Inverse Stress Relaxation and Viscoelastic Recovery of Multifilament Textile Yarns in Different Test Cycles
The article presents the results of the experimental research of inverse stress relaxation (IR) and viscoelastic recovery (VR) that take place in acetate and polyester multifilament yarns in dependance on the mechanical pre-history. The above-mentioned time-effects are investigated in two different – stress relaxation (R-) and creep (C-) testing cycles. The fact that inverse stress relaxation process takes place in Ctest cycle, i.e. after previous sustaining the specimen at constant load is experimentally confirmed. It is shown that viscoelastic recovery is the slower process than the inverse stress relaxation. At identical elongations of the yarns at the end of loading period the inverse relaxation and viscoelastic recovery processes go on similarly regardless of the character of testing cycle.
Relationship between Stress Relaxation and Tensile Recovery of Filament Yarns
Effects have been investigated of the strain and the time under strain on the tensile recovery of three kinds of filament yarns, viscose rayon, polyester and nylon filament yarns elongated at the constant rate of extension, and the following results have been obtained. The tensile recovery behaviour is directly dependent on the stress-relaxation characteristics. Filament yarns which are poor in nonlinearity show quantitatively similar tensile recovery to that theoretically predicted. In the case of filament yarns which have plastic deformatin, the effect of strain and time under strain on the tensile recovery can not theoretically be predicted by their stress-relaxation characteristics.
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