Research on reliability analysis for low-altitude and high-speed payload fairing separation

Smart transmitters are increasingly being deployed in safety critical systems. Although the processing and diagnostic features provided by digital systems are advantageous, it introduces additional complexity in reliability modelling of systems. The conventional Fault Tree Analysis (FTA) method for system reliability analysis has its shortcomings in modelling digital systems, to incorporate its dynamic system interaction and failure modes in detail. This is because some of the failure modes may arise due to the dynamic interactions between the modules of the system. Dynamic Flowgraph Methodology (DFM) was identified as one of the optimistic approaches to handle these interactions. DFM approach combines multi‐valued logic modelling and analysis capabilities to handle systems consisting of components that have multiple degraded states and exhibit dynamic behaviour. However, only few DFM tools have been developed and some of them are not available in public domain. The DFM approach relies heavily on development and implementation of its decision tables. The logic information present within the decision tables can be meticulously implemented using Petri Nets. Also, there are plenty of free Petri Nets tools available online. Thus, the idea of DFM was used in this work to capture the dynamic interactions by developing decision tables. The decision tables were transformed into the Petri Net models to perform the analysis. The paper demonstrates the potential of the hybrid DFM – Petri Net approach for dynamic reliability analysis of smart transmitter.

Failure mode, effects and criticality analysis (FMECA) is a well-known reliability analysis tool for recognizing, evaluating and prioritizing the known or potential failures in system, design, and process. In conventional FMECA, the failure modes are evaluated by using three risk factors, severity (S), occurrence (O) and detectability (D), and their risk priorities are determined by multiplying the crisp values of risk factors to obtain their risk priority numbers (RPNs). However, the conventional RPN has been considerably criticized due to its various shortcomings. Although significant efforts have been made to enhance the performance of traditional FMECA, some drawbacks still exist and need to be addressed in the real application. In this paper, a new FMECA model for risk analysis is proposed by using an integrated approach, which introduces Z-number, Rough number, the Decision-making trial and evaluation laboratory (DEMATEL) method and the VIsekriterijumska optimizacija i KOmpromisno Resenje (VIKOR) method to FMECA to overcome its deficiencies in real application. The novelty of this paper in theory is that the proposed approach integrates the strong expressive ability of Z-numbers to vagueness and uncertainty information, the strong point of DEMATEL method in studying the dependence among failure modes, the advantage of rough numbers for aggregating experts’ diversity evaluations, and the strength of VIKOR method to flexibly model multi-criteria decision-making problems. Based on the integrated approach, the proposed risk assessment model can favorably capture and aggregate FMECA team members’ diversity evaluations and prioritize failure modes under different types of uncertainties with considering the failure propagation. In terms of application, the proposed approach was applied to the risk analysis of failure modes in offshore wind turbine pitch system, and it can also be used in many industrial fields for risk assessment and safety analysis.

Studies on the theory of structural system reliability includes identifi- cation of main the failure modes and calculation of inclusive failure probabilities for the structural system. The efficient and accurate identification of failure modes in structural systems is difficult and represents a key focus for research in sys- tem reliability. The fundamental theory of the branch and bound algorithm for stage critical strength is reviewed in this paper. Some deficiencies in this method are highlighted. Corresponding approaches to overcome these deficiencies are pro- posed. Calculated system reliability solutions to the classical model, a truss with 10 elements, indicate that the improvement measures proposed in this paper increase the efficiency of recognising the main failure modes of the structural system, and are readily validated. The outcomes of this type of benchmark analysis suggest that the proposed methodology may be capable of representing a suitable basis for the structural system reliability analysis of complex truss-like structures, includ- ing transmission towers. Using the proposed approach, the principal failure modes and system reliability of a transmission tower are calculated. Based on practical engineering considerations, effective methods to improve this structural system re- liability are proposed.

This study proposes a system reliability analysis of rack storage facilities subjected to forklift colliding events. The proposed system reliability analysis consists of two steps: the first step is to identify dominant failure modes that most contribute to the failure of the whole rack facilities, and the second step is to evaluate the system failure probability. In the first step, dominant failure modes are identified by using a simulation-based selective searching technique where the contribution of a failure mode to the system failure is roughly estimated based on the distance from the origin in the space of the random variables. In the second step, the multi-scale system reliability method is used to compute the system reliability where the first-order reliability method (FORM) is initially used to evaluate the component failure probability (failure probability of one member), and then the probabilities of the identified failure modes and their statistical dependence are evaluated, which is called as the lower-scale reliability analysis. Since the system failure probability is comprised of the probabilities of the failure modes, a higher-scale reliability analysis is performed again based on the results of the lower-scale analyses, and the system failure probability is finally evaluated. The illustrative example demonstrates the results of the system reliability analysis of the rack storage facilities subjected to forklift impact loadings. The numerical efficiency and accuracy of the approach are compared with the Monte Carlo simulations. The results show that the proposed two-step approach is able to provide accurate reliability assessment as well as significant saving of computational time. The results of the identified failure modes additionally let us know the most-critical members and their failure sequence under the complicated configuration of the member connections.

In recent years, time‐variant reliability issues have garnered widespread attention, particularly due to their consideration of the cumulative effects of material degradation and the time dependency of stochastic process loads. Methods based on the outcrossing rate are typically employed for time‐variant reliability analysis. However, they fail to effectively capture the correlations among multiple failure modes. To address this limitation, this paper proposes a time‐variant reliability analysis method that accounts for the correlation of multiple failure modes by integrating copula and PHI2. The method first utilizes Copula to analyze the correlations among various failure modes, followed by applying the PHI2 method for the time‐dependent reliability analysis of each individual failure mode. Ultimately, case studies confirm that the proposed method proficiently evaluates the time‐variant reliability of systems with multiple failure modes, yielding a maximum relative error below 5% compared to MCS and significant performance enhancements.

While offshore salt caverns, as part of the carbon capture and storage (CCS) systems, could offer significant advantages in storage carbon dioxide, they are still not widely implemented, partially due the challenges in maintaining the safe operation of such systems with a long-projected storage time. The presented study provided a Fault Tree (FT) analysis for the causal relationships of storage system failures with respect to the root causes, and further the potential integration of the FT with the dynamic Bayesian network (DBN) in order to monitor offshore salt caverns in the long-term operations. The presented study can incorporate both physics-of-failure models and sensory data to update the failure probabilities of the components in the offshore salt cavern storage system. The fault tree considers unintentional flow as the main failure mode and divides the system into three subsystems: the wellhead, the well and the cavern itself. Then, each individual subsystem is studied based on the components in the subsystem and the NORSOK standards for safe well design. The fault tree presented in this study also outlines the relationship between the failure modes and the effect they have on the system failure. Th fault tree analysis tool can then be converted into a DBN to provide a long-term monitoring framework for offshore CCS systems with limited observability, where real-time data can be utilized in order to update the probabilities of failure of components over time.

Complex slopes are characterized by large numbers of failure modes, cut sets or link sets, or by statistical dependence between the failure modes. For such slopes, a systematic quantitative method, or matrix-based system reliability method, was described and improved for their reliability analysis. A construction formula of event vector cE was suggested to solve the difficulty of identifying any component E in sample space, and event vector c of system events can be calculated based on it, then the bounds of system failure probability can be obtained with the given probability information. The improved method was illustrated for four copper mine slopes with multiple failure modes, and the bounds of system failure probabilities were calculated by self-compiling program on the platform of the software MATLAB. Comparison in results from matrix-based system reliability method and two generic system methods suggests that identical accuracy could be obtained by all methods if there are only a few failure modes in slope system. Otherwise, the bounds by the Ditlevsen method or Cornell method are expanded obviously with the increase of failure modes and their precision can hardly satisfy the requirement of practical engineering while the results from the proposed method are still accurate enough.

The completeness and accuracy of the front pages of electronic medical records (EMRs) are crucial for evaluating hospital performance and for health insurance payments to inpatients. However, the quality of the first page of EMRs in China's medical system is not satisfactory, which can be partly attributed to deficiencies in the EMR system. Failure mode and effects analysis (FMEA) is a proactive risk management tool that can be used to investigate the potential failure modes in an EMR system and analyze the possible consequences. The purpose of this study was to preemptively identify the potential failures of the EMR system in China and their causes and effects in order to prevent such failures from recurring. Further, we aimed to implement corresponding improvements to minimize system failure modes. From January 1, 2020, to May 31, 2022, 10 experts, including clinicians, engineers, administrators, and medical record coders, in Zhejiang People's Hospital conducted FMEA to improve the quality of the front page of the EMR. The completeness and accuracy of the front page and the risk priority numbers were compared before and after the implementation of specific improvement measures. We identified 2 main processes and 6 subprocesses for improving the EMR system. We found that there were 13 potential failure modes, including data messaging errors, data completion errors, incomplete quality control, and coding errors. A questionnaire survey administered to random physicians and coders showed 7 major causes for these failure modes. Therefore, we established quality control rules for medical records and embedded them in the system. We also integrated the medical insurance system and the front page of the EMR on the same interface and established a set of intelligent front pages in the EMR management system. Further, we revamped the quality management systems such as communicating with physicians regularly and conducting special training seminars. The overall accuracy and integrity rate of the front page (P<.001) of the EMR increased significantly after implementation of the improvement measures, while the risk priority number decreased. In this study, we were able to identify the potential failure modes in the front page of the EMR system by using the FMEA method and implement corresponding improvement measures in order to minimize recurring errors in the health care services in China.

Efficient system reliability analysis illustrated for a retaining wall and a soil slope

The challenges of lifelong learning in biological and artificial systems.

Nonparametric Bayesian reliability analysis of masked data with dependent competing risks

Identification of Failure Modes in the Collision Avoidance System of an Autonomous Ferry using Adaptive Stress Testing

&amp;lt;p&amp;gt;It is broadly accepted that magmatism plays a key dynamic role in continental and oceanic rifting. However, these dynamics remain poorly studied, largely due to the difficulty of consistently modelling liquid/solid interaction across the lithosphere. The RIFT-O-MAT project seeks to quantify the role of magma in rifting by using models that build upon the two-phase flow theory of magma/rock interaction. A key challenge is to extend the theory to account for the non-linear rheological behaviour of the host rocks, and investigate processes such as diking, faulting and their interaction (Keller et al., 2013). Here we present our progress in consistent numerical modelling of poro-viscoelastic-viscoplastic (VEVP) flow. We show that a VEVP model with a new, hyperbolic yield surface can help to robustly simulate both shear and tensile modes of plastic failure in a two-phase system.&amp;amp;#160;&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;Failure of rocks (plasticity) is an essential ingredient in geodynamics models because Earth materials cannot sustain unbounded stresses. However, plasticity represents a non-trivial problem even for single-phase flow formulations with shear failure only. In two-phase systems, tensile failure of rocks can also occur due to an overpressured liquid phase. Robustly solving a discretised model that includes this physics presents severe challenges, and many questions remain as to effective solvers for these strongly nonlinear systems.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;An appropriate rheological model is required to meet this challenge. The most straightforward choice is a Maxwell visco-elasto-plastic model, but this leads to grid-scale localisation and hence mesh-dependence. To obtain mesh-independent shear localisation, we employ the visco-elasto-viscoplastic model by introducing a viscous dashpot in parallel to the plasticity element. Whilst this formulation has shown promise in regularising shear failures in a single-phase flow model (de Borst and Duretz, 2020), its incorporation within two-phase systems has not been examined. We will show that the linear Griffith criteria for the tensile failure can lead to convergence issues whereas a new, hyperbolic yield surface is proposed to resolve these numerical issues. This yield surface provides a smooth transition between the two modes of failure.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;The underlying PDEs are discretised using a conservative, finite-difference, staggered-grid framework implemented with PETSc (FD-PDE) that supports single-/two-phase flow magma dynamics. Here, we present simplified model problems using the FD-PDE framework for poro-viscoelastic-viscoplastic models designed to characterise the solution quality and assess both the discretisation and solver robustness. It has been observed that employing the hyperbolic yield surface improved the robustness in simulating plastic failures in both modes.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;&amp;amp;#160;&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;&amp;lt;strong&amp;gt;References&amp;lt;/strong&amp;gt;&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;Keller, T., May, D. A., &amp;amp; Kaus, B. J. P., (2013). Numerical modelling of magma dynamics coupled to tectonic deformation of lithosphere and crust,&amp;amp;#160;Geophysical Journal International, v195, 1406-1442, https://doi.org/10.1093/gji/ggt306.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;de Borst, R., Duretz, T., (2020). On viscoplastic regularisation of strain-softening rocks and soils. International Journal for Numerical and Analytical Methods in Geomechanics, v44, 890-903. https://doi.org/10.1002/nag.3046.&amp;lt;/p&amp;gt;

Modular multi‐level converter (MMC) with press‐packing IGBT devices is the popular and key equipment of VSC‐HVDC system, its reliability is directly related to the equipment safe operation. However, it is difficult to analyse the reliability using the failure statistical approach due to less fault data. In order to improve the reliability analyses accuracy, it is necessary to use the physical failure method by considering the main components fatigue failure mode. The reliability analysis models are presented for the MMC sub‐module with the press‐packing IGBT device and metallised film capacitors. First, based on the MMC‐HVDC simulation model, the losses and the junction temperatures of the IGBT devices were derived by the temperature field model, which the failure rates can be calculated. Furthermore, based the corrosion failure mode, the failure rate calculation of the metallised film capacitor was investigated using the voltage stress and thermal stress, the reliability calculation of the MMC sub‐module was presented by combining the main components failure rates. Finally, the reliability of the VSC‐HVDC based MMC was also presented with the different operation mode. The achievement is helpful to assess and improve the reliability of the VSC‐HVDC.

This paper introduces the concepts of friction, wear, and surface contact which are a necessary background for an understanding of tribological behaviour. It then outlines the probable modes of failure in systems consisting of a hard ceramic coating on a hardened steel surface, summarises the results of a finite element analysis of this situation for a variety of coating architectures and material properties, and suggests ways in which the probability of coating failure could be reduced.