Failure Analysis of a Gas Well Tubing due to Corrosion: A Case Study

In this study, failure analysis of a gas tubing string was investigated. Visual inspection of the tubing string showed that some of the tubings were corroded locally at pin thread ends, which resulted in abrupt replacement. In order to determine the cause of failure, chemical composition, mechanical strength, Charpy impact, and hardness, and microstructures of the corroded and non-corroded pins were investigated. The chemical composition of the tubing material was found to be API 5CT Grade C-75-2. The samples taken from the body of both the corroded and non-corroded tubings showed the same impact energy, yield strength, ultimate tensile strength, and elongation. In addition, the hardness of the body and thread ends of tubings were the same except for corroded tubings, which showed locally more hardness at thread region. Our analyses indicate that cold working the tube strings, during the make-up process in the field, caused localized corrosion of the male pins.     

Lamellar Tearing: A Failure Case Study

A variety of materials are used in the Oil & Gas industry ranging from carbon steel, stainless steel to nickel alloys, etc. including non-metallic materials as well. Amongst these, carbon steel is the industry favorite because of many of its desirable attributes like machinability, weldability, availability, and cost. Wide use of carbon steel in the industry is also due to the presence of required properties for the specific application. In spite of carbon steel’s wide uses, poor workmanship, improper heat treatment, or negligent manufacturing processes can reduce its service life and also can lead to unexpected failures. One such failure case involves carbon steel plate meant for construction of a tank that failed by cracking immediately after the welding operation. A detailed investigation was carried out by means of visual examination, metallographic and chemical analysis, SEM, and EDAX analysis. Microstructure revealed banded pearlitic structure along with a number of inclusions, a few of which were elongated. In conclusion, stresses due to weld joint restraint, elongated inclusions, and high transverse direction stresses after welding resulted in lamellar tearing which propagated in the linear direction along the weld line.     

Failure Analysis Case Study on a Fractured Tailwheel Fork

A failure analysis investigation was conducted on a fractured aluminum tailwheel fork which failed moments after landing of a privately owned, 1955 twin-engine airplane. Non-destructive evaluation via dye-penetrant inspection revealed no discernible surface cracks. The chemical composition of the sand-cast component was identified via optical emission spectroscopy and is comparable to an aluminum sand-cast alloy, AA 712.0. Metallographic evaluation via optical microscopy and scanning electron microscopy revealed a high degree of porosity in the microstructure as well as the presence of deleterious intermetallic compounds within interdendritic regions. Macro-hardness testing produced hardness values which are noticeably higher than standard hardness values for 712.0. The primary fracture surfaces indicate evidence of mixed mode fracture, via intergranular cracking, cleaved intermetallic particles, and dimpled cellular regions in the matrix. The secondary fracture surface demonstrates similar features of intergranular fracture.     

一起流动式起重机倾覆事故的技术分析

本文通过介绍一起流动式起重机的倾翻事故及其原因分析,探讨在起重机安装中两台流动式起重机吊运主梁时事故隐患,得出了起重机倾覆事故原因及预防措施,对于杜绝流动式起重机倾覆事故的发生,减少人民生命财产的损失,有着重要的实际意义。     

Failure Analysis of Wire Rope Used for Hoisting in Mining: A Case Study

Wire ropes are used in vast range of applications and many of the applications are safety critical. In the mining industry wire ropes are extensively used for hoisting/haulage. Due to the hostile operating load conditions, many wire ropes degrade in service. Fatigue of wires in rope in combination with other detrimental factors is frequently responsible for rope deterioration and premature failure during operation. In this paper the causes of failure of a wire rope used for hoisting in an Indian mine are determined with only a minimum level of information provided by the customer. Samples of the failed rope were obtained and analyzed and potential remedial measures to prevent such degradation are discussed. Reprinted with permission from Proceedings of AIME 2006, held on January 20–21, 2006 organized by Jamia Milia Islamia (a central university) New Delhi-110025, pp. 122–132.     

Corrosion Failure in the Sugar Industry: A Case Study

Pitting corrosion of structural steel used in an evaporator vessel for the sugar industry has been investigated. A significant number of inclusion stringers and a banded microstructure in the ordinary mild steel used were main reasons the pitting initiated. A low-carbon (0.08% C max) copper-bearing structural steel processed by a modified rolling practice that included intensive cross rolling was developed to minimize the incidence of pitting in such vessels.     

A Case Study on Fatigue Failure of a Transmission Gearbox Input Shaft

In this paper, a root cause analysis of premature failure of a gearbox input shaft, manufactured of AISI 1045-H, was performed through standard procedures for failure analysis. Shaft failed on cross oil hole through a helical fracture and therefore did not meet bogie 100,000 cycles during the verification with 10 Hz frequency cyclic testing. The fracture in the oil hole implied evidence of fatigue (i.e., beach marks on the fracture surface were clearly visible). Prior to improving the fatigue life and suggesting required remedial actions, mechanism of failure has to be understood, especially the initiating point of cracking. To this end, chemical analysis, microstructural characterization, fractography, hardness measurements, and finite element simulation were used to assess the nature of fracture in detail. The fractography analysis showed that fatigue beach marks originate from transition zone of the case on the cross oil hole. This is possibly due to the fact that torsional strength in this area is lower than torsional fatigue strength which leads to fatigue crack initiation, crack growth, and final fracture. At the end of this paper, proper remedial actions have been proposed.     

Maintenance Error Detection Procedure and A Case Study of Failure Analysis Locomotive Diesel Engine Bearings

Journal of Failure Analysis and Prevention - This paper presents a maintenance error detection algorithm. Proposed algorithm is used to determine failure analysis of a locomotive...     

通用桥式起重机钢丝绳断裂失效分析

为查明某玻璃厂一台通用桥式起重机钢丝绳断裂导致货物坠落的事故原因,对断裂的钢丝绳进行了理化检验,并对钢丝绳滑轮组和防跳绳安全保护装置的结构进行了分析。结果表明：钢丝绳断裂为挤压磨损致使钢丝绳不能承受较大载荷而产生的一次性大应力断裂,导致事故的直接原因是防跳绳安全保护装置的结构设计存在严重缺陷,使钢丝绳脱出滑轮槽在轴衬套上运行,产生较大的滑动摩擦力,使钢丝绳磨损变形。     

塔机提升系统输入齿轮失效分析

通过宏观检验、化学成分分析、非金属夹杂物检验、硬度测试以及金相检验等方法,对塔机提升系统输入齿轮失效的原因进行了分析。结果表明：该输入齿轮损坏属于接触疲劳失效,趋网状分布的铁素体降低了材料的硬度、耐磨性和疲劳寿命,是造成齿轮早期失效的主要原因。同时提出了预防控制措施。     

A Failure Mode Effect and Criticality Analysis of Conventional Milling Machine Using Fuzzy Logic: Case Study of RCM

The purpose of this paper is to select the appropriate maintenance strategies for each failure mode of functionally significant item of conventional milling machine. In order to describe the criticality analysis of conventional milling machine, this paper presents a study on reliability‐centered maintenance with fuzzy logic and its comparison with conventional method. On the basis of fuzzy logic, failure mode and effect analysis is introduced integrating with fuzzy linguistic scale method. After that, weighted Euclidean distance formula and centroid defuzzification is used for calculating risk priority number. The results indicate that based on risk priority number, value criticality ranking was decided, and appropriate maintenance strategies were suggested for each failure mode. It also reflects that a more accurate ranking can be performed by the application of fuzzy logic using linguistic rule to failure mode and effect analysis. Copyright © 2016 John Wiley & Sons, Ltd.     

Statistical Analysis of Geometrical Tolerances: A Case Study

Tolerancing is one of the most important but complex activities in design. Tolerance information takes place at every phase of design activity. It represents the fundamental link between the theoretical model of the mechanical product and the actual one. During the two previous decades, engineering projects and scientific researches demonstrated that ongoing miniaturization increased the influence of geometric tolerances. They also admit that mass production is mainly based on statistical techniques. On the other hand, the decomposition of the global tolerancing process into functional-level, assembly-level, part-level, and manufacturing-level, reduces dramatically the domain of the solution. In this paper, the global tolerancing process is described and a novel method for statistical analysis of geometrical tolerances is discussed. Then the statistical approach is introduced and its performance is evaluated on a best case study. The analysis of the technical drawing of a part is given in order to highlight the advantages of the statistical approach.     

弹壳开裂失效分析

对某型H68黄铜弹壳进行检查时发现大量弹壳存在裂纹。通过对弹壳进行宏观和微观观察、能谱分析、金相检验和残余应力测定等,分析了弹壳开裂的原因。结果表明:弹壳的开裂性质为应力腐蚀开裂,其原因是由于收口位置存在一定的残余拉应力,且该位置的晶粒尺寸较大,在外界介质的协同作用下产生了应力腐蚀裂纹。     

Design and Analysis of Storing Experiments: A Case Study

In order to achieve robust and stable food products of desired quality and characteristics, all stages of the food production process, including storage conditions, should be considered during product development projects. This article describes a multistage production development project on low-fat mayonnaise, where experimental design was used to set up a pilot plant study involving ingredient factors, processing factors, and storage factors and their effect on mayonnaise viscosity. The article discusses three alternative empirical modeling approaches to analyze the data—namely, a simple graphics approach, a robustness approach, and a mixed models approach—considering their multistratum (split-plot) structure and repeated measurements of each subsample. In the case study, all information relevant for business decisions was obtained through the combination of graphical analysis and the robustness approach. This information could also be extracted by a practitioner, while the mixed model analysis clearly requires a graduate statistician. In order to obtain valid and useful information for the practitioner in an efficient way, the authors believe that, usually, the first two approaches would be sufficient. The more complex mixed model strategy might be advisable if a deeper understanding is required or desired.     

大块式动力基础的振动分析与加固处理

根据一大块式曲柄连杆机构的机器钢筋混凝土基础的振动测试与振动分析 ,诊断了基础发生工程事故的原因 ,并结合工程特点 ,在不改变基础设计的动力参数的情况下 ,确定了灌浆加固处理方法 ,并介绍了灌浆加固处理的效果。     

Learning from a Drastic Failure: The Case of the Airbus A380 Program

How do organizations learn from a drastic failure? We distinguish between ad hoc and systematic reactions and discuss their effectiveness for dealing with two basic challenges: (1) identifying and solving the problems that caused the failure; and (2) changing the organization accordingly. We apply this conceptual perspective to illustrate the dynamics of learning from the drastic failure that occurred during the development of the Airbus A380 “superjumbo.” Our findings echo extant observations that efforts to redesign organizational behavior in an ad hoc manner are often insufficient. Instead, the organizational system must provide scaffolding that allows experiencing a critical event in a rich and systematic manner. When seen from a dynamic perspective, however, we find that even imperfect ad hoc efforts may play a vital role. By enforcing changes, providing stability, and raising awareness, they can act as a helpful prelude to more systematic problem solving and change.     

镀硬铬故障一例

阳极处理(反向腐蚀)是镀硬铬的一道极为重要的工序。有的单位镀硬铬镀槽所用整流器无换向(倒顺)开关装置,对工件不进行阳极处理。在这样的设备、工艺条件下,能否镀得结合力良好的铬层,本文就此进行了探索。 某乡镇企业的电镀车间,新增镀硬铬业务。首批试镀样品50件,经磨削加工,发生30余件不同程度的壳皮(崩铬),其余所谓合格,实际上也存在结合力不好的隐患。另外,整个镀层外观无光泽且粗糙。 笔者应邀去考察发现,该车间增设的镀硬铬生产线是凭多年镀装饰铬经验自建的:(1)镀槽为水泥结构,以3mm厚的塑料作内衬,其容积约180 L;(2)电源为1000 A整流器,以新、旧各1台电源串联使用,其输出线路与装饰镀铬一样直通槽体,而无换向开关装置;(3)镀液为250 g/L铬酸的传统配方,以普通铁质电热管加温;(4)镀前用洗衣粉(浸湿)手工去油及清洗;(5)槽温为40～45℃;(6)施镀时阴极电流密度约20A/dm~2(开始)到35A/dm~2(正常);(7)时间为1.5 h左右,镀层厚度要求30μm。