On high-speed turning of a third-generation gamma titanium aluminide

Gamma titanium aluminides are heat-resistant intermetallic alloys predestined to be employed in components suffering from high mechanical stresses and thermal loads. These materials are regarded as difficult to cut, so this makes process adaptation essential in order to obtain high-quality and defect-free surfaces suitable for aerospace and automotive parts. In this paper, an innovative approach for longitudinal external high-speed turning of a third-generation Ti-45Al-8Nb- 0.2C-0.2B gamma titanium aluminide is presented. The experimental campaign has been executed with different process parameters, tool geometries and lubrication conditions. The results are discussed in terms of surface roughness/integrity, chip morphology, cutting forces and tool wear. Experimental evidence showed that, due to the high cutting speed, the high temperatures reached in the shear zone improve chip formation, so a crack-free surface can be obtained. Furthermore, the use of a cryogenic lubrication system has been identified in order to reduce the huge tool wear, which represents the main drawback when machining gamma titanium aluminides under the chosen process condition

Assessing the use of NMR chemical shifts for prediction of VLE in non-ideal binary liquid mixtures

A method of estimating vapour liquid equilibrium (VLE) using NMR chemical shift data has been proposed by Xu et al. (2012). This method is based on the concept that the average local composition around each species is determined by the thermodynamics of the system, and also determines the screening of the NMR active groups within that molecule, and so their NMR chemical shifts. Xu et al.‘s method has been replicated and verified; results are confirmed to be accurate for alcohol + hydrocarbon mixtures, giving VLE predictions of comparable accuracy to the UNIFAC, generally considered the best predictive activity coefficient model available. However, for more strongly non-ideal mixtures, the method becomes less reliable, giving significantly less accurate predictions of total pressure than UNIFAC. Several causes for this are identified. The model proposed by Xu et al. (2012) is unable to fit minima or maxima in chemical shifts, which are observed experimentally in some binary mixtures. Different NMR resonances within the same molecule lead to different predictions of VLE, clearly an un-physical result. The thermodynamics of strongly non-ideal mixtures are determined by more complex interactions than a simple description of average local composition around each component in the mixtures, for example strong and directional hydrogen bonds. Different groups within the same molecule may have different local compositions in their immediate vicinity; for example in the case of alcohol + water mixtures, one would expect a clustering of water molecules around the hydroxyl group but not the aliphatic group. Hence, the concept of a simple local composition model is not valid for these more complex cases, and it is therefore not surprising that a model based on this simple concept is often not effective in predicting VLE.C. D’Agostino would like to acknowledge Wolfson College, Cambridge, for supporting his research activities.This is the accepted manuscript. The final version is available from Elsevier at http://www.sciencedirect.com/science/article/pii/S0009250914004461

Spring salmon enhancement on the Delphi Fishery, Ireland

This paper summarises the results of an Atlantic salmon (Salmo salar) enhancement programme on the Delphi Fishery in the west of Ireland between 1991 and 1995. The aim of the programme was to increase salmon rod catches in the wake of a sea trout stock collapse. Smolts from two other Irish rivers, Burrishoole and Corrib, were released alongside Delphi fish and differentially tagged. Record angling catches were subsequently recorded. Catch rates varied from 0.6 to 12.7 per 1,000 smolts released. The comparative performance of the different stocks is assessed, with significant differences emerging between the stocks and between year classes In terms of survival/exploitation rates, run limes, sex ratios and homing patterns. The Delphi fish produced consistently lower overall returns than the Burrishoole groups, but consistently much higher numbers of early-running multi-sea-winter (MSW) salmon. These MSW salmon were predominantly female, while Delphi grilse were predominantly male. The Corrib fish performed relatively poorly. The smaller MSW salmon component of the non-indigenous groups ran later in the season than their Delphi counterparts. Important size differences in adult returns were noted and related to stock, sex, husbandry and selection by interceptory fisheries. It is suggested that the MSW salmon component of Delphi stocks is attributable to genetic factors, possibly linked to low freshwater temperature regimes. The programme has contributed to an increase in estuarine droll netting. Exploitation of grilse by all forms of coastal net ranged from 56% to 87%. Exploitation of MSW salmon by nets was lower, ranging from 0% to 54%, the lowest rates being achieved by the early-running Delphi MSW salmon. The programme is expensive and cannot be justified in terms of direct angling revenue. But when related accommodation income is taken into account, the financial results and the sustainment of the fishery's capital value broadly justify the programme to date