The study of crack propagation behavior in functionally graded plate due to thermal load

本研究项目包括两个部分：[1]功能梯度板（FGP）在热冲击作用下的裂纹生成模式，[2]功能梯度板在热冲击作用下的裂纹扩展模式。热冲击作用下功能梯度板（FGP）裂纹生成模式的数值模拟结果如下：(1)热应力可以在裂纹附近区域释放。(2)由于远离裂纹的边界表面的热应力随时间均匀增加，因此无法确定裂纹的起始位置。然而，最小裂纹空间可以确定。[2]功能梯度板（FGP）在热冲击作用下的裂纹扩展模式(1)我们可以分析带有Griffith裂纹的FGP的热应力问题。然而，我们正在研究具有两个Griffith裂纹的FGP的热应力问题。由于材料的非均质性，双裂纹FGP的求解非常困难。(2)情况A：具有两个初始裂纹的FGP中的裂纹扩展模式。(1)裂纹扩展模式有四种：1)裂纹沿厚度直线扩展，在某一位置止裂；2)两个方向相反的裂纹曲线相互远离；3)两个方向相反的裂纹曲线相互接近；4)两个方向相同的裂纹曲线。(2)双裂纹时的分层深度小于单裂纹时的分层深度。(3)裂纹间距、加热温度和FGP成分分布对裂纹扩展方向影响较大。(4)当各裂纹相互接近时，各裂纹不接触，沿厚度方向转动。(5)当各裂纹沿同一方向弯曲时，后裂纹会避开前裂纹而扩展。(3)情形B: FGP中具有三个相同长度初始裂纹的裂纹扩展模式。(1)中间裂纹直线扩展，在一定位置止裂。(2)外裂纹扩展模式的行为与双裂纹扩展模式基本相同。(3)各裂纹不接触。少

This Research project consists of two parts : [1]the crack generation patterns in the functionally graded plate (FGP) under thermal shock, and [2]the crack propagation patterns in the FGP under thermal shock.[1]the crack generation patterns in the functionally graded plate (FGP) under thermal shockWe could obtain following results by numerical simulations. (1)The thermal stresses can be released in the region near the crack. (2)Since the thermal stresses on the boundary surface far away from the crack uniformly increase with time, the position where a crack initiates cannot be determined. However, minimum crack space can be determined.[2]the crack propagation patterns in the functionally graded plate (FGP) under thermal shock(1)We could analyze the thermal stresses problems in the FGP with a Griffith crack. However we are studying the thermal stresses problems in the FGP with two Griffith cracks. It is very difficult to solve the FGP with two cracks due to non-homogeneous material prop … More erties.(2)Case A : Cracks propagation patterns in the FGP with two initial cracks.(1)There are four cracks propagation patterns : 1)The crack propagate straightly along the thickness and arrests at the certain position, 2)Two cracks curve with opposite direction going away for each other, 3)Two cracks curve with opposite direction approaching for each other, 4) Two cracks curve with same direction.(2)The delamination depth in the case of two cracks is shorter than that of a single crack.(3)The space between the cracks, heating temperature and composition profile of the FGP largely affect the crack propagation direction.(4)When each crack approaches for each other, each crack does not contact and turns along the thickness.(5)When each crack curves with same direction, the latter crack propagates by avoiding the former crack.(3)Case B : Cracks propagation patterns in the FGP having three initial cracks with same length.(1)The middle crack propagates straightly and arrests at certain position.(2)The behavior of the crack propagation patterns of the outer cracks is about same as two crack propagation pattern.(3)Each crack does not contact. Less