Information Technology Reference
In-Depth Information
behaviour after yielding of polymers [10,11,12,13]. However to date, the inves-
tigationoftheviscoplasticresponseofpolymersisstillanimportantchallenge.
Moreover,aratherdelicatequestionishowthematerialparametersofamodel
canbe estimated. Various viscoplasticconstitutivemodels proposedin the lit-
eratureinvolvenumerousparameters.Theexperimentaldeterminationofthese
materialconstantscanbeverycomplicatedfortheentirerangeofpossibleap-
plications (e.g. in terms of strain rates or temperatures) and often demands
sophisticated and expensive conditions. On the other hand, a great precision
of these values is necessary to extend the numerical simulations in a realistic
manner beyond the experimental range. In practice, only a limited number of
experimental tests can be provided, and they are carried out for a restricted
rangeofvelocitiesandtemperatures.Formerworksofauthors[14,15,16,17]fo-
cusedonapplicationoftheChaboche'smodeltocapturenonlinearpropertiesof
specialgranularstructures.Subsequentworksrevealedthatsuchanapproachin
notprecisewhenvariousstrainratesareappliedtothegranularstructure.Inthis
work,theidentificationofviscoplasticparametersofconstitutiveequationsfor
structurescreatedonthebasisofpolymergrainsisconsidered.Theoriginalver-
sionofBodner-Partomviscoplasticflowmodel[18]istakenintoconsideration.
Next, analyticalmethodologiesofparameterdeterminationarepresented.The
special granularstructures experimental sample is investigated experimentally
underdifferentunderpressurevalues.Thecapacityoftheproposedviscoplastic
models is studied and the eciency of the analytical, deterministic method of
parametersidentificationisdiscussed.
2 Experiments
Speciallyperformed experimentalsampleofvacuum packedparticleshasbeen
depictedinFig.1.
Fig. 1. Experimentalsample
AccordingtoFig.1,thespecimenconsistedontworigiddisks(2)connectedby
asoftplastomersleeve(4).Thespecialvalve(3)wasgluedontotheairtighten-
velope,enablingairtobepumpedoutofthesystem(generatingunderpressure).
Polypropylenegrains(5)wereplacedinsideasample.
Specialhandles(1)werescrewedintosteeldiscstoenablefastandeasymount-
ingoftheinvestigatedspecimenintotheuniversalstrengthdeviceMTS809.
 
Search WWH ::




Custom Search