Topic
Stress relaxation
About: Stress relaxation is a research topic. Over the lifetime, 12959 publications have been published within this topic receiving 270815 citations.
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TL;DR: In this paper, the shear orientation of viscoelastic clay-polymer solutions was investigated by means of rheology and flow birefringence (Δn).
Abstract: The shear orientation of viscoelastic clay-polymer solutions was investigated by means of rheology and flow birefringence (Δn). The polymer chains are in dynamic adsorption/desorption equilibrium with the clay particles to form a “network”. The elastic behavior of the network was characterized by constant stress, oscillatory shear, and stress relaxation experiments. Constant stress experiments indicated a yield stress upon which shear flow started and no strain recovery could be observed. Oscillatory shear experiments showed a broad elastic region followed by flow when a critical strain was reached. Stress relaxation experiments showed several relaxation times when the same critical strain was reached. Experiments under steady flow characterized the transient behavior of the network. With increasing steady shear rate a pronounced minimum in birefringence was observed at a critical shear rate. The shear rate dependent viscosity showed near power law behavior and no corresponding critical feature. While birefringence detects orientational effects on a microscopic length scale, rheology averages over macroscopic changes in the sample. The same degree of orientation could be achieved under constant shear rate or constant stress conditions.
92 citations
TL;DR: Investigation of the stress release properties of four thermoplastic materials used to make orthodontic aligners found that stress release may cause significant changes in the behavior of the polymers at 24 hours from the application of orthodentic loads, which may influence programmed tooth movement.
Abstract: Objective: To investigate the stress release properties of four thermoplastic materials used to make orthodontic aligners when subjected to 24 consecutive hours of deflection. Materials an...
92 citations
TL;DR: In this article, SiC-based fibers, HiNiclaon™, Hi-Nicalon™ type S and Tyranno™-SA, were heat treated at 1300-1900 °C in Ar for 1 h. After heat treatment, room temperature tensile strength and 1-h bend stress relaxation (BSR) were evaluated for these fibers.
92 citations
TL;DR: In this paper, it is shown that creep strain transients can be adequately described by invoking anelastic strain contributions to both primary creep and unloading transients at all stress levels.
92 citations
TL;DR: In this paper, the authors developed a lubricated squeezing technique for molten polymers and applied the technique to two different polymers, and tested the separability hypothesis for extensional flow generated with a Rheometrics RDS-LA.
Abstract: Stress relaxation after rapid extensional strain was measured to obtain the extensional relaxation modulus. The research had the objectives of developing the lubricated squeezing technique for molten polymers, of applying the technique to two different polymers, and of testing the “separability hypothesis.” Equibiaxial extensional flow was generated with a Rheometrics RDS‐LA, using the lubricated squeezing technique. The time dependence of the relaxation modulus was found to be the same in extension as in shear, given by the relaxation modulus of linear viscoelasticity. The strain dependence was markedly different than in shear. Separation of time and strain dependence into a product of two functions is suggested by the experimental results. This is a strong support for the separability hypothesis and simplifies the formulation of rheological constitutive equations. A polymer with linear macromolecules (PS) exhibited stronger strain dependence than a polymer with long chain branched macromolecules (LDPE)....
92 citations