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Pros and Cons of High Strength Steel


Metal fatigue is another issue that should be considered when upgrading steel structures. When steel is subjected to many cycles where a structure is loaded and unloaded, cracks can form in the steel at stress levels that are well below the yield point. The fatigue resistance of steel does increase with increased yield strength, but for many cyclically loaded structures, the load limits needed to resist fatigue are determined by design features, particularly weldments. In such cases the fatigue resistance of the structure must be improved to successfully upgrade the steel in the structure. In this situation many different approaches can be used. Weld quality can be improved or welds can be moved to areas with lower stresses or eliminated entirely by changing to bolting or other joining techniques.


In summary, maximizing the benefits of stronger steels does require the designer to find creative solutions to address issues such as deflection, instability and fatigue. Despite this, many manufacturers have successfully upgraded their equipment using stronger steels to make them lighter, more capable and more damage resistant.


Smart design improves fatig Tracks ΔM Δσ ΔM


ΔM Δσ


ΔM


Figure 5. The lower picture is the preferred way to attach brackets to increase the life of the welded structure. Notice the difference in fatigue resistance between the two different approaches!


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