A study on non-uniform deformation of backward flow forming and its influencing factors

Abstract

Non-uniform deformation in the thickness of tubular spun parts is a common problem in the flow forming process and has a significant impact on the performance of spun parts. In this paper, the plastic strain distribution in the wall thickness of tubular spun parts made of Haynes230 superalloy was obtained by the finite element method and microindentation hardness measurements. Moreover, the causes of the non-uniformity in plastic strain distribution were analysed, particularly the effect of main processing factors such as thickness reduction, feed rate and forming passes on plastic strain distribution in the thickness direction. The results indicate that the factors that have significant impacts on uniformity of deformation are thickness reduction and forming passes; deformation in the material is mainly concentrated in the outer layer of the spun part and less so in the inner layer. Furthermore, the plastic strain increases with an increase in thickness reduction, and the number of forming passes with the former process more favourably increasing the plastic strain in the inner layer than the latter. Therefore, in order to improve deformation uniformity in the spun parts, thickness reduction should be increased and the number of forming passes should be decreased when determining the total thickness reduction. This study is equally applicable to other materials.