Simulations utilizing local constitutive equations for strain‐softening materials are known to be pathologically mesh‐dependent. The rational solution to this problem is to use nonlocal material models. In this paper, we discuss the application of the integral‐based approach to the simulation of non‐local damage accumulation and fracture. Various combinations of non‐localities with common spatial symmetries are analysed analytically and numerically. The symmetries include the plane strain and the axisymmetric cases, as well as the presence of symmetry planes and cyclic symmetries. Although not a symmetry, the practically important case of thin plates is also analysed. We show that the delocalization procedure should be executed using symmetry‐adapted averaging kernels. For the considered spatial symmetries, analytical closed‐form expressions are obtained. Moreover, a new easy‐to‐use averaging kernel is suggested, the same for 3D, plane strain and plane stress applications. To showcase the delocalization procedures, we consider a ductile damage model, based on the multiplicative decomposition of the deformation gradient, as well as hyperelastic relations between stresses and strains. FEM solutions for a series of problems are presented, including graduate damage accumulation, crack initiation and fracture.
We analyze the applicability of the smooth particle hydrodynamics (SPH) to the solution of boundary value problems involving large deformation of solids. The main focus is set on such issues as the reduction of artificial edge effects by implementing corrected kernels and their gradients, accurate and efficient computation of the deformation gradient tensor, evaluation of the internal forces from the given stress field. For demonstration purposes, a hyperelastic body of neo-Hookean type and a visco-elastic body of Maxwell type are considered; the formulation of the Maxwell material is based on the approach of Simo and Miehe (1992). For the implementation of constitutive relations efficient and robust numerical schemes are used. A solution for a series of test problems is presented. The performance of the implemented algorithms is assessed by checking the preservation of the total energy of the system. As a result, a functional combination of SPH-techniques is identified, which is suitable for problems involving large strains, rotations and displacements coupled to inelastic material behaviour. The accuracy of the SPH-computations is assessed using nonlinear FEM as a benchmark.
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