The Mechanical Properties Of Electromagnetic Riveting Joint Of Large Diameter Steel Rivet For Commercial Vehicle Frame

Commercial vehicle frame is usually assembled by bolt joint and riveting.In the practical application,the bolt joint process is easy to loose,the state of the bolt needs to be checked frequently,and the weight of the bolt itself is too large,which is not conducive to the lightweight of the vehicle.Frame riveting is a combination of hot riveting and hydraulic riveting.In practical riveting,there is often the problem of uneven interference,which affects the fatigue performance.Moreover,hot riveting process requires heating rivets,which has low efficiency and low degree of automation.Therefore,commercial vehicle frame riveting urgently needs a new riveting method to solve the above problems,and electromagnetic riveting technology provides a solution for commercial vehicle frame riveting.Electromagnetic riveting(EMR)process has the characteristics of high impact force,fast riveting speed,low relative noise,excellent fatigue performance,and is easy to realize automatic riveting.Therefore,EMR is suitable for solving the current commercial vehicle frame riveting problems.Based on this,this paper explores the mechanical properties of electromagnetic riveting joint of large diameter steel rivet for commercial vehicle frame,providing guidance for the application of electromagnetic riveting process in commercial vehicle frame.Firstly,the process parameters of large diameter steel rivet were selected.Using the riveting evaluation criteria of the manufactured head size,the optimal discharge energy range of the joint with the prefabricated hole diameters of 10.1 mm and 10.3mm was determined.Combined with the evaluation criteria of the rivet interference,the optimum discharge parameter of electromagnetic riveting joint of 10 mm steel rivet is 15 k J,and the diameter of prefabricated hole is 10.1 mm.Secondly,the finite element model of electromagnetic riveting joints with double rivet were established.The finite element model was used to explore the dynamic forming process of electromagnetic riveting,and then the stress distribution of the two distributed joints of double rivets after electromagnetic riveting was completed was analyzed.Analyzing the dynamic forming process,the driven head of rivet formed an adiabatic shear band,the interference of the rivet rod is uniform,and the joint performance is good.For the two joints of double rivets,the residual compressive stress at the lower plate is low,and the tensile stress is high,which leads to easy cracks and fatigue fractures.Under the tensile load condition,the tensile stress at the junction between the manufactured head and the rod of the rivet is relatively large,which may become the initial fatigue crack initiation zone.Finally,the shear and fatigue mechanical properties of the two distributed joints of double rivets were tested.The shear tensile failure process was compared and no difference was found in shear mechanical properties.Then the Basquin equation was used to fit the fatigue test data,and the fatigue load-life curve was obtained.It was found that the cyclic stress of 192.45 MPa was the intersection point of fatigue life of the two joints.The joint with transverse distribution is suitable for high stress tensile state,and the joint with vertical distribution is suitable for low stress tensile state.Fatigue failure mode is divided into type I and type II.Type I failure represents the failure of the manufactured head,type II failure represents the failure of plate on the side of the manufactured head.At the same time,combined with the fatigue fracture,it is found that the type I failure occurs from the joint of the nail rod and the manufactured head with high tensile stress,and the type II failure occurs from the lower plate with low residual compressive stress and high maximum principal stress.Electromagnetic riveting with large diameter steel rivets was carried out on the frame parts,and it was found that the electromagnetic riveting quality was good.Electromagnetic riveting of commercial vehicle frame is feasible.