Stress relaxation

About: Stress relaxation is a research topic. Over the lifetime, 12959 publications have been published within this topic receiving 270815 citations.

The Preconditioning and Stress Relaxation of Skin Tissue

Abstract: This paper reports our recent study on the preconditioning effects and stress relaxation behaviour of fresh swine skin. Uniaxial cyclic tensile loading and stress relaxation tests were performed with swine skin samples in two different directions to study the effects of fibre direction on mechanical properties. With stress relaxation tests, skin samples were loaded to different strains to observe its effects on stress relaxing over time. Mathematical modelling was performed to compare the data obtained from stress relaxation tests. Fibre direction effects were demonstrated in results of cyclic preconditioning as well as stress relaxation tests. The stress relaxation experimental results indicated that strain and time independency only appears at certain strain levels. The skin tissue has stress relaxation characteristics at strain of 15% and below. Under such strain amplitudes, the samples exhibited greater stress decaying rate in the first 200 seconds of the relaxation period, and began to approach steady decay after 200 seconds. With quasi-linear viscoelastic theory and reduced relaxation function, the modelling has adapted the experimental data sufficiently. This study is a significant step towards understanding skin tissue rheological behaviour and its multidiscipline properties.

Relaxation and inverse relaxation of yarns after dynamic loading

Abstract: 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.

Rheology of suspensions of spherical particles in a Newtonian and a non-Newtonian fluid

Abstract: Properties of suspensions of spherical glass beads (25–38 μm dia.) in a Newtonian fluid and a non-Newtonian (NBS Fluid 40) fluid were measured at volume fractions, φ, of 0%, 10%, 20% and 30%. Measurements were made using a modified and computerized Weissenberg Rheogoniometer. Properties measured included steady shear viscosity, η( γ . ), first normal stress difference, N1( γ . ), linear viscoelastic properties, η′(ω) and G′(ω), shear stress relaxation, σ− ( γ . , t), and growth, σ+( γ . , t) and normal stress relaxation, N1−( γ . , t). For a the Newtonian fluid, increasing φ causes both η and η′ to increase, with η′ showing a slight frequency dependence. Both N1 and G′ are zero and stress relaxation and growth occur essentially instantaneously. For the NBS fluid, both η and η′ increse with φ at all γ . and ω, respectively, the increase being greater as γ . and ω approach zero. N1 and G′ are less affected by the presence of the particles than η and η′ with the effect on G′ being more pronounced than on N1. For fixed γ . , stress relaxation and growth exhibit greater non-linear effects as φ is increased. A model for predicting a priori the linear viscoelastic properties for suspensions was found to yeild reasonable estimates up to φ = 20%.