Relationships Among Rate-Dependent Stiffnesses of Asphalt Concrete Using Laboratory and Field Test Methods

1998 ◽  
Vol 1630 (1) ◽  
pp. 3-9 ◽  
Author(s):  
Jo Sias Daniel ◽  
Y. Richard Kim
Keyword(s):  
Asphalt Concrete ◽  
Creep Compliance ◽  
Complex Modulus ◽  
Relaxation Modulus ◽  
Test Methods ◽  
Rate Dependent ◽  
Creep Stiffness ◽  
Linear Viscoelastic ◽  
Linear Viscoelastic Theory ◽  
Falling Weight

As the application of nondestructive testing on pavements in service becomes more frequent, it is increasingly important to relate the resulting stiffnesses to those from laboratory test methods. The relationship among stiffnesses measured from five test methods currently used for asphalt concrete is addressed: creep compliance, complex modulus, impact resonance, falling weight deflectometer, and surface wave. Established relationships from linear viscoelastic theory are used to relate stiffnesses, including a comparison of creep stiffness, S( t), and relaxation modulus, E( t), calculated from creep compliance, D( t). Using laboratory and field measured stiffnesses, a linear relationship was discovered between stiffness and frequency on a log-log scale.

Interconversion of Frequency Domain Complex Modulus to Time Domain Modulus and Compliance of Asphalt Concrete: Numerical Modeling and Laboratory Validation

2016 ◽  
Author(s):  
A. S. M. Asifur Rahman ◽  
Rafiqul A. Tarefder
Keyword(s):  
Viscoelastic Material ◽  
Asphalt Concrete ◽  
Creep Compliance ◽  
Complex Modulus ◽  
Relaxation Modulus ◽  
Modulus Function ◽  
Approximate Methods ◽  
Material Functions ◽  
Linear Viscoelastic Material ◽  
Linear Viscoelastic

Viscoelastic material functions such as time domain functions, such as, relaxation modulus and creep compliance, or frequency domain function, such as, complex modulus can be used to characterize the linear viscoelastic behavior of asphalt concrete in modeling and analysis of pavement structure. Among these, the complex modulus has been adopted in the recent pavement Mechanistic-Empirical (M-E) design software AASHTOWare-ME. However, for advanced analysis of pavement, such as, use of finite element method requires that the complex modulus function to be converted into relaxation modulus or creep compliance functions. There are a number of exact or approximate methods available in the literature to convert complex modulus function to relaxation modulus or creep compliance functions. All these methods (i.e. exact or approximate methods) are applicable for any linear viscoelastic material up to a certain level of accuracy. However, the applicability and accuracy of these interconversion methods for asphalt concrete material were not studied very much in the past and thus question arises if these methods are even applicable in case of asphalt concrete, and if so, what is the precision level of the interconversion method being used. Therefore, to investigate these facts, this study undertaken an effort to validate a numerical interconversion technique by conducting representative laboratory tests. Cylindrical specimens of asphalt concrete were prepared in the laboratory for conducting complex modulus, relaxation modulus, and creep compliance tests at different test temperatures and loading rates. The time-temperature superposition principle was applied to develop broadband linear viscoelastic material functions. A numerical interconversion technique was used to convert complex modulus function to relaxation modulus and creep compliance functions, and hence, the converted relaxation modulus and creep compliance are compared to the laboratory tested relaxation modulus and creep compliance functions. The comparison showed good agreement with the laboratory test data. Toward the end, a statistical evaluation was conducted to determine if the interconverted material functions are similar to the laboratory tested material functions.

Obtaining shear relaxation modulus and creep compliance of linear viscoelastic materials from instrumented indentation using axisymmetric indenters of power-law profiles

2009 ◽  
Vol 24 (10) ◽  
pp. 3013-3017 ◽  
Author(s):  
Yang-Tse Cheng ◽  
Fuqian Yang
Keyword(s):  
Inverse Problem ◽  
Laplace Transform ◽  
Power Law ◽  
Creep Compliance ◽  
Relaxation Modulus ◽  
Instrumented Indentation ◽  
Loading Paths ◽  
Linear Viscoelastic ◽  
Shear Relaxation ◽  
Analytical Expressions

Using Laplace transform, we solve the inverse problem of obtaining the shear relaxation modulus and creep compliance of linear viscoelastic solids from indentation by axisymmetric indenters of power-law profiles. We identify several simple, though nontrivial, loading paths for carrying out indentation measurements such that the inverse problem has analytical solutions. We show that the shear relaxation modulus and creep compliance may be readily obtained using the newly derived analytical expressions together with proposed indentation loading paths.

scholarly journals A New Viscoelasticity Dynamic Fitting Method Applied for Polymeric and Polymer-Based Composite Materials

Materials ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 5213
Author(s):  
Vitor Dacol ◽  
Elsa Caetano ◽  
João Correia
Keyword(s):  
Composite Materials ◽  
Dynamic Behaviour ◽  
Creep Compliance ◽  
Complex Modulus ◽  
Relaxation Modulus ◽  
Viscoelastic Behaviour ◽  
Harmonic Load ◽  
Load Case ◽  
Accurate Analysis ◽  
Complex Moduli

The accurate analysis of the behaviour of a polymeric composite structure, including the determination of its deformation over time and also the evaluation of its dynamic behaviour under service conditions, demands the characterisation of the viscoelastic properties of the constituent materials. Linear viscoelastic materials should be experimentally characterised under (i) constant static load and/or (ii) harmonic load. In the first load case, the viscoelastic behaviour is characterised through the creep compliance or the relaxation modulus. In the second load case, the viscoelastic behaviour is characterised by the complex modulus, E*, and the loss factor, η. In the present paper, a powerful and simple implementing technique is proposed for the processing and analysis of dynamic mechanical data. The idea is to obtain the dynamic moduli expressions from the Exponential-Power Law Method (EPL) of the creep compliance and the relaxation modulus functions, by applying the Carson and Laplace transform functions and their relationship to the Fourier transform, and the Theorem of Moivre. Reciprocally, once the complex moduli have been obtained from a dynamic test, it becomes advantageous to use mathematical interconversion techniques to obtain the time-domain function of the relaxation modulus, E(t), and the creep compliance, D(t). This paper demonstrates the advantages of the EPL method, namely its simplicity and straightforwardness in performing the desirable interconversion between quasi-static and dynamic behaviour of polymeric and polymer-composite materials. The EPL approximate interconversion scheme to convert the measured creep compliance to relaxation modulus is derived to obtain the complex moduli. Finally, the EPL Method is successfully assessed using experimental data from the literature.

Effectiveness of static and dynamic backcalculation approaches for asphalt pavement

2020 ◽  
Vol 47 (7) ◽  
pp. 846-855
Author(s):  
Dandan Cao ◽  
Changjun Zhou ◽  
Yanqing Zhao ◽  
Guozhi Fu ◽  
Wanqiu Liu
Keyword(s):  
Asphalt Concrete ◽  
Elastic Moduli ◽  
Complex Modulus ◽  
Asphalt Pavement ◽  
Falling Weight Deflectometer ◽  
Fixed Frequency ◽  
Dynamic Approach ◽  
Layer Effect ◽  
Static Approach ◽  
Falling Weight

In this study, the field falling weight deflectometer (FWD) data for asphalt pavement with various base types were backcalculated through dynamic and static backcalculation approaches, and the effectiveness of backcalculation approaches was studied. Asphalt concrete (AC) was treated as a viscoelastic material and the complex modulus was obtained using the dynamic approach. The dynamic modulus at a fixed frequency was computed for comparison purposes. The coefficient of variance and the compensating layer effect were assumed as two characteristics for the effectiveness of backcalculation approaches. The results show that the layer property from the dynamic backcalculation approach for different stations were more consistent and showed smaller coefficient of variance, which were more appropriate for the characterization pavement behavior. The elastic moduli from the static approach were more variable and exhibited a compensating layer effect in which a portion of the modulus of one layer was backcalculated into other layers. The dynamic approach is more effective than static approaches in backcalculation of layer properties.

Interpretation of Indirect Tension Test Based on Viscoelasticity

1997 ◽  
Vol 1590 (1) ◽  
pp. 45-52 ◽  
Author(s):  
A. Drescher ◽  
D. E. Newcomb ◽  
W. Zhang
Keyword(s):  
Asphalt Concrete ◽  
Complex Modulus ◽  
Resilient Modulus ◽  
Traditional Approach ◽  
Test Methods ◽  
Tension Test ◽  
Current Test ◽  
Indirect Tension ◽  
Materials Used ◽  
Indirect Tension Test

The diametral indirect tension test is a convenient configuration for determining the modulus of asphalt concrete samples. The resilient modulus test has been a traditional approach to characterizing the stiffness of asphalt concrete, but it leaves much to be desired when considering the viscous behavior this material exhibits, even at low temperatures. A method for determining the complex compliance, complex modulus, and phase angle of asphalt mixtures using the indirect tensile test and a haversine load history is presented here. This test may be performed over a range of frequencies and temperatures as demonstrated on materials used in the Minnesota Road Research Project. The use of the haversine loading simplifies the test when compared with the pulse loading and rest time used in the resilient modulus test, and it allows for the characterization of the elastic and viscous components of the material's overall behavior, which is very difficult, at best, with the current test methods.

Mechanistic-Based Approach to Utilize Traffic Speed Deflectometer Measurements in Backcalculation Analysis

2020 ◽  
Vol 2674 (5) ◽  
pp. 208-222
Author(s):  
Zia U. A. Zihan ◽  
Mostafa A. Elseifi ◽  
Patrick Icenogle ◽  
Kevin Gaspard ◽  
Zhongjie Zhang
Keyword(s):  
Asphalt Concrete ◽  
Traffic Control ◽  
Parametric Study ◽  
Complex Modulus ◽  
Falling Weight Deflectometer ◽  
Software Application ◽  
Traffic Speed ◽  
Definition Of ◽  
Falling Weight ◽  
Surface Deflections

Backcalculation analysis of pavement layer moduli is typically conducted based on falling weight deflectometer (FWD) deflection measurements; however, the stationary nature of the FWD requires lane closure and traffic control. In recent years, traffic speed deflection devices such as the traffic speed deflectometer (TSD), which can continuously measure pavement surface deflections at traffic speed, have been introduced. In this study, a mechanistic-based approach was developed to convert TSD deflection measurements into the equivalent FWD deflections. The proposed approach uses 3D-Move software to calculate the theoretical deflection bowls corresponding to FWD and TSD loading configurations. Since 3D-Move requires the definition of the constitutive behaviors of the pavement layers, cores were extracted from 13 sections in Louisiana and were tested in the laboratory to estimate the dynamic complex modulus of asphalt concrete. The 3D-Move generated deflection bowls were validated with field TSD and FWD data with acceptable accuracy. A parametric study was then conducted using the validated 3D-Move model; the parametric study consisted of simulating pavement designs with varying thicknesses and material properties and their corresponding FWD and TSD surface deflections were calculated. The results obtained from the parametric study were then incorporated into a Windows-based software application, which uses artificial neural network as the regression algorithm to convert TSD deflections to their corresponding FWD deflections. This conversion would allow backcalculation of layer moduli using TSD-measured deflections, as equivalent FWD deflections can be used with readily available tools to backcalculate the layer moduli.

Characterization of Viscoelastic Behavior of Stereoregular Poly(Isoprenes) by Relaxation Experiments

1974 ◽  
Vol 47 (1) ◽  
pp. 1-18
Author(s):  
L. Szilagyi ◽  
T. Riccò ◽  
F. Danusso
Keyword(s):  
Viscoelastic Behavior ◽  
Supermolecular Structure ◽  
Relaxation Modulus ◽  
Mechanical Relaxation ◽  
Recent Theory ◽  
Mean Values ◽  
Linear Viscoelastic ◽  
Viscoelastic Theory ◽  
Linear Viscoelastic Theory ◽  
Relationship Of

Abstract The mechanical relaxation of twelve samples of unvulcanized cis poly-(isoprene)s, including both natural and synthetic polymers, was studied over a range of temperatures. Master curves of relaxation modulus obtained from these data were used to derive relaxation spectra according to linear viscoelastic theory. A recent theory was used to calculate mean values of quantities related to the supermolecular structure which occurs spontaneously in these materials and is responsible for their viscoelastic properties. This structure is schematized in a model consisting of a system of macromolecules which interact with each other by elastic forces and frictions corresponding to points of entanglement between chains. The analysis leads to the determination, for each sample, of the number of entanglements per molecule, the physical network density, the value of relaxation parameters, and the relationship of each of these quantities to molecular weight.

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