Title

An Investigation of Add-on Damping Treatment for Life Extension of the F-15 Upper Outer Wing Skin

Report Number

WL-TR-91-3078 Volume I, p. BAB-1 thru BAB-30

Creator

Parin, M.

Levraea, V.

Pacia, A.

Rogers, L.

Corporate Author

Flight Dynamics Directorate, Wright Laboratory

Laboratory

Wright Laboratory

Date

1991

Date Issued

1991-08

Extent

30

Contract

Laboratory Research - No Contract

DoD Project

2401

DoD Task

240104

Identifier

ADA241311

Format

1 online resource

Abstract

The purpose of this investigation was to design, fabricate,
and verify candidate add-on damping treatments for the F-15 upper-outer wing skin. The F-15 upper-outer wing skin has experienced high cycle fatigue cracks caused by separated flow on the upper wing surface. The separated flow results during high load factor maneuvers and in turn induces large vibratory loads on the upper wing skin and associated substructure. The capability of the F-15 to sustain these maneuvers allows the excitation to occur for sufficiently long periods of time to result in damage. Damage accumulates due to the resonant vibration of local skin/stiffener modes. The cracks initiate at the fastener holes adjacent to the integrally machined "T"
stiffeners and tend to propagate parallel to the stiffeners. Two damping treatments resulted from the investigation and were recommended for F-15 fleet retrofit. One was an external constrained-layer treatment and the other was an internal "stand-off" treatment. Laboratory vibration, corrosion, and thermal aging tests were conducted as part of the development of the add-on damping treatments. Life extension factors were estimated for both damping treatments.

Description

The purpose of this investigation was to design, fabricate,
and verify candidate add-on damping treatments for the F-15 upper-outer wing skin. The F-15 upper-outer wing skin has experienced high cycle fatigue cracks caused by separated flow on the upper wing surface. The separated flow results during high load factor maneuvers and in turn induces large vibratory loads on the upper wing skin and associated substructure. The capability of the F-15 to sustain these maneuvers allows the excitation to occur for sufficiently long periods of time to result in damage. Damage accumulates due to the resonant vibration of local skin/stiffener modes. The cracks initiate at the fastener holes adjacent to the integrally machined "T"
stiffeners and tend to propagate parallel to the stiffeners. Two damping treatments resulted from the investigation and were recommended for F-15 fleet retrofit. One was an external constrained-layer treatment and the other was an internal "stand-off" treatment. Laboratory vibration, corrosion, and thermal aging tests were conducted as part of the development of the add-on damping treatments. Life extension factors were estimated for both damping treatments.

Distribution Classification

1

Distribution Conflict

No

DTIC Record Exists

No

Illinois Tech Related

No

Photo Quality

Complete

Report Availability

Full text available

Type

article

Is Part Of

Proceedings of Damping '91: 13-15 February 1991 San Diego, California (Pages AAC-1 through DCC-19)