Finite element analysis to assess the effect of initial plasticity on transient creep for defects under mechanical loading

Finite element (FE) transient creep analyses have been performed for geometries of differing constraint levels, namely compact and centre-cracked tension specimens and circumferentially-cracked cylinders. Elastic-creep and elastic–plastic-creep behaviour with the same stress exponents in power-law creep and plasticity were considered. The complete time history between initial transient creep response and steady state conditions has been analysed for a range of load levels. Estimates of J( t) and C( t) have been compared with computed values. The known asymptotic behaviour in the limits as time, t→0 and t→∞ has been confirmed. At intermediate times, estimation formulae are suggested which compare well with the FE results. The suggested expressions modify existing formulae in the literature and provide improved agreement with the FE results.