For high strain rates, however, a wider range of the pre-existing flaw population leads to crack initiation prior to failure, making the analysis significantly more complex.
FEM analysis on the stress field distribution induced by the presence of a pre-existing flaw provided better understanding for the influence of flaw inclination angle on the initiation position and initiation angle of the potential cracks.
Investigators looking into the crash of an American Airlines flight in Queens in November have so far found no pre-existing flaw in the jet's tail section and are now focusing on the performance of the pilots, who they believe triggered the airplane's wild rolling and yawing in the seconds before it went down.
With reference to the experimental observation of crack initiation and propagation from pre-existing flaws in rock specimens under compression, the influences of pre-existing flaw inclination angle on the cracking processes were analyzed by means of finite element method (FEM) and non-linear dynamics method.
Closed form expressions for the instantaneous anisotropic compliance tensor with respect to the key physical parameters of the wing-cracks (the number density of cracks, the pre-existing flaw orientations and flaw sizes, the instantaneous length of wing-cracks, and the friction coefficient on the flaw surfaces) are derived through a kinematic approach.
After a crack initiates from a pre-existing flaw, the manner in which this crack propagates dictates whether the bridging fibers will be ruptured or pulled out.
The strength criterion states that the tensile stress σcr to initiate a crack from a pre-existing flaw must be below the bridging capacity of the fibers σ0 crossing that crack.
Three types of flaw geometries were evaluated numerically against experimental results: Type A for intact specimen, and Types B and C for flawed cylindrical specimens with different macroscopic pre-existing flaws, respectively.
Fracture mechanics analysis was performed with consideration of pre-existing flaws at the fatigue-sensitive region.
Compressive failure of brittle materials is driven primarily by crack growth from pre-existing flaws in the material.
The effect of pre-existing flaws on the fracture behavior is analyzed both for flaws inside the particle as well as flaws on the particle/matrix interface.
