Condition For Materials Research Articles

On the yield condition for anisotropic porous materials

The plastic yield condition for a porous material that explicitly reflects pore shapes and orientations is constructed. The cases of plastic isotropy and transverse isotropy are analyzed in detail. The agreement with the available experimental data is reasonably good.

K-0422 ビッカース圧痕形状に及ぼす接合界面の影響(G03-13 接合)(G03 材料力学部門一般講演)

It is important to evaluate the interface bonding condition for the composite materials used for machine and electronic parts. As a model specimen with the bonding interface, the laminated composite of S45C/S10C/S45C was made by diffusion bonding at temperatures of 973K, 1073K and 1173K in a vacuum furnace. Using these specimens, micro-Vickers indentations were impressed on the interface and the base parts, and then the shape of the indentation was examined using a laser microscope. As a result, the diagonal length across the interface of the indentation was longer than that along the interface between S10C and S45C steels, although they were almost same for the base parts. It was also noticed that the piling-up near the edge of the indentation was caused especially for the weak bonding interface with delamination or imperfect bonding.

TheK-primed approach to high-pressure equations of state

SUMMARY The variation with pressure of the derivative K′≡dK/dP, where K is the bulk modulus and P is the pressure, is more sensitive to the precise form of an equation than are the variations of density, ρ, or of K. Also, it leads more directly to estimates of thermal properties via the Gruneisen parameter, γ. Recent discussions have focused on equations relating K′ to P/K to make use of the infinite pressure extrapolation 1/K′∞=(P/K)∞. The fundamental significance of K′∞ is emphasized by a thermodynamic demonstration that, for solids, it has the same value for isothermal and adiabatic moduli, their isothermal and adiabatic derivatives and as the limit for both isothermal and adiabatic equations of state. However, this proof conflicts with the assumption, used to estimate K′∞ for regions of the Earth's deep interior, that a linear relationship between μ/K and P/K, where μ is the rigidity, extrapolates to (μ/K)∞=0. The new relationship requires K′∞≥1+γ∞, where the equality is a special condition, applicable to ideal gases, but the inequality appears to be the normal condition for real materials. For solids the usual theories of γ all converge to the relationship γ∞=K′∞/2−1/6, in which case the thermodynamic inequality becomes K′∞>5/3. Most finite strain theories fail this test. It compels reassessment of K′∞ for the lower mantle of the Earth and of equations of state suitable for the deep Earth. A new empirical relationship now appears to satisfy all requirements: where B=1−K′∞/K′0=−K0K″0/K′2∞, subscripts zero indicating zero-pressure values. Its use avoids the bias introduced by theories, such as that due to Birch, that impose values of K′∞ determined by the forms of the equations and not by the fitted data. It is important also to constrain K′0 by information additional to earth model data.

A continuous model for investigation of physically nonlinear deformation of orthotropic sandwich plates

A phenomenological yield condition for quasi-brittle and plastic orthotropic materials with initial stresses is suggested. All components of the yield tensor are determined from experiments on uniaxial loading. The reliability estimates of the criterion suggested is discussed. For a plastic material without initial stresses, the given condition transforms into the Marin—Hu criterion. The defining equations of the deformation theory of plasticity with isotropic and “anisotropic” hardening, associated with the yield condition suggested, are obtained. These equations are used as the basis for a highly accurate nonclassical continuous model for nonlinear deformation of thick sandwich plates. The approximations with respect to the transverse coordinate take into account the flexural and nonflexural deformations in transverse shear and compression. The high-order approximations allow us to model the occurrence of layer delamination cracks by introducing thin nonrigid interlayers without violating the continuity concept of the theory.

Some dynamic properties of incompressible, transversely isotropic elastic media

This paper investigates various dynamic properties of incompressible, transversely isotropic elastic media. The propagation condition for such materials allows the wave speeds to be obtained in explicit form. An examination of the slowness surface and direction of energy flux as the extensional modulus along the fibre tends to infinity is then easily carried out. The paper also includes an investigation of the dynamic response of such materials to a particular line impulsive force. This is done using integral transforms. These transforms are invertible in closed form.

Nonlinear mode II crack-tip fields for some Hookean materials

Abstract This paper presents a modified nonlinear Mode II crack model which is shown to satisfy the nonpenetrating crack surface boundary condition for homogeneous isotropic Hookean materials taking into account finite deformations. A recent investigation of the problem by Knowles [1] reveals apparent interpenetration of the crack surfaces which is considered nonphysical and therefore invalid. This observation is confirmed when a general solution based on Knowles's perturbation boundary layer method to characterize the finite deformation effects on Mode II crack-tip fields for the materials is derived. By deducing complete 2nd order solutions of the problem, the Poynting nonlinear effect becomes self-evident at the crack tip and for Hookean materials with v 1 2 there always exists the penetrating phenomenon between upper and lower crack surfaces.

Elasticity theory equations and fracture condition for materials of varying moduli

Many massive rocks and composite materials belong to the class of materials of varying moduli with definite distinct deformation and strength properties under tension and compression. The results of experiments indicate that the difference between the properties of materials of different moduli is not limited to tension and compression cases but can also appear clearly for any change in the form of the state of stress. Elasticity theory equations are constructed here to describe the strain of materials of varying moduli as well as the dependence of the strength properties on the form of the state of strain. Tests were done on coal, limestone, diabase and cement and results are shown. Using the dependencies obtained, Poisson's ratio and the elastic modulus can be calculated for these rocks. The equations and conditions of fracture proposed, are written in a simple invariant form.

Yield condition of oriented porous solid

In the paper a general yield condition for anisotropic ductile porous materials is developed employing the tensor functions representations. It is assumed that directional mechanical properties of a porous material are described by the structural permeability second order tensor. Such procedure enables us to disclose rotation and translations of the yield surface to shear and hydrostatic stress axes. The isotropic case is analysed in detail. Specific forms of yield criteria for simple stress states are discussed and the necessary measurements are proposed to determine the material constants.

Kinematic Hardening and Plastic Instability under Plane Stress

AbstractThe main objective of this paper is to develop a criterion of tensile plastic instability which should be sufficiently general to include both the Bauschinger effect and anisotropy. The criterion so developed reduces to Moore and Wallace's condition for anisotropic materials, in case the Bauschinger effect is either completely neglected or it is negligible at the onset of deformation process. However, this analysis shows significant change in instability condition if the material exhibits the Bauschinger effect initially.It is also shown that localised neck can also take place in biaxial loading for stress ratios greater than half. This would depend upon the anisotropy coefficients and the degree of the Bauschinger effect initially exhibited by the material.

Limit condition and flow rule for granular materials. -A generalised Mohr-Coulomb condition is proposed as limit condition for granular materials : 3R. Deutsche Beit. Zur Geotechnik, N2, 1974, P28–30

Limit condition and flow rule for granular materials. -A generalised Mohr-Coulomb condition is proposed as limit condition for granular materials : 3R. Deutsche Beit. Zur Geotechnik, N2, 1974, P28–30

The fundamental inequality in thermodynamics

A theory of thermodynamics of processes can be developed on the basis of the so-called “fundamental inequality”, which is closely related to Clausius' first formulation of the second law. Some transformations of this inequality are given which permit one to derive other, although weaker, inequalities in the cases in which thermostatic stability conditions hold. A conjecture is made on the form of a thermostatic stability condition for solid materials.

Limit Analysis of Circular Orthotropic Plates

The limit analysis of simply supported circular orthotropic plates subjected to uniformly distributed load is investigated. The analysis is based on the yield condition for orthotropic metals suggested by Hill, which reduces to the well-known Mises yield condition for isotropic materials. Both the classical method and a proposed variational method are used in the investigation. The comparison of the results shows that the multipliers obtained by the proposed variational method and the classical method are in close agreement. However, the variational method yields the multiplier through the solution of simple algebraic equations without regards to the yield conditions, which usually presents difficulty in the classical method. Thus, the proposed variational method provides a convenient means for estimating the safety factor.

On the yield condition for anisotropic materials

On the yield condition for anisotropic materials