PhD ProposalElaboration and identification strategy of a joint macromodel for the simulation of bolted assemblies

ContextBolted joints are widely encountered

in mechanical engineering especially in aeronautics structures (e.g. 3,000,000 joints on a A380, 50,000 on a Rafale). In spite of well-established design rules and assembly procedures, important sources of uncertainty remain due to a high sensitivity of the joint mechanical behavior to dispersions (tightening procedure, f r i c t i o n a l e f f e c t s , g e o m e t r i c a l tolerances…). Mass and cost optimization of bolted assemblies for complex loadings and new materials such as composites, requires more e laborated des ign strategies that account for phenomena occurring in joints (contact, frictional effects, clearances…) more finely.

Research programIn this work a two-scale modeling

strategy is proposed. The first scale called macroscopic scale, is associated with a character istic length of the entire

assembly. At this level, the components of the assembly a re cons idered as she l l structures that remain in their elastic domain. Joints are simply

seen as interface elements or connectors between shells, the

nonlinear behavior of which being identified thanks to a finer scale

study. Generally, such connectors can be easily integrated in FE commercial

codes.

At the second sca le , ca l l ed mesoscopic scale, only the joint is considered. All the geometrical details (bolt, plates, clearances) and physical phenomena (fr ictional contact) are described at a level that is too fine for a large scale computation on the entire assembly. Scale coupling is done through the identification procedure of the connector macromodel either from mesoscale simulations on the joint or from joint data tests [1,2].

The scientific challenge of the approach is the proposal of a joint

macromodel in quasistatic state that is simple enough for a use at the assembly scale but also robust, considering the nonl inear aspect of the involved phenomena. Robustness will be achieved by giving a strong mechanical sense to the model parameters [3]. Moreover, a suitable computational strategy [4] will be required for the identification process that i n v o l v e s c o s t l y 3 D m e s o s c a l e computations with nonlinear frictional contact conditions. The strategy will be validated by results coming from testing activities performed on bolted assemblies by CARAB Project partners.

The candidate should have a good knowledge of structural mechanics computation by finite element approach and numerical algorithms for integrating non l inear const i tu t i ve equat ions . Competences in the design of bolted assemblies as well as in the use of c o m m o n F E c o m m e r c i a l c o d e s (ABAQUS, SAMCEF…) would be appreciated.

References (1) Boucard, P. -A. , Derumaux, M. ,

Ladevèze, P., Roux, Ph., Macro-meso mode l s fo r j o i n t submi t ted to pyrotechnic shock. 2d MIT Conference on computational fluid and Solid Mechanics, 1:139-142, 2003

(2) McCarthy, M.A., McCarthy, C.T., Padhi, G.S., A simple method for determining the effects of bolt–hole clearance on load distribution in single-column multi-bolt composite joints, Composite Structures 73:78-87, 2006

(3) C l o i r e c , M . , B o u c a r d , P. - A . , Champaney, L., Guinard, S., Sen Gupta, J. Study for design and identification of a bolted joint model. Complas IX, 2:889-892, 2007.

(4) Boucard, P.-A., Champaney, L., A suitable computational strategy for the parametric analysis of problems with multiple contact. IJNME, International Journal Methods in Engineering, 57:1259-1282, 2003

LABORATORYLMT-Cachan(ENS Cachan / CNRS / UPMC /PRES UniverSud Paris)61 avenue du Président Wilson94235 Cachan Cedex, Francewww.lmt.ens-cachan.fr

INDUSTRIAL PARTNERSPartners of FUI Project Conception Avancée Robuste pour les Assemblages Boulonnés (CARAB)SAFRAN (Messier, Snecma, Turbomeca), Liebherr, SAMCEF, CETIM…

RESEARCH TEAMLMT-CachanPr. P. A. BoucardDr. P.A. Guidault

CONTACTSboucard@lmt.ens-cachan.fr

guidault@lmt.ens-cachan.fr

SALARY2025 € /month (gross)

Duration: 3 years

DOCTORAL POSITION AT ENS-CACHAN

September

2012

Keywords: identification, bolted joints, frictional contact, nonlinear