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Introduction to MechanicalDesign

Welcome to the Design World!!

Gyung-Jin Park

Professor

Department of Mechanical Engineering

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Syllabus

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What is Design?

Think!!!!!!

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Homework: Survey what the design is.

Present your opinion about design.

Due: next week

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An Early Aspiration of Humans: Fly like a bird!

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Leonardo's Flying Machine

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Leonardo's Flying Machine

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What was wrong with these ideas?

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They lacked Functional Thinking!

They tried to imitate the physical feature ofthe bird.

They should have thought about the FUNCTIONSa flying machine must satisfy!

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Your future role as leaders:

You will deal with

-- i.e, design, lead, correct, analyze --

systems of various different kinds.

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Systems of interest:

machines

universities

software systems

airplanes

biological systems

social systems

factories

Hanyang University

robots

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Two basic approaches in dealing with systems

Analysis -- scientific reductionism, modeling,simulation, etc.

Taught in physics, mathematics, etc.

Synthesis (design) -- creating a new system Often in the absence of prior examples

Before you can analyze a system, you

have to design it first. Sometimes weanalyze an existing system to determinewhat is wrong with and how to improve it.

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If you have a system that is poorly designed, itmay result in the following system failures:

Crash of airplanes, bridges, etc.

Failure of nuclear reactors

Poor products

Social systems that often break down

Short life

High manufacturing cost

High cost for maintenance

Inefficient engines

etc.

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Leaders must know how to DESIGN

systems.

Properly designed systems satisfy many

different functional requirements (FRs)within a given set of constraints.

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Important design problems of the 21st Century

Energy

Environment

Water

Sustainability

Healthcare

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Important technologies of the 21st Century

In addition to EEWSH, we will continue to advancethe following fields:

Transportation

Telecommunications

Food stuff

Materials

Information technology

Manufacturing

Entertainment technologies

etc.

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Characteristics of a system:

1. They have to perform required FUNCTIONs, often manyfunctions at the same time.

2. They have to satisfy Functions without violatingconstraints.

3. They have to operate within the boundary conditionsimposed on the system. Or change the boundary

conditions.

4. Initially there is not much to analyze until it is designedfirst.

5. FUNCTIONS can be satisfied in many different ways.

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Important Ideas Related to System Design:

1. You have to know what are the NEEDs you are trying tosatisfy and CONSTRAINTs.

2. Functional thinking -- FRs

3. Separation of What from How.

4. Mapping from What to How -- A definition of Design

5. Top/Down Process

6. Independence of FRs -- eliminating coupling

7. Decomposability

8. Minimizing complexity and information

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Flying machine:They lacked Functional Thinking!

What is Functional Thinking?

It is the ability to define goals without thinking

about how to satisfy the goals.

Functional Thinking leads to FRs, which

are selected by the designer amongmany possible FRs.

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Flying machine:They lacked Functional Thinking!

What functions should a flying machine satisfy tobe able to fly?

1. Move upward against the gravitational force

2. Stay in the air

3. Go forward

4. Turn

5. Land

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Homework Problems

1. Consider a thermoplastic cup that can be used todispense hot coffee from a vending machine. The

coffee cup must be stiff enough so that it can be

held in hand and also must have enough thermal

insulation since it must be held by hand without

burning the hand of the holder. Its cost must also

be low to be competitive with other products. What

are the functional requirements (FRs)? What arethe constraints? Explain why you chose those FRs

and constraints you have chosen.

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Homework Problems

2. The government policy is to provide education toeveryone who wants to receive college education in

Korea. At the same time, Korean people are eager to

have one of the Korean universities to be in the top

ten among all the universities in the world. State

functional requirements (FRs) for achieving these

dual goals. What are the constraints? Explain why

you chose those FRs and constraints you havechosen.

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Homework Problems

3. What are the FRs of your intended professionalcareer? What are the constraints? Explain why you

chose those FRs and constraints you have chosen.

4. What are the FRs of an electrical connector for your

PC? Explain why you chose those FRs and

constraints you have chosen.

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Homework Problems

5. The current urban transportation system for peopledepends on automobiles which use internal

combustion engines. As a result, many urban areas are

congested or snarled by traffic jams. Furthermore, the

quality of air in these highly populated mega-cities is

below the acceptable level set for human habitat. Your

job is to design a new people transport system. What

should be the FRs for such a system?