Papers by Keyword: Anisotropy

Abstract: During the last three decades, numerical simulation has gradually extended its applicability in the field of sheet metal forming. Constitutive modeling is one of the domains closely related to the development of numerical simulation tools. The paper is devoted to a comprehensive testing of the advanced materials models as implemented in the finite-element code. The test proves the capability of the advanced materials models response of DC04 steel sheet to describe the effects of the plastic anisotropy of the sheet metals subjected to industrial forming processes.

Abstract: Tissue elasticity measurements by an ultrasonic wave are a promising technique to qualitative diagnosis of tumor or liver diseases. The elasticity in the soft tissue can quantitatively be estimated by velocity of a shear wave propagating through the tissue. For safer and more accurate estimation of the velocity, an elasticity imaging method using continuous vibration wave excitation has been proposed. This method utilizes wave number vector analysis to individually estimate the velocity of the shear waves generated by multiple reflections. In this paper, applicability of the wave number filtering method is discussed to separate the plural shear waves through a phantom experiment. Then, an in-vivo experiment shows possibility to extract anisotropic information of muscle fiber for applying the tissue elasticity measurement.

Abstract: The phase-field model coupling with the concentration field and flow field was used to simulate the dendrite growth during isothermal solidification of Fe-C alloy in a forced flow. The effects of anisotropy modulus and anisotropy strength on the dendrite growth are studied. The results indicate that the dendrites have four preferential growth orientation and the side-branches growth is not perpendicular to the primary branch while the dendrite along with crystallographic directions. When the dendrite along with crystallographic directions, the dendrites have six preferential growth orientation and the side-branches are parallel to the neighborly primary branch. At a anisotropy strength of 0.01, the crystal have no apparent principal branch and grows into coral shapes.With an increase in anisotropy strength, the tip solute concentration decreases, makes the dendrite growth become fast, the tip velocity increased continuously.

Abstract: Anisotropic Pr12.5Fe72.5Co6Cr2B7 magnetic powders are obtained by varying the desorption H2-pressure of the hydrogenation disproportionation desorption recombination (HDDR) process. The magnetic powders with a desorption H2-pressure of 30 kPa have the magnetic properties of Br =0.96 T, iHc=8.2 kOe and Br/Bs =0.78, whereas the magnetic powders obtained with a higher and a lower desorption H2-pressure are isotropic. A distinct lamella crystal is observed in the 30 kPa desorption H2-pressure products and may be related to the anisotropy in the HDDR-treated powders. It is believed that the desorption H2-pressure has great effect on the formation of crystal texture in the HDDR Pr-Fe-B powders.

Abstract: The dependence of hysteretic properties of FeMn/CoFeB (AF/FM) thin bilayers on AF thickness and magnetic annealing temperature is systematically investigated for possible applications in spin-valve devices. Inducement of an easy axis after magnetic annealing is established. The anisotropy is studied by investigating the coercivity along and perpendicular to the induced easy axis using Magneto-Optic Kerr Effect (MOKE) and the AF texture is ascertained by XRD. The existence of an optimum annealing temperature, for which the maximum change in coercivity occurs for a particular AF thickness, is evidenced. The maxima in HC of the bilayer with thickness of AF layer were correlated with FCC FeMn (111) texture of the sample.

Abstract: Phase field models are widely used for the study of microstructures and their evolution. They can also be used as computer experiments. As computer experiments, they serve two important roles: (a) theoretical results which are hard to verify/validate experimentally can be verified/validated on the computer using phase field models; and, (b) when severe assumptions are made in a theory, they can be relaxed in the phase field model, and hence, results with wider reach can be obtained. In this paper, we discuss some such computer experiments in general, and the growth kinetics of precipitates in systems with tetragonal and cubic interfacial anisotropies in particular.

Abstract: The Earth deforms dominantly by solid-state creep. Diffusion creep is known to be important. It is less clear whether mechanisms in which grain boundary sliding is accompanied by other processes (dislocation activity), and/or are associated with stress exponents closer to 2 than to 1 are important. Since the mechanisms of superplasticity are themselves not fully resolved, we cannot say for sure whether the Earth deforms superplastically. Models for diffusion creep are relevant for the Earth and possibly for superplastic materials. Modelling shows that large strains may not necessarily obliterate initial textures because grain rotations, although they occur, slow down as microstructures evolve. Modelling also predicts major strength anisotropy induced by grain shape alignment. Models for two-phase diffusion creep can be constructed for when the second phase is inert (insoluble). If both phases are soluble and can participate in diffusion, the basic theory for single phase diffusion creep cannot be applied and new insight is required.

Abstract: This paper presents an experimental investigation on the failure surface and plastic potential in deviatoric plane of Bangkok Clay. The results of torsional shear hollow cylinder and triaxial tests with various principal stress directions and magnitudes of intermediate principal stress on undisturbed Bangkok Clay specimens are presented. The obtained stress-strain behaviors assert clear evidences of anisotropic characteristics of Bangkok Clay. Both failure surface and plastic potential in deviatoric plane of Bangkok Clay are demonstrated as isotropic and of circular shape (Drucker-Prager type) which implies an associated flow rule. Concerning the behavior of Bangkok Clay found from this study, the discussions on the effects of employed constitutive modeling approach on the resulting numerical analysis are made.

Abstract: High anisotropic Nd13Fe75Co4B8 magnetic powders are obtained with low desorption H2-pressure of the hydrogenation disproportionation desorption recombination (HDDR) process. Scanning electron microscopy (SEM) indicates a lamella structure in the 20 kPa desorption H2-pressure HDDR products and may be related to the high anisotropy. The magnetic powders with a desorption H2-pressure of 20 kPa have the magnetic properties of Br =0.86 T and Mr/Ms =0.81.This shows that the H2-pressure has great effect on the formation of crystal texture in the HDDR Nd-Fe-B powders.

Abstract: In designing earth structures, various kinds of complex soils and rocks are constantly encountered. These geomaterials exhibit heterogeneous, nonlinear, and anisotropic behavior. A failure criterion for such complicated materials is proposed. This model is highly comprehensive. It characterizes heterogeneity, nonlinearity, and anisotropy simultaneously in one equation. Many classical failure criteria employed in geomechanics and plasticity are its special cases. The material parameters in the proposed criterion may be determined from tests of unconfined compression, uniaxial tension, biaxial compression, and direct shear. The case study illustrates the potential of the proposed model in engineering application.