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Michael Rubinstein - One of the best experts on this subject based on the ideXlab platform.
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elastic plastic transformation of polyelectrolyte complex hydrogels from chitosan and sodium hyaluronate
Macromolecules, 2018Co-Authors: Ran Shi, Tao Lin Sun, Feng Luo, Tasuku Nakajima, Takayuki Kurokawa, Yue Zhen Bin, Michael RubinsteinAbstract:Hydrogels formed by polyelectrolyte complexation (PEC) of oppositely charged biopolymers, free of any chemical additives, are promising biomaterials. In this work, the mechanical behavior of hydrogels consisting of positively charged chitosan and negatively charged sodium hyaluronate (HA) at balanced charge composition is investigated. These hydrogels exhibit strong tensile strain and strain rate dependence. They are elastic-like, independent of the strain rate at small strain, but exhibit plastic-like behavior above the Yield Point by showing a monotonous decrease of the stress. The cyclic tensile test demonstrates that these hydrogels exhibit small and quickly recoverable hysteresis in the elastic-like region but large and partially recoverable hysteresis above the Yield Point. The stress relaxation experiment shows a plateau in the reduced stress followed by an abrupt fracture, and the time to failure decreases exponentially with increasing applied step strain. Such elastic-to-plastic-like transformati...
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Elastic–Plastic Transformation of Polyelectrolyte Complex Hydrogels from Chitosan and Sodium Hyaluronate
2018Co-Authors: Ran Shi, Tao Lin Sun, Feng Luo, Tasuku Nakajima, Takayuki Kurokawa, Yue Zhen Bin, Michael Rubinstein, Jian Ping GongAbstract:Hydrogels formed by polyelectrolyte complexation (PEC) of oppositely charged biopolymers, free of any chemical additives, are promising biomaterials. In this work, the mechanical behavior of hydrogels consisting of positively charged chitosan and negatively charged sodium hyaluronate (HA) at balanced charge composition is investigated. These hydrogels exhibit strong tensile strain and strain rate dependence. They are elastic-like, independent of the strain rate at small strain, but exhibit plastic-like behavior above the Yield Point by showing a monotonous decrease of the stress. The cyclic tensile test demonstrates that these hydrogels exhibit small and quickly recoverable hysteresis in the elastic-like region but large and partially recoverable hysteresis above the Yield Point. The stress relaxation experiment shows a plateau in the reduced stress followed by an abrupt fracture, and the time to failure decreases exponentially with increasing applied step strain. Such elastic-to-plastic-like transformation of the biopolymer PEC gels is quite different from the behaviors of PEC hydrogels formed by oppositely charged vinyl-type synthetic polyelectrolytes due to the difference in flexibility, charge density, and ionic bond strength of these polymers
Ran Shi - One of the best experts on this subject based on the ideXlab platform.
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elastic plastic transformation of polyelectrolyte complex hydrogels from chitosan and sodium hyaluronate
Macromolecules, 2018Co-Authors: Ran Shi, Tao Lin Sun, Feng Luo, Tasuku Nakajima, Takayuki Kurokawa, Yue Zhen Bin, Michael RubinsteinAbstract:Hydrogels formed by polyelectrolyte complexation (PEC) of oppositely charged biopolymers, free of any chemical additives, are promising biomaterials. In this work, the mechanical behavior of hydrogels consisting of positively charged chitosan and negatively charged sodium hyaluronate (HA) at balanced charge composition is investigated. These hydrogels exhibit strong tensile strain and strain rate dependence. They are elastic-like, independent of the strain rate at small strain, but exhibit plastic-like behavior above the Yield Point by showing a monotonous decrease of the stress. The cyclic tensile test demonstrates that these hydrogels exhibit small and quickly recoverable hysteresis in the elastic-like region but large and partially recoverable hysteresis above the Yield Point. The stress relaxation experiment shows a plateau in the reduced stress followed by an abrupt fracture, and the time to failure decreases exponentially with increasing applied step strain. Such elastic-to-plastic-like transformati...
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Elastic–Plastic Transformation of Polyelectrolyte Complex Hydrogels from Chitosan and Sodium Hyaluronate
2018Co-Authors: Ran Shi, Tao Lin Sun, Feng Luo, Tasuku Nakajima, Takayuki Kurokawa, Yue Zhen Bin, Michael Rubinstein, Jian Ping GongAbstract:Hydrogels formed by polyelectrolyte complexation (PEC) of oppositely charged biopolymers, free of any chemical additives, are promising biomaterials. In this work, the mechanical behavior of hydrogels consisting of positively charged chitosan and negatively charged sodium hyaluronate (HA) at balanced charge composition is investigated. These hydrogels exhibit strong tensile strain and strain rate dependence. They are elastic-like, independent of the strain rate at small strain, but exhibit plastic-like behavior above the Yield Point by showing a monotonous decrease of the stress. The cyclic tensile test demonstrates that these hydrogels exhibit small and quickly recoverable hysteresis in the elastic-like region but large and partially recoverable hysteresis above the Yield Point. The stress relaxation experiment shows a plateau in the reduced stress followed by an abrupt fracture, and the time to failure decreases exponentially with increasing applied step strain. Such elastic-to-plastic-like transformation of the biopolymer PEC gels is quite different from the behaviors of PEC hydrogels formed by oppositely charged vinyl-type synthetic polyelectrolytes due to the difference in flexibility, charge density, and ionic bond strength of these polymers
Fusahito Yoshida - One of the best experts on this subject based on the ideXlab platform.
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A plasticity model describing Yield-Point phenomena of steels and its application to FE simulation of temper rolling
International Journal of Plasticity, 2008Co-Authors: Fusahito Yoshida, Yuya Kaneda, Shigeo YamamotoAbstract:Abstract To describe the Yield-Point phenomena of steels, an extended version of the first author’s model (Yoshida, F., 2000. A constitutive model of cyclic plasticity. International Journal of Plasticity 16, 359–380) is proposed on the premise that the material behavior of sharp Yield Point and the subsequent abrupt Yield drop result from a rapid dislocation multiplication and the stress-dependence of dislocation velocity. A specific feature of this model is that it describes well a high upper Yield Point, the rate-dependent Luders strain at the Yield plateau and the subsequent workhardening, as well as cyclic plasticity characteristics, such as the Bauschinger effect and rate-dependent ratcheting. Using this model, an FE simulation of temper rolling process is conducted in order to clarify its role for the elimination of the Yield Point of steel sheets. Particularly, the effect of upper Yield Point on the deformation characteristics in the process is discussed.
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effect of stress concentration on upper Yield Point in mild steel
Materials Transactions, 2006Co-Authors: Hongbing Sun, Yuya Kaneda, Masanobu Ohmori, Fusahito YoshidaAbstract:The effect of stress concentration on the upper Yield stress was investigated for an annealed mild steel wire by performing uniaxial tension tests. In order to avoid such a situation that initial Yielding occurs at the specimen-clamping ends due to stress concentration, a non-uniform annealing method (the annealing temperature was the highest at the center of the specimen) was employed. For a non-uniformly annealed specimen the upper Yield stress was almost twofold of the lower Yield stress. In contrast, for a uniformly annealed specimen, the difference between the upper and lower Yield stresses was not so considerably high, because the site of clamping-induced plastic pre-strain played a role of starting Point of Yielding. To examine the effect of stress concentration on the upper-Yield Point phenomena, FE simulation of the uniaxial tension tests was conducted using a viscoplastic constitutive model proposed by one of the authors (F. Yoshida, Int. J. Plasticity 16 (2000) 359). The results of numerical simulation were in good agreement with the experimental observations. From the results of the experiments and the numerical simulation, it is concluded that, although a material element itself possesses considerably high upper-Yield stress, the observed one in ordinal uniaxial tension experiment is generally not so high because of the stress concentration.
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A constitutive model of cyclic plasticity
International Journal of Plasticity, 2000Co-Authors: Fusahito YoshidaAbstract:Abstract This paper addresses a constitutive model of cyclic plasticity with special emphasis on the Yield-Point phenomena. In order to Point out the deformation characteristics of a mild steel, four types of experiments were conducted, i.e. uniaxial tension at several crosshead speeds, cyclic straining, and stress- and strain-controlled ratchetting. A viscoplastic constitutive model of cyclic plasticity is proposed on the premise that the phenomena of sharp Yield Point and the subsequent abrupt Yield drop result from rapid dislocation multiplication and the stress-dependence of dislocation velocity. Besides, cyclic plasticity behavior, such as the Bauschinger effect, cyclic hardening/softening characteristics and ratchet-strain accumulation, is described by some kinematic and isotropic hardening rules. The cyclic stress–strain responses predicted by this model agree well with the corresponding experimental results.
Ertugrul Taciroglu - One of the best experts on this subject based on the ideXlab platform.
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modeling techniques for strain range dependent hardening behavior of low Yield Point steel shear panel dampers
Journal of Structural Engineering-asce, 2017Co-Authors: Liyan Xu, Ertugrul TacirogluAbstract:AbstractShear panel dampers made of the low-Yield-Point steel exhibit significant overstrength under cyclic loading—a phenomenon that has been observed to depend not only on accumulated plastic def...
Weiguo Yang - One of the best experts on this subject based on the ideXlab platform.
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experimental cyclic behavior and constitutive modeling of low Yield Point steels
Construction and Building Materials, 2017Co-Authors: Meng Wang, Larry A Fahnestock, Fengxia Qian, Weiguo YangAbstract:Abstract To fundamentally define the cyclic behavior of low Yield Point steel (LYP) and obtain representative material constitutive parameters for structural analysis, experimental studies of LYP100 and LYP160 steels were conducted under a range of loading scenarios. Monotonic and cyclic loading patterns were used to evaluate overall response characteristics and to quantify strength, ductility and energy dissipation capacity. Based on this experimental data, the essential material parameters of two constitutive models were calibrated. These constitutive models were then employed in structural analysis of previous large-scale steel plate shear wall test specimens, and the analysis results agreed well with the test data. Together, the experiments and analyses conducted in this study indicate that, although the Yield strengths of LYP steels are by design less than conventional and high strength steels, characteristics that are important for seismic behavior – such as cyclic response, ductility and energy dissipation capacity – are improved. Cyclic response of LYP steel is characterized by combined isotropic and kinematic hardening, and the isotropic component plays a more significant role. LYP steel is a promising structural material that can be employed more effectively when its cyclic behavior, including appreciable hardening, is defined through experimental studies and constitutive modeling as presented here.
