Rotating beam testing machine RRM

fatigueRR Mooremanual

● Theory of Operation Advance Instrument’s rotating beam fatigue testing system (RRM) design is based on the rotating beam principle. The specimen functions as a simple beam symmetrically loaded at two points. When rotated one half revolution, the stresses in the fibers originally below the neutral axis are reversed from tension to compression and vice versa. Upon completing the revolution, the stresses are again reversed so that during one revolution the test specimen passes through a complete cycle of flexural stress (tension and compression). ● Specimen Loading The AI RRM can be equipped to test straight shank specimens. The standard specimen length is 78mm. The specimen shape can be rod or tube. Specimens approximately 25mm (1 in) longer or 25mm (1 in) shorter can be used without affecting the calibration of the machine. Straight shank specimens are held in place using precision specimen collets. Stress is applied to the specimen by direct application of deadweights to ensure precise loading. Maximum fiber stress in a specimen having a 4.3 mm diameter is 3200 MPa. While minimum fiber stress in a specimen having a 11 mm diameter is 20 MPa. The system is equipped with a 7" LCD controller that provides easy-to-use in determination of the load weights needed to produce a particular stress at a simple calculation. ● Load Frame Features The standard machine operates at an adjustable integrated variable servo speed of 10 RPM to 6,000 RPM. Speed control is important in testing certain alloys that heat up when highly stressed, and it also allows certain correlations of results between high-speed tests and previous lower speed tests.