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【新文速递】2024年1月22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 1 篇,Mechanics of Materials 1 篇,International Journal of Plasticity 1 篇,Thin-Walled Structures 2 篇

International Journal of Solids and Structures

M-Voronoi and other random open and closed-cell elasto-plastic cellular materials: Geometry generation and numerical study at small and large strains

Z. Hooshmand-Ahoor, Haoming Luo, K. Danas

doi:10.1016/j.ijsolstr.2024.112680

M-Voronoi和其他随机开闭孔弹塑性细胞材料:小应变和大应变的几何生成和数值研究

The present study deals with a numerical design strategy of a novel class of three-dimensional random Voronoi-type geometries, called M-Voronoi. These materials comprise random, non-quadratic convex void shapes and non-uniform intervoid ligament thicknesses, and can span high-to-low relative densities. The starting point for their generation is a random adsorption algorithm (RSA) construction with spherical voids embedded in an incompressible, nonlinear elastic matrix phase. The initial RSA geometry is subjected to large elastic volume changes by prescribing Dirichlet boundary conditions. Due to the incompressibility of the matrix phase, the externally imposed volume changes lead to significant void growth. The numerical growth process may be stopped at any desired porosity. The proposed M-Voronoi process is general and allows the formation of isotropic (or anisotropic) designs. As a byproduct of the developed approach, we also present a novel remeshing technique allowing to read arbitrary geometries of one or multiple phases. The elasto-plastic properties of the M-Voronoi porous materials are numerically investigated at small strains as well as large compressive and shear loads. Their response is assessed by comparison with other well-known random and periodic porous geometries such as polydisperse porous materials with spherical voids (RSA), classical TPMS Gyroid geometries and random Spinodoid topologies. The results show that M-Voronoi and RSA (with spherical voids) geometries exhibit the stiffest elastic and highest flow stress response compared to the other two geometries. This study shows unambiguously that randomness may or may not lead to enhanced mechanical response such as higher stiffness or flow stress.

本研究涉及一种新型三维随机voronoi型几何图形的数值设计策略,称为M-Voronoi。这些材料包括随机的,非二次凸空隙形状和非均匀空隙间韧带厚度,并且可以跨越高到低的相对密度。其生成的起点是随机吸附算法(RSA)的构造,其中球形空隙嵌入在不可压缩的非线性弹性矩阵相中。通过规定狄利克雷边界条件,使初始RSA几何结构受到较大弹性体积变化的影响。由于基体相的不可压缩性,外部施加的体积变化导致显著的空隙生长。数值生长过程可以在任何期望的孔隙率处停止。提出的M-Voronoi过程是通用的,允许形成各向同性(或各向异性)设计。作为开发方法的副产品,我们还提出了一种新的重网格技术,允许读取一个或多个相位的任意几何形状。对M-Voronoi多孔材料在小应变和大压缩、剪切载荷下的弹塑性特性进行了数值研究。通过与其他已知的随机和周期性多孔几何结构(如具有球形孔洞的多分散多孔材料(RSA),经典TPMS Gyroid几何结构和随机Spinodoid拓扑结构)进行比较,评估了它们的响应。结果表明,与其他两种几何形状相比,M-Voronoi和RSA(带球面孔洞)几何形状具有最硬的弹性和最大的流动应力响应。这项研究明确地表明,随机性可能会也可能不会导致机械响应的增强,如更高的刚度或流动应力。


Journal of the Mechanics and Physics of Solids

On the role of plastic relaxation in stress assisted grain boundary oxidation

Y. Piao, D.S. Balint

doi:10.1016/j.jmps.2024.105552

应力辅助晶界氧化中塑性松弛的作用

The influence of plasticity on the high-temperature stress-assisted grain boundary oxidation of nickel-based superalloys used in applications such as turbine rotor discs is investigated using the method of discrete dislocation plasticity (DDP). The misfit stress fields of nib-shaped intrusions are captured by a continuous distribution of edge dislocations whose extra half planes represent the volumetric misfit of the oxide, which is implemented in a planar formulation of DDP by invoking the linear superposition principle. DDP simulations show that stresses generated by an intrusion several microns or more in size are large enough to generate dislocation pileups with associated stresses at the intrusion interface on the order of 1 GPa, which in turn lead to localised growth and morphology change of the intrusion by stress-assisted diffusion. This morphology change relaxes the compression stress inside the intrusion near the base, and therefore increases the fracture resistances of the intrusion. The effects of applied loading and background plasticity on the growth rate of the intrusion in defect-free and prestrained samples are predicted. It is found that applied tensile stress generally increases grain boundary oxidation, while in prestrained samples the enhancement of the intrusion growth rate by the applied load is insignificant due to dislocation pile-ups ahead of the oxidation process.

采用离散位错塑性(DDP)方法研究了塑性对涡轮转子盘等镍基高温合金高温应力辅助晶界氧化的影响。尖状侵入体的错配应力场由边缘位错的连续分布捕获,其额外的半平面表示氧化物的体积错配,这是通过调用线性叠加原理在DDP的平面公式中实现的。DDP模拟结果表明,几微米或更大尺寸的侵入所产生的应力足以在侵入界面产生1 GPa量级的位错堆积和相关应力,从而导致应力辅助扩散侵入的局部生长和形态变化。这种形态变化使侵入体内部靠近基部的压应力松弛,从而提高了侵入体的抗破裂能力。预测了外加载荷和本底塑性对无缺陷和预应变试样中侵入体生长速率的影响。结果表明,施加拉伸应力通常会增加晶界氧化,而在预应变样品中,由于在氧化过程之前存在位错堆积,施加载荷对侵入生长速率的提高不显著。


Mechanics of Materials

Enhanced mechanical and thermal properties in 3D printed Al2O3 lattice/ epoxy interpenetrating phase composites

Yida Zhao, Xiu Yun Yap, Pengcheng Ye, Ian P. Seetoh, Huilu Guo, Changquan Lai, Du Zehui, Chee Lip Gan

doi:10.1016/j.mechmat.2024.104930

3D打印Al2O3晶格/环氧互渗相复合材料的力学和热性能增强

Interpenetrating phase composites (IPCs) with 3D printed alumina microlattices infiltrated with epoxy have been fabricated. Mechanical analysis shows that the IPCs under quasi-static compression generally exhibit fracture behaviour similar to that of their ceramic-lattice constituent but in a gradual manner. The IPCs with Simple Cubic lattices initiate the fractures at the struts in the outer lattice planes, while IPCs with Octet Truss and Kelvin Cell lattices tend to fracture at their (110) or (111) planes. The compressive strength and energy absorption of IPCs follow the order of Simple Cubic > Kelvin Cells > Octet Truss when the ceramic volume fraction is 0.3. The IPCs display compressive strengths up to 120% higher and energy absorption 100% greater than the iso-strain combined properties of the lattice and epoxy up to the lattice's point of failure. The factors governing the fracture behaviour and the strengthening and energy absorption mechanisms were thoroughly discussed. Furthermore, the IPCs show much better retention of mechanical strength and dimensional stability at elevated temperatures compared with many commonly used particle or fiber-reinforced epoxy matrix composites.

制备了3D打印氧化铝微晶格的互穿相复合材料(IPCs)。力学分析表明,IPCs在准静态压缩下的断裂行为与它们的陶瓷晶格成分相似,但断裂是渐进的。具有简单立方晶格的IPCs首先在外晶格面的支撑处断裂,而具有八元桁架和开尔文晶格的IPCs则倾向于在(110)或(111)面断裂。当陶瓷体积分数为0.3时,IPCs的抗压强度和吸能大小依次为:Simple Cubic > Kelvin Cells > Octet Truss。在晶格失效点之前,IPCs的抗压强度比晶格和环氧树脂的等应变组合性能高出120%,能量吸收高出100%。对影响断裂行为的因素、强化和吸能机理进行了深入探讨。此外,与许多常用的颗粒或纤维增强环氧基复合材料相比,IPCs在高温下具有更好的机械强度和尺寸稳定性。


International Journal of Plasticity

Tensile properties and microstructural evolution of 17-4 PH stainless steel fabricated by laser hybrid additive manufacturing technology

Nan Li, Qiang Wang, Michael Bermingham, Wenjuan Niu, Peng Han, Nan Guo, Shenao Li

doi:10.1016/j.ijplas.2024.103885

激光复合增材制造技术制备17-4 PH不锈钢拉伸性能及显微组织演变

Wire-based laser directed energy deposition (LDED) technology is an attractive and efficient additive manufacturing technology, which shows great potential in the process of manufacturing high-value engineering components. However, the thermal effect will lead to a large amount of residual tensile stress in the components, and the large crystal structures after solidification seriously affects the tensile performance. The pursuit of high mechanical properties in additive manufacturing components have prompted researchers to seek new strengthening process to produce high-strength components. Therefore, in this paper, laser shock peening (LSP) composite wire-based LDED were used for the additive manufacturing of 17-4 PH stainless steel under the specified experimental conditions, and the effects of LSP on microstructure evolution, microhardness, and tensile properties of wire-based LDED components were systematically studied. Results showed that uniform grains with an average size of 2.31 μm were generated on the top surface of specimen due to the ultra-high plastic strain induced by LSP shock wave. The size of hierarchical martensitic units shows varying degrees of reduction after LSP treatment, which is shown by the width decrease of packet, block and lath. Dynamic recrystallization caused by rearrangement and annihilation of high-density dislocations promoted the grain refinement. Meanwhile, the residual stress was completely converted from tensile state into compressive state with a maximum value of 425 MPa, and the microhardness was also enhanced to a peak value of 432 HV. In addition, we observed that the high-density dislocation environment created by LSP treatment promoted the further precipitation, and the aggregation phenomenon of precipitates was observed in the dense dislocation area. Furthermore, the tensile strength and elongation of LSP treated specimen were improved significantly, which was attributed to the combined effects of grain refinement, introduction of dislocation structures, precipitation strengthening and gradient residual compressive stress. In summary, laser hybrid additive manufacturing technology provides a new idea and method for the production of high-performance precipitation hardening stainless steel components.

线基激光定向能沉积(LDED)技术是一种极具吸引力的高效增材制造技术,在制造高价值工程部件的过程中显示出巨大的潜力。但热效应会导致构件中存在大量残余拉伸应力,凝固后的大晶体结构严重影响拉伸性能。增材制造部件对高机械性能的追求促使研究人员寻求新的强化工艺来生产高强度部件。因此,本文在规定的实验条件下,采用激光冲击强化(LSP)复合丝基LDED对17-4 PH不锈钢进行增材制造,系统研究了LSP对丝基LDED构件的微观组织演变、显微硬度和拉伸性能的影响。结果表明:由于LSP激波引起的超高塑性应变,试样上表面形成了平均尺寸为2.31 μm的均匀晶粒;LSP处理后,分层马氏体单元的大小有不同程度的减小,表现为分组、块和条的宽度减小。高密度位错的重排和湮灭引起的动态再结晶促进了晶粒的细化。同时,残余应力完全由拉伸状态转化为压缩状态,最大值为425 MPa,显微硬度也有所提高,峰值为432 HV。此外,我们观察到LSP处理造成的高密度位错环境促进了进一步的析出,并且在密集位错区域观察到析出物的聚集现象。此外,LSP处理试样的抗拉强度和伸长率显著提高,这是晶粒细化、位错组织引入、沉淀强化和梯度残余压应力共同作用的结果。综上所述,激光混合增材制造技术为生产高性能沉淀硬化不锈钢构件提供了新的思路和方法。


Thin-Walled Structures

Axial compressive behavior of pre-damaged concrete-filled square steel tube columns repaired with section circularization and CFRP composites

Kang Zhao, Zhongjun Hu, Boxin Wang, Weicheng Liao, Yan Xu

doi:10.1016/j.tws.2024.111606

预损伤方钢管混凝土柱经截面圆化和CFRP复合材料修复后的轴压性能

This study focused on repair treatments for the effective reuse of damaged concrete-filled square steel tube (CFSST) columns with carbon fiber-reinforced polymer (CFRP) composites. Forty specimens were designed to investigate the effects of pre-damage levels, section circularization, and the number of CFRP layers on the compressive behavior of the repaired CFSST columns. Test results indicated that the method of section circularization and CFRP wrapping effectively restored the degraded initial axial stiffness of the pre-damaged CFSST columns and increased the ultimate bearing capacity of the pre-damaged CFSST columns by 49-180% compared to their undamaged condition. Considering the influence of the pre-damage level and the contribution of section circularization, the ultimate bearing capacity calculation model was suggested for predicting the compressive behavior of the repaired CFSST columns. The experimental results and collected test data have well verified the accuracy and applicability of the calculation model.

本文主要研究了用碳纤维增强聚合物(CFRP)复合材料修复受损方钢管混凝土(CFSST)柱的有效再利用。设计了40个试件,研究了预损伤水平、截面圆度和CFRP层数对修复后CFSST柱抗压性能的影响。试验结果表明,截面圆化和CFRP包覆能有效恢复预损伤CFSST柱初始轴向刚度的退化,使预损伤CFSST柱的极限承载力比未损伤状态提高49 ~ 180%。考虑预损伤程度的影响和截面圆弧化的贡献,提出了预测修复后CFSST柱抗压性能的极限承载力计算模型。实验结果和收集的测试数据很好地验证了计算模型的准确性和适用性。


Behaviour and design of CFS stud walls under both sides fire exposure

Son Tung Vy, Anthony Ariyanayagam, Mahen Mahendran

doi:10.1016/j.tws.2024.111619

两侧受火作用下CFS钉墙的性能与设计

Cold-formed steel (CFS) stud wall systems fabricated using CFS channel studs, tracks and fire-rated sheathing materials are increasingly used in Australia, New Zealand, Europe and North America. Although a large number of research studies has focused on the behaviour of load-bearing CFS stud wall systems at ambient temperature and in fire, the knowledge related to the behaviour as well as suitable design methods of these wall systems exposed to fire on both sides is very limited. Recently, the safety of CFS stud walls under both sides fire exposure has become a concern to fire engineers. In this study, detailed investigations of load-bearing CFS stud walls under both sides fire exposure were undertaken using thermal and sequentially coupled structural finite element (FE) models. These models were validated against the standard fire test results of CFS stud walls under one side fire exposure available in the literature. Using the thermal and sequentially coupled structural FE analysis results, the effects of cavity insulation, thickness of gypsum plasterboards and both sides fire exposure on the behaviour and fire resistance level (FRL) of CFS stud walls were investigated and the results were compared with those for CFS stud walls under one side fire exposure. These results highlighted the major differences between the CFS stud walls under one side and both sides fire exposures in terms of their thermal and structural behaviour and FRL. Finally, appropriate design guidelines using the direct strength method in the CFS design standards are proposed.

在澳大利亚、新西兰、欧洲和北美,使用冷弯型钢(CFS)螺柱、轨道和防火护套材料制成的冷弯型钢(CFS)螺柱墙系统的应用越来越广泛。虽然大量的研究都集中在承重CFS螺柱墙系统在环境温度和火灾下的性能,但有关这些墙系统在两侧火灾下的性能以及合适的设计方法的知识非常有限。近年来,混凝土柱墙两侧受火情况下的安全问题一直是消防工程师关注的问题。在这项研究中,采用热耦合结构有限元(FE)模型对两侧火灾暴露下的承重CFS钉墙进行了详细的研究。这些模型与文献中可用的单侧火灾暴露下CFS螺柱墙的标准防火测试结果进行了验证。利用热学和序列耦合结构有限元分析结果,研究了空腔保温、石膏板厚度和两侧受火对CFS柱墙性能和耐火水平的影响,并与单侧受火下CFS柱墙的结果进行了比较。这些结果突出了在一侧和两侧火灾暴露下的CFS钉墙在其热学和结构行为以及FRL方面的主要差异。最后,提出了适用于CFS设计标准中直接强度法的设计准则。



来源:复合材料力学仿真Composites FEM
MeshingACTMechanicalAdditiveSystem断裂复合材料非线性通用增材消防材料试验
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首次发布时间:2024-11-05
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【新文速递】2024年1月5日固体力学SCI期刊最新文章

今日更新:International Journal of Solids and Structures 2 篇,Journal of the Mechanics and Physics of Solids 1 篇,Mechanics of Materials 1 篇,Thin-Walled Structures 2 篇International Journal of Solids and StructuresAnalytical 3D model for coupled magneto-mechanical behaviors of ferromagnetic shape memory alloyQi Peng, Jiahui Chen, Ke Ni, Ze Liu, Long-Qing Chen, Zhengzhi Wangdoi:10.1016/j.ijsolstr.2023.112619铁磁形状记忆合金耦合磁力学行为的三维分析模型Ferromagnetic shape memory alloys (FSMA), a type of smart material, are promising for engineering applications due to their large, high-frequency, and reversible magnetic-field-induced-strain (MFIS). However, the magneto-mechanical behaviors of FSMA are still not well understood due to the intrinsically coupled and cross-scale magneto-mechanical responses, limiting the design and optimization of FSMA-based devices such as sensors and actuators. In this work, a fully-analytical 3D model containing only basic material parameters and incorporating all key mechanisms for the magneto-mechanical performances of FSMA is developed based on a new magneto-mechano-decoupled energy minimization approach. It is shown that the coupled magneto-mechanical responses of FSMA-based sensors (cyclic stress with constant magnetic field) and actuators (cyclic magnetic field with constant stress) predicted by the model are in excellent agreement with existing experimental measurements. Based on these analytical predictions, the optimal ranges for the constant field and demagnetization factor are determined to achieve simultaneous complete strain recovery and considerable magnetization change as required by the FSMA-based sensors. In addition, the dependences of switching and saturating fields of MFIS on the constant stress and demagnetization factor are quantified for the FSMA-based actuators. Finally, a phase diagram is constructed to quantitatively determine the critical magnetic fields and stresses for predicting the strain induction and recovery under various loading conditions. The analytical model provides a simple, reliable, and versatile tool to reveal the comprehensive mechanisms for the coupled magneto-mechanical behaviors of FSMA and to guide the design of FSMA-based sensors and actuators with customized and on-demand performances.铁磁形状记忆合金(FSMA)是一种智能材料,由于其具有大尺寸、高频率和可逆磁场诱导应变(MFIS)的特点,因此在工程应用中大有可为。然而,由于其内在耦合和跨尺度磁力学响应,人们对 FSMA 的磁力学行为仍不甚了解,从而限制了基于 FSMA 的传感器和致动器等设备的设计和优化。在这项工作中,基于一种新的磁-机-解耦能量最小化方法,开发了一种仅包含基本材料参数的全分析三维模型,该模型包含了 FSMA 磁-机械性能的所有关键机制。结果表明,该模型预测的基于 FSMA 的传感器(恒定磁场的循环应力)和致动器(恒定应力的循环磁场)的耦合磁力学响应与现有的实验测量结果非常吻合。根据这些分析预测,确定了恒定磁场和退磁因子的最佳范围,以实现基于 FSMA 的传感器所需的完全应变恢复和显著磁化变化。此外,还量化了基于 FSMA 的致动器的 MFIS 开关场和饱和场对恒定应力和退磁因子的依赖关系。最后,构建了一个相图,以定量确定临界磁场和应力,从而预测各种加载条件下的应变感应和恢复。该分析模型提供了一种简单、可靠和通用的工具,可用于揭示 FSMA 磁力学耦合行为的综合机制,并指导设计具有定制和按需性能的基于 FSMA 的传感器和致动器。Nonlocal interfaces accounting for progressive damage within continuum-kinematics-inspired peridynamicsMarie Laurien, Ali Javili, Paul Steinmanndoi:10.1016/j.ijsolstr.2023.112641非局部界面在连续运动学启发的周动力学中解释渐进损伤In this work, we present a modeling approach to nonlocal material interfaces in the framework of continuum-kinematics-inspired peridynamics. The nonlocal model accounts for progressive damage within a finite-thickness interface, as opposed to the more common practice of abrupt bond breakage across a zero-thickness interface. Our approach is based on an overlap of the constituents within the interface. Interfacial bonds between initially overlapping partner points are governed by a constitutive law reminiscent of a traction-separation-law. The governing equations for continuum-kinematics-inspired peridynamics in the presence of an interface are derived using a rate-variational principle. The damage formulation is established using the classical concept of internal variables. Following the notion of a standard dissipative material, thermodynamic consistency of the constitutive laws and the evolution of the internal variables is ensured. The latter results in a straightforward evaluation of a damage function. We give details about the computational implementation comprising a peridynamic discretization and a Newton–Raphson scheme. A sound approach to approximate the interface normal during deformation is presented, which allows to penalize material penetration across the interface. The proposed model is explored in a series of numerical examples, i.e., classical peeling and shearing tests, for a variety of damage functions. A key feature of our interface model are the nonlocal characteristics that are assumed to play a role especially at small scales. We, first, observe that an increasing thickness of the nonlocal interface leads to stronger interfacial bonding and less damage. Second, an increase in horizon size results in stiffer material behavior. When studying the wrinkling and delamination behavior of a compressed bilayer, it is found that an increase in interface stiffness leads to a smaller wrinkling wavelength. Moreover, delamination due to progressive damage of interfacial bonds in the post-wrinkling regime is observed, which, to the best of our knowledge, has not been studied in a nonlocal model before.在这项工作中,我们在连续介质动力学启发的周动力学框架内提出了一种非局部材料界面建模方法。非局部模型考虑了有限厚度界面内的渐进式损坏,而不是更常见的零厚度界面上的突然断裂。我们的方法基于界面内成分的重叠。最初重叠的伙伴点之间的界面键受类似于牵引分离定律的构成定律支配。在存在界面的情况下,连续介质启发的周动力学控制方程是利用速率变异原理推导出来的。利用经典的内部变量概念建立了损伤公式。根据标准耗散材料的概念,确保了构成定律和内部变量演变的热力学一致性。后者可直接评估损伤函数。我们详细介绍了由周动态离散化和牛顿-拉斐森方案组成的计算实施。我们还介绍了在变形过程中近似界面法线的合理方法,该方法允许对跨界面的材料渗透进行惩罚。在一系列数值示例中,即经典的剥离和剪切试验中,针对各种损伤函数,对所提出的模型进行了探讨。我们的界面模型的一个主要特点是假定非局部特征在小尺度上发挥作用。首先,我们观察到非局部界面厚度的增加会导致更强的界面结合力和更小的损伤。其次,地平线尺寸的增加会导致材料更坚硬。在研究压缩双分子层的起皱和分层行为时,我们发现界面刚度的增加会导致起皱波长变小。此外,我们还观察到了由于界面键在起皱后逐渐损坏而导致的分层现象,据我们所知,这种现象以前从未在非局部模型中进行过研究。Journal of the Mechanics and Physics of SolidsMorphomechanics of growing curled petals and leavesTing Wang, Chenbo Fu, Michel Potier-Ferry, Fan Xudoi:10.1016/j.jmps.2023.105534 卷曲花瓣和叶片生长的形态力学Petals and leaves are usually curled and exhibit intriguing morphology evolution upon growth, which contributes to their important biological functions. To understand the underlying morphoelastic mechanism and to determine the crucial factors that govern the growth-induced instability patterning in curved petals and leaves, we develop an active thin shell model that can describe variable curvatures and spontaneous growth, within the framework of general differential geometry based on curvilinear coordinates and hyperelastic deformation theory. Analytical solutions of distinguished growing shapes such as saddle surface and cylindrical mode are then derived. We reveal distinct morphological evolutions of doubly curved leaves/petals with different curvatures κx (along the main vein) and κy (perpendicular to the main vein) upon differential growth. Compared to the flat (zero curvature) configuration, leaves/petals with longitudinal curvature κx experiences a global bending deformation. With the increase of growth strain, the leaf/petal undergoes a coupling behavior of edge wrinkling and global bending deformation, associated with a pitchfork bifurcation. Conversely, the transverse curvature κy does not lead to significant bending behavior, but results in delayed critical buckling threshold and reduced wrinkling amplitude. Physical insights into curvature effects on morphology evolutions are further provided by the analysis of nonlinear competition between bending and membrane energies. Moreover, we explore the effect of vein constraint on pattern formation, showing that different from edge wrinkling observed in leaves with strong vein constraint, the ones with weak vein constraint are prone to grow into a saddle shape, which is consistent with analytical solutions. The results uncover the intricate interplay between configurational curvature and vein confinement on plant morphogenesis, providing fundamental insights into a variety of growing shapes of curled petals and leaves.花瓣和叶片通常是卷曲的,在生长过程中会出现奇妙的形态演变,这有助于它们发挥重要的生物功能。为了了解其潜在的形态弹性机制,并确定支配弯曲花瓣和叶片生长诱导不稳定形态的关键因素,我们在基于曲线坐标和超弹性变形理论的一般微分几何框架内,建立了一个能描述可变曲率和自发生长的主动薄壳模型。然后推导出不同生长形状(如鞍面和圆柱模式)的解析解。我们揭示了双曲线叶片/花瓣在微分生长过程中不同曲率κx(沿主脉)和κy(垂直于主脉)的独特形态演变。与扁平(零曲率)结构相比,纵向曲率为 κx 的叶片/花瓣会出现整体弯曲变形。随着生长应变的增加,叶片/花瓣会出现边缘起皱和整体弯曲变形的耦合行为,这与干叉形分叉有关。相反,横向曲率 κy 不会导致明显的弯曲行为,但会导致临界屈曲阈值延迟和皱缩幅度减小。通过分析弯曲和膜能之间的非线性竞争,我们进一步了解了曲率对形态演变的物理影响。此外,我们还探讨了叶脉约束对形态形成的影响,结果表明,与在强叶脉约束下观察到的边缘起皱不同,弱叶脉约束下的叶片容易长成马鞍形,这与分析解一致。这些结果揭示了构型曲率和叶脉约束对植物形态发生的复杂相互作用,为研究各种卷曲花瓣和叶片的生长形状提供了基本见解。Mechanics of MaterialsA nonlinear continuum framework for constitutive modeling of active polymer gelsPriyanka Nemani, Ravi Sastri Ayyagari, Pratyush Dayaldoi:10.1016/j.mechmat.2023.104908活性聚合物凝胶构成建模的非线性连续体框架Chemo-mechanical transduction is one of the key mechanisms that has formed the basis for designing bio-inspired self-driven synthetic systems from soft materials. Polymer hydrogels that use Belousov–Zhabotinsky (BZ) reaction are a unique class of dynamical reaction–diffusion (RD) systems that can continuously transduce internal chemical energy, from the reaction, to produce sustained mechanical work. In particular, BZ gels represent a complex nonlinear chemo-mechanical system, wherein, the autocatalytic oscillatory BZ reaction drives the rhythmic mechanical deformations through polymer-solvent interdiffusion. The objective of our work is to develop a standardized finite element (FE) framework for chemically driven active hydrogels that captures nonlinear elastic deformations with limited chain extensibility. The distinguishing feature of our approach is that, unlike other approaches, it combines reaction kinetics, solvent transport, elastodynamics of the polymeric network, and polymer-solvent friction under a unified FE framework. Moreover, we adapt our approach to a specific case of BZ gels and capture its swelling-deswelling characteristics. We first implement our FE framework in MATLAB that subsequently, forms the basis for constructing a three-dimensional user element subroutine (3D-UEL) in ABAQUS. Ultimately, through our simulations, we are able to capture all the essential features of BZ gels that includes chemically driven mechanical deformations. In addition, we also demonstrate that our 3D-UEL efficiently captures the chemo-mechanical response of “stent-shaped” BZ gels–a non-standard 3D geometry. In essence, our FE approach not only allows us to simulate BZ gels but also provides a template for other active, dynamical, RD-based systems, driven by chemo-mechanical transduction, irrespective of internal or external mechanisms.化学机械传导是一种关键机制,是利用软材料设计生物启发自驱动合成系统的基础。使用别洛乌索夫-扎博金斯基(Belousov-Zhabotinsky,BZ)反应的聚合物水凝胶是一类独特的动态反应-扩散(RD)系统,可持续地将反应产生的内部化学能转化为持续的机械功。特别是,BZ 凝胶代表了一种复杂的非线性化学机械系统,其中,自催化振荡 BZ 反应通过聚合物-溶剂相互扩散驱动有节奏的机械变形。我们的工作目标是为化学驱动的活性水凝胶开发一个标准化的有限元(FE)框架,以捕捉具有有限链伸展性的非线性弹性变形。与其他方法不同的是,我们的方法在统一的有限元框架下结合了反应动力学、溶剂传输、聚合物网络弹性动力学以及聚合物-溶剂摩擦。此外,我们还根据 BZ 凝胶的具体情况调整了我们的方法,并捕捉到了其溶胀-消肿特性。我们首先在 MATLAB 中实现了我们的 FE 框架,并在此基础上在 ABAQUS 中构建了三维用户元素子程序(3D-UEL)。最终,通过模拟,我们能够捕捉到 BZ 凝胶的所有基本特征,包括化学驱动的机械变形。此外,我们还证明了我们的 3D-UEL 能够有效捕捉 "支架状 "BZ 凝胶(非标准三维几何形状)的化学机械响应。从本质上讲,我们的 FE 方法不仅能模拟 BZ 凝胶,还能为其他基于 RD 的活性、动态系统提供模板,这些系统由化学机械传导驱动,不受内部或外部机制的影响。Thin-Walled StructuresA Comprehensive Formulation for Determining Static Characteristics of Mosaic Multi-Stable Composite Laminates under Large Deformation and Large RotationM.S. Taki, R. Tikani, S. Ziaei-Raddoi:10.1016/j.tws.2023.111545确定大变形和大旋转下镶嵌式多稳复合层压板静态特性的综合公式Multi-stable composite laminates are composite materials that exhibit multi-stable states, making them highly suitable for use in morphing structures. These materials are capable of maintaining each stable state without expending any energy. As a result, they are used extensively in numerous applications and garnered the interest of scholars and aerospace organizations. In the context of practical applications, such as morphing structures, it is insufficient for designers to rely solely on common bi-stable composite laminates that exhibit large deformations and medium rotations to achieve their desired objectives. Consequently, based on the objectives of the design, there are two potential resolutions to address this limitation. A designer may utilize mosaic multi-stable composite laminates to achieve a morphing structure that exhibits high flexibility, significant deformation, and substantial rotation. The utilization of a series connection between a bi-stable composite laminate and a symmetric composite laminate results in the formation of a mosaic bi-stable composite laminate with variable stiffness. Furthermore, the amalgamation of two asymmetric composite laminates with inverted orientations engenders a mosaic tri-stable composite laminate. The present research examines the static characteristics of mosaic bi-stable and tri-stable composite laminates. It also seeks to analyze the factors affecting the behavior of these types of laminates. A geometrically exact model was formulated for this objective. Apart from the geometrically exact model, a widely used and uncomplicated model relying on the conventional Classical Laminated-Plate Theory (CLPT) and Von-Karman nonlinear strains was employed. The proposed models were validated through finite element simulations. The system's static equations were derived using the virtual work principle and the Rayleigh-Ritz method. The present study examines and explores quasi-static snap-through behavior between stable states through the application of concentrated forces. The findings indicate a high level of concurrence between the outcomes derived from the geometrically exact model and the finite element analyses, particularly in composite laminates exhibiting significant deformations and rotations.多稳定复合层压板是一种呈现多稳定状态的复合材料,因此非常适合用于变形结构。这些材料能够在不消耗任何能量的情况下保持每一种稳定状态。因此,它们被广泛应用于众多领域,并引起了学者和航空航天组织的兴趣。在变形结构等实际应用中,设计人员仅依靠表现出大变形和中等旋转的普通双稳态复合材料层压板来实现预期目标是不够的。因此,根据设计目标,有两种可能的解决方案来解决这一限制。设计者可以利用镶嵌式多稳定复合材料层压板来实现具有高柔性、大变形和大幅度旋转的变形结构。利用双稳态复合材料层压板与对称复合材料层压板之间的串联,可形成刚度可变的镶嵌式双稳态复合材料层压板。此外,将两个方向相反的非对称复合材料层压板组合在一起,还能产生一种镶嵌式三稳复合材料层压板。本研究探讨了马赛克双稳态和三稳态复合层压板的静态特性。研究还试图分析影响这些类型层压板行为的因素。为此,研究人员建立了一个几何精确模型。除几何精确模型外,还采用了一个广泛使用的简单模型,该模型依赖于传统的经典层压板理论(CLPT)和 Von-Karman 非线性应变。通过有限元模拟对所提出的模型进行了验证。系统的静态方程是利用虚功原理和 Rayleigh-Ritz 方法推导出来的。本研究通过施加集中力,检查并探索了稳定状态之间的准静态快速通过行为。研究结果表明,几何精确模型和有限元分析得出的结果高度一致,尤其是在复合材料层压板出现明显变形和旋转时。Experimental investigation on residual capacity of steel-reinforced concrete-filled thin-walled steel tubular columns subjected to combined loading and temperatureWen-Da Wang, Wen-Jing Mao, Kan Zhoudoi:10.1016/j.tws.2024.111557钢筋混凝土填充薄壁钢管柱在荷载和温度共同作用下的残余承载力试验研究Steel-reinforced concrete-filled thin-walled steel tube (SRCFST) is gaining popularity in construction, primarily due to its superior structural performance. However, there is still a scarcity of existing studies examining the residual capacity of SRCFST columns after exposure to fire. Comprehensive research was conducted in this, involving both experimental testing and numerical simulations, to investigate the residual capacity of SRCFST columns. Six SRCFST columns were tested under combined loading and temperature to achieve the temperature distribution, failure modes, residual strength, and structural response within the cross-section. The developed finite element (FE) model was used to validate the test results. Three different paths, including after exposure to fire and without initial load, full-rang fire, and the actual path in the current test, were considered to assess the influence of different time-load-temperature paths on the mechanical properties of SRCFST columns. Results reveal that the region comprised of profiled steel and surrounded concrete forms a composite constraint area, with little loss of strength and stiffness occurring in the core region. The initial load level and heating time ratio were found to have a significant negative influence on the residual load-carrying capacity and ductility of SRCFST columns. By contrast, circular SRCFST columns are more resistant to the effects of fire compared to square SRCFST columns. Finally, the existing design methods were used and extended to evaluate the residual load-carrying capacity of SRCFST columns subjected to a complete temperature-load-time process.钢筋混凝土填充薄壁钢管(SRCFST)在建筑领域越来越受欢迎,这主要归功于其优越的结构性能。然而,目前仍很少有研究探讨 SRCFST 柱在遭受火灾后的剩余承载力。本研究通过实验测试和数值模拟,对 SRCFST 柱的剩余承载力进行了全面研究。对六根 SRCFST 柱进行了综合载荷和温度测试,以了解截面内的温度分布、破坏模式、剩余强度和结构响应。开发的有限元(FE)模型用于验证测试结果。考虑了三种不同的路径,包括暴露于火灾后且无初始荷载、全范围火灾以及本次试验中的实际路径,以评估不同时间-荷载-温度路径对 SRCFST 柱力学性能的影响。结果显示,由型钢和环绕混凝土组成的区域形成了一个复合约束区域,核心区域的强度和刚度损失很小。研究发现,初始荷载水平和加热时间比对 SRCFST 柱的剩余承载能力和延性有显著的负面影响。相比之下,圆形 SRCFST 柱比方形 SRCFST 柱更能抵抗火灾的影响。最后,使用并扩展了现有的设计方法,以评估 SRCFST 柱在完整的温度-荷载-时间过程中的剩余承载能力。来源:复合材料力学仿真Composites FEM

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