JP7586129B2 - Test method for evaluating crashworthiness of evaluation components and method for evaluating crashworthiness - Google Patents

Description

The present invention relates to a crashworthiness evaluation test method and a crashworthiness evaluation method for evaluation members corresponding to structural members for automobile bodies.

In recent years, collision safety standards in the automotive sector have become increasingly strict from the perspective of passenger protection, and there is a strong demand for expanded use of high-strength steel and the development of vehicles with superior collision safety performance. In particular, the automotive industry in Europe, the United States, and China has been rapidly shifting from gasoline-powered vehicles to electric vehicles (EVs) in an effort to create a carbon-free society, and the EV market is expected to expand in Japan in the future.

From the perspective of collision deformation, structural components for automobile bodies can be broadly divided into two types: cabin frame components that are placed around the cabin and therefore do not allow deformation during a collision due to their high load-bearing capacity, and energy absorbing components that have a certain degree of load-bearing capacity and absorb collision energy while allowing some deformation. Components such as side sills fall into the former cabin frame components, and are required to have high load-bearing capacity against bending deformation modes in the component's longitudinal direction during a side collision in particular, to prevent the impact object from entering the cabin. However, in reality, in conventional gasoline-powered vehicles, side sills are often designed to increase energy absorption capacity by allowing the components to intrude to the extent that it does not affect the occupant injury value, while diverting the load to the surrounding structure.

On the other hand, in EV vehicle design, particularly in the design of the battery surrounding structure, there is a tendency for high energy absorption performance to be required due to the increased vehicle weight caused by the loading of batteries. However, from the perspective of battery protection, the battery surrounding structure itself is very robust and allows almost no deformation, so it does not contribute much to energy absorption performance. Furthermore, from the perspective of aiming for longer driving range, there are many cases where a platform structure with a wider battery loading area is adopted, in which case the side sill will be responsible for absorbing the majority of the energy in a side collision. Given such a design, the side sill is required to have a high load capacity due to being made of high strength materials equal to or greater than current ones, while also being capable of large deformation and having high energy absorption performance.

Generally, cabin structural components have high load-bearing capacity due to the use of high-strength materials, but because they are high-strength materials, they often have low ductility. In this case, when a single component in an EV experiences a large deformation greater than that expected in a conventional gasoline-powered vehicle, the crash load may decrease due to fracture, and the expected amount of energy absorption may not be achieved. For this reason, EV cabin structural components are required to have excellent fracture properties and energy absorption properties when subjected to large deformation in the bending deformation mode. In addition, it is important to be able to easily evaluate the above-mentioned crash properties at the material development stage.

As a test method for evaluating the crashworthiness of metal sheet materials for automobile bodies, Patent Document 1 discloses a test method in which a flat test piece made of metal sheet material is subjected to a primary bending deformation into a V shape, and then a bending test device is used to subject the test piece that has undergone primary bending deformation to a secondary bending deformation in a direction intersecting the primary bending deformation direction.

International Publication No. 2020/129903

However, the method in Patent Document 1 is a test method for reproducing the fracture of a component when it is crushed in the axial direction, and the deformation mode is thought to be different from cases where fracture occurs due to large bending deformation, such as that expected in a side collision of an EV, as described above.

Therefore, in order to solve the above-mentioned problems, the present invention aims to propose an evaluation test method and evaluation method for collision performance that can be easily performed at the material development stage to measure the collision fracture characteristics that occur when a material breaks due to large bending deformation, such as that expected in a side collision of an EV.

The present invention provides a method for evaluating the collision performance of a member to be evaluated, which advantageously achieves the above object, comprising:
A crashworthiness evaluation test method is provided, comprising the steps of: processing an evaluation member , which is made of a metal plate material and has at least a top plate portion and a pair of side walls each continuing to both widthwise ends of the top plate portion, and which corresponds to a structural member for an automobile body; using a testing machine having a moving part and a fixed part, the moving part is moved relative to the fixed part, and the evaluation member is subjected to a clamping deformation between the moving part and the fixed part , the method comprising the steps of:
A punch having an arc-shaped or rectangular cross section and a longitudinal direction perpendicular to the cross section is connected to the moving part,
A flat floor surface is used as the fixing portion,
The evaluation member is fixed or installed to the fixing portion at the opposite end of the side wall portion facing the top plate portion or a flange portion continuous with the opposite end of the side wall portion, in a direction in which the longitudinal direction of the evaluation member intersects with the longitudinal direction of the punch .

Further, a method for evaluating the collision performance of an evaluation member according to the present invention, which advantageously achieves the above object, comprises the steps of:
A collision performance evaluation test of the evaluation member is carried out by the collision performance evaluation test method,
The present invention is characterized in that the occurrence or non-occurrence of fracture of the evaluation component after the test and/or the occurrence and propagation behavior of fracture during the test due to clamping deformation of the evaluation component are judged or evaluated based on information obtained from at least one of visual inspection, photographed images, test load, and other measurement results.

The present invention provides a structural member for an automobile body that advantageously achieves the above object, comprising:
A structural member for an automobile body manufactured based on an evaluation by the collision performance evaluation method of the evaluation member,
The evaluation component is characterized in that it is manufactured using a metal plate material that has been processed into an evaluation component that has been evaluated as having a low risk of fracture by carrying out the method for evaluating the collision performance of the evaluation component.

In the collision performance evaluation test method of the present invention, an evaluation member is made by processing a metal plate material into a shape having at least a top plate portion and a pair of side wall portions each continuing to both widthwise ends of the top plate portion, which corresponds to a structural member for an automobile body, and a testing machine having a moving portion and a fixed portion is used to fix or place the evaluation member on the fixed portion at the opposite end portion of the side wall portion facing the top plate portion or a flange portion continuing to the opposite end portion, and the evaluation member is clamped and deformed by moving the moving portion relative to the fixed portion.

Therefore, according to the collision performance evaluation test method of the present invention, it is possible to easily test the collision fracture characteristics and collision performance of evaluation components corresponding to structural components for automobile bodies in deformation modes expected during a side collision of an EV, compared to conventional evaluation tests.

In the method for evaluating the collision performance of an evaluation member of the present invention , a punch having an arc-shaped or rectangular cross section and a shape with a longitudinal direction perpendicular to the cross section is connected to the moving part , a flat floor surface is used as the fixing part, and the evaluation member is fixed or placed on the fixing part at the opposite end of the side wall part relative to the top plate part or a flange part continuous with the opposite end of the side wall part in a direction in which the longitudinal direction of the evaluation member intersects with the longitudinal direction of the punch . In this way, it is possible to easily test the collision fracture characteristics and collision performance in a bending deformation mode assumed during a side collision of an EV.

Furthermore, in the collision performance evaluation method of the present invention, a collision performance evaluation test of the evaluation member is carried out by the collision performance evaluation test method, and the occurrence or absence of fracture of the evaluation member after the test due to clamping deformation of the evaluation member and/or the occurrence and propagation behavior of the fracture during the test are determined or evaluated based on information obtained from at least one of visual inspection, photographed images, the test load, and other measurement results.

Therefore, the method for evaluating the collision performance of evaluation components of the present invention makes it easier than ever to evaluate the collision fracture characteristics and collision performance of evaluation components corresponding to structural components for automobile bodies in deformation modes expected during a side collision of an EV.

In addition, the structural components for automobile bodies manufactured based on the evaluation using the method for evaluating the collision performance of the evaluation components are manufactured using metal plate material that has been processed into an evaluation component that has been evaluated as having a low risk of fracture by implementing the method for evaluating the collision performance of the evaluation component.

Therefore, by using a structural component for an automobile body according to the present invention, it is possible to provide a structural component for an automobile body that has excellent fracture characteristics and energy absorption characteristics when subjected to large deformation in the bending deformation mode expected in the event of a side collision of an EV.

1A, 1B and 1C are an end view, a side view and a perspective view showing an evaluation member used in a crash performance evaluation test method for an evaluation member according to one embodiment of the present invention. 3A and 3B are an end view and a side view showing a crashworthiness evaluation test machine used in the crashworthiness evaluation test method of the evaluation member of the above embodiment. FIG. 4 is a characteristic diagram showing the results of a collision performance test performed using the collision performance evaluation test method for the evaluation member according to the embodiment. 6A to 6E are photographs sequentially showing the deformation process when a collision performance test was conducted on the evaluation member of Example 3 using the collision performance evaluation test method for evaluation members of the above embodiment. 6A to 6E are photographs sequentially showing the deformation process when a collision performance test was conducted on the evaluation member of Example 5 using the collision performance evaluation test method for evaluation members of the above embodiment. Photographs (a) to (e) show, in the upper part, the appearance of the broken state after the collision performance test for the evaluation members of Examples 1 to 5, which was conducted using the collision performance evaluation test method for the evaluation member of the above embodiment, and in the lower part, an enlarged view of the outlined portion of the appearance of the broken state.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. Here, Fig. 1(a), Fig. 1(b) and Fig. 1(c) are an end view, a side view and a perspective view showing an evaluation member used in a method for evaluating the collision performance of an evaluation member according to one embodiment of the present invention. The method for evaluating the collision performance of this embodiment is for performing a collision performance evaluation test of an evaluation member E having a hollow cross section extending in the longitudinal direction, which corresponds to an automobile structural member such as a side sill.

In the collision performance evaluation test of the evaluation member by the collision performance evaluation test method of this embodiment, the evaluation member, which is made of a metal plate material processed into a cross-sectional shape having at least a top plate portion and a pair of side wall portions each continuing to both widthwise ends of the top plate portion, is subjected to clamping deformation by moving the moving part relative to the fixed part using a testing machine having a moving part and a fixed part. The movement of the moving part relative to the fixed part at this time is performed by fixing or placing the evaluation member on the fixed part at the opposite end of the side wall portion relative to the top plate portion or a flange portion continuing to the opposite end.

To explain this collision performance evaluation test in detail, as shown in Figures 1(a), (b) and (c), the evaluation member E has a hollow hat-shaped cross-sectional shape that is extended in the longitudinal direction (left-right direction in Figure 1(b)) and is composed of a top plate portion 1, a pair of side wall portions 2 each continuing to both widthwise ends of the top plate portion 1, and a pair of flange portions 3 each continuing to the opposite ends of the side wall portions 2 facing the top plate portion 1.

The width of the top plate 1 and each of the vertical wall portions 2 is 40 mm, the width of each of the flange portions 3 is 20 mm, the angle between the top plate 1 and each of the two vertical wall portions 2 is 90°, the angle between the two vertical wall portions 2 and each of the two flange portions 3 is 90°, and the top plate 1 and each of the vertical wall portions 2 and each of the vertical wall portions 2 and each of the flange portions 3 are connected via fillet-shaped ridge portions with an inner bending radius R of 5 mm.

The material of the evaluation member E was a metal plate material such as a steel plate having a tensile strength of 1180 MPa or more, and the plate thickness was 1.4 mm. The above cross-sectional shape of the evaluation member E was extended by 80 mm in the direction perpendicular to the cross section (longitudinal direction). In order to fix the evaluation member E, a thick plate-shaped installation jig J having dimensions of 100 mm x 100 mm x 10 mm was prepared, the evaluation member E was placed on the installation jig J, and the flange portion 3 of the evaluation member E and the installation jig J were welded and joined by a welded portion W, for example by arc welding.

2(a) and 2(b) are end and side views showing a crash performance evaluation test machine used in the crash performance evaluation test method of the evaluation member of the embodiment described above. The crash performance evaluation test machine used in the crash performance evaluation test method of this embodiment is configured with an evaluation member E joined onto an installation jig J, a moving part M of the test machine, and a fixed part F of the test machine. The moving part M and fixed part F of the test machine can be configured, for example, with a test machine such as an Amsler type test machine in which a slide as a moving part is raised and lowered by a hydraulic cylinder relative to a table as a fixed part.

A punch P having a highly rigid arc-shaped cross section is connected to the moving part M of the testing machine. The fixed part F of the testing machine is a flat floor surface having a high rigidity. The collision test by the method for evaluating the collision performance of the evaluation member of this embodiment is performed by connecting a punch P having an arc-shaped cross section and a shape whose longitudinal direction is perpendicular to the cross section to the moving part M, installing an evaluation member E on the testing machine in such a direction that the installation jig J is in contact with the floor surface as the fixed part F and the longitudinal direction of the evaluation member intersects with the longitudinal direction of the punch P , and lowering the punch P, i.e. , moving it relative to the fixed part , and clamping the evaluation member E between the punch P and the floor surface as the fixed part F.

The material, plate thickness, dimensions, cross-sectional shape, installation or fixing method of the evaluation member E, the state of the moving part M and the fixed part F, and the cross-sectional shape of the punch P are merely examples. The test method of this embodiment is a more standard and simple test condition for testing in the material development stage to evaluate impact performance, but it may be adjusted to more specific conditions, such as making the cross-sectional shape of the punch P rectangular, according to the expected impact mode and boundary conditions.

Furthermore, the cross-sectional shape of the evaluation member E may be composed of only the top plate portion 1 and the vertical wall portion 2 without the flange portion 3. The end portion of the vertical wall portion 2 opposite to the top plate portion 1 may be directly joined or fixed to the fixed portion F, or may simply be placed thereon. Furthermore, the method of joining the evaluation member E to the fixed portion F or the installation jig J may be a method such as bolt fastening or adhesive other than welding. As a reference example , the evaluation member E may be fixed to the moving portion M side, and the shape of the fixed portion F side may be an arc-shaped cross-sectional shape like the punch P, instead of a flat shape.

A collision test was conducted based on the collision performance evaluation test method for the evaluation member of the above embodiment. Two types of steel plates with different characteristics, tensile strength of 1180 MPa class (Examples 1 and 2) and three types of steel plates with tensile strength of 1470 MPa class (Examples 3 to 5), were prepared, and evaluation member E was produced from each of them by bending and arc welding. The moving speed of punch P of the testing machine was 10 mm/min. and the moving stroke of punch P was 30 mm. The reaction force applied to punch P and moving part M during the collision test and the moving stroke of punch P were recorded, and photographs were taken at intervals of one photograph/sec. to observe and evaluate the deformation and fracture state of evaluation member E during the collision test.

Figure 3 shows a characteristic diagram of the load-stroke curve (F-S curve) created from the punch load and punch stroke data collected during the above-mentioned collision test. Figures 4(a)-(e) and 5(a)-(e) show photographs of the deformation process for Examples 3 and 5, taken in sequence at the points indicated by the arrows at the top of Figure 3.

As shown in FIG. 3, the vertical wall portion 2 buckles and deforms to a peak load at time (2), and the deformation and load fluctuation are similar until the cross section collapses at time (3). However, at time (4), no break occurs in Example 3 shown by curve E3, whereas a break (BR) occurs in Example 5 shown by curve E5, and the break penetrates the plate thickness, causing the evaluation member E to split and a sudden load drop to begin. In the method for evaluating the collision performance of an evaluation member of one embodiment of the present invention, which uses an evaluation test according to the method for evaluating the collision performance of an evaluation member of the above embodiment, the occurrence of breakage is evaluated from the photographs and the sudden load drop as described above, and the punch stroke at the time when the break first occurs is taken as the break stroke.

Figures 6(a)-(e) show the appearance of the fractured state after testing for Examples 1-5 at the top, and an enlarged view of the outlined area of the appearance of the fractured state at the bottom. Table 1 below shows the strength level (MPa class), fracture state evaluation (fracture stroke (only when fracture occurs) (mm)), and energy absorption amount (kJ) of the materials for Examples 1-5. Here, the fracture state evaluation was rated on a three-level scale: × when fracture occurred, △ when a crack occurred but did not penetrate the plate thickness and did not break, and ◯ when no crack or fracture was confirmed. The energy absorption amount was calculated by integrating the punch load up to the fracture stroke by the punch stroke.

According to the collision performance evaluation method of the evaluation member of this embodiment, it was possible to evaluate that cracks, breakage, and energy absorption are different even at the same strength level. Furthermore, in Example 5 with a strength level of 1470 MPa, breakage was confirmed, and it was found that the energy absorption was the lowest, including Examples 1 and 2 with lower strength. From the perspective of increasing the tension (high tensile strength) from 1180 MPa class material to 1470 MPa class material, it was evaluated that the material of Example 5 has a high risk of breakage and there is a concern that the energy absorption will also decrease, while the material of Example 3 can be expected to have an increased energy absorption with the same risk of breakage as the 1180 MPa class material.

Therefore, according to the collision performance evaluation test method and collision performance evaluation method of the evaluation member of this embodiment, it is possible to easily perform tests on the collision fracture characteristics and collision performance of the evaluation member E corresponding to a structural member for an automobile body in a deformation mode expected in a side collision of an EV, compared to conventional evaluation tests, and it is also possible to easily evaluate the collision performance based on the test results, compared to conventional methods.

Furthermore, the structural member for automobile bodies manufactured based on the evaluation using the collision performance evaluation method for the evaluation member of the above embodiment is manufactured using metal plate material that has been processed into an evaluation member that has been evaluated as having a low risk of fracture by implementing the collision performance evaluation method for evaluation member E, and therefore can be an automobile body structural member with excellent fracture characteristics and energy absorption characteristics when subjected to large deformation in a bending deformation mode anticipated during a side collision of an EV.

Although the above description is based on the illustrated example, the present invention is not limited to the above example. For example, in the above embodiment, both of the two flanges 3 or vertical wall portions 2 of the evaluation member E are fixed or installed on the moving or fixed portion of the testing machine via the installation jig J or directly. However, depending on the arrangement of the corresponding automobile body structural member, for example, one of the two flanges 3 or vertical wall portions 2 may be fixed to the installation jig J and the other may be simply placed on the installation jig J, and the installation jig J may be fixed or installed on the moving or fixed portion of the testing machine.

Thus, the collision performance evaluation test method of the present invention for evaluation components makes it possible to more easily test the collision fracture characteristics and collision performance of evaluation components corresponding to structural components for automobile bodies in deformation modes expected during a side collision of an EV, compared to conventional evaluation tests.

In addition, the method for evaluating the collision performance of evaluation components of the present invention makes it easier than ever to evaluate the collision fracture characteristics and collision performance of evaluation components corresponding to structural components for automobile bodies in deformation modes expected during a side collision of an EV.

Furthermore, by using a structural component for an automobile body according to the present invention, it is possible to provide a structural component for an automobile body that has excellent fracture characteristics and energy absorption characteristics when subjected to large deformation in the bending deformation mode anticipated during a side collision of an EV.

E: Evaluation member E1 to E5: Examples F: Fixed part J: Installation jig P: Punch M: Moving part W: Welded part 1: Top plate part 2: Vertical wall part 3: Flange part

Claims (2)

A crashworthiness evaluation test method is provided, comprising the steps of: processing an evaluation member , which is made of a metal plate material and has at least a top plate portion and a pair of side walls each continuing to both widthwise ends of the top plate portion, and which corresponds to a structural member for an automobile body; using a testing machine having a moving part and a fixed part, the moving part is moved relative to the fixed part, and the evaluation member is subjected to a clamping deformation between the moving part and the fixed part , the method comprising the steps of:
A punch having an arc-shaped or rectangular cross section and a longitudinal direction perpendicular to the cross section is connected to the moving part,
A flat floor surface is used as the fixing portion,
a flange portion continuous with the opposite end portion of the side wall portion facing the top plate portion or a flange portion continuous with the opposite end portion of the side wall portion, the flange portion being fixed or placed on the fixing portion in a direction such that the longitudinal direction of the evaluation member intersects with the longitudinal direction of the punch . A collision performance evaluation test of the evaluation member is carried out by the collision performance evaluation test method according to claim 1 ,
A method for evaluating the collision performance of an evaluation member, characterized in that the occurrence or absence of fracture of the evaluation member after testing due to clamping deformation of the evaluation member and/or the occurrence and propagation behavior of the fracture during the test are determined or evaluated based on information obtained from at least one of visual inspection, photographed images, the test load, and other measurement results.