Method for evaluating collision performance of metal plate material, method for designing impact absorbing member, and method for manufacturing impact absorbing member

Abstract

To provide a collision performance evaluation technique of a metal plate material capable of evaluating collision performance with high accuracy.SOLUTION: A collision performance evaluation method of a metal plate material is performed for an evaluation material that constitutes a closed cross section shape by connecting a flange section and an occlusion member of the metal plate material processed into a hat-shaped cross section that has: a top plate section: a longitudinal wall section that is connected via a first ridge section on both sides in a width direction of the top plate section; and the flange section connected to each of the longitudinal wall section via a second ridge section. The method includes: a preparation step of forming a bead-shaped section for each of the first and second ridge sections at the same position along a longitudinal direction, which is perpendicular to a closed cross-section of the evaluation material; a test step of bringing both ends in the longitudinal direction of the evaluation material into contact with a movable section and a non-movable section, respectively, and moving the movable section in the longitudinal direction of the evaluation material to axially compressively deform the evaluation material; and an evaluation step of evaluating collision performance of the metal plate material based on test results.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for evaluating the collision performance of a metal plate material, a method for designing an impact absorbing member, and a method for manufacturing an impact absorbing member. [Background technology]

[0002] In the automotive field, improvements in collision safety are required for vehicle bodies from the perspective of protecting vehicle occupants. As a result, collision safety standards for vehicle bodies are becoming stricter. Furthermore, in recent years, there has been a shift from gasoline-powered vehicles to electric vehicles (EVs) in order to reduce CO2 emissions. Coupled with the increased vehicle weight of EVs due to the loading of batteries, improvements in fuel efficiency are also required. Therefore, there is a strong demand for the expanded use of high-strength steel in frame components and the development of vehicles with excellent collision safety performance.

[0003] Automotive structural components can be broadly divided into two categories. One is the cabin structural components, which are located around the cabin and, from the perspective of collision deformation, have high load-bearing capacity and do not allow deformation during a collision. The other is energy absorption (EA) components, which have a certain degree of load-bearing capacity but allow some deformation to absorb collision energy. Among these, when making energy absorption components such as crash boxes and front side members ultra-high strength, the large deformation that occurs during a collision poses a challenge, as they can easily be damaged by fracture, resulting in a decrease in energy absorption performance. Therefore, when developing materials with excellent energy absorption performance, it is important to correctly evaluate the relationship between impact fracture and energy absorption properties, clarify the necessary properties, and use this information to guide the development of new materials.

[0004] For example, Patent Document 1 discloses a method for evaluating energy absorbing components that allows for targeted bending of the desired portion of the evaluation component, enabling accurate bending evaluation even in destructive evaluation involving large deformation. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2018-194445 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the above-mentioned conventional techniques have the following problems to be solved. That is, the evaluation method described in Patent Document 1 is a test in a compression bending deformation mode in which the part is bent from a certain point while being compressed in the axial direction. A different evaluation method is required for tests in an axial compression deformation mode that does not involve axial bending. In the axial compression deformation mode, parts undergo more complex deformation and fracture, so in order to correctly evaluate their energy absorption characteristics, it is necessary to develop an evaluation method that is appropriate for that deformation mode.

[0007] The present invention has been made to solve the above-mentioned problems, and its purpose is to provide a technology for evaluating the crashworthiness of metal plates that can accurately evaluate crashworthiness, such as fracture state and energy absorption characteristics, in an axial compression test. Furthermore, the present invention also aims to propose a method for designing and manufacturing an impact absorbing member using the crashworthiness evaluation of metal plates. [Means for solving the problem]

[0008] In order to solve the above problems, the present invention was completed after studying the shape and processing method of the evaluation component to enable highly accurate evaluation of collision performance, such as the fracture state and energy absorption characteristics, through axial compression testing.

[0009] That is, the gist of the present invention is as described below. [1] A method for evaluating the collision performance of metal plate material, using a testing machine having a movable part and a non-movable part, for evaluating a metal plate material having a hat-shaped cross section, the metal plate material having a top plate part, a pair of vertical wall parts connected to both sides of the top plate part in the width direction via a first ridge part, and a pair of flange parts connected to each of the vertical wall parts via a second ridge part, and the flange parts are joined to a closure member to form a closed cross section. The method for evaluating the collision performance of metal plate material includes the following steps: a preparation step of forming a bead-shaped part for each of the first ridge part and the second ridge part at the same position in the longitudinal direction, which is perpendicular to the closed cross section of the evaluation part; a test step of abutting both longitudinal ends of the evaluation part with the movable part and the non-movable part, respectively, and moving the movable part in the longitudinal direction of the evaluation part to axially compress the evaluation part; and an evaluation step of evaluating the collision performance of the metal plate material based on the test results. [2] The method for evaluating the collision performance of a metal plate material according to the above [1], wherein the preparation step includes forming a bead-shaped portion near an end of the evaluation member in the longitudinal direction. [3] The method for evaluating the collision performance of a metal plate material according to the above [1], wherein the preparation step includes forming a bead-shaped portion in the center of the evaluation member in the longitudinal direction. [4] In the above [1], in the testing step, the longitudinal position of the bead-shaped portion to be formed in the evaluation component is tested under multiple conditions, and in the evaluation step, the collision performance is evaluated from the test results under the multiple conditions. [5] A method for designing an impact absorbing member, comprising: a step of evaluating the impact performance of metal plate materials of a plurality of specifications by the method described in any one of [1] to [4] above; and a step of determining the specifications of the metal plate material to be used in the impact shock absorbing member based on the evaluation of the impact performance of the obtained metal plate material. [6] A method for manufacturing an impact absorbing member, comprising: a step of evaluating the impact performance of metal plate materials of a plurality of specifications by the method described in any one of [1] to [4] above; a step of determining the specifications of the metal plate material to be used in the impact impact absorbing member based on the evaluation of the impact performance of the obtained metal plate material; and a step of manufacturing the impact absorbing member using the metal plate material that satisfies the determined specifications of the metal plate material. In this specification, the first ridgeline and the second ridgeline are also referred to as the top plate ridgeline and the flange ridgeline, respectively. [Effects of the Invention]

[0010] According to the present invention, compared with conventional evaluation tests, it is possible to evaluate the collision performance of metal plate materials corresponding to the deformation mode in axial crushing deformation, i.e., "axial compressive deformation," and this can be utilized for the development of materials with excellent collision performance. Furthermore, by designing a material with excellent collision performance, an impact absorbing member made from this material has excellent energy absorption properties, which contributes to the collision safety of, for example, automobile frame parts and is therefore industrially useful. [Brief explanation of the drawings]

[0011] [Figure 1] 1A and 1B are schematic diagrams showing the shape of an evaluation member used in a method for evaluating the collision performance of a metal plate material according to one embodiment of the present invention, in which (a) is a schematic cross-sectional view illustrating a closed cross-sectional structure, (b) is a schematic cross-sectional view illustrating a bead-shaped portion, and (c) is a schematic perspective view. [Figure 2] FIG. 2 is a schematic front view showing an apparatus configuration for explaining an axial compression test method according to the embodiment. [Figure 3] 10(a) to 10(c) are photographic images showing deformations of the evaluation member as a result of an axial compression test according to the embodiment. [Figure 4] 10 is a graph showing the relationship between the stroke, the test load, and the absorbed energy in an axial compression test according to the embodiment. [Figure 5] 1A and 1B are diagrams showing the shape and dimensions of evaluation members used in the examples, where (a1) is a schematic cross-sectional shape diagram, (a2) is a schematic front view, (b1) is a schematic cross-sectional view showing the bead shape, and (b2) and (b3) are cross-sectional views taken along lines AA and BB, respectively. [Figure 6] 10(a) to 10(e) are perspective views showing patterns of bead-shaped portions provided on the evaluation members according to the above-mentioned examples. [Figure 7]Photographs illustrating the initial buckling in the above example, where (a) shows a case where a bead-shaped portion is formed in the longitudinal center of the evaluation member, and (b) shows a case where a bead-shaped portion is formed near the longitudinal end of the evaluation member. [Figure 8] 10 is an example of a photographic image showing the influence of the bead shape forming position and material strength on the buckling deformation shape according to the above example. DETAILED DESCRIPTION OF THE INVENTION

[0012] The following describes in detail embodiments of the present invention. Note that the drawings are schematic and may differ from the actual product. Furthermore, the following embodiments exemplify components, devices, and methods for embodying the technical concept of the present invention, and are not intended to limit the configuration to the following. In other words, the technical concept of the present invention can be modified in various ways within the technical scope defined in the claims.

[0013] (Evaluation component) The structure of each part of an evaluation member suitable for use in the method for evaluating the collision performance of a metal plate material according to this embodiment will be described. An evaluation member 100 is shown in FIGS. 1(a) to 1(c). The evaluation member 100 is produced by welding a processed part 110, which is fabricated into the cross-sectional shape shown in FIG. 1(a) by pressing, bending, or the like, and a closing member 120. The processed part 110 has a top plate portion 111, a pair of vertical wall portions 112, 112, and a pair of flange portions 113, 113. The vertical wall portions 112 are connected to both sides of the top plate portion 111 in the width direction via top plate ridge portions 114. The flange portions 113 are connected to each of the vertical wall portions 111 via flange ridge portions 115 and extend outward from the processed part to form a hat shape. The closing member can be a flat plate material 120 as shown in FIG. 1(a), or a hat-shaped member.

[0014] Welding can be performed by spot welding 130 as shown in Figure 1(c) or by other methods such as arc welding. If the weld at the flange 113 of the processed part 110 breaks during a crash test, resulting in a gap deformation between the welded surfaces, it can reduce the crash load, i.e., the impact absorption load. This can interfere with the evaluation of the energy absorption capacity, which reflects the presence or absence of base material fracture. Therefore, weld fracture must be avoided by welding under conditions that increase the fracture strength of the weld or increase the fusion zone. Spot welding can also shorten the welding pitch. This allows the flange 113 to maintain its connection even if one weld fractures during crash deformation due to the remaining nearby weld. In this way, welding is performed with care to avoid gap deformation of the flange 113. Mechanical joining, such as gluing or riveting, is also possible instead of welding. In Figure 1(c), a jig 140 for installation in an axial compression testing machine is attached to the bottom end of the evaluation component 100.

[0015] <Preparation process> The bead 116 at the ridgeline is formed by a method such as press forming, either simultaneously with the bending of the ridgeline itself or after the bending process. A bead shape is a partially convex or concave shape given to a part. For each of the top plate ridgeline 114 (the first ridgeline) and the flange ridgeline 115 (the second ridgeline), a bead-shaped portion 116 is formed at the same position in the longitudinal direction, which is perpendicular to the closed cross section of the evaluation component 100. The process of forming this bead-shaped portion 116 on each ridgeline is referred to as the preparation process. Adding the bead-shaped portion 116 controls the starting position of initial buckling of the evaluation component 100 during axial compression deformation testing. This makes it possible to reproduce the same deformation mode when conducting multiple tests using the same material and test specimen conditions.

[0016] <Testing process> Next, in the testing process, an axial compression test is performed using an axial compression testing machine, clamping both longitudinal ends of the evaluation component 100 and subjecting the evaluation component 100 to axial compression deformation. The buckling deformation in the axial compression test reflects subtle individual differences in the molding and joining positions and conditions of each evaluation component 100. In other words, different deformation modes tend to occur over multiple tests, such as a mode in which deformation occurs sequentially from the end of the evaluation component 100 in the longitudinal direction, or a mode in which deformation occurs from somewhere in the middle portion. Because different deformation modes in the axial compression test change the pattern of collision load generation, performing the test in the same deformation mode reduces load variation in the test.

[0017] In particular, the upper axial end of the evaluation component 100 in this embodiment is free to deform during a crash test, resulting in a reduction in the crash load and energy absorption compared to deformation of the general parts other than the end. This is thought to be due to a loss of deformable area. Furthermore, when the flat parts of the end, i.e., the top plate 111, vertical wall 112, flange 113, and flat plate 120, collapse, the subsequent ridges collapse and deform, contacting the collapsed surface in order. Any fractures that occur in these deformed parts tend to be small and not large.

[0018] On the other hand, in the case of deformation in the longitudinal center without deformation of the ends, stress is applied from above and below to the buckling deformation portion, which tends to cause the fracture to progress significantly. Therefore, the difference in the deformation mode, whether or not the ends are deformed during collision deformation, affects the variation in energy absorption and the severity of fracture. Therefore, to eliminate the variation in test load, it is necessary to conduct tests in a unified deformation mode, either with or without deformation of the longitudinal ends of the evaluation component 100. Therefore, a structure is required, either to suppress deformation of the ends by attaching a fixing jig to the cross-sectional end, or to control the buckling deformation position by forming a bead shape on the ridge line of the evaluation component.

[0019] Furthermore, because the ease of fracture propagation in the bending deformation portion changes depending on whether or not there is collapse deformation at the end, as described above, the desired impact fracture level and impact deformation mode in the test can be changed by changing the position of the ridge bead 116 of the evaluation member 100. For example, if all test materials used in the test are made of materials with excellent impact fracture properties, forming a bead in the axial middle (the center portion in the longitudinal direction) will create test conditions in which impact fracture is more likely to occur. Conversely, if all test materials are made of materials with poor impact fracture properties, forming a bead near the free end in the longitudinal direction will create test conditions in which impact fracture is less likely to occur. As described above, changing the impact fracture level to match the test materials makes it easier to evaluate differences in impact performance between test materials.

[0020] That is, in order to perform an evaluation that is tailored to the expected deformation of an actually applied part, a bead-shaped portion 116 can be formed near the longitudinal end of the evaluation component 100. In this case, when the evaluation component is used as an impact absorbing component that assumes deformation from the longitudinal end, the collision performance due to deformation from the longitudinal end can be evaluated. Note that the "near the longitudinal end" referred to here depends on the shape and material of the evaluation component, but can be exemplified as a range from 5% to less than 20% of the entire longitudinal length from the free longitudinal end of the evaluation component 100.

[0021] Furthermore, in order to perform evaluations that are tailored to the expected deformation of actual application parts, a bead-shaped portion 116 can be molded in the longitudinal center of the evaluation component 100. In this case, when the evaluation component is used as an impact absorbing component that assumes deformation from the longitudinal center, the collision performance due to deformation from the longitudinal center can be evaluated. Note that the "longitudinal center" referred to here depends on the shape and material of the evaluation component 100, but can be exemplified as a range from 25 to 75% of the entire longitudinal length of the evaluation component 100 from the free end of the longitudinal direction.

[0022] Furthermore, the axial compressive deformation test may be performed under multiple conditions for the longitudinal position of the bead-shaped portion 116 formed in the evaluation component 100, and the collision performance may be evaluated from the test results under multiple conditions. By using such an evaluation method, the collision performance of the metal plate material can be efficiently evaluated even when the collision fracture characteristics of the metal plate material to be evaluated cannot be predicted.

[0023] When joining the installation jig 140 to one end cross section in the extending direction of the cross-sectional shape, a highly rigid material such as steel or aluminum is used. Then, the end cross section of the evaluation member 100 is butted against the installation jig 140 and joined by a method such as fillet welding.

[0024] An example of a testing mechanism is shown in a schematic front view in FIG. 2. The crash testing machine of this embodiment is composed of an evaluation component 100, a testing component movable section 210, and a testing component non-moving section 220, all of which are joined to an installation jig 140. A flat, highly rigid punch 230 is connected to the testing component movable section 210. The testing component non-moving section 220 is a flat, highly rigid floor surface. A crash performance evaluation test is performed by placing the evaluation component 100 on the floor so that the installation jig 140 is in contact with it. The punch 230 is moved in the extension direction of the closed cross section of the evaluation component 100, clamping the evaluation component 100 between the punch 230 and the floor surface to subject it to axial compressive deformation. That is, in the testing process, both longitudinal ends of the evaluation component 100 are brought into contact with the testing component movable section 210 and the testing component non-moving section 220, respectively, and the testing component movable section 210 is moved in the longitudinal direction of the evaluation component 100 to perform an axial compressive deformation test to subject the evaluation component 100 to axial compressive deformation.

[0025] <Evaluation process> The evaluation process of the method for evaluating the collision performance of a metal plate material according to this embodiment will be described. In the collision performance evaluation test, the fracture state of the evaluation member 100 can be evaluated by visual evaluation or by measuring the number of fracture locations and fracture line length using CT images, etc. In addition, the evaluation can be performed using the energy absorption amount calculated by integrating the axial compression deformation test load of the evaluation member 100 over the test stroke, or the average load calculated by dividing the energy absorption amount by the test stroke.

[0026] Figures 3(a) to 3(c) are photographs illustrating the deformation of the evaluation component 100. Figure 4 is a graph illustrating the evaluation of the energy absorption amount. The photograph in Figure 3 shows a typical example of the deformation of the evaluation component 100 after an axial compression deformation test, classified into three states. The fracture state focused on bending fracture of the plate material excluding the joint. Figure 3(a) shows a case where no fracture was observed from the outside, and was evaluated as "no fracture." Figure 3(b) shows a case where localized bending fracture occurred but the bellows-deformed part shape was maintained, and was evaluated as "minor crack." Figure 3(c) shows a case where the bending fracture progressed significantly, leading to a fracture accompanied by separation of the part, and was evaluated as "major crack." Figure 4 also shows a graph illustrating typical results of the test load and absorbed energy during an axial compression deformation test. The solid line shows the relationship between the punch travel, i.e., the load applied to the punch relative to the test stroke, i.e., the test load. The dashed line shows the relationship between the test stroke and the absorbed energy. The absorbed energy can be calculated by integrating the test load over the test stroke.

[0027] In this way, the collision performance of a metal plate material can be evaluated as follows. (1) Visual evaluation of the state of crack occurrence, for example, no fracture, minor cracks, major cracks, etc., can be used. (2) Load, that is, evaluation based on impact absorption load, for example, the average load up to a specified stroke or the maximum load during that stroke, can be used. (3) It can be evaluated by the amount of energy absorbed. It is also possible to carry out multiple tests and evaluate the average, maximum, minimum, and variation of these values.

[0028] In another embodiment, the collision performance of metal plate materials with multiple specifications is evaluated using the evaluation method disclosed above, and the specifications of the metal plate material to be used in the collision impact absorbing member are determined based on this evaluation, and the impact absorbing member can be designed through this specification determination process.

[0029] For example, a plurality of types of metal plate materials having different tensile strengths, yield strengths, plate thicknesses, etc. are prepared, and collision performance evaluation tests are conducted on these metal plate materials.

[0030] For impact absorbing components where deformation from the ends is expected, a metal plate material is selected that gave the best results in an axial compression deformation test of an evaluation component 100 with beads 116 attached to the longitudinal ends.The shape of the impact absorbing component can then be designed by estimating the impact energy that can be absorbed by this metal plate material.

[0031] For impact absorbing components that are expected to deform from the longitudinally stable portion, a metal plate material is selected that gave the best results in an axial compression deformation test of an evaluation component 100 with a bead 116 attached to the longitudinal center. The shape of the impact absorbing component can then be designed by estimating the impact energy that can be absorbed by this metal plate material.

[0032] In yet another embodiment, the collision performance of metal plate materials of a plurality of specifications is evaluated using the evaluation method disclosed above, specifications of the metal plate material to be used in the collision impact absorbing component are determined based on the evaluation, and the specifications are reflected in the design of the impact absorbing component through this specification determination process.The impact absorbing component can then be manufactured using metal plate materials that satisfy the determined specifications of the metal plate material. [Example]

[0033] Based on the above embodiment, the collision performance of the metal plate material was evaluated. The dimensions of the evaluation components used in the axial compression deformation tests are shown in Figures 5(a1) to 5(b3). The evaluation components were fabricated by press-forming the top plate, vertical walls, flanges, and ridge beads on metal plates and spot welding the flanges to flat plates. The tensile strengths of the materials were 980 MPa and 1180 MPa grade steel plates. The metal plates were 1.2 mm thick. The closure members were equivalent to the metal plates. In cross-sectional view, the top plate height (i.e., the distance between the top plate and the flanges and the distance between the vertical walls) were both 40 mm. In cross-sectional view, the flange width (i.e., the distance from the vertical walls to the flange tip) was 20 mm. The angles between the top plate and the two vertical walls were each 90°, the angles between the two vertical walls and the two flanges were each 90°, and the inner bending radius of the top plate ridge and the vertical wall ridge was 5 mm. The cross-section of the evaluation component had a length of 200 mm in the extension direction. The ridge bead was machined to have an inner curvature radius of 4 mm and a depth of 2 mm at the deepest point of the bead, as shown in Figures 5(b2) and (b3). Spot welding was performed with a nugget diameter of 5.5 mm and a welding point pitch of 22.5 mm to prevent flange opening deformation due to spot fracture during testing.

[0034] To perform the axial compression deformation test on the above evaluation component, an installation jig with dimensions of 120 mm x 120 mm x 6 mm was prepared, and the evaluation component was placed on the installation jig. The flange of the evaluation component and the installation jig were joined with fillet welding, so that the component could be placed in the testing machine without being fixed in place and the test could be performed.

[0035] Table 1 shows the tensile strength grade (TS) of the material of the evaluated components, the presence or absence of ridge beads on the top plate side and flange side (ridge), the conditions of the bead forming position (axial direction), and the initial buckling position and fracture state of the six tests (N1 to N6) corresponding to those conditions.In addition, Table 1 shows the average, maximum, and minimum values ​​for the energy absorption (EA) of the six tests, the difference between the average and the standard deviation (1σ) of the variation.

[0036] The initial buckling position was divided into five regions, each 40 mm from the top of the evaluation component, and these regions are indicated from top to bottom as "upper end," "upper part," "middle part," "lower part," and "lower end." The fracture state was evaluated below based on bending fracture in the base material, which could be confirmed from photographs taken during the axial compression deformation test and from the appearance of the test specimen after the axial compression deformation test. If no fracture was observed, it was recorded as "no fracture." -If one or more fractures were confirmed but no fractures had progressed to a length of 20 mm or more, it was considered a "minor crack." -If one or more fractures with a fracture length of 20 mm or more were confirmed, it was considered a "major crack."

[0037] The bead forming position is indicated as "top end" when it is 35 mm from the top end in the axial direction of the evaluation component, and as "mid-section" when it is 100 mm from the top end. The specimen shape pattern (specimen) is classified by bead forming location and forming position using symbols in Figure 6. Figure 6 shows an external view of the specimen shape pattern. The difference between the maximum and minimum values ​​and the average value of the energy absorption amount EA is one index that shows the variation in EA depending on the N number.

[0038] The axial compression deformation test was performed using a bending tester. A flat punch was placed on the moving part of the bending tester, and the evaluation component was placed so that its axial direction coincided with the direction of the punch movement. The punch speed was 10 mm / min, and the moving stroke was 100 mm. The reaction force applied to the punch and the moving stroke of the punch during the axial compression deformation test were recorded. In addition, photographs were taken at an interval of one frame per second to observe and evaluate the deformation and fracture state of the evaluation component during the test. The test was performed six times under each condition.

[0039] Six tests were conducted, and the test method was deemed to have passed if initial buckling occurred at the same axial position in all six tests, while it was deemed to have failed if initial buckling occurred at a different axial position even once.

[0040] [Table 1]

[0041] Figure 7 shows an example of the occurrence of pre-buckling in a test specimen with only a flange-side ridge bead at the longitudinal center, without a top-side ridge bead. In Figure 7(a), pre-buckling occurs at the bead location. In contrast, in Figure 7(b), pre-buckling occurs near the top end where no bead is present. In other words, even when only a flange-side ridge bead is present, the pre-buckling occurrence location is not determined to be a single location. Furthermore, the results shown in Table 1 indicate that when there is no bead, the pre-buckling central location is not determined to be a single location. It can also be seen that pre-buckling does not necessarily occur at the bead location when only a top-side ridge bead or a flange-side ridge bead is present. On the other hand, when beads are present on both the top-side and flange-side ridges, pre-buckling occurs at the axial position where the bead is located in all test specimens. Furthermore, even if there are beads on both the top plate ridge and the flange ridge, if they are not formed at the same position in the extension direction of the part cross section, initial buckling will occur at either the bead position on the top plate ridge or the flange ridge, making it impossible to generate initial buckling at a specific position in the longitudinal direction of the part. As described above, to stabilize the deformation mode of the axial compression deformation test, the top plate ridge bead and the flange ridge bead must be formed at the same position in the extension direction of the part cross section. Note that, if the difference in the extension direction (longitudinal direction) of the part cross section where each bead is formed is within 5% of the longitudinal length of the test specimen, they can be considered to be at the same position in the extension direction (longitudinal direction).

[0042] Figure 8 shows the fracture state at a stroke of 60 mm when the ridge bead was formed at positions 35 mm and 100 mm from the top edge of the part for 980 MPa and 1180 MPa grade steel sheets. In the case of the 980 MPa grade material (980 material), no fracture was observed in the base metal at either the top edge of 35 mm or 100 mm. In the case of the 1180 MPa grade material (1180 material), fracture occurred in the bent deformation part of the base metal at the edge of 35 mm, but did not progress to a large crack. On the other hand, when the top edge was 100 mm (mid-section), the fracture progressed significantly. Comparing the results shown in Table 1 for the same bead position, at the top edge, there was no fracture with the 980 material, and minor cracking with the 1180 material, and the variation from the EA average was small for both materials. On the other hand, when the bead position is in the middle, three of the six 980 specimens had minor cracks, while all six 1180 specimens had large cracks, indicating that the 1180 specimen, which suffers from large cracks, has a large variation in EA. In the mode in which deformation occurs from the top end, although there are differences in the fracture state depending on the material, when a fracture occurs, the degree of fracture progression is small, and even in the 1180 specimen, it does not progress to a large crack, so there is no effect on the EA variation. On the other hand, in the mode in which deformation occurs from the middle, there are differences in the fracture state depending on the material, and when a fracture occurs, the degree of fracture progression is large, and large cracks occur in the 1180 specimen, indicating that this also affects the EA variation.

[0043] As described above, it has been found that the ease of fracture propagation changes depending on the fracture buckling deformation position, and by changing the molding position of the ridge bead, it is possible to adjust to the desired collision fracture level and collision deformation mode. [Explanation of symbols]

[0044] 100 Evaluation materials 110 Processed parts (hat-shaped parts) 111 Top plate 112 Vertical wall section 113 Flange 114 Top plate ridge 115 Flange ridge 116 (ridge line) bead (shape) 120 Flat plate material (blocking member) 130 Spot welding 140 Installation jig 210 (Testing machine) Moving parts 220 (Testing Machine) Non-moving Parts 230 Punch

Claims

1. A method for evaluating the collision performance of a metal plate material is performed using a testing machine having a movable portion and a non-movable portion on an evaluation member having a closed cross-sectional shape formed by joining a flange portion and a closing member to the metal plate material, the evaluation member having a hat-shaped cross section and including a top plate portion, a pair of vertical wall portions connected to both sides of the top plate portion in a width direction via first ridge portions, and a pair of flange portions connected to each of the vertical wall portions via second ridge portions, a preparation step of forming a bead-shaped portion at the same position in a longitudinal direction, which is a direction perpendicular to the closed cross section of the evaluation member, for each of the first ridge line portion and the second ridge line portion; a testing step of abutting both longitudinal ends of the evaluation member with the movable portion and the non-movable portion, respectively, and moving the movable portion in the longitudinal direction of the evaluation member to axially compress and deform the evaluation member; an evaluation step of evaluating the collision performance of the metal plate material based on the test results; A method for evaluating the collision performance of a metal plate material, including:

2. In the preparation step, a bead-shaped portion is formed near an end portion in a longitudinal direction of the evaluation member. The method for evaluating the collision performance of a metal plate material according to claim 1.

3. In the preparation step, a bead-shaped portion is formed in a central portion of the evaluation member in a longitudinal direction. The method for evaluating the collision performance of a metal plate material according to claim 1.

4. In the test step, a test is performed under a plurality of conditions for the longitudinal position of the bead-shaped portion to be formed in the evaluation member, In the evaluation step, collision performance is evaluated based on test results under a plurality of conditions. The method for evaluating the collision performance of a metal plate material according to claim 1.

5. A step of evaluating the collision performance of metal plate materials of a plurality of specifications by the method according to any one of claims 1 to 4; determining specifications for the metal plate material to be used in the collision impact absorbing member based on the evaluation of the collision performance of the obtained metal plate material; A method for designing an impact absorbing member, comprising:

6. A step of evaluating the collision performance of metal plate materials of a plurality of specifications by the method according to any one of claims 1 to 4; determining specifications for the metal plate material to be used in the collision impact absorbing member based on the evaluation of the collision performance of the obtained metal plate material; a step of manufacturing an impact absorbing member using a metal plate material that satisfies the determined specifications of the metal plate material; A method for manufacturing an impact absorbing member, comprising:

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