Theoretical analysis on the damages for tungsten plasma facing surface under superposition of steady-state and transient heat loads
Theoretical analysis on the damages for tungsten plasma facing surface under superposition of steady-state and transient heat loads
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稳态与瞬态热载荷叠加下钨等离子体面对表面损伤的理论分析
DOI：
10.1016/j.fusengdes.2018.05.054
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发表时间：
2018-07
影响因子：
1.7
通讯作者：
Chen Junling
中科院分区：
文献类型：
--
作者：
Li Changjun;Zhu Dahuan;Wang Baoguo;Chen Junling
在ITER和未来的聚变装置中，面向等离子体的表面预计将受到稳态和瞬时热负荷的叠加。极高的瞬时热流密度导致材料表面的劣化，从粗化到开裂甚至熔化。对预热钨的高热流密度试验表明，稳态热负荷引起的表面初始基面温度对瞬时热流引起的损伤有很大影响。本文试图从热力分析的角度，通过有限元模拟来解释这一现象的机理。成功地模拟了在稳态热载荷对应于基温(20-600 °C)和瞬时热流密度(5 ms，0-900 MW m−2)的叠加作用下，圆柱形钨铜块的表面温度和应力应变分布及演化。将应力-应变与温度的对应关系与屈服强度-温度关系进行比较，分析了加热和冷却阶段表面事件的演化，揭示了基面温度对瞬时热流致损伤的影响。分析结果从理论上证明了稳态热负荷预热确实影响了瞬时热流致损伤。当基面温度超过韧脆转变温度时，即使在接近熔化阈值的极高瞬时热流密度下也不会产生裂纹，且在一定的基面温度下，随着瞬时热流密度的增加，表面也呈现出由粗化到开裂的劣化过程，这与实验结果吻合较好。
In ITER and future fusion devices, the plasma facing surfaces are expected to suffer from the superposition of steady-state and transient heat loads. The extreme high transient heat fluxes cause the deterioration of material surface that increases from roughing to cracking even melting. And, the high heat flux tests on pre-heated tungsten implied that the steady-state heat load induced initial surface base temperature would have great influence on the transient heat flux induced damages. The present efforts tried to explain the mechanism of this phenomenon in view of the thermal-mechanical analysis by means of finite element simulation.The surface temperature and stress-strain distribution and evolution of a cylindrical W/Cu block under superposition of the steady-state heat loads corresponding to base temperature (20–600 °C) and transient heat fluxes (5 ms, 0–900 MW m−2) were successfully simulated. The corresponding relations between stress-strain and temperature are compared with the yield strength-temperature relation to analyze the surface event evolution during the heating and cooling phases, which showed how the base temperature influenced the transient heat flux induced damages. The analysis results theoretically identified that the pre-heating by steady-state heat load indeed influenced the transient heat flux induced damages. Typically, no any crack would be generated even under extreme high transient heat fluxes close to the melting threshold if the base temperature exceeded the ductile to brittle transition temperature, and the surface also showed deterioration from roughing to cracking while then roughing with increasing of transient heat flux under a certain base temperature, which were in good agreement with the experiments results.
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