Effects of Grain Size and Temperature on Flat Fracture Propagation and Arrest in Mild Steel
SourceThe paper presents results from an experimental program whose objective is the determination of the effects of grain size and temperature on flat fracture propagation and arrest in mild steel. Small laboratory test specimens, containing nitrided notches and surfaces so as to eliminate respectively the initiation barrier and shear lip formation, have been deformed by four-point bending. The onset of crack arrest has been correlated with the applied loading, and the fracture surface appearance during both propagation and arrest has been studied in detail; cleavage rather than ductile fracture is the predominent failure mechanism for a wide range of testing conditions. The results are discussed in relation to theoretical models describing the micromechanics of flat fracture propagation and arrest.