DE19858432A1 - Energy absorbent element for vehicle has a thin walled structure with a profiling for a controlled collapse under pressure - Google Patents

Abstract

An energy absorbent element e.g. for use in a vehicle, has a tubular structure between mounting flanges (4) and with a thin walled construction for a controlled crush effect. The thin wall is profiled with a cellular pattern of concave cells in a waffle pattern. The size and shape of the pattern is selected to provide a controlled crush resistance over the whole crush path. The magnitude of the crush resistance is greater w.r.t initial peak than is the case with smooth walls, providing a greater degree of energy absorption. The cells of the structure are bounded by zig-zag fold lines.

Description

The invention relates to an energy-absorbing deformation element according to the Preamble of claim 1.

Impact dampers and energy-absorbing carriers for vehicles are used for passive purposes Safety by joining you in an accident situation such as a frontal, angled or side crash Part of the kinetic energy of the vehicle by deforming and plasticizing the Pick up material. At the same time, they should be in normal, i.e. H. crash-free, driving operation have good dimensional stability. Thin-walled during axial deformation Crash elements from cylindrical flat materials or rectangular hollow profiles occurs first an excessive force peak, hereinafter called the initial force peak, before the flat material is then deformed by so-called fold bulges with significantly less force. This The initial force peak is limited by the fact that the deformation element already plastically deformed by the force shock during the axial crash before the plastic one Deformation of the side member of the vehicle, which is connected to the crash element, starts.

For the axial deformation of a thin-walled, smooth cylinder or a hollow profit the material is initially dimensionally stable because the force flow only in the direction of a wall, d. H. in Membrane direction, and the material becomes uniform, mainly through Compressive stress, loaded. This uniform loading of the thin wall causes the Wall can take up a significant axial load without plasticizing too to fail. This creates the initial force peak of a cylindrical wall or a hollow profile under axial load. If the axial load increases beyond this initial force peak, occur as a result of imperfection, for example an unavoidable lateral deflection the wall, the bending deformations of the material are so large that the thin wall becomes unstable, locally buckling and thereby losing a significant part of their axial rigidity. So the first dents appear in the originally flat wall. Solidify these first bumps through plastic collapse when the wall is further axially deformed.  

As a result, the wall becomes more dimensionally stable until a new point of instability occurs and a further axial bulge takes place in the flat wall. This process, which continues as the axial deformation progresses, is called fold bulges. The number of these bumps on the circumference of the cylindrical, thin wall is approximately 3 if the starting material is flat. In the case of rectangular or square, thin-walled hollow profiles, the geometrical dimension of the axial fold bulges corresponds approximately to the width of the hollow profile. The. The ratio of the average deformation force in the axial buckling of the folds to the initial force peak is approximately one third, for an originally flat wall.

A larger value of the ratio of the mean deformation force to the initial force peak can be achieved in principle in the axial deformation of a thin wall in that uses a corrugated or corrugated wall as the starting material. With a perpendicular to axial load corrugated or corrugated wall is the initial peak force at axial Deformation significantly lower than that of the flat wall because the structure is in the wall behave like imperfections and so an earlier buckling or plastic deformation of the Trigger wall. The disadvantage here, however, is that, for example, with these thin walls not only the initial force peak, but also the mean deformation force clearly is lower than on the flat wall. This results in a lower specific Energy absorption of walls structured in this way.

From VDI Reports No. 818, 1990, pages 187 to 207, ("Simulation of crash behavior of a car stem in the pre-development phase with a simplified FEM model ") an energy absorbing deformation element in the shape of a hat profile made of smooth Sheet with cover sheet known, in which an initial force peak of approx. 80 kN and then a buckling of folds with an average deformation force of about 25 to 30 kN at axial crash occur. This corresponds to a value of approximately 31 to 37% based on the Ratio of mean deformation force at buckling to the initial force peak.

From VDI Reports No. 818, 1990, pages 209 to 237, ("Targeted for Influence introduced geometrical imperfections on the deformation behavior of Longitudinal beam structures ") is a thin-walled hollow profile with a rectangular or square cross-section known, in which the axial folding of the front  Vehicle side members positive with the help of specifically introduced geometric imperfections being affected. The number of bumps increases in contrast to the smooth ones Vehicle side members, which have no targeted imperfections, and thus achieved you get a more even wrinkle. The result is about a third, in relation to the ratio of the average deformation force for buckling to the Initial power peak. This is unsuitable in practice.

The invention has for its object to improve the deformation elements. The is achieved with the features of the claims. The deformation element receives one high specific energy absorption, based on its deformation length. It will achieves that the crash element has a low initial force peak in relation to the middle one Has deformation force in the buckling of folds. Deformation elements with a large specific energy consumption, in which the average deformation force at plastic deformation is increased in relation to the initial force peak Deformation element has a large initial force peak based on its weight.

In particular, the structures of flat materials, especially the structure folds dent structured flat materials, arranged so that the structure folds partially oblique to Direction of the crash load. This causes the structure folds to deform when axial crash due to bending and shear deformations evenly. This is how it can be done spontaneously Partial buckling of the structured material caused by instabilities avoid.

As far as buckling structures are published, the publications contain no reference to the invention. In detail: in the German patent DE 43 11 978 C 1 A method for bulging thin walls and foils is described, in which thin Materials or foils wound in one or more layers on spaced support elements and from the outside by overpressure in a staggered dent structure with square dent folds is transferred. In this DE 43 11 978 C1 only the basic Energy-absorbing property of square, dented, thin flat materials hingcwicsch. Dabci fold the axial folds of the quadrilaterally bulged, cylindrical Material under axial load. More details regarding the  Energy absorption of square, dented, thin cylinder walls under the axial one Loads are not described in DE 43 11 978 C1. Furthermore, they are structured Known material webs, the regular, staggered, preferably hexagonal folding structures (European patent 0693008; PCT / EP96 / 01608) or heraldic folding structures (PCT / EP97 / 01465). Furthermore, there are multi-buckled material webs known in which larger dents are provided with smaller counter dents (DE 196 34 244 A1; DE 196 51 937 A1). In European patent 0693008, PCT / EP96 / 01608, PCT / EP97 / 01465, DE 196 34 244 Al and DE 196 51 937 A1 there are no indications or Information on energy absorption in the case of axial or predominantly axial plastic deformation of deformation elements.

The specific energy consumption in the case of plastic deformation according to the invention Elements in the form of square dented thin cylinders is under axial load not yet optimized because the axial buckling of square structured materials spontaneously buckle while the bulging folds arranged perpendicular to it bend slightly allow to squeeze.

Surprisingly, however, it has already been shown that the average deformation force at the axial, plastic deformation in relation to the initial force peak at high specific Energy intake can be increased by being structured, in particular Hexagonal or polyhedral dent-structured, thin walls as deformation elements uses, in which the structures, in particular the dent folds, preferably obliquely to Direction of the axial deformation force are aligned. Because the structure folds deformed mainly by bending and shear deformation, this becomes spontaneous Avoid buckling of the wall or at least reduced. In contrast to the minor mean deformation force for corrugated or corrugated deformation elements dent structured with preferably arranged obliquely to the direction of deformation Structural folds have a high mean deformation force, the value of which is comparable or only is slightly lower than that of the flat, d. H. not structured, Deformation element of the same wall thickness. However, since the flat deformation element is one significantly higher initial force peak compared to the dented deformation element has the same wall thickness, the wall thickness must be reduced until the predetermined permissible value of the initial force peak is reached. This will decrease  also the average deformation force and the specific energy absorption, based on the available deformation length of the element or the beam.

Another embodiment of the method according to the invention is hexagonal or heraldic or polyhedral bulged, thin webs of material transverse to it Direction of transport to round a cylinder or to a rectangular hollow profile to bend. For example, you turn a hexagonally textured material web whose zigzag Zack-shaped dent folds run in the direction of the material web, around 90 ° and round it across to. their direction of transport to a cylinder. This results in zigzag shapes Dent folds that are aligned in the axial direction of this cylinder. This zigzag shaped bulges deform evenly when the cylinder is axially loaded mainly due to bending deformation, and so there is a lower initial force peak and a uniform deformation force in the axial deformation of the cylinder. Instead of the hexagonal bulged material web can also be crest-shaped or otherwise polyhedral dent or similar using mechanical molding tools structured, thin walls for cylindrical deformation elements or beams come. The dent structuring is self-organizing or analogous to that of a Embossed with a hexagon, crest or polyhedral pattern. Can also for example, also hexagonal dent structured material webs transverse to the transport direction the material web are bent into four-sided or polygonal hollow profiles, in which the Bending folds preferably run in the direction of the zigzag-shaped, axial buckling folds. Similarly, structured open profiles, open shapes or shell elements can also be used are used. The zigzag-shaped folds contribute significantly to that the initial force peak is lower compared to the flat wall and that one gives more uniform deformation force.

A further embodiment of the method according to the invention is that the mean deformation force and the specific energy absorption of hexagonal or heraldic or polyhedral dent or with the help of mechanical Forming tools similarly structured, thin walls is further increased by the fact that the Structured walls have bumps with smaller counterbumps that can only be broken by one greater deformation force can be deformed axially, for example the zigzag  deform the axial buckling folds mainly by bending. The brace themselves Bumps that are stiffened geometrically and mechanically by the small counter dents are solidified against the larger dent folds and thus increase the deformation force at the axial deformation of the structured wall. Since at the same time the Initial force peak increases, bulged or mechanically structured walls that provide have small dents, not only as energy-absorbing deformation elements, but also as dimensionally stable supports or dimensionally stable walls. The The initial force peak of walls structured in this way can be approximately as high as that of the levels, d. H. unstructured wall of the same thickness. However, the values for the specific energy absorption and the bending stiffness higher than for the flat wall same thickness.

Another embodiment of the method according to the invention is that two or more dent or mechanically structured cylinders or hollow profiles or open ones Profiles are arranged one inside the other or next to one another, in which one of the cylinders or Profiles is slightly shorter than the others. As a result, only the longer cylinder or the longer profile deforms before the shorter element deformed. So it is possible to reduce the initial force peak so that it is almost has the same value as the mean deformation force. So one can Produce a deformation element whose ratio of average deformation force to Initial power peak is almost 1.

Another embodiment of the method according to the invention is that two or more bulged or mechanically structured cylinders or hollow profiles from different cross-section arranged centrally to each other and the space completely or partially with light material such as plastic or Filled with metal foam or fabric layers. Similarly, open profiles or open forms are filled with light material, and so there are multilayered Composite elements or blocks. The elements arranged inside or next to each other support each other and ensure not only in the event of an axial crash, but also high specific energy absorption even in the event of a side impact. These point improved rigidity at the same time. Come with dented or  mechanically structured walls with small counter dents are used Elements and beams that have both a high degree of structural rigidity and a high have specific energy absorption.

The idea of the invention is subsequently explained by way of example:

Fig. 1 shows schematically the side view and the cross section of a cylindrical, hexagonal structured deformation element with axial, zigzag structure folds.

Figure. 2 shows a schematic force-displacement diagram for the axial deformation of a cylindrical, hexagonal structured deformation element with axial, zigzag shaped structure folds.

Fig. 3 shows schematically the side view and the cross section of a cylindrical, hexagonal structured deformation element with circumferential, zigzag-shaped structural folds.

Fig. 4 shows a schematic force-displacement diagram for the axial deformation of a cylindrical, hexagonal structured deformation element with circumferential, zigzag structure folds.

Fig. 5 is a schematic force-path diagram showing the axial deformation of a cylindrical deformation element from initially flat material.

Fig. 6 is a schematic force-path diagram showing the axial deformation of three cylindrical, hexagonal structured deformation elements having different output lengths.

Fig. 7 shows schematically the top view of different geometric shapes of buckling structures.

Fig. 8 shows schematically the top view of hexagonal and coat-of-arms structured, thin walls with smaller counterbumps.

Fig. 1 shows a side view and in cross section of the basic structure of a cylindrical, hexagonal structured deformation element with axial, zigzag structure folds 1 for applying the method according to the invention. The folds 2 are arranged in the circumferential direction of the cylinder. During the axial deformation, predominantly the zigzag-shaped folds 1 bend, and the bulging domes 3 bulge deeper. The two flanges 4 stabilize the cylinder above and below. The number of structures on the circumference is 4 to 16, preferably 6 to 9. An analog number of

FIG. 2 shows a schematic force-displacement diagram for the axial deformation of a cylindrical, hexagonally bulged deformation element with axial, zigzag-shaped structural folds 1 in FIG. 1. The initial force peak 5 is only slightly higher than the deformation force 6 . The ratio of the average deformation force to the initial force peak can assume the values 40% to 80%, preferably 55% to 65% and is determined in particular by the structure depth, size and geometry and material.

Figure. 3 shows a side view and in cross section of the basic structure of a cylindrical, hexagonal structured deformation element with circumferential, zigzag structural folds 7 . The axial structure folds 8 can be shorter or longer than the structure folds of a symmetrical hexagon. Shorter axial structure folds behave stiffer in the axial deformation, and so a larger number of structure traps can be arranged on the deformation element. Longer axial structure folds can buckle more easily. The circumferential, zigzag-shaped structural folds 7 predominantly bend without buckling, and the bulging domes 9 bulge in the process.

FIG. 4 shows a schematic force-displacement diagram for the axial deformation of a cylindrical, hexagonally bulged deformation element with circumferential, zigzag-shaped structural folds 7 in FIG. 3. The initial force peak 10 is higher than the deformation force 11 . The ratio of average deformation force to the initial force peak can assume the values 35% to 75%, preferably 45% to 55%.

FIG. 5 shows a schematic force-displacement diagram for the axial deformation of a cylindrical, flat, ie originally not structured deformation element. The initial force peak 12 is approximately three times higher than the mean value of the deformation force 13 .

Fig. 6 shows a schematic force-displacement diagram for the axial deformation of three cylindrical, hexagonal dent structured deformation elements, which are arranged one inside the other, in which one of the cylinders is slightly longer than the others. In FIG. 6, the three cylinders 14, 15, arranged side by side schematic table 16. In the axial deformation, only the longer cylinder 14 is initially deformed axially before the shorter cylinders 15 and 16 also deform. It is thus possible to reduce the initial force peak 17 to such an extent that it is only slightly higher than the mean deformation force 18 . A deformation element can thus be produced, the ratio of the average deformation force to the initial force peak almost reaching the value 1. A deformation element with two cylinders arranged one inside the other behaves analogously to this. With three cylinders of different lengths arranged one inside the other, a force-displacement diagram can be obtained which even has a progressive course.

Shown in FIG. 1 to FIG. 6 illustrated cylindrical deformation elements and force-path diagrams can be analogously also be transferred to four or more rectangular hollow sections.

Fig. 7 shows schematically the plan view of different geometric shapes of a hexagonal 19, hexagonal 90 ° rotated 20, crest-shaped 21, crest-shaped rotated by 90 ° and about 22 diamond-shaped Beulstruktur 23rd The approximately diamond-shaped structure 23 has further advantages in that its zigzag-shaped folds are longer than the other two folds, and there are more zigzag-shaped folds on the cylindrical deformation element. So you can increase the number of axial, zigzag structural folds that are mainly stressed on bending in the axial deformation.

FIG. 8 schematically shows the top view of a hexagonal structured, thin wall 24 or crest-shaped, bulge-structured, thin wall 25 , in which the bulges are arranged with smaller counterbumps 26 and 27 . The smaller counterbumps 26 and 27 stiffen the structured wall and thus hinder the large structural folds in the axial deformation of the deformation element. As a result, the mean deformation force of structured walls with smaller counterbumps increases considerably, with the initial force peak also increasing somewhat. This results in a higher specific energy absorption in relation to the weight of the deformation element. The ratio of average deformation force to the initial force peak can assume the values 35% to 80%, preferably 60% to 70%.

Since the initial force peak of walls structured in this way almost corresponds to the initial force peak of the planes Wall can reach the same thickness, offer dent structured or mechanically structured  Walls that have small counter dents, not only as energy-absorbing ones Deformation elements, but also as dimensionally stable supports or as dimensionally stable walls Benefits.

Analogous to Figs. 1 to FIG. 8, the number of structures on the periphery of the deformation elements, such as cylinders, hollow or open profiles, the value of 4 to 16, preferably 6 to 9. This number preferably corresponds to the number of bulge structures on the circumference, which result in a self-organizing manner on a cylinder or on a curved shell or by means of an embossing which is predetermined analogously. For passenger vehicles, for example, the material thicknesses of structural elements made of steel structured in this way have the values 0.4 mm to 1.5 mm, preferably 0.7 mm to 1.2 mm, and aluminum has the values 0.4 mm to 2.5 mm, preferably 0 , 8 mm to 1.8 mm. The geometric dimensions of the structures have the values 16 mm to 60 mm, preferably 30 mm to 45 mm.

The values for the material thicknesses of deformation elements for buses and trucks etc. are higher and corresponding to the kinetic energy of the vehicle to be absorbed are preferably adapted to the larger buckling structures in such a way that Self-organization or analogously by stamping the hexagonal, coat of arms, Set diamond-shaped or polyhedral structures in the wall.

Claims (27)

1. Deformation element made of a thin material web, in particular with a profiling and for vehicle construction or for the construction industry, characterized in that the material web is provided with a buckling structure, the individual buckling folds being partially oblique to the direction of deformation and the bumps between the folds being a depression have. 2. Deformation element according to claim 1, characterized in that the dents have round and / or angular structure. 3. Deformation element according to claim 2, characterized by a rotated square or hexagonal or further polyhedral dent structure or a dent structure in Coat of arms or diamond shape. 4. Deformation element according to claim 2 or 3, by a symmetrical and / or asymmetrical dent structure and / or an elongated dent structure. 5. Deformation element according to one of claims 1 to 4, characterized by a Buckling structure with folds, which are partly in the longitudinal direction of the web and / or partly Extend transversely to the longitudinal direction of the web and / or an oblique to the longitudinal direction of the web Sequence of the dents. 6. Deformation element according to claim 5, characterized by a zigzag shape running wrinkles. 7. Deformation element according to one of claims 1 to 6, characterized by the same and / or different dents.   8. Deformation element according to one of claims 1 to 7, characterized in that at least individual bumps are provided with a counter bump. 9. Deformation element according to one of claims 1 to 8, characterized by embossed and / or self-organizing bumps or embossing of bumps, whose dimensions correspond to self-organizing bumps. 10. Deformation element according to one of claims 1 to 9, characterized by several Material web layers. 11. Deformation element according to claim 10, characterized in that the Material web layers are close to each other or a distance from each other have. 12. Deformation element according to claim 11, characterized in that the cavities are at least partially filled and / or the web layers are attached to one another. 13. Deformation element according to claim 12, thereby using a resilient Filling material and / or a fabric insert or intermediate layer 14. Deformation element according to claim 13, characterized by the use of Plastic foam or metal foam as filling material. 15. Deformation element according to one of claims 1 to 14, characterized in that the web material is bent and / or folded. 16. Deformation element according to claim 15, characterized by a hollow shape or Pipe shape or cylindrical shape or a block shape. 17. Deformation element according to claim 16, by open or closed forms and / or edges and / or curves in the direction of deformation and / or oblique and / or across it.   18. Deformation element according to claim 16 or 17, characterized in that the Hollow forms is seamless or has a welded seam. 19. Deformation element according to one of claims 10 to 18, characterized in that with different material web layers at least two layers in the direction of deformation have a different length. 20. Deformation element according to one of claims 17 to 19, characterized by at least one stabilizing flange. 21. Deformation element according to one of claims 1 to 20, by sequential arrangement and / or juxtaposition with other deformation elements. 22. Deformation element according to one of claims 1 to 21, characterized in that the number of dents lying side by side in the circumferential direction on a hollow mold is at least four and / or at most 16. 23. Deformation element according to claim 22, characterized in that the number is at least 6 and / or at most 9. 24. Deformation element according to one of claims 1 to 23, characterized by the Use steel for the sheeting with a thickness of at least 0.4 mm and / or at most 1.5 mm for passenger cars and / or the use of Aluminum for the sheet material with a thickness of 0.4 mm to 2.5 mm for Passenger cars. 25. Deformation element according to claim 24, characterized by a thickness of at least 0.7 mm and / or at most 1.2 mm for steel and by a thickness of at least 0.8 mm and / or at most 1.8 mm for aluminum. 26. Deformation element according to one of claims 1 to 25, characterized by a Diameter or length or width dimension of the dents of at least 16 mm and / or at most 60 mm.   27. Deformation element according to claim 26, characterized by a diameter or Length or width dimension of the dents of at least 30 mm and at most 45 mm.