Bending Fatigue Behavior and Damage Mechanism of the Ti-6Al-4V Titanium Alloy

The bending fatigue behavior of Ti-6Al-4V(TC4) titanium alloy without the effect of axial tensile stress was studied. A cantilever bending fatigue testing machine was designed to perform a bending fatigue test on TC4 titanium alloy. The ABAQUS finite element simulation software combined with a damage model was employed to predict the life of TC4 bending fatigue. Through the test and simulation of seven different bending fatigue amplitudes of TC4 titanium alloy, the stress distribution and mechanism of the damage and fracture of TC4 titanium alloy during bending fatigue were studied. The fracture mode of TC4 titanium alloy under different bending fatigue amplitudes was analyzed by scanning electron microscopy(SEM). The results showed that the bending fatigue lives obtained by the numerical simulation and test were within the double dispersion band. The fracture positions of the numerical simulation and test were located at the maximum stress section, 1 mm away from the central section of the arc section. The initiation and propagation of bending fatigue cracks were mainly controlled by stress. The cracks originated from the maximum stress on the upper and lower surfaces and gradually developed toward the specimen center until the specimen broke. When the bending amplitude was small, a large number of tearing ridges and secondary cracks existed on the fatigue fracture of the specimen, which were quasi-cleavage fracture characteristics. When the bending amplitude was further increased, the internal deformation of the material was enhanced, the stress of the sample was increased, dimple characteristics occurred on the fatigue fracture, and the fracture mode changed to ductile fracture. © 2021, Editorial Board of Journal of Tianjin University(Science and Technology). All right reserved.