When visco-elastic materials are held stretched during extending, the stress in them gradually decays. It may drop to a limiting value or it may disappear completely. This phenomenon is known as relaxation. When their materials are held retracted during stress recovery, the stress in them may increase with time under some conditions. This phenomenon is known as inverse relaxation. We have investigated inverse relaxation on sewn fabrics at various stitch density on some stitch tightening ratios.
The relaxation, mix-relaxation and inverse relaxation were examined from the sewn fabrics with or without cycle-loading test. The inverse relaxation index was increased with increasing the force retraction. The inverse relaxation index of sewn fabrics did not correlate with the stitch tightness factor. The inverse relaxation index corresponded to that of the loop-sewing thread per unit stitch. The fact suggested that the inverse relaxation phenomena of sewn fabrics may be regarded from the linear model of fabric parts and seam parts.
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