Preventing cracks at bolted or riveted joints of aircraft structural parts

Patent metadata

Field	Value
Publication number	US-10633116-B2
Application number	US-201514838912-A
Country	US
Kind code	B2
Filing date	Aug 28, 2015
Priority date	Sep 8, 2014
Publication date	Apr 28, 2020
Grant date	Apr 28, 2020

Abstract

A method for joining two aircraft structural parts by a bolted or riveted joint and for preventing cracks at said joint includes providing a first metallic aircraft structural part and a second aircraft structural part, wherein the first aircraft structural part includes a first joint region and a second aircraft structural part includes a second joint region. Furthermore, the method includes inducing compressive residual stresses in a first area of the first joint region for preventing cracks by applying parallel crack retarding regions formed as stripes in the first area, drilling fastener holes in the first and second areas of the first. Finally, the method includes a step of fastening together the first and second aircraft structural parts at the first and second joint regions by a bolted or riveted joint.

First claim

The invention claimed is:

1. A method for joining two aircraft structural parts by a bolted or riveted joint and for preventing cracks at said joint, the method comprising:
providing a first metallic aircraft structural part and a second aircraft structural part, wherein the first aircraft structural part comprises a first joint region and the second aircraft structural part comprises a second joint region;
overlaying a first area of the first joint region with a first opaque overlay;
overlaying the first opaque overlay with a first transparent overlay;
inducing compressive residual stresses in the first area of the first joint region for preventing cracks by applying parallel crack retarding regions formed as stripes in the first area by shooting a laser pulse thereon;
overlaying a second area of the second joint region with a second opaque overlay;
overlaying the second opaque overlay with a second transparent overlay;
inducing compressive residual stresses in the second area of the second joint region for preventing cracks by applying parallel crack retarding regions formed as stripes in the second area by shooting a laser pulse thereon;
applying a plurality of layers of laser shock peening treatment onto the first area and the second area;
drilling at least a first fastener hole in the first area and at least a second fastener hole in the second area of the first aircraft structural part and the second aircraft structural part, respectively, after inducing compressive residual stresses in the first area and the second area;
drilling at least a third fastener hole outside the second area in the second joint area configured to be aligned with the first hole and at least a fourth fastener hole outside the first area in the first joint area configured to be aligned with the second hole;
arranging the first aircraft structural part and the second aircraft structural part in such a way that the first area and the second area do not overlap and the first and second joint regions overlap with one another; and
installing a plurality of fasteners through the drilled fastener holes for creating the riveted or bolted joint of the first and second aircraft structural parts, such that the first and second aircraft structural parts are fastened together at the first and second joint regions by the bolted or riveted joint, wherein a first of the plurality of fasteners is installed through the first fastener hole in the first area and the third hole in the second joint region and a second of the plurality of fasteners is installed through the second fastener hole in the second area and the fourth hole in the first joint region,
wherein the first area and second area do not overlap when fastening together the first and second aircraft structural parts.

2. The method according to claim 1 , wherein the second aircraft structural part is metallic.

3. The method according to claim 2 , wherein the first and second aircraft structural parts are fastened together by a shear-joint.

4. A method for joining two aircraft structural parts by a bolted or riveted joint and for preventing cracks at said joint, wherein the first and second aircraft structural parts are fastened together by a butt-joint, the method comprising:
providing a first metallic aircraft structural part and a second aircraft structural part, wherein the first aircraft structural part comprises a first joint region and the second aircraft structural part comprises a second joint region;
overlaying a first area of the first joint region with a first opaque overlay;
overlaying the first opaque overlay with a first transparent overlay;
inducing compressive residual stresses in the first area of the first joint region for preventing cracks by applying parallel crack retarding regions formed as stripes in the first area by shooting a laser pulse thereon;
overlaying a second area of the second joint region with a second opaque overlay;
overlaying the second opaque overlay with a second transparent overlay;
inducing compressive residual stresses in the second area of the second joint region for preventing cracks by applying parallel crack retarding regions formed as stripes in the second area by shooting a laser pulse thereon;
drilling at least a first fastener hole in the first area, and at least a second hole in the second area of the first aircraft structural part and the second aircraft structural part, respectively, after inducing compressive residual stresses in the first area and the second area;
drilling at least a third hole outside the first area in the first joint region and at least a fourth hole outside the second area in the second joint region;
providing a butt-joint specimen for connecting the first and second aircraft structural parts;
overlaying a third area of the butt-joint specimen with a third opaque overlay;
overlaying the third opaque overlay with a third transparent overlay;
inducing compressive residual stresses in the third area of the butt-joint specimen by shooting a laser pulse thereon;
drilling at least a fifth fastener hole and a sixth fastener hole in the butt-joint specimen in the third area after inducing compressive residual stresses in the butt-joint specimen in the third area;
drilling at least a seventh fastener hole and an eighth fastener hole in the butt-joint specimen outside the third area, wherein the fifth and the sixth fastener holes are configured to be aligned with the third hole and the fourth hole, respectively, and the seventh fastener hole and the eighth fastener hole are configured to be aligned with the first and second fastener holes, respectively; and
connecting the first and second aircraft structural parts by the butt-joint specimen by installing a plurality of fasteners through the drilled holes in the first and second joint regions of the first and second aircraft structural parts and the butt-joint specimen for creating the riveted or bolted joint of the first and second aircraft structural parts, wherein a first of the plurality of fasteners is installed through the first fastener hole and the seventh hole, a second of the plurality of fasteners is installed through the second fastener hole and the eighth hole, a third of the plurality of fasteners is installed through the fifth hole and the third hole, and a fourth of the plurality of fasteners is installed through the sixth hole and the fourth hole,
wherein the first area and the third area do not overlap with one another when the butt-joint specimen overlaps with the first joint region, and
wherein the second area and the third area do not overlap with one another when the butt-joint specimen overlaps with the second joint region.

5. The method according to claim 1 , wherein the compressive residual stresses are induced such that the residual stresses range between −10 MPa and a Yield Strength of a material of the first aircraft structural part, wherein the Yield Strength is a negative value.

6. The method of claim 1 , further comprising:
drilling at least a fifth fastener hole outside the first area; and
drilling at least a sixth fastener hole outside the second area,
wherein the step of installing fasteners comprises installing a fastener through the fifth fastener hole outside the first area in the first joint region and through the sixth fastener hole outside the second area in the second joint region.

7. The method of claim 4 , further comprising drilling a ninth fastener hole in the first joint region outside the first area or in the second joint region outside the second area; and
drilling a tenth fastener hole in the butt-joint specimen outside the third area.

8. The method of claim 7 , wherein the step of installing fasteners comprises installing a fastener th

Assignees

• Airbus Operations Gmbh

Inventors

• Furfari Domenico
• Ohrloff Nikolaus

Classifications

• F16B17/008

  of sheets or plates mutually (joining sheets by riveting without the use of separate rivets F16B5/045) · CPC title

• B64F5/10 Primary

  Manufacturing or assembling aircraft, e.g. jigs therefor · CPC title

• B21J15/142

  Aerospace structures · CPC title

• B64C1/12

  Construction or attachment of skin panels · CPC title

• C21D10/005

  by laser shock processing · CPC title