Shock-absorbing member

Abstract

A shock absorbing member of the present disclosure is a shock absorbing member including a first hollow member (11) and a second hollow member (12) that are made of aluminum alloy and are weld joined to each other, in which a weld material and weld beads (W) do not project from a side on which a joined surface between the first hollow member (11) and the second hollow member (12) is located.

Claims

1. A shock absorbing member comprising: a first hollow member; and a second hollow member, wherein the first hollow member and the second hollow member are made of aluminum alloy and are joined to each other by a weld bead to form a joined surface that is used to receive shocks, the second hollow member has a step adjacent to the first hollow member that is receded from the joined surface, in a state before the joining of the first hollow member and the second hollow member, the step is open toward a front of the joined surface, a surface of an edge of an upper surface of the first hollow member and a surface of an edge of an under surface of the second hollow member are joined are each other in the step, and the weld bead does not project above the joined surface.

2. The shock absorbing member according to claim 1, wherein the second hollow member has a triangular cross-section, and the first hollow member and the second hollow member have surfaces flush with each other on a crash surface side.

3. The shock absorbing member according to claim 1, wherein at least one of the first hollow member or the second hollow member is formed of an extruded material.

4. The shock absorbing member according to claim 1, wherein the first hollow member is a bumper reinforcement, the second hollow member is a raised member, and the shock absorbing member constitutes a bumper structure.

5. The shock absorbing member according to claim 2, wherein at least one of the first hollow member or the second hollow member is formed of an extruded material.

6. The shock absorbing member according to claim 2, wherein the first hollow member is a bumper reinforcement, the second hollow member is a raised member, and the shock absorbing member constitutes a bumper structure.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a top view of a shock absorbing member in an embodiment of the present disclosure;

(2) FIG. 2 is a cross-sectional view of the shock absorbing member taken along the line X-X in FIG. 1;

(3) FIG. 3 is a top view of a bumper structure in a Comparative Example;

(4) FIG. 4 is a cross-sectional view of the bumper structure taken along the line X-X in FIG. 3;

(5) FIG. 5 is a top view of a bumper structure in another Comparative Example;

(6) FIG. 6 is a cross-sectional view of the bumper structure taken along the line X-X in FIG. 5; and

(7) FIG. 7 is a graph of load-stroke curves illustrating results of full-wrap crash analysis in Examples.

DESCRIPTION OF EMBODIMENTS

(8) Hereinafter, specific features of the present disclosure will be described based on an embodiment of the present disclosure.

(9) FIG. 1 is a top view of a shock absorbing member of the present disclosure, and FIG. 2 is a cross-sectional view of the shock absorbing member illustrated in FIG. 1.

(10) As illustrated in FIGS. 1 and 2, a shock absorbing member 10 of the present disclosure includes a first hollow member 11 and a second hollow member 12, both of which are made of aluminum alloy. In the present embodiment, as illustrated in FIG. 2, a surface of an edge of the upper surface of the first hollow member 11 and a surface of an edge of the under surface of the second hollow member 12 are joined to each other by welding. Therefore, a welding surface in this case is a surface defined by the surfaces of the edges and specifically means a joined surface indicated by the line A-A in FIG. 2.

(11) In the present embodiment, a step 16 is formed on the joined surface indicated by the line A-A. By welding between an edge of the upper surface of the first hollow member 11 and an edge of the under surface of the second hollow member 12 being performed in the step 16, the first hollow member 11 and the second hollow member 12 are weld-joined.

(12) Note that, in the drawing, a sign W represents at least one of weld material or weld beads.

(13) As described above, in the present embodiment, the step 16 is formed on the joined surface A-A between the first hollow member 11 and the second hollow member 12, and welding is performed in the step 16. Thus, the weld material and weld beads W never project forward of the shock absorbing member beyond the joined surface A-A. Therefore, even when a shock is applied to the shock absorbing member 10 from, for example, the front thereof, energy due to the shock becomes dispersed throughout the shock absorbing member 10 without concentrating on the weld material and weld beads W. As a result, it is possible to maintain strength and shock absorbency of the shock absorbing member 10 at a high level.

(14) The first hollow member 11 and the second hollow member 12 are made of aluminum alloy. Thus, it is possible to provide the shock absorbing member 10 the weight of which is reduced and thereby cope with environmental problems.

(15) As an aluminum alloy constituting the first hollow member 11 and the second hollow member 12, a general-purpose aluminum alloy, such as aluminum 1000 series alloy, aluminum 2000 series alloy, aluminum 3000 series alloy, aluminum 4000 series alloy, aluminum 5000 series alloy, aluminum 6000 series alloy, and aluminum 7000 series alloy, can be used.

(16) As a welding method for joining the first hollow member 11 and the second hollow member 12 to each other, a general-purpose method, such as arc welding, gas welding, electron beam welding, laser welding, MIG welding, and TIG welding, can be used.

(17) Further, in place of performing welding in the step 16, for example, a groove may be formed and welding may be performed in the groove in such a way that the weld material and weld beads W do not project forward beyond the joined surface A-A. Furthermore, in place of forming a step or a groove, the amount of weld material or strength of welding may be adjusted in such a way that the weld material and weld beads W do not project beyond the joined surface A-A.

(18) In the present embodiment, a cross-section of the second hollow member 12 is formed into a triangular shape, as is evident from FIG. 2. On the joined surface A-A side, in other words, on the front side of the shock absorbing member 10, that is, the crash surface side, in this case, the first hollow member 11 and the second hollow member 12 are configured to have surfaces flush with each other (surfaces including the joined surface A-A).

(19) Since the cross-sectional shape of the second hollow member 12 is formed into a triangular shape as described above, it is possible to reduce the weight of the second hollow member 12 by, for example, approximately 10%. Since the first hollow member 11 and the second hollow member 12 are configured to have surfaces flush with each other on the crash surface side, it is possible to make both the first hollow member 11 and the second hollow member 12 receive shock from the outside efficiently. Therefore, effective energy dispersion enables high strength and high shock absorbency to be achieved.

(20) At least either and preferably both of the first hollow member 11 and the second hollow member 12 are formed of an extruded material. Because of this configuration, each of the first hollow member 11 and the second hollow member 12 can be integrally formed in such a way as to have a desired cross-section, thereby having no joint portion. Therefore, it is possible to achieve the first hollow member 11 and second hollow member 12 of desired strength.

(21) In the present embodiment, when the first hollow member 11 and the second hollow member 12 are configured as a bumper reinforcement and a raised member, respectively, it is possible to construct the shock absorbing member 10 as a bumper structure. Therefore, it is possible to provide a bumper structure that has high strength and high shock absorbency and the weight of which is reduced and thus also possible to cope with environmental problems. However, the shock absorbing member 10 of the present embodiment is not limited to a bumper structure and can be used for any other member, such as a mechanical member and a jig, that is required to absorb shock.

EXAMPLES

(22) Although representative Examples of the present disclosure will be described below to clarify the present disclosure more specifically, it is needless to say that the present disclosure is not limited by the description of such Examples. It should be understood that, in addition to not only the following Example but also the specific description described above, various changes, modifications, improvements, and the like can be added to the present disclosure, based on knowledge of those skilled in the art without departing from the spirit of the present disclosure.

(23) A result of full-wrap crash analysis performed on a model of Inventive Example of the present disclosure and models of Comparative Examples that the configurations of which fall outside the scope of the present disclosure will be described below. Note that, in all the following analysis, the shock absorbing member 10 is constructed as a bumper structure including the first hollow member 11 and the second hollow member 12 as a bumper reinforcement and a raised member, respectively. In order to exhibit advantageous effects of Inventive Example of the present disclosure, a bumper structure that does not include a raised component (Comparative Example 1, see FIGS. 3 and 4) and a bumper structure in which weld material and weld beads W project forward beyond the joined surface A-A (Comparative Example 2, see FIGS. 5 and 6) were prepared as Comparative Examples.

(24) Regarding a material model in the FEM analysis, the bumper reinforcement was assumed to be formed of a 7000 series aluminum alloy extruded material the 0.2% proof stress of which is approximately 400 MPa. In addition, an energy absorbing member and the raised component were assumed to be formed of a 6000 series aluminum alloy extruded material the 0.2% proof stress of which is 180 MPa.

(25) For the FEM analysis, general-purpose finite element analysis software RADIOSS (registered trademark) was used. Constraint conditions at the ends of the energy absorbing member were defined in such a way as to, assuming a case where a single plate is installed by welding, represent a mode in which displacements and rotations other than those in a crushing direction are constrained and the energy absorbing member is thrust by a rigid body.

(26) Full-lap crash analyses were performed by use of the above-described software, and load-stroke curves were generated and are illustrated in FIG. 7.

(27) As illustrated in FIG. 7, it is revealed that, in Inventive Example of the present disclosure, the load rises rapidly and reaches a high load in a short stroke. In other words, it is revealed that it becomes possible to absorb energy due to shock earlier because the load rises at an initial stage of a stroke and the shock absorbing member 10 of the present disclosure thus has excellent strength and excellent shock absorbency as a bumper structure.

(28) On the other hand, in Comparative Example 1 in which no raised member is included, although the load actually rises rapidly and shows a similar tendency to the Inventive Example of the present disclosure, a maximum load is lower than that of the Inventive Example of the present disclosure. The reason for the result is considered to be that, in the Comparative Example 1, dispersion and absorption of energy due to shock is inferior to those in Inventive Example of the present disclosure because no raised member is included.

(29) In Comparative Example 2 in which the weld material and weld beads W project forward beyond the joined surface A-A, although a maximum load is actually similar to that in Inventive Example of the present disclosure, the load rises more slowly.

(30) In Comparative Example 2, weld material and the like project forward beyond the joined surface A-A. The reason for the above result is considered to be that, because of this structural feature, energy due to shock initially concentrates on the projections and is subsequently dispersed to and absorbed by the bumper reinforcement or the raised member.

(31) The foregoing describes some example embodiments for explanatory purposes. Although the foregoing discussion has presented specific embodiments, persons skilled in the art will recognize that changes may be made in form and detail without departing from the broader spirit and scope of the invention. Accordingly, the specification and drawings are to be regarded in an illustrative rather than a restrictive sense. This detailed description, therefore, is not to be taken in a limiting sense, and the scope of the invention is defined only by the included claims, along with the full range of equivalents to which such claims are entitled.

(32) This application claims the benefit of Japanese Patent Application No. 2018-105078, filed on May 31, 2018, the entire disclosure of which is incorporated by reference herein.

INDUSTRIAL APPLICABILITY

(33) A shock absorbing member according to the present disclosure is suitably used as a constituent member of a bumper for a vehicle, such as an automobile.

REFERENCE SIGNS LIST

(34) 10 Shock absorbing member 11 First hollow member 12 Second hollow member 16 Step W Weld material and weld beads