چكيده به لاتين
Considering the close interaction between spare parts logistics and maintenance planning, this research presents a model for joint optimization of condition-based maintenance and spare parts inventory in a two-echelon supply chain with two local suppliers and one central depot. The proposed model is implemented on a single-unit deteriorating system. Simultaneous use of perfect and imperfect preventive maintenance and a novel policy for spare part ordering is a significant contribution to the research. The replenishment policy is defined based on the deterioration level of the system. This research also proposes a method to determine the next inspection time at each decision point which not only considers restraints of both maintenance and spare parts provision policies but also uses an event-driven approach in order to prevent unnecessary inspections. Moreover, both positive and negative impacts are considered. Positive impact means that the imperfect maintenance cost is usually low. Negative impact implies that (i) the imperfect maintenance restores the system to a state between good-as-new and bad-as-old and (ii) each imperfect preventive action may accelerate the speed of the system's deterioration process. Defined decision variables such as upper limit for spare parts order quantity, preventive maintenance threshold, re-ordering level of degradation, and the maximum level of successive imperfect actions will be optimized by simulation. The optimization follows two objectives: (i) system should reach the expected availability (ii) and cost function as an objective function must be minimized. Minimum level for the availability of the system, which is determined by the decision maker, is considered to propose an adaptive maintenance policy which can help to take the advantage of opportunistic approach. According to the high complexity of the descriptive model which is defined based on the specific characteristics of the deteriorating system, Monte Carlo simulation is used to evaluate the optimization model. To illustrate the use of the proposed model, a real case problem is introduced and its results are presented in detail.
Key words: maintenance planning, spare parts inventory management, deteriorating system, joint optimization, imperfect preventive maintenance, Monte Carlo simulation
