The service life of radial shaft seals (RSS) is decisively limited by their contact temperature, as it governs the elastomer ageing process at the sealing lip. However, reliable methods for predicting this ageing-related service life are not yet available to users. Against this background, this contribution presents a prediction model based on application-oriented static ageing tests, which could support the improved design of RSS sealing systems in the future. Furthermore, the model is necessary for the investigation of an active contact temperature reduction. This concept relies on additively manufactured shafts with an open-porous core, enabling air permeation in dedicated bench tests and serving as a hybrid porous machine element. An application-oriented characterization of the cooling potential in the tribological system of the RSS and its counter surface was carried out. The incorporation of the observed cooling potential into the ageing model indicates significant service life extensions while providing a tangible metric for designers.

This study investigates the influence of different friction modeling approaches on the gear contact behavior of spur gears made from a hybrid and porous (HyPo) steel-aluminium foam material combination. Two friction models are presented and integrated into a simulation framework: a fixed friction coefficient based on standard ISO/TS 6336-20 and a physically detailed model derived from elastohydrodynamic lubrication (EHL) theory incorporating asperity load share. The FE model enables the use of spatially graded material properties to represent the HyPo structure. The discussion of these approaches focuses on the advantages of the more detailed modeling approach as it incorporates the influence of tribological effects, such as local lubricant film thickness and surface topography. Particular attention is given to the implications for future applications in thermal simulation and wear prediction. The findings highlight the necessity of realistic tribological modeling in the simulation of novel, lightweight hybrid gear materials.

IntroductionFast switching frequency inverters are a key component in modern electric drive trains. They provide high efficiency in a wide speed range, which is why they are frequently used in vari...

In layered systems with porous substrates and a dense solid surface, stiffness and strength are inherently coupled through porosity-dependent relations, influencing their load-bearing behaviour. This work presents a systematic methodology for the assessment and design of such layer-substrate systems based on a criterion of balanced material utilization. A dimensionless parameter is defined to characterize the stress state in both components relative to their admissible limits, from which the optimal layer thickness is determined at equal stress levels in both constituents. Stress distributions are calculated using a numerical half-space model for layered contacts and evaluated through material-dependent equivalent stress criteria. The relationship between material utilization and load-carrying capacity is reduced to a scaling factor that combines the influence of porosity-dependent parameters. The approach establishes a direct link between the governing material parameters and structural design variables. Across the investigated parameter range, the utilization rate scales linearly with optimal layer thickness, whereas the load-carrying capacity follows a cubic relation. For a representative Ashby strength scaling coefficient of $C_{\sigma }=0.3$, for example, a substrate porosity of 90% leads to a scaling factor of 1.6, corresponding to a possible load amplification of 60% relative to the homogeneous reference.