What are Fatigue Cracks?
Fatigue cracks are cracks caused by repeated stress on a structure over a period of time. Many times, fatigue cracks can be superficial, but at other times, they can cause a catastrophic failure leading to disastrous results. Fatigue cracks are a serious engineering concern that can only be discovered by inspectors, who are able to tell how serious the cracks are. Perhaps the best known example of how disastrous fatigue cracks can be comes from an incident in Minneapolis on 1 August 2007. On that day, during the afternoon rush hour, a bridge on Interstate 35 over the Mississippi River collapsed, causing 13 people to plunge to their deaths below. It was a national tragedy that caused many states to step up their bridge inspection policies immediately. It was later determined by the National Transportation Safety Board that the bridge collapsed due to the inadequate size of large steel plates used to connect pieces of the bridge together. The inadequate size caused fatigue cracks that ev
