CN112685687A - Unidirectional tensile test data analysis method based on anisotropy - Google Patents
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Abstract
The invention discloses an anisotropy-based unidirectional tensile test data analysis method, which converts the traditional manual plotting and curve fitting into the automatic plotting and optimal solution solving process of a computer, and avoids random errors introduced by manual operation. The invention serially connects the steps of real stress-real strain conversion, hardening curve fitting, r value solving and the like by keying in measurement parameters, greatly improves the processing efficiency of the data based on the anisotropic unidirectional tensile test, and realizes the aim of fast and high-precision processing of the test data. Through centralized visualization, a complicated calculation link can be omitted, and visual comparison of force-displacement, engineering stress-engineering strain, real stress-real strain curves and the like based on the anisotropism RD, DD and TD is realized. The method has the advantages that the real stress-real plastic strain curves are fitted by adopting several classical hardening constitutive models, the fitting effect of the fitting curves and the experiment curves can be visually compared, and the method is efficient, convenient and accurate.
Description
Technical Field
The invention belongs to the field of mechanical properties of materials, and relates to a unidirectional tensile test data analysis method based on anisotropy.
Background
The work hardening characteristics of materials are now mostly still limited to be studied by the information provided in the true stress-strain curve of the material. The actual stress-strain curve of a typical material, which may also be referred to as an equivalent stress-equivalent strain relationship curve based on a single curve assumption, is made using unidirectional tension, unidirectional compression, torsion, or bending. From the scientific and technical literature data disclosed at present, the actual stress-strain curve mostly takes a tensile experiment as a main research means, and the mechanical property indexes of the material, such as strength limit, and plastic indexes, such as section shrinkage and elongation, are obtained through the tensile experiment. In the stretching experiment, the material can obtain the deformation degree of about 20-30% because the instability generates the necking phenomenon. Such a degree of deformation is insufficient for analyzing a plastic forming process having a large deformation characteristic, regardless of theoretical analysis or numerical simulation. Although theoretically, the unidirectional compression or torsion experiment can obtain a larger deformation degree, the literature document in the aspect is not uncommon. Actually, the manufacturing method of the above-mentioned true stress-strain curve is mostly close to a simple loading process, and this loading manner can be regarded as a special case in the plastic forming process. The information provided by these experimental methods is not sufficient to support a complete understanding of the hardening characteristics of the metallic material. Generally, a plurality of groups of test data under different working conditions such as temperature, stretching rate and the like are collected, so in the data processing process, the test data is required to be data before the maximum force value, and then an engineering stress-engineering strain curve, a real stress-real strain curve and a real plastic strain-real stress curve are obtained through calculation. And fitting the calculated hardening equation by using different mathematical models, and calculating by using the slope of slop to obtain a r value so as to further obtain a plastic constitutive equation. Both mapping translation and data fitting software such as Origin are required, with data being preprocessed by alternative self-research programs. The processing mode is time-consuming and labor-consuming, errors of manual operation are large, and the data precision of the main curve is difficult to guarantee, so that the processing efficiency of test data is low, and the curve precision is insufficient. In view of the above reasons, the invention develops anisotropic-based uniaxial tensile test data analysis software by adopting a computer and an object-oriented advanced programming technology, selects rows of imported data, analyzes and screens the imported data, can automatically solve a hardening curve, outputs a plurality of coefficients such as parameters, r values and the like of fitting equations of the hardening curve, can obviously shorten the pretreatment time of integrity analysis before finite element software, improves the data processing speed and precision, and further can provide important technical support for calibrating yield equations.
At the present day, the experimental data are usually processed by data fitting software such as Origin. The disadvantages of processing the test data are as follows: firstly, in order to eliminate random errors in the test process, a plurality of test pieces need to be selected at the same stretching rate to be stretched simultaneously, so that the data volume to be processed is large. A large amount of test data are calculated completely by a manual mode, and the initial point position is considered to be translated for multiple times, so that time and labor are wasted, and the processing efficiency is extremely low; secondly, when the translation is carried out, the curve to be translated needs to be horizontally moved to be approximately coincident with the target curve. The coincidence condition of the two curves cannot be guaranteed only by means of naked eye judgment and manual translation, and the accuracy of the translation distance directly influences the calculation accuracy, so that the actual mechanical property parameters are influenced. Therefore, random errors are easily introduced by manual operation, and the processing precision of test data cannot be guaranteed; third, the use of Origin, et al, software to perform the trial data processing process involves multiple processes and lacks a fully functional data processing environment. Data conversion and transmission are frequently carried out, so that artificial errors are easily caused; finally, because the processing precision of the test data cannot be guaranteed, the design error is increased in the process of calibrating the yield equation. In summary, this technique has become an important tool for experimental data analysis.
Disclosure of Invention
The invention aims to solve the problems that the traditional method is complex in calculation and large in error when obtaining a hardening curve of a dog bar test piece before the maximum force, and yield equation calibration parameters are difficult to obtain, and provides an anisotropy-based unidirectional tensile test data analysis method
In order to achieve the purpose, the invention adopts the following technical scheme to realize the purpose:
a unidirectional tensile test data analysis method based on anisotropy comprises the following steps:
in the formula: l0Is the original gauge length, Delal is the deformation, F is the load on the sample, A0For the original cross-sectional area, σ, of the specimeneIs true stress,. epsiloneIs true strain;
εtp＝εt-σt/E (4)
in the formula: l0Is the original gauge length, Delal is the deformation, F is the load on the sample, A0The original cross-sectional area of the specimen, E is the modulus of elasticity, σtIs true stress,. epsilontFor true strain,. epsilontpTrue plastic strain;
removing the elastic deformation stage to obtain a hardening curve;
step 3, finding out before fittingYield point, determining the intersection point of the straight line passing through the point (0.002, 0) and the real stress-real plastic strain curve of the material with the elastic modulus E of the material as the slope, and the abscissa corresponds to the yield strain epsilons(ii) a For parameters of a nonlinear formula in a mathematical model formula, fitting real stress-real strain data behind a yield point, editing the mathematical model formula, and fitting by using a least square method;
step 4, obtaining a hardening curve in the elastic removal stage, and fitting by adopting a hardening constitutive model after translation to finish the parameter calibration process of the hardening constitutive model;
the measurement of the anisotropy coefficient in thickness direction is determined by the uniaxial tensile test of sheet metal, the value of which is the strain epsilon of the test specimen in the width direction1With strain in the thickness direction epsilon2Expressed as a ratio of (i):
in the formula: r is a thickness direction special-shaped coefficient; epsilon2Is the strain in the width direction of the sample; epsilon3Is the strain in the thickness direction of the sample; b is the width of the sample after the sample is stretched; b0Is the initial width of the sample; t is the width of the sample after the sample is stretched; t is t0Is the initial thickness of the metal plate;
measuring the value of the thickness anisotropy coefficient r, calculating the dependent variable through grid deformation, taking the average value of the dependent variable as a judgment standard, and verifying the reliability of the judgment by a stamping test; the r value is determined from samples taken in three directions, and the average value is:
in the formula: r is0Is a rolling direction value, r45At a value of 45 DEG to the rolling direction, r90At a value of 90 deg. to the rolling direction.
The invention further improves the following steps:
in the step 4, the hardening constitutive model respectively adopts a Swift model, a Voce model, a Swift-Voce model, a Ludwik model, a Hockett-Sherby model and a Swift-Hockett Sherby model to fit the real stress-real plastic strain curves of the aluminum alloy plates in different rolling directions obtained by the test, and the concrete steps are as follows:
the Swift model formula is: k (e0+ x) n
The Voce model formula is as follows: a- (A-B) 'exp (-C' x)
The Swift-Voce model formula is as follows: k (e0+ x) n + A- (A-B) exp (-C x))/2
The Ludwik model formula is: s0+ K x ^ n
The Hockett-Sherby model formula is: a- (A-B) 'exp (-C' x ^ D)
The Swift-HockettSherby model formula is as follows: (K (e0+ x) n + A- (A-B) exp (-C x D))/2.
In the step 5, in the process of measuring the thickness, according to the volume invariant condition epsilon3＝-(ε1+ε2) In which epsilon1For longitudinal strain, equation (6) can be simplified as:
in the formula: epsilon1Strain in the lengthwise direction of the sample,. l0Is the gauge length, l is the gauge length after stretching.
In the step 5, each direction in the plane of the sheet material is also in plastic anisotropy, that is, the plastic plane anisotropy of the sheet material, which has a large influence on the lug at the mouth of the drawing part and can be represented by a thickness anisotropy difference Δ r, as follows:
compared with the prior art, the invention has the following beneficial effects:
1) according to the invention, through the modularized encapsulation of the engineering data processing method, the self-research program and the standardized data processing flow, the traditional manual plotting and curve fitting are converted into the processes of automatic plotting and optimal solution solving of a computer, so that random errors caused by manual operation are avoided, and the data processing precision is improved.
2) The invention connects the steps of real stress-real strain conversion, hardening curve fitting, r value solving and the like in series by keying in the measurement parameters, so that the data stream transmission among the steps is completely and automatically completed by a computer, the processing efficiency of anisotropic unidirectional tensile test data is greatly improved, and the aim of fast and high-precision processing of the test data is fulfilled.
3) According to the invention, through centralized visualization, a complicated calculation link can be omitted, and the visual comparison of force-displacement, engineering stress-engineering strain, real stress-real strain curves and the like based on the anisotropism RD, DD and TD can be realized. The method has the advantages that the real stress-real plastic strain curves are fitted by adopting several classical hardening constitutive models, the fitting effect of the fitting curves and the experiment curves can be visually compared, and the method is efficient, convenient and accurate.
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In order to more clearly explain the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention, and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.
FIG. 1 is a system data flow diagram of the present invention;
FIG. 2 is a diagram illustrating the extraction of the force-displacement curve before the maximum force value in the embodiment of the present invention;
FIG. 3 is a calculation of a true stress-true plastic strain curve according to an embodiment of the present invention;
FIG. 4 is a fitting result of a hardening model according to an embodiment of the present invention;
FIG. 5 shows the calculation result of r value in the embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. The components of embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations.
Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, it need not be further defined and explained in subsequent figures.
In the description of the embodiments of the present invention, it should be noted that if the terms "upper", "lower", "horizontal", "inner", etc. are used for indicating the orientation or positional relationship based on the orientation or positional relationship shown in the drawings or the orientation or positional relationship which is usually arranged when the product of the present invention is used, the description is merely for convenience and simplicity, and the indication or suggestion that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and thus, cannot be understood as limiting the present invention. Furthermore, the terms "first," "second," and the like are used merely to distinguish one description from another, and are not to be construed as indicating or implying relative importance.
Furthermore, the term "horizontal", if present, does not mean that the component is required to be absolutely horizontal, but may be slightly inclined. For example, "horizontal" merely means that the direction is more horizontal than "vertical" and does not mean that the structure must be perfectly horizontal, but may be slightly inclined.
In the description of the embodiments of the present invention, it should be further noted that unless otherwise explicitly stated or limited, the terms "disposed," "mounted," "connected," and "connected" should be interpreted broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
The invention is described in further detail below with reference to the accompanying drawings:
the hardening constitutive relation of a material generally refers to a mathematical relation describing the mechanical properties of the material. The establishment of the elastic-plastic constitutive relation of the common aviation aluminum alloy plate can not only provide a digital visual model, but also further improve the accuracy of the subsequent finite element simulation plate moulding. In the elastic stage, the stress-strain relationship of the material is linearly related and can be constructed by using Hooke's law; in the plasticity stage, the relation between stress and strain changes in a nonlinear way, the strain is not only related to the stress state, but also related to the deformation history, and then the true stress-strain curve of the aluminum alloy plate is fitted by adopting a mathematical model.
Referring to fig. 1, the anisotropic-based uniaxial tensile test data analysis method of the present invention includes the following steps:
according to the invention, firstly, a relation curve of load F and sample deformation delta l at each time point in the material stretching process along different rolling directions is obtained according to a 3D-DIC experiment, and according to the length, width and thickness measured before the experiment, an engineering stress-strain curve is obtained by calculation according to the following formulas (1) and (2):
in the formula: l0Is originalGauge length, delta l is deformation, F is load borne by the sample, A0For the original cross-sectional area, σ, of the specimeneIs true stress,. epsiloneIs true strain;
and calculating the real stress-real strain and the real stress-real plastic strain before necking according to the engineering stress-engineering strain curve directly converted from the tensile test, and calculating according to the formulas (3), (4) and (5). Then removing the elastic deformation stage to obtain a hardening curve:
εtp＝εt-σt/E (4)
in the formula: l0Is the original gauge length, Delal is the deformation, F is the load on the sample, A0The original cross-sectional area of the specimen, E is the modulus of elasticity, σtIs true stress,. epsilontFor true strain,. epsilontpTrue plastic strain;
before fitting, a yield point is firstly found, an intersection point of a straight line which takes the elastic modulus E of the material as a slope and passes through a point (0.002, 0) and a real stress-real plastic strain curve of the material is determined, and the abscissa corresponds to the yield strain epsilons. And for parameters of a nonlinear formula in the mathematical model formula, fitting the real stress-real strain data after the yield point, editing the mathematical model formula, and fitting by using a least square method.
After obtaining the hardening curve of the removal elastic phase and translating, several classical hardening constitutive models are used for fitting. Two types of metal elastoplasticity constitutive models are commonly used, one is a power model proposed by Hol-Lomon, Ludwik and Gh osh, and the other is an exponential model proposed by Vote and Hockett. According to the method, a Swift model, a Voce model, a Swift-Voce model, a Ludwik model, a Hockett-Sherb y model and a Swift-Hockett Sherby model are respectively adopted to fit the real stress-real plastic strain curves of the aluminum alloy plates in different rolling directions obtained by the test.
The Swift model formula is: k (e0+ x) n
The Voce model formula is as follows: a- (A-B) 'exp (-C' x)
The Swift-Voce model formula is as follows: k (e0+ x) n + A- (A-B) exp (-C x))/2
The Ludwik model formula is: s0+ K x ^ n
The Hockett-Sherby model formula is: a- (A-B) 'exp (-C' x ^ D)
The Swift-HockettSherby model formula is as follows: (K (e0+ x) n + A- (A-B) exp (-C x D))/2
The process of calibrating the parameters of the hardened constitutive model is completed, and the process of calibrating the anisotropic parameters r is carried out below.
The metal plate can show different forming performances in all directions in the stamping forming process, and the phenomenon is caused by the fact that the rolling direction of the plate is single in the processing process, namely the anisotropy of the plate. The thickness anisotropy coefficient (i.e., plastic strain ratio) also has a large influence on the calendering performance of the sheet material. Taking a drawing part as an example, the flange part is stressed in two directions of compression and tension simultaneously in the forming process, and simultaneously, the material of the flange part flows into a female die. Generally, the larger the thick anisotropy index is, the larger the flow difference of the metal plate is, the more obvious the anisotropy in the plate plane is, the more irregular the edge of the drawing part is, a lug is formed, and the aesthetic degree and the utilization rate are influenced. The specific change is that the larger the r value is, the poorer the deformability of the plate in the thickness direction is, namely the plate is not easy to thin or thicken along with the change of stress; conversely, the smaller the r value, the more thinning or thickening easily occurs. Therefore, the r value is increased, the occurrence of instability phenomena such as wrinkling and cracking can be reduced, and drawing is facilitated and the product quality is improved. In general, the measurement of the anisotropy coefficient of thickness is carried out by the uniaxial tensile test of sheet metal, the value of which is expressed as the strain ε of the specimen in the width direction1Strain in the thickness directionε2Is expressed by the ratio of (i) to (ii)
In the formula: r is a thickness direction special-shaped coefficient; epsilon2Is the strain in the width direction of the sample; epsilon3Is the strain in the thickness direction of the sample; b is the width of the sample after the sample is stretched; b0Is the initial width of the sample; t is the width of the sample after the sample is stretched; t is t0Is the initial thickness of the metal plate.
In the process of measuring the thickness, the uncertainty of measuring the value of the thickness anisotropy coefficient of the plate is caused by the nonuniformity of the initial thickness of the plate and the change of the surface quality of the sample after the test. Can be based on the condition of constant volume3＝-(ε1+ε2) (wherein ε1Is a strain in the longitudinal direction), equation (6) can be expressed as
In the formula: epsilon1Strain in the length direction of the sample; l0Is a gauge length; l is the gauge length after stretching.
The thickness anisotropy coefficient r is generally not determined from the calculated epsilon2And epsilon3The value is obtained. But according to the size of the test piece or the deformation of the coordinate grid, the invention calculates the dependent variable through the grid deformation; and because the sheet metal is different in rolling direction, the values obtained when the thickness anisotropy values of the samples forming different angles with the sheet metal lines are measured are different, so the average value of the sheet metal is taken as a judgment standard, and the reliability of the judgment is verified by a stamping test. When the thickness anisotropy coefficient r value is measured by using the size variation of a uniaxial tension sample, the measurement is required at the stage of uniform plastic deformation of a material, the deformation of the inner part of the material is generated when the material is close to necking, the measurement data is inaccurate, and the material is generally not fractured and unstable in the actual part forming, so the r value obtained when the material is fractured has no significance. The r value is taken according to three directionsThe average value of the measured samples is as follows:
in the formula: r is0Is the rolling direction value; r is45Is at a value of 45 DEG to the rolling direction; r is90At a value of 90 deg. to the rolling direction.
In the formula r45This is doubled by the fact that the line 0 returns to 0 from left to right, passing through only one of 0 ° and 90 °, but two of 45 °. In addition, each direction in the plane of the sheet also presents plastic anisotropy, namely the plastic plane anisotropy of the sheet, the plastic plane anisotropy has a large influence on a lug at the opening part of a drawing part, and can be represented by a thickness anisotropy difference value delta r as follows:
the principle of the invention is as follows:
FIG. 1 is a system data flow diagram of the present invention. The software architecture after encapsulation is mainly divided into three modules: the system comprises a data automatic processing module, a hardening curve fitting module and an r value solving module. The data automatic processing module is the bottom technical principle of software operation; the hardening curve fitting module is a main software module which is visible and visible for a user; the r value solving module is a normal processing flow for calibrating the yield equation.
Since Windows operating system applications adopt a message loop mechanism to implement multitasking operation of the system, the concept of sequential execution differs from that of DOS operating systems in terms of code design ideas. The program design and operation of each experiment in the software can be divided into three parts of data input and correction, calculation and graph drawing and data processing result and graph output.
The method has the advantages that the structure level of software is clearer, the software is easy to read, modify, reuse and expand, and the data protection is convenient. Several modules are described below.
1. Data input module
The module comprises two parts of user information input and raw experiment data input. Because more data parameters need to be processed, the input parameters are classified according to the types and properties to establish a database, and the rich database tool provided by MATLAB and internal controls such as Textbox, Label, Commandbox, Optionbutton and the like are utilized to realize the unified management of a plurality of parameters. The data interface combines Label and Textbox, and the Label frame made by Label shows the meaning and dimension of Textbox text box, so that the user can use the software correctly. The movement of the cursor can be realized by using a Tab key or a mouse when data is input. The database is opened in a sharing mode, a DAO (data Access objects) technology is introduced, links between programs and the database are established by defining Workspace, DbEngine, Recordset and SQL statements, all input data information is stored in the database, and corresponding storage data of original data and data processing results can be called out according to user information stored in the database.
(1) User information input section
Prompting the Textbox information by a Label Label, guiding the user to register, applying a database, connecting by using a DAO technology, and storing the registration information. And storing the registered information into a database, and simultaneously exiting the registration interface and entering a login interface. And inputting user information by using the Textbox text box, verifying the user information and the related information in the database, if the user information is consistent with the related information, entering a data input interface, and if the user information is not consistent with the related information in the database, continuously and thrice mistakes are performed, exiting the system.
(2) Raw Experimental data input section
Declaring a global variable by using Public statements to act on the whole application program; and assigning a value to the database through the text attribute of the text box. The code function of the data input part of the program is explained in connection with the measurement experiment of the uniaxial tension.
2. Computing module
The module comprises two parts of experimental data calculation and graph drawing.
(1) Data calculation section
The data processing is carried out by combining the definition array, input sentences, output sentences and the like with least square method straight line fitting, nonlinear fitting, numerical integration and other mathematical methods, a large number of complex calculation formulas are programmed into program codes, and a computer can extract data from memory variables according to the formulas and calculate the data to obtain results only by inputting experimental data on an input interface by a user.
(2) Drawing part of graphics
And designing a corresponding drawing interface and a coordinate system according to the specific requirements of the experiment by using a defined coordinate system and drawing functions such as Line, Circle and the like. The types of patterns involved in the experiments can be classified into linear and curvilinear types. For the linear graph, in order to ensure the accuracy and precision of the obtained linear graph, a calculation formula of least square normal linear fitting is programmed into a program, so that plotted data points are uniformly distributed on two sides of the linear graph, the slope, intercept and correlation coefficient of the linear graph can be displayed in a data interface, and the result is accurate; and processing the curve graph by adopting mathematical methods such as nonlinear fitting, numerical integration and the like, and then drawing a graph.
3. Data and graph output module
By pressing the "calculate" button in the data processing interface, the data processing result will be displayed accurately. After the data processing result is obtained, pressing a 'graph' button in the input interface, the corresponding graph can be displayed in the drawing interface.
4. Printing module
The Print function is used for writing a printing program, and a data processing result or a graph can be printed by clicking a printing item in a data or graph output interface menu.
As shown in fig. 2-5, the results output module interface. By means of the DIC method, the force-displacement relationship can be measured, as shown in fig. 1. The maximum force is indicated by the black pentagram, which is generally considered to be the point where necking begins, after which deformation will be concentrated near the necking location and no longer uniform. Therefore, the experimental data after maximum force is not used to calculate the stress-strain relationship. The engineering strain and engineering stress can be calculated by definition from the force-displacement curve before the maximum force shown in fig. 2. The engineering stress-engineering strain relationship and the real stress-real strain relationship shown in fig. 3 are obtained through calculation (the engineering stress-engineering strain curve is far smaller than the real stress-real strain curve). The real strain comprises a small part of elastic strain and a large plastic strain, and the elastic strain can be removed from the real strain through a superposition relation to obtain the real plastic strain. Therefore, by using the true stress-true strain curve shown in fig. 3, the common hardening curve equations such as Swift and Voce can be fitted, and the fitting result is shown in fig. 4. Through comparison with experimental data, it can be seen that the goodness of fit with the experimental results is very high. Similarly, the true strain in the width direction can be calculated by definition. The r-value is calculated by taking the average of the slopes of the curves shown in fig. 5 based on the definition of the r-value of the anisotropy parameter and the principle of the plastic deformation volume invariance. Note that in this interface, it is necessary to select an experimental data curve to be output, or a hardening curve fitting curve and a r value to solve a slop curve, and simultaneously, automatically store all data calibration results in a working directory.
When the method is specifically implemented, firstly, software is started, and a software main interface is entered; setting a working directory through a file menu, and inputting test data such as sample size, elastic modulus, Poisson ratio and the like; pressing a button for reading data and calculating, entering a data automatic processing module, and performing data processing by using mathematical methods such as least square method linear fitting, nonlinear fitting, numerical integration and the like, so as to eliminate errors generated in the drawing process and obtain a more correct and more scientific real data processing result; pressing down a drawing button, entering a hardening curve fitting and r value solving module to facilitate further calibration of a yield equation, wherein the right side can select the type of a fitted curve; pressing the Clear button can Clear the current calculation and drawing operation; and sixthly, the data enters a result output module, and the processing result can be stored in the working directory by selecting the data content to be output.
The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes will occur to those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (4)
1. A unidirectional tensile test data analysis method based on anisotropy is characterized by comprising the following steps:
step 1, obtaining a relation curve of load F and sample deformation delta l at each time point in the material stretching process along different rolling directions according to a 3D-DIC experiment, and calculating according to the length, width and thickness measured before the experiment and the formulas (1) and (2) to obtain an engineering stress-strain curve of the material according to the following formula:
in the formula: l0Is the original gauge length, Delal is the deformation, F is the load on the sample, A0For the original cross-sectional area, σ, of the specimeneIs true stress,. epsiloneIs true strain;
step 2, calculating real stress-real strain and real stress-real plastic strain before necking according to an engineering stress-engineering strain curve directly converted from a tensile test, and calculating according to the formulas (3), (4) and (5) to obtain:
εtp＝εt-σt/E (4)
in the formula: l0Is the original gauge length, Delal is the deformation, F is the load on the sample, A0The original cross-sectional area of the specimen, E is the modulus of elasticity, σtIs true stress,. epsilontFor true strain,. epsilontpTrue plastic strain;
removing the elastic deformation stage to obtain a hardening curve;
step 3, finding out a yield point before fitting, determining an intersection point of a straight line passing through a point (0.002, 0) and a real stress-real plastic strain curve of the material by taking the elastic modulus E of the material as a slope, wherein the abscissa corresponds to the yield strain epsilons(ii) a For parameters of a nonlinear formula in a mathematical model formula, fitting real stress-real strain data behind a yield point, editing the mathematical model formula, and fitting by using a least square method;
step 4, obtaining a hardening curve in the elastic removal stage, and fitting by adopting a hardening constitutive model after translation to finish the parameter calibration process of the hardening constitutive model;
step 5, calibrating an anisotropic parameter r;
the measurement of the anisotropy coefficient in thickness direction is determined by the uniaxial tensile test of sheet metal, the value of which is the strain epsilon of the test specimen in the width direction1With strain in the thickness direction epsilon2Expressed as a ratio of (i):
in the formula: r is a thickness direction special-shaped coefficient; epsilon2Is the strain in the width direction of the sample; epsilon3Is the strain in the thickness direction of the sample; b is the width of the sample after the sample is stretched; b0Is the initial width of the sample; t is the width of the sample after the sample is stretched; t is t0Is the initial thickness of the metal plate;
measuring the value of the thickness anisotropy coefficient r, calculating the dependent variable through grid deformation, taking the average value of the dependent variable as a judgment standard, and verifying the reliability of the judgment by a stamping test; the r value is determined from samples taken in three directions, and the average value is:
in the formula: r is0Is a rolling direction value, r45At a value of 45 DEG to the rolling direction, r90At a value of 90 deg. to the rolling direction.
2. The anisotropy-based uniaxial tensile test data analysis method according to claim 1, wherein in the step 4, the hardening constitutive model is respectively fitted to the real stress-real plastic strain curves of the aluminum alloy plates in different rolling directions obtained by the test by adopting a Swift model, a Voce model, a Swift-Voce model, a Ludwik model, a Hockett-Sherby model and a Swift-Hockett Sherby model, and the concrete steps are as follows:
the Swift model formula is: k (e0+ x) n
The Voce model formula is as follows: a- (A-B) 'exp (-C' x)
The Swift-Voce model formula is as follows: k (e0+ x) n + A- (A-B) exp (-C x))/2
The Ludwik model formula is: s0+ K x ^ n
The Hockett-Sherby model formula is: a- (A-B) 'exp (-C' x ^ D)
The Swift-HockettSherby model formula is as follows: (K (e0+ x) n + A- (A-B) exp (-C x D))/2.
3. The method for analyzing data of anisotropic-based uniaxial tension test according to claim 1, wherein in the step 5, the thickness is measured according to a volume-invariant condition e3＝-(ε1+ε2) In which epsilon1For longitudinal strain, equation (6) can be simplified as:
in the formula: epsilon1Strain in the lengthwise direction of the sample,. l0Is the gauge length, l is the gauge length after stretching.
4. An anisotropy-based uniaxial tensile test data analysis method according to claim 3, wherein, in the step 5, each direction in the plane of the sheet is also plastic anisotropy, that is, the plastic plane anisotropy of the sheet, which has a large influence on the lug at the mouth of the drawing part and can be expressed by a thickness anisotropy difference Δ r, as follows:
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| CN116371942A (en) * | 2023-06-05 | 2023-07-04 | 东北大学 | Transverse thickness distribution prediction method based on uneven transverse strength of strip steel |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN111339703A (en) * | 2020-02-27 | 2020-06-26 | 中国科学院金属研究所 | Virtual prediction method for material hardening behavior under large strain condition |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
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| CN111339703A (en) * | 2020-02-27 | 2020-06-26 | 中国科学院金属研究所 | Virtual prediction method for material hardening behavior under large strain condition |
Non-Patent Citations (1)
| Title |
|---|
| 程超等: "IF钢硬化模型试验", 《精密成形工程》 * |
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| CN113720679A (en) * | 2021-07-26 | 2021-11-30 | 桂林电子科技大学 | Method for testing mechanical constitutive equation of micron-sized electronic solder |
| CN113720679B (en) * | 2021-07-26 | 2024-03-01 | 桂林电子科技大学 | Method for testing mechanical constitutive equation of micron-size electronic solder |
| CN116371942A (en) * | 2023-06-05 | 2023-07-04 | 东北大学 | Transverse thickness distribution prediction method based on uneven transverse strength of strip steel |
| CN116371942B (en) * | 2023-06-05 | 2023-10-20 | 东北大学 | Transverse thickness distribution prediction method based on uneven transverse strength of strip steel |
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