Weimin Cui

Application of Prognostic and Health Management technology on aircraft fuel system

Prognostic and Health Management (PHM), which could provide the ability of fault detection (FD), fault isolation (FI) and estimation of remaining useful life (RUL), has been applied to detect and diagnose device faults and assess its health status, with aiming to enhance device reliability, safety, and reduce its maintenance costs. In this paper, taking an aircraft fuel System as an example, with virtual instrument technology and computer simulation technology, an integrated approach of signal processing method and model-based method is introduced to build the virtual simulation software of aircraft fuel PHM system for overcoming the difficulty in obtaining the failures information from the real fuel system. During the process of constructing the aircraft fuel PHM system, the first step is to analyze the fuel system failure modes and status parameters that can identify the failure modes. The main failure modes are determined as joints looseness, pipe broken, nozzle clogging, and fuel tank leakage. The status parameters are fuel pressure and fuel flow. Then, the status parameter model is constructed to imitate the behavior of sensor which detecting fuel system status. On this basis, utilizing the signal processing module provided by Labview software, the outputs from the virtual sensors, which collect the failure data, are processed to realize the simulation of failure detection and failure diagnosis. All the result shows that the virtual simulation software well accomplishes the task of the aircraft fuel system failure detection and diagnosis.

Failure simulation and identification of shock absorber in carrier-based aircraft landing gear

The gas-oil leakage in the shock absorber of carrier-based aircraft landing gear is a frequent and common failure, which can deteriorate the absorbing performance. However rarely research is done to quantitatively analysis the coupling effect of gas-oil leakage on the absorbing performance. In this paper, the failure simulation and identification of shock absorber is studied by numerical modeling and simulation experiment. To analyze the effect of gas-oil leakage on the shock absorber, the equivalent air spring stiffness is deduced. And Kringing model is introduced to surrogate gas-oil leakage to further present the relation of corresponding shock absorber time to residual gas quantity and oil volume. Then an efficient method is proposed to identify the failure of gas-oil leakage. The simulation experiment is designed to verify the theory presented in this paper. The result of numerical model explains that the gas cushioning property is influenced by both gas and oil property. The simulation model is used to obtain the coupling effect curve of gas-oil leakage on the absorbing time. Eventually the analytical results show that the shock absorber performance varies with different gas-oil ratio caused by gas-oil leakage.

The Reliability and Sensibility Analysis for an Aircraft Lock Mechanism Based on the Surrogate Models

In order to analyze the reliability of the new lock mechanism which is an important part of aircraft cabin door system, this paper studies the reliability and sensitivity for the lock mechanism based on surrogate models and variance methods respectively. Function hazard analysis (FHA) and failure mode effects analysis (FMEA) of lock mechanism is studied firstly. Then, based on dynamics simulation model, performance function and various random variables, the widely used surrogate models of lock mechanism is established and verified. Based on the most accurate metamodel which has been established, the unlocking reliability which is the most hazardous function is calculated. Finally, the variance-based sensitivity method is used for sensitivity analysis of influence factors, the result shows that the tension of lock-hook from lock-ring is the largest influence factor on the unlocking reliability, which could contribute to the analysis and further improvement of lock mechanism.Copyright

Kriging-Based Reliability Analysis and Variance-Based Sensitivity Analysis for an Idler Shaft

In order to analyze the reason of failure and improve the reliability of the idler shaft, this paper studies the reliability and sensitivity for the idler shaft based on Kriging model and Variance Methods respectively. The finite element analysis (FEA) of idler shaft is studied in ABAQUS firstly. Then, combining the performance function and various random variables, the Kriging model of idler shaft is established and verified. Based on Kriging model which has been established, the relationship between random variables and the response value is studied, and the function reliability is calculated which explains why the failure of the idler shaft occurred frequently in service. Finally, the variance-based sensitivity method is used for sensitivity analysis of influence factors, the result shows that the reliability of idler shaft is sensitive to the inner diameter of body A and inner diameter of body B, which could contribute for the analysis and further improvement of idler shaft.Copyright

A model-based fault injection system for aerocraft wing structure

Fault injection technologies, which are important component of prognostic and health management (PHM) system and being paid more and more attention, have been applied to estimate the health status of aerocraft, with aiming to enhance the safety and reduce the maintenance costs. This paper presents a method that can inject faults such as joint failures and skin damages into a finite element model of wing structure for overcoming the difficulty in simulating an actual structural fault. The fault modes of wing structure are analyzed and its influence can be reflected in the finite element (FE) model by controlling the command stream. The parameters such as linear displacement, angular displacement, constraint force and maximal node stress can be used to identify the corresponding fault mode. A Fault injection system, the integration of the fault injection controller compiled by Visual C++ with the finite element analysis (FEA) software ANSYS, is established. User can set parameters including fault mode, location and extent on the interactive interface of the software. With the command stream generated by fault injection controller, the FE model in normal or abnormal condition can be set up for simulating. The results for representative cases show that the outputs from the FEA software coincide with those analyzed through the theory of structural mechanics.

The research on failure issues for a hydraulic system

The hydraulic systems are widely used in industry, but they would inevitably give rise to some failures. Firstly, this paper describes some hydraulic system failures in a reliability test. Secondly, it makes a detailed analysis for the reasons of failure. Lastly, some corresponding solutions are given for the different failures.

The failure mode analysis for a hydraulic system and sealing gasket design

Firstly, this paper conducted the failure modes and effects analysis (FMEA) for the certain hydraulic system; secondly, it calculated the impact load of the hydraulic system when it works; and based on above results of FMEA and the calculation of impact load, it has made the finite element analysis to key components in Abaqus which caused most failures. Finally, it optimized the design of the sealing gasket according to the results of finite element analysis.

Analysis and calculation method of wear reliability for a lock ring and hook

Firstly, the wear between the lock ring and hook of a retractable undercarriagedoor lock machine under the action of the periodic load has been discussed. Secondly, the calculations based on the Acrhard model has been established to confirm the incremental wear gap in a given time. Thirdly, the analysis and calculation model of the wear reliability were given when the size parameters, load, material properties and permissible wear distribute randomly. Finally, agree with the experimental data, the calculations and the analysis of the reliability prove that the model established in the paper is appropriate and practical.

The strength reliability analysis of a lock ring

As the lock ring of the door lock mechanism has a complex structure which needs to be tough enough to withstand heavy load during the high-load-factor maneuver of the aircraft. Special attention should be paid to its strength issue. In order to assess its strength reliability, this paper firstly demonstrated a strength analysis with a simplified finite element model using Patran and MD Nastran. Then the reliability analysis was carried out by the Monte Carlo method based on the load distribution obtained from the reliability test.

An analysis of mechanism kinematics accuracy based on linear elastic

The simulation-based prediction of the mechanism kinematics accuracy is of great importance in engineering application. For widely used and low-cost open-loop mechanism having no feedback signals, it is important to take a balance between economic consideration and high accuracy requirement, thus containing high research value. Based on current widely used methods, this paper proposes a more precise method to revise the kinematics accuracy of movement mechanism. Considering the manufacture error and joint clearance in mechanism, we reckon in elastic deformation displacement caused by gravity load and inertia force, that the analytic expression of displacement correction is presented, and that it is independent of the Business Software. Theoretical analysis and case studies show that this amendment for the precision request is necessary.