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  • Print publication year: 2010
  • Online publication date: June 2012

2 - Physical Basis of Fracture Mechanics

Summary

In this chapter, the classical theories of failure are summarized first, and their inadequacy in accounting for the failure (fracture) of bodies that contain crack(s) is highlighted. The basic development of fracture mechanics, following the concept first formulated by A. A. Griffith, is introduced. The concepts of strain energy release rate and stress intensity factor, and their identification as the driving force for crack growth are introduced. The experimental determinations of these factors are discussed. Fracture behavior of engineering materials is described, and the importance of fracture mechanics in the design and sustainment of engineered systems is considered.

Classical Theories of Failure

Classical theories of failure are based on concepts of maximum stress, strain, or strain energy and assume that the material is homogeneous and free from defects. Stresses, strains, and strain energies are typically obtained through elastic analyses.

Maximum Principal Stress (or Tresca) Criterion

The maximum principal stress criterion for failure simply states that failure (by yielding or by fracture) would occur when the maximum principal stress reaches a critical value (i.e., the material's yield strength, σYS, or fracture strength, σf, or tensile strength, σUTS).

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Fracture Mechanics
  • Online ISBN: 9780511806865
  • Book DOI: https://doi.org/10.1017/CBO9780511806865
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REFERENCES
Griffith, A. A., “The Phenomenon of Rupture and Flow in Solids,” Phil. Trans. Royal Soc. of London, A221 (1921), 163–197.
Griffith, A. A., “The Theory of Rupture,” Proc. 1st Int. Congress Applied Mech. (1924), 55–63. Biezeno and Burgers, eds., Waltman (1925).
Tresca, H., “On the “flow of solids” with practical application of forgings, etc.,” Proc. Inst. Mech. Eng., 18 (1867), 114–150.
Mises, R., “Mechanik der plastischen Formänderung von Kristallen,” ZAMM-Zeitschrift für Angewandte Mathematik und Mechanik, 8, 3 (1928), 161–185.
Inglis, C. E., “Stresses in a Plate due to the Presence of Cracks and Sharp Corners,” Trans. Inst. Naval Architects, 55 (1913), 219–241.
Orowan, E., “Energy Criterion of Fracture,” Welding Journal, 34 (1955), 1575–1605.
Irwin, G. R., “Fracture Dynamics,” in Fracturing of Metals, ASM publication (1948), 147–166.
Irwin, G. R., and Kies, J. A., “Fracturing and Fracture Dynamics,” Welding Journal Research Supplement (1952).
Irwin, G. R., and Kies, J. A., “Critical Energy Rate Analysis of Fracture Strength of Large Welded Structures,” The Welding Journal Research Supplement (1954).
ASTM STP 527, Fracture Toughness Evaluation by R-Curve Method, American Society for Testing and Materials, Philadelphia, PA (1973).