KR100558784B1 - Method for measuring tube hydroforming property - Google Patents

Abstract

The present invention is a device for measuring tube hydroformability (Tube Hydroformability) and a method for measuring the same, in the process of measuring the tube hydroformability while the middle portion of the tube is inflated to prevent the end of the tube flowing in the direction of the middle portion It is an object of the present invention to provide an apparatus and a measuring method thereof capable of measuring accurate tube hydroforming properties.

According to the present invention, molds 1HL having semicircular grooves 11 formed on the opposite ends of the tube 3 to face the tube 3 are positioned up and down at both ends of the tube 3 so as to clamp both ends of the tube 3. Hydro with 1HR, 1LL, 1LR, and punches 4L, 4R which move toward both ends of the tube 3 to seal both ends and inject fluid into the interior of the tube 3 through a hollow formed therein. In the formability measuring apparatus, the dies 10HL, 10HR, 10LL, 10LR chamfered 13 along the outer edge of the semicircular groove 11 corresponding to both ends of the tube 3, and the ends of the tube 3, respectively. A hydroformability measuring apparatus is provided that includes punches 20L and 20R chamfered 23 along an edge of a cross section toward.

Description

Tube hydroformability measurement method

1 is a schematic diagram showing a general hydroforming process sequence,

Figure 2 is a photograph showing the failure of the tube occurred when performing the hydroforming process,

Figure 3 is a photograph showing the buckling failure of the tube generated when performing the hydroforming process,

Figure 4 is a schematic diagram showing a free bulging test process for measuring the hydroforming property according to the prior art,

5 is a perspective view of a hydroformability measuring apparatus according to an embodiment of the present invention,

Figure 6 is a schematic diagram showing a free bulging test process using the hydroformability measuring apparatus shown in FIG.

       ♠ Explanation of symbols on the main parts of the drawing ♠

Mold: 1H, 1L, 1HL, 1HR, 1LL, 1LR, 10HL, 10HR, 10LL, 10LR

3: Tube 4L, 4R, 20L, 20R: Punch

13, 23: Chamfer 40L, 40R: Hydraulic system

The present invention relates to a device for measuring tube hydroformability (Tube Hydroformability) and a method of measuring the same, in particular, in the measurement of tube hydroforming properties through free bulging test, while the middle of the tube inflates both ends of the tube The present invention relates to an apparatus and a method for measuring the same, which can prevent the inflow into the intermediate portion and accurately measure the hydrophobicity of the tube.

At present, due to the social demand for weight reduction of the automobile body, the use of new parts processing methods that can sufficiently maintain the required strength while reducing the weight of the vehicle parts are emerging in automobile production.

Among these new processing methods, tube hydroforming technology has been developed. This tube hydroforming has many advantages such as reduced production cost, increased strength, and lighter parts. It is applied to many automobile parts production.

In the drawings, Figure 1 is a schematic diagram showing a general hydroforming process sequence, Figure 2 is a photograph showing the failure of the tube generated when performing the hydroforming process, Figure 3 is a buckling defect of the tube generated when performing the hydroforming process 4 is a schematic view showing a process of performing a hydroforming process of a T-shaped component.

As shown in FIG. 1, the tube hydroforming process is performed by placing the cylindrical tube 3 before molding in the upper and lower molds 1H and 1L in which the cavity 5 is formed, and closing the upper and lower molds 1H and 1L. Both ends of the tube 3 are sealed using punches 4L and 4R. Then, when a fluid is injected into the tube 3 to apply a high pressure, the tube 3 is inflated to the same shape as the cavity 5 formed in the upper and lower molds 1H and 1L, and the same as the cavity 5. A tube 3 having a shape is molded. At this time, both ends of the tube 3 are sealed by the punches 4L and 4R, and the hydraulic pressure is developed to act on the inner circumferential surface of the tube 3, and the punch is changed according to the pressure applied inside the tube 3. Adjust the length at which 4L and 4R are fed in the longitudinal direction of the tube 3.

At this time, the internal pressure of the tube 3 and the feeding length should be properly maintained, but the bursting of the tube 3 as shown in FIG. 2 or the buckling of the tube 3 as shown in FIG. Can be prevented.

On the other hand, it is very important to evaluate the hydroforming property of the tube because the material in the tube hydroforming process uses a tube formed by the plate, not the plate state. The reason is that when the sheet is tubed, it is work hardened to have molding properties that are completely different from those of the original sheet. In addition, in the tube hydroforming process, the tube is not formed by a punch or the like, but the fluid is injected into the tube and molded by hydraulic pressure. Thus, in the conventional method of evaluating the formability of a plate, the tube has a hydroforming property. It should not be evaluated, and moldability should be evaluated under similar conditions to hydroforming processes.

Considering these various conditions, the free bulging test was developed to measure tube hydroforming properties.

As shown in FIG. 4, the free bulging test seals both ends of the tube 3 with a sealing device, and then increases the pressure inside the tube 3 until a burst occurs in the middle of the tube 3. Then, after the burst occurs by the internal pressure, the hydroforming property of the tube 3 is measured by comparing the maximum circumferential length of the tube 3 with the circumferential length of the initial tube 3. In this free bulging test, the middle part of the tube 3 is inflated during the test process, and both ends of the tube 3 enter the middle part.

In this way, the inflow into the axial direction of the tube 3 generated during the free bulging test is influenced by the gap between the tube 3 and the molds 1HL, 1LL, 1HR, 1LR, surface characteristics, and the like. Eventually, the experimental data of the hydroforming property differ depending on the amount of material flowing in the axial direction during the test.

Table 1 below shows the results of the free bulging test, and it can be seen that the hydroforming property is better as the inflow of the tube end increases for the same tube. As described above, the amount of material flowing in the axial direction during the test is influenced by external factors of the material tube, and since this affects the test result, the conventional free bulging test measures the exact hydroforming property of the tube. There is a disadvantage that it is difficult.

In addition, since the inner diameter of the tubes having the same outer diameter is different depending on the tube thickness, a sealing punch having a different diameter must be provided. Therefore, there is a disadvantage in that various sealing punches should be provided according to tubes having different inner diameters.

The present invention is provided to solve the problems of the prior art as described above, in the case of free bulging test to block the inflow of both ends of the tube to the middle part to improve the repeatability and accuracy of the measurement results, and also has the same outer diameter SUMMARY OF THE INVENTION An object of the present invention is to provide a tube hydroforming property measuring apparatus capable of measuring the hydroforming property of tubes having different inner diameters according to thickness, and a measuring method thereof.

According to the present invention for achieving the object as described above, the mold is formed with a semi-circular groove so as to surround the tube on the upper and lower sides and the upper and lower facing portions of the tube to clamp both ends of the tube and the tube, A hydroforming measuring apparatus having a punch for injecting a fluid into the tube through a hollow formed therein, which moves toward both ends of the tube and closes both ends, the outer side of the semicircular groove corresponding to both ends of the tube. A hydroformability measuring apparatus is provided that includes a mold chamfered along an edge and a punch chamfered along an edge of a section towards the end of the tube.

In addition, according to the present invention, the hydroformability is measured by fixing both ends of the tube with a mold and injecting fluid into the inside of the tube to compare the maximum circumferential length after the middle part of the tube expands and bursts with the circumferential length of the initial tube. The method of claim 1, further comprising: inserting punches at both ends of the fixed tube to expand the inner diameter at both ends of the tube, and pressing the punch at both ends of the expanded tube to fix the mold and the punch. And a step of injecting fluid into the inside of the tube, and measuring the difference between the circumferential length of the largest expanded portion of the tube and the circumferential length of the first tube when the intermediate portion of the tube is blown by hydraulic pressure. Provided is a method of measuring friction characteristics of a hydroforming tube comprising.

In the following, with reference to the accompanying drawings, preferred embodiments of the tube hydroformability measuring apparatus and measuring method according to the present invention will be described in detail.

5 is a perspective view of a hydroformability measuring apparatus according to an embodiment of the present invention, Figure 6 is a schematic diagram showing a free bulging test process using the hydroformability measuring apparatus shown in FIG.

As shown in FIG. 5, the tube hydroforming measuring apparatus includes upper molds 10HL and 10HR and lower molds 10LL and 10LR that wrap and clamp both ends of the tube 3. The upper and lower molds 10HL, 10HR, 10LL, and 10LR have left upper and lower molds 10HL and 10LL and right upper and lower molds 10HR and 10LR spaced at intervals of the length of the tube 3, and the upper and lower molds 10HL and 10LR. 10HL and 10LL and the right upper and lower molds 10HR and 10LR are positioned to correspond to each other, and semicircular grooves 11 are formed on the opposite surfaces to surround the tube 3.

Then, a bracket 30 supporting punches 20L and 20R is formed outside the left and right upper and lower molds 10HL, 10HR, 10LL, and 10LR, and the punches 20L and 20R penetrate the bracket 30. It is located toward both ends of the clamped tube (3). In addition, the hydraulic systems 40L and 40R for transferring the punches 20L and 20R are provided at the outside of the two brackets 30, respectively.

In such punches 20L and 20R, hollows 21 are formed therein along the lengths of the punches 20L and 20R, and in the state in which the punches 20L and 20R are in contact with both ends of the tube 3, the hollows 21 The fluid is injected into the tube 3 through).

On the other hand, as shown in Fig. 6, the end faces of the punches 20L and 20R, that is, the end faces of the punches 20L and 20R facing the end of the tube 3, are chamfered 23 along the edge thereof, so that a predetermined slope In the semicircular groove 11 formed in the left and right upper and lower molds 10HL, 10HR, 10LL, and 10LR to clamp the tube 3, the outer side of the semicircular groove 11, that is, the punches 20L and 20R Is chamfered (13) along the outer edge facing ().

The operation relationship of the tube hydroformability measuring apparatus configured as described above will be described in detail.

Therefore, with the tube 3 seated in the semicircular groove 11 of the lower molds 10LL and 10LR and the upper molds 10HL and 10HR moved downward to clamp the tube 3, the hydraulic system 40L, The stroke of 40R extends so that the punches 20L and 20R move in the end direction of the tube 3. Then, the ends of the punches 20L and 20R are inserted into the ends of the tube 3, and in this state, when the punches 20L and 20R continue to move in the middle direction of the tube 3, the ends of the tubes 3 expand. Then, it is bitten and fixed between the chamfer 13 site | part of mold 10HL, 10HR, 10LL, and 10LR, and the chamfer 23 site | part of punch 20L, 20R.

In this state, if the fluid continues to be injected into the inside of the tube 3 through the hollows 21 of the punches 20L and 20R, the middle portion of the tube 3 is inflated by hydraulic pressure. An intermediate portion of 3) occurs between the left upper and lower molds 10HL and 10LL and the right upper and lower molds 10HR and 10LR. In addition, since the both ends of the tube 3 are sealed by the punch 20L, 20R, it does not leak.

In addition, even if the intermediate portion of the tube 3 is inflated, both ends of the tube 3 are fixed between the punches 20L and 20R and the molds 10HL, 10HR, 10LL, and 10LR, so that the end of the tube 3 is fixed. It can block the flow into the middle part.

As such, when the fluid is continuously injected into the tube 3, the middle part of the tube 3 eventually floats, where the maximum outer circumference of the inflated tube 3 and the initial tube 3 for free bulging test The hydroformability of the tube 3 is measured by measuring the difference in the outer circumferential length.

A method for measuring tube hydroforming properties configured as described above will be described in detail.

In order to measure the hydroformability of the tube 3, first, the tube 3 is cut to a certain length, the burrs formed on the cut surface are completely removed, and foreign substances in the tube 3 are removed. Then, the tube 3 is seated in the semicircular groove 11 formed in the left and right lower molds 10LL and 10LR. Next, the upper molds 10HL and 10HR are lowered to clamp the tube 3 located between the upper and lower molds 10HL, 10HR, 10LL and 10LR. Then, the punches 20L and 20R respectively positioned at both ends of the tube 3 are moved in the tube direction to extend both ends of the tube 3. The edges of both ends of the tube 3 thus expanded are clamped between the left and right upper and lower molds 10HL, 10HR, 10LL and 10LR and the punches 20L and 20R.

Then, the fluid is injected into the tube 3 through the hollows 21 of the punches 20L and 20R. As such, when the fluid is continuously injected, the middle part of the tube 3 is inflated by hydraulic pressure, and eventually bursts. The hydraulic systems 40L and 40R are then retracted to retreat the punches 20L and 20R, and the upper molds 10HL and 10HR are moved upward to remove the popped tube 3 from the lower molds 10LL and 10LR.

Then, the circumferential length of the largest expanded portion of the tube 3 is measured, and this is compared with the circumferential length of the initial tube 3 to calculate the expansion ratio, which is expressed as the hydroforming property of the tube.

Below, the hydroforming property was measured using the above-described tube hydroforming property measuring apparatus of the present invention.

Cut a tube with a diameter of 50.8 mm and a thickness of 3.2 mm to a length of 300 mm to remove burrs on the cut surface, prepare a tube specimen by removing foreign matter inside the tube, and then place the tube specimen on the lower left and right molds.

The initial test pressure was set to 200 Bar and the final pressure to 1000 Bar, and fluid was injected into the tube specimen. At this time, the pressure was changed linearly with time to measure the hydroforming property of the tube.

The test was repeated three times on the same tube specimen. The maximum tube length of the tube was 203.9 mm, and the tube diameter of 50.8 mm was 127.8%. At this time, the repetition error was within ± 0.005.

As a result of measuring the length of the tube before and after the test, it was confirmed that the end of the tube did not flow into the middle part while the middle part of the tube was inflated.

As described in detail above, the tube hydroforming property measuring apparatus and the measuring method of the present invention can improve the accuracy of the hydroforming properties by measuring both ends of the tube does not flow into the middle part in the process of inflating the middle part of the tube. There is an advantage.

In addition, the tube hydroforming property measuring apparatus and the measuring method of the present invention is economical because the hydroformability measurement can be performed with the same punch even if the thickness of the tube having the same outer diameter is different, even if the inner diameter is different, the measurement time There is an advantage that can be reduced.

Although the technical idea of the apparatus for measuring the tube hydroforming property and the measuring method of the present invention has been described with reference to the accompanying drawings, this is illustrative of the best embodiment of the present invention and is not intended to limit the present invention. In addition, it is obvious that any person skilled in the art can make various modifications and imitations without departing from the scope of the technical idea of the present invention.

Claims (2)

delete In the tube hydroformability measuring method of injecting a fluid into the tube to compare the maximum circumferential length of the tube and the maximum circumferential length after the middle portion of the tube is expanded and burst, A first step of respectively fixing the tubes at both ends up and down with a plurality of molds chamfered along outer edges at both ends of the semicircular grooves surrounding the tube; A second step of inserting punches having chamfered edges at both ends of the tube to expand inner diameters at both ends of the tube; A third step of tightly fixing the tube between the mold and the punch while pressing the punches on both ends of the expanded tube; A fourth step of injecting fluid into the tube through the hollow formed in the punch; And And a fifth step of measuring and comparing the difference between the circumferential length of the largest tube and the circumferential length of the first tube after the middle portion of the tube is blown off by hydraulic pressure.

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