Thermo-mechanical fatigue simulation of exhaust manifolds

Loading conditions and complex geometry have led the exhaust manifolds heads to become the most challenging parts of diesel engines. Thermal fatigue failure of the engine components easily happens due to excessive temperature gradient and thermal stress. Modern exhaust systems must withstand severe cyclic mechanical and thermal loads throughout the whole life cycle. This study focuses on the Thermo-mechanical Fatigue (TMF) analysis for exhaust manifolds. The three-dimensional model of the exhaust manifolds was simulated in abaqus software and a chaboche model was utilized to investigate the elastic and plastic behavior of the exhaust manifolds. The numerical results showed that the temperature and thermal stresses have the most critical values at the confluence region of the exhaust manifolds. This area was under the cyclic tensile and compressive stress and then is under low cycle fatigue. After several cycles the fatigue cracks will appear in this region.The lifetime of this part can be determined through finite element analysis instead of experimental tests.