Introduction: For many non-ferrous ductile materials, the elastic limit (also called the yield stress) is not clearly defined. The linear region of the stress-strain plot gradually becomes a curve. Engineers often define the yield strength (stress) or elastic limit as that stress for which there is a 0.15 - 0.2 % offset; that is, the strain is 0.0015 to 0.002.

Problem: For a 0.15 % offset, what is the yield stress for copper?

Solution: Using the equation for the elastic modulus and the data from Table 12.1...