KR101654164B1 - Test apparatus and method of tension compression specimen during electricity pulsing - Google Patents

Abstract

The present invention relates to a method and apparatus for applying a current pulse for reducing a springback occurring in a press forming process using a material such as a high strength steel plate or a lightweight plate such as aluminum or magnesium, And more particularly, to a tensile compression test apparatus for a specimen-
The tubing specimen tensile compression test apparatus includes a pair of grip portions for pressing both ends of the specimen together with a power terminal; A power supply line including a power supply line for supplying a power supply pulse to the power supply terminal and the power supply terminal; And a pair of holder portions on which the grip portions, respectively, which are held on one side of the specimen, are provided to provide tension or compressive force to the specimen,
It is possible to precisely measure the characteristic of each material in which the stress caused by the springback phenomenon caused by the pressing of the material is reduced by the current pulse by providing the uniaxial tensile force or compressive force, So that the springback can be effectively reduced.

Description

TECHNICAL FIELD [0001] The present invention relates to a tensile compression test apparatus,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a specimen testing apparatus for press forming, and more particularly, to a specimen testing apparatus for press molding, The present invention relates to an apparatus for testing tensile compression test of a specimen and a method for testing the tensile compression characteristics of each specimen using an applied current pulse.

Generally, press processing refers to a processing technique for producing a molded product having a desired shape by applying pressure to a material such as a high-strength steel plate or a lightweight plate using a metal mold.

Such press processing is very effective in that a product can be easily produced by pressing a plate material by using a press apparatus, and mass production of the product is enabled.

However, due to the fundamental problem of not completely eliminating the elasticity of the material, an elastic restoring action, such as generating an angle change by bending the elasticity of the corner at the time of press working, bending the wall portion of the part, Thereby increasing the defect rate of the product.

Accordingly, a 'springback measuring device' of Korean Patent No. 10-0815739 is a device in which a groove is formed in an upper mold member for press working and a projecting bead is formed at a position corresponding to a groove in a lower mold member in which a molding groove is formed, The upper mold member and the lower mold member are prevented from moving by the protruding beads and the grooves during press working using the pressing member, so that the uniform springback phenomenon is always generated so that the spring back can be accurately measured to suppress the occurrence of spring back during press working .

In addition, Korean Patent No. 10-1074976 entitled " Compression and Tensile Strength Measuring Apparatus " describes a technique for measuring various loads by height by forming a support bar for supporting an actuator and a load cell into a plurality of stacked space blocks .

In addition, Korean Patent No. 10-1368108 discloses a method of calculating molding data of a molded product by calculating the molding data of a molded product by using a computer-determinable recording medium in which a springback cause analysis method, a springback cause analysis device, And decomposes the bending moment components and generates independent decomposition forming data before the calculation. After calculation, the independent decomposition forming data is generated to analyze the two spring back shapes, and the stress of each of the areas calculated from the respective spring back shapes A technique for analyzing the cause of springback by analyzing and displaying the degree of influence on springback strain is disclosed.

In the "press forming analysis method" of Korean Patent Laid-Open Publication No. 10-2013-0129457, the shape and residual stress distribution data of the press-molded product before the release molding are calculated, and based on the data before the mold release, And the residual stress distribution of the press-molded article after the mold release is calculated. The residual stress distribution of the press-molded article in the local coordinate system is calculated by the coordinate transformation. At the same time, The shape data of the press-molded product after the mold release is calculated and the springback effective stress distribution in the entire coordinate system is calculated by the coordinate transformation from the difference of the stress distribution before and after the mold release to the springback effective stress, To calculate the shape data of the subsequent press-molded object, And calculating the difference between the image data to determine the degree of influence on the overall shape of the analysis target area discloses a technique which allows to interpret the springback phenomenon.

 That is, the above-described conventional techniques are limited to analyzing the springback using the shape change after occurrence of the springback phenomenon.

However, in order to reduce the springback occurring in the development of light-weight plate products such as high-strength steel plates and aluminum or magnesium, a technique of applying current pulses during molding or at the final stage of molding is under development. Therefore, in order to evaluate the springback reduction characteristics when a current pulse of a material is applied, a device capable of evaluating the tensile compressive behavior of the plate while applying a current pulse is required.

However, no technology has been developed to evaluate the tensile compressive behavior of a sheet material while applying a current pulse.

In addition, when a current pulse is applied, a conventional sample fixture is made of a material having high electrical conductivity such as steel to ensure reliable specimen restraint, and therefore, there is a high risk of a tester failure and accidents due to the flow of electricity to an universal testing machine . Therefore, it is required to solve the problem of reliable specimen restraint and insulation using an insulator and steel.

In addition, since the conventional vertical tensile compression apparatus has a structure in which the upper and lower ends are clamped in a state in which the specimens are arranged in the vertical direction to apply tensile force and compressive force in the vertical direction, it is difficult to accurately align the specimens. The applied force can not be uniaxially stretched and uniaxially compressed, and the reliability of the test result is deteriorated.

Further, in the tensile compression test of the plate members of the prior art, buckling phenomena unintended to the specimen and the characteristics of the material under various conditions corresponding to the energizing environment of the specimen can not be analyzed.

Vertical buckling prevention system, which is widely used at present, has a problem in that buckling occurs in the clamped portion due to failure to detect thickness change of material which increases during uniaxial tensioning.

SUMMARY OF THE INVENTION Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and it is an object of the present invention to provide a method of manufacturing a single- Which can accurately analyze the reduction of the springback phenomenon caused by the application of the plate material to the material of the plate material, and a method thereof.

In order to accomplish the above object, the present invention provides a tensile compression test apparatus for a specimen to be used for compressing a specimen, comprising: a tensile compression test apparatus for testing a reduction effect of a springback by applying a tensile force or a compressive force to the specimen, A pair of grip portions for clamping both ends of the specimen together with the power terminal; A power supply line including a power supply line for supplying a power supply pulse to the power supply terminal and the power supply terminal; And a pair of holders each of which is mounted at one end of the specimen to provide tensile or compressive force to the specimen.

Wherein the specimen includes a grip plate having a material of a sheet material to be press-molded and formed such that a fixing hole through which a specimen fixing protrusion of a conductor pressure plate passes is fixed by a grip portion; And a connection portion extending between the two grip plates.

Wherein the grip portion comprises: a conductor pressing plate closely contacted to fix the grip plate of the specimen; An insulating block made of an insulating material and to which the conductor pressing plate is mounted; And a pressing block body having an alignment plate fixing flange formed with an alignment groove groove and an alignment plate groove in the holder side direction and on which the insulation block is mounted so that the conductor pressure plates are opposed to each other with the grip plate of the specimen interposed therebetween And a pair of grip bodies which are in close contact with each other.

The pair of grip bodies are formed such that a specimen fixing protrusion groove is formed on the conductor platen of one of the grip bodies and the conductor pressing plate of the other grip body passes through a fixing hole formed in the specimen, And a specimen fixing protrusion to be inserted is formed.

The conductor pressing plate may further include a plurality of protrusions protruding from a surface of the specimen which is in close contact with the grip plate.

The conductor platen may further include a power terminal seating portion formed to have a flat surface so that a power terminal of the power line portion closely contacts with the power terminal portion.

The pressing block body may be formed to increase in thickness in a direction opposite to the specimen from the specimen side so as to be mounted on the holder and prevented from detaching from the holder upon tension.

The grip portion includes a grip portion seating portion which is open at one side to protrude from the grip portion and protrude from the grip portion, a width at an inner side of the grip portion is narrow and a width at a side opposite to the open side is widened, ; ≪ / RTI >

Wherein the holder portion includes an alignment rod protruding inside the opposite side of an open area of the grip portion seating portion and inserted through an alignment rod groove of the grip portion; And a tensioning or compressing force is applied to the specimen by being in contact with one end of the specimen formed integrally with the end of the aligning rod and seated in the alignment groove of the grip portion and fixed by the grip portion. And an alignment plate for preventing the specimen from separating from the grip portion.

The tubing specimen tensile compression test apparatus includes a pair of buckling prevention plates which are respectively in close contact with both side surfaces of a connection portion of the specimen; A pair of reinforcing plates formed on opposite sides of a surface of the pair of buckling preventing plates that are in contact with the connecting portion; A fastening member for closely fixing the pair of reinforcing plates with each other with the connecting portion interposed therebetween; And a restoring elastic member coupled to the fastener and reducing the buckling force of the specimen during a compression test of the specimen by providing an elastic force to the reinforcing plate. .

The tubing specimen tensile compression testing apparatus may further comprise a measuring unit measuring a change in length of the specimen in tension or compressing the specimen and measuring a stress applied to the specimen.

According to another aspect of the present invention, there is provided a method of testing tensile compression of a specimen for buckling, the method comprising: a buckling preventing fixture mounting step of attaching a buckling preventing fixture to a connecting portion of a specimen; A grip plate protruded to both sides of the specimen is fixed by using the first grip body and the second grip body of the grip portion and the grip portion with the specimen fixed thereto is attached to the holder portion, A specimen fixing process to be fixed to a compression test apparatus; A buckling preventing effect judging step of measuring whether buckling is prevented or not by performing tension or compression without applying a current pulse in a state where the specimen is fixed; And a springback property evaluating step of evaluating a spring back property of the material by applying tensile or compressive force while applying a current pulse.

The present invention having the above-mentioned constitution is characterized in that a specimen made of a plate material to be press-molded is mounted on a specimen tensile compression testing apparatus and then a current pulse is applied while applying a tensile force or a compressive force to apply a current pulse It is possible to grasp the characteristic of the material at the time of application of the current pulse during tension or compression by the material, and by this means, Thereby providing an effect of minimizing the white phenomenon

Further, by solving the problem of reliable specimen restraint and insulation using an insulator and steel, it is possible to prevent electric power from flowing into a universal testing machine or the like during tensile compression test using a specimen for penetration, . ≪ / RTI >

Further, in the present invention, when the upper and lower ends of a specimen are clamped and a tensile force and a compressive force are applied in the up and down direction, the alignment state of the specimen is precisely adjusted by the buckling prevention fixture to ensure uniaxial tension and uniaxial compression, And the like.

In addition, the present invention detects buckling at the clamping portion by detecting the thickness change of the material increasing during the uniaxial tensile test using the return spring mounted on the buckling prevention jig, thereby preventing buckling ) Phenomenon and the material characteristics under various conditions corresponding to the energizing environment of the test piece can be analyzed.

1 is a perspective view of a specimen tensile compression test apparatus 10 according to an embodiment of the present invention.
Fig. 2 is a rear perspective view of the tensile compression test apparatus 10 of Fig. 1; Fig.
3 is a view showing an example of a test piece 50 applied to the present invention.
4 is a perspective view of the buckling preventing jig 100 shown in Fig.
5 is a view showing a state in which the buckling preventing jig 100 shown in Fig. 4 is coupled to the test piece 50 for preventing buckling of the test piece 50. Fig.
6 is a perspective view of the grip portion 200 of FIG.
7 is a view showing a process of fixing the test piece 50 using the grip portion 200;
8 is a view showing a state in which the test piece 50 is fixed using the buckling preventing jig 100 and the grip portion 200. Fig.
9 is a view showing a state in which the grip portion 200 to which the test piece 50 is fixed is attached to the holder 300. Fig.
10 is a flow chart showing a process of a test method for tensile compression test of a specimen of the present invention.
11 is a graph showing the buckling of a specimen in the case where the non-running compression test is performed in a state where the return spring (s) as the restoring elastic member is not applied to the buckling preventing jig 100.
12 is a graph showing buckling of a specimen when a non-running compression test is performed with a return spring applied to the buckling preventing jig 100. Fig.
13 is a graph showing a stress reduction state according to a current pulse applied during a tensile test on the test piece 50 using the tensile compression test apparatus 10 of Fig.
14 is a graph showing a stress reduction state according to a current pulse applied during a compression test for the test piece 50 using the tensile compression test apparatus 10 of FIG.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings showing embodiments of the present invention.

In the following description of the present invention, detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

Embodiments in accordance with the concepts of the present invention can make various changes and have various forms, so that specific embodiments are illustrated in the drawings and described in detail in this specification or application. It should be understood, however, that it is not intended to limit the embodiments according to the concepts of the present invention to the particular forms of disclosure, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the present invention.

It is to be understood that when an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, . On the other hand, when an element is referred to as being "directly connected" or "directly connected" to another element, it should be understood that there are no other elements in between. Other expressions that describe the relationship between components, such as "between" and "between" or "neighboring to" and "directly adjacent to" should be interpreted as well.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In this specification, the terms "comprises ",or" having ", or the like, specify that there is a stated feature, number, step, operation, , Steps, operations, components, parts, or combinations thereof, as a matter of principle.

Fig. 1 is a perspective view of a specimen tensile compression test apparatus 10 according to an embodiment of the present invention, and Fig. 2 is a rear perspective view of the tensile compression test apparatus 10 of Fig.

1, the tubular specimen tensile compression testing apparatus (hereinafter referred to as a testing apparatus 100) includes a tension compression section 20 for providing a pressure for tension or compression to a test piece 50, A buckling preventing jig 100 coupled to the specimen to prevent buckling of the specimen and a test apparatus 100 for testing both ends of the specimen 50 A grip portion 200 for clamping and fixing each of both ends of the test piece 50 to fix the test piece 50 to the test piece 50 and fixing the grip portion 200 to provide a tensile force or a compressive force to the test piece 50 through the grip portion 200, A holder unit 300 including a pair of holders 310 and 350 coupled to the compression unit 20 and the fixing unit 30, a power source to be contacted with the test piece 50 by the grip unit 200, And a power line part 400 including a power line having a terminal and applying a current pulse to the test piece 50 And a measuring unit 500 for measuring the tensile or compression state, length and thickness variation of the test piece 50 during the tensile or compression test.

The tensile compressing unit 20 may be configured such that tensile force or compressive force is applied to the specimen coupled to the holders 310 and 350 by the grip unit 200 by moving the holders 310 and 350 coupled to the ends by hydraulic pressure, .

Hereinafter, the detailed configuration of each of the above configurations will be described in more detail with reference to the embodiments.

3 is a view showing an example of the test piece 50 applied to the present invention.

As shown in Fig. 3, the specimen 50 is manufactured using the material of the plate to be press-molded. As described above, the manufactured specimen 50 is mounted on the testing apparatus 100. Thereafter, the measuring unit 500 measures the characteristic of the material when the current pulse is applied while the tensile force or the compressive force is applied by the testing apparatus 100, and when the current pulse is applied during tension or compression, It is possible to grasp the deformation characteristics of each material when the current pulse is applied at the time of compression so that the springback phenomenon caused by the material at the time of press forming can be remarkably reduced.

The measuring unit 500 may be a device including a function of measuring a strain of a specimen as a laser extensometer or the like.

The test piece 10 is mounted on the first conductor platen (not shown) of the grip portion 200 so that the test piece 50 is mounted on the test apparatus 10 through the grip portion 200 and the holder 300 And a connecting portion 57 connecting the pair of grip plates 55 and the pair of grip plates 55 formed on both sides with the fixing holes 51 through which the specimen fixing projections 213 of the pair As shown in Fig.

In the above configuration, the connecting portion 57 has a plate-like structure having a dumbbell shape as a whole, since the connecting portion 57 becomes smaller than the width of the pair of grip plates 55 toward the center portion. This shape can easily apply a tensile force or a compressive force to the specimen 50 through the grip plate 55 and the narrow connecting portion 57 is easily deformed by the tensile force or the compressive force, So that strain of the specimen due to tensile force or compressive force can be easily measured.

4 is a perspective view of the buckling preventing jig 100 shown in Fig.

4, the buckling preventing jig 100 includes a first buckling preventing portion 110 and a second buckling preventing portion 120 which are tightly coupled to the connecting portion 57 at both sides of the specimen 50, And a plurality of fasteners including a plurality of bolts (b) and nuts (n) for closely contacting the first and second buckling preventing portions (110) and (120).

The first buckling preventing portion 110 and the second buckling preventing portion 120 include a pair of buckling preventing plates 111 and 121 made of a steel material so as to be brought into close contact with both sides of the connecting portion 57 of the test piece 50, And a first reinforcing plate 113 and a second reinforcing plate 123 coupled to the buckling preventing plates 111 and 121, respectively.

When the bolt b is inserted into the bolt b and then the bolt b is coupled to the nut n by supporting between the head of the bolt b and the outer surface of the buckling prevention part 120 The first and second buckling preventing portions 110 and 120 may be formed of a material capable of preventing the first and second buckling preventing portions 110 and 120 from being deformed when the tensile force or the compressive force of the test piece 50 is applied to the back surface of the first or second buckling preventing portion 110 or 120, 120 as a restoring elastic member for reducing the buckling force of the specimen 50 by providing an elastic force to closely adhere the specimen 50 to the specimen 50.

5 is a view showing a state in which the buckling preventing jig 100 shown in Fig. 4 is coupled to the test piece 50 in order to prevent buckling of the test piece 50. Fig.

5, the first buckling preventing plate 110 and the first buckling preventing plate 111 of the second buckling preventing portion 120 and the first buckling preventing plate 111 of the second buckling preventing portion 120 The two buckling prevention plates 121 are in close contact with the opposite side surfaces of the connecting portion 57 of the test piece 50, respectively. Thereafter, after the return spring s is inserted into the bolt b, the end portion of the bolt b passes through the buckling preventing jig 100 and is coupled to the nut n, So that the specimen 50 is prevented from buckling during the tensile compression test. Since the return spring s keeps the first buckling preventing portion 110 and the second buckling preventing portion 120 in close contact with each other in accordance with the thickness change of the test piece 50 during tensile compression, To prevent further.

6 is a perspective view of the grip portion 200 of FIG.

As shown in FIG. 6, the grip portion 200 includes a pair of grip bodies constituted of a first grip body 210 and a second grip body 250.

The first grip body 210 and the second grip body 250 are respectively connected to a pair of first and second conductor pressure plates 211 and 212 which are in close contact with each other to fix the grip plate 55 of the specimen 50, The first and second insulating blocks 215 and 255 and the first and second insulating blocks 215 and 255 are mounted so that the first and second conductor pressing plates 211 and 251 are insulated from each other. And a second pressing block body (217, 257).

The first and second insulating blocks 215 and 255 are made of an insulating material so that a current pulse applied during the tensile or compression test of the test piece 50 is applied to the outside of the measuring device 100 or the measuring part 500 Thereby preventing device failure and safety accidents due to current pulses.

In each of the first and second pressing block bodies 217 and 257, first and second alignment rod grooves 221 and 261 and first and second alignment rod grooves 221 and 261 are formed on the first and second holders 310 and 350, First and second alignment plate fixing flanges 219 and 259 having alignment plate grooves 223 and 263 are provided.

A specimen fixing protrusion 213 passing through the fixing hole 51 of the specimen 50 is formed on one of the first and second conductor pressing plates 211 and 251 and a specimen fixing protrusion is inserted into the other A specimen fixing protrusion groove 253 is formed to prevent the specimen 50 held by the grip portion 200 from separating from the grip portion 200. [ That is, in the case of the embodiment of the present invention, a specimen fixing protrusion 213 is formed on the first conductor pressing plate 211, and a specimen fixing protrusion groove 253 is formed on the second conductor pressing plate 251.

A plurality of protrusions 201 protrude from the surfaces of the first and second conductor pressing plates 211 and 251 which are in close contact with the grip plate 55 of the test piece 50. This further increases the fixing force to the grip plate 55, thereby preventing unwanted detachment of the specimen 50 from the grip portion 200.

The first and second conductor pressing plates 211 and 251 are formed with a power terminal seating portion 252 formed in a flat surface so that the power terminal of the power line portion 400 closely contacts closely.

The first and second pressing block bodies 217 and 257 are mounted on the first and second holders 310 and 350 so that they can be prevented from being separated from the holders 310 and 350 when tensioned or compressed. The side on which the test piece is stuck is thin and the side on which the first and second alignment plate fixing flanges 219 and 259 are formed is configured to have a thick wedge shape.

Each of the first and second alignment plate fixing flanges 219 and 259 formed on the first and second pressing block bodies 217 and 257 has a first alignment rod groove 221 and a second alignment rod groove 261 And a first alignment groove groove 223 and a second alignment groove groove 263 are formed under the first and second alignment groove recesses 221 and 261, respectively.

The first alignment rod groove 221 and the second alignment rod groove 261 and the first alignment groove groove 223 and the second alignment groove groove 263 of the above- When the block body 217 and the second pressing block body 257 of the second grip body 250 are engaged with each other, the first and second alignment grooves 223 and 263 are held by the holders 310 and 350, And a through hole into which the alignment rod 305 formed therein is inserted. The first alignment plate groove 223 and the second alignment plate groove 263 are coupled to each other to form a hollow portion having an open front face so that the alignment plate 306 coupled to the end of the alignment rod 305 is seated.

Next, a process of mounting the test piece 50 having the above-described structure to the test apparatus 10 will be described.

7 is a view illustrating a process of fixing the test piece 50 using the grip portion 200 and FIG. 8 is a view showing a state in which the test piece 50 is fixed using the buckling preventing jig 100 and the grip portion 200 FIG.

7 and 8, in order to mount the test piece 50 to the test apparatus 10, the buckling preventing jig 100 is first coupled to the connecting portion 57 of the test piece 50. Next, each of the grip plates 55 on both sides of the test piece 50 should be engaged using the two grip parts 200. [ The test piece 50 is inserted into the first grip body 210 so that the test piece fixing protrusion 213 formed on the first conductor pressing plate 211 of the first grip body 210 is inserted through the fixing hole 51 of the test piece 50, (Not shown). Next, the power source terminal 410 is seated on the power source terminal seating portion 252. The specimen fixing protrusion 213 passing through the fixing hole 51 is inserted into the specimen fixing protrusion groove 253 of the second grip body 250 so that the second grip body 250 is inserted into the first grip body 210 . The power terminal 410 is seated on the power terminal seating portion 252 to connect the first conductor pressure plate 211 of the first grip body 210 and the second gripping plate 55 of the second grip 210 together with the grip plate 55 of the test piece 50, And is pressed and fixed by the second conductor pressing plate 251 of the body 250.

The clamping process of the grip plate 55 as described above is performed in the same way as the grip plate 55 which is not subjected to the other manipulation so that the grip portions 200 are respectively held on both sides of the test piece 50.

9 is a view showing a state in which the grip portion 200 to which the test piece 50 is fixed is attached to the holder 300. Fig.

As shown in Fig. 9, the grip portion 300, in which the test piece 50 is deflected by the description of Fig. 7, is mounted to the first holder 310 and the second holder 350, respectively. At this time, the first and second alignment plate fixing flanges 219 and 259 are positioned on the side of the alignment plate rod 305 formed in the clogged portion of the grip portion seating portion 301 in the holders 310 and 350 And is fixed by fasteners 303. [ At this time, due to the shape of the pressing block bodies 217 and 257, the grip portion 200 is formed into a wedge shape in which the width on the open side is narrow and the width on the closed side is widened inside the grip portion seating portion 301, The grip portion 200 is prevented from being disengaged from the holders 310 and 350 when it is applied.

Referring to FIG. 1 again, the first holder 310 of one of the two holders 310 and 350 described above is mounted on the tensile compressing section 20 formed on the upper portion of the testing apparatus 10. And the other second holder 350 is mounted on the upper end of the fixing part 30 formed at the lower part of the test apparatus 10. [

The grip portion 55 of the test piece 50 is clamped through the grip portion 200 and then the grip portion 200 is fixed to the grip portion seating portion 301 corresponding to the wedge shape, It is possible to apply a uniaxial tensile force or a compressive force at the time of testing, so that a uniform springback characteristic test can be performed for each material, and such an experimental procedure becomes a test method for tensile compression test of the present invention.

10 is a flow chart showing the process of the tensile compression test method of the specimen for transferring of the present invention.

As shown in Fig. 10, the above-mentioned specimen tensile compression test method of the penetration type specimen. A buckling preventing fixture mounting process S10 for mounting the buckling preventing fixture 100 on the connecting portion 57 of the test piece 50 and a grip plate 55 protruding from both sides of the test piece 50 to the grip portion 200 And the grip portion 200 to which the test piece 50 is fixed is attached to the holder portion 300 so as to be used for the tensile or compressive test (S20) of fixing the specimen (50) to the electrification tensile compression testing apparatus (10), and a method of determining whether or not buckling is prevented by performing tensile or compression without applying a current pulse while the specimen (50) A buckling prevention effect judgment step S30 for measuring the buckling prevention effect; The buckling preventing fixture 100 is brought into close contact with the specimen by the restoring elastic member (return string) s according to the change in thickness reduction of the specimen 50 when tension or compression is applied while applying the current pulse And a springback property evaluation process (S40) for preventing buckling of the test piece 50 and evaluating a spring back property of the test piece 50. [

The grip portion 200 is mounted on the holder and the alignment rod 305 and the alignment plate 306 formed on the grip portion seating portion 301 are separated from the grip portion 200 of the specimen 50 And the grip portion 200 is prevented from being separated from the holder portion 300 by the triangular sectional shape of the grip portion seating portion 301 of the grip portion 200 and the holder portion 300, By providing axial tensile or compressive forces, tensile or compressive tests can be carried out on precisely controlled specimens.

11 is a graph showing the buckling of a specimen in the case where the non-conduction tensile compression test is performed in the state that the return spring (s) is not applied to the buckling preventing jig 100. Fig. 12 is a graph showing the buckling preventing jig 100, And the buckling of the specimen in the case where the non-running tensile compression test is carried out with the return spring (s) applied thereto.

Figs. 11 and 12 show the buckling preventing effect by the return spring s.

Figs. 11 and 12 were carried out using specimens of AZ31B material, 1.4 mm thickness, 15 mm length and 0.8 mm / min. When the return spring s is not applied to the buckling preventing fixture 100 and the tensile force is strong without application of the current pulse, buckling occurs after 2 to 3% of compression as shown in Fig. However, when the return spring s is applied to the buckling preventing fixture 100, buckling occurs after 7 to 8% compression as shown in Fig. 12, and the compression elongation is increased three times or more.

13 is a graph showing a stress reduction state according to a current pulse applied during a compression test for the test piece 50 using the tensile compression testing apparatus 10 of Fig. 1, and Fig. 14 is a graph showing a stress reduction state ) In a tensile test on the test piece 50. In the graph of FIG.

Figures 13 and 14 show the result of applying a current pulse with a current pulse of 83.3 mm / A with a currentless pulse period of 30 ns and a current pulse period of 0,5 ns and performing tensile and compression tests on the specimen, respectively .

13 and 14, when a current pulse is applied for 0.5 ns at the apex at which each non-current pulse period advances, the stress generated in the process of performing tensile or compressive abruptly decreases Able to know. In addition, it can be seen that the tensile force, the compressive force and the distribution of the stress in each currentless pulse cycle and the current pulse application period are uniformly measured.

That is, the present invention provides a single-axis tensile force or compressive force, interrupts the electric current leakage of the current pulse, accurately measures the material-specific characteristics in which the stress causing the springback phenomenon caused by press- So that the springback can be effectively reduced.

10: Tensile compression test equipment
20: tensile compressing section 30:
50: Specimen 51: Fixing hole
55: grip plate 57:
100: buckling prevention jig 110: first buckling prevention part
111: first buckling prevention plate 113: first reinforcing plate
120: second buckling preventing portion 121: second buckling preventing plate
123: second reinforcing plate
200: grip part 210: first grip body
211: first conductor pressure plate 213: specimen fixing projection
215: first insulation block 216: second pressure block
217: first pressing block body 250: second grip body
251: second conductor pressure plate 252: power terminal seating portion
253: specimen fixing protrusion groove 255: second insulating block
256: second pressing block 257: second pressing block body
259: second alignment plate fixing flange 263: second alignment plate groove
300: holder part 310: first holder
320: second holder 400: power supply part
410: power terminal 500: measuring part
b: bolt n: nut
s: restoring elastic member (return spring)

Claims (12)

And an alignment plate fixing flange formed of an insulating material and having an alignment block groove and an alignment plate groove formed in the holder side direction and having an insulation block on which the conductor pressure plate is mounted, And a pair of grip bodies which are in close contact with and opposed to each other with the grip plate of the specimen interposed therebetween, both ends of the specimen being clamped and fixed together with the power terminal A pair of grip portions;
A power supply line including a power supply line for supplying a power supply pulse to the power supply terminal and the power supply terminal;
And a grip portion seating portion formed on one side of the grip portion so as to protrude from the grip portion and protruding from the grip portion and having an inner width narrowed toward the open side and wider toward the opposite side of the open side, A pair of holder portions to which the grip portions respectively mounted on one end of the specimen are mounted to provide tension or compressive force to the specimen; And
A pair of buckling prevention plates which are respectively in close contact with both side surfaces of the connection portion of the specimen, a pair of reinforcing plates formed on opposite sides of the side of the pair of buckling prevention plates which are in contact with the connection portion, And a pair of reinforcing plates for supporting the pair of reinforcing plates in close contact with each other, and a reinforcing plate coupled to the reinforcing plate to provide an elastic force to press the specimen in accordance with a change in thickness of the specimen during a compression test of the specimen, A buckling prevention fixture comprising a restoring elastic member for reducing a buckling force according to a change;
And a tensile compression test apparatus for the specimen.
[2] The method of claim 1,
A press forming apparatus comprising:
Grip plates on both sides formed with fixing holes through which the specimen fixing projections of the conductor pressure plate penetrate and are fixed by the grip portions; And
And a connecting portion extending between the two grip plates. The apparatus of claim 1,
delete [2] The apparatus according to claim 1,
A specimen fixing protrusion groove is formed on the conductor platen of one of the grip bodies,
Wherein the conductor pressing plate of another grip body is formed with a specimen fixing protrusion inserted through the fixing hole formed in the specimen and inserted into the specimen fixing protrusion groove.
The conductive pressure plate according to claim 1,
And a plurality of protrusions protruding from a surface of the specimen which is in close contact with the grip plate.
[6] The apparatus according to claim 5,
And a power terminal seating part formed on the flat surface so that the power terminal of the power source part is closely contacted with the power terminal part.
The press machine according to claim 1,
And the thickness of the specimen is increased in a direction opposite to the specimen from the specimen side so that the specimen is detached from the holder when the specimen is pulled.
delete [2] The apparatus according to claim 1,
An alignment rod protruding from the inside of the opposite side of the open region of the grip portion seating portion and inserted through the alignment load groove of the grip portion; And
And a tensile or compressive force is applied to the specimen by being in contact with one end of the specimen secured by the grip portion after being seated in the alignment groove of the grip portion integrally formed at the end of the alignment rod. And an alignment plate for preventing the specimen from separating from the grip portion.
delete The method according to claim 1,
Further comprising a measuring part measuring a change in length of the specimen during tension or compression of the specimen and measuring a stress applied to the specimen.
And an alignment plate fixing flange formed of an insulating material and having an alignment block groove and an alignment plate groove formed in the holder side direction and having an insulation block on which the conductor pressure plate is mounted, And a pair of grip bodies which are in close contact with and opposed to each other with the grip plate of the specimen interposed therebetween, both ends of the specimen being clamped and fixed together with the power terminal A pair of grip portions; A power supply line including a power supply line for supplying a power supply pulse to the power supply terminal and the power supply terminal; And a grip portion seating portion formed on one side of the grip portion so as to protrude from the grip portion and protruding from the grip portion and having an inner width narrowed toward the open side and wider toward the opposite side of the open side, A pair of holder portions to which the grip portions respectively mounted on one end of the specimen are mounted to provide tension or compressive force to the specimen; And a pair of reinforcing plates formed on opposite sides of a surface of the pair of buckling prevention plates which are in close contact with the connecting portions, And a pair of reinforcing plates which are located on the outer circumferential surface of the specimen and which are pressed against the specimen during the compression test of the specimen by providing an elastic force to the reinforcing plate, And a restoring elastic member for reducing a buckling force according to a change in thickness, the buckling preventing jig comprising:
A buckling fixture mounting process in which a buckling prevention fixture is attached to a connection portion of a specimen;
A grip plate protruded to both sides of the specimen is fixed by using the first grip body and the second grip body of the grip portion and the grip portion with the specimen fixed thereto is attached to the holder portion, A specimen fixing process to be fixed to a compression test apparatus;
When the tensile or compression is performed without applying a current pulse in a state where the specimen is fixed, the relative spacing of the pair of reinforcing plates is differentiated by the restoring elastic member of the buckling preventing jig as the thickness of the specimen decreases A buckling prevention effect judging step of measuring whether or not buckling of the specimen is prevented by bringing the pair of buckling preventing plates into close contact with or close to each other; And
The buckling preventing fixture is closely adhered to the test piece by the restoring elastic member in accordance with the decrease in the thickness of the test piece when tension or compression is applied while applying the current pulse to prevent buckling of the test piece, And evaluating a spring back property of the specimen.

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