The Component Parts of fatigue testing machine

A fatigue is a failure of material or machine due to the action of repeated or fluctuating stress on a machine member for some number of times.This failure begins with a small crack. The initial crack is so minute that it cannot be detected by  the naked eye and is even quite difficult to locate in a magniflux or x-ray inspection. The crack will develop at a point of  discontinuity in the material such as a change in cross section, a keyway,a hole or a notch.   The fatigue testing machine is of the rotating beam type. The specimen functions as a single beam symmetrically loaded at two points. When rotated one-half revolution the stress in the fibres originally above the neutral axis of the specimen are reversed from compression to tension for equal intensity. Upon completing the revolution,the stresses are again reversed, so that during one complete revolution the test specimen passes through a complete cycle flexural stress.   The fatigue testing machine consists of the following components: A. AHP electric motor B. Bearing and its housing assembly C. Weight hanger assembly D. Dead weight E. Bearing spindling F. Digital counter G. Magnetic cyclic pick up (dynamo) H. Variable speed control I. Switch, J. Specimen K. Drill chunks, L. The metal desk