• Proceedings of the Korean Reliability Society Conference
• /
• 2004.07a
• /
• pp.303-311
• /
• 2004

This paper presents the reliability estimation of door hinge for home appliances, which consists of bushing and shaft. The predominant failure mechanism of bushing made of polyoxymethylene(POM) is brittle fracture due to decrease of strength caused by voids existing, and that of shaft made of acrylonitrile-butadiene-styrene(ABS) is creep due to plastic deformation caused by excessive temperature and lowering of glass transition temperature by absorbed moisture. Since the brittle fracture of bushing is overstress failure mechanism, the load-strength interference model is used to estimate the failure rate of it along with failure analysis. By the way, the creep of shaft is wearout failure mechanism, and an accelerated life test is then planned and implemented to estimate its lifetime. Through the technical review about failure mechanism, temperature and humidity are selected as accelerating variables. Assuming Weibull lifetime distribution and Eyring model, the life-stress relationship and acceleration factor, B$_{10}$ life and its lower bound with 90% confidence at worst case use condition are estimated by analyzing the accelerated life test data.a.

• Tribology and Lubricants
• /
• v.31 no.2
• /
• pp.35-41
• /
• 2015

A water-pump located in the cooling area of a car circulates cooling water. A particular bearing element, known as a water-pump bearing, installed in the rotating part carries the entire load. The failure of this water-pump bearing has a direct impact on the failure of the automobile engine, and so securing its reliability is crucial. Several researchers have examined the design principles of the water-pump bearing, but there are no reports on the life characteristic of the bearing yet. Herein, we report the construction of test equipment to reproduce the spalling of the roller contact, which is the main failure mode of the chosen water-pump bearing. We chose the radial load as an accelerated stress factor and validated the failure mode by monitoring the surface defects. We conducted the accelerated life test after determining the accelerated stress level through a combination of finite element analysis and a preliminary test. In the life tests, we used an accelerometer to perform failure diagnosis. In the last stage of this study, we present a statistical reliability analysis. Thus, we fully estimated the shape parameter of the water-pump bearing, accelerating level on the load , and the lifetime (MTTF and B₁₀ life) under real use conditions, and finally proposed an interval estimation value considering the uncertainty of the estimated value.

• Journal of the Korea Safety Management & Science
• /
• v.15 no.1
• /
• pp.109-120
• /
• 2013

As information-oriented industry has been developed and electronic devices has come to be smaller, lighter, multifunctional, and high speed, the components used to the devices need to be much high density and should have find pattern due to high integration. Also, diverse reliability problems happen as user environment is getting harsher. For this reasons, establishing and securing products and components reliability comes to key factor in company's competitiveness. It makes accelerated test important to check product reliability in fast way. Out of fine pattern failure modes, failure of Electrochemical Migration(ECM) is kind of degradation of insulation resistance by electro-chemical reaction, which it comes to be accelerated by biased voltage in high temperature and high humidity environment. In this thesis, the accelerated life test for failure caused by ECM on fine pattern substrate, $20/20{\mu}m$ pattern width/space applied by Semi Additive Process, was performed, and through this test, the investigation of failure mechanism and the life-time prediction evaluation under actual user environment was implemented. The result of accelerated test has been compared and estimated with life distribution and life stress relatively by using Minitab software and its acceleration rate was also tested. Through estimated weibull distribution, B10 life has been estimated under 95% confidence level of failure data happened in each test conditions. And the life in actual usage environment has been predicted by using generalized Eyring model considering temperature and humidity by developing Arrhenius reaction rate theory, and acceleration factors by test conditions have been calculated.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.39 no.12
• /
• pp.1275-1280
• /
• 2015

A large-sized exciter that vibrates a two-ton component is required to simulate the field operating conditions of a counterweight of an excavator. However, it is difficult for a small-medium sized company to obtain a large exciter for the life test of a counterweight which is an equivalent counterbalancing weight that balances a load. Therefore, in this study, we developed life test equipment for evaluating the reliability of construction machinery weighing about two tons. It simulates the field operating conditions using rotational vibrators consisting of electric motors. A failure analysis of the counterweight was also performed for the major components. Field data acquired from various sites were applied to the life test design of the counterweight. Finally, a zero-failure qualification test based on the accelerated life test was designed, and there was no failure during the test, which guarantees a life of $B_5$ 10,000 hours.

• Journal of Power System Engineering
• /
• v.16 no.6
• /
• pp.59-65
• /
• 2012

Torque Generator is a product which has function to transform hydraulic energy to mechanical energy of torque and rotating speed, and be used for direction change device of agricultural machines. This study proposes failure analysis and test analysis on torque generator and introduces a process that reliability of a product is enhanced by design improvement. And also it presents improvements of maximum output torque by modifying design and surface treatment. Lastly it verifies reliability improvement by analyzing test results of before and after life test.

• Journal of Applied Reliability
• /
• v.9 no.4
• /
• pp.343-349
• /
• 2009

One of the recent hot issues in the manufacturing business is how to incorporate environmental attributes into product and process design. Design for environment considers the potential environmental impact of a product throughout its life-cycle. In the case of something breaks, it can become waste immediately, hence reliability and durability is the essential part of product design. This paper presents reliability technology for sustainable product design to improve the product longevity that extends performance life, serviceability and durability. The presented method will help to develop a sound design and avoid weak links to minimize the waste.

• International Journal of Reliability and Applications
• /
• v.8 no.1
• /
• pp.83-94
• /
• 2007

In this paper, we consider a standby redundant structure with a function of switchover processing which may not be not perfect. The switchover processing is governed by a control module whose failure may cause the failure of the whole system. The parameters measuring such an effect of failure of the control module is included in our reliability model. We compute several reliability measures such as reliability function, failure rate, MTBF, mean residual life function, and the steady state availability. We also compare a single unit structure and the redundant structure with regard to those reliability measures. An example is given to illustrate our results.

• Women's Health Nursing
• /
• v.20 no.4
• /
• pp.255-265
• /
• 2014

Purpose: Polycystic Ovary Syndrome Questionnaire (PCOSQ) was developed to measure health-related quality of life of women who had polycystic ovary syndrome. The purpose of this study was to exam reliability and validity of the Korean version of PCOSQ. Methods: A sample of 101 women who had polycystic ovarian syndrome was recruited from outpatient gynecology clinics. Factor analysis was carried out to verify the composition of dimensions of the Korean version of PCOSQ. Concurrent validity was examined by assessing the correlation between the PCOSQ and health related quality of life, and convergent validity was evaluated by testing correlation between PCOSQ and depression. Reliability was assessed using Cronbach's ${\alpha}$. Results: The content validitywas satisfactory (CVI=0.85). Factor analysis identified 5 factors, and factor loadings of the PCOSQ ranged from .48 to .90. Correlation was found between the PCOSQ and health related quality of life (Physical component score: r=.33, p=.001; Mental component score: r=.44, p<.001) and between the PCOSQand depression (r=-.36, p<.001). The Cronbach's ${\alpha}$ of the PCOSQ was .93, indicating reliable reliability. Conclusion: These results demonstrate that the Korean version of PCOSQ is a reliable and valid instrument for evaluating Korean-speaking women with polycystic ovarian syndrome.

• Journal of Applied Reliability
• /
• v.16 no.3
• /
• pp.238-244
• /
• 2016

Purpose: Domestic electric railway Regenerative Energy Storage System seriously affects the maintenance cost of the total operating expenses of nearly 60% of the total LCC (Life Cycle Cost) due to high dependence on foreign Leading company. Therefore by developing the system, it is important to lower the maintenance cost in the domestic supply. This study about the capacitor Reliability test and the purpose of this study is development electric railway Regenerative Energy Storage System. Methods: In case of, having a close relation between the temperature and the reaction rate, Accelerated Model was known that according to Arrhenius' law of chemical activity. If you apply this formula in using allowable temperature range of the capacitor can induce the Arrhenius empirical formula used in much Manufacture Fields. We evaluate the capacitors Leading company through the Arrhenius model. in order to providing a base for the localization of Ultra Capacitor. Conclusion: In this paper, we conducted a reliability test. And it was performed by the accelerated life test and Cycle Test with temperature and C-rate. and then MTBF and B10 life are estimated by analyzing the accelerated life test result. This is thought to need detailed study applying complex stress than about whether it matches the actual behavior in electric railway.

• Journal of Korean Society of Industrial and Systems Engineering
• /
• v.38 no.4
• /
• pp.142-148
• /
• 2015

Due to advancements in technology and manufacturing capability, it is not uncommon that life tests yield no or few failures at low stress levels. In these situations it is difficult to analyse lifetime data and make meaningful inferences about product or system reliability. For some products or systems whose performance characteristics degrade over time, a failure is said to have occurred when a performance characteristic crosses a critical threshold. The measurements of the degradation characteristic contain much useful and credible information about product or system reliability. Degradation measurements of the performance characteristics of an unfailed unit at different times can directly relate reliability measures to physical characteristics. Reliability prediction based on physical performance measures can be an efficient and alternative method to estimate for some highly reliable parts or systems. If the degradation process and the distance between the last measurement and a specified threshold can be established, the remaining useful life is predicted in advance. In turn, this prediction leads to just in time maintenance decision to protect systems. In this paper, we describe techniques for mapping product or system which has degrading performance parameter to the associated classical reliability measures in the performance domain. This paper described a general modeling and analysis procedure for reliability prediction based on one dominant degradation performance characteristic considering pseudo degradation performance life trend model. This pseudo degradation trend model is based on probability modeling of a failure mechanism degradation trend and comparison of a projected distribution to pre-defined critical soft failure point in time or cycle.