A Probabilistic Method of Determining Fatigue Lives of Some Selected Structural Components of an Aircraft to Maintain the Required Flight Safety Level - An Outline

A Probabilistic Method of Determining Fatigue Lives of Some Selected Structural Components of an Aircraft to Maintain the Required Flight Safety Level - An Outline The paper has been intended to outline a method of determining fatigue life of a structural component of an aircraft for some assumed flight safety level. What has been used in the method in question are as follows: • Operation-effected spectrum of loading an aircraft's structural component, • The Paris relationship that determines fatigue-crack propagation rate approached in a deterministic way, • A difference equation to describe the crack growth by means of a probabilistic approach, • A density function of crack growth in a structural component in the form of a solution to the Fokker-Planck equation. The results gained allowed of finding the density function of time (i.e. flying time) indispensable to exceed the permissible crack length. With this function determined, one could determine reliability of the component to be then used to find fatigue life of this structural component. Two solutions have been given consideration, both depending on the m coefficient in the Paris relationship, i.e. for m = 2 and m ≠ 2.