基于波纹管简化模型的排气系统模态分析

Modal analysis of exhaust system based on bellows' simplified model

为了探究汽车排气系统波纹管简化模型的合理性,对简化模型进行数值分析和理论研究.首先,以某重型卡车排气系统为研究对象建立有限元模型,将波纹管简化为零长度的CBUSH单元,对系统自由模态进行分析;其次,用波纹管将排气系统分隔开简化为二自由度模型进行理论计算;最后,综合对比分析表明,第7阶和第8阶模态频率接近于零,主要原因是绕X,Z轴刚度较小,验证了波纹管在该方向的隔振效果良好.理论方法与数值计算具有普遍性和工程指导意义.

In order to explore the rationality of simplified model of bellows in exhaust system,numerical analysis and theoretical study for the simplified model were developed in the project.Firstly,a heavy truck exhaust system was used as the research target to build a finite element model and the bellows was simplified as zero-length CBUSH unit to analyze the exhaust system＇s freedom modal.Secondly,in order to conduct the theoretical calculation,the exhaust system was divided into two degree of freedom model using bellows.Finally,the comprehensive comparison and analysis result that the 7th and 8th modal frequencies were both close to zero,which was mainly resulted from the weak stiffness rotated around the Xand Zaxis.It also met the desired research result and verified the premise of good vibration isolation effect of bellows in the Xand Z axis.Furthermore,the theoretical method and numerical calculation are universal and have engineering guiding significance.