Enhanced spin-down diagnostics for nondestructive evaluation of high-value systems

Abstract

The nature of some high-value systems requires that damage be detected without disassembly of the test article. Spin-down testing, one such nondestructive evaluation method, involves spinning a test article and observing its angular deceleration. An increase in angular deceleration compared to an identical test of a healthy system indicates damage has occurred. However, current testing is limited, providing only a binary result of “damaged” or “undamaged”. More sophisticated techniques are required to identify the location, extent, and type of damage. To achieve this, non-contact and surface-mounted sensors were used to monitor the test article in this experiment. A spin-down unit was used to test both a healthy specimen and a specimen with simulated damage. The signals from each sensor were compared across tests. Correlation of anomalous signals with rotational position and multi-sensor triangulation techniques were used to localize damage. Analysis of the frequency content and amplitude of output signals allowed for a degree of characterization of the damage. Through these techniques, spin-down testing was enhanced from a binary detector to a more thorough testing method giving detailed information about the type and location of damage.