فهرس المقالات thermo-mechanical fatigue

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  1 - Thermo-mechanical fatigue simulation of exhaust manifolds
  Hojat Ashori
  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 أکثر

  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. تفاصيل المقالة
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  2 - Effect of residual stress in low cycle fatigue for coated exhaust manifold
  Hojjat ashouri
  The exhaust manifolds are subjected to higher loads than before, due to the increasing power output, fuel consumption and exhaust gas emission. Thus, simulation and analysis of fatigue cracks is essential. The effect of residual stress on the thermal stress and low cycl أکثر

  The exhaust manifolds are subjected to higher loads than before, due to the increasing power output, fuel consumption and exhaust gas emission. Thus, simulation and analysis of fatigue cracks is essential. The effect of residual stress on the thermal stress and low cycle fatigue (LCF) life of exhaust manifolds using strain life methods was investigated. For this purpose, Solidworks software was used to model the exhaust manifolds. Then the thermo-mechanical analysis was carried out to determine the temperature and stress distribution in ANSYS software. Finally, the fatigue life prediction that considers residual stress effect was done. The simulated results proved that the thermal stresses and number of cycles to failure have the most critical values at the confluence region of the exhaust manifolds. The LCF results showed that the number of failure cycles for coated exhaust manifold is about 89% higher than the results obtained from the uncoated exhaust manifolds. Evaluating the residual stress, the TBC improves the number of failure cycles approximately 52% in comparison the uncoated exhaust manifold. The results of FEA proved a very good agreement between numerical simulation results and LCF analysis results, performed in references. تفاصيل المقالة
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  3 - Low cycle fatigue prediction for cylinder head considering notch stress-strain correction proposed by Neuber
  Hojjat Ashouri
  Due to the complex geometry and loading conditions, engines cylinder heads are the most challenging components among all parts internal combustion engines. They must withstand severe cyclic thermo-mechanical loading throughout their lifetime. Low cycle fatigue (LCF) pre أکثر

  Due to the complex geometry and loading conditions, engines cylinder heads are the most challenging components among all parts internal combustion engines. They must withstand severe cyclic thermo-mechanical loading throughout their lifetime. Low cycle fatigue (LCF) prediction for cylinder head considering notch stress-strain correction proposed by Neuber was investigated. For this purpose, first Solidworks software was used to model the cylinder head. Then Ansys Workbench software was used to determine temperature and stress distribution of the cylinder head. Finally, in order to study the fatigue life based on LCF approach, the results were fed into the nCode Design Life software. The thermo-mechanical analysis showed that the maximum temperature and stress happen in the valves bridge between the two exhaust valves. The results of the FEA correspond with experimental tests performed by researchers, and demonstrated the cylinder heads cracked in this region. The numerical results showed that the area where the maximum temperature and stress is occurred is where the least LCF is predicted. تفاصيل المقالة
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  4 - Analysis of Fatigue Cracks of Diesel Engines Cylinder Heads using a Two-Layer Viscoplasticity Model and Considering Viscousity Effects
  حجت عاشوری بابک بهشتی محمد رضا ابراهیم زاده
  Loading conditions and complex geometry have led the cylinder heads to become the most challenging parts of diesel engines. One of the most important durability problems in diesel engines is due to the cracks valves bridge area. The purpose of this study is a thermo-mec أکثر

  Loading conditions and complex geometry have led the cylinder heads to become the most challenging parts of diesel engines. One of the most important durability problems in diesel engines is due to the cracks valves bridge area. The purpose of this study is a thermo-mechanical analysis of cylinder heads of diesel engines using a two-layer viscoplasticity model. The results of the thermo-mechanical analysis indicate that the maximum temperature and stress exist in the valves bridge. The results of the finite element analysis correspond with the experimental tests, carried out in references, and illustrate the cylinder heads cracked in this region. The results of the thermo-mechanical analysis show that when the engine is running the stress in the region is compressive caused by the thermal loading and combustion pressure. When the engine shuts off the compressive stress turns into the tensile stress because of assembly loads. The valves bridge is 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. Viscous strain is more than the plastic strain which is not negligible تفاصيل المقالة