今日更新：International Journal of Solids and Structures 2 篇，Mechanics of Materials 1 篇，Thin-Walled Structures 6 篇International Journal of Solids and StructuresStatic, dynamic and buckling behavior of functionally graded beams with tunable inclusionsZhenbo Xu, Lei Zhang, Rongqiao Xu, Weiqiu Chen, Guannan Wangdoi:10.1016/j.ijsolstr.2023.112620含可调夹杂物的功能梯度梁的静力、动力和屈曲行为The introduction of microstructurally tunable materials endorses functionally graded (FG) beams with distinctly inspiring functionalities and mechanical properties. In order to facilitate the multiscale design of FG beams and evaluations of corresponding mechanical behavior, analytical solutions are developed in the present research on the static, dynamic and buckling responses of FG beams reinforced with graphene platelets, porosity or origami inclusions, etc. To facilitate the analytical derivation as well as numerical extension, this paper establishes a theoretical framework, firstly formulating the principle of virtual work and reciprocal theorem of work for the FG beams, and then deriving and proving the principles of minimum potential and complementary energies, the former of which is used for the establishment of the variational principles for the static bending, free vibration and buckling phenomenon in the present work. Following the proposed variational principles and considering Timoshenko beam theory, the strong-form partial differential governing equations as well as the corresponding boundary conditions can be obtained for static bending, free vibration and buckling responses of FG beams. The Ritz method is finally employed to obtain the explicit expressions of transverse bending and rotation as well as the frequencies and critical loads for FG beams with different boundary conditions. What’s more, it should be noted that the FG of the beams is achieved through tailoring micromechanical parameters, such as volume fraction and distribution of reinforcement, which are usually unevenly distributed. The mechanical responses of FG beams are also predicted through micromechanics approaches, such as Halpin-Tsai expression. Conventional GPL distributions as well as graphene origami (GOri) distributions with negative Poisson's ratios (NPR) are also presented to validate the analytical derivation and solutions. Finally, the proposed solutions are employed to investigate the effect of the microstructural parameters on the effective behavior of FG beams.微结构可调材料的引入支持功能梯度(FG)梁具有明显鼓舞人心的功能和机械性能。为了方便FG梁的多尺度设计和相应的力学性能评估，本文对石墨烯片、孔隙或折纸包体等增强FG梁的静力、动力和屈曲响应进行了分析。为了便于解析推导和数值推广，本文建立了理论框架，首先给出了FG梁的虚功原理和功的互易定理，然后推导并证明了最小势能和互补能原理，本文利用最小势能和互补能原理建立了静态弯曲、自由振动和屈曲现象的变分原理。根据所提出的变分原理，并考虑Timoshenko梁理论，可以得到FG梁的静态弯曲、自由振动和屈曲响应的强形式偏微分控制方程和相应的边界条件。最后利用Ritz法得到了不同边界条件下FG梁的横向弯曲和转动的显式表达式以及频率和临界荷载。此外，需要注意的是，梁的FG是通过定制微力学参数来实现的，例如体积分数和配筋分布，这些参数通常分布不均匀。利用Halpin-Tsai表达式等细观力学方法预测了FG梁的力学响应。本文还提出了传统的GPL分布以及负泊松比(NPR)的石墨烯折纸(GOri)分布来验证解析推导和解。最后，利用所提出的解研究了微结构参数对FG梁有效性能的影响。A single-surface multi-failure strength domain for masonryG. Bertani, L. Patruno, A.M. D’Altri, G. Castellazzi, S. de Mirandadoi:10.1016/j.ijsolstr.2023.112624砌体单面多破坏强度域In this paper, we propose a simple approach to derive a single-surface multi-failure strength domain for the in-plane behaviour of masonry. The approach, that lays the basis for homogeneous continuum model developments relies on micro-mechanical analyses employing a block-based model for masonry in which blocks, modelled as finite strength continuum bodies, interact through zero-thickness interfaces. In order to derive the strength domain, firstly three failure mechanism typologies are identified, namely crushing failure, joint failure and mixed joint-block failure. Then, the limit surface for each mechanism is obtained relying on limit equilibrium considerations, also introducing a novel rational treatment of the mixed mechanism. Accordingly, a multi-surface strength domain is built by intersecting all the limit surfaces. Finally, such multi-surface strength domain is reduced to a single-surface one exploiting the RealSoftMax function, which allows to preserve the multi-failure nature of the approach, i.e. the explicit distinction between all the failure mechanisms. Following the proposed procedure, the resulting strength domain inherits the material parameters characterizing the block-based model. A finite element block-based model and available experimental data are employed to validate the proposed strength domain. The good agreement obtained with reference results confirms the soundness of the approach.在本文中，我们提出了一种简单的方法来推导砌体面内行为的单面多破坏强度域。该方法为均匀连续体模型的发展奠定了基础，它依赖于采用基于块体的砌体模型的微观力学分析，其中块体被建模为有限强度连续体，通过零厚度界面相互作用。为了推导强度域，首先确定了三种破坏机制类型，即破碎破坏、节理破坏和混合节理块破坏。然后，基于极限平衡的考虑，得到了各机构的极限曲面，并引入了一种新的合理处理混合机构的方法。因此，通过将所有极限曲面相交，构建了一个多表面强度域。最后，利用RealSoftMax函数将这种多表面强度域简化为单表面强度域，这允许保留该方法的多故障性质，即所有故障机制之间的明确区分。根据提出的程序，得到的强度域继承了表征基于块的模型的材料参数。利用基于有限元块的模型和现有的实验数据对提出的强度域进行了验证。所得结果与参考结果吻合较好，证实了该方法的合理性。Mechanics of MaterialsActive compliant mechanisms for optimized actuation by LCE-based artificial musclesWenhui Chen, Ruicheng Wang, Ke Liudoi:10.1016/j.mechmat.2023.104879 基于lce的人工肌肉优化驱动的主动柔性机构Compliant mechanisms leverage deformation of materials for precise, lightweight solution to transfer force and motion. By incorporating smart materials, active compliant mechanisms are formed with self-embedded actuation source. Here, we propose lightweight active compliant mechanisms that mimic biological joints, which are capable of transmitting displacements and forces from the linear contraction of artificial muscles into desired magnitudes and directions using a compact structural design. The artificial muscles are braided from liquid crystal elastomer (LCE) fibers and heating threads, competent of generating large force and stroke. Meanwhile, the compliant mechanisms are designed by topology optimization to imitate the functions of biological joints. Combining the braided artificial muscles and optimized compliant mechanisms, these active compliant mechanisms effectively achieve transmission of centralized linear actuation into multiple and various output motions, which is verified by both numerical simulations and experiments. Furthermore, we demonstrate that the active compliant mechanisms can be used for potential surgical procedures such as in-body grasping, cavity dilation, drug delivery, and suturing. The demonstrated biomimetic motions of the active compliant mechanisms hold significant potential for applications in medical devices and soft robots.柔性机构利用材料的精确变形，轻量级的解决方案，以传递力和运动。结合智能材料，形成具有自嵌入驱动源的主动柔性机构。在这里，我们提出了一种轻量级的主动柔性机构，它模仿生物关节，能够通过紧凑的结构设计将人工肌肉线性收缩的位移和力传递到所需的大小和方向。人造肌肉由液晶弹性体(LCE)纤维和加热螺纹编织而成，能够产生大的力和冲程。同时，通过拓扑优化设计柔性机构，模拟生物关节的功能。将编织人工肌肉与优化后的柔性机构相结合，有效地实现了将集中的线性驱动传递到多个不同的输出运动中，并通过数值仿真和实验验证了这一点。此外，我们证明了主动顺应机制可以用于潜在的外科手术，如体内抓取、腔扩张、药物输送和缝合。所展示的主动柔性机构的仿生运动在医疗设备和软机器人中具有重要的应用潜力。Thin-Walled StructuresImprovement of Laser Welded TC4/CFRTP Joint Strength by Combination of Surface Modification of MAO and Laser TexturingHongbo Xia, Baiyun Yang, Jianhui Su, Yifan Liu, Xuan Su, Chong Wang, Xin Qiang, Tao Wu, Caiwang Tandoi:10.1016/j.tws.2023.111409结合 MAO 表面改性和激光纹理处理提高激光焊接 TC4/CFRTP 接头强度Laser texturing and MAO (micro-arc oxidation) hybrid process was adopted to enhance the tensile-shear strength of laser welded CFRTP/TC4 joint. Introduction of porous MAO coating enhanced wetting ability of molten peek from CFRTP and increased surface roughness. Porous structure could also provide a mechanical interlocking effect in CFRTP/TC4 interface and improve the resistance to tensile-shear load. Highest tensile-shear force of 1587 N was obtained when 2.3 μm MAO coating was prepared. Based on this, influence of various laser texturing patterns with different MAO coating thickness on the tensile-shear forces was clarified by combination of experiment and reasonable SVR (Support Vector Regression) model. Maximum predicated surface roughness of 3.075 mm was produced at texturing width of 0.327 mm, texturing depth of 100.54 μm and MAO duration of 1.667 min. Furthermore, highest predicated tensile-shear force of 2995.1 N was achieved at texturing width of 0.331 mm, texturing of depth of 100.6 μm and MAO duration time of 1.718 min.采用激光织构和微弧氧化复合工艺提高激光焊接CFRTP/TC4接头的抗拉剪切强度。多孔结构还可以在CFRTP/TC4界面中提供机械联锁效应，提高CFRTP/TC4的抗拉剪切能力。Semi-analytical dynamic modeling and fluid-structure interaction analysis of L-shaped pipelineWeijiao Chen, Yiming Cao, Xumin Guo, Hui Ma, Bangchun Wen, Bo Wangdoi:10.1016/j.tws.2023.111485l型管道半解析动力学建模及流固耦合分析The traditional semi-analytic modeling is mainly aimed at the straight pipeline with simple boundary conditions. In contrast, the actual aero-engine pipeline needs to consider the effects of complex configuration, boundary and multiple clamps, so proposing an improved semi-analytic method to model an arbitrary fluid-conveying L-shaped pipeline is challenging. Based on the Hamiltonian principle, the differential equations of the L-shaped pipeline are derived. Then, the modal shape functions are determined under the conditions that the elastic support points and the joints of the straight pipeline and the curved pipeline meet the deformation coordination requirements. The proposed semi-analytical model is verified by comparing the natural frequencies and mode shapes obtained from the finite element method using ANSYS and experiment; the error of each order natural frequency is less than 5%. In addition, the model is verified under various working conditions: different center angle and boundary conditions (clamp position and pipeline end constraints). The effects of the fluid velocity and pressure on the natural characteristics of the L-shaped pipeline are also analyzed. The results show that under the critical pressure of 60.51MPa and the critical velocity of 247m/s, the natural frequency decreases with the increase of fluid velocity and pressure. The proposed method can provide theoretical support for efficient and accurate modeling of complex spatial pipeline systems.传统的半解析建模主要针对边界条件简单的直线管道。而实际的航空发动机管道需要考虑复杂的结构、边界和多个卡箍的影响，因此提出一种改进的半解析方法来模拟任意流体输送的l型管道是一项挑战。基于哈密顿原理，推导了l型管道的微分方程。然后，在直线管道和弯曲管道的弹性支撑点和结合部满足变形协调要求的条件下，确定了管道的模态振型函数。利用ANSYS和实验对比了有限元法得到的固有频率和振型，验证了所提半解析模型的正确性;各阶固有频率误差均小于5%。此外，还在各种工况下对模型进行了验证:不同的中心角和边界条件(夹紧位置和管道端约束)。分析了流体流速和压力对l型管道自然特性的影响。结果表明:在临界压力为60.51MPa、临界速度为247m/s时，固有频率随流体速度和压力的增加而减小;该方法可为复杂空间管道系统的高效、准确建模提供理论支持。The imperfection sensitivity of trapezoid origami crash boxesChenhao Teng, Zhibo Song, Caihua Zhou, Peng Hao, Bo Wangdoi:10.1016/j.tws.2023.111486梯形折纸碰撞盒的缺陷灵敏度Diamond and trapezoid origami crash boxes (DOCBs and TOCBs, respectively) have attracted widespread attention due to their favorable mechanical properties. It has been confirmed that geometric imperfections significantly affect the crashworthiness of DOCBs. To explore the impact of imperfections on the crashworthiness of TOCBs, the TOCB profile was globally scanned, and the imperfections were characterized. It was verified that point and surface imperfections were the two main geometric imperfections. Based on the theoretical analysis of the deformation process of the TOCB, the imperfection-sensitivity mechanism was revealed. The experimental and numerical results validated that the point imperfections ratio (Ai/t, defined as the ratio between the point imperfections Ai in TOCB and the box thickness t) at the crease intersections were the main reason for the change in the TOCB deformation process, while the surface imperfections ρ affected the initial peak force. Numerical models with imperfections were established to compare the crashworthiness of the TOCB and DOCB with the same imperfections. When the surface imperfections ρ ≤ 0.12 and point imperfection ratio Ai/t ≤ 3.0, the average crushing force Fave of the TOCB decreased by 4.7% and increased by 3.4%, respectively. Correspondingly, those of the DOCB decreased by 5.7% or 19.4%, respectively; thus, the TOCB had a much lower imperfection sensitivity than the DOCB.菱形和梯形折纸防撞箱（分别为 DOCB 和 TOCB）因其良好的机械性能而受到广泛关注。研究证实，几何缺陷会严重影响 DOCB 的耐撞性。为了探索缺陷对 TOCB 耐撞性的影响，对 TOCB 的轮廓进行了全局扫描，并对缺陷进行了表征。结果表明，点缺陷和面缺陷是两种主要的几何缺陷。基于对 TOCB 变形过程的理论分析，揭示了缺陷敏感机制。实验和数值结果验证了折痕交叉点的点缺陷率（Ai/t，定义为 TOCB 中点缺陷 Ai 与箱体厚度 t 之比）是 TOCB 变形过程变化的主要原因，而表面缺陷 ρ 则影响初始峰值力。为了比较具有相同缺陷的 TOCB 和 DOCB 的耐撞性，建立了具有缺陷的数值模型。当表面缺陷ρ≤0.12和点缺陷率Ai/t≤3.0时，TOCB的平均压溃力Fave分别降低了4.7%和增加了3.4%。相应地，DOCB 的平均压碎力 Fave 分别下降了 5.7% 或 19.4%；因此，TOCB 的缺陷敏感性远低于 DOCB。Quantitative assessment of corrosion-induced wall thinning in L-shaped bends using ultrasonic feature guided wavesXinyi Yuan, Weibin Li, Mingxi Dengdoi:10.1016/j.tws.2023.111493利用超声特征导波定量评价l型弯道腐蚀引起的管壁减薄The utilization of L-shaped bends has become widespread due to their versatility and ease of application in various industrial fields. Nevertheless, the geometric configuration of these bends makes them susceptible to stress concentration in the bending zone, which can lead to wall thinning caused by accelerated corrosion. This poses a profound challenge to the bearing capacity and reliability of L-shaped bends and highlights the urgent necessity for an effective technique to assess corrosion-induced wall thinning in the bending zone. In this study, we propose a nondestructive testing (NDT) method based on ultrasonic feature guided waves (FGWs) for the evaluation of local corrosion-induced wall thinning in L-shaped bends. Propagation characteristics of FGWs in L-shaped bends were analyzed using the semi-analytical finite element (SAFE) method and perfectly matched layer (PML) technique. Time-reversal (TR) method was employed to address the dispersion and multi-modes phenomenon of the selected guided wave modes and improve the signal-to-noise ratio (SNR) of measured FGW signals. Enhanced SNR of two types of FGW modes signals at different frequencies were verified by experimental and numerical results. Obtained results reveal that FGWs can effectively detect corrosion-induced wall thinning inside L-shaped bends, with improving the signal reflection coefficient by TR method.l型弯头由于其通用性和易于应用于各种工业领域而得到广泛的应用。然而，这些弯道的几何结构使它们容易受到弯曲区应力集中的影响，这可能导致腐蚀加速导致管壁变薄。这对l型弯道的承载能力和可靠性提出了深刻的挑战，并强调了一种有效的技术来评估弯曲区腐蚀引起的壁面减薄的紧迫性。在这项研究中，我们提出了一种基于超声特征导波(FGWs)的无损检测(NDT)方法来评估l型弯道局部腐蚀引起的壁厚变薄。采用半解析有限元(SAFE)方法和完全匹配层(PML)技术对FGWs在l型弯道中的传播特性进行了分析。采用时间反转(TR)方法解决了所选导波模的色散和多模现象，提高了被测FGW信号的信噪比。实验和数值结果验证了两种FGW模式信号在不同频率下的信噪比提高。结果表明，FGWs可以有效检测l型弯道内腐蚀引起的壁厚变薄，并通过TR方法提高了信号反射系数。Response and damage mechanism of carbon/aramid intra-ply hybrid weft-knitted reinforced composites under low-velocity impactTingting Dong, Ziyu Zhao, Baoping Zheng, Chaoyu Chen, Pibo Madoi:10.1016/j.tws.2023.111495低速冲击下碳/芳纶复合纬编增强复合材料的响应与损伤机理Carbon and aramid fiber hybridization is an effective method to improve the impact toughness of composites, thus this paper attempts to develop carbon/aramid hybrid weft-knitted reinforced composites to improve the impact resistance of carbon fiber composites. Three hybrid and two non-hybrid weft-knitted reinforced composites employing carbon and aramid bundles were prepared. Low-velocity impact tests at different impact energies were performed, and the impacted samples were analyzed for visual and internal damages utilizing a three-dimensional optical microscope, ultrasonic C-scan, and micro-CT to explore the damage mechanisms. The results demonstrate that the knitted stitches and loop configuration affect the peak load, deflection, and damage crack initiation and expansion of the composites. The alternating configurations of carbon and aramid fiber in the in-plane and thickness directions incorporate the advantages of the high strength of carbon fibers and the toughness of aramid, exhibiting good impact mechanical properties and damage tolerance. The tight loop laminated structure had excellent impact resistance, with prominent peak loads and tiny damage volumes, but it encountered internal delamination and loop breakages.碳纤维与芳纶纤维杂化是提高复合材料冲击韧性的有效方法，因此本文试图开发碳/芳纶杂化纬编增强复合材料，以提高碳纤维复合材料的抗冲击性能。制备了三种杂化和两种非杂化纬编增强复合材料。进行了不同冲击能下的低速冲击试验，利用三维光学显微镜、超声c扫描和微ct对冲击试样的视觉损伤和内部损伤进行了分析，探讨了损伤机理。结果表明，针脚和环的形态对复合材料的峰值载荷、挠度、损伤裂纹的萌生和扩展都有影响。碳纤维与芳纶纤维在面内方向和厚度方向的交替配置，结合了碳纤维的高强度和芳纶的韧性的优点，具有良好的冲击力学性能和损伤容限。紧环层合结构具有优异的抗冲击性能，峰值荷载突出，损伤体积小，但存在内部分层和环断裂问题。Energy absorption and topology optimization of self-similar inspired multi-cell square tubesJiapeng Sun, Yulong He, Xiujuan Zhang, Xin Li, Minghui Lu, Yanfeng Chendoi:10.1016/j.tws.2023.111491自相似启发多胞方管的能量吸收与拓扑优化Due to their low cost and lightweight properties, multi-cell square tubes have been widely used in impact protection as energy absorbers. In this study, two kinds of multi-cell square tubes were constructed according to the local self-similar and global self-similar layout strategies. The experiments and numerical simulations were conducted to investigate their quasi-static compression deformation and energy absorption. The results demonstrated that self-similar layout strategies can significantly enhance the crashworthiness of multi-cell square tubes, and the global self-similar layout appears to be more effective at energy absorption. A simplified theoretical model for the mean crushing force (MCF) was developed for its constituent elements of the proposed square tubes. Furthermore, the COPRAS method and the non-dominated sorting genetic algorithm II (NSGA-II) were employed for optimal structure selection and multi-objective optimization. The results showed that the 2nd-order global self-similar multi-cell square tube (MSTG1-2) had prominent crashworthiness compared with some typical self-similar square tubes. The current optimization and topology design strategies can be used in other polygonal multi-cell tubes, which provides an effective guide for enhancing the crashworthiness of these multi-cell tubes.多孔方管具有成本低、重量轻的特点，因此作为能量吸收装置被广泛应用于冲击防护领域。本研究根据局部自相似和全局自相似布局策略构建了两种多孔方管。实验和数值模拟研究了它们的准静态压缩变形和能量吸收。结果表明，自相似布局策略可显著提高多孔方管的耐撞性，而全局自相似布局似乎在能量吸收方面更为有效。针对拟议方管的组成元素，建立了一个简化的平均压溃力（MCF）理论模型。此外，还采用 COPRAS 方法和非支配排序遗传算法 II（NSGA-II）进行了最佳结构选择和多目标优化。结果表明，与一些典型的自相似方管相比，二阶全局自相似多单元方管（MSTG1-2）具有突出的耐撞性。目前的优化和拓扑设计策略可用于其他多边形多孔管，为提高这些多孔管的耐撞性提供了有效指导。来源：复合材料力学仿真Composites FEM
