Browsing by Author "Colville, Kevin William"

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    Friction models in the solution of nonstationary contact problems
    (1993) Colville, Kevin William; Ronda, Jacek
    In most implementations of the finite element method for the solution of contact problems the model of friction used is the classic Amontons-Coulomb. This dissertation is an attempt to rectify the current situation by considering four more advanced friction models, and coding them in FORTRAN for use with the finite element program ABAQUS. The new models are: a quasi-steady-state sliding model proposed by Zhang, Moslehy and Rice; a nonlinear pressure-dependent model proposed by Wriggers, vu Van and Stein; and a model that includes a film of lubricant proposed by Wilson, Hsu and Huang. The friction models are described in detail, including the algorithmic implementation. The contact problem is then formulated in the Total Lagrangian and Updated Lagrangian formulations for contact between an elastic-plastic (Mises plasticity) body and a rigid tool. The variational (weak) form of the formulation is given and this is then discretised by the finite element method. To test and compare the models three common metal forming processes are simulated: hemispherical punching of a disk, two-dimensional plane strain and three-dimensional cold rolling of a strip, and axisymmetric cup deep-drawing. The results are presented in the form of contour plots of the second invariant of stress (Mises), and the plastic yield and maximum stress. Also graphs for the thickness strain are given. These results are presented for each combination of friction model and process to allow easy comparison of frictional behaviour.