Research on fatigue crack growth behavior of AZ31B magnesium alloy electron beam welded joints based on temperature distribution around the crack tip

Fatigue crack growth (FCG) behavior of AZ31B magnesium alloy electron beam welded (EBWed) joints undergoing cyclic load was investigated by infrared thermography. Four superficial temperature variation stages of crack tip in weld were observed during test: an initial temperature increase, a temperature equilibrium, an abrupt temperature increase and a temperature drop after failure. Theoretical model was formulated to explain generation and distribution of plastically dissipated energy around crack tip. Experimental results indicate that ΔT as a function of ΔK can be utilized as an index to predict FCG of weld. Finally, transform of fracture mechanism was related to temperature change.