Ultrasonic Contact Impedance Hardness Testing

UCI hardness testing is ideal for situations in which classic hardness measurement methods (Vickers, Rockwell, Brinell) are inapplicable or impractical – such as inspection of goods upon arrival at warehouses, production control of integrated components or maintenance work on integrated systems.

The method measures the difference in vibration frequency f of a resonator between two different test forces and converts this difference into a hardness value, using non-contact technology that does not damage samples.

What is Ultrasonic Contact Impedance Testing?

UCI hardness testing is a non-destructive non-contact method of hardness measurement that employs an ultrasound vibration sensor rod to measure hardness without damaging workpieces, making it suitable for pipe weld inspection, Ion-nitride stamping dies and molds inspection, thin-walled parts such as gear teeth flanks testing or difficult access areas that cannot be reached with traditional rockwell, brinell or Leeb testers.

This non-destructive test procedure uses a vibration bar with a 136-degree diamond at one end that produces ultrasonic vibration, then pushes the workpiece against it for testing. Frequency changes of vibration are converted to hardness values using UCI host software and then converted to various industry scales such as HRC or HB. This non-destructive, fast, and user-friendly test method is suitable for field and workshop conditions alike.

How is Ultrasonic Contact Impedance Testing Done?

The UCI method, or modified Vickers procedure, measures the test indentation size on a Vickers diamond electronically within fractions of a second and displays it digitally.

Mechanical Resonator of Probe. When introduced into test materials, an excitable mechanical resonator of 78kHz frequency vibrating longitudinally is introduced and forced through. This causes contact resistance between probe and material and vibratory frequency change which directly correlates to hardness of material tested. When predetermined test force threshold is met, this frequency change is precisely evaluated, providing us with hardness data on any given sample material tested.

FOERSTER offers mobile UCI hardness testing that’s ideal for use anywhere with its SONODUR 3 instrument. This portable instrument works with cable-connected probes from SONO-H/M/S series available in various versions and test loads – making it suitable for applications such as pipe weld inspections or quality assurance during production on components with complex geometries.

What is the Difference Between Ultrasonic Contact Impedance Testing and Dynamic Impact Style Testing?

UCI testing is less destructive, leaving a smaller imprint on test diamonds than most bench top hardness testers, making it ideal for thin walls or complex shapes that cannot support Leeb probe testing or where Leeb probe application may not be possible. As such, NOVOTEST T-U2 makes a great choice.

UCI testers utilize a vibrating bar with a 136 degree diamond at one end – also known as a Vickers pressure head – that presses down onto the test surface, producing ultrasonic vibrations which are then measured and recorded to establish material hardness values.

Results are displayed digitally and saved to the memory of the unit, then used to calculate a hardness value using a formula which takes into account both modulus of elasticity E and hardness value HV values known. This method can be utilized for various applications including HAZ testing as well as weld inspection on pipe welds.

What are the Advantages of Ultrasonic Contact Impedance Testing?

Ultrasonic contact impedance testing offers a fast, nondestructive way of comparative hardness measurements. It can test parts in difficult or impossible positions such as tooth flanks of gears where rebound testers cannot reach, such as measuring their hardness values.

Rebound method measurements may provide more precise readings since the probe creates smaller indentation than its rebound method counterpart. This feature can be especially beneficial to manufacturers who must verify that material thickness meets specified forces and stresses on various parts.

Ultrasonic contact impedance testing can also be used on metals and alloys that cannot be tested using other portable hardness testers due to not requiring Vickers indenter. This makes ultrasonic contact impedance testing ideal for weld inspection, hardness control of metal coatings and rapid measurement of small forgings, cast materials, heat-affected zones, Ion-nitride stamping dies/molds, forms presses thin-walled parts bearings tooth flanks etc.