| Matching with the transmission chain, multi-row sprocket is generallyapplied to transfer and convert the rotary motion among parallel axes in theworking process and widely utilized in the transmission system of machineriesand equipments. As a kind of irregular part with toothed profile, multi-rowsprocket possesses a complex structure, works in a poor environment andgenerally requires higher strength and abrasion resistance in practical work.Generally, multi-row sprocket is manufactured by the method of casting, forgingor machining with which the machining allowance of tooth shape and theroughness of tooth surface for sprocket work-piece is larger, the strength and theabrasion resistance are relatively lower and the production cycle is longeraccordingly, which can easily cause bad phenomena of vibrating, sliding,jumping and swirling for sprocket transmission system in practical application,seriously influence the normal working of the sprocket system and reduce theservice life and the service cycle of mechanical equipments.According to the above-mentioned problems, combining numericalsimulation with experimental validation, taking an example for multi-row sprocket06B, analyzing the geometric shape, the tooth profile and structurecharacteristics of GB/T1243-2006part, the forming process of semi-precisionforging for multi-row sprocket was newly put forward. The new tooth profilewith two arcs and one line for sprocket forging was designed on the basis of theprocess. Both billet deformation and filling the die cavity of semi-precisionforging for multi-row sprocket were simulated and analyzed by using the finiteelement (FE) software Deform-3D V10.2. The key objects such as tooth profilemachining allowance, billet shape, central slug position and the diameter ofupper die core were optimized and the optimum structure form of semi-precisionforging was obtained. Forging drawings of the solid billet and the hollow billetwere designed and the optimum structure of the forming part for the die wasconfirmed in accordance with the simulative results. Then, the upper die with aflange, pre-stressed bottom die, sprocket ejector and other key parts of the diestructure were designed respectively. Finally, using the module of die stressanalysis of the simulated software, the strength of die insert and shrink ring wasverified. The floating-die assembly drawings of the semi-precision forging formulti-row sprocket were proposed and the related tests were carried out usingthe die structure.The simulative results show that the maximum effective stresses of thesolid billet and the hollow billet in fully filling the die cavity are133MPa and147MPa, respectively. The stress concentration and the deformation stress of thesolid billet under the same conditions are smaller than that of the hollow billet. Central slug position takes the1/3height from the end face of the forging andthe more reasonable value of the core diameter for the upper die is26mm. Theaxial and radial distributions of the maximum effective stress for bottom die are1380.46MPa and1226.83MPa and of the shrink ring are808.41MPa and856.73MPa respectively, which are significantly less than the yield limit of diematerials. The strength of two-layer combined bottom die basically meets theprocess requirements in semi-precision forging of the sprocket. Based onexisting laboratory facilities,1060aluminum alloy was employed to verify thefeasibility of semi-precision forging process. Load curves, optimal temperature,forming effects and shape sizes of forming sprocket were obtained, respectively.The results show that sprocket forgings obtained with the designed die structurepresent better-fully tooth fillings, better-shaped tooth profiles and less-residualflashes. The maximum loads for solid billet and hollow billet in fully filling thedie cavity are1784.79KN and1468.48KN at room temperature. The maximumload of the test is884.23KN and of the simulated is854.24KN at thetemperature of350℃. The simulative results are basically in consistent with theexperimental ones, which further demonstrate the feasibility of the process andthe rationality of the die design. |
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