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An electronic tensile tester is the product of the linkage of electronic skills and mechanical transmission, fully developed the respective expertise of mechanical and electrical, and then composed of a large fine tensile tester. The tensile testing machine is designed to test a wide range of materials in tension, compression, flexure, bursting, shear, tear, elongation, constant load, elastic, thread slip, peeling and other mechanical properties, with wide measurement range, high accuracy, fast efficiency, and timely display, documentation and printing of the data.
Table of Contents
★ Principle and Structure of Tensile Tester
Electronic tensile tester is composed of a measuring system, driving system, control system and other structures.
1 Measuring system of the tensile testing machine
1.1 Measurement of force value
The system consists of a force measuring sensor, an expander and a data processing system, and the most commonly used force measuring sensor is a strain gauge type sensor.
The so-called strain gauge sensor is composed of strain gauges, elastic elements and certain accessories (compensation elements, shields, wiring sockets, loading parts), which can turn some mechanical quantity into electrical output. There are many types of strain gauge type force sensors, including barrel type force sensors, spoke type force sensors, S-double hole type sensors, cross beam type sensors, etc.
It is known from mechanics that the strain Ɛ at a point of an elastic element is proportional to the force applied to the elastic element under the premise of small deformation. Take the S-type sensor as an example, when the sensor is subjected to the effect of a tensile force P, because the elastic element has strain gauges attached to its exterior, the strain of the elastic element is proportional to the change of the external force P. Then, the strain gauges are connected to the measurement circuit, the output voltage can be measured, and then the magnitude of the force is measured.
Briefly, the external force P provokes the deformation of the strain gauge in the sensor, which causes the imbalance of the bridge, and then provokes the transformation of the output voltage of the sensor, and we can know the magnitude of the force by measuring the transformation of the output voltage.
1.2 Measurement of deformation
Deformation device, which is used to measure the deformation of the specimen in the experimental process.
The device has two collets, through the sensor and photoelectric encoder connected together, when the interval between the two collets onset change, drive the shaft of the photoelectric encoder rotation, the photoelectric encoder will have pulse signal output. The signal is then processed by the processor and the deformation of the specimen can be obtained.
1.3 Measurement of beam displacement
The principle is roughly the same as that of deformation measurement, which is to obtain the displacement of the beam by measuring the number of output pulses of the photoelectric encoder.
2 Drive system of the tensile testing machine
The main purpose is used to control the movement of the beam of the tensile testing machine, the principle is that the rotation of the motor is controlled by the servo system, The motor drives the screw shift through a series of transmission devices, and then achieves the purpose of controlling the movement of the beam. Change the speed of the motor, you can change the speed of the beam movement.
3 The control system of the tensile testing machine
It is the system to control the operation of the machine, people can control the operation of the tensile testing machine through the console, through the display can be informed of the form of the test machine and the experimental parameters. If the tensile strength machine with a computer, the computer can also complete the functions and data processing, experimental results printing. The communication between the tester and the computer is generally the use of the RS232 serial communication method, which is more convenient to use through the serial port on the back of the computer for communication.
★ Important Factors Determine the Performance and Accuracy of the Tensile tester
1 Force sensor
The quality of the sensor determines the accuracy and stability of the tensile tester, the current market tension machine with sensor, small force values generally use S-type sensors, large force values generally use the spoke type sensor. The internal sensor is generally resistive strain gauge type, if the strain gauge accuracy is not high or fixed strain gauge with bad ageing resistance ability of the adhesive, or the sensor material is not good, these will affect the accuracy and service life of the sensor. Tensile testing machine of TESTEX uses well-known sensors, which are highly accurate, linear and very stable, and will not change for decades.
2 The part that drives the movement of the sensor: ball screw
If there is a gap in the screw, the tension test will directly affect the maximum test deformation and elongation after break. At present, some of the tension machines on the market are with T-shaped ordinary screw, so that the gap is relatively large, and the friction is relatively large, resulting in short life. The screw used in the tension machine of TESTEX is a high-precision backlash-free ball screw with high surface quenching and hardness, and the service life can reach decades, and ensure the same accuracy.
3 Transmission system of tensile tester
Currently on the market, the transmission system of ordinary tensile tester, some use reducer, some use ordinary belt, the main drawback of these two transmission methods is: the former requires regular lubrication, the latter does not ensure the synchronization of transmission affects the test results. The transmission system of TESTEX tensile testing machine using full-arc synchronous belt deceleration, to ensure the synchronization of transmission accuracy, high transmission accuracy, high efficiency, smooth transmission, low noise, and long service life.
4 Power sourece of tensile testing machine: motor
Currently on the market, some tensile tester use ordinary three-phase motors or frequency motors, such motors use analog signal control, slow control response, inaccurate positioning, general speed range is narrow, there is a high speed without low speed or low speed without high speed, and speed control is not accurate. The motor used by TEXTEX tensile tester is a full digital AC servo motor, the control method uses full digital pulse control, speed range is wide, up to 0.01-1000mm/min, control positioning accurate, fast response, the motor can ensure full range speed control accurate, and long service life, can reach decades.
5 Measurement and control system
Measurement and control system is a combination of software and hardware, most of the current market, the measurement and control system of tensile testing machine using 8-bit microcontroller control, low sampling rate, and poor anti-interference ability, in addition, if the number of bits of the AD converter is also low resolution, then the measurement will not be accurate.
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