The introduction of advanced welding methods as an alternative joining process to riveting in the manufacture of primary aircraft structure has the potential to realize reductions in both manufacturing costs and structural weight. Current design and analysis methods for aircraft panels have been developed and validated for riveted fabrication. For welded panels, considering the buckling collapse design philosophy of aircraft stiffened panels, strength prediction methods considering welding process effects for both local-buckling and post-buckling behaviours must be developed and validated. This article reports on the work undertaken to develop analysis methods for the crippling failure of stiffened panels fabricated using laser beam and friction stir welding. The work assesses modifications to conventional analysis methods and finite-element analysis methods for strength prediction. The analysis work is validated experimentally with welded single stiffener crippling specimens. The experimental programme has demonstrated the potential static strength of laser beam and friction stir welded sheet-stiffener joints for post-buckling panel applications. The work undertaken has demonstrated that the crippling behaviour of welded stiffened panels may be analysed considering standard-buckling behaviour. However, stiffened panel buckling analysis procedures must be altered to account for the weld joint geometry and process altered material properties.
A "finite elempnt" mechanical model, capable of utilizing experimentelly determined mate:ial propprties, is presented for analyzing the deformation processes in a finite, constrained flexible filament subjected to transverse impact.The model is then used to analyze the results of experimentally (transversely) impacted finite lengths of nylon yarns rigidly clamped at both ends. The experimental analysis is pi'esented in Part I of this work.The analysis is used to determine the effects of an elastic foundation transversely supporting a flexible filament subjected to transverse impact.Finally, results of a finite element analysis of a transversely impacted isotropic membrane are presented to indicate the direction for future research.An appendix is attached which demonstrates the ability to include ratedependent material properties in the analyses described above.
This paper describes the construction and testing of a low cost dual beam spectrometer for the determination of chemical concentration in coloured liquids. The principle of operation is based on the partial extinction of light by chemical absorption. The spectrometer incorporates an optical bridge system which consists of a pulsed high intensity LED, two general purpose photodiodes and two 4-quadrant multiplier based PSDs. These components ensure that the signal-tonoise is maximized at minimum cost. The range of absorbance measurements which can be made with the present system may be extended using high intensity yellow, green and blue LEDs.
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