By considering learning effects during the process of maintenance, this article investigates an availability-based warranty policy from the manufacturer's perspective. Imperfect preventive maintenance activities are implemented to reduce the number of equipment failures so as to meet the product's availability requirement and minimize warranty servicing cost during the warranty period. Hybrid hazard rate model is used to describe imperfect preventive maintenance actions; maintenance plan and warranty servicing cost are optimized by considering learning effects. Preventive maintenance schedule within a warranty period is optimized cycle by cycle, and the warranty cost rate is minimized under the requirement of availability within each cycle. Numerical example of a wind turbine gearbox is provided to verify the effectiveness of the proposed availability-based warranty policy. Sensitivity analysis shows that by considering learning effects on maintenance, the gearbox can maintain a higher availability level with a lower warranty cost than the case without consideration of learning effects.

Selecting complex equipment with availability requirements as the object of study, this article investigates an availability-based warranty policy. Under this policy, apart from providing repairs or replacements upon failures, the manufacturer guarantees a negotiated availability level of products during the warranty period. In order to satisfy the availability requirement of the warranted products with rational cost, two-dimensional preventive maintenance strategy is carried out by the manufacturer, which is scheduled by considering the age and usage of the warranted items. By optimizing two-dimensional preventive maintenance strategy, this study aims to meet products’ availability requirement with the lowest cost from the manufacturer’s perspective. Moreover, customized preventive maintenance programs are designed for different customer categories. Finally, we provide a numerical example to verify the effectiveness of the proposed availability-based warranty policy. The results demonstrate that two-dimensional preventive maintenance strategy is superior in terms of warranty cost and operational availability. Meanwhile, customized preventive maintenance policy is more beneficial to both the transaction sides.

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Abstract.A two-dimensional (2D) availability-based warranty policy is investigated from the view of the manufacturer. Under the policy, the manufacturer guarantees a negotiated availability for the products during the warranty period. In order to satisfy the availability requirement with rational cost, 2D preventive maintenance (PM) strategy is carried out, which is scheduled every K units of age or L units of usage. This study is to meet products' availability requirement with the lowest cost by optimizing 2D PM strategy. A numerical example is provided to verify the effectiveness of the proposed policy. The results show that compared with age-based or usage-based PM strategy, 2D PM strategy is superior in terms of warranty cost and operational availability.

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