CN112257302B - Method for constructing plate forming limit curve by adopting limit thickness - Google Patents
Method for constructing plate forming limit curve by adopting limit thickness Download PDFInfo
- Publication number
- CN112257302B CN112257302B CN202010954176.6A CN202010954176A CN112257302B CN 112257302 B CN112257302 B CN 112257302B CN 202010954176 A CN202010954176 A CN 202010954176A CN 112257302 B CN112257302 B CN 112257302B
- Authority
- CN
- China
- Prior art keywords
- strain
- thickness
- limit
- forming
- epsilon
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
Images
Classifications
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F30/00—Computer-aided design [CAD]
- G06F30/20—Design optimisation, verification or simulation
- G06F30/23—Design optimisation, verification or simulation using finite element methods [FEM] or finite difference methods [FDM]
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F2119/00—Details relating to the type or aim of the analysis or the optimisation
- G06F2119/14—Force analysis or force optimisation, e.g. static or dynamic forces
Landscapes
- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Theoretical Computer Science (AREA)
- Computer Hardware Design (AREA)
- Evolutionary Computation (AREA)
- Geometry (AREA)
- General Engineering & Computer Science (AREA)
- General Physics & Mathematics (AREA)
- Shaping Metal By Deep-Drawing, Or The Like (AREA)
Abstract
The invention relates to a method for constructing a sheet forming limit curve by adopting limit thickness, and belongs to the technical field of sheet forming tests. The technical scheme of the invention is as follows: and performing bulging forming simulation on the measured metal plate through stamping forming CAE software, determining the strain increment ratio under different strain paths, obtaining the limit thickness values under different strain paths by combining with a limit thickness criterion, reading the main and secondary strain values corresponding to the limit thicknesses under different strain paths from a finite element simulation result, and drawing a graph under the same coordinate system to obtain a forming limit curve of the plate. The invention has the beneficial effects that: the method has the advantages that a finite element simulation is matched with a bulging experiment, a limit thickness criterion is combined to further obtain a forming limit curve of the plate, the operation is simple, the experiment workload is small, the cost is low, and the precision is high.
Description
Technical Field
The invention relates to a method for constructing a sheet forming limit curve by adopting limit thickness, and belongs to the technical field of sheet forming tests.
Background
The forming limit diagram is the most simple and visual means for judging and evaluating the formability of the plate, reflects the forming performance of the plate under different strain states, and is an important criterion for the success or failure of a part stamping process.
At present, a forming limit curve of a metal plate is obtained by performing a test through a national standard GB/T15825.8-2008' measuring guideline for forming performance and test method of a metal sheet-Forming Limit Diagram (FLD), the metal plate is required to be cut into 9 (at least 3 pieces of each) pieces with different sizes, then grid printing is performed by using an electrochemical method, then a bulging test is performed, and grid data is processed, so that primary and secondary strain under different strain paths is obtained, and the forming limit curve of the metal plate is obtained.
In the method for determining the forming limit of the metal plate, which is disclosed in CN 103424318A, the metal plate is subjected to stamping forming simulation through DYNAFORM software, FLD0 is determined, and then the forming limit curve of the plate is obtained through calculation through a keeler formula. However, the keeler formula is only suitable for calculating the forming limit curve of the mild steel with the strength less than 340Mpa, the forming limit curve of the high-strength steel has large calculation error, the FLD0 right shift phenomenon cannot be represented, and the limitation is large.
Disclosure of Invention
The invention aims to provide a method for constructing a sheet forming limit curve by adopting limit thickness, which combines finite element simulation with a bulging experiment and combines a limit thickness criterion to further obtain the sheet forming limit curve, has the advantages of simple operation, small experimental workload, low cost and high precision, and effectively solves the problems in the background art.
The technical scheme of the invention is as follows: a method for constructing a plate forming limit curve by adopting limit thickness comprises the following steps:
(1) Taking a trapezoidal sample with the length of 180mm and the width of a gauge length section of 20mm after being processed by the metal to be measured, carrying out bulging test on a forming tester according to national standards, stopping the sample after the sample shrinks, recording the stroke h of a male die, and measuring the thickness t of a material sheet at the shrunk position 0 ；
(2) Carrying out a tensile experiment on the metal to be measured to obtain a stress-strain curve and a work hardening index n of the metal to be measured;
(3) According to the size of a die in a national standard bulging test, establishing the die, wherein the die comprises a male die, a female die and a blank holder; establishing a geometric model of the material sheet, wherein the geometric model comprises nine trapezoidal material sheet geometric models with the length of 180mm and the widths of gauge length sections of 20mm, 40mm, 60mm, 80mm, 100mm, 120mm, 140mm, 160mm and 180 mm;
(4) Introducing the die and the material sheet geometric model into Autoform or Dynaform stamping forming simulation CAE software, setting boundary conditions according to technological parameters of a national standard bulging experiment by using parameters obtained in the step (2) as material parameters, keeping the stamping depth consistent with the convex die stroke in the step (1), and carrying out forming process simulation calculation;
(5) Taking the difference value of the secondary strain and the main strain of the last frame and the last frame of the simulation result, and dividing to obtain a strain increment ratio alpha (delta epsilon 2/delta epsilon 1) and obtain strain increment ratios under nine different strain paths;
(6) Calculating to obtain the minimum thickness value t of the plate under different strain paths according to the limit thickness criterion;
the limiting thickness criterion is as follows:
wherein: t is t 0 The thickness of the sheet with the gauge length section width of 20mm when the sheet is expanded and contracted is obtained through experimental measurement in the step (1); n is the work hardening index of the material obtained in the step (2); alpha is the strain increment ratio obtained in the step (5);
(7) And (4) finding out a main strain epsilon 1 and a secondary strain epsilon 2 corresponding to the thickness values according to the limit thickness values under different strain paths obtained by calculation in the step (6).
(8) And drawing the nine (epsilon 1, epsilon 2) coordinate points in a coordinate system with the secondary strain epsilon 2 as a horizontal axis and the main strain epsilon 1 as a vertical axis to obtain a forming limit curve of the measured metal plate.
The measured metal is a steel material with the thickness of 0.5-6 mm.
The invention has the beneficial effects that: the method has the advantages that a finite element simulation is matched with a bulging experiment, a limit thickness criterion is combined to further obtain a forming limit curve of the plate, the operation is simple, the experiment workload is small, the cost is low, and the precision is high.
Drawings
FIG. 1 is a web for a bulging test of the present invention;
FIG. 2 is a nine web simulation of finite elements of the present invention;
FIG. 3 is a finite element simulation geometry model of the present invention;
FIG. 4 is a comparison of a limit curve for forming a sheet material constructed by using a limit thickness according to the present invention and an experimental measurement curve;
in the figure: sheet material 1, terrace die 2, die 3, blank holder frame 4.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions of the embodiments of the present invention with reference to the drawings of the embodiments, and it is obvious that the described embodiments are a small part of the embodiments of the present invention, rather than all embodiments, and all other embodiments obtained by a person of ordinary skill in the art without creative work based on the embodiments of the present invention belong to the protection scope of the present invention.
A method for constructing a sheet forming limit curve by adopting limit thickness comprises the following steps:
(1) Taking a trapezoidal sample with the length of 180mm after the measured metal is processed and the width of a gauge length section being 20mm, performing an expansion experiment on a forming tester according to national standards, stopping after the sample shrinks with force, recording the stroke h of a male die, and measuring the thickness t of a material sheet at the shrinking position 0 ；
(2) Carrying out a tensile experiment on the metal to be measured to obtain a stress-strain curve and a work hardening index n of the metal to be measured;
(3) According to the size of a die in a national standard bulging test, establishing the die, wherein the die comprises a male die, a female die and a blank holder; establishing a geometric model of a material sheet, wherein the geometric model comprises nine trapezoidal material sheet geometric models with the length of 180mm and the widths of gauge length sections of 20mm, 40mm, 60mm, 80mm, 100mm, 120mm, 140mm, 160mm and 180 mm;
(4) Introducing the die and the material sheet geometric model into Autoform or Dynaform stamping forming simulation CAE software, setting boundary conditions according to technological parameters of a national standard bulging experiment by using parameters obtained in the step (2) as material parameters, keeping the stamping depth consistent with the convex die stroke in the step (1), and carrying out forming process simulation calculation;
(5) Taking the difference value of the secondary strain and the main strain of the last frame and the last frame of the simulation result, and dividing to obtain a strain increment ratio alpha (delta epsilon 2/delta epsilon 1) and obtain strain increment ratios under nine different strain paths;
(6) Calculating to obtain the minimum thickness value t of the plate under different strain paths according to the limit thickness criterion;
the limiting thickness criterion is as follows:
wherein: t is t 0 The thickness of the sheet with the gauge length section width of 20mm when the sheet is expanded and contracted is obtained through experimental measurement in the step (1); n is the work hardening index of the material obtained in the step (2); alpha is the strain increment ratio obtained in the step (5);
(7) And (4) finding out the main strain epsilon 1 and the secondary strain epsilon 2 corresponding to the thickness values in the simulation result of the step (4) according to the limit thickness values under different strain paths obtained by calculation in the step (6).
(8) And drawing the nine (epsilon 1, epsilon 2) coordinate points in a coordinate system with the secondary strain epsilon 2 as a horizontal axis and the main strain epsilon 1 as a vertical axis to obtain a forming limit curve of the measured metal plate.
The measured metal is a steel material with the thickness of 0.5-6 mm.
Example (b):
the construction of the forming limit curve of DC04 with the thickness of 1.0mm in a certain steel mill is taken as an example, and the specific embodiment of the invention is explained by combining the attached drawings.
(1) Processing DC04 with thickness of 1.0mm into a trapezoidal sample with length of 180mm and gauge length width of 20mm on a forming testerAnd (3) performing bulging experiment, stopping the sample after the sample is shrunk, measuring the thickness t of a material sheet at the shrunk position, wherein the stroke h of a male die is 43mm 0 Is 0.678;
(2) Performing a tensile experiment on the DC04 to obtain a stress-strain curve of the DC04, and simultaneously obtaining a work hardening index n of 0.24;
(3) According to the size of a die of a national standard bulging experiment, nine geometric models of a ball head male die with the diameter of 100mm, a corresponding female die with the diameter of 105mm, a blank holder and nine trapezoidal material sheets with the length of 180mm and the width of gauge length sections of 20mm, 40mm, 60mm, 80mm, 100mm, 120mm, 140mm, 160mm and 180mm are established;
(4) Introducing the die and the geometric model of the material sheet into Dynaform stamping forming simulation CAE software, using the stress-strain curve and the work hardening value obtained by measurement in the step (2) as material parameters, setting the blank holder force to be 50000N, adding virtual ribs at the same time, ensuring that the material sheet does not flow, setting the stamping depth to be 43mm, and performing bulging simulation calculation;
(5) Taking the difference value of the secondary strain and the main strain of the last frame and the last frame of the simulation result, dividing the difference value, and calculating the strain increment ratio alpha (delta epsilon 2/delta epsilon 1) to obtain the strain increment ratios of 9 types of material sheets with different sizes: -0.72, -0.68, -0.63, -0.512, -0.429, -0.1,0.2,0.27,0.32; (ratio of increase in Strain in the order of tablets from Small to Large)
(6) Calculating the minimum thickness values t of the plate under different strain paths according to the limit thickness criterion to be 0.710,0.708,0.699,0.680,0.666,0.608,0.523,0.505,0.485 respectively;
the limiting thickness criterion is as follows:
wherein: t is t 0 0.678, n is 0.24; alpha is the strain increment ratio obtained in the step (6);
(7) And (4) finding 9 groups of main strain epsilon 1 and secondary strain epsilon 2 corresponding to the thickness value according to the ultimate thickness values under different strain paths calculated in the step (6) and the simulation result of the step (4) corresponding to the dimension of the material sheet.
(8) Drawing nine (epsilon 1, epsilon 2) coordinate points in a coordinate system with a secondary strain epsilon 2 as a horizontal axis and a main strain epsilon 1 as a vertical axis to obtain a forming limit curve of the DC04 metal plate;
(9) The forming limit curve obtained by the method is compared with the forming limit curve obtained by experimental measurement, and the error between the forming limit curve and the forming limit curve is found to be very small and within 5 percent, which shows that the method for obtaining the plate forming limit curve is reliable.
Claims (1)
1. A method for constructing a plate forming limit curve by adopting limit thickness is characterized by comprising the following steps:
(1) Taking a trapezoidal sample with the length of 180mm after the measured metal is processed and the width of a gauge length section being 20mm, performing an bulging experiment on a forming tester according to national standards, stopping after the sample is necked, recording the stroke h of a male die, and measuring the thickness t of a material sheet at the necked position 0 ；
(2) Carrying out a tensile experiment on the metal to be measured to obtain a stress-strain curve and a work hardening index n of the metal to be measured;
(3) Establishing a die according to the die size of a national standard bulging test, wherein the die comprises a male die, a female die and a blank holder; establishing a geometric model of the material sheet, wherein the geometric model comprises nine trapezoidal material sheet geometric models with the length of 180mm and the widths of gauge length sections of 20mm, 40mm, 60mm, 80mm, 100mm, 120mm, 140mm, 160mm and 180 mm;
(4) Introducing the die and the material sheet geometric model into Autoform or Dynaform stamping forming simulation CAE software, setting boundary conditions according to the parameters obtained by measurement in the step (2) and the technological parameters of the national standard bulging test, keeping the stamping depth consistent with the convex die stroke in the step (1), and carrying out forming process simulation calculation;
(5) Taking the difference value of the secondary strain and the main strain of the last frame and the last frame of the simulation result, and dividing the difference value to obtain a strain increment ratio alpha = delta epsilon 2/delta epsilon 1, so as to obtain the strain increment ratios under nine different strain paths;
(6) Calculating to obtain the minimum thickness value t of the plate under different strain paths according to the limit thickness criterion;
the limiting thickness criterion is as follows:
wherein: t is t 0 The thickness of a material sheet with the gauge length section width of 20mm when the material sheet is subjected to necking during bulging is obtained through experimental measurement in the step (1); n is the work hardening index of the material obtained in the step (2); alpha is the strain increment ratio obtained in the step (5);
(7) According to the limit thickness values under different strain paths obtained by calculation in the step (6), finding out a main strain epsilon 1 and a secondary strain epsilon 2 corresponding to the thickness values in the simulation result of the step (4);
(8) Drawing nine (epsilon 1, epsilon 2) coordinate points in a coordinate system with the secondary strain epsilon 2 as a horizontal axis and the main strain epsilon 1 as a vertical axis to obtain a forming limit curve of the measured metal plate;
the measured metal is a steel material with the thickness of 0.5-6 mm.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010954176.6A CN112257302B (en) | 2020-09-11 | 2020-09-11 | Method for constructing plate forming limit curve by adopting limit thickness |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010954176.6A CN112257302B (en) | 2020-09-11 | 2020-09-11 | Method for constructing plate forming limit curve by adopting limit thickness |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN112257302A CN112257302A (en) | 2021-01-22 |
| CN112257302B true CN112257302B (en) | 2023-04-18 |
Family
ID=74232108
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202010954176.6A Active CN112257302B (en) | 2020-09-11 | 2020-09-11 | Method for constructing plate forming limit curve by adopting limit thickness |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN112257302B (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113128001B (en) * | 2021-05-17 | 2022-04-15 | 同济大学 | Forming limit test method |
| CN113418776B (en) * | 2021-05-24 | 2022-08-16 | 鞍钢股份有限公司 | Method for judging stamping performance of automobile steel by using limit forming margin |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103424318B (en) * | 2012-05-23 | 2017-10-10 | 上海工程技术大学 | A kind of determination method of metal sheet forming limit curve |
| JP5900427B2 (en) * | 2013-07-09 | 2016-04-06 | Ｊｆｅスチール株式会社 | Forming limit measuring method and apparatus |
| CN103870641A (en) * | 2014-03-04 | 2014-06-18 | 湖南大学 | Construction and using method of VRB (Variable Thickness Rolled Blank) forming limit stress diagram |
| CN110618023B (en) * | 2019-09-20 | 2021-10-26 | 大连理工大学 | Test method for obtaining large bidirectional strain by utilizing male die bulging based on thinned test piece |
| CN111595697B (en) * | 2020-04-10 | 2023-08-25 | 唐山钢铁集团有限责任公司 | Method for judging shearing resistance forming capability of material during stamping |
-
2020
- 2020-09-11 CN CN202010954176.6A patent/CN112257302B/en active Active
Non-Patent Citations (1)
| Title |
|---|
| 基于厚度梯度准则的薄板成形极限图建立方法;陈炜等;《中国机械工程》;20070930;第18卷(第18期);2246-2249页 * |
Also Published As
| Publication number | Publication date |
|---|---|
| CN112257302A (en) | 2021-01-22 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN111896373B (en) | Test and calculation method for determining equivalent plastic strain forming limit diagram | |
| CN112257302B (en) | Method for constructing plate forming limit curve by adopting limit thickness | |
| Bidabadi et al. | Experimental and numerical study of bowing defects in cold roll-formed, U-channel sections | |
| Shinkin | Simplified calculation of the bending torques of steel sheet and the roller reaction in a straightening machine | |
| CN102818763B (en) | Hot-rolled steel plate residual stress calculating method suitable to production field | |
| CN103424318B (en) | A kind of determination method of metal sheet forming limit curve | |
| Chen et al. | Determination of formability considering wrinkling defect in first-pass conventional spinning with linear roller path | |
| ZHU et al. | Sensitivity of springback and section deformation to process parameters in rotary draw bending of thin-walled rectangular H96 brass tube | |
| Sachnik et al. | Burr-free cutting edges by notch-shear cutting | |
| Abbasi et al. | Analytical method for prediction of weld line movement during stretch forming of tailor-welded blanks | |
| Ma et al. | Research and verification on neutral layer offset of bar in two-roll straightening process | |
| CN105180886B (en) | A kind of method for measuring cold-reduced sheet Strain Distribution | |
| CN106777502B (en) | method for manufacturing three-dimensional principal stress theoretical forming limit diagram for plastic forming of pipe | |
| CN103512802A (en) | Testing method for measuring plane strain points in thin steel sheet forming limit diagram | |
| CN112364549B (en) | Method for establishing rolling variable-thickness plate forming limit field | |
| CN102107250A (en) | Method for determining expansion process parameters of tube and tube plate of AP1000 nuclear evaporator | |
| JP4622688B2 (en) | Method and apparatus for predicting surface strain of press-formed product | |
| JP7464176B1 (en) | Method, device and program for determining press-molded cracks, and method for manufacturing press-molded products | |
| Lindgren | Validation of finite element model of roll forming | |
| Khamis et al. | Mild steel sheet metal forming using Abaqus software: Influence of drawbeads in minimize springback | |
| Shao et al. | Research on springback compensation for multi-point forming of corrosion-resistant aluminum alloy hyperbolic component | |
| MULIDRAN et al. | OPTIMIZATION OF THE FORMING PROCESS OF GUTTER END CAP USING THE FINITE ELEMENT METHOD. | |
| Singh | Sheet Metal Forming Processes Recent Technological Advances | |
| Olayinka et al. | Numerical investigation of bipolar plates manufactured using hydroforming process | |
| Rui-bin et al. | Modelling of PSM to predict the stress in sheet drawing |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |