A method and device for forming an ultra-thin-wall sheet metal bulge of an aero-engine

Abstract

The present application relates to the technical field of aircraft engine component manufacturing, and discloses a forming method and device for an ultrathin-wall sheet metal bulge of an aircraft engine, wherein the actual minimum extrusion force received by an arc-shaped wall structure between a concave die and a convex die is obtained by analyzing the stamping force value when the convex part and the concave part are formed on the arc-shaped wall structure, and the value of the minimum extrusion force can satisfy the condition that the arc-shaped wall structure is always in a compacted state during stamping and no wrinkling phenomenon occurs; moreover, it can be ensured that no wrinkling phenomenon occurs in other areas outside the forming area during the stamping forming process, whether the convex part is stamped first, the concave part is stamped first, or the convex part and the concave part are simultaneously stamped, so as to ensure the forming surface quality of the part.

Description

Technical Field

[0001] This invention relates to the field of aero-engine component manufacturing technology, and discloses a method and apparatus for forming ultra-thin-walled sheet metal bulges for aero-engines. Background Technology

[0002] The sheet metal protective cover of the aircraft engine is an ultra-thin-walled sheet metal part. The ultra-thin-walled sheet metal part has a recessed part that is recessed into the inner side of the arc-shaped wall structure and a protruding part that is protruding out of the arc-shaped wall structure. The forming process is to first use a pre-formed blank to stamp the main structure of the part (arc-shaped wall structure), and then locally form the protruding and recessed parts on the arc-shaped wall structure separately.

[0003] In existing technologies, traditional stamping dies (direct pressing with punches and dies) are used to form local features of curved wall structures. However, during stamping, uneven internal stress is generated within the material. Furthermore, the parts are thin-walled (around 0.3mm thick) with poor rigidity, resulting in fine wrinkles around the concave or convex portions of the formed curved wall structure. This leads to wrinkling, thinning, and cracking during forming, resulting in unstable part quality, low yield, and a high likelihood of part scrap. Summary of the Invention

[0004] The purpose of this invention is to provide a method and apparatus for forming bulges in ultra-thin-walled sheet metal for aero-engines. This method ensures that during the stamping process, whether the protrusion is stamped first, the concave part is stamped first, or both protrusions and concave parts are stamped simultaneously, wrinkling will not occur in other areas outside the forming area, thereby ensuring the surface quality of the formed parts.

[0005] To achieve the above-mentioned technical effects, the technical solution adopted by the present invention is as follows:

[0006] A method for forming a bulge in ultra-thin-walled sheet metal for aero-engines, wherein the ultra-thin-walled sheet metal is an arc-shaped wall structure, and the bulge includes a concave portion and a convex portion. The concave portion is formed by stamping the arc-shaped wall structure towards the inner side using a first stamping rod, and the convex portion is formed by stamping the arc-shaped wall structure towards the outer side using a second stamping rod. The ultra-thin-walled sheet metal bulge forming process includes:

[0007] Based on the material and dimensional parameters of the protrusions and recesses of the arc-shaped wall structure, the first punching force applied by the first punching rod to the arc-shaped wall structure and the second punching force applied by the second punching rod to the arc-shaped wall structure are analyzed and obtained.

[0008] Based on the analysis of the first stamping force, the surface area of ​​the arc-shaped wall structure, and the cross-sectional area of ​​the stamping end of the first stamping rod, the minimum clamping force required to press the inner and outer walls of the arc-shaped wall structure without causing wrinkling of the arc-shaped wall structure when stamping the concave part is obtained.

[0009] Based on the analysis of the second stamping force, the surface area of ​​the arc-shaped wall structure, and the cross-sectional area of ​​the stamping end of the second stamping rod, the second minimum clamping force required to press the inner and outer walls of the arc-shaped wall structure without causing wrinkling of the arc-shaped wall structure when stamping the protrusion is obtained.

[0010] The maximum value of the first minimum clamping force and the second minimum clamping force is taken as the actual minimum clamping force on the inner and outer walls of the arc-shaped wall structure during the bulge stamping process. The arc-shaped wall structure is clamped by a die and a punch. The die is fitted to the outer wall of the arc-shaped wall structure, and a first through hole is provided on the die at a position corresponding to the recess, with the first stamping rod disposed in the first through hole. The punch is fitted to the inner wall of the arc-shaped wall structure, and a second through hole is provided on the punch at a position corresponding to the protrusion, with the second stamping rod movably disposed in the second through hole. The die has a first groove for forming the protrusion, and the punch has a second groove for forming the recess.

[0011] A first stamping rod is used to apply a first stamping force to the outer wall of the arc-shaped wall structure to form a concave part on the arc-shaped wall structure, and a second stamping rod is used to apply a second stamping force to the inner wall of the arc-shaped wall structure to form a protruding part on the arc-shaped wall structure.

[0012] Furthermore, the method for obtaining the minimum clamping force required to press the inner and outer walls of the arc-shaped wall structure without causing wrinkling during the stamping process of the recess is as follows: based on the first stamping force, the surface area of ​​the arc-shaped wall structure, and the cross-sectional area of ​​the stamping end of the first stamping rod, the minimum clamping force is determined by... Where Fmin1 is the first minimum clamping force, S0 is the surface area of ​​the arc-shaped wall structure, S1 is the cross-sectional area of ​​the stamping end of the first stamping rod, σ0 is the yield strength of the arc-shaped wall structure material, F1 is the first stamping force, and k1 is a coefficient with a value range of 1.2 to 1.5.

[0013] Furthermore, the method for obtaining the second minimum clamping force required to press the inner and outer walls of the arc-shaped wall structure without causing wrinkling during stamping of the protrusion is as follows: based on the second stamping force, the surface area of ​​the arc-shaped wall structure, and the cross-sectional area of ​​the stamping end of the second stamping rod, the following method is adopted: Where Fmin2 is the second minimum clamping force, S0 is the surface area of ​​the arc-shaped wall structure, S2 is the cross-sectional area of ​​the stamping end of the second stamping rod, σ0 is the yield strength of the arc-shaped wall structure material, F2 is the second stamping force, and k2 is a coefficient with a value range of 1.2 to 1.5.

[0014] To achieve the above-mentioned technical effects, the present invention also provides an apparatus for forming bulges in ultra-thin-walled sheet metal for aero-engines. This apparatus is used to implement the aforementioned method for forming bulges in ultra-thin-walled sheet metal for aero-engines, comprising:

[0015] A stamping die includes a die and a punch for clamping an arc-shaped wall structure. The die is fitted to the outer wall of the arc-shaped wall structure. A first through hole is provided on the die at a position corresponding to the recess, and a first stamping rod is disposed in the first through hole. The punch is fitted to the inner wall of the arc-shaped wall structure. A second through hole is provided on the punch at a position corresponding to the protrusion, and a second stamping rod is movably disposed in the second through hole. The die has a first groove for forming the protrusion, and the punch has a second groove for forming the recess.

[0016] The punching force analysis module is used to analyze and obtain the first punching force applied by the first punching rod to the arc-shaped wall structure and the second punching force applied by the second punching rod to the arc-shaped wall structure based on the material of the arc-shaped wall structure and the size parameters of the protrusions and concave parts.

[0017] The clamping force analysis module is used to analyze the first punching force, the surface area of ​​the arc-shaped wall structure, and the cross-sectional area of ​​the punching end of the first punching rod to determine the first minimum clamping force required to clamp the inner and outer walls of the arc-shaped wall structure when forming the concave part, without causing wrinkling of the arc-shaped wall structure; and to analyze the second punching force, the surface area of ​​the arc-shaped wall structure, and the cross-sectional area of ​​the punching end of the second punching rod to determine the second minimum clamping force required to clamp the inner and outer walls of the arc-shaped wall structure when forming the protrusion part, without causing wrinkling of the arc-shaped wall structure; and to take the maximum value of the first minimum clamping force and the second minimum clamping force as the actual minimum clamping force on the inner and outer walls of the arc-shaped wall structure during the bulge stamping process;

[0018] A clamping force application module is used to control the arc-shaped wall structure between the punch and the die to apply the actual minimum clamping force.

[0019] A first driving assembly is used to drive a first stamping rod to apply a first stamping force to the outer wall of the arc-shaped wall structure.

[0020] The second drive assembly is used to drive the second stamping rod to apply a second stamping force to the inner wall of the arc-shaped wall structure.

[0021] Furthermore, the clamping force analysis module adopts... The analysis yields the first minimum clamping force Fmin1, where S0 is the surface area of ​​the arc-shaped wall structure, S1 is the cross-sectional area of ​​the first stamping rod's stamping end, σ0 is the yield strength of the arc-shaped wall structure material, F1 is the first stamping force, and k1 is a coefficient with a value ranging from 1.2 to 1.5.

[0022] Furthermore, the clamping force analysis module adopts... The analysis yields the second minimum clamping force Fmin2, where S0 is the surface area of ​​the arc-shaped wall structure, S2 is the cross-sectional area of ​​the stamping end of the second stamping rod, σ0 is the yield strength of the arc-shaped wall structure material, F2 is the second stamping force, and k2 is a coefficient with a value range of 1.2 to 1.5.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention analyzes and obtains the actual minimum extrusion force on the arc-shaped wall structure between the die and the dies based on the stamping force value when forming protrusions and concave parts on the arc-shaped wall structure. The use of this minimum extrusion force value can ensure that the arc-shaped wall structure is always in a compressed state during the stamping process and will not produce wrinkling. Moreover, it can ensure that during the stamping process, whether the protrusion is stamped first, the concave part is stamped first, or the protrusion and concave parts are stamped simultaneously, wrinkling will not occur in other areas outside the forming area, thereby ensuring the forming surface quality of the part. Attached Figure Description

[0024] Figure 1 This is a flowchart of the method for forming ultra-thin-walled sheet metal bulges for aero-engines in the embodiment;

[0025] Figure 2 This is a schematic diagram of the ultra-thin-walled sheet metal structure in the embodiment;

[0026] Figure 3 This is a diagram showing the installation structure of the arc-shaped wall structure in the stamping die in the embodiment;

[0027] Figure 4 This is a schematic diagram of the three-dimensional structure of the stamping die in the embodiment;

[0028] Figure 5 This is a schematic diagram of the structure of the ultra-thin-wall sheet metal bulge forming device for aero-engines in the embodiment;

[0029] Among them, 1. Arc-shaped wall structure; 2. Recess; 3. Protrusion; 4. First stamping rod; 5. Second stamping rod; 6. Die; 7. Punch; 8. First groove; 9. Second groove; 10. Stamping force analysis module; 11. Clamping force analysis module; 12. Clamping force application module; 13. First drive assembly; 14. Second drive assembly. Detailed Implementation

[0030] The present invention will now be described in further detail with reference to the embodiments and accompanying drawings. However, this should not be construed as limiting the scope of the above-described subject matter of the present invention to the following embodiments; all technologies implemented based on the content of the present invention fall within the scope of the present invention.

[0031] Example

[0032] See Figures 1-5 A method for forming a bulge in ultra-thin-walled sheet metal for aero-engines, wherein the ultra-thin-walled sheet metal is an arc-shaped wall structure 1, and the bulge includes a recess 2 and a protrusion 3. The recess 2 is formed by stamping the arc-shaped wall structure 1 inwards using a first stamping rod 4, and the protrusion 3 is formed by stamping the arc-shaped wall structure 1 inwards using a second stamping rod 5. The ultra-thin-walled sheet metal bulge forming process includes:

[0033] Based on the material of the arc-shaped wall structure 1 and the size parameters of the protrusion 3 and the recess 2, the first punching force applied by the first punching rod 4 to the arc-shaped wall structure 1 and the second punching force applied by the second punching rod 5 to the arc-shaped wall structure 1 are analyzed and obtained.

[0034] Based on the analysis of the first stamping force, the surface area of ​​the arc-shaped wall structure 1 and the cross-sectional area of ​​the stamping end of the first stamping rod 4, the first minimum clamping force required to press the inner and outer walls of the arc-shaped wall structure 1 without causing the arc-shaped wall structure 1 to wrinkle is obtained when stamping the concave part 2.

[0035] Based on the analysis of the second stamping force, the surface area of ​​the arc-shaped wall structure 1 and the cross-sectional area of ​​the stamping end of the second stamping rod 5, the second minimum clamping force required to press the inner and outer walls of the arc-shaped wall structure 1 when stamping the protrusion 3, without causing the arc-shaped wall structure 1 to wrinkle, is obtained.

[0036] The maximum value of the first minimum clamping force and the second minimum clamping force is taken as the actual minimum clamping force on the inner and outer walls of the arc-shaped wall structure 1 during the bulge stamping process. The arc-shaped wall structure 1 is clamped by a die 6 and a punch 7. The die 6 is fitted to the outer wall of the arc-shaped wall structure 1. A first through hole is provided on the die 6 at a position corresponding to the recess 2 along the radial direction of the die 6. The first stamping rod 4 is disposed in the first through hole. The punch 7 is used to fit to the inner wall of the arc-shaped wall structure 1. A second through hole is provided on the punch 7 at a position corresponding to the protrusion 3 along the radial direction of the punch 7. The second stamping rod 5 is movably disposed in the second through hole. A first groove 8 is provided on the die 6 for forming the protrusion 3. A second groove 9 is provided on the punch 7 for forming the recess 2.

[0037] A first stamping rod 4 is used to apply a first stamping force to the outer wall of the arc-shaped wall structure 1 to form a recess 2 on the arc-shaped wall structure 1, and a second stamping rod 5 is used to apply a second stamping force to the inner wall of the arc-shaped wall structure 1 to form a protrusion 3 on the arc-shaped wall structure 1.

[0038] In this embodiment, when the arc-shaped wall structure 1 needs to be stamped with protrusions 3 and recesses 2, the arc-shaped wall structure 1 is first placed vertically along its axial direction between the die 6 and the punch 7. Then, the die 6 and the punch 7 are fitted together to clamp the arc-shaped wall structure 1, so that the die 6 and the punch 7 work together to clamp the arc-shaped wall structure 1. Then, the first stamping rod 4 is used to form the recesses 2 on the arc-shaped wall structure 1, and the second stamping rod 5 is used to form the protrusions 3 on the arc-shaped wall structure 1. In this embodiment, the minimum value of the extrusion force (i.e., the actual minimum extrusion force) experienced by the arc-shaped wall structure 1 between the die 6 and the punch 7 is the maximum value between the first minimum clamping force and the second minimum clamping force. Therefore, it can be ensured that during the stamping process, whether the protrusions 3 are stamped first, the recesses 2 are stamped first, or the protrusions 3 and recesses 2 are stamped simultaneously, wrinkling will not occur in other areas outside the forming area, thereby ensuring the surface quality of the formed part.

[0039] Based on the same inventive concept, this embodiment also provides a device for forming bulges in ultra-thin-walled sheet metal for aero engines, comprising:

[0040] A stamping die includes a concave die 6 and a convex die 7 for clamping an arc-shaped wall structure 1. The concave die 6 is fitted to the outer wall of the arc-shaped wall structure 1. A first through hole is provided on the concave die 6 at a position corresponding to the recess 2, and a first stamping rod 4 is disposed in the first through hole. The convex die 7 is fitted to the inner wall of the arc-shaped wall structure 1. A second through hole is provided on the convex die 7 at a position corresponding to the protrusion 3, and a second stamping rod 5 is movably disposed in the second through hole. A first groove 8 is provided on the concave die 6 for forming the protrusion 3, and a second groove 9 is provided on the convex die 7 for forming the recess 2.

[0041] The punching force analysis module 10 is used to analyze and obtain the first punching force applied to the arc-shaped wall structure 1 by the first punching rod 4 and the second punching force applied to the arc-shaped wall structure 1 by the second punching rod 5, based on the material of the arc-shaped wall structure 1 and the size parameters of the protrusion 3 and the concave part 2. In this embodiment, the punching force analysis module 10 can obtain the first punching force F1 and the second punching force F2 by force analysis method or by simulation analysis software, based on the material of the arc-shaped wall structure 1 and the size parameters of the protrusion 3 and the concave part 2.

[0042] The clamping force analysis module 11 is used to analyze the first punching force, the surface area of ​​the arc-shaped wall structure 1, and the cross-sectional area of ​​the punching end of the first punching rod 4 to determine the first minimum clamping force required to clamp the inner and outer walls of the arc-shaped wall structure 1 when stamping the concave part 2 without causing wrinkling of the arc-shaped wall structure 1; and to analyze the second punching force, the surface area of ​​the arc-shaped wall structure 1, and the cross-sectional area of ​​the punching end of the second punching rod 5 to determine the second minimum clamping force required to clamp the inner and outer walls of the arc-shaped wall structure 1 when stamping the protrusion part 3 without causing wrinkling of the arc-shaped wall structure 1; and to take the maximum value of the first minimum clamping force and the second minimum clamping force as the actual minimum clamping force on the inner and outer walls of the arc-shaped wall structure 1 during the bulge stamping process;

[0043] In this embodiment, the clamping force analysis module 11 adopts... The analysis yields the first minimum clamping force Fmin1, where S0 is the surface area of ​​the arc-shaped wall structure 1, S1 is the cross-sectional area of ​​the stamping end of the first stamping rod 4, σ0 is the yield strength of the material of the arc-shaped wall structure 1, F1 is the first stamping force, and k1 is a coefficient ranging from 1.2 to 1.5. The clamping force analysis module 11 employs... The analysis yielded the second minimum clamping force Fmin2, where S0 is the surface area of ​​the arc-shaped wall structure 1, S2 is the cross-sectional area of ​​the stamping end of the second stamping rod 5, σ0 is the yield strength of the material of the arc-shaped wall structure 1, F2 is the second stamping force, and k2 is a coefficient ranging from 1.2 to 1.5.

[0044] The clamping force application module 12 is used to control the arc-shaped wall structure 1 between the punch 7 and the die 6 to apply the actual minimum clamping force.

[0045] The first driving component 13 is used to drive the first stamping rod 4 to apply a first stamping force to the outer wall of the arc-shaped wall structure 1.

[0046] The second drive assembly 14 is used to drive the second stamping rod 5 to apply a second stamping force to the inner wall of the arc-shaped wall structure 1.

[0047] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for forming a bulge in an ultra-thin-walled sheet metal for an aero-engine, wherein the ultra-thin-walled sheet metal is an arc-shaped wall structure, the bulge includes a concave portion and a protruding portion, the concave portion is formed by stamping the arc-shaped wall structure towards the inner side using a first stamping rod, and the protruding portion is formed by stamping the arc-shaped wall structure towards the outer side using a second stamping rod; characterized in that... The ultra-thin-wall sheet metal bulge forming method includes: Based on the material and dimensional parameters of the protrusions and recesses of the arc-shaped wall structure, the first punching force applied by the first punching rod to the arc-shaped wall structure and the second punching force applied by the second punching rod to the arc-shaped wall structure are analyzed and obtained. Based on the analysis of the first stamping force, the surface area of ​​the arc-shaped wall structure, and the cross-sectional area of ​​the stamping end of the first stamping rod, the minimum clamping force required to press the inner and outer walls of the arc-shaped wall structure without causing wrinkling of the arc-shaped wall structure when stamping the concave part is obtained. Based on the analysis of the second stamping force, the surface area of ​​the arc-shaped wall structure, and the cross-sectional area of ​​the stamping end of the second stamping rod, the second minimum clamping force required to press the inner and outer walls of the arc-shaped wall structure without causing wrinkling of the arc-shaped wall structure when stamping the protrusion is obtained. The maximum value of the first minimum clamping force and the second minimum clamping force is taken as the actual minimum clamping force on the inner and outer walls of the arc-shaped wall structure during the bulge stamping process. The arc-shaped wall structure is clamped by a die and a punch. The die is fitted to the outer wall of the arc-shaped wall structure, and a first through hole is provided on the die at a position corresponding to the recess, with the first stamping rod disposed in the first through hole. The punch is fitted to the inner wall of the arc-shaped wall structure, and a second through hole is provided on the punch at a position corresponding to the protrusion, with the second stamping rod movably disposed in the second through hole. The die has a first groove for forming the protrusion, and the punch has a second groove for forming the recess. A first stamping rod is used to apply a first stamping force to the outer wall of the arc-shaped wall structure to form a concave part on the arc-shaped wall structure, and a second stamping rod is used to apply a second stamping force to the inner wall of the arc-shaped wall structure to form a protruding part on the arc-shaped wall structure.

2. The method for forming ultra-thin-walled sheet metal bulges for aero-engines according to claim 1, characterized in that, The method for obtaining the minimum clamping force required to press the inner and outer surfaces of the arc-shaped wall structure without causing wrinkling during the stamping process of the recess is as follows: Based on the first stamping force, the surface area of ​​the arc-shaped wall structure, and the cross-sectional area of ​​the stamping end of the first stamping rod, the minimum clamping force is determined by... Analysis yields the first minimum clamping force ,in The first minimum clamping force, Let be the surface area of ​​the arc-shaped wall structure. Let be the cross-sectional area of ​​the stamping end of the first stamping rod. The yield strength of the material for the arc-shaped wall structure. For the first impact force, This is a coefficient, with a value range of 1.2 to 1.

5.

3. The method for forming ultra-thin-walled sheet metal bulges for aero-engines according to claim 1, characterized in that, The method for obtaining the second minimum clamping force required to press the inner and outer walls of the arc-shaped wall structure without causing wrinkling during stamping of the protrusion is as follows: based on the second stamping force, the surface area of ​​the arc-shaped wall structure, and the cross-sectional area of ​​the stamping end of the second stamping rod, the following method is adopted: Analysis yields the second minimum clamping force ,in The second minimum clamping force, Let be the surface area of ​​the arc-shaped wall structure. This refers to the cross-sectional area of ​​the stamping end of the second stamping rod. The yield strength of the material for the arc-shaped wall structure. For the second impact force, This is a coefficient, with a value range of 1.2 to 1.

5.

4. A device for forming bulges in ultra-thin-walled sheet metal for aero-engines, the device being used to implement the method for forming bulges in ultra-thin-walled sheet metal for aero-engines as described in any one of claims 1-3, characterized in that, include: A stamping die includes a die and a punch for clamping an arc-shaped wall structure. The die is fitted to the outer wall of the arc-shaped wall structure. A first through hole is provided on the die at a position corresponding to the recess, and a first stamping rod is disposed in the first through hole. The punch is fitted to the inner wall of the arc-shaped wall structure. A second through hole is provided on the punch at a position corresponding to the protrusion, and a second stamping rod is movably disposed in the second through hole. The die has a first groove for forming the protrusion, and the punch has a second groove for forming the recess. The punching force analysis module is used to analyze and obtain the first punching force applied by the first punching rod to the arc-shaped wall structure and the second punching force applied by the second punching rod to the arc-shaped wall structure based on the material of the arc-shaped wall structure and the size parameters of the protrusions and concave parts. The clamping force analysis module is used to analyze the first punching force, the surface area of ​​the arc-shaped wall structure, and the cross-sectional area of ​​the punching end of the first punching rod to determine the first minimum clamping force required to clamp the inner and outer walls of the arc-shaped wall structure when forming the concave part, without causing wrinkling of the arc-shaped wall structure; and to analyze the second punching force, the surface area of ​​the arc-shaped wall structure, and the cross-sectional area of ​​the punching end of the second punching rod to determine the second minimum clamping force required to clamp the inner and outer walls of the arc-shaped wall structure when forming the protrusion part, without causing wrinkling of the arc-shaped wall structure; and to take the maximum value of the first minimum clamping force and the second minimum clamping force as the actual minimum clamping force on the inner and outer walls of the arc-shaped wall structure during the bulge stamping process; A clamping force application module is used to control the arc-shaped wall structure between the punch and the die to apply the actual minimum clamping force. A first driving assembly is used to drive a first stamping rod to apply a first stamping force to the outer wall of the arc-shaped wall structure. The second drive assembly is used to drive the second stamping rod to apply a second stamping force to the inner wall of the arc-shaped wall structure.

5. The device for forming ultra-thin-walled sheet metal bulges for aero-engines according to claim 4, characterized in that, The clamping force analysis module adopts Analysis yields the first minimum clamping force ,in Let be the surface area of ​​the arc-shaped wall structure. Let be the cross-sectional area of ​​the stamping end of the first stamping rod. The yield strength of the material for the arc-shaped wall structure. For the first impact force, This is a coefficient, with a value range of 1.2 to 1.

5.

6. The device for forming ultra-thin-walled sheet metal bulges for aero-engines according to claim 4, characterized in that, The clamping force analysis module adopts Analysis yields the second minimum clamping force ,in, Let be the surface area of ​​the arc-shaped wall structure. This refers to the cross-sectional area of ​​the stamping end of the second stamping rod. The yield strength of the material for the arc-shaped wall structure. For the second impact force, This is a coefficient, with a value range of 1.2 to 1.5.

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