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DIN 7190-compliant verification of an interference fit
Implementation of the FKM guideline with Ansys for an interference fit of a spur-gear unit

Ansys implementation for an interference fit of a spur-gear unit

Sector: Machinery and plant engineeringSpecialist field: Structural mechanics

Gearbox manufacturer Stiebel provides DIN 7190-compliant design and verification for the connection of shaft and gear using an interference fit with Ansys FE analysis.

Summary

Task

The shaft and gear of a spur-gear unit are frictionally connected using an interference fit. DIN 7190 provides valuable information on the design and layout of such interference fits. FEM is used to take the real geometry of the hub (gear) and the complex interference conditions into account.

Solution

The path of verification specified by DIN 7190 represents the starting point for the selection of load cases and analysis parameters for the FE analysis in ANSYS.

Customer benefits

The appropriate combination of FE analysis and set of rules allows reliable design and verification of shafts and interference fits.

Project Details

Task

The shaft and gear of a spur-gear unit are connected by means of an interference fit through friction. DIN 7190 provides valuable information on the design and layout of such interference fits, although simplified geometric conditions are assumed for the analytical calculation. Using FEM, the real geometry of the hub (gear) and the complex interference conditions must be taken into account. Furthermore, the notch stress in the shaft mounting must be calculated in detail and evaluated in terms of static and fatigue strength using the FKM guideline.


Customer Benefit

The appropriate combination of FE analysis and set of rules allows reliable design and verification of shafts and interference fits. In addition to the purely elastic design, DIN 7190 also allows limited plasticization of the hub cross-section, which can be quantified using nonlinear FE analysis.


Solution

The path of verification specified by DIN 7190 represents the starting point for the selection of load cases and analysis parameters for the FE analysis. The following scenarios were analyzed:

• Strength verification (static and fatigue) for the shaft: Use of the submodel technique in ANSYS in order to be able to precisely record the notch stress details for the FKM evaluation using a sort of “zoom function” on a refined mesh section.

• Necessary cooling or heating of shaft or hub to achieve the required joint play during assembly.

• Calculation of the interference fit: Particular attention should be paid to calculating the non-linear contact conditions in the joint as precisely as possible.

The preferred ANSYS option for this purpose is the so-called Pure Lagrange contact, which measures the pressure in the joint extremely precisely. The minimum interference resulting from the fit as well as the roughness and the coefficient of adhesion of the friction pairing determine the level of this pressure distribution. This results in the maximum transmittable torque.

Images: © Stiebel


Head of Professional Development
Dr.-Ing. Marold Moosrainer

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