CN106270100A - Hydraulic punching and flanging method and segmented punching and flanging device - Google Patents

Abstract

The invention discloses a kind of hydro piercing method for flanging and sectional type punching flanging device, method for flanging includes: calculate punching and whether flange gap location material ftractures, and whether gap location material height of projection is less than allowing height.If punching hole diameter and flange diameter meet said two condition simultaneously, use Integral hydraulic piercing and flanging；Otherwise, sectional type hydro piercing flange is used.Sectional type punching flanging device includes upper die and lower die, pierce punch, flange block, flange drift.

Description

Hydraulic punching and flanging method and block type punching and flanging device

Technical Field

The invention relates to a pipe fitting hydraulic forming device and a pipe fitting hydraulic forming method, in particular to a hydraulic punching and flanging method and a sectional punching and flanging device.

Background

The hydroforming technology is suitable for producing hollow variable cross-section light components, improves the strength and rigidity of formed parts, saves materials and reduces cost, and therefore, the hydroforming technology has wide application in the fields of aviation, aerospace and automobiles. The hydraulic punching is to synchronously complete punching in a hydraulic forming die by taking the pressure of liquid in a pipe as a lower die, and compared with the punching outside the die, the hydraulic punching can greatly improve the production efficiency and improve the punching position precision. The hydraulic punching flanging is used for simultaneously performing hydraulic punching and flanging for a certain height.

In recent years, as the application field of hydroformed parts is expanded, the connection relationship of the corresponding parts is more complicated. Meanwhile, with the rapid development of light materials such as aluminum alloy, magnesium alloy and the like, a welding method is not applicable any more, connection modes are more and more diversified, and some hydroformed parts need to be flanged for a certain height after being punched so as to be embedded with other parts or be used for machining internal threads for assembly.

For hydraulic punching and flanging, because the diameter of the flanging part of the punch is larger than that of the punching part, in order to avoid the outward protrusion or the cracking of the material at the position of a middle gap under the action of internal pressure, an insert type flanging punch is designed, namely the flanging insert or a nut is nested in the punching punch, and after the punch finishes punching, the flanging is finished through the flanging insert or the nut. However, in the method, the flanging is realized through a smaller R angle of the flanging insert or the nut, the cracking is easy to occur, the flanging height is limited, the flanging insert is pressed into the flanging hole of the forming part and needs to be manually taken out, and the nut is embedded into the flanging hole in the mode, so that the tensile strength and the torsional strength are insufficient. In another method, a blind hole is designed in the center of the punch, a spring is installed inside the blind hole, cracking in the hydraulic bulging process is avoided, internal pressure is continuously increased after hydraulic bulging is finished, punching from inside to outside is achieved, then the punch moves downwards to achieve flanging, but in the mode, high internal pressure is needed in the punching stage, and with the current low-pressure hydraulic forming application, punching from inside to outside is difficult to achieve by equipment.

Disclosure of Invention

The invention aims to provide a hydraulic punching and flanging method and a sectional punching and flanging device, aiming at the problems that hydraulic punching is easy to crack, the flanging height is limited and high internal pressure is required in the prior art.

In order to achieve the purpose, the invention adopts the following technical scheme:

a hydraulic punching and flanging method comprises the following steps: calculating whether the material at the gap between the punching hole and the flanging cracks or not and whether the protruding height of the material at the gap is smaller than the allowable height or not; if the punching diameter and the flanging diameter simultaneously meet two conditions, adopting integrated hydraulic punching and flanging; otherwise, the sectional type hydraulic punching flanging is adopted.

According to an embodiment of the present invention, the method for determining whether cracking occurs is to determine whether:

$\frac{\mathrm{\&pi;}}{4}\&times;(d_1^2-d_2^2)\&times;p_{MAX}<\mathrm{\&eta;}\&times;\mathrm{\&pi;}\&times;(d_1+d_2)\&times;t\&times;{\mathrm{\&sigma;}}_{\mathrm{\&tau;}}$

wherein d1 is the flanging diameter, d2 is the punching diameter, pMAX is the maximum internal pressure in the whole shaping process, η is the coefficient, the value range is 0.65-0.8, and sigma is_τThe shear strength of the material; t is the tube thickness.

According to an embodiment of the present invention, the method for determining whether the height of the material protrusion at the gap is less than the allowable height is to determine whether:

$\frac{p_{MAX}\&times;r}{t}<{\mathrm{\&sigma;}}_s^{\&prime;},$ wherein, ${\left(\frac{d_1-d_2}{4}\right)}^2+{(r-h)}^2=r^2;$

wherein r is the free bulging radius; sigma'_sIs the flow stress of the material at maximum pressure; h is the bulging protrusion height.

According to an embodiment of the invention, the integrated hydraulic punching and flanging method comprises the following steps: the integrated hydraulic punching flanging punch moves downwards to complete punching; the punch continues to move downwards, and the flanging is completed through the arc transition section of the integrated hydraulic punching flanging punch; and (5) retracting the punch to complete punching and flanging.

According to an embodiment of the invention, the method for block type hydraulic punching and flanging comprises the following steps: in the hydraulic bulging process, the arc-shaped section of the flanging punch pin is freely bulged under the action of internal pressure corresponding to the material, but the protrusion height is smaller than an allowable value, and the flanging punch pin is not jacked up under the action of a flanging stop block; in the punching stage, firstly, the punching punch moves downwards, the wedge-shaped sliding block is acted by the sliding block stop block, the compression spring is pressed, and only the punching punch moves downwards to complete punching; the lower end face of the cube at the rear end of the punching punch is contacted with the upper end face of the cube at the rear end of the flanging punch, and the flanging punch is pushed to move downwards to complete flanging; the punching punch retracts, and the wedge-shaped sliding block is embedded into the wedge-shaped groove of the sliding block stop block under the action of the compression spring; and the punching punch continues to retreat, and the wedge-shaped sliding block drives the flanging punch to retreat to the original position.

In order to achieve the purpose, the invention also adopts the following technical scheme:

a block type punching flanging device comprises an upper die, a lower die, a punching punch, a flanging stop block and a flanging punch. The upper die is a concave-shaped component, a punching punch, a flanging stop block and a flanging punch are arranged at a concave position in the middle of the upper die, a groove matched with the upper portion of the lower die is formed in the bottom of the upper die, the lower die is similar to a cuboid, and a groove matched with the bottom of the upper die is formed in the upper portion of the lower die. The flanging stop block is fixed in the upper die, a first through hole is formed in the center of the flanging stop block, the flanging punch is arranged below the flanging stop block and provided with a second through hole, and the first through hole and the second through hole are arranged in an aligned mode. The punching punch is a convex-shaped part, the convex part of the punching punch extends into the second through hole, and the punching punch and the flanging punch are movably arranged in the upper die.

According to one embodiment of the invention, a tubular cavity is formed between the upper die and the lower die, and sealing heads are arranged at two ends of the tubular cavity.

According to one embodiment of the invention, a wedge-shaped slide block is arranged between the punching punch and the flanging stop, and the wedge-shaped slide block is connected with the punching punch through a compression spring.

According to one embodiment of the invention, the punching surface of the flanging punch comprises a plane part and an arc part.

In the technical scheme, the hydraulic punching and flanging method and the sectional punching and flanging device can solve the problems that hydraulic punching is easy to crack, the flanging height is limited, and high internal pressure is required.

Drawings

FIG. 1 is a top view of an integrated hydraulic punching flanging punch;

FIG. 2 is a sectional view of an integrated hydraulic punching and flanging punch A-A;

FIG. 3 is a partial enlarged view of the integrated hydraulic punching flanging punch;

FIG. 4 is a schematic view of a bulging protrusion of a material in a punching and flanging gap;

FIG. 5 is a top view of a block type hydraulic punching flanging punch;

FIG. 6 is a sectional view of a block type hydraulic punching flanging punch B-B;

FIG. 7 is a sectional view of a block type hydraulic piercing and flanging punch C-C;

FIG. 8 is a partial enlarged sectional view of a segmented hydraulic piercing and flanging punch C-C;

FIG. 9 is a partial enlarged view of the bulging protrusion of the segmented hydraulic punch flanging punch.

Detailed Description

The technical scheme of the invention is further explained by combining the drawings and the embodiment.

The invention firstly discloses a hydraulic punching and flanging method which comprises a judging step and a selecting step. The judging step is as follows: and calculating whether the material at the gap between the punching hole and the flanging cracks or not, and whether the protruding height of the material at the gap is smaller than the allowable height or not. The selection steps are as follows: if the punching diameter and the flanging diameter simultaneously meet two conditions, adopting integrated hydraulic punching and flanging; otherwise, the sectional type hydraulic punching flanging is adopted.

At the hydraulic bulging in-process, intraductal maximum pressure takes place at plastic transition fillet stage, or the stage of punching a hole, guarantees to push down at this process is the biggest, and clearance department material can not take place to cut the fracture and arouse the failure of taking shape, and clearance material shear fracture is equivalent to from inside to outside towards the annular hole, needs to satisfy:

$\frac{\mathrm{\&pi;}}{4}\&times;(d_1^2-d_2^2)\&times;p_{MAX}<\mathrm{\&eta;}\&times;\mathrm{\&pi;}\&times;(d_1+d_2)\&times;t\&times;{\mathrm{\&sigma;}}_{\mathrm{\&tau;}}$

where d1 is the cuff diameter,

d2 is the punch diameter;

pMAX is the maximum internal pressure in the whole shaping process;

eta is coefficient, generally 0.65-0.8;

σ_τthe shear strength of the material;

t is the thickness of the tube 1.

Secondly, need guarantee under the biggest interior pressure, the protruding height of bulging is less than the allowable height takes place for the material of clearance department, can not take place the bulging fracture, and follow-up turn-ups can expand the arch, guarantees turn-ups face quality, and material free bulging in this annular gap is equivalent to under the biggest interior pressure, needs to satisfy:

$\frac{p_{MAX}\&times;r}{t}<{\mathrm{\&sigma;}}_s^{\&prime;},$ in which, as shown in figure 4, ${\left(\frac{d_1-d_2}{4}\right)}^2+{(r-h)}^2=r^2$

wherein r is the free bulging radius;

σ′_sthe average value of the yield strength and the tensile strength can be adopted to simplify the calculation for the flow stress of the material under the maximum pressure, and the bulging cracking is avoided because the average value is less than the tensile strength;

h is the height of the bulging protrusion, and in order to enable the subsequent flanging protrusion to be expandable and ensure the quality of the flanging surface, the allowable height of the protrusion can be an empirical value of 2 t.

When the punching diameter and the flanging diameter meet the two conditions of the judging step, an integrated hydraulic punching and flanging punch 5 is designed, as shown in figures 1-5. In the hydraulic bulging process, the material in the gap between the punched hole and the flanging is bulged, as shown in figure 4, but shear cracking and bulging cracking do not occur, and the height h of the bulge is less than 2 times of the wall thickness. In the hydraulic punching process, the integrated hydraulic punching flanging punch 5 moves downwards to complete punching firstly, the punch continues to move downwards, flanging is completed through the circular arc transition section 52 of the integrated hydraulic punching flanging punch 5, and then the punch returns to complete punching flanging.

When the punching diameter and the flanging diameter do not meet the conditions of the judging step, a sectional type hydraulic punching and flanging punch 5 is adopted, and as shown in fig. 6, 7, 8 and 9, the method specifically comprises the following steps:

in the hydraulic bulging process, the arc-shaped section of the flanging punch 5 is freely bulged under the action of internal pressure corresponding to the material, but the projection height is smaller than an allowable value, and the flanging punch 5 is not jacked up under the action of a flanging stop block 7;

in the punching stage, firstly, the punching punch 6 descends, the wedge-shaped sliding block 9 is acted by the sliding block stop block 10, the compression spring 8 is pressed, and only the punching punch 6 moves downwards to complete punching;

the lower end face of the cube at the rear end of the punching punch 6 is contacted with the upper end face of the cube at the rear end of the flanging punch 5, and the flanging punch 5 is pushed to move downwards to complete flanging;

the punching punch 6 retracts, and the wedge-shaped slide block 9 is embedded into the wedge-shaped groove of the slide block stop block 10 under the action of the compression spring 8;

the punching punch 6 continues to retreat, and the wedge-shaped sliding block 9 drives the flanging punch 5 to retreat to the original position.

In addition, the invention also discloses a block type punching flanging device adopted in the method, which mainly comprises an upper die 2, a lower die 3, a punching punch 6, a flanging stop 7, a flanging punch 5 and the like.

The upper die 2 is a concave-shaped component, a punching punch 6, a flanging stop dog 7 and a flanging punch 5 are arranged at a concave position in the middle of the upper die 2, and a groove matched with the upper part of the lower die 3 is formed in the bottom of the upper die 2. The lower die 3 is similar to a cuboid, and the upper part of the lower die is provided with a groove matched with the bottom of the upper die 2. The upper die 2 and the lower die 3 where the punch is located are correspondingly grooved, a tubular cavity is formed between the upper die 2 and the lower die 3, and sealing heads 4 are arranged at two ends of the tubular cavity.

The flanging stop 7 is fixed in the upper die 2, and a first through hole is formed in the center of the flanging stop for controlling the retraction height of the flanging punch 5 and preventing the flanging punch 5 from being jacked up in the bulging process.

The flanging punch 5 is arranged below the flanging stop 7 and is provided with a second through hole, and the first through hole and the second through hole are arranged in alignment. And (3) processing or assembling a cube at the rear end of the flanging punch 5, keeping a distance between the upper end surface of the cube and the lower end surface of the cube at the rear end of the punching punch 6, and pushing the flanging punch 5 to downwards move to realize flanging after the punching punch 6 downwards moves for the distance.

The punching punch 6 is a convex-shaped component, the convex part of the punching punch 6 extends into the second through hole, and the punching punch 6 and the flanging punch 5 are movably arranged in the upper die 2. Specifically, the rear end of the punching punch 6 is machined or assembled with a cube, and rectangular grooves are machined in both side end faces of the cube. A wedge-shaped sliding block 9 is arranged between the punching punch 6 and the flanging stop dog 7, and the wedge-shaped sliding block 9 is connected with the punching punch 6 through a compression spring 8.

The punching surface of the flanging punch 5 comprises a plane part and an arc part. The width of the arc-shaped part is as large as possible to ensure the flanging quality, the minimum width of the plane part is obtained by calculating the maximum gap distance that the pipe fitting 1 is not cracked, and the height of the bulge is smaller than an allowable value.

The minimum width of the plane part of the flanging punch 5 is calculated according to the following formula, and firstly, in order to ensure that the material at the corresponding gap of the arc part cannot be sheared and cracked to cause forming failure under the maximum internal pressure in the bulging process, the requirements are met:

$\frac{\mathrm{\&pi;}}{4}\&times;\&lsqb;d_1^2-{(d_2+l)}^2\&rsqb;\&times;p_{MAX}<\mathrm{\&eta;}\&times;\mathrm{\&pi;}\&times;(d_1+d_2+l)\&times;t\&times;{\mathrm{\&sigma;}}_{\mathrm{\&tau;}}$

where d1 is the cuff diameter,

d2 is the punch diameter;

l is the width of the plane part of the flanging punch 5;

pMAX is the maximum internal pressure in the whole shaping process;

eta is coefficient, generally 0.65-0.8;

σ_τthe shear strength of the material;

t is the thickness of the tube 1.

Secondly, need to guarantee under the biggest interior pressure, the protruding height of bulging is less than the height of allowwing for the material emergence bulge in the corresponding clearance department of arc part, needs to satisfy:

$\frac{p_{MAX}\&times;r}{t}<{\mathrm{\&sigma;}}_s^{\&prime;},$ in which, as shown in figure 5, ${\left(\frac{d_1-d_2-2l}{4}\right)}^2+{(r-h)}^2=r^2$

wherein r is the free bulging radius;

l is the width of the plane part of the flanging punch 5;

σ′_sthe average value of the yield strength and the tensile strength can be adopted to simplify the calculation for the flow stress of the material under the maximum pressure, and the bulging cracking is avoided because the average value is less than the tensile strength;

h is the height of the bulging protrusion, and in order to enable the subsequent flanging protrusion to be expandable and ensure the quality of the flanging surface, the allowable height of the protrusion can be an empirical value of 2 t.

The above solution is further illustrated below by 2 examples:

examples 1

Assuming that the material of the pipe fitting 1 is DC03, the wall thickness is 2.5mm, the punching diameter is 6mm, the flanging diameter is 12mm, the maximum internal pressure in the hydraulic bulging process is 150MPa, sigma_sTaking 200MPa, sigma_bTaking 305MPa and plastic material sigma_τApproximately 0.6 sigma_b。

And calculating to meet the conditions of the first step and the second step, and adopting an integrated punch.

Examples 2

Assuming that the material of the pipe fitting 1 is 6061-T4 and the wall thickness is 1.5mm, punchingThe diameter of the flange is 9mm, the diameter of the flange is 18mm, and the maximum internal pressure in the hydraulic bulging process is 150MPa, sigma_sTaking 164MPa, sigma_bTaking 277MPa, plastic material sigma_τApproximately 0.6 sigma_b。

And (4) calculating that the conditions of the step one and the step two are not met, and adopting a sectional type punching and flanging punch 5.

The minimum width l of the plane part of the flanging punch 5 is calculated according to the following formula, and firstly, in order to ensure that the material at the position of the corresponding gap of the arc part cannot be sheared and cracked to cause forming failure under the maximum internal pressure in the bulging process, the requirements are met:

$\frac{\mathrm{\&pi;}}{4}\&times;\&lsqb;d_1^2-{(d_2+l)}^2\&rsqb;\&times;p_{MAX}<\mathrm{\&eta;}\&times;\mathrm{\&pi;}\&times;(d_1+d_2+l)\&times;t\&times;{\mathrm{\&sigma;}}_{\mathrm{\&tau;}}$

calculated that l is more than or equal to 2.34mm

Secondly, need to guarantee under the biggest interior pressure, the protruding height of bulging is less than the height of allowwing for the material emergence bulge in the corresponding clearance department of arc part, needs to satisfy:

$\frac{p_{MAX}\&times;r}{t}<{\mathrm{\&sigma;}}_s^{\&prime;},$ in which, as shown in figure 4, ${\left(\frac{d_1-d_2-2l}{4}\right)}^2+{(r-h)}^2=r^2$

calculated that l is more than or equal to 0.385mm

The width of the planar section 51 of the pierce-and-flange punch 5 is taken to be 2.34 mm.

It should be understood by those skilled in the art that the above embodiments are only for illustrating the present invention and are not to be used as a limitation of the present invention, and that changes and modifications to the above described embodiments are within the scope of the claims of the present invention as long as they are within the spirit and scope of the present invention.

Claims (9)

1. A hydraulic punching and flanging method is characterized by comprising the following steps:

calculating whether the material at the gap between the punching hole and the flanging cracks or not and whether the protruding height of the material at the gap is smaller than the allowable height or not;

if the punching diameter and the flanging diameter simultaneously meet the two conditions, adopting integrated hydraulic punching and flanging; otherwise, the sectional type hydraulic punching flanging is adopted.

2. The hydraulic punching and flanging method according to claim 1, wherein the method for judging whether cracking occurs is as follows:

judging whether the following conditions are met:

$\frac{\mathrm{\&pi;}}{4}\&times;(d_1^2-d_2^2)\&times;p_{MAX}<\mathrm{\&eta;}\&times;\mathrm{\&pi;}\&times;(d_1+d_2)\&times;t\&times;{\mathrm{\&sigma;}}_{\mathrm{\&tau;}}$

wherein d1 is the cuff diameter,

d2 is the punch diameter;

pMAX is the maximum internal pressure in the whole shaping process;

eta is a coefficient, and the value range is 0.65-0.8;

σ_τthe shear strength of the material;

t is the tube thickness.

3. The hydraulic punching and flanging method of claim 1, wherein the method for judging whether the height of the material bulge at the gap is less than the allowable height comprises the following steps:

judging whether the following conditions are met:

$\frac{p_{MAX}\&times;r}{t}<{\mathrm{\&sigma;}}_s^{\&prime;},$ wherein, ${\left(\frac{d_1-d_2}{4}\right)}^2+{(r-h)}^2=r^2;$

wherein r is the free bulging radius;

σ_s' is the flow stress of the material at maximum pressure;

h is the bulging protrusion height.

4. The hydraulic punching and flanging method according to claim 1, wherein the integrated hydraulic punching and flanging method comprises the following steps:

the integrated hydraulic punching flanging punch moves downwards to complete punching;

the punch continues to move downwards, and the flanging is completed through the arc transition section of the integrated hydraulic punching flanging punch;

and (5) retracting the punch to complete punching and flanging.

5. The hydraulic punching and flanging method according to claim 1, wherein the method for the block-type hydraulic punching and flanging comprises the following steps:

in the hydraulic bulging process, the arc-shaped section of the flanging punch pin is freely bulged under the action of internal pressure corresponding to the material, but the protrusion height is smaller than an allowable value, and the flanging punch pin is not jacked up under the action of a flanging stop block;

in the punching stage, firstly, the punching punch moves downwards, the wedge-shaped sliding block is acted by the sliding block stop block, the compression spring is pressed, and only the punching punch moves downwards to complete punching;

the lower end face of the cube at the rear end of the punching punch is contacted with the upper end face of the cube at the rear end of the flanging punch, and the flanging punch is pushed to move downwards to complete flanging;

the punching punch retracts, and the wedge-shaped sliding block is embedded into the wedge-shaped groove of the sliding block stop block under the action of the compression spring;

and the punching punch continues to retreat, and the wedge-shaped sliding block drives the flanging punch to retreat to the original position.

6. The utility model provides a sectional type flanging device that punches a hole which characterized in that includes:

the device comprises an upper die, a lower die, a punching punch, a flanging stop block and a flanging punch;

the upper die is a concave-shaped component, the punching punch, the flanging stop block and the flanging punch are arranged at the concave position in the middle of the upper die, and the bottom of the upper die is provided with a groove matched with the upper part of the lower die;

the lower die is similar to a cuboid, and the upper part of the lower die is provided with a groove matched with the bottom of the upper die;

the flanging stop block is fixed in the upper die, and a first through hole is formed in the center of the flanging stop block;

the flanging punch is arranged below the flanging stop block and provided with a second through hole, and the first through hole and the second through hole are arranged in alignment;

the punching punch is a convex-shaped part, the convex part of the punching punch extends into the second through hole, and the punching punch and the flanging punch are movably arranged in the upper die.

7. The apparatus of claim 6, wherein a tubular cavity is formed between the upper and lower dies, and sealing heads are provided at both ends of the tubular cavity.

8. The apparatus of claim 6, wherein a wedge-shaped slider is disposed between the punch and the flanging stop, and the wedge-shaped slider is connected to the punch via a compression spring.

9. The segmented punch flanging device of claim 6 wherein the punch face of said flanging punch includes a planar portion and an arcuate portion.