Design and analysis of the precision-driven unit for nano-indentation and scratch test

This paper presents a kind of precision-driven unit consisting of the piezoelectric actuator and flexure hinge to realize precision motion of the indenter in a self-made indentation device. Two important parameters of the flexure hinge, thickness tt and width ww, were analyzed via finite element method and the results showed that the output displacement was a monotonic decreasing function of thickness tt and width ww. The stiffness was a monotonic increasing function of thickness tt and width ww. But almost all the first-order modal frequencies of flexure hinges with different thickness tt and width ww were higher than 3800 Hz which indicated that flexure hinges had good stability at low frequency condition. Output performance of the unit was tested and analyzed. Experimental results showed that the average maximum output displacement was 12.88 μm when the voltage was 120 V and the resolution was about 0.537 μm/V. The hysteresis was very small and it was about 8.91%. At last, the designed unit was assembled on a self-made indentation device. Preliminary indentation experiments proved that the unit worked well. So, the piezoelectric mechanism can be used in the indentation device and it is beneficial to ensure the miniaturization and realize in situ indentation experiments in the SEM and TEM.