Abstract:

This paper introduces simply the basic conception and method of structure damage tolerance analysis and damage tolerance structure reliability assessment.The possible damage and failure states of the damage tolerance structure are defined, and the possible loss caused by each state is analysed. Because structure maintenance cost includes both inspection cost and repairing cost mainly, the paper explores the relationship between the structure maintenance cost and the structure damage loss,through analysing that the structure maintenance program has an influence on the mutual transfer of the structurte damage and failure states. On the basis of which are presented above, the series mathematical models to calculate the sum of the expected cost and the expected loss in the period of the remainder of structure life are developed. Further, the mathematical formula is advanced to compute the sum of all the expected cost and the expected loss in the designed economic life period of the damage tolerance structure when some maintenance program is taken. The criterion to make the sum of all the expected cost and the expected loss minimized is proposed, which is applied to optimize the structure maintenance program, and the approach to select the optimal structure maintenance program is presented by using dynamic programming. One example optimizing the maintenance program of some item of aircraft structure is also given.

Key words: maintenance program, damage tolerance, transfer probability, dynamic progr-amming, optimization