Numerical Simulation And Experimental Study On Material Fracture Splitting Performance Of Rear Axles' Reducer Shell Bearing Seat

Rear axle reducer housing is a key component of medium and heavy-duty automobile transmission system.During driving of car,its bearing seat(the shell bearing seat)bears axial forces of both sides,which can easily cause misalignment between bearing cover and shell bearing seat.It can influence drive smoothness and reliability.Fracture-splitting machining is a new manufacturing process,which can realize three-dimensional precise meshing between shell and bearing cover.Thereby greatly improving its shear resistance and load bearing capacity.At the same time,this process has advantages of low processing cost,fewer procedures,and high production efficiency.One of key steps of shell bearing seat fracture splitting machining is slotting,that is,prefabricated fracture splitting notch.A load perpendicular to predetermined fracture surface is exerted.Higher stress concentration can be induced near the tip of notch.It makes material crack at the tip and propagate rapidly until shell bearing seat is divided into two parts,that is,the shell and the bearing.This paper mainly simulates fracture splitting process of shell bearing seat of two materials,QT450 and RuT380,by ABAQUS.By comparing and analyzing crack initiation position,fracture-split load,plastic deformation and out-of-roundness of two materials in different crack groove depths,finally best material is suitable for fracture splitting of shell bearing seat is determined.Microstructure of rear axle main reducer shell bearing seat material QT450 with 25% P+75% F and 50% P + 50% F is compared to study internal relation between structure and fracture splitting performance.Best matrix tissue for fracture splitting is determined.The reliability of numerical analysis is verified through experiments,which provides a rational basis for application of fracture splitting processing technology to actual production.The main contents and conclusions of this paper are as follows:(1)This paper analyzes applicable scope of each fracture criterion,uses linear elastic fracture mechanism to output J integral,and uses J integral method to judge crack initiation.(2)Prefabricated crack groove has a depth range of 0.8 mm~2.4 mm.Numerical analysis of crack initiation of two materials,QT450(50% P + 50% F)and RuT380.The result shows that both materials crack initiation at groove root in the middle of thickness and near flat end face side.As the depth of crack groove increases,stress concentration near the crack tip continues to increase,which causes fracture-split load to decrease,plastic deformation to decrease,and out-of-roundness of bearing hole to decrease.QT450 has larger fracture-split load than RuT380,but its stress concentration is more significant,and its plastic deformation and out-of-roundness are smaller.QT450 material is not only stronger than RuT380 in terms of strength,stiffness and plastic toughness,but also has good fracture splitting processing performance,which is suitable for production of shell bearing seats by fracture splitting processing.(3)Microstructure of QT450 with 25% P + 75% F and 50% P + 50% F is analyzed.Fracture-split load,overall stress and strain field distribution,stress and strain state in local area of crack groove and out-of-roundness with two different matrix structures are analyzed.The results show that QT450 with 50% P + 50% F is more suitable for fracture splitting than QT450 with 25% P + 75% F.Strength and stiffness of QT450 material depend on the content of pearlite.With the increase of pearlite content,brittleness of material,notch sensitivity and fracture splitting performance are all improved.The shell bearing seat produced by QT450 with 25% P + 75% F matrix has an out-of-roundness of more than 0.2mm,which can not complete subsequent finishing and assembly.The shell bearing seat produced by QT450 material with 50% P + 50% F has an out-of-roundness of less than 0.2mm,and plastic deformation caused by fracture splitting is small,so it can well meet requirement of actual process.(4)The experiments have verified the validity of simulation.The results show that QT450 shell bearing seat with 50% P + 50% F as the matrix structure is more suitable for fracture splitting.In order to obtain better process parameters and better cracking quality,the optimal crack groove depth range is finally determined to be 1.8~2.2 mm by studyingcracking process of QT450 shell bearing seat with matrix structure of 50% P + 50% F.This paper provides a reference for the design of cracking equipment and the formulation of process.