Case Studies in Engineering Failure Analysis

A peculiar type of edge discoloration defect on the surface of some galvanized fuel tank was observed, causing significant appearance problems. In the present study, the surface defect was characterized by visual inspection, optical microscopy, scanning electron microscopy and energy dispersive spectroscopic analysis to understand the source and mechanism of the defect. In the visual inspection, these peculiar surface appearances were observed in fuel tank at three distinct locations. The SEM examination exhibited two distinct regions on the surface apart from the normal galvanized surface: (1) galvannealed, (2) mixture of galvanized and galvannealed texture. The energy dispersive spectroscopic analysis of galvannealed region indicated enrichment of Zn and Al whereas in the region of galvanized majorly Zn was observed. Surface texture of galvannealed region showed majorly zeta crystals along with skin pass marks; whereas no such zeta crystals were observed in case of galvanized regions. Based on the preliminary results, the following hypothesis was made: Coil processed during galvanizing to galvannealing transition. Thickness and width changed to wider and thicker section, which resulted into lower line speed. Due to the lower Al content, lower speed and thicker section combination resulted in formation of partial GA in the coil owing to the internal heat content of the coil. This paper presents the results of the investigation.

Jitendra Mathur

Hrishikesh Jugade

Shomick Roy

Souvik Das

Sandip Bhattacharyya

Failure analysis of edge discoloration of galvanized fuel tank

镀锌油箱边缘变色失效分析

In this work we present a technical description related to the rupture of a titanium alloy pedicle screw and connecting bar implanted in dorsal vertebras of a patient. Only metallurgical facts are described, with no attempt to identify any imperfections in the clinical aspects related to the rupture. The results described here are based on extensive analysis of the broken materials in a material sciences specialized laboratory. Excluding an incorrect prosthesis implantation in the surgical procedure and a possible low bone density, an information not available to the research team, with high probability the rupture of metallic pieces used in the prosthetic implant, was produced by the low fatigue resistance resulting by an improper machining process and excessive bending of the connecting bar prior to implant.

Giorgio E.O. Giacaglia

Wendell de Queiroz Lamas

Pedicle screw rupture: A case study

椎弓根螺钉断裂：病例研究

The analysis of an abnormal crack of a forging plate is presented in this work. The crack was found after forging process. Macro-analysis, SEM, composition inspection, metallographic analysis, inclusion analysis, EPMA and EDS were implemented. SEM shows that cleavage fracture is the main feature of the fracture surface, according to which it can be decided that the fracture is brittle fracture. XRF and carbon and sulphur analyzer indicate regular composition condition of the plate. EPMA and EDS suggest phosphorus segregation spread a lot around the crack. The results indicate that: brittleness caused by phosphorus segregation around crack zone is the main reason that cracks generate in the 12Cr13 steel during forging. As all we know, phosphorus has deleterious effect on toughness of steel because of its enrichment on grain boundaries, which can weaken the bond strength of grain boundary. Its existence should be avoided and microstructure of the steel should be homogeneous when good plasticity and toughness are wanted.

Wei-min Guo

Na Xu

Ning Ding

Jun-bo Shi

C.M. Lawrence Wu

An analysis of crack evolution of a 12Cr13 stainless steel during forging process

12Cr13不锈钢锻造过程中裂纹演化分析

Failure of a cracked steering wheel is studied in this paper. Steering wheel, mounted on a speed boat, had cracks emanating from one of the fastener holes until final fracture occurred. Failure analysis, combining experimental and numerical techniques, was performed. Experimentally, fasteners torque moments were measured, visual inspection performed and material type determined (aluminum alloy AA 6061). Additionally, scanning electron microscopy examination was employed to characterize the microstructure of the fractured surface. Using finite element analysis, stress analysis of a cracked steering wheel was conducted. Stress intensities of uncracked and cracked steering wheel were compared to find out about stress concentration points. Possible causes of crack occurrence include excessive fastener torque moment, fretting between fastener and hole combined with poor machining that left marks that serve as potential crack initiation points. Obtained results are valuable for predicting fracture behavior of the cracked steering wheel and can be taken as a reference for design and exploitation process of such component.

Goran Vukelic

Failure study of a cracked speed boat steering wheel

破损快艇方向盘的失效研究

Tyre bead grade wire is used for tyre making application. The wire is used as reinforcement inside the polymer of tyre. The wire is available in different size/section such as 1.6-0.80 mm thin Cu coated wire. During tyre making operation at tyre manufacturer company, wire failed frequently. In this present study, different broken/defective wire samples were collected from wire mill for detailed investigation of the defect. The natures of the defects were localized and similar in nature. The fracture surface was of finger nail type. Crow feet like defects including button like surface abnormalities were also observed on the broken wire samples. The defect was studied at different directions under microscope. Different advanced metallographic techniques have been used for detail investigation. The analysis revealed that, white layer of surface martensite was formed and it caused the final breakage of wire. In this present study we have also discussed about the possible reason for the formation of such kind of surface martensite (hard-phase).

Piyas Palit

Metallurgical investigation of wire breakage of tyre bead grade

轮胎钢丝断裂的金相研究

This paper relates to an upgraded Industrial tracked vehicle which was found with a failed Balance arm during disassembly. The failure analysis of an actual Balance Arms surface was carried out using Fractography and Non Destructive testing techniques to dig out the root cause. The analysis revealed microscopic signatures categorically pointing towards post failure surface mechanical damage. The factor causing to promote failure was improper manufacturing i.e. casting which was further attributed to MnS inclusions.

Ayaz M. Khan

Khalid Mahmood

Syed Waheed ul Haq

Rizwan Saeed Choudhry

Shahbaz Mahmood Khan

Root cause failure analysis of a tracked vehicle balance arm

履带车辆平衡臂的根因失效分析

In recent years, there has been a rise in the number of product liability cases involving the failure of toilet water supply line acetal plastic nuts. These nuts can fail in service, causing water leaks that result in significant property and financial losses. This study examines three possible failure modes of acetal plastic toilet water supply nuts. The three failure modes tested were all due to over load failure of the acetal nut and are as follows: (1) Overtightening of the supply line acetal nut, (2) Supply line lateral pull and, (3) Embrittled supply line lateral pull. Additionally, a “hand-tight” torque survey was conducted. The fracture surfaces and characteristics of these failure tests were examined with Stereo Microscopy and Scanning Electron Microscopy (SEM). The failure modes were compared and contrasted to provide guidance in determination of cause in these investigations.

Anthony Timpanaro

Ryan Scherzer

Orion P. Keifer

Paul D. Eason

Analysis of acetal toilet fill valve supply line nut failure

乙缩醛马桶补水阀供应管螺母失效分析

Inspection is one of the important activities to detect and fix failures in repairable system. Optimization of inspection intervals has critical role in maintenance cost and operating system. When a component fails, it is renewed or repaired. A great deal of periodic inspection research is for hidden failure and considered one of the perfect (renew) and minimal repair policies. In literature, the lack of simultaneous consideration of both perfect and minimal repair in reliability model has been observed. This study presents new reliability model by synchronous consideration of both minimal and perfect repair. As well as, the expected total maintenance cost is presented and modeled to figure out the optimal inspection interval. The proposed model is more comprehensive model in reliability evaluation and can be applied in different pertinent problems. The model is applied to steam turbine system which the rotor considered as soft component and filter as hard component. The result revealed that the system should be inspected every 12 month.

Esmaeil Rezaei

A new model for the optimization of periodic inspection intervals with failure interaction: A case study for a turbine rotor

故障交互作用下周期性检查间隔优化的新模型：涡轮转子案例研究

This paper presents the failure analysis of carbon steel roller shaft of continuous pad steam machine used in textile industry. The fracture position was located at a stepped diameter. The failed component was the shaft made of carbon steel AISI 1040. Standard procedure for failure analysis was employed in this investigation. Visual examination, chemical analysis, hardness and tensile strength measurements, microstructural characterization, fractography analysis by Scanning Electron Microscopy (SEM) and Finite Element Analysis (FEA) were used for the failure analysis. Using this failure analysis approach, we pinpointed the root cause of failure and developed a means of solving this type of failure in the future. Firstly, the chemical composition of the shaft is done by an Optical Emission Spectroscopy (OES) method, the found chemical composition was matching with required standard value. Mechanical testing consists of two test i.e. tensile test and hardness test and it was found out that the strength and hardness of specimens were within the required capacity. For metallurgical analysis, the microstructure of the shaft was developed by using an optical microstructure. Equal distribution of ferrite perlite shows that heat treatment was performed well and carbon percentage in a material is satisfying the standard values. Thus, it proves that the material used was of good quality and indicates that failure is not due to material property. Further for the fractography, the fractured surface was examined by SEM. The cross-section was taken in a quarter segments and divided into four regions i.e. A, B, C, and D. Fractography morphology mainly showed that the failure of roller shaft was caused due to fatigue. To examine the stress distribution at the fractured surface the Finite Element Method (FEM) was also carried out. Based on the shaft size, a precise ANSYS model was developed. The result of FEM shows that stress concentration was significant at roller shaft step which could reduce the material reliability to some extent. Based on the failure analysis it could be concluded that due to stress concentration a micro crack is initiated along the weak interface and further it converted into the major fatigue failure. Fractography morphology of failed roller shaft also confirms the fatigue failure.

Santosh D. Dalvi

None Hariom

D. Chandrababu

Sunil Satav

None Vijoykumar

Failure analysis of a carbon steel roller shaft of continuous pad steam machine

连续垫片蒸汽机碳钢滚轴失效分析

Rolling bearing is an important and fragile component in the wind turbine transmission system. The failure of rolling bearing is one of the highest risk events which may result in unexpected economic loss. To give a proper condition assessment of rolling bearing, especially for early fault detection, is of great importance and become an urgent issue to the wind energy industry. In this paper, sample entropy is studied through the field data of wind turbine transmission system measured from Lu Nan Wind Farm in China. Compared with several frequently used statistical indicators, sample entropy features advantages in detecting and evaluating the progress of the early faults of the rolling bearing. The studies show that the sample entropy is an effective and practical tool for condition monitoring of rolling bearing for a wind turbine transmission system.

Qing Ni

Ke Feng

Kesheng Wang

Binyuan Yang

Yu Wang

A case study of sample entropy analysis to the fault detection of bearing in wind turbine

风力发电机轴承故障检测的样本熵分析案例研究

出版信息	出版商: Elsevier Ltd，出版周期: ，期刊类型: journal，开源期刊: 否
基本数据	创刊年份: 2013，原创研究文献占比: ，自引率:， Gold OA占比:

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