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Note added at 10 mins (2020-01-13 09:38:39 GMT)
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Composite normalized yield stress (0.2% offset yield stress divided by the matrix offset yield stress)
http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd...

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Note added at 13 mins (2020-01-13 09:41:18 GMT)
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Proof stress also refers to the stress that will cause a specified small, permanent extension of a tensile test piece...

Proof stress is also called offset yield stress. Typically, the stress needed to produce 0.2 percent of plastic deformation is considered proof stress. It's important to determine the value or level of stress that can be applied before a material "yields" or changes its composition, size, or shape.

http://www.thebalancesmb.com/what-is-the-definition-of-proof...