B. James, E. Guyer, S. Lieberman, Exponent Failure Analysis Associates, Menlo Park, CA; C. McVeigh, Medtronic, Galway, Ireland
Ultrasonic cleaning is often used as part of the manufacturing process of small medical devices, such as guide wires and vascular implants. However, exposure to ultrasonic cleaning with frequencies close to the natural frequency of the device can result in a resonance condition, resulting in significant mechanical damage and premature failure. This paper provides case studies of ultrasonic cleaning-induced fatigue and corresponding failures in medical devices. Preventative measures, such as analytical tools to ensure that ultrasonic cleaning frequencies do not result in resonance and stresses sufficient to cause fatigue damage are discussed.
Summary: Small medical devices can be susceptible to damage from ultrasonic cleaning. Exposure to ultrasonic energy at frequencies close to the natural frequency of the device can result in resonance, resulting in fatigue crack initiation and growth. Finite element analysis techniques can be used to predict whether resonance will occur at ultrasonic cleaning frequencies.
