Gear tooth side wear in planetary gearboxes represents one of the main reasons for damage occurring in these gears. Wear magnitude is unpredictable and depends on temperature, lubrication, load, material and other random variables. Wear is a non-stationary process which is impossible to describe using a mathematical model, or to accurately assess its intensity, magnitude and distribution along the tooth sides. This paper suggests a probability assessment model for gear tooth side wear, based on experimental tests and a statistical representation of obtained results. Experimental tests of planetary gearbox gears were performed within a closed power circuit, using a previously prepared testing table, and the results of wear probability distribution were analysed. Wear probability distribution was represented using the Weibull distribution model. Obtained results of this statistical analysis have shown good compliance with the experimental ones, hence this model is applicable to all gearboxes. This method represents a considerable contribution to wear probability distribution assessment and can be used in order to assess the work life and elementary reliability of gears.

Paper presents stress calculation in the stationary temperature domain for a hybrid structure with standard epoxy-carbon fiber composite and metallic part, showing different thermal behaviour. The thermal stress analysis is based on the finite element method. A sample problem involving such a composite plate and metallic part of structure or mould at two different temperature levels, corresponding to curing process (co-curing) and operating temperatures, respectively, is calculated and discussed. The specific properties of composite are emphasized particularly for thermal coefficients, especially if the shear coefficient is different than zero, causing completely different behaviour compared to isotropic materials.

Paper presents stress calculation in the stationary temperature domain for a hybrid structure with standard epoxy-carbon fiber composite and metallic part, showing different thermal behaviour. The thermal stress analysis is based on the finite element method. A sample problem involving such a composite plate and metallic part of structure or mould at two different temperature levels, corresponding to curing process (co-curing) and operating temperatures, respectively, is calculated and discussed. The specific properties of composite are emphasized particularly for thermal coefficients, especially if the shear coefficient is different than zero, causing completely different behaviour compared to isotropic materials.

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