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Tensile Tester: The Complete Guide

This will be the most comprehensive guide on the subject of the tensile tester. In this guide, you will learn about the classification of the tensile tester, the principles of construction, the factors affecting performance and accuracy, and how to buy a tensile tester.

 

 

Introduction of Tensile Tester

1 What is the tensile strength test? What machine is used for tensile testing?

The tensile test, also known as the tensile strength test, is a test method to determine the properties of materials under axial tensile load. Usually, a variety of tests such as tensile, compression, bending, shear, peel, tear, etc. can be performed. The machine that performs the above tests is called a tensile testing machine or a tensile machine.

2 Why the tensile strength test?

The data obtained by using the tensile test can determine the elastic limit, elongation, elastic modulus, proportional limit, area reduction, tensile strength, yield point, tear strength test, yield strength, and other tensile performance indicators of the material. It can help factories accurately determine the mechanical properties of various materials, so as to better judge the quality, safety, durability of materials, etc. For Example, such as the production of electric wire, to do testing on its toughness, and metal hardness, the production of clothing and footwear, to do testing on the durability of the fabric, stability of the button, wear resistance of shoes, etc.

3 What materials can the tensile machine test?

Tensile Tester is mainly used for mechanical experiments on various materials and can be used for testing metal and non-metal materials, such as rubber, plastic, wire and cable, fiber optic cable, seat belt, insurance belt, leather belt composite material, plastic profile, waterproof coil, steel pipe, copper, profile, spring steel, bearing steel, stainless steel (and other high hardness steel), casting, steel plate, steel strip, non-ferrous metal wire, etc. It is a  universal tensile testing machine used in factories and laboratories, and most of the products are under tension testing. Of course, different models of tensile strength testing machines can test different materials, you should consult the manufacturer.

 

 

4 How does a Tensile Tester work?

The universal tensile machine fully exploits the characteristics of the combination of electronic and mechanical technology, accurate measurement, high efficiency, and the configuration of the computer can be synchronized with the output measurement results. The tensile tester equipment is composed of the measuring system, driving system, control system, and computer parts.

  1. Measurement of tensile force value

Tensile testing machine force measurement is done by force sensors, a data measurement system.

  1. Measurement of deformation

Mainly by deformation value to measure the deformation caused to the material in the test.

  1. Measurement of measured displacement

The displacement data of the beam is mainly obtained by measuring the number of output pulses of the photoelectric encoder.

  1. Drive system of tensile strength tester

The main role in the displacement of the beam, and servo system principle is the same, through the computer control to change the speed of the motor, so as to change the displacement speed of the beam machine.

  1. Tensile testing machine control system

The operator can control the control tester through the computer to obtain the test parameters of the tester.

  1. Computer

For the operation of the machine, data collection, analysis, and summary.

5 What is the Structure of a Tensile Tester?

Different brands and models of tensile machines have different structures, take TESTEX Tensile Tester TF001 as an example.

 

Protective Cover: to protect the instrument from moisture and rust, as well as dust.

Fixture holders (upper and lower): for fixing two fixtures.

 

Limit (upper and lower): the upper and lower limit position where the fixture can be moved (different fixture has different limit position).

Crossbeam, Sensor: the crossbeam is used to install the sensor and the fixture, which can control the stroke, and the sensor is placed inside the crossbeam.

the function of the sensor is to convert the tension into an electrical signal that can be measured, and thus obtain the test results.

 

Horizontal Beads: used to adjust the instrument to a balanced position to facilitate accurate measurement.

Sample: the actual sample used for testing.

Emergency stop button: when pressed in an emergency, the machine stops running.

A computer also needs to be configured.

Structure of the back of Tensile Tester TF001

Part of  the fixtures and accessories

 

6 How to test tensile strength? Testing process.

  1. Make specimens: make specimens according to the requirements of the test standard, and measure their dimensions and other data.
  2. Turn on the machine: first, open the software measurement and control system on the computer (the manufacturer provides the installation package), and then turn on the power of the universal tensile machine. According to the test to be carried out select the appropriate type of test.
  3. Trial run: Select the appropriate speed to make the tester lift and run a little to determine the normal operation of the tensile strength tester.
  4. Tensile testing machine new records: according to the number of tests to be conducted, the number of new test records; and fill in the corresponding batch number, number, test environment, specimen size, and other relevant data.
  5. Load the specimen: adjust the position of the specimen on the tester and load the specimen.
  6. Select the range: According to the range of test force and deformation required for the test, the pull tester machine will be adjusted to the appropriate test force and deformation of the gear (range).
  7. Clear zero: the test force, deformation, displacement zero.
  8. The tensile strength test speed: according to the standard test process requirements, set the appropriate test speed; standard speed requirements, set a more appropriate speed, speed is not too large, so as not to affect the test results.
  9. Test starting: point “test start” button to start the test.
  10. The tensile strength test end: the test is completed after the “test end” button is automatically pressed. If you need to end the test in the middle, you can also press the “test end” button to end the test manually.
  11. Test results: Tap the “Analysis” button to view the corresponding test results. Continue the test: Tap the “Test” button to return to the test operation interface, and tap the “Next” button to switch the test record to the next one.
  12. Save data: If the test data needs to be saved, press the “Save” button to save the test data to the database for reference. Print report: If the test results need to be printed, press the “Output Report” button to output the test results to a Word document and print.
  13. After the test, clean up the sample, remove the fixture, and do the daily maintenance.
  14. Test shutdown: first turn off the test machine power, and then turn off the software measurement and control system and computer.

The above is a generic version of the tensile strength test process, more detailed operating instructions need to be provided by the manufacturer with the corresponding machine manual.

Test software interface schematic (TF001 for example)

1. Quick grasp

The main interface of the software is shown in Figure. A complete test process consists of three steps: setting up before the test, executing the test, and getting test results.

2. the implementation of testing:

Switch to the interface before testing and select a test standard. The test will be tested according to this standard. At the end of the test, the corresponding results will be output according to this standard. As shown in Figure.

 

 

3. the implementation of testing:

Click the Start Test button, or press the Start test shortcut F7 to start the test button into the green pull-up state, indicating that the current testing process, waiting for the test to automatically end or manually end the test.

4. get the test results: After the test, will automatically get the test results. As shown in Figure

 

 

The expanded knowledge of Tensile Tester

1. Tensile tester drive method

1.1 Hydraulic type tensile tester

The hydraulic type tensile tester is driven by hydraulic cylinders moving up and down to move the fixture up and down to achieve the various functions of the pulling machine. The advantage is that it can do higher tensile strength tests, the disadvantage is that the control precision is not high and not very hygienic. It is mainly applied to metal materials, bridge bearings, large plates, construction materials, composite materials, and other industries. Its load is generally above 300KN (30T).

Working principle: the motor drives the oil pump to rotate, and the oil pump suctions oil, converting mechanical energy into hydraulic oil pressure energy. The hydraulic valve realizes the direction, pressure, and flow regulation by the integrated block, through the external pipeline transmission to the hydraulic machinery cylinder or oil motor, so as to control the hydraulic machine direction change, the size of the force, and speed, to promote the hydraulic machinery to do work.

  • Hydraulic tensile tester, limited by the configuration of the oil source, the test speed is low.
  • Compared with the tensile strength tester, the small tonnage (<300kN) comprehensive cost performance is low and scalability is poor.
  • The servo valve requires high filtration precision for the hydraulic oil of the oil source, and the hydraulic oil needs to be replaced regularly.
  • The hydraulic connection lines and joints are prone to oil leakage and the oil source is relatively noisy.
  • The hydraulic oil source needs to be equipped with a cooling system (air-cooled or water-cooled), and high energy consumption.
  • Hydraulic tensile tester on the foundation requirements are very high, especially the large force value of the machine, the foundation needs to be prepared in accordance with the drawings provided by the tensile strength testing machine manufacturer, and the whole machine occupies a large space.
  • Hydraulic drive, strong power, more reliable and stable when doing large tonnage material mechanics test.

1.2 Mechanical tensile tester

The mechanical tensile tester is mainly driven by the motor spiral screw rotation, the screw rotation drives the fixture up and down to achieve the tensile tester tensile, compression peel, tear, shear, three-point bending resistance, and other functions, the advantage is the high precision control.

tensile tester

Mechanical tensile tester mainframe for single rod structure or door structure, mainly suitable for rubber, plastic, textile, geotextile, waterproof material, wire and cable, net rope, metal wire, metal bar, metal plate, and other materials tensile test, increase the attachment can do bending, tearing, peeling and other tests.

  • Servo motor drive, compact structure, high efficiency of energy use, easy to use and maintain, low noise, stable and reliable.
  • Three closed-loop controls for load control, strain control, and displacement control can be achieved.
  • Wide range of force measurement, between 0.4% and 100% of the full range, the accuracy of force measurement can reach 0.5 grade.
  • Test speed range can be adjusted, test speed can be 0.001mm/min-1000mm/min, test stroke can be determined according to needs, and more flexible.
  • Flexible test methods: test fixtures can be freely selected and replaced for models with a test range below 300kN, and external sensors and corresponding fixtures can be extended to meet different types of material mechanics tests (e.g. tensile, compression, bending, peeling, tearing, shearing, pulling and twisting tests).
  • High-temperature ovens, high and low-temperature chambers, or other environmental chambers can be added for environmental simulation tests.
  • Large tonnage is more costly to manufacture.

 

2 Classification of the tensile tester

2.1 According to the degree of automation can be divided into …

Pointer type tensile tester: This traditional type of tensile tester has been largely eliminated by the digital display type tensile tester due to its low testing accuracy and low-cost performance. But in the small force range, is our common tensile strength meter, often used by factories for simple force testing of small products, because of its low price, quite popular.

Digital display type tensile tester, also known as microcomputer type tensile tester: the test data is directly displayed on the LCD screen, the test items are relatively single, commonly used in factories for quality control.

Computerized system tensile tester: the most versatile tensile tester, as the test data is collected through the computer and then processed by the software program to produce the final data desired by the user, and can be printed out by way of a report. Commonly used in scientific research units, testing institutions, new product development, etc.

2.2 According to the control system can be divided into …

Frequency conversion system tensile tester: using a frequency conversion motor control system, the speed of stretching and compression is controlled by a frequency conversion speed regulator.

Servo system tensile tester: using servo motor control system, the speed of tensile and compression, displacement control more accurate. A servo control system, using intelligent feedback type operation, can be a fixed speed tests, cycle tests, programming tests, etc.

Another drive mode tensile tester: through the DC motor control, the drive mode tensile tester due to low-cost performance, has been gradually eliminated.

2.3 According to the industry and functional characteristics can be divided into …

Metal tensile tester: metal materials with high tensile strength and small elongation, need to be equipped with a metal point elongation gauge.

Rubber tensile tester: rubber or elastomer elongation is relatively large, and needs to be accompanied by a large mark point elongation device, while the fixture design should be considered suitable for the characteristics of rubber, not slippery. Can be equipped with an O-ring fixture, tire industry with fixture, etc.

Plastic tensile tester: the tensile strength of plastic than rubber, elongation has a large and small, and often need to test the three-point bending test.

Fabric tensile tester: the textile industry needs to test fabric peeling, puncture, tearing, single yarn stretching, and other tests, fixtures and software are special.

Paper tensile tester: paper needs to test tensile strength, ring strength, vertical compression, flat compression, edge compression, peel strength, etc., with many fixtures.

Leather tensile tester: Leather needs to test tensile strength, tearing strength, etc. The testing items are relatively simple.

Factors Influencing Performance and Accuracy of Tensile tester

The tensile tester is a large precision test instrument combining modern electronic technology with mechanical transmission technology, giving full play to the special features of electromechanical integration, with a wide measuring range, high precision, and fast response. The tensile tester works reliably and efficiently and can display and record and print test data in real-time. It consists of a measuring system, a driving system, a control system, and a computer structure.

1 Measurement of force values

Force is measured by means of the load cell, amplifiers, and data processing systems. The most commonly used load cell is the strain gauge sensor.

A strain gauge sensor is a device that consists of a strain gauge, an elastic element, and certain accessories (compensation elements, shields, wiring sockets, loading parts) that can turn a certain mechanical quantity into an electrical output. There are many types of strain gauge sensors, mainly barrel force sensors, spoke force sensors, S-double-linked hole type sensors, cross beam sensors, and other types.

It is known from the mechanics of materials that the strain Ɛ at a certain point of an elastic element is proportional to the force applied to the elastic element and to the deformation of the elasticity under conditions of small deformation. For example, when a sensor is subjected to a pulling force P, the strain gauge is attached to the surface of the elastic element because the strain on the elastic element is proportional to the magnitude of the external force P, therefore, the strain gauges are connected to the measurement circuit and the output voltage can be measured to determine the force.

For the force sensor, a differential full bridge measurement is generally used, where the strain gauges are attached to form a bridge circuit. In simple terms, the external force P causes the deformation of the strain gauges in the transducer, resulting in an unbalanced bridge, which causes a change in the output voltage of the transducer.

Generally speaking, the output signal of the sensor is very weak, usually, only a few millivolts, if we measure this signal directly, it is very difficult and can not meet the requirements of high precision measurement. This weak signal must therefore be amplified by means of an amplifier, which amplifies the signal voltage up to 10V. At this point the signal is analog, this analog signal is transformed into a digital signal by means of a multiplex switch and an A/D converter chip, and then the data processing is carried out, at which point the force measurement comes to an end.

The quality of the sensor determines the accuracy and stability of the tensile machine, In the current market tensile tester with sensor, small force values generally use S-type sensors, and large force values generally use the spoke type sensor. The internal sensor is generally a resistive strain gauge type, if the strain gauge accuracy is not high or fixed strain gauge with bad aging resistance ability of the adhesive, or the sensor material is not good, these will affect the accuracy and service life of the sensor. The tensile machine of TESTEX uses well-known sensors, which are highly accurate, linear, and very stable, and will not change for decades.

2 Measurement of deformation and cross-beam displacement

This is measured by means of a deformation measuring device, which is used to measure the deformation of the specimen during the test.

The device has two collets which are connected by a series of drives to an optical encoder mounted on the top of the measuring device. When the distance between the two holders changes, the shaft of the photoelectric encoder is rotated and a pulse signal is an output from the photoelectric encoder. This signal is then processed by a microcontroller to give the amount of deformation of the specimen.

The principle of measuring the displacement of the cross-beam is roughly the same as that of deformation measurement, which is obtained by measuring the number of pulses output from the photoelectric encoder to obtain the displacement of the cross-beam.

The transmission is mainly done by the screw, if there is a gap in the screw, the tension test will directly affect the maximum test deformation and elongation after the break. At present, some of the tensile testers on the market are with T-shaped ordinary screws, so the gap is relatively large, and the friction is relatively large, resulting in a short life. The screw used in the universal tensile testing 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 Drive system of the tensile tester

The drive system is mainly used for the movement of the beam of the universal material testing machine. Its working principle is to control the motor by the servo system, and the motor drives the rotation of the screw through a series of transmission mechanisms such as a reduction box, so as to control the movement of the beam. By changing the speed of the motor, the movement speed of the beam can be changed.

Currently, on the market, some pull tester machines 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 TESTEX universal tensile machine 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 accuracy, and long service life can reach decades.

4 Control system of the tensile tester

As the name suggests, it is the system that controls the operation of the computer servo system of the universal material testing machine, people can control the operation of the test machine through the console, and know the status and the test parameters of the test machine through the display. If the machine is equipped with a computer, it is also possible to realize various functions and carry out data processing and analysis, and print test results. The communication between the tester and the computer is generally in the form of RS232 serial communication, which is carried out through the serial port (COM number) on the back of the computer, which is a mature, reliable, and easy-to-use technology.

Most of the current market, the measurement, and control system of a tensile tester use 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.

How to Choose Tensile Tester?

Now there are many brands of the tensile tester on the market, with many types of tests and varying prices and quality. So as a buyer or business owner, how should we go about choosing a tensile tester? How to determine which brand of the tensile tester is good? What is the reference basis? Below I will do a detailed analysis for you.

When buying a tensile tester, you will probably follow three principles: testing needs, machine performance, and manufacturer service. Firstly, choose a tensile tester with the appropriate specification parameters according to the type of test. In addition, the tensile tester has high requirements for both hardware and software, so choose the right manufacturer based on service and quality. Here are the details.

1 Determine what tests need to be done.

Determine what tests to do in order to determine what instruments we need to buy. First of all, we must make sure that we choose the right machine to prevent the machine that buying back is not what we thought it would be, because in some industries some tests are dedicated to special machines.

For example, in the spring tensile fatigue test, in theory, the tensile tester can also, but the best test instrument is not a tensile tester, but a spring fatigue test machine, which is a professionally built machine for the spring test. Another example is the rubber tensile tester. We all know that rubber products need to be tested for tensile damage in order to test their mechanical properties such as tensile strength and extension. But because the deformation of rubber is very large in the stretching, especially in latex products, elongation may be as high as 1000% or more. So before the rubber specimen breaks, it is necessary to ensure that the effective stroke of the universal tensile machine is large enough, it is necessary to use it in conjunction with the use of a large deformation extensometer. Therefore, it is more important to choose the right one than a good one.

2 Determine the maximum test force of the material.

Determine the maximum destructive force will be able to determine the range of the tensile tester equipment because it is based on the range of the sensor to distinguish the model of the tensile tester. First of all, different ranges of the machine sensor are different, in addition, the screw, motor, gearbox, and other accessories of the tensile tester are different, and finally, the structure of the tensile tester will also be different, for example, 0-500kg range is single-column type tensile tester, 1-20T range is double-column type electronic tensile tester, more than 30T range are hydraulic multi-column type electronic tensile tester.

3 Determine whether the function meets the requirements.

Determine what tests the tensile tester can do: computer-type tensile tester can generally achieve tensile, compression, bending, peel, tear, shear, puncture, low fatigue, and other tests, but some simple digital display type tensile tester can not test the peel, fatigue, shear, and other functions.

4 Determine whether the test stroke and test speed are consistent.

Test stroke is based on the characteristics of the material to determine, the stroke of metal and other hard materials is usually not very large, and the standard pull tester machine can meet. But for some soft packaging film, rubber, silica gel, and other materials, the test stroke is very large, some may need to increase the stroke of the tensile tester to meet the measurement. Test speed is also an important parameter of the tensile tester, the general tensile tester in 0.1-500mm/min, this speed range has been able to meet the majority of test requirements, some special products may require 1000mm/min or even greater test speed, these are required to determine in advance.

5 Determine the brand of the core spare parts of the machine.

We all know that the core parts of the tensile tester are: sensors, screws, motors, gearbox, and even including the controller, etc. Domestic and foreign manufacturers of the universal testing machine tensile tester, none of the accessories used 100% of their own production, so some of the core accessories are outsourced, which also involves the brand of these accessories. A good brand not only has precision, quality convenience better, but for the overall performance of the machine, stability, and reliability also has an important impact. Therefore, the core accessories are also used as an important basis for comparative reference.

6 Determine whether the accuracy of the machine meets the requirements.

The accuracy standard of a common tensile tester is 1 level, that is, the accuracy of the machine within ±1%; of course, there is a higher 0.5 level, the measurement accuracy error within ±0.5%. Just choose according to your actual needs when selecting.

7 Determine whether the brand is directly sold by the manufacturer and whether the after-sales service is guaranteed.

As a tensile tester for their own use, we have to determine whether the supplier is a factory direct sales, after-sales service is guaranteed, after all, there are many electronic products of the tensile strength equipment, there may be all kinds of failure, so the choice of what kind of supplier is equally important.

8 Compare prices and choose a brand with a good reputation

After the above is no problem, the last is to examine the price, after all, the price is still very important. On price advice: according to your company’s budget to choose a brand, not the blind pursuit of big brands, but definitely not to buy far below the normal market price, unless you buy just use to see.

Brand Recommendations of Electronic Universal Tensile Tester

In addition to assessing the brand from the quality of the tensile tester, we can also assess them by after-sales service, compliance with testing standards, simplicity of operation, and price. Here is a brief list of some of the better brands to meet different purchasing needs.

Japan Shimadzu tensile tester. Japan’s electronic technology has been very well developed, its Panasonic AC servo motor in various industries can be seen, and Japan’s NTS sensor is also a well-known sensor worldwide.

Germany ZWICK tensile tester. German industrial manufacturing is indeed the heritage of the times, with exquisite craftsmanship and dedication plus Schneider series brand accessories so that ZWICK tensile tester wears the top title.

MTS tensile tester from the USA. The United States MTS tensile tester is famous for its stability, no matter what, its quality is guaranteed, and is a hundred-year tradition of the old brand.

American Instron tensile tester, from 1946 to the present well-known historical brand, belongs to the quality is still a good instrument.

Taiwan Gotech tensile tester, Taiwan has always been known for its quality and dedication, but also a world-renowned brand.

Guangdong TESTEX tensile tester, test stable, specifically for rubber, plastic, fibers, and other organic polymer materials, is more professional.

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If you want to know more about the specifications and how to operate the tensile tester, look here.

 

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