Aerospace and Electrical System Reliability
Yehia F. Khalil
Abstract
This research provides a reliability-based quantitative failure analysis of different architectural designs of the environmental control system (ECS) in commercial aircraft. The scope of analysis includes the two-, three-, and four-wheel ECS architectures. Reliability block diagrams (RBD) are developed ...
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This research provides a reliability-based quantitative failure analysis of different architectural designs of the environmental control system (ECS) in commercial aircraft. The scope of analysis includes the two-, three-, and four-wheel ECS architectures. Reliability block diagrams (RBD) are developed and quantified for the three architectures and quantified using recently published components failure rate data. Components contributions to the reliability of each of the modeled ECS architectures are calculated as well as their Birnbaum’s components importance measures. The results of this analysis show that the two-wheel architecture has a mean time between failure (MTBF) of » 21,438 hours, while the three-wheel architecture has an MTBF of » 14,050 hours, and the four-wheel architecture has an MTBF of » 13,634 hours. ECS reliability decreased by » 34.5% through adoption of the three-wheel architecture, and by 36.4% through adoption of the four-wheel architecture, as compared to the simple two-wheel ECS architecture. The calculated Birnbaum’s importance measures show that the most critical component in the two-wheel architecture is the cabin air circulation fan (CACF). For the three-wheel and four-wheel ECS architectures, the most important component is the condenser. The key contributions of this research are: 1) addressing current gap in the state of knowledge about ECS design life prediction and 2) providing insights into ECS reliability-based failure analysis.
Failure Probability
Saran Srikanth Bodda; Abhinav Gupta; BuSeog Ju; Minho Kwon
Abstract
Safety of critical industrial facilities such as Nuclear power plants has gained significant attention against external events in the last decade. Fukushima Daiichi nuclear power station disaster occurred due to flooding of the plant which was caused by the Great East Japan earthquake and the subsequent ...
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Safety of critical industrial facilities such as Nuclear power plants has gained significant attention against external events in the last decade. Fukushima Daiichi nuclear power station disaster occurred due to flooding of the plant which was caused by the Great East Japan earthquake and the subsequent tsunami. In the US, failure of floodwall system during hurricane Katrina caused widespread damage. Floodwalls are essential to mitigate the effects of rising sea-levels due to climate change. Critical industrial facilities are being increasingly protected from the effects of floods through the use of flood protection systems such as floodwalls, dams, and weirs. This paper evaluates the fragilities for failure of a concrete floodwall due to various failure modes under a multi-hazard scenario (flooding and seismic events). Structural failure of the concrete floodwall is characterized by excessive deformation failure mode for seismic loads. The failure modes considered for flooding loads are rigid body failure and foundation failure.
Uncertainties Evaluation of Loads and Loading Conditions
Franziska Schmidt; Marcel Nowak; Mariia Nesterova; Oliver Fischer
Abstract
When dealing with the construction of a bridge or the assessment of an existing bridge to traffic loads, one important point is the prediction of reliability levels for critical details to the expected traffic loads in its remaining lifetime: this is done here for details of a steel-orthotropic bridge ...
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When dealing with the construction of a bridge or the assessment of an existing bridge to traffic loads, one important point is the prediction of reliability levels for critical details to the expected traffic loads in its remaining lifetime: this is done here for details of a steel-orthotropic bridge deck based on limited traffic monitoring data. A comparison of results from different statistical approaches is made by analyzing the recorded data for the traffic actions: to do that, the work begins with the writing of limit state functions for the ultimate limit state using various probability distributions, to evaluate the corresponding reliability indexes. Indeed, three methods to assess extreme values, Generalized Extreme Value, Peaks-over-Threshold and Level Crossing Counting, are applied. Therefore, one of the extrapolation methods that have been used in the background works for the European Norms (Eurocode 1) is treated here. Moreover, the comparison with the European design load model and the corresponding ultimate limit state is made.
