某电传操纵系统弹簧拉杆可调叉形接头断裂原因

某飞机电传操纵系统弹簧拉杆可调叉形接头在运行过程中发生断裂,通过宏微观分析和金相检验等方法对拉杆接头的断裂原因进行了分析。结果表明:拉杆接头断裂为疲劳断裂,断裂的根本原因是其显微组织不均匀的同时出现了魏氏组织,使接头的抗疲劳性能严重降低,导致疲劳裂纹的萌生与扩展;而拉杆的受力不均匀则加速了其疲劳裂纹的扩展。     

某转向横拉杆断裂原因分析

某左转向横拉杆断裂的原因和过程是判定一起车祸责任的关键.本次事故发生时间较长,首断件丢失,给事故原因的分析带来了极大的困难.在进行了断口宏微观形貌观察、材质检验、模拟实验和碰撞痕迹观察的基础上,对横拉杆断裂的原因进行了深入的分析,从断口和碰撞痕迹等几个方面证实了左转向横拉杆是在车辆失控后翻转过程中发生的断裂,并且球头帽在碰撞过程中丢失.     

3044 t/h超超临界锅炉磨煤机拉杆断裂原因

某电厂3044 t/h超超临界锅炉磨煤机拉杆发生断裂,通过化学成分分析、断口分析、力学性能测试和金相检验等方法对拉杆断裂原因进行了分析.结果表明:该拉杆供货态热处理质量较差,导致强度和冲击韧性指标不合格,且磨损补焊处因热处理不到位而产生冷裂纹,长期在往复拉应力及弯曲应力的作用下,裂纹疲劳扩展,最终导致拉杆疲劳断裂.     

某地铁受电弓拉杆球铰轴承失效原因

某地铁受电弓拉杆球铰轴承在运行过程中发生失效断裂.采用宏观分析、断口分析、金相检验、硬度测试及化学成分分析等方法对球铰轴承的失效原因进行了分析.结果表明:该受电弓拉杆球铰轴承的断裂模式属于高周低应力疲劳断裂.球铰轴承在服役过程中承受频繁的振动和交变载荷作用,折角处的微裂纹成为疲劳裂纹源区,裂纹在交变载荷作用下不断扩展,...     

冷剪机刀架拉杆疲劳断裂研究

扭杆是剪切机中的关键零件,在剪切过程中受交变裁荷作用,在实际生产中常出现疲劳断裂现象。本文利用有限元对某厂冷剪机的拉杆进行疲劳分析,结果表明,在剪切力发生倾斜条件下,拉杆强度不能满足疲劳寿命长时间运行要求,有可能引起疲劳断裂。     

超强钢18Ni(250)的剪切断裂韧性行为

针对马氏体时效钢18Ni(250)在动态拉伸和不同速度泰勒杆冲击下呈现剪切断裂破坏的特征,为了理解其剪切及Ⅱ型断裂韧性在复合型断裂中所起到的作用,借助Hopkinson拉杆装置,对18Ni(250)进行了高加载率下的复合受力试验。并根据该材料在不同加载率下剪切断裂模式的特征,重点对该材料进行了不同加载率下的Ⅱ型动态断裂韧性试验研究。结果表明:随着加载率的提高,18Ni(250)钢的起裂时间逐渐减小,但其Ⅱ型动态断裂韧性值不断增大;通过SEM微观分析发现,在不同加载率下18Ni(250)钢Ⅱ型动态断裂呈现以晶面滑移为主的绝热剪切特性。     

横拉杆断裂失效分析

某车辆在下线时发生横拉杆断裂失效。使用扫描电镜、光谱仪、硬度计等仪器设备对断裂的横拉杆进行了失效分析,并利用二维有限元数值计算方法模拟了钢材冷挤压过程中心部裂纹的形成过程。结果表明:该失效件是在冷挤压变形加工过程中受到了过大的载荷,内部产生了多处开裂,使有效连接面积大幅减小,因而当车辆行驶时,横拉杆即发生断裂失效。     

汽车转向直拉杆断裂原因分析

采用化学成分分析、硬度测试、金相检验及断口的宏、微观形貌观察的方法,对汽车转向直拉杆的断裂原因进行了分析。结果表明:在正常的交变载荷作用下,在直拉杆弧形部位内侧的腐蚀坑处发生应力集中而形成断裂源,疲劳裂纹不断扩展,导致直拉杆发生疲劳断裂。     

高炉拉杆的断裂分析及防断方法

本文利用断裂力学方法，对引起重大事故的断裂拉杆断口进行分析，从而确定造成拉杆断裂的原因及断裂特性，同时提出了相关的解决措施，     

客车直拉杆断裂分析

通过宏观检验、化学成分分析、断口分析以及金相检验,对客车直拉杆断裂的原因进行了分析。结果表明:直拉杆的146°弯处在使用前存在微裂纹,在客车行驶过程中该直拉杆受交变应力的作用,微裂纹以疲劳的方式扩展,当扩展到一定程度,剩余截面不能承受外力作用时发生断裂。     

Al-7Si-0.3Mg铸造合金的旋转弯曲疲劳性能研究

研究了M-7Si-0.3Mg铸造铝合金的室温旋转弯曲疲劳性能。结果表明,A1-7Si-0.3Mg铸造铝合金在10~7次疲劳寿命下的极限应力为88 MPa;结合对疲劳试样断口的分析发现,在高应力低寿命区,A1-7Si-0.3Mg合金试样的表面划痕和缺陷造成了材料的表面破坏模式;而在低应力高寿命区,试样内部近表面区的铸造孔洞则是引起材料疲劳破坏的主要原因。使用Paris公式推导出孔洞尺寸和疲劳寿命之间的关系,并计算出不同应力水平条件下的临界孔洞尺寸。     

Schwingbruchstrukturen an faserverstärkten Kunststoffen

Structures of Fatigue Fractures in Fibre-Reinforced Plastics The report deals with macrofractographic and microfractographic structures in non-reinforced epoxide resins as well as in glass-fibre reinforced plastics and carbon-fibre reinforced plastics after fatigue stresses. Epoxide resins show fatigue striations and fracture lines similar to those in metals. The distance between the fatigue striations amounts to between 0.70 and 150 m?m and increases continuously in the direction of fracture propagation. The instantaneous fractures in non-reinforced resin show parabolic cusps besides Wallner-lines and lance-shaped structures. Surfaces of delamination fractures of glass-fibre reinforced plastics show fatigue striations which are characteristic for fibre-reinforced composites, but their morphology differs from the fatigue striations in non-reinforced resin. This was the first time that fatigue striations could be discovered in fibre-reinforced composites of a fibre content of 70 per cent by volume. These fatigue striations are strongly marked at the positions of the fibres and will probably arise only in case of a sufficiently high local stress intensity. Moreover, the amounts of the local slicing and shearing stress components, of which is composed the stress causing the fracture, could be partly responsible for the formation of fatigue striations. The formation of the fatigue striations allows to draw conclusions with respect to the fracture-causing local stress distribution and the local crack propagation in fibre-reinforced plastics. The surfaces of instantaneous fractures in glass-fibre reinforced plastics and carbon-fibre reinforced plastics show parabolic cusps. This is another distinguishing characteristic as compared with the surfaces of fatigue fractures.     

皮卡车钢板弹簧断裂分析

通过断口分析、化学成分分析、金相检验和硬度测试对皮卡车的钢板弹簧断裂的原因进行了分析。结果表明:钢板弹簧表面存在凹坑造成了应力集中,而且板材的非金属夹杂物超标,降低了疲劳强度,在交变应力载荷的作用下,最终造成钢板弹簧发生了早期疲劳断裂。     

船舶动力装置高温高压管道破前漏分析

将破前漏（LBB）方法运用于船舶动力装置高温高压管道的安全分析。探讨由于水下冲击、摇摆、温度和内压变化引起的管道载荷特性。以典型π型管道为研究对象,统计出疲劳应力谱。基于断裂力学理论和有限元方法,预测管道表面裂纹疲劳扩展行为,确保管道在运行期间不发生泄漏。采用J积分撕裂模量汇交法计算管道穿透裂纹的临界裂纹尺寸,并与最小可监测裂纹尺寸比较,确保即使发生泄漏,也有足够的安全余量在裂纹被发现前不发生失稳断裂。研究表明:尽管摇摆产生的管道交变应力幅较小,但循环次数高,对裂纹扩展的影响不可忽略;在水下冲击载荷作用下,管道承受最大应力,最有可能导致裂纹失稳扩展。     

汽车板簧的断裂分析

汽车板簧在路试中出现早期疲劳断裂。采用化学成分分析、硬度测试、断口分析和金相检验等方法对断裂的汽车板簧进行了分析。结果表明,焊接时,飞溅的熔滴在板簧表面形成烧伤坑并形成淬火马氏体及淬火裂纹,在路试中产生应力集中而成为疲劳源,在交变应力作用下使裂纹扩展而最终断裂。     

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.     

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。     

抽油杆用钢的腐蚀疲劳性能分析

对三种抽油杆用钢试样在清水介质中进行了旋转弯曲疲劳试验，测定了这三种钢的腐蚀疲劳极限，绘出了P-S-N曲线，并进行了综合性的分析。测试结果表明，在清水介质条件下它们的疲劳强度值相近且偏低。     

Analysis of the fatigue failure of a mountain bike front shock

We present an analysis of a mountain bike front shock failure. The failure of the 1-year-old shock occurred catastrophically as the bike was ridden off of a 1-m drop. The failure was the result of fast fracture through both shock tubes at the location where the tubes were press fit into the shock upper crown. Examination of the fracture surfaces of the tubes revealed regions of fatigue crack growth that nearly penetrated the entire thickness of both tubes. An estimate of the forces during use, coupled with stress analysis, revealed three stresses near the fracture site—axial compression, bending, and hoop stresses. During operation, the axial compressive stress is negligible while the hoop and bending stresses are significant. Based on fracture mechanics, and an estimate of the bending stress from a 1-m drop, it is confirmed that the fatigue cracks present on the fracture surface were large enough to induce fast fracture. Prior to the existence of the fatigue cracks, the stresses were magnified locally near the fracture site by a significant stress concentration caused by the sharp transition from the shock tube to the crown. The fatigue cracks initiated at a circumferential location in the tube commensurate with high tensile bending stress and the stiffest region of the crown (highest stress concentration). Based on the evidence, the most probable cause of the bike shock fatigue failure was the shock design, which facilitated high local stresses during use.     

储液筒吸气管断裂分析

通过化学成分分析、宏观检验、金相检验和断口分析等方法分析了压缩机储液筒吸气管根部断裂的原因。结果表明:储液筒吸气管在外加大应力作用下产生了低周疲劳断裂;二次焊接时导致的晶粒粗大降低了吸气管的抗疲劳性能。