Theoretical study of the dependences of the young’s and torsion moduli of thin single-layer carbon zigzag and armchair nanotubes on the geometric parameters

The Young’s and torsion moduli of single-layer carbon (m, 0) and (m, m) nanotubes are studied. It is demonstrated that both moduli depend on the chirality, diameter, and length of the nanotube. It is found for the first time that the torsion modulus increases with the nanotube diameter and diminishes with an increase in its length. By considering nanotubes with various values of the diameter-to-length ratio, it is shown that the Young’s and torsion moduli of the nanotubes saturate at a diameter-to-length ratio of ～0.3. The values of the torsion modulus as calculated from the Young’s modulus we obtained and from the deformation energy do not coincide, which can be attributed to the effect of dangling bonds at the open ends of the nanotubes. Energy calculations are performed using the Goodwin modification of the semiempirical Harrison tight-binding method.     

Investigation of the photoplastic effect in vitreous semiconductors by cyclic nanoindentation

The dynamics of photoinduced changes in the internal friction and the Young’s modulus for films in the As-Se system is investigated by cyclic nanoindentation at infralow frequencies. It is revealed that the irradiation of the films leads to an increase in the Young’s modulus, a retardation of relaxation processes, and a decrease in the viscosity and nanohardness of the material. The results obtained are discussed in the framework of the concept of microheterogeneous glass structure.     

Nontrivial tensile behavior of rutile TiO<Subscript>2</Subscript> nanowires: a molecular dynamics study

In this paper, we study the tensile behavior of cylindrical rutile TiO₂ nanowires, employing molecular dynamics (MD) simulation technique. The third-generation charge optimized many-body (COMB3) has been used for interatomic potential modeling. The influence of temperature and nanowire diameter on Young’s modulus is investigated. Our simulations exhibit the anisotropic behavior of Young’s modulus as a function of diameter for different crystallographic orientations. Although our results are in good accord with the existing results in [1 0 0] direction, Young’s modulus adds up monotonically with increasing the cross-sectional diameter of nanowire in [0 0 1] direction. It is found that Young’s modulus of the nanowires are lower (higher) than the bulk value for [0 0 1] ([1 0 0]) direction. Furthermore, simulation results also indicate that Young’s modulus of rutile TiO₂ nanowire increases as a function of temperature for a given diameter, unexpectedly. The obtained results may be useful in the field of nanotechnology for optimizing mechanical performance to gain specific applications.     

Negative Poisson’s ratio for cubic crystals and nano/microtubes

The paper systemizes numerous cubic crystals which can have both positive and negative Poisson’s ratios (the so-called partial auxetics) depending on the specimen orientation in tension. Several complete cubic auxetics whose Poisson’s ratio is always negative are indicated. The partial cubic auxetics are classified with the use of two dimensionless elastic parameters. For one of the parameters, a critical value is found at which the orientation behavior of the crystals changes qualitatively. The behavior of mesotubes obtained by rolling up plates of cubic crystals (crystals with rectilinear anisotropy) is considered in detail. Such mesotubes with curvilinear cubic anisotropy can have micron and nanometer lateral dimensions. It is shown that uniform tension of nano/microtubes of cubic crystals is possible only in the particular case of zero chirality angle (the angle between the crystallographic axis and the axis of a stretched tube). It is demonstrated by the semi-inverse Saint-Venant method that solution of the axial tension problem for cylindrically anisotropic nano/microtubes of cubic crystals with a non-zero chirality angle is possible with radially inhomogeneous fields of three normal stresses and one shear stress. In the examples considered, the cylindrically anisotropic nano/microtubes of cubic crystals are auxetics even if they are initially non-auxetics with rectilinear anisotropy.     

金属管杨氏模量与温度关系的实验研究

采用动力学共振法测量不同管径金属管的共振频率,运用origin软件对实验数据进行二次函数拟合,代入管状材料杨氏模量的计算公式得到试样的杨氏模量。通过加热控温设备改变金属管温度,研究金属管杨氏模量与温度的关系。实验结果表明金属管杨氏模量的大小与温度成线性关系。     

Photothermoacoustic oscillations in a solid-piezoelectric layered structure

Photothermoacoustic oscillations in a thin plane-layered structure consisting of an isotropic solid and a piezoelectric crystal of class 6mm (or piezoelectric ceramics) are studied theoretically and experimentally. Expressions for the potential difference across an arbitrary layer of the piezoelectric transducer are derived. For the case of a two-layer transducer, the amplitude-frequency and phase-frequency dependences of the signal are analyzed. It is shown that, from these experimental dependences, one can determine certain elastic and thermal parameters of a solid. An experiment is performed with samples of Cu, Zn, and TsTS-19 piezoceramics in the frequency range within 9–1000 Hz. The experimental data are used to determine the values of the reduced Young’s modulus and the thermal diffusivity of the materials under study.     

游标卡尺在测定金属杨氏模量中的应用

根据拉伸法测量金属杨氏模量的原理,利用现有的杨氏模量仪,设计了一套应用游标卡尺测定金属杨氏模量的方法。     

Elasticity,anelasticity, and microplasticity of directionally crystallized aluminum-germanium alloys

The structure, Young’s modulus defect, and internal friction in aluminum-germanium alloys have been studied under conditions of longitudinal elastic vibrations with a strain amplitude in the range of 10^?6?3 × 10^?4 at frequencies about 100 kHz. The ribbon-shaped samples of the alloys with the germanium content from 35 to 64 wt % have been produced by drawing from the melt by the Stepanov method at a rate of 0.1 mm/s. It has been shown that the dependences of the Young’s modulus defect, logarithmic decrement, and vibration stress amplitude on the germanium content in the alloy at a constant strain amplitude have an extremum at 53 wt % Ge. This composition corresponds to the eutectic composition. The dependences of the Young’s modulus defect, the decrement, and vibration stress amplitude at a constant microstrain amplitude have been explained by the vibrational displacements of dislocations, which depend on the alloy structure.     

Recovery of Young’s modulus upon annealing of nanostructured niobium produced through severe plastic deformation

The effect of temperature (in the range 20–500°C) on the Young’s modulus of nanostructured niobium with Ta impurity content <0.5 wt % and that of O₂ < 0.1 wt % and with a mean grain size of ?200 nm is studied. The transformation of polycrystalline niobium into a nanostructured state is performed through severe plastic deformation by equal-channel angular pressing. The Young’s modulus is found to increase in two stages as the temperature of isothermal annealing is gradually increased. The mechanisms of recovery of the elastic modulus upon annealing of the nanostructured niobium are discussed in the context of the modern concepts of the defect structure of deformed metals.     

Nanoindentation of a hard ceramic coating formed on a soft substrate

The hardness and Young’s modulus of the thin hydroxyapatite-based coatings deposited by RF magnetron sputtering onto magnesium alloy, titanium, and steel substrates are studied. As the penetration depth increases, the hardness and Young’s modulus of these coatings are found to tend toward the values that are characteristic of the substrates. It is shown that the difference between the values of hardness and Young’s modulus at small penetration depths (h < 80–100 nm) can be caused by the difference between the physicomechanical properties inside the coatings and that this difference at large penetration depths (h > 100 nm) can be induced by an additional effect of the strength properties of the substrate material.     

杨氏弹性模量测量的设计性实验

首先分析指出杨氏弹性模量测量作为设计性实验符合设计性实验的选题原则;然后,简介测量金属丝伸长量的几种方案,通过不确定度分析,指出进一步提高杨氏弹性模量测量精度的关键;最后,总结了本设计性实验的意义.     

对液压法测杨氏模量的实验研究

引入了液压法测量杨氏模量,用液压微位移放大原理来表征微小变化量,用液压微位移放大器对传统的实验装置进行改进,通过实验原理、误差分析,结合测量结果,对此实验方法进行分析与讨论,由此给出了一种测量杨氏模量新的方法.     

Measurement of the elastic moduli of dense layers of oriented carbon nanotubes by a scanning force microscope

A technique is developed for measuring the modulus of elasticity of a material with a Nanoscan scanning force microscope on the basis of measuring the dependence of probe vibration frequency on the penetration depth of the needle into the specimen. This technique makes it possible to study materials with elastic moduli from 50 to 1000 GPa. The Young moduli of dense films of carbon nanotubes oriented at angles of 45° and 90° to the quartz substrate are measured. From their ratio, the Young modulus in the direction perpendicular to the tubes and the anisotropy of the elastic moduli are determined. A comparison of these values with the corresponding values obtained for a nanotube film deposited on a silicon substrate is carried out. On the basis of this comparison, a conclusion is made concerning the interaction between single-layer nanotubes and between nanotubes in a mixture of single-layer and multilayer ones.     

Surface waves and mode conversion at a surface coated with an elastic heavy layer

A surface wave of frequency lying within bulk band of transverse waves is found in an elastic medium coated with a thin layer endowed with a surface mass density, surface Young's modulus and surface bending modulus. The wave is a particular case of surface resonance with infinite lifetime. In materials with negative Poisson's ratio (auxetics) the wave exists even for coating material with zero bending modulus, whereas with positive Poisson's ratio it requires the surface bending modulus to be larger than the surface Young's modulus. The manifestation of this wave in the reflection coefficient seems promising for fabrication of devices showing monochromator properties.     

Nanoindentation study of Cu52Zr37Ti8In3 bulk metallic glass

In this paper, Cu₅₂Zr₃₇Ti₈In₃ bulk metallic glass has been studied by nanoindentation. Three different ways for nanoindentation tests were employed. Load-control nanoindentation was used to investigate the effect of the loading rate on the hardness and Young’s modulus. Young’s modulus of the specimen shows a loading rate dependence. The constant-load indentation creep measurement was performed. The creep data were fitted with the generalized Kelvin model, and the compliance spectrum and retardation spectrum were derived. Furthermore, the storage compliance and loss compliance were also discussed. For characterizing the change of the hardness and Young’s modulus with increasing indentation depth, depth-control nanoindentation analysis was conducted. The results show that both the hardness and Young’s modulus decrease with nanoindentation depth.     

Surface topography,nano-mechanics and secondary structure of wheat gluten pretreated by alternate dual-frequency ultrasound and the correlation to enzymolysis

The effects of alternate dual-frequency ultrasound (ADFU) pretreatment on the degree of hydrolysis (DH) of wheat gluten (WG) and angiotensin I-converting enzyme (ACE) inhibitory activity were investigated in this research. The surface topography, nano-mechanics and secondary structure of WG were also determined using atomic force microscope (AFM) and circular dichroism (CD). The correlations of ACE inhibitory activity and DH with surface topography, nano-mechanics and secondary structure of WG were determined using Pearson’s correlation analysis. The results showed that with an increase in either pretreatment duration or power, the ACE inhibitory activity of the hydrolysate also increases, reaching maximum at 10 min and 150 W/L, respectively, and then decreases thereafter. Similarly, AFM analysis showed that as the pretreatment duration or power increases, the surface roughness also increase and again a decrease occurs thereafter. As the pretreatment duration or power increased, the Young’s modulus and adhesion of WG also increased and then declined. Young’s modulus and adhesions average values were compared with ACE inhibitory activity reversely. The result of the CD spectra analysis exhibited losses in the relative percentage of α-helix of WG. Pearson’s correlation analysis showed that the average values of Young’s modulus and the relative percentage of α-helix correlated with ACE inhibitory activity of the hydrolysates linearly and significantly (P < 0.05); the relative percentage of β-sheet correlated linearly with DH of WG significantly (P < 0.05). In conclusion, ADFU pretreatment is an efficient method in proteolysis due to its physical and chemical effect on the Young’s modulus, α-helix and β-sheet of WG.     

Mechanical properties of silicon nanobeams with an undercut evaluated by combining the dynamic resonance test and finite element analysis

Mechanical properties of silicon nanobeams are of prime importance in nanoelectromechanical system applications.A numerical experimental method of determining resonant frequencies and Young’s modulus of nanobeams by combining finite element analysis and frequency response tests based on an electrostatic excitation and visual detection by using a laser Doppler vibrometer is presented in this paper.Silicon nanobeam test structures are fabricated from silicon-oninsulator wafers by using a standard lithography and anisotropic wet etching release process,which inevitably generates the undercut of the nanobeam clamping.In conjunction with three-dimensional finite element numerical simulations incorporating the geometric undercut,dynamic resonance tests reveal that the undercut significantly reduces resonant frequencies of nanobeams due to the fact that it effectively increases the nanobeam length by a correct value △L,which is a key parameter that is correlated with deviations in the resonant frequencies predicted from the ideal Euler-Bernoulli beam theory and experimentally measured data.By using a least-square fit expression including △L,we finally extract Young’s modulus from the measured resonance frequency versus effective length dependency and find that Young’s modulus of a silicon nanobeam with 200-nm thickness is close to that of bulk silicon.This result supports that the finite size effect due to the surface effect does not play a role in the mechanical elastic behaviour of silicon nanobeams with thickness larger than 200 nm.     

利用横向共振法对牛骨杨氏模量测定的讨论

一般的静态法检测某些材质的杨氏模量时,常因易碎(如陶瓷)、多孔疏松不能恢复(骨质等)等诸多原因难以准确测量。而较为精准的激光散斑法又比较复杂。动态实验方法测量材料的杨氏模量是力学研究分析的一个有力工具。文章采用横向共振法测定骨质的弹性模量,并用静态法(激光散斑法)来验证其准确性。结果表明横向共振法测得的牛骨杨氏模量与激光散斑法的结果基本吻合,且实验结果稳定,误差小,可以在较短时间内取得很有价值的数据。另外,还对样品在不同温度下的杨氏模量的测量作了分析。     

Adhesion and Young’s Modulus Estimation for Chemically Treated Argan Nut Shell Particles Reinforced Poly-Lactic Acid Polymer

Abstract

The use of natural fillers as reinforcements for polymer plastics takes place in a variety of industrial applications. Henceforth, the use of theoretical models to predict the properties of such bio-composites is essential. In this work, we estimated the Young’s modulus of poly-lactic acid (PLA) bio-composites reinforced with argan nut shell (ANS) chemically treated particles (successive alkali treatment, bleaching and silane treatments) using five theoretical models and compared the predicted results with our prior experimental results. These models allowed us to study the assumed spherical form of the ANS particles and the adhesion/distribution of these particles in a PLA matrix. The results indicated that the ANS chemically treated particles could be considered as spherical particles having good adhesion with the PLA matrix. In addition, three other mathematical models were used to predict Young’s modulus of the ANS chemically treated particles. The results showed that the highest value of Young modulus among the three treatments was obtained for the ANS alkali-bleached particles. In addition, the silane treatment enhanced the adhesion between the ANS particles and the PLA matrix, but decreased the Young’s modulus value compared to the other two treatments.     

Elasticity and inelasticity of the SiC/Al-13Si-9Mg biomorphic metal ceramics

The acoustic investigations of the elastic (Young’s modulus) and microplastic properties of a composite material, the SiC/Al-13Si-9Mg biomorphic metal ceramic, were performed. The ceramic was prepared by infiltration of the Al-13Si-9Mg melt into porous silicon carbide derived from wood of two species of trees, beech and sapele. The measurements were performed with a composite piezoelectric vibrator under resonance conditions, with rod-shaped samples vibrated longitudinally at about 100 kHz over a wide range of vibrational strain amplitudes, which included both the linear (amplitude-independent) and nonlinear (microplastic) regions. It was shown that the Young’s modulus and the microplastic properties of the composite are anisotropic and depend substantially on the tree species, particularly when longitudinal vibrations are excited in samples cut along the tree fibers.