Energy-absorbing structure

• US 20030127841A1
• Filed: 02/20/2003
• Published: 07/10/2003
• Est. Priority Date: 11/21/1998
• Status: Active Grant

• Current Assignee: Cellbond Limited
• Original Assignee: Cellbond Limited
• Inventors: Ashmead, Michael
• Granted Patent: US 6,908,143 B2
• Time in Patent Office: Days
• US Class Current: 280/751
• CPC Class Codes: F16F 7/121 the members having a cellular, e.g. honeycomb, structure

Abstract

A method of making an energy-absorbing structure in the form of a sheet having a pattern of alternating front and rear projections in front of and behind a median plane with each projection having an end face, a pitch region spaced from the end face, and a transition region therebetween including varying at least one parameter of the structure from the group consisting of local variation in sheet thickness in the pitch region, local variation in slope in the pitch region, geometry of the end face and geometry of the transition region, analyzing the energy absorption characteristics of the structure in response to the variation of the or each parameter, selecting the value of the or each parameter which gives a desired absorption characteristic and making a structure with the selected values of the or each parameter.

Claims

1. A method of making an energy-absorbing structure in the form of a sheet having a pattern of alternating front and rear projections in front of and behind a median plane with each projection having an end face, a pitch region spaced from the end face and a transition region therebetween comprising:

(a) varying at least one parameter of a structure selected from the group consisting of local variation in sheet thickness in the pitch region, local variation in slope in the pitch region, geometry of the end face and geometry of the transition region;

(b) analysing the energy absorption characteristics of the structure in response to the variation of the at least one parameter;

(c) selecting the value of the at least one parameter which gives a desired absorption characteristic; and

,

(d) making an energy-absorbing structure with the selected values of the at least one parameter.

2. The method of making an energy-absorbing structure of claim 1, further comprising:

varying the geometry of the end face by forming an indentation therein.

3. The method of making an energy-absorbing structure of claim 1, further comprising:

varying the geometry of the transition region such that when absorbing impact energy, the projection deforms by a traveling hinge deformation mechanism.

4. The method of making an energy-absorbing structure of claim 3, further comprising:

setting the pitch region at an angle of at least 80°

to the median plane.

5. The method of making an energy-absorbing structure of claim 1, further comprising:

introducing at least one line or region of weakness into the pitch region of at least one projection.

6. The method of making an energy-absorbing structure of claim 5, further comprising:

providing at least one groove in a surface of a projection to form the at least one line of weakness.

7. The method of making an energy-absorbing structure of claim 6, further comprising:

providing a pattern of alternating grooves on both rear and front surfaces of a projection.

8. The method of making an energy-absorbing structure of claim 6, further comprising:

configuring each groove to have a depth of approximately one-tenth of the thickness of each projection.

9. The method of making an energy-absorbing structure of claim 5, further comprising:

forming at least one ridge or step in a surface of the pitch region to define the at least one line of weakness.

10. The method of making an energy-absorbing structure of claim 5, further comprising:

providing a series of holes to define the at least one line of weakness.

11. The method of making an energy-absorbing structure of claim 5, further comprising:

providing at least one slot to define the at least one line of weakness.

12. The method of making an energy-absorbing structure of claim 5, further comprising:

controlling the thickness of the sheet in the pitch region to form at least one thinned region which defines the at least one region of weakness.

13. The method of making an energy-absorbing structure of claim 12, wherein the at least one thinned region has a thickness less than half the thickness of the rest of the sheet.

14. The method of making an energy-absorbing structure of claim 5, further comprising:

introducing the at least one line or region of weakness into the pitch region such that when absorbing impact energy, the projection deforms by buckling in the pitch region.

15. The method of making an energy-absorbing structure of claim 14, wherein the at least one line or region of weakness substantially encircles the projection.

16. The method of making an energy-absorbing structure of claim 5, further comprising:

introducing at least one line of weakness which extends radially from a central axis of the projection.

17. The method of making an energy-absorbing structure of claim 1, further comprising:

selecting the value of the at least one parameter so that the structure absorbs energy in such a way as to provide a plateau at a predetermined level in the stress-deformation curve.

18. The method of making an energy-absorbing structure of claim 16, further comprising:

selecting the value of the at least one parameter to extend the plateau in the stress-deformation curve.

19. The method of making an energy-absorbing structure of claim 1, further comprising:

selecting the value of the at least one parameter so that the structure has a stress-deformation curve such that for increasing deformation, the stress rises to a peak and then falls away substantially until densification effects come into play.

20. The method of making an energy-absorbing structure of claim 1, wherein the making step (d) comprises:

moulding the structure to have the selected parameters.

21. An energy-absorbing structure comprising:

a sheet having a pattern of alternating front and rear projections in front of and behind a median plane wherein each projection comprises an end face;

a pitch region spaced from the end face; and

,

a transition region between projections wherein at least one line or region of weakness is formed in the pitch region of at least one projection, to obtain a desired energy absorption characteristic.

22. The energy absorbing structure of claim 21, wherein the at least one projection comprises a plurality of lines of weakness.

23. The energy absorbing structure of claim 21, wherein the form of the at least one line of weakness is selected from the group consisting of a ridge in a surface of the pitch region, a continuous groove in a surface of the pitch region, a series of holes extending through the surface of the pitch region and a slot extending through the pitch region.

24. The energy absorbing structure of claim 23, wherein the form of the at least one line of weakness comprises a pattern of alternating grooves on both rear and front surfaces of a projection.

25. The energy absorbing structure of claim 23, wherein the form of the at least one line of weakness comprises a continuous groove in a surface of the pitch region and wherein each groove has a depth of approximately one-tenth of the thickness of each projection.

26. The energy absorbing structure of claim 21, further comprising at least one thinned region which defines at least one region of weakness.

27. The energy absorbing structure of claim 26, wherein the at least one thinned region has a thickness less than half the thickness of the rest of the sheet.

28. The energy absorbing structure of claim 21, wherein the at least one line or region of weakness in the pitch region causes buckling in the pitch region as the respective projection deforms when absorbing impact energy.

29. The energy absorbing structure of claim 28, wherein the at least one line of weakness substantially encircles the projection.

30. The energy absorbing structure of claim 21, wherein the at least one line or region of weakness in the pitch region causes a plateau at a predetermined level in the stress-deformation curve upon energy absorption by the structure.

31. The energy absorbing structure of claim 30, wherein the at least one line or region of weakness extends the plateau in the stress-deformation curve.

32. The energy absorbing structure of claim 22, wherein the plurality of lines of weakness extend radially from a central axis of the at least one projection.

33. The energy absorbing structure of claim 21, having a stress-deformation curve such that for increasing deformation, the stress rises to a peak and then falls away substantially until densification effects come into play.

39. A vehicle comprising an energy absorbing structure of claim 21.

34. An energy-absorbing structure comprising:

a sheet having a pattern of alternating front and rear projections in front of and behind a median plane wherein each projection comprises an end face;

a pitch region spaced from the end face; and

,

a transition region between the end face and the pitch region wherein at least one of the end face and the transition region are configured such that upon energy absorption, the sheet deforms by a traveling hinge deformation pattern, whereby a desired energy absorption characteristic is obtained.

35. The energy absorbing structure of claim 34, wherein the end face comprises an indentation configured to produce traveling hinge deformation.

36. The energy absorbing structure of claim 34, wherein the transition region has a sharp transition from the pitch region to the end face.

37. The energy absorbing structure of claim 36, having a pitch region at an angle of at least 80°

to the median plane.

38. The energy absorbing structure of claim 37, having a pitch region at an angle of at least 85°

to the median plane.