花键轴断裂失效分析

对断裂的花键轴进行了断口宏微观观察、化学成分分析、金相组织检查、硬度检测及静态拉伸测试.结果表明:花键轴的断裂性质为疲劳断裂;花键轴的显微组织中存在魏氏组织,导致其硬度和强度低于技术要求,是造成花键轴断裂的根本原因.     

波音777飞机APU引气活门蝶形瓣片断裂分析

波音777飞机的辅助动力装置APU启动后自动停车,排故检查后发现APU引气活门蝶形片断裂.本文对蝶形片断裂进行了断口宏观、微观、金相组织等分析,分析结果证实,引气活门蝶形片属于疲劳断裂,导致疲劳断裂的原因与断裂处过渡R角及棱边尖锐有关.     

微动疲劳中的应力状态参数和微动磨损参数的研究

本文对微动疲劳中的力学参数作出了研究。微动接触面上的力学参数可分为应力状态参数（SSP）和微动磨损参数（FWP）两类，并将应力状态参数综合为当量应力σ-1E,而将微动磨损参数用摩擦功W来表示．对桥式微动疲劳试件和燕尾型榫联接试件的数值分析表明，在微动接触面上疲劳断裂处的σ-1E和W值较大。因此，有可能使用了σ-1E和W值作为预测微动疲劳失效的两个基本参数。     

BJ2021型汽车座椅滑道断裂分析

分析了ＢＪ２０２１型汽车座椅滑道断裂失效的模式和原因。结果表明，座椅滑道失效模式为典型的疲劳断裂，其原因系座椅支架固定不牢，在运行过程中断裂处出现交变应力作用所致。     

叉车桥壳端轴断裂分析

某叉车桥壳端轴在使用约1 000h后发生断裂,通过对断裂件的断口、化学成分、力学性能、显微组织等进行分析,找出了断裂原因。结果表明:该叉车桥壳端轴断裂属于疲劳断裂;断裂处过渡圆角半径过小且加工刀痕明显,导致此处产生应力集中;另外热处理工艺控制不当;一方面导致材料显微组织严重不均匀产生较大的内应力,另一方面未进行调质处理使材料力学性能和疲劳强度大幅度下降;上述因素是造成桥壳端轴疲劳断裂的主要原因。     

B50ZC摩托车花键轴热处理工艺改进

本文介绍了B50ZC三轮摩托车后桥花键轴热处理工艺改进过程。对三种不同的热处理工艺进行了对比,并经理论分析和实际跑车试验,科学地探索出了适用于后桥花键轴的最佳热处理工艺,解决了花键轴过早失效的重大质量问题,提高了产品质量及使用寿命。     

某发动机二级涡轮叶片断裂失效分析

在叶片断口宏微观断裂特征观察的基础上,结合叶片的金相组织、力学性能、硬度以及化学成分等,对叶片断裂失效的原因进行了研究.结果表明,发动机二级涡轮叶片失效是由于其中一片涡轮叶片低周疲劳断裂所致.该叶片的低周疲劳断裂失效与源区附近的R槽中的微裂纹、Zr含量偏高、HRC偏高以及断裂处在高应力区等因素有关,且叶片经历了短时超温,其温度约在1050～1100℃之间.     

混炼机螺杆断裂机理分析

断裂失效的花键轴位于混炼机简体内部，介质为聚乙烯熔融树脂，工作温度为140—240℃。花键轴材质为PCrNi3MoV，抗拉强度1000MPa，屈服强度895MPa。花键轴表面进行氮化处理，渗氮层为0．4—0．5ram，氮化后的表面硬度大于HRC51。花键轴直径为138mm，全长为4710mm，花键部分长度为3970mm。     

无缝钢管生产用芯棒断裂失效分析

某无缝钢管生产用的芯棒在使用过程中频繁在尾部断裂,通过宏观检查、化学成分分析、金相检验、力学性能试验等方法对断裂原因进行了分析。结果表明:芯棒尾部异常受力引起疲劳弯曲是导致芯棒尾部断裂的外在因素;芯棒结构不合理使尾部受力时芯棒过渡锥面与尾杆交接处产生较大弯矩与应力集中,且芯棒断裂处显微组织带状偏析较严重、横向冲击吸收能量较低、韧性较差是导致芯棒断裂的内在因素。     

高速动车组吊耳装置结构参数优化分析

目前对高速列车转向架零部件异常振动问题的处理大多侧重于成因分析,从产生异常振动的源头上提出控制措施,不能从根本上解决异常振动的问题。在零部件结构可调整的情况下,参数优化对解决异常振动问题更加有效。现场试验发现,我国某型高速动车组在运营过程中出现吊耳装置异常振动且个别出现明显断裂裂纹的现象,针对此问题,采用有限元法,对其结构进行参数优化。对吊耳装置开展运行状态下的振动、应力特性和静态力锤模态特性测试,掌握了吊耳装置的加速度和应力响应频谱特性,分析异常振动的成因,确定目标变量。然后建立吊耳装置有限元分析模型,分析吊耳装置的振动特性、应力特性和疲劳寿命,研究吊耳装置的厚度和倒圆角半径对其振动特性、应力水平和疲劳寿命的影响。结果表明,吊耳装置厚度增加3 cm、6 cm、9 cm,振动显著频段加速度有效值分别降低4.6 dB、6.1 dB和8.9 dB,断裂处应力分别降低11.8%、19.0%和23.9%,疲劳寿命分别提高1.9倍、3.3倍和4.3倍;倒圆角半径增大3 mm、6 cm和9 cm,显著频段加速度有效值分别降低6.8 dB、10.9 dB和15.7 dB,1阶弯曲模态对应频率逐渐远离轴箱激励的显著区域,断裂处横向应力分别降低25.7%、38.6%和52.9%,疲劳寿命分别提高1.8倍、3.6倍和5.1倍。吊耳装置优化后的结构参数为:厚度20 cm,倒圆角半径9 cm,中间幅板宽度30 cm,螺孔半径8.5 cm。相关研究可为吊耳装置的设计提供参数范围,对降低运营过程中吊耳装置的异常振动、降低应力以减少断裂发生和提高疲劳寿命提供参考。     

Investigation on the failure of the gear shaft connected to extruder

In respect to the fracture of the gear shaft of an extruder, the torque on the shaft replaced the fractured one is measured under typical work conditions. The fatigue and material mechanics properties of the fractured shaft are obtained by tensile and fatigue test. Based on the analysis of cyclic fatigue load and the stress of gear shaft, the reason of the shaft fracture is discussed. The analysis indicates that when the extruder is running, high mean stress occurs in the gear shaft, the failure of the gear shaft was caused by fatigue and material strength degradation. Finally, suggestions are given to guide the future operating of the extruder to prevent the gear shaft from fracture.     

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.     

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。     

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.     

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。     

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.     

Classical Fatigue Design Techniques as a Failure Analysis Tool

The classical method for designing against high-cycle fatigue fracture is based primarily on statistical models derived from laboratory experimental data. This paper considers a number of actual fatigue failures where the analyses of the failures, in part, made use of classical high-cycle fatigue resistance design methodology as an analytical tool. This paper uses failure analyses to demonstrate that the long-taught classical methodology is useful and accurate as both a design and an analysis tool. The usefulness and accuracy of the method is verified in that it is shown to have predicted actual failures, given known materials, manufacturing histories, and service operating conditions. Example analyses include: a fatigue-cracked roll from a paper-making machine, a fractured anvil on a steam powered forge, and a fractured shaft on a helical ribbon dryer.     

坦克扭力轴表面缺陷对疲劳寿命的影响

为探求坦克扭力轴过早产生疲劳断裂的原因,应用弹性有限元方法模拟了坦克扭力轴表面各种形状、尺寸的凹坑处产生的应力集中现象,结合坦克在某一训练科目下的载荷谱,使用疲劳分析软件计算了具有不同形状和尺寸缺陷的扭力轴的疲劳寿命(存活率为99%).结果表明:一旦扭力轴表面出现了凹坑,尤其是出现了狭长的裂纹状凹坑时,其疲劳寿命会急剧下降;当出现狭长的裂纹状凹坑时,将其扩展成等径凹坑(不增大凹坑深度),可使凹坑对扭力轴疲劳寿命的影响降至最低.     

Fatigue life estimation of adhesive bonded shaft joints

Fatigue tests and analytical investigation of adhesive bonded shaft joints were conducted to propose the estimation method of fatigue strength. Two kinds of adhesive bonded joints were studied: one, shaft joints connected with adhesive coupling, the other, adhesive joints of thin wall tubes to obtain standard fatigue strength. Both pulsating tensile and torsional fatigue tests were conducted with each adhesive joint. Furthermore, the stress distributions under tensile and torsional load conditions were analyzed by finite element method. Based on the analytically computed maximum normal shear stress in the adhesive layer, fatigue strength of the shaft joints was tandardized and compared with that of adhesive joints of thin wall tubes. As a result, it is confirmed that the maximum normal and shear stresses are key parameters for estimating fatigue strength under pulsating tensile and forsional load conditions, respectively. Furthermore, this study indicates an improved method of estimating fatigue strength by using tapered coupling order to reduce the stress concentration at the end of the adhesive layer.