Optimal key design for shaft hub connections

Key connections in shaft hub assemblies are typically used due to the price of production but also the possibility for using it as an overload protection and safety device is important. The design of keyways and keys is specified in standards, different designs are available but typically the contact area is flat. The connection fatigue strength is improved if the stress concentration is reduced; important here is both the key shape and also the tolerances between key and keyway. The present designs described in standards are to some extend the result of previous possibilities for production. Today larger variations are possible without increasing the production price significantly. New designs with improved strength are presented and the design evaluation is done using both 2D and 3D finite element models including contact modeling. The design is primarily described by the super elliptical shape, that is, the design parameterization is simple. Improvement in the stress level found is significant, a maximum reduction of 78% is found, indicating that the fatigue strength can be significantly increased.