Abstract
An experimental study was conducted to examine the initiation of cracks in the AZ31B magnesium (Mg) alloy for tensile overload effects, exploring the influence of overload cycle number, magnitude, and multiplicity of the applied overloads (OL). The number of cycles to failure increased from 8 % to 15 % for overload ratio (OLR) of 1.5 and 2.0 respectively applied as first cycle when compared with constant amplitude loading (CAL). However, the number of cycles to failure increased from 25 % to 43 % for OLR of 1.5 and 2.0 respectively when overload was applied at 5000th cycle. The onset of cracks was delayed when two overloads were applied as the first and 5000th loading cycles. The longitudinal-transverse (L-T) specimens were tested using a two-step high-low sequence loading procedure by varying maximum and minimum load. The fractography results also depict variations in the initial crack formations under different overload conditions. The effects of different overloads on the fracture surfaces of Compact Tension specimens were examined using the Field Emission Scanning Electron Microscopy, indicating substantial reduction in both the number and size of microcracks. 3D profilometer tests were performed, indicating a surface roughness of 0.20 μm to 0.30 μm.
Published Version
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