive. The results of microstructure investigation (of control samples and samples of the reinforced hardened cement paste) have shown that introduction of mineral fibers in the amount of 0.1-2 % by weight of cement provides the structure of the homogeneous microporous material with uniform distribution of the crystalline phase provided by densely packed hydrates.« less

Induction of a Hardening Phenomenon and Quantitative Changes of Ceramides in Stratum Corneum

PubMed Central

Park, Sook Young; Kim, Jin Hye; Cho, Soo Ick; Kim, Kyeong Il; Cho, Hee Jin; Park, Chun Wook; Lee, Cheol Heon

2014-01-01

Background Hardening phenomenon of human skin after repeated exposure to the irritants is well-known, but the precise mechanism remains elusive. Objective To modify the previous experimental model of hardening phenomenon by repeated applications of two different concentrations of sodium lauryl sulfate (SLS) solutions to Korean healthy volunteers and to investigate the quantitative changes of ceramides in stratum corneum before and after chronic repeated irritation. Methods Eight hundred microliters of distilled water containing 0.1% and 2% SLS was applied for 10 minutes on the forearm of 41 healthy volunteers for 3 weeks. After an intervening 3-week rest, 24-hour patch tests with 1% SLS were conducted on previously irritated sites. Transepidermal water loss (TEWL), erythema index and quantity of ceramide were measured in the stratum corneum before and after irritation. Results TEWL values on the sites preirritated with 2% SLS were lower than those with 0.1% SLS. Hardening phenomenon occurred in 24 volunteers at day 44. The changes in ceramide levels were not significantly higher in the hardened skin than in the non-hardened skin. Conclusion Repetitive stimulation with a higher concentration of SLS can more easily trigger skin hardening. PMID:24648684

Precipitation hardening austenitic superalloys

DOEpatents

Korenko, Michael K.

1985-01-01

Precipitation hardening, austenitic type superalloys are described. These alloys contain 0.5 to 1.5 weight percent silicon in combination with about 0.05 to 0.5 weight percent of a post irradiation ductility enhancing agent selected from the group of hafnium, yttrium, lanthanum and scandium, alone or in combination with each other. In addition, when hafnium or yttrium are selected, reductions in irradiation induced swelling have been noted.

Aging and human sexual behavior: biocultural perspectives - a mini-review.

PubMed

Gray, Peter B; Garcia, Justin R

2012-01-01

In this mini-review, we consider an evolutionary biocultural perspective on human aging and sexuality. An evolutionary approach to senescence highlights the energetic trade-offs between fertility and mortality. By comparing humans to other primates, we situate human senescence as an evolutionary process, with shifts in postreproductive sexual behavior in this light. Age-related declines in sexual behavior are typical for humans but also highly contingent on the sociocultural context within which aging individuals express their sexuality. We briefly review some of the most comprehensive studies of aging and sexual behavior, both from the USA and cross-culturally. We frame these patterns with respect to the long-term relationships within which human sexual behavior typically occurs. Because sexuality is typically expressed within pair-bonds, sexual behavior sometimes declines in both members of a couple with age, but also exhibits sex-specific effects that have their roots in evolved sex differences. Copyright © 2012 S. Karger AG, Basel.

Predictors of Prosocial Behavior: Differences in Middle Aged and Older Adults.

PubMed

Wenner, Jennifer R; Randall, Brandy A

2016-10-01

Generativity, contributing to the next generation, is important for well-being throughout middle and late life. Therefore, it is crucial to understand what contributes to generativity during these life stages. Parenting and work are common, but not the only, ways people engage generatively; prosocial behavior is another. A community connection may encourage generative contributions in adults. However, older adults may face obstacles to being generative, and may need an additional drive to engage in these behaviors. Given this, it was expected that community cohesion would predict prosocial behavior despite age, and that grit would provide motivation for older adults, so the current study examined whether age moderated the relation between grit and prosocial behavior. Data were used from 188 upper-Midwest adults (aged 37-89). Multiple regression analyses showed that age moderated the relation between grit and prosocial behavior such that grit predicted prosocial behavior in older adults but not middle age adults. A sense of community cohesion was predictive of prosocial behavior despite age. While grit may promote generative acts in different ways depending on age, a sense of community cohesion may foster community contributions despite age. The discussion focuses on future directions and ways to promote generativity using this research.

Predictors of Prosocial Behavior: Differences in Middle Aged and Older Adults

PubMed Central

Wenner, Jennifer R.; Randall, Brandy A.

2016-01-01

Generativity, contributing to the next generation, is important for well-being throughout middle and late life. Therefore, it is crucial to understand what contributes to generativity during these life stages. Parenting and work are common, but not the only, ways people engage generatively; prosocial behavior is another. A community connection may encourage generative contributions in adults. However, older adults may face obstacles to being generative, and may need an additional drive to engage in these behaviors. Given this, it was expected that community cohesion would predict prosocial behavior despite age, and that grit would provide motivation for older adults, so the current study examined whether age moderated the relation between grit and prosocial behavior. Data were used from 188 upper-Midwest adults (aged 37-89). Multiple regression analyses showed that age moderated the relation between grit and prosocial behavior such that grit predicted prosocial behavior in older adults but not middle age adults. A sense of community cohesion was predictive of prosocial behavior despite age. While grit may promote generative acts in different ways depending on age, a sense of community cohesion may foster community contributions despite age. The discussion focuses on future directions and ways to promote generativity using this research. PMID:28163344

Plant resistance to cold stress: mechanisms and environmental signals triggering frost hardening and dehardening.

PubMed

Beck, Erwin H; Heim, Richard; Hansen, Jens

2004-12-01

This introductory overview shows that cold, in particular frost, stresses a plant in manifold ways and that the plant's response, being injurious or adaptive, must be considered a syndrome rather than a single reaction. In the course of the year perennial plants of the temperate climate zones undergo frost hardening in autumn and dehardening in spring. Using Scots pine (Pinus sylvestris L.) as a model plant the environmental signals inducing frost hardening and dehardening, respectively, were investigated. Over 2 years the changes in frost resistance of Scots pine needles were recorded together with the annual courses of day-length and ambient temperature. Both act as environmental signals for frost hardening and dehardening. Climate chamber experiments showed that short day-length as a signal triggering frost hardening could be replaced by irradiation with far red light, while red light inhibited hardening. The involvement of phytochrome as a signal receptor could be corroborated by respective night-break experiments. More rapid frost hardening than by short day or far red treatment was achieved by applying a short period (6 h) of mild frost which did not exceed the plant's cold resistance. Both types of signals were independently effective but the rates of frost hardening were not additive. The maximal rate of hardening was - 0.93 degrees C per day and frost tolerance of less than < - 72 degrees C was achieved. For dehardening, temperature was an even more effective signal than day-length.

Simulating the influence of scatter and beam hardening in dimensional computed tomography

NASA Astrophysics Data System (ADS)

Lifton, J. J.; Carmignato, S.

2017-10-01

Cone-beam x-ray computed tomography (XCT) is a radiographic scanning technique that allows the non-destructive dimensional measurement of an object’s internal and external features. XCT measurements are influenced by a number of different factors that are poorly understood. This work investigates how non-linear x-ray attenuation caused by beam hardening and scatter influences XCT-based dimensional measurements through the use of simulated data. For the measurement task considered, both scatter and beam hardening are found to influence dimensional measurements when evaluated using the ISO50 surface determination method. On the other hand, only beam hardening is found to influence dimensional measurements when evaluated using an advanced surface determination method. Based on the results presented, recommendations on the use of beam hardening and scatter correction for dimensional XCT are given.

Method for increasing the rate of compressive strength gain in hardenable mixtures containing fly ash

DOEpatents

Liskowitz, John W.; Wecharatana, Methi; Jaturapitakkul, Chai; Cerkanowicz, deceased, Anthony E.

1997-01-01

The present invention relates to concrete, mortar and other hardenable mixtures comprising cement and fly ash for use in construction. The invention provides a method for increasing the rate of strength gain of a hardenable mixture containing fly ash by exposing the fly ash to an aqueous slurry of calcium oxide (lime) prior to its incorporation into the hardenable mixture. The invention further relates to such hardenable mixtures, e.g., concrete and mortar, that contain fly ash pre-reacted with calcium oxide. In particular, the fly ash is added to a slurry of calcium oxide in water, prior to incorporating the fly ash in a hardenable mixture. The hardenable mixture may be concrete or mortar. In a specific embodiment, mortar containing fly ash treated by exposure to an aqueous lime slurry are prepared and tested for compressive strength at early time points.

Assessment of BART Fire-Hardening Programs.

DOT National Transportation Integrated Search

1982-09-01

This report presents the results of an assessment of the Bay Area Rapid Transit District (BART) vehicle fire hardening. The report assesses the overall effort to improve the fire safety of the current BART vehicles through the removal of prospective ...

Developments in Radiation-Hardened Electronics Applicable to the Vision for Space Exploration

NASA Technical Reports Server (NTRS)

Keys, Andrew S.; Frazier, Donald O.; Patrick , Marshall C.; Watson, Michael D.; Johnson, Michael A.; Cressler, John D.; Kolawa, Elizabeth A.

2007-01-01

The Radiation Hardened Electronics for Space Exploration (RHESE) project develops the advanced technologies required to produce radiation hardened electronics, processors, and devices in support of the anticipated requirements of NASA's Constellation program. Methods of protecting and hardening electronics against the encountered space environment are discussed. Critical stages of a spaceflight mission that are vulnerable to radiation-induced interruptions or failures are identified. Solutions to mitigating the risk of radiation events are proposed through the infusion of RHESE technology products and deliverables into the Constellation program's spacecraft designs.

Update on radiation-hardened microcomputers for robotics and teleoperated systems

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

Sias, F.R. Jr.; Tulenko, J.S.

1993-12-31

Since many programs sponsored by the Department of Defense are being canceled, it is important to select carefully radiation-hardened microprocessors for projects that will mature (or will require continued support) several years in the future. At the present time there are seven candidate 32-bit processors that should be considered for long-range planning for high-performance radiation-hardened computer systems. For Department of Energy applications it is also important to consider efforts at standardization that require the use of the VxWorks operating system and hardware based on the VMEbus. Of the seven processors, one has been delivered and is operating and other systemsmore » are scheduled to be delivered late in 1993 or early in 1994. At the present time the Honeywell-developed RH32, the Harris RH-3000 and the Harris RHC-3000 are leading contenders for meeting DOE requirements for a radiation-hardened advanced 32-bit microprocessor. These are all either compatible with or are derivatives of the MIPS R3000 Reduced Instruction Set Computer. It is anticipated that as few as two of the seven radiation-hardened processors will be supported by the space program in the long run.« less

The effect of hydrogenation on strain hardening and deformation mechanisms in <113> single crystals of Hadfield steel

NASA Astrophysics Data System (ADS)

Astafurova, Elena; Maier, Galina; Melnikov, Eugene; Koshovkina, Vera; Moskvina, Valentina; Smirnov, Alexander; Bataev, Vladimir

2015-10-01

The effect of hydrogenation on the strain-hardening behavior and the deformation mechanisms of <113>-oriented single crystals of Hadfield steel was investigated under tension at room temperature. The stages of plastic flow and deformation mechanisms for hydrogen-charged specimens are similar to one in hydrogen-free state: slip → slip + single twinning → slip + multiple twinning. Hydrogen alloying favors to mechanical twinning, micro- and macrolocalization of plastic flow.

Zinc coated sheet steel for press hardening

NASA Astrophysics Data System (ADS)

Ghanbari, Zahra N.

Galvanized steels are of interest to enhance corrosion resistance of press-hardened steels, but concerns related to liquid metal embrittlement have been raised. The objective of this study was to assess the soak time and temperature conditions relevant to the hot-stamping process during which Zn penetration did or did not occur in galvanized 22MnB5 press-hardening steel. A GleebleRTM 3500 was used to heat treat samples using hold times and temperatures similar to those used in industrial hot-stamping. Deformation at both elevated temperature and room temperature were conducted to assess the coating and substrate behavior related to forming (at high temperature) and service (at room temperature). The extent of alloying between the coating and substrate was assessed on undeformed samples heat treated under similar conditions to the deformed samples. The coating transitioned from an α + Gamma1 composition to an α (bcc Fe-Zn) phase with increased soak time. This transition likely corresponded to a decrease in availability of Zn-rich liquid in the coating during elevated temperature deformation. Penetration of Zn into the substrate sheet in the undeformed condition was not observed for any of the processing conditions examined. The number and depth of cracks in the coating and substrate steel was also measured in the hot-ductility samples. The number of cracks appeared to increase, while the depth of cracks appeared to decrease, with increasing soak time and increasing soak temperature. The crack depth appeared to be minimized in the sample soaked at the highest soak temperature (900 °C) for intermediate and extended soak times (300 s or 600 s). Zn penetration into the substrate steel was observed in the hot-ductility samples soaked at each hold temperature for the shortest soak time (10 s) before being deformed at elevated temperature. Reduction of area and elongation measurements showed that the coated sample soaked at the highest temperature and longest soak time

Effect of strain rate on bake hardening response of BH220 steel

NASA Astrophysics Data System (ADS)

Das, Anindya; Tarafder, Soumitro; Sivaprasad, S.; Chakrabarti, Debalay

2015-09-01

This study aims at understanding the bake hardening ability of ultra low carbon BH220 steel at different strain rates. The as-received material has been pre-strained to four different levels and then deformed in tension under (a) as pre-strained state and (b) after baking at 170 ∘C for 20 minutes, at three different strain rates of 0.001, 0.1 and 100/s. In both the conditions, yield stress increased with pre-strain and strain rate, but bake hardening ability was found to decrease when strain rate was increased. The strain rate sensitivity of the material was also found to decrease with bake hardening. Generation of dislocation forests and their subsequent immobility during baking treatment enables them to act as long range obstacles during further deformation. At higher strain rates, less amount of dislocations are produced which can interact with themselves and produce hardening, because of which bake hardening ability and the strain rate drops. A dislocation based strengthening model, as proposed by Larour et al. 2011 [7], was used to predict the yield stress values obtained at different conditions. The equation produced excellent co-relation with the experimental data.

Cognitive work hardening: a return-to-work intervention for people with depression.

PubMed

Wisenthal, Adeena; Krupa, Terry

2013-01-01

Mental health claims in the workplace are rising, particularly those due to depression. Associated with this is an increase in disability costs for the employer and the disability insurer, but even more important is the human suffering that results. While treatments are available for the depression there is a gap in interventions that specifically target return-to-work preparation. This paper presents cognitive work hardening, a treatment intervention that can bridge this gap by addressing the unique functional issues inherent in depression with a view to increasing return-to-work success. Cognitive work hardening applies the proven principles of classical work hardening (which has typically been applied to people with physical injuries) to the mental health domain. This paper explains how the occupational therapy principle of occupation and the core competency, enablement, are utilized and applied in cognitive work hardening. Key skills of the occupational therapist are also discussed. In addition, the paper considers the relationship of cognitive work hardening to recovery and mental illness, and the role it plays among workplace-based return-to-work interventions in the current movement toward non-clinical return-to-work interventions.

Method for increasing the rate of compressive strength gain in hardenable mixtures containing fly ash

DOEpatents

Liskowitz, J.W.; Wecharatana, M.; Jaturapitakkul, C.; Cerkanowicz, A.E.

1997-10-28

The present invention relates to concrete, mortar and other hardenable mixtures comprising cement and fly ash for use in construction. The invention provides a method for increasing the rate of strength gain of a hardenable mixture containing fly ash by exposing the fly ash to an aqueous slurry of calcium oxide (lime) prior to its incorporation into the hardenable mixture. The invention further relates to such hardenable mixtures, e.g., concrete and mortar, that contain fly ash pre-reacted with calcium oxide. In particular, the fly ash is added to a slurry of calcium oxide in water, prior to incorporating the fly ash in a hardenable mixture. The hardenable mixture may be concrete or mortar. In a specific embodiment, mortar containing fly ash treated by exposure to an aqueous lime slurry are prepared and tested for compressive strength at early time points. 2 figs.

Radiation-hardened transistor and integrated circuit

DOEpatents

Ma, Kwok K.

2007-11-20

A composite transistor is disclosed for use in radiation hardening a CMOS IC formed on an SOI or bulk semiconductor substrate. The composite transistor has a circuit transistor and a blocking transistor connected in series with a common gate connection. A body terminal of the blocking transistor is connected only to a source terminal thereof, and to no other connection point. The blocking transistor acts to prevent a single-event transient (SET) occurring in the circuit transistor from being coupled outside the composite transistor. Similarly, when a SET occurs in the blocking transistor, the circuit transistor prevents the SET from being coupled outside the composite transistor. N-type and P-type composite transistors can be used for each and every transistor in the CMOS IC to radiation harden the IC, and can be used to form inverters and transmission gates which are the building blocks of CMOS ICs.

Age and interviewer behavior as predictors of interrogative suggestibility.

PubMed

Dukala, Karolina; Polczyk, Romuald

2014-05-01

The main objective was to explore the influence of interviewer behavior-abrupt versus friendly-and the age of participants on interrogative suggestibility. The study involved 42 young adults and 50 elderly participants. The Gudjonsson Suggestibility Scale 2 was used. Data analysis involved a 2-factor between-subjects design (interviewer behavior × age) and mediation analysis. The scores of elderly participants were significantly lower than younger adults on memory indices and significantly higher on some suggestibility indexes. Some suggestibility indices in the abrupt experimental condition were higher than those in the friendly experimental condition. Elderly participants who were interviewed under the abrupt condition were more likely to change their answers after receiving negative feedback than younger adults. Memory quality was a mediator of the relationship between age and the tendency to yield to suggestive questions. Self-appraisal of memory was a mediator between both age and interviewer behavior and the tendency to change answers after negative feedback. Mechanisms of the relationship between age, interviewer behavior, and suggestibility are discussed on the basis of the mediational analyses. The findings suggest that a friendly manner should be adopted when interrogating witnesses.

Options for Hardening FinFETS with Flowable Oxide Between Fins

DTIC Science & Technology

2017-03-01

thus hardening by process is needed. Using the methodology of CV measurements on inexpensive experimental blanket oxides we have determined options...NY 10598 Abstract: A methodology using radiation-induced charge measurements by CV techniques on blanket oxides is shown to aid in the choice...of process options for hardening FinFETs. Net positive charge in flowable oxides was reduced by 50 % using a simple non -intrusive process change

Impact of Scaled Technology on Radiation Testing and Hardening

NASA Technical Reports Server (NTRS)

LaBel, Kenneth A.; Cohn, Lewis M.

2005-01-01

This presentation gives a brief overview of some of the radiation challenges facing emerging scaled digital technologies with implications on using consumer grade electronics and next generation hardening schemes. Commercial semiconductor manufacturers are recognizing some of these issues as issues for terrestrial performance. Looking at means of dealing with soft errors. The thinned oxide has indicated improved TID tolerance of commercial products hardened by "serendipity" which does not guarantee hardness or say if the trend will continue. This presentation also focuses one reliability implications of thinned oxides.

Constitutive behavior of tantalum and tantalum-tungsten alloys

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

Chen, S.R.; Gray, G.T. III

1996-10-01

The effects of strain rate, temperature, and tungsten alloying on the yield stress and the strain-hardening behavior of tantalum were investigated. The yield and flow stresses of unalloyed Ta and tantalum-tungsten alloys were found to exhibit very high rate sensitivities, while the hardening rates in Ta and Ta-W alloys were found to be insensitive to strain rate and temperature at lower temperatures or at higher strain rates. This behavior is consistent with the observation that overcoming the intrinsic Peierls stress is shown to be the rate-controlling mechanism in these materials at low temperatures. The dependence of yield stress on temperaturemore » and strain rate was found to decrease, while the strain-hardening rate increased with tungsten alloying content. The mechanical threshold stress (MTS) model was adopted to model the stress-strain behavior of unalloyed Ta and the Ta-W alloys. Parameters for the constitutive relations for Ta and the Ta-W alloys were derived for the MTS model, the Johnson-Cook (JC), and the Zerilli-Armstrong (ZA) models. The results of this study substantiate the applicability of these models for describing the high strain-rate deformation of Ta and Ta-W alloys. The JC and ZA models, however, due to their use of a power strain-hardening law, were found to yield constitutive relations for Ta and Ta-W alloys that are strongly dependent on the range of strains for which the models were optimized.« less

On the behavior of certain ink aging curves.

PubMed

Cantú, Antonio A

2017-09-01

This work treats writing inks, particularly ballpoint pen inks. It reviews those ink aging methods that are based on the analysis (measurement) of ink solvents (e.g., 2-phenoxyethanol, which is the most common among ballpoint pen inks). Each method involves measurements that are components of an ink aging parameter associated with the method. Only mass independent parameters are considered. An ink solvent from an ink that is on an air-exposed substrate will evaporate at a decreasing rate and is never constant as the ink ages. An ink aging parameter should reflect this behavior. That is, the graph of a parameter's experimentally-determined values plotted against ink age (which yields the ink aging curve) should show this behavior. However, some experimentally-determined aging curves contain outlying points that are below or above where they should be or points corresponding to different ages that have the same ordinate (parameter value). Such curves, unfortunately, are useless since such curves show that an ink can appear older or younger than what it should be in one or more of its points or have the same age in two or more of its points. This work explains that one cause of this unexpected behavior is that the parameter values were improperly determined such as when a measurement is made of an ink solvent that is not completely extracted (removed) from an ink sample with a chosen extractor such as dry heat or a solvent. Copyright © 2017 Elsevier B.V. All rights reserved.

The surface fatigue life of contour induction hardened AISI 1552 gears

NASA Astrophysics Data System (ADS)

Townsend, Dennis P.; Turza, Alan; Chaplin, Mike

1995-07-01

Two groups of spur gears manufactured from two different materials and heat treatments were endurance tested for surface fatigue life. One group was manufactured from AISI 1552 and was finished ground to a 0.4 micron (16 micro-in.) rms surface finish and then dual frequency contour induction hardened. The second group was manufactured from CEVM AISI 9310 and was carburized, hardened, and ground to a 0.4 micron (16 micro-in.) rms surface finish. The gear pitch diameter was 8.89 cm (3.5 in.). Test conditions were a maximum Hertz stress of 1.71 GPa (248 ksi), a bulk gear temperature of approximately 350 K (170 F) and a speed of 10,000 rpm. The lubricant used for the tests was a synthetic paraffinic oil with an additive package. The test results showed that the 10 percent surface fatigue (pitting) life of the contour hardened AISI 1552 test gears was 1.7 times that of the carburized and hardened AISI 9310 test gears. Also there were two early failures of the AISI 1552 gears by bending fatigue.

The Surface Fatigue Life of Contour Induction Hardened AISI 1552 Gears

NASA Technical Reports Server (NTRS)

Townsend, Dennis P.; Turza, Alan; Chaplin, Mike

1995-01-01

Two groups of spur gears manufactured from two different materials and heat treatments were endurance tested for surface fatigue life. One group was manufactured from AISI 1552 and was finished ground to a 0.4 micron (16 micro-in.) rms surface finish and then dual frequency contour induction hardened. The second group was manufactured from CEVM AISI 9310 and was carburized, hardened, and ground to a 0.4 micron (16 micro-in.) rms surface finish. The gear pitch diameter was 8.89 cm (3.5 in.). Test conditions were a maximum Hertz stress of 1.71 GPa (248 ksi), a bulk gear temperature of approximately 350 K (170 F) and a speed of 10,000 rpm. The lubricant used for the tests was a synthetic paraffinic oil with an additive package. The test results showed that the 10 percent surface fatigue (pitting) life of the contour hardened AISI 1552 test gears was 1.7 times that of the carburized and hardened AISI 9310 test gears. Also there were two early failures of the AISI 1552 gears by bending fatigue.

Investigation of radiation hardened SOI wafer fabricated by ion-cut technique

NASA Astrophysics Data System (ADS)

Chang, Yongwei; Wei, Xing; Zhu, Lei; Su, Xin; Gao, Nan; Dong, Yemin

2018-07-01

Total ionizing dose (TID) effect on Silicon-on-Insulator (SOI) wafers due to inherent buried oxide (BOX) is a significant concern as it leads to the degradation of electrical properties of SOI-based devices and circuits, even failures of the systems associated with them. This paper reports the radiation hardening implementation of SOI wafer fabricated by ion-cut technique integrated with low-energy Si+ implantation. The electrical properties and radiation response of pseudo-MOS transistors are analyzed. The results demonstrate that the hardening process can significantly improve the TID tolerance of SOI wafers by generating Si nanocrystals (Si-NCs) within the BOX. The presence of Si-NCs created through Si+ implantation is evidenced by high-resolution transmission electron microscopy (HR-TEM). Under the pass gate (PG) irradiation bias, the anti-radiation properties of H-gate SOI nMOSFETs suggest that the radiation hardened SOI wafers with optimized Si implantation dose can perform effectively in a radiation environment. The radiation hardening process provides an excellent way to reinforce the TID tolerance of SOI wafers.

Smoking dependence in 18 European countries: Hard to maintain the hardening hypothesis.

PubMed

Fernández, Esteve; Lugo, Alessandra; Clancy, Luke; Matsuo, Keitaro; La Vecchia, Carlo; Gallus, Silvano

2015-12-01

When the prevalence of smoking decreases in a population, there is a hypothesis-the so-called "hardening hypothesis"-that the remaining smokers form a subgroup of "hardcore smokers." Our aims were to test the hardening hypothesis and to analyze the determinants of high dependence taking into account both individual and country-level characteristics. Within the Pricing Policies and Control of Tobacco in Europe (PPACTE) project, we conducted a face-to-face survey on smoking between January and July 2010 in 18 European countries, including 2882 male and 2254 female smokers with complete information on smoking dependence. The Heaviness of Smoking Index (HSI) was used as a measure of tobacco dependence. We correlated smoking prevalence and dependence using the country as unit of analysis. Moreover, we fitted multilevel logistic regression models. Country-specific prevalence of smoking was positively, although not significantly, correlated with the proportion of highly tobacco-dependent smokers (overall rsp=0.203, p=0.419), both in men (rsp=0.235, p=0.347) and women (rsp=0.455, p=0.058). Using individual-level analysis, high dependence was positively related to age, and, although not significantly, to smoking prevalence, and inversely related to level of education. The lack of a smoking ban at home was positively related to smoking dependence. Using both ecological and individual-level analyses, the relations between smoking prevalence and HSI were not significant, but in the opposite direction as compared to that assumed by the "hardening hypothesis." Therefore, our data provide empirical evidence against this theory, thus supporting the feasibility of an endgame strategy. Copyright © 2015. Published by Elsevier Inc.

Safe emergency department removal of a hardened steel penile constriction ring.

PubMed

Peay, Jeremy; Smithson, James; Nelson, James; Witucki, Peter

2009-10-01

Penile constriction devices are used for the enhancement of sexual performance. These devices have the potential to become incarcerated, leading to necrosis and amputation if not removed promptly. This article presents a step-by-step approach for the safe removal of a hardened steel penile constriction device using somewhat unorthodox tools found in a hospital. We present a case of an incarcerated hardened steel penile constriction ring that was not able to be removed with conventional techniques. We describe a novel technique using an electric grinder and laryngoscope blade. The technique described in this article is a valuable and relatively safe technique for the Emergency Physician to facilitate the timely removal of a hardened steel constriction device.

Precipitation Behavior During Aging in α Phase Titanium Supersaturated with Cu

NASA Astrophysics Data System (ADS)

Mitsuhara, Masatoshi; Masuda, Tomoya; Nishida, Minoru; Kunieda, Tomonori; Fujii, Hideki

2016-04-01

Age hardening of Ti-2.3 mass pct Cu (Ti-2.3Cu) at 673 K to 873 K (400 °C to 600 °C) after solution treatment at 1063 K (790 °C) was observed. The relationship between precipitates formed during aging and changes in hardness was investigated. During aging at 673 K (400 °C), the hardness increased rapidly up to 200 hours, and subsequently increased more slowly up to 1000 hours. At 873 K (600 °C), the hardness began to decrease immediately. Transmission electron microscopy showed that fine disk-shaped precipitates of 20 to 40 nm in diameter grew in the α phase. It is concluded that these precipitates interacted with dislocations and increased the hardness. At 873 K (600 °C), precipitates of 1 µm in length and Ti2Cu particles of 200 nm in length were observed. The decrease in hardness may have resulted from the precipitate formation decreasing the concentration of Cu in the α phase. Bright/dark contrast of the three atomic layers and small atomic shift of the hcp structure were observed in the atomic resolution imaging of the precipitates. This suggests that the precipitates are not just Cu-enriched zones and have structures with similar periodicity to the Ti2Cu phase, which is thermally stable at those aging temperatures.

Nonlinear behavior of shells of revolution under cyclic loading.

NASA Technical Reports Server (NTRS)

Levine, H. S.; Armen, H., Jr.; Winter, R.; Pifko, A.

1973-01-01

A large deflection elastic-plastic analysis is presented applicable to orthotropic axisymmetric plates and shells of revolution subjected to monotonic and cyclic loading conditions. The analysis is based on the finite-element method. It employs a new higher order, fully compatible, doubly curved orthotropic shell-of-revolution element using cubic Hermitian expansions for both meridional and normal displacements. Both perfectly plastic and strain hardening behavior are considered. Strain hardening is incorporated through use of the Prager-Ziegler kinematic hardening theory, which predicts an ideal Bauschinger effect. Numerous sample problems involving monotonic and cyclic loading conditions are analyzed.

Nanoprecipitates and Their Strengthening Behavior in Al-Mg-Si Alloy During the Aging Process

NASA Astrophysics Data System (ADS)

Li, Hui; Liu, Wenqing

2017-04-01

The different nanoprecipitates formed in a 6061 aluminum alloy during aging at 453 K (180 °C), with or without 168 hours of pre-natural aging (NA), and the age-hardening response of the alloy were investigated by atom probe tomography (APT) and hardness testing. A hardness plateau developed between 2 and 8 hours in both the artificial aging (AA) and artificial aging with pre-natural aging (NAAA) samples. The hardness of NAAA samples was lower than that of AA samples when artificially aged for the same time. A 168-hour NA led to the formation of solute atom clusters in the matrix. The NA accelerated the precipitation kinetics of the following AA. The solute atom clusters gave the highest hardness increment per unit volume fraction. The β″ precipitates were dominant in the samples at the hardness plateau. The average normalized Mg:Si ratios of the solute atom clusters and GP zones were near 1. The average Mg:Si ratio of β″ precipitates increased from 1.3 to 1.5 upon aging for 2 hours. The microstructural evolution of samples with or without NA and its influence on the strengthening effects are discussed based on the experimental results.

Effect of nitrogen on high temperature low cycle fatigue behaviors in type 316L stainless steel

NASA Astrophysics Data System (ADS)

Kim, Dae Whan; Ryu, Woo-Seog; Hong, Jun Hwa; Choi, Si-Kyung

1998-04-01

Strain-controlled low cycle fatigue (LCF) tests were conducted in the temperature range of RT-600°C and air atmosphere to investigate the nitrogen effect on LCF behavior of type 316L stainless steels with different nitrogen contents (0.04-0.15%). The waveform of LCF was a symmetrical triangle with a strain amplitude of ±0.5% and a constant strain rate of 2×10 -3/s was employed for most tests. Cyclic stress response of the alloys exhibited a gradual cyclic softening at RT, but a cyclic hardening at an early stage of fatigue life at 300-600°C. The hardening at high temperature was attributed to dynamic strain aging (DSA). Nitrogen addition decreased hardening magnitude (maximum cyclic stress — first cyclic stress) because nitrogen retarded DSA for these conditions. The dislocation structures were changed from cell to planar structure with increasing temperature and nitrogen addition by DSA and short range order (SRO). Fatigue life was a maximum at 0.1% nitrogen content, which was attributed to the balance between DSA and SRO.

Low-Temperature Aging Characteristics of Type 316L Stainless Steel Welds: Dependence on Solidification Mode

NASA Astrophysics Data System (ADS)

Abe, Hiroshi; Watanabe, Yutaka

2008-06-01

Thermal aging embrittlement of light water reactor (LWR) components made of stainless steel cast has been recognized as a potential degradation issue, and careful attention has been paid to it. Although welds of austenitic stainless steels have γ-δ duplex microstructure, which is similar to that of the stainless steel cast, examination of the thermal aging characteristics of the stainless steel welds is very limited. In this investigation, two types of type 316L stainless steel weld metal with different solidification modes were prepared using two kinds of filler metals having tailored Ni equivalent and Cr equivalent. Differences between the two weld metals in the morphology of microstructure, in the composition of δ-ferrite, and in hardening behaviors with isothermal aging at 335 °C have been investigated. The hardness of the ferrite phase has increased with aging time, while the hardness of austenite phase has stayed the same. The mottled aspect has been observed in δ-ferrite of aged samples by transmission electron microscopy (TEM) observation. These characteristics suggest that spinodal decomposition has occurred in δ-ferrite by aging at 335 °C. The age-hardening rate of δ-ferrite was faster for the primary austenite solidification mode (AF mode) sample than the primary ferrite solidification mode (FA mode) sample in the initial stage of the aging up to 2000 hours. It has been suggested that the solidification mode can affect the kinetics of spinodal decomposition.

Process for hardening the surface of polymers

DOEpatents

Mansur, Louis K.; Lee, Eal H.

1992-01-01

Hard surfaced polymers and the method for making them is generally described. Polymers are subjected to simultaneous multiple ion beam bombardment, that results in a hardening of the surface and improved wear resistance.

Mechanical Characteristics of Hardened Concrete with Different Mineral Admixtures: A Review

PubMed Central

2014-01-01

The available literature identifies that the addition of mineral admixture as partial replacement of cement improves the microstructure of the concrete (i.e., porosity and pore size distribution) as well as increasing the mechanical characteristics such as drying shrinkage and creep, compressive strength, tensile strength, flexural strength, and modulus of elasticity; however, no single document is available in which review and comparison of the influence of the addition of these mineral admixtures on the mechanical characteristics of the hardened pozzolanic concretes are presented. In this paper, based on the reported results in the literature, mechanical characteristics of hardened concrete partially containing mineral admixtures including fly ash (FA), silica fume (SF), ground granulated blast furnace slag (GGBS), metakaolin (MK), and rice husk ash (RHA) are discussed and it is concluded that the content and particle size of mineral admixture are the parameters which significantly influence the mechanical properties of concrete. All mineral admixtures enhance the mechanical properties of concrete except FA and GGBS which do not show a significant effect on the strength of concrete at 28 days; however, gain in strength at later ages is considerable. Moreover, the comparison of the mechanical characteristics of different pozzolanic concretes suggests that RHA and SF are competitive. PMID:24688443

Mechanical characteristics of hardened concrete with different mineral admixtures: a review.

PubMed

Ayub, Tehmina; Khan, Sadaqat Ullah; Memon, Fareed Ahmed

2014-01-01

The available literature identifies that the addition of mineral admixture as partial replacement of cement improves the microstructure of the concrete (i.e., porosity and pore size distribution) as well as increasing the mechanical characteristics such as drying shrinkage and creep, compressive strength, tensile strength, flexural strength, and modulus of elasticity; however, no single document is available in which review and comparison of the influence of the addition of these mineral admixtures on the mechanical characteristics of the hardened pozzolanic concretes are presented. In this paper, based on the reported results in the literature, mechanical characteristics of hardened concrete partially containing mineral admixtures including fly ash (FA), silica fume (SF), ground granulated blast furnace slag (GGBS), metakaolin (MK), and rice husk ash (RHA) are discussed and it is concluded that the content and particle size of mineral admixture are the parameters which significantly influence the mechanical properties of concrete. All mineral admixtures enhance the mechanical properties of concrete except FA and GGBS which do not show a significant effect on the strength of concrete at 28 days; however, gain in strength at later ages is considerable. Moreover, the comparison of the mechanical characteristics of different pozzolanic concretes suggests that RHA and SF are competitive.

Self-assessed driving behaviors associated with age among middle-aged and older adults in Japan.

PubMed

Arai, Asuna; Arai, Yumiko

2015-01-01

With the increasing number of older drivers, road traffic safety is an urgent public health issue. It is not easy for older drivers or their relatives to detect early signs of dangerous driving behaviors. We examine the types of driving behavior that increase in frequency with age. We surveyed people aged 40 and over among the general public in Japan using a self-administered questionnaire on sociodemographic factors, driving status, frequency of driving, 12-items on physical symptoms possibly related to driving performance, and 28-items on driving behaviors. Multiple logistic regression models were used to estimate the odds ratios (OR) of occurrence of each of the 28 driving behaviors for a 5-year increase in age. Significant associations with a 5-year increase in age after adjusting for confounding factors were found for the following directly unsafe driving behaviors: (1) little or no sign of attempts to avoid dangerous situations (OR for a 5-year increase in age=1.38, 95% CI: 1.18-1.63); (2) lack of attention to other people and cars (1.33, 1.12-1.60); (3) improper maneuvering around curves (1.33, 1.09-1.65); and (4) improper or no turn signals (1.33, 1.06-1.69). Information about these driving behaviors should be given to drivers and their stakeholders and used to caution participants when implementing educational programs for older drivers. Self-assessment of driving ability in older drivers provides useful information to raise awareness of their driving performance. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

Secondary hardening steel having improved combination of hardness and toughness

DOEpatents

Parker, Earl R.; Zackay, Victor F.; Bhat, Manjeshwar S.; Garrison, Jr., Warren M.

1979-01-01

A secondary hardening alloy steel composition consisting essentially of about 0.25-0.5% carbon, about 0.5-1.0% manganese, about 1.5-3.0% nickel, about 0-1.0% chromium, about 1.75-2.5% molybdenum, about 0-0.4% vanadium, and an additive selected from about 1-3% aluminum and a combination of at least about 1% aluminum and at least about 1% silicon for a combined Al+Si content of about 2-4%, the balance being iron and impurity elements. The present steel composition has the following characteristics: it exhibits a flat tempering response, it is hardenable upon tempering to a Rockwell C hardness of at least 50, and it has an improved combination of hardness vs. toughness properties after tempering in the secondary hardening range. A method of preparation is also described.

On the Spectral Hardening at gsim300 keV in Solar Flares

NASA Astrophysics Data System (ADS)

Li, G.; Kong, X.; Zank, G.; Chen, Y.

2013-05-01

It has long been noted that the spectra of observed continuum emissions in many solar flares are consistent with double power laws with a hardening at energies gsim300 keV. It is now widely believed that at least in electron-dominated events, the hardening in the photon spectrum reflects an intrinsic hardening in the source electron spectrum. In this paper, we point out that a power-law spectrum of electrons with a hardening at high energies can be explained by the diffusive shock acceleration of electrons at a termination shock with a finite width. Our suggestion is based on an early analytical work by Drury et al., where the steady-state transport equation at a shock with a tanh profile was solved for a p-independent diffusion coefficient. Numerical simulations with a p-dependent diffusion coefficient show hardenings in the accelerated electron spectrum that are comparable with observations. One necessary condition for our proposed scenario to work is that high-energy electrons resonate with the inertial range of the MHD turbulence and low-energy electrons resonate with the dissipation range of the MHD turbulence at the acceleration site, and the spectrum of the dissipation range ~k -2.7. A ~k -2.7 dissipation range spectrum is consistent with recent solar wind observations.

Tension-compression asymmetry of a rolled Mg-Y-Nd alloy

NASA Astrophysics Data System (ADS)

Song, Bo; Pan, Hucheng; Ren, Weijie; Guo, Ning; Wu, Zehong; Xin, Renlong

2017-07-01

In this work, tension and compression deformation behaviors of rolled and aged Mg-Y-Nd alloys were investigated. The microstructure evolution and plastic deformation mechanism during tension and compression were analyzed by combined use of electron backscatter diffraction and a visco-plastic self-consistent crystal plasticity model. The results show that both rolled and aged Mg-Y-Nd sheets show an extremely low yield asymmetry. Elimination of yield asymmetry can be ascribed to the tilted basal texture and suppression of {10-12} twinning. The rolled sheet has almost no yield asymmetry, however exhibits a remarkable strain-hardening behavior asymmetry. Compressed sample shows lower initial strain hardening rate and keeps higher strain hardening rate at the later stage compared with tension. The strain-hardening asymmetry can be aggravated by aging at 280 C. It is considered the limited amount of twins in compression plays the critical role in the strain hardening asymmetry. Finally, the relevant mechanism was analyzed and discussed.

Radiation Hardened 10BASE-T Ethernet Physical Layer (PHY)

NASA Technical Reports Server (NTRS)

Lin, Michael R. (Inventor); Petrick, David J. (Inventor); Ballou, Kevin M. (Inventor); Espinosa, Daniel C. (Inventor); James, Edward F. (Inventor); Kliesner, Matthew A. (Inventor)

2017-01-01

Embodiments may provide a radiation hardened 10BASE-T Ethernet interface circuit suitable for space flight and in compliance with the IEEE 802.3 standard for Ethernet. The various embodiments may provide a 10BASE-T Ethernet interface circuit, comprising a field programmable gate array (FPGA), a transmitter circuit connected to the FPGA, a receiver circuit connected to the FPGA, and a transformer connected to the transmitter circuit and the receiver circuit. In the various embodiments, the FPGA, transmitter circuit, receiver circuit, and transformer may be radiation hardened.

Behavior in Prader-Willi syndrome: relationship to genetic subtypes and age.

PubMed

Dykens, Elisabeth M; Roof, Elizabeth

2008-09-01

Some behavioral features of Prader-Willi syndrome (PWS) are associated with the major genetic subtypes of this disorder. While most agree that those with maternal uniparental disomy (UPD) have a distinctive cognitive and psychiatric profile, findings are more controversial regarding possible differences among persons who vary in paternal deletion size. Caregivers of 88 persons with PWS aged 5 to 51 years (M = 22 years) were administered measures of problem behavior, compulsivity, hyperphagia, and adaptive skills. The sample was well characterized as having relatively large, Type I (n = 26) or smaller, Type II (n = 29) deletions, or UPD (n = 33). No significant behavioral differences were found between the Type I versus Type II deletion groups. Within each genetic subtype, however, differences emerged in how advancing age related to behavior. Although age did not emerge as a significant correlate of behavior in the Type II or UPD groups, in the Type I group age was consistently associated with lower problem behaviors, adaptive skills, and externalizing symptoms. Although differences between deletion subtypes were not found, significant within-subtype differences emerged in relationships between age and behavior. Negative associations between age and behavior in the Type I group only may relate to non-imprinted genes that are deleted in Type I but not Type II cases, including CYFIP1. Altered expression of CYFIP1 is seen in other developmental disabilities, including 15q disorders, and haploinsufficiency of CYFIP1 in Type I PWS cases may be associated with age-related phenotypic effects. Findings underscore the importance of a life-span perspective in phenotypic research.

Process for hardening the surface of polymers

DOEpatents

Mansur, L.K.; Lee, E.H.

1992-07-14

Hard surfaced polymers and the method for making them is generally described. Polymers are subjected to simultaneous multiple ion beam bombardment, that results in a hardening of the surface and improved wear resistance. 1 figure.

Forming characteristics of artificial aging Al-Mg-Si-Cu sheet alloys

NASA Astrophysics Data System (ADS)

Klos, Artur; Kellner, Sven; Wortberg, Daniel; Walter, Philipp; Bassi, Corrado; Merklein, Marion

2017-10-01

AA6111 is a commonly used aluminum alloy for body-in-white (BIW) components with good bake-hardening response, high strength and excellent formability. For industrial applications various process strategies are considered to reach strength of about 250 MPa in the final body part with that type of alloy. The purpose of this paper is to discuss recent process strategies of high-strength AA6111 sheets to evaluate the forming characteristics, precipitation kinetics dissolution and mechanical properties in the final condition. The forming behavior is investigated by four potential process chains after single-stage or multi-stage heat treatment including T4 (pre-aged at > 80 °C after quenching), T61 (T4 + artificial aged at 120-150 °C for 10-18 h), T6 (T4 + artificial aged at 180-220°C up to 12 h) and PFHT (T4 + post form heat treatment at 205°C for 30 min). The experimental input for characterization of the formability consists of tensile tests, bending tests and drawing tests. Differential Scanning Calorimetry (DSC) is used, to correlate the forming behavior with the precipitation distribution in the advanced stages of aging. The study shows that the forming behavior is strongly dependent on the condition the alloy.

Evaluation of Microstructure and Toughness of AISI D2 Steel by Bright Hardening in Comparison with Oil Quenching

NASA Astrophysics Data System (ADS)

Torkamani, H.; Raygan, Sh.; Rassizadehghani, J.

2011-12-01

AISI D2 is used widely in the manufacture of blanking and cold-forming dies, on account of its excellent hardness and wear behavior. Increasing toughness at a fixed high level of hardness is growing requirement for this kind of tool steel. Improving microstructure characteristics, especially refinement of coarse carbides, is an appropriate way to meet such requirement. In this study, morphology and size of carbides in martensite matrix were compared between two kinds of samples, which were bright hardened (quenching in hot alkaline salt bath consisting of 60% KOH and 40% NaOH) at 230 °C and quenched in oil bath at 60 °C. Results showed that morphology and distribution of carbides in samples performed by bright hardening were finer and almost spherical compared to that of oil quenched. This microstructure resulted in an improvement in toughness and tensile properties of alloy.

RHOBOT: Radiation hardened robotics

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

Bennett, P.C.; Posey, L.D.

1997-10-01

A survey of robotic applications in radioactive environments has been conducted, and analysis of robotic system components and their response to the varying types and strengths of radiation has been completed. Two specific robotic systems for accident recovery and nuclear fuel movement have been analyzed in detail for radiation hardness. Finally, a general design approach for radiation-hardened robotics systems has been developed and is presented. This report completes this project which was funded under the Laboratory Directed Research and Development program.

Numerical analysis of drilling hole work-hardening effects in hole-drilling residual stress measurement

NASA Astrophysics Data System (ADS)

Li, H.; Liu, Y. H.

2008-11-01

The hole-drilling strain gage method is an effective semi-destructive technique for determining residual stresses in the component. As a mechanical technique, a work-hardening layer will be formed on the surface of the hole after drilling, and affect the strain relaxation. By increasing Young's modulus of the material near the hole, the work-hardening layer is simplified as a heterogeneous annulus. As an example, two finite rectangular plates submitted to different initial stresses are treated, and the relieved strains are measured by finite element simulation. The accuracy of the measurement is estimated by comparing the simulated residual stresses with the given initial ones. The results are shown for various hardness of work-hardening layer. The influence of the relative position of the gages compared with the thickness of the work-hardening layer, and the effect of the ratio of hole diameter to work-hardening layer thickness are analyzed as well.

Walnuts improve neuronal and behavioral function in aging

USDA-ARS?s Scientific Manuscript database

Introduction Walnuts are rich in polyunsaturated fatty acids (PUFAs) and polyphenols which have been shown to improve neurochemical and behavioral function. Objectives This study investigated the mechanisms associated with age-related behavioral improvements in rats fed diets supplemented with walnu...

Sex differences in neurochemical markers that correlate with behavior in aging mice.

PubMed

Frick, K M; Burlingame, L A; Delaney, S S; Berger-Sweeney, J

2002-01-01

Sex differences in neurochemical markers that correlate with behavior in aging mice NEUROBIOL AGING. We examined whether the enzymatic activities of choline acetyltransferase (ChAT) and glutamic acid decarboxylase (GAD) were altered similarly with age in male and female mice, and whether these changes were correlated with age-related alterations in memory and anxiety. ChAT and GAD activities were measured in neocortex, hippocampus, and striatum of behaviorally characterized male and female C57BL/6 mice (5, 17, and 25 months). Generally, ChAT activity was increased, and GAD activity decreased, with age. However, disparate changes were revealed between the sexes; activities of both enzymes were decreased in 17-month males, whereas alterations in females were not observed until 25-months. Furthermore, enzyme-behavior correlations differed between the sexes; in males, ChAT activity was related to one behavioral task, whereas in females, activities of both enzymes were correlated with multiple tasks. Significant enzyme-behavior correlations were most evident at 17 months of age, likely the result of behavioral and enzymatic sex differences at this age. These data represent the first comprehensive report illustrating differential alterations of ChAT and GAD activities in aging male and female mice.

Effects of TEA·HCl hardening accelerator on the workability of cement-based materials

NASA Astrophysics Data System (ADS)

Pan, Wenhao; Ding, Zhaoyang; Chen, Yanwen

2017-03-01

The aim of the test is to research the influence rules of TEA·HCl on the workability of cement paste and concrete. Based on the features of the new hardening accelerator, an experimental analysis system were established through different dosages of hardening accelerator, and the feasibility of such accelerator to satisfy the need of practical engineering was verified. The results show that adding of the hardening accelerator can accelerate the cement hydration, and what’s more, when the dosage was 0.04%, the setting time was the shortest while the initial setting time and final setting time were 130 min and 180 min, respectively. The initial fluidity of cement paste of adding accelerator was roughly equivalent compared with that of blank. After 30 min, fluidity loss would decrease with the dosage increasing, but fluidity may increase. The application of the hardening accelerator can make the early workability of concrete enhance, especially the slump loss of 30 min can improve more significantly. The bleeding rate of concrete significantly decreases after adding TEA·HCl. The conclusion is that the new hardening accelerator can meet the need of the workability of cement-based materials in the optimum dosage range.

Aging mothers' and their adult daughters' perceptions of conflict behaviors.

PubMed

Fingerman, K L

1995-12-01

Aging parents tend to perceive greater compatibility between themselves and offspring than do off-spring, but there is little research examining differences in perceptions of conflicts. Ninety-six older mothers (M age = 76) and their daughters (M age = 44) together selected a conflictual incident, then individually rated the degree to which they and the other person had engaged in destructive, constructive, or avoidant conflict behaviors. Mothers and daughters reported using constructive approaches more than other approaches. Mothers claimed to engage in constructive behaviors more than daughters recognized. Daughters reported engaging in destructive and avoidant behaviors more than mothers realized. Mothers also thought daughters felt better about the incident than daughters reported feeling about it. Findings suggest older mothers' underestimate daughters' negative behaviors and feelings in conflict situations.

[Behavioral characteristics of children with Prader-Willi syndrome in preschool and school age: an exploratory study on ritualistic behavior].

PubMed

Sarimski, Klaus; Ebner, Sarah; Wördemann, Claudia

2012-01-01

Parents of 64 children and youths with Prader-Willi syndrome (PWS) describe their children's behaviour on the "Temperament and Atypical Behavior Scale" (TABS) and the German version of the "Developmental Behavior Checklist" (VFE). In the younger age group, there are no specific behavioural abnormalities which characterize a behavioral phenotype. In the older age group the data reveal elevated levels of abnormal behaviors (communication disturbance, social relations and disruptive behaviors). Parents stress ritualistic behaviors as especially challenging. The results concerning form and age-dependency of abnormal behaviors are discussed in the context of prevention and treatment options.

Aging Behavior and Performance Projections for a Polysulfide Elastomer

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

Celina, Mathias C.; Giron, Nicholas Henry; Quintana, Adam

The accelerated aging behavior and aging state of a 30 year old field retrieved polysulfide elastomer was examined. The material is used as an environmental thread sealant for a stainless steel bolt in a steel threaded insert in an aluminum assembly. It is a two component curable polysulfide elastomer that is commercially available in a similar formulation as was applied 30 years ago. The primary goal of this study was to establish if aging over 30 years under moderate aging conditions (mostly ambient temperature and humidity) resulted in significant property changes, or if accelerated aging could identify developing aging pathwaysmore » which would prevent the extended use of this material. The aging behavior of this material was examined in three ways: A traditional accelerated thermo-oxidative aging study between 95 to 140°C which focused on physical and chemical properties changes, an evaluation of the underlying oxidation rates between RT and 125°C, and an assessment of the aging state of a small 30 year old sample. All three data sets were used to establish aging characteristics, their time evolution, and to extrapolate the observed behavior to predict performance limits at RT. The accelerated aging study revealed a relatively high average activation energy of ~130 kJ/mol which gives overconfident performance predictions. Oxidation rates showed a decreasing behavior with aging time and a lower E a of ~84 kJ/mol from time - temperature superposition , but also predicted sufficient additional performance at RT. Consistent with these projections for extended RT performance, only small changes were observed for the 30 year old material. Extrapolations using this partially aged material also predict ongoing use as a viable option. Unexpected RT degradation could only develop into a concern should the oxidation rate not trend lower over time as was observed at elevated temperature. Considering all data acquired in this limited aging study , there are no

Multi-species beam hardening calibration device for x-ray microtomography

NASA Astrophysics Data System (ADS)

Evershed, Anthony N. Z.; Mills, David; Davis, Graham

2012-10-01

Impact-source X-ray microtomography (XMT) is a widely-used benchtop alternative to synchrotron radiation microtomography. Since X-rays from a tube are polychromatic, however, greyscale `beam hardening' artefacts are produced by the preferential absorption of low-energy photons in the beam path. A multi-material `carousel' test piece was developed to offer a wider range of X-ray attenuations from well-characterised filters than single-material step wedges can produce practically, and optimization software was developed to produce a beam hardening correction by use of the Nelder-Mead optimization method, tuned for specimens composed of other materials (such as hydroxyapatite [HA] or barium for dental applications.) The carousel test piece produced calibration polynomials reliably and with a significantly smaller discrepancy between the calculated and measured attenuations than the calibration step wedge previously in use. An immersion tank was constructed and used to simplify multi-material samples in order to negate the beam hardening effect of low atomic number materials within the specimen when measuring mineral concentration of higher-Z regions. When scanned in water at an acceleration voltage of 90 kV a Scanco AG hydroxyapatite / poly(methyl methacrylate) calibration phantom closely approximates a single-material system, producing accurate hydroxyapatite concentration measurements. This system can then be corrected for beam hardening for the material of interest.

Oscillating brittle and viscous behavior through the earthquake cycle in the Red River Shear Zone: Monitoring flips between reaction and textural softening and hardening

NASA Astrophysics Data System (ADS)

Wintsch, Robert P.; Yeh, Meng-Wan

2013-03-01

Microstructures associated with cataclasites and mylonites in the Red River shear zone in the Diancang Shan block, Yunnan Province, China show evidence for both reaction hardening and softening at lower greenschist facies metamorphic conditions. The earliest fault-rocks derived from Triassic porphyritic orthogneiss protoliths are cataclasites. Brittle fractures and crushed grains are cemented by newly precipitated quartz. These cataclasites are subsequently overprinted by mylonitic fabrics. Truncations and embayments of relic feldspars and biotites show that these protolith minerals have been dissolved and incompletely replaced by muscovite, chlorite, and quartz. Both K-feldspar and plagioclase porphyroclasts are truncated by muscovite alone, suggesting locally metasomatic reactions of the form: 3K-feldspar + 2H+ = muscovite + 6SiO2(aq) + 2K+. Such reactions produce muscovite folia and fish, and quartz bands and ribbons. Muscovite and quartz are much weaker than the reactant feldspars and these reactions result in reaction softening. Moreover, the muscovite tends to align in contiguous bands that constitute textural softening. These mineral and textural modifications occurred at constant temperature and drove the transition from brittle to viscous deformation and the shift in deformation mechanism from cataclasis to dissolution-precipitation and reaction creep. These mylonitic rocks so produced are cut by K-feldspar veins that interrupt the mylonitic fabric. The veins add K-feldspar to the assemblage and these structures constitute both reaction and textural hardening. Finally these veins are boudinaged by continued viscous deformation in the mylonitic matrix, thus defining a late ductile strain event. Together these overprinting textures and microstructures demonstrate several oscillations between brittle and viscous deformation, all at lower greenschist facies conditions where only frictional behavior is predicted by experiments. The overlap of the depths of

Observations of Dynamic Strain Aging in Polycrystalline NiAl

NASA Technical Reports Server (NTRS)

Weaver, M. L.; Noebe, R. D.; Kaufman, M. J.

1996-01-01

Dynamic strain aging has been investigated at temperatures between 77 and 1100 K in eight polycrystalline NiAl alloys. The 0.2% offset yield stress and work hardening rates for these alloys generally decreased with increasing temperature. However, local plateaus or maxima were observed in conventional purity and carbon doped alloys at intermediate temperatures (600-900 K). This anomalous behavior was not observed in low interstitial high-purity, nitrogen doped, or in titanium doped materials. Low or negative strain rate sensitivities (SRS) were also observed in all eight alloys in this intermediate temperature range. Coincident with the occurrence of negative SRS was the occurrence of serrated flow in conventional purity alloys containing high concentrations of Si in addition to C. These phenomena have been attributed to dynamic strain aging (DSA). Chemical analysis of the alloys used in this study suggests that the main species causing strain aging in polycrystalline NiAl is C but indicate that residual Si impurities can enhance the strain aging effect.

Experimental identification and mathematical modeling of viscoplastic material behavior

NASA Astrophysics Data System (ADS)

Haupt, P.; Lion, A.

1995-03-01

Uniaxial torsion and biaxial torsion-tension experiments on thin-walled tubes were carried out to investigate the viscoplastic behavior of stainless steel XCrNi18.9. A series of monotonic tests under strain and stress control shows nonlinear rate dependence and suggests the existence of equilibrium states, which are asymptotically approached during relaxation and creep processes. Strain controlled cyclic experiments display various hardening and softening phenomena that depend on strain amplitude and mean strain. All experiments indicate that the equilibrium states within the material depend on the history of the input process, whereas the history-dependence of the relaxation and creep behavior appears less significant. From the experiments the design of a constitutive model of viscoplasticity is motivated: The basic assumption is a decomposition of the total stress into an equilibrium stress and a non-equilibrium overstress: At constant strain, the overstress relaxes to zero, where the relaxation time depends on the overstress in order to account for the nonlinear rate-dependence. The equilibrium stress is assumed to be a rate independent functional of the total strain history. Classical plasticity is utilized with a kinematic hardening rule of the Armstrong-Frederick type. In order to incorporate the amplitude-dependent hardening and softening behavior, a generalized arc length representation is applied [14]. The introduction of an additional kinematic hardening variable facilitates consideration of additional hardening effects resulting from the non-radiality of the input process. Apart from the common yield and loading criterion of classical plasticity, the proposed constitutive model does not contain any further distinction of different cases. The experimental data are sufficient to identify the material parameters of the constitutive model. The results of the identification procedure demonstrate the ability of the model to represent the observed phenomena

Temperature influence on water transport in hardened cement pastes

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

Drouet, Emeline; Poyet, Stéphane, E-mail: stephane.poyet@cea.fr; Torrenti, Jean-Michel

2015-10-15

Describing water transport in concrete is an important issue for the durability assessment of radioactive waste management reinforced concrete structures. Due to the waste thermal output such structures would be submitted to moderate temperatures (up to 80 °C). We have then studied the influence of temperature on water transport within hardened cement pastes of four different formulations. Using a simplified approach (describing only the permeation of liquid water) we characterized the properties needed to describe water transport (up to 80 °C) using dedicated experiments. For each hardened cement paste the results are presented and discussed.

Laser hardening techniques on steam turbine blade and application

NASA Astrophysics Data System (ADS)

Yao, Jianhua; Zhang, Qunli; Kong, Fanzhi; Ding, Qingming

Different laser surface hardening techniques, such as laser alloying and laser solution strengthening were adopted to perform modification treatment on the local region of inset edge for 2Cr13 and 17-4PH steam turbine blades to prolong the life of the blades. The microstructures, microhardness and anti-cavitation properties were investigated on the blades after laser treatment. The hardening mechanism and technique adaptability were researched. Large scale installation practices confirmed that the laser surface modification techniques are safe and reliable, which can improve the properties of blades greatly with advantages of high automation, high quality, little distortion and simple procedure.

Nonlinear behavior of shells of revolution under cyclic loading

NASA Technical Reports Server (NTRS)

Levine, H. S.; Armen, H., Jr.; Winter, R.; Pifko, A.

1972-01-01

A large deflection elastic-plastic analysis is presented, applicable to orthotropic axisymmetric plates and shells of revolution subjected to monotonic and cyclic loading conditions. The analysis is based on the finite-element method. It employs a new higher order, fully compatible, doubly curved orthotropic shell-of-revolution element using cubic Hermitian expansions for both meridional and normal displacements. Both perfectly plastic and strain hardening behavior are considered. Strain hardening is incorporated through use of the Prager-Ziegler kinematic hardening theory, which predicts an ideal Bauschinger effect. Numerous sample problems involving monotonic and cyclic loading conditions are analyzed. The monotonic results are compared with other theoretical solutions.

Aggressive Versus Nonaggressive Antisocial Behavior: Distinctive Etiological Moderation by Age

PubMed Central

Burt, S. Alexandra; Neiderhiser, Jenae M.

2015-01-01

Research has supported the existence of distinct behavioral patterns, demographic correlates, and etiologic mechanisms for aggressive (AGG) versus nonaggressive but delinquent (DEL) antisocial behavior. Though behavioral genetic studies have the potential to further crystallize these dimensions, inconsistent results have limited their contribution. These inconsistencies may stem in part from the limited attention paid to the impact of age. In the current study, the authors thus examined age-related etiological moderation of AGG and DEL antisocial behavior in a sample of 720 sibling pairs (ranging in age from 10 to 18 years) with varying degrees of genetic relatedness. Results reveal that the magnitude of genetic and environmental influences on AGG remained stable across adolescence. By contrast, genetic influences on DEL increased dramatically with age, whereas shared environmental influences decreased. Subsequent longitudinal analyses fully replicated these results. Such findings highlight etiological distinctions between aggression and delinquency, and offer insights into the expression of genetic influences during development. PMID:19586186

Development of a Pressure-Dependent Constitutive Model with Combined Multilinear Kinematic and Isotropic Hardening

NASA Technical Reports Server (NTRS)

Allen Phillip A.; Wilson, Christopher D.

2003-01-01

The development of a pressure-dependent constitutive model with combined multilinear kinematic and isotropic hardening is presented. The constitutive model is developed using the ABAQUS user material subroutine (UMAT). First the pressure-dependent plasticity model is derived. Following this, the combined bilinear and combined multilinear hardening equations are developed for von Mises plasticity theory. The hardening rule equations are then modified to include pressure dependency. The method for implementing the new constitutive model into ABAQUS is given.

Short-term hot-hardness characteristics of five case hardened steels

NASA Technical Reports Server (NTRS)

Anderson, N. E.; Zaretsky, E. V.

1975-01-01

Short-term hot-hardness studies were performed with carburized and hardened AISI 8620, CBS 1000, CBS 1000M, CBS 600, and Vasco X-2 steels. Case and core hardness measurements were made at temperatures from 294 to 811 K (70 to 1000 F). The data were compared with data for high-speed tool steels and AISI 52100. The materials tested can be ranked as follows in order of decreasing hot-hardness retention: (1) Vasco X-2; equivalent to through-hardened tool steels up to 644 K (700 F) above which Vasco X-2 is inferior; (2) CBS 1000, (3) CBS 1000M; (4) CBS 6000; better hardness retention at elevated temperatures than through-hardened AISI 52100; and (5) AISI 8620. For the carburized steels, the change in hardness with temperature of the case and core are similar for a given material. The short-term hot hardness of these materials can be predicted with + or - 1 point Rockwell C.

Effect of Annealing on Microstructures and Hardening of Helium-Hydrogen-Implanted Sequentially Vanadium Alloys

NASA Astrophysics Data System (ADS)

Jiang, Shaoning; Wang, Zhiming

2018-03-01

The effect of post-irradiation annealing on the microstructures and mechanical properties of V-4Cr-4Ti alloys was studied. Helium-hydrogen-irradiated sequentially V-4Cr-4Ti alloys at room temperature (RT) were undergone post-irradiation annealing at 450 °C over periods of up to 30 h. These samples were carried out by high-resolution transmission electron microscopy (HRTEM) observation and nanoindentation test. With the holding time, large amounts of point defects produced during irradiation at RT accumulated into large dislocation loops and then dislocation nets which promoted the irradiation hardening. Meanwhile, bubbles appeared. As annealing time extended, these bubbles grew up and merged, and finally broke up. In the process, the size of bubbles increased and the number density decreased. Microstructural changes due to post-irradiation annealing corresponded to the change of hardening. Dislocations and bubbles are co-contributed to irradiation hardening. With the holding time up to 30 h, the recovery of hardening is not obvious. The phenomenon was discussed by dispersed barrier hardening model and Friedel-Kroupa-Hirsch relationship.

Rapid growth rate results in remarkably hardened breast in broilers during the middle stage of rearing: A biochemical and histopathological study

PubMed Central

Iwasaki, Tomohito; Yamada, Michi; Yoshida, Takashi

2018-01-01

The high incidence of meat of impaired quality poses a serious problem in the poultry industry. In recent years, the incidence of the pectoralis major muscle that appeared pale colored, remarkably hardened, and exudative, called “wooden breast” or “woody breast” has increased in slaughter houses. In the present study, 19-day-old Ross 308 broiler chickens affected (n = 10) and unaffected (n = 10) with remarkably hardened breast were selected from a commercial broiler farm, and reared to 55 days of age under a controlled environment. Among the affected birds, 5 of 10 birds appeared exhausted with markedly suppressed weight gain and 4 of 10 birds died during the rearing period. In contrast, all unaffected birds survived and most gained weight. Four of 10 unaffected birds lost the ability of back-to-back wing contact by the late stage of rearing. The biochemical analysis of blood plasma samples of 20-day-old birds revealed that creatine kinase and L-aspartate aminotransferase values in most affected birds were higher than those in unaffected birds; however, these values in unaffected birds increased rapidly with lost wing contactability and increasing age. Postmortem examinations revealed that the mean diameter of myofibers in affected birds was smaller than that in unaffected birds. Moreover, symptoms of degenerative and regenerative muscles were observed in most birds in both groups. Among them, a decrease in, or defect of, the characteristic polygonal shape of myofibers was the most common change within the pectoralis major muscles in both groups. The present study demonstrated that broilers affected with remarkably hardened breast during the middle stage of rearing would have suppressed physical status and weight gain, or would die. It was suggested that rapid growth in broilers might be a cause of remarkably hardened breast. PMID:29474396

Rapid growth rate results in remarkably hardened breast in broilers during the middle stage of rearing: A biochemical and histopathological study.

PubMed

Kawasaki, Takeshi; Iwasaki, Tomohito; Yamada, Michi; Yoshida, Takashi; Watanabe, Takafumi

2018-01-01

The high incidence of meat of impaired quality poses a serious problem in the poultry industry. In recent years, the incidence of the pectoralis major muscle that appeared pale colored, remarkably hardened, and exudative, called "wooden breast" or "woody breast" has increased in slaughter houses. In the present study, 19-day-old Ross 308 broiler chickens affected (n = 10) and unaffected (n = 10) with remarkably hardened breast were selected from a commercial broiler farm, and reared to 55 days of age under a controlled environment. Among the affected birds, 5 of 10 birds appeared exhausted with markedly suppressed weight gain and 4 of 10 birds died during the rearing period. In contrast, all unaffected birds survived and most gained weight. Four of 10 unaffected birds lost the ability of back-to-back wing contact by the late stage of rearing. The biochemical analysis of blood plasma samples of 20-day-old birds revealed that creatine kinase and L-aspartate aminotransferase values in most affected birds were higher than those in unaffected birds; however, these values in unaffected birds increased rapidly with lost wing contactability and increasing age. Postmortem examinations revealed that the mean diameter of myofibers in affected birds was smaller than that in unaffected birds. Moreover, symptoms of degenerative and regenerative muscles were observed in most birds in both groups. Among them, a decrease in, or defect of, the characteristic polygonal shape of myofibers was the most common change within the pectoralis major muscles in both groups. The present study demonstrated that broilers affected with remarkably hardened breast during the middle stage of rearing would have suppressed physical status and weight gain, or would die. It was suggested that rapid growth in broilers might be a cause of remarkably hardened breast.

Drought tolerance and transplanting performance of holm oak (Quercus ilex) seedlings after drought hardening in the nursery.

PubMed

Villar-Salvador, Pedro; Planelles, Rosa; Oliet, Juan; Peñuelas-Rubira, Juan L; Jacobs, Douglass F; González, Magdalena

2004-10-01

Drought stress is the main cause of mortality of holm oak (Quercus ilex L.) seedlings in forest plantations. We therefore assessed if drought hardening, applied in the nursery at the end of the growing season, enhanced the drought tolerance and transplanting performance of holm oak seedlings. Seedlings were subjected to three drought hardening intensities (low, moderate and severe) for 2.5 and 3.5 months, and compared with control seedlings. At the end of the hardening period, water relations, gas exchange and morphological attributes were determined, and survival and growth under mesic and xeric transplanting conditions were assessed. Drought hardening increased drought tolerance primarily by affecting physiological traits, with no effect on shoot/root ratio or specific leaf mass. Drought hardening reduced osmotic potential at saturation and at the turgor loss point, stomatal conductance, residual transpiration (RT) and new root growth capacity (RGC), but enhanced cell membrane stability. Among treated seedlings, the largest response occurred in seedlings subjected to moderate hardening. Severe hardening reduced shoot soluble sugar concentration and increased shoot starch concentration. Increasing the duration of hardening had no effect on water relations but reduced shoot mineral and starch concentrations. Variation in cell membrane stability, RT and RGC were negatively related to osmotic adjustment. Despite differences in drought tolerance, no differences in mortality and relative growth rate were observed between hardening treatments when the seedlings were transplanted under either mesic or xeric conditions.

Synthesis of a new hardener agent for self-healing epoxy resins

NASA Astrophysics Data System (ADS)

Raimondo, Marialuigia; Guadagno, Liberata; Naddeo, Carlo; Longo, Pasquale; Mariconda, Annaluisa; Agovino, Anna

2014-05-01

Actually, the development of smart composites capable of self-repair in aeronautical structures is still at the planning stage owing to complex issues to overcome. One of the critical points in the development of self-healing epoxy resin is related to the impossibility to employ primary amines as hardeners. In this paper, the synthesis of a new hardener for self-healing resins is shown together with applicability conditions/ranges.

A kinematic hardening constitutive model for the uniaxial cyclic stress-strain response of magnesium sheet alloys at room temperature

NASA Astrophysics Data System (ADS)

He, Zhitao; Chen, Wufan; Wang, Fenghua; Feng, Miaolin

2017-11-01

A kinematic hardening constitutive model is presented, in which a modified form of von Mises yield function is adopted, and the initial asymmetric tension and compression yield stresses of magnesium (Mg) alloys at room temperature (RT) are considered. The hardening behavior was classified into slip, twinning, and untwinning deformation modes, and these were described by two forms of back stress to capture the mechanical response of Mg sheet alloys under cyclic loading tests at RT. Experimental values were obtained for AZ31B-O and AZ31B sheet alloys under both tension-compression-tension (T-C-T) and compression-tension (C-T) loadings to calibrate the parameters of back stresses in the proposed model. The predicted parameters of back stresses in the twinning and untwinning modes were expressed as a cubic polynomial. The predicted curves based on these parameters showed good agreement with the tests.

Age-related differences in trunk muscle reflexive behaviors.

PubMed

Shojaei, Iman; Nussbaum, Maury A; Bazrgari, Babak

2016-10-03

Reports of larger passive and similar intrinsic trunk stiffness in older vs. younger populations suggest a diminishing demand for reflexive contributions of trunk muscles to spinal stability with aging. It remains unclear, though, whether such diminishing demands result in deterioration of trunk muscle reflexive behaviors. A cross-sectional study was completed to assess age-related differences in the latency and likelihood of trunk muscle reflexive responses to sudden perturbations. Sixty healthy individuals, aged 20-70 years, were recruited to form five equal-sized and gender-balanced age groups. Using a displacement-control, sudden perturbation paradigm, the latency and likelihood of trunk muscle reflexive responses to sudden perturbations were estimated, and the influences of age, gender, and level of effort (20% versus 30% of maximum voluntary exertion-MVE) were evaluated. There were no consistent age-related differences found in any of the measures of trunk muscle reflexive behavior. However, the latency of muscle response to perturbation was generally higher among older individuals, and this difference was significant in the condition involving 30% MVE effort. With an increase in level of effort (from 20% to 30% of MVE), there was a ~7% increase in the latency of trunk muscle responses to anteriorly-directed perturbations as well as ~ 15% (21%) decrease (increase) in response likelihood during anteriorly (posteriorly) directed perturbations. Furthermore, the reflexive response likelihood of trunk muscles was 28% (58%) larger (smaller) in female vs. male participants during anteriorly (posteriorly) directed perturbations. Our results did not, in general, support the hypothesis of an age-related decay in reflexive trunk muscle behaviors. Larger reflexive responses were associated with lower trunk intrinsic stiffness among females and during a lower level of effort, suggesting a secondary role for reflexive responses in spinal stability. Such secondary

Intensive Behavioral Intervention for School-Aged Children with Autism: Una Breccia nel Muro (UBM)--A Comprehensive Behavioral Model

ERIC Educational Resources Information Center

Fava, Leonardo; Vicari, Stefano; Valeri, Giovanni; D'Elia, Lidia; Arima, Serena; Strauss, Kristin

2012-01-01

Although, reviews and outcome research supports empirical evidence for Early Intensive Behavior Intervention in pre-scholars, intensive behavioral service provision for school-aged children with autism spectrum disorders (ASD) are less subject to research studies. In order to provide effective behavioral interventions for school-aged children it…

Investigation of Thermal Hardening of the FCC Material Containing Strengthening Particles with an L12 Superstructure

NASA Astrophysics Data System (ADS)

Daneyko, O. I.; Kulaeva, N. A.; Kovalevskaya, C. A.; Kolupaeva, S. N.

2015-07-01

A mathematical model of plastic deformation of dispersion-hardened materials with an fcc matrix containing strengthening particles with an L12 superstructure having a coherent relationship with the matrix is presented. The model is based on the balance equations of deformation defects of different types with taking into account their transformation during plastic deformation. The influence of scale characteristics of the hardening phase, temperature, and deformation rate on the evolution of the dislocation subsystem and strain hardening of an alloy with an fcc matrix hardened by particles with an L12 super structure is studied. A temperature anomaly of mechanical properties is found for the materials with different fcc matrices (Al,Cu, Ni). It is shown that the temperature anomaly is more pronounced for the material with larger volume fraction of the hardening phase.

Construction procedures using self hardening fly ash

NASA Astrophysics Data System (ADS)

Thornton, S. I.; Parker, D. G.

1980-07-01

Fly ash produced in Arkansas from burning Wyoming low sulfur coal is self-hardening and can be effective as a soil stabilizing agent for clays and sands. The strength of soil-self hardening fly ash develops rapidly when compacted immediately after mixing. Seven day unconfined compressive strengths up to 1800 psi were obtained from 20% fly ash and 80% sand mixtures. A time delay between mixing the fly ash with the soil and compaction of the mixture reduced the strength. With two hours delay, over a third of the strength was lost and with four hours delay, the loss was over half. Gypsum and some commercial concrete retarders were effective in reducing the detrimental effect of delayed compaction. Adequate mixing of the soil and fly ash and rapid compaction of the mixtures were found to be important parameters in field construction of stabilized bases.

Dynamic strain aging in the high-temperature low-cycle fatigue of SA508 Cl. 3 forging steel

NASA Astrophysics Data System (ADS)

Lee, Byung Ho; Kim, In Sup

1995-10-01

The effect of dynamic strain aging on cyclic stress response and fatigue resistance of ASME SA508 Cl.3 forging steel for nuclear reactor pressure vessels has been evaluated in the temperature range of room temperature to 500°C. Total strain ranges and strain rates were varied from 0.7 to 2.0% and from 4 × 10 -4 to 1 × 10 -2 s -1, respectively. The cyclic stress response depended on the testing temperature, strain rate, and range. Generally, the initial cyclic hardening was immediately followed by cyclic softening at all strain rates. However, at 300°C, the operating temperature of nuclear reactor pressure vessels, the variation of cyclic stress amplitude showed the primary and secondary hardening stages dependent on the strain rate and strain range. Dynamic strain aging was manifested by enhanced cyclic hardening, distinguished secondary hardening, and negative strain rate sensitivity. A modified cell shutting model was described for the onset of the secondary hardening due to the dynamic strain aging and it was in good agreement with the experimental results. Fatigue life increased in strain rate at all testing temperatures. Specifically the fatigue life was longer at the dynamic strain aging temperature. Further, the dynamic strain aging was easy to initiate the crack, while crack propagation was retarded by crack branching and suppression of plastic zone, hence the dynamic strain aging caused the improvement of fatigue resistance.

Long-term aging behaviors in a model soft colloidal system.

PubMed

Li, Qi; Peng, Xiaoguang; McKenna, Gregory B

2017-02-15

Colloidal and molecular systems share similar behaviors near to the glass transition volume fraction or temperature. Here, aging behaviors after volume fraction up-jump (induced by performing temperature down-jumps) conditions for a PS-PNIPAM/AA soft colloidal system were investigated using light scattering (diffusing wave spectroscopy, DWS). Both aging responses and equilibrium dynamics were investigated. For the aging responses, long-term experiments (100 000 s) were performed, and both equilibrium and non-equilibrium behaviors of the system were obtained. In the equilibrium state, as effective volume fraction increases (or temperature decreases), the colloidal dispersion displays a transition from the liquid to a glassy state. The equilibrium α-relaxation dynamics strongly depend on both the effective volume fraction and the initial mass concentration for the studied colloidal systems. Compared with prior results from our lab [X. Di, X. Peng and G. B. McKenna, J. Chem. Phys., 2014, 140, 054903], the effective volume fractions investigated spanned a wider range, to deeper into the glassy domain. The results show that the α-relaxation time τ α of the samples aged into equilibrium deviate from the classical Vogel-Fulcher-Tammann (VFT)-type expectations and the super-Arrhenius signature disappears above the glass transition volume fraction. The non-equilibrium aging response shows that the time for the structural evolution into equilibrium and the α-relaxation time are decoupled. The DWS investigation of the aging behavior after different volume fraction jumps reveals a different non-equilibrium or aging behavior for the considered colloidal systems compared with either molecular glasses or the macroscopic rheology of a similar colloidal dispersions.

Importance of calcium and magnesium in water - water hardening

NASA Astrophysics Data System (ADS)

Barloková, D.; Ilavský, J.; Kapusta, O.; Šimko, V.

2017-10-01

Basic information about importance of calcium and magnesium in water, about their properties, effect to human health, problems what can cause under the lower (< 1 mmol/L) and higher (> 5 mmol/L) concentrations in water supply distribution systems, the most commonly used methods of water hardening are presented. The article contains the water hardening results carried out during the pilot plant experiments in WTP Hriňová and WTP Turček. For water hardening, treated water at the end of the process line, i.e., after coagulation, sedimentation and filtration, saturated with CO2 and filtrated through half-burnt dolomite material (PVD) was used. The results show that the filtration rate is 17.1 m/h in the case of WTP Hriňová and 15.2 m/h in the case of WTP Turček to achieve the recommended concentration of Ca and Mg in the treated water after the addition of CO2 and filtration through PVD. The longer the water contact time with PVD (depending on the CO2 content), the more water is enriched with magnesium, but the calcium concentration has not so much increased.

Beam hardening correction for interior tomography based on exponential formed model and radon inversion transform

NASA Astrophysics Data System (ADS)

Chen, Siyu; Zhang, Hanming; Li, Lei; Xi, Xiaoqi; Han, Yu; Yan, Bin

2016-10-01

X-ray computed tomography (CT) has been extensively applied in industrial non-destructive testing (NDT). However, in practical applications, the X-ray beam polychromaticity often results in beam hardening problems for image reconstruction. The beam hardening artifacts, which manifested as cupping, streaks and flares, not only debase the image quality, but also disturb the subsequent analyses. Unfortunately, conventional CT scanning requires that the scanned object is completely covered by the field of view (FOV), the state-of-art beam hardening correction methods only consider the ideal scanning configuration, and often suffer problems for interior tomography due to the projection truncation. Aiming at this problem, this paper proposed a beam hardening correction method based on radon inversion transform for interior tomography. Experimental results show that, compared to the conventional correction algorithms, the proposed approach has achieved excellent performance in both beam hardening artifacts reduction and truncation artifacts suppression. Therefore, the presented method has vitally theoretic and practicable meaning in artifacts correction of industrial CT.

Low-level lead exposure and autistic behaviors in school-age children.

PubMed

Kim, Kyoung-Nam; Kwon, Ho-Jang; Hong, Yun-Chul

2016-03-01

The association between lead exposure and autism spectrum disorder is inconclusive. We hypothesized an association between higher blood lead concentrations and more autistic behaviors, including impaired social interactions and communication, stereotypical behaviors, and restricted interests, among school-age children. Data from 2473 Korean children aged 7-8years who had no prior history of developmental disorders were analyzed. Two follow-up surveys were conducted biennially until the children reached 11-12years of age. Blood lead concentrations were measured at every survey, and autistic behaviors were evaluated at 11-12years of age using the Autism Spectrum Screening Questionnaire (ASSQ) and Social Responsiveness Scale (SRS). The associations of blood lead concentration with ASSQ and SRS scores were analyzed using negative binomial, logistic, and linear regression models. Blood lead concentrations at 7-8years of age (geometric mean: 1.64μg/dL), but not at 9-10 and 11-12years of age, were associated with more autistic behaviors at 11-12years of age, according to the ASSQ (β=0.151; 95% confidence interval [CI]: 0.061, 0.242) and SRS (β=2.489; 95% CI: 1.378, 3.600). SRS subscale analysis also revealed associations between blood lead concentrations and social awareness, cognition, communication, motivation, and mannerisms. Even low blood lead concentrations at 7-8years of age are associated with more autistic behaviors at 11-12years of age, underscoring the need for continued efforts to reduce lead exposure. Copyright © 2016. Published by Elsevier B.V.

Recent developments in turning hardened steels - A review

NASA Astrophysics Data System (ADS)

Sivaraman, V.; Prakash, S.

2017-05-01

Hard materials ranging from HRC 45 - 68 such as hardened AISI H13, AISI 4340, AISI 52100, D2 STL, D3 STEEL Steel etc., need super hard tool materials to machine. Turning of these hard materials is termed as hard turning. Hard turning makes possible direct machining of the hard materials and also eliminates the lubricant requirement and thus favoring dry machining. Hard turning is a finish turning process and hence conventional grinding is not required. Development of the new advanced super hard tool materials such as ceramic inserts, Cubic Boron Nitride, Polycrystalline Cubic Boron Nitride etc. enabled the turning of these materials. PVD and CVD methods of coating have made easier the production of single and multi layered coated tool inserts. Coatings of TiN, TiAlN, TiC, Al2O3, AlCrN over cemented carbide inserts has lead to the machining of difficult to machine materials. Advancement in the process of hard machining paved way for better surface finish, long tool life, reduced tool wear, cutting force and cutting temperatures. Micro and Nano coated carbide inserts, nanocomposite coated PCBN inserts, micro and nano CBN coated carbide inserts and similar developments have made machining of hardened steels much easier and economical. In this paper, broad literature review on turning of hardened steels including optimizing process parameters, cooling requirements, different tool materials etc., are done.

Age and HIV Risk and Protective Behaviors among African American Women

ERIC Educational Resources Information Center

Corneille, Maya A.; Zyzniewski, Linda E.; Belgrave, Faye Z.

2008-01-01

Though HIV prevention efforts have focused on young adult women, women of all ages may engage in HIV risk behaviors and experience barriers to condom use. This article examines the effect of age on sexual risk and protective attitudes and behaviors among African American women. Unmarried heterosexual African American women between the ages of 18…

Effect of silica fume on the fresh and hardened properties of fly ash-based self-compacting geopolymer concrete

NASA Astrophysics Data System (ADS)

Memon, Fareed Ahmed; Nuruddin, Muhd Fadhil; Shafiq, Nasir

2013-02-01

The effect of silica fume on the fresh and hardened properties of fly ash-based self-compacting geopolymer concrete (SCGC) was investigated in this paper. The work focused on the concrete mixes with a fixed water-to-geopolymer solid (W/Gs) ratio of 0.33 by mass and a constant total binder content of 400 kg/m3. The mass fractions of silica fume that replaced fly ash in this research were 0wt%, 5wt%, 10wt%, and 15wt%. The workability-related fresh properties of SCGC were assessed through slump flow, V-funnel, and L-box test methods. Hardened concrete tests were limited to compressive, splitting tensile and flexural strengths, all of which were measured at the age of 1, 7, and 28 d after 48-h oven curing. The results indicate that the addition of silica fume as a partial replacement of fly ash results in the loss of workability; nevertheless, the mechanical properties of hardened SCGC are significantly improved by incorporating silica fume, especially up to 10wt%. Applying this percentage of silica fume results in 4.3% reduction in the slump flow; however, it increases the compressive strength by 6.9%, tensile strength by 12.8% and flexural strength by 11.5%.

Atypical soil hardening during the Tohoku earthquake of March 11, 2011 ( M w = 9.0)

NASA Astrophysics Data System (ADS)

Pavlenko, O. V.

2017-10-01

Based on the records of KiK-net vertical arrays, models of soil behavior down to depths of 100-200 m in the near-fault zones during the Tohoku earthquake are examined. In contrast to the regular pattern observed during strong earthquakes, soft soils have not broadly demonstrated nonlinear behavior, or a reduction (with the onset of strong motions) and recovery (after strong motions finished) of the shear modulus in soil layers. At the stations where anomalously high peak ground accelerations were recorded (PGA > 1g), the values of the shear modulus in soil layers increased with the onset of strong motions and reached a maximum when motions were the most intensive, which indicated hardening of soils. Soil behavior was close to linear, here. The values of the shear moduli decrease along with a decrease in intensity of strong ground motions, and at soft soil stations, this was accompanied by a stepwise decrease in the frequency of motion.

Precipitation hardening behaviour of Al-Mg-Si alloy processed by cryorolling and room temperature rolling

NASA Astrophysics Data System (ADS)

Hussain, Maruff; Nageswara rao, P.; Singh, Dharmendra; Jayaganthan, R.

2018-04-01

The precipitation hardenable aluminium alloy (Al-Mg-Si) plates were solutionized and subjected to rolling at room temperature and liquid nitrogen temperature (RTR, CR) up to a true strain of ∼2.7. The rolled sheets were uniformly aged at room temperature and above room temperature (125 °C) to induce precipitation. The rolled and aged samples were analysed using differential scanning calorimetry (DSC), X-ray diffraction (XRD), transmission electron microscopy (TEM), hardness and tensile tests. The strength and ductility were simultaneously improved after controlled ageing of the cryorolled (CR) and room temperature rolled (RTR) samples. However, the increment in strength is more in RTR material than CR material with same ductility. Transmission electron microscopy analysis revealed the formation of ultrafine grains (UFG) filled with dislocations and nanosized precipitates in the CR and RTR conditions after ageing treatment. The behaviour of CR and RTR alloy is same under natural ageing conditions.

The influence of copper precipitation and plastic deformation hardening on the impact-transition temperature of rolled structural steels

NASA Astrophysics Data System (ADS)

Aróztegui, Juan J.; Urcola, José J.; Fuentes, Manuel

1989-09-01

Commercial electric arc melted low-carbon steels, provided as I beams, were characterized both microstructurally and mechanically in the as-rolled, copper precipitation, and plastically pre-deformed conditions. Inclusion size distribution, ferrite grain size, pearlite volume fraction, precipitated volume fraction of copper, and size distribution of these precipitates were deter-mined by conventional quantitative optical and electron metallographic techniques. From the tensile tests conducted at a strain rate of 10-3 s-1 and impact Charpy V-notched tests carried out, stress/strain curves, yield stress, and impact-transition temperature were obtained. The spe-cific fractographic features of the fracture surfaces also were quantitatively characterized. The increases in yield stress and transition temperature experienced upon either aging or work hard-ening were related through empirical relationships. These dependences were analyzed semi-quantitatively by combining microscopic and macroscopic fracture criteria based on measured fundamental properties (fracture stress and yield stress) and observed fractographic parameters (crack nucleation distance and nuclei size). The rationale developed from these fracture criteria allows the semiquantitative prediction of the temperature transition shifts produced upon aging and work hardening. The values obtained are of the right order of magnitude.

Radiation hardening of rare-earth doped fiber amplifiers

NASA Astrophysics Data System (ADS)

Vivona, Marilena; Girard, Sylvain; Marcandella, Claude; Pinsard, Emmanuel; Laurent, Arnaud; Robin, Thierry; Cadier, Benoît; Cannas, Marco; Boukenter, Aziz; Ouerdane, Y.

2017-11-01

We investigated the radiation hardening of optical fiber amplifiers operating in space environments. Through a real-time analysis in active configuration, we evaluated the role of Ce in the improvement of the amplifier performance against ionizing radiations. Ce-codoping is an efficient hardening solution, acting both in the limitation of defects in the host glass matrix of RE-doped optical fibers and in the stabilization of lasing properties of the Er3+-ions. On the one hand, in the near-infrared region, radiation induced attenuation measurements show the absence of radiation induced P-related defect species in host glass matrix of the Ce-codoped active fibers; on the other hand, in the Ce-free fiber, the higher lifetime variation shows stronger local modifications around the Er3+-ions with the absence of Ce.

Tensile properties and flow behavior analysis of modified 9Cr-1Mo steel clad tube material

NASA Astrophysics Data System (ADS)

Singh, Kanwarjeet; Latha, S.; Nandagopal, M.; Mathew, M. D.; Laha, K.; Jayakumar, T.

2014-11-01

The tensile properties and flow behavior of modified 9Cr-1Mo steel clad tube have been investigated in the framework of various constitutive equations for a wide range of temperatures (300-923 K) and strain rates (3 × 10-3 s-1, 3 × 10-4 s-1 and 3 × 10-5 s-1). The tensile flow behavior of modified 9Cr-1Mo steel clad tube was most accurately described by Voce equation. The variation of instantaneous work hardening rate (θ = dσ/dε) and σθ with stress (σ) indicated two stage behavior characterized by rapid decrease at low stresses (transient stage) followed by a gradual decrease in high stresses (Stage III). The variation of work hardening parameters and work hardening rate in terms of θ vs. σ and σθ vs. σ with temperature exhibited three distinct regimes. Rapid decrease in flow stress and work hardening parameters and rapid shift of θ vs. σ and σθ vs. σ towards low stresses with increase in temperature indicated dynamic recovery at high temperatures. Tensile properties of the material have been best predicted from Voce equation.

Multi-MGy Radiation Hardened Camera for Nuclear Facilities

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

Girard, Sylvain; Boukenter, Aziz; Ouerdane, Youcef

There is an increasing interest in developing cameras for surveillance systems to monitor nuclear facilities or nuclear waste storages. Particularly, for today's and the next generation of nuclear facilities increasing safety requirements consecutive to Fukushima Daiichi's disaster have to be considered. For some applications, radiation tolerance needs to overcome doses in the MGy(SiO{sub 2}) range whereas the most tolerant commercial or prototypes products based on solid state image sensors withstand doses up to few kGy. The objective of this work is to present the radiation hardening strategy developed by our research groups to enhance the tolerance to ionizing radiations ofmore » the various subparts of these imaging systems by working simultaneously at the component and system design levels. Developing radiation-hardened camera implies to combine several radiation-hardening strategies. In our case, we decided not to use the simplest one, the shielding approach. This approach is efficient but limits the camera miniaturization and is not compatible with its future integration in remote-handling or robotic systems. Then, the hardening-by-component strategy appears mandatory to avoid the failure of one of the camera subparts at doses lower than the MGy. Concerning the image sensor itself, the used technology is a CMOS Image Sensor (CIS) designed by ISAE team with custom pixel designs used to mitigate the total ionizing dose (TID) effects that occur well below the MGy range in classical image sensors (e.g. Charge Coupled Devices (CCD), Charge Injection Devices (CID) and classical Active Pixel Sensors (APS)), such as the complete loss of functionality, the dark current increase and the gain drop. We'll present at the conference a comparative study between these radiation-hardened pixel radiation responses with respect to conventional ones, demonstrating the efficiency of the choices made. The targeted strategy to develop the complete radiation hard camera

Seminal characteristics and sexual behavior in men of different age groups: is there an aging effect?

PubMed

Zavos, Panayiotis M; Kaskar, Khalied; Correa, Juan R; Sikka, Suresh C

2006-05-01

To assess the seminal characteristics as well as the sexual behavior of men of various age groups to establish the presence of an aging effect on those characteristics. Semen samples were collected from men (n = 792) undergoing in vitro fertilization or intrauterine insemination in cases of female factor infertility only. Samples were collected using a seminal collection device at intercourse and evaluated manually according to World Health Organization (WHO) standards. Men were divided into four groups according to their ages: (i) 20-30, (ii) 31-40, (iii) 41-50 and (iv) 51-60 years, and their seminal characteristics and responses to a sexual behavior questionnaire were compared. The data showed statistically significant differences in the seminal characteristics tested, most notably in the sperm concentration, motility, grade of motility, hypo-osmotic swelling and normal sperm morphology. Furthermore, the decline in normal sperm morphology with age was more pronounced when using strict criteria rather than WHO standards. There were also differences in total sperm count, total motile sperm and total functional sperm fraction (assessed by both WHO and strict criteria). Significant differences were also observed in the sexual behavior patterns in older men in terms of the number of years they have been trying to conceive, sexual frequency and sexual satisfaction. The data clearly illustrate an aging effect on semen characteristics and sexual behavior in men as they age. It is suggested that the aging effect be taken into consideration when proposing normal standard values for semen characteristics in routine semen analysis as outlined by WHO standards.

Hardened Solar Array High Temperature Adhesive.

DTIC Science & Technology

1981-04-01

SHERWOOO. D SASIU.IS F3361S-0-C-201S UNCLASSI ED 1AC-SCG-IOOIIR AFVAL-TR-OL-201? NLm,,hinii EhhhEE11I1 AFWAL-TR-81- 2017 i : HARDENED SOLAR ARRAY D HIGH...Tg and as a consequence forms a film on the container and also precipitates as tacky waxlike particles, rather than the desired flocullated

Anneal-Hardening Behavior of Cr-Fe-C Alloy Deposits Prepared in a Cr3+-Based Bath with Fe2+ Ions

PubMed Central

Huang, Ching An; Chen, Jhih You; Wang, Hai

2017-01-01

Cr-Fe-C alloy deposits were successfully prepared on high-carbon tool steel in a Cr3+-based electroplating bath containing Fe2+ ions and suitable complex agents. A Cr-based alloy deposit was obtained with an electroplating current density higher than 25 Adm−2, and a Fe-based alloy deposit was obtained using a current density of 20 Adm−2. Following electroplating, these alloy deposited specimens were annealed via rapid thermal annealing (RTA) at 500 °C for different periods up to 30 s. The experimental results show that Cr- and Fe-based alloy deposits could be significantly hardened after RTA at 500 °C for a few seconds. The maximum hardness was that of the Cr-Fe-C alloy deposit annealed at 500 °C for 10 s. The maximum hardness of 1205 Hv was detected from the annealed Cr-based alloy deposit prepared with 30 ASD. The hardening mechanism of annealed Cr- and Fe-based alloy deposits is attributed to the precipitation of C-related membranes. The hardness values of the annealed Cr- and Fe-based alloy deposits increase with the increasing degree of crystallization of the C-related membranes. PMID:29206206

Embrittlement behavior of neutron irradiated RAFM steels

NASA Astrophysics Data System (ADS)

Gaganidze, E.; Schneider, H.-C.; Dafferner, B.; Aktaa, J.

2007-08-01

The effects of neutron irradiation on the embrittlement behavior of reduced activation ferritic/martensitic (RAFM) steel EUROFER97 for different heat treatment conditions have been investigated. The irradiation to 16.3 dpa at different irradiation temperatures (250-450 °C) was carried out in the Petten High Flux Reactor in the framework of the HFR Phase-IIb (SPICE) irradiation project. Several reference RAFM steels (F82H-mod, OPTIFER-Ia, GA3X) and MANET-I were also irradiated at selected temperatures. The embrittlement behavior and hardening were investigated by instrumented Charpy-V tests with subsize specimens. The neutron irradiation induced embrittlement and hardening of as-delivered EUROFER97 are comparable to those of investigated reference steels, being mostly pronounced for 250 °C and 300 °C irradiation temperatures. Heat treatment of EUROFER97 at higher austenization temperature substantially improves the embrittlement behavior at irradiation temperatures of 250 °C and 350 °C.

Nitrogen nutrition and drought hardening exert opposite effects on the stress tolerance of Pinus pinea L. seedlings.

PubMed

Villar-Salvador, Pedro; Peñuelas, Juan L; Jacobs, Douglass F

2013-02-01

Functional attributes determine the survival and growth of planted seedlings in reforestation projects. Nitrogen (N) and water are important resources in the cultivation of forest species, which have a strong effect on plant functional traits. We analyzed the influence of N nutrition on drought acclimation of Pinus pinea L. seedlings. Specifically, we addressed if high N fertilization reduces drought and frost tolerance of seedlings and whether drought hardening reverses the effect of high N fertilization on stress tolerance. Seedlings were grown under two N fertilization regimes (6 and 100 mg N per plant) and subjected to three drought-hardening levels (well-watered, moderate and strong hardening). Water relations, gas exchange, frost damage, N concentration and growth at the end of the drought-hardening period, and survival and growth of seedlings under controlled xeric and mesic outplanting conditions were measured. Relative to low-N plants, high-N plants were larger, had higher stomatal conductance (27%), residual transpiration (11%) and new root growth capacity and closed stomata at higher water potential. However, high N fertilization also increased frost damage (24%) and decreased plasmalemma stability to dehydration (9%). Drought hardening reversed to a great extent the reduction in stress tolerance caused by high N fertilization as it decreased frost damage, stomatal conductance and residual transpiration by 21, 31 and 24%, respectively, and increased plasmalemma stability to dehydration (8%). Drought hardening increased tissue non-structural carbohydrates and N concentration, especially in high-fertilized plants. Frost damage was positively related to the stability of plasmalemma to dehydration (r = 0.92) and both traits were negatively related to the concentration of reducing soluble sugars. No differences existed between moderate and strong drought-hardening treatments. Neither N nutrition nor drought hardening had any clear effect on seedling

Reduction of metal artifacts: beam hardening and photon starvation effects

NASA Astrophysics Data System (ADS)

Yadava, Girijesh K.; Pal, Debashish; Hsieh, Jiang

2014-03-01

The presence of metal-artifacts in CT imaging can obscure relevant anatomy and interfere with disease diagnosis. The cause and occurrence of metal-artifacts are primarily due to beam hardening, scatter, partial volume and photon starvation; however, the contribution to the artifacts from each of them depends on the type of hardware. A comparison of CT images obtained with different metallic hardware in various applications, along with acquisition and reconstruction parameters, helps understand methods for reducing or overcoming such artifacts. In this work, a metal beam hardening correction (BHC) and a projection-completion based metal artifact reduction (MAR) algorithms were developed, and applied on phantom and clinical CT scans with various metallic implants. Stainless-steel and Titanium were used to model and correct for metal beam hardening effect. In the MAR algorithm, the corrupted projection samples are replaced by the combination of original projections and in-painted data obtained by forward projecting a prior image. The data included spine fixation screws, hip-implants, dental-filling, and body extremity fixations, covering range of clinically used metal implants. Comparison of BHC and MAR on different metallic implants was used to characterize dominant source of the artifacts, and conceivable methods to overcome those. Results of the study indicate that beam hardening could be a dominant source of artifact in many spine and extremity fixations, whereas dental and hip implants could be dominant source of photon starvation. The BHC algorithm could significantly improve image quality in CT scans with metallic screws, whereas MAR algorithm could alleviate artifacts in hip-implants and dentalfillings.

Modeling and Analysis of Deformation for Spiral Bevel Gear in Die Quenching Based on the Hardenability Variation

NASA Astrophysics Data System (ADS)

Zhang, Yingtao; Wang, Gang; Shi, Wankai; Yang, Lin; Li, Zhichao

2017-07-01

Spiral bevel gears are widely used to transmit energy between intersecting axes. The strength and fatigue life of the gears are improved by carburizing and quenching. A die quenching process is used to control the deformation of the gear. The deformation is determined by the variations in the hardenability for a certain die quenching process. The relationship between hardenability, phase transformation and deformation needs to be studied to minimize deformation during the adjustment of the die quenching process parameters. In this paper, material properties for 22CrMoH steel are determined by the results of Jominy tests, dilatometry experiments and static mechanical property tests. The material models were built based on testing results under the consideration of hardenability variation. An finite element analysis model was developed to couple the phase transformation and deformation history of the complete carburizing and die quenching process for the spiral bevel gears. The final microstructures in the gear were bainite for low hardenability steel and a mixture of bainite and ferrite for high hardenability steel. The largest buckling deformation at the gear bottom surface is 0.375 mm at the outer circle for the low hardenability gear and 0.091 mm at the inner circle for the high hardenability gear.

A Review of NASA's Radiation-Hardened Electronics for Space Environments Project

NASA Technical Reports Server (NTRS)

Keys, Andrew S.; Adams, James H.; Patrick, Marshall C.; Johnson, Michael A.; Cressler, John D.

2008-01-01

NASA's Radiation Hardened Electronics for Space Exploration (RHESE) project develops the advanced technologies required to produce radiation hardened electronics, processors, and devices in support of the requirements of NASA's Constellation program. Over the past year, multiple advancements have been made within each of the RHESE technology development tasks that will facilitate the success of the Constellation program elements. This paper provides a brief review of these advancements, discusses their application to Constellation projects, and addresses the plans for the coming year.

The effect of tungsten on dislocation recovery and precipitation behavior of low-activation martensitic 9Cr steels

NASA Astrophysics Data System (ADS)

Abe, F.; Araki, H.; Noda, T.

1991-10-01

The effect of W on dislocation recovery and precipitation behavior was investigated for martensitic 9Cr-(0,l,2,4)W-0.1C (wt pct) steels after quenching, tempering, and subsequent prolonged aging. The steels were low induced-radioactivation martensitic steels for fusion reactor structures, intended as a possible replacement for conventional (7 to 12)Cr-Mo steels. During tempering after quenching, homogeneous precipitation of fine W2C occurred in martensite, causing secondary hardening between 673 and 823 K. The softening above the secondary hardening temperature shifted to higher temperatures with increasing W concentration, which was correlated with the decrease in self-diffusion rates with increasing W concentration. Carbides M23C6 and M7C3 were precipitated in the 9Cr steel without W after high-temperature tempering at 1023 K. With increasing W concentration, M7C3 was replaced by M23C6, and M6C formed in addition to M23C6. During subsequent aging at temperatures between 823 and 973 K after tempering, the recovery of dislocations, the agglomeration of carbides, and the growth of martensite lath subgrains occurred. Intermetallic Fe2W Laves also precipitated in the δ-ferrite grains of the 9Cr-4W steel. The effect of W on dislocation recovery and precipitation behavior is discussed in detail.

Surface hardening of Al alloys through controlled ball-milling and sintering.

PubMed

Kim, Seek Hyeoun; Kim, Yong Jin; Ahn, Jung-Ho

2012-07-01

One of the drawbacks of aluminum and its alloys is the lack of proper heat-treatment for surface-hardening. In the present work, a new and simple method of hardening the surface of aluminum and its alloys was developed. Low-energy ball-milling using specific process control agents (PCAs) was employed, using subsequent sintering in a controlled atmosphere. The PCAs in the present work were very effective both for milling and the formation of hard nanocrystalline dispersoids during sintering. The residual oxygen in a sintering atmosphere also played an important role in the formation of AIN or Al-O-N dispersoids. Through the proper control of the processing atmosphere and PCAs, the hardness and thickness of the hardened layers could be adjusted. The results of the wear test showed that the present aluminum alloys can be effectively utilized as light-weight components with a good wear resistance. Furthermore, the present method involves a simple forming process of die-compaction and sintering.

On the effects of irradiation and helium on the yield stress changes and hardening and non-hardening embrittlement of ˜8Cr tempered martensitic steels: Compilation and analysis of existing data

NASA Astrophysics Data System (ADS)

Yamamoto, Takuya; Odette, G. Robert; Kishimoto, Hirotatsu; Rensman, Jan-Willem; Miao, Pifeng

2006-09-01

Data on irradiation hardening and embrittlement of 8-10Cr normalized and tempered martensitic steel (TMS) alloys has been compiled from the literature, including results from neutron, spallation proton (SP) and He-ion (HI) irradiations. Limitations of this database are briefly described. Simple, phenomenological-empirical fitting models were used to assess the dose (displacement-per-atom, dpa), irradiation temperature ( Ti) and test temperature ( Tt) dependence of yield stress changes (Δ σy), as well as the corresponding dependence of sub-sized Charpy V-notch impact test transition temperature shifts (Δ Tc). The Δ σy are generally similar for SP and neutron irradiations, with very high and low helium to dpa ratios, respectively. Further, the Δ σy trends were found to be remarkably consistent with the Ti and dpa hardening-dependence of low alloy steels irradiated at much lower doses. The similar Ti and (low) dose dependence of Δ σy and Δ Tc, as well as an analysis of paired Δ Tc-Δ σy datasets, show that embrittlement is typically dominated by a hardening mechanism below about 400 °C. However, the corresponding hardening-Charpy shift coefficient, Cc = Δ Tc/Δ σy ≈ 0.38 ± 0.18 °C/MPa is lower than that for the fracture toughness reference temperature, T0, with Δ T0/Δ σy ≈ 0.58 ± 0.1 °C/MPa, indicating that sub-sized Charpy tests provide non-conservative estimates of embrittlement. The Cc increases at Ti > 400 °C, and Δ Tc > 0 are sometimes observed in association with Δ σy ⩽ 0, indicative of a non-hardening embrittlement (NHE) contribution. Analysis of limited data on embrittlement due to thermal aging supports this conclusion, and we hypothesize that the NHE regime may be shifted to lower temperatures by radiation enhanced diffusion. Possible effects of helium on embrittlement for Ti between 300 and 400 °C are also assessed based on observed trends in Cc. The available data is limited, scattered, and potentially confounded. However

Evolution of radiation defect and radiation hardening in heat treated SA508 Gr3 steel

NASA Astrophysics Data System (ADS)

Jin, Hyung-Ha; Kwon, Junhyun; Shin, Chansun

2014-01-01

The formation of radiation defects and corresponding radiation hardening in heat-treated SA508 Gr3 steel after Fe ion irradiation were investigated by means of transmission electron microscopy and a nano-indentation technique. As the residual dislocation density is increased in the matrix, the formation of radiation defects is considerably weakened. Comparison between the characteristics of the radiation defect and an evaluation of radiation hardening indicates that a large dislocation loop contributes little to the radiation hardening in the heat-treated SA508 Gr3 steel.

Sex differences and sex hormones in anxiety-like behavior of aging rats.

PubMed

Domonkos, Emese; Borbélyová, Veronika; Csongová, Melinda; Bosý, Martin; Kačmárová, Mária; Ostatníková, Daniela; Hodosy, Július; Celec, Peter

2017-07-01

Sex differences in the prevalence of affective disorders might be attributable to different sex hormone milieu. The effects of short-term sex hormone deficiency on behavior, especially on anxiety have been studied in numerous animal experiments, mainly on young adult rats and mice. However, sex differences in aged animals and the effects of long-term hypogonadism are understudied. The aim of our study was to analyze sex differences in anxiety-like behavior in aged rats and to prove whether they can be attributed to endogenous sex hormone production in males. A battery of tests was performed to assess anxiety-like behavior in aged female, male and gonadectomized male rats castrated before puberty. In addition, the aged gonadectomized male rats were treated with a single injection of estradiol or testosterone or supplemented with estradiol for two-weeks. Female rats displayed a less anxious behavior than male rats in most of the conducted behavioral tests except the light-dark box. Long-term androgen deficiency decreased the sex difference in anxiety either partially (open field, PhenoTyper cage) or completely (elevated plus maze). Neither single injection of sex hormones, nor two-week supplementation of estradiol in gonadectomized aged male rats significantly affected their anxiety-like behavior in the elevated plus maze. In conclusion, our results confirm sex differences in anxiety in aged rats likely mediated by endogenous testosterone production in males. Whether long-term supplementation with exogenous sex hormones could affect anxiety-like behavior in elderly individuals remains to be elucidated. Copyright © 2017 Elsevier Inc. All rights reserved.

The High Strain Rate Deformation Behavior of High Purity Magnesium and AZ31B Magnesium Alloy

NASA Astrophysics Data System (ADS)

Livescu, Veronica; Cady, Carl M.; Cerreta, Ellen K.; Henrie, Benjamin L.; Gray, George T.

The deformation in compression of pure magnesium and AZ31B magnesium alloy, both with a strong basal pole texture, has been investigated as a function of temperature, strain rate, and specimen orientation. The mechanical response of both metals is highly dependent upon the orientation of loading direction with respect to the basal pole. Specimens compressed along the basal pole direction have a high sensitivity to strain rate and temperature and display a concave down work hardening behavior. Specimens loaded perpendicularly to the basal pole have a yield stress that is relatively insensitive to strain rate and temperature and a work hardening behavior that is parabolic and then linearly upwards. Both specimen orientations display a mechanical response that is sensitive to temperature and strain rate. Post mortem characterization of the pure magnesium was conducted on a subset of specimens to determine the microstructural and textural evolution during deformation and these results are correlated with the observed work hardening behavior and strain rate sensitivities were calculated.

Nutritional interventions protect against age-related deficits in behavior: from animals to humans

USDA-ARS?s Scientific Manuscript database

Aged rats show impaired performance on motor and cognitive tasks. Similar changes in behavior occur in humans with age, and the development of methods to retard or reverse these age-related neuronal and behavioral deficits could increase healthy aging and decrease health care costs. In the present s...

Stress corrosion cracking evaluation of precipitation-hardening stainless steel

NASA Technical Reports Server (NTRS)

Humphries, T. S.; Nelson, E. E.

1970-01-01

Accelerated test program results show which precipitation hardening stainless steels are resistant to stress corrosion cracking. In certain cases stress corrosion susceptibility was found to be associated with the process procedure.

Recovery of diminished mealtime-associated anticipatory behavior by aniracetam in aged rats.

PubMed

Tanaka, Y; Kurasawa, M; Nakamura, K

2000-08-01

Disease- or age-related neuropsychiatric symptoms and cognitive and chronobiological impairments greatly aggravate the activities of daily living (ADL) in patients. The present study evaluates the effects of aniracetam on a decline in mealtime-associated anticipatory behavior in aged rats, as an animal model of temporally regulated behaviors or habitual daily activities. Aged rats showed a lower but typical nocturnal motor activity rhythm than young rats when the animals were fed ad lib. Mealtime-associated anticipatory behavior emerged in young rats when the rats were fed at a fixed time for 6 days, but the activity in aged rats was diminished. Repeated administration of aniracetam (100 mg/kg PO) or physostigmine (0.1 mg/kg SC) for 7 days ameliorated the impaired anticipatory behavior in aged rats. Nefiracetam (10 mg/kg PO) was ineffective. All compounds tested had no effect on appetite or motor ability. These results indicate that aging disturbs the timing or temporal regulation of anticipatory behavior, probably resulting from dysfunction in a food-entrainable oscillator linked to central cholinergic systems. The restoration of the time-keeping ability by aniracetam may be mediated by the facilitation of reticulothalamic cholinergic neurotransmission, and the action may lead to the improvement of declined ADL in stroke patients.

Preschool Gender-Typed Play Behavior at Age 3.5 Years Predicts Physical Aggression at Age 13 Years.

PubMed

Kung, Karson T F; Li, Gu; Golding, Jean; Hines, Melissa

2018-05-01

Gender differences in play behavior and physical aggression have been consistently reported. Theoretical perspectives concerning evolutionary, social, and social-cognitive mechanisms suggest that male-typical play behavior during childhood increases subsequent physical aggression. The evidence supporting these connections is limited, however. The present study investigated the association between gender-typed play behavior in early childhood and physical aggression in early adolescence using a sample drawn from a longitudinal, population study, the Avon Longitudinal Study of Parents and Children. Based on gender-typed play behavior as measured by the Pre-School Activities Inventory at age 3.5 years, samples of masculine (64 boys, 60 girls), feminine (80 boys, 66 girls), and randomly selected control children (55 boys, 67 girls) were recruited at age 13 years and administered the Reinisch Aggression Inventory. After controlling for a range of sociodemographic variables, maternal characteristics, and behavioral problems, including hyperactivity and conduct problems at age 3.5, significant group differences in physical aggression at age 13 were found among children classified as masculine, control, and feminine at age 3.5. Masculine children exhibited significantly more physical aggression than control children or feminine children, and control children exhibited significantly more physical aggression than feminine children. The association between gender-typed play behavior and physical aggression was not moderated by sex. These results suggest that the degree of childhood gender-typed play behavior independently predicts the degree of physical aggression at adolescence in boys and in girls.

Beliefs about behavior account for age differences in the correspondence bias.

PubMed

Stanley, Jennifer Tehan; Blanchard-Fields, Fredda

2011-03-01

Older adults tend to exhibit the correspondence bias to a greater extent than young adults. The current study examined whether these age differences are a function of the degree to which an individual subscribes to a lay theory of attitude-behavior consistency. First, participants responded to questions regarding their beliefs about attitude-behavior consistency. Approximately 2 weeks later, 144 (67 young adults and 77 older adults) participants completed the correspondence bias task. As expected, older adults were more biased than young adults. Analyses revealed that the degree to which an individual holds attitude-behavior consistency beliefs in the dishonesty domain accounted for age-related differences in the correspondence bias. The results of this study suggest that age differences in the correspondence bias task are in part driven by older adults holding stronger attitude-behavior consistency beliefs than young adults.

Fractography of induction-hardened steel fractured in fatigue and overload

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

Santos, C.G.; Laird, C.

1997-07-01

The fracture surfaces of induction-hardened steel specimens obtained from an auto axle were characterized, macroscopically and microscopically, after being fractured in fatigue and monotonic overload. Specimens were tested in cyclic three-point bending under load control, and the S-N curve was established for specimens that had been notched by spark machining to facilitate fractography. Scanning electron microscopy of the fractured surfaces obtained for lives spanning the range 17,000 to 418,000 cycles revealed diverse fracture morphologies, including intergranular fracture and transgranular fatigue fracture. The results are being offered to assist in the analysis of complex field failures in strongly hardened steel.

Radiation hardening of components and systems for nuclear rocket vehicle applications

NASA Technical Reports Server (NTRS)

Greenhow, W. A.; Cheever, P. R.

1972-01-01

The results of the analysis of the S-2 and S-4B components, although incomplete, indicate that many Saturn 5 components and subsystems, e.g., pumps, valves, etc., can be radiation hardened to meet NRV requirements by material substitution and minor design modifications. Results of these analyses include (1) recommended radiation tolerance limits for over 100 material applications; (2) design data which describes the components of each system; (3) presentation of radiation hardening examples of systems; and (4) designing radiation effects tests to supply data for selecting materials.

Prosocial Behavior Increases with Age across Five Economic Games

PubMed Central

Matsumoto, Yoshie; Yamagishi, Toshio; Li, Yang; Kiyonari, Toko

2016-01-01

Ontogenic studies of human prosociality generally agree on that human prosociality increases from early childhood through early adulthood; however, it has not been established if prosociality increases beyond early adulthood. We examined a sample of 408 non-student residents from Tokyo, Japan, who were evenly distributed across age (20–59) and sex. Participants played five economic games each separated by a few months. We demonstrated that prosocial behavior increased with age beyond early adulthood and this effect was shown across all five economic games. A similar, but weaker, age-related trend was found in one of three social value orientation measures of prosocial preferences. We measured participants’ belief that manipulating others is a wise strategy for social success, and found that this belief declined with age. Participants’ satisfaction with the unilateral exploitation outcome of the prisoner’s dilemma games also declined with age. These two factors—satisfaction with the DC outcome in the prisoner’s dilemma games and belief in manipulation—mediated the age effect on both attitudinal and behavioral prosociality. Participants’ age-related socio-demographic traits such as marriage, having children, and owning a house weakly mediated the age effect on prosociality through their relationships with satisfaction with the DC outcome and belief in manipulation. PMID:27414803

Simulation of Thermo-viscoplastic Behaviors for AISI 4140 Steel

NASA Astrophysics Data System (ADS)

Li, Hong-Bin; Feng, Yun-Li

2016-04-01

The thermo-viscoplastic behaviors of AISI 4140 steel are investigated over wide ranges of strain rate and deformation temperature by isothermal compression tests. Based on the experimental results, a unified viscoplastic constitutive model is proposed to describe the hot compressive deformation behaviors of the studied steel. In order to reasonably evaluate the work hardening behaviors, a strain hardening material constant (h0) is expressed as a function of deformation temperature and strain rate in the proposed constitutive model. Also, the sensitivity of initial value of internal variable s to the deformation temperature is discussed. Furthermore, it is found that the initial value of internal variable s can be expressed as a linear function of deformation temperature. Comparisons between the measured and predicted results confirm that the proposed constitutive model can give an accurate and precise estimate of the inelastic stress-strain relationships for the studied high-strength steel.

Age and sex influence marmot antipredator behavior during periods of heightened risk.

PubMed

Lea, Amanda J; Blumstein, Daniel T

2011-08-01

Animals adjust their antipredator behavior according to environmental variation in risk, and to account for their ability to respond to threats. Intrinsic factors that influence an animal's ability to respond to predators (e.g., age, body condition) should explain variation in antipredator behavior. For example, a juvenile might allocate more time to vigilance than an adult because mortality as a result of predation is often high for this age class; however, the relationship between age/vulnerability and antipredator behavior is not always clear or as predicted. We explored the influence of intrinsic factors on yellow-bellied marmot (Marmota flaviventris) antipredator behavior using data pooled from 4 years of experiments. We hypothesized that inherently vulnerable animals (e.g., young, males, and individuals in poor condition) would exhibit more antipredator behavior prior to and immediately following conspecific alarm calls. As expected, males and yearlings suppressed foraging more than females and adults following alarm call playbacks. In contrast to predictions, animals in better condition respond more than animals in below average condition. Interestingly, these intrinsic properties did not influence baseline time budgets; animals of all ages, sexes, and condition levels devoted comparable amounts of time to foraging prior to alarm calls. Our results support the hypothesis that inherent differences in vulnerability influence antipredator behavior; furthermore, it appears that a crucial, but poorly acknowledged, interaction exists between risk and state-dependence. Elevated risk may be required to reveal the workings of state-dependent behavior, and studies of antipredator behavior in a single context may draw incomplete conclusions about age- or sex-specific strategies.

Aerobic exercise prevents age-dependent cognitive decline and reduces anxiety-related behaviors in middle-aged and old rats.

PubMed

Pietrelli, A; Lopez-Costa, J; Goñi, R; Brusco, A; Basso, N

2012-01-27

Recent research involving human and animals has shown that aerobic exercise of moderate intensity produces the greatest benefit on brain health and behavior. In this study we investigated the effects on cognitive function and anxiety-related behavior in rats at different ages of aerobic exercise, performed regularly throughout life. We designed an aerobic training program with the treadmill running following the basic principles of human training, and assuming that rats have the same physiological adaptations. The intensity was gradually adjusted to the fitness level and age, and maintained at 60-70% of maximum oxygen consumption (max.VO(2)). In middle age (8 months) and old age (18 months), we studied the cognitive response with the radial maze (RM), and anxiety-related behaviors with the open field (OF) and the elevated plus maze (EPM). Aerobically trained (AT) rats had a higher cognitive performance measured in the RM, showing that exercise had a cumulative and amplifier effect on memory and learning. The analysis of age and exercise revealed that the effects of aerobic exercise were modulated by age. Middle-aged AT rats were the most successful animals; however, the old AT rats met the criteria more often than the middle-aged sedentary controls (SC), indicating that exercise could reverse the negative effects of sedentary life, partially restore the cognitive function, and protect against the deleterious effects of aging. The results in the OF and EPM showed a significant decrease in key indicators of anxiety, revealing that age affected most of the analyzed variables, and that exercise had a prominent anxiolytic effect, particularly strong in old age. In conclusion, our results indicated that regular and chronic aerobic exercise has time and dose-dependent, neuroprotective and restorative effects on physiological brain aging, and reduces anxiety-related behaviors. Copyright © 2011 IBRO. Published by Elsevier Ltd. All rights reserved.

Synergetics of hardening construction systems

NASA Astrophysics Data System (ADS)

Tolstoy, A. D.; Lesovik, V. S.; Glagolev, E. S.; Krymova, A. I.

2018-03-01

The study of hardening high-strength systems indicates the relation between the potential of synergetics and issues related to structure formation of aggregates produced on the basis of rationally selected construction mixes. The paper considers challenges of the general principles of synergetics and sustainable development of open dissipative systems and their use in industry, as well as their understanding as complete self-regulating nonequilibrium systems. The main objective of the study was to demonstrate that the principles of self-regulating systems development can be applied in construction technology.

A Study on Low-Cost Case Hardening of Mild and Alloy Steels Utilizing Cassava Leaf Media

NASA Astrophysics Data System (ADS)

Gordon, Renee Erica

Conventional case hardening processes have major drawbacks in being expensive and hazardous to perform. A novel cyaniding technique has been developed to case harden steel which involves the use of cassava leaf. Cassava is ideal for use in this process as it contains varying degrees of cyanogenic glucoside (15-1000 mg of HCN per kg of cassava). The entire hardening process involves direct thermal decomposition of the HCN, which produced C and N gas that then diffused into the steel creating a hardened surface. Pulverized cassava leaf was involved in the pack-cyaniding of AISI 1018 and Nitralloy 135 within three varying process atmospheres. The use of barium carbonate (BaCO3) as an energizer was employed at the high temperature regime while barium chloride (BaCl2) was utilized at low temperatures. Vickers microhardness testing, microstructural characterization, and diffraction techniques were utilized for analysis. While no improvement was observed at low temperatures, processing within the high temperature regime showed significant hardening. The addition of BaCO3 to pulverized cassava leaf accelerated the hardening process by substantially increasing the resident surface microhardness while generating a shallow case layer distance. Diffusion theory was used to identify changes experienced with the variation in parameters. The presence of barium carbonate during processing decreased the diffusivity of hardening agents. This manifested in a very large, initial mass transfer of diffusing species localized in the case region followed by a minimum of any further increase in case depths, even as treatment time intervals were increased. The level of influence each parameter delivered was assessed using stepwise regression analysis and a unified model was constructed.

Beliefs About Behavior Account for Age Differences in the Correspondence Bias

PubMed Central

Blanchard-Fields, Fredda

2011-01-01

Objectives. Older adults tend to exhibit the correspondence bias to a greater extent than young adults. The current study examined whether these age differences are a function of the degree to which an individual subscribes to a lay theory of attitude–behavior consistency. Methods. First, participants responded to questions regarding their beliefs about attitude–behavior consistency. Approximately 2 weeks later, 144 (67 young adults and 77 older adults) participants completed the correspondence bias task. Results. As expected, older adults were more biased than young adults. Analyses revealed that the degree to which an individual holds attitude–behavior consistency beliefs in the dishonesty domain accounted for age-related differences in the correspondence bias. Discussion. The results of this study suggest that age differences in the correspondence bias task are in part driven by older adults holding stronger attitude–behavior consistency beliefs than young adults. PMID:21071624

Microstructural and Mechanical Study of Press Hardening of Thick Boron Steel Sheet

NASA Astrophysics Data System (ADS)

Pujante, J.; Garcia-Llamas, E.; Golling, S.; Casellas, D.

2017-09-01

Press hardening has become a staple in the production of automotive safety components, due to the combination of high mechanical properties and form complexity it offers. However, the use of press hardened components has not spread to the truck industry despite the advantages it confers, namely affordable weight reduction without the use of exotic materials, would be extremely attractive for this sector. The main reason for this is that application of press hardened components in trucks implies adapting the process to the manufacture of thick sheet metal. This introduces an additional layer of complexity, mainly due to the thermal gradients inside the material resulting in though-thickness differences in austenitization and cooling, potentially resulting in complex microstructure and gradient of mechanical properties. This work presents a preliminary study on the press hardening of thick boron steel sheet. First of all, the evolution of the sheet metal during austenitization is studied by means of dilatometry tests and by analysing the effect of furnace dwell time on grain size. Afterwards, material cooled using different cooling strategies, and therefore different effective cooling rates, is studied in terms of microstructure and mechanical properties. Initial results from finite element simulation are compared to experimental results, focusing on the phase composition in through thickness direction. Results show that industrial-equivalent cooling conditions do not lead to gradient microstructures, even in extreme scenarios involving asymmetrical cooling.

Factors contributing to enhanced freezing tolerance in wheat during frost hardening in the light.

PubMed

Janda, Tibor; Szalai, Gabriella; Leskó, Kornélia; Yordanova, Rusina; Apostol, Simona; Popova, Losanka Petrova

2007-06-01

The interaction between light and temperature during the development of freezing tolerance was studied in winter wheat (Triticum aestivum L. var. Mv Emese). Ten-day-old plants were cold hardened at 5 degrees C for 12 days under normal (250 micromol m(-2)s(-1)) or low light (20 micromol m(-2)s(-1)) conditions. Some of the plants were kept at 20/18 degrees C for 12 days at high light intensity (500 micromol m(-2)s(-1)), which also increased the freezing tolerance of winter wheat. The freezing survival rate, the lipid composition, the antioxidant activity, and the salicylic acid content were investigated during frost hardening. The saturation level of hexadecanoic acid decreased not only in plants hardened at low temperature, but also, to a lesser extent, in plants kept under high light irradiation at normal growth temperature. The greatest induction of the enzymes glutathione reductase (EC 1.6.4.2.) and ascorbate peroxidase (EC 1.11.1.11.) occurred when the cold treatment was carried out in normal light, but high light intensity at normal, non-hardening temperature also increased the activity of these enzymes. The catalase (EC 1.11.1.6.) activity was also higher in plants grown at high light intensity than in the controls. The greatest level of induction in the activity of the guaiacol peroxidase (EC 1.11.1.7.) enzyme occurred under cold conditions with low light. The bound ortho-hydroxy-cinnamic acid increased by up to two orders of magnitude in plants that were cold hardened in normal light. Both high light intensity and low temperature hardening caused an increase in the free and bound salicylic acid content of the leaves. This increase was most pronounced in plants that were cold treated in normal light.

Age-related striatal BOLD changes without changes in behavioral loss aversion.

PubMed

Viswanathan, Vijay; Lee, Sang; Gilman, Jodi M; Kim, Byoung Woo; Lee, Nick; Chamberlain, Laura; Livengood, Sherri L; Raman, Kalyan; Lee, Myung Joo; Kuster, Jake; Stern, Daniel B; Calder, Bobby; Mulhern, Frank J; Blood, Anne J; Breiter, Hans C

2015-01-01

Loss aversion (LA), the idea that negative valuations have a higher psychological impact than positive ones, is considered an important variable in consumer research. The literature on aging and behavior suggests older individuals may show more LA, although it is not clear if this is an effect of aging in general (as in the continuum from age 20 and 50 years), or of the state of older age (e.g., past age 65 years). We also have not yet identified the potential biological effects of aging on the neural processing of LA. In the current study we used a cohort of subjects with a 30 year range of ages, and performed whole brain functional MRI (fMRI) to examine the ventral striatum/nucleus accumbens (VS/NAc) response during a passive viewing of affective faces with model-based fMRI analysis incorporating behavioral data from a validated approach/avoidance task with the same stimuli. Our a priori focus on the VS/NAc was based on (1) the VS/NAc being a central region for reward/aversion processing; (2) its activation to both positive and negative stimuli; (3) its reported involvement with tracking LA. LA from approach/avoidance to affective faces showed excellent fidelity to published measures of LA. Imaging results were then compared to the behavioral measure of LA using the same affective faces. Although there was no relationship between age and LA, we observed increasing neural differential sensitivity (NDS) of the VS/NAc to avoidance responses (negative valuations) relative to approach responses (positive valuations) with increasing age. These findings suggest that a central region for reward/aversion processing changes with age, and may require more activation to produce the same LA behavior as in younger individuals, consistent with the idea of neural efficiency observed with high IQ individuals showing less brain activation to complete the same task.

Age-related striatal BOLD changes without changes in behavioral loss aversion

PubMed Central

Viswanathan, Vijay; Lee, Sang; Gilman, Jodi M.; Kim, Byoung Woo; Lee, Nick; Chamberlain, Laura; Livengood, Sherri L.; Raman, Kalyan; Lee, Myung Joo; Kuster, Jake; Stern, Daniel B.; Calder, Bobby; Mulhern, Frank J.; Blood, Anne J.; Breiter, Hans C.

2015-01-01

Loss aversion (LA), the idea that negative valuations have a higher psychological impact than positive ones, is considered an important variable in consumer research. The literature on aging and behavior suggests older individuals may show more LA, although it is not clear if this is an effect of aging in general (as in the continuum from age 20 and 50 years), or of the state of older age (e.g., past age 65 years). We also have not yet identified the potential biological effects of aging on the neural processing of LA. In the current study we used a cohort of subjects with a 30 year range of ages, and performed whole brain functional MRI (fMRI) to examine the ventral striatum/nucleus accumbens (VS/NAc) response during a passive viewing of affective faces with model-based fMRI analysis incorporating behavioral data from a validated approach/avoidance task with the same stimuli. Our a priori focus on the VS/NAc was based on (1) the VS/NAc being a central region for reward/aversion processing; (2) its activation to both positive and negative stimuli; (3) its reported involvement with tracking LA. LA from approach/avoidance to affective faces showed excellent fidelity to published measures of LA. Imaging results were then compared to the behavioral measure of LA using the same affective faces. Although there was no relationship between age and LA, we observed increasing neural differential sensitivity (NDS) of the VS/NAc to avoidance responses (negative valuations) relative to approach responses (positive valuations) with increasing age. These findings suggest that a central region for reward/aversion processing changes with age, and may require more activation to produce the same LA behavior as in younger individuals, consistent with the idea of neural efficiency observed with high IQ individuals showing less brain activation to complete the same task. PMID:25983682

An evolving effective stress approach to anisotropic distortional hardening

DOE PAGES

Lester, B. T.; Scherzinger, W. M.

2018-03-11

A new yield surface with an evolving effective stress definition is proposed for consistently and efficiently describing anisotropic distortional hardening. Specifically, a new internal state variable is introduced to capture the thermodynamic evolution between different effective stress definitions. The corresponding yield surface and evolution equations of the internal variables are derived from thermodynamic considerations enabling satisfaction of the second law. A closest point projection return mapping algorithm for the proposed model is formulated and implemented for use in finite element analyses. Finally, select constitutive and larger scale boundary value problems are solved to explore the capabilities of the model andmore » examine the impact of distortional hardening on constitutive and structural responses. Importantly, these simulations demonstrate the tractability of the proposed formulation in investigating large-scale problems of interest.« less

An evolving effective stress approach to anisotropic distortional hardening

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

Lester, B. T.; Scherzinger, W. M.

A new yield surface with an evolving effective stress definition is proposed for consistently and efficiently describing anisotropic distortional hardening. Specifically, a new internal state variable is introduced to capture the thermodynamic evolution between different effective stress definitions. The corresponding yield surface and evolution equations of the internal variables are derived from thermodynamic considerations enabling satisfaction of the second law. A closest point projection return mapping algorithm for the proposed model is formulated and implemented for use in finite element analyses. Finally, select constitutive and larger scale boundary value problems are solved to explore the capabilities of the model andmore » examine the impact of distortional hardening on constitutive and structural responses. Importantly, these simulations demonstrate the tractability of the proposed formulation in investigating large-scale problems of interest.« less

Paving asphalts : reduction of oxidative hardening of asphalts by treatment with hydrated lime : a mechanistic study

DOT National Transportation Integrated Search

1977-04-01

This study showed that lime treatment removes polar, viscosity-building components and reduces the susceptibility of the asphalt to laboratory oxidative hardening. The beneficial effects of lime treatment in reducing asphalt oxidative hardening were ...

Childhood bullying behaviors at age eight and substance use at age 18 among males. A nationwide prospective study.

PubMed

Niemelä, S; Brunstein-Klomek, A; Sillanmäki, L; Helenius, H; Piha, J; Kumpulainen, K; Moilanen, I; Tamminen, T; Almqvist, F; Sourander, A

2011-03-01

Childhood bullying behaviors (bullying and victimization) were studied as risk factors for substance use among Finnish males. The study design was a nationwide prospective general population study, where information was collected in 1989 and 1999. Bullying behaviors and childhood psychopathology at age eight were collected from teachers, parents and boys themselves. At age 18, self-reports of frequent drunkenness (once a week or more often), daily heavy smoking (10 cigarettes or more per day), and illicit drug use during the past six months were obtained from 78% of the boys attending the study at age eight (n=2946). Being frequently victimized at age eight predicted daily heavy smoking, and this was evident even after adjusting for childhood family background, psychopathology at age eight and at age 18, and other forms of substance use. In multivariate analysis, bullying others frequently predicted illicit drug use, while being a victim of bullying associated with a lower occurrence of illicit drug use. Bullying behaviors had no association with frequent drunkenness independent of other factors. Accordingly, being a victim of bullying predisposes in particular to subsequent smoking. Bullying others in childhood can be regarded as an early indicator to illicit drug use later in life. The screening and intervention possibilities in order to recognize the risk group for later health compromising behaviors are emphasized. Copyright © 2010 Elsevier Ltd. All rights reserved.

Multi-scale simulation of radiation damage accumulation and subsequent hardening in neutron-irradiated α-Fe

DOE PAGES

Dunn, Aaron; Dingreville, Remi; Capolungo, Laurent

2015-11-27

A hierarchical methodology is introduced to predict the effects of radiation damage and irradiation conditions on the yield stress and internal stress heterogeneity developments in polycrystalline α-Fe. Simulations of defect accumulation under displacement cascade damage conditions are performed using spatially resolved stochastic cluster dynamics. The resulting void and dislocation loop concentrations and average sizes are then input into a crystal plasticity formulation that accounts for the change in critical resolved shear stress due to the presence of radiation induced defects. The simulated polycrystalline tensile tests show a good match to experimental hardening data over a wide range of irradiation doses.more » With this capability, stress heterogeneity development and the effect of dose rate on hardening is investigated. The model predicts increased hardening at higher dose rates for low total doses. By contrast, at doses above 10 –2 dpa when cascade overlap becomes significant, the model does not predict significantly different hardening for different dose rates. In conclusion, the development of such a model enables simulation of radiation damage accumulation and associated hardening without relying on experimental data as an input under a wide range of irradiation conditions such as dose, dose rate, and temperature.« less

Hardening neutron spectrum for advanced actinide transmutation experiments in the ATR.

PubMed

Chang, G S; Ambrosek, R G

2005-01-01

The most effective method for transmuting long-lived isotopes contained in spent nuclear fuel into shorter-lived fission products is in a fast neutron spectrum reactor. In the absence of a fast test reactor in the United States, initial irradiation testing of candidate fuels can be performed in a thermal test reactor that has been modified to produce a test region with a hardened neutron spectrum. Such a test facility, with a spectrum similar but somewhat softer than that of the liquid-metal fast breeder reactor (LMFBR), has been constructed in the INEEL's Advanced Test Reactor (ATR). The radial fission power distribution of the actinide fuel pin, which is an important parameter in fission gas release modelling, needs to be accurately predicted and the hardened neutron spectrum in the ATR and the LMFBR fast neutron spectrum is compared. The comparison analyses in this study are performed using MCWO, a well-developed tool that couples the Monte Carlo transport code MCNP with the isotope depletion and build-up code ORIGEN-2. MCWO analysis yields time-dependent and neutron-spectrum-dependent minor actinide and Pu concentrations and detailed radial fission power profile calculations for a typical fast reactor (LMFBR) neutron spectrum and the hardened neutron spectrum test region in the ATR. The MCWO-calculated results indicate that the cadmium basket used in the advanced fuel test assembly in the ATR can effectively depress the linear heat generation rate in the experimental fuels and harden the neutron spectrum in the test region.

Innovative Structural Materials and Sections with Strain Hardening Cementitious Composites

NASA Astrophysics Data System (ADS)

Dey, Vikram

The motivation of this work is based on development of new construction products with strain hardening cementitious composites (SHCC) geared towards sustainable residential applications. The proposed research has three main objectives: automation of existing manufacturing systems for SHCC laminates; multi-level characterization of mechanical properties of fiber, matrix, interface and composites phases using servo-hydraulic and digital image correlation techniques. Structural behavior of these systems were predicted using ductility based design procedures using classical laminate theory and structural mechanics. SHCC sections are made up of thin sections of matrix with Portland cement based binder and fine aggregates impregnating continuous one-dimensional fibers in individual or bundle form or two/three dimensional woven, bonded or knitted textiles. Traditional fiber reinforced concrete (FRC) use random dispersed chopped fibers in the matrix at a low volume fractions, typically 1-2% to avoid to avoid fiber agglomeration and balling. In conventional FRC, fracture localization occurs immediately after the first crack, resulting in only minor improvement in toughness and tensile strength. However in SHCC systems, distribution of cracking throughout the specimen is facilitated by the fiber bridging mechanism. Influence of material properties of yarn, composition, geometry and weave patterns of textile in the behavior of laminated SHCC skin composites were investigated. Contribution of the cementitious matrix in the early age and long-term performance of laminated composites was studied with supplementary cementitious materials such as fly ash, silica fume, and wollastonite. A closed form model with classical laminate theory and ply discount method, coupled with a damage evolution model was utilized to simulate the non-linear tensile response of these composite materials. A constitutive material model developed earlier in the group was utilized to characterize and

Unraveling the Age Hardening Response in U-Nb Alloys

DOE PAGES

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

2016-11-15

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

Wear behavior of austenite containing plate steels

NASA Astrophysics Data System (ADS)

Hensley, Christina E.

As a follow up to Wolfram's Master of Science thesis, samples from the prior work were further investigated. Samples from four steel alloys were selected for investigation, namely AR400F, 9260, Hadfield, and 301 Stainless steels. AR400F is martensitic while the Hadfield and 301 stainless steels are austenitic. The 9260 exhibited a variety of hardness levels and retained austenite contents, achieved by heat treatments, including quench and tempering (Q&T) and quench and partitioning (Q&P). Samples worn by three wear tests, namely Dry Sand/Rubber Wheel (DSRW), impeller tumbler impact abrasion, and Bond abrasion, were examined by optical profilometry. The wear behaviors observed in topography maps were compared to the same in scanning electron microscopy micrographs and both were used to characterize the wear surfaces. Optical profilometry showed that the scratching abrasion present on the wear surface transitioned to gouging abrasion as impact conditions increased (i.e. from DSRW to impeller to Bond abrasion). Optical profilometry roughness measurements were also compared to sample hardness as well as normalized volume loss (NVL) results for each of the three wear tests. The steels displayed a relationship between roughness measurements and observed wear rates for all three categories of wear testing. Nanoindentation was used to investigate local hardness changes adjacent to the wear surface. DSRW samples generally did not exhibit significant work hardening. The austenitic materials exhibited significant hardening under the high impact conditions of the Bond abrasion wear test. Hardening in the Q&P materials was less pronounced. The Q&T microstructures also demonstrated some hardening. Scratch testing was performed on samples at three different loads, as a more systematic approach to determining the scratching abrasion behavior. Wear rates and scratch hardness were calculated from scratch testing results. Certain similarities between wear behavior in scratch testing

SEGR- and SEB-hardened structure with DSPSOI in power MOSFETs

NASA Astrophysics Data System (ADS)

Tang, Zhaohuan; Fu, Xinghua; Yang, Fashun; Tan, Kaizhou; Ma, Kui; Wu, Xue; Lin, Jiexing

2017-12-01

Single event irradiation-hardened power MOSFET is the most important device for DC/DC converter in space environment application. Single event gate rupture (SEGR) and single event burnout (SEB), which will degrade the running safety and reliability of spacecraft, are the two typical failure modes in power MOSFETs. In this paper, based on recombination mechanism of interface between oxide and silicon, a novel hardened power MOSFETs structure for SEGR and SEB is proposed. The structure comprises double stagger partial silicon-on-insulator (DSPSOI) layers. Results show that the safety operation area (SOA) of a 130 V N-channel power MOSFET in single event irradiation environment is enhanced by up to 50% when the linear-energy-transfer value of heavy ion is a constant of 98 MeV·cm2/mg in the whole incident track, and the other parameters are almost maintained at the same value. Thus this novel structure can be widely used in designing single event irradiation-hardened power MOSFETs. Project supported by the National Natural Science Foundation of China (No. 61464002), the Grand Science and Technology Special Project in Guizhou Province of China (No. [2015]6006), and the Ministry of Education Open Foundation for Semiconductor Power Device Reliability (No. 010201).

Behavioral determinants of healthy aging: good news for the baby boomer generation.

PubMed

Hartman-Stein, Paula E; Potkanowicz, Edward S

2003-01-01

The first of the Baby Boomer generation will officially enter the beginning of old age in 2011 by turning 65. Recent research findings suggest that if the members of this cohort group engage in certain healthy behaviors and thought patterns in their middle years, they will experience a vital, satisfying life in their 70s and beyond. This article reviews the existing literature, including the results of longitudinal studies showing variables that predicted successful aging. Focusing on a lifespan psychology perspective of aging, the authors provide behavioral recommendations for middle age individuals that are likely to prevent disease-related disability, cognitive impairment, and late life depression. These include regular physical exercise, engaging in cognitively stimulating activities, maintaining an optimistic mental outlook, and finding meaning in life. The good news for the Baby Boomers is that there is increasing evidence that their behavior at age 50 will impact how they feel at age 80.

Radiation hardening of optical fibers and fiber sensors for space applications: recent advances

NASA Astrophysics Data System (ADS)

Girard, S.; Ouerdane, Y.; Pinsard, E.; Laurent, A.; Ladaci, A.; Robin, T.; Cadier, B.; Mescia, L.; Boukenter, A.

2017-11-01

In these ICSO proceedings, we review recent advances from our group concerning the radiation hardening of optical fiber and fiber-based sensors for space applications and compare their benefits to state-of-the-art results. We focus on the various approaches we developed to enhance the radiation tolerance of two classes of optical fibers doped with rare-earths: the erbium (Er)-doped ones and the ytterbium/erbium (Er/Yb)-doped ones. As a first approach, we work at the component level, optimizing the fiber structure and composition to reduce their intrinsically high radiation sensitivities. For the Erbium-doped fibers, this has been achieved using a new structure for the fiber that is called Hole-Assisted Carbon Coated (HACC) optical fibers whereas for the Er/Ybdoped optical fibers, their hardening was successfully achieved adding to the fiber, the Cerium element, that prevents the formation of the radiation-induced point defects responsible for the radiation induced attenuation in the infrared part of the spectrum. These fibers are used as part of more complex systems like amplifiers (Erbium-doped Fiber Amplifier, EDFA or Yb-EDFA) or source (Erbium-doped Fiber Source, EDFS or Yb- EDFS), we discuss the impact of using radiation-hardened fibers on the system radiation vulnerability and demonstrate the resistance of these systems to radiation constraints associated with today and future space missions. Finally, we will discuss another radiation hardening approach build in our group and based on a hardening-by-system strategy in which the amplifier is optimized during its elaboration for its future mission considering the radiation effects and not in-lab.

The cyclic stress-strain behavior of a nickel-base superalloy at 650 C

NASA Technical Reports Server (NTRS)

Gabb, T. P.; Welsch, G. E.

1986-01-01

It is pointed out that examinations of the monotonic tensile and fatigue behaviors of single crystal nickel-base superalloys have disclosed orientation-dependent tension-compression anisotropies and significant differences in the mechanical response of octahedral and cube slip at intermediate temperatures. An examination is conducted of the cyclic hardening response of the single crystal superalloy PWA 1480 at 650 C. In the considered case, tension-compression anisotropy is present, taking into account primarily conditions under which a single slip system is operative. Aspects of a deformation by single slip are considered along with cyclic hardening anisotropy in tension and compression. It is found that specimens deforming by octahedral slip on a single slip system have similar hardening responses in tensile and low cycle fatigue loading. Cyclic strain hardening is very low for specimens displaying single slip.

Shear punch and ball microhardness measurements of 14 MeV neutron irradiation hardening in five metals

NASA Astrophysics Data System (ADS)

Shinohara, K.; Lucas, G. E.; Odette, G. R.

1985-08-01

The irradiation hardening response of five metals irradiated in RTNS-II was investigated using a combination of ball microhardness and shear punch test techniques. The specimens were transmission electron microscopy disks of pure nickel, Ni-5wt%Si, pure iron, solution annealed prime candidate alloy (PCA) for Path A, and 40% cold worked MFE 316 stainless steel. Specimens were irradiated in RTNS-II to fluences in the range 6 × 10 16 to 6 × 10 17 n/cm 2. Only limited ball microhardness data could be obtained because of disk thickness. However, the ball microhardness data obtained were in good agreement with shear punch data. It was found that the pure metals exhibited little hardening after exposure to fluences of ~1 × 10 17 n/cm 2, but Ni-5 Si exhibited significant hardening after 6 × 10 17 n/cm 2. Hardening in PCA was similar to that observed in solution annealed 316 stainless steel; and hardening in 40% cold worked MFE 316 was relatively small after 6 × 10 17 n/cm 2. The Ni-5 Si response may be due to irradiation induced precipitation.

Accelerated aging studies of UHMWPE. I. Effect of resin, processing, and radiation environment on resistance to mechanical degradation.

PubMed

Edidin, A A; Herr, M P; Villarraga, M L; Muth, J; Yau, S S; Kurtz, S M

2002-08-01

The resin and processing route have been identified as potential variables influencing the mechanical behavior, and hence the clinical performance, of ultra-high molecular weight polyethylene (UHMWPE) orthopedic components. Researchers have reported that components fabricated from 1900 resin may oxidize to a lesser extent than components fabricated from GUR resin during shelf aging after gamma sterilization in air. Conflicting reports on the oxidation resistance for 1900 raise the question of whether resin or manufacturing method, or an interaction between resin and manufacturing method, influences the mechanical behavior of UHMWPE. We conducted a series of accelerated aging studies (no aging, aging in oxygen or in nitrogen) to systematically examine the influence of resin (GUR or 1900), manufacturing method (bulk compression molding or extrusion), and sterilization method (none, in air, or in nitrogen) on the mechanical behavior of UHMWPE. The small punch testing technique was used to evaluate the mechanical behavior of the materials, and Fourier transform infrared spectroscopy was used to characterize the oxidation in selected samples. Our study showed that the sterilization environment, aging condition, and specimen location (surface or subsurface) significantly affected the mechanical behavior of UHMWPE. Each of the three polyethylenes evaluated seem to degrade according to a similar pathway after artificial aging in oxygen and gamma irradiation in air. The initial ability of the materials to exhibit post-yield strain hardening was significantly compromised by degradation. In general, there were only minor differences in the aging behavior of molded and extruded GUR 1050, whereas the molded 1900 material seemed to degrade slightly faster than either of the 1050 materials. Copyright 2002 Wiley Periodicals, Inc.

Health perceptions and behaviors of school-age boys and girls.

PubMed

Graham, M V; Uphold, C R

1992-01-01

This study described and compared the health perceptions and behaviors of 83 school-age boys and girls. An age-appropriate interview schedule was designed to collect data related to demographic characteristics, health perceptions, safety, life-style practices, nutrition, dental health, and care of minor injuries. Findings indicated that most boys and girls viewed themselves as healthy and managed their own care fairly well in the areas of seat belt use, exercise, and dental health. Nutrition was identified as an area of concern, with 10% of the children skipping breakfast, and over half eating snacks with empty calories. Generally, children were found to be knowledgeable in the management of simple injuries and how to respond in the event of an emergency. Boys and girls were similar in all areas of health perceptions and behaviors except for dental health, with boys reporting more regular visits to the dentist than did girls. Further research is needed to learn more about the process by which school-age children acquire positive health behaviors to assist nurses to design and implement intervention programs that appropriately address the needs of this age group.

Role of copper in precipitation hardening of high-alloy Cr-Ni cast steels

NASA Astrophysics Data System (ADS)

Gajewski, Mirosław

2006-02-01

The mechanism of strengthening with second-phase particles that results from heat treatment, i.e., precipitate hardening, plays an important role in modern alloys. The strengthening effect of such particles can result from their coherence with the matrix, inhibition of dislocation slip, inhibition of grain boundary slip, as well as hampering recovery processes due to dislocation network pinning. The results of investigations into high-alloy Cr-Ni-Cu cast steels precipitate hardened with highly dispersed ɛ phase particles are presented within. The influence of heat treatment on changes in microstructure, mechanical properties, and morphology of fracture surfaces obtained under loading have been analyzed. It has been demonstrated that, with the appropriate selection of heat treatment parameters, it is possible to control the precipitation of the hardening ɛ phase and, thus, to change the final mechanical and functional properties.

A comparison of two different approaches to characterizing the heterogeneity within antisocial behavior: age-of-onset versus behavioral sub-types.

PubMed

Burt, S Alexandra; Hopwood, Christopher J

2010-04-01

There are two common approaches to sub-typing the well-documented heterogeneity within antisocial behavior: age-of-onset (i.e., child-onset versus adolescent-onset; see Moffitt, 1993) and behavioral (i.e., physical aggression versus nonaggressive rule-breaking). These approaches appear to be intimately connected, such that aggression is particularly characteristic of child-onset antisocial behavior whereas rule-breaking is largely specific to adolescent-onset antisocial behavior (see Moffitt, 2003). Even so, it remains unclear which approach, if either, substantively drives these different manifestations of antisocial behavior. We examined this question in a sample of 1,726 adults in treatment for alcoholism, evaluating the two approaches in regards to their prediction of anger and alcohol dependency. Although age-of-onset predicted both outcomes when analyzed alone, these associations fully dissipated once we controlled for aggression and rule-breaking. Such findings suggest that the behavioral sub-types may prove to be a stronger predictor of antisocial behavior outcomes than is age-of-onset.

Serrated Flow and Dynamic Strain Aging in Fe-Mn-C TWIP Steel

NASA Astrophysics Data System (ADS)

Lan, Peng; Zhang, Jiaquan

2018-01-01

The tensile behavior, serrated flow, and dynamic strain aging of Fe-(20 to 24)Mn-(0.4 to 0.6)C twinning-induced plasticity (TWIP) steel have been investigated. A mathematical approach to analyze the DSA and PLC band parameters has been developed. For Fe-(20 to 24)Mn-(0.4 to 0.6)C TWIP steel with a theoretical ordering index (TOI) between 0.1 and 0.3, DSA can occur at the very beginning of plastic deformation and provide serrations during work hardening, while for TOI less than 0.1 the occurrence of DSA is delayed and twinning-dominant work hardening remains relatively smooth. The critical strain for the onset of DSA and PLC bands in Fe-Mn-C TWIP steels decreases as C content increases, while the numbers of serrations and bands increase. As Mn content increases, the critical strain for DSA and PLC band varies irregularly, but the numbers of serrations and bands increase. For Fe-(20 to 24)Mn-(0.4 to 0.6)C TWIP steel with grain size of about 10 to 20 μm, the twinning-induced work hardening rate is about 2.5 to 3.0 GPa, while the DSA-dominant hardening rate is about 2.0 GPa on average. With increasing engineering strain from 0.01 to 0.55 at an applied strain rate of 0.001s-1, the cycle time for PLC bands in Fe-Mn-C TWIP steel increases from 6.5 to 162 seconds, while the band velocity decreases from 4.5 to 0.5 mm s-1, and the band strain increases from 0.005 to 0.08. Increasing applied strain rate leads to a linear increase of band velocity despite composition differences. In addition, the influence of the Mn and C content on the tensile properties of Fe-Mn-C TWIP steel has been also studied. As C content increases, the yield strength and tensile strength of Fe-Mn-C TWIP steel increase, but the total elongation variation against C content is dependent on Mn content. As Mn content increases, the yield strength and tensile strength decrease, while the total elongation increases, despite C content. Taking both tensile properties and serrated flow behavior into

Comparison of lead attenuation and lead hardening equivalence of materials used in respect of diagnostic X-ray shielding.

PubMed

Okunade, Akintunde Akangbe

2002-12-01

Present interest is in the shielding of diagnostic X-ray units. Numerical comparison has been made of the attenuation and hardening properties of lead and some particular alternative materials: steel, plate glass and gypsum wallboard. Results show, for particular choices of thickness, that lead and steel can be made to provide closely similar attenuation and spectral hardening, values of lead attenuation equivalent (LAE) and lead hardening equivalent (LHE) thicknesses being nearly the same. Significant differences in the attenuation and hardening properties of lead are found in comparison with plate glass and gypsum wallboard. LAE produces better matching of exposure for lead-plate glass and lead-gypsum wallboard than LHE.

Comparison of single and consecutive dual frequency induction surface hardening of gear wheels

NASA Astrophysics Data System (ADS)

Barglik, J.; Ducki, K.; Kukla, D.; Mizera, J.; Mrówka-Nowotnik, G.; Sieniawski, J.; Smalcerz, A.

2018-05-01

Mathematical modelling of single and consecutive dual - frequency induction surface hardening systems are presented and compared. The both models are solved by the 3D FEM-based professional software supported by a number of own numerical procedures. The methodology is illustrated with some examples of surface induction hardening of a gear wheel made of steel 41Cr4. The computations are in a good accordance with experiments provided on the laboratory stand.

A radiation-hardened, computer for satellite applications

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

Gaona, J.I. Jr.

1996-08-01

This paper describes high reliability radiation hardened computers built by Sandia for application aboard DOE satellite programs requiring 32 bit processing. The computers highlight a radiation hardened (10 kGy(Si)) R3000 executing up to 10 million reduced instruction set instructions (RISC) per second (MIPS), a dual purpose module control bus used for real-time default and power management which allows for extended mission operation on as little as 1.2 watts, and a local area network capable of 480 Mbits/s. The central processing unit (CPU) is the NASA Goddard R3000 nicknamed the ``Mongoose or Mongoose 1``. The Sandia Satellite Computer (SSC) uses Rational`smore » Ada compiler, debugger, operating system kernel, and enhanced floating point emulation library targeted at the Mongoose. The SSC gives Sandia the capability of processing complex types of spacecraft attitude determination and control algorithms and of modifying programmed control laws via ground command. And in general, SSC offers end users the ability to process data onboard the spacecraft that would normally have been sent to the ground which allows reconsideration of traditional space-grounded partitioning options.« less

Effects of moderate prenatal ethanol exposure and age on social behavior, spatial response perseveration errors and motor behavior

PubMed Central

Hamilton, Derek A.; Barto, Daniel; Rodriguez, Carlos I.; Magcalas, Christy; Fink, Brandi C.; Rice, James P.; Bird, Clark W.; Davies, Suzy; Savage, Daniel D.

2014-01-01

Persistent deficits in social behavior are among the major negative consequences associated with exposure to ethanol during prenatal development. Prior work from our laboratory has linked deficits in social behavior following moderate prenatal alcohol exposure (PAE) in the rat to functional alterations in the ventrolateral frontal cortex [21]. In addition to social behaviors, the regions comprising the ventrolateral frontal cortex are critical for diverse processes ranging from orofacial motor movements to flexible alteration of behavior in the face of changing consequences. The broader behavioral implications of altered ventrolateral frontal cortex function following moderate PAE have, however, not been examined. In the present study we evaluated the consequences of moderate PAE on social behavior, tongue protrusion, and flexibility in a variant of the Morris water task that required modification of a well-established spatial response. PAE rats displayed deficits in tongue protrusion, reduced flexibility in the spatial domain, increased wrestling, and decreased investigation, indicating that several behaviors associated with ventrolateral frontal cortex function are impaired following moderate PAE. A linear discriminant analysis revealed that measures of wrestling and tongue protrusion provided the best discrimination of PAE rats from saccharin-exposed control rats. We also evaluated all behaviors in young adult (4-5 mos.) or older (10-11 mos.) rats to address the persistence of behavioral deficits in adulthood and possible interactions between early ethanol exposure and advancing age. Behavioral deficits in each domain persisted well into adulthood (10-11 mos.), however, there was no evidence that age enhances the effects of moderate PAE within the age ranges that were studied. PMID:24769174

Maternal Depression Trajectories and Children's Behavior at Age 5 Years.

PubMed

van der Waerden, Judith; Galéra, Cédric; Larroque, Béatrice; Saurel-Cubizolles, Marie-Josèphe; Sutter-Dallay, Anne-Laure; Melchior, Maria

2015-06-01

To assess the relationship between trajectories of maternal depression from pregnancy to the child's age of 5 years and children's emotional and behavioral difficulties at age 5 years. Mother-child pairs (n = 1183) from the EDEN mother-child birth cohort study based in France were followed from 24 to 28 weeks of pregnancy to the child's fifth birthday. Children's behavior at age 5 years was assessed with the Strengths and Difficulties Questionnaire. Maternal depression was assessed repeatedly with the Center for Epidemiological Studies Depression questionnaire (pregnancy, 3, and 5 years of age) and the Edinburgh Postnatal Depression Scale (4, 8, and 12 months postpartum). Homogeneous latent trajectory groups of maternal depression were identified within the study population and correlated with Strengths and Difficulties Questionnaire scores by the use of multivariate linear regression analyzes. Five trajectories of maternal symptoms of depression were identified: no symptoms (62.0%); persistent intermediate-level depressive symptoms (25.3%); persistent high depressive symptoms (4.6%); high symptoms in pregnancy only (3.6%); and high symptoms in the child's preschool period only (4.6%). Children whose mothers had persistent depressive symptoms--either intermediate or high--had the greatest levels of emotional and behavioral difficulties at age 5 years. In addition, compared with children whose mothers were never depressed, those whose mothers had high symptoms in the preschool period also had increased levels of emotional symptoms, conduct problems, and peer problems. Maternal depression symptoms are related to children's emotional and behavioral problems, particularly if they are persistent (29.9%) or occur during early childhood (4.6%). Copyright © 2015 Elsevier Inc. All rights reserved.

Fiber-Reinforced Concrete For Hardened Shelter Construction

DTIC Science & Technology

1993-02-01

reduced cost and weight versus the symmetrically rebar reinforced beam design using normal-weight, standard-strength concrete currently used by the...while possibly reducing their cost and weight. Emphasis is placed on modular construction using prefabricated fiber- and rebar -reinforced concrete ...fiber- and rebar -reinforced concrete structural members into U.S. Air Force hardened structure designs. vii (The reverse of this page is blank) PREFACE

Health-Risk Behaviors among Persons Aged 12-21 Years: United States, 1992.

ERIC Educational Resources Information Center

Center for Disease Control (DHHS/PHS), Atlanta, GA.

Noting that health-risk behaviors among youth may result in immediate health problems or extend into adulthood and increase risk for chronic diseases, this report examines the prevalence of health-risk behaviors among a nationally representative sample of persons aged 12 to 21 years and presents age group comparisons of the most important…

Effect of micro-structural modifier on the morphology of silicon rich secondary phase and strain hardening behavior of eutectic Al-Si alloy

NASA Astrophysics Data System (ADS)

Mansoor, M.; Salam, I.; Tauqir, A.

2016-08-01

Eutectic Al-Si alloys find their applications in moderate to severe tribological conditions, for example: pistons, casings of high speed pumps and slide sleeves. The higher hardness, so the better tribological properties, are originated by the formation of a silicon rich secondary phase, however, the morphology of the secondary phase drastically influence the toughness of the alloy. Microstructural modifiers are used to control the toughness which modifies the Si rich secondary phase into dispersed spherical structure instead of needle-like network. In the present study, a mixture of chemical fluxes was used to modify the Si phase. The alloy was cast into a sand mold and characterized by scanning electron microscopy, energy dispersive spectroscopy, hardness testing and tensile testing. It was found that the morphology of the Si phase was altered to acicular structure due to the modification process. In comparison, the un-modified alloy contained Si phase in needle-like structure. The effect of modifier was also pronounced on the mechanical properties, where increase of 50% in yield strength, 56% in tensile strength and 200% in elongation occurred. A discernable raise in strain hardening component indicated the improved strain harden ability and formability of the modified alloy.

Features of surface phase formation during case-hardening of iron- and titanium-based alloys

NASA Astrophysics Data System (ADS)

Vintaikin, B. E.; Kamynin, A. V.; Kraposhin, V. S.; Smirnov, A. E.; Terezanova, K. V.; Cherenkova, S. A.; Sheykina, V. I.

2017-11-01

The article provides a detailed analysis of formation features for surface phases in technical iron and Cr20-Ni80 alloy samples that undergo case-hardening at a temperature of 850°C for 2, 4 and 6 hours of saturation in two different environments: acetylene, and molten salt consisting of sodium tetraborate and amorphous boron. We carried out an X-ray phase analysis to determine the phase structure of surface material layers that formed as a result of the case-hardening process. We discovered that after carburising it was possible to detect Fe3C and Fe-α phases on the surface of technical iron samples, and after boriding we found FeB, Fe2B and Fe3B phases; we noted a lack of characteristic Fe-α and Fe-γ peaks on the X-ray diffraction pattern. We detected many different phases in the Cr20-Ni80 alloy after the same type of case-hardening. Titanium oxides appeared after case-hardening of titanium in air at 800°C. We provide data on surface structure of samples subjected to vacuum carburising: over a 2 to 6 hour interval, the layer thickness is a parabolic function of time. When carrying out electrolysis-free liquid boriding, increasing exposure time from 2 to 6 hours alters the thickness of the strengthened layer only slightly, so, when carrying out case-hardening, it is less efficient to increase saturation time in molten salt containing sodium tetraborate and amorphous boron.

Hardening of ODS ferritic steels under irradiation with high-energy heavy ions

NASA Astrophysics Data System (ADS)

Ding, Z. N.; Zhang, C. H.; Yang, Y. T.; Song, Y.; Kimura, A.; Jang, J.

2017-09-01

Influence of the nanoscale oxide particles on mechanical properties and irradiation resistance of oxide-dispersion-strengthened (ODS) ferritic steels is of critical importance for the use of the material in fuel cladding or blanket components in advanced nuclear reactors. In the present work, impact of structures of oxide dispersoids on the irradiation hardening of ODS ferritic steels was studied. Specimens of three high-Cr ODS ferritic steels containing oxide dispersoids with different number density and average size were irradiated with high-energy Ni ions at about -50 °C. The energy of the incident Ni ions was varied from 12.73 MeV to 357.86 MeV by using an energy degrader at the terminal so that a plateau of atomic displacement damage (∼0.8 dpa) was produced from the near surface to a depth of 24 μm in the specimens. A nanoindentor (in constant stiffness mode with a diamond Berkovich indenter) and a Vickers micro-hardness tester were used to measure the hardeness of the specimens. The Nix-Gao model taking account of the indentation size effect (ISE) was used to fit the hardness data. It is observed that the soft substrate effect (SSE) can be diminished substantially in the irradiated specimens due to the thick damaged regions produced by the Ni ions. A linear correlation between the nano-hardeness and the micro-hardness was found. It is observed that a higher number density of oxide dispersoids with a smaller average diameter corresponds to an increased resistance to irradiation hardening, which can be ascribed to the increased sink strength of oxides/matrix interfaces to point defects. The rate equation approach and the conventional hardening model were used to analyze the influence of defect clusters on irradiation hardening in ODS ferritic steels. The numerical estimates show that the hardening caused by the interstitial type dislocation loops follows a similar trend with the experiment data.

7 CFR 58.622 - Hardening and storage rooms.

Code of Federal Regulations, 2012 CFR

2012-01-01

... of satisfactory material for this purpose. The rooms shall be maintained in a clean and orderly... 7 Agriculture 3 2012-01-01 2012-01-01 false Hardening and storage rooms. 58.622 Section 58.622... Specifications for Dairy Plants Approved for USDA Inspection and Grading Service 1 Rooms and Compartments § 58...

7 CFR 58.622 - Hardening and storage rooms.

Code of Federal Regulations, 2014 CFR

2014-01-01

... of satisfactory material for this purpose. The rooms shall be maintained in a clean and orderly... 7 Agriculture 3 2014-01-01 2014-01-01 false Hardening and storage rooms. 58.622 Section 58.622... Specifications for Dairy Plants Approved for USDA Inspection and Grading Service 1 Rooms and Compartments § 58...

An Evaluation of the Corrosion and Mechanical Performance of Interstitially Surface Hardened Stainless Steel

DTIC Science & Technology

2013-05-10

Performance of Interstitially Surface Hardened Stainless Steel 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) Jones, Jennifer Lynn...interstitial carbon atoms into stainless steel surfaces without the formation of carbides. Surface hardening of machine elements such as impellors or...the corrosion resistance of the stainless steel is retained, rather than degraded, is of particular interest for marine applications. This project

Impulse control and underlying functions of the left DLPFC mediate age-related and age-independent individual differences in strategic social behavior.

PubMed

Steinbeis, Nikolaus; Bernhardt, Boris C; Singer, Tania

2012-03-08

Human social exchange is often characterized by conflicts of interest requiring strategic behavior for their resolution. To investigate the development of the cognitive and neural mechanisms underlying strategic behavior, we studied children's decisions while they played two types of economic exchange games with differing demands of strategic behavior. We show an increase of strategic behavior with age, which could not be explained by age-related changes in social preferences but instead by developmental differences in impulsivity and associated brain functions of the left dorsolateral prefrontal cortex (DLPFC). Furthermore, observed differences in cortical thickness of lDLPFC were predictive of differences in impulsivity and strategic behavior irrespective of age. We conclude that egoistic behavior in younger children is not caused by a lack of understanding right or wrong, but by the inability to implement behavioral control when tempted to act selfishly; a function relying on brain regions maturing only late in ontogeny. Copyright © 2012 Elsevier Inc. All rights reserved.

Low-cycle fatigue behavior of NIMONIC PE16 at room temperature

NASA Astrophysics Data System (ADS)

Singh, V.; Sundararaman, M.; Chen, W.; Wahi, R. P.

1991-02-01

The fatigue behavior of NIMONIC PE16 has been investigated at room temperature as a function of γ' particle size (from 10 to 30 nm) and total strain amplitude (0.44 to 2.60 pct). All specimens initially harden and then soften on further deformation. The degrees of hardening and softening show a marked variation with γ' particle size and strain amplitude. Cyclic stress-strain and Coffin-Manson plots show a bilinear behavior with a change of slope at Δɛp/2, the plastic strain amplitude, of about 0.3 pct. These results are interpreted in terms of microstructural observations, namely, the number of slip systems activated and mutual interaction of dislocations on these systems, as well as their interaction with γ' particles.

Trajectories of externalizing behavior from age 2 to age 9: relations with gender, temperament, ethnicity, parenting, and rater.

PubMed

Miner, Jennifer L; Clarke-Stewart, K Alison

2008-05-01

Trajectories of children's externalizing behavior were examined using multilevel growth curve modeling of data from the NICHD Study of Early Child Care and Youth Development. According to ratings by both mothers and caregivers/teachers when children were 2, 3, 4, 7, and 9 years old, externalizing behavior declined with age. However, mothers rated children as higher in externalizing behavior than did caregivers and teachers. Higher levels of age 9 externalizing behavior were predicted by the following factors: child male gender (for caregiver/teacher reports only), infant difficult temperament (for children with harsh mothers only), harsher maternal attitude toward discipline, higher level of maternal depression (for maternal reports only), and lower level of maternal sensitivity (especially for boys). Caregivers and teachers reported higher levels of externalizing behavior in African American children than in European American children, increasingly so over time; mothers' ratings revealed the reverse. The declining slope of externalizing behavior was predicted by infant difficult temperament for mother reports only. Additional analyses suggested that the association between parenting and externalizing behavior was bidirectional. (PsycINFO Database Record (c) 2008 APA, all rights reserved).

Study on boring hardened materials dryly by ultrasonic vibration cutter

NASA Astrophysics Data System (ADS)

Zhang, Jiangzhong; Zhang, Heng; Zhang, Yue

2011-05-01

It has been one of the difficulties that high-precision hole on hardened materials is machined. The supersonic vibration boring acoustic system in the lathe in which supersonic wave energy is applied on tool is introduced to create pulse power on the cutting process. The separation vibration cutting is achieved by the pulse force. The comparative tests on boring accuracy and surface quality are carried. The quality of surface machined by this method is compared to that by grinding. This cutting is the green cutting. The boring process system is stability. Under the condition that the cutting speed is less than or equal to 1/3 the tool vibration speed, the cutting force is pulse force and the Cutting energy is of high concentration in time, space and direction. The pulse energy effects on the cutting unit in less than one ten-thousandth second. Traditional cutting of irregular movement elastic compression are eliminated. The cutting force is greatly reduced. The cutting temperature is at room temperature. The tool life is greatly increased. Shape precision and surface quality is greatly improved. The regulations of the ultrasonic vibration boring dry cutting of hardened material are also summarized. The test results show that the ultrasonic vibration cutting tool boring is of very superior cutting mechanism and is a high-precision deep-hole machining of hardened materials, efficient cutting methods.

Combined surface hardening and laser patterning approach for functionalising stainless steel surfaces

NASA Astrophysics Data System (ADS)

Garcia-Giron, A.; Romano, J. M.; Liang, Y.; Dashtbozorg, B.; Dong, H.; Penchev, P.; Dimov, S. S.

2018-05-01

The paper reports a laser patterning method for producing surfaces with dual scale topographies on ferritic stainless steel plates that are hardened by low temperature plasma surface alloying. Nitrogen and carbon based gasses were used in the alloying process to obtain surface layers with an increased hardness from 172 HV to 1001 HV and 305 HV, respectively. Then, a nanosecond infrared laser was used to pattern the plasma treated surfaces and thus to obtain super-hydrophobicity, by creating cell- or channel-like surface structures. The combined surface hardening and laser patterning approach allowed super-hydrophobic surfaces to be produced on both nitrided and carburised stainless steel plates with effective contact angles higher than 150°. The hardened layers on nitrided samples had cracks and was delaminated after the laser patterning while on plasma carburised samples remained intact. The results showed that by applying the proposed combined approach it is possible to retain the higher hardness of the nitrided stainless steel plates and at the same time to functionalise them to obtain super-hydrophobic properties.

Kids, Candy, Brain and Behavior: Age Differences in Responses to Candy Gains and Losses

PubMed Central

Luking, Katherine R; Luby, Joan; Barch, Deanna M

2014-01-01

The development of reward-related neural systems, from adolescence through adulthood, has received much recent attention in the developmental neuroimaging literature. However, few studies have investigated behavioral and neural responses to both gains and losses in pre-pubertal child populations. To address this gap in the literature, in the present study healthy children aged 7–11 years and young-adults completed an fMRI card-guessing game using candy pieces delivered post-scan as an incentive. Age differences in behavioral and neural responses to candy gains/losses were investigated. Adults and children displayed similar responses to gains, but robust age differences were observed following candy losses within the caudate, thalamus, insula, and hippocampus. Interestingly, when task behavior was included as a factor in post-hoc mediation analyses, activation following loss within the caudate/thalamus related to task behavior and relationships with age were no longer significant. Conversely, relationships between response to loss and age within the hippocampus and insula remained significant even when controlling for behavior, with children showing heightened loss responses within the dorsal/posterior insula. These results suggest that both age and task behavior influence responses within the extended reward circuitry, and that children seem to be more sensitive than adults to loss feedback particularly within the dorsal/posterior insula. PMID:24534632

Development of Ballistic Protection Based on Precipitation-Hardened Composite Material

NASA Astrophysics Data System (ADS)

Chernyshov, E. A.; Romanov, A. D.; Romanova, E. A.; Myl'nikov, V. V.

2018-03-01

The possibility of application of an aluminum-based precipitation-hardened composite material for purposes of ballistic protection is considered. Experimental data on A6 aluminum-based alloy reinforced with alumina particles are presented.

A Combined Precipitation, Yield Stress, and Work Hardening Model for Al-Mg-Si Alloys Incorporating the Effects of Strain Rate and Temperature

NASA Astrophysics Data System (ADS)

Myhr, Ole Runar; Hopperstad, Odd Sture; Børvik, Tore

2018-05-01

In this study, a combined precipitation, yield strength, and work hardening model for Al-Mg-Si alloys known as NaMo has been further developed to include the effects of strain rate and temperature on the resulting stress-strain behavior. The extension of the model is based on a comprehensive experimental database, where thermomechanical data for three different Al-Mg-Si alloys are available. In the tests, the temperature was varied between 20 °C and 350 °C with strain rates ranging from 10-6 to 750 s-1 using ordinary tension tests for low strain rates and a split-Hopkinson tension bar system for high strain rates, respectively. This large span in temperatures and strain rates covers a broad range of industrial relevant problems from creep to impact loading. Based on the experimental data, a procedure for calibrating the different physical parameters of the model has been developed, starting with the simplest case of a stable precipitate structure and small plastic strains, from which basic kinetic data for obstacle limited dislocation glide were extracted. For larger strains, when work hardening becomes significant, the dynamic recovery was linked to the Zener-Hollomon parameter, again using a stable precipitate structure as a basis for calibration. Finally, the complex situation of concurrent work hardening and dynamic evolution of the precipitate structure was analyzed using a stepwise numerical solution algorithm where parameters representing the instantaneous state of the structure were used to calculate the corresponding instantaneous yield strength and work hardening rate. The model was demonstrated to exhibit a high degree of predictive power as documented by a good agreement between predictions and measurements, and it is deemed well suited for simulations of thermomechanical processing of Al-Mg-Si alloys where plastic deformation is carried out at various strain rates and temperatures.

Monitoring of hardening and hygroscopic induced strains in a calcium phosphate bone cement using FBG sensor.

PubMed

Bimis, A; Karalekas, D; Bouropoulos, N; Mouzakis, D; Zaoutsos, S

2016-07-01

This study initially deals with the investigation of the induced strains during hardening stage of a self-setting calcium phosphate bone cement using fiber-Bragg grating (FBG) optical sensors. A complementary Scanning Electron Microscopy (SEM) investigation was also conducted at different time intervals of the hardening period and its findings were related to the FBG recordings. From the obtained results, it is demonstrated that the FBG response is affected by the microstructural changes taking place when the bone cement is immersed into the hardening liquid media. Subsequently, the FBG sensor was used to monitor the absorption process and hygroscopic response of the hardened and dried biocement when exposed to a liquid/humid environment. From the FBG-based calculated hygric strains as a function of moisture concentration, the coefficient of moisture expansion (CME) of the examined bone cement was obtained, exhibiting two distinct linear regions. Copyright © 2016 Elsevier Ltd. All rights reserved.

Low temperature tolerance, cold hardening and acclimation in tadpoles of the neotropical túngara frog (Engystomops pustulosus).

PubMed

Vo, Pacific; Gridi-Papp, Marcos

2017-05-01

Many frogs from temperate climates can tolerate low temperatures and increase their thermal tolerance through hardening and acclimation. Most tropical frogs, on the other hand, fail to acclimate to low temperatures. This lack of acclimation ability is potentially due to lack of selection pressure for acclimation because cold weather is less common in the tropics. We tested the generality of this pattern by characterizing the critical temperature minimum (CTMin), hardening, and acclimation responses of túngara frogs (Engystomops pustulosus). These frogs belong to a family with unknown thermal ecology. They are found in a tropical habitat with a highly constant temperature regime. The CTMin of the tadpoles was on average 12.5°C. Pre-metamorphic tadpoles hardened by 1.18°C, while metamorphic tadpoles hardened by 0.36°C. When raised at 21°C, tadpoles acclimated expanding their cold tolerance by 1.3°C in relation to larvae raised at 28°C. These results indicate that the túngara frog has a greatly reduced cold tolerance when compared to species from temperate climates, but it responds to cold temperatures with hardening and acclimation comparable to those of temperate-zone species. Cold tolerance increased with body length but cold hardening was more extensive in pre-metamorphic tadpoles than in metamorphic ones. This study shows that lack of acclimation ability is not general to the physiology of tropical anurans. Copyright © 2017 Elsevier Ltd. All rights reserved.

Experimental validation of plastic constitutive hardening relationship based upon the direction of the Net Burgers Density Vector

NASA Astrophysics Data System (ADS)

Sarac, Abdulhamit; Kysar, Jeffrey W.

2018-02-01

We present a new methodology for experimental validation of single crystal plasticity constitutive relationships based upon spatially resolved measurements of the direction of the Net Burgers Density Vector, which we refer to as the β-field. The β-variable contains information about the active slip systems as well as the ratios of the Geometrically Necessary Dislocation (GND) densities on the active slip systems. We demonstrate the methodology by comparing single crystal plasticity finite element simulations of plane strain wedge indentations into face-centered cubic nickel to detailed experimental measurements of the β-field. We employ the classical Peirce-Asaro-Needleman (PAN) hardening model in this study due to the straightforward physical interpretation of its constitutive parameters that include latent hardening ratio, initial hardening modulus and the saturation stress. The saturation stress and the initial hardening modulus have relatively large influence on the β-variable compared to the latent hardening ratio. A change in the initial hardening modulus leads to a shift in the boundaries of plastic slip sectors with the plastically deforming region. As the saturation strength varies, both the magnitude of the β-variable and the boundaries of the plastic slip sectors change. We thus demonstrate that the β-variable is sensitive to changes in the constitutive parameters making the variable suitable for validation purposes. We identify a set of constitutive parameters that are consistent with the β-field obtained from the experiment.

Working, sex partner age differences, and sexual behavior among African American youth.

PubMed

Bauermeister, José A; Zimmerman, Marc; Xue, Yange; Gee, Gilbert C; Caldwell, Cleopatra H

2009-10-01

Participation in the workplace has been proposed as a potential structural-level HIV/STI prevention strategy for youth. Only a few cross-sectional studies have explored the effect of work during adolescence and young adulthood on sexual behavior and their results have been mixed. This study builds on this literature by exploring whether work influences youths' sexual behavior in a cohort of African American youth (N = 562; 45% males; M = 14.5 years, SD = 0.6) followed from adolescence to young adulthood (ages 13-25 years). Using growth curve modeling, we tested whether working was associated with older sex partners. Then, we explored the association between sex partner age differences and sexual behaviors (i.e., number of sex partners, condom use, and frequency of sexual intercourse). Finally, we tested whether the relationship between sex partner age differences and sexual behaviors was confounded by working. Working greater number of hours was not significantly associated with having older sex partners. Sex partner age differences was associated with number of partners, condom use, and higher sex frequency. These associations were larger for females. Working was associated with higher sex frequency, after accounting for age differences. We discuss the implications of these findings for future research and program planning, particularly in the context of youth development programs.

Efficient simulation of press hardening process through integrated structural and CFD analyses

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

Palaniswamy, Hariharasudhan; Mondalek, Pamela; Wronski, Maciek

Press hardened steel parts are being increasingly used in automotive structures for their higher strength to meet safety standards while reducing vehicle weight to improve fuel consumption. However, manufacturing of sheet metal parts by press hardening process to achieve desired properties is extremely challenging as it involves complex interaction of plastic deformation, metallurgical change, thermal distribution, and fluid flow. Numerical simulation is critical for successful design of the process and to understand the interaction among the numerous process parameters to control the press hardening process in order to consistently achieve desired part properties. Until now there has been no integratedmore » commercial software solution that can efficiently model the complete process from forming of the blank, heat transfer between the blank and tool, microstructure evolution in the blank, heat loss from tool to the fluid that flows through water channels in the tools. In this study, a numerical solution based on Altair HyperWorks® product suite involving RADIOSS®, a non-linear finite element based structural analysis solver and AcuSolve®, an incompressible fluid flow solver based on Galerkin Least Square Finite Element Method have been utilized to develop an efficient solution for complete press hardening process design and analysis. RADIOSS is used to handle the plastic deformation, heat transfer between the blank and tool, and microstructure evolution in the blank during cooling. While AcuSolve is used to efficiently model heat loss from tool to the fluid that flows through water channels in the tools. The approach is demonstrated through some case studies.« less

Age Differences and Changes of Coping Behavior in Three Age Groups: Findings from the Georgia Centenarian Study

ERIC Educational Resources Information Center

Martin, Peter; Kliegel, Matthias; Rott, Christoph; Poon, Leonard W.; Johnson, Mary Ann

2008-01-01

With increasing age, older adults are more likely to be challenged by an increasing number of physical, functional and social losses. As a result, coping with losses becomes a central theme in very late life. This study investigated age differences and age changes in active behavioral, active cognitive and avoidance coping and related coping to…

[A prospective cohort study on injuries among school-age children with and without behavior problems].

PubMed

Peng, Ying-chun; Ni, Jin-fa; Tao, Fang-biao; Wu, Xi-ke

2003-08-01

To study the annual incidence of injuries and the relationship between behavior problems and injuries among school-age children. A prospective cohort study on injuries for 1-year follow-up period was conducted among 2 005 school-age children selected by cluster sampling from three primary schools in Maanshan city. They subjects were divided into two groups with or without exposure according to behavior problems rated by the Rutter Child Behavior Questionnaire at the beginning of the study. Nonparametric test was performed to analyze the differences in injuries between the two groups of children, and the influential factors for injuries were analyzed with multi-classification ordinal response variable logistic regression model. The overall incidence rate for injuries in school-age children was 42.51%, while among children with and without behavior problems were 64.87% and 38.85%, respectively. There were significant differences between the two groups (u = -6.054, P = 0.000). However, the incidence rates of injuries in school-age children with antisocial (A) behavior, neurotic (N) behavior and mixed (M) behavior were 66.99%, 67.41% and 61.40%, respectively. No significant differences were found among them (u(A,N) = -0.052, P = 0.958; u(A,M) = -0.400, P = 0.689; u(N,M) = -0.364, P = 0.716). Multivariate analysis indicated that injuries in school-age children were associated with children behavior problems, maternal age at childbirth, bad conditions during mother pregnancy, education background of mother, prevention measures for safety at home and the child accompanied to travel between school and home by adults. Behavior problems of children seemed to be the major risk factors for injuries. Children with behavior problems represented a significant risk group for injuries among school-age children. When planning intervention strategies on injuries, behavior problems should be emphasized to ensure optimal effectiveness of intervention.

Induction Hardening of External Gear

NASA Astrophysics Data System (ADS)

Bukanin, V. A.; Ivanov, A. N.; Zenkov, A. E.; Vologdin, V. V.; Vologdin, V. V., Jr.

2018-03-01

Problems and solution of gear induction hardening are described. Main attention is paid to the parameters of heating and cooling systems. ELTA 7.0 program has been used to obtain the required electrical parameters of inductor, power sources, resonant circuits, as well as to choose the quenching media. Comparison of experimental and calculated results of investigation is provided. In order to compare advantages and disadvantages of single- and dual-frequency heating processes, many variants of these technologies were simulated. The predicted structure and hardness of steel gears are obtained by use of the ELTA data base taken into account the Continuous Cooling Transformation diagrams.

DISPERSION HARDENING OF URANIUM METAL

DOEpatents

Arbiter, W.

1963-01-15

A method of hardening U metal involves the forming of a fine dispersion of UO/sub 2/. This method consists of first hydriding the U to form a finely divided powder and then exposing the powder to a very dilute O gas in an inert atmosphere under such pressure and temperature conditions as to cause a thin oxide film to coat each particle of the U hydride, The oxide skin prevents agglomeration of the particles as the remaining H is removed, thus preserving the small particle size. The oxide skin coatings remain as an oxide dispersion. The resulting product may be workhardened to improve its physical characteristics. (AEC)

Reward components of feeding behavior are preserved during mouse aging

PubMed Central

Harb, Mazen R.; Sousa, Nuno; Zihl, Joseph; Almeida, Osborne F. X.

2014-01-01

Eating behavior depends on associations between the sensory and energetic properties of foods. Healthful balance of these factors is a challenge for industrialized societies that have an abundance of food, food choices and food-related cues. Here, we were interested in whether appetitive conditioning changes as a function of age. Operant and pavlovian conditioning experiments (rewarding stimulus was a palatable food) in male mice (aged 3, 6, and 15 months) showed that implicit (non-declarative) memory remains intact during aging. Two other essential components of eating behavior, motivation and hedonic preference for rewarding foods, were also found not to be altered in aging mice. Specifically, hedonic responding by satiated mice to isocaloric foods of differing sensory properties (sucrose, milk) was similar in all age groups; importantly, however, this paradigm disclosed that older animals adjust their energy intake according to energetic need. Based on the assumption that the mechanisms that control feeding are conserved across species, it would appear that overeating and obesity in humans reflects a mismatch between ancient physiological mechanisms and today's cue-laden environment. The implication of the present results showing that aging does not impair the ability to learn stimulus-food associations is that the risk of overeating in response to food cues is maintained through to old age. PMID:25278876

Reward components of feeding behavior are preserved during mouse aging.

PubMed

Harb, Mazen R; Sousa, Nuno; Zihl, Joseph; Almeida, Osborne F X

2014-01-01

Eating behavior depends on associations between the sensory and energetic properties of foods. Healthful balance of these factors is a challenge for industrialized societies that have an abundance of food, food choices and food-related cues. Here, we were interested in whether appetitive conditioning changes as a function of age. Operant and pavlovian conditioning experiments (rewarding stimulus was a palatable food) in male mice (aged 3, 6, and 15 months) showed that implicit (non-declarative) memory remains intact during aging. Two other essential components of eating behavior, motivation and hedonic preference for rewarding foods, were also found not to be altered in aging mice. Specifically, hedonic responding by satiated mice to isocaloric foods of differing sensory properties (sucrose, milk) was similar in all age groups; importantly, however, this paradigm disclosed that older animals adjust their energy intake according to energetic need. Based on the assumption that the mechanisms that control feeding are conserved across species, it would appear that overeating and obesity in humans reflects a mismatch between ancient physiological mechanisms and today's cue-laden environment. The implication of the present results showing that aging does not impair the ability to learn stimulus-food associations is that the risk of overeating in response to food cues is maintained through to old age.

Privacy and human behavior in the age of information.

PubMed

Acquisti, Alessandro; Brandimarte, Laura; Loewenstein, George

2015-01-30

This Review summarizes and draws connections between diverse streams of empirical research on privacy behavior. We use three themes to connect insights from social and behavioral sciences: people's uncertainty about the consequences of privacy-related behaviors and their own preferences over those consequences; the context-dependence of people's concern, or lack thereof, about privacy; and the degree to which privacy concerns are malleable—manipulable by commercial and governmental interests. Organizing our discussion by these themes, we offer observations concerning the role of public policy in the protection of privacy in the information age. Copyright © 2015, American Association for the Advancement of Science.

Maternal depressive symptoms and child care during toddlerhood relate to child behavior at age 5 years.

PubMed

Giles, Lynne C; Davies, Michael J; Whitrow, Melissa J; Warin, Megan J; Moore, Vivienne

2011-07-01

Disentangling the effects of maternal depression in toddlerhood from concurrent maternal depression on child behavior is difficult from previous research. Child care may modify any effects of maternal depression on subsequent child behavior, but this has not been widely investigated. We examined the influence of maternal depressive symptoms during toddlerhood on children's behavior at the age of 5 years and investigated if formal or informal child care during toddlerhood modified any relationship observed. Data were available from 438 mothers and their children (227 girls and 211 boys); the mothers who completed questionnaires during the children's infancy, in toddlerhood, and at the age of 5 years. Recurrent maternal depressive symptoms in toddlerhood (when study children were aged 2 and 3½ years) was a significant risk factor for internalizing, externalizing, and total behavior problems when children were aged 5 years. Intermittent maternal depressive symptoms (study child age 2 or 3½ years) did not significantly affect child behavior problems. Formal child care at the age of 2 years modified the effect of recurrent maternal depressive symptoms on total behavior problems at age 5 years. Informal child care in toddlerhood did not significantly affect child behavior problems. Recurrent, but not intermittent, maternal depressive symptoms when children were toddlers were associated with child behavior problems at age 5 years. As little as half a day in formal child care at the age of 2 years significantly modified the effect of recurrent maternal depressive symptoms on total behavior problems. Formal child care for toddlers of depressed mothers may have positive benefits for the child's subsequent behavior. Copyright © 2011 by the American Academy of Pediatrics.

Cognitive functioning and its influence on sexual behavior in normal aging and dementia.

PubMed

Hartmans, Carien; Comijs, Hannie; Jonker, Cees

2014-05-01

Motivational aspects, emotional factors, and cognition, all of which require intact cognitive functioning may be essential in sexual functioning. However, little is known about the association between cognitive functioning and sexual behavior. The aim of this article is to review the current evidence for the influence of cognitive functioning on sexual behavior in normal aging and dementia. A systematic literature search was conducted in PubMed, Ovid, Cochrane, and PsycINFO databases. The databases were searched for English language papers focusing on human studies published relating cognitive functioning to sexual behavior in the aging population. Keywords included sexual behavior, sexuality, cognitive functioning, healthy elderly, elderly, aging and dementia. Eight studies fulfilled our inclusion criteria. Of these studies, five included dementia patients and/or their partners, whereas only three studies included healthy older persons. Although not consistently, results indicated a trend that older people who are not demented and continue to engage in sexual activity have better overall cognitive functioning. Cognitive decline and dementia seem to be associated with diminished sexual behavior in older persons. The association between cognitive functioning and sexual behavior in the aging population is understudied. The results found are inconclusive. Copyright © 2013 John Wiley & Sons, Ltd.

Prediction of the bending behavior after pre-strain of an aluminum alloy

NASA Astrophysics Data System (ADS)

Pradeau, A.; Thuillier, S.; Yoon, J. W.

2016-10-01

The present work is focused on the modeling of sheet metal mechanical behavior up to rupture, including anisotropy and hardening. The mechanical behavior of an AA6016 alloy was characterized at room temperature in tension, simple shear and hydraulic bulging. The initial anisotropy was described with the Yld2004-18p yield criterion coupled to a mixed hardening law. Concerning rupture, an uncoupled phenomenological criterion of Mohr-Coulomb type will be used. For the material parameter identification, an inverse methodology was used with the objective of reducing the gap between experimental and numerical data. Finally, validation of the results was performed on bending tests with different amplitudes of tension pre-strain in order to reach or not rupture in the bent area.

Aging and loading rate effects on the mechanical behavior of equine bone

NASA Astrophysics Data System (ADS)

Kulin, Robb M.; Jiang, Fengchun; Vecchio, Kenneth S.

2008-06-01

Whether due to a sporting accident, high-speed impact, fall, or other catastrophic event, the majority of clinical bone fractures occur under dynamic loading conditions. However, although extensive research has been performed on the quasi-static fracture and mechanical behavior of bone to date, few high-quality studies on the fracture behavior of bone at high strain rates have been performed. Therefore, many questions remain regarding the material behavior, including not only the loading-rate-dependent response of bone, but also how this response varies with age. In this study, tests were performed on equine femoral bone taken post-mortem from donors 6 months to 28 years of age. Quasi-static and dynamic tests were performed to determine the fracture toughness and compressive mechanical behavior as a function of age at varying loading rates. Fracture paths were then analyzed using scanning confocal and scanning-electron microscopy techniques to assess the role of various microstructural features on toughening mechanisms.

Kids, candy, brain and behavior: age differences in responses to candy gains and losses.

PubMed

Luking, Katherine R; Luby, Joan L; Barch, Deanna M

2014-07-01

The development of reward-related neural systems, from adolescence through adulthood, has received much recent attention in the developmental neuroimaging literature. However, few studies have investigated behavioral and neural responses to both gains and losses in pre-pubertal child populations. To address this gap in the literature, in the present study healthy children aged 7-11 years and young-adults completed an fMRI card-guessing game using candy pieces delivered post-scan as an incentive. Age differences in behavioral and neural responses to candy gains/losses were investigated. Adults and children displayed similar responses to gains, but robust age differences were observed following candy losses within the caudate, thalamus, insula, and hippocampus. Interestingly, when task behavior was included as a factor in post hoc mediation analyses, activation following loss within the caudate/thalamus related to task behavior and relationships with age were no longer significant. Conversely, relationships between response to loss and age within the hippocampus and insula remained significant even when controlling for behavior, with children showing heightened loss responses within the dorsal/posterior insula. These results suggest that both age and task behavior influence responses within the extended reward circuitry, and that children seem to be more sensitive than adults to loss feedback particularly within the dorsal/posterior insula. Copyright © 2014 The Authors. Published by Elsevier Ltd.. All rights reserved.

Irradiation hardening of pure tungsten exposed to neutron irradiation

DOE PAGES

Hu, Xunxiang; Koyanagi, Takaaki; Fukuda, Makoto; ...

2016-08-26

In this paper, pure tungsten samples have been neutron irradiated in HFIR at 90–850 °C to 0.03–2.2 dpa. A dispersed barrier hardening model informed by the available microstructure data has been used to predict the hardness. Comparison of the model predictions and the measured Vickers hardness reveals the dominant hardening contribution at various irradiation conditions. For tungsten samples irradiated in HFIR, the results indicate that voids and dislocation loops contributed to the hardness increase in the low dose region (<0.3 dpa), while the formation of intermetallic second phase precipitation, resulting from transmutation, dominates the radiation-induced strengthening beginning with a relativelymore » modest dose (>0.6 dpa). Finally, the precipitate contribution is most pronounced for the HFIR irradiations, whereas the radiation-induced defect cluster microstructure can rationalize the entirety of the hardness increase observed in tungsten irradiated in the fast neutron spectrum of Joyo and the mixed neutron spectrum of JMTR.« less

Work-Hardening Induced Tensile Ductility of Bulk Metallic Glasses via High-Pressure Torsion

PubMed Central

Joo, Soo-Hyun; Pi, Dong-Hai; Setyawan, Albertus Deny Heri; Kato, Hidemi; Janecek, Milos; Kim, Yong Chan; Lee, Sunghak; Kim, Hyoung Seop

2015-01-01

The mechanical properties of engineering materials are key for ensuring safety and reliability. However, the plastic deformation of BMGs is confined to narrow regions in shear bands, which usually result in limited ductilities and catastrophic failures at low homologous temperatures. The quasi-brittle failure and lack of tensile ductility undercut the potential applications of BMGs. In this report, we present clear tensile ductility in a Zr-based BMG via a high-pressure torsion (HPT) process. Enhanced tensile ductility and work-hardening behavior after the HPT process were investigated, focusing on the microstructure, particularly the changed free volume, which affects deformation mechanisms (i.e., initiation, propagation, and obstruction of shear bands). Our results provide insights into the basic functions of hydrostatic pressure and shear strain in the microstructure and mechanical properties of HPT-processed BMGs. PMID:25905686

Work Hardening, Dislocation Structure, and Load Partitioning in Lath Martensite Determined by In Situ Neutron Diffraction Line Profile Analysis

NASA Astrophysics Data System (ADS)

Harjo, Stefanus; Kawasaki, Takuro; Tomota, Yo; Gong, Wu; Aizawa, Kazuya; Tichy, Geza; Shi, Zengmin; Ungár, Tamas

2017-09-01

A lath martensite steel containing 0.22 mass pct carbon was analyzed in situ during tensile deformation by high-resolution time-of-flight neutron diffraction to clarify the large work-hardening behavior at the beginning of plastic deformation. The diffraction peaks in plastically deformed states exhibit asymmetries as the reflection of redistributions of the stress and dislocation densities/arrangements in two lath packets: soft packet, where the dislocation glides are favorable, and hard packet, where they are unfavorable. The dislocation density was as high as 1015 m-2 in the as-heat-treated state. During tensile straining, the load and dislocation density became different between the two lath packets. The dislocation character and arrangement varied in the hard packet but hardly changed in the soft packet. In the hard packet, dislocations that were mainly screw-type in the as-heat-treated state became primarily edge-type and rearranged towards a dipole character related to constructing cell walls. The hard packet played an important role in the work hardening in martensite, which could be understood by considering the increase in dislocation density along with the change in dislocation arrangement.

Properties of Shock Hardened 7050 Aluminum Alloy.

DTIC Science & Technology

1981-11-12

AD-ALO 887 NAVAL AIR DEVELOPMENT CENTER WARMINSTER PA AIRCRAFT -ETC F/6 11/6 PROPERTIES OF SHOCK HARDENED 7050 ALUMINUM ALLOT. (UI NOV 81 C E NEU...Systems Technology Directorate NAVAL AIR DEVELOPMENT CENTER Warminster, Pennsylvania 18974 12 NOV 1981 PHASE REPORT AIRTASK NO. WF54591201 :3l’ Work Unit...No. ZMIOI )** >,,, A APPROVED FOR PUBLIC RELEASE;DISTRIBUTION UNLIMITED Prepared forg NAVAL AIR SYSTEMS COMMAND Department of the Navy Washington, D.C

Behavioral health needs and problem recognition by older adults receiving home-based aging services.

PubMed

Gum, Amber M; Petkus, Andrew; McDougal, Sarah J; Present, Melanie; King-Kallimanis, Bellinda; Schonfeld, Lawrence

2009-04-01

Older adults' recognition of a behavioral health need is one of the strongest predictors of their use of behavioral health services. Thus, study aims were to examine behavioral health problems in a sample of older adults receiving home-based aging services, their recognition of behavioral health problems, and covariates of problem recognition. The study design was cross-sectional. Older adults (n = 141) receiving home-based aging services completed interviews that included: Structured Clinical Interview for DSM-IV; Brief Symptom Inventory-18; attitudinal scales of stigma, expectations regarding aging, and thought suppression; behavioral health treatment experience; and questions about recognition of behavioral health problems. Thirty (21.9%) participants received an Axis I diagnosis (depressive, anxiety, or substance); another 17 (12.1%) were diagnosed with an adjustment disorder. Participants were more likely to recognize having a problem if they had an Axis I diagnosis, more distress on the BSI-18, family member or friend with a behavioral health problem, and greater thought suppression. In logistic regression, participants who identified a family member or friend with a behavioral health problem were more likely to identify having a behavioral health problem themselves. Findings suggest that older adults receiving home-based aging services who recognize behavioral health problems are more likely to have a psychiatric diagnosis or be experiencing significant distress, and they are more familiar with behavioral health problems in others. This familiarity may facilitate treatment planning; thus, older adults with behavioral health problems who do not report familiarity of problems in others likely require additional education. (c) 2008 John Wiley & Sons, Ltd.

Softening due to Grain Boundary Cavity Formation and its Competition with Hardening in Helium Implanted Nanocrystalline Tungsten

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

Cunningham, W. Streit; Gentile, Jonathan M.; El-Atwani, Osman

The unique ability of grain boundaries to act as effective sinks for radiation damage plays a significant role in nanocrystalline materials due to their large interfacial area per unit volume. Leveraging this mechanism in the design of tungsten as a plasma-facing material provides a potential pathway for enhancing its radiation tolerance under fusion-relevant conditions. In this study, we explore the impact of defect microstructures on the mechanical behavior of helium ion implanted nanocrystalline tungsten through nanoindentation. Softening was apparent across all implantation temperatures and attributed to bubble/cavity loaded grain boundaries suppressing the activation barrier for the onset of plasticity viamore » grain boundary mediated dislocation nucleation. An increase in fluence placed cavity induced grain boundary softening in competition with hardening from intragranular defect loop damage, thus signaling a new transition in the mechanical behavior of helium implanted nanocrystalline tungsten.« less

Softening due to Grain Boundary Cavity Formation and its Competition with Hardening in Helium Implanted Nanocrystalline Tungsten

DOE PAGES

Cunningham, W. Streit; Gentile, Jonathan M.; El-Atwani, Osman; ...

2018-02-13

The unique ability of grain boundaries to act as effective sinks for radiation damage plays a significant role in nanocrystalline materials due to their large interfacial area per unit volume. Leveraging this mechanism in the design of tungsten as a plasma-facing material provides a potential pathway for enhancing its radiation tolerance under fusion-relevant conditions. In this study, we explore the impact of defect microstructures on the mechanical behavior of helium ion implanted nanocrystalline tungsten through nanoindentation. Softening was apparent across all implantation temperatures and attributed to bubble/cavity loaded grain boundaries suppressing the activation barrier for the onset of plasticity viamore » grain boundary mediated dislocation nucleation. An increase in fluence placed cavity induced grain boundary softening in competition with hardening from intragranular defect loop damage, thus signaling a new transition in the mechanical behavior of helium implanted nanocrystalline tungsten.« less

Violent television viewing during preschool is associated with antisocial behavior during school age.

PubMed

Christakis, Dimitri A; Zimmerman, Frederick J

2007-11-01

The effect of violent television programming on preschoolers' behaviors is poorly understood. The objective of this study was to test the hypothesis that exposure to violent television viewing when children are 2 to 5 years of age would be associated with antisocial behavior at ages 7 to 10. Data were derived from the Panel Study of Income Dynamics. Our primary outcome was being in the 88th percentile of the Behavioral Problem Index antisocial subdomain. Our primary predictor was exposure to violent screen content. Data were available for 184 boys and 146 girls at both time periods. Adjusting for baseline Behavioral Problem Index scores and age, parental education, maternal depression, and cognitive and emotional support, violent television programming was associated with an increased risk for antisocial behavior for boys but not for girls. Neither educational nor nonviolent programming was associated with increased risk for boys or girls. Viewing of violent programming by preschool boys is associated with subsequent aggressive behavior. Modifying the content that is viewed by young children may be warranted.

Low-Cycle Fatigue Behavior of Die-Cast Mg Alloy AZ91

NASA Astrophysics Data System (ADS)

Rettberg, Luke; Anderson, Warwick; Jones, J. Wayne

An investigation has been conducted on the influence of microstructure and artificial aging response (T6) on the low-cycle fatigue behavior of super vacuum die-cast (SVDC) AZ91. Fatigue lifetimes were determined from total strain-controlled fatigue tests for strain amplitudes of 0.2%, 0.4% and 0.6%, under fully reversed loading at a frequency of 5 Hz. Cyclic stress-strain behavior was determined using incremental step test (IST) methods. Two locations in a prototype casting with different thicknesses and, therefore, solidification rates, microstructure and porosity, were examined. In general., at all total strain amplitudes fatigue life was unaffected by microstructure refinement and was attributed to significant levels of porosity. Cyclic softening and a subsequent increased cyclic hardening rate, compared to monotonic tests, were observed, independent of microstructure. These results, fractography and damage accumulation processes, determined from metallographic sectioning, are discussed.

Influences of Steelmaking Slags on Hydration and Hardening of Concretes

NASA Astrophysics Data System (ADS)

Kirsanova, A. A.; Dildin, A. N.; Maksimov, S. P.

2017-11-01

It is shown that the slag of metallurgical production can be used in the construction industry as an active mineral additive for concrete. This approach allows us to solve environmental problems and reduce costs for the production of binder and concrete simultaneously. Most often slag is used in the form of a filler, an active mineral additive or as a part of a binder for artificial conglomerates. The introduction of slag allows one to notice a part of the cement, to obtain concretes that are more resistant to the impact of aggressive sulfate media. The paper shows the possibility of using recycled steel-smelting slags in the construction industry for the production of cement. An assessment was made of their effect on the hydration of the cement stone and hardening of the concrete together with the plasticizer under normal conditions. In the process of work, we used the slag of the Zlatoust Electrometallurgical Factory. Possible limitations of the content of steel-slag slag in concrete because of the possible presence of harmful impurities are shown. It is necessary to enter slag in conjunction with superplasticizers to reduce the flow of water mixing. Slags can be used as a hardening accelerator for cement concrete as they allow one to increase the degree of cement hydration and concrete strength. It is shown that slags can be used to produce fast-hardening concretes and their comparative characteristics with other active mineral additives are given.

Working, Sex Partner Age Differences, and Sexual Behavior among African American Youth

PubMed Central

Bauermeister, José A.; Zimmerman, Marc; Xue, Yange; Gee, Gilbert C.; Caldwell, Cleopatra H.

2009-01-01

Participation in the workplace has been proposed as a potential structural-level HIV/STI prevention strategy for youth. Only a few cross-sectional studies have explored the effect of work during adolescence and young adulthood on sexual behavior and their results have been mixed. This study builds on this literature by exploring whether work influences youths’ sexual behavior in a cohort of African American youth [N = 562; 45% males; M = 14.5 years, SD = 0.6] followed from adolescence to young adulthood (ages 13 to 25). Using growth curve modeling, we tested whether working was associated with older sex partners. Then, we explored the association between sex partner age differences and sexual behaviors (i.e., number of sex partners, condom use, and frequency of sexual intercourse). Finally, we tested whether the relationship between sex partner age differences and sexual behaviors was confounded by working. Working greater number of hours was not significantly associated with having older sex partners. Sex partner age differences was associated with number of partners, condom use, and and higher sex frequency. These associations were larger for females. Working was associated with higher sex frequency, after accounting for age differences. We discuss the implications of these findings for future research and program planning, particularly in the context of youth development programs. PMID:18574686

Reduce beam hardening artifacts of polychromatic X-ray computed tomography by an iterative approximation approach.

PubMed

Shi, Hongli; Yang, Zhi; Luo, Shuqian

2017-01-01

The beam hardening artifact is one of most important modalities of metal artifact for polychromatic X-ray computed tomography (CT), which can impair the image quality seriously. An iterative approach is proposed to reduce beam hardening artifact caused by metallic components in polychromatic X-ray CT. According to Lambert-Beer law, the (detected) projections can be expressed as monotonic nonlinear functions of element geometry projections, which are the theoretical projections produced only by the pixel intensities (image grayscale) of certain element (component). With help of a prior knowledge on spectrum distribution of X-ray beam source and energy-dependent attenuation coefficients, the functions have explicit expressions. Newton-Raphson algorithm is employed to solve the functions. The solutions are named as the synthetical geometry projections, which are the nearly linear weighted sum of element geometry projections with respect to mean of each attenuation coefficient. In this process, the attenuation coefficients are modified to make Newton-Raphson iterative functions satisfy the convergence conditions of fixed pointed iteration(FPI) so that the solutions will approach the true synthetical geometry projections stably. The underlying images are obtained using the projections by general reconstruction algorithms such as the filtered back projection (FBP). The image gray values are adjusted according to the attenuation coefficient means to obtain proper CT numbers. Several examples demonstrate the proposed approach is efficient in reducing beam hardening artifacts and has satisfactory performance in the term of some general criteria. In a simulation example, the normalized root mean square difference (NRMSD) can be reduced 17.52% compared to a newest algorithm. Since the element geometry projections are free from the effect of beam hardening, the nearly linear weighted sum of them, the synthetical geometry projections, are almost free from the effect of beam

Maillard-reaction-induced modification and aggregation of proteins and hardening of texture in protein bar model systems.

PubMed

Zhou, Peng; Guo, Mufan; Liu, Dasong; Liu, Xiaoming; Labuza, Teodore P

2013-03-01

The hardening of high-protein bars causes problems in their acceptability to consumers. The objective of this study was to determine the progress of the Maillard reaction in model systems of high-protein nutritional bars containing reducing sugars, and to illustrate the influences of the Maillard reaction on the modification and aggregation of proteins and the hardening of bar matrices during storage. The progress of the Maillard reaction, glycation, and aggregation of proteins, and textural changes in bar matrices were investigated during storage at 25, 35, and 45 °C. The initial development of the Maillard reaction caused little changes in hardness; however, further storage resulted in dramatic modification of protein with formation of high-molecular-weight polymers, resulting in the hardening in texture. The replacement of reducing sugars with nonreducing ingredients such as sugar alcohols in the formula minimized the changes in texture. The hardening of high-protein bars causes problems in their acceptability to consumers. Maillard reaction is one of the mechanisms contributing to the hardening of bar matrix, particularly for the late stage of storage. The replacement of reducing sugars with nonreducing ingredients such as sugar alcohols in the formula will minimize the changes in texture. © 2013 Institute of Food Technologists®

Health-seeking behavior and transmission dynamics in the control of influenza infection among different age groups

PubMed Central

You, Shu-Han; Chen, Szu-Chieh; Liao, Chung-Min

2018-01-01

Background It has been found that health-seeking behavior has a certain impact on influenza infection. However, behaviors with/without risk perception on the control of influenza transmission among age groups have not been well quantified. Objectives The purpose of this study was to assess to what extent, under scenarios of with/without control and preventive/protective behaviors, the age-specific network-driven risk perception influences influenza infection. Materials and methods A behavior-influenza model was used to estimate the spread rate of age-specific risk perception in response to an influenza outbreak. A network-based information model was used to assess the effect of network-driven risk perception information transmission on influenza infection. A probabilistic risk model was used to assess the infection risk effect of risk perception with a health behavior change. Results The age-specific overlapping percentage was estimated to be 40%–43%, 55%–60%, and 19%–35% for child, teenage and adult, and elderly age groups, respectively. Individuals perceive the preventive behavior to improve risk perception information transmission among teenage and adult and elderly age groups, but not in the child age group. The population with perceived health behaviors could not effectively decrease the percentage of infection risk in the child age group, whereas for the elderly age group, the percentage of decrease in infection risk was more significant, with a 97.5th percentile estimate of 97%. Conclusion The present integrated behavior-infection model can help health authorities in communicating health messages for an intertwined belief network in which health-seeking behavior plays a key role in controlling influenza infection. PMID:29563814

Method for determining the hardness of strain hardening articles of tungsten-nickel-iron alloy

DOEpatents

Wallace, Steven A.

1984-01-01

The present invention is directed to a rapid nondestructive method for determining the extent of strain hardening in an article of tungsten-nickel-iron alloy. The method comprises saturating the article with a magnetic field from a permanent magnet, measuring the magnetic flux emanating from the article, comparing the measurements of the magnetic flux emanating from the article with measured magnetic fluxes from similarly shaped standards of the alloy with known amounts of strain hardening to determine the hardness.

Sewall Wright, shifting balance theory, and the hardening of the modern synthesis.

PubMed

Ishida, Yoichi

2017-02-01

The period between the 1940s and 1960s saw the hardening of the modern synthesis in evolutionary biology. Gould and Provine argue that Wright's shifting balance theory of evolution hardened during this period. But their account does not do justice to Wright, who always regarded selection as acting together with drift. This paper presents a more adequate account of the development of Wright's shifting balance theory, paying particular attention to his application of the theory to the geographical distribution of flower color dimorphism in Linanthus parryae. The account shows that even in the heyday of the hardened synthesis, the balance or interaction of evolutionary factors, such as drift, selection, and migration, occupied pride of place in Wright's theory, and that between the 1940s and 1970s, Wright developed the theory of isolation by distance to quantitatively represent the structure of the Linanthus population, which he argued had the kind of structure posited by his shifting balance theory. In the end, Wright arrived at a sophisticated description of the structure of the Linanthus population, where the interaction between drift and selection varied spatially. Copyright © 2016 Elsevier Ltd. All rights reserved.

Scatter and beam hardening reduction in industrial computed tomography using photon counting detectors

NASA Astrophysics Data System (ADS)

Schumacher, David; Sharma, Ravi; Grager, Jan-Carl; Schrapp, Michael

2018-07-01

Photon counting detectors (PCD) offer new possibilities for x-ray micro computed tomography (CT) in the field of non-destructive testing. For large and/or dense objects with high atomic numbers the problem of scattered radiation and beam hardening severely influences the image quality. This work shows that using an energy discriminating PCD based on CdTe allows to address these problems by intrinsically reducing both the influence of scattering and beam hardening. Based on 2D-radiographic measurements it is shown that by energy thresholding the influence of scattered radiation can be reduced by up to in case of a PCD compared to a conventional energy-integrating detector (EID). To demonstrate the capabilities of a PCD in reducing beam hardening, cupping artefacts are analyzed quantitatively. The PCD results show that the higher the energy threshold is set, the lower the cupping effect emerges. But since numerous beam hardening correction algorithms exist, the results of the PCD are compared to EID results corrected by common techniques. Nevertheless, the highest energy thresholds yield lower cupping artefacts than any of the applied correction algorithms. As an example of a potential industrial CT application, a turbine blade is investigated by CT. The inner structure of the turbine blade allows for comparing the image quality between PCD and EID in terms of absolute contrast, as well as normalized signal-to-noise and contrast-to-noise ratio. Where the absolute contrast can be improved by raising the energy thresholds of the PCD, it is found that due to lower statistics the normalized contrast-to-noise-ratio could not be improved compared to the EID. These results might change to the contrary when discarding pre-filtering of the x-ray spectra and thus allowing more low-energy photons to reach the detectors. Despite still being in the early phase in technological progress, PCDs already allow to improve CT image quality compared to conventional detectors in terms of

Hall coefficient measurement for residual stress assessment in precipitation hardened IN718 nickel-base superalloy

NASA Astrophysics Data System (ADS)

Velicheti, Dheeraj; Nagy, Peter B.; Hassan, Waled

2017-02-01

We investigated the feasibility of residual stress assessment based on Hall coefficient measurements in precipitation hardened IN718 nickel-base superalloy. As a first step, we studied the influence of microstructural variations on the galvanomagnetic properties of IN718 nickel-base superalloy. We found that the Hall coefficient of IN718 increases from ≈ 8.0×10-11 m3/C in its fully annealed state of 15 HRC Rockwell hardness to ≈ 9.4×10-11 m3/C in its fully hardened state of 45 HRC. We also studied the influence of cold work, i.e., plastic deformation, at room temperature and found that cold work had negligible effect on the Hall coefficient of fully annealed IN718, but significantly reduced it in hardened states of the material. For example, measurements conducted on fully hardened IN718 specimens showed that the Hall coefficient decreased more or less linearly with cold work from its peak value of ≈ 9.4×10-11 m3/C in its intact state to ≈ 9.0×10-11 m3/C in its most deformed state of 22% plastic strain. We also studied the influence of applied stress and found that elastic strain significantly increases the Hall coefficient of IN718 regardless of the state of hardening. The relative sensitivity of the Hall coefficient to elastic strain was measured as a unitless gauge factor K that is defined as the ratio of the relative change of the Hall coefficient ΔRH/RH divided by the axial strain ɛ = σ/E, where σ is the applied uniaxial stress and E is the Young's modulus of the material. We determined that the galvanomagnetic gauge factor of IN718 is κ ≈ 2.6 - 2.9 depending on the hardness level. Besides the fairly high value of the gauge factor, it is important that it is positive, which means that compressive stress in surface-treated components decreases the Hall coefficient in a similar way as plastic deformation does, therefore the unfortunate cancellation that occurs in fully hardened IN718 in the case of electric conductivity measurements will not

Tensile stress-strain and work hardening behaviour of P9 steel for wrapper application in sodium cooled fast reactors

NASA Astrophysics Data System (ADS)

Christopher, J.; Choudhary, B. K.; Isaac Samuel, E.; Mathew, M. D.; Jayakumar, T.

2012-01-01

Tensile flow behaviour of P9 steel with different silicon content has been examined in the framework of Hollomon, Ludwik, Swift, Ludwigson and Voce relationships for a wide temperature range (300-873 K) at a strain rate of 1.3 × 10 -3 s -1. Ludwigson equation described true stress ( σ)-true plastic strain ( ɛ) data most accurately in the range 300-723 K. At high temperatures (773-873 K), Ludwigson equation reduces to Hollomon equation. The variations of instantaneous work hardening rate ( θ = dσ/ dɛ) and θσ with stress indicated two-stage work hardening behaviour. True stress-true plastic strain, flow parameters, θ vs. σ and θσ vs. σ with respect to temperature exhibited three distinct temperature regimes and displayed anomalous behaviour due to dynamic strain ageing at intermediate temperatures. Rapid decrease in flow stress and flow parameters, and rapid shift in θ- σ and θσ- σ towards lower stresses with increase in temperature indicated dominance of dynamic recovery at high temperatures.

Ages for the Middle Stone Age of southern Africa: implications for human behavior and dispersal.

PubMed

Jacobs, Zenobia; Roberts, Richard G; Galbraith, Rex F; Deacon, Hilary J; Grün, Rainer; Mackay, Alex; Mitchell, Peter; Vogelsang, Ralf; Wadley, Lyn

2008-10-31

The expansion of modern human populations in Africa 80,000 to 60,000 years ago and their initial exodus out of Africa have been tentatively linked to two phases of technological and behavioral innovation within the Middle Stone Age of southern Africa-the Still Bay and Howieson's Poort industries-that are associated with early evidence for symbols and personal ornaments. Establishing the correct sequence of events, however, has been hampered by inadequate chronologies. We report ages for nine sites from varied climatic and ecological zones across southern Africa that show that both industries were short-lived (5000 years or less), separated by about 7000 years, and coeval with genetic estimates of population expansion and exit times. Comparison with climatic records shows that these bursts of innovative behavior cannot be explained by environmental factors alone.

Age Differences in Coping, Behavioral Dysfunction and Depression Following Colostomy Surgery.

ERIC Educational Resources Information Center

Keyes, Kathryn; And Others

1987-01-01

Examined the responses of a group of middle-aged and older adults (N=34) to colostomy surgery. Analyzed the relationship between the method and focus of coping and age, sickness-related dysfunction, and depression. Found that neither a lower level of active behavioral coping nor age itself was correlated with depression or dysfunction. (Author/ABB)

Effects of anisotropy and irradiation on the deformation behavior of Zircaloy 2. Final report

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

Pelloux, R.M.; Ballinger, R.; Lucas, G.

1979-01-01

An experimental program investigated the effects of texture anisotropy and irradiation on the mechanical behavior of Zircaloy-2. Short time and time dependent mechanical behavior were considered. Irradiation effects were simulated through the use of 4.75 MeV protons. The temperature ranges investigated were 298/sup 0/K and 573 to 673/sup 0/K. Both cold worked-stress relieved and annealed material were used in this experimental program. Short time yield behavior of different crystallographic textures was determined by uniaxial and plane strain tests in the temperature range 298/sup 0/K and 573 to 673/sup 0/K. Monotonic flow loci were constructed for each texture. Yield behavior ismore » a strong function of the crystallographic texture number f at all temperatures investigated. The rotation of texture with increasing plastic strain was investigated as a function of initial texture at 298/sup 0/K and 623/sup 0/K. The rate of texture rotation df/epsilon/sub p/ was found to be a unique function of the initial texture for plastic strains less than 0.08. Time dependent mechanical behavior was investigated in the range 573 to 673/sup 0/K using constant load creep and stress relaxation tests. The tensile creep strength is proportional to the resolved fraction of basal poles in the test direction. In variable stress and temperature tests, the time-hardening rule was found to be inapplicable. The strain-hardening rule was applied with success to data obtained at temperatures less than or equal to 648/sup 0/K. Irradiation creep tests were conducted in vacuum at 598/sup 0/K and 102 to 241 MPa on 80..mu..m thick Zircaloy-2 foil specimens in both the recrystallized and cold worked-stress relieved condition. In the irradiation creep tests irradiation hardening and enhanced irradiation creep were observed. Radiation hardening effects were significant in annealed material but were attenuated in cold worked-stress relieved material.« less

On the relationships between hardness and the elastic and plastic properties of isotropic power-law hardening materials

NASA Astrophysics Data System (ADS)

Lan, Hongzhi; Venkatesh, T. A.

2014-01-01

A comprehensive understanding of the relationship between the hardness and the elastic and plastic properties for a wide range of materials is obtained by analysing the hardness characteristics (that are predicted by experimentally verified indentation analyses) of over 9000 distinct combinations of material properties that represent isotropic, homogeneous, power-law hardening metallic materials. Finite element analysis has been used to develop the indentation algorithms that provide the relationships between the elastic and plastic properties of the indented material and its indentation hardness. Based on computational analysis and virtual testing, the following observations are made. The hardness (H) of a material tends to increase with an increase in the elastic modulus (E), yield strength (σy) and the strain-hardening exponent (n). Several materials with different combinations of elastic and plastic properties can exhibit identical true hardness (for a particular indenter geometry/apex angle). In general, combinations of materials that exhibit relatively low elastic modulus and high yield strength or strain-hardening exponents and those that exhibit relatively high elastic modulus and low yield strength or strain-hardening exponents exhibit similar hardness properties. Depending on the strain-hardening characteristics of the indented material, (i.e. n = 0 or ?), the ratio H/σy ranges, respectively, from 2.2 to 2.6 or 2 to 20 (for indentations with a cone angle of 70.3°). The materials that have lower σy/E and higher n exhibit higher H/σy ratios. The commonly invoked relationship between hardness and the yield strength, i.e. H ≈ 3σy, is not generally valid or applicable for all power-law hardening materials. The indentation hardness of a power law hardening material can be taken as following the relationship H ≈ (2.1-2.8)σr where σr is the representative stress based on Tabor's representative strain for a wide range of materials.

Latent hardening size effect in small-scale plasticity

NASA Astrophysics Data System (ADS)

Bardella, Lorenzo; Segurado, Javier; Panteghini, Andrea; Llorca, Javier

2013-07-01

We aim at understanding the multislip behaviour of metals subject to irreversible deformations at small-scales. By focusing on the simple shear of a constrained single-crystal strip, we show that discrete Dislocation Dynamics (DD) simulations predict a strong latent hardening size effect, with smaller being stronger in the range [1.5 µm, 6 µm] for the strip height. We attempt to represent the DD pseudo-experimental results by developing a flow theory of Strain Gradient Crystal Plasticity (SGCP), involving both energetic and dissipative higher-order terms and, as a main novelty, a strain gradient extension of the conventional latent hardening. In order to discuss the capability of the SGCP theory proposed, we implement it into a Finite Element (FE) code and set its material parameters on the basis of the DD results. The SGCP FE code is specifically developed for the boundary value problem under study so that we can implement a fully implicit (Backward Euler) consistent algorithm. Special emphasis is placed on the discussion of the role of the material length scales involved in the SGCP model, from both the mechanical and numerical points of view.

Influence of Glass Fiber on Fresh and Hardened Properties of Self Compacting Concrete

NASA Astrophysics Data System (ADS)

Bharathi Murugan, R.; Haridharan, M. K.; Natarajan, C.; Jayasankar, R.

2017-07-01

The practical need of self-compacting concrete (SCC) is increasing due to increase in the infrastructure competence all over the world. The effective way of increasing the strength of concrete and enhance the behaviour under extreme loading (fire) is the keen interest. Glass fibers were added for five different of volume fractions (0%, 0.1%, 0.3%, 0.5% and 0.6%) to determine the optimum percentage of glass fiber without compensating the fresh properties and enhanced hardened properties of SCC concrete. The fresh state of concrete is characterized by slump flow, T-50cm slump flow, and V-funnel and L- box tests. The results obtained in fresh state are compared with the acceptance criteria of EFNARC specification. Concrete specimens were casted to evaluate the hardened properties such as compressive strength, split tensile strength, flexural strength and modulus of elasticity. Incorporation the glass fiber into SCC reduces the workability but within the standard specification. The hardened properties of SCC glass fiber reinforced concrete were enhanced, due to bridging the pre-existing micro cracks in concrete by glass fiber addition.

Childhood Fears, Neurobehavioral Functioning and Behavior Problems in School-Age Children

ERIC Educational Resources Information Center

Kushnir, Jonathan; Sadeh, Avi

2010-01-01

The objective is to examine underlying associations between childhood fears, behavior problems and neurobehavioral functioning (NBF) in school-age children. Healthy, regular school children (N = 135), from second, fourth and sixth grade classes were assessed. Data regarding children's fears and behavioral problems were obtained with the Revised…

Joining precipitation-hardened nickel-base alloys by friction welding

NASA Technical Reports Server (NTRS)

Moore, T. J.

1972-01-01

Solid state deformation welding process, friction welding, has been developed for joining precipitation hardened nickel-base alloys and other gamma prime-strengthened materials which heretofore have been virtually unweldable. Method requires rotation of one of the parts to be welded, but where applicable, it is an ideal process for high volume production jobs.

Hardening digital systems with distributed functionality: robust networks

NASA Astrophysics Data System (ADS)

Vaskova, Anna; Portela-Garcia, Marta; Garcia-Valderas, Mario; López-Ongil, Celia; Portilla, Jorge; Valverde, Juan; de la Torre, Eduardo; Riesgo, Teresa

2013-05-01

Collaborative hardening and hardware redundancy are nowadays the most interesting solutions in terms of fault tolerance achieved and low extra cost imposed to the project budget. Thanks to the powerful and cheap digital devices that are available in the market, extra processing capabilities can be used for redundant tasks, not only in early data processing (sensed data) but also in routing and interfacing1

Reducing beam hardening effects and metal artefacts in spectral CT using Medipix3RX

NASA Astrophysics Data System (ADS)

Rajendran, K.; Walsh, M. F.; de Ruiter, N. J. A.; Chernoglazov, A. I.; Panta, R. K.; Butler, A. P. H.; Butler, P. H.; Bell, S. T.; Anderson, N. G.; Woodfield, T. B. F.; Tredinnick, S. J.; Healy, J. L.; Bateman, C. J.; Aamir, R.; Doesburg, R. M. N.; Renaud, P. F.; Gieseg, S. P.; Smithies, D. J.; Mohr, J. L.; Mandalika, V. B. H.; Opie, A. M. T.; Cook, N. J.; Ronaldson, J. P.; Nik, S. J.; Atharifard, A.; Clyne, M.; Bones, P. J.; Bartneck, C.; Grasset, R.; Schleich, N.; Billinghurst, M.

2014-03-01

This paper discusses methods for reducing beam hardening effects and metal artefacts using spectral x-ray information in biomaterial samples. A small-animal spectral scanner was operated in the 15 to 80 keV x-ray energy range for this study. We use the photon-processing features of a CdTe-Medipix3RX ASIC in charge summing mode to reduce beam hardening and associated artefacts. We present spectral data collected for metal alloy samples, its analysis using algebraic 3D reconstruction software and volume visualisation using a custom volume rendering software. The cupping effect and streak artefacts are quantified in the spectral datasets. The results show reduction in beam hardening effects and metal artefacts in the narrow high energy range acquired using the spectroscopic detector. A post-reconstruction comparison between CdTe-Medipix3RX and Si-Medipix3.1 is discussed. The raw data and processed data are made available (http://hdl.handle.net/10092/8851) for testing with other software routines.

Age and motivation predict gaze behavior for facial expressions.

PubMed

Nikitin, Jana; Freund, Alexandra M

2011-09-01

This study investigated age-related differences between younger (M = 25.52 years) and older (M = 70.51 years) adults in avoidance motivation and the influence of avoidance motivation on gaze preferences for happy, neutral, and angry faces. In line with the hypothesis of reduced negativity effect later in life, older adults avoided angry faces and (to a lesser degree) preferred happy faces more than younger adults did. This effect cannot be explained by age-related changes in dispositional motivation. Irrespective of age, avoidance motivation predicted gaze behavior towards emotional faces. The study demonstrates the importance of interindividual differences beyond young adulthood.

Metabolites and hormones are involved in the intraspecific variability of drought hardening in radiata pine.

PubMed

De Diego, N; Saiz-Fernández, I; Rodríguez, J L; Pérez-Alfocea, P; Sampedro, M C; Barrio, R J; Lacuesta, M; Moncaleán, P

2015-09-01

Studies of metabolic and physiological bases of plant tolerance and hardening against drought are essential to improve genetic breeding programs, especially in productive species such as Pinus radiata. The exposure to different drought cycles is a highly effective tool that improves plant conditioning, but limited information is available about the mechanisms that modulate this process. To clarify this issue, six P. radiata breeds with well-known differences in drought tolerance were analyzed after two consecutive drought cycles. Survival rate, concentration of several metabolites such as free soluble amino acids and polyamines, and main plant hormones varied between them after drought hardening, while relative growth ratio and water potential at both predawn and dawn did not. Hardening induced a strong increase in total soluble amino acids in all breeds, accumulating mainly those implicated in the glutamate metabolism (GM), especially L-proline, in the most tolerant breeds. Other amino acids from GM such as γ-aminobutyric acid (GABA) and L-arginine (Arg) were also strongly increased. GABA pathway could improve the response against drought, whereas Arg acts as precursor for the synthesis of spermidine. This polyamine showed a positive relationship with the survival capacity, probably due to its role as antioxidant under stress conditions. Finally, drought hardening also induced changes in phytohormone content, showing each breed a different profile. Although all of them accumulated indole-3-acetic acid and jasmonic acid and reduced zeatin content in needles, significant differences were observed regarding abscisic acid, salicylic acid and mainly zeatin riboside. These results confirm that hardening is not only species-dependent but also an intraspecific processes controlled through metabolite changes. Copyright © 2015 Elsevier GmbH. All rights reserved.

Some new results on irradiation characteristics of synthetic quartz crystals and their application to radiation hardening

NASA Technical Reports Server (NTRS)

Bahadur, H.; Parshad, R.

1983-01-01

The paper reports some new results on irradiation characteristics of synthetic quartz crystals and their application to radiation hardening. The present results show how the frequency shift in quartz crystals can be influenced by heat processing prior to irradiation and how this procedure can lead to radiation hardening for obtaining precise frequencies and time intervals from quartz oscillators in space.

Expecting the Unexpected: Radiation Hardened Software

NASA Technical Reports Server (NTRS)

Penix, John; Mehlitz, Peter C.

2005-01-01

Radiation induced Single Event Effects (SEEs) are a serious problem for spacecraft flight software, potentially leading to a complete loss of mission. Conventional risk mitigation has been focused on hardware, leading to slow, expensive and outdated on-board computing devices, increased power consumption and launch mass. Our approach is to look at SEEs from a software perspective, and to explicitly design flight software so that it can detect and correct the majority of SEES. Radiation hardened flight software will reduce the significant residual residual risk for critical missions and flight phases, and enable more use of inexpensive and fast COTS hardware.

Reproduction studies in the rat with shea oleine and hardened shea oleine.

PubMed

Baldrick, P; Robinson, J A; Hepburn, P A

2001-09-01

Shea oleine is an oil fraction derived from the nut of the tree Butyrospermum parkii, which grows in central and western Africa. There are several uses of shea oleine including its use as a frying oil and, after hardening, in margarine and toffee fat. This investigation was performed to examine the toxicity of 7 or 15% hardened shea oleine in comparison with 7 or 15% unhardened shea oleine and various commercially available materials, sheanut and palm oils, cocoa butter and toffee powder following dietary administration to rats during pre-mating, mating, pregnancy and offspring weaning in two separate investigations. Reproduction was assessed using number of litters and pups born plus survival and body weights at birth and at weaning on day 21. Skeletal evaluation using X-ray, clinical pathology and a macroscopic examination were also performed for F1 rats. Study measures for parent animals comprised evaluation of body weight, food consumption, clinical pathology, organ weights and macroscopic examination. Fatty acids and hydrocarbon levels were measured and an evaluation for lipogranulomata was made for various tissues. Results showed that shea oleine, whether unhardened or hardened, produced no evidence of reproduction toxicity and gave a similar profile to the other commercially available materials used in this study in the rat. Minor findings with shea oleine were not related to reproduction performance but comprised slightly reduced body weight gain and reduced cholesterol and raised alkaline phosphatase levels. None of the findings in this study were considered to be of toxicological significance. Thus, no evidence of reproduction toxicity was seen for both unhardened and hardened shea oleine in this investigation in the rat at levels equating to greater than 7.5 g/kg/day.

Anomalous temperature dependence of yield stress and work hardening coefficient of B2-stabilized NiTi alloys

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

Hosoda, Hideki; Mishima, Yoshinao; Suzuki, Tomoo

Yield stress and work hardening coefficient of B2-stabilized NiTi alloys are investigated using compression tests. Compositions of NiTi alloys are based on Ni-49mol.%Ti, to which Cr, Co and Al are chosen as ternary elements which reduce martensitic transformation temperatures of the B2 phase. Mechanical tests are carried out in liquid nitrogen at 77 K, air at room temperature (R.T.) and in an argon atmosphere between 473 K and 873 K. Only at 77 K, some alloys show characteristic stress-strain curves which indicate stress induced martensitic transformation (SIMT), but the others do not. Work hardening coefficient is found to be betweenmore » 2 and 11GPa in all the test temperature range. The values are extremely high compared with Young`s modulus of B2 NiTi. Yield stress and work hardening coefficient increase with test temperature between R.T. and about 650 K in most alloys. The anomalous temperature dependence of mechanical properties is not related to SIMT but to precipitation hardening and/or anomalous dislocation motion similar to B2-type CoTi. Solution hardening by adding ternary elements is evaluated to be small for Cr and Co additions, and large for Al addition, depending on difference in atomic size of the ternary element with respect to Ni or Ti.« less

Hardening of electromechanical properties in piezoceramics using a composite approach

NASA Astrophysics Data System (ADS)

K. V., Lalitha; Riemer, Lukas M.; Koruza, Jurij; Rödel, Jürgen

2017-07-01

Piezoelectric applications such as ultrasonic motors, transformers and therapeutic ultrasonics demand high power generation with low losses, which is facilitated by "hard" ferroelectrics. Hardening of piezoelectric properties, characterized by high mechanical quality factor (Qm), is usually achieved by doping with lower valence elements, thereby tailoring the domain wall dynamics. In the present study, we demonstrate a hardening mechanism by developing composites of 0.94(Na1/2Bi1/2)TiO3-0.06BaTiO3 (NBT-6BT) with ZnO inclusions, as an alternative to chemical modifications. A decrease in the saturation polarization and total strain, higher internal bias fields, lower hysteretic losses and a two-fold increase in Qm are observed in comparison to NBT-6BT. The composite with 0.1 mole ratio of ZnO exhibits the highest Qm of 320 with d33 = 125 pC/N and Kp = 0.29. A one-to-one correspondence between the increase in Qm and the decrease in the domain wall mobility is established from the ac field dependence of permittivity, in the framework of the Rayleigh law. A further increase in ZnO content beyond a mole ratio of 0.1 reduces Qm, but retains it at a higher level, as compared to NBT-6BT. The results are explained based on the poling-induced strain incompatibility between the matrix and the hard ZnO phase. This composite approach is therefore considered a generic hardening concept and can be extended to other ferroelectric systems.

A simulation-based study on the influence of beam hardening in X-ray computed tomography for dimensional metrology.

PubMed

Lifton, Joseph J; Malcolm, Andrew A; McBride, John W

2015-01-01

X-ray computed tomography (CT) is a radiographic scanning technique for visualising cross-sectional images of an object non-destructively. From these cross-sectional images it is possible to evaluate internal dimensional features of a workpiece which may otherwise be inaccessible to tactile and optical instruments. Beam hardening is a physical process that degrades the quality of CT images and has previously been suggested to influence dimensional measurements. Using a validated simulation tool, the influence of spectrum pre-filtration and beam hardening correction are evaluated for internal and external dimensional measurements. Beam hardening is shown to influence internal and external dimensions in opposition, and to have a greater influence on outer dimensions compared to inner dimensions. The results suggest the combination of spectrum pre-filtration and a local gradient-based surface determination method are able to greatly reduce the influence of beam hardening in X-ray CT for dimensional metrology.

A comparison of heavy ion induced single event upset susceptibility in unhardened 6T/SRAM and hardened ADE/SRAM

NASA Astrophysics Data System (ADS)

Wang, Bin; Zeng, Chuanbin; Geng, Chao; Liu, Tianqi; Khan, Maaz; Yan, Weiwei; Hou, Mingdong; Ye, Bing; Sun, Youmei; Yin, Yanan; Luo, Jie; Ji, Qinggang; Zhao, Fazhan; Liu, Jie

2017-09-01

Single event upset (SEU) susceptibility of unhardened 6T/SRAM and hardened active delay element (ADE)/SRAM, fabricated with 0.35 μm silicon-on-insulator (SOI) CMOS technology, was investigated at heavy ion accelerator. The mechanisms were revealed by the laser irradiation and resistor-capacitor hardened techniques. Compared with conventional 6T/SRAM, the hardened ADE/SRAM exhibited higher tolerance to heavy ion irradiation, with an increase of about 80% in the LET threshold and a decrease of ∼64% in the limiting upset cross-section. Moreover, different probabilities between 0 → 1 and 1 → 0 transitions were observed, which were attributed to the specific architecture of ADE/SRAM memory cell. Consequently, the radiation-hardened technology can be an attractive alternative to the SEU tolerance of the device-level.

Behavioral deficits during early stages of aging in Caenorhabditis elegans result from locomotory deficits possibly linked to muscle frailty.

PubMed Central

Glenn, Charles F.; Chow, David K.; Gami, Minaxi S.; Iser, Wendy B.; Hanselman, Keaton B.; Wolkow, Catherine A.; David, Lawrence; Goldberg, Ilya G.; Cooke, Carol A.

2005-01-01

Many behavioral responses require the coordination of sensory inputs with motor outputs. Aging is associated with progressive declines in both motor function and muscle structure. However, the consequences of age-related motor deficits upon behavior have not been clearly defined. Here, we examined the effects of aging on behavior in the nematode, Caenorhabditis elegans. As animals aged, mild locomotory deficits appeared that were sufficient to impair behavioral responses to sensory cues. In contrast, sensory ability appeared well-maintained during aging. Age-related behavioral declines were delayed in animals with mutations in the daf-2/insulin-like pathway governing longevity. A decline in muscle tissue integrity was correlated with the onset of age-related behavioral deficits, although significant muscle deterioration did not. Treatment with a muscarinic agonist significantly improved locomotory behavior in aged animals, indicating that improved neuromuscular signaling may be one strategy for reducing the severity of age-related behavioral impairments. PMID:15699524

Laser Welding of Coated Press-hardened Steel 22MnB5

NASA Astrophysics Data System (ADS)

Siltanen, Jukka; Minkkinen, Ari; Järn, Sanna

The press-hardening process is widely used for steels that are used in the automotive industry. Using ultra-high-strength steels enables car manufacturers to build lighter, stronger, and safer vehicles at a reduced cost and generating lower CO2 emissions. In the study, laser welding properties of the coated hot stamped steel 22BMn5 were studied. A constant 900 °C temperature was used to heat the steel plates, and two different furnace times were used in the press-hardening, being 300 and 740 seconds. Some of the plates were shot blasted to see the influence of the partly removed oxide layer on the laser welding and quality. The welding set-up, welding, and testing of the weld specimens complied with the automotive testing code SEP 1220.

Computer program for predicting creep behavior of bodies of revolution

NASA Technical Reports Server (NTRS)

Adams, R.; Greenbaum, G.

1971-01-01

Computer program, CRAB, uses finite-element method to calculate creep behavior and predict steady-state stresses in an arbitrary body of revolution subjected to a time-dependent axisymmetric load. Creep strains follow a time hardening law and a Prandtl-Reuss stress-strain relationship.

Hardening parts by chrome plating in manufacture and repair

NASA Astrophysics Data System (ADS)

Astanin, V. K.; Pukhov, E. V.; Stekolnikov, Y. A.; Emtsev, V. V.; Golikova, O. A.

2018-03-01

In the engineering industry, galvanic coatings are widely used to prolong the service life of the machines, which contribute to the increase in the strength of the parts and their resistance to environmental influences, temperature and pressure drops, wear and fretting corrosion. Galvanic coatings have been widely applied in engineering, including agriculture, aircraft building, mining, construction, and electronics. The article focuses on the manufacturing methods of new agricultural machinery parts and the repair techniques of worn parts by chrome plating. The main attention is paid to the unstable methods of chromium deposition (in pulsed and reversing modes) in low-concentration electrolytes, which makes it possible to increase the reliability and durability of the hardened parts operation by changing the conditions of electrocrystallization, that is, directed formation of the structure and texture, thickness, roughness and microhardness of chromium plating. The practical recommendations are given on the current and temperature regimes of chromium deposition and composition of baths used for the restoration and hardening of the machine parts. Moreover, the basic methods of machining allowances removal are analysed.

Laser quench hardening of steel: Effects of superimposed elastic pre-stress on the hardness and residual stress distribution

NASA Astrophysics Data System (ADS)

Meserve, Justin

Cold drawn AISI 4140 beams were LASER surface hardened with a 2 kW CO2 LASER. Specimens were treated in the free state and while restrained in a bending fixture inducing surface tensile stresses of 94 and 230 MPa. Knoop hardness indentation was used to evaluate the through thickness hardness distribution, and a layer removal methodology was used to evaluate the residual stress distribution. Results showed the maximum surface hardness attained was not affected by pre-stress during hardening, and ranged from 513 to 676 kg/mm2. The depth of effective hardening varied at different magnitudes of pre-stress, but did not vary proportionately to the pre-stress. The surface residual stress, coinciding with the maximum compressive residual stress, increased as pre-stress was increased, from 1040 MPa for the nominally treated specimens to 1270 MPa for specimens pre-stressed to 230 MPa. The maximum tensile residual stress observed in the specimens decreased from 1060 MPa in the nominally treated specimens to 760 MPa for specimens pre-stressed to 230 MPa. Similarly, thickness of the compressive residual stress region increased and the depth at which maximum tensile residual stress occurred increased as the pre-stress during treatment was increased Overall, application of tensile elastic pre-stress during LASER hardening is beneficial to the development of compressive residual stress in AISI 4140, with minimal impact to the hardness attained from the treatment. The newly developed approach for LASER hardening may support efforts to increase both the wear and fatigue resistance of parts made from hardenable steels.

The Relationship between Apparent Age and Helping Behavior.

ERIC Educational Resources Information Center

Sigmon, Scott B.; And Others

A group of 240 men and women of various ages were given the opportunity to express altruistic behavior in an interpersonal situation by granting a favor of permitting the experimenters, one white woman and two white men in their mid-twenties to enter a store check-out line ahead of them during the Christmas rush. The researchers hypothesized that…

[A study of Rutter behavior problems in school aged children with cleft lip and/or palate].

PubMed

Wu, Zheng-yi; Zhang, Yong; Chen, Li-qin

2008-08-01

To study the difference of behavior problems in school aged children with cleft of lip and/or palate. The Rutter Children Behavior Parent Checklist was used in 100 school aged children with cleft lip and/or palate and 135 school aged normal children in Shanghai.The questionnaire were filled and analyzed with chi2 test and logistic regression using SPSS 10.0 software packageî The positive rate of Rutter behavior problems in school aged children with cleft of lip and/or palate was significantly higher than that in normal children (P<0.05). The positive rate of behavior problems and Rutter behavior problem A in boys was significantly higher than in girls. Primary mental health intervention is necessary to promote the psychiatric health.

A physics-based crystallographic modeling framework for describing the thermal creep behavior of Fe-Cr alloys

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

Wen, Wei; Capolungo, Laurent; Patra, Anirban

This Report addresses the Milestone M2MS-16LA0501032 of NEAMS Program (“Develop hardening model for FeCrAl cladding), with a deadline of 09/30/2016. Here we report a constitutive law for thermal creep of FeCrAl. This Report adds to and complements the one for Milestone M3MS-16LA0501034 (“Interface hardening models with MOOSE-BISON”), where we presented a hardening law for irradiated FeCrAl. The last component of our polycrystal-based constitutive behavior, namely, an irradiation creep model for FeCrAl, will be developed as part of the FY17 Milestones, and the three regimes will be coupled and interfaced with MOOSE-BISON.

Reduced gamma frequency in the medial frontal cortex of aged rats during behavior and rest: implications for age-related behavioral slowing.

PubMed

Insel, Nathan; Patron, Lilian A; Hoang, Lan T; Nematollahi, Saman; Schimanski, Lesley A; Lipa, Peter; Barnes, Carol A

2012-11-14

Age-related cognitive and behavioral slowing may be caused by changes in the speed of neural signaling or by changes in the number of signaling steps necessary to achieve a given function. In the mammalian cortex, neural communication is organized by a 30-100 Hz "gamma" oscillation. There is a putative link between the gamma frequency and the speed of processing in a neural network: the dynamics of pyramidal neuron membrane time constants suggest that synaptic integration is framed by the gamma cycle, and pharmacological slowing of gamma also slows reaction times on behavioral tasks. The present experiments identify reductions in a robust 40-70 Hz gamma oscillation in the aged rat medial frontal cortex. The reductions were observed in the form of local field potentials, later peaks in fast-spiking neuron autocorrelations, and delays in the spiking of inhibitory neurons following local excitatory signals. Gamma frequency did not vary with movement speed, but rats with slower gamma also moved more slowly. Gamma frequency age differences were not observed in hippocampus. Hippocampal CA1 fast-spiking neurons exhibited interspike intervals consistent with a fast (70-100 Hz) gamma frequency, a pattern maintained across theta phases and theta frequencies independent of fluctuations in the average firing rates of the neurons. We propose that an average lengthening of the cortical 15-25 ms gamma cycle is one factor contributing to age-related slowing and that future attempts to offset cognitive declines will find a target in the response of fast-spiking inhibitory neurons to excitatory inputs.

Reduced gamma frequency in the medial frontal cortex of aged rats during behavior and rest: implications for age-related behavioral slowing

PubMed Central

Insel, Nathan; Patron, Lilian A.; Hoang, Lan T.; Nematollahi, Saman; Schimanski, Lesley A.; Lipa, Peter; Barnes, Carol A.

2012-01-01

Age-related cognitive and behavioral slowing may be caused by changes in the speed of neural signaling or by changes in the number of signaling steps necessary to achieve a given function. In the mammalian cortex, neural communication is organized by a 30–100 Hz “gamma” oscillation. There is a putative link between the gamma frequency and the speed of processing in a neural network: the dynamics of pyramidal neuron membrane time constants suggest that synaptic integration is framed by the gamma cycle, and pharmacological slowing of gamma also slows reaction times on behavioral tasks. The present experiments identify reductions in a robust 40–70 Hz gamma oscillation in the aged rat medial frontal cortex. The reductions were observed in the form of local field potentials (LFPs), later peaks in fast-spiking neuron autocorrelations, and delays in the spiking of inhibitory neurons following local excitatory signals. Gamma frequency did not vary with movement speed, but rats with slower gamma also moved more slowly. Gamma frequency age differences were not observed in hippocampus. Hippocampal CA1 fast-spiking neurons exhibited inter-spike intervals consistent with a fast (70–100 Hz) gamma frequency, a pattern maintained across theta phases and theta frequencies independent of fluctuations in the neurons’ average firing rates. We propose that an average lengthening of the cortical 15–25 ms gamma cycle is one factor contributing to age-related slowing, and that future attempts to offset cognitive declines will find a target in the response of fast-spiking inhibitory neurons to excitatory inputs. PMID:23152616

Method of Electrolyte-Plasma Surface Hardening of 65G and 20GL Low-Alloy Steels Samples

NASA Astrophysics Data System (ADS)

Rakhadilov, Bauyrzhan; Zhurerova, Laila; Pavlov, Alexander

2016-08-01

This work is devoted to formation of modified surface layers in 65G and 20GL steels which using for the manufacture of railway transport parts, as well as the study of influence of the parametersof electrolyte-plasma surface hardening methodon the changes in structural-phase states, improving of wear-resistance. The process of electrolyte-plasma surface hardening of 65G and 20GL steels samples conducted in the electrolyte from water solution of 20% sodium carbonate, in the mode ~850°C - 2 seconds, ∼⃒1200°C - 3 seconds. It is established that in the initial state 20GL steel has ferrite-pearlite structure, and the 60G steel consists of pearlite and cement structure. After application of electrolyte-plasma surface hardening is observed the formation of carbides particles and martensite phase components in the structure of 20GL and 60G steels. It is determined that after electrolyte-plasma surface hardening with heating time - 2 seconds, the abrasive wear-resistance of 65G and 20GL steels increased to 1.3 times and 1.2 times, respectively, and the microhardness is increased to 1.6 times and 1.3 times, respectively.

Pulsed-laser capabilities at the Laser-Hardened Materials Evaluation Laboratory (LHMEL)

NASA Astrophysics Data System (ADS)

Royse, Robert W.; Seibert, Daniel B., II; Lander, Michael L.; Eric, John J.

2000-08-01

Pulsed laser capabilities at the Laser Hardened Material Evaluation Laboratory are described relevant to optical coupling, impulse generation and laser propulsion. Capabilities of the Nd:Glass laser are presented as well as supporting test systems.

[Assessment of comprehensive nutritional status and eating behavior among 311 middle aged and aged women with osteoporosis in Chengdu].

PubMed

Zhao, R P; Wang, W Z; Cheng, G P; Zhang, H J; Zhou, F M; Li, Y Y; Wu, C; Yang, L Q; Zeng, G

2017-06-06

Objective: To investigate the comprehensive nutritional status and diet behavior of middle aged and elderly women with osteoporosis, and thereby to explore the relationship between diet behavior and comprehensive nutritional status. Methods: 311 middle-aged and elderly women with osteoporosis in Chengdu were included in this study. Mini Nutritional Assessment (MNA) was applied to assess their comprehensive nutritional status. Information of social-demographic characteristics and diet behavior (about meals, snacks and water drinking, etc.) of the subjects was collected by questionnaire. Chi square test was used to assess the differences in nutritional status among patients who have different eating behaviors. Logistic regression analysis was performed to evaluate the relationship between diet behaviors and comprehensive nutritional status. Results: The mean MNA score of subjects was 25.8±2.5. 20.3% (63/311) of the subjets were at risk of potential malnutrition, but there was no malnourished subjects found. 46.9% (46/311) of the subjects were in good appetite. 95.2% (296/311) of them had a fixed food intake each meal. 65.8% (198/311) of them had snacks every day, and the most common choice was fruit (86.4% (248/287)). 54.8% (165/311) of them had initiative drinking water habits, and the most common choice was plain boiled water (79.9%, 246/308). 76.5% (238/311) of them had daily portable water less than 1 500 ml. After adjusting the effects of age, occupation and education level, bad appetite ( OR= 3.50, 95% CI: 1.18-10.62), unfixed food intake ( OR= 7.27, 95% CI: 1.40-35.83), and seldom or never intake of snack ( OR= 3.71, 95% CI: 1.42-9.72) were risk factors for malnutrition risk, while tea drinking was protective factor( OR= 0.31, 95% CI: 0.11-0.93). Conclusion: Risk of potential malnutrition and unhealthy diet behavior among the middle aged and elderly women with osteoporosis should be paid more attention. Unhealtghy diet behavior has a negative effect on their

Changes in androgen receptor, estrogen receptor alpha, and sexual behavior with aging and testosterone in male rats.

PubMed

Wu, Di; Gore, Andrea C

2010-07-01

Reproductive aging in males is characterized by a diminution in sexual behavior beginning in middle age. We investigated the relationships among testosterone, androgen receptor (AR) and estrogen receptor alpha (ERalpha) cell numbers in the hypothalamus, and their relationship to sexual performance in male rats. Young (3months) and middle-aged (12months) rats were given sexual behavior tests, then castrated and implanted with vehicle or testosterone capsules. Rats were tested again for sexual behavior. Numbers of AR and ERalpha immunoreactive cells were counted in the anteroventral periventricular nucleus and the medial preoptic nucleus, and serum hormones were measured. Middle-aged intact rats had significant impairments of all sexual behavior measures compared to young males. After castration and testosterone implantation, sexual behaviors in middle-aged males were largely comparable to those in the young males. In the hypothalamus, AR cell density was significantly (5-fold) higher, and ERalpha cell density significantly (6-fold) lower, in testosterone- than vehicle-treated males, with no age differences. Thus, restoration of serum testosterone to comparable levels in young and middle-aged rats resulted in similar preoptic AR and ERalpha cell density concomitant with a reinstatement of most behaviors. These data suggest that age-related differences in sexual behavior cannot be due to absolute levels of testosterone, and further, the middle-aged brain retains the capacity to respond to exogenous testosterone with changes in hypothalamic AR and ERalpha expression. Our finding that testosterone replacement in aging males has profound effects on hypothalamic receptors and behavior has potential medical implications for the treatment of age-related hypogonadism in men. Copyright 2010 Elsevier Inc. All rights reserved.

The Involvement of Hemocyte Prophenoloxidase in the Shell-Hardening Process of the Blue Crab, Callinectes sapidus

PubMed Central

Alvarez, Javier V.; Chung, J. Sook

2015-01-01

Cuticular structures of arthropods undergo dramatic molt-related changes from being soft to becoming hard. The shell-hardening process of decapod crustaceans includes sclerotization and mineralization. Hemocyte PPO plays a central role in melanization and sclerotization particularly in wound healing in crustaceans. However, little is known about its role in the crustacean initial shell-hardening process. The earlier findings of the aggregation of heavily granulated hemocytes beneath the hypodermis during ecdysis imply that the hemocytes may be involved in the shell-hardening process. In order to determine if hemocytes and hemocyte PPO have a role in the shell-hardening of crustaceans, a knockdown study using specific CasPPO-hemo-dsRNA was carried out with juvenile blue crabs, Callinectes sapidus. Multiple injections of CasPPO-hemo-dsRNA reduce specifically the levels of CasPPO-hemo expression by 57% and PO activity by 54% in hemocyte lysate at the postmolt, while they have no effect on the total hemocyte numbers. Immunocytochemistry and flow cytometry analysis using a specific antiserum generated against CasPPO show granulocytes, semigranulocytes and hyaline cells as the cellular sources for PPO at the postmolt. Interestingly, the type of hemocytes, as the cellular sources of PPO, varies by molt stage. The granulocytes always contain PPO throughout the molt cycle. However, semigranulocytes and hyaline cells become CasPPO immune-positive only at early premolt and postmolt, indicating that PPO expression in these cells may be involved in the shell-hardening process of C. sapidus. PMID:26393802

Multipurpose hardened spacecraft insulation

NASA Technical Reports Server (NTRS)

Steimer, Carlos H.

1990-01-01

A Multipurpose Hardened Spacecraft Multilayer Insulation (MLI) system was developed and implemented to meet diverse survivability and performance requirements. Within the definition and confines of a MLI assembly (blanket), the design: (1) provides environmental protection from natural and induced nuclear, thermal, and electromagnetic radiation; (2) provides adequate electrostatic discharge protection for a geosynchronous satellite; (3) provides adequate shielding to meet radiated emission needs; and (4) will survive ascent differential pressure loads between enclosed volume and space. The MLI design is described which meets these requirements and design evolution and verification is discussed. The application is for MLI blankets which closeout the area between the laser crosslink subsystem (LCS) equipment and the DSP spacecraft cabin. Ancillary needs were implemented to ease installation at launch facility and to survive ascent acoustic and vibration loads. Directional venting accommodations were also incorporated to avoid contamination of LCS telescope, spacecraft sensors, and second surface mirrors (SSMs).

Non-linear acceleration at supernova remnant shocks and the hardening in the cosmic ray spectrum

NASA Astrophysics Data System (ADS)

Recchia, S.; Gabici, S.

2018-02-01

In the last few years, several experiments have shown that the cosmic ray spectrum below the knee is not a perfect power law. In particular, the proton and helium spectra show a spectral hardening by ˜0.1-0.2 in spectral index at particle energies of ˜ 200-300 GeV nucleon-1. Moreover, the helium spectrum is found to be harder than that of protons by ˜0.1 and some evidence for a similar hardening was also found in the spectra of heavier elements. Here, we consider the possibility that the hardening may be the result of a dispersion in the slope of the spectrum of cosmic rays accelerated at supernova remnant shocks. Such a dispersion is indeed expected within the framework of non-linear theories of diffusive shock acceleration, which predict steeper (harder) particle spectra for larger (smaller) cosmic ray acceleration efficiencies.

Genetic and environmental origins of gambling behaviors from ages 18 to 25: A longitudinal twin family study.

PubMed

King, Serena M; Keyes, Margaret; Winters, Ken C; McGue, Matt; Iacono, William G

2017-05-01

Gambling behaviors tend to increase in prevalence from late adolescence to young adulthood, and the underlying genetic and environmental influences during this period remain largely understudied. We examined the genetic and environmental influences on gambling behaviors contributing to stability and change from ages 18 to 25 in a longitudinal, behavioral genetic mixed-sex twin study design. Participants were enrolled in the Minnesota Twin Family Study. A range of gambling behaviors (maximum frequency, average frequency, money lost, and gambling problems) were assessed at ages 18 and 25. The results of our study support the following conclusions: (a) the genetic and environmental factors impacting a range of gambling behaviors are largely similar in men and women, (b) genetic factors increase in influence from 18 to 25 (21% at age 18 to 57% at age 25), (c) shared environmental factors are influential at age 18, but tend to decrease from ages 18 to 25 (55% at age 18 to 10% at age 25), and (d) nonshared environmental influences are similarly significant and are small to moderate in magnitude at both ages. The findings add to a small yet important research area regarding determinants of youth gambling behaviors and have the potential to inform prevention and intervention efforts. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

Static Strain Aging Behavior of a Manganese-Silicon Steel After Single and Multi-stage Straining

NASA Astrophysics Data System (ADS)

Seraj, P.; Serajzadeh, S.

2016-03-01

In this work, static strain aging behavior of an alloy steel containing high amounts of silicon and manganese was examined while the influences of initial microstructure and pre-strain on the aging kinetics were evaluated as well. The rate of strain aging in a low carbon steel was also determined and compared with that occurred in the alloy steel. The rates of static strain aging in the steels were defined at room temperature and at 95 °C by means of double-hit tensile testing and hardness measurements. In addition, three-stage aging experiments at 80 °C were carried out to estimate aging behavior under multi-pass deformation processing. The results showed that in-solution manganese and silicon atoms could significantly affect the aging behavior of the steel and reduce the kinetics of static strain aging as compared to the low carbon steel. The initial microstructure also played an important role on the aging behavior. The rapidly cooled steel having mean ferrite grain size of 9.7 μm showed the least aging susceptibility index during the aging experiments. Accordingly, the activation energies for static strain aging were calculated as 93.2 and 85.7 kJ/mole for the alloy steel having fine and coarse ferrite-pearlite structures, respectively while it was computed as 79.1 kJ/mole for the low carbon steel with ferrite mean grain size of about 16.2 μm.

Trajectories of Externalizing Behavior from Age 2 to Age 9: Relations with Gender, Temperament, Ethnicity, Parenting, and Rater

ERIC Educational Resources Information Center

Miner, Jennifer L.; Clarke-Stewart, K. Alison

2008-01-01

Trajectories of children's externalizing behavior were examined using multilevel growth curve modeling of data from the NICHD Study of Early Child Care and Youth Development. According to ratings by both mothers and caregivers/teachers when children were 2, 3, 4, 7, and 9 years old, externalizing behavior declined with age. However, mothers rated…

Effects of MAOA-Genotype, Alcohol Consumption, and Aging on Violent Behavior

PubMed Central

Tikkanen, Roope; Sjöberg, Rickard L.; Ducci, Francesca; Goldman, David; Holi, Matti; Tiihonen, Jari; Virkkunen, Matti

2009-01-01

Background Environmental factors appear to interact with a functional polymorphism (MAOA-LPR) in the promoter region of the monoamine oxidase A gene (MAOA) in determining some forms of antisocial behavior. However, how MAOA-LPR modulates the effects of other factors such as alcohol consumption related to antisocial behavior is not completely understood. Methods This study examines the conjunct effect of MAOA-LPR, alcohol consumption, and aging on the risk for violent behavior. Recidivism in severe impulsive violent behavior was assessed after 7 to 15 years in a sample of 174 Finnish alcoholic offenders, the majority of whom exhibited antisocial or borderline personality disorder or both, and featured impulsive temperament traits. Results The risk for committing new acts of violence increased by 2.3% for each kilogram of increase in yearly mean alcohol consumption (p = 0.004) and decreased by 7.3% for every year among offenders carrying the high activity MAOA genotype. In contrast, alcohol consumption and aging failed to affect violent behavior in the low activity MAOA genotyped offenders. MAOA-LPR showed no main effect on the risk for recidivistic violence. Conclusions Violent offenders carrying the high activity MAOA genotype differ in several ways from carriers with the low activity MAOA risk allele previously associated with antisocial behavior. Finnish high activity MAOA genotyped risk alcoholics exhibiting antisocial behavior, high alcohol consumption, and abnormal alcohol-related impulsive and uncontrolled violence might represent an etiologically distinct alcohol dependence subtype. PMID:19120058

Effects of MAOA-genotype, alcohol consumption, and aging on violent behavior.

PubMed

Tikkanen, Roope; Sjöberg, Rickard L; Ducci, Francesca; Goldman, David; Holi, Matti; Tiihonen, Jari; Virkkunen, Matti

2009-03-01

Environmental factors appear to interact with a functional polymorphism (MAOA-LPR) in the promoter region of the monoamine oxidase A gene (MAOA) in determining some forms of antisocial behavior. However, how MAOA-LPR modulates the effects of other factors such as alcohol consumption related to antisocial behavior is not completely understood. This study examines the conjunct effect of MAOA-LPR, alcohol consumption, and aging on the risk for violent behavior. Recidivism in severe impulsive violent behavior was assessed after 7 to 15 years in a sample of 174 Finnish alcoholic offenders, the majority of whom exhibited antisocial or borderline personality disorder or both, and featured impulsive temperament traits. The risk for committing new acts of violence increased by 2.3% for each kilogram of increase in yearly mean alcohol consumption (p = 0.004) and decreased by 7.3% for every year among offenders carrying the high activity MAOA genotype. In contrast, alcohol consumption and aging failed to affect violent behavior in the low activity MAOA genotyped offenders. MAOA-LPR showed no main effect on the risk for recidivistic violence. Violent offenders carrying the high activity MAOA genotype differ in several ways from carriers with the low activity MAOA risk allele previously associated with antisocial behavior. Finnish high activity MAOA genotyped risk alcoholics exhibiting antisocial behavior, high alcohol consumption, and abnormal alcohol-related impulsive and uncontrolled violence might represent an etiologically distinct alcohol dependence subtype.

Development of constitutive models for cyclic plasticity and creep behavior of super alloys at high temperature

NASA Technical Reports Server (NTRS)

Haisler, W. E.

1983-01-01

An uncoupled constitutive model for predicting the transient response of thermal and rate dependent, inelastic material behavior was developed. The uncoupled model assumes that there is a temperature below which the total strain consists essentially of elastic and rate insensitive inelastic strains only. Above this temperature, the rate dependent inelastic strain (creep) dominates. The rate insensitive inelastic strain component is modelled in an incremental form with a yield function, blow rule and hardening law. Revisions to the hardening rule permit the model to predict temperature-dependent kinematic-isotropic hardening behavior, cyclic saturation, asymmetric stress-strain response upon stress reversal, and variable Bauschinger effect. The rate dependent inelastic strain component is modelled using a rate equation in terms of back stress, drag stress and exponent n as functions of temperature and strain. A sequence of hysteresis loops and relaxation tests are utilized to define the rate dependent inelastic strain rate. Evaluation of the model has been performed by comparison with experiments involving various thermal and mechanical load histories on 5086 aluminum alloy, 304 stainless steel and Hastelloy X.

Radiation-hardened-by-design clocking circuits in 0.13-μm CMOS technology

NASA Astrophysics Data System (ADS)

You, Y.; Huang, D.; Chen, J.; Gong, D.; Liu, T.; Ye, J.

2014-01-01

We present a single-event-hardened phase-locked loop for frequency generation applications and a digital delay-locked loop for DDR2 memory interface applications. The PLL covers a 12.5 MHz to 500 MHz frequency range with an RMS Jitter (RJ) of 4.70-pS. The DLL operates at 267 MHz and has a phase resolution of 60-pS. Designed in 0.13-μm CMOS technology, the PLL and the DLL are hardened against SEE for charge injection of 250 fC. The PLL and the DLL consume 17 mW and 22 mW of power under a 1.5 V power supply, respectively.

Advanced time integration algorithms for dislocation dynamics simulations of work hardening

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

Sills, Ryan B.; Aghaei, Amin; Cai, Wei

Efficient time integration is a necessity for dislocation dynamics simulations of work hardening to achieve experimentally relevant strains. In this work, an efficient time integration scheme using a high order explicit method with time step subcycling and a newly-developed collision detection algorithm are evaluated. First, time integrator performance is examined for an annihilating Frank–Read source, showing the effects of dislocation line collision. The integrator with subcycling is found to significantly out-perform other integration schemes. The performance of the time integration and collision detection algorithms is then tested in a work hardening simulation. The new algorithms show a 100-fold speed-up relativemore » to traditional schemes. As a result, subcycling is shown to improve efficiency significantly while maintaining an accurate solution, and the new collision algorithm allows an arbitrarily large time step size without missing collisions.« less

Advanced time integration algorithms for dislocation dynamics simulations of work hardening

DOE PAGES

Sills, Ryan B.; Aghaei, Amin; Cai, Wei

2016-04-25

Efficient time integration is a necessity for dislocation dynamics simulations of work hardening to achieve experimentally relevant strains. In this work, an efficient time integration scheme using a high order explicit method with time step subcycling and a newly-developed collision detection algorithm are evaluated. First, time integrator performance is examined for an annihilating Frank–Read source, showing the effects of dislocation line collision. The integrator with subcycling is found to significantly out-perform other integration schemes. The performance of the time integration and collision detection algorithms is then tested in a work hardening simulation. The new algorithms show a 100-fold speed-up relativemore » to traditional schemes. As a result, subcycling is shown to improve efficiency significantly while maintaining an accurate solution, and the new collision algorithm allows an arbitrarily large time step size without missing collisions.« less

Tensile and compressive stress-strain behavior of heat treated boron-aluminum

NASA Technical Reports Server (NTRS)

Kennedy, J. M.; Tenney, D. R.; Herakovich, C. T.

1978-01-01

An experimental study was conducted to assess the effects of heat treatment and cyclic mechanical loading on the tensile and compressive stress-strain behavior of six boron-aluminum composites having different laminate orientations and being subjected to different heat treatments. The heat treatments were as-fabricated, T6, and T6N consisting of T6 treatment followed by cryogenic quench in liquid nitrogen prior to testing. All laminates were tested in monotonic and cyclic compression, while the tensile-test data are taken from the literature for comparison purposes. It is shown that the linear elastic range of the T6- and T6N-condition specimens is larger than that of the as-fabricated specimens, and that cyclic loading in tension or compression strain hardens the specimens and extends the linear elastic range. For laminates containing 0-deg plies, the stress-strain behavior upon unloading is found to be nonlinear, whereas the other laminates exhibit a linear behavior upon unloading. Specimens in the T6 and T6N conditions show higher strain hardening than the as-fabricated specimens.

Design of rapid hardening engineered cementitious composites for sustainable construction

NASA Astrophysics Data System (ADS)

Marushchak, Uliana; Sanytsky, Myroslav; Sydor, Nazar

2017-12-01

This paper deals with design of environmentally friendly Rapid Hardening Engineered Cementitious Composite (RHECC) nanomodified with ultrafine mineral additives, polycarboxylate ether based superplasticizer, calcium hydrosilicate nanoparticles and dispersal reinforced by fibers. The incremental coefficient of surface activity was proposed in order to estimation of ultrafine supplementary materials (fly ash, methakaolin, microsilica) efficiency. A characterization of RHECC's compressive and flexural properties at different ages is reported in this paper. Early compressive strength of ECC is 45-50 MPa, standard strength - 84-95 MPa and parameter Rc2/Rc28 - 65-70%. The microstructure of the cement matrix and RHECC was investigated. The use of ultrafine mineral supplementary materials provides reinforcement of structure on micro- and nanoscale level (cementing matrix) due to formation of sub-microreinforcing hydrate phase as AFt- and C-S-H phases in unclinker part of cement matrix, resulting in the phenomena of "self-reinforcement" on the microstructure level. Designed RHECC may be regarded as lower brittle since the crack resistance coefficient is higher comparison to conventional fine grain concrete.

Deformation and recrystallization behavior of super high-purity niobium for SRF cavity

NASA Astrophysics Data System (ADS)

Yamaguchi, Y.; Doryo, H.; Yuasa, M.; Miyamoto, H.; Yamanaka, M.

2017-05-01

Deformation and recyrstallization behavior of pure niobium was investigated in order to clarify the origin of its low hydro-formability despite of its high ductility comparable with pure iron. It was found that pure niobium exhibits lower strain hardening in cold rolling compared with pure iron. Furthermore, in post-deformation annealing, the hardness of niobium decreased monotonously with an increase of temperature, and the typical sharp drop by recrystallization was not evident. This softening behavior was contrasted with the high-purity iron. It is suggested that niobium exhibit the so-called in-situ recrystallization possibly because of low elastic modulus and low accumulative plastic strain energy in spite of high melting temperature. The low hydro-formability of pure niobium sheets or tubes is caused by its low strain hardening and its unique plastic anisotropy which is associated with this recovered residual rolled texture.

The Use of a Simple Enzyme Assay in 'Seed-Hardening' Studies

ERIC Educational Resources Information Center

Ead, J.; Devonald, V. G.

1975-01-01

Describes a single technique for an enzyme assay of catalase. The method shows that vegetable seeds submitted to pre-sowing 'hardening' cycles of imbition and drying have greater catalase activity and more rapid germination than do the controls. (LS)

Different macaque models of cognitive aging exhibit task-dependent behavioral disparities.

PubMed

Comrie, Alison E; Gray, Daniel T; Smith, Anne C; Barnes, Carol A

2018-05-15

Deficits in cognitive functions that rely on the integrity of the frontal and temporal lobes are characteristic of normative human aging. Due to similar aging phenotypes and homologous cortical organization between nonhuman primates and humans, several species of macaque monkeys are used as models to explore brain senescence. These macaque species are typically regarded as equivalent models of cognitive aging, yet no direct comparisons have been made to support this assumption. Here we used adult and aged rhesus and bonnet macaques (Macaca mulatta and Macaca radiata) to characterize the effect of age on acquisition and retention of information across delays in a battery of behavioral tasks that rely on prefrontal cortex and medial temporal lobe networks. The cognitive functions that were tested include visuospatial short-term memory, object recognition memory, and object-reward association memory. In general, bonnet macaques at all ages outperformed rhesus macaques on tasks thought to rely primarily on the prefrontal cortex, and were more resilient to age-related deficits in these behaviors. On the other hand, both species were comparably impaired by age on tasks thought to preferentially engage the medial temporal lobe. Together, these results suggest that rhesus and bonnet macaques are not equivalent models of cognitive aging and highlight the value of cross-species comparisons. These observations should enable improved design and interpretation of future experiments aimed at understanding changes in cognition across the lifespan. Copyright © 2018 Elsevier B.V. All rights reserved.

Cuprizone-induced demyelination in mice: age-related vulnerability and exploratory behavior deficit.

PubMed

Wang, Hongkai; Li, Chengren; Wang, Hanzhi; Mei, Feng; Liu, Zhi; Shen, Hai-Ying; Xiao, Lan

2013-04-01

Schizophrenia is a mental disease that mainly affects young individuals (15 to 35 years old) but its etiology remains largely undefined. Recently, accumulating evidence indicated that demyelination and/or dysfunction of oligodendrocytes is an important feature of its pathogenesis. We hypothesized that the vulnerability of young individuals to demyelination may contribute to the onset of schizophrenia. In the present study, three different age cohorts of mice, i.e. juvenile (3 weeks), young-adult (6 weeks) and middle-aged (8 months), were subjected to a 6-week diet containing 0.2% cuprizone (CPZ) to create an animal model of acute demyelination. Then, age-related vulnerability to CPZ-induced demyelination, behavioral outcomes, and myelination-related molecular biological changes were assessed. We demonstrated: (1) CPZ treatment led to more severe demyelination in juvenile and young-adult mice than in middle-aged mice in the corpus callosum, a region closely associated with the pathophysiology of schizophrenia; (2) the higher levels of demyelination in juvenile and young-adult mice were correlated with a greater reduction of myelin basic protein, more loss of CC-1-positive mature oligodendrocytes, and higher levels of astrocyte activation; and (3) CPZ treatment resulted in a more prominent exploratory behavior deficit in juvenile and young-adult mice than in middle-aged mice. Together, our data demonstrate an age-related vulnerability to demyelination with a concurrent behavioral deficit, providing supporting evidence for better understanding the susceptibility of the young to the onset of schizophrenia.

Biological sources of inflexibility in brain and behavior with aging and neurodegenerative diseases

PubMed Central

Hong, S. Lee; Rebec, George V.

2012-01-01

Almost unequivocally, aging and neurodegeneration lead to deficits in neural information processing. These declines are marked by increased neural noise that is associated with increased variability or inconsistency in behavioral patterns. While it is often viewed that these problems arise from dysregulation of dopamine (DA), a monoamine modulator, glutamate (GLU), an excitatory amino acid that interacts with DA, also plays a role in determining the level of neural noise. We review literature demonstrating that neural noise is highest at both high and low levels of DA and GLU, allowing their interaction to form a many-to-one solution map for neural noise modulation. With aging and neurodegeneration, the range over which DA and GLU can be modulated is decreased leading to inflexibility in brain activity and behavior. As the capacity to modulate neural noise is restricted, the ability to shift noise from one brain region to another is reduced, leading to greater uniformity in signal-to-noise ratios across the entire brain. A negative consequence at the level of behavior is inflexibility that reduces the ability to: (1) switch from one behavior to another; and (2) stabilize a behavioral pattern against external perturbations. In this paper, we develop a theoretical framework where inflexibility across brain and behavior, rather than inconsistency and variability is the more important problem in aging and neurodegeneration. This theoretical framework of inflexibility in aging and neurodegeneration leads to the hypotheses that: (1) dysfunction in either or both of the DA and GLU systems restricts the ability to modulate neural noise; and (2) levels of neural noise and variability in brain activation will be dedifferentiated and more evenly distributed across the brain; and (3) changes in neural noise and behavioral variability in response to different task demands and changes in the environment will be reduced. PMID:23226117

Effects of prenatal marijuana exposure on child behavior problems at age 10.

PubMed

Goldschmidt, L; Day, N L; Richardson, G A

2000-01-01

This is a prospective study of the effects of prenatal marijuana exposure on child behavior problems at age 10. The sample consisted of low-income women attending a prenatal clinic. Half of the women were African-American and half were Caucasian. The majority of the women decreased their use of marijuana during pregnancy. The assessments of child behavior problems included the Child Behavior Checklist (CBCL), Teacher's Report Form (TRF), and the Swanson, Noland, and Pelham (SNAP) checklist. Multiple and logistic regressions were employed to analyze the relations between marijuana use and behavior problems of the children, while controlling for the effects of other extraneous variables. Prenatal marijuana use was significantly related to increased hyperactivity, impulsivity, and inattention symptoms as measured by the SNAP, increased delinquency as measured by the CBCL, and increased delinquency and externalizing problems as measured by the TRF. The pathway between prenatal marijuana exposure and delinquency was mediated by the effects of marijuana exposure on inattention symptoms. These findings indicate that prenatal marijuana exposure has an effect on child behavior problems at age 10.

Comparison of properties of fresh and hardened concrete in bridge decks.

DOT National Transportation Integrated Search

1971-01-01

A study was made on 17 bridge decks constructed in 1963 under regular construction procedures. The purpose was (1) to compare important properties of concrete as freshly placed in randomly selected bridge decks with those after hardening of the concr...

A microstructure-based yield stress and work-hardening model for textured 6xxx aluminium alloys

NASA Astrophysics Data System (ADS)

Khadyko, M.; Myhr, O. R.; Dumoulin, S.; Hopperstad, O. S.

2016-04-01

The plastic properties of an aluminium alloy are defined by its microstructure. The most important factors are the presence of alloying elements in the form of solid solution and precipitates of various sizes, and the crystallographic texture. A nanoscale model that predicts the work-hardening curves of 6xxx aluminium alloys was proposed by Myhr et al. The model predicts the solid solution concentration and the particle size distributions of different types of metastable precipitates from the chemical composition and thermal history of the alloy. The yield stress and the work hardening of the alloy are then determined from dislocation mechanics. The model was largely used for non-textured materials in previous studies. In this work, a crystal plasticity-based approach is proposed for the work hardening part of the nanoscale model, which allows including the influence of the crystallographic texture. The model is evaluated by comparison with experimental data from uniaxial tensile tests on two textured 6xxx alloys in five temper conditions.

Quantitative Residual Strain Analyses on Strain Hardened Nickel Based Alloy

NASA Astrophysics Data System (ADS)

Yonezawa, Toshio; Maeguchi, Takaharu; Goto, Toru; Juan, Hou

Many papers have reported about the effects of strain hardening by cold rolling, grinding, welding, etc. on stress corrosion cracking susceptibility of nickel based alloys and austenitic stainless steels for LWR pipings and components. But, the residual strain value due to cold rolling, grinding, welding, etc. is not so quantitatively evaluated.

Male sexual behavior is associated with LHRH neuron number in middle-aged rats.

PubMed

Tsai, Y F; Tsai, H W; Tai, M Y; Huang, R L; Peng, M T

1997-11-21

LHRH administration is reported to facilitate male sexual behavior. The aim of the present study was to investigate whether male sexual behavior is associated with the number of LHRH neurons in the forebrain in middle-aged rats. Male Long-Evans rats (18-19 months) were assigned to three groups on the basis of sexual performance: (1) group MEI consisted of rats showing complete copulatory patterns, including mounts, intromissions and ejaculations, (2) group MI was composed of rats showing mounts and intromissions, but no ejaculation and (3) group NC were non-copulators, i.e. they did not show any copulatory behavior. Young adult rats (4-5 months), displaying sexual behavior, were used as controls. Following the sexual behavior tests, the number of LHRH neurons in the medial septum (MS), organum vasculosum of the lamina terminalis (OVLT), preoptic area (POA) and anterior hypothalamus (AH) was determined by immunocytochemistry. No difference was seen in the total number of LHRH neurons in these combined brain areas between group MIE and young controls. In the three middle-aged groups, the total number of LHRH neurons was greatest in group MIE, less in group MI, and lowest in group NC. In general, a similar trend was seen separately in the MS, OVLT and POA. These results suggest that changes in the number of LHRH neurons in the forebrain, in most cases, are age-related, at least in the middle-aged rats, but they also seem to be associated with male sexual performance.

Simulation of the Press Hardening Process and Prediction of the Final Mechanical Material Properties

NASA Astrophysics Data System (ADS)

Hochholdinger, Bernd; Hora, Pavel; Grass, Hannes; Lipp, Arnulf

2011-08-01

Press hardening is a well-established production process in the automotive industry today. The actual trend of this process technology points towards the manufacturing of parts with tailored properties. Since the knowledge of the mechanical properties of a structural part after forming and quenching is essential for the evaluation of for example the crash performance, an accurate as possible virtual assessment of the production process is more than ever necessary. In order to achieve this, the definition of reliable input parameters and boundary conditions for the thermo-mechanically coupled simulation of the process steps is required. One of the most important input parameters, especially regarding the final properties of the quenched material, is the contact heat transfer coefficient (IHTC). The CHTC depends on the effective pressure or the gap distance between part and tool. The CHTC at different contact pressures and gap distances is determined through inverse parameter identification. Furthermore a simulation strategy for the subsequent steps of the press hardening process as well as adequate modeling approaches for part and tools are discussed. For the prediction of the yield curves of the material after press hardening a phenomenological model is presented. This model requires the knowledge of the microstructure within the part. By post processing the nodal temperature history with a CCT diagram the quantitative distribution of the phase fractions martensite, bainite, ferrite and pearlite after press hardening is determined. The model itself is based on a Hockett-Sherby approach with the Hockett-Sherby parameters being defined in function of the phase fractions and a characteristic cooling rate.

Iron supplementation in infancy contributes to more adaptive behavior at 10 years of age.

PubMed

Lozoff, Betsy; Castillo, Marcela; Clark, Katy M; Smith, Julia B; Sturza, Julie

2014-06-01

Most studies of behavioral/developmental effects of iron deficiency anemia (IDA) or iron supplementation in infancy have found social-emotional differences. Differences could relate to behavioral inhibition or lack of positive affect and altered response to reward. To determine long-term behavioral effects, the study was a follow-up of a randomized controlled trial of behavioral/developmental effects of preventing IDA in infancy. Healthy Chilean infants free of IDA at age 6 mo were randomly assigned to iron supplementation or no added iron (formula with iron/powdered cow milk, vitamins with/without iron) from ages 6 to 12 mo. At age 10 y, 59% (666 of 1123) and 68% (366 of 534) of iron-supplemented and no-added-iron groups were assessed. Social-emotional outcomes included maternal-reported behavior problems, self-reported behavior, examiner ratings, and video coding of a social stress task and gamelike paradigms. Examiners rated the iron-supplemented group as more cooperative, confident, persistent after failure, coordinated, and direct and reality-oriented in speech and working harder after praise compared with the no-added-iron group. In a task designed to elicit positive affect, supplemented children spent more time laughing and smiling together with their mothers and started smiling more quickly. In the social stress task they smiled and laughed more and needed less prompting to complete the task. All P values were <0.05; effect sizes were 0.14-0.36. There were no differences in behaviors related to behavioral inhibition, such as anxiety/depression or social problems. In sum, iron supplementation in infancy was associated with more adaptive behavior at age 10 y, especially in affect and response to reward, which may improve performance at school and work, mental health, and personal relationships. © 2014 American Society for Nutrition.

Behavioral aging is associated with reduced sensory neuron excitability in Aplysia californica.

PubMed

Kempsell, Andrew T; Fieber, Lynne A

2014-01-01

Invertebrate models have advantages for understanding the basis of behavioral aging due to their simple nervous systems and short lifespans. The potential usefulness of Aplysia californica in aging research is apparent from its long history of neurobiological research, but it has been underexploited in this model use. Aging of simple reflexes at both single sensory neuron and neural circuit levels was studied to connect behavioral aging to neurophysiological aging. The tail withdrawal reflex (TWR), righting reflex, and biting response were measured throughout sexual maturity in 3 cohorts of hatchery-reared animals of known age. Reflex times increased and reflex amplitudes decreased significantly during aging. Aging in sensory neurons of animals with deficits in measures of the TWR and biting response resulted in significantly reduced excitability in old animals compared to their younger siblings. The threshold for firing increased while the number of action potentials in response to depolarizing current injection decreased during aging in sensory neurons, but not in tail motoneurons. Glutamate receptor-activated responses in sensory neurons also decreased with aging. In old tail motoneurons, the amplitude of evoked EPSPs following tail shock decreased, presumably due to reduced sensory neuron excitability during aging. The results were used to develop stages of aging relevant to both hatchery-reared and wild-caught Aplysia. Aplysia is a viable aging model in which the contributions of differential aging of components of neural circuits may be assessed.

Behavioral aging is associated with reduced sensory neuron excitability in Aplysia californica

PubMed Central

Kempsell, Andrew T.; Fieber, Lynne A.

2014-01-01

Invertebrate models have advantages for understanding the basis of behavioral aging due to their simple nervous systems and short lifespans. The potential usefulness of Aplysia californica in aging research is apparent from its long history of neurobiological research, but it has been underexploited in this model use. Aging of simple reflexes at both single sensory neuron and neural circuit levels was studied to connect behavioral aging to neurophysiological aging. The tail withdrawal reflex (TWR), righting reflex, and biting response were measured throughout sexual maturity in 3 cohorts of hatchery-reared animals of known age. Reflex times increased and reflex amplitudes decreased significantly during aging. Aging in sensory neurons of animals with deficits in measures of the TWR and biting response resulted in significantly reduced excitability in old animals compared to their younger siblings. The threshold for firing increased while the number of action potentials in response to depolarizing current injection decreased during aging in sensory neurons, but not in tail motoneurons. Glutamate receptor-activated responses in sensory neurons also decreased with aging. In old tail motoneurons, the amplitude of evoked EPSPs following tail shock decreased, presumably due to reduced sensory neuron excitability during aging. The results were used to develop stages of aging relevant to both hatchery-reared and wild-caught Aplysia. Aplysia is a viable aging model in which the contributions of differential aging of components of neural circuits may be assessed. PMID:24847260

Neutron energy spectrum influence on irradiation hardening and microstructural development of tungsten

DOE PAGES

Fukuda, Makoto; Kiran Kumar, N. A. P.; Koyanagi, Takaaki; ...

2016-07-02

We performed a neutron irradiation to single crystal pure tungsten in the mixed spectrum High Flux Isotope Reactor (HFIR). In order to investigate the influences of neutron energy spectrum, the microstructure and irradiation hardening were compared with previous data obtained from the irradiation campaigns in the mixed spectrum Japan Material Testing Reactor (JMTR) and the sodium-cooled fast reactor Joyo. The irradiation temperatures were in the range of ~90–~800 °C and fast neutron fluences were 0.02–9.00 × 10 25 n/m 2 (E > 0.1 MeV). Post irradiation evaluation included Vickers hardness measurements and transmission electron microscopy. Moreover, the hardness and microstructuremore » changes exhibited a clear dependence on the neutron energy spectrum. The hardness appeared to increase with increasing thermal neutron flux when fast fluence exceeds 1 × 10 25 n/m 2 (E > 0.1 MeV). Finally, irradiation induced precipitates considered to be χ- and σ-phases were observed in samples irradiated to >1 × 10 25 n/m 2 (E > 0.1 MeV), which were pronounced at high dose and due to the very high thermal neutron flux of HFIR. Although the irradiation hardening mainly caused by defects clusters in a low dose regime, the transmutation-induced precipitation appeared to impose additional significant hardening of the tungsten.« less

Neutron energy spectrum influence on irradiation hardening and microstructural development of tungsten

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

Fukuda, Makoto; Kiran Kumar, N. A. P.; Koyanagi, Takaaki

We performed a neutron irradiation to single crystal pure tungsten in the mixed spectrum High Flux Isotope Reactor (HFIR). In order to investigate the influences of neutron energy spectrum, the microstructure and irradiation hardening were compared with previous data obtained from the irradiation campaigns in the mixed spectrum Japan Material Testing Reactor (JMTR) and the sodium-cooled fast reactor Joyo. The irradiation temperatures were in the range of ~90–~800 °C and fast neutron fluences were 0.02–9.00 × 10 25 n/m 2 (E > 0.1 MeV). Post irradiation evaluation included Vickers hardness measurements and transmission electron microscopy. Moreover, the hardness and microstructuremore » changes exhibited a clear dependence on the neutron energy spectrum. The hardness appeared to increase with increasing thermal neutron flux when fast fluence exceeds 1 × 10 25 n/m 2 (E > 0.1 MeV). Finally, irradiation induced precipitates considered to be χ- and σ-phases were observed in samples irradiated to >1 × 10 25 n/m 2 (E > 0.1 MeV), which were pronounced at high dose and due to the very high thermal neutron flux of HFIR. Although the irradiation hardening mainly caused by defects clusters in a low dose regime, the transmutation-induced precipitation appeared to impose additional significant hardening of the tungsten.« less

Occupational contact dermatitis caused by 1,3-benzenedimethanamine, N-(2-phenylethyl) derivatives in hardeners for epoxy paints and coatings.

PubMed

Pesonen, Maria; Kuuliala, Outi; Suomela, Sari; Aalto-Korte, Kristiina

2016-12-01

Amines in epoxy hardeners are significant causes of occupational allergic contact dermatitis among workers who use epoxy resin systems. To describe a novel group of contact allergens: N-(2-phenylethyl) derivatives of the reactive amine 1,3-benzenedimethanamine (1,3-BDMA). We describe the clinical examinations and exposure of 6 patients with occupational contact allergy to derivatives of 1,3-BDMA. Of the 6 patients, 4 were spray painters who used epoxy paints, 1 was a floor layer who handled a variety of epoxy coatings, and 1 was a worker in epoxy hardener manufacture. We were able to confirm exposure to epoxy hardeners that contained derivatives of 1,3-BDMA in 5 of the 6 sensitized patients. Despite the close structural resemblance between derivatives of 1,3-BDMA and m-xylylenediamine (MXDA), only 3 patients reacted positively to MXDA. Concomitant contact allergy to diglycidyl ether of bisphenol A resin was seen in 2 of the 6 patients. Because of the lack of a commercially available patch test substance, the diagnosis of contact allergy to derivatives of 1,3-BDMA requires patch testing with either the epoxy hardener product or a hardener ingredient that contains the derivatives of 1,3-BDMA. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Differences in Affective and Behavioral Health-Related Variables Associated with Age.

ERIC Educational Resources Information Center

Bausell, R. Barker; Soeken, Karen L.

Although considerable data exist linking individual lifestyle variables to health outcomes, little is known about how the elderly differ from younger adults with respect to both their health seeking behavior and their beliefs about health. A national survey contrasted 155 persons aged 65 years of age or older with 1100 younger adults in order to…

Chronic acarbose treatment alleviates age-related behavioral and biochemical changes in SAMP8 mice.

PubMed

Tong, Jing-Jing; Chen, Gui-Hai; Wang, Fang; Li, Xue-Wei; Cao, Lei; Sui, Xu; Tao, Fei; Yan, Wen-Wen; Wei, Zhao-Jun

2015-05-01

The administration of maintaining the homeostasis of insulin/insulin-like growth factor 1 (IGF-1) signaling and/or glucose metabolism may reverse brain aging. In the present study, we investigated the effect of acarbose, an inhibitor of α-glucosidase, on age-related behavioral and biochemical changes. The SAMP8 mice were randomly divided into old control group and acarbose-treatment group. The mice in the acarbose group were administered acarbose (20 mg/kg/d, dissolved in drinking water) orally from 3 to 9 months of age when a new group of 3-month-old mice was added as young controls. The results showed that the aged controls exhibited declines in sensorimotor ability, open field anxiety, spatial and non-spatial memory abilities, decreased serum insulin levels, increased IGF-1 receptor and synaptotagmin 1 (Syt1) levels and decreased insulin receptor, brain-derived neurotrophic factor (BDNF) and syntaxin 1 (Stx1) levels in the hippocampal layers. The age-related behavioral deficits correlated with the serological and histochemical data. Chronic acarbose treatment relieved these age-related changes, especially with respect to learning and memory abilities. This protective effect of acarbose on age-related behavioral impairments might be related to changes in the insulin system and the levels of BDNF, IGF-1R, and the pre-synaptic proteins Syt1 and Stx1. In conclusion, long-term treatment with acarbose ameliorated the behavioral deficits and biochemical changes in old SAMP8 mice and promoted successful aging. This study provides insight into the potential of acarbose for the treatment of brain aging. Copyright © 2015 Elsevier B.V. All rights reserved.

Cyclic Axial-Torsional Deformation Behavior of a Cobalt-Base Superalloy

NASA Technical Reports Server (NTRS)

Bonacuse, Peter J.; Kalluri, Sreeramesh

1995-01-01

The cyclic, high-temperature deformation behavior of a wrought cobalt-base super-alloy, Haynes 188, is investigated under combined axial and torsional loads. This is accomplished through the examination of hysteresis loops generated from a biaxial fatigue test program. A high-temperature axial, torsional, and combined axial-torsional fatigue database has been generated on Haynes 188 at 760 C. Cyclic loading tests have been conducted on uniform gage section tubular specimens in a servohydraulic axial-torsional test rig. Test control and data acquisition were accomplished with a minicomputer. The fatigue behavior of Haynes 188 at 760 C under axial, torsional, and combined axial-torsional loads and the monotonic and cyclic deformation behaviors under axial and torsional loads have been previously reported. In this paper, the cyclic hardening characteristics and typical hysteresis loops in the axial stress versus axial strain, shear stress ,versus engineering shear strain, axial strain versus engineering shear strain. and axial stress versus shear stress spaces are presented for cyclic in-phase and out-of-phase axial-torsional tests. For in-phase tests, three different values of the proportionality constant lambda (the ratio of engineering shear strain amplitude to axial strain amplitude, are examined, viz. 0.86, 1.73, and 3.46. In the out-of-phase tests, three different values of the phase angle, phi (between the axial and engineering shear strain waveforms), are studied, viz., 30, 60, and 90 degrees with lambda equals 1.73. The cyclic hardening behaviors of all the tests conducted on Haynes 188 at 760 C are evaluated using the von Mises equivalent stress-strain and the maximum shear stress-maximum engineering shear strain (Tresca) curves. Comparisons are also made between the hardening behaviors of cyclic axial, torsional, and combined in-phase (lambda = 1.73 and phi = 0) and out-of-phase (lambda = 1.73 and phi = 90') axial-torsional fatigue tests. These comparisons