Research On Headless Rivet In Electromagnetic Riveting By Simulation And Process Experiment

Headless rivet has the advantages of rivet shaft deformation uniform,fine sealing performance and high fatigue life of structures,and it has been widely used in the field of aerospace industry.The electromagnetic riveting(EMR)of headless rivet has been widely used at abroad,but little is known about this kind of report owing to lack of technologies confidential.In order to research the process of headless rivet with electromagnetic riveting systematically,the influence of process parameters on the rivet interference were studied from macro and micro aspects by numerical simulation and experiments combination methods in this paper.First of all simulation model has been established,the EMR process of headless rivet has been simulated by using the loose coupling method.The dynamic deformation and stress-strain distributions of headless rivet were analyzed.The effects of process parameters on rivet deformation were studied.The results showed that discharge voltage,loading way,countersink structure,die form,die angle and interlayer thickness had a great influence on the rivet deformation.The countersink structure and die form can effectively reduce strain concentration.Based on the simulation results,the effect of process parameters(loading way,countersink structure,die form,etc.)on the rivet deformation was analyzed by headless rivet electromagnetic riveting process experiment.The experiment results showed that the interference of bidirectional loading was larger and more uniformly than unidirectional loading.And countersink structure had a more uniform rivet distribution.It was favorable to improve rivet interference if concave die is adopted,die angle decreases,the voltage improves and rivet overhang decreases.The less thickness of connection plate,the more uniform of interference distribution is.Based on study of process parameters effect,which the process parameters were optimized,the joining of aluminum-to-aluminum material was achieved.Rivet forming complies with process requirements.The performance test of connectors results showed that the pulled off strength depend partly on the size of upset head.The pulled off strength of milling flat heading was smaller than not milling flat.When the strength of upset head can meet the requirement,the size of upset head had little effect on the pulled off strength.Shear strength increases with the increase of the interference.The pulled off strength,shear strength and actual micro connection of bidirectional loading were superior to that of the unidirectional loading.The microscopic analysis of rivet indicated that countersink structure and die form can make rivet upper head deformation uniform and the upper head without obvious shear band produced.