Nanoindentation at impact rates - Dr Jon Molina-Aldareguia

The nano-impact test is a technique for high strain rate mechanical characterization of materials at the nano/microscale. However, its use has been limited so far because the dynamic hardness has traditionally been computed using an energy-based approach.
This work overcomes this limitation by instrumenting the test device with force-sensing capability by means of a piezoelectric load cell. The methodology was evaluated on six materials covering a wide spectrum of mechanical behaviour.
The work shows that the energy-based approach used so far yields significant errors on the determination of dynamic hardness, explaining contradictory results existing in literature, and identifies the main sources of error with the aid of finite element simulations.
In parallel, a FEM-based inverse analysis methodology was devised to transform the direct outputs of the combined nanoindentation and nano-impact tests into material parameters needed to calibrate the rate-dependent constitutive behaviour of a wide range of materials.
During this talk, Dr Molina will show:
• How to use the new instrumentation to obtain load-displacement curves at high strain rate.
• How to use this new capability to study strain rate dependent phenomena at the microscale