A novel torsion testing technique for micro-scale specimens based on electromagnetism

A novel torsion apparatus for micro-scale specimens is developed based on electromagnetism, in which a coil-magnet component is used for actuating and torque measuring. When the current gets through the coil, the torque, produced by Ampere force, can be easily measured by recording the current. A laser displacement sensor is applied to measure the rotation angle. The torque is calibrated using Sartorius BP211D balance. The calibration results demonstrate there is a perfect linear relationship between the torque and the current. The torque capacity is 4.0 × 10^-4N m with noise-floor of less than 10^-8N m. The rotation angle capacity is 60° with noise-floor of less than 0.02°. Two sets of copper wire specimens, with diameter of 100 μm and 140 μm, are tested using this apparatus. Experimental results, with good resolution and repeatability, successfully demonstrate the effectiveness of the torsion testing technique for micro-scale specimens.