CN-122020778-A - Discrete element fatigue damage simulation method based on parallel bonding damage model

CN122020778ACN 122020778 ACN122020778 ACN 122020778ACN-122020778-A

Abstract

A discrete element fatigue damage simulation method based on parallel bonding damage model belongs to the technical field of discrete element simulation, and aims to solve the problems that an existing PFC embedded model cannot directly simulate fatigue damage, and the fatigue damage model corrected on the basis of the PFC model has poor applicability and insufficient theoretical support, and comprises two main core contents of parallel bonding damage model development and discrete element microscopic fatigue damage realization, and the Paris law is used as a fatigue damage rule and is carried out The integral correction is introduced into a linear parallel bonding model, so that a parallel bonding damage model is provided, compared with the traditional model, the fatigue damage criterion is optimized, the mechanical theoretical support of the damage criterion is ensured, the nonlinear damage evolution under the fatigue load can be accurately represented, and the problems of insufficient linear representation and lack of theoretical basis of the traditional model are solved.

Inventors

GU ZHANGYI
LI HUI
YANG ZHUODONG
CAO JIANTAO
ZHANG GANGCHENG
XIN HONGSHENG
LIU HAIGUANG

Assignees

浙江交投高速公路运营管理有限公司

Dates

Publication Date: 20260512
Application Date: 20251229

Claims (6)

1. The discrete element fatigue damage simulation method based on the parallel bonding damage model is characterized by comprising the following steps of parallel bonding damage model development and discrete element microscopic fatigue damage realization: S1, firstly, establishing a discrete meta-model of a target material, and initializing the model to a balanced stable state; S2, developing a parallel bonding damage model, taking the parallel bonding damage model as a constitutive model, taking the linear parallel bonding model as a base, and introducing warp The integral corrected Paris law is used as a fatigue damage criterion for defining damage variables, damage assumptions and radius reduction rules; s3, determining a microscopic contact parameter and a fatigue damage parameter by a system calibration method combining an indoor test and a virtual test; S4, applying fatigue load to the model, traversing all contacts in the model, judging whether contact stress meets a damage triggering condition in each time step, calculating damage increment if the contact stress meets the damage triggering condition, then calculating a damage value of the current step, calculating a radius reduction coefficient according to the damage value of the current step, and further updating a bonding radius, a rigidity matrix and stress; S5, taking the damage value obtained in the S4 as the initial damage of the current step, judging whether the stress meets the damage triggering condition, and calculating the damage increment again if the stress meets the damage triggering condition; s6, repeating the steps S4-S5 for damage iteration until the bonding bond is broken or the preset cycle times are reached; S7, outputting a simulation result.
2. The method for simulating fatigue damage by discrete elements based on parallel bonding damage model as recited in claim 1, wherein the parallel bonding damage model in S2 is characterized in that the parallel bonding damage model is formed by introducing warp threads The integral corrected Paris law serves as a fatigue damage criterion that the bond radius reduces when the damage condition is met.
3. The method for simulating fatigue damage by discrete elements based on parallel bonding damage model according to claim 2, wherein the fatigue damage criterion is expressed as Wherein In order for the bond crack length to be uniform, Is of a cohesive diameter, wherein , Is the bonding radius; Substituting Paris's law into An increase in damage is available, expressed as Wherein Is the number of load cycles; And Is a material fatigue related parameter; is the stress intensity factor magnitude in cyclic loading; by means of The integration is used to correct Paris's law as follows: ; Wherein, the And In order to be able to carry out the fatigue-related parameters, Is determined by the following formula: ; Wherein, the In the form of a poisson's ratio, Elastic modulus, stress intensity factor is when I type is cracked The stress intensity factor is when cracking in type II The stress intensity factor expression is specifically as follows: ; ; ; Wherein, the 、 The normal stress is the maximum and minimum respectively; 、 Respectively the maximum and minimum tangential stress values, Is a geometric correction factor in the case of type I cracking, Is a geometric correction factor in type II cracking; Calculation by Tada study of shape factor in rectangular plate single cracking process The integration is specifically as follows: ; Will be Substituted into 、 And The resulting formula is as follows: ; ; ; Along with the evolution of the fatigue damage variable and the increase of the fatigue displacement in the normal direction and the shearing direction, the fatigue displacement increment is related to the fatigue damage increment variable, and the linear parallel bonding model bonding bond diameter expression after the damage is obtained is synthesized as follows: ; Wherein, the An initial value representing the bond diameter; is under the action of fatigue load Integrating; And Determining a basic value range according to trial calculation for a material constant related to damage, then calculating to obtain fatigue damage rate by using an orthogonal simulation test, and calibrating the two key parameters according to a corresponding indoor test result; the tensile stress among the current particles in the parallel bonding damage model is as follows; the damage stress threshold value in the parallel bonding damage model is set; the bonding strength among particles in the parallel bonding damage model is as follows; Is the time step of radius reduction.
4. A discrete element fatigue damage simulation method based on a parallel bonding damage model according to claim 3, wherein the damage assumption in S2 is specifically as follows: The target material is fiber cement stabilized macadam which comprises cement stabilized sand, coarse aggregate and fiber, and fatigue damage only occurs in contact of the linear parallel bonding model, namely the inside of the cement stabilized sand, the inside of a single fiber and the interface between the cement stabilized sand and the coarse aggregate and the fiber; The triggering condition of the bond radius reduction is that the inter-particle tensile stress is greater than the damage stress threshold ; When the tensile stress among the particles is more than or equal to the bonding strength When the bonding bond is broken directly; the fatigue damage rate is controlled by the energy release rate among particles and is causally related to the stress magnitude and the energy release rate.
5. The method for simulating fatigue damage based on discrete elements of a parallel bond damage model according to claim 4, wherein the fatigue load applied in S4 is selected to be a half sine wave load.
6. The discrete element fatigue damage simulation method based on the parallel bonding damage model according to claim 5, wherein the following calculation efficiency optimization measures are adopted in S4, S5 and S6, and are specifically as follows: Updating inter-particle stress and strain data every several time steps; The time step magnification factor is introduced in the calculation of the damage increment.

Description

Discrete element fatigue damage simulation method based on parallel bonding damage model Technical Field The invention relates to the technical field of discrete element simulation, in particular to a discrete element fatigue damage simulation method based on a parallel bonding damage model. Background In the field of road engineering, cement stabilized macadam and fiber cement stabilized macadam are used as common road surface base materials, and the materials are easy to generate fatigue cracking under the action of vehicle cyclic load, and macroscopically show crack initiation and expansion until penetration, and microscopically originate from gradual degradation and failure of bonding bonds among internal particles. Discrete Element Method (DEM), especially particle flow Program (PFC), has been widely used in mechanical behavior study of asphalt mixture and concrete materials by virtue of its unique advantages in discontinuous system mechanical analysis, large deformation motion simulation and microscopic cracking process visualization, but existing built-in constitutive models (such as linear models and linear parallel bonding models) of PFC have essential defects, specifically, these models assume that inter-particle bonding parameters are kept constant in the loading process, cracking is allowed to occur only when stress exceeds bonding strength, and under the action of fatigue load, internal stress of the material is usually smaller than bonding strength, so that contact model parameters cannot be automatically degraded along with the loading process, and further the PFC cannot directly embody bonding performance attenuation caused by fatigue damage. In order to overcome the defects, two methods are generally adopted in research to simulate fatigue damage, namely a viscoelastic element model represented by Burgers model and a correction model based on bond radius reduction. The Burgers model can better describe the viscoelastic mechanical response of asphalt mixture, but because cement stabilized macadam belongs to brittle materials and does not have the self-repairing capability of asphalt, the fatigue fracture mechanism of the cement stabilized macadam is obviously different from that of the asphalt mixture, so that the model is difficult to be applied, and in a radius reduction model, a stress corrosion model (PSC) proposed by DavidO.Potyondy is used for referencing subcritical crack propagation rules in elastic fracture mechanics of a line, and fatigue damage can be characterized by linearly reducing the bonding radius. However, such models were originally designed to solve the problem of rock creep and therefore cannot describe the evolution of nonlinear damage under fatigue loading, and furthermore, the nonlinear parallel bond stress corrosion (NPSC) model proposed by Song et al defines damage as a logarithmic function of time, while simulating cyclic loading, is essentially a time dependent model, requiring readjustment of parameters as load level and frequency change, not only poor ductility, but also lack support for fracture damage mechanics theory. Furthermore, the core defect of the existing fatigue damage model is that the damage reduction criterion lacks physical rationality. Traditional PSC model dependencyAndThe fatigue damage essence is the physical process of crack evolution and energy dissipation of materials under cyclic load, is directly related to the stress magnitude and the energy release rate, the physical essence cannot be accurately reflected by defining the damage evolution only through time or linear rules, and the Paris law is used as a classical theory of fatigue crack research, has a firm damage mechanical basis, is simple in form, can be matched with the fatigue damage essence of materials, has been successfully applied to fatigue crack propagation analysis of materials such as metals, concrete and the like, and can be remarkably improved by introducing the Paris law into a PFC model to define a bonding radius reduction criterion. The existing PFC embedded model cannot directly simulate fatigue damage, and the fatigue damage model corrected on the basis has the problems of poor applicability and insufficient theoretical support, and is difficult to meet the research requirements of fatigue cracking mechanisms of complex brittle composite materials such as fiber cement stabilized macadam, and therefore, a discrete element simulation method which is applicable to the brittle composite materials and can accurately capture the evolution process of the fatigue damage of a fine scale based on a reasonable damage criterion is urgently needed to be developed. Aiming at the problems, a discrete element fatigue damage simulation method based on a parallel bonding damage model is provided. Disclosure of Invention The invention aims to provide a discrete element fatigue damage simulation method based on a parallel bonding damage model, which is used for working, so that the prob