THE USE OF CHEVRON-NOTCHED SPECIMENS FOR FRACTURE-TOUGHNESS DETERMINATION OF BEARING STEELS

The use of three-point-bending of chevron notched specimens for plane strain fracture toughness determination was studied on two bearing steels with various levels of tempering. For specimen- and notch geometry used the load-time (displacement) curves were presented and fracture behaviour was explained on the basis of fractographic observations. The aproximative procedure based on Bluhm's slice model was proposed for calculation of stress intensity factor, K(ICV), and the validity of the model mentioned for these purposes was supported experimentally. Very good agreement of fracture toughness data obtained on chevron notched specimens, K(ICV), was stated when compared with fracture toughness data, K(IC), measured by means of standard specimens with cyclic precracking.