Study On Simulation Thermal-Dynamical Coupled Effects By High-intensity Pulsed Ion Beam Irradiation

High-intensity pulsed ion beam (HIPIB) characterized by short pules width less than1ms and high power density107-1014W/cm2was used to evaluate first wall materials and in surface strengthening because its high energy density and significant thermal-dynamic effects when irradiation onto materials. The simulation of temperature and stress field in HIPIB irradiation process can over come difficult in experimental investigation to investigate the thermal-dynamic process of irradiation. But irradiation process with ultrafast surface remelting and solidification, ablation, phase transformation and other complex physical state change make it very difficult simulate, previous work mainly focused on temperature simulation, stress is less considered and often simplify consider little about thermal-dynamic effects, thus those works cannot describe the physical state change and dynamic effects of the irradiation. To investigate coupled thermal-dynamic effects of HIPIB irradiation and analysis the phenomenon of irradiation experimental, a study of HIPIB coupled thermal-dynamic effects simulation was carry out.A two-dimensional axisymmetric finite element model builded by MSC.Marc code to simulate the HIPIB irradiation of first wall material tungsten, Zerilli-Armstrong constitutive equation was used to consider the temperature and strain rate effects on the flow strain stress, by assume the thermophysical parameters vary with temperature and consider fluid as very soft solid to simulate the phase transform effects, element adding and removing method was used to simulate the boundary degradation due to material ablation. The irradiation experiment of tungsten was carried out to study the thermal-dynamic effects of phase transform, plastic strain, surface softening, selective ablation and surface cracking behavior at high temperature.The simulate result of surface melting and ablation depth, temperature, thermal stress, residual stress and stain distribution evolution obtained at ion current densities of50-200A/cm2were used to analyze the failure mechanism and ablation behavior observed at irradiation experiment. The result of stress and temperature field evolve progress of irradiated tungsten surface was given, explain the surface roughness considerably decreased with the rising of shot number and surface selective remelt and ablation effect and the formation of crack and residual stress. The model is applicable for all the cases of coupled thermal-dynamic effects during interaction between high power beams and materials. The numerical calculation is in good accordance with the experimental results of surface remelting, selective ablation and surface cracking.The W irradiated by HIPIB at ion current densities of50-200A/cm2with5shots at different initial temperature, and the irradiation process was simulated by FEM model. The calculate results showed that high initial temperature introduce a low temperature gradient thus reduce the thermal-stress and made tungsten easier to deformation, as a result the residual stress after irradiation was smaller compare to room temperature, explain the effect of surface cracking reduced at high initial temperature.A thermal FEM model was builded to simulate the remelting and selective ablation cause by unevenness and roughness of material surface. The results show that the temperature is higher at raised parts than flat and concave, thus fragment and. protuberance of material surface is easier to melt and ablation, explain the effect of surface microhardness and morphology change due to irradiation.