Temperature dependence of material length scale for strain gradient plasticity and its effect on near-tip opening displacement

Abstract

This paper investigates the temperature dependence of the material length scale in the conventional mechanism-based strain gradient (CMSG) plasticity theory. The work reported here also examines the plastic strain gradient effect on the opening displacement near a sharp crack tip. The study examines the mechanical properties of two typical structural steels (S355 and S690) in onshore and offshore structures at two different temperatures (20 and 300 °C) through both the uniaxial tension test and the indentation test. The CMSG-based finite element analysis then confirms a constant material length scale for these two steels at the two tested temperatures, despite the apparent temperature dependence of the macroscopic material parameters measured from the tension test. Using the calibrated material length scale, the subsequent numerical study demonstrates that the magnitude of the near-tip crack opening displacement computed by the CMSG theory remains significantly lower than that computed from the classical plasticity. © 2013 Wiley Publishing Ltd.