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Structural Research Series 438PDF


Title:Analysis Procedure for Frictional Contact Problems Using Interface Finite Elements
Author(s):Urzua, J.L.; Pecknold, D.A.; Lopez, L.A.; Munse, W.H.
Subject(s):bolted joints
stress analysis
finite element method
Abstract:An important class of structural mechanics problems deals with the stress analysis of bodies in contact. The primary objective of this study was to develop a system capable of solving large and complex frictional contact problems with special emphasis on truss-type bolted connections in three dimensions. Isoparametric finite elements were used in this study to allow effective modeling of irregular geometries. A variational principle was developed which provided a convenient means for carrying out the finite element discretization and for arriving at a symmetrical system of simultaneous equations. An important feature of this study is the incorporation of the interbody tractions on the contact surface as primary variables, thus avoiding the need to return to the element level to compute and average the contact stress after each load step. This was accomplished without modification of the standard finite element method by the development of special interface elements which are used along the interbody surfaces. These elements contain "stress nodes" whose unknowns are the interface tractions. The numerical procedure presented allows either incremental loading or iteration with total loads for those problems in which the solution is independent of applied load level. It accounts for frictionless as well as frictional contact. For the incremental procedure, the load pattern is applied at each step and a load factor is computed for each IIstress node". Each factor represents the lowest fraction of the load which will cause that node to change IImode ll • The minimum load factor determines the size of the load step. The procedure was implemented in a general-purpose finite element program called FINITE, which features user-oriented input, and reaccess, substructuring and static condensation capabilities. Use of static condensation allows the incremental or iterative solution to be carried out on a relatively small number of nodes. The procedure presented here applies to surfaces which are initially in contact. However, it can be easily extended to include interferences or initial clearances. The results for several examples were presented and compared with experimental and analytical solutions. The comparisons indicate that geometrically more complex bolted connections can be handled with good accuracy.
Issue Date:1977-03
Publisher:University of Illinois Engineering Experiment Station. College of Engineering. University of Illinois at Urbana-Champaign.
Series/Report:Civil Engineering Studies SRS-438
Genre:Technical Report
Date Available in IDEALS:2009-10-07
Identifier in Online Catalog:2938661

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