Study on Thermal Failure of Marine Diesel Engine Cylinder Head Scale Specimen
To investigate the progressive failure in marine diesel engine cylinder heads under low-cycle thermal cycling loads,a simulation experiment using a"four-hole plate"scale specimen was conducted.A simulation method based on the temperature dependent Chaboche combined hardening material model and an improved Ostergren plastic energy damage model were utilized to analyze the thermal failure behavior and the mechanism of plastic deformation and thermal fatigue cracking.The research findings demonstrate high accuracy in the simulation predictions with a maximum deviation of 10.5％for predicting out-of-round deformation of circular holes.Additionally,the crack initiation position was accurately predicted,and the predicted life was close to the actual failure cycle number.Cyclic temperature gradients influence the scale specimen,resulting in mismatched thermal bending deformation across the entire structure and causing local asymmetric tensile and compressive stresses that induce plastic deformation.With increasing cycles,stress relaxation occurs,and plastic deformation decreases non-linearly from fast to slow.The cracking and damage of the high-stress region of the round hole bridge are attributed to the increase in tensile plastic strain energy and stress triaxiality during the cooling stage.
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维普
