Test specimen and test method

Abstract

To provide a test body of a simple constitution and a test method that enable a performance evaluation test corresponding to a deformation mode of an actual part at the time of automobile collision.SOLUTION: A test body 10 includes a first member 12 and a second member 14. The first member 12 extends in the X direction and has a hat shape in a cross section orthogonal to the X direction. The second member 14 extends in the X direction and is connected to a pair of flange portions 24 of the first member 12 so as to form a closed cross section together with the first member 12. At one end portion of the test body 10 in the X direction, a bent portion 22b is formed in a central portion of a top plate portion 20 of the first member 12 in a width direction, and a bent portion 14b is formed in a central portion of the second member 14 in the width direction. Between the one end portion 11 and the other end portion 13 of the test body 10, a bend-inducing portion 32 for causing the first member 12 to be laterally bent and deformed to a side opposite to the second member 14 when viewed from the width direction is formed in the first member 12.SELECTED DRAWING: Figure 11

Description

[Technical Field]

[0001] The present invention relates to a test specimen and a test method that can be used to evaluate the crashworthiness of vehicle structural members. [Background technology]

[0002] In order to improve the collision safety of automobiles, it is necessary for the automobile frame to appropriately absorb collision energy. Therefore, various techniques have been proposed for appropriately absorbing collision energy in the automobile frame.

[0003] For example, Patent Document 1 discloses a front side frame that has an energy absorbing section in the front and a bending section behind the energy absorbing section. The front side frame disclosed in Patent Document 1 is configured so that, when subjected to a frontal collision load, buckling deformation occurs in the energy absorbing section, followed by lateral bending deformation in the bending section. This configuration is believed to stabilize the deformation behavior of the front side frame during a collision and enable appropriate absorption of collision energy. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-179301 Summary of the Invention [Problem to be solved by the invention]

[0005] When a new material (such as steel plate) is developed for use in the above-mentioned frames, it is often necessary to evaluate the individual component to see whether it will provide the required performance (mainly crashworthiness) when installed in an automobile body. In this case, if a test is conducted using a test specimen that faithfully reproduces the dimensions and shape of the component being evaluated, simulating the complex impact inputs that occur during an automobile collision, it becomes difficult to proceed with development efficiently.

[0006] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a test piece and a test method with a simple configuration that enable performance evaluation tests corresponding to the deformation modes of actual parts during an automobile collision. [Means for solving the problem]

[0007] (1) A test specimen according to one embodiment of the present invention is a first member extending in a first direction and having a hat shape in a cross section perpendicular to the first direction, the first member including a top plate portion, a pair of side wall portions, and a pair of flange portions; a plate-like second member extending in the first direction and connected to the pair of flange portions so as to form a closed cross section together with the first member in a cross section perpendicular to the first direction, When a direction parallel to the top plate portion and perpendicular to the first direction is defined as a width direction, and a direction from the second member toward the top plate portion along a direction perpendicular to the first direction and the width direction is defined as a height direction, a first bent portion bent toward the height direction is formed at a center portion in the width direction of the top plate portion at one end portion in the first direction, At the one end, a second bent portion bent toward the height direction is formed in a central portion in the width direction of the second member, The present invention is characterized in that, between the one end and the other end opposite the one end in the first direction, a bending induction portion is formed in the first member to cause the first member to bend laterally in the opposite direction to the second member when viewed from the width direction.

[0008] (2) At the one end in the first direction, a third bent portion bent inward in the width direction may be formed in a central portion in the height direction of each of the side wall portions.

[0009] (3) The bending induction portion is a recess formed in the thickness direction of the top plate portion so as to be recessed toward the second member side and extend in the width direction, The recessed portion may have a recessed depth of 5% or more and less than 30% of the height of the first member.

[0010] (4) A through hole may be formed in the first member between the one end and the other end.

[0011] (5) The pair of flange portions and the second member may be spot-welded.

[0012] (6) The height of the first member is 20 to 200 mm, The width of the top plate portion may be 20 to 300 mm.

[0013] (7) A test method according to one embodiment of the present invention includes: A test method for evaluating collision performance using the above test specimen, comprising: The method is characterized in that, while the test body is supported from the other end side in the first direction, a load is input to the test body from the one end side in the first direction so as to crush the test body in the first direction. [Effects of the Invention]

[0014] According to the present invention, a performance evaluation test corresponding to the deformation mode of an actual part during an automobile collision can be carried out using a test specimen with a simple configuration. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a plan view showing the front part of an automobile body 1. FIG. [Figure 2] FIG. 2 is a diagram for explaining an example of a deformation mode of the front side member 2 when a collision load is input to the automobile body 1 from the front. [Figure 3] FIG. 3 is a diagram showing a test specimen. [Figure 4] FIG. 4 is a diagram for explaining the drop weight test. [Figure 5]FIG. 5 is a schematic diagram showing an example of deformation of the tip of the test specimen obtained by computer simulation. [Figure 6] FIG. 6 is a schematic diagram showing another example of deformation of the tip of the test specimen. [Figure 7] Figure 7 shows the test specimen (analysis model) after deformation caused by applying an impact load to the tip. [Figure 8] FIG. 8 is a diagram showing an example of the shape of the tip of the test piece. [Figure 9] FIG. 9 is a view of the test specimen as seen from one side in the longitudinal direction. [Figure 10] FIG. 10 is a diagram showing another example of the shape of the tip of the test specimen. [Figure 11] FIG. 11 is a perspective view showing a test specimen according to one embodiment of the present invention. [Figure 12] FIG. 12 is a view of the test specimen as seen from one side in the longitudinal direction. [Figure 13] FIG. 13 is a schematic diagram showing the test specimen after the drop weight test. [Figure 14] FIG. 14 is a perspective view showing a test specimen according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0016] (Study by the inventors) FIG. 1 is a plan view showing the front portion of an automobile body 1. Specifically, FIG. 1 shows a front side member 2, a crash box 3, and a bumper beam 4. The bumper beam 4 is connected to the front end of the front side member 2 via the crash box 3. Normally, two front side members 2 are arranged symmetrically on the left and right sides of the front portion of the automobile body 1, but FIG. 1 shows only one front side member 2.

[0017] FIG. 2 is a diagram illustrating an example of a deformation mode of the front side member 2 when a collision load is input to the automobile body 1 from the front. In the example shown in FIG. 2, when a collision load is input to the automobile body 1 from the front, the front portion of the front side member 2 is crushed and deformed into an accordion-like shape together with the crash boxes 3. In addition, the central portion of the front side member 2 in the fore-and-aft direction is laterally bent and deformed toward the outside in the width direction of the automobile body 1. In this example, the front side member 2 is configured so that after the front portion is crushed and deformed into an accordion-like shape, the central portion is laterally bent and deformed. By deforming the front side member 2 in this deformation mode, the collision energy input to the automobile body 1 can be appropriately absorbed.

[0018] However, in the past, when evaluating the performance of energy absorption parts such as front side members, no test specimen with a simple configuration capable of reproducing the above-mentioned deformation mode has been proposed. Therefore, the present inventors conducted research on a test specimen and test method that can reproduce the above-mentioned deformation mode with a simple configuration. Specifically, the inventors attempted to reproduce, with a test specimen with a simple configuration, the deformation mode of an energy absorption part used in an automobile body frame that undergoes bellows-like crushing deformation and then lateral bending deformation when an impact load is applied in the longitudinal direction of the part.

[0019] The inventors first attempted to reproduce a deformation mode in which a specimen 100 shown in FIG. 3 undergoes bellows-like crushing deformation followed by lateral folding deformation. In FIG. 3(a), (a) is a side view of the specimen 100, and (b) is an end view showing the cross section taken along line bb in (a). In FIG. 3(b), hatching indicating cross sections has been omitted to avoid cluttering the drawing. In FIG. 3(b), arrows indicating the mutually orthogonal X, Y, and Z directions are added to clarify the positional relationship of each part of the specimen 100. Arrows indicating the X, Y, and Z directions are also added as appropriate in the figures described below. The direction parallel to the X direction is the length direction of the specimen 100, the Y direction is the height direction of the specimen 100, and the direction parallel to the Z direction is the width direction of the specimen 100.

[0020] The test specimen 100 shown in Fig. 3 has a first member 102 and a second member 104. The first member 102 extends in the X direction and has a hat shape in a cross section perpendicular to the X direction. Specifically, the first member 102 has a top plate portion 102a, a pair of side wall portions 102b, and a pair of flange portions 102c. The second member 104 is formed in a plate shape and is provided so as to extend in the X direction.

[0021] The inventors fabricated the test specimen 100 using a steel plate (thickness: 1.6 mm, tensile strength: 980 MPa class) taken from a laboratory material. Specifically, a steel plate having a width of 170 mm and a length of 300 mm taken from the laboratory material was press-formed to fabricate the first member 102. A steel plate having a width of 100 mm and a length of 300 mm taken from the laboratory material was also used as the second member 104. The second member 104 was joined to a pair of flange portions 102c of the first member 102 so as to form a closed cross section together with the first member 102 in a cross section perpendicular to the X direction. Specifically, the first member 102 was joined to the pair of flange portions 102c by spot welding.

[0022] 3(a), a recess 102d is formed in the top plate portion 102a so as to be recessed toward the second member 104 and extend in the Z direction. The recess 102d is formed to induce lateral bending deformation of the test piece 100 in a drop weight test, which will be described later.

[0023] The length L of the test piece 100 was 300 mm, and the distance D from the center of the recess 102d to one end of the test piece 100 was 120 mm. The recess 102d was formed by statically applying a load to the top plate portion 102a using a punch with a tip curvature radius of 30 mm. The recess 102d had a depression amount in the Y direction (punch depression amount) of 7 mm. The width W1 of the top plate portion 102a was 60 mm, the height H of the first member 102 was 40 mm, and the width (length in the Z direction) of the first member 102 and the width W2 of the second member 104 were 100 mm.

[0024] The inventors conducted a drop weight test on the test specimen 100 having the above-described configuration. FIG. 4 is a diagram for explaining the drop weight test. As shown in FIG. 4, in the drop weight test, the test specimen 100 was fixed on a support plate 200 so that the length direction (X direction) of the test specimen 100 was parallel to the up-down direction. In this state, a plate-shaped weight 300 with a mass of 751 kg was dropped on the tip end 101 of the test specimen 100, thereby inputting an impact load in the length direction (X direction) of the test specimen 100. The falling speed of the weight 300 was set to 23 km / h.

[0025] As a result of the drop weight test, the targeted crushing deformation did not occur at the upper end of test piece 100, but crushing deformation occurred only in recess 102d. In other words, when an impact load was applied in the longitudinal direction, the front end was crushed like an accordion, followed by lateral bending deformation in the central or rear portion, which was the targeted deformation mode of an energy absorbing part in an actual vehicle, and it was not possible to reproduce this.

[0026] Therefore, the inventors performed a computer simulation to analyze how each part of the test specimen 100 deforms during a drop weight test. FIG. 5 is a schematic diagram showing an example of the deformation of the tip portion 101 of the test specimen 100 obtained by the computer simulation. Note that in FIG. 5, the deformation of the tip portion 101 of the test specimen 100 is shown at a magnification of 10 times. Also in FIG. 5, the deformation direction of each part of the tip portion 101 is indicated by dashed arrows.

[0027] As shown in FIG. 5, computer simulation results indicate that when an impact load is applied to the tip portion 101, the relatively wide and low-rigid central portions of the top plate portion 102a and the second member 104 deform so as to bend toward the center of gravity of the tip portion 101 (the inner side of the closed cross section). Meanwhile, the ridge portions 102e on both sides of the top plate portion 102a and the ridge portion 102f between the side wall portion 102b and the flange portion 102c rotate in response to the bending of the top plate portion 102a and the second member 104, maintaining their original shapes. As a result, the pair of side wall portions 102b deform so as to bend outward. Furthermore, the pair of flange portions 102c and both end portions of the second member 104 (portions fixed to the flange portion 102c) deform so as to bend toward the opposite side of the top plate portion 102a in the Y direction. Thus, the second member 104 bends in opposite directions at the central portion and both end portions. For this reason, it is believed that cross-sectional collapse was unlikely to occur at the tip portion 101, and the test piece 100 could not be stably deformed in the bellows shape in the length direction.

[0028] Therefore, the inventors further conducted analysis and considered deforming the tip portion 101 of the test specimen 100 as shown in Fig. 6 when an impact load is input to the tip portion 101 of the test specimen 100. The tip portion 101 shown in Fig. 6 differs from the tip portion 101 shown in Fig. 5 in that the top plate portion 102a, the pair of flange portions 102c, and both end portions of the second member 104 are deformed so as to bend in the height direction.

[0029] As a result of the computer simulation, it was found that when an impact load is input to the tip 101 of the test specimen 100, the tip 101 is deformed as shown in FIG. 6, and as a result, the tip 101 side of the test specimen 100 is crushed and deformed like an accordion, as shown in FIG. 7, and then a lateral bending deformation occurs at the recess 102d. Note that FIG. 7 shows the results obtained by the computer simulation, and illustrates the test specimen 100 (analysis model) after the tip 101 is deformed by inputting an impact load to it. In FIG. 7, (a) is a view of the test specimen 100 as seen from the side, and (b) is a view of the test specimen 100 as seen from the height direction. In FIG. 7, the deformation magnification in the X direction is set to 0 times to make the deformation mode of the test specimen 100 easier to see.

[0030] In the tip portion 101 shown in FIG. 6, the top plate portion 102a and the central portion of the second member 104 are bent in the height direction, and further, both of the pair of side wall portions 102b are bent inward. As a result of the tip portion 101 being deformed in this manner, at the initial stage of the collision, as shown in FIG. 7, both of the top plate portion 102a and the second member 104 are tilted in the height direction, and both of the pair of side wall portions 102b are deformed so as to be tilted inward. As a result of the tip portion 101 being deformed in this manner at the initial stage of the collision, the top plate portion 102a and the second member 104 are subsequently more likely to deform to exhibit waveforms of the same phase, and the pair of side wall portions 102b are more likely to deform to exhibit waveforms of opposite phase. This is thought to enable stable bellows-like crushing deformation to be generated on the tip portion 101 side of the test specimen 100.

[0031] 6, the center and both end portions (joints with the flange portions 102c) of the second member 104 are deformed so as to bend in the height direction. This bending of the center and both end portions of the second member 104 in the same direction at the beginning of the collision is thought to make it easier for cross-sectional collapse to occur in the tip portion 101. This is thought to make it possible to more stably produce bellows-like crushing deformation in the test specimen 100.

[0032] Next, the inventors analyzed a configuration for causing deformation as shown in Fig. 6 in tip portion 101 when an impact load is input. As a result, as shown in Fig. 8 and Fig. 9, it was found that by forming bent portions 106, 108 that are bent so as to be recessed in the height direction in the center of top plate portion 102a and the center of second member 104 in tip portion 101 of test body 100, deformation as shown in Fig. 6 can be caused.

[0033] Specifically, referring to FIGS. 6, 8, and 9, by forming bent portions 106 in advance in top plate portion 102a, when an impact load is input to tip portion 101, top plate portion 102a can be deformed so as to bend in the height direction. At this time, ridge portion 102e rotates in response to the bending of top plate portion 102a so as to maintain its original shape. This allows pair of side wall portions 102b to be deformed so as to bend inward. Furthermore, by rotating ridge portion 102f in response to the bending of pair of side wall portions 102b so as to maintain its original shape, pair of flange portions 102c and both end portions of second member 104 can be deformed so as to bend in the height direction. Furthermore, by forming bent portions 108 in advance in second member 104, not only both end portions of second member 104 but also the central portion of second member 104 can be deformed so as to bend in the height direction.

[0034] 10, bent portions 110 bent inward in the width direction may be formed in the center of each side wall portion 102b at the tip portion 101 of the test specimen 100. In this case, when an impact load is applied to the tip portion 101, the pair of side wall portions 102b are more likely to bend inward. As a result, when an impact load is applied, deformation such as that shown in FIG. 6 is more likely to occur at the tip portion 101.

[0035] (Description of the embodiment of the present invention) The present invention has been made based on the above findings. A test specimen and a test method according to an embodiment of the present invention will be described below.

[0036] FIG. 11 is a perspective view showing a test specimen 10 according to one embodiment of the present invention. In FIG. 11, arrows indicating the mutually orthogonal X, Y, and Z directions are added to clarify the positional relationship of each part of the test specimen 10. Arrows indicating the X, Y, and Z directions are also added as appropriate in each of the drawings described below. In this embodiment, the direction parallel to the X direction corresponds to the first direction. In this embodiment, the direction parallel to the X direction is the length direction, the Y direction is the height direction, and the direction parallel to the Z direction is the width direction.

[0037] As shown in FIG. 11 , the test piece 10 according to this embodiment has a first member 12 and a second member 14. The first member 12 extends in the X direction and has a hat shape in a cross section perpendicular to the X direction. In this embodiment, the first member 12 has a top plate portion 20, a pair of side wall portions 22, and a pair of flange portions 24. The second member 14 is formed in a plate shape and is provided so as to extend in the X direction. The first member 12 and the second member 14 are made of a metal material (for example, a steel plate having a thickness of 1.0 to 3.2 mm). In this embodiment, the first member 12 and the second member 14 can be made, for example, using a steel plate taken from a laboratory material, similar to the first member 102 and the second member 104 described above.

[0038] Fig. 12 is a view of the test specimen 10 as viewed from one side in the longitudinal direction (the X-direction side). As shown in Figs. 11 and 12, each flange portion 24 is provided so as to extend in the X-direction. In this embodiment, each flange portion 24 includes a flat portion 24a and a ridge portion 24b. The flat portion 24a is a flat portion provided so as to face the second member 14. The ridge portion 24b is an arc-shaped curved portion provided so as to rise from the inner end of the flat portion 24a in the width direction.

[0039] The pair of side wall portions 22 are provided to face each other in the width direction. In this embodiment, each side wall portion 22 includes a flat portion 22a and a bent portion 22b. The flat portion 22a is a flat portion extending from the ridge portion 24b toward a ridge portion 20b (described later) of the top plate portion 20. The bent portion 22b is a portion bent at one edge of the side wall portion 22 (more specifically, the flat portion 22a) in the length direction so as to be recessed inward in the width direction. The bent portion 22b is formed in the center in the height direction of the side wall portion 22. In this embodiment, the bent portion 22b corresponds to the third bent portion. In this embodiment, it is preferable to form the bent portion 22b so that the center of the bent portion 22b coincides with the center of the flat portion 22a in the height direction. Note that the center of the bent portion 22b does not have to completely coincide with the center of the flat portion 22a in the height direction. However, it is preferable that the deviation in height between the center of the bent portion 22b and the center of the flat portion 22a is within 30% of the width Wc (length in the Y direction) of the flat portion 22a.

[0040] The top plate portion 20 is provided to connect the pair of side wall portions 22. In this embodiment, the top plate portion 20 includes a flat portion 20a, a pair of ridge portions 20b, and a bent portion 20c. The flat portion 20a is a flat portion that extends in the X direction and is provided to face the second member 14 in the thickness direction of the second member 14. The pair of ridge portions 20b are provided on both sides of the flat portion 20a in the width direction. The ridge portion 20b is an arc-shaped curved portion that connects the flat portion 20a and the flat portion 22a of the side wall portion 22. The bent portion 20c is a portion that is bent at an edge on one side in the length direction of the top plate portion 20 (more specifically, the flat portion 20a) so as to be recessed toward the height direction. The bent portion 20c is formed in the center of the top plate portion 20 in the width direction. In this embodiment, the bent portion 20c corresponds to the first bent portion. In this embodiment, it is preferable to form the bent portion 20c so that the center of the bent portion 20c and the center of the flat portion 20a coincide with each other in the width direction. Note that the centers of the bent portion 20c and the flat portion 20a do not have to coincide completely with each other in the width direction. However, it is preferable that the deviation between the centers of the bent portion 20c and the flat portion 20a in the width direction is within 30% of the width Wa of the flat portion 20a.

[0041] The second member 14 is connected to a pair of flange portions 24 of the first member 12 so as to form a closed cross section together with the first member 12 in a cross section perpendicular to the X direction. In this embodiment, the second member 14 includes a flat portion 14a and a bent portion 14b. In this embodiment, the flat portion 14a of the second member 14 is joined to the pair of flange portions 24 by a plurality of spot welds 30 formed in a line in the longitudinal direction. The bent portion 14b is a portion that is bent so as to be recessed in the height direction at an edge on one side in the longitudinal direction of the second member 14 (more specifically, the flat portion 14a). The bent portion 14b is formed in the center in the width direction of the second member 14. In this embodiment, the bent portion 14b corresponds to the second bent portion. In this embodiment, it is preferable to form the bent portion 14b so that the center of the bent portion 14b coincides with the center of the flat portion 14a in the width direction. Note that the center of the bent portion 14b does not have to completely coincide with the center of the flat portion 14a in the width direction. However, it is preferable that the deviation in the width direction between the center of the bent portion 14b and the center of the flat portion 14a be within 30% of the width Wb of the flat portion 14a. The method of joining the second member 14 and the pair of flange portions 24 is not limited to spot welding, and various known methods can be used. For example, the second member 14 and the pair of flange portions 24 may be joined by laser welding or using fastening members (bolts and nuts).

[0042] Similar to the above-described bent portions 106, 108, and 110 of test specimen 100, bent portions 20c, 14b, and 22b are provided at one end 11 of test specimen 10 in order to stably crush and deform test specimen 10 into an accordion-like shape in the longitudinal direction when a test is conducted in which an impact load is input to one end 11 of test specimen 10. Referring to Fig. 12, the width Wt of bent portion 20c, the width Ws of bent portion 14b, and the width Wp of bent portion 22b may be set appropriately depending on the requirements of test specimen 10 (test specimen dimensions, material strength, material thickness, etc.), test conditions, etc.

[0043] However, if the width Wt of the bent portion 20c is too small, there is a risk that the top plate portion 20 will not be able to bend sufficiently in the height direction when an impact load is input to one end portion 11 of the test piece 10. For this reason, the width Wt of the bent portion 20c is preferably 10% or more of the width Wa of the flat portion 20a, more preferably 20% or more, and even more preferably 30% or 40% or more.

[0044] On the other hand, if the width Wt of the bent portion 20c is too large, there is a risk that the cross-sectional strength required of the test specimen 10 may not be sufficiently ensured. For this reason, the width Wt of the bent portion 20c is preferably 100% or less of the width Wa of the flat portion 20a. In other words, the bent portion 20c is preferably formed more inward in the width direction than the pair of ridge portions 20b. The width Wt of the bent portion 20c is more preferably 90% or less of the width Wa of the flat portion 20a.

[0045] Similarly, if the width Ws of the bent portion 14b is too small, there is a risk that the second member 14 will not be able to bend sufficiently in the height direction when an impact load is input to the one end 11 of the test piece 10. For this reason, the width Ws of the bent portion 14b is preferably 10% or more of the width Wb of the flat portion 14a, more preferably 20% or more, and even more preferably 30% or 40% or more. In this embodiment, the bent portion 14b is formed more inward than the pair of side wall portions 22 in the width direction.

[0046] Furthermore, if the width Wp of the bent portion 22b (the length in the height direction of the test piece 10) is too small, the effect of the bent portion 22b cannot be sufficiently obtained. For this reason, the width Wp of the bent portion 22b is preferably 10% or more of the width Wc of the flat portion 22a (the length in the height direction of the test piece 10), more preferably 20% or more, and even more preferably 30% or 40% or more.

[0047] On the other hand, if the width Wp of the bent portion 22b is too large, it may be difficult to ensure the cross-sectional strength required of the test piece 10. For this reason, the width Wp of the bent portion 22b is preferably 100% or less of the width Wc of the flat portion 22a, and more preferably 90% or less.

[0048] Similarly, the depth Dt of the bent portion 20c, the depth Ds of the bent portion 14b, and the depth Dp of the bent portion 22b may be appropriately set depending on the requirements of the test specimen 10 (such as the test specimen dimensions, material strength, and material thickness) and the test conditions. However, if the depth Dt of the bent portion 20c is too small, the effect of the bent portion 20c may not be fully obtained. Therefore, the depth Dt of the bent portion 20c is preferably at least 0.5 times the thickness of the first member 12, and more preferably at least the thickness of the first member 12. On the other hand, if the depth Dt of the bent portion 20c is too large, fracture may occur in the bent portion 20c. Therefore, the depth Dt of the bent portion 20c is preferably at most 10 times the thickness of the first member 12. Similarly, the depth Ds of the bent portion 14b is preferably at least 0.5 times the thickness of the second member 14, more preferably at least the thickness of the second member 14, and preferably at most 10 times the thickness of the second member 14. Similarly, the depth Dp of the bent portion 22b is preferably at least 0.5 times the thickness of the first member 12, more preferably at least the thickness of the first member 12, and preferably at most 10 times the thickness of the first member 12.

[0049] Referring to FIG. 11, the length Lt of the bent portion 20c in the longitudinal direction of the specimen 10 is not particularly limited. However, if the length Lt of the bent portion 20c is too short, the effect of the bent portion 20c may not be sufficiently obtained. For this reason, the length Lt of the bent portion 20c is preferably 1 mm or more, more preferably 2 mm or more. On the other hand, if the length Lt of the bent portion 20c is too long, the cross-sectional strength required of the specimen 10 may not be sufficiently ensured. For this reason, the length Lt of the bent portion 20c is preferably 40% or less of the width Wt of the bent portion 20c (see FIG. 12). The lengths of the bent portions 14b and 22b in the longitudinal direction of the specimen 10 are also not particularly limited. For the same reason, the lengths of the bent portions 14b and 22b are preferably 1 mm or more, more preferably 2 mm or more. Furthermore, the lengths of the bent portions 14b and 22b are preferably 40% or less of the widths Ws and Wp of the bent portions 14b and 22b.

[0050] As shown in Fig. 11, a bending induction portion 32 is formed in the first member 12. Specifically, the bending induction portion 32 is formed in the first member 12 between one end 11 of the test piece 10 and the other end 13 opposite to the one end 11 in the longitudinal direction of the test piece 10. In this embodiment, the bending induction portion 32 is formed closer to the other end 13 than to the center portion in the longitudinal direction of the test piece 10. In addition, in this embodiment, the bending induction portion 32 is formed so as to be continuous across the top plate portion 20, the pair of side wall portions 22, and the pair of flange portions 24.

[0051] The bending induction portion 32 is a portion for causing the first member 12 to undergo lateral bending deformation in the direction opposite to the second member 14 when an impact load is applied to one end 11 of the test specimen 10, as viewed from the Z direction. In this embodiment, the cross-sectional strength of the bending induction portion 32 is set relatively lower than that of the surrounding portion. As a result, when an impact load is applied to one end 11 of the test specimen 10, the bending induction portion 32 acts as a starting point for lateral bending deformation of the first member 12 in the height direction. As a result, the test specimen 10 undergoes lateral bending deformation in the height direction. The bending induction portion 32 can be formed, for example, by partially changing the heat treatment conditions for the first member 12.

[0052] The bend inducement portion may be configured using the same configuration as that of a known front side member. For example, the bend inducement portion may be formed by forming a notch in the top plate portion 20, or by forming a through-hole in the pair of ridge portions 20b. Alternatively, a recess similar to the recess 102d of the test specimen 100 described above may be formed as the bend inducement portion. However, if the recess depth is too small, the test specimen 10 may not be able to undergo stable lateral bending deformation. For this reason, the recess depth is preferably 5% or more of the height h of the first member 12 (see FIG. 12 ). On the other hand, if the recess depth is too large, the bellows-like crushing deformation may not be able to be stably generated before lateral bending deformation occurs. For this reason, the recess depth is preferably less than 30% of the height h of the first member 12.

[0053] In this embodiment, the dimensions of each part of the test specimen 10 can be set smaller than those of actual parts of an automobile body. Referring to FIG. 12, in this embodiment, the height h of the first member 12 is, for example, 20 to 200 mm, and the width Wo of the top plate portion 20 is, for example, 30 to 200 mm. In the test specimen 10 shown in FIG. 12, the width Wo of the top plate portion 20 is set larger than the height h of the first member 12, but the width Wo of the top plate portion 20 may be equal to or smaller than the height h of the first member 12. In this case, too, by forming the bent portion 20c in the first member 12 and the bent portion 14b in the second member 14, the test specimen 10 can be more stably crushed and deformed into a bellows shape.

[0054] In the test method according to the embodiment of the present invention, similar to the drop weight test described with reference to Fig. 4, the other end 13 of the test specimen 10 is fixed to the support plate 200 so as to support the other end 13 in the longitudinal direction. In this state, an impact load is input to the test specimen 10 from the one end 11 side so as to crush the test specimen 10 in the longitudinal direction. The effects of the present invention will be described below using examples, but the present invention is not limited to the following examples. [Example]

[0055] A specimen similar to the specimen 10 shown in FIG. 11 was fabricated, except that a recess similar to the recess 102d shown in FIG. 3 was formed as a bending induction portion. The length of the specimen was 300 mm, and the distance from the center of the recess to the other end 13 of the specimen was 120 mm. The recess depth was 7 mm. The width Wo of the top plate portion 20 was 60 mm, the height h of the first member 12 was 40 mm, and the widths of the first member 12 and the second member 14 were 100 mm. The width Wt of the bending portion 20c was 35 mm, the depth Dt was 3 mm, the width Ws of the bending portion 14b was 45 mm, the depth Ds was 3 mm, and the width Wp of the bending portion 22b was 25 mm, and the depth Dp was 3 mm. The lengths of the bending portions 20c, 14b, and 22b in the longitudinal direction of the specimen were each 7 mm. The drop weight test described in FIG. 4 was performed on this specimen. Specifically, with the test specimen fixed to the support plate 200, a weight 300 with a mass of 751 kg was dropped onto one end 11 of the test specimen to apply an impact load in the longitudinal direction of the test specimen. The falling speed of the weight 300 was set to 23 km / h.

[0056] FIG. 13 is a schematic diagram showing a test specimen after a drop weight test. As shown in FIG. 13, in a drop weight test using the test specimen according to this example, bellows-like crushing deformation occurred at one end 11 of the test specimen, followed by lateral bending deformation starting from a recess serving as a bending-inducing portion. This confirms that a test specimen with a simple configuration, consisting of a hat-shaped first member 12 and a plate-shaped second member 14, can be used to conduct performance evaluation tests corresponding to the deformation modes of actual parts during an automobile collision. In addition, in the test specimen according to this example, the first member 12 and the second member 14 are joined by spot welding. Therefore, it is also possible to evaluate the fracture characteristics of the spot weld when an impact load is applied to the test specimen.

[0057] (Variation) As shown in Fig. 14, a through hole 34 may be formed in the first member 12 between one end 11 and the other end 13 in the longitudinal direction of the test specimen 10. In this embodiment, the through hole 34 is formed on one side of a pair of side wall portions 22. By forming the through hole 34 in the first member 12 in this manner, it becomes possible to evaluate the influence of, for example, the hole expandability (λ value) of the steel plate on fracture occurrence from the edge of the through hole 34. Note that the through hole 34 is preferably provided in the vicinity of the bend induction portion 32.

[0058] In the above-described embodiment, the dimensions of each part of the test piece 10 (for example, the height h of the first member 12: 20 to 200 mm, the width Wo of the top plate portion 20: 30 to 200 mm) are described as being smaller than those of the actual part, but the test piece may also be made with dimensions equivalent to those of the actual part.

[0059] In the above-described embodiment, the pair of side wall portions 22 are provided so as to extend parallel to the Y direction when viewed from the X direction, but the pair of side wall portions 22 may be inclined with respect to the Y direction. For example, the pair of side wall portions 22 may be inclined with respect to the Y direction so that the distance between the pair of side wall portions 22 increases toward the second member 14 when viewed from the X direction.

[0060] In the above embodiment, the bent portions 22b are formed on each side wall portion 22, but it is not necessary to form the bent portions 22b on each side wall portion 22.

[0061] (Evaluation target) The parts to be subjected to performance evaluation using the test specimen 10 according to this embodiment are, for example, members that absorb collision energy input in the longitudinal direction in the front or rear part of an automobile body. Specifically, the test specimen 10 is used to evaluate the performance of materials (steel plates) used for the front side frame, upper frame, underframe, rear side frame, etc. [Industrial Applicability]

[0062] According to the present invention, it is possible to carry out a performance evaluation test corresponding to the deformation mode of an actual part during an automobile collision using a test specimen with a simple configuration. [Explanation of symbols]

[0063] 10 Test specimen 12 First member 14 Second member 14b Bending section 20 Top plate 20c Bent section 22 Side wall 22b Bending section 24 flange 32 Bending induction section 34 Through hole 102d Concave portion (bending induction portion)

Claims

1. a first member extending in a first direction and having a hat shape in a cross section perpendicular to the first direction, the first member including a top plate portion, a pair of side wall portions, and a pair of flange portions; a plate-like second member extending in the first direction and connected to the pair of flange portions so as to form a closed cross section together with the first member in a cross section perpendicular to the first direction, When a direction parallel to the top plate portion and perpendicular to the first direction is defined as a width direction, and a direction from the second member toward the top plate portion along a direction perpendicular to the first direction and the width direction is defined as a height direction, a first bent portion bent toward the height direction is formed at a center portion in the width direction of the top plate portion at one end portion in the first direction, a second bent portion bent toward the height direction is formed at a center portion in the width direction of the second member at the one end portion, A test specimen in which a bending induction portion is formed in the first member between the one end and the other end opposite the one end in the first direction, for causing the first member to bend laterally in the opposite direction to the second member when viewed from the width direction.

2. 2. The test specimen according to claim 1, wherein a third bent portion bent inward in the width direction is formed at the center of each side wall portion in the height direction at the one end in the first direction.

3. the bending induction portion is a recess formed in the thickness direction of the top plate portion toward the second member and extending in the width direction, The test specimen according to claim 1 , wherein the recess has a depth of 5% or more and less than 30% of the height of the first member.

4. The test specimen according to claim 1 , wherein a through hole is formed in the first member between the one end and the other end.

5. The test specimen according to claim 1 , wherein the pair of flange portions and the second member are spot-welded.

6. The height of the first member is 20 to 200 mm, The test specimen according to claim 1, wherein the width of the top plate portion is 20 to 300 mm.

7. A test method for evaluating collision performance using the test specimen according to any one of claims 1 to 6, comprising: A testing method in which, while supporting the test specimen from the other end side in the first direction, a load is input to the test specimen from the one end side in the first direction so as to crush the test specimen in the first direction.

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