基于模态分析的发动机排气歧管开裂问题研究

Analysis of the Exhaust Manifold Cracking Based on the Modal Analysis

研究某柴油机排气歧管在可靠性实验中出现开裂故障的原因,通过建立排气歧管有限元模型并离散成多自由度系统,利用有限元分析软件ABAQUS对模型进行模态分析。结果表明7阶自由振动模态频率为149.87Hz,接近发动机基频,在超负荷工况高温高转速的工作条件下可能会出现共振问题,且发生振动时扭转对称中心与试验中发生开裂故障的位置相同,说明了振动可能导致排气歧管开裂。

This article focuses on the cracking causes of an exhaust manifold during the reliability test. By establishing the finite element model for the exhaust manifold assembly, the model is divided into many systems with freedom, a modal analysis is carried out used ABAQUS software. The results show that the modal frequency of the 7 order free vibration is 149.87, and the fundamental frequency of the engine is close to the fundamental frequency of the engine. When the torsional symmetry center occurred during the vibration, the position of the cracking occurred in the test was same, and the vibration may cause the exhaust manifold cracking. By applying effective fixed boundary restraint and reasonable selection, the vibration frequency can be changed to avoid the cracking caused by resonance.