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

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2012.11a
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• pp.154-154
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• 2012

• Magazine of the Korea Concrete Institute
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• v.17 no.4 s.87
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• pp.34-40
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• 2005

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2002.03a
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• pp.67-74
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• 2002

An experimental assessment on the dynamic behavior of saturated sand which can consider the irregular characteristics of earthquakes was proposed. The equivalent uniform stress concept presented by Seed and Idriss has been applied to evaluate the liquefaction resistance strength to simplify earthquake loading. However, it was known that the liquefaction resistance strength of soil based on the equivalent uniform stress concept can't exactly mirror the dynamic characteristics of the irregular earthquake motion. In this study, estimation of the criterion of the liquefaction resistance strength was determined by applying real earthquake loading to the cyclic triaxial test. From the test results, relationships between excess pore water pressure and the earthquake characteristics such as magnitude or duration were determined. Magnitude scaling factors to determine the soil liquefaction resistance strength in seismic design were also proposed.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.10a
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• pp.415-418
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• 1999

This paper presents a study in the ductility of reinforced concrete beam-column-slab joints Three assemblies were designed 2/3 scale (f'c=240kg/$\textrm{cm}^2$, f'c=700kg/$\textrm{cm}^2$) and tested to investigate seismic behavior. From the test results, 1) flexural cracks emerge to inside of beam deeply for high strength concrete member, 2) the high-strength specimens degraded in stiffness and strength, and unstable hysteretic behaviors were observed, owing to the brittleness of high-strength concrete beyond its range. 3) The confinement provided by the additional hoops to the column bar is probably the main reason for this improvement in behavior.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2005.05a
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• pp.119-124
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• 2005

It is necessary for prediction of recycled aggregate concrete(RAC) strength at the early stage that facilitate concrete form removal and scheduling for construction. However, to predict RAC strength is difficult because of being influenced by complicated many factors. Therefore, this research suggest optimized estimation method that can reflect many factors. One way is Case-Based Reasoning(CBR) that solved new problems by adapting solutions to similar problems solved in the past, which are solved in the case library. Other way is Artificial Neural Networks(ANN) that solved new problems by training using a set of data, which is representative of problem domain. This study is to propose comparing accuracy of the estimating the compressive strength of recycled aggregate concrete using Case-Based Reasoning(CBR) and Artificial Neural Networks(ANN).

• Journal of Welding and Joining
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• v.18 no.3
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• pp.68-75
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• 2000

The incomplete penetration(IP) discontinuity in butt joint weld, which is detected during safety analysis of the steel bridge by nondestructive evaluation(NDE) method, is classified as unacceptable defect according to the NDE codes and standards. In fact, there are a little allowance in butt joint weld in the view point of design criterion, and also detected IP discontinuity should be classified and evaluated for the fatigue strength and residual life estimation. In this study, we performed fatigue test to evaluate the fatigue strength of high strength steel(SWS490A) containing IP discontinuities in various size, the results compared and classified according to the bridge construction standard specification which published by korea administration of construction and traffic. Experimental results could be used to evaluate and estimate the IP discontinuities considering different stress range in butt joint bridge weld during periodic safety inspection.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.223-228
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• 2000

Although construction company try to get good quality control it's enough to study about developing objective evaluation method and checking quality method. It is important to meaning concrete quality at placing point, immediate quality checking method is limited. The purpose of this study is to develop new method to know early 28-day concrete for getting faithful quality control. The results of this study are as follows :1) With sealed molds, reduced moisture volatilization to more than 50% and enlarged 20% accelerated compressive strength than before one. 2) Accelerated compressive strength of concrete specimen shows higher strength when it was in the air for long time 3)Interrelation with 7-day and 28-day strength were 0.781,0.90, It is higher than before one

• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.103-106
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• 2000

Nondestructive tests are useful method in rapidly evaluating the condition of existing concrete structures. An objective of this work is to investigate the factors influencing the longitudinal wave velocity-strength relationship, such as w/c ratio, curing temperature, curing condition. Test results show that a change in the w/c ratio ranging from 0.46 to 0.88 and in the curing temperature from 1$0^{\circ}C$ to 3$0^{\circ}C$ did not alter the velocity-strength relationship. however, curing methods had significant effects on the velocity-strength relationship. Therefore, the estimation of compressive strength until 28 day can be accomplished by only a nonlinear equation with consideration of curing condition.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.979-984
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• 2003

Quality control of ready-mixed concrete is most important in the production step because, the performance of hardened concrete is revealed due to ready-mixed concrete. Hardened concrete has several properties physically. Above all things compressive strength of concrete has a greate effect in the design of structures, analysis, and durability. Compressive strength is simple predicted by w/c up to date, but there are some limits because different compressive strengths can be revealed in the same w/c. Therefore this study contributes to the quality control of ready-mixed concrete through statistical analysis for the relation between mix factors in mix design and compressive strength, predictable equation for compressive strength.