Effect of Using CuO–Oil Nanofluid on Surface Roughness and Thermal Performance during Superfinishing Process

This research aims to investigate the effect of adding copper oxide nanoparticles to the oil Gr-6004 base fluid and its concentration changes from 0.1% to 0.4% on the surface roughness of gudgeon pin and the thermal conductivity of the nanofluids during the superfinishing process. The main novelty of this investigation is analyzing the impact of utilizing CuO/oil Gr-6004 nanofluid on thermal conductivity of oil and surface quality of gudgeon pin during superfinishing process. Based on the results, adding nanoparticles to the oil Gr-6004 has significantly reduced the surface roughness. In addition, by increasing the concentration of nanoparticles to 0.4%, the surface roughness has decreased by 57% compared to oil Gr-6004. Also, by adding nanoparticles, the thermal conductivity of the nanofluids has increased to 19.5%. In addition, dispersing CuO nanoparticles into base fluid reduces oil temperature by 17.44%.     

Fracture Characteristics of Torsion-Bending Fatigue and Impact Fatigue Failure of Two Steel Pins in a Crawler Excavator

The arms of crawler excavators used in diverse quarries work under extremely harsh conditions. A common failure during their operation is the fracture of the steel pin joints that permit free movement of the two adjacent booms closer to the machine housing, as well as the motion of the backhoe bucket against its nearest boom. This work presents examples of two steel pin joint failures. The pins had a diameter of 90 mm, and the failures resulted in high stand-by time for repairs. The first failure was caused by the combination of bending and torsion fatigue, and the second fracture occurred because of impact fatigue. Optical metallography and scanning electron microscopy/electron dispersive x-ray analysis (SEM/EDS) analysis provided a better understanding of the failure mechanism of the two steel pins, since these particular components exhibited excellent fatigue characteristics in both mating fracture surfaces.     

Imperfections in tree stand failures

Analyses of two climbing tree stand accidents are presented to show that serious imperfections in the chains would not have produced the failures had the tree stands been used within rated capacity. Stress analysis and tests demonstrated that roller chain with cracked links could operate at rated capacity without further crack growth and showed that loads approximately three times rated capacity were required to cause the pullout of an improperly staked pin. Although the chains in the tree stands involved in both accidents had serious imperfections, the imperfections did not produce a failure of the product within the rated capacity of the tree stands. However, operating conditions in excess of the rated capacity exposed the imperfections and led to the failures. Neither imperfection should have been considered a defect because they did not reduce the capacity of the tree stands below the rated capacity.     

Full Length Symmetric Versus Partial Length Un-symmetric Pin Loading Failure and Analysis for Clevis Attachments

In this paper, testing failure of the clevis–pin attachments for full length symmetric versus partial length un-symmetric configuration is considered. Theoretically and analytically it can be shown that due to higher stress levels in the partial length un-symmetric pin clevis configuration failure occurs sooner than in a full length symmetric pin clevis configuration. However, here by placement of the two different configurations at opposite ends of one axial tensile test setup the theory was put in test. The test results also indicated that the partial length clevis–pin attachment fails sooner than the full length clevis–pin attachment. Experimental procedures are described here in this paper. Both theoretical and finite element analyses are performed to validate the failure.     

A study on axial cracking failure of drill pipe body

Frequently happening drill pipe failure accidents in oil and gas wells not only affect drilling speed, but cause enormous economic losses and many safety issues. Most of these accidents are transverse cracking of drill pipe body and pin thread or axial cracking of box thread. Based on the axial cracking failures of drill pipe body in an ultra-deep well in China, this paper give a systematic analysis of axial cracking failure in consideration of service condition, material quality and stress corrosion mechanism. Measurement and inspection are performed on macroscopic and microscopic morphology of crack surface, corrosion products and circumferential residual stress. Then stress corrosion cracking experiments against hydrogen sulfide is conducted. Finally, the critical stress value for sulfide stress corrosion cracking of the drill pipe material is obtained, and the mechanisms of axial cracking failure and corresponding preventive measures are proposed.     

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.     

The modelling of degraded and critical failures for components with dormant failures

The failures reported in reliability data bases are often classified into sseverity classes, e.g., as critical or degraded failures. This paper presents models for the failure mechanism causing the degraded and critical failures, and estimators for the failure intensities of the models are provided. The discussions mainly focus on dormant (hidden) failures of a standby component. The suggested models are based on exponentially distributed random variables, but they give non-exponential (phase-type) distributions for the time to failure, and thus provide alternatives to the more common Weibull model. The main model is adapted to the information available in modern reliability data bases. Using this model it is also possible to quantify the reduction in the rate of critical failures, achieved by repairing degraded failures. In particular the so-called ‘naked failure rate’ (defined as the rate of critical failures that would be observed if no repair of degraded failures was carried out) is derived. Further, the safety unavailability (Mean Fractional Deadtime) of a dormant system is obtained for the new model.     

Warranty claim analysis considering human factors

Warranty claims are not always due to product failures. They can also be caused by two types of human factors. On the one hand, consumers might claim warranty due to misuse and/or failures caused by various human factors. Such claims might account for more than 10% of all reported claims. On the other hand, consumers might not be bothered to claim warranty for failed items that are still under warranty, or they may claim warranty after they have experienced several intermittent failures. These two types of human factors can affect warranty claim costs. However, research in this area has received rather little attention.In this paper, we propose three models to estimate the expected warranty cost when the two types of human factors are included. We consider two types of failures: intermittent and fatal failures, which might result in different claim patterns. Consumers might report claims after a fatal failure has occurred, and upon intermittent failures they might report claims after a number of failures have occurred. Numerical examples are given to validate the results derived.     

The Value of Investigating and Trending Minor Failures to Prevent Major Incidents

Catastrophic or major incidents are typically investigated immediately, but what about the near misses or minor failures that might be precursors to major incidents? Are they investigated? Major failures often do not occur as one isolated issue or event; there are often less severe precursors to a major event. This paper presents a best practice and reasons for reviewing minor equipment failures in order to avoid major events as demonstrated through the judicious analysis of minor failures. Several case histories and the lessons learned from these minor equipment failure investigations are presented to encourage investigation of what may initially appear as insignificant failures, for their value in prevention of major incidents.     

Failure Analysis of a Cyclic Contact Testing Machine Pin

The goal of this paper is to investigate the failure of a mandrel pin mounted on a rolling contact test bench. For this purpose, different methods of analysis were conducted, including metallography and stress analysis. The stress values in the failed pin were determined by Finite Elements. The high notch effect and the incorrect mounting of the specimens were identified as the failure causes. A pin design change is proposed to reduce the maximum stress even in the case of incorrect specimen mounting.     

Bolted Joints in Three Axially Braided Carbon Fibre/Epoxy Textile Composites with Moulded-in and Drilled Fastener Holes

Experimental behaviour of bolted joints in triaxial braided (0°/±45°) carbon fibre/epoxy composite laminates with drilled and moulded-in fastener holes has been investigated in this paper. Braided laminates were manufactured by vacuum infusion process using 12 K T700S carbon fibres (for bias and axial tows) and Araldite LY-564 epoxy resin. Moulded-in fastener holes were formed using guide pins which were inserted in the braided structure prior to the vacuum infusion process. The damage mechanism of the specimens was investigated using ultrasonic C-Scan technique. The specimens were dimensioned to obtain a bearing mode of failure. The bearing strength of the specimens with moulded-in hole was reduced in comparison to the specimens with drilled hole, due to the increased fibre misalignment angle following the pin insertion procedure. An improvement on the bearing strength of moulded-in hole specimens might be developed if the specimen dimensions would be prepared for a net-tension mode of failure where the fibre misalignment would not have an effect as significant as in the case of bearing failure mode, but this mode should be avoided since it leads to sudden catastrophic failures.     

Automated multiple failure FMEA

Failure mode and effects analysis (FMEA) is typically performed by a team of engineers working together. In general, they will only consider single point failures in a system. Consideration of all possible combinations of failures is impractical for all but the simplest example systems. Even if the task of producing the FMEA report for the full multiple failure scenario were automated, it would still be impractical for the engineers to read, understand and act on all of the results.This paper shows how approximate failure rates for components can be used to select the most likely combinations of failures for automated investigation using simulation. The important information can be automatically identified from the resulting report, making it practical for engineers to study and act on the results. The strategy described in the paper has been applied to a range of electrical subsystems, and the results have confirmed that the strategy described here works well for realistically complex systems.     

An analytical model for interactive failures

In some systems, failures of certain components can interact with each other, and accelerate the failure rates of these components. These failures are defined as interactive failure. Interactive failure is a prevalent cause of failure associated with complex systems, particularly in mechanical systems. The failure risk of an asset will be underestimated if the interactive effect is ignored. When failure risk is assessed, interactive failures of an asset need to be considered. However, the literature is silent on previous research work in this field. This paper introduces the concepts of interactive failure, develops an analytical model to analyse this type of failure quantitatively, and verifies the model using case studies and experiments.     

Performance and reliability of a star topology grid service with data dependency and two types of failure

The paper considers grid computing systems in which the Resource Management System (RMS) divides a service task into subtasks and then sends the subtasks to different specialized resources for execution. In order to provide the desired level of service reliability the RMS can assign the same subtasks to several independent resources for parallel execution. Because of data dependency, some subtasks cannot be executed until they have received input data that is the result of other subtasks. This imposes precedence constraints on the order of subtask execution. Usually, there are two types of failure in resources and communication channels: permanent failures and transient failures. Permanent failures render the equipment unavailable and whilst transient failures do not make the equipment unavailable they do prevent the completion of the performed actions. Service reliability and performance indices are introduced and a fast numerical algorithm for their evaluation for any given subtask distribution in a grid with a star architecture is presented. This algorithm is based on the universal generating function technique. Illustrative examples are presented.     

WJ5AI发动机中央传动锥齿轮组件故障分析及改进措施

通过对ＷＪ５ＡＩ发动机中央传动锥齿轮组件故障进行调查、分析，阐明了原中央传动锥齿轮组件结构设计存在不安全因素。中央传动锥齿轮与轴的配合紧度小，圆柱销在变化载荷作用下传递扭矩，与其孔的配合表面产生微动磨损，微动磨损进一步发展造成了中央传动锥齿轮组件传扭失效。     

Modelling discrete failures in composites with interface elements

The application of cohesive zone interface elements to modelling discrete matrix dominated failures in polymer composites is reviewed. It is shown that because they can accurately represent the physical mechanisms controlling damage development and failure, they are able to give excellent simulations of a wide variety of phenomena including delamination, laminate in-plane failure, behaviour at notches, impact damage and structural failure due to debonding.     

Early life failures

Device failures can be classified as event-dependent, time-dependent, and a combination of the two, event/time-dependent failures. Early life failure are dominated by event-dependent failures, i.e. Electrostatic Discharge (ESD) failures, and mechanical failures (bonds, cracks, etc.) that result from a stress event. Test and failure analysis results supporting the above are reviewed. This paper was presented at the 1985 Semiconductor Device Reliability NATO Workshop.     

The analysis of failure data in the presence of critical and degraded failures

Reported failures are often classified into severityclasses, e.g., as critical or degraded. The critical failures correspond to loss of function(s) and are those of main concern. The rate of critical failures is usually estimated by the number of observed critical failures divided by the exposure time, thus ignoring the observed degraded failures. In the present paper failure data are analyzed, applying an alternative estimate for the critical failure rate, also taking the number of observed degraded failures into account. The model includes two alternative failure mechanisms, one being of the shock type, immediately leading to a critical failure, another resulting in a gradual deterioration, leading to a degraded failure before the critical failure occurs. Failure data on safety valves from the OREDA (Offshore REliability DAta) data base are analyzed using this model. The estimate for the critical failure rate is obtained and compared with the standard estimate.     

A case study in the integration of accident reports and constructivedesign documents

Accident reports are intended to explain the causes of system failures. They are based upon the evidence of many different teams of experts and are, typically, the result of a lengthy investigation process. They are important documents from a software engineering perspective because they guide the intervention of regulatory authorities that must reduce the impact and frequency of system failures. There are, however, a number of problems with current practice. For example, the Rand report recently highlighted the lack of techniques that can investigate the role of software failure in major incidents. Similarly, there are no established techniques, which help to insure that these failures are used to inform subsequent design. This paper, therefore, shows how a number of relatively simple graphical notations can be used to improve the next generation of accident reports.     

The effectiveness of stress relief features in austenitic drillcollar connections

Standards designs for stress relief features and unmodified joints in non-magnetic (austenitic) drillcollar connections are investigated using finite element stress analysis. An NC-61 connection containing API pin and box stress relief grooves and box boreback features are compared. In addition to the recognized problem of fatigue failure from critically loaded threads, instances of stress corrosion cracking in pin bores have focused attention on this region and the effect which the presence of a pin stress relief groove has on the stresses there. The results of the analyses confirm the failure sites noted in service, and predict that the pin stress relief groove gives considerable benefit in terms of reducing the pin last engaged thread peak stress (fluctuations in which can cause fatigue), but causes an unexpected increase in the maximum pin bore axial stress (which can drive stress corrosion cracking).