1. A beam with a 0.5mm crack is under a pair of splitting tensile load, P. If the compliance of the cracked plate is determined as , where E = 200GPa and I = 10e-9m4, and the R-curve of this material is knwon as R=300(1-e^(-(a-a0))), determine the failure load for unstable crack propagation (assuming the thickness of the plate is B=1).

2. A plate with an inclined crack (beta = 30deg) is subjected toa biaxial tension (sigma_1/sigma_2=0.5) as shown in the figure above, determine the possible direction of crack propagation.