LOADING NATURE OF THE INTERFACIAL CRACKS IN A JOINT COMPONENT UNDER FUSION-RELEVANT THERMAL LOADS

One of the standard design concepts for divertor components in a fusio n reactor is the bonded joint structure. Understanding the loading nat ure of interfacial cracks are significant for the assessment of struct ural integrity of divertor joint components. In this paper, the thermo mechanical loading nature of interfacial cracks is discussed. A bi-mat erial joint element consisting of the CFC/TZM system is considered. A typical fusion operation condition is simulated assuming a pulsed high heat flux loading. Stress singularities near the interfacial crack ti ps are characterized quantitatively in terms of the fracture mechanica l parameters. The evolution of the stress intensity factors and the en ergy release rate during the given transient thermal load are determin ed. The difference in loading characteristics between the edge crack a nd the center crack is discussed. High hear flux cycling tests are per formed on brazed CFC/TZM divertor elements in an electron beam test fa cility. The microstructures of the damaged interface agree with the pr edicted fracture modes. The loading nature and possible failure mechan isms are discussed for a fusion-relevant thermal loading. (C) 1998 Els evier Science S.A.