CN117350105A - Method for correcting and checking data in consideration of bulging in metal compression experiment - Google Patents
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Abstract
The invention provides a method for correcting and checking data in consideration of bulging in a metal compression experiment, which relates to the technical field of metal deformation, and comprises the steps of firstly carrying out isothermal compression experiment to obtain a pseudo-true stress-strain curve, and carrying the pseudo-true stress-strain curve into a strain-strain database of a finite element model; establishing a three-dimensional model of the workpiece and the die by using simulation software with a drawing function, performing isothermal compression experiment simulation test, and obtaining the horizontal displacement distribution condition of each node of the workpiece in the compression process through finite element simulation; and calculating to obtain true stress by using the ratio of the load obtained by the test to the central cross-sectional area, further obtaining a corrected rheological curve, obtaining a true stress-strain curve, and introducing the true stress-strain curve into a strain-strain database of a finite element model, checking comparison of the bulge size, comparison of the metal streamline and comparison of the load-displacement curve, if the comparison result has deviation, ending the calculation, and if the comparison result has no deviation, repeating the steps.
Description
Technical Field
The invention relates to the technical field of metal deformation, in particular to a method for correcting and checking data when bulging is considered in a metal compression experiment.
Background
When the thermal simulation tester and the like perform compression experiments, parameters such as temperature, displacement, force, speed, stress, strain and the like can be simulated, and the thermal simulation tester and the like are important reference sources for finite element simulation and process establishment of materials. Has important academic significance and engineering value for accurately expressing and researching the thermal deformation process.
The rheological curve of the metal material is often obtained through a thermal simulation compression test, wherein the data of the true stress is calculated under the condition that the material is uniformly deformed, however, in the actual compression process, due to the influences of friction and temperature gradient, the material can form obvious bulging in the compression process, so that a certain deviation exists between the true stress value directly calculated and the actual true stress value. At present, individual students utilize a correction formula to correct data to a certain extent according to the influences of friction and temperature gradients, but most formulas used in the correction process are empirical formulas, so that the compression experiment of different materials and different deformation states has certain limitation.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a method for correcting and checking data in consideration of belly swelling in metal compression experiments, which realizes correction and check of experimental data.
The technical scheme adopted by the invention is as follows:
a method for correcting and checking data in consideration of belly swelling in a metal compression experiment comprises the following steps:
step 1, carrying out isothermal compression experiments, calculating pseudo-true strain and the value of the pseudo-true stress by a traditional calculation method to obtain a pseudo-true stress-strain curve, and introducing the pseudo-true stress-strain curve into a strain-strain database of a finite element model;
the traditional calculation method specifically comprises the following steps: the data system is utilized to collect data of the displacement sensor and the pressure sensor in the isothermal compression experiment process, and the collected data are calculated, so that values of pseudo-true strain epsilon and pseudo-true stress sigma are obtained, and the calculation formulas are shown in the formulas (1) and (2):
wherein, I 0 Is the initial length of the sample, mm; Δl is displacement of the sample during compression, mm; s is the cross-sectional area of the sample, mm 2 The method comprises the steps of carrying out a first treatment on the surface of the F is the experimentally obtained load, kgf; d, d 0 The initial diameter of the sample, mm;
step 2, establishing a three-dimensional model of the workpiece and the die by using a self-contained drawing function of simulation software;
step 3, performing isothermal compression experiment simulation test, wherein in the simulation process, the workpiece adopts a rigid plastic body, the initial temperature is the same as the deformation temperature designed in the isothermal compression experiment, and the simulation compression process adopts speed to control the movement of the die, and because the workpiece is provided with an upper symmetry plane and a lower symmetry plane, the strain rate is increasedThe conversion formula with the velocity v is shown in formula (3), which is a functional relation of velocity and stroke:
in the method, in the process of the invention,is the strain rate, s -1 The method comprises the steps of carrying out a first treatment on the surface of the h is the height of the sample before compression and mm; s is the compression stroke of the upper die under the condition of each deformation parameter, and mm.
Step 4, obtaining the horizontal displacement distribution condition of each node of the workpiece in the compression process through finite element simulation;
the distribution situation is specifically as follows: the horizontal displacement of the upper end and the lower end of the compressed sample is about zero;
step 5, calculating to obtain true stress by using the ratio of the load obtained by the test to the central cross-sectional area, and further obtaining a corrected rheological curve to obtain a true stress-strain curve;
step 6, using a true stress-strain curve to be brought into a strain-strain database of a finite element model, checking the comparison of the bulge size, the comparison of a metal streamline and the comparison of a load-displacement curve, if the comparison result has deviation, finishing calculation, and if the comparison result has no deviation, repeating the steps 2-5;
the beneficial effects of adopting above-mentioned technical scheme to produce lie in:
the invention provides a method for correcting and checking data in consideration of belly swelling in a metal compression experiment. The actual area of the belly in the compression process is obtained through point tracking, and finally, the ratio of the load in the test to the belly area in the simulation is used for carrying out recirculation calculation to obtain more accurate rheological stress data, so that the rheological curve is corrected, and the true stress which finally approaches to the real situation is obtained, thereby providing more accurate basic data for dynamic recrystallization, sub-dynamic recrystallization, static recrystallization, deformation numerical simulation and the like.
The calculation method and the calculation process can be used for manually calculating the true stress-strain after the displacement-force data are derived, and can also be used for automatically calculating through experimental equipment such as a thermal simulation experiment machine.
Drawings
FIG. 1 is a diagram showing the belly of a sample after an experiment according to the present invention;
FIG. 2 is a schematic diagram of a numerical simulation three-dimensional model according to the present invention;
FIG. 3 is a schematic diagram of the simulation results of the present invention;
FIG. 4 is a process diagram of an isothermal hot compression test of 34CrNi3MoV steel provided by an embodiment of the invention;
FIG. 5 is a graph showing the true stress-true strain curve of 34CrNi3MoV steel provided by the example of the present invention under different deformation conditions;
FIG. A-Under the conditions of (b) -t=1000 ℃;
FIG. 6 is a microstructure of 34CrNi3MoV steel provided by an embodiment of the invention;
graph (a) -t=900 ℃,under the conditions of (b) t=1000 ℃, -f>Under the condition that;
fig. 7 shows a graph of t=1000 degrees celsius provided in the example of the present invention,under the condition, each node is distributed in the horizontal direction;
FIG. 8 is a graph of the relationship between the intermediate cross-sectional area and compressive strain under different deformation conditions provided by an embodiment of the present invention;
FIG. A-Under the conditions of (b) t=1000 ℃;
FIG. 9 is a graph comparing an original rheology curve and a finite element corrected rheology curve provided by an embodiment of the present invention;
picture (a)Under the condition of (b) the following>Under the condition of (c) ->Under the condition, the graphUnder the condition that;
FIG. 10 is a graph comparing test and finite element load-displacement provided by an embodiment of the present invention;
FIG. A-Under the conditions of (b) t=1000 ℃.
Detailed Description
The following describes in further detail the embodiments of the present invention with reference to the drawings and examples. The following examples are illustrative of the invention and are not intended to limit the scope of the invention.
A method for correcting and checking data in consideration of belly swelling in a metal compression experiment comprises the following steps:
step 1, carrying out isothermal compression experiments, calculating pseudo-true strain and the value of the pseudo-true stress by a traditional calculation method to obtain a pseudo-true stress-strain curve, and introducing the pseudo-true stress-strain curve into a strain-strain database of a finite element model;
the traditional calculation method specifically comprises the following steps: in order to obtain a true stress-true strain curve, acquiring data of values of a displacement sensor and a pressure sensor in the process of an equivalent temperature compression experiment by using a data system, and calculating the acquired data to obtain values of pseudo-true strain epsilon and pseudo-true stress sigma, wherein the calculation formulas are shown in the formulas (1) and (2):
wherein, I 0 Is the initial length of the sample, mm; Δl is displacement of the sample during compression, mm; s is the cross-sectional area of the sample, mm 2 The method comprises the steps of carrying out a first treatment on the surface of the F is the experimentally obtained load, kgf; d, d 0 The initial diameter of the sample, mm;
the traditional calculation method can be used for calculating through data of derived displacement-force, and can also be used for automatically calculating through experimental equipment such as a thermal simulation experiment machine. The calculation results do not accurately consider the influence of the belly, and the belly-bulging photo of the sample after the experiment is shown in fig. 1. In particular, when the deformation is large, the error is larger, so that the curve obtained by the traditional calculation method is a pseudo-true stress-strain curve.
Step 2, a three-dimensional model of the workpiece and the die is built by using simulation software with a drawing function, as shown in fig. 2, in the embodiment, in order to reduce the simulation operation time, 1/8 of the cylinder is taken for calculation;
step 3, performing isothermal compression experiment simulation test, wherein in the simulation process, the workpiece adopts a rigid plastic body, the initial temperature is the same as the deformation temperature designed in the isothermal compression experiment, the motion of the die is controlled by adopting speed in the simulation compression process,because the workpiece is provided with an upper symmetry plane and a lower symmetry plane, the strain rateThe conversion formula with the velocity v is shown in formula (3), which is a functional relation of velocity and stroke:
in the method, in the process of the invention,is the strain rate, s -1 The method comprises the steps of carrying out a first treatment on the surface of the h is the height of the sample before compression and mm; s is the compression stroke of the upper die under the condition of each deformation parameter, and mm.
Step 4, obtaining the horizontal displacement distribution condition of each node of the workpiece in the compression process through finite element simulation;
the distribution situation is specifically as follows: the horizontal displacement of the upper end and the lower end of the compressed sample is about zero; this is because there is a large friction between the specimen and the indenter, and the upper and lower ends of the specimen are difficult to deform in the horizontal direction during the compression process. However, the crystal grains in the region are flattened by the external force in the vertical direction at the center of the sample, and when the deformation amount increases, the crystal grains flow to both sides, so that the compressed sample forms a belly drum. The simulation result of the belly is schematically shown in fig. 3.
Step 5, calculating to obtain true stress by using the ratio of the load obtained by the test to the central cross-sectional area, and further obtaining a corrected rheological curve to obtain a true stress-strain curve;
step 6, using a true stress-strain curve to be brought into a strain-strain database of a finite element model, checking the comparison of the bulge size, the comparison of a metal streamline and the comparison of a load-displacement curve, if the comparison result has deviation, finishing calculation, and if the comparison result has no deviation, repeating the steps 2-5;
the test sample of this example was 34CrNi3MoV steel after industrial hot rolling, and the compressed test sample had a specification of Φ8mm×12mm. Work of single pass compression processThe process diagram is shown in fig. 4, the temperature rising rate of the sample is controlled to be 20 ℃/s under the action of resistance heating, the sample is kept at the temperature of 1200 ℃ for 180s, the complete austenitization of the sample is ensured, the temperature reducing rate is controlled to be 10 ℃/s, the temperature is reduced to the deformation parameter temperature, the temperature is kept for 30s, the uniform temperature distribution of the sample is ensured, and finally the compression test is completed. Deformation parameters of the compression process: the temperatures were set at 800, 900, 1000, 1100 and 1200 ℃ and the strain rates were 0.01, 0.1, 1 and 10s -1 The maximum deformation was 50% (true strain 0.6931). The compressed sample was quenched with water and the morphology of the compressed grains was observed by a metallographic microscope (Olympus).
The traditional calculation method obtains a pseudo-true stress-strain curve:
FIG. 5 shows the true stress-true strain curve of 34CrNi3MoV steel under different deformation conditions calculated by using the formulas (1) and (2) after the experiment, and FIG. 5 (a) shows that the strain rate is 0.01s -1 The rheological curves at the respective deformation temperatures show that no peak stress occurs at the deformation temperatures of 900 ℃ and 1000 ℃. FIG. 5 (b) shows the rheological profile at various strain rates at a deformation temperature of 1000℃and it can be seen that the strain rate is 10s -1 In the process, the compression process is fast, the operation difficulty is high, the condition of unloading in advance occurs, and the strain rate can be seen to be 1s -1 And 10s -1 Peak stress does not occur. However, the metallographic observation under the compression conditions indicated above showed that Dynamic Recrystallization (DRX) occurred, as shown in FIG. 6, the deformation conditions were 900-0.1 s -1 And 1000-10 s -1 Microstructure, it can be seen that DRX occurs under this condition.
The method is characterized in that in the actual compression experiment process, a certain temperature gradient exists between the friction force between the pressure head and the end face of the sample and the inside of the sample in the compression process, so that the deformation of the sample in the compression process is uneven, namely, a certain belly drum exists in the sample in the compression process. Therefore, in the formula (2), there is a certain error in the calculation method of the cross-sectional area S, so that the calculated true stress value deviates from the actual true stress value.
If the streamline curve data obtained by directly using the formula (2) is calculated, the conclusion that whether DRX occurs is wrong can be judged by directly using peak stress, and the establishment of the constitutive model and the DRX related model in the later period also deviates from the true value, so that larger errors are caused, and therefore, it is necessary to eliminate the error influence caused by the belly phenomenon.
The finite element simulation software is used for simulating an experimental process, and the actual area of the middle cross section of the sample in the compression process is obtained by utilizing point tracking, so that the rheological curve is corrected.
Establishing a finite element simulation model:
a three-dimensional model is built by selecting simulation software with a drawing function, as shown in fig. 2, a 34CrNi3MoV steel is adopted as a workpiece material, a stress-strain curve of the material is experimental data obtained through experiments, other material constants are obtained through calculation by using a JMapro software, and in order to reduce simulation operation time, 1/8 of the cylindrical shape is taken for calculation.
Setting a simulation step length of 0.1mm in the simulation process, wherein a workpiece adopts a rigid plastic body, the initial temperature is the same as the deformation temperature of the test design, and the heat transfer coefficient of the workpiece and the environment is 0.01 (N/sec/mm/DEG C). The die was a rigid body, the initial temperature was 20 ℃, the friction coefficient between the workpiece and the die was set to 0.3, and the transmission coefficient was 1 (N/sec/mm/. Degree.C). The simulated compression process adopts speed to control the movement of the die, and the conversion formula of the strain rate and the speed is shown as formula (3) which is a functional relation of the speed and the stroke because the workpiece is provided with an upper symmetry plane and a lower symmetry plane.
Calculating the area of the belly drum:
the horizontal displacement distribution of each node of the sample during compression can be obtained by finite element simulation, as shown in fig. 7. From the lower right-hand angular distribution cloud chart of fig. 7, it can be seen that the horizontal displacement of the upper and lower ends of the sample after compression is almost zero because of the large friction between the sample and the ram, and the deformation of the upper and lower ends of the sample in the horizontal direction is difficult during compression. However, the crystal grains in the region are flattened under the action of external force in the vertical direction at the central part of the sample, and when the deformation amount is increased, the crystal grains flow to two sides to enable the compressed sample to form a belly drum and the central cross section P 1 At the pointThe displacement value reaches a maximum.
To calculate the area of the center cross section of the compressed sample at different compression amounts, P can be obtained by point tracking 1 The point is at a displacement value in the horizontal direction at different compression amounts. The curve in FIG. 7 shows that the deformation condition is 1000℃for 0.1s -1 The displacement value of the node at the center cross section is increased along with the increase of the compression quantity according to the acquired data result, but the displacement value under the finite element simulation is obviously larger than the displacement value under the theoretical uniform deformation, and the difference between the displacement value and the displacement value is gradually increased along with the increase of the compression quantity, wherein the maximum displacement value after the compression of the test is obtained through the finite element simulation calculation is 2.07.
According to the above-mentioned point tracking displacement results, a relation graph of the change of the cross-sectional area S along with the compression amount at the belly under different deformation conditions can be obtained by calculation, however, because the load data at the later stage of the thermal compression experiment have larger fluctuation, and the deformation amount in the actual process is smaller than 50% (the strain amount is 0.6931), the paper only carries out statistical calculation on the data of the corresponding variable in the range of 0-0.6931, the result is shown in fig. 8, wherein the dotted line is a theoretical area value under uniform deformation, and it can be seen that the belly area value is larger than the theoretical area value under uniform deformation in the actual compression process, which indicates that obvious non-uniformity exists in the deformation of the sample in the actual compression process. Fig. 8 (a) shows that the cross-sectional area at the belly increases with the increase of the deformation temperature, because the higher the temperature, the higher the internal plasticity of the metal, the higher the fluidity of the material at the time of compression, and the more pronounced the belly, and thus the larger the cross-sectional area at the center. Fig. 8 (b) shows that at the same deformation temperature, the cross-sectional area at the belly of the sample tends to increase along with the reduction of the strain rate, because the smaller the strain rate of the material is in compression, the longer the time for completing the same compression amount is, the sufficient time is available for flowing in the metal, meanwhile, the longer the contact time between the test sample and the pressure head is, the more obvious the temperature drop of the upper end and the lower end of the sample is caused, so that the temperature gradient in the sample is larger, and the cross-sectional area at the belly of the sample is larger under the action of double.
Comparison of rheological curves after finite element correction:
the ratio of the load obtained by the test to the central cross-sectional area can be used for calculating the true stress, the corrected rheological curve is obtained by drawing, and a comparison diagram of the original rheological curve and the finite element corrected rheological curve is shown in fig. 9. As can be seen from fig. 9, the rheological curves after finite element correction are lower than the original rheological curves, and the difference between the two is smaller in the initial stage of deformation, but the difference between the two gradually increases with the increase of the deformation.
To more clearly describe the error conditions before and after correction, the average relative error (R AV ) Calculation statistics were performed and the results are shown in table 1. It can be seen that as the deformation temperature increases, the strain rate decreases, and the compressive true strain increases, the average error gradually increases, and these errors are all caused by the formation of significant bulging during compression. R when the deformation temperature is increased from 800 ℃ to 1200 DEG C AV From 4.54% to 7.57%, strain rate from 10s -1 Down to 0.1s -1 When R is AV From 4.28% to 7.69%, the error gradually increases, and thus correction is required. The error effect caused by the true strain is larger, when the deformation amount is smaller (less than 0.2), R AV The influence is small, the error is as high as 11.0% when the true strain exceeds 0.5, and the error is too large if no correction is performed, so that the accuracy of the industrial process design by utilizing the numerical simulation is seriously influenced.
TABLE 1 average relative error Table 2Average relative error before and after flow curve correction (R) av ,％)
Comparison of simulation and test results (bulge size comparison):
in the thermal deformation compression process, the formation of the bulging is related not only to the friction force of the end face but also to the temperature gradient inside the sample. Therefore, in the finite element simulation, the setting of the friction coefficient and the thermal conductivity coefficient is critical, however, whether the setting of the correlation coefficient is suitable or not can be judged according to the comparison of the deformed sizes of the samples in the experimental and simulation results, and table 2 shows the deformed sizes of the samples in the experimental and simulation results under different deformation strips. Because the compression amount is not consistent under different deformation conditions due to the compression test operation and the like, the compression amount needs to be controlled through a step length in the simulation process so as to ensure that the compression amount in the simulation is the same as the compression amount in the test, and the bulge size of the compressed sample is compared. In table 2, the height h is the height of the compressed sample, d is the diameter of the belly, and it can be seen from table 2 that the simulation result is substantially similar to the experimental result, and the average relative error is only 1.06%, so that it can be demonstrated that the friction coefficient and the thermal conductivity are properly set in the simulation process, and meanwhile, the belly area value obtained by tracking the utilization point in the simulation process is reliable.
TABLE 2 dimension Table 2The size of the specimen after deformation in experimental and simulation results under different deformation strips after sample deformation in experimental and simulation results under different deformation strips
Comparison of simulation and test results (metal flow line comparison):
in the thermal deformation process of the metal material, the grains are extruded and elongated along the plastic forming direction under the action of external force to form a fiber structure, and after proper corrosion treatment, streamline stripes are macroscopically formed, namely, the metal streamline. FIGS. 1 and 3 show deformation conditions at 1000℃for 0.1s -1 The distribution diagram of the metal streamline after compression, wherein fig. 1 is a metal streamline obtained through corrosion after test, and fig. 3 is a distribution diagram of the metal streamline obtained through simulation, and it can be seen that the distribution of the metal streamline in the simulation result is basically consistent with the distribution of the metal streamline in the test. The metal streamline of the upper and lower end surfaces of the sample is vertical, because of the sampleThe end face and the pressure head have larger friction, so that the deformation in the horizontal direction of the end face of the sample is difficult to occur, the grains which are closer to the center section of the sample are extruded and elongated along the normal direction of the surface of the forging piece are more obvious as a whole, and the bending degree of the metal streamline curve at the center section is higher when the metal streamline curve is higher from the center, which means that the displacement in the horizontal direction is larger as the metal streamline curve is farther from the center.
Also, fig. 3 shows that the internal temperature distribution is uneven after the sample is compressed. The temperature of the end face of the sample is reduced due to heat transfer between the end face and the pressure head, and meanwhile, in a thermal compression test, the temperature of the central section of the sample is kept unchanged in a resistance heating mode, so that the temperature of the central section is higher than the temperature of the two end faces at the end of the test, and the temperature gradient deepens the non-uniformity of deformation of the sample in the compression process.
Comparison of simulation and test results (load-displacement curve comparison):
substituting the corrected rheological curve into finite elements to carry out simulation calculation again, deriving load-displacement data in the simulation results before and after correction, and comparing the load-displacement data with the load in the experiment, as shown in fig. 10. It can be seen from fig. 10 that the load obtained by the simulation before correction of the rheological profile is larger than the load value in the test, which is an error due to the increase in the area of the bulge caused by friction and temperature gradient. The load value obtained by the secondary simulation after correction is basically similar to the load value in the test, which indicates that the corrected rheological curve is very similar to the real flow force curve of the material.
Conclusion of this example:
in this example, by obtaining a rheological curve of 34CrNi3MoV steel, correction of the rheological curve by finite elements for non-uniformity of sample deformation during compression can be summarized as follows:
(1) The deformation of the sample in the compression process has obvious bulging condition, and the bulging effect on the stress is very obvious and not negligible when the sample is deformed greatly.
(2) The rheology curves after finite element correction are all lower than the original rheology curves. In the initial stage of deformation, the difference between the two is small, but as the deformation amount increases, the uncorrected error gradually increases.
(3) The belly size and the metal streamline in the finite element simulation result are basically consistent with the test result, wherein the error of the belly size is only 1.06%, which indicates that the belly area value obtained by utilizing point tracking in the simulation process is reliable.
(4) Substituting the corrected rheological curve into finite elements to carry out simulation calculation again, wherein the obtained load value is basically similar to the load value in the test, which proves that the corrected rheological curve is very similar to the real flow force curve of the material, and can also prove that the method is feasible. The research lays a good foundation for more accurate analysis of constitutive equation construction, recrystallization experiments, finite element simulation and the like.
The foregoing description is only of the preferred embodiments of the present disclosure and description of the principles of the technology being employed. It will be appreciated by those skilled in the art that the scope of the invention in the embodiments of the present disclosure is not limited to the specific combination of the above technical features, but encompasses other technical features formed by any combination of the above technical features or their equivalents without departing from the spirit of the invention. Such as the above-described features, are mutually substituted with (but not limited to) the features having similar functions disclosed in the embodiments of the present disclosure.
Claims (4)
1. The method for correcting and checking the data in the metal compression experiment considering the belly swelling is characterized by comprising the following steps:
step 1, carrying out isothermal compression experiments, calculating pseudo-true strain and the value of the pseudo-true stress by a traditional calculation method to obtain a pseudo-true stress-strain curve, and introducing the pseudo-true stress-strain curve into a strain-strain database of a finite element model;
step 2, establishing a three-dimensional model of the workpiece and the die by using a self-contained drawing function of simulation software;
step 3, performing isothermal compression experiment simulation test;
step 4, obtaining the horizontal displacement distribution condition of each node of the workpiece in the compression process through finite element simulation;
step 5, calculating to obtain true stress by using the ratio of the load obtained by the test to the central cross-sectional area, and further obtaining a corrected rheological curve to obtain a true stress-strain curve;
and 6, using a true stress-strain curve to be brought into a strain-strain database of the finite element model, checking the comparison of the bulge size, the comparison of the metal streamline and the comparison of the load-displacement curve, if the comparison result has deviation, ending the calculation, and if the comparison result has no deviation, repeating the steps 2-5.
2. The method for correcting and checking data in consideration of belly swelling in a metal compression experiment according to claim 1, wherein the conventional calculation method in step 1 is specifically: the data system is utilized to collect data of the displacement sensor and the pressure sensor in the isothermal compression experiment process, and the collected data are calculated, so that values of pseudo-true strain epsilon and pseudo-true stress sigma are obtained, and the calculation formulas are shown in the formulas (1) and (2):
wherein, I 0 Is the initial length of the sample, mm; Δl is displacement of the sample during compression, mm; s is the cross-sectional area of the sample, mm 2 The method comprises the steps of carrying out a first treatment on the surface of the F is the experimentally obtained load, kgf; d, d 0 Is the initial diameter of the sample, mm.
3. The method for correcting and checking data in consideration of belly swelling in a metal compression experiment according to claim 1, wherein in the isothermal compression experiment simulation test in step 3, a workpiece adopts a rigid plastic body in the simulation process, the initial temperature is the same as the deformation temperature designed in the isothermal compression experiment,the speed is adopted to control the movement of the die in the simulated compression process, and the strain rate is caused by the fact that the workpiece is provided with an upper symmetry plane and a lower symmetry planeThe conversion formula with the velocity v is shown in formula (3), which is a functional relation of velocity and stroke:
in the method, in the process of the invention,is the strain rate, s -1 The method comprises the steps of carrying out a first treatment on the surface of the h is the height of the sample before compression and mm; s is the compression stroke of the upper die under the condition of each deformation parameter, and mm.
4. The method for correcting and checking data in consideration of belly swelling in a metal compression experiment according to claim 1, wherein the distribution condition in the step 4 is specifically: the horizontal displacement of the upper and lower ends of the compressed sample tends to zero.
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