Qiang Feng

Availability-based engineering resilience metric and its corresponding evaluation methodology

Several resilience metrics have been proposed for engineering systems (e.g., mechanical engineering, civil engineering, critical infrastructure, etc.); however, they are different from one another. Their difference is determined by the performances of the objects of evaluation. This study proposes a new availability-based engineering resilience metric from the perspective of reliability engineering. Resilience is considered an intrinsic ability and an inherent attribute of an engineering system. Engineering system structure and maintenance resources are principal factors that affect resilience, which are integrated into the engineering resilience metric. A corresponding dynamic-Bayesian-network-based evaluation methodology is developed on the basis of the proposed resilience metric. The resilience value of an engineering system can be predicted using the proposed methodology, which provides implementation guidance for engineering planning, design, operation, construction, and management. Some examples for common systems (i.e., series, parallel, and voting systems) and an actual application example (i.e., a nine-bus power grid system) are used to demonstrate the application of the proposed resilience metric and its corresponding evaluation methodology.

Heuristic hybrid game approach for fleet condition-based maintenance planning

The condition-based maintenance (CBM) method is commonly used to select appropriate maintenance opportunities according to equipment status over a period of time. The CBM of aircraft fleets is a fleet maintenance planning problem. In this problem, mission requirements, resource constraints, and aircraft statuses are considered to find an optimal strategy set. Given that the maintenance strategies for each aircraft are finite, fleet CBM can be treated as a combinatorial optimization problem. In this study, the process of making a decision on the CBM of military fleets is analyzed. The fleet CBM problem is treated as a two-stage dynamic decision-making problem. Aircraft are divided into dispatch and standby sets; thus, the problem scale is significantly reduced. A heuristic hybrid game (HHG) approach comprising a competition game and a cooperative game is proposed on the basis of heuristic rule. In the dispatch set, a competition game approach is proposed to search for a local optimal strategy matrix. A cooperative game method for the two sets is also proposed to ensure global optimization. Finally, a case study regarding a fleet comprising 20 aircraft is conducted, with the results proving that the approach efficiently generates outcomes that meet the mission risk-oriented schedule requirement.

Accelerated Degradation Test and Predictive Failure Analysis of B10 Copper-Nickel Alloy under Marine Environmental Conditions

This paper studies the corrosion behavior of B10 copper-nickel alloy in marine environment. Accelerated degradation test under marine environmental conditions was designed and performed based on the accelerated testing principle and the corrosion degradation mechanism. With the prolongation of marine corrosion time, the thickness of Cu2O film increased gradually. Its corrosion product was Cu2(OH)3Cl, which increased in quantity over time. Cl− was the major factor responsible for the marine corrosion of copper and copper alloy. Through the nonlinear fitting of corrosion rate and corrosion quantity (corrosion weight loss), degradation data of different corrosion cycles, the quantitative effects of two major factors, i.e., dissolved oxygen (DO) and corrosion medium temperature, on corrosion behavior of copper alloy were analyzed. The corrosion failure prediction models under different ambient conditions were built. One-day corrosion weight loss under oxygenated stirring conditions was equivalent to 1.31-day weight loss under stationary conditions, and the corrosion rate under oxygenated conditions was 1.31 times higher than that under stationary conditions. In addition, corrosion medium temperature had a significant effect on the corrosion of B10 copper sheet.

Accelerated storage degradation test and life extension assessment method for hermetically sealed electromagnetic relay

For products which are required for long-term storage, its difficult to assess their reliability or life extension due to lack of historical usage data or test data. This paper presents a life extension assessment method based on the accelerated storage degradation test (ASDT) and the degradation model with random performance parameters. The typical failure modes and mechanisms of hermetically sealed electromagnetic relay under the storage condition are analyzed. The degradation process of contact resistance (contact failure) is described using the Arrhenius model. In the accelerated storage degradation test, the contact resistance is selected as the major performance parameter to be measured. The composite activation energy parameter in the Arrhenius model was obtained by the degradation model with random performance parameters. Then, the life extension and the reliability are assessed combining with the historical storage environment data. The assessment result shows that the electromagnetic relay used in the airborne electronic part can satisfy the operating requirement of life extension for 10-year.

Cooperative game approach based on agent learning for fleet maintenance oriented to mission reliability

Abstract Fleet maintenance oriented to mission reliability is a multi-level maintenance planning problem that becomes highly difficult due to the various reliability models of equipment and fleet. A three-level decision structure for fleet maintenance is established, the objective is maintenance cost, the constraints is the reliability of fleet, and the variables are the maintenance statuses of line replaceable modules. Then, the fleet maintenance process is translated into game behavior among considerable equipment with different statuses. A cooperative game framework based on agent learning is developed. A convergence condition for optimization is proposed by a simulated annealing approach. In the game method, three types of learning signals and their evaluation rules are introduced to establish the equipment’s reduced strategy space. Thus, the computation amount of game can be controlled, and the reliability constraints can be satisfied during the game process. Furthermore, the assessment method for the equipment payoff with a penalty factor is established, and the rapid search algorithm of Pareto optimal solution is provided on the basis of the total revenue of game. A case study is performed on a fleet of 15 aircrafts to prove that the proposed approach can reduce the maintenance cost effectively and can meet the fleet mission reliability requirements.

An Optimization Method for Condition Based Maintenance of Aircraft Fleet Considering Prognostics Uncertainty

An optimization method for condition based maintenance (CBM) of aircraft fleet considering prognostics uncertainty is proposed. The CBM and dispatch process of aircraft fleet is analyzed first, and the alternative strategy sets for single aircraft are given. Then, the optimization problem of fleet CBM with lower maintenance cost and dispatch risk is translated to the combinatorial optimization problem of single aircraft strategy. Remain useful life (RUL) distribution of the key line replaceable Module (LRM) has been transformed into the failure probability of the aircraft and the fleet health status matrix is established. And the calculation method of the costs and risks for mission based on health status matrix and maintenance matrix is given. Further, an optimization method for fleet dispatch and CBM under acceptable risk is proposed based on an improved genetic algorithm. Finally, a fleet of 10 aircrafts is studied to verify the proposed method. The results shows that it could realize optimization and control of the aircraft fleet oriented to mission success.

Dynamic scheduling of carrier aircraft based on improved ant colony algorithm under disruption and strong constraint

Aircraft scheduling is a typical dynamic scheduling problem when carrying out certain missions. Due to unfixed mission, disruption and limited time, space and resources, aircraft scheduling generally has strong constraint and many uncertainties. In this paper, we propose an improved direct graph to describe the complex scheduling process. We add the temporary point to deal with the strong constraint, and all disturbance are processed as the occupation of nodes and path. The objectives for planning scheduling strategies to shift the aircrafts among nodes on direct graph containing the occupancy with better scheduling efficiency, cost and reliability. Then, we given an optimal algorithm based on improved ant colony optimization (ACO) to find optimal scheduling strategy. Finally, with a simple case, the effectiveness of the model and algorithm is verified. And the given algorithm can basically solve path planning and resource allocation problems for the scheduling system which is often influenced by uncertain disturbances. And in the scheduling process, we reduce the waste of resources, get rid of conflicts in using, and increase the reliability as much as possible.

Process reengineering method for synthesis design of reliability maintainability supportability and performance

Many problems have existed in synthesis design of reliability, maintainability, supportability (RMS) and performance, such as RMS design activities are numerous and optional, variable feedback branches can satisfy same RMS requirement, some iteration among RMS and Performance activities is necessary, and many uncertainty exist in the design process. A process reengineering method for synthesis design of RMS and performance is put forward with respect to the above problems. A reorganizing method for different levels of design process is proposed first, include the process improvement method for global level and the process redesign method based on design structure matrix (DSM) for local level. A multi-view process modeling method is given to describe the synthesis design process from different aspects. Further, a conflict checking method is utilized to verify the feasibility of the process and simulation method based on DSM is also introduced to analysis the comprehensive benefits of the synthesis design process. The criterion architecture is established to evaluate the process ability. Finally, the software platform is developed to support the process reengineering for synthesis design of RMS and performance.

An Alternative Lifetime Model for White Light Emitting Diodes under Thermal–Electrical Stresses

The lifetime prediction using accelerated degradation test (ADT) method has become a main issue for white light emitting diodes applications. This paper proposes a novel lifetime model for light emitting diodes (LEDs) under thermal and electrical stresses, where the junction temperature and driving current are deemed the input parameters for lifetime prediction. The features of LEDs’ lifetime and the law of lumen depreciation under dual stresses are combined to build the lifetime model. The adoption of thermal and electrical stresses overcomes the limitation of single stress, and junction temperature in accelerated degradation test as thermal stress is more reliable than ambient temperature in conventional ADT. Furthermore, verifying applications and cases studies are discussed to prove the practicability and generality of the proposed lifetime model. In addition, the lifetime model reveals that electrical stress is equally significant to the thermal stress in the degradation of LEDs, and therefore should not be ignored in the investigation on lumen decay of LEDs products.

A Time-Variant Reliability Model for Copper Bending Pipe under Seawater-Active Corrosion Based on the Stochastic Degradation Process

In the degradation process, the randomness and multiplicity of variables are difficult to describe by mathematical models. However, they are common in engineering and cannot be neglected, so it is necessary to study this issue in depth. In this paper, the copper bending pipe in seawater piping systems is taken as the analysis object, and the time-variant reliability is calculated by solving the interference of limit strength and maximum stress. We did degradation experiments and tensile experiments on copper material, and obtained the limit strength at each time. In addition, degradation experiments on copper bending pipe were done and the thickness at each time has been obtained, then the response of maximum stress was calculated by simulation. Further, with the help of one kind of Monte Carlo method we propose, the time-variant reliability of copper bending pipe was calculated based on the stochastic degradation process and interference theory. Compared with traditional methods and verified by maintenance records, the results show that the time-variant reliability model based on the stochastic degradation process proposed in this paper has better applicability in the reliability analysis, and it can be more convenient and accurate to predict the replacement cycle of copper bending pipe under seawater-active corrosion.