4H300 - Deformation and failure of materials


Mechanical deformation and/or failure are both important design criteria for products and components, as well as for the processes by which they are manufactured. Analytical and numerical models are used in the design process to predict the performance and ensure the integrity of products during service. The course will be a combined mechanics/materials course that will introduce quantitative models that are based on the physical understanding of various materials processes. The course will be divided into two parts as follows:

  1. Deformation and fracture mechanisms for a range of engineering materials including metals, ceramics and polymers will be discussed. This includes:
    1. the underlying mechanisms of plastic flow in metals: Dislocations and dislocation hardening.
    2. failure mechanisms under uniaxial loading: ideal strength, cleavage mechanisms, ductile fracture, transgranular and intergranular creep failure, rupture, fracture mechanism maps, failure mechanisms in polymers.
    3. deformation and failure under multiaxial loading: elastic constitutive law, stress invariants, plastic deformation of isotropic materials, yield and failure criteria for metals, ceramics and polymers, fracture surfaces in multiaxial stress space, 3-D creep deformation
  2. The main concepts of fracture mechanics will be described in terms of stress analysis, failure mechanisms and design methods. The methods will be applied to a wide range of engineering application from thin film design in electronics to fatigue life assessment of nuclear pressure. The main ideas covered will include
    1. Fracture of thin films and of weldments
    2. Prediction of fracture toughness
    3. R-curves: the tear resistance of metals, composites and biological tissues
    4. Fatigue crack growth: Threshold, Paris law, variable amplitude loading for aircraft and S-N curves

Learning objectives

To develop an understanding of the main mechanisms by which materials deform and fail, and to quantitatively analyse these modes.