Already for over one month the R&D department of Lumag company has had the new Compressibility tester of 03.04.06.00 type, made by Honeywell Bemsbelag GmbH. Such units are used by leading manufacturers of brake pads, braking systems and vehicles. We are the first user of such a testing equipment in Poland. Until now this kind of compressibility tests was performed by us in a co-operation with our German partners or we used to use the universal strength testing machine which is however not so precise for such measurements.
The unit is explicit designed for measurements of cold and hot compressibility, or warm-up-expansion or heat transfer of brake pads or other materials. It is also possible to measure a compressibility of damping elements. The procedure of measurement is defined in ISO 6310-2001.
The compressibility d is the change in the pad thickness caused by a single-dimensional pressure load towards the normal plane of the friction surface.
The heat transmission of a disc brake pad is the backing plate temperature reached on contact of the friction surface with a 400 °C ± 5 K hot surface and a defined pressure load in 10 minutes.
The pad swell is the thermal change in the thickness of brake pads on contact of their friction surface with a 400 °C ± 5 K hot surface and a defined pressure determined over a period of 10 minutes.
Based on the results of measurements it is possible to estimate the ability of brake pads to damp vibrations (comfort properties) and to simulate the jump to brake pedal.
For the manufacturers of braking system, brake pads and vehicles such properties are very essential, especially in case of OE deliveries where this kind of tests is certainly required.
The measurements can be performed in the room temperature and in the temperature up to 500’C.
The course of the program is controlled by a PC. During the load cycles we can observe a force and displacement on the screen, shown in a graphic form.  At the same time the PC makes statistical calculations, which can be used after testing the batch of samples.
The statistical data and graphs are landed to data base so they are available for the later analyze.
Having our own compressibility tester we are able to perform the regular tests which will result in making more friendly products to the end users.

Prepared by Tomasz Orlowski – R&D manager