The simulation for damage of metal powder compacts during forming
The main models of describe metal powder compacting are introduced in this paper. Based on a new model derived from Lee's metal powder compacting model and plastic theory for porous material, the scent of damage status of two-level flanged metal powder compacts during forming is simulated and the damage state and cracking process of compacts in different load process are followed up.
Stage 1 Compaction Behaviour of Tool Steel Powder Under Die Pressing
Abstract The stage 1 compaction behaviour of tool steel powder under die pressing was studied. The effects of friction between the powder and the die wall were also investigated under different die pressing modes. The e1astop1asticconstitutive equations based on the yield functions by Fleck et al. and by Shima and Oyane were implemented in a finite element programme to simulate die compaction processes. Finite element calculations were compared with experimental data for densification and density distributions of tool steel powder under single and double action die pressing. Finite element calculations using the yield function by Fleck et al. agreed better with experimental data than those by Shima and Oyane. PM/0775
Effect of Aeration and Agitation Regimes on Lipase Production by Newly Isolated Rhodotorula mucilaginosa–MTCC 8737 in Stirred Tank Reactor Using Molasses as Sole Production Medium
The influence of media and process parameters (aeration and agitation) on fermentation broth rheology and biomass formation has been studied in 1.5-l stirred tank reactor for lipase production using Rhodotorula mucilaginosa MTCC 8737. Molasses, as sole production medium, is used for lipase production by varying aeration (1, 2, and 3 vvm) and agitation speeds (100, 200, and 300 rpm). Maximum lipase activity of 72 U/ml was obtained during 96 h of fermentation at 2 vvm, 200 rpm, pH 7, and 25 ± 2°C temperature. Lipase production kinetics with respect to dry cell weight of biomass showed YP/S of 25.71 U/mg, specific product formation of 10.9 U/mg DC, and YX/S 2.35 mg/mg. Maximum lipase activity (MC 2) of 56 U/ml was observed at 1% molasses, and a further increase in the molasses concentration of (%) 1.5 and 2 inhibited the product formation of lipase with 15 and 8.5 U/ml, respectively. The production kinetics of molasses media showed YP/X was 14 U/mg DC, YP/S 16 U/mg, and YX/S 1.14 mg/mg during 96 h of bioreactor operation. The kLa values for all batches (MC 1–MC 4) at 96 h of fermentation were 32, 28, 21, and 19/h, and the |oxygen transfer rate were 54.4, 56, 35.7, and 17.29 mg/l h, respectively. Increase in molasses concentration resulted in decreased lipase activity by increase in viscosity of the fermentation broth.