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Modelling of Innovative Controllable Structures
Made of Granular Materials
RobertZalewski
1
andPawełSkalski
2
1
InstituteofMachinesDesignFundamentals,
84NarbuttaSt.,Warsaw,02-524,Poland
robertzalewski@wp.pl
2
InstituteofAviation,CentreofNewTechnologies,
110/114 al.Krakowska,Warsaw,02-256,Poland
pawel.skalski@ilot.edu.pl
Abstract.
Theviscoplasticbehaviorof”innovative”structureisconsid-
ered.Investigatedstructuresarecreatedonthebasisofvacuumpacked
particles. Partial vacuum generated inside a hermetic sleeve filled with
loosegranularmaterialtransformsthesystemfromsemi-liquidtosemi-
solid state. Such phenomenon, known as a ”jamming mechanism”, is
strongly nonlinear in considered structures. Special granular structures
haverecentlyfoundinterestingengineeringandbiomedicalapplications
such as vacuum mattresses, orthopedic orthesis, universal robotic grip-
pers and flexible endoscopes. To capture a response of the specially
designed granular sample to external loading, a Bodner-Partom vis-
coplastic constitutive model has been chosen. The identification proce-
dureisbasedonexperimentalcompressiontestsrealizedatvariousstrain
ratesandunderpressurelevels.
Keywords:
vacuum packed particles, Bodner-Partom model, identifi-
cation,experiments.
1
Introduction
Structures composed of loose PVC grains encapsulated in a plastic envelope
andsubjecttoapartialvacuum(underpressure)revealmotivatingandunusual
features.Theunderpressurevaluehasagreatimpactonthebehaviourandprop-
ertiesofsuch a material.Thisparticularcharacteristiccouldbe verypractical
insomespecific,realisticapplications.Thetypicalexamplecanbe semi-active
dampingofharmfulvibrations[1,2],oracontrollablecomponentincreasingreli-
abilityofacomplextechnicalsystem[3].Theconstructionideaofthisgranular
mediumconsistsoffillingatightenvelope,havingunlimitedshapeanddimen-
sions, with a loose material. Typical material for envelopes could be latex or
asoftplastomer.Theenvelopeshouldbereasonablyflexibletoprovideanun-
boundedchangeofthecontour,accordingtotheconstructionaldemands.
Thegranularmaterialenclosedinatightspaceenableseasychangeofstruc-
turalformandfunctionaluseofitasakindofaplasticbulkfillingthespecial
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