Characterization of thermomechanical damage on tungsten surfaces during long-duration plasma transients

• Published in: Journal of nuclear materials 2014-12, Vol.455 (1-3), p.500-506
• Main Authors: Rivera, David, Crosby, Tamer, Sheng, Andrew, Ghoniem, Nasr M.
• Format: Article
• Language: English
• Subjects: Compressive properties; Dislocations; Elastoplasticity; Exposure; Finite element method; Fracture mechanics; Heat flux; Heat transfer
• ISSN: 0022-3115; 1873-4820
• DOI: 10.1016/j.jnucmat.2014.07.007

A new experimental facility constructed at UCLA for the simulation of high heat flux effects on plasma-facing materials is described. The gun is used to impart high intermittent heat flux to metal samples mounted within a cylindrical chamber. The system is capable of delivering an instantaneous heat flux in the range of 30-300 MW/m super(2) depending on sample proximity to the gun. Results from a Finite Element (FE) thermo-elastoplasticity model indicate that during the heat-up phase of a plasma transient pulse, the majority of the sample surface is under compressive stresses leading to plastic deformation of the surface. Micro-compression mechanical tests of W micro-pillars show that the material has significant plasticity, failing by a "barreling" mode before plasma exposure, and by normal dislocation slip and localized shear after plasma exposure. Ongoing modeling of the complex thermo-fracture process, coupled with elasto-plasticity is based on a phase field approach for distributed fracture, and a discrete cracking approach, with cracks represented by Volterra dislocations.