Development of a Fuzzy Rule-based Decision-making System for Evaluating the Lifetime of a Rubber Fender

If a rubber fender, whose purpose is to absorb the shock energy that is generated when a ship is berthing, fails because of deterioration and vulcanization, the ship and the pier structure may incur serious damage. In this paper, we introduce a fuzzy rule‐based decision‐making system to predict the maintenance timing of rubber fenders by diagnosing their faults and evaluating their lifetimes on the basis of the knowledge and experience of experts. First, we built a case library containing information concerning fender lifetimes and points in these lifetimes when faults occurred. This was gathered on the basis of the results of testing the lifetime of rubber materials under accelerated conditions and a knowledge base of the physical properties of fenders in order to evaluate the deterioration in a rubber fender. Moreover, after representing the key factors affecting the deterioration of rubber fenders as a fuzzy cognitive map that reflects the knowledge and experience of domain experts, we drew inferences regarding the heuristic factors of the lifetime of rubber, the conceptual centrality of which is relatively high according to the cause‐and‐effect relationship between key factors. Finally, we propose a diagnostic process for the performance deterioration of rubber fenders based on the various factors that affect the lifetime of rubber and its multiple physical properties in the form of a decision‐making tree. We then applied it to rule‐based and case‐based reasoning.