Ben-Gurion University of the Negev
Materials Engineering
Name of the module: Mechanical properties of materials 1
Number of module: 365-1-3111
BGU Credits: 4
Course Description
ECTS credits: 6
The course is a comprehensive but introductory course on the mechanical behavior
Academic year: 2013- 2014
of metals and ceramics, from the basic definitions to advanced topics. It is the only
Semester: Fall
course on the subject for the route of electronic materials.
Hours of instruction: 3 lecture hours +
The first part of the course is devoted to study the elastic behavior of materials and
1exercise class hour per week
establishes the basis to the rest of the course. Ws start with definition of the stress
Location of instruction: room 203
and strain tensors, elastic constants, Hook's law and elastic energy. Then important
bulding 28
states of stress and the distribution of stress are studied. They include: uniform
Language of instruction: Hebrew
normal stresses, thermal stress, shear stress, bending, torsion, introduction to point
Cycle: First cycle
force loading, Saint Venant principle, stress concentration and residual stresses.
Position: a mandatory module for 3
rd
The rules of transformation of stress and strain, leading to the identification of the
year undergraduate students in the
principle stresses and strains and to the definition of resolved shear stress are learnt
Department of Materials Engineering
in 2D (Mohr circle). Experimental methods for strain measurements (strain gages
to be taken on Fall semester
and photoelasticity) are mentioned. Mechanical testing and applications for the
Field
of
Education:
Materials
design of machine components (bolts, gears, springs bearings and buckling) are
Engineering
learnt as home duties.
Responsible department: Materials
The second part of the course is a summary of the theory of dislocations. The main
Engineering
aim is to establish an intuitive picture of dislocation theory, emphasizing its ability
General prerequisites: students should
to explain the plastic behavior of metals and ceramics and its power to predict the
complete modules Materials 1 and 2
effects of microstructure and processing on the mechanical properties.
Grading scale: the grading scale
Strengthening mechanisms of metals are discussed as an important application of
would be determined on a scale of 0 –
the dislocation theory and as a basis for the classification of metallic alloys.
100 (0 would indicate failure and 100
The third part of the course considers two fracture phenomena: catastrophic
complete success 0 to 100), passing
fracture and fatigue. Elements of fractography are learnt along the course and basic
grade is 56.
notions of fracture mechanics are introduced through a discussion of an energetic
criterion for crack propagation. Fracture toughness is defined as an advanced
Lecturer: Prof. Roni Shneck
characteristic of materials and is related to the microstructure and ductility.
Contact details: room 9, building 59
Applications of fracture mechanics in modern design are illustrated. Fatigue is
Office phone: 08-6472493
introduces as the main failure mechanism of engineering components and the main
Email: roni@bgu.ac.il
drawback of plastic deformation. The mechanisms of crack initiation and
Office hours: Tuesday, from 11 to
propagation, S-N curve and mechanical factors affecting fatigue life are learnt.
13AM.
Mechanical and metallurgical approaches to prevent fatigue and fracture are
discussed. The course summarized by discussing of the claim that defects
Module evaluation: at the end of the
(dislocations and microcracks) are determining the strength of (ductile and of
semester the students will evaluate the
brittle) materials.
module, in order to draw conclusions,
Learning outcomes of the course
and for the university's internal needs.
1.
Acquaintance with basic concepts of stress, strain, stress distribution,
elastic constants, elastic energy, stress concentration, residual stresses,
stress intensity factor and fracture toughness
2.
An ability to perform basic analysis of the stress state in engineering
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Ben-Gurion University of the Negev
Materials Engineering
Confirmation:
the
syllabus
components.
was
confirmed by the faculty academic
3.
normal stresses, thermal stress, shear stress, bending and torsion.
advisory committee to be valid on
2013-2014.
Ability of elementary stress calculations in basic states of stress: uniform
4.
Knowledge of the transformation rule of stress and strain and
determination of principle stresses
Last update:
5.
Understand basic dislocation mechanisms and the relation between
dislocation behavior and material strength, plasticity, processing and
fracture behavior. Apply this knowledge for metal selection and
processing.
6.
Elementary knowledge on fracture mechanics, its applications to predict,
analyze and prevent fracture of engineering components
7.
Elementary knowledge on the mechanism fatigue, its engineering
significance and approaches to fatigue prevention.
Aims
To provide an overview of the three regions in the mechanical behavior of
materials, from elastic states of stress, plastic behavior and fracture. Derive the
implications on the strength of metals and brittle materials.
Objectives of the module
The objectives of the course are to learn, understand and earn the ability to apply in
engineering design and materials selection the mechanical behavior of metals and
ceramics. These aims include elementary stress analysis and calculations,
familiarity with dislocation behavior and strengthening mechanisms of metals,
criterion for fast crack propagationin brittle and ductile materials, the phenomenon
of fatigue and its prevention.
Attendance regulation: attendance and participation in class is mandatory.
Teaching arrangement and method of instruction: The module consists of lectures
and exercises.
Assessment:
1.
Exam
70% (or 85% for the student who has lower grade in the quiz)
2.
Quiz
15% (not mandatory)
3.
Homeworks 15%
100%
Work and assignments: Student will conduct 6 home works related to the exercises
in the class.
Quiz: midterm, open questions.
Exam: at the end of semester, open questions.
Time required for individual work: in addition to attendance in class, the students
are expected to do their assignment and individual work: at least two hours per
week, 10 hours before the quiz and 24 hours before exam.
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Ben-Gurion University of the Negev
Module Content / schedule and outlines
Materials Engineering
Introduction to mechanical response of materials in the elastic regime 2h
(a)
Elasticity and mechanical design
Definition of stresses, strains and elastic moduli; Hook's law
2h
Simple states of compression/tension and shear
2h
External forces, diagrams of internal forces and moments
2h
Understanding of bending state of stress, calculation of normal and shear stress distribution. Distinction between pure,
transverse and eccentric bending
7h
Calculation of deflection and solution of statically indeterminate problems 1h Plastic bending and residual stresses 1h
Stress concentration and failure of engineering components. Contact stress and Saint Venant principle
1h
Calculation of stress and deflection in torsion of round rods
2h
Machine design of engineering components (screws, gears, springs and bearings), buckling (self learning (reading
duty).
Experimental
measurement of strain
(b)
1h
Dislocation theory
Geometry of slip planes, Burgers vector, screw, edge and mixed dislocations
2h
Mechanisms of motion of dislocations: glide, climb and cross slip. Interaction between dislocations
1h
Dislocation loops and multiplication of dislocations. Relation of slip lines to dislocation sources
2h
Line tension of a dislocation. The critical stress to activate a source and to overcome an obstacle. The phenomenon
of yielding.
1h
Partial dislocations, implication on ease of plastic deformation. Twinning – an alternative plastic mechanism 2h
Dislocations in grain boundaries. Patterning of dislocations during high plastic strain. Annealing of deformed
metals
1h
Experimental evidence of dislocations (presentation of photographs and movies).
Summary: The anisotropic, inhomogeneous and irreversible character of plastic deformation.
Strengthening mechanisms in metals: strain hardening, grain size, precipitation hardening, second phase and
martensitic transformation. Classification of commercial metallic alloys
3h
Plastic deformation in ceramic materials
1h
(c) Fracture
Elements of fractography and failure analysis
2h
Inglish and Irwin stress approach to fracture mechanics. Griffith's energy criterion to fast crack propagation
1h
The dual notions of strain energy release rate and stress intensity factor; materials resistance to crack propagation and
fracture toughness
1h
Test methods of fracture toughness, comparison to tension test. Metallurgical approaches to increase the fracture
toughness of metals and ceramics
1h
The central dilemma of materials: the compromise between ductility or fracture toughness and strength.
Engineering aspects of the fatigue of metals: S-N and Goodman diagrams, roles of stress concentration, surface quality;
residual stress, material strength and size (reading duty).
Fatigue crack initiation due to irreversible plastic deformation. Mechanism of fatigue crack propagation.
1.5h
Metallurgical approaches to improve fatigue resistance. Modern engineering practice to prevent fatigue and fracture.
1.5h
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Ben-Gurion University of the Negev
Materials Engineering
Exercises:
Calculation of stress and strain in simple states of stress
Application of free body and determination of external forces
Internal forces and moment diagrams
Stresses in bending
Deflection in bending and singularity functions
Stress and deflection in torsion
Transformation of stress and strain in 2D
Demonstration of stress fields and formation of dislocation walls by computer
Basic applications of fracture mechanics
Required reading:
1 F. P. Beer and E.R. Johnston, Mechanics of Materials, McGraw Hill, 1985.
(TA405 B39 1985). or
2. I. Alperovitz, Theory of strength and elasticity (in Hebrew) Ort, 1987 (TA 405.A46 1987)
3 G.E. Dieter, Mechanical Metallurgy, McGraw Hill, 1988 (TA405 D53 1988).
4. Lecture notes: (a) Introduction to mechanical properties. (b) Who is afraid of dislocations ?
(c) Strengthening mechanisms (c) Fracture mechanics (d) Fatigue.
5 Short guides: (a) Screws and Bolts (b) Gears (c) Buckling (d) Springs (e) Bearings
Additional literature:
1
E.P. Popov, Mechanics of Materials, Prentice Hall International, 1978.
(TA405 P68 1978)
2.
R. W. Hertzberg, Deformation and Fracture Mechanics of Engineering Materials, Wiley, 1996.
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