Thermomechanical and isothermal fatigue crack propagation testing method for 316LN austenitic stainless steel.

Investigating fatigue crack growth behavior of materials is crucial to the life design and safety evaluation of engineering structures. During the practical service condition, the temperature keeps changing, which cannot be studied by the traditional fatigue crack growth test method at constant temperature. In this study, we focus on constructing a new thermomechanical fatigue (TMF) crack propagation testing method, developing a thermal deformation compensation method, and proposing an equivalent compliance method suitable for variable temperature conditions based on ASTM E647 standard to measure the crack length. Furthermore, the load‐ and strain‐controlled TMF tests under different phase angles are carried out to prove the validity of the new method. Highlights: A temperature compensation method for the variable temperature test is proposed.A modified compliance method for crack length measurement is developed.The thermomechanical fatigue (TMF) crack propagation testing method was standardized.Only the stress intensity factor range ΔK cannot be used to characterize the fatigue crack growth rate. [ABSTRACT FROM AUTHOR]