Richard Chapman Karl-Arne Hegewald Steve Humphreys Scott Meckstroth
Dept. of Mech. Eng., Univ. of Colorado, Boulder, CO 80309
An investigation into the vibrational behavior of an alpine ski excited by a single-point force applied at the tip of the ski was conducted. The single-point force was used to model small amplitude perturbations in the snow for a flat running ski to investigate ski chatter. In this respect, the bindings were assumed to remain in constant contact with the snow surface and the test ski was clamped at these locations for the experiment. An accelerometer and a personal computer were used to measure the ski's response to tip excitation and a FFT was used to determine the ski's harmonics. Numerical models were constructed utilizing (i) a finite element approximation, and (ii) a finite difference solution, to determine frequencies at 21 distinct points of the ski. Results from the model were then compared with experimental data and the model was validated. Experimental results showed the first three harmonics for the front of the ski to be 2(plus or minus)0.5 Hz, 22(plus or minus)1 Hz, and 43(plus or minus)4 Hz. This compared with theoretical values of 5, 25, and 37 Hz. Experimental results for the higher harmonics and other parts of the ski were found to be within an order of magnitude of the theoretically predicted values.