PHYSICAL PROPERTIESDOE-HDBK-1017/1-93Properties of MetalA straight line is drawn through Point (D)Figure 5 Typical Brittle Material Stress-Strain Curveat the same slope as the initial portion ofthe stress-strain curve. The point ofintersection of the new line and the stress-strain curve is projected to the stress axis.The stress value, in pounds per squareinch, is the yield strength. It is indicatedin Figure 5 as Point 3. This method ofplotting is done for the purpose ofsubtracting the elastic strain from the totalstrain, leaving the predetermined"permanent offset" as a remainder. Whenyield strength is reported, the amount ofoffset used in the determination should bestated. For example, "Yield Strength (at0.2% offset) = 51,200 psi."Some examples of yield strength for metals are as follows.Aluminum3.5 x 104 to 4.5 x 104 psiStainless steel4.0 x 104 to 5.0 x 104 psiCarbon steel3.0 x 104 to 4.0 x 104 psiAlternate values are sometimes used instead of yield strength. Several of these are brieflydescribed below.The yield point, determined by the divider method, involves an observerwith a pair of dividers watching for visible elongation between two gagemarks on the specimen. When visible stretch occurs, the load at thatinstant is recorded, and the stress corresponding to that load is calculated.MS-02Page 22Rev. 0
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