Numerical simulation method and system for fatigue failure of ECC and concrete laminated structure

Abstract

The invention provides a numerical simulation method and system for fatigue failure of an ECC and concrete laminated structure. The method comprises the following steps: acquiring parameter information of a target component of the ECC and concrete laminated structure; based on the parameter information of the target component and the spatial topological relation, establishing a geometric model of the target component by using a full-discrete idea; discretizing the geometric model in a computational domain, and establishing a near-field dynamics full-discrete fatigue crack model of the ECC and concrete laminated structure based on the full-discrete model and a near-field dynamics theory of a material fatigue failure process; based on the near-field dynamics full-discrete fatigue crack model, numerical simulation of fatigue failure of the ECC and concrete laminated structure is carried out, and a final numerical simulation result is obtained. The technical scheme of the invention has a certain significance for deeply knowing the performance of the laminated structure in the fatigue fracture process, and also has a reference value for improving the anti-fatigue performance of the laminated structure.

Description

Technical Field

[0001] The invention belongs to the technical field of data signal simulation, and in particular relates to a numerical simulation method and system for fatigue failure of an ECC and concrete laminated structure. Background Art

[0002] ECC (fiber reinforced cementitious composite) material has significant strain hardening characteristics, high ductility and durability, which makes it have broad prospects as a protective reinforcement material when subjected to impact, fatigue and other loads. The ductility and crack resistance of the reinforcement and repair material are important indicators of its performance, which are closely related to the reinforcement effect. At the same time, the bonding performance of the reinforcement and repair material with the original concrete structure is the key to ensuring the overall performance and service life of the ECC and concrete composite structure. In order to make ECC play a huge role in the repair and reinforcement of existing concrete, it is necessary to focus on the study of the interface between ECC and concrete.

[0003] The theory of peridynamics (PD) was first proposed by Dr. Silling of Sandia Laboratory in the United States in 2000. Peridynamics is a reconstruction method of traditional continuum mechanics. It solves the problem of solving differential equilibrium equations near discontinuous regions by reformulating the equilibrium equations in the form of spatial integrals. Compared with traditional methods, the advantage of peridynamics is that it does not rely on meshing. This method successfully overcomes the problem of tip singularity when simulating cracks, so it is very applicable in the study of failure problems and can be used to simulate the dynamic expansion of cracks.

[0004] At present, there have been many experiments and theoretical analyses on the failure and damage of the ECC and concrete interface. These studies mainly focus on the mechanical properties of ECC and concrete laminated structures under quasi-static loads, while there are few studies on the mechanical response under dynamic loads. Since traditional numerical methods are difficult to simulate the crack propagation problem at the bi-material interface, the peridynamic theory has significant advantages in describing discontinuity problems. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention provides a numerical simulation method and system for fatigue failure of an ECC and concrete laminated structure, which are used to study the failure behavior of the interface between ECC and concrete.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] A numerical simulation method for fatigue failure of an ECC and concrete laminated structure comprises the following steps:

[0008] S1: Obtain parameter information of target components of ECC and concrete laminated structure;

[0009] S2: Based on the parameter information and spatial topological relationship of the target component, a geometric model of the target component is established using a full discrete concept;

[0010] S3: Discretizing the geometric model in the computational domain, and establishing a peridynamic fully discrete fatigue crack model of the ECC and concrete laminated structure based on the fully discrete model and the peridynamic theory of material fatigue failure process;

[0011] S4: Based on the peridynamic fully discrete fatigue crack model, a numerical simulation of fatigue failure of the ECC and concrete laminated structure is performed to obtain a final numerical simulation result.

[0012] Preferably, in step S2, the method of establishing the geometric model of the target component using the full discrete concept is:

[0013] Based on the parameter information and spatial topological relationship of the target component, the ECC is modeled using a fully discrete modeling method to obtain a discretized fiber and cement matrix;

[0014] Based on the fully discrete model, the fiber and the cement matrix are modeled separately to obtain a fiber model and a cement matrix model;

[0015] Based on the fiber model and the cement matrix model, a fiber-matrix interaction model is obtained;

[0016] Based on the fiber-matrix interaction model, the interface modeling between ECC and concrete is performed to obtain the geometric model of the target component.

[0017] Preferably, in step S3, the method for establishing a peridynamic fully discrete fatigue crack model of the ECC and concrete laminated structure is:

[0018] Discretizing the geometric model in a computational domain to obtain equally spaced material points; the material points include fiber material points and matrix material points;

[0019] Based on the discretized geometric model, a bond breaking criterion of a material point of the target component under fatigue failure is obtained;

[0020] Based on the bond breaking criterion, material parameters are obtained; wherein the fiber material points are fiber bonds, the matrix material points are matrix bonds, and the fiber material points and the matrix material points are interface bonds;

[0021] A cyclic loading model is introduced. Based on the material parameters and discrete material point model, the fracture process of the target component under fatigue conditions is simulated through cyclic loading calculation, and the establishment of a peri-field dynamics fully discrete fatigue crack model of the ECC and concrete laminated structure is completed.

[0022] Preferably, based on the bond breaking criterion, the method for obtaining material parameters is:

[0023] Based on the maximum and minimum values ​​of the bond stretch under a single cyclic load, the cyclic strain of the bond under a single cyclic load is obtained;

[0024] Based on the cyclic strain amount and the number of loading cycles, obtaining the remaining life of the key;

[0025] Based on the remaining life of the bond and the damage value of the material point, the life of the crack initiation stage and the life of the crack propagation stage are analyzed to obtain the bond breaking criteria of the crack initiation stage and the crack propagation stage in the bond breaking process of fatigue crack;

[0026] Based on the bond breaking criteria of the crack initiation stage and the crack propagation stage in the bond breaking process of fatigue crack, the material parameters of the crack initiation stage and the crack propagation stage in the bond breaking process of fatigue crack are obtained.

[0027] Preferably, in step S4, the method for numerical simulation of fatigue failure of ECC and concrete laminated structure is:

[0028] S41: Acquire parameter information of a geometric model, discretize the geometric model and create material points;

[0029] S42: Based on the need to preset cracks, an initial crack is formed by removing the peridynamic interaction bonds passing through the preset cracks, a virtual mass matrix is ​​constructed using an adaptive dynamic relaxation algorithm, and initial conditions are applied to all material points to obtain an initial model;

[0030] S43: Based on the initial model and the load conditions, a cyclic block is introduced, and after one cyclic loading, a quasi-static solution is obtained, and the crack initiation stage and the crack propagation stage are judged based on the quasi-static solution; wherein the quasi-static solution includes the displacement of the material point, the bond strain and the bond damage value;

[0031] S44: In the crack initiation stage, if the bond strain is greater than the critical bond strain S0, after a cyclic loading step length ΔN, the cumulative damage value is calculated; otherwise, according to the bond damage evolution model, the damage variable D and the damaged microelastic modulus corresponding to the current number of cycles are updated after one cyclic loading. Calculate the damage value based on the value of , and evaluate the crack state based on the damage value;

[0032] S45: In the crack propagation stage, if the bond strain is greater than the critical bond strain S0, the bond fails immediately, indicating that the crack begins to propagate; otherwise, the remaining bond life λ after the cyclic loading step ΔN is calculated according to the peridynamics fully discrete fatigue crack model, and all bonds satisfying λ<0 are destroyed;

[0033] S46: Repeat steps S43-S45 to calculate the next cyclic loading step ΔN and solve the quasi-static solution. If the quasi-static solution meets the preset requirements, stop the cycle, complete the numerical simulation of fatigue failure of the ECC and concrete laminated structure, and obtain the final numerical simulation result.

[0034] The present invention also provides a numerical simulation system for fatigue failure of ECC and concrete laminated structure, which is used to implement the numerical simulation method, comprising:

[0035] A parameter information acquisition module is used to acquire parameter information of a target component of an ECC and concrete laminated structure;

[0036] A geometric model building module is used to build a geometric model of the target component based on the parameter information and spatial topological relationship of the target component using a full discrete concept;

[0037] A fatigue crack model building module discretizes the geometric model in the computational domain, and establishes a peridynamic fully discrete fatigue crack model of the ECC and concrete laminated structure based on the fully discrete model and the peridynamic theory of material fatigue failure process;

[0038] The numerical simulation module is used to perform numerical simulation of fatigue failure of ECC and concrete laminated structure based on the peridynamic fully discrete fatigue crack model to obtain the final numerical simulation result.

[0039] Preferably, the geometric model building module includes:

[0040] An ECC modeling unit is used to model the ECC based on the parameter information and the spatial topological relationship of the target component using a full discrete modeling method to obtain a discretized fiber and cement matrix;

[0041] A discrete modeling unit, used for separately modeling the fiber and the cement matrix based on a fully discrete model to obtain a fiber model and a cement matrix model;

[0042] A fiber-matrix modeling unit, used for obtaining a fiber-matrix interaction model based on the fiber model and the cement matrix model;

[0043] The interface modeling unit is used to perform interface modeling between ECC and concrete based on the fiber-matrix interaction model to obtain the geometric model of the target component.

[0044] Preferably, the fatigue crack model building module includes:

[0045] Discrete units are used to discretize the geometric model in a computational domain to obtain equally spaced material points; the material points include fiber material points and matrix material points;

[0046] A bond breaking criterion acquisition unit, used for obtaining the bond breaking criterion of the material point of the target component under fatigue failure based on the discretized geometric model;

[0047] A material parameter acquisition unit, used to obtain material parameters based on the bond breaking criterion; wherein the fiber material points are fiber bonds, the matrix material points are matrix bonds, and the fiber material points and the matrix material points are interface bonds;

[0048] The model building unit is used to introduce a cyclic loading model, and based on the material parameters and the discrete material point model, simulate the fracture process of the target component under fatigue conditions through cyclic loading calculation, and complete the establishment of a near-field dynamics fully discrete fatigue crack model of the ECC and concrete laminated structure.

[0049] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention has good reliability and accuracy, and can perform good numerical simulation of fatigue damage. The fully discrete model more realistically describes the behavior of the fiber and reflects the interaction between the fiber and the matrix. In the fatigue model, the model introduces the concept of new damage variables and cycle blocks, which can more accurately describe the fatigue life and damage accumulation process of the material, which is of certain significance for in-depth understanding of the performance of the laminated structure in the fatigue fracture process, and also has reference value for improving the fatigue resistance of the laminated structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] In order to more clearly illustrate the technical solution of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0051] Figure 1 This is a flow chart of a numerical simulation method for fatigue failure of an ECC and concrete laminated structure according to an embodiment of the present invention;

[0052] Figure 2 The material points after the ECC material is discretized according to the embodiment of the present invention;

[0053] Figure 3 This is a flow chart of fatigue failure according to an embodiment of the present invention;

[0054] Figure 4 A schematic diagram of the size and boundary conditions of the ECC and concrete composite structure model according to an embodiment of the present invention;

[0055] Figure 5 1 is a crack propagation path when the tension layer of an embodiment of the present invention is a concrete layer; wherein (a) is a PD simulation result diagram, and (b) is a lattice model simulation result diagram;

[0056] Figure 6 1 is a crack propagation path when the tensile layer of an embodiment of the present invention is an ECC layer; wherein (a) is a PD simulation result diagram, and (b) is a lattice model simulation result diagram;

[0057] Figure 7 This is the crack propagation path of fatigue failure in an embodiment of the present invention. DETAILED DESCRIPTION

[0058] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0059] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0060] Embodiment 1

[0061] like Figure 1 As shown, a numerical simulation method for fatigue failure of an ECC and concrete laminated structure includes the following steps:

[0062] S1: Obtain parameter information of a target component of an ECC and concrete laminated structure; wherein the parameter information includes but is not limited to geometric parameters, material parameters, boundary conditions and PD discrete parameters, wherein the material parameters include elastic modulus, fatigue performance, fracture toughness, etc. of ECC and concrete materials.

[0063] S2: Based on the parameter information and spatial topological relationship of the target component, the geometric model of the target component is established using the full discrete idea;

[0064] A further implementation method is to establish a geometric model of a target component using a fully discrete concept as follows:

[0065] Based on the parameter information and spatial topological relationship of the target component, the ECC is modeled using a fully discrete modeling method to obtain discretized fibers and cement matrix; specifically, the fiber concrete (ECC) is modeled using a fully discrete modeling method, so that the entire geometric model is discretized into a set of nodes in the computational domain, and the sum of the volumes of the nodes is the total volume of the object. The fibers and the matrix are discretized independently. A cement matrix model is established based on the bond damage method of damage mechanics, and then the fibers are independently modeled, using fiber units to represent the random distribution of multiple fibers, and their bending and rotation are not considered. The interaction between the fiber and the matrix is ​​considered to be transmitted through interface bonds.

[0066] Based on the fully discrete model, the fiber and cement matrix are modeled separately to obtain the fiber model and cement matrix model.

[0067] In this example, the cement matrix is ​​modeled independently:

[0068] The cement matrix model is established based on the bond damage method of damage mechanics, and the modified point force function F can be expressed as:

[0069] F = (1-d)f,

[0070] Where d is the damage variable, ranging from 0 to 1, d = 0 means that the bond is not damaged, and d = 1 means that the bond is completely damaged.

[0071] The expression of d(s) obtained after fitting the concrete damage model proposed by Mazars is:

[0072]

[0073] Where s ec and et represents the linear elastic extension of the bond in compression and tension, and s 0c and 0t The critical elongation of the corresponding key when stretched and compressed.

[0074] The fibers are modeled independently, assuming that the elastic modulus of the fiber before the fiber point bond breaks is E f remains unchanged, the microelastic modulus c of the bond between fiber points f for:

[0075] Critical elongation of the bond between fiber points s c :

[0076]

[0077] Where σ ft is the fiber tensile strength, E fis the elastic modulus of the fiber before rupture.

[0078] Based on the fiber model and cement matrix model, the fiber-matrix interaction model is obtained;

[0079] For the modeling of fiber-matrix interaction, the relationship between the interface point force f and the interface shear stress τ can be expressed as:

[0080]

[0081] The interface modeling between ECC and concrete is used to obtain the corrected bond force:

[0082] f(η,ξ)=k avg cη·μ(ξ,t),

[0083] Where k avg is the surface correction factor for any loading direction, where k x , k y are the correction factors for the bonds in the x and y directions between two material points, h is the correction factor at the interface point,

[0084] Based on the fiber-matrix interaction model, the interface between ECC and concrete is modeled to obtain the geometric model of the target component.

[0085] S3: Discretizing the geometric model in the computational domain, and establishing a peridynamic fully discrete fatigue crack model of the ECC and concrete laminated structure based on the fully discrete model and the peridynamic theory of material fatigue failure process;

[0086] A further implementation method is that the method for obtaining the peridynamic fully discrete fatigue crack model is:

[0087] The geometric model is discretized in the computational domain to obtain equally spaced material points; the material points include fiber material points and matrix material points; in this embodiment, the fiber and matrix are discretized independently, and the entire model is discretized into a set of nodes in the computational domain, so that the sum of the volumes of the nodes is the total volume of the object, and the discretized fiber units are randomly embedded in the discretized matrix points. A matrix point can establish adjacent relationships with all matrix points and fiber points in the near field, and a fiber point can establish relationships with all matrix points and fiber points belonging to the same fiber unit in its near field. The discretized material points are as follows: Figure 2 shown.

[0088] Based on the discretized geometric model, the bond breaking criterion of the material point of the target component under fatigue failure is obtained;

[0089] Based on the bond breaking criterion, the material parameters are obtained; among them, the fiber material points are fiber bonds, the matrix material points are matrix bonds, and the fiber material points and the matrix material points are interface bonds;

[0090] A cyclic loading model is introduced. Based on the material parameters and discrete material point model, the fracture process of the target component under fatigue conditions is simulated through cyclic loading calculation, and the establishment of a peri-field dynamics fully discrete fatigue crack model of the ECC and concrete laminated structure is completed.

[0091] A further implementation method is that, based on the bond breaking criterion, the method for obtaining material parameters is:

[0092] Based on the maximum and minimum values ​​of the bond stretch under a single cyclic load, the cyclic strain of the bond under a single cyclic load is obtained:

[0093] ε=|s + -s - |, use s + Indicates the elongation of the key when subjected to the maximum cyclic load, s - Indicates the elongation of the key when subjected to the minimum cyclic load.

[0094]

[0095] Where ξ is the relative position vector (original bond length) and η is the relative displacement vector.

[0096] Based on the cyclic strain and the number of loading cycles, the remaining life of the bond is obtained:

[0097]

[0098] Where λ is the remaining life of the bond, N represents the number of loading cycles, ε is the cyclic strain of the bond, and A and m are positive parameters. The values ​​of A and m are different in the crack initiation stage and the crack extension stage.

[0099] Based on the remaining life of the bond and the damage value of the material point, the life of the crack initiation stage and the crack propagation stage are analyzed, and the bond breaking criteria in the crack initiation stage and the crack propagation stage of the bond breaking process of fatigue crack are obtained; the bond breaking criterion of the bond in the process of fatigue crack bond breaking is determined: λ(N)≤0, where N represents the number of loading cycles and λ is the remaining life of the bond.

[0100] Specifically, the total fatigue life includes two parts: the life of the crack initiation stage and the life of the crack stable extension stage, N = N initiation +N propagation .

[0101] The damage evolution model of the bond was established during the analysis of the crack initiation stage:

[0102] Before the macroscopic fatigue crack appears, each bond ε is in the initiation stage of the fatigue process, and the parameters A and m can be expressed as:

[0103] A=A1,m=m1

[0104] In order to calibrate A1 and m1 with experimental data, the cyclic strain in each bond is assumed to be independent of N, and the bond ξ1 connected to a certain point x1 is the maximum cyclic bond strain ε1 in the domain. Since A1 and m1 are independent of position and are both positive parameters, bond ξ1 is the first bond to start damage.

[0105] right Points can be obtained Therefore, the crack starts to initiate at N1:

[0106]

[0107] In the fatigue crack growth stage, the following formula is used as the fatigue life of crack growth:

[0108]

[0109] Where m2 and A2 are positive parameters in the macro crack extension stage.

[0110] The following formula is used as the relationship between the crack growth rate da / dN and the cyclic strain of the core bond:

[0111]

[0112] Where A2 and m2 represent the material parameters of fatigue crack growth, the constant β is related to the structure and represents the influencing factor of strain distribution in the structure, and ε core It represents the maximum cyclic strain in the core part of the bond where the material point x is located during the crack growth stage.

[0113] The following formula is used as the damage function of the material point:

[0114]

[0115] when When the model is in the initial state, the bonds around the material point are not broken; when When the material point is completely destroyed, all the surrounding bonds have failed. H x is the near field range of the material point x with a near field radius of δ, and V is the volume of the material point x.

[0116] Fatigue crack transitions from the initiation stage to the extension stage: When the damage value of a specific material point reaches 0.38 to 0.5, cracks will appear on the surface of the object. When it is greater than or equal to the threshold of 0.5, visible macroscopic cracks appear on the object, marking the transition of fatigue cracks from the initiation stage to the extension stage.

[0117] Based on the bond breaking criteria of the crack initiation stage and the crack propagation stage in the bond breaking process of fatigue crack, the material parameters of the crack initiation stage and the crack propagation stage in the bond breaking process of fatigue crack are obtained.

[0118] Determination of material parameters at the crack initiation stage:

[0119]

[0120] right Take the logarithm and use the linear function y=ax+b for fitting, and then the material parameters m1 and A1 can be obtained.

[0121] Determination of material parameters during the crack growth phase:

[0122] The Paris semi-empirical formula for fatigue crack growth based on fracture mechanics theory is:

[0123]

[0124] Where ΔK represents the range of stress intensity factor, and C and M are regarded as material parameters.

[0125] The parameter m2 can be directly obtained from the Paris curve of the material. The Paris curve represents the logarithmic relationship between the crack growth rate da / dN and the stress intensity factor amplitude ΔK, that is, the relationship between log(da / dN) and log(ΔK).

[0126] m2=M,

[0127] In order to determine A2, assuming an arbitrary A' value and a certain m2 value, the PD method is used to simulate the fatigue crack growth behavior and obtain a certain crack growth rate (da / dN)'. Since the actual crack growth rate da / dN is linearly related to A, A2 can be solved by calculating the ratio of the crack growth rates.

[0128]

[0129] S4: Based on the peridynamic fully discrete fatigue crack model, a numerical simulation of fatigue failure of the ECC and concrete laminated structure is performed to obtain a final numerical simulation result.

[0130] A further implementation method is that in step S4, the method for numerical simulation of fatigue failure of ECC and concrete laminated structure is:

[0131] S41: Obtain parameter information of the geometric model (elastic modulus, fatigue performance, fracture toughness, etc. of ECC and concrete materials), discretize the geometric model and create material points; in this embodiment, first determine the size and basic physical parameters of the target component and initialize the matrix, select a suitable time step for time domain integration, as well as the near-field radius and material point spacing, and then discretize the object to generate material points, and find other material points in the near-field domain of each material point to reflect the local mechanical behavior of the structure.

[0132] S42: Based on the need to preset cracks, the initial cracks are formed by removing the peridynamic (PD) interaction bonds passing through the preset cracks, and the virtual mass matrix is ​​constructed using an adaptive dynamic relaxation algorithm to ensure numerical stability. Initial conditions (initial displacement, velocity, etc.) are applied to all material points to obtain the initial model;

[0133] In this embodiment, the dynamic relaxation method in traditional dynamics can be used to solve the quasi-static problem. By introducing the local damping term, the steady-state part of the transient response dynamic solution can be obtained. This can be achieved by adding the local damping term to the motion equation:

[0134]

[0135] where D represents the virtual diagonal density matrix, c is the damping coefficient, and F is the sum of the peridynamic force and the body force.

[0136] Using the explicit central difference method to solve, the displacement and velocity at the n+1th step can be expressed as:

[0137]

[0138] Where Δt is the time step, which is usually 1, however, for the first iteration, It cannot be solved directly, but can be calculated using the following equation:

[0139]

[0140] In the ADR (Adaptive Dynamic Relaxation) method, the damping coefficient c of the nth step needs to meet the following conditions:

[0141]

[0142] Where K is the local diagonal stiffness matrix, which is expressed as:

[0143] S43: Based on the initial model and the load conditions, a cyclic block is introduced, and after one cyclic loading, a quasi-static solution is obtained, and the crack initiation stage and the crack propagation stage are judged based on the quasi-static solution; wherein the quasi-static solution includes the displacement of the material point, the bond strain and the bond damage value;

[0144] S44: Update damage value: In the crack initiation stage, if the bond strain is greater than the critical bond strain S0, after a cyclic loading step length ΔN, the cumulative damage value is calculated. Otherwise, according to the bond damage evolution model, after one cyclic loading, the damage variable D and the damaged microelastic modulus corresponding to the current number of cycles are updated. The damage value is calculated based on the value of , and the crack state is evaluated based on the damage value. In the crack initiation stage, the damage value is updated after each cyclic loading step ΔN. If the damage value of a bond exceeds the critical value, the bond is marked as a damaged bond and the crack state is further judged.

[0145] S45: Calculate the remaining life of the bond: In the crack propagation stage, if the bond strain is greater than the critical bond strain S0, the bond is directly destroyed (the bond fails immediately), indicating that the crack begins to propagate; otherwise, the remaining life λ of the bond after the cyclic loading step ΔN is calculated according to the peridynamics fully discrete fatigue crack model, and all bonds satisfying λ<0 are destroyed;

[0146] In the fatigue crack growth stage, assuming that λ ij To connect the material points x i and x j The remaining life of the key can be discretized to obtain:

[0147]

[0148] S46: Repeat steps S43-S45 to calculate the next cyclic loading step ΔN and solve the quasi-static solution. If the quasi-static solution meets the preset requirements, stop the cycle, complete the numerical simulation of fatigue failure of the ECC and concrete laminated structure, and obtain the final numerical simulation result.

[0149] Specifically, the preset requirements for the quasi-static solution in this embodiment include: evaluating whether the number of cycles exceeds the total fatigue life, whether the damage point exceeds 0.5, and whether the elongation exceeds a critical threshold to determine the result.

[0150] In particular, in order to improve the calculation efficiency, the present invention introduces the concept of cyclic blocks in the fatigue crack initiation and propagation stages.

[0151] In the initiation stage, given the cycle block accuracy ΔN, the damage variable D and damaged microelastic modulus corresponding to the current cycle number are updated after one cycle loading. and use the damaged microelastic modulus in the next ΔN cycles Perform calculations.

[0152] In the extension phase, the cyclic strain ε is updated after one cyclic loading. The cyclic strain value is considered to remain unchanged in the next ΔN cycles, and this value is used to calculate the remaining life of the bond until the bond breaks when λ<0. The algorithm program is as follows: Figure 3 shown.

[0153] The present invention establishes a complete high fatigue failure numerical simulation method under near-field dynamics, which can simulate and analyze the fatigue failure of ECC and concrete laminated beams under different factors, and the present invention has high reliability, good accuracy and good calculation effect.

[0154] The present invention further illustrates the effect of the method of the present invention by simulating fatigue failure of ECC and concrete laminated structure through the following example:

[0155] The present invention studies the fatigue failure of ECC and concrete laminated beams under three-point bending, and simulates the crack propagation path of failure under static load and fatigue load by adding ECC layer or concrete layer on the tension side under three-point bending. Figure 4 As shown. The elastic modulus of the cement matrix is ​​18GPa, the density is 2000kg / m3, and the tensile strength is 3.77MPa; while the elastic modulus of concrete is 33.2GPa, the density is 2355kg / m3, and the tensile strength is 4.76MPa. The fiber volume fraction of the simulation specimen is 2%, the fiber length is 12mm, the diameter is 40μm, the tensile strength of the fiber is 1620MPa, and the elastic modulus is 42.8GPa. When the fiber content is 2%, 500 fiber units are added, and each fiber unit represents 4 fibers. For the parameters between the fiber and the matrix, the interface shear stiffness κ is 40GPa, and the damage coefficient and shape coefficient are 1.01 and 0.2, respectively. The maximum shear stress τ max and initial friction stress τ f The mesh division of fiber points and matrix points is the same, the spacing of material points is x = 1mm, the near field range is δ = 4Δx, and the time step is t = 2×10-8s.

[0156] Figure 4 A schematic diagram of the size and boundary conditions of the ECC and concrete composite structure model according to an embodiment of the present invention; Figure 5 1 is a crack propagation path when the tension layer of an embodiment of the present invention is a concrete layer; wherein (a) is a PD simulation result diagram, and (b) is a lattice model simulation result diagram; Figure 6 1 is a crack propagation path when the tensile layer of an embodiment of the present invention is an ECC layer; wherein (a) is a PD simulation result diagram, and (b) is a lattice model simulation result diagram; Figure 7 This is the crack propagation path of fatigue failure in an embodiment of the present invention.

[0157] from Figure 5 and Figure 6 It can be seen that adding an ECC layer to the tensile side of the beam under static load has a better reinforcement and repair effect than adding a concrete layer. When the added layer is a concrete layer, the composite structure shows obvious brittleness, and the cracks that appear overall are single macro cracks, and there are also cracks extending along the interface direction at the interface. When the ECC layer is added, many obvious cracks appear in the ECC layer. These cracks will extend along the interface when passing through the interface, and then continue to extend upward in the upper concrete layer. The experimental and simulation results are basically consistent with the crack propagation obtained using peridynamics.

[0158] Will Figure 6 and Figure 7 By comparison, it can be seen that multiple cracks appear in the ECC layer under both static load and fatigue load, but the difference is that the cracks expand significantly along the width direction under fatigue load, and the final damage is caused by a crack in the ECC layer opening significantly and then expanding into the concrete layer. Therefore, it can be concluded that the bending fatigue damage is determined by a single dominant fatigue crack extension behavior.

[0159] Through the above simulation, it can be known that the method of the present invention has good reliability and accuracy, and can perform good numerical simulation of fatigue damage. The fully discrete model more realistically describes the behavior of the fiber and reflects the interaction between the fiber and the matrix. In the fatigue model, the model introduces the concept of new damage variables and cycle blocks, which can more accurately describe the fatigue life and damage accumulation process of the material. It is of certain significance for in-depth understanding of the performance of the laminated structure in the fatigue fracture process, and it also has reference value for improving the fatigue resistance of the laminated structure.

[0160] Embodiment 2

[0161] The present invention also provides a numerical simulation system for fatigue failure of ECC and concrete laminated structure, which is used to implement the numerical simulation method, including:

[0162] A parameter information acquisition module is used to acquire parameter information of a target component of an ECC and concrete laminated structure;

[0163] The geometric model building module is used to build the geometric model of the target component based on the parameter information and spatial topological relationship of the target component using the full discrete idea;

[0164] The fatigue crack model building module discretizes the geometric model in the computational domain, and establishes a peridynamic fully discrete fatigue crack model of the ECC and concrete laminated structure based on the fully discrete model and the peridynamic theory of material fatigue failure process;

[0165] The numerical simulation module is used to perform numerical simulation of fatigue failure of ECC and concrete laminated structure based on the fully discrete fatigue crack model of peri-field dynamics to obtain the final numerical simulation results.

[0166] A further embodiment is that the geometric model building module comprises:

[0167] An ECC modeling unit is used to model ECC based on parameter information and spatial topological relationship of the target component using a fully discrete modeling method to obtain discretized fibers and cement matrix;

[0168] A discrete modeling unit is used to separately model the fiber and the cement matrix based on a fully discrete model to obtain a fiber model and a cement matrix model;

[0169] A fiber-matrix modeling unit is used to obtain a fiber-matrix interaction model based on a fiber model and a cement matrix model;

[0170] The interface modeling unit is used to model the interface between ECC and concrete based on the fiber-matrix interaction model to obtain the geometric model of the target component.

[0171] A further implementation is that the fatigue crack model building module includes:

[0172] Discrete units are used to discretize the geometric model in the computational domain to obtain equally spaced material points; the material points include fiber material points and matrix material points;

[0173] A bond breaking criterion acquisition unit is used to obtain the bond breaking criterion of the material point of the target component under fatigue failure based on the discretized geometric model;

[0174] A material parameter acquisition unit, used to obtain material parameters based on a bond breaking criterion; wherein fiber material points are fiber bonds, matrix material points are matrix bonds, and fiber material points and matrix material points are interface bonds;

[0175] The model building unit is used to introduce the cyclic loading model. Based on the material parameters and the discrete material point model, the fracture process of the target component under fatigue conditions is simulated through cyclic loading calculation, and the establishment of the near-field dynamics fully discrete fatigue crack model of the ECC and concrete laminated structure is completed.

[0176] The embodiments described above are only descriptions of the preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A numerical simulation method for fatigue failure of ECC and concrete laminated structure, characterized in that: The following steps are involved: S1: Obtain parameter information of target components of ECC and concrete laminated structure; S2: Based on the parameter information and spatial topological relationship of the target component, a geometric model of the target component is established using a full discrete concept; S3: Discretizing the geometric model in the computational domain, and establishing a peridynamic fully discrete fatigue crack model of the ECC and concrete laminated structure based on the fully discrete model and the peridynamic theory of material fatigue failure process; S4: Based on the peridynamic fully discrete fatigue crack model, a numerical simulation of fatigue failure of the ECC and concrete laminated structure is performed to obtain a final numerical simulation result.

2. The numerical simulation method for fatigue failure of ECC and concrete laminated structure according to claim 1 is characterized in that: In step S2, the method of establishing the geometric model of the target component using the full discrete idea is: Based on the parameter information and spatial topological relationship of the target component, the ECC is modeled using a fully discrete modeling method to obtain a discretized fiber and cement matrix; Based on the fully discrete model, the fiber and the cement matrix are modeled separately to obtain a fiber model and a cement matrix model; Based on the fiber model and the cement matrix model, a fiber-matrix interaction model is obtained; Based on the fiber-matrix interaction model, the interface modeling between ECC and concrete is performed to obtain the geometric model of the target component.

3. The numerical simulation method for fatigue failure of ECC and concrete laminated structure according to claim 1 is characterized in that: In step S3, the method for establishing a peridynamic fully discrete fatigue crack model of the ECC and concrete laminated structure is: Discretizing the geometric model in a computational domain to obtain equally spaced material points; the material points include fiber material points and matrix material points; Based on the discretized geometric model, a bond breaking criterion of a material point of the target component under fatigue failure is obtained; Based on the bond breaking criterion, material parameters are obtained; wherein the fiber material points are fiber bonds, the matrix material points are matrix bonds, and the fiber material points and the matrix material points are interface bonds; A cyclic loading model is introduced. Based on the material parameters and discrete material point model, the fracture process of the target component under fatigue conditions is simulated through cyclic loading calculation, and the establishment of a peri-field dynamics fully discrete fatigue crack model of the ECC and concrete laminated structure is completed.

4. The numerical simulation method for fatigue failure of ECC and concrete laminated structure according to claim 3 is characterized in that: Based on the bond breaking criterion, the method for obtaining material parameters is: Based on the maximum and minimum values ​​of the bond stretch under a single cyclic load, the cyclic strain of the bond under a single cyclic load is obtained; Based on the cyclic strain amount and the number of loading cycles, obtaining the remaining life of the key; Based on the remaining life of the bond and the damage value of the material point, the life of the crack initiation stage and the life of the crack propagation stage are analyzed to obtain the bond breaking criteria of the crack initiation stage and the crack propagation stage in the bond breaking process of fatigue crack; Based on the bond breaking criteria of the crack initiation stage and the crack propagation stage in the bond breaking process of fatigue crack, the material parameters of the crack initiation stage and the crack propagation stage in the bond breaking process of fatigue crack are obtained.

5. The numerical simulation method for fatigue failure of ECC and concrete laminated structure according to claim 4 is characterized in that: In step S4, the method for numerical simulation of fatigue failure of ECC and concrete laminated structure is: S41: Acquire parameter information of a geometric model, discretize the geometric model and create material points; S42: Based on the need to preset cracks, an initial crack is formed by removing the peridynamic interaction bonds passing through the preset cracks, a virtual mass matrix is ​​constructed using an adaptive dynamic relaxation algorithm, and initial conditions are applied to all material points to obtain an initial model; S43: Based on the initial model and the load conditions, a cyclic block is introduced, and after one cyclic loading, a quasi-static solution is obtained, and the crack initiation stage and the crack propagation stage are judged based on the quasi-static solution; wherein the quasi-static solution includes the displacement of the material point, the bond strain and the bond damage value; S44: In the crack initiation stage, if the bond strain is greater than the critical bond strain S0, after a cyclic loading step length ΔN, the cumulative damage value is calculated; otherwise, according to the bond damage evolution model, the damage variable D and the damaged microelastic modulus corresponding to the current number of cycles are updated after one cyclic loading. Calculate the damage value based on the value of , and evaluate the crack state based on the damage value; S45: In the crack propagation stage, if the bond strain is greater than the critical bond strain S0, the bond fails immediately, indicating that the crack begins to propagate; otherwise, the remaining bond life λ after the cyclic loading step ΔN is calculated according to the peridynamics fully discrete fatigue crack model, and all bonds satisfying λ<0 are destroyed; S46: Repeat steps S43-S45 to calculate the next cyclic loading step ΔN and solve the quasi-static solution. If the quasi-static solution meets the preset requirements, stop the cycle, complete the numerical simulation of fatigue failure of the ECC and concrete laminated structure, and obtain the final numerical simulation result.

6. A numerical simulation system for fatigue failure of ECC and concrete laminated structures, used to implement the numerical simulation method according to any one of claims 1 to 5, characterized in that: include: A parameter information acquisition module is used to acquire parameter information of a target component of an ECC and concrete laminated structure; A geometric model building module is used to build a geometric model of the target component based on the parameter information and spatial topological relationship of the target component using a full discrete concept; A fatigue crack model building module discretizes the geometric model in the computational domain, and establishes a peridynamic fully discrete fatigue crack model of the ECC and concrete laminated structure based on the fully discrete model and the peridynamic theory of material fatigue failure process; The numerical simulation module is used to perform numerical simulation of fatigue failure of ECC and concrete laminated structure based on the peridynamic fully discrete fatigue crack model to obtain the final numerical simulation result.

7. The numerical simulation system for fatigue failure of ECC and concrete laminated structure according to claim 6, characterized in that: The geometric model building module includes: An ECC modeling unit is used to model the ECC based on the parameter information and the spatial topological relationship of the target component using a full discrete modeling method to obtain a discretized fiber and cement matrix; A discrete modeling unit, used for separately modeling the fiber and the cement matrix based on a fully discrete model to obtain a fiber model and a cement matrix model; A fiber-matrix modeling unit, used for obtaining a fiber-matrix interaction model based on the fiber model and the cement matrix model; The interface modeling unit is used to perform interface modeling between ECC and concrete based on the fiber-matrix interaction model to obtain the geometric model of the target component.

8. The numerical simulation system for fatigue failure of ECC and concrete laminated structure according to claim 6, characterized in that: The fatigue crack model building module includes: Discrete units are used to discretize the geometric model in a computational domain to obtain equally spaced material points; the material points include fiber material points and matrix material points; A bond breaking criterion acquisition unit, used for obtaining the bond breaking criterion of the material point of the target component under fatigue failure based on the discretized geometric model; A material parameter acquisition unit, used to obtain material parameters based on the bond breaking criterion; wherein the fiber material points are fiber bonds, the matrix material points are matrix bonds, and the fiber material points and the matrix material points are interface bonds; The model building unit is used to introduce a cyclic loading model, and based on the material parameters and the discrete material point model, simulate the fracture process of the target component under fatigue conditions through cyclic loading calculation, and complete the establishment of a near-field dynamics fully discrete fatigue crack model of the ECC and concrete laminated structure.

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