Equivalent Strain Field Research Articles

An implicit BEM formulation to model strong discontinuities in solids

A boundary element method (BEM) formulation to predict the behavior of solids exhibiting displacement (strong) discontinuity is presented. In this formulation, the effects of the displacement jump of a discontinuity interface embedded in an internal cell are reproduced by an equivalent strain field over the cell. To compute the stresses, this equivalent strain field is assumed as the inelastic part of the total strain. As a consequence, the non-linear BEM integral equations that result from the proposed approach are similar to those of the implicit BEM based on initial strains. Since discontinuity interfaces can be introduced inside the cell independently on the cell boundaries, the proposed BEM formulation, combined with a tracking scheme to trace the discontinuity path during the analysis, allows for arbitrary discontinuity propagation using a fixed mesh. A simple technique to track the crack path is outlined. This technique is based on the construction of a polygonal line formed by segments inside the cells, in which the assumed failure criterion is reached. Two experimental concrete fracture tests were analyzed to assess the performance of the proposed formulation.

Explicit Dynamic FEM Analysis of Multipass Vertical-Horizontal Rolling

Three passes of plate rolling during vertical-horizontal rolling process are simulated with explicit dynamic finite element method and updating geometric method. The equivalent strain and stress fields, and shape change at the head and tail of slab during rolling are obtained. The calculated result of the shape at the head and tail of slab is in good agreement with the measured one. The explicit dynamic finite element method and updating geometric method can be used effectively to analyze the multipass vertical-horizontal (V-H) rolling process.

Relationship between corotating vortex-pair equilibria and a single vortex in an external deformation field

Two-dimensional corotating vortex pairs are computed as equilibrium solutions of the Euler equations and the influence of one vortex on the other is characterized in terms of a deformation field acting on an isolated vortex region. It is shown, by computing equilibrium states for a single vortex within an equivalent strain field, that the external rotating strain accounts for the elliptic deformation of the streamlines near the center of each vortex. Critical states, as a function of the strain rate, are reached when stagnation points start to penetrate the vortex regions at the outer boundary. While critical states for a single vortex within a uniform external rotating strain field consist of elliptical corner solutions, the vortex shapes lose the elliptical symmetry in the corotating case. We show that these asymmetric equilibrium states can be captured by a single vortex model if we consider higher order terms in the deformation field. We also demonstrate that the critical strain rates are of the same order of magnitude for both the single-vortex model and the interacting vortex pair.

Contact analysis of impact in magnetic head disk interfaces

Three-dimensional finite element analysis of head and disk contact effects induced by impact in magnetic head disk interface (HDI) are presented. Elastic–plastic contact simulations are performed using abaqus. The entire contact–impact procedures during head disk collision under the dynamic loading of half-sine pulse acceleration with profiles of 300 and 500 g amplitude and 1.0 ms in duration are described in detail. Simulation results for the contact pressure distribution at HDI, von Mises equivalent stress, and equivalent plastic strain fields are examined and interpreted in terms of impact history. A comprehensive history of head disk relative displacement and von Mises equivalent stresses within contact region are provided and the evolution of plasticity are discussed. It is shown that finite element method can provide the simulation of the contact behavior resulting from the dynamic loading.