Abstract:
A three-dimensional nite element method computer program was developed to establish
the elastic–plastic, residual and service stress distributions in thick-walled cylinders with ush and
non-protruding plain cross bores under internal pressure. The displacement formulation and eightnoded
brick isoparametric elements were used. The incremental theory of plasticity with a 5 per cent
yield condition (an element is assumed to have yielded when the effective stress is within 5 per cent of
the material yield stress) and von Mises yield criterion were assumed. The frontal solution technique
was used. The incipient yield pressure and the pressure resulting in a 0.3 per cent overstrain ratio were
established for various cylinder thickness ratios and cross bore–main bore radius ratios. For a
thickness ratio of 2.25 and a cross bore–main bore radius ratio of 0.1, the stresses were determined for
varying overstrain and an optimum overstrain ratio of 37 per cent was established. To nd the
accuracy of the results, the more stringent yield condition of 0.5 per cent was also considered. The
bene ts of autofrettage were presented and alternative autofrettage and yield condition procedures
proposed.
