HXD1机车牵引电机转轴组件断裂失效分析

HXD1型电力机车的牵引电机转轴和小齿轮轴采用圆锥过盈配合传动结构(下称转轴组件),使用中该组件出现了早期断裂失效.本文通过理化检测、断口和配合面宏/微观形貌观察等失效分析技术对失效组件进行了分析.结果表明,材料成分、组织和显微硬度正常,小齿轮轴和电机转轴的失效形式分别为高周疲劳断裂和微动疲劳断裂.造成组件失效的原因和过程是,小齿轮轴近齿端油槽-油孔交界线处有较大的结构应力集中,油槽底部周向加工刀痕造成附加应力集中,在应力集中和旋转弯曲疲劳载荷作用下油孔边两个应力集中点萌生了疲劳裂纹并扩展;随小齿轮轴裂纹的不断扩展转轴组件结构刚度减小,继而诱发了与小齿轮轴匹配的电机轴配合面的微动疲劳,电机轴疲劳裂纹萌生于微动区的边缘处;电机转轴先于小齿轮轴完全断裂.基于本文的分析结果提出了提高组件抗疲劳断裂的技术措施.     

齿轮箱轴断裂分析

采用化学成分分析、断口分析、金相检验和力学性能测试,对某齿轮箱轴发生断裂的原因进行了分析。结果表明：其断裂模式为疲劳断裂,起源于退刀槽尖角位置,直角退刀槽造成应力集中产生疲劳裂纹;而原材料的锻造和热处理工艺不合理,加速了轴的疲劳断裂。     

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.     

火电机组给水前置泵轴断裂原因分析

某火电厂4号机组B给水前置泵轴投运仅19h即发生断裂。经对断裂泵轴进行宏观分析、化学成分分析、常温力学性能测试、金相检验及断口扫描电镜分析,探讨并明确了泵轴断裂原因,同时提出了防范措施。结果表明：该给水前置泵轴断裂为疲劳断裂,在弯曲及扭转载荷作用下于变截面的应力集中部位的不连续及夹杂物处形成疲劳裂纹,同时大量夹杂物及沿晶分布的粗大a铁素体的存在严重降低了基体强度,使轴体所能承受的循环应力大大降低,即在较低的循环应力作用下疲劳裂纹不断扩展并最终断裂。     

挤出机摩擦离合器螺栓断裂分析

某挤出机中气动摩擦离合器与减速器端连接的螺栓在使用过程中经常发生断裂,改用另一种材料的螺栓后情况未有很好改善。采用化学成分分析、力学性能测试、断口分析和金相检验等方法,对螺栓断裂的原因进行了分析。结果表明：起裂源位于螺栓的加工刀痕、表面擦伤处及因微动疲劳所致的螺纹微裂纹处,这些部位均存在应力集中,在振动作用下,萌生的裂纹不断扩展,使有效承载面积不断减小,最终引起螺栓疲劳断裂。     

压力机偏心齿轮主轴断裂分析

采用扫描电镜及光学显微镜对压力机偏心齿轮主轴断口进行了系统的分析。确定了主轴断裂属于疲劳断裂,并具有低周疲劳断裂的特征。找出了齿轮主轴断裂的主要原因－主轴油孔处的奕力集中以及超负荷运行造成轴的工作应力过大引起断裂。     

蜗轮连接螺栓断裂失效分析

装卸料机上的蜗轮连接螺栓材料为35钢,强度等级为10.9级,在设备运行大约10a后发生断裂。对断裂螺栓进行宏观、化学成分、硬度、金相、能谱和断口分析后得出,该螺栓的断裂性质为双向弯曲疲劳断裂,螺栓表面的脱碳和螺纹颈部的应力集中降低了该部位的疲劳性能。通过综合分析和螺栓受力估算后得出,螺栓断裂的主要原因是螺栓和内齿轮螺栓孔之间存在较大的间隙,使螺栓的受力状态和受力大小过早地发生了变化,造成连接螺栓疲劳断裂。     

马达花键轴断裂原因分析

采用ＡＮＳＹＳ有限元软件对在疲劳试验中发生疲劳断裂的某马达花键轴进行了工作应力计算分析。结果表明,花键轴断裂处存在严重的应力集中,花键轴断裂处过渡圆弧半径过小以及未对螺栓柠紧力进行控制是导致轴产生高周疲劳破坏的主要原因。据此提出改进建议。     

Failure Analysis of Reverse Shaft in the Transmission System of All-Terrain Vehicles

This paper presents a failure analysis of a reverse shaft in the transmission system of an all-terrain vehicle (ATV). The reverse shaft with splines fractured into two pieces during operation. Visual examination of the fractured surface clearly showed cracks initiated from the roots of spline teeth. To find out the cause of fracture of the shaft, a finite element analysis was carried out to predict the stress state of the shaft under steady loading and shock loading, respectively. The steady loading was produced under normal operation, while the shock loading could be generated by an abrupt change of operation such as start-up or sudden braking during working. Results of stress analysis reveal that the highest stressed area coincided with the fractured regions of the failed shaft. The maximum stress predicted under shock loading exceeded the yield strength and was believed to be the stimulant for crack initiation and propagation at this weak region. The failure analysis thus showed that the premature fatigue fracture of the shaft was caused by abnormal operation. Finally, some suggestions to enhance service durability of the transmission system of ATV are discussed.     

Failure Analysis of High-Speed Pinion Gear Shaft

The failure of a high-speed pinion gear shaft was investigated. The pinion gear was an integral part of a system used to compress the natural gas. It was a high-speed gear mounted on two roller bearings. An abnormal wear pattern was observed on the shaft surface, beneath the inner race of the bearing. The material from shaft was observed to be dislodged and stuck to the surface of the inner race. This transfer of material imparted an imbalance to the assembly, and abnormal sounds and fumes were observed two days before failure. The macrofeatures of the fracture surface resemble these of fatigue but electron microscopy showed brittle and mostly intergranular fracture. Fatigue features such as striations were not found on the fracture surfaces. Fatigue samples made from the same material and heat-treated to the same hardness were tested under uniaxial fatigue and the fracture features were compared with the original crack surface. The microfeatures of fracture surfaces were almost identical. The root cause of failure was determined to be fatigue, and cracks on the pinion shaft in the region beneath the inner bearing race lead to the transfer of material.     

汽车发动机曲轴断裂分析

某6缸发动机曲轴在运行8910km时,第六曲拐颈断裂。对断裂曲轴进行了断口观察、化学成分复验、基体硬度和显微组织检验。结果表明,曲轴的拐颈断裂为扭转疲劳断裂,断裂疲劳源位于油道孔与倒圆角曲面交接处,此处的切削加工刀痕及金属损伤形成应力集中且处于最大主应力面上,因而引发扭转疲劳断裂。     

电厂外供泵轴断裂原因分析

某外供泵在运行期间其泵轴发生断裂。通过宏观和微观检验、化学成分分析以及硬度测试等方法对泵轴断裂的原因进行了分析。结果表明:该轴的热处理没有达到要求,使各项强度指标显著降低,加上在应力集中部位键槽根部产生了疲劳裂纹,并进一步扩展,最终导致泵轴断裂。     

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。     

Failure analysis on fracture of worm gear connecting bolts

The worm gear connecting bolts of refueling machines of a nuclear power plant, with implementing standard of ANSI/ASME B18.3 and ASTM A574-08 and strength grade of 10.9, fractured at the thread neck position after running for about 10 years, and means such as macro examination, chemical compositions analysis, hardness testing, metallographic examination and fracture analysis, were used to analyze the fracture property and reasons of the bolts. The results show that the fracture of the bolts is due to two-way bending fatigue fracture. Surface decarburization of the bolts and stress concentration at the bolt thread neck decreased the fatigue strength of this position and resulted in the initiation of fatigue cracks. By comprehensive analysis and stress estimating, it was concluded that the main reason for fracture of the bolts is that there was a big gap between the bolts and the bolt holes, which resulted in fatigue fracture of the worm gear connecting bolts.     

Failure analysis of an automobile differential pinion shaft

Differential is used to decrease the speed and to provide moment increase for transmitting the movement coming from the engine to the wheels by turning it according to the suitable angle in vehicles and to provide that inner and outer wheels turn differently. Pinion gear and shaft at the entrance are manufactured as a single part whereas they are in different forms according to automobile types. Mirror gear which will work with this gear should become familiar before the assembly. In case of any breakdown, they should be changed as a pair. Generally, in these systems there are wear damages in gears. The gear inspected in this study has damage as a form of shaft fracture.

In this study, failure analysis of the differential pinion shaft is carried out. Mechanical characteristics of the material are obtained first. Then, the microstructure and chemical compositions are determined. Some fractographic studies are carried out to asses the fatigue and fracture conditions.     

Fretting fatigue fracture of the supporting shaft in a rotary kiln

The fracture failure of the supporting shaft in a rotary kiln was analyzed to determine the failure mechanism. The rotary kiln was used to heating and mixing nickel ores and was supported by four group riding wheels with two wheels in each group. One of the supporting shafts was found fractured after it was used for about two years. The fracture was located at the interface between the supporting shaft and the sleeve. This location was 100–120 mm far from the transition arc of the supporting shaft where high stress concentration usually occur. A failure analysis was carried out, using characterization techniques such as scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and so on. Obvious fatigue propagation zone caused by multi-initial cracks were observed at the circle edge of the fracture surface. Adhesive wear and some circumferential cracks were found on the outside surface of the supporting shaft. It was considered that fatigue due to the fretting wear between the shaft and sleeve was the most probable mechanism.     

Failure of two overhead crane shafts

The failure analysis of two overhead crane shafts is presented: the failure of an overhead crane drive shaft and the failure of an overhead crane gearbox shaft, due to rotating-bending fatigue. The fracture of the overhead crane drive shaft originated in small radius fillet between two different diameters of the shaft. A new shaft was made with a larger-size fillet, resulting in reduced stress concentration in this region. The failure of the overhead crane gearbox shaft originated at the intersection of two stress raisers, at the change in shaft diameter and in the keyway corner. A new shaft was made with a larger-size fillet and a larger size radius of the keyways corner to minimize stress concentration in this section. In both cases the installed couplings were replaced by gear couplings in order to allow parallel and angular misalignment as well as to avoid additional load due to misalignment. The analysis shows that the fatigue life can be significantly increased with a simple change in the structural details.     

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 Analysis of a Diesel Engine Gear System Consisting of Camshaft and Crankshaft Gears

A failure investigation was conducted on a diesel engine gear system consisting of a driven camshaft and drive crankshaft gears that were used in a truck. The gears are made from a nitrided 42CrMo steel. Adjacent teeth fracture and plastic deformation regions appeared on the gears after a 400 h run test of the gear system. Fractography indicates that fatigue fracture is the dominant failure mechanism for the gear teeth. Although the appearance of needle-like nitrides in the nitrided layer and the narrow depth of the compound layer may decrease the fatigue strength of the camshaft gear, these do not suffice to lead to the premature fracture of the gear teeth. Geometrical analysis of the gears was performed and compared with an analysis of unfailed gears that had experienced a run test for 1800 h. The comparison reveals that the small fillet radius at the root area of the camshaft gear concentrated the stresses and is mainly responsible for fatigue fracture of the teeth. The camshaft gear is the component that initiated trouble in the gear system. The appearance of severe plastic deformation on the gear faces is caused by the fractured teeth crushing the teeth faces and being embedded in the grooves between teeth.     

Analysis of fatigue failure on the keyway of the reduction gear input shaft connecting a diesel engine caused by torsional vibration

The vibratory torque of a diesel engine caused by the reciprocating motion of the mass and gas pressure force of a cylinder is one of the main causes of the failure of the driving shaft of the diesel engine and the connecting shaft to the reduction gear. Because high cycle torsional fatigue can occur in the reduction gear shaft connecting the engine under vibratory torsional stress, the US Navy restricts it under the MIL G 17859D(SH) standard and suggests a procedure for evaluating the safety of the shaft for the reduction gear. In this study, the structural safety of the reduction gear input shaft in which fatigue failure occurs in typical naval vessels is investigated in accordance with the VDI 3822 RCA (root cause analysis) procedure based on the MIL G 17859D(SH) standard. When evaluating the safety factor in accordance with the MIL G 17859D(SH) standard, the alternating bending moment from the lateral vibration and the stress concentration factor under static load are considered. In addition, an improved design is suggested by CAE to satisfy the safety factor suggested by the MIL G 17859D(SH) standard.