Effect of Material Orientation

The orientations of the crack plane and crack growth direction are defined in terms of these definitions for example, LT designates a specimen that has its crack in the TS plane and is to be loaded in the L direction. 

2 Metallurgical Considerations (Krafft s Tensiie Ligament Instabiiity Modei [4]) 

To provide a linkage between fracture toughness and some controlling microstruc-tural parameter of the material, a simple model was proposed by Krafft [4]. The model envisioned the presence of an array of inclusions aligned ahead of the 

The essence of Krafft s model involves the relationship between the onset of crack growth with that of plastic flow instability in these tensile ligaments ahead of the crack tip. Assuming that the strains within the crack tip plastic zone are constrained by the surrounding elastic material, the strain inside the plastic zone would follow a singularity as dictated by the surrounding elastic stress-strain field namely, 

He proposed that crack growth instability, or fracture, would correspond to the onset of plastic flow instability (or necking) in the tensile ligament(s) at the crack tip or when e at r = dj. Thus, 

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Wust, S., Muller, R., Hofmann, S., 2015. 3D bioprinting of complex channels-Effects of material, orientation, geometry, and cell embedding. J. Biomed. Mater. Res. A 103, 2558-2570. 

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