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1

Dynamic reliability calculation of random structures by conditional probability method

Kubica Jan, Ahmed Bilal, Muhammad Akbar, Usama Aslam Muhammad

Eksploatacja i Niezawodność

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2024

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Vol. 26, no. 2

art. no. 181133

EN

Reliability is sometimes computed as the likelihood of achieving an intended function in the presence of uncertainties, and this is known as dynamic reliability by the conditional probability approach. These techniques can produce incredibly accurate reliability estimates. This work uses the dynamic response spanning action Markov hypothesis for the composite random reliability problem. Two steps are needed to describe conditional probability: first, the Taylor expansion approach is used to derive a 2nd-order approximate formula for determining the dynamic reliability of the random structure. The second step is to come up with a mathematical sampling strategy based on the statistical analysis's Kriging model. The Kriging interpolation model's sampling process satisfies the nonlinear association between structural random boundaries and dynamic reliability. Consequently, the finite element results can be used immediately to anatomize the impact of random structural parameters on dynamic reliability, bypassing the arduous and time-consuming theoretical derivation. The numerical example results show that the sampling method based on the Kriging model is unconcerned about the ratio used to represent dispersion and provides extra benefits in computational verisimilitude and calculation productivity.

2

Dynamic reliability evaluation of buried corroded pipeline under rockfall impact

Wang Yifei, Xie Mingjiang, Su Chun

Eksploatacja i Niezawodność

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2022

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Vol. 24, no. 2

275--288

EN

Load impact, such as the rockfall, may bring significant threats to the integrity management of pipeline. This study is intended to evaluate the reliability of buried pipeline under rockfall impact, and so as to reduce the possible failure and unnecessary downtime. Firstly, the dynamic response of the buried pipeline under load is analyzed by Euler Bernoulli foundation beam. After that, the process of rockfall impact on buried corroded pipeline is simulated with nonlinear finite element method. Furthermore, the influence of rockfall’s parameters (including rockfall mass, impact velocity, impact position, etc.) on the pipeline’s equivalent stress is quantitatively analyzed. Eventually, a time-varying reliability model is established to calculate the failure probability. The results indicate that the mass and velocity of the rockfall have obvious influence on the pipeline’s failure probability, and the change of impact’s position has small influence. The proposed method can provide a theoretical reference for the design and maintenance of buried pipeline.

3

Fatigue reliability analysis of the brake pads considering strength degradation

Zhang Nan, Jiang Guang-Jun, Wu Dong-Wei, Chen Hong-Xia, Wu Jian-Xin

Eksploatacja i Niezawodność

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2020

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Vol. 22, no. 4

620--626

EN

Reliability prediction of the brake pads is indispensable to guarantee their safety. In the paper, the fatigue reliability of brake pads is analyzed by dynamic stress-strength interference (SSI) model considering strength degradation. Firstly, reliability model of the brake pads was established based on stress-strength interference model considering the influence of impact load. Then reliability of the brake pads was predicted under different impact load frequency and initial strength. Finally, the influence of random degradation strength on reliability was studied by contrast. The analysis results show that random strength degradation, impact load and initial strength have great influence on reliability prediction for the brake pads. Therefore, the reliability prediction of the brake pads fatigue strength considering strength degradation is more in line with the actual situation and the calculation accuracy is higher.

4

Safety and reliability models of time-dependent systems

Babczyński T., Kowalski M., Łukowicz M., Magott J., Skrobanek P.

Journal of Polish Safety and Reliability Association

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2011

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Vol. 2, No. 1

11--22

EN

The paper concerns models with time dependencies that can be used in modelling dynamic reliability and complex maintenance processes. Emphasis is put on models that have been elaborated with authors participation. The following models are presented: fault trees with time dependencies, probabilistic fault trees with time dependencies, reliability enhanced activity diagrams. The above models are illustrated by examples. Both types of fault trees are used in modelling the time coordination of distance protections in high voltage transmission line. Then reliability enhanced activity diagrams that express the maintenance process of computer system with redundant components. Components are submitted to failures and repairs.

5

Modelowanie dynamiczno-niezawodnościowe systemów z uszkodzeniami o wspólnej przyczynie w warunkach obciążenia losowego

Wang Z., Kang R., Xie L.

Eksploatacja i Niezawodność

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2009

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nr 3

47-54

PL

Artykuł przedstawia nową metodę tworzenia modeli dynamiczno-niezawodnościowych systemów, w których niezawodność i stopa ryzyka wyrażane są jako funkcje obciążenia, wytrzymałości i czasu. W pierwszej części artykułu przedstawiono sposób tworzenia modeli niezawodnościowych systemów z uszkodzeniami o wspólnej przyczynie stosując model interferencji pomiędzy obciążeniem a wytrzymałością, oraz wyprowadzono funkcje rozkładu kumulacyjnego oraz gęstości prawdopodobieństwa wytrzymałości dla różnych systemów. Utworzono także modele niezawodnościowe systemów w warunkach cyklicznego obciążenia losowego. Następnie opisano proces obciążania jako proces stochastyczny Poissona oraz wyprowadzono dynamiczne modele niezawodnościowe systemów o nie zmniejszającej się i zmniejszającej się wytrzymałości. Na koniec omówiono związek pomiędzy niezawodnością i czasem oraz stopę ryzyka systemów. Wyniki pokazują, że nawet przy nie zmniejszającej się wytrzymałości, niezawodność systemów zmniejsza się wraz z upływem czasu, podobnie jak ich stopa ryzyka. Gdy spada wytrzymałość, niezawodność systemów zmniejsza się szybciej wraz z upływającym czasem. Proponowane modele można wykorzystywać przy ustalaniu czasu trwania pracy próbnej, czasu niezawodnej pracy oraz harmonogramu eksploatacyjnego. Są one pomocne w zarządzaniu cyklem życia systemów.

EN

This paper presents a new method for developing the dynamic reliability model of systems, in which reliability and hazard rate of systems are expressed as functions of load, strength and time. First, reliability models of systems with common cause failure are developed by applying the load-strength interference model, and the cumulative distribution function and the probability density function of strength for different systems are derived. Reliability models of systems under repeated random load are developed. Then, the loading process is described as a Poisson stochastic process, the dynamic reliability models of systems without strength degeneration and those with strength degeneration are derived. Finally, the relationship between reliability and time, and the hazard rate of systems, are discussed. The results show that even if strength does not degenerate, the reliability of systems decreases over time, and the hazard rate of systems decreases over time, too. When strength degenerates, the reliability of systems decreases over time more rapidly, and the hazard rate curves of systems are bathtub-shaped. The models proposed can be applied to determine the duration of a trial run, the reliable operation life and the maintenance schedule. It is helpful for the life cycle management of systems.