An EPQ model for delayed deteriorating items with quadratic demand

Abstract

In this paper, we develop an EPQ model for delayed deteriorating items where the demand before deterioration sets in is assumed to be time dependent quadratic demand. Three stages are going to be considered: (i) the production build up stage (0 ≤ t ≤ L₁), (ii) before deterioration starts (L₁ ≤ t ≤ L₂), and (iii) after deterioration sets in (L₂ ≤ t ≤ L). No demands during production build up period. The demand before deterioration begins is assumed to be quadratic time dependent while that after deterioration sets in is assumed to be constant. It is also assumed in this paper that shortages are not allowed. The best cycle length which optimizes the total inventory cost and the economic production quantity are obtained. Numerical examples are given to illustrate the applicability of the model and sensitivity analysis carried out to see the effect of changes on some system parameters.