Microstructure control in precious metal coatings for high temperature applications,obtained by metallorganic chemical vapour deposition

In most high temperature applications, efficiency increases with service temperature of the component. Especially in combustion chambers, higher efficiency is translated into less propellant consumption and therefore a lower weight and a reduction of operational cost. In these components, the use of high performance coatings may simultaneously increase the service temperature and decrease its price. From the many available coating processes, Metal organic Chemical Vapour Deposition (MO‐CVD) is one of the few capable of producing coatings of most precious metals in internal surfaces with intricate geometry. Nevertheless the microstructure control of the films is extremely complicated and characterised by the formation of dendrite structures. This morphology eliminates the coating efficiency, as it is not compact. EADS has had the chance to use the research infrastructure of the AMTT in Seibersdorf to characterise the coatings and determine how the transformation from the compact to the non‐compact microstructure takes place. The understanding of this phenomenon should allow us to develop a process able to produce 100 % dense coatings independently of the coating thickness in an industrial scale.     

Influence of hot deformation on the transformation behaviour and structure of pearlitic steels

A study was made of the influence of hot deformation on the transformation behaviour, the structure and the mechanical properties of a pearlitic steel containing 0.65% C. The production parameters of a modern hot strip mill were taken as a basis for the deformation schedule and cooling performed with the aid of a hot deformation simulator (Wumsi). Parameters to be pointed out as significantly influencing the transformation behaviour are, in particular, the finishing temperature and the cooling rate after hot deformation. By exploiting the possibility of raising the cooling rate after deformation in the same measure as is attainable on a hot strip mill, a yield strength increase of at least 150 MPa is achievable.     

Note on the Design of an Equiripple DC-Notch FIR Filter

An extremely robust analytical procedure for the effective evaluation of the impulse response of a highly selective optimal equiripple DC-notch finite-impulse response (FIR) filter is presented. The DC-notch filter is optimal in the Chebyshev sense. The computational superiority of the presented procedure over the standard approach is emphasized     

Numerical study on the spectroscopic ellipsometry of lamellar gratings made of lossless dielectric materials

The spectroscopic ellipsometry of lamellar gratings made of lossless dielectric materials is studied numerically by using the rigorous coupled-wave method with the use of Li's Fourier factorization rules [J. Opt. Soc. Am. A 13, 1870 (1996)], which are known to improve the convergence on the analyses of metallic gratings. Numerical results show that the calculation method also provides fast convergence on lossless gratings, and accurate values of the ellipsometric angles are obtained in very short computation times. Moreover, estimation of grating parameters is investigated by using a cost function defined by the average distance on the Poincaré sphere, and it is shown that the computation required for accurate estimation is possible in reasonable computation time.     

Effect of Bi(III) concentration on the stripping voltammetric response of in situ bismuth-coated carbon paste and gold electrodes

The effect of Bi(III) concentration (over the wide concentration range of 10⁻⁷ to 10⁻⁴ M) on the determination of Pb and Cd metal ions (in the 10⁻⁸ to 10⁻⁵ M range), by means of anodic stripping voltammetry (ASV) at in situ bismuth-coated carbon paste (CPE) and gold electrodes, has been studied. It is shown that in square wave anodic stripping voltammetry (SWASV) experiments the sensitivity of the technique generally depends on the Bi(III)-to-metal ion concentration ratio. It was found that, unlike the usually recommended at least 10-fold Hg(II) excess in anodic stripping experiments at in situ prepared mercury film electrodes, Bi(III)-to-metal ion ratios less than 10 are either optimal or equally effective at CPE and Au electrode substrates. Detection limits down to 0.1 μg L⁻¹ for Pb(II) and 0.15 μg L⁻¹ for Cd(II) were estimated at CPEs under conditions of small or moderate Bi(III) excess. Depending on Bi(III) concentration and deposition time, multiple stripping peaks attributed to Bi were recorded (especially in the case of Au substrates), indicating various forms of Bi deposits.     

Effect of die wall cooling or heating on extrudate swell

A general purpose finite element program was used to study polymer extrudate swelling. It is shown that viscosity variations due to externally applied cooling or heating have a significant influence on the swelling ratios of axisymmetric and planar extrudates. The effect is more pronounced at high Peclet and Weissenberg numbers. Swelling due to thermal effects and swelling due to viscoelasticity are not additive because of interrelations between the various mechanisms.     

Determination of Turboprop Reduction Gearbox System Fatigue Life and Reliability

Two computational models to determine the fatigue life and reliability of a commercial turboprop gearbox are compared with each other and with field data. These models are (1 Zaretsky, E. V. 1992. “STLE Life Factors for Rolling Bearings,”, STLE SP–34 Park Ridge, IL: STLE.  [Google Scholar]) Monte Carlo simulation of randomly selected lives of individual bearings and gears comprising the system and (2 Weibull, W. 1939. “A Statistical Theory of the Strength of Materials,”. In Ingenioersvestenskapsakademiens. Handl. 151 [Google Scholar]) two-parameter Weibull distribution function for bearings and gears comprising the system using strict-series system reliability to combine the calculated individual component lives in the gearbox. The Monte Carlo simulation included the virtual testing of 744,450 gearboxes. Two sets of field data were obtained from 64 gearboxes that were first-run to removal for cause, were refurbished and placed back in service, and then were second-run until removal for cause. A series of equations were empirically developed from the Monte Carlo simulation to determine the statistical variation in predicted life and Weibull slope as a function of the number of gearboxes failed. The resultant L ₁₀ life from the field data was 5,627 h. From strict-series system reliability, the predicted L ₁₀ life was 774 h. From the Monte Carlo simulation, the median value for the L ₁₀ gearbox lives equaled 757 h. Half of the gearbox L ₁₀ lives will be less than this value and the other half more. The resultant L ₁₀ life of the second-run (refurbished) gearboxes was 1,334 h. The apparent load-life exponent p for the roller bearings is 5.2. Were the bearing lives to be recalculated with a load-life exponent p equal to 5.2, the predicted L ₁₀ life of the gearbox would be equal to the actual life obtained in the field. The component failure distribution of the gearbox from the Monte Carlo simulation was nearly identical to that using the strict-series system reliability analysis, proving the compatibility of these methods.     

Anisotropy-enhanced deviation functions in superconducting zinc and cadmium

The thermodynamic critical fields of zinc, cadmium, and molybdenum were measured down to 25 mK using an ac susceptibility method. Considerable downward shifts of the deviation function were found for Zn and Cd and analyzed in terms of anisotropic Eliashberg theory with large electron-phonon coupling anisotropy parameters a ². In contrast to these two elements, isotropic behavior was found in superconducting molybdenum.     

Agent-Based Approach to Mass-Oriented Production Planning: Case Study

This paper discusses the potential of multiagent planning techniques in the production-planning domain, with special focus on mass-oriented production. The research presented in the paper has been centered around ExPlanTech-a specific implementation of a production-planning multiagent system. Suitability of ExPlanTech for mass-oriented and project-driven manufacturing is also discussed in the paper. Applicability of multiagent concepts is demonstrated on a multiagent planning architecture and production-planning case study at a Skoda Auto Engine Plant     

A systematic approach to material eligibility for the cold-spray process

This article represents an effort to systematize an understanding of the cold-spray process and the suitability of materials for such a process. The evaluation is based on a brief analysis of the powder particle impact and literature research concerning shock-compression phenomena in matter and related physical effects, such as impact heating and dynamic yielding. The finite-element modeling (FEM) allows the estimation of the maximum impact pressures, the deformation rates, and the deformation kinetics during impact. The calculations can be verified experimentally and are supported by the published data. From a brief analysis of the equations of state applied to shock compression, key material parameters are derived and investigated. A parameterization of physical properties and correlation with the crystal types endeavors to provide a qualitative ranking of material suitability. The original version of this article was published as part of the ASM Proceedings, Thermal Spray 2003: Advancing the Science and Applying the Technology, International Thermal Spray Conference (Orlando, FL), May 5–8, 2003, Basil R. Marple and Christian Moreau, Eds., ASM International, 2003.