Method for controlling pipe end forming of hydraulic forming pipe fitting

Abstract

The invention discloses a method for controlling pipe end forming of a hydraulic forming pipe fitting. The method comprises the following steps that S1, the forming material supplementing direction is designed according to the shape of a target pipe fitting; s2, designing the section shape of the sealing section of the hydraulic forming process part of the original pipe, wherein S21, the straight edge of the sealing section of the section shape of the sealing section of the hydraulic forming process part is collinear with the straight edge of the opening part of the target pipe fitting; and S22, the proportion of the sealing section fillet R0 of the hydraulic forming process part to the section fillet Rp of the corresponding position of the target pipe fitting is set. According to the method, the gap with the set distance is reserved between the sealing section of the hydraulic forming process part and the opening part of the target pipe fitting and serves as the machining allowance, the sealing section of the hydraulic forming process part and the opening part of the target pipe fitting are supplemented, and therefore the forming process part is designed, a bridging section between the sealing section and a finished product is omitted, materials of the bridging section can be saved, and the production cost is reduced. The material utilization rate is increased, the material fluidity is improved, and the problems of product cracking are reduced.

Description

Technical Field

[0001] The invention relates to the technical field of tube end molding of hydraulically formed parts, and more particularly to a method for controlling tube end molding of hydraulically formed tube parts. Background Art

[0002] The hydroforming process uses liquid as the medium to apply pressure to the inside of the pipe, forming it into the designed shape under the constraints of the mold.

[0003] See also Figure 1 When selecting the diameter of the hydroformed tube, it is necessary to analyze the circumference of each section to select the tube with the appropriate diameter.

[0004] See also Figure 2 According to the selected tube blank, the hydraulic forming process parts are designed. Generally, a sealing section 1 will be designed for the hydraulic forming process parts. The cross-sectional circumference of the sealing section is generally equivalent to the diameter of the tube blank. If the cross-sectional circumference of the mouth of the finished product is not equal to that of the tube blank, a bridging section 2 will generally be formed to ensure that the sealing section is evenly bridged with the finished product.

[0005] In order to seal and fill materials in hydraulic forming, the sealing section 1 is usually indispensable, but the bridging section 2 can be cancelled; for products with complex cross-sectional shapes and a mouth cross-sectional circumference greater than the tube blank, the length of the bridging section is usually 30mm-50mm, which will result in more material waste and affect material flow, resulting in reduced material utilization and increased risks of part cracking and wrinkling. Summary of the invention

[0006] The technical problem to be solved by the present invention is how to design a hydraulic forming process part without a bridging section.

[0007] The present invention solves the above technical problems through the following technical means: a method for controlling the forming of a hydraulically formed pipe end, comprising the following steps:

[0008] S1. Design the forming and feeding direction according to the shape of the target pipe;

[0009] S2. Design the cross-sectional shape of the sealing section of the hydraulic forming process part of the original pipe, including:

[0010] S21, the straight edge of the sealing section cross-sectional shape of the hydraulic forming process part is collinear with the straight edge of the mouth of the target pipe part;

[0011] S22, the fillet R0 of the sealing section of the hydraulic forming process part and the cross-sectional fillet R of the corresponding position of the target pipe part p To set the ratio, the cross-sectional perimeter of the sealing section of the hydroforming process part is adjusted by adjusting the size of the fillet R0;

[0012] S23, the cross-sectional curve of the designed sealing section of the hydraulic forming process part is stretched along the feeding direction to form the sealing section of the hydraulic forming process part, and a gap of a set distance is left between the sealing section of the hydraulic forming process part and the mouth of the target pipe part;

[0013] S3. Supplement the gap between the sealing section of the hydraulic forming process part and the finished part, and preliminarily design the hydraulic forming process part.

[0014] As a preferred technical solution, it also includes S4, designing a sealing section for the pre-forming process part;

[0015] The ratio of the major semi-axis to the minor semi-axis of the sealing section of the pre-forming process part is equal to 0.8-1.2 times the ratio of the length to the width of the target pipe section; the ratio c of the circumference of the cross-section of the sealing section of the pre-forming process part to the circumference of the original pipe is equal to 0.9-0.94 times the ratio a of the cross-section of the sealing section of the hydraulic forming process part to the circumference of the original pipe; the ratio of the major semi-axis to the minor semi-axis of the cross-section of the sealing section of the pre-forming process part is λ, and the sealing section of the pre-forming process part is obtained by stretching along the molding and filling direction.

[0016] As a preferred technical solution, it also includes simulating the expansion of the sealing section of the pre-forming process part and the sealing section of the hydraulic forming process part, and adjusting the ratio c of the circumference of the cross-section of the sealing section of the pre-forming process part to the circumference of the original pipe, the ratio λ of the major semi-axis to the minor semi-axis of the cross-section of the sealing section of the pre-forming process part, and the radius R0 of the sealing section of the hydraulic forming process part according to the simulation results.

[0017] As a preferred technical solution, whether the sealing section of the pre-formed process part is qualified is determined according to the result of the expansion simulation, and the determination method is:

[0018] After expansion, the principal strain at all positions of the sealing section of the preformed process part does not exceed cε b , where ε b is the total elongation of the maximum force of the original pipe. If it exceeds, it is determined whether it is concentrated in a certain local position, and the principal strains at other positions do not exceed 0.6 times the maximum principal strain. If so, it is necessary to reduce the ratio of the major semi-axis and the segment semi-axis of the ellipse. If not, that is, there is and the ratio of the principal strain at other positions to the maximum principal strain does not exceed 0.6; then reduce the cross-sectional perimeter of the ratio of the perimeter of the hydraulic forming process part to the perimeter of the pre-forming process part c.

[0019] As a preferred technical solution, if the maximum principal strain point appears near the intersection of the major semi-axis of the sealing section of the pre-formed process part and the sealing section of the pre-formed process part, it is necessary to adjust the ratio of the major semi-axis to the minor semi-axis of the sealing section of the pre-formed process part.

[0020] As a preferred technical solution, the expansion of the sealing section of the hydraulic forming process is simulated to determine whether cracking occurs. If cracking occurs, corresponding adjustments need to be made according to the cracking situation. If there is no cracking during the expansion, the process is completed.

[0021] As a preferred technical solution, the adjustment includes:

[0022] If the crack is located at the fillet, increase the fillet radius R0 of the forming process part;

[0023] If the crack is located on the short side of the sealing section, reduce the ratio λ of the major semi-axis to the minor semi-axis of the sealing section ellipse of the preformed process part;

[0024] If the crack position is located on the long side of the sealing section, reduce the ratio of the perimeter of the hydroforming process part or the perimeter of the preforming process part and appropriately reduce the ratio λ of the major semi-axis to the minor semi-axis.

[0025] As a preferred technical solution, the ratio a of the equivalent cross-sectional perimeter of the sealing section of the hydraulic forming process part to the equivalent cross-sectional perimeter of the original pipe does not exceed the maximum force total elongation ε of the original pipe. b .

[0026] As a preferred technical solution, the cross-section of the sealing section of the pre-formed process part is elliptical.

[0027] As a preferred technical solution, the set gap is 3 mm.

[0028] The beneficial effects of the present invention are:

[0029] (1) In the present invention, a gap of a set distance is left between the sealing section of the hydraulic forming process part and the mouth of the target pipe part as a processing allowance, and the sealing section of the hydraulic forming process part and the mouth of the target pipe part are supplemented to design a forming process part, thereby eliminating the bridging section between the sealing section and the finished product, saving material of the bridging section, improving material utilization, improving material fluidity, and reducing problems such as product cracking. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The overall structural diagram provided for the background technology of the present invention;

[0031] Figure 2 A schematic diagram of the sealing section and the bridging section structure provided as the background technology of the present invention;

[0032] Figure 3 A schematic diagram of the finished product structure provided by an embodiment of the present invention;

[0033] Figure 4 The embodiment of the present invention provides Figure 3 Schematic diagram of the cross-sectional structure of the finished product mouth;

[0034] Figure 5 The embodiment of the present invention provides Figure 3 Schematic diagram of the cross-sectional structure of the sealing section;

[0035] Figure 6 A schematic diagram of a supplementary gap structure provided by an embodiment of the present invention;

[0036] Figure 7 A schematic diagram of the maximum strain point provided by an embodiment of the present invention;

[0037] Figure 8 A schematic diagram of a crack located at a rounded corner provided in an embodiment of the present invention;

[0038] Fig. 9 A schematic diagram of a crack located on a short side provided in an embodiment of the present invention;

[0039] Fig.10 A schematic diagram of a crack located on a long side provided in an embodiment of the present invention;

[0040] Fig.11 A flow chart of a tube end forming method provided by an embodiment of the present invention;

[0041] Figure numbers: 1, sealing section; 2, bridging section; 3, finished straight edge; 4, sealing section straight edge; 5, maximum strain point; 6, rounded corner; 7, short edge; 8, long edge; 9, notch. DETAILED DESCRIPTION

[0042] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0043] See also Figure 3 , Figure 4 , Figure 5 , Figure 6 , Fig.11 A method for controlling the forming of a pipe end of a hydraulically formed pipe fitting comprises the following steps:

[0044] S1. Design the direction of forming and filling material according to the shape of the finished product, i.e. the target pipe. In this embodiment, the direction of forming and filling material is the center line of the blank, i.e. the original pipe;

[0045] S2, designing the cross-sectional shape of the sealing section 1 of the hydraulic forming process part of the original pipe, including the following steps:

[0046] S21, the sealing section straight edge 4 of the cross-sectional shape of the sealing section 1 of the hydraulic forming process part is set to be collinear with the finished product straight edge 3 of the mouth of the target pipe part;

[0047] S22. Design the fillet R0 of the sealing section of the hydraulic forming process part. R0 is approximately equal to 1-1.2 times the cross-sectional fillet R0 of the target pipe part at the corresponding position. p , 1-1.2 is the set value; the cross-sectional perimeter of the sealing section 1 of the hydroforming process part is adjusted by adjusting the size of the fillet R0, and the ratio a of the equivalent cross-sectional perimeter of the sealing section 1 of the hydroforming process part to the equivalent cross-sectional perimeter of the tube blank, i.e., the original tube, does not exceed the maximum force total elongation ε of the raw material b ;

[0048] S23. At this time, the cross-sectional shape curve of the sealing section of the hydraulic forming process part can be preliminarily obtained, and the sealing section of the hydraulic forming process part is stretched along the forming and filling direction to form a sealing section of the hydraulic forming process part. A gap of about 3 mm is left between the sealing section of the hydraulic forming process part and the mouth of the target pipe as a processing allowance for the subsequent process; at this time, the design of the sealing section of the hydraulic forming process part is completed;

[0049] It should be noted that the stretching here does not refer to the stretching process, but to the design stretching. The cross-sectional shape of the sealing section 1 is generally a quadrilateral, and the fillet R0 of the quadrilateral is a design variable.

[0050] S3, supplement the gap 9 between the sealing section and the finished part, that is, the gap described in S23, at which time the hydraulic forming process part is preliminarily designed;

[0051] It should be noted that in the hydraulic forming process, the hydraulic forming process part forms a sealing section of the hydraulic forming process part after hydraulic forming, and the shape of the sealing section of the hydraulic forming process part needs to be expanded and formed by the forming sealing head; however, since the shape and expansion amount of the sealing section of the hydraulic forming process part are greatly different from those of the tube blank; therefore, it is necessary to perform secondary expansion on the basis of the sealing section of the pre-forming process part; the sealing section of the pre-forming process part needs to be expanded and formed in the pre-forming process, and the shape design of the sealing section of the pre-forming process part affects whether the sealing section of the hydraulic forming process part can be successfully expanded and formed;

[0052] S4. Design of sealing section for pre-formed process parts:

[0053] The sealing section of the pre-forming process part is generally designed to be an ellipse, and the ratio of its major semi-axis to its minor semi-axis is approximately equal to 0.8-1.2 times the ratio of the length to the width of the finished product section; the ratio of the circumference of the ellipse to the circumference of the tube blank c is approximately equal to 0.9-0.94 times the ratio of the section of the sealing section of the hydraulic forming process part to the circumference of the tube blank a; the design variables of the sealing section of the pre-forming process part are the circumference c of the ellipse and the ratio of the major semi-axis to the minor semi-axis of the ellipse λ, and the sealing section of the pre-forming process part is obtained by stretching along the forming and filling direction; the expansion of the pre-forming sealing section and the forming sealing section is simulated, and the circumference c of the ellipse and the ratio of the major semi-axis to the minor semi-axis λ of the pre-forming sealing section, as well as the fillet R0 in the forming process part are adjusted according to the simulation results;

[0054] S5. Perform expansion simulation on the sealing section of the pre-formed process part, and determine whether the sealing section of the pre-formed process part is qualified according to the result of the expansion simulation. The determination method is as follows:

[0055] After expansion, the principal strain at all positions of the sealing section shall not exceed cε b ,in,

[0056] c: Ratio of the circumference of the hydroforming process part to the circumference of the preforming process part;

[0057] ε b : Total elongation at maximum force;

[0058] If the conditions cannot be met, it is necessary to determine whether the maximum principal strain position is concentrated in a certain local position, and the principal strains at other positions do not exceed 0.6 times the principal strain;

[0059] If yes: then the ratio λ of the major semi-axis to the segment semi-axis of the ellipse needs to be reduced;

[0060] If not, that is, there is and the ratio of the principal strain at other positions to the maximum principal strain does not exceed 0.6; in this case, it is necessary to reduce the ratio of the perimeter of the hydroforming process part to the perimeter of the pre-forming process part c to the cross-sectional perimeter of the ellipse;

[0061] In other cases, see Figure 7 , if the maximum principal strain point 5 appears near the intersection of the major semi-axis of the ellipse and the ellipse, the ratio of the major semi-axis / minor semi-axis needs to be adjusted;

[0062] S6. Simulation of sealing section expansion of hydraulic forming process parts. Whether cracking occurs is judged by simulation. The criterion for judging whether the sealing section expansion is qualified is: no cracking occurs during expansion; if cracking occurs, corresponding adjustments shall be made according to the cracking situation:

[0063] See also Figure 8 , if the cracking position is at the fillet 6 position, increase the fillet radius R0 of the forming process part;

[0064] See also Fig. 9, if the crack position is located on the short side 7 of the sealing section, reduce the ratio λ of the major semi-axis to the minor semi-axis of the sealing section ellipse of the preformed process part;

[0065] See also Fig.10 , if the crack position is located on the long side 8 of the sealing section, reduce the ratio c of the perimeter of the hydroforming process part or the perimeter of the preforming process part and appropriately reduce the ratio λ of the major semi-axis to the minor semi-axis;

[0066] If there is no cracking, the design requirements are met.

[0067] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for controlling the forming of a hydraulically formed pipe end, characterized in that: The steps include: S1. Design the forming and feeding direction according to the shape of the target pipe; S2. Design the cross-sectional shape of the sealing section of the hydraulic forming process part of the original pipe, including: S21, the straight edge of the sealing section cross-sectional shape of the hydraulic forming process part is collinear with the straight edge of the mouth of the target pipe part; S22, the fillet R0 of the sealing section of the hydraulic forming process part and the cross-sectional fillet R of the corresponding position of the target pipe part p To set the ratio, the cross-sectional perimeter of the sealing section of the hydroforming process part is adjusted by adjusting the size of the fillet R0; S23, the cross-sectional curve of the sealing section of the hydraulic forming process part is stretched along the forming and feeding direction to form the sealing section of the hydraulic forming process part, and a gap of a set distance is left between the sealing section of the hydraulic forming process part and the mouth of the target pipe part; S3, supplementing the gap between the sealing section of the hydraulic forming process part and the finished part to obtain the hydraulic forming process part.

2. A method for controlling the forming of a hydroformed pipe end according to claim 1, characterized in that: It also includes S4, design of sealing section for pre-formed process parts; The ratio of the major semi-axis to the minor semi-axis of the sealing section of the pre-forming process part is equal to 0.8-1.2 times the ratio of the length to the width of the target pipe section; the ratio c of the circumference of the cross-section of the sealing section of the pre-forming process part to the circumference of the original pipe is equal to 0.9-0.94 times the ratio a of the cross-section of the sealing section of the hydraulic forming process part to the circumference of the original pipe; the ratio of the major semi-axis to the minor semi-axis of the cross-section of the sealing section of the pre-forming process part is λ, and the sealing section of the pre-forming process part is obtained by stretching along the molding and filling direction.

3. A method for controlling the forming of a hydroformed pipe end according to claim 2, characterized in that: It also includes expansion simulation of the sealing section of the pre-forming process part and the sealing section of the hydraulic forming process part, and adjusts the ratio c of the circumference of the cross-section of the sealing section of the pre-forming process part to the circumference of the original pipe, the ratio λ of the major semi-axis to the minor semi-axis of the cross-section of the sealing section of the pre-forming process part, and the fillet R0 of the sealing section of the hydraulic forming process part according to the simulation results.

4. A method for controlling the forming of a hydroformed pipe end according to claim 3, characterized in that: According to the results of the expansion simulation, it is determined whether the sealing section of the pre-formed process part is qualified. The determination method is as follows: After expansion, the principal strain at all positions of the sealing section of the preformed process part does not exceed cε b , where ε b is the total elongation of the maximum force of the original pipe. If it exceeds, it is determined whether it is concentrated in a certain local position, and the principal strains at other positions do not exceed 0.6 times the maximum principal strain. If so, it is necessary to reduce the ratio of the major semi-axis and the segment semi-axis of the ellipse. If not, that is, there is and the ratio of the principal strain at other positions to the maximum principal strain does not exceed 0.6; then reduce the cross-sectional perimeter of the ratio of the perimeter of the hydraulic forming process part to the perimeter of the pre-forming process part c.

5. A method for controlling the forming of a hydroformed pipe end according to claim 4, characterized in that: If the maximum principal strain point appears near the intersection of the major semi-axis of the sealing section of the preformed process part and the sealing section of the preformed process part, the ratio of the major semi-axis to the minor semi-axis of the sealing section of the preformed process part needs to be adjusted.

6. A method for controlling the forming of a hydroformed pipe end according to claim 4, characterized in that: Simulate the expansion of the sealing section of the hydraulic forming process part and determine whether it is cracked. If cracking occurs, corresponding adjustments need to be made according to the cracking situation: if there is no cracking during the expansion, it is completed.

7. A method for controlling the forming of a hydroformed pipe end according to claim 6, characterized in that: The adjustments include: If the crack is located at the fillet, increase the fillet radius R0 of the forming process part; If the crack is located on the short side of the sealing section, reduce the ratio λ of the major semi-axis to the minor semi-axis of the sealing section ellipse of the preformed process part; If the crack position is located on the long side of the sealing section, reduce the ratio of the perimeter of the hydroforming process part or the perimeter of the preforming process part and appropriately reduce the ratio λ of the major semi-axis to the minor semi-axis.

8. A method for controlling the forming of a hydroformed pipe end according to claim 1, characterized in that: The ratio a of the equivalent cross-sectional perimeter of the sealing section of the hydraulic forming process part to the equivalent cross-sectional perimeter of the original pipe does not exceed the maximum force total elongation v of the original pipe b .

9. A method for controlling the forming of a hydroformed pipe end according to claim 2, characterized in that: The sealing section of the preformed process part has an elliptical cross section.

10. A method for controlling the forming of a hydroformed pipe end according to claim 1, characterized in that: The set gap is 3 mm.

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