The Effect On Usage Of Multi-layers Container With Autofrettage Technology

The container is the most great general character part of large extrusion instrument.It bears high temperature pressure during extrusion process. The interface between innerlayer and extrusion billet suffered the extremely high material flow speed and thisalways cause abrasion, those facts lead the container’s life to be short. As traditionallydesign process of extrusion containers, the layers are only consider of ideal elasticmaterial which means the standard of rational design is that the peak stress is under theadmissible stress. In order to decrease the peak stress on inner face， the pre-loadstructure of assembly multi layers with interference between inter face of each layers. Inthis paper a method that combine the autofrettage to assembly are presented and thestress distribution on layers are analyzed. And also some researches about materialhardening of the inner layers are down. Mainly works are as follows:①Based on the elasticity knowledge, equations to analysis the stress distribution ofmulti-layers container are obtained; based on the elastic-plasticity knowledge, equationsto obtain the stress distribution of multi-layers container with plasticity deformation hasbeen presented.②Utilized the famous FEM program ABAQUS to analyze the stress distributionon multi-layers container in the case of interference of inner pressure loaded. The resultshow a good agreement with analytic expression presented in chapter2. When thematerial of inner layer is ideal elasticity， the peak stress could be much over than theplastic yield stress. As the elastic-plasticity materials section are loaded on inner layers，there would be a plastic depth.③After inner pressure released, residual stress of inner layer are the plus stress ofresidual stress of plastic deformation and stress of interference, the equations has beeninduced and confirmed the correct by FEM. Comparison of two autofrettage proposalhas been made and the proposal two turned out to be the proper one.④Different intensification pressure, interference value and radial ratio of innerlayer has different effect on the stress and deformation distribution, the results show thateach factor has the proper choose span. Some discussion on the material of inner layerhas been made and it turned out that the double line hardening model is proper than theideal elastic model compare to the reality situation. ⑤Outer layer of assembly container have those structures as heating holes, cooling holesand grooves which may cause stress concentration, in order to decrease the peak stress, somechange on structure has been made and shows a good result.Methods shown in this paper has significant meanings on design of extrusionmulti-layer containers.