Introduction to each type of shaker

Various types of shakers:

Mechanical shaker

Mechanical vibration table can be divided into unbalanced weight and cam type. The unbalanced weighted block type uses the centrifugal force generated when the unbalanced weight rotates to excite the vibration table top, and the exciting force is proportional to the unbalanced moment and the square of the rotational speed. The vibration table can generate sinusoidal vibration, its structure is simple, low cost, but can only work in the frequency range of about 5Hz ~ 100Hz, the maximum displacement of 6mm peak - value, the maximum acceleration of about 10g, can not be random vibration, cam type The displacement of the moving part of the vibratory table depends on the eccentricity of the cam and the arm length of the crankshaft, and the exciting force varies with the mass of the moving part. In the low-frequency region, the vibration table can achieve a large displacement, such as 100mm, when the excitation force is large. However, the operating frequency of this vibration table is limited to low frequencies, and the upper limit frequency is about 20 Hz. The maximum acceleration is about 3g, and the acceleration waveform is very distorted. Due to the limitations of its performance, the mechanical vibration table will be used in smaller quantities in the future.

2. Electro-hydraulic shaker

The working mode of the electro-hydraulic vibrating table is to drive a servo valve that can be controlled with a small electrodynamic vibratory table, and the vibrator is caused to vibrate by the hydraulic pressure. Such a vibratory table can generate a large amount of exciting force and displacement, such as an exciting force of up to 104 kN, a displacement of up to 2.5 m, and a very large exciting force at a very low frequency. The large-scale vibration hydraulic platform is cheaper than the same-thrust electric vibratory platform. The limitation of the electro-hydraulic table is that its high frequency performance is poor, the upper limit operating frequency is low, and the waveform distortion is large. Although random vibration can be performed, the rms rating of the random vibration excitation force can only be 1/3 or less of the sine rating. Because of its large thrust and large displacement, this vibratory table can make up for the lack of electric vibrating table and will still play a role in the future vibration test, especially in the ship and automobile industries.

3. Electric vibration table

The electric vibration table is currently the most widely used vibration device. Its frequency range is wide, the frequency range of the small vibration table is 0~10kHz, the frequency range of the large-scale vibration table is 0~2kHz, the dynamic range is wide, it is easy to realize automatic or manual control; the acceleration waveform is good, it is suitable for generating random waves; Acceleration. The electric vibration table is set according to the principle of electromagnetic induction. When a constant magnetic field at a live conductor is subjected to a force, a vibration is generated when an alternating current is applied to a semiconductor. The drive coil of the vibrator is formally in a gap of high magnetic induction. When the required vibration signal is generated from the signal generator or the vibration controller and amplified by the power amplifier and then passed to the drive coil, the vibrator needs to be generated. Vibration waveform.

The electric vibrating table basically consists of five parts: a driving coil and a moving part, a moving part suspending and guiding device, an excitation and a degaussing unit, a table body and a supporting device. The complex structure of the driving coils and moving parts, the calculation of the first-order resonance frequency is very difficult, and it is necessary to rely on empirical estimation, which often leads to design errors. In 802, the finite element method was not used for the first time to calculate the resonant frequency of moving parts of an electrodynamic shaker. It not only improved the accuracy of the calculation results, but also facilitated the optimal design of the structure and greatly increased the design reliability of the shaker table.

Precautions:

First, equipment inspection

1. Check the position of the vibration isolation mechanism; let the magnetic steel of the vibration table in a reasonable position;

2. Check whether the controller signal output line is connected reliably;

3, if the level test, according to the device's instruction manual related to the contents of the table will be flipped to the horizontal state and make the appropriate checks;

Second, the installation of the specimen

1, open the air pump, manually adjust the center airbag pressure to the center position;

2. Fixtures and specimens shall be installed strictly in accordance with the requirements of the test task book;

3. The installation of the sensation sensor shall be strictly adhered to in accordance with the requirements of the test task book and shall be used as the designated purpose;

4. Connect the sensor with the corresponding signal line to the controller channel specified in the test task book;

Third, the boot sequence

1. Turn on the system power supply, confirm that the gain switch is in the reset position, and close the amplifier leakage circuit breaker;

2. Correctly set the test parameters according to the requirements of the test task and save them. If the test data is called, check whether the test settings are consistent with the test task.

3, press the power button, after the fan starts. Turn on the gain knob to the proper position (refer to the instruction manual). At this time, the “ready”, “start”, and “power” lights are on and the system enters the waiting state.

4. Run the test, record the state of the test piece and the state of the test equipment in real time, and save the corresponding test data:

Related standards

Standards compliant:

Shaking table meets GB/T13309, IEC68-2-6 (FC) and other national standards.

Control standards:

â—† Constant frequency test (50Hz) and frequency sweep test (30 Hz-60 Hz)

â—† Can test the test piece reliability in the laboratory

â—† Can do assessment and screening for the integrity of the product structure on the production line.