How do portable hardness testers work

The UCI probe is used for measuring of the hardness of small items, objects with a thin wall, complex shape, and to measure the hardness of surface hardened layers.

But you can not use UCI probe for measuring the hardness of non-ferrous metals, cast iron, coarse-grained materials, massive products etc. Combined portable hardness tester works with both UCI ultrasonic and Leeb dynamic probes. You will get the benefits of two methods of measurement — it is the maximum that can be obtained from portable hardness tester.

As for the price of devices, the Leeb hardness testers — are the most affordable, UCI — are a little more expensive. Combined hardness testers — are the most functional models, but, as a result they are also the most expensive. So that, the second question is what is the method of measuring you need?

If you are have enough financial opportunities, the best choice would be combined hardness tester. If your budget is limited you have to sacrifice functionality of the device and choose between UCI or Leeb hardness tester, considering the material and the dimensions of the mostly tested objects. The type and the method of measuring are have been chosen. How to choose the model of the device? The model of portable hardness tester directly affects the usability of hardness tester.

Depending on the chosen model of hardness tester, the functionality of the device can greatly different. So, the operating conditions of the instrument would be different. Choosing the model of hardness testers, consider the next functions: weight and size of the device; the size of the display and keyboard; ability to communicate with a PC; the ability to save the calibration settings, measurement results and other instrument settings; the ability to print the measurement results with the portable printer; ability to take photo of the measuring objects with reference to the measurement value at certain points on the testing object; and other.

The shift in frequency arises from the additional mass on the end of the probe, upon contact with the test material. The frequency shift is proportional to the area of contact, which is the area of indentation generated by the Vickers diamond. The frequency shift also depends on the Young's Modulus of the material, and calibration on a material with a similar Young's modulus to the test material must be carried out before testing.

The following equations are employed in the UCI method:. The Rebound, or Leeb's method, determines the indenter velocity immediately before impact by using a magnet in the indenter to generate an induction voltage during its travel toward the test material. The voltage is proportional to the velocity. The indenter rebounds and the velocity immediately after impact can be determined in the same way.

These values are used to calculate hardness on the Leeb scale HL :. The value of Leeb hardness is then converted to the more widely used scales by means of conversion charts. The Rockwell principle involves applying a preliminary test force f o , and determining the depth to which that force indents the surface. The measurements from the Brinell hardness tester are based on the penetration of the indenter into the tested material under load and consequent measurement of the mean diameter of the restored indentation.

Though a stationary tester provides more direct measurements, portable hardness testers have several advantages over their stationary lab cousins. When using a traditional large stationary hardness tester, samples must be brought to the testing equipment.

This may not be possible in many situations , so portable testers can be used. Portable hardness testers are suitable for conducting measurements in the field, including chemical utilities, small factories, and existing pipelines. Portable hardness testers are especially useful for immovable equipment that cannot be brought to a testing lab or have samples cut off. They can measure hardness directly on a manufactured detail and in hard-to-reach places. Portable hardness testers can be used on much smaller surface areas than traditional hardness testers.

Furthermore, they cab test individual parts of one material, e. What are the benefits of this? This ensures the materials testing is tested to the max of quality control on-site. As Vickers hardness is simply defined as the ratio between test load and indentation size the diagonals of the indentation , the TDT-measurement of the diagonal length immediately produces a Vickers hardness value for the applied test load.

The physical method of TDT hardness testing — traced back to Vickers hardness — allows mobile testing of different materials without the necessity of calibrating the instrument. By viewing through the diamond under load, TDT opens up mobile hardness testing not only to new applications like coils, thin layers and coatings but also to different materials like plastics, glass and high-tech materials such as ceramics or intermetallics. While testing under load by viewing through the diamond, the TDT instruments even allow to measure the hardness of elastic or soft materials.

Other types of tests, such as Brinell, Vickers or Knoop tests, have their difficulties. The TDT method eliminates that problem. It involves pressing a diamond punch of known geometry into the surface of a material.

The indentation size will be monitored under load during the test. But as the testing of rubbers, plastics, and polymers becomes more commonplace, even the softest metals will seem comparatively hard. It is a relative term. Applications for testing soft materials are nonetheless widespread. The automotive industry tests the hardness of paints and tires. The microelectronics and photonics industries test low-dielectric constant films, chemical and mechanical polishing pads, bond pads, solders, and electronic packaging materials.

The biomaterials industry tests polymer joint-implant materials, nail polish and drug particles. The medical field even tests biological samples such as liver, cartilage, and arterial tissues. Determining meaningful hardness values for soft materials has always been challenging, and despite recent advances in methods and instruments, continues to be so. The innovation with this technique is the evaluation of the Vickers diamond indentation, which takes place by viewing through the Vickers diamond using a CCD camera.

For that purpose it is necessary to light up the inner surfaces of the diamond using light-emitting diodes LED geometrically arranged. In order to obtain the highest resolution of the indentation picture it is necessary to match the wavelength of the LED light and the spectral sensitivity characteristics of the CCD chip.

A special lens system was developed and adjusted to the LED to ensure maximum resolution. A first step locates the approximate position of the indentation. Finally the indentation surface and the diagonals are determined using the intersections of the calculated borders and the edges of the Vickers diamond. According to the definition of Vickers, the HV value is calculated for the applied test load. The interface between instrument and probe serves as power supply for the probe as well as connector for all control functions.

With special software the data can be evaluated, the diagonals measured and the hardness value calculated. Depending on the resolution and the test load, different hardness ranges can be analyzed. For softer materials a lower test load has to be applied.

In principle, all kind of materials can be tested as long as the hardness value is in the range of the TDT probe used for the measurement.