JP5374832B2 - Metal hollow columnar member for impact absorbing member and manufacturing method thereof - Google Patents

Description

TECHNICAL FIELD The present invention relates to a hollow columnar member made of high-tensile steel of 590 MPa class or higher for an impact absorbing member and a method for manufacturing the same, and in particular, used as a frame member constituting a housing, and a thin hollow columnar shape made of high- tensile steel of 590 MPa class or higher It relates to members.

  In recent years, there has been an urgent demand for cost reduction at manufacturing sites due to high fuel and high raw materials. However, the deterioration of product performance due to cost reductions may lead to the loss of manufacturer confidence. In particular, deterioration of the performance of the frame member constituting the housing must be avoided in terms of safety. In the automobile field, in order to maintain collision safety and improve fuel efficiency, there are many examples in which ultra high tension is applied to a frame member mounted on a vehicle body. That is, the cost is reduced by changing the quality of the material.

  As a technique for maintaining or improving product quality and enabling cost reduction, there is a cost reduction method by changing the material itself, but development of a new material requires a long time and enormous development cost. Another possible cost reduction method is to optimize the member shape. This method is excellent in terms of development period and development cost, and various studies have been conducted in the past.

  As a prior art related to the present invention, Patent Document 1 discloses a shock absorbing member in which a cross-sectional shape in at least a part in the axial direction is a closed cross section having a plurality of vertices and forms a groove portion recessed toward the inside. Is disclosed.

  Moreover, in the energy absorption member which consists of an aluminum alloy extrusion member which has a hollow rectangular cross section in patent document 2, the member which has a convex part of a rectangular cross section on the outer side of a wall surface part is described.

  Further, in Patent Document 3, as a front side frame structure of an automobile having a substantially rectangular cross-sectional shape, a bead that extends in the axial direction on the side surface and has a convex shape on the inside and a bead that has a convex shape on the outside are formed. A structure is disclosed.

JP 2006-207724 A JP 2002-12165 A JP-A-8-108863

  However, even including the above-mentioned patent documents, a convenient design guideline that can be applied to design specifically and immediately has not been disclosed so far. There are no examples of statistically summarized cross-sectional shapes that have excellent energy absorption capability and are less likely to cause overall buckling due to local bending, and rely heavily on human resource development, repeated designers' experience and member-level verification. However, it takes a lot of time and development costs, and there is a big difference in quality at various design sites. Therefore, a design guideline that reduces the degree of dependence on the designer's experience and does not consume unnecessary costs can promote high quality maintenance and shorten the development period, and as a result, increase development competitiveness and its sustainability.

  Here, the overall buckling refers to a phenomenon in which the columnar member is not sufficiently deformed into a bellows shape and is locally bent. In general, energy absorption ability and resistance to overall buckling caused by local bending are in a contradictory relationship, and it is difficult to make the two compatible in the first place. If the energy absorption capacity is improved, it becomes easy to buckle as a whole, and if it is attempted to increase the bending rigidity in order to prevent the overall buckling, the energy absorption capacity is reduced. For this reason, designers are required to have a design that balances energy absorption ability and overall buckling resistance.

  From the above points, the member described in Patent Document 1 has a problem that the overall buckling resistance is greatly reduced in order to increase the energy absorption ability. The member shown in Patent Document 1 has a possibility of exhibiting excellent shock absorption capability (hereinafter referred to as energy absorption capability) when the load is continuously applied in a certain range.

  However, the load direction applied with the deformation of the member is usually complicated, and a cross-sectional structure with low bending rigidity easily causes overall buckling. The invention described in Patent Document 1 has an object of “securing a predetermined shock absorption capacity by buckling in a bellows shape” (paragraph number 0032 of Patent Document 1). As shown in the figure, the shape based on the octagonal cross section by cutting the corner part greatly reduces the bending rigidity, so that it does not undergo bellows-like deformation that repeats small buckling, and causes overall buckling due to bending. Cheap. Therefore, the actual energy absorption capacity may be extremely lower than the assumed energy absorption capacity.

  Moreover, although the shape of the square cross section which has a corner part (corner part, the same hereafter) is described in FIG. 17, FIG. 18, FIG. 19 (a) etc. of patent document 1, the curvature and dimension of a corner part are also described. However, if it is assumed that the inner corner is formed at a right angle as shown in the figure, the corner portion of the disclosed figure is likely to cause a plate reduction due to processing, and is likely to become a weak portion as a result. Similarly, since the member molded in a polygon causes local reduction at the time of molding at each corner, there is a risk of breaking easily.

In addition, the side length defined in claim 5 of Patent Document 1 is a fairly wide range, and includes large variations in energy absorption capacity. For example, a square shape, the recess in each of the sides there is one in the center, and a thickness t = 1.6 and [mm], according to the provisions of claim 5, the width W ₁ of the recess portion 6.4 (= 4 × 1.6) <W ₁ <104 (= 65 × 1.6), and the width Xi (i = 1, 2) of each remaining region is 6.4 <Xi <104 You can choose from. Among them, when X ₁ = X ₂ = 100 [mm] and W ₁ = 10 [mm] are adopted, that is, the width of the recess is 10 mm on each of the four sides, and the width of each of the remaining areas is 100 mm. In this case, even if the corner has a substantially large curvature, the C value defined in the present invention, which will be described later, is 2 (= 20 (10/100)), and the member has a very low energy absorption capability. Thus, if the cross-sectional shape is made extremely asymmetric, there is a possibility that the entire buckling due to bending is likely to occur without being deformed into a bellows shape.

  Patent Document 2 has one or a plurality of convex portions on the side of a hollow rectangular cross section, and attempts to improve the energy absorption amount of the member by increasing the corner portions by forming the convex portions. However, the thin hollow columnar member formed with the convex portion does not have a corner portion as shown by reference numeral A in FIG. 25 on the intersection of the straight lines extending the outer periphery of the convex portion, and therefore, as shown in FIG. In addition, in the case of a member that does not have a corner portion, the bending rigidity is greatly reduced, and it is easy to cause overall buckling due to bending without causing a bellows-like deformation that repeats small buckling. Therefore, depending on the load direction, the actual energy absorption capacity may be extremely lower than the assumed energy absorption capacity.

  Patent Document 3 has one or a plurality of indentations on a substantially square side as in the present invention. However, Patent Document 3 is intended to increase the energy absorption capacity by weakening the buckling resistance similarly to Patent Document 1, and since a clear design guideline is not given, for example, in the center of the frame member. There are many shapes that may easily cause overall buckling due to bending from the center, such as providing a dent only locally, and there is a risk that the energy absorption capacity may be reduced contrary to the purpose.

Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to achieve both energy absorption ability and overall buckling resistance by deformation in various thin-walled cross-sectional shapes, and is excellent in energy absorption ability. It is another object of the present invention to provide a design guideline for a thin-walled hollow columnar member that is difficult to buckle, and to provide a high- tensile steel hollow columnar member of 590 MPa class or higher for a shock absorbing member and a method for producing the same.

  In accordance with the above object, the present inventors have investigated the energy absorption ability and the overall buckling resistance by changing the cross-sectional shape variously, and as a result, the hollow member having corner portions at the four corners is excellent in resistance to bending, and the shape thereof. Found that the function (C value) of the minimum side length / maximum side length of the closed cross section and the total number of ridges correlates with the minimum cross section secondary radius, which is an index of energy absorption and ease of buckling. That is, it has been found that the C value can serve as a design guideline for a thin-walled hollow columnar member excellent in energy absorption ability and overall buckling resistance. Therefore, if the installation space of the members in the structure can be grasped, the best member shape can be searched based on the C value. The cross-sectional shape does not need to be constant in the axial direction, and there may be a portion that does not satisfy the C value in a part of the axial direction. However, since the portion may become a structural weak portion against bending, it is desirable that the portion be formed in a cross-sectional shape having no bending portion and having a high bending rigidity.

That is, in order to solve the above problems, the gist of the present invention is as follows.
Invention (1)
A hollow columnar member made of high-tensile steel of 590 MPa or higher for a hollow shock absorbing member having a corner portion at four corners and having a substantially rectangular cross-sectional shape including the corner portion and forming a closed cross-section,
At least one of the four sides has one or more dents, and the ratio Lmin / Lmax between the minimum side length Lmin and the maximum side length Lmax in the cross section is multiplied by the total number N of ridge lines in the cross section. C value (= N (Lmin / Lmax)) obtained in the above is 10 or more and 40 or less,
And the total perimeter of the closed section is π, the member thickness t is 1.6 mm or less, the ratio π / t is 160 or more,
A hollow columnar member made of high-tensile steel of 590 MPa class or more for impact absorbing members, characterized by having flange portions on the outside of two corner portions or on the outside between two opposing sides.
However, the side length and the total number of ridge lines are defined as follows.
Side length:
The side length of the dent portion located in the middle of one side is a distance obtained by connecting the shoulder end points of adjacent convex portions with a straight line.
The side length of the convex portion at the end of one side is the linear distance from the shoulder end point located on the side opposite to the end of the convex portion to the end.
The side length of the convex portion located in the middle of one side is the linear distance between the shoulder end points on both sides of the convex portion.
Total ridges:
The total number of straight lines when the vertices with the curvature removed in a closed section are connected by straight lines.

Invention (2)
In the invention (1), a high-tensile steel hollow columnar member of 590 MPa class or higher for an impact absorbing member, characterized in that the use is for automobiles.

Invention (3)
A method for producing a hollow columnar member made of high-tensile steel of 590 MPa or higher for the impact absorbing member of the invention (1) or (2), wherein two plate members are formed by bending or pressing, and the flange portion is a drill screw or bolt A method for producing a hollow columnar member made of high-tensile steel of 590 MPa or more for impact absorbing members, characterized by being joined by rivets, welding or adhesion.

Invention (8)
A method for producing a metal hollow columnar member according to the invention (1) or (2), wherein the seamless pipe is formed by hydroforming or roll forming.

  In addition, in this invention, a substantially square means that the figure formed by the intersection of the straight line which extended each edge | side except a hollow part is a rectangle.

  According to the present invention, in a predetermined installable space, a metal hollow columnar member that has the best cross-sectional shape that is unlikely to cause overall buckling due to bending regardless of the load direction and that has an excellent energy absorption capability, and a method for manufacturing the same. Can be provided.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments for implementing a thin hollow columnar member of the present invention will be described in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

First, the said invention (1) is demonstrated.
First, when a load is applied to the thin metal hollow columnar member, the entire buckling due to bending must be avoided from the viewpoint of energy absorption capability. Even when a load is applied in the axial direction, the load direction becomes complicated due to deformation, and the load is not applied in a constant axial direction. Therefore, in order to prevent overall buckling due to bending, bending rigidity, that is, the minimum moment of inertia of the section The size of is important. FIG. 2 shows a vertical length of 80 mm and a horizontal length of 80 mm. FIG. 3 shows various cross-sectional shapes and their minimum secondary moments in a square having a vertical length of 60 mm and a horizontal length of 100 mm. Is a comparison. The six thin-walled metal hollow columnar members having the cross-sectional shapes shown in FIGS. 2 and 3 both used JSC590Y as a material. The plate thickness is 1.6 mm. The shape shown in the figure is a schematic view of each cross-sectional shape. Each arrow in the figure corresponds to each shape and the minimum moment of inertia of the cross section. From the figure, it can be seen that the cross-sectional shape having a recess at the corner in the square (the right-hand squares in FIGS. 2 and 3) has an extremely low minimum second-order moment as compared to the other cross-sectional shapes. That is, in order to prevent the overall buckling due to bending, it is considered that the best cross-sectional shape is a substantially quadrilateral having corner portions at four corners and forming a closed cross section including the corner portions.

Secondly, the present inventors examined the minimum secondary radius of the cross-section in various cross-sectional shapes with a substantially square shape. The minimum cross-sectional secondary radius r _min [M] is a geometrical variable represented by the following equation by the minimum cross-sectional secondary moment I _min [M ⁴ ] and the cross-sectional area A [M ² ].

The minimum secondary radius r _min [M] is an index generally indicating buckling resistance, but since the minimum secondary moment is divided by the cross-sectional area, the bending without the influence of the plate thickness is used. It can be regarded as an index representing rigidity. That is, the minimum secondary cross-sectional radius r _min serves as an index of overall buckling, and a member having a cross-sectional shape with a large minimum cross-sectional secondary radius r _min is a member that is unlikely to generate overall buckling.

FIG. 4 shows a result of comparison between the C value and the minimum secondary radius r _min for each cross-sectional shape. FIG. 4 shows the results when the vertical length of the substantially square is 80 mm and the horizontal length is 80 mm. From the figure, it can be confirmed that the minimum secondary radius r _min decreases as the C value increases. In particular, when the C value is as small as about 3, the variation in the minimum secondary radius r _min is large. Further, it can be confirmed that when the C value increases to some extent, the fluctuation of the minimum secondary radius r _min decreases.

Here, the C value is a design guideline value newly invented by the present inventors. As described above, the minimum side length L _min [M] and the maximum side length L _{max in} the cross section of the hollow metal columnar member are used. It is a value obtained by multiplying the ratio L _min / L _max with [M] by the total number of ridgelines N in the cross section. Generally, when the total number of ridges N is increased to some extent, the amount of absorbed energy tends to be improved. However, the amount of absorbed energy varies greatly depending on the position, total number, and size of the recesses. It is difficult to accurately evaluate performance. Therefore, the present inventors multiply the total number of ridge lines N by the ratio L _min / L _max of the minimum side length L _min [M] and the maximum side length L _max [M], thereby not only affecting the total number of ridge lines. The design guideline value C was invented so that the influence of the position, total number, and size of the dents could be taken into account.

  Thirdly, the present inventors studied the amount of absorbed energy in various cross-sectional shapes with a substantially square shape by numerical analysis based on FEM. The model used in the FEM was a steel thin-walled hollow columnar member having a longitudinal length of 400 mm, and a forced displacement of 100 mm was applied in the axial direction and compression direction by a rigid wall. The same analysis was performed for a plurality of cross-sectional shapes, and the energy absorption amount for each cross-sectional shape was examined. FIG. 5 shows a comparison between the C value and the absorbed energy E [J] for each cross-sectional shape. FIG. 5 shows the results when the vertical length of the substantially rectangular shape is 80 mm and the horizontal length is 80 mm. From the figure, it can be confirmed that the absorbed energy E increases as the C value increases. It can also be confirmed that as the C value increases, the increase in absorbed energy E is saturated.

  From these findings, it has been found that the performance of a substantially rectangular metal thin hollow columnar member with high bending rigidity can be better summarized by the C value. Moreover, the present inventors are not only made of steel but also a thin hollow columnar member having a C value of 4 to 40 in aluminum, stainless steel, titanium, etc., and is a member excellent in energy absorption ability and overall buckling resistance. I found. When the C value is less than 4, the energy absorption capability is drastically reduced, so that it may not function as a frame material constituting the housing of the structure. In addition, a member having a C value exceeding 40 is a member having a large total number of ridge lines, which makes it difficult to manufacture and increases manufacturing costs. Further, since the amount of increase in the amount of energy absorption and the amount of decrease in the minimum secondary radius of the cross section are very small, this is a C value region where no advantage can be found. A C value closer to 4 means a member having a relatively high absorbed energy and a very high overall buckling resistance. On the contrary, as the C value is closer to 40, the absorbed energy is very large and the overall buckling resistance is relatively large. Therefore, the C value is 4 or more, preferably 5 or more, more preferably 10 or more. The upper limit of the C value is 40 or less, preferably 30 or less, more preferably 20 or less.

It is desired to install a member considering the C value appropriately depending on the installation location. In addition, it is a space that can be basically installed in the design, but in order to increase the energy absorption amount and overall buckling resistance of the thin hollow columnar member, the area of the substantially square should be increased to 1500 mm ² or more as much as possible. And a shape close to a square, that is, the ratio of two sides of a substantially square is preferably 1 to 1.2.

Furthermore, since a sharp reduction can be avoided by giving a curvature at the corner portion of the cross-sectional shape, it is preferably 2.5 mm ⁻¹ or less, and 0 in order to improve the overall buckling resistance. 0.02 mm ⁻¹ or more is preferable.

Incidentally, the ratio _L min _{/ L max} the C value minimum edge length _{L min} and a maximum edge length _{L max,} is a value obtained by multiplying the total ridge count N at the closed cross section, shown in detail in FIG. Each side length is calculated based on the shape when the curvature is removed from the convex portion 4 generated by the formation of the substantially rectangular corner portion 2 and the concave portion 3. For the convex part 4 at the end, the length of the straight line connecting the shoulder end point 5 to the end part 6 of the convex part is the side length, and for the concave part 3, the shoulder end point 5 of the adjacent convex part 4 is a straight line. The length connected with is the side length. In the case of a convex portion in the middle (not shown), the straight distance between the shoulder end points of the convex portion is used. When giving curvature to the end points 5 and 7, the minimum side length L _min and the maximum side length L _max are calculated based on the shape when the radius of curvature is 0 mm. Accordingly, the shortest one in the closed cross section is set to L _min [M], and the longest one is set to L _max [M]. The total number of ridge lines is the total number of straight lines when the vertices are connected by straight lines. The numbers in circles in the figure are examples when the ridge lines in one side are counted from the left end. In the case of FIG. 6, the number of ridge lines is 5 for one side of a substantially square, so the remaining three sides have the same shape. If so, the total number of ridge lines is 20.

Next, the above invention (2) will be described.
First, in order to improve the overall buckling resistance, the radius of curvature R given to the end of one side of the substantially quadrilateral must not be too large. Secondly, the radius of curvature R given to the end of one side of the substantially quadrilateral must not be too small in order to avoid sharp reduction of corners. Therefore, if the length obtained by dividing the length of one side of the substantially quadrangle by n corresponds to the radius of curvature R, the total circumferential length π of the closed section of the substantially quadrangle can be approximately expressed by the following equation (1).

  Here, the total perimeter of the closed cross section refers to the perimeter of a substantially square shape even when the cross section has a recess (for example, in the case of FIG. 2 described above, π = 320 ( = 4 × 80), and in the case of FIG. 3, π = 320 (= 2 × (60 + 100)). When both sides of the equation (1) are divided by the thickness t, the following equation (2) is obtained.

Further, the maximum strain ε _f generated by bending is expressed by the following equation (3).

Therefore, the ratio between the total circumferential length π of the closed cross section in the substantially quadrangular shape and the plate thickness t can be described by the following equation (4) from the equations (2) and (3).

In the above formula, two conditions of n> 10 for the overall buckling resistance and ε _f <1 for preventing a sudden reduction in the thickness are necessary conditions for the highly functional metal hollow columnar member.

  From the above, the ratio π / t between the total circumference π and the plate thickness t is set to 20 or more, preferably 80 or more, more preferably 160 or more, in order to further improve the overall buckling resistance and energy absorption performance. Is preferred.

Next, the above (3) will be described.
The design guideline by C value is applicable also to the thin hollow columnar member which has a flange part. The present inventors investigated the energy absorption amount and the minimum secondary radius of the cross section of two types of thin-walled hollow columnar members provided with flange portions in the cross-sectional shape of FIG. The dimensions of each cross-sectional shape are shown in FIGS. Both members are made of steel (JSC590Y steel), the length is 400 mm, the thickness t is 1.6 mm, and a curvature of 0.25 mm ⁻¹ is given to all corners. The curvature of all corners of the member in FIG. 7A is also 0.25 mm ⁻¹ . A thin-walled hollow columnar member shown in FIG. 7 (a) having no flange portion with respect to the amount of energy absorbed when a forced displacement of 100 mm is applied in the axial direction and the compression direction by the rigid wall and the minimum secondary radius of the member. And the thin hollow columnar members shown in FIGS. 10 and 11 were compared. The results are shown in FIGS.

  12 and 13 compare the minimum secondary cross-sectional radius and the amount of absorbed energy in each cross-sectional shape. From these examples, the minimum cross-sectional secondary radius and the amount of absorbed energy are within the range where the C value is assumed within the range of 4 to 40 regardless of the presence or absence of the flange portion, even when the flange portion is provided. It can be seen that the C value provides a good design guideline.

  When the flange shown in FIG. 10 is applied to adjacent corners of a substantially quadrangular shape, the amount of energy absorption is slightly higher than that of the shape having no flange, and the minimum secondary radius of the cross section is also slightly larger. Therefore, it is considered that the shape with the flange part attached to the adjacent corners of a substantially rectangular shape is the best. However, if the flange part is too large, the bending rigidity in the cross section becomes extremely uneven due to the high bending rigidity of the flange part. It tends to cause overall buckling.

  When the flange shown in FIG. 11 is provided on the outer sides of two opposing sides of a substantially square shape, the amount of energy absorption is greatly improved although the minimum secondary radius of the cross section is slightly reduced as compared with the shape having no flange portion. This is thought to be due to the fact that the bending rigidity in the cross section is relatively symmetric, the minimum secondary radius of the cross section is reduced, and the amount of energy absorption is increased due to deformation in a bellows shape. Although the amount of energy absorption has been improved by providing the flange portion, when the flange portion is too large, it does not undergo bellows-like deformation that repeats small buckling, and tends to cause overall buckling due to bending.

  Moreover, when a flange part is too small, joining will become difficult and there exists a possibility that a junction part may become weak. In accordance with the above knowledge, it is desirable that the length of the flange portion is 4 t or more in order to prevent the joint portion from weakening, and the length of the flange portion is 12 t or less in order to make it difficult to cause overall buckling.

Next, the above invention (4) will be described.
In the automotive field, many designers and researchers have responded to many issues such as further improvement in collision safety performance, further reduction in body weight to improve fuel efficiency, and reduction in the development period of many models for global expansion. We are working.

  In relation to collision safety performance, in Japan, a standard equivalent to the protection of passengers at the time of offset collision of UN unified standard (ECE rule) R94 has been established and has been applied since the new passenger car in 2007. The application has been expanded to commercial vehicles of 2.5 t or less. In the United States, it is planned to add a 32 km / h pole side impact to FMVSS 214 from 2009. FMVSS 301 is amended and the 80 km / h offset collision will be applied in stages from 2006.

  Regarding fuel efficiency, in Japan, the “Heavy Vehicle Fuel Efficiency Standard” was established in April 2006 as a target achievement year by amendment of the Law Concerning Rational Use of Energy (Energy Saving Law). In the United States, the federal announced amendments to the 2008-2011 light truck CAFE system. In both the Federal and California states, next-generation regulations are being discussed.

  With regard to global expansion, the export volume of automobiles has been increasing steadily in recent years, and has rapidly increased to about 22% even when comparing 2001 and 2005. Overseas production is expected to exceed domestic production in the future, such as Japanese manufacturers entering Russia.

  From the background as described above, the present invention is effective in reducing the burden on the designer and solving the above-mentioned problems promptly in order to shorten the design period that proceeds at a rapid pitch, to reduce the weight of the vehicle body, and to further improve the collision safety. It will be a useful tool. There are many members that are subjected to dynamic loads during automobile collisions, but the shape of the front side member that contributes significantly to absorbing collision energy especially during frontal collisions, or the shape of the rear side member that contributes significantly to absorbing collision energy during rearward collisions It is believed that the present invention can make a significant contribution when making decisions.

Next, the above invention (5) will be described.
When manufacturing a thin hollow columnar member having the cross-sectional shape shown in FIG. 7 (a), first, a plate material having the cross-sectional shape shown in FIG. 14 (a) is prepared, and two concave portions as shown in FIG. 14 (b) are prepared. 11 and bent portions 12 are formed on both ends by pressing. The curvature of the corner can be controlled within an appropriate range by controlling the press load and, if necessary, the wrinkle presser load. Next, the center plane portion 10 sandwiched between the recess portions 11 is fixed by a jig so as to be sandwiched up and down, and as shown in FIG. 14C, the bent portions 14 are formed again by pressing at both ends of the jig. Next, as shown in FIG. 14D, both end portions 13 of the plate materials overlapped in the above process are joined by welding to form a predetermined shape. The total number and position of the recesses can be adjusted by changing the mold used for press molding or combining a cam.

  The pad back pressure and press load at the time of pressing differ depending on the material and member dimensions, but in the case of the thin hollow columnar member shown in FIG. 7A using JSC590Y steel, the press load is 50 t or more, and the pad back pressure is 5 t or more. Is desirable. Similarly, in the next bending process, the press load is preferably 100 t or more and the pad back pressure is preferably 10 t or more. In order to facilitate the molding process, it is desirable that the fixing portions at both ends of the jig can be detached and the molded member can be taken out by pulling it out in the longitudinal direction.

  As another forming method, roll forming may be used. First, a plate material having a cross-sectional shape shown in FIG. 15A is prepared, and a single plate material is finally formed by a plurality of rolls as shown in FIG. Part 18 is formed. The curvature of the corner can be controlled within an appropriate range by controlling the rolling load of the roll. Next, as shown in FIG. 15C, both end portions 19 of the plate materials overlapped in the above process are joined by welding to form a predetermined shape.

  In joining, when this molded member is used as an impact absorbing member, it is desirable to use laser welding with a small heat-affected zone in order to reduce local weak parts.

Next, the above invention (6) will be described.
When manufacturing a thin hollow columnar member having a cross-sectional shape shown in FIG. 7A, a welded steel pipe is expanded by hydroforming to form two recessed portions 21 and four bent portions 22. The curvature of the corner can be controlled within an appropriate range by controlling the hydroform mold and the pressure of the medium. The total number and position of the dents can be adjusted by changing the mold used for the hydroform.

  The axial push amount and internal pressure during hydroforming vary depending on the material and member dimensions. When the thin hollow columnar member shown in FIG. 7A is formed using JSC590Y steel, first, the cross section shown in FIG. A plate material having a shape is prepared, and a welded steel pipe shown in FIG. Thereafter, in order to form a rough shape, it is desirable that the welded steel pipe is sandwiched between molds as shown in FIG. 16 (c), and an internal pressure of 40 MPa or more and a shaft pressing amount of 50 mm or more are loaded in the steel pipe. Next, in order to form the details of the shape, it is desirable to load only the internal pressure of 100 MPa or more without loading the shaft pressing amount. Thereby, the thin hollow columnar member shown in FIG.

  As another forming method, roll forming may be used. First, a plate material having a cross-sectional shape shown in FIG. 17A is prepared, and a welded steel pipe shown in FIG. Then, as shown in FIG. 17C, the two recessed portions 25 and the corner portions 26 are finally formed on the welded steel pipe by the rolls 23 and 24 using a plurality of rolls. The control of the curvature of the corner is the same as in FIG.

  Moreover, in order to reduce a local weak part, the welded steel pipe which uses laser welding with few heat-affected parts is desirable.

Next, the said invention (7) is demonstrated.
When manufacturing a thin hollow columnar member having the cross-sectional shape shown in FIG. 7 (a), first, a plate material having a cross-sectional shape shown in FIG. 18 (a) is prepared, and two bent portions as shown in FIG. 18 (b) are prepared. One dent 31 is formed between 32 by pressing. The control of the curvature of the corner is the same as in FIG. Two flange portions 33 are provided at both ends of the press-formed product. And as shown in FIG.18 (c), the flange part 33 of the two members shape | molded by the same formation process is piled up, and welding is performed. The total number and position of the recesses can be adjusted by changing the mold used for press molding or combining a cam.

  The pad back pressure and press load at the time of pressing differ depending on the material and member dimensions, but in the case of the thin hollow columnar member shown in FIG. 7A using JSC590Y steel, the press load is 100 t or more and the pad back pressure is 10 t or more. Is desirable. In joining, when this molded member is used as an impact absorbing member, it is desirable to use laser welding with a small heat-affected zone in order to reduce local weak parts.

Next, the above invention (8) will be described.
When manufacturing a thin hollow columnar member having a cross-sectional shape shown in FIG. 7A, first, a seamless pipe having a cross-sectional shape shown in FIG. 19A is prepared. As shown in FIG. 19B, a seamless pipe is prepared. Is inserted into a mold and expanded with a hydroform, and as shown in FIG. 19 (c), two indentations 41 and four bent portions 42 are formed. The total number and position of the dents can be adjusted by changing the mold used for the hydroform. The control of the curvature of the corner is the same as in FIG.

  Axial pressing amount and internal pressure during hydroforming vary depending on the material and member dimensions, but when forming the thin hollow columnar member shown in FIG. 7 (a) using JSC590Y steel, first, in order to form a rough shape, As shown in FIG. 19 (b), it is desirable that the welded steel pipe is sandwiched between molds, and an internal pressure of 40 MPa or more and a shaft pressing amount of 50 mm or more are loaded in the steel pipe. Next, in order to form the details of the shape, it is desirable to load only the internal pressure of 100 MPa or more without loading the shaft pressing amount.

  As another forming method, roll forming may be used. First, a seamless pipe having a cross-sectional shape shown in FIG. 20 (a) is prepared, and the seamless pipe is inserted into a plurality of rolls as shown in FIG. 20 (b), and finally, as shown in FIG. 20 (c). Two recessed portions 45 and a corner portion 46 are formed on the welded steel pipe by the roll 43 and the roll 44. The control of the curvature of the corner is the same as in FIG.

  The shape of the recess 3 is such that the internal angle of the corner shared with the shoulder end point 5 of the protrusion 4 is 90 ° or more, and the depth of the recess 4 is at least 5 times the plate thickness. Desirable for improving energy absorption.

Hereinafter, the present invention will be specifically described with reference to examples in which the present invention is specifically implemented. A member having a substantially square cross section with a longitudinal length and a lateral length of 100 mm and 60 mm, respectively, can be installed as an installation space for the metal thin hollow columnar member, and there is no unevenness on at least one side surface of the columnar member. The cross-sectional shape in which the entire buckling hardly occurs within the range was searched. JSC590Y was used as the material. For example, as an example of the present invention, a member having a cross-sectional shape shown in FIG. 7A was pressed from a single steel plate and manufactured by welding the ends. A hollow columnar member with an axial length of 400 mm and a plate thickness of 1.6 mm. That is, it corresponds to π / t = 200. Further, a curvature of 0.25 mm ⁻¹ is given to all corners. The interior angles of the shoulder end points were all 110 degrees. Moreover, the depth of the dent part was 10 mm. The C value of the member in Fig. 7 is 6.66 (= 12 (33.3 / 60), which is within the scope of the present invention. The rigid wall is crushed by 100 mm in the axial direction and in the compression direction, and the amount of absorbed energy is reduced. Examined.

  FIG.7 (b) is a FEM mesh division | segmentation figure of the hollow columnar member whose cross-sectional shape is Fig.7 (a). FIG.7 (c) is a deformation | transformation figure after crushing 200 mm to an axial direction and a compression direction in order to grasp | ascertain the final deformation | transformation condition. From FIG.7 (c), it has confirmed that it was deform | transforming into a bellows shape and it was crushed in the cross-sectional shape which provided the dent part like Fig.7 (a).

  The same analysis was performed for other shapes having C values different from 2, 12, 22, and 28, and the amount of absorbed energy and the secondary radius of the minimum cross section were compared. The dimensions of the substantially square, the radius of curvature of the corner portion, the inner angle of the shoulder end point, and the plate thickness were all the same as those of the member of FIG. That is, the C values are different cross-sectional shapes, but all are π / t = 200 (= (2 · 160 / 1.6)). The results are shown in FIGS. Compared with the hollow columnar member having a C value of 2.66, the hollow columnar member having a C value of 6.66 to 28 has relatively good overall buckling resistance from FIG. It was confirmed that the amount was larger.

  Further, the C values are 2, 7, 12, 22, and 28, respectively, and the substantially square dimensions, the radius of curvature of the corner portion, and the inner angle of the shoulder end point are the same, but the plate thickness is 4 mm and 8 mm (respectively π / t = 80 = 2 · 160/4, equivalent to π / t = 40 = 2 · 160/8), the same analysis was performed, and the minimum secondary radius and energy absorption amount due to the difference in C values The change was investigated. The results are shown in FIG. 21, FIG. 22, FIG. 23, and FIG.

  FIGS. 21 and 22 are comparison diagrams of the minimum cross-sectional secondary radius and the energy absorption amount due to the difference in C value for a member with π / t = 80, respectively, and FIGS. 23 and 24 are for a member with π / t = 40, respectively. It is a comparison figure of the minimum cross-section secondary radius and energy absorption amount by the difference in C value. From the above results, even for thin hollow columnar members having different π / t, there is a slight difference, but the minimum cross-sectional secondary radius and energy absorption amount tend to be the same as in FIGS. 8 and 9 due to the difference in C value. It was confirmed that the members satisfying the C value = 4 to 40 are less likely to be buckled as a whole and have a high ability to absorb input energy due to load.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to the example which concerns. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Understood.

It is explanatory drawing which shows typically the cross-sectional shape in a part of axial direction of the hollow columnar member which is an example of this invention. Is an explanatory view showing a change in the minimum second moment of I _min with or without a corner portion of the substantially rectangular vertical length and horizontal length are both 80mm cross-section. Is an explanatory diagram vertical length and lateral length of the cross-section showing a variation of the minimum second moment of I _min with or without a corner portion of substantially square is 60mm and 100mm, respectively. Is a graph showing the vertical length and horizontal length are both 80mm of C and minimum cross-sectional secondary radius r _min of the thin hollow cylindrical member relations section. It is a graph which shows the relationship between C value and energy absorption amount E of a thin hollow columnar member whose longitudinal direction length and horizontal direction length of a cross section are both 80 mm. It is explanatory drawing which shows minimum edge length _Lmin , maximum edge length _Lmax, and the total ridgeline number N in a cross section. (a) is explanatory drawing which shows the cross-sectional shape which is one of the examples of this invention, (b) is the FEM mesh division | segmentation figure used in order to calculate energy absorption amount, (c) is an axial direction by 200 mm, and It is a deformation | transformation figure when squashed in the compression direction. The relationship between the C value of the thin hollow columnar member whose longitudinal length and lateral length are 60 mm and 100 mm, and the plate thickness is 1.6 mm (that is, π / t = 200), respectively, and the minimum secondary radius r _min It is a graph to show. A graph showing the relationship between the C value and the energy absorption amount E of a thin-walled hollow columnar member having a longitudinal length and a transverse length of 60 mm and 100 mm, and a plate thickness of 1.6 mm (ie, π / t = 200), respectively. is there. It is explanatory drawing of the detail of the cross-sectional shape which has a flange part on the outer side of the two corner parts which are one of the examples of this invention, respectively. It is explanatory drawing of the detail of the cross-sectional shape which has a flange part on the outer side between two sides which is one of the examples of this invention, respectively. In the cross-sectional shape is a longitudinal length and a lateral length of 60mm and 100mm, respectively cross-section is an explanatory diagram showing a change in the minimum cross-sectional secondary radius r _min due to differences in the presence and position of the flange portion. It is explanatory drawing which shows the change of the energy absorption amount E by the difference in the presence or absence and position of a flange part by the cross-sectional shape whose vertical direction length and horizontal direction length of a cross section are 60 mm and 100 mm, respectively. It is explanatory drawing which shows the process of forming the cross-sectional shape of this invention member by shape | molding one board | plate material by bending or press work, and joining edge parts by a drill screw, a volt | bolt, a rivet, welding, or adhesion | attachment. It is explanatory drawing which shows the process of shape | molding one board | plate material by roll forming, and joining the edge parts by a drill screw, a volt | bolt, a rivet, welding, or adhesion | attachment, and forming the cross-sectional shape of this invention member. It is explanatory drawing which shows the process of forming the cross-sectional shape of this invention member by shape | molding one board | plate material by bending or press work, welding edge parts, and re-forming with a hydroform. It is explanatory drawing which shows the process of forming the cross-sectional shape of this invention member by shape | molding one board | plate material by bending or press work, welding edge parts, and re-forming by roll forming. It is explanatory drawing which shows the process of forming the cross-sectional shape of this invention member by shape | molding two board | plate materials by bending or press work, and joining a flange part by a drill screw, a volt | bolt, a rivet, welding, or adhesion | attachment. It is explanatory drawing which shows the process of shape | molding a seamless pipe with a hydroform and forming the cross-sectional shape of this invention member. It is explanatory drawing which shows the process of shape | molding a seamless pipe by roll forming and forming the cross-sectional shape of this invention member. The relationship between the C value and the minimum secondary radius r _min of the thin hollow columnar member whose longitudinal and transverse lengths are 60 mm and 100 mm and the plate thickness is 4.0 mm (ie, π / t = 80), respectively. It is a graph to show. A graph showing the relationship between the C value and the energy absorption amount E of a thin-walled hollow columnar member having a longitudinal length and a transverse length of 60 mm and 100 mm, and a plate thickness of 8.0 mm (that is, π / t = 80), respectively. is there. The relationship between the C value of the thin hollow columnar member having the longitudinal and transverse lengths of 60 mm and 100 mm and the plate thickness of 8.0 mm (ie, π / t = 40) and the minimum secondary radius r _min It is a graph to show. A graph showing the relationship between the C value and energy absorption amount E of a thin-walled hollow columnar member having a longitudinal length and a transverse length of 60 mm and 100 mm, respectively, and a plate thickness of 8.0 mm (ie, π / t = 40). is there. It is explanatory drawing of the corner part A located on the intersection of the straight lines which extended the outer periphery of the convex part of the thin hollow columnar member which formed the convex part which is a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Metal hollow columnar member 2 Corner part 3 Recessed part 4 Part 5 Shoulder end point

Claims (3)

A hollow columnar member made of high-tensile steel of 590 MPa or higher for a hollow shock absorbing member having a corner portion at four corners and having a substantially rectangular cross-sectional shape including the corner portion and forming a closed cross-section,
At least one of the four sides has one or more dents, and the ratio Lmin / Lmax between the minimum side length Lmin and the maximum side length Lmax in the cross section is multiplied by the total number N of ridge lines in the cross section. The C value (= N (Lmin / Lmax)) obtained in this way is 10 or more and 40 or less, the entire circumference of the closed section is π, the member thickness t is 1.6 mm or less, and the ratio π / t is A hollow columnar member made of high-tensile steel of 590 MPa or more for impact absorbing members, which is 160 or more and has a flange portion on the outside of two corner portions or on the outside between two opposing sides.
However, the side length and the total number of ridge lines are defined as follows.
Side length: The side length of the recessed portion located in the middle of one side is a distance obtained by connecting the shoulder end points of adjacent convex portions with a straight line.
The side length of the convex portion at the end of one side is the linear distance from the shoulder end point located on the side opposite to the end of the convex portion to the end.
The side length of the convex portion located in the middle of one side is the linear distance between the shoulder end points on both sides of the convex portion.
Total ridges:
The total number of straight lines when the vertices with the curvature removed in a closed section are connected by straight lines. The use is for automobiles, and the hollow columnar member made of high-tensile steel of 590 MPa class or higher for shock absorbing member according to claim 1. 3. A method for producing a high-tensile steel hollow columnar member of 590 MPa class or higher for an impact absorbing member according to claim 1 or 2, wherein two plate members are formed by bending or pressing, and the flange portion is formed by a drill screw or bolt. A method for producing a hollow columnar member made of high-tensile steel of 590 MPa or more for impact absorbing members, characterized by being joined by rivets, welding or adhesion.