scholarly journals Bi-Material Negative Thermal Expansion Inverted Trapezoid Lattice based on A Composite Rod

Materials ◽  
2019 ◽  
Vol 12 (20) ◽  
pp. 3379 ◽  
Author(s):  
Weipeng Luo ◽  
Shuai Xue ◽  
Meng Zhang ◽  
Cun Zhao ◽  
Guoxi Li
Keyword(s):  
Finite Element ◽  
Thermal Expansion ◽  
Experimental Verification ◽  
Negative Thermal Expansion ◽  
Engineering Application ◽  
Vertical Direction ◽  
Aerospace Engineering ◽  
Large Temperature ◽  
Composite Rod ◽  
Order Of Magnitude

Negative thermal expansion (NTE) lattices are widely used in aerospace engineering where the structures experience large temperature variation. However, the available range of NTE of the current lattices is quite narrow, which severely limits their engineering application. In this paper, we report an inverted trapezoid lattice (ITL) with large NTE. The NTE of the ITL is 2.6 times that of a typical triangular lattice with the same height and hypotenuse angle. Theoretically, with a pin-jointed assumption, the ITL can improve the NTE by order of magnitude if the length ratio of the composite rod is changed. In the presented ITL, a composite rod is utilized as the base of the ITL. The composite rod has large inner NTE. The inverted trapezoid structure converts the inner NTE to the vertical direction contraction and obtains an extra NTE. Finite element simulations and experimental verification by interferometric measurement were conducted to verify the large thermal expansion of the ITL.

Designing Lightweight Tensegrity-Based Structures and Materials of Tailorable Thermal Expansion

2019 ◽  
Author(s):  
Rochelle E. Silverman ◽  
Edwin A. Peraza Hernandez
Keyword(s):  
Thermal Expansion ◽  
Thermal Stresses ◽  
Low Complexity ◽  
Aerospace Engineering ◽  
Positive Zero ◽  
Large Temperature ◽  
New Materials ◽  
Temperature Changes ◽  
Wide Range ◽  
First Time

Abstract In this work, we analyze and design structures and materials that possess custom thermal expansion. These structures and materials are composed of a base unit inspired by the tensegrity “D-bar” (or double-pyramid) topology. We derive, for the first time, analytical equations for the linearized and geometrically exact coefficients of thermal expansion (CTEs) of bi-material D-bar structures with arbitrary shape and complexity. Numerical results obtained using the geometrically exact CTE equations are compared with results obtained using the linearized CTE equations, showing that the latter are accurate only in cases where temperature changes are small. Further results show that D-bar structures of low complexity can produce a wide range of CTEs, including positive, zero, and negative values. These CTE values are exhibited for a range of materials that allows for easy manufacturing (materials with CTE ratios as low as 2). Thus, it is concluded that D-bar structures show promise for applications in aerospace engineering and other fields where new materials of tailorable thermal expansion are needed to decrease the substantial thermal stresses caused by large temperature changes.

Plutonium Elastic Moduli, Electron Localization, and Temperature

2008 ◽  
Vol 1104 ◽  
Author(s):  
Albert Migliori ◽  
Izabella Mihut-Stroe ◽  
Jon B. Betts
Keyword(s):  
Thermal Expansion ◽  
Elastic Moduli ◽  
Negative Thermal Expansion ◽  
Orthorhombic Phase ◽  
Elastic Stiffness ◽  
Cubic Phase ◽  
Electron Localization ◽  
Face Centered Cubic ◽  
Order Of Magnitude ◽  
Almost All

AbstractIn almost all materials, compression is accompanied naturally by stiffening. Even in materials with zero or negative thermal expansion, where warming is accompanied by volume contraction it is the volume change that primarily controls elastic stiffness. Not so in the metal plutonium. In plutonium, alloying with gallium can change the sign of thermal expansion, but for the positive-thermal-expansion monoclinic phase as well as the face-centered-cubic phase with either sign of thermal expansion, and the orthorhombic phase, recent measurements of elastic moduli show soften on warming by an order of magnitude more than expected, the shear and compressional moduli track, and volume seems irrelevant. These effects point toward a novel mechanism for electron localization, and have important implication for the pressure dependence of the bulk compressibility.

Development of Strong Surfaces Using Functionally Graded Composites Inspired by Natural Teeth—Finite Element and Experimental Verification

2009 ◽  
Vol 132 (1) ◽  
Author(s):  
Th. Zisis ◽  
A. Kordolemis ◽  
A. E. Giannakopoulos
Keyword(s):  
Finite Element ◽  
Experimental Verification ◽  
High Surface ◽  
Engineering Application ◽  
Strength Properties ◽  
Functionally Graded ◽  
Element Analysis ◽  
Surface Strength ◽  
Human Teeth ◽  
Local Material Properties

Functionally graded materials (FGMs) are composite materials that exhibit a microstructure that varies locally in order to achieve a specific type of local material properties distribution. In recent years, FGMs appear to be more interesting in engineering application since they present an enhanced performance against deformation, fracture, and fatigue. The purpose of the present work is to present evidence of the excellent strength properties of a new graded composite that is inspired by the human teeth. The outer surface of the teeth exhibits high surface strength while it is brittle and wear resistant, whereas the inner part is softer and flexible. The specific variation in Young’s modulus along the thickness of the presented composite is of particular interest in our case. The present work presents a finite element analysis and an experimental verification of an actual composite with elastic modulus that follows approximately the theoretical distribution observed in the teeth.

A Fracture Mechanics Based Parametric Study of the Copper-to-Copper Direct Thermo-Compression Bonded Interface Using Finite Element Method

2013 ◽  
Author(s):  
Ah-Young Park ◽  
Satish Chaparala ◽  
Seungbae Park
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Parametric Study ◽  
Initial Crack ◽  
Bonding Interface ◽  
Interface Condition ◽  
Large Temperature ◽  
Bonded Interface ◽  
The Impact ◽  
Element Method

Through-silicon via (TSV) technology is expected to overcome the limitations of I/O density and helps in enhancing system performance of conventional flip chip packages. One of the challenges for producing reliable TSV packages is the stacking and joining of thin wafers or dies. In the case of the conventional solder interconnections, many reliability issues arise at the interface between solder and copper bump. As an alternative solution, Cu-Cu direct thermo-compression bonding (CuDB) is a possible option to enable three-dimension (3D) package integration. CuDB has several advantages over the solder based micro bump joining, such as reduction in soldering process steps, enabling higher interconnect density, enhanced thermal conductivity and decreased concerns about intermetallic compounds (IMC) formation. Critical issue of CuDB is bonding interface condition. After the bonding process, Cu-Cu direct bonding interface is obtained. However, several researchers have reported small voids at the bonded interface. These defects can act as an initial crack which may lead to eventual fracture of the interface. The fracture could happen due to the thermal expansion coefficient (CTE) mismatch between the substrate and the chip during the postbonding process, board level reflow or thermal cycling with large temperature changes. In this study, a quantitative assessment of the energy release rate has been made at the CuDB interface during temperature change finite element method (FEM). A parametric study is conducted to analyze the impact of the initial crack location and the material properties of surrounding materials. Finally, design recommendations are provided to minimize the probability of interfacial delamination in CuDB.

scholarly journals Theoretical analysis and experimental research on multi-layer elastic damping track structure

2021 ◽  
Vol 13 (2) ◽  
pp. 168781402199497
Author(s):  
Guanghui Xu ◽  
Shengkai Su ◽  
Anbin Wang ◽  
Ruolin Hu
Keyword(s):  
Finite Element ◽  
Analytical Solution ◽  
Finite Element Simulation ◽  
Reaction Force ◽  
Vibration Reduction ◽  
Vertical Direction ◽  
Propagation Path ◽  
Track Structure ◽  
Test Results ◽  
Element Simulation

The increase of axle load and train speed would cause intense wheelrail interactions, and lead to potential vibration related problems in train operation. For the low-frequency vibration reduction of a track system, a multi-layer track structure was proposed and analyzed theoretically and experimentally. Firstly, the analytical solution was derived theoretically, and followed by a parametric analysis to verify the vibration reduction performance. Then, a finite element simulation is carried out to highlight the influence of the tuned slab damper. Finally, the vibration and noise tests are performed to verify the results of the analytical solution and finite element simulation. As the finite element simulation indicates, after installation of the tuned slab damper, the peak reaction force of the foundation can be reduced by 60%, and the peak value of the vertical vibration acceleration would decrease by 50%. The vibration test results show that the insertion losses for the total vibration levels are 13.3 dB in the vertical direction and 21.7 dB in the transverse direction. The noise test results show that the data of each measurement point is smoother and smaller, and the noise in the generating position and propagation path can be reduced by 1.9 dB–5.5 dB.

scholarly journals Comparison of one versus two maxillary molars distalization with iPanda: a finite element analysis

2021 ◽  
Vol 22 (1) ◽  
Author(s):  
Kamontip Sujaritwanid ◽  
Boonsiva Suzuki ◽  
Eduardo Yugo Suzuki
Keyword(s):  
Finite Element ◽  
Stress Distribution ◽  
Alveolar Bone ◽  
Vertical Direction ◽  
Minimal Amount ◽  
Element Analysis ◽  
Molar Distalization ◽  
Second Molar ◽  
Maxillary Molars ◽  
Displacement Patterns

Abstract Background The purpose of this study was to compare the stress distribution and displacement patterns of the one versus two maxillary molars distalization with iPanda and to evaluate the biomechanical effect of distalization on the iPanda using the finite element method. Methods The finite element models of a maxillary arch with complete dentition, periodontal ligament, palatal and alveolar bone, and an iPanda connected to a pair of midpalatal miniscrews were created. Two models were created to simulate maxillary molar distalization. In the first model, the iPanda was connected to the second molar to simulate a single molar distalization. In the second model, the iPanda was connected to the first molar to simulate “en-masse” first and second molar distalization. A varying force from 50 to 200 g was applied. The stress distribution and displacement patterns were analyzed. Results For one molar, the stress was concentrated at the furcation and along the distal surface in all roots with a large amount of distalization and distobuccal crown tipping. For two molars, the stress in the first molar was 10 times higher than in the second molar with a great tendency for buccal tipping and a minimal amount of distalization. Moreover, the stress concentration on the distal miniscrew was six times higher than in the mesial miniscrew with an extrusive and intrusive vector, respectively. Conclusions Individual molar distalization provides the most effective stress distribution and displacement patterns with reduced force levels. In contrast, the en-masse distalization of two molars results in increased force levels with undesirable effects in the transverse and vertical direction.

Polarization- and Strain-Mediated Control of Negative Thermal Expansion and Ferroelasticity in BiInO3–BiZn1/2Ti1/2O3

2021 ◽  
Vol 33 (4) ◽  
pp. 1498-1505
Author(s):  
Takumi Nishikubo ◽  
Takahiro Ogata ◽  
Lalitha Kodumudi Venkataraman ◽  
Daniel Isaia ◽  
Zhao Pan ◽  
...  
Keyword(s):  
Thermal Expansion ◽  
Negative Thermal Expansion
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