Cracking simulation test method for rubber modified asphalt mixtures

Abstract

The application discloses a kind of cracking simulation test methods for rubber modified asphalt mixture, comprising: establishing synchronous docking test and the pre-model of simulation;Pre-model built-in relaxation modulus function, relaxation modulus function reflects the influence result of viscoelastic parameter and fracture energy input parameter;Establish extended finite element simulation simulation, and send simulation analysis result to pre-model to the influence result compared with relaxation modulus function verification;Through dynamic modulus test, the master curve of dynamic modulus is established, the master curve of dynamic modulus is converted to relaxation modulus with a specific scale factor, and data results are obtained according to relaxation modulus function, and the data results are compared and verified with the influence results. The application solves the problem that it is difficult to accurately and reliably obtain road cracking data due to the poor flexibility of crack adaptation for various shapes in the prior art for the cracking research of asphalt pavement, the indoor test method has human subjectivity, and the software technology is used to simulate the pavement structure.

Description

Technical Field

[0001] This invention relates to the field of road engineering quality technology, and more specifically, to a cracking simulation test method for rubber-modified asphalt mixtures. Background Technology

[0002] Currently, rubber-asphalt pavements are prone to fatigue cracking under repeated vehicle loads and temperature changes, especially since temperature changes significantly affect the fatigue life of asphalt pavements. Existing technologies often employ approximate methods, such as applying laboratory tests to actual road surfaces, to study the fatigue life of asphalt pavements. However, laboratory tests are highly subjective, making it difficult to obtain accurate fatigue cracking data.

[0003] Furthermore, with the widespread application of software in road engineering, researchers have begun to use software technology to simulate the deformation and failure of pavement structures, such as the finite element method (CFEM). Currently, when dealing with crack problems, the CFEM must set the crack surface as the edge of the element. A very high mesh density is required in the high stress zone near the crack tip. At the same time, the mesh needs to be re-distributed when simulating crack growth. It also has poor flexibility in adapting to cracks of different shapes. The above problems also restrict the accuracy and reliability of the simulation results. Summary of the Invention

[0004] To address these issues, this invention provides a cracking simulation test method for rubber-modified asphalt mixtures. This method solves the problems in existing technologies for studying asphalt pavement cracking. The existing methods, which use indoor tests and then apply them to actual pavement, are subject to human subjectivity. Furthermore, the software technology used to simulate pavement structures has poor flexibility in adapting to cracks of various shapes, making it difficult to obtain accurate and reliable road fatigue cracking data.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A cracking simulation test method for rubber-modified asphalt mixtures includes the following steps:

[0007] Establish a pre-model for synchronous docking experiments and simulations;

[0008] The pre-model has a built-in relaxation modulus function, which can directly reflect the influence of the viscoelastic parameters and fracture energy input parameters of the rubber-modified asphalt mixture.

[0009] An extended finite element simulation was established based on viscoelastic parameters and fracture energy input parameters. The simulation results were sent to the pre-model and compared with the influence results directly reflected by the relaxation modulus function for verification.

[0010] Through dynamic modulus tests, the master curve of the dynamic modulus of rubber-modified asphalt mixture was established, and the master curve of the dynamic modulus was transformed into the relaxation modulus with a specific proportional coefficient. Furthermore, data results were obtained based on the relaxation modulus function, and the data results were compared and verified with the influence results directly reflected by the relaxation modulus function.

[0011] Based on the above technical solution, the present invention is further described as follows:

[0012] As a further aspect of the present invention, it also includes:

[0013] Before the dynamic modulus test, the displacement loading curves of rubber-modified asphalt mixtures under different aging time conditions were studied through aging tests.

[0014] As a further aspect of the present invention, the aging test of the rubber-modified asphalt mixture specifically includes:

[0015] A semi-cylinder is prefabricated, and a foundation crack is prefabricated at the center of the plane of the semi-cylinder. The plane of the semi-cylinder is placed face down on the extensometer, and the foundation crack corresponds to the displacement reading end of the extensometer.

[0016] The universal testing machine was used to apply a downward loading pressure head to the center of the curved surface of a semi-cylinder at a loading rate of 5 mm / min. The opening displacement of the foundation crack of the semi-cylinder was read with time using an extensometer. This study investigated the displacement loading curve of the rubber asphalt mixture under different aging time conditions.

[0017] As a further aspect of the present invention, the prefabricated semi-cylinder, with a foundation crack prefabricated at the center of the plane of the semi-cylinder, specifically includes:

[0018] A standard cylinder with a diameter × height of 100mm × 150mm is cut into smaller cylinders with a height of 100mm × 50mm. The smaller cylinders are then cut in half to form two sets of semi-cylinders. A foundation crack with a length of 10mm and a width of 3mm is cut at the center of the plane of the semi-cylinder.

[0019] As a further aspect of the present invention, the step of establishing an extended finite element simulation based on viscoelastic parameters and fracture energy input parameters specifically includes:

[0020] Based on the generalized Maxwell model parameters, the viscoelastic parameters and fracture energy input parameters of rubber-modified asphalt mixtures are defined. Based on the characteristic principle that the extended finite element method (XFEM) allows modeling in discontinuous states / states with underlying cracks, the cracking behavior of rubber-modified asphalt mixture specimens is simulated and analyzed using the extended finite element method (XFEM).

[0021] As a further aspect of the present invention, the step of establishing an extended finite element simulation based on viscoelastic parameters and fracture energy input parameters further includes:

[0022] A velocity boundary condition is applied to the node at the top of the simulation graphic, and the velocity is applied at the middle position of the top of the graphic. The area of ​​the velocity application is equal to the area of ​​the test loading head applied to the center position of the precast semi-cylindrical surface. The magnitude of the velocity application is consistent with the loading rate of the test loading head, which is 5 mm / min, i.e. 8.333e-5 m / s.

[0023] As a further aspect of the present invention, the step of establishing an extended finite element simulation based on viscoelastic parameters and fracture energy input parameters further includes:

[0024] The area of ​​the applied velocity and the area of ​​the test loading head acting on the center of the precast semi-cylindrical surface are both 5mm × 50mm.

[0025] As a further aspect of the present invention, the step of establishing an extended finite element simulation based on viscoelastic parameters and fracture energy input parameters further includes:

[0026] The simulation element type is an eight-node quadrilateral quadratic plane stress-reduced integral element (CPS8R), and the global seeding density of the corresponding element is 1.5 mm.

[0027] The analysis step is set to 45 seconds for the specimen, the load increment step is set to 10,000 steps, and the minimum step size is 10e. -5 The maximum step size is set to 100 to ensure that the simulation calculation model converges normally.

[0028] As a further aspect of the present invention, the step of establishing the master curve of the dynamic modulus of rubber-modified asphalt mixture through dynamic modulus testing specifically includes:

[0029] Based on the test results of the dynamic modulus test, the master curve of the dynamic modulus of rubber modified asphalt mixture was established by applying the time-temperature equivalence principle and the Sigmoidal function fitting method.

[0030] As a further aspect of the present invention, the establishment of a pre-model for synchronous docking tests and simulations specifically includes:

[0031] The pre-model's variable input / output options include stress, strain, and displacement output variables, which are used to match and interface with the stress-to-strain ratio and displacement parameters in the dynamic modulus test.

[0032] The present invention has the following beneficial effects:

[0033] This method uses foam-modified warm-mix flame-retardant rubber asphalt mixture as the basic research object when designing road-use foam-modified warm-mix flame-retardant rubber asphalt mixture. It establishes a pre-model for experimental and simulation research on the cracking behavior of foam-modified warm-mix flame-retardant rubber asphalt mixture, thereby verifying the expected experimental results and preparing model sketches for subsequent simulation research. The results of the pre-model are mutually verified by combining numerical simulation and experiments, which reduces the influence of human subjectivity on test data. It also has strong flexibility in adapting to cracks of different shapes, improves the accuracy and reliability of road fatigue cracking data, and enhances the overall functionality and practicality of the method. Attached Figure Description

[0034] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. The structures, proportions, sizes, etc., drawn in this specification are only used to complement the content disclosed in the specification, so that those skilled in the art can understand and read them. Any modifications to the structure, changes in the proportional relationships, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0035] Figure 1 This is a schematic diagram of the overall process of the cracking simulation test method for rubber-modified asphalt mixtures provided in the embodiments of the present invention.

[0036] Figure 2 This is a schematic diagram of the structure of the semi-cylindrical specimen of asphalt mixture in the cracking simulation test method for rubber-modified asphalt mixture provided in the embodiments of the present invention.

[0037] Figure 3 This is a schematic diagram of stress distribution simulation analysis of the cracking behavior of asphalt mixture in the cracking simulation test method for rubber-modified asphalt mixture provided in the embodiments of the present invention. Detailed Implementation

[0038] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] The terms "upper," "lower," "left," "right," and "middle" used in this specification are merely for clarity of description and are not intended to limit the scope of the invention. Any changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention.

[0040] like Figures 1 to 3 As shown, this invention provides a cracking simulation test method for rubber-modified asphalt mixtures. This method serves as the basis for establishing a pre-model to study the cracking behavior of rubber-modified asphalt mixtures during the design of road-use foamed warm-mix flame-retardant rubber-modified asphalt mixtures. It allows for the verification of expected experimental results and the preparation of model sketches for subsequent simulation studies. The pre-model results are then mutually verified through a combination of numerical simulation and experimental methods. This reduces the influence of human subjectivity on test data and offers strong flexibility in adapting to cracks of various shapes, improving the accuracy and reliability of obtained road fatigue cracking data. Specifically, the method includes the following steps:

[0041] S1: Establish a pre-model for synchronous docking tests and simulations;

[0042] Specifically, the pre-model's variable input / output options include stress, strain, and displacement output variables, which are used to match and interface with the stress-strain ratio and displacement parameters in the dynamic modulus test.

[0043] S2: The pre-model has a built-in relaxation modulus function, which can directly reflect the influence of the viscoelastic parameters and fracture energy input parameters of the rubber-modified asphalt mixture.

[0044] S3: Establish an extended finite element simulation based on the viscoelastic parameters and fracture energy input parameters, such as... Figure 3 The simulation analysis of stress distribution in the cracking behavior of asphalt mixture is shown. The simulation results are sent to the pre-model and compared with the influence results directly reflected by the relaxation modulus function for verification.

[0045] Specifically, the viscoelastic parameters and fracture energy input parameters of rubber-modified asphalt mixtures are defined based on the generalized Maxwell model parameters. Based on the characteristic principle that the extended finite element method (XFEM) allows modeling in discontinuous states / states with underlying cracks, the cracking behavior of rubber-modified asphalt mixture specimens is simulated and analyzed using the extended finite element method (XFEM).

[0046] The Extended Finite Element Method (XFEM) is an effective numerical method for solving discontinuity problems such as cracks and holes. This method adds an improved function term that reflects the discontinuity problem to the displacement mode of the traditional finite element method.

[0047] A velocity boundary condition is applied to the node at the top of the simulation graphic, and the velocity is applied at the middle position of the top of the graphic. The area of ​​the velocity application is equal to the area of ​​the test loading head applied to the center position of the precast semi-cylindrical surface. Both the area of ​​the velocity application and the area of ​​the test loading head applied to the center position of the precast semi-cylindrical surface are 5mm×50mm. The magnitude of the velocity application is consistent with the loading rate of the test loading head, which is 5mm / min, i.e., 8.333e-5m / s.

[0048] The simulation element type is an eight-node quadrilateral quadratic plane stress-reduced integral element (CPS8R), and the global seeding density of the corresponding element is 1.5 mm.

[0049] The analysis step is set to 45 seconds for the specimen, the load increment step is set to 10,000 steps, and the minimum step size is 10e. -5 The maximum step size is set to 100 to ensure that the simulation calculation model converges normally.

[0050] S4: Before the dynamic modulus test, the displacement loading curves of rubber-modified asphalt mixture under different aging time conditions were studied through aging tests of rubber-modified asphalt mixture.

[0051] Specifically, the aging test of the rubber-modified asphalt mixture includes:

[0052] A semi-cylinder is prefabricated, and a foundation crack is prefabricated at the center of the plane of the semi-cylinder. The plane of the semi-cylinder is placed face down on the extensometer, and the foundation crack corresponds to the displacement reading end of the extensometer.

[0053] The universal testing machine was used to apply a downward loading pressure head to the center of the curved surface of a semi-cylinder at a loading rate of 5 mm / min. The opening displacement of the foundation crack of the semi-cylinder was read with time using an extensometer. This study investigated the displacement loading curve of the rubber asphalt mixture under different aging time conditions.

[0054] Please refer to Figure 2 The prefabricated semi-cylinder, with a foundation crack prefabricated at the center of the plane of the semi-cylinder, specifically includes:

[0055] A standard cylinder with a diameter × height of 100mm × 150mm is cut into smaller cylinders with a height of 100mm × 50mm. The smaller cylinders are then cut in half to form two sets of semi-cylinders. A foundation crack with a length of 10mm and a width of 3mm is cut at the center of the plane of the semi-cylinder.

[0056] Based on the test results of the dynamic modulus test, the master curve of the dynamic modulus of rubber modified asphalt mixture was established by applying the time-temperature equivalence principle and the Sigmoidal function fitting method.

[0057] S5: Through dynamic modulus tests, establish the master curve of dynamic modulus of rubber modified asphalt mixture, transform the master curve of dynamic modulus to relaxation modulus with a specific proportional coefficient, and further obtain data results based on relaxation modulus function. Compare and verify the data results with the influence results directly reflected by relaxation modulus function.

[0058] According to the definition in elasticity mechanics, the modulus of a material is the ratio of stress to strain. Under dynamic loading, a material undergoes a corresponding dynamic deformation response under periodic or non-periodic dynamic loads. The load or stress changes with time and is a function of time; the corresponding deformation or strain response is also a function of time; the ratio of stress to strain, i.e., the dynamic modulus, is also a function of time, and the mathematical relationship between them is E(t) = σ(t) / ε(t). Therefore, the dynamic modulus of a material changes with time.

[0059] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A method for simulating cracking in rubber-modified asphalt mixtures, characterized in that, Includes the following steps: Establish a pre-model for synchronous docking experiments and simulations; The pre-model has a built-in relaxation modulus function, which can directly reflect the influence of the viscoelastic parameters and fracture energy input parameters of the rubber-modified asphalt mixture. An extended finite element simulation was established based on viscoelastic parameters and fracture energy input parameters. The simulation results were sent to the pre-model and compared with the influence results directly reflected by the relaxation modulus function for verification. Through dynamic modulus tests, the master curve of the dynamic modulus of rubber-modified asphalt mixture was established, and the master curve of the dynamic modulus was transformed into the relaxation modulus with a specific proportional coefficient. Furthermore, data results were obtained based on the relaxation modulus function, and the data results were compared and verified with the influence results directly reflected by the relaxation modulus function.

2. The cracking simulation test method for rubber-modified asphalt mixtures according to claim 1, characterized in that, Also includes: Before the dynamic modulus test, the displacement loading curves of rubber-modified asphalt mixtures under different aging time conditions were studied through aging tests.

3. The cracking simulation test method for rubber-modified asphalt mixtures according to claim 2, characterized in that, The aging test of the rubber-modified asphalt mixture specifically includes: A semi-cylinder is prefabricated, and a foundation crack is prefabricated at the center of the plane of the semi-cylinder. The plane of the semi-cylinder is placed face down on the extensometer, and the foundation crack corresponds to the displacement reading end of the extensometer. The universal testing machine was used to apply a downward loading pressure head to the center of the curved surface of a semi-cylinder at a loading rate of 5 mm / min. The opening displacement of the foundation crack of the semi-cylinder was read with time using an extensometer. This study investigated the displacement loading curve of rubber-modified asphalt mixture under different aging time conditions.

4. The cracking simulation test method for rubber-modified asphalt mixtures according to claim 3, characterized in that, The precast semi-cylinder, with a foundation crack precast at the center of its plane, specifically includes: A standard cylinder with a diameter × height of 100mm × 150mm is cut into smaller cylinders with a height of 100mm × 50mm. The smaller cylinders are then cut in half to form two sets of semi-cylinders. A foundation crack with a length of 10mm and a width of 3mm is cut at the center of the plane of the semi-cylinder.

5. The cracking simulation test method for rubber-modified asphalt mixtures according to claim 3 or 4, characterized in that, The establishment of the extended finite element simulation based on viscoelastic parameters and fracture energy input parameters specifically includes: Based on the generalized Maxwell model parameters, the viscoelastic parameters and fracture energy input parameters of rubber-modified asphalt mixtures are defined. Based on the characteristic principle that the extended finite element method (XFEM) allows modeling in discontinuous states / states with underlying cracks, the cracking behavior of rubber-modified asphalt mixture specimens is simulated and analyzed using the extended finite element method (XFEM).

6. The cracking simulation test method for rubber-modified asphalt mixtures according to claim 5, characterized in that, The extended finite element simulation based on viscoelastic parameters and fracture energy input parameters further includes: A velocity boundary condition is applied to the node at the top of the simulation graphic, and the velocity is applied at the middle position of the top of the graphic. The area of ​​the velocity application is equal to the area of ​​the test loading head applied to the center position of the precast semi-cylindrical surface. The magnitude of the velocity application is consistent with the loading rate of the test loading head, which is 5 mm / min, i.e. 8.333e-5 m / s.

7. The cracking simulation test method for rubber-modified asphalt mixtures according to claim 6, characterized in that, The extended finite element simulation based on viscoelastic parameters and fracture energy input parameters further includes: The area of ​​the applied velocity and the area of ​​the test loading head acting on the center of the precast semi-cylindrical surface are both 5mm × 50mm.

8. The cracking simulation test method for rubber-modified asphalt mixtures according to claim 6, characterized in that, The extended finite element simulation based on viscoelastic parameters and fracture energy input parameters further includes: The simulation element type is an eight-node quadrilateral quadratic plane stress-reduced integral element (CPS8R), and the global seeding density of the corresponding element is 1.5 mm. The analysis step is set to 45 seconds for the specimen, the load increment step is set to 10,000 steps, and the minimum step size is 10e. -5 The maximum step size is set to 100 to ensure that the simulation calculation model converges normally.

9. The cracking simulation test method for rubber-modified asphalt mixtures according to claim 1, characterized in that, The establishment of the master curve for the dynamic modulus of rubber-modified asphalt mixture through dynamic modulus testing specifically includes: Based on the test results of the dynamic modulus test, the master curve of the dynamic modulus of rubber modified asphalt mixture was established by applying the time-temperature equivalence principle and the Sigmoidal function fitting method.

10. The cracking simulation test method for rubber-modified asphalt mixtures according to claim 1, characterized in that, The establishment of a pre-model for synchronous docking experiments and simulations specifically includes: The pre-model's variable input / output options include stress, strain, and displacement output variables, which are used to match and interface with the stress-to-strain ratio and displacement parameters in the dynamic modulus test.

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