Materials testing is the quantification of values associated with properties of materials such as plastics, elastomers, metals, composites, and textiles. This testing is performed by manufacturers, research institutes, civil engineers, and anyone else who needs to understand how materials respond to different forms of physical stress, resulting in a systematic organization.
In general, the materials testing machine has an optical encoder module and a built-in load cell (strain gauge sensor) that can measure forces up to 7100 Newtons (N) (1600 lbs). Two lead screws (also called power or translation lead screws) raise or lower a load bar with a crank-gear system. Force data from the load cells and displacement data from the encoder modules can be recorded, displayed, and analyzed via the PASCO interface with PASCO data acquisition software.
The sensor cable of the materials testing kit connects to the PASSPORT input port, and the integrated materials testing system includes an AirLink port that connects to a USB port on the computer. The materials testing machine includes a calibration rod and nut, a load rod round nut, and Velcro® hook safety guards.
All material testing can be classified as destructive or non-destructive testing. A destructive test involves applying force to a sample of material until it fails or ruptures. In non-destructive testing, force is applied to a sample, but it is released before permanent damage is caused. There are many different types of materials testing, the most common tests are described below.
1) Dynamic testing
For dynamic testing, the load periodically affects the sample over an extended period of time, or the sample is subjected to shock loads. Dynamic material testing is the (destructive) testing of components or materials in which there is rapid (dynamic) movement. Examples include drop weight testing machines, pendulum impact testing machines, and high-speed testing (puncture or high-speed tensile testing).
2) (quasi) static testing
In (quasi)static testing, or static material testing, the load on the sample is slow and constant. In static material testing, the deformation behavior and strength of components and specimens mainly subjected to compression, tension, shear, torsion, and bending are established. Static material testing is performed at a lower test speed than dynamic material testing.
3) Cyclic material testing
In cyclic material testing, the load on the sample is applied in successive repeated load cycles. These load cycles can be tension/compression, pulsating, triangular, or sinusoidal alternating loads, depending on the machine.
4) Destructive material testing
In destructive material testing, samples are removed from the material and tested for chemical or mechanical loading. The sample is altered (surface) or destroyed. The part or material sample under test shall not be used after the test. Destructive material testing plays a particularly important role in aerospace engineering and the automotive industry, where material fatigue presents an extremely high-risk factor. However, material and component testing has also become crucial in medical engineering. In most testing techniques, samples are destroyed.
#1. Tensile test
The tensile test measures the response of a material to a tensile force (pull). By doing this, tensile testing can determine how strong a material is and how much it can stretch. The most commonly measured tensile properties are tensile strength, tensile modulus, elongation, and Poisson’s ratio
#2. Compression test
Compression testing is used to determine how a material will behave under an applied crushing load. The most commonly measured compressive properties are elastic limit, proportional limit, yield point, yield strength, and compressive strength of some materials.
#3. Bend/Bend Test
A bend test, sometimes called a bend test, measures how a material behaves under a simple beam load. For this reason, bend testing is often used to evaluate a material’s response to realistic loading situations. Common properties measured include flexural strength, flexural modulus, modulus of rupture, and maximum fiber stress.
#4. Torsion Test
Torsion testing evaluates the performance of a material or device under angular displacement stress. Torsion testing is commonly used to measure the shear modulus of elasticity, yield shear strength, ultimate shear strength, and shear modulus of rupture.
#5. Fatigue Test
Fatigue testing applies cyclic loading to a test specimen to see how it will behave under similar conditions in actual use. The load application can be a repetitive application of a fixed load or a simulation of a load in use. Load applications may be repeated millions of times, up to hundreds of times per second.
#6. Impact Test
Shock testing is the ability to test objects against high-rate loads. The impact test is a test to determine the energy absorbed by the specimen when it breaks at high speed. People usually think of one object hitting another object at a relatively high speed. The two main forms of impact testing are the drop weight impact test and the pendulum impact test.
#7. HDT/Vicat Test
Plastic and thermoplastic materials are temperature sensitive. HDT and Vicat testing involves determining the temperature at which a stressed sample deflects: in HDT testing, the sample is bent, and in Vicat testing, the sample is pierced by a point.
#8. Peel Test
The peel test measures the mechanical properties of the adhesive. Peel testing involves applying a pulling force to a flexible substrate that is adhesively bonded to another flexible or rigid substrate. Initial peak force, average force on the seal, and peel strength are common results for peel testing.
#9. Rheology test
Rheological testing measures the deformation of a substance under the influence of applied stress by analyzing the material’s internal response to force. In all conversion and production processes, the flow properties of polymers are crucial: the material is forced to flow, and the rheological properties determine its processability.
5) Non-destructive material testing
When using non-destructive material testing, the quality of a workpiece can be tested without damaging it. Using this method, you can ensured that the material is of sufficiently high quality for further processing and can withstand loads reliably over the long term. Nondestructive testing techniques include:
- Static and dynamic friction test
- Component test
- Hardness Testing
- Function test
- Rebound test
Materials testing machines come in many different types and force capacities in order to perform specific types of tests. Despite their wide variety, all testing machines share a common set of features that allow them to test and adequately characterize materials, components, and finished products. Below are the components of a materials testing machine.
1) Test framework
The test frame has strong, precise guide posts to ensure minimal bending of the sample under load. In addition to preloaded bearings, precision ball screws, extra-thick crossheads and base beams, and low-stretch drive belts, high-quality test frames ensure excellent performance and longevity. Powered by maintenance-free brushless AC servo motors, they provide synchronized motion of ball screws, preventing crosshead tilt and assisting in system alignment.
2) Test software
All test systems require software to operate the machine and collect and interpret the resulting data. Modern software should prioritize data security and feature user-friendly interfaces and intuitive workflows.
3) Load cell
A load cell is a sensor that converts force into a measurable electrical signal. Load cells must be calibrated periodically to ensure their accuracy. They should have high accuracy over a wide measurement range and have high stiffness and resistance to offset loads.
4) Jigs and Fixtures
A wide variety of grips and fixtures are available to help secure the large number of different material types and specimens tested on these machines. These grips range from tension grips to compression platens, peel and bend grips, custom grips for testing biomedical and electronic components, and many others.
Any company that produces a tangible product engages in materials testing in some way. Although this testing takes place behind the scenes in research and quality labs, it is responsible for the reliability of a wide range of products, including auto parts, bridges, medical supplies, and simple packaging. Most Common Materials Below is a partial list of industries where materials testing plays a quiet but critical role.
1) Plastic test
The range of applications for plastics is limitless, from packaging to biomedical, automotive, and electronics applications. Tensile strength, yield strength, modulus, and elongation are the key properties evaluated during testing. Key plastic testing standards include ASTM D638, ASTM D790, ISO 8295, ISO 527, and ISO 178 Definitive Guide to Flexural Testing of Plastics.
2) Metal testing
Metals are widely used in the automotive and construction industries. Key measurements for metals include r-value, n-value, modulus, tensile strength, strain, biased yield strength, and upper and lower yield strength. Common metal testing standards include ASTM E8, ASTM A370, and ISO 6892.
3) Composite material testing
Composites are complex materials made from fiber-reinforced polymers such as glass, aramid, or carbon. They are widely used in applications such as aerospace and wind energy where high-strength, lightweight materials are required. Key composite testing standards include ASTM D3039 and ISO 527-4. Among the most important measurements are tensile strength, shear strength, yield strength, and fracture toughness.
4) Elastomer test
Elastomers are high-elongation materials such as natural rubber, silicones, and polyurethanes that are used in the manufacture of tires, medical devices, sealants, and many other products. Tensile strength, total elongation, and tensile stress at a given location are key properties. Key testing standards include ASTM D412, ASTM D642, and ISO 34.
Universal materials testing machines can be configured for a variety of applications simply by you selecting the appropriate load cell, grips to hold the sample, optional materials testing software, and accessories such as extensometers, heating cabinets, and furnaces. The Lloyd range of materials testers consists of machines with different maximum load frames. Thirteen “Plus” machines cover the 1kN-300kN (225lbf-67443lbf) range.
A strong, high-stiffness load frame is at the heart of every materials testing system, while advanced electronics ensure accurate data collection, exceeding the requirements of BS EN 7500-1 and ASTM E4. Single-column configurations are used for lower-force instruments, while dual-column configurations are used for higher-force requirements.
1) Single-column testing machine
For applications requiring forces of 1-5 kN (225-1124 lbf), single-column instruments are designed. These benchtop testers offer a spacious work area.
2) Double-column testing machine
Bench-mounted instruments (5-50 kN (1124-22481 lbf) and floor-mounted instruments (100-300kN (22481-67443 lbf)) are available. Benchtop instrument ideal for routine quality control testing or complex multi-stage testing in the mid-force range. Floor-standing materials testing machines are rugged, heavy-duty testing machines with large work areas.
3) Load system compliance compensation
Advanced frame design and load chain compliance (or stiffness) compensation mean many compression and bending tests without the use of an extensometer. An extension error of less than 5 microns is achievable at full load. In most cases, the deformation of the instrument is small compared to that of the sample, so errors are negligible. However, in applications where system deformation accounts for a large proportion of the total measurement, stiffness compensation can improve measurement accuracy.
4) High elongation sample test
For all single and double-column systems, extended height frames are available for testing highly elastic materials or testing samples up to 2.5 m (98.4 in).
5) Customized material testing machine
Many materials testing applications require specially adapted instrumentation for a variety of reasons, which may be related to the particular application itself, or simply due to space constraints for equipment placement.
In the process of using materials testing machines, they can help you:
• Extensive product development testing is required to develop world-class products
• Helps manufacture the highest quality products in a cost-effective manner
• Demonstrates superior product performance
• Ensures products are manufactured to international or industry standards
• Validates supplier specifications
• Provides traceable test results
Materials testing is a complex process that can have a lasting impact on your business. When evaluating potential suppliers, it is important to consider not only the test equipment itself but also the depth of their expertise for your specific application and the accessibility and responsiveness of their service department. Vendors should be prepared to work with you long-term and work with you as your testing needs change over time. If you are looking for a supplier of material testing systems, please feel free to contact Linkotest.