An improved torsion pendulum based on image processing for single fibers

摘要

An improved torsion pendulum technique based on image processing is developed, which allows the measurement of the torsional oscillation of individual fibers. The torsion pendulum is composed of a length of fiber specimen and a ring-shaped mass attached to one of its ends. The oscillation motion of the mass is recorded with a video camera overhead. An image processing method is developed to accurately calculate the twist angle of single fibers in the torsion pendulum. All images are firstly converted into matrices and then the edge detection is applied to calculate the twist angle at corresponding time to obtain the angle-time relation. The oscillation frequency is determined by the fast Fourier transform (FFT) method. By applying this technique, we have performed tests on four types of fibers, namely T300 carbon fiber, copper, silver and tungsten wires. The longitudinal shear modulus measured for each type of these fibers is presented.