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针对 含定向非均匀体的横向各向同性复合材料(即TI介质), 采用球形有效体散射等效的方法, 根据TI材料下的D, Nij表达式, 对横向各向同性条件下Eshelby 张量的积分通用表达式进行化简, 推导出了复合材料的具有横向各向同性特性的有效弹性模量的表达式, 并依此进行了数值分析. 计算结果表明: 利用本方法计算的有效模量随非均匀体含量的增大而减小; 定向排列的非均匀体影响横向各向同性介质的固有各向异性, 水平指向的非均匀体会增大材料的横向各向同性, 模拟结果对评价含非均匀体各向异性介质的特征具有指导意义. 相似文献
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一.引言 作者在前文1里求得了横观各向同性体的弹性力学空间问题的通解,并且作了初步应用。本文的目的在应用前文的通解来具体地讨论横观各向同性的半无限体(假定物体的各向同性面与它的表面平行)的若干问题。这些问题是实用上比较重要的问题,包括:(i)已知半无限体表面上的载荷;(ii)已知表面上各点的位移;(iii)已知表面上各点的法应力和切向位移;(iv)已知表面上各 相似文献
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关联核模型很好地描写了大角度处高能强子-核散射. 但在许多工作中, 忽略了和关联一样重要的非弹性道效应. 本文中, 在强子-核弹性散射过程中, 我们计入了两次非弹性过程并导出了一简单公式. 具体计算了1GeV P+C12的弹性散射. 结果表明: 非弹性效应在所观察的角度对定量结果的影响是很小的. 相似文献
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一阶速度-应力Biot双相各向同性介质弹性波 总被引:1,自引:0,他引:1
提出一种等价的一阶双曲型速度一应力Biot双相各向同性介质弹性波波动方程,以实现双相介质混合波场中纯快慢纵波和纯横波波场分离的问题.应用散度和旋度理论证明双相介质等价方程波场分离的可行性,采用高阶交错网格有限差分法构建高精度正演算子,推导其PML吸收边界条件和稳定性条件,并对均匀双相介质和层状非均匀双相介质模型进行数值... 相似文献
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各向异性、双相孔隙以及非均匀性是描述油气储层时应综合考虑的. 结合随机介质理论和双相介质模型建立了双相各向异性随机介质模型,采用伪谱法模拟了双相各向异性随机介质地震波场,结果表明:双相各向异性随机介质地震波场存在散射波、旅行时扰动等复杂的波场特征,这些特征强烈依赖于随机介质模型参数. 在大非均匀空间尺度下,非均匀幅度主要影响波的旅行时扰动;在小非均匀空间尺度下,非均匀幅度主要影响波的散射. 该研究使人们有可能在统计意义下反演油气储层的非均匀特征,有益于加深对地震波在油气储层中传播规律的认识.
关键词:
双相各向异性
随机介质
伪谱法
地震波 相似文献
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本文分析了在无限大各向同性均匀弹性板表面法向点力激发的兰姆波.给出超声楔形换能器的兰姆波指向性图案公式,对部份推导结果作了实验验证. 相似文献
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一.引言 作者在前文里提出了在无体积力作用时横观各向同性弹性体的平衡问题的一般解法,并应用这个解法讨论了圆锥的弯曲问题和半无限体的各种边值问题。本文的目的在于找寻在体积力作用下横观各向同性弹性体的平衡问题的特解。利用这个特解将体积力消去后,便可应用前文的结果来设法满足所设的边界条件。作为本文方法的初步应用,我们计算了在横观各向同性的 相似文献
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过渡金属Tc及其氮化物TcN,TcN$lt;sub$gt;2$lt;/sub$gt;,TcN$lt;sub$gt;3$lt;/sub$gt;与TcN$lt;sub$gt;4$lt;/sub$gt;低压缩性的第一性原理计算研究
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采用基于密度泛函理论的第一性原理计算方法研究了Tc及其氮化物的弹性性质、电子结构、原子布局数等,并分析和计算了它的氮化物的理论硬度. 结果表明随着Tc中氮的掺入量的渐增,出现层状结构,它们的弹性模量并非单调增加,其中TcN的体弹模量最大而剪切模量最小;层状结构的TcN3的剪切模量最大而体弹模量最小,TcN4的理论计算硬度最大. 说明在Tc的氮化物中,其体弹模量与材料的晶体结构、平均每个原子上的电荷密度和材料的质量密度有关;化学键的共价性结构和氮元素的含量对理论计算硬度有正作用;而剪切模量的极大值则与其层状结构及体系中一定量的方向基本一致的N—N键相关.
关键词:
第一性原理
弹性性质
电子结构 相似文献
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E. Pelletier J. P. Montfort F. Lapique J. L. Loubet A. Tonck J. M. Georges 《Il Nuovo Cimento D》1994,16(7):789-793
Summary The viscoelastic properties of liquids close to solid surfaces differ from the bulk. Nanorheology has been performed by using
a surface force apparatus adapted to operate as a rheometer in a sphere-plane geometry. Axial oscillatory measurements have
been carried out with high polymer solutions filling the gap. The deformations were kept sufficiently small not to perturb
the film structure and were applied in a large range of frequency (10−3 to 102 s−1). It is shown that the complex modulus characterizing the confined medium can be split into two components: a shear modulus
(it accounts for the viscous dissipation due to the flow of solvent molecules through the mesh created by the long polymer
chains which connect the two solid surfaces) and a compression modulus which is related to the normal stress response of the
chains confined between the solid surfaces. The hydrodynamic screening lengthξ
h and the correlation length ξ deduced from the two moduli are compared and are found to scale in the same way as a function
of the distance between the two surfaces.
Paper presented at the I International Conference on Scaling Concepts and Complex Fluids, Copanello, Italy, July 4–8, 1994. 相似文献
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利用基于密度泛函理论的第一性原理平面波赝势方法 并结合准谐徳拜模型研究了NaCl结构的TiC在高压下的弹性性质、电子结构和热力学性质. 计算所得零温零压下的晶格常数、体弹模量及弹性常数与实验值符合得很好. 零温下弹性常数和弹性模量随压强增大而增大. 通过态密度和电荷密度的分析, Ti-C键随压强增大而增强. 运用准谐德拜模型, 成功计算了TiC在高温高压下的体弹模量、熵、热膨胀系数、徳拜温度、 Grüneisen参数和比热容. 结果表明压强对体弹模量、热膨胀系数和徳拜温度的影响大于温度对其的影响. 热容随着压强升高而减小, 在高温高压下, 热容接近Dulong-Petit极限. 相似文献
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Asymmetric plate impact experiments are conducted on LY12 aluminium alloy in a pressure range of 85-131 GPa. The longitudinal sound speeds axe obtained from the time-resolved particle speed profiles of the specimen measured with Velocity Interferometer System for Any Reflector (VISAR) technique, and they are shown to be good agreement with our previously reported data of this alloy in a pressure range of 20-70 GPa, and also with those of 2024 aluminium reported by McQueen. Using all of the longitudinal speeds and the corresponding bulk speeds calculated from the Gruneisen equation of state (EOS), shear moduli of LY12 aluminium alloy are obtained. A comparison of the shear moduli in the solid phase region with those estimated from the Steinberg model demonstrate that the latter are systematically lower than the measurements. By re-analysing the pressure effect on the shear modulus, a modified equation is proposed, in which the pressure term of P/η^1/3 in the Steinberg model is replaced by a linear term. Good agreement between experiments and the modified equation is obtained, which implies that the shear modulus of LY12 aluminium varies linearly both with pressure and with temperature throughout the whole solid phase region. On the other hand, shear modulus of aluminium in a solid-liquid mixed phrase region decreases gradually and smoothly, a feature that is very different from the drastic dropping at the melting point under static conditions. 相似文献
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Asymmetric plate impact experiments are conducted on LY12 aluminium
alloy in a pressure range of 85--131\,GPa. The longitudinal sound
speeds are obtained from the time-resolved particle speed profiles of
the specimen measured with Velocity Interferometer System for Any
Reflector (VISAR) technique, and they are shown to be good agreement
with our previously reported data of this alloy in a pressure range
of 20--70\,GPa, and also with those of 2024 aluminium reported by
McQueen. Using all of the longitudinal speeds and the corresponding
bulk speeds calculated from the Gruneisen equation of state (EOS),
shear moduli of LY12 aluminium alloy are obtained. A comparison of
the shear moduli in the solid phase region with those estimated from
the Steinberg model demonstrate that the latter are systematically
lower than the measurements. By re-analysing the pressure effect on
the shear modulus, a modified equation is proposed, in which the
pressure term of $P/\eta^{1/3}$ in the Steinberg model is replaced by
a linear term. Good agreement between experiments and the modified
equation is obtained, which implies that the shear modulus of LY12
aluminium varies linearly both with pressure and with temperature
throughout the whole solid phase region. On the other hand, shear
modulus of aluminium in a solid-liquid mixed phrase region decreases
gradually and smoothly, a feature that is very different from the
drastic dropping at the melting point under static conditions. 相似文献
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Modulus–porosity relationships are critical for engineered bone tissue scaffold materials such as hydroxyapatite (HA), where porosity is essential to biological function. Resonant ultrasound spectroscopy (RUS) measurements revealed that the Young's modulus, E, and shear modulus, G, of both alumina and HA decrease monotonically with increasing volume fraction porosity, P, for 0.06 < P < 0.39 (alumina) and 0.05 < P < 0.51 (HA). Although the elastic moduli of porous materials have been measured by a number of different ultrasonic resonance techniques (of which the RUS technique is one example) and over the last decade the elastic moduli of many solids have been measured by the RUS technique, this study is the first systematic RUS study of porous materials. Comparison of E versus P data for alumina (which has been studied extensively) with literature data from several measurement techniques indicates the RUS technique is effective for modulus–porosity measurements. Another key result is that although the HA specimens included in this study have a unimodal pore size distribution, the details of the decrease in E and G with increasing P agree well with literature data for HA with both unimodal and bimodal pore size distributions. In addition, Poisson's ratio exhibits a local minimum in the porosity range of 0.2 < P < 0.25 for both HA and alumina, which may be related to the pore morphology evolution during sintering. 相似文献
17.
Empirical modeling of longitudinal tension and compression of graphene nanoparticles and nanoribbons
Longitudinal tension and compression of graphene nanoparticles and nanoribbons have been studied using an empirical model.
The pseudo-Young’s modulus of graphene nanoparticles and nanoribbons has been calculated. The size effect, i.e., the dependence
of the elastic modulus on linear parameters of graphene objects, has been studied. An increase in pseudo-Young’s modulus discontinues
as the length increases during the nanoparticle-to-nanoribbon transition. For the same perimeter, the graphene ribbon edges
are characterized by smaller pseudo-Young’s moduli in comparison with uniaxial carbon nanotubes. Elastic deformation of graphene
nanoparticles and nanoribbons has been observed in the relative length variation range of 0.93–1.12. 相似文献
18.
Using new supercells, the influence of the alloying elements Co, Cr, Ta, Re, and Ru on the elastic properties of ternary and quaternary nickel-base superalloys are systematically studied by the first-principles pseudopotential method. The calculated results of the five ternary and three quaternary superalloys suggest that the alloying elements can increase the elastic moduli. Re is found to be most effective in increasing the moduli of ternary alloys. Among the quaternary alloys, the Ni-Al-Re-Ru system has the largest moduli. Our calculated values of the elastic moduli agree very well with the experimental results. The charge density redistribution and partial density of states are calculated for the quaternary system including both Re and Ru. Covalent-like bonding between Re and its nearest neighbor is observed. The hybridization between the Re-d orbital and the host Ni-p, d orbitals are the origin of the modulus strengthening effect. 相似文献
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We argue that the paradoxal softness of the red blood cells (RBC) in fluctuation experiments is apparent. We show that the effective surface shear modulus mus of the RBC obtained from fluctuation data and that measured in static deformation experiments have the same order of magnitude. In the RBC model developed for this purpose the spectrin network cytoskeleton with the bulk shear modulus estimated as mu approximately 105-165 Pa contributes to both normal and tangent fluctuations of the system and confines the membrane fluctuations. The calculated ratio of the mean-square amplitudes / is 2-3 orders of magnitude smaller than it is in the free membrane with the same bending and shear moduli. 相似文献