Analysis of the characteristics and sensory utilization potential of the electrical impedance of power-transmitting involute gears

• Applicant: Professor Dr.-Ing. Eckhard A. Kirchner
• Subject Area: Engineering Design, Machine Elements, Product Development
• Term: since 2026
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 569255052

The aim is to analyze the statistical properties of the electrical impedance of involute gears over a wide operating range and their phenomenological description as the basis for a new diagnostic method for incipient surface damage. The focus is on oil-lubricated spur and helical gears with involute splines with splash lubrication. These investigations serve to derive potential uses for the measurable electrical impedance of gears for the early detection of damage in drive technology using machine learning methods. In order to achieve this overarching goal, the following research questions are being addressed as part of the project: RQ 1: How can the electrical impedance of the tooth contact be characterized quantitatively with regard to its temporal course, magnitude and phase position as well as their frequency distributions as a function of the acting load? RQ 2: What quantitative influence do lubricant quantity and viscosity have on the impedance and the metrological differentiability of lubrication conditions? RQ 3: What quantitative influence does the profile overlap have on the measurable electrical impedance signal and thus on the differentiability of the tooth contact path? RQ 4: What is the qualitative effect of surface changes on the tooth flanks on the impedance and how can the cause-effect relationships be used to identify tooth flank damage using ML methods? RQ 5: What are the potentials and limitations of the sensory use of the electrical impedance of spur and helical gears in real gears? A combined experimental and analytical approach is used to answer the first three research questions before investigating damage mechanisms and discussing potential uses. Based on the given meshing path and lubrication, the primary influence of the mechanical operating conditions is investigated in order to provide a quantitative, phenomenological understanding of the electrical behavior. Analytical, semi-analytical and empirical equations from the current state of research are used for interpretation. For the experimental procedure, a test setup is used that is designed for the short-term experimental investigation of electrical impedance. Speed and torque are applied by two dynamically controllable electric machines in four-quadrant operation in a back-to-back arrangement. The lubricant is not varied and the tests are only carried out with oil, as the viscosity can be actively influenced by temperature control. The effects of lubricant ageing are avoided as far as possible by filtering and regularly replacing the oil. Individual endurance tests will be carried out at the end of the project period at loads above the fatigue strength for verification purposes.

• DFG Programme: Research Grants