INDENTATION TECHNIQUE FOR EVALUATION OF MASTER CURVE OF CREEP COMPLIANCE

The indentation tests performed under several temperature-controlled conditions in order to obtain the master curve of creep compliance were investigated. An atomic force microscope (AFM) was used to extract the true viscoelastic deformation from the measured penetration depth. The applied stress in the tensile creep tests was 5.5 MPa. The maximum indentation depth and force of the system were 10 μm and 1961 mN, respectively. The depth resolution was 1 nm and the force resolution was 0.196 μN. The indentation tests at each temperature condition were carried out five times, and the average penetration and time relation that was, h-t curve, were obtained. The indentation tests were repeated until the same h-t curve as the average one was available then the shape of the impression was measured by the AFM every 15 min to 24 h. The result showed that the creep compliance evaluated by indentation and tensile tests were plotted on almost the same curve in each temperature condition.