• K Ankamma

      Articles written in Sadhana

    • In-plane anisotropy in tensile deformation and its influence on the drawability of Nimonic C–263 alloy sheets

      K Ankamma D V V Satyanarayana G Chandramohan Reddy M Komaraiah N Eswara Prasad

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      An effort has been made to comprehensively evaluate and rationalize the in-plane anisotropy in tensile properties and the effect of aging on the nature of deformation (strain hardening behaviour) and formability characteristics, especially the limit drawing ratio and forming limit diagram. Despite weak crystallographic texture and excellent ductility and high work hardening exponents, the alloy sheets of C-263 exhibit significant extent of in-plane anisotropy in its tensile properties and yield loci. The absolute magnitudes of yield stress and the exact nature of anisotropy that can be predicted from the tensile part of the yield locus need to be employed with caution. This is because when the magnitudes of the yield stresses, obtained from yield locus are more than 5 times higher as compared to the yield and ultimate tensile strength values and the nature and degree of in-plane anisotropy under tensile loading matches with that of only the compressive yield stresses of yield locus. The alloy sheet, due to weak crystallographic texture and relatively high strengths, is found to be far more suitable for structural applications, rather than for deep drawing applications, which was reflected in low limit drawing ratio values (1.34 for CR+ST and 1.23 for peak aged conditions). Further, the study conducted reveals that the safer forming limits in strain space is higher for CR+ST condition; while, the safer forming limits in stress space are higher for peak aged (CR+ST+1073 K/8 h) condition. Finally, detailed studies are outlined to arrive at suitable microstructural and textural characteristics that provide significantly enhanced drawability in the Nimonic C-263 alloy sheets.

    • Optimization of burnishing parameters and determination of select surface characteristics in engineering materials

      P Ravindra Babu K Ankamma T Siva Prasad A V S Raju N Eswara Prasad

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      The present study is aimed at filling the gaps in scientific understanding of the burnishing process, and also to aid and arrive at technological solutions for the surface modifications based on burnishing of some of the commonly employed engineering materials. The effects of various burnishing parameters on the surface characteristics, surface microstructure, micro hardness are evaluated, reported and discussed in the case of EN Series steels (EN 8, EN 24 and EN 31), Aluminum alloy (AA6061) and Alpha-beta brass. The burnishing parameters considered for studies principally are burnishing speed, burnishing force, burnishing feed and number of passes. Taguchi technique is employed in the present investigation to identify the most influencing parameters on surface roughness. Effort is also made to identify the optimal burnishing parameters and the factors for scientific basis of such optimization. Finally, a brief attempt is made to construct the Burnishing maps with respect to strength level (in this case, average micro hardness of unburnished material).

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