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.
Relaxation and Inverse Relaxation of Yarns After Dynamic Loading
During weaving, warp yams are subjected to dynamic loading before stress relaxation during a loom stop. A test method is presented for simulating this behavior. There are three types of relaxation curves—simple relaxation, inverse relaxation, and mixed relaxation—depending on the previous load history of the yam. One can calculate the residual force at infinite time in a relaxation test from a model for the tensile curve of spun yams. There seems to be good correlation with the results of tests made using this method.
Timber, its nature and behaviour
Preface. Acknowledgements. Chapter 1 - Structure of Timber. Chapter 2 - Appearance of Timber in Relation to its Structure. Chapter 3 - Mass Volume Relationships. Chapter 4 - Movement in Timber. Chapter 5 - Flow in Timber. Chapter 6 - Deformation Under Load. Chapter 7 - Strength and Failure in Timber. Chapter 8 - Durability of Timber. Chapter 9 - Processing of Timber. Index.