D. G. Nguyen’s research while affiliated with The University of Queensland and other places

For repairable products sold with warranty, the manufacturer has the option of either repairing a failed item or replacing it by a new one should the failure occur during the warranty period. This paper formulates a model to make optimal decisions regarding replace-repair strategies for a fairly general warranty policy.

In this paper we study a policy involving repair cost limit as a decision variable for minimizing the cost of servicing items sold under warranty.

For products sold with warranty, the reliability of the product affects not only the manufacturing cost but also the cost of servicing the warranty. Thus, decisions regarding reliability allocation must include both these costs. In this paper we develop a general model for obtaining the optimal reliability allocation for products sold with warranty.

On passe en revue des polices de garantie «sans panne» pour des produits non reparables et on examine, quelques extensions et generalisations. Les polices de garantie pour des produits reparables prennent en compte d'autres facteurs comme le type de reparation ou la decision de reparer au lieu de remplacer

This paper deals with product development to improve product quality. It examines two stochastic models incorporating development testing and derives the optimal testing plans to minimize expected costs for products sold with warranty.

This paper studies a formulation where the warranty is imposed on the manufacturer and the warranty stipulates that the sold item be replaced by either a new or a repaired item should it fail in the warranty period subsequent to the sale, and that the replaced items are themselves replaced similarly should they also fail in the warranty period. The replacements are done at no cost to the purchaser. As a result, the purchaser is assured of a working item for at least the length of the warranty period with each purchase. With each replacement, the manufacturer receives a failed item in exchange for the replacement, and he has the option to either repair it and use it for a subsequent replacement or discard it.

On considere un systeme a deux composantes avec une interaction des pannes d'un type specifique et on obtient des expressions pour l'esperance du cout d'exploitation du systeme pour des temps fini et infini

The literature on multicomponent systems, though extensive, has dealt mainly with formulations where the failure of a component has no effect or influence on the operation or failure of other components in the system. In many real-life multicomponent systems, the failure of a component has some effect on one or more of the remaining components. The paper considers a two-component system with a specific type failure interaction and obtains expressions for the expected cost of operating the system for both finite and infinite time.

For a product sold with a warranty period T, the manufacturer must pay all repair costs for failures in [O, T]. This paper presents a model to estimate warranty liability associated with this type of warranty policy. The quantities estimated are: (i) the expected total warranty cost and prediction interval for a fixed lot size of sales, and (ii) the expected number of units returned for repair and the expected warranty costs incurred in any time interval during the product life cycle, when sales occur continuously. The results are applicable for any failure time distribution and for various types of repair. A numerical example is given to illustrate the application of the model.

This article analyzes two general warranty policies involving an initial free replacement period, followed by a pro rata period. We examine the short-run total costs and longrun average costs under these policies. Formulas for both consumer costs and manufacturer profits under warranty are derived. We also study the expected number of purchases over the product life cycle under both policies. Bounds for the expected total costs and expected number of purchases are obtained for the case where the failure distribution of the item is new better than used.