GB2089464A

GB2089464A - Energy Absorbing Structure

Info

Publication number: GB2089464A
Application number: GB8110795A
Authority: GB
Original assignee: Ford Motor Co Ltd; Ford Motor Co
Current assignee: Ford Motor Co Ltd; Ford Motor Co
Priority date: 1980-12-15
Filing date: 1981-04-07
Publication date: 1982-06-23

Abstract

An energy absorbing structure suitable for example for use in a motor vehicle body panel to absorb impact loads comprises a wall having a plurality of corrugations extending in a longitudinal direction corresponding to the expected direction of an applied load, and at least one reinforcement extending transversely to the corrugations. The dimensions of the corrugations and the position of the reinforcement is arranged so that the wall undergoes progressive collapse under impact loads. <IMAGE>

Description

SPECIFICATION Energy Absorbing Structure This invention relates to energy absorbing structures.

Energy absorbing structures are used in assemblies which are susceptible to impact loads to control the amount of damage suffered by the assembly or to protect the occupants or contents thereof. For example energy absorbing structures are incorporated in motor vehicles to absorb impact energy and thereby reduce the risk of injury to passengers; in containers for cargo to protect the cargo from damage by impact loads; and in air landing pallets to absorb ground impact loads when the pallet has been dropped from an aircraft, thereby protecting the load carried by the pallet.

In a paper presented by Porsche at the 8th International Technical Conference on Experimental Safety Vehicles in Wolfsburg in October 1 980 there is disclosed a vehicle body panel supporting a front road wheel suspension assembly and incorporating two plane parallel tubes arranged longitudinally of the vehicle. The tubes collapse under longitudinal impact loads thereby absorbing the energy of the impact load and reducing the amount of damage suffered by the rest of the vehicle.

We have observed that in energy absorbing structures which include a wall which is designed to buckle or fold under impact loads, thereby absorbing energy, the buckling or folding usually proceeds in a relatively uncontrolled manner, particularly where the wall is not in the form of a tube. For example the wall may form an initial fold which then acts as a hinge around which the whole structure can then bend. After such large scale bending of the structure has started to occur the structure offers little resistance to the applied load and the amount of additional energy absorbed by the structure is relatively small.

According to the present invention there is provided an energy absorbing structure comprising a wall having a plurality of corrugations therein extending in a longitudinal direction, and at least one reinforcement secured to the wall and extending transversely to the corrugations. By providing appropriate longitudinal spacing between the or each reinforcement and the ends of the wall and by choosing appropriate dimensions for the corrugations, the structure undergoes a progressive collapse, without bending, when a load is applied thereto in the longitudinal direction.

The precise spacing of the or each reinforcement in relation to the ends of the wall, and the precise dimensions of the corrugations used will depend upon the material used for the wall, and the thickness and shape of the wall.

However, the optimum spacing and the dimensions can easily be established by routine experiment.

Preferably the corrugations each include at least one longitudinally extending ridge. For example the corrugations may be generally Ushaped or, preferably, V-shaped.

The wall of the structure may be of any shape.

For example it may be tubular or alternatively it may be planar or curved. In general however the corrugations should extend along straight lines in the direction in which an impact load is expected to be applied.

The reinforcements may generally take the form of straps. Where the wall is tubular, the reinforcement may be in the form of a plate extending diametrically across the tube.

Any deformable material may be used for the wall. In some cases where only light compact loads are expected, a flexible plastics material may be used. Where heavier loads are expected however, a metal would be more suitable.

Aluminium is a preferred metal in view of its light weight.

The invention is especially suitable, but not exclusively so, for use in motor vehicle body panels. For example the body panel may be in the form of a vehicle suspension mounting panel which in use is aligned in the fore-and-aft direction. In this case, the corrugations also extend in the fore-and-aft direction so that the structure absorbs frontal impact loads.

Alternatively, the body panel may comprise a motor vehicle floor pan, especially a rear seat support and the corrugations extend in the transverse direction of the vehicle so that the structure absorbs side impact loads.

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of a first energy absorbing structure in accordance with the invention; Figure 2 is a partial cross section of the structure of Figure 1 taken along line lI-Il; Figure 3 is a perspective view of the structure of Figures 1 and 2 under a load; Figure 4 is a perspective view of a structure not forming part of the present invention under a similar load to that illustrated in Figure 3.

Figure 5 is a perspective view of part of a second energy absorbing structure in accordance with the invention; Figure 6 is a partial cross-section of the structure of Figure 3 taken along line VI--VI Figure 7 is a perspective view of a third energy absorbing structure in accordance with the invention; and Figure 8 is a perspective view of the structure of Figure 7 after collapse under a load; Figure 9 is a perspective view of a first body panel of a motor vehicle incorporating a structure in accordance with the invention.

Figure 10 is a perspective view of a second body panel of a motor vehicle incorporating a structure in accordance with the invention; and Figure 11 is a perspective view of a container incorporating a structure in accordance with the invention.

Referring to Figures 1 and 2, an energy absorbing structure 1 comprises a wall 2 composed of a sheet metal such as aluminium.

The sheet is formed with a plurality of corrugations 3 which extend parallel to each other in a longitudinal direction. The corrugations may be formed by carrying out a series of bending operations on a flat blank of metal, or by passing the flat blank between two dies.

As best illustrated in Figure 2, the corrugations are generally U-shaped with inclined side walls so that each corrugation has two parallel ridges 4, 5 extending longitudinally along its length.

The wall 2 carries a set of spaced reinforcements in the form of straps 6 which are also made of aluminium. The straps extend transversely to the corrugations and are fixed in pairs opposite each other on either side of the wall by means of rivets 7. Alternatively the straps may be secured to the wall by welding or by a suitable adhesive such as an epoxide resin. The structure may be shaped to any desired curvature in the transverse direction, provided that the corrugations remain aligned along parallel straight lines.

If a longitudinal compressive load is applied to the structure in the direction of the arrows A (Fig.

1), it is found that, provided that the straps 6 are properly spaced in relation to each other and the ends of the wall and that the corrugations 3 are properly shaped, the structure collapses progressively from one end in the longitudinal direction.

The precise dimensions necessary to achieve this regular collapse will depend upon the thickness and nature of the material from which the wall 3 is composed, and are best determined by routine experiment. By way of example however, a structure in which the wall and straps are formed from 20 gauge aluminium sheet bent into the configuration shown in Figures 1 and 2, the distances a and b in Figure 2 being both 20 mm, and the angles 01 and 62 being both 300, and the straps are 2.5 cm wide and separated from each other and from the ends of the wall 3 by no more than 1 5 cm, has good collapse characteristics.

Figure 3 illustrates the behaviour of such a structure under such a load. It can be seen that each corrugation 3 folds into a large number of convolutions 8 whilst the structure 1 itself retains its generally longitudinal alignment without bending. Continued application of the load causes the folding to continue progressively along the structure past each of the straps 6 in turn. Since the formation of each successive fold in the wall required additional energy, the total amount of energy absorbed by the structure is extremely high.

Referring now to Figure 4, a structure 10 similar to that shown in Figure 2 is illustrated after having been loaded in a manner similar to that described with reference to Figure 3.

Although the structure 10 has corrugations 3 similar to the structure 2 of Figure 2, it has no reinforcing straps 6. It can be seen that the application of a compressive load in the direction of the arrow A causes bending of the structure generally about a central pivot region 11. Once such bending has started the structure offers a much smaller resistance to the load and rapidly collapses in an uncontrolled manner. The total energy absorbed by the structure is therefore substantially less than that absorbed by the structure of the invention.

Figures 5 and 6 illustrate an alternative structure in accordance with the invention in which the corrugations 3' are shaped similarly to that illustrated in Figures 1 and 2. The straps 6', 6' however are provided with tabs 12, 1 2 which project from the spine 13 of the straps 6' outwardly and downwardly into the channels between adjacent corrugations 3'. The straps may then be secured to the wall by riveting or welding at the ends of the tabs 12, as indicated at 14, and at the spine 13, as indicated at 1 5 in Figure 6.

Figures 7 and 8 illustrate a further alternative embodiment of the invention, before and after collapase under load. In this structure, the wall 2" is tubular with V-shaped corrugations 3" arranged axially. The reinforcements comprise hexagonal plates 1 5, 1 5 arranged diametrically across the interior of the tubular wall. The plates each have upstanding flanges 1 6 which are riveted to the corrugations as indicated at 1 7.

In this example the tube is 1 5 cm in diameter, the reinforcements 15, 1 5 and the walls 2" are composed of 20 gauge aluminium plate, the corrugations are formed with two 25 mm side walls inclined at 600 and the spacings between the two reinforcements and the ends of the tube are no greater than 15 cm.

Figure 8 illustrates the tube after having been collapsed. A compressive axial load in the direction of the arrow A of more than 68 kN is required to effect this collapse. As indicated in the drawings, the collapse occurs progressively on a controlled manner by the sequential formation of folds along the ridges 4" of the corrugations 3".

Figures 9 and 10 illustrate motor vehicle body panels incorporating energy absorbing structures in accordance with the invention. In Figure 9 the panel 19 is a mounting for a road wheel suspension arm illustrated schematically at 20.

The panel extends generally on the fore-and-aft direction of the vehicle and the forward part of the panel includes a corrugated sheet 25, the corrugations 26 of which are aligned parallel with the fore-and-aft direction. Straps 27 are secured to both forces of the sheet 25 in the manner described with reference to Figures 1 and 2. By suitably shaping the corrugations and spacing the straps 27, the panel 19 will collapse in a controlled manner on application of a frontal force indicated by the arrow 28.

In Figure 10 the panel 30 comprises a floor pan of a motor vehicle which is shaped to form the base of a rear seat in the vehicle adjacent a door aperture 31. The panel comprises corrugations 32 which extend transversely of the vehicle and straps 33' secured to both faces of the panel and extending at right angles to the corrugations. By suitably shaping the corrugations and spacing the straps 33, the panel will collapse in a controlled manner on application of a side load indicated by the arrow 34.

Figure 11 illustrates a container for a road or rail vehicle incorporating an energy absorbing structure in accordance with the invention. The container comprises a cylindrical tank 40 having a domed end 41 carrying two tubular structures 42, 43 in accordance with the invention mounted concentrically. Each structure 42, 43 comprises a set of axially extending corrugations 44 and circumferential straps 45. An end plate 46 is mounted on the ends of the energy absorbing structures 42, 43. By shaping the corrugations and spacing the straps 45 appropriately, the structures 42, 43 will collapse in a controlled manner on the application of an axial load in the direction indicated by the arrow 45, thereby protecting the tank 40 from damage.

Although the energy absorbing structures has been described in relation to road and rail vehicles it will be appreciated that the structures of the invention have many more possible uses.

Claims

1. An energy absorbing structure comprising a wall having a plurality of corrugations therein extending in a longitudinal direction and at least one reinforcement secured to the wall and extending transversely to the corrugations, the longitudinal spacing between the or each reinforcement and the ends of the wall and the dimensions of the corrugations being such that the wall undergoes a progressive collapse when a load is applied thereto in the longitudinal direction.

2. A structure according to claim 1 wherein the corrugations each include at least one longitudinally extending ridge.

3. A structure according to claim 1 wherein the corrugations are V-shaped.

4. A structure according to any one of Claims 1 to 3 wherein the wall is tubular.

5. A structure according to claim 4 wherein the reinforcement comprises a plate extending diametrically across the tube.

6. A structure according to any one of claims 1 to 4 wherein the reinforcement comprises a strap.

7. A structure according to any one of claims 1 to 6 wherein the wall is composed of aluminium.

8. A motor vehicle body panel incorporating a structure according to any one of claims 1 to 7.

9. A body panel according to claim 8 in the form of a suspension mounting which in use extends generally in the fore-and-aft direction of the vehicle, the corrugations extending in the fore-and-aft direction.

10. A body panel according to claim 8 in the form of a floor pan which in use extends generally in the transverse direction of the vehicle, the corrugations extending in the transverse direction.