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A Rheological Model with Integer and Non-Integer Orders Nonlinearities for Predicting Stress Relaxation Behavior in Viscoelastic Materials
Yélomè Judicaël Fernando Kpomahou,
Koffi Judicaël Agbélélé,
Arnaud Edouard Yamadjako,
Bachir Koladé Adélakoun Ambelohoun
Issue:
Volume 12, Issue 1, January 2023
Pages:
1-7
Received:
21 November 2022
Accepted:
13 December 2022
Published:
4 March 2023
Abstract: Viscoelastic materials are widely used as devices for vibration control in modern engineering applications. They exhibit both viscous and elastic characteristic when undergoing deformation. They are mainly characterized by three time-dependent mechanical properties such as creep, stress relaxation and hysteresis. Among them, stress relaxation is one of the most important features in the characterization of viscoelastic materials. This phenomenon is defined as a time-dependent decrease in stress under a constant strain. Due to the inherent nonlinearity shown by the material response over a certain range of strain when viscoelastic materials are subjected to external loads, nonlinear rheological models are needed to better describe the experimental data. In this study, a singlenonlinear differential constitutive equation is derived froma nonlinear rheological model composed of a generalized nonlinear Maxwell fluid model in parallel with a nonlinear spring obeying a power law for the prediction of the stress relaxation behavior in viscoelastic materials. Under a constant strain-history, the time-dependent stress is analytically derived in the cases where the positive power law exponent, α ˂ 1 and α ˃1. The Trust Region Method available in MATLAB Optimization Toolbox is used to identify the material parameters. Significant correlations are found between the experimental relaxation data taken from literature and exact analytical predictions. The obtained results show that the developed rheological model with integer and non-integer orders nonlinearities accurately describes the experimental relaxation data of some viscoelastic materials.
Abstract: Viscoelastic materials are widely used as devices for vibration control in modern engineering applications. They exhibit both viscous and elastic characteristic when undergoing deformation. They are mainly characterized by three time-dependent mechanical properties such as creep, stress relaxation and hysteresis. Among them, stress relaxation is on...
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Consolidation of the Paper Works with Cellulose Nanofibers
Kobra Dadmohamadi,
Mohsen Mohammadi Achachluei,
Mohammad Taghi Jafari
Issue:
Volume 12, Issue 1, January 2023
Pages:
8-14
Received:
20 November 2022
Accepted:
1 March 2023
Published:
16 March 2023
Abstract: Consolidation is considered as an important step in the conservation of cultural and historical documents and books and the main purpose is to emphasize the strength of the paper support. Consolidant materials are used in the restoration of paper cultural heritage in order to improve the strength of the paper structure, which has decreased due to the passage of time and also the impact of environmental factors. Paper works are gradually degraded by various destructive factors due to their structural properties. For this reason, it is necessary to applying consolidation treatments for strengthening of degraded paper. The purpose of this research is to evaluate the effect of cellulose nanofibers and its use as a consolidant agent to restore durability to paper works. In this study, to consolidation of the paper, cellulose nanofibers with a concentration of 1% by weight were prepared as a suspension with water and used to treat the samples. In order to evaluate the effect of treatment, the samples were exposed to dry- heat and moist-heat aging and pH, colorimetric, and tensile strength tests were performed before and after aging. The results showed that the pH of the samples increased after treatment with cellulose nanofibers. After dry- heat and moist-heat aging, the pH of the samples decreased slightly. Cellulose nanofiber treatment increased the tensile strength of the samples. However, after two stages of aging, the tensile strength of the samples has decreased compared to the previous stage. The use of cellulose nanofiber treatment made the color of the samples brighter but after aging, the brightness of the samples decreased.
Abstract: Consolidation is considered as an important step in the conservation of cultural and historical documents and books and the main purpose is to emphasize the strength of the paper support. Consolidant materials are used in the restoration of paper cultural heritage in order to improve the strength of the paper structure, which has decreased due to t...
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Study on High Temperature Properties of Fiber-Free SMA Mixture
Xiaosen Wang,
Zhibin Wang,
Haidong Li,
Shaobo Zhang,
Yang Luan
Issue:
Volume 12, Issue 1, January 2023
Pages:
15-19
Received:
15 February 2023
Accepted:
4 March 2023
Published:
16 March 2023
Abstract: The high temperature performance of asphalt mixture is an important factor to determine pavement life. Through rut test, dynamic modulus test and repeated load creep test, the high-temperature properties of two kinds of SMA asphalt mixtures were compared by different indexes, and the performance characteristics of non-fiber SMA asphalt mixtures were evaluated. The dynamic stability of the mixture and the slope of the creep curve showed that the non-fiber SMA mixture had an advantage in rut development rate compared with ordinary SMA. The estimated road life and flow number Fn based on rutting showed that the non-fiber SMA mixture could bear nearly 80% more standard axle load than the normal SMA flow number Fn by 11%. When the permanent deformation of the mixture reaches the failure stage, the non-fiber SMA can bear more loads. The main curves of dynamic moduli of the two SMA mixtures at different reference temperatures are basically the same, and the dynamic moduli characterizing the mechanical properties of the mixtures have little difference. Compared with ordinary SMA mixture, the asphalt film thickness on the surface of non-fiber SMA mixture is thinner, and the skeleton effect between coarse aggregates is more prominent, which is an important reason for the improvement of high temperature stability of the mixture.
Abstract: The high temperature performance of asphalt mixture is an important factor to determine pavement life. Through rut test, dynamic modulus test and repeated load creep test, the high-temperature properties of two kinds of SMA asphalt mixtures were compared by different indexes, and the performance characteristics of non-fiber SMA asphalt mixtures wer...
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