Punch for bending impact test, bending impact test device, and bending impact test method

Abstract

To provide a bending impact test capable of accurately reproducing bending impact tests for various collision forms with a simple configuration.SOLUTION: Provided is a punch 1 for bending impact test loads a load on an evaluation member 7. An abutting part to the evaluation member 7 is constituted of a plurality of tubular hollow bodies 3 whose peripheral surface side is directed to the evaluation member 7 side in the punch 1 for bending impact test.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a technique for bending impact testing of evaluation components, and is particularly suitable for evaluating bending performance using crash-absorbing components as evaluation components, such as bending impact tests of automobile body structural components. [Background technology]

[0002] In recent years, collision safety standards have become increasingly strict in the automotive industry from the perspective of passenger protection. This has led to a strong demand in the automotive industry for the expanded use of high-strength steel and the development of vehicles with superior collision safety performance. As a result, each automobile manufacturer conducts full-car (actual vehicle) collision tests using an entire vehicle body in order to design a vehicle body with excellent collision safety. However, in the design stage of individual modular components that make up a vehicle, evaluation of those components is often carried out through evaluation tests that are broken down into evaluations for each component. This is done to reduce costs and delivery times, and also to simplify the evaluation targets.

[0003] When conducting evaluation tests on individual components, it is important that the evaluation test method can be carried out under the same restraint conditions and deformation modes as those in actual full-car crash tests.

[0004] Here, the collision deformation modes of automobile components (body structural components) during an automobile collision can be broadly divided into bending crush and axial crush. Bending crush is a collision deformation mode in which the axial direction of the component is bent. Axial crush is a collision deformation mode in which the component is deformed by a load in the axial direction. Of the two collision deformation modes, bending crush is a deformation mode in which the cross section of the structural component is plastically deformed when a collision load is applied from a direction perpendicular to the axial direction of the structural component. This type of deformation mode occurs in body structural components such as B-pillars and door impact beams in a side collision of an automobile.

[0005] When performing a test to evaluate such deformation modes on a component-by-component basis, for example, a three-point bending impact test is employed. Long components such as door impact beams undergo bow-like deformation during a side collision, followed by bending crushing. Therefore, when performing a test on a component-by-component basis, appropriate translational and rotational constraints are applied to the support points of the component to evaluate bending crushing. A simple evaluation method is a test method that evaluates the load generated at bending crushing. For example, this method is performed with both ends of the component being rotationally supported. Furthermore, this method applies a bending load by pressing a punch into the center of the longitudinal direction of the component being evaluated. It is believed that this evaluation method can be used to evaluate the load leading to bending crushing.

[0006] Here, we consider the case where the shape of the punch (tip shape) that contacts the evaluation component is a simple arc-shaped cross section, such as a hemisphere or cylinder. In this case, the deformation mode of the evaluation component is likely to be one in which the load from the punch is concentrated at one point on the evaluation component, leading to bending collapse.

[0007] However, because body structural members are installed in vehicles with measures in place to reduce injuries to occupants in the event of a side collision, there is a risk that if a three-point bending impact test is performed using a punch with a simple shape, the evaluation test will not be in the same deformation mode as an actual full-car crash test. Here, a crash test simulating a full-car side collision is conducted by crashing a barrier trolley into the side of the vehicle (see Figure 5(a)). In this case, the door impact beam is designed to disperse the load received from the barrier trolley over a wide area to prevent bending and crushing. The reason for this is that if the door impact beam were to bend and crush due to the concentrated load at one point, the door's intrusion speed relative to the occupant would increase, leading to an increase in occupant injury levels.

[0008] Therefore, when a body structural member such as a door impact beam is used as the evaluation member, it is necessary to devise a test method that can reproduce the following: In other words, it is necessary to devise a test method that can reproduce the input state (shear force, moment, etc.) that is applied to the evaluation member in the actual vehicle when a load is input.

[0009] Such ingenious testing methods include those described in Patent Documents 1 and 2. Patent Document 1 proposes a method of applying a bending load to an evaluation member using a punch with an arc-shaped cross section while applying a tensile load to both ends of the evaluation member using an actuator, thereby reproducing the input to the door impact beam of a full car.

[0010] Furthermore, Patent Document 2 proposes a method of applying a load to a long member such as a door impact beam by adding a rigid body that covers the upper surface of the test piece, thereby reproducing the input of a full car. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] Japanese Patent Application Publication No. 2018-194446 [Patent Document 2] Japanese Patent Application Laid-Open No. 2017-116494 Summary of the Invention [Problem to be solved by the invention]

[0012] However, in the method of Patent Document 1, a tensile force is applied to the evaluation component in the axial direction. For this reason, the method of Patent Document 1 requires large-scale equipment such as an actuator and a rotation restriction jig. As a result, the introduction cost of Patent Document 1 is high, and it is likely that opportunities for its implementation will be limited. Furthermore, the method of Patent Document 1 is configured to apply a load to one longitudinal point of the evaluation member using a punch with an arc-shaped cross section. For this reason, the side collision mode that the method of Patent Document 1 targets is limited to reproducing a pole side collision in which the load is concentrated at one point and an impact is input (see Figure 5(b)). In other words, the method of Patent Document 1 cannot reproduce input conditions such as a collision with a barrier bogie with a predetermined collision surface from the side of the vehicle body. The predetermined collision surface corresponds to the surface of the punch that comes into contact with the evaluation member at the abutment point.

[0013] Furthermore, Patent Document 2 is based on the premise that evaluation is performed together with a rigid body covering the upper surface of the test specimen. Therefore, when attempting to accommodate complex component shapes such as actual automobile components, the method of Patent Document 2 is likely to be limited in the shape of the rigid body covering the upper surface. Therefore, the method of Patent Document 2 may have difficulty in reproducing changes in input state due to various collision conditions.

[0014] Furthermore, in the four-point bending impact test described in Patent Document 2, the evaluation member has contact portions consisting of convex portions or contact portions at two points spaced apart in the longitudinal direction of the rigid body that constitutes the punch.The evaluation member contacts the contact portions at these two points, transmitting a load to the evaluation member.However, the contact portions described in Patent Document 2 are rigid bodies.As a result, the input load is concentrated locally at the contact points of the evaluation member, which poses a problem in that it may be impossible to reproduce the input state caused by a side collision of a barrier trolley.

[0015] The present invention has been made in light of the above points, and aims to provide a bending impact test that can more accurately reproduce bending impact tests targeting various collision types with a simple configuration. [Means for solving the problem]

[0016] The inventors discovered that by configuring the contact portion of the punch to be deformable, the load applied to the evaluation component can be dispersed over a wide area, making it possible to prevent the load from concentrating on one point. The inventors then considered various means for controlling the input load with a simple configuration, while taking into consideration that the input load is a bending impact load on a metal body, and developed the present invention.

[0017] In order to solve the problem, one aspect of the present invention is a punch for a bending impact test that applies a load to an evaluation component, wherein the abutment portion that applies the load to the evaluation component is composed of a plurality of tubular hollow bodies with their peripheral surfaces facing the evaluation component. Another aspect of the present invention is a bending impact test method in which a load is applied to an evaluation member using a punch having a contact portion that contacts the evaluation member and that is made up of a plurality of tubular hollow bodies. [Effects of the Invention]

[0018] According to one aspect of the present invention, the contact portion (load input portion) of the punch that contacts the evaluation component is made of a tubular hollow body. The cross section of the contacting tubular hollow body deforms in response to the load input to the evaluation component. This automatically alleviates the concentration of the input load at the contact portion, resulting in load dispersion. As a result, this aspect of the present invention allows the evaluation component to be controlled so that it undergoes bending deformation over a wide area. Furthermore, it is possible to perform evaluation of the component itself, approximating the impact deformation mode that occurs in structural components during actual automobile crash tests.

[0019] Furthermore, according to an aspect of the present invention, by constructing the contact portion of the punch from a tubular hollow body such as a steel pipe, it becomes easy to adjust the load input when the punch contacts, and it becomes possible to respond to various collision conditions with a simple configuration. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a perspective view showing a punch according to an embodiment of the present invention; [Figure 2]1A and 1B are diagrams showing a punch according to an embodiment of the present invention, in which (a) is a plan view seen from the evaluation member side, and (b) is a cross-sectional view. [Figure 3] FIG. 1 is a schematic diagram showing the configuration of a bending impact test. [Figure 4] 1A and 1B are diagrams showing an example of an evaluation member, in which (a) is a top view and (b) is a cross-sectional view taken along the line AA. [Figure 5] These are schematic diagrams showing side collision tests using a full car (actual vehicle). (a) shows a collision test using a barrier trolley, and (b) shows a collision test using a pole (rigid body). [Figure 6] FIG. 10 is a diagram illustrating an example of strain distribution in a comparative impact test. [Figure 7] FIG. 10 is a diagram illustrating an example of strain distribution in a full-car crash test. [Figure 8] FIG. 10 is a diagram showing moment diagrams for a comparative impact test and a full car crash test. [Figure 9] Schematic diagrams showing the collision state of a punch. (a) is an example of a comparative punch. (b) is an example of a virtual punch. [Figure 10] FIG. 10 is a diagram illustrating an example of strain distribution in a virtual punch. [Figure 11] FIG. 10 is a diagram showing a moment diagram for a virtual punch. [Figure 12] FIG. 10 is a diagram illustrating an example of strain distribution in an improved bending impact test. [Figure 13] FIG. 10 is a diagram showing a moment diagram in an improved bending impact test. [Figure 14] 10A and 10B are diagrams illustrating examples of strain distribution when strength and spacing are changed. [Figure 15] FIG. 10 is a diagram showing moment diagrams when the strength and spacing are changed. [Figure 16] FIG. 10 is a diagram showing a moment diagram when adjusting a contact portion. [Figure 17] FIG. 2 is a diagram showing the relationship between each tubular hollow body. [Figure 18] FIG. 2 is a diagram showing the composition of evaluation members in the examples. [Figure 19]1 shows the results of an example, where (a) shows the test results of an example, and (b) shows the test results of a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0021] Next, an embodiment of the present invention will be described with reference to the drawings. In this embodiment, the evaluation component is assumed to be a body structural component for an automobile, but the present invention is also applicable to bending impact tests on components other than body structural components for an automobile. The evaluation member may be in the shape of a flat plate such as a strip, but in order to evaluate bending impact, it is preferable that the evaluation member be processed into a three-dimensional shape that imitates a molded product.

[0022] In a bending impact test, a test piece (test specimen) is supported at both longitudinal ends by support members, and a punch is pressed into the longitudinal center of the test piece. In other words, a bending impact test is an impact test in which a load is input by pressing the tip of the punch into the test piece, causing bending deformation of the test piece. There are two methods for pressing the punch: a static method in which the punch is stroked at a constant speed, and a dynamic method in which the punch is stroked with acceleration. The present invention is applicable to either stroke method. One of the features of this embodiment is the structure of the contact portion of the punch that comes into contact with the evaluation member.

[0023] (Punch 1) The punch 1 of this embodiment is a punch for a bending impact test that applies a load to a member to be evaluated. The punch 1 of this embodiment has a configuration as shown in Figures 1 and 2. The punch 1 of this embodiment includes a punch body and a base portion 4 provided on the back side of the punch body.

[0024] <Punch body> The punch body includes a plate-shaped base portion 2 and a contact portion provided on one surface 2A of the base portion 2. The one surface 2A is the surface that faces the evaluation member. The contact portion is composed of a plurality of protrusions that protrude from one surface 2A of the base portion 2 toward the evaluation member side. In this embodiment, each protrusion constituting the abutment portion is composed of a tubular hollow body 3. The multiple tubular hollow bodies 3 are arranged along the surface 2A of the base portion 2. In this example, the multiple tubular hollow bodies 3 are arranged side by side in one direction with spaces between them. In this example, the multiple tubular hollow bodies 3 are arranged so that their axes are parallel to each other. Furthermore, the surface 2A of the base portion 2 constitutes the surface opposite to the surface on which the load of the evaluation member is applied. The surface opposite to the surface on which the load of the evaluation member is applied may be an imaginary plane.

[0025] [Base 2] One surface 2A of the base 2 is formed with a plurality of notches 2Aa for positioning the tubular hollow bodies 3. Each notch 2Aa extends in a direction perpendicular to the arrangement direction of the tubular hollow bodies 3. In FIG. 1, a notch 2Aa with a triangular cross section is shown as an example. However, there are no restrictions on the cross-sectional shape of the notch 2Aa as long as it is possible to position the tubular hollow bodies 3. Furthermore, the base portion 2 has two or more through holes 2B penetrating through in the thickness direction at positions that do not interfere with the tubular hollow body 3 (protruding portion) to be fixed.

[0026] [Tubular hollow body 3] Each tubular hollow body 3 is positioned in a groove formed by a notch 2Aa in the base part 2. That is, the axis of the tubular hollow body 3 is oriented in the same direction as the extension direction of the notch 2Aa. In this state, the circumferential surface (outer diameter surface) of the tubular hollow body 3 is fixed to each notch 2Aa of the base part 2. The tubular hollow body 3 is fixed to the notch 2Aa by, for example, welding. 1 shows an example in which there are three tubular hollow bodies 3 serving as abutment parts protruding from the base part 2. The number of tubular hollow bodies 3 may be two, or may be four or more.

[0027] The tubular hollow body 3 in this embodiment is made of a metal pipe such as a steel pipe. Since it is a punch for performing a bending impact test, the tubular hollow body 3, which is the contact part, is required to have a certain rigidity. For this reason, the tubular hollow body 3 is made of metal. Here, the tubular hollow body 3 is preferably fixed to the base part 2 in a state where the cross-sectional center of the tubular hollow body 3 is displaced toward the evaluation member side (pressing side) from one surface 2A of the base part 2. By making the cross-sectional center protrude from one surface 2A of the base part 2 in this way, the tubular hollow body 3 becomes more susceptible to cross-sectional deformation in response to a load.

[0028] The tubular hollow body 3 of this embodiment is exemplified as a hollow body having a circular cross section. The cross section of the tubular hollow body 3 may be a polygonal shape other than a circular cross section. However, a shape without corners along the circumferential direction, such as a circle or an ellipse, is preferable. It is also simple and preferable that the tubular hollow body 3 be made from a pipe. However, a part with an arc-shaped cross section, such as a pipe split vertically, may also be used for the tubular hollow body. In this case, both left and right ends along the arc shape are fixed to the base 2 with the convex direction of the arc facing the evaluation member. In this way, a tubular hollow section is formed between the base 2 and the member with an arc-shaped cross section, thereby forming the tubular hollow body.

[0029] <Base part 4> The base 4 is a plate-like member provided on the back side of the base 2. The base 4 also serves as a stiffening plate that increases the rigidity of the punch body. The base 4 also serves as a connecting part that connects the punch body to the tip of the load transmission part. The base 4 is configured to be detachably connected to the base 2. For this purpose, the base 4 has a through hole 4C that opens coaxially with the through hole 2B of the base 2 (see FIG. 2(b)). The base 4 has multiple through holes so that multiple types of punch bodies can be connected. Furthermore, a recess 4Ba for positioning the tip of the load transmitting part 5 is formed on a surface 4B of the base part 4 opposite to the base part 2 side (see FIG. 2(b)).

[0030] Then, a bolt (not shown) is passed through the through hole 2B of the base part 2 from one surface 2A side of the base part 2. Furthermore, the tip of the bolt that passes through the through hole 2B of the base part 2 and the through hole 4C of the base part 4 is screwed into the female thread provided at the tip of the load transmission part 5. In this way, the punch 1 is detachably connected to the load transmission part 5. The other end of the load transmission portion 5 is used by being connected to the rod of a cylinder device that serves as an actuator that generates a load.

[0031] Here, the tubular hollow body 3 constituting the protruding portion (contact portion) is expected to deform more during evaluation as the strength of the evaluation component increases. Therefore, when the tubular hollow body 3 of the punch body undergoes plastic deformation during a bending impact test, the punch body must be replaced. In this embodiment, to reduce costs, the base portion 2 having the tubular hollow body 3 that serves as the contact portion is designed to be detachable from the base portion 4. In this embodiment, these two portions 2 and 4 are constrained by bolts or the like, so that when the tubular hollow body 3 undergoes plastic deformation, only the portion having the protruding shape can be replaced.

[0032] Furthermore, when conducting bending impact tests under multiple conditions, multiple types of punch bodies that differ in at least one condition, such as the strength or rigidity of the tubular hollow body 3, the arrangement of the tubular hollow body 3 (protrusion spacing, protrusion amount, etc.), or the number of tubular hollow bodies 3 that make up the abutment portion, can be prepared and used for each bending impact test.

[0033] (Bending impact test equipment) As shown in Fig. 3, the bending impact test device of this embodiment includes the punch 1 of this embodiment described above and left and right support parts 6. The left and right support parts 6 support both longitudinal end sides of an evaluation member 7 (test piece). The punch 1 is configured to be able to stroke toward the evaluation member 7 (test piece). In the bending impact tester, the abutment portion of the punch 1 is brought into contact with the middle portion of the evaluation member 7 in the longitudinal direction while both longitudinal ends of the evaluation member 7 are supported by the left and right support portions 6. Next, the punch 1 is further stroked in the pushing direction. In this example, the axis of the tubular hollow body 3, which is the abutment portion of the punch 1, is positioned parallel to the evaluation reference surface on which the load of the evaluation member 7 is applied. In addition, the axis of the tubular hollow body 3, which is the abutment portion of the punch 1, is positioned perpendicular to the longitudinal direction of the evaluation member 7. The end of the evaluation member 7 may be supported by the support portion 6 in a rotational or fixed manner. Any known support method used in a three-point bending test may be used as the support method.

[0034] At the beginning of the load input from the punch 1, as shown in FIG. 3, each peripheral surface (outer diameter surface) of the multiple tubular hollow bodies 3 protruding from the surface of the base portion 2 abuts on the upper surface of the evaluation member 7. From this state, a load is input from the contact portion of the punch 1 to the evaluation member 7 via the load transmission portion 5. At this time, as the punch 1 is pressed into the evaluation member 7, an impact load (impact load) is input from the multiple tubular hollow bodies 3 to the evaluation member 7. In this way, a bending impact test using the punch 1 is carried out.

[0035] In the bending impact test, the punch 1 is pushed in (stroke) until the evaluation member 7 buckles, for example. The bending impact test evaluates the evaluation member 7 based on, for example, the shear force and moment distribution generated in the evaluation member 7 before buckling, and the shear force and moment distribution generated when buckling occurs.

[0036] Here, it is preferable to adjust the strength and rigidity of the tubular hollow bodies 3 constituting the contact portion, the spacing between adjacent tubular hollow bodies 3, the protrusion amount of each tubular hollow body 3 from the base portion 2, the number of tubular hollow bodies 3, etc. The adjustments can be made, for example, according to the target value to be generated in the evaluation member 7 due to the impact of a vehicle collision. The target value is, for example, the bending moment and strain distribution that will be generated in the evaluation member 7 during a side collision of an actual vehicle. That is, the input target value is an input condition that can reproduce the form of bending deformation that will occur in a body structural member corresponding to the evaluation member 7 installed in a vehicle during a vehicle crash test. That is, the target input is an input that can reproduce the form of bending deformation that will occur in a body structural member during a vehicle crash test. Then, for example, as described below, the bending moment and moment distribution generated by the form of target bending deformation are determined by CAE analysis, and the input condition using the punch 1 can reproduce a state that is close to the determined bending moment and moment distribution. (action)

[0037] The bending impact test of this embodiment was evaluated by CAE analysis. Then, CAE was used to consider punch specifications that would achieve the target bending moment and moment distribution range for the evaluation member 7. Based on the results of this consideration, the position, shape, strength, etc. of the tubular hollow body 3 were determined.

[0038] Here, a test piece simulating a door impact beam as shown in FIG. 4 was used as the evaluation member 7. The material composition of the test piece was the same as that shown in FIG. 18, which will be described later. Furthermore, a steel pipe was used as an example of each tubular hollow body 3. The steel pipe used was a Φ34 pipe with a tensile strength of 1.5 GMPa.

[0039] In this example, the tubular hollow body 3 is made of a steel pipe. As a result, in this example, the contact portion of the punch (load input portion) is not a rigid body but a deformable body. This makes it easier to control the state of load input from the contact portion of the punch 1. If the contact portion that contacts the evaluation member 7 is made of a rigid body, a large load will be concentrated at the location of the evaluation member where the contact portion contacts. This makes it difficult to control the input from the punch. In contrast, by making the load input portion (contact portion) a deformable body structure as in this embodiment, the load concentration at the contact portion where the contact portion contacts is alleviated. As a result, it is possible to input the load over a larger surface, and the accuracy of reproducing the input due to a side collision of the barrier bogie is improved. Furthermore, by configuring the contact portion with two or more tubular hollow bodies 3, the load input surface is further increased, making it possible to more accurately reproduce the input due to a side collision of the barrier bogie. Furthermore, by making the tubular hollow body 3 out of metal, it becomes possible to deform the body while transmitting a predetermined load.

[0040] The load input from the contact portion becomes an impact load on the evaluation member 7. Examples of the impact load include a direct input load, and a moment and strain distribution that occur in the evaluation member 7 due to the load input.

[0041] Here, FIG. 5(a) is an image diagram of a side collision test using a barrier bogie 11 and an actual vehicle 10. In this example, the test is conducted by colliding a collision body 12 with a large area at the tip with the side of the vehicle body. Also, FIG. 5(b) is an image diagram of a pole collision test in which a pole 13 made of a rigid body collides with the side of the vehicle body. The bending impact test of this embodiment is a technique that can mainly reproduce a barrier bogie side collision test. However, the bending impact test of this embodiment can also reproduce a pole collision collision test.

[0042] In the following example, the contact portion is formed of three tubular hollow bodies 3. Here, the load input at the contact portion becomes an impact load on the evaluation member 7, and examples of this impact load include a direct input load and a moment generated in the evaluation member 7 by this load input. As described above, the input and the timing of the input can be controlled by the strength of the steel pipes, the arrangement of the steel pipes (protrusion interval, protrusion amount), and the number of steel pipes that make up the contact portion.

[0043] <Example of comparative analysis> CAE was used to investigate the input to the door impact beam constituting the evaluation member 7 in a full-car crash test and a comparative impact test. The full-car crash test is a crash test in which a collision body 12 of a barrier trolley 11 collides sideways with the side of an actual car 10 (see FIG. 5(a)). Hereinafter, this crash test will be referred to as the full-car crash test. The comparative impact test was a three-point bending impact test using a pole 13 made of a rigid body with an arc-shaped cross section at the tip as a punch. The analysis condition was that the punch was pushed in until buckling occurred.

[0044] The results are shown in FIGS. Figure 6 is a diagram of the strain distribution generated in the evaluation member 7 due to the comparative impact test. Figure 7 is a diagram of the strain distribution generated in the evaluation member 7 due to the full car crash test. Note that Figures 6 and 7 show the strain distribution when the moment in the evaluation member 7 is at its maximum. Figure 8 shows moment diagrams for the comparative impact test and the full car crash test. The X-axis in Figure 8, "Line L," indicates the longitudinal direction of the evaluation member 7, and the vicinity of X=0 is the contact position of the punch 1. The longitudinal direction of the door impact beam corresponds to the overall length of the vehicle.

[0045] 6 to 8, it was found that in the comparative impact test, strain and moment were concentrated at the center of the door impact beam, which was the contact position of the punch consisting of the pole 13. On the other hand, in the full car crash test, it was found that both strain and moment were distributed over a wide area.

[0046] This is conceptually illustrated (model-wise) in Figure 9. In the comparative impact test, as shown in Figure 9(a), a load is input from a punch 20 simulating a pole 13 to a single point in the longitudinal direction of the evaluation member 7. On the other hand, in the full car collision test, as shown in Figure 9(b), the pressure-receiving area from a virtual punch 21 simulating a collision body 12 expands from the early stage of the collision. The load is input so as to suppress stress concentration at the center of the door impact beam, which is the evaluation member 7. In this case, the door impact beam undergoes a deformation mode in which it deforms in a bow shape during a side collision, and then undergoes bending crushing.

[0047] <An analysis example of Virtual Punch 21> Therefore, the inventors conducted a bending impact test with a contact shape (tip shape) of the virtual punch 21 as shown in Figure 9(b). At this time, the conditions other than the punch shape were the same as those in the comparative impact test. The virtual punch 21 was a rigid body. That is, in order to suppress stress concentration, a bending load was input to the center of the door impact beam by the virtual punch 21, and a bending impact test was analyzed.

[0048] The results are shown in FIGS. Fig. 10 is a diagram showing the strain distribution generated in the evaluation member 7 due to a bending impact test using a virtual punch 21. Fig. 10 shows the strain distribution when the moment in the evaluation member 7 is at its maximum. Fig. 11 is a moment diagram showing the same. Fig. 11 also shows moment diagrams for a comparative impact test and a full car crash test.

[0049] As shown in Fig. 11, by using this virtual punch 21, it was possible to suppress the stress concentration at the center of the door impact beam and to reproduce a wider range of moment distribution. However, because the virtual punch 21 is a rigid body, it was found that it was difficult to control the maximum value of the moment.

[0050] Based on this new knowledge, the inventors considered constructing the contact portion that contacts the evaluation member 7 from an elastic-plastic body. The inventors then considered representing the above-mentioned virtual punch 21 with a plurality of steel pipes (tubular hollow bodies 3) lined up in the longitudinal direction of the evaluation member 7 in a plan view. When making the contact portion an elastic-plastic body, by constructing the contact portion from a plurality of steel pipes (tubular hollow bodies 3), it becomes possible to easily manufacture the contact portion that becomes an elastic-plastic body and adjust its rigidity, strength, etc.

[0051] <Analysis Example of This Embodiment> A CAE analysis was carried out on a bending impact test using a punch 1 having a contact portion made up of three steel pipes based on this embodiment. Hereinafter, this bending impact test will be referred to as an improved bending impact test.

[0052] The results are shown in Figures 12 and 13. Fig. 12 is a diagram showing the strain distribution generated in the evaluation member 7 in the improved bending impact test. Fig. 12 shows the strain distribution when the moment in the evaluation member 7 is at its maximum. Fig. 13 is a moment diagram in the improved bending impact test. Fig. 13 also shows moment diagrams for the comparative impact test and the full car crash test. As can be seen from Figures 12 and 13, it was found that by using an elastic-plastic steel pipe for the contact part of punch 1 with the door impact beam, it is possible to suppress stress concentration and control the moment value.

[0053] Here, the strength conditions of the steel pipe were determined using CAE to reproduce the inputs from a full-car crash test. An evaluation of these decisions revealed that a steel pipe with a tensile strength of 1500 MPa and a wall thickness of 2 mm was suitable. It was also found that the moment value could be controlled by changing the strength of this steel pipe.

[0054] In this improved bending impact test, a load is input from three steel pipes at the initial stage of contact with punch 1. Furthermore, in this improved bending impact test, as punch 1 pushes in and the central part of the door impact beam bends downward, the input from the central steel pipe becomes relatively smaller. This behavior also shows that when the contact part is made up of two steel pipes without the central steel pipe, the input load at the initial stage of the collision changes compared to when the contact part is made up of three steel pipes.

[0055] Furthermore, in this improved bending impact test, the contact portion is made of a steel pipe that can deform as the input load increases. This prevents the load from concentrating at the contact portion of the steel pipe. As a result, it is possible to apply deformation so that the evaluation member 7 bends over its entire length in the longitudinal direction, at least up to the middle of the pressing stroke of the punch 1. In other words, it is clear that the area that receives the input pressure can be increased. This behavior is similar to the deformation mode observed in full-car crash tests. In other words, during a side collision of an actual vehicle, the door impact beam undergoes a bow-like deformation followed by bending crushing. The improved bending impact test can achieve a deformation mode similar to this.

[0056] <Analysis example of steel pipe strength and spacing changes> Figures 14 and 15 show examples of changes in the strength and spacing of steel pipes. CAE was used to confirm the results when the strength of each steel pipe was improved. Specifically, in the above example, it was found that the moment value improved by increasing the tensile strength (TS) of each steel pipe from the initial value of 1.5 GPa to 1.8 GPa. Furthermore, when the spacing between the steel pipes at the right end shown in Figure 14 was increased, it was found that the range of wire L where the maximum moment occurred expanded to the right, as shown in Figure 15.

[0057] These results show that it is possible to control the input to the door impact beam by adjusting the strength of the steel pipes and the spacing between them.

[0058] In this way, it is advisable to appropriately design and select the arrangement and strength of the tubular hollow body 3 attached to the punch 1. This makes it possible to perform bending impact tests that are tailored to the collision conditions and target input values ​​(moment value and strain distribution) required for various collision tests.

[0059] <Example of control (adjustment) of the contact portion made of the tubular hollow body 3> An example of a method for controlling the contact portion made up of the tubular hollow body 3 will be further described with reference to FIGS. (1) Distance W between contact parts As shown in FIG. 17, the distance W between the contacting portions is the distance between two tubular hollow bodies 3 that are located at the outermost ends in the arrangement direction among the tubular hollow bodies 3 that form the contacting portions. This distance W between the contact parts can be determined by the range of "line L" (longitudinal position) where a high moment occurs in Figure 16. For example, if you want to widen the range where a high moment occurs, you can adjust the distance between the contact parts to be wider.

[0060] (2) Height of the contact portion (amount of protrusion of each tubular hollow member from the base portion 2) The height of the contact part can be changed within the high moment generating range if it is desired to generate a high moment locally. For example, as shown in Figures 16 and 17, by increasing the protrusion amount of the tubular hollow body 3 at the position where the L wire position value is 60 by ΔH compared to the other tubular hollow bodies, it is possible to locally increase the moment at the protruding position. That is, when it is desired to generate a high moment locally, it is sufficient to increase the protrusion amount of the tubular hollow body 3 near that position. Furthermore, by configuring the contact portion with a tubular hollow body, it is possible to prevent excessive localized concentrated load near the position of the protruding tubular hollow body.

[0061] (3) Strength and rigidity of the contact portion (tubular hollow body 3) The strength is approximated by the yield stress of the material of the tubular hollow body 3. The rigidity is an index of the resistance to deformation of the tubular hollow body 3. For example, if a steel pipe is used as the tubular hollow body 3, the rigidity here can be expressed as the ratio of the wall thickness of the steel pipe to the diameter of the steel pipe. The strength and rigidity of the tubular hollow body 3 can be changed by changing the target moment value of the evaluation member 7. Furthermore, if at least one of the strength and rigidity of the tubular hollow body 3 is increased, the moment value and moment slope increase even without changing the conditions of the bending impact test (conditions such as the thrust stroke of the punch 1 and the fulcrum distance) (see Figure 16).

[0062] (4) Diameter of the tubular hollow body 3 In the bending impact test of this embodiment, the range in which a high moment is loaded (input) gradually expands as the stroke of the punch 1 increases. By increasing the diameter of the pipe constituting the outermost tubular hollow body 3 in the arrangement direction among the tubular hollow bodies 3 that form the abutment portion, the rate of increase in the high moment load range with increasing stroke can be increased.

[0063] The above adjustment examples are just examples. For example, a target value (collision condition to be reproduced) is determined by CAE analysis. Then, to approach the target value, CAE analysis is performed using parameters such as the number of tubular hollow bodies 3, the spacing between the tubular hollow bodies 3, the strength and rigidity of the tubular hollow bodies 3, and the difference in protrusion amount between each tubular hollow body 3. Then, based on the results of the CAE analysis, the conditions of the tubular hollow bodies 3 can be controlled so that the input becomes the target value.

[0064] (others) The present disclosure may also have the following configuration. (1) A punch for a bending impact test that applies a load to an evaluation component, The contact portion that applies a load to the evaluation member is composed of a plurality of tubular hollow bodies with their peripheral surfaces facing the evaluation member. Punch for bending impact testing. (2) The plurality of tubular hollow bodies are arranged along a surface of the evaluation member opposite to the surface to which the load is applied. (3) A plate-shaped base portion is provided, each of the tubular hollow bodies protrudes from one surface of the base portion facing the evaluation member toward the evaluation member; The base portion has a surface opposite to the one surface thereof, and a tip end of a load transmission member that transmits a load to the contact portion is detachably connected to the surface. (4) Equipped with a punch for bending impact testing according to the present disclosure; Bending impact test equipment. (5) applying a load to the evaluation member using a punch having a contact portion that contacts the evaluation member and is made up of a plurality of tubular hollow bodies; Bending impact test method. (6) The input to the evaluation member by the punch is controlled by changing one or more conditions selected from the arrangement position of the plurality of tubular hollow bodies, the strength of each tubular hollow body, the rigidity of each tubular hollow body, the cross-sectional shape of each tubular hollow body, and the number of the tubular hollow bodies. (7) Depending on the target input to the evaluation component, one or more conditions selected from the arrangement position of the plurality of tubular hollow bodies, the strength of each tubular hollow body, the rigidity of each tubular hollow body, the cross-sectional shape of each tubular hollow body, and the number of tubular hollow bodies are adjusted, and a bending impact test is performed using the adjusted punch. (8) The evaluation component is a body structural component of an automobile, The target input is an input that can reproduce the form of bending deformation that occurs in the vehicle body structural member in the automobile crash test. [Example]

[0065] An example based on this embodiment will be described. (Example) A bending impact test was carried out on the evaluation member 7 using the punch 1 according to this embodiment. <Test conditions> The conditions of the example are as follows. Three tubular hollow bodies 3 are used as the contact portions. The conditions for each tubular hollow body 3 are as follows: The tubular hollow body 3 was made of a steel pipe. The dimensions of the steel pipe were 200 mm in length, 2 mm in thickness, and Φ34 mm in diameter. The material of the steel pipe was STKM13A, and the interval between adjacent pipes was set to 83 mm.

[0066] The evaluation member 7 was made of a steel material having the shape shown in Fig. 4. This evaluation member 7 was a test piece simulating a door impact beam. The material of the evaluation member 7 is shown in FIG.

[0067] Then, both longitudinal ends of the evaluation member 7 were supported at a support interval of 842 mm, and a bending impact test was performed in which the central portion of the longitudinal direction of the evaluation member 7 was pressed with a punch 1. The stroke speed of the punch 1 at this time was set to 0.01 km / h.

[0068] (Comparative Example) For comparison, a conventional three-point bending impact test (comparative example) was also carried out. A bending impact test was carried out under the same conditions as in the example, except that a punch with an arc-shaped cross section with a tip of R100 was used. The material of the punch was the same as that of the tubular hollow body 3, but the punch in the comparative example was a solid body.

[0069] (Evaluation results) Figure 19 shows the state of the test piece after the bending impact test. Figure 19(a) shows the test results for the example, and Figure 19(b) shows the test results for the comparative example. As can be seen from FIG. 19(a), the bending impact test of the example was able to reproduce a mode of deformation over a wide range, similar to the full-car collision test using a barrier trolley. 19(b), in the bending impact test of the comparative example, deformation was concentrated at the part that came into contact with the punch, resulting in bending of the evaluation member 7. In other words, it was found that the bending impact test of the comparative example was unable to reproduce a mode in which deformation occurred over a wide range. [Explanation of symbols]

[0070] 1 punch 2 Base part (punch body) 2Aa Notch 3. Tubular hollow body (punch body) 4 Base 5 Load transmission section 6 Support part 7 Evaluation materials

Claims

1. A punch for a bending impact test that applies a load to an evaluation member, the contact portion that applies a load to the evaluation member is composed of a plurality of tubular hollow bodies with their circumferential surfaces facing the evaluation member, the plurality of tubular hollow bodies are arranged along a surface of the evaluation member opposite to a surface on which the load is applied, Each tubular hollow body is made of a pipe. Punch for bending impact testing.

2. It has a plate-shaped base part, each of the tubular hollow bodies protrudes from one surface of the base portion facing the evaluation member toward the evaluation member; a tip end of a load transmission member that transmits a load to the abutment portion is detachably connected to a surface of the base portion facing the opposite side to the one surface thereof; 2. A punch for a bending impact test according to claim 1.

3. A punch for a bending impact test according to claim 1 or 2 is provided. Bending impact test equipment.

4. applying a load to the evaluation member using a punch having a contact portion that contacts the evaluation member and that is made up of a plurality of tubular hollow bodies; the plurality of tubular hollow bodies are arranged along a surface of the evaluation member opposite to a surface on which the load is applied, Each tubular hollow body is made of a pipe. Bending impact test method.

5. The input to the evaluation member by the punch is controlled by changing one or more conditions selected from the arrangement positions of the plurality of tubular hollow bodies, the strength of each tubular hollow body, the rigidity of each tubular hollow body, the cross-sectional shape of each tubular hollow body, and the number of the tubular hollow bodies.

5. The bending impact test method according to claim 4.

6. adjusting one or more conditions selected from the arrangement positions of the plurality of hollow tubular bodies, the strength of each hollow tubular body, the rigidity of each hollow tubular body, the cross-sectional shape of each hollow tubular body, and the number of hollow tubular bodies according to a target input to the evaluation member, and performing a bending impact test using the punch after adjustment; 5. The bending impact test method according to claim 4.

7. The evaluation member is a body structural member of an automobile, the target input is set to an input capable of reproducing a form of bending deformation occurring in the vehicle body structural member in a collision test of the automobile; 7. A bending impact test method according to claim 6.

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