• 한국신뢰성학회지:신뢰성응용연구
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• 제17권2호
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• pp.83-91
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• 2017

Purpose: The purpose of this study is to develop a quality assurance model and to determine appropriate warranty period for a guided missile using its field data. Methods: 10 years of actual firing data is collected from the defense industry company and military. Parametric maximum likelihood estimation for a reliability function is determined with the data. Results: The reliability function estimates average lifetime of the missile. That function shows a user requirement, 80% reliability (lifetime) is come up when 8 years have passed, which is longer than the estimates in the missile's development phase. Conclusion: Quality assurance warranty for a guided missile must be established with actual test data. It is necessary to update and modify the reliability prediction and the warranty period with actual field test data.

• Journal of the Korean Data and Information Science Society
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• 제24권4호
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• pp.773-781
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• 2013

최근에 기본 보증이 종료된 이후에 주어지는 시스템의 연장된 보증에 대한 관심이 증가되고 있다. 따라서 본 논문에서는 사용자 측면에서 최소수리보증이 있는 연장된 보증이 종료된 이후의 예방보전모형을 제안하였다. 이 때, 기본 보증과 연장된 보증 하에서 고장이 발생된 시스템에는 판매자에 의해서 무료로 최소수리가 이루어진다. 이러한 제안된 예방보전모형에 대하여 기대순환길이, 총기대비용 그리고 단위시간당 기대비용을 유도하였다. 또한, 유도된 단위시간당 기대비용을 최소화 하는 최적의 예방보전 주기와 예방보전 횟수를 결정하였다. 끝으로 시스템의 고장시간이 와이블 분포를 따를 때 수치적 예를 통하여 이를 설명하였다.

• Communications for Statistical Applications and Methods
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• 제17권6호
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• pp.865-877
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• 2010

본 논문에서는 보증기간이 종료된 이후의 수리가 가능한 시스템에 대한 주기적인 예방보전모형을 고려하는데, 무료수리보증, 비례수리보증 그리고 혼합수리보증과 같은 세 종류의 수리보증정책을 고려한다. 이러한 세 종류의 수리보증기간이 종료된 이후의 수리가 가능한 시스템에 대한 주기적인 예방보전모형에 대하여 각각 기대순환길이, 총기대비용 그리고 단위시간당 기대비용을 유도한다. 또한 유도된 단위시간당 기대 비용을 최소화하는 최적의 예방보전정책인 최적의 예방보전주기와 예방보전횟수를 결정하는 방법에 대하여 설명한다. 끝으로 고장시간이 와이블분포를 하는 경우에 최적의 주기적 예방보전정책을 결정하여 본다.

• 한국신뢰성학회:학술대회논문집
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• 한국신뢰성학회 2004년도 신뢰성해외전문가초청세미나
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• pp.97-106
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• 2004

Contractual agreement (relating to product performance). Established on sale of product. Requires the manufacturer to either rectify failures occurring over the warranty period or compensate through refunding a fraction of the sale price.(omitted)

• 품질경영학회지
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• 제24권1호
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• pp.1-9
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• 1996

Ritchken(1985) analyzes free replacement and pro-rata warranty policies for products receiving renewable warranies. He shows that for constant failure rates pro-rata warranty policies are more attractive to risk-averse manufacturers than shorter term free replacement policies that result in the same average warranty cost. This paper considers the case when product lifetimes distributions are of phase-type. When this is so, Ritchken's performance measures can be simplified considerably. It is found, that irrespective of the pattern of failure rates, pro-rata warranty policies are preferable to free replacement policies. But the warranty period of the equivalent free replacement policy decreases and then increases, as product reliability(the average time between failures) increases.

• 품질경영학회지
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• 제22권1호
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• pp.113-121
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• 1994

Present worth of warranty cost for an irrepairable item is derived under free-replacement, prorata and hybrid warranty policies, respectively. In this paper, it is assumed that the lifetime distribution is a Gamma, and warranty period is not renewed but maintained as promised at the selling time regardless of replacements due to warranty contract. A numerical example on the relationship between present worth of warranty cost and mean time to failure is included.

• International Journal of Reliability and Applications
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• 제15권1호
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• pp.51-64
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• 2014

This paper develops a warranty cost model for complex systems with imperfect repair within a warranty period by addressing a practical case that the first inter-failure interval is longer than any other inter-failure intervals. The product is in its best condition before the first failure if repair is imperfect. After the imperfect repair, other inter-failure intervals which are explained by renewal processes, are stochastically smaller than the first inter-failure interval. Based on this idea, we suggest the failure-interval-failure-criterion model. In this model, we consider two random variables, X and Y where X represents failure intervals and Y represents failure criterion. We also obtain the distribution of the number of failures and conduct the warranty cost analysis. We investigate different types of warranty cost models, reliabilities and other measures for various systems including series-parallel configurations. Several numerical examples are discussed to demonstrate the applicability of the methodologies derived in the paper.

• 산업공학
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• 제23권2호
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• pp.176-181
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• 2010

Warranty claim data analysis is a useful tool for the manufacturer because it contains many useful informations regarding reliability of the product in the real-world environments. Because of the nature of uncertainty and the incompleteness of data, some bias patterns are observed on warranty claim rate known as 'spikes'. Two types of spikes are considered. One is due to manufacturing-related failures. The other is caused by customer's behavior. This paper proposes a model by considering two types of spikes. Warranty claim data is analyzed with the proposed model. To represent spikes observed on the early warranty period, we classify failures into manufacturing-related failures and usage-related failures. Uniform distribution is assumed for the time delayed to diagnose and report by customers. By reducing maximum value of the delayed time by customers, the proposed model characterizes customer's rush in the vicinity of the warranty expiration limit. Experimental results by using the real warranty claim data show that the proposed model is better than the existing one in respect to MSE(Mean Squared Error). Moreover it is expected to estimate the failure rate more realistically with proposed model because it considers the delayed time to diagnose and report by customers.

• 대한안전경영과학회지
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• 제16권1호
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• pp.139-146
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• 2014

As Crosby notes, the most companies spend 15 to 20% of their sales dollars on quality costs. Generally the most effective way to manage quality costs is to avoid having defects in the first place. In this paper we have studied about the repair(service) problem of domestic gas boiler within warranty period. We develop a system, which man could find the cause of the problem at an early stage and could devise a countermove to the problem under supposing that the service(repair) rate follows exponential distribution and the product is manufactured lot-for-lot continually. Using the developed early sensing system. it is expected to improve the reliability of the product, to save expenses of company and to improve customer's satisfaction. And the system will be expended to incorporate information technology, which can detect the repair rate automatically.

• 한국건축시공학회지
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• 제17권4호
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• pp.385-391
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• 2017

공동주택의 공종별 책임 하자 보증기간은 과학적인 분석에 근거를 두지 않고 있어. 기간의 적절성이 분쟁의 원인이 되고 있다. 이에 따라 본 연구에서는 2010~2011기준 국토교통부 하자심사 분쟁조정위원회에 접수된 하자제기건수 중 공동주택 하자 중 가장 많이 제기된 마감공사의 하자실태를 파악하여 하자보수기간의 적절성을 평가하고자 하였다. 마감공사의 하자청구건수를 분석한 결과 대부분의 공종별 하자는 2년 이후에도 나타나고 있으며, 60% 정도만이 하자담보책임기간 내에 청구되고 있는 실정이다. 공종별 하자는 상호간에 연관성을 가지고 있으며 이러한 점은 시공의 관리 차원에서 고려되어 공법의 개선이 필요한 것으로 나타났다. 공동주택의 선호도에 큰 영향을 끼치는 시공능력평가 순위와 하자발생의 상관성이 낮은 것으로 보아 실제 수행하는 전문업체의 하자관련 검증 절차가 필요한 것으로 판단된다.