Viscoelasticplastic–Fracture Modeling of Asphalt Mixtures Under Monotonic and Repeated Loads

Abstract

Rutting and cracking occur simultaneously in asphalt mixtures as observed in the field and laboratory. Existing mechanical models have not properly addressed viscoelastic and viscoplastic deformation together with cracking due to model deficiencies, parameter calibration and numerical inefficiency. This study develops viscoelastic-plastic-fracture (VEPF) models characterizing viscoelasticity (VE) by Prony model and viscoplasticity (VP) by Perzyna's flow rule with a Generalized Drucker-Prager (GD-P) yield surface and a non-associated plastic potential. Viscofracture (VF) damage is modelled by a viscoelastic Griffith criterion and a pseudo J-integral Paris' law for crack initiation and propagation, respectively. The VEPF models are implemented in a finite element (FE) program using a weak form partial differential equation (PDE) modeling technique with no need to program user-defined material subroutines. Model parameters were derived from fundamental material properties using dynamic modulus, strength and repeated load tests. Simulations indicate that the VE-VP-VF characteristics are effectively modelled by the VEPF models for different asphalt mixtures at different confinements and temperatures. An asphalt mixture under monotonic compressive loads exhibits a sequenced process including a pure VE deformation stage, a coupled VE-VP deformation stage, a VE-VP deformation coupled with VF initiation and propagation stage, and then a VE-VF rupture stage with saturated VP deformation. The asphalt mixture under repeated loads yields an increasing VP strain at an increasing rate during the first half of the haversine load while a decreasing VP strain increment with load cycles. The PDE-based FE is capable of effectively modeling the coupled VE-VP-VF behaviors of the asphalt mixtures.

Modeling Stress-Dependent Anisotropic Elastoplastic Unbound Granular Base in Flexible Pavements

“…The viscoplastic and viscofracture properties of the asphalt concrete have also been coupled in the viscoelastic constitutive models based on the weak-form PDE based FE method (26). It demonstrates that accurate viscoelastic and viscoplastic responses can be modeled and predicted for the asphalt concrete.…”

“…The viscoelastic constitutions of asphalt concrete have been successfully modeled using a weak-form partial differential equation (PDE)-based FEM technique in COMSOL Multiphysics program ( 22 ). The viscoplastic and viscofracture properties of the asphalt concrete have also been coupled in the viscoelastic constitutive models based on the weak-form PDE based FEM method ( 26 ). It demonstrates that accurate viscoelastic and viscoplastic responses can be modeled and predicted for the asphalt concrete.…”

“…Unlike using Abaqus, there is no need for this method to program a user-defined material subroutine. In this study, the authors continue modeling the asphalt concrete using the PDE FEM method while only considering its viscoelastic responses, details of which are referred to the above two publications ( 22, 26 ).…”

Backcalculation of damage density of in‐service asphalt pavements using artificial intelligence‐based finite element model updating

“…The effective stress has been successfully applied in the damage characterization of asphalt mixtures under different loading modes 25,26 . The relations between apparent and effective stresses and strains are presented in Equations 1 and 2, 27 where and are the apparent stress and strain tensors; and are the effective stress and strain tensors; is the damage density.…”

“…As Equation 7, the stress–strain relation of viscoelastic materials can be expressed as Equation 18. By introducing the damage density and apparent stress and strain tensors, the final form of the stress–strain relation of viscoelastic materials in this study is shown in Equation 19, 27 …”