Test method for automotive structural member with welded joint, evaluation method for automotive structural member with welded joint, and specimen used for testing automotive structural member with welded joint

Abstract

To provide a test method and an evaluation method for an automotive structural member with a welded joint, and a specimen, which enable evaluation of the strength performance of the welded joint by reproducing the automotive structural member using a small-scale specimen.SOLUTION: A test method for an automotive structural member with a welded joint according to the present invention includes as components of a specimen: a first component having a U-shaped cross-section; a second component having a hat-shaped cross-section; a third component forming a closed cross-sectional space with the second component; and a fourth component having an opening portion into which one end of the first component can be fitted into a shape corresponding to the hat shape of the second component and connected to one end portion of the second component without closing the closed cross-sectional space, wherein in a state that longitudinal directions of the first and second components are matched with each other, one end of the first component is fitted into the closed cross-sectional space from the side where the fourth component is connected to the second component, a part of a first top plate of the first component to a part of a second top plate of the second component are welded to form a welded joint, and a compressive force in a longitudinal direction of the specimen from the other end of the first component.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for testing an automotive structural member having a welded joint, a method for evaluating an automotive structural member having a welded joint, and a test specimen used for testing an automotive structural member having a welded joint. [Background technology]

[0002] In recent years, the automotive industry has seen increasingly strict crash safety standards from the perspective of passenger protection, leading to a strong demand for expanded use of high-strength steel and the development of vehicles with superior crash safety performance. To design vehicle bodies with superior crash safety, each automobile manufacturer conducts crash tests using an entire vehicle. Meanwhile, at the modular component design stage, evaluations are often conducted through crash tests that evaluate components individually in order to reduce costs and delivery times or simplify the evaluation targets. When conducting evaluation tests on a component-by-component basis, it is important that the test method can test the target components under the same restraint conditions, deformation, and fracture modes as in actual automobile crash tests.

[0003] Most welding methods used in automotive parts are spot welding and arc welding. If welds used in the main frame fracture during a collision, it can lead to a reduction in occupant protection. Therefore, when designing parts, it is necessary to understand the strength of each welding method during a collision. Weld fracture modes can be broadly divided into three types: peeling, shearing, and a combination of peeling and shearing. Shearing and a combination of peeling and shearing are the most common fracture modes during a collision. However, peeling is known to reduce weld strength by approximately half compared to shearing, so part design requires ingenuity to prevent peeling during a collision. Weld fracture due to shearing during a collision can occur at the weld joint between the kick reinforcement and the rear end of the front side member during a frontal collision. This area is fractured due to shearing forces exerted by the load input during the collision. If this fracture occurs, the front side member will penetrate the dash panel, resulting in a reduction in occupant protection. Therefore, to prevent this weld fracture, measures such as increasing the number of spot welds or adding arc welds are implemented.

[0004] Methods for evaluating the shear strength of welds have been established, including tensile shear strength (TSS) and cross tensile strength (CTS). These methods involve performing tensile tests on specimens of a predetermined shape after welding until the specimen breaks, making it possible to measure strength under static conditions. However, actual automobile collisions are dynamic phenomena in which steel plates with given component shapes are welded together, and loads and deformations are applied to the welds. Simulating these conditions as closely as possible and evaluating weld strength can lead to component designs that take more realistic automobile collisions into account. Patent Document 1 proposes a method for applying constraint conditions to the main structure of an automobile and applying dynamic inputs to evaluate the structure. Furthermore, Patent Document 2 proposes a structure that improves the accuracy of constraint conditions for the main structure during dynamic testing, simplifies condition setting, and enables the restraint mechanism to operate stably even at speeds of 50 km / h or more. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 4902027 Publication [Patent Document 2] Patent No. 7252524 Summary of the Invention [Problem to be solved by the invention]

[0006] However, Patent Document 1 requires large-scale equipment such as actuators and rotation restraint jigs, resulting in high implementation costs and likely limiting opportunities for testing. Patent Document 1 also fails to describe welding evaluation for parts other than center pillars, making its versatility unclear. Patent Document 2, like Patent Document 1, requires large-scale equipment and fails to describe evaluation of welds. Patent Document 2 also assumes bending deformation, as occurs in center pillars during side collisions, and is unclear as to whether it can reproduce shear forces, such as those observed at the impact points between the rear end of a front side member and a kick reinforcement during a frontal collision. A typical method for evaluating welding performance involves, for example, stacking flat plates, welding their centers together, and applying a tensile load to the end of the test piece opposite the welded joint. While this method is an elemental evaluation, there have been few cases in which the performance of welded joints with given part shapes has been investigated.

[0007] The present invention has been made in consideration of the above-mentioned problems, and its object is to provide a test method for an automotive structural member having a welded joint, a method for evaluating an automotive structural member having a welded joint, and a test specimen to be used for testing an automotive structural member having a welded joint, which allows the automotive structural member to be reproduced using a small-scale test specimen and the strength performance of the welded joint to be evaluated. [Means for solving the problem]

[0008] In order to solve the above problems and achieve the objectives, (1) A method for testing an automotive structural member having a welded joint according to the present invention includes: a first part having a U-shaped cross section, the first part having a first top plate portion and first vertical wall portions connected to both sides of the first top plate portion in the width direction; a second part having a hat-shaped cross section, the second part having a second top plate portion, second vertical wall portions connected to both sides of the second top plate portion in the width direction, and a pair of flange portions connected to the second vertical wall portions; a third part having a flat plate shape, which is joined to the pair of flange portions of the second part and forms a closed cross section space together with the second part; and a third part having a flat plate shape, which is joined to the hat shape of the second part. The test specimen has as its components a fourth part having an opening in an aligned shape into which one longitudinal end of the first part can be fitted, and which is connected to one longitudinal end of the second part without blocking the closed cross-sectional space, and with the longitudinal directions of the first part and the second part aligned, one longitudinal end of the first part is fitted into the closed cross-sectional space from the side of the second part to which the fourth part is connected, a portion of the first top plate portion and a portion of the second top plate portion are welded to form a welded joint, and a compressive force is applied in the longitudinal direction of the test specimen from the other longitudinal end side of the first part.

[0009] (2) The method for testing an automotive structural component having a welded joint according to the present invention is the same as the above (1), in which the second top plate portion of the second component has a slot-shaped hole portion having a pair of straight portions extending in the width direction of the second top plate portion, and the edge of one of the pair of straight portions in the hole portion is arc-welded to the first top plate portion of the first component.

[0010] (3) The method for testing an automotive structural member having a welded joint according to the present invention is the invention (2) above, in which a first test is conducted using the test specimen in which the edge of one of the straight portions of the hole is arc-welded to the first top plate portion, and a second test is conducted using the test specimen in which the edge of the other straight portion of the hole is arc-welded to the first top plate portion, and the results of the first test and the second test are compared.

[0011] (4) The method for testing an automobile structural member having a welded joint according to the present invention is the above-mentioned (1) invention, in which the welded joint is formed by spot welding at one or two or more points.

[0012] (5) The method for testing an automotive structural component having a welded joint according to the present invention is any one of the inventions (1) to (4) above, in which a flat-plate-shaped member is connected to the end face of the first component on the side that does not mate with the second component and / or the end face of the second component on the side that does not mate with the first component, to cover the end face.

[0013] (6) The method for evaluating an automotive structural component having a welded joint according to the present invention involves conducting a test using any one of the above-mentioned inventions (1) to (4) and obtaining any one of the maximum load, energy amount, and stroke amount until the welded joint breaks.

[0014] (7) A test specimen used in testing an automotive structural member having a welded joint according to the present invention comprises a first part having a U-shaped cross section, which has a first top plate portion and first vertical wall portions connected to both sides of the first top plate portion in the width direction; a second part having a hat-shaped cross section, which has a second top plate portion, second vertical wall portions connected to both sides of the second top plate portion in the width direction, and a pair of flange portions connected to the second vertical wall portions; a third part having a flat plate shape, which is joined to the left and right flange portions of the second part and forms a closed cross section space together with the second part; and a third part having a flat plate shape, which is joined to the left and right flange portions of the second part and forms a closed cross section space together with the second part. The device has as its components: a fourth part having an opening shaped to match the hat shape and into which one longitudinal end of the first part can be fitted, and which is connected to one longitudinal end of the second part without blocking the closed cross-sectional space; when the longitudinal directions of the first part and the second part are aligned, one longitudinal end of the first part is fitted into the closed cross-sectional space from the side of the second part to which the fourth part is connected; a welded joint is provided where a portion of the first top plate portion and a portion of the second top plate portion are welded; and a compressive force is applied in the longitudinal direction from the other end of the first part. [Effects of the Invention]

[0015] The test method for automotive structural members having welded joints, the evaluation method for automotive structural members having welded joints, and the test specimen used for testing automotive structural members having welded joints according to the present invention have the effect of reproducing automotive structural members using small-scale test specimens, applying dynamic forces to the welded joints, and making it possible to evaluate the strength performance of the welded joints by reproducing actual collision phenomena. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a top perspective view showing a schematic configuration of a test specimen used in a method for testing and evaluating an automotive structural member having a welded joint according to an embodiment. [Figure 2] FIG. 2 is a bottom perspective view showing a schematic configuration of a test specimen used in the testing method and evaluation method for an automotive structural member having a welded joint according to the embodiment. [Figure 3] Fig. 3(a) is a view of the first component as seen from diagonally above, and Fig. 3(b) is a view of the first component as seen from the longitudinal direction. [Figure 4] Fig. 4(a) is a view of the second component as seen obliquely from above, Fig. 4(b) is a view of the second component as seen from above, and Fig. 4(c) is a view of the second component as seen from the longitudinal direction. [Figure 5] Fig. 5(a) is a view of the fourth part as seen from diagonally above, Fig. 5(b) is a view of the fourth part as seen from one side in the longitudinal direction, and Fig. 5(c) is a view of the fourth part as seen from the other side in the longitudinal direction. [Figure 6] Fig. 6(a) is a view of the sixth component as seen obliquely from above, and Fig. 6(b) is a view of the sixth component as seen from the longitudinal direction. [Figure 7] FIG. 7 is a diagram showing an example of a schematic configuration of a testing machine used in the testing method for an automotive structural member according to the embodiment. [Figure 8] FIG. 8 is a diagram showing arc welding positions in holes in a second top plate portion having a shape suitable for arc welding. [Figure 9] FIG. 9 is a diagram showing the arc length. [Figure 10] Fig. 10(a) is a cross section taken along line AA in Fig. 8, showing the load input when arc welding is performed at the first arc welding position, and Fig. 10(b) is a cross section taken along line AA in Fig. 8, showing the load input when arc welding is performed at the second arc welding position. [Figure 11] Fig. 11(a) is a diagram showing an example of the results of CAE analysis of deformation of a welded joint when a compression test is performed on a test specimen that does not have a fourth component, and Fig. 11(b) is a diagram showing an example of the results of CAE analysis of deformation of a welded joint when a compression test is performed on a test specimen that has a fourth component. [Figure 12] FIG. 12 is a load-stroke graph showing a case where a compression test was conducted on a test specimen that did not have a fourth part as a constituent element, and a case where a compression test was conducted on a test specimen that had a fourth part. [Figure 13] FIG. 13 shows the results of a CAE analysis of the deformation of the welded joint due to differences in material strength. [Figure 14] FIG. 14 is a load-stroke graph of Example No. 1 of the present invention using 980 material, Example No. 2 of the present invention using 1180 material, and Example No. 5 of the present invention using 1470 material. [Figure 15] FIG. 15 shows the results of a CAE analysis of deformation of a welded joint due to differences in arc welding positions. [Figure 16] FIG. 16 is a load-stroke diagram of Example No. 2 of the present invention, which was arc-welded at the first arc-welding position, and Example No. 3 of the present invention, which was arc-welded at the second arc-welding position. [Figure 17] FIG. 17 shows the results of a CAE analysis of the deformation of the welded joint due to differences in arc length. [Figure 18] FIG. 18 is a load-stroke graph of Example No. 2 of the present invention, in which arc welding was performed at the first arc welding position with an arc length of 22 mm, and Example No. 4 of the present invention, in which arc welding was performed at the first arc welding position with an arc length of 10 mm. [Figure 19]FIG. 19 shows the results of a CAE analysis of the deformation of the welded joint with and without the fourth part. [Figure 20] FIG. 20 is a load-stroke graph of Example No. 1, which has a fourth part as a constituent element of the test specimen, and Comparative Example No. 6, which does not have a fourth part as a constituent element of the test specimen. [Figure 21] FIG. 21 shows the results of a CAE analysis of deformation of a welded joint due to differences in spot welding points. [Figure 22] FIG. 22 is a load-stroke graph of invention No. 7 in which the spot welding was performed at one spot welding point and invention example No. 8 in which the spot welding was performed at two spot welding points. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, embodiments of the method for testing an automotive structural member having a welded joint, the method for evaluating an automotive structural member having a welded joint, and a test specimen used for testing an automotive structural member having a welded joint according to the present invention will be described, but the present invention is not limited to these embodiments.

[0018] Fig. 1 is a top perspective view showing the schematic configuration of a test specimen 1 used in the test method and evaluation method for an automotive structural member having a welded joint according to an embodiment. Fig. 2 is a bottom perspective view showing the schematic configuration of a test specimen 1 used in the test method and evaluation method for an automotive structural member having a welded joint according to an embodiment.

[0019] The test specimen 1 according to the embodiment has, as its constituent elements, a first part 11, a second part 12, a third part 13, a fourth part 14, a fifth part 15, and a sixth part 16. Note that it is sufficient for the test specimen 1 to have at least the first part 11, the second part 12, the third part 13, and the fourth part 14 as its constituent elements, and the fifth part 15 and the sixth part 16 are not essential constituent elements.

[0020] Fig. 3(a) is a view of the first component 11 seen from diagonally above. Fig. 3(b) is a view of the first component 11 seen from the longitudinal direction. Fig. 3(b) also shows an example of the dimensions of each part of the first component 11.

[0021] The first component 11 has a first top panel portion 111 and a pair of first vertical wall portions 112 connected to both sides of the first top panel portion 111 in the width direction. The first component 11 has a U-shaped cross section perpendicular to the longitudinal direction formed by the first top panel portion 111 and the pair of first vertical wall portions 112. The first component 11 simulates a U-shaped kick reinforcement used in automobile parts.

[0022] Fig. 4(a) is a view of the second component 12 seen from diagonally above. Fig. 4(b) is a view of the second component 12 seen from above. Fig. 4(c) is a view of the second component 12 seen from the longitudinal direction. Figs. 4(b) and 4(c) also show an example of the dimensions of each part of the second component 12.

[0023] The second component 12 has a second top panel portion 121, a pair of second vertical wall portions 122 connected to both sides of the second top panel portion 121 in the width direction, and a pair of flange portions 123 on the left and right in the width direction connected to each of the pair of second vertical wall portions 122. The second component 12 has a hat-shaped cross section perpendicular to the longitudinal direction due to the second top panel portion 121, the pair of second vertical wall portions 122, and the pair of flange portions 123.

[0024] 2, the third component 13 has a flat plate shape, and is joined to the surface of the pair of flange portions 123 of the second component 12 opposite to the second top plate portion 121 side. The third component 13, together with the second top plate portion 121 and the pair of second vertical wall portions 122, forms a closed cross-sectional space whose cross-sectional shape perpendicular to the longitudinal direction is a square shape.

[0025] The second part 12 and the third part 13 are welded together to form a hat-shaped closed part (parts that form a closed cross-sectional space), simulating a front side member of an automobile part.

[0026] In this way, in the test specimen 1 according to the embodiment, the first component 11, the second component 12, and the third component 13 replicate the front side member and kick reinforcement of an automobile component. Also, in the test specimen 1 according to the embodiment, the first top plate portion 111 of the first component 11 and the second top plate portion 121 of the second component 12 are joined by resistance spot welding or arc welding. In this way, the test specimen 1 according to the embodiment replicates the welded joint between the front side member and kick reinforcement of an automobile component.

[0027] It is desirable that the outer width (outside length in the width direction) of the first top panel portion 111 of the first component 11 is equal to the inner width (inside length in the width direction) of the second top panel portion 121 of the second component 12. However, it is acceptable to have a gap of about the plate thickness of the first component 11 or the second component 12.

[0028] There are no particular restrictions on the height of the first vertical wall portion 112 of the first part 11 (the length in the height direction perpendicular to the longitudinal and width directions), as long as the first part 11 is tall enough to enter the closed cross-sectional space from the longitudinal direction. The height of the first vertical wall portion 112 may be set to match the shape of the automobile part to be evaluated. In addition, the roundness of the ridge line connecting the first top panel portion 111 and the first vertical wall portion 112 of the first part 11 can have a radius of curvature of 2 mm to 8 mm, for example, taking into account the automobile part to be evaluated, and the radius of curvature may be set to match the shape of the automobile part to be evaluated.

[0029] The first component 11, the second component 12, and the third component 13 are made using automotive steel sheets as metal sheets. The tensile strength of the steel sheets is assumed to be, for example, 590 MPa to 1700 MPa, but no particular limitations are imposed. Furthermore, taking into account the automotive components to be evaluated, the thickness of the steel sheets is assumed to be 1.0 mm to 2.0 mm, but no particular limitations are imposed.

[0030] Fig. 5(a) is a view of the fourth component 14 seen from diagonally above. Fig. 5(b) is a view of the fourth component 14 seen from one side in the longitudinal direction. Fig. 5(c) is a view of the fourth component 14 seen from the other side in the longitudinal direction. Figs. 5(b) and 5(c) also show an example of the dimensions of each part of the fourth component 14.

[0031] The fourth component 14 is flat and has an opening 141 shaped to fit the hat-shaped second component 12, allowing one longitudinal end of the first component 11 to fit into it. The fourth component 14 is connected to one longitudinal end of the second component 12 without blocking the closed cross-sectional space. The fourth component 14 is made of a material with high deformation resistance and is welded to the second component 12 and the third component 13 by arc welding or other welding techniques. This is intended to prevent cross-sectional deformation between the second component 12 and the third component 13. If this portion were to deform easily, bending input would be applied to the welded joint rather than shear force, making it difficult to reproduce the desired deformation mode. A hole is drilled in the center of the fourth component 14, allowing the first component 11 to move axially when subjected to the input. This action reproduces shear input at the welded joint.

[0032] As shown in FIG. 1, the fifth component 15 has a flat plate shape and is connected to the end face of the first component 11 on the side that does not mate with the second component 12 so as to close that end face. The fifth component 15 is made of a material with high deformation resistance, and an input is applied from the fifth component 15 by the testing machine 2. The input speed can be either static or dynamic. This makes it possible to cover a wide range of impact speeds.

[0033] Fig. 6(a) is a view of the sixth component 16 seen from diagonally above. Fig. 6(b) is a view of the sixth component 16 seen from the longitudinal direction. Fig. 6(b) also shows an example of the dimensions of each part of the sixth component 16.

[0034] The sixth component 16 has a flat plate shape and is connected to the end face of the second component 12 on the side that does not mate with the first component 11 so as to close that end face. The sixth component 16 is made of a material with high deformation resistance, and is welded to the second component 12 and the third component 13 by arc welding or the like. The sixth component 16 also has bolt holes 161 at its four corners for fastening to the testing machine 2 with bolts.

[0035] Here, an example of the procedure for assembling the test specimen 1 when the components are a first part 11, a second part 12, a third part 13, and a fourth part 14 will be described. First, the pair of flange portions 123 of the second part 12 and the third part 13 are welded and joined to form the closed cross-sectional space. Next, the fourth part 14 is connected to one longitudinal end of the second part 12 without closing the closed cross-sectional space, and the fourth part 14 is welded and joined to the second part 12 and the third part 13. Next, with the longitudinal directions of the first part 11 and the second part 12 aligned, the one longitudinal end of the first part 11 is inserted into the closed cross-sectional space from the side of the second part 12 where the fourth part 14 is connected. Next, a portion of the first top plate portion 111 of the first component 11 and a portion of the second top plate portion 121 of the second component 12 are welded together to form the welded joint 10. Then, in the testing method for an automobile component having a welded joint according to the embodiment, a compression test is carried out on the test piece 1, in which a compressive force is applied in the longitudinal direction of the test piece 1 from the other longitudinal end side of the first component 11 using a testing machine 2 (see FIG. 7 ) described below.

[0036] FIG. 7 is a diagram showing an example of a schematic configuration of a testing machine 2 used in the testing method for automotive structural members according to the embodiment.

[0037] The testing machine 2 includes an upper fixing member 21, a shaft member 22, an upper mold 23, a load cell 24, and a lower mold 25 that also serves as a lower fixing member. When installing the test specimen 1 in the testing machine 2, the sixth part 16 is placed on the load cell 24 and bolted together so that the fifth part 15 is located on the upper mold 23 side and the sixth part 16 is located on the lower mold 25 side. In the testing machine 2, the shaft member 22 extends relative to the upper fixing member 21, causing the upper mold 23 to move downward and press against the fifth part 15 from above, thereby compressing the test specimen 1 in the longitudinal direction. The load cell 24 can measure the load input to the test specimen 1 by the upper mold 23 during testing, and data on the measured load is transmitted to the control device 3. The shaft member 22 can measure the stroke amount when the shaft member 22 extends relative to the upper fixing member 21, and data on the measured stroke amount is transmitted to the control device 3. Examples of methods for measuring the stroke amount include using a cylindric cylinder for the shaft member 22, measuring the distance between the upper fixing member 21 and the upper mold 23 with a displacement meter, or measuring the distance between the upper mold 23 and the lower mold 25 with a distance meter.

[0038] Here, there are two types of configurations of second top plate portion 121 of second component 12: a shape for arc welding as shown in Fig. 4, and a shape for spot welding as shown in Fig. 1. In the shape for arc welding, second top plate portion 121 of second component 12 has elongated hole-shaped hole portion 124 having a pair of linear portions 1241, 1242 extending in the width direction of second top plate portion 121. On the other hand, in the shape for spot welding, second top plate portion 121 of second component 12 has a flat plate shape over the entire surface and does not have hole portion 124.

[0039] Fig. 8 is a diagram showing the arc welding position in the hole 124 in the second top plate portion 121 having a shape suitable for arc welding. Fig. 9 is a diagram showing the arc length.

[0040] 8, in the test specimen 1 according to the embodiment, the position at which the edge of one straight portion 1241 of the hole 124 of the second top plate portion 121 is arc-welded to the first top plate portion 111 of the first component 11 is defined as a first arc welding position Pa1. The one straight portion 1241 of the hole 124 is the straight portion of the pair of straight portions of the hole 124 that is located upstream in the load input direction in the compression test by the testing machine 2.

[0041] 8, in the test piece 1 according to the embodiment, the position at which the edge of the other straight portion 1242 of the hole 124 of the second top plate portion 121 and the first top plate portion 111 of the first component 11 are arc-welded is defined as a second arc welding position Pa2. The other straight portion 1242 of the hole 124 is the straight portion of the pair of straight portions of the hole 124 that is located downstream in the load input direction in the compression test by the testing machine 2.

[0042] In the test specimen 1 according to the embodiment, the second top plate portion 121 of the second component 12 and the first top plate portion 111 of the first component 11 are arc-welded at a first arc welding position Pa1 to form a welded joint 101. Alternatively, in the test specimen 1 according to the embodiment, the second top plate portion 121 of the second component 12 and the first top plate portion 111 of the first component 11 are arc-welded at a second arc welding position Pa2 to form a welded joint 102. Note that in the test specimen 1 according to the embodiment, the widthwise length of the welded joint 101 on the second component 12 and the widthwise length of the welded joint 102 on the second component 12 are defined as the arc length, as shown in FIG. 9 .

[0043] In the test specimen 1 according to the embodiment, the direction of the force applied to the welded joint (welded joints 101, 102) during the compression test can be varied depending on whether welding is performed at the first arc welding position Pa1 or the second arc welding position Pa2.

[0044] Fig. 10(a) is a cross section taken along line AA in Fig. 8, showing the load input when arc welding is performed at the first arc welding position Pa1. Fig. 10(b) is a cross section taken along line AA in Fig. 8, showing the load input when arc welding is performed at the second arc welding position Pa2.

[0045] As shown in FIG. 10(a), when arc welding is performed at the first arc welding position Pa1, the force applied to the welded joint 101 is a shear force. On the other hand, as shown in FIG. 10(b), when arc welding is performed at the second arc welding position Pa2, the force applied to the welded joint 102 is a compressive force. During an actual automobile collision, a compressive force may be applied to the welded joint. Therefore, in this embodiment, the shape of the test specimen 1 is designed to be capable of reproducing both the case where a shear force is applied to the welded joint and the case where a compressive force is applied to the welded joint, and to be capable of evaluating both deformation modes.

[0046] For example, in this embodiment, a first test is performed using a test specimen 1 in which the edge of one straight portion 1241 of the hole 124 in the second top plate portion 121 is arc-welded to the first top plate portion 111, as the first arc-welded position Pa1 of the welded joint 101. Furthermore, in this embodiment, a second test is performed using a test specimen 1 in which the edge of the other straight portion 1242 of the hole 124 in the second top plate portion 121 is arc-welded to the first top plate portion 111, as the second arc-welded position Pa2 of the welded joint 102. Then, by comparing the results of the first test and the second test, it is possible to compare and evaluate the results of both deformation modes, when a shear force is applied to the welded joint 101 and when a compressive force is applied to the welded joint 102.

[0047] As a result of the above, it is possible to simulate the front side member and kick reinforcement of automobile parts when they are joined by various welding processes.

[0048] Here, in the test specimen 1 according to the embodiment, the fourth part 14 is an essential component. The reason for this will be explained using CAE analysis.

[0049] Fig. 11(a) is a diagram showing an example of the results of a CAE analysis of deformation of a welded joint when a compression test is performed on a test specimen 1 that does not include a fourth component 14. Fig. 11(b) is a diagram showing an example of the results of a CAE analysis of deformation of a welded joint when a compression test is performed on a test specimen 1 that includes a fourth component 14. Note that the fourth component 14 is not shown in Fig. 11(b).

[0050] Figures 11(a) and 11(b) show the CAE analysis results of a compression test conducted under the conditions that the load input speed to test specimen 1 was set to 5 km / h and the input of load to test specimen 1 was stopped when the absorbed energy reached approximately 290 J. The color maps in Figures 11(a) and 11(c) show the equivalent plastic strain.

[0051] As shown in Figure 11(a), when a compression test is performed on a test specimen 1 that does not have the fourth part 14 as a constituent element, the deformation is concentrated at the end of the second top plate portion 121, making it impossible to properly evaluate the crashworthiness of the welded joint. On the other hand, as shown in Figure 11(b), when a compression test is performed on a test specimen 1 that has the fourth part 14 as a constituent element, the deformation does not concentrate at the end of the second top plate portion 121, making it possible to properly evaluate the crashworthiness of the welded joint.

[0052] FIG. 12 is a load-stroke diagram showing a case where a compression test was conducted on a test specimen 1 that does not have the fourth part 14 as a constituent element, and a case where a compression test was conducted on a test specimen 1 that has the fourth part 14. The vertical axis of FIG. 12 represents the load applied to the test specimen 1. The horizontal axis of FIG. 12 represents the stroke of the shaft member 22 in the testing machine 2. The arrows in FIG. 12 indicate the direction in which the load and stroke values ​​change. In this compression test, the input of load to the test specimen 1 was completed when the absorbed energy reached approximately 290 [J].

[0053] The load-stroke diagram shown in Figure 12 reveals the maximum load, absorbed energy (load integrated over stroke), and maximum stroke (stroke just before the load suddenly decreases). It can also be assumed that the greater the load increase with a smaller stroke, the greater the shear force applied to the welded joint. Conversely, if the load increase is small with a large stroke, bending deformation is likely to occur at the welded joint, and the shear force applied to the welded joint will decrease accordingly.

[0054] Therefore, from the load-stroke diagram shown in Figure 12, when a compression test is performed on specimen 1 that includes fourth part 14 as a constituent element, it can be evaluated that the load increase is large with a small stroke, and shear force is applied to the welded joint. Also, from the load-stroke diagram shown in Figure 12, when a compression test is performed on specimen 1 that does not include fourth part 14 as a constituent element, it can be considered that the load increase is small with a large stroke, and bending deformation is applied to the welded joint. It can be evaluated that the shear force applied to the welded joint is reduced accordingly. [Example]

[0055] In this example, specimens 1 shown as Nos. 1 to 8 in Table 1 were fabricated, and compression tests were performed using a testing machine 2. The dimensions of the first part 11, the second part 12, the fourth part 14, and the sixth part 16 used as components of specimen 1 in this example are as shown in FIGS. 3 to 6. The length of the first part 11 in the longitudinal direction is 60 mm, and the length of the second part 12 in the longitudinal direction is 75 mm. In specimen 1, the length of the overlapping portion between the first part 11 (first top plate portion 111) and the second part 12 (second top plate portion 121) in the longitudinal direction is 20 mm. The thickness of the first part 11, the second part 12 and the third part 13 is 1.4 mm, the thickness of the fourth part 14 is 3.0 mm, and the thickness of the fifth part 15 and the sixth part 16 is 6.0 mm.

[0056] The compression test conditions using the testing machine 2 were that the load input speed (stroke speed) to the test piece 1 was 5.2 km / h (1.44 m / sec). The compression test was conducted while the load and stroke amount output from the testing machine 2 were collected by the control device 3, and was terminated when the absorbed energy reached 280 J or more.

[0057] Table 1 shows the test conditions, including the welding conditions for the first component 11 and the second component 12, and the test results for the test specimens 1 No. 1 to No. 8.

[0058] [Table 1]

[0059] In Example No. 1, a test specimen 1 was fabricated using a first component 11, a second component 12, a third component 13, a fourth component 14, a fifth component 15, and a sixth component 16 as constituent elements. The first component 11 to the sixth component 16 were fabricated using automotive steel sheet (980 material) with a tensile strength of 980 MPa as the metal plate. A hole 124 for arc welding was formed in the second top plate portion 121 of the second component 12, and the first component 11 and the second component 12 were joined by arc welding at a first arc welding position Pa1. The arc welding length was 22 mm.

[0060] In Example No. 2, a test specimen 1 was fabricated using a first component 11, a second component 12, a third component 13, a fourth component 14, a fifth component 15, and a sixth component 16 as constituent elements. The first component 11 to the sixth component 16 were fabricated using automotive steel sheet (1180 material) with a tensile strength of 1180 MPa as the metal plate. A hole 124 for arc welding was formed in the second top plate portion 121 of the second component 12, and the first component 11 and the second component 12 were joined by arc welding at a first arc welding position Pa1. The arc welding length was 22 mm.

[0061] In Example No. 3, a test specimen 1 was fabricated using a first component 11, a second component 12, a third component 13, a fourth component 14, a fifth component 15, and a sixth component 16 as constituent elements. The first component 11 to the sixth component 16 were fabricated using an automotive steel sheet (1180 material) with a tensile strength of 1180 MPa as the metal plate. A hole 124 for arc welding was formed in the second top plate portion 121 of the second component 12, and the first component 11 and the second component 12 were joined by arc welding at a second arc welding position Pa2. The arc welding length was 22 mm.

[0062] In Example No. 4, a test specimen 1 was fabricated using a first component 11, a second component 12, a third component 13, a fourth component 14, a fifth component 15, and a sixth component 16 as constituent elements. The first component 11 to the sixth component 16 were fabricated using automotive steel sheet (1180 material) with a tensile strength of 1180 MPa as the metal plate. A hole 124 for arc welding was formed in the second top plate portion 121 of the second component 12, and the first component 11 and the second component 12 were joined by arc welding at a first arc welding position Pa1. The arc welding length was 10 mm.

[0063] In Example No. 5, a test specimen 1 was fabricated using a first component 11, a second component 12, a third component 13, a fourth component 14, a fifth component 15, and a sixth component 16 as constituent elements. The first component 11 to the sixth component 16 were fabricated using automotive steel sheet (1470 material) with a tensile strength of 1470 MPa as the metal plate. A hole 124 for arc welding was formed in the second top plate portion 121 of the second component 12, and the first component 11 and the second component 12 were joined by arc welding at a first arc welding position Pa1. The arc welding length was 22 mm.

[0064] In Comparative Example No. 6, specimen 1 was fabricated using first component 11, second component 12, third component 13, fifth component 15, and sixth component 16 as constituent elements, without fourth component 14. First component 11 to sixth component 16 were fabricated using automotive steel sheet (980 material) with a tensile strength of 980 MPa as the metal plate. A hole 124 for arc welding was formed in second top plate portion 121 of second component 12, and first component 11 and second component 12 were joined by arc welding at first arc welding position Pa1. The arc welding length was 22 mm.

[0065] In Example No. 7, a test specimen 1 was fabricated using a first component 11, a second component 12, a third component 13, a fourth component 14, a fifth component 15, and a sixth component 16 as constituent elements. The first component 11 to the sixth component 16 were fabricated using automotive steel sheet (980 material) with a tensile strength of 980 MPa as the metal plate. The second top plate portion 121 of the second component 12 was not provided with a hole 124 for arc welding, and the first component 11 and the second component 12 were joined by spot welding using one spot welding point (one welding point). The nugget diameter of the spot welding was 5.92 mm.

[0066] In Example No. 8, a test specimen 1 was fabricated using a first component 11, a second component 12, a third component 13, a fourth component 14, a fifth component 15, and a sixth component 16 as constituent elements. The first component 11 to the sixth component 16 were fabricated using automotive steel sheet (980 material) with a tensile strength of 980 MPa as the metal plate. The second top plate portion 121 of the second component 12 was not provided with holes 124 for arc welding, and the first component 11 and the second component 12 were joined by spot welding using two spot welding points (two welding points). The nugget diameter of the spot welding was 5.92 mm.

[0067] Figure 13 shows the results of a CAE analysis of deformation of welded joints due to differences in material strength. Specifically, Figure 13(a) shows the results of the CAE analysis of Example No. 1, which uses 980 steel. Figure 13(b) shows the results of the CAE analysis of Example No. 2, which uses 1180 steel. Figure 13(c) shows the results of the CAE analysis of Example No. 5, which uses 1470 steel. Figure 14 shows load-stroke diagrams for Example No. 1, which uses 980 steel, Example No. 2, which uses 1180 steel, and Example No. 5, which uses 1470 steel.

[0068] The test conditions for Example No. 1, Example No. 2, and Example No. 5 were the same except for the strength level (material strength) of the metal plates. Example No. 1, which used 980 steel, had a maximum load of 28 kN and a maximum stroke of 11.5 mm at which the absorbed energy reached 285 J. Example No. 2, which used 1180 steel, had a maximum load of 35 kN and a maximum stroke of 9.1 mm at which the absorbed energy reached 280 J. Example No. 5, which used 1470 steel, had a maximum load of 40 kN and a maximum stroke of 8.0 mm at which the absorbed energy reached 283 J. These results demonstrate that the test and evaluation methods for automotive structural members having welded joints according to the present embodiment can evaluate the effect of material strength on the required stroke length for a given energy absorption.

[0069] In this way, the test method and evaluation method for an automotive structural member having a welded joint according to the embodiment can evaluate the strength performance of the welded joint depending on the difference in material strength.

[0070] Fig. 15 shows the results of a CAE analysis of deformation of a welded joint due to differences in arc welding positions. Specifically, Fig. 15(a) shows the results of the CAE analysis of Example No. 2, which was arc-welded at the first arc-welding position Pa1. Fig. 15(b) shows the results of the CAE analysis of Example No. 3, which was arc-welded at the second arc-welding position Pa2. Fig. 16 is a load-stroke diagram of Example No. 2, which was arc-welded at the first arc-welding position Pa1, and Example No. 3, which was arc-welded at the second arc-welding position Pa2.

[0071] The conditions for Example No. 2 and Example No. 3 were the same except for the arc welding position. Example No. 2, which was arc-welded at the first arc welding position Pa1, had a shear force applied to the welded joint, a maximum load of 35 kN, and a maximum stroke of 9.1 mm at which the absorbed energy reached 280 J. Example No. 3, which was arc-welded at the second arc welding position Pa2, had a compressive force applied to the welded joint, a maximum load of 35 kN, and a maximum stroke of 14.7 mm at which the absorbed energy reached 282 J. Example No. 3 exhibited a decrease in load when the stroke was between 5 mm and 11 mm. Example No. 3 was evaluated when a bending-based input was applied to the arc weld, while Example No. 2 was evaluated when a shear-based input was applied. In this way, in the test method and evaluation method for an automotive structural member having a welded joint according to the embodiment, it is possible to perform evaluation by changing the input conditions in arc welding.

[0072] In this way, the testing and evaluation methods for automotive structural components having welded joints according to the embodiment allow the strength performance of the welded joint to be evaluated under both conditions in which a shear force is applied to the welded joint and conditions in which a compressive force is applied to the welded joint.

[0073] Fig. 17 shows the results of a CAE analysis of deformation of a welded joint due to differences in arc length. Specifically, Fig. 17(a) shows the results of the CAE analysis of Example No. 2, in which arc welding was performed at the first arc welding position Pa1 with an arc length of 22 mm. Fig. 17(b) shows the results of the CAE analysis of Example No. 4, in which arc welding was performed at the first arc welding position Pa1 with an arc length of 10 mm. Fig. 18 shows a load-stroke diagram of Example No. 2, in which arc welding was performed at the first arc welding position Pa1 with an arc length of 22 mm, and Example No. 4, in which arc welding was performed at the first arc welding position Pa1 with an arc length of 10 mm.

[0074] The conditions for Example No. 2 and Example No. 4 were the same except for the arc length. Example No. 2, in which arc welding was performed at first arc welding position Pa1 with an arc length of 22 mm, had a maximum load of 35 kN and a maximum stroke of 9.1 mm at which the absorbed energy was 280 J. Example No. 4, in which arc welding was performed at first arc welding position Pa1 with an arc length of 10 mm, had a maximum load of 28 kN and a maximum stroke of 11.5 mm at which the absorbed energy was 284 J.

[0075] In this way, in the test method and evaluation method for an automotive structural member having a welded joint according to the embodiment, the arc length can be changed to evaluate the strength performance of the welded joint relative to the arc length.

[0076] FIG. 19 shows the results of a CAE analysis of the deformation of a welded joint with and without the fourth component 14. Specifically, FIG. 19(a) shows the results of the CAE analysis of Example No. 1, which has the fourth component 14 as a constituent element of the test specimen 1. Note that the fourth component 14 is not shown in FIG. 19(a). FIG. 19(b) shows the results of the CAE analysis of Comparative Example No. 6, which does not have the fourth component 14 as a constituent element of the test specimen 1. FIG. 20 is a load-stroke diagram of Example No. 1, which has the fourth component 14 as a constituent element of the test specimen 1, and Comparative Example No. 6, which does not have the fourth component 14 as a constituent element of the test specimen 1.

[0077] The No. 1 example and the No. 6 comparative example were identical in all conditions except for the presence or absence of a fourth component 14 as a component of the test specimen 1. In the No. 1 example, which had the fourth component 14 as a component of the test specimen 1, the maximum load was 28 kN, and the maximum stroke at which the absorbed energy was 285 J was 11.5 mm. In the No. 6 comparative example, which did not have the fourth component 14 as a component of the test specimen 1, the maximum load was 27 kN, and the maximum stroke at which the absorbed energy was 285 J was 19.3 mm. In the No. 6 comparative example, which did not have the fourth component 14 as a component of the test specimen 1, the second component 12 buckled early, making it impossible to increase the load with a small stroke.

[0078] Thus, in the testing and evaluation method for automotive structural components having welded joints according to the embodiment, if the fourth part 14 is not included as a constituent element of the test specimen 1, the strength performance of the welded joint cannot be accurately evaluated.

[0079] Fig. 21 shows the results of CAE analysis of deformation of welded joints due to differences in spot welding locations. Specifically, Fig. 21(a) shows the results of CAE analysis of Example No. 7, in which one spot welding location (one spot) was performed at a first spot welding location Ps1 in the center of the second top plate portion 121 in the width direction. Fig. 21(b) shows the results of CAE analysis of Example No. 8, in which two spot welding locations (two spots) were performed at a second spot welding location Ps2 and a third spot welding location Ps3 at both ends of the second top plate portion 121 in the width direction. Fig. 22 shows a load-stroke graph of Example No. 7, in which one spot welding location was used, and Example No. 8, in which two spot welding locations were used.

[0080] The conditions for Example No. 7 and Example No. 8 were the same except for the spot welding position and the number of spot welding points. Example No. 7, which was spot welded with one spot welding point, had a maximum load of 25 kN and a maximum stroke of 13.9 mm at which the absorbed energy was 286 J. Example No. 8, which was spot welded with two spot welding points, had a maximum load of 64 kN and a maximum stroke of 5.7 mm at which the absorbed energy was 282 J.

[0081] Furthermore, by comparing Example No. 7 of the invention, which has one spot impact point, with Example No. 8 of the invention, which has two spot impact points, from Figure 22, it can be seen that by increasing the number of spot impact points, it is possible to increase the amount of load increase with a small stroke amount.

[0082] In this way, the test method and evaluation method for an automotive structural member having a welded joint according to the embodiment can evaluate the strength performance of the welded joint relative to the number of spot welding points. [Explanation of symbols]

[0083] 1 Test specimen 2 Testing Machine 3. Control device 10 Welded joints 11 First Part 12 Second part 13 Third Part 14 Fourth Part 15 The Fifth Part 16 Sixth Part 21 Upper fixing member 22 Shaft member 23 Upper mold 24 load cells 25 Lower mold 101 Welded joints 102 Welded joints 111 First top plate 112 First vertical wall 121 Second top plate 122 Second vertical wall 123 Flange 124 Hole 141 Opening 161 Bolt holes 1241 Straight section 1242 Straight section Pa1 First arc welding position Pa2 Second arc welding position Ps1 First spot welding position Ps2 Second spot welding position Ps3 Third spot welding position

Claims

1. a first component having a U-shaped cross section including a first top panel portion and first vertical wall portions connected to both sides of the first top panel portion in a width direction; a second component having a hat-shaped cross section, the second component including a second top panel portion, second vertical wall portions connected to both sides of the second top panel portion in the width direction, and a pair of flange portions connected to the second vertical wall portions; a third part having a flat plate shape, joined to the pair of flange portions of the second part, and forming a closed cross-sectional space together with the second part; a fourth part having a flat plate shape, the fourth part having an opening shaped to match the hat shape of the second part and into which one end of the first part in the longitudinal direction can be fitted, the fourth part being connected to the one end of the second part in the longitudinal direction without closing the closed cross-sectional space; as a component of the test specimen, With the longitudinal directions of the first part and the second part aligned, one end side of the first part in the longitudinal direction is fitted into the closed cross-sectional space from the side of the second part to which the fourth part is connected, a portion of the first top plate portion and a portion of the second top plate portion are welded together to form a welded joint; applying a compressive force in the longitudinal direction of the test specimen from the other end side of the longitudinal direction of the first component; Test methods for automotive structural components with welded joints.

2. The second top plate portion of the second component has a slot-shaped hole portion having a pair of straight line portions extending in a width direction of the second top plate portion, and an edge of one of the pair of straight line portions in the hole portion is arc-welded to the first top plate portion of the first component. A method for testing an automotive structural member having the welded joint according to claim 1.

3. a first test is performed using the test specimen in which an edge of one of the linear portions of the hole and the first top plate portion are arc-welded; moreover, a second test is performed using the test specimen in which the edge of the other linear portion of the hole and the first top plate portion are arc-welded; comparing the results of the first test and the second test; A method for testing an automotive structural member having the welded joint according to claim 2.

4. The welded joint is formed by one or more spot welding points. A method for testing an automotive structural member having the welded joint according to claim 1.

5. a flat-plate-shaped member is connected to an end face of the first component on a side that does not mate with the second component and / or an end face of the second component on a side that does not mate with the first component, the flat-plate-shaped member closing the end face; A method for testing an automotive structural member having the welded joint according to any one of claims 1 to 4.

6. A test is performed using the test method for an automotive structural member having a welded joint according to any one of claims 1 to 4, and any one of the maximum load, the amount of energy, and the amount of stroke until the welded joint fractures is obtained. A method for evaluating automotive structural members having welded joints.

7. a first component having a U-shaped cross section including a first top panel portion and first vertical wall portions connected to both sides of the first top panel portion in a width direction; a second component having a hat-shaped cross section, the second component including a second top panel portion, second vertical wall portions connected to both sides of the second top panel portion in the width direction, and a pair of flange portions connected to the second vertical wall portions; a third component having a flat plate shape, joined to the left and right flange portions of the second component, and forming a closed cross-sectional space together with the second component; a fourth part having a flat plate shape, the fourth part having an opening shaped to match the hat shape of the second part and into which one end of the first part in the longitudinal direction can be fitted, the fourth part being connected to the one end of the second part in the longitudinal direction without closing the closed cross-sectional space; as components, With the first component and the second component aligned in their longitudinal directions, one end of the first component in the longitudinal direction is fitted into the closed cross-sectional space from a side of the second component to which the fourth component is connected, a welded joint formed by welding a portion of the first top plate portion and a portion of the second top plate portion; A compressive force is applied in the longitudinal direction from the other end of the first component. A specimen used to test automotive structural components with welded joints.

Images