【新文速递】2024年7月5日固体力学SCI期刊最新文章

今日更新：International Journal of Solids and Structures 1 篇，Mechanics of Materials 1 篇，Thin-Walled Structures 3 篇International Journal of Solids and StructuresCompliant frame geometry for DEMES-based gripper and flapping wing actuators: A comprehensive design studyAman Khurana, M.M. Joglekar, Paul Motzki, Stefan Seeleckedoi:10.1016/j.ijsolstr.2024.112969基于 DEMES 的抓手和拍翼致动器的顺应性框架几何结构：综合设计研究Dielectric elastomer minimum energy structures (DEMES) have attracted significant attention in the recent past because of their ability to switch between multiple equilibrium states. The DEMES is formed when a pre-stretched elastomer film adheres to an inextensible frame and is further allowed to attain an equilibrium configuration as a result of energy minimization. While several researchers have investigated; both theoretically and experimentally, the underlying mechanics of DEMES, a majority of them deploy simplistic boundary frames (square/rectangular/circular) to obtain the requisite minimum energy configuration. In this paper, we demonstrate that this seemingly restrictive choice of using simplistic frame-geometries can be given away with by designing more complex-shaped compliant frames capable of producing useful modes of deformation. To demonstrate this idea, two prototypes; namely, the four-arm gripper actuator and the flapping-wing actuator, are studied numerically and experimentally. In both cases, a single compliant frame is used to realize the respective configuration, thus circumventing the need to assemble multiple MES on a common platform. In tandem, we investigate the role of reinforcements in (a) controlling the warping in MES and (b) maximizing actuation in the desired mode of deformation. Finite element analyses are carried out using the ABAQUS to determine the equilibrium configuration of the actuators, and subsequently their electromechanical behavior. Experimental investigations involve the utilization of the commercially available VHB-4910 acrylic tape in conjunction with PET frames and 3D printed reinforcements. Excellent qualitative agreement is achieved between the numerical predictions and the experimental observations. Finally, we allude to a few innovative frame architectures leading the MES of engineering interest.近年来，介电弹性体最小能量结构（DEMES）因其能够在多种平衡状态之间切换而备受关注。当预先拉伸的弹性体薄膜附着在一个不可拉伸的框架上，并在能量最小化的作用下进一步达到平衡构型时，就形成了介电弹性体最小能量结构。虽然一些研究人员已经从理论和实验两方面对 DEMES 的基本力学原理进行了研究，但他们大多采用简单的边界框架（方形/矩形/圆形）来获得所需的最小能量配置。在本文中，我们证明了可以通过设计形状更复杂、能够产生有用变形模式的顺应性框架来放弃这种看似限制性的简单框架几何结构选择。为了证明这一想法，我们对两个原型，即四臂抓手致动器和拍翼致动器进行了数值和实验研究。在这两种情况下，我们都使用单个顺应框架来实现各自的配置，从而避免了在通用平台上组装多个 MES 的需要。同时，我们还研究了加强筋在以下方面的作用：(a) 控制 MES 中的翘曲；(b) 在所需的变形模式中最大限度地发挥致动作用。我们使用 ABAQUS 进行了有限元分析，以确定致动器的平衡配置以及随后的机电行为。实验研究使用了市售的 VHB-4910 丙烯酸胶带、PET 框架和 3D 打印加固材料。数值预测与实验观察之间取得了极好的定性一致。最后，我们简要介绍了几种创新的框架结构，这些框架结构引领着工程领域的 MES。Mechanics of MaterialsOn the effect of strain rate during the cyclic compressive loading of liquid crystal elastomers and their 3D printed latticesBo Song, Dylan Landry, Thomas Martinez, Christopher N. Chung, Kevin N. Long, Kai Yu, Christopher M. Yakackidoi:10.1016/j.mechmat.2024.105086液晶弹性体及其 3D 打印晶格循环压缩加载过程中应变率的影响Nematic liquid crystal elastomers (LCEs) are a unique class of network polymers with the potential for enhanced mechanical energy absorption and dissipation capacity over conventional network polymers because they exhibit both conventional viscoelastic behavior and soft-elastic behavior (nematic director changes under shear loading). This additional inelastic mechanism makes them appealing as candidate damping materials in a variety of applications from vibration to impact. The lattice structures made from the LCEs provide further mechanical energy absorption and dissipation capacity associated with packing out the porosity under compressive loading.Understanding the extent of mechanical energy absorption, which is the work per unit mass (or volume) absorbed during loading, versus dissipation, which is the work per unit mass (or volume) dissipated during a loading cycle, requires measurement of both loading an unloading. In this study, a bench-top linear actuator was employed to characterize the loading-unloading compressive response of polydomain and monodomain LCE polymers and polydomain LCE lattice structures with two different porosities (nominally, 62% and 85%) at both low and intermediate strain rates at room temperature. As a reference material, a bisphenol-A (BPA) polymer with a similar glass transition temperature (9°C) as the nematic LCE (4°C) was also characterized at the same conditions for comparing to the LCE polymers. Based on the loading-unloading stress-strain curves, the energy absorption and dissipation for each material at different strain rates (0.001, 0.1, 1, 10 and 90 s-1) were calculated with considerations of maximum stress and material mass/density. The strain-rate effect on the mechanical response and energy absorption and dissipation behaviors was determined. The energy dissipation ratio was also calculated from the resultant loading and unloading stress-strain curves. All five materials showed significant but different strain rate effects on energy dissipation ratio. The solid LCE and BPA materials showed greater energy dissipation capabilities at both low (0.001 s-1) and high (above 1 s-1) strain rates, but not at the strain rates in between. The polydomain LCE lattice structure showed superior energy dissipation performance compared with the solid polymers especially at high strain rates.向列液晶弹性体（LCE）是一类独特的网络聚合物，与传统的网络聚合物相比，具有增强机械能吸收和耗散能力的潜力，因为它们既表现出传统的粘弹性行为，又表现出软弹性行为（剪切加载下的向列方向变化）。这种额外的非弹性机制使它们成为从振动到冲击等各种应用中的理想阻尼材料。由 LCE 制成的晶格结构还能进一步吸收机械能，并在压缩载荷作用下通过填充孔隙率来消散能量。机械能吸收是指加载过程中单位质量（或体积）所吸收的功，而耗散是指加载周期中单位质量（或体积）所耗散的功，要了解机械能吸收和耗散的程度，需要对加载和卸载进行测量。在这项研究中，我们使用了台式线性致动器来表征多域和单域 LCE 聚合物以及具有两种不同孔隙率（名义上分别为 62% 和 85%）的多域 LCE 晶格结构在室温下的低应变率和中应变率条件下的加载-卸载压缩响应。作为参考材料，双酚 A (BPA) 聚合物的玻璃化转变温度（9°C）与向列 LCE 相似（4°C），也在相同条件下进行了表征，以便与 LCE 聚合物进行比较。根据加载-卸载应力-应变曲线，考虑到最大应力和材料质量/密度，计算了每种材料在不同应变速率（0.001、0.1、1、10 和 90 s-1）下的能量吸收和耗散。确定了应变速率对机械响应以及能量吸收和耗散行为的影响。还根据加载和卸载应力应变曲线计算了能量耗散率。所有五种材料对能量耗散比的应变率影响都很明显，但又各不相同。固体 LCE 和双酚 A 材料在低应变速率（0.001 s-1）和高应变速率（高于 1 s-1）下都表现出更强的能量耗散能力，但在两者之间的应变速率下则没有。与固体聚合物相比，多域 LCE 晶格结构显示出更优越的能量耗散性能，尤其是在高应变速率下。Thin-Walled StructuresPrediction of Aerodynamic Forces at the Tip of the Compressor Blades Based on Multi-scale 1DCNN Combined with CBAMMinghui Yao, Shaohua Wu, Yan Niu, Qiliang Wu, Renduo Song, Bin Baidoi:10.1016/j.tws.2024.112190基于多尺度 1DCNN 和 CBAM 的压缩机叶片顶端空气动力预测The compressor is a crucial component of aircraft engines, and the blades are the critical factor affecting the performance of the compressor. Based on multi-scale one-dimensional convolution neural network (1DCNN) with Convolutional Block Attention Module (CBAM), a data-driven model is proposed for predicting the aerodynamic characteristics of the blade tips. The model is trained using the Adam with decoupled weight decay (AdamW) optimizer and a staged learning rate scheduling strategy. Due to the distinct aerodynamic pressure distributions on the suction and pressure sides, separate models are constructed in order to reveal the aerodynamic performance of the blade tips accurately. During the model validation, Root Mean Square Error (RMSE) and the coefficient of determination (R2) are taking as evaluation criterions, where high reliability is demonstrated compared to Computational Fluid Dynamics (CFD) results.压气机是飞机发动机的重要组成部分，而叶片是影响压气机性能的关键因素。基于带有卷积块注意模块（CBAM）的多尺度一维卷积神经网络（1DCNN），提出了一种数据驱动模型，用于预测叶尖的空气动力学特性。该模型采用带解耦权值衰减（AdamW）优化器和分阶段学习率调度策略进行训练。由于吸气侧和压力侧的气动压力分布不同，为了准确揭示叶尖的气动性能，分别构建了不同的模型。在模型验证过程中，以均方根误差（RMSE）和判定系数（R2）作为评价标准，与计算流体动力学（CFD）结果相比，显示出较高的可靠性。Machine learning-based active control for lightweight antenna with force density method and nested genetic algorithmRunzhi Lu, Huizhong Zhang, Qian Zhang, Honghu Jiang, Jian Feng, Marco Meloni, Jianguo Caidoi:10.1016/j.tws.2024.112212基于机器学习的轻型天线主动控制与力密度法和嵌套遗传算法This work proposes the integration of a tensegrity structure composed of struts and cables into an antenna, thus achieving a lightweight and optimized design for the large-scale system. Active control is introduced to ensure the deformation accuracy of the cable-strut antenna, while a shape sensing method based on force density information is adopted to obtain the deformation field of actual wind cases from monitoring the cable forces. Numerical simulations are performed to verify the accuracy of the method, and a multi-objective optimization framework is employed to determine the optimal positions and control of actuators for active control. A machine learning-based framework is proposed to achieve rapid response of the active control system under actual wind cases. The framework is composed of a two-stage control system that combines the shape sensing method with the multi-objective optimization approach. The machine learning framework establishes a quick response system that monitors changes in the cable forces, thus ensuring structural accuracy control under wind load without structural analysis.本研究提出将支柱和缆索组成的张弦结构集成到天线中，从而实现大型系统的轻量化和优化设计。为确保缆索-支柱天线的变形精度，引入了主动控制，同时采用了基于力密度信息的形状传感方法，通过监测缆索力获得实际风况下的变形场。通过数值模拟验证了该方法的准确性，并采用多目标优化框架确定了主动控制的最佳位置和致动器控制。提出了一个基于机器学习的框架，以实现主动控制系统在实际风况下的快速响应。该框架由两阶段控制系统组成，结合了形状感应方法和多目标优化方法。机器学习框架建立了一个快速响应系统，可监测拉索力的变化，从而确保在风荷载下的结构精度控制，而无需进行结构分析。Bending behaviour of surface corroded and perforated corroded steel tubes repaired by laser cladding additive manufacturingLan Kang, Peng Songdoi:10.1016/j.tws.2024.112213通过激光熔覆快速成型技术修复的表面腐蚀和穿孔腐蚀钢管的弯曲性能In recent years, laser cladding (LC) technology has been increasingly applied and investigated for repairing damaged surface on metal structural components. However, there are limited experimental studies on the bending behaviour of the LC repaired steel components. And an effective repair method for the perforated corroded steel components is still lacking, therefore, this paper introduces a novel LC repair method for such steel tube. Four-point bending tests were conducted on four specimens, including one intact steel tube (IT), one surface corroded steel tube (SCT), one surface corroded steel tube repaired by LC (SRT), and one perforated corroded steel tube repaired by LC (PRT) to verify the effectiveness of the LC repair methods by evaluating their structural performance in terms of bending capacity, rotational stiffness, and ductility. The experimental results showed that the bending strength and rotational stiffness of the SRT and PRT can be fully restored and even slightly higher than those of the IT. The strain analysis indicated that the LC repair method can significantly reduce stress/strain concentration caused by surface corrosion and perforation corrosion. The experiments were replicated numerically by means of finite element (FE) analysis and parametric studies were performed to investigate the effect of different factors on the bending behaviour of the PRT and SRT. Furthermore, design formula for predicting the elastic bending capacity of the LC repaired steel tube was developed.近年来，用于修复金属结构件受损表面的激光熔覆（LC）技术得到了越来越多的应用和研究。然而，对经 LC 修复的钢构件的弯曲性能的实验研究还很有限。因此，本文介绍了一种针对此类钢管的新型 LC 修复方法。本文对四种试样进行了四点弯曲试验，包括一种完整钢管（IT）、一种表面腐蚀钢管（SCT）、一种经 LC 修复的表面腐蚀钢管（SRT）和一种经 LC 修复的穿孔腐蚀钢管（PRT），通过评估它们在弯曲能力、旋转刚度和延展性方面的结构性能来验证 LC 修复方法的有效性。实验结果表明，SRT 和 PRT 的弯曲强度和旋转刚度可以完全恢复，甚至略高于 IT。应变分析表明，LC 修复方法能显著减少表面腐蚀和穿孔腐蚀引起的应力/应变集中。通过有限元（FE）分析对实验进行了数值复 制，并进行了参数研究，以探讨不同因素对 PRT 和 SRT 弯曲行为的影响。此外，还开发了用于预测 LC 修复钢管弹性弯曲能力的设计公式。来源：复合材料力学仿真Composites FEM