发动机排气歧管螺栓断裂仿真分析及试验研究

FEA Simulation Analysis and Experimental Research of an Engine Exhaust Manifold Bolt Fracture

排气歧管是汽车发动机的重要零件,工作热负荷大,且工作温度通常是循环交变的,极易发生失效。某增压发动机在进行800h循环耐久试验时,出现排气歧管1号螺栓断裂的故障。通过螺栓断裂部位及排气歧管螺栓孔的压痕判断为排气歧管受热变形后与1号螺栓产生挤压,导致1号螺栓受到排气歧管的剪切而断裂。本文通过对排气歧管的受热变形进行仿真分析,验证了歧管受热变形后对螺栓产生剪切作用的判断,从而提出加大螺栓孔直径,以增加螺栓与螺栓孔初始间隙的方案,该方案最终通过了试验验证。

Exhaust manifold is an important pars of automotive engine. It is exposed to high thermal load, and its working temperature is usually cycling between low and high, making it prone to failure. During an 800 hour cyclic endurance test of a turbo engine, the NO. 1 bolt on the exhaust manifold has fracture. By analyzing the bolt fracture spot and exhaust manifold bolt holes indenta- tion, it is proposed that the exhaust manifold deformed under thermal load and sheared the bolt as a result. In the paper, this assumption is verified through simulation analysis of the exhaust manifold deformation under thermal load. Based on that, a solution is proposed by increasing the bolt hole diameter so as to increase the bolt and bolt hole initial clearance. In the end, the effectiveness of this solution is verified by testing.