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:
“Anyone who is practically acquainted with scientific work is aware that those who refuse to go beyond fact rarely get as far as fact; and anyone who has studied the history of science knows that almost every great step therein has been made by the “anticipation of Nature.””
—Thomas Henry Huxley (1825–95)
“Let it suffice that in the light of these two facts, namely, that the mind is One, and that nature is its correlative, history is to be read and written.”
—Ralph Waldo Emerson (1803–1882)
“I am ashamed to see what a shallow village tale our so-called History is. How many times must we say Rome, and Paris, and Constantinople! What does Rome know of rat and lizard? What are Olympiads and Consulates to these neighboring systems of being? Nay, what food or experience or succor have they for the Esquimaux seal-hunter, or the Kanaka in his canoe, for the fisherman, the stevedore, the porter?”
—Ralph Waldo Emerson (1803–1882)