Numerical investigations of fracture parameters for a cracked hydraulic cylinder barrel and its redesign

Abstract

Failure of machine structures is a very common phenomenon in industries. The study of development of cracks on machine structures thus becomes crucial. The present investigation was motivated by one such in-service failure of the main cylinder barrel of a hydraulic press, made of IS 1030 GRADE 280-580W steel subjected to an internal pressure due to the hydraulic oil, which over the time develops a body crack extending through the thickness of the cylinder. A combination of fracture mechanics concepts and Finite Element Method (FEM) has been used to explain the possibility of crack formation in the concerned locality and the crack has been characterised in terms of the Stress Intensity Factors (SIFs), J-integral values and the crack propagation life. It was observed that the energy released when a crack initiates is more than the energy released during propagation. It was also observed that, for the present crack configuration, Mode-1 fracture predominates. On failure, depending on the feasibility and economic constraints, the hydraulic cylinder is either repaired or replaced in an industry. Because of this very importance redesign holds in an industry in case of failure, further, a possible redesign of the cracked hydraulic cylinder has been proposed by comparing the two chosen weld profiles made of Aluminium alloy for the cracked region - rectangular and prismatic welds by removal of material around the cracked region. It was observed that, prismatic weld would ensure a longer operational life in comparison with the rectangular weld.