Development of a creep-damage model for a wide stress range

The research objective is to develop a comprehensive non-isothermal creep-damage model based on transitions of creep and long-term strength in a wide stress range. The study comprises the following topics: basic assumptions of creep constitutive modeling; conventional isotropic and anisotropic creep-damage models; comprehensive non-isothermal creep-damage models for a wide stress range. The proposed creep-damage model is based on several assumptions derived from creep experiments and microstructural observations for various advanced heat resistant steels. The constitutive equation affects the stress range dependent behavior demonstrating the power-law to linear creep transition with a decreasing stress. To take into account the primary creep behavior a strain hardening function is introduced. To characterize the creep-rupture behavior the constitutive equation is generalized by introduction of two damage internal state variables and appropriate evolution equations. The examples of long-term strength analysis for various industrial components are highlighted to illustrate the importance of the continuum damage mechanics approach for the life-time assessments in structural analysis.