STRETCH ZONE GEOMETRICAL MEASUREMENT, A PARTICULAR WAY TO MEASURE FRACTURE-TOUGHNESS

Stretch zone geometry (height and length) has been measured using five methods (Transmission Electron Microscopy, Retrodiffused Electron Mic roscopy, Nickel Plating, Roughness Measurement, Ondulation Method). Ex perimental investigations show that the major difficulty of these meas urements is the great scatter of experimental results. However, it is seen that Transmission Electron Microscopy and Nickel Plating give suf ficiently accurate results. By using these different methods, we have found a linear relationship between stretch zone geometry and the clas sical fracture toughness parameter J(k). Rolling direction, grain size , loading rate, yield stress and the material texture are the influent ial parameters determining the stretch zone geometry.