热疲劳斜裂纹应力强度因子有限元分析

用有限元方法和最大周向应力准则计算了热疲劳斜裂纹的应力强度因子和开裂角的周期变化规律.计算表明:在加热过程中,模型内产生压缩热应力,使两裂纹面相互挤压、错开;由于加热过程生成的压缩塑性变形不能自由恢复,在降温过程的后期产生拉应力使裂纹张开;热疲劳斜裂纹在加热过程以及降温过程的前期是纯Ⅱ型,KⅡ在加热过程结束时达到最大值,在降温过程的后期是Ⅰ,Ⅱ复合型,降温过程结束时KⅠ,Ke达到最大值,裂纹在此时最易开裂.

Using FEM to Analyze Stress Intensity Factors of Slanted Thermal Fatigue Cracking

Stress intensity factors of slanted thermal fatigue cracking and the periodic change patterns of cracking growth angle were calculated using the finite element method(FEM) and maximum tangential stress criterion.During the heating process,thermal compression stress was generated inside the model causing squeezing and staggering between the two crack faces.Due to the fact that deformation caused by heat-induced compression plasticity was not freely reversible,tensile stress generated during the latter part of the cooling process made the crack open. Slanted thermal fatigue cracking during the heating process and during the initial part of the cooling process was entirely mode Ⅱ,and KⅡ reached maximum as the heating process finished;a Ⅰ-Ⅱ mixed mode occurred during the latter part of the cooling process.Both KⅠ and Ke maximized at the end of cooling period,and cracking growth was most prevalent this period.