Finite Element Model Development for Structural Integrity of Shafts with Circumferential and Arbitrary Oriented Cracks

Abstract

Tubular drive shafts are subjected to combined axial tension, torsional moment and bending moment. The structural integrity of the driveshaft is investigated by evaluating the change in strength, stiffness and the life of the driveshaft with the change in the crack length. A review of driveshaft failure analysis case histories identifies circumferential crack and arbitrarily oriented cracks to be critical. The singular stress field around a crack tip in a general shell structure is characterized by mixed mode membrane and bending stress intensity factors. Accurate determination of these stress intensity factors (less than 1%) are carried out by a subprogram named as 3MBSIF. The validation of Finite element model using ABAQUS and post processing subprogram 3MBSIF together is carried out using benchmarks, a set of standard test problems with known target solutions. Further SIFs are derived for cylindrical shell and the driveshaft under the action of bending moment. To quantify the change in the compliance of cylindrical shell and the driveshaft with change in crack lengths is studied by performing Modal Analysis. It was observed that the variation in frequency is higher for smaller crack angles.