Bending test equipment and bending test method for metal sheet for automobile body and bending performance evaluation method based on the bending test equipment

Abstract

A bending test device for a metal sheet material for an automobile body is provided with the aim of photographing the strain state of the bent outer surface of a test piece by a camera without losing focus during a bending test, and is characterized in that it comprises: a supporting member (1) for supporting two supporting portions (2) of a flat test piece (P) formed of a metal sheet material for an automobile body; a punch (4) for performing a bending test in which the test piece (P) is bent and deformed by pressing a portion between the two supporting portions (2) of the test piece (P) from a side opposite to the supporting member (1); and a camera (5) for photographing the bent outer surface of the test piece (P) in the bending test performed by the punch (4) from the side of the supporting member, wherein the relative positions of the punch (4) and the camera (5) in the bending test are fixed.

Description

Technical Field

[0001] The present invention relates to a bending test device and a bending test method for a metal plate for an automobile body, and a bending performance evaluation method based on the bending test device. Background Art

[0002] In recent years, the use of high-strength steel sheets as vehicle body materials has been progressing in order to reduce weight while maintaining collision performance. However, as the ductility of the material decreases with the increase in material strength, the risk of fracture during a collision increases.

[0003] In particular, energy absorbing members arranged at the front and rear of the vehicle body are required to absorb collision energy by plastic deformation of the member during collision. In the axial crushing of the energy absorbing member, fracture often occurs due to large local strain. When such fracture progresses to large rupture and the member is damaged, the collision load is greatly reduced, which may lead to unstable energy absorption performance. The unstable energy absorption performance has become an important issue in the application of high-strength steel plates to vehicle bodies.

[0004] It is known that fracture in the above-mentioned axial crushing deformation cannot be evaluated by indicators such as uniform elongation and local elongation in a tensile test, and various material testing methods have been proposed in the past to determine the presence or absence of such fracture.

[0005] For example, in the VDA238-100 bending test method standardized by the German Association of the Automotive Industry (Verband der Automobilindustreie: VDA), a method is proposed in which a plate is placed on two rollers arranged in parallel, and the plate is pressurized from the top with a sharp punch to bend the plate to evaluate the limiting bending radius of the plate. The limiting bending radius obtained by this method corresponds to the local deformation during a collision.

[0006] Patent Document 1 proposes improving the bending test method of the VDA standard and evaluating the crack generation state after the limit bending radius based on the load-stroke curve obtained by the test, thereby predicting the fracture resistance of the component during collision.

[0007] According to the evaluation test of the prior art described above, the fracture resistance during axial crushing can be evaluated for each material. Moreover, according to such an evaluation test, not only the punch load and stroke of the bending test are measured, but also the strain state of the material during the test is observed. In addition to information related to the macroscopic fracture phenomenon, the progress of the strain that reaches local fracture, the limit fracture strain, and other extremely useful information in developing materials with excellent fracture resistance can be obtained.

[0008] Prior Art Literature

[0009] Patent Literature

[0010] Patent Document 1: Japanese Patent Application Publication No. 2016-080464 Summary of the invention

[0011] Summary of the Invention

[0012] Problems to be solved by the invention

[0013] However, since the bending test is usually performed by moving the punch, it is difficult to make the camera capture the strain state of the outer surface of the bend without losing focus during the test. In addition, when evaluating by the bending test of the VDA standard, in order to use the camera to capture the outer surface of the bend, it is necessary to capture the sample surface with high resolution from the gap between the two rollers, which makes it difficult to ensure the brightness of the sample and the field of view.

[0014] Therefore, an object of the present invention is to provide a bending test apparatus and a bending test method for a metal sheet for an automobile body, and a bending performance evaluation method using the bending test apparatus, which advantageously solve the problems of the conventional test methods as described above.

[0015] Solutions to Solve Problems

[0016] The bending test equipment for metal sheet materials for automobile bodies of the present invention for achieving the above-mentioned object is characterized by comprising:

[0017] A supporting member supports two supporting portions of a flat test piece formed of a metal plate for an automobile body;

[0018] a punch for performing a bending test of pressing a portion between the two supporting portions of the test piece from a side opposite to the supporting member side to bend and deform the test piece; and

[0019] a camera for photographing, from the side of the supporting member, the curved outer surface of the test piece in the bending test performed by the punch,

[0020] The relative positions of the punch and the camera in the bending test are fixed.

[0021] In addition, the bending test method of the metal sheet material for automobile body of the present invention for achieving the above-mentioned object is characterized by:

[0022] A flat test piece made of a metal plate for an automobile body is supported at two supporting portions by a supporting member.

[0023] When a bending test is performed in which a portion between the two supporting portions of the test piece is pressed with a punch from a side opposite to the supporting member side to bend and deform the test piece,

[0024] The curved outer surface of the test piece is photographed from the support member side by a camera whose relative positional relationship with the punch is fixed.

[0025] In addition, the bending performance evaluation method of a metal sheet material for an automobile body of the present invention is characterized in that the bending performance of the test piece is evaluated based on information on the strain distribution and its changes on the bending outer side of the test piece, the occurrence and progression of cracks, and / or the distribution of cracks obtained from an image of the bending outer side of the test piece captured by the camera during the bending test, and the bending test is performed by the bending test equipment.

[0026] Effects of the Invention

[0027] According to the bending test equipment and bending test method of metal sheets for automobile bodies of the present invention, a supporting member is used to support the supporting parts of two locations of a flat test piece formed by metal sheets for automobile bodies, and a bending test is performed by pressing a portion between the supporting parts of the two locations of the test piece from the side opposite to the supporting member side with a punch to bend and deform the test piece. In the bending test, a camera having a fixed relative position relationship with the punch is used to photograph the bent outer surface of the test piece from the supporting member side, so that the strain state of the bent outer surface of the test piece can be photographed without defocusing during the test.

[0028] Furthermore, according to the bending performance evaluation method of the present invention, the bending performance of the test piece is evaluated based on information on the strain distribution and its changes on the bending outer side of the test piece, the occurrence and progression of cracks, and / or the distribution of cracks obtained from the image of the bending outer side of the test piece captured by the camera during the bending test. The bending test is performed by the bending test equipment. Therefore, in addition to information related to macroscopic fracture phenomena, information extremely useful in developing materials with excellent fracture resistance, such as the progression of strain reaching local fracture and the limit fracture strain, can be obtained.

[0029] It should be noted that in the bending test equipment and bending test method of the present invention, the supporting member for supporting the supporting parts at two locations of the test piece may be two rollers that are spaced apart from each other and arranged parallel and horizontally. In this way, the bending test method specified in VDA standard 238-100 can be implemented.

[0030] Furthermore, in the bending test equipment and the bending test method of the present invention, at least one of the two rollers may be a roller having a rotating axis portion and a portion of the circular cross-section observed from the rotating axis direction being missing. In this way, the field of view and brightness can be ensured through the missing portion of the roller, and the camera can be used to photograph the curved outer surface of the test piece from the supporting member side, thereby obtaining a clearer image.

[0031] In addition, in the bending test equipment and the bending test method of the present invention, there may also be a testing machine that enables the movable part to move forward and backward relative to the non-movable part, the punch and the camera are arranged on the non-movable part, and the supporting member is arranged on the movable part. In this way, the punch and the camera will not be affected by vibrations and the like associated with the movement of the movable part relative to the non-movable part during the bending test, thereby being able to more reliably prevent the focus of the camera from deviating.

[0032] Furthermore, in the bending performance evaluation method of the present invention, the above information may be obtained by digital image correlation (DIC), thereby enabling more detailed bending performance evaluation. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a perspective view showing a bending test device for a metal sheet for an automobile body according to one embodiment of the present invention and a bending test method for a metal sheet for an automobile body according to one embodiment of the present invention using the bending test device.

[0034] Figure 2 It is a perspective view showing a bending test apparatus for a metal sheet for an automobile body according to another embodiment of the present invention and a bending test method for a metal sheet for an automobile body according to another embodiment of the present invention using the bending test apparatus.

[0035] Figure 3 Yes means Figure 1 Modification of the bending test apparatus for metal sheet for automobile body of the embodiment shown and a bending test apparatus using the same Figure 1 A perspective view of a modified example of the bending test method for a metal sheet for an automobile body according to the embodiment shown.

[0036] Figure 4 Yes means Figure 2 Modification of the bending test apparatus for metal sheet for automobile body of the embodiment shown and a bending test apparatus using the same Figure 2 A perspective view of a modified example of the bending test method for a metal sheet for an automobile body according to the embodiment shown.

[0037] Figure 5 Yes means Figure 2Another modification of the bending test apparatus for metal sheet for automobile body of the embodiment shown and a bending test apparatus using the same Figure 2 A perspective view of another modified example of the bending test method for a metal sheet for an automobile body according to the embodiment shown.

[0038] Figure 6 It means that you are using Figure 4 Bending test equipment for metal sheet for automobile body according to the modified example shown Figure 4 The photographs are of images of the fracture strain of each material captured in the bending test method of the metal sheet material for automobile bodies according to the modified example shown. DETAILED DESCRIPTION

[0039] Hereinafter, embodiments of the present invention will be described in detail based on the accompanying drawings. Figure 1 It is a perspective view showing a bending test device for a metal sheet for an automobile body according to one embodiment of the present invention and a bending test method for a metal sheet for an automobile body according to one embodiment of the present invention using the bending test device.

[0040] The bending test equipment for metal plates for automobile bodies of this embodiment comprises a testing machine such as an Amsler type testing machine, which is fixed to the test object via a support frame 1 with a gap between them, while applying a load to the test object by a sliding member that moves in a direction approaching and separating from a fixed table, and measuring the magnitude of the load and the displacement of the sliding member. Figure 1 The fixed table T as a non-movable part is indicated by an imaginary line in the figure, and two dies 2 as supporting members support two supporting parts near the two ends of the flat and rectangular test piece P made of a metal plate for an automobile body; the above-mentioned test machine is fixed to the Figure 1 In the figure, a V-shaped punch 4 is shown as a mounting surface on a slide S as a movable part by an imaginary line; a camera 5 is fixed in relative position to the punch 4 by a connecting frame 3 and has its lens directed toward the gap between the two dies 2 .

[0041] In addition, the bending test method of the metal plate for automobile body of the present embodiment uses the bending test equipment of the above-mentioned embodiment to perform a bending test in which the center portion between the above-mentioned two supporting portions of the test piece P is moved from the side opposite to the die 2 side by the punch 4 by displacing the slider S of the above-mentioned testing machine in the approach direction relative to the fixed table T. Figure 1 The test piece P is pressed downward from the upper part of the two dies 2 to be bent and deformed into a V shape by pressing the test piece P into the V-shaped gap between the two dies 2, and the test piece P in the bending test is photographed from below through the gap between the two dies 2 on the lower side of the test piece P. Figure 1Downward curved outer surface.

[0042] According to the bending test equipment and bending test method for metal sheets for automobile bodies of the above-mentioned embodiment, in the bending test of the test piece P, the bent outer surface of the test piece P is photographed from the die 2 side using the camera 5 having a fixed relative position relationship with the punch 4, so that the strain state of the bent outer surface of the test piece P can be photographed without deviating from the focus during the test.

[0043] Furthermore, one embodiment of the bending performance evaluation method of the present invention inputs an image of the strain state of the outer bending surface of the test piece P photographed from the die 2 side during the bending test of the test piece P in the bending test method of the above-mentioned embodiment into a conventional computer, and through an evaluation program such as digital image correlation (DIC) executed by the computer, analyzes at least one of the information on the strain distribution on the outer bending side of the test piece P and changes in the distribution, the occurrence and progression of cracks, and the distribution of cracks to evaluate the bending performance of the test piece P. According to the bending performance evaluation method of this embodiment, in addition to information related to macroscopic fracture phenomena, information extremely useful in developing materials with excellent fracture resistance, such as the progression of strain to local fracture and the limit fracture strain, can be obtained.

[0044] Figure 2 It is a perspective view showing a bending test apparatus for a metal sheet for an automobile body according to another embodiment of the present invention and a bending test method for a metal sheet for an automobile body according to another embodiment of the present invention using the bending test apparatus.

[0045] The bending test equipment for the metal plate for automobile body of this embodiment comprises: the testing machine as described above, which is arranged parallel to each other and horizontally with a gap therebetween and is pivotally supported by a support frame 1 so as to be rotatable. Figure 2 The fixed table T as a non-movable part is indicated by an imaginary line in the figure, and two rollers 6 as supporting members support two supporting parts near the two ends of the flat and rectangular test piece P made of a metal plate for an automobile body; the above-mentioned test machine is fixed to the connecting frame 3 via the connecting frame 3. Figure 2 The slide member S as the movable part of the mounting surface is indicated by an imaginary line, and the central part between the above-mentioned two supporting parts of the test piece P is moved from the side opposite to the roller 6 side. Figure 2 A sharp blade-shaped punch 7 for a bending test in which the test piece P is bent and deformed into an acute angle by pressing downward from the upper part thereof; a camera 5 having a lens facing the gap between the two rollers 6 and fixing the relative positional relationship with respect to the punch 7 by a connecting frame 3.

[0046] In addition, the bending test method of the metal sheet material for automobile body of the present embodiment uses the bending test equipment of the above-mentioned embodiment to perform a bending test in which the center portion between the above-mentioned two supporting portions of the test piece P is moved from the side opposite to the roller 6 side by the punch 7 by displacing the slider S of the above-mentioned testing machine in the approach direction relative to the fixed table T. Figure 2 The test piece P is pressed downward from the top of the roller 6 and is pressed into the gap between the two rollers 6 to be bent and deformed into an acute angle, and the test piece P in the bending test is photographed from below through the gap between the two rollers 6 on the lower side of the test piece P using a camera 5. Figure 2 The downward curved outer surface of the.

[0047] According to the bending test equipment and bending test method for metal sheets for automobile bodies of the above-mentioned embodiment, in the bending test of the test piece P, the bent outer surface of the test piece P is photographed from the roller 6 side using the camera 5 having a fixed relative position relationship with the punch 7. Therefore, it is possible to carry out, for example, a VDA238-100 bending test while photographing the strain state of the bent outer surface of the test piece P without defocusing during the test.

[0048] Furthermore, another embodiment of the bending performance evaluation method of the present invention inputs an image of the strain state of the outer bending surface of the test piece P obtained by photographing it from the roller 6 side during the bending test of the test piece P in the bending test method of the above-mentioned embodiment into a conventional computer, and through an evaluation program such as digital image correlation (DIC) executed by the computer, the strain distribution on the outer bending side of the test piece P and the change in the distribution, the occurrence and progression of cracks, and at least one of the crack distributions are analyzed to evaluate the bending performance of the test piece P. According to the bending performance evaluation method of this embodiment, in the VDA238-100 bending test, in addition to information related to macroscopic fracture phenomena, information such as the progression of strain reaching local fracture and the limit fracture strain can also be obtained.

[0049] Figure 3 Yes means Figure 1 Modification of the bending test apparatus for metal sheet for automobile body of the embodiment shown and a bending test apparatus using the same Figure 1 A perspective view of a modified example of the bending test method for a metal sheet for an automobile body according to the embodiment shown.

[0050] The bending test equipment for the metal sheet for automobile body of this modified example is relative to Figure 1 The bending test apparatus of the embodiment shown has an upside-down configuration, and two dies 2 as supporting members are fixed to the through holes of the above-mentioned testing machine via a supporting frame 1 with a gap between them. Figure 3The imaginary line in the middle represents the sliding member S as the movable part of the mounting surface. With the aid of a sponge or the like not shown, the sliding member S supports the two supporting parts near the two ends of the flat and rectangular test piece P made of a metal plate for an automobile body. The punch 4 with a V-shaped cross section is fixed to the through hole of the above-mentioned test machine via a connecting frame 3. Figure 3 The imaginary line in the middle indicates a fixed stage T as a non-movable part of the mounting surface. The camera 5 is fixed in relative position to the punch 4 via the connecting frame 3 , and the lens is directed toward the gap between the two dies 2 .

[0051] In addition, the bending test method of the metal sheet for automobile body of this modified example uses the bending test equipment of the modified example to perform a bending test, wherein the center portion between the two supporting portions of the test piece P is moved from the side opposite to the die 2 side by the punch 4 by displacing the slider S of the testing machine in the approach direction relative to the fixed table T. Figure 3 The test piece P is pressed upward from the bottom of the test piece P and is pressed into the V-shaped gap between the two dies 2 to be bent and deformed into a V-shape. The test piece P in the bending test is photographed from above through the gap between the two dies 2 on the upper side of the test piece P by using a camera 5. Figure 3 The outer surface is curved upward.

[0052] According to the bending test equipment and bending test method for metal plates for automobile bodies of the above-mentioned modified example, in the bending test of the test piece P, the camera 5 whose relative position relationship with the punch 4 is fixed is used to photograph the bent outer surface of the test piece P from the die 2 side, so that the strain state of the bent outer surface of the test piece P can be photographed without defocusing during the test, and the punch 4 and the camera 5 are fixed to the fixed table T which is a non-movable part, so that the influence of vibration caused by the displacement of the sliding part S in the bending test on the punch 4 and the camera 5 can be reduced, and the setting operation of the fixing fixture, wiring, etc. for the punch 4 and the camera 5 can be performed more simply.

[0053] Furthermore, the bending performance evaluation method of the modified example of the embodiment of the present invention will be Figure 3 In the bending test of the test piece P in the bending test method of the modified example shown, an image of the strain state of the outer surface of the bending of the test piece P obtained by photographing it from the die 2 side is input into a conventional computer, and an evaluation program such as digital image correlation (DIC) executed by the computer is used to analyze at least one of the information on the strain distribution on the outer side of the bending of the test piece P and the change in the distribution, the occurrence and progress of cracks, and the distribution of cracks to evaluate the bending performance of the test piece P. Through the bending performance evaluation method of this embodiment, in addition to information related to macroscopic fracture phenomena, information extremely useful in developing materials with excellent fracture resistance, such as the progress of strain to local fracture and the limit fracture strain, can be obtained.

[0054] Figure 4 Yes means Figure 2 Modification of the bending test apparatus for metal sheet for automobile body of the embodiment shown and a bending test apparatus using the same Figure 2 A perspective view of a modified example of the bending test method for a metal sheet for an automobile body according to the embodiment shown.

[0055] The bending test equipment for the metal sheet for automobile body of this modified example is relative to Figure 2 The bending test device of the embodiment shown has an upside-down configuration, and two rollers 6 as supporting members are arranged parallel to each other and horizontally with a gap therebetween, and are pivotally supported by the support frame 1 so as to be rotatable on the through hole of the testing machine as described above. Figure 4 The imaginary line in the middle represents the sliding member S as the movable part of the mounting surface. With the aid of a sponge or the like not shown, the sliding member S supports the two supporting parts near the two ends of the flat and rectangular test piece P made of a metal plate for an automobile body. The sharp blade-shaped punch 7 is fixed to the through hole of the above-mentioned test machine via the connecting frame 3. Figure 4 The imaginary line in the middle indicates a fixed stage T as a non-movable part of the mounting surface. The camera 5 is fixed in relative position to the punch 7 by the connecting frame 3 , and the lens is directed toward the gap between the two rollers 6 .

[0056] In addition, the bending test method of the metal sheet for automobile body of this modified example uses the bending test equipment of the modified example to perform a bending test, wherein the center portion between the two supporting portions of the test piece P is moved from the side opposite to the roller 6 side by the punch 7 by displacing the slider S of the testing machine in the approach direction relative to the fixed table T. Figure 4 The test piece P is pressed upward from the bottom of the test piece P and is pressed into the gap between the two rollers 6 to be bent and deformed into an acute angle. The test piece P in the bending test is photographed from above through the gap between the two rollers 6 on the upper side of the test piece P by using a camera 5. Figure 4 The outer surface is curved upward.

[0057] According to the bending test equipment and bending test method for metal sheets for automobile bodies of the above-mentioned modified example, in the bending test of the test piece P, the camera 5 whose relative position relationship with the punch 7 is fixed is used to photograph the bent outer surface of the test piece P from the roller 6 side. Therefore, it is also possible to carry out, for example, a VDA238-100 bending test while photographing the strain state of the bent outer surface of the test piece P without defocusing during the test. Moreover, the punch 7 and the camera 5 are fixed to the fixed table T which is a non-movable part. Therefore, the influence of vibration caused by the displacement of the sliding part S in the bending test on the punch 7 and the camera 5 can be reduced, and the setting operation of the fixing fixture, wiring, etc. for the punch 7 and the camera 5 can be carried out more simply.

[0058] Furthermore, a bending performance evaluation method according to another modified example of the embodiment of the present invention will be described in Figure 4 In the bending test of the test piece P in the bending test method of the modified example shown, an image of the strain state of the outer surface of the bending of the test piece P obtained by photographing it from the roller 6 side is input into a conventional computer, and an evaluation program such as digital image correlation (DIC) executed by the computer is used to analyze at least one of the information on the strain distribution on the outer side of the bending of the test piece P and the change in the distribution, the occurrence and progress of cracks, and the distribution of cracks to evaluate the bending performance of the test piece P. According to the bending performance evaluation method of this modified example, in addition to information related to macroscopic fracture phenomena, information extremely useful in developing materials with excellent fracture resistance, such as the progress of strain to local fracture and the limit fracture strain, can be obtained.

[0059] Figure 5 Yes means Figure 2 Another modification of the bending test apparatus for metal sheet for automobile body of the embodiment shown and a bending test apparatus using the same Figure 2 A perspective view of another modified example of the bending test method for a metal sheet for an automobile body according to the embodiment shown.

[0060] The bending test equipment for the metal sheet for automobile body of this modified example will Figure 2 A modified example of the bending test device of the embodiment shown is Figure 4 At least one of the two conventional cylindrical rollers 6 in the bending test apparatus shown in the figure, in the example shown in the figure, is replaced by a half roller 8 having a rotation axis portion and a portion of a circular cross section viewed from the rotation axis direction is missing, and the other portion is the same as Figure 4 The bending test device shown is constructed in the same way.

[0061] In addition, the bending test method of the metal sheet for automobile body of this modified example uses the bending test equipment of the modified example to perform a bending test, wherein the center portion between the two supporting portions of the test piece P is moved from the side opposite to the half roller 8 side by the punch 7 by displacing the slider S of the testing machine in the approach direction relative to the fixed table T. Figure 5 The test piece P is pressed upward from the bottom of the test piece P and is pressed into the gap between the two half rollers 8 to be bent and deformed into an acute angle. The test piece P in the bending test is photographed from above through the gap between the two half rollers 8 on the upper side of the test piece P using a camera 5. Figure 5 The outer surface is curved upward.

[0062] According to the bending test apparatus and bending test method for a metal sheet material for automobile bodies of the above-mentioned modified example, in the bending test of the test piece P, the camera 5 whose relative positional relationship with the punch 7 is fixed is used to photograph the outer surface of the bending of the test piece P from the half roller 8 side, so that the strain state of the outer surface of the bending of the test piece P can be photographed without defocusing during the test while performing the VDA238-100 bending test, for example. In addition, since the punch 7 and the camera 5 are fixed to the fixed table T as a non-movable part, the influence of the vibration caused by the displacement of the slider S in the bending test on the punch 7 and the camera 5 can be reduced, and the setting operation of the fixing jig and wiring for the punch 7 and the camera 5 can be performed more simply. In addition, since the camera 5 can ensure the field of view and brightness through the missing part of the half roller 8, and can photograph the outer surface of the bending of the test piece P from the half roller 8 side, a clearer image can be obtained.

[0063] Furthermore, a bending performance evaluation method according to another modified example of the embodiment of the present invention will be Figure 5 In the bending test of the test piece P of the bending test method of the modified example shown, a clearer image of the strain state of the outer surface of the bending of the test piece P obtained by photographing it from the side of the half roller 8 is input into a conventional computer. Through the evaluation program such as the digital image correlation method (DIC) executed by the computer, the strain distribution on the outer side of the bending of the test piece P and the change of the distribution, the occurrence and progress of cracks and at least one of the distribution of cracks are analyzed to evaluate the bending performance of the test piece P. According to the bending performance evaluation method of this modified example, in addition to the information related to the macroscopic fracture phenomenon, the progress of the strain to reach local fracture, the limit fracture strain, etc., which are extremely useful information in the development of materials with excellent fracture resistance characteristics, can be obtained.

[0064] It should be noted that in the bending test equipment of the above-mentioned embodiments and modified examples of the present invention, Figure 1 and Figure 3The two dies 2 shown in the figure support the support parts at two locations near the two ends of the test piece P by using, for example, a die having an opening in the center. Moreover, as the camera 5, for example, a single-lens reflex film camera, a digital camera, etc. can be used, and a remote shutter device is pre-set in the camera 5 so that it can take pictures at any time. Moreover, in the bending test equipment of the above-mentioned embodiment and the modified example, the number of cameras 5 to be used is determined according to the effective utilization method of the camera 5. For example, when there are many shooting locations, or when a three-dimensional DIC analysis of the shot image is performed, Figure 1 to Figure 5 Two cameras are provided as shown, or a structure is provided in which two or more cameras can be used. In addition, the camera 5 is preferably a camera having a lens and an imaging element with the highest possible resolution, taking into account the size of an image to be captured and the size of the tester.

[0065] [Example]

[0066] use Figure 4 The bending test equipment and bending test method of the modified example shown in the figure performed a bending test in accordance with the VDA238-100 standard, and captured an image of the outer side of the bend of the test piece P in the bending test. The test pieces P were made of three types of materials A, B, and C, each of which was 50 mm square and ground after cutting a sheet of high-strength steel plate for automobile bodies. The interval between the two rollers 6 was set to the plate thickness of the test piece P × 2 + 0.5 mm, and the radius of the front end of the punch 7 was set to 0.4 mm. In the above bending test, the test piece P placed between the punch 7 and the roller 6 was bent and deformed by the roller 6 fixed on the slide S as the movable part of the test machine and the punch 7 fixed on the fixed table T as the non-movable part of the test machine. The punch speed was set to 5 mm / min. The load acting on the slide S and the stroke (displacement) of the slide S during this process were measured, and a load-stroke curve was output. The load-stroke curve shows that the load increases with the start of bending deformation, and the bending deformation portion breaks at a certain deformation stroke to show the maximum load, and then the load decreases. The deformation stroke showing the maximum load is defined as the breaking stroke.

[0067] In order to photograph the deformation state of the outer side of the bend of the test piece P and perform a three-dimensional DIC analysis of the image, two single-lens reflex cameras 5 are adjusted to a position where they can photograph the outer side of the bend of the test piece P from between the two rollers 6, and fixed on a fixed table T which is a non-movable part of the test machine. The bending test starts, the bending deformation starts, and the camera 5 starts to continuously photograph as the load increases, and the photographing speed is set to 1 frame / second. The above bending test ends at an appropriate time after the load is reduced due to the fracture of the test piece P.

[0068] Then, the three-dimensional DIC analysis was applied to the continuous photographs taken by the above method by the bending performance evaluation method of the above modification, and the strain amount of the bending outer side of the test piece P when the strain in the flat state before the test was set to 0 was analyzed, and the strain amount of the bending outer side of the test piece P at the above fracture stroke was obtained. The above strain amount was defined as the fracture strain. Figure 6 Table 1 shows the material properties, fracture path, and fracture strain of each material.

[0069] [Table 1]

[0070]

[0071] As shown in Table 1, in this embodiment, the fracture strain of material C is the largest, and the fracture strains of different materials can be measured by the bending test equipment and bending test method of the above-mentioned modified example and the bending performance evaluation method of the above-mentioned modified example. This means that the amount of strain that can be allowed in bending deformation varies according to the material, and it can be confirmed that the bendability of the material can be evaluated based on the difference in the above-mentioned fracture strain.

[0072] The above description is based on the illustrated examples, but the present invention is not limited to the above examples. For example, in the above embodiments, the metal plate of the test object is set as a high-strength steel plate, but it can also be replaced by a normal steel plate or other plate material, such as an aluminum plate.

[0073] In addition, in the above embodiment, using Figure 4 The bending test apparatus and method of the modified example shown perform a bending test in accordance with VDA Standard 238-100, but a bending test apparatus and a bending test method of other embodiments and modified examples may be used instead.

[0074] Industrial Applicability

[0075] Thus, according to the bending test equipment and bending test method of metal sheet materials for automobile bodies of the present invention, a supporting member is used to support the supporting parts of two locations of a flat test piece formed by metal sheet materials for automobile bodies, and a bending test is performed in which a punch is used to press a portion between the supporting parts of the two locations of the test piece from the side opposite to the supporting member to cause the test piece to bend and deform. In this bending test, a camera having a fixed relative positional relationship with the punch is used to photograph the bent outer surface of the test piece from the supporting member side, thereby being able to photograph the strain state of the bent outer surface of the test piece without defocusing during the test.

[0076] Furthermore, according to the bending performance evaluation method of the present invention, the bending performance of the test piece is evaluated based on information on the strain distribution and its changes on the outer side of the bend of the test piece, the occurrence and progression of cracks, and / or the distribution of cracks obtained from the image of the outer side of the bend of the test piece captured by the camera during the bending test. The bending test is performed by the bending test equipment, so in addition to information related to macroscopic fracture phenomena, information extremely useful in developing materials with excellent fracture resistance, such as the progression of strain to local fracture and the limit fracture strain, can be obtained.

[0077] Description of symbols

[0078] 1 Support frame

[0079] 2 Die

[0080] 3 Linking framework

[0081] 4 Punch

[0082] 5. Camera

[0083] 6 Rollers

[0084] 7 Punch

[0085] 8 Half Rollers

[0086] P Test piece

[0087] S Slide

[0088] T fixed table.

Claims

1. A bending test equipment for metal sheets for automobile bodies, characterized in that: have: A supporting member supports two supporting portions of a flat test piece formed of a metal plate for an automobile body; a punch for performing a bending test of pressing a portion between the two supporting portions of the test piece from a side opposite to the supporting member side to bend and deform the test piece; and a camera for photographing, from the side of the supporting member, the curved outer surface of the test piece in the bending test performed by the punch, The relative positions of the punch and the camera in the bending test are fixed. The bending test equipment for a metal plate for an automobile body includes a testing machine that moves a movable portion forward and backward relative to a non-movable portion, the punch and the camera are provided at the non-movable portion, and the supporting member is provided at the movable portion.

2. The bending test equipment for metal sheet for automobile body according to claim 1, characterized in that: The supporting member is two rollers that are disposed in parallel and horizontally with a distance therebetween.

3. The bending test equipment for metal sheet for automobile body according to claim 2, characterized in that: At least one of the two rollers has a rotation axis portion and is a roller in which a part of a circular cross section viewed from the rotation axis direction is missing.

4. A bending test method for a metal sheet for an automobile body, characterized in that: A flat test piece made of a metal plate for an automobile body is supported at two supporting portions by a supporting member. When performing a bending test in which a punch is used to press a portion between the two supporting portions of the test piece from a side opposite to the supporting member side to bend and deform the test piece, a camera having a fixed relative positional relationship with the punch is used to photograph the curved outer surface of the test piece from the supporting member side, The punch and the camera are provided on the non-movable portion of a testing machine that moves a movable portion forward and backward relative to a non-movable portion, and the support member is provided on the movable portion.

5. The bending test method of the metal sheet for automobile body according to claim 4, characterized in that: The supporting member is two rollers that are disposed in parallel and horizontally with a distance therebetween.

6. The bending test method of the metal sheet for automobile body according to claim 5, characterized in that: At least one of the two rollers has a rotation axis portion and is a roller in which a part of a circular cross section viewed from the rotation axis direction is missing.

7. A method for evaluating the bending performance of a metal sheet for an automobile body, characterized in that: A bending test is performed by a bending test apparatus for a metal sheet material for an automobile body according to any one of claims 1 to 3, wherein the bending performance evaluation method for a metal sheet material for an automobile body evaluates the bending performance of the test piece based on information on the strain distribution and its changes on the bending outer side of the test piece, the occurrence and progress of cracks, and / or the distribution of cracks obtained from an image of the bending outer side of the test piece captured by the camera during the bending test.

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