Journal of Quality Engineering and Production OptimizationArticles in Press20210310A New mathematical Model for Stochastic Dynamic Unequal Area Facility Layout Problems323810.22070/jqepo.2021.5101.1124ENRahelehAlamiparvinDepartment of Industrial Engineering, Faculty of Industrial and Mechanical Engineering, Qazvin Branch, Islamic Azad University, Qazvin, Iran.EsmaeilMehdizadehDepartment of Industrial Engineering, Faculty of Industrial and Mechanical Engineering, Qazvin Branch, Islamic Azad University, Qazvin, Iran.HamedSoleimaniDepartment of Industrial Engineering, Faculty of Industrial and Mechanical Engineering, Qazvin Branch, Islamic Azad University, Qazvin, Iran.Journal Article20200105Organizing the positions of facilities or departments in a given area is categorized as a facility layout problem. This research has formulated unequal area stochastic dynamic facility layout problems in order to minimize the sum of the material handling costs while considering their upper bound, i.e. minimizing the upper bound of the sum of the material handling costs, and the sum of the shifting costs in the whole time planning horizon. In the proposed model, the area and shape of each department are stable during the implementation of an algorithm, while product demands are normally distributed with a known expected value and variance. This type of problems is very complex and NP-hard; therefore, meta-heuristic approaches must be employed to solve them. In this article,particle swarm optimization (PSO) was proposed and a theoretical problem instances were presented to evaluate the efficiency and effectiveness of the algorithm. The results manifested efficiency and validity of the proposed algorithm.