scholarly journals Fault Severity Evaluation and Improvement Design for Mechanical Systems Using the Fault Injection Technique and Gini Concordance Measure

2014 ◽  
Vol 2014 ◽  
pp. 1-20 ◽  
Author(s):  
Jianing Wu ◽  
Shaoze Yan
Keyword(s):  
Fault Injection ◽  
Dynamic Properties ◽  
Mechanical Systems ◽  
Fault Tree Analysis ◽  
Normal Operation ◽  
Solar Array ◽  
Injection Technique ◽  
Reliability Design ◽  
Fault Severity ◽  
Series Of Experiments

A new fault injection and Gini concordance based method has been developed for fault severity analysis for multibody mechanical systems concerning their dynamic properties. The fault tree analysis (FTA) is employed to roughly identify the faults needed to be considered. According to constitution of the mechanical system, the dynamic properties can be achieved by solving the equations that include many types of faults which are injected by using the fault injection technique. Then, the Gini concordance is used to measure the correspondence between the performance with faults and under normal operation thereby providing useful hints of severity ranking in subsystems for reliability design. One numerical example and a series of experiments are provided to illustrate the application of the new method. The results indicate that the proposed method can accurately model the faults and receive the correct information of fault severity. Some strategies are also proposed for reliability improvement of the spacecraft solar array.

scholarly journals Incorporating Uncertainty in Diagnostic Analysis of Mechanical Systems

2002 ◽  
Author(s):  
Gregory Mocko ◽  
Robert Paasch
Keyword(s):  
Life Cycle ◽  
Failure Modes ◽  
Mechanical Systems ◽  
Fault Tree Analysis ◽  
Joint Probability ◽  
Fault Isolation ◽  
Diagnostic Model ◽  
Component Reliability ◽  
Bayes Formula ◽  
Alternative Designs

The increase in complexity of modern mechanical systems can often lead to systems that are difficult to diagnose, and therefore require a great deal of time and money to return to a normal operating condition. Analyzing mechanical systems during the product development stages can lead to systems optimized in the area of diagnosability, and therefore to a reduction of life cycle costs for both consumers and manufacturers and an increase in the useable life of the system. A methodology for diagnostic evaluation of mechanical systems incorporating indication uncertainty is presented. First, Bayes formula is used in conjunction with information extracted from the Failure Modes and Effects Analysis (FMEA), Fault Tree Analysis (FTA), component reliability, and prior system knowledge to construct the Component-Indication Joint Probability Matrix (CIJPM). The CIJPM, which consists of joint probabilities of all mutually exclusive diagnostic events, provides a diagnostic model of the system. The Replacement Matrix is constructed by applying a predetermined replacement criterion to the CIJPM. Diagnosability metrics are extracted from a Replacement Probability Matrix, computed by multiplying the transpose of the Replacement Matrix by the CIJPM. These metrics are useful for comparing alternative designs and addressing diagnostic problems of the system, to the component and indication level. Additionally, the metrics can be used to predict cost associated with fault isolation over the life cycle of the system.

A Project in the Determination of the Moment of Inertia

2005 ◽  
Vol 33 (4) ◽  
pp. 319-338
Author(s):  
Ron P. Podhorodeski ◽  
Paul Sobejko
Keyword(s):  
Dynamic Properties ◽  
Equations Of Motion ◽  
Mechanical Systems ◽  
Moment Of Inertia ◽  
Educational Goal ◽  
Centre Of Mass ◽  
Comparison Of Results ◽  
Physical Testing ◽  
The Moment

Analysis of the forces involved in mechanical systems requires an understanding of the dynamic properties of the system's components. In this work, a project on the determination of both the location of the centre of mass and inertial properties is described. The project involves physical testing, the proposal of approximate models, and the comparison of results. The educational goal of the project is to give students and appreciation of second mass moments and the validity of assumptions that are often applied in component modelling. This work reviews relevant equations of motion and discusses techniques to determine or estimate the centre of mass and second moment of inertia. An example project problem and solutions are presented. The value of such project problems within a first course on the theory of mechanisms is discussed.

Active Synthesis of Discrete Systems as a Tool for Reduction Vibration

2013 ◽  
Vol 198 ◽  
pp. 427-432 ◽  
Author(s):  
Andrzej Dymarek ◽  
Tomasz Dzitkowski
Keyword(s):  
Force Feedback ◽  
Dynamic Properties ◽  
Vibration Reduction ◽  
Mechanical Systems ◽  
Discrete Systems ◽  
Mechanical Effect ◽  
Active Force ◽  
Active Synthesis ◽  
Proper Selection ◽  
Selection Of

The paper presents the problem of vibration reduction in designed discrete mechanical systems. The method of reduction has been based on active synthesis, which makes it possible to obtain the desired mechanical effect through the proper selection of dynamic properties of the system, including the calculation of the active force as a function of the system force feedback.

scholarly journals Reliability Design of Mechanical Systems Such as Compressor Subjected to Repetitive Stresses

2021 ◽  
Vol 3 (1) ◽  
pp. 14
Author(s):  
Seongwoo Woo ◽  
Dennis L. O’Neal ◽  
Samson Mekbib Atnaw ◽  
Muluneh Mekonnen Tulu
Keyword(s):  
Fatigue Failure ◽  
Life Stress ◽  
Failure Modes ◽  
Action Plan ◽  
Mechanical Systems ◽  
Valve Plate ◽  
Pressure Loading ◽  
Reliability Design ◽  
Mechanical Products ◽  
Reed Valve

This paper suggests parametric accelerated life testing (ALT) as a systematic reliability technique to generate the reliability quantitative (RQ) specification such as mission cycle for identifying design flaws in mechanical systems as exerting the accelerated load, defined as the reverse of stress ratio, R. Parametric ALT therefore is a procedure to improve the fatigue for mechanical products subjected to repetitive loading. It includes: (1) a system BX lifetime shaped on the parametric ALT plan; (2) a fatigue failure and design; (3) tailored ALTs with alternatives; and (4) an assessment of whether the design(s) of the product attains the targeted BX lifetime. A BX life ideas, a life-stress model, and a sample size formulation for parametric ALT are proposed. A reciprocating compressor in a domestic refrigerator is utilized to explain this methodology. The compressor was subjected to repetitive impact loading due to the pressure difference between condenser and evaporator, which results in the compressor field failure. To analyze and conduct parametric ALTs, as mass/energy balance was utilized on the vapor-compression refrigerating cycle, a simple pressure loading of the compressor in operating the refrigerator was investigated. At the first ALT, the compressor was locked due to the fractured suction reed valve made of Sandvik 20C carbon steel (1 C, 0.25 Si, 0.45 Mn). The dominant failure modes of the suction reed valve in the parametric ALTs were established to be very close to that of the fractured product from the marketplace. The root cause of the fatigue failure of the suction reed valve was an amount of overlap between the suction reed valve and the valve plate in combination of repeated pressure loading in the compressor. To supply sufficient mechanical strength, the design faults were altered by the trespan dimensions tumbling process, a ball peening and brushing process for the valve plate. At the second ALT, a compressor was locked due to the intrusion between the crankshaft and the thrust washer. The corrective action plan was to give heat treat the surface of crankshaft made of cast iron (0.45 C, 0.25 Si, 0.8 Mn, 0.03 P). After these alternations, there were no issues at the third ALT. The lifetime of the compressor was ensured to have B1 life 10 years.

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