Thesis (PhD)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Dunnage bags are an inflatable dunnage variant, positioned and inflated between
goods in multi-modal containers to restrain and protect the goods while
in transit. This project endeavours to develop a simple method of generating
new numerical prototypes for dunnage bags suitable for simulating operational
loading of the bags. Previous research has produced a model that simulates
the inflation of a paper dunnage bag using a simple pressure load.
A dunnage bag reinforced with plain-woven polypropylene was chosen as
the test case. Woven polypropylene is a highly non-linear, non-continuous,
non-homogeneous material that requires specialised material models to simulate.
A key aspect of this project was to develop a simple method for characterising
woven-polypropylene and replicating it's response with material models
native to LS-DYNA. The mechanical response of the plain-woven polypropylene
was tested using a bi-axial tensile test device. The material response from
physical testing was then mapped to two material models using the numerical
optimiser LS-OPT. The response of the calibrated material models was found
to correlate well with the measured response of the woven material.
Dunnage bags are subjected to cyclic loading in operation. In order to
capture the effects of compressing the contained gas, a gas inflation model was
added to the model that calculates the pressure in the bag based on the Ideal
Gas Law. A full bag model making use of the calibrated material models and
the inflation model was subjected to a cycled boundary condition simulating
loading and unloading of an inflated dunnage bag. The two prototype models
captured the pressure drop in the bag due to material plastic deformation and
the restraining force produced by the bag to within 10 %. The prototype models
were also found suitable for predicting burst pressure in voids of arbitrary
size and shape. / AFRIKAANSE OPSOMMING: Stusakke is 'n opblaasbare soort stumateriaal wat tussen goedere in multimodale
vraghouers geposisioneer en opgeblaas word om sodoende die goedere
vas te druk en te beskerm tydens vervoer. Hierdie projek poog om 'n eenvoudige
manier te ontwikkel om nuwe numeriese prototipes vir stusakke, geskik
om operasionele lading van die sakke te simuleer, te ontwikkel. Vorige navorsing
het 'n model ontwikkel wat die opblaas van 'n papier stusak met eenvoudige
drukkrag simlueer.
'n Hoë-vlak stusak versterk met plein-geweefde polipropileen, is gekies om
getoets te word. Geweefde polipropoleen is 'n hoogs nie-lineêre, onderbroke,
nie-homogene materiaal wat gespesialiseerde materiaalmodelle nodig het vir
simulasie. Een van die fokuspunte van hierdie projek is om 'n eenvoudige
metode te ontwikkel om die karaktereienskappe van polipropoleen te identifiseer en die gedrag daarvan na te maak met die materiaalmodelle van LSDYNA.
Die meganiese reaksie van die plein-geweefde polipropoleen is getoets
met 'n biaksiale/tweeassige trektoets-toestel. Die materiaal se reaksie op die
fisiese toets is ingevoer op 'n numeriese optimiseerder, LS-OPT, om op die
materiaalmodelle te toets. Die reaksie van die gekalibreerde materiaalmodelle
het goed gekorelleer met die gemete reaksie van die geweefde materiaal.
Stusakke word tydens diens onderwerp aan sikliese lading. Om die effek van
die saamgepersde gas vas te stel is 'n gas-opblaasbare model bygevoeg by die
model wat die druk in die sak bereken, soos gebaseer op die Ideale Gas Wet. 'n
Volskaalse sakmodel wat gebruik maak van die gekalibreerde materiaalmodelle
en die opblaas-model is onderwerp aan sikliese grensvoorwaardes wat die lading
en ontlading van 'n opblaasbare stusak simuleer. Die twee prototipe modelle
het die drukverlies in die sak a.g.v. die materiaal-plastiek vervorming en die
bedwingingskrag van die sak beperk tot 10 %. Die protoyipe modelle is ook
geskik bevind om barsdruk in arbitrêre leemtes te voorspel.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/97124 |
| Date | 03 1900 |
| Creators | Venter, Martin Philip |
| Contributors | Venter, G., Stellenbosch University. Faculty of Engineering. Dept of Mechanical and Mechatronic Engineering. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | 173 pages : illustrations |
| Rights | Stellenbosch University |
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