scholarly journals Reliability Design of Mechanical Systems Subjected to Repetitive Stresses

2020 ◽  
Vol 2 (1) ◽  
Author(s):  
Seong-woo Woo ◽  
Dereje E. Woldemichael ◽  
Samson M. Atnaw ◽  
Muluneh Mekonnen Tulu ◽  
Dennis L. O’Neal
Keyword(s):  
Mechanical Systems ◽  
Reliability Design

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.

Spatial Layouts of Complex Mechanical Systems

2005 ◽  
Author(s):  
Yu-Xin Wang ◽  
Yong-Shan Wang ◽  
Alex H. B. Duffy
Keyword(s):  
Fitness Function ◽  
Mechanical Systems ◽  
Spatial Layout ◽  
Adaptive Genetic Algorithm ◽  
Layout Problem ◽  
Reliability Design ◽  
Spatial Layouts ◽  
Parallel Connections ◽  
Set Up ◽  
Complex Mechanical Systems

Spatial layouts for complex mechanical systems are important both for the reliability design and industrial esthetics design of products. Existing of extra constrains caused by specific connections among basic mechanisms makes the layout problem particular and complex. In this paper, several common connecting relations existing in complex mechanical systems are generalized into three kinds of connections, serial connections, parallel connections, and closed connections, and then constrain equations caused by these connections are set up based on transforming matrixes. Expressing spatial spaces occupied by basic mechanisms with cuboid model, and dealing with constrains and interferences in mechanical systems with the fitness function, the spatial layout problem of complex mechanical systems is calculated based on an adaptive genetic algorithm. At last, taking a complex mechanical system consisting of eight basic mechanisms with parallel and serial connections as an example, the efficiency and validity of the algorithm presented in this paper have been verified.

Optimizing reliability design for mechanical systems using geometric programming

2006 ◽  
Vol 17 (3) ◽  
pp. 235-249 ◽  
Author(s):  
Yuo-Tern Tsai ◽  
Hwei-Yuan Teng ◽  
Yeong-Jern Chen
Keyword(s):  
Geometric Programming ◽  
Mechanical Systems ◽  
Reliability Design

scholarly journals Reliability design of mechanical systems subjected to repetitive stresses

2021 ◽  
Vol 349 ◽  
pp. 03009
Author(s):  
Seong-woo Woo ◽  
Dennis L. O’Neal ◽  
Yimer Mohammed Hassen
Keyword(s):  
Life Stress ◽  
Failure Modes ◽  
Plastic Material ◽  
Action Plan ◽  
Mechanical Systems ◽  
Life Time ◽  
Design Parameters ◽  
Repeated Impact ◽  
Reliability Design ◽  
Reliability Method

To enhance the design of mechanical systems, parametric Accelerated Life Testing (ALT) as a systematic reliability method is proposed as a way to evaluate the design of mechanical systems subjected to repeated impact stresses. It requires: (1) a parametric ALT scheme shaped on system BX lifetime, (2) a load inspection, (3) parametric ALTs with the associated design modifications, and (4) an assessment of whether the revised product design(s) reach the targeted BX life-time. We propose using a general life-stress model and sample size equation. A test example using both market data and parametric ALT was the redesign of a hinge kit system (HKS) in a refrigerator. To conduct parametric ALTs, a force and moment balance analysis was utilized. The mechanical impact loadings of the HKS were evaluated for an working refrigerator door. For the first ALT, the HKS failure happened in the crack/fracture of the kit housing and oil spilled from the damper when the HKS was disassembled. The failure modes and mechanisms constructed in the 1st ALT were similar to those of the unsuccessful samples found from the marketplace. The missing design parameters of the HKS included stress raisers such as corner roundings and the rib of the housing in HKS, the seal in the oil damper, and the material of the cover housing. In the second ALT, the cover housing fractured. The design defect of the cover housing in the HKS was the plastic material. As a corrective action plan, the cover housing was modified from plastic to aluminium. After the second ALT, the lifetime of the modified HKS was reassured to be B1 life 10 years with a yearly failure rate of 0.1%.

Second Order Design Sensitivity Analysis of Kinematically-Driven Mechanical Systems

1992 ◽  
Author(s):  
Qiushu Cao ◽  
Prakash Krishnaswami
Keyword(s):  
Sensitivity Analysis ◽  
Mechanical Systems ◽  
Design Sensitivity ◽  
Second Order ◽  
Design Sensitivity Analysis ◽  
System Response ◽  
Reliability Design ◽  
Constrained Mechanical Systems ◽  
Minimum Sensitivity ◽  
Element Technique

Abstract Second order design sensitivity information is required for several design applications, including second order optimization, minimum sensitivity design and reliability design. The problem of computing this information in a generalized manner becomes difficult when the dependence of system response on design is not explicitly known, as in the case of kinematic systems. This paper presents a general method for second order design sensitivity analysis of constrained mechanical systems. This method uses the constrained multi-element technique for kinematic analysis combined with a direct differentiation approach for obtaining first and second order design sensitivities of the system response. The method was implemented in a computer program on which several examples were solved. Three of the examples are presented in this papers. For each example, the second order sensitivities are checked against values obtained by finite differencing. In all cases, the agreement is seen to be very close, indicating that the proposed method is accurate and reliable.

Study on Reliability Tests to a Few Samples of Mechanical System

2010 ◽  
Vol 42 ◽  
pp. 339-342
Author(s):  
Shu Yi Guo ◽  
Yong Qi Qi
Keyword(s):  
Mechanical System ◽  
Fatigue Failure ◽  
Mechanical Systems ◽  
Auxiliary Information ◽  
Economic Loss ◽  
Test Sample ◽  
Small Samples ◽  
Reliability Test ◽  
Reliability Design ◽  
Mechanical Devices

The reliability tests play more and more important role in mechanical systems. A new method named a few samples and combined the probability and the fuzzy mathematics has been set up to explore the unknown system of a few samples with the help of the life samples of the known probabilistic distribution. The method reduced the traditional reliability test samples by some auxiliary information. It converted lots of reliability test into a few samples. This paper introduced two engineering examples to verify the method as an effective way to carry out the reliability tests. It provides the theory basis for the reliability of complicated mechanical systems. The loss caused by fatigue failure is as high as 3%~4% of Gross National Product. Fatigue fracture owned to the cycle load accounts for 95% of the total number of mechanical structure failure. Unfortunately no evidence of failure is observed when fatigue failure reaches its life. This causes human casualties and great economic loss. So the reliability research on complicated mechanical systems has to realize from reliability assessment to the active reliability design. One of the key problems of the active reliability design for complicated mechanical system is to reduce the great waste of the resources used in the probability reliability test. For example, dozens of the high precision gears made of certain material may be run out in the fatigue test which would be running day and night for several months. It has been described many methods about system reliability design in the former research [1-3]. But for many high technological products and important mechanical devices, it is impossible to get the test sample to carry out probability analysis. To exert the advantages of the active reliability design and to realize the green reliability design [4], the only way is to study small samples in the reliability tests and to develop new technique. It is named as a few samples reliability tests method of the complicated mechanical systems.

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.

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