Download - Ch#1 MET 304 Mechanical design
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MET 304
Mechanical Design 1
Dr. Salah Gasim Ahmed
ACX F92
543210
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Objectives To integrate knowledge learned in the mechanics,
structures, materials, and manufacturing courses.
Systematically analyze an engineering problem and obtain a suitable solution
Understand the concepts of factor of safety and stress concentration
To obtain a working knowledge in the use of the proper failure theories under steady and variable loadings.
Design shafts and keys under various types of loading.
Select standard V-belts.
Select standard anti friction bearings
Design mechanical joints, mainly; welded, riveted and screw fastened joints.
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Student Learning Outcome
1. Students will demonstrate ability to analyseengineering problems and obtain possible solutions [1,]
2. Students will demonstrate ability to write design specifications for engineering systems. [1]
3. Student will demonstrate ability to design shafts and keys under various types of loading [2,3,4,5]
4. Students will demonstrate ability to select standard components: belts and bearings for various applications. [3,6,7]
5. Students will demonstrate ability to design different types of mechanical joints. [ 3, 8]
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Mechanical design 1:
Design Process
Stress and factor of safety
Design of shafts
Selection of belts
Bearings
Welded joints
Riveted joints
Screw fasteners
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Textbook and References
Mechanical Engineering Design, , Joseph E. Shigley, Charles R. Mischke and Richard G. Budyans McGraw Hill , International editions, Seventh edition, 2004
Fundamentals of machine Component Design, Robert C. Juvinall, Kurt M. Marshek, John Wilely & Sons, Forth edition, 2005
Machinery’s Handbook, , Eric Oberg, Franklin D. Jones and Holbrook L. Horton. Industrial Press Inc., 27th edition, 2004
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Engineers Provide:
Engineering Products:
Washing machines, food
processors, trucks, weapons, tooth
brush, etc
Engineering services:
operation, maintenance, etc
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Life of engineering product:
Design
Manufacture
Test
Develop
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A product design must be:
Functional :The product must perform to fill its intended need
Safe :The product is not hazardous to users
Reliable :The product will perform its intended function satisfactory at a given age.
Manufacturable:The product can be manufactured with the available technology with required quantities
Marketable:The product can be bought and service, repair, is available
Competitive : the product is contender, challenger, in its market
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The Design Process
Definition
of problem
Presentation
Recognition
of need
Synthesis
Analysis and
optimisationEvaluation
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Synthesis :
• It is the methods of obtaining alternative
solution, Ideas
• It is sometimes called the invention of the
concept
• In this stage as many solutions or ideas as
possible are required
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Factor which drives invention or creativity
Inherited qualities ,talent: we cannot all inherit Leonardo's genes, but each of us must have some talents qualities.
Thinking Methods:you can employ proven techniques to increase your inventive powers
Attitude:you must be positive, you can invent!
Knowledge and experience:your understanding of how related problems are solved can be increased
Effort:Edison (inventor of the light bulb) put more effort to develop and improve his invention
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Methods of obtaining alternative solution
Standard parts
Method of Inversion
Solution at stages
Black-box concept
Brain storming
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Standard parts
Copy an existing solution
Change manual system into automatic one
Change the system from batch to
continuous production
If the required system is very large and only
part of it is available, use the available
parts and fill the gap with new design
Look for similar systems and modify to suit
the required one
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Method of Inversion
Inverse the characteristics of the
system to get new ideas
Change shape: convex to concave etc.
Change motion: rotary to linear, moving to stationary etc.
Change position: front to rear, top to bottom, vertical to horizontal inside to outside etc
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Solution at stages
Divide the complex system into stages
Find alternative solution for each stage.
Combine the best and compatible solution from each stage
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Black-box concept
Consider the system as consisting of
black boxes
Do not investigate the details of each
box at this stage
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Brain storming
It is a free association of ideas where each idea is recorded and actively encouraged to initiate further ideas
A group of people with different backgrounds
A leader
No criticism during ideation
Any idea which gives birth to other ideas cannot be wholly daft,
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General guidelines for writing design
specification
Title
Role of equipment
Inputs
Outputs
Environment and location
Measures of value
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Title
The title should be very specific
Does not mix with other or previous
specifications.
Words should give specific meaning
and can be easily translated to other
languages
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Role of equipment
It describes broadly what the system is supposed to do
It does not provide a solution to the problem
The role of equipment is very important for the designer as well as the user.
Also it helps the manufacturer in understanding the required specifications.
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Inputs
It describes the characteristics of the
inputs to the system
– Nature (electric current, gas pressure, mechanical
movement)
– Quantity, (weight volume, distance speed etc.)
– The rate of change (kg/sec, m3/min..etc.)
– The shape of change (sine wave, constant, arbitrary)
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Outputs
Similarly the output from the system
should be described
Without mentioning the relation
between the inputs and outputs
Unless the customer insists in a
certain way of transforming the inputs
to ouputs
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Environment and location Environment
all factors which may influence the design and has not been mentioned in previously.
location is the relative position of the system to other systems and equipment.
– Human
Equipment are in direct or indirect relation with humans.
Man has a role in their design, manufacture, assembly, use, or maintenance.
Dimensions of human body
Natural abilities of human body Comfort.
– Auxiliary services
services needed for the system (compressed
air, water supply, electricity, hydraulic power )
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Measures of value
Measure of value may includes:
Performance
Initial cost
Operation cost
Maintenance cost EQUIPMENT RENT COST
Total life
Comfort and ease of use
Appearance
Safety
Training
Reliability
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Thank You