Experimental validation of stress intensity factor solutions for the pin loaded lug

Abstract

Predicting crack growth behaviour is an important element of managing the structural integrity of aircraft fleets. It is common for fleet managers to employ software packages, such as AFGROW, to automate the prediction of crack growth behaviour. Stress intensity factor solutions employed in these software packages must be appropriately verified in order for results to be utilised in structural integrity management. Two independent research programs were conducted at Purdue University to review stress intensity factor solutions for cracked, pin-loaded lugs. The purpose of the research was to experimentally validate stress intensity factor solutions derived from representative StressCheck® Finite Element Models (FEMs). Component fatigue tests were conducted on corner and through cracked, pin loaded aluminium lugs and non-dimensional stress intensity factor (geometry factor) solutions calculated utilising a backtracking method. For the through crack configuration, experimental and StressCheck® geometry factors closely correlated and were an improvement to the solutions provided in AFGROW at the time. Based on the results of this research, StressCheck® pin-loaded lug geometry factors have since been incorporated into the AFGROW software. In the case of the corner crack configuration, the correlation between experimental and StressCheck® results was dependant on the choice of pin-loading boundary conditions in the FEM. The results of this research have been utilised to define the default AFGROW software pin-loaded lug boundary condition assumptions. © Springer Science+Business Media B.V. 2009.