a vibration machine used for testing and calibration. Parts being vibration-tested, or the sensors of a vibrometer being calibrated, are mounted on the operating platform. There are all-purpose and specialized vibration benches.
The amplitude and frequency of the vibrations of all-purpose vibration benches are infinitely variable over a pre-determined range and are sometimes controlled by an automatic programmed device. One-component vibration benches, with rectilinear vibration of the operating platform perpendicular to its surface, are the most common. Vibration benches are often equipped with a device permitting tilting of the platform at an angle of 0° to 90° to the horizontal. Percussion and vibration-percussion benches, in which vibration of the operating platform is accompanied by impacts, are also used. The main types of vibration benches are mechanical, hydraulic, electrodynamic, magnetostrictive, and piezoelectric.
Mechanical vibration benches usually have vibrations produced by a cam (impact benches), crank (with a flexible or rigid connecting rod), or centrifugal drive. They generally vibrate at frequencies of 0-300 hertz (Hz). The load capacity of hydraulic vibration benches is normally between 100 kg and 100 tons, and their frequency range is 0-100 Hz; the figures for electrodynamic benches are 10 g to 100 kg and 5 Hz-10 kHz respectively. High-capacity electrodynamic vibration benches are very cumbersome, have high power consumption, and require a powerful amplifier and a cooling system. Magnetostrictive and piezoelectric benches operate at frequencies up to 100 kHz. Their load capacity is small, and they are generally used for calibration, along with the mechanical and electrodynamic models.
Items are tested for fatigue strength and resistance to vibration to demonstrate that the equipment being tested will function normally when subjected to vibration and to deter-mine instrument errors and the rate of distortion in the apparatus being tested.
Calibrating vibration benches must reproduce the induced vibrations with greater accuracy—for example, for sinusoidal vibrations, they must reproduce the predetermined amplitude and frequency with great accuracy and an extremely low level of distortion by higher and lower harmonics. The reading of the amplitude, amplitude-frequency, phase-frequency, and thermal characteristics of the equipment and the establishment of the transverse and rotary sensitivity of the vibration sensors are part of the process of calibrating vibration-measuring apparatus.
REFERENCESVasil’eva, R. V. Vibrostendy v priborostroenii. Moscow, 1958.
Vibrostendy. Edited by A. N. Burago. Leningrad, 1960.
I. I. BYKHOVSKH
B. G. GOL’DSHTEIN