Some issues on finite element modelling of plasticity induced crack closure due to constant amplitude loading

An investigation of plasticity induced crack closure (PICC) behaviour using finite element (FE) method is presented for cracks subjected to constant amplitude loading and small scale yielding (SSY) conditions. Undeflected cracks have been examined under both plane strain and plane stress conditions. Anomalous near-tip closure in FE models has been identified to occur under both plane stress and plane strain conditions and is seen to vary with baseline load levels and crack propagation algorithms. In the case of plane strain models, propagation algorithms are seen to influence pre-crack closure. In general terms it may be said that none of the plane strain models showed crack closure that could be related to ongoing/steady-state crack growth: crack closure in all cases was dominated by pre-crack contact, and/or anomalous near-tip contact, even for the relatively long crack propagation used in the low loading range models.