Nonlocal Strains Research Articles

微視的な不均質構造によって生じる巨視的な不均一変形のモデル化に関する研究

Engineering materials typically have a heterogeneous microstructure, and it induces microscopic non-uniform deformation even under the macroscopically uniform stress state. With the decrease in the dimension of engineering structural components, such a microscopic non-uniform deformation affects the macroscopic deformation state. In this study, the development of the microscopic heterogeneity-induced non-uniform deformation is modeled using the rate-form nonlocal constitutive equation. First, the inelastic strain is decomposed into local and nonlocal inelastic strains. Then, the nonlocal strain is assumed to be developed by the distribution of plastic compliance, which is characterized by an intrinsic size of the material microstructure. Finally, the multiaxial rate-form constitutive equation, in which the stress on the material points is calculated by both the local and nonlocal strains, is formulated. The finite element simulations of the tensile tests of specimens with curved and parallel gauge sections are performed using the proposed model. The obtained results clarified that the mechanical response and the non-uniform deformation are characterized by the microscopic heterogeneity of the material.

Temperature-dependent mechanical behavior of three-dimensionally ordered macroporous tungsten

Abstract

Theoretical Estimation of The Influence of Plastic Deformation on Average Coefficient of Friction in the Process of Nanostructuring Burnishing of Metal Samples

The problem of burnishing metal samples with a smooth surface using a spherical indenter is considered. The nonlocal plastic strains in the burnished sample are taken into account. The dimensionless parameters are found that determine the effective friction coefficient under the influence of external oscillations. Numerical modeling is used to obtain the dependencies of the effective friction coefficient on the dimensionless parameters.

Higher order continuous approximation for the assessment of nonlocal-gradient based damage model

ABSTRACTIn this work we present an implicit nonlocal gradient damage model. A scalar damage variable which is a function of monotonically increasing function of history parameter is introduced to account for damage. The nonlocal model accounts for spatial interaction of neighboring material element at different length scales. The history parameter accounting for damage is obtained by considering nonlocal equivalent strains. To study the influence of nonlocal nature of approximation method on the proposed damage model, for numerical implementation, in a Galerkin framework, the influence of Cp − 1 and C0 continuous approximation schemes are explored. Cp − 1 approximations are achieved by using Bezier and B-spline basis functions. C0 approximations are achieved by using standard Lagrangian basis functions. From numerical examples, it is observed that Cp − 1 approximations are more nonlocal and results in better results than C0 approximations.

An investigation on nonlocal continuum damage models for composite laminated panels

The performance of nonlocal approaches based on nonlocal strains, damage driving forces and damage variables is investigated for progressive damage analysis of thick/moderately thick laminated panels under uniform transverse loading using eight-noded isoparametric finite element based on a global higher-order shear deformation theory including zig-zag function and first-order theory. The nonlocal variables are obtained from corresponding local variables using layerwise finite element with quadratic through the thickness variation in each layer. The effect of nonlocal parameter on convergence of failure load, maximum deflection and damage variables with successive mesh refinement is investigated. It is concluded that the convergence improvement based on all the three nonlocal models is almost same and the nonlocal scale parameter in the range of 0.5–3% of plate/panel dimensions yields a good convergence rate.