Using full field data to produce a single indentation test for fully characterising the mooney rivlin material model.

Simple item page
dc.contributor.advisorVenter, Martin Philipen_ZA
dc.contributor.advisorGerhard Venteren_ZA
dc.contributor.authorVan Tonder, John Deanen_ZA
dc.contributor.otherStellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering.en_ZA
dc.date.accessioned2024-02-22T15:41:54Zen_ZA
dc.date.accessioned2024-04-26T17:41:19Zen_ZA
dc.date.available2024-02-22T15:41:54Zen_ZA
dc.date.available2024-04-26T17:41:19Zen_ZA
dc.date.issued2024-02en_ZA
dc.descriptionThesis (PhD)--Stellenbosch University, 2024.en_ZA
dc.description.abstractENGLISH ABSTRACT: In the field of material characterization, a well-known problem in literature has been identified. The problem involves the solutions obtained from inverse Finite Element analysis when characterizing hyperelastic material model parameters, which are often non-unique. A gap in the literature exists regarding the handling of the non-uniqueness issue. Providing a solution for this has meaningful implications for engineering applications. The nature of these non-unique solutions is that they fit the dataset of the load case they were characterized on with indistinguishable errors from the actual optimal set of model parameters. These solutions prove to be sub-optimal when applied to load cases for which they were not characterized, failing to predict accurate material behaviour. The research presented in this dissertation addresses this non-uniqueness problem for the Mooney Rivlin model by introducing a novel contribution. The contribution involves a newly discovered concept known as hyperplanes, which manifest as flat, plane-like regions in the low-error regions of the design space. This discovery enables the isolating of a single, optimal set of material coefficients. The hyperplanes serve as the foundation for a new inverse Finite Element characterization method formulated as a constrained optimization problem. The main contribution of this formulation is that allows the the user to specify which loading state of the material deformation path they wish to fit. This is achieved by specifying specific measurement points. Additionally, this formulation allows for tolerances to be applied on these measurement points adding an additional level of compliance to the material characterisation. The behaviour of these hyperplanes was investigated, initially through a simulated indentation test that involved full-field digital image correlation experiments. However, these simulations provided a controlled environment to explore the characteristics of hyperplanes under noise-free conditions, leading to the development of the constrained optimization method. The applicability of the hyperplane concept was then validated using physical test data and compared with material testing standards. The results of this comparison study indicated that using hyperplanes in the inverse characterization process produced a more comprehensive set of material parameters than the test standards. In conclusion, this dissertation asserts the indispensable role of hyperplanes in isolating the true optimal set of Mooney Rivlin model parameters, thus addressing the identified gap in the literature and delivering a valuable contribution to the field of material characterization.en_ZA
dc.description.abstractAFRIKAANSE OPSOMMING: In die veld van materiaal karakterisasie, het ’n welbekende probleem in die literatuur na vore gekom. Die probleem hou verband met die oplossings vir die inverse Eindige Element-analise wanneer die parameters van hyperelastiese materiaalmodelle gekarakteriseer word, wat dikwels nie-uniek is nie. Daar bestaan ’n gaping in die literatuur rakende die hantering van hierdie nie-uniekheid. ’n Oplossing vir hierdie probleem het betekenisvol implikasies vir ingenieurswesetoepassings. Die aard van hierdie nie-unieke oplossings is dat hulle voorkom asof hulle pas by die datastel van die lasgeval waarop hulle gekarakteriseer is, met foutwaardes wat amper ononderskeidbaar is van die werklike optimale stel modelparameters. Hierdie oplossings blyk egter suboptimaal te wees wanneer hulle op ongekarakteriseerde lasgevalle toegepas word en kan nie akkurate materiaalgedrag voorspel nie. Die navorsing in hierdie proefskrif spreek hierdie nie-uniekheidsprobleem vir die Mooney Rivlin model aan deur ’n nuwe bydrae te lewer. Hierdie bydrae behels ’n nuut ontdekte konsep genaamd ’hyperplanes’, wat as plat, vlakagtige areas in die lae-foutgebiede van die ontwerpruimte voorkom. Hierdie ontdekking maak dit moontlik om ’n enkele, optimale stel materiaalkoëffisiënte te isoleer. Die hyperplanes dien as die basis vir ’n nuwe inverse Eindige Element-karakteriseringsmetode, wat as ’n beperkte optimaliseringsprobleem geformuleer is. Die hoofbydrae van hierdie formulering is dat dit die gebruiker in staat stel om te spesifiseer in watter belastingstoestand van die materiaalvervormingspad hulle wil pas. Dit word bereik deur spesifieke meetpunte te spesifiseer. Daarbenewens maak hierdie formulering dit moontlik dat toleransies op hierdie meetpunte toegepas kan word, wat ’n addisionele vlak van nakoming aan die materiaal karakterisering toevoeg. Die gedrag van hierdie hyperplanes is sorgvuldig ondersoek, aanvanklik deur gesimuleerde induksietoetse met volveld Digitale Beeldkorrelasie eksperimente. Hierdie simulasies het ’n gekontroleerde omgewing gebied om die eienskappe van die hyperplanes onder geraasvrye toestande te ondersoek, wat die pad gebaan het vir die ontwikkeling van die beperkte optimaliseringsmetode. Die toepaslikheid van die hyperplane-konsep is daarna bevestig deur gebruik te maak van fisiese toetsdata en dit te vergelyk met materiaaltoetsstandaarde. Die resultate van hierdie vergelykingsstudie het aangedui dat die gebruik van hyperplanes in die inverse karakteriseringsproses ’n meer omvattende stel materiaalparameters lewer as die standaarde, selfs al het die materiaalmodelparameters soortgelyke waardes. Ten slotte bevind hierdie proefskrif die onontbeerlike rol van hyperplanes in die isolering van die ware optimale stel Mooney Rivlin modelparameters en adresseer sodoende die geïdentifiseerde gaping in die literatuur deur ’n waardevolle bydrae aan die materiaalkarakteriseringsveld te lewer.af_ZA
dc.description.versionDoctorateen_ZA
dc.format.extentxvii, 145 pages : illustrationsen_ZA
dc.identifier.urihttps://scholar.sun.ac.za/handle/10019.1/130440en_ZA
dc.language.isoen_ZAen_ZA
dc.language.isoen_ZAen_ZA
dc.publisherStellenbosch : Stellenbosch Universityen_ZA
dc.rights.holderStellenbosch Universityen_ZA
dc.subject.lcshFinite element methoden_ZA
dc.subject.lcshMooney-Rivlin modelen_ZA
dc.subject.lcshMaterial characterizationen_ZA
dc.subject.lcshUCTDen_ZA
dc.titleUsing full field data to produce a single indentation test for fully characterising the mooney rivlin material model.en_ZA
dc.typeThesisen_ZA
Files
Original bundle
Now showing 1 - 1 of 1
Thumbnail Image
Name:
vantonder_using_2024.pdf
Size:
9.24 MB
Format:
Adobe Portable Document Format
Description:
Download
Collections
Doctoral Degrees (Mechanical and Mechatronic Engineering)