Stress and fracture analysis of short flat bars with projections using boundary element method

Abstract

Mechanical components generally contain geometric discontinuities such as fillet, grooves and sharp edges. These discontinuities are often known as stress raisers since stress concentrates around and caused the local stress to be significantly high. Cracks are likely to initiate and propagate from these high localized stress points. This poses the potential of mechanical components to fail earlier than expected.

Short flat bars with projections which contain fillets which is a geometric discontinuity are studied in this project and Boundary Element Method based computational program – BIE2DRSE-A was employed to generate results for analysis.

In the first part of the project, stress analysis was carried out on short flat bars with projections subjected to different types of loading – axial or shear, and restraint – remote or local. High stress concentration region was identified through the analysis of stress distribution profile. The effect of varying geometric parameters had on SCF was also examined. Comparisons were done between the results obtained in this report and the published finite element analysis data. It was concluded that the results are in good agreement. Results have shown that stress concentrates around the fillet region and the increase in fillet radius reduces the stress concentration effect.

In the second part of the project, crack was modelled at the highest localized stress point of the fillet region to facilitate fracture analysis of the short flat bars with projections. Studies were conducted over a range of crack inclination angle to understand the effect of varying geometric parameters and crack size have on the overall SIF which is an important parameter in characterizing crack behavior. It was found that overall SIF increases with crack size and decreases with increasing geometric parameter ratios studied. Furthermore, results have also shown that the direction of crack propagation does not change much with its initial crack angle.