Enhancing the mechanical properties of titanium alloys with rapid heat treatment

This article shows that a significant improvement in the mechanical properties of high-strength titanium alloys can be reached by using a special heat treatment based on rapid heating into the β-field. Such a treatment allows the production of a high-temperature β-phase with a fine-grained microstructure and optimal chemical inhomogeneity, which strongly determines the mechanism and kinetics of phase transformations on cooling and further annealing or aging. A wide range of final microstructures with an enhanced combination of mechanical properties can be obtained.     

An optical roughness sensor for real-time quality measurement

As part of the intelligent processing efforts of the Spray Forming Technology Group at the David Taylor Research Center, a laser stripe sensor has been implemented to monitor preform characteristics. The preform surface roughness is measured in real time and the correlation to preform quality in terms of porosity levels is assessed. The laser stripe method is not a direct indicator of quality, but it can be used with other sensors and advanced control techniques for control of the spray-forming process.     

Ion mobility in Nafion-117 membranes

Transport phenomena in Nafion-117 perfluorosulphonic membranes have been studied by different techniques. Membrane electric conductivity has been measured under alternative current as a function of the equilibrating concentrations of MCI (M = Li, Na, K) and HCl solutions. Conductivities were found to increase for lithium and sodium membrane forms and decrease for the potassium form with an electrolyte concentration increase. The obtained data were compared with the results of diffusion permeability, ion-exchange kinetics, ⁷Li and ³⁵Cl NMR measurements. In all cases permeability increased with electrolyte concentration growth. Diffusion coefficients and transport numbers for different counter- and co-ions were determined. The obtained data are discussed with the use of the two-phase membrane structure model. The selectivity of membrane sorption was found to increase with growth of cation radius.     

Laser remelting of cast iron: a Mössbauer study

The Mössbauer spectroscopy in backscattering technique (CXMS) was used to analyse cw-CO₂ laser-treated samples of cast iron. The depth profile as revealed by Mössbauer phase analysis is discussed in connection with the initial microstructure.     

Petri nets in dynamic process planning

A framework for combining Petri Nets with Computer Aided Process Planning (CAPP) systems is presented. The Petri Nets are used to provide realtime facility status information while the CAPP system is used to generate the revised process plans. Combining these two methodologies overcomes most of the weaknesses with the traditional CAPP systems. The result is a dynamic, realtime CAPP system.     

Relationships between the static and the dynamic moduli of elasticity in cement stabilised materials

Relationships between the static and the dynamic moduli of elasticity are presented for a range of cement stabilised materials and discussed in relation to published data for materials of this type and for concrete. The relationships are basically empirical but an attempt is made to allow for density and for strengths in tension and in compression.     

Stabilite des carrieres souterraines: Methodes d'ausculation dynamique

Bulletin of Engineering Geology and the Environment - Les études de stabilité des carrières souterraines nécessitent notamment une évaluation de l'état de...