Comparative Fatigue Crack Growth Analysis of Modified Single-Edge-Notched Bend Specimens under Three- and Four-Point Loading using Finite Element Modeling

In engineering components with geometric discontinuities, the fatigue crack growth of structures subjected to cyclic loading is of utmost importance. This study numerically investigates the modified Single Edge Notched Bend (SENB) specimen with a hole adjacent to the crack tip under three-point bending (3SENB) and four-point bending (4SENB) conditions. The Finite Element Method (FEM) was implemented using ANSYS Workbench 19.2. Specialized meshing was performed to determine the stress field and predict the fatigue crack propagation using the Paris’ Law. This study quantitatively compares the effects of these two loading conditions on the fracture mechanics parameters of this non-standard geometry for the first time. The findings indicate that the specimen response is significantly different; the 3SENB configuration, with twice the maximum bending moment of the 4SENB, has 1.931 times the maximum von Mises stress, 1.823 times the maximum von Mises strain, and 1.965 times the stress intensity factor. The main contribution of this analysis is the development of a strong and quantifiable correlation between the maximum bending moment, and the fracture severity as defined by this work. Consequently, the predicted fatigue life of the 3SENB specimen is substantially reduced due to higher stress intensity factors. It has been found that the selection of bending configuration has a decisive and quantifiable influence on fatigue life of the modified SENB specimen with a geometric discontinuity under the specified loading condition.