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Experimental results are presented for carefully controlled plane-strain strip drawing experiments. Transparent aluminum oxide (sapphire) dies have been used to make direct observations of the die-work interface in strip drawing, including the distortion of scribed lines which were used for estimating velocity profiles at the interface. Such profiles can be used as input to theoretical models (Appleby et al., 1984), thus permitting the calculation of interface friction rather than requiring its assumption. Experiments were conducted with tungsten carbide, as well as sapphire, dies in which process parameters such as reduction, speed, die angle, lubricant, and back tension were varied, and die separating forces and drawing loads were measured. In general the frictiot~ was lower for the sapphire dies, but the variation with process parameters was similar. For one experiment, residual stresses in the product strip were measured. The results are believed to be documented in sufficient detail to be of general use in evaluating theoretical models.

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This study investigates four characteristic damage mechanisms of fiber Bragg grating (FBG) sensors, with fatigue crack propagation in aluminum alloy. The multipeak wavelength distinguish algorithm was developed for FBG spectrum quantitative analysis. The results distinguish a subordinate peak skewing significantly, associated with strain patterns along the FBG, corresponding to various crack lengths. For parallel bonded direction grating, the subordinate peak skewing appears at the strain pattern transition region. This is located at the ratio 32%-34% of crack length lying in the crack tip. Meanwhile, the four damage characteristics correspond to subordinate peak skewing. When the strain is distributed along the grating, spectral distortion occurs. In this region, the cubic strain pattern determines the shorter wavelength location of subordinate peaks. This corresponds to the 15%-17% ratio of crack length lying in the grating, causing spectral oscillations.