A cost-effective voice coil motor-based portable micro-indentation device for in situ testing

To evaluate the mechanical properties of structures in service, a portable micro-indentation device was developed and built. The basic design principle of the indentation device, i.e. measurement of the indentation depth and the indentation force with sufficient accuracy, was discussed. To avoid using load cell to decrease the machine compliance, a new method that using the current through voice coil motor to calculate the indentation force was proposed. After analyzing the equivalent mechanical model of the developed device, an eddy current displacement sensor was installed on the device to improve the measurement accuracy of indentation depth. Indentation tests were performed on polymethylmethacrylate (PMMA) and unplasticized polyvinyl chloride (UPVC) with the developed device and the commercial indentation device ZHU2.5 to demonstrate the validity and accuracy of the developed micro-indentation device.