JP2009103140A - Manufacturing method for impact energy absorption member, and impact energy absorption member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method for an impact energy absorption member capable of certainly fixing a foamed metal body into a cylindrical hollow part in a conventional process in which the foamed metal body is filled in the cylindrical hollow part, and an impact energy absorption member. <P>SOLUTION: The foamed metal body 3 having a slightly larger cross section dimension than a cross section dimension of the hollow part 2 is press-fitted from an opening part side of the hollow part 2 of the cylindrical body 1 made of metal having a closed cross section while plastically deforming a surface layer part 4 of the foamed metal body 3. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention is used, for example, in structural members such as automobiles, railway vehicles, ships, etc., and when receiving a compression impact load at the time of collision, a method for producing an impact energy absorbing member that deforms and absorbs impact energy; The present invention relates to an impact energy absorbing member manufactured by the manufacturing method.

  As an impact energy absorbing member (crash box) that absorbs impact energy at the time of a car collision or the like, a steel hollow member having a closed cross section has been conventionally used. When this hollow steel member is subjected to compressive impact energy in the axial direction or the cross-sectional direction, it collapses and absorbs the impact energy. At this time, in order to absorb larger energy with a limited amount of deformation, it is effective to increase the size and thickness of the member. However, when these are increased, the volume and weight of the steel hollow member are increased, which is not preferable because the fuel efficiency is deteriorated and the damage to the collision partner at the time of collision is increased.

  In addition, by using a high-strength mild steel sheet (HITEN) instead of a mild steel sheet, an increase in the volume and weight of the steel hollow member is also suppressed, but the high-strength mild steel sheet has poor formability. There are also inconveniences such that the shape of the member is restricted and the molding process is increased.

  On the other hand, in recent years, foam metal such as foam aluminum having good recyclability has attracted attention and is actually used as an impact energy absorbing member (crash box). This crush box is made of a foam metal such as aluminum foam in a prismatic or cylindrical shape. In addition, this impact energy absorbing member is arranged so that its axial direction coincides with the collision direction, absorbs the collision energy by being crushed by the compressive stress at the time of collision, and impacts on the occupant, the structure, and the collision partner Is intended to decrease.

  However, there is a concern that there is a problem in strength as an impact energy absorbing member only by using such a foam metal such as foam aluminum, so that a hollow cylindrical metal body having a circular or rectangular cross-sectional shape is used. Patent Documents 1, 2, 3, 4 and the like have been proposed in which the part is filled with foam metal.

  Among these patent documents, the impact energy absorbing member described in Patent Document 1 is a hollow structural member filled with a molded body made of a porous metal (foam metal) such as foam aluminum, In order to securely bond the structural member and the porous metal, a foamed resin is filled in a gap between the structural member and the porous metal to form a foamed resin layer.

  Thus, it seems that the use of the foamed resin layer makes it possible to reliably fill and fix the molded body made of a porous metal such as foamed aluminum inside the hollow structural member. However, there is a possibility that a foamed resin layer in which the foaming rate is not necessarily the same in all parts may be formed due to the difference in surface tension due to the wide and narrow gaps and the uneven temperature distribution inside the hollow structural member. Moreover, there is a possibility that the axial center of the structural member and the porous metal may be shifted due to the difference in the foaming rate. Therefore, there is a concern that the performance assumed as the impact energy absorbing member may not be exhibited. Furthermore, it is necessary to prepare a material different from a metal called foamed resin, and there is a problem that an extra process is required for preparation up to the manufacturing operation and manufacturing itself, which requires labor.

  In addition, the impact energy absorbing member described in Patent Document 2 includes a tubular body having a substantially circular or polygonal cross-sectional shape, and a foam metal filled in a hollow portion of the tubular body. The compression molding is performed in advance by applying compressive forces in two directions orthogonal to each other on a plane perpendicular to the axial compressive force received by the tubular body.

  According to claim 9 of this Patent Document 2, after filling the hollow portion of the tube with foam metal, the compressive force in two directions orthogonal to each other on the plane perpendicular to the axial compressive force received by the tube is obtained. In addition, there is a description that compression molding is applied to the foam metal, and with this configuration, it seems that the foam metal can be reliably filled and fixed in the hollow portion of the tubular body. However, the foam metal when the foam metal is press-fitted into the hollow portion of the tube body is in an unstable state in the hollow portion of the tube body, and the foam metal is subjected to compression molding in a state of being temporarily supported in the hollow portion of the tube body. There is a problem that it has to be done and requires a lot of work.

  Further, Patent Documents 3 and 4 also describe an impact energy absorbing member formed by filling a hollow portion of a metal cylindrical body with a foam metal body, but the metal cylinder of the foam metal body is described. No particular attention was paid to fixing the body to the hollow part.

JP 2003-28224 A Japanese Patent Laid-Open No. 2005-199737 JP-A-8-164869 JP-A-11-59298

  The present invention has been made in order to solve the above-described conventional problems, and the hollow of the metal cylindrical body is maintained in the conventional manufacturing process in which the foamed metal body is filled into the hollow portion of the metal cylindrical body. It is an object of the present invention to provide a manufacturing method of an impact energy absorbing member capable of reliably fixing a foam metal body into a part. It is another object of the present invention to provide an impact energy absorbing member capable of reliably fixing a foam metal body into a hollow portion of a metallic cylindrical body and capable of reliably exhibiting assumed performance. .

  The invention according to claim 1 is a method of manufacturing an impact energy absorbing member in which a hollow metal metal body having a closed cross section is filled with a foam metal body. Impact energy absorption, characterized in that, from the opening side, the foam metal body having a cross-sectional dimension slightly larger than the cross-sectional dimension of the hollow part is press-fitted while only the surface layer portion of the foam metal body is plastically deformed. It is a manufacturing method of a member.

  In the invention according to claim 2, the thickness dimension of the cross section of the foam metal body before press-fitting is 0.1% to 3.0% larger than the thickness dimension of the cross section of the hollow portion of the cylindrical body. The impact energy absorbing member manufacturing method according to claim 1.

  The invention described in claim 3 is characterized in that the difference between the thickness dimension of the foam metal body before press-fitting and the thickness dimension of the hollow portion of the cylindrical body are substantially the same in the entire circumference. It is a manufacturing method of the described impact energy absorption member.

  According to a fourth aspect of the present invention, when the metal foam body is press-fitted into the hollow portion of the cylindrical body, only the surface layer portion of the metal foam body is compressed and sheared. It is a manufacturing method of the impact energy absorption member in any one of claim | item 3.

Claim invention of claim 5, wherein the average density of the metal foam body after the press-fitting, which is a 0.1g ^/ cm ³ ~0.7g / cm 3 except the surface layer portion which is plastically deformed It is a manufacturing method of the impact energy absorption member in any one of Claim 1 thru | or 4.

  According to a sixth aspect of the present invention, the metal foam body is heated to a temperature equal to or lower than its melting point, and then press fit into the hollow portion of the cylindrical body, followed by a shrink fit to cool. Item 6. A method for producing an impact energy absorbing member according to Item 5.

  The invention according to claim 7 is characterized in that after the metal foam body is press-fitted into the hollow portion of the cylindrical body, a cold fit is performed to cool to a cryogenic temperature. It is a manufacturing method of the impact energy absorption member as described above.

  The invention according to claim 8 is characterized in that the inner surface of the cylindrical body is formed in an uneven shape, the inner surface of the cylindrical body and the outer surface of the metal foam body press-fitted into the hollow portion of the cylindrical body, The impact energy absorbing member manufacturing method according to any one of claims 1 to 7, wherein the impact energy absorbing member is fixed with an adhesive.

  According to the ninth aspect of the present invention, after the metal foam body is press-fitted into the hollow portion of the cylindrical body, a heat source is irradiated from the outer surface side of the cylindrical body, and the inner surface of the cylindrical body and the foamed body The method for manufacturing an impact energy absorbing member according to any one of claims 1 to 7, wherein an outer surface of the metal body is welded.

  The invention according to claim 10 is characterized in that after the metal foam body is press-fitted into the hollow portion of the cylindrical body, the cross-sectional area of the hollow portion of the cylindrical body is reduced. It is a manufacturing method of the impact energy absorption member in any one of.

  The invention according to claim 11 is an impact absorbing member formed by filling a hollow portion of a metal cylindrical body having a closed section with a foam metal body, and the foam metal body has a density of a surface layer portion thereof. The impact energy absorbing member is characterized in that the density is larger than the inner density of the surface layer portion.

  According to the manufacturing method of the impact energy absorbing member according to claim 1 of the present invention, the metal cylindrical body of the metal cylindrical body remains in the conventional manufacturing process in which the metal foam is filled into the hollow portion of the metal cylindrical body. The foam metal body can be reliably fixed in the hollow portion. In addition, since the foam metal body can be reliably filled while maintaining its axis, the manufactured impact energy absorbing member can reliably exhibit the assumed performance.

  According to the manufacturing method of the impact energy absorbing member according to claim 2 of the present invention, the press-fitting into the metal foam body into the hollow portion of the metallic cylindrical body can be reliably performed without a large load. In addition, the foam metal body can be reliably filled and fixed in the hollow portion of the metal cylindrical body.

  According to the method for manufacturing an impact energy absorbing member according to claim 3 of the present invention, since the foam metal body can be surely press-fitted while maintaining its axis, the manufactured impact energy absorbing member ensures the assumed performance. Can be demonstrated.

  According to the method for manufacturing an impact energy absorbing member according to claim 4 of the present invention, a large frictional resistance is imparted between the inner surface of the metal cylindrical body and the metal foam body due to compression and shear deformation. Stable energy absorption characteristics can be exhibited without exhibiting an unstable buckling mode.

  According to the method for producing an impact energy absorbing member according to claim 5 of the present invention, when the foam metal body is press-fitted, the cell structure of the foam metal body other than the surface layer portion can be press-fit without being damaged, and the produced impact energy. The absorbing member can reliably exhibit the assumed performance.

  According to the method for producing an impact energy absorbing member according to claim 6 of the present invention, due to shrink fitting, the metallic cylindrical body contracts with its thermal expansion coefficient, so that a contracting force can be imparted to the foam metal body, Filling and fixing of the foam metal body into the hollow portion of the metallic cylindrical body can be made more reliable.

  According to the manufacturing method of the impact energy absorbing member according to claim 7 of the present invention, the metal cylindrical body contracts with its thermal expansion coefficient due to the cold fit, so that the contraction force can be applied to the foam metal body, Filling and fixing of the foam metal body into the hollow portion of the metallic cylindrical body can be made more reliable.

  According to the method for producing an impact energy absorbing member of claim 8 of the present invention, filling and fixing of the foam metal body into the hollow portion of the metal cylindrical body can be further ensured by the adhesive.

  According to the manufacturing method of the impact energy absorbing member of claim 9 of the present invention, the filling and fixing of the metal foam body into the hollow portion of the metal cylindrical body can be further ensured by welding.

  According to the method for manufacturing an impact energy absorbing member according to claim 10 of the present invention, filling and fixing of the foam metal body into the hollow portion of the metal cylindrical body by reducing the cross-sectional area of the hollow portion of the cylindrical body, Furthermore, it can be ensured.

  According to the impact energy absorbing member of the eleventh aspect of the present invention, the foam metal body can be reliably fixed in the hollow portion of the metal cylindrical body, and the density of the foam is increased only in the surface layer portion. In this case, since the fixing can be surely performed, the assumed performance of the impact energy absorbing member itself can be surely exhibited.

  Hereinafter, the present invention will be described in more detail based on embodiments and drawings.

  1 shown in FIG. 1 is a metal cylindrical body. The cylindrical body 1 is a closed cross-section member having a circular cross section formed of, for example, an aluminum alloy, steel, or the like, and the inside thereof is a hollow portion 2. Reference numeral 3 denotes a foam metal body having a uniform cell structure, which is a columnar member formed by foaming pure aluminum or an aluminum alloy containing Zn, Mg or the like. The impact energy absorbing member A is manufactured by press-fitting the foam metal body 3 into the hollow portion 2 of the cylindrical body 1.

  As described above, the impact energy absorbing member A is manufactured by press-fitting the foam metal body 3 into the hollow portion 2 of the cylindrical body 1, but the press-fitted foam metal body 3 is formed by a uniform cell structure. Therefore, the press-fitting can be easily performed without applying a particularly large force. The press-fitting of the metal foam body 3 is performed as described below.

  First, the cylindrical body 1 and the metal foam body 3 are prepared. The outer diameter of the metal foam body 3 before being press-fitted into the hollow portion 2 of the cylindrical body 1 is 0.1% to 3.0% larger than the inner diameter of the cylindrical body 1, that is, the diameter of the hollow portion 2. And Of course, since the cross-sectional shape of the hollow part 2 of the cylindrical body 1 and the cross-sectional shape of the metal foam body 3 are both circular, the difference in diameter (thickness dimension) is substantially the same over the entire circumference.

  The foam metal body 3 is press-fitted from one opening side of the hollow portion 3 of the cylindrical body 1, but the surface layer portion 4 of the foam metal body 3 is press-fit while being plastically deformed during press-fitting. . Although the detail is shown in FIG. 2, the outer surface of the metal foam body 3 will be pressed by the cylindrical body 1, and only the surface layer part 4 will be crushed by compression and shear deformation. At that time, the cell structure inside the surface layer portion 4 of the metal foam body 3 is press-fitted without being crushed. In FIG. 2, a compression / shear deformation region is shown as 5.

The average density of the metal foam body 3 before the press ^fit, if ^{0.1g / cm 3 ~0.7g / cm 3} , an average density of the portion excluding the surface layer portion 4 of the metal foam body 3 after the press-fitting, may be the same 0.1g ^/ cm ³ ~0.7g ^/ cm 3 and before press-fitting. By setting the metal foam body 3 to this average density, it is possible to produce an impact energy absorbing member A that can reliably absorb impact energy at the time of a car collision or the like. In addition, if the average density of the metal foam body 3 is less than 0.1 g / cm ³ , it does not make sense as the impact energy absorbing member A, and if it exceeds 0.7 g / cm ³ , the metal foam body 3 The press-fitting into the cylindrical body 1 becomes very difficult.

  In the above description, the outer diameter of the metal foam body 3 before press-fitting is described as being 0.1% to 3.0% larger than the inner diameter of the cylindrical body 1, but the difference is less than 0.1%. If there is, the filling and fixing of the metal foam body 3 press-fitted into the cylindrical body 1 will be insufficient. On the other hand, if the difference exceeds 3.0%, it is difficult to press-fit the foam metal body 3 into the cylindrical body 1 or impossible to press-fit.

  As mentioned above, although one Embodiment of this invention was described based on FIG.1 and FIG.2, the cross-sectional shape of the cylindrical body 1 and the foam metal body 3 does not necessarily need to be circular, for example, is a rectangle etc. Also good. When these cross-sectional shapes are rectangular, the inner diameter of the cylindrical body 1 (the diameter of the hollow part 2) and the outer diameter of the foamed metal body 3 are the thickness dimension of the hollow part 2 and the thickness dimension of the foamed metal body 3, respectively. It can be explained by replacing.

  Hereinafter, various other manufacturing methods of the present invention different from the manufacturing method of the impact energy absorbing member A will be described.

  First, in the first manufacturing method, the foam metal body 3 before press-fitting is heated to a temperature equal to or lower than the melting point of the metal foam body 3 (or lower than the solid phase line when the metal foam body 3 is an alloy). The heated metal foam body 3 is press-fitted into the hollow portion 2 of the cylindrical body 1 and, after completing the press-fitting, is cooled by shrink fitting. Due to this shrinkage fitting, the metallic cylindrical body 1 contracts with its thermal expansion coefficient, so that it is possible to impart a contracting force to the foamed metallic body 3 and foam into the hollow portion 2 of the metallic cylindrical body 1. The filling and fixing of the metal body 3 can be made more reliable.

  In another manufacturing method, after the metal foam body 3 is press-fitted into the hollow portion 2 of the cylindrical body 1, it is cooled to an extremely low temperature (−123 ° C.) in an atmosphere of liquid nitrogen (−195.8 ° C.). Perform a fit. Due to this cold fitting, the metallic cylindrical body 1 contracts with its thermal expansion coefficient, so that a shrinking force can be applied to the foamed metallic body 3, and foaming into the hollow portion 2 of the metallic cylindrical body 1 is achieved. The filling and fixing of the metal body 3 can be made more reliable.

  In a further different manufacturing method, first, fine irregularities are formed on the inner surface of the cylindrical body 1. By fixing the inner surface of the cylindrical body 1 and the outer surface of the foam metal body 3 press-fitted into the hollow portion 2 of the cylindrical body 1 with an adhesive, the hollow body 2 into the hollow portion 2 of the cylindrical body 1 is fixed. The filling and fixing of the metal foam body 3 is made more reliable. As the adhesive, a liquid adhesive may be applied in advance to the outer surface of the foam metal body 3 before press-fitting, or a hot melt sheet-like structural adhesive is foamed before press-fitting. The outer surface of the metal foam 3 is bonded to the inner surface of the cylindrical body 1 by wrapping around the outer surface of the metal body 3 in advance and dissolving the adhesive by means such as irradiating a heat source after press-fitting. It may be a thing.

  Further, in another manufacturing method, after the metal foam body 3 is press-fitted into the hollow portion 2 of the cylindrical body 1, a heat source is irradiated from the outer surface side of the cylindrical body 1, thereby performing arc welding and laser welding, The outer surface of the foam metal body 3 is welded to the inner surface of the body 1. By this welding, filling and fixing of the foam metal body 3 into the hollow portion 2 of the cylindrical body 1 is further ensured.

  Furthermore, in another manufacturing method, after the metal foam body 3 is press-fitted into the hollow part 2 of the cylindrical body 1, the hollow area 2 of the cylindrical body 1 is reduced by reducing the cross-sectional area of the hollow part 2 of the cylindrical body 1. The filling and fixing of the metal foam body 3 to the inside is further ensured.

  As a method for reducing the cross-sectional area of the hollow portion 2 of the cylindrical body 1, (1) compressive deformation from the outer surface side of the cylindrical body 1, extrusion deformation, roll rolling, etc. A method for reducing the cross-sectional area of the hollow portion 2 of the cylindrical body 1, (2) a cylindrical tube 1 into which the foam metal body 3 is press-fitted is subjected to a contraction tube by electromagnetic forming, and an even load is instantaneously applied from the circumferential direction. A method of reducing the cross-sectional area of the hollow portion 2 of the cylindrical body 1 by applying, (3) a material that reduces the volume of the cylindrical body 1 by phase transformation below the melting point of the foamed metal body 3, for example, There is a method of reducing the cross-sectional area of the hollow portion 2 of the cylindrical body 1 by using a Ni—Ti-based shape memory alloy and heating below the melting point of the metal foam body 3.

The cylindrical body and the metal foam body used in this example are as described below. The cylindrical body is formed of a closed cross-section member having a circular cross section formed of 5502-H34 aluminum alloy. The plate thickness is 1 mm, the inner diameter is 80 mm, and the axial dimension is 200 mm. On the other hand, the foam metal body is a cylindrical body formed by foaming pure aluminum, and has a density of 0.24 g / cm ³ , an outer diameter of 80.5 mm, and an axial dimension of 200 mm. That is, the outer diameter of the metal foam body is 0.5 mm larger than the inner diameter of the cylindrical body.

  The foam metal body having the above configuration is press-fitted into the hollow portion of the cylindrical body. This press-fitting was gradually performed at a speed of 5 mm / min using a model universal testing machine (model number: 4200, load capacity: 5 ton) manufactured by Instron. The average load at the time of press fitting was about 20 kN.

  Formed by inserting a foam metal body produced by the above-mentioned method by press-fitting a foam metal body into a cylindrical body, and inserting a foam metal body having an outer diameter of 80 mm into a cylindrical body having an inner diameter of 80 mm. The test specimen (Comparative Example 1), the specimen (Comparative Example 2) made of the foam metal body having an outer diameter of 80 mm, and the specimen (Comparative Example 3) made of the cylindrical body having an inner diameter of 80 mm A static compression test was performed to examine the influence of the following factors on the energy absorption of each specimen when the axial dimension of each specimen was deformed to 50% (100 mm).

  Factors affecting the improvement of the energy absorption amount of each specimen are (a) the cylindrical body itself, (b) the foam metal body itself, (c) the effect of inserting the foam metal body into the cylindrical body, ( d) It is thought that there are four types of restraining force imparting effects due to press-fitting a large-diameter metal foam into the cylindrical body. FIG. 3 shows the contribution ratios of the factors that have influenced the amount of energy absorption of each specimen.

  Since Comparative Example 2 is a single foam metal body and Comparative Example 3 is a single cylinder body, factors that affect the amount of energy absorbed by each specimen are (a) the tubular body itself or (b) foam body. Only the metal body itself.

  On the other hand, in Comparative Example 1 and Examples, a plurality of factors affect the improvement of the energy absorption amount of each specimen. In Comparative Example 1, in addition to (a) the cylindrical body itself, (b) the foam metal body itself, (c) the effect of inserting the foam metal body into the cylindrical body has an effect on the improvement of the energy absorption amount of the specimen. It is exerting. In the example, (d) the restraint force imparting effect by press-fitting a large-diameter foam metal body into the cylindrical body affects the improvement of the energy absorption amount of the specimen.

  According to FIG. 3, in the example, (c) the effect of inserting the foam metal body into the cylindrical body and (d) the effect of imparting the restraining force by press-fitting the large-diameter foam metal body into the cylindrical body, respectively. The contribution rate that affected the improvement of the energy absorption amount of the specimen was substantially the same, and the energy absorption amount of the example was (d) larger than the energy absorption amount of Comparative Example 1 (d) It can be seen that the restraining force imparting effect due to the press-fitting of the foam metal body is improved to about 1.4 times. In this embodiment, the outer diameter of the metal foam body is 0.5 mm larger than the inner diameter of the cylindrical body, but if the difference is further larger than 0.5 mm (however, only the surface layer portion of the metal foam body is As long as it is crushed by the deformation and the inner cell structure is not crushed), the amount of energy absorption can be further improved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows an embodiment of the present invention, and is a perspective view before a metal foam body is filled in a hollow portion of a cylindrical body. FIG. 4 is an enlarged vertical cross-sectional view of a main part in a state where the hollow metal part is filled with a foam metal body, showing the same embodiment. It is explanatory drawing which shows the contribution rate of each factor which affects the energy absorption amount of each specimen.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Cylindrical body 2 ... Hollow part 3 ... Foam metal body 4 ... Surface layer part A ... Impact energy absorption member

Claims (11)

A method for producing an impact energy absorbing member formed by filling a hollow metal metal body having a closed cross section with a foam metal body,
From the opening side of the hollow part of the cylindrical body, the foam metal body whose cross-sectional dimension is slightly larger than the cross-sectional dimension of the hollow part is press-fitted while only the surface layer part of the foam metal body is plastically deformed. A method for producing an impact energy absorbing member.   2. The thickness dimension of the cross section of the metal foam body before press-fitting is 0.1% to 3.0% larger than the thickness dimension of the cross section of the hollow portion of the cylindrical body. The manufacturing method of the impact energy absorption member of description.   3. The impact energy absorbing member according to claim 2, wherein a difference between the thickness dimension of the metal foam body before being press-fitted and the thickness dimension of the hollow portion of the cylindrical body is substantially the same in the entire circumference. Method.   4. When the metal foam body is press-fitted into the hollow portion of the cylindrical body, only the surface layer portion of the metal foam body is compressed / shear-deformed. 5. A method for producing an impact energy absorbing member. The average density of the metal foam body after the press-fitting, one of claims 1 to 4, characterized in that it is 0.1g ^/ cm ³ ~0.7g / cm 3 except the surface layer portion which is plastically deformed The manufacturing method of the impact energy absorption member as described in any one of.   6. The shrink-fitting is performed according to claim 1, wherein the metal foam body is heated to a temperature equal to or lower than its melting point, and then press-fitted into the hollow portion of the cylindrical body and then cooled. A method for producing an impact energy absorbing member.   The impact energy absorbing member according to any one of claims 1 to 5, wherein after the metal foam body is press-fitted into the hollow portion of the cylindrical body, a cold fit for cooling to a cryogenic temperature is performed. Manufacturing method.   The inner surface of the cylindrical body is formed in an uneven shape, and the inner surface of the cylindrical body and the outer surface of the metal foam body press-fitted into the hollow portion of the cylindrical body are fixed with an adhesive. The manufacturing method of the impact energy absorption member in any one of Claim 1 thru | or 7.   After the metal foam body is press-fitted into the hollow portion of the cylindrical body, a heat source is irradiated from the outer surface side of the cylindrical body to weld the inner surface of the cylindrical body and the outer surface of the metal foam body. The method for manufacturing an impact energy absorbing member according to any one of claims 1 to 7.   The impact energy according to any one of claims 1 to 9, wherein after the metal foam body is press-fitted into a hollow portion of the cylindrical body, a cross-sectional area of the hollow portion of the cylindrical body is reduced. Manufacturing method of absorbent member. A shock absorbing member formed by filling a hollow portion of a metal cylindrical body having a closed cross section with a foam metal body,
The metal foam body has an impact energy absorbing member characterized in that the density of the surface layer portion is larger than the density inside the surface layer portion.

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