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Investigating an inverse finite element approach for characterising soft materials
Thesis (MEng)--Stellenbosch University, 2020.
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| Format: | Thesis |
| Language: | English |
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Stellenbosch : stellenbosch University
2020
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| _version_ | 1867613800951185408 |
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| access_status_str | Open Access |
| author | Bresler, Franciena Helena |
| author2 | Muller, Jacobus Hendrik |
| author_browse | Bresler, Franciena Helena Muller, Jacobus Hendrik |
| author_facet | Muller, Jacobus Hendrik Bresler, Franciena Helena |
| author_sort | Bresler, Franciena Helena |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (MEng)--Stellenbosch University, 2020. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/108068 |
| institution | Stellenbosch University (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:41:54.752Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2020 |
| publishDateRange | 2020 |
| publishDateSort | 2020 |
| publisher | Stellenbosch : stellenbosch University |
| publisherStr | Stellenbosch : stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/108068 Investigating an inverse finite element approach for characterising soft materials Bresler, Franciena Helena Muller, Jacobus Hendrik Venter, Gerhard Stellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering. Finite element method Soft materials Micro-indentation Gradient optimisation UCTD Thesis (MEng)--Stellenbosch University, 2020. ENGLISH ABSTRACT: Micro-indentation was investigated as a method for characterising soft materials. This research characterised a soft silicone rubber using an inverse finite element (FE) approach with six different indentation tests. Four tests consisted of a cylindrical indenter, with the variability factors being the number of indenters and orientation of the indenter. Two tests consisted of a spherical indenter, with the difference between the tests being the number of indenters used. Each indentation test consisted of two FE models, one containing a known MooneyRivlin three parameter material model and one which needed characterisation. MSC Marc Mentat (2019) was used to perform all FE analysis. The remeshing feature within Marc was implemented within the FE analysis to minimise the element distortion present when deforming a non-linear material to a complex deformation field. Python was used to develop a numerical pipeline, which controlled and linked the different software and procedures. Two optimisation algorithms were investigated, Sequential Quadratic Programming (SQP) and Sequential Linear Programming (SLP). Radial Basis Functions (RBF) were used to interpolate the FE analysis results. The root mean square (RMS) error of the displacement fields, was minimised as objective function within the optimisation procedure. It was found that one cylindrical indenter, applied in a diagonal orientation across a square test sample, obtained the best material model using the SQP optimisation algorithm. From the observations within the results, it was concluded that a material model either matched the displacement field or the engineering vs. stretch nearly perfectly, but not both simultaneously. AFRIKAANSE OPSOMMING: Mikro-indentasie is ondersoek as ’n metode om sagte materiale te karakteriseer. ’n Sagte silikoonrubber is ondersoek waarvan die meganiese gedrag gekenmerk is deur ses verskillende indentasietoetse te gebruik. Vier toetse het bestaan uit ’n silindriese indentator, met die veranderlikheidsfaktore, die aantal indentators en oriëntasie van die indentator. Twee toetse het bestaan uit ’n sferiese indentator, met die aantal indentators, die verskil tussen die toetse. Hierdie tesis was gebaseer op twee eindige element modelle per indentasie toets. Een met ’n bekende materiaalmodel en een wat gekarakteriseer moet word. ’n Inverse eindige element benadering is gebruik om die een eindige element model volgens die bekende materiaal veranderlikes te karakteriseer met behulp van die MooneyRivlin drie parametermodel. Die "remesh"metode, vanuit MSC Marc Mentat (2019), is binne die eindige elementanalise geïmplementeer, om die element verdraaiings wat voorkom in ’n komplekse vervormingsveld van ’n nie-lineêre materiaal, tot ’n minimum te beperk. ’n Numeriese pyplyn is ontwikkel om die verskillende sagteware en metodes met mekaar te verbind. Twee beperkte gradiënt gebaseerde optimeringsalgoritmes is vir elke indentasietoets ondersoek naamlik, Sekwensiële Kwadratiese Programmering (SQP) en Sekwensiële Lineêre Programmering (SLP). ’n Latin Hypercube (LHC) -ontwerp van eksperimente is gebruik om uitvoerbare veranderlikes vir die optimaliseringsprosedure te verkry. ’n Radiale basisfunksie (RBF) het die resultate vanaf die twee eindige element analise geïnterpoleer om bymekaar te pas. Die fout, bepaal vanaf die verskil tussen die twee eindigende element modelle se verplasingsvelde, word geminimaliseer tydens die optimaliseringsprosedure. Daar is gevind dat een silindriese indentator, toegepas in ’n diagonale oriëntasie oor ’n vierkantige toetsmonster, die beste materiaalmodel verkry met behulp van die SQP-optimeringsalgoritme. ’n Finale gevolgtrekking vanuit die resultate het voorgestel dat die materiaal model of die verplasingsveld perfek pas of die ingenieurs stress teenoor strek, maar nie albei gelyktydig nie. Masters 2020-02-25T13:00:32Z 2020-04-28T12:17:27Z 2020-02-25T13:00:32Z 2020-04-28T12:17:27Z 2020-04 Thesis http://hdl.handle.net/10019.1/108068 en Stellenbosch University xvii, 120 leaves : illustrations (some color) application/pdf Stellenbosch : stellenbosch University |
| spellingShingle | Finite element method Soft materials Micro-indentation Gradient optimisation UCTD Bresler, Franciena Helena Investigating an inverse finite element approach for characterising soft materials |
| title | Investigating an inverse finite element approach for characterising soft materials |
| title_full | Investigating an inverse finite element approach for characterising soft materials |
| title_fullStr | Investigating an inverse finite element approach for characterising soft materials |
| title_full_unstemmed | Investigating an inverse finite element approach for characterising soft materials |
| title_short | Investigating an inverse finite element approach for characterising soft materials |
| title_sort | investigating an inverse finite element approach for characterising soft materials |
| topic | Finite element method Soft materials Micro-indentation Gradient optimisation UCTD |
| url | http://hdl.handle.net/10019.1/108068 |
| work_keys_str_mv | AT breslerfrancienahelena investigatinganinversefiniteelementapproachforcharacterisingsoftmaterials |