Residual Strength Analysis of AA2198 Laser Beam Welded Integral Structures Aerospace ...

109 Pages·2014·19.27 MB·English

by  Andre C. Marta

Residual Strength Analysis of AA2198 Laser Beam Welded
Integral Structures
Alexandre Amorim Carvalho
Thesis to obtain the Master of Science Degree in
Aerospace Engineering
Supervisors: Prof. Luís Filipe Galrão dos Reis and Prof. Miguel António Lopes de
Matos Neves
Examination Committee
Chairperson: Prof. Fernando José Parracho Lau
Supervisor: Prof. Luís Filipe Galrão dos Reis
Member of the Committee: Dr. Nikolai Kashaev
Member of the Committee: Prof. Rui Fernando dos Santos Pereira Martins
November 2014
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Dedicatedtomyfamily.
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Acknowledgments
The research work was accomplished at Helmholtz-Zentrum Geesthacht (HZG), at the Institute of Ma-
terialsResearch/MaterialMechanics-DepartmentofJoiningandAssessment(WMF)
IcannotthankenoughthehelpIhadatHZG,forallthatIwastaughtandforgivingmethisopportu-
nity. SpecialthankstoDr. NikolaiKashaevforhisguidancethroughoutmywork,foralwayshavingtime
todiscussanytechnicalandpersonalaspect.
To all the other colleagues at the WMF department I owe gratitude. Some dedicated acknowledg-
ments must go to Stefan Riekehr for sharing his knowledge and suggestions on technical details, to
Volker Ventzke for the help with SEM and EBSD, to Sergey Chupakihn for helping me to lear Python,
Patran and Abaqus and to Jin Lu, Anne Groth, Josephin Enz and Rielson Falck for productive discus-
sionsandsuggestions.
I am also extremely grateful for Prof. Luis Reis and Prof. Miguel Neves for accompanying me
throughout my daily work in this thesis. For all the productive discussions, suggestions, sharing their
knowledgeandbeingdemanding,theygavemotivationandinspiration.
AndfinallytomyfamilyandfriendswhomImissedalotduringmystayinGermany.
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Resumo
Indo ao encontro das exigeˆncias da indu´stria aeroespacial tendo em conta seguranc¸a, produtividade,
pesoecustos,novosmateriaiseconceitosdeligac¸o˜esmecaˆnicasforamdesenvolvidos. Recentemente,
desenvolvimentosnocampometalu´rgicopermitiramautilizac¸a˜odeligasdealum´ınio(AA)dase´rie2xxx
soldadas por laser. Um exemplo e´ o AA2198 que possui elevado´ındice de eficieˆncia estrutural devido
a` sua elevada resisteˆncia e baixa densidade. O procedimento europeu para a integridade estrutural
SINTAP juntamento como me´todo dos elementosfinitos (FEM) foram usados para avaliara mecaˆnica
de fratura de estruturas integrais soldadas com feixe de laser. Neste trabalho e´ apresentado um pro-
gramaexperimentalrealizadoparacaracterizarmecaˆnicamenteoAA2198nosrevenidosT3eT8. Este
programaincluiuensaiosdetracc¸a˜o,resisteˆnciaa` fraturaeresisteˆnciaresidual. Duasestruturasforam
modeladas numericamente utilizando elementos casca e os factores de intensidade de tenso˜es foram
extra´ıdosusandome´todosenerge´ticoscomoointegralJeoVirtualCrackClosureTechnique(VCCT).
Previso˜es da resisteˆncia residual foram feitas com sucesso usando o SINTAP e o comportamento de
toleraˆnciaadanosdoAA2198foicomparadocomoAA6013revelandooportunidadesparaoAA2198.
Palavras-chave:
Soldadura com feixe de laser, alum´ınio l´ıtio, SINTAP, paine´is, toleraˆncia a
dano,elementosfinitos
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Abstract
To meet the future demands of the aerospace industry with respect to safety, productivity, weight and
cost, new materials and joining concepts have been developed. Recent developments in the metallur-
gical field now make it possible to use laser-weldable Aluminum Alloys (AA) of the 2xxx series, such
as the AA2198, with a high structural efficiency index due to their high strength and low density. The
Europeanstructuralintegrityassessmentprocedure(SINTAP)combinedwithFEMapproachwasused
for the assessment of the fracture mechanical behavior of the laser beam-welded integral structures.
An experimental program which included tensile, CTOD and residual strength tests was performed to
mechanicallycharacterizetheAA2198intheT3andT8tempers. Structureswerenumericallymodeled
using shell elements and the stress intensity factors were extracted using energy methods such as the
J-integral and Virtual crack closure technique. Residual strength predictions were successfully made
provingthereliabilityoftheSINTAPprocedure. ThedamagetolerancebehavioroftheAA2198integral
structureswascomparedwiththeAA6013integralstructuresandrevealedthepromisingcapabilitiesof
theAA2198.
Keywords:
Laser beam welding, aluminum lithium, SINTAP, stiffened panels, damage toler-
ance,FEM
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