Molybdenum coated gearbox synchronizers are tested in a mu-comp test rig under varying loading conditions until failure. Four different parameters used to describe the thermomechanical load are evaluated just before failure to compare their ability to predict failure. The parameters evaluated are the synchronized kinetic energy, the synchronization power, and the focal as well as the average surface temperature increase. The focal surface temperature increase as well as the average surface temperature increase is found to predict failure with relatively good accuracy. It is shown that there exists a threshold which divides the synchronizer into either a very long or a very short service life. Additionally, a method to determine the average surface temperature in the gearbox management system is proposed.

Transmission performance is crucial for heavy trucks and connected vehicles in general and for platooning of trucks in particular. Gearbox synchronizers are highly loaded conical friction brakes used during gear shifts. Service life and, thus, the gear shifting reliability, of the synchronizer depend on the local thermomechanical loading of the contact surface. To achieve a robust and cost-efficient system, more knowledge is needed of how manufacturing tolerances affect the local thermomechanical loading and therefore service life and reliability of a synchronizer. The effects from angle deviations between the mating cones and cone out-of-roundness on focal maximum temperature during a synchronization sequence have been studied with transient thermomechanical simulations. It is shown that thermomechanical effects will significantly magnify the nominal effects on synchronization performance caused by shape deviations given by the specified manufacturing tolerances.

A state-dependent method to model contact nonlinearities in rolling contacts is proposed. By pre-calculation of contact stiffness and contact filters as functions of vertical relative displacement, a computationally efficient modelling approach based on a moving point force description is developed. Simulations using the state-dependent model have been analysed by comparison with measurements. Results from the investigated case consisting of a steel ball rolling over a steel beam having two different degrees of roughness - show good agreement between nonlinear simulations and measured beam vibrations. The promising results obtained with the proposed method are potentially applicable to wheel rail interaction and rolling element bearings.

The strong market trend toward lower fuel consumption for heavy road transports requires more frequent gear shifting and increased gear shift performance, i.e. shorter shift time. Increased shift performance means higher loads for the synchronizer which brings component and shifting process optimization more into focus.

Traditionally, synchronizer development has relied on physical testing of complete synchronizers in general gearbox test rigs or in specialized synchronization test rigs leaving much of the causes of the observed effects unclear. This paper presents a generalized FE-based thermomechanical simulation model to be used for model-based synchronizer analysis and design. The model is targeted for studies of how different external loads and the values of different synchronizer design parameters affect the temperature transient in the friction lining. Recommendations of how major modeling complications should be treated are presented. The developed simulation model is verified and validated with a combination of analytical means and transient temperature measurements of bulk and surface temperatures. The applicability of the presented model, as well as its limitations, are discussed and exemplified with different design cases.

Gear life and operation are largely determined by the properties of the contacting surfaces, which inevitably change over the gear life. The initial topography transformation, a characteristic effect of running-in, is very important. This paper focuses on how the running-in of the surface topography can be characterized and what methodology can be used for this purpose. To characterize running-in, gears were run in an FZG back-to-back test rig and the changes in surface topography were measured in situ using a Form Talysurf Intra. This enables the same gear tooth surface to be measured with enough precision to follow its development through the different stages of running-in. Gear tooth surfaces as manufactured were measured on three occasions: in initial manufactured condition, after a standard running-in procedure, and after an efficiency test. Running-in was characterized both qualitatively by plotting roughness profiles and quantitatively by analyzing a selected set of roughness parameters. This paper demonstrates that: the asperity peaks were worn off in the initial running-in stage; roughness, waviness, and form can be separated using a carefully chosen polynomial fit and the Gaussian filter; surface topography can be examined initially, after running-in, and after operation in situ; and complete wear of the initial surface can be observed in specific circumstances.

Rolling contacts present in passenger cars such as in bearings and transmission elements are sources of noise and vibration, principally for interior comfort concerns. Moreover, tyre/road noise is the main source of road traffic noise which in turn leads to sleep disturbance and annoyance. In order to simulate friction losses as well as generated noise and vibrations in any rolling contact, it is crucial to have a correct description of the dynamic excitation caused by the roughness of the surfaces in contact. In this paper, a state-dependent modelling approach previously proposed by the authors is applied to a well-defined steel-steel rolling contact. A parametric study investigating the influence of rolling speed on contact conditions is performed, indicating the limits for the use of linear point force expressions for the rolling contact investigated. The state-dependent method is based on pre-calculation of contact stiffness and contact filtering as functions of vertical relative displacement. This leads to a computationally efficient way to include the influence of surface roughness and shape of the contacting bodies in a point force expression. Only vertical contact forces are studied within the scope of this work. Tangential friction forces are likely to affect the resulting vibrations and should therefore be further studied. 

Transmission performance directly influences vehicle behaviour, energy efficiency, and perceived quality. A modern transmission is an aggregate of interacting sub-systems, e. g. gears, bearings, synchronisers and other shifting elements. New transmission trends ask for increased shift performance with higher loads for the synchronising components. Synchroniser development has traditionally required exhaustive physical testing and few analytical methods exist. A numerical method for assessing pre-synchronisation performance, using a multi-physics FEM software, is presented. Simulations show that grooves in the synchroniser surface have a positive effect on pre-synchronisation, and that the presence of grooves seems to be more important than the groove design.

The presented work focuses on gear web design using powder metal (PM) by utilizing the finite element method (FEM) to reduce weight and inertia taking into account root bending strength and tooth deflection.A topological optimization is used to determine feasible candidates for different web designs which have as objective to reduce volume. Similar geometric topologies were shown during different loading conditions; and hence, this topology was chosen as a suitable candidate. This candidate was further developed into a parametric model which incorporated the same overall shape shown in the topological optimization. A shape optimization procedure was used utilizing the parametric model having as state variables root bending strength and tooth deflection; and as objective the decrease in inertia, and in consequence weight, of the gear. To analyze a gear which is thoroughly studied, a similar gear to the FZG C type gear is used.Another aspect studied in this paper is the damping properties of three different gears, wrought, conventional PM and double density. Their damping properties are measured using their reverberation time and their frequency response function.Sound characteristics results show that a significant increase in dampening can be observed in PM gears when compared to conventional wrought gears. Finally results from the shape optimizations show how gears can be designed with PM to reduce weight and inertia, with marginal effects on strength and stiffness.