Mixed-mode fatigue crack propagation in thin T-sections under plane stress

Abstract

Data that can be used in the fatigue analysis of¯at T-section bars subjected to axial loading and local restraint are presented. The paper describes how ®nite element analysis has been used to obtain stress ®elds in the vicinity of a crack or crack-like¯aw introduced into the ®llet (i.e. high-stress) region of the component. The effect of both the position and inclination of the crack has been investigated. The inclination of the crack to the transverse direction is varied in such a way that a combination of mode I (tension opening) and mode II (in-plane shear) crack tip conditions are created in the component when subjected to axial loading which is applied to the entire¯at shoulder of the projection. Linear elastic fracture mechanics ®nite element analyses have been performed, and the results are presented in the form of J integrals and notch and crack con®guration factors for a wide range of component and crack geometric parameters. These parameters are chosen to be representative of typical practical situations and have been determined from evidence presented in the open literature. The extensive range of notch and crack con®guration factors obtained from the analyses are then used to obtain equivalent prediction equations using a statistical multiple non-linear regression model. The accuracy of this model is measured using a multiple coef®cient of determination, R 2 , where 0 < R 2 < 1. This coef®cient is found to be greater than or equal to 0.98 for all cases considered in this study, demonstrating the quality of the model ®t to the data. Predictive equations for stress intensity factors and J-integral values, which are based on the elastic stress concentration factor, are also developed. A crack propagation methodology, based on existing theory coupled with these predictive equations, is then presented for this type of component and loading.

Estimation of C*-Integral in Thin T-Sections Subjected to Projection and Remote Loading Base on Elastic Stress Concentration Factor

“…4. Due to lack of creep crack study in T-section component at first, some elastic finite element analyses have been done and the results were compared with data available [5] . This comparison confirmed that the level of mesh refinement and the use of the crack tip elements in current study would provide accuracy to within ±3%.…”

“…To determined stress concentration factor K t in a T-section component subjected to loaded projection the following relation ship was reported [5] , using a statistical multiple nonlinear regression model: In a similar way to [5] , the following equation is derived for the stress concentration factor of a T-section component under remote loading condition:…”

“…Also, the crack tip stress solution for flanked notches [4] . J-Integral and stress concentration factor for T-sections were also reported [5] .…”