Distributed Design of Two-Scale Structures With Unit Cells

2019 ◽  
Author(s):  
Xingchen Liu
Keyword(s):  
Material Property ◽  
Material Properties ◽  
Volume Fraction ◽  
Base Material ◽  
Structure Design ◽  
Unit Cell ◽  
Steady Increase ◽  
Coarse Scale ◽  
Cell Structures ◽  
Wide Range

Abstract The use of unit cell structures in mechanical design has seen a steady increase due to their abilities to achieve a wide range of material properties and accommodate multi-functional requirements with a single base material. We propose a novel material property envelope (MPE) that encapsulates the attainable effective material properties of a given family of unit cell structures. The MPE interfaces the coarse and fine scales by constraining the combinations of the competing material properties (e.g., volume fraction, Young’s modulus, and Poisson’s ratio of isotropic materials) during the design of coarse scale material properties. In this paper, a sampling and reconstruction approach is proposed to represent the MPE of a given family of unit cell structures with the method of moving least squares. The proposed approach enables the analytical derivatives of the MPE, which allows the problem to be solved more accurately and efficiently during the design optimization of the coarse scale effective material property field. The effectiveness of the proposed approach is demonstrated through a two-scale structure design with octet trusses that have cubically symmetric effective stiffness tensors.

Three-Dimensional Unit Cell Study of a Porous Bulk Metallic Glass Under Various Stress States

2019 ◽  
Vol 86 (6) ◽  
Author(s):  
S Gouripriya ◽  
Parag Tandaiya
Keyword(s):  
Volume Fraction ◽  
Hydrostatic Stress ◽  
Three Dimensional ◽  
High Strength ◽  
Absorption Capacity ◽  
Unit Cell ◽  
Wide Range ◽  
Tension And Compression ◽  
Softening Parameter ◽  
Stress States

Porous bulk metallic glasses (BMGs) exhibit an excellent combination of superior mechanical properties such as high strength, high resilience, large malleability, and energy absorption capacity. However, a mechanistic understanding of their response under diverse states of stress encountered in practical load-bearing applications is lacking in the literature. In this work, this gap is addressed by performing three-dimensional finite element simulations of porous BMGs subjected to a wide range of tensile and compressive states of stress. A unit cell approach is adopted to investigate the mechanical behavior of a porous BMG having 3% porosity. A parametric study of the effect of stress triaxialities T = 0, ±1/3, ±1, ±2, ±3, and ±∞, which correspond to stress states ranging from pure deviatoric stress to pure hydrostatic stress under tension and compression, is conducted. Apart from the influence of T, the effects of friction parameter, strain-softening parameter and Poisson’s ratio on the mechanics of deformation of porous BMGs are also elucidated. The results are discussed in terms of the simulated stress-strain curves, pore volume fraction evolution, strain to failure, and development of plastic deformation near the pore. The present results have important implications for the design of porous BMG structures.

Modeling and Analysis of 1-3 Piezoelectric Composites

2002 ◽  
Author(s):  
Sanjay Nakhwa ◽  
Anil Saigal
Keyword(s):  
Boundary Conditions ◽  
Material Properties ◽  
Volume Fraction ◽  
Transversely Isotropic ◽  
Unit Cell ◽  
Coupling Constants ◽  
Upper And Lower Bounds ◽  
Piezoelectric Composite ◽  
Piezoelectric Composites ◽  
Material Constants

Theoretical results of the material properties of piezoelectric composites are generally limited to the transversely isotropic composites and are usually given in the form of upper and lower bounds. In most of these analyses all the material constants cannot be determined. However, the method of effective field has been used on a transversely isotropic piezoelectric composite to theoretically calculate all the ten material properties. In this work an alternative method to determine all the elastic, dielectric and piezoelectric coupling constants of 1-3 piezoelectric composite with periodic arrangement of fibers are investigated by using finite element analysis on a unit cell model. FEA of unit cell models for hexagonal, square with diagonal and square with edge orientation topologies are performed. Different mechanical and electrical loading patterns and their corresponding boundary conditions are formulated and simulated to get data necessary for deriving the various anisotropic material constants. FEA results are compared with those of the theoretical work. Effect of different parameters e.g. volume fraction, topology and electrical boundary conditions on the different material constants are discussed.

Comparison of Parent and Butt-Fusion Material Properties of Unimodal High-Density Polyethylene

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
P. Krishnaswamy ◽  
D.-J. Shim ◽  
S. Kalyanam
Keyword(s):  
Material Property ◽  
Material Properties ◽  
High Density Polyethylene ◽  
Fracture Resistance ◽  
Structural Integrity ◽  
Slow Crack Growth ◽  
Base Material ◽  
High Density ◽  
Nuclear Industry ◽  
Service Water

The U.S. nuclear power industry is seeking U.S. Nuclear Regulatory Commission (USNRC) approval to use high-density polyethylene (HDPE) in safety-related applications. The USNRC had granted approval for the use of HDPE for safety-related service water applications, with limitations, to Catawba (Duke Energy Corp., Catawba, SC) and Callaway (Union Electric Co., Callaway, MO) based on separate relief requests submitted by the licensees. The nuclear industry continues to show increasing interest in utilizing HDPE in safety-related piping systems. In order to evaluate and maintain the structural integrity of HDPE pipes, the material properties and the fracture resistance behavior must be fully characterized. Although there has been extensive work on material property development of HDPE, most of the investigations have been focused on the parent (base) material. Hence, the material property and fracture resistance behavior of the butt-fusion region have not been comprehensively investigated. In this paper, tensile, dynamic mechanical analysis (DMA), and slow crack growth (SCG) tests were performed for unimodal PE 4710 HDPE material. Specimens were machined from both parent piping material and butt-fusion regions. The test results indicate that the tensile and DMA properties show no significant differences between parent and butt-fusion joint materials. However, in terms of SCG resistance, the time to failure for butt-fusion joint material was an order of magnitude lower than that of the parent material.

Instability and Bifurcation Behavior of Orthotropic S-FGM Plates Under Lateral Stochastic Loads Considering Variation of Material Properties

2016 ◽  
Vol 16 (03) ◽  
pp. 1450108 ◽  
Author(s):  
Majid Abedi ◽  
Alireza Asnafi
Keyword(s):  
Material Property ◽  
Material Properties ◽  
Nonlinear Behavior ◽  
Mean Value ◽  
Effective Parameters ◽  
Wide Range ◽  
The Mean ◽  
Stochastic Loads ◽  
Bifurcation Behavior

In this paper, all the parameters affecting the nonlinear behavior of S-FGM plates under lateral stochastic white noise excitations are investigated. First the governing equation for a general S-FGM plate is derived for the assumed problem. Then it is rewritten by introducing some nondimensional parameters such that the results are applicable for a wide range of plates. Without loss of generality and using an example, the effective parameters on the instability and bifurcation of the transverse vibration of plates are studied, including the mean value of the lateral load with the in-plane forces and the material property. Especially, the role of material property is highlighted and some analogical figures are drawn to compare the behavior of the FGM plates with the homogenous ones. It is shown that the material property can affect the behavior of instability and bifurcation of the plate and its occurrence.

Comparison of Parent and Butt Fusion Material Properties of High Density Polyethylene

2009 ◽  
Author(s):  
D.-J. Shim ◽  
P. Krishnaswamy ◽  
E. Focht
Keyword(s):  
Material Property ◽  
Material Properties ◽  
High Density Polyethylene ◽  
Fracture Resistance ◽  
Slow Crack Growth ◽  
Base Material ◽  
High Density ◽  
Nuclear Industry ◽  
Service Water ◽  
Fusion Material

The US nuclear power industry is seeking U. S. Nuclear Regulatory Commission (USNRC) approval to use high density polyethylene (HDPE) in safety-related applications. The USNRC has granted approval for the use of HDPE for safety-related service water applications, with limitations, to Catawba (Duke Energy Corp.) and Callaway (Union Electric Co.) based on separate relief requests submitted by the licensees. The nuclear industry continues to show increasing interest in utilizing HDPE in safety-related piping systems. In order to evaluate and maintain the structural integrity of HDPE pipes, the material properties and the fracture resistance behavior must be fully characterized. Although there has been extensive work on material property development of HDPE, most of the investigations have been focused on the parent (base) material. Hence, the material property and fracture resistance behavior of the butt fusion region have not been comprehensively investigated. In this paper, tensile, dynamic mechanical analysis (DMA), and slow crack growth (SCG) tests have been performed for PE 4710 HDPE material. Specimens were machined from both parent piping material and butt fusion regions. The test results indicate that the tensile and DMA properties show no significant differences between parent and butt fusion materials. However, in terms of SCG resistance, the time to failure for butt fusion material was an order of magnitude lower than that of the parent material.

scholarly journals Factors Affecting Acoustic Properties of Natural-Fiber-Based Materials and Composites: A Review

Textiles ◽  
2021 ◽  
Vol 1 (1) ◽  
pp. 55-85
Author(s):  
Tufail Hassan ◽  
Hafsa Jamshaid ◽  
Rajesh Mishra ◽  
Muhammad Qamar Khan ◽  
Michal Petru ◽  
...  
Keyword(s):  
Sound Absorption ◽  
Natural Fiber ◽  
Volume Fraction ◽  
Fiber Type ◽  
Alkali Treatment ◽  
Acoustic Properties ◽  
Synthetic Fiber ◽  
Sound Insulation ◽  
Factors Affecting ◽  
Wide Range

Recently, very rapid growth has been observed in the innovations and use of natural-fiber-based materials and composites for acoustic applications due to their environmentally friendly nature, low cost, and good acoustic absorption capability. However, there are still challenges for researchers to improve the mechanical and acoustic properties of natural fiber composites. In contrast, synthetic fiber-based composites have good mechanical properties and can be used in a wide range of structural and automotive applications. This review aims to provide a short overview of the different factors that affect the acoustic properties of natural-fiber-based materials and composites. The various factors that influence acoustic performance are fiber type, fineness, length, orientation, density, volume fraction in the composite, thickness, level of compression, and design. The details of various factors affecting the acoustic behavior of the fiber-based composites are described. Natural-fiber-based composites exhibit relatively good sound absorption capability due to their porous structure. Surface modification by alkali treatment can enhance the sound absorption performance. These materials can be used in buildings and interiors for efficient sound insulation.

scholarly journals Fabrication and Compressive Behavior of a Micro-Lattice Composite by High Resolution DLP Stereolithography

Polymers ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 785
Author(s):  
Chow Shing Shin ◽  
Yu Chia Chang
Keyword(s):  
High Resolution ◽  
Lattice Structure ◽  
Low Cost ◽  
Hierarchical Structures ◽  
Dip Coating ◽  
Unit Cell ◽  
Digital Light Processing ◽  
Unit Cell Size ◽  
Wide Range ◽  
And Performance

Lattice structures are superior to stochastic foams in mechanical properties and are finding increasing applications. Their properties can be tailored in a wide range through adjusting the design and dimensions of the unit cell, changing the constituent materials as well as forming into hierarchical structures. In order to achieve more levels of hierarchy, the dimensions of the fundamental lattice have to be small enough. Although lattice size of several microns can be fabricated using the two-photon polymerization technique, sophisticated and costly equipment is required. To balance cost and performance, a low-cost high resolution micro-stereolithographic system has been developed in this work based on a commercial digital light processing (DLP) projector. Unit cell lengths as small as 100 μm have been successfully fabricated. Decreasing the unit cell size from 150 to 100 μm increased the compressive stiffness by 26%. Different pretreatments to facilitate the electroless plating of nickel on the lattice structure have been attempted. A pretreatment of dip coating in a graphene suspension is the most successful and increased the strength and stiffness by 5.3 and 3.6 times, respectively. Even a very light and incomplete nickel plating in the interior has increase the structural stiffness and strength by more than twofold.

scholarly journals Conduction and convection heat transfer characteristics of water-based au nanofluids in a square cavity with differentially heated side walls subjected to constant temperatures

2014 ◽  
Vol 18 (suppl.1) ◽  
pp. 189-200 ◽  
Author(s):  
Primoz Ternik ◽  
Rebeka Rudolf
Keyword(s):  
Heat Transfer ◽  
Rayleigh Number ◽  
Base Fluid ◽  
Volume Fraction ◽  
Heat Transfer Characteristics ◽  
Square Cavity ◽  
Onset Of Convection ◽  
Transfer Characteristics ◽  
Wide Range ◽  
Water Based

The present work deals with the natural convection in a square cavity filled with the water-based Au nanofluid. The cavity is heated on the vertical and cooled from the adjacent wall, while the other two horizontal walls are adiabatic. The governing differential equations have been solved by the standard finite volume method and the hydrodynamic and thermal fields were coupled together using the Boussinesq approximation. The main objective of this study is to investigate the influence of the nanoparticles? volume fraction on the heat transfer characteristics of Au nanofluids at the given base fluid?s (i.e. water) Rayleigh number. Accurate results are presented over a wide range of the base fluid Rayleigh number and the volume fraction of Au nanoparticles. It is shown that adding nanoparticles in a base fluid delays the onset of convection. Contrary to what is argued by many authors, we show by numerical simulations that the use of nanofluids can reduce the heat transfer rate instead of increasing it.

scholarly journals Microstructure and magnetic properties of Nd-Fe-B-(Re, Ti) alloys

Nukleonika ◽  
2015 ◽  
Vol 60 (1) ◽  
pp. 29-33
Author(s):  
Mariusz Hasiak
Keyword(s):  
Magnetic Properties ◽  
Phase Composition ◽  
Volume Fraction ◽  
Magnetic Characteristics ◽  
Ti Alloys ◽  
Wide Range ◽  
Magnetically Hard ◽  
Ti Addition ◽  
Microstructure And Magnetic Properties

Abstract The microstructure and magnetic properties of nanocomposite hard magnetic Nd-Fe-B-(Re, Ti) materials with different Nd and Fe contents are studied. The role of Re and Ti addition in phase composition and volume fraction of the Nd-Fe-B phase is determined. All samples are annealed at the same temperature of 993 K for 10 min. Mössbauer spectroscopy shows that the addition of 4 at.% of Re to the Nd8Fe78B14 alloy leads to creation of an ineligible amount of the magnetically hard Nd2Fe14B phase. Moreover, the microstructure and magnetic characteristics recorded in a wide range of temperatures for the Nd8Fe79−xB13Mx (x = 4; M = Re or Ti) alloys are also analyzed.

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