A viscoplastic model for rate-dependent hardening for asphalt concrete in compression

The discrete element method (DEM) represents a convenient and powerful tool for studying effects of material microstructure on fracture mechanisms in asphalt concrete. In this paper, the rate-dependency of asphalt concrete is investigated using a cohesive zone model with bulk viscoelastic properties combined with bilinear post-peak softening. Details of the constitutive models implemented in the DEM, with particular emphasis on the verification of viscoelastic models, are presented. Experimental test results based on a disk-shaped compact tension test are obtained under different loading rates and those are compared to numerical simulations with the help of the rate-dependent model. Homogeneous and heterogeneous model results are compared, where heterogeneous models are constructed to consider aggregate morphology for particles larger than 1.18 mm. The relative importance of time-dependence and the consideration of material heterogeneity in the simulation of monotonic Mode I fracture tests are demonstrated.

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A new viscoplastic model and experimental characterization for thermosetting resins

10.31224/osf.io/e257f ◽

2021 ◽

Author(s):

Ehsan Shafiei

Keyword(s):

Stress Tensor ◽

Hydrostatic Stress ◽

Three Dimensional ◽

Shear Loading ◽

Model Parameters ◽

Rate Dependency ◽

Viscoplastic Model ◽

Rate Dependent ◽

Initial Modulus ◽

Dependent Model

Resins as matrix materials for structural composites show nonlinear rate-dependent mechanical behaviors. In thepresent work, a new viscoplastic constitutive equation based on a potential function is proposed to predict themechanical response of an epoxy matrix to any three-dimensional loading condition. The proposed potentialfunction is a combination of the second and third invariants of the deviatoric stress tensor as well as the firstinvariant of the stress tensor, i.e. the hydrostatic stress. Series of tensile and shear constant-rate straining testswere performed on epoxy resin specimens up to the fracture. Under shear loading, the nonlinearity of the stressstrain curve and the rate dependency of the initial modulus and strength are more significant than that undertensile loading. The viscoplastic model parameters are derived from the experimental data, and the fracturepatterns of the specimens under tensile and shear loadings are studied. Further, the model predictions arecompared with a known rate-dependent model to show the accuracy of the presented model.

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An Elastic–Viscoplastic Model for Excised Facial Tissues

Journal of Biomechanical Engineering ◽

10.1115/1.2834762 ◽

1998 ◽

Vol 120 (5) ◽

pp. 686-689 ◽

Cited By ~ 33

Author(s):

M. B. Rubin ◽

S. R. Bodner ◽

N. S. Binur

Keyword(s):

Relaxation Time ◽

Constitutive Equations ◽

Inelastic Deformation ◽

Viscoplastic Model ◽

Rate Dependent ◽

Hardening Effect ◽

Superficial Musculoaponeurotic System ◽

Time Period ◽

Highly Nonlinear ◽

Nonlinear Elastic

Unified constitutive equations for elastic–viscoplastic materials were modified and used to model the highly nonlinear elastic and rate-dependent inelastic response exhibited in recent experiments on excised facial tissues. These included the skin and the underlying supportive tissue SMAS (the Superficial Musculoaponeurotic System). This study indicates a number of relevant results: The skin is more strain rate dependent than the SMAS; the nonlinearity of the elasticity of the skin is greater than that of the SMAS; both tissues exhibit a hardening effect indicated by increased resistance to inelastic deformation due to stress acting over a time period; the hardening effect leads to a decrease in time dependence and an increased elastic range, which is more pronounced for SMAS. Consequently, the SMAS can be viewed as the firmer elastic foundation of the more viscous skin. Moreover, the relaxation time for the skin is fairly short so the skin would be expected to conform to the deformation of the SMAS if it remained attached to the SMAS during stretching. This is relevant when it is undesirable to separate the skin from the SMAS for physiological reasons.

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Cyclic Elasto-viscoplastic Model for Asphalt Concrete Materials

Road Materials and Pavement Design ◽

10.1080/14680629.2007.9690074 ◽

2007 ◽

Vol 8 (2) ◽

pp. 239-255 ◽

Cited By ~ 7

Author(s):

Dang-Truc Nguyen ◽

Boumediene Nedjar ◽

Philippe Tamagny

Keyword(s):

Asphalt Concrete ◽

Viscoplastic Model ◽

Concrete Materials

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A damage-coupled viscoplastic model for compressed asphalt concrete

Journal of Physics Conference Series ◽

10.1088/1742-6596/1748/6/062059 ◽

2021 ◽

Vol 1748 ◽

pp. 062059

Author(s):

Guowei Zeng ◽

Lei Liu ◽

Fan Bai

Keyword(s):

Asphalt Concrete ◽

Viscoplastic Model

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

Transportation Research Record Journal of the Transportation Research Board ◽

10.3141/1630-01 ◽

1998 ◽

Vol 1630 (1) ◽

pp. 3-9 ◽

Cited By ~ 6

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.

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