JP2019219235A - Biaxial compression tensile test tool and biaxial compression tensile test method - Google Patents

Abstract

To provide a biaxial compression tensile test tool used for a biaxial compression tensile test for measuring distortion by a strain gauge, and a biaxial compression tensile test method.SOLUTION: A biaxial compression tensile test tool 1 used for a biaxial compression tensile test for measuring distortion caused in a central portion 101 of a tabular test piece 100 by acting a compressive load and/or a tensile load on a cross shaped tabular test piece 100 having a strain gauge 105 stuck thereon comprises: a central die 11 clamping a central portion 101 of the tabular test piece 100; a pressing mechanism 21 for applying a predetermined clamping force to the central portion 101; and side part dies 31 and 41 for acting the compressive load and/or the tensile load on the central portion 101 through each piece portion 103 of the tabular test piece 100. The central die 11 includes: a pressing part 15 for pressing the central portion 101; and a soft member 17 provided in a portion contacting a strain gauge 105 in the pressing part 15 and having a Young's modulus of 1500 MPa or more and 3000 MPa or less.SELECTED DRAWING: Figure 1

Description

The present invention relates to a biaxial compression / tension test jig and a biaxial compression / tension test method used for a biaxial compression / tension test in which a compression load and / or a tensile load are applied to a cruciform plate-like test piece.

  In press forming of a metal sheet material such as a steel sheet, not only a uniaxial load (uniaxial stress) state in which a load acts from one direction but also a biaxial load (a uniaxial load) in which a load acts in two orthogonal directions in a plane of the metal sheet material. It is considered that the metal plate material is deformed in the state of (biaxial stress). Therefore, in order to perform press forming analysis using a metal plate material as a workpiece with high accuracy, the stress-strain characteristics of the metal plate material in a biaxial stress state are grasped in advance by a material test such as a tensile test or a compression test. Need to be kept.

  As a technique for performing a material test in a biaxial stress state, for example, a technique disclosed in Patent Document 1 is cited. This technique is performed using a lower holding member having a support portion for supporting the lower side of a flat test piece, a stress loading member that applies stress from the upper surface of the test piece, and an upper holding member that holds the stress loading member. A test piece is deformed in a saddle shape by applying a stress downward to the upper surface of the test piece by a stress applying member in a state where the lower surface of the test piece is supported by the support portion of the lower holding member. Thus, a biaxial stress state of a tensile stress on the upper surface side of the test piece and a compressive stress on the lower surface side in an axial direction orthogonal to the axial direction on which the tensile stress acts is formed. Then, the upper and lower portions of the test piece are irradiated with laser light, and the amount of change in the distance between the detection positions of the laser light before and after the biaxial stress state is measured, whereby the deflection amount of the test piece in the biaxial stress state is measured. (Displacement).

  As described above, the technique disclosed in Patent Document 1 can determine the displacement of a test piece in a biaxial stress state in which a compressive load and a tensile load are applied in the in-plane direction of the test piece. It is not possible to apply only stress or biaxial tensile stress to a test piece.

  Therefore, the inventors have proposed a technique disclosed in Patent Document 2 as a technique for applying a biaxial compressive stress or a biaxial tensile stress. According to this technique, in a state in which both the upper surface and the lower surface of the central portion of the cruciform plate-shaped test piece are sandwiched and pressed in the thickness direction, the compressive load and / or By applying a tensile load, a biaxial compressive stress or a biaxial tensile stress can be applied to the central portion of the plate-shaped test piece.

JP-A-9-318510 JP 2018-80923 A

  In the technique disclosed in Patent Document 2, in order to prevent buckling in the thickness direction when a compressive load in the in-plane direction is applied to the center of the plate-shaped test piece, a center mold is used. A predetermined load is applied in the thickness direction while sandwiching the central portion to bring the central portion into a biaxial stress state. It is stated that the strain generated at the center of the plate-shaped test piece in a biaxial stress state can be measured optically or by a strain gauge.

  When strain is measured with a strain gauge among these two measurement methods, the strain gauge is attached to the center of the plate-shaped test piece, so that the center mold can be used repeatedly. In addition, it is possible to perform a material test easily and inexpensively. Some commonly used strain gauges have a resin base having a thickness of several tens of μm. However, when such a strain gauge is attached to a plate-shaped test piece, and the plate-shaped test piece is sandwiched by a central mold and a predetermined load is applied in the thickness direction, the strain gauge may be damaged, or the strain gauge may be damaged. There is a problem that a connection portion with a lead wire to be connected to the device is damaged, and strain cannot be measured.

  The present invention has been made in order to solve the above-described problems, and is intended to reduce the strain in a plate-shaped test piece under biaxial stress in which a tensile load and / or a compressive load is applied from a biaxial direction. It is an object of the present invention to provide a biaxial compression / tensile test jig and a biaxial compression / tensile test method capable of preventing a loss of the strain gauge when measuring with a strain gauge attached to a test piece.

(1) The jig for a biaxial compression-tensile test according to the present invention applies a compressive load and / or a tensile load to a cruciform plate-like test piece to which a strain gauge is attached, and generates a strain generated in the plate-like test piece. Is used in a biaxial compression-tensile test to be measured by the strain gauge, wherein a pair of rectangular central molds sandwiching the plate-shaped test piece from both sides, and the plate-shaped test piece in the central mold Clamping force applying means for applying a predetermined clamping force in the plate thickness direction, and sandwiches each cross-shaped piece portion of the plate-shaped test piece disposed on the four sides of the central mold from both sides; A pair of side molds for applying a predetermined load in the in-plane direction of the plate-shaped test piece, and the center mold has a comb-shaped unevenness formed on the edges of four sides thereof. A mold comb tooth portion, which was sandwiched by the central mold surrounded by the central mold comb tooth portion. A pressing portion for pressing the central portion of the plate-shaped test piece, and a soft member having a Young's modulus of 1500 MPa or more and 3000 MPa or less provided at a portion in contact with the strain gauge in the pressing portion, and each of the side molds Is characterized in that it has a holding portion for holding a piece portion of the plate-shaped test piece, and a side mold comb tooth portion which can be inserted into and removed from the central mold comb tooth portion at an end portion. It is.

(2) The biaxial compression / tension test method according to the present invention is directed to applying a compression load and / or a tensile load to a cross-shaped plate-shaped test piece using the biaxial compression / tension test jig according to the above (1). A strain gauge is attached to a central portion of the plate-shaped test piece, and the soft member provided on the pressing portion is brought into contact with the strain gauge attached to the plate-shaped test piece, and the pressing is performed. While pressing the central portion of the plate-shaped test piece with a predetermined pressing load at the portion, while holding each piece of the plate-shaped test piece in the holding portion of the side mold, the plate-shaped test piece The present invention is characterized in that a compressive load and / or a tensile load is applied to a central portion and strain is measured by the strain gauge.

In the present invention, a compressive load and / or a tensile load are applied to a cruciform plate-shaped test piece to which a strain gauge is attached, and a strain generated in the plate-shaped test piece is measured by the strain gauge. A pair of rectangular central molds for clamping the plate-shaped test piece from both sides, and clamping to apply a predetermined clamping force to the central mold in the thickness direction of the plate-shaped test piece. A force applying means, a cross-shaped piece of the plate-shaped test piece, which is arranged on four sides of the central mold and is sandwiched from both sides, and a predetermined load is applied in the in-plane direction of the plate-shaped test piece. And a pair of side molds that act on the central mold, wherein the central mold has a central mold comb tooth portion formed of comb-like irregularities formed on edges of four sides thereof, and the central mold comb. Pressing the center of the plate-shaped test piece, which is surrounded by the teeth and held by the center mold, Pressing portion, and a soft member having a Young's modulus of 1500 MPa or more and 3000 MPa or less provided at a portion in contact with the strain gauge in the pressing portion, and each of the side molds is a piece of the plate-shaped test piece. Having a holding portion for holding the side mold comb teeth at the end portion which can be inserted into and removed from the center mold comb teeth, prevents breakage of the strain gauge, and prevents the plate-shaped test piece from being damaged. Even if a compressive load is applied in the in-plane direction, a biaxial compression test can be performed without causing buckling, and the central mold can be used repeatedly.
In addition, a uniaxial compression / other-axis tensile test in which a compressive load is applied in a uniaxial direction in a plate-shaped test piece and a tensile load is applied in an axial direction orthogonal to the uniaxial direction, and further, in a biaxial direction of the plate-shaped test piece. A biaxial compression tensile test in which an arbitrary stress state is applied in the biaxial direction on the plate-like test piece, such as an in-plane reversal load test for applying a biaxial compression load after applying a tensile load, can be easily performed. .

It is an explanatory view explaining each component of a jig for a biaxial compression tension test concerning an embodiment of the invention, (a) is a state at the time of attaching a jig for a biaxial compression tension test, (b) is a view showing the arrangement of a plate-shaped test piece to be tested in a jig for biaxial compression and tension test, and (c) is a view showing a state where the plate-shaped test piece is sandwiched by the jig for biaxial compression and tension test. is there. It is a figure showing the shape of the plate-shaped test piece used as a test object in this embodiment. It is a figure showing the state where the jig for the biaxial compression tension test concerning this embodiment was disassembled. It is a figure explaining the state where the plate-shaped test piece used as a test object in this embodiment was installed in the jig for biaxial compression tension test. FIG. 3 is a diagram illustrating a soft member provided in a pressing portion of a central mold in the present embodiment. FIG. 4 is a diagram illustrating a preferred range of the Young's modulus of the soft member in the present embodiment. It is a figure showing the shape of the tabular test piece used in the example of the present invention. It is the measurement result of the relationship of the plastic strain-true stress obtained by the biaxial compression test in the Example of this invention.

  In the present invention, first, a plate-shaped test piece to be subjected to a biaxial tension-compression test will be described, and then a biaxial compression-tensile test jig and a biaxial compression-tensile test method according to an embodiment of the present invention will be described. .

<Plate-shaped test piece>
As shown as an example in FIG. 2, the plate-shaped test piece 100 has a cross shape, and has a rectangular central portion 101 serving as a center of the cross shape, and four rectangular portions extending outward from four sides of the central portion 101. It has the one part 103.

  The central part 101 is a part to be measured for strain, stress, and the like in a biaxial compression-tension test. FIG. 2 illustrates an example in which the central portion 101 is square, but in the present invention, the central portion may be rectangular.

  The piece 103 is composed of two sets of pieces 103a and 103b opposed to each other with the central part 101 interposed therebetween, and the direction in which the part 103a extends with respect to the central part 101 and the direction in which the piece 103b extends. Are orthogonal to each other in the central portion 101, and these directions correspond to biaxial directions in which a compressive load and / or a tensile load are applied to the plate-shaped test piece 100.

  That is, in order to perform the biaxial compression test on the plate-shaped test piece 100, the test piece 100 is directed toward the central portion 101 via one set of the pieces 103a and the other set of the pieces 103b. By applying a compressive load in each axial direction, the central portion 101 is brought into a biaxially compressed state.

  In addition, in order to perform a uniaxial compression / diaxial tension test on the plate-shaped test piece 100, for example, a compressive load is applied to the central portion 101 through one set of the pieces 103 a of the pieces 103. At the same time, a tension load is applied to the central portion 101 via the other pair of pieces 103b, thereby bringing the central portion 101 into a uniaxially compressed / diaxially tensioned state.

  Further, in order to perform a biaxial tensile test on the plate-shaped test piece 100, for example, the center of the plate-shaped test piece 100 is formed through both one set of the piece 103a and the other set of the piece 103b. By applying a tensile load to the portion 101, the central portion 101 is set in a biaxial tension state.

  As described above, a compressive load and / or a tensile load are applied to the central portion 101 via one set of the piece 103a and one set of the piece 103b, and a biaxial stress state (a biaxial compressed state, a uniaxial compressed / other state) is applied. The strain and stress of the central portion 101 in the axial tension state and the biaxial tension state) are measured by a strain gauge 105 attached to the central portion 101 (see FIGS. 1C and 4).

  The jig for biaxial compression and tension test and the biaxial compression and tension test method according to the present invention are not limited to using the plate-shaped test piece 100 having the shape shown in FIG. The shape of the plate-shaped test piece 100 can be appropriately changed according to the load conditions and the like.

<Jig for biaxial compression and tension test>
The jig 1 for a biaxial compression / tension test according to the embodiment of the present invention performs a biaxial compression / tension test in which a compressive load and / or a tensile load is applied to a cross-shaped plate-shaped test piece 100 shown as an example in FIG. As shown in FIG. 1, a center mold 11, a pressing mechanism 21, and two sets of a first side mold 31 and a second side mold which are opposed to each other with the center mold 11 interposed therebetween are used. A mold 41 is provided. Hereinafter, each configuration of the jig 1 for a biaxial compression-tensile test will be described.

  The jig for a biaxial compression / tensile test according to the present invention is intended to be used by attaching to an existing biaxial compression / tensile tester. The function and function of the jig for a biaxial compression / tension test according to the present invention does not differ even if the dimensions and the shape of the jig for an axial compression / tension test are appropriately changed.

≪Central mold≫
As shown in FIG. 3, the center mold 11 is a pair of substantially rectangular shapes that sandwich the plate-shaped test piece 100 from both upper and lower surfaces, and has a comb-like shape formed at the edges of the four sides of the rectangular shape. A central mold comb tooth portion 13 having irregularities, a pressing portion 15 surrounded by the four central mold comb teeth portions 13 to press the central portion 101 of the plate-shaped test piece 100, and a soft member provided on the pressing portion 15. It has a member 17 (FIG. 1 (c)). In addition, as shown in FIGS. 1 and 3, the four corners of the central mold 11 are fixed to the base 23 of the holding mechanism 21 by positioning pins 19 in order to prevent movement in the in-plane direction.

  As shown in FIG. 3, the central mold comb tooth portion 13 includes a pair of central mold comb teeth portions 13a and a pair of central mold comb teeth portions 13b opposed to each other with the pressing portion 15 interposed therebetween. The direction in which the central mold comb tooth 13a extends and the direction in which the other central mold comb tooth 13b extends are orthogonal to each other in the pressing portion 15. These directions correspond to biaxial directions in which a compressive load and / or a tensile load are applied to the central portion 101 via the pieces 103a and 103b of the plate-shaped test piece 100, as shown in FIG.

  The pressing portion 15 shown in FIG. 3 and FIG. 1C is a plate-shaped test piece 100 sandwiched by the central mold 11 surrounded by two sets of central mold comb teeth 13a and central mold comb teeth 13b. The pressing mechanism 21 presses the central portion 101 of the plate-shaped test piece 100 with a predetermined holding force.

  The soft member 17 has a Young's modulus of 1500 MPa or more and 3000 MPa or less, which is provided at a portion of the pressing portion 15 that contacts the strain gauge 105. The soft member 17 is provided at least on the pressing portion 15 of the central mold 11a on the side where the strain gauge 105 is attached.

  FIG. 5 shows an example of the soft member 17 provided on the pressing portion 15. FIG. 5 shows the central mold 11a and 11b (see FIG. 4A) sandwiching the upper and lower surfaces of the plate-shaped test piece 100 on the side of the strain gauge 105 attached to the plate-shaped test piece 100. 11a is illustrated with the lower surface side up. FIG. 5A shows a central mold 11c having no pressing member 15a which is not provided with the soft member 17 and directly abuts on the plate-shaped test piece 100.

  The central mold 11a used in the jig 1 for a biaxial compression-tensile test according to the present embodiment is provided with a rectangular recess in the pressing surface 15a of the central mold 11c shown in FIG. The soft member 17 is fitted into the bent portion 15b (FIG. 5B) (FIG. 5C).

  As described above, since the soft member 17 is provided on the entire surface of the pressing portion 15 in contact with the plate-shaped test piece 100, when the plate-shaped test piece 100 is sandwiched by the central mold 11, the plate-shaped test piece is The soft member 17 can be brought into contact with the strain gauge 105 attached to the central portion 101 of the 100.

In addition, as a material of the soft member 17, a resin can be exemplified, and a material having a Young's modulus in the range of 1500 MPa or more and 3000 MPa or less may be selected.
Further, the soft member 17 shown in FIG. 5C is provided, for example, on the entire surface of the pressing portion 15 to be brought into contact with the plate-shaped test piece 100. However, in the present invention, it may be provided at a part of the pressing portion 15 where the plate-shaped test piece 100 comes into contact with the strain gauge 105 (not shown). In this case, in the pressing portion 15, a soft member may be provided so that the surface to be brought into contact with the plate-shaped test piece 100 and the soft member are flush.

≪Holding mechanism≫
As shown in FIG. 1B, the holding mechanism 21 is a holding force applying unit that applies a predetermined holding force to the central mold 11 in the thickness direction of the plate-shaped test piece 100. It comprises a plate portion 25 and a bolt 27, and is held by the base portion 23 and the top plate portion 25 from above and below the central mold 11.

  In the holding mechanism 21, a predetermined clamping force is applied to the central mold 11 by tightening the four corners of the base portion 23 and the top plate 25 with bolts 27 with an arbitrary tightening force. Can press the central portion 101 of the plate-shaped test piece 100.

  On the upper surface (upper surface corresponding to the pressing portion 15) of the central mold 11 on the lower surface of the top plate portion 25 (the central mold 11 side), a convex portion (not shown) is provided at a contact position. When applying a clamping force for pressing the central portion 101 of the test piece 100, the central mold 11 can be clamped without bringing the top plate 25 into contact with the central mold comb teeth 13. .

  For this reason, even when the convex portion is brought into contact with the pressing portion 15 of the central mold 11 and the pressing mechanism 21 applies a clamping force to the central mold 11, the first side mold 31 and the second The side mold 41 can be moved.

<< First side mold and second side mold >>
As shown in FIGS. 1 and 3, the first side mold 31 and the second side mold 41 are disposed on the four sides of the central mold 11 as side molds, and a plate-like test is performed. The piece portion 103 of the piece 100 is sandwiched from both upper and lower surfaces, and a predetermined load (compression and / or tension) is applied in the in-plane direction of the plate-shaped test piece 100.

  As shown in FIG. 3, the first side mold 31 includes a pair of first side molds 31 a and 31 b disposed to face each other with the pressing portion 15 of the central mold 11 interposed therebetween. The one-side molds 31a and 31b have holding portions 33a and 33b for holding a pair of pieces 103a of the plate-shaped test piece 100. Further, side mold comb teeth 35a, 35b which can be inserted into and removed from the central mold comb teeth 13a of the central mold 11 are formed at the ends of the first side molds 31a, 31b.

  Similarly, the second side mold 41 is composed of a pair of second side molds 41a and 41b disposed to face each other with the pressing portion 15 of the central mold 11 interposed therebetween. The dies 41a and 41b have holding parts 43a and 43b for holding the piece 103b of the plate-shaped test piece 100. Further, side mold comb teeth 45a, 45b that can be inserted into and removed from the central mold comb teeth 13b of the central mold 11 are formed at the ends of the second side molds 41a, 41b.

  The first side mold 31 and the second side mold 41 are respectively set on rollers 37 and 47 provided on the upper surface of the base 23, and the side mold comb teeth 35 and the side molds are provided. Each of the comb teeth portions 45 is detachably moved while being engaged with the central mold comb teeth portions 13a and 13b of the central mold 11.

<Biaxial compression and tension test method>
Next, with respect to the biaxial compression / tension test method according to the embodiment of the present invention, the case where a compressive load is applied in the biaxial direction orthogonal to the plate-shaped test piece 100 using the jig 1 for biaxial compression / tension test is described. This will be described as an example.

  First, a plate-shaped test piece 100 is arranged between a pair of upper and lower central molds 11, a predetermined clamping force is applied to the central mold 11 by a pressing mechanism 21, and the plate-shaped test piece clamped by the central mold 11. The central part 101 of 100 is pressed by the soft member 17 provided on the pressing part 15.

  Next, with the center part 101 pressed, the side mold comb teeth 35 of the first side mold 31 can be inserted and withdrawn while being engaged with the center mold comb teeth 13 a of the center mold 11. The first side mold 31 is disposed such that the side mold comb teeth 45 of the second side mold 41 are engaged with the center mold comb teeth 13b so as to be removable. The second side die 41 is disposed at the second position.

  Here, the upper and lower surfaces of the piece portion 103a of the plate-shaped test piece 100 are held by the holding portions 33 of the pair of upper and lower first side molds 31, and the holding portions 43 of the pair of upper and lower second side molds 41 are held. The upper and lower surfaces of the piece portion 103b of the plate-shaped test piece 100 are held with the.

  Then, with the first side mold 31 holding the piece 103a and the second side mold 41 holding the piece 103b, the first side mold 31 and the second side mold 41 are held together. It is moved toward the central mold 11.

  Since the first side mold 31 and the second side mold 41 can be moved toward the center mold 11 without interfering with each other, the center part 101 of the plate-shaped test piece 100 is biaxial. It can be in a compressed state.

  Here, in the jig 1 for the biaxial compression / tensile test, since the pair of upper and lower central dies 11 is sandwiched by the pressing mechanism 21 and the entire surface of the central portion 101 of the plate-shaped test piece 100 is pressed by the pressing portion 15, There is no portion where a pressing load cannot be applied to the central portion 101. Therefore, buckling deformation of the central portion 101 can be prevented even when a biaxial compressive load is applied to the central portion 101.

  In the present embodiment, the strain in the biaxially compressed state is measured by the strain gauge 105 attached to the central portion 101 of the plate-shaped test piece 100, but in such a manner that the soft member 17 contacts the strain gauge 105. The plate-shaped test piece 100 is pressed by the pressing portion 15 of the central mold 11 (see FIG. 1C).

As described above, the soft member 17 has a Young's modulus of 1500 MPa or more and 3000 MPa or less.
When a soft member 17 having a Young's modulus of less than 1500 MPa is used, as shown in FIG. 6A, when a compressive load is applied to the central portion 101 of the plate-shaped test piece 100, the central portion 101 buckles and wrinkles occur. , The measurement accuracy of the strain gauge 105 is reduced.

  When the soft member 17 having a Young's modulus of more than 3000 MPa is used, as shown in FIG. 6B, when the pressing portion 15 presses the plate-shaped test piece 100, the strain gauge 105 itself, or the strain gauge 105 and the lead wire are used. The connection of 107 is damaged. As described above, a commonly used strain gauge having a resin base having a thickness of several tens of μm is used. However, when such a strain gauge is attached to a plate-shaped test piece, and the plate-shaped test piece is sandwiched by a central mold and a predetermined load is applied in the thickness direction, the strain gauge may be damaged, or the strain gauge may be damaged. In some cases, the connection portion with the lead wire connected to the cable may be damaged, making it impossible to measure the strain.

  As described above, as the strain gauge 105, a thin base plate (not shown) with a thickness of about 10 μm can be used. When a load is applied, it is necessary to press the center portion 101 with a predetermined load in order to prevent buckling in the plate thickness direction, so that the strain gauge 105 is easily damaged. Furthermore, since the lead wire 107 connected to the strain gauge 105 has a wire diameter of about 0.1 mm and is thicker than the strain gauge 105, the connection portion may be damaged.

  On the other hand, by using the soft member 17 having a Young's modulus of 1500 MPa or more and 3000 MPa or less, the measurement accuracy that a compressive load is applied in the in-plane direction of the plate-shaped test piece 100 is not reduced, and the strain gauge 105 is defective. Can be prevented and strain in a biaxially compressed state can be measured.

  Although the above description has been made on the case of performing a biaxial compression test, the biaxial compression / tension test method according to the present invention is assumed to be performed using an existing biaxial compression / tension tester. Things. Therefore, by moving a set of the first side mold 31 and a set of the second side mold 41 that hold the piece 103 of the plate-shaped test piece 100 independently of each other, A compressive load or a tensile load may be applied to the central portion 101.

  For example, in a state where the central portion 101 of the plate-shaped test piece 100 is pressed by the pressing portion 15 of the central mold 11, the first side mold 31 holding the piece 103 a of the plate-shaped test piece 100 is moved to the central mold 11. And the second side mold 41 holding the piece 103b is moved in a direction away from the central mold 11, so that the plate-shaped test piece 100 can be uniaxially moved while preventing out-of-plane buckling. A uniaxial compression / other-axis tension test in which a compressive load and a uniaxial tensile load are applied can be performed.

  Similarly, both the first side mold 31 holding one set of the piece 103a of the piece 103 and the second side mold 41 holding the piece 103b are attached to the plate-shaped test piece 100. By moving in a direction away from the central portion 101 and applying a tensile load, a biaxial tensile test in which a biaxial tensile load is applied to the plate-shaped test piece 100 can be performed.

  Further, the jig 1 for a biaxial compression / tensile test used in the biaxial compression / tensile test method according to the present invention includes a first side die 31 for holding a piece 103a of a plate-shaped test piece 100 and a piece 103b. Since the holding second side mold 41 can be moved independently of each other, not only the biaxial compressive load but also the biaxial tensile load and the uniaxial Not only can a compressive load and a tensile load on another axis be applied, but also the ratio (stress ratio) of loads applied in each axial direction can be arbitrarily set.

  Further, in the biaxial compression / tension test method using the biaxial compression / tension test jig 1, for example, as described above, the first side mold 31 and the second side mold 41 are used to form the plate-like test piece 100. After applying a tensile load to the plate-shaped test piece 100, the first side mold 31 and the second side mold 41 are respectively moved toward the central portion 101 of the plate-shaped test piece 100 to apply a compressive load. The in-plane reversal load test can be performed while preventing outer buckling.

  Also, in the above description, the plate-shaped test piece 100 is arranged horizontally, so that the central mold 11, the first side mold 31, and the second side mold 41 are attached to the plate-shaped test piece 100. Although it is arranged on both upper and lower surfaces, the present invention is not limited to the arrangement of the jig for biaxial compression and tension test, the plate-shaped test piece in a biaxial compression and tension tester What is necessary is just to arrange according to the installation direction.

  The first side mold 31 and the second side mold 41 are in a state where the respective side mold comb teeth 35 and 45 are engaged with the central mold comb teeth 13 a and 13 b of the central mold 11. For example, a Teflon (registered trademark) sheet may be interposed between the plate-shaped test piece 100 and the central mold 11 in order to reduce the frictional force when the sheet is moved.

  A specific experiment was performed to confirm the effects of the jig for a biaxial compression and tension test and the method of the biaxial compression and tension test according to the present invention, which will be described below.

  In the present embodiment, the jig 1 for a biaxial compression-tensile test shown in FIG. 1 is used to apply a compressive load to the cross-shaped plate-like test piece 110 shown in FIG. Was measured.

  The plate-shaped test piece 110 is made of a cold-rolled steel sheet having a tensile strength of 590 MPa class and a thickness of 1.2 mm as a test material, and has a square central portion 111 and two sets of opposed pairs extending outward with the central portion 111 interposed therebetween. It has a cross shape having one part 113a and one part 113b. Here, the width of the central portion 111 was 30 mm, and the length of the plate-shaped test piece 110 in the axial direction (the X-axis direction and the Y-axis direction in FIG. 7) of each of the pieces 113a and 113b was 320 mm.

  In the biaxial compression test, first, a strain gauge (base thickness: 13 μm) connected to a lead wire (copper wire, φ0.14 mm) was attached to the central portion 111 of the plate-shaped test piece 110. Then, the central portion 111 of the plate-shaped test piece 110 is sandwiched by the central mold 11, and the piece portion 113 is held by the first side mold 31 and the second side mold 41, and a biaxial stress tester (illustrated) None). When the central portion 111 was sandwiched by the central mold 11, the soft member 17 was brought into contact with a strain gauge attached to the plate-shaped test piece 110.

  Then, a compressive load was applied to the central portion 111 in two axial directions (the X-axis direction and the Y-axis direction in FIG. 7), and the strain generated in the central portion 111 was measured with a strain gauge. Further, the stress acting on the central portion 111 was calculated for each axial direction from the load applied to the plate-shaped test piece 110 and the cross-sectional area of the piece of the plate-shaped test piece.

  In the present embodiment, a case where a resin having a Young's modulus of 1500 MPa or more and 3000 MPa or less, which is within the range of the present invention, is used as the soft member 17,

  FIG. 8 shows the measurement results of the relationship between the plastic strain and the true stress in the X-axis direction and the Y-axis direction when a biaxial compressive load is applied using polyurethane having a Young's modulus of 2000 MPa as the soft member 17.

  The horizontal axis in FIG. 8 is the value of the plastic strain when the strain on the tensile side is positive (plus). From FIG. 8, the relationship between the measured plastic strain and the true stress was almost the same in the X-axis direction and the Y-axis direction, and by using the jig 1 for a biaxial compression-tensile test according to the present invention, the plastic strain was measured. Can be measured down to -0.012 (compression).

  In the present embodiment, a case where a central mold 11c (see FIG. 5 (a)) provided with a pressing surface portion 15a that directly contacts the plate-shaped test piece 110 without using a soft member is used as a conventional example. The test was performed by applying a compressive load to the plate-shaped test piece 110 from the biaxial directions in the same manner as in the above-described invention examples. However, when the plate-shaped test piece 110 to which the strain gauge was attached was sandwiched by the central mold 11c and pressed with a predetermined load, the strain gauge was damaged, and the strain could not be measured.

Further, in this example, as a comparative example of the invention example, a case where a resin whose Young's modulus of the soft member 17 is out of the range of the present invention (less than 1500 MPa or more than 3000 MPa) was used as a comparative example. Also in the comparative example, the strain was measured by a strain gauge attached to the plate-shaped test piece 110, and the conditions (loading conditions, test piece shape, etc.) other than the type and the Young's modulus of the resin used for the soft member 17 were the same as those of the invention. Identical.
Table 1 shows the types of resins used as the material of the soft member 17 in this example and the Young's modulus of each resin.

  Table 1 also shows the results of the test availability when a biaxial compressive load was applied. "Wrinkles" shown in the column of the experiment availability indicate that the central portion 111 buckled and wrinkled when a biaxial compressive load was applied, and "gauge loss" means that the strain gauge was broken or the connection with the lead wire. In the case where the strain could not be measured due to the damage of the sample, “○” indicates that neither wrinkles in the central portion 111 nor loss of the strain gauge occurred. It shows what the strain could be measured. Furthermore, the type and the Young's modulus of the soft member 17 were different, and the measured values of the strain in the invention examples were the same.

From Table 1, in the invention example, if the Young's modulus is 1500 MPa or more and 3000 MPa or less irrespective of the type of resin used for the soft member 17, both generation of buckling in the central portion 111 and damage to the strain gauge are reduced. Could be prevented.
On the other hand, in the comparative example, wrinkles occur when the Young's modulus is smaller than the range of the present invention regardless of the type of the soft member 17, and when the Young's modulus is larger than the range of the present invention, the strain gauge Was lost and could not be tested.

  As described above, according to the jig for a biaxial compression / tensile test according to the present invention, even when a compressive load is applied to a cruciform plate-shaped test piece, it is possible to perform the biaxial compression / tensile test by preventing out-of-plane buckling. Demonstrated what can be done. Furthermore, it was shown that by performing a biaxial compression-tensile test using the jig for a biaxial compression-tensile test according to the present invention, material properties (strain-stress relationship) significant for press-forming analysis can be obtained.

DESCRIPTION OF SYMBOLS 1 Biaxial compression-tensile test jig 11, 11a, 11b Central mold 11c Central mold (conventional example)
13, 13a, 13b Central mold comb tooth portion 15 Pressing portion 15a Pressing surface portion 15b Site 17 Soft member 19 Positioning pin 21 Pressing mechanism 23 Base portion 25 Top plate portion 27 Bolts 31, 31a, 31b First side mold 33, 33a, 33b Holder 35, 35a, 35b Side mold comb tooth 37 Roller 41, 41a, 41b Second side mold 43, 43a, 43b Holder 45, 45a, 45b Side mold comb tooth 47 Roller 100 Plate-shaped test piece 101 Central part 103, 103a, 103b Single part 105 Strain gauge 107 Lead wire 110 Plate-shaped test piece 111 Central part 113, 113a, 113b Single part

Claims (2)

Biaxial compression used in a biaxial compression-tensile test in which a compressive load and / or a tensile load is applied to a cruciform plate-like test piece to which a strain gauge is attached, and strain generated in the plate-like test piece is measured by the strain gauge. A tensile test jig,
A rectangular central mold consisting of a pair of the plate-shaped test pieces sandwiched from both sides,
Clamping force applying means for applying a predetermined clamping force to the central mold in the thickness direction of the plate-shaped test piece,
A pair of cross-shaped pieces arranged on the four sides of the central mold and sandwiching the cross-shaped pieces of the plate-shaped test piece from both sides, and applying a predetermined load in the in-plane direction of the plate-shaped test piece. A side mold,
The central mold has a central mold comb tooth portion formed of comb-shaped irregularities formed on the edges of the four sides thereof, and the central mold is surrounded by the central mold comb tooth portion and held by the central mold. A pressing portion for pressing the central portion of the plate-shaped test piece, and a soft member having a Young's modulus of 1500 MPa or more and 3000 MPa or less, which is provided at a portion in contact with the strain gauge in the pressing portion,
Each of the side molds has a holding portion for holding a piece of the plate-shaped test piece, and a side mold comb tooth portion that can be inserted into and removed from the central mold comb tooth portion is formed at an end. A jig for a biaxial compression / tensile test characterized by the above-mentioned. A biaxial compression / tensile test method for applying a compressive load and / or a tensile load to a cruciform plate-like test piece using the biaxial compression / tensile test jig according to claim 1,
Attach a strain gauge to the center of the plate-shaped test piece,
The soft member provided in the pressing portion is brought into contact with a strain gauge attached to the plate-shaped test piece, and the pressing portion presses a central portion of the plate-shaped test piece with a predetermined pressing load, and With each piece of the plate-shaped test piece held by the holding portion of the mold, a compressive load and / or a tensile load are applied to the center of the plate-shaped test piece, and strain is measured by the strain gauge. A biaxial compression-tension test method, characterized in that: