A New Tensile Model for Rotor Spun Yarns

This paper reports a refined model to predict the tensile behavior of rotor spun yarn from the knowledge of specimen specifications and yarn strain. Fundamental approaches used in modeling include a discrete fiber-modeling principle, an energy method, and a “shortest-path” hypothesis. The study is based on a coaxial-helix structural model, taking account of nonuniform yarn packing density. Most importantly, a changing-pitch system is introduced for the first time in yarn modeling. A pitch function is thus determined with the aid of a nonlinear regression method and a curve-fitting approach using images obtained from a tracer fiber technique. The model is also compared with experimental data, together with a theoretical analysis of fiber strain distribution, confirming that, due to the introduction of the changing-pitch system, the model is very successful in explain ing the experimental observations.