Behaviour of Long-Lasting Stress Relaxation of Various Types of Yarns

Abstract

The main goal of this researcher is estimating of the possibility of long-lasting (even until 200,000 s) stress relaxation by empirical investigation, which was performed for a few thousands of seconds. The empirical investigations of longlasting stress relaxation of different types of yarns (multifilament polyester, cotton and woollen) at different levels of elongation, i.e. at 3%, 5%, 7% and 10%, were carried out. The method of long-lasting relaxation behaviour prediction by the break-point of relaxation rate as well as the linear dependence of second part of relaxation were used. It was found that the behaviour of relaxation can be described using time logarithmic scale by two straight lines, and the value of stress relaxation in long time period could be estimated by the second line. The break-point of relaxation rate of all kinds of yarns occurs in the area of 100-200 s after relaxations started. The obtained results showed that the place of relaxation break-point depends on the level of elongation but does not depend on the type of yarns.

Influence of orthopedic support structure and construction on compression and behavior during stress relaxation

“…At the initial point of relaxation, tensile force values of these samples differed in 17%, however, after 2,00,000 s stress relaxation the tensile force values of both variants were very similar. It is because of the inner changes in the elastomeric yarns during the long period of the stress relaxation and it is based on the stress relaxation theory [17].…”

“…It is already known that compression values of knitted compression products are not equal during exploitation and decrease during the time they are being worn. Alteration of compression during the wearing time may be explained by the stress relaxation process, which appears after putting on or securing product to the body [14,16,17]. However, compression generated by knitted orthopedic supports as well as other knitted compression products is usually estimated at the moment of stretching.…”

Engineering hybrid textile braids for tendon and ligament repair application

“…Understanding the behavior of the stress relaxation process is essential for the design of a textile scaffold with the required properties for an extended period. 72 The reported data on relaxation behavior at different initial strains may be a good indicator of scaffold recoil after a long-lasting stretch. It was observed that higher PLA content leads to higher relaxation of the textile structure, and this result is relevant for the choice of braid composition for the application envisaged.…”

Mechanical characterization and modeling stress relaxation behavior of acrylic–polyurethane‐based graft‐interpenetrating polymer networks

“…Stress relaxation behavior is observed when materials under a fixed strain relax over time. [ 5,6 ] As the stress slowly decreases, the modulus ( E ) changes from E 0 to E ∞ . [ 7 ] The speed of this process is denoted as the stress relaxation time constant, τ . In polymeric materials, this decrease in stress occurs because the macromolecular conformation is not in the same state.…”

“…Stress relaxation behavior is observed when materials under a fixed strain relax over time. [5,6] As the stress slowly decreases, the modulus (E) changes from E 0 to E ∞ . [7] The speed of this process is denoted as the stress relaxation time constant, τ.…”