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Research Papers

Designing Microstructural Architectures With Thermally Actuated Properties Using Freedom, Actuation, and Constraint Topologies

[+] Author and Article Information
Jonathan B. Hopkins

e-mail: hopkins30@llnl.gov

Kyle J. Lange

e-mail: lange9@llnl.gov

Christopher M. Spadaccini

e-mail: spadaccini2@llnl.gov
Lawrence Livermore National Laboratory,
7000 East Avenue,
Livermore, CA 94551

Contributed by the Design Automation Committee of ASME for publication in the JOURNAL OF MECHANICAL DESIGN. Manuscript received April 6, 2012; final manuscript received March 5, 2013; published online May 9, 2013. Assoc. Editor: Shinji Nishiwaki.This material is declared a work of the US Government and is not subject to copyright protection in the United States. Approved for public release; distribution is unlimited.

J. Mech. Des 135(6), 061004 (May 09, 2013) (10 pages) Paper No: MD-12-1196; doi: 10.1115/1.4024122 History: Received April 06, 2012; Revised March 05, 2013

In this paper, we demonstrate how the principles of the freedom, actuation, and constraint topologies (FACT) approach may be applied to the synthesis, analysis, and optimization of microstructural architectures that possess extreme or unusual thermal expansion properties (e.g., zero or large negative-thermal expansion coefficients). FACT provides designers with a comprehensive library of geometric shapes, which may be used to visualize the regions wherein various microstructural elements can be placed for achieving desired bulk material properties. In this way, designers can rapidly consider and compare a multiplicity of microstructural concepts that satisfy the desired design requirements before selecting the final concept. A complementary analytical tool is also provided to help designers rapidly calculate and optimize the desired thermal properties of the microstructural concepts that are generated using FACT. As a case study, this tool is used to calculate the negative-thermal expansion coefficient of a microstructural architecture synthesized using FACT. The result of this calculation is verified using a finite element analysis (FEA) package called ale3d.

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Figures

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Fig. 3

The system's complementary freedom and constraint space pair (a). The flexible constraints lie within the system's constraint space (b).

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Fig. 4

The system's actuation space (a). Selecting thermally actuated constraints from within the actuation space (b). Selectively heating each thermally actuated constraint by different temperatures causes the stage to move with various combinations of its DOFs (c).

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Fig. 5

A blank 2D lattice for synthesizing thermally actuated microstructural architectures (a) and a general design space sector for achieving a microstructural architecture with a negative-thermal expansion coefficient (b)

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Fig. 2

A parallel flexure system's three DOFs (a)–(c) and its freedom space (d)

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Fig. 6

Two negative-thermal-expansion sectors with actuation elements that do not lie within the system's actuation space (a) and (b). The sectors' unit cells (c) and (d).

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Fig. 7

A sector example with no flexure bearing elements (a) and its unit cell (b).

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Fig. 1

2D microstructural architecture designs (a) and (b) that consist of unit cells made up of triangular sectors. These sectors (c) are designed using the geometric shapes of FACT (d).

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Fig. 8

Parameters necessary to calculate the thermal expansion coefficient of a unit cell, which is modeled as small rigid bodies (shown in black) connected by flexible elements

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Fig. 9

Parameters and conventions necessary to construct Eq. (3) for a general microstructural architecture

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Fig. 10

Dimensions for the microstructural architecture (a). An ale3d mesh of the deformed architecture when subject to an increase in temperature (b).

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Fig. 11

Comparison of this architecture's thermal expansion coefficient calculated using FEA verses the analytical tool of this paper

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