A study on the optimisation of the fillet roller burnishing process for marine diesel engine crankshafts based on RSM

Current research on optimising the fillet rolling process for marine high-speed diesel engine crankshafts tends to focus on the effect of single process parameters on individual surface quality indicators, often overlooking the combined influence of multiple parameters and resulting in suboptimal process designs. To address this gap, this study employed response surface methodology (RSM) combined with finite element simulation to optimise the fillet rolling process of a 34CrNi3Mo marine diesel crankshaft. The investigation evaluated the effects of rolling force, number of rolling passes and spindle speed on three key surface integrity indicators of residual stress, hardness and protrusion deformation in the fillet region. The results showed that residual stress, hardness and protrusion deformation all increased with the increment of rolling force, initially increased and then stabilised with more rolling passes, but were largely unaffected by the spindle speed. The RSM analysis revealed that the number of rolling passes had the greatest influence on surface quality, followed by rolling force and then spindle speed. In terms of parameter interactions, the combination of rolling force and number of passes was most significant, followed by rolling force with spindle speed, and finally passes with speed. The optimal parameters were identified as 10 rolling passes, a rolling force of 23,000 N and a spindle speed of 50 rpm. Compared to the original process, the optimised parameters increased compressive residual stress by 6.14%, enhanced surface hardness by 12.9% and limited protrusion height growth to only 0.001 mm. This study provides a practical methodology for optimising roller burnishing processes in high-performance shaft-type components.