Anisothermal cyclic plasticity modelling of martensitic steels

Abstract

Tempered martensitic steels were investigated in isothermal and thermomechanical fatigue conditions and general features of their cyclic behaviour are reported. A cyclic anisothermal constitutive model with internal variables was formulated to describe their behaviour; it allows the description of the Baushinger effect, the continuous cyclic softening, the strain rate dependence and the plastic strain memorisation. When compared to experimental results, isothermal and anisothermal model predictions show good coherence. This model is helpful to understand and explain some experimental results such as the increase in strain softening when strain rate decreases in isothermal testing, as well as the relations between mean stress and temperature range or cyclic softening with strain amplitude in anisothermal conditions.

Thermo-mechanical fatigue behaviour of welded tubular parts made of ferritic stainless steel

“…Real-time thermal strain compensation was achieved using a linear thermal strain temperature relationship in the form ǫ th = λT + µ. Coefficients λ et µ were determined during thermal tests under zero load prior to the test campaign [23].…”

Thermal-mechanical fatigue simulation of a P91 steel in a temperature range of 400–600°C

“…Equations (10) and (11) can be substituted into equation (8). Differentiating Equation (8), with respect to ε p , by assuming that χ 1 has a negligible effect on the hardening of χ 2 , gives…”

“…However, the viscoplasticity model is rarely used to represent the behaviour of power plant materials. Research carried out on martensitic hot worked tool steels, which exhibits cyclic softening behaviour, has been used to develop an alternative type of viscoplasticity model [8].…”

Creep-Fatigue Interaction in the AISI H11 Tool Steel

“…from 0.702 mm to 1.260 mm at 400 MPa). Velay, Bernhart et al investigated the cyclic behavior of tempered martensitic hot-work tool steels with particular reference to the AISI H11 tool steel [10][11][12]. Cyclic softening of the material was observed, which could be divided into three stages: an initial strong softening followed by a slow steady softening that took the major part of the material life, and finally a drastic softening driven by crack propagation.…”