Quantification of weld size parameters for throat failure prevention in a brake flange axle weld subjected to torsional loading with structural stress approach

Abstract

PurposeThe brake reaction test performed on a rear axle assembly revealed that the brake flange weld could not sustain the load needed to pass the minimum requirement of the test. Evaluation of the failure mode indicated that the fracture of the weld originated at the root of the weld and cracked through the fusion zone of the weld instead of cracking through base material (toe failure). The paper aims to discuss these issues.Design/methodology/approachA computational methodology is presented to quantify the critical parameters to prevent throat failure. The torsion dominated loading created high in-plane shear stress on the weld which can contribute significantly to the premature failure.FindingsThe failure through the fusion zone, often termed as weld throat/root failure, was not accounted for during the design phase by numerical simulation which led to the wrong conclusion that the design will pass the test requirement. Although weld sizing and weld penetration depth can explain such unexpected failure modes, fatigue life of this particular failure was still over-predicted using the Master SN curve formulation of structural stress approach which is well established for Mode I type of failure. Accounting for the shear component in the structural stress approach led to good correlation with the test specimen. Weld throat depth is a significant parameter contributing to throat failure.Practical implicationsThe failure of the weld joining the brake flange and the tube of an axle is a high severity failure mode which can result in loss of vehicle control and injury or death and hence the failure should be prevented at any cost.Originality/valueMost of the previous work of welded components relates to Mode I loading. There is very few research performed to discuss the Mode III loading and failure. This research illustrates the importance of considering the throat failure mode and quantifies the weld parameters to prevent such failures in design applications.