In view of the cracking of the exhaust manifold of a six-cylinder heavy duty diesel engine

the failure mechanism was studied by simulation analysis. Results show that under high load operating conditions

the pipe body is plastically deformed due to compressive stress

while under low load operatingconditions

the plastic deformation area cannot be restored to its original state in time and is instead subjected to tensile stress. Under the repeated action of such compressive and tensile stresses

fatigue cracks will occur in the pipe body. To this end

the Sehitoglu thermomechanical fatigue(TMF) theory is used to predict the life of the exhaust manifold.