GRIRTEUR GROUP FOR AERONAUTICAL RESEARCH AND TECHNOLOGY IN EUROPE

1 FRANCE GERMANY M E NETHERLANDS SWEDEN UNITED KINGDOM

DISTRIBUTION

Mr. L. Sombroek Secretary GARTEUR GoR/SM Nationaal Lucht-en Ruimtevaartlaboratorium (NLR) P.O. Box 90502 1006 BM Amsterdam THENETHERLANDS

(15 copies for distribution among Responsibles and Industrial Points of Contact)

Mr. K.A. Jonasson Secretary GARTEUR XC Flygtekniska Forsoksanst alten (FFA) P.O. Box 11021 S 16111 Bromma SWEDEN

(8 copies for distribution among XC members and for GARTEUR files)

Mr. Marc Balzano Aerospatiale Aeronautique Dkpartement Structure, A/BTE/EG/ST/F Etablissement de Toulouse Route de Bayome 316 31060 Toulouse Cedex 03 FRANCE

Mr. Richard Collins British Aerospace Airbus Fatigue & Damage Tolerance Department, B56 Floor C1, Technical Centre Filton Bristol BS99 7AR UNITED KINGDOM

Dr. Peter Horst Dairnler-Benz Aerospace Airbus GmbH Department EMR Kreetslag 10 21129 Hamburg GERMANY

continued ...

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Mr. Robin Cook Defence Research Agency (DRA) Structural Materials Centre Room 2008, A7 Building Farnborough Hampshire GU14 6TD UNITED KINGDOM

Dr. Karl-Fredrik Nilsson Flygtekniska ForsZiksanst alten (FFA) Structures Department P.O. Box 11021 S 16111 Bromma SWEDEN

Mr. Gise Wit Fokker Aeros truct ures Department FAE/EG - SO59 - 40 P.O. Box 7600 1117 ZJ Schiphol Oost THE NETHERLANDS

Mr. Harold Ottens Nationd Lucht-en Ruimtevaartlaboratorium (NLR) Structures Department P.O. Box 153 8300 AD Emmeloord THE NETHERLANDS

Mr. Stephen McBurney Short Brothers P.O. Box 241 Airport Road Belfast BT3 9DZ UNITED KINGDOM

GRRTEUR GROUP FOR AERONAUTICAL RESEARCH AND 'TECHNOLOGY IN EUROPE

FRANCE GERMANY THE NETHERLANDS SWEDEN UNITED KINGDOM

EXECUTIVE SUMMARY

GARTEUR Structures & Materials Action Group SM18 was established in April 1994 to increase the understanding of the problem of Multiple Site Damage (MSD) in highly loaded joints, and to reduce some of the deficien- cies in existing methodologies for predicting the development of MSD in such components. Membership of the Action Group comprised both indus- trial companies and research institutes from across the European aerospace community, representing a wide range of concerns on the issue of ageing air- craft. This final report gives a summary of the work undertaken within the Action Group. and the principal conclusion^ arising from the project.

In accordance with the original objectives of the Action Group, the tasks performed during this research programme covered three areas, viz.

the initiation and growth of MSD in open hole and riveted joint speci- mens, and the residual strength of unstiffened and stiffened panels, was investigated through detailed experiments, including non-destructive inspection of initiation and damage growth, and extensive theoretical analysis.

useful experience was gained in the application of probabilistic tech- niques - both analytical methods such as binomial or order statistics, and numerical methods such as the Monte Carlo procedure - to the problem of fatigue crack initiation. Limitations in existing determinis- tic prediction methods were reduced by comparing results from different approaches through a. series of 'round robin' studies.

the data base of experimental evidence of MSD was increased through a series of fatigue crack growth and residual strength tests undertaken specifically for the project by members of the Action Group. Additional data were oltixled by an exchange agreement with the Federal Aviation Administration (FAA).

Following the dissolution of the Action Group, financial support for con- tinued collaboration in the field of Widespread Fatigue Damage was secured from the European Commission under the Fourth Framework Programme for Research and Technological Development (1994-1998). The GARTEUR ac- tivity, and the insights into the problem of MSD which arose in consequence, were major contributing factors in the success of this proposal. As a re- sult, all the members of GARTEUR Action Group SM18, with the exception of Shorts, have since become partners in Brite/EuRam Project No. BE95- 1053, 'Structural Maintenance of Ageing Aircraft' (SMAAC), which began in January 1996. In this new research programme, the original Action Group

GrnRTEUR GROLIP FOR AERONAUTICAL RESEARCH AND TECHNOLOGY IN EUROPE

1 FRANCE GERMANY M E NETHERLANDS SWEDEN UNITED KINGDOM

members have been joined by four additional industrial partners - Alenia, AerMacchi, SAAB and Hellenic Aerospace Industry (HAI) - along with two research institutes - the 'Instituto de Engenharia M&ca' (IDMEC) at the University of Porto and the 'Institute of Structures & Advanced Mate- rials' (ISTRAM) at the University of Patras - thus expanding the activity into a truly pan-European collaborative venture. The new partners will be given access to the data base of test information generated within the Action Group.

A conference paper describing the work of GARTEUR Action Group SM18 has been accepted for oral presentation at the forthcoming symposium of the International Committee on Aeronautical Fatigue (ICAF) at Edinburgh in June, 1997.

GROUP FOR AERONAUTICAL RESEARCH AND TECHNOLOGY IN EUROPE

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CONTENTS

1 INTRODUCTION ................................................... - 3

2 PARTICIPATION AND ORGANISATION ........................... 4

........................................ 2.1 Action Group Membership - 4

2.2 Meeting Venues ................................................... - 4

........................................ 2.3 Action Group Management 5

3 SUMMARY OF WORK PROGRAMME ............................. 6

.......................................... 3.1 Action Group Objectives - 6

3.2 Development of Probabilistic Analysis Methods .................... 6

3.3 Development of Deterministic Analysis Methods .................. 6

3.4 Joint Activities ..................................................... 7

4 NUMERICAL 'ROUND ROBIN' TESTS ............................. 8

4.1 Crack growth in the presence of MSD ............................. 8

4.1.1 NLRIFAA multiple open hole specimen .......................... 9

................................... 4.1.2 NLRIFAA lap joint specimen 11

...................... 4.1.3 DRA two hole crack interaction specimen 12

4.1.4 DRA multiple hole & asymmetric/symmetric joint specimens . . 13

4.2 Residual strength in the presence of MSD ........................ 14

........................................ 4.2.1 NlST MSD-90 specimen 14

4.2.2 hlLR unstiffened/stiffened sheet specimens ..................... 15

....................................................... 4.3 Conclusions 15

...................................................... 5 REFERENCES 16

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6 APPElVDlX A - SPECIMEN DETAILS

. . . individual partner contributions

7 APPENDIX 6 - Aerospatiale Aeronautique

- compiled b y Alain Santgema & Marc Balzano

8 APPENDIX C - British Aerospace Airbus

- compiled b y Richard Collins

9 APPENDIX D - Daimler-Benz Aerospace Airbus

- compiled b y Peter Horst

10 APPENDIX E - Defence Research Agency

- compiled b y Robin Cook & Andrew Young

11 APPENDIX F - Flygtekniska FZirsZiksanstalten

- compiled b y Karl-Fredrik Nilsson

12 APPENDIX G - Nationaal Lucht-en Ruimtevaartlaboratorium

- compiled b y Henk Jan ten Hoeve

13 APPENDIX H - Short Brothers

- compiled b y Stephen McBurney

GROUP FOR AERONAUTICAL RESEARCH AND TECHNOLOGY IN EUROPE

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