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Modeling the interaction between inclusions and nanocracks in flexoelectric solid 柔性电固体中夹杂物与纳米裂纹相互作用的模拟
IF 2.6 4区 工程技术 Q2 Engineering Pub Date : 2023-06-02 DOI: 10.1115/1.4062659
Mengkang Xu, Xinpeng Tian, Q. Deng, Qun Li
Natural defects such as nano inclusions and nanocracks are inevitable in dielectric materials. When materials are subjected to mechanical loading, the strain gradient around crack tips and inclusions would become large and induce significant flexoelectric fields. In contrast to classical crack-inclusion problems, the interactions between these flexoelectric fields may locally change the electromechanical behaviors of materials, and result in some interesting phenomena. To better understand the crack-inclusion interactions in flexoelectric solids, in this work, we use a collocation mixed finite element method to model and analyze the flexoelectric fields around the crack tip and inclusion. Based on the J-integral, we analyze how the flexoelectric effect affect the interactions energy between nanocracks and nearby nano inclusions. This work proposes a new coupling mechanism in crack-inclusion problems and may inspire future experiments in flexoelectric solids.
在介质材料中,纳米夹杂物、纳米裂纹等自然缺陷是不可避免的。当材料受到机械载荷时,裂纹尖端和夹杂物周围的应变梯度会变大,并产生显著的挠曲电场。与经典的裂纹夹杂问题不同,这些柔性电场之间的相互作用可能会局部改变材料的机电行为,并导致一些有趣的现象。为了更好地理解挠曲电固体中裂纹-夹杂物的相互作用,本文采用搭配混合有限元法对裂纹尖端和夹杂物周围的挠曲电场进行了建模和分析。基于j积分,分析了挠曲电效应对纳米裂纹与附近纳米夹杂之间相互作用能的影响。这项工作提出了裂纹包含问题的一种新的耦合机制,并可能启发未来在柔性电固体中的实验。
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引用次数: 1
Reshape of the bistable and multistable properties of conical structures through integrated modification of local cross-section 通过局部截面的综合修正来重塑锥形结构的双稳性和多稳性
IF 2.6 4区 工程技术 Q2 Engineering Pub Date : 2023-06-01 DOI: 10.1115/1.4062655
Jian Zhao, Qifeng Fang, Jian Zhang, Yu Huang, Hongyuan Wang, Pengbo Liu
Multistable structures can maintain multiple steady states without additional loads. However, the presence of geometric and material nonlinearities in multistable structures adds complexity and difficulty to their optimal design. In this paper, a novel method is proposed to achieve multistability in conical structures by local cross-section modification. A conical multistable structure with varying cross-section is designed based on this method. The finite element model considering the nonlinear large deformation mechanics and rubber material's hyperelasticity was established for analyzing the multistable properties and meanwhile verified by experiments. The influence of geometric parameters of the cross-section (thickness, width, position) on the multistabilities (number, distribution, and snapping threshold) was analyzed. The steady-state number can be effectively used to redesign the multistable properties by local reinforcement. It is also observed that the quasi-zero stiffness region of the force-displacement curve can be extended by 61.7% compared to the original conical structure. Moreover, the optimized QZS structure allows for an actively-designable stepped dynamic response under forced vibration.
多稳态结构可以在没有附加载荷的情况下保持多个稳态。然而,多稳定结构中几何非线性和材料非线性的存在增加了其优化设计的复杂性和难度。本文提出了一种通过局部截面修正来实现圆锥结构多稳定性的新方法。在此基础上设计了一个变截面圆锥多稳结构。建立了考虑非线性大变形力学和橡胶材料超弹性的有限元模型,分析了橡胶材料的多稳态特性,并进行了实验验证。分析了截面几何参数(厚度、宽度、位置)对多稳定性(数量、分布和断裂阈值)的影响。通过局部加固,可以有效地利用稳态数来重新设计结构的多稳态特性。与原锥形结构相比,力-位移曲线的准零刚度区可延长61.7%。此外,优化后的QZS结构允许在强制振动下主动设计阶梯式动态响应。
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引用次数: 0
Justification of a new original homogenized model for ionic diffusion in porous media. 多孔介质中离子扩散的一种新的原始均匀化模型的证明。
IF 2.6 4区 工程技术 Q2 Engineering Pub Date : 2023-06-01 DOI: 10.1115/1.4062657
M. K. Bourbatache, O. Millet, G. Gagneux
In this work, a new original justification of an homogenized model for ionic diffusion in porous media is proposed. The approach used enables to specify clearly the domain of validity of this homogenized model, involving a source term characterizing the electrical double layer effect at the macroscale. This homogenized model is obtained from the formal periodic homogenization of Nernst-Planck-Poisson system at the pore scale accounting for conductivity of the solid phase which is generally neglected. The Poisson equation is defined in both fluid and solid phases and the discontinuity of fluxes at the solid-fluid interface is modeled by a jump of the electrical field, linked to the surface electrical charge of the solid interface. Numerical simulations are carried out at the scale of the unit cell to underscore the influence of the contrast on the electrical permittivity between fluid and solid phases. The comparison of the concentrations and the electrical potential given at the macro-scale by the homogenized model and by a direct pore scale model reveals the accuracy of the homogenized model which is very simple to use.
在这项工作中,为离子在多孔介质中的均匀扩散模型提出了一个新的原始理由。所使用的方法能够清楚地指定这种均匀化模型的有效域,包括在宏观尺度上表征电双层效应的源项。该均匀化模型是从孔尺度上的能斯特-普朗克-泊松系统的形式周期均匀化获得的,考虑到固相的电导率,而固相的电导率通常被忽略。泊松方程在液相和固相中都有定义,并且通过与固体界面的表面电荷相关的电场跳跃来模拟固体-流体界面处通量的不连续性。在晶胞的尺度上进行了数值模拟,以强调对比度对液相和固相之间的介电常数的影响。均化模型和直接孔尺度模型在宏观尺度上给出的浓度和电势的比较揭示了使用非常简单的均化模型的准确性。
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引用次数: 0
A New Contact Model of Sphere Asperity in the Fully Plastic Regime Considering Strain Hardening 一种考虑应变硬化的全塑性状态下球面粗糙度的新接触模型
IF 2.6 4区 工程技术 Q2 Engineering Pub Date : 2023-06-01 DOI: 10.1115/1.4062656
Jinli Xu, Jiwei Zhu
Understanding the contact characteristics of rough surfaces is essential to explain engineering phenomenon in interface. In order to improve accuracy of contact model, a novel simplified fully plastic contact model of sphere asperity was proposed considering material properties based on fractal theory. Firstly based on Von Mises yield criteria maximum contact pressure factor was derived. Secondly relationships taking into consideration strain hardening were proposed to describe contact area based on definition of the fully plastic contact area index and contact pressure. Then the critical interference at inception of fully plastic deformation was derived. Lastly validations were conducted for different materials. The results show that present work is remarkably consistent with experiment results and has higher accuracy than other models.
了解粗糙表面的接触特性对解释界面工程现象至关重要。为了提高接触模型的精度,基于分形理论,考虑材料的特性,提出了一种简化的球面粗糙度全塑性接触模型。首先基于Von Mises屈服准则推导出最大接触压力因子;其次,在全塑性接触面积指数和接触压力定义的基础上,提出了考虑应变硬化的接触面积描述关系;在此基础上推导了全塑性变形初始临界干涉。最后对不同材料进行了验证。结果表明,本文的工作与实验结果非常吻合,并且比其他模型具有更高的精度。
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引用次数: 2
Defect-Defect Interactions in the Buckling of Imperfect Spherical Shells 不完全球壳屈曲中的缺陷-缺陷相互作用
IF 2.6 4区 工程技术 Q2 Engineering Pub Date : 2023-05-24 DOI: 10.1115/1.4062774
F. Derveni, A. Abbasi, P. Reis
We perform finite element simulations to study the impact of defect-defect interactions on the pressure-induced buckling of thin, elastic, spherical shells containing two dimpled imperfections. Throughout, we quantify the critical buckling pressure of these shells using their knockdown factor. We examine cases featuring either identical or different geometric defects and systematically explore the parameter space, including the angular separation between the defects, their widths and amplitudes, and the radius-to-thickness ratio of the shell. As the angular separation between the defects is increased, the buckling strength initially decreases, then increases before reaching a plateau. Our primary finding is that the onset of defect-defect interactions, as quantified by a characteristic length scale associated with the onset of the plateau, is set by the critical buckling wavelength reported in the classic shell-buckling literature. Beyond this threshold, within the plateau regime, the buckling behavior of the shell is dictated by the largest defect.
我们进行了有限元模拟来研究缺陷-缺陷相互作用对含有两个凹陷缺陷的薄弹性球壳的压力诱导屈曲的影响。在整个过程中,我们使用它们的击倒因子来量化这些壳的临界屈曲压力。我们研究了具有相同或不同几何缺陷的情况,并系统地探索了参数空间,包括缺陷之间的角间距,它们的宽度和振幅,以及壳的半径与厚度比。随着缺陷间角间距的增大,屈曲强度先减小后增大,最后达到平台。我们的主要发现是缺陷-缺陷相互作用的开始,作为与平台开始相关的特征长度尺度的量化,是由经典壳屈曲文献中报道的临界屈曲波长设定的。超过这个阈值,在平台区域内,壳的屈曲行为是由最大缺陷决定的。
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引用次数: 0
A nonlinear repeated impact model of auxetic honeycomb structures considering geometric nonlinearity and tensile/compressive deformation 考虑几何非线性和拉伸/压缩变形的蜂窝结构非线性重复冲击模型
IF 2.6 4区 工程技术 Q2 Engineering Pub Date : 2023-05-23 DOI: 10.1115/1.4062592
Yunfei Liu, Zhao-ye Qin, F. Chu
This study aims to improve the impact protection performance of composite structures by combining a honeycomb core with negative Poisson's ratio and graphene platelets reinforced (GPR) face sheets. The paper investigates the nonlinear repeated low-velocity impact responses of auxetic honeycomb composite plates, taking into account loading-unloading-reloading processes. Effective material properties of the auxetic honeycomb core and GPR face sheets are obtained by using the proposed modified Gibson function and Halpin-Tsai model. Then, taking into account geometric nonlinearity, the nonlinear equations of motion for the system were derived by the Hamilton's principle. Afterward, the time-varying contact force between the composite plate and a spherical impactor is defined by the modified nonlinear Hertz contact theory. The Galerkin method and variable-step Runge-Kutta algorithm are selected to obtain nonlinear impact responses. The proposed methods are verified by finite element simulation and experiment. Finally, the study evaluates the effects of key parameters on the nonlinear repeated low-velocity impact responses.
本研究旨在通过将具有负泊松比的蜂窝芯与石墨烯片增强(GPR)面板相结合,提高复合材料结构的冲击防护性能。本文研究了考虑加载-卸载-再加载过程的饱胀蜂窝复合材料板的非线性重复低速冲击响应。利用改进的Gibson函数和Halpin Tsai模型,获得了膨胀蜂窝芯和GPR面板的有效材料性能。然后,考虑到几何非线性,利用汉密尔顿原理导出了系统的非线性运动方程。然后,利用修正的非线性赫兹接触理论定义了复合材料板与球形冲击器之间的时变接触力。采用伽辽金法和变步长龙格-库塔算法求解非线性冲击响应。通过有限元仿真和实验验证了所提出的方法。最后,评估了关键参数对非线性重复低速冲击响应的影响。
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引用次数: 2
Axial crushing behaviors of metal density gradient foam-filled square taper tubes: Analytical model and numerical calculation 金属密度梯度泡沫填充方锥管轴向破碎行为:解析模型与数值计算
IF 2.6 4区 工程技术 Q2 Engineering Pub Date : 2023-05-22 DOI: 10.1115/1.4062577
Xiwei Wu, Jianxun Zhang
Metal tube is a traditional energy-absorbing structure, and metal foam is a lightweight material with advantages, i.e. high energy absorption and high specific strength. The foam-filled square tube can improve the crashworthiness and has better energy absorption, which is higher than the sum of the energy absorption of the tube and foam. Axial crushing behaviors of metal density gradient foam (DGF) filled square taper tubes are studied analytically and numerically in this paper. An analytical model is presented to study the crushing behavior of DGF filled square taper metal tube under axial loading, in which the interaction between square taper tube and DGF is considered. The numerical calculation is conducted, and the deformation mode is obtained. The analytical predictions are well consistent with the experimental and numerical results. The influences of taper angle, foam strength, maximum relative density and minimum relative density of gradient foam on the compressive behavior of metal DGF filled square taper tube under axial loading are considered. It is demonstrated that when the taper angle is less than 85°, the average crushing force increases as the minimum density of the DGF increases. However, when the taper angle is greater than 85°, the average crushing force decreases with the increase of the minimum density of gradient. This proposed analytical model can effectively predict the axial crushing behaviors of metal DGF filled square taper tube.
金属管是传统的吸能结构,金属泡沫是一种轻质材料,具有吸能高、比强度高等优点。填充泡沫的方管可以提高耐撞性,并且具有较好的吸能性,比填充泡沫的方管和泡沫的吸能之和要高。本文对金属密度梯度泡沫(DGF)填充方锥管的轴向破碎行为进行了分析和数值研究。建立了考虑DGF与方锥管相互作用的轴向载荷作用下填充DGF的方锥金属管破碎特性分析模型。进行了数值计算,得到了变形模态。分析预测结果与实验和数值结果吻合较好。考虑了轴向载荷作用下,锥形角、泡沫强度、梯度泡沫的最大相对密度和最小相对密度对金属DGF填充方锥管压缩性能的影响。结果表明,当锥角小于85°时,平均破碎力随着DGF最小密度的增大而增大。而当锥角大于85°时,平均破碎力随最小梯度密度的增大而减小。该分析模型可以有效地预测金属DGF填充方锥管的轴向破碎行为。
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引用次数: 0
Constitutive relation development for FDM 3D printing materials and simulation of printing direction combination FDM 3D打印材料本构关系发展及打印方向组合仿真
IF 2.6 4区 工程技术 Q2 Engineering Pub Date : 2023-05-16 DOI: 10.1115/1.4062535
Meng Li, B. Sun
Due to the forming or curing process, the materials of three-dimensional (3D) printing have periodic mesodefects, which result in complex constitutive relations and anisotropy. Fused deposition modeling (FDM), which is a typical 3D printing process, inevitably introduces stacking pore defects due to the three-dimensional stacking of materials along the printing direction. At present, research focuses on the mechanical properties of materials printed along only one single direction. To consider the possibility of changing the mechanical properties of materials by adjusting the printing direction, the change in the properties of printing materials along the multiple printing direction combinations was analyzed in this paper. First, based on a continuous medium model, the constitutive model proposed by Garzon-Hernandez et al. was considered, and then to improve the prediction accuracy of the model in the plastic stage, a model describing the porosity change rate of porous materials was introduced to obtain better prediction results. Then, the finite element method (FEM) was developed using the new constitutive relation model implemented by the User Defined Material subroutine (USERMAT) into ANSYS software. Second, through the finite element subroutine, the mechanical response of the FDM 3D printing plate with two different printing direction combinations was simulated. The results show that by adjusting the print direction combination of the double-layer FDM 3D printing materials, the materials show a different anisotropy, maximum bearing capacity of tension and shear and buckling resistance
由于成型或固化过程,三维打印材料具有周期性的介电缺陷,导致了复杂的本构关系和各向异性。熔融沉积建模(FDM)是一种典型的3D打印工艺,由于材料沿打印方向的三维堆叠,不可避免地会引入堆叠孔隙缺陷。目前,研究的重点是沿单一方向印刷的材料的力学性能。为了考虑通过调整印刷方向改变材料力学性能的可能性,本文分析了印刷材料沿多个印刷方向组合的性能变化。首先,在连续介质模型的基础上,考虑了Garzon Hernandez等人提出的本构模型,然后为了提高模型在塑性阶段的预测精度,引入了描述多孔材料孔隙率变化率的模型,以获得更好的预测结果。然后,利用用户定义材料子程序USERMAT在ANSYS软件中实现的新的本构关系模型,开发了有限元法。其次,通过有限元子程序,模拟了FDM 3D打印板在两种不同打印方向组合下的力学响应。结果表明,通过调整双层FDM 3D打印材料的打印方向组合,材料表现出不同的各向异性、最大拉剪承载力和抗屈曲性能
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引用次数: 0
Dislocation in a strained layer embedded in a semi-infinite matrix 嵌入半无限矩阵的应变层中的位错
IF 2.6 4区 工程技术 Q2 Engineering Pub Date : 2023-05-16 DOI: 10.1115/1.4062537
J. Colin
The misfit stress in a thin layer embedded in a semi-infinite matrix has been first determined near the free-surface of the structure, using the virtual dislocation formalism. From a Peach-Koehler force analysis, the different equilibrium positions (unstable and stable) of an edge dislocation gliding in a plane of the layer inclined with respect to the upper interface and emerging at the point of intersection of the upper interface and this free-surface have been then characterized with respect to the lattice mismatch and the inclination angle of the gliding plane. It has been found that the dislocation may exhibit stable equilibrium position near the interface and/or near the free-surface. A diagram of the position stability has been then determined versus the misfit parameter and the inclination angle. The energy variation due to the introduction of an edge dislocation from the free-surface until the matrix-layer interface has been finally determined, when the dislocation is gliding in the plane inclined with respect to the interface horizontal axis. A critical thickness of the layer beyond which the formation of the dislocation in the interfaces is energetically favorable has been finally determined as well as its position with respect to the free-surface in the lower interface.
嵌入半无限矩阵的薄层中的失配应力首先使用虚拟位错形式在结构的自由表面附近确定。根据Peach-Koehler力分析,边缘位错在相对于上界面倾斜的层的平面中滑动并出现在上界面和该自由表面的交叉点处的不同平衡位置(不稳定和稳定),然后就晶格失配和滑动平面的倾斜角进行了表征。已经发现位错可以在界面附近和/或自由表面附近表现出稳定的平衡位置。然后确定了位置稳定性与缺火参数和倾角的关系图。当位错在相对于界面水平轴倾斜的平面中滑动时,由于从自由表面引入边缘位错直到基体层界面的能量变化已经最终确定。最终确定了层的临界厚度,超过该临界厚度在界面中位错的形成在能量上是有利的,以及其相对于下界面中自由表面的位置。
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引用次数: 0
Bifurcations and stability analysis of elastic slender structures using static discrete elastic rods method 用静态离散弹性杆法分析弹性细长结构的分岔及稳定性
IF 2.6 4区 工程技术 Q2 Engineering Pub Date : 2023-05-16 DOI: 10.1115/1.4062533
Weicheng Huang, Yingchao Zhang, T. Yu, Mingchao Liu
Discrete Elastic Rods (DER) method provides a computationally efficient means of simulating the nonlinear dynamics of one-dimensional slender structures. However, this dynamic-based framework can only provide first-order stable equilibrium configuration when combined with the dynamic relaxation method, while the unstable equilibria and potential critical points (i.e. bifurcation and fold point) cannot be obtained, which are important for understanding the bifurcation and stability landscape of slender bodies. Our approach modifies the existing DER technique from dynamic simulation to a static framework and computes eigenvalues and eigenvectors of the tangential stiffness matrix after each load incremental step for bifurcation and stability analysis. This treatment can capture both stable and unstable equilibrium modes, critical points, and trace solution curves. Three representative types of structures -- beams, strips, and gridshells -- are used as demonstrations to show the effectiveness of the modified numerical framework, which provides a robust tool for unveiling the bifurcation and multistable behaviors of slender structures.
离散弹性杆(DER)方法为模拟一维细长结构的非线性动力学提供了一种计算效率高的方法。然而,这种基于动态的框架与动态松弛方法相结合,只能提供一阶稳定平衡构型,而无法获得不稳定平衡和潜在临界点(即分岔点和折弯点),这对于理解细长体的分岔和稳定景观具有重要意义。该方法将现有的DER技术从动态模拟改进为静态框架,并在每个载荷增量步骤后计算切向刚度矩阵的特征值和特征向量,用于分岔和稳定性分析。这种处理方法可以捕获稳定和不稳定的平衡模式、临界点和痕量溶液曲线。三种具有代表性的结构类型——梁、条和网格壳——被用作演示,以显示改进的数值框架的有效性,它为揭示细长结构的分岔和多稳定行为提供了一个强大的工具。
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引用次数: 3
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Journal of Applied Mechanics-Transactions of the Asme
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