\n\tThe National Institute of Standards and Technology, Gaithersburg, Md., and collaborators have demonstrated a nondestructive acoustic method for detecting cracks in ceramic capacitors before they go bad. The method relies on acoustic measurements at frequencies much higher than humans can hear. Researchers briefly apply an electric field across the electrodes of a capacitor, causing a vibration at a specific frequency. They then measure the decay over time (called ringdown) of the signal. These data are analyzed to determine slight shifts in frequency versus the magnitude of the vibration. These shifts are greater when cracks are present. This nonlinear approach \u2014 focusing on frequency shifts relative to signal strength, rather than the frequency shifts alone \u2014 is especially useful because it is not affected by slight variations in size of the capacitors.<\/p>\n
\n\tNIST researchers invented the technique, and the study of crack detection levels was carried out with collaborators from the University of Maryland, NASA Goddard Space Flight Center, and Colorado State University. In the study, the prototype method led to the rejection of more than 90% of sample capacitors with visible cracks. Once further studies quantify and confirm detection levels, the new technique may help prevent failures in medical devices such as cardiac pacemakers and defibrillators, and also avert electronics failures in satellites and other spacecraft. The new method may also detect structural flaws in other types of materials.<\/span><\/p>\n