Full
Outline
To investigate the mechanism of water-cooled valve seat sealing failure on the high-temperature exhaust side of the cylinder head of marine diesel engines due to progressive thermal deformation during long-term service, a finite element simulation method incorporating temperature history effects was proposed, based on a thermal viscoplastic constitutive model. The Chaboche nonlinear combined hardening equations and the Norton-Bailey creep equations were utilized to describe the nonlinear deformation induced by thermal fatigue and creep, respectively, and investigate their coupling mechanism. On the basis, introducing the load attenuation to analyze the impact of creep fatigue loading on structural stiffness degradation, thereby elucidating the evolution of valve seat sealing performance. Research findings reveal that the average error in deformation of cylinder head valve seat holes is approximately 16%, with a 19% improvement in calculation accuracy compared to existing methods. Moreover, the maximum attenuation of the sealing load for the valve seat hole reaches 75%, resulting in sealing failure and water leakage. Progressive deformation is primarily controlled by plastic strain during the heating and cooling stages of the thermal cycle, with influence from the creep-enhanced plastic deformation mechanism during the high-temperature holding stage. This underscores that progressive plastic deformation over long-term service periods is the fundamental cause of valve seat sealing failure.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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