Research On Forming Limit Based On Fracture During Hot Power Backward Spinning For As-casting 7075 Aluminum Alloy Tube

Fracture is one of main defects during the process of as-cast 7075 aluminum alloy tube hot power backward spinning,which determines the performance and qualification rate of the product.Therefore,based on ABAQUS/Explicit finite element sofaware,this paper used orthogonal experiment method to obtain three important factors of six parameters which are thickness reduction,preheating temperature of tube,mandrel rotation speed,feed speed of rollers,the friction coefficient between mandrel and tubes,the friction coefficient between rollers and mandrel.The three factors have a significant impact on the damage value of 7075 as-cast aluminum alloy tubes spinning forming.Regression model of the damage value and these three factors was established and the forming limit diagram of 7075 aluminum alloy tube spinning based on fracture was obtained,which provides some reference for the actual processing.The research contents and conclusions obtained in this paper are as follows:(1)The primary and secondary order of the influence of each pass parameters on the damage value and the significant and important factors of the influence of each pass on the spinning of 7075 as-cast aluminum alloy tube were determined through the visual analysis and variance analysis of the orthogonal experiment.The results are as follows:The the primary and secondary order of the first pass:the thickness reduction A>the friction coefficient between mandrel and tube E>the friction coefficient between rollers and tube F>preheating temperature of tube B>feed speed of rollers C>mandrel rotation speed D;the second pass: the friction coefficient between mandrel and tube E >the thickness reduction A>the friction coefficient between rollers and tube F>feed speed of rollers C>preheating temperature of tube B>mandrel rotation speed D;the third pass: the thickness reduction A>preheating temperature of tube B>feed speed of rollers C>mandrel rotation speed D>the friction coefficient between mandrel and tube E>the friction coefficient between rollers and tube F;the fourth pass:the thickness reduction A>preheating temperature of tube B>feed speed of rollers C>the friction coefficient between mandrel and tube E>the friction coefficient between rollers and tube F>mandrel rotation speed D.In the first and second pass,the thickness reduction,the friction coefficient between mandrel and tubes,the friction coefficient between rollers and tube have significant and important impact on the damage and fracture of the spinning process;in the third and fourth pass,the thickness reduction,preheat temperature of tube,feed speed of rollers have significant and important impact on the damage and fracture of the spinning process.(2)The relationship between the damage value and the three process parameters which have significant impact on the damage was obtained based on regression analysis.The reliability of the coupling model between damage value and these three process parameters was verified.(3)The function relationship between the maximum thickness reduction in each pass and the other two factors was solved based on the regression model between damage value and significant process parameters.The each pass forming limit diagram of the 7075 as-cast aluminum alloy tube hot power backward spinning was established based on the functional relationship.