Crack on rear toggle

alvin · 05-01-2010, 08:39 PM

Not a professional either. But read somewhere they call it metal's fatigue strength.

"All metals will fail under repeatedly changing load conditions at a lower stress than they will if the load is applied steadily in one direction. A wire that might support a continuous load of 5000 MPa indefinitely will probably fail in time if a load of 3000 MPa is alternately and repeatedly imposed and then released. The piston rod on a steam locomotive is subjected to tension for a half-cycle, then to compression for a half-cycle, thousands of times every day. Structural members in a bridge are constantly subject to changing load conditions. In all such applications, fatigue strength, which is always lower than tensile strength and sometimes much lower, must be considered by a designer."

Please see page 7 of this book. Pattern matches pretty well.

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05-01-2010, 08:39 PM	#3
alvin User Join Date: Jul 2007 Location: US Posts: 3,843 Thanks: 132 Thanked 729 Times in 438 Posts	Not a professional either. But read somewhere they call it metal's fatigue strength. "All metals will fail under repeatedly changing load conditions at a lower stress than they will if the load is applied steadily in one direction. A wire that might support a continuous load of 5000 MPa indefinitely will probably fail in time if a load of 3000 MPa is alternately and repeatedly imposed and then released. The piston rod on a steam locomotive is subjected to tension for a half-cycle, then to compression for a half-cycle, thousands of times every day. Structural members in a bridge are constantly subject to changing load conditions. In all such applications, fatigue strength, which is always lower than tensile strength and sometimes much lower, must be considered by a designer." Please see page 7 of this book. Pattern matches pretty well.