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

2013 ◽  
Vol 135 (6) ◽  
Author(s):  
Jonathan B. Hopkins ◽  
Kyle J. Lange ◽  
Christopher M. Spadaccini
Keyword(s):  
Thermal Expansion ◽  
Bulk Material ◽  
Negative Thermal Expansion ◽  
Element Analysis ◽  
Thermal Expansion Coefficients ◽  
Design Requirements ◽  
Expansion Coefficients ◽  
Thermally Actuated ◽  
Constraint Topologies

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.

Synthesizing the Compliant Microstructure of Thermally Actuated Materials Using Freedom, Actuation, and Constraint Topologies

2012 ◽  
Author(s):  
Jonathan B. Hopkins ◽  
Kyle J. Lange ◽  
Christopher M. Spadaccini
Keyword(s):  
Thermal Expansion ◽  
Screw Theory ◽  
Bulk Material ◽  
Negative Thermal Expansion ◽  
Thermal Expansion Coefficients ◽  
Final Design ◽  
Expansion Coefficients ◽  
Thermally Actuated ◽  
Constraint Topologies

The aim of this paper is to demonstrate how the principles of the Freedom, Actuation, and Constraint Topologies (FACT) synthesis approach may be applied to the design of compliant 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 every microstructural concept that best satisfies the design requirements before selecting the final design. A screw-theory-based analytical tool is also provided in this paper to help designers calculate and optimize the thermal properties of microstructural concepts, which 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.

Design of Nonperiodic Microarchitectured Materials That Achieve Graded Thermal Expansions

2016 ◽  
Vol 8 (5) ◽  
Author(s):  
Jonathan B. Hopkins ◽  
Lucas A. Shaw ◽  
Todd H. Weisgraber ◽  
George R. Farquar ◽  
Chris D. Harvey ◽  
...  
Keyword(s):  
Thermal Expansion ◽  
Compliant Mechanism ◽  
System Level ◽  
Element Analysis ◽  
Ambient Temperatures ◽  
Thermal Expansion Coefficients ◽  
Layered Coatings ◽  
Unit Cells ◽  
Expansion Coefficients

The aim of this paper is to introduce an approach for optimally organizing a variety of nonrepeating compliant-mechanism-like unit cells within a large deformable lattice such that the bulk behavior of the lattice exhibits a desired graded change in thermal expansion while achieving a desired uniform stiffness over its geometry. Such lattices with nonrepeating unit cells, called nonperiodic microarchitectured materials, could be sandwiched between two materials with different thermal expansion coefficients to accommodate their different expansions and/or contractions induced by changing ambient temperatures. This capability would reduce system-level failures within robots, mechanisms, electronic modules, or other layered coatings or structures made of different materials with mismatched thermal expansion coefficients. The closed-form analytical equations are provided, which are necessary to rapidly calculate the bulk thermal expansion coefficient and Young's modulus of general multimaterial lattices that consist first of repeating unit cells of the same design (i.e., periodic microarchitectured materials). Then, these equations are utilized in an iterative way to generate different rows of repeating unit cells of the same design that are layered together to achieve nonperiodic microarchitectured material lattices such that their top and bottom rows achieve the same desired thermal expansion coefficients as the two materials between which the lattice is sandwiched. A matlab tool is used to generate images of the undeformed and deformed lattices to verify their behavior and an example is provided as a case study. The theory provided is also verified and validated using finite-element analysis (FEA) and experimentation.

scholarly journals Organizing Cells Within Non-Periodic Microarchitectured Materials That Achieve Graded Thermal Expansions

2015 ◽  
Author(s):  
Jonathan B. Hopkins ◽  
Lucas A. Shaw ◽  
Todd H. Weisgraber ◽  
George R. Farquar ◽  
Christopher D. Harvey ◽  
...  
Keyword(s):  
Finite Element Analysis ◽  
Thermal Expansion ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Element Analysis ◽  
Thermal Expansion Coefficients ◽  
Large Lattice ◽  
Unit Cells ◽  
Expansion Coefficients ◽  
Bulk Behavior

The aim of this paper is to introduce an approach for optimally organizing a variety of different unit cell designs within a large lattice such that the bulk behavior of the lattice exhibits a desired Young’s modulus with a graded change in thermal expansion over its geometry. This lattice, called a graded microarchitectured material, can be sandwiched between two other materials with different thermal expansion coefficients to accommodate their different expansions or contractions caused by changing temperature while achieving a desired uniform stiffness. First, this paper provides the theory necessary to calculate the thermal expansion and Young’s modulus of large multi-material lattices that consist of periodic (i.e., repeating) unit cells of the same design. Then it introduces the theory for calculating the graded thermal expansions of a large multimaterial lattice that consists of non-periodic unit cells of different designs. An approach is then provided for optimally designing and organizing different unit cells within a lattice such that both of its ends achieve the same thermal expansion as the two materials between which the lattice is sandwiched. A MATLAB tool is used to generate images of the undeformed and deformed lattices to verify their behavior and various examples are provided as case studies. The theory provided is also verified and validated using finite element analysis and experimentation.

Negative Thermal Expansion of Yb2Mo3O12 and Lu2Mo3O12

2008 ◽  
Vol 368-372 ◽  
pp. 1662-1664 ◽  
Author(s):  
X.L. Xiao ◽  
M.M. Wu ◽  
J. Peng ◽  
Y.Z. Cheng ◽  
Zhong Bo Hu
Keyword(s):  
Thermal Expansion ◽  
Solid State ◽  
Solid State Reaction ◽  
Linear Thermal Expansion ◽  
Negative Thermal Expansion ◽  
Orthorhombic Structure ◽  
Conventional Solid State Reaction ◽  
Temperature Range ◽  
Thermal Expansion Coefficients ◽  
Expansion Coefficients

Compounds Yb2Mo3O12 and Lu2Mo3O12 were prepared by conventional solid-state reaction. Their crystal structures and thermal expansion properties were investigated. It was found that Yb2Mo3O12 and Lu2Mo3O12 adopt orthorhombic structure and show negative thermal expansion (NTE) in the temperature range of 200-800 °C. Their a-axis and c-axis exhibit stronger contraction in the temperature range of 200-800 °C, while b-axis slightly expands in the temperature range of 200-300 °C and then contracts in the temperature range of 300-800 °C. The linear thermal expansion coefficients al of Yb2Mo3O12 and Lu2Mo3O12 are −5.17 × 10−6 °C−1 and −5.67 × 10−6 °C−1, respectively.

scholarly journals Thermal expansion coefficient of few-layer MoS2 studied by temperature-dependent Raman spectroscopy

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Zhongtao Lin ◽  
Wuguo Liu ◽  
Shibing Tian ◽  
Ke Zhu ◽  
Yuan Huang ◽  
...  
Keyword(s):  
Raman Spectroscopy ◽  
Thermal Expansion ◽  
Thermal Expansion Coefficient ◽  
Expansion Coefficient ◽  
Negative Thermal Expansion ◽  
Thermal Parameter ◽  
Temperature Dependent ◽  
Bending Vibrations ◽  
Thermal Expansion Coefficients ◽  
Expansion Coefficients

AbstractThe thermal expansion coefficient is an important thermal parameter that influences the performance of nanodevices based on two-dimensional materials. To obtain the thermal expansion coefficient of few-layer MoS2, suspended MoS2 and supported MoS2 were systematically investigated using Raman spectroscopy in the temperature range from 77 to 557 K. The temperature-dependent evolution of the Raman frequency shift for suspended MoS2 exhibited prominent differences from that for supported MoS2, obviously demonstrating the effect due to the thermal expansion coefficient mismatch between MoS2 and the substrate. The intrinsic thermal expansion coefficients of MoS2 with different numbers of layers were calculated. Interestingly, negative thermal expansion coefficients were obtained below 175 K, which was attributed to the bending vibrations in the MoS2 layer during cooling. Our results demonstrate that Raman spectroscopy is a feasible tool for investigating the thermal properties of few-layer MoS2 and will provide useful information for its further application in photoelectronic devices.

THERMAL EXPANSION OF ZrO2-ZrW2O8 COMPOSITES PREPARED USING CO-PRECIPITATION ROUTE

2009 ◽  
Vol 23 (06n07) ◽  
pp. 1449-1454 ◽  
Author(s):  
HONGFEI LIU ◽  
ZHIPING ZHANG ◽  
XIAONONG CHENG ◽  
JUAN YANG
Keyword(s):  
Thermal Expansion ◽  
Negative Thermal Expansion ◽  
Ceramic Composites ◽  
Sem Analysis ◽  
X Ray Diffraction ◽  
X Ray ◽  
Thermal Expansion Coefficients ◽  
Expansion Coefficients ◽  
Co Precipitation ◽  
Scanning Electron

In this work, a series of ZrO 2/ ZrW 2 O 8 ceramic composites with different amounts of ZrW 2 O 8 were successfully prepared by calcining the precursors synthesized using co-precipitation route at 1150°C for 3 h. The X-ray diffraction (XRD) data confirmed that the composites only consisted of α- ZrW 2 O 8 phase and m - ZrO 2 phase. The scanning electron microscopy (SEM) analysis of the synthesized ZrO 2/ ZrW 2 O 8 composites showed that the specimens had good mixed-uniformities. In addition, the thermal expansion coefficients of the composites decreased with increased amounts of negative thermal expansion ZrW 2 O 8, specimen with 26wt% ZrW 2 O 8 shows almost zero thermal expansion and its average thermal expansion coefficient is -0.5897×10-6K-1 in the temperature range from 30°C to 600°C.

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