18MTY – EN - 1.Materials

Ing. Jaroslav Valach, Ph.D.

valach@fd.cvut.cz

Schedule of lectures# Title MTY #

1 Mechanical properties of materials, structure of materials 1, 2

2 Crystal structure, lattice defects 3

3 Solid solutions, thermodynamics and binary diagrams 4

4 Steel and cast iron, quenching, tempering, annealing 5

5 Fe-C diagram, special steels and alloys. Non-ferrous metals 6, 7

6 Polymers, structure, processing, mechanical properties 8, 9

7 Composites - properties, advantages, synergies, fibers and matrix 11, 12

8 Degradation of materials, nondestructive testing 13

There is only 7 lectures left before Xmas holiday, we need at least one more!Proposal some odd-week Wednesday from 15:00 to 16:30 at F008.Odd - week Wednesdays till end of this year:Nov. 7th, Nov. 21st, Dec. 5th, Dec. 19th

Informations & presentations

• http://mech.fd.cvut.cz/education/bachelor/18mty-en

• (do not exist yet, will be on-line next week)

• Syllabus

• Presentations

• …

W. Callister: Materials science and engineering. An introduction

libgen.io

Properties of materials

Bonds Structure Defects Properties

Basic schematics of Materials Science and Engineering

Structure

PropertiesProcessing

Investigation of material properties

Input OBJECT effect

A possible response of material to loading

A A2*A

𝜀 =Δl

𝑙

Ϭ=𝐺

𝐴

List of fundamental notions and terms• Relative elongation, true deformation, transversal

deformation, Poisson ratio

• Deformation elastic (reversible) a plastic (permanent)

• Force and stress, tension and compression, shear and torsion

• Elasticity, Hooke law

• Young’s modul of elasticity, stiffness vs. compliance, rigid body

• Strength, ultimate strength, yield point

• Hardness vs. softness

• Toughness vs. fragility

Why we need material tests?

Study of material properties

Material tests

Design and strength calculation

(Material parameters)

Production quality control

(improving material’s quality, analysis of failures)

Universal testing machine

Tensile testductilefragile

𝑙0 = 𝑆0 ∗ 5.6

5.6 ≈ 5 ∗4

𝜋

forc

e

elongation elongation

forc

e

forc

e

forc

e

Phase 1

Phase 2

Phase 3Phase 4

Tensile test – cont.

A…elongation (= eu)

E, Rm, A

Stress – strain curve Compression

Tensionsteel

Cast iron

Metallic foam

High strength steel

Mild steel

Alluminiumalloy

Copper alloyMagnesium alloy

Cast iron

Stress [MPa]

Strain [1]

Hardness

2.5 gold

5 toothenamel

4.5-5 nail

Engineeringmaterials

Hardness of Au alloys

Hardness tests

Vickers

Rm3*HB

𝐻𝐵 =𝐹

𝜋∙𝐷

2(𝐷− 𝐷2−𝑑2

, F[kp], d[mm2]

Rockwell hardness test. Indentation by cone

Brinnel hardness test. Indentation by sphere

Impact tests

Charpy hammer

Notches U a V Potential energydifference

Atoms and atomic bonds

Materials are hierarchical structures

Shape

Polycrystalline structure

Lattice defects

Atomic bonds

Bonds Structure Defects Properties

Size of atom

=: :

Mp=2000 * Me

Bonding potential

Tm~E0

Young’s modulus

1

E

Cohesive force

r

F F

Equilibrium distance

Electronegativity of elements

Interatomic bonds - ionic

Interatomic bonds - covalent

Interatomic bonds – metallic

Implication of bond type to toughness/fragility of materials

Molecular bonds – hydrogen bonds

Molecular bonds – van der Waals forces

graphite

Material classes - summaryProperty Ceramics Metals Polymers

Hardness High Medium-high Low

Stiffness (Young’smodulus of elasticity)

high Medium-high low

Strength High, but brittle High and ductile Low strength, high ductility

Thermal expansion Low High High

Ductility Low High High

Wear resistance High Low-medium Low

Metals Ceramics and glass Polymers

Good conductors ofelectricity and heat

Electrical and thermal insulators(at the same timesemiconductors and superconductors)

Electrical and thermal insulators

Strong and ductile Hard, fragile, non-ductile Soft, low strength, highly deformable

Nontransparent Some transparent Some transparent

Prone to corrosion damage Corrosion resistant, resistant against aggresive chemical compounds

Corrosion resistant

High density Medium density Low density

Iron, steel, Cu, Al, brass SiC, WC, Al2O3, NaCl,… Polymers, rubbers, …

Material classes - summary