CN112613214B - Method for loading stamping damage in finite element analysis - Google Patents
Method for loading stamping damage in finite element analysis Download PDFInfo
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Abstract
The invention discloses a loading method of stamping damage in finite element analysis, which comprises the following steps: drawing a material forming limit diagram, and drawing a forming limit diagram of a material forming the part; performing stamping forming simulation analysis on the part, performing stamping forming simulation on the part by using stamping forming simulation software through a multi-step forming method, and combining the simulation analysis result with a forming limit diagram of a material to obtain the forming limit diagram containing stamping forming strain; calculating the stamping approximate damage of the part, and calculating the stamping approximate damage of the part by a proportional loading hypothesis method based on a forming limit diagram containing stamping forming strain; obtaining a stamping damage correction function; correcting the stamping approximate damage of the part by using a stamping damage correction function to obtain the stamping real damage of the part; and mapping the stamping damage into a finite element model, and mapping the stamping real damage of the part into a corresponding part unit in the finite element model.
Description
Technical Field
The invention relates to the field of automobile design and manufacture, in particular to a finite element analysis technology in the automobile design and manufacture process.
Background
With the improvement of the economic level of China, an automobile becomes one of main transportation tools for people to go out, automobile collision accidents are increased, and the accidents bring great harm to passengers in the automobile, so that the safety of the automobile becomes one of the core required performances of the automobile. There are many regulations on automobile safety in the national standard, such as "GB 15083-2009 automobile seat, seat fixing device and headrest strength requirements and test methods", which stipulate the requirement of the rear seat against trunk impact (hereinafter referred to as trunk impact requirement). The following description is provided for GB15083-2009 automobile seat, seat fixing device, and headrest strength requirements and test method with reference to fig. 1a and 1b, where fig. 1a is a setup diagram of a trunk impact test, and fig. 1b is a schematic diagram of a trunk impact acceleration curve channel.
According to the national standard test regulations, the test is carried out on a trolley, two test specimen blocks with a weight of 18KG are placed on the trunk floor according to the requirements of fig. 1a, the two specimen blocks are symmetrical about the vehicle central axis and are at a distance of 50mm and at a distance of 200mm from the seat back, and the trolley is decelerated or accelerated to simulate the crash process, the deceleration or acceleration-time curves of which are required being within the range shown in fig. 1 b. In addition to the requirement for seat deformation in terms of seat evaluation, regulations stipulate that no seat failure occurs after the test.
At present, more and more digital technologies are applied to the research and development stage of automobiles, and finite element analysis (also called simulation analysis) belonging to the field of computer aided engineering is a widely applied digital technology, and the simulation analysis can be used for predicting the performance of a structure, finding problems in the early stage of development and providing corresponding guidance for the optimization of the structure.
In the simulation analysis work of the automobile industry, methods for judging material damage include a constant strain failure method, a damage accumulation failure method and the like, and the damage accumulation failure method shows advantages along with the development of theoretical research. The damage judgment method used here is a damage accumulation failure method-HSR
The method is characterized in that the HSR method is a damage accumulation failure method applied to explicit simulation analysis, the processing method is to divide the whole deformation process into a plurality of small incremental steps, the damage value is calculated for each incremental step, then the damage of each incremental step is accumulated, when the damage value is accumulated to 1, the material is damaged, and the damage is expressed as unit deletion in a simulation model.
One problem with prior art finite element simulations is that the parts are assumed to be intact and the material is not damaged during the finite element simulation. However, the actual situation is that the material of the part is damaged by stamping in the stamping process. The material is deformed when being formed into a part through stamping forming, namely when the trunk impact test is not started, the stamped part in the seat has damage caused by stamping forming (hereinafter referred to as stamping damage), but the stamping damage is not considered into a simulation analysis model by the existing finite element simulation analysis technology, so that the simulation analysis can not completely expose the damage risk under certain situations.
The judgment of material damage is always a difficult problem in the research and development and manufacturing of automobiles. In actual conditions, the stress-strain state of a part is very complex, and the judgment of damage is more difficult after the material is subjected to a complex forming process. However, safety is one of the important properties of automobiles, so in the development and manufacture of automobiles and related parts, a damage treatment and judgment method which considers the molding effect and can be accepted by engineering application is very important.
Disclosure of Invention
According to an embodiment of the present invention, a method for loading a stamping damage in a finite element analysis is provided, which includes the following steps:
drawing a material forming limit diagram, and drawing a forming limit diagram of a material forming the part;
performing stamping forming simulation analysis on the part, performing stamping forming simulation on the part by using stamping forming simulation software through a multi-step forming method, and combining the simulation analysis result with a forming limit diagram of a material to obtain the forming limit diagram containing stamping forming strain;
calculating the stamping approximate damage of the part, and calculating the stamping approximate damage of the part by a proportional loading hypothesis method based on a forming limit diagram containing stamping forming strain;
obtaining a stamping damage correction function;
correcting the stamping approximate damage of the part by using a stamping damage correction function to obtain the stamping real damage of the part;
and mapping the stamping damage into a finite element model, and mapping the stamping real damage of the part into a corresponding part unit in the finite element model.
In one embodiment, in the step of drawing the material forming limit diagram, the thickness of the material is determined according to the shape and the size of the part, and then the forming limit diagram of the material at the thickness is calculated and drawn according to test method of thin steel plate Forming Limit Diagram (FLD) JB 4409.8-88.
In one embodiment, in the step of analyzing the stamping forming simulation of the component, the stamping forming simulation software used in the step is auto form, and the process of performing the stamping forming simulation on the component includes:
geometric preparation and grid processing;
generating pressed noodles and process supplement noodles;
determining stamping parameters;
setting material characteristics;
performing stamping simulation calculation to obtain the strain of the part;
and drawing the strain of the part into a material forming limit diagram to obtain a forming limit diagram containing stamping forming strain.
In one embodiment, in the step of calculating the stamping approximate damage of the component, assuming that the load applied to the material during the stamping process conforms to the proportional loading, the load is represented by a straight line passing through the origin in a forming limit diagram containing the stamping strain, and as the load increases during the stamping process, the straight line intersects the FLD curve, and the damage occurs at the intersection, according to the proportional loading assumption, the damage is estimated by using the ratio of the current strain state to the distance from the origin to each of the strain limits:
wherein D is apr Approximation of damage value, epsilon, for stamping c Is the current strain state after stamping is finished, epsilon lim The strain limit at which failure of the material occurs.
In one embodiment, the step of obtaining the punch damage correction function comprises:
manufacturing a solid test sample piece by using the material;
carrying out destructive test on a solid test sample to obtain a test failure load F st ；
Establishing a finite element model of a test sample;
punch forming simulation analysis is carried out on the finite element model of the test sample piece and the test sample is calculatedPress damage approximation of a part F sc ；
Comparative test failure load F st And press approximate damage F sc If the error of the two meets the error threshold value, outputting the real damage F of the stamping sr If the error of the two kinds of damage does not meet the error threshold, the stamping damage is adjusted, then the stamping approximate damage is calculated again, and the stamping real damage F is output until the error of the two kinds of damage meets the error threshold sr ；
Damage to press approximation F sc And true damage F sr And performing linear fitting to obtain a fitting function, wherein the fitting function is a stamping damage correction function.
In one embodiment, a plurality of solid test samples are manufactured, the bending angles are respectively 15 °, 30 °, 45 °, 60 °, 75 ° and 90 ° according to different forming deformation degrees, and the damage tests are respectively performed at a plurality of thicknesses.
In one embodiment, at least 5 failure tests are performed for each bend angle and each thickness of the solid test sample, and the average of the test failure loads of the failure tests is calculated as the test failure load F st 。
In one embodiment, in the step of mapping the stamping damage into the finite element model, for the finite element software Pam-crash, the mapping process is as follows: the stamping real damage of the part is written into an M01 file, then a simulation model is imported through an import function of Pam-coast, and the stamping real damage is mapped to a corresponding finite element unit according to the coordinate position of the part.
The loading method of the stamping damage in the finite element analysis can truly process the stamping damage, improves the analysis precision compared with the traditional method without considering the stamping damage, effectively improves the precision of simulation analysis, and plays an important role in the analysis and optimization of target parts.
Drawings
The above and other features, properties and advantages of the present invention will become more apparent from the following description of the embodiments with reference to the accompanying drawings, in which like reference numerals refer to like features throughout,
wherein:
FIG. 1a is a set-up diagram of a trunk impact test.
FIG. 1b is a schematic diagram of a trunk shock acceleration curve channel.
FIG. 2 is a flow chart illustrating a method for loading punch damage in a finite element analysis according to an embodiment of the invention.
FIG. 3 discloses an example of a material forming limit map plotted in a loading method of stamping damage in a finite element analysis according to an embodiment of the present invention.
Fig. 4 discloses a forming limit diagram including a punch forming strain obtained after punch forming simulation analysis in a loading method of a punch damage in finite element analysis according to an embodiment of the present invention.
FIG. 5 is a schematic diagram illustrating a proportional loading assumption method in a loading method of stamping damage in finite element analysis according to an embodiment of the present invention.
FIG. 6 is a flow chart illustrating obtaining a punch damage correction function in a method for loading punch damage in a finite element analysis according to an embodiment of the invention.
FIG. 7 is a schematic diagram of a solid test piece in a loading method of stamping damage in a finite element analysis according to an embodiment of the invention.
FIG. 8 illustrates a process for comparing a test failure load and a punch approximated damage in a loading method of punch damage in finite element analysis according to an embodiment of the present invention.
FIG. 9 discloses a schematic diagram of a linear fit of an approximated damage and a true damage in a method for loading a stamped damage in a finite element analysis according to an embodiment of the invention.
FIGS. 10a, 10b, 10c, 10d and 10e illustrate a comparison of the impact damage assessment results of finite element analysis of the prior art and the present invention on a component.
Detailed Description
In order to overcome the defects in the finite element simulation model in the prior art, punching damage needs to be introduced into the simulation model. In the trial process, the following method has also been tried: firstly establishing a simulation of a stamping forming process, then dividing the forming process into a plurality of small incremental steps, calculating information such as strain of each incremental step, calculating damage caused by stamping deformation of each incremental step, and finally accumulating all the damage to obtain final stamping damage. However, this method has two difficulties: firstly, the self-adaptive grid is generally used in the conventional stamping forming simulation calculation, the size of the unit is reduced along with the increase of deformation, the quantity of the unit is increased, and various data accumulation of one unit, such as a strain tensor, cannot be recorded all the time. Secondly, when the increment step is kept very small, the workload of analysis setting of punch forming analysis, extraction of punch forming result data and damage calculation is very huge, long time is consumed for operation, and the method has no value of practical application.
The invention thus proposes a method for introducing stamping damage into a finite element simulation model with less computation by means of the proportional loading assumption. FIG. 2 is a flow chart illustrating a method for loading punch damage in a finite element analysis according to an embodiment of the invention. Referring to fig. 2, the method for loading the stamping damage in the finite element analysis comprises the following steps:
and S1, drawing a material forming limit diagram. And drawing a forming limit diagram FLD of the material forming the part. In one embodiment, in the step S1 of drawing the material forming limit diagram, the thickness of the material is determined according to the shape and size of the component, and then the forming limit diagram of the material at the thickness is calculated and drawn according to test method of thin steel plate Forming Limit Diagram (FLD) JB 4409.8-88. The forming limit diagram (FLD diagram) is a strip-shaped region or curve formed by local instability limit strain or real strain of a plate under different strain paths, and the curve can be obtained by a test method of a JB4409.8-88 thin steel plate Forming Limit Diagram (FLD) test, and it should be noted that when parts with the same material but different thicknesses exist, the strain level of the forming limit diagram is influenced by the thickness, and the FLD diagram corresponding to the thickness needs to be obtained by performing the test respectively for different thicknesses. FIG. 3 discloses an example of a material forming limit map plotted in a loading method of stamping damage in a finite element analysis according to an embodiment of the present invention. Fig. 3 shows an FLD diagram of an intermediate bracket connecting a rear seat and a vehicle body, in fig. 3, the horizontal axis and the vertical axis represent the first principal strain and the second principal strain, respectively, the vertical axis represents the first principal strain, and the horizontal axis represents the second principal strain. The curve shown in fig. 3 is referred to as the FLD curve.
S2, performing simulation analysis on stamping forming of the parts, performing stamping forming simulation on the parts by a multi-step forming method by using stamping forming simulation software, and combining the simulation analysis result with the forming limit diagram of the material to obtain the forming limit diagram containing stamping forming strain. The stamping simulation technology is divided into a one-step forming method and a multi-step forming method, wherein the one-step forming method does not consider the intermediate state of part forming, and the calculated information such as strain and the like has certain errors. In one embodiment, in step S2 of analyzing the stamping forming simulation of the component, the stamping forming simulation software used is auto, and the process of performing the stamping forming simulation on the component includes:
geometric preparation and gridding processing, including the processing of determining the initial contour of the material, gridding, filling holes and the like.
And (3) generating a pressing surface and a process supplement surface, wherein the pressing surface and the process supplement surface comprise the arrangement of the draw beads for adjusting and controlling the pressing surface.
The settings of the stamping parameters, such as stamping direction, blank holding force, gap, etc., are determined.
Setting material characteristics;
performing stamping simulation calculation to obtain the strain of the part;
and drawing the strain of the part into a material forming limit diagram to obtain a forming limit diagram containing stamping forming strain. And obtaining a first main strain and a second main strain of each unit after the punching simulation analysis is completed, and drawing the punching forming strain into the FLD (flash liquid crystal display) graph obtained in the step S1 to obtain a forming limit graph containing the punching forming strain. Fig. 4 discloses a forming limit diagram including a punch forming strain obtained after punch forming simulation analysis in a loading method of a punch damage in finite element analysis according to an embodiment of the present invention. Comparing fig. 3 and 4, fig. 4 is a graph in which the punch forming strain of the component part, which is an intermediate bracket connecting the rear seat and the vehicle body in this example, is superimposed below the FLD curve of fig. 3.
And S3, calculating the stamping approximate damage of the part, and calculating the stamping approximate damage of the part by a proportional loading hypothesis method based on a forming limit diagram containing stamping forming strain. In one embodiment, in step S3 of calculating the stamping approximate damage of the component, assuming that the material is subjected to a load in proportion to the proportional loading during the stamping forming process, the ratio of the first principal strain and the second principal strain of a certain unit is not changed, and is represented by a straight line passing through the origin in a forming limit diagram (FLD diagram) containing the stamping forming strain, and as the load increases during the forming process, the straight line intersects with the FLD curve, and the failure occurs at the intersection. As an approximation, the ratio of the current strain state to the distance of the strain limit from the origin, respectively, can be used to estimate the size of the lesion, which is the principle of the proportional loading hypothesis. FIG. 5 is a schematic diagram illustrating a proportional loading assumption method in a loading method of stamping damage in finite element analysis according to an embodiment of the present invention. Based on the forming limit diagram containing the stamping forming strain shown in FIG. 4, the load applied to the material in the stamping forming process conforms to the proportional loading, which is reflected as a straight line, epsilon, passing through the origin in the FLD diagram lim The length of the line segment from the origin to the point of intersection with the FLD curve on this line represents the strain limit at which failure of the material occurs. Epsilon c The length of a line segment of the stamping forming strain of the part on the straight line represents the current strain state after the stamping is finished. According to the proportional loading assumption, the magnitude of the damage is estimated using the ratio of the current strain state to the distance of the strain limit from the origin, respectively:
wherein D is apr Approximation of damage value, epsilon, for stamping c Is the current strain state after stamping is finished, epsilon lim The strain limit at which failure of the material occurs.
And S4, obtaining a stamping damage correction function. The press approximate damage value calculated in step S3 is assumed to be proportional-loaded, and although the press approximate damage can be roughly calculated, the press approximate damage is deviated from the actual damage, and the determination of the material breakage risk is affected. The correction method comprises the steps of firstly finding out the relation between an approximate value and a true value under the conditions of a certain material, thickness and deformation degree through a standardized sample test, namely a correction function, and then correcting the stamping approximate damage value of the part by using the correction function. FIG. 6 is a flow chart illustrating obtaining a punch damage correction function in a method for loading punch damage in a finite element analysis according to an embodiment of the invention. Referring to fig. 6, the step of obtaining the press damage correction function includes:
and S61, manufacturing a solid test sample by using the material. In one embodiment, a plurality of solid test samples are manufactured, the bending angles are 15 °, 30 °, 45 °, 60 °, 75 ° and 90 ° according to different forming deformation degrees, and the breaking tests are respectively performed at a plurality of thicknesses. In consideration of the actual molding condition of the stamped part, the bending angles are divided into 15 °, 30 °, 45 °, 60 °, 75 ° and 90 ° in order to take account of different degrees of molding deformation. As with the forming limit diagram FLD, the same material needs to be subjected to sample destruction tests under different thicknesses. FIG. 7 is a schematic diagram of a solid test piece in a loading method of stamping damage in a finite element analysis according to an embodiment of the invention. Referring to fig. 7, the experimental conditions of the test pieces were as follows, the area a was fixed by a jig, the collet of the loading arm was fixed to the area B, the force was applied in a direction parallel to the a/B plane, and the direction indicated by the black arrow in the drawing was the force application direction. The size of the sample piece can be adjusted according to actual conditions aiming at different materials and thicknesses.
S62, carrying out destructive test on the solid test sample to obtain test failure load F st . In one embodiment, at least 5 failure tests are performed for each bend angle and each thickness of the solid test sample, and the average of the test failure loads of the failure tests is calculated as the testFailure test load F st . Table 1 below lists examples of 5 failure tests performed on solid test pieces of each bending angle and each thickness, 5 failure tests were performed, and the average of the test failure loads of the 5 failure tests was calculated as a test failure load F st . In table 1, each test is assigned a spline number.
TABLE 1
And S63, establishing a finite element model of the test sample.
S64, performing punch forming simulation analysis on the finite element model of the test sample piece and calculating the approximate stamping damage F of the test sample piece sc . The step S64 is performed in the same manner as the steps S2 and S3, namely, the step S2 of simulation analysis of stamping forming of the part and the step S3 of calculating the approximate stamping damage of the part are applied to the finite element model of the test sample, and the approximate stamping damage F of the test sample is calculated sc 。
S65, comparing failure load F of test st And press approximate damage F sc If the error of the two meets the error threshold value, outputting the real damage F of the stamping sr If the error of the two kinds of damage does not meet the error threshold, the stamping damage is adjusted, then the stamping approximate damage is calculated again, and the stamping real damage F is output until the error of the two kinds of damage meets the error threshold sr . The actual stamping damage was determined by a finite element analysis of a spline test and benchmarking of a physical test. Test failure load F obtained by actual test st Setting different damage values of the spline test finite element analysis model for the standard mark, and enabling the stamping approximate damage F obtained by the simulation calculation sc And the damage value set in the model is the real damage value at the moment, wherein the damage value is equal to the average test failure load obtained by the test. Considering experimental errors and resource consumption, the load error is not more than 1% as a judgment standard for correctness, and smaller errors have no engineering application value. FIG. 8 discloses aIn the loading method of the stamping damage in the finite element analysis of one embodiment of the invention, the process of testing the failure load and the stamping approximate damage is compared. Firstly, a spline finite element model containing approximate damage is established. Then, the press approximate damage is calculated according to the aforementioned steps S2 and S3, and F is obtained by simulation calculation sc . Failure load F of lead-in test st A comparison is made. And if the deviation of the failure load is within 1%, determining that the damage value at the moment is a correct value, and if the deviation of the failure load is more than or equal to 1%, adjusting the stamping damage. F is obtained by carrying out simulation calculation again after the stamping damage is adjusted sc And again with the test failure load F st A comparison is made. And if the error threshold value is not met, continuously adjusting the punching damage until the error threshold value reaches the target interval. And recording the damage value at the moment, namely the real stamping damage, namely obtaining the real stamping damage of the sample strip. The process then ends.
S66 method for approximating damage to stamping sc And true damage by pressure F sr And performing linear fitting to obtain a fitting function, wherein the fitting function is a stamping damage correction function. After the approximate values and the true values of the press damage are obtained through step S65, the numerical values are fitted, and the present invention uses linear fitting. FIG. 9 illustrates a schematic diagram of a linear fit of approximate damage and true damage in a method for loading punch damage in a finite element analysis according to an embodiment of the invention. The abscissa in fig. 9 is an approximate damage, the ordinate is a real damage, the obtained linear function is a fitting function, and the fitting function is a stamping damage correction function.
And S5, correcting the stamping approximate damage of the part by using the stamping damage correction function to obtain the stamping real damage of the part.
And S6, mapping the stamping damage into a finite element model, and mapping the stamping real damage of the part into a corresponding part unit in the finite element model. The mapping process of different finite element software is different, and in one embodiment, the stamping damage is mapped into the step S6 of the finite element model, and for the finite element software Pam-crash, the mapping process is as follows: and writing the stamping real damage of the part into an M01 file, importing the stamping real damage into a simulation model through an import function of Pam-coast, and mapping the stamping real damage onto a corresponding finite element unit according to the coordinate position of the part.
The effect of the present invention will be described by way of an example, and fig. 10a, 10b, 10c, 10d and 10e show a comparison of the effect of the finite element analysis of the prior art and the present invention on the impact damage assessment of the component. The part to be evaluated is an intermediate bracket connecting the rear seats and the vehicle body, and fig. 10a and 10b disclose the mounting position of the intermediate bracket in the vehicle body overall structure and the body configuration of the intermediate bracket. The rear row seats are connected with the vehicle body through the middle support, when the trunk impact working condition test is carried out, the middle support is directly impacted by the test sample block, and loads of the test sample block and the backs of the rear row seats are also transmitted to the floor through the support.
FIG. 10c shows a graphical representation of the impact damage assessment effect of prior art finite element analysis on a mid-stent. In the finite element analysis of the prior art, the stamping damage of the parts in the stamping forming process is not considered, so that when the finite element simulation of the trunk impact working condition is carried out, the initial damage value of the middle bracket is 0, and after the finite element simulation of the trunk impact working condition is completed, as shown in fig. 10c, the maximum damage value on the middle bracket is 0.68, which indicates that the middle bracket is not damaged and is not broken. However, as a result of the actual trunk impact condition test, the middle bracket is broken, and the middle bracket is broken at the position where the maximum damage value is shown in fig. 10 c. The finite element analysis result in the prior art does not accord with the actual test result, has appeared comparatively obvious deviation, does not foresee the risk that spare part destroys the fracture, has great potential safety hazard.
FIGS. 10d and 10e show a graphical representation of the impact damage assessment effect of finite element analysis of the present invention on the intermediate stent. The maximum punching approximate damage on the middle support is calculated by a proportional loading hypothesis method to be at the bending position, and the punching approximate damage value at the bending position is 0.62. Then correcting according to a stamping damage correction function, wherein D rea For stamping true damage values, D apr Approximate damage values for stamping for proportional loading hypothesis:
D rea ＝0.87·D apr -0.03
the real damage value of the stamping at the bending position after correction is 0.51, and the position is shown in fig. 10 d. The material damage of the intermediate bracket caused by punch forming during the 0.51 stamping damage is needed to be loaded into a finite element model of the intermediate bracket as an initial damage, and then the finite element simulation of the trunk impact condition is continued based on the initial damage. After the finite element simulation of the trunk impact condition is completed, as shown in fig. 10e, the maximum damage value on the middle bracket exceeds 1, which indicates that the middle bracket is damaged and broken. Fig. 10e shows the position of the middle bracket where the fracture occurs under the finite element simulation, and the result of fig. 10e is basically the same as the actual luggage case impact condition test result, which illustrates that the finite element analysis of the present invention can more accurately simulate the actual impact damage effect after considering the stamping damage of the parts.
It should be noted that fig. 10c, fig. 10d and fig. 10e are all output screen shots from the finite element analysis software, and in order to maintain the integrity of the results, the text marks, characters, gray scales, etc. are not processed, and the details of these screen shots are not the focus of the present invention. The focus of the present invention is on the location of the maximum lesion occurrence and the estimated maximum lesion value in fig. 10c, 10d and 10e, which are clearly shown in fig. 10c, 10d and 10 e. The damage value at the maximum damage position in fig. 10c is 0.68, the damage value at the maximum damage position in fig. 10d is 0.51, and the damage value at the maximum damage position in fig. 10e is greater than 1, indicating fracture.
The loading method of the stamping damage in the finite element analysis can truly process the stamping damage, improves the analysis precision compared with the traditional method without considering the stamping damage, effectively improves the precision of simulation analysis, and plays an important role in the analysis and optimization of target parts.
The above-described embodiments are provided to enable persons skilled in the art to make or use the invention, and that persons skilled in the art may make modifications or changes to the above-described embodiments without departing from the inventive concept thereof, and therefore the scope of protection of the invention is not limited by the above-described embodiments but should be accorded the widest scope consistent with the innovative features recited in the claims.
Claims (6)
1. A loading method of stamping damage in finite element analysis is characterized by comprising the following steps:
drawing a material forming limit diagram, and drawing a forming limit diagram of a material forming the part;
performing stamping forming simulation analysis on the part, performing stamping forming simulation on the part by using stamping forming simulation software through a multi-step forming method, and combining the simulation analysis result with a forming limit diagram of a material to obtain the forming limit diagram containing stamping forming strain;
calculating the stamping approximate damage of the part, and calculating the stamping approximate damage of the part by a proportional loading hypothesis method based on a forming limit diagram containing stamping forming strain;
obtaining a stamping damage correction function;
correcting the stamping approximate damage of the part by using a stamping damage correction function to obtain the stamping real damage of the part;
mapping the stamping damage into a finite element model, and mapping the stamping real damage of the part into a corresponding part unit in the finite element model;
in the step of calculating the approximate damage of the stamping of the part, assuming that the load borne by the material in the stamping forming process conforms to the proportional loading, the load is reflected in a forming limit diagram containing the stamping forming strain as a straight line passing through an origin, the straight line can be intersected with an FLD curve along with the increase of the load in the forming process, and the damage occurs at the intersection, and according to a proportional loading assumption method, the damage is estimated by using the ratio of the distance between the current strain state and the strain limit respectively relative to the origin:
wherein D is apr Approximation of damage value, epsilon, for stamping c Is the current strain state after stamping is finished, epsilon lim A strain limit at which failure of the material occurs;
wherein the step of obtaining the stamping damage correction function comprises:
using the material to manufacture a solid test sample piece;
carrying out destructive test on the solid test sample to obtain test failure load F st ；
Establishing a finite element model of a test sample;
performing punch forming simulation analysis on the finite element model of the test sample piece and calculating the approximate stamping damage F of the test sample piece sc ；
Comparative test failure load F st And press approximation damage F sc If the error of the two meets the error threshold value, outputting the real damage F of the stamping sr If the error of the two kinds of damage does not meet the error threshold, the stamping damage is adjusted, then the stamping approximate damage is calculated again, and the stamping real damage F is output until the error of the two kinds of damage meets the error threshold sr ；
Damage to press approximation F sc And true damage by pressure F sr And performing linear fitting to obtain a fitting function, wherein the fitting function is a stamping damage correction function.
2. The method for loading the stamping damage in the finite element analysis according to claim 1, wherein in the step of drawing the material forming limit diagram, the thickness of the material is determined according to the shape and the size of the part, and then the forming limit diagram of the material at the thickness is calculated and drawn according to test method of steel sheet Forming Limit Diagram (FLD) JB4409.8-88 ".
3. The method for loading stamping damage in finite element analysis according to claim 2, wherein in the step of analyzing stamping forming simulation of the component, the stamping forming simulation software used is auto form, and the process of performing stamping forming simulation on the component includes:
geometric preparation and grid processing;
generating pressed noodles and process supplement noodles;
determining stamping parameters;
setting material characteristics;
performing stamping simulation calculation to obtain the strain of the part;
and drawing the strain of the part into a material forming limit diagram to obtain a forming limit diagram containing stamping forming strain.
4. The method of loading punch damage in finite element analysis of claim 1, wherein a plurality of solid test pieces are manufactured, the bending angles are 15 °, 30 °, 45 °, 60 °, 75 ° and 90 ° according to different degrees of forming deformation, and the breaking tests are performed at a plurality of thicknesses respectively.
5. The method of loading a stamping damage in finite element analysis as set forth in claim 1, wherein at least 5 failure tests are performed for each bending angle and each thickness of the solid test piece, and an average value of test failure loads of the failure tests is calculated as a test failure load F st 。
6. The method for loading stamping damage in finite element analysis according to claim 1, wherein in the step of mapping the stamping damage into the finite element model, for the finite element software Pam-crash, the mapping process is: the stamping real damage of the part is written into an M01 file, then a simulation model is imported through an import function of Pam-coast, and the stamping real damage is mapped to a corresponding finite element unit according to the coordinate position of the part.
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