风电渗碳齿轮内部疲劳断裂可靠性研究

齿轮内部疲劳断裂作为风电渗碳齿轮典型失效形式，是限制风电齿轮箱服役性能提升的瓶颈之一。基于应力强度模糊干涉函数和齿轮材料强度退化理论，结合风电LDD载荷与Dang Van多轴疲劳准则建立渗碳齿轮内部疲劳断裂可靠度分析模型，通过与某2 MW风电齿轮失效样本进行对比验证了模型的适用性。采用因子试验设计方法分析齿轮硬度梯度和微观修形对内部疲劳断裂失效的影响，通过材料暴露系数回归方程进行望小优化设计获得主因子最佳参数匹配。研究结果表明心部硬度、齿向鼓形对内部疲劳断裂失效影响权重最大，通过优化设计将该齿轮副内部疲劳断裂可靠度由0.968 399提高至0.972 678。     

行星齿轮减速器总成失效分析

某运载车辆在行驶了约6000km后一套行星齿轮减速器总成失效.根据齿轮的硬度、化学成分、金相组织以及断口分析结果,综合行星齿轮减速器的工作原理,最终确定外齿圈为肇事件.行星齿轮减速器外齿圈淬火区不完整导致齿面局部硬度偏低,致使外齿圈齿面发生疲劳磨损是导致此次故障的根本原因,行星齿轮心部硬度偏高也促进了轮齿的断裂.     

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。     

风机齿轮箱齿轮失效分析

某发电厂的风力发电机在运行中齿轮箱出现故障,经现场检查发现在风机某一级传动齿轮中有一个齿轮出现断齿现象,断裂部位在轮齿的中间腰部位置.为了判断风机齿轮箱的断裂性质及原因,对风机齿轮箱断齿残片进行了宏微观观察,对断齿残片基体及断口源区进行了能谱分析,测定了断齿表面残余应力,还对齿轮进行了断口定量分析.结果表明,风机齿轮箱齿轮轮齿失效性质为弯曲疲劳断裂.可基本排除齿轮设计、材质、使用维护方面的异常,齿轮断裂原因在于断裂部位存在夹渣缺陷.     

传动渗碳齿轮断裂失效分析

对齿轮的断裂部位的形貌特征,齿面加工情况等进行观察,从断裂区组织与硬度、齿轮材质、渗碳层深度等方面对断裂的渗碳齿轮进行检测、分析。分析结果表明,齿轮断裂是由于淬火裂纹引起的。     

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。     

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。     

小螺旋锥齿轮断裂失效分析

对小螺旋锥齿轮的断裂失效进行了分析，结果表明，齿轮在传动中出现偏载，造成了连续冲击过载，而使齿轮过早疲劳断裂，本文还讨论了造成偏载的可能性。     

某船用齿轮断裂分析

本文提供了一个失效分析实例,作者利用扫描电镜、电子探针等微观分析手段,结合x射线应力分析、金相和硬度等方法对某船用齿轮的断裂失效原因进行了综合分析。结果表明,在齿轮淬硬层与基体界面存在的大量Al_2O_3、FeO等夹杂物引起了齿轮的疲劳断裂。     

风能发电机组结构件的失效分析与预防(待续) 第2讲齿轮的失效分析与预防

齿轮(齿轴)是风能发电机组上非常重要的结构件。对齿轮的主要失效形式及其特征做了介绍。从齿轮正常服役时的受力特点、选材特点、工艺特点以及使用特点等几个方面论述了齿轮失效的内在原因和外部原因。结合实际案例分析,对经常失效的风能发电机组上齿轮(齿轴)的失效原因做了归纳,发现疲劳断裂和氢脆型断裂是其最常见的失效形式,材料的冶金质量是目前国产风能发电机组上齿轮(齿轴)发生失效的主要原因,提出了风能发电机组上齿轮(齿轴)失效的预防措施。     

Detection and Diagnosis of Gear Fault By the Single Gear Tooth Analysis Technique

This paper, presents a procedure of single gear tooth analysis for early detection and diagnosis of gear faults. The objective of this procedure is to develop a method for more sensitive detection of the incipient faults and locating the faults in the gear. The main idea of the single gear tooth analysis is that the vibration signals collected with a high sampling rate are divided into a number of segments with the same time interval. The number of signal segments is equal to that of the gear teeth. The analysis of individual segments reveals more sensitively the changes of the vibration signals in both time and frequency domain caused by gear faults. In addition, the location of a failed tooth can be indicated in terms of the position of the segment that deviates from the normal segments. An experimental investigation verified the advantages of the single gear tooth analysis.     

齿轮调幅调频所引起的室内啸叫噪声分析与控制

某前置后驱车型在加速过程中室内存在啸叫异响,在特定转速下尤为明显。试验数据显示后主减速器壳体振动和辐射噪声均存在相应的频谱特性。对室内噪声及主减速器壳体的噪声与振动在匀速和加速工况下进行数据采集,采用频谱分析和调制谱分析,确认该啸叫噪声为主减速器齿轮啮合引起的齿轮振动调制现象。该调制以主减速器齿轮啮合频率的高次谐频为载波频率,主减速器主动齿轮轴的转频为调制频率。在一定程度上提高齿轮加工精度可使室内啸叫噪声明显减弱。整个试验分析过程为后期齿轮异响问题排查提供一种新的思路。     

Failure of an intermediate gearbox of a helicopter

An intermediate gearbox of a helicopter failed resulting in an accident. A systematic failure analysis was conducted to find out the cause of failure. Examination revealed that fatigue fracturing of the driving gear was responsible for the gearbox failure. The teeth of the gear were severely damaged by spalling. Fractographic study revealed multiple fatigue crack initiation at the tooth root regions. It was established that the failure was caused due to improper assembly of the gear. A detailed analysis of the failure is presented in this paper.     

Partial Load: A Key Factor Resulting in the Failure of Gear in the Wind Turbine Gearbox

Gearbox is a critical component in the wind turbine system which can transfer wind energy into wind power to replace some fossil energy in order to reduce the environmental pollution. A 1.5-MW wind turbine gearbox failed after about 5 years of service; however, the design life of the gearbox is 20 years. In this paper, the failure mechanism of the gearbox was investigated based on standard failure analysis procedures and finite element (FE) simulation. The failure of gear could be attributed to fatigue fracture, because typical macroscopic features—beach marks and ratcheting marks—could be observed on the fracture surface. Furthermore, contact fatigue caused the formation of pits on the failed working tooth flank, even brought some microcracks. It should be emphasized that fatigue pitting mainly concentrated at the left end of the failed gear. Based on the physical, chemical analysis, and FE simulation, the failure of gear should be essentially ascribed to abnormal load rather than the material defects. Finally, based on the failure characteristics, partial load should be responsible for the failure of the gear in the wind turbine gearbox.     

Brittle Cracking of a Cylindrical Spiral Gear of Axle Gearbox

A cylindrical spiral gear of locomotive axle gearbox failed after standing in site for 10 days. The failed gear had been assembled with the spiral gear-shaft. Inspection in site found that cracking occurred on the spoke plate between the shaft bore and the oil-pressed hole. The gear teeth are required to be carburized, but the surfaces of the shaft bore and the oil-pressed hole of gear are surface-coated to prevent carburizing. The crack initiated from the surface of oil-pressed hole and propagated along the radial of the oil-pressed hole. Metallurgical examination reveals that anti-carburizing measure was not conducted on the surface of oil-pressed hole as the specification. A simplified evaluation of the maximum hoop tensile on the wall of oil-pressed hole subjected to internal pressure for swelling bore is far insufficient to lead to brittle fracture. Delayed fracture of gear, the predominance of intergranular fracture micro-mechanism, and the presence of several secondary micro-cracks in the depth of case layer on the oil-pressed hole surface are a clear indication of hydrogen embrittlement. Hydrogen absorption occurred during gas carburizing process.     

Fatigue failure of a star–ratchet gear

We present an analysis of the fatigue failure of an 18 tooth star–ratchet gear (SRG). The subject gear was implemented in the freewheel assembly of a mountain bicycle. After 6 years of service, the gear failed unexpectedly during a typical off-road ride. The unique geometry of SRGs precluded a simple comparison to existing gear lifetimes. Scanning Electron Microscopy (SEM) analysis of the failed gears showed crack initiation at the root of the gear teeth, followed by fatigue crack propagation and eventual chip-out. A biomechanical analysis of pedaling forces, coupled with explicit power data obtained from instrumented rides over the same trails, in conjunction with a Finite Element Analysis (FEA) of the gear, were used to determine stress amplitudes for fatigue calculations. Energy dispersive spectroscopy (EDS) determined the alloy composition of the gear and thus set the strength and fatigue properties of the gear. Basquin’s law, Goodman’s mean stress correction, and Miner’s rule were used to estimate the lifetime, in bike rides, of the gear. Our analysis led to an estimate of 2288 rides, while failure was reported after roughly 312 rides. Given the uncertainties in fatigue life estimation and service use, we find this estimate acceptable.     

立式高速泵齿轮断齿分析

立式高速泵在进行出厂前水力试验时，低速轴上的大齿轮和中轴小齿轮的轮齿发生断裂。对齿轮材料的化学成分、金相组织、力学性能、齿轮硬化层深度及断口进行了分析。认为，齿轮轮齿断裂性质为疲劳断裂；断裂原因系工作时受力过大所致，所受力为脉动偏载力。     

齿轮轴退火开裂分析

用理化分析方法,对２０ＣｒＭｎＴｉ钢制齿轮轴退火开裂进行了分析,结果表明,该齿轮轴铬,锰含量超标,齿轮轴热处理退火后出现较大应力,导致齿轮轴开裂。