Elastic-plastic-creep behaviour of a compact-tension specimen

Abstract

Elastic, elastic-plastic, elastic-creep, and elastic-plastic-creep finite element calculations have been performed for a compact-tension specimen under plane-stress conditions. The von-Mises effective stress criterion and the Prandtl-Reuss flow rule were assumed for both the plastic and creep deformations. A 4-line stress-strain relationship with a UTS value 1.48 times greater than the yield stress was used. A strain hardening, Norton-Bailey creep law was assumed.

A fairly course mesh of 8 noded, isoparametric elements was found to be adequate for determining reference stress, crack tip opening displacement, J-contour integral, and C∗-contour integral values.

The UTS zone, rather than the yield zone, was found to have a significant effect on the C∗-contour integrals and CTOD rates. An approximate method of determining C∗ values was found to give reasonable results, particularly for low load cases, i.e., when the UTS zones are small. Hence, provided care is taken not to perform tests at very high loads, accurate C∗ values can be determined from experimentally determined pin displacement rates.