1. THE NATURE OF MATERIALS
Atomic Structure and the Elements
Bonding between Atoms and Molecules
Crystalline Structures
Noncrystalline (Amorphous) Structures
Engineering Materials
John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing

2. Periodic Table of Elements
Transition Zone contains metalloids or semi‑metals
John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing

3. Primary Bonds Ionic Bonding Metallic Bonding Covalent Bonding
John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing

4. Two Examples of Covalent Bonding
John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing

5. Body-Centred Cubic (BCC) Crystal Structure
Unit cell
Atoms indicated as point locations in 3d axis system
Unit cell model
Closely packed atoms sometimes called hard-ball model
Repeated pattern of the BCC structure
John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing

6. Three Crystal Structures in Metals
Body-centered cubic
Face-centered cubic
Hexagonal close-packed
Chromium
Iron
Molybdenum
Tungsten
Aluminum
Copper
Gold
Lead
Silver
Nickel
Magnesium
Titanium
Zinc

7. Point Defects in Crystal Structures
Displaced ion
Interstitialcy – lattice distortion produced by an extra atom in structure
John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing

8. Line Defects in Crystal Structures
Edge of an extra plane of atoms that exists in the lattice
Spiral within the lattice structure wrapped around an imperfection line
John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing

9. Deformation of Crystal Structures
Original Lattice
Elastic Deformation
Plastic Deformation
Elastic strain - no permanent change in positions of atoms
Plastic strain - atoms in the lattice are forced to move to new “homes”
John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing

10. Effect of Dislocations on Strain
John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing

11. Crystalline versus Noncrystalline
Crystalline structure
Noncrystalline structure
Volume changes for a pure metal (a crystalline structure)
Versus
Volumetric changes in glass (a noncrystalline structure)
John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing

12. MECHANICAL PROPERTIES OF MATERIALS
Stress‑Strain Relationships
Tensile - tend to stretch the material
Compressive - tend to squeeze it
Shear - tend to cause adjacent portions of material to slide against each other
John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing

13. Tensile Stress-Strain Relationship
Setup
Tensile Test
Typical Test Specimen
John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing

14. Tensile Test Sequence (1) beginning of test, no load
(2) uniform elongation and reduction of cross‑sectional area
(3) continued elongation, maximum load reached
(4) necking begins, load begins to decrease
(5) fracture
(6) final length measured with pieces put back together
John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing

15. Stress-Strain Relationship
s = engineering stress
F = applied force
Ao = original area of test specimen
e = engineering strain
L = length at any point during elongation
Lo = original gage length
John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing

16. Typical Engineering Stress-Strain Plot of Metal
Tensile Strength
Yield point S
Hooke's Law: s = E e
E = modulus of elasticity
John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing

17. Ductility Measure – Elongation EL
EL = elongation
Lf = specimen length at fracture
Lo = original specimen length
AR = area reduction
Af = area of cross section at point of fracture
Ao = original cross-sectional area
Strain hardening - means that the metal is becoming stronger as strain increases
John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing

18. In-class example
A tensile test uses a test specimen that has a gage length of 50 mm and an area = 200 mm2. During the test the specimen yields under a load of 98,000 N. The corresponding gage length = mm. This is the 0.2 percent yield point. The maximum load = 168,000 N is reached at a gage length = 64.2 mm.
Determine (a) yield strength, (b) modulus of elasticity, and (c) tensile strength.
Fracture occurs at a gage length of 67.3 mm.
Determine (d) the percent elongation. (e) If the specimen necked to an area = 92 mm2, determine the percent reduction in area.
John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing

19. ASSIGNMENT – STUDENT MUST SHOW SOLUTION TO PROFESSOR DURING LAB PERIOD
A test specimen in a tensile test has a gage length of 2.0 in and an area = 0.5 in2. During the test the specimen yields under a load of 32,000 lb. The corresponding gage length = in. This is the 0.2 percent yield point. The maximum load = 60,000 lb is reached at a gage length = 2.60 in.
Determine (a) yield strength, (b) modulus of elasticity, and (c) tensile strength.
Fracture occurs at a gage length of 2.92 in.
Determine (d) the percent elongation. (e) If the specimen necked to an area = 0.25 in2, determine the percent reduction in area.
John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing