Mina Emadi - Textile Engineering Department, Yazd University, Yazd, Iran; and Center of Excellence for Machine Vision in Textile and Apparel Industry, Yazd University, Yazd, Iran.
Pedram Payvandy - Textile Engineering Department, Yazd University, Yazd, Iran; and Center of Excellence for Machine Vision in Textile and Apparel Industry, Yazd University, Yazd, Iran.
Mohammad Ali Tavanaie - Textile Engineering Department, Amirkabir University of Technology, Tehran, Iran; and Center of Excellence for Machine Vision in Textile and Apparel Industry, Yazd University, Yazd, Iran.
Mohammad Mahdi Jalili - Mechanical Engineering Department, Yazd University, Yazd, Iran.

The main aim of this study is to obtain a detailed information about textile string vibration and the effect of physical properties changes on it. This is based on the fact that modal parameters are the functions of physical properties. Video cameras propose the unique capability of collecting high density spatial data from a distant view and supply a reliable method for measuring vibrations and displacements in structures. They could be employed as inspection sensors because of their normal use, ease, and low cost. In this research, some laboratory equipment with a high-speed digital camera was designed to measure the vibration behavior of polypropylene monofilaments. The vibration was recorded by the high-speed camera at all the points of the string, and video processing was done to extract the free decays. The natural frequency, amplitude and phase were obtained by the Fourier series. The logarithmic decrement and the damping coefficient for monofilaments were calculated. The experimental results were compared to the results of a theoretical model for a plucked string with viscous damping, and the vibration properties of monofilaments were obtained. As the results showed, the theoretical model could successfully predict the vibration behavior of the filaments with error less than ۲۳%. The trend of changes in the monofilament physical properties was easily specified based on the trend of the variations in the damping coefficient and the natural frequency. It was found that an increase in the monofilament linear density would cause a decrease in the damping coefficient and its natural frequency.

Vibration Analysis, monofilament, high-speed camera, computer vision