CN-122021218-A - Discrete element modeling method of composite material

CN122021218ACN 122021218 ACN122021218 ACN 122021218ACN-122021218-A

Abstract

A discrete element modeling method of composite material belongs to engineering material modeling technical field, which aims to solve the problems of insufficient systematicness, undefined physical meaning of parameter, limited applicable working condition and long calibration time consumption existing in inversion calibration interface and internal contact parameter depending on macroscopic experiment in Discrete Element (DEM) simulation, according to the invention, the basic components are calibrated step by step to the composite components, and the mechanical properties and the contact behaviors of different components are considered by combining various test means such as an unconfined compressive strength test, an indirect tensile strength test and a direct tensile test, so that the obtained contact parameters are definite in physical meaning and wide in application range, and the problems of insufficient systematicness and weak parameter generalization capability of the traditional parameter calibration method are effectively solved.

Inventors

ZHAN YUAN
GU ZHANGYI
YU YANG
CHEN SONGQIANG
ZHANG GANGCHENG
LIU HAIGUANG
CAO JIANTAO
XIN HONGSHENG

Assignees

浙江交投高速公路运营管理有限公司

Dates

Publication Date: 20260512
Application Date: 20260224

Claims (6)

1. The discrete element modeling method of the composite material is characterized by comprising the steps of performing system calibration, discrete element modeling and parameter verification on a target material, and specifically comprises the following steps: The method comprises the following steps of S1, defining basic components and internal contact types of target materials, wherein the target materials are fiber cement stabilized macadam and comprise three basic components of coarse aggregate, fiber and cement stabilized sand, and the internal contact types comprise eight types of coarse aggregate-coarse aggregate contact, cement stabilized sand-cement stabilized sand contact, cement stabilized sand-coarse aggregate contact, cement stabilized sand-fiber contact, single fiber internal contact, fiber-fiber contact, fiber-coarse aggregate contact and contact in a coarse aggregate rigid cluster; S2, simplifying and determining the contact type inside the fiber cement stabilized macadam, namely, simplifying the modeling process by assuming that the contact between fibers, the contact between fibers and coarse aggregate and the contact inside a coarse aggregate rigid cluster do not exist under the premise of ensuring the verification accuracy because the fiber cement stabilized macadam discrete element modeling relates to various contact types and has complex mechanical mechanism and numerous parameters; According to the actual physical structure and contact characteristics of the internal particles of the fiber cement stabilized macadam, the internal contact types can be divided into eight types, and five main contact types are finally reserved after the assumption and simplification are introduced, wherein the five main contact types comprise coarse aggregate-coarse aggregate contact, cement stabilized sand-cement stabilized sand contact, cement stabilized sand-coarse aggregate contact, cement stabilized sand-fiber contact and single fiber internal contact; S3, gradually calibrating the contact parameters of the system based on basic components and composite components, wherein the basic components comprise coarse aggregate, fiber and cement stabilized sand, the composite components comprise fiber cement stabilized sand and cement stabilized macadam, and the corresponding indoor test and virtual test are used for obtaining the microscopic parameters of each contact type; S4, discrete element modeling, namely, based on the contact parameters calibrated in the step S3, generating a three-phase particle system in a synergic mode in the geometric domain of a test piece according to the grading proportion of coarse aggregate, fiber and cement stabilized sand, and integrally constructing a discrete element integral model of the fiber cement stabilized macadam through rigid cluster reconstruction, flexible cluster conversion and contact parametrization; And S5, verifying the contact parameters of the constructed discrete element integral model by adopting a three-point bending beam test, and verifying and confirming the validity of the parameters by comparing the load-displacement curve and crack distribution of the indoor three-point bending beam test and the virtual three-point bending beam test.
2. The method for modeling discrete elements of a composite material according to claim 1, wherein the specific basis for the contact type assumption and simplification in S2 is as follows: The fiber is selected from chopped fibers with the length of 15mm, and because the content of the chopped fibers in the fiber cement stabilized macadam is low, the chopped fibers are separated from each other, and a few of the chopped fibers in contact with each other do not have binding power, the fiber-fiber contact is assumed to be absent; The fiber surface is coated with cement mortar so that the fiber surface is in very little contact with the coarse aggregate and the fiber surface is not cohesiveness, so the contact between the fiber and the coarse aggregate is assumed to be absent; meanwhile, the single coarse aggregate is characterized by adopting a rigid cluster, and the internal particles are fixedly connected into a rigid body without relative displacement and internal contact, so that the internal contact is assumed to be absent.
3. A method for modeling discrete elements of a composite material according to claim 2, wherein in S3, the calibration of the contact parameters of the basic components comprises the following steps: calibrating internal contact parameters of single fibers, namely adopting a uniaxial tensile test to the virtual fibers to obtain stress-strain curves for reflecting the tensile properties of the fibers, and expressing the internal contact behaviors of the single fibers through a linear parallel bonding model; The cement stabilized sand-cement stabilized sand contact parameter calibration is carried out by adopting an unconfined compressive strength test and an indirect tensile strength test for combined calibration, which is used for reflecting the mechanical behaviors of the cement stabilized sand in stretching and compressing, and expressing the contact behavior between the cement stabilized sand and the cement stabilized sand through a joint model; The coarse aggregate-coarse aggregate contact parameter calibration is that the coarse aggregate has stable property and small difference, so that the microscopic parameters of the coarse aggregate are directly valued according to the data in the literature, and the contact behavior between the coarse aggregate and the coarse aggregate is expressed through a linear model.
4. A method for modeling discrete elements of a composite material according to claim 3, wherein in S3, the calibration of the contact parameters of the composite component comprises the following steps: The cement stabilized sand-fiber contact parameter calibration is that the cement stabilized sand-fiber contact model is a linear parallel bonding model, based on the contact parameters between cement stabilized sand and the contact of the inside of single fiber, macroscopic mechanical parameters are obtained by using an unconfined compressive strength test and an indirect tensile strength test of indoor fiber cement stabilized sand, and then corresponding fiber cement stabilized sand discrete element models are respectively established for jointly calibrating interface parameters of cement stabilized sand and fiber, namely, microscopic parameters of the linear parallel bonding model corresponding to cement stabilized sand-fiber contact; The cement stabilized sand-coarse aggregate contact parameter calibration is that the cement stabilized sand-coarse aggregate contact model is a joint model, macroscopic mechanical parameters are obtained by using an unconfined compressive strength test and an indirect tensile strength test of indoor cement stabilized macadam based on cement stabilized sand-cement stabilized contact parameter sand and coarse aggregate-coarse aggregate contact parameters, and then corresponding cement stabilized macadam discrete element models are respectively established for jointly calibrating interface parameters of cement stabilized sand and coarse aggregate, namely mesoscopic parameters of the joint model corresponding to cement stabilized sand-coarse aggregate contact.
5. The method for modeling discrete elements of a composite material according to claim 4, wherein in S4, the discrete element modeling comprises the following specific steps: The construction of a discrete element integral model comprises the steps of firstly generating a wall body according to the shape and the size of a test piece, then randomly and uniformly generating round particles with corresponding gradations according to gradations and proportions of coarse aggregate, fiber and cement stabilized sand in the range of the wall body, manufacturing a rigid cluster template according to the outline shape of each component particle, then replacing the original round particles according to an area equivalent principle, converting the rigid clusters into breakable flexible clusters to simulate the fiber, and finally realizing refined modeling according to the corresponding contact type, calibration parameters and servo loading; The irregular geometric form of the coarse aggregate is reconstructed by adopting rigid cluster particles, and a discrete element coarse aggregate model with real geometric characteristics is constructed, specifically, a space inside the rigid cluster particles is filled by utilizing unequal diameters pebble according to a central axis approximation method, the ratio of the minimum diameter to the maximum diameter is 0.15, and the particle crossing angle is 150 degrees; the construction of a single fiber model, namely, generating the shape of the fiber in a discrete element by means of a rigid cluster, wherein pebble inside the rigid cluster is in rigid connection and cannot simulate the situation that the fiber is broken, so that when a flexible fiber which can be broken is simulated, the rigid cluster is converted into the flexible cluster which can be broken, and a linear parallel bonding model is added for servo, so that the fiber is attached to surrounding cement stable sand particles; The cement stabilized sand model is constructed by capturing cracking behavior of cement stabilized sand by using a joint model, and then generating cement stabilized sand particles by command, wherein the grain size of sand grains ranges from 1.18mm to 4.75mm and obeys normal distribution.
6. The method for modeling discrete elements of a composite material according to claim 5, wherein in S5, the specific steps of parameter verification are as follows: Preparing 3 parallel test pieces in a group as required, pre-cutting cracks in the middle of the bottom after the test piece is maintained, applying monotone load by utilizing a multifunctional hydraulic servo pavement material dynamic test system, recording a load-displacement curve, and taking a beam body crack photo; establishing a three-point bending beam discrete element model with corresponding size based on the discrete element modeling method in the step S4, setting pre-cutting cracks at positions corresponding to the test pieces, applying the same load conditions as the indoor test, and obtaining a simulated load-displacement curve and crack distribution; And (3) verifying and comparing the development trend and deviation of the load-displacement curves of the indoor test and the virtual test, wherein the development trend is consistent with the development trend of the load-displacement curves and the deviation is controlled within a preset threshold range, and meanwhile, the crack form is highly consistent with the distribution characteristic, so that the calibrated contact parameters are accurate and reliable.

Description

Discrete element modeling method of composite material Technical Field The invention relates to the technical field of engineering material modeling, in particular to a discrete element modeling method of a composite material. Background Cement stabilized macadam is widely used in road base construction, however cracking of the material affects the performance of the road structure, while fiber cement stabilized materials have excellent properties in controlling shrinkage deformation and crack growth. However, the traditional macroscopic test is difficult to reveal the internal cracking mechanism of the material, and has the defects of time consumption, high discreteness and the like. Currently, the Discrete Element Method (DEM) exhibits significant advantages in conducting microscopic analysis, and is a common method for researching cracking behavior of numerous engineering materials. The evolution and fracture process of the internal crack of the material can be intuitively monitored by means of the DEM, but the parameter calibration in the current discrete element simulation usually adopts a method for inverting various interface parameters and internal contact parameters of the DEM model based on a material macroscopic experiment, the method lacks systematicness, the material parameters with definite physical meaning cannot be obtained, the result is difficult to adapt to various loading conditions and the calibration process consumes a great deal of time, so that the development of a system calibration method is needed, and a discrete element model capable of accurately reflecting the mechanical behavior of the composite material is constructed by combining a fine modeling technology and an effective parameter verification means. Aiming at the problems, a discrete element modeling method of the composite material is provided. Disclosure of Invention The invention aims to provide a discrete element modeling method of a composite material, which adopts the method to work, so as to solve the problems of insufficient systematicness, undefined physical meaning of parameters, limited applicable working conditions and long calibration time consumption existing in the Discrete Element (DEM) simulation depending on macroscopic experiment inversion calibration interface and internal contact parameters in the background. In order to achieve the purpose, the invention provides a discrete element modeling method of a composite material, which comprises the steps of performing system calibration, discrete element modeling and parameter verification on a target material, and specifically comprises the following steps: The method comprises the following steps of S1, defining basic components and internal contact types of target materials, wherein the target materials are fiber cement stabilized macadam and comprise three basic components of coarse aggregate, fiber and cement stabilized sand, and the internal contact types comprise eight types of coarse aggregate-coarse aggregate contact, cement stabilized sand-cement stabilized sand contact, cement stabilized sand-coarse aggregate contact, cement stabilized sand-fiber contact, single fiber internal contact, fiber-fiber contact, fiber-coarse aggregate contact and contact in a coarse aggregate rigid cluster; S2, simplifying and determining the contact type inside the fiber cement stabilized macadam, namely, simplifying the modeling process by assuming that the contact between fibers, the contact between fibers and coarse aggregate and the contact inside a coarse aggregate rigid cluster do not exist under the premise of ensuring the verification accuracy because the fiber cement stabilized macadam discrete element modeling relates to various contact types and has complex mechanical mechanism and numerous parameters; According to the actual physical structure and contact characteristics of the internal particles of the fiber cement stabilized macadam, the internal contact types can be divided into eight types, and five main contact types are finally reserved after the assumption and simplification are introduced, wherein the five main contact types comprise coarse aggregate-coarse aggregate contact, cement stabilized sand-cement stabilized sand contact, cement stabilized sand-coarse aggregate contact, cement stabilized sand-fiber contact and single fiber internal contact; S3, gradually calibrating the contact parameters of the system based on basic components and composite components, wherein the basic components comprise coarse aggregate, fiber and cement stabilized sand, the composite components comprise fiber cement stabilized sand and cement stabilized macadam, and the corresponding indoor test and virtual test are used for obtaining the microscopic parameters of each contact type; S4, discrete element modeling, namely, based on the contact parameters calibrated in the step S3, generating a three-phase particle system in a synergic mode in the geometric domain of a te