History
Structures upon which human life depends have long been recognized as needing an element of fail-safety. When describing his flying machine, Leonardo Da Vinci noted that "In constructing wings one should make one chord to bear the strain and a looser one in the same position so that if one breaks under the strain, the other is in the position to serve the same function."
Prior to the 1970s, the prevailing engineering philosophy of aircraft structures was to ensure that airworthiness was maintained with a single part broken, a redundancy requirement known as fail-safety. However, advances in fracture mechanics, along with infamous catastrophic fatigue failures such as those in the DeHavilland Comet prompted a change in requirements for aircraft. It was discovered that a phenomenon known as "multiple-site damage" could cause many small cracks in the structure, which grow slowly by themselves, to join one another over time, creating a much larger crack, and significantly reducing the expected time until failure
Read more about this topic: Damage Tolerance
Famous quotes containing the word history:
“America is the only nation in history which, miraculously, has gone directly from barbarism to degeneration without the usual interval of civilization.”
—Attributed to Georges Clemenceau (1841–1929)
“If you look at history you’ll find that no state has been so plagued by its rulers as when power has fallen into the hands of some dabbler in philosophy or literary addict.”
—Desiderius Erasmus (c. 1466–1536)
“The custard is setting; meanwhile
I not only have my own history to worry about
But am forced to fret over insufficient details related to large
Unfinished concepts that can never bring themselves to the point
Of being, with or without my help, if any were forthcoming.”
—John Ashbery (b. 1927)