scholarly journals Some theoretical considerations on the dynamic properties of plastics

1949 ◽  
Vol 196 (1044) ◽  
pp. 92-105 ◽  
Keyword(s):  
Experimental Data ◽  
Mechanical Stress ◽  
Mechanical Behaviour ◽  
Dynamic Properties ◽  
Velocity Of Sound ◽  
Stress Strain ◽  
Plastic Materials ◽  
Starting Point ◽  
Strain Relationship ◽  
Theoretical Considerations

There is a marked similarity between the mechanical behaviour of plastics and the electric behaviour of certain dielectrics. This provides a starting-point for the derivation of a mechanical stress-strain relationship for plastic materials, from which expressions are deduced for the velocity of sound in, and for the transmission and reflexion of sound by, plastic plates. The effect of absorption on departures from Rayleigh’s theory is indicated, and limited experimental data are reported.

scholarly journals Static and Dynamic Properties and Temperature Sensitivity of Emulsified Asphalt Concrete

2018 ◽  
Vol 2018 ◽  
pp. 1-9
Author(s):  
Bin Huang ◽  
Yuting Zhang ◽  
Tian Qi ◽  
Hongxing Han
Keyword(s):  
Temperature Sensitivity ◽  
Asphalt Concrete ◽  
Dynamic Modulus ◽  
Dynamic Properties ◽  
Damping Ratio ◽  
Great Influence ◽  
Temperature Control System ◽  
Stress Strain ◽  
Strain Relationship ◽  
Emulsified Asphalt

Asphalt concrete is a typical rheological material, which is hard brittle at low temperature and reflects soft plastic facture at high temperature; the temperature has a great influence on the mechanical properties of asphalt concrete. In order to eliminate the environmental pollution caused by hot asphalt construction, cationic emulsified asphalt can be used. This paper transforms the temperature control system for static and dynamic triaxial test equipment, which has achieved static and dynamic properties of emulsified asphalt concrete under different temperatures, and researched the temperature sensitivity of emulsified asphalt concrete materials including static stress-strain relationship, static strength, dynamic modulus of elasticity, damping ratio, and so on. The results suggest that (1) temperature has a great influence on the triaxial stress-strain relationship curve of the asphalt concrete. The lower the temperature, the greater the initial tangent modulus of asphalt concrete and the higher the intensity; the more obvious the softening trend, the smaller the failure strain of the specimen and the more obvious the extent of shear dilatancy. When the temperature is below 15.4°C, the temperature sensitivity of the modulus and strength is stronger significantly. (2) With the temperature rising, the asphalt concrete gradually shifts from an elastic state to a viscoelastic state, the dynamic modulus gradually reduces, and the damping ratio increases. When the temperature is above 15.4°C, the temperature sensitivity is obviously stronger for the dynamic elastic modulus and damping ratio. (3) The static and dynamic properties of asphalt concrete are very sensitive to the temperature. The test temperature should be made clear for the static and dynamic tests of asphalt concrete. The specimen temperature and the test ambient temperature must be strictly controlled.

Bending of Blood Vessel Wall: Stress-Strain Laws of the Intima-Media and Adventitial Layers

1995 ◽  
Vol 117 (1) ◽  
pp. 136-145 ◽  
Author(s):  
Jiaping Xie ◽  
Jianbo Zhou ◽  
Y. C. Fung
Keyword(s):  
Experimental Data ◽  
Stress State ◽  
Beam Theory ◽  
Nonlinear Least Squares ◽  
Wall Stress ◽  
Wall Material ◽  
Stress Strain ◽  
Strain Relationship ◽  
Residual Strains ◽  
Residual Stresses And Strains

In order to determine the stress-strain relationship of the inner (intima and media) and outer (adventitia) layers of blood vessels in the neighborhood of the zero-stress state, bending experiments were performed on aortic strips of rats. In the experiments, one end of a strip was clamped, and a force was applied on the other end. The deflection curves of the strips were measured. By regarding the aortic strip as a curved beam, the classical beam theory was employed to analyze the strain distribution from the experimental data. A computer program dealing with nonlinear equations and nonlinear least squares optimization was developed. Strains were referred to the zero-stress state. The load-deflection relationship was then used to determine the stress-strain relationship. Certain forms of the stress-strain laws were assumed. The linear laws fit the experimental data accurately, probably because the strains during bending are quite small, although the rotations are large. The Young’s modulus of the inner layer, which consists of endothelial and smooth muscle cells and elastic lamina, was found to be three to four times larger than that of the outer layer which consists of collagen with a small amount of fibroblasts and elastin. The residual stresses and strains at the no-load state were calculated from the deduced stress-strain relationship. It is shown that large errors (up to 50 percent) in the values of the residual strains will occur if the wall material was treated as homogeneous, i.e., if the layered constitution was ignored.

scholarly journals INFLUENCE OF INCREASED TEMPERATURE ON THE DYNAMIC PROPERTIES OF ASPEN

2021 ◽  
Vol 83 (1) ◽  
pp. 5-21
Author(s):  
A.M. Bragov ◽  
A.Yu. Konstantinov ◽  
A.K. Lomunov ◽  
T.N. Yuzhina
Keyword(s):  
Experimental Data ◽  
Elevated Temperatures ◽  
Dynamic Properties ◽  
Stress Strain ◽  
Horizontal Section ◽  
Mean Values ◽  
Damping Material ◽  
Deformation Properties ◽  
Relaxation Of Stresses ◽  
Strength And Deformation

As a damping material in the structures of containers for the transportation of hazardous materials, along with plastic metals, fiber-claydite concrete and synthetic foams, it is proposed to use wood of different species. Since containers are transported in different climate regimes, there is an urgent need to study the properties of wood at elevated temperatures. The paper presents the results of dynamic tests of aspen under uniaxial compression under conditions of temperature increased to +60°C. The tests were carried out according to the Kolsky method on a Hopkinson split-bar setup. To study the anisotropy of properties, aspen samples were made and tested by cutting samples along and across the direction of the grains. As a result of processing the experimental data, dynamic stress-strain curves were obtained. According to the experimental data, there are determined the stresses at which the integrity of the samples were violated. The mean values of the moduli of deformation in the active loading regions of stress-strain curves are also presented. The highest slope of the load sections and the highest breaking stresses were observed for the specimens when loaded along the grains, and the smallest values of these parameters were noted when loaded across the grains. For specimens loaded along grains at strain rates above 1500 s–1, after reaching the limiting stress values, a decrease (relaxation) of stresses is observed with increasing deformations. For specimens loaded across the grains, an almost horizontal section the diagrams of deforming or even with some strengthening is more typical. The effect of elevated temperature on the strength and deformation properties of aspen is estimated. There is a tendency towards some decrease in the diagrams at a temperature of +60 °C in comparison with the diagrams at room temperature. In this case, both the moduli in the loading and unloading sections and the limiting (breaking) stresses decrease. The obtained features of the behavior of aspen specimens at elevated temperatures should be taken into account when modeling deforming wood.

scholarly journals An Incremental Formulation of Constitutive Equations for Deposited Snow

1980 ◽  
Vol 25 (92) ◽  
pp. 289-307 ◽  
Author(s):  
J. Desrues ◽  
F. Darve ◽  
E. Flavigny ◽  
J.P. Navarre ◽  
A. Taillefer
Keyword(s):  
Experimental Data ◽  
Axial Strain ◽  
Triaxial Tests ◽  
Stress Strain ◽  
Theoretical Formulation ◽  
Non Linear ◽  
Incremental Formulation ◽  
Strain Relationship ◽  
Strain Paths ◽  
Incremental Form

Abstract The behaviour of a snow mass under natural loadings (gravity forces, boundary conditions) can be computed by the finite-element method, in so far as a convenient formulation of the stress–strain relationship for snow is available. This paper deals with such a formulation given in incremental form. Experiments have been performed, which show that deposited snow can be considered as a non-linear visco-elastic material with memory effect. The proposed theoretical formulation takes into account these properties. The elastic part of the deformation is assumed to be isotropic and non-linear; the viscous part is expressed in terms of a creep-rate, which results from a superposition of elementary creep-rates according to Boltzmann’s principle. The values of parameters can be obtained from isotropic creep experiments. The experimental data and the resulting parameters are reported. Since the parameters were determined, the formulation of the rheological law was then tested by integration on “stress–strain paths" corresponding to other experiments of a different type, performed on the same snow. The experiments are triaxial tests at constant axial strain-rate, with a preliminary stage of isotropic compression. Experimental data are compared to theoretical curves obtained by integration of the rheological law. The calculated behaviour is consistent with the experimental results.

Mechanical Behavior of FRP-Confined Rectangular Concrete Column

2010 ◽  
Vol 163-167 ◽  
pp. 3804-3807
Author(s):  
Ping Wu ◽  
Feng Yu
Keyword(s):  
Experimental Data ◽  
Experimental Study ◽  
Cross Section ◽  
Strain Softening ◽  
Axial Strain ◽  
Concrete Column ◽  
Stress Strain ◽  
Strain Relationship ◽  
Rectangular Concrete Column ◽  
Strain Model

According to the analysis of existing experimental data, it is well known that the behavior of FRP-confined rectangular concrete column were mainly related to the cross section coefficient of concrete, the confinement effect coefficient and the strength of concrete. Based on experimental study and theoretical analysis, the formula for bearing capacity and ultimate axial strain of FRP-confined rectangular concrete column were proposed, and the stress-strain model with strain-hardening components or strain-softening components. The effects of every parameter on the stress-strain relationship were carefully considered. The predictions of the model agree well with test data.

Mathematical and mechanical modeling of stress-strain relationship of pericardium

1975 ◽  
Vol 229 (4) ◽  
pp. 896-900 ◽  
Author(s):  
SW Rabkin ◽  
PH Hsu
Keyword(s):  
Experimental Data ◽  
Mechanical Model ◽  
Soft Tissues ◽  
Mechanical Modeling ◽  
Stress Strain ◽  
Mathematical Expressions ◽  
Strain Relationship ◽  
Relationship Of

Several mathematical expressions (models) were compared for use in describing the stress-strain (sigma - epsilon) relationship of pericardium. The expression sigma = alpha[ebeta epsilon - 1] was preferred because of its simpler form, theoretical consistency, and "good fit" of experimental data. A method was developed for estimating the precisions of the estimates of the parameters alpha and beta. This approach can have general usefulness in assessing the significance of a change in stress-strain relationship of various soft tissues following different interventions. A mechanical model was formulated for the pericardium which consisted of springs representing the collagen and elastin fibers connected in parallel. It could be simulated by the above equation and could describe the behavior of the pericardium.

scholarly journals Comparing thixotropic and Herschel–Bulkley parameterizations for continuum models of avalanches and subaqueous debris flows

2018 ◽  
Vol 18 (1) ◽  
pp. 303-319 ◽  
Author(s):  
Chan-Hoo Jeon ◽  
Ben R. Hodges
Keyword(s):  
Experimental Data ◽  
Debris Flows ◽  
Fluid Model ◽  
Liquid Mixtures ◽  
High Yield ◽  
Aging Effects ◽  
Stress Strain ◽  
Experimental Conditions ◽  
Wide Range ◽  
Strain Relationship

Abstract. Avalanches and subaqueous debris flows are two cases of a wide range of natural hazards that have been previously modeled with non-Newtonian fluid mechanics approximating the interplay of forces associated with gravity flows of granular and solid–liquid mixtures. The complex behaviors of such flows at unsteady flow initiation (i.e., destruction of structural jamming) and flow stalling (restructuralization) imply that the representative viscosity–stress relationships should include hysteresis: there is no reason to expect the timescale of microstructure destruction is the same as the timescale of restructuralization. The non-Newtonian Herschel–Bulkley relationship that has been previously used in such models implies complete reversibility of the stress–strain relationship and thus cannot correctly represent unsteady phases. In contrast, a thixotropic non-Newtonian model allows representation of initial structural jamming and aging effects that provide hysteresis in the stress–strain relationship. In this study, a thixotropic model and a Herschel–Bulkley model are compared to each other and to prior laboratory experiments that are representative of an avalanche and a subaqueous debris flow. A numerical solver using a multi-material level-set method is applied to track multiple interfaces simultaneously in the simulations. The numerical results are validated with analytical solutions and available experimental data using parameters selected based on the experimental setup and without post hoc calibration. The thixotropic (time-dependent) fluid model shows reasonable agreement with all the experimental data. For most of the experimental conditions, the Herschel–Bulkley (time-independent) model results were similar to the thixotropic model, a critical exception being conditions with a high yield stress where the Herschel–Bulkley model did not initiate flow. These results indicate that the thixotropic relationship is promising for modeling unsteady phases of debris flows and avalanches, but there is a need for better understanding of the correct material parameters and parameters for the initial structural jamming and characteristic time of aging, which requires more detailed experimental data than presently available.

An Incremental Formulation of Constitutive Equations for Deposited Snow

1980 ◽  
Vol 25 (92) ◽  
pp. 289-307 ◽  
Author(s):  
J. Desrues ◽  
F. Darve ◽  
E. Flavigny ◽  
J.P. Navarre ◽  
A. Taillefer
Keyword(s):  
Experimental Data ◽  
Axial Strain ◽  
Triaxial Tests ◽  
Stress Strain ◽  
Theoretical Formulation ◽  
Non Linear ◽  
Incremental Formulation ◽  
Strain Relationship ◽  
Strain Paths ◽  
Incremental Form

AbstractThe behaviour of a snow mass under natural loadings (gravity forces, boundary conditions) can be computed by the finite-element method, in so far as a convenient formulation of the stress–strain relationship for snow is available. This paper deals with such a formulation given in incremental form.Experiments have been performed, which show that deposited snow can be considered as a non-linear visco-elastic material with memory effect. The proposed theoretical formulation takes into account these properties. The elastic part of the deformation is assumed to be isotropic and non-linear; the viscous part is expressed in terms of a creep-rate, which results from a superposition of elementary creep-rates according to Boltzmann’s principle.The values of parameters can be obtained from isotropic creep experiments. The experimental data and the resulting parameters are reported.Since the parameters were determined, the formulation of the rheological law was then tested by integration on “stress–strain paths" corresponding to other experiments of a different type, performed on the same snow. The experiments are triaxial tests at constant axial strain-rate, with a preliminary stage of isotropic compression. Experimental data are compared to theoretical curves obtained by integration of the rheological law. The calculated behaviour is consistent with the experimental results.

scholarly journals Comparison of Stress-Strain Relationship for Confined Concrete Using Two-Dimensional Fiber-Based Cross-Sectional Analysis

2021 ◽  
Vol 4 (2) ◽  
pp. 93
Author(s):  
Nia Dwi Puspitasari ◽  
Aulia Dewi Fatikasari
Keyword(s):  
Experimental Data ◽  
Reinforced Concrete ◽  
Constitutive Model ◽  
Concrete Column ◽  
Two Dimensional ◽  
Reinforced Concrete Column ◽  
Stress Strain ◽  
Cross Sectional ◽  
Strain Relationship ◽  
Sectional Analysis

Stress-strain relationship is the main parameter to identify the strength, ductility and behavior of the structure. Various constitutive models were created in order to simplify the analytical approach of concrete behavior. In this paper, the behavior of reinforced concrete column is modeled using Attard and Setunge�s (1996) and Mander�s (1988) stress-strain constitutive model. The appropriate model for reinforced concrete column was determined based on the existing experimental data. Two-dimensional simulation of reinforced concrete column using fiber-based cross-sectional analysis in MATLAB is sighted. And the performance of the reinforced concrete column from the experimental data is compared with the analysis result from the simulation. There are two comparation methods used in this research. The first method is to compare the linear regression with the reference line. The smallest degree between the linear regression and the referrence line is expected. The second method is to compare the Root Mean Square Defiation (RMSD) value. The smallest RMSD value is expected to get the most suitable constitutive model compared to the experimental data. From the computational process, it was found that Mander�s Constitutive model is preferaed to be used in further analysis problem concerning reinforced concrete column

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