UCI or Leeb method?

3D Character and Blank Board

There are two different physical methods which are particularly recognized in the practical field: the static Ultrasonic Contact Impedance (UCI) method and dynamic rebound hardness testing (Leeb). The decision as to which method is to be used mainly depends on the testing task.
For selecting the suitable method of measuring, primarily user has to know two main parameters of the tested object: Weight and Wall thickness.

3D Character and Chance - He is the Dicer


If testing object mass is more than 5 kg and it’s wall thickness is more than 10 mm this is the case to use dynamic rebound hardness testing.
Requirements for testing object when use dynamic rebound hardness testing (Leeb) method
No support required > 5 Kg
Requires Support 2 to 5 Kg
Wall thickness > 10 mm



repairman with the tool on a white background. 3D image


The Leeb method creates quite a large short duration force at the moment of the impact. Thin and lightweight materials flex causes  erroneous values. A solution for testing small simple shaped objects is a machined support that matches the contour of the back surface of it. The support reinforces the object to make it ridged.



Testing small objects is the case to use Ultrasonic Contact Impedance (UCI) method.


Requirements for testing object when use Ultrasonic Contact Impedance (UCI) method
No support required > 100 g
Wall thickness > 1 mm


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The UCI method is recommended for testing fine grained material having any shape and size. It is especially used where material properties are to be processed with narrow tolerances, e.g. for determination of strain hardening on drop forged parts. With the small indent of the UCI probes, determination of the hardness can be made on welded parts in the critical area of the weld, the heat affected zone (HAZ).



Application comparison UCI & Leeb probes

Application UCI probe Leeb probe
Solid parts. Molds etc + ++
Coarse grain materials. Cast iron parts etc ++
Steel and aluminum cast alloys o ++
HAZ of welds ++
Tubes, pipes etc. with wall thickness greater than 20mm (0.75″) ++ ++
Tubes, pipes etc. with wall thickness less than 20mm (0.75″) ++
Semi finished/rough surfaces +
Thin walls or cross-sections. Sheet, plate, ribs, enclosures etc ++
Difficult to access positions. Turbine blades, gears, grooves etc ++ +


++ — especially suited

+ — well suited

o — suited sometimes

— not recommended