Click on vibration platform network /products/161 I. Overview
The vibration test is one of the mechanical environment tests. The vibrating table is a specialized mechanical environment testing device for such tests.
two. Description of vibration
1. What is vibration?
Vibration is a kind of fluctuation. Mechanical vibration is the mechanical movement of an object repeatedly around the equilibrium point.
2. Classification of vibration
Vibration can be divided into random vibration and periodic vibration.
Periodic vibrations include positive harmonics, multiharmonic, square waves, and sawtooth waves.
The periodic vibration can be decomposed into a series of simple harmonic vibrations.
According to whether there is external force, the vibration can be divided into free vibration and forced vibration.
3. Description of positive harmonic motion
3.1 Frequency, angular frequency
Both frequency and angular frequency are used to describe the number of vibrations per unit time.
The number of vibrations per second, called the frequency of vibration, is usually expressed by f. The unit is: number of times per second, expressed in Hz.
If the vibration is described by the number of arcs per revolution of the mechanical rotor exciter, the angular frequency of the vibration is called Ï‰. The unit is: radians / second.
The relationship between frequency and angular frequency has the following relationship:
3.2 Displacement, velocity, acceleration
Displacement, velocity and acceleration are all used to describe the magnitude of the vibration.
Displacement refers to the large distance of the object from the equilibrium position when vibrating, which is usually indicated by A. The unit is: meters (m).
Speed â€‹â€‹refers to the large speed of the object movement when vibrating, which is usually expressed by v. The unit is: meters per second (m/s).
Acceleration refers to the large acceleration of the object movement when vibrating, which is usually expressed by a. The unit is: meter / squared per second (m / s2). Sometimes it is also expressed by the gravitational acceleration g: g=9.8m/s2.
In the case of sinusoidal vibration and using the International System of Units, there are the following relationships between displacement, velocity, and acceleration:
four. Classification, principle and characteristics of the vibration table
According to their working principle, the vibrating table can be divided into three types: electric table, mechanical table and hydraulic table.
The electric stage is based on the output excitation force. Its frequency range is wide, usually 5-3000Hz. The large displacement of zui is generally Â±12-25mm. The large acceleration of zui is generally up to 100g. With horizontal slides for horizontal vibration. With a random controller, it can be used for random vibration. The accuracy index is good. However, its countertop size is small, and it is often necessary to provide an auxiliary countertop; the running cost and price are relatively high. It is commonly used in high frequency and high acceleration vibration tests of electrical and electronic components.
The mechanical table takes the large load of zui as the main specification. The frequency range is generally 5-80 Hz. The large displacement of zui is generally Â±3-5mm. The large acceleration of zui is generally up to 10g. The size of the countertop is large. Generally, horizontal vibration can be performed without a horizontal slide. The price is low. However, it is noisy and cannot be randomly vibrated. It is commonly used in the vibration test of electrical machinery, electronics, optical instruments and other products.
The hydraulic table is based on the output excitation force. The frequency range is generally 1-200 Hz. The large displacement of zui is generally Â±100-200mm. The large acceleration of zui is generally up to 10g. With horizontal slides for horizontal vibration. With a random controller, it can be used for random vibration. But it is more noisy, and the running cost and price are higher. It is commonly used in vehicle vibration testing of automobiles and other products; seismic simulation vibration test of buildings and hydraulic engineering.
The above three types of vibration tables can achieve certain accuracy indicators in terms of distortion, lateral vibration, uniformity, etc., and meet the corresponding standards.
In addition to the above three types of vibrating tables, there is also a vibrating table (often called a vibrator) that operates on the principle of an electromagnet, and its displacement amplitude is about 1-3 mm. Can be used as a vibration test in the process. However, it cannot be assessed in terms of distortion, lateral vibration, and uniformity.
1. Electric bench
The electric vibration table is a kind of three kinds of vibration tables (electric, mechanical, hydraulic) with a wide frequency range and a good performance. It is based on the working principle that the energized conductor is subjected to the ampere force in the magnetic field, and inputs an alternating current to the moving coil in a constant magnetic field, thereby generating an alternating exciting force in the direction of the moving coil axis, and is connected with the moving coil. The integrated vibration table is transmitted to the test piece. By changing the frequency and amplitude of the input current, you can adjust the frequency and amplitude of the output vibration.
The electric table can perform exponential positioning shift-fixed speed-fixed acceleration reciprocating automatic sweeping vibration within a specified frequency range, and its sweep rate can be adjusted (including 1 octave/minute).
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