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On nonlinear rheology of masonries and granular media 关于砌体和颗粒介质的非线性流变学
IF 6.6 1区 工程技术 Q1 Engineering Pub Date : 2024-03-06 DOI: 10.1016/j.ijengsci.2024.104053
Emanuele Reccia, Victor A. Eremeyev

We introduce a new rheological nonlinear model for some granular media such as masonries. The latter may demonstrate a rather complex behaviour. In fact, considering a masonry one can see that relative rotations of bricks are most important in comparison with deformation of bricks themselves. As a result, one gets stresses and couple stresses as static characteristics of such a medium. Using the Cosserat point approach for modelling of orientational interactions between masonry elements we provide a deformation energy for such a medium which takes into account both material and geometrical nonlinearity.

我们为某些粒状介质(如砌石)引入了一种新的流变非线性模型。后者可能表现出相当复杂的行为。事实上,考虑到砌体,我们可以看到砖块的相对旋转与砖块本身的变形相比是最重要的。因此,应力和耦合应力是这种介质的静态特征。我们使用 Cosserat 点方法对砌体元素之间的方向相互作用进行建模,为这种介质提供了变形能量,其中考虑到了材料和几何非线性因素。
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引用次数: 0
Influence of material anisotropy on the mechanics of surface damage 材料各向异性对表面损伤力学的影响
IF 6.6 1区 工程技术 Q1 Engineering Pub Date : 2024-02-23 DOI: 10.1016/j.ijengsci.2024.104025
A.V. Savikovskii , A.S. Semenov , M.L. Kachanov

The problem of multiple cracks originating at free surface (surface damage) in an anisotropic material is considered. We focus on the effect of material anisotropy on the mechanics of crack interactions – in particular, on the suppressing effect of interactions on crack nucleation and growth under the tensile loading (stress shielding). Importantly, this effect may change to the opposite one of enhancement, under the shear loading. These effects strongly depend on the material anisotropy. Calculations were performed for the orthotropic materials and the effect of anisotropy was examined by case studies of specific configurations that included comparison with the case of the isotropic material.

本研究考虑了各向异性材料中自由表面产生的多重裂纹(表面损伤)问题。我们将重点放在材料各向异性对裂纹相互作用力学的影响上--特别是在拉伸载荷(应力屏蔽)作用下,相互作用对裂纹成核和生长的抑制作用。重要的是,在剪切荷载下,这种效应可能会转变为相反的增强效应。这些效应在很大程度上取决于材料的各向异性。我们对正交材料进行了计算,并通过与各向同性材料进行比较的特定配置案例研究来检验各向异性的影响。
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引用次数: 0
Modelling issues and advances in nonlocal beams mechanics 非局部梁力学的建模问题和进展
IF 6.6 1区 工程技术 Q1 Engineering Pub Date : 2024-02-20 DOI: 10.1016/j.ijengsci.2024.104042
Raffaele Barretta , Raimondo Luciano , Francesco Marotti de Sciarra , Marzia Sara Vaccaro

Nonlocal continuum mechanics presents still open questions about applicability of integral constitutive theories to nanostructures of current interest in Engineering Science. Nevertheless, nonlocal elasticity is widely exploited to model size effects in small-scale structures since it represents an effective tool to avoid computationally expensive procedures. The known strain-driven approach proposed by Eringen has shown an intrinsic incompatibility between constitutive and equilibrium requirements when applied to structures. Such an issue has been acknowledged by the scientific community merely for bounded continua. For structural problems defined in unbounded domains, obstruction to equilibrium caused by the strain-driven formulation is a still open issue. The present contribution definitely proves inapplicability of the strain-driven spatial convolution to structural mechanics and proposes a consistent nonlocal approach for both bounded and unbounded structures. The presented methodology is based on stress-driven spatial convolutions, representing the key paradigm to formulate a well-posed theory of integral elasticity and to effectively model scale effects in nanobeams of applicative interest in Nano-Mechanics.

非局部连续介质力学对工程科学领域当前关注的纳米结构的整体构成理论的适用性提出了仍未解决的问题。尽管如此,非局部弹性仍被广泛用于模拟小尺度结构的尺寸效应,因为它是避免昂贵计算程序的有效工具。由 Eringen 提出的已知应变驱动方法在应用于结构时显示出构成要求和平衡要求之间的内在不兼容性。科学界仅仅针对有界连续体承认了这一问题。对于定义在无界域中的结构问题,应变驱动公式对平衡的阻碍仍然是一个悬而未决的问题。本论文无疑证明了应变驱动空间卷积在结构力学中的不适用性,并为有界和无界结构提出了一致的非局部方法。本文提出的方法基于应力驱动的空间卷积,代表了一种关键范式,可用于制定积分弹性理论,并有效模拟纳米力学中具有应用价值的纳米梁的尺度效应。
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引用次数: 0
Thermomechanical modeling of functionally graded materials based on bimaterial fundamental solutions 基于双材料基本解的功能分级材料热力学建模
IF 6.6 1区 工程技术 Q1 Engineering Pub Date : 2024-02-20 DOI: 10.1016/j.ijengsci.2024.104040
Chunlin Wu , Liangliang Zhang , George J. Weng , Huiming Yin

The Green’s function technique has been used to directly calculate the local fields of a functionally graded material (FGM) under thermomechanical loading, thus predicting its effective material properties. For a bi-phase FGM continuously switching the particle and matrix phases, the particle size and material gradation play a complex role in its effective material behavior. Using Eshelby’s equivalent inclusion method, particles are simulated by a source of eigen-fields in a bounded bi-layered domain, while the boundary effects are evaluated by the boundary integrals of the fundamental solutions. Using the volume integral of Green’s functions, over 10,000 particles are used to simulate an FGM under thermal and mechanical loading, respectively. The dual equivalent inclusion method is used to solve for the temperature and stress fields coupled with temperature loading. The averaged thermomechanical field distribution in the gradation direction is evaluated under different loading conditions. The effective stiffness, thermal expansion coefficient, and heat conductivity significantly change with the loading condition, particle size, and material gradation. The homogenization methods, which approximate an FGM as a continuously graded material with thermoelastic properties depending on the volume fraction only, cannot capture these micromechanical features of FGMs, while the present cross-scale approach with the inclusion-based boundary element method (iBEM) directly evaluates local fields and predicts effective material behaviors with high fidelity and efficiency.

格林函数技术被用于直接计算热机械加载下功能分级材料(FGM)的局部场,从而预测其有效材料特性。对于颗粒相和基体相连续切换的双相 FGM,颗粒尺寸和材料级配在其有效材料行为中起着复杂的作用。利用 Eshelby 的等效包含法,粒子由有界双层域中的特征场源模拟,而边界效应则由基本解的边界积分评估。利用格林函数的体积积分,超过 10,000 个粒子分别用于模拟热负荷和机械负荷下的 FGM。采用二元等效包含法求解与温度加载耦合的温度场和应力场。评估了不同加载条件下梯度方向上的平均热机械场分布。有效刚度、热膨胀系数和热导率随加载条件、粒度和材料级配的变化而显著改变。均质化方法将烟气脱硫材料近似为热弹性特性仅取决于体积分数的连续分级材料,无法捕捉烟气脱硫材料的这些微观力学特征,而本跨尺度方法采用基于包容的边界元方法 (iBEM) 直接评估局部场,并高保真、高效地预测有效的材料行为。
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引用次数: 0
Electro-mechanical surface wrinkling of a finite block of dielectric elastomers accounting for the pre-stretch and the aspect ratio 考虑预拉伸和长宽比的有限块状电介质弹性体的电动机械表面起皱技术
IF 6.6 1区 工程技术 Q1 Engineering Pub Date : 2024-02-19 DOI: 10.1016/j.ijengsci.2024.104041
Lingling Chen , Xu Yang , Chuo Zhao , Shengyou Yang

Surface instability of elastomers is of great interest in engineering science, especially in the characterization of flexible electronic materials and the manufacture of micro-nano surface topography. There is limited research on how the geometry of the block affects wrinkle appearance in a multiphysics environment. In this paper, we formulate the boundary-value problem and its incremental forms to analyze the sinusoidal surface instability of a neo-Hookean dielectric block subjected to electromechanical loads. We discover that the competition between the Maxwell stress, induced by the voltage, and the mechanical stress caused by the stretch, plays a crucial role in inducing surface wrinkling. Furthermore, we find that the aspect ratio of the block can modify the critical value of the combination of voltage and pre-stretch required for wrinkling. In addition to this, the aspect ratio also affects the shape of the wrinkling. Specifically, if the elastomer block has a smaller aspect ratio, its sinusoidal wrinkling will have a larger wavenumber. Our paper enhances the understanding of surface instability in electrostrictive elastomers and provides guidance on triggering it without breaking down the elastomer.

弹性体的表面不稳定性在工程科学中,尤其是在柔性电子材料的表征和微纳表面形貌的制造中,具有极大的意义。在多物理场环境中,关于块体的几何形状如何影响皱纹外观的研究十分有限。在本文中,我们提出了边界值问题及其增量形式,以分析新胡克介电块在机电负载作用下的正弦表面不稳定性。我们发现,电压引起的麦克斯韦应力和拉伸引起的机械应力之间的竞争在引起表面起皱方面起着关键作用。此外,我们还发现块体的长宽比可以改变起皱所需的电压和预拉伸组合的临界值。除此之外,长宽比还会影响起皱的形状。具体来说,如果弹性体块的高宽比较小,其正弦起皱的波数就会较大。我们的论文加深了人们对电致伸缩弹性体表面不稳定性的理解,并为在不破坏弹性体的情况下触发表面不稳定性提供了指导。
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引用次数: 0
A midsurface elasticity model for a thin, nonlinear, gradient elastic plate 非线性梯度弹性薄板的中表面弹性模型
IF 6.6 1区 工程技术 Q1 Engineering Pub Date : 2024-02-08 DOI: 10.1016/j.ijengsci.2024.104026
C. Rodriguez

In this paper, we derive a dynamic surface elasticity model for the two-dimensional midsurface of a thin, three-dimensional, homogeneous, isotropic, nonlinear gradient elastic plate of thickness h. The resulting model is parameterized by five, conceivably measurable, physical properties of the plate, and the stored surface energy reduces to Koiter’s plate energy in a singular limiting case. The model corrects a theoretical issue found in wave propagation in thin sheets and, when combined with the author’s theory of Green elastic bodies possessing gradient elastic material boundary surfaces, removes the singularities present in fracture within traditional/classical models. Our approach diverges from previous research on thin shells and plates, which primarily concentrated on deriving elasticity theories for material surfaces from classical three-dimensional Green elasticity. This work is the first in rigorously developing a surface elasticity model based on a parent nonlinear gradient elasticity theory.

本文为厚度为 h 的三维、均质、各向同性、非线性梯度弹性薄板的二维中表面推导了一个动态表面弹性模型。该模型由五种可以测量的薄板物理特性参数化,在奇异极限情况下,存储的表面能可还原为 Koiter 板能。该模型纠正了薄板中波传播的一个理论问题,并与作者关于拥有梯度弹性材料边界面的绿色弹性体理论相结合,消除了传统/经典模型中断裂的奇异性。我们的方法有别于以往对薄壳和薄板的研究,后者主要集中于从经典三维格林弹性中推导出材料表面的弹性理论。这项研究首次在母体非线性梯度弹性理论的基础上严格开发了表面弹性模型。
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引用次数: 0
Interaction of in-plane waves with a structured penetrable line defect in an elastic lattice 面内波与弹性晶格中结构化可穿透线缺陷的相互作用
IF 6.6 1区 工程技术 Q1 Engineering Pub Date : 2024-02-06 DOI: 10.1016/j.ijengsci.2023.104011
M.J. Nieves , B.L. Sharma

We consider the scattering of in-plane waves that interact with an edge of a structured penetrable inertial line defect contained in a triangular lattice, composed of periodically placed masses interconnected by massless elastic rods. The steady state problem for a time-harmonic excitation is converted into a vector Wiener–Hopf equation using the Fourier transform. The matrix Wiener–Hopf kernel of this equation describes the dynamic phenomena engaged in the scattering process, which includes instances where localised interfacial waves can emerge along the structured defect. This information is exploited to identify the dependency of the existence of these waves on the incident wave parameters and the properties of inertial defect. Symmetry in the structure of the scattering medium allows us to convert the vectorial problem into a pair of uncoupled scalar Wiener–Hopf equations posed along the lattice row containing the defect. The solution embodies an exact representation of the scattered field, in terms of a contour integral in the complex plane, that includes the contributions of evanescent and propagating waves. The solution reveals that in the remote lattice, the reflected and transmitted components of incident field are accompanied by dynamic modes from three symmetry classes, which include localised interfacial waves. These classes correspond to tensile modes acting transverse to the defected lattice row, shear modes that act parallel to this row, and wave modes represented as a mixture of these two responses. Benchmark finite element calculations are also provided to validate the results against our semi-analytical solution which involves, in particular, numerical computation of the contour integrals. Graphical illustrations demonstrate special dynamic responses encountered during the wave scattering process, including dynamic anisotropy, negative reflection and negative refraction.

我们考虑了平面内波的散射问题,该散射与三角形晶格中包含的结构化可穿透惯性线缺陷的边缘相互作用,该三角形晶格由周期性放置的质量块和无质量的弹性杆相互连接组成。利用傅立叶变换将时谐激励的稳态问题转换为矢量维纳-霍普夫方程。该方程的矩阵维纳-霍普夫内核描述了散射过程中的动态现象,包括沿结构缺陷出现局部界面波的情况。利用这些信息可以确定这些波的存在与入射波参数和惯性缺陷特性的关系。散射介质结构的对称性使我们能够将矢量问题转换为一对非耦合标量维纳-霍普夫方程,该方程是沿着包含缺陷的晶格行提出的。解法体现了散射场的精确表示,即复数平面上的等值线积分,其中包括蒸发波和传播波的贡献。求解结果表明,在远程晶格中,入射场的反射和透射分量伴随着来自三个对称类别的动态模式,其中包括局部界面波。这些类别分别对应于横向作用于有缺陷晶格行的拉伸模式、平行于该行的剪切模式,以及这两种响应的混合波模式。此外,我们还提供了基准有限元计算结果,以便根据我们的半解析解验证结果,半解析解尤其涉及轮廓积分的数值计算。图表说明了在波散射过程中遇到的特殊动态响应,包括动态各向异性、负反射和负折射。
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引用次数: 0
Moving load excited dynamics of multi-layered imperfect microplates based on various micromechanical models 基于各种微机械模型的多层不完美微板的移动载荷激励动力学
IF 6.6 1区 工程技术 Q1 Engineering Pub Date : 2024-02-02 DOI: 10.1016/j.ijengsci.2024.104017
Behrouz Karami, Mergen H. Ghayesh

This paper presents an investigation into the importance of micromechanical models in the analysis of forced vibrations of multi-layered microplates under a moving load. The microplate has a core fabricated from functionally graded materials and face sheets consisting of metal foam. The problem is modelled via a quasi-3D shear deformable method and the modified couple stress theory. This study assumes that the core material follows a power gradation pattern. Various micromechanical models, i.e., the Hashin-Shtrikman bounds, Voigt-Reuss-Hill, Voigt, Reuss, and Tamura, are applied to estimate the material characteristics of the core. The face sheets, composed of metal foams, possess closed- and open-cell solid porosities. System's response of time history type is determined by numerically solving the coupled motion equations obtained using a force-moment balance method. A finite element analysis is conducted for a simplified macroplate system, and the agreement between the numerical results, via the proposed theoretical approach and the theory developed in this paper, is found to be very good. The results show that the micromechanical models influence the modelled mechanical properties of the core layer, consequently impacting the numerical results for the moving-load excited response of the multi-layered microsystem.

本文研究了微机械模型在分析移动负载下多层微板受迫振动中的重要性。微孔板的核心由功能分级材料制成,面板由金属泡沫组成。该问题通过准三维剪切变形方法和修正耦合应力理论进行建模。本研究假设芯材遵循功率分级模式。各种微观力学模型,即 Hashin-Shtrikman 约束、Voigt-Reuss-Hill、Voigt、Reuss 和 Tamura,都被用来估算芯材的材料特性。面片由金属泡沫组成,具有闭孔和开孔固体孔隙率。采用力矩平衡法对耦合运动方程进行数值求解,从而确定系统的时间历程型响应。对一个简化的宏观板系统进行了有限元分析,发现通过所提出的理论方法得出的数值结果与本文所开发的理论之间的一致性非常好。结果表明,微机械模型会影响核心层的建模机械特性,从而影响多层微系统的移动负载激励响应的数值结果。
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引用次数: 0
Multi-fields in multiferroic materials induced by eigenfields and remote loads 特征场和远程负载诱发多铁氧体材料中的多重场
IF 6.6 1区 工程技术 Q1 Engineering Pub Date : 2024-02-01 DOI: 10.1016/j.ijengsci.2024.104028
Xiaochang Liu , Wei Ye

This work presents the analytical solution to the multi-fields in the whole domain of 3D multiferroic materials with an ellipsoidal inclusion/inhomogeneity induced by eigenfields and remote loads. It is a unified approach for the fully-coupled analysis of single-phase multiferroic materials and multiferroic composite materials, which are verified by comparing with available results in the literature and finite element analysis. It is found that, inside the inclusion, the magnetic field due to the spontaneous polarization and the electric field due to the spontaneous magnetization increase monotonically with the aspect ratio of the inclusion for single-phase multiferroic materials, but they first increase and then decrease with the aspect ratio of the inclusion for multiferroic composite materials with much larger maximum magnitudes. Moreover, in the matrix of the piezoelectric-piezomagnetic heterostructure, some components of the multi-fields change dramatically with the aspect ratio of the inhomogeneity, but other components vary insignificantly. Furthermore, although the generalized strain field is usually not uniform in the matrix, the uniformity condition could be still achieved by tuning the eigenfields and remote loads even regardless of the specific shape of the ellipsoidal inhomogeneity. These results could be helpful for the design of multiferroic materials.

本研究提出了由特征场和远程载荷诱导的具有椭圆形内含物/非均质性的三维多铁素体材料全域多场的分析解法。这是对单相多铁素体材料和多铁素体复合材料进行全耦合分析的统一方法,并通过与现有文献和有限元分析结果的比较进行了验证。研究发现,对于单相多铁氧体材料,在包体内部,自发极化产生的磁场和自发磁化产生的电场随包体的长宽比单调增大,但对于多铁氧体复合材料,它们随包体的长宽比先增大后减小,且最大值更大。此外,在压电压磁异质结构的基体中,多场的某些分量会随着不均匀性的纵横比发生急剧变化,但其他分量变化不大。此外,尽管广义应变场在基体中通常并不均匀,但即使椭圆形非均质体的具体形状如何,仍可通过调整特征场和远程载荷实现均匀性条件。这些结果有助于多铁氧体材料的设计。
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引用次数: 0
Palladium-free multicomponent high temperature shape memory alloys 无钯多组分高温形状记忆合金
IF 6.6 1区 工程技术 Q1 Engineering Pub Date : 2024-02-01 DOI: 10.1016/j.ijengsci.2024.104027
N. Resnina , S. Belyaev , A. Bazlov , I. Ponikarova , A. Sibirev , A. Ivanov , R. Bikbaev , I. Strochko

One of the challenges is the design of the relatively cheap Pd-free multicomponent high-temperature shape memory alloys. This paper presents the route for solving this problem by an increasing the Hf concentration in Ti–Hf–Zr–Ni–Cu–Co alloys. It was found that an increase in the Hf concentration from 23 to 32 at.% increased the transformation temperatures: Af changed from 90 °C to 220 °C, Ms varied from 35 °C to 172 °C, while the hysteresis was constant and equal to 45–48 °C. Further increase in the Hf concentration increased the Af temperature by 20 °C but hardly affected the Ms temperatures. Recoverable strain variation was studied on cooling under stress (in torsion mode) and heating without stress. Strain jumps were observed on γ(T) curves which were attributed to a large martensite plate appeared on cooling or disappeared on heating within large grain, which was accompanied by the abrupt strain variation. An increase in the Hf concentration decreased recoverable strain, as well as the strain up to failure. This was due to an increase in the size and volume of the brittle [Ti]2[Ni] and [Hf]2[Ni] precipitates. A maximum recoverable strain of 5 % was found in the alloy with 23 at.% of Hf, whereas the recoverable strain did not exceed 1 % in the alloys with 32 and 38 at.% of Hf.

挑战之一是设计相对便宜的不含 Pd 的多组分高温形状记忆合金。本文介绍了通过增加 Ti-Hf-Zr-Ni-Cu-Co 合金中的 Hf 浓度来解决这一问题的途径。研究发现,将 Hf 浓度从 23% 提高到 32% 会提高转化温度:Af从90 °C变为220 °C,Ms从35 °C变为172 °C,而滞后不变,等于45-48 °C。进一步增加 Hf 浓度会使 Af 温度升高 20 °C,但几乎不会影响 Ms 温度。研究了应力冷却(扭转模式)和无应力加热时的可恢复应变变化。在 γ(T) 曲线上观察到了应变跳跃,这是由于大晶粒内的大马氏体板在冷却时出现或在加热时消失,同时伴随着突然的应变变化。Hf 浓度的增加降低了可恢复应变以及直至破坏的应变。这是由于脆性[Ti]2[Ni]和[Hf]2[Ni]沉淀的尺寸和体积增大所致。Hf 含量为 23% 的合金的最大可恢复应变为 5%,而 Hf 含量为 32% 和 38% 的合金的可恢复应变不超过 1%。
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引用次数: 0
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