Application of fuzzy sets theory in an EOQ model for items with imperfect quality and shortage backordering

This article investigates an inventory model for items received with imperfect quality and shortage backordering in the fuzzy sense, where, upon the arrival of order lot, 100% screening process is performed and the items of imperfect quality are sold as a single batch at a discounted price, prior to receiving the next shipment. The objective here is to determine the optimal order lot size and the optimal backordering quantity to maximise the annual total profit. Two fuzzy models have been proposed. We first propose a model with fuzzy defective rate. Then, the model with fuzzy defective rate and fuzzy annual demand is presented. For each case, we employ the signed distance, a ranking method for fuzzy numbers, to find the estimate of the total profit per unit time in the fuzzy sense, and then derive the corresponding optimal lot size and optimal backordering quantity. Numerical examples are provided to illustrate the results of proposed models.