In the process of making equipment, machinery, and other products, different materials are used. Understanding each of these materials and how they react is crucial in choosing the right ones to go together. Some materials are soft at room temperature, such as rubber, and some become soft when heated. Some solids can’t be softened by heat, and some will downright crumble under stress or high temperature.
The hardness of a material is an excellent method of assessing how the material behaves or its resistance to cutting, scratching, and bending. In scientific terms, hardness is a material’s ability to resist deformation, indentation, abrasion, impact, or scratching. It is measured by hardness tests such as Vickers, Rockwell, Brinell, and Knoop testing methods.
Rockwell hardness testing is a crucial process used in evaluating materials, quality control in manufacturing processes, and in research and development. It gives you an indication of other material properties such as ductility, strength, and wear resistance.
Hardness testing is done by forcing a rigid indenter into a softer test specimen for some time and measuring the indentation. The test must follow the standards available to ensure reliable and accurate results.
Applications of Hardness Testers
Everything man-made under the sun was made using a specific material for a reason. For example, screwdrivers and the rods used to build houses are made of steel iron because it’s a tough material. Hardness testing is most commonly applied to evaluate metal hardness for quality testing or choosing the right metal for a specific purpose. When an indenter is forced into a metal specimen, the indentation tells the user what they need to know about its hardness and other properties.
That said, hardness testing is not conducted on metals alone. It’s also applied to ceramics and sintered carbides to evaluate their toughness. Vickers test method can be used to test fracture toughness of a ceramic. It can also be applied on minerals using a scratch test where a harder mineral scratched a softer one. Last but not least, you can use a vickers hardness tester to evaluate PCBs and how they react to force, temperature, and stress.
The material in question determines the test method to be used and the load because different materials have different properties, thus requiring different tests.
How to Test the Hardness of Plastic？
In an era where almost everything is made of plastic, knowing the hardness level of that specific plastic is crucial in quality control. Manufacturers must be able to assure high-quality standards for the products they make, and hardness testing is one way to do that.
Types of plastic
There are many types of plastics, depending on the polymer used. Plastic materials that are mostly tested for hardness include plastic sheeting and molded parts. However, you can also test other forms of plastics like cellulose acetate, Formica, thermos-polystyrene, thermos-plastics, and plexiglass.
For example, the Rockwell testing method is used to test harder plastics polycarbonate, acetal and polystyrene.
Hardness testing for plastic
Hardness testing of plastic is conducted the same way as metal testing. An external force is applied on a plastic test specimen using an indenter and the resulting indentation is measured. The indenter has to be placed at the centre of the specimen using a certain force. The deeper the indentation in the plastic, the softer that material is, meaning if the indenter is having trouble penetrating, then the plastic is very hard.
Hardness testing of plastic is incredibly easy if conducted the right way. The test may fail to give accurate results if the load is too heavy or the setup is incorrect. This can also occur if you use the wrong indenter or position it wrong when penetrating the surface.
The types of hardness testing methods used on plastics are Rockwell, Knoop and Vickers tests and shore-durometer hardness tests. The tests must comply with different testing standards to give the right results.