| 摘要: |
| 某型无人机在试飞试验中螺旋桨的4根30CrMnSiA联接螺栓发生早期断裂失效故障。综合材料失效分析、表面完整性分析、断裂强度分析、结构动力学分析、载荷-时间历史分析、螺纹联接设计分析和螺纹加工工艺分析的多学科分析方法，确定了造成接螺栓早期断裂失效的多重因素。结果表明，除4号螺栓外，其余3根螺栓均属于疲劳断裂失效。造成疲劳断裂的主要原因如下：该无人机海运中联接螺栓未进行腐蚀防护，导致螺栓遭受了海洋大气环境腐蚀，加上较大的螺栓预紧力，螺纹根部产生了腐蚀剥落和应力腐蚀损伤，大幅降低了螺栓的抗疲劳性能；试飞时发动机工作转速与螺旋桨的1节径3阶模态固有频率吻合，致使螺旋桨产生了共振，从而使联接螺栓遭受了共振疲劳载荷作用。在此基础上提出抗疲劳建议：在储运和使用中对螺栓进行腐蚀防护；避免发动机长时间工作在共振转速附近；应采用滚压加工螺纹以提高螺栓的疲劳强度；调整螺旋桨盘螺栓孔的位置，降低螺栓工作载荷；将螺钉联接设计改为螺栓联接设计，以避免铝合金内螺纹变形；适当减小螺栓预紧扭矩，以降低疲劳载荷的平均应力水平。 |
| 关键词: 无人机 螺栓 疲劳断裂 应力腐蚀 共振 |
| DOI：10.11933/j.issn.1007-9289.20180330002 |
| 分类号:V267.45 |
| 基金项目:北京市自然科学基金（309327） |
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| Multi-disciplinary Analysis and Improvement on Fracture Failure of Propeller's Connection Bolts of a Pilotless Aircraft |
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ZHU You-li, HOU Shuai, DU Xiao-kun, NI Yong-heng, LI Zhan-ming
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Department of Equipment Support and Remanufacturing, Army Academy of Armored Forces, Beijing 100072
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| Abstract: |
| Four connection bolts made of 30CrMnSiA high strength steel of the propeller on a pilotless aircraft broke prematurely during a test fly. Multi-disciplinary analysis combining material failure analysis, surface integrity analysis, fracture strength analysis, structural dynamic analysis, loading history analysis, bolts connection design analysis and thread processing analysis methods were used to find the causes of the premature failure comprehensively. Results show that bolts No.1 to No.3 are broken due to fatigue fracture, while bolt No.4 sufferes from over load failure. Causes of the failure are as follows. The pilotless aircraft was ocean shipped without corrosion protection of the connection bolts, resulted in corrosion of the bolts. Exfoliation and stress corrosion damage were formed on the surface of the thread due to higher moment of pretension in corrosion environment, which notably reduced the fatigue performance of the bolts. During the test fly, engine rotor ran at a speed nearby the first nodal diameter and the third resonance frequency of the propeller and led to resonance vibration of the propeller, which in turn resulted in fatigue loading of the bolts. To avoid fatigue failure, the following measures are proposed. In storage and conveyance, the bolts should be protected from corrosion attack. The engine running at frequencies around resonance frequency of the propeller should be avoided. Using cold rolled bolts can be used to enhance fatigue performance of the bolts. The position of connection bolts can be used adjusted to reduce service load. Instead of screw connection, bolt connection can be used to avoid deformation of the aluminum internal thread. Decreasing moment of pretension of the bolts is to reduce fatigue mean stress level. |
| Key words: pilotless aircraft bolts fatigue fracture stress corrosion resonance vibration |
