A novel test rig for narrow band random fatigue under rotating bending

Rotating bending fatigue tests are the most usual way to investigate the fatigue behaviour of a material or a component and, due to their speed, they have also been widely used in researches on short crack growth rates and thresholds. The main drawback of this proof method is the impossibility to carry out random fatigue tests. In modern hydraulic axial test machines it is possible to easily perform this type of experiments, however, test frequencies are much lower than in rotating bending experiments. In order to overcome these problems, we studied and built a novel rotating bending fatigue apparatus designed to be coupled to a servo-hydraulic machine. The main features of the new test rig are: the possibilities to obtain variable bending moments and to carry out tests on specimens having geometrical tolerances wider than usual pieces; a dynamic response expressly studied for crack propagation experiments.