齿轮硬化层疲劳剥落强度研究与应用

发布时间：2018-06-07 23:54

本文选题：硬齿面齿轮 + 剪切应力　；参考：《机械科学研究总院》2016年博士论文

【摘要】：随着科学技术的进步,齿轮传动正逐渐向轻量化、低能耗方向发展。齿轮装置是机械传动系统的核心设备,随着工业技术的迅速发展,对其承载能力和经济性提出了更高的要求。由于硬齿面齿轮具有强度高、体积小、质量轻等一系列优点,目前硬齿面热处理工艺已得到普遍使用。但是,热处理工艺过程中的节能降耗却是对齿轮热处理生产的重要考验。节能是热处理技术发展中的一项意义重大但又艰巨的任务,节能工艺的推广应用,在齿轮行业具有重要的意义。采用硬齿面齿轮替代软齿面或中硬齿面齿轮,是齿轮轻量化的重要手段。然而,齿面剥落作为硬齿面齿轮主要的失效形式严重制约了齿轮承载能力的大幅度提高。齿轮剥落失效的产生不仅与齿面下的剪应力分布有关,而且与硬化层的深度、硬化层的硬度梯度等因素有关。表面硬化齿轮的有效硬化层深度与齿轮的强度、可靠性等性能密切相关,是保证齿轮承载能力充分发挥的关键。增加硬化层的深度有利于齿轮承载能力的提高,防止疲劳剥落失效。然而,过大的硬化层深度又会带来如工艺难度加大、工艺周期增长、畸变增加等诸多问题,造成齿轮生产成本和能源消耗的增加。合理硬化层深度设计的要点是既要保证过渡区有足够的强度防止深层剥落,又不过分加大安全余度。设计最佳的齿轮硬化层深度,无论是对提高齿轮齿面承载能力和产品质量,还是节能降耗都是极其重要的。因此,进一步开展能够防止齿轮疲劳剥落并节能的最佳硬化层深度研究已成为齿轮设计中的一项十分重要的工作。但目前为止,还没有一种行之有效的硬化层深度设计方法可用于齿轮的抗剥落计算。本文从剥落产生的力学角度出发,对齿轮疲劳剥落强度进行了研究及试验验证。论文主要研究内容有：(1)利用弹性力学理论,在不考虑摩擦因数和考虑摩擦因数的情况下,分别分析了齿面下两种剪切应力的分布特点,以及不同摩擦因数条件下齿轮剪切应力的变化规律。为了更方便、直观地了解齿面下剪切应力的分布,采用克里格插值方法得到了正交剪切应力和最大剪切应力的空间分布图。利用有限元方法对齿轮接触的剪切应力进行了计算,并与理论方法计算结果进行了对比分析。(2)讨论了齿轮硬化层深度的力学意义,分析了齿轮曲率半径、心部硬度、残余应力及齿面加工质量等与齿轮硬化层剥落的关系。根据最大剪切应力和判据,提出了一种抗齿面剥落的硬化层深度设计方法,并根据剪切应力与剪切强度的关系,得到了齿轮最低要求的硬度分布曲线。在此基础上提出了定量确定齿轮最小有效硬化层深度的计算方法。(3)根据齿轮有效硬化层深设计方法,推导了计算齿轮齿面下最大剪切应力和齿轮有效硬化层深的公式,为定量确定齿轮有效硬化层深度提供了一种简便可行的方法。基于齿轮有效硬化层深度的计算公式,得到了齿轮有效硬化层分布模型,实现了对齿轮有效硬化层深的定量分析。通过对齿轮硬化层深的影响因素进行分析研究,找出了齿轮参数中对硬化层深度影响最大的因素。(4)考虑到不同硬化层深度对齿轮接触疲劳强度的影响,把安全系数和可靠性计算与硬化层深度联系起来,建立了考虑硬化层深度影响的齿轮安全系数和可靠度计算模型,得到了不同硬化层深度与安全系数和可靠度的对应关系,使齿轮硬化层深度的选取更加直观、更加科学。(5)利用齿轮抗剥落硬化层深度设计方法对试验齿轮疲劳剥落强度进行了计算,根据齿面下的应力与强度的分布规律对齿轮是否发生剥落失效及齿面下疲劳裂纹萌生的位置进行了预测,并通过齿轮接触疲劳试验进行了验证。分别从材料的化学成分、夹杂物的检测、金相组织分析、应力分析、硬化层深度分析、偏载、过载分析等方面对齿轮剥落失效产生的原因进行了分析。(6)结合热处理工艺试验,利用力学判据对风电齿轮箱中齿圈以及三峡升船机齿条硬化层的疲劳剥落强度进行了分析,通过对比分析齿轮所需硬度与实际热处理硬度沿深度方向的分布特点,对目前风电齿轮和升船机齿轮所采用的硬化层深度进行了评估和验证。
[Abstract]:With the progress of science and technology, the gear transmission is gradually developing to light weight and low energy consumption. The gear device is the core equipment of the mechanical transmission system. With the rapid development of industrial technology, the bearing capacity and economy of the gear are higher. The hard tooth gear has a series of advantages, such as high strength, small volume, and light quality. At present, the heat treatment process of hard tooth surface has been widely used. However, energy saving and consumption reduction in heat treatment process is an important test for the production of gear heat treatment. Energy saving is a significant but arduous task in the development of heat treatment technology. The popularization and application of energy saving technology is of great significance in the gear industry. Face gear instead of soft tooth or medium hard tooth gear is an important means of gear light weight. However, the main failure mode of the tooth surface exfoliation as the main failure form of the hard tooth gear restricts the large increase of the bearing capacity of the gear. The production of the spalling failure of the gear is not only related to the shear stress distribution under the tooth surface, but also with the depth of the hardened layer. The depth of the effective hardening layer of the surface hardening gear is closely related to the strength and reliability of the gear. It is the key to ensure the full play of the gear carrying capacity. The depth of the hardened layer is beneficial to the improvement of the gear bearing capacity and the fatigue failure. However, the depth of the oversize hardened layer will be the same. There are many problems such as increasing process difficulty, increasing process cycle, increasing distortion and so on, resulting in the increase of gear production cost and energy consumption. The main point of the design of reasonable hardened layer depth is not only to ensure that the transition zone has enough strength to prevent deep exfoliation, but also not to increase the safety redundancy too much. It is very important to improve the bearing capacity and product quality of gear teeth and the energy saving and reducing consumption. Therefore, it has become a very important work in gear design to further study the optimum depth of hardened layer which can prevent the gear fatigue and energy saving. But so far, there is no effective depth of hardened layer. The method can be used to calculate the anti peeling of gear. From the mechanical angle of exfoliation, the fatigue strength of gear is studied and tested. The main contents of this paper are as follows: (1) using the theory of elastic mechanics, two shear stresses under the tooth surface are analyzed without considering the friction factor and the friction factor. The distribution of the shear stress of the gear under the conditions of different friction factors and the distribution of the shear stress under the tooth surface can be easily understood. The spatial distribution of the orthogonal shear stress and the maximum shear stress is obtained by Kriging interpolation. The shear stress of the gear contact is carried out by the finite element method. The calculation is compared with the calculation results of the theoretical method. (2) the mechanical significance of the depth of the gear hardening layer is discussed. The relationship between the curvature radius of the gear, the hardness of the heart, the residual stress and the machining quality of the tooth surface is analyzed. The hardening layer of the tooth surface exfoliation is put forward according to the maximum shear stress and criterion. On the basis of the relationship between shear stress and shear strength, the minimum required hardness distribution curve of gear is obtained. On this basis, a calculation method for determining the minimum effective hardening layer depth of gear is put forward. (3) the maximum shear stress and tooth under the gear surface are calculated according to the design method of the effective hardening layer of gear. The formula to effectively harden the depth of the layer provides a simple and feasible method for quantitative determination of the depth of the effective hardening layer of a gear. Based on the calculation formula of the depth of the effective hardening layer of the gear, the distribution model of the effective hardening layer of the gear is obtained, and the quantitative analysis of the depth of the effective hardening layer of the gear is realized. In line analysis, the factors that have the greatest influence on the depth of the hardened layer are found. (4) considering the influence of the depth of different hardened layer on the contact fatigue strength of gear, the calculation of safety factor and reliability and the depth of the hardened layer are linked, and the calculation model of gear safety factor and reliability considering the influence of hardened layer depth is established. The corresponding relationship between the depth of different hardening layers and the safety factor and reliability makes the selection of the depth of the gear hardened layer more intuitive and more scientific. (5) the calculation of the fatigue exfoliation strength of the test gear is carried out by the method of the depth design of the gear resistance to the exfoliation hardening layer, and the distribution of the stress and strength under the tooth surface will occur to the gear. The position of the exfoliation failure and the initiation of the fatigue crack under the tooth surface was predicted and verified by the gear contact fatigue test. The reasons for the spalling failure of the gear were analyzed from the aspects of the chemical composition of the material, the inclusion, the metallographic analysis, the stress analysis, the depth analysis of the hardened layer, the partial load, and the overload analysis. (6) combined with the heat treatment process test, the fatigue exfoliation strength of the gear box in the wind electric gear box and the rack hardening layer of the Three Gorges ship lifting machine is analyzed by the mechanical criterion. By comparing and analyzing the characteristics of the hardness of the gear and the distribution characteristic of the actual heat treatment hardness along the depth direction, the hardening of the current wind power gear and the ship lift gear is hardened. The depth of the layer is evaluated and verified.
【学位授予单位】：机械科学研究总院
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TH132.41

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