Evaluation (Validation and Verification) - Medical Device Design: Innovation from Concept to Market - page 216

Figure 9.2
Typical vibration test setup. (Courtesy Staffordshire University)
9.3.2.1 Vibration
How do vibrations affect your device? Do things become loose (e.g., screws and nuts)? Do
components crack or break (fatigue)? Do innocuous components wear through the sterile
package? What vibration sources exist in use and in transit?
Once the parameters are identified vibration tests can be easily performed, but specialist
equipment is required. Most universities with a mechanical engineering department would
have this equipment and some stand-alone companies offer this as a service. Figure 9.2
illustrates a typical vibration test. The normal equipment required is a signal source (normally
a single sine wave at fixed frequency and amplitude or a white noise source), a power
amplifier, and an electromagnetic shaker. Measurements are conducted using a combination
of load cells and accelerometers. The component is mounted, or supported, as it will be in
real life and then vibrated for a simulated lifetime. Failures are then observed or measured.
9.3.2.2 Cyclic Loading
Is your device subjected to cyclic loading? Are these cyclic loads mechanical, electromagnetic,
or thermal? How many cycles do you expect over the life of the component? By and large this is
going to ascertain fatigue life (as it is important we shall look at fatigue in greater detail later).
Once again, specialist equipment is normally required and, as noted earlier most universities
would have this equipment in their mechanical engineering or materials technology
laboratories. Commonly, the component in question is mounted as close to the real life