scholarly journals Study on the Generalized Formulations with the Aim to Reproduce the Viscoelastic Dynamic Behavior of Polymers

2020 ◽  
Vol 10 (7) ◽  
pp. 2321
Author(s):  
Andrea Genovese ◽  
Francesco Carputo ◽  
Antonio Maiorano ◽  
Francesco Timpone ◽  
Flavio Farroni ◽  
...  
Keyword(s):  
Experimental Data ◽  
Low Frequency ◽  
Maxwell Model ◽  
Wide Frequency Range ◽  
Material Behavior ◽  
Viscoelastic Materials ◽  
Optimum Parameters ◽  
Generalized Maxwell Model ◽  
Minimum Number ◽  
Real Behavior

Appropriate modelling of the real behavior of viscoelastic materials is of fundamental importance for correct studies and analyses of structures and components where such materials are employed. In this paper, the potential to employ a generalized Maxwell model and the relative fraction derivative model is studied with the aim to reproduce the experimental behavior of viscoelastic materials. For both models, the advantage of using the pole-zero formulation is demonstrated and a specifically constrained identification procedure to obtain the optimum parameters set is illustrated. Particular emphasis is given on the ability of the models to adequately fit the experimental data with a minimum number of parameters, addressing the possible computational issues. The question arises about the minimum number of experimental data necessary to estimate the material behavior in a wide frequency range, demonstrating that accurate results can be obtained by knowing only the data of the upper and low frequency plateaus plus the ones at the loss tangent peak.

Generalized Maxwell model for the viscoelastic behavior of a soda-lime-silica glass under low frequency shear loading

1997 ◽  
Vol 36 (2) ◽  
pp. 173-186
Author(s):  
Lucas Duffrène *, † , Ren&#x ◽  
Hélène Burlet ◽  
Roland Piques ◽  
Annelise Faivre ◽  
Anas Sekkat ◽  
...  
Keyword(s):  
Silica Glass ◽  
Low Frequency ◽  
Viscoelastic Behavior ◽  
Maxwell Model ◽  
Soda Lime ◽  
Shear Loading ◽  
Generalized Maxwell Model ◽  
Soda Lime Silica Glass

Generalized Maxwell model for the viscoelastic behavior of a soda-lime-silica glass under low frequency shear loading

1997 ◽  
Vol 36 (2) ◽  
pp. 173-186 ◽  
Author(s):  
Lucas Duffr�ne ◽  
Ren� Gy ◽  
H�l�ne Burlet ◽  
Roland Piques ◽  
Annelise Faivre ◽  
...  
Keyword(s):  
Silica Glass ◽  
Low Frequency ◽  
Viscoelastic Behavior ◽  
Maxwell Model ◽  
Soda Lime ◽  
Shear Loading ◽  
Generalized Maxwell Model ◽  
Soda Lime Silica Glass

Generalized Maxwell model for micro-cracked viscoelastic materials

2015 ◽  
Vol 26 (5) ◽  
pp. 697-710 ◽  
Author(s):  
ST Nguyen ◽  
M-H Vu ◽  
MN Vu ◽  
TN Nguyen
Keyword(s):  
Maxwell Model ◽  
Viscoelastic Materials ◽  
Generalized Maxwell Model

scholarly journals Experimental Study on Dynamic Properties of a Recycled Composite Sleeper and Its Theoretical Model

Symmetry ◽  
2020 ◽  
Vol 13 (1) ◽  
pp. 17
Author(s):  
Zhenhang Zhao ◽  
Ying Gao ◽  
Chenghui Li
Keyword(s):  
Complex Modulus ◽  
Dynamic Properties ◽  
Low Frequency ◽  
Maxwell Model ◽  
Theoretical Models ◽  
Mechanical Analysis ◽  
Factors Affecting ◽  
Track System ◽  
Generalized Maxwell Model ◽  
Temperature Superposition

As a symmetrical structure in track system, the dynamic properties of recycled composite sleepers are important factors affecting the vibration characteristics of track structure. To study the viscoelastic dynamic properties of the composite sleeper, dynamic mechanical analysis (DMA) tests of a composite sleeper at −5 to 30 °C and 1–60 Hz were first carried out, and then the time-temperature superposition (TTS) and the Williams–Landel–Ferry (WLF) formula were used to predict the dynamic properties of a composite sleeper at a wider frequency range. Finally, the generalized Maxwell model was adopted to characterize the dynamic properties of the composite sleeper, which provides parameters and theoretical models for dynamic analysis. The research results show that the composite sleeper has obvious viscoelasticity. Its modulus is large at low temperature or high frequency. On the contrary, the modulus is small at high temperature or low frequency. Under the test conditions, its complex modulus ranges from 1500 to 2700 MPa. The loss factor is in the range of 0.08–0.13. Using the generalized Maxwell model (n = 4), which can better reflect the dynamic properties of the composite sleeper.

scholarly journals Minimum Number of Experimental Data for the Thermal Characterization of a Hot Water Storage Tank

Energies ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4741
Author(s):  
María Gasque ◽  
Federico Ibáñez ◽  
Pablo González-Altozano
Keyword(s):  
Experimental Data ◽  
Water Temperature ◽  
Temperature Profile ◽  
Storage Tank ◽  
Water Storage ◽  
Hot Water ◽  
Experimental Temperature ◽  
Inlet Temperature ◽  
Water Storage Tank ◽  
Minimum Number

This paper demonstrates that it is possible to characterize the water temperature profile and its temporal trend in a hot water storage tank during the thermal charge process, using a minimum number of thermocouples (TC), with minor differences compared to experimental data. Four experimental tests (two types of inlet and two water flow rates) were conducted in a 950 L capacity tank. For each experimental test (with 12 TC), four models were developed using a decreasing number of TC (7, 4, 3 and 2, respectively). The results of the estimation of water temperature obtained with each of the four models were compared with those of a fifth model performed with 12 TC. All models were tested for constant inlet temperature. Very acceptable results were achieved (RMSE between 0.2065 °C and 0.8706 °C in models with 3 TC). The models were also useful to estimate the water temperature profile and the evolution of thermocline thickness even with only 3 TC (RMSE between 0.00247 °C and 0.00292 °C). A comparison with a CFD model was carried out to complete the study with very small differences between both approaches when applied to the estimation of the instantaneous temperature profile. The proposed methodology has proven to be very effective in estimating several of the temperature-based indices commonly employed to evaluate thermal stratification in water storage tanks, with only two or three experimental temperature data measurements. It can also be used as a complementary tool to other techniques such as the validation of numerical simulations or in cases where only a few experimental temperature values are available.

Investigations of the Optical Properties of LaNi5 and LaNi4.5Sn0.5

2013 ◽  
Vol 321-324 ◽  
pp. 495-498 ◽  
Author(s):  
Dong Chen ◽  
Chao Xu
Keyword(s):  
Experimental Data ◽  
Refractive Index ◽  
Optical Properties ◽  
Density Functional ◽  
Low Frequency ◽  
Potential Method ◽  
Frequency Region ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Pseudo Potential

The reflectivity, loss function, refractive index, extinction coefficient and dielectric function of the LaNi5and LaNi4.5Sn0.5intermetallic compounds are investigated through the plane-wave pseudo-potential method based on the density functional theory. The effects of Sn impurity are discussed and some interesting features are found in the low frequency region. Some important optical properties such as static dielectric constant and static refractive index are obtained. The equation [n (0)]2=ε1(0)is satisfied according to our calculation, which indicates that our results are correct and reasonable. Nevertheless, the calculated results need to be testified in the future due to the lack of experimental data.

scholarly journals Using Waveguides to Model the Dynamic Stiffness of Pre-Compressed Natural Rubber Vibration Isolators

Polymers ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1703
Author(s):  
Michael Coja ◽  
Leif Kari
Keyword(s):  
Natural Rubber ◽  
Dynamic Stiffness ◽  
Low Frequency ◽  
Complex Problem ◽  
Wide Frequency Range ◽  
Vibration Isolators ◽  
Standard Linear Solid ◽  
Standard Linear ◽  
Frequency Magnitude ◽  
Good Agreement

A waveguide model for a pre-compressed cylindrical natural rubber vibration isolator is developed within a wide frequency range—20 to 2000 Hz—and for a wide pre-compression domain—from vanishing to the maximum in service, that is 20%. The problems of simultaneously modeling the pre-compression and frequency dependence are solved by applying a transformation of the pre-compressed isolator into a globally equivalent linearized, homogeneous, and isotropic form, thereby reducing the original, mathematically arduous, and complex problem into a vastly simpler assignment while using a straightforward waveguide approach to satisfy the boundary conditions by mode-matching. A fractional standard linear solid is applied as the visco-elastic natural rubber model while using a Mittag–Leffler function as the stress relaxation function. The dynamic stiffness is found to depend strongly on the frequency and pre-compression. The former is resulting in resonance phenomena such as peaks and troughs, while the latter exhibits a low-frequency magnitude stiffness increase in addition to peak and trough shifts with increased pre-compressions. Good agreement with nonlinear finite element results is obtained for the considered frequency and pre-compression range in contrast to the results of standard waveguide approaches.

EXPERIMENTAL RESEARCH ON VISCOELASTICITY PROPERTY OF DIFFERENT LAYERS PERIODONTAL LIGAMENT UNDER COMPRESSION

2021 ◽  
pp. 2150050
Author(s):  
JINLAI ZHOU ◽  
YANG SONG ◽  
CHENGUANG XU ◽  
CHUNQIU ZHANG ◽  
XUE SHI
Keyword(s):  
Elastic Modulus ◽  
Periodontal Ligament ◽  
Creep Compliance ◽  
Relaxation Modulus ◽  
Maxwell Model ◽  
Kelvin Model ◽  
Generalized Maxwell Model ◽  
Relaxation Stress ◽  
Generalized Kelvin Model ◽  
Fitting Accuracy

The periodontal ligament (PDL) exhibits different material mechanical properties along the long axis of the teeth. To explore the creep and the relaxation effects of dissimilar layers of PDL, this paper took the central incisors of porcine mandibular as experimental subjects and divided them perpendicular to the teeth axis into five layers. Creep experiments and relaxation experiments on five layers were conducted to obtain the creep compliance and relaxation modulus at different layers. Linear elastic model, generalized Kelvin model, and generalized Maxwell model were used to describe the major characteristics of the PDL: Instantaneous elasticity, creep and relaxation. Fitting accuracy of three-parameter, five-parameter, and seven-parameter of the model was compared, and the constitutive equations of different layers were established by the least square method. The results presented that the creep strain and the relaxation stress of PDL were exponentially correlated with time under different loading conditions. Different layers showed a significant effect on the creep strain and relaxation stress of PDL. Along the long axis of the teeth, the changing rule of the creep compliance and relaxation modulus of each layer showed quite the contrary, and the instantaneous elastic modulus first decreased to the minimum, then increased to the maximum. Higher instantaneous elastic modulus led to lower creep compliance and higher relaxation modulus. The generalized Kelvin model and the generalized Maxwell model well characterized the creep and relaxation properties of PDL. Fitting accuracy increased with the number of model parameters. The relaxation time of PDL was about one order of magnitude shorter than the creep retardation time, which indicated that the relaxation effect lasted shorter than the creep effect.

Development of a Methodology for the Evaluation of Motion Sickness Incidence in Railways

2013 ◽  
Author(s):  
Claudio Braccesi ◽  
Filippo Cianetti ◽  
Renzo Scaletta
Keyword(s):  
Experimental Data ◽  
Theoretical Model ◽  
Motion Sickness ◽  
Evaluation Method ◽  
Low Frequency ◽  
Comparison With Experimental Data

The present paper illustrates an evaluation method developed by the authors to quantify the index of motion sickness incidence (MSI) in railways motion conditions. This index is formerly defined in literature to quantify diseases coming from low frequency motions (kinetosis). The proposed method, suggested as alternative to the only one existing in reference norm, involves PCT index, well known in railways context, and weighting curves for accelerometric signals, which are also specified in railways regulations. The approach of the method, consistent with the theoretical model, developed by the authors themselves in previous works, allows to obtain MSI index versus time and/or track progressive distance. The model is validated through comparison with experimental data available in literature and with measures recorded and obtained on regular trains during tests performed in Slovenia (EU).

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