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Outline
To address the premature cracking of a certain type of transmission sleeve, a comprehensive failure analysis was performed using methods including chemical composition analysis, hardness testing, case-hardening depth measurement, metallographic examination and microscopic fractography. The results indicate that the failure was primarily caused by two synergistic factors. Firstly, excessive blocky ferrite in the core microstructure led to insufficient core hardness, resulting in poor hardness compatibility with the connected main shaft and sun gear. Secondly, the actual fillet radius at the root of the internal spline was below the design lower limit, which aggravated the local stress concentration effect. Under cyclic loading, the combined action of these two effects initiated and propagated cracks at the fillet of the internal spline tooth root, leading to the final failure. Based on these findings, corresponding improvement measures are proposed from the aspects of optimizing the material heat treatment process and controlling critical structural dimensions.
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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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