Individual Failure Modes Research Articles

Reliability analysis of rolling bearings considering failure mode correlations

AbstractAs an essential mechanical component, a rolling bearing can exhibit multiple failure modes that may occur independently or in correlation with one another. A reliability analysis method that meticulously accounts for the interdependencies among various bearing failure modes is presented in this paper. The examination of wear and fatigue failure mechanisms in rolling bearings is carried out using the Physics of Failure (PoF) approach. By considering the influence of uncertain variables, the limit state functions for individual failure modes are formulated through the application of stress‐strength interference theory. In the context of wear failure, the limit state function is derived using working clearance as the characteristic quantity. On the other hand, the limit state function for fatigue failure is constructed with a focus on fatigue damage accumulation. The Copula function is used to characterize the relationship between wear failure and fatigue failure, and a reliability calculation model for rolling bearings is developed, considering the correlation between these failure modes. Ultimately, the proposed method is utilized to assess the reliability of bearings under two different sets of test conditions. The feasibility of this method is confirmed through test data, demonstrating its effectiveness in predicting bearing reliability. Through the application of this method, engineers can optimize bearing size parameters, select appropriate initial clearances, and enhance the reliability design of bearing.

Downhill progressive landslide hazard assessment: a simple framework for prediction of triggering thresholds and failure modes

The pronounced discrepancies in triggering intensities and failure modes observed in downhill progressive landslides pose significant challenges to their risk prediction and mitigation. Instead of focusing on an individual triggering event and/or failure mode as done in previous studies, this study systematically explores the instability issues of downhill progressive failure in long slopes. A unified analytical model is proposed to understand these observed discrepancies, in which criteria for the initiation of slope failure corresponding to all possible failure modes are formulated. Accordingly, a simple framework is established that is capable of predicting possible triggering thresholds and failure modes in advance. This would improve the accuracy of landslide hazard assessment, which is often reduced by the unknowns of the failure mechanisms and inaccurate assumptions of stress distribution along the failure surface. Furthermore, three practical cases are analyzed based on the established framework, and the findings are compared with field observations and existing studies, showing good consistency. This work gives an insight into a systematic understanding of the various failure phenomena in downhill progressive landslides and provides a reference for their risk assessment and subsequent decision-making.

Robustness of Cloud Manufacturing System Based on Complex Network and Multi-Agent Simulation

Cloud manufacturing systems (CMSs) are networked, distributed and loosely coupled, so they face great uncertainty and risk. This paper combines the complex network model with multi-agent simulation in a novel approach to the robustness analysis of CMSs. Different evaluation metrics are chosen for the two models, and three different robustness attack strategies are proposed. To verify the effectiveness of the proposed method, a case study is then conducted on a cloud manufacturing project of a new energy vehicle. The results show that both the structural and process-based robustness of the system are lowest under the betweenness-based failure mode, indicating that resource nodes with large betweenness are most important to the robustness of the project. Therefore, the cloud manufacturing platform should focus on monitoring and managing these resources so that they can provide stable services. Under the individual server failure mode, system robustness varies greatly depending on the failure behavior of the service provider: Among the five service providers (S1-S5) given in the experimental group, the failure of Server 1 leads to a sharp decline in robustness, while the failure of Server 2 has little impact. This indicates that the CMS can protect its robustness by identifying key servers and strengthening its supervision of them to prevent them from exiting the platform.

Failure modes and effects analysis study for accelerator-based Boron Neutron Capture Therapy.

Boron Neutron Capture Therapy (BNCT) has recently been used in clinical oncology thanks to recent developments of accelerator-based BNCT systems. Although there are some specific processes for BNCT, they have not yet been discussed in detail. The aim of this study is to provide comprehensive data on the risk of accelerator-based BNCT system to institutions planning to implement an accelerator-based BNCT system. In this study, failure mode and effects analysis (FMEA) was performed based on a treatment process map prepared for the accelerator-based BNCT system. A multidisciplinary team consisting of a medical doctor (MD), a registered nurse (RN), two medical physicists (MP), and three radiologic technologists (RT) identified the failure modes (FMs). Occurrence (O), severity (S), and detectability (D) were scored on a scale of 10, respectively. For each failure mode (FM), risk priority number (RPN) was calculated by multiplying the values of O, S, and D, and it was then categorized as high risk, very high risk, and other. Additionally, FMs were statistically compared in terms of countermeasures, associated occupations, and whether or not they were the patient-derived. The identified FMs for BNCT were 165 in which 30 and 17 FMs were classified as high risk and very high risk, respectively. Additionally, 71 FMs were accelerator-based BNCT-specific FMs in which 18 and 5 FMs were classified as high risk and very high risk, respectively. The FMs for which countermeasures were "Education" or "Confirmation" were statistically significantly higher for S than the others (p=0.019). As the number of BNCT facilities is expected to increase, staff education is even more important. Comparing patient-derived and other FMs, O tended to be higher in patient-derived FMs. This could be because the non-patient-derived FMs included events that could be controlled by software, whereas the patient-derived FMs were impossible to prevent and might also depend on the patient's condition. Alternatively, there were non-patient-derived FMs with higher D, which were difficult to detect mechanically and were classified as more than high risk. In O, significantly higher values (p=0.096) were found for FMs from MD and RN associated with much patient intervention compared to FMs from MP and RT less patient intervention. Comparing conventional radiotherapy and accelerator-based BNCT, although there were events with comparable risk in same FMs, there were also events with different risk in same FMs. They could be related to differences in the physical characteristics of the two modalities. This study is the first report for conducting a risk analysis for BNCT using FMEA. Thus, this study provides comprehensive data needed for quality assurance/quality control (QA/QC) in the treatment process for facilities considering the implementation of accelerator-based BNCT in the future. Because many BNCT-specific risks were discussed, it is important to understand the characteristics of BNCT and to take adequate measures in advance. If the effects of all FMs and countermeasures are discussed by multidisciplinary team, it will be possible to take countermeasures against individual FMs from many perspectives and provide BNCT more safely and effectively.

Criticality analysis for safety-critical software in nuclear power plant distributed control system

Abstract Software criticality analysis examines the degree of contribution that each individual failure mode of a software component has on the reliability of software. Higher safety integrity levels are assigned to software modules whose failures cause an unacceptable impact on the operation of the system, and these levels require the implementation of more rigorous software quality assurance measures as defined in IEEE Std 1012 and in the customer’s system requirements specification. In this paper, a novel software criticality analysis method is proposed, the results of which can be used to guide the development of newly developed software and the procurement of Commercial-Off-The-Shelf (COTS) software. The software structure is first analyzed and the software is divided into modules according to their functions. Then the criticality levels of software components are preliminarily classified by means of a safety criticality preliminary analysis tree, followed by their verification through the software hazard and operability analysis (HAZOP). Finally, the target Safety Integrity Level (SIL) of each software module is determined based on its criticality level and the overall safety objective (i. e., SIL) of the system it resides in. As an example, this proposed method is applied to a nuclear power plant safety-critical system to demonstrate the detail application process and to verify the feasibility of the method. Compared with the existing software criticality analysis methods, this method has better operability and verifiability, and can be utilized as a technical guidance for the software criticality analysis of nuclear power plant digital control systems.

Conditional time-dependent limit state function model considering damages and its application in reliability evaluation of CRTS II track slab

On-site observations show that several damages have occurred in CRTS II slab-type ballastless track system, such as crack and interface debonding between different structural layers, which will trigger the occurrence of some failure modes of CRTS II track slab. As the damages are the prior for specific failure modes, time-dependent reliability of CRTS II track slab should be conducted considering the uncertainties associated with both the failure mode and the damage, which is defined as the conditional time-dependent reliability in this study. To appropriately express the causal relationship among the failure modes and prior damages, a conditional limit state function (LSF) model is proposed with explicit expressions provided. With the aid of the proposed model, conditional time-dependent reliability of CRTS II track slab for two individual failure modes are investigated, which are the steel yielding failure mode under longitudinal cracking, and the vertical instability failure mode under interface debonding. Furthermore, conditional time-dependent system reliability of the track slab has also been analyzed considering four safety failure modes. The advantage of the proposed method is that prior damages have been accounted in establishing the failure criteria and incorporated in the formulation of time-dependent reliability, which provides a general formwork for structural reliability involving the causal relationship among the failure modes and damages.

Technical reliability of shipboard technologies for the application of alternative fuels

BackgroundNaval traffic is highly dependent on depleting fossil resources and causes significant greenhouse gas emissions. At the same time, marine transportation is a major backbone of world trade. Thus, alternative fuel concepts are highly needed. Different fuels such as ammonia, methanol, liquefied natural gas and hydrogen have been proposed. For some of them, first prototype vessels have been in operation. However, practical experience is still limited. Most studies so far focus on aspects such as efficiency and economics. However, particularly in marine applications, reliability of propulsion systems is of utmost importance, because failures on essential ship components at sea pose a huge safety risk. If the respective components lose their functionality, repair can be much more challenging due to large distances to dockyards and the complicated transport of spare parts to the ship. Consequently, evaluation of reliability should be a core element of system analysis for new marine fuels.ResultsIn this study, reliability was studied for four potential fuels. The analysis involved several steps: estimation of overall failure rates, identification of most vulnerable components and assessment of criticality by including severity of fault events. On the level of overall failure rate, ammonia is shown to be very promising. Extending the view over a pure failure rate-based evaluation shows that other approaches, such as LOHC or methanol, can be competitive in terms of reliability and risk. As different scenarios require different weightings of the different reliability criteria, the conclusion on the best technology can differ. Relevant aspects for this decision can be the availability of technical staff, high-sea or coastal operation, the presence of non-naval personnel onboard and other factors.ConclusionsThe analysis allowed to compare different alternative marine fuel concepts regarding reliability. However, the analysis is not limited to assessment of overall failure rates, but can also help to identify critical elements that deserve attention to avoid fault events. As a last step, severity of the individual failure modes was included. For the example of ammonia, it is shown that the decomposition unit and the fuel cell should be subject to measures for increasing safety and reducing failure rates.

Methodology for Determining Time-Dependent Lead Battery Failure Rates from Field Data

The safety requirements in vehicles continuously increase due to more automated functions using electronic components. Besides the reliability of the components themselves, a reliable power supply is crucial for a safe overall system. Different architectures for a safe power supply consider the lead battery as a backup solution for safety-critical applications. Various ageing mechanisms influence the performance of the battery and have an impact on its reliability. In order to qualify the battery with its specific failure modes for use in safety-critical applications, it is necessary to prove this reliability by failure rates. Previous investigations determine the fixed failure rates of lead batteries using data from teardown analyses to identify the battery failure modes but did not include the lifetime of these batteries examined. Alternatively, lifetime values of battery replacements in workshops without knowing the reason for failure were used to determine the overall time-dependent failure rate. This study presents a method for determining reliability models of lead batteries by investigating individual failure modes. Since batteries are subject to ageing, the analysis of lifetime values of different failure modes results in time-dependent failure rates of different magnitudes. The failure rates of the individual failure modes develop with different shapes over time, which allows their ageing behaviour to be evaluated.

Sheathing-fastener connection strength based design method for sheathed CFS point-symmetric wall frame studs

Cold-formed steel (CFS) in construction delivers cost effectiveness and design flexibility. The instability failures of CFS Structural members significantly influences the failures of sheathing boards attached as an external cover. Therefore, present study experimentally examines the structural behavior of sheathing fastener connection in cold-formed steel wall frame. As a first attempt, strength and stiffness of the sheathing fastener connection is determined against the failure modes of point symmetric CFS wall frame studs. A new test setup has been developed to investigate the individual sheathing fastener failure modes. Parameters investigated include sheathing board types (varying thickness) and different dimensions of point-symmetric CFS studs. A total of forty-one individual fastener connection tests were carried out. The experimental investigation revealed that the fastener connection strength varies depending on the geometric dimensions of CFS stud and material composition of sheathing board. The result indicated that the bracing effect provided by plain gypsum board (fiber less) is insignificant and should not be considered for design. For sheathing boards with fiber composition, a generic parameter [ratio to design moment (Mx or My) to CFS stud depth (h)] is introduced to consider the structural bracing effect in CFS wall panel design. The limitations to consider the bracing effect of sheathing in the design of CFS wall frame studs are suggested for minor axis buckling and major axis buckling.

Bibliometric analysis of human factors in aviation accident using MKD

AbstractThis study aims to provide a better understanding of human factors and human performance mechanism in aviation accident analysis by visualisation and taxonomy analysis using mapping knowledge domain (MKD). An overview of aviation accident analysis involving human factors is first conducted, followed by an introduction of several conceptual models and human reliability analysis methods. Finally, a specific framework for risk assessment of human factors in aviation is proposed. The human factors analysis and classification system structure combined with the quantitative method is the most frequently used mode in aviation accident analysis. From a macro ergonomic perspective, systematic consideration has been emphasised frequently in existing research. Pilots or individuals are thought to be associated with the organisations and environment they located in. On the other hand, the micro ergonomic aspect prefers a quantitative and probabilistic way to reveal the individual's failure mode or error rate. Based on previous studies, the proposed framework provides a systematic view to help with the evaluation of human performance in aviation, taking into account human issues as well as management and environmental factors.

Reliability analysis of CRTS II track slab considering multiple failure modes

The safety of supporting structures for high-speed trains has motivated many researchers to develop an effective method for reliability analysis of the structure as a whole. In this study, a unitless model for system limit state function is developed, which enables the system reliability analysis of the CRTS II track slab on viaduct with multiple failure modes. The method of moments is employed to determine the system reliability, and the influences of important variables on the system reliability of the track slab are investigated. It is found that the reliability of the CRTS II track slab would be overestimated if only individual failure modes are considered independently, which vindicates the importance to conduct system reliability analysis for CRTS II track slab. It is also found that the randomness of the number of load cycles significantly affects the system reliability of the track slab. The merit of the developed unitless model for system limit state function is its facilitation of the efficient and accurate analysis of system reliability for the CRTS II track slab with no conditions and constraints.

System reliability analysis of soldier-piled excavation in unsaturated soil by combining random finite element and sequential compounding methods

The stability of excavation in unsaturated soil is closely related to the variation of soil properties and matric suction. Determination of different failure modes and identifying the contribution of each one in an unsaturated soldier-piled excavation are the vital aspects of system reliability analysis. To address these issues, this paper provided a stochastic framework with a random elasto-plastic finite element–based program coded in MATLAB to evaluate the reliability indices of individual failure modes with considering the inherent uncertainty of real site soil properties and unsaturated state. In the next step, the sequential compounding method (SCM) was utilized to obtain the system reliability index by compounding the reliability indices of individual failure modes. Numerical results of a case study showed that in all failure modes, considering unsaturated state not only increases the mean value of factor of safety (FS) but also decreases the related standard deviation, which can be counted as a goal of reliability analysis. Among the reliability indices of the components, the most critical one is attributed to the lateral displacement. Furthermore, the safety ratio concerning the shear force has the maximum reliability index compared to the others. Moreover, based on the coefficient of variation (COV) of the components, it was found that the uncertainty of the soil parameters has the most significant effect on the global safety factor of the excavation.

The comparison of the veritable response to impact load of conventional and Thin-Ply types of fibre metal laminates

Impact resistance is one of the critical issues for thin-walled structures made of composite materials used e.g. in aerospace fuselage elements. There are two strategies to improve the impact behaviour of composites. One of them involves thin-ply technology, and the second employs fibre metal laminates. The aim of this paper is to explain the response of Aluminium/Thin-Ply-Glass laminates to a wide range of impact energies in comparison with conventional Aluminium/Glass laminates by using deep and multi-criteria experimental evaluation. As demonstrated, the failure mechanisms are similar for both types of laminates. However, the noted differences in the order and importance of individual failure modes may affect damage propagation. The major factor of the earlier perforation initiation process of thin-ply FMLs in comparison to conventional FMLs is the domination of bending stress instead of tensile stress.

Ductility limit diagrams for superplasticity and forging of high temperature polycrystalline materials

A mechanistic understanding of the ductility limit diagrams is of critical importance, but it still remains elusive for a multitude of high temperature materials processing techniques, such as superplastic forming and hot forging. The relevant failure modes for the former are necking at high strain rates and intergranular cavitation at low strain rates, while those for the latter include the competition between longitudinal fracture and shear band. The comparison between the Arrhenius processes for grain boundary diffusion and grain interior creep defines a length scale that dictates whether the grain boundary cavity growth is diffusive or creep-constrained. A quantitative assessment of these damage evolution processes leads to the delineation of the dominant parametric spaces for individual failure modes, and thus superplasticity and forging limit diagrams are derived and compared to available experiments in literature.

Ductility Limit Diagrams for Superplasticity and Forging of High Temperature Polycrystalline Materials

A mechanistic understanding of the ductility limit diagrams is of critical importance, but it still remains elusive for a multitude of high temperature materials processing techniques, such as superplastic forming and hot forging. The relevant failure modes for the former are necking at high strain rates and intergranular cavitation at low strain rates, while those for the latter include the competition between longitudinal fracture and shear band. The comparison between the Arrhenius processes for grain boundary diffusion and grain interior creep defines a length scale that dictates whether the grain boundary cavity growth is diffusive or creep-constrained. A quantitative assessment of these damage evolution processes leads to the delineation of the dominant parametric spaces for individual failure modes, and thus superplasticity and forging limit diagrams are derived and compared to available experiments in literature.

Reliability-based partial factors for flood defenses

The Netherlands is protected against major floods by a system of primary flood defenses. These primary flood defenses have to comply with flood protection standards. Since 2017, these are defined in terms of maximum allowable probabilities of flooding. This is why a new set of tools and guidelines had to be developed, allowing for probabilistic as well as semi-probabilistic assessments. Semi-probabilistic assessments rest on a Load and Resistance Factor Design (LRFD) approach. Since major levee systems are essentially series systems with little to no redundancy, the difference between component and system reliability is essential for reliability analyses of flood defenses. This paper discusses the code calibration procedure that was developed to ensure consistency between probabilistic and semi-probabilistic assessments of flood protection systems and their components. Example applications are provided for two failure modes: slope instability and dune erosion. The newly calibrated semi-probabilistic rules allow practitioners to assess the reliability of flood protection systems on the basis of component-level semi-probabilistic LRFD analyses for individual failure modes.

Characterization of failure mechanism in glass, carbon and their hybrid composite laminates in epoxy resin by acoustic emission monitoring

ABSTRACTFibre reinforced plastic (FRP) composites are being widely utilized in various industries because of their superior mechanical properties. Besides their advantages, failure of these composites can occur either by an individual or an associated of various failure modes which are very difficult to distinguish and discriminate the damages. This paper focuses on solving this issue, by characterizing the various failure modes in glass, carbon and their hybrid composite laminates in epoxy resin under uni-axial tensile loading with acoustic emission (AE) monitoring. AE data recorded during the testing of a pure-resin specimen and the single-layer specimen were used to identify the matrix cracking and debonding, respectively, whereas delamination was predominant in a two-layer specimen. The fibre failure was obtained from the resin impregnated single fibre strand. The parametric studies using AE amplitude, duration, AE cumulative counts, AE cumulative energy, rise angle (RA) and peak frequency were used to describe the damage mechanism of the different stacking sequence of glass fibre reinforced plastic (GFRP), carbon fibre reinforced plastic (CFRP) and their hybrid composite laminates. The mechanical parameter and AE parameter was successfully correlated for discrimination of damage mechanism. The individual failure mode of glass, carbon and their hybrid composite laminates with the most critical damage mechanisms and the time-to-failure were investigated.

Local and global behavior of walls with cut-out openings in multi-story reinforced concrete buildings

This paper presents the finite element analysis (FEA) results of a multi-story reinforced concrete (RC) building having precast and cast-in-place load bearing walls. Door-type cut-out openings (height: 2.1 m, width: 0.9–4.4 m) were created at the first and second story of the building. Results from experimental tests on axially loaded RC panels were used to verify the modeling approach. The influence of cut-out openings on the response of individual RC panels, failure modes, and load redistribution to adjacent members under increasing gravitational loads was analyzed. Moreover, the wall bearing capacities obtained from FEA were compared with the values calculated from design equations. The results revealed that the robustness of multi-story buildings having RC load bearing wall systems decrease considerably with the creation of cut-out openings. However, owing to the initial robustness of the buildings, large cut-out openings could be created under normal service conditions without strengthening of the building structure. Furthermore, design equations provided very conservative predictions of the ultimate axial capacity characterizing the solid walls and walls with small openings, whereas similar FEA and analytically predicted capacities were obtained for walls with large openings.

Определение поврежденных проводов при коротком замыкании в многопроводной сети

The adaptive relay protection methods, which have received development in recent years, are engaged in solving the problem of recognizing failed wires in an n-wire network. The multitude of individual wire failure modes is divided into subsets of partial failure modes. In the course of training the recognizing structure (phase selector), each subset is represented in the form of domains on the measurement planes. The failure modes are replicated by the simulating network model. An algorithmic model, which produces measurements from the observed currents and voltages, plays a special role. This model, which simulates the healthy network, is a constituent part of the phase selector and converts the input quantities into voltages related to the n-wire network output. The measurements come as the ratios of the output and input voltage phasors. As an example, the phase selector for a three-phase network is considered. The procedure of revealing failed wires eliminates the need to restructure the domains reflecting the subsets of partial modes.

Quantifying the benefit of a developmental test program: Probabilistic Risk Assessment and Red Bull Stratos

Reaching new milestones in space, historically, has been achieved through the execution of a comprehensive developmental test program of increasing complexity, which validates engineering design models and provides operational experience. In this paper, the Red Bull Stratos program, which culminated with Felix Baumgartner's successful space dive on October 14, 2012, has been assessed in order to evaluate the quantitative enhancement to safety by its experimental test program. The analysis is carried out using Probabilistic Risk Assessment (PRA).11PRA: Probabilistic Risk Assessment. The PRA is a technique for mature systems to quantify complete system risk. Required inputs include numerical likelihood estimates for each individual failure mode or failure event; accurate results are dependent upon full and complete data sets, derived from the evaluation of mature systems. By contrast, test programs and one-off missions themselves frequently do not have the statistically significant number of past events and thus are not candidates for such evaluations. As such, this analysis is unable to reasonably quantify the absolute risk to the Red Bull Stratos mission. Instead, it is meant to show the relative value of enhancements to safety that were realized through the development program that follows a robust test program of increasing complexity in order to validate design models and reduce risks. The PRA is applied to the experimental test program and compared against the quantified results of the hypothetical test program that would have been performed had the project been completed in a single step, without the developmental test program. In addition to the planned test flights, the Stratos project also benefitted from past experience of other manned stratospheric balloon projects, including Project Manhigh (1955–58), Project Excelsior (1959–60), the Russian Volga (1962) and the Strato Jump project (1965–66). This study is attempting to quantify the safety benefit associated with a developmental test program and shows a marked improvement in quantified safety as a result of implementing lessons learned from testing and prior manned balloon flights. Initially, interest in a stratospheric jump program was from the US Air Force who was focused on the viability for a crew escape system from a reentry vehicle. There is renewed interest on this capability from the commercial industry that is looking to provide suborbital flight and access to Low Earth Orbit.