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【新文速递】2024年11月14日固体力学SCI期刊最新文章

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今日更新:International Journal of Solids and Structures 1 篇,Journal of the Mechanics and Physics of Solids 2 篇,Mechanics of Materials 1 篇

International Journal of Solids and Structures

A new porous constitutive model for additively manufactured PLA

P. Areias, N. Silvestre, M.F. Vaz, M. Leite

doi:10.1016/j.ijsolstr.2024.113131

一种新的增材制造聚乳酸多孔本构模型

We introduce a new specific hyperelastic/plastic model and porosity evolution law able to capture the deformation and damage of additively manufactured PLA-N polymers (Fused Filament Fabrication - FFF). Porosity growth is driven by projecting the right Cauchy–Green tensor in the normal to the deposition direction and by solving a local maximization problem. Fracture energy is introduced directly in the resulting law by means of a length scale. A full finite-strain plasticity model is adopted, based on the Hosford yield criterion. Strain softening is regularized with a gradient-enhanced technique, which is solved in tandem with the equilibrium equations. A comprehensive analysis of the hyperelastic transversely isotropic/porous constitutive law is performed, with physical insight on the directional strain softening behavior. A normalized CT test specimen is used to qualitatively assess the effect of deposition direction on the crack path and to investigate the effect of mesh density in the load/displacement curves. We then present a comparison with our experimental results for a cellular PLA-N beam composed of 3 × 13 cells, in terms of crack behavior and load/displacement results. Sequential collapse of the cells and strain localization match the experimental observations.

我们引入了一种新的特定的超弹/塑性模型和孔隙度演化规律,能够捕捉增材制造PLA-N聚合物(熔融长丝制造- FFF)的变形和损伤。孔隙度的增长是通过向沉积方向投射正确的柯西-格林张量和解决局部最大化问题来驱动的。断裂能通过长度尺度直接引入到结果律中。采用基于霍斯福德屈服准则的全有限应变塑性模型。采用梯度增强技术对应变软化进行正则化,并与平衡方程串联求解。对超弹性横向各向同性/多孔本构律进行了全面分析,并对定向应变软化行为进行了物理观察。采用归一化CT试样定性评价沉积方向对裂纹路径的影响,研究网格密度对载荷/位移曲线的影响。然后,我们在裂纹行为和荷载/位移结果方面,将我们的实验结果与由3 × 13个单元组成的细胞PLA-N梁进行了比较。细胞的顺序塌陷和应变定位与实验观察相符。


Journal of the Mechanics and Physics of Solids

Double-eigenvalue bifurcation and multistability in serpentine strips with tunable buckling behaviors

Qiyao Shi, Weicheng Huang, Tian Yu, Mingwu Li

doi:10.1016/j.jmps.2024.105922

具有可调屈曲行为的蛇形带的双特征值分岔和多稳定性

Serpentine structures, composed of straight and circular strips, have garnered significant attention as potential designs for flexible electronics due to their remarkable stretchability. When subjected to stretching, these serpentine strips buckle out of plane, and previous studies have identified two distinct buckling modes whose order of appearance may interchange in serpentine structures with a single cell. In this study, we employ anisotropic rod theory to model serpentine strips as a multi-segment boundary value problem (BVP), with continuity conditions enforced at the interface between the straight and curved strips. We solve the BVP using methods of continuation, and our results reveal that: (1) the exchange of the two buckling modes in a single-cell serpentine strip is induced by a double-eigenvalue and associated secondary bifurcations, which also alter the stability of the two buckling modes; (2) a variety of stable states with reversible symmetry can be manually obtained in tabletop models and are found to be disconnected from the planar branch in numerical continuation. Furthermore, we demonstrate that modulating the strip thickness across different cells leads to the initiation of buckling in the thinnest section, thereby allowing for the tuning of buckling modes in serpentine strips. In structures with two cells, the sequence of the two buckling modes can also be controlled by designing serpentine strips with nonuniform height. This work could enhance the mechanical design of serpentine-interconnect-based flexible structures and could have applications in multistable actuators and mechanical memory devices.

蛇形结构由直条和圆形条组成,由于其显著的可拉伸性,作为柔性电子产品的潜在设计,已经引起了极大的关注。当受到拉伸时,这些蛇形条会弯曲出平面,先前的研究已经确定了两种不同的屈曲模式,其外观顺序可能在蛇形结构中与单个细胞互换。在本研究中,我们采用各向异性杆理论将蛇形带材建模为一个多段边值问题(BVP),并在直线带材和弯曲带材的界面处施加连续性条件。结果表明:(1)单细胞蛇形带中两种屈曲模态的交换是由双特征值和相关的二次分叉引起的,这也改变了两种屈曲模态的稳定性;(2)在桌面模型中可以人工获得多种可逆对称的稳定状态,在数值延拓中发现这些稳定状态与平面分支是不相连的。此外,我们证明了在不同单元之间调制条带的厚度会导致最薄部分的屈曲起始,从而允许调整蛇形条带的屈曲模式。在双单元结构中,还可以通过设计高度不均匀的蛇形条来控制两种屈曲模式的顺序。这项工作可以提高基于蛇形互连的柔性结构的机械设计,并在多稳态执行器和机械存储器件中具有应用价值。


Poroelastic fracture of polyacrylamide hydrogels: Enhanced crack tip swelling driven by chain scission

Qifang Zhang, Junjie Liu, Gang Zhang, Yuhong Li, Nan Hu, Jinglei Yang, Yan Yang, Shaoxing Qu, Qianhua Kan, Guozheng Kang

doi:10.1016/j.jmps.2024.105954

聚丙烯酰胺水凝胶的孔弹性断裂:链断裂驱动裂纹尖端膨胀增强

The deformation of hydrogels is accompanied by water migration, a process that plays a crucial role in their fracture behaviors. Previous investigations primarily focus on how the water migration between the environment and hydrogel affects the fracture of hydrogels. Herein, a novel mechanism of the rate-dependent fracture of hydrogels induced by interior water migration is uncovered. Notched polyacrylamide (PAAm) hydrogels are stretched at various stretch rates in both oil and deionized (DI) water environments. Notably, the critical stretches to crack propagation are positively correlated with the stretch rates in both the two environments. This rate-dependent fracture is attributed to the crack tip swelling of PAAm hydrogels. Delayed fracture tests conducted in oil further verify the co-existence of delayed fracture and rate-dependent fracture resulted from interior water migration in PAAm hydrogels. The experimental findings are interpreted by considering the imperfection of a real polymer network, in which the scission of short chains in the region neighboring the crack tip reduces the average crosslinking density locally, thereby greatly amplifying the degree of crack tip swelling and its influence on the fracture of hydrogels. A constitutive model coupling the evolution of polymer network and the diffusion of water molecules is proposed, which can predict the crack tip swelling of notched PAAm hydrogels through the finite element method. Assuming that the decrease in fracture toughness is positively related to the swelling along the crack propagation surface, the predicted normalized fracture toughness matches the experimental results of PAAm hydrogels stretched in water well, and satisfies those in oil environment qualitatively. This work highlights the significant influence of interior water migration on the fracture of hydrogels and provides insights that may guide the design of hydrogels with enhanced fracture resistance.

水凝胶的变形伴随着水的运移,这一过程对水凝胶的破裂行为起着至关重要的作用。以往的研究主要集中在水凝胶与环境之间的水迁移如何影响水凝胶的破裂。本文揭示了一种由内部水运移引起的速率依赖性水凝胶破裂的新机制。缺口聚丙烯酰胺(PAAm)水凝胶在油和去离子水环境中以不同的拉伸速率拉伸。值得注意的是,在两种环境下,裂纹扩展的临界拉伸量与拉伸率呈正相关。这种速率依赖性断裂归因于PAAm水凝胶的裂纹尖端膨胀。在油层中进行的延迟裂缝试验进一步验证了PAAm水凝胶内部水运移导致的延迟裂缝和速率依赖性裂缝的共存。实验结果考虑了真实聚合物网络的不完全性,其中裂纹尖端附近区域短链的断裂降低了局部平均交联密度,从而极大地放大了裂纹尖端膨胀的程度及其对水凝胶破裂的影响。提出了一种耦合聚合物网络演化与水分子扩散的本构模型,该模型可以通过有限元方法预测缺口PAAm水凝胶的裂纹尖端膨胀。假设断裂韧性的降低与裂缝扩展面膨胀成正相关,则预测的归一化断裂韧性与PAAm水凝胶在井中拉伸的实验结果相吻合,定性地满足油环境下的实验结果。这项工作强调了内部水运移对水凝胶破裂的重要影响,并为设计具有增强抗裂性的水凝胶提供了指导。


Mechanics of Materials

Relaxing strong compatibility at atomistic-continuum interface: consistent linear coupling method

Pouya Towhidi, Manouchehr Salehi

doi:10.1016/j.mechmat.2024.105204

原子-连续介质界面松弛强相容:一致线性耦合方法

In this paper, we develop a brand-new coupling method called consistent linear coupling (CLC) with a view to resolving the difficulty of scaling down of the interface elements in the strong compatibility coupling (SCC), employed in the most accurate multiscale methods such as quasicontinuum. To this end, the CLC determines some conditions required to be satisfied to reproduce the SCC rigorously, regardless of the size of the interface elements. Therefore, it can produce a solution as accurate as the SCC with two additional features: significantly less computational cost and easier implementation. The CLC-based schemes are compared with well-known coupling methods including the SCC in terms of solving quasi-static 3D nanoscale contact and a 2D crystal under uniaxial tension. Numerical results demonstrate the superiority of the CLC with regard to the accuracy and computational efficiency.

本文提出了一种全新的耦合方法——一致线性耦合(CLC),以解决准连续统等高精度多尺度方法中使用的强相容耦合(SCC)中界面元按比例缩小的困难。为此,无论界面元素的大小如何,CLC都确定了严格重现SCC所需满足的一些条件。因此,它可以产生与SCC一样精确的解决方案,并具有两个额外的特性:显著减少计算成本和更容易实现。在求解准静态三维纳米尺度接触和单轴张力下的二维晶体方面,将基于clc的方案与SCC等知名耦合方法进行了比较。数值结果表明了该方法在精度和计算效率方面的优越性。



来源:复合材料力学仿真Composites FEM
ACTMechanicalAdditiveDeform断裂电子增材ADS裂纹理论多尺度控制试验
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首次发布时间:2024-11-21
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【新文速递】2024年11月11日固体力学SCI期刊最新文章

今日更新:Journal of the Mechanics and Physics of Solids 3 篇,International Journal of Plasticity 2 篇,Thin-Walled Structures 6 篇Journal of the Mechanics and Physics of SolidsFracture of polymer-like networks with hybrid bond strengthsChase M. Hartquist, Shu Wang, Bolei Deng, Haley K. Beech, Stephen L. Craig, Bradley D. Olsen, Michael Rubinstein, Xuanhe Zhaodoi:10.1016/j.jmps.2024.105931具有杂化键强度的类聚合物网络断裂The design and functionality of polymeric materials hinge on failure resistance. While molecular-level details drive crack evolution in polymer networks, the connection between individual chain scission and bulk failure remains unclear and difficult to probe. In this work, we systematically study the fracture mechanics of polymer-like networks with hybrid bond strengths. We reveal that varying the ratio of strong and weak strands within otherwise identical networks gives a non-monotonic relationship between intrinsic fracture energy and strong strand fraction. Networks with some weak strands can counterintuitively outperform those with exclusively strong strands. Experiments on poly(ethylene glycol) gels and architected polymer-like lattices together with simulations unveil these properties. We show through computational visualization that strand type concentrations impact crack growth patterns and fracture energy trends. Cracks propagate through weak layers at low strong strand fractions. Aggregate clusters deflect or pin cracks at similar concentrations of strong and weak strands. Cracks blunt due to dispersed weak strand failure at high strong strand fractions. The sacrificial weak strands can notably deconcentrate stress near the crack tip, which toughens by delaying crack advancement. The interplay between concentration and clustering of strand types in networks with hybrid bond strengths, combined with crack growth phenomena and nonlocal energy release, provides insights into unusual fracture characteristics. Results shed light on fracture in polymer networks and percolated lattices.高分子材料的设计和功能取决于抗破坏能力。虽然分子水平的细节驱动了聚合物网络中的裂缝演化,但单个链断裂和整体破坏之间的联系仍然不清楚,也难以探究。在这项工作中,我们系统地研究了具有混合键强度的类聚合物网络的断裂力学。我们发现,在其他相同的网络中,改变强链和弱链的比例给出了内在断裂能和强链分数之间的非单调关系。与直觉相反,一些弱链的网络比那些只有强链的网络表现得更好。对聚乙二醇凝胶和结构聚合物样晶格的实验以及模拟揭示了这些特性。我们通过计算可视化显示,链型浓度影响裂纹扩展模式和断裂能趋势。裂纹在弱层中以低强链分数传播。在强弱股的浓度相似的情况下,聚集簇会偏转或钉住裂缝。在高强度链分数下,由于分散的弱链失效,裂纹变钝。牺牲的弱链可以明显地分散裂纹尖端附近的应力,从而通过延迟裂纹的扩展来增韧。混合键强度网络中链类型的集中和聚集之间的相互作用,结合裂纹扩展现象和非局部能量释放,提供了对异常断裂特征的见解。结果揭示了聚合物网络和渗透晶格的断裂。Micromechanics-based variational phase-field modeling of fatigue fractureMina Sarem, Nuhamin Eshetu Deresse, Els Verstrynge, Stijn Françoisdoi:10.1016/j.jmps.2024.105932基于细观力学的疲劳断裂变分相场模型In this paper, we extend the micromechanics-based phase-field model to simulate fatigue failure. The coupling of a micromechanics-based framework with the phase-field approach helps to differentiate between failure modes, by distinguishing between open and closed microcracks. This integrated framework links continuum field variables, such as plastic strain and damage variable, to micromechanical mechanisms like frictional sliding and microcrack opening. We first improve the algorithm’s stability during loading-unloading in the tensile regime through a modification of the plasticity evolution equations. Next, we incorporate fatigue damage accumulation and deterioration due to cyclic loading into the micromechanics-based phase-field model. A fatigue degradation function, driven by free energy accumulation, is introduced to degrade the fracture energy upon reaching a specified threshold during cyclic loading. Various cyclic loads are applied to benchmark tests, both with and without imperfections (e.g. holes, inclusions, voids), under plane strain conditions to capture diverse failure modes. The results demonstrate the model’s capability to accurately describe tensile, shear, and mixed-mode fracture under cyclic loading. Furthermore, the model effectively simulates key features of fatigue behavior, including crack nucleation, growth, and coalescence.在本文中,我们扩展了基于微力学的相场模型来模拟疲劳失效。基于微力学的框架与相场方法的耦合有助于通过区分开微裂纹和闭微裂纹来区分失效模式。该集成框架将连续场变量(如塑性应变和损伤变量)与微力学机制(如摩擦滑动和微裂纹打开)联系起来。首先,通过对塑性演化方程的修正,提高了算法在拉伸状态下的加载-卸载稳定性。接下来,我们将疲劳损伤积累和恶化纳入到基于微力学的相场模型中。在循环加载过程中,引入自由能积累驱动的疲劳退化函数,在达到指定阈值时对断裂能进行退化。在平面应变条件下,各种循环载荷应用于基准测试,包括有缺陷和没有缺陷(例如孔、夹杂物、空隙),以捕获不同的失效模式。结果表明,该模型能够准确描述循环荷载下的拉伸、剪切和混合模式断裂。此外,该模型有效地模拟了疲劳行为的关键特征,包括裂纹形核、扩展和合并。Magnetostriction of soft-magnetorheological elastomersEric M. Stewart, Lallit Ananddoi:10.1016/j.jmps.2024.105934软磁流变弹性体的磁致伸缩Soft-magnetorheological elastomers (s-MREs) are particulate composites made of a non-magnetic elastomeric matrix dispersed with micron-sized particles of a “soft-magnetic” material. The phenomenon of magnetostriction in specimens made from s-MREs is the change in their shape when they are subjected to an external magnetic field. Experiments in the literature show that for circular cylindrical specimens subjected to an axially applied magnetic field the magnetostriction is strongly dependent on their aspect-ratio, with specimens with a low ratio of the length to the diameter exhibiting a larger tensile magnetostrictive strain than specimens with a large aspect-ratio — the “shape-effect.” This response is also hysteretic because of the underlying viscoelasticity of the matrix material. In this paper we report on a large deformation magneto-viscoelasticity theory for s-MREs and its finite element implementation. Using our theory we show that we can model this non-intuitive geometry-dependent magnetostrictive response of cylindrical s-MRE specimens. We show that the effect of the magnetization m of the cylinder is to decrease the magnetic field h within the cylinder relative to the applied magnetic field h_app outside the cylinder, the well-known demagnetization effect, and that this demagnetization is diminished in more slender cylinders due to magnetic fringing at the boundaries of the cylinder. This is the physical reason behind the macroscopically-observed “shape-effect.” Our magneto-viscoelasticity theory is quite broad, and it has many potential applications beyond modeling the magnetostriction of cylindrical specimens. As an example we apply the theory to study the bending actuation response of beams of s-MREs when they are subjected to magnetic fields at different incidence angles to their longitudinal axis.软磁流变弹性体(s-MREs)是一种由非磁性弹性基体和微米级“软磁”材料颗粒组成的颗粒复合材料。s-MRE样品中的磁致伸缩现象是指在外部磁场作用下其形状的变化。文献中的实验表明,对于轴向施加磁场的圆柱形样品,其磁致伸缩强度强烈依赖于其长径比,长径比较小的样品比长径比较大的样品表现出更大的拉伸磁致伸缩应变——这就是“形状效应”。这种响应也具有滞后性,因为基体材料的粘弹性特性是其基础。在这篇论文中,我们报告了s-MRE的大变形磁流变弹性理论及其有限元实现。利用我们的理论,我们可以模拟圆柱形s-MRE样品中这种非直观的、与几何形状相关的磁致伸缩响应。我们证明了圆柱体的磁化强度m的作用是使圆柱体内部的磁场h相对于圆柱体外部的施加磁场h_app减小,这是众所周知的去磁效应。在更细的圆柱体中,由于圆柱体边界处的磁边缘效应,去磁效应会减弱。这是宏观上观察到的“形状效应”背后的物理原因。我们的磁致电弹性理论非常广泛,除了用于模拟圆柱形样品的磁致伸缩外,还有很多潜在的应用。例如,我们将该理论应用于研究当S-MREs在不同入射角的磁场作用下弯曲时的驱动响应。International Journal of PlasticityThe evolution of grain boundary structure mediated by disclinations in magnesium alloys under superplastic deformationChunfeng Du, Yipeng Gao, Min Zha, Cheng Wang, Jian Wang, Hui-Yuan Wangdoi:10.1016/j.ijplas.2024.104167 超塑性变形下由位错介导的镁合金晶界组织演化Superplastic deformation in metals and alloys, characterized by ultrahigh ductility (exceeding 300%) without cracking at elevated temperatures, is a critical process for manufacturing complex-shaped components. While a few grain-boundary (GB)-mediated deformation mechanisms have been identified as essential contributors to superplasticity in fine-grained polycrystals (grain size is typically less than 10 μm), it is still a challenge to maintain a steady fine-grained microstructure and sustainable plastic flow at high temperatures. Partially due to the lack of a quantitative description of dislocation-GB reactions, it has not been well recognized how grain coarsening can be suppressed by the external loading during superplastic deformation. In this work, we address this challenge by formulating a disclination-dislocation coupling equation within the Lie-algebra framework, providing a quantitative understanding of the interactions between disclinations, dislocations, and GBs. Using quasi-in-situ electron backscattered diffraction (EBSD) analysis in Mg alloys, we systematically investigate the multiscale interactions of the defects and their impact on grain structure evolution. Three key mechanisms that suppress conventional grain coarsening have been identified, i.e., disclination-assisted GB accommodation, disclination-GB pinning, and disclination-induced sub-GB crossing, all of which are captured by the proposed equation. This study contributes to the broader field of plasticity by linking macroscopic deformation behavior with microscopic mechanisms, offering new insights into the theory of superplastic deformation in metals and alloys.金属和合金的超塑性变形是制造复杂形状部件的关键工艺,其特点是在高温下具有超高的延展性(超过300%)而不开裂。虽然一些晶界(GB)介导的变形机制已被确定为细晶多晶(晶粒尺寸通常小于10 μm)超塑性的重要贡献者,但在高温下保持稳定的细晶组织和可持续的塑性流动仍然是一个挑战。由于缺乏位错- gb反应的定量描述,人们还没有很好地认识到在超塑性变形过程中,外部载荷如何抑制晶粒粗化。在这项工作中,我们通过在李代数框架内制定斜位错-位错耦合方程来解决这一挑战,提供了对斜位错、位错和gb之间相互作用的定量理解。利用准原位电子背散射衍射(EBSD)技术,系统地研究了镁合金中缺陷的多尺度相互作用及其对晶粒组织演化的影响。本文确定了抑制常规晶粒粗化的三个关键机制,即斜倾角辅助的GB调节、斜倾角-GB钉住和斜倾角诱导的亚GB杂交,所有这些机制都被所提出的方程所捕获。该研究通过将宏观变形行为与微观机制联系起来,为金属和合金的超塑性变形理论提供了新的见解,从而拓宽了塑性研究领域。Multiscale-informed irradiation growth model of Zr-Sn-Nb alloysChangqiu Ji, Yang Li, Zhipeng Sun, Aiya Cui, Yong Xin, Yinan Cuidoi:10.1016/j.ijplas.2024.104177Zr-Sn-Nb合金的多尺度辐照生长模型A systematic multiscale-informed model is developed to predict the irradiation growth behavior of Zr-Sn-Nb alloys, which considers the anisotropy and temperature dependence of both plasticity and irradiation, as well as the alloying effect of Zr alloys. This model consists of a cluster dynamics submodel to consider the kinetics of irradiation defect, an alloying effect submodel informed by atomic simulations and experiments, a microstructure transition submodel derived from discrete dislocation dynamics, and a continuous irradiation growth submodel based on crystal plasticity. It effectively captures the irradiation-induced coevolution of multiple microstructures, including point defects, mobile clusters, dislocation lines and irradiation loops on the prismatic and basal plane, as well as Nb-induced precipitates. It is suitable for high-dose irradiation conditions as it reasonably considers the transition from high-density irradiation loops to tangled dislocation network. The predicted irradiation growth strain, as well as the density and size of irradiation loops, are in good agreement with almost all the available experiments for pure Zr, Zr-Sn, Zr- Nb, and Zr-Sn-Nb alloys at different irradiation doses in the temperature range of 473 - 673 K. This work is hoped to provide a powerful tool for developing irradiation resistance cladding materials.考虑了Zr- sn - nb合金的各向异性和温度依赖性,以及Zr合金的合金化效应,建立了Zr- sn - nb合金辐照生长行为的系统多尺度信息模型。该模型由考虑辐照缺陷动力学的簇动力学子模型、基于原子模拟和实验的合金化效应子模型、基于离散位错动力学的微观结构转变子模型和基于晶体塑性的连续辐照生长子模型组成。它有效地捕获了辐照诱导的多种微观结构的共同演化,包括棱柱面和基面上的点缺陷、移动团簇、位错线和辐照环,以及nb诱导的析出相。该方法合理考虑了高密度辐照环向缠结位错网络的过渡,适用于高剂量辐照条件。在473 ~ 673 K温度范围内,对纯Zr、Zr- sn、Zr- Nb和Zr- sn -Nb合金在不同辐照剂量下的辐照生长应变、辐照环密度和辐照环尺寸的预测与几乎所有实验结果都吻合。本研究为开发耐辐照包层材料提供了有力的工具。Thin-Walled StructuresHigh-velocity impact characteristics of 3D auxetic composite cylindrical shell panels: Theory and experimentHui Li, Yichen Deng, Zhengwei Zhang, Junxue Hou, Jin Zhou, Haizhou Wang, Haiyang Zhang, Xiangping Wang, Zhongwei Guandoi:10.1016/j.tws.2024.112648三维复合材料圆柱壳板的高速冲击特性:理论与实验The high-velocity impact characteristics of 3D auxetic composite cylindrical shell panels are studied theoretically and experimentally. First, to predict the high-velocity impact parameters, including the residual velocity of the projectile, the energy absorption, and the ballistic limit, an analytical model of such structures consisting of two fiber/resin skins, two adhesive films, and a 3D auxetic lattice core is proposed, in which Reddy's higher-order shear deformation theory is employed to define the displacement variables. After taking into account the equivalent material properties of the core and various failure modes, energy absorption mechanisms, strain rate effect, and impact damage evolution issues of the constituent elements, governing equations and solutions are successfully obtained. To validate the model developed, detailed high-velocity impact tests with different initial velocities are then performed on such shell panel specimens with nylon and metal auxetic lattice cores fabricated by 3D printing technology. Finally, the influences of key geometric parameters of the core on impact properties are investigated, with some important design recommendations being refined to improve the impact resistance and energy absorption capabilities of the studied structure.对三维复合材料圆柱壳板的高速冲击特性进行了理论和实验研究。首先,为了预测弹丸的剩余速度、能量吸收和弹道极限等高速冲击参数,提出了由两层纤维/树脂皮、两层胶膜和三维形变晶格核组成的高速冲击结构的解析模型,其中采用Reddy的高阶剪切变形理论定义位移变量。在考虑了芯材的等效材料特性和各失效模式、能量吸收机制、应变率效应、冲击损伤演化等问题后,成功地得到了控制方程和解。为了验证所开发的模型,然后在使用3D打印技术制造的尼龙和金属辅助晶格芯的壳板样品上进行了不同初始速度的详细高速冲击试验。最后,研究了核心关键几何参数对冲击性能的影响,并提出了一些重要的设计建议,以提高所研究结构的抗冲击和吸能能力。Free vibration analysis of damaged laminated piezoelectric plates and composite plates with piezoelectric patch based on the Extended Layerwise MethodYaogang Wu, Yuliang Duan, Jinyu Shao, Dinghe Li, Jianxin Xudoi:10.1016/j.tws.2024.112666基于扩展分层法的损伤压电层合板和带压电片的复合材料板的自由振动分析The dynamic analytical models for a laminated piezoelectric plate and a laminated composite plate with piezoelectric patch containing the delamination, transverse crack and debonding damages are established by the Extended Layerwise Method (XLWM). The virtual kinetic energy is introduced into Hamilton’s principle, so resulting in mass matrices and displacement-dependent second mode derivatives in the finite element (FE) governing equations. Then, the FE governing equations for the laminated piezoelectric plate, and the characteristic equations of natural frequencies for the laminated piezoelectric plate with delamination and transverse crack are derived. The coupling model of the laminated composite plate and the piezoelectric patch is established by the displacement continuity and internal force equilibrium conditions at the nodes of the contact area. Based on the degrees of freedom (DoFs) in contact, the final governing equations is deduced, followed by the analysis of free vibration responses for both plates with various damages. The accuracy of natural frequencies for each plate is verified by comparing the results with those of FE simulation by ANSYS.采用扩展分层法(XLWM)建立了含分层、横向裂纹和脱粘损伤的层压板和带压电片的层压复合材料板的动力分析模型。在Hamilton原理中引入虚动能,得到了质量矩阵和与位移相关的有限元控制方程二阶模态导数。在此基础上,推导了层压板的有限元控制方程,以及具有分层和横向裂纹的层压板的固有频率特征方程。根据接触区域节点处的位移连续性和内力平衡条件,建立了层合复合材料板与压电贴片的耦合模型。在接触自由度的基础上,推导了最终控制方程,并对两种损伤板的自由振动响应进行了分析。通过与ANSYS有限元模拟结果的比较,验证了各板固有频率的准确性。Free vibration and nonlinear transient analysis of blast-loaded FGM sandwich plates with stepped face sheets: Analytical and artificial neural network approachesPeng Shi, Vu Ngoc Viet Hoang, Jian Yang, Haoge Shou, Qi Li, Ferruh Turandoi:10.1016/j.tws.2024.112667层状夹层板的自由振动和非线性瞬态分析:解析和人工神经网络方法This study investigates the free vibration and transient dynamic response of functionally graded material (FGM) sandwich plates with stepped face sheets (FGM-SPSFS) supported by viscoelastic foundation under blast loading. The research focuses on the effects of geometric configurations and material property variations across segments. Each plate comprises three layers: a homogeneous hard core and two FGM face sheets, divided horizontally into two segments with differing face sheet thicknesses, which enhance structural stiffness while maintaining a consistent total thickness. The material properties of the sandwich plates follow a power-law distribution. The formulations are based on higher-order shear deformation plate theory and von Kármán geometric nonlinearity, and are solved using Galerkin’s method. Validation is achieved by comparing the results with published literature and finite element analysis (FEA). Artificial neural network (ANN) models are developed to predict natural frequencies without extensive computational runs, employing Bayesian Regularization (BR) and Levenberg–Marquardt (LM) algorithms in MATLAB. A new graphical user interface (GUI) tool facilitates frequency predictions using the proposed ANN model. Key findings indicate that modifications to the stepped face sheets and core layers affect stiffness, natural frequency, and vibration amplitudes. Increasing the core-to-total thickness ratio enhances stiffness, resulting in higher frequencies and reduced displacement amplitudes. The LM algorithm outperforms the BR algorithm, with errors generally below 1%, compared to 2% to 4% for BR with the log-sigmoid function. This study offers valuable insights into the design and analysis of FGM sandwich structures for engineering applications.研究了粘弹性基础支撑的功能梯度材料夹层板(FGM- spfs)在爆炸荷载作用下的自由振动和瞬态动力响应。研究的重点是几何结构和材料性能的变化在段间的影响。每个板由三层组成:一个均匀的硬芯和两个FGM面板,水平分为两个面板厚度不同的部分,在保持总厚度一致的同时增强结构刚度。夹层板的材料性能服从幂律分布。该公式基于高阶剪切变形板理论和von Kármán几何非线性,并采用伽辽金方法求解。通过将结果与已发表的文献和有限元分析(FEA)进行比较,实现了验证。在MATLAB中,利用贝叶斯正则化(BR)和Levenberg-Marquardt (LM)算法,开发了人工神经网络(ANN)模型来预测固有频率,而无需大量的计算运行。一个新的图形用户界面(GUI)工具便于使用所提出的人工神经网络模型进行频率预测。主要研究结果表明,对阶梯式面板和核心层的修改会影响刚度、固有频率和振动幅值。增加岩心与总厚度之比可以增强刚度,从而产生更高的频率和更小的位移幅值。LM算法优于BR算法,其误差通常低于1%,而使用log-sigmoid函数的BR的误差为2%至4%。该研究为FGM夹层结构的设计和分析提供了有价值的见解。Machine learning-based axial compressive capacity estimation of cold-formed steel build-up sectionsJiaqiang Hu, Liqiang Jiang, Yi Hu, Jianguang He, Xinyuan Cheng, Jianjun Yangdoi:10.1016/j.tws.2024.112669基于机器学习的冷弯型钢拼装截面轴向抗压能力估计To consider the highly nonlinear and complex buckling behaviour of various sections of cold-formed steel (CFS) built-up columns, experimental and finite element (FE) methods are commonly used for calculating their axial compressive capacity, although these methods are time-consuming and costly. This paper proposes machine learning (ML) methods to overcome the issues of traditional methods for predicting the maximum axial load capacity (MALC) of CFS built-up columns. A total of 3839 samples from more than 33 different types of sections were collected from 43 published papers, including 817 experimental data and 3,022 FE simulation data. A total of 15 characteristic parameters, such as the second moment of area, the radius of gyration, and the polar second moment of area, are considered when nine different ML models are trained. The robustness of these models was compared via the Monte Carlo simulation method, and the predicted results were compared with the calculated results from the current codes. The results show that the extreme gradient boosting (XGB) model has higher accuracy and smaller prediction errors in estimating the MALC. The proportion of data with a relative percentage error less than 10% in the prediction results of the AISI-DSM codes is 45.31%, whereas the XGB model achieves a proportion of 87.57%, and the results calculated from current codes tend to be more conservative, with a large deviation, which needs to be further considered.考虑到冷弯型钢(CFS)组合柱的各种截面高度非线性和复杂的屈曲行为,通常采用实验和有限元(FE)方法来计算其轴向抗压能力,尽管这些方法既耗时又昂贵。本文提出了机器学习(ML)方法来克服传统方法预测CFS组合柱最大轴向承载力(MALC)的问题。在43篇已发表的论文中,共收集了33个不同类型截面的3839个样本,其中实验数据817个,有限元模拟数据3022个。在训练9种不同的ML模型时,总共考虑了15个特征参数,如面积的第二矩、旋转半径和面积的极秒矩。通过蒙特卡罗模拟方法对模型的鲁棒性进行了比较,并将预测结果与现行规范的计算结果进行了比较。结果表明,极端梯度增强(XGB)模型在估计MALC时具有较高的精度和较小的预测误差。AISI-DSM代码预测结果中相对百分比误差小于10%的数据占比为45.31%,而XGB模型预测结果占比为87.57%,目前代码计算结果趋于保守,偏差较大,有待进一步考虑。Multiscale fail-safe topology optimization for lattice structuresHuili Huang, Wei Ding, Huanfei Jia, Wenjie Zuo, Fei Chengdoi:10.1016/j.tws.2024.112693晶格结构的多尺度故障安全拓扑优化In this paper, we address the critical issue of lattice structures losing functionality under local damage, which is a common safety deficiency in traditional lattice designs. A novel multiscale fail-safe topology optimization method is proposed to enhance the robustness of lattice structures. The method uses a simplified local damage model, aiming to minimize strain energy under the most critical failure scenarios, with design variables including macroscopic topology and geometric parameters of microscopic unit cells. By predefining an equivalent material model for the parameterized lattice structure, computational costs are significantly reduced. To overcome the non-differentiability of maximum strain energy, the Kreisselmeier-Steinhauser function is introduced as a substitute. Consequently, numerical simulation results demonstrate that this method effectively enhances lattice structure safety by providing more load-bearing paths to resist local damage. Compared to other fail-safe topology optimization methods, this approach expands the design space while maintaining the same computational cost, and it does not require adjustments to the predefined unit cell configuration for different working conditions.本文讨论了传统晶格结构在局部损伤下失去功能的关键问题,这是传统晶格设计中常见的安全缺陷。为了提高晶格结构的鲁棒性,提出了一种新的多尺度故障安全拓扑优化方法。该方法采用简化的局部损伤模型,设计变量包括微观单元胞的宏观拓扑和几何参数,以在最关键的破坏场景下最小化应变能为目标。通过预先定义参数化晶格结构的等效材料模型,大大降低了计算成本。为了克服最大应变能的不可微性,引入了Kreisselmeier-Steinhauser函数作为替代。数值模拟结果表明,该方法通过提供更多的承重路径来抵抗局部损伤,有效地提高了点阵结构的安全性。与其他故障安全拓扑优化方法相比,该方法在保持相同计算成本的同时扩展了设计空间,并且不需要根据不同的工作条件调整预定义的单元配置。Developing Lightweight Steel Profile and Lattice Polymeric Core Composite for Structural UseIeva Misiūnaitė, Arvydas Rimkus, Viktor Gribniakdoi:10.1016/j.tws.2024.112697开发结构用轻钢型材和点阵聚合物芯复合材料Embracing modular construction, advanced materials, and digital technologies can drive innovation in the building industry, address global material consumption challenges, and foster a sustainable future. This paper presents the innovative concept of the lightweight hybrid lattice-filled profile (HLFP) for modular engineering, which combines a thin-walled steel tubular shell and additively manufactured lattice structure (AMLS) as a lightweight core. The AMLS achieves precise shape, internal structure, and stiffness, ensuring the decided structural performance with minimum materials. This study provides a theoretical model of HLFP, focusing on adhesively bonded AMLS. The experimental verification demonstrates that the adhesively bonded AMLS ensures an additional 130% during the elastic stage and, even after partial debonding, maintains 50% of the mechanical resistance compared to the theoretical sum of the HLFP components. Reducing the infill density does not severely affect the load-bearing capacity of the HLFP—a fourfold decrease of the ALMS density (from 10% to 2.5%) results in a 20% decrease in the ultimate load. However, the sparse lattice structure alters the failure mechanism of ALMS, changing it from favorable ductile to dangerous brittle and determining the object for further optimization. The parametric study reveals the efficiency of the theoretical model for predicting the load-bearing capacity of HLFP. However, the finite element model developed in this study should be used for a more detailed analysis of the HLFP's structural behavior.采用模块化建筑、先进材料和数字技术可以推动建筑行业的创新,解决全球材料消耗挑战,并促进可持续发展的未来。提出了面向模块化工程的轻量化混合网格填充型材(HLFP)的创新概念,该结构将薄壁钢管壳和增材制造的网格结构(AMLS)作为轻量化核心相结合。AMLS可以实现精确的形状、内部结构和刚度,以最少的材料确保确定的结构性能。本研究提供了一个HLFP的理论模型,重点研究粘接的AMLS。实验验证表明,粘接的AMLS在弹性阶段保证了额外的130%的机械阻力,即使在部分脱粘后,与HLFP组件的理论总和相比,仍保持了50%的机械阻力。降低填充密度不会严重影响hlfp的承载能力- ALMS密度降低四倍(从10%降至2.5%)导致极限载荷降低20%。然而,稀疏晶格结构改变了ALMS的破坏机制,使其从良好的延性变为危险的脆性,从而确定了进一步优化的目标。参数化研究表明,该理论模型对高强度混凝土结构承载力的预测是有效的。然而,在本研究中开发的有限元模型应该用于更详细的分析高铁的结构行为。来源:复合材料力学仿真Composites FEM

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