[Show abstract][Hide abstract] ABSTRACT: Drawbeads are often applied in the deep drawing process to improve control of the material flow during the forming operation. Drawbeads restrain the sheet from flowing freely into die cavity. This paper deals with analysis of effect of draw bead geometry in sheet metal drawing process. Finite element analysis of drawing of circular blanks into axi-symmetric hemispherical cup was done. Circular and rectangular drawbeads were introduced into the Finite Element models and their influence in distribution of strain and thickness were investigated. DYNAFORM and LS-DYNA, a commercially available explicit FEA code were used to model and analyze the forming process respectively. These outcomes are compared with experimental results. The numerical results were found in good agreement with the experimental results. Plastic strain and Von-Mises stresses produced by rectangular drawbeads are higher when compared with the use of circular drawbead. Due to its geometry rectangular drawbead bends and unbends the sheet four times and restrains the material more than circular drawbead.
ARABIAN JOURNAL FOR SCIENCE AND ENGINEERING 04/2012; 37(6). DOI:10.1007/s13369-012-0276-4 · 0.37 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Predicting inhomogeneous deformation in any forging process will definitely be helpful in deciding the tool, billet material, lubrication, annealing sequences, and number of stages to make products. In this work, the influence of varied friction conditions on the hardness and effective strain variation during simple upsetting is studied. Also, hardness variation in a typical cold forging process is predicted by relating hardness and effective strain evolution in a simple upsetting operation empirically. Four different lubricants, viz., castor oil (m=0.33), soap (m=0.25), grease (m=0.2), teflon (m=0.16), are considered for experimentation. The friction factors of these lubricants were obtained from a Ring Compression Test (RCT) and are used in FE simulations of upsetting and forging operations. It is found from the analyses that: (1) Teflon shows relatively less variation in hardness and effective strain depicting homogeneous upsetting operation, whereas other lubricants show a larger variation in hardness and effective strain in radial and axial directions; (2) hardness is observed to vary linearly with effective strain; (3) the empirical relationship between hardness and effective strain obtained from a simple upsetting operation, which is common for all the lubricants, predicts the hardness distribution during the forging-extrusion process with moderate accuracy. This depends on the interface friction conditions, i.e., solid and semi-solid lubricants with better holdability like Teflon and soap show good correlation between experimental and predicted hardness values than liquid lubricant, i.e., castor oil.
Journal of Testing and Evaluation 07/2008; 36(4):371-383. DOI:10.1520/JTE101443 · 0.38 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In this study, salt bath nitrocarburizing and oxidizing of 304, 316, 304L and 316L were experimented. The salt bath nitrocarburizing experiment was carried out at a temperature of 560 0 C and for a time period of 120, 150 and 180 minutes. The oxidation process was carried out at a temperature of 373 0 C and for duration of 60 minutes. Vickers' micro hardness and salt spray test were carried out for the above-mentioned stainless steels before and after diffusion hardening. It was found that salt bath nitrocarburizing effectively increases the hardness of stainless steels 304, 316 304L and 316L. From the microstructure of the nitrocarburized and oxidized specimens, the case depth was measured. The depth of diffusion layer could be attributed to the attraction between the alloying elements Molybdenum and Nitrogen. Also the corrosion resistance of nitrocarburized and oxidized steels is observed to be superior to the untreated specimens.