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DC Field | Value | Language |
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dc.contributor.advisor | Sowerby, R. | - |
dc.contributor.author | Tsoi, Davy Chi keung | - |
dc.date.accessioned | 2024-08-30T15:16:04Z | - |
dc.date.available | 2024-08-30T15:16:04Z | - |
dc.date.issued | 2001-05 | - |
dc.identifier.uri | http://hdl.handle.net/11375/30116 | - |
dc.description.abstract | One of the goals of this thesis was to establish how the texture i.e. the preferred orientation of the grains, evolved during the cold rolling of a low carbon steel. The material was reduced in a commercial cold rolling mill, located at the Dofasco steel company in Hamilton. The original intention was to vary the reduction at each roll stand and to alter the front and back tension of the sheet between each stand, to see what effect this would have on the resulting texture. However, this proved to be too ambitious since the company did not want a commercial piece of equipment to be out of service for long periods of time. Consequently only one mill setting was investigated, using a 5-stand, 4- high mill. Nonetheless this provided a rare opportunity to measure mechanical and metallurgical properties after each roll stand - information which is usually not available in the open literature. The mill was stopped during production and samples were cut from the sheet between each roll stand for subsequent analysis. The texture after each roll stand was revealed by a metallurgical examination through the use of pole figures. The texture that ensued was typical of a cold rolled steel, as observed by previous workers, and did not change much after passing through the first stand. The dominant crystallographic orientation was (100) and (110) planes lying in the plane of the rolled sheet. Texture measurements were performed at the Los Alamos National Laboratories in New Mexico, who had also developed software to predict the texture evolution. However, it was decided to keep the experimental measurements and the theoretical predictions separate, and researchers at Queen’s University agreed to handle the analysis using a software package developed by Van Houtte. As described in the text, the approach invoked the use of Crystallite Orientation Distribution Functions (CODFs) analysis based on the following, a) Some measured pole figures for the as-received material only, b) an assumed deformation mode in each roll stand, c) an assumed crystallographic slip system and d) some mechanical property data. It turned out that the measured and predicted pole figures showed very good agreement, and so established the predictive capabilities of the software package for the cold rolling process. In addition to predicting the texture, CODF analysis can predict the corresponding plane stress crystallographic yield loci along with the variation in the normalized yield stress and the r-value at any orientation 0 to the rolling direction. A great deal of time was devoted to establishing a reliable anisotropic yield function that could be used in the modelling of deformation processes. The work due to Barlat and his co-workers seemed very promising, although many of the details required to independently develop these models were not given in the original publications. The necessary algorithms were developed as part of this work. Under normal circumstances various coefficients in the analytical yield function would be determined from mechanical property data e.g. ro, r45, Co3 <*b etc., as explained in the text. In the present study this information was not available and instead theoretical values from the CODF analysis performed at Queen’s University were used. These data are referred to in the text as pseudo-experimental. It turned out that Barlat’s yield model can duplicate with good accuracy the crystallographic yield loci predicted at Queen’s University3 and therefore some confidence can be placed in the predictive capabilities of the model. As a further check on the accuracy of Barlat’s model a number of other anisotropic yield functions were compared. Some of these plane stress yield functions could accommodate an applied shear stress while others could not. Barlat’s model was the most effective in predicting not only the shape of the crystallographic yield loci, but also the variation in the normalized yield stress and the r-value in the plane of the rolled sheet with the angle 0 to the rolling direction. Results arising from the use of the SEM showed little evidence of macroscopic shear banding which is often observed in heavily cold rolled material. However, coarse slip bands were present and these increased with increasing deformation. The tensile ductility of the material was exhausted i.e. the yield stress and the ultimate stress were the same, after passing through the first stand. As would be expected both the yield stress and the hardness of the material increase with increasing reduction and these values are examined in the text. | en_US |
dc.language.iso | en | en_US |
dc.title | Texture Evolution in Cold Rolled Low Carbon Steel Sheet and the Development of Some Corresponding Anisotropic Yield Functions | en_US |
dc.type | Thesis | en_US |
dc.contributor.department | Mechanical Engineering | en_US |
dc.description.degreetype | Thesis | en_US |
dc.description.degree | Master of Engineering (ME) | en_US |
Appears in Collections: | Digitized Open Access Dissertations and Theses |
Files in This Item:
File | Description | Size | Format | |
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Tsoi_Davy_C_K_2001May_masters.pdf | 8.37 MB | Adobe PDF | View/Open |
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