The usual approach for the strength calculation of gears is described in ISO 6336. The normative approach is a relatively fast way for the calculation as it is based on analytical formula. Different influencing parameters, as for example geometric boundary conditions or material properties, are considered by coefficients which are called influencing factors. The efficiency of a gear stage is not considered.
However, high requirements on the power density, efficiency and friction of modern power transmissions demand highly accurate calculation approaches for the economic design of gear boxes. Therefore, the development, improvement and validation of local approaches for the strength and efficiency calculation for gears is a core theme of the research work performed by the gear department of WZL. The basis of the calculation approaches is the FE-based tooth contact analysis, which enables the consideration of local effects in an accurate and time-efficient way.
The design of gears is a manifold and complex topic. Especially local influences on the load capacity, as for example manufacturing deviations, surface structure or load induced deformation of the gear box, are difficult to consider beforehand. Likewise, the consideration of the heat treatment process and the resulting local material parameters is a great challenge during gear design. Furthermore, the design of gears has to meet contrasting target dimensions such as load capacity, weight and efficiency.
Besides the design of gears, the evaluation of damage pattern is a very challenging topic. The precise and purposeful analysis of root causes for damages is very important in order to avoid high downtime costs. Causal mechanisms of action have to be found in a short time, for which very accurate simulation and analyzation tools are needed.
The local approaches for the strength and efficiency calculation of gears developed at WZL are advanced steadily and validated by means of experimental tests and industrial use cases. They enable a comprehensive design of gears with the objective of an application adapted tooth flank and tooth root load capacity. Different aims can be targeted, e.g. highest possible overall load capacity or highest possible efficiency.
For the analysis of gear damages, the local strength calculation enable a fast and highly accurate way for the determination of the mechanism of action and for the fast definition of counter measures. As well long-term steps can be derived for the purposeful optimization of the gear box.
The Aim: Individual Solutions
- Knowledge-based, comprehensive support during the design of gears concerning load carrying capacity and efficiency including the consideration of local influencing factors
- Linkage of gear design and gear manufacturing
- Damage and causal analysis of damage pattern as well as fast and purposeful definition of counter- and optimization-measure
- Optimization of power density by calculation approaches for local load carrying capacity as well as the tribological contact
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