A stochastic model on an additional warranty service contract

In general, a newly purchased item or system is warranted for a specific period. When the system fails during the warranty period, it is repaired free of charge. Even if the system is repairable, there exist some warranty services under which the manufacturer replaces the failed system during the warranty period. This study considers a case where a manufacturer offers an additional warranty service under which the failed system is replaced by a new one for its first failure, but minimal repairs are carried out to the system for its succeeding failures before the warranty expires. In this paper, we propose a mathematical model for setting a suitable charge of such an additional warranty service. Numerical examples assuming a personal computer are also presented

Optimal design of uptime-guarantee contracts under IGFR valuations and convex costs

An uptime-guarantee contract commits a service provider to maintain the functionality of a customer’s equipment at least for certain fraction of working time during a contracted period. This paper addresses the optimal design of uptime-guarantee contracts for the service provider when the customer’s valuation of a contract with a given guaranteed uptime level has an Increasing Generalized Failure Rate (IGFR) distribution. We first consider the case where the service provider proposes only one contract and characterize the optimal contract in terms of price as well as guaranteed uptime level assuming that the service provider’s cost function is convex. In the second part, the case where the service provider offers a menu of contracts is considered. Given the guaranteed uptime levels of different contracts in the menu, we calculate the corresponding optimal prices. We also give the necessary and sufficient conditions for the existence of optimal contract menus with positive expected profits

Discrete Optimal Testing/Maintenance . . .

In this paper, we focus on the optimal software testing/maintenance problem considered in Rinsaka and Dohi (2004), and develop a stochastic model in discrete operation circumstance, under the difference between the software testing environment and the operational environment can be characterized by an environment parameter. More precisely, the total expected software cost is formulated via the discrete NHPP type of software reliability models. In the special case with the geometric fault-detection time distribution, we derive analytically the optimal testing period (release time) which minimizes the total expected software cost under a milder condition. We call the time length to complete the operational maintenance after the release a planned maintenance limit, and also derive the optimal planned maintenance limit which minimizes the total expected software cost. In numerical examples with real data, we calculate numerically the joint optimal testing/maintenance policy, combined by testing period and planned maintenance limit