Fracture mechanics and fatigue crack propagation in armor steel welds

The welding process of armor steel is a complex process due to possible welding faults appearing in all zones of weld metal joint in the form of cracks and pores, as results of high percentage of carbon in the base metal. Military armored vehicles, are exposed to dynamic and impact loads. Hence, it is important to know the fracture toughness and fatigue crack propagation in all zones of the weld joint. Fatigue crack propagation testing was made on SEN (B) specimens. Fatigue threshold for weld metal is the lowest Delta Kth = 10.1 MPa*m1/2, and for base metal is the highest Delta Kth = 13.4 MPa*m1/2, while the notch values in HAZ is Delta Kth = 12.6 MPa*m1/2. Due to a significant interest in quantification of material resistance to crack initiation and propagation, the fatigue crack growth rate was measured in the base metal, HAZ and welded metal zone. Accordingly, the most important attention should be paid to the zone of the base metal, while the weld metal and HAZ are safe zones.