Physics of Failure(PoF)-Based Reliability and Performance Integrating Modeling Method and Software for Electromechanical Product

Electromechanical product's reliability is affected by uncertainty as well as performance degeneration during its life cycle.The present reliability and performance integrating modeling methods have obvious deficiencies in long period reliability analysis and assessment when applied to such system.A novel integrating modeling method based on physics of failure(PoF)and a simulation algorithm that considers uncertainty and degeneration are proposed in this paper to compute maintenance free operation period or maintenance free operation period survivability which is used to assess long period reliability of system.Furthermore,the concept design of this kind of software based on the above theory is also introduced.A case study of servo valve demonstrates the feasibility of the method and usability of the software in this research.

Reliability modeling of mutual DCFP considering failure physical dependency

Degradation and overstress failures occur in many electronic systems in which the operation load and environmental conditions are complex.The dependency of them called dependent competing failure process(DCFP),has been widely studied.Electronic system may experience mutual effects of degradation and shocks,they are considered to be interdependent.Both the degradation and the shock processes will decrease the limit of system and cause cumulative effect.Finally,the competition of hard and soft failure will cause the system failure.Based on the failure mechanism accumulation theory,this paper constructs the shock-degradation acceleration and the threshold descent model,and a system reliability model established by using these two models.The mutually DCFP effect of electronic system interaction has been decomposed into physical correlation of failure,including acceleration,accumulation and competition.As a case,a reliability of electronic system in aeronautical system has been analyzed with the proposed method.The method proposed is based on failure physical evaluation,and could provide important reference for quantitative evaluation and design improvement of the newly designed system in case of data deficiency.

System reliability evaluation method considering physical dependency with FMT and BDD analytical algorithm

Recently, the physics-of-failure(PoF) method has been more and more popular in engineering to understand the failure mechanisms(FMs) of products.However, due to the lack of system modeling methods and problem-solving algorithms,the information of FMs cannot be used to evaluate system reliability.This paper presents a system reliability evaluation method with failure mechanism tree(FMT) considering physical dependency(PDEP) such as competition, trigger, acceleration, inhibition, damage accumulation, and parameter combination.And the binary decision diagram(BDD) analytical algorithm is developed to establish a system reliability model.The operation rules of ite operators for generating BDD are discussed.The flow chart of system reliability evaluation method based on FMT and BDD is proposed.The proposed method is applied in the case of an electronic controller drive unit.Results show that the method is effective to evaluate system reliability from the perspective of FM.

Performance simulation method and state of health estimation for lithium-ion batteries based on aging-effect coupling model

Accurate simulation of characteristics performance and state of health(SOH)estimation for lithium-ion batteries are critical for battery management systems(BMS)in electric vehicles.Battery simplified electrochemical model(SEM)can achieve accurate estimation of battery terminal voltage with less computing resources.To ensure the applica-bility of life-cycle usage,degradation physics need to be involved in SEM models.This work conducts deep analysis on battery degradation physics and develops an aging-effect coupling model based on an existing improved single particle(ISP)model.Firstly,three mechanisms of solid electrolyte interface(SEI)film growth throughout life cycle are analyzed,and an SEI film growth model of lithium-ion battery is built coupled with the ISP model.Then,a series of identification conditions for individual cells are designed to non-destructively determine model parameters.Finally,battery aging experiment is designed to validate the battery performance simulation method and SOH estimation method.The validation results under different aging rates indicate that this method can accurately es-timate characteristics performance and SOH for lithium-ion batteries during the whole life cycle.

A critique of reliability prediction techniques for avionics applications

Avionics （aeronautics and aerospace） industries must rely on components and systems of demonstrated high reliability. For this, handbook-based methods have been traditionally used to design for reliability, develop test plans, and define maintenance requirements and sustainment logistics, However, these methods have been criticized as flawed and leading to inaccurate and mis- leading results. In its recent report on enhancing defense system reliability, the U.S. National Academy of Sciences has recently discredited these methods, judging the Military Handbook （MIL- HDBK-217） and its progeny as invalid and inaccurate. This paper discusses the issues that arise with the use of handbook-based methods in commercial and military avionics applications. Alter- native approaches to reliability design （and its demonstration） are also discussed, including similarity analysis, testing, physics-of-failure, and data analytics for prognostics and systems health management.

A novel testability model for health management of heading attitude system

Prognostics and health management （PHM） is very important to guarantee the reliability and safety of aerospace systems, and sensing and test are the precondition of PHM. Integrating design for testability into early design stage of system early design stage is deemed as a fundamental way to improve PHM performance, and testability model is the base of testability analysis and design. This paper discusses a hierarchical model-based approach to testability modeling and analysis for heading attitude system health management. Quantified directed graph, of which the nodes represent components and tests and the directed edges represent fault propagation paths, is used to describe fault-test dependency, and quantitative testability information is assigned to nodes and directed edges. The fault dependencies between nodes can be obtained by functional fault analysis methodology that captures the physical architecture and material flows such as energy, heat, data, and so on. By incorporating physics of failure models into component, the dynamic process of a failing or degrading component can be projected onto system behavior, i.e., system symptoms. Then, the analysis of extended failure modes, mechanisms and effects is utilized to construct fault evolution-test dependency. Using this integrated model, the designers and system analysts can assess the test suite＇s fault detectability, fault isolability and fault predictability. And heading attitude system application results show that the proposed model can support testability analysis and design for PHM very well.

Thermography analyses of rock fracture due to excavation and overloading for tunnel in 30° inclined strata

Large-scale physical model test of 30°inclined strata was conducted to investigate the damage mechanisms during the excavation and overloading using infrared detection.The experiment results were presented with thermal images which were divided into three stages including a full face excavation stage,a staged excavation stage,and an overloading stage.The obtained results were compared with the previously reported results from horizontal,45?,60?,and vertical strata models.Infrared temperature(IRT)for 30°inclined strata model descended with multiple fluctuations during the full-face excavation.For the staged excavation,the excavation damage zone(EDZ)showed enhanced faulting-like strips as compared in the 45?,60?,and vertical models,indicating the intensified stress redistribution occurred in the adjacent rock mass.In contrast,EDZ for the horizontal strata existed in a plastic-formed manner.During the overloading,abnormal features in the thermal images were observed preceding the coalescence of the propagating cracks.The ultimate failure of the model was due primarily to the floor heave and the roof fall.