Adaptive ultrasonic method for controlling the basis weight of knitted fabrics

Abstract

Two main methods employed in designing knitted fabrics for production rely on a given surface density or on the basis weight (grams per square meter). The actual value of these parameters may differ. Normally, the actual basis weight of knitted fabrics is determined by weighing a sample of a certain width and length and subsequently performing the relevant conversion (ISO 3801:1977). This method involves a destruction or wasting of the material. A non-destructive ultrasonic method for determining the basis weight of textile materials was developed, which is based on a determination of the amplitude ratio of ultrasonic waves falling on the fabric and the waves passing through it. However, this method has limitations in determining the basis weight of textile materials with variable porosity, such as knitted fabrics. To improve the developed method, it is proposed to continue the measuring of an amplitude of the reflected wave from the fabric surface. In this case, it is possible to monitor the fabric porosity changes. If the distance and pore size of the controlled fabric have increased or decreased relative to the control sample, the amplitude and magnitude of the reflected wave (part of the reflected ultrasonic signal) changes and the ultrasonic device will be adapted to the fabric structure. Our studies have demonstrated the possibility of determining the fabric porosity by using an amplitude of the reflected ultrasonic wave from the fabric surface, which allows adaptively to determine the basis weight using an amplitude of transmitted ultrasonic wave. Further development of ultrasonic non-contact methods and relative devises is very important for production control.