Ultimate Tensile Strength:
The UTS (ultimate tensile strength) is the maximum resistance to fracture. It is equal to the maximum load which could be carried through one square inch of cross-sectional area while the load is applied as simple tension. It is expressed in pounds per square inch.
UTS = maximum load/ area of original cross section = Pmax/ Ao = psi (2-12)
The ultimate tensile strength appears as the stress coordinate value of the highest point on the curve if the complete engineering stress-strain curve is available. Materials which elongate greatly before breaking undergo like a huge reduction of cross-sectional area in which the material will carry less load in the last stages of the test (this was noted in Figure through the decrease in stress only prior to rupture). A marked decrease in cross-section is known as "necking." Ultimate tensile strength is frequently shortened to "tensile strength" or even to "the ultimate." "Ultimate strength" is several times used but could be misleading and, thus, is not used in a few disciplines.