JP2021179410A - Method for evaluating crack resistance property of plate material - Google Patents

Abstract

To provide a method for evaluating the crack resistance property of a plate material for easily evaluating the crushing property of an impact absorption member on which shape processing is performed.SOLUTION: A method for evaluating the crack resistance property of a plate material 2 includes: preparing the plate material 2; performing preprocessing on the plate material 2; and executing a bending test for a portion of the plate material 2 on which the preprocessing is performed.SELECTED DRAWING: Figure 9

Description

The present invention relates to a method for evaluating crack resistance of a plate material.

High collision safety performance is required for impact absorbing members such as front side members or rear side members of vehicle skeleton members. In order to exhibit high collision safety performance, it is preferable that the shock absorbing member crushes in a bellows shape in the axial direction at the time of a collision and absorbs a large amount of collision energy.

However, in order to improve the fuel efficiency and safety of automobiles, high-strength steel plates called high-tensile steel are often used as the material of the shock absorbing member. Therefore, the ductility of the shock absorbing member is lowered, and the possibility of cracking at the time of collision is high. If the shock absorbing member is cracked, the bellows-shaped crushing may be hindered and the intended shock energy absorbing performance may not be exhibited. Therefore, there is a demand for a method for evaluating crushing characteristics including cracking of a shock absorbing member. It is preferable to perform a collision experiment simulating an actual collision with a complete vehicle skeleton, but there is a concern that it will be large-scale and costly. Therefore, at the development stage, a method for simply evaluating the crushing characteristics of the impact absorbing member is required.

For example, Non-Patent Document 1 discloses a method for simply evaluating the crushing property of a shock absorbing member from the crack resistance property of a plate material constituting the shock absorbing member. This method is called the VDA bending test and is standardized as VDA238-100 by the German Association of the Automotive Industry (VDA: Verband der Automobilindustrie). The VDA bending test is a bending test of a plate material for the purpose of evaluating the cracking behavior when a member is crushed. There is a correlation between the bending angle at the maximum load until cracking occurs in the VDA bending test (hereinafter, also referred to as VDA bending angle) and the crushing characteristics in the axial direction of the impact absorbing member. That is, the VDA bending angle is an index that can quantitatively evaluate the crushing characteristics of the shock absorbing member in the axial direction.

P. Larour, H. Pauli, T. Kurz, T. Hebesberger., "Influence of post uniform strength and bending properties on the crash behavior of AHSS and press-hardening", IDDRG 2010 conference, 31.05-02-06, Graz , Austria 2010

In the evaluation method of Non-Patent Document 1, the VDA bending test, which is a bending test for a simple flat plate, is adopted. Therefore, if the impact absorbing member to be crushed is molded, it may not be evaluated accurately. Specifically, when the shock absorbing member is subjected to a molding process such as bending process, a ridge line portion is generated in the shock absorbing member by the bending process. Since strain is accumulated in the ridgeline portion due to the molding process, cracks are likely to occur. Since a large load is applied to the ridgeline portion at the time of collision, if the ridgeline portion is cracked, the impact energy absorption performance of the impact absorbing member is greatly deteriorated. Such a decrease in the impact energy absorption performance of the impact absorbing member may not be quantitatively evaluated by the VDA bending test. Therefore, in order to easily and quantitatively evaluate the crushing characteristics of the shock absorbing member, it is necessary to evaluate the crack resistance characteristics of the plate material in consideration of the molding process.

It is an object of the present invention to provide a method for evaluating the crack resistance property of a plate material for simply and quantitatively evaluating the crushing property of a shock absorbing member that has been molded.

The present invention provides a method for evaluating crack resistance of a plate material, which comprises preparing a plate material, preprocessing the plate material, and performing a bending test on the preprocessed portion of the plate material. ..

According to this method, when the plate material constituting the shock absorbing member is molded, the molding process can be simulated by preprocessing. Therefore, the crushing characteristics of the impact absorbing member can be evaluated with high accuracy through the evaluation of the crack resistance characteristics of the plate material. The pre-processing here preferably reproduces the deformed state at the time of molding and crushing of the shock absorbing member. For example, preprocessing may include processing such as bending, tensioning, compression, forging, or shearing. Further, the pre-processing may be a combination of these processes.

The pre-processing may include bending processing.

According to this method, when the shock absorbing member made of a plate material is bent, the bending process can be simulated by preprocessing. Therefore, the crushing characteristics of the impact absorbing member can be evaluated with high accuracy through the evaluation of the crack resistance characteristics of the plate material.

The pre-processing may include a bending-back processing that returns the bending process to the original state.

According to this method, the shape of the plate material can be restored to a flat plate shape by the pre-processing bending back processing, and the strain accumulated during crushing can be simulated. Since the plate material has a flat plate shape, the bending test following the preprocessing can be easily performed. Further, at the stage of the bending test, since the strain is accumulated in the plate material, the bending test of the plate material in consideration of the molding process of the shock absorbing member can be executed as compared with a simple flat plate which has not been preprocessed.

In the bending process of the preprocessing, the bending strain of the surface layer of the plate material may be 0.032 or more.

According to this method, since the bending strain received by the impact absorbing member of a general vehicle skeleton member due to the molding process is about 0.032 or more, the bending strain can be numerically simulated. Therefore, by the above-mentioned method for evaluating the crack resistance of the plate material, the crushing property of the shock absorbing member of a general vehicle skeleton member can be evaluated with high accuracy. It should be noted that the strain here is a nominal strain, and the strain whose numerical value is specified in the following description of the strain is assumed to be a nominal strain.

The bending direction of the preprocessing and the bending direction of the bending test may be parallel or orthogonal to each other.

According to this method, the reproducibility of the bending test can be improved and a stable bending test can be realized.

The plate material may be a high-strength steel plate for vehicles.

According to this method, by matching the material of the plate material with the actual vehicle, the crushing characteristics of the impact absorbing member of the vehicle skeleton member can be evaluated with high accuracy. Here, the high-strength steel plate means a steel material having a strength equal to or higher than that of a steel material called high-tensile steel.

The bending test may be a VDA bending test.

According to this method, the improvement of the above correlation can be confirmed accurately and easily.

As a method for evaluating the crack resistance of the plate material, a shock absorbing member having a central axis manufactured from the plate material is prepared, a crush test of the shock absorbing member in the central axis direction is performed, and the result of the crush test and the above are described. It may further include confirming the correlation with the result of the bending test.

According to this method, it is possible to confirm how accurately the crushing property of the shock absorbing member can be evaluated by the method for evaluating the crack resistance property of the plate material.

The shock absorbing member may be a front side member or a rear side member of a vehicle skeleton member.

According to this method, it is possible to confirm how accurately the crushing characteristics of the front side member or the rear side member can be evaluated by the crack resistance evaluation method of the plate material.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a method for evaluating the crack resistance property of a plate material for easily evaluating the crushing property of a shock absorbing member that has been molded by performing preprocessing.

Perspective view of the shock absorbing member. Top view of the hat member. The front view which shows the example of the cracking score 1. The front view which shows the example of the cracking score of 2. The front view which shows the example of the cracking score of 3. The front view which shows the example of the cracking score of 4. The front view which shows the example of the cracking score of 5. A perspective view of a plate material to which a method for evaluating crack resistance characteristics of a plate material according to an embodiment is applied. The perspective view which shows the plate material which pre-processed the V-bending. The perspective view which shows the plate material which preprocessed the bending back. The perspective view which shows the plate material which performed the VDA bending test. The first graph showing the relationship between the VDA bending angle BA and the crack score. The second graph showing the relationship between the VDA bending angle BA and the crack score. The perspective view which shows the plate material which performed the VDA bending test different from FIG. A third graph showing the relationship between the VDA bending angle BA and the crack score. The perspective view which shows the plate material which performed the VDA bending test different from FIGS. 11 and 14. A fourth graph showing the relationship between the VDA bending angle BA and the crack score.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

In this embodiment, a method for evaluating the crack resistance of the plate material will be described. It is known that the crack resistance property of a plate material correlates with the crushing characteristic of a shock absorbing member formed by using the plate material. Therefore, the crushing property of the shock absorbing member can be evaluated by using the method for evaluating the crack resistance property of the plate material of the present embodiment.

In the present embodiment, in the method for evaluating the crack resistance of the plate material, the above correlation is improved by preprocessing the plate material. In order to confirm the improvement of this correlation, the results of the crushing test of the impact absorbing member and the bending test of the plate material are shown below in order.

First, with reference to FIG. 1, a crush test of the shock absorbing member 1 was performed.

The shock absorbing member 1 has a central axis L and has a closed cross-sectional shape in a cross section perpendicular to the central axis L. The shock absorbing member 1 includes a hat member 10 and a closing plate 20.

With reference to FIG. 2, the hat member 10 is formed by bending a flat plate, and the cross-sectional shape perpendicular to the central axis L is a hat shape. Specifically, the hat member 10 has a convex portion 11 having a substantially inverted U shape, and flange portions 12 and 13 extending horizontally from both ends of the convex portion 11 to the outside.

Specifically, the convex portion 11 includes side walls 11a and 11b and a top wall 11c connecting the side walls 11a and 11b. The side walls 11a and 11b are arranged so as to be inclined by 5 degrees from the vertical direction (θ = 5 °). The top wall 11c of the convex portion 11 extends 45.0 mm in the horizontal direction (d1 = 45 mm). The bending radius of the connecting portions 11d and 11e between the top wall 11c and the side walls 11a and 11b is 5.2 mm (R1 = 5.2 mm). The flange portions 12 and 13 extend 30.0 mm in the horizontal direction (d2 = 30.0 mm). The flange portions 12 and 13 are separated by 55.5 mm (d3 = 55.5 mm). The bending radius of the connecting portions 14 and 15 between the flange portions 12 and 13 and the side walls 11a and 11b is 5.0 mm (R2 = 5.0 mm). The height of the hat member 10 is 61.2 mm (d4 = 61.2 mm). The length of the hat member 10 (in the L direction of the central axis) is 200 mm.

As shown in Table 1 below, hat members 10 having a total of 18 types of material properties, abbreviations C1 to C10 and G1 to G8, were prepared. The materials of the abbreviations C1 to C10 are cold-rolled steel sheets (CR), and the thickness is 1.4 mm. The materials of the abbreviations G1 to G8 are alloyed hot-dip galvanized steel sheets (GA), and the thickness is 1.6 mm. In these abbreviations C1 to C10 and G1 to G8, the strength class (MPa), the yield stress YS (MPa), the tensile strength TS (MPa), and the VDA bending angle BA (degrees) are variously set as shown in the table. ing.

With reference to FIG. 1 again, the closing plate 20 has a flat plate shape. The closing plate 20 is arranged in parallel with the flange portions 12 and 13 of the hat member 10, and is spot welded to the flange portions 12 and 13. Spot welding is performed at a plurality of points at intervals of 25 mm (not shown). In this way, the closing plate 20 is arranged so as to close the convex portion 11 of the hat member 10. The closed plate 20 is a cold-rolled steel sheet (CR) having a thickness of 1.4 mm and a strength class of 590 MPa class or an alloyed hot-dip galvanized steel sheet (GA) having a thickness of 1.6 mm and a strength class of 590 MPa class. The former closing plate 20 was used for the hat members 10 of the above-mentioned abbreviations C1 to C10, and the latter closing plate 20 was used for the hat members 10 of the abbreviations G1 to G8.

In the crushing test, the impact absorbing member 1 was sandwiched between the flat floor surface 5 and the top surface 6 and fixed, and the impact load W was applied to the impact absorbing member 1 via the top surface 6 in the direction of the central axis L. The impact load W corresponds to the load when a weight weighing 188 kg is dropped from a height of 12.0 m at a speed of about 50.0 km / h. The crushing characteristics of the shock absorbing member 1 at this time were evaluated on a scale of 5 from cracking scores 1 to 5 according to the crushing state. As for the crack score, 5 is the best, and 4, 3, 2, 1 and so on, which are worse in order. The crack score was visually determined based on the following criteria based on the results of the crushing test.

FIG. 3 shows an example of a state in which the crack score is 1. The hat member 10 is cracked to form a large opening. The large opening means that the length of the crack is, for example, 80 mm or more. Further, the case where the hat member 10 is not only cracked but also completely divided is evaluated as a crack score 1.

FIG. 4 shows an example of a state in which the crack score is 2. The hat member 10 is cracked to form a medium opening. A medium opening is one in which the length of the crack is, for example, 40 mm or more and less than 80 mm.

FIG. 5 shows an example of a state in which the crack score is 3. The hat member 10 is cracked to form a small opening. The small opening means that the length of the crack is less than 40 mm, for example.

FIG. 6 shows an example of a state in which the crack score is 4. The hat member 10 has no opening but has minute cracks. It is crushed unevenly due to minute cracks, and is not evenly crushed in a bellows shape.

FIG. 7 shows an example of a state in which the crack score is 5. The hat member 10 is not cracked. Further, the hat member 10 is crushed substantially evenly in a bellows shape.

Next, the crack resistance property of the plate material was evaluated in order to correlate with the crushing property (cracking score) of the shock absorbing member 1 obtained as described above. In addition, regarding this correlation, we confirmed the difference in the evaluation method of the crack resistance of the plate material depending on the presence or absence of preprocessing.

A method for evaluating the crack resistance of the plate material 2 of the present embodiment will be described with reference to FIGS. 8 to 11.

First, as shown in FIG. 8, a rectangular flat plate-shaped plate 2 having the same material characteristics as the hat member 10 is prepared. That is, 18 types of plate materials 2 having the abbreviations C1 to C10 and G1 to G8 shown in Table 1 above are prepared. The plate material 2 having such material characteristics is often used as a high-strength steel plate for vehicles, and is preferable when evaluating the crushing characteristics of the impact absorbing member 1 of the vehicle skeleton member.

Next, as shown in FIG. 9, bending processing is performed as preprocessing. The bending process is performed using a V-bending die having a bending angle of 90 degrees and a bending radius of 5.0 mm. By this V-bending, a ridge line portion 2a is formed on the plate material 2.

The bending conditions are not limited to those of the present embodiment. For example, in order to evaluate the correlation with the crushing characteristics of the impact absorbing member 1 (see FIG. 1) of the vehicle skeleton member, the bending strain of the surface layer of the plate material 2 is 0.032 or more regardless of the bending angle and bending radius. Is preferable. As a result, since the bending strain received by the shock absorbing member used for the general vehicle skeleton member due to the molding process is about 0.032 or more, the bending strain can be numerically simulated. Therefore, the crushing characteristics of the impact absorbing member 1 of a general vehicle skeleton member can be evaluated with high accuracy.

Next, as shown in FIG. 10, bending back processing is performed as preprocessing. The bending back processing is a processing for restoring the V bending shown in FIG. 9 above. As a result, the plate material 2 is returned to a flat state. A broken line is attached to the portion shown as the ridge line portion 2a in FIG. After the bending back processing, the shape of the plate material 2 is substantially the same when the plate material 2 is flat and not preprocessed, but is different from the case where the plate material 2 is not preprocessed in that strain is accumulated inside. The bending back processing here may be to return the plate material 2 to a completely flat state in consideration of the bending habit of V bending remaining due to the springback after the bending back processing, or it may be slightly bent. It may be returned to the state.

Next, as shown in FIG. 10, a VDA bending test is carried out under the conditions compliant with VDA238-100 of the German Association of the Automotive Industry. In the VDA bending test, bending is performed in the direction parallel to the ridgeline of the V-bending in FIG. 9 (specifically, the bending ridges match) and in the direction opposite to the direction of the V-bending, and the limit bending angle (VDA bending angle) until cracking occurs. BA) was acquired. When acquiring the test results, data processing was performed to eliminate the influence of the bending habit of the V-bending remaining due to the springback after the bending back processing.

In this way, the VDA bending angle BA is acquired as the crack resistance characteristic of the plate material 2 when the preprocessing is performed, and the VDA bending angle BA when the preprocessing is not performed (in the rightmost column of Table 1 above). Shown).

FIG. 12 shows the relationship between the VDA bending angle BA and the crack score. The horizontal axis of the graph shows the VDA bending angle BA (degrees), and the vertical axis shows the crack score. FIG. 12 shows the results of the abbreviations C1 to C10. Black circles in the graph indicate the case of preprocessing, and white circles indicate the case of no preprocessing. The curve shown by the solid line in the graph shows the result of regression analysis of the preprocessed data (indicated by black circles) using a logistic function. The coefficient of determination ^{R 2} of the regression analysis was 0.83. The curve shown by the broken line in the graph shows the result of regression analysis of the data (indicated by white circles) without preprocessing using a logistic function. The coefficient of determination ^{R 2} of the regression analysis was 0.73. Therefore, regarding the results of the abbreviations C1 to C10, the correlation between the crushing characteristics (cracking score) of the impact absorbing member 1 and the cracking resistance characteristics (VDA bending angle BA) of the plate material was improved by performing the preprocessing. I was able to confirm.

FIG. 13 shows the relationship between the VDA bending angle BA and the crack score. The horizontal axis and the vertical axis of the graph are the same as those in FIG. FIG. 13 shows the results of the abbreviations G1 to G8. The black triangles in the graph indicate the case of preprocessing, and the white triangles indicate the case of no preprocessing. The curve shown by the solid line in the graph shows the result of regression analysis of the preprocessed data (indicated by the black triangle) using a logistic function. The coefficient of determination ^{R 2} of the regression analysis was 0.91. The curve shown by the broken line in the graph shows the result of regression analysis using the logistic function of the data (indicated by the white triangle) without preprocessing. The coefficient of determination ^{R 2} of the regression analysis was 0.74. Therefore, regarding the results of the abbreviations G1 to G8, the correlation between the crushing characteristics (cracking score) of the impact absorbing member 1 and the cracking resistance characteristics (VDA bending angle BA) of the plate material was improved by performing the preprocessing. I was able to confirm.

According to the method for evaluating the crack resistance of the plate material of the present embodiment, the following effects are obtained.

When the shock absorbing member 1 formed by using the plate material 2 is subjected to molding processing, the molding processing can be simulated by preprocessing. Therefore, the crushing property of the impact absorbing member 1 can be evaluated with high accuracy through the evaluation of the crack resistance property of the plate material 2.

Further, since the bending process and the bending back process are adopted as the preprocessing in this embodiment, the shape of the plate material 2 can be restored to a flat plate shape, and the strain accumulated during crushing can be simulated. Since the plate material 2 has a flat plate shape, the VDA bending test following the preprocessing can be easily performed. Further, at the stage of the VDA bending test, since strain is accumulated in the plate material 2, it is possible to carry out the VDA bending test in consideration of the molding process of the shock absorbing member 1 as compared with a simple flat plate which has not been preprocessed.

The bending back processing in the present embodiment may be omitted. That is, only bending may be performed as preprocessing. By adopting only the bending process as the preprocessing, even when the shock absorbing member 1 made of the plate material 2 has the ridge line portion 2a like the hat member 10, the ridge line portion 2a can be simulated by the bending process of the preprocessing. Therefore, the crushing property of the impact absorbing member 1 can be evaluated with high accuracy through the evaluation of the crack resistance property of the plate material 2.

Further, in the present embodiment, since the bending direction (bending ridge line) of the preprocessing and the bending direction (bending ridge line) of the VDA bending test are parallel, the reproducibility of the VDA bending test can be improved and a stable VDA bending test can be performed. realizable.

Further, in this embodiment, the VDA bending test is adopted as the bending test. Since the VDA bending test is known to have a correlation with the crushing characteristics of the shock absorbing member 1, the degree of improvement in the correlation can be confirmed accurately and easily. As the bending test, not only the VDA bending test but also any bending test similar thereto may be adopted.

In the present embodiment, since it can be confirmed numerically as the coefficient of determination R ² to improve the correlation, whether the degree precision by the evaluation method of anti-crack properties of the sheet material 2 can be evaluated crushing characteristics of the shock absorbing component 1 You can check.

Further, as the shock absorbing member 1, a front side member or a rear side member of a vehicle skeleton member may be specifically adopted. This makes it possible to confirm how accurately the crushing characteristics of the front side member or the rear side member can be evaluated by the crack resistance evaluation method of the plate material.

(First modification)
With reference to FIG. 14, in the first modification, a bending test different from the bending test (see FIG. 11) performed in the above embodiment is performed.

The bending test of this modification is the same as that of the above embodiment in that the VDA bending test is carried out under the conditions conforming to VDA238-100 of the German Association of the Automotive Industry, but the bending direction opposite to the bending direction of FIG. 11 is performed. Perform the VDA bending test to be performed. That is, the bending process was performed in the same direction as the V-bending direction in parallel with the ridgeline portion 2a of the V-bending in FIG. 9 (matched in this modification), and the limit bending angle (VDA bending angle BA) at which cracks occur was obtained. In this modified example as well, when acquiring the test results, data processing was performed to eliminate the influence of the bending habit of the V-bending remaining due to the springback after the bending back processing.

The results thus obtained are shown in FIG. FIG. 15 shows the relationship between the VDA bending angle BA and the crack score. The horizontal axis and the vertical axis of the graph are the same as those in FIGS. 12 and 13. FIG. 15 shows the results of the abbreviations G1 to G8 in Table 1 above. The gray triangles in the graph show the case of pre-processing. Although not shown when no preprocessing is performed, the data is the same as the data (white triangle) shown in FIG. The curve shown by the solid line in the graph shows the result of regression analysis of the preprocessed data (shown by the gray triangle) using the logistic function. The coefficient of determination R2 for this regression analysis was 0.91. The coefficient of determination R2 in the case of no preprocessing was 0.74 as described above with reference to FIG. Therefore, regarding the results of the abbreviations G1 to G8, the correlation between the crushing characteristics (cracking score) of the impact absorbing member 1 and the cracking resistance characteristics (VDA bending angle BA) of the plate material was improved by performing the preprocessing. It could be confirmed.

(Second modification)
With reference to FIG. 16, in the second modification, a bending test different from the bending test (see FIGS. 11 and 14) performed in the above-described embodiment and the first modification is performed.

The bending test of this modification is the same as the above embodiment in that the VDA bending test is carried out under the conditions conforming to VDA238-100 of the German Association of the Automotive Industry, but it is orthogonal to the bending ridge line (bending direction) in FIG. Perform a VDA bending test to perform bending to form a bending ridge (bending direction). That is, the bending process is performed in the direction orthogonal to the V-bending ridge line portion 2a (indicated by the broken line in FIG. 16) in FIG. 9, a new ridge line portion 2b is formed, and the limit bending angle (VDA bending angle BA) at which cracking occurs. ) Was acquired. In this modified example as well, when acquiring the test results, data processing was performed to eliminate the influence of the bending habit of the V-bending remaining due to the springback after the bending back processing.

The results thus obtained are shown in FIG. FIG. 17 shows the relationship between the VDA bending angle BA and the crack score. The horizontal axis and the vertical axis of the graph are the same as those in FIGS. 12 and 13. FIG. 17 shows the results of the abbreviations C1 and C3 to C10 in Table 1 above. The gray circles in the graph indicate the case of preprocessing. Although not shown when no preprocessing is performed, the data is the same as the data (white circles) shown in FIG. The curve shown by the solid line in the graph shows the result of regression analysis of the preprocessed data (indicated by the gray circle) using the logistic function. The coefficient of determination R2 for this regression analysis was 0.84. The coefficient of determination R2 in the case of no preprocessing was 0.73 as described above with reference to FIG. Therefore, by preprocessing the results of the abbreviations C1 and C3 to C10, the correlation between the crushing characteristics (cracking score) of the impact absorbing member 1 and the cracking resistance characteristics (VDA bending angle BA) of the plate material was improved. I was able to confirm that.

As shown in the first modification and the second modification, the correlation is improved even if the relationship between the bending direction of the pre-machining and the bending direction of the bending test is changed in various ways. It is considered that this is because the molded member such as the hat member 10 has accumulated strain inside, and it is possible to simulate a state in which strain is accumulated in the plate material 2 by preprocessing. Therefore, the pre-machining is not limited to the bending process, but the correlation is expected to be improved in the same way even in the process of accumulating strains such as tension, compression, forging, and shearing. It is also clear that the pre-processing may be a combination of these processes.

Although the specific embodiment of the present invention and the modification thereof have been described above, the present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the present invention.

1 Shock absorbing member 2 Plate material 2a, 2b Ridge part 5 Floor surface 6 Top surface 10 Hat member 11 Convex part 11a, 11b Side wall 11c Top wall 11d, 11e Connection part 12, 13 Flange part 14, 15 Connection part 20 Closing plate

Claims (9)

Prepare the board and
The plate material is preprocessed and
A method for evaluating crack resistance of a plate material, which comprises performing a bending test on the preprocessed portion of the plate material. The method for evaluating crack resistance of a plate material according to claim 1, wherein the preprocessing includes bending processing. The method for evaluating crack resistance of a plate material according to claim 2, wherein the pre-processing includes a bending-back process for returning the bending process to the original state. The method for evaluating crack resistance of a plate material according to claim 2 or 3, wherein in the bending process of the preprocessing, the bending strain of the surface layer of the plate material is 0.032 or more. The method for evaluating crack resistance of a plate material according to any one of claims 2 to 4, wherein the bending direction of the preprocessing and the bending direction of the bending test are parallel or orthogonal to each other. The method for evaluating crack resistance of a plate material according to any one of claims 1 to 5, wherein the plate material is a high-strength steel plate for vehicles. The method for evaluating crack resistance of a plate material according to any one of claims 1 to 6, wherein the bending test is a VDA bending test. A shock absorbing member having a central axis manufactured from the above-mentioned plate material is prepared.
A crush test of the shock absorbing member in the direction of the central axis was performed.
The method for evaluating crack resistance of a plate material according to any one of claims 1 to 7, further comprising confirming a correlation between the result of the crushing test and the result of the bending test. The method for evaluating crack resistance of a plate material according to claim 8, wherein the shock absorbing member is a front side member or a rear side member of a vehicle skeleton member.

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