Engineering design is… the process of devising a system, component or process to meet needs a decision-making process in which science and mathematics.

Engineering design is…

the process of devising a system, component or process to meet needsa decision-making process in which science and mathematics are applied to convert resources to meet objectivesestablishing objectives & criteria, synthesis, analysis, construction, testing, and evaluation

Problem Characteristics

Engineering Problem Problem statement

incomplete, ambiguous

No readily identifiable closure

Solutions neither unique nor compact

Solution needs integration of many specialties

Science Problem Succinct problem

statement Identifiable closure Unique solution Problem defined

and solved with specialized knowledge

Engineering Design

Creativity Open-ended problems Use design theory and methods Formulate design problem statements and specifications Consider alternative solutions Consider feasibility

Engineering Design ProcessBackup Chart

1. Identify a need2. Establish design criteria and

constraints3. Evaluate alternatives4. Build prototype 5. Test/evaluate against design criteria6. Analyze, redesign, retest7. Communicate the design

The Engineering Design Process

Design is an Iterative ProcessBegins with a recognition of need for a product, service, or systemDuring the idea phase encourage a wide variety of solutions through brainstorming, literature search, and talking to usersBest solutions are selected for further refinement

Models or prototypes are made and problems that arise may require new ideas to solve and a return to an earlier stage in the processFinally drawings are released to manufacturing for production

Engineering Design Process

Customer Needor Opportunity

Implementation ofOptimal Design

Evaluation of Designs/Selection of Optimal Design

Development ofAlternative Designs

Data & InformationCollection

Problem Definition/Specifications

Source: Accrediting Board For Engineering and Technology

Primary Design Features

1. Meets a need, has a “customer”2. Design criteria and constraints3. Evaluate alternatives (systems or

components)4. Build prototype (figuratively)5. Test/evaluate against test plans (criteria)6. Analyze, “tweak” (), redesign (),

retest7. Project book: record, analyses, decisions,

specs

Criteria & Constraints“Design criteria are requirements you specify for your

design that will be used to make decisions about how to build the product”

Aesthetics

Geometry

Physical Features

Performance

Inputs-Outputs

Use Environment

Usability

Reliability

Some Design Constraints

CostTimeKnowledgeLegal, ethical Physical: size, weight, power, durabilityNatural, topography, climate, resourcesCompany practices

Evaluate Alternatives

Needs best stated as function, not formLikely to find good alternatives for cheapest, fastest, lightest, and encourage discoveryResearch should reveal what has been doneImprove on what has been donePlay alternatives off criteria and constraintsBrainstorming helps

Best Design

Choose best design that meets criteriaDemonstrate tradeoff analyses (among criteria and constraints) are high qualityCost (lifecycle) is always considerationResist overbuilding; drives complexity, cost, time, resourcesA quality design meets customers expectations!

Prototype

Prototype is implementation of chosen design alternativeIt is a proof of design, production and suitabilityPrototypes are often cost prohibitive: Models and simulations may sufficeQuality design does not include redesigning a lot of prototypes

Test and Redesign

Documentation

Project data bookA complete record

All key decisions

Good drawings

Test plans

Results

Conclusions

Things learned

Archimedes' Principle

Any object completely or partially submerged in a fluid is buoyed up by a

force whose magnitude is equal to the weight of the

fluid displaced by the object.

Buoyancy and Archimedes’ Principle

For a floating object, the fraction that is submerged is given by the ratio of the object’s density to that of the fluid.

Bernoulli’s Equation

A fluid can also change its height. By looking at the work done as it moves, we find:

This is Bernoulli’s equation. One thing it tells us is that as the speed goes up, the pressure goes down.

Concept of Drag

Drag is the resistive force exerted on a moving body in a fluid mediumIt does not attempt to turn the object, simply to slow it downIt is a function of the speed of the body, the size (and shape) of the body, and the fluid through which it is moving

Drag Force

The drag force due to a fluid acting on an object can be found by:

FD = ½ ρ CDV2A

where: FD = drag force (N)

CD = drag coefficient (no units)

V = velocity of object (m/s)A = projected area (m2)ρ = density of air (kg/m3) {1.2

kg/m3}