Materials Processing in Automotive Engineering - Chapter 2.pdf

Materials Processing in Automotive Engineering - Chapter 2

1. MATERIALS PROCESSING IN
AUTOMOTIVE ENGINEERING
DEPARTMENT OF METAL FORMING
SCHOOL OF MECHANICAL ENGINEERING
Lecturer: Assoc.Prof.Dr. Nguyen Dac Trung
E-mail: [email protected]

2. CONTENT OF COURSE
Chapter 1. Introduction and Overview of Materials Processing in Automotive Engineering
1.1 Introduction into Materials Processing
1.2 Overview of Parts in the car
1.3 Development of manufacturing technology
Chapter 2. Materials used in automotive engineering
2.1 Concept of materials
2.2 Metal and Alloy
2.3 Polymers and composite materials
2.4 Material Properties
2.5 Influence factors on material properties
Chapter 3. Materials Processing
3.1 Casting Process
3.2 Metal Forming
3.3 Machining
3.4 Welding and Joining
3.5 Pressing
3.6 Injection molding
Chapter 4. Equipments for Material Processing
4.1 Equipments for metal processing
4.2 Equipments for polymers and composite materials
4.3 Selection equipments and auxiliary devices
Chapter 5. Manufacturing and Support Systems
5.1 Automation Technologies for Manufacturing Systems
5.2 Integrated Manufacturing Systems
5.3 Process Planning and Production Control

3. Chapter 2. Materials used in automotive engineering
2.1 Concept of materials
Material is anything made of matter,
constituted of one or more substances.
Metal, ceramic, polymer, wood, cement,
hydrogen, air, water… and any other
matter are all examples of materials.
Materials - things needed for doing
or making something

4. Chapter 2. Materials used in automotive engineering
2.1 Concept of materials
CLASSIFICATION OF MATERIALS
Solid materials have been conveniently grouped into three basic classifications:
metals, ceramics, and polymers. This scheme is based primarily on chemical
makeup and atomic structure, and most materials fall into one distinct grouping or
another, although there are some intermediates.
In addition, there are the composites, combinations of two or more of the above
three basic material classes.
Another classification is advanced materials used in high-technology applications:
semiconductors, biomaterials, smart materials, and nanoengineered materials.

5. Chapter 2. Materials used in automotive engineering
2.1 Concept of materials
Most important criteria of materials used in automobile
manufacturing:
➢Light weight, this criterion is the most important one for an
automotive company, in the context of the high emphasis on
greenhouse gas reductions, reduction of emissions and
improving fuel efficiency.
➢Economic effectiveness, having in view that one of the most
important consumer driven factors in automotive industry is
the cost, that determines whether any new material has an
opportunity to be selected for a vehicle component;
➢Safety, which criterion have in view the ability to absorb
impact energy through controlled failure modes and
mechanisms and be survivable for the passengers;
➢Recyclability of their products and life cycle considerations.

6. Polymers include the familiar plastic and rubber materials. Many of them are
organic compounds that are chemically based on carbon, hydrogen, and other
nonmetallic elements (viz. O, N, and Si).
polyethylene (PE), nylon, poly(vinyl chloride) (PVC), polycarbonate (PC),
polystyrene (PS), and silicone rubber.
Carbon fiber reinforced polymer – CFRP
Glass fiber reinforced polymer – GFRP
Chapter 2. Materials used in automotive engineering
2.1 Concept of materials

7. Chapter 2. Materials used in automotive engineering
2.1 Concept of materials

8. Chapter 2. Materials used in automotive engineering
2.1 Concept of materials

9. Chapter 2. Materials used in automotive engineering
2.1 Concept of materials

10. 2.2 Metal and Alloy
Chapter 2. Materials used in automotive engineering
Metals have crystalline structures in the solid state, almost without exception. The unit cells of
these crystal structures are almost always BCC, FCC, or HCP.
The atoms of the metals are held together by metallic bonding, which means that
their valence electrons can move about with relative freedom (compared with the
other types of atomic and molecular bonding). These structures and bonding generally make
the metals strong and hard. Many of the metals are quite ductile (capable of being deformed,
which is useful in manufacturing), especially the FCC metals. Other general properties of
metals related to structure and bonding include high electrical and thermal conductivity,
opaqueness (impervious to light rays), and reflectivity (capacity to reflect light rays).
Although some metals are important as pure elements (e.g., gold, silver, copper), most
engineering applications require the improved properties obtained by alloying.
Through alloying, it is possible to enhance strength, hardness, and other properties
compared with pure metals. This section defines and classifies alloys; it then discusses
phase diagrams which indicate the phases of an alloy system as a function of composition and
temperature.
An alloy is a metal composed of two or more elements, at least one of which is metallic.

11. Structure of Crystalline Solid
Chapter 2. Materials used in automotive engineering
2.2 Metal and Alloy

12. Imperfection in Solids
2.2 Metal and Alloy
Chapter 2. Materials used in automotive engineering

13. 2.2 Metal and Alloy
Chapter 2. Materials used in automotive engineering
An alloy is a metal composed of two or more elements, at least one of which is metallic. The
two main categories of alloys are solid solutions and intermediate phases.
Solid Solutions A solid solution is an alloy in which one element is dissolved in another to
form a single-phase structure. Solid solutions come in two forms. The first is a
substitutional solid solution, in which atoms of the solvent element are replaced in its unit
cell by the dissolved element. The second type of solid solution is an interstitial solid
solution, in which atoms of the dissolving element fit into the vacant spaces between base
metal atoms in the lattice structure.
Two forms of solid solutions:
(a) substitutional solid solution, and
(b) interstitial solid solution

14. 2.2 Metal and Alloy
Chapter 2. Materials used in automotive engineering
Intermediate Phases There are usually limits to the solubility of one element in another.
When the amount of the dissolving element in the alloy exceeds the solid solubility limit of the
base metal, a second phase forms in the alloy. The term intermediate phase is used to
describe it because its chemical composition is intermediate between the two pure elements.
Its crystalline structure is also different from those of the pure metals. Depending on
composition, and recognizing that many alloys consist of more than two elements, these
intermediate phases can be of several types, including metallic compounds consisting of a
metal and nonmetal such as Fe3C; and intermetallic compounds—two metals that form a
compound, such as Mg2Pb. The composition of the alloy is often such that the intermediate
phase is mixed with the primary solid solution to form a two-phase structure, one phase
dispersed throughout the second. These two-phase alloys are important because they can be
formulated and heat-treated for significantly higher strength than solid solutions.

15. 2.2 Metal and Alloy
Chapter 2. Materials used in automotive engineering

16. 2.2 Metal and Alloy
Chapter 2. Materials used in automotive engineering
Low carbon steels contain less than 0.20% C and are by far the most widely used steels. Typical
applications are automobile sheet-metal parts, plate steel for fabrication, and railroad rails. These
steels are relatively easy to form, which accounts for their popularity where high strength is not
required. Steel castings usually fall into this carbon range, also.
Medium carbon steels range in carbon between 0.20% and 0.50% and are specified for
applications requiring higher strength than the low-C steels. Applications include machinery
components and engine parts such as crankshafts and connecting rods.
High carbon steels contain carbon in amounts greater than 0.50%. They are specified for still
higher strength applications and where stiffness and hardness are needed. Springs, cutting tools and
blades, and wear-resistant parts are examples.
Stainless steels are a group of highly alloyed steels designed to provide high corrosion resistance.
The principal alloying element in stainless steel is chromium, usually above 15%.
Austenitic stainless steels have a typical composition of around 18% Cr and 8% Ni and are the
most corrosion resistant of the three groups. Owing to this composition, they are sometimes identified
as 18-8 stainless. They are nonmagnetic and very ductile; but they show significant work hardening.
The nickel has the effect of enlarging the austenite region in the iron–carbon phase diagram, making
it stable at room temperature. Austenitic stainless steels are used to fabricate chemical and food
processing equipment, as well as machinery parts requiring high corrosion resistance.
Ferritic stainless steels have around 15% to 20% chromium, low carbon, and no nickel. This
provides a ferrite phase at room temperature. Ferritic stainless steels are magnetic and are less
ductile and corrosion resistant than the austenitics. Parts made of ferritic stainless range from kitchen
utensils to jet engine components.

17. 2.2 Metal and Alloy
Chapter 2. Materials used in automotive engineering
Martensitic stainless steels have a higher carbon content than ferritic stainlesses, thus
permitting them to be strengthened by heat treatment. They have as much as 18% Cr but
no Ni. They are strong, hard, and fatigue resistant, but not generally as corrosion resistant
as the other two groups. Typical products include cutlery and surgical instruments.
Precipitation hardening stainless steels, which have a typical composition of 17% Cr and
7% Ni, with additional small amounts of alloying elements such as aluminum, copper,
titanium, and molybdenum. Their distinguishing feature among stainlesses is that they can
be strengthened by precipitation hardening. Strength and corrosion resistance are
maintained at elevated temperatures, which suits these alloys to aerospace applications.
Duplex stainless steels possess a structure that is a mixture of austenite and ferrite in
roughly equal amounts. Their corrosion resistance is similar to the austenitic grades, and
they show improved resistance to stress-corrosion cracking. Applications include heat
exchangers, pumps, and wastewater treatment plants.

18. Cast iron is an iron alloy containing from 2.1% to
about 4% carbon and from 1%
to 3% silicon.
2.2 Metal and Alloy
Chapter 2. Materials used in automotive engineering
The nonferrous metals include metal elements and alloys not based on iron. The most
important engineering metals in the nonferrous group are aluminum, copper, magnesium,
nickel, titanium, and zinc, and their alloys.
Although the nonferrous metals as a group cannot match the strength of the steels, certain
nonferrous alloys have corrosion resistance and/or strength-to weight ratios that make them
competitive with steels in moderate-to-high stress applications.
Copper has one of the lowest electrical resistivity among metals and is widely used for
electrical wire. Aluminum is an excellent thermal conductor. Zinc has a relatively low melting
point, so zinc is widely used in die casting operations. The common nonferrous metals have
their own combination of properties that make them attractive in a variety of applications.

19. Chapter 2. Materials used in automotive engineering
2.3 Ceramics, Polymers and composite materials
Ceramic molecules are characterized by ionic or covalent bonding, or both. The general
properties of ceramics are high hardness, stiffness (even at elevated temperatures), brittleness
(no ductility), electric insulated, non-conductive, refractory (thermally resistant), and chemically
inert.
The importance of ceramics as engineering materials derives from their abundance (diversity)
in nature and their mechanical and physical properties, which are quite different from those of
metals.
Ceramic - an inorganic compound consisting of a metal (or semimetal) and one or more
nonmetals (silicon dioxide SiO2, aluminum oxide Al2O3)
Oxide ceramics (alumina, aluminum oxide) have properties: good hardness, low thermal
conductivity, electrical insulation, good corrosion resistance.
Carbide ceramics - silicon carbide (SiC), tungsten carbide (WC), titanium carbide (TiC),
tantalum carbide (TaC), and chromium carbide (Cr3C2). They are valued for their hardness and
wear resistance, chemical stability, oxidation resistance.
Nitride ceramics - silicon nitride (Si3N4), boron nitride (BN), titanium nitride (TiN) - hard, brittle,
electrical insulated, melt at high temperatures.

20. Chapter 2. Materials used in automotive engineering
2.3 Ceramics, Polymers and composite materials
Polymer is a compound consisting of long-chain molecules, each molecule made up of
repeating units connected together.
Most polymers are based on carbon and therefore considered organic chemicals.
Polymers can be separated into plastics and rubbers.
Thermoplastic polymers, also called thermoplastics (TP), are solid materials at
room temperature, but they become viscous liquids when heated to temperatures of
only a few hundred degrees. This characteristic allows them to be easily and
economically shaped into products.
Thermosetting polymers, or thermosets (TS), cannot tolerate repeated heating
cycles as thermoplastics can. When initially heated, they soften and flow for molding,
but the elevated temperatures also produce a chemical reaction that hardens the
material into an infusible solid. If reheated, thermosetting polymers degrade and char
rather than soften.
Elastomers are the rubbers. Elastomers (E) are polymers that exhibit extreme
elastic extensibility when subjected to relatively low mechanical stress. Some
elastomers can be stretched by a factor of 10 and yet completely recover to their
original shape. Although their properties are quite different from thermosets, they
have a similar molecular structure that is different from the thermoplastics.

21. Chapter 2. Materials used in automotive engineering
2.3 Ceramics, Polymers and composite materials
Polymers are synthesized by joining many small molecules together to form very large
molecules, called macromolecules, that possess a chain-like structure.
The small units, called monomers, are generally simple unsaturated organic molecules such
as ethylene C2H4.
The atoms in these molecules are held together by covalent bonds.

22. Chapter 2. Materials used in automotive engineering
2.3 Ceramics, Polymers and composite materials

23. Chapter 2. Materials used in automotive engineering
Mechanical Behavior of Polymers
The stress–strain behavior for brittle (curve A),
plastic (curve B), and highly elastic (elastomeric)
(curve C) polymers.
Schematic stress–strain
curve for a plastic polymer
showing how yield and tensile
strengths are determined.

24. Room-Temperature Mechanical Characteristics of some Polymers
Chapter 2. Materials used in automotive engineering
Mechanical Behavior of Polymers

25. Chapter 2. Materials used in automotive engineering
Influence factors on Behavior of Polymers
The influence of temperature on the stress–strain
characteristics of poly (methyl - methacrylate)

26. Chapter 2. Materials used in automotive engineering
Polymers Creation
The synthesis of these large molecules (polymers) is termed polymerization; it is
simply the process by which monomers are linked together to generate long chains
composed of repeat units. Most generally, the raw materials for synthetic polymers
are derived from coal, natural gas, and petroleum products. The reactions by which
polymerization occur are grouped into two general classifications—addition and
condensation—according to the reaction mechanism.
Addition polymerization (sometimes called chain reaction
polymerization) is a process by which monomer units are attached
one at a time in chainlike fashion to form a linear macromolecule.
The composition of the resultant product molecule is an exact
multiple for that of the original reactant monomer.

27. Condensation (or step reaction) polymerization is the formation of polymers by stepwise
intermolecular chemical reactions that may involve more than one monomer species. There is
usually a small molecular weight byproduct such as water that is eliminated (or condensed).
No reactant species has the chemical formula of the repeat unit, and the intermolecular
reaction occurs every time a repeat unit is formed. For example, consider the formation of the
polyester, poly(ethylene terephthalate) (PET), from the reaction between ethylene glycol and
terephthalic acid.
Chapter 2. Materials used in automotive engineering
Polymers Creation

28. FORMING TECHNIQUES FOR PLASTICS
Chapter 2. Materials used in automotive engineering
Schematic diagram of a compression molding apparatus.

29. FORMING TECHNIQUES FOR PLASTICS
Chapter 2. Materials used in automotive engineering
Schematic diagram of an injection molding apparatus
Schematic diagram of an extruder

30. Chapter 2. Materials used in automotive engineering
2.3 Ceramics, Polymers and Composite materials
❖Composites have been used extensively in industries such as marine and transportation for
more than 50 years.
❖Composites are just now becoming a primary material of choice in some modern industries.
❖Use Composites rapidly: Save natural metal recourses, reduce life cycle environmental,
cost impacts, create new properties…
An engineered combination of materials that
result in a finished material with better overall
properties than the starting constituents.
At a microscopic level, the constituent materials
remain distinct within the finished structure.
Composite

31. Chapter 2. Materials used in automotive engineering
2.3 Ceramics, Polymers and Composite materials

32. Chapter 2. Materials used in automotive engineering
2.3 Ceramics, Polymers and Composite materials

33. Chapter 2. Materials used in automotive engineering
2.3 Ceramics, Polymers and Composite materials
Many composite materials are composed of just two phases; one is termed the matrix,
which is continuous and surrounds the other phase, often called the dispersed phase.
The properties of composites are a function of the properties of the constituent phases, their
relative amounts, and the geometry of the dispersed phase.
“Dispersed phase geometry” in this context means the shape of the particles and the
particle size, distribution, and orientation.

34. Chapter 2. Materials used in automotive engineering
2.3 Ceramics, Polymers and Composite materials

35. Chapter 2. Materials used in automotive engineering
2.3 Ceramics, Polymers and Composite materials

36. Chapter 2. Materials used in automotive engineering
2.3 Ceramics, Polymers and Composite materials
Photomicrograph of a
WC–Co carbide
In these expressions, E and V denote the elastic modulus and volume fraction, respectively,
whereas the subscripts c, m, and p represent composite, matrix, and particulate phases.
Particle-Reinforced Composites

37. Fiber-Reinforced Composites
Chapter 2. Materials used in automotive engineering
2.3 Ceramics, Polymers and Composite materials
(a)one-dimensional reinforcement,
in which maximum strength and
stiffness are obtained in the
direction of the fiber;
(b)planar reinforcement, in some
cases in the form of a two-
dimensional woven fabric;
(c)random or three-dimensional in
which the composite material
tends to possess
isotropic properties.

38. Fiber-Reinforced Composites
Chapter 2. Materials used in automotive engineering
2.3 Ceramics, Polymers and Composite materials

39. Material Matrix
Chapter 2. Materials used in automotive engineering
2.3 Ceramics, Polymers and Composite materials

40. PROCESSING OF FIBER -REINFORCED COMPOSITES
Chapter 2. Materials used in automotive engineering
2.3 Ceramics, Polymers and Composite materials

41. PROCESSING OF FIBER -REINFORCED COMPOSITES
Chapter 2. Materials used in automotive engineering
2.3 Ceramics, Polymers and Composite materials

42. PROCESSING OF FIBER -REINFORCED COMPOSITES
Chapter 2. Materials used in automotive engineering
2.3 Ceramics, Polymers and Composite materials

43. Chapter 2. Materials used in automotive engineering
2.4 Material Properties

44. Chapter 2. Materials used in automotive engineering
2.4 Material Properties

45. Chapter 2. Materials used in automotive engineering
2.4 Material Properties
Mechanical properties: Young modulus, Poisson's coefficient, hardness,
ductility, yield strength, tensile strength
Physical properties: electrical conductivity, thermal conductivity, density,
specific heat
r
kg/dm
3
c
J/(kg K) N/mm
2
Steels ca. 7.8 ca. 500 400-1200
Al-Alloys ca. 2.7 ca. 1000 100-300
Cu-Alloys ca. 8.7 ca. 400 200-400
Ti-Alloys ca. 4.5 ca. 600 750-1500mean


46. Chapter 2. Materials used in automotive engineering
2.4 Material Properties
Engineering Strain & True Strain
l
0
l
l
1
intermediate
configuration
initial
configuration
final
configuration
F F
dl

47. Strain
Mechanical engineering:Elongation is based to the initial lengthò
-
==®=
1
0
0
01
00
dd
d
l
l
l
ll
l
l
l
l
ee
True strain
Forming technology:Elongation is related to the actual length,
useful to describe the large amounts of deformationò
==®=
1
0
0
1
ln
dd
d
l
l
l
l
l
l
l
l
jj
Relationship between true strain and engineering strain()
1
0
01
0
010
0
1
1 1ln
l
1ln
l
lnln ej +=
÷
÷
ø
ö
ç
ç
è
æ-
+=
÷
÷
ø
ö
ç
ç
è
æ -+
==
l
l
l
ll
l
l
Le_1998_ba
2.4 Material Properties
Strain rate
Time derivation of the true strain

48. Definition of the Flow Curve
The flow curve of metals defined in the plastic state is the function( , , )
f T e e
where, for the von Mises yield criterion, the terms are:( )( )( )( )
22 2
2 2 2
..
1
6
2
f v M xx yy yy zz zz xx xy yz zx          

= = - + - + - + + +
 ( )( )
2 2 2 2 2 22
2
3
xx yy zz xy yz zxe e e e e e e= + + + + +
 t
dtee=ò
and
Usually we understand from the term flow curve just:()
f
e
2.4 Material Properties

49. Flow Curves
Flow stresses depend on individual materials
Flow curves of C25 by hot forming
2.4 Material Properties

50. Material: C15
Flow Curves
2.4 Material Properties

51. n
fCe= 0()
n
fC e e=+ n
fABe=+ 2
0 1 2fA A A e e= + + + Ludwik (Hollomon) Expression:
Swift Expression:
Polynomial Expression:
Exponential Expression:
n: strain hardening exponent
Flow Curve: Mathematical Representation
(Cold Flow Curves)
2.4 Material Properties

52. Typical Cold Flow Curves
Material
f0(MPa)C(MPa) n Material
f0(MPa)C(MPa) n
St38
*
730 0.10042CrMo4 420 1100 0.149
St42
*
850 0.23016MnCr5
*
810 0.090
St60
*
890 0.15020MnCr5
*
950 0.150
C10
*
800 0.240100Cr6
*
1160 0.180
Ck10
*,**
260 730 0.216Al99.5
*
110 0.240
Ck15
**
280 760 0.165Al99.5
**
60 150 0.222
Ck22
**
320 760 0.157Al99.8
**
60 150 0.222
Ck35
*
960 0.150AlMgSi1
**
130 260 0.197
Ck35
**
340 950 0.178AlMg3
*
390 0.190
Ck45
**
390 1000 0.167CuZn10
**
250 600 0.331
Cf53
**
430 1140 0.170CuZn30
**
250 880 0.433
15Cr3
*
850 0.090CuZn37
**
280 880 0.433
34Cr4
**
410 970 0.118CuZn40
*
800 0.330
2.4 Material Properties

53. Flow Curve: Mathematical Representation
(Warm and Hot Flow Curves)m
fKe= nm
fK e e=
Warm Flow Curves:
Hot Flow Curves:
n: strain hardening exponent
m: strain-rate sensitivity exponent
2.4 Material Properties

54. Typical Warm/Hot Flow Curves
Material m K(MPa) T(
o
C) Material m K(MPa)T(
o
C)
C15** 0.154 99/84 1100/1200CuAl5** 0.163 102 800
C35** 0.144 89/72 1100/1200Al99.5** 0.159 24 450
C45** 0.163 90/70 1100/1200AlMn** 0.135 36 480
C60** 0.167 85/68 1100/1200AlCuMg1** 0.122 72 450
X10Cr13** 0.091105/88 1100/1250AlCuMg2** 0.131 77 450
X5CrNi189** 0.094137/1161100/1250AlMgSi1** 0.108 48 450
X5CrNiTi189**0.176100/74 1100/1250AlMgMn** 0.194 70 480
E-Cu** 0.127 56 800 AlMg3** 0.091 80 450
CuZn28** 0.212 51 800 AlMg5** 0.110 102 450
CuZn37** 0.201 44 750 AlZnMgCu1,5*
*
0.134 81 450
CuZn40Pb2** 0.218 35 650
CuZn20Al** 0.180 70 800
CuZn28Sn** 0.162 68 800
2.4 Material Properties

55. Recovery
Heating the deformed metal in a range of 0.3 T
m < T < 0.5 T
m will activate
diffusion of atoms.
This diffusion of atoms enables the motion of some dislocations which will
cancel each other or restructure themselves.
Stored energy is relieved.
Residual stresses will be removed, yield stress will reduce slightly and
ductility will increase.
Electrical and thermal properties will be recovered as well.
Chapter 2. Materials used in automotive engineering
2.5 Influence factors on material properties

56. Chapter 2. Materials used in automotive engineering
2.5 Influence factors on material properties
RecrystallizationTime
TT > 0.5
m
Primary
Recrystallization
Secondary
Yield Stress
Ductility
Definition:
Temperature at which the
whole structure is completely
recrystallized within one hour
is named as recrystallization
temperature

57. Chapter 2. Materials used in automotive engineering
2.5 Influence factors on material properties
(a) 220
0
C (b) 525
0
C
(c) 550
0
C (d) 650
0
C
Dislocations will be re-arranged.
Heat treatment

58. Material
Recrystallization
Temperature
Material
Recrystallization
Temperature
C-Steel 550
o
C tin 0 to 40
o
C
Pure-Al 290 to 300
o
C zinc 50 to 100
o
C
Dur-Al 360 to 400
o
C Mo 870
o
C
Cu
200
o
C
(changes
drastically with
alloying elements)
W 900-1000
o
C
Lead -50 to 50
o
C Ni 400-600
o
C
Typical Recrystallization Temperatures
Chapter 2. Materials used in automotive engineering
2.5 Influence factors on material properties