Inconel 625波纹管高温疲劳公式的建立

通过高温疲劳试验,得到了Inconel 625材料波纹管720℃时的高温疲劳公式,同时对EJMA标准附录G中的高温疲劳公式算法提出了改进。最后利用推导出的高温疲劳公式对现有的设计做出了评价,并对实际工程提出了建议。     

大型高炉煤气重力除尘波纹管的失效分析

利用光学显微镜、扫描电镜和电子能谱等测试手段,从微观组织、断口形貌以及腐蚀产物成分等角度,分析了某大型高炉煤气重力除尘波纹管开裂失效的原因.结果表明,波纹管的失效是由于应力腐蚀开裂所致.提出了两方面的改进措施,即通过改进波纹管波形参数以增加疲劳寿命,以及通过改进波纹管材料以增加波纹管耐腐蚀性能.     

DHB型补偿器波纹管开裂失效分析

用金相显微镜，扫描电镜，俄歇电子能谱对补偿器波纹管开裂失效分析，结果表明：较高的氯离子浓度，残余应力和工作应力的叠加，是造成波纹管应力腐蚀开裂的主要原因。安装补偿器时，预先经冷紧处理，可降低波纹管因膨胀造成的工作应力，延长使用寿命 。     

321不锈钢焊接波纹管失效分析

应用光学显微镜、扫描电镜和能谱仪等手段对321不锈钢焊接波纹管表面腐蚀物的化学成分、焊缝区域的显微组织、腐蚀裂纹的形态特征等方面进行检验和分析。结果表明，波纹管局部电镀端内壁腐蚀导致漏气失效，即加工应力、焊接残余应力与含Cl^-或含Cl^-和溶解氧的腐蚀性介质的联合作用使波纹管局部电镀端产生了点蚀和应力腐蚀开裂；退火工艺设计的不合理和钎焊工艺控制不恰当使焊缝热影响区敏化而出现了晶间腐蚀。据此提出了降低和避免321不锈钢焊接波纹管因腐蚀而漏气的措施。     

Incoloy 800波纹管膨胀节开裂失效分析

金属波纹管膨胀节具有热补偿功能,应用越来越广,同时其失效开裂问题也日益显现.为此,从宏观形貌、化学成分、金相显微组织、SEM微现形貌方面,对开裂的Incoloy 800波纹管膨胀节进行了分析.结果表明,波纹管膨胀节开裂的原因是高轴向拉应力条件下的材料失稳破裂,并提出了相应的改进措施.     

城镇供热管网波纹管腐蚀失效及预防措施研究现状

随着波纹管补偿器在热力工程中的广泛应用,作为核心元件的波纹管的腐蚀失效也受到关注.结合部分波纹管失效案例,综述了城镇供热管网不锈钢波纹管常见的腐蚀失效形式及影响因素,并从不同角度总结了对供热波纹管腐蚀失效的预防措施.最后指出了目前对波纹管腐蚀失效研究的局限性与不足,以期对未来波纹管的腐蚀性能研究方向提供思路和参考.     

S135钻杆失效分析

采用扫描电镜、电子探针以及光谱仪等手段对某油田S135钻杆的刺穿失效进行了分析.结果表明,因氯离子在钻杆表面形成点蚀,在应力作用下引发腐蚀疲劳开裂形成刺穿造成钻杆失效,提出了相关预防措施.     

石油钻杆失效分析

钻杆是石油钻柱的三大部分组成之一,是石油钻井的重要工具,服役条件十分恶劣。在钻井过程中,钻杆在任何部位失效都会造成严重的后果,甚至使井报废。所以钻杆失效事故频繁,损失巨大,对石油生产和安全造成了严重影响。本文就钻杆失效现象及原因进行了简要分析。     

安全阀用弹簧断裂失效分析

某安全阀用弹簧在使用半年后断裂，对失效弹簧进行了理论检验，检验结果表明，弹簧断裂的性质为腐蚀疲劳，断裂过程为腐蚀疲劳起源并放源，裂纹扩展到一定长度后快速断裂；弹簧断裂的原因是由于腐蚀作用的存在和材料抗疲劳性能较差所致，建议加强密封，以防工作介质进入弹簧所在的位置。     

有限元在波纹管稳定性分析中的应用

本文简要介绍了结构稳定性理论和有限元屈曲分析理论,通过建立波纹管材料简化模型和有限元模型,对不同单元模型下的波纹管进行内、外压屈曲分析,并对结果与实验值进行了分析。     

波纹管膨胀节实际应用中的腐蚀分析与防护对策

腐蚀破坏是波纹管膨胀节失效的一个重要原因。通过对催化裂化装置用波纹管膨胀节及城市区域供热用外压波纹管膨胀节的腐蚀破坏情况进行分析 ,探讨其腐蚀机理 ,提出了相应的防护对策。     

DN50不锈钢波纹软管开裂失效分析

通过宏观检验、扫描电镜观察以及X射线能谱分析等手段,对某304奥氏体不锈钢DN50波纹软管开裂原因进行了分析。结果表明:软管开裂是由于腐蚀疲劳所致,软管的管壁内、外表面在腐蚀介质和外界应力的综合作用下产生沿晶微裂纹和蜂窝状腐蚀形貌,并受到交变应力作用,因而发生双向多源疲劳开裂失效。     

疲劳损伤对波纹管耐连多硫酸腐蚀性能的影响

针对催化裂化装置用波纹管使用中所面临的连多硫酸应力腐蚀问题,采用热态连多硫酸腐蚀模拟装置,试验研究了固溶态Incoloy825波纹管的耐连多硫酸应力腐蚀性能,并利用金相显微镜、SEM、EDX等手段分析了腐蚀波纹管的表面形貌和断口特征,探讨了设计疲劳寿命及累积疲劳损伤对波纹管连多硫酸应力腐蚀敏感性的影响规律。结果表明,在60℃的H2SxO6溶液中,设计疲劳寿命及累积疲劳损伤对固溶态Incoloy825波纹管的腐蚀敏感性影响显著。设计疲劳寿命越低、累积疲劳损伤越大,则越易形成应力腐蚀裂纹。     

多层焊接不锈钢波纹管开裂失效分析

针对某电厂多层焊接不锈钢波纹管发生开裂的情况,采用宏观观察、能谱分析、金相检验、显微硬度测试等方法,分析了波纹管开裂的原因。结果表明:波纹管的失效形式为疲劳开裂,失效原因为纵焊缝余高超标,加大了该部位的塑性变形和硬化程度,降低了抗疲劳性能,柴油机运行中波纹管的振动诱发了疲劳开裂。     

Failure analysis of an AM 350 steel bellows

The failure of an AM 350 steel bellows, which was to be used in the control rod drive mechanism (CRDM) of the fast breeder test reactor (FBTR), was noticed during helium leak testing. The leak test was carried out before performance testing in a test rig. Visual examination of the leak area did not indicate any obvious defect. Stereo microscopy and optical microscopy indicated the presence of pits. A few of these pits had propagated through the thickness. EDAX of the corrosion products revealed the presence of chlorides. The exposure of the bellows to a marine atmosphere during a storage period of 13 years was suspected to have caused the pitting.     

Failure Analysis of a Steel Motorcycle Kickstand

A fractured steel motorcycle kickstand was metallurgically investigated using a range of failure analysis tools [visual examination, energy dispersive X-ray (EDX) analysis, electron microprobe analysis (EPMA), scanning electron microscopy (SEM), fractography, optical microscopy, hardness testing and non-destructive testing (NDT)]. The steel kickstand’s composition, its microstructure, electron fractographs, and mechanical test results have been critically interpreted. Some evidence of wear damage, in the failed kickstand, was observed. The microstructural and fractographic analyses showed pre-existing micro-cracks which were believed to have grown to result in ductile failure followed by acceleration of corrosion. Recommendations have been made to avoid the failure of the motorcycle kickstand.     

Failure analysis of bursting on the inner pipe of a jacketed pipe in a tubular heat exchanger

In order to identify the causes of a bursting incident that occurred on the inner pipe of a jacketed pipe in a tubular heat exchanger for synthesis of high pressure polyethylene, series of characterization analysis were conducted. Metallurgical structure and chemical composition of the pipe’s metal matrix were inspected by metallographic microscope (MM) and photoelectric direct reading spectrometer; scanning electron microscope (SEM) and energy dispersive spectroscope (EDS) were applied to observe the microscopic morphology and micro-area composition on the ruptured surface; compositions of the coolant, i.e. the circulating cooling water were examined by inductively coupled plasma-atomic emission spectrometry (ICP-AES), ion chromatography (IC) and Fourier transform infrared spectroscopy (FTIR). In addition to these, finite element analysis (FEA) was employed to study the erosive effect of on the pipe. Analysis results revealed that interaction between corrosion and erosion both led by scaling, was the main cause that accelerated its thinning and eventually resulted in its premature failure. Finally countermeasures and suggestions were proposed.     

Failure analysis of the conical press-fit connections in a locomotive drive system

The nose-suspension drive designs with overhanging pinion are commonly applied in freight electrical locomotives because of simple, space-saving and cost-effective. The failures of conical press-fit connections in a nose-suspension drive system are analyzed in this paper. It was showed by the analysis that the crack on the inner conical surface of motor shaft is initiated by the combination of fretting and corrosion. Sharp oil groove edge and emergency of crack at the mouth of radial oil hole in pinion will accelerate the formation of fretting wear groove, and consequently the initiation of cracks. Coexist of tensile normal stress under the contact surface within the fretting zone will benefit the propagation of the fretting fatigue cracks.