齿轮传动箱断裂失效分析及预防

齿轮传动箱在使用中产生疲断裂，通过电镜观察，金相检验力学性能测试及力计算等方法进行分析，找出了引起疲劳破坏原因，并提出了改进措施。     

齿轮的失效分析

采用光学显微镜、扫描电子显微镜和电子能谱仪等方法对开裂齿轮进行了分析。结果表明,齿根强度低,材料中含有大量硫化物类夹杂物,同时在服役过程中啮合应力过大,使得该齿轮在应力集中齿根部位产生疲劳而失效。     

薄壁主动齿轮失效分析及工艺改进

针对薄壁主动齿轮失效原因,提出了提高薄壁主动齿轮性能的工艺改进方案,即从强力喷丸,提高齿根粗糙度,改进组装工艺以降低齿根拉应力,从而提高齿轮的疲劳强度和运行寿命.     

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。     

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.     

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。     

再沸器疲劳失效分析

在奥氏体不锈钢制再沸器的上管板与壳程筒体焊接的管板一侧发生蒸气泄漏.采用化学成分分析、力学性能测定、宏、微观检验、有限元应力计算及振动测试等方法对再沸器的材料、加工工艺和工作状况进行了综合分析.结果表明,管板材料性能较差,在制造该再沸器过程中受焊接热循环和较高应力水平的影响,造成在热影响区形成微裂纹,进而又在工作介质和应力的作用下在该区域发生疲劳损伤而形成宏、微观裂纹致蒸气泄漏.提出了预防和改进措施.     

浅论煤矿机械齿轮失效的原因及预防对策

齿轮失效在机械设备中较为常见,特别是煤矿设备因负荷大、易超载、工作环境差等,齿轮失效最为突出。通过对齿轮失效原因的分析,提出了若干可行的预防措施。     

20CrMo 齿轮失效分析

目的某厂生产的20Cr Mo齿轮在使用不久后,发现凹坑缺陷后失效,需寻找失效原因。方法通过应用金相组织分析、硬度分析和能谱分析等方法,对该齿轮的失效原因进行了分析。结果试验后分析结果表明,齿轮次表面存在的白亮层组织破坏了材料的连续性,是其失效的主要原因。结论建议改进热处理工艺,保证组织的均匀性,并选用成分均匀的钢材,以避免失效。     

粉末冶金齿轮失效分析研究

通过对发生断齿的粉末冶金齿轮进行了金相分析、扫描电镜断口分析及化学成分分析等,分析结果发现,粉末冶金齿轮断齿原因是齿轮烧结质量不好所致.     

塑料齿轮轮齿疲劳折断机理初析

对塑料齿轮疲劳破坏过程作了讨论和分析，提出了疲劳裂纹的萌生与扩展的银纹模式，认为轮齿表面节点附近热拉伸内应力是导致银纹形成的重要原因。     

减速器主动齿轮断裂失效研究

本文对减速器主动齿轮断裂行为进行了分析。结果表明,齿根倒圆与齿面交接处部位的两长裂纹由大应力造成,裂纹分布、走向及扩展均具有节径型共振特征。辐板与齿轮外圆端面交接处的两小裂纹与二者之间的组织应力有关。     

A Brief Assessment of a Dam and Its Failure Prevention

Dams are artificial lakes created to reserve water for a particular purpose. Reports on failure of dams are common things nowadays. Effects of dam’s failure on man and environment are well known, which require preventive measures. This article presents a brief assessment of a dam in Nigeria and suggested necessary failure preventive measures. The dam site was visited (up and down streams), selected soil and geological properties of the dam were conducted with a particular attention to the release of water from the reservoir as seepage, or filling of the reservoir by silt from erosion. Hydrology and hydraulic data of the study area and spillway were obtained and analyzed. The study revealed that the soil is mainly sandy-loamy soil of averagely sand (73.99 ± 3.12), clay (8.53 ± 0.18), and silt (17.48 ± 1.88). Geological structure of the soil revealed that the study area is in basement complex. The reservoir capacity is 177,000,000 m³ with about 18.5-m hydraulic high, silting rate of 0.301% per year. Hydraulic conductivity, transmissivity, and specific discharge were found to be of high side of 9.31 × 10⁻⁴ m/s, 5.08 × 10⁻⁴ m²/s, and 98.25 m/year, respectively. It was concluded that the current problems of the dam are high silting rate and seepage, big trees on the embankment and beside the spillway. All these may lead to failure of the dam in the following ways: lack of water in the reservoir due to seepage and silting, eutrophication and non-potable of the water due to silting and collapse of the embankment due to the presence of big trees. It was suggested that necessary and urgent solutions such as removal of trees from embankment, desilting and seepage control must be provided for safety of lives and properties.     

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。     

基于内部失效机理预测评估渗碳Cr-Ni齿轮钢的超高周疲劳强度

对渗碳Cr-Ni齿轮钢进行应力比为0和0.3的室温超高周疲劳实验,观测试样中诱发裂纹萌生的夹杂和疲劳断口形貌,以全面评估渗碳Cr-Ni齿轮钢疲劳性能。将疲劳失效模式分为有细颗粒区(Fine granular area,FGA)的内部疲劳失效和有表面光滑区(Surface smooth area, SSA)的表面疲劳失效,并阐明了渗碳Cr-Ni齿轮钢的超高周内部疲劳破坏机制。基于累积损伤和位错能量法并结合细颗粒区形成机理和夹杂的最大评估尺寸,分别构建了两种渗碳Cr-Ni齿轮钢内部疲劳强度的预测模型。利用FGA尺寸与夹杂尺寸的比值和夹杂应力强度因子及应力比之间的关系,修正所提出的两种疲劳强度预测模型并给出了最大夹杂尺寸下的l_FGA-S-N曲线。结果表明,基于累积损伤法和位错能量法分别构建的疲劳强度预测模型都可用于预测评估渗碳Cr-Ni齿轮钢在多种应力比下的内部疲劳强度,基于位错能量法的强度预测模型精度较高。     

齿轮开裂失效分析

采用断口分析、化学成分分析、低倍检验、金相检验和硬度测试等方法对某批经渗碳、淬火热处理及磨齿加工后放置一段时间发生开裂的齿轮的失效原因进行分析。结果表明：齿轮渗碳层碳化物级别过高,加上淬火后齿轮齿部应力集中,磨齿时又产生磨削裂纹,齿轮在放置期间由于应力导致裂纹扩展而开裂。     

Fatigue Failure of Flanged Thermowell

A fractured flanged thermowell was received for analysis. The fracture was located at the root of “U” insertion/immersion length which was welded to the flange. The failure of flanged thermowell was attributed to the vortex-induced fatigue. The failure was initiated by the weld failure to withstand the fluctuating load resulted from vortex after years of service. This weld failure then created stress raisers, as evidenced by the ratchet marks and river marks near the outer surface.     

Failure Analysis of Cracked Gear Shafts

Two gear shafts cracked during the fabrication. The cracks are through the grooves associated with the gear teeth and propagated completely across the shaft. Fractography on the cracked teeth indicates that the crack origins are about 3.5 to 4.0 mm from the groove and exhibit pointlike features. Fracture surfaces near the crack origin regions were intergranular, and the fracture appeared to have occurred instantaneously. Metallurgical analysis indicates that decarburization had occurred on the surfaces of the gear shafts, but occurrence of decarburization has no relation to the cracking. Cracking occurred during the carburization-quenching process and originated at a cluster of Al₂O₂ complex inclusions. The thermal stress produced by quenching drove the cracking process.