Analysis of the Probability of Collapse of a Fail-Safe Aircraft Structure Consisting of Parallel Elements

摘要

A study was made of the probability of collapse of a fail-safe structure, consisting of a number of parallel members, and subjected to a random load spectrum. In the individual member a fatigue crack is first initiated and failure of the member occurs due to a heavy load on the weakened member. The probability of element failure is obtained by a combination of the probabilities of crack initiation and of meeting a load exceeding the residual strength of the member. The probability of consecutive element failures is deduced from the probability of failure of the individual members. Collapse occurs when all members are broken, or, in practice, after a critical number of element failures within one inspection interval. The probability of collapse of the assembly during the whole service life results from a combination of the probabilities of all the inspection intervals. A numerical procedure for calculating the probability of collapse was developed and evaluations made for an assembly of six identical, parallel members. Some preliminary fatigue testing of single specimens and assemblies with six members was carried out in order to get information regarding the basic assumptions made in the theoretical investigation. (Author)