Materials Testing
An Introduction


Materials testing is the quantification of values associated with the properties of materials such as plastics, elastomers, metals, composites, and textiles. This testing is is performed by manufacturers, research institutions, civil engineers, and anyone else who needs to understand how a material responds to different forms of physical stress. This guide will introduce you to the different types of materials testing that is performed, discuss the most important properties of key materials, and provide an overview of the equipment used in this testing.

Types of Materials Testing

All materials testing can be classified as either destructive or non-destructive testing. Destructive testing applies force to a material sample until it fails, or breaks. Non-destructive testing applies force to the material sample but releases that force before it permanently damages the material. There are many different types of materials testing, and the most common ones are explained below.

 

Tensile Testing

A tensile test applies tensile (pulling) force to a material and measures the specimen's response to the stress. By doing this, tensile tests determine how strong a material is and how much it can elongate. The most common tensile properties measured are tensile strength, tensile modulus, elongation, and Poisson's ratio.
 

Compression Testing

Compression tests are used to determine a material’s behavior under applied crushing loads. The most common compressive properties measured are elastic limit, proportional limit, yield point, yield strength, and, for some materials, compressive strength.

 

Bend / Flexural Testing

Bend testing, sometimes called flexure testing, measures the behavior of materials subjected to simple beam loading. For this reason, bend testing is commonly used to evaluate the reaction of materials to realistic loading situations. Common properties measured are flexural strength, flexural modulus, modulus of rupture, and maximum fiber stress.  

 

Torsion Testing

Torsion testing evaluates the properties of materials or devices while under stress from angular displacement. The most common mechanical properties measured by torsion testing are modulus of elasticity in shear, yield shear strength, ultimate shear strength, modulus of rupture in shear, and ductility.
  

fatigue testing

Fatigue Test

Fatigue testing applies cyclic loading to a test specimen to understand how it will perform under similar conditions in actual use. The load application can either be a repeated application of a fixed load or simulation of in-service loads. The load application may be repeated millions of times and up to several hundred times per second.

drop tower impact tester

Impact Test

Impact testing is testing an object's ability to resist high-rate loading. An impact test is a test for determining the energy absorbed in fracturing a test piece at high velocity. It is commonly thought oft as one object striking another object at a relatively high speed. The two primary forms of impact test are drop weight and pendulum impact tests.

 

HDT Vicat testers

HDT / Vicat Testing

Plastics and thermoplastics materials are temperature sensitive. The HDT and Vicat tests consist of determining the temperature at which a stressed sample undergoes deflection: in the HDT test the sample undergoes flexion, while in the Vicat test the sample is penetrated by a point.
  

peel testing fixture

Peel Test

Peel testing measures the mechanical properties of an adhesive bond. Peel tests involve applying a tensile force to a flexible substrate that is bound by an adhesive to either another flexible substrate  or a rigid substrate. Common results from a peel test are initial peak force, average force over the seal, and peel strength.

melt flow and rheology testers

Rheology Testing

Rheology testing is measuring the deformation of matter under the influence of imposed stress, by analyzing the internal response of materials to forces. Polymer flow characteristics are critical in all the conversion and production processes: the material is forced to flow and the rheological characteristics determine the processability.




Materials Testing Machines



Materials testing machines come in a variety of different types and force capacities in order to perform specific types of testing. Despite this variety, all testing machines have a common set of features that enable them to test and adequately characterize materials, components, and finished products.  


Components of a Universal Testing Machine 
Test Frame
Test frames feature robust, precise guidance columns that ensure minimal specimen bending under load. High-quality test frames feature pre-loaded bearings, precision ball screws, an extra thick crosshead and base beam, and low-stretch drive belts to ensure superior performance and longevity. They are powered by maintenance-free brushless AC servomotors and a dual-belt system to provide synchronous movement of the ball screws, eliminating crosshead tilt and aiding system alignment.
Test Software
All test systems require software in order to operate the machine and collect and interpret results data. Modern software should prioritize data security and feature a user-friendly interface and intuitive workflows.
Load Cell
A load cell is a transducer that converts force into an electrical signal that can be measured. Load cells must be regularly calibrated in order to ensure their accuracy. They should be highly accurate over a wide range of measurements with high stiffness and resistance to offset loads.
Grips and Fixtures
A wide variety of grips and fixtures are available to help secure the vast array of different material types and specimens that undergo testing on these machines. These fixtures range from tensile grips to compression platens, peel and flex fixtures, custom fixtures for testing biomedical and electronic components, as well as many others.


Key Materials



Any company that produces tangible products engages in materials testing in some way. Though it occurs behind the scenes in research and quality laboratories, this testing is responsible for the reliability of products as wide ranging as automobile components, bridges, medical supplies, and simple packaging. The most common materials Below is a partial list of industries in which materials testing plays a quiet - but critical - role.

 


plastics thumbnail


Plastics Testing

Plastics are used for an unlimited number of applications, from packaging to biomedical, automotive, and electronics applications. Key properties evaluated during testing are tensile strength, yield strength, modulus, and elongation. Major plastics testing standards include ASTM D638, ASTM D790, ISO 8295, ISO 527, and The Definitive Guide to ISO 178 Flexure Testing for Plastics



metal specimens



Metals are widely used in the automotive and construction industries. Key measurements for metals include r-value, n-value, modulus, tensile strength, strain, offset yield, and upper and lower yield strength. Common metals testing standards include ASTM E8, ASTM A370, and ISO 6892



composite specimens



Composites are complex materials made from polymers reinforced with a fiber such as glass, aramid, or carbon. They are used extensively in applications such as aerospace and wind energy that demand high strength, lightweight materials. Key composites testing standards include ASTM D3039 and ISO 527-4. Important measurements include tensile strength, shear strength, yield strength, and fracture toughness.



elastomer testing


Elastomer Testing

Elastomers are high-elongation materials such as natural rubber, silicone, and polyurethanes that are used for making tires, medical devices, sealants, and many other products. Tensile strength, total elongation, and tensile stress at a given location are key properties. Major testing standards include ASTM D412, ASTM D642, and ISO 34

Products for Materials Testing

As the leading global manufacturer of testing equipment for the material and structural testing markets, Instron's product line includes systems for nearly every form of mechanical testing. Our large product portfolio allows technicians to evaluate materials ranging from biological tissue to advanced high-strength alloys by performing a variety of tests such as compression, cyclic, fatigue, impact, multi-axis, rheology, tensile, and torsion.

 

universal testing systems 
Universal Testing Systems

Universal Testing Systems include electromechanical series and industrial series to perform static testing, including tensile and compression applications.

dynamic and fatigue testing systems 
Dynamic & Fatigue Testing Systems

Dynamic testing systems are used to perform fatigue, fracture mechanics, bi-axial, multi-axial, high strain rate and thermo-mechanical fatigue tests.

crash simulation systems 
Crash Simulation Systems

Acceleration sled systems are used for the evaluation of vehicle safety systems and parts and for the investigation of structures during crash events.

 

structural durability 
Structural Durability

Growing demands on the comfort and reliability of vehicles require functional and life-time tests of components or complete systems to avoid hazards for humans and the environment or damage in the economic field. 

impact drop tower and pendulum testers 
Impact Drop Towers & Pendulums

Impact resistance is one of the most important properties for component designers to consider. Impact resistance is a critical measure of service life and it involves the perplexing problem of product safety and liability.

automated testing systems 
Automated Test Systems

Automated Testing Systems enable a new dimension of testing productivity, improve safety, reduce variability, save time and increase throughput. Options are tailored to your testing operations and throughput requirements.

 

rheometers and melt flow testers 
Rheometers & Melt Flow Testers

The Instron line of CEAST Rheology systems are used to measure the rheological properties of thermoplastics to characterize the polymer melt flow behavior in the process conditions.
 

HDT and vicat testing systems 
HDT & Vicat Systems

HDT and Vicat systems are used to characterize the behavior of plastic materials at high temperatures, measuring the heat deflection temperature (HDT) and the Vicat softening temperature (Vicat).

torsion testers 
Torsion Testers

Instron's low and medium capacity torsion testers provide dependable mulit-turn capability. Available in capacities ranging from 22 - 5,650 N-m (200 - 50,000 in lb), these systems are ideal for many applications.


Choosing A Testing Partner

Implementing a materials testing program is a complex process that can have major and lasting effects on your business. When evaluating potential suppliers, it is important to consider not just the testing equipment itself but also the depth of their expertise with your particular application as well as the accessibility and responsiveness of their service departments. A supplier should be prepared to partner with you for the long term and work with you through changes to your testing needs over time. Instron has been a leading provider of materials testing systems since 1946, and our systems are designed by industry experts familiar with trends in testing standards and emerging technologies. All of our installed systems around the world are supported by a global network of skilled and experienced service technicians. This comprehensive approach allows us to back each Instron system with an unmatched level of industry and application expertise designed to support it throughout its lifetime.

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