The Numerical Simulation Of Hot Forging And Die Optimization For The Balance Shaft

With the rapid development of China's economy,the automobile industry has been prosperous and the output of automobiles has been increasing steadily.With the improvement of people's living standard,the demand for middle and high end automobiles is more and more big,so the demand for high precision,high quality and complex shape forgings in auto parts market is also increasing.The balance shaft is generally used in high-end car,is an important part of automobile engine.When the engine is working,the force is complex and changeable.Besides the inertial force and centrifugal force caused by the rotation of the engine,it also suffers the alternating load.With the rapid development of modern science and technology,automotive engines require low noise and good engine performance.The rotation of crankshaft generates the vibration source of the engine,and the crankshaft is equipped with eccentric block,but when the crankshaft rotates it only can balance the rotational torque,can not balance the reciprocating inertia force and torque,so it is need to use the special parts,balance shaft.The shape of the balance shaft is complex and difficult to form.In the process of hot forging,the defects such as folding,filling and cracking are often occurred.In this paper,a balance shaft as the research object,and analyze process of the balance shaft combined with shape,structure characteristics and the actual production.Determine the forming process of the pre forging and finish forging,and put forward the reasonable process chain.According to the layout structure of two moulds,the forging process of the balance shaft is simulated by DEFORM 3D software.In the two schemes,point tracing analysis,equivalent stress contrast analysis and filling rate contrast analysis are carried out respectively on the metal billet.Obtain the law of metal flow and the filling rate of billet metal in the forming process and determine the layout mode and die structure of the balance shaft in pre forging and final forging.The numerical simulation results of DEFORM 3D software show that the forming load and die stress of the final forging are larger,and the main problem is the folding defects of the forgings.By analyzing the flow deformation of billet metal in forming process,it is known that the reason of the defects in the forging is that the structure of the balance die is unreasonable,the formation of metal concentration in the bottom corner of balance shaft reinforcing rib,here leads to produce metal creases;uneven metal flow in the gap between the reinforcing rib and the balance block causes a dent.In addition,the final forging load of the balance shaft is large,which makes the mould wear seriously and reduces the die life.In order to solve the forging defects of the balance shaft,the response surface analysis method was used to optimize the structural parameters of the pre forging die.Using the design method of Box-Behnken Design,the design variables are the balance cavity draft angle ?1(A),rib height H(B)and unilateral reinforcing rib cavity draft angle ?2(C),the response targets are the folding angle(R1)at the joint of the balance block and the stiffener,and the folding angle(R2)at the corner of the stiffener corner.Obtain the response surface model by fitting the DEFORM simulation data,and analyze the model to minimize the response target value,and obtain the optimal combination of the structural parameters of the die,namely the factor A is 10°,factor B is 8mm,factor C is 145°.The final forging load of the balance shaft is very large,which leads to the severe wear of the die.In order to reduce the forming load and the die wear,the Central Composite Design method in the response surface is used to optimize the forming process parameters.The design variables are billet preheating temperature T1(A),mold preheating temperature T2(B)and press down speed V(C),and the response target are final forging forming load(R1)and final forging die wear(R2).Similarly,obtain the response surface model by fitting the DEFORM simulation data,and obtain the optimal combination of the process parameters by analyzing the model.Namely,the factor A is 1200?,the factor B is 294?,and the factor C is 46mm/s.Through the actual production verification,it shows that through the optimization of the die structure and process parameters,the folding defects of the balance shaft can be effectively avoided,and the forming load and die wear are significantly reduced.