�?�?t ρ l k + �?�?x i ρ l k v l = �?�?x j μ + μ t σ k �?k �?x j + G k �?ρ l ε �?Y M Comparing time required for parallel fractures and wedge fractures to succeed in steady loss, it is located that there is a diameter expansion at the doorway on the wedge fracture relative on the exit. The existence of the expansion