Durability improvement of axle housings by compressive residual stress inducement

Abstract This paper deals with durability improvement of axle housings used in a typical commercial vehicle by inducing surface compressive residual stresses to overcome the failure before acceptance. Analysis reveals life enhancement up to 88% at the failure location. Fatigue life estimates is more influenced by the mechanical strength of the material used for axle housings. However, the strength of housing material is altered by the manufacturing processes, which the component is subjected too. During design stage of the housing, the life estimate is observed to be 600,000 fatigue cycles. However, the actual proto samples validation in bench testing has provided a lower life of 460,000 fatigue cycles. This variation is primarily due to the alteration in the SN curve of the component caused by the manufacturing process, which has lowered down its tensile strength limits. This paper presents the influence of heating during forming process, which altered the tensile limits, resulting in housing failure at high tensile stress zones. Investigation of failure reveals design to be reinforced with higher sections. Limitations from customer due to higher weight and cost, combined with non-availability of space in suspension led to design constraints. As an alternate method, life enhancement is proposed by deforming the surface layer beyond its elastic limits at failure zone to a certain depth by inducing compressive residual stress through localized shot peening. This paper presents the process followed to estimate the minimum value of compressive stress and its tensor. FE calculations using FEMFAT software indicate improvement in life at the zones were the compressive stresses is induced. This enhancement helps customer by providing significant weight and cost savings.