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The torsional mesh stiffness is one of the most important characteristics of spur gears. This paper presents the development of detailed two-and three-dimensional finite element models which can be used to calculate the torsional mesh stiffness. Using the parametrical design language of the FE software ANSYS the models offer the possibility to generate various different pairs of spur gears and include an adaptive meshing algorithm for the contact zones. Due to the short computation times the 2D model is well suited to simulate a variety of different gear pairs in a short time period. The more complex 3D model features more options in terms of investigating tooth face modifications for further studies. The resulting values of the torsional stiffness can be used -for example -in multi body simulations of gearboxes.The results from the 2D FEA are used to derive a simple formula for the combined torsional stiffness of spur gears in mesh. The results presented are based on the individual stiffness of the three main components -body, teeth and contact. Hence, the introduced formula uses these three parts to determine the overall stiffness for a wide range of gears and gear ratio combinations.Finally, the results from both the two-and three-dimensional finite element model and the derived formula are compared and the results from the 3D model are checked against results obtained by analytical equations.

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In the course of increasing electric mobility, the effect of electricity on parts of machines is more significant than before. Rolling bearings and their lubrication, as a part of electric motors, are subjected to harmful currents, which lead to damage in the bearing in the long term. In order to avoid such damage, the influence of the lubricant in the bearing is becoming increasingly important. The electrical behaviour of the system can be investigated by analysing the discharge currents and the breakdown voltage in rolling bearings with lubricants of different compositions. This paper presents a procedure for characterizing the breakdown voltage at the rolling bearing and the influence of conductivity of the lubricants on harmful electrical phenomena.

Today there are a lot of findings to determine losses caused by contact forces inside roller bearings. But there are also losses in bearings caused by displacement of lubricant. These are known as churning or drag losses. In general the bearing manufacturers give recommendations how to reduce them. The most common solution is the reduction of the oil bath level. Some bearing manufacturers even provide models or empirical equations to calculate the resistance resulting from rolling elements moving through the oil. These models take the operating conditions such as the viscosity of the oil at the operating temperature, oil level, bearing type and rotational speed into consideration. A comparison between calculated and experimental results shows that there is still a deviation because of further effects which are not considered in those analytical models. This paper presents experimental studies and numerical simulations which illustrate the influence of the oil quantity on the total friction torque of tapered roller bearings and identify the resulting losses. Highlights• Method for investigation of drag and churning losses. • Influence of viscosity, oil quantity and rotational speed. • CFD simulation of a single-phase flow considering air content in lubricant. • Influence of the air content on the drag and churning losses.