Course Contents:

Fracture: Energy release rate, Linear elastic fracture mechanics: crack tip stress and deformation fields, Stress intensity factor (SIF) for plane and penny shaped crack, First order estimate of plastic zone using Irwin’s and Dugdale approach; Elasto-plastic fracture: HRR fields, J-integral and CTOD, Mixed mode fracture; Evaluation of SIF from experimental measurements, numerical simulations. Determination of fracture toughness under small scale yielding and elasto-plastic situations. Fatigue fracture: Crack nucleation and growth, Fatigue life prediction, Advanced topics.

Lecture wise Breakup

I. Introduction (4):

• Background; Griffith theory of fracture, energy release rate (ERR), conditions for stable and unstable crack growth, crack arrest

II. Linear elastic fracture mechanics (14):

• Williams analysis of stress field at the tip of a crack
• Solution of stress and displacement field for plane cracks using complex methods in plane elasticity (Westergaards or Kolosov-Muskhelishvili approach)
• Stress intensity factor (SIF) for plane and penny shaped cracks
• Equivalence of SIF and ERR, fracture toughness

III. Elasto-plastic fracture mechanics (10):

• First order estimate of crack tip plastic zone using Irwin’s and Dugdle’s approach
• Plastic zone for plane stress and plane strain situation and effect on fracture toughness
• Review of small strain plasticity
• Crack tip fields in an elasto-plastic material (Discussion on HRR fields)
• J-integral as a fracture parameter and crack tip opening displacement

IV. Mixed mode fracture (3):

• Prediction of crack path and critical condition for crack extension under mixed mode loading using Maximum tensile stress, Minimum strain energy density and Maximum energy release rate criteria

V. Experimental measurement of SIF and fracture toughness (3):

• SIF measurement using strain gages, optical techniques
• Evaluation of fracture toughness

VI. Fatigue crack growth (4):

• Mechanism of crack nucleation and growth under cyclic loading
• Determination of life of a cracked solid using Paris-Erdogan law and its variants

VII. Advanced topics (one from the following) (4):

• Computational fracture mechanics, Dynamic fracture, Bi-material fracture

References:

1. Fracture Mechanics, C.T. Sun and Z.H. Jin
2. Fracture Mechanics, T.L. Anderson
3. Fracture Mechanics, An Introduction, E.E. Gdoutos