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| Thermo-Mechanical Analysis of Piston Thermal Stress and Fatigue Life for Diesel Engine |
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| Key Words:diesel engine piston thermal load fatigue life finite element analysis |
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| Abstract:A finite element model of a piston including its skirt profile, optimized combustion chamber and oil gallery was established to investigate its temperature field, thermal stress and fatigue life at the rated condition by means of the finite element software PERMAS. Besides that, the sizes of the piston ring grooves and skirt profile were measured after a thermal shock test for 800 h. The analysis results show that high temperature areas are mainly found at top of the piston, with the maximum temperature reaching about 301 ℃, and the mean temperature reaching 194 ℃ is found in the top ring insert, much lower than 230 ℃ for oil coking. So they are all acceptable even when the fuel injection quantity is increased by 20%. The piston inclines to the thrusting side under the coupled thermos-mechanical force, and the thrusting side bears a stress of 44 N/mm2. The peak stress of about 98 N/mm2in piston pin bore is found at the rear end of the bore and they all are acceptable. The lowest piston fatigue life occurs at the bottom and bowl rim of the combustion chamber, and their theoretical service lives are 6.9 and 7.7 respectively, and the sizes of piston ring grooves and skirt profile have a little change after the 800 h test, satisfying the requirements of use. |
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