Elastic Modulus Adjustment Improved Convergement Schemes Using Variable Local Constraints

Elastic modulus adjustment procedures (EMAP) have been employed to determine limit loads of pressure components. On the basis of linear elastic Finite Element Analysis (FEA) with non-hardening elastic properties, i.e., by specifying spatial variations in the elastic modulus, numerous set of statically admissible and kinematically admissible distributions can be generated, and both lower and upper bounds on limit loads can be obtained. Some methods such as the classical, r-node and mα methods provide limit loads on the basis of partly-converged distributions, whereas the accuracy of linear matching procedures rely on fully converged distributions. In this paper, a criterion for establishing the degree of convergence of EMAP is developed, and a simple procedure for achieving improved convergence is described. The procedure is applied to some practical pressure component configurations.