Ultrasonic Cutting with High-Gain Blades

Abstract

The design of high power ultrasonic cutting devices is based on tuning a blade to a longitudinal mode of vibration at a low ultrasonic frequency, usually in the range 20-100 kHz. To achieve the required cutting amplitude, gain is designed into the blade via profiling. It is expected that the use of higher-gain blades could enable longitudinal-mode guillotine-type cutting of a range of materials traditionally difficult to cut using this technology. Using a conventional high-gain blade, a feasibility study of ultrasonic cutting of bone is conducted using compact tension specimens of bovine femur. Finite element (FE) models are created, based on the assumption that the ultrasonic blade causes a crack to propagate in a controlled mode 1 opening. The models are compared with the experimental data collected from ultrasonic bone cutting experiments. Although the proposed cutting mechanism is supported by the data, the blade gain is insufficient to enable through cutting of long bone or other difficult to cut materials. Consequently, the paper examines the relationship between gain, profile, stress and nodal position for a range of ultrasonic cutting blades with increased gain.