The document discusses design processes and engineering materials. It describes the typical steps in a design process as identifying problems, generating solutions, prototyping, testing, and refining. It also outlines various material properties like elasticity, plasticity, ductility. Common engineering materials discussed include steels, cast irons, aluminium and their alloys. Key characteristics and applications of these materials are provided.

1. Unit II
Design Fundamentals
Basic Mechanical Engineering
F.E-Semester II

2.  What is Design?
Design is also a process that is used to
systematically solve problems.
What is a Design Process?
A design process is a systematic problem-solving strategy,
with criteria and constraints, used to develop many possible
solutions to solve or satisfy human needs or wants and to
narrow down the possible solutions to one final choice.
• Design Process:
1. Identifying problems/Needs
and opportunities
2. Framing a design brief
3. Investigation and research
4. Generating alternative
solutions
5. Choosing a solution
6. Developmental work
7. Modeling and prototyping
8. Testing and evaluating
9. Redesigning and improving

3. 1. Define a Problem
2. Brainstorm
3. Research and Generate Ideas
4. Identify Criteria and Specify
Constraints
5. Explore Possibilities
6. Select an Approach
7. Develop a Design Proposal
8. Make a Model or Prototype
9. Test and Evaluate the Design using
Specifications
10. Refine the Design
11. Create or Make Solution
12. Communicate Processes and Results
Example Design Process

4. Stress Strain Curve: Ductile Material

5. Stress Strain Curve: Brittle Material

6. Proportional Limit: It is the point on stress strain
curve up to which stress strain curve is linear i.e.
Hooke’s law is applicable
Elastic Limit: It is the point on stress strain curve
up to which deformations are elastic i.e. original
shape is regained once the load is released
Yield Point: The point on stress strain curve at
material strain momentarily starts increasing
without any appreciable increase in stress
Stress Strain Curve: Ductile Material

7. Ultimate Strength: It is the maximum stress that a
body can withstand before ‘fracture’.
Rupture Strength: The stress at failure is called
rupture strength.
Stress Strain Curve: Ductile Material

8. Material Properties: Elasticity, Plasticity
Elasticity: The ability of material to regain
its original shape after removal of applied
load is called elasticity. e.g.-rubber.
Plasticity: It is the ability of material to
retain the deformation produced under the
load permanently. e.g.- sheet metals.

9. Material Properties
Ductility: The ability of material to get drawn into
wire under the application of tensile load is called
ductility.
(ability of material to undergo plastic deformation
under tensile load without fracture)
Malleability: The ability of material to get
flattened into thin sheets under the application of
compressive load is called malleability.
(ability of material to be formed by hammering or
rolling)

10. Material Properties:
 Hardness: It is the ability of material to resist
plastic deformation.
(resistance to scratch & abrasion/wear)
 Toughness: It is the total amount of energy
absorb by material before failure.
 Resilience: It is the amount of energy absorb
by material during elastic deformation.
e.g.- essential in springs, shock absorber.
 Strength: The ability of material to withstand external
stress/force is called strength. (N/mm2)
 Ultimate Strength (σut): It is the maximum stress that
a body can withstand before ‘fracture’.

11. Stress Strain Curve: Brittle vs Tough

12. Material Properties
 Stiffness: Ability of material to resist deformation under
the load. (N/mm)
 Brittleness: Property of breaking of material with little
distortion.
 Fatigue: When material is subjected to repeated stress or
loading, it fails at stress below yield point stress, such
failure is called as fatigue. e.g. consider in design of shaft,
gears etc.
 Creep: When material is subjected to constant stress at
high temperature for long time, it will undergo slow &
permanent deformation which is called as creep.
e.g. consider in design of Boilers, IC engine, turbine etc.

13. Material Properties: Fatigue
Crack Growth Area
Crack Initiation Site
Overload Area, Sudden
Tearing happens here
rsime.com

14. Engineering Materials: Ferrous Alloys
Engineering
Materials
Metals
Ferrous
Alloy
Cast
Iron
Alloy
C.I.
Steel
Alloy
Steel
Non-
Ferrous
Alloy
Copper
& its
Alloy
Aluminium
& its Alloy
Non-Metals
Rubber
Plastic
Wood

15. Types of Engineering Materials
Metals & Alloys are futher classified as:
Metals & Alloys
Ferrous Non-ferrous
Steels Cast Irons
Cu-Alloys
Ni-Alloys
Al-Alloys
Plain Carbon Steels
Alloy Steels
White Cast Iron
Malleable Cast Iron
Grey Cast Iron
S.G. Cast Iron
Chilled Cast Iron

16. Engineering Materials: Steel
Steel: Steel is a alloy of iron and carbon, it contains
carbon less than 2.1% by weight. Other alloying
elements may be added to alter the properties of
steel
Plain Carbon Steel: It contains carbon as main alloying
element and other alloying element are present in
negligible quantity
Low Carbon Steel: It contains less than 0.3% carbon
by weight

17. Engineering Materials: Steel
Medium Carbon Steel: It contains 0.3% to 0.6%
carbon by weight
High Carbon Steel: It contains more than 0.6% carbon
by weight
As percentage of carbon increases hardness and
strength of steel increases but toughness, ductility
and malleability decreases

18. Engineering Materials: Steel
Low Carbon Steel:
 Properties: They are cheap, soft, ductile, and malleable
and can be easily forged into different shapes
 Applications: Wires, sheets, structural parts, frames,
storage tanks, nut-bolts, etc
Medium Carbon Steel:
 Properties:They are stronger and harder as compared to
low carbon steels and used where high strength is
required
 Applications: Gears, axles, rails, springs, cams, chains

19. Engineering Materials: Steel
High Carbon Steel:
 Properties: They are very hard but brittle and are
generally used to make cutting tools
 Applications: Knives, chisels, razor blades, hacksaw
blades, cutting tools, drill bits

20. Engineering Materials: Cast Iron
Cast Iron: Cast iron is an alloy of steel and contains
carbon more than 2.1% by weight
Gray Cast Iron: Gray cast iron contains carbon in the
form of graphite flakes
 When liquid mixture of iron and carbon cooled down
slowly carbon will be present in the form graphite phase.
Small amount silicon is added to facilitate formation
graphite.
 The fractured surface of gray cast iron will look gray
because of graphite flakes hence the name

21. Engineering Materials: Cast Iron
White Cast Iron: White cast iron contains carbon in
the form of iron carbide/cementite (Fe3C)
 When liquid mixture of iron and carbon cooled down
rapidly carbon will chemically combine with iron and iron
carbide will be formed
 Iron carbide is very hard phase hence white cast iron is
hard as compared to gray cast iron
 The fractured surface of white cast iron will look white
because of iron carbide phase hence the name

22. Engineering Materials: Cast Iron
Malleable Cast Iron: Malleable cast iron contains
carbon in the form of graphite spheroids
 When white cast iron is heated about 9000 the Fe3C
structure will break and when the mixture cooled down
very slowly carbon atoms will segregate and graphite
spheroids are formed
 As graphite is not uniformly distributed, the malleable
cast iron has properties similar to pure iron
 Unlike gray and white cast iron it soft, malleable (similar
to pure iron) hence the name

23. Engineering Materials: Cast Iron
Properties of Cast Iron:
 Cast irons have good castability as compared pure ion or
alloy steel
 It is a low cost material and used as substitution of steel
and iron wherever possible
 Cast iron is hard, brittle
 It shows good resistance to abrasion and wear
 It has excellent machinability
 Gray and malleable cast irons have good vibration
damping capability hence they are widely used to make
machine beds

24. Engineering Materials: Cast Iron
Applications of Cast Iron:
 It is used as journal surface in sliding contact bearings
because of better wear resistance
 It is used to make machine beds
 It is extensively used to make I.C. Engine cylinder block
because of excellent casting properties
 It used to make brake drums, discs and clutch plates
because of better wear resistance low cost
 Cast iron is used as substitution of steel and iron
wherever possible because of its low cost

25. Engineering Materials: Alloy Steels
Alloy Steels: Alloy steels contain carbon less than 2.1%
by weight along with other alloying elements such as
Cr, Ni, Mn, Ti, Mo, V,W etc in significant proportion
 Properties of alloy steels can be tweaked significantly by
changing the composition of alloying elements
 Wherever high quality reliable service is required form
the component and whenever engineering properties of
materials are demanding alloy steels are preferred over
plain carbon steels and cast iron

26. Engineering Materials: Alloy Steels
Effect of alloying elements on properties Alloy Steels:
 Cr: Improves corrosion resistance significantly but needs to
be added in large amount (stainless steel contains 12% cr)
 Ni: Increases strength, toughness
 Mn: Acts as a desulpherizing and deoxidizing agent (sulpher
increases brittleness). Improves hot working properties
 Mo, W: Increases hardness, strength at high temperature
 Ti: Improves strength, corrosion resistance
 V: Improves creep life, fatigue strength

27. Engineering Materials: Alloy Steels
Applications of Alloy Steels:
 Aircraft engine parts, missile parts, turbine blades
 High performance gears
 Various cutting tools like milling cutters, drills, broaches
 Combustion chamber, furnace parts, burners
 Measuring instruments, wrist watches

28. Engineering Materials: Aluminium
Aluminium: Aluminium is most abundant metal
in earth’s crust and overall third most
abundant element after oxygen and silicon
Properties:
1. Light Weight
2. High strength to weight ratio
3. Good thermal and electrical conductivity
4. Excellent corrosion resistance
5. Good Malleability and Ductility
6. It is non magnetic in nature
7. Very high reflectivity

29. Engineering Materials: Aluminium
Applications: Aluminium is most widely used non
ferrous metal
1. Electrical wires and cables
2. Aircraft structure
3. IC Engine blocks, Pistons
4. Kitchen utensils
5. Packaging (cans, foil)
6. Coins
7. Marine Equipments (Due to high corrosion
resistance )
8. Aluminium powder is used in silver colored paint
9. Mirror Coatings

30. Engineering Materials: Copper
Copper: Copper is one of the most
widely used non ferrous metal
Properties:
1. Excellent thermal and electrical conductivity
(Second Highest thermal and electrical
conductivity among metals (After Silver))
2. Good Malleability and Ductility
3. High Corrosion Resistance
4. Ability to kill wide range of harmful microbes in
rapid time (within 2 hrs)
5. It forms colorful compounds
6. Non magnetic

31. Engineering Materials: Coppeer
Applications:
1. Electrical wires and cables
2. Heat Exchangers
3. Automobile Radiators
4. Kitchen utensils
5. Copper alloys are used to
make antimicrobial touch
surfaces
6. Copper compounds are
colorful and are used as
pigment in various paints
7. Coins
Radiator
Copper Carbonate

32. Engineering Materials: Brass
Brass: Brass is an alloy of
copper and zinc
Properties:
1. It has pleasant color
(Golden)
2. Corrosion resistance
3. Low coefficient of friction
4. Good acoustic properties
5. Ability to kill wide range of
harmful microbes
6. Good Castability and
Machinability

33. Engineering Materials: Brass
Applications:
1. Used for decorative purpose
2. Extensively used in musical
instruments
3. Used in sliding contact
bearings
4. Used marine component
because of better corrosion
resistance
5. Used to make knobs, pipes,
valves
6. Used in ammunition cases

34. Engineering Materials: Rubber
Natural Rubber: Natural rubber is
obtained from latex, a milky liquid
extracted from certain tropical
trees
Synthetic Rubber: Synthetic rubber
primarily is obtained from
polymerization of various petroleum
based products

35. Engineering Materials: Rubber
Properties of Rubber:
1. Rubber has high resilience and elasticity
2. It is a bad conductor of electricity and heat
3. Rubber has high chemical and corrosion resistance
4. Rubber is non crystalline in nature
5. It is water proof

36. Engineering Materials: Rubber
Applications of Rubber:
1. Around 55% of annually produced rubber is
consumed by tire industry
2. Rubber is used make various products such as
pipes, tubes, conveyor belts, seals, electrical
insulators, gloves, containers, balloons, balls,
erasers, shoes,

37. Engineering Materials: Plastic
Plastic: Plastic is a synthetic material obtained from
polymerization of petroleum products
Thermoplastics: Thermoplastics are the plastics that do
not undergo chemical change when heated and can be
molded repeatedly.
Example. polyethylene, polypropylene, polystyrene, Poly
Venyl Chloride (PVC)
Thermosets: These plastics undergo irreversible
chemical change once heated and hence cannot be
molded repeatedly.
Example: Epoxies, Phenolics

38. Engineering Materials: Plastic
Properties of Thermoplastics:
1. They become soft when heated and can once
again become hard after cooling
2. They can be molded repeatedly
3. They are soft and ductile in nature
4. They have low melting point

39. Engineering Materials: Plastic
Applications of Thermoplastics:
 They used to make toys, bags, bottles, hoses,
photographic film, electrical insulations,

40. Engineering Materials: Plastic
Properties of Thermosets:
1. They become soft during first heating and can o
become hard permanently after cooling
2. When heated once again they degrade and loose
their properties
3. They can not be molded repeatedly
4. They are hard, strong and brittle in nature
5. They have high melting point and can withstand
at higher temperature than thermoplastics

41. Engineering Materials: Plastic
Applications of Thermoplastics:
 They used to make radio and T.V. frame,
automobile parts, electrical plugs, telephone
receivers