Fragmentation characteristics of a welded spherical titanium pressure vessel: Part I — inhomogeneity of local strains and strain rates

Abstract

Developed in this work is a methodology for assessing the fragmentation characteristics of a welded spherical titanium pressure vessel. The presentation is divided into two parts. Part I makes use of the incremental theory of plasticity such that the nonlinear constitutive behavior for each material element can be determined individually in accordance with the local strain and strain rate. This enables the coverage of a much wider range of the strain rate dependent deformation in contrast to the conventional approach where each material element is governed by a single constitutive relation. That is no limitation would be placed on the change in local strain rates. Details of the weldment and region near the vessel opening are analyzed as sites of potential failure initiation. Particular emphases are placed on an accurate evaluation of the volume energy density contours from which failure by fragmentation could be predicted in terms of location and critical pressure. Part II is concerned with determining the energy imparted to the fragments, which are characterized by size, velocity and distance traveled.