Corrosion and some aspects of design can play a significant role in fatigue performance and must be considered in a complete comparative analysis. The type of wind loading that can occur will also vary with the application. For example, the wind patterns caused by large vehicles must be considered for highway poles.
Aluminum highway poles are increasingly failing due to fatigue and stainless steel is a logical alternative. The exceptional fatigue performance of austenitic stainless steels (e.g. 201, 304, 316, etc.) is well known. Since poles will be cold worked (rolled, stretched, etc.), which increases their strength, it is interesting to note that duplex stainless steels have a higher fatigue limit than the austenitics at the same static strength. The fatigue limit increases with the static strength for both stainless steel alloy families.
The duplex and austenitic stainless steels are also much less notch sensitive than carbon steel. Furthermore, the effect of strength on notch sensitivity is significant for carbon steel but almost non-existent in these stainless steels.(1) Please see the Structural Design section of IMOA’s website for more information.
Impact toughness can be important for some applications. The graph below provides general guidance on the relative impact toughness of different stainless steel families. Special processing, thickness, the level of cold work and welding are among the parameters that can affect the actual performance. The austenitics have the best performance of all pole options for low design temperatures.