Research On Ultrasonic Vibration Assisted Clinching Process Of Aluminum Alloy And Mechanical Property Of Joint

Automobile lightweight has become the trend of automobile manufacturing industry.Aluminum alloy is widely used in automobile bodies,and the connection between aluminum alloy plates has become a hot topic in current research.Clinching has a great advantage in connecting aluminum alloy plates,but in the process of clinching,the joint neck thickness and interlock value do not match due to the disharmonious deformation of the materials,which restricts the comprehensive mechanical properties of the joint.According to the above problem,this paper introduces ultrasonic vibration assisted plastic forming technology clinching process,using the finite element simulation,experiment process and performance test method,system research of aluminium alloy materials in ultrasonic vibration aided in the process of clinching deformation behavior,the effects of process parameters,shear and tensile resistance performance,joint failure behavior,etc.In order to give full play to the unique technical advantages of ultrasonic vibration,the key problems such as small interlock value of joints,low comprehensive mechanical properties of joints and large forming load in clinching process are clarified.The main work contents and conclusions are as follows:(1)For 5052-H32 aluminum alloy,the conventional and different ultrasonic amplitudes tensile test and ring upsetting test were carried out,and the mechanical properties of the material and the friction coefficient between the die and the material under different ultrasonic amplitudes were obtained.The data of material mechanical properties and the contact conditions between die and sheet metal are provided for the follow-up routine and different ultrasonic amplitudes of clinching finite element analysis.By comparing the mechanical properties of materials under conventional and different ultrasonic amplitudes,it is found that the higher the ultrasonic amplitudes,the lower the yield strength of materials.The tensile strength and elongation at fracture increase first and then decrease with the increase of ultrasonic amplitude.The friction coefficient between tool head and material decreases with the increase of amplitude.(2)The clinching tool was designed and the clinching experiment device assisted by ultrasonic vibration was built.The clinching experiment under conventional and different ultrasonic amplituaries was carried out.The finite element analysis model of ultrasonic vibration assisted clinching was established,and the reliability of the model was verified by experiments.The deformation process of clinched joint assisted by ultrasonic vibration was analyzed by combining finite element analysis and experiment,and the influence of ultrasonic amplitude on the forming of clinched joint was discussed.The results show that the flow stress of the material decreases after applying ultrasonic.The greater the ultrasonic amplitude,the greater the reduction of stress,so the clinching forming load decreases.Ultrasonic vibration can promote material flow and increase flow velocity.The higher the ultrasonic amplitude,the higher the plastic strain and the interlock value of clinched joints.(3)The strength,failure displacement,failure mode and energy absorption values of clinched joints were analyzed by single-lap shear test,T-type tensile test and cross tensile test.The experimental results show that the shear strength and tensile strength of the joint are improved,and the failure displacement and energy absorption values are increased in different degrees.In single-lap shear test,ultrasonic vibration has no obvious effect on failure mode of clinched joints.Ultrasonic vibration has a significant effect on failure modes of clinched joints in T-type and cross tensile tests.The mechanical properties of clinched joints are the best when the ultrasonic amplitude is 4.63 μm.