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Item Precipitation hardening in Al-Zn-Mg-Al2O3(p) composite(1999) Kiran, K.S.; Srinivasan, K.The precipitation hardening of a Al-Zn-Mg-Al2O3(p) composite is explored. It is found that the peak hardness achieved is almost double that of precipitation hardening of Al-Zn-Mg alloy or dispersion strengthening of Al-Zn-Mg with 5% Al2O3(p). Toughness is marginally improved and tensile strength is one and half times that of precipitation hardened Al-Zn-Mg alloys. The ageing time for peak hardness is reduced due to acceleration of formation of precipitate. Indian Academy of Sciences.Item High temperature compression testing and determination of warm working temperature for commercial purity aluminium(1999) Rao, B.K.; Khadar, M.S.A.; Srinivasan, K.CP aluminium was subjected to axysymmetric compression testing at 303, 373, 473, 573 and 673 K. Strength coefficient and strain hardening exponent were determined from log-log plot of true stress and true strain at different temperatures. True stress vs temperature at different strains indicated that dynamic strain ageing (DSA) occurred between 473 and 673 K. Warm working is to be done between 423 K and 473 K, so that optimum substructure hardening and strain hardening can be achieved during mechanical processing. Indian Academy of Sciences.Item Influence of die angle on containerless extrusion of commercially pure titanium tubes(2007) Srinivasan, K.; Venugopal, P.Containerless tube extrusion has been investigated with commerically pure titanium at room temperature and a strain rate of 0.07 s-1 using 20 conical dies of five different strains and four different angles with MoS2 lubricant. Theoretical punch pressures have been calculated using appropriate equations from slab analysis of the process and compared with experimentally determined punch pressures. It is found that there exists an optimum angle at which the punch pressure is the least at a given strain.Item Hardness-stress-strain correlation in titanium open die extrusion: an alternative to visioplasticity(1999) Srinivasan, K.; Venugopal, P.A heterogeneous process such as open die extrusion has been done on CP titanium and the extent of heterogeneity has been determined. The pressure for carrying out the process has been calculated theoretically, measured experimentally and calculated indirectly from hardness measurement in the deformation zone. Hardness-stress-train correlation is very useful here. A nomogram has been given so that knowing, ?, ?, ? and hardness, the punch pressure can be read off. It is a steady-reckoner that is very relevant for the shop floor in industry or the laboratory.Item Hardness-stress-strain correlation in copper and brass through compression testing(1996) Dharmaveera, N.; Srinivasan, K.A simple method of characterizing local stress and local strain variation in metal working is suggested. It is an alternative to complex and time consuming visioplastic technique. A power law expression exists for hardness and strain similar to that of stress and strain. A linear expression relating hardness and stress has been estahlished. These are valid not only for pure metals but also for their alloys. Meshap Science Publishers.Item Hardness-stress-strain correlation in aluminium - A simpler alternative to visioplasticity in metal forming(1996) Dharmaveera, N.; Srinivasan, K.Local stress and strain variations in the deformation zone can be ascertained by measuring hardness. Hardness is correlated with strain and stress. The expressions discussed later are useful in determining the local variations in stress and strain from hardness measurement. It is a simple method compared to visioplasticity. One can estimate the forces required for a forming process. It helps in the choice of equipment, design of tooling and selection of lubricant for the particular process.Item Friction factor of CP aluminium and aluminium-zinc alloys(2006) Vidhya, Sagar, N.; Anand, K.S.; Mithun, A.C.; Srinivasan, K.Friction factor has been determined for CP aluminium and aluminium-zinc alloys using ring compression test at different temperatures from 303 K to 773 K. It is found that CP aluminium exhibits sticking whereas Al-Zn alloys do not exhibit sticking at elevated temperatures. Hot working of Al-Zn alloy is easier than that of CP aluminium at 773 K. As zinc content increases up to 10 wt% the friction factor decreases up to 0.02. Indian Academy of Sciences.Item Formability limit in containerless (open die) extrusion of commercial purity titanium rods and tubes(2008) Srinivasan, K.; Venugopal, P.Containerless extrusion requires far less forces compared to conventional direct extrusion of rods and tubes due to the elimination of container wall-billet friction. But the strains that can be imparted are less in the former due to the unsupported billet which gets upset first if the axial stress exceeds yield stress of the billet material. If this stress is equal to yield stress, it corresponds to the limit of the process of pure containerless extrusion. It is found that this limit strain as predicted by theory is far less compared to what is observed experimentally. This discrepancy is explained on the basis of heating that takes place in the deformation zone due to ideal, frictional, and shear work done in carrying out the extrusion process.Item Finite element analysis of open die extrusion of al-5zn-1mg alloy [Analiza izguravanja legure al-5zn-1mg kroz otvoreni kalup pomo]u kon?nih elemenata](2009) Geethalakshmi, K.; Srinivasan, K.In this work, an effort has been made to study the open die extrusion of Al-5Zn-1Mg alloy using finite element analysis. The two basic parameters of open die extrusion, i.e., die included angle and the extrusion strain are varied to find the corresponding limiting strain values. Effect of main parameters on the open die extrusion is analyzed, and the limiting range of deformation is obtained. The results obtained are verified by means of contrasting with the experimental data. Pure open die extrusion is found to be possible for extrusion strain (relative strain during extrusion) up to 0.28. However, as the extrusion strain increases from 0.09 to 0.28, upsetting dominates over pure extrusion on varying the die angle from 12 to 40 .Item Direct and inverted open die extrusion (ODE) of rods and tubes(2004) Srinivasan, K.; Venugopal, P.Open die extrusion (ODE) has been done on AISI 1020 steel, commercial purity aluminium and commercial purity titanium, in both direct and inverted modes. It was found that inverted extrusion requires lesser forces than direct extrusion. Limit strains are more for the former than for the later as measured experimentally and as calculated theoretically. Theoretical limit strains are lesser than experimental ones in both the case of rods and tubes. ODE is only for shorter components due to unsupported billet and interference from buckling. It is also only for smaller strains due to interference from upsetting of unsupported billet above the die rather than extrusion through the die. 2004 Elsevier B.V. All rights reserved.