Load sensitive spline shaft with sensory material

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The development and operation of highly resource-efficient machines greatly depends on the availability of high-quality information on the actual loads. Information gained directly from the critical parts in the field is the most valuable. This requires comprehensive digitization of machines, which in itself depends on inexpensive and readily available measuring systems. A major challenge in the development of such systems is energy self-sufficiency; conventional systems like strain gauges require a constant electrically powered measurement operation at high frequency. In the context of priority program 2305 "Sensor-integrating machine elements" (SiME), a material-integrated, sensory peripheral zone condition on a splined shaft as a possible solution satisfying the stated requirements featuring drastically lowered power demand compared to state of the art technology is researched. The principle of the sensor material is based on a structural transformation from metastable austenite to martensite when stressed above a limit load. The structural transformation can be detected via eddy-current analysis. The sensory material stores the load information, requires no electric power supply and can be read at arbitrary intervals.. The sensory material peripheral zone can tailored locally by laser heat treatment. The research program shall establish the possibility of developing reproducible SiME via material sensors characterized by low power requirements, high quality of information, and negligible impact on the main function of the machine element. Focus lies on the methodological study of structural design for incorporation, the analysis of the sensors impact on the machine element, and the certification of the sensor material. Verification is achieved using an energy efficient prototype eddy current reader unit powered by energy harvesting developed in the project on shaft-hub connection specimens in a test rig. Finally, the updateability and the expandability concerning further measurands is considered.