A Dual-Stiffness-Energy Sensor for Crack Detection in Spur Gears

Helicopter transmission fault diagnostics and prognostics continue to receive a considerable amount of attention in the rotorcraft community. It is widely acknowledged that the conventional vibration-based damage detection methodologies have their limitations. For example, they can hardly detect an incipient crack and they are sensitive to the propagation of the crack either. This paper provides a novel approach to address the problems of an incipient crack as well as the tracking of the propagation of a gear crack on a spur gear. A new mechanical multifunctional dual-stiffness sensor for stiffness and energy density measurements was developed at the University of Maryland. The sensor has the ability to predit the elastic field of a given host structure based on the strain state of two strain sensors of different stiffness integrated into the structure. The sensor concept is used on a finite element model of a spur gear under quasi-static loading conditions. A crack model is developed and allowed to grow. The growth of this crack is tracked using the dual stiffness sensor. Experiment is carried out to verify the numerical simulations. Results illustrate that the sensor represents a promising approach for transmission health diagnostics and prognostics analysis.