Page 36 - T. Anderson-Fracture Mechanics - Fundamentals and Applns.-CRC (2005)

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16 Fracture Mechanics: Fundamentals and Applications

FIGURE 1.10 The damage tolerance approach to design.

1.4 EFFECT OF MATERIAL PROPERTIES ON FRACTURE

Figure 1.11 shows a simplified family tree for the field of fracture mechanics. Most of the early
work was applicable only to linear elastic materials under quasistatic conditions, while subsequent
advances in fracture research incorporated other types of material behavior. Elastic-plastic fracture
mechanics considers plastic deformation under quasistatic conditions, while dynamic, viscoelastic,
and viscoplastic fracture mechanics include time as a variable. A dashed line is drawn between
linear elastic and dynamic fracture mechanics because some early research considered dynamic
linear elastic behavior. The chapters that describe the various types of fracture behavior are shown
in Figure 1.11. Elastic-plastic, viscoelastic, and viscoplastic fracture behavior are sometimes
included in the more general heading of nonlinear fracture mechanics. The branch of fracture
mechanics one should apply to a particular problem obviously depends on material behavior.
Consider a cracked plate (Figure 1.8) that is loaded to failure. Figure 1.12 is a schematic plot
of failure stress vs. fracture toughness K . For low toughness materials, brittle fracture is the governing
Ic

FIGURE 1.11 Simplified family tree of fracture mechanics.