A miniaturized biaxial tensile apparatus based on torsional loading design.

A miniaturized biaxial tensile apparatus is presented. Based on a torsional loading design, the total dimensions and weight of the apparatus have been reduced, while the output force has been increased. Owing to the use of four independent stepping motors, the apparatus can realize arbitrary displacement ratios during the loading processes. The apparatus is designed to be applied with a laser scanning confocal microscope realizing in situ mechanical tests. Through a proof-of-principle experiment with an optimized cruciform shaped specimen, the developed biaxial tensile apparatus is proved to be suitable for in situ tests of biaxial stress analysis.