Multiaxial fatigue of 4140 and 4340 steels with MICRO defects: New tests and modelling

A new multiaxial fatigue model for metallic materials containing small defects (SWTmod) was recently presented by the authors [1] , [2] ). This model correlates the uniaxial fatigue limit derived from the area parameter [3] of high-strength steel containing small defects with the amplitude and maximum value of the principal stress vector, whose calculation under non-proportional loading is non-trivial. The Maximum Rectangular Hull (MRH) and the Fast Maximum Variance Method (FMVM) are used to compute the amplitude of the principal stress vector. The model's performance is further evaluated with new multiaxial fatigue data from AISI 4140 and 4340 steels under various loading conditions, including specimens with only their natural defects and specimens with a superficial microhole. The proposed model provided satisfactory fatigue strength estimates, with a simple, fast, and cost-effective calibration process, which is of great interest for engineering calculation purposes.