Research On Composite Forming Of Double-Sided Boss With Hole For Mid-Thick Aluminum Alloy Plate

The use of the internal hole double boss structure on the part not only enhances the strength of the part fitting on the shaft,but also improves the axial positioning accuracy of the part.The traditional internal hole double bosses are mainly formed by cutting.This forming process not only has low utilization of raw materials,but also has low production efficiency.Sheet-volume composite forming is a complex plastic forming process that can increase material utilization and enhance mechanical properties of parts.If the volumetric composite forming process can be applied to the forming of the double-sided boss structure on the inner hole,it not only can overcome the shortcomings of the traditional cutting processing,but also can make use of the advantages of the sheet-volume composite forming process.Therefore,it is of great significance to study the application of the double-hole boss composite forming process for the inner hole double boss structure in the manufacture of parts.This paper firstly analyzes the forming process based on the double hole boss structure of the inner hole to determine the feasible forming process of the double-sided boss of the inner hole of the medium-thickness plate.On the basis of the determination of the process plan,the two-dimensional finite element model building work such as grid division,material model definition,boundary condition setting,and selection of fracture criteria was completed in Deform-2D software.Based on the two-dimensional finite element model of double-sided bosses in medium and thick plates,the metal flow,stress-strain distribution,equivalent strain distribution and average stress during the composite forming process of the double-hole bosses in the plate were analyzed.Distribution,stroke load curve,and boss face quality.Prediction of the location of cracks after reaching the forming limit during the formation of double-sided bosses.Based on the analysis of the basic deformation laws,the influence of parameters such as fillet radius,sheet thickness,boss thickness,friction coefficient,and extrusion speed on the maximum punch load and the quality of the boss end face was studied.In the cross-experimental design,variance analysis method was used to determine the influence degree of each process parameter on a single target.Then,the maximum punch load and the height difference of the end surface of the boss were the optimization objectives.The above process parameters were optimized and the most determined.Good combination of process parameters.Through the mold structure design,the composite forming experiment of the double-sided bosses in the aluminum plate of the medium-thick plate was completed.The accuracy of the finite element simulation and the feasibility of the process scheme were verified.The parts were cracked after the excessive deformation and the cracks appeared.And the direction of the expansion is consistent with the results of the finite element simulation.Through the metallographic test of the double-sided convex part of the inner hole,the distribution of the grain morphology and the distribution of the microhardness in different regions were obtained,the macroscopic deformation law based on the finite element simulation and the microstructure distribution rule obtained by the metallographic experiment.The relationship between the macroscopic deformation and the microstructure evolution of the double-hole boss composite forming was established.Through the micro-tensile test,the influence of the double-hole boss composite forming on the mechanical properties of medium-thickness aluminum alloy was analyzed.