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Aerospace Systems Engineering A Modern Approach


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Title: Aerospace Systems Engineering A Modern Approach

Aerospace Systems EngineeringA Modern Approach
  • Dr. Daniel P. Schrage
  • Professor and Director,
  • Center of Excellence in Rotorcraft
  • Center for Aerospace Systems Analysis (CASA)

Course Materials
  • Primary Text, Dieter, Engineering Design A
    Materials and Processing Approach, 3rd Edition,
    McGraw Hill, 2000
  • Secondary Text,Systems Engineering Fundamentals
    Defense Systems Management College, 1998

The Product Design Process(Chapter 1, Dieter)
  • Introduction and Importance of Product Design
  • The Design Process A Simplified Approach
  • Considerations of a Good Design
  • Detailed Description of Design Process
  • Marketing
  • Organization for Design
  • Computer-Aided Engineering
  • Designing to Codes and Standards
  • Design Review
  • Technological Innovation and the Design Process

Some Important Concepts
  • Design to fashion after a plan (Webster
  • leaves out the essential fact that to design is
    to create something that has never been
  • Synthesis pulling together
  • Ability to design is both a science and an art
  • The science can be learned through techniques
  • The art is best learned by doing design
  • Discovery getting the first sight of, or the
    first knowledge of something, as when Columbus
    discovered America
  • Invention requires the design be a step beyond
    the limits of existing knowledge (beyond the
    state of the art). Some designs are truly
    inventive, but most are not

Integrated Synthesis and AnalysisVarying
Fidelity of Synthesis, Sizing Analysis
ynthesis Sizing
Integrated Routines

Table Lookup
Sophistication and


Conceptual Design Tools
First-Order Methods)
Approximating Functions
Direct Coupling of Analyses

Preliminary Design Tools
Higher-Order Methods)
Definition of Design(per Dieter)
  • Design establishes and defines solutions to and
    pertinent structures for problems not solved
    before, or new solutions to problems which have
    previously been solved in a different way

Good Design requires both Synthesis Analysis
  • Typically, we approach complex problems like
    design by decomposing the problem into manageable
    parts or components
  • Because we need to understand how the part will
    perform in service we must be able to calculate
    as much about the parts behavior as possible by
    using the appropriate disciplines of science and
    engineering science and the necessary
    computational tools
  • This is called Analysis and usually involves the
    simplification of the real world through models
  • Synthesis involves the identification of the
    design elements that will comprise the product,
    its decomposition into parts, and the combination
    of the part solutions into a total workable
  • In the typical design you rarely have a way of
    knowing the correct answer. Hopefully, your
    design works, but is it the best, most efficient
    design that could have been achieved under the
    conditions? Only time will tell

The Four Challenges (Cs) of the Design
  • Creativity
  • Requires creation of something that has not
    existed before or not existed in the designers
    mind before
  • Complexity
  • Requires decisions on many variables and
  • Choice
  • Requires making choices between many possible
    solutions at all levels, from basic concepts to
    smallest detail of shape
  • Compromise
  • Requires balancing multiple and sometimes
    conflicting requirements

Product Design Process
  • Engineering design process can be applied to
    several different ends
  • Design of Products, whether they be consumer
    goods and appliances or highly complex products
    such as missile systems or jet planes
  • Another is a complex engineered system such as an
    electric power generating station or a
    petrochemical plant
  • Yet another is the design of a building or bridge
  • The principles and methodology of design can be
    usefully applied in each of these situations.
    However, the emphasis in Dieters book is on
    product design and in this course is complex
    product design, specifically Aerospace Systems

Dieters Book Goal
  • Provide insight into the current best practices
    for doing product design
  • The design process should be conducted so as to
    develop quality cost-competitive products in the
    shortest time possible
  • Is necessary, but insufficient for Aerospace
    Systems Design

Japanese Auto Industry and The U.S. Auto Industry
The Quality Engineering Process provides
Recomposition Methods Tools
Knowledge Feedback
Quality Function Deployment Off-Line
Seven Management and Planing Tools Off-Line
Statistical Process Control On-Line
Robust Design Methods (Taguchi, Six - Sigma,
DOE) Off-Line
  • Identify Important Items
  • Variation Experiments
  • Make Improvements
  • Hold Gains
  • Continuous Improvement
  • Needs

Having heard the voice of the customer, QFD
prioritizes where improvements are needed
Taguchi provides the mechanism for identifying
these improvements
Traditional Design Development Using only a Top
Down Decomposition Systems Engineering Process
IPPD Environment for System Level Design Trades
and Cycle Time Reduction
Typical System Life Cycle Cost
100 75 50 25 0

Cumulative Percent of LCC

Life Cycle Cost Actually Expended

Production, Deployment, Operations and Support
Con Exp
Ramifications of the Quality Revolution
  • Decisions made in the design process cost very
    little in terms of the overall product cost but
    have a major effect on the cost of the product
  • Quality cannot be built into a product unless it
    is designed into it
  • The design process should be conducted so as to
    develop quality cost-competitive products in the
    shortest time possible

Design Process Paradigm Shift(Research
Opportunities in Engineering Design, NSF
Strategic Planning Workshop Final Report, April
  • A paradigm shift is underway that attempts to
    change the way complex systems are being designed
  • Emphasis has shifted from design for performance
    to design for affordability, where affordability
    is defined as the ratio of system effectiveness
    to system cost profit
  • System Cost - Performance Tradeoffs must be
    accommodated early
  • Downstream knowledge must be brought back to the
    early phases of design for system level tradeoffs
  • The design Freedom curve must be kept open until
    knowledgeable tradeoffs can be made

Static vs Dynamic Products
  • Some products are static, in that the changes in
    their design concept take place over a long time
    period rather, incremental changes occur at the
    subsystem and component levels (most air vehicles
    are static)
  • Other products are dynamic, like
    telecommunications systems and software, that
    change the basic design concept fairly frequently
    as the underlying technology changes (avionics
    and mission equipment software are dynamic)

Simplified Design Process
  • Definition of the Problem
  • Gathering Information
  • Generation of Alternative Solutions
  • Evaluation of Alternatives
  • Communication of the Results

Georgia Tech Generic IPPD Methodology
Detailed Description of Design Problems(Morris
Asimows Morphology of design)
  • Phase I. Conceptual Design
  • Phase II. Embodiment Design (Preliminary Design)
  • Phase III. Detail Design
  • Phase IV. Planning for Manufacture
  • Phase V. Planning for Distribution
  • Phase VI. Planning for Use
  • Phase VII. Planning for Retirement of the Product

Discrete Steps in Engineering Design Process
Design Depends on Individual Who Defines Problem
Classification of Products Based on Market
  • Platform Product
  • Is built around a preexisting technological
    subsystems, e.g. Apple Macintosh operating
  • Is similar to a technology-push product
  • Process-Intensive Products
  • Manufacturing process places strict constraints
    on the properties of the product
  • Examples are automotive sheet, steel, food
    products, semiconductors chemicals and paper
  • Customized Products
  • Variations in configuration and content created
    in response to a s

The Total Materials Cycle
The Systems Engineering Process
  • Process Input
  • Customer Needs/Objectives/ Requirements
  • - Missions
  • - Measures of Effectiveness
  • - Environments
  • - Constraints
  • Technology Base
  • Output Requirements from Prior Development
  • Program Decision Requirements
  • Requirements Applied Through
  • Specifications and Standards

System Analysis Control (Balance)
  • Requirements Analysis
  • Analyze Missions Environments
  • Identify Functional Requirements
  • Define/Refine Performance Design
  • Constraint Requirement
  • Trade-Off Studies
  • Effectiveness Analysis
  • Risk Management
  • Configuration Management
  • Interface Management
  • Performance Measurement
  • - SEMS
  • - TPM
  • - Technical Reviews

Requirement Loop
  • Functional Analysis/Allocation
  • Decompose to Lower-Level Functions
  • Allocate Performance Other Limiting
    Requirements to
  • All Functional Levels
  • Define/Refine Functional Interfaces
  • Define/Refine/Integrate Functional Architecture

Design Loop
  • Synthesis
  • Transform Architectures (Functional to Physical)
  • Define Alternative System Concepts,
  • Items System Elements
  • Select Preferred Product Process Solutions
  • Define/Refine Physical Interfaces

Related Terms Customer
Organization responsible for Primary Functions
Primary Functions Development,
Production/Construction, Verification,
Deployment, Operations,
Support Training, Disposal Systems Elements
Hardware, Software, Personnel, Facilities, Data,
Services, Techniques
  • Process Output
  • Development Level Dependant
  • - Decision Data Base
  • - System/Configuration Item
  • Architecture
  • - Specification Baseline

Systems Engineering, Its Purpose
  • To satisfy a mission need with a system
  • that is cost effective, operationally
  • suitable, and operationally effective.

Systems Engineering Objectives
  • Translate customer needs into balanced
    system/subsystem design requirements and product
  • Integrate technical inputs of the entire
    development community and all technical
    disciplines into a coordinated program effort
  • Transition new technologies into product and
    abatement program
  • Ensure the compatibility of all functional and
    physical interfaces
  • Verify that the product meets the established
  • Conduct a formal risk management and

What Is a System?
  • A system is a collection of components
    (subsystems) that
  • Interact with one another
  • Have emergent capabilities - capabilities above
    and beyond what the same collection of
    components would if they did not interact
  • Interacting components implies architecture

Elements of a System
  • Elements
  • Equipment Hardware
  • Software
  • Facilities
  • Personnel
  • Data
  • All elements are interrelated

System Element Constituents
  • Equipment Hardware
  • Mission hardware
  • Ground equipment
  • Maintenance equipment
  • Training equipment
  • Test equipment
  • Special equipment
  • Real Property
  • Spares

System Element Constituents (cont.)
  • Software
  • Instructions
  • Commands
  • Data
  • Facilities
  • Industrial
  • Operational
  • Training
  • Depot

Systems Engineering Principles Apply to All
Acquisition Phases at All Levels of the
Engineering Hierarchy
Levels in the System Hierarchy
System analysis/ control/evaluation
Requirements analysis
Functional analysis
  • System ofsystems
  • System
  • Segment
  • Subsegment
  • Item

CED - Concept Exploration/Definition PDRR -
Program Definition Risk Reduction
EMD - Engineering/Manufacturing Definition P/D -
Systems Engineering In IPD
Product Teams
Concurrent Development
Systems Engineering Process
Systems Engineering Process
Ability to Influence Cost
System Element Constituents (cont.)
  • Personnel
  • Training
  • Tasks
  • Number
  • Types and skills
  • Data
  • Parts Manuals
  • Maintenance Manuals
  • Operating Manuals

Systems Thinking
Roles of Systems Engineers
  • Requirements Owner
  • System Designer
  • System Analyst
  • Validation/Verification Engr
  • Logistics/Ops Engineer
  • Glue Among Subsystems
  • Customer Interface
  • Technical Manager
  • Information Manager
  • Process Engineer
  • Coordinator
  • Classified Ads SE

Source Twelve Roles of Systems Engineers, Sarah
Sheard URL
What Is a System?
  • A system is a collection of components
    (subsystems) that
  • Interact with one another
  • Have emergent capabilities - capabilities above
    and beyond what the same collection of
    components would if they did not interact
  • Interacting components implies architecture

Examples of Systems
  • Aircraft engine vs a collection of parts
  • Aircraft with engines and avionics
  • Air traffic control with aircraft, airfields,
    radars, controllers, CCS
  • Air transportation with air traffic control,
    airlines, passengers, cargo, maintenance,
    pickup and delivery

More Complex SystemsSystems of Systems
  • Individual systems can operate on their own
  • Systems of systems not owned and controlled as a
    whole by single entity
  • Mark Maier, Architecting Principles for
    Systems-of-Systems, Journal of the International
    Council on Systems Engineering, Vol I, 1998

Examples of Systems of Systems
  • Internet
  • Auto and truck transportation
  • Air Defense System maybe
  • National Airspace System (NAS)
  • Future Combat Systems (FCS) for the Objective
    Force Brigade (Unit of Action)

Technical Director Is the Systems Thinker
  • If not, objectives, approaches, and decisions
    will not reflect systems thinking
  • Technical Directors who dont think systems
    inhibit systems thinking on their project

Why Is Systems Thinking Good?
  • Intractable problems often have solutions in the
    design space of the larger system
  • Solutions in the larger systems space are often
    less costly or less risky
  • Integration with external systems are addressed
    early in the development

A Community Example
  • The Problem (or so they thought)
  • Trees, fuels and other natural resources are
    being used up, so we need to recycle them
  • The Solution (or so they thought)
  • Collect selected trash separately and sell it to
    recycling facilities

A Dose of Reality
  • Separate trash collections for recycleable would
    double the cost
  • Market for recycled newspaper and aluminum cans
    was saturated
  • Unsold recycleables would have to be stored --
    at additional cost

Starting to Think Systems
  • Who currently collects trash?
  • From whom?
  • What is done with the trash?

Answers and More Questions
  • Two trash collectors
  • One collects from homes
  • One collects from businesses
  • Does the collector from businesses separate the
  • Both put trash in land fills
  • Both pay to put trash in land fills
  • How much does it cost to put trash in a land

The Land Fills as Part of the System
  • 17 per ton to dump trash in the land fill
  • Expected to reach 30 per ton in 15 years
  • Land fills charge 150 per ton in New York
  • Gee, maybe we should think about conserving the
    land fills?

A Systems Solution
  • Two collections per week
  • One for recycleables
  • One for non-cycleable trash
  • Slight increase in fees for storing recycleables
  • Market demand of recycled paper and aluminum
    increase soared in 5 years

Consequences of Systems Thinking
  • The original objective (saving resources) was
  • Current costs were contained
  • Future cost containment made the slight increase
    saleable to the public

Dieter Chapter 2Need Identification and Problem
  • Of all the steps in the engineering design
    process, problem definition is the most important
  • Before the Problem-Definition Step Design
    projects commonly fall into one of five types
  • Variation of an existing product
  • Improvement of an existing product
  • Development of a new product for low-volume
    production run
  • Development of a new product for mass production
  • One-of-a-kind- design
  • Identifying Customer Needs
  • Gathering Information from Customers

Dieter Chapter 2Need Identification and Problem
  • Constructing a Survey Instrument
  • Benchmarking
  • Customer Requirements
  • Quality Function Deployment
  • Product Design Specification
  • The basic control and reference document for the
    design and manufacture of the product
  • In-Use Purposes and Market
  • Functional Requirments
  • Corporate Constraints
  • Social, Political and Legal Requirements

Presentation Outline
  • Synthesis and Sizing of Aerospace Vehicles
  • Maneuverability and Agility Considerations for
    Aerial Vehicles
  • Autonomous Vehicle Considerations
  • Summary and Conclusions

Synthesis and Sizing of Aerial Vehicles
  • For Aerial Vehicles Synthesis and Sizing provides
    the Closure between Mission Requirements and
    Geometric Configuration Solutions
  • A Fuel and Thrust/Power Balance Approach is used
    which allows for analytical design optimization
    (min. GW, etc.) through the coupling of a few
    critical design parameters (FWaspect ratio, wing
    loading RWdisk loading)
  • Maneuverability and Agility can be related to
    Energy Principles (differences between
    Thrust/Power Available and Thrust/Power
    Required), Handling Qualities and the design of
    the Flight Control System

Maneuverability and Agility Considerations for
Aerial Vehicles
  • Fixed Wing Fighter Aircraft normally have a good
    high speed capability, good maneuverability at
    normal combat speeds (medium to high subsonic and
    transonic speeds), high specific excess power,
    good to excellent avionics, and the ability to
    employ guns and a wide range of air-to-air
    missiles. To achieve these capabilities, their
    optimum maneuvering speeds are usually rather
    high, impacting on low speed maneuverability
  • Rotary Wing Aircraft have excellent low speed
    capability due to the rotor hub control moments
    which provides excellent control power in any
    axix. This allows rotary wing aircraft to fly
    Nap-of-the-Earth and stress aggressive concealed
    movement to take full advantage of masking
    provided by trees and terrain and attacking from
    a position of advantage at maximum standoff range

Summary and Conclusions
  • Aerial Vehicle Design and Performance is highly
    dependent on the Mission identified and use of a
    Fuel and Thrust/Power Synthesis Approach
  • For high speed, high altitude, high maneuvering
    attack missions, such as Suppression of Enemy Air
    Defense (SEAD), Fixed Wing Aerial Vehicle are the
  • For low speed, low altitude, high agility(along
    with vertical takeoff and landing
    (VTOL)capability) reconnaissance and attack
    missions, such as Urban Warfare, Rotary Wing
    Aerial Vehicles are the Choice

Technological Innovation and The Design Process
  • The advancement of technology has three phases
  • Invention The creative act whereby an idea is
  • Innovation The process by which an invention or
    idea is brought into successful practice and is
    utilized by the economy
  • Diffusion The successive and widespread
    initiation of successful innovation
  • The technological innovation activity can
    considered to be

Commerc Exploitation
Develop ment
Ident. Of Mkt Need
Product idea
Pilot lot
Trial sales
Successful products delineate four factors that
lead to success
  1. Product planning and research Products where
    adequate time was spent in problem definition
    concept development
  2. Product superiority Having a superior
    high-quality product that delivers real value to
    the customer makes all the differences between
    winning and losing
  3. Quality marketing High in importance is how well
    the marketing activities were executed from
    concept of the idea to the launch of the product
    in the marketplace
  4. Proper organizational design Successful products
    are most often developed by a cross-functional
    team, led by a product champion, supported by top
    management, and accountable for the entire
    project from beginning to end

Product and Process Cycles
  • Product Life Cycle and Cash Flow Analysis
  • Technology Development Cycle and S- Curves
  • Process Development Cycle
  • Uncoordinated development
  • Segmental development
  • Systematic development
  • Producition and Consumption Cycle

Societal Considerations in Engineering
  • Characteristics of an Environmentally Responsible
  • Five roles of government in interacting with
  • Technology Identification, Evaluation and
    Selection (TIES)

Dieter Chapter 3 Team Behavior and Tools
  • A team is a small number of people with
    complementary skills who are committed to a
    common purpose, performance goals, and approach
    for which they hold themselves mutually
  • Differences between a working group and a team
  • Working Group Team
  • -Strong, clearly focused leader -Individual
    mutual accountability
  • -The group,s purpose is the - Specific team
    purpose that the team
  • Same as the broader org.msn. Itself develops
  • Individual work products - Collective work
  • Runs efficient meetings - Encourages open-ended
  • and active problem-solving meetings
  • Measures its effectiveness - Measures performance
    directly by
  • indirectly by its influence assessing collective
    work products
  • -Discusses,decides and delegates - Discusses,
    decides and does real work
  • together

Dieter Chapter 3 Team Behavior and Tools
  • What It Means to be an Effective Team Member
  • Take responsibility for the success of the team
  • Be a person who delivers on commitments
  • Be a contributor to discussions
  • Give your full attention to whomever is speaking
    and demonstrate this by asking helpful questions
  • Develop techniques for getting your message
    across to the team
  • Learn to give and receive useful feedback
  • The following are characteristics of an effective
  • Team goals are as important as individual goals
  • The team understands the goals and is committed
    to achieving them
  • Trust replaces fear and people feel comfortable
    taking risks
  • Respect, collaboration and open-mindedness are
  • Team members communicate readily diversity of
    opinions are encouraged
  • Decisions are made by consensus and have the
    acceptance and support of the members of the team

Dieter Chapter 3 Team Behavior and Tools
  • TEAM ROLES Within a team members assume
    different roles in addition to being an active
    team member
  • TEAM DYNAMICSStudents of team behavior have
    observed that most teams go through five stages
    of development
  • EFFECTIVE TEAM MEETINGS Students who complain
    about design projects taking too much time often
    are really expressing their inability to organize
    their meetings and manage their time effectively
  • PROBLEMS WITH TEAMS A well-functioning team
    achieves its objectives quickly and efficiently
    in an environment that induces energy and

Dieter Chapter 3 Team Behavior and Tools

Dieter Chapter 5 Concept Generation and
  • With a clear product design specification
    developed in Chap. 2 we have arrived at the point
    where we are ready to generate design concepts,
    evaluate them, and decide which one will be
    carried forward to a final product
  • The principle that grades this work is that put
    forth by the American architect-engineer Louis
    Henri Sullivan, form follows function
  • By this we mean, if the functions of the design
    are clearly understood, then its appropriate form
    or structure will be easier to determine

Dieter Chapter 5 Concept Generation and
  • A design concept is an idea that is sufficiently
    developed that it can be evaluated in terms of
    physical realizability, i.e., the means of
    performing each major function has been
  • The process that is applied in this chapter will
    result in the generation of multiple design
  • Then, with a set of design concepts we will
    subject them to an evaluation scheme to determine
    the best concept or small subset of best concepts
  • Finally, a decision process will be used to
    decide on the best concept to develop into the
    final design

Dieter Chapter 5.2
-Creativity and Problem Solving
  • Creative thinkers are distinguished by their
    ability to synthesize new combinations of ideas
    and concepts into meaningful and useful forms
  • A characteristic of the creative process is that
    initially the idea is only imperfectly understood
  • Usually the creative individual senses the total
    structure of the idea but initially perceives
    only a limited number of the details
  • The creative process be viewed as moving from an
    amorphous idea to a well-structured idea, from
    the chaotic to the organized, from the implicit
    to the explicit
  • Engineers, by nature and training, usually value
    order and explicit detail and abhor chaos and
    vague generality
  • To achieve a truly creative solution to a problem
    a person must utilize two thinking styles
    vertical or convergent thinking and lateral or
    divergent thinking
  • Vertical thinking is the type of analytical
    though process reinforced by most engineering
    courses where one moves forward in sequential
    steps after a positive decision has been made
    about the idea
  • In lateral thinking your mind moves in may
    different directions, combining different pieces
    of information into new patterns (synthesis)
    until several solution concepts appear

Dieter Chapter 5.3 -Creativity Methods5.4
Creative Idea Evaluation
  • Mental Blocks Perceptual blocks, Emotional
    blocks, Cultural blocks, Environmental blocks,
    Intellectual blocks
  • Brainstorming Carefully define the problem at
    the start Allow 5 minutes for each individual to
    think the problem on their own before starting
    the group process SCAMPER checklist to aid in
  • Synectics technique for creative thinking which
    draws on analogical thinking Direct analogies,
    Personal analogies, Symbolic analogies, Fantasy
  • Force-Fitting Methods SCAMPER is one of most
    widely used methods
  • Mind Map Concept map

Dieter Chapter 5.5 Theory of Inventive Problem
Solving (TRIZ)
  • Developed in Russia, starting around 1946,
    Genrich Altshuller,etc. Studied over 1.5 million
  • They organized the problem solutions from the
    patent literature into five levels
  • Level 1 Routine design solutions (30)
  • Level 2 Minor corrections to an existing system
  • Level 3 Fundamental improvements which resolve
    contradiction (20) This is where creative
    design solutions would appear
  • Level 4 Solutions based on appln of new
    scientific principle to perform the primary
    functions of the design (4)
  • Level 5 Pioneering inventions based on rare
    scientific discovery (lt1)

Dieter Chapter 5.6 Conceptual Decomposition
  • Two chief approaches to conceptual decomposition
  • Decomposition in the physical domain
  • Decomposition in the functional domain the
    great advantage of functional decompostion is
    that the method facilitates the examination of
    options that most likely would not have been
  • Decomposition in the Physical Domain an
    important emerging design consideration is
    product architecture scheme by which the
    functional elements of the product are arranged
    into physical building blocks
  • Functional Decomposition systems functions are
    described as a transformation between an initial
    state and a desired final state originated with
    the German school of design methodology

Dieter Chapter 5.7 Generating Design Concepts
  • Concept Development
  • Morphological Chart
  • Combining Concepts

Dieter Chapter 5.8 Axiomatic Design
  • Axiom 1 The independence axiom
  • Maintain the independence of functional
    requirements (FRs)
  • Axiom 2 The information axiom
  • Minimize the information content

Dieter Chapter 6Embodiment (Preliminary) Design
  • Many U.S. writers divide the design process into
    3 phases
  • Conceptual Design
  • Preliminary (Embodiment) Design
  • Detail Design
  • Others call embodiment design analytical design
    because it is the design phase where most of the
    detailed analysis and calculation occurs
  • Dieter adopts the terminology conceptual design,
    embodiment design, and detail design because they
    seem to be more descriptive of what takes place
    in each of these design phases
  • Moving the setting of dimensions and tolerances
    into embodiment design (from detail design) is in
    keeping with the current trend for utilizing CAE
    so as to move the decision making as early as
    possible in the desing process to compress the
    product development cycle

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Dieter Chapter 6
  • Three different forms of design
  • Routine design the attributes that define the
    design and the strategies and methods for
    attaining them are well known
  • Innovative design not all attributes of the
    design may be known beforehand, but the knowledge
    base for creating the design is known
  • Creative design neither the attributes of the
    design nor the strategies for achieving them are
    known ahead of time
  • The Conceptual design phase is most central to
    innovative design
  • At the opposite pole is selection design or
    catalog design, which is more central to routine

Dieter Chapter 6Product Architecture
  • Product architecture is the arrangement of the
    physical elements of a product to carry out its
    required functions
  • It is in the Embodiment design phase that the
    layout and architecture of the product must be
    established by defining what the basic building
    blocks of the product should be in terms of what
    they do and what their interfaces will be between
    each other. Some organizations refer to this as
    system-level design
  • There are two entirely opposite styles of product
    architecture, modular and integral
  • Modular components (chunks) implement only one
    or a few functions and the interactions are well
  • Integral implementation of functions uses only
    one or a few components (chunks) leading to
    poorly defined interactions between components
  • In integral product achitectures components
    perform multiple functions
  • Products designed with high performance as a
    paramount attribute often have an integral

Dieter Chapter 6Product Architecture
  • A modular design makes it easier to evolve the
    design over time, to adapt it to the needs of
    different customers, to replenish components as
    they wear out or are used up, and to reuse the
    product at the end of its useful life by
  • Modular design may even be carried to the point
    of using the same component in multiple products,
    a product family
  • Integral desing is often adopted when constraints
    of weight,k space, or cost require that
    performance be maximized
  • There is a natural tension between component
    integration to minimize costs and product
  • The best approach is to consider integration of
    components only within a single chunk (set of
    components) of the product architecture
  • Thus, the product architecture has strong
    implications for manufacturing costs
  • A modular architecture tends to shorten the
    product development cycle becasuse module can be
    deveolped independently provided there is not
    coupling of functon betgween modules, and
    provided that interfaces are well laid out and

Dieter Chapter 6Product Architecture
  • Four step process for establishing the product
  • Create a schematic diagram of the product (FFBD,
    Schematic Block Diagram)
  • Cluster the elements of the schematic (DSM,
  • Create a rough geometric layout (3-view drawing)
  • Identify the fundamental and incidental
    interactions (Interrelationship Diagraph,
    Compatibility Matrix)

Dieter Chapter 6Configuration Design
  • In configuration design we establish the shape
    and general dimensions of components. Exact
    dimensions and tolerances are established in
    parametric design
  • The term component is used in the generic sense
    to include special-purpose parts, standard parts,
    and standard assemblies or modules
  • A part is a designed object that has no assembly
    operations in its manufacture
  • A standard part is one that has a generic
    function and is manufactured routinely w/o regard
    to a particular product (bolts, washers, etc.)
  • A special-purpose part is designed and
    manufactured for a specific purpose in a specific
    product line
  • An assembly is a collection of two or more parts
  • A subassembly is an assembly that is included
    within another assembly or subassembly
  • A standard assembly or standard module is an
    assembly or subassembly which has a generic
    function and is manufactured routinely (electric
    motors, pumps, etc.)

Dieter Chapter 6Configuration Design
  • Steps in starting Configuration design
  • Review the PDS
  • Establish the spatial constraints that pertain to
    th product or the subassembly being designed.
    Most have been set by the product architecture
  • Create and refine the interfaces or connections
    between components
  • Maintain functional independence in the design of
    an assembly or component
  • Answer the following questions
  • Can the part be eliminated or combine with
    another part?
  • Can a standard part or module be used
  • Generally, the best way to get started with
    configuration design is to just start sketching
    alternative configurations of a part

Dieter Chapter 6Parametric Design
  • In configuration design the emphasis was on
    starting with the product architecture and then
    working out the best form for each component
  • In parametric design the attributes of parts
    identified in configuration design become the
    design variables for parametric design
  • A design variable is an attribute of a part whose
    value is under the control of the designer
  • Robustness means achieving excellent performance
    under the wide range of conditions that will be
    found in service

Dieter Chapter 6Parametric Design
  • Read Table 6.2 Questions for revealing part
    configuration design risks
  • Failure Modes and Effects Analysis (FMEA)
  • Design for Reliability
  • Robust Design
  • Tolerances
  • Design Guidelines for Best Practices

Dieter Chapter 7Modeling and Simulation
  • The Role of Models in Engineering Design
  • Descriptive model
  • Predictive model
  • Static or dynamic
  • Deterministic or probabilistic
  • Iconic-analog-symbolic
  • Simulation
  • The Prototype

Dieter Chapter 7Modeling and Simulation
  • Mathematical Modeling
  • The components of a system are represented by
    idealized elements that have the essential
    characteristics of the real components and whose
    behavior can be described by mathematical
  • Techniques for treating large and complex systems
    by isolating the critical components and modeling
    them are at the heart of the growing discipline
    called systems engineering
  • Important simplification results when the
    distributed properties of physical quantities are
    replaced by their lumped equivalents.
  • A system is said to have lumped parameters if it
    can be analyzed in terms of the behavior of the
    endpoints of a finite number of discrete elements
  • Once the chief components of the system have been
    identified, the next step is to list the
    important physical and chemical quantities that
    describe and determine the behavior of the system

Dieter Chapter 7Modeling and Simulation
  • Dimensional Analysis
  • Buckingham Pi Theorem
  • Similitude and Scale Models
  • Scale models
  • Geometric similarity
  • Model dimension scale factor x prototype
  • Static similarity-same portion as geometric dim
    under cons. stress
  • Kinematic similarity- ratio of time
  • Dynamic similarity- fixed ratio of forces

Dieter Chapter 7Modeling and Simulation
  • Simulation
  • Finite-Difference Method
  • A method of approximate solution of partial
    differential equations
  • Monte Carlo Method
  • A way of generating information for a simulation
    when events occur in a random way
  • Geometric Modeling on the Computer
  • From it initiation,CAD has promised 5 important
    benefits to the engineering design process
  • Automation of routine design tasks
  • Ability to design in 3D
  • Design by Solid Modeling
  • Electronic transfer of the design db to manuf
  • A paperless design process

Dieter Chapter 7Modeling and Simulation
  • Surface Modeling
  • Methods of Generating Solids
  • Constraint-Based Modeler and Features
  • Finite-Element Analysis
  • Types of Elements
  • Steps in the FEA Process
  • Preprocessing Geometry, Matl constit reln, FE
    mesh, Bndy Conds
  • Postprocessing Data interpret., Error estim.,
    Design optim

Dieter Chapter 7Modeling and Simulation
  • Computer Visualization
  • Dynamic Analysis
  • Interactive Product Simulation
  • Rapid Prototyping

Dieter Chapter 8Materials Selection and
Materials in Design
  • The selection of the correct materials for a
    design is a key step in the process because it is
    the crucial decision that links computer
    calculations and lines on an engineering drawing
    with a working design
  • Materials, and the manufacturing processes which
    convert the material into a useful part, underpin
    all engineering design
  • The adoption of concurrent engineering methods
    has brought materials engineers into the design
    process at an earlier stage, and the importance
    given to manufacturing in present day product
    design has reinforced the fact that materials and
    manufacturing are closely linked in determining
    final product performance
  • The extensive activity in materials science
    worldwide has created a variety of new materials
    and focused our attention on the competition
    between six broad classes of materials metals,
    polymers, elastomers, ceramics, glasses, and

Dieter Chapter 8Materials Selection and
Materials in Design
  • Relation of Materials Selection to Design
  • An incorrectly chosen material can lead not only
    to failure of the part but also to unnecessary
    life-cycle cost
  • Selecting the best material for a part involves
    more than selecting a material that has the
    properties to provide the necessary performance
    in service it is also intimately connected with
    the processing of the material into the finished
    part (Fig. 8.1)
  • As design proceeds from concept design, the
    material and process selection becomes more
  • Figure 8.2 compares the design methods and tools
    used at each design stage with the materials and
    processes selection
  • Thus, material and process selection is a
    progressive process of narrowing from a large
    universe of possibilities to a specific material
    and process selection

Dieter Chapter 8Materials Selection and
Materials in Design
  • General Criteria for Selection Materials are
    selected on the basis of four general criteria
  • Performance characteristics (properties)
  • Processing characteristics
  • Environmental profile
  • Business considerations
  • The chief business consideration that affects
    materials selection is the cost of the part that
    is made from the material
  • This considers both the purchase cost of the
    material and the cost to process it into a part.
    A more rational basis for selection is life cycle
    cost (LCC), which includes the cost of replacing
    failed parts and the cost of disposing of the
    material at the end of its useful life

Dieter Chapter 8Materials Selection and
Materials in Design
  • Performance Characteristics of Materials
  • The performance or functional requirements of
    material usually is expressed in terms of
    physical, mechanical, thermal, electrical, or
    chemical properties
  • Material properties are the link between the
    basic structure and composition of the material
    and the service performance of the part (Figure
  • We can divide structural engineering materials
    into metals, ceramics, and polymers Further
    division leads to the categories of elastomers,
    glasses, and composites Finally, there is the
    technology driving class of electronic, magnetic,
    and semiconductor materials
  • The chief characteristics of metals, ceramics,
    and polymers are given in Table 8.1

Dieter Chapter 8Materials Selection and
Materials in Design
  • Performance Characteristics of Materials
  • The ultimate goal of materials science is to
    predict how to improve the properties of
    engineering materials by understanding how to
    control the various aspects of structure
  • Figure 8.4 relates various dimensions of
    structure with typical structural elements
  • The first task in materials selection is to
    determine which material properties are relevant
    to the situation
  • Figure 8.5 shows the relations between some
    common failure modes and the mechanical
    properties most closely related to the failures
  • The material properties usually are formalized
    through specifications Performance and Product
  • Table 8.2 provides a fairly complete listing of
    material performance characteristics
  • Figure 8.6 illustrates the generic tree that is
    developed by expanding the category of fatigue

Dieter Chapter 8Materials Selection and
Materials in Design
  • The Materials Selection Process
  • The problem is not only often made difficult by
    insufficient or inaccurate property data but is
    typically one of decision making in the face of
    multiple constraints without a clear-cut
    objective function
  • A problem of materials selection usually involves
    one of two different situations
  • Selection of the materials for a new product or
  • Reevaluation of an existing product or design to
    reduce cost, increase reliability, improve
    performance, etc.
  • It generally is not possible to realize the full
    potential of a new material unless the product is
    redesigned to exploit both the properties and the
    manufacturing characteristics of the material
  • In other words, a simple substitution of a new
    material without changing the design rarely
    provides optimum utilization of the material

Dieter Chapter 8Materials Selection and
Materials in Design
  • Materials selection for a new product or new
    design The steps that must be followed are
  • Define the functions that the design must perform
  • Define the manufacturing parameters
  • Compare the needed properties and parameters with
    large database
  • Investigate the candidate materials in more
  • Develop design data and/or a design specification
  • Materials substitution in an existing design
  • Characterize the currently used material in terms
    of performance, manufacturing requirements, and
  • Determine which characteristics must be improved
    for enhanced product function
  • Search for alternative matls processing routes
  • Compile a short list of matls processing routes
    and use these to estimate the costs of
    manufactured parts
  • Evaluate the results of Step 4 make a
    recommendation for a replacement material

Dieter Chapter 8Materials Selection and
Materials in Design
  • Design Process and Materials Selection
  • There are two approaches to determing the
    material-process combination for a part
  • Material first approach the designer begins by
    selecting a material class and narrowing it down
  • Process first approach the designer begins by
    selecting the manufacturing process
  • While materials selection issues arise at every
    stage in the design process, the opportunity for
    greatest innovation in materials selection occurs
    at the conceptual design stage
  • Ashby Charts Figure 8.7a Youngs modulus vs
    density Figure 8.7b Strength vs density

Dieter Chapter 8Materials Selection and
Materials in Design
  • Materials Selection in Embodiment (Preliminary)
  • Detailed materials selection is typically carried
    out in the embodiment design phase using the
    process illustrated in Fig. 8.8
  • When the material process selection is deemed
    adequate for the requirements, the process passes
    to a detailed specification of the material and
    the design
  • Once the component goes into production, the
    early runs will be used to fine tune the
    manufacturing process and to gauge the market
    receptivity to the product

Dieter Chapter 8Materials Selection and
Materials in Design
  • Sources of Information on Materials Properties
  • The purpose of this section is to provide a guide
    to material property data that are readily
    available in the published technical literature
  • Scatter or variability of material property
    results is considerable, however, it is rare to
    find a property data presented in a proper
    statistical manner by a mean value and the
    standard deviation (See Chap. 10)
  • Obviously, for critical applications in which
    reliability is of great importance, it is
    necessary to determine the frequency distribution
    of both the material property and the parameter
    that describes the service behavior
  • Figure 8.9 shows that when the two frequency
    distributions overlap, there will be a
    statistically predictable number of failures

Dieter Chapter 8Materials Selection and
Materials in Design
  • Sources of Information on Materials Properties
  • Conceptual Design
  • Typical material selection references, such as
    Ashby scheme
  • Embodiment (Preliminary) Design
  • Design decisions are being made on the layout and
    size of parts and components
  • Design calculations require materials properties
    for a narrower class of materials but specific to
    a particular heat treatment or manufacturing
  • These data are typically found in handbooks and
    computer dbs.
  • Detail Design
  • Very precise data is required
  • This goes beyond just material properties to
    include information on manufacturability, cost,
    the experience in other applns, avail in the
    sizes and forms needed, and issues of repeat. of
    properties QA
  • Two often overlooked factors are whether the
    manufacturing process will produce different
    properties in different directions in the part,
    and whether the part will contain a detrimental
    state of residual stress after manufacture

Dieter Chapter 8Materials Selection and
Materials in Design
  • Economics of Materials
  • Ultimately the decision on a particular design
    will come down to a trade-off between performance
    and cost
  • Where performance doesnt dominate the
    manufacturer must provide a value to cost ratio
    that is no worse, and preferably better,
  • than the competition
  • By value we mean the extent to which the
    performance criteria appropriate to the
    application are satisfied. Cost is what must be
    paid to achieve that level of value
  • Because cost is such an overpowering
    consideration in material selection we need to
    give this factor additional attention
  • Scarcity - Cost amount of energy required to
  • Basic supply demand for the material
  • Increases in properties, like yield strength,
    beyond those of the basic material are produced
    by changes in structure brought about by
    compositional changes and additional processing

Dieter Chapter 8Materials Selection and
Materials in Design
  • Methods of Materials Selection
  • There is no method or small number of methods of
    materials selection that has evolved to a
    position of prominence
  • Since the final choice is a trade-off between
    cost and performance (properties), it is logical
    to attempt to express that relation as carefully
    as possible
  • Figure 8.10 shows the costs of substituting
    lightweight magterials to achieve weight saving
    (fuel economy) in automobiles
  • It is important to realize that the cost of a
    material expressed in dollars per pound may not
    always be the most valid criterion
  • Total LLC is the most appropriate cost to
  • Consideration of factors beyond just the initial
    materials cost leads to relations like the
    relation shown in Figure 8.11
  • A classic situation regarding cost is the choice
    between two or more materials with different
    initial costs and different expected lives. This
    is a standard problem in the field of engineering
    economy (See Chap. 13)

Dieter Chapter 8Materials Selection and
Materials in Design
  • Selection with Computer-Aided Databases
  • Use of a Merit Factor approach similar to an OEC
  • Material Performance Indices
  • A materials performance index is a group of
    material properties which governs some aspect of
    the performance of a component
  • Decision Matrices
  • Pugh Selection Method
  • Weighted Property Index
  • Materials Selection by Expert Systems
  • Value Analysis

Dieter Chapter 8Materials Selection and
Materials in Design
  • Design for Brittle Fracture An important advance
    in engineering knowledge has been the ability to
    predict the influence of cracks and crack-like
    defects on the brittle fracture of materials
    through the science of fracture mechanics
  • Design for Fatigue Failure Materials subjected
    to a repetitive or fluctuating stress will fail
    at a stress much lower than required to cause
    fracture on a single application of load
  • Infinite-life design
  • Safe-life design
  • Fail-safe design
  • Damage-tolerance design
  • Design for Corrosion Resistance
  • Designing with Plastics
  • Designing with Brittle Materials

Dieter Chapter 9Materials Processing and Design
  • Role of Processing in Design
  • Producing the design is a critical link in the
    chain of events that starts with a creative idea
    and ends with a successful product in the
  • A serious problem has been the tendency
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