A study of damping and its field-dependence in magnetic materials is presented. An optical heterodyne interferometer is used as detector of the longitudinal vibration of a slender rod located within a solenoid. Two different experiments are carried out in order to investigate damping in the demagnetized and saturated states. In one, the attenuation constant is determined by examining the free vibration of the sample. In the other, damping is indirectly measured from the sharpness of its resonance curve. Logarithmic decrement and its variation with the magnetic field is calculated. The detection and excitation systems used do not interact with the sample. Nickel rods and wires ranging in diameter from 2 mm to 10 mm are used as samples. Young's modulus is also determined.

The study of the damage of aeronautical materials is important because it may change the microscopic surface structure profiles. The modification of geometrical surface properties can cause small instabilities and then a displacement of the boundary layer. One of the irregularities we can often find is surface roughness. Due to an increase of roughness and other effects, there may be extra momentum losses in the boundary layer and a modification in the parasite drag. In this paper we present a speckle method for measuring the surface roughness on an actual unmanned aircraft wing. The results show an inhomogeneous roughness distribution on the wing, as expected according to the anisotropic influence of the winds over the entire wing geometry. A calculation of the uncertainty of the technique is given.

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