A coarse-grained molecular dynamics-based asphalt zero-shear viscosity simulation method
By combining coarse-grained molecular dynamics and non-equilibrium SLLOD algorithms with Fourier transform filters, the problems of high computational cost and scale limitations of traditional methods in simulating asphalt's zero-shear viscosity at 60 °C are solved. Stable viscosity data under low shear rate are achieved, providing accurate simulation of the high-temperature performance of asphalt.
Patent Information
- Application Number
- CN202610490891.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-04-14
- Publication Date
- 2026-07-07
AI Technical Summary
Traditional all-atom molecular dynamics methods are computationally expensive when simulating asphalt at zero shear viscosity at 60 °C, making it difficult to effectively simulate rheological behavior under low shear rates. Furthermore, traditional methods are insufficient to reveal the complex microstructure of asphalt and the mechanisms underlying its high-temperature performance.
By employing coarse-grained molecular dynamics combined with the non-equilibrium SLLOD algorithm, a full-atom and coarse-grained model is established, a shear flow field is applied, and a Fourier transform filter is used to filter out high-frequency noise. The zero-shear viscosity of asphalt is then fitted using the Cross and Carreau models.
It significantly expanded the simulated shear rate range, improved the simulation signal-to-noise ratio, successfully observed the zero-shear viscosity plateau region, and provided a reliable evaluation index for the high-temperature performance of asphalt.
Smart Images
Figure CN122348002A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the interdisciplinary field of road engineering materials and computational materials science, and relates to a method for simulating the zero-shear viscosity of asphalt, specifically a method for simulating the zero-shear viscosity of asphalt based on coarse-grained molecular dynamics. Background Technology
[0002] The zero-shear viscosity of asphalt at 60 °C is one of the important indicators for evaluating its high-temperature deformation resistance. The high-temperature performance of asphalt is affected by the coupling effect of its complex chemical composition and multi-level structural characteristics. Traditional test methods are difficult to reveal the complex microstructure of asphalt and its mechanism of action, resulting in a lack of clear mechanistic guidance for improving its high-temperature performance.
[0003] Molecular dynamics simulations provide an effective means of studying the relationship between the microstructure and macroscopic properties of materials. Traditional all-atom molecular dynamics methods require explicit characterization of each atom, resulting in high computational costs and limited simulation time and spatial scales. While they can simulate the shear-thinning behavior of asphalt at high shear rates, at low shear rates, the time required for the system to reach steady state is long, and the computational cost of all-atom simulations is extremely high, making it difficult to effectively simulate the 60 °C zero-shear viscosity plateau region of asphalt. Coarse-grained molecular dynamics methods, by mapping several atoms or atomic groups as coarse-grained beads, significantly reduce the model's degrees of freedom and expand the simulation time and spatial scales, providing a new approach for simulating the long-term rheological behavior of asphalt. Summary of the Invention
[0004] This invention provides a method for simulating the zero-shear viscosity of asphalt based on coarse-grained molecular dynamics. It aims to combine a coarse-grained model with the non-equilibrium SLLOD algorithm to simulate the rheological behavior of asphalt at different shear rates, particularly its zero-shear viscosity, as a reliable evaluation index for the high-temperature performance of asphalt. Compared to existing technologies, this invention overcomes the scale limitations of traditional all-atom simulations at low shear rates, significantly improves the simulation signal-to-noise ratio, and for the first time obtains the zero-shear viscosity plateau region of asphalt through simulation, providing a feasible method for the accurate simulation of the high-temperature performance of asphalt.
[0005] The objective of this invention is achieved through the following technical solution:
[0006] A method for simulating zero-shear viscosity of asphalt based on coarse-grained molecular dynamics includes the following steps:
[0007] Step 1: Establish a fully atomic and coarse-grained model of asphalt:
[0008] A variety of matrix asphalt samples with different high-temperature performance were obtained, and their element content, component content and viscosity at 60℃ were tested. Based on the element content and component content, the representative molecular types and proportions contained in the asphalt were determined. The molecules were combined in proportion and the asphalt’s all-atom (AA) and coarse-grained (CG) models were established.
[0009] Step 2: Obtain the equilibrium structure through molecular dynamics simulations:
[0010] The equilibrium structures of the AA and CG systems at 333.15 K (60 °C) were obtained by MD simulation;
[0011] Step 3: Apply the shear flow field using the SLLOD algorithm to simulate the rheological behavior of asphalt under different shear rates:
[0012] Step 31: Use the SLROD algorithm in An in-plane shear flow field is applied, where The direction is the flow direction. The direction is the direction of the velocity gradient;
[0013] Step 32: Set the simulated deformation rate respectively. For: 10 -3 10 -4 10 -5 10 -6 10 -7 10 -8 10 -9 10 -10 and 10 -11 nm / ps;
[0014] Step 33: Set the shear simulation time to 30~500 ns according to the different shear rates;
[0015] Step 4: Perform frequency domain analysis on the shear stress signal using a Fourier transform filter:
[0016] Step 41: Use a Fourier transform filter to perform frequency domain analysis on the simulated shear stress time series, set a reasonable high-frequency cutoff threshold, filter out high-frequency noise, and retain only the low-frequency stress response signal.
[0017] Step 42: Calculate the signal-to-noise ratio (SNR) of the shearing simulation process using the SNR formula under logarithmic scaling to evaluate the stability and effectiveness of the simulation;
[0018] Step 5: Calculate the shear rate and shear viscosity using the following formulas:
[0019]
[0020] In the formula, Shear rate; To along the height of the box Deformation rate in the direction; For the box in The height of the direction;
[0021]
[0022] In the formula, Shear viscosity, Pressure in the shear direction; Shear stress;
[0023] Step 6: Fit the zero-shear viscosity of asphalt using the Cross and Carreau models respectively.
[0024] Compared with the prior art, the present invention has the following advantages:
[0025] 1. This invention combines coarse-grained molecular dynamics with the non-equilibrium SLLOD algorithm to successfully extend the shear rate range for asphalt shear viscosity simulation, from approximately 10 in traditional all-atom methods. 5 ~10 9 s -1 Expand to 1~10 9 s -1 It can cover a wider range of rheological behaviors.
[0026] 2. This invention significantly improves the simulation signal-to-noise ratio through a coarse-graining method, and for the first time successfully observes the zero-shear viscosity plateau region of asphalt through simulation.
[0027] 3. This invention employs a Fourier transform filter to effectively filter out high-frequency noise, overcoming the problem that stress signals are masked by thermal fluctuation noise under low shear rates, ensuring the stability of viscosity data in the low-speed region, and providing a reliable basis for the physical extrapolation of zero-shear viscosity. Attached Figure Description
[0028] Figure 1 The following are schematic diagrams of the full-atom and coarse-grained simulation steps and structures: (a) AAMD, (b) CGMD.
[0029] Figure 2 The diagram shows a simulation of asphalt shearing: (a) equilibrium structure, (b) velocity profile, (c) shear rate profile, and (d) shear structure.
[0030] Figure 3 The simulated signal-to-noise ratio diagrams for the AA and CG systems are shown.
[0031] Figure 4 The figure shows the simulation results of the viscosity of the AA and CG systems at 60℃.
[0032] Figure 5The figures show the fitting results of zero-shear viscosity at 60℃ based on simulated data: (a) Viscosity at 60℃ fitted based on the Cross model, and (b) Viscosity at 60℃ fitted based on the Carreau model. Detailed Implementation
[0033] The technical solution of the present invention will be further described below with reference to the accompanying drawings, but it is not limited thereto. Any modifications or equivalent substitutions to the technical solution of the present invention that do not depart from the spirit and scope of the technical solution of the present invention should be covered within the protection scope of the present invention.
[0034] This invention provides a method for simulating the zero-shear viscosity of asphalt based on coarse-grained molecular dynamics. The method first establishes an all-atom and coarse-grained model of asphalt, obtaining the equilibrium structure through molecular dynamics simulation. Then, the SLLOD algorithm is used to apply a shear flow field, simulating the rheological behavior of asphalt under different shear rates. To effectively filter out high-frequency noise, a Fourier transform filter is used to perform frequency domain analysis on the shear stress signal, filtering out high-frequency noise and retaining low-frequency signals to ensure the stability of viscosity data at low shear rates. Finally, the zero-shear viscosity of asphalt is obtained by fitting the Cross model and the Carreau model. The specific steps are as follows:
[0035] Step 1: Select three base asphalt samples with significantly different high-temperature properties and test their elemental content, component content, and viscosity at 60 °C. Based on the elemental and component contents, determine the representative molecular types and proportions in the asphalt. Combine the molecules proportionally and establish a full-atom and coarse-grained model of the asphalt. The modeling steps are as follows: Figure 1 As shown.
[0036] Step 2: Obtain the equilibrium structure of the AA and CG systems at 333.15 K (60 ℃) through MD simulation. The size of the equilibrium box is approximately 20 nm × 20 nm × 20 nm.
[0037] Step 3: Using the SLROD algorithm in An in-plane shear flow field is applied, where The direction is the flow direction. The direction is the velocity gradient direction. The simulated deformation rate is set accordingly. For: 10 -3 10 -4 10 -5 10 -6 10 -7 10 -8 10 -9 10 -10 and 10 -11nm / ps. Considering that the smaller the shear rate, the longer the time required for the system to reach steady state, the shear simulation time is set to 30~500 ns depending on the shear rate. Specifically, the AA simulation uses a 1 fs time step, while the CG simulation uses 5 fs and 10 fs time steps. The shear simulation is illustrated in the diagram below. Figure 2 As shown.
[0038] Step 4: A Fourier transform filter is used to perform frequency domain analysis on the simulated shear stress time series. A reasonable high-frequency cutoff threshold is set to filter out high-frequency noise, retaining only the low-frequency stress response signal. The signal-to-noise ratio (SNR) of the shear simulation process is calculated using the logarithmic scale formula to evaluate the stability and effectiveness of the simulation. The SNR of the AA and CG systems varies with shear rate as follows: Figure 3 As shown.
[0039]
[0040] In the formula, Signal-to-noise ratio (dB); The effective power of the signal (W); The effective power of the noise (W); The smoothed shear stress sequence (MPa); To simulate the difference between shear stress and smooth shear stress (MPa); The length of the signal or noise sequence.
[0041] Step 5: Calculate the shear rate and shear viscosity using the following formulas:
[0042]
[0043] In the formula, Shear rate (1 / ps); To along the height of the box Deformation rate in the direction (nm / ps); For the box in Height in the direction (nm).
[0044] Simulated shear viscosity Calculated based on Newton's fluid constitutive relation:
[0045]
[0046] In the formula, Shear rate (1 / ps); Pressure (bar) in the shear direction; Shear stress (MPa).
[0047] Two parallel simulations were performed for each operating condition, and the final viscosity value was the average of the two parallel simulations. The viscosity simulation results for the AA and CG system at 60℃ are as follows: Figure 4 As shown.
[0048] Step Six: Fit the zero-shear viscosity of asphalt using the Cross and Carreau models respectively. Based on the simulation data, fit the zero-shear viscosity at 60℃ as follows: Figure 5 As shown.
[0049] The formulas for the Cross and Carreau models are as follows:
[0050]
[0051]
[0052] In the formula, Shear viscosity (Pa·s); This is the first Newtonian viscosity, i.e., the zero-shear viscosity (Pa·s); The viscosity (Pa·s) in the second Newtonian zone of the flow curve. The shear rate is 1 / s. , denoted as a characteristic constant of the material.
Claims
1. A method for simulating zero-shear viscosity of asphalt based on coarse-grained molecular dynamics, characterized in that... The method includes the following steps: Step 1: Establish the all-atom AA and coarse-grained CG models of asphalt; Step 2: Obtain the equilibrium structure through molecular dynamics simulation; Step 3: Apply the shear flow field using the SLLOD algorithm to simulate the rheological behavior of asphalt under different shear rates; Step 4: Perform frequency domain analysis on the shear stress signal using a Fourier transform filter; Step 5: Calculate the shear rate and shear viscosity; Step 6: Fit the zero-shear viscosity of asphalt using the Cross and Carreau models respectively.
2. The method for simulating zero-shear viscosity of asphalt based on coarse-grained molecular dynamics according to claim 1, characterized in that... The specific steps of step 1 are as follows: Multiple base asphalt samples with significant differences in high-temperature performance were obtained, and their elemental content, component content, and viscosity at 60℃ were tested. Based on the elemental and component contents, the representative molecular types and proportions contained in the asphalt were determined, and the molecules were combined in proportion to establish a fully atomic and coarse-grained model of the asphalt.
3. The method for simulating zero-shear viscosity of asphalt based on coarse-grained molecular dynamics according to claim 1, characterized in that... In step 2, the equilibrium structure of the AA and CG systems at 333.15 K is obtained through MD simulation.
4. The method for simulating zero-shear viscosity of asphalt based on coarse-grained molecular dynamics according to claim 1, characterized in that... The specific steps of step 3 are as follows: Step 31: Use the SLROD algorithm in An in-plane shear flow field is applied, where The direction is the flow direction. The direction is the direction of the velocity gradient; Step 32: Set the simulated deformation rate respectively. For: 10 -3 10 -4 10 -5 10 -6 10 -7 10 -8 10 -9 10 -10 and 10 -11 nm / ps; Step 33: Set the shear simulation time to 30~500 ns according to the different shear rates.
5. The method for simulating zero-shear viscosity of asphalt based on coarse-grained molecular dynamics according to claim 1, characterized in that... The specific steps of step 4 are as follows: Step 41: Use a Fourier transform filter to perform frequency domain analysis on the simulated shear stress time series, set a reasonable high-frequency cutoff threshold, filter out high-frequency noise, and retain only the low-frequency stress response signal. Step 42: Calculate the signal-to-noise ratio (SNR) of the shearing simulation process using the SNR formula under logarithmic scaling to evaluate the stability and effectiveness of the simulation.
6. The method for simulating zero-shear viscosity of asphalt based on coarse-grained molecular dynamics according to claim 1, characterized in that... In step 5, the formula for calculating the shear rate is: In the formula, Shear rate; To along the height of the box Deformation rate in the direction; For the box in The height of the direction.
7. The method for simulating zero-shear viscosity of asphalt based on coarse-grained molecular dynamics according to claim 1, characterized in that... In step 5, the formula for calculating shear viscosity is: In the formula, Shear viscosity, For shear rate, Pressure in the shear direction; Shear stress.
8. The method for simulating zero-shear viscosity of asphalt based on coarse-grained molecular dynamics according to claim 1, characterized in that... In step 6, the formulas for the Cross and Carreau models are as follows: In the formula, Shear viscosity; The viscosity is the first Newtonian viscosity. This refers to the viscosity in the second Newtonian zone. Shear rate; , denoted as a characteristic constant of the material.