• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.10a
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• pp.672-675
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• 1995

Because of a sudden growth of the research of fatigue failure, recent machines or structures have been designed by damage tolerance design in many fields. Consequently, it is the most primary factor to clarity the specific character of fatique failure in the design of machines or structures considering reliability. A statistical analysis is required to analyze the outcome of an experiment or a life estimate by reason of that fatigue failure contains lots of random elements. Reliability analysis which has tukenn the place of the existing analyses in the consideration of the uncertainty of a material, is a very efficient way. Even reliability analysis, however, is not a perfect way to analyses the uncertainties of all the materials. This thesis would refer to a newly conceived data analysis that the coefficient of a system could cause the ambiguity of the relationship of an input and output.

• Journal of Technologic Dentistry
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• v.40 no.3
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• pp.151-162
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• 2018

Purpose: The main purpose of this study is to develop assessment measures for the quality of service for dental labs. Methods: In order to construct the measure of service quality assessment for dental labs, relevant modifications were extracted around theoretical studies, and the survey was conducted on dental technician workers through internet survey. final scale questions were extracted through exploratory factor analysis and confirmed factor analysis of measurement variables, the demographic characteristics of the subjects and the perceptual difference of dental labs were analyzed for the extracted variables. Results: The final five variants of the interactive factor analysis that include the ability to change employee growth, reliability, responsiveness, materiality, interoperability, confirmatory factor analysis excludes variations in employee growth wages, welfare benefits, by changing its name to network capabilities, the quality of service factors for the final dental labs consisted of five variations: network competence, reliability, responsiveness, materiality and interoperability. Conclusion : The service quality of the dental labs showed that the reliability of the product related to the dental materials and the product production responsiveness related to the production order, the Materiality of the materials and equipment of the dental labs, the Interoperability responsiveness related to dental orders, And the importance of network capability to form a mutual network.

• Journal of Korean Society for Quality Management
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• v.37 no.3
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• pp.33-38
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• 2009

When we estimate the parameters of software reliability models, we usually use maximum liklihood estimator(MLE). But this method is required a large data set. In particular, when we want to estimate it with small observed data such as early stages of testing, we give rise to the non-existence of MLE. Therefore, it is interesting to look into the influence of parameter estimators obtained using MLE. In this paper, we use two non-homogenous poisson process software reliability growth model: delayed S-shaped model and log power model. In this paper, we calculate the sensitivity of estimators about failure intensity function for two SRGMs respectively.

• Journal of Applied Reliability
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• v.12 no.3
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• pp.165-176
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• 2012

Hydrostatic bearing improves performance and life time of a product by avoiding solid friction and reducing viscosity friction with the help of creating pressure equilibrium between two faces doing relative motion. This study suggests failure analysis and test evaluation for a ball joint that adopts the hydrostatic bearing and introduces the entire process to improve reliability of the product by design improvement. A typical failure is growth of friction torque by solid friction, and its failure cause is determined and the improvement is proposed. Finally, reliability improvement is established by analysis of the results of before and after acceleration test.

• Journal of the Korea Safety Management & Science
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• v.8 no.2
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• pp.91-102
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• 2006

Korea Railroad Research Institute developed the driverless rubber-tired Korean-AGT system from 1999 to 2005 and has done its performance and reliability tests on the test line at Gyeongsan-city. We made the reliability management program to control required the RAMS(reliability, availability, maintainability & safety) of the K-AGT system. Therefore, we demonstrated the development and application of Reliability DB program. The main functions of K-AGT Reliability DB program manages failures and maintenance data systematically from the test line through test period and provides various analysis results based on the inputted data.

• International Journal of Automotive Technology
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• v.8 no.5
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• pp.623-628
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• 2007

Reliability analysis based on fracture mechanics requires knowledge of the on statistical parameters m and C in the fatigue crack growth law $da/dN=C({\Delta}K)^m$. The purpose of the present study is to investigate if it is possible to explain the change of parameter m by the fluctuation of C only. In this study, we apply the Paris-Erdogan law treating the parameter C as random and the parameter m as constant. Fluctuations in crack growth rate are assumed to be dependent only on C. The material resistance to fatigue crack growth(Z=1/C) is treated as a spatially random process, that varies along the crack path. The theoretical crack growth rates at various stress intensity factors are discussed. Additionally, the results of constant ${\Delta}K$ fatigue crack growth tests are reported for the structural steel, SM45C. The experimental data have been analyzed to determine the probability distribution of fatigue crack growth resistanc.

• Journal of Applied Reliability
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• v.18 no.3
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• pp.271-279
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• 2018

Purpose: Probabilistic safety analysis was performed to enhance the safety and reliability of nuclear power plants because traditional deterministic approach has limitations in predicting the risk of failure by crack growth. The study introduces a probabilistic approach to establish a basis for probabilistic safety assessment of passive components. Methods: For probabilistic modeling of fatigue crack growth rate (FCGR), various FCGR tests were performed either under constant load amplitude or constant ${\Delta}K$ conditions by using heat treated X-750 at low temperature with adequate cathodic polarization. Bayesian inference was employed to update uncertainties of the FCGR model using additional information obtained from constant ${\Delta}K$ tests. Results: Four steps of Bayesian parameter updating were performed using constant ${\Delta}K$ test results. The standard deviation of the final posterior distribution was decreased by a factor of 10 comparing with that of the prior distribution. Conclusion: The method for developing a probabilistic crack growth model has been designed and demonstrated, in the paper. Alloy X-750 has been used for corrosion fatigue crack growth experiments and modeling. The uncertainties of parameters in the FCGR model were successfully reduced using the Bayesian inference whenever the updating was performed.

• Journal of the Society of Naval Architects of Korea
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• v.30 no.2
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• pp.161-176
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• 1993

For the purpose of assessing structural integrity at a level of complexity and accuracy appropriate for the situation, integrity assessment methods are formulated with the following methods. One is three-tier assessment method of the revised BSI PD 6493 which considers stable crack growth effect, the others are limit load analysis which estimates the plastic collapse load and stability assessment method which considers stable crack growth of ductile material exactly using J-integral and tearing modulus. Besides, integrity assessments for center cracked panel(CCP) specimen and the circumferential through-cracked pipe are carried out and reliability analysis is accomplished by the first order reliability method which is one of the conventional reliability methods. Also the accuracy of the present method is verified by Monte Carlo method.

• Korean Journal of Materials Research
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• v.15 no.1
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• pp.54-60
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• 2005

Recently a lots of problems have observed in high densified and high integrated electronic components. One of them is ion migration phenomena, which induce the electrical short of electrical circuit. ion migration phenomena has been observed in the field of exposing the specific environment and using for a long tin e. This study was evaluated the generation time of ion migration and was investigated properly test method through water drop test and high temperature high humidity test. Also we observed direct causes and confirmed generation mechanism of dendritic growth as we reproduced the ion migration phenomena. We utilized PCB(printed circuit board) having a comb pattern as follows 0.5, 1.0, 2.0 mm pattern distance. Cu, SnPb and Au were electroplated on the comb pattern. 6.5 V and 15 V were applied in the comb pattern and then we measured the electrical short time causing by ion migration. In these results, we examined a difference of ion migration time depending on pattern materials, applied voltage and pattern spacing of PCB conductor.

• Journal of the Korean Data and Information Science Society
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• v.19 no.4
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• pp.1361-1369
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• 2008

The analysis of software reliability model provides the means to analysts, software engineers, and systems analysts and developers who want to predict, estimate, and measure failure rate of occurrences in software. In this paper, reliability growth model, in which the operating time between successive failure is a continuous random variable, is proposed. This model is based on order statistics of two parameters Burr type XII distribution. We propose the measure based on U-plot. Also the performance of the suggested model is tested on real data set.