Necking. Localized reduction of cross section area of a specimen under tensile load. It is disregarded in calculating engineering stress but is taken into account in determining true stress.

Nil ductility transition temperature. Temperature above which a specimen no longer shows brittle fracture in a drop weight test. (ASTM E-208).

Nominal stress. Stress calculated on the basis of the net cross section of a specimen without taking into account the effect of geometric discontinuities such as holes, grooves, fillets, etc.

Notch brittleness. Phenomena by which brittle fracture occurs more readily in notched specimens than in notch free specimens.

Notch ductility. Reduction in area of a notched specimen at fracture in a tension test.

Notch sensitivity. Measure of reduction in load-carrying ability caused by stress concentration in a specimen.