今日更新:International Journal of Solids and Structures 1 篇,International Journal of Plasticity 1 篇,Thin-Walled Structures 10 篇
Interfacial crack-tip fields in beaded fiber composites
Min Xu, H. Daniel Wagner, Bingbing An
doi:10.1016/j.ijsolstr.2024.112718
珠状纤维复合材料中的界面裂纹尖端场
Beaded fiber composites represent ingenious design strategies capable of resolving the conflicts between strength and toughness in most engineering materials. Although intermittent beading holds great potential for improving mechanical properties, the underlying mechanisms responsible for strengthening and toughening of beaded fiber composites are largely unknown. In this study, we explore near-tip fields of an interface crack between the fiber and the polymeric bead, which is associated with fiber-bead debonding in the course of fiber pullout. The post-yield strain softening followed by strain hardening of polymer matrix, and friction between the bead and matrix are accounted for in the numerical analyses. It is found that pullout of fibers leads to development of multiple shear bands near the tip of the interface crack between the fiber and bead, and coalescence of shear bands gives rise to a zone of high plastic strain. Compared with the low level of friction between the bead and matrix, the bead-matrix interface with high friction coefficient can generate a larger zone of high plastic strain, increasing the propensity of interfacial debonding between the fiber and bead. Furthermore, we have revealed the role of thin coating of carbon nanotubes (CNT). Adding a CNT coating on the fiber enables the emergence of a small zone of high plastic strain near the interface crack tip and reduces the shear stress levels, thereby delaying bead debonding. Additionally, the introduction of CNT coating facilitates stress transfer from the bead to fiber, leading to high pullout force. The findings of this study provide important mechanistic insight into the design principles of beaded fiber composites.
珠状纤维复合材料是一种巧妙的设计策略,能够解决大多数工程材料中强度和韧性之间的矛盾。虽然间歇性串珠在改善机械性能方面具有巨大潜力,但串珠纤维复合材料的强化和增韧机理在很大程度上还不为人知。在本研究中,我们探讨了纤维与聚合珠之间界面裂纹的近端场,这种裂纹与纤维拉拔过程中纤维与珠的脱粘有关。数值分析中考虑了聚合物基体的屈服后应变软化和应变硬化,以及珠子和基体之间的摩擦。研究发现,纤维的拉拔会导致纤维和珠子之间的界面裂纹尖端附近出现多条剪切带,剪切带的凝聚会产生高塑性应变区。与微珠和基体之间的低摩擦相比,摩擦系数高的微珠-基体界面会产生更大的高塑性应变区,从而增加纤维和微珠之间的界面脱粘倾向。此外,我们还发现了碳纳米管(CNT)薄涂层的作用。在纤维上添加碳纳米管涂层可使界面裂纹尖端附近出现一小块高塑性应变区,并降低剪应力水平,从而延缓珠子脱落。此外,引入碳纳米管涂层还能促进应力从珠到纤维的传递,从而产生较高的拉拔力。这项研究的结果为珠状纤维复合材料的设计原理提供了重要的机理启示。
Coupling effect of loading mode and temperature on the deformation behaviors of TWIP β Ti alloy: From superior tensile strength-ductility synergy to low Charpy impact toughness
Q. Wang, B. Sang, J.Q. Ren, C. Xin, Y.H. Zhang, Q. Gao, W.F. Liu, Z.L. Ning, J.T. Yu, X.F. Lu
doi:10.1016/j.ijplas.2024.103920
加载模式和温度对 TWIP β Ti 合金变形行为的耦合效应:从优异的拉伸强度-电导率协同作用到较低的夏比冲击韧性
The Ti-8.5Cr-1.5Sn β Ti alloy with twinning induced plasticity (TWIP) effect was selected for the quasi-static tensile and Charpy impact tests at 298 K and 77 K to determine whether the strengthening and toughening strategy by TWIP effect can be extended to the cryogenic temperature. As the impact deformation temperature decreased from 298 K to 77 K, the Charpy impact toughness decreased obviously, even though a superior strength-ductility synergy was obtained under quasi-static tensile deformation at 77 K. Because the inhibition of deformation twins (DTs) activity under Charpy impact deformation at 77 K, together with the premature cracking along the formed twin boundaries (TBs), the density and width of the activated {332} DTs were significantly reduced. Meanwhile, the secondary DTs and {5 8 11} DTs also were restrained due to the width of primary DTs was too narrow. The above influencing factors resulted in the size of plastic deformation region at crack tip at 77 K was obviously smaller than that at 298 K. The crack preferentially initiated and propagated along primary TBs, and finally a low Charpy impact absorbed energy was displayed at 77 K.
选择具有孪晶诱导塑性(TWIP)效应的 Ti-8.5Cr-1.5Sn β Ti 合金在 298 K 和 77 K 下进行准静态拉伸和夏比冲击试验,以确定 TWIP 效应的强化和增韧策略是否可以扩展到低温。随着冲击变形温度从 298 K 降到 77 K,夏比冲击韧性明显降低,尽管在 77 K 的准静态拉伸变形下获得了优异的强度-韧性协同作用。由于在 77 K 的夏比冲击变形下变形孪晶(DTs)的活性受到抑制,加上沿形成的孪晶边界(TBs)过早开裂,活化的 {332} DTs 的密度和宽度显著降低。DTs 的密度和宽度明显降低。同时,次生 DT 和{5 8 11} DT 也因孪晶边界(TB)的形成而受到约束。DT 也由于一级 DT 的宽度过窄而受到限制。上述影响因素导致 77 K 时裂纹尖端塑性变形区的尺寸明显小于 298 K 时的尺寸,裂纹优先沿着一级 DT 引发并扩展,最终在 77 K 时显示出较低的夏比冲击吸收能。
A new double superposition-based shear deformation theory for static analysis of multilayered composite and sandwich doubly-curved shells
Dongyong Yao, M. Lezgy-Nazargah
doi:10.1016/j.tws.2024.111703
基于双重叠加的剪切变形新理论,用于多层复合材料和夹层双曲面壳体的静力分析
The accuracy of a laminated shell theory usually increases by increasing the number of unknown parameters involved in defining its kinematical relations. On the other hand, the computational cost of the analysis also increases by increasing the number of unknown parameters of a laminated shell theory. Therefore, developing accurate shell models with a low number of unknown parameters is a key issue. In this study, a novel shear deformation shell theory with only seven unknown parameters is proposed. The kinematical relations of the presented multilayered shell model are derived based on the double superposition concept. The z/R term (ratio of thickness co-ordinate to radii of curvature) is considered in formulation for capturing cross-sectional warping effects. Governing equations of shells under static loads have been solved by developing an eight-node shell element. Numerical comparisons show that the presented shell model is an efficient tool for static analysis of cross-ply, angle-ply, and soft-core sandwich shells with various deepness and length-to-thickness ratios.
层叠壳理论的精度通常会随着定义其运动学关系的未知参数数量的增加而提高。另一方面,分析的计算成本也会随着层叠壳理论未知参数数量的增加而增加。因此,开发具有较少未知参数的精确壳模型是一个关键问题。本研究提出了一种只有七个未知参数的新型剪切变形壳理论。所提出的多层壳模型的运动学关系是基于双重叠加概念推导出来的。在公式中考虑了 z/R 项(厚度坐标与曲率半径之比),以捕捉横截面翘曲效应。通过开发八节点壳体元素,解决了静载荷下壳体的控制方程。数值比较表明,所提出的壳体模型是对具有不同深度和长厚比的交叉层、角层和软芯夹层壳体进行静态分析的有效工具。
A multiscale strategy for exploring the mechanical behavior of 3D braided composite thin-walled cylinders
Yutong Liu, Yuliang Hou, Thaneshan Sapanathan, Renjie Nie, Liang Meng, Yingjie Xu
doi:10.1016/j.tws.2024.111705
探索三维编织复合薄壁圆柱体力学行为的多尺度策略
The mechanical behavior of 3D braided composite (3DBC) thin-walled cylinders is investigated using a multiscale modeling approach. A curved-surface equivalent block-stacking based (EBSB) cell, is developed using local homogenization, to facilitate the trans-scale information transfer. It enables to simplify the complex architectures of 3DBCs with the reservation of local braided characteristics. The macroscale models have been constructed by arranging the EBSB cells. Subsequently, axial compression tests have been experimentally and numerically carried out on 3DBC thin-walled cylinders. The prediction errors are less than 4%, revealing a good agreement with the experimental measurements. Besides, the macroscale modeling only takes 0.33 h (20 min), confirming the high accuracy and efficiency of the multiscale modeling approach. The experimental and numerical results indicate that matrix cracking is the dominant damage mode for the thin-walled cylinder under axial compression. Moreover, various numerical simulations are performed on four types of grid-stiffened thin-walled cylinders, to analyze the enhancement effect of the stiffening-grid designs. In the axial compression loading case, the square-grid-stiffened (SGS) pattern provides higher enhancement of load-carrying capacity, while the cylinder with the X-grid-stiffened (XGS) pattern performs better during internal pressure, torsional, as well as the combined loading conditions. The numerical results reveal that the damage is prone to initiates within the skin-stiffener transition region, while the skin cracking results in the final failure of the grid-stiffened cylinders.
本文采用多尺度建模方法研究了三维编织复合材料(3DBC)薄壁圆柱体的力学行为。利用局部均质化技术开发了基于曲面等效块堆积(EBSB)单元,以促进跨尺度信息传递。它通过保留局部编织特性,简化了三维BC 的复杂结构。通过排列 EBSB 单元,构建了宏观模型。随后,对 3DBC 薄壁圆柱体进行了轴向压缩试验和数值试验。预测误差小于 4%,显示出与实验测量结果的良好一致性。此外,宏观建模仅需 0.33 小时(20 分钟),证实了多尺度建模方法的高精度和高效率。实验和数值结果表明,基体开裂是薄壁圆柱体在轴向压缩下的主要破坏模式。此外,还对四种网格加劲薄壁圆柱体进行了各种数值模拟,以分析加劲网格设计的增强效果。在轴向压缩加载情况下,方格栅加固(SGS)模式可提高承载能力,而采用 X 格栅加固(XGS)模式的气缸在内压、扭转和组合加载条件下表现更佳。数值结果表明,损伤容易在表皮-加劲件过渡区域内发生,而表皮开裂导致网格加劲圆柱体最终失效。
Rate-dependent behaviour of additively manufactured topology optimised lattice structures
Sami E. Alkhatib, Shanqing Xu, Guoxing Lu, Ali Karrech, Timothy B. Sercombe
doi:10.1016/j.tws.2024.111710
叠加制造拓扑优化晶格结构的速率依赖行为
Lattice structures offer a wide range of tuneable qualities that cannot be achieved with bulk materials. While lattice structures offer a range of tuneable qualities, including isotropic properties achievable in bulk materials, the advent of additive manufacturing (AM) advances research in this domain. Although several studies have characterized the quasi-static mechanical properties of lattice structures, there is limited experimental data available on their rate-dependent behaviour. Additionally, most lattice structures are anisotropic, making them unsuitable for applications where loading directions are unknown. In this study, a topology-optimised unit cell with nearly perfect isotropic stiffness is investigated for its isotropic specific energy absorption under high strain rates. The dynamic response of the structure is evaluated using 3 different materials: CPTi, AlSi10Mg, and 316LSS, and both experimental and numerical methods are employed. The influence of topology and relative density on the mechanical properties of the structure are explored, and the specific energy absorption isotropy is determined by loading the lattices in various orientations numerically. This research fills the gap in knowledge regarding the rate-dependent behaviour of lattice structures and offers insight into the potential for isotropic lattice structures in engineering applications.
晶格结构具有多种可调特性,而这些特性是块状材料无法实现的。虽然晶格结构提供了一系列可调整的特性,包括各向同性的特性,这些特性在块体材料中是可以实现的,但增材制造(AM)技术的出现推动了这一领域的研究。虽然已有多项研究对晶格结构的准静态机械特性进行了描述,但有关其速率依赖行为的实验数据却十分有限。此外,大多数晶格结构是各向异性的,因此不适合加载方向未知的应用。本研究对拓扑优化的单元格进行了研究,该单元格具有近乎完美的各向同性刚度,可在高应变速率下吸收各向同性的比能量。使用 3 种不同的材料对结构的动态响应进行了评估:采用实验和数值方法对 CPTi、AlSi10Mg 和 316LSS 这三种不同材料的结构进行了动态响应评估。研究探讨了拓扑结构和相对密度对结构机械性能的影响,并通过数值加载不同方向的晶格确定了比能量吸收的各向同性。这项研究填补了有关晶格结构随速率变化行为的知识空白,并为各向同性晶格结构在工程应用中的潜力提供了启示。
Effect of fiber layout on low-velocity impact response of intralaminar hybrid carbon/glass fiber braided composite pipes under internal pressure.
Lin Shi, Hua Yang, Zhenyu Wu, Laihu Peng, Qingqing Ni, Qinchuan Li
doi:10.1016/j.tws.2024.111711
纤维布局对内压下层内混合碳/玻璃纤维编织复合管道低速冲击响应的影响
This study investigated the low-velocity impact behaviors of intralaminar hybrid carbon/glass braided composite pipes under internal pressure. The effects of intralaminar fiber layout and internal pressure on the mechanical responses, damage extension, and material cost-effectiveness were analyzed. The internal damage distribution of composite pipes with different hybrid fiber alternating numbers but identical mix ratios was evaluated through Micro-CT three-dimensional damage reconstructions. The yarn splitting of brittle carbon fiber materials was mutually prevented by the induction of intra-yarn debonding and delamination damages by hybridization with ductile glass fiber materials, which were prone to produce out-of-plane displacement and shear stresses under impact loading. A smaller hybrid fiber alternating unit was conducive to exploiting the hybrid impact toughening effect by avoiding pure reinforced fiber materials aggregated under the impactor. Internal pressure had a supporting effect on the composite pipe and was effectively synergistic with the hybridization effect. The change in the dominant damage mode resulted in significant reductions in impact deformation and damage severity compared to the unpressurized case.
本研究探讨了层内混合碳/玻璃编织复合材料管道在内压作用下的低速冲击行为。分析了层内纤维布局和内压对力学响应、损伤扩展和材料成本效益的影响。通过 Micro-CT 三维损伤重建评估了不同混合纤维交替数量但混合比相同的复合管道的内部损伤分布。脆性碳纤维材料的纱线开裂与韧性玻璃纤维材料的纱线内脱胶和分层损伤相互防止,而韧性玻璃纤维材料在冲击载荷下容易产生平面外位移和剪切应力。较小的混合纤维交替单元有利于利用混合冲击增韧效应,避免纯增强纤维材料在冲击器下聚集。内部压力对复合管具有支撑作用,并与混合效应有效协同。与未加压情况相比,主要破坏模式的改变导致冲击变形和破坏严重程度显著降低。
Global dynamic characteristics analysis of GTF star gear transmission system considering ring gear elastic deformation
Haoran Zou, Sanmin Wang, Peng Chen, Jinshuai Ge, Linlin Liu
doi:10.1016/j.tws.2024.111712
考虑环形齿轮弹性变形的 GTF 星形齿轮传动系统的全局动态特性分析
For the purpose of weight reduction and load sharing, the ring gear in the geared turbofan engine(GTF) gearbox is relatively thin, which will cause significant deformation of the ring gear during operation, so that the influence of the elastic deformation of ring gear on the system's dynamic characteristics cannot be ignored. The cross-section structure of the ring gear in actual gearbox is relatively complex, which is not conducive to solve the ring gear elastic deformation. Therefore, the original ring gear with complex cross-section is simplified as a T-shaped section ring in this paper. And using material mechanics and elastic theory to derive the elastic deforming equation of the T-shaped section ring. In the derivation of the dynamic equation of the system, the elastic deforming equation of the equivalent ring gear is cleverly embedded in the dynamic equation, and an improved dynamic model of GTF star gear transmission system(GTF-SGT) with ring gear elastic deformation is formed. Then, the computation results of the improved dynamic model with ring gear elastic deformation, the dynamic model without ring gear elastic deformation and experimental results in existing literature are compared to check the necessity of considering ring gear elastic deformation and the accuracy of the improved dynamic model. Finally, the two-parameter plane of the ring thickness(h)-rim thickness ratio(λ) and the ring thickness(h)-width thickness ratio(ξ) is constructed, and the distribution map of GTF-SGT dynamic characteristic in parameter plane is obtained. From the global perspective, to study how the matching law between different structural size parameters of equivalent ring gear affects the dynamic characteristics of GTF-SGT. This is important for selecting the ring gear structural size.
出于减重和分担载荷的目的,齿轮传动涡扇发动机(GTF)变速箱中的环形齿轮相对较薄,在运行过程中会引起环形齿轮的显著变形,因此环形齿轮的弹性变形对系统动态特性的影响不容忽视。实际变速箱中的环形齿轮截面结构相对复杂,不利于解决环形齿轮的弹性变形问题。因此,本文将原来具有复杂截面的环形齿轮简化为 T 形截面环。并利用材料力学和弹性理论推导出 T 形截面齿圈的弹性变形方程。在推导系统动态方程时,巧妙地将等效环形齿轮的弹性变形方程嵌入动态方程中,形成了带环形齿轮弹性变形的 GTF 星齿轮传动系统(GTF-SGT)改进动态模型。然后,将带环形齿轮弹性变形的改进动力学模型、不带环形齿轮弹性变形的动力学模型的计算结果与现有文献中的实验结果进行比较,以检验考虑环形齿轮弹性变形的必要性和改进动力学模型的准确性。最后,构建了齿圈厚度(h)-齿圈厚度比(λ)和齿圈厚度(h)-齿宽厚度比(ξ)的双参数平面,得到了 GTF-SGT 动力特性在参数平面上的分布图。从全局角度研究等效环形齿轮不同结构尺寸参数之间的匹配规律对 GTF-SGT 动态特性的影响。这对于选择环形齿轮结构尺寸具有重要意义。
Nonlinear wave propagation in graphene incorporating second strain gradient theory
Bo Yang, Nicholas Fantuzzi, Michele Bacciocchi, Francesco Fabbrocino, Mahmoud Mousavi
doi:10.1016/j.tws.2024.111713
包含第二应变梯度理论的石墨烯非线性波传播
The exploration of graphene has attracted extensive interest owing to its significant structural and mechanical properties. In this research, we numerically investigate wave propagation in defect-free single-layer graphene, considering its geometrically nonlinear behavior through second-strain gradient elasticity. To capture the geometric nonlinearity, firstly, the nonlinear strain–displacement relations are introduced. The governing equation and associated boundary conditions are derived using Hamilton’s principle. Then, the weak form, including the element matrices, is established. The eigenvalue problem is solved for 2D wave propagation through periodic structures theory. Finally, the dynamical properties such as band structures, mode shapes, energy flow, and wave beaming effects are analyzed. The numerical results reveal that the geometric nonlinearity through the second strain gradient influences the wave propagation characteristics in graphene. The findings are significant and contribute to the understanding of graphene’s dynamic response, with implications for the engineering applications of graphene-based nanostructures.
由于石墨烯具有显著的结构和机械特性,对它的探索引起了广泛的兴趣。在本研究中,我们通过二次应变梯度弹性对无缺陷单层石墨烯中的波传播进行了数值研究,并考虑了其几何非线性行为。为了捕捉几何非线性,首先引入了非线性应变-位移关系。利用汉密尔顿原理推导出支配方程和相关边界条件。然后,建立包括元素矩阵在内的弱形式。通过周期结构理论求解了二维波传播的特征值问题。最后,分析了带状结构、模态形状、能量流和波束效应等动力学特性。数值结果表明,几何非线性通过第二应变梯度影响石墨烯的波传播特性。这些发现意义重大,有助于理解石墨烯的动态响应,对石墨烯基纳米结构的工程应用具有重要意义。
Low-frequency bandgap and vibration mitigation performance of metamaterial-tailored concrete-filled steel tube columns
F.M. Ren, J.R. Xiong, S.F. Li, S.Y. Tian, Y.S. Li, C.L. Lai, J.X. Mo
doi:10.1016/j.tws.2024.111714
超材料定制混凝土填充钢管柱的低频带隙和减振性能
Low-frequency vibrations, such as earthquakes and wind loads, may negatively affect the proper operation of buildings and bridges and even lead to structural failure. Even though, in the past two decades, metamaterial-based structures have been utilized in structure vibration suppression, it is mainly used in the mitigation of high-frequency vibrations, It has been an open challenge to suppress low-frequency vibrations below 100 and ensure adequate bearing capacity in engineering structures. In this work, we present metamaterial composite column structures with built-in local resonators to achieve the low-frequency vibration mitigation effect. Compared to ordinary concrete-filled steel tube (CFST) columns, the metamaterial columns (meta-columns) can utilize the rubber shear modulus to create a low-frequency flexural bandgap in 30-50Hz. Dynamic stiffness is introduced in the Timoshenko beam and Bloch's theorem, the metamaterial analytical model is established, and the bandgap generation mechanism and vibration reduction effect are analyzed in conjunction with numerical simulations. Then, the bandgap effect and vibration attenuation law of the meta-columns are investigated by shaker tests at different acceleration amplitudes. Guided by theory and simulations, we have successfully fabricated several meta-composite columns with low-frequency bandgaps, which attenuate up to half of the vibrational energy near the bandgap center. The bandgap ranges derived from the theoretical and numerical models show a high degree of consistency with the experimental results, with deviations generally within 10%, all indicating that a bandgap exists near the resonator self-oscillation frequency. Additionally, the bandgap is significantly affected by the number of unit cells and resonators, especially the meta-column with fewer resonators fails to form a bandgap where the top response is smaller than the bottom response. As the number of resonators and metamaterial units increases, the meta-columns exhibit wider bandgap and stronger vibration reduction performance.
地震和风荷载等低频振动可能会对建筑物和桥梁的正常运行产生负面影响,甚至导致结构失效。尽管在过去二十年中,基于超材料的结构已被用于结构振动抑制,但它主要用于缓解高频振动,而如何抑制 100 以下的低频振动并确保工程结构具有足够的承载能力一直是一个公开的挑战。在这项工作中,我们提出了内置局部谐振器的超材料复合材料柱结构,以实现低频振动缓解效果。与普通混凝土填充钢管(CFST)柱相比,超材料柱(meta-columns)可利用橡胶剪切模量在 30-50Hz 范围内产生低频挠曲带隙。在季莫申科梁和布洛赫定理中引入了动态刚度,建立了超材料分析模型,并结合数值模拟分析了带隙产生机理和减振效果。然后,通过不同加速度振幅下的振动台试验研究了超材料柱的带隙效应和振动衰减规律。在理论和模拟的指导下,我们成功地制造出了几种具有低频带隙的元复合材料柱,它们在带隙中心附近最多可衰减一半的振动能量。理论和数值模型得出的带隙范围与实验结果高度一致,偏差一般在 10%以内,这表明带隙存在于谐振器自振频率附近。此外,带隙还受到单元单元和谐振器数量的显著影响,尤其是谐振器数量较少的元柱无法形成带隙,即顶部响应小于底部响应。随着谐振器和超材料单元数量的增加,元柱表现出更宽的带隙和更强的减振性能。
Mechanical properties of bionic lattice and its hybrid structures based on the microstructural design of pomelo peel
Zhixuan Sun, Yu Gong, Zheng Bian, Jianyu Zhang, Libin Zhao, Ning Hu
doi:10.1016/j.tws.2024.111715
基于柚子皮微结构设计的仿生晶格及其混合结构的力学性能
Bionic design has been widely used in real life, while providing ideas for innovative design of structures. In this work, a bionic lattice structure (Y-structure) with negative Poisson's ratio effect is obtained based on the principle of bionic design by taking design inspiration from the microstructure of pomelo peel. Meanwhile, in order to reduce the fabrication difficulty, the Y structure is combined with the BCC structure to obtain four overall lattice structures containing the Y structure. The required samples are prepared by additive manufacturing technique using PA2200 as the matrix material. Quasi-static compression tests are performed on the specimens at room temperature, and the mechanical properties and energy absorption capacity of the bionic lattice structure are examined under different compression directions, considering the anisotropy of the structure. Through the experimental results, it can be found that, compared with the traditional BCC structure, the four lattice structures containing the bionic lattice show obvious anisotropy, and exhibit good mechanical properties in different directions, while the energy absorption capacity is also generally improved. However, the change in the occupancy ratio of the BCC structure has a significant effect on the mechanical properties of the mixed lattice structure. The results obtained in this study can provide valuable references for further creative new developments of lattice structures based on bionic principles.
仿生设计在现实生活中得到了广泛应用,同时也为结构的创新设计提供了思路。本研究基于仿生设计原理,从柚子皮的微观结构中汲取设计灵感,得到了一种具有负泊松比效应的仿生晶格结构(Y 结构)。同时,为了降低 制造难度,将 Y 结构与 BCC 结构相结合,得到了包含 Y 结构的四种整体晶格结构。以 PA2200 为基体材料,通过增材制造技术制备出所需样品。在室温下对试样进行准静态压缩试验,考虑到结构的各向异性,考察了仿生晶格结构在不同压缩方向下的力学性能和能量吸收能力。通过实验结果可以发现,与传统的 BCC 结构相比,含有仿生晶格的四种晶格结构表现出明显的各向异性,在不同方向上均表现出良好的力学性能,能量吸收能力也普遍提高。然而,BCC 结构占有率的变化对混合晶格结构的力学性能有显著影响。本研究获得的结果可为进一步创造性地开发基于仿生原理的新晶格结构提供有价值的参考。
A graded acoustic metamaterial rod enabling ultra-broadband vibration attenuation and rainbow reflection
Jia Lou, Hui Fan, Aibing Zhang, Menghui Xu, Jianke Du
doi:10.1016/j.tws.2024.111716
可实现超宽带振动衰减和彩虹反射的梯度声超材料棒
Broadband vibration suppression poses a significant engineering challenge, and researchers have turned to acoustic metamaterials (AMs) as a promising solution. Traditional periodic AMs, though effective, often have narrow band gaps that limit their practicality. This study focuses on the design of a graded AM rod that achieves ultra-broadband vibration attenuation and rainbow reflection. The graded rod consists of various sections with seamlessly interconnected band gaps. The design is based on the dispersion analysis of an infinite uniform AM rod, complemented by the transmission calculation of a finite graded AM rod. The study emphasizes the importance of incorporating a specific number of identical unit cells in each section and introducing a small amount of damping in each resonator for effective ultra-broadband vibration suppression. The designed AM rod effectively blocks the propagation of longitudinal waves, regardless of their incident direction. Furthermore, the research demonstrates the orderly filtration of frequency components along the wave propagation path, showcasing the phenomenon of acoustic rainbow reflection. This phenomenon is illustrated through finite element simulations. This work not only addresses the pressing engineering challenge of broadband vibration attenuation but also paves the way for the separation, collection and energy harvesting of elastic waves.
宽带振动抑制是一项重大的工程挑战,研究人员已将声学超材料(AMs)作为一种有前途的解决方案。传统的周期性超材料虽然有效,但通常具有狭窄的带隙,限制了其实用性。本研究的重点是设计一种可实现超宽带振动衰减和彩虹反射的分级 AM 棒。分级调幅棒由带隙无缝连接的不同部分组成。设计基于无限均匀 AM 棒的色散分析,并辅以有限分级 AM 棒的传输计算。研究强调了在每个部分加入特定数量的相同单元和在每个谐振器中引入少量阻尼以有效抑制超宽带振动的重要性。无论纵波的入射方向如何,所设计的调幅杆都能有效阻挡纵波的传播。此外,研究还展示了沿波传播路径对频率成分的有序过滤,展示了声虹反射现象。这一现象通过有限元模拟进行了说明。这项工作不仅解决了宽带振动衰减这一紧迫的工程难题,还为弹性波的分离、收集和能量采集铺平了道路。
Nonlinear properties prediction and inverse design of a porous auxetic metamaterial based on neural networks
Hongru Yan, Hongjun Yu, Shuai Zhu, Zelong Wang, Yingbin Zhang, Licheng Guo
doi:10.1016/j.tws.2024.111717
基于神经网络的多孔辅助超材料非线性特性预测与反设计
Auxetic metamaterials are widely applied in energy-absorbing systems and soft robots due to their superior mechanical properties. The properties of auxetic metamaterials are determined by their architectures, which means it is feasible to obtain metamaterials with target performance through structural design. This paper proposes a framework with neural networks to generate a nearly real-time prediction of the auxeticity and stiffness simultaneously of porous materials. Trained neural networks accurately provide computationally inexpensive predictions on response histories. Based on the prediction database given by the neural network, the parametric analysis can be conducted to provide the mutual influence and trend relationship of auxeticity and stiffness of the porous metamaterial. In addition, inverse design can also be conducted for seeking optimal architecture in terms of the auxeticity and stiffness quickly and accurately. With the method, the target nonlinear properties can be accurately and rapidly designed for porous metamaterials. The relative error of neural network predictions is less than 1.5% compared with experimental results, and less than 8.0% compared with the numerical results given by the finite element method. The proposed framework can be extended to more structural materials to provide design guideline.
辅助超材料因其卓越的机械性能而被广泛应用于能量吸收系统和软机器人中。辅助超材料的性能由其结构决定,这意味着通过结构设计获得具有目标性能的超材料是可行的。本文提出了一种神经网络框架,可同时对多孔材料的辅助性和刚度进行近乎实时的预测。经过训练的神经网络可以准确地对响应历程进行计算成本低廉的预测。根据神经网络提供的预测数据库,可以进行参数分析,以提供多孔超材料的辅助eticity 和刚度的相互影响和趋势关系。此外,还可以进行逆向设计,快速准确地寻求辅助系数和刚度的最佳结构。利用该方法,可以准确、快速地设计多孔超材料的目标非线性特性。与实验结果相比,神经网络预测的相对误差小于 1.5%,与有限元法给出的数值结果相比,相对误差小于 8.0%。所提出的框架可以扩展到更多的结构材料,为设计提供指导。