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ENGINEERING TRIPOS PART IIA - 2012/2013

Module 3C9 - Fracture Mechanics of Materials and Structures

Leader:	Prof V S Deshpande
Lab Leader:	Dr G McShane
Timing:	Lent
Prerequisites:	Module 3C7 assumed
Structure:	16L + coursework

AIMS

The main concepts of fracture mechanics will be described in terms of stress analysis, failure mechanisms and design methods. Both linear elastic fracture mechanics (LEFM) and ductile fracture will be discussed. The methods will be applied to a wide range of enigineering application from thin film design in electronics to fatigue life assessment of nuclear pressure vessels and damage mechanics of concrete.

LECTURE SYLLABUS

Introduction: lessons learned from the history of engineering disasters

Elastic stress analysis (7L) Prof Deshpande
- Williams solution using the Airy stress function
- LEFM and interfacial fracture
- Energy appraoch to fracture
- Practical K-calibrations and use of superposition
- Fracture of thin films and of weldments
- Prediction of fracture toughness
Small Scale Yielding (2L) Prof Deshpande
- plastic zone size and crack tip opening displacement
- R-curves: the tear resistance of metals, composites and biological tissues
Large Scale Yielding (3L) Prof Deshpande
- Dugdale model for a large plastic zone from a crack tip, and transition to bulk plasticity
- Application to adhesive joints and crazing of polymers, and to pressure vessels
- Void nucleation and growth in a plastic field
Fatigue crack growth (4L) Prof Deshpande
- Threshold, Paris law, variable amplitude loading for aircraft
- S-N curves for fatigue crack initiation and growth

Possible additional topics: stress corrosion cracking, creep crack growth?

OBJECTIVES

To explain the physical processes underlying fracture from a single dominant crack and from a distribution of cracks. Quantitative design methods are physically based and used to predict fatigue life, creep life and residual strength of damaged structures from thin films to aircraft structures.

COURSEWORK

Measurement of toughness of polymers as used in underground pipelines, and to assess their safety in service.

REFERENCES

Fracture Mechanics: fundamentals and applications, T.L.Anderson,Taylor Francis,2005.

Last updated: June 2012

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