Tension–Torsion Combined Loading Test Equipment for a Minute Beam Specimen

Abstract

In this article, the development of quasi-static tension–torsion combined loading test equipment for a microscale beam specimen is described. The equipment is composed of a piezoelectric actuator in actuator case for uniaxial tensile loading, a load cell for measuring X-Y-Z-axes forces and θ-axis torque, a stepping motor for rotating sample stage, X-Y-Z-stages for alignment, and a CCD camera for measuring tensile elongation using original image analysis software. The shape and dimension of all the mechanical jigs were designed by means of finite element analysis (FEA). The tension and torsion loading systems are able to be individually operated, so that uniaxial tension, pure torsion, and combined tension–torsion loadings can be realized. The specimen that was designed in consideration of typical optical microelectromechanical systems (MEMS) devices consists of a mirror plate supported by two microbeam structures, four springs, and a frame with chucking holes. Single crystal silicon (SCS) specimens were fabricated by deep reactive ion etching (DRIE). It was confirmed that the above-described three types of loadings were able to be successfully applied to the beam specimens. All the specimens fractured in a brittle manner and showed different-shape fracture surfaces under different deformation modes.