Griffith concept

To give the Griffith concept of fracture a concrete structure, which can... 

The importance of inherent flaws as sites of weakness for the nucleation of internal fracture seems almost intuitive. There is no need to dwell on theories of the strength of solids to recognize that material tensile strengths are orders of magnitude below theoretical limits. The Griffith theory of fracture in brittle material (Griflfith, 1920) is now a well-accepted part of linear-elastic fracture mechanics, and these concepts are readily extended to other material response laws. 

Although Griffith put forward the original concept of linear elastic fracture mechanics (LEFM), it was Irwin who developed the technique for engineering materials. He examined the equations that had been developed for the stresses in the vicinity of an elliptical crack in a large plate as illustrated in Fig. 2.66. The equations for the elastic stress distribution at the crack tip are as follows. 

Ozmen (2004, especially for chemical bonding) and Coll und Treagust (2003, chemistiy of metals) can help to develop a first overview. Numerous authors (e g. Pfund, 1975 Schldpke, 1991 Griffith and Preston, 1992 Mas et al., 1987) describe parallels between students conceptions and historical scientific ideas. Schldpke (1991), for example, points out similarities between students conceptions concerning properties of matter and ideas in alchemist thinking. Lee, Eichinger, Anderson, Berkheimer, and Blakeslee (1993) mentions semblances between the ideas of Aristotle and students conceptions about general aspects of the particulate nature of matter and the horror vacui . 

As the results of Pfundt (1981), Griffith (1987) and Lee et al. (1993) show, students have problems in dealing with the idea of empty spaces between particles. In her studies, Pfundt presented students with different representations of atoms. The students had to choose the one that represented their ideas at best. Numerous students chose representations of cubic or hexagonal atoms, because they fit without gaps between them (Pfundt, 1981, p. 87). Griffith and Preston (1992) could explicitly show that students suppose that the size of a crystal corresponded to the shape of its atoms. Furthermore, they discuss the parallels between this students conception and the corresponding historical idea of Rene Hairy. 

The principle behind the phenomenon of fracture of materials can be described by having recourse to Griffith s theory. Alternatively, this can be done by introducing the concept of fracture toughness. 

Fisk, George W. A new sense of destiny from ancient symbols renewal of vision through the lost language / George W. Fisk illustrations by Robert C. Griffith. St Joseph (MI) Cosmic Concepts Press, 1988. 124, [2] p. ISBN 0962050709... 

Brittle fracture mechanisms of the type first proposed by Griffiths [122] are based on the concept of cpmpetition between a decrease of... 

There is a large body of literature on FTIR spectroscopy including, for example, Bracewell (1965), Horlick (1968), Bell (1972), Griffiths (1975, 1983), Ferraro and Basile (1978), Koenig (1981), Griffiths and de Haseth (1986), Perkins (1986, 1987), Mackenzie (1988). Cameron and Moffatt (1984), and Gillette et al. (1985) have explained the basic mathematical concepts of deconvolution, derivation and smoothing in FTIR spectroscopy. 

The energy balance considerations in Griffith s original concept were later refined by Orowan and Irwin to include the effects of plasticity and elasticity for applicability to metals (Orowan, 1952 Irwin, 1957). Metals fail by ductile fracture, where the crack growth occurs in the direction of the primary slip system. When the slip plane is inclined to the crack, atoms across the slip plane slide past one another, relieving the stress, which results in a zigzag crack path. This is illustrated in Figure 10.14. 

In fact, the first quantitative attempt to incorporate the dynamics of the crack into the Griffith energy balance concept was given by Mott (1948). He suggested that unlike the Griffith case of fracture initiation or nucleation... 

Spier RE Griffiths B (1984) An examination of the data and concepts germane to the oxygenation of cultured animal cells. Developments in Biological Standardization 55 81-92. 

Irwin proposed the concept of quasi-elastic fracture, which allows us to extend the limits of applicability of Griffith s theory [11], Irwin s criterion is valid not only for brittle materials, but also for elastic-plastic materials with significant plastic deformation developing until the moment of actual destruction of a material. 

The concept of quasi-brittle fracture implies that some materials that exhibit the characteristics of plastic materials at standard test, collapse in tests of the sample with a crack due to the quasi-brittle mechanism, that is, plastic deformation is concentrated in a narrow layer near the tip of a crack. For such materials, Griffith s criterion is relevant instead of the value of the surface energy to introduce the work of plastic deformation at the crack tip. 

---