The Charpy impact tester measures a material's toughness, its ability to absorb energy before fracturing, by swinging a heavy pendulum from a fixed height to strike and break a notched bar specimen and recording how much of the pendulum's energy the fracture absorbed from how high it swings afterward. The French engineer Georges Charpy standardized the test in 1901, refining an existing pendulum impact method into the specific notched-bar configuration and calculation that carries his name, developed to give industry a quick way to detect steels that were strong under slow loading but dangerously brittle under sudden impact. The Charpy test's finding that many steels fail suddenly below a specific transition temperature became central to understanding brittle fractures, including the wartime failures of welded Liberty ship hulls, and the test remains a standard specification requirement for structural and pressure-vessel steel.
Facts
SignificanceAdoption of Charpy testing standards was driven by brittle fractures in the welded Liberty ships of World War II. 1 FAQs
Why did the Liberty ship failures make the Charpy impact test so important?
Because the Liberty ships cracked in cold weather, and the Charpy test shows the temperature at which a steel turns from tough to brittle.
The Liberty ships were cheap cargo ships built in great numbers with welded steel plate instead of rivets. Of the roughly 4,700 built by 1946, about 1,250 had suffered brittle fractures by 1953, and 12 broke in two. Little was known then about the ductile to brittle transition that happens at low temperature in all steels, so the real question was at what temperature a given steel turns brittle. The Charpy impact test answers that, because it measures how much energy a notched bar absorbs when a pendulum breaks it, and test results from ship steel, including Liberty ship plate, showed that the steel in use was worse than what was available at the time. That is why Charpy testing became a standard requirement for structural steel.
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1. Wikipedia: Charpy impact test
History, 1901 standardization sentence
In 1901, Georges Charpy proposed a standardized method
History, Liberty ships sentence
Liberty ships program of World War II
In Group: Materials Testing Instruments, Article body
In materials science, the Charpy impact test, also known as the Charpy V-notch test, is a standardized high strain rate test which determines the amount of energy absorbed by a material during fracture.
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