Fatigue Testing Machines for Tensile and Bending Loaded Bolt Connections Using Sympathetic Vibration

Abstract

In this paper previous tension and bending fatigue testing machines for bolt connections are presented. Their weak points are discussed, in order to show the difficulty of machine load and the demands of a load distribution in the bolt connection similar to the operating state, a measurement of stresses on the bolt and an economical actuation. A new principle using the sympathetic vibration of a frame for applying the load is presented in comparison. It can be employed for tensile and bending load. The barrel of the bolt remains accessible for direct measurement of it’s strains. Formulas for the dimensioning of the frames considering their natural frequency and the tensile/bending load combination of the bolt connection are derived using the mechanics of elastic beams. The testing machines and their details are described.