فهرست مطالب ehsan moghimihadji

Attracting customers and keeping market share have become more important for manufacturers in today’s competitive market. Offering warranty for their products is one of the techniques that manufacturers use to attract customers. There are different types of warranty policies. Most research in this area has focused on two-stage warranties and little attention has been paid to three-stage warranties. Hence, in this study, a three-stage non-renewing warranty is investigated in which, the length of warranty period is divided into three phases. In the first phase, if the product fails, the cost of repair is fully covered by the manufacturer. In the next phase, if failure happens, most of the repair cost is still covered by the manufacturer while the customer must pay for the rest of it. Finally, in the third phase, if the product faces any failure, most of the repair cost is paid by the customer as the product has been used for quite some time by then. In this study, a repairable system under this type of warranty policy is investigated and warranty cost during this period is derived. To minimize the cost of warranty period, the optimum length of each phase is obtained. Numerical examples are provided to verify the proper performance and applicability of the proposed model.

In recent years, offering warranty services has become a regular practice in the selling process. Manufacturers try to offer suitable warranty services on their products as an efficient tool to attract new customers and satisfy their current customers. The failure rate curve of many systems shows a bathtub shape with three distinguishable phases. In the first phase, it shows a decreasing rate. During this phase, manufacturers use burn-in methods to eliminate products with early failures. In the second phase, where the curve shows approximately a flat rate, manufacturers offer warranty services. These services assure consumers about the manufacturer's support for the purchased products in case they face failure during the warranty period. In this study, a non-repairable component with a bathtub-shaped failure rate function is considered. In the first phase, if a component fails during the burn-in period, the manufacturer replaces it with a new component. In the second phase, the manufacturer offers a new pro-rata warranty service if a component fails. Considering these assumptions, a cost model is constructed and optimal burn-in time and warranty period are obtained. A numerical illustration is presented to evaluate the impact of the proposed model by calculating the optimum values of burn-in and warranty periods.

Failure rate curve based on the failure rate function of many electrical and mechanical systems shows a bathtub-shape form. In the first phase of this curve, where the failure rate has a decreasing form with a high slope, manufacturers use the burn-in method to eliminate defective products before reaching the market. In this phase most of the failures are minor (since the component is completely new, this type of error generally takes happen because of bad assembling, displacement of a socket, and so on) or major type failures (for example because of wrong design, selecting unsuitable raw materials, and so on). In the second phase, where the failure rate curve shows a constant value, manufacturers offer warranty services to their customers to ensure them about the quality and performance of their products. In this paper, we investigate the total cost incurred during the burn-in and warranty periods from the manufacturer's point of view. We consider different types of repair services and obtain the expected total cost in each phase. We present an optimization example to illustrate the efficacy of the proposed model in finding optimal values for burn-in and warranty periods.