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Examines the inelastic strains of ductile metals with a multilayer shell kinematics. Formulation of elasto-plastic constitutive law by using the multiplicative decomposition of the deformation gradient; Enhancement of strain concept; Capability of the multilayer shell kinematics.

The objective of this contribution is the development of theoretical and numerical models applicable to large strain analysis of hyperelastic shells confining particular attention to incompressible materials. The theoretical model is developed on the basis of a quadratic displacement approximation in thickness coordinate by neglecting transverse shear strains. In the case of incompressible materials this leads to a three-parametric theory governed solely by mid-surface displacements. The material incompressiblity is expressed by two equivalent equation sets considered at the element level as subsidiary conditions. For the simulation of nonlinear material behaviour the Mooney-Rivlin model is adopted including neo-Hookean materials as a special case. After transformation of nonlinear relations into incremental formulation doubly curved triangular and quadrilateral elements are developed via the displacement method. Finally, examples are given to demonstrate the ability of these models in dealing with large strain as well as finite rotation shell problems. [ABSTRACT FROM AUTHOR]

For composite laminates consisting of an arbitrary number of orthotropic laminae first a finite-rotation theory is presented as basis of isoparametric finite-element formulations. The derivation is achieved by a Reissner-Mindlin type kinematic assumption which allows a constant shear deformation distribution across the thickness. The constitutive equations are presented in a general form such that orthotropic material behaviour with material axes varying arbitrarily across the thickness may easily be considered in numerical implementation, also when using curvilinear coordinates. Special attention is taken to predict the force distribution in the deformed shell structure. This theory is then transformed into a four-node isoparametric assumed-strain finite element. Unlike in the degeneration approach, interpolation polynomials are introduced directly for rotation variables determining the deformed position of the unit normal vector. The capability of the finite element developed to deal with strongly nonlinear situations is demonstrated by many examples. Also numerical results are presented permitting a systematical comparison of classical and isoparametric approaches concerning the numerical efficiency. [ABSTRACT FROM AUTHOR]

For shells of finite deformations, a non-linear theory will be derived using the Kirchhoff-Love assumption. Its derivation is accomplished by a variational procedure ensuring a consistent formulation. Special attention is confined to the correct derivation of the dynamic boundary conditions which succeeds by introduction of a rotation vector connected with the rotational movement of the normal vector of the middle surface. The paper closes with the operator formulation of the theory which demonstrates the characteristic properties of the non-linear theories in a very general manner. [ABSTRACT FROM AUTHOR]

This paper briefly presents some important aspects of the theory of fourth-order tensors proposed in ]I[. The theory involves an operation algebra, differentiation rules, eigenvalue problems, an application to isotropic tensor functions and some other relevant problems. A most important application field the theory finds in large strain elasticity, where fourth-order tensors appear as elastic moduli. [ABSTRACT FROM AUTHOR]