Strain-Dependent Properties of Polymers I

Abstract Dynamic elastic moduli of homogeneous, amorphous polymers decrease at moderate to high strains. Under the same strain magnitudes the loss factor goes through a broad maximum. At low strains, dynamic properties are independent of strain amplitude. This paper shows that strain dependence is a basic property of homogeneous, amorphous polymers. Strain dependence is shown to occur in gum, as well as filled, vulcanizates. In addition it is shown that self heating due to flexing at high strains cannot fully explain strain dependent dynamic properties. Testing has been performed on specimens with greatly varying geometries (and, hence, different amounts of self-heating) and at controlled specimen temperatures. These tests have verified the existence of a basic strain-dependency. Strain dependence is here related to time-temperature dependent properties of polymers as described by the well-known work of Williams, Landel, and Ferry. The magnitude of strain dependence and the strain amplitudes at which strain dependence occurs appear to be controlled by the time-temperature dependence of polymers.

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Experimental and Numerical Study on Dynamic Properties of Viscoelastic Microvibration Damper Considering Temperature and Frequency Effects

Journal of Computational and Nonlinear Dynamics ◽

10.1115/1.4034566 ◽

2016 ◽

Vol 11 (6) ◽

Author(s):

Chao Xu ◽

Zhao-Dong Xu ◽

Teng Ge ◽

Ya-Xin Liao

Keyword(s):

Loss Factor ◽

Numerical Study ◽

Dynamic Properties ◽

Frequency Effect ◽

Solid Model ◽

Temperature Dependent ◽

Frequency Effects ◽

Proposed Model ◽

Different Temperatures ◽

Increasing Temperature

This work presents an experimental and numerical study on the dynamic properties of viscoelastic (VE) microvibration damper under microvibration conditions at different frequencies and temperatures. The experimental results show that the storage modulus and the loss factor of VE microvibration damper both increase with increasing frequency but decrease with increasing temperature. To explicitly and accurately represent the temperature and frequency effects on the dynamic properties of VE microvibration damper, a modified standard solid model based on a phenomenological model and chain network model is proposed. A Gaussian chain spring and a temperature-dependent dashpot are employed to reflect the temperature effect in the model, and the frequency effect is considered with the nature of the standard solid model. Then, the proposed model is verified by comparing the numerical results with the experimental data. The results show that the proposed model can accurately describe the dynamic properties of VE microvibration damper at different temperatures and frequencies.

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Influence of the temperature- and frequency-dependent dynamic properties of rail pads on the vibration characteristics of rails at low temperature

Proceedings of the Institution of Mechanical Engineers Part F Journal of Rail and Rapid Transit ◽

10.1177/0954409720913767 ◽

2020 ◽

pp. 095440972091376

Author(s):

Wang Ping ◽

Dou Yinling ◽

Wang Shaohua ◽

Wang Feng ◽

Kai Wei

Keyword(s):

Decay Rate ◽

Dynamic Properties ◽

Temperature Dependent ◽

Frequency Dependent ◽

First Order ◽

Railway Tracks ◽

System Vibration ◽

Temperature Dependent Properties ◽

Rolling Noise ◽

Attenuation Characteristics

The dynamic properties of railway tracks and rail pads are significant for accurately predicting both the wheel–rail system vibration and rolling noise. The effect that the dynamic properties of rail pads have on the dynamic characteristics of railway tracks at extremely low temperatures was not adequately studied in previous research. In order to better predict the attenuation of the rail vibration, the viscoelastic dynamic properties of rail pads varying nonlinearly with temperature and frequency were first tested, in a wide temperature range (−60 ℃ to 20 ℃), and represented by the fractional derivative Zener model. Then, rail vibration and its attenuation characteristics were investigated by accounting for the frequency-dependent, temperature-dependent and frequency- and temperature-dependent properties, respectively. To be more specific, the frequency and amplitude of the rail first-order bending resonance and pinned–pinned resonance, as well as the rail decay rate were analyzed for the three cases. In conclusion, the study shows that the temperature/frequency-dependent properties of the rail pad have a significant effect on the first-order bending resonance of the rail, but no influence on the pinned–pinned resonance frequency. The rail decay rate indicates a clear increasing trend in the entire frequency domain with the decrease of temperature (especially below about −20 ℃). The frequency dependence mainly affects the vibration and its attenuation characteristics of the rail below about 400 Hz, which should not be ignored in the track dynamics modelling. Therefore, when the analyzed environmental temperature is below −20 ℃, the temperature dependence of rail pads should be considered.

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Evaluation of Static and Dynamic Residual Mechanical Properties of Heat-Damaged Concrete for Nuclear Reactor Auxiliary Buildings in Korea Using Elastic Wave Velocity Measurements

Materials ◽

10.3390/ma12172695 ◽

2019 ◽

Vol 12 (17) ◽

pp. 2695 ◽

Cited By ~ 5

Author(s):

Seong-Hoon Kee ◽

Jun Won Kang ◽

Byong-Jeong Choi ◽

Juho Kwon ◽

Ma. Doreen Candelaria

Keyword(s):

Mechanical Properties ◽

Elastic Modulus ◽

Elastic Wave ◽

Wave Velocity ◽

Elastic Moduli ◽

Nuclear Reactor ◽

Dynamic Properties ◽

Velocity Measurements ◽

Heating And Cooling ◽

Dynamic Elastic Moduli

The main objectives of this study are (1) to investigate the effects of heating and cooling on the static and dynamic residual properties of 35 MPa (5000 psi) concrete used in the design and construction of nuclear reactor auxiliary buildings in Korea; and (2) to establish the correlation between static and dynamic properties of heat-damaged concrete. For these purposes, concrete specimens (100 mm × 200 mm cylinder) were fabricated in a batch plant at a nuclear power plant (NPP) construction site in Korea. To induce thermal damages, the concrete specimens were heated to target temperatures from 100 °C to 1000 °C with intervals of 100 °C, at a heating rate of 5 °C/min and allowed to reach room temperature by natural cooling. The dynamic properties (dynamic elastic modulus and dynamic Poisson’s ratio) of concrete were evaluated using elastic wave measurements (P-wave velocity measurements according to ASTM C597/C597M-16 and fundamental longitudinal and transverse resonance tests according to ASTM C215-14) before and after the thermal damages. The static properties (compressive strength, static elastic modulus and static Poisson’s ratio) of heat-damaged concrete were measured by the uniaxial compressive testing in accordance with ASTM C39-14 and ASTM C469-14. It was demonstrated that the elastic wave velocities of heat-damaged concrete were proportional to the square root of the reduced dynamic elastic moduli. Furthermore, the relationship between static and dynamic elastic moduli of heat-damaged concrete was established in this study. The results of this study could improve the understanding of the static and dynamic residual mechanical properties of Korea NPP concrete under heating and cooling.

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Effect of Cylinder Size on the Modulus of Elasticity and Compressive Strength of Concrete from Static and Dynamic Tests

Advances in Materials Science and Engineering ◽

10.1155/2015/580638 ◽

2015 ◽

Vol 2015 ◽

pp. 1-12 ◽

Cited By ~ 13

Author(s):

Byung Jae Lee ◽

Seong-Hoon Kee ◽

Taekeun Oh ◽

Yun-Yong Kim

Keyword(s):

Compressive Strength ◽

High Strength Concrete ◽

Elastic Moduli ◽

Dynamic Properties ◽

High Strength ◽

Primary Objective ◽

Dynamic Tests ◽

Strength Concrete ◽

Dynamic Elastic Moduli ◽

Static And Dynamic Tests

The primary objective of this study is to investigate the effects of cylinder size (150 by 300 mm and 100 by 200 mm) on empirical equations that relate static elastic moduli and compressive strength and static and dynamic elastic moduli of concrete. For the purposes, two sets of one hundred and twenty concrete cylinders, 150 by 300 mm and 100 by 200 mm, were prepared from three different mixtures with target compressive strengths of 30, 35, and 40 MPa. Static and dynamic tests were performed at 4, 7, 14, and 28 days to evaluate compressive strength and static and dynamic moduli of cylinders. The effects of the two different cylinder sizes were investigated through experiments in this study and database collected from the literature. For normal strength concrete (≤40 MPa), the two different cylinder sizes do not result in significant differences in test results including experimental variability, compressive strength, and static and dynamic elastic moduli. However, it was observed that the size effect became substantial in high strength concrete greater than 40 MPa. Therefore, special care is still needed to compare the static and dynamic properties of high strength concrete from the two different cylinder sizes.

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Temperature-Dependent Properties of Molten Li2BeF4 Salt Using Ab Initio Molecular Dynamics

ACS Omega ◽

10.1021/acsomega.1c02528 ◽

2021 ◽

Author(s):

Khagendra Baral ◽

Saro San ◽

Ridwan Sakidja ◽

Adrien Couet ◽

Kumar Sridharan ◽

...

Keyword(s):

Molecular Dynamics ◽

Ab Initio ◽

Ab Initio Molecular Dynamics ◽

Temperature Dependent ◽

Temperature Dependent Properties

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Green’s function for an elastic layer with temperature-dependent properties

Materials Science ◽

10.1007/s11003-013-9544-z ◽

2013 ◽

Vol 48 (5) ◽

pp. 607-613 ◽

Cited By ~ 3

Author(s):

S. J. Matysiak ◽

D. M. Perkowski

Keyword(s):

Green’S Function ◽

Green's Function ◽

Elastic Layer ◽

Temperature Dependent ◽

Temperature Dependent Properties

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Crystal structure and temperature-dependent properties of Na2H4Ga2GeO8 – a novel gallogermanate

Zeitschrift für Naturforschung B ◽

10.1515/znb-2020-0159 ◽

2020 ◽

Vol 75 (9-10) ◽

pp. 805-813

Author(s):

Irma Peschke ◽

Lars Robben ◽

Christof Köhler ◽

Thomas Frauenheim ◽

Josef-Christian Buhl ◽

...

Keyword(s):

Crystal Structure ◽

Decomposition Temperature ◽

Spectroscopic Techniques ◽

Charge Balance ◽

Temperature Dependent ◽

Raman Spectroscopic ◽

Debye Temperatures ◽

Diffraction Lattice ◽

Temperature Dependent Properties ◽

Balance Structure

AbstractSynthesis, crystal structure and temperature-dependent behavior of Na2H4Ga2GeO8 are reported. This novel gallogermanate crystallizes in space group I41/acd with room-temperature powder diffraction lattice parameters of a = 1298.05(1) pm and c = 870.66(1) pm. The structure consists of MO4 (M = Ga, Ge) tetrahedra in four-ring chains, which are connected by two different (left- and right-handed) helical chains of NaO6 octahedra. Protons coordinating the oxygen atoms of the GaO4 tetrahedra not linked to germanium atoms ensure the charge balance. Structure solution and refinement are based on single crystal X-ray diffraction measurements. Proton positions are estimated using a combined approach of DFT calculations and NMR, FTIR and Raman spectroscopic techniques. The thermal expansion was examined in the range between T = 20(2) K and the compound’s decomposition temperature at 568(5) K, in which no phase transition could be observed, and Debye temperatures of 266(11) and 1566(65) K were determined for the volume expansion.

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A new boundary element algorithm for modeling and simulation of nonlinear thermal stresses in micropolar FGA composites with temperature-dependent properties

Advanced Modeling and Simulation in Engineering Sciences ◽

10.1186/s40323-021-00193-6 ◽

2021 ◽

Vol 8 (1) ◽

Author(s):

Mohamed Abdelsabour Fahmy

Keyword(s):

Modeling And Simulation ◽

Boundary Element ◽

Thermal Stresses ◽

Computation Time ◽

Functionally Graded ◽

Temperature Dependent ◽

Time Step ◽

Kirchhoff Transformation ◽

Nonlinear Temperature ◽

Temperature Dependent Properties

AbstractThe main aim of this article is to develop a new boundary element method (BEM) algorithm to model and simulate the nonlinear thermal stresses problems in micropolar functionally graded anisotropic (FGA) composites with temperature-dependent properties. Some inside points are chosen to treat the nonlinear terms and domain integrals. An integral formulation which is based on the use of Kirchhoff transformation is firstly used to simplify the transient heat conduction governing equation. Then, the residual nonlinear terms are carried out within the current formulation. The domain integrals can be effectively treated by applying the Cartesian transformation method (CTM). In the proposed BEM technique, the nonlinear temperature is computed on the boundary and some inside domain integral. Then, nonlinear displacement can be calculated at each time step. With the calculated temperature and displacement distributions, we can obtain the values of nonlinear thermal stresses. The efficiency of our proposed methodology has been improved by using the communication-avoiding versions of the Arnoldi (CA-Arnoldi) preconditioner for solving the resulting linear systems arising from the BEM to reduce the iterations number and computation time. The numerical outcomes establish the influence of temperature-dependent properties on the nonlinear temperature distribution, and investigate the effect of the functionally graded parameter on the nonlinear displacements and thermal stresses, through the micropolar FGA composites with temperature-dependent properties. These numerical outcomes also confirm the validity, precision and effectiveness of the proposed modeling and simulation methodology.

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