集成排气歧管低周疲劳寿命研究

Study on Low Cycle Fatigue Life of Integrated Exhaust Manifold

集成排气歧管的设计使排气部分收到高低温载荷的反复冲击,因此在局部区域会产生较大的应力集中,超过材料的屈服强度,产生塑性变形,会有低周疲劳破坏的风险。本文基于有限元的方法,计算某冲击循环的瞬态温度场结果,并基于此结果进行交变工况下的应力应变分析,研究排气部位危险位置的温度、应力和应变的变化规律,并基于局部应力应变法得到该位置的疲劳寿命,为缸盖设计提供一种分析方法。

The design of the integrated exhaust manifold makes the exhaust part receive repeated impact of high and low temperature loads,so there will be a large stress concentration in the local area,which exceeds the yield strength of the material,resulting in plastic deformation and the risk of low cycle fatigue failure.Based on the finite element method,this paper calculates the transient temperature field results of an impact cycle,and based on the results of the stress and strain analysis under alternating conditions,studies the temperature,stress and strain change law of the dangerous position of the exhaust part,and obtains the fatigue life of the position based on the local stress strain method,which provides an analysis method for the cylinder head design.