Study Of Rim Flare Forming Defects Considering Welding Influence

The rim,as an important part of the construction vehicle structure,has to ensure smooth and safe driving while meeting the load of the vehicle.Therefore,for the production of wheel rims ensuring the quality of their production performance becomes of paramount importance.As rims mature in the production field,defects such as cracked welds still exist in the manufacturing process,and the weld joint area is prone to micro-cracking during the forming process after welding,or in severe cases,complete cracking,which can increase the repair welding process in light cases,or even scrap directly,causing serious waste to the company.In order to solve the long-standing problem of rim weld cracking quality in production,this paper takes the structural parts of engineering steel rims as the research object and carries out a systematic analysis of rim flaring forming defects considering the influence of welding by means of numerical simulation and physical experiments.Firstly,the rim flare cracked joints were analysed from macroscopic and microscopic perspectives.The fracture forms were mainly brittle fractures,with fractures exhibiting features such as rivers,tongues,fans and destructive step patterns,and there were also ductile fractures,exhibiting features such as tough nests and quasi-destructive fractures with tough-brittle transformation.Weiss ferrite and coarse grain areas mainly constitute the metallographic characteristics of the weld joint area,resulting in reduced toughness.Microstructural factors such as the presence of coarse Weissite,inclusions and coarse grain size in the rim weld are the main causes of rim weld cracking.Based on the thermal-elasticity method and the Mises yield criterion,the SIMUFACT software is used to establish a coupled numerical model of the rim forming process chain,and the numerical simulation of the rim flaring forming considering the influence of welding finds that:stress concentration occurs in the weld area at the flaring end of the rim,with a maximum stress value of 567.27 MPa,which is greater than the measured maximum strength of 540 MPa.The residual compressive stress in the flaring deformation area is gradually transformed into tensile stress,resulting in an increase in the circumferential shear force.The greater the coefficient of friction,the greater the plastic strain at the centre of the weld on the inside of the flaring end of the rim,the greater the risk of cracking of the weld.Improving the quality of the weld joint,adopting suitable stress relief and strengthening the lubrication between the tool and the workpiece can effectively reduce the tendency of rim weld cracking.Around improving the quality of rim weld performance,the flash butt welding parameters firing distance,firing speed,top forging distance and charged top forging time designed four-factor three-level experiments,through the study of the impact of each parameter on the performance of the welded joint analysis found that:joint tensile test joint fracture occurred in the base material area,joint tensile strength in 584.13～611.02MPa,can match the strength of the base material,elongation Using BP neural network and NSGA II algorithm,the optimal welding parameters:firing distance 18mm,firing speed 1.1mm/s,top forging distance 10mm and charged top forging time 0.35s.Under the welding parameters,the plasticity and toughness of the material in the weld area simultaneously reach optimal Corresponding to the measured elongation of 25.10%,the impact absorption work of 22.6J/cm~2.Finally,based on the simulation model of the rim forming process chain,the analysis and calculation by changing the flaring angle and mould structure reveals that:as the mould angle increases,the risk of flaring cracking at the weld seam increases;the equivalent plastic strain at the weld seam is smaller for the circular convex mould compared to the conical one,which means that the risk of flaring cracking is significantly reduced for the circular mould.Therefore,the rim is designed with a small angle of flaring die and circular convex die as far as possible,which effectively improves the flaring rate of the rim and the rim is controlled within 15%of the actual cracking rate,providing some guidance for the efficient production of the enterprise.