Investigation of cracking behaviors in divertor armor-blocks under cyclic loading

Abstract Optimal design of materials and configurations is necessary to assure intended functions of divertor module against nuclear fusion plasma. Relevant activities performed not only diverse numerical analyses of armor-blocks and structures but also material property tests of specimens and limited experiments of mock-ups under harsh environments. As recent studies reported remarkable cracks in the tungsten-armored multiple-block subjected to cyclic loading, this research is intended to investigate cracking behaviors and to establish a promising numerical approach for engineering application. First of all, three sets of traction-separation law(TSL) parameters for a tungsten material were assumed based on reference data under a severe heat flux of 20 MW/m2. Extended finite element analyses were carried out mainly for the mock-up that consists of five blocks to determine a proper set of TSL parameters by comparing with experimental observation. Subsequently, parametric analyses were conducted to examine further realistic situations by changing the number of blocks and joining restraints. As results of analyses, crack propagation directions and amounts as well as initiation locations were predicted in the simulated blocks. Different cracking behaviors were also evaluated in relation to the number of applied cycles followed by a discussion of key findings from the thermal fatigue and failure assessment standpoint.