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Title: The relationship between texture and formability in sheet metals
Author: Da Costa Viana, Carlos Sergio
ISNI:       0000 0001 3401 4695
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 1978
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The study of the relationship between texture and the anisotropy of mechanical properties can lead to a better understanding of materials behaviour and, from this, to the development of conveniently textured materials so that their anisotropy can be utilized in an advantageous manner. In the present work mechanical properties, yield loci,formability parameters, earing and the stretching behaviour of a range of differently textured FCC and BCC materials were investigated both theoretically and expereimentally. The Crystallite Orientation Distribution. Function (CODF), expressed in terms of a series of spherical harmonics, waa used to provide a quantitative description of the textures. The crystallographic yield strength anisotropy was assessed via predicted lower bound and upper bound yield loci using both restricted and pencil glide deformation modes. Predicted formability parameters were obtained from the crystallographic upper bound loci. The contribution of individual orientation to the final yield behaviour was also analysed using single crystal yield loci. An experimental assessment of the anisotropy of plastic flow was made by means of both Knoop hardness measurements and tensile and plane-strain compression tests. From the latter, formability and hardening parameters were obtained and compared with the predicted behaviour. The earing behaviour of some FCC and BCC sheet materials was predicted using a crystallogaphic model based on yield locus data. Theoretical and experimental cup profiles of copper, aluminium and steel in different textural conditions were compared and analysed with respect to the influence of specific texture components. The strains reached by a metal sheet undar biaxial stretching before failure by localised necking may depend on the anisotropy of plastic flow. This is in turn a function of the sheet's texture. A quatitative model for the prediction of such limit.strains, based on the crystallographic upper bound yield loci, was developed. This was then used for the calculation of forming limit diagram (FLD) of copper and steels in different textural conditions. These results were compared with experimental limit strains obtained from a testing technique designed to reproduce closely the theoretical conditions. The work also contains a review of the relevant contributions in the areas of texture, yield loci, deep drawing, earing and stretching behaviour of sheet metals.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral