concentration factor was larger than that of gas pore and gasshrinkage
pore. Accordingly, with the increasing tensile stress, the
crack would firstly initiate at the shrinkage pore, then propagate
along the direction roughly perpendicular to the tensile stress.
With the crack propagation, the efficient force bearing area would
decrease, and the stress at the tips of gas pore and gas-shrinkage
pore would gradually increase to the fracture stress level and ultimately
led to the initiation of the secondary cracks.