紫铜焊接脆化原因分析

通过对材料的金相组织和断口的SEM观察,对压缩机贮液罐用铜导管的脆断进行了分析,认为铜管氧含量过高,钎焊时被C2H2还原是造成脆化的重要原因。     

Inconel 625合金波纹管失效分析

采用化学分析,透射电子显微镜(TEM)、X射线光电子能谱仪(XPS)和扫描电子显微镜(SEM)等微观测试手段对失效波纹管化学成分、力学性能、断口腐蚀产物及断口微观形貌进行综合分析。研究结果表明,波纹管的失效是材料在腐蚀性环境下局部高应力处首先发生高温氧化、硫化腐蚀,产生疲劳裂纹源,在交变应力的作用下发生腐蚀疲劳而造成的。通过降低腐蚀和波纹管应力可以防止或减轻腐蚀疲劳发生,延长波纹管使用寿命。     

三相分离器失效分析研究

分析了三相分离器失效的原因，认为造成该分离器失效的主要原因为沟状腐蚀。阐述了沟状腐蚀发生的原因及过程，最后提出了防止该类分离器失效的措施及方法。     

泵体端盖螺栓失效分析

以某企业HWD100-400燃料油泵端盖的紧固螺栓为研究对象,介绍了紧固螺栓的服役条件及常见失效形式,并通过宏观形貌分析、化学成分测试、金相组织分析、硬度测试分析等分析方法,分析了该紧固螺栓断裂的原因。结果表明,紧固螺栓在安装时预紧力过大,而产生的应力集中造成该紧固螺栓失效。     

Failure Analysis on Diesel-Engine Valve Springs

A diesel engine used in a truck had a trouble when servicing. Inspection indicated that four exhaust and intake valve springs and two exhaust and intake valves were fractured. Fractographic studies indicated that fatigue fracture is the main failure mechanism for all of the four valve springs. Under the action of the maximum normal stress, the fatigue crack initiated in the spring wire of coil 1.3-1.5 from the upper end of the spring. This region is also the most damaged location by contact friction wear. The fracture of the intake and exhaust valve stems also suggests fatigue failure probably as a result of the failure of the associated valve springs.     

翅片管路焊接接头断裂原因分析

通过KYKY2800扫描电镜等技术手段对翅片管路焊接接头进行失效分析。分析表明,焊缝与2#环管的焊趾处存在有不连续的咬边,造成应力集中;在交变应力的作用下于咬边处产生微裂纹,并沿一定方向扩展（同时材料的不均匀性也为裂纹的扩展提供了有利条件）,直至最后疲劳断裂,造成失效。最后提出了预防措施。     

摆动凸轮失效分析

采用化学成分分析、硬度测试和断口分析等方法分析了某载重车辆钢摆动凸轮断裂的原因。结果表明：摆动凸轮断裂是由于回火脆而导致的脆性断裂。     

宝钢冷轧1550电镀锌机组导电辊失效分析

宝钢1550电镀锌机组导电辊表面筒体使用的是哈氏合金材料。在长期使用过程中哈氏合金的焊缝腐蚀和开裂,是导电辊最大的问题。因此,本文主要对采用填丝TIG焊的导电辊哈氏合金筒体的失效进行了分析,揭示了其产生应力腐蚀开裂并最终导致失效的原因,为采取相应的改进措施,提高导电辊焊缝的抗蚀性提供理论依据。     

S135钻杆内螺纹接头胀扣失效分析

本文对某油井发生的Ф127mmS135钻杆内螺纹接头胀扣失效事故进行了调研，并对其胀扣失效原因进行分析。结果表明，钻杆接头的材质符合行业标准要求；钻杆内螺纹接头胀扣失效的原因是外螺纹接头密封台肩面倒角直径过小，井下钻柱扭矩过大。内螺纹接头密封台肩面承受的接触压力超过材料屈服强度，导致内螺纹接头密封台肩面下陷，外螺纹接头密封台肩面进入内螺纹接头镗孔段，致使内螺纹接头发生胀扣失效。     

Failure analysis of impeller made of FV520B martensitic precipitated hardening stainless steel

This paper presents the failure analysis of a centrifugal compressor impeller. The impeller made of FV520B martensitic precipitated hardening stainless steel, fractured after service for 4 months in moist H₂S condition. Efforts were made to analyze the failure impeller in both experiment and FE methods. Sulfide Stress Cracking (SSC) was the primary failure mechanism for this investigated impeller. The martensite structure, the H₂S medium, and the applied stress consisted of the SSC system. This paper exhibits the details of investigation and suggests remedial measures to improve performance of this type impeller under H₂S corrosive environment.     

Failure Analysis of a High-Pressure Component

Martensitic stainless steel nuts were received for failure analysis. A few of these nuts cracked at the immediate stress loading while the others fractured after 2 years of service. These nuts were subjected to different metallurgical tests such as visual examination, optical microscopy, chemical analysis, hardness testing, and fractography. It was concluded that improper heat treatment weakened the structure and subsequently fractured on the application of load.     

A View on the General Practice in Engineering Failure Analysis

Analysis of engineering failures is a complex process that requires information from personnel having expertise in many areas. From the information gathered, a failure analyst tries to discover what was fundamentally responsible for the failure. This fundamental cause is termed the “root cause” and helps in the determination of the sequence of events that led to the final failure. Root cause analysis also helps in finding solutions to the immediate problem and provides valuable guidelines as to what needs to be done to prevent recurrence of similar failures in future. However, experience suggests that most failure analyses fall short of this goal. A significant number of failure analysts incorrectly use the term “root cause” when what they really establish is the primary cause of failure or simple physical cause. This paper examines a few service failures to demonstrate that the term root cause is not adequately understood.     

锅炉顶棚过热器管开裂原因分析

对某热电厂3号锅炉的无损探伤检查,发现该炉部分顶棚过热器管的背火面上存在裂纹。通过对过热器管的裂纹形貌、化学成分、金相组织和断口等的分析,确认3号锅炉顶棚过热器管的开裂失效性质属于热疲劳破坏。     

Premature Failure in Orthopedic Implants: Analysis of Three Different Cases

The increasing lifetime of the population on a world-wide scale over the last decades has led to a significant growth in the use of surgical implants for replacement of bones and teeth in affected patients. Other factors, such as scientific-technological development and more frequent exposure of individuals to trauma risk, have also contributed to this general trend. Metallic materials designed for applications in surgical implants, no matter whether orthopedic or dental, must show a group of properties in which biocompatibility, mechanical strength, and resistance to degradation (by wear or corrosion) are of primary importance. In order to reach these aims, orthopedic materials must fulfill certain requirements, usually specified in standards. These requirements include chemical composition, microstructure, and even macrographic appearances. In the present work, three cases of implant failure are presented. These cases demonstrate the most frequent causes of premature failure in orthopedic implants: inadequate surgical procedures and processing/design errors. Evaluation techniques, including optical and scanning electron microscopy (SEM), were used to evaluate macroscopic and microstructural aspects of the failed implants, and the chemical composition of each material was analyzed. These evaluations showed that design errors and improper surgical procedures of outright violation of standards were the cause of the failures.     

200系列不锈钢钢丝失效分析

本文应用扫描电镜、能谱分析、电子显微镜等多种分析方法,对201及200Cu两种不锈钢钢丝的断裂原因进行了研究分析。结果表明,由于200系不锈钢的奥氏体稳定性较差,较易发生晶界腐蚀,在拉制过程中因所受应力不均匀,导致微裂纹产生,在随后的多次拉拔工艺中发生扩展开裂。     

二氯乙烷管线腐蚀失效分析

采用宏观分析,金相分析,硬度检测,扫描电子显微镜分析,能谱分析及X射线衍射分析等多种方法对某氯碱厂二氯乙烷输送管线爆裂泄露的原因进行综合分析。结果表明：管线三通处介质流向发生突变,使管壁受到严重的冲刷腐蚀作用,是管线失效的主要原因。物料中含有水分,与二氯乙烷反应得到氯化氢,加剧管线腐蚀。钢材本身存在一定的冶金缺陷易引发局部腐蚀。Cl^-在腐蚀坑处富集可加剧局部腐蚀。     

Failure Analysis of a Location Axle in Tracked Tractor

In this study, a failure analysis was performed on the location axle (brace axle) of a blade on a tracked tractor used in agricultural areas. The analysis included evaluation of the macrostructure of the damage and the microstructure of the material, as well as a chemical analysis of the material. A commercial finite element method software package was used to determine the behavior of the location axle under the defined boundary conditions. After all the examination steps were completed, the main reason for the damage was determined to be manufacture and material error despite the presence of fatigue tracks in the damaged area. In addition, a heat treatment was carried out with the specimens taken from the damaged area and microstructure was re-examined. The experimental and simulation evaluation results provide a technical basis for suggestions to prevent future damage to the location axle.     

Failure Analysis of Ethylene Cracking Tube

Radiant tubes of an ethane furnace at a petrochemical plant fabricated from an austenitic heat resistant steel casting (HP grade) failed along longitudinal direction after a fraction of anticipated service life. To study the cause of failure, microstructures of as-received and used tubes were investigated by optical and scanning electron microscopy and the microchemical composition of tubes and precipitated carbide were determined by energy dispersive X-ray (EDS). Also, the morphology of deposited coke particles was determined by SEM/EDS. Finally to measure the extent of carbon penetration, hardness testing was performed on the inner and outer surface of tube. The experimental results show that the improper coking and decoking cycles remove the protective oxide layer (Cr₂O₃) that forms on the exposed surfaces and that, with this layer removed, the coke could easily deposit on inner, non-protected surface. The carbon diffusion into the metal was accelerated with deposited coke and caused microstructural degradation and drastically reduced the ductility of material at high temperatures.     

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.     

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.