• Journal of the Korean Data and Information Science Society
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• 제20권3호
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• pp.601-614
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• 2009

This paper derives noninformative priors for scale parameter of exponential distribution when the data are collected in multiple step stress accelerated life tests. We nd the objective priors for this model and show that the reference prior satisfies first order matching criterion. Also, we show that there exists no second order matching prior. Some simulation results are given and using artificial data, we perform Bayesian analysis for proposed priors.

• 설비공학논문집
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• 제17권12호
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• pp.1169-1176
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• 2005

In this paper, thermal reliability of a closed type BLDC (Brushless DC) motor for high speed axial fan was analyzed by the accelerated life test. The closed type BLDC (Model No. MB1-8855-J01) motor was controlled by PCB module, which was composed of various electrical components. The failure of the closed type BLDC motor happened in PCB module due to high temperature. Failure mechanism of the closed type BLDC motor appears to be electrolyte dry out of capacitor. The accelerate life test was performed in temperature stress of $85^{\circ}C\;and\;105^{\circ}C$, respectively The failure data from the accelerated life test were analyzed and the life in each stress level was estimated with 960h and 261 h. At last, both life expression according to operating temperature of PCB module and life of the closed type BLBC motor in normal condition $(50^{\circ}C)$ were suggested.

• 한국안전학회지
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• 제28권6호
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• pp.11-16
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• 2013

This paper presents a study on the analyzing reliability of smoke fire detector using accelerated life test. In general, the smoke fire detector is broken by dust which flow in smoke detection chamber. In order to conduct accelerated life test of smoke fire detector dust is set accelerated factor in this paper. The dust is fly-ash which is test particle 5th regulated by KS A 0090. The dust accelerated level is 60 g, 180 g and 360 g and failure time is measured by smoke sensitivity testing. It is considered to failure of detector if detector don't operate within 30 secconds when subjected to an air stream having a velocity of 20 cm/s~40 cm/s containing smoke with a concentration of 15% of rate of light-response of 1 m. The goodness of fit test and mean life prediction conduct using the failure time. The result show that life distribution fits the weibull distribution for failure time data and the mean lifes calculate 22.5 year in domestic product and 14.7 years in overseas product applied dust stress only.

• 한국기계가공학회지
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• 제21권6호
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• pp.67-73
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• 2022

Industrial inverters are used in a variety of fields for electric power supply. They may be exposed to vibration and heat once they are installed. This study focused on a framework of accelerated life testing of an industrial inverter considering fatigue damage as the primary source of deterioration. Instead of analyzing detailed failure mechanisms and the product's vulnerability to them, the potential of fatigue failure is considered using the fatigue damage spectrum calculated from the environmental vibration signals. The acceleration and temperature data were gathered using field measurement and spectral analysis was conducted to calculate the vibration signal's power spectral density (PSD). The fatigue damage spectrum is then calculated from the input PSD data and is used to design an accelerated fatigue life testing. The PSD for the shaker table test is derived that has the equivalent fatigue damage to the original input signal. The tests were performed considering the combined effect of random vibration and elevated temperature, and the product passed all the planned tests. It was successfully demonstrated that the inverter used in this study could survive environmental vibration up to its guarantee period. The fatigue damage spectrum can effectively be used to design accelerated fatigue life testing.

• 유공압시스템학회논문집
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• 제2권4호
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• pp.14-22
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• 2005

The safety factor of hydraulic piston pumps & motors due to high pressurization, high speedization and low weight/volume realization to enhance the output density shows a tendency to decrease. Therefore more effective test methods are necessary to predict the exact life. The failure of hydraulic pumps & motors operating in high pressure and high speed mainly occurs in piston-shoe assemblies, and the major failure mode is wearout of the shoe surface. The sensitive parameters in the endurance life test are speed, pressure and temperature, and the failure production increases in proportion to the operating time. In this research, the authors propose the combined accelerated life test model using the analysis method of the combined accelerated life test results of piston-shoe assemblies by applying simultaneously high speed, high pressure and high temperature in accordance with variation of speed, pressure and temperature to reduce the life test time.

• 한국신뢰성학회지:신뢰성응용연구
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• 제17권4호
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• pp.355-361
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• 2017

Purpose: The purpose of this research is to establish the life test method for ceramic heater and identify the failure mechanisms. Methods: We do accelerated life test in the condition of thermal shock and failure analysis for failed samples. Conclusion: The main failure mechanisms of ceramic heater are identified as overstress failure mechanisms as results of failure analysis and the shape parameters of weibull distribution by accelerated life test are identified as 0.8, 1.2 and 0.4 each at $400^{\circ}C$, $600^{\circ}C$ and $900^{\circ}C$. At $900^{\circ}C$, the shape parameter 0.4 means that It is exactly initial failure caused that the stress exceeds the strength of ceramic heater highly and the shape parameters 0.8, 1.2 at $400^{\circ}C$, $600^{\circ}C$ means that the shape parameters are around 1.0 so that the main failure mechanism is overstress failure which is same result as failure analysis. It means that the appropriate life test method for ceramic heater is reliability qualification test method rather than accelerated life test.

• 한국산업융합학회 논문집
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• 제24권5호
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• pp.537-546
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• 2021

Remanufacturing is one of the most important resource recycling technology in response to resource depletion and environmental pollution. Domestic remanufacturing industry don't invigorate compared to other advanced countries because of low price and reliability of remanufactured product. In this study, remanufactured hydraulic pump and solenoid valve were evaluated durability by accelerated life test. In order that standard remanufacturing process was developed by core analysis and failure mode and effect analysis. And cores were remanufactured by standard remanufacturing process. For accelerated life test, the evaluation item and criteria were deduced by results of FMEA, reliability standards and enterprise interior criteria. To evaluate durability of remanufactured product, the remanufactured hydraulic pump and solenoid valve were evaluated performance after accelerated life test and the results were satisfied with criteria. This study showed that remanufactured products have a similar level of durability to new products by definition of remanufacturing.

• 한국도로학회논문집
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• 제19권6호
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• pp.75-81
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• 2017

PURPOSES : So far, aged cement concrete pavement on express highways has been rehabilitated mainly with asphalt concrete inlay. However, potholes were the major problem, and they shortened the life of the inlay mainly owing to the poor drainage of water once it infiltrated the interface of the concrete and asphalt. The purpose of this study is to compare the performance and economic efficiency of asphalt overlay and inlay. METHODS : Overlay and inlay were compared through accelerated pavement testing, and a life-cycle cost analysis was conducted in this study using the CA4PRS program. RESULTS and CONCLUSIONS : It was found from accelerated pavement testing that the overlay exhibited reflective crack resistance that was more than twice as effective as that of inlay. The total cost (construction cost + user cost) within the analysis period (20 years) of the overlay was 37% lower than that of the inlay.

• International Journal of Reliability and Applications
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• 제13권1호
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• pp.19-35
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• 2012

This paper presents an optimum design of step-stress partially accelerated life test (PALT) plan which allows the test condition to be changed from use to accelerated condition on the occurrence of fixed number of failures. Various life distribution models such as exponential, Weibull, log-logistic, Burr type-Xii, etc have been used in the literature to analyze the PALT data. The need of different life distribution models is necessitated as in the presence of a limited source of data as typically occurs with modern devices having high reliability, the use of correct life distribution model helps in preventing the choice of unnecessary and expensive planned replacements. Truncated distributions arise when sample selection is not possible in some sub-region of sample space. In this paper it is assumed that the lifetimes of the items follow Truncated Logistic distribution truncated at point zero since time to failure of an item cannot be negative. Optimum step-stress PALT plan that finds the optimal proportion of units failed at normal use condition is determined by using the D-optimality criterion. The method developed has been explained using a numerical example. Sensitivity analysis and comparative study have also been carried out.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2005년도 춘계학술대회 논문집
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• pp.14-19
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• 2005

An accelerated life test (ALT) is used to estimate the reliability of machinery parts and system with a design specification as soon as possible. However, accelerated life test results with simple and severe conditions are inconsistent with physical phenomena in real service condition. Therefore, to assure the safety of the machinery system, it is necessary to establish the appropriate test condition of the ALT of machinery element. In this study, fatigue analysis of the spur gear as a part of the gear box system in the rolling stock was performed. Moreover, based on the results, appropriate test condition of the ALT is developed using both the probabilistic model of the linear damage rule and accelerated durability analysis simulation.