the load per unit area that a structure can withstand without being permanently deformed by more than a specified amount.
Origin of proof stress
First recorded in 1860–65
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British Dictionary definitions for proof stress
engineering the equivalent of yield stress in materials which have no clearly defined yield point
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012