<Dl> <Dd> Modulus of resilience = Yield stress / 2 (Young's modulus) </Dd> </Dl> <Dd> Modulus of resilience = Yield stress / 2 (Young's modulus) </Dd> <P> The toughness of a material can be measured using a small specimen of that material . A typical testing machine uses a pendulum to strike a notched specimen of defined cross-section and deform it . The height from which the pendulum fell, minus the height to which it rose after deforming the specimen, multiplied by the weight of the pendulum is a measure of the energy absorbed by the specimen as it was deformed during the impact with the pendulum . The Charpy and Izod notched impact strength tests are typical ASTM tests used to determine toughness . </P> <P> Tensile toughness (or, deformation energy, U) is measured in units of joule per cubic metre (J m) in the SI system and inch - pound - force per cubic inch (in lbf in) in US customary units . 1.00 N m.m ≃ 0.000 145 in lbf in and 1.00 in lbf in ≃ 6.89 kN m.m . </P>

During ductile failure a large amount of energy is absorbed