• Communications for Statistical Applications and Methods
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• v.18 no.6
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• pp.697-705
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• 2011

This paper proposes an optimal replacement policy following the expiration of a free renewing replacement-non-renewing minimal repair warranty. To do so, the free renewing replacement-non-renewing minimal repair warranty is defined and then the maintenance model following the expiration of free renewing replacement-non-renewing minimal repair warranty from the user's point of view is studied. As the criteria to determine the optimality of the maintenance policy, we consider the expected cost rate per unit time from the user's perspective. We derive the expressions for the expected cycle length and the expected total cost to obtain the expected cost rate per unit time. Finally, the numerical examples are presented for illustrative purposes.

• Communications for Statistical Applications and Methods
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• v.17 no.6
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• pp.865-877
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• 2010

This paper considers the periodic preventive maintenance model for a repairable system following warranty expiration. We consider three types of warranty policies: free repair warranty, pro-rata repair warranty, and combination repair warranty. Under these preventive maintenance models, we derive the expressions for the expected cycle length, the total expected cost, and the expected cost rate per unit time. In addition, we explain the optimal preventive maintenance period and the optimal preventive maintenance number by minimizing the expected cost rate per unit time. Finally, the optimal periodic preventive maintenance policy is given for a Weibull distribution case.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.20 no.43
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• pp.357-364
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• 1997

After the buyer purchases the product, the seller's role does not end. If the product fails to function properly before the end of the warranty period, the seller is responsible for its repair or replacement under the seller's warranty policy. There are two common types of warranty policies: the free replacement warranty and the rebate warranty. Under the free replacement warranty policy, replacement or repairs during the warranty period are provided by the seller free of charge to the buyer. Under the rebate warranty policy, a failed item is replaced by a new one or is repaired at a cost to the age of the failed item. The rebate warranty is most often used for items such as a battery or an automobile tire which wear out and must be replaced at failure. This paper proposes a easy way of estimating the warranty cost under the free replacement warranty policy assuming an exponential product failure function on repairable products.

• The Korean Journal of Applied Statistics
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• v.23 no.6
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• pp.1147-1156
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• 2010

This paper proposes a replacement policy following the expiration of a non-renewing free replacement-repair Warranty(NFFRW). The non-renewing free replacement-repair warranty is defined and then the maintenance model following the expiration of the NFRRW is studied from the user's point of view. As the criteria to determine the optimality of the maintenance policy, we consider the expected cost rate per unit time from the user's perspective. All maintenance costs of the system incurred after the expiration of the warranty are paid by the user. Given the cost structures during the life cycle of the system, we determine the optimal maintenance period following the expiration of a NFRRW. Finally, the numerical examples are presented for illustrative purposes.

• Journal of the Korean Data and Information Science Society
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• v.22 no.4
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• pp.775-784
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• 2011

In this paper, we consider the periodic preventive maintenance model for repairable system following the expiration of non-renewing free replacement-repair warranty (NFRRW). Under this preventive maintenance model, we derive the expressions for the expected cycle length, the expected total cost and the expected cost rate per unit time. Also, we determine the optimal preventive maintenance period and the optimal preventive maintenance number by minimizing the expected cost rate per unit time. Finally, the optimal periodic preventive maintenance policy is given for Weibull distribution case.

• Journal of the Korean Data and Information Science Society
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• v.20 no.6
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• pp.999-1007
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• 2009

This paper considers the optimal periodic preventive maintenance (PM) policy following the expiration of free-repair warranty. We assume that two periodic PM models with random maintenance quality which were proposed by Wu and Clements-Croome (2005) and Jung (2006b), respectively. Given the cost structure to the user during the cycle of the product, we derive the expressions for the expected cost rate per unit time. Also, we obtain the optimal PM number and the optimal PM period by minimizing the expected cost rate per unit time. The numerical examples are presented for illustrative purpose.

• Journal of Korean Institute of Industrial Engineers
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• v.13 no.2
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• pp.59-63
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• 1987

An age replacement policy is considered for a system under a stepdown warranty. It is assumed that only minimal repairs are performed for failures occurred before age T.A unique optimal value of T which minimiges the expected cost rate is obtained. The cases of the free replacement warranty, prorata warranty and hybrid warranty are also considered and some numerical examples are given.

• International Journal of Reliability and Applications
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• v.12 no.1
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• pp.41-48
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• 2011

This paper considers the maintenance model suggested by Jung and Park (2010) to adopt the Bayesian approach and obtain an optimal replacement policy following the expiration of NFRRW. As the criteria to determine the optimal maintenance period, we use the expected cost during the life cycle of the system. When the failure times are assumed to follow a Weibull distribution with unknown parameters, we propose an optimal maintenance policy based on the Bayesian approach. Also, we describe the revision of uncertainty about parameters in the light of data observed. Some numerical examples are presented for illustrative purpose.

• Journal of Korean Institute of Industrial Engineers
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• v.14 no.2
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• pp.81-90
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• 1988

This paper is concerned with warranty cost models for a product with two types of failure ; type 1 failures corrected by minimal repair and type 2 failures removed only by replacement. Two warranty policies involving an initial free service period followed by a pro-rata period are considered ; the difference is whether the warranty is renewed or not when type 2 failure occures during its free service period. Expected warranty costs under the two policies are obtained, and their behaviors are examined for the case where type 1 and 2 failure distributions are Weibull and exponential, respectively.

• The Korean Journal of Applied Statistics
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• v.26 no.1
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• pp.151-162
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• 2013

Due to a growing demand for the second-hand product, especially for the expensive one, the warranty and maintenance policies for such products have been studied to improve the product reliability of late. In this paper we study a periodic maintenance model for the second-hand product which is purchased by the customer at the age of $x$. When purchased, the dealer provides a warranty of a fixed length during which the product is maintained periodically to reduce the failure rate of the product and thus, to improve the reliability after each maintenance is served. If a failure occurs between two successive maintenances, only minimal repair is conducted. As for the warranty policy, we adopt free non-renewing repair action on each failure, in addition to the periodic maintenance service during the warranty period. Thus, under the given warranty policy, all the maintenance and repair costs incurred during the warranty period are charged to the dealer. For the proposed periodic maintenance scheme, we formulate a cost model to evaluate the expected total cost charged to the dealer during the warranty period and derive an optimal upgrade level of the failure rate at each maintenance to minimize the expected total warranty cost from the perspective of the dealer. We also present numerical results for an optimal upgrade level based on the proposed methods.