Study On Positive-negative Forming Theory Of Revolving Shell And Bulging Technology Of Aotomobile Axle Housings

Revolving shell details including three-way union, four-way union, corrugated pipe, corrugated sleeve and automobile axle housings etc. has been used in such industrial departments as machine, electron, aerospace and aviation, transportation etc. At present, the research related to positive-negative forming theory of revolving shell is imperfect in some aspects(such as push sinking mechanism of shell), and is deficiency in some aspects(such as forming mechanism of compound bulging).Production urgently needs studying the forming theory in depth.In this paper, based on the problems existing in the test of compound hydro-bulging for automobile axle housings(the technology consists of sinking end zones for the selected tube according to the detail drawing at first and compound hydro-bulging with axial compression force for the central part to be expanded subsequently), the positive-negative forming theory of revolving shell is investigated. The Technology of hydro-bulging for automobile axle housings is formulated on the base of the research achievement and perfected by experiments.In this paper, the mechanical model of positive-negative formation for revolving shell is analyzed, the classification method is given according to the stress yield criterion. The strain yield condition of shell formation is proposed, the stain locus method solving the limit forming coefficient is given. The shell formation of free push sinking(negative forming) is analyzed, sinking stress calculated, and the formula calculating the limit push smking coefficient given. The relation between the equivalent strain and the Lode's stress parameter is deduced, the function between and the geometric parameters after sinking is given. The formula calculating the limit compound bulging(positive forming) coefficient is deduced, the idea of matching force parameter is advanced, and the ratio of longitudinal strain to latitudinal strain is determined. The mechanism of compound bulging(positive forming) small latitudinal corner is studied, the stress equilibrium equation is derived, and the matching condition of bulging force parameter is given. The compound technology of shell sinking-bulging(positive-negative forming) is analyzed, the stress equilibrium equation deduced, and the formula calculating the stress field given.In this paper, the concept of generalized slip-line is advanced, which develops the classic concept to the locus of principal shear stress in a plane from that of the maximum shear stress in a plastic deformation body. With the generalized slip-line equations deduced, the classic slip-line method ,which only is used to calculate plastic plane-strain problemsand partial plane-stress problems, is developed to resolve axial symmetric problems and three-dimensional problems with a principal stress known. The generalized slip-line field is constructed for the first step of hydro-bulging and the final step of forming the small latitudinal corner for the automobile axle housings, the corresponding plastic stress field and elastic stress field calculated.The research achievement of positive-negative forming theories is used to direct the technology practice of the compound hydro-bulging of automobile axle housings. The forming program is determined for sinking ends and bulging the central part of the axle housings, the push sinking die and the slide bulging mould is designed, the technology parameters of sinking and compound bulging is formulated and perfected by experiments. The fruits is applied to production.The research of positive-negative forming theory of revolving shell perfects the mechanism of shell push sinking(negative forming) and fills in gaps in mechanism of compound bulging(positive forming). The achievement is not only used to the compound bulging of automobile axle housings, but also developed to automobile corrugated sleeve.Based on the study of hydro-bulging technique, producing axle housings with advanced and scientific hydro-bulging technology will lead to transform the method of automobile axle...