Fig. 3. Typical force-time (A) and force-displacement (B) curves for the disc obtained with the micro-force tester. During the loading process (L), the platform was moved upwards and the disc brought into contact with the glass plate, thus increasing the compression force. Then, the disc and the glass plate were kept in contact for a certain time (resting time, R), during which a rapid decrease in the interacting force (relaxation) is observed. Finally, the platform was moved downwards, unloading the disc (U).