牙轮钻头圆柱滚子轴承接触力学性质及弹流润滑理论研究

发布时间：2018-04-11 03:34

本文选题：接触力学 + 凸度设计　；参考：《北京化工大学》2011年硕士论文

【摘要】：要加快我国石油天然气的勘探开发速度,提高钻井工程技术的国际竞争能力,提高钻头尤其是牙轮钻头的工作性能和工作寿命十分重要。现阶段应综合应用接触力学、润滑理论等学科的知识,对滚子凸度设计、空心圆柱滚子及其润滑状态等关键问题进行深入研究,进而研制开发长寿命、高转速的滚动轴承牙轮钻头。本文首先针对Hertz点接触问题的求解方法进行了研究,得到了关于点接触问题精确高效的完全数值算法；从计算速度、计算精度和计算方便性等方面对几种典型算法进行了对比研究,得出了各算法在不同条件下的适用情况；并将完全数值算法应用于牙轮钻头滚动轴承中的全圆弧凸型滚子,分析了其接触参数在不同条件下的变化。然后,采用MSC.Marc有限元软件对迄今常见代表性凸型滚子的应力分布规律和特点进行了分析,提出采用多段变曲率圆弧组合替代Lundberg理论对数凸型的工程化模拟技术,给出了较为合理的圆弧组合数目；分析了空心圆柱滚子及其进行凹端处理后的应力分布规律。结果表明,合理的空心度可减小接触应力的边缘效应,但等效应力在滚子两端的应力集中始终存在；在相同空心度下,等效应力和接触应力随载荷的变化规律不同；且不同载荷作用下,最佳空心度的理论值不同；空心度较大时,滚子内壁等效应力会超过外壁成为危险区域,同时应考虑弯曲应力的影响,避免滚子内壁发生弯曲疲劳断裂；较之普通空心滚子,凹端空心圆柱滚子有效克服了滚子端部的应力集中现象。最后,采用多重网格法对牙轮钻头实心圆柱滚子和空心圆柱滚子的弹流润滑情况进行了分析,通过对无限长滚子线接触弹流润滑问题的研究,揭示了实心圆柱滚子油膜压力和膜厚随载荷参数、速度参数和材料参数的变化规律；空心圆柱滚子空心度的变化会引起速度参数和载荷参数的变化,但并没有引起接触区域中部油膜厚度以及最小膜厚的明显变化；空心度的增加可以降低油膜压力,但合理空心度的选取应考虑其对滚子内壁应力分布的影响。有限长线接触弹流润滑中最大油膜压力和最小膜厚都位于滚子端部,故滚子端部为易破坏部位；滚子中部润滑状况与无限长滚子几乎一致,可按无限长处理；空心度对滚子端部润滑情况的影响与中部相同,由于端部油膜压力大于中部,故二次峰值和最小油膜厚度较之中部都更靠近出口区。本文的研究成果为国内自主实现滚动轴承牙轮钻头的长寿命和高转速化,乃至为工程实际中广泛存在的重载低速滚子轴承系统工作性能的提高奠定了坚实基础,同时也值得标准或通用滚子轴承、铁路机车、冶金轧机等行业的研究人员借鉴。
[Abstract]:It is very important to speed up the exploration and development of petroleum and natural gas in China, to improve the international competitiveness of drilling engineering technology, and to improve the working performance and service life of bit, especially the cone bit.At this stage, the key problems such as roller crown design, hollow cylindrical roller and its lubrication state should be thoroughly studied by applying the knowledge of contact mechanics, lubrication theory and so on, and the long life of the roller should be researched and developed.High speed roller bit for rolling bearing.In this paper, the method of solving the point contact problem of Hertz is studied, and the exact and efficient complete numerical algorithm for the point contact problem is obtained.Several typical algorithms are compared and studied in terms of calculation accuracy and calculation convenience, and the application of each algorithm under different conditions is obtained, and the complete numerical algorithm is applied to the full arc convex roller in roller bearing of cone bit.The change of contact parameters under different conditions was analyzed.Then, the stress distribution law and characteristics of typical convex roller are analyzed by using MSC.Marc finite element software, and the engineering simulation technology is put forward to replace the logarithmic convex type of Lundberg theory with multi-segment variable curvature circular arc combination.A reasonable number of arc combinations is given and the stress distribution of hollow cylindrical rollers and their concave ends are analyzed.The results show that reasonable hollow degree can reduce the edge effect of contact stress, but the stress concentration of equivalent stress always exists at both ends of roller, and under the same hollow degree, the variation law of equivalent stress and contact stress with load is different.Under different loads, the theoretical values of the optimum hollow degree are different. When the hollow degree is large, the equivalent stress of the inner wall of the roller will exceed the outer wall and become a dangerous area. At the same time, the influence of bending stress should be considered to avoid the bending fatigue fracture of the inner wall of the roller.Compared with common hollow roller, hollow cylindrical roller at concave end overcomes the stress concentration phenomenon at the end of roller effectively.Finally, the elastohydrodynamic lubrication of solid cylindrical roller and hollow cylindrical roller of cone bit is analyzed by using multi-mesh method.The variation of oil film pressure and film thickness with load parameter, velocity parameter and material parameter are revealed, the change of hollow degree of hollow cylinder roller will cause the change of velocity parameter and load parameter.However, the oil film thickness and the minimum film thickness in the middle of the contact area are not changed obviously, and the increase of the hollow degree can reduce the oil film pressure, but the reasonable selection of the hollow degree should consider its influence on the stress distribution of the inner wall of the roller.The maximum oil film pressure and the minimum film thickness are located at the end of the roller, so the tip of the roller is easily destroyed, and the lubrication condition of the middle part of the roller is almost the same as that of the infinite length roller, which can be treated as infinite length.The effect of the hollow degree on the lubrication of the end part of the roller is the same as that of the middle part. Because the oil film pressure at the end part is larger than that in the middle part, the secondary peak value and the minimum oil film thickness are both closer to the outlet region than the middle part.The research results of this paper have laid a solid foundation for the independent realization of long life and high speed of roller bit in China, and even for the improvement of the working performance of heavy load low speed roller bearing system, which is widely existed in engineering practice.At the same time, it is also worth standard or universal roller bearings, railway locomotives, metallurgical mills and other industries for reference.
【学位授予单位】：北京化工大学
【学位级别】：硕士
【学位授予年份】：2011
【分类号】：TH133.33

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