| KX84系列牙轮钻头牙爪大跑道的失效分析 |
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| 引用本文： | 李芳芳,刘冰,史志武,张宇.KX84系列牙轮钻头牙爪大跑道的失效分析[J].失效分析与预防,2023,18(1):55-61. |
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| 作者姓名： | 李芳芳 刘冰 史志武 张宇 |
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| 作者单位： | 1.辽宁科技学院，辽宁 本溪 117004 |
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| 摘 要： | KX84系列牙轮钻头工作一段时间后，因牙爪大跑道失效而报废。通过赫兹应力分析、显微硬度测试、剖面金相观察和断口分析，对牙轮钻头牙爪大跑道的失效形式进行分析，并对裂纹萌生的深度进行预测。结果表明:牙爪大跑道失效形式为接触疲劳。当轴压低于6.895 MPa时，45°切应力τzy45°与最大水平切应力τ0max低于疲劳极限σ-1，疲劳裂纹不会萌生；当轴压超过6.895 MPa，疲劳裂纹开始萌生；当轴压达到13.79 MPa时，可以利用接触面半宽b对裂纹深度进行预测。KX84-250和KX84-310牙轮钻头的牙爪大跑道裂纹预测深度为0.27、0.34 mm，实际深度为0.28、0.38 mm。为了提高牙轮钻头的钻孔深度，牙轮钻头在安装时注意避免极端情况的出现，同时控制轴压，避免疲劳裂纹的萌生。
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| 关 键 词： | 赫兹应力 牙轮钻头 45°切应力(τzy45°) 最大水平切应力(τ0max) 接触疲劳 |
| 收稿时间： | 2022-10-26 |
Failure Analysis of Raceway of Leg for KX84 Series Roller Cone Bit |
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| LI Fang-fang,LIU Bing,SHI Zhi-wu,ZHANG Yu.Failure Analysis of Raceway of Leg for KX84 Series Roller Cone Bit[J].Failure Analysis and Prevention,2023,18(1):55-61. |
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| Authors: | LI Fang-fang LIU Bing SHI Zhi-wu ZHANG Yu |
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| Abstract: | After working for a period of time, KX84 series cone bit was scrapped due to the failure of raceway. We analyzed the failure mode of the raceway of leg of KX84 series roller cone bit with Hertzman stress analysis, microhardness test, cross-section metallographic observation, and fracture morphology observation. Meanwhile, the depth of crack initiation was also predicted. The result show that contact fatigue is the main form of raceway failure. When the pressure is weaker than 6.895 MPa, both 45° shear stress τzy45° and the maximum horizontal shear stress τ0max are lower than the fatigue limit σ-1, no fatigue crack is formed. However, fatigue cracks emerge when the pressure exceeds 6.895 MPa. In addition, the depth of cracks can be predicted with half-width of contact face b at 13.79 MPa. For instance, the predicted depths of cracks of KX84-250 and KX84-310 are 0.27, 0.34 mm, respectively, while the actual depths are 0.28, 0.38 mm, accordingly. In order to improve the drilling depth of the cone bit, the occurrence of extreme situations should be avoided during the installation. At the same time, the axial pressure should be controlled to avoid the initiation of fatigue cracks. |
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