Optimal allocation of reliability improvement target based on the failure risk and improvement cost

In this paper, we consider the problem of assigning a given reliability improvement target of an existing series system to its constituent subsystems in view of the failure risk and improvement cost. Previous research has solved this problem by developing an allocation weight under the assumption that the failure risk and improvement cost are independent, and by improving every subsystem in proportion to the allocation weight. Differently, we develop an optimization model to maximize the profit from reliability improvement for the given reliability improvement target. The profit is derived from the functional relationship between the failure risk and improvement cost. The optimal solution shows that not all subsystems are improved, and the priority of subsystem improvement is determined by the difference between the failure severity and the rate of increase in the improvement cost. A numerical example is given to illustrate the advantage of the proposed method over the previous method.