Tools and Methodologies for Improving Light Truck Design Architectures University of Louisville IMPA

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Tools and Methodologies for Improving Light Truck
Design Architectures University of Louisville
IMPACT TeamGlen Prater, Jr., Associate
ProfessorEllen G. Brehob, Assistant
ProfessorMichael L. Day, ProfessorJ.B. Speed
Scientific SchoolUniversity of
LouisvilleLouisville, KY 40292July 21, 1999
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Product Architecture
A machine, or product, is a combination of
physical components that perform functions -
particularly use, transformation, or transmission
of energy, force, or motion - for a specific
purpose. The architecture of a product is the
way in which functional elements are implemented
in the form of physical components, and the way
the groups interact.
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Product Architecture - Continued
Components may consist of single or multiple
parts, depending on the complexity of the overall
design or the assembly level of the current
design effort A fundamental design decision is
the assignment, or mapping, of functions to
components

• Designs where components are associated with one
  function or few functions, are described as
  modular
• Designs where components are associated with many
  functions are described as integral

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Product Architecture - Example
Function Mapping for an IBM XT Personal Computer
- Modular Architecture
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Product Architecture - Example
Function Mapping for a Laptop Computer - Integral
Architecture
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Implications of Product Architecture

• Production cost
• Form synthesis, aesthetics
• Product variety
• Life cycle - maintenance, replacement of
  consumable components, recycling and disposal
• Design evolution
• Component standardization
• Material and manufacturing process selection
• Strength and performance

Effect of Architecture Decisions on Production
Costs.
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Integral Architecture

• Production Costs The small number of parts
  associated with integral architecture can yield
  economies of scale.
• Form Synthesis May be more efficiently packaged
  than modular equivalents, resulting in more
  graceful shapes.
• Variety Integral designs tend to be difficult to
  change. Adaptation to new uses may require
  massive redesign.
• Life Cycle Difficult to separate out high wear
  components for replacement. Disassembly for
  recycling may be difficult.
• Design Evolution Changes tend to affect many
  components.
• Component Standardization The few components
  present in a integral design tend to be optimized
  for that special configuration.

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Integral Architecture - Continued

• Materials and Manufacturing Processes Molding
  and casting work well with integral
  architectures.
• Strength and Performance Combining functions in
  fewer components often reduces volume and weight,
  resulting in increased performance. Fewer
  components also results in fewer joints, a
  primary source of wear and failure. Internal load
  distributions can be optimized, improving
  strength.

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Modular Architecture

• Production Costs The large number of parts
  associated with modular architecture yield
  smaller economies of scale compared with integral
  architecture.
• Form Synthesis Functional components groups must
  be assembled, creating packaging difficulties,
  particularly in the area of joints. A modular
  product may look lumpy.
• Variety Sub-variants may be developed for new
  uses by changing a relatively small number of
  components. Option packages can be marketed.
• Life Cycle High wear components can be easily
  replaced. Disassembly for recycling is
  facilitated.
• Design Evolution Technological or stylistic
  changes can be made to appropriate components
  without affecting large numbers of other
  components.

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Modular Architecture - Continued

• Component Standardization The few components
  present in a integral design tend to be optimized
  for that special configuration.
• Strength and Performance Component proliferation
  may increase volume and weight, deducing
  performance. More components result in more joint
  interfaces, which may reduce strength and
  reliability.

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Design architecture is thus seen to play a
critical part in every aspect of the product life
cycle.
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Architecture Assessment
Methodology 1. Develop a product schematic that
identifies functional and physical system
elements. This schematic can is an excellent
starting point for the conceptual/preliminary
phase of the traditional design
process. 2. Cluster elements of the schematic
into functionally and geometrically related
systems (architecture units Ulrichs
chunks). 3. Identify fundamental and
incidental interactions show connections between
system elements. 4. Use interaction metrics to
assess modularity, joint strength, specific cost,
etc.
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Architecture Schematic for a DTM Selective Laser
Sintering Machine (Ulrich and Eppinger, 1995).
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Architecture Schematic for a DTM Selective Laser
Sintering Machine Displayed as an Interaction
Graph (Ulrich and Eppinger, 1995).
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Architecture Metrics
A number of parameters have been proposed for use
in assessing design architecture. Most begin by
defining component modules that perform single
basic functions, and then identifying the
interactions among those modules. Allen (1998)
proposes a modularity metric, am, and an
interaction metric, ai, defined by
Here Nm and Np denote the number of modules and
parts, respectively, while Nia denotes the total
number of interactions between modules. am ranges
between a very small value (for one module and
many parts, corresponding to an integrated
design), to 1.0 for a fully modular design where
each part performs a separate function.
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Architecture Metrics - Continued
Part connectivity, r, is is an excellent
architecture metric for structural systems whose
primary function is to transmit loads and control
motion (Steiner, 1999). r may initially
calculated based upon a simple average of the
number of connections per part. A normalized
part connectivity, rn, scales this to a quantity
from zero to one. Finally, an adjusted part
connectivity, ra, is calculated based upon the
practical upper boundary, rn,p, and minimum
limit, rn,min , of rn
Joint strength can be incorporated into the
modularity calculations associated with
structural systems, allowing the effect of
architecture on strength and stiffness to be
assessed.
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Architecture Metrics - Continued

• In addition to modularity, many other design
  parameters can be assessed from an architectural
  standpoint by using interaction graphs and the
  concept of component connectivity, including
• Assembly strength
• Stiffness
• Joint extent
• Specific cost
• These same parameters can be assessed for
  different external load configurations.

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IMPACT Architecture Group

• By adapting and extending these methodologies,
  the IMPACT Architecture Working Group will
  develop parametric and performance and cost
  prediction models that allow qualitative and
  qualitative assessment of vehicle design
  architecture. These methodologies will
• Allow association of physical and functional
  elements in the design.
• Permit specification of interactions (internal
  force flow, geometric constraints,
  thermal/acoustic energy transfer, corrosion
  paths), between element groups.
• Qualitatively depict the relationships between
  element groups using interaction graphs.
• Define metrics that quantitatively assess the
  efficiency of the design architecture in terms of
  applicable cost and performance models.

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IMPACT Architecture Group - Continued

• The group will implement these methodologies in a
  computer program. Program features include
• Direct interface with Ford CAD programs (SDRC
  Open Architecture).
• Sophisticated user interface, including online
  help and automatic report generation.
• Ability to be used for parametric studies.

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UL IMPACT Architecture Team - Faculty
Glen Prater Architecture methodologies and
metrics, software algorithm, group project
management, archival documentation (Phase I, 1.5
m-month, Phase II, 8.2 m-month). Ellen G. Brehob
Software interface features, software HTML help
system, intra-team interaction, monthly
documentation, software documentation (Phase I,
1.0 m-month, Phase II, 4.6 m-month). Michael L.
Day CAD integration, joint strengths, cost
metrics (Phase I, 0.7 m-month, Phase II, 3.0
m-month). Research Faculty 1 Architecture
methodologies and metrics (Phase II, 12
m-months). Research Faculty 2 Software
algorithm, coding and validation (Phase II, 12
m-months).
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UL IMPACT Architecture Team - Staff
Graduate Research Assistant 1 Software coding
and validation, Architecture modeling and
assessment, Phase I parametric studies (Phase I,
6 m-month). Graduate Research Assistant 2
Architecture modeling and assessment, Phase II
parametric architecture studies (Phase I, 6
m-month). Technician Hardware and software
computing support, experimental mechanics testing
in support of joint strength effort. (Phase II,
5.0 m-month).
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Bibliography
Allen, K.R. and Carlson-Skalak, S., Defining
Product Architecture During Conceptual Design,
Proceedings of DETC98 1998 ASME Design
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Identification of Limiting Factors for Improving
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Bibliography - Continued
Pancerella, C.M. and Whiteside, R.A., The
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