Video camera–based vibration measurement for the detection of the apparent properties of monofilaments

Abstract

The vibration behavior of monofilaments was investigated to identify their physical and apparent properties. The investigation is based on the general belief that the modal parameters of a given structure are the functions of its physical properties. Therefore, a laboratory instrument with a high-speed digital camera was designed to measure the vibration behavior of simple monofilaments, knotted monofilaments, two-monofilament samples with no twist, and twisted monofilaments. The vibration was recorded by the high-speed camera at all the points of the strings. Video processing was done to extract the vibration diagrams and to obtain the signal features of the monofilament. Certain physical changes made in the strings affected their signal features. As the results showed, with an increase in the number of knots, the energy parameter would undergo the highest percentage of change; 1.68%, 4.69%, 18.95% and 22.64% changes were recorded for 1, 2, 4 and 8 knots respectively. In addition, an increase in the number of strings and twists could cause the most changes in four-momentum; 57.79%, 29.06%, 2.32% and −18.63% changes were recorded for two-monofilament samples with no twist, 1, 5 and 10 twists respectively. The existence of knots and the increase in the number of monofilaments led to the reduction of the effective frequency but the increase of the damping coefficient. An increase in the number of twists also caused an increase in the effective frequency. The existence of only one twist was associated with a significantly low damping coefficient, but, as the number of twists increased, the damping coefficient increased too. Knot displacement did not affect the effective frequency and the damping coefficient, but the symmetric distribution of the knots reduced the damping coefficient.