Decoupling Analysis Of Powertrain Mounting System Based On The Finite Element Method

The traditional method for the decoupling analysis of the powertrain mounting system at low frequency 0-50 Hz is usually to establish a rigid body-mount model and decouple based on the dynamics of multi-body system method.This method does not consider the coupling effect of the suspension system,the body flexibility,the tire-unsprung mass system and the powertrain mounting system.The suspension and the unitized body(or frame)based on the powertrain are assumed to be rigid foundation;or assume that the powertrain foundation is a rigid body whose mass approaches infinity,assuming that the powertrain is attached to it by structural damping or spring-viscous damping.With the increasing development of lightweight body,the influence of the flexibility of the support structure on the decoupling rate of the powertrain mounting system has become negligible.The traditional method of decoupling the rigid body-mount model based on the dynamics of multi-body system method is difficult to reflect the true decoupling rate under real vehicle conditions,so the decoupling rate is extended from the single rigid body system to the multi-rigid system,considering the coupling effect of each subsystem on the decoupling rate of the mounting system.Decoupling analysis in this case results in a decoupling ratio closer to the actual engineering.Compared with a variety of numerical analysis methods,this thesis uses the finite element method to decouple the powertrain mounting system.As a method to decouple the powertrain mounting system,the research ideas of this thesis are: the realization and verification of the method,the profitability of the method,and the optimization of the method.Firstly,taking a vehicle provided by an automobile enterprise as the research object,the decoupling analysis of the 6-degree-of-freedom powertrain mounting system is based on the finite element method.Secondly,decoupling analysis of 6-degree-of-freedom powertrain mounting system with the same parameters based on the dynamics of multi-body system method is completed.And the decoupling rate based on the dynamics of multi-body system method is used as an evaluation index to verify the feasibility and accuracy of decoupling analysis based on finite element method.Thirdly,based on the finite element method,the decoupling analysis of the 13-degree-of-freedom vehicle-powertrain mounting coupling system considering the coupling of more vehicle subsystem and mounting system is completed.The decoupling ratio closer to the actual engineering is obtained,and the profitability of the finite element method is explained.Then,the boundary condition of the powertrain mounting bracket is placed at the vehicle level,and the stress of the mounting bracket is checked based on the finite element method to verify whether the design of the mounting bracket is reasonable,indicating the profitability of the finite element method II.Finally,the finite element method is used to optimize the decoupling ratio of the powertrain mounting system,thereby improving the vibration isolation performance of the mounting system and improving vehicle comfort.