Also known as a tensile tester, universal testing machines (UTMs) are multi-purpose test instruments used to determine the mechanical properties of materials under various loads, including composites, metals, and plastics. Along with ensuring accuracy and repeatability, a universal testing machine also offers superior control and stability during the testing process.
As the name suggests, they are a universal design that can perform many different test types and not just tensile tests.
What tests can be performed on a universal testing machine?
Typical tests for universal testing machines include:
3 point bend test
4 point bend test
Bend test
Coefficient of friction test
Compressive test
Creep test
Cyclitic test
Fatigue test
Peel test
Puncture test (static)
Shear test
Tensile test.
Different types of universal testing machines
Universal testing machines generally use electromechanical systems. However, there are also servo-hydraulic material testing machines, which are powered by a separate hydraulic power unit that is placed next to the materials testing machine.
Hydraulic tensile testing machines often have two test areas. These allow two types of test on the machine without removing the grips and fixtures. Hydraulic tensile testing machines can be specified for static or cyclic tests, and are generally class 0.5 % of 1% of the applied load according to ISO 7500-1. However older machines may be 2 or 3%.
All UTMs use a rigid test frame with a moveable cross head. Additionally, they are moved by an electric motor and gearbox (electromechanical UTM), or by hydraulic ram and a load cell (servo-hydraulic UTM).
You can also choose from single and twin-column formats. Single column universal testing machines are generally more compact and lightweight, and best suited to low to medium force testing applications.
Dual column UTMs offer greater versatility and can withstand greater tensile force, making them ideal for medium to high force testing.
Key universal testing machine components
Adapters – Enable different grips and fixtures to be attached to the load cell.
Columns/Load Frame – Provide the area and accurate guidance for the moving cross head. This critical load bearing element also provides rigidity and stiffness to the frame.
Control System and Software – Allows the operator to set test parameters, monitor force and strain in real-time, and collect and evaluate data for analysis. All modern UTMs have comprehensive software to provide analysis of the test results.
Cross Head – This is the moveable part of the UTM that is controlled to move up or down during the testing process.
Drive System – Electromechanical or hydraulic.
Grips/Fixtures – UTMs can be fitted with a vast range of different grips and fixtures, which are used to securely hold the samples for testing, preventing misalignment and inaccurate test results. They can accommodate the many different tests UTMs can perform, including compression, tension, and bend/flex applications.
Load Cell – The load cell attaches to the cross head and converts force into a measurable electrical output. A real-time reading of force in both compression and tension is then displayed on the UTM software. Our load cells come in different rated capacities from 500kg to 100 tonnes, and are based on the maximum force rating of the UTM.
Universal testing machine accessories
Additional extras can seamlessly be integrated with UTMs to suit your set-up. From extensometers used to measure strain directly on the specimen to environmental chambers used to simulate environmental conditions such as temperature, easily adapt your instrument to your specific needs with our tensile tester accessories.
Non-contact extensometers like the Vector U70 and Vector U200 are also available. They use lasers to measure strain without touching the sample.
How does a universal testing machine work?
A UTM works by applying controlled force to a test specimen while measuring the response. By automating the testing process, modern UTMs provide highly accurate and reproducible results, reducing human error in material analysis.
The test process will typically follow these steps:
The test specimen is prepared according to industry standards, including ensuring the surface has no defects.
Select the appropriate grips, fixtures, and testing parameters, before adjusting and securing the test specimen between the grips or fixtures. There must be no slippage, as misalignment could skew your test results. Don’t forget to check your UTM is calibrated correctly too.
Once you’re happy the sample is in situ correctly and the instrument will be able to apply even forces during the testing process, the test can begin.
During the test, your UTM will apply a controlled force through the moving crosshead by following a preset load rate as stipulated by the operator in the control system. The type of force (compressive, tensile, etc.) will depend on the nature of the test. Sensors and load cells continuously record changes in stresses and strain, while extensometers or other measuring devices monitor any deformation in the material.
The force is steadily increased until the specimen reaches its breaking point or fractures permanently.
The final step is analysing, recording, and exporting the collected data, offering important insights into how the material performs under stress.
Typical sizes / capacities of Universal Testing Machines
The amount of travel or space between the columns can be specified your needs. Modern UTMs generally have an accuracy of 0.5% of the applied force, as per the requirements of ISO 7500-1. However, some of the larger and older machines could be 1% of the applied load.
Types of tensile testing equipment
Tensile testing machines come in different shapes and sizes, from a simple force gauge to a robotic tensile testing machine.
Force gauges
Force gauges are the simplest, lowest accuracy, and lowest cost type of tensile testing equipment. Additionally, these are normally combined with a test stand. Force gauges are typically for low force tests under 5 kN, with most force gauges being under 1 kN.
Traditionally force gauges have an integrated load cell, but there are options to have a separate load cell plugged into the force gauge.
Force gauges don’t meet the requirements of ISO 7500-1, meaning they are not suited for testing to the majority of the ISO, ASTM, & BS standards. However, there are many test applications where a UTM would be too costly or simply overkill for the intended test.
Furthermore, we often supply force gauges and test stands for in-house comparative testing, or testing of small components or parts.
High temperature tensile testing machines
High temperature tensile testing machines are standard tensile testing machines or universal testing machines fitted with a chamber, furnace, or oven used for tensile testing at high temperatures.
As well as high temperature tensile tests, most chambers can also perform tests at low temperatures. Moreover, high temperature tensile testing machine ovens and furnaces can achieve elevated chambers up to 1280℃. However, this depends on the model of oven or furnace specified. Low temperature tensile tests can generally be performed down to -200℃.
A typical universal tensile testing chamber will cover the range of -70℃ to 280℃. However, there are custom options or specialist chambers to increase this range.
These chambers and ovens are not limited to tensile testing. In fact, just about any test can be performed at low or high temperatures providing the correct type of grips or fixtures are used.
Additionally, high temperature tensile testing machine chambers can be fitted to a wide range of material testing machines, from small single column universal testing machines to the largest hydraulic materials testing machines best suited to testing metals and building materials.
High temperature tensile testing machine tests are common in most industries including steel making, plastics, packaging, composites, medical devices, nuclear, product design and testing.
Why choose AML Instruments as your universal testing machine supplier?
Whether you require a UTM for material testing, quality control, or research and development purposes. AML Instruments is a leading and trusted supplier of universal testing machines worldwide. We work alongside renowned manufacturers such as Barrus and Grip Engineering to deliver universal testing machines made to the highest standards.
We also supply thousands of different grips and fixtures to suit your industry and testing application, as well as being able to design and manufacture bespoke solutions.
Not sure which of our universal testing machines is right for you? Contact us and our highly-trained technical sales team will be happy to help.
