Drag torques of gearboxes are an important part of the overall losses in today's vehicle drive trains. From measurements it is well known that overall drag torques of vehicle gearboxes vary significantly over the range of operating points and speeds, depending on the interaction of the losses of the single gearbox elements like bearings, gearings, etc. Because today's vehicle emission regulations are becoming stricter and stricter "drag torque design" of gearboxes will be even more important in the future. Prediction of losses helps to save cost (e.g. drag torque measurements), speeds up the development and allows to assess many concepts in short time. We collected detailed semi-analytical drag models for the common gearbox components from literature and from manufacturer information and implemented them in a Modelica library. This library contains models for radial shaft seals, rotary unions, synchronizers, multi-disc clutches, helical gearings, planetary gearings, various kinds of bearings, lubrication systems and lubricant characteristics. Using this library drag torques of any vehicle gearbox may be computed for any operating condition (engaged gear, speed, torque, temperature). Simulation results for a 7 speed double clutch transmission show good correlation with measurements.

The quasi-static, static, and cyclic compressive behavior of a novel epoxy matrix cellular composite reinforced with glass foam granules is investigated. Three different grain-size fractions of the granules are used: 0.5-1, 1-2, and 2-4 mm. The density of the cellular composite varies between 0.65 and 0.82 g/cm 3 . The material exhibits high specific compressive strength and stiffness within the class of cellular materials; these properties can be varied using appropriate size of granules. The glass foam granules increase the stiffness of the cellular composite compared to neat epoxy foam with the same weight. The measured elastic properties are in good agreement with results obtained from analytical and numerical homogenization methods. The fatigue behavior is determined in static tests and in cyclic tests at 1 and 20 Hz on one type of cellular composite. The fatigue process for cyclic loading is a result of an interaction between static and cyclic damage. The sensitivity to static damage is found to be higher than to cyclic damage. The damage behavior is investigated by evaluation specimen's stiffness and using scanning electron microscopy.

The fatigue behavior of a cellular composite with an epoxy matrix and glass foam granules is analyzed and modeled by means of continuum damage mechanics. The investigated cellular composite is a particular type of composite foam, and is very similar to syntactic foams. In contrast to conventional syntactic foams constituted by hollow spherical particles (balloons), cellular glass, mineral, or metal place holders are combined with the matrix material (metal or polymer) in the case of cellular composites. A microstructural investigation of the damage behavior is performed using scanning electron microscopy. For the modeling of the fatigue behavior, the damage is separated into pure static and pure cyclic damage and described in terms of the stiffness loss of the material using damage models for cyclic and creep damage. Both models incorporate nonlinear accumulation and interaction of damage. A cycle jumping procedure is developed, which allows for a fast and accurate calculation of the damage evolution for constant load frequencies. The damage model is applied to examine the mean stress effect for cyclic fatigue and to investigate the frequency effect and the influence of the signal form in the case of static and cyclic damage interaction. The calculated lifetimes are in very good agreement with experimental results.

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The damage behavior of cellular composites under creep and cyclic tensile loading conditions is investigated. Tensile cyclic tests at 1 Hz and 20 Hz test frequency and creep tests are performed and compared to previous investigations under compressive loading. In contrast to the compressive loading, no frequency effect is identified in tensile loading and the fatigue curves have steeper slopes. The damage behavior is analyzed by means of scanning electron microscope (SEM) and high resolution 3D X-ray tomography. It is found that microcracks are forming in the glass foam granules first; the final failure is caused by a macrocrack passing through the glass foam granules and the matrix. The damage evolution is measured in terms of stiffness loss of the specimen and is found to have different behavior than in compression.