Simulation of the High Cycle Fatigue Life Reduction due to Internal Hydrogen Embrittlement Using a Commercial Finite Element Program

The effect of internal hydrogen on the high cycle fatigue (HCF) life duration of Inconel X-750® in the hydrogen concentration range between 5 and 39 wppm at ambient temperature was investigated using an ultrasonic HCF test bench. For an alternating stress equal to 0.6 times the yield stress of the hydrogen-free material, a drop of two orders of magnitude in the high-cycle fatigue durability of the material has been measured over the investigated hydrogen concentration range. New tools have been developed to predict with little efforts the drop in life duration due to internal hydrogen embrittlement and the localization of the fracture area by Finite Element simulations. A simple approach has been considered to rapidly get a first assessment of the drop magnitude in HCF life duration of a structure due to internal hydrogen embrittlement at steady state hydrogen concentration conditions. The core of this proposed Finite Element calculation-based method is the “double Wöhler curve”, i.e. a three-dimensional Wöhler curve with the hydrogen concentration as the third dimension