Hydraulic universal testing machine working principle

The universal material test is a combination of modern electronic technology and mechanical transmission technology. It is a large-scale precision test instrument that makes full use of the respective specialties of electromechanics. It can perform stretching, compression, bending, peeling, and shearing on various materials. Performance test, with a wide range of measurement, high precision, fast response and so on. Reliable work, high efficiency, real-time display and printing of test data.

Universal material testing machine is composed of measurement system, drive system, control system and computer (computer system tensile testing machine) and other structures.

First, the universal material testing machine measurement system 1. Force measurements are measured using load cells, amplifiers, and data processing systems. The most common force sensors are strain gage sensors.

The so-called strain gauge sensor is a device that can change a mechanical quantity into a power output by a strain gauge, an elastic element, and certain accessories (compensation components, shields, wiring jacks, and loaders). There are a wide variety of strain gauge and pressure sensors at home and abroad, including cylindrical force sensors, spoke type force sensors, S double hole type sensors, and cross beam type sensors.

From the material mechanics, it is known that under small deformation conditions, the strain ε at a certain point of an elastic element is proportional to the force received by the elastic element and is also proportional to the change of elasticity. Take the S-type sensor as an example. When the sensor is subjected to a pulling force P, a strain gauge is attached to the surface of the elastic element. Since the strain of the elastic element is proportional to the magnitude of the external force P, the strain gauge is inserted into the measurement circuit. By measuring its output voltage, the force is measured.

For the sensor, differential full bridge measurement is generally used. The strain gauge pasted is composed of bridges. R1, R2, R3, and R4 are actually four (or eight) strain gauges with equal resistance, that is, R1=R2= R3=R4, when the sensor is subjected to external force (tension or pressure), the elastic element of the sensor produces strain to change the resistance value, and the change values ​​thereof are ΔR1Δ, R2, ΔR3, and ΔR4 respectively, and the result is originally balanced. The bridge is now unbalanced and the bridge has a voltage output. Set △E

Then △E=[R1R2/(R1+R2)2]△R1/R1-△R2/R2+ΔR3/R3-△R4/R4)U

In the formula, U is the voltage of the external power supply bridge to further simplify the â–³ E = [R2 / 4R2] (â–³ R1/R-â–³ R2 / R + â–³ R3 / R-â–³ R4 / R) U

Substituting △Ri/Ri=Kεi with the above formula, there is △E=[UK/4](ε1-ε2+ε3-ε4)

In simple terms, the external force P causes deformation of the strain gage in the sensor, resulting in imbalance of the bridge, which causes a change in the output voltage of the sensor. We can know the magnitude of the force by measuring the change in the output voltage.

In general, the output signal of the sensor is very weak, usually only a few mV, if we directly measure this signal, it is very difficult, and can not meet the high-precision measurement requirements. Therefore, this weak signal must be amplified by an amplifier, and the amplified signal voltage can reach 10V. The signal at this time is an analog signal. This analog signal is converted into a digital signal through a multi-way switch and A/D conversion chip, and then data processing is performed. At this point, the measurement of force came to an end.

2. The deformation measurement is measured by a deformation measuring device, which is used to measure the deformation of the sample during the test.

There are two chucks on the device, which is connected to the photoelectric encoder mounted on the top of the measuring device through a series of transmission mechanisms. When the distance between the two chucks changes, the axis of the photoelectric encoder is driven to rotate. The encoder will have a pulsed signal output. The signal is processed by the processor to determine the amount of deformation of the sample.

3. The principle of measurement of beam displacement is the same as that of deformation measurement. The displacement of the beam is obtained by measuring the number of output pulses of the photoelectric encoder.

Second, the universal material testing machine drive system is mainly used for test machine beam movement, its working principle is the servo system to control the motor, the motor through the gear box and a series of transmission mechanism to drive the screw rotation, so as to achieve the purpose of controlling the beam movement . By changing the speed of the motor, you can change the speed of the beam.

Third, the universal material testing machine control system, as the name suggests, is to control the test machine operation system, people can control the operation of the test machine through the console, through the display screen can be informed of the test machine status and the test parameters, if the machine with In the case of computers, computers can also implement various functions and perform data processing analysis and test results printing. The communication between the testing machine and the computer generally uses the RS232 serial communication mode. It communicates through the serial port (COM port) behind the computer. This technology is mature, reliable, and easy to use.

Fourth, the computer is used to collect and process analysis data. After entering the test interface, the computer will continuously collect all kinds of test data, draw the test curve (common force-displacement curve) in real time, and automatically calculate the test parameters and output reports.

V. Quality Assurance Equipment shall be considered as a formal delivery after the formal acceptance of the ordering party. The equipment three-pack period is one year from the date of formal delivery. During the three-guarantee period, the supplier provided timely and free maintenance services for all types of equipment failures, and damaged all kinds of non-human-made parts and replaced them in time for free. The equipment outside the warranty period will fail during use. The supplier shall promptly provide services to the ordering party and actively assist the orderer in completing the maintenance task.