• International Journal of Reliability and Applications
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• 제14권1호
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• pp.41-54
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• 2013

In this paper, cost analysis is conducted using inter-failure interval under renewable warranty subject to imperfect repair for multi-component system. One way to model the imperfect repair is to use the quasi-renewal process (Wang and Pham 1996). Two alternative quasi-renewal processes were suggested by Park and Pham (2010) using quasi-renewal process; first is an altered quasi-renewal process with random variable parameter and second is a mixed quasi-renewal process considering replacement service and repair service, simultaneously. In this study, we use the altered and mixed quasi-renewal processes and develop the warranty cost model to obtain the expected value of warranty cost and to help company make important decisions regarding the warranty policy. Numerical examples are used to demonstrate the applicability of the methodology derived in the paper.

• 대한치과보철학회지
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• 제34권2호
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• pp.233-245
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• 1996

The purpose of this study was to evaluate the effect of thermocycling on bond strength between metal and resin cement according to thermocycling, and to observe the bond failure modes with optical microscope(X30). For this purpose, Super-Bond C & B and Panavia 21 resin cement were used. Metal specimens were made of Vera-Bond and the surface of specimens were sandblasted with $50{\mu}m$ aluminum oxide. All experimental groups were stored in $37^{\circ}C$ distilled water for 72 hours, followed by thermocycling between $5^{\circ}C$ and $55^{\circ}C$ with 15 second dwell time. 500, 1000, 2000 cycles of thermocycling were executed and the tensile bond strength was measured by Instron Universal Testing Machine(Model 4201) The obtained results were as follows : 1. Super-Bond C & B and Panavia 21 did not show statistically significant difference accor-ding to thermocycling test(P>0.05). 2. Super-Bond C & B specimens exhibited statistically significant higher tensile bond stre-ngth than Panavia 21 for all experimental groups(P<0.05). 3. Super-Bond C & B exhibited mixed mode failure with partial adhesive and partial cohe-sive failure, and most of Panavia 21 exhibited cohesive failure and some mixed mode failure.

• Journal of the Korean Statistical Society
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• 제28권4호
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• pp.399-413
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• 1999

• Communications for Statistical Applications and Methods
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• 제18권6호
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• pp.741-750
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• 2011

본 논문에서는 소프트웨어의 고장수리 과정 중 완전 수리와 불완전 수리를 모두 고려하는 혼합수리 모형을 제안하려고 한다. 이를 위해 소프트웨어가 가지고 있는 전체 결함의 유형을 고치기 쉬운 결함 유형과 고치기 어려운 결함 유형으로 나누고, 고치기 쉬운 결함의 경우에서는 수리 과정 중 결함을 완전하게 고친다고 가정한다. 또한 고치기 어려운 결함 유형은 완전 또는 불완전 수리가 가능하도록 가정하며, 이러한 가정과 마코프 과정(Markov process)하에서 소프트웨어 성능 평가를 위한 측도 중에 하나인 소프트웨어 가용성(software availability)을 제시하고자 한다.

• Ecology and Resilient Infrastructure
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• 제10권1호
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• pp.1-10
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• 2023

제방은 기본적으로 물이 넘치지 않도록 하기 위하여 조성되는 구조물이다. 개발된 제방보강 기술은 바이오폴리머와 골재를 혼합하여 제방의 붕괴로 발생되는 대규모 재난을 방지하기 위한 기술로 제방의 세굴 및 붕괴 등을 억제하는데 목적이 있다. 개발된 기술은 호안 사면 등에도 활용이 가능하지만 시공성이 수월하여 월류파괴에 대한 대응 기술로 적용하기 용이하다. 개발된 기술을 현장에 적용하기 위해서는 기술의 안전성을 확보해야 하므로 현장시범사업 등 실제 적용에 대한 연구가 필요하다. 하지만 월류 파괴는 현장에서 시범사업을 수행할 수 없으므로 본 연구에서는 실규모 실험을 통해 현장 적용성 연구를 수행하였다. 실규모실험은 안동에 위치한 하천실험센터에서 수행하였으며, 인위적인 월류를 통하여 제방 세굴 및 붕괴 상황을 검토하였다. 실험결과 개발기술이 월류파괴에 대해 대응 가능하고 붕괴를 억제할 수 있는 기술로의 실증을 수행하였다.

• 한국신뢰성학회:학술대회논문집
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• 한국신뢰성학회 2000년도 추계학술대회
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• pp.373-373
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• 2000

Bum-in procedures are developed far limited failure populations in which defective products fail soon after they are put in operation and non-defective ones never fail during the technological life of the products. The situation where products are produced from a production process with variable fraction defective is considered. Bum-in schemes guaranteeing pre-specified outgoing quality of products are derived using the mixed binomial prior distribution for the number of defectives in a batch.

• 대한안전경영과학회지
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• 제1권1호
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• pp.135-143
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• 1999

This paper discusses an optimal burn-in procedure to minimize total costs based on the assumption that the failure rate pattern follows a bimodal mixed Weibull distribution. The procedure will consider warranty period as a factor of the total expected bum-in cost. A cost model is formulated to find the optimal burn-in time that minimizes the expected burn-in cost. Conditional reliability for warranty period will be discussed. An illustrative example is included to show how to use the cost model in practice.

• 대한기계학회논문집A
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• 제23권6호
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• pp.1039-1047
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• 1999

It is necessary to evaluate the fatigue behavior of rail steel under the multi-axial stress state to assure the railway vehicle's safety. For this purpose, the stress analysis to investigate the crack initiation criteria, static failure and fatigue behavior under mixed-mode are performed. The stress analysis results show that the initiation of the transverse fissure depends on the maximum shear stress below the surface. For the mixed mode, the fatigue crack growth behavior which is represented by the projection crack length and comparative S.I.F, ${\Delta}K_v$, shows the more conservative results. Also, its rate is lower than that of the case of the mode I, and this difference decreases with increasing the stress ratio, R.

• 한국정밀공학회지
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• 제18권9호
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• pp.131-139
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• 2001

The use of fracture mechanics has traditionally concentrated on crack growth under an opening mechanism. However, many service failure occur from cracks subjected to mixed mode loadings. Hence, it is necessary to evaluate the fatigue behavior under mixed mode loading. Under mixed mode loading conditions, not only the fatigue crack propagation rate is of importance, but also the crack propagation direction. The mode I and II stress intensity factors of CTS specimen were calculated using elastic finite element method. The propagation behavior of the fatigue crack of the STS304 steeds under mixed mode loading condition was evacuated by using stress intensity factors $K_I$ and $K_II. The MTS criterion and effective stress intensity factor were applied to predict the crack propagation direction and the fatigue crack propagation rate.

• Restorative Dentistry and Endodontics
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• 제46권4호
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• pp.59.1-59.14
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• 2021

Objectives: This study compared the Biodentine, MTA Repair HP, and Bio-C Repair bioceramics in terms of bond strength to dentin, failure mode, and compression. Materials and Methods: Fifty-four slices obtained from the cervical third of 18 single-rooted human mandibular premolars were randomly distributed (n = 18). After insertion of the bioceramic materials, the push-out test was performed. The failure mode was analyzed using stereomicroscopy. Another set of cylindrically-shaped bioceramic samples (n = 10) was prepared for compressive strength testing. The normality of data distribution was analyzed using the Shapiro-Wilk test. The Kruskal-Wallis and Friedman tests were used for the push-out test data, while compressive strength was analyzed with analysis of variance and the Tukey test, considering a significance level of 0.05. Results: Biodentine presented a higher median bond strength value (14.79 MPa) than MTA Repair HP (8.84 MPa) and Bio-C Repair (3.48 MPa), with a significant difference only between Biodentine and Bio-C Repair. In the Biodentine group, the most frequent failure mode was mixed (61%), while in the MTA Repair HP and Bio-C Repair groups, it was adhesive (94% and 72%, respectively). Biodentine showed greater resistance to compression (29.59 ± 8.47 MPa) than MTA Repair HP (18.68 ± 7.40 MPa) and Bio-C Repair (19.96 ± 3.96 MPa) (p < 0.05). Conclusions: Biodentine showed greater compressive strength than MTA Repair HP and Bio-C Repair, and greater bond strength than Bio-C Repair. The most frequent failure mode of Biodentine was mixed, while that of MTA Repair HP and Bio-C Repair was adhesive.