KR0128119B1 - The device measuring friction charcter for plate - Google Patents

Abstract

The friction property measuring apparatus(100) is comprised of a bead part(10) for forming a bead of a predetermined depth in a test material; a drawing part(20) for drawing the test material in a constant speed, making bending deformation and bending-annealing deformation in the test material; a main body(30) for supporting the bead part(10) and the drawing part(20); a data processing part(40) for processing a fine signal generated when the test material is passed through the bead part(10) and is drawn; a process controlling part(50) for controlling the bead part(10) and the drawing part(20).

Description

Friction property measuring device of plate

1 is a schematic cross-sectional view of a conventional double acting press used in a stamping process.

2 shows an example of an apparatus for measuring frictional characteristics of a sheet according to the present invention, wherein a) is a partial cross-sectional view and b) is a left side view.

Figure 3 is an exploded perspective view of the ruler bead portion of the friction characteristic measuring apparatus according to the present invention.

Figure 4 is an exploded perspective view of the fixed bead portion of the friction characteristic measuring apparatus according to the present invention.

5 is a graph showing the change in drawing force and pressing force according to the drawing distance for the roller bead and the fixed bead.

* Explanation of symbols for the main parts of the drawings

10: bead portion, 11: roller bead portion,

13: fixed bead part, 20: drawing part,

20: drawing part, 21: drawing grip,

24: screw portion, 30: the body,

40: process control, 41: amplifier,

42: A / D converter, 50: data processing unit,

51: solenoid valve, 52: process logic controller

The present invention relates to an apparatus for measuring the friction characteristics of a thin plate widely used as a steel sheet for automobiles.

Usually, in the automobile manufacturing process, a completed panel is manufactured through the stamping process of deforming a board | plate material and creating the required three-dimensional panel. However, since most panel shapes are determined in the first step, drawing mold, it is very important to make a perfect product without molding defects such as breakage and wrinkles in this process. The causes of such molding failure include the mechanical properties and friction characteristics of the material (plate material) as well as the processing conditions of the press die.

A typical stamping process will be described with reference to FIG. 1 showing a stamping process by a double-acting press as follows.

Press molding is carried out by inserting the plate (4) to be molded, the blank holder (1) is lowered to press the outer peripheral portion of the plate (4) with a suitable force and lower the biasing (2) when the outer peripheral portion of the plate (4) is This is achieved by inflow into the interior 5 of the lower die 3.

It is common that the upper surface 6 of the blank holder 1 of the drawing mold for stamping molding of an automobile panel is set with a draw bead 7 having a circular cross section or a square cross section as shown in FIG. The inflow resistance force acting on the plate 4 to pass through this draw bead 7 is the plastic strain and the sheet 4 and draw bead required for the material to repeat the continuous bending and unwinding deformation in the draw bead 7. It is determined by the sum of the frictional forces acting between the surfaces of (7). The magnitude of the inflow resistance in the draw bead 7 plays an important role in preventing the panel from breaking or buckling by adjusting the inflow and tension of the material into the die 5. The magnitude of the inrush resistance in the draw beads depends on the shape of the bead, the thickness of the steel plate and the mechanical properties of the material, the blank holder force and the friction between the plate and the draw bead face. Therefore, when the type, thickness, and processing conditions of the sheet to be formed are determined, the amount of frictional force acting between the sheet and the draw bead surface plays an important role in determining the formability of the sheet. Conventional methods for evaluating the frictional properties of the plates acting during the stamping process include the production of two die sets that reproduce the typical shapes of the draw beads used in the automotive stamping process, and then test them by connecting them to a tensile tester. have. However, this method has the disadvantage of always using a tensile tester and also has the disadvantage of alternately fastening two dies, called fixed beads and roller beads, in measuring the Corom friction coefficient.

The present invention has been proposed in order to improve the disadvantages of the above-described conventional method, it is possible to measure the friction characteristics alone without relying on the tensile tester, and also can be automated to accurately and quickly measure the friction characteristics of the plate An object of the present invention is to provide an apparatus for measuring friction characteristics.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated.

The friction measuring apparatus of the present invention is a bead portion forming a bead of a predetermined depth on the specimen, the draw portion to be drawn while repeating the bending deformation and the bending deformation on the specimen by passing the specimen through the bead, the bead portion and the drawn portion And a process controller for controlling the main body, the bead part, and the drawing part, and a data processing part for processing the minute signals that are drawn when the specimen is drawn through the bead part.

Hereinafter, the present invention will be described in detail by the drawings.

As shown in FIG. 2, the friction measuring apparatus 100 according to the present invention includes a bead portion 10 for forming a bead having a predetermined depth in a specimen, and a specimen at a constant speed while repeating bending deformation and bending deformation in the specimen. A drawer 20 for drawing into the drawer 20, a main body 30 for holding the bead 10 and the drawer 20, and a data processor for processing minute signals that are drawn when the specimen is drawn through the bead 10. 40 and a process control section 50 for controlling the bead section 10 and the drawing section 20.

The bead part 10 consists of a roller bead part 11 and a fixed bead part 13. The roller bead portion 11 has a pair of upper roller beads 113 which are rotatably held at regular intervals as shown in the exploded perspective view of FIG. 3 and a pair of upper roller beads which hold the upper roller beads 113. Retaining body 11, the first upper fixing plate 111 for fixing the upper roller bead holding body 112, the lower roller bead 117 is rotatably maintained facing the roller bead 11 at regular intervals And a first lower fixing plate 115 for holding the lower roller bead 117.

The interval between the roller beads of the pair of upper roller beads 111 is the gap between the upper roller bead 113 and the lower roller bead 117 when the roller bead 11 is in a pressurized state. It should be chosen to be slightly larger than the thickness, to avoid ironing of the specimen as it passes between the roller beads.

The first upper fixing plate 111 is formed with a first upper groove 111a and two first lower grooves 111b, and a roller bead fixing groove 112a is formed in the upper roller bead holder 112. .

The upper roller bead holder 112 is fixed to the first upper fixing plate 111 by being inserted into the lower groove 111b and being processed by a bolt or the like. The roller bead 113 is rotatably fixed to the roller bead fixing groove 112c.

A plurality of roller bearings 114 for supporting the roller beads 113 are embedded in the bearing accommodation part 112b.

The lower roller bead holding groove 115a and the roller bead holding groove 115b are formed in the first lower fixing plate 115, and the lower roller bead holding groove 115a supports the lower roller bead 117. Lower roller bead support 116, a plurality of lower roller bearings 118 positioned below the lower roller bead 117 to support the lower roller bead 117 and a plurality of bearing boxes for receiving the lower roller bearing 118 ( 119) will be placed. In addition, a first guide roller 120 is rotatably provided on the first lower fixing plate 115, and the first guide roller 120 not only guides the specimen but also completely surrounds the radius of the roller bead. To be deformed.

The lower roller support 116 is formed with a protrusion 116a, and the protrusion 116a is fixed to the lower roller support 116 by a bolt or the like in a state where the protrusion 116a is inserted into the roller support fixing groove 115b. The bearing box 119 is also fixed by a bolt or the like.

The first upper and lower fixing plates 111 and 115 are embedded in the upper and lower frames 31 and 32 of the main body 30, respectively, and the first upper fixing plate 111 is the first fixing tool 14a. It is fixed to the upper frame (31a) through.

A first pressure plate 15a is positioned below the first lower fixing plate 115, and a first load cell 16a fixed to the first load cell support 17a is positioned below the first pressure plate 15a. The first load cell support 17a is fixed to the first moving body 18a configured to move up and down by the first cylinder 19a.

The first cylinder 19a is connected to the hydraulic motor 191 by the first hydraulic pressure supply pipe 19a, and is fixed to the cylinder support 34 of the main body 30 by bolts or the like.

As shown in FIG. 4, the fixed bead part 13 includes a pair of upper fixed beads 133 which are fixed at regular intervals, and a pair of upper fixed bead holders for holding the upper fixed beads 133 ( 132), a second upper fixing plate 131 for fixing the upper fixing bead holder 132, a lower fixing bead 137 and the lower fixing bead which are held while facing the upper fixing bead 133 at a predetermined interval. A lower fixed bead holder 135 for holding 137 and a second lower fixed plate 134 for holding the lower fixed bead holder 135 are included.

The interval between the fixed beads of the pair of fixed beads 133 is, when the lower fixed beads 137 are in a pressurized state, the interval between the upper fixed beads 133 and the lower fixed beads 137 is to be tested. It should be chosen so that it is slightly larger than the thickness, so that ironing does not occur in the specimen as it passes between the fixed beads.

A second upper groove 131a and two second lower grooves 131b are formed in the second upper fixing plate 131, and fixed bead fixing grooves 132a are formed in the upper fixing bead holder 132. It is.

The upper fixing bead holder 132 is fixed to the second upper fixing plate 131 by being inserted into the second lower groove 131b and fixed by a bolt or the like. The upper fixing bead 133 is fixed to the fixing bead fixing groove 132a.

A lower fixing bead holding groove 134a and a fixing bead holding body fixing groove 134b are formed in the second lower fixing plate 134, and the lower fixing bead 134a supports a lower fixing bead 137. The fixed bead holder 135 is accommodated and fixed by bolts, and the lower fixed bead support 136 for fixing the lower fixed bead 137 is fixed on the lower fixed bead holder 135.

In addition, the second lower fixing plate 134 is rotatably maintained with a second guide roller 138 to guide the incoming test piece, the second guide roller 138 guides the specimen as well as the specimen bead fixed It completely encloses the radius of the to allow it to deform.

A protrusion 135a is formed at a lower portion of the lower fixed bead holder 135, and the protrusion 135a is inserted into the lower fixed bead holding groove 134a.

The second upper and lower fixing plates 133 and 134 are embedded in the upper, lower frames 31 and 32 of the main body 30, respectively, and the first upper fixing plate 131 is the second fixing member 14b. It is fixed to the upper frame 31 through).

A second pressure plate 15b is positioned below the second lower fixing plate 134, and a second load cell 16b fixed to the second load cell support 17b is positioned below the second pressure plate 15a. The second load cell support 17b is fixed to the second moving body 18b configured to move up and down by the second cylinder 19b.

The second cylinder 19b is connected to the hydraulic motor 191 via the second hydraulic supply pipe 191b, and is fixed to the cylinder support 34 of the main body 30 by bolts or the like.

The drawing part 20 is connected to a drawing grip 21 having a guide 21a, a third load cell 22 for measuring a drawing load, and a crucible part 24 formed to reciprocate. , A connector 23 connecting the third load cell 22 and the screw part 24, a screw guide block 25 and a fixing block 26 for guiding the guide 21a. The guide block 25 is provided with a guide groove 25a for guiding the guide 21a, and the guide 21a has a built-in bearing to minimize the frictional force caused by the guide.

The motor 27 is provided with an inverter 28 for changing the rotational speed of the motor so that the drawing speed of the drawing grip 21 can be set according to the test purpose. The drawing grip 21 has a pin receiving hole 21la for receiving the pin 21c held between the upper and lower blades of the drawing grip, and is configured to impart opening and closing of the drawing grip 21b. Is provided.

The screw guide block 25 and the fixed block 26 are fixed on the bed 36 of the body 30.

The screw portion 24 is preferably covered with a bellows type casing made of rubber or the like so that oil and foreign matter do not fall off.

The first, second and third load cells 16a, 16b, and 22 are configured to measure the pressing force at the time of pressurization and the pulling force at the time of drawing, and any of the first, second and third load cells 16a, 16b, and 22 can be used.

In general, since a load cell is loaded with a load on a load button, the weight is applied to an object that causes distortion, so that distortion occurs in proportion to the weight, and the electrical resistance of the distortion gauge changes according to the amount of distortion. Based on this, the pressing force and the pulling force can be measured.

In the present invention, it is not limited to the above-described load cell as a means for measuring the pressing force and the pulling force, it can be provided with means commonly used in the art.

On the other hand, the rear portion of the main body 30, as shown in Figure 2 (b), the first proximity switch 61 and the second for controlling the upward movement of the first and second cylinders (19a) and (19b) Proximity switches (not shown) are attached.

The data processor 40 is electrically connected to the first, second, and third load cells 16a, 16b, and 22 to receive and amplify the minute signals generated therefrom. A / D converter 42 for converting into a signal and a control terminal 43 for processing a digital signal input from the A / D converter 42 to obtain a friction coefficient.

In addition, the process control unit 50 is respectively installed in the first hydraulic supply pipe 191a and the second hydraulic supply pipe 191b connecting the first and second hydraulic cylinders 19a and 19b to the hydraulic pump 191, respectively. First solenoid valve 51a and second solenoid valve 51b and the A / D converter 42, first proximity switch 61 and second proximity switch, first and second solenoid valves 51a and 51b. ), A hydraulic pump 191 and a process logic controller 52 electrically connected to the inverter 28.

Operation of the process logic controller 52 is initiated by a control terminal 43 electrically connected via an amplifier 41. Hereinafter, a method of measuring friction characteristics using the friction characteristic measurement apparatus of the present invention configured as described above will be described.

In order to measure the friction characteristics according to the present invention, first, the specimen 4 is cut to a certain size in the rolling direction of the coil to completely remove the most magnetic burr on the cut surface, and wipe off the foreign matter and oil on the surface of the specimen 4 and evaluate as necessary. After applying the desired lubricant, one end of the test piece is passed between the lower bead portion 11 and the upper and lower beads of the fixed bead portion l3 to be fixed to the drawing grip 21.

Next, the process logic controller 52 is activated by the start signal of the calculator 43, and the process logic controller 52 raises the signal for operating the hydraulic pump 191 and the first cylinder 19a. Sends a signal for operating the first solenoid valve to the pump 191 and the first solenoid valve 191a to operate the pump 191 and the first solenoid valve 191a to raise the first cylinder 19a, As a result, the lower roller bead 117 is raised to retract the screw portion 24 by a predetermined distance by the operation of the motor 27 while pressing the specimen to draw the specimen at a constant speed.

At this time, when the first cylinder 90a rises above the predetermined height, the first proximity switch 61 is stopped.

Next, by lowering the first roller 19a by operating the first solenoid valve 191a in reverse, the lower roller bead 117 is lowered to release the pressurization state of the roller bead portion 11, and then the lower roller The lower fixed bead 137 is raised in the same manner as the bead 117 is raised, and the screw portion 24 is moved backward by a predetermined distance by the operation of the motor 27 while the specimen 4 is pressed. Draw the specimen at speed. At this time, when the second cylinder 19b rises by a predetermined height or more, it is stopped by the second proximity switch.

On the other hand, the signal for the pressing force measured by the first load cell 16a and the second load cell 16b and the pullout force measured by the third load cell 22 are amplified by the amplifier 41, and then A / A. It is converted into a digital signal by the D converter 42 and input to the control terminal 43. By the monitor, the pressing force acting on each bead according to the drawing distance and the drawing force applied to the drawing grip can be displayed on the x-y coordinate.

In the above, the blow speed change of the specimen is made possible by continuously changing the rotational speed of the motor 27 by an inverter 28 connected to the process logic controller 52.

In addition, the pressing depth of the roller bead and the fixed bead is preferably adjusted by installing a position sensor or the like on the frame, in order to measure the friction coefficient of the plate according to the present invention, the pressing depth of the roller bead and the fixed bead must be the same. do.

The control terminal 43 obtains the Corom friction coefficient (μ) by using the average value of the pressing force and the pulling force according to the input draw distance, which will be described below.

That is, the pulling force acting on the specimen when the specimen 4 passes through the fixed bead portion 13 by the rigidity of the fixed bead portion 13 is continuously passed through the frictional force between the fixed bead surface and the surface of the specimen and the bead. Bending strain--expressed as the sum of plastic strain forces for repeating bending loosening strain.

On the other hand, the pulling force acting on the specimen by the pressurization of the roller bead portion 11 is represented by plastic deformation force only because the friction force between the roller bead surface and the specimen surface is negligible.

Therefore, the frictional force acting on the fixed bead surface is obtained by subtracting the pulling force Td when the roller bead portion acts from the pulling force Tftd when the fixed bead portion acts.

Here, assuming that the contact pressure is uniform across all surfaces of the specimen in contact with the stationary bead, the friction coefficient (μ) is the ratio of the frictional force (Tftd-Td) to the applied force (Nftd) acting on the stationary bead according to the Kurrom friction law. It can be obtained and expressed by these formulas are as follows.

μ = (Tftd- Td) / II Nftd

Hereinafter, the present invention will be described in detail through examples.

Example

45 mm in width and 600 mm in depth were cut in the rolling direction of the deep drawing automotive steel coil having a thickness of 0.8 mm to completely remove the edge burr of the cut surface, and then wipe the foreign matter with alcohol, and then apply lubricant to prepare a specimen.

Normally the panel of the press bead at a speed of about 1000 mm / min is drawn using the friction coefficient measuring device of the present invention made of SKD 11 tool steel having rod and fixed beads of about 610 (Hv 100 g) as a Vickers hardness tester. The Coulomb friction coefficient for the specimen prepared as described above was measured as 9.52 mm, which is twice the average radius of the beads used in the stamping process of 4.76 mm.

At this time, the draw distance-draw load and draw distance-pressurization load curves for the roller beads and the fixed beads measured by the load cell were as shown in FIG. 5, and the Coulomb friction coefficient value measured as described above was 0.152 for this specimen. The experiment was repeated three times and the error of friction coefficient was within ± 0.002.

As described above, in the present invention, the friction test and the drawing force-drawing distance data are input to the computer and automatically processed. Unlike the conventional friction tester, the friction coefficient can be measured alone without being attached to the accreditation tester. In addition, it is effective to provide a friction coefficient measuring device having a very good reproducibility of the test because the error of the friction coefficient in the repeated friction coefficient for the same steel sheet is within ± 0.002.

Claims (4)

Holding the bead portion 10 to form a bead of a predetermined depth on the specimen, the draw portion 20 for drawing the specimen while repeating the bending deformation and the bending loosening deformation on the specimen, the bead portion 10 and the draw portion 20 To control the data processing unit 40 and the bead unit 10 and the draw unit 20 which calculate friction coefficients by processing the fine signals that are generated when the body 30 and the specimen are drawn through the bead unit 10. It includes a process control unit 50, the bead portion 10 is composed of a roller bead portion 11 and a fixed bead portion 13, the roll bead portion 11 is the upper frame 31 of the main body 30 The lower roller bead 117 is maintained rotatably in the upper roller bead 113, the lower frame 32, the upper and lower movements by the first cylinder (19a) and rotational movement in the lower frame (32) And a first load cell 16a positioned below the first pressing plate 15a positioned below the lower roller 11. The fixed bead part 13 has a pair of upper fixed beads 133 held in the upper frame 31 of the main body 30 by the second cylinder 19b in the lower frame 32. It has a lower fixed bead 137 to be maintained and a second load cell 16b to be positioned below the second pressing plate 15b to be held under the lower fixed bead 137, and the drawing portion 20 is a specimen A screw portion 24 for reciprocating by the drawing grip 21 and the motor 27 to be coupled to draw the specimen, and a third load cell 22 installed between the drawing grip 21 and the screw portion 24. The data processor 40 has an amplifier 41 electrically connected to the first, second and third Lloyd cells 16a, 16b, and 22 to receive and amplify minute signals generated therefrom, An A / D converter 42 for converting the amplified signal into a digital signal and a calculator 43 for calculating the coefficient of friction by processing digital sinusoids and The process control unit 50 is installed in the first hydraulic supply pipe 191a and the second hydraulic supply pipe 19b respectively connecting the first and second hydraulic cylinders 19a and 19b to the hydraulic pump 191, respectively. First and second proximity switches for controlling the heights of the first and second solenoid valves 51a and 51b and the A / D converter 42 and the first and second cylinders 19a and 19b. It consists of a process logic controller 52 electrically connected to the solenoid valves 51a and 51b, the hydraulic pump 191 and the motor 27, so that the roller beads and the fixed beads are pressurized and released by the process logic controller. A device for measuring friction characteristics of a plate configured to obtain friction coefficients by drawing specimens by a drawing part while sequentially causing the movement to be performed by measuring the pressing force applied to each bead and the drawing force applied to the drawing grip according to the drawing distance. The apparatus of claim 1, wherein an inverter (28) is provided between the motor (27) and the process logic controller (52). According to claim 1 or 2, wherein the first guide roller 120 and the second guide roller 138 for guiding the specimen is installed in front of the lower roller bead 117 and the lower fixed bead 137 Apparatus for evaluating the friction characteristics of a plate, characterized in that. 4. The screw guide block 25 according to claim 3, wherein the drawing grip 21 has a guide 21a, and the drawing portion 20 has a guide groove 25a for guiding the guide 21a. Apparatus for evaluating the friction characteristics of a plate, characterized in that it further comprises a).