电动车减速器齿轮疲劳断裂分析与改进

为研究电动车减速器台架疲劳试验中出现的齿轮齿根断裂现象,利用Palmgren-Miner线性损伤累计理论进行齿根疲劳损伤计算,确定齿根断裂的主要原因是齿根疲劳寿命不足。采用增大齿轮螺旋角、齿根倒角以及齿面修形等方法进行齿轮结构优化。结果表明：优化后的齿轮未发生断裂,满足疲劳寿命要求。     

圆柱斜齿轮动态强度与疲劳损伤仿真

为更好满足使用要求,对圆柱斜齿轮进行精确设计与加工,利用非线性有限元仿真软件MSC Marc对圆柱斜齿轮动态啮合过程齿面接触应力和齿根弯曲应力变化规律进行研究,利用疲劳分析软件MSC Fatigue对轮齿齿根弯曲疲劳寿命进行仿真计算,并根据设计寿命计算出安全寿命系数,为齿轮设计提供理论依据.     

齿轮动态啮合有限元分析

齿轮传动是机械传动中最重要、应用最广泛的一种传动。通常齿轮安装于轴上并通过键连接,转矩从驱动轴经键、齿轮体和轮齿最终传递到从动轮的齿轮。在这一过程中,齿轮承受应力作用。另外,为了润滑齿轮传动与减少齿轮传动时产生的热量,通常在齿轮轮体上开设润滑油孔（图1）。油孔的开设位置将影响齿轮的应力及其分布,进而影响齿轮疲劳寿命。     

某汽轮机甩负荷运行工况强度分析

为分析汽轮机甩负荷运行时的应力状况,选取某机组高压第一级动叶片和转子轮槽为分析对象,采用有限元法分析在高压蒸汽4个阶段降温冲击下的应力.结果表明,动叶片以及转子材料内应力对温度的变化反应敏感;温度不变时,应力集中处的内应力需要很长时间才能消退并趋于均匀化;在该温度曲线的操纵下,逐步的降温造成应力累加,导致应力峰值呈波浪...     

汽轮机长叶片弹塑性分析及寿命评估方法

在当前汽轮机的某些极限设计工况下,基于无限寿命的线弹性考核规范已经无法满足当前的工程设计要求,需要发展弹塑性强度计算方法以及有工程意义的强度评估准则,并在此基础上引入低周疲劳寿命考核方法对零部件寿命进行分析预测.对某汽轮机末级长叶片进行弹塑性有限元分析,提出将基于局部应力 应变法的低周疲劳分析理论与商用疲劳分析软件相结合的方法对叶片进行强度设计的方法和流程.结果表明：所提出的弹塑性分析以及疲劳寿命评估方法能很好地反映长叶片的实际强度,有助于进一步制定一套完善的适合工程应用的长叶片强度评估标准,从而提高叶片的设计水平.     

Modified involute helical gears: computerized design,simulation of meshing and stress analysis

The contents of the paper cover: (i) computerized design, (ii) methods for generation, (iii) simulation of meshing, and (iv) enhanced stress analysis of modified involute helical gears. The approaches proposed for modification of conventional involute helical gears are based on conjugation of double-crowned pinion with a conventional helical involute gear. Double-crowning of the pinion means deviation of cross-profile from an involute one and deviation in longitudinal direction from a helicoid surface. The pinion-gear tooth surfaces are in point contact, the bearing contact is localized and oriented longitudinally, edge contact is avoided, the influence of errors of alignment on the shift of bearing contact and vibration and noise are reduced substantially. The developed theory is illustrated with numerical examples that confirm the advantages of the gear drives of the modified geometry in comparison with conventional helical involute gears.     

Computerized design of modified helical gears finished by plunge shaving

Among the several types of gear shaving operations, plunge shaving is used for finishing gears in mass-production due to the low cost and short machining time. Plunge shaving may be used to apply surface modifications with the purpose of reducing noise and vibration by the predesign of favorable functions of transmission errors, and modify gear tooth surfaces to avoid edge contacts and increase gear endurance, safety, and service life. A new geometry for helical gear tooth surfaces that combine the advantages of gear drives with lineal and localized contacts is proposed and obtained by plunge shaving. The shaver tooth surfaces are conjugated to those of an ideal helical gear with surface modifications. In this way, the to-be-shaved gear and the shaving cutter will be in line contact, and only a radial feed motion of the shaver is needed to generate the required pressure for the shaver to cut the excess of material on the gear tooth surfaces. A numerical example of design illustrates the advantages of the proposed geometry.     

Analysis and correction of the machining errors of small plastic helical gears by ball-end milling

Many small-size precise plastic helical involutes gears are used in electrical appliances to transmit rotary movements continuously and smoothly.Ball-end milling is an effective method for trial manufacture or small batch production of this type of gear,but the precision of the gear is usually low.In this research,the main sources of the errors of the gear,machining errors of the tooth profile and trace of the gear obtained were analyzed.The correction amounts for these errors are then determined by using a CNC gear tester.They are used to generate a new 3D-CAD model for gear machining with better precision.     

Generalized concept of meshing and contact of involute crossed helical gears and its application

A general approach for generation and design of standard and non-standard involute crossed helical gears is proposed. The conjugation of gear tooth surfaces is based on application of two generating rack-cutters with a common normal section. The investigation of the geometry is based on a new approach for presentation of the line of action A (the line of points of contact of tooth surfaces). Line A is represented in a plane Π that is tangent to the pinion base cylinder and position of A is determined analytically. Edge contact of tooth surfaces is avoided by limitation of shift of line of action caused by errors Δγ and ΔE of the crossing angle and the shortest distance, respectively. Simulation of meshing and contact is computerized by developed computer program. Enhanced stress analysis approach is proposed. The developed theory is illustrated with numerical examples.     

含间隙同步锥齿轮锁定后的非光滑动力学分析

针对周边环形桁架天线展开锁死后,分析齿轮副间隙由于空间冷—热环境交替对天线所产生的影响.因为整个桁架结构复杂,间隙种类众多,所以文中只研究一对同步直齿锥齿轮锁定后间隙的非光滑动力学行为.文中首先介绍了三种碰撞力模型,即恢复系数模型、Hertz接触力模型和非线性弹簧—阻尼模型,然后对物理模型进行简化得到动力学模型,最后建立了动力学方程.由于动力学方程中存在分段,直接求得解析解难度过大,文中直接采用数值仿真的方法进行分析,从仿真结果中得知含间隙的同步锥齿轮在外力的作用下整个系统会出现单倍周期、倍周期分岔和混沌等复杂的非线性响应.     

Crack propagation assessment for spur gears using model-based analysis and simulation

Model-based gear dynamic analysis and simulation has been a promising way for developing effective gearbox vibration monitoring approaches. In this paper, based on the dynamic model of a one-stage gearbox with spur gears and one tooth crack, statistical indicators and the discrete wavelet transform (DWT) technique are investigated to identify effective and sensitive health indicators for reflecting the crack propagation level. The results suggest that the root mean square (RMS) indicator is a better statistical indicator than the Kurtosis indicator to reflect the crack propagation in the early stage; the RMS indicator based on the residual signal segments that are strongly affected by the crack is more sensitive; the proposed DWT approach can improve the sensitivity of the RMS indicator, and the RMS indicator becomes more sensitive with the increase of the DWT level up to a best DWT level, beyond which either the monotonicity is lost or the sensitivity decreases; the proposed approach is effective with the presence of noise; with the increase of the noise level, the DWT level at which the best performance is achieved, and thus the sensitivity, decreases. Gearbox systems with different sizes and different input shaft frequencies are also investigated, and it is found that the observations presented above hold for different gearbox system settings.     

某型圆柱螺旋弹簧设计与疲劳寿命分析

圆柱螺旋弹簧是某型机械传动系统的关键部件,其设计的可靠性直接影响该结构的稳定和安全.首先对某型圆柱螺旋弹簧进行工况分析,进而基于机械设计原则对其刚度、强度进行理论校核,最后基于有限元应力仿真,在MSC Fatigue中计算出该弹簧最危险节点的寿命.所得结论表明设计弹簧的疲劳寿命满足疲劳可靠性的要求.     

锥齿轮齿根应力有限元模型和分析

从齿轮加工原理出发,利用渐开线和齿根过渡曲线方程生成轮齿的精确齿形,建立2种等效直齿锥齿轮三维轮齿几何模型,研究渐开线直齿锥齿轮的精确建模方法.分别使用h-单元和p-单元分析计算直齿锥齿轮齿根应力,建立直齿锥齿轮三维轮齿齿根应力有限元计算模型和计算基准.计算结果与ISO国标公式比较,证明模型的正确性、精确性和可靠性.     

螺旋弹簧冷绕成形与回弹的数值分析

螺旋弹簧冷绕成形过程中的各种参数对弹簧回弹量影响很大。通过对螺旋弹簧冷绕成形及回弹过程的分析,基于大型非线性有限元分析软件ABAQUS 6.8,建立了螺旋弹簧冷绕成形及回弹的有限元计算模型。计算了成形过程中不同张力大小、不同芯轴直径与簧丝直径的比值及不同绕簧节距对弹簧回弹量的影响和回弹后弹簧中径各节点位移的变化。仿真分析表明张力大小对回弹影响很大,张力越大,成形过程中簧丝的内应力越稳定且内应力也越大,簧丝截面内塑性区域所占比重越大,回弹量越小;当簧丝直径一定时,芯轴直径越大,即芯轴直径与簧丝直径的比值越大,回弹量越大;当芯轴直径一定时,簧丝直径越小,横截面的内应力越大,回弹量越小;绕簧节距越大,簧丝内应力越不稳定,平均内应力越小,回弹量越大也越不稳定;回弹后弹簧中径和节距显著增大,弹簧应力由卡盘连接处开始慢慢减小。     

The influence of ion dynamics on the breaking of plane electron oscillations

The influence of ion dynamics on the breaking of plane relativistic electron oscillations is studied by numerical modeling. An algorithm in Euler’s variables for finite-difference simulation is developed, and preliminary analytical study is performed. A new type of breaking of long-lived oscillations, different from the earlier-known one, is presented. Part of the computations were performed on the Chebyshev supercomputer (Lomonosov Moscow State University).