GB495780A - - Google Patents

Abstract

495,780. Testing physical qualities of materials. SIEMENS & HALSKE AKTGES. May 18, 1937, Nos. 13897 and 13898. Convention dates, May 18, 1936 and Feb. 10, 1937. [Classes 106 (ii) and 106 (iv)] Comprises an arrangement for measuring the vibratory properties of bodies, wherein a body to be tested is supported upon members, for example wires, which do not appreciably damp the vibrations and at least one of such members is also utilized to impart vibrations to the body and/or to transmit vibrations of the body to vibration measuring apparatus. In Fig. 1, a rod 1 to be tested is suspended by means of wires 2 from an armature 3 disposed between the two poles of a permanent magnet 4 and surrounded by a coil 5 in which an A.C. is produced upon movement of the armature, the current being fed to a measuring instrument 7 through an amplifier 6. The exciter comprises a yielding armature 8 arranged between poles, as shown, to the centre of which is connected a rod 9. A low-resistance coil 10 surrounds the armature and is fed from an audible frequency generator, not shown. When the coil is excited, the arm 8 vibrates by bending as a result of which the rod 9 oscillates longitudinally and transmits the oscillations by wires 11 to the rod 1. In Figs. 2, 3, a receiver is coupled back to the exciter through an amplifier so that a special generator is not required. By means of a variable condenser 12 the tuning may be so selected that different harmonic vibrations are set up. In Fig. 3, it is possible to vary the degree of coupling between the receiver end of the amplifier and the exciter by a potentiometer 13. In the form shown in Fig. 2, the natural frequency is measured by comparison with a sound transmitter by observation of the beats. In another form, the rod is arranged horizontally and suspended at two points by wires. When the body tested is very large, it may be supported at the nodes so that the wires do not take any part of the weight of the body. Natural oscillations of the supporting members may be damped out at one or more points by cotton wire &c. The test may be carried out at high temperatures, the members connecting the vibrator and receiver to the body and also the vibrator and receiver being suitably screened from the heat.