Full Text Available
Note: Clicking the button above will open the full text document at the original institutional repository in a new window.
A microtexture based analysis of surface roughening in ductile metals during tensile deformation
This thesis examines the cause and mechanism for the occurrence of parallel surface ridges during the deformation of two specific ductile metal alloys, namely AISI 430 ferritic stainless steel and an aluminium alloy designated AA3002. The investigation considers, in particular, the development of pa...
Saved in:
| Main Author: | |
|---|---|
| Other Authors: | |
| Format: | Thesis |
| Language: | English |
| Published: |
Centre for Materials Engineering
2016
|
| Subjects: | |
| Tags: |
No Tags, Be the first to tag this record!
|
| _version_ | 1867613228146622464 |
|---|---|
| access_status_str | Open Access |
| author | Wittridge, Nicola Janette |
| author2 | Knutsen, Robert D |
| author_browse | Knutsen, Robert D Wittridge, Nicola Janette |
| author_facet | Knutsen, Robert D Wittridge, Nicola Janette |
| author_sort | Wittridge, Nicola Janette |
| collection | Thesis |
| description | This thesis examines the cause and mechanism for the occurrence of parallel surface ridges during the deformation of two specific ductile metal alloys, namely AISI 430 ferritic stainless steel and an aluminium alloy designated AA3002. The investigation considers, in particular, the development of parallel ridges during uniaxial tension, and their effect on the overall surface roughening of the sheet material. A detailed account of the microstructure and texture of the individual sample sheet materials is presented and proposals for the mechanisms of surface roughening are based on plasticity analysis of the actual material data. Both the microstructural characterisation and the texture determination was carried out using mainly electron microscopy techniques. Electron backscattered diffraction techniques were used to measure the microtexture, and analysis of this data allowed the calculation of the plastic flow behaviour of discrete volumes of the sample material. The yield behaviour was implemented in a finite element model to simulate the material behaviour under uniaxial tensile conditions. Analysis of microtexture results has indicated that elongated texture clusters are visible in the aluminium sample material which exhibits severe surface roughening during elongation in the rolling direction. It is proposed that initially surface roughening is the result of a variation in plastic flow of the surface grains due to the local texture clustering. With continued straining, the condition described by the MK analysis for strain localisation is able to arise and this leads to through-thickness strain localisation and necking, and so results in the formation of a ribbed profile. Ridging in stainless steel on the other hand can be attributed to an asymmetric distribution of texture components or plastic flow properties about the mid-plane of the material. An asymmetric arrangement yield properties initiates the development of differential transverse strains about the mid-plane of the material. The variation in transverse strain in turn results in a series of localised bending events which, on a macroscopic level, produces longitudinal corrugations and an overall ridged surface morphology. |
| format | Thesis |
| id | oai:open.uct.ac.za:11427/22543 |
| institution | University of Cape Town (South Africa) |
| language | eng |
| last_indexed | 2026-06-10T12:32:47.627Z |
| license_str | Not specified — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UCTD — University of Cape Town Open Access Repository |
| publishDate | 2016 |
| publishDateRange | 2016 |
| publishDateSort | 2016 |
| publisher | Centre for Materials Engineering |
| publisherStr | Centre for Materials Engineering |
| record_format | dspace |
| source_str | UCTD — University of Cape Town Open Access Repository |
| spelling | oai:open.uct.ac.za:11427/22543 A microtexture based analysis of surface roughening in ductile metals during tensile deformation Wittridge, Nicola Janette Knutsen, Robert D Materials Engineering This thesis examines the cause and mechanism for the occurrence of parallel surface ridges during the deformation of two specific ductile metal alloys, namely AISI 430 ferritic stainless steel and an aluminium alloy designated AA3002. The investigation considers, in particular, the development of parallel ridges during uniaxial tension, and their effect on the overall surface roughening of the sheet material. A detailed account of the microstructure and texture of the individual sample sheet materials is presented and proposals for the mechanisms of surface roughening are based on plasticity analysis of the actual material data. Both the microstructural characterisation and the texture determination was carried out using mainly electron microscopy techniques. Electron backscattered diffraction techniques were used to measure the microtexture, and analysis of this data allowed the calculation of the plastic flow behaviour of discrete volumes of the sample material. The yield behaviour was implemented in a finite element model to simulate the material behaviour under uniaxial tensile conditions. Analysis of microtexture results has indicated that elongated texture clusters are visible in the aluminium sample material which exhibits severe surface roughening during elongation in the rolling direction. It is proposed that initially surface roughening is the result of a variation in plastic flow of the surface grains due to the local texture clustering. With continued straining, the condition described by the MK analysis for strain localisation is able to arise and this leads to through-thickness strain localisation and necking, and so results in the formation of a ribbed profile. Ridging in stainless steel on the other hand can be attributed to an asymmetric distribution of texture components or plastic flow properties about the mid-plane of the material. An asymmetric arrangement yield properties initiates the development of differential transverse strains about the mid-plane of the material. The variation in transverse strain in turn results in a series of localised bending events which, on a macroscopic level, produces longitudinal corrugations and an overall ridged surface morphology. 2016-11-16T13:20:19Z 2016-11-16T13:20:19Z 1998 Doctoral Thesis Doctoral PhD http://hdl.handle.net/11427/22543 eng application/pdf Centre for Materials Engineering Faculty of Engineering and the Built Environment University of Cape Town |
| spellingShingle | Materials Engineering Wittridge, Nicola Janette A microtexture based analysis of surface roughening in ductile metals during tensile deformation |
| thesis_degree_str | Doctoral |
| title | A microtexture based analysis of surface roughening in ductile metals during tensile deformation |
| title_full | A microtexture based analysis of surface roughening in ductile metals during tensile deformation |
| title_fullStr | A microtexture based analysis of surface roughening in ductile metals during tensile deformation |
| title_full_unstemmed | A microtexture based analysis of surface roughening in ductile metals during tensile deformation |
| title_short | A microtexture based analysis of surface roughening in ductile metals during tensile deformation |
| title_sort | microtexture based analysis of surface roughening in ductile metals during tensile deformation |
| topic | Materials Engineering |
| url | http://hdl.handle.net/11427/22543 |
| work_keys_str_mv | AT wittridgenicolajanette amicrotexturebasedanalysisofsurfacerougheninginductilemetalsduringtensiledeformation AT wittridgenicolajanette microtexturebasedanalysisofsurfacerougheninginductilemetalsduringtensiledeformation |