Method and device for characterizing anisotropic mechanical properties of small-caliber pipe

Abstract

The invention discloses a characterization method and device for anisotropic mechanical properties of a small-caliber pipe. The characterization method comprises the steps that a real stress-strain curve and real microstructure characteristics of a small-caliber pipe sample in the rolling direction are obtained; constructing an anisotropic mechanical property characterization model of the small-caliber pipe, and obtaining a simulated stress-strain curve and simulated microstructure characteristics of the small-caliber pipe sample based on the model; and comparing the real stress-strain curve with the simulated stress-strain curve to obtain a first comparison result, comparing the real microstructure characteristics with the simulated microstructure characteristics to obtain a second comparison result, and if the first comparison result and the second comparison result both meet preset values, determining that the real microstructure characteristics are different from the simulated microstructure characteristics. The model parameter is the anisotropic mechanical property characterization parameter of the small-caliber pipe. By constructing the small-caliber pipe anisotropic mechanical property characterization model, the small-caliber pipe anisotropic mechanical property characterization method can accurately characterize the small-caliber pipe anisotropic mechanical property.

Description

Technical Field

[0001] The present application belongs to the technical field of testing and characterizing the mechanical properties of pipes, and specifically relates to a method and device for characterizing the anisotropic mechanical properties of small-diameter pipes. Background Art

[0002] Small-diameter pipes (generally referring to pipes with a diameter of less than 25 mm) are a typical type of lightweight components with hollow structures. They are widely used in high-pressure pipeline systems in high-end manufacturing fields such as aviation, aerospace, nuclear power and automobiles. However, the raw materials of such pipes have obvious texture orientation during the preparation process such as rolling or extrusion, which leads to anisotropic mechanical responses in different directions during the deformation of such materials. In addition, due to the small diameter of small-diameter pipeline components, it is difficult to cut out standard specimens that meet the test requirements. Therefore, it is impossible to obtain non-axial mechanical properties by annular tensile tests of large-diameter pipes, and it is even more impossible to take samples in different directions for mechanical property testing like plates. This makes it difficult to accurately characterize and obtain the anisotropic mechanical properties of small-diameter pipes, making it difficult to achieve accurate quality control of such pipes. For this reason, there is an urgent need for a characterization method for the anisotropic mechanical properties of small-diameter pipes to achieve accurate prediction and precise control of the plastic deformation behavior of materials. Summary of the invention

[0003] In view of the problems existing in the prior art, the purpose of this application is to propose a method and device for characterizing the anisotropic mechanical properties of small-diameter pipes. This application aims to characterize the anisotropic mechanical properties of small-diameter pipes, so as to accurately predict their deformation behavior.

[0004] To achieve the above-mentioned purpose, the present application provides a method for characterizing the anisotropic mechanical properties of small-diameter pipes, the method comprising: obtaining a true stress-strain curve and a true microstructure characteristic of a small-diameter pipe sample along a rolling direction; constructing a characterization model for the anisotropic mechanical properties of small-diameter pipes, and obtaining a simulated stress-strain curve and a simulated microstructure characteristic of the small-diameter pipe sample based on the model; comparing the true stress-strain curve with the simulated stress-strain curve to obtain a first comparison result, and comparing the true microstructure characteristic with the simulated microstructure characteristic to obtain a second comparison result. If both the first comparison result and the second comparison result meet a preset value, the model parameters are the anisotropic mechanical properties characterization parameters of the small-diameter pipe.

[0005] Optionally, obtaining the true stress-strain curve of the small-diameter pipe sample along the rolling direction includes: calculating the cross-sectional area of ​​the small-diameter pipe sample; converting the external load acting on the small-diameter pipe sample into stress based on the cross-sectional area of ​​the small-diameter pipe sample; and drawing the true stress-strain curve of the small-diameter pipe sample based on the stress and recorded strain data.

[0006] Optionally, the construction of the anisotropic mechanical properties characterization model for small-diameter pipes includes: obtaining a material property data set of small-diameter pipes through a microstructure characterization test; constructing a material model for small-diameter pipes based on a viscoplastic self-consistent model based on the data set; and setting boundary conditions for the material model, thereby completing the construction of the anisotropic mechanical properties characterization model for small-diameter pipes.

[0007] Optionally, the comparing the true stress-strain curve and the simulated stress-strain curve includes: calculating the residual sum of squares of the true stress-strain curve and the simulated stress-strain curve, and calculating the mean square error of the true stress-strain curve and the simulated stress-strain curve based on the residual sum of squares; performing a fitting analysis on the true stress-strain curve and the simulated stress-strain curve based on the mean square error of the true stress-strain curve and the simulated stress-strain curve to evaluate the degree of fit between the true stress-strain curve and the simulated stress-strain curve.

[0008] Optionally, the comparing of the real microstructure features and the simulated microstructure features includes: extracting quantitative indicators in the microstructure features; calculating relative errors of the quantitative indicators, and analyzing the matching degree between the real microstructure features and the simulated microstructure features based on the relative errors.

[0009] In addition, the present application also provides a device for characterizing the anisotropic mechanical properties of small-diameter pipes, the device comprising: an acquisition module for acquiring a real stress-strain curve and a real microstructure characteristic of a small-diameter pipe sample along the rolling direction; a model construction module for constructing a small-diameter pipe anisotropic mechanical property characterization model, and obtaining a simulated stress-strain curve and a simulated microstructure characteristic of the small-diameter pipe sample based on the model; a comparison module for comparing the real stress-strain curve and the simulated stress-strain curve to obtain a first comparison result, and comparing the real microstructure characteristic and the simulated microstructure characteristic to obtain a second comparison result. If both the first comparison result and the second comparison result meet the preset value, the model parameter is the anisotropic mechanical property characterization parameter of the small-diameter pipe.

[0010] Optionally, the acquisition module includes: a calculation submodule, used to calculate the cross-sectional area of ​​the small-diameter pipe sample; a conversion submodule, used to convert the external load acting on the small-diameter pipe sample into stress based on the cross-sectional area of ​​the small-diameter pipe sample; and a drawing submodule, used to draw a true stress-strain curve of the small-diameter pipe sample based on the stress and the recorded strain data.

[0011] In addition, the present application also provides a computer storage medium, wherein the computer storage medium stores computer executable instructions, and the computer executable instructions are used to execute any of the above methods.

[0012] In addition, the present application also provides an electronic device, which includes: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements any of the methods described above when executing the program.

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] This application constructs an anisotropic mechanical properties characterization model, and adaptively adjusts the model parameters by comparing simulation with real data, so as to accurately predict the stress-strain curve of small-diameter pipes in the non-rolling direction. In addition, this application adopts a two-dimensional verification method, that is, the real curve and the simulated curve, as well as the real microstructure characteristics and the simulated microstructure characteristics are compared at the same time, to ensure the accuracy of the anisotropic mechanical properties characterization of small-diameter pipes. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a flow chart of a method for characterizing anisotropic mechanical properties of small-diameter pipes provided in one embodiment of the present application;

[0016] Figure 2 This is a schematic diagram of a titanium alloy whole tube tensile specimen provided by an embodiment of the present application;

[0017] Figure 3 is a schematic diagram of the plastic deformation, slip and twinning mechanism of a titanium alloy tube provided by an embodiment of the present application;

[0018] Figure 4 This is a true stress-strain curve diagram of a titanium alloy tube after stretching provided by an embodiment of the present application;

[0019] Figure 5 It is a schematic diagram comparing a simulated stress-strain curve and a real stress-strain curve of a titanium alloy pipe provided by an embodiment of the present application;

[0020] Figure 6This is a schematic diagram of the initial texture distribution of a titanium alloy tube provided by an embodiment of the present application;

[0021] FIG. 7( a ) is a schematic diagram of the actual microstructure characteristics of a titanium alloy tube when the strain value is 0.04 provided in one embodiment of the present application;

[0022] FIG. 7( b ) is a schematic diagram of the actual microstructure characteristics of a titanium alloy tube when the strain value is 0.16 provided in one embodiment of the present application;

[0023] FIG8( a ) is a schematic diagram of simulated microstructure characteristics of a titanium alloy tube when the strain value is 0.04 provided in one embodiment of the present application;

[0024] FIG8( b ) is a schematic diagram of simulated microstructure characteristics of a titanium alloy tube when the strain value is 0.16 provided in one embodiment of the present application;

[0025] Fig. 9 It is a schematic diagram of stress-strain curves of a titanium alloy tube in non-rolling directions of 45°, 90° and thickness direction under optimal parameters provided by an embodiment of the present application;

[0026] Fig.10 It is a structural schematic diagram of a device for characterizing anisotropic mechanical properties of small-diameter pipes provided in one embodiment of the present application;

[0027] Fig.11 is a schematic diagram of the structure of a storage medium provided by an embodiment of the present application;

[0028] Fig.12 It is a schematic diagram of the structure of an electronic device provided by an embodiment of the present application. DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0030] It should be noted that all directional indications in the embodiments of the present application (such as up, down, left, right, front, back, etc.) are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0031] In this application, unless otherwise clearly specified and limited, the terms "connection", "fixation", etc. should be understood in a broad sense. For example, "fixation" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0032] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present application, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the meaning of "and / or" appearing in the full text includes three parallel schemes. Taking "A and / or B" as an example, it includes scheme A, or scheme B, or a scheme that satisfies both A and B. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in the field to implement. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by this application.

[0033] Figure 1 This is a method for characterizing the anisotropic mechanical properties of small-diameter pipes proposed in one embodiment of the present application. The execution subject of the method is an electronic device, which can be a computer, a server, etc. Figure 1 As shown, the method includes:

[0034] S100: Obtain the true stress-strain curve and true microstructure characteristics of small-diameter pipe samples along the rolling direction;

[0035] S200: constructing a characterization model for anisotropic mechanical properties of small-diameter pipes, and obtaining simulated stress-strain curves and simulated microstructure characteristics of the small-diameter pipe specimens based on the model;

[0036] S300: Compare the real stress-strain curve with the simulated stress-strain curve to obtain a first comparison result, and compare the real microstructure characteristics with the simulated microstructure characteristics to obtain a second comparison result. If both the first comparison result and the second comparison result meet preset values, the model parameters are the anisotropic mechanical property characterization parameters of the small-diameter pipe.

[0037] This embodiment obtains the real stress-strain curve and microstructure characteristics of the small-diameter pipe sample along the rolling direction, and combines it with the constructed anisotropic mechanical property characterization model to accurately evaluate and characterize the mechanical response differences of small-diameter pipes in different directions, solving the problem that traditional methods are difficult to accurately measure the non-axial mechanical properties of small-diameter pipes. In addition, this embodiment compares the real and simulated stress-strain curves and microstructure characteristics, and can obtain its anisotropic mechanical property parameters without destructive testing of the pipe, thereby reducing the test cost and the damage to the pipe.

[0038] Figure 2 This is a tensile schematic diagram taking a titanium alloy pipe sample as an example. Figure 2 In the figure, the parameter d represents the inner diameter of the pipe, D represents the outer diameter of the pipe, L represents the length of the pipe sample, L0 represents the test gauge section, and Lc represents the distance between the plugs. Specifically, the small-diameter pipe selected in this embodiment is a TA18 titanium alloy pipe, whose diameter (D) is 8 mm and thickness (t) is 0.55 mm. The sample is cut along the length direction of the pipe by wire cutting, and the sample is subjected to different loads on an electronic universal testing machine with a pressure head rate of 2 mm / min for uniaxial stretching. In addition, in the process of stretching based on each load, the strain field of the gauge section of the pipe sample is measured by digital image correlation technology (Digital Image Correlation, DIC), and the strain data corresponding to the pipe sample and each load are recorded, so that the true stress-strain curve of the pipe sample during the uniaxial tensile test can be obtained. In addition, by performing electron backscatter diffraction (EBSD) analysis on the stretched titanium alloy pipe sample, the true microstructure characteristics of the titanium alloy pipe sample can be obtained.

[0039] Specifically, the method of obtaining the true stress-strain curve of the small-diameter pipe sample based on the above data includes:

[0040] S101: Calculate the cross-sectional area of ​​small-diameter pipe specimens;

[0041] In this step, since the cross section of the small-diameter pipe sample is generally circular, the diameter of the sample is first measured, and then the area of ​​the circle is calculated based on the formula A0 = π (R 2 -r 2 ) is used to calculate the cross-sectional area of ​​the small-diameter pipe sample. In this embodiment, the diameter of the small-diameter pipe sample is known, so the cross-sectional area of ​​the small-diameter pipe sample can be easily obtained.

[0042] S102: converting an external load acting on the small-diameter pipe sample into stress based on a cross-sectional area of ​​the small-diameter pipe sample;

[0043] In this step, the external load acting on the small-diameter pipe sample can be converted into stress based on the following calculation formula:

[0044]

[0045] Where P represents the load and A0 represents the cross-sectional area.

[0046] S103: Drawing a true stress-strain curve based on the stress and the recorded strain data.

[0047] In this step, the stress calculated based on step S102 is used as the y-axis, and the recorded true strain is used as the x-axis to draw the true stress-strain curve of the small-diameter pipe sample. It should be noted that within the elastic range, the curve is linear, and the slope is the elastic modulus E.

[0048] On the basis of the above embodiments, the present application also proposes a method for constructing a model for characterizing the anisotropic mechanical properties of small-diameter pipes, the method comprising:

[0049] S201: Obtaining material property data sets of small-diameter pipes through microstructure characterization tests;

[0050] In this step, first, it is necessary to collect the original mechanical properties data of multiple small-diameter pipes of the same type, including the critical shear stress (Schmid factor), elastic modulus, Poisson's ratio, yield strength, hardness and anisotropy coefficient of each slip system; second, it is necessary to obtain the initial texture data of multiple small-diameter pipes of the same type before stretching based on the electron backscatter diffraction (EBSD) experiment, including the number of grains, the Euler angle information of the corresponding texture and the texture distribution characteristics. Then the original mechanical properties data and initial texture data of multiple small-diameter pipes of the same type constitute the material property data set of small-diameter pipes.

[0051] It should be noted that, in order to ensure the calculation accuracy of the model, it is necessary to select sufficient grain orientations to represent the initial texture of the tube. Specifically, the number of grains of the TA18 tube sample selected in this embodiment is 51277.

[0052] S202: constructing a material model for small-diameter pipes based on a viscoplastic self-consistent model based on the data set;

[0053] In this step, since the TA18 pipe sample is used in this embodiment, it is necessary to establish a corresponding material model of the TA18 pipe. First, the slip and twinning mechanisms of the TA18 material need to be determined, and then the viscoplastic self-consistent model is digitized with the help of Matlab. Finally, the parameters of the viscoplastic self-consistent model are optimized and calculated using a neural network algorithm.

[0054] Specifically, the digitization of the viscoplastic self-consistent model by means of Matlab comprises the following steps:

[0055] 1. In MATLAB, you need to write code to implement these constitutive equations based on the theoretical model. This includes using MATLAB's built-in functions and toolboxes, such as ODE solvers (ordinary differential equation solvers) to solve stress states under time or strain evolution.

[0056] In this step, you write code in MATLAB to implement the constitutive equations of the theoretical model, especially for the viscoplastic self-consistent model in materials science. You usually need to follow these steps:

[0057] 1.1. Define basic parameters and functions, such as elastic modulus E, Poisson's ratio ν, initial grain size, Schmid factor of each slip system, etc. For example, the basic parameters and functions can be defined by executing the following code:

[0058] %Define basic parameters

[0059] E = 110e9; % elastic modulus, unit Pa

[0060] nu=0.33; %Poisson's ratio

[0061] G = E / (2 * (1 + nu)); % shear modulus

[0062] % Schmid factors and other parameters of slip and twinning mechanisms

[0063] schmid_factors_slip = [1.0, 0.8, 0.6]; % Assume the Schmid factors of three typical slip systems

[0064] threshold_stresses = [200e6, 300e6, 400e6]; % corresponds to the threshold stress of the slip system, unit: Pa

[0065] schmid_factors_twinning = [0.9, 0.7]; % Assume the Schmid factors of the two twin systems

[0066] threshold_twin_stresses = [500e6, 600e6]; % corresponds to the threshold stress of the twin system, unit: Pa

[0067] 1.2. Define the constitutive relationship, taking the extended Voce hardening model as an example:

[0068] function[stress]=extendedVoceHardening(strain,initial_yield_stress,Voce_constant,Voce_exponent)

[0069] % Extended Voce hardening model

[0070] stress=initial_yield_stress+Voce_constant*(1-exp(-Voce_exponent*strain));

[0071] end

[0072] 1.3. Simulate the deformation process of materials under specific loads, taking uniaxial tension as an example:

[0073] % Assumed strain history

[0074] strain_history = linspace(0,0.1,100); % strain from 0 to 0.1, divided into 100 steps

[0075] % Initialize stress and hardening parameters

[0076] stress=zeros(size(strain_history));

[0077] hardening_parameter = zeros(size(strain_history)); % Assume a hardening parameter

[0078] for i=1:length(strain_history)

[0079] strain = strain_history(i);

[0080] % Stress calculation for each simulation step

[0081] for each_slip_system=1:length(schmid_factors_slip)

[0082] If strain>0% tensile condition

[0083] effective_stress=extendedVoceHardening(strain,threshold_stresses(each_slip_system),hardening_parameter(i),10); % Hardening parameter example

[0084] if effective_stress>0% slip activation condition simplifies processing

[0085] % Calculate the stress contributed by slip. The specific calculation is omitted here. In practical applications, the slip rate, etc. need to be considered.

[0086] end

[0087] end

[0088] % Treat twin mechanisms similarly

[0089] end

[0090] % Calculate the total stress by considering the contribution of all slip systems and twin systems. Here is a simplified example

[0091] stress(i) = some_combined_stress_calculation(); % Specific implementation is required in actual applications

[0092] end

[0093] 2. Define all variables and parameters in the model, such as stress, strain, hardening parameters, etc., and initialize these parameters.

[0094] This step can be specifically achieved by executing the following procedures:

[0095] %Define basic material properties

[0096] E = 110e9; % elastic modulus, unit Pa

[0097] nu=0.3;%Poisson's ratio

[0098] % Define initial conditions

[0099] initial_strain=0;% initial strain

[0100] initial_stress=0;% initial stress

[0101] %Define hardening parameters

[0102] Voce_constant=1000;% Constant term in Voce hardening model

[0103] Voce_exponent=10; % Exponential term in the Voce hardening model

[0104] %Define model parameter initialization

[0105] initial_hardening_parameter=200e6;% Initial value of self-hardening parameter, unit: Pa

[0106] 3. Write code to implement the calculation logic of the material model, including the activation criteria for slip and twinning, the calculation of self-hardening and interaction hardening, etc. This usually involves iterative calculation until the convergence criteria are reached.

[0107] This step can be specifically achieved by executing the following procedures:

[0108] 3.1. Define the initial conditions, model parameters and activation functions of the materials;

[0109] %Material parameter definition

[0110] E = 110e9; % elastic modulus

[0111] nu=0.3;%Poisson's ratio

[0112] thresholds_slip = [200e6, 300e6, 400e6]; % threshold stress of each slip system

[0113] thresholds_twin = [500e6, 600e6]; % threshold stress of twin

[0114] hardening_constants = [100,200]; % Self-hardening coefficient

[0115] hardening_exponents = [10,15]; % Self-hardening index

[0116] % Initial conditions

[0117] strain=0;

[0118] stress=0;

[0119] %Activation function example, determine whether the slip or twin is activated

[0120] function isActivated=activationCriterion(strain,stress,threshold,currentStress)

[0121] isActivated=(stress>=threshold)&&(currentStress<0);%

[0122] end

[0123] 3.2. Define the functions for self-hardening and interaction hardening calculations:

[0124] % Define the function for calculating the material hardening stress increment

[0125] function[newStress]=computeHardening(strain,currentStress,constant,exponent)

[0126] %strain: Current strain value, used to calculate hardening increment

[0127] %currentStress: Current stress value, basis for hardening calculation

[0128] % constant: The constant term in the Voce hardening model, which determines the slope of the hardening curve

[0129] %exponent: exponential term in Voce hardening model, affecting the change of hardening rate

[0130] % Calculate the new hardening stress according to the Voce hardening model formula

[0131] %The formula is: σ_new=σ_old+C*(1-exp(-ε*n))

[0132] % Among them, σ_new is the stress after hardening, σ_old is the current stress, C is the hardening constant, ε is the strain, and n is the hardening exponent

[0133] newStress=currentStress+constant*(1-exp(-exponent*strain));

[0134] % Returns the calculated new stress value

[0135] End

[0136] The above code defines a MATLAB function named computeHardening, which calculates the hardening stress increment of the material under given strain conditions according to the Voce hardening model. The function receives four input parameters: current strain (strain), current stress (currentStress), hardening constant (constant) and hardening exponent (exponent), and returns the new stress value (newStress) after hardening calculation.

[0137] 3.3. Implement iterative calculation of the model, including activation of slip and twinning, stress update and hardening parameter update. The following procedures can be executed:

[0138]

[0139]

[0140] The method of optimizing the parameters of the viscoplastic self-consistent model using a neural network algorithm comprises the following steps:

[0141] 1. Collect or generate a set of experimental data under different loading conditions, including true stress-strain curves and microstructure characteristic data, as the basis for training the neural network.

[0142] 2. Use the neural network toolbox in MATLAB to build a neural network model. The input of the network can be material parameters (such as hardening parameters, grain size, etc.), and the output is the stress-strain curve or microstructure characteristics predicted by the model.

[0143] This step specifically includes:

[0144] 2.1. Define the network architecture: You can use the feedforwardnet function to create a feedforward neural network. For example, you can define a simple three-layer network (input layer, hidden layer, output layer).

[0145] 2.2. Use trainlm (Levenberg-Marquardt back propagation algorithm) as the training function;

[0146] 2.3. Use net.inputNames and net.outputNames to assign input and output variable names. For details, refer to the following procedures:

[0147] % Assuming the inputs are hardening parameters and grain size

[0148] net.inputNames={'Hardening_Parameter','Grain_Size'};

[0149] % Output may be multiple points on a stress-strain curve, or a quantitative indicator of microstructural characteristics

[0150] net.outputNames={'Stress_Strain_Points','Microstructure_Features'};

[0151] 3. Train the neural network and adjust the network weights and biases through the back propagation algorithm to make the network prediction value as close to the experimental value as possible. Specifically, the train function in MATLAB can be used to help complete the training process.

[0152] This step can be specifically achieved by executing the following procedures:

[0153] 3.1. Divide the data into training set, validation set and test set. For example, the division ratio can be 70%, 15%, and 15%.

[0154] Further, use the train function to train the network. You can refer to the following program:

[0155] % Use the training data set to train the neural network

[0156] [net,tr]=train(net,inputsTrain,targetsTrain);

[0157] %net - configured but untrained neural network model

[0158] %inputsTrain-The input part of the training data set, which contains various material parameters used to train the model (such as hardening parameters, grain size, etc.)

[0159] %targetsTrain - the target output portion of the training data set, corresponding to the true stress-strain curve or microstructure characteristic data

[0160] %The function train() will return the trained neural network model net and relevant statistical information tr of the training process, such as training error, number of iterations, etc.

[0161] 3.2. Use the validation set and test set to evaluate the generalization ability of the network. You can refer to the following procedures:

[0162] %Use the trained neural network model to predict the test data set

[0163] outputsTest=sim(net, inputsTest);

[0164] %net - trained neural network model

[0165] %inputsTest-The input part of the test data set, which is used to test the generalization ability of the model and contains material parameter inputs similar to those of the training set

[0166] The %sim() function is used to simulate the output of the neural network and predict the corresponding stress-strain curve or microstructure characteristics based on the input data

[0167] %outputsTest - The outputs predicted by the neural network model, which can be compared with the outputs of the real test set to evaluate the model performance

[0168] S203: setting boundary conditions for the material model, that is, completing the construction of the anisotropic mechanical property characterization model of the small-diameter pipe.

[0169] In this step, the boundary conditions include, for example, setting a slip mechanism and a twinning mechanism. In this embodiment, the main slip mechanisms of the titanium alloy include: Figure 3 The cylindrical slip Pr shown 、Conical surface slip Py and cone slip Py<c+a> , the twin mechanism includes Figure 3 Tensile twins TTW and compressive twins CTW are shown.

[0170] After completing the above steps, the construction of the anisotropic mechanical property characterization model of the small-diameter pipe is completed. The corresponding load can be applied to the small-diameter pipe sample according to the required analysis type (such as tension, compression, bending, torsion, etc.) to calculate the stress state of each crystal and the overall average stress-strain response. The simulated stress-strain curve and simulated microstructure characteristics of the small-diameter pipe sample corresponding to the material property data set obtained in step S201 can be extracted.

[0171] Furthermore, since the anisotropic mechanical properties characterization model constructed based on the above steps describes finite deformation through velocity gradient, the initial texture information read by the model calculation is determined by three Euler angle data and their corresponding volume fractions. Since these Euler angles represent three continuous rotation angles generated by rotating the sample coordinate axis to the crystal coordinate axis, the sample coordinate system and the velocity gradient tensor reference coordinate system are the same. In this embodiment, the coordinate system of the EBSD sample is defined as follows: RD=1, TD=2, ND=3. Therefore, the velocity gradient tensor expression for the uniaxial tensile test along the RD, TD, and ND directions is shown in Table 1:

[0172] Table 1

[0173]

[0174] Note: Strain rate The direction is positive in tension and negative in compression.

[0175] In the characterization model constructed based on the above steps, the key equations use the extended Voce self-hardening equation and the interactive hardening constitutive equation to show the evolution of the threshold stress with the accumulation of shear stress in each grain. Specifically, the expression of the extended Voce hardening equation is as follows:

[0176]

[0177] in, represents the instantaneous critical shear stress, Γ represents the cumulative shear deformation of the grain, represents the initial instantaneous critical shear stress, s represents the minimum shear stress required for the pipe to enter the flow state from the static state, represents the final instantaneous critical shear stress, represents the initial hardening rate, Indicates the saturation hardening rate.

[0178] In addition to self-hardening, the mutual hardening effect between the slip systems is expressed as follows:

[0179]

[0180] Among them, Δτ s represents the increment of the instantaneous critical shear stress in a slip system, represents the instantaneous critical shear stress, Δγ s′ represents the shear increment, h ss′ represents the interactive hardening parameter introduced to enable the model to undergo self-strengthening and potential strengthening, s represents the minimum shear stress required for the pipe to enter the flow state from the static state, s' represents the dynamic shear stress, and Γ represents the accumulated shear deformation of the grain.

[0181] Based on the above embodiments, in an exemplary embodiment, the present application compares the real stress-strain curve and the simulated stress-strain curve by the following method:

[0182] S301: calculating the residual sum of squares of the true stress-strain curve and the simulated stress-strain curve, and calculating the mean square error of the true stress-strain curve and the simulated stress-strain curve based on the residual sum of squares;

[0183] In this step, the residual sum of squares (RSS) is calculated based on the following formula:

[0184]

[0185] The mean square error (MSE) is calculated based on the following formula:

[0186]

[0187] Where n represents the number of data points, y obs,i represents the observed value of the i-th data point, y pred,i Represents the predicted value of the ith data point.

[0188] S302: Evaluate the degree of fit between the true stress-strain curve and the simulated stress-strain curve based on the mean square error between the true stress-strain curve and the simulated stress-strain curve.

[0189] In this step, if the mean square error of the true stress-strain curve and the simulated stress-strain curve meets the preset standard, that is, less than 10%, it can be preliminarily determined that the current model parameter settings (such as self-hardening and interactive hardening parameters) can accurately describe the mechanical behavior of small-diameter pipes, and the deformation behavior of small-diameter pipes under different deformation conditions can be preliminarily and accurately simulated based on the current model parameter settings. Otherwise, the trial and error method or orthogonal test is used to adjust the model parameters until the above requirements are met.

[0190] Based on the above embodiments, in an exemplary embodiment, the present application compares the real microstructure features and the simulated microstructure features by the following method, including:

[0191] S3001: Extract quantitative indicators of microstructural characteristics including average grain size, grain shape factor, and texture index;

[0192] In this step, the average grain size can be extracted based on the X-ray diffraction method, specifically:

[0193] The grain size was estimated by measuring the broadening of the diffraction peak using the Scherrer formula.

[0194] Scherrer's formula is:

[0195]

[0196] Where D is the grain diameter, k is the shape factor, λ is the wavelength of the X-ray, β is the half-width of the peak width, and θ is the Bragg angle.

[0197] The grain shape factor can be obtained based on the image analysis method, specifically:

[0198] The outline of the grains was extracted from the microscopic image, and the perimeter L and area S of each grain were calculated. The shape factor formula S / L was used 2The shape factor of each grain is calculated. The shape factors of all grains are combined to obtain the average grain shape factor. In addition, the texture index can be obtained through the texture analysis of Channel 5, recording the diffraction intensity of a specific crystal plane and quantifying the texture intensity using the texture factor or texture coefficient. Then the March-Dollase correction is applied to deal with the texture effect.

[0199] S3002: Calculate the relative error of the quantitative index, and analyze the matching degree between the real microstructure characteristics and the simulated microstructure characteristics based on the relative error.

[0200] In this step, the relative error is calculated based on the following formula:

[0201]

[0202] Among them, y pred Represents the predicted value, y obs Represents the observed value.

[0203] In this embodiment, if the relative error between the real microstructure characteristics and the simulated microstructure characteristics is less than 10%, and the mean square error between the real stress-strain curve and the simulated stress-strain curve is less than 10%, it can be determined that the parameter setting of the model at this time can characterize the anisotropic mechanical properties of small-diameter pipes, and the deformation behavior of small-diameter pipes under different deformation conditions can be accurately simulated based on the current model parameter setting. Otherwise, as mentioned above, the model parameters need to be adjusted by trial and error or orthogonal test until the relative error between the two is less than 10%.

[0204] Below, this application specifically combines Figure 4 Figure 8 is a detailed description of the stress-strain curve and microstructure characteristics of the pipe sample. Figure 4 It is the true stress-strain curve of the titanium alloy tube after stretching; Figure 5 This is a schematic diagram comparing the simulated stress-strain curve and the real stress-strain curve of the titanium alloy pipe. Figure 4 and Figure 5 It can be seen that the simulated stress-strain curve is consistent with the real stress-strain curve. Figure 6Schematic diagram of initial texture distribution of titanium alloy tube; FIG. 7(a) is a schematic diagram of real microstructure characteristics of titanium alloy tube when the strain value is 0.04 provided in one embodiment of the present application; FIG. 7(b) is a schematic diagram of real microstructure characteristics of titanium alloy tube when the strain value is 0.16 provided in one embodiment of the present application; FIG. 8(a) is a schematic diagram of simulated microstructure characteristics of titanium alloy tube when the strain value is 0.04 provided in one embodiment of the present application; FIG. 8(b) is a schematic diagram of simulated microstructure characteristics of titanium alloy tube when the strain value is 0.16 provided in one embodiment of the present application; It can be seen from FIG. 7(a), FIG. 7(b), FIG. 8(a) and FIG. 8(b) that the real microstructure characteristics and the simulated microstructure characteristics are basically consistent, therefore, it can be determined that the setting parameters of the model at this time are the anisotropic mechanical properties characterization parameters of small-diameter tubes, then the deformation behavior of the small-diameter tubes can be accurately characterized based on the parameters, specifically, the parameter settings are as shown in Table 2:

[0205] Table 2

[0206]

[0207]

[0208] In Table 2, Pr represents cylindrical slip, Py represents the conical slip of surface a, Py<c+a> represents the conical slip of the c+a plane, TTW represents tensile twinning, CTW represents compression twinning, τ0 represents the initial instantaneous critical shear stress, τ1 represents the final reverse instantaneous critical shear stress, θ0 represents the initial hardening rate, θ1 represents the saturated hardening rate, and h Pr The interaction hardening parameter for cylindrical slip, h B represents the interaction hardening parameter of basal slip, B represents the basal surface, h Py<c+a> The interaction hardening parameter h represents the conical sliding of the c+a surface. Tt represents the interaction hardening parameter of tensile twin TTW, h Ct Represents the interaction hardening parameter of compression twinning CTW.

[0209] Furthermore, in this embodiment, tensile loading conditions in the directions of 45°, 90° (TD), and wall thickness (ND) are set for small-diameter pipes. The model set based on the parameters shown in Table 2 can output the following: Fig. 9 The stress-strain curve of a small diameter pipe specimen is shown.

[0210] On the basis of the above embodiments, the present application also provides a device for characterizing the anisotropic mechanical properties of small-diameter pipes, the device comprising: an acquisition module for acquiring a real stress-strain curve and a real microstructure characteristic of a small-diameter pipe sample along a rolling direction; a model construction module for constructing a small-diameter pipe anisotropic mechanical property characterization model, and obtaining a simulated stress-strain curve and a simulated microstructure characteristic of the small-diameter pipe sample based on the model; a comparison module for comparing the real stress-strain curve and the simulated stress-strain curve to obtain a first comparison result, and comparing the real microstructure characteristic and the simulated microstructure characteristic to obtain a second comparison result. If both the first comparison result and the second comparison result meet the preset values, the model parameters are the anisotropic mechanical property characterization parameters of the small-diameter pipe.

[0211] Optionally, the acquisition module includes: a calculation submodule, used to calculate the cross-sectional area of ​​the small-diameter pipe sample; a conversion submodule, used to convert the external load acting on the small-diameter pipe sample into stress based on the cross-sectional area of ​​the small-diameter pipe sample; and a drawing submodule, used to draw a true stress-strain curve of the small-diameter pipe sample based on the stress and the recorded strain data.

[0212] Based on the above embodiments, Fig.11 The present application also provides a computer storage medium, which is a CD 40, on which a computer program (i.e., a program product) is stored. When the computer program is executed by a processor, each step recorded in the above method implementation will be implemented, for example, obtaining the real stress-strain curve and real microstructure characteristics of the small-diameter pipe sample along the rolling direction; constructing a small-diameter pipe anisotropic mechanical property characterization model, and obtaining the simulated stress-strain curve and simulated microstructure characteristics of the small-diameter pipe sample based on the model; comparing the real stress-strain curve and the simulated stress-strain curve to obtain a first comparison result, comparing the real microstructure characteristics and the simulated microstructure characteristics to obtain a second comparison result, if the first comparison result and the second comparison result both meet the preset value, then the model parameter is the anisotropic mechanical property characterization parameter of the small-diameter pipe. The specific implementation method of each step is not repeated here.

[0213] It should be noted that the computer-readable storage medium includes but is not limited to phase change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other optical or magnetic storage media, which are not listed here one by one.

[0214] Based on the above embodiments, the present application also provides an electronic device, as shown below: Fig.11 An electronic device for downloading a file according to an exemplary embodiment of the present application is described.

[0215] Fig.12 A block diagram of an exemplary electronic device 50 suitable for implementing the embodiments of the present application is shown, and the electronic device 50 may be a computer system or a cloud server. Fig.12 The electronic device 50 shown is only an example and should not bring any limitation to the functions and scope of use of the embodiments of the present application.

[0216] like Fig.12 As shown, the electronic device 50 includes but is not limited to: one or more processors or processing units 501, a system memory 502, and a bus 503 connecting different system components (including the system memory 502 and the processing unit 501).

[0217] The electronic device 50 typically includes a variety of computer system readable media. These media can be any available media that can be accessed by the electronic device 50, including volatile and non-volatile media, removable and non-removable media.

[0218] The system memory 502 may include computer system readable media in the form of volatile memory, such as random access memory (RAM) 5021 and / or cache memory 5022. The electronic device 50 may further include other removable / non-removable, volatile / non-volatile computer system storage media. By way of example only, the ROM 5023 may be used to read and write non-removable, non-volatile magnetic media ( Fig.12 is not shown in the Fig.12 As shown in FIG. 5 , a disk drive for reading and writing a removable non-volatile disk (e.g., a "floppy disk") and an optical disk drive for reading and writing a removable non-volatile optical disk (e.g., a CD-ROM, a DVD-ROM, or other optical media) can be provided. In these cases, each drive can be connected to bus 503 via one or more data medium interfaces. System memory 502 may include at least one program product having a set (e.g., at least one) of program modules that are configured to perform the functions of each embodiment of the present application.

[0219] A program / utility 5025 having a set (at least one) of program modules 5024 may be stored, for example, in system memory 502, and such program modules 5024 include, but are not limited to, an operating system, one or more application programs, other program modules, and program data, each of which or some combination may include an implementation of a network environment. Program modules 5024 generally perform the functions and / or methods of the embodiments described herein.

[0220] The electronic device 50 may also communicate with one or more external devices 504 (e.g., a keyboard, a pointing device, a display, etc.). Such communication may be performed via an input / output (I / O) interface 505. Furthermore, the electronic device 50 may also communicate with one or more networks (e.g., a local area network (LAN), a wide area network (WAN), and / or a public network, such as the Internet) via a network adapter 506. Fig.11 As shown, the network adapter 506 communicates with other modules (such as the processing unit 501, etc.) of the electronic device 50 via the bus 503. It should be understood that although Fig.11 Not shown, other hardware and / or software modules may be used in conjunction with the electronic device 50 .

[0221] The processing unit 501 executes various functional applications and data processing by running the program stored in the system memory 502, for example, obtaining the real stress-strain curve and the real microstructure characteristics of the small-diameter pipe sample along the rolling direction; constructing a small-diameter pipe anisotropic mechanical property characterization model, and obtaining the simulated stress-strain curve and the simulated microstructure characteristics of the small-diameter pipe sample based on the model; comparing the real stress-strain curve with the simulated stress-strain curve to obtain a first comparison result, and comparing the real microstructure characteristics with the simulated microstructure characteristics to obtain a second comparison result. If both the first comparison result and the second comparison result meet the preset values, the model parameters are the anisotropic mechanical property characterization parameters of the small-diameter pipe.

[0222] The above are only preferred embodiments of the present application, and are not intended to limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A method for characterizing anisotropic mechanical properties of small-diameter pipes, characterized in that: The method comprises: Obtain the true stress-strain curve and true microstructure characteristics of small-diameter pipe samples along the rolling direction; Constructing a characterization model for the anisotropic mechanical properties of small-diameter pipes, and obtaining simulated stress-strain curves and simulated microstructural characteristics of the small-diameter pipe specimens based on the model; The real stress-strain curve and the simulated stress-strain curve are compared to obtain a first comparison result, and the real microstructure characteristics and the simulated microstructure characteristics are compared to obtain a second comparison result. If both the first comparison result and the second comparison result meet the preset values, the model parameters are the anisotropic mechanical property characterization parameters of the small-diameter pipe.

2. The method according to claim 1, characterized in that The method of obtaining the true stress-strain curve of the small-diameter pipe sample along the rolling direction comprises: Calculating the cross-sectional area of ​​the small-diameter pipe sample; converting an external load acting on the small-diameter pipe sample into a stress based on a cross-sectional area of ​​the small-diameter pipe sample; A true stress-strain curve of the small-diameter pipe sample is plotted based on the stress and the recorded strain data.

3. The method according to claim 1, characterized in that: The construction of the small-diameter pipe anisotropic mechanical property characterization model includes: Obtain material property data sets for small-diameter pipes through microstructure characterization tests; constructing a material model for small-diameter pipes based on a viscoplastic self-consistent model based on the data set; Boundary conditions are set for the material model, thus completing the construction of the anisotropic mechanical property characterization model for small-diameter pipes.

4. The method according to claim 1, characterized in that The comparing the real stress-strain curve with the simulated stress-strain curve comprises: Calculating a residual sum of squares of the true stress-strain curve and the simulated stress-strain curve, and calculating a mean square error of the true stress-strain curve and the simulated stress-strain curve based on the residual sum of squares; The degree of fit between the true stress-strain curve and the simulated stress-strain curve is evaluated based on the mean square error between the true stress-strain curve and the simulated stress-strain curve.

5. The method according to claim 1, characterized in that The comparison of the real microstructure characteristics and the simulated microstructure characteristics includes: Extract quantitative indicators from microstructural characteristics; The relative error of the quantitative index is calculated, and the matching degree between the real microstructure feature and the simulated microstructure feature is analyzed based on the relative error.

6. A device for characterizing the anisotropic mechanical properties of small-diameter pipes, characterized in that: The device comprises: Acquisition module, used to obtain the real stress-strain curve and real microstructure characteristics of small-diameter pipe samples along the rolling direction; A model building module, used to build a characterization model of anisotropic mechanical properties of small-diameter pipes, and obtain simulated stress-strain curves and simulated microstructure characteristics of the small-diameter pipe specimens based on the model; A comparison module is used to compare the real stress-strain curve with the simulated stress-strain curve to obtain a first comparison result, and to compare the real microstructure feature with the simulated microstructure feature to obtain a second comparison result. If both the first comparison result and the second comparison result meet the preset value, the model parameter is the anisotropic mechanical property characterization parameter of the small-diameter pipe.

7. The device according to claim 6, characterized in that The acquisition module comprises: A calculation submodule, used for calculating the cross-sectional area of ​​the small-diameter pipe sample; A conversion submodule, for converting an external load acting on the small-diameter pipe sample into stress based on a cross-sectional area of ​​the small-diameter pipe sample; The drawing submodule is used to draw the real stress-strain curve of the small-diameter pipe sample based on the stress and the recorded strain data.

8. A computer storage medium, characterized in that The computer storage medium stores computer executable instructions, and the computer executable instructions are used to execute any one of the methods of claims 1 to 5.

9. An electronic device, characterized in that: The electronic device comprises: A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein: When the processor executes the program, the method according to any one of claims 1 to 5 is implemented.

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