Crack advance resistance

The temperature distribution during crack propagation is shown in Fig. 4, and corresponds to the circle in the resistance curves in Fig. 3. During crack advance, the heat continues to diffuse along the normal to the craze surfaces but the extension of the hot zone is confined to a size comparable to that of the craze opening. 

Suppose that the final or steady-state depth of penetration of the crack is flc which may be smaller than, equal to, or larger than the film thickness hf. The amount of work per unit crack advance in the a -direction which must be supplied to overcome the resistance of the material is... 

Note Stress ratio A = 0.1, at 20 to 28 Hz compact specimens, (a) NI - normal interstitial, LI = low interstitial, ELI = extra low interstitial. Source R. L. Ibbler and R.P. Reed, Fatigue Crack (Srowth Resistance of Structural Alloys at Cryogenic Temperatures, in Advances in Cryogenic Engineering, KD. Timmerhaus et al., EkL, Vol 24, Plenum Press, 1978, p 82-90... 

As tire technology has advanced, achievable improvements in crack formation resistance of butadiene rubber were at the center of focus. The best compromise between crack formation and crack propagation can be achieved with NR/BR blends (40 to 70 wt.% BR). 

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. 

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