Fracture Mechanics

Fracture Mechanics

1. Stress Concentration

2. Griffith Energy Balance

   • Rate of strain energy release with crack extension must be equal to (or greater than) the rate of energy absorption needed to overcome the resistance to crack growth.

3. Linear Elastic Fracture Mechanics

   • Deformation Modes:
     • Any crack deformation can be presented by an appropriate superposition.
     • Mode 1 - Opening
     • Mode 2 - Sliding/Shearing
     • Mode 3 - Tearing
   • Stress Intensity Factor, K:
     • Applications:
       • Static/Residual strength of a cracked structure.
       • Rate of crack growth under fatigue loading.
       • Rate of crack growth in a loaded structure in a corrosive environment.
     • Crack Tip Displacement & Stress Fields
       • Westergaard's Stress Function:
     • Non-dimensional Function of Geometry, Y:
       • Crack size and shape
       • Loading type
       • Geometrical configuration of the structure
   • Relationship between G & K
   • Residual Strength
     • Failure Criterion - Fracture Toughness:
       • Plane Strain
       • Plane Stress

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