Weight function analyses and stress intensity factors for corner/surface crack in straight and tapered lugs

Lug is one of the most important lap joints in many engineering structures, especially airframes. Through-thickness and part-through cracks emanating from pin-loaded lug hole are frequently encountered due to stress concentration. Stress intensity factors for various crack geometries are the prerequisite for damage tolerance design of attachment lug. In this paper, analytical 2D weight functions for through-thickness crack in lug are derived considering the contact condition between the pin and lug. With the derived 2D weight function, a highly efficient 3D slice synthesis weight function method (SSWFM) is then developed to determine 3D SIFs of hole-edge corner/surface crack in straight and tapered lugs under various pin loadings. The resulting 3D SIFs are verified by comparisons with the numerical FEM/Franc3D solutions and literature data. The SSWFM is about 1800 times faster than the numerical FEM/Franc3D and therefore will significantly enhance damage tolerance analysis capability for attachment lugs. Accurate and wide-range weight functions of pin-loaded cracked lug are derived considering the contact constraint .A 3D weight function method for corner and surface cracks of lug is established.It is accurate and much faster than FEM for SIF calculation.