Multi-response optimization of the bulging-processed parameters for enhanced residual stress state of TC4-rolled rings

The existence of an unreasonable residual stress state in the ring blank forgings of thin-walled casings harms the dimensional stability and service life of the parts. Stress control of rolled rings is achieved by using a segmental mandrel bulging process, the effectiveness of which is closely related to the process parameters. The objective of this investigation was to enhance the effectiveness of the bulging in controlling the residual stresses during the manufacturing process. The residual stress evolution mechanism for the bulging process was analyzed. The residual stress results obtained from response surface experimental procedures were established to relate the empirical relationship between each process parameter and the stress response. A quadratic regression model based on an analysis of variance was developed, and the validity of its response parameters was verified. The results indicate that the prediction model can effectively arrange the parameter settings to obtain the stress condition with optimal index.