Research On The Spinning Mechanism Of Hollow Parts With Non-Circular Cross-Section

Metal spinning is an important integral part of modern advanced manufacturingtechnologies, and is considered as the preferred forming process for the production ofthin-walled revolution parts. Non-circular spinning is the latest breakthrough of metalspinning technology, which has became the forefront in the international research field ofplasticity engineering. In recent years, researchers in China and abroad have preliminaryproved the feasibility of non-circular spinning and find that there are many differencesbetween non-circular spinning and traditional spinning on the aspects such as wall thicknessdistribution, spinning force variation, etc. The causes of the above phenomena can't be founduntil in-depth research on the mechanism of non-circular spinning was done. The variation ofthe cross-section of the non-circular spinning part changes the motion status of the roller, andmakes its radial movement change from static or quasi-static during traditional spinning todynamic. Coupled with a more complex shape of the non-circular cross-section, themechanism of non-circular spinning is extreme complex.The research of this thesis was financially supported by National Natural ScienceFoundation of China (Subject title: Research on spinning method and deformation mechanismof hollow parts with non-circular cross-section; Subject No.:50775076). The hollow partswith circular, arc-type or straight-edge-type cross-section were selected as the study objects,and the most widely used spinning process: conventional spinning process with a flat sheetmetal blank was adopted, and combined with the theoretical analysis, numerical simulationand experimental investigation, in-depth research on the spinning mechanism of the hollowparts with non-circular cross-section was carried out.The classification of spinning of the hollow parts with non-circular cross-section hasbeen carried out, and the motion characteristic of the roller during non-circular spinning hasbeen revealed, which is that the distance from the outer contour of the part to the rotationalcenter varies repeatedly during every rotation of the mandrel. The deformation characteristicduring non-circular spinning was studied, and a deformation degree analysis method using therelative height and relative radius was put forward. By graphical analysis method, the motioncharacteristic of the roller and its effects on the forming speed, contact area and so on werestudied, and the variation characteristic of the contact position between the roller and blankwas revealed comprehensively, which does not only move along the axial direction for theroller's axial feeding, but also moves along the radial, axial and circumferential directions forthe variation of the non-circular cross-section. Based on the above variation characteristic, the calculating methods for the contact area and the roller radial feed track were established. Thesoftware MSC.ADAMS was used to analyze the motion of the roller during non-circularspinning, and the calculated result of the roller radial feed track by graphical analysis methodwas verified. The result shows that the calculated result is reliable.The basic theory of finite element method (FEM) of the large elastic-plastic deformationwas introduced. The key techniques of the numerical simulation, including the blank design,meshing, motion control of the roller, parallel simulation and so on, were researched. Asubroutine for the motion control of the roller during multi-core parallel simulation wasdeveloped. The3D elastic-plastic FE numerical simulation model for the non-circularspinning was established using the software MSC.MARC. By changing the meshing method,boundary condition and using parallel simulation, the numerical simulation efficiency wasimproved effectively. The research results show that by using the stationary boundarycondition of the blank and multi-core parallel simulation, the simulation time can be reducedby76.97%while the simulation accuracy unaffected.With3D elastic-plastic numerical simulation, systematic studies on the spinning processof the hollow parts with circular, arc-type or straight-edge-type cross-section were carried out,and an analysis of the similarities and differences of the deformation model, equivalent stressand strain distributions, strain state, wall thickness distribution and springback was done. Theeffects of the geometry parameters of the non-circular part, such as the offset distance, relativeheight and relative radius, were revealed. Taking the hollow part with three straight-edgeround-corner cross-section as the study object and combining with the orthogonalexperimental design, the effects of the main process parameters, such as the roller diameter,roller nose radius, relative clearance between the roller and mandrel, spindle rotational speedand roller feed rate, on the forming accuracy (the wall thinning, springback, eta) wereobtained.A device for the non-circular spinning was designed and manufactured. And a series ofexperiments was carried out. The hollow part with three straight-edge round-cornercross-section was manufactured by spinning process successful, which is one of the mostcomplex spun parts recently. By the grid experiment, the distributions of the strain andequivalent strain of the hollow part with triangular arc-type cross-section were obtained. Bythe electrical measuring method, the variation of the spinning force and the influence of theprocess parameters on the spinning force were investigated. The theoretical results andnumerical simulation results were fully verified by experiments. Judged by the formingprocess, height of spun part, wall thinning and spinning force, the simulation model established in this thesis is high reliable. The experimental results were used to compare withthe simulation results on the aspects of the strain distribution, strain state, spinning force andthe effect of process parameters on the forming accuracy, and good agreements are observed.