Design considerations and engineering materials

PRESENTATION
ON
“DESIGN CONSIDERATIONS”
AND
“ENGINEERING MATERIALS”
DESIGN OF MACHINE ELEMENTS
SUBMITTED BY:
HIMANSHI GUPTA (140120119057)/ ME/A2
PRACHI SHARMA (140120119216) / ME /A2
(2151907)
GA N D H IN A GA R IN STITU TE OF
TEC H N OLOGY

INTRODUCTION TO
MACHINE DESIGN
• Machine design is defined as the use of
scientific principles, technical information and
imagination in the description of a machine or
a mechanical system to perform specific
functions with maximum economy and
efficiency.
• Example: The process of design of a belt
drive.

DESIGN PROCEDURE
1. Definition of
problem
2. Synthesis
3. Analysis of forces
4. Selection of material
5. Determination of
mode of failure
6. Selection of factor
of safety
7. Determination of
dimensions
8. Modification of
dimensions
9. Preparation of
drawings
10. Preparation of
design report

DESIGN CONSIDERATIONS
 Strength
 Rigidity
 Reliability
 Safety
 Cost
 Weight
 Ergonomics
 Aesthetics
 Manufacturing
considerations
 Assembly considerations
 Conformance to standards
 Friction and wear
 Life
 Vibrations
 Thermal considerations
 Lubrication
 Maintenance
 Flexibility
 Size and shape
 Stiffness
 Corrosion
 Noise
 Environmental
considerations

AESTHETIC CONSIDERATIONS
IN DESIGN
• Appearance is an outward expression of
quality of the product and is the first
communication of product with the user.
• Aesthetics is defined as the set of principles of
appreciation of beauty. It deals with the
appearance of the product.

ASPECTS OF AESTHETIC DESIGN
Form(shape)
Symmetry and shape
Color
Continuity
Variety
Proportion
Noise
Contrast
Impression and
purpose
Style
Material and surface
finish
Tolerance

ERGONOMICS CONSIDERATIONS
IN DESIGN
• Ergonomics is defined as the study of the man -
machine - working environment relationship
• It aims at decreasing the physical and mental stresses to
the user
 Areas covered under ergonomics
• Communication between man (user) and machine
• Working environment
• Human anatomy and posture while using the machine
• Energy expenditure in hand and foot operations

MANUFACTURING
CONSIDERATIONS IN DESIGN
Minimum total number of parts in a product
Minimum variety of parts
Use standard parts
Use modular design
Design parts to be multifunctional
Design parts for multiple use
Select least costly material
Design parts for ease of manufacture
Shape the parts for minimizing the operations

FOR CASTINGS
 Design parts to be in compression then in tension
 Strengthen parts under tension by use of external devices
 Shape the casting for orderly solidification
 Avoid abrupt change in cross-section
 Provide more thickness at the boss
 Round off the corners
 Avoid concentration of metal at junctions
 Avoid thin sections
 Make provision for easy removal of pattern from the
mould

FOR FORGINGS
Keep fibre lines parallel to tensile and
compressive forces and perpendicular to shear
forces
Avoid deep machining cuts
Keep vertical surfaces of forged parts tapered
Keep the parting line in one plane
Provide adequate fillet and corner radii
Avoid thin sections

IN WELDING
 Use the minimum possible number of welds
 Select the same thickness for the parts to be welded
together
 Locate the welds at the areas in the design where stresses
and/or deflections are not critical
 Effect of shrinkage and distortion should be minimized by
post welding annealing and stress relief operations
 Decide proper welding sequence
 Design welding in the flat or horizontal position and not in
the overhead position
 Use only the amount of weld metal that is absolutely
required

STANDARDIZATION
• It is the process of establishing the set of norms to
which a specified set of characteristics of a
component or a product should conform
• Example: Standardizing the shaft consists of
specifying the set of shaft diameters and material
Objectives of standardization
• To make the interchangeability of the components
possible
• To make the mass production of components easier

PREFERRED SERIES AND
ITS SELECTION
• Preferred series are series of numbers obtained by
geometric progression and rounded off
• The four basic preferred series are designated as:
• The other series are called derived series and are
obtained by multiplying or dividing the basic sizes by
10, 100, etc.

MECHANICAL PROPERTIES
OF MATERIALS
Strength
Stiffness/Rigidity
Elasticity
Plasticity
Ductility
Brittleness
Malleability
Toughness
Machinability
Resilience
Creep
Fatigue
Hardness

EFFECT OF
ALLOYING ELEMENTS
Chromium
Nickel
Manganese
Silicon
Molybdenum
Vanadium
Tungsten

STEELS DESIGNATED ON THE BASIS
OF MECHANICAL PROPERTIES
• These steels are carbon and low alloy steels where the main
criterion in the selection and inspection of steel is the tensile
strength or yield stress.
• According to Indian standard these steels are designated by a
symbol ‘Fe’ or ‘Fe E’ depending on whether the steel has
been specified on the basis of minimum tensile strength or
yield strength, followed by the figure indicating the minimum
tensile strength or yield stress in 𝑁/𝑚𝑚2
• For example ‘Fe 290’ means a steel having minimum tensile
strength of 290 𝑁/𝑚𝑚2 and ‘Fe E 220’ means a steel having
yield strength of 220 𝑁/𝑚𝑚2
.

STEELS DESIGNATED ON THE BASIS
OF CHEMICAL COMPOSITION
• According to Indian standard, steels are designated in the
following order :
• (a) Figure indicating 100 times the average percentage of
carbon content,
• (b) Letter ‘C’, and
• (c) Figure indicating 10 times the average percentage of
manganese content. The figure after multiplying shall be
rounded off to the nearest integer.
• For example 20C8 means a carbon steel containing 0.15 to
0.25 per cent (0.2 per cent on an average) carbon and 0.60 to
0.90 per cent (0.75 per cent rounded off to 0.8 per cent on an
average) manganese.

INDIAN STANDARD DESIGNATION OF
LOW AND MEDIUM ALLOY STEELS
• According to Indian standard, low and medium alloy steels
shall be designated in the following order :
1. Figure indicating 100 times the average percentage carbon.
2. Chemical symbol for alloying elements each followed by the
figure for its average percentage content multiplied by a factor as
given below :
• For example 40 Cr 4 Mo 2 means alloy steel having average
0.4% carbon, 1% chromium and 0.25% molybdenum.

INDIAN STANDARD DESIGNATION
OF HIGH SPEED TOOL STEEL
• According to Indian standard, the high speed tool steels are
designated in the following order :
1. Letter ‘XT’.
2. Figure indicating 100 times the percentage of carbon
content.
3. Chemical symbol for alloying elements each followed by
the figure for its average percentage content rounded off to
the nearest integer, and
4. Chemical symbol to indicate specially added element to
attain the desired properties.
• For example, XT 75 W 18 Cr 4 V 1 means a tool steel with
average carbon content 0.75 percent, tungsten 18 per cent,
chromium 4 per cent and vanadium 1 per cent.

HEAT TREATMENT OF STEELS
• A combination of operations involving the heating
and cooling of a metal or an alloy in the state for the
purpose of obtaining certain desirable conditions or
properties without change in chemical composition
 Various heat treatment processes are:
• Normalizing
• Annealing
• Spheroidising
• Hardening
• Tempering
• Surface or case
hardening

AIM OF HEAT TREATMENT
• To increase the hardness of metals
• To relieve the stresses set up in the material after hot
or cold working
• To improve machinability
• To soften the metal
• To modify the structure of the material to improve its
electrical and magnetic properties
• To change the grain size
• To increase the qualities of a metal to provide better
resistance to heat, corrosion and wear

MATERIAL SELECTION PROCESS
• The different steps involved in the material
selection process are as follows:
Analysis of desired material properties
Screening of candidate materials
Selection of most suitable material

Design considerations and engineering materials

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