Method for manufacturing an acoustic element of a sound absorption structure from at least one sheet of material
A method for manufacturing an acoustic element of a sound absorption structure including at least one cylindrical, conical or truncated conical chamber obtained from a flat preform shaped and then assembled in order to obtain the cylindrical, conical or truncated conical shape of the chamber. This manufacturing method makes it possible to obtain an acoustic element that has thin walls and is made from a material suited to its environment. An acoustic element obtained using the manufacturing method, a sound absorption structure comprising at least one such acoustic element and an aircraft powerplant comprising at least one such structure are also described.
1. A method for manufacturing an acoustic element of a sound absorption structure comprising at least one chamber having a cylindrical, conical or truncated conical shape, wherein the method comprises:
cutting at least one preform out of a plate or sheet of material;
shaping the preform by rolling;
assembling two side edges of the preform to obtain the cylindrical, conical or truncated conical shape of the chamber; and
cutting at least one series of slits in the flat preform, before the shaping said preform.
2. The manufacturing method according to claim 1 , wherein the slits are approximately positioned in planes containing the axis of rolling of the preform when said preform is shaped and extend from a curved edge of the preform.
3. The manufacturing method according to claim 1 , wherein the slits extend from a concave curved edge of the preform and define first tabs and wherein the manufacturing method further comprises:
folding the first tabs, after the shaping and assembling the preform; and
joining the first tabs so that a bottom wall of the chamber is obtained.
4. The manufacturing method according to claim 1 , wherein the preform comprises a first series of first slits extending from a convex curved edge of the preform.
5. The manufacturing method according to claim 1 , wherein the preform comprises a second series of second slits extending from a convex curved edge of the preform so that the second series of second slits define second tabs and wherein the manufacturing method comprises:
cutting, shaping and assembling the preform so that a first chamber is obtained;
positioning the first chamber in a second chamber including a second side wall that has a first edge; and
folding the second tabs, around the first edge of the second side wall, to press the second tabs against an outer face of the second wall of the second chamber to obtain an assembly of the first and second chambers.
6. The manufacturing method according to claim 1 , further comprising obtaining at least one a hole in the flat preform, before the shaping said preform.
7. The manufacturing method according to claim 6 , wherein the at least one hole is made at an end of one of the slits away from an edge of the preform.
8. The manufacturing method according to claim 1 , further comprising cutting and shaping a bottom preform, so that a dish shape is obtained; and
assembling the bottom preform with the cylindrical or truncated conical shape of the chamber so that a chamber with a bottom wall is obtained.
9. The manufacturing method according to claim 1 , wherein the preform comprises first and second side edges that each have several unaligned segments, configured to obtain, after the shaping and assembly, a side wall including several superposed truncated conical shapes.
10. An acoustic element of a sound absorption structure obtained using the manufacturing method according to claim 1 , the acoustic element comprising a first chamber having at least one first side wall, that extends between first and second edges, obtained from a first preform cut flat, shaped and assembled, together with a second chamber having at least one second side wall, that extends between first and second edges, obtained from a second preform cut, shaped and assembled, wherein the first and second chambers are connected at the first edges of the first and second side walls.
11. The acoustic element of a sound absorption structure according to claim 10 , wherein the second chamber comprises a second bottom wall formed by tabs of the second preform folded and connected to each other in a joining zone.
12. The acoustic element of a sound absorption structure according to claim 11 , wherein the tabs are delimited by the at least one series of slits and folded along folding lines, the at least one series of slits having holes positioned on the folding lines of the tabs.
13. The acoustic element of a sound absorption structure according to claim 10 , wherein the second chamber comprises a dish shape having a bottom and a curved peripheral edge connected to the second edge of the second side wall.
14. The acoustic element of a sound absorption structure according to claim 13 , wherein the curved peripheral edge comprises several tabs delimited by a second series of slits and folded along folding lines, the second series of slits having holes positioned on the folding lines of the tabs.
15. The acoustic element of a sound absorption structure according to claim 10 , wherein the first and second chambers are connected by a continuous or discontinuous contact joining zone on the perimeter of the first and second chambers, that adjoins the first edges, that extends over the entire periphery of the first edges and over a given height.
16. The acoustic element of a sound absorption structure according to claim 10 , wherein the first chamber comprises a plurality of tabs, on the first edge of the first side wall, folded around the first edge of the second side wall to obtain a connection between the first and second chambers.
17. The acoustic element of a sound absorption structure according to claim 10 , wherein the first side wall comprises a third series of slits extending from its first edge.
18. The acoustic element of a sound absorption structure according to claims 15 , wherein the first side wall comprises a third series of slits extending from its first edge, and
wherein the third series of slits have a length greater than the given height of the contact joining zone.
19. The acoustic element of a sound absorption structure according to claim 10 , wherein the acoustic element comprises a third chamber, positioned between the first and second chambers, and comprising a side wall delimited by a first edge, connected to at least one of the first and second chambers, as well as by a second edge, opposite the first edge, that defines an edge of an acoustic orifice.
20. A sound absorption structure comprising at least one acoustic element according to claim 10 .
21. An aircraft powerplant comprising at least one sound absorption structure according to claim 20 .