Assessment Method for Early Fatigue Failure of Crankshaft Based on Dispersion of Impact Energy
Considering scattering behaviors of strength and fatigue life characteristics of actual materials, a method for evaluating the early fatigue failure of crankshafts has been proposed. The micro-mechanism of the scatter of strength and life characteristics is the nonuniform distribution of microstruct...
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| Main Author: | |
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| Format: | Article |
| Language: | zho |
| Published: |
Editorial Office of Journal of Shanghai Jiao Tong University
2025-01-01
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| Series: | Shanghai Jiaotong Daxue xuebao |
| Subjects: | |
| Online Access: | https://xuebao.sjtu.edu.cn/article/2025/1006-2467/1006-2467-59-1-111.shtml |
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| Summary: | Considering scattering behaviors of strength and fatigue life characteristics of actual materials, a method for evaluating the early fatigue failure of crankshafts has been proposed. The micro-mechanism of the scatter of strength and life characteristics is the nonuniform distribution of microstructures (including micro-defects) inside the material, which can be uniformly characterized by the probability distribution of initial damage. For the same grade of alloy, the median values of strength and fatigue life can be basically the same, but the dispersion can be significantly different, which must be determined by sufficient sampling tests. For a diesel engine crankshaft forging made of the 34CrNi3MoA alloy, the dispersion of fatigue limit was estimated based on the scatter of impact sampling test data, while the mean value of probability distribution of fatigue limit was determined by structural fatigue tests. The safety factor recommended in the conventional design manual only implicitly assumes material dispersion. Considering the actual dispersion of the tested material, the quantitative relationship between safety factor and reliability has been established. Early fatigue failure of the crankshaft can easily occur when the actual dispersion of material fails to meet the specified reliability requirement. |
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| ISSN: | 1006-2467 |