Durability Methods Development. Volume IV. Initial Quality Representation.

摘要

The initial fatigue quality of the durability critical parts of an aircraft structure is one of the key input parameters for the durability analysis to be performed in the present investigation. We considered that either the EIFS (Equivalent Initial Flaw Size) or TTCI (Time-To-Crack-Initiation) represents such an initial quality that controls the durability of aircraft. A statistical characterization of the EIFS data is attempted by fitting various probability distribution functions thereto. The EIFS data considered consist of three samples of size 37, 37 and 38. These data sets are examined to see if they fit; (a) the distributions of the Johnson family including the log-normal distribution; (b) the Weibull distribution; (c) the distributions of the Pearson family; (d) the asymptotic distributions of largest values; and (e) the TTCI compatible distributions. It is found that, with respect to the data examined, the Weibull compatible, log-normal compatible, and second asymptotic distributions provide the best fit.