Environmental effects of physical life span of a reusable unit following functional and physical failures in a remanufacturing system

Abstract

Reuse of product components is an effective way to conserve natural resources. Likewise, remanufacturing is a new trend in the field of environmentally friendly products. A product undergoes functional failure or physical failure in a remanufacturing environment, where the former failure is equivalent to the state in which the product cannot be used because of functional insufficiency or obsolescence and the latter failure is equivalent to the state of malfunction or breakdown of a product. A unit intended for reuse should be designed to be durable for a period equal to at least two functional lives through remanufacturing. Utilization of excess materials-for example, for improvement of unit strength-can enable a reusable unit to endure over a period equal to at least two functional lives. However, if the environmental impact of such excessive use of materials is taken into account, a strong doubt arises as to whether such a method truly reduces the environmental load from the viewpoint of lifecycle design. In order to analyse this issue, the present study examines the optimal physical life span of a reusable unit and its effect on the environment. A mathematical model of a remanufacturing system is constructed, taking into account functional and physical failures of a product. A minimization problem of the incurred total environmental impact per unit time for a reusable unit is formulated under the decision variables of a design parameter vector of the unit and the maximum number of times of reuse. The design parameter vector is closely related with physical life span. The maximum number of times of reuse can cause environmental loss if a product has a long residual physical life span brought on by the small number of times of reuse. The effects of physical life span of a reusable unit on environmental impact are analysed to show the potential value of the developed model by means of varying stochastic characteristics and the parameters of the remanufacturing environment.