A Generic Validation Methodology and its Application to a Set of Multi-Axial Creep Damage Constitutive Equations

A generic validation methodology for a set of multi-axial creep damage constitutive equations is proposed and its use is illustrated with 0.5Cr0.5Mo0.25V ferritic steel which is featured as brittle or intergranular rupture. The objective of this research is to develop a methodology to guide systematically assess the quality of a set of multi-axial creep damage constitutive equations in order to ensure its general applicability. This work adopted a total quality assurance approach and expanded as a Four Stages procedure (Theories and Fundamentals, Parameter Identification, Proportional Load, and Non-proportional load). Its use is illustrated with 0.5Cr0.5Mo0.25V ferritic steel and this material is chosen due to its industry importance, the popular use of KRH type of constitutive equations, and the available qualitative experimental data including damage distribution from notched bar test. The validation exercise clearly revealed the deficiencies existed in the KRH formulation (in terms of mathematics and physics of damage mechanics) and its incapability to predict creep deformation accurately. Consequently, its use should be warned, which is particularly important due to its wide use as indicated in literature. This work contributes to understand the rational for formulation and the quality assurance of a set of constitutive equations in creep damage mechanics as well as in general damage mechanics.