ch#1 met 304 mechanical design

MET 304

Mechanical Design 1

Dr. Salah Gasim Ahmed

ACX F92

543210

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.

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]

Mechanical design 1:

Design Process

Stress and factor of safety

Design of shafts

Selection of belts

Bearings

Welded joints

Riveted joints

Screw fasteners

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

Engineers Provide:

Engineering Products:

Washing machines, food

processors, trucks, weapons, tooth

brush, etc

Engineering services:

operation, maintenance, etc

Life of engineering product:

Design

Manufacture

Test

Develop

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

The Design Process

Definition

of problem

Presentation

Recognition

of need

Synthesis

Analysis and

optimisationEvaluation

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

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

Methods of obtaining alternative solution

Standard parts

Method of Inversion

Solution at stages

Black-box concept

Brain storming

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

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

Solution at stages

Divide the complex system into stages

Find alternative solution for each stage.

Combine the best and compatible solution from each stage

Black-box concept

Consider the system as consisting of

black boxes

Do not investigate the details of each

box at this stage

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,

General guidelines for writing design

specification

Title

Role of equipment

Inputs

Outputs

Environment and location

Measures of value

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

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.

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)

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

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 )

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

Thank You