External damping of tree limbs due to the limb moving through the air is nonlinear and appears to be proportional to velocity squared. Very good agreement was found between the experimental results and the analytical solution when the twigs and leaves were removed from the limb. When leaves were on the tree the experimental data was in good agreement with analytical results except near the second natural frequency. The results of this experi¬ment show that it is necessary to analyze tree limbs using both nonproportional and nonlinear damping.
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