International Journal of Reliability, Risk and Safety: Theory and Application
Volume:1 Issue: 1, Dec 2018

MEMS reliability analysis is a challenging area of research which comprises various physics of failure and diverse failure mechanisms. Reliability issues are critical in both design and fabrication phases of MEMS devices as their commercialization is still delayed by these problems. In this research, a hybrid methodology is developed for the reliability evaluation of MEMS devices. Its first step is the identification of dominant failure modes by FMEA, evaluation of failure mechanisms and an updated lifetime estimation by the Bayesian method. The reliability of MEMS devices is studied using probabilistic physics of failure (PPoF) by determining the dominant failure mechanism. Accordingly, a deterministic model is selected for the analysis of the life and reliability of the dominant failure mechanisms. To convert the deterministic model to a probabilistic model, the uncertainty sources affecting the dielectric lifetime are determined. This model is simulated by the utilization of the Monte Carlo method. In the final stage, the results of life estimation are updated using the Bayesian method. Considering wide application and advantages of RF MEMS capacitive switches, it has been selected as a case study. A framework is developed for reliability evaluation of these switches failures due to stiction mechanism. The results contain FMEA table, lifetime estimation in different voltages, number of duty cycles and at the end, updated results of life estimation using the Bayesian method.

In the study of technical systems in reliability engineering, multi-state systems play a useful role. A multi-state system is a system consisting n components that system and its components may have several level performance. In the present paper, we introduce the multi-state (r, s)-out-of-n system consisting n elements having the property that each element consists two dependent components and each component of the elements and the system can be in one of m+1 possible states: 0, 1, 2,..., m. We investigate an efficient method to compute the exact reliability by using the distribution of bivariate order statistics. Depending on the number of active components of the multi-state (r, s)-out-of-n systems at time t, the mean residual lifetime function of the system is studied. Also, an example and illustrative graph is provided.

The flight control system must meet extremely high levels of functional integrity and availability. The control algorithm is processed by onboard computer (OBC). To meet the reliability requirements for onboard computers, various type of redundancy must be employed. In this paper, we concerned with the triple modular redundancy (TMR) for an onboard computer with aerospace application. In the proposed architecture, control inputs and system states are measured using designated sensors. According to the acquired data, mission scenario and control algorithm are processed by the processing unit. Thereafter, the results are applied to the system by actuators.TMR technology in component level is used to improve the reliability of OBC according to the system requirements. All of the constituent modules of OBC, comprising processing unit, bus interface, sensor, actuators, and IO devices, benefits from triple redundancy. The case study shows that the similar architecture is used for high reliable flight computer of passenger airplanes except that our architecture is based on the available multicore microcontrollers. The reliability of the designed onboard computer is evaluated analytically, which indicates that the proposed OBC can meet the reliability requirements.

The use of capacitor banks in distribution system has many outstanding usages include improving the power factor of a system, voltage profile, and reliability besides the reducing of the power flow losses of the component’s reactive due to the compensation. These benefits depend greatly on how capacitors are placed in the distribution system. Hence, in order to achieve the high reliable construction, switching capacitor has been placed to improve the main challenges of the network designing (reliability and reduce power loss) in the radial distribution system. As regards, the importance of the reliability and power losses are ignored in the distribution networks; the aim of this paper is primarily to establish an objective function for the parallel optimization of these aforementioned parameters. In the simulation process, ten parameters have been compared, which are: System Average Interruption Frequent Index (SAIFI) and its cost, System Average Interruption Duration Index (SAIDI) and its cost, power loss and its cost, the installed capacity and it's cost and values of two objective functions. Honey-bee mating optimization (HBMO) algorithm has been used to solve this problem. Then, the developed technique has been used on the IEEE standard distribution network as a problem-solving system.

Software often controls the behavior of mechanical and electrical systems, as well as interactions among their components in cyber-physical systems (CPS). The risks in CPS systems could result in losing tools, features, performance, and even life. Therefore, safety analysis for software in these systems is a highly critical and serious issue. The use of reliability block diagram is a method for checking the safety and reliability of systems. A reliability block diagram is a diagrammatic method for showing how component reliability contributes to the success or failure of a complex system. In this paper, a method for generating RBDs is presented analysis and demonstration of this method capability to evaluation of a software safety by use-case analysis, use-case diagram review, and use-case specification. Then, a Fuzzy VIKOR-based FMEA is used for further evaluation due to the presence of uncertain data. Finally, it is applied to a real CPS.

Lifetime of pipelines is very important for safe and sanitary water transmission pipelines and water distribution networks. For this purpose reliability assessment analysis is a good tool and made it easy or feasible to make more better decision for inspections during maintenance and utilization process. In this study, a non-linear state model of corrosion has been used for the structural analysis of corroded water transmission pipelines, stressed by internal pressure and substance corrosion are considered simultaneous base on a limit state function. In order to take the uncertainty associated with the design and environmental variables into account and obtaining failure probability (reliability index), a improved harmony search meta-heuristic optimization algorithm has been selected. Sensitivity analysis of associated parameters is carried out to measure the effectiveness of each ones on the probability of pipe failure. Results obtained for steel  pipeline of Karevandar to Kash water transmission project is discussed as a case study.