Assessment of microstructural influences on fatigue crack growth by the strip-yield model

• Application of the strip-yield model in thermal fatigue analyses.
• Strip-yield model using location (and temperature) dependent yield stresses.
• Implementation of microstructural aspects of crack growth.
• Description of stress–strain curves by means of the rheological Masing model.
• Fatigue crack growth calculation based on cyclic crack tip opening displacement.

The strip-yield model is a common tool to calculate the cyclic crack tip opening displacement and the fatigue crack growth life of structures in case of isothermal fatigue loading. The incorporation of a temperature-dependent yield stress already enables its application in thermal fatigue analyses. A further extension of the strip-yield model is presented here together with simulation results: The rheological Masing model consisting of spring-slider elements connected in parallel is used to describe the material’s stress–strain curve. It results in different yield stresses belonging to the numerous sliding frictional elements. These different yield stresses are randomly arranged along the crack ligament line instead of the usually applied constant yield stress. They depend on temperature as the procedure should still be used at non-isothermal loading. Besides an improved modelling of the mechanical material behavior the consideration of microstructural aspects of fatigue crack growth becomes possible by influencing the values of the yield stresses near the crack initiation site.