No abstract

A simple method for constructing tension curves of thin fibers is proposed which consists of determining the dependence of the frequencies of small transverse vibrations of thin fibers on their tensile strain. The fiber stress at these frequencies is calculated using the classical formula of string vibrations. Instead of force and strain, it is proposed to measure frequency and strain. This method has a number of advantages, in particular, it is more accurate. Resonant frequencies are determined by recording the accompanying electric field resulting from the variation in the charge distributed over the fiber surface. The effectiveness of the method is demonstrated by constructing copolymer fibers of various diameters.Introduction. To develop and (or) calibrate rheological models of fibers and strings, it is necessary to use stress-strain curves which are determined experimentally using expensive equipment, in particular, high-precision instruments for measuring small forces. In the present paper, we propose a simple and less expensive method for constructing such curves for fibers that admit large strains before fracture. This method is based on measuring the frequencies of small transverse vibrations of a stretched string of such a fiber at specified strain. The required stressstrain relation is then calculated using the theory of small elastic vibrations of a stretched string. Frequencies are measured by recording variations in the electric field induction component by a transducer antenna during transverse vibrations of precharged fibers. This method has a number of advantages. The antenna is located at a distance from the source and, hence, does not introduce errors to he measured values. The method can be used under complicated environmental conditions (severe media and high temperatures), does not require complex equipment, eliminates external noise, and the samples are prepared using conventional techniques. An advantage of the proposed method over direct measurements of forces and displacements is accurate determination of frequencies whereas measuring small forces with a small error is difficult to perform. The method of determining vibration frequencies, modes, and damping is described in [1,2], along with the results of measurements of transverse vibrations of glass fibers fixed as an elastic cantilever and the observed relationship between the time of charge dissipation from the fiber surface and the degree of damage to this surface.