铀表面Al/Ti复合镀层热应力的有限元分析

Finite Element Analysis on Thermal Stress for Al/Ti Composite Coatings on Uranium Substrate

摘要:

对铀表面Al/Ti复合镀层的热应力进行了热弹塑性有限元分析,表明Ti镀层内为压应力,Al镀层内为拉应力,并达到铝的屈服强度,靠近试样侧边,存在边缘效应引起的应力分布不均匀性,离试样侧边2倍镀层厚度处,不均匀性逐渐消失,试样侧边U-Al界面剪切应力大于中部区域.对沉积温度、镀层厚度及镀层力学性能对镀层热应力和塑性应变的研究表明,随着沉积温度升高,镀层内热应力和塑性应变明显增大,减薄Al镀层和增厚Ti镀层可降低镀层内热应力和塑性应变,Al镀层屈服强度及Ti镀层弹性模量对镀层热应力和塑性应变有重要影响.

Abstract:

The thermal stress for Al/Ti coatings on uranium substrate was analyzed by using a thermal elastic plastic finite element method (FEM). The results indicate that the thermal stress is compressive inside the Ti coating and tensile inside the Al coating, which reaches the yield strength of Al. There is an uneven thermal stress distribution at the free side of specimen due to the end effect, which is vanished gradually at about 2h (where h is the coating thickness) from the free side of specimen. The shear stress of U-Al at the free side is larger than that in the middle of specimen. The effect of deposition temperature, coating thickness and mechanical properties on the thermal stress and plastic strain in coatings were also investigated. The results show that the thermal stress and plastic strain increase remarkably with the deposition temperature increasing. It is helpful to decrease the thermal stress and plastic strain by decreasing the thickness of Al coating and increasing the thickness of Ti coating. The yield strength of Al coating and the elastic modulus of Ti coating have large effects on the thermal stress and plastic strain of the coatings.