Study of the Stress Intensity Factors and Crack Path in 3-2-1 Lozenge Pattern Riveted Joints using Maximum Energy Release Rate Based Crack Advancement

Riveted joints are widely used in engineering applications ranging from aerospace to automotive, ships to bridge construction, and boilers to high-pressure vessels. Numerous investigations have been carried out on different types of riveted joints, mostly with regular arrangements of rivets like single and double rows, to establish the effect of rivet diameter, pitch, interference, and squeezing force on the total life of the component. The onset of initial flaws at the critical locations, such as holes in the riveted joints during their service life or through the manufacturing process, reduces the overall structural integrity of the joints. To address this kind of real-life problem where the components include initial cracks, fracture mechanics approach, i.e., the study of Stress Intensity Factor (SIF) and the effect of other parameters on it has to be considered. The Lozenge joint is a special riveted joint known for its better strength and stability due to the even load distribution. Literature on the Lozenge pattern mainly emphasizes the effect of initial crack, interference, and back pitch of rivets on SIF by assuming crack propagation to be plane perpendicular to the loading direction. This work analyzes the deviation of SIF and crack path in 3-2-1 Lozenge pattern riveted joints by incorporating maximum energy release rate (MERR) criteria for crack advancement. Three different interference levels, 0%, 0.1%, and 0.15%, have been considered for a maximum 17 mm crack length at four locations of rivet holes. For a 6 mm initial crack, mixed-mode fracture occurred consistently at all locations and interference levels. At 0% interference, SIF deviations from perpendicular crack propagation were most pronounced at the single rivet hole of the end row. Increasing the interference level causes a maximum of 39.4-degree crack path deviations from perpendicular assumptions. At 0.1% and 0.15% interference, cracks at the middle hole of the first row displayed 23% and 14% more SIF compared to the perpendicular assumption, respectively. Based on this study, one can say that MERR criteria yielded more SIF that indicates the higher severity of a particular crack length compared to the plane perpendicular crack path estimate.