Stress field

About: Stress field is a research topic. Over the lifetime, 11926 publications have been published within this topic receiving 226417 citations.

Contact Analyses for Bodies With Frictional Heating and Plastic Behavior

Abstract: The stress field within machine components is an important indicator for contact failures. Since both thermal stresses due to frictional heating and plasticity are significant in engineering application, it is critical to predict the total stress field. In this work, the steady-state thermal effect is considered and a thermo-elastic-plastic contact model is developed. The model is applicable for rolling and/or sliding contact problem, as far as small equivalent plastic strain hypothesis is respected. Influence coefficients for surface normal displacement, temperature, and strain and stress tensors are used with the discrete convolution and fast Fourier transform algorithm. The single-loop conjugate gradient iteration scheme is also applied to achieve fast convergence speed. Simulations are presented for several academic examples ranging from elastic to thermo-elastic-plastic. The thermo-elastic-plastic analyses show that the heat factor in a contact situation has significant effect not only on the critical Hertzian pressure and on the pressure distribution, but also on the magnitude and depth of the maximum von Mises stress during loading and the residual ones found after unloading.

Second-order theory for the effective behavior and field fluctuations in viscoplastic polycrystals

Abstract: A recently developed “second-order” homogenization procedure (Ponte Castaneda (J. Mech. Phys. Solids 50 (2002a, b) 737, 759)) is extended to viscoplastic polycrystals and applied to compute the effective response of a certain special class of isotropic polycrystals. The method itself reduces to a simple expression requiring the computation of the averages of the stress field and the covariances of its fluctuations over the various grain orientations in an optimally selected “linear comparison polycrystal”. Therefore, the method not only allows the determination of the effective behavior of the polycrystal, but as a byproduct also yields information on the heterogeneity of the stress and strain-rate fields within the polycrystal. An application is given for a model 2-dimensional, isotropic polycrystal with power-law behavior for the constituent grains. The resulting predictions for the effective behavior are found to satisfy sharp bounds available from the literature and to be consistent with the results of recent numerical simulations. The associated averages and fluctuations of the stresses and strain rates are found to depend strongly on the strain-rate sensitivity (i.e., nonlinearity) and grain anisotropy. In particular, the stress and strain-rate fluctuations were found to grow and become strongly anisotropic with increasing values of the nonlinearity and grain anisotropy parameters.

Thermoelastic stress: How important as a cause of earthquakes in young oceanic lithosphere?

Abstract: Thermoelastic or thermal stress is a potentially important contributor to the state of stress in the oceanic lithosphere. The present paper provides several simple models for the state of thermoelastic stress in a young oceanic lithosphere, taking into account a comparison of the predictions of these models with the characteristics of near-ridge earthquakes. Attention is given to the characteristics of near-ridge earthquakes, sources of stress in an oceanic lithosphere, previous models of thermal stress, the calculation of thermal stress, and thermal stress models. A test is conducted of the hypothesis that thermoelastic stress is a significant component of the stress field in a young oceanic lithosphere. The considered models support the hypothesis that thermoelastic stress is a significant component of the stress field in a young oceanic lithosphere.

Implementing image stresses in a 3D dislocation simulation

Abstract: A three-dimensional (3D) dislocation simulation has been developed in the last few years in order to fill the gap between atomistic simulations and the more macroscopic approaches. The specific role of such a simulation is to combine all mechanisms responsible for the hardening (e.g. the forest mechanism) and the multiplication of dislocations which typically occur in three dimensions. Many problems involve the presence of interfaces, which can come from cracks, oxide layers, particles etc. The present work deals with a method to tackle such problems in a 3D simulation. It is firstly restricted to the image stress case. A method of calculating the image stress field of dislocation segments due to the presence of a semi-infinite free surface has been proposed by Gosling and Willis. An alternative method is proposed here based on the Boussinesq problem of point loading in a half-space. It is firstly shown on simple cases that the methods are equivalent. The latter one is used in the present simulation, and the image stress field due to populations of dislocations is investigated. From a practical point of view, we calculate the depths within which all dislocations have to be taken into account, in order to get reasonable accuracy on the image stresses, and we also investigate how this stress field decays in space.

Acoustoelastic Lamb Wave Propagation in Biaxially Stressed Plates (Preprint)

Abstract: : Acoustoelasticity, or the change in elastic wave speeds with stress, is a well-studied phenomenon for bulk waves The effect of stress on Lamb waves is not as well understood, although it is clear that anisotropic stresses will produce anisotropy in the Lamb wave dispersion curves Here the theory of acoustoelastic Lamb wave propagation is developed for isotropic media subjected to a biaxial, homogeneous stress field It is shown that, as expected, dispersion curves change anisotropically for most stresses, modes and frequencies Interestingly, for some mode-frequency combinations, changes in phase velocity dispersion curves are isotropic even for a biaxial stress field Theoretical predictions are compared to experimental results for several Lamb wave modes and frequencies for uniaxial loads applied to an aluminum plate, and the agreement is reasonably good