Effect of Process Parameters on Coefficient of Friction in Tube Hydroforming

In tube hydroforming, a desired shape is obtained by applying internal pressure and axial feeding instantaneously. To yield the material, the internal pressure offers the stress required, whereas axial feeding facilities metal flow which help to produce a part without crinkles and with even wall thickness. Pressure hydroforming applies loading path with fluctuating pressures. In this research work, hydroforming with high pressure is used to manufacture metal expansion bellows experimentally. Four process parameters are selected in pressure loading path to decide most dominating parameter. Using Taguchi DOE (design of experiments) with four parameters and three levels for each parameter, 9 experiments are conducted to study the effects of pressure parameters on the parts defects with shape accuracy. S/N ratio and ANOVA (analysis of variance) are applied to regulate the important process parameters affecting the final part in terms of wear rate and COF (coefficient of friction) for three different materials such as SS304, SS316, and SS316L. Three linear regressions without any interaction between the parameters are extracted for three quality responses and are evaluated through three extra experiments. The results show reasonable agreement between the experimental and linear regression models. The results of the present study could be used as a basis of designing a new type of the metal bellows manufactured by tube hydroforming.