Growth, XRD, Mechanical, Optical and SHG Studies of L-Lysine L-Tartaric Acid Crystals

Single crystals of L-lysine L-tartaric acid (LLLT) were grown by solution method using double distilled water as the solvent. The grown crystals LLLT were subjected to characterization studies like XRD studies, mechanical studies, optical studies and SHG studies. From XRD studies, it is ascertained that LLLT crystal crystallizes in monoclinic structure. The grown crystal has high transmittance in the visible region and it has high optical band gap. The mechanical parameters like hardness, work hardening coefficient, yield strength, stiffness constant, brittleness index, corrected hardness and resistance pressure of LLLT crystal have been evaluated by using Vickers microhardness method. The relative SHG efficiency of LLLT crystal has been determined by Kurtz-Perry powder technique.

Autowave nature of plasticity. Scale invariance

The generality of localization of plastic deformation, which is observed at the stage of linear work hardening for HCP, BCC and FCC monoand polycrystals of pure metals and alloys, is considered. It was found previously that the motion rate of localized flow autowave is related to the reciprocal value of the work hardening coefficient by a linear law, which is universal in character. This is further substantiated by the results of the given study. The waves of plastic flow localization are found to have dispersion law. It has been established that in order to address the autowave of localized deformation, a quasi-particle may be introduced. The quasi-particle’s characteristics have been defined.

Effects of Anisotropic Yield Functions on Prediction of Forming Limit Diagram for AHS Steel

In this study, experimental and numerical analyses of Forming Limit Diagram (FLD) for Advanced High Strength (AHS) steel grade 980 were performed. Forming limit curve was first determined by means of the Nakazima stretch-forming test. Then, analytical calculations of the FLD based on the Marciniak-Kuczynski (M-K) model were carried out. Different yield criteria, namely, Hill’48 (r-value and stress-based), Yld89 (r-value and stress-based) and Barlat2000 (Yld2000-2d) were investigated. The strain hardening law according to Swift was applied. To identify parameters of each model, uniaxial tension, balanced bi-axial bulge test and in-plane biaxial tension test were performed. As a result, predicted plastic flow stresses and plastic anisotropies of the AHS steel by various directions were evaluated. In addition, effects of the anisotropic yield functions, strain rate sensitivities, imperfection values and work hardening coefficient on the predicted FLD were studied and discussed. It was found that the FLD based on the Yld2000-2d yield criterion was in better agreement with the experimental curve. Accuracy of the FLD predictions based on the M-K theory, especially in the biaxial state of stress, significantly depended on the applied yield criteria, for which yield stresses and r-values of different loading directions were required.

Experimental and Numerical Simulation Study of Plasticity-Induced and Roughness-Induced Fatigue Crack Closure

In this study, fatigue crack closure behavior was investigated in the aluminum alloy 6061-T6 and the carbon steel JIS. S25C. It was found that crack closure in the aluminum alloy 6061-T6 showed the characteristics of plasticity-induced fatigue crack closure (PIFCC), whereas the carbon steel JIS. S25C showed the characteristics of roughness-induced fatigue crack closure (RIFCC). The experiments included the determination of the crack-opening levelsKopas a function of stress intensity factor range ΔKand the effect of surface removal on the crack-opening level. In order to simulate the behaviors of the plasticity-and the roughness-induced fatigue crack closure, the finite element method was adopted. The results of FEM were in good agreement with the experimental results. It was cconcluded that at a given yield strength level , a low Youngs modulus and a low work-hardening coefficient will favor PIFCC, whereas a high Youngs modulus and a high work-hardening coefficient will favor RIFCC.

Accurate Evaluation Method for the Hydraulic Bulge Test

Optical measuring systems provide much more detail on the deformation of the blank in the bulge test than conventional contact height measuring systems. A significant increase in accuracy of the stress-strain curve can be achieved by fitting the surface to more complicated equations than the traditional spherical surface and by considering the local strain data to approximate the curvature for the midplane. In particular an ellipsoid shape is shown to be very accurate in describing the surface of the blank. Contact height measuring systems provide insufficient data to fit a surface to an ellipsoid shape and to establish local strain data. Pragmatic equations are proposed using the work hardening coefficient from the tensile test to approximate the same accuracy in stress-strain curves as obtained by optical measuring systems using the before mentioned evaluation method.

The Effect of EDTA on the Nucleation Kinetics and Mechanical Properties of KDP Crystal

Potassium di-hydrogen phosphate (KDP) has been successfully grown in pure form and doped with ethylene diamine tetra acetic acid (EDTA) by low temperature solution growth technique and nucleation kinetics of KDP crystals in doped and undoped solutions were measured and analyzed. The induction period ? was measured and experiments were performed at selected degrees of supersaturation and the critical nucleation parameters like energy of formation of the critical nucleus (?G*), radius of the critical nucleus r*, nucleation rate J, number of the molecules in the critical nucleus i* have been calculated based on the classical theory of nucleation. The grown crystals have been subjected to study the mechanical property. The microhardness test was carried out on (100) plane. The load dependent hardness and work hardening coefficient was measured.© 2012 JSR Publications. ISSN: 2070-0237 (Print); 2070-0245 (Online). All rights reserved.doi: http://dx.doi.org/10.3329/jsr.v4i3.9415 J. Sci. Res. 4 (3), 533-540 (2012)

The Influences of Constitutive Models on the Collapses of OFHC Copper Cylindrical Shells under Impact Compression

An axial collapse test of Oxygen-Free High-Conductivity copper (OFHC) cylindrical specimen subjected to impact against a steel plane target at the velocity range between 64 m/s and 165 m/s was performed on a single gas gun. The deformation process of the OFHC cylindrical shell in the specimen was a sequence of the thermovisco-plastic wave propagation between target plate and the structural plate. The experimental results were simulated numerically by use of LS-DYNA. The influences of OFHC constitutive models on the deformations of OFHC cylindrical shells were shown in the paper. It seems that the Johnson－Cook(J-C) constitutive model gave a better prediction of the shape of the OFHC cylindrical shell in such an impact test. The deformation of cylindrical shell is sensitive to the work-hardening coefficient. The energy absorption behaviors of the OFHC cylindrical shells were also investigated. The energy absorption capability of the shells influenced by their geometries were also shown in the paper.

Mechanical Characterization of Lapping Plate Materials in Diamond Charging Process

In the lapping of magnetic heads and other electronic components composed of multiple materials, differences in the processing characteristics of the composite materials result in “residual steps” forming on the surface at composite interfaces. Residual step heights have been reduced to as little as a few nanometers. We investigated using fine abrasives in fixed abrasive lapping for this purpose, which requires highly secure, high-density embedding of the abrasives on the lapping plate. To this end, we modeled the abrasive embedding process and investigated the relationship between the mechanical properties of the lapping plate and the retention of the abrasive, to determine the direction of further research and development. The results of this investigation revealed a correlation between the work hardening in the plate and the resulting abrasive density and cutting edge height. The investigation also showed that it is possible to suppress the reduction in lapping rate that occurs during use by increasing the work hardening coefficient of the plate.