W/ODS铁素体钢功能梯度材料热应力分析

Analysis of Thermal Stress for Functionally Graded Material of W/ODS Ferrite Steel

目的研究W/ODS铁素体钢功能梯度材料(W/ODSFGM)服役条件下的热应力,期望获得较合理的W/ODSFGM材料设计,以达到热应力优化的效果。方法采用有限元分析方法,结合偏滤器的服役条件,通过改变W/ODSFGM材料梯度层成分分布指数p、梯度层厚度HFGM以及金属W涂层厚度HW,探索各参量的变化对热应力大小及分布的影响。结果梯度层成分分布指数p值增大,梯度层的应力值会随之增大,而W层的热应力先减小后增大。当p=0.5时,最大热应力出现在梯度层的中段;当p=1、2时,最大应力由FGM层中段转移至FGM/W层的交界处。梯度层厚度HFGM增大,涂层的热应力会大幅提高。梯度层厚度较厚或较薄都会导致热应力在FGM/W交界处集中。W涂层厚度HW增大,会导致W/FGM界面的热应力增大,增添了涂层自身的不稳定性。结论梯度层成分分布指数和厚度的增大均会引起涂层热应力的增大,并导致最大热应力区的转移。W涂层的增厚会使结构的热应力增大,且最大应力值位于W/FGM界面,不利于涂层寿命的提高。HW=HODS=1mm、HFGM=8mm、p=0.5和HW=HODS=1mm、HFGM=4mm、p=1的最大热应力区位于梯度层中段,且后者的最大应力值小于前者,故HW=HODS=1mm、HFGM=4mm、p=1的结构较优。

The work aims to obtain a reasonable W/ODS FGM material design by studying the thermal stress under the service conditions of W/ODS ferrite steel functionally graded material (W/ODS FGM), so as to achieve the optimization effect of thermal stress. By changing the W/ODS FGM material gradient layer composition distribution index, the gradient layer thickness, and the metal W coating thickness with finite element analysis method under the service conditions of the divertor, the influence of the variation of each parameter on the thermal stress size and distribution was explored. The stress of the gradient layer increased with the increase of the distribution index p value, while the thermal stress of the W layer decreased first and then increased with the increase of the p value. When p = 0.5, the maximum thermal stress occurred in the middle of the gradient layer. When p=1 or 2, the maximum stress was transferred to the junction of the FGM/W layer from the middle of FGM layer. The thermal stress of the coating increased greatly as the HFGM increases. The thicker or thinner HFGM could both cause thermal stress to concentrate at the FGM/W junction. The increasing HW could increase the thermal stress at the W/FGM interface, thus leading to the instability of the coating. With the increase of p and HFGM, the thermal stress increases and also causes the translocation of largest thermal-stress zone. On the other hand, increasing thickness of W layer leads to the increase of thermal stress and the maximum stress is at the W/FGM interface, which is not conducive to improving the coating life. The maximum thermal stress areas are located in the middle of the gradient layer of HW=HODS=1 mm, HFGM=8 mm, p=0.5 and HW=HODS=1 mm, HFGM=4 mm, p=1. Moreover, the maximum thermal stress of latter is less than that of the former, so the latter one has more ideal FGM material structure.