Tangent stiffness matrix

About: Tangent stiffness matrix is a research topic. Over the lifetime, 1031 publications have been published within this topic receiving 21140 citations.

Implicit integration and consistent linearization for yield criteria of the Mohr-Coulomb type

Abstract: In this paper, we discuss the efficient treatment of yield criteria that are of the Mohr–Coulomb type for elastic and plastic isotropy. On the basis of the fully implicit method, we derive the explicit expression for the integrated stress along with a flow rule that represents volumetric non-associativity. The integration algorithm covers all the possible cases of regular, corner and apex solutions including the suitable indicator for each case. We also establish the consequent consistently linearized tangent stiffness modulus tensor, which is shown to appear in the form of an additive modification of the continuum tangent stiffness tensor. The convergence properties of the consistent tangent stiffness tensor are compared with its feasible approximations. The results indicate the strongly sensitivity to the proper treatment of the corner conditions at the establishment of the ATS-tensor.

A time‐integration method for the viscoelastic–viscoplastic analyses of polymers and finite element implementation

Abstract: The present study introduces a time-integration algorithm for solving a non-linear viscoelastic–viscoplastic (VE–VP) constitutive equation of isotropic polymers. The material parameters in the constitutive models are stress dependent. The algorithm is derived based on an implicit time-integration method (Computational Inelasticity. Springer: New York, 1998) within a general displacement-based finite element (FE) analysis and suitable for small deformation gradient problems. Schapery's integral model is used for the VE responses, while the VP component follows the Perzyna model having an overstress function. A recursive-iterative method (Int. J. Numer. Meth. Engng 2004; 59:25–45) is employed and modified to solve the VE–VP constitutive equation. An iterative procedure with predictor–corrector steps is added to the recursive integration method. A residual vector is defined for the incremental total strain and the magnitude of the incremental VP strain. A consistent tangent stiffness matrix, as previously discussed in Ju (J. Eng. Mech. 1990; 116:1764–1779) and Simo and Hughes (Computational Inelasticity. Springer: New York, 1998), is also formulated to improve convergence and avoid divergence. Available experimental data on time-dependent and inelastic responses of high-density polyethylene are used to verify the current numerical algorithm. The time-integration scheme is examined in terms of its computational efficiency and accuracy. Numerical FE analyses of microstructural responses of polyethylene reinforced with elastic particle are also presented. Copyright © 2009 John Wiley & Sons, Ltd.

Geometrically Non-linear Analysis of Functionally Graded Material (FGM) Plates and Shells using a Four-node Quasi-Conforming Shell Element

Abstract: The four-node quasi-conforming shell element was extended in the present article to the case of geometrically non-linear behavior of the FGM plates and shells. The high stress occurring in the FGM structures will affect its integrity and the structures is susceptible to failure. Therefore, we focus on the effect of volume fraction of the constituent materials in the mechanical behavior of FGM plates and shells. The material properties are assumed to be varied in the thickness direction according to a sigmoid function in terms of the volume fraction of the constituents. The series solutions of sigmoid FGM (S-FGM) plates, based on the first-order shear deformation theory and Fourier series expansion are provided as the reference solution for the numerical results. In quasi-conforming formulation, the tangent stiffness matrix is explicitly integrated. This makes the element computationally efficient in the non-linear analysis. Several selected examples of non-linear analysis of FGM shells are included in the...

Affine connections for the Cartesian stiffness matrix

Abstract: We study the 6/spl times/6 Cartesian stiffness matrix. We show that the stiffness of a rigid body subjected to conservative forces and moments is described by a (0,2) tensor which is the Hessian of the potential function. The key observation of the paper is that since the Hessian depends on the choice of an affine connection in the task space, so will the Cartesian stiffness matrix. Further, the symmetry of the Hessian and thus of the stiffness matrix depends on the symmetry of the connection. The connection that is implicit in the definition of the Cartesian stiffness matrix through the joint stiffness matrix (Salisbury, 1980) is made explicit and shown to be symmetric. In contrast, the direct definition of the Cartesian stiffness matrix in Griffis (1993), Ciblak and Lipkin (1994) and Howard et al. (1996) is shown to be derived from an asymmetric connection. A numerical example is provided to illustrate the main ideas of the paper.