Waviness Factor Research Articles

Study of nanotube waviness influence on the behaviors of spherical nanocomposites

Considering the prominent properties of nanocomposites, the closer their modeling is to reality, the more suitable it is for engineering applications. One of the steps that can be taken for this purpose is to include the waviness of the reinforcements in the study of nanocomposites. In this article, for the first time, the effects of the waviness of reinforcing nanotubes in spherical nanocomposites on the behavior of mechanical waves have been studied. Several different ideas, such as adopting random contact model, the excluded volume of two spherocylinders, microscopic images and experimental results, are used for modeling wavy nanotubes in spherical nanocomposites, each of which has its own characteristics. For modeling the spherical nanocomposite itself, three-dimensional elasticity theory in spherical coordinates is used. For several different cases, the results of the present models are compared and calibrated with the results of experimental tests, which adds to the attractiveness of the work. The influences of various parameters such as radius of spherical nanocomposite, waviness factor, nanotubes volume fraction and wave number on the results are also investigated. From the results of this article, the idea can come to mind that the effects of the waviness of the nanotubes cannot be ignored in some cases and should be included in the modeling, otherwise it will produce significant errors in the results.

Analysis of surface deviation impact on bio-mass sensing application of Boron Nitride Nanotubes

The Boron Nitride Nanotube (BNNT) is capable of sensing the masses even below the zeptogram level when it is used as a resonator. The surface of BNNT is considered to be straight in most of the existing literatures. In this work, wavy surface of BNNT is considered, and its effect on the mass sensing capabilities of BNNT is investigated. A nonlinear mathematical model is developed by applying the continuum mechanics approach on surface deviated (wavy) BNNT of a hollow cylindrical geometry with thin wall. The model is normalized to the nanoscale level, and the degrees of nonlinearity arise due to waviness are identified in BNNT mass sensing application. The deformation in nanostructures is nonlinear that causes oscillations of large amplitude. The midplane stretching and waviness factor of a single walled BNNT, which is clamped at both of its end, are considered to investigate its frequency response to the attached mass. It is proposed to include waviness surface of BNNT to develop more accurate biomass sensor. It is further found that there is a shift in the resonance frequency due to surface waviness of BNNT as compared to straight BNNT. The future perspective of this study is to investigate methods to optimize the wavy structure of BNNTs for improved biomolecule detection. This could involve studying the effect of different wave patterns, sizes, and amplitudes on the sensor's sensitivity and selectivity.

Optimization for dense location and geometrical parameter of wavy microchannel to improve temperature distribution

In this article, a new locally denser sinusoidal wavy microchannel is proposed to improve the uniformity of temperature distribution. The influence of dense location and geometrical parameters, that is, wavelength (λ 3 = 600–1600 μm) and amplitude (A 3 = 40–200 μm), waviness factor γ (0.04–0.2) are studied by numerical simulation. Results show, compared with rectangular microchannels, dense wavy microchannels can effectively enhance heat transfer with a larger pressure drop penalty of 53.5–152.6%, but only 29.6–79.9% of locally denser wavy microchannels. Besides, it’s found that dense location influences severe heat transfer performance, but less for pressure drops. Heat transfer performance of downstream dense wavy microchannel is best, and the maximum temperature is reduced by 23 K under Re = 348. But the upstream dense type increases the maximum temperature difference than wave microchannel. Under the same pumping power, the thermal resistance of downstream dense wavy microchannel is reduced by 46% and 20% than straight microchannel and wavy microchannels. Decreasing wavelength and increasing wave amplitude could enhance heat transfer, and the effects become weaker. But the pressure drop is significantly increased. The best overall thermal performance is found for downstream dense wavy microchannel with γ = 0.12 of A 3 = 120 μm and λ 3 = 1000 μm, in which thermal resistance is reduced 48.6% under same pumping power.

Influence of MWCNT’s waviness and aggregation factors on wave dispersion response of MWCNT-strengthened nanocomposite curved beam

This article focuses on the impact of waviness and aggregation of nanofillers on wave dispersion behavior of the nanocomposite curved beam strengthened with multi-walled carbon nanotubes (MWCNTs). In fact, the aggregation phenomenon is an inevitable subject in the manufacturing process of strengthened nanocomposite materials. Furthermore, in reality, usage of straight nanoreinforcements is almost impossible. So, MWCNTs can be wavy. These noted topics can significantly affect mechanical behavior of reinforced nanocomposite structures. In the current investigation, aggregation and waviness factors are accounted for through a modified Halpin-Tsai micromechanical homogenization model. The relations of kinetic and kinematic of MWCNTs-reinforced nanocomposite curved beam are expressed by employing Euler-Bernoulli beam theory. The governing equations are obtained by using Hamiltonian approach. The obtained equations are solved via an analytical solution to attain the wave dispersion values. The precision of the obtained outcomes is verified by the reported outcomes in the literature. Finally, the impacts of various important parameters such as aggregation and waviness factor, wave number and opening angles are examined.

Nonlinear vibration analysis of curvy single-walled boron nitride nanotube using mathematical modeling for dynamic responses

This work explores the feasibility of nonlinear behavior of doubly clamped single-walled boron nitride nanotube (SW-BNNT)-based nanoresonator. A nonlinear mathematical model of wavy SW-BNNT has been developed for analyzing the geometrical nonlinearity. Dynamic responses of nonlinear model have been analyzed for different waviness factors varying from 0.01 to 0.06 using various tools like time series, phase space, Poincaré map and Fast Fourier Transforms (FFTs). For the analysis, 20[Formula: see text]nm length of SW-BNNT has been considered. It has been observed from nonlinear analysis, that for responses with a lower value of waviness (e.g., 0.01) for 20[Formula: see text]nm long BNNT, the system’s nature loses its periodicity and shows onset of chaos with dense spectrum in Poincaré maps and irregular pattern in time response. Thus, it is concluded that chaotic response with a less strange attractor has been observed when waviness is 0.01. It is also concluded that, with increase in waviness factor from 0.02 to 0.06, the system showed the multi-periodic response with 2-T, 3-T and 4-T periods. The dynamic responses with varying waviness showed that the system behavior is changing from chaotic to periodic. This change in periodicity is one of the characteristics of chaotic solution.

Digital twins of high aspect ratio wavy nanotube composite performance for model-informed manufacturing

The design of a nanotube grouping in a composite at the local scale to form representative volume elements (RVEs) and the resultant stiffness under displacement is investigated due to the challenges of experimentally isolating factors that influence performance in nanotube-reinforced composites (NRCs). Criteria for known nanotube features are considered in this work, including waviness, diameter, and alignment. The influence of the nanotube waviness on the effective modulus is analyzed for CNTs. Waviness has the most significant effect on the NRC, changing the final performance by 20.9%. We evaluate the effect of these parameters on the model's local scale using virtual testing and analysis of variance (ANOVA), which reveal that the waviness factor has the most significant effect on the composite's modulus and give possible explanations for the modulus reduction caused by the presence of highly wavy nanotubes. This work will impact the model-informed manufacturing of future nanocomposite material structures.

PSXII-1 CNV and Cnvr Detection from High-Density SNP Genotyping in Holstein Cattle

Abstract Copy number variation (CNV) represents an important source of genetic variation complementary to single nucleotide polymorphism (SNP) and provides valuable insights into the genetic architecture of complex traits in humans and livestock animals. However, many factors affect CNV detection, including sample size. Previous studies in Holstein cattle have only used hundreds of individuals. Therefore, in the present study, CNVs were identified from high-density genotype array data in 3,529 Holstein cows from 16 herds located in 7 U.S. states. CNVs were derived from 546,802 autosomal SNP markers with MAF > 0.05 and call rate > 0.90 using the intensity signals at each SNP position in a hidden Markov model implemented in PennCNV software. The log R ratio (LRR) values were corrected based on the guanine-cytosine content in the genomic regions located 500 kb upstream and downstream of each marker. After detection, CNVs presenting LRR ≤ 0.30, B allele frequency drift < 0.01, waviness factor ≤ 0.05, number of SNPs > 10 and length > 1 kb were merged into CNV regions (CNVR) using CNVRanger. A total of 1,881 non-redundant CNV events spanning the entire genome were identified in 1,771 cows, with a mean of 10 CNVs per individual and ranging from 1 to 27. The highest percentage of CNV calls was located on BTA7 (16%), while only 9 CNVs were identified on BTA9. The CNV calls were grouped into 685 CNVRs covering 3.07% of the bovine autosomal genome. The number of CNVRs with copy loss and gain were 356 and 310, and both types were observed in 19 regions. The chromosomal distribution of CNVR revealed that BTA7 harbors 38 CNVRs, while only 2 were detected on BTA28. These results will support further research on the contribution of CNVs and CNVRs to the genetic architecture of complex traits in Holstein cattle.

Mathematical analysis to predict tensile strength of banana/glass hybrid polymer composite

AbstractThis article presents a mathematical model to predict the tensile strength of banana/glass hybrid polymer composites. Equivalent fiber surface efficiency factor and fiber waviness factor have been introduced in the proposed model and their effects on tensile strength have been discussed. The hybrid composites were fabricated with the different proportions of volume fraction of each of the glass fibers and banana fibers keeping the total volume fraction (VF) of combined fibers from 20% to 50%. The tensile test of hybrid composites was carried out as per ASTM D3039. The proposed model has been tested versus experimental results as well as the literature results, which shows quite good approximation of tensile strength. The proposed model is generalized and can be applied to any hybrid reinforced composites with the combination of low‐elongated and high‐elongated fibers with varying fiber loading.

Wave dispersion analysis of embedded MWCNTs-reinforced nanocomposite beams by considering waviness and agglomeration factors

In the current investigation, the influences of waviness and agglomeration factor of nanofillers on wave dispersion of embedded nanocomposite beams reinforced with multi-walled carbon nanotubes (MWCNTs) is investigated for the first time. These beams are supported on Winkler–Pasternak elastic foundation. The effective mechanical properties of nanocomposite beam are estimated by employing a blend of a new form of Halpin–Tsai micromechanical model and rule of mixture. The kinematic and kinetic relations of nanocomposite beam are computed based upon refined higher-order shear deformation theory. Moreover, the governing equations are derived by utilizing the Hamiltonian approach. Afterward, an analytical method is used in order to solve the obtained governing equations. Effects of the wide range of variants such as volume fraction of MWCNTs, slenderness ratio, waviness factor, random orientation factor, agglomeration factor and elastic foundation coefficient on the variation of wave frequency and phase velocity have been illustrated comparatively. Furthermore, the results are thoroughly discussed to obtain the highlights of each figure.

Wave Dispersion Analysis of Fluid Conveying Nanocomposite Shell Reinforced by MWCNTs Considering the Effect of Waviness and Agglomeration Efficiency.

The current paper is aimed to investigate the effects of waviness, random orientation, and agglomeration factor of nanoreinforcements on wave propagation in fluid-conveying multi-walled carbon nanotubes (MWCNTs)-reinforced nanocomposite cylindrical shell based on first-order shear deformable theory (FSDT). The effective mechanical properties of the nanocomposite cylindrical shell are estimated employing a combination of a novel form of Halpin-Tsai homogenization model and rule of mixture. Utilized fluid flow obeys Newtonian fluid law and it is axially symmetric and laminar flow and it is considered to be fully developed. The effect of flow velocity is explored by implementing Navier-Stokes equation. The kinetic relations of nanocomposite shell are calculated via FSDT. Moreover, the governing equations are derived using the Hamiltonian approach. Afterward, a method which solves problems analytically is applied to solve the obtained governing equations. Effects of a wide range of variants such as volume fraction of MWCNTs, radius to thickness ratio, flow velocity, waviness factor, random orientation factor, and agglomeration factor on the phase velocity and wave frequency of a fluid conveying MWCNTs-reinforced nanocomposite cylindrical shell were comparatively illustrated and the results were discussed in detail.

An improved model based on real gas state equation and fog formation for condensation heat and mass transfer

In order to predict the condensation heat transfer coefficient precisely, this work aimed at proposing a generalized model with a wide scope of parameters applicability, namely, we presented an improved model that can predict the condensation characteristics which based on heat and mass transfer analogy with consideration of gas compressibility factor, fog formation factor, film waviness factor, suction factor and eddy diffusion factor. The improved model is suitable for those conditions: low pressure condensation at plate-shape and curved-shape surface with natural/forced convection, high pressure condensation at curved shape surface with natural convection. The improved model shows good applicability with the scope of the pressure is up to 2 MPa and the non-condensable (NC) gas mass fraction up to 90%. Six experimental databases (including 436 data) were chosen to validate this model. More than 97% of the results predicted by the improved model were within ±30% bands.

A new micromechanics approach for predicting the elastic response of polymer nanocomposites reinforced with randomly oriented and distributed wavy carbon nanotubes

A comprehensive investigation is carried out into the elastic behavior of carbon nanotube-reinforced polymer nanocomposites using two combined analytical micromechanical methods. A unit cell-based micromechanical method is developed to model the random distribution of carbon nanotubes within the polymer matrix. Also, the Eshelby method is used for modeling the random orientation state of carbon nanotubes within the matrix. Two fundamental aspects affecting the mechanical behavior of carbon nanotube/polymer nanocomposites, including the carbon nanotube waviness and the interphase formed due to the non-boned interaction between the carbon nanotube and the surrounding polymer, are considered in the unit cell method. Comparisons between the results of present method and experimental data reveal that for more realistic predictions, five important factors including, random orientation and random distribution of carbon nanotubes, interphase, waviness and transversely isotropic behavior of carbon nanotube should be considered in the modeling of carbon nanotube-reinforced polymer nanocomposites. The effects of volume fraction, number of waves and waviness factor of carbon nanotube as well as the type of random distribution of CNTs within the matrix on the elastic modulus of the polymer nanocomposites are studied.

Influence of interfacial geometry on the energy absorption capacity and load sharing mechanisms of nacreous composite shells

The excellent mechanical properties of nacreous composites are partly attributed to its staggered microstructure, which is made of multiple layers of mineral tablets bonded through a soft protein matrix. An important parameter that could affect the load sharing mechanism in nacre is the waviness of aragonite tablets. In this work, a continuum model of nacre composite is developed, which takes into account the waviness factor. The tablets are subjected to tensile loading and are initially modeled to have dovetail shapes with varying slopes. The load sharing efficiency of nacre is evaluated through displacements, stresses and strain energy density (SED) of the unit cell. The SEDs of unit cells, tablet and matrix are presented for different overlapping lengths and inclination angles, from which maximum SEDs and optimum overlapping lengths are determined. Parametric studies show that larger inclinations of nacre tablets result in higher energy absorbing capacity. A more general case is also presented, where nacre’s platelet is modeled to have sinusoidal waviness of different wavelengths. By varying the wavelength while maintaining the periodicity of the unit cell, stresses, SEDs and displacements are obtained and compared. Analytical results on the optimum waviness of designed unit cells are validated with observed nacreous microstructures.

Influence of Waviness and Vacancy Defects on Carbon Nanotubes Properties

Previous and present theoretical and experimental research of polymer and other composites have shown that carbon nanotubes, acting as an reinfocements, significantly affect the final mechanical properties of aforementioned composites, thanks to its exceptional mechanical properties. However, the properties of carbon nanotube can be affected by the shape of nanotube, as well as various vacancy deffects within the structure of carbon nanotube. Thus, the waviness and the vacancy deffects decreases the final properties of nanocomposite structures. In this paper, the properties of straight and waved carbon nanotube are compared, on examples with different waviness factor, using the finite element method. Also, different vacancy defects are considered on the same straight and waved nanotube models.

On Joint Roughness: Measurements and Use in Rock Mass Characterization

The paper focuses on the methods commonly used for measuring and quantifying the joint roughness in the current rock mass characterization practice. Among the different parameters traditionally employed to express roughness, major relevance seems to be gained by the “Joint Roughness factor” (jR) applied in the Palmstrom’s rock mass characterization index system, having this factor also been integrated in some quantitative methods recently proposed for estimating the geological strength index of a rock mass. Therefore, a new quantitative approach for a more objective estimation of this factor has been fine-tuned and is presented in the paper. The new method has been specifically designed to assist engineering geologists in gaining consistent values of jR on the base of conventional routine field measurements. It can suitably integrate and support the traditional semi-qualitative Palmstrom’s classification of joint roughness, mostly related to more subjective descriptions, to estimate the most representative values of jR to be considered for rock mass characterization. In its original definition, the factor jR is evaluated for two-dimensional joint profiles by the product of a small-scale roughness factor (the joint smoothness or unevenness factor, js) with a large-scale roughness factor (the joint waviness factor, jw). In order to reduce the subjectivity on the estimate of these partial factors, a simple analytic equation relating them with some parameters traditionally used to quantify 2D joint roughness is here proposed, providing a continuous gradation among the different ratings of the jR scale and also facilitating the implementation of the factor in probabilistic approaches for managing its inherent uncertainty and variability. The presented method applies best for characterizing hard rock masses well-exposed after blasting (e.g., in dam foundation or quarry slopes) or favourably outcropping on natural rocky slopes, where joint surfaces can generally be easily attained and analysed.

Laser rapid manufacturing on vertical surfaces: Analytical and experimental studies

Analytical and experimental studies on geometrical aspects of the deposited tracks were carried out at different processing parameters for laser rapid manufacturing (LRM) in vertical surface configuration using AISI type 304 stainless steel powder on the substrate of the same material. The vertical downward shift of the deposited track and its peak due to the gravity flow of the melt were found to follow quadratic dependence on the track height. The downward rounded bulging was found to be quite significant for the scan speeds lesser than 200mm/min, while this was insignificant for the scan speeds more than 400mm/min. A set of consolidated processing parameters for continuous material deposition was identified. The threshold value of laser energy and powder fed, both per unit traverse length for the continuous deposition were found to be ~96J/mm and ~0.006g/mm respectively. The maximum powder catchment efficiency was ~42% for stand-off distances in the range of 15–18mm. The surface waviness factor was found to decrease from ~0.95 to ~0.05 when the overlap index was increased from 30% to 80%. The study provides a deeper insight into the ensuing geometrical aspects of the tracks using LRM in vertical configuration.

Role of graphene waviness on the thermal conductivity of graphene composites

The waviness effect of graphene nanoplates (GNPs) on the thermal conductivity of GNP-based composites is investigated. Two types of wrinkled GNPs (w-GNPs) and flat GNPs (f-GNPs) are used to fabricate GNP/epoxy composites. Thermal conductivity enhancement is observed in both types of composites. However, under the same processing, f-GNPs exhibit a higher thermal conductivity enhancement than w-GNPs. We finally introduce a concept, the waviness factor, to theoretically analyze the thermal conductivity considering the waviness effect of GNPs. The theoretical predictions are found to show good agreement with experimental observations.

Numerical Simulation of Modal Vibration Response of Wavy Carbon Nanotubes

The potential use of carbon nanotubes (CNTs) in applications such as reinforcing materials in nanocomposites has motivated interest in the measurement of their mechanical properties. Several researchers have used the experimentally measured resonance frequencies of CNTs, along with classical beam theory for straight beams to `back out' CNT modulus values. However, from photomicrographic images of CNTs, it is clear that they are not straight, and that they typically have significant waviness or curvature associated with them. This research involves the development of carbon nanotube models using the finite element (FE) approach and the benchmarking of the developed models against results from other models and experiments. Subsequently, the FE models were used to study the effect of waviness and aspect ratio on the modal vibration response of CNTs, so that a better understanding of the characterization of their mechanical properties can be established. It was found that significant errors in `backed out' modulus values of CNTs can occur when waviness is not accounted for in modal analysis. For example, with a change in waviness factor (amplitude of waviness divided by the projected length of the CNT) from 0 to 0.6, frequency values can change by 29% for the fundamental mode, and the corresponding change in the `backed out' modulus from the straight beam equation can be as high as 66%. The analysis of vibrating CNTs is also important in studies of the sonication process for improving dispersion of CNTs in manufacturing of nanocomposites.

Detection and measurement of waviness on thin metallic wires.

We propose a model for determining the far-field diffraction pattern of wires with waviness. Analytical solutions are obtained by means of the stationary phase method, which allows us to determine dimensional parameters such as wire diameter and waviness factor. Experimental results are presented, which are in accordance with our theoretical description.