Fabric surfaces with ridges formed by weft and warp yarns are arranged periodically in two directions. At crossover points of the warp and weft, yarn protrudes from the body of the fabric, intensely influencing the fabric smoothness, frictional properties and surface appearance. Without the interaction of yarns at the interlocked points, a woven fabric would be equivalent to two separate sheets, made of parallel but isolated yarns. The fabric surface protrusion depends not only on the fabric geometry and fabric finishing, but also on the yarn structure as influence by the spinning systems, and the bending behavior of yarn. In this work role of weft yarn diameter on the weft yarn deflection was studied. . In order to study the effect of diameter of the weft yarn on protruding yarn, five different yarn counts were spun in a ring spinning system. The fibers use were made of cotton. The weft yarn is considered as an elastic beam supported at both ends and deflected at the middle by a vertical load. An analytical model based on the elastic theory and small deflection case was adopted to study the factors affecting the maximum deflection of the yarn or the yarn protrusion from the fabric surface. In this work the effect of the yarn diameter affecting the moment of inertia of the cross-section of the yarn was investigated. The maximum deflection of the weft in a plain weave fabric was measured and compared with the theoretical small deflection equation. The experimental results showed an acceptable agreement with the theoretical model
