Forming method for composite structure stamping parts based on strain path control

Abstract

The present application relates to the technical field of metal plate stamping forming, and discloses a composite structure stamping part forming method based on strain path regulation, which comprises the following steps: defect digital diagnosis and strain state analysis, strain path reverse planning, partition collaborative design and implementation, process solidification and verification. The composite structure stamping part forming method based on strain path regulation realizes synchronous elimination of cracking and wrinkling defects of box type and saddle type composite structure stamping parts through defect digital diagnosis and strain state analysis, strain path reverse planning, partition collaborative design and implementation.

Description

Technical Field

[0001] This invention relates to the field of metal sheet stamping technology, and more specifically to a method for forming composite structure stamped parts based on strain path control. Background Technology

[0002] With the automotive industry's ever-increasing demands for lightweight and high-strength components, the application of complex high-strength steel structural parts (such as automotive beams and brackets) is becoming increasingly widespread. To achieve specific functions and performance, these parts are often designed with composite geometric features combining "box-shaped" (deep cavity) and "saddle-shaped" (reverse arch) characteristics. This structure leads to complex and interfering material flow paths during deep drawing: the "box-shaped" structure requires sufficient material flow to resist cracking, while the "saddle-shaped" structure is prone to wrinkling due to material accumulation and instability under pressure. These two defects are physically contradictory, and traditional single process adjustments (such as simply changing the blank holder force or drawbeads) often alleviate one defect while exacerbating the other, creating a "seesaw" effect.

[0003] In existing technologies, computer simulation-based optimization of stamping processes has been applied, with forming limit diagrams (FLDs) serving as a core analytical tool for defect identification. However, current methods often focus on local remediation of identified defects or rely on engineers' experience for parameter trial and error, lacking a systematic approach that extends from defect mechanism analysis to strain path reverse design. Particularly when dealing with composite structures, it is impossible to quantitatively provide specific technical pathways for how to coordinate material inflow and surface shaping to simultaneously shift the strain states of different regions into the FLD safety zone.

[0004] Meanwhile, the existing technology mainly has the following problems: 1. The challenge of decoupling the causes of composite defects and quantifying the key areas: Existing analysis based on forming limit diagrams usually treats cracking and wrinkling as independent phenomena and makes point-like distinctions. For the "box-saddle" composite structure, these two defects physically originate from the imbalance and incoordination of global material flow. Their causes are coupled and lack a quantitative definition method. That is, how to break through the existing static discrimination mode of FLD and quantify the critical interaction between the excessive thinning path that leads to "cracking" and the compressive instability path that leads to "wrinkling" by analyzing the strain path evolution of specific areas ("box" sidewall and "saddle" top) during the forming process? This would fundamentally decouple the macroscopic appearance of composite defects into quantifiable material flow contradictions. 2. Addressing the Challenges of Coordinated Strain Path Design and Control in Composite Structures: After decoupling the causes of defects, traditional methods attempt to move strain points on the FLD by adjusting single global process parameters (such as blank holder force). However, this approach fails to achieve differentiated regional control and struggles to design coordinated, asymmetric strain paths for the diametrically opposed flow requirements of the "box-shaped" region (requiring flow promotion and crack prevention) and the "saddle-shaped" region (requiring flow restriction and wrinkle prevention). This necessitates solving how to inversely map the target safety zone on the FLD into precise modification instructions for local surface geometry (such as drawbead cross-section and punch fillet) and friction conditions (such as local lubrication). This would enable precise diversion of material inflow and zoned control of stress state, rather than blind global adjustments. 3. The challenge of constructing a systematic process for multi-objective collaborative optimization: From analysis to design, an executable and iterative systematic approach is needed. Existing technologies rely on trial and error and lack repeatable optimization logic. That is, how to construct a closed-loop systematic process from "defect identification → mechanism decoupling → path reverse design → process parameter mapping → effect verification"? This process needs to clarify the data transmission relationship and judgment criteria of each step to ensure that a coordinated process modification plan for multiple regional objectives can be automatically or semi-automatically generated based on a simulation result, thereby transforming the "art" of solving complex defects into a "technical engineering" approach that can be followed.

[0005] Therefore, there is an urgent need for a process design method that can systematically and collaboratively solve such composite defects and achieve precise forming of composite structure stamping parts based on strain path control. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of the above-mentioned technologies by providing a composite structure stamping forming method based on strain path control. Through digital defect diagnosis and strain state analysis, strain path reverse planning, and zoned collaborative design and implementation, the method can simultaneously eliminate cracking and wrinkling defects in box-shaped and saddle-shaped composite structure stampings.

[0007] To achieve the above objectives, the composite structure stamping method based on strain path control involved in this invention includes the following steps: S1) Defect Digital Diagnosis and Strain State Analysis: Using CAE software, a finite element model of the deep drawing process of the target part is established and calculated. The forming limit diagram, thickness reduction rate cloud map and material flow vector map of the entire part are extracted. Cracking risk points and wrinkling risk areas are identified and marked on the forming limit diagram. For each cracking risk point and wrinkling risk area, the values ​​and signs of its principal compressive strain and secondary strain are analyzed. Combined with the material flow direction, the defect-dominant mechanism is determined. S2) Strain path reverse planning: For crack risk points, the planned strain path is to move the position of the crack risk point on the forming limit diagram in a direction that significantly reduces the principal compressive strain while the secondary strain remains unchanged or changes slightly, and enter the safe zone, thereby increasing the amount of material flowing into the crack risk point. For the wrinkling risk area, the planned strain path is to move the position of the wrinkling risk area on the forming limit diagram in the direction of increasing secondary strain, while controlling the principal compressive strain to change from negative to positive or decrease the principal compressive strain, so as to enter the safe zone. This is achieved by changing the local shape and introducing tensile components. S3) Zonal Collaborative Design and Implementation: Based on the strain path planned for the cracking risk point, trace back to the sheet boundary and delineate the boundary segment on the sheet boundary that is related to the material flow source of the cracking risk point as the material inflow priority control zone. Increase the material inflow by increasing the sheet size in this zone and / or reducing the drawbead resistance. Based on the strain path planned for the wrinkling risk area, a local shape optimization area is defined on the part surface, and the strain state is adjusted by reducing or increasing the height within the local shape optimization area. The material inflow priority control zone and the local shape optimization zone are simultaneously iteratively simulated in CAE software until the forming limit diagram shows that all risk points have fallen into the safe zone and no new defects are generated. S4) Process solidification and verification: Apply the optimized process scheme to mold design and manufacturing, and conduct actual stamping tests for verification.

[0008] Preferably, in step S1), the defect-dominant mechanism includes uneven drawing leading to localized excessive thinning and compressive stress leading to unstable material accumulation.

[0009] Preferably, in step S1), the cracking risk point is located in the second quadrant, near the fracture boundary, and the wrinkling risk area is located below the first quadrant or in the third quadrant.

[0010] Preferably, for the local shape optimization area in step S3), the area where material accumulates due to the compression of the sidewall of the box structure is defined as the height reduction area. By reducing the height of the punch or concave mold surface at this location, the compression stroke and material demand are directly reduced, thereby reducing the principal compressive strain.

[0011] Preferably, for the local shape optimization area in step S3), the area where the material needs to be stretched to eliminate wrinkles due to the saddle structure is defined as the height enhancement area. By increasing the height of the surface at this location, the material is geometrically forced to undergo a greater degree of tensile deformation, effectively increasing the secondary strain and promoting the transformation of the strain state to bitension.

[0012] Preferably, in step S3), increasing the sheet size means asymmetrically increasing the local size of the sheet outline.

[0013] Preferably, it is applicable to stamping of high-strength steel plates, aluminum alloy plates and other metal plates.

[0014] Preferably, it is applicable to the forming of automotive beams, brackets, door frames, A-pillars, and battery pack housing structures with composite geometric features of box and saddle shapes.

[0015] A composite structure stamping forming system based on strain path collaborative control includes a CAE simulation module, a path planning module, a process design module, and an iterative verification module; The CAE simulation module is used to perform numerical simulation of sheet metal forming and output forming limit diagrams and strain fields. The path planning module is used to identify cracking risk points and wrinkling risk areas based on the forming limit diagram, and to plan strain paths for the cracking risk points and wrinkling risk areas. The process design module is used to generate material inflow control schemes and local shape optimization schemes based on the planned strain path. The iterative verification module is configured to perform iterative simulation verification of the material inflow control scheme and the local shape optimization scheme in the CAE environment.

[0016] An automotive structural component has a composite geometric feature of box and saddle shapes, and is formed by stamping using the aforementioned composite structure stamping forming method based on strain path control.

[0017] Compared with the prior art, the present invention has the following advantages: 1. From “passive remediation” to “proactive design”: This invention transforms process design from trial and error based on experience to proactive design based on reverse planning of strain paths, thus realizing scientific guidance for practice; 2. Solved the industry problem of collaborative control of complex defects: Through the combination strategy of "adding material" (material inflow regulation) and "reshaping" (local shape optimization), the contradiction of material flow caused by the "box" and "saddle" structures was accurately resolved, and cracking and wrinkling were simultaneously eliminated. 3. Improved development efficiency and success rate: This method significantly shortens the mold debugging cycle (reducing the number of mold trials by 30%-50%), lowers production costs, and makes the process plan highly reliable and predictable; 4. It has broad industry application value: The concept and framework of this method are applicable to all stamped parts with complex material flow conflicts, which is of great significance to promoting the technological progress of the entire stamping industry. Attached Figure Description

[0018] Figure 1 This is a flowchart of the composite structure stamping forming method based on strain path control according to the present invention. Detailed Implementation

[0019] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0020] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0021] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0022] like Figure 1 As shown, a method for forming composite structure stamping parts based on strain path control includes the following steps: S1) Defect Digital Diagnosis and Strain State Analysis: A finite element model of the deep drawing process of the target part is established using CAE software and calculations are performed. The forming limit diagram, thickness reduction rate cloud map, and material flow vector map of the entire part are extracted. Cracking risk points and wrinkling risk areas are identified and marked on the forming limit diagram. Generally, cracking risk points are located in the second quadrant, near the fracture boundary, while wrinkling risk areas are located below the first quadrant or in the third quadrant. For each cracking risk point and wrinkling risk area, the values ​​and signs of its principal compressive strain and secondary strain are analyzed. Combined with the material flow direction, the defect-dominant mechanism is determined. The defect-dominant mechanism includes uneven deep drawing leading to local excessive thinning and compressive stress leading to material instability and accumulation. S2) Strain path reverse planning: For crack risk points, the planned strain path is to move the position of the crack risk point on the forming limit diagram in a direction that significantly reduces the principal compressive strain while the secondary strain remains unchanged or changes slightly, and enter the safe zone, thereby increasing the amount of material flowing into the crack risk point. For the wrinkling risk area, the planned strain path is to move the position of the wrinkling risk area on the forming limit diagram in the direction of increasing secondary strain, while controlling the principal compressive strain to change from negative to positive or decrease the principal compressive strain, so as to enter the safe zone. This is achieved by changing the local shape and introducing tensile components. S3) Zonal Collaborative Design and Implementation: Based on the strain path planned for the cracking risk point, trace back to the sheet boundary and delineate the boundary segment on the sheet boundary that is related to the material flow source of the cracking risk point as the material inflow priority control zone. Increase the material inflow by increasing the sheet size in this zone and / or reducing the drawbead resistance. Increasing the sheet size is to asymmetrically increase the local size of the sheet profile. Based on the strain path planned for the wrinkling risk area, local shape optimization zones are delineated on the part surface. The strain state is adjusted by reducing or increasing the height within these local shape optimization zones. Specifically, for areas where material accumulates due to sidewall compression of the box-shaped structure, a height reduction zone is defined. By reducing the height of the punch or die surface at this location, the compression stroke and material demand are directly reduced, thereby reducing the principal compressive strain. For areas where the material needs to be stretched to eliminate wrinkles due to the saddle structure, a height increase zone is defined. By increasing the surface height at this location, the material is geometrically forced to undergo a greater degree of tensile deformation, effectively increasing the secondary strain and promoting the transformation of the strain state to bitensile strain. The material inflow priority control zone and the local shape optimization zone are simultaneously iterated and simulated in CAE software until the forming limit diagram shows that all risk points have fallen into the safe zone and no new defects are generated. S4) Process solidification and verification: Apply the optimized process scheme to mold design and manufacturing, and conduct actual stamping tests for verification.

[0023] This invention relates to a composite structure stamping forming method based on strain path control, which is applicable to the stamping forming of high-strength steel plates, aluminum alloy plates and other metal plates, and is also applicable to the forming of automotive beams, brackets, door frames, A-pillars and battery pack shell structures with box-shaped and saddle-shaped composite geometric features.

[0024] In addition, this embodiment also provides a composite structure stamping forming system based on strain path collaborative control, including a CAE simulation module, a path planning module, a process design module and an iterative verification module; The CAE simulation module is used to perform numerical simulations of sheet metal forming and output forming limit diagrams and strain fields. The path planning module is used to identify cracking risk points and wrinkling risk areas based on the forming limit diagram, and to plan strain paths for cracking risk points and wrinkling risk areas. The process design module is used to generate material inflow control schemes and local shape optimization schemes based on the planned strain path; The iterative verification module is configured to perform iterative simulation verification of material inflow control schemes and local shape optimization schemes in the CAE environment.

[0025] In this embodiment, an automotive structural component is also involved, which has a composite geometric feature of box and saddle shape, and is stamped using a composite structure stamping forming method based on strain path control.

[0026] Taking a high-strength steel automotive beam (0.8mm thick) of a certain model HC220YD-Z as an example, the problem is that the initial CAE simulation showed a high risk of cracking at the corner of the box-shaped part (strain point located in the danger zone) and a significant risk of wrinkling in the saddle area (strain state). The present invention adopts the composite structure stamping part forming method based on strain path control. Steps S1) to S2) are executed to plan the strain path of the crack risk point and the strain path of the wrinkling risk area. Step S3) is executed to delineate the material inflow priority control area on the sheet metal, increase the sheet metal to 1450×620mm and optimize the draw beads, and delineate the local shape optimization area on the part surface, in which the height reduction area is reduced by 5mm and the height increase area is increased by 8mm. After CAE iteration verification, all strain points are moved into the safe area. Finally, step S4) is executed to carry out trial production. The surface quality of the obtained part is intact, without cracking or wrinkling, which verifies the effectiveness of the method.

[0027] This invention relates to a composite structure stamping forming method based on strain path control. Through digital defect diagnosis and strain state analysis, strain path reverse planning, and zoned collaborative design and implementation, it achieves the simultaneous elimination of cracking and wrinkling defects in box-shaped and saddle-shaped composite structure stampings. It transforms process design from experience-based trial and error to proactive design based on strain path reverse planning. By combining material addition and shaping, it precisely resolves the material flow contradictions caused by box-shaped and saddle-shaped structures. It significantly shortens the mold debugging cycle, reduces production costs, and improves development efficiency and success rate. It is applicable to all stampings with complex material flow conflicts and has broad industry application value.

[0028] It should be noted that the above description of the technical solutions is exemplary, and this specification may be embodied in different forms and should not be construed as limiting it to the technical solutions set forth herein. Rather, providing these descriptions will ensure that the disclosure of this invention is thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. Furthermore, the technical solutions of this invention are defined only by the scope of the claims.

[0029] Finally, it should be noted that the above description is a further detailed explanation of the invention in conjunction with specific embodiments. It should not be considered that the specific implementation of the invention is limited to these descriptions. For those skilled in the art, any simple substitutions made without departing from the concept of the invention should be considered within the scope of protection of this invention. The above embodiments are merely representative examples of the invention. Obviously, the invention is not limited to the above embodiments and many variations are possible. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the invention should be considered within the scope of protection of this invention.

[0030] For those skilled in the art, several simple deductions or substitutions can be made without departing from the concept of the present invention, and the above structures should all be considered to fall within the protection scope of the present invention.

Claims

1. A method for forming composite structure stamping parts based on strain path control, characterized in that: Includes the following steps: S1) Defect Digital Diagnosis and Strain State Analysis: Using CAE software, a finite element model of the deep drawing process of the target part is established and calculated. The forming limit diagram, thickness reduction rate cloud map and material flow vector map of the entire part are extracted. Cracking risk points and wrinkling risk areas are identified and marked on the forming limit diagram. For each cracking risk point and wrinkling risk area, the values ​​and signs of its principal compressive strain and secondary strain are analyzed. Combined with the material flow direction, the defect-dominant mechanism is determined. S2) Strain path reverse planning: For crack risk points, the planned strain path is to move the position of the crack risk point on the forming limit diagram in a direction that significantly reduces the principal compressive strain while the secondary strain remains unchanged or changes slightly, and enter the safe zone, thereby increasing the amount of material flowing into the crack risk point. For the wrinkling risk area, the planned strain path is to move the position of the wrinkling risk area on the forming limit diagram in the direction of increasing secondary strain, while controlling the principal compressive strain to change from negative to positive or decrease the principal compressive strain, so as to enter the safe zone. This is achieved by changing the local shape and introducing tensile components. S3) Zonal Collaborative Design and Implementation: Based on the strain path planned for the cracking risk point, trace back to the sheet boundary and delineate the boundary segment on the sheet boundary that is related to the material flow source of the cracking risk point as the material inflow priority control zone. Increase the material inflow by increasing the sheet size in this zone and / or reducing the drawbead resistance. Based on the strain path planned for the wrinkling risk area, a local shape optimization area is defined on the part surface, and the strain state is adjusted by reducing or increasing the height within the local shape optimization area. The material inflow priority control zone and the local shape optimization zone are simultaneously iteratively simulated in CAE software until the forming limit diagram shows that all risk points have fallen into the safe zone and no new defects are generated. S4) Process solidification and verification: Apply the optimized process scheme to mold design and manufacturing, and conduct actual stamping tests for verification.

2. The composite structure stamping forming method based on strain path control as described in claim 1, characterized in that: In step S1), the defect-dominant mechanism includes uneven drawing leading to localized excessive thinning and compressive stress leading to unstable material accumulation.

3. The composite structure stamping forming method based on strain path control as described in claim 1, characterized in that: In step S1), the cracking risk point is located in the second quadrant, near the fracture boundary, and the wrinkling risk area is located below the first quadrant or in the third quadrant.

4. The composite structure stamping forming method based on strain path control as described in claim 1, characterized in that: For the local shape optimization area in step S3), the area where material accumulates due to the compression of the sidewall of the box structure is defined as the height reduction area. By reducing the height of the punch or concave mold surface at this location, the compression stroke and material demand are directly reduced, thereby reducing the principal compressive strain.

5. The composite structure stamping method based on strain path control as described in claim 1, characterized in that: For the local shape optimization area in step S3), the area where the material needs to be stretched to eliminate wrinkles due to the saddle structure is defined as the height enhancement area. By increasing the height of the surface at this location, the material is geometrically forced to undergo a greater degree of tensile deformation, which effectively increases the secondary strain and promotes the transformation of the strain state to bitension.

6. The composite structure stamping forming method based on strain path control as described in claim 1, characterized in that: In step S3), increasing the size of the sheet metal means asymmetrically increasing the local size of the sheet metal outline.

7. The composite structure stamping forming method based on strain path control as described in claim 1, characterized in that: It is suitable for stamping and forming of high-strength steel plates, aluminum alloy plates and other metal plates.

8. The composite structure stamping method based on strain path control as described in claim 1, characterized in that: It is suitable for forming automotive beams, brackets, door frames, A-pillars, and battery pack housing structures with composite geometric features of box and saddle shapes.

9. A composite structure stamping forming system based on strain path coordinated control, characterized in that: It includes a CAE simulation module, a path planning module, a process design module, and an iterative verification module; The CAE simulation module is used to perform numerical simulation of sheet metal forming and output forming limit diagrams and strain fields. The path planning module is used to identify cracking risk points and wrinkling risk areas based on the forming limit diagram, and to plan strain paths for the cracking risk points and wrinkling risk areas. The process design module is used to generate material inflow control schemes and local shape optimization schemes based on the planned strain path. The iterative verification module is configured to perform iterative simulation verification of the material inflow control scheme and the local shape optimization scheme in the CAE environment.

10. An automotive structural component, characterized in that: It has composite geometric features of box and saddle shapes, and is stamped using the composite structure stamping method based on strain path control as described in any one of claims 1 to 8.

Images