A new method of shrink fit design for large-sized prestress die of hot extrusion: An example of large fan shaft

Abstract

Due to the remarkable increase in the geometric size, interference fit amount and assembly difficulty of large-sized hot extrusion prestress die, the conventional methods (such as thick wall cylinder theory and empirical value method) of shrink fit design were inapplicable to the pre-stressed die for hot extrusion of fan shaft with a maximum radius of 255 mm. In this study, a new shrink fit design method for large-sized prestress die was proposed by using the finite element method, and two sets of the formulas and nomograms that were easy to use were obtained to determine the interference fit ratio β, the radius ratio of die and stress ring a₂₁, a₃₁. Finally, the shrink fit of the prestressed die for the hot extrusion of the large fan shaft was designed by adopting the introduced new approach, and the hot extrusion experiment was carried out. The results show that the prestressed die for hot extrusion of the large fan shaft designed by the new method not only reduced the material cost by 58.6% compared with the integral die, which had considerable economic advantages but also had outstanding stress-bearing capacity, which could be safely applied for the manufacture of large aero-engine fan shaft, which also verified the feasibility of the new shrink fit design method for large-sized hot extrusion prestress die.