Stress-Intensity Factor Solutions for Tapered Lugs with Oblique Pin Loads

This paper summarizes five years of research into new stress-intensity factor (SIF) solutions for radially advancing cracks at holes in tapered and obliquely loading lugs. To our knowledge, these solutions are the first direct methods capable of analyzing these fracture critical connections. The new SIF solutions rely on weight function (WF) methods, remain tractable for engineering fatigue and fracture analyses, and span a very wide range of applicable geometries (including loading angles between 0 and 90° and independent lug taper angles between 0 and 90°). These solutions support cracks on either side of the pin hole (the “short ligament” or “long ligament” sides). For cracks on long ligaments, users can select the crack location based on maximum principal stresses or Mises stresses. These solutions are verified by a large database of independent high-fidelity three-dimensional finite element analyses (FEA) generated using an automated approach that accelerates the evaluation process while ensuring solution quality. This work also discusses the underlying sensitivity studies used to determine appropriate boundary conditions and material properties. The powerful new methods used here to generate SIFs for tapered lugs—automated FEA generation of tables of stresses in uncracked bodies, interpolation of these stresses in WF formulations, and automated verification using independent benchmark FEA SIF solutions—can easily be extended to build reliable new SIF solutions for other complex combinations of loads and cracked geometries.