Design of an Ultrasonic Blade for Cutting Bone

Damaging temperature effects observed during ultrasonic cutting operations are typically a result of friction between the vibrating blade and material, and combustion of debris. In order to prevent the high temperatures causing damage, the ultrasonic blade has to cut with a sufficient speed. This can be achieved either by applying a relatively high static load or by increasing the working vibration amplitude of the cutting edge, however, the result can be poor operational control and exceeding the fatigue limit of the blade, respectively. In this paper, the effect of blade tip profile is considered, particularly with reference to the influence of the cutting edge contact area on temperature under different static loading conditions. Titanium blades, with different cutting edge profiles are tested in a series of experiments that monitor cutting speed, static load, temperature around the cut site, and vibration amplitude at the cutting edge. The blades are tested cutting bovine femur and artificial bone material, and the cut surfaces are examined for signs of damage after each test. The experimental data reveal that blades with a small cutting edge contact area cut at a lower temperature, and that signs of thermal damage are less evident.