Novel criterion for W-Cu interlayer joint delamination in divertor target monoblock under heating through ANSYS-CZM parametric studies

To evaluate the possibility of delamination in the joint interface between the divertor target tungsten monoblock and the copper interlayer, the stress and displacement distributions around the joint interface under monotonic heat loading up to the equivalent level of the disruption (20 MW/m 2 ) were investigated in this study, by the finite element analysis applying the Cohesive Zone Model (CZM). Parametric studies were performed regarding the strength and critical energy release rate of the joint interface. Each kinetic parameter was set so that not to exceed the corresponding one of the weaker base material (the copper or tungsten) in Mode I failure. The interfacial shear stress and displacement reached their thresholds respectively, while the normal stress showed compression (Mode Ⅱ failure) regardless of inputs of CZM parameters (strength and critical energy release rate of the joint). Consequently, it is suggested that the dominant failure mode during heating is mode II. In addition, a conservative delamination criterion regarding the relation between strength and critical energy release rate of the joint interface was obtained based on the CZM parameters of mode Ⅰ, which are lower than those of mode II. This criterion indicates an increased possibility of the delamination due to neutron irradiation, considering degradation of the critical energy release rate of tungsten and the strength of bulk copper as reported in previous studies.