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hardness testing

There are three types of Hardness Testing:

  1. 01 UCI (ultrasonic contact impedance)
  2. 02 Rebound Type
  3. 03 Diamond Pyramid Hardness Test
01 UCI (Ultrasonic Contact Impedance)

This is the one we use in ESB etc.........To carry out the UCI principle, a probe containing a rod with a Vickers diamond attached to the contact end is resonated by piezoelectric ceramics at an ultrasonic frequency. A spring applies the load and the frequency of the rod changes in proportion to the contact area of the indentation produced by the Vickers diamond. Therefore, the hardness value is not visually determined by the diagonals of the indent, but by an electronic measurement of the frequency shift within seconds.

The instrument constantly monitors the frequency, performs the calculation and instantaneously displays the hardness value.

The frequency shift, nevertheless, also depends on the Young's modulus of elasticity, which is a material constant. For the practical application of the UCI-method, the Young's modulus therefore has to be considered. The instrument has to be calibrated when the hardness of different materials with different values of the Young's modulus has to be determined.

After completing the calibration, the UCI method can be used for all materials showing this modulus of elasticity. When being manufactured, the probes are calibrated on low- alloyed or unalloyed steels; however, modern test instruments can be calibrated quickly, also at the test location, to other materials as well, such as titanium or copper.

02 Rebound Type

Hardness testers using the Rebound method operate in a slightly different manner. Although the size of the test indentation generated is connected with the material hardness even in this case, it is indirectly measured via the loss of energy of a so-called impact body. A mass is accelerated to the surface of the test object and impinges on it at a defined speed, i.e. kinetic energy. The impact creates a plastic deformation of the surface, i.e. an indentation, due to which the impact body loses part of its original speed - or energy. It will lose more velocity when creating a bigger indentation on softer material.

Technically, this principle of measurement is implemented by means of an impact body which has a spherical tungsten carbide tip and which is accelerated onto the test surface by spring force. The velocities after and before the impact are each measured in a non-contact mode, which when adjusted give specific hardness values.

03 Diamond Pyramid Hardness Test

Fixed Lab equipment - .An indentation hardness test in which a diamond-pyramid indenter, with a 136° angle between opposite faces, is forced under variable loads into the surface of a test specimen. Also known as Vickers hardness test. The Vickers Pyramid Hardness Testing Machine was designed and developed by the Vickers Company to be the standard instrument to perform the Vickers Hardness Test.


news at wis

WIS have implemented and are now accredited to the following: EN ISO 9001:2015, EN ISO 14001:2015 and EN ISO 45001:2018.

WIS have attended courses and examinations at QSA-Global in Houston, Texas and now have technicians trained and qualified in Servicing & Maintenance of the QSA-Global equipment. WIS also have technicians trained and qualified in Source Retrieval, this entailed the actual retrieval of a live source, which other companies providing this service do not carry out. WIS intend to roll out these services to NDT Contractors nationwide.