Abstract
A practical and low cost instrument for accurately measuring small impact force is proposed. In the various industrial and research applications such as materials testing, the requirements for evaluating the mechanical characteristics of materials and structure have increased. In this paper, the mechanical characteristics of material against small impact force are determined by means of the newly developed pendulum mechanism that based on the levitation mass method (LMM). In this method, a pendulum mechanism is used as a substitute for expensive pneumatic linear bearing. A mass that is suspended using a newly developed pendulum mechanism with negligible friction and a stable restoring force, is made to collide with the object under test. A pendulum mechanism with 6 wires is used to realize the static motion of mass that is the swing part of pendulum. Mass is suspended by 3 triangles formed using 6 wires. The Doppler frequency shift of a laser beam reflecting on the mass is highly accurately measured using an optical interferometer. The velocity, position, acceleration and inertial force of the mass are calculated from the measured time-varying Doppler frequency shift. The performance of the proposed method is demonstrated by evaluating the viscoelasticity (i.e. hysteresis curve between force and displacement, curve between force and velocity) of a small silicon-gel block under an impact load.
