Overstrain in flush optimal-chamfered cross-bored cylinders

Abstract

A three-dimensional finite-element method computer program was developed to establish the elastic—plastic, residual, and service stress distributions in cylinders with flush and non-protruding optimal-chamfered cross-bores under internal pressure. Eight-noded brick and four-noded tetrahedral isoparametric elements and the displacement formulation were used. The incremental theory of plasticity with a 5 per cent yield condition and von Mises yield criterion were assumed. The incipient and 5 per cent overstrain (ov) pressures were established for various thickness ratios and cross-bore to main bore radius ratios. For the optimum chamfer angle geometrical configuration, the stresses were determined for varying ov. The maximum and minimum effective stresses were located 7.5° from the meridional and transverse planes, respectively. Meridional plane through thickness yielding occurred at an ov of 41 per cent. The service stress gradients at the cross-bore chamfer end increased with ov for ovs >30 per cent. Stress reversals were eliminated for overstrain >27 per cent. Alternative autofrettage and yield condition procedures were proposed.