FRACTURE MECHANICS.docx

# Furthermore the crack growth directions were

• 14

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Furthermore, the crack growth directions were determined by different methods i.e. the minimum strain energy density criterion, the maximum principal stress criterion, the maximum energy release rate criterion, SED, local SED, generalized maximum tangential stress, critical distance theory, finite fracture mechanics, and cohesive zone model. The stress intensity factor was developed to describe the stress state at the crack tip and was used in crack growth direction estimation. J-integral method was defined to calculate the stress intensity factors by using the integral paths around a crack tip. Additionally, fracture toughness of different materials could be

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P a g e | 3 obtained through stress intensity factor computations. A typical example for a large crack problem is the geothermal energy extraction from hot, dry rock mass. The cracks are artificially induced for use as heat exchange surfaces, through which water is circulated from the ground surface to the underground rock. The sizes of cracks considered are as long as several kilometers. This discipline is referred to as Crustal Rock Fracture Mechanics. The fracture phenomenon of a minute part of engineering structures is generally difficult to evaluate using the bulk material. The first example is a lifetime prediction of an optical glass fiber. The treated optical glass fiber has a diameter of 125 mm. A stable crack may extend perpendicular to the fiber axis when it is sufficiently small and extend in an unstable manner when it grows to its critical size. The crack usually is microns to several tens microns in size. Engineering structures of today generally include the combination of a mechanical and electronic and/ or microelectronic components. Fracture mechanics methods can be used to predict the fatigue life in structures. Fatigue failure prediction has two different stages. The first stage is prediction of crack nucleation in the sense of continuum mechanics. Then at a material point and the second stage is estimation of the crack growth using the geometrical variables and energy release rates. Extended finite element method (XFEM) can be accompanied with methods describing the crack growth rate as a function of number of cycles in order to predict the fatigue crack growth in structures. Rubber-based structures are subjected to high cyclic loading conditions in comparison with other load-carrying
P a g e | 4 structures. Hence, it is worthwhile to investigate the mechanical properties analysis of rubber- based materials subjected to the fatigue loads. Linear Elastic Fracture Mechanics Linear elastic fracture mechanics (LEFM) was presented to solve the crack initiation and crack propagation in the elastic solids. This method has been widely used in several fields including soft matter domain and geology in order to predict the crack behavior. From the LEFM point of view, there are several crack propagation possibilities depending on loading conditions and materials. One of the most famous cases is the brittle fracture, by which several approaches have

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• Fall '16
• Dr Salim Zahir
• Fracture mechanics, crack tip, crack growth, fatigue crack growth, crack growth rate, fatigue crack

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