今日更新:International Journal of Solids and Structures 3 篇,Journal of the Mechanics and Physics of Solids 1 篇,International Journal of Plasticity 1 篇,Thin-Walled Structures 1 篇
A multiscale model to predict the equation of state of a saturated cement paste
Y.S. Karinski, V.R. Feldgun, D.Z. Yankelevsky
doi:10.1016/j.ijsolstr.2024.112851
用多尺度模型预测饱和水泥浆体的状态方程
An advanced multiscale analytical approach for predicting the Equation of State (EOS) of fully saturated cement pastes is presented. This approach models the matrix as an elastic–plastic material with linear hardening that includes capillary pores filled with water. The model takes into account both the stochastic variation of pore sizes and their spatial distribution. The microscale level is represented by a spherical medium having the mechanical properties of the cement paste matrix. A single spherical pore that is filled with compressible water is located at the center of the micro-domain. The behavior of the compressible water is modeled by the nonlinear Tait equation of state. The EOS at the macro level is obtained by averaging the micro level domain strains over the pore sizes and pore wall thicknesses. It is shown that the solution depends only on the ratio between the minimum pore wall thickness and the lower limit of capillary pore radius and is independent of each of these parameters separately. The EOS obtained by the proposed model shows good agreement with experimental data for cement paste with water/cement ratio w/c = 0.50. The performed parametric study shows that the bulk modulus and yield stress of undisturbed cement gel matrix significantly affect the EOS, while the variation of Poison ratio, plastic hardening parameter and minimum limit pore size and wall thickness (within physically accepted range) slightly affect the cement paste bulk behavior.
提出了一种预测全饱和水泥浆体状态方程的先进多尺度分析方法。该方法将基体建模为具有线性硬化的弹塑性材料,其中包括充满水的毛细孔。该模型既考虑了孔隙大小的随机变化,又考虑了孔隙大小的空间分布。微尺度用具有水泥膏体基质力学性能的球形介质来表示。微畴的中心是一个充满可压缩水的球形孔。用非线性泰特状态方程来模拟可压缩水的行为。宏观上的EOS是通过对孔径和孔壁厚度上的微观域应变进行平均得到的。结果表明,溶液仅与最小孔壁厚度与毛细孔半径下限之比有关,与上述参数无关。对于水灰比w/c = 0.50的水泥浆体,模型得到的EOS与实验数据吻合较好。The performed parametric study shows that the bulk modulus and yield stress of undisturbed cement gel matrix significantly affect the EOS, while the variation of Poison ratio, plastic hardening parameter and minimum limit pore size and wall thickness (within physically accepted range) slightly affect the cement paste bulk behavior.
Progressive failure analysis of z-pin reinforced composite pi joints
James G. Finlay, Anthony M. Waas, Paul Davidson, Jonathan Bartley-Cho, Nav Muraliraj
doi:10.1016/j.ijsolstr.2024.112849
z销增强复合材料pi节点的递进破坏分析
A finite element model of a z-pin reinforced composite pi joint has been developed and correlated against experimental results. A smeared cohesive zone modeling approach was implemented to represent the effect of z-pinning in an efficient and scalable manner. In the smeared approach, cohesive properties governing the traction-separation response of the z-pin reinforced areas were defined to account for the effective fracture toughness caused by z-pinning in an averaged sense. The crack band method was used to account for diffuse damage and failure in the weave of the pi preform. The damage in the preform developed due to delamination suppression caused by the z-pinning. The numerical model was calibrated using experimental data from pristine and defective z-pinned pi joints subjected to pull-off and side-bend loading. Comparisons of experimental and numerical results show good agreement in terms of structural response, critical loads, and failure modes.
建立了z销增强复合材料pi节点的有限元模型,并与实验结果进行了对比。为了高效、可扩展地表示z轴固定的效果,实现了一种涂抹内聚区建模方法。在涂抹方法中,定义了控制z-pin增强区域的牵引-分离响应的内聚特性,以便在平均意义上解释z-pin引起的有效断裂韧性。采用裂纹带法对预制坯组织中的弥漫性损伤和破坏进行了分析。预成形中的损伤是由于z形钉钉抑制分层造成的。数值模型使用原始和有缺陷的z-钉pi关节在拉脱和侧弯载荷下的实验数据进行校准。实验结果与数值结果的比较表明,在结构响应、临界荷载和破坏模式方面,两者具有良好的一致性。
Geometrically exact 3D beam theory with embedded strong discontinuities for modeling of localized failure in bending
Suljo Ljukovac, Adnan Ibrahimbegovic, Rosa-Adela Nava-Mejia, Ismar Imamovic
doi:10.1016/j.ijsolstr.2024.112850
具有嵌入强不连续的几何精确三维梁理论用于弯曲局部破坏建模
In this work, we propose the elastoplastic model of a three-dimensional (3D) geometrically exact beam, which can capture localized bending deformation leading to a plastic hinge. This is a follow-up work to Tojaga et al. (2023), where we only studied the fracture of fiber-like beam structures that break in mode I or mode II, here extended to handle beam-like behavior with bending failure and the main difficulty of the non-vectorial character of large 3D rotations. The Reissner model is chosen for representing the large elastic and large plastic deformations of such a beam model, which leads to the multiplicative decomposition of the rotation tensor. We shown how to replace this with the corresponding additive decomposition of the rotation vector derivatives, to be performed in the material description in the tangent space of SO(3) manifold in the initial configuration. The plasticity model for which we give a more detailed implementation employs a Rankin-like multi-surface plasticity criteria, where each moment vector component (i.e. torsion or bending) is considered separately. The non-local variational formulation is proposed to deal with the softening phenomena characteristic of localized bending failure, where the fracture energy is introduced as the main parameter for softening. The discrete approximation is built in terms of the embedded-discontinuity finite element method (ED-FEM), which introduces a jump in rotation vector that can be handled at the level of a particular beam element. This kind of approach builds upon the best approximation property of the FEM discrete approximation in the energy norm and provides the best-approximation property for the dissipated energy computations, and thus optimal computational accuracy if the quantity of interest is inelastic dissipation. The computations are carried out by the operator split method, which separates the computations of global state variables (displacements and moments) from local (plastic curvature) variables. Several illustrative examples are provided to confirm an excellent performance of the proposed methodology.
在这项工作中,我们提出了三维(3D)几何精确梁的弹塑性模型,该模型可以捕获导致塑性铰链的局部弯曲变形。这是Tojaga等人(2023)的后续工作,我们只研究了在I型或II型模式下断裂的纤维状梁结构的断裂,这里扩展到处理弯曲破坏的类梁行为以及大3D旋转的非矢量特征的主要困难。选择Reissner模型来表示这种梁模型的大弹性和大塑性变形,从而导致旋转张量的乘法分解。我们展示了如何用相应的旋转矢量导数的加性分解来代替它,在初始构型的SO(3)流形的切空间中的材料描述中执行。我们给出更详细实现的塑性模型采用了类似rankin的多面塑性标准,其中每个矩矢量分量(即扭转或弯曲)被单独考虑。针对局部弯曲破坏的软化现象,提出了非局部变分公式,引入断裂能作为软化的主要参数。离散近似是根据嵌入不连续有限元法(ED-FEM)建立的,该方法引入了旋转矢量的跳跃,可以在特定梁单元的水平上处理。这种方法建立在能量范数中有限元离散近似的最佳近似性质之上,为耗散能量计算提供了最佳近似性质,从而在目标量为非弹性耗散时获得了最佳计算精度。计算采用算子分割法,将全局状态变量(位移和矩)的计算与局部状态变量(塑性曲率)的计算分离开来。给出了几个说明性的例子来证实所提出的方法的优良性能。
Heterostructured mechanical metamaterials inspired by the shell of Strombus gigas
Juzheng Chen, Hao Wu, Jingzhuo Zhou, Ziyong Li, Ke Duan, Ruihan Xu, Tianyi Jiang, Hongyuan Jiang, Rong Fan, Roberto Ballarini, Yang Lu
doi:10.1016/j.jmps.2024.105658
受巨藻壳启发的异质结构机械超材料
Despite being highly mineralized, the shells of molluscs exhibit superior strength and toughness because their architectural designs control the evolution of cracks and other types of localized deformation such as shear bands. The crossed-lamellar design of the shell of Strombus gigas, whose hierarchy consists of four distinct lamellar-shaped features assembled in a three-dimensional arrangement, represents the toughest of all seashells. A mechanical metamaterial that adapts the geometrical design of this queen conch is anticipated to circumvent the typical trade-offs between strength-ductility and strength-density. Inspired by the three-dimensional hierarchical and interactive architecture of the crossed-lamellar microstructure, we instruct the design of bio-inspired metamaterials that mitigate failure from the extension of a single shear band and instead develop numerous smaller bands confined within the individual plank-like zones introduced in their layered geometric design. The measured strength properties of these materials are found to increase in inverse proportion to the square root of the thickness of the layers in the hierarchy as a result of progressive deformation enabled by cross-layer interactions. The results provide a new perspective on the design of strong and tough mechanical metamaterials.
尽管是高度矿化的,软体动物的壳表现出优越的强度和韧性,因为它们的结构设计控制了裂缝的演变和其他类型的局部变形,如剪切带。巨螺壳的交叉层状设计,其层次结构由四个不同的层状特征组成,它们以三维的方式排列,代表了所有贝壳中最坚硬的。一种机械超材料,适应这种皇后海螺的几何设计,有望规避典型的强度-延展性和强度-密度之间的权衡。受交叉层状微观结构的三维分层和交互结构的启发,我们指导了仿生超材料的设计,以减轻单个剪切带延伸造成的破坏,而不是在分层几何设计中引入的单个板状区域内发展许多较小的带。这些材料的测量强度特性被发现与层间相互作用导致的渐进变形成反比,与层次中各层厚度的平方根成反比。研究结果为强韧性机械超材料的设计提供了新的思路。
Symmetry breaking induced asymmetric dislocation-planar fault interactions in ordered intermetallic alloys
Cheng Chen, Fei Xu, Jun Song
doi:10.1016/j.ijplas.2024.103982
对称破缺引起有序金属间合金的不对称位错-平面断层相互作用
In this study, we present the first comprehensive examination of symmetry breaking in the interactions between dislocation and superlattice planar faults, including anti-phase boundary (APB), complex stacking fault (CSF), superlattice intrinsic stacking fault (SISF), to reveal the underlying asymmetric dislocation reaction mechanisms depending on the sense of applied stress, employing both large-scale atomistic simulations and continuum dislocation theory. Four ordered intermetallic alloy systems including γ−Ni/γ′−Ni3Al and γ−Ni/γ′−Ni3Fe, γ−Al/γ−TiAl, and α−Ti/α2−Ti3Al were selected as the representative model systems, with two primary symmetry breaking effects, i.e., translational and three-fold rotational symmetry breaking considered. Detailed atomic steps of asymmetrical dislocation reactions and the corresponding asymmetrical dislocation bypassing mechanisms of precipitation have been elucidated, shown to be highly dependent on the geometrical configuration of the precipitate and the relative magnitudes of APB, CSF and SISF fault energies. A continuum model framework was then developed, which, for the first time, provides accurate and quantitative predictions of the threshold conditions triggering critical asymmetrical dislocation slips, verified to be in good agreement with the simulation results. Our study also successfully reproduced the experimentally observed dislocation-induced APB-SISF transformation, with a new dislocation reaction mechanism proposed to explain the transformation process. The findings are expected to be a key enabling stepstone for future innovation in intermetallic alloys strengthened through ordered phases for advanced applications in aeronautic and automotive industries.
在这项研究中,我们首次采用大规模原子模拟和连续位错理论,对位错与超晶格平面断层(包括反相边界(APB)、复杂堆积断层(CSF)和超晶格本征堆积断层(SISF))之间相互作用的对称性破坏进行了全面研究,以揭示取决于外加应力的非对称位错反应机制。选取了γ-Ni/γ′-Ni3Al和γ-Ni/γ′-Ni3Fe、γ-Al/γ-TiAl和α-Ti/α2-Ti3Al等四个有序金属间合金体系作为代表性模型体系,考虑了两种主要的对称性破缺效应,即平移对称性破缺和三重旋转对称性破缺。阐明了非对称位错反应的详细原子步骤以及相应的非对称位错析出绕过机制,并证明其高度依赖于析出物的几何构型以及 APB、CSF 和 SISF 断裂能的相对大小。随后,我们建立了一个连续模型框架,首次对触发临界非对称位错滑移的阈值条件进行了精确的定量预测,经证实与模拟结果十分吻合。我们的研究还成功再现了实验观察到的位错诱发 APB-SISF 转变,并提出了一种新的位错反应机制来解释转变过程。这些发现有望成为未来金属间合金创新的重要基石,通过有序相强化金属间合金,使其在航空和汽车工业中得到先进应用。
Temperature influence on the natural and forced vibrations of laminate plates with fractional Zener viscoelastic layers
Przemysław Litewka, Roman Lewandowski
doi:10.1016/j.tws.2024.111943
温度对分数齐纳粘弹性层合板自然振动和强迫振动的影响
The paper is devoted to the analysis of the influence of ambient temperature on the linear free and non-linear harmonic vibrations of laminate plates with viscoelastic layers. The Zener fractional material model is adopted. The plate kinematics is described using the refined zig-zag theory. The formulation of vibrations of the plate is based on the physical law with the separation of deviatoric and volumetric deformation. The temperature influence is included using the frequency-temperature superposition principle. The shift factor applied to modify the damping properties of the viscoelastic material is computed using the Willams-Landel-Ferry formula.The paper contains the results of several analyses of laminate plates with various viscoelastic materials for which the material data were available in the literature. In particular, the analyses focus on determination of the properties characteristic for the plates with Zener fractional model under the influence of the ambient temperature.
本文研究了环境温度对粘弹性层合板线性自由振动和非线性谐波振动的影响。采用齐纳分式材料模型。板的运动学用精细的锯齿形理论来描述。板的振动公式是基于物理定律,分离了偏变形和体积变形。利用频率-温度叠加原理考虑了温度的影响。采用williams - landel - ferry公式计算了用于改变粘弹性材料阻尼特性的位移因子。本文包含了几种不同粘弹性材料层压板的分析结果,这些材料数据在文献中是可用的。重点分析了齐纳分数阶模型板在环境温度影响下的性能特性。