Sigmatech (United States)

Abstract To investigate the effect of altitude on vibrations in a turbocharger, an aircraft compression-ignition engine was operated in both a sea level cell and an altitude chamber up to 25,000 ft (7620 m). The turbocharger was instrumented with a nonintrusive stress measurement system to analyze the frequencies, magnitudes, and critical speeds of the blade bending modes as the ambient pressure, ambient temperature, and engine power varied. The measurements were also compared to data from accelerometers mounted on the compressor housing. At sea level conditions, the largest deflection amplitudes were associated with excitations of the first blade bending mode. These deflections grew in amplitude as the altitude increased and the turbocharger/engine worked harder to produce the required pressure rise and power. There was also evidence of a higher-order mode being excited at elevated altitudes. By understanding the factors contributing to resonance and flutter in aircraft turbomachinery, modeling and prediction tools can be improved to update operating envelopes for current designs and minimize these phenomena in future, aviation-specific designs.

This second part aims to investigate the modelling of the bending behaviour of all-thermoplastic sandwich structures with improved aesthetic properties, manufactured by isothermal compression moulding. The aesthetic thermoplastic sandwiches exhibit specific features such as thick multi-layered faces and significant core properties variation due to processing conditions. Considering these specific features, a three-step calculation methodology has been developed to determine an accurate analytic model, to predict the equivalent shear properties of the core after manufacturing and to take into account the influence of the glass veil layer used to improve the surface quality of the part. Finally, a finite element modelling of the linear elastic behaviour of a simply supported sandwich plate under a concentrated load is achieved to validate the proposed methodology.

A new technique for the measurement of particles in powder processing has been developed to identify the shape, size and position of multiform particles simultaneously and instantaneously. A new Multiplexed Matched Spatial Filter which is a single exposure hologram was employed for the new technique. In the identification tests, the input objects were discriminated by their autocorrelation peaks and their positions were acculately determined. It was concluded from the theoretical and experimental studies that the present method could be applied to simultaneously and instantaneously identify the shape, size, number and position of multiform particles in powder processing.