Study On The Structure Analysis And Optimization Design Of The Rear Sub-frame In A Car

With the continuous improvement of domestic economic level,automobile has become an important part of people's life.As an important part of automobile chassis,the rear sub-frame is connected with the body and suspension system.not only to meet its design requirements,but also for noise vibration(harshness(NVH))performance,fatigue performance,lightweight,etc,also have a large contribution.reasonable rear sub-frame design,not only can improve the generality of the auto parts and assembly convenience,but also be able to connect to adjust its structure and bushing stiffness of rubber,etc.,raise the stability control of the car,riding comfort and ride comfort.Taking the optimization design of a rear sub-frame as an example,this paper briefly describes the structure analysis,combined with vehicle performance requirements at the same time,by optimizing the structure size and material thickness,etc.,to enhance the purpose of the constraint modal and lightweight design,at the same time meet the requirements of strength and fatigue durability.First of all,according to the basic model of the rear sub-frame.the load data of the key points of the structure connected between the rear sub-frame and the suspension system should be obtained.Secondly,the finite element model of the rear sub-frame is established,the analysis result show the risk of the structure,the vehicle assembly modal parameter 102.2 Hz,within the scope of the vehicle noise produced,the risk of resonant,and for the the sub-frame structure optimization design provides direction and optimization.Then using Hyper Mesh software,do the frame shape,size and the thickness of the material optimization design.After the optimized,the sub-frame structure can meet the strength analysis,monomer constraint modal analysis,modal analysis of the vehicle assembly.Ensure the rationality of the optimization design.The results show that the optimized assembly mode at 130.5 Hz,increase of 27.7%.the weight of two drive model loss 22.9%,four drive model loss 16%,the overall lightweight effect is good.Finally,the optimized auxiliary frame after phsical bench test,according to the results can meet the design requirements.The rear sub-frame structure after optimized completely meet the requirements of dynamic and static performance,in particular for assembly mode optimization analysis,avoid the noise frequency range of the vehicle,reduce the vehicle noise 2db~ 4 db,improve the vehicle NVH performance,achieve good effect of weight loss at the same time,play a key role for the vehicle performance improment.In this paper,the use of the rear sub-frame structure analysis and optimization design and analysis method,can be used as an sub-frame design verification of general development process,the structure optimization design method can also be used as a generic technology is widely used.