Partition oiling regulation-based plate forming method

Abstract

The invention provides a plate forming method based on partition oiling regulation and control, relates to the technical field of material forming, and aims to solve the problem of poor forming effect caused by consistent oiling quantity on the surface of a plate. The forming method comprises the steps that the surface of a first target plate is divided into a plurality of areas; forming the first target plate by adopting a set of production process parameters comprising the basic oil coating quantity Q0 to obtain a first component; judging the risk type of each region; establishing an oiling quantity-friction coefficient function relational expression mu = f (Q); constructing a finite element simulation model, and determining an optimized friction coefficient [mu] wrinkle corresponding to the wrinkling risk area and an optimized friction coefficient [mu] crack corresponding to the cracking necking risk area; according to the mu wrinkles, the mu cracks and the function relational expression, determining a target oiling quantity Q wrinkles corresponding to the wrinkling risk area and a target oiling quantity Q cracks corresponding to the cracking necking risk area; and on the basis of Q0, Q wrinkle and Q crack partition oil coating, the second target plate is put into actual forming production, and a qualified target component is obtained.

Description

Technical Field

[0001] This invention relates to the field of material forming technology, and in particular to a sheet metal forming method based on zoned oiling control. Background Technology

[0002] During material forming, the sheet metal deforms under the action of the mold and forming force, ultimately obtaining the desired shape. However, due to the uneven distribution of friction during forming, defects such as cracking, necking, and wrinkling may occur in the components. These defects not only affect the quality of the components but also lead to waste of raw materials and reduced production efficiency. The contact friction between the sheet metal and the mold plays a crucial role in forming quality. To control friction during the forming process, the traditional approach is to uniformly apply oil to the entire surface of the sheet metal. However, this traditional oiling strategy has certain limitations. Due to the different shapes and stress conditions of the formed parts, different areas of the sheet metal have different friction requirements. For example, the edge areas of the formed part may require a higher coefficient of friction to avoid excessive deformation, while the central area may require lower friction to reduce the risk of springback and wrinkling.

[0003] Although some methods have been developed to improve forming quality by altering the way the sheet material is oiled, such as using different types of lubricants or coating materials, most methods still rely on uniformly oiling the entire sheet surface. This uniform oiling method does not adequately consider the friction requirements of different areas of the sheet, resulting in excessive or insufficient friction in certain critical areas. This, in turn, affects deformation control during the forming process and leads to defects.

[0004] Meanwhile, most raw material manufacturers, during the oiling stage, primarily consider the uniformity of the oil layer and the convenience of the spraying process, often employing simplified electrostatic oiling methods, failing to fully optimize for the friction requirements of different areas of the formed part. While OEMs can adjust process parameters according to actual conditions during forming, the adjustment process often relies on worker experience, lacking clear standards for controlling the amount of oil applied, making it difficult to scientifically quantify and precisely optimize process parameters. This approach not only affects the controllability of forming quality but also increases the uncertainty and human interference during the adjustment process. Therefore, there is an urgent need to develop a zoned oiling control method to overcome the limitations of traditional oiling processes. Summary of the Invention

[0005] The present invention aims to solve or improve the technical problem in the prior art where the amount of oil applied to the surface of the sheet is inconsistent, resulting in poor forming effect.

[0006] The first aspect of the present invention is to provide a sheet metal forming method based on zoned oiling control, comprising the following steps: dividing the surface of a first target sheet metal into multiple regions; employing a set of methods including a basic oiling amountQ The production process parameters were set to 0, and the first target sheet was subjected to the first actual forming to obtain the first component. Based on the FLD analysis method, the risk type of each area was determined, including wrinkling risk areas, cracking and necking risk areas, and non-risk areas. A functional relationship between oil application amount and friction coefficient was established. μ = f ( Q The mold parameters of the first target component are obtained, and a finite element simulation model is constructed based on the mold parameters and production process parameters. Iterative simulation experiments are conducted using the finite element simulation model to determine the optimized friction coefficients corresponding to the wrinkling risk areas. μ 皱 And the optimized friction coefficient corresponding to the cracking and necking risk area. μ 裂 ;according to μ 皱 Based on the functional relationship, determine the target amount of oil applied to the area at risk of wrinkling. Q 皱 ;according to μ 裂 Based on the functional relationship, determine the target oil application amount corresponding to the cracking and necking risk area. Q 裂 The surface of the second target board is treated with zoned oiling, with the oil amount applied to the wrinkle-prone areas being [amount missing]. Q 皱 The amount of oil applied to areas at risk of cracking and necking is Q 裂 The amount of oil applied to non-risk areas is Q 0; The second target sheet, after being coated with oil, is put into actual forming production and formed under the conditions of the production process parameters to obtain a qualified target component.

[0007] In the above technical solution, optionally, iterative simulation experiments are conducted using a finite element simulation model to determine the optimized friction coefficient corresponding to the wrinkling risk area. μ 皱 And the optimized friction coefficient corresponding to the cracking and necking risk area. μ 裂 The steps specifically include: using the base amount of oil applied. Q The initial friction coefficient corresponding to 0 is taken as the starting point. For cracked or necked areas, the coefficient is adjusted in steps Δ. μ 裂 Gradually decrease the friction coefficient until the cracking or necking defects in the simulation disappear, and record the friction coefficient at this point. μ 裂 For wrinkled areas, with a step size Δ μ 皱 Gradually increase the friction coefficient until the wrinkling defects in the simulation disappear, and record the friction coefficient at this point. μ皱 ;where Δ μ 裂 ∈ (0, 0.01], Δ μ 皱 ∈ (0, 0.01).

[0008] In the above technical solution, optionally, the step of establishing the functional relationship between oil application amount and friction coefficient specifically includes: conducting friction tests on multiple groups of oil application amount samples and measuring the corresponding friction coefficient; fitting the oil application amount using fitting software. Q With coefficient of friction μ The mapping relationship is established, and a functional relationship between oil application amount and friction coefficient is created. μ = f ( Q ).

[0009] In the above technical solutions, the fitting software may optionally include one or a combination of the following: MATLAB, Origin, Excel, and Python.

[0010] In the above technical solution, the friction test may optionally include one or a combination of the following: flat plate sliding friction test, drawbead friction test, tensile bending friction test, and reverse identification test.

[0011] In the above technical solution, optionally, the surface of the first target plate has a dot matrix grid. The step of determining the risk type of each region based on the FLD analysis method specifically includes: performing photogrammetry on the surface of the formed first component to obtain the changes in the major and minor axes of each point in the dot matrix grid relative to the original circle, and calculating the principal strain and secondary strain of each grid; determining the actual strain data of each region based on the principal strain and secondary strain of each point after deformation; generating the FLD based on the actual strain data; and determining the risk type of each partition based on the FLD.

[0012] In the above technical solutions, the finite element simulation software may optionally include one or a combination of the following: LS-DYNA, AutoForm, AI-FORM, and ABAQUS.

[0013] In the above technical solution, the mold parameters may optionally include punch structure parameters, die structure parameters, and pressure ring structure parameters.

[0014] In the above technical solution, the production process parameters may optionally include blank holder force, forming force, stamping speed, and blank holder lifting height.

[0015] Compared with existing processes, the present invention has the following advantages: 1. Under the premise of keeping other process conditions constant, the present invention can suppress the generation of defects by simply changing the amount of oil applied to a local area of ​​the board. This effectively avoids the problem of production stability being compromised by manually adjusting the blank holder force or mold balance block and other equipment and mold parameters.

[0016] 2. This invention optimizes the production process using high-precision virtual manufacturing technology. Based on specific forming requirements, it calculates the optimal friction coefficient for different regions, thereby determining the best match between the oiling area and the amount of oil applied. This avoids excessive consumption of raw materials during the production debugging phase, significantly reducing downtime while saving production costs.

[0017] 3. This invention develops customized processes for raw material manufacturers or OEMs, enabling precise control. Raw material manufacturers implement zoned oiling based on the production needs of different products, ensuring that each batch of boards better meets the specific requirements of the OEM, avoiding the need for uniform oiling of the entire board surface as in traditional methods. This flexibility not only helps reduce production delays caused by improper oiling but also shortens the production cycle and improves overall production efficiency. OEMs can also adapt to different production tasks more quickly, reducing debugging time. Simultaneously, the customized oiling solution can precisely control the amount of oil applied according to the actual needs of each area, thus avoiding unnecessary waste. This not only reduces oil consumption costs but also helps improve resource utilization, effectively reducing overall production costs in the long run. As market demand for high-quality, customized products increases, the precise oiling solution for raw material manufacturers will be able to meet the specific needs of more customers, thereby enhancing their competitiveness in the industry.

[0018] 4. OEMs no longer need to rely on tedious, experience-based adjustments; they can directly use sheet metal with high-precision and stable coating results. This significantly improves production efficiency, shortens production cycles, and reduces rework and scrap costs caused by defects. Because the coating process is meticulously designed and calculated, the distribution of friction is precisely controlled. Therefore, this method allows OEMs to achieve more stable shape control, reduce instability caused by improper friction matching, and improve process consistency and stability.

[0019] 5. This invention utilizes customized zone control based on virtual manufacturing technology to precisely control the lubrication process, achieving efficient lubrication optimization in various forming processes. This technology is not only applicable to traditional oil-based lubricants but also widely applicable to other lubricants such as lubricating powders and solid lubricants. By adjusting the lubrication amount and method according to the needs of each process stage and area, this technology can be extended to various forming processes such as drawing, bending, progressive forming, and spinning, achieving forming under optimal lubrication conditions, thereby ensuring product quality, reducing energy consumption, and improving production efficiency. Therefore, this technology has application potential in multiple industries and helps improve the quality and production efficiency of various components.

[0020] 6. This invention, based on customized zone control using virtual manufacturing technology, is not only applicable to different forming processes but also allows for flexible adjustments to suit the characteristics of various materials, ensuring that the forming process for different materials can proceed under optimal lubrication conditions. Whether it is a metallic material (such as steel, aluminum, magnesium, titanium, etc.) or a non-metallic material (such as plastics, composite materials, etc.), this technology can precisely adjust the lubrication method and amount according to the material's strength, fluidity, surface morphology requirements, and frictional characteristics, thereby optimizing the forming quality.

[0021] Additional aspects and advantages of the invention will become apparent in the following description or may be learned by practice of the invention. Attached Figure Description

[0022] The above and / or additional aspects and advantages of embodiments of the present invention will become apparent and readily understood from the description of the embodiments in conjunction with the following drawings, wherein: Figure 1 A flowchart of a forming method according to an embodiment of this application is shown; Figure 2 A structural diagram of a sheet metal with an oil coating, according to an embodiment of this application, is shown. Figure 3 This application shows a shaped door panel partition diagram according to one embodiment of the present application; Figure 4 This paper presents a comparison diagram of FLD results from the AH region according to an embodiment of this application; Figure 5 A graph showing the functional relationship between the amount of oil applied and the coefficient of friction according to an embodiment of this application is provided. Figure 6 A mold structure diagram of a door panel according to an embodiment of this application is shown; Figure 7 Figure a shows a simulation result diagram of region F before partition oiling according to an embodiment of this application; Figure 7b shows a cloud map of the thickness reduction rate distribution of region F before partition oiling, according to an embodiment of this application; Figure 8 Figure a shows a simulation result diagram of region G before partition oiling according to an embodiment of this application; Figure 8 b shows a cloud map of the thickness reduction rate distribution of region G before partitioning oiling, according to an embodiment of this application; Figure 9 This paper shows the FLD result diagram of the F region before zonal oiling according to an embodiment of this application; Figure 10 This paper shows the FLD result diagram of region G before zonal oiling according to an embodiment of this application; Figure 11 The following is a simulation result diagram of region F and region G before and after partitioning and oiling according to an embodiment of this application; Figure 12 A schematic diagram illustrating the principle of adjusting the amount of oil applied according to the location of a defect, according to one embodiment of this application, is shown. Figure 13 This paper shows the FLD result diagram of region F after partitioning and oiling according to an embodiment of this application; Figure 14 This paper presents a comparison diagram of FLD results for uniform oiling of region F and partial oiling according to an embodiment of this application; Figure 15 This paper shows the FLD result diagram of region G after partitioning and oiling according to an embodiment of this application; Figure 16 The diagram shows a comparison of FLD results between uniform oiling and partitioned oiling in region G of an embodiment of this application. Detailed Implementation

[0023] To better understand the above aspects, features, and advantages of the embodiments of the present invention, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0024] like Figure 1 As shown, the forming method provided in this embodiment includes the following steps: S102: Divide the surface of the board into multiple areas; This step provides a spatial framework for subsequent defect localization and analysis. The division is not arbitrary but based on the specific geometric characteristics of the target product components and engineering experience. It typically follows these principles: In areas where the mold surface changes drastically (such as deep cavities, steep sidewalls, and the root of bulges), denser divisions are made, as these areas are prone to necking or even cracking.

[0025] In areas where material flow is poor or where it is easy to accumulate (such as large flat surfaces or small rounded corner transition areas), denser divisions should be made, as wrinkles are prone to occur in these areas.

[0026] Each region should be of moderate size, allowing for precise defect location without overwhelming the analysis with too many regions. For example, a car door inner panel can be naturally divided into 10-20 analysis regions based on its reinforcing ribs, windows, and other features. Here, the selection of 10-20 locations is actually a special case; only one region can be observed. The reason for choosing these areas is primarily because they are prone to defects during production. Any area prone to defects can be used as an inspection area. Excessive drawing depth in localized areas, unreasonable die corner radius design, and poor draw bead design can all lead to cracking, necking, and even wrinkling.

[0027] S104: Uses a set of base oiling materials Q The production process parameters of 0 are used to perform the first actual forming of the first target sheet to obtain the first component; The purpose of this step is to obtain a real sample containing defects for subsequent analysis. Production process parameters refer to all parameters, except for the oil application amount, that are commonly used and stable on the current production line, including but not limited to blank holder force, forming force, stamping speed, and blank holder ring lift height. Basic oil application amount. Q 0 refers to the amount of oil that is typically applied evenly under the current process. The result of this forming (the first component) may be a defective product, but its value lies in its accurate reflection of the location and type of defects under the current process conditions.

[0028] The forming process here includes, but is not limited to: stamping, stretch forming, spinning, incremental forming, etc.

[0029] S106: Based on the FLD analysis method, determine the risk type of each area. The risk types include wrinkling risk area, cracking and necking risk area and non-risk area. This step involves precise testing and analysis of the first component. The specific procedures are as follows: Before forming, a high-density lattice mesh needs to be fabricated on the first target substrate using electrochemical etching technology. After forming, these meshes deform along with the substrate. A photogrammetry instrument is used to scan the deformed mesh, obtaining the changes in the major and minor axes of each point in the lattice mesh relative to the original circle to calculate the principal and secondary strains of each mesh. Based on the principal and secondary strains of each point after deformation, the actual strain data of each region is determined. Plotting the data on the forming limit curve yields the FLD (Flexible Dropout).

[0030] By comparing the data points with the "non-risk area", "cracking and necking risk area" and "wrinkling risk area" in the figure, the risk type of each area is determined one by one.

[0031] S108: Establish the functional relationship between oil application amount and friction coefficient. μ = f ( Q ),according to μ 皱 Based on the functional relationship, determine the target amount of oil applied to the area at risk of wrinkling. Q 皱 ,according to μ 裂 Based on the functional relationship, determine the target oil application amount corresponding to the cracking and necking risk area. Q 裂 ; This step converts the virtual optimization results into actual production instructions. (Functional relationship) μ = f ( Q This was established through extensive prior tribological experiments: for different amounts of oil applied... Q Friction tests (such as sliding friction test of flat plate or friction test of draw bead) were performed on the sheet metal samples, and the corresponding coefficients of friction were recorded. μ Finally, the functional relationship is obtained through data fitting (such as polynomial fitting).

[0032] S110: Obtain the mold parameters of the first target component, and construct a high-precision finite element simulation model based on the mold parameters and production process parameters; This step involves creating a digital virtual model for process optimization. "Die parameters" refer to the geometric data of the die used to produce the component, including the surface data and fillet radii of the punch, die, and blank holder. This geometric data, along with production process parameters (blank force, friction coefficient, etc.), is input into finite element simulation software (such as LS-DYNA, AutoForm, AI-FORM, ABAQUS) to construct a digital model capable of simulating the actual forming process.

[0033] S112: Iterative simulation experiments were conducted using a finite element simulation model to determine the optimized friction coefficients corresponding to the wrinkling risk areas. μ 皱 And the optimized friction coefficient corresponding to the cracking and necking risk area. μ 裂 ; This step involves process optimization in a virtual environment. The specific iterative method is as follows: For areas identified as having a risk of cracking and necking: In the simulation, the iteration step size is Δ... μ 裂(e.g., 0.01) Gradually decrease the friction coefficient of this region (simulate increasing the amount of oil applied), and rerun the simulation until the material thinning rate of this region is below the critical value and no longer shows the risk of cracking and necking. Record the friction coefficient of this region at this point as the optimized value. μ 裂 For areas identified as having a risk of wrinkling: in the simulation, the step size Δ μ 皱 (e.g., 0.01) Gradually increase the friction coefficient of this area (simulating a reduction in the amount of oil applied), and rerun the simulation until the wrinkling phenomenon in this area disappears. Record the friction coefficient of this area at this point as the optimized value. μ 皱 This process is only performed in the high-risk area; the friction coefficient remains unchanged in the non-high-risk area.

[0034] S114: Obtain the optimized friction coefficient μ 皱 and μ 裂 Then, the functional relationship between oil application amount and friction coefficient established by the above steps is used. μ = f ( Q The precise amount of oil required to achieve this friction coefficient can be calculated through function inversion. Q 皱 and Q 裂 .

[0035] S116: Apply oil to the surface of the second target material in sections, wherein the amount of oil applied to the wrinkle-prone areas is... Q 皱 The amount of oil applied to areas at risk of cracking and necking is Q 裂 The amount of oil applied to non-risk areas is Q 0; This step involves applying an optimized solution. Using oiling equipment (such as an electrostatic oiler or roller coater) and cleaning equipment (such as a cleaning machine), a differentiated and non-uniform oiling process is performed on the second, brand-new board material, based on the identified risk areas and the calculated target oiling amount. The equipment precisely applies less oil to areas at risk of wrinkling. Q 皱 Apply more oil to the area at risk of cracking and necking. Q 裂 Maintain the original base oil volume in other areas. Q 0.

[0036] S118: The second target sheet that has been coated with oil is put into actual forming production and formed under the conditions of production process parameters (except for the amount of oil) to obtain a qualified target component.

[0037] Using sheet metal that has undergone zoned oiling treatment, and maintaining all other process parameters exactly the same as in the first forming, formal production proceeds. Because friction conditions have been precisely controlled and material flow optimized, the components produced this time will effectively avoid cracking, necking, and wrinkling defects, thus obtaining qualified target components. The core of this method lies in achieving defect suppression simply by adjusting localized oiling strategies, without changing the mold or other complex process parameters, resulting in low cost and high efficiency.

[0038] In the above technical solution, optionally, iterative simulation experiments are conducted using a finite element simulation model to determine the optimized friction coefficient corresponding to the wrinkling risk area. μ 皱 And the optimized friction coefficient corresponding to the cracking and necking risk area. μ 裂 The steps specifically include: using the base amount of oil applied. Q Starting with the initial friction coefficient corresponding to 0, and targeting the cracked and constricted region, the step size Δ is used. μ 裂 Gradually decrease the friction coefficient until the cracking and necking defects in the simulation disappear, and record the friction coefficient at this point. μ 裂 For wrinkled areas, with a step size Δ μ 皱 Gradually increase the friction coefficient until the wrinkling defects in the simulation disappear, and record the friction coefficient at this point. μ 皱 ;where Δ μ 裂 ∈ (0, 0.01], Δ μ 皱 ∈ (0, 0.0.01).

[0039] In the above technical solution, optionally, the step of establishing the functional relationship between oil application amount and friction coefficient specifically includes: conducting friction tests on multiple groups of oil application amount samples and measuring the corresponding friction coefficient; fitting the oil application amount using fitting software. Q With coefficient of friction μ The mapping relationship is established, and a functional relationship between oil application amount and friction coefficient is created. μ = f ( Q ).

[0040] In the above technical solutions, the fitting software may optionally include one or a combination of the following: MATLAB, Origin, Excel, and Python.

[0041] In the above technical solution, the friction test may optionally include one or a combination of the following: flat plate sliding friction test, drawbead friction test, tensile bending friction test, and reverse identification test.

[0042] In the above technical solution, optionally, the surface of the first target plate has a dot grid. The step of determining the risk type of each region based on the FLD analysis method specifically includes: performing photogrammetry on the surface of the first component after forming, obtaining the changes of the major and minor axes of each point in the dot grid relative to the original circle to calculate the principal strain and secondary strain of each grid; determining the actual strain data of each region based on the principal strain and secondary strain of each point after deformation; generating FLD based on the actual strain data; comparing each data point in the FLD with the preset defect judgment boundary line; and determining the risk type of each partition based on the FLD.

[0043] In this technical solution, the first target plate needs to be pretreated before the first actual forming. Electrochemical etching technology is used to create a dense, uniform lattice mesh on the plate surface. The mesh size is between 1.5-5mm, and the error between the actual mesh size and the nominal value is within ±2%. Its advantages include permanent marking, resistance to detachment or blurring during forming oil lubrication and plastic deformation, ensuring data reliability. The high density ensures sufficient data points for accurate strain calculation even in areas with large deformation gradients, avoiding analysis distortion due to data sparsity.

[0044] After the first actual forming process yields the first component, a high-precision photogrammetric device is used to scan the component's surface. The device captures high-resolution images of the dot matrix mesh and uses algorithms to accurately identify and calculate the primary and secondary strains of each etched point under the current deformation state. This step digitizes the physical deformation, providing fundamental data for subsequent calculations.

[0045] The system automatically identifies each deformed point and calculates the principal and secondary strains of each grid by measuring the changes in the major and minor axes of the deformed grid points relative to the original circle.

[0046] By combining calculations from multiple directions, the principal and secondary strains at each point can be determined. The strain data from all points are collected to form the "actual strain data for each region," which generates the FLD (Fault Line Data), thereby determining the risk type of each zone.

[0047] In the above technical solutions, the finite element simulation software may optionally include one or a combination of the following: LS-DYNA, AutoForm, AI-FORM, and ABAQUS.

[0048] In the above technical solution, the mold parameters may optionally include punch structure parameters, die structure parameters, and pressure ring structure parameters.

[0049] In the above technical solution, the production process parameters may optionally include blank holder force, forming force, stamping speed, and blank holder lifting height.

[0050] The applicant will now use automobile door panel stamping as an example to describe in detail the forming method of this application.

[0051] In this embodiment, CR3 sheet metal was selected, a type of hot-dip galvanized cold-rolled automotive sheet commonly used in automobile manufacturing. The sheet thickness was 0.80 mm. CR3 sheet metal has a yield strength of 164 MPa, a tensile strength of 290 MPa, and an elongation of 43%. For the forming process, six hydraulic cylinders were configured, each with a blank holder force of 410 kN. This configuration ensures that the sheet metal is subjected to uniform stress under high pressure, avoiding inconsistent deformation due to uneven blank holder force. The amount of oil film on the upper and lower surfaces of the sheet metal was precisely controlled between 0.74 ± 0.05 g / m² (i.e., the aforementioned basic oil coating amount). Q 0), the initial shape of the board and the amount of base oil applied, such as Figure 2 As shown.

[0052] First, dense dot-like markings are created on the surface of the sheet metal using electrochemical etching technology, forming a high-precision measurement grid. Next, the marked sheet metal is placed into a stamping die for forming. During this process, the sheet metal undergoes tensile deformation, and the dot grid on the surface also shifts and deforms accordingly. After forming, a measurement area (one of areas A to H, e.g., ...) is selected. Figure 3 As shown in the figure, the principal and secondary strains of each grid are calculated by measuring the changes in the major and minor axes of the deformed grid points relative to the original circle, thus calculating the actual deformation data of each region. The FLD is generated by combining the degree of deformation and stress state of each region (e.g., which parts are excessively stretched, which parts are under compression and wrinkling). Figure 4 As shown, it visually displays which areas are at risk of cracking, necking, or wrinkling.

[0053] FLD analysis shows that regions F and G are significantly below the safety margin. The minimum forming limit value for region F is 1.10%, while the minimum forming limit value for region G is 2.55%. The target values ​​for both regions should be greater than 10%. Figure 4 As shown, the minimum forming limit values ​​in regions F and G are significantly lower than the target values, indicating that the risk of cracking and necking defects during forming in these regions is extremely high, and their ability to resist fluctuations in process parameters, mold conditions, and material properties is poor, seriously affecting the quality and yield of stamped parts.

[0054] The relationship between oil application amount and friction coefficient was further quantified by mapping the actual oil application amount in the production process to the friction coefficient in finite element simulation. A detailed study was conducted based on flat plate sliding friction tests, and friction coefficient datasets were collected under different oil application amounts using multi-gradient oil application settings. Regression analysis was used to fit a curve showing the relationship between oil application amount and friction coefficient, such as... Figure 5As shown in the figure, this relationship curve provides a scientific basis for the variation law of oil application amount and friction coefficient, enabling precise control of oil application amount in actual production to ensure that the lubrication effect in the molding process reaches the optimal balance.

[0055] in, Figure 6 This is a schematic diagram of a stamping die for a door panel. S1 is the punch, S2 is the die, S3 is the pressure ring, and S4 is the sheet metal.

[0056] Figure 7 and Figure 8 The finite element simulation results for regions F and G are shown, and a detailed FLD mesh analysis is provided. Figure 7 a and Figure 8 In section 'a', green represents the safe zone, while yellow represents the high-risk areas for cracking and necking that require close monitoring. Finite element analysis results show that regions F and G both exhibit significant risks of cracking and necking under the current oiling conditions. Figure 7 b and Figure 8 The thickness reduction contour plot of b also shows results that are highly consistent with the finite element simulation.

[0057] Figure 9 and Figure 10 This further confirms that regions F and G have insufficient safety margins during the forming process. Figure 9 The black line represents the forming limit curve; exceeding this critical line indicates that cracking or necking will occur. The purple line represents the safety margin line, according to... Figure 9 As can be clearly seen, there are some red areas on the safety margin line (purple line), indicating a risk of cracking or necking. Figure 10 Similarly, some red areas can be seen on the safety margin line (purple line), indicating that both regions F and G are at risk of cracking or necking. These analytical results provide important basis for subsequent optimization of the oiling scheme and offer new ideas for regional control of lubrication conditions, thereby reducing the risk of forming defects.

[0058] By changing only the friction coefficient while keeping other process parameters constant, high-fidelity benchmarking of the forming process was achieved through iterative simulation. To gain a deeper understanding and optimize the oiling process, the geometric model of the sheet metal was divided into three characteristic regions based on the defect locations observed in actual production. Specifically, these were: two defect-sensitive regions (the sheet metal regions corresponding to flattened regions F and G during forming), and another reference region (e.g., the sheet metal region corresponding to flattened region A). Regions F and G were considered high-risk areas prone to defects during forming; therefore, the friction coefficient in these two regions was reduced in the simulation to simulate the oiling effect of reduced friction, while the standard reference friction coefficient was maintained in other regions. μ 0 (i.e., base coat amount) Q(The friction coefficient corresponding to 0). During iterative simulation, the friction coefficients of regions F and G are gradually adjusted. Regions F and G can be adjusted separately or simultaneously to simulate the effect of different oil application amounts on the forming effect, until the defects in regions F and G completely disappear in the final simulation results. The simulation results are as follows: Figure 11 As shown.

[0059] Figure 11 The red line represents the forming limit curve; exceeding this critical line indicates cracking or necking. The yellow and green lines represent safety margin lines, and the blue line represents the wrinkling critical line; exceeding the blue line indicates wrinkling. The friction coefficient used in the simulation, also known as the optimized friction coefficient, represents the minimum forming limit values ​​of regions F and G, which can be increased under the effect of this optimized friction coefficient, thereby avoiding the risk of cracking and necking in subsequent production processes. Simulation results show that the final forming state of the part meets the main quality requirements. Notably, localized wrinkling was observed in the process supplement section of the part (i.e., the outer flange area). Evaluation revealed that this wrinkled area is completely outside the second-order trimming line. This means that in subsequent trimming processes, the wrinkled material will be completely removed without affecting the geometric quality, dimensional accuracy, or structural performance of the final product.

[0060] The optimized friction coefficient determined by partitioned simulation μ 裂 The target amount of oil applied is calculated using the oil application amount-friction coefficient relationship model. Q 裂 . Figure 12 In the middle, +0.51g / m 2 Indicates the amount of base oil applied. Q Based on 0, region F should increase by 0.51 g / m 2 +0.40g / m 2 Indicates the amount of base oil applied. Q Based on 0, region G should increase by 0.40 g / m 2 In other words, during the oiling process of the board, areas A, B, C, D, E, and H are non-risk areas, and the amount of oil applied is... Q 0. Areas F and G are at risk of cracking and necking; the amount of oil applied is... Q 裂 .

[0061] In actual production, this application can precisely control the amount of oil applied to each area according to the different needs of each area, thereby achieving zoned and directional oiling and minimizing the occurrence of defects.

[0062] Actual forming production was carried out on the sheet metal after zoned oiling. Mesh strain analysis was performed on the formed parts. The black line represents the forming limit curve, and the orange line below the black line represents the safety margin line. All areas are below the safety margin line. The analysis results are as follows: Figure 13 and Figure 15 As shown, zoned oiling can overcome the risks of cracking and necking in regions F and G. The forming limit of region F has significantly increased from 1.10% to 11.10%, and the safety margin has increased from less than 1.10% to more than 10%. Figure 14 As shown, the forming limit of region G increased from 2.55% to 11.70%, successfully achieving the goal of a safety margin greater than 10%, as... Figure 16 As shown, this improvement not only demonstrates the effectiveness of the zoned oiling process but also indicates that the lubrication and friction conditions in that area have been precisely optimized. Through the zoned oiling technology of this invention, the amount of oil applied to each area can be precisely controlled according to the characteristics of different areas, thereby ensuring that the friction conditions in each area are at their optimal state, achieving high-precision control during the forming process.

[0063] Another embodiment of the present invention provides a sheet metal forming method based on zoned oil coating control, comprising the following steps: Step 1: Based on the actual forming production process, for the target board, multiple areas are divided and electrochemical etching of dot grid is used. The board is uniformly coated with oil for actual production, and the results are analyzed by FLD to determine the risk type. Step 2: Conduct friction tests on the sheet metal samples with different amounts of oil to obtain the coefficient of friction corresponding to different amounts of oil. Step 3: Use software with fitting capabilities to numerically fit the friction coefficient and the corresponding amount of oil applied in Step 2, and establish a functional relationship expression between the amount of oil applied and the friction coefficient. Step 4: Extract the die parameters such as sheet metal profile, punch, die, and blank holder, as well as process parameters such as blank holder force, stamping speed, blank holder ejection height, and stamping stroke. Based on the actual forming production process parameters, set the material properties (including elastic modulus, Poisson's ratio, hardening equation, strengthening model, yield model, forming limit), interaction conditions, boundary conditions, and mesh properties in the simulation software, and submit the simulation job to obtain the simulation results of the component. Step 5: Ensure the accuracy of the finite element simulation results by comparing the simulation results with the actual FLD results and sheet thinning rate of the formed parts; Step 6: Based on the simulation results in Step 5, divide the areas in the sheet metal where cracking and necking occur, requiring a reduction in the coefficient of friction. The number of areas is... i and for all regions from X 1- X iMark it here i Greater than or equal to 1; Step 7: Based on the simulation results in Step 5, divide the areas in the board material where wrinkling or other issues require increased friction coefficients into several regions. The number of regions is... j and for all regions from Y 1- Y j Mark it here j Greater than or equal to 1; Step 8: If the defects mentioned in Step 6 occur, reduce the area in the finite element simulation software. X i The friction coefficient is calculated, and the simulation job is submitted to continue obtaining simulation results until the defect disappears. The current friction coefficient is then recorded as follows: μ 裂 Here, the step size of the friction coefficient change is greater than 0 and less than 0.01, Δ μ 裂 ∈ (0, 0.01], Δ μ 皱 ∈ (0, 0.01]; Step 9: If the defects mentioned in Step 7 occur, increase the area in the finite element simulation software. Y j The friction coefficient is calculated, and the simulation job is submitted to continue obtaining simulation results until the defect disappears. The current friction coefficient is then recorded as follows: μ 皱 Here, the step size of the friction coefficient change is greater than 0 and less than 0.01, Δ μ 裂 ∈ (0, 0.01], Δ μ 皱 ∈ (0, 0.01]; Step 10: Calculate the regions using the functional relationship expressions established in Step 3. X i and region Y j The amount of oil applied corresponding to the optimized friction coefficient; Step 11: Divide the sheet metal needed for producing the components into sections according to Step 6 or Step 7. X i Each region and Y j The area is divided into zones, and the oiling amount obtained in step 10 is used to apply oil to the zones. The areas not included in the division will retain the original oiling amount. Step 12: Put the re-oiled sheet material into actual forming production to obtain high-quality formed parts.

[0064] In the above embodiments, optionally, the step size Δ μ 裂 With Δ μ皱 The range of values ​​is Δ μ 裂 ∈ (0, 0.01], Δ μ 皱 The step size and range can be adjusted according to the specific component shape and the number of defects. The range (0, 0.01) is a recommended value. In the above embodiments, optionally, the forming defect type is determined by FLD. If the primary and secondary strain values ​​of the measurement point fall above the safety margin line, it is a risk area that is prone to cracking or necking. If they fall below the uniaxial tension line, it is a risk area that is prone to wrinkling. In the above embodiments, optionally, the region is reduced in the finite element simulation software. X i The coefficient of friction. In actual production, the amount of oil applied to the upper and lower surfaces of the sheet is increased accordingly to achieve a lubrication effect that matches the reduced coefficient of friction in the simulation; In the above embodiments, optionally, the region is increased in the finite element simulation software. Y j The coefficient of friction. In the actual production process, the original oil on the upper and lower surfaces of the board is first cleaned using a cleaning machine, and then oiling is carried out in the oiling machine according to the newly formulated process; In the above embodiments, optionally, the simulation process uses finite element simulation software, including but not limited to LS-DYNA, AutoForm, AI-FORM, and ABAQUS. The software used to fit the experimental data includes, but is not limited to, MATLAB, Origin, Excel, and Python. In the above embodiments, the friction test may optionally include, but is not limited to, flat plate sliding friction test, drawing friction test, bending friction test, reverse identification test, etc. Furthermore, the more test groups of oil application amount used, the higher the accuracy of the established functional relationship between oil application amount and friction coefficient.

[0065] In embodiments of the present invention, the terms "first," "second," and "third" are used only for descriptive purposes and should not be construed as indicating or implying relative importance; the term "multiple" refers to two or more unless otherwise expressly defined. The terms "install," "connect," "link," and "fix" should be interpreted broadly. For example, "connect" can be a fixed connection, a detachable connection, or an integral connection; "link" can be a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in embodiments of the present invention according to the specific circumstances.

[0066] Furthermore, although the operations are described in a specific order, this should be understood as requiring that such operations be performed in a specific order or sequential order, or requiring that all illustrated operations be performed to achieve the desired result. In certain environments, multitasking and parallel processing may be advantageous. Similarly, although several specific implementation details are included in the above discussion, these should not be construed as limiting the scope of the invention. Certain features described in the context of individual embodiments may also be implemented in combination in a single implementation. Conversely, various features described in the context of a single implementation may also be implemented individually or in any suitable sub-combination in multiple implementations.

[0067] Although the subject matter has been described using language describing specific structural features and / or methodological logic, it should be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or actions described above. Rather, the specific features and actions described above are merely illustrative examples of implementing the claims.

[0068] The above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Those skilled in the art will recognize that various modifications and variations are possible with respect to the embodiments of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the embodiments of the present invention should be included within the protection scope of the embodiments of the present invention.

Claims

1. A sheet metal forming method based on zoned oiling control, characterized in that, Includes the following steps: The surface of the first target material is divided into multiple regions; Use a set of basic oiling materials Q Using the production process parameters of 0, the first target sheet is subjected to the first actual forming to obtain the first component; Based on the FLD analysis method, the risk type of each region is determined. The risk types include wrinkling risk region, cracking and necking risk region and non-risk region. Establish a functional relationship between oil application amount and friction coefficient. μ = f ( Q ); Obtain the mold parameters of the first target component, and construct a finite element simulation model based on the mold parameters and the production process parameters; Iterative simulation experiments were conducted using the finite element simulation model to determine the optimized friction coefficients corresponding to the wrinkling risk areas. μ 皱 And the optimized friction coefficient corresponding to the cracking and necking risk area. μ 裂 ; according to μ 皱 Based on the aforementioned functional relationship, determine the target amount of oil applied to the wrinkling risk area. Q 皱 ; according to μ 裂 Based on the aforementioned functional relationship, determine the target oil application amount corresponding to the cracking and necking risk area. Q 裂 ; The surface of the second target board is treated with oil in sections, with the amount of oil applied to the areas at risk of wrinkling being [amount missing]. Q 皱 The amount of oil applied to areas at risk of cracking and necking is Q 裂 The amount of oil applied to non-risk areas is Q 0; The second target sheet, after being coated with oil, is put into actual forming production and formed under the conditions of the stated production process parameters to obtain a qualified target component.

2. The sheet metal forming method based on zoned oiling control according to claim 1, characterized in that, The iterative simulation experiments conducted using the finite element simulation model were used to determine the optimized friction coefficients corresponding to the wrinkling risk areas. μ 皱 And the optimized friction coefficient corresponding to the cracking and necking risk area. μ 裂 The steps specifically include: Based on the aforementioned base oil application amount Q The initial friction coefficient corresponding to 0 is the starting point; For the cracked and necked areas, with a step size Δ μ 裂 Gradually decrease the friction coefficient until the cracking or necking defects in the simulation disappear, and record the friction coefficient at this point. μ 裂 ; For wrinkled areas, with a step size Δ μ 皱 Gradually increase the friction coefficient until the wrinkling defects in the simulation disappear, and record the friction coefficient at this point. μ 皱 ; Among them, D μ 裂 ∈(0, 0.01], Δ μ 皱 ∈(0, 0.01].

3. The sheet metal forming method based on zoned oiling control according to claim 1, characterized in that, The step of establishing the functional relationship between oil application amount and friction coefficient specifically includes: Friction tests were conducted on multiple groups of oil coating samples to determine the corresponding coefficients of friction. The amount of oil applied was fitted using fitting software. Q With coefficient of friction μ The mapping relationship is established, and a functional relationship between oil application amount and friction coefficient is created. μ = f ( Q ).

4. The sheet metal forming method based on zoned oiling control according to claim 3, characterized in that, The fitting software includes one or a combination of the following: MATLAB, Origin, Excel, and Python.

5. The sheet metal forming method based on zoned oiling control according to claim 3, characterized in that, The friction test includes one or a combination of the following: flat plate sliding friction test, drawbead friction test, tensile bending friction test, and reverse identification test.

6. The sheet metal forming method based on zoned oiling control according to claim 1, characterized in that, The surface of the first target plate has a dotted grid. The step of determining the risk type of each region based on the FLD analysis method specifically includes: Photogrammetry is performed on the surface of the first component after forming to obtain the changes in the major and minor axes of each point in the lattice grid relative to the original circle after deformation, so as to calculate the principal strain and secondary strain of each grid. Based on the primary and secondary strains at each point after deformation, determine the actual strain data for each region; Based on the actual strain data, an FLD is generated; Based on the FLD, determine the defect type of each partition.

7. The sheet metal forming method based on zoned oiling control according to claim 1, characterized in that, The finite element simulation software includes one or a combination of the following: LS-DYNA, AutoForm, AI-FORM, and ABAQUS.

8. The sheet metal forming method based on zoned oiling control according to claim 1, characterized in that, The mold parameters include punch structure parameters, die structure parameters, and blank holder structure parameters, and the production process parameters include blank holder force, forming force, stamping speed, and blank holder lifting height.

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