Identification of overloads on splined shafts by means of eddy current testing technology

For the development of resource-efficient machines, the availability of high-quality information about the actual loads that occur is a key prerequisite. By continuously monitoring the loads on the component, critical events can be detected, and thus component failure prevented. Future product generations can also be designed in a resource-saving way depending on the loads that actually occur. The information is most useful when it is obtained directly from the highly loaded areas of the component. In this study, a concept is presented that enables in-situ detection of mechanical overloads on splined shafts by eddy current techniques. Splined shaft connections are among the most heavily stressed machine elements in the drive train and are usually located centrally in the powertrain. To monitor mechanical overloads, a material-integrated sensor will be developed. The structural change that takes place in the sensor as a result of overloads can be monitored with the help of eddy current testing technology. To ensure permanent monitoring of the sensor area, a compact eddy current testing system has to be integrated into the component. This consists of a printed circuit board coil, an evaluation unit, a data transmission module and an energy-harvesting module. The measurement principle for the stainless steels employed is based on the microstructural transformation from metastable austenite to martensite when the material is stressed beyond a threshold value. The threshold at which the structural transformation occurs can individually be adjusted in the sensor area by a local laser heat treatment.