| Summary: | 碩士 === 南開科技大學 === 車輛與機電產業研究所 === 101 === For pre-stress die design, the theory of thick-walled cylinder is conventionally used. It is suitable to do die design for a simple straight cylinder die, whereas it is very difficult to predict the local maximum effective stress of the die insert with a complex shape by using the thick-walled cylinder theory. In this paper, a pre-stress die design method for a non-axisymmetric hot forging with an inner square shape die is proposed. The optimum inner radius of stress ring, interference and maximum allowance inner pressure are obtained by using the thick-walled cylinder theory first, then according to these optimum values, the two process variables are set at three levels, respectively, and then 9 combinations of process parameters are constituted totally. A finite element based code is utilized to investigate the elastic deformation characteristic under different process parameters, and the response surface method is then applied to synthesize the data sets obtained from the numerical simulation, then a prediction model is established. From the prediction model, the optimum inner radii of stress ring and the interferences has been found. The proposed method has been applied in a practice die sets for the pre-stressed die design.
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