A new nanoindentation creep technique using constant contact pressure

Abstract

Abstract

Nanoindentation creep testing: Advantages and limitations of the constant contact pressure method

“…Therefore, various indentation creep and relaxation test procedures have been developed for investigating the local, time-dependent mechanical properties. These test procedures promise to provide results comparable to macroscopic tests [7][8][9][10][11][12][13][14]. However, a direct comparison of macroscopic and indentation loading protocols reveals significant differences.…”

“…To overcome the limitations of the constant load and hold test, namely the declining indentation stress and indentation strain rate, we have recently presented a new constant contact pressure (CCP) indention creep method [11], in which the contact pressure, respectively, the stiffness based hardness [8,11,18]: is kept constant throughout the entire creep segment by controlling P/S 2 , where P is the applied load and S is the contact…”

“…1 can be used to determined directly the contact pressure, assuming a constant and depth independent Young's modulus. This contact pressure, determined at a frequency of 45 Hz, is thus based on the current contact situation and is independent of pile-up or thermal drift effects [8,11,18].…”

“…1). The plastic zone thus expands with the increasing load, while the resulting indentation strain rate declines with creep time until a plateau in the indentation strain rate is reached [11].…”

“…This allows to assess much smaller strain rates in comparison with constant strain rate (CSR) and strain rate jump (SRJ) experiments, which keep the strain rate constant and allow only a limited variation in indentation strain rate (10 -1 -10 -3 s −1 ). Further details and results of experiments performed with the CCP test methodology on fused silica and ultrafine grained alloys can be found in [11].…”