Hysteresis of Tensile load — Strain Route of Knitted Fabrics under Extension and Recovery Processes Estimated by Strain History

Abstract

Hysteresis phenomenon of tensile load (stress) under extension and recovery processes were estimated in terms of time dependence of tensile load by using several kinds of knitted fabrics. The measurements were done under strip biaxial extension corresponding to uniaxial extension with a fixed dimension in the direction perpendicular to elongation. The present concept was based on tensile load (stress) relaxation in elongation and restricted sides. To attempt mathematical evaluation, a simple hypothesis described by hereditary integral was proposed to explain the hysteresis of tensile load (strain), strain routes under extension, and recovery processes, in which the extension and recovery routes were formulated as addition and subtraction of step function of strain history, respectively. The calculated curves were in good agreement with the experimental curves in the large deformation region. The theoretical calculation to give the best fit with experimental curve could be realized by using n adopted as an exponent to describe the “linearizing method” ( F = Yen, where F is the tensile load and e is strain of a fabric) proposed by Kawabata et al. The present evaluation improved on their proposal, since the present theory can represent the hysteresis routes by using the same value of parameter n.