JP2003056617A - Impact energy absorption structure member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize lightness, and minimize a reaction force peak caused just after a collision when applied is, for example, to an automotive structural member. SOLUTION: This impact energy absorption structure member comprises a metallic tube 2 of a substantially circular or polygonal sectional form, and a porous body 3 collapsible while maintaining a constant reaction force when loaded with a compressive stress. The porous body 3 is foamed body consisting of foam metal, and the porous body 3 coats the periphery of the tube 2 about the axis.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an impact energy absorbing structural member used as a structural member of an automobile, for example, to absorb impact energy at the time of a collision and to absorb the impact.

[0002]

2. Description of the Related Art Conventionally, as a member similar to the above-mentioned impact energy absorbing structural member, there is, for example, one in which a portion surrounded by an aluminum frame of a vehicle body is filled with aluminum foam.

This utilizes the characteristics of aluminum foam which has a plateau region that deforms while exhibiting a substantially constant reaction force during compression deformation. The plateau region is controlled by controlling the material and density of this aluminum foam. Is set to an appropriate value, the frame is stably buckled and deformed at the time of a collision, and the collision energy from the front part of the vehicle is efficiently absorbed (Japanese Patent Laid-Open No. 8-164869).

As another impact energy absorbing structural member, for example, there is one shown in FIG. 13, which has a hollow portion 100a of a tubular body 100 and a foamed aluminum 10 formed therein.
The amount of absorbed energy due to buckling deformation at the time of collision is increased by filling 1 (JE Sie).
bels, "Derivation of Mater"
als energy absorption re
qualitys from crash situ
ation ”, Metal Foams and Po
rous Metal Structures, Ed.
by J. Banhart, M .; F. Ashby, N .;
A. Flick MIT Verlag, 1999).

Here, this impact energy absorbing structural member
FIG. 14 shows the relationship between the average reaction force and the amount of collapse in (C). Figure 1
As can be seen from FIG. 4, in this impact energy absorbing structure member, the average reaction force at the time of buckling deformation of the member is increased and the amount of absorbed energy is increased, as compared with the aluminum tube alone (D) also shown in FIG. ing. The amount of absorbed energy at this time is
It is equal to or more than the sum of the absorbed energy amount of the aluminum tube alone and the absorbed energy amount of the foam aluminum 101 alone. That is, it has been proved that the amount of absorbed energy is increased by filling the hollow portion of the metal tubular body with the porous body.

[0006]

However, aluminum foam 10 is formed in the hollow portion 100a of the conventional tubular body 100.
In the impact energy absorbing structural member of the type filled with 1, the amount of absorbed energy is increased, but the weight is increased due to the fact that the entire foam aluminum 101 is filled. Increasing the wall thickness of the tubular body 100 itself rather than filling 100 is more effective in increasing the amount of absorbed energy per unit mass of the member, that is, it is not effective in reducing the mass of the member. there were.

Further, the impact energy absorbing structural member has a problem that a reaction force peak C1 in which the reaction force immediately after a collision becomes significantly large occurs, as in the case of a single metallic tube. Solving these problems has been a conventional problem.

[0008]

SUMMARY OF THE INVENTION The present invention has been made by paying attention to the above-mentioned conventional problems, and it is possible to realize weight reduction. For example, when it is used as a structural member of an automobile, a reaction that occurs immediately after a collision occurs. It is an object of the present invention to provide an impact energy absorbing structure member capable of suppressing a force peak as small as possible.

[0009]

According to a first aspect of the present invention, there is provided a shock energy absorbing structural member which comprises a metal tube having a substantially circular or polygonal cross section and a compressive stress applied thereto. It is characterized in that it has a porous body that collapses while maintaining a constant reaction force, and has a structure in which the circumference around the axis of the tubular body is covered with a porous body. This is a means for solving the above-mentioned conventional problems.

According to a second aspect of the impact energy absorbing structural member of the present invention, the density of the porous body is 30% or less of the density of the porous body material, and the porous body maintains a constant anti-compatibility when a compressive stress is applied. The force is 0.5% or more of the strength of the metal tube, the mass ratio of the porous body to the metal tube is 1/2 or less, and the thickness of the porous body is from the axial center of the tube to the porous body. It is configured to be 15% or more of the distance to the outer surface.

In the impact energy absorbing structural member according to claim 2 of the present invention, the reason why the density of the porous body is set to 30% or less of the density of the porous body material is that the porous body is When compressive stress is applied, the porous body no longer spreads in the direction orthogonal to the compressive stress loading direction (Masahisa Otsuka Translated "Cell structure" Uchida Old Crane Field), so the metal tube buckles. This is because even when the porous body is deformed and bent outward of the closed cross section, the porous body can be compressed within the cross section of the member without expanding in the circumferential direction of the cross section of the member.

In the impact energy absorbing structural member according to the second aspect of the present invention, the constant reaction force maintained by the porous body under compressive stress is limited to 0.5% or more of the strength of the metallic tube. The reason for this is that by limiting in this way, when the metal pipe body bends to the outside of the closed cross section due to buckling deformation, the metal pipe is compressed by the reaction force when the porous body is compressed in the member cross section. This is because the bending of the body can be controlled.

Further, in the impact energy absorbing structure member according to claim 2 of the present invention, the reason why the mass ratio of the porous body to the metal tube body is 1/2 or less is that the unit mass per member is This is because it is possible to increase the absorbed energy capacity of the porous body to that of a metal tubular body alone, and further, the thickness of the porous body is 15% or more of the distance from the axial center of the tubular body to the outer surface of the porous body. The reason for doing this is that by defining the thickness of the porous body in this way, when the metal tube bends to the outside of the closed cross section due to buckling deformation, the porous body exerts a constant stress in the member cross section. This is because the metal tube can be collapsed while being maintained and the bending of the metal tube body can be controlled.

The impact energy absorbing structural member according to the present invention has, as claim 3, a structure in which a porous body that covers the periphery of the axial center of the tubular body is continuous in the surrounding direction. The porous body covering the periphery of the body has a discontinuous portion in the surrounding direction, and this discontinuous portion has a breaking strength higher than the tensile strength of the porous body itself, such as bonding or brazing. It is configured to be joined by means.

According to a fifth aspect of the impact energy absorbing structural member of the present invention, the porous body is formed of foamed aluminum, foamed magnesium, foamed iron, polyurethane foam or metal.
(Stainless steel, aluminum, etc.) A foamed body made of a foamed metal such as a fiber sintered body is used.
The foamed body made of foamed metal is foamed at the stage of covering the metal tube body and metallically joined to the periphery of the axis of the metal tube body.

According to a seventh aspect of the impact energy absorbing structural member of the present invention, the density distribution in the radial direction of the porous body covering the circumference of the metallic tube around the axis is monotonically increased toward the outside. And the average density of the porous body covering the circumference around the axis of the metal tubular body is 14 to 23% with respect to the density of the material constituting the porous body, and Radial density distribution toward the outside 1/2.
The configuration is such that the inclination is reduced by 5 or more.

The impact energy absorbing structural member according to the present invention has a structure used as a structural member for an automobile according to claim 9.

[0018]

Since the impact energy absorbing structural member according to the first to fifth aspects of the present invention has the above-mentioned structure,
For example, when used as a structural member of an automobile, the reaction force peak generated immediately after a collision is suppressed to be low, and the amount of absorbed energy per unit mass of the member is increased as compared with the case of a single metal tube body. In particular, in the impact energy absorbing structure member according to claim 2, when the metal tube bends outward due to buckling deformation in the closed cross section, the porous body is compressed in the member cross section. The bending force of the metal pipe body can be controlled by the reaction force.

Since the impact energy absorbing structural member according to claim 6 of the present invention has the above-mentioned structure, the foam made of the foam metal is prevented from moving in the axial direction and the peripheral direction of the metal pipe body. Therefore, in the impact energy absorbing structural member according to claim 7 of the present invention, since it has the above-mentioned configuration, the density gradient of the porous body covering the periphery around the axis of the metal pipe body (of the metal pipe body) If the density of the porous body that covers the circumference around the axis is larger outside the radial inside of the metal tube, it is defined as minus, and the density inside the radial direction is divided by the density outside). When is negative, the energy absorption amount increases as compared with the case where the porous body has no density gradient (when the density gradient is 1), and the impact energy according to claim 8 of the present invention. With absorbing structural member Since the above structure is adopted, when the density gradient of the porous body covering the periphery around the axis of the metal tubular body is positive and 2.5 or more, the density gradient is 1 and the porous body is uniform. The energy absorption amount increases as compared with the case of having the density.

Since the impact energy absorbing structural member according to claim 9 of the present invention is configured as described above, the impact energy can be efficiently absorbed without causing a large reaction force peak immediately after a vehicle collision. Become.

[0021]

Since the impact energy absorbing structural member according to claims 1 to 5 of the present invention has the above-mentioned structure, for example, when it is used as a structural member of an automobile, a reaction force peak generated immediately after a vehicle collision occurs. While keeping it as low as possible,
The amount of absorbed energy per unit mass of the member can be increased. Particularly, in the impact energy absorbing structural member according to claim 2, when the metal tube bends outward due to buckling deformation, the bending It has a very excellent effect of being able to control.

Since the impact energy absorbing structural member according to claim 6 of the present invention has the above-mentioned structure, it is possible to reliably prevent the foam made of the foam metal from moving in the axial direction and the peripheral direction with respect to the metal pipe body. It has a very excellent effect of being able to do.

Since the impact energy absorbing structural member according to claim 7 of the present invention has the above-mentioned structure, when the density gradient of the porous body covering the circumference of the metal tube body around the axis is negative, The energy absorption amount can be increased as compared with the case where the porous body does not have a density gradient, and the impact energy absorption structural member according to claim 8 of the present invention has the above-mentioned configuration, and therefore is made of metal. Compared with the case where the density gradient of the porous body covering the circumference around the axis of the tubular body is positive and 2.5 or more, the density gradient is 1 and the porous body has a uniform density. Therefore, it is possible to realize an increase in the amount of absorbed energy, which is a very excellent effect.

Since the impact energy absorbing structural member according to claim 9 of the present invention has the above-mentioned structure, the reaction force peak generated immediately after the vehicle collision is suppressed to a small level and the impact energy is efficiently absorbed. It has a very excellent effect that it is possible.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of a shock energy absorbing structure member according to the present invention.

As shown in FIG. 1, the impact energy absorbing structural member 1 is made of foamed aluminum (aluminum) around a shaft center of a tubular body 2 having a diameter of 60 mm and a length of 300 mm, which is formed from a 270 MPa class steel plate having a thickness of 1.6 mm. A porous body 3 is used for coating.

In this case, the foamed aluminum 3 covering the circumference around the axis of the tubular body 2 is continuous in the surrounding direction, and its thickness is constant in the longitudinal direction. Further, the foamed aluminum 3 is only placed in close contact with the tube body 2, and no joining means such as welding or adhesion is used. In addition, in order to prevent the foamed aluminum 3 exposed on the surface from being chipped, it is desirable to coat the foamed aluminum 3 with a resin or the like.

FIG. 2 shows the relationship between the average reaction force and the crush amount of the member when a mass body of 300 kg is collided with the impact energy absorbing structure member in the longitudinal direction at a velocity of 8 m / s. A has a constant stress in the plateau region of about 1.7.
The relationship between the average reaction force and the amount of crushing of a shock energy absorbing structural member formed by covering a steel pipe (tube) with a thickness of 10 mm of foamed aluminum having a density of 240 kg / m ³ which is set to MPa is shown. On the other hand, symbol B indicates the relationship between the average reaction force and the crush amount of the member in the case of a single steel pipe not including aluminum foam.

As can be seen from FIG. 2, the impact energy absorbing structural member according to the present invention exhibits a higher average reaction force than that of the steel pipe alone, and has a higher energy absorbing capacity than that of the steel pipe alone. . Further, the peak B1 of the average reaction force immediately after the collision, which is seen in the case of the steel pipe alone, hardly appears in the case of the impact energy absorbing structural member according to the present invention.

Therefore, the amount of absorbed energy per unit mass of the impact energy absorbing structure member of Example 1 shown in FIG. 1 and the impact energy absorbing structure member of Example 2 used in FIG. The results shown in are obtained. For comparison, Table 1 also shows the amount of absorbed energy per unit mass of the impact energy absorbing structural members according to Comparative Examples 1 to 6.

[0032]

[Table 1]

As can be seen from Table 1, in the impact energy absorbing structural member of Example 1 and the impact energy absorbing structural member of Example 2, as compared with Comparative Examples 1 and 2 which are steel pipes alone, per unit mass of the member The amount of absorbed energy of
That is, while maintaining the energy absorption capacity of the member,
It is possible to reduce the mass of the member.

On the other hand, in the impact energy absorbing structural member of Comparative Example 3, the density of the foam aluminum is set to 945 kg / m ³ so as to be about 35% of the density of aluminum,
In this case, the foamed aluminum is distorted in a direction other than the direction in which the stress is applied and expands in the circumferential direction of the member due to the buckling of the tubular body, resulting in the buckling mode of the tubular body. Comparative Examples 1 and 2 in which the steel pipe alone cannot be controlled.
Compared with the above case, the energy absorption amount of the member has not yet been increased.

Further, in the impact energy absorbing structural member of Comparative Example 4, the density of the foamed aluminum was set to 140 kg / m ^3, and the constant reaction force in the plateau region was set to about 0.5 MPa. Also in this case, The buckling mode of the tubular body can hardly be controlled by the foamed aluminum, and the energy absorption amount of the member has not yet been increased as compared with the cases of Comparative Examples 1 and 2 which are single steel tubes.

Furthermore, in the impact energy absorbing structural member of Comparative Example 5, the mass of foam aluminum is about 0.9 with respect to the mass of the steel pipe. In this case, the amount of energy absorbed by the member increases, but the mass of the member also increases. Since it greatly increases, the amount of energy absorbed per unit mass of the member has not been increased as compared with the cases of Comparative Examples 1 and 2 which are steel pipes alone.

Furthermore, in the impact energy absorbing structural member of Comparative Example 6, the thickness of the foamed aluminum is 2 mm, and in this case, the compression strain of the foamed aluminum in the circumferential direction of the member due to bending at the time of buckling of the steel pipe. Becomes large and it is impossible to maintain a constant reaction force when the foamed aluminum is compressed. Therefore, the buckling mode of the tubular body can hardly be controlled, and the energy absorption amount of the member has not been increased even compared with the cases of Comparative Examples 1 and 2.

In each of the impact energy absorbing structural members of Examples 1 and 2, the tubular body has a cylindrical shape with a diameter of 60 mm, but the cross-sectional shape of the metallic tubular body is square, rectangular, octagonal or the like. Even if it has a polygonal shape, the same effects as those of the impact energy absorbing structural members according to the first and second embodiments can be expected.

Next, a case where the impact energy absorbing structural member according to the present invention is used as a structural member for automobile will be exemplified.

As shown in FIG. 4, the impact energy absorbing structure member 11 is a front side member M of the vehicle body (see FIG. 3).
(Refer to (1)), the periphery of the tapered tubular body 12 around the axis is covered with the metallic porous body 13, and the axial movement of the metallic porous body 13 relative to the tapered tubular body 12 poses a problem. In such a case, the both are joined by joining means such as welding or adhesion.

In this impact energy absorbing structure member 11,
At the time of a vehicle front collision, the impact energy can be absorbed without causing a large reaction force peak immediately after the collision, and in addition, the absorbed energy amount per unit mass of the front side member M can be increased. .

FIG. 5 shows a case where the impact energy absorbing structural member according to the present invention is used as a bumper stay for fixing the front bumper FB of the vehicle.

As shown in FIG. 5, the impact energy absorbing structure member 21 is formed by covering the circumference of the metal tube 22 around the axis with a metal porous body 23. In No. 21, it is possible to efficiently absorb the impact energy by buckling as a bumper stay at the time of a vehicle frontal collision.

FIG. 6 shows a case where the impact energy absorbing structural member according to the present invention is applied to a burring edge portion of a door inner D of a vehicle.

As shown in FIG. 6, the impact energy absorbing structure member 31 includes a porous metal body 3 around the axis of a burring edge portion (tube body) 32 of a vehicle door inner D.
In this impact energy absorbing structure member 31, the buckling of the burring edge portion 32 is utilized in the impact energy absorbing structure member 31 so that the door inner efficiently absorbs the impact energy at the time of a side collision of the vehicle.

FIG. 7 shows a case where the impact energy absorbing structure member according to the present invention is applied to a rear side member of a vehicle body.

As shown in FIG. 7, the impact energy absorbing structure member 41 has a porous metal body around the axial center of the tapered tube body 42 located at the rear end of the rear side member RM (see FIG. 3) of the vehicle body. In this case as well, when the movement of the porous metal body 43 in the axial direction with respect to the tapered tubular body 42 poses a problem, the both are joined by a joining means such as welding or adhesion.

Even with this impact energy absorbing structural member 41, at the time of a vehicle rear surface collision, it is possible to absorb the impact energy without causing a large reaction force peak immediately after the collision, and, in addition, the unit of the rear side member RM. The amount of absorbed energy per mass can also be increased.

FIG. 8 shows a case where the impact energy absorbing structure member according to the present invention is attached to a dash panel P (see FIG. 3) of a vehicle.

As shown in FIG. 8, the impact energy absorbing structure member 51 has a metal porous body 53 covering the circumference of the axis of a metal tubular body 52 provided on a base plate 54. Plural pieces are arranged on the front surface of the dash panel P. By utilizing the buckling of the impact energy absorbing structure member 51, it is possible to efficiently absorb the impact energy at the time of a frontal collision of the vehicle.

FIG. 9 shows another embodiment of the impact energy absorbing structure member according to the present invention.

As shown in FIG. 9, the impact energy absorbing structure member 61 has a tubular body 62 made of aluminum, which is covered with a foamed aluminum 63 as a foamed material around the axial center thereof. Is the tube 62
Is foamed at the stage of coating and is metallically bonded to the periphery of the tube body 62 around its axis.

When the impact energy absorbing structure member 61 is manufactured, a cylindrical molding die 70 having a sufficient heat capacity is fitted in a tubular body 62 made of aluminum with a margin to form the tubular body 62 and the cylindrical molding die 70. After pouring the aluminum melted by adding the foaming material such as titanium hydroxide into the gap S formed between the two, the molten aluminum containing the foaming material is foamed and then sufficiently cooled. The foamed aluminum 63 is metallically joined to the circumference of the tubular body 62 around the axis.

When the molten aluminum is poured into the gap S, and there is a possibility that the tubular body 62 made of aluminum will soften and become bent, a jig having heat resistance inside the tubular body 62 will be used. It is desirable to insert.

In this impact energy absorbing structure member 61,
Aluminum tube 62 and aluminum foam 63
Since and are integrated, the aluminum foam 63 is prevented from moving in the axial direction and the circumferential direction of the tubular body 62.

FIG. 10 (a) shows another embodiment of the impact energy absorbing structural member according to the present invention, which is a foam for covering the periphery of the axis of the metallic tube 72 having a closed cross section. 7 shows a foamed aluminum 73, which has a density distribution in the radial direction.

FIG. 10 (b) is a view of the impact energy absorbing structural member 71 as seen from the axial direction, and shows a metal tube body 72 having a closed cross section and the axial center of the metal tube body 72. The foamed aluminum 73 covers the surroundings, and the foamed aluminum 73 is between the portion 73a close to the metal pipe body 72 and the portion 73b far from the metal pipe body 72 in the radial direction r of the pipe body 72. It is assumed that there is a density gradient.

FIG. 11 shows the relationship between the density distribution in the radial direction r of the metallic tube 72 in the foamed aluminum 73 and the energy absorption amount, and the horizontal axis shows the density gradient,
The vertical axis represents the energy absorption amount. The density gradient is defined as a minus when the density of the foamed aluminum 73 covering the periphery of the axis of the metal tubular body 72 is greater outside the radius r direction inner side of the metal tubular body 72, and the radius r It is the value obtained by dividing the density on the inside of the direction by the density on the outside.

As can be seen from FIG. 11, in the case of the foamed aluminum 73 as the porous body, when the density gradient is negative.
In (region 1), the amount of energy absorption increases as compared with the case where the porous body does not have a density gradient (when the density gradient is 1).

On the other hand, even when the density gradient of the foamed aluminum 73 covering the circumference around the axis of the metal tubular body 72 is positive and is 2.5 or more (region 2), the density gradient is 1 and the porosity is high. Compared to the case where the body has a uniform density,
Energy absorption increases.

FIG. 12 shows the experimental results. The thick solid line shows the case where the density gradient is uniformly 3, and the broken line shows the case where the porous body has a uniform density (density gradient 1). ing.

From FIG. 12, it can be seen that the member having the density gradient 3 increased the energy absorption amount by about 4% as compared with the member having the uniform density gradient 1.

[Brief description of drawings]

FIG. 1 is a perspective explanatory view showing an embodiment of a shock energy absorbing structure member according to the present invention.

FIG. 2 is a graph showing a relationship between an average reaction force and a crush amount when an impact load is applied to the impact energy absorbing structure member of FIG.

FIG. 3 is an overall perspective view showing a vehicle body in which the impact energy absorbing structure member according to the present invention can be used.

FIG. 4 is a perspective explanatory view (a) and a sectional explanatory view (b) showing a situation in which the impact energy absorbing structural member according to the present invention is applied to a front side member as a structural member for an automobile.

FIG. 5 is a perspective explanatory view (a) and an enlarged perspective explanatory view (b) showing a situation in which the impact energy absorbing structural member according to the present invention is applied to a bumper stay as a structural member for an automobile.

FIG. 6 is a perspective explanatory view showing a situation in which the impact energy absorbing structural member according to the present invention is applied to a burring edge portion of a door inner as a structural member for an automobile.

FIG. 7 is a perspective explanatory view showing a situation in which the impact energy absorbing structural member according to the present invention is applied to a rear side member as a structural member for an automobile.

FIG. 8 is a perspective explanatory view (a) and an enlarged perspective explanatory view (b) showing a state in which the impact energy absorbing structure member according to the present invention is attached to a dash panel of an automobile.

FIG. 9 is a perspective explanatory view showing a situation in which the impact energy absorbing structural member according to the present invention is manufactured using a molding die.

FIG. 10 is a perspective explanatory view (a) and a front explanatory view (b) showing an embodiment of the impact energy absorbing structural member according to the present invention.

FIG. 11 is a diagram showing a relationship between a radial density distribution of a metal tube body and an energy absorption amount in a porous body used for an impact energy absorption structure member according to the present invention.

FIG. 12 is a graph showing an experimental result of the impact energy absorbing structure member according to the present invention.

FIG. 13 is a perspective explanatory view showing a conventional impact energy absorbing structure member.

14 is a graph showing a relationship between an average reaction force and a crush amount when an impact load is applied to the impact energy absorbing structure member of FIG.

[Explanation of symbols]

1, 11, 21, 31, 41, 51, 61, 71 Impact energy absorbing structural member 2, 12, 22, 32, 42, 52, 62, 72 Tube body 3, 13, 23, 33, 43, 53, 63 , 73 Porous body

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hironori Sakamoto             Nissan, Takaracho, Kanagawa-ku, Yokohama-shi, Kanagawa Nissan             Inside the automobile corporation (72) Inventor Yu Makuji             Nissan, Takaracho, Kanagawa-ku, Yokohama-shi, Kanagawa Nissan             Inside the automobile corporation (72) Inventor Shigeo Watanabe             Nissan, Takaracho, Kanagawa-ku, Yokohama-shi, Kanagawa Nissan             Inside the automobile corporation F term (reference) 3J066 AA01 AA23 BA03 BB01 BC01                       BD05

Claims (9)

[Claims] 1. A tubular body comprising a metallic tubular body having a substantially circular or polygonal cross section and a porous body that collapses while maintaining a constant reaction force when a compressive stress is applied. An impact energy absorbing structural member characterized in that the periphery around the axis is covered with a porous body. 2. The density of the porous body is 30% or less of the density of the porous body material, and the constant reaction force maintained by the porous body under compressive stress is 0.5% or more of the strength of the metal tubular body. And the mass ratio of the porous body to the metal tube is 1/2 or less,
The impact energy absorbing structural member according to claim 1, wherein the thickness of the porous body is 15% or more of the distance from the axial center of the tubular body to the outer surface of the porous body. 3. The impact energy absorbing structural member according to claim 1 or 2, wherein a porous body covering the circumference of the tubular body around the axis is continuous in the surrounding direction. 4. A porous body covering a periphery of an axis of a tubular body has a discontinuous portion in an enclosing direction, and the discontinuous portion has a breaking strength higher than the tensile strength of the porous body itself. The impact energy absorbing structural member according to claim 1 or 2, which is joined by means. 5. The impact energy absorbing structural member according to claim 1, wherein the porous body is a foam made of foam metal. 6. The impact according to claim 5, wherein the foamed body made of foamed metal is foamed at the stage of covering the metal tube body and metallically joined to the periphery of the axis of the metal tube body. Energy absorbing structural member. 7. The impact according to claim 1, wherein the density distribution in the radial direction of the porous body covering the circumference around the axis of the metal tubular body is monotonically increased toward the outside. Energy absorbing structural member. 8. The average density of the porous body covering the periphery of the axis of the metal tube is 14 to 23% of the density of the material constituting the porous body, and the density distribution in the radial direction. The impact energy absorbing structural member according to any one of claims 1 to 7, wherein the impact energy absorbing structural member is reduced toward the outside with a slope of 1 / 2.5 or more. 9. The use as a structural member for automobiles according to claim 1.
9. The impact energy absorbing structural member according to any one of 1 to 8.