铝合金圆板上碳化硅涂层热应力有限元分析

Thermal Stress Analysis of SiC Coatings on Circular Al-ailoy Substrate by Finite Element Methods

假设涂层和基体界面处于理想结合状态下,且不考虑涂层中缺陷的影响,采用有限元软件(ANSYS 8.0)分析了5～30μm厚碳化硅涂层中的热变形和热应力。结果表明,在平面法线方向(z方向)上,涂层/基体系统在热应力作用下发生热屈曲,圆心处z方向热变形为0.05mm,而在边缘处z方向热变形为-0.08mm;热变形呈现轴对称的特点,其危险区域在上下表面的圆心部位,该处的热变形最大,也最容易造成该处涂层胀裂失效;对于不同直径的圆板,发生热屈曲时均存在一个类似的z方向零位移环,并且该z方向零位移环的位置与圆盘半径有关,而与涂层厚度无关;计算得出5～30μm厚碳化硅涂层中的热应力约为2.45～11.00GPa,该值远高于1mm厚4043铝合金基体中产生的热应力(24.68MPa);圆板热屈曲后拱起高度和热应力均随涂层厚度的增加而增加。

It is supposed that the interfaces of the SiC coating and 4043 Al-alloy substrate are in a perfect status and the flaw＇s effect in the SiC coating is also ignored. A finite element soft （ANSYS 8. 0） is used to analyze the thermal stress and the thermal displacement of SiC coatings with 5 - 30μm thickness. The results show that the disk is curved because of the thermal stress in the coatings/substrate system. The z-direction displacement in the centre of disk is 0. 05ram and that on the edge of the disk is --0. 08mm. The displacement of the disk is axis-symmetrical. The latent danger zone lies in the surface of the disk centre, where the displacement value is maximal, and it is easy to crack and fail in these locations. There is a zero displacement （z direction） loop for the disks with different diameters. The zero displacement loop is relevant to the diameter of disk, and it is irrespective of the thickness of the coatings. The thermal stress of the SiC coatings with 5~30~m thickness is about 2. 45411.00GPa,which is greatly higher than the thermal stress value（24. 68MPa） in the 4043 Al-alloy substrate. The thermal displacement and the thermal stress increase with the increasing thickness of the SiC coatings.