齿轮轴断齿分析

齿轮轴运行近1a（年）后发生相邻两齿断裂。采用宏、微观检验以及硬度试验等方法对轴的断裂原因进行了分析。结果表明,齿轮轴断齿属于疲劳断裂。因齿轮箱供油不足,造成齿轮轴在高温状态下其强度和硬度急剧下降,导致齿轮轴断齿而失效。     

轧机分配减速箱齿轮轴和齿轮的轮齿堆塌原因分析

轧机分配减速箱齿轮轴和齿轮在使用过程中发生轮齿堆塌而失效,通过化学成分分析、力学性能测试和金相检验等手段分析了堆塌产生的原因。结果表明:由于出现润滑故障,形成干摩擦,致使齿轮轮齿表面局部温升产生热塑流变现象,最终导致齿肉损伤,形成堆塌失效。提出防止此类失效的根本对策是防止出现供油系统故障。     

尾减输入齿轮疲劳失效分析

对某发动机尾减系统尾减输入齿轮疲劳失效的原因进行了系统的分析。通过宏观检查、断口分析、金相检验以及受力分析等,确认了该齿轮的失效过程为：在大弯曲载荷作用下疲劳裂纹于锥齿中部齿根部位起始,裂纹初期沿径向呈15°左右的小角度疲劳扩展;齿部出现裂纹后,齿轮振动频率发生变化,进而导致齿轮出现节径型振动,使得裂纹逐渐沿径向疲劳扩展;出现径向裂纹后剩余齿由于截面减少以及起始部位已基本无渗碳层其强度较低等原因,导致剩余齿出现弯曲疲劳断裂。     

盘齿轮失效分析

采用化学成分分析、宏微观检验和力学性能测试手段,对失效盘齿轮进行了分析。结果表明,齿轮的渗碳层普遍存在深约25μm的黑色组织和较多的残余奥氏体,齿面、齿槽存在明显的加工刀痕,且齿根处有根切。以上几种缺陷的共同作用,使齿轮的疲劳强度大大降低,在外力较大的服役条件下,造成盘齿轮发生早期疲劳失效。     

齿轮轴失效分析

对失效齿轮轴进行了断口的宏观检查、金相检验、断口扫描电镜分析,结果表明残余拉应力是齿轮轴开裂的主要原因,聚集的非金属夹杂物和混晶对开裂有重要的促进作用.     

齿轮磨削裂纹成因分析

某齿轮磨削后表面产生了裂纹,其中齿顶裂纹为常规的磨削裂纹,而齿根裂纹为纵深较大的非常规磨削裂纹,采用化学成分分析、非金属夹杂物检验、金相检验等方法对裂纹产生的原因进行了分析,并从应力角度对磨削裂纹进行了分类。结果表明:磨削齿轮时进刀量过大使得摩擦应力陡增,在该摩擦应力与热应力的共同作用下材料表面被拉裂,导致该齿轮齿顶、齿根产生裂纹;从致使磨削裂纹产生的主导应力角度将磨削裂纹分为内应力主导的磨削裂纹和摩擦应力主导的磨削裂纹,该齿轮齿顶裂纹属于内应力主导的磨削裂纹,齿根裂纹属于摩擦应力主导的磨削裂纹。     

行星齿轮箱典型故障对内齿圈齿根应变的作用机理研究

行星齿轮箱由于具有优良的特性被广泛应用于多领域的机械传动系统中,但恶劣的工作条件导致其故障频发,因此开展行星齿轮箱故障诊断方法的研究工作十分必要。传统的基于振动信号的故障诊断方法在识别行星齿轮箱早期微弱故障方面具有局限性,为此提出基于内齿圈齿根应变信号的行星齿轮箱故障诊断方法,并主要开展行星齿轮箱典型故障对内齿圈齿根应变的作用机理研究工作。分析行星齿轮箱内齿圈齿根应变模型的构建方法,将内齿圈齿根应变模型分解为行星轮-内齿圈啮合力模型、内齿圈轮齿的齿形系数模型和齿间载荷分配系数模型;利用行星齿轮箱的纯扭转模型计算行星轮-内齿圈啮合力,利用材料力学理论推导内齿圈轮齿的齿形系数,并对行星轮-内齿圈啮合过程中的齿间载荷分配系数进行分析;研究行星齿轮箱典型故障对啮合刚度的影响,并根据内齿圈齿根应变模型计算得到典型故障下内齿圈齿根应变的变化规律。建模仿真计算分析结果表明,不同类型、不同部位、不同剧烈程度的故障会对行星齿轮箱内齿圈齿根应变信号造成不同影响,利用内齿圈齿根应变信号可有效识别行星齿轮箱的故障行为。     

变速箱双联齿和512齿轮失效分析

某型号变速箱在台架试验过程中,双联齿和与之啮合的512齿轮均发生失效事件。采用断口分析、金相检验、硬度测试以及化学成分分析等方法对失效件进行了检验。结果表明:由于双联齿和512齿轮的齿面存在严重的异常接触,加之双联齿的有效硬化层深度和心部硬度均低于技术要求,从而导致在台架试验过程中双联齿表面发生严重的接触疲劳剥落,与之啮合的512齿轮发生弯曲疲劳断齿。     

50Mn钢齿圈断齿原因分析

50Mn钢齿圈在使用很短时间后即发生断齿失效,为确定齿圈断裂的原因,对其进行了化学成分分析、宏观检验、硬度测试、断口分析、金相检验。结果表明:该50Mn钢齿圈的化学成分、外径面硬度等指标符合技术协议要求。齿部淬硬层可见多条裂纹,淬硬层深度和表面硬度不均匀,且不符合要求。齿圈齿部断齿是由淬硬层裂纹引起的疲劳开裂,失效原因与其齿部热处理工艺控制不当有关。     

齿根安全条件下多状态啮合齿轮传动系统安全-吸引盆侵蚀与分岔

轮齿折断是齿轮主要失效形式之一。以包含单双齿交替啮合、轮齿脱啮和齿背接触等的多状态啮合直齿圆柱齿轮传动系统为研究对象,计算齿根危险截面上的弯曲应力,以齿根许用弯曲应力为边界条件,建立防止轮齿折断的齿根安全条件。基于胞映射方法,用四阶Runge-Kutta法数值计算考察区域内随负载和齿侧间隙变化时系统的吸引盆及其演变过程。判断齿根安全条件下吸引盆中不同运动类型吸引域的安全特性得到系统的安全-吸引盆。借助吸引子、多初值分岔图和最大Lyapunov指数图(TLE)分析安全-吸引盆的侵蚀与分岔机理。研究发现:吸引盆中不同运动类型吸引域在齿根安全条件下的安全特性不同;吸引子的出现和消失直接导致安全-吸引盆的分岔;多初值分岔图中出现周期跳跃和分岔是引发安全-吸引盆分岔的主要原因。研究结果可为直齿轮传动系统安全运行提供参考。     

42CrMo钢齿轮轴断裂原因分析

采用化学成分分析、断口分析、金相检验和力学性能测试等方法,对42CrMo钢齿轮轴断裂的原因进行了分析。结果表明:由于齿轮轴制造过程中的热处理工艺或方法不当,导致齿轮轴的力学性能偏低,在使用过程中发生了疲劳断裂。     

斜齿轮动力学建模中啮合刚度处理与对比验证

为准确建立斜齿轮动力学模型,更好分析斜齿轮系统振动特性,提出基于轮齿承载接触分析、考虑齿轮轴扭转变形的轮齿啮合刚度计算方法。分析国内文献普遍采用的基于啮合刚度分解建立斜齿轮动力学模型,指出其与理论力学相悖之处,提出基于力、振动位移分解法建立综合考虑时变啮合刚度激励、啮入冲击激励的斜齿轮啮合型弯-扭-轴耦合振动模型。以某斜齿轮副为例进行的仿真计算结果表明,基于承载接触分析的轮齿啮合刚度计算方法能准确、方便求得轮齿啮合刚度,文献[8]动力学响应结果与理论实际存在明显差别,而基于力、振动位移分解法的响应则能与理论实际较好吻合。     

17CrNiMo6齿轮轴断裂原因分析及改进

目的研究常用的减速机高速工作中,材料为17CrNiMo6齿轮轴断齿现象的原因以及改进措施。方法通过化学成分分析、硬度检测、显微组织分析等方法,研究分析17CrNiMo6齿轮轴断齿现象的原因,并根据产生断齿的原因提出改进措施。结果 17CrNiMo6齿轮轴断裂为疲劳断裂,断齿的主要因素为调制热处理工艺不当、非金属杂物超标产生应力集中现象等。结论通过改进热处理工艺、优化结构设计、提高加工精度等措施可改善17CrNiMo6齿轮轴的断齿现象。     

Failure of a swing pinion shaft of a dragline

The causes of failure of a swing pinion shaft of a coal handling dragline have been investigated in the present work. Along with the failed shaft, a small piece of material from the tooth of another shaft that rendered design life in service has also been analyzed. The chemical composition and general heat treatment of the shafts were as per recommendation. The microstructure of both the shafts was tempered bainite, which is usual for such pinion shafts. The mechanical properties met the requirement for such applications. The investigation included metallography, microscopy (SEM), hardness and fractography. Analysis revealed fatigue cracks initiated at a number of places along the length of the tooth, and grew to a considerable depth. Improper surface hardening of the pinion teeth is believed to have rendered the teeth susceptible to bending fatigue failure. Other factors like lubrication and impact loads in the tooth roots might have aggravated the failure.     

Interior fatigue fracture of gear teeth

A new type of gear tooth fatigue failure is presented and analysed. It is initiated in the interior of the tooth and is given the self-explanatory name tooth interior fatigue fracture (TIFF).
A fractographic examination of TIFF is presented. The fracture surface of TIFF has characteristic features that distinguish it from other gear failures.
A hypothesis for TIFF initiation is presented. The crack-initiating stresses in the interior of the gear tooth are: (i) a residual tensile stress due to case hardening; and (ii) alternating stresses due to idler usage of the gear.
A finite element analysis is used to compute the stress state history of engaging gear teeth throughout the load cycle. The critical plane fatigue criterion of McDiarmid is employed. The analysis shows that the risk of fatigue initiation is high in the root of the tooth and in a large region in the interior of the tooth. These findings agree with test results where both modes of failure occurred.     

变速器中间轴齿轮断裂分析

某轿车变速器中间轴在进行耐久性试验时发生断裂。采用化学成分分析、金相检验、扫描电镜观察及硬度测定等方法对失效件进行了分析。结果表明：齿根表面淬火层非淬硬组织过深和硬度过低,造成中间轴齿轮承载能力下降,最终导致在耐久性试验中发生弯曲疲劳断裂。并提出了改进意见。     

基于齿根动应力的船用人字齿轮疲劳分析与优化

为了合理预估人字齿轮齿根动应力疲劳寿命,利用考虑啮合刚度激励、啮合冲击激励和齿面摩擦激励的十二自由度人字齿轮弯-扭-轴耦合动力学模型,同时考虑了参与啮合齿对之间的齿根应力关联性,并由此合理有效地计算出了人字齿轮齿根受拉侧的动应力变化趋势。通过对轮齿疲劳寿命机理分析,选取三种常用载荷工况下小轮齿根中点受拉侧动应力作为疲劳寿命计算对象,采用考虑应力幅值和应力均值双参数的雨流计数法,结合Miner线性累积损伤理论对人字齿轮受拉侧齿根弯曲疲劳寿命进行了预估。同时比较了考察啮合轮齿在进入啮合前其它齿对产生的反向压缩应力对疲劳寿命的影响。通过三维修形技术,对人字齿轮齿面进行了以综合载荷工况下齿根动应力疲劳寿命为目标的优化设计,优化结果表明修形后齿根动应力变化趋势平缓,疲劳寿命增加25%。     

Ermittlung des Verformungs- und Steifigkeitsverhaltens von bombierten Profilwellenverbindungen mit Evolventenverzahnung

Crowned shaft couplings with involute splines are an important transmission element in mechanical engineering and offer a wide variety of applications in the field of gears and transmissions. The advantages are the simple mount methods and the possibility to transmit large and impulsive torques. Especially the straight cylindrical involute splines are one of the most effective and powerful shaft-hub joints. One of the significant parameters for the design of shaft-hub joint is the knowledge of the deformation and stiffness behaviour. This exciting topic has filled a multitude of publications in the past decades. In the current technical literature exists no acceptable reference of contemporary dimensioning for specific gear tooth shapes. This includes crowned gear tooth shapes with involute splines which are for example applied in gear couplings. The following pages will show that the deformation and stiffness behaviour of gear tooth profiles according to DIN 3960 and DIN 5480 can be calculated simple and sufficient with current analytical methods.     

Design systems for gear elements made of cotton fiber-reinforced plastics

We look on the cotton fiber reinforced plastics as industrial gear materials, and have been developing design systems for industrial gears made of cotton fiber-reinforced plastics. In this report, we deal with a method estimating for tooth root stresses caused by bending movements under running conditions. The gear material used was cotton fiber plain woven cloth reinforced phenolic resin laminates. Paper-reinforced phenolic resin laminates, a commonly used material, was used as a control for comparison. The main dimensions of the gears were module 3–5 mm and tooth width 25 mm. First, accelerations of gears were measured under running conditions to estimate dynamic performance. Second, fracture tests of gear teeth were carried out under bending loads. Different fracture modes at tooth roots for cotton fiber-reinforced plastics and phenolic resin gears were observed. The fractures occurred at a high position from the tooth root in the case of the cotton fiber-reinforced plastics gear because the cotton fiber-reinforced plastics had excellent cleavage and shear strength. This gear also had higher strength for tooth bending loads. Third, the mechanical properties of the gears were researched by tensile, bending, and shearing tests. It was clear that the cotton fiber-reinforced plastics had excellent properties in cleavage fracture between laminates and shear strength. Finally, we proposed a design method for this gear, which considers the cleavage and shear strength.