Showing papers in "Journal of Applied Mechanics in 1981"

Shock Waves and High-Strain-Rate Phenomena in Metals

Abstract: These proceedings of EXPLOMET 90, the International Conference on the Materials Effects of Shock-Wave and High-Strain-Rate Phenomena, held August 1990, in La Jolla, California, represent a global and up-to-date appraisal of this field. Contributions (more than 100) deal with high-strain-rate deforma

A Micromechanical Description of Granular Material Behavior

Abstract: Considered is a sample of cohesionless granular material, in which the individual granules are regarded rigid, and which is subjected to overall macroscopic average stresses. On the basis of the principle of virtual work, and by an examination of the manner by which adjacent granules transmit forces through their contacts, a general representation is established for the macroscopic stresses in terms of the volume average of the (tensorial) product of the contact forces and the vectors which connect the centroids of adjacent contacting granules. Then the corresponding kinematics is examined and the overall macroscopic deformation rate and spin tensors are developed in terms of the volume average of relevant microscopic kinematical variables. As an illustration of the application of the general expressions developed, two explicit macroscopic results are deduced: (1) a dilatancy equation which both qualitatively and quantitatively seems to be in accord with experimental observation, and (2) a noncoaxiality equation which seems to support the vertex plasticity model. Since the development is based on a microstructural consideration, all material coefficients entering the results have well-defined physical interpretations.

Fatigue Failure Criteria for Unidirectional Fiber Composites

Abstract: : Three dimensional fatigue failure criteria for unidirectional fiber composites under states of cyclic stress are established in terms of quadratic stress polynomials which are expressed in terms of the transversely isotropic invariants of the cyclic stress. Two distinct fatigue failure modes, fiber mode and matrix mode, are modelled separately. Material information needed for the failure criteria are the S-N curves for single stress components. A preliminary approach to incorporate scatter into the failure criteria is presented. (Author)

The Penny-Shaped Crack and the Plane Strain Crack in an Infinite Body of Power-Law Material

Abstract: A study is carried out of the problem of a penny-shaped crack in an infinite body of power-law material subject to general remote axisymmetric stressing conditions. The plane strain version of the problem is also examined. The material is incompressible and is characterized by small strain deformation theory with a pure power relation between stress and strain. The solutions presented also apply to power-law creeping materials and to a class of strain-rate sensitive hardening materials. Both numerical and analytical procedures are employed to obtain the main results. A perturbation solution obtained by expanding about the trivial state in which the stress is everywhere parallel to the crack leads to simple formulas which are highly accurate even when the remote stress is perpendicular to the crack.

Topics in finite elasticity

Abstract: Kinematics: Stress Elastic materials, Change of observer Material symmetry Simple shear The Piola-Kirchhoff Stress Hyperelasticity The elasticity tensor The boundary-value problem Variational formulational stability and uniqueness Incompressible materials Deformations of a cube Anti-Plane Shear.

Viscoelastic Analysis of Adhesively Bonded Joints

Abstract: In this paper an adhesively bonded lap joint is analyzed by assuming that the adherends are elastic and the adhesive is linearly viscoelastic. After formulating the general problem a specific example for two identical adherends bonded through a three parameter viscoelastic solid adhesive is considered. The standard Laplace transform technique is used to solve the problem. The stress distribution in the adhesive layer is calculated for three different external loads namely, membrane loading, bending, and transverse shear loading. The results indicate that the peak value of the normal stress in the adhesive is not only consistently higher than the corresponding shear stress but also decays slower.

On the Characterization of Strain-Hardening in Plasticity.

Abstract: : In the context of a purely mechanical, rate-type theory of elastic-plastic materials and utilizing a strain space formulation, this paper is concerned mainly with developments pertaining to strain-hardening behavior consisting of three distinct types of material response, namely hardening, softening and perfectly plastic behavior. It is shown that such strain-hardening behavior may be characterized by a rate-independent quotient of quantities occurring in the loading criteria of strain space and the corresponding loading conditions of stress space. With the use of special constitutive equations, the predictive capability of the results obtained are illustrated for strain-hardening response and saturation hardening in a uniaxial tension test.

Self-Consistent Determination of Time-Dependent Behavior of Metals

Abstract: Though Kroner's self-consistent model is not fully consistent in the elastic-plastic defor­ mation of poly crystals, it is found to be perfectly consistent in the time-dependent defor­ mation of such materials. Hill's model, on the other hand, should be used with a modified constraint tensor containing the elastic moduli of the matrix in that case. Kroner's model is supplemented with a physically consistent constitutive equation for the slip system; these, together with Weng's inverse method, form the basis of a self-consistent determina­ tion of time-dependen t behavior of metals. The kinematic component of the latent hard­ ening law and the residual stress introduced in more favorably oriented grains are the two major driving forces for recovery and the Bauschinger effect in creep. The proposed meth­ od was applied to predict the creep and recovery strains of a 2618-T61 Aluminum alloy under pure shear, step and nonradial loading. The predicted results are seen to be in gen­ erally good agreement with the test data.