1,242,617. Fatigue testing. UNITED AIRCRAFT CORP. Aug.20, 1969 [Dec.17, 1968], No. 41584/69. Heading G1S. A beam comprising a specimen 12 to be tested for bending fatigue is supported by a pair of trestles 33 and vibrationally excited by electromagnetics 16 and 18 driven by oscillator 20 and acting on magnets 38 adhered to the beam, the trestles being at the nodal points of the vibrations. The beam comprises a specimen 12 e.g. of expoxy resin-carbon fibre or aluminium-boron composite connected to steel extension bars 32 by fibre-glass clamping strips 34, the extension bars carrying weights 36 at their ends adjustable transversly of the beam to compensate for torsional bending on the beam. Alternatively the beam may comprise a single piece of test material. The trestles comprise a piece of wire or rubber cord 33 mounted for vertical adjustment and can be adjusted horizontally by movement along a slot 26 in metal piece 24 supported by the electromagnets 16 and 18. In use increasing stress is applied to the beam, and fatigue is indicated by a shift in the resonant frequency or by a static deflection test.
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