A method for analyzing tensile strain mark defects

Abstract

An embodiment of the present application provides a method for analyzing tensile strain mark defects, comprising: obtaining the yield plateau length of a high-strength steel to be tested; performing a bulging test on the high-strength steel to be tested to obtain a part to be tested that exhibits tensile strain marks; performing a strain analysis on the part to be tested to determine a first strain value when the tensile strain mark appears on the part to be tested, and a second strain value when the tensile strain mark disappears on the part to be tested; and determining a strain analysis table for the high-strength steel to be tested based on the yield plateau length, the first strain value, and the second strain value. The technical solution of the embodiment of the present application can, to a certain extent, clarify the correspondence between the yield plateau and the strain amount when the tensile strain mark defect occurs, thereby taking corresponding measures based on the strain amount or the yield plateau length.

Description

Technical Field

[0001] The present application relates to the field of stamping technology, and in particular to a method for analyzing tensile strain mark defects. Background Art

[0002] Cold-rolled low-alloy high-strength steel is a high-strength steel developed for automotive structural parts. It has high strength and good formability. However, due to the existence of a yield platform, dislocations break free from the pinning of two-phase particles during the forming process, and dendritic tensile strain marks at a certain angle to the rolling direction are easily present on the product surface, seriously affecting the product forming quality and coating effect.

[0003] Based on this, how to clarify the correspondence between the yield platform and the strain amount when the tensile strain mark defect occurs, and then take corresponding measures according to the strain amount or the length of the yield platform is a technical problem that needs to be solved urgently. Summary of the Invention

[0004] The embodiments of the present application provide a method, apparatus, computer program product or computer program, computer-readable medium, and electronic device for analyzing tensile strain mark defects, which can, at least to a certain extent, clarify the correspondence between the yield platform and the strain amount when the tensile strain mark defect occurs, thereby taking corresponding measures based on the strain amount or the length of the yield platform.

[0005] Other features and advantages of the present application will become apparent from the following detailed description, or may be learned in part by practice of the present application.

[0006] According to one aspect of an embodiment of the present application, a method for analyzing tensile strain mark defects is provided, the method comprising: obtaining a yield platform length of a high-strength steel to be tested; performing a bulging test on the high-strength steel to be tested to obtain a part to be tested having tensile strain marks; performing a strain analysis on the part to be tested to determine a first strain value when a tensile strain mark appears on the part to be tested, and determining a second strain value when the tensile strain mark on the part to be tested disappears; and determining a strain analysis table for the high-strength steel to be tested based on the yield platform length, the first strain value, and the second strain value.

[0007] In some embodiments of the present application, obtaining the yield platform length of the high-strength steel to be tested includes: conducting mechanical property testing along the rolling direction and transverse direction of the high-strength steel to be tested to determine the mechanical strain curve corresponding to the high-strength steel to be tested; and determining the yield platform lengths corresponding to the rolling direction and transverse direction of the high-strength steel to be tested respectively according to the mechanical strain curve.

[0008] In some embodiments of the present application, the bulging test on the high-strength steel to be tested includes: performing a bulging test on the high-strength steel to be tested in at least one loading mode, the loading mode including plane strain, uniaxial tension and biaxial tension; for the bulging test in any loading mode, based on the set clamping force and stamping parameters, the high-strength steel to be tested is subjected to a bulging test of at least one stamping height through a forming testing machine.

[0009] In some embodiments of the present application, before performing a bulging test of at least one stamping height on the high-strength steel to be tested by a forming testing machine based on the set blank holding force and stamping parameters, the method further includes: preparing a bulging specimen, selecting the high-strength steel to be tested and preparing a bulging specimen of a predetermined size, and then cleaning the surface of the bulging specimen with alcohol; grid printing, performing grid printing on the bulging specimen using a grid meter, and etching dots arranged in a grid matrix on the bulging specimen.

[0010] In some embodiments of the present application, the performing grid printing on the bulging sample using a grid meter includes: performing grid printing on half of a long side of the bulging sample using a grid meter.

[0011] In some embodiments of the present application, the performing strain analysis on the part to be measured includes: performing strain detection analysis on the surface of the part to be measured using optical equipment and analysis software.

[0012] In some embodiments of the present application, determining the first strain value when tensile strain marks appear on the part to be measured, and determining the second strain value when the tensile strain marks on the part to be measured disappear, include: determining the minimum strain value corresponding to the tensile strain marks appearing on the part to be measured as the first strain value; and determining the second strain value according to the maximum strain value corresponding to the tensile strain marks disappearing on the part to be measured.

[0013] In some embodiments of the present application, determining the strain analysis table of the high-strength steel to be tested based on the yield platform length, the first strain value, and the second strain value includes: determining the strain value range in which tensile strain marks appear in the high-strength steel to be tested based on the first strain value and the second strain value; and mapping the strain value range to the yield platform length to determine the strain analysis table of the high-strength steel to be tested.

[0014] In some embodiments of the present application, after determining the strain analysis table of the high-strength steel to be tested, the method further includes: obtaining the strain analysis table corresponding to the high-strength steel to be tested; analyzing the strain of the formed part of the high-strength steel to be tested according to the strain analysis table corresponding to the high-strength steel to be tested, and determining the yield platform control range of the high-strength steel to be tested.

[0015] In some embodiments of the present application, after determining the strain analysis table of the high-strength steel to be tested, the method further includes: obtaining the strain analysis table corresponding to the high-strength steel to be tested; and adjusting the stamping process according to the strain condition of the formed part of the high-strength steel to be tested based on the strain analysis table corresponding to the high-strength steel to be tested, so as to avoid the occurrence of tensile strain mark defects on the formed part.

[0016] Based on the above technical solution, this application has at least the following advantages or improvements:

[0017] The present application provides an analysis method for tensile strain mark defects, which can obtain the critical strain value and strain range of tensile strain marks generated in high-strength steel plates under different forming methods, and establish a strain analysis table between the yield section length, strain mode, and strain amount when tensile strain marks are generated in high-strength steel with a yield platform. The strain analysis table can be used to guide the selection of yield section performance or process optimization during stamping processing of high-strength steel with a yield platform, thereby improving the surface quality of the product formed.

[0018] It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings are incorporated into and constitute a part of the specification, illustrating embodiments consistent with the present application and, together with the specification, explaining the principles of the present application. Obviously, the drawings described below are only some embodiments of the present application, and those skilled in the art can derive other drawings based on these drawings without inventive effort. In the drawings:

[0020] Figure 1 A flow chart showing a method for analyzing tensile strain mark defects according to one embodiment of the present application is shown;

[0021] Figure 2 A flow chart showing a method for analyzing tensile strain mark defects according to one embodiment of the present application is shown;

[0022] Figure 3 A simplified diagram of the mechanical strain curve of high-strength steel according to an embodiment of the present application is shown;

[0023] Figure 4 A flow chart showing a method for analyzing tensile strain mark defects according to one embodiment of the present application is shown;

[0024] Figure 5 A simplified structural diagram of a bulging die in one embodiment of the present application is shown;

[0025] Figure 6 A flow chart showing a method for analyzing tensile strain mark defects according to one embodiment of the present application is shown;

[0026] Figure 7 A flow chart showing a method for analyzing tensile strain mark defects according to one embodiment of the present application is shown;

[0027] Figure 8 A flow chart showing a method for analyzing tensile strain mark defects according to one embodiment of the present application is shown;

[0028] Figure 9 A flow chart showing a method for analyzing tensile strain mark defects according to one embodiment of the present application is shown;

[0029] Figure 10 A flow chart of a method for analyzing tensile strain mark defects according to one embodiment of the present application is shown. DETAILED DESCRIPTION

[0030] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be implemented in many forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that this application will be thorough and complete and will fully convey the concepts of the example embodiments to those skilled in the art.

[0031] The flowcharts shown in the accompanying drawings are for illustrative purposes only and do not necessarily include all contents and operations / steps, nor must they be executed in the order described. For example, some operations / steps may be decomposed, while others may be combined or partially combined. Therefore, the actual execution order may vary depending on the actual situation.

[0032] It should be noted that the term "plurality" used in this document refers to two or more. "And / or" describes a relationship between associated objects, indicating that three possible relationships exist. For example, "A and / or B" can represent: A alone, A and B together, or B alone. The character " / " generally indicates an "or" relationship between the associated objects.

[0033] It should be noted that the terms "first," "second," and the like in the specification and claims of this application and the accompanying drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or precedence. It should be understood that the terms used in this manner are interchangeable where appropriate, such that the embodiments of the present application described herein can be implemented in an order other than that illustrated or described.

[0034] The following is a detailed description of the implementation details of the technical solution of the embodiment of the present application:

[0035] See also Figure 1 .

[0036] Figure 1A flowchart of a method for analyzing tensile strain mark defects according to one embodiment of the present application is shown. The method may include steps S101-S104:

[0037] Step S101: Obtain the yield platform length of the high-strength steel to be tested.

[0038] Step S102 : performing a bulging test on the high-strength steel to be tested to obtain a part to be tested with tensile strain marks.

[0039] Step S103 , performing strain analysis on the part to be tested, determining a first strain value when a tensile strain mark appears on the part to be tested, and determining a second strain value when the tensile strain mark on the part to be tested disappears.

[0040] Step S104 : determining a strain analysis table of the high-strength steel to be tested according to the yield platform length, the first strain value, and the second strain value.

[0041] In this application, through bulging tests and strain analysis, the critical strain value and strain range of tensile strain marks generated in high-strength steel plates under different forming methods can be obtained, and a strain analysis table between the yield section length and the strain mode and strain amount when tensile strain marks are generated in high-strength steel with a yield platform is established. Technical personnel in this field can select the yield section performance of high-strength steel during stamping processing or optimize the stamping process based on the strain analysis table, which can effectively improve the surface quality of the product forming.

[0042] See also Figure 2-3 .

[0043] Figure 2 A flowchart of a method for analyzing tensile strain mark defects according to one embodiment of the present application is shown. The method for obtaining the yield platform length of the high-strength steel to be tested may include steps S201-S202:

[0044] Step S201 : Conduct mechanical property testing along the rolling direction and the transverse direction of the high-strength steel to be tested, and determine the mechanical strain curve corresponding to the high-strength steel to be tested.

[0045] Step S202 : determining the yield platform lengths corresponding to the rolling direction and the transverse direction of the high-strength steel to be tested respectively according to the mechanical strain curve.

[0046] Figure 3 A simplified diagram of the mechanical strain curve of high-strength steel according to an embodiment of the present application is shown in FIG. Figure 3 As shown in the figure, 301 is the yield platform length of a certain high-strength steel to be tested.

[0047] See also Figure 4-5 .

[0048] Figure 4A flow chart of a method for analyzing tensile strain mark defects according to one embodiment of the present application is shown. The method for performing a bulging test on the high-strength steel to be tested may include steps S401-S402:

[0049] Step S401 : performing a bulging test on the high-strength steel to be tested using at least one loading method, wherein the loading method includes plane strain, uniaxial tension, and biaxial tension.

[0050] Step S402 : For a bulging test in any loading mode, a bulging test of at least one stamping height is performed on the high-strength steel to be tested by a forming testing machine based on the set blank holder force and stamping parameters.

[0051] In this application, based on the set blank holding force and stamping parameters, expansion tests at different heights are carried out using a forming testing machine. The expansion die can use a hemispherical punch with a diameter of 10 cm, and the expansion height parameter setting can be 5mm, 7mm, 9mm, 12mm, 15mm and 21mm to observe the surface changes after different expansions.

[0052] Figure 5 FIG. 1 shows a simplified structural diagram of a bulging die in one embodiment of the present application. Figure 5 As shown, 501 is the blank holder of the bulging die, 502 is the sheet material of the bulging die, 503 is the concave die of the bulging die, and 504 is the convex die of the bulging die.

[0053] See also Figure 6 .

[0054] Figure 6 A flowchart of a method for analyzing tensile strain mark defects according to one embodiment of the present application is shown. Before performing a bulging test of at least one punching height on the high-strength steel to be tested using a forming testing machine based on set blank holder force and punching parameters, the method may further include steps S601-S602:

[0055] Step S601, preparing a bulging specimen, selecting the high-strength steel to be tested and preparing a bulging specimen of a predetermined size, and then cleaning the surface of the bulging specimen with alcohol.

[0056] Step S602 , grid printing, is to perform grid printing on the bulge sample using a grid meter, and to etch dots arranged in a grid matrix on the bulge sample.

[0057] In the present application, a grid meter may be used to perform grid printing on half of the long side of the bulge sample.

[0058] In this application, plane strain bulging specimens along the longitudinal and transverse directions of the plate can be prepared respectively, the specimen size is selected as 100*180mm, and the surface is cleaned with alcohol.

[0059] In this application, a grid printer can be used to perform grid printing on the prepared specimen. Grid printing involves etching a grid matrix of small dots onto the specimen surface, with a center-to-center spacing of 2 cm. When printing the grid, only half of the specimen's long side can be printed to ensure that tensile strain marks can be clearly observed after straining.

[0060] In one embodiment of the present application, the method of performing strain analysis on the part to be measured may include: performing strain detection and analysis on the surface of the part to be measured using optical equipment and analysis software.

[0061] See also Figure 7 .

[0062] Figure 7 A flowchart of a method for analyzing a tensile strain mark defect according to one embodiment of the present application is shown. The method of determining a first strain value when a tensile strain mark appears on the part to be tested and determining a second strain value when the tensile strain mark disappears on the part to be tested may include steps S701-S702:

[0063] Step S701: determining the minimum strain value corresponding to the tensile strain mark appearing on the part to be tested as the first strain value.

[0064] Step S702 : determining a second strain value by using the maximum strain value corresponding to when the tensile strain mark on the part to be measured disappears.

[0065] In this application, strain analysis can be performed on the boundary area where the strain mark of the part to be tested is generated to obtain the corresponding strain values. The strain values correspond to the minimum strain when the tensile strain mark is generated and the maximum strain when the defect disappears, respectively, and are marked as εMin and εMax. Among them, the minimum strain value εMin corresponding to the tensile strain mark is the minimum strain value measured more than three times on samples of different stamping heights under the same loading method, and εMax is the maximum strain value measured more than three times on samples of different stamping heights under the same loading method.

[0066] See also Figure 8 .

[0067] Figure 8 A flowchart of a method for analyzing a tensile strain mark defect according to one embodiment of the present application is shown. The method for determining a strain analysis table for the high-strength steel to be tested based on the yield platform length, the first strain value, and the second strain value may include steps S801-S802:

[0068] Step S801: determining a strain value range in which a tensile strain mark appears in the high-strength steel to be tested according to the first strain value and the second strain value.

[0069] Step S802 : Mapping the strain value range to the yield platform length to determine a strain analysis table for the high-strength steel to be tested.

[0070] In the present application, the strain value range in which tensile strain marks are likely to appear or actually appear on the part to be tested can be determined based on the first strain value and the second strain value.

[0071] Table 1 shows a strain analysis table in one embodiment of the present application. Figure 1 As shown in the figure, the longitudinal yield platform length of H340LAD+Z high-strength steel is 3.2%, and the strain range of tensile strain marks generated under plane strain is between 1% and 3.5%. That is, when the strain of the part is less than 1% or greater than 3.5%, the tensile strain mark defect can be avoided.

[0072] Table 1

[0073]

[0074] See also Figure 9 .

[0075] Figure 9 A flowchart of a method for analyzing tensile strain mark defects according to one embodiment of the present application is shown. After determining the strain analysis table of the high-strength steel to be tested, the method may further include steps S901-S902:

[0076] Step S901: Obtain a strain analysis table corresponding to the high-strength steel to be tested.

[0077] Step S902 : analyzing the strain of a formed part of the high-strength steel to be tested according to a strain analysis table corresponding to the high-strength steel to be tested, and determining a yield platform control range of the high-strength steel to be tested.

[0078] In the present application, the strain of the formed part can be analyzed based on the obtained strain analysis table, and the yield platform control range of the metal sheet can be determined based on the strain conditions of each region thereof.

[0079] See also Figure 10 .

[0080] Figure 10 A flowchart of a method for analyzing tensile strain mark defects according to one embodiment of the present application is shown. After determining the strain analysis table of the high-strength steel to be tested, the method may further include steps S1001-S1002:

[0081] Step S1001: Obtain a strain analysis table corresponding to the high-strength steel to be tested.

[0082] Step S1002 , adjusting the stamping process according to the strain analysis table corresponding to the high-strength steel to be tested and the strain condition of the formed part of the high-strength steel to be tested, so as to avoid tensile strain mark defects on the formed part.

[0083] In this application, the stamping process can be adjusted for the strain condition of the parts according to the obtained strain analysis table, the strain condition of each area can be optimized, and the tensile strain mark defects can be reduced or avoided.

[0084] In order to enable those skilled in the art to have a deeper understanding of the technical solution of the present application, the present application will be described in detail below with reference to a specific embodiment.

[0085] The technical solution provided in this application can be applied to the stamping of door outer panel parts of a certain automobile manufacturer's vehicle model. During the forming process of the part, a large area of tensile strain mark defects appears on the surface of the part.

[0086] Mechanical and mesh strain analysis, combined with a comparison to the strain analysis table for the corresponding steel grade, revealed a yield plateau length of 3.5% and a principal strain of 3.24% in the area of the stamped part where the tensile strain mark defect occurred, falling squarely within the strain range indicated by the strain analysis table as prone to defects. Based on the statistical results from the mapping table, the rolling process was adjusted to optimize the yield plateau length to less than 2%. Furthermore, the press force during stamping was increased from 180 tons to 200 tons, increasing the material strain in this area. After this stamping process, the tensile strain mark defect on the part's surface disappeared, and the part's surface quality improved.

[0087] Those skilled in the art will readily conceive of other embodiments of the present application after considering the specification and practicing the embodiments disclosed herein. This application is intended to cover any variations, uses, or adaptations of the present application that follow the general principles of this application and include common knowledge or customary techniques in the art that are not disclosed herein.

[0088] It should be understood that the present application is not limited to the exact structures described above and shown in the drawings, and that various modifications and changes may be made without departing from the scope thereof. The scope of the present application is limited only by the appended claims.

Claims

1. A method for analyzing tensile strain mark defects, characterized in that: The method comprises: Obtain the yield platform length of the high-strength steel to be tested; Performing a bulging test on the high-strength steel to be tested to obtain a part to be tested that has a tensile strain mark; Performing strain analysis on the part to be tested to determine a first strain value when a tensile strain mark appears on the part to be tested, and determining a second strain value when the tensile strain mark on the part to be tested disappears; determining a strain analysis table of the high-strength steel to be tested according to the yield platform length, the first strain value, and the second strain value; The bulging test on the high-strength steel to be tested comprises: Performing a bulging test on the high-strength steel to be tested using at least one loading method, wherein the loading method includes plane strain, uniaxial tension, and biaxial tension; For any loading mode of bulging test, based on the set blank holder force and punching parameters, a bulging test of at least one punching height is performed on the high-strength steel to be tested by a forming test machine; The determining of a first strain value when a tensile strain mark appears on the part to be measured, and determining a second strain value when the tensile strain mark disappears on the part to be measured, comprises: Determining the minimum strain value corresponding to the tensile strain mark appearing on the part to be tested as the first strain value; Determine the second strain value by using the maximum strain value corresponding to when the tensile strain mark on the part to be tested disappears; The minimum strain value corresponding to the appearance of the tensile strain mark is the minimum strain value measured more than three times on samples with different stamping heights under the same loading method, and the maximum strain value corresponding to the disappearance of the tensile strain mark is the maximum strain value measured more than three times on samples with different stamping heights under the same loading method.

2. The method according to claim 1, characterized in that The step of obtaining the yield platform length of the high-strength steel to be tested includes: Conducting mechanical property testing along the rolling direction and transverse direction of the high-strength steel to be tested to determine the mechanical strain curve corresponding to the high-strength steel to be tested; According to the mechanical strain curve, the yield platform lengths corresponding to the rolling direction and the transverse direction of the high-strength steel to be tested are respectively determined.

3. The method according to claim 1, characterized in that Before performing a bulging test of at least one punching height on the high-strength steel to be tested using a forming test machine based on the set blank holding force and punching parameters, the method further includes: Preparation of bulging specimens: selecting the high-strength steel to be tested and preparing bulging specimens of predetermined size, and then cleaning the surface of the bulging specimens with alcohol; Grid printing: grid printing is performed on the bulging sample using a grid meter, and dots arranged in a grid matrix are etched on the bulging sample.

4. The method according to claim 3, characterized in that The method of performing grid printing on the bulging sample by using a grid meter comprises: A grid printer is used to print a grid along half of the long side of the bulge sample.

5. The method according to claim 1, wherein The performing strain analysis on the part to be tested includes: Optical equipment and analysis software are used to perform strain detection and analysis on the surface of the part to be tested.

6. The method according to claim 1, characterized in that Determining the strain analysis table of the high-strength steel to be tested according to the yield platform length, the first strain value, and the second strain value includes: Determining a strain value range in which a tensile strain mark appears on the high-strength steel to be tested according to the first strain value and the second strain value; The strain value range is mapped to the yield platform length to determine a strain analysis table for the high-strength steel to be tested.

7. The method according to claim 1, characterized in that After determining the strain analysis table of the high-strength steel to be tested, the method further includes: Obtaining a strain analysis table corresponding to the high-strength steel to be tested; According to the strain analysis table corresponding to the high-strength steel to be tested, the strain of the formed part of the high-strength steel to be tested is analyzed to determine the yield platform control range of the high-strength steel to be tested.

8. The method according to claim 1, characterized in that After determining the strain analysis table of the high-strength steel to be tested, the method further includes: Obtaining a strain analysis table corresponding to the high-strength steel to be tested; According to the strain analysis table corresponding to the high-strength steel to be tested, the stamping process is adjusted according to the strain condition of the formed part of the high-strength steel to be tested, so as to avoid tensile strain mark defects on the formed part.

Images