Fractures, longitudinal

Figure 17.7 Section of longitudinally fractured subterranean cooling water line. Note that the crack runs the entire length of the line.

The preceding analysis is premised on having continuous fibers of equal strength all of which fracture at the same longitudinal position. However, fibers under tension do not all have the same fracture strength nor do they fracture in the same place. Rather, because surface imperfections vary from fiber to fiber, the individual fibers have different fracture strengths. A statistical analysis is then necessary to rationally define the strength of a composite material. 

Other researchers have substantially advanced the state of the art of fracture mechanics applied to composite materials. Tetelman [6-15] and Corten [6-16] discuss fracture mechanics from the point of view of micromechanics. Sih and Chen [6-17] treat the mixed-mode fracture problem for noncollinear crack propagation. Waddoups, Eisenmann, and Kaminski [6-18] and Konish, Swedlow, and Cruse [6-19] extend the concepts of fracture mechanics to laminates. Impact resistance of unidirectional composites is discussed by Chamis, Hanson, and Serafini [6-20]. They use strain energy and fracture strength concepts along with micromechanics to assess impact resistance in longitudinal, transverse, and shear modes. 

Lange,/, length longitude tallness, -bruch, m. longitudinal fracture. — der Lange nach, lengthwise. 

Many of the mesogenic molecules are stericaUy asymmetric, which is determined by the fractures and bending of the molecular core as well as by the presence of the tail chains of different nature, including the branched, biforked or polyphilic moieties (Fig. 2c-f). In terms of the multipole model of molecular asymmetry introduced by Petrov and Derzhanski [34], we can speak about longitudinal or transverse steric dipoles or multipoles (Fig. 3). 

Fracture tips in half longitudinally with a razor blade and a hammer (using a binocular microscope). 

Figure 13. Impact energy at 100% ductile fracture temperature, which is shelf energy, as a function of REM-to-sulfur ratio retained in the 80,000 psi steel. Note the progressive effect of increasing REM additions on the transverse impacts while the longitudinal values remain virtually unchanged. The X points represent untreated steel.

Under the title Shear Fracture, Cook (Ref 4, p 346) noted that under conditions in which the tensile forces cannot develop or are restricted, a type of fracturing that can be associated with trajectories of maximum shear stress may develop. Rinehart 8t Pearson (Ref 1) detonated a 1/8 inch layer of expl on the cylindrical surface of a 2)4 inch OD aluminum (24S-T) cylindrical block with a 3/4 inch cylindrical relief hole drilled thru the longitudinal axis. The shock wave moving in toward the relief hole developed at each point of the block two mutually orthogonal trajectories of maximum shear stress. The trajectories, where the shear stress was maximal, spread out in 8 to 12 curved continuous lines from points on the surface of the relief hole. The shear fraction patterns observed along trajectories of maximum shear resembled the "Luder s... 

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