Manufacturing processes’ role over the residual stress state evolution of crankshafts

Different residual stress magnitude and profile are generated after every crankshaft manufacturing stage. The processes are often investigated separately, regardless of their possible influence. The acknowledgement of the stress evolution can be useful when investigating crankshaft fatigue behavior. This study contributes to the matter by evaluating the resultant residual stress generated at the fillet region after crankshaft’s machining and deep rolling processes. Prior to it, a procedure was developed to guarantee the position of the samples in the X-ray diffractometer after surface electropolishing and depth measurement. Repeatability and reproducibility analyses attest the measurements’ accuracy. An in-depth profile assessment was made at the crankpin radii top and bottom regions in two stress directions. The influence of the machining process over the residual stress left after deep rolling can be inferred. The results were also compared with the outcomes from a finite element model for the deep rolling process. They pointed out that new features should be included in its development in order to account for the influence of previous processes. Moreover, unexpected residual stress results, and consequently fatigue behavior, can be better understood with more data regarding the whole manufacturing chain.