Damping Measurement of Bending Vibration in Alpine Skis: An Improvement of Standard ISO 6267
The ISO 6267 standard defines a damping measuring method in terms of the half-time of the vibration of clamped alpine skis that is mainly related to the first vibration mode only. By means of the experimental test done in laboratory, it is shown that this method is not able to completely characterize the damping of the skis that depends on the vibration mode considered. For example in the case a ski sample, damping ratio varies from 0.45%±0.05% of the first mode to 2.1%±0.1% of the fourth one. The experimental test done on ski tracks by means of piezo-accelerometers placed on the skis running at speed of 12.5 m/s showed that the skis vibrate according to a combination of at least the first 4 vibration modes and that the snow better excites frequencies greater than the first one. As the excitation frequencies on the skis during the descent are much higher than the first natural frequency of the ski, it appears not correct to hypothesize that only the damping coefficient relative to the first natural frequency is representative of the ski vibrations. To improve the UNI ISO 6267 standard, a new method based on the Fourier Transform filtering to separate the time history into the vibration components is proposed for the characterization of the ski damping that is variable with its natural modes.
Patrick Sean Keogh
G. Fanti et al., "Damping Measurement of Bending Vibration in Alpine Skis: An Improvement of Standard ISO 6267", Applied Mechanics and Materials, Vols. 5-6, pp. 199-206, 2006