AO4071 Fatigue and Fracture Mechanics Syllabus:
AO4071 Fatigue and Fracture Mechanics Syllabus – Anna University PG Syllabus Regulation 2021
COURSE OBJECTIVES:
This course will make students
1. To learn the fundamentals aspects of fatigue & fracture mechanics.
2. To gain knowledge on the statistical aspects of fatigue behaviour of materials.
3. To get insights into the physical aspects of fatigue.
4. To evaluate the strength of the cracked bodies.
5. To provide knowledge on fatigue design and testing of aerospace structures.
UNIT I BASIC CONCEPTS & OVERVIEW
Historical Perspective – Case Studies – Review of Material Behaviour – Linear & Non-Linear Response – Temperature and Strain Rate Effect – Strain Hardening – Different Mechanisms of Failure – Typical Defects & Elements of Dislocation Theories – Atomic View of Fracture – Fractographic Examination of Failure Surfaces of Different Materials – Overview of Design Approach – Safe Life Design.
UNIT II FATIGUE OF STRUCTURES
S.N. curves – Endurance limit – Effect of mean stress – Goodman, Gerber and Soderberg relations and diagrams – Notches and stress concentrations – Stress concentration factors – Notched S-N curves – Low cycle and high cycle fatigue – Coffin-Manson’s relation – Transition life – Cyclic Strain hardening and softening – Load History Analysis – Cycle counting techniques – Cumulative damage theory
UNIT III PHYSICAL ASPECTS OF FATIGUE
Fracture mechanism in metals – Phase in fatigue life – Crack source – Cleavage initiation – Crack growth – Ductile-brittle transition – Final fracture – Dislocations – Fatigue fracture surface of inter and intra-granular fracture – Environmental effects – Terminology and classification – Corrosion principles – Stress corrosion cracking – Hydrogen embrittlement – Influencing parameters on crack behaviour
UNIT IV LINEAR ELASTIC FRACTURE MECHANICS
Stress analysis and strength of a cracked body – Stress concentration – potential energy and surface energy – Energy release rate – Griffith’s theory – Irwin extension of Griffith’s theory to ductile materials – Plastic zone shape – Effect of thickness on fracture toughness – Stress intensity factors for typical geometries – Instability of the R-curve – K-controlled fracture – Plane strain fracture toughness – Mixed mode – Interaction of cracks – Limitations of the linear elastic fracture theory
UNIT V FRACTURE TOUGHNESS TESTING
General considerations for metallic specimens – Specimen configuration – Stress intensity factors – Pre-cracking – Grooving – ASTM E-399 and similar standards – K-R curve – J-testing on metals – Determination of crack parameters – CTOD testing – Testing of metals in the ductile brittle transition region – Quantitative toughness tests – Charpy & Izod tests –- Mathematical modelling concepts
TOTAL: 45 PERIODS
COURSE OUTCOMES:
Upon completion of this course, students will be able
CO1: To identify and describe the basic fracture and fatigue mechanisms and apply that knowledge to failure analysis.
CO2: To correctly apply linear elastic fracture to predict material failure.
CO3: To predict lifetimes for fatigue and environmentally assisted cracking.
CO4: To demonstrate fatigue design and testing of structures.
CO5: To realise the importance of composite materials in Aerospace structures.
REFERENCES:
1. Barrois, W &Ripley,L, “Fatigue of Aircraft Structures”, Pergamon Press, Oxford, 1983.
2. Brock,D, “Elementary Engineering Fracture Mechanics”, Noordhoff International Publishing Co., London, 1994.
3. Knott,JF, “Fundamentals of Fracture Mechanics”, Butterworth & Co. Ltd., London, 1983.
4. Sih,CG, “Mechanics of Fracture, Vol.1”, Sijthoff and Noordhoff International Publishing Co., Netherland, 1989.