Method, system and terminal for simulating oxidation film cracks of T91 steel in liquid metal environment

Abstract

The invention belongs to the technical field of material corrosion, and particularly relates to an oxidation film crack simulation method and system for T91 steel in a liquid metal environment and a terminal thereof. Comprising the following steps: step 1, constructing a T91 steel matrix and internal and external oxidation film models based on near-field dynamics; 2, setting a time-varying model interface in the near-field dynamic model; and 3, a near-field dynamics quasi-static solver based on a nonlinear conjugate gradient method and a Griffith fracture criterion is developed, the mechanical response and the damage degree of the T91 steel matrix and the internal and external oxidation films under the influence of the sampling temperature load are simulated and calculated, and a simulation result is exported. The method has the beneficial effects that the T91 steel model containing the oxidation film is constructed, the influence of the sampling temperature load is reflected by introducing the sampling temperature load parameters into the near-field dynamic constitutive force function and the critical key strain function, and simulation of the cracking process of the T91 steel containing the oxidation film is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of material corrosion, and in particular relates to a method, a system and a terminal for simulating oxide film cracks of T91 steel in a liquid metal environment. Background Art

[0002] The study of corrosion of structural materials in high-temperature liquid metals, including the corrosion embrittlement mechanism of structural materials, the principle of fatigue caused by flow-induced vibration, the influence of irradiation and temperature change on corrosion fatigue, etc., is crucial to the structural material design, safety assessment, and life prediction of the next generation of nuclear reactors. Liquid Metal Embrittlement (LME) refers to the phenomenon that normal ductile metals or metal alloys experience a decrease in plasticity and strength when they are in contact with liquid wet metals and loaded. In extreme cases, brittle fracture will occur directly without any plastic deformation.

[0003] T91 steel oxidizes in oxygen-saturated liquid metal to form a double oxide layer consisting of an outer Fe3O4 (magnetite spinel) and an inner Fe(Fe,Cr)2O4 spinel-type oxide layer. The oxide layer is mainly divided into: the inner growth of chromium-rich spinel (Fe 2.4 Cr 0.6 O4) inner oxide layer; magnetite (Fe3O4) outer oxide layer growing outward; inner oxidation zone (IOZ). And the thickness of the two oxide layers increases with the increase of corrosion time.

[0004] In engineering, many metal structures require protective layers in high-temperature oxidizing environments to obtain good corrosion resistance. When the stress exceeds the critical value, cracks will be induced and propagated in the oxide, leading to structural damage. A variety of mechanisms have been proposed to explain the damage during oxidation, most of which focus on the stress generation caused by growth strain during oxidation. Some also believe that stress and diffusion coupling effects must be considered to predict the evolution of oxidation stress during oxidation. Other proposed mechanisms include thermal mismatch between the oxide film and the substrate, phase change, etc. Among them, the effects of thermal mismatch stress and subsequent cracking behavior seem to be ignored.

[0005] However, according to experimental observations, newly generated oxide films are rarely observed in the crack gaps between the inner oxide layer and the steel matrix. This is inconsistent with the assumption that cracking is caused by growth stress during the growth of the oxide layer. Therefore, the formation of cracks can be expected to occur after the oxide layer is formed. According to experimental observations, after long-term corrosion in liquid metal, porous bands were observed in the internal oxide layer of the T91 sample, and cracks of different lengths were formed on the porous bands. The length of some cracks perpendicular to the steel surface even reached the entire oxide layer thickness. Not only were the above cracks observed on T91 steel subjected to stress in high-temperature static liquid metal, but similar phenomena were also observed in flowing liquid metal corrosion tests. Judging from the shape of the cracks, it can be predicted that they are caused by thermal mismatch stresses formed during the cooling process of the sampling due to the shrinkage of the oxide layer and the different thermal expansion coefficients of the steel and oxide layer.

[0006] Through the above analysis, the problems and defects of the prior art are as follows:

[0007] (1) The existing inference of the crack mechanism, including the stress caused by growth strain during oxidation, is inconsistent with the experimental phenomenon that new oxide film is rarely observed in the crack gap between the inner oxide layer and the steel matrix. It cannot be used to reflect the crack formation mechanism.

[0008] (2) When studying cracking behavior, the existing finite element model based on classical continuum mechanics is limited by the singularity of continuum mechanics in solving spatial discontinuities such as cracks. It is difficult to directly consider the influence of the "crack" factor in the model, and it is also difficult to obtain the entire cracking process from crack initiation to expansion to the formation of crack form.

[0009] The difficulty in solving the above problems and defects lies in the fact that there is currently no mature simulation solution or ideal simulation results for the introduction of crack damage and the study of the continuous cracking process in the above-mentioned cracking problem of T91 steel containing oxide film. Summary of the invention

[0010] The purpose of the present invention is to provide a method, system and terminal for simulating oxide film cracks of T91 steel in a liquid metal environment, which can realize further research on the formation mechanism of cracks in the T91 steel matrix and internal and external oxide films, and help researchers have a more intuitive understanding of the control scheme of oxide layer cracks and the correlation between cooling conditions and crack patterns.

[0011] The technical solution of the present invention is as follows: A method for simulating oxide film cracks of T91 steel in a liquid metal environment, comprising the following steps:

[0012] Step 1: Construct a model of T91 steel matrix and internal and external oxide films based on peridynamics;

[0013] Step 2: Set up the time-dependent model interface in the peridynamic model.

[0014] Step 3: Develop a peridynamic quasi-static solver based on the nonlinear conjugate gradient method and Griffith fracture criterion to simulate the mechanical response and damage degree of the T91 steel matrix and internal and external oxide films under the influence of sampling temperature loads, and export the simulation results.

[0015] The step 1 discretizes the model into multiple material points containing three types of material information. The model includes: using any existing mathematical software to generate a rectangular structure uniform grid and record the coordinate information of the material points; for the material points at the corresponding positions of the thickness of the inner and outer oxide layers and the steel matrix, the corresponding mechanical properties and thermodynamic properties information are assigned; and all material points in the near field corresponding to each material point are calculated and recorded.

[0016] The control equation of the peridynamic model after discretization in step 1 is described as follows:

[0017]

[0018] Where i is the material point to be calculated, j is the other material points in the near field of material point i, u is the displacement vector field, f is the near field force connecting points x and x′, ξ = x′-x is the relative position of the two material points, η = u(x′, t)-u(x, t) is the relative displacement of the two material points, and H x It is a region called the "near field". In this region, there is a pairwise force interaction between any point x' and the central material point x. b(x, t) is the external force received by the material point. The near field is usually regarded as a disk with a radius of δ, δ is called the near field radius, and T is the temperature of the material point i.

[0019] The calculation of the near-field force is described as follows:

[0020]

[0021] Among them, f is the interaction force of the near-field bond connecting two material points, ξ and η are the relative position and relative displacement of the two material points, respectively, c(ξ) is the peridynamic micromodulus corresponding to the elastic modulus of the material, s and s0 are the bond elongation and critical bond elongation of the near-field bond, T is the temperature, α is the thermal expansion coefficient of the material, c is a parameter related to the elastic modulus of the material, g is the magnitude of the near-field force, and h is a parameter for recording damage information.

[0022] The step 2 includes setting a time-dependent model interface in the peridynamic model, which is achieved by setting the thermodynamic properties of the material to a changeable fitting time-dependent function.

[0023] The time-dependent interface involved in step 2 is: the change of the linear thermal expansion coefficient of the material with temperature, which is a time-varying model when the temperature is set to a quasi-static time step-dependent function.

[0024] The quasi-static solver and simulation calculation based on the nonlinear conjugate gradient method and the Griffith fracture criterion in step 3 include:

[0025] After introducing the sampling temperature load, the T91 steel matrix and internal and external oxide film models are solved to obtain the elongation of the near-field bond of the material point, to determine whether the elongation of the near-field bond meets the failure condition, and to obtain the partial damage degree of the oxide film;

[0026] Among them, the equation for solving the elongation of the near-field bond of the material point is: Among them, ξ=x′-x is the relative position of the two material points, and η=u(x′, t)-u(x, t) is the relative displacement of the two material points;

[0027] Among them, the elongation is the failure condition, that is, the solution equation of the damage information is as follows:

[0028]

[0029] Among them, s and s0 are the bond elongation and critical bond elongation of the near-field bond, T is the temperature, α is the thermal expansion coefficient of the material, and the calculation equation for the critical bond elongation s0 is:

[0030]

[0031] Among them, G0 is the critical fracture energy of the material, E is the elastic modulus of the material, and δ is the near field radius;

[0032] Among them, the post-processing parameter of the degree of damage to the oxide film is the "damage factor" d, and its calculation formula is:

[0033]

[0034] Among them, h is the above damage information, H x For the near field.

[0035] In the step 3, the model material point information is used as the initial condition in the next iterative time step, the parameters are updated, and the quasi-static solution under the new time step is solved; until all time steps of the T91 steel containing oxide film are completed, the whole process simulation of the cracking of the T91 steel containing oxide film under the sampling temperature load is output; wherein, the current model material point information includes the spatial position and the degree of damage; wherein, the degree of damage is described by the material point damage factor as the post-processing amount, which represents the proportion of the number of damaged near-field bonds in the near-field domain to all near-field bonds in the near-field domain, and the calculation formula is as follows:

[0036]

[0037] Where d is the material point damage factor, H x is the near-field radius of the material point.

[0038] The simulation results in step 3 include a displacement field cloud map, a strain energy density cloud map and a peridynamic damage factor cloud map of the structure at each time step, as well as a demonstration animation of crack initiation and propagation on the overall structure until the final crack mode is formed.

[0039] A T91 steel oxide film crack system in a liquid metal environment using a T91 steel oxide film crack simulation method in a liquid metal environment, comprising: a model building module, a model interface setting module, and a simulation calculation module;

[0040] The model building module is used to build a T91 steel matrix and internal and external oxide film model based on peridynamics; the model includes: using any existing mathematical software to generate a rectangular structure uniform grid and record the coordinate information of the material points; for the material points at the corresponding positions of the thickness of the inner and outer oxide layers and the steel matrix, the corresponding mechanical properties and thermodynamic properties are assigned; using the basic theory of peridynamics, all material points in the near field corresponding to each material point are calculated and recorded, the overall geometric structure of the model, and the distribution of the inner and outer oxide layer materials and the steel matrix;

[0041] The model interface setting module is used to set the time-varying model interface of internal and external factors in the model. When implementing, the corresponding function is constructed and called according to experience or measured data. Among them, the time-related interface involved is the change of the linear thermal expansion coefficient of the material with temperature;

[0042] The simulation module is used to develop a peridynamic quasi-static solver based on the nonlinear conjugate gradient method and the Griffith fracture criterion, simulate the mechanical response and damage degree of the T91 steel matrix and the internal and external oxide films under the influence of the sampling temperature load, and export the simulation results;

[0043] The implementation method of the Griffith fracture criterion in the simulation calculation module is to solve the T91 steel matrix and the internal and external oxide film models to obtain the elongation of the near-field bond of the material point, determine whether the elongation of the near-field bond meets the failure condition, and obtain the degree of damage to the oxide film part;

[0044] The elongation of the near-field bond of the material point is solved by solving the equation, and the solution equation is: Among them, ξ=x′-x is the relative position of the two material points, and η=u(x′, t)-u(x, t) is the relative displacement of the two material points;

[0045] Among them, the elongation is the failure condition, that is, the solution equation of the damage information is as follows:

[0046]

[0047] Among them, s and s0 are the bond elongation and critical bond elongation of the near-field bond, T is the temperature, α is the thermal expansion coefficient of the material, and the calculation equation for the critical bond elongation s0 is:

[0048]

[0049] Among them, G0 is the critical fracture energy of the material, E is the elastic modulus of the material, and δ is the near field radius;

[0050] Among them, the post-processing parameter of the degree of damage to the oxide film is the "damage factor" d, and its calculation formula is:

[0051]

[0052] Among them, h is the above damage information, H x For the near field.

[0053] A computer device comprises a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor executes the following steps: constructing a peridynamic model to simulate the natural formation of cracks in a T91 steel matrix and internal and external oxide film structures under typical sampling temperature load conditions.

[0054] A computer-readable storage medium stores a computer program, which, when executed by a processor, causes the processor to perform the following steps:

[0055] A peridynamic model is constructed to simulate the natural formation of structural cracks in the T91 steel matrix and internal and external oxide films under typical sampling temperature load conditions, and to simulate the active control of cracks in the T91 steel matrix and internal and external oxide films under the design of active crack control.

[0056] An information data processing terminal is used to implement the T91 steel oxide film crack system in a liquid metal environment.

[0057] The beneficial effects of the present invention are:

[0058] (1) The present invention provides a method for simulating cracks of oxide films of T91 steel in a liquid metal environment. The design of active crack control is introduced by adding pre-cracks in the model. The advantages of near-field dynamics in simulating discontinuous deformation and failure of solid materials are applied to the experimental problem of cracking of T91 steel matrix and internal and external oxide films. A T91 steel model containing oxide film is constructed. The sampling temperature load parameter is introduced into the near-field dynamics constitutive force function and the critical bond strain function to reflect the influence of the sampling temperature load, thereby realizing the simulation of the cracking process of T91 steel containing oxide film.

[0059] (2) The calculation results of the present invention can reflect relevant information such as the crack initiation position, crack evolution path and final crack mode of the T91 steel matrix; based on this information, the crack formation mechanism can be further understood.

[0060] (3) The present invention adopts a GPU parallel acceleration computing solution with CUDA and CUBLAS libraries (NVIDIA) to solve the problem of excessive computational cost in the nonlinear conjugate gradient algorithm in the quasi-static solver, thereby significantly improving the computational efficiency.

[0061] The present invention simulates the process of deformation, crack initiation, expansion and crack morphology formation of T91 steel matrix and internal and external oxide films, demonstrating the calculation accuracy, effectiveness and practicality of the present invention. The present invention is also used to study the process of structural parts from deformation to crack initiation and expansion and crack morphology formation, and analyze the formation mechanism of different types of crack forms. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] Figure 1 It is a flow chart of a method for simulating oxide film cracks of T91 steel in a liquid metal environment provided by an embodiment of the present invention;

[0063] Figure 2 It is a schematic diagram of a method for simulating oxide film cracks of T91 steel in a liquid metal environment provided by an embodiment of the present invention;

[0064] Figure 3 It is a schematic diagram of a T91 steel substrate and internal and external oxide film model provided by an embodiment of the present invention;

[0065] Figure 4 It is a schematic diagram of the simulation results of the natural formation process of cracks of the T91 steel substrate and the inner and outer oxide films under 1000h corrosion provided by Example 2 of the present invention;

[0066] Figure 5 It is a schematic diagram of the final morphological results of the natural formation of cracks of the T91 steel substrate and the inner and outer oxide films under 500h / 1000h corrosion provided by Example 3 of the present invention;

[0067] Figure 6 It is the linear thermal expansion coefficient-temperature curve. DETAILED DESCRIPTION

[0068] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0069] Peridynamics is a numerical method based on the idea of ​​nonlocal action. As an alternative framework to continuum mechanics, the governing equations in the peridynamic model use spatial integrals instead of differentials in classical continuum mechanics, making it suitable for the occurrence and development of displacement discontinuities such as crack damage, and avoiding the singularity of solving the crack tip differential equation in traditional continuum mechanics. The peridynamic model allows cracks or damage to be generated and extended autonomously, which makes it successfully applied to many problems involving complex fracture evolution. The peridynamic model is very suitable for studying the crack characteristics of the oxide film in this problem, such as the randomness of the cracks and the complex interaction between micro-cracks and macro-cracks.

[0070] In view of the problems existing in the prior art, the present invention provides a method for simulating oxide film cracks of T91 steel in a liquid metal environment, which describes the specific experimental problems of the influence of sampling temperature load and damage evolution of T91 steel matrix and internal and external oxide films through non-local theory, constructs a near-field dynamics model, and realizes the simulation of the natural formation of structural cracks of T91 steel matrix and internal and external oxide films under typical sampling temperature load conditions, and realizes the simulation of active control of cracks of T91 steel matrix and internal and external oxide films under the design of active crack control.

[0071] A method for simulating oxide film cracks of T91 steel in a liquid metal environment specifically comprises the following steps:

[0072] Step 1: Construct a model of T91 steel matrix and internal and external oxide films based on peridynamics;

[0073] The model is discretized into multiple material points containing three types of material information. The specific contents of the model are as follows: using any existing commercial mathematical software to generate a uniform rectangular grid and record the coordinate information of the material points; for the material points at the corresponding positions of the thickness of the inner and outer oxide layers and the steel matrix, the corresponding mechanical and thermodynamic properties are assigned; using the basic theory of perifield dynamics, all material points in the near field corresponding to each material point are calculated and recorded. The overall geometric structure of the model, as well as the distribution of the inner and outer oxide layer materials and the steel matrix, refer to Figure 3 shown.

[0074] The control equations of the above peridynamic model after discretization are described as follows:

[0075]

[0076] Where: i is the material point for which force is to be calculated, j is the other material points in the near field of material point i; u is the displacement vector field, f is the near field force connecting points x and x′, ξ = x′-x is the relative position of the two material points, η = u(x′, t)-u(x, t) is the relative displacement of the two material points; H x is a region called the "near field" where there is a pairwise interaction between any point x' and the central material point x; b(x, t) is the external force received by the material point. The near field is usually regarded as a disk with a radius of δ, which is called the near field radius. T is the temperature of the material point i.

[0077] The calculation of the near-field force is described as follows:

[0078]

[0079] Where f is the interaction force of the near-field bond connecting two material points, ξ and η are the relative position and relative displacement of the two material points, respectively. c(ξ) is the peridynamic micromodulus corresponding to the elastic modulus of the material, s and s0 are the bond elongation and critical bond elongation of the near-field bond. T is the temperature (℃), and α is the thermal expansion coefficient of the material. c is a parameter related to the elastic modulus of the material, called the "micromodulus"; δ is the magnitude of the near-field force; and h is a parameter for recording damage information.

[0080] Step 2: Set up a time-dependent model interface in the peridynamic model by setting the thermodynamic properties of the material to a variable fitting time-dependent function. The implementation is based on experience or measured data.

[0081] Construct the corresponding function that changes with time and depth and call it. The time (quasi-static time step) related interface involved is:

[0082] The change of the linear thermal expansion coefficient of the material with temperature is a time-varying model when the temperature is set to a quasi-static time step correlation function. The specific setting of the linear thermal expansion coefficient-temperature curve is as follows Figure 6 As shown, the horizontal axis is temperature, and the vertical axis is the linear thermal expansion coefficient corresponding to the temperature. In the legend, the solid line represents the outer oxide layer material (i.e. magnetite), and the dotted line represents the inner oxide layer material (i.e. iron-chromium spinel).

[0083] Step 3: Develop a peridynamic quasi-static solver based on the nonlinear conjugate gradient method and Griffith fracture criterion to simulate the mechanical response and damage degree of the T91 steel matrix and internal and external oxide films under the influence of sampling temperature loads, and export the simulation results.

[0084] Among them, the quasi-static solver and simulation calculation based on the nonlinear conjugate gradient method and Griffith fracture criterion include:

[0085] After introducing the sampling temperature load, the T91 steel matrix and internal and external oxide film models are solved to obtain the elongation of the near-field bond of the material point, to determine whether the elongation of the near-field bond meets the failure condition, and to obtain the partial damage degree of the oxide film;

[0086] Among them, the equation for solving the elongation of the near-field bond of the material point is: Among them, ξ=x′-x is the relative position of the two material points, and η=u(x′, t)-u(x, t) is the relative displacement of the two material points.

[0087] Among them, the elongation is the failure condition, that is, the solution equation of the damage information is as follows:

[0088]

[0089] Where s and s0 are the bond elongation and critical bond elongation of the near-field bond. T is the temperature (°C), and α is the thermal expansion coefficient of the material. The calculation equation for the critical bond elongation s0 is:

[0090]

[0091] Among them, G0 is the critical fracture energy of the material, E is the elastic modulus of the material, and δ is the near field radius.

[0092] Among them, the post-processing parameter of the degree of damage to the oxide film is the "damage factor" d, and its calculation formula is:

[0093]

[0094] Among them, h is the above damage information, H x For the near field.

[0095] The model material point information is used as the initial condition in the next iterative time step, the parameters are updated, and the quasi-static solution in the new time step is solved; until all time steps of T91 steel containing oxide film are completed, the whole process simulation of the cracking of T91 steel containing oxide film under the sampling temperature load is output; wherein the current model material point information includes the spatial position and the degree of damage.

[0096] Among them, the degree of damage is described by the material point damage factor as a post-processing quantity, which represents the proportion of the number of damaged near-field bonds in the near-field domain to all near-field bonds in the near-field domain. The calculation formula is as follows:

[0097]

[0098] Where d is the material point damage factor, H x is the near-field radius of the material point.

[0099] The simulation results in step 3 include the displacement field cloud map, strain energy density cloud map and peridynamic damage factor cloud map of the structure at each time step, as well as a demonstration animation of crack initiation and propagation on the overall structure until the final crack mode is formed.

[0100] The present invention also provides a T91 steel oxide film crack system in a liquid metal environment using the T91 steel oxide film crack simulation method in a liquid metal environment, comprising: a model building module, a model interface setting module, and a simulation calculation module;

[0101] The model building module is used to build a T91 steel matrix and internal and external oxide film model based on peridynamics. The specific contents of the model are: using any existing commercial mathematical software to generate a rectangular structure uniform grid and record the coordinate information of the material points; for the material points at the corresponding positions of the thickness of the inner and outer oxide layers and the steel matrix, the corresponding mechanical properties and thermodynamic properties are assigned; using the basic theory of peridynamics, all material points in the near field corresponding to each material point are calculated and recorded. The overall geometric structure of the model, as well as the distribution of the inner and outer oxide layer materials and the steel matrix, refer to Figure 3 shown.

[0102] The model interface setting module is used to set the time-varying model interface of internal and external factors in the model. When implementing, the corresponding function is constructed and called according to experience or measured data. Among them, the time (quasi-static time step) related interface involved is the change of the material linear thermal expansion coefficient with temperature, which has been described in step 2.

[0103] The simulation calculation module is used to develop a peridynamic quasi-static solver based on the nonlinear conjugate gradient method and Griffith fracture criterion, simulate the mechanical response and damage degree of the T91 steel matrix and internal and external oxide films under the influence of sampling temperature loads, and export the simulation results.

[0104] Specifically, the implementation method of the Griffith fracture criterion in the simulation calculation module is to solve the T91 steel matrix and the internal and external oxide film models to obtain the elongation of the near-field bond of the material point, determine whether the elongation of the near-field bond meets the failure condition, and obtain the degree of damage to the oxide film part;

[0105] Among them, the equation for solving the elongation of the near-field bond of the material point is: Among them, ξ=x′-x is the relative position vector of the two material points, and η=u(x′, t)-u(x, t) is the relative displacement of the two material points.

[0106] Among them, the elongation is the condition for judging bond fracture, that is, the solution of the damage information function is as follows:

[0107]

[0108] Where s and s0 are the bond elongation and critical bond elongation of the near-field bond. T is the temperature (°C), and α is the thermal expansion coefficient of the material. The calculation equation for the critical bond elongation s0 is:

[0109]

[0110] Among them, G0 is the critical fracture energy of the material, E is the elastic modulus of the material, and δ is the near field radius.

[0111] The post-processing parameter for the degree of damage to the oxide film is the "damage factor" d, which is calculated as follows:

[0112]

[0113] Where h is the damage information function mentioned above, H x For the near field.

[0114] The present invention provides a computer device, the computer device comprising a memory and a processor, the memory storing a computer program, and when the computer program is executed by the processor, the processor executes the following steps:

[0115] The non-local theory is used to describe the specific experimental problems of the influence of sampling temperature load and damage evolution of T91 steel matrix and internal and external oxide films. A peri-field dynamic model is constructed to simulate the natural formation of structural cracks in T91 steel matrix and internal and external oxide films under typical sampling temperature load conditions.

[0116] The present invention provides a computer-readable storage medium storing a computer program, wherein when the computer program is executed by a processor, the processor executes the following steps:

[0117] The specific experimental problems of the influence of sampling temperature load and damage evolution of T91 steel matrix and internal and external oxide films are described by non-local theory, and a peri-field dynamic model is constructed to simulate the natural formation of structural cracks in T91 steel matrix and internal and external oxide films under typical sampling temperature load conditions, and to simulate the active control of cracks in T91 steel matrix and internal and external oxide films under the design of active crack control.

[0118] Another object of the present invention is to provide an information data processing terminal, which is used to implement the T91 steel oxide film crack system in a liquid metal environment.

[0119] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0120] In view of the problems existing in the prior art, the present invention provides a method and system for simulating oxide film cracks of T91 steel in a liquid metal environment, which can simulate the natural formation of cracks in the matrix and internal and external oxide films of T91 steel under typical sampling temperature load conditions, and further simulate the active crack control of introducing pre-cracks. The technical solution of the present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0121] like Figure 1 As shown, the method for simulating oxide film cracks of T91 steel in a liquid metal environment provided by an embodiment of the present invention comprises the following steps:

[0122] S101, constructing a model of T91 steel matrix and internal and external oxide films based on peridynamics;

[0123] S102, setting up time-varying model interfaces of various internal and external factors in the model, and constructing and calling corresponding functions that vary with time and depth based on experience or measured data during implementation;

[0124] S103, develop a peridynamic quasi-static solver based on the nonlinear conjugate gradient method and Griffith fracture criterion, simulate and calculate the mechanical response and damage degree of the T91 steel matrix and internal and external oxide films under the influence of sampling temperature load, and derive the simulation results.

[0125] The principle diagram of the simulation method of the oxide film crack of T91 steel in a liquid metal environment provided by the embodiment of the present invention is shown in Figure 2 .

[0126] like Figure 3 As shown, the oxide film crack system of T91 steel in a liquid metal environment provided by the embodiment of the present invention includes:

[0127] Model building module 1, used to build the T91 steel matrix and internal and external oxide film model based on peri-field dynamics;

[0128] Model interface setting module 2 is used to set the time-varying model interface of various internal and external factors in the model. When implementing, the corresponding functions that vary with time and depth are constructed and called according to experience or measured data;

[0129] The simulation calculation module 3 is used to develop a peridynamic quasi-static solver based on the nonlinear conjugate gradient method and the Griffith fracture criterion, simulate the mechanical response and damage degree of the T91 steel matrix and the internal and external oxide films under the influence of the sampling temperature load, and export the simulation results.

[0130] The active crack control simulation method for the T91 steel matrix and the inner and outer oxide films provided by the present invention is described in detail below in conjunction with specific embodiments.

[0131] Example 1

[0132] A method and system for simulating active crack control of T91 steel matrix and internal and external oxide films based on peri-field dynamics. Specifically, the advantages of peri-field dynamics in simulating discontinuous deformation and destruction of solid materials are applied to the specific experimental problems of active crack control of T91 steel matrix and internal and external oxide films, and a peri-field dynamics model is constructed to simulate the natural formation of cracks in the T91 steel matrix and internal and external oxide film structures under typical sampling temperature load conditions. Furthermore, the simulation of the crack form of the T91 steel matrix and internal and external oxide film structures under the design of active crack control is realized. To achieve the above purpose, the present invention adopts the following technical solutions:

[0133] In the first aspect, the present invention constructs a T91 steel matrix and internal and external oxide film model based on peridynamics, and discretizes the model into multiple material points containing three material information of internal and external oxide films and steel matrix according to the size of the oxide film. The control equation of the peridynamic model after discretization is described as follows:

[0134]

[0135] where u is the displacement vector field, f is the near-field force connecting points x and x′, ξ = x′-x is the relative position of the two material points, and η = u(x′, t)-u(x, t) is the relative displacement of the two material points; H x It is a region called the "near field" where there is a pairwise interaction between any point x and the central material point x; b(x, t) is the external force received by the material point. The near field is usually regarded as a disk with a radius of δ, δ is called the near field radius.

[0136] The calculation of the near-field force is described as follows:

[0137]

[0138] in, is the elongation of the near-field bond, or bond strain, s0 is the critical bond strain associated with the material; T is the material point temperature, ε sh is the contraction strain and α is the thermal expansion coefficient of the material.

[0139] In the second aspect, the present invention constructs the corresponding function that varies with time and space based on the existing experimental research and mathematical model, and introduces the time-varying property of the relevant parameters into the model.

[0140] In the third aspect, the present invention constructs a simulation system for active crack control of T91 steel matrix and internal and external oxide films based on a quasi-static solver of a nonlinear conjugate gradient algorithm. The process includes: after introducing a sampled temperature load, solving the T91 steel matrix and internal and external oxide film models to obtain the elongation of the near-field bonds of the material points, judging whether the elongation of the near-field bonds meets the destruction conditions, and obtaining the partial damage degree of the oxide film; using the current model material point information (including spatial position and damage degree) as the initial condition in the next iterative time step, updating the parameters described in the second aspect, and solving the quasi-static solution under the new time step; until all time steps of T91 steel containing oxide film are completed, the whole process is output to simulate the cracking of T91 steel containing oxide film under the sampled temperature load. Among them, the degree of damage is described by the material point damage factor d as a post-processing quantity, which represents the proportion of the number of damaged near-field bonds in the near-field domain to all near-field bonds in the near-field domain, and the calculation formula is as follows:

[0141]

[0142] The calculation results of the active crack control simulation system for the T91 steel matrix and internal and external oxide films as described above are specifically expressed in the following forms: displacement field cloud map, strain energy density cloud map and near-field dynamic damage factor cloud map of the structure at each time step, as well as a demonstration animation of crack initiation and propagation on the overall structure until the final crack mode is formed.

[0143] In a fourth aspect, the present invention provides a computer-readable storage medium storing a computer program, wherein when the computer program is executed by a processor, the processor executes and completes the methods described in aspects 1, 2, and 3. The computer instructions use a GPU parallel acceleration computing solution with CUDA and CUBLAS libraries (NVIDIA) to speed up the calculation.

[0144] The present invention applies the advantages of near-field dynamics in simulating discontinuous deformation and failure of solid materials to the experimental problem of cracking of T91 steel matrix and internal and external oxide films, constructs a T91 steel model containing oxide film, and introduces the sampling temperature load parameter into the peri-field dynamics constitutive force function and critical bond strain function to reflect the influence of the sampling temperature load, thereby realizing the simulation of the oxide film cracking process.

[0145] The calculation results of the present invention can reflect the mechanical response of the T91 steel matrix and the internal and external oxide film structures, and understand the changing trend of the load borne by the structure, the crack initiation position, the crack evolution path, and the final crack mode and other related information. Based on this information, researchers can further understand the crack formation mechanism, have a more intuitive understanding of the active crack control scheme and the correlation between the sampling temperature load conditions and the crack mode, which is helpful to propose a reasonable design scheme for active crack control based on the actual environmental conditions in the experiment. The present invention adopts a GPU parallel acceleration calculation solution with CUDA and CUBLAS libraries (NVIDIA) to solve the problem of excessive computational cost in the nonlinear conjugate gradient algorithm in the quasi-static solver, which significantly improves the computational efficiency.

[0146] Example 2

[0147] This example considers the natural crack formation process of T91 steel plate containing oxide film under conventional sampling temperature load, and the specific process is:

[0148] (1) Based on peri-field dynamics, a model of the T91 steel matrix and the inner and outer oxide films is constructed, with a width of 200 μm and a thickness of 10 μm for the inner and outer oxide layers. The model is discretized into multiple material points.

[0149] The material parameters used in this embodiment are as follows: the Young's modulus of the outer oxide layer is 230 GPa, and the critical fracture energy is 10 J / m 2 , the thermal expansion coefficient is 15×10 -6 / ℃; the Young's modulus of the inner oxide layer is 220GPa, and the critical fracture energy is 15J / m 2 , the thermal expansion coefficient is 15×10 -6 / ℃; the Young's modulus of T91 steel matrix is ​​200GPa, and the critical fracture energy is 200J / m 2 , the thermal expansion coefficient is 12.3×10 -6 / ℃;

[0150] In this embodiment, the material point spacing is set to 0.2 μm, and the model is discretized into 352,352 material points.

[0151] Figure 4 The time evolution of damage and strain energy density in the T91 steel with oxide film in this example is shown in Figure 2. The simulation results reveal the typical morphology of oxide film cracks observed in the field, such as continuous longitudinal cracks, horizontal cracks at the interface between the inner oxide layer and the substrate, and multiple microcracks.

[0152] Example 3

[0153] Based on Example 2, this example compares the effects of different oxide layer thicknesses on crack forms.

[0154] Figure 5The results of the analysis of the effect of the pre-crack spacing on the crack morphology in this embodiment are as follows: Figure 5 The oxide layer thicknesses of D and E are 10 and 20 μm respectively, and the thicknesses of the inner and outer oxide layers are the same.

[0155] The above Examples 2 and 3 respectively simulate the process of deformation, crack initiation, expansion and crack morphology formation of the T91 steel matrix and the inner and outer oxide films under the two conditions of natural environment and active crack control scheme, demonstrating the calculation accuracy, effectiveness and practicality of the present invention. For different types of materials, structures and sampling temperature loads, technicians can find suitable experimental schemes. Therefore, the present invention will have broad application prospects.

[0156] In the above embodiments, it can be implemented in whole or in part by software, hardware, firmware or any combination thereof. When the use is implemented in whole or in part in the form of a computer program product, the computer program product includes one or more computer instructions. When the computer program instructions are loaded or executed on a computer, the process or function described in the embodiment of the present invention is generated in whole or in part. The computer may be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions may be stored in a computer-readable storage medium, or transmitted from one computer-readable storage medium to another computer-readable storage medium. For example, the computer instructions may be transmitted from one website site, computer, server or data center by wired (e.g., coaxial cable, optical fiber, digital subscriber line (DSL) or wireless (e.g., infrared, wireless, microwave, etc.) mode) to another website site, computer, server or data center. The computer-readable storage medium may be any available medium that a computer can access or a data storage device such as a server or data center that includes one or more available media integrated. The available medium may be a magnetic medium (e.g., a floppy disk, a hard disk, a tape), an optical medium (e.g., a DVD), or a semiconductor medium (e.g., a solid-state hard disk Solid State Disk (SSD)), etc.

[0157] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with the technical field within the technical scope disclosed by the present invention and within the spirit and principle of the present invention should be covered by the protection scope of the present invention.

Claims

1. A method for simulating oxide film cracks of T91 steel in a liquid metal environment, characterized in that: The following steps are involved: Step 1: Construct a model of T91 steel matrix and internal and external oxide films based on peridynamics; Step 2: Set up the time-dependent model interface in the peridynamic model. Step 3: Develop a peridynamic quasi-static solver based on the nonlinear conjugate gradient method and Griffith fracture criterion to simulate the mechanical response and damage degree of the T91 steel matrix and internal and external oxide films under the influence of sampling temperature loads, and export the simulation results.

2. The method for simulating oxide film cracks of T91 steel in a liquid metal environment according to claim 1, characterized in that: The step 1 discretizes the model into a plurality of material points containing information of three materials, and the model includes: using any existing mathematical software to generate a uniform grid of rectangular structure and record the coordinate information of the material points; for the material points at the positions corresponding to the thickness of the inner and outer oxide layers and the steel matrix, the corresponding mechanical properties and thermodynamic properties information are assigned; Calculate and record all material points in the near field corresponding to each material point.

3. A method for simulating oxide film cracks of T91 steel in a liquid metal environment as claimed in claim 1 or 2, characterized in that: The control equation of the peridynamic model after discretization in step 1 is described as follows: Where i is the material point to be calculated, j is the other material points in the near field of material point i, u is the displacement vector field, f is the near field force connecting points x and x′, ξ = x′-x is the relative position of the two material points, η = u(x′, t)-u(x, t) is the relative displacement of the two material points, and H x It is a region called "near field", in which there is a pairwise force interaction between any point x' and the central material point x, b(x, t) is the external force received by the material point, and the near field is usually regarded as a disk with a radius of δ, δ is called the near field radius, and T is the temperature of the material point i; The calculation of the near-field force is described as follows: Among them, f is the interaction force of the near-field bond connecting two material points, ξ and η are the relative position and relative displacement of the two material points, respectively, c(ξ) is the peridynamic micromodulus corresponding to the elastic modulus of the material, s and s0 are the bond elongation and critical bond elongation of the near-field bond, T is the temperature, α is the thermal expansion coefficient of the material, c is a parameter related to the elastic modulus of the material, δ is the magnitude of the near-field force, and h is a parameter for recording damage information.

4. The method for simulating oxide film cracks of T91 steel in a liquid metal environment as claimed in claim 1, characterized in that: The step 2 includes setting a time-dependent model interface in the peridynamic model, which is achieved by setting the thermodynamic properties of the material to a changeable fitting time-dependent function.

5. A method for simulating oxide film cracks of T91 steel in a liquid metal environment as claimed in claim 1 or 4, characterized in that: The time-dependent interface involved in step 2 is: the change of the linear thermal expansion coefficient of the material with temperature, which is a time-varying model when the temperature is set to a quasi-static time step-dependent function.

6. The method for simulating oxide film cracks of T91 steel in a liquid metal environment as claimed in claim 1, characterized in that: The quasi-static solver and simulation calculation based on the nonlinear conjugate gradient method and the Griffith fracture criterion in step 3 include: After introducing the sampling temperature load, the T91 steel matrix and internal and external oxide film models are solved to obtain the elongation of the near-field bond of the material point, to determine whether the elongation of the near-field bond meets the failure condition, and to obtain the partial damage degree of the oxide film; Among them, the equation for solving the elongation of the near-field bond of the material point is: Among them, ξ=x′-x, is the relative position of the two material points, η=u(x′, t)-u(x, t) is the relative displacement of the two material points; Among them, the elongation is the failure condition, that is, the solution equation of the damage information is as follows: Among them, s and s0 are the bond elongation and critical bond elongation of the near-field bond, T is the temperature, α is the thermal expansion coefficient of the material, and the calculation equation for the critical bond elongation s0 is: Among them, G0 is the critical fracture energy of the material, E is the elastic modulus of the material, and δ is the near field radius; Among them, the post-processing parameter of the degree of damage to the oxide film is the "damage factor" d, and its calculation formula is: Among them, h is the above damage information, H x For the near field.

7. A method for simulating oxide film cracks of T91 steel in a liquid metal environment as claimed in claim 6, characterized in that: In the step 3, the model material point information is used as the initial condition in the next iterative time step, the parameters are updated, and the quasi-static solution under the new time step is solved; until all time steps of the T91 steel containing oxide film are completed, the whole process simulation of the cracking of the T91 steel containing oxide film under the sampling temperature load is output; wherein, the current model material point information includes the spatial position and the degree of damage; wherein, the degree of damage is described by the material point damage factor as the post-processing amount, which represents the proportion of the number of damaged near-field bonds in the near-field domain to all near-field bonds in the near-field domain, and the calculation formula is as follows: Where d is the material point damage factor, H x is the near field radius of the material point.

8. A method for simulating oxide film cracks of T91 steel in a liquid metal environment as claimed in claim 6, characterized in that: The simulation results in step 3 include a displacement field cloud map, a strain energy density cloud map and a peridynamic damage factor cloud map of the structure at each time step, as well as a demonstration animation of crack initiation and propagation on the overall structure until the final crack mode is formed.

9. A T91 steel oxide film crack system in a liquid metal environment using a T91 steel oxide film crack simulation method in a liquid metal environment, characterized in that: include: Model building module, model interface setting module, simulation calculation module; The model building module is used to build a model of the T91 steel matrix and internal and external oxide films based on peridynamics; the model includes: using any existing mathematical software to generate a uniform rectangular structure grid and record the coordinate information of the material points; for the material points at the corresponding positions of the thickness of the internal and external oxide layers and the steel matrix, the corresponding mechanical and thermodynamic properties are assigned; Using the basic theory of peridynamics, calculate and record all material points in the near field corresponding to each material point, the overall geometric structure of the model, and the distribution of the inner and outer oxide layer materials and the steel matrix; The model interface setting module is used to set the time-varying model interface of internal and external factors in the model. When implementing, the corresponding function is constructed and called according to experience or measured data. Among them, the time-related interface involved is the change of the linear thermal expansion coefficient of the material with temperature; The simulation module is used to develop a peridynamic quasi-static solver based on the nonlinear conjugate gradient method and the Griffith fracture criterion, simulate the mechanical response and damage degree of the T91 steel matrix and the internal and external oxide films under the influence of the sampling temperature load, and export the simulation results; The implementation method of the Griffith fracture criterion in the simulation calculation module is to solve the T91 steel matrix and the internal and external oxide film models to obtain the elongation of the near-field bond of the material point, determine whether the elongation of the near-field bond meets the failure condition, and obtain the degree of damage to the oxide film.

10. The system according to claim 9, characterized in that: The elongation of the near-field bond of the material point is solved by solving the equation, and the solution equation is: Among them, ξ=x′-x, is the relative position of the two material points, η=u(x′, t)-u(x, t) is the relative displacement of the two material points; Among them, the elongation is the failure condition, that is, the solution equation of the damage information is as follows: Among them, s and s0 are the bond elongation and critical bond elongation of the near-field bond, T is the temperature, α is the thermal expansion coefficient of the material, and the calculation equation for the critical bond elongation s0 is: Among them, G0 is the critical fracture energy of the material, E is the elastic modulus of the material, and δ is the near field radius; Among them, the post-processing parameter of the degree of damage to the oxide film is the "damage factor" d, and its calculation formula is: Among them, h is the above damage information, H x For the near field.

11. A computer device, characterized in that: The computer device includes a memory and a processor, the memory stores a computer program, and when the computer program is executed by the processor, the processor performs the following steps: constructing a peridynamic model to simulate the natural formation of cracks in a T91 steel matrix and internal and external oxide film structures under typical sampling temperature load conditions.

12. A computer-readable storage medium, characterized in that: A computer program is stored, and when the computer program is executed by a processor, the processor performs the following steps: A peridynamic model is constructed to simulate the natural formation of structural cracks in the T91 steel matrix and internal and external oxide films under typical sampling temperature load conditions, and to simulate the active control of cracks in the T91 steel matrix and internal and external oxide films under the design of active crack control.

13. An information data processing terminal, characterized in that: The information data processing terminal is used to implement the T91 steel oxide film crack system in a liquid metal environment.

Images