Cracking behavior of zinc coating on pre-cracked hot-dip galvanized steel plate under static tension

This paper focuses on the cracking behavior of zinc coating on hot-dip galvanized steel plate subjected to static tension. Two pre-cracked hot-dip galvanized steel plates with different pre-crack lengths were designed and tested under static tension, to investigate the cracking behavior of zinc coating from different perspectives, such as the fracture mode, crack propagation and crack morphology. Numerical analysis was then conducted by extended finite element method (XFEM) to further reveal the crack propagation process and stress intensity factor of both zinc coating and steel substrate, and to identify the key parameters affecting the critical cracking load of zinc coating. Furthermore, a calculation formula was proposed to correct the stress intensity factor and to achieve the critical cracking load of zinc coating on hot-dip galvanized steel plate using the fracture mechanics theory. The results reveal that the fracture failure of zinc coating exhibited significant brittleness, while that of steel substrate showed slight ductility characteristics. Comparatively, the zinc coating cracked considerably earlier than the steel substrate, and the crack propagation rate was much faster for the zinc coating. The stress intensity factor at crack tip increased nonlinearly with the increasement of crack depth dc, and the stress intensity factor of edge pre-crack was slightly higher than that of center pre-crack. The proposed theoretical calculation formula of critical cracking load took the influence of location, length and depth of pre-crack into account, and it could predict the critical cracking load of zinc coating relatively well.