Applied fractures

The application of fracture mechanics to foods is novel and has a different purpose than the one traditionally used in the plastics industry. In the latter industry, the goal was to apply fracture mechanics to develop stronger, tougher plastics, so as to avoid fracture. For foods, the requirements are different - food products are required to break and should do so in a desired fashion. This requirement holds as much for mastication purposes as for cutting foods with knives in the kitchen. 

When fracture occurs out of the linear domain (fracture with yielding), e.g., for highly toughened thermosets or at high temperatures, it is still possible to apply fracture mechanics, with the energetic theory. For instance, the J-integral may be used for bulk materials (Williams, 1984) or Essential Work for Fracture for thin films (Mai and Powell, 1991 Liu and Nairn, 1998). 

For many engineering applications, impact fracture behavior is of prime practical importance. While impact properties of plastics are usually characterized in terms of notched or un-notched impact fracture energies, there has been an increasing tendency to also apply fracture mechanics techniques over the last decade [1, 2 and 3]. For quasi-brittle fracture, a linear elastic fracture mechanics (LEFM) approach with a force based analysis (FBA) is frequently applied to determine fracture toughness values at moderate loading rates. 

The results above suggest that it may be possible to apply fracture mechanics data to determine failure loads of more complex structures, provided that (i) the adhesives used are not too ductile, (ii) bondline thickness is known and controlled, (iii) non-linear behaviour due to adherend and interface damage is limited, and (iv) the specimens employed to determine... 

Applying fracture mechanics techniques to characterize brittle materials has become an important subfield of materials science, and a reasonable understanding of the relation between toughness, composition, and microstructure is available. Silicate glasses have toughness values of 0.7-1,0 MPam, alumina ceramics values of 4-5 MPam, and glass ceramics values of 1-4 MPam, (the fracture toughness of metals is often > 50 MPam "),... 

The poor injectivity found in thermal processes is largely a result of the nature of the reservoir crudes. Operators have applied fracture technology in coimection with the injectionof fluids in thermal processes. This has helped in many reservoirs. 

Zhou, X.E Li, J.L. 2011. Hoek-Brown criterion apphed to circular tunnel using elastoplasticity and in situ axial stress. Theoretical and Applied Fracture Mechanics 56(2), 95-103. 

Huang, N.C. and Liu, X.Y. (1994) Debonding and fiber pull-out in reinforced composites. Theoretical and Applied Fracture Mechanics, 21, 157-176. 

Fig. 4.18. Typical plot of versus applied fracture energy.

Irwin has reviewed fracture mechanics as applied to adhesive systems. Griffith was the first to apply fracture mechanics to solids. His formulation of fracture mechanics begins with Eq. (54) above, except that the fracture criterion in his formulation was the amount of energy expended to create... 

The development of the fracture mechanics approach to metals lead to Kaplan s (1961) proposal to apply fracture mechanics to concretes, using also relations applied in other fields of materials science. The Griffith s approach to cracks in perfectly brittle and homogeneous materials was extensively followed in numerous studies of cracking processes in cementitious materials, (cf. Section 10.1.1). Then the question arose whether the cracks themselves, and which of them, were governed by the Griffith s approach. Later, however, it became clear that the situation in these materials is much more complex and requires a more diversified approach. The answer for the above question is therefore also more complex the Griffith s approach is applicable to those materials, but with several restrictions and complementary assumptions. Various related questions are the subject of further developments of new theories and proposals (cf. Section 10.1). 

In such a way there are two approaches to apply fracture mechanics the use of a stress intensity concept or an energy one. Both are equivalent and give identical results in the case of an ideal brittle material and they are related as follows ... 

Trantina [55] applied fracture mechanics to adhesive joints with some success and applied the failure criteria to a finite element model to find adhesive fracture energies. The influence of the glueline thickness was not accounted for. Hu [56] used a shear lag analysis and applied failure criteria in terms of Jc and it was shown that this gave good predictions of failure and was also able to account for the adhesive thickness. It was noted that this is consequently a good method of predicting failure for adhesive materials loaded in shear. 

Fig. 19. Generalized crack speed as a function of applied fracture energy.

By contrast, it is current technology to apply fracture mechanics with several modifications to short fiber-reinforced composites. 

Wang JL, Pamianpour M, Shirazi-Adl A et al. (1997) Development and vaUdation of a viscoelastic finite element model of an L2/L3 motion segment. Theoretical and Applied Fracture Mechanics 28 81-93... 

Applying fracture mechanics to impact problems has other difficulties. Local finer meshes, which are often used near stress concentration points in static finite element methods, are not suitable for dynamic calculation because the step of time integral depends on the smallest mesh size in the analytical model, and total calculation time increases drastically even if only one small mesh is used. Therefore, finite element analysis for fracture mechanics, which needs finer meshes near the crack tips for calculating the stress intensity factors, consumes time and computer resources. 

APPLYING FRACTURE MECHANICS METHODS TO MODEL COATING DELAMINATION... 

Applying Fracture Mechanics Methods to Model Coating Delamination... 

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