Numerical Simulation And Optimization Design Of Ultrasonic Vibration-assisted Clinching Process

The introduction of ultrasonic vibration into plastic forming can improve the surface quality of products,and increase the maximum deformation of materials.In addition,the deformation performance of metal materials can be improved,and the loading of the plastic forming can be obviously reduced..At present,ultrasonic vibration assisted plastic forming has been applied in drawing,bending,upsetting and other processes and presentes good performance.However,the research on ultrasonic vibration-assisted clinching process is very limited.The introduction of ultrasonic vibration is expected to solve the technical problems of large forming load and poor matching of joint size parameters in the clinching process without rivets.Therefore,the ultrasonic vibration was introduced into the plate clinching to form the ultrasonic vibration assisted clinching.AA5052 aluminum alloy was adopted,which is widely used in industry.The formation process and ultrasonic effect of the clinching joint under the condition of ultrasonic vibration of the sheet material were numerically studied,and the influence of the vibration parameter and the die parameter on the forming of the clinching joint was analyzed.Moreover,response surface method and genetic algorithm were used to optimize the parameters and good deformation conditions of the joints was obtained.The main contents and conclusions of this article are as follows:(1)This research established a finite element simulation model of clinching assisted by ultrasonic vibration.The stress and strain state of each region of the sheet material under the condition of applying ultrasonic vibration were analyzed.The load and joint size during clinching without or without ultrasonic vibration variation of parameters were evaluated,and discussed the effect of ultrasonic vibration on joint forming.According to the joint forming process and load change,the clinching process can be divided into four stages that is elastic deformation stage,free bulging stage,extrusion deformation stage and interlock forming stage.(2)The effect of amplitude,frequency and vibration excitation mode in the process of clinching assisted by ultrasonic vibration were investigated.The changes of load,stress,strain and velocity field in the process of joint forming were analyzed,and the influence of different ultrasonic vibration parameters on the geometric size of the joint after forming was studied.The results showed that with the increase of vibration frequency and amplitude,the maximum load of joint forming decreases,and the thickness of sheet metal neck increases,but the interlocking value decreases correspondingly.Through the analysis of the finite element simulation results,when the amplitude is 6 ?m and the frequency is 20kHz,the joint with small relative difference between interlock value and neck thickness can be obtained.(3)The effects of the clinching tool head radius,clinching tool head fillet radius,draft angle,groove radius,die depth,and die entrance fillet radius on ultrasonic vibration-assisted clinching joint forming were systematically studied.The finite element simulation results showed that as the tool head radius increased,the joint interlock value and neck thickness decreased simultaneously.With the increases of the radius of the concave groove inlet,the groove radius,the tool head fillet radius and the draft angle,the joint neck thickness increased and the interlock value decreased.As the die depth increased,the interlock value increased and the neck thickness decreased accordingly.The research results showed that the influence of mold parameters on the maximum load after joint forming is as follows:the maximum load after joint forming decreases with the increase of the tool head radius and the tool head fillet radius,and increases with the increase of the draft angle.As the depth of the die and the radius of the groove increase,the maximum load decreases first and then increases,while changing the fillet radius of the entrance of the die has little effect on the maximum load.(4)The interlock value and neck thickness was taken as the objective function,and selecting the interlock value and neck thickness as the parameters to be optimized,the optimal process of ultrasonic vibration assisted clinching was explored through central composite test design,response surface method and genetic algorithm parameter.Using the relationship between the objective function and the design variables obtained by the response surface method,a program was written with optimizing the solution using Matlab software further,and 16 groups of Pareto non-inferior solutions was obtained.The optimal parameter combination was obtained through the satisfaction function calculation.The preferred parameters after rounding are as follows:the tool head radius is 0.3 mm,the tool head radius is 2.8 mm,and the ultrasonic amplitude is 6?m.