scholarly journals Effects of Structural Parameters on the Poisson's Ratio and Compressive Modulus of 2D Pentamode Structures Fabricated by Selective Laser Melting

Engineering ◽  
2020 ◽  
Vol 6 (1) ◽  
pp. 56-67 ◽  
Author(s):  
Lei Zhang ◽  
Bo Song ◽  
Ruijie Liu ◽  
Aiguo Zhao ◽  
Jinliang Zhang ◽  
...  
Keyword(s):  
Selective Laser Melting ◽  
Poisson’S Ratio ◽  
Structural Parameters ◽  
Compressive Modulus ◽  
Poisson's Ratio ◽  
Laser Melting

scholarly journals The development of TiNi-based negative Poisson's ratio structure using selective laser melting

2016 ◽  
Vol 105 ◽  
pp. 75-83 ◽  
Author(s):  
Sheng Li ◽  
Hany Hassanin ◽  
Moataz M. Attallah ◽  
Nicholas J.E. Adkins ◽  
Khamis Essa
Keyword(s):  
Selective Laser Melting ◽  
Poisson’S Ratio ◽  
Poisson's Ratio ◽  
Negative Poisson’S Ratio ◽  
Laser Melting ◽  
Negative Poisson's Ratio

A study of tubular braided structure with negative Poisson’s ratio behavior

2017 ◽  
Vol 88 (24) ◽  
pp. 2810-2824 ◽  
Author(s):  
Ning Jiang ◽  
Hong Hu
Keyword(s):  
Poisson’S Ratio ◽  
Structural Parameters ◽  
Uniaxial Extension ◽  
Poisson's Ratio ◽  
Negative Poisson’S Ratio ◽  
Yarn Diameter ◽  
Wrap Angle ◽  
Negative Poisson's Ratio ◽  
Braided Structure ◽  
Braiding Angle

Textile structures with negative Poisson’s ratio (PR) behavior are called auxetic textile structures. They have received increasing attention in recent years and have been designed and fabricated through spinning, knitting, weaving and non-woven methods. However, auxetic textile structures fabricated using braiding method have not been reported so far. This paper reported a novel type of auxetic braided structure based on a helical structural arrangement. The geometry of the structure and its deformation mechanism were first introduced and described. Then a special manufacturing process was developed by the modification of commonly used tubular braiding technology. Various auxetic braids were fabricated with different structural parameters and yarns and tested under uniaxial extension conditions. The results showed that all manufactured braids exhibited high negative PR behavior and maintained this behavior until the fracture of the component wrap yarn. Among three structural parameters discussed, namely wrap angle, braiding angle and braiding yarn diameter, the wrap angle had more effects on the tensile properties of auxetic braided structure than the other two parameters. The success of fabricating auxetic braids with commercially available yarns in this study provides an alternative way to manufacture auxetics from positive PR materials.

Variation of Poisson’s ratio of fabrics woven with helical composite auxetic weft yarns in relation to fabric structural parameters

2019 ◽  
Vol 50 (2) ◽  
pp. 149-169
Author(s):  
Asal Lolaki ◽  
Mohsen Shanbeh
Keyword(s):  
Poisson’S Ratio ◽  
Structural Parameters ◽  
Processing Technique ◽  
Poisson's Ratio ◽  
Image Processing Technique ◽  
Weft Yarn ◽  
Warp Yarn ◽  
Dimensional Changes ◽  
Weft Direction ◽  
Yarn Count

Auxetic textiles are defined as textiles with negative Poisson’s ratio. These textiles possess unique properties that render them suitable for special applications. This work aims to investigate the effect of fabric structural parameters such as thread densities, weave design and warp yarn count. Thus, 30 fabric samples were woven at 3 weft and 2 warp densities, respectively. Two warp counts and three weave designs of plain, basket 3/3 and weft-backed satin 6 were used. The samples were uniaxially loaded in weft direction and dimensional changes at various strains levels were evaluated. The evaluation was carried out using the image processing technique based on MATLAB software. The weft yarns used were found to exhibit auxetic behavior at the whole spectrum of the strain level used. The least weft yarn Poisson’s ratio was found to be −0.9. It was established that in general the fabric samples exhibit auxetic effect within the stated range of strain. Additionally, it was concluded that while fabric thread densities together with warp count influence the minimum fabric Poisson's ratio, auxetic behavior of the samples is not dependent on weave design alone. Rather, it was illustrated that the combined effect of weave design in association with stated structural parameters on auxetic feature cannot be ignored.

DFT study of SmXO3 (X = Al and Co) for elastic, mechanical and optical properties

2018 ◽  
Vol 32 (32) ◽  
pp. 1850362 ◽  
Author(s):  
A. Afaq ◽  
Abu Bakar ◽  
Sajid Anwar ◽  
Waheed Anwar ◽  
Fazal-e-Aleem
Keyword(s):  
Optical Properties ◽  
Poisson’S Ratio ◽  
Density Functional ◽  
Structural Parameters ◽  
Poisson's Ratio ◽  
Published Data ◽  
Generalized Gradient ◽  
Elastic Parameters ◽  
Functional Theory ◽  
Anisotropic Factor

The first-principles study of cubic perovskites SmXO3 (X = Al and Co) for elastic, mechanical and optical properties is done in the framework of density functional theory (DFT). Optimized structural parameters are obtained first to find mechanical and optical properties of the materials. These obtained structural parameters are in accordance with the published data. The cubic elastic parameters C[Formula: see text], C[Formula: see text] and C[Formula: see text] are then calculated by using generalized gradient approximation (GGA) as an exchange correlation functional in Kohn–Sham equations. Poisson’s ratio, shear modulus, Young’s modulus and anisotropic factor are deduced from these elastic parameters. These compounds are found to be elastically anisotropic and SmAlO3 is brittle while SmCoO3 is ductile. Their covalent nature is also discussed by using Poisson’s ratio. In addition, optical properties like absorption coefficient, extinction coefficient, energy loss function, dielectric function, refractive index, reflectivity and optical conductivity are studied. This study predicts that SmAlO3 and SmCoO3 are suitable for optoelectronic devices.

scholarly journals Structure and properties of corrosion-resistant steel obtained by selective laser melting

2019 ◽  
pp. 91-97
Author(s):  
A. A. Smetkin ◽  
S. A. Oglezneva ◽  
K. V. Kalinin ◽  
E. F. Khanipov
Keyword(s):  
Selective Laser Melting ◽  
Cellular Structure ◽  
Structural Parameters ◽  
Heat Removal ◽  
Steel Powder ◽  
Coherent Scattering ◽  
12Kh18n10t Steel ◽  
Laser Melting ◽  
Differential Distribution ◽  
Gaussian Form

The objects of study were stainless steel powder 12Kh18N10T of the 20–63 μm fraction and experimental samples obtained on the basis of it by selective laser melting (SLM). The powder was obtained by spraying with argon at a temperature of 1640 °C and a pressure of 27 bar. The particles have the dendritic-cellular structure, with a decrease in their size (<35 μm), the cellular structure prevails, and the dendritic one almost disappears. The distinctive particle size is d50 = 37 μm, d100 = 67 μm. The differential distribution curve is close to the Gaussian form, and asymmetry is associated with satellite and the presence of a small number of particles less than 20 microns in size. The fluidity of the powder was 3,27 g/s, and the bulk density was 4,41 g/cm3. The density of the 12Kh18N10T steel samples grown at the Concept Laser M2 facility with a laser power of 180 W and a speed of 700 mm/s averaged 7,89 g/cm3. Since the density of compact steel is 7,95 g/cm3, the obtained material has enough high density. The microstructure of the 12Kh18N10T sample was described by continuity, the absence of pores and cracks. It was a solid solution of austenite. The average size of coherent scattering regions in the grain volume was 19 nm. The observed arcuate boundaries of parallel semicircular tracks are due to heat removal during crystallization through SLM. The elongated crystallites in the tracks are oriented inward from this boundary. The microhardness of the samples in the transverse plane of the thin section is higher than the microhardness of the planar plane. But the microhardness of the samples obtained from the powder by the SLM is higher than that of the standard compact alloy. Tensile strength and elongation are 651 MPa and 47 %, respectively. The increase in strength is probably due to the grinding of structural parameters in SLM. The fracture surface of the samples is characterized by a pronounced viscous type.

Tuning the Optical Properties Through Bandgap Engineering in Si-Doped YAuPb: ab Initio Study

2021 ◽  
Author(s):  
Fida Rehman ◽  
A. Dahshan ◽  
Muhammad Shariq ◽  
Pervaiz Ahmed ◽  
Y. Saeed
Keyword(s):  
Optical Properties ◽  
Band Gap ◽  
Poisson’S Ratio ◽  
Density Functional ◽  
Structural Parameters ◽  
Poisson's Ratio ◽  
Optical Parameters ◽  
Full Potential ◽  
G Ratio ◽  
Band Gap Structure

Abstract In order to probe the band gap engineering to tune optical properties in YAuPb1-xSix (x = 0, 0.25, 0.50, 0.75 and 1) alloys, we used all electron full-potential linearized augmented plane wave (FP-LAPW+lo) method within the frame work of the density functional theory. The optimized structural parameters were in good agreement with other theoretical and experimental results. The calculated results of elastic constant satisfy the condition for mechanical stability at each composition for cubic symmetry. In addition, the study of elastic parameters are summarized for the calculation bulk modulus, Young’s modulus, shear modulus, Kleinman parameters, Poisson’s ratio and Lame’s co-efficient. To predict the brittle (ductile) nature of this composition, the Cauchy pressure, Poisson’s ratio and B/G ratio were also calculated. Using modified Becke and Johnson GGA, the band gap values of each composition were computed precisely. Further, it was observed that for 0.25 < x < 0.75, band gap structure revealed a direct band gap configuration. In order to analyze the electronic structure of each composition, the total and partial densities of states have been investigated in detail. Furthermore, the investigation of optical parameters in terms of dielectric functions revealed the potential of these alloys for optoelectronic devices.

scholarly journals Study on Negative Poisson Ratio and Energy Absorption Characteristics of Embedded Arrow Honeycomb Structure

2020 ◽  
Vol 12 (2) ◽  
pp. 47-57
Author(s):  
Wenzheng Liu ◽  
Shiqing Huang ◽  
Jiachu Xu
Keyword(s):  
Energy Absorption ◽  
Poisson’S Ratio ◽  
Poisson Ratio ◽  
Structural Parameters ◽  
Impact Resistance ◽  
Honeycomb Structure ◽  
Absorption Efficiency ◽  
Poisson's Ratio ◽  
Negative Poisson’S Ratio ◽  
Negative Poisson's Ratio

 Impact collision exists widely in people's daily life and threatens people's life safety. Negative Poisson's ratio structure has good mechanical properties. Therefore, it is of great significance to design and study the energy absorption structure with negative Poisson's ratio effect. Based on the traditional symmetrical concave honeycomb structure (SCHS) with negative Poisson's ratio, two modified negative Poisson's ratio honeycomb structures are proposed by adding embedded straight rib arrow structure and embedded curved rib arrow structure, which are respectively called embedded straight rib arrow honeycomb structure (SRAH) and embedded curved rib arrow honeycomb structure (CRAH). Through finite element simulation experiment, the negative Poisson's ratio characteristics of two cellular cells were studied and the influence of structural parameters of the cells on the Poisson's ratio was discussed. ANSYS/LS-DYNA was used to analyze the energy absorption of the proposed three cellular structures at different impact velocities. Numerical simulation results show that the SRHS and CRAH have greater stress platform value, specific energy absorption and impact force efficiency than SCHS, indicating that the SRAH and CRAH exhibited better energy absorption efficiency and impact resistance performance.

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