DBEM Crack Growth Simulation for a Riveted Aeronautic Reinforcement under Non-linear Contact Conditions

A special specimen was created cutting a rectangular notched area from the surrounding of the upper left corner of a wide body aircraft door. Then a fatigue traction load was applied in order to induce an MSD crack initiation and propagation. An innovative DBEM (Dual Boundary Element Method) modelling approach was devised, capable of explicitly modelling the different test article layers with their rivet connections even in a 2d approach. The rivets that are close to the propagating crack are coupled with the corresponding holes by non linear contact conditions, and the accuracy improvements are assessed in comparison with a previous linear analysis, in which traction and displacements continuity conditions on the hole-rivet interface had been imposed. The importance of such influence on the simulation precision need to be assessed due to the strong impact that a non linear analysis produces on computational times. For such a complex problem (three different panels, made of different materials, each one with a variable thickness and connected by numerous rivets), experimental crack propagation data were available for the numerical-experimental comparison. With such non linear approach, a significant improvement on the growth rate correlation is obtained, that justify the increased computational effort.