Finite Element Modelling of Shot Peening and Peen Forming Processes and Characterisation of Peened Aa2024-T351 Aluminium Alloy

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Finite Element Modelling of Shot Peening and Peen Forming Processes and Characterisation of Peened Aa2024-T351 Aluminium Alloy UNIVERSITE´ DE MONTREAL´ FINITE ELEMENT MODELLING OF SHOT PEENING AND PEEN FORMING PROCESSES AND CHARACTERISATION OF PEENED AA2024-T351 ALUMINIUM ALLOY ALEXANDRE GARIEPY´ DEPARTEMENT´ DE GENIE´ MECANIQUE´ ECOLE´ POLYTECHNIQUE DE MONTREAL´ THESE` PRESENT´ EE´ EN VUE DE L'OBTENTION DU DIPLOME^ DE PHILOSOPHIÆ DOCTOR (GENIE´ MECANIQUE)´ SEPTEMBRE 2012 © Alexandre Gari´epy, 2012. UNIVERSITE´ DE MONTREAL´ ECOLE´ POLYTECHNIQUE DE MONTREAL´ Cette th`eseintitul´ee : FINITE ELEMENT MODELLING OF SHOT PEENING AND PEEN FORMING PROCESSES AND CHARACTERISATION OF PEENED AA2024-T351 ALUMINIUM ALLOY pr´esent´ee par : GARIEPY´ Alexandre en vue de l'obtention du dipl^ome de : Philosophiæ Doctor a ´et´ed^ument accept´eepar le jury d'examen constitu´ede : M. GOSSELIN Fr´ed´eric, Doct., pr´esident M. LE´VESQUE Martin, Ph.D., membre et directeur de recherche M. BOCHER Philippe, Ph.D., membre et codirecteur de recherche M. CHAMPLIAUD Henri, Ph.D., membre Mme ROUHAUD Emmanuelle, Ph.D., membre iii A` ma famille iv ACKNOWLEDGEMENTS I would like to first thank Pr. Martin L´evesque and Claude Perron for their guidance and trust throughout this project. Your confidence allowed me to explore hypotheses that made my work interesting, challenging and, I hope, useful. I would also like to thank Pr. Philippe Bocher at Ecole´ de Technologie Sup´erieure for welcoming the computer savvy mechanical engineering student I was in his group and introducing me to the fascinating field of materials science. The time and expertise provided by the National Research Council Canada - Aerospace is also greatly appreciated. I would like to thank Simon Larose for his generous help and advice and well as Christian Corbeil and Xavier Pelletier for their support. I would like to acknowledge the contributions of Hongyan Miao, Julien Cyr, Derek Berri- gan and Dave Demers at Ecole´ Polytechnique de Montr´eal as well as Florent Bridier, Vincent Savaria, Majid Hoseini and Jean-Charles Stinville at ETS´ through fruitful discussions du- ring this project. The technical advice and support of B´en´edict Besner and Isabelle Nowlan (Polytechnique) as well as Radu Romanica and Jean-Guy Gagnon (ETS)´ is also gratefully acknowledged. The help and explanations of Fran¸cois M´enard and Abel Chouinard at the Laboratoire de Recherche en Fabrication Virtuelle (metrology) were also very useful. I would like to thank the Natural Sciences and Engineering Research Council of Ca- nada (NSERC), Rio Tinto Alcan and Fondation de Polytechnique for their financial support through scholarships. These scholarships made this project possible. Finally, I would like to express my gratitude to my family for sticking together throughout the good and bad times of the past four years. I could not have done it without you. v RESUM´ E´ Le grenaillage est un traitement de surface couramment utilis´epour am´eliorer la dur´ee de vie en fatigue de diff´erentes pi`ecesm´etalliques. Un grand nombre de petites particules dures sont projet´ees sur la surface du composant `ahaute vitesse. Chaque particle d´eforme plastiquement le mat´eriau et les impacts r´ep´et´es produisent un ´etat de contraintes r´esiduelles compressives b´en´efique `ala surface. Le grenaillage modifie de plus les propri´et´es m´ecaniques locales de m^eme que la microstructure du mat´eriau. Le proc´ed´eaugmente toutefois la rugosit´e et peut occasionner des dommages en surface. Son influence sur la vie en fatigue et la limite de fatigue d´epend donc d'une combinaison de plusieurs effets. La mise en forme par grenaillage (MEFG) est une m´ethode de fabrication d´eriv´eedu gre- naillage. Le champ de contraintes compressives g´en´er´epar le grenaillage modifie l'´equilibre m´ecanique de la pi`eceet est utilis´epour courber des composants minces. Ce proc´ed´eest utilis´edepuis les ann´ees 1950 dans l'industrie a´erospatiale pour mettre en forme de grands panneaux requ´erant des courbures l´eg`eres, comme des panneaux de voilure et de fus´ees. La MEFG est une alternative ´economique aux techniques de mise en forme conventionnelles puisqu'elle ne n´ecessite pas un ensemble de matrices pour chaque forme `ar´ealiser. De plus, diff´erents contours peuvent ^etre r´ealis´es en modificant simplement les traitements de gre- naillage appliqu´es`adiff´erentes r´egions de la pi`ece. Cependant, cette flexibilit´en'est peut-^etre pas employ´ee`ason plein potentiel puisque les applications actuelles sont g´en´eralement bas´ees sur le savoir-faire empirique et une approche par essai-erreur. Cette th`esevisait le d´eveloppement et la validation d'outils de simulation par ´el´ements finis (EF)´ pour le grenaillage et la mise en forme par grenaillage. L'objectif ´etait d'arriver `ades pr´edictions quantitatives pour ces deux proc´ed´eset de d´emontrer le potentiel de la mod´elisation EF´ tant pour des ´etudes fondamentales que pour des applications industrielles. Premi`erement, un mod`ele am´elior´ed'impacts dynamiques prenant en consid´eration la nature al´eatoire du grenaillage a ´et´epropos´een ´etudiant avec soin ses dimensions, en in- troduisant la dispersion des tailles des particules et en r´eduisant significativement le temps de calcul. De plus, des essais m´ecaniques cycliques ont ´et´er´ealis´esafin de d´efinir une loi de comportement appropri´eepour l'alliage d'aluminium (AA) 2024-T3/T351 soumis au proc´ed´e de grenaillage. En combinant un mod`ele r´ealiste et une loi de comportement adapt´ee, de bonnes pr´edictions ont ´et´eobtenues en termes de contraintes r´esiduelles pour trois ensembles de param`etres de grenaillage. Deuxi`emement, l'´etat de l'AA2024-T351 grenaill´edans des conditions repr´esentatives des applications d'am´elioration de vie en fatigue a ´et´ecaract´eris´eexp´erimentalement et nu- vi m´eriquement. Diff´erentes techniques telles que la micro-indentation, la d´etermination de contraintes r´esiduelles et l'imagerie par diffraction des ´electrons r´etrodiffus´esont ´et´ecom- bin´eesafin de mieux comprendre les effects du grenaillage sur le mat´eriau. Les applications potentielles de la simulation EF´ dans le but de compl´ementer les r´esultats exp´erimentaux ont aussi ´et´ediscut´ees.L'´etat h´et´erog`ene r´esultant de la s´equence d'impacts al´eatoires a ´et´e ´etudi´eet il a ´et´enot´eque la mod´elisation d'impacts pourrait apporter des informations utiles sur cette h´et´erog´en´eit´e. Troisi`emement, une nouvelle m´ethodologie de simulation de la MEFG a ´et´eintroduite. La mod´elisation d'impacts a fourni les donn´eesinitiales n´ecessaires dans le cadre d'une approche multi´echelles. Les profils de contraintes induites hors-´equilibre pr´edits num´eriquement ont ´et´eintroduits dans des ´el´ements coques et la d´eform´ee`al'´equilibre a ´et´eobtenue par une analyse de retour ´elastique. De plus, une m´ethode d'interpolation simplifi´eea ´et´epropos´ee pour mod´eliser la nature incr´ementale de la MEFG avec un co^ut de calcul raisonnable. Le proc´ed´ea donc ´et´esimul´epar une s´erie d'analyses de retour ´elastique. Cette approche a d'abord ´et´evalid´ee `al'aide de donn´ees obtenues par des tests `apetite ´echelle. L'effet possible de l'orthotropie des mat´eriaux lamin´esa ensuite ´et´e´etudi´enum´erique- ment et exp´erimentalement. Ce facteur pourrait avoir une influence importante pour les applications industrielles puisque plusieurs pi`eces mises en forme par grenaillage proviennent de feuilles et plaques lamin´ees.Les essais exp´erimentaux ont montr´eque l'orientation de la direction de laminage a un effet notable sur les courbures apr`es grenaillage pour de pe- tites plaques d'AA2024-T3. Les propri´et´es´elastiques orthotropiques ainsi que l'´etat initial de contraintes r´esiduelles des ´echantillons ont ´et´eintroduits dans les simulations de mise en forme et les pr´edictions concordaient bien avec les donn´eesexp´erimentales pour un des deux ensembles de param`etres de grenaillage `al'´etude. Par la suite, la m´ethodologie de simulation a ´et´eam´elior´eede mani`ere `atenir compte de la trajectoire de la buse de grenaillage sur la pi`ece. Ceci a men´e`aune repr´esentation plus r´ealiste des proc´edures de MEFG couramment utilis´ees pour de grands panneaux, o`u l'´equipement de grenaillage est d´eplac´esur les surfaces. La trajectoire de grenaillage et les conditions aux fronti`eres utilis´eesdans les essais `apetite ´echelle ont g´en´er´edes distributions complexes de rayons de courbure qui ont qualitativement ´et´ebien pr´edites par les simulations de mise en forme. Finalement, les applications possibles de cette nouvelle strat´egie de simulation ont ´et´e d´emontr´eesen simulant la mise en forme par grenaillage de panneaux de voilure typiques. Les composants mod´elis´esavaient des caract´eristiques r´ealistes, comme des ´epaisseurs va- riables et des raidisseurs int´egr´es, et plusieurs traitements de mise en forme ont ´et´esimul´es successivement. vii La principale contribution de cette th`ese est une approche multi´echelle exp´erimentalement valid´eepour la simulation de mise en forme par grenaillage. Cette strat´egie combine des analyses dynamiques d'impacts et des simulations statiques de retour ´elastique et prend en consid´eration la nature incr´ementale du proc´ed´eavec un fondement physique. Les besoins en termes d'´etalonnage exp´erimental ont aussi ´et´er´eduits par rapport aux m´ethodes existantes. Des ph´enom`enes complexes reli´es `al'orthotropie des plaques et `ala trajectoire de grenaillage ont ´et´epr´edits avec une bonne pr´ecision. Bien que la m´ethodologie n'ait pu ^etre valid´ee pour un composant a´eronautique r´eelde pleine grandeur, ses applications potentielles ont ´et´e illustr´ees.
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