Tube expansion method of tubular material and tubular material part manufactured by using same

Abstract

The invention relates to a tube expansion method of tubular material and a tubular material part manufactured by using the method. The tube expansion method of a tubular material includes extruding a tubular material formed with a hollow portion, inserting the tubular material into a cavity of a mold corresponding to a shape of a component to be manufactured, and performing hydroforming by injecting a pressure medium into the hollow portion of the tubular material at a predetermined pressure or higher, the tubular material extruded by the extrusion step includes portions having different thicknesses in the circumferential direction. Tube expansion can be performed on one-piece tubular materials with different cross-sectional dimensions.

Description

Technical Field

[0001] Embodiments of the present invention relate to a method for expanding a tubular material, and more particularly, to a forming method utilizing hydroforming, and a tubular material component manufactured using the method. Background Art

[0002] Hydroforming is a production technology suitable for component integration and weight reduction, but it has limitations in forming complex shapes due to the molding restrictions of materials and the difficulty in controlling the molding process.

[0003] Formable shapes include eccentric expansion, pre-bent expansion, asymmetric expansion and flange expansion.

[0004] In other words, there are significant molding limitations depending on the material, and blowouts may occur during part molding, or defects such as wrinkling or buckling may appear due to improper process control.

[0005] Due to the above-mentioned problems occurring in hydraulic molding of hollow materials, it is impossible to mold an integrated tube product having portions with different cross-sectional dimensions, and thus the product is manufactured as a separate combined structure of extruded and pressed products.

[0006] For example, when the cross-sectional dimensions of each part are different, e.g. Figure 1 and Figure 2 As shown, the oval tubular material 1 having a single thickness may break during hydroforming, as shown in FIG. Figure 3 and Figure 4 As shown, a prismatic tubular material 2 having a single thickness may fracture during hydroforming.

[0007] The contents described in the above related art are intended to help understand the background of the present invention and may include contents that are not previously known to those of ordinary skill in the art to which the present invention belongs. In other words, the statements in this background section only provide background information related to the present invention and may not constitute prior art. Summary of the Invention

[0008] Embodiments of the present invention are directed to a method for expanding a single piece of tubular material, wherein portions of the tubular material have different cross-sectional dimensions, and a tubular material component manufactured using the method.

[0009] Other purposes and advantages of the present invention can be understood by the following description and become clear with reference to the specific embodiments of the present invention. Likewise, it will be appreciated by those skilled in the art that the present invention belongs to that the purposes and advantages of the present invention can be achieved by the claimed means and combinations thereof.

[0010] According to an embodiment of the present invention, a method for expanding a tubular material includes: extruding a tubular material having a hollow portion formed therein; inserting the tubular material into a cavity of a mold corresponding to the shape of a component to be manufactured; and performing hydroforming by injecting a pressure medium at a predetermined pressure or higher into the hollow portion of the tubular material. The tubular material extruded by the extrusion step includes portions having different thicknesses along the circumferential direction.

[0011] Furthermore, the tubular material may include a portion having different thicknesses in the circumferential direction, including a first portion having a first thickness and a second portion having a second thickness. The first thickness is greater than the second thickness. The strain of the first portion formed by hydroforming may be greater than the strain of the second portion formed by hydroforming.

[0012] Furthermore, the tubular material may include portions having different thicknesses in the circumferential direction, including a first portion having a first thickness and a second portion having a second thickness. The first thickness is greater than the second thickness. During hydroforming, the first portion may contact the inner wall surface of the die later than the second portion.

[0013] Furthermore, the tubular material may include portions having different thicknesses in the circumferential direction, including a first portion having a first thickness and a second portion having a second thickness. The first thickness is greater than the second thickness. The gap between the first portion and the inner wall surface of the mold facing the first portion may be greater than the gap between the second portion and the inner wall surface of the mold facing the second portion.

[0014] Furthermore, components formed by hydroforming may have portions having different cross-sectional perimeter lengths.

[0015] In addition, the tubular material extruded by the extrusion step includes three or more portions having different thicknesses in the circumferential direction. For example, the tubular material has three or more portions having different thicknesses in the circumferential direction.

[0016] Furthermore, portions of the tubular material having different thicknesses in the circumferential direction may be formed at a plurality of positions in the longitudinal direction of the tubular material.

[0017] Furthermore, in portions of the tubular material having different thicknesses in the circumferential direction, thickness variation between adjacent portions having different thicknesses in the circumferential direction may be linear, whereas thickness variation between mutually non-adjacent portions having different thicknesses may be nonlinear.

[0018] Next, a one-piece tubular material component can be manufactured by the tube expansion method according to the present invention (ie, it can be manufactured as a single piece).

[0019] The tubular material includes sections having different outer circumference lengths. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 FIG. 1 is a schematic diagram illustrating a tubular material according to an example.

[0021] Figure 2 To show Figure 1 Schematic diagram of the state of the tubular material during hydroforming.

[0022] Figure 3 FIG. 1 is a schematic diagram illustrating a tubular material according to another example.

[0023] Figure 4 To show Figure 3 Schematic diagram of the state of the tubular material during hydroforming.

[0024] Figure 5A is a schematic diagram showing the shape of a component that can be manufactured by the tube expansion method according to an embodiment of the present invention; Figure 5B-5D Shown respectively Figure 5A Schematic diagram of the cross section of the component along CC, BB, and AA.

[0025] Figure 6 Schematic diagram showing a state before forming by a tube expansion method of a tubular material according to an embodiment of the present invention.

[0026] Figure 7 Schematic diagram showing a state after forming by a tube expansion method of a tubular material according to an embodiment of the present invention.

[0027] Figure 8 FIG. 1 is a schematic diagram showing one example of the thickness of a tubular material before hydroforming according to an embodiment of the present invention.

[0028] Figure 9 Schematic diagram showing a state during forming by a tube expansion method of a tubular material according to an embodiment of the present invention.

[0029] The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. DETAILED DESCRIPTION

[0030] For a fuller understanding of the invention and its operating advantages and objectives attained by its practice, reference should be made to the accompanying drawings in which embodiments of the invention are illustrated, and to the descriptive statements therein.

[0031] In describing the embodiments of the present invention, known technologies may be reduced or omitted, or descriptions may be repeated to avoid unnecessarily obscuring the subject matter of the present invention.

[0032] An embodiment of the present invention provides a method for manufacturing a Figure 7 The method comprises preparing a tubular material 10 by extruding the tubular material 10 using an extruder to shape and manufacture a hollow part as shown. Figures 5A-5D The tubular material 10 shown. Figure 6 As shown, the method further includes inserting the tubular material into a cavity C of a mold corresponding to the shape of the final product, and performing hydroforming by applying high pressure to the inside of the tubular material to expand the tubular material. An embodiment of the present invention also provides a tubular material component manufactured using the method.

[0033] According to an embodiment of the present invention, in tube expansion, as Figures 5A-5D As shown, tube expansion of the tubular material 10 including portions having different cross-sectional dimensions is possible, making it possible to reduce weight without sacrificing quality due to hydroforming and to overcome limitations on the shape of the material to be manufactured.

[0034] In other words, when a hollow tubular material having portions with different cross-sectional dimensions or a polygonal cross-sectional shape is hydroformed, a product that cannot be formed due to fracture according to the related art can be formed by hydroforming.

[0035] To this end, according to the tube expansion method of the tubular material according to the embodiment of the present invention, the tubular material 10 is extruded and prepared before being hydroformed. Figure 8 , in tubular materials of different shapes, the thickness t3 of the portion 11 requiring large strain in the circumferential direction is extruded and manufactured to be larger than the thickness t1 of the portion 12 requiring relatively less forming (e.g., strain or less deformation) to overcome the occurrence of bursting during hydroforming.

[0036] In other words, an embodiment of the present invention provides a technology in which a portion requiring relatively less forming (or deformation) resulting in a relatively smaller (e.g., faster / earlier) time for contact between the tubular material and the mold has a relatively thinner (e.g., thinner) thickness, and a segment (or portion) requiring more (e.g., larger) forming (or deformation) resulting in a relatively later (e.g., later) time for contact between the tubular material and the mold has a relatively thicker (e.g., thicker, larger) thickness, thereby expanding the uniformly elongated section.

[0037] When preparing the tubular material 10 for hydroforming, as Figure 8 The thickness shown varies in the circumferential direction, refer to Figure 6 、 Figure 7 and Figure 9, except for the portion 12 (requiring less molding) in which the strain ε is small even if it contacts the mold (upper mold and lower mold) from the beginning or contacts the mold earlier in the final molding, when the thickness of the portion 11 (requiring more molding) is thicker, in which the contact with the mold is expected to be delayed and thus the strain ε is expected to be large, the effective area A defined by the product of the thickness and length of the portion is 厚 Larger than the effective area A of the portion having a thin thickness 薄 , thus, the force F generated by the molding pressure is the same in the thick part and the thin part, so that the stress applied locally to the thin part becomes greater than the stress applied to the thick part. In this case, when the molding pressure is appropriately applied, since the stress applied to the thin part exceeds the yield stress and the stress applied to the thick part is less than the yield stress, the thin part begins to deform first, and the stress δ of the thick part 厚 Less than the stress δ of the thin part 薄 and yield stress, so that the thick part has not yet deformed. In addition, as the deformation of the thin part continues, it comes into contact with the mold, and deformation is suppressed due to friction and the limitation of the mold shape.

[0038] Next, as the applied force increases due to the increasing molding pressure, while deformation in the thinner sections is suppressed, the stress in the thicker sections exceeds the yield stress, causing the thicker sections to begin to deform. Because the material thickness is designed to increase continuously from the thinnest to the thickest sections, deformation begins at the thinnest section, which is in contact with the die. Deformation then continuously shifts to the thicker sections, with deformation occurring later in the order in which they come into contact with the die. Ultimately, this results in uniform deformation throughout the entire tubular material, allowing it to be formed into the desired part shape.

[0039] Therefore, when the same force is applied, the strain ε of the thick portion is smaller than that of the other thin portions due to the external mold shape, and the deformation of the thick portion progresses more slowly over time. Therefore, the plastic deformation allowance of the thick portion is greater than that of the thin portion, and forming can be achieved at a level similar to the inherent elongation of the material without defects, making it possible to expand (expand) the tube into complex shapes.

[0040] The extruded tubular material is loaded into a mold having the final part shape, a punch is used to seal both ends of the tubular material, a medium injector is used to inject a pressure medium into the tube, and high pressure is applied so that the extruded tubular material is formed into a final product through a tube expansion (expansion) process. Defects that occur during the forming process include bursting, bending, and wrinkling. Defects can be prevented by optimizing the process schedule. According to embodiments of the present invention, material bursting can be particularly avoided.

[0041] Furthermore, the thickness of the thin and thick portions of the tubular material can be designed and applied to vary linearly or nonlinearly.

[0042] In other words, the thickness variation between thick and thin portions of the tubular material that are adjacent to each other may be linear, whereas the thickness variation between portions that are different in thickness and not adjacent to each other may be non-linear.

[0043] Recent vehicle development trends are moving toward environmentally friendly electric vehicles, and with the electrification of batteries and drive units, there is an urgent need to reduce vehicle body weight.

[0044] Hydroforming is gaining attention as a production technology for components suitable for weight reduction. However, conventional hydroforming methods struggle to overcome the molding limitations of materials, resulting in limitations in the products that can be formed. The method proposed in this invention variably adjusts the thickness of a tubular material in the circumferential direction to achieve uniform strain throughout the entire material. This, when forming using internal pressure, can suppress the occurrence of material bursting (increasing the uniform elongation zone and delaying the onset of concentrated stress).

[0045] Furthermore, a component can be molded into a form that cannot be molded due to defects according to the related art, thereby making it possible to easily manufacture a vehicle component that requires weight reduction.

[0046] Although the present invention has been described with reference to the accompanying drawings, it should be apparent to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the present invention, without being limited to the embodiments disclosed herein. Accordingly, it should be noted that such replacements or modifications fall within the scope of the claims of the present invention, and the scope of the present invention should be interpreted based on the appended claims.

Claims

1. A method for expanding a tubular material, comprising: Extruding a tubular material having a hollow portion; Inserting the tubular material into the cavity of a mold corresponding to the shape of the part to be manufactured; as well as Hydroforming is performed by injecting a pressure medium into the hollow portion of a tubular material at a predetermined pressure or higher. The tubular material extruded through the extrusion step includes portions having different thicknesses along a circumferential direction.

2. The method for expanding a tubular material according to claim 1, wherein: The tubular material has portions with different thicknesses in a circumferential direction including a first portion having a first thickness and a second portion having a second thickness, wherein the first thickness is greater than the second thickness; The strain of the first portion is greater than the strain of the second portion.

3. The method for expanding a tubular material according to claim 1, wherein: The tubular material has portions with different thicknesses in a circumferential direction including a first portion having a first thickness and a second portion having a second thickness, wherein the first thickness is greater than the second thickness; When the hydroforming is performed, the first portion contacts the inner wall surface of the die later than the second portion.

4. The method for expanding a tubular material according to claim 1, wherein: The tubular material has portions with different thicknesses in a circumferential direction including a first portion having a first thickness and a second portion having a second thickness, wherein the first thickness is greater than the second thickness; A gap between the first portion and an inner wall surface of the mold facing the first portion is larger than a gap between the second portion and an inner wall surface of the mold facing the second portion.

5. The method for expanding a tubular material according to claim 1, wherein: A component formed by hydroforming has portions having different lengths of the outer perimeter of the cross section.

6. The method for expanding a tubular material according to claim 1, wherein: The tubular material has three or more portions of different thicknesses in the circumferential direction.

7. The method for expanding a tubular material according to claim 1, wherein: Portions of the tubular material having different thicknesses in the circumferential direction are formed at a plurality of positions in the longitudinal direction of the tubular material.

8. The method for expanding a tubular material according to claim 1, wherein: In portions of the tubular material having different thicknesses in the circumferential direction, thickness variation between adjacent portions having different thicknesses in the circumferential direction is linear, whereas thickness variation between mutually non-adjacent portions having different thicknesses is nonlinear.

9. A tubular material component manufactured in a single piece by the tube expansion method according to claim 1.

10. The tubular material member according to claim 9, wherein: The tubular material member includes portions having different outer circumferential lengths.

Images