JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD

Course Objective

This course is primarily designed to develop the fundamental aspects of

mechanics of deformation and fracture of materials by destructive testing.

Course Outcome

At the end of the course, the student will be able to identify and analyze

the deformation mechanisms that occur in metals and alloys so that the metal forming operations can be easily understood.

UNIT - I

Plastic Deformation in Metals and Alloys: Critical resolved shear stress. Defects in crystalline materials Point defects and line defects. The concept of dislocation - Edge dislocation and screw dislocation. Interaction between dislocations, sessile dislocation, glissile dislocation, dislocation climb, Jogs, Forces on dislocations Energy of a dislocation. Frank Reed source, slip and twinning.

UNIT - II

Fracture: Elementary theories of fracture, Griffith’s theory of brittle fracture, Ductile Fracture, Notch sensitivity. Hardness Test: Methods of hardness testing Brinells, Vickers, Rockwell, Rockwell superficial, Shore and Poldi methods, Microhardness test, relationship between hardness and other mechanical properties.

UNIT - III

Tension Test: Mechanism of elastic action, linear elastic properties. Engineering stress and Engineering strain, True stress-strain curve. Tension Test and tensile properties, conditions for necking, effect of temperature and strain rate on tensile properties. Compression Test: Elastic and in elastic action in compression, compression Test. Impact Test: Notched bar impact test and its significance, Charpy and Izod Tests, significance of transition temperature curve, Metallurgical factors affecting the transition temperature, temper embrittlement. DBTT curve and its importance. Fracture toughness testing - COD and CTOD tests.

UNIT - IV

Fatigue Test: Introduction, Stress cycles, S-N Curve, Effect of mean stress, Mechanism of fatigue failure, effect of stress concentration, size, surface condition and environments on fatigue. Effect of metallurgical variables on fatigue. Low cycle fatigue - High cycle fatigue.

UNIT - V

Creep and Stress Rupture: Introduction, The creep curve, Stress-rupture test, Structural changes during creep, Mechanism of creep deformation, theories of creep. Fracture at elevated temperature, Effect of Metallurgical variables on creep.

TEXT BOOKS:

• 1. Mechanical Metallurgy - GE Dieter
• 2. Mechanical Behavior of Material - A. H. Courtney

REFERENCES:

• 1. Engineering Materials Science - CW Richards
• 2. Mechanical Metallurgy - White & Le May.