冲击载荷下小模数齿轮动态应力研究

以冲击电钻小模数变速齿轮为研究对象,采用有限元方法研究,冲击电钻在堵转时所引起的不同的冲击载荷和冲击时间,对小模数齿轮齿根动态应力的影响,并分析比较在相同的静载荷作用下的静应力状态,以及不同的齿根过渡曲线对齿轮强度的影响。     

双圆弧齿轮的弯曲应力分析

基于任意转角位置的双圆弧齿轮齿廓数学模型,运用Pro/E软件对双圆弧齿轮的弯曲应力进行了有限元分析,讨论了双圆弧齿轮各段弯曲应力的分布情况,并着重研究了轮齿的不同构成参数对齿轮弯曲应力的影响。其分析结果将为双圆弧齿轮设计、参数优化选择等提供参考依据。     

ZL50装载机螺旋锥齿轮断齿原因分析及优化

20CrMnTi合金渗碳钢作为ZL50装载机驱动桥螺旋锥齿轮的主要材料,通过考察螺旋锥齿轮的设计参数、产品技术要求、热处理工艺以及1000 h的满负荷试验,分析螺旋锥齿轮断齿原因和明确了齿轮断齿因素。结果表明:齿轮氧含量超标、心部硬度和有效硬化层深度偏低是螺旋锥齿轮断齿的主要因素;增大齿轮齿根圆角半径和轮齿压力角,可提高齿轮齿根弯曲强度;齿轮表面采用强力喷丸处理可增加齿轮表面的接触应力,从而进一步提高齿轮的使用寿命。     

齿根过渡圆角处应力的分析计算

分别用传统的材料力学的方法计算了在齿轮设计过程中，轮齿齿根处弯曲应力和在同样的条件下，用有限元方法分析了不同齿根过渡圆角齿形的齿根剖面上各点以及过渡圆角处各节点的应力值。此结果和方法为选择正确的应力集中系数，得到适合于各种具体场合的优化齿形以及进一步进行齿根过渡圆角的优化设计提供可靠的帮助。     

Detecting gear tooth fatigue cracks in advance of complete fracture

Some results from using vibration-based methods to detect gear tooth fatigue cracks are presented. An experimental test rig was used to fail a number of spur-gear specimens through bending fatigue. The gear tooth fatigue crack in each test was initiated through a small notch in the fillet area of a tooth on the gear. The primary purpose of these tests was to verify analytical predictions of fatigue crack propagation direction and rate as a function of gear rim thickness. The vibration signal from a total of three tests was monitored and recorded for gear fault detection research. The damage consisted of complete rim fracture on the two thin rim gears and single tooth fracture on the standard full rim test gear. Vibration-based fault detection methods were applied to the vibration signal both on-line and after the tests were completed. The objectives of this were to identify methods capable of detecting the fatigue crack, and determine how far in advance of total failure positive detection was given. Results showed that the fault detection methods failed to respond to the fatigue crack prior to complete rim fracture in the thin rim gear tests. In the standard full rim gear test all of the methods responded to the fatigue crack in advance of tooth fracture; however, only three of the methods responded to the fatigue crack in the early stages of crack propagation.     

Optimization of asymmetric spur gear drives to improve the bending load capacity

In a given size of symmetric involute gear designed through conventional approach, as the load carrying capacity is restricted at the higher pressure angle due to tipping formation, the use of the asymmetric toothed gear to improve the fillet capacity in bending is examined in this study. Non-standard asymmetric rack cutters with required pressure angles and module are developed to generate the required pinion and gear of a drive with asymmetric involute surfaces and trochoidal fillet profiles. The respective profiles thus generated are optimized for balanced fillet stresses that are equal and possibly the lowest also. For this study of optimization, several non-standard asymmetric rack cutters are designed to accommodate different combinations in the values of pressure angle, top land thickness ratio, profile shift, speed ratio and the asymmetric factors. However for any drive with a given center distance and a speed ratio, only two non-standard asymmetric rack cutters, one for the pinion and other for the gear are used to generate a required numbers of pinion and gear with different cutter shift values for the purpose of optimization. The influence of these parameters on the maximum fillet stress has been analyzed to suggest the optimum values of these parameters that improve the fillet capacity in bending. The optimization of the asymmetric spur gear drive is carried out using an iterative procedure on the calculated maximum fillet stresses through FEM for different rack cutter shifts and finally the optimum values of rack cutter shifts are suggested for the given center distance and the speed ratio of an asymmetric gear drive. Comparisons have also been made successfully with the results of the AGMA and the ISO codes for symmetric gears to justify the results of the finite element method pertaining to this study.     

Gear crack propagation investigations

Analytical and experimental studies were performed to investigate the effect of gear rim thickness on crack propagation life. The FRANC (FRacture Analysis Code) computer program was used to simulate crack propagation. The FRANC program used principles of linear elastic fracture mechanics, finite element modelling, and a unique re-meshing scheme to determine crack tip stress distributions, estimate stress intensity factors, and model crack propagation. Various fatigue crack growth models were used to estimate crack propagation life, based on the calculated stress intensity factors. Experimental tests were performed in a gear fatigue rig to validate predicted crack propagation results. Test gears were installed with special crack propagation gauges in the tooth fillet region to measure bending fatigue crack growth. Good correlation between predicted and measured crack growth was achieved when the fatigue crack closure concept was introduced into the analysis. As the gear rim thickness decreased, the compressive cyclic stress in the gear tooth fillet region increased. This retarded crack growth and increased the number of crack propagation cycles to failure.     

变位系数对齿轮齿根弯曲应力影响的研究

利用有限元法计算齿轮整个啮合过程的齿根弯曲应力,得到了不同变位系数与齿根弯曲应力的对应关系。分析结果表明,变位系数对于小齿轮齿根弯曲应力的影响较大,而对于大齿轮影响则较小。当变位系数在一定范围内变化时,齿根应力存在一个最小值。     

风电齿轮齿根弯曲应力及裂纹特性分析

以风电齿轮为例,利用有限元分析软件ABAQUS,建立了太阳轮简化力学模型,并进行了齿根弯曲应力的分析计算。分析结果与传统计算方法得出的结果基本一致,从而验证了简化模型的正确性。在此基础上,研究了齿轮齿根裂纹特性,分析了初始裂纹长度和外加载荷对应力强度因子(SIF)的影响。结果表明,随着初始裂纹长度的增加,应力强度因子也随之增加,并且应力强度因子与载荷等比例增加。在初始裂纹长度和载荷相同的情况下,应力强度因子KⅠ远大于KⅡ和KⅢ,即在弯曲应力作用下张开型裂纹为风电齿轮轮齿折断失效的主要原因。     

自升式平台齿轮齿条参数优化研究

基于有限元软件ANSYS对某自升式平台齿轮齿条的强度进行了分析。从齿条齿宽和齿轮齿条齿根圆角半径2个方面研究探讨了提高齿轮强度的方法,并对齿条齿宽和齿轮齿条的齿根圆角半径进行了优化。研究结果表明,适当增大齿条齿宽可以减小齿轮齿条的接触应力,增大齿轮齿条的齿根圆角半径可以提高齿轮齿条的齿根弯曲强度。     

常见齿轮过渡曲线对应齿轮弯曲应力的比较分析

为了全面而深刻地了解齿轮过渡曲线,延长齿轮的工作寿命,从齿轮加工刀具入手对常见齿轮过渡曲线对应的齿轮弯曲应力进行了有限元分析,并将常规齿轮弯曲应力计算中的齿轮单对齿啮合区上界点引入到有限元载荷计算中,以提高有限元计算精度,最后将有限元计算的齿轮最大弯曲应力点与齿轮危险截面弦齿厚进行了对比,以验证结果的正确性。研究表明,应用齿轮过渡曲线设计方法所生成的齿轮,不但使齿形描述方便,而且使弯曲应力的分析更加准确。     

提高齿轮弯曲强度的有效措施——加大齿根过渡圆角

本文用有限元计算及疲劳寿命试验法研究了不同齿根圆角对齿轮弯曲强度的影响。证明了加大齿根过渡圆角后的寿命相当于原有的三倍,所以是强化设计变速器的有力措施。本文还研究了加大齿根圆角的适用范围,提出了供设计时选择参数用的线图。并对加大刀刃圆角的剃前滚刀提出了设计方案。     

基于ANSYS的多齿差摆线齿轮有限元分析

应用ANSYS分析软件对多齿差摆线齿轮进行建模,推导出不同啮合相位角摆线齿轮根部应力计算公式,计算和分析了不同啮合相位角摆线齿轮根部应力,找出了齿轮齿根过渡圆弧半径与齿根处最大应力的关系和摆线齿轮根部过渡圆弧半径对齿轮根部应力的影响.     

Effect of hob wear on the surface layer properties of hobbed gear teeth

Results of investigations of the effect of hob wear on the surface layer properties of hobbed gear teeth are presented in this paper. The influence of hob wear on the microhardness, surface roughness, residual stresses and surface layer thickness were investigated. On the basis of the experimental results it was found that hob wear has a significant influence on the surface layer properties of the gear teeth. This influence is most noticeable on the dedendum and root fillet where the gear tooth space is shaped by the bluntest part of the hob cutting edges.     

行星齿轮内齿圈的多柔体动力学分析

以多柔体动力学理论为基础,研究了行星齿轮内齿圈在啮合过程中的动力学行为.构建了基于UG的虚拟样机模型.对系统进行了分析、计算及数值仿真,求解得到轮缘厚度系数与内齿圈应力/应变的定量关系及动应力沿内齿圈的分布规律,并对内齿圈进行了结构优化.结果表明,适当降低内齿圈的轮缘厚度系数,可有效降低振动、冲击与噪声,从而提高机构的疲劳寿命.     

基于层次分析法的行星齿轮传动多目标优化设计

传统的行星齿轮优化一般仅从最小体积出发,其最优解并未考虑对机构其他参数的影响.通过分析行星齿轮机构的多种性能指标,包括外形尺寸、体积、齿面接触强度和齿根弯曲强度,从机构总体最优出发建立模型,采用层次分析法进行多目标优化.结果表明该模型能有效的满足设计要求.     

准双曲面齿轮准静态接触分析和试验研究

建立了精确的准双曲面齿轮的轮齿面和过渡曲面数学模型;选择用平均接触椭圆长半轴、接触线方向角和传动误差曲线交点来评价齿面接触斑点和传动误差;以一个准双曲面齿轮副为计算实例,建立了适合准静态齿面接触分析的准双曲面齿轮传动系统有限元分析模型;通过准静态加载齿面接触特性分析,得到齿根弯曲应力、接触应力和传动误差的变化规律,分析载荷的影响情况,并比较了有限元结果与经验公式计算结果。开发了准双曲面齿轮试验台,进行齿面接触斑点和齿根弯曲应力检测,试验结果与仿真结果的一致性较好。     

减速齿轮传动中主动轮齿根弯曲疲劳的计算

传动齿轮强度理论认为,齿间滑动摩擦对齿轮齿根弯曲疲劳的影响可忽略不计。针对此说法,本文作者对带惰轮的起重减速齿轮传动中主动轮受国情况展开全面的分析研究,推导出包括齿间滑动摩擦力在内的,实际外载荷作用下的主动轮齿根弯曲疲劳应力计算公式。结果表明,齿间摩擦力对含惰轮的减速齿轮传动中主动轮齿根弯曲疲劳强度的影响不可忽视。     

时变位姿下行星齿轮传动系统动应力计算模型及其参数影响研究

考虑行星轮系内部非惯性和机体时变位姿外部非惯性的综合影响,推导了任意时变位姿下带有机匣的行星轮系构件运动方程,计入时变啮合刚度、啮合误差、侧隙和啮入冲击,建立了时变位姿下行星齿轮传动系统级动力学模型,并采用精细积分时程法（Precision integration method,PIM）求解得到了动态啮合力序列。根据齿间载荷分配关系进一步得到单齿啮合力序列。最后结合修正Heywood公式与Hertz公式构建了时变位姿下行星齿轮传动系统齿根弯曲动应力和接触动应力计算模型,并研究了机体平飞、滚转和筋斗位姿参数对接触动应力、弯曲动应力的影响规律。结果表明：不同时变位姿参数对弯曲、接触动应力影响显著,且对不同齿轮副影响不同,即加剧了齿轮副间承载不均;筋斗运动角速度对动应力影响比平飞加速度、滚转角速度以及筋斗回转半径对其影响复杂;机匣对动应力影响随加速度增大而增加。研究成果为时变位姿下行星齿轮传动动应力计算与高可靠性设计提供了理论依据。     

功能梯度材料应用在齿轮上的可行性分析

为解决齿轮热处理过程中存在畸变、齿根处弯曲应力增加、齿轮的寿命降低等问题,将功能材料技术应用到齿轮工作接触面处(简称功能梯度齿轮)。首先,开展了单质齿轮性能与单质齿轮热处理后性能的对比分析;然后,建立了单质圆柱渐开线齿轮模型与功能梯度材料圆柱渐开线齿轮模型,对其进行了弯曲应力有限元计算,并对其性能进行了对比分析。将未经热处理的单质齿轮作为桥梁,建立了单质齿轮热处理后的性能与功能梯度材料齿轮性能之间的关系。功能梯度材料不仅在轮齿表面硬度与齿根弯曲应力方面比热处理后的齿轮有更好的性能,而且能避免齿轮热处理过程中产生的畸变、渗碳层不均匀等缺陷。分析结果表明:将功能梯度材料应用到齿轮上是可行的。