Static and Dynamic Characteristics of Cylindrical Yarn Packages in Compressive Deformation

Abstract

A remarkable increase in the winding speed of modern take-up winders has given rise to attach a great importance to understand vibrational, behaviors of the take-up winders. Mechanical vibrations of take-up winders are cou pled ones between their component parts through dynamic characteristics of yarn packages. Hence theoretical analysis of vibration of winders requires a thorough knowledge of the dynamic characteristics of yarn packages. In this study are reported static and dynamic compressive characteristics of cylindrical packages of POY polyester filaments investigated by experiments. The packages were compressed repeatedly using a servo-hydraulic testing machine, and the load and the deformation were measured and recorded. The results obtained are summarized as follows :(1) Static compressive characteristics as well as dynamic ones are non-linear and hysteretic.(2) Static load vs. indentation curves over a range of large deformation can be expressed by a simple mathematical expression, i.e., (q/qmax) =(i/imax) a. Where i is indentation of the package ; q, compressive load, and a subscript max indicates the maximum value ; a is a constant.(3) The dynamic compressive characteristics are approximated by those of a complex spring constant to simplify the mathematical treatment.(4) The absolute value of the modulus of the complex spring constant is almost constant up to a frequency of the exciting harmonic deformation of about 30 Hz, and suddenly increases above this frequency. The phase angle of the complex spring constant is nearly constant below 10 Hz, and gradually increases above this frequency.(5) The modulus and the phase angle depend on the amplitude of the exciting deformation, the median value of the induced load and the package diameter.