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Considering measurement accuracies, different models used for the prediction of longterm static fatigue for optical fibres under stress were studied. Optical fibres were wound onto an alumina mandrel with various diameters and immersed in hot water at different temperatures. The determination of model parameters was based on the fit of experimental data to model expressions relating time to failure, applied stress and environmental conditions. It is shown that the differences in allowed stress predictions between models become quite close at short times. The time-to-failure depends on the applied stress applied but also and above all on the ageing temperature and the humidity level. Results from tested fibres indicate a clear strength reduction with increasing temperature or applied stress. [ABSTRACT FROM AUTHOR]

The authors study the shape optimization of a complex cracked shell under complex criteria. The shell is one of various cases of a turboshaft, and optimization criteria are associated to the cost, the technology, and above all the working conditions for the turboshaft. The optimization criteria involved are of course the weight of the structure, but also the plastic instability and critical stress intensity factor. All computations have been made with the Ansys finite element program in which an optimization module exists. [ABSTRACT FROM AUTHOR]