No Crack Growth Approach for Analyzing a Helicopter Main Rotor Blade

In this article, no crack growth approach is used for analyzing the main rotor blade of a helicopter. The blade is comprised of many different parts such as spar, skin, abrasive strip, doublers, box beam doublers, etc. and it supports complex random load spectra. At first,threshold stress intensity range of the spar is obtained based on ASTM E647 test method. Then, a finite element analysis is carried out to extract the stress distribution in the blade parts. Afterwards, crack growth analysis is done for the main parts of the blade using Zencrack software. In order to calculate the length of the smallest growing cracks, no crack growth approach were used. A comprehensive investigation was carried out on the effect of initial crack length and aspect ratio on growth or no growth of cracks in the blade. Safety factor against the crack growth diagrams were obtained for different initial crack lengths and aspect ratios considering the critical maneuvers

Keywords:

Helicopter fatigue life , Blade life estimation , Damage Tolerance , Fracture mechanics , No crack growth