Measuring the Strength of Materials
Material hardness is determined by measuring either the depth or width of the indentation. Different shaped indenters and different methods of measuring the size of the Indent are required for different materials.
Older hardness testers were bench mounted and measured strength by applying a given force to a probe and making an indentation which causes plastic deformation.
These machines were not suitable for fixed structures or very large or very small and thin items. This resulted in the development of less accurate portable instruments using different methods of measurement.
Dynamic Leeb Method
The two common methods were the dynamic Leeb method, used for large items, where a spring loaded probe impacts the surface and its bounce back distance is measured. The second method was the ultrasonic contact impedance method, where different forces are used for different materials, used for small items and for the thin surface finish on an item.
The Latest Digital Technology
The latest digital technology has allowed a European manufacturer to offer a device of extreme accuracy that uses both a Leeb and an ultrasonic contact impedance probe and tests according to either US or European standards. This instrument is also unique as it has a camera to record the position of the probe on the item and any identifying number on the test item. The instrument can also provide a digital readout of hardness and statistics on the tests. The instrument is also able to detect and reject inaccurate Leeb readings. All the information from the tests can be stored in the instrument and later downloaded to a PC.
The accuracy and calibration of this instrument can be checked in the same way as for bench testers by performing hardness tests on a range of certified test blocks of known hardness.
This instrument gives the user many of the features previously only available on sophisticated bench mount testers at a price similar to much simpler portable instruments.
Contact Hylec Controls to learn more.