| Summary: | 碩士 === 國立台灣工業技術學院 === 機械工程技術研究所 === 85 === A methodology for formulating an elasto-plastic finite-
element model,whichbased on an updated Lagrangian formulation ,
Prandtl-Reuss flow rule and vonMises yield condition , is
developed to simulate the hole-flanging process.An extended r-
min algorithm is proposed to formulate the boundary conditions
,such as nodal penetration and separation , alteration of
sliding direction offriction which vary throughout the entire
process of sheet bending , lineariz-ation of strain increment
and rotatnal increment and altered elasto-plasticstate of
material.A modified Coulomb's friction law is introduced to
describethe alternation between the sliding state and the
sticking state of frictionthe contact interface . The
corresponding stiffness equations and solutionalgorithms are
introduced . According to the developed finite element model
,the hole-flanging process is simulated under the axisymmetrical
condition. Thesimulation results , such as (1) the whole
deformation histroy,(2) the entireloading process histroy , (3)
final shape of workpiece after unloading and (4)thickness of the
workpiece , are compared with the experimental data . A
goodagreement between the simulation results and the
experimental data is observed.According to the experimental data
, the prediction of the phenomenon ofneccking of the hole-
flanging occurs at the inner hole is investigated. The
smulation clearly demonstrates the efficiency of the model to
simulatehole-flanging processes that are carried out under large
deformation and con-tact history . This thesis has provided an
improved understanding of the hole-flanging processes for
improving the manufacturing processes and thedesign oftools.
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