Mechanical behavior on residual stress in a tungsten-copper duplex structure after cyclic heat loads for a divertor application

Cyclic thermal tests have been carried out on the tungsten-copper duplex structures using an electron-beam test facility, with a particular emphasis on the redistribution of the residual stress after the cyclic heat loads of 14 MW/m2–2 s. The residual stresses on the tungsten surfaces were measured by the strain gauge method and compared with those by thermoelasto–plastic analysis. Good agreement was approximately obtained for both their stress magnitude and distribution. Both radial and hoop stress components σR and σθ on the tungsten top surface slightly increased after first heat cycle and then decreased with the increase of the number of heat load cycles. Axial stress component σz on the tungsten side surface also behaved in the same manner as stresses on the top surface, while hoop stress component increased with the increase of the number of heat cycles. Relaxation of residual stress was induced with the elastic-plastic deformation of copper heat sink by cyclic heat loads.