Fatigue and Brittle Failure

All metals may be subjected to fatigue under repeated heavy load conditions.

While high-strength steel is susceptible to fatigue, this seldom happens in practice. Aluminium brackets and clips have been known to fail by fatigue and this should be considered in designing such items.

Other metals, such as lead and copper, are restricted in length or overall panel size to avoid cracking by fatigue. Sharply folded corners should be avoided on these materials and the minimum radii requirements should be followed.

Hydrogen embrittlement can occur when folded items such as external gutter brackets are subjected to post-forming hot dip galvanizing. This can be avoided by forming to radii appropriate to the material grade and thickness being formed.