BASIC MANUFACTURING

PROCESS
MANUFACTURING

Manufacturing is the application of physical and chemical

processes to alter the geometry, properties, and appearance of
a starting material to make parts or products for a given
application.
PURPOSE OF MANUFACTURING

The key point is manufacturing adds value by changing its

shape or properties, or by combining with other materials that
have been similarly altered.
Manufacturing is the transformation of materials into items of
greater value by one or more processing and/or assembly
operations.
MATERIALS IN MANUFACTURING

Most engineering materials

can be classified into one of
four basic categories:
IN THIS SESSION WE LEARN ABOUT

States of matter

Bonding

Crystal Defects
STATES OF MATTER
DIAMOND
Hardest metal
Transparent
Electrically insulating
Highest thermal conduction of any
material known

GRAPHITE
One of the softest material
Opaque
Electrically conductive in basal plane
Thermal conductive in basal plane
ELEMENT GROUPINGS

The elements can be grouped into families and relationships

established between and within the families by means of the Periodic
Table
Metals occupy the left and center portions of the table
Nonmetals are on right
Between them is a transition zone containing metalloids or
semi-metals
Periodic Table
ATOMIC STRUCTURE AND THE ELEMENTS

The basic structural unit of matter is the atom

Each atom is composed of a positively charged nucleus,
surrounded by a sufficient number of negatively charged
electrons so the charges are balanced
More than 100 elements, and they are the chemical building
blocks of all matter
SIMPLE MODEL OF ATOMIC STRUCTURE FOR
SEVERAL ATOMS

(a) Hydrogen, (b) helium, (c) fluorine, (d) neon, and (e) sodium
BONDING BETWEEN ATOMS AND
MOLECULES

Atoms are held together in molecules by various types of bonds

Primary bonds - generally associated with formation of

molecules
Secondary bonds - generally associated with attraction
between molecules

Primary bonds are much stronger than secondary bonds

PRIMARY BONDS

Characterized by strong atom-to-atom attractions that involve

exchange of valence electrons
Types:
Ionic
Covalent
Metallic
IONIC BONDING

Atoms of one element give

up their outer electron(s),
which are in turn attracted
to atoms of some other
element to increase
electron count in the
outermost shell to eight
COVALENT BONDING

Electrons are shared (as

opposed to transferred)
between atoms in their
outermost shells to
achieve a stable set of
eight
TWO EXAMPLES OF COVALENT BONDING
 METALLIC BONDING
Atoms of the metallic element generally posses too
few electrons in their outermost orbit to complete
the outer shell for all atoms.
Instead of sharing on an atom to atom basic,
metallic bonding involve sharing of outer shell
electrons by all atoms to form a general electron
cloud that permeates the entire block.
This cloud provide the attractive forces to hold
atoms together and forms a strong rigid structure.
SECONDARY BONDS

Whereas primary bonds involve atom-to-atom attractive forces,

secondary bonds involve attraction forces between molecules
No transfer or sharing of electrons
Bonds are weaker than primary bonds
Three forms:
1. Dipole forces
2. London forces
3. Hydrogen bonding
DIPOLE FORCES
Arise in a molecule comprised of two atoms with
equal and opposite electrical charges.
Each molecule therefore forms a dipole that
attracts other molecules
LONDON FORCES
Attractive force between non-polar molecules,
i.e., atoms in molecule do not form dipoles
However, due to rapid motion of electrons in
orbit, temporary dipoles form when more
electrons are on one side
WHAT IS NON POLAR MOLECULES?
A non-polar molecule is one that the electrons
are distributed more symmetrically and thus
does not have an abundance of charges at the
opposite sides. The charges all cancel out each
other.
 HYDROGEN BONDING
Occurs in molecules containing hydrogen atoms
covalently bonded to another atom (e.g., H2O)

Since electrons to complete shell of hydrogen atom

are aligned on one side of nucleus, opposite side has
a net positive charge that attracts electrons in other
molecules

A hydrogen bond is the electrostatic

attraction between polar groups that
occurs when a hydrogen (H) atom
bound to a highly electronegative
atom such as nitrogen (N), oxygen (O)
or fluorine (F) experiences attraction to
some other nearby highly
electronegative atom.
MACROSCOPIC STRUCTURES OF MATTER
Atoms and molecules are the building blocks of
a more macroscopic structure of matter
When materials solidify from the molten state,
they tend to close ranks and pack tightly,
arranging themselves into one of two
structures:
Crystalline
Non crystalline
CRYSTALLINE STRUCTURE

Structure in which atoms are located at regular and recurring

positions in three dimensions
Unit cell - basic geometric grouping of atoms that is repeated
The pattern may be replicated millions of times within a given
crystal
Characteristic structure of virtually all metals, as well as many
ceramics and some polymers
THREE CRYSTAL STRUCTURES IN METALS

(a) Body-centered cubic, (b) face-centered cubic, and (c) hexagonal

close-packed
CRYSTAL STRUCTURES FOR COMMON
METALS

Room temperature crystal structures for some of the common metals:

Body-centered cubic (BCC)
Chromium, Iron, Molybdenum, Tungsten
Face-centered cubic (FCC)
Aluminum, Copper, Gold, Lead, Silver, Nickel
Hexagonal close-packed (HCP)
Magnesium, Titanium, Zinc
IMPERFECTIONS (DEFECTS) IN CRYSTALS
Imperfections often arise due to inability of solidifying
material to continue replication of unit cell, e.g., grain
boundaries in metals
Imperfections can also be introduced purposely; e.g.,
addition of alloying ingredient in metal
Types of defects: (1) point defects, (2) line defects, (3)
surface defects
POINT DEFECTS
Imperfections in crystal structure involving either a
single atom or a small number of atoms

Point defects: (a) vacancy, (b) ion-pair vacancy, (c)

interstitialcy, (d) displaced ion (Frenkel Defect).
POINT DEFECTS

Vacancy: Involving a missing atom within the lattice structure.

Ion pair vacancy: Which involves a missing pair of ions opposite
charge in compound that has an overall charge balance.
Interstitialcy: A lattice distortion produced by the presence of an
extra atom in the structure.
Frenkel defect : Occurs when an ion becomes removed from a
regular structure and inserted into in interstitial position not
normally occupied by such an iron.
LINE DEFECTS

Connected group of point defects that forms a line in the lattice

structure
Most important line defect is a dislocation, which can take two forms:
Edge dislocation
Screw dislocation
EDGE DISLOCATION
Edge dislocation is the edge of an extra plane of
atoms that exists in the lattice
SCREW DISLOCATION

Spiral within the

lattice structure
wrapped around
an imperfection
line, like a screw is
wrapped around
its axis
SURFACE DEFECTS
Surface defects are the boundaries, or planes, that
separate a material into regions, each region having
the same crystal structure but different orientations
Examples:
External: the surface of a crystalline object is an
interruption in the lattice structure
Internal: grain boundaries are internal surface
interruptions
ELASTIC STRAIN
When a crystal experiences a gradually increasing
stress, it first deforms elastically

Deformation of a crystal structure: (a) original lattice: (b)

elastic deformation, no permanent change in positions of
atoms
PLASTIC STRAIN
If the stress is higher
than forces holding
atoms in their lattice
positions, then a
permanent shape change
occurs

Plastic deformation (slip), in which atoms in the

crystal lattice structure are forced to move to new
"homes
CRYSTALLINE VERSUS NONCRYSTALLINE
STRUCTURES OF MATERIALS
Difference in structure between: (a) crystalline and (b) noncrystalline
materials
Crystal structure is regular, repeating; noncrystalline structure is less
tightly packed and random