今日更新:Journal of the Mechanics and Physics of Solids 1 篇,International Journal of Plasticity 1 篇,Thin-Walled Structures 3 篇
A constitutive model that couples light propagation direction and deformation for photo-responsive polymers and polymeric gels
Haohui Zhang, Yuhang Hu
doi:10.1016/j.jmps.2024.105786
光响应聚合物和聚合物凝胶的光传播方向与变形耦合的本构模型
Light serves a pivotal function in polymer systems, creating a dynamic interplay with the materials. It initiates various photochemical processes such as polymerization, phase transitions, photo-isomerization, photo-ionization, etc, endowing the polymers with diverse functionalities. Concurrently, as these materials undergo the changes, their shape and optical properties evolve, which also change the light behaviors in terms of reflection, refraction, and propagation. This mutual interaction is intricate and can lead to novel phenomena. Understanding this complex coupling is crucial for generating new insights and paves the way for innovative design possibilities. In this study, we combine principles of geometrical optics with a nonlinear chemomechanical theory to investigate the interdependent effects of light direction and polymer behavior, including reactions and deformations. We apply this conceptual framework to a light-responsive hydrogel, illustrating a novel design of an optical fiber actuator through simulations. This example highlights how the interaction between light direction and the hydrogel’s photo-induced swelling governs actuation, and we discuss strategies to leverage this understanding for enhanced control and functionality of such devices. Additionally, we employ the model to analyze the growth morphology of the light-responsive hydrogel, offering a detailed examination of how these interactive forces contribute to the gel’s photo-induced morphological evolution.
光在聚合物系统中起着关键作用,与材料产生动态的相互作用。它引发了各种光化学过程,如聚合、相变、光异构化、光电离等,使聚合物具有多种功能。同时,随着这些材料的变化,它们的形状和光学性质也在变化,这也改变了光在反射、折射和传播方面的行为。这种相互作用是复杂的,可以导致新的现象。理解这种复杂的耦合对于产生新的见解和为创新设计铺平道路至关重要。在这项研究中,我们将几何光学原理与非线性化学力学理论相结合,研究了光方向和聚合物行为(包括反应和变形)的相互作用。我们将这一概念框架应用于光响应水凝胶,通过仿真说明了一种新型光纤致动器的设计。这个例子强调了光方向和水凝胶的光致膨胀之间的相互作用是如何控制驱动的,我们讨论了利用这种理解来增强这种装置的控制和功能的策略。此外,我们采用该模型来分析光响应水凝胶的生长形态,提供了这些相互作用力如何促进凝胶光诱导形态进化的详细检查。
Effects of local strain on the plastic deformation and fracture mechanism of heterogeneous multilayered aluminum
Yiping Xia, Xin Bai, Huijun Fang, Xuewen Li, Xinbo Ni, He Wu, Kesong Miao, Rengeng Li, Honglan Xie, Hao Wu, Lin Geng, Guohua Fan
doi:10.1016/j.ijplas.2024.104078
局部应变对非均质多层铝塑性变形及断裂机制的影响
Elucidating the effect of local strain on the mechanical properties is of great significance for the design of high-performance layered metals. For this purpose, we conceived the present study, featured by tailoring the local strain by layer thickness design, and simultaneous monitoring of local strain and geometrically necessary dislocations (GNDs) via coupling in-situ electron backscatter diffraction (EBSD) and high-resolution digital image correlation (DIC). In addition, synchrotron X-ray micro-computed tomography (μCT) was employed to analyze the microcracks that serve as another form of strain localization. Such detailed experimental studies revealed that the interfacial strain gradient was rapidly elevated, and the strain localization band was effectively dispersed as the layer thickness decreased. This leads to two typical transitions, from grain-boundary-related to layer-interface-related plastic deformation mode, and from macroscopic shear to zig-zag fracture mode. Their influences on the mechanical properties, as well as underlying mechanisms, were discussed based on the relationship among the layer thickness, strain gradient, strain localization, GND density, and microcracks. Our work not only contributes to the fundamental understanding of the mechanical behavior of multilayered metals but also offers guidance for the structural design of high-performance metals aimed at achieving superior strength-ductility combinations.
阐明局部应变对层状金属力学性能的影响对高性能层状金属的设计具有重要意义。为此,我们设想了本研究,其特点是通过层厚度设计定制局部应变,并通过耦合原位电子背散射衍射(EBSD)和高分辨率数字图像相关(DIC)同时监测局部应变和几何必要位错(GNDs)。此外,采用同步加速器x射线微计算机断层扫描(μCT)对作为另一种应变局部化形式的微裂纹进行了分析。详细的实验研究表明,随着层厚的减小,界面应变梯度迅速升高,应变局部化带有效分散。这导致了两种典型的转变,即从晶界相关到层界面相关的塑性变形模式,以及从宏观剪切到之字形断裂模式。基于层厚、应变梯度、应变局部化、GND密度和微裂纹之间的关系,讨论了它们对复合材料力学性能的影响及其机制。我们的工作不仅有助于对多层金属力学行为的基本理解,而且为高性能金属的结构设计提供指导,旨在实现卓越的强度-延性组合。
Experiment and numerical investigation on beetle elytra inspired lattice structure: enhanced mechanical properties and customizable responses
Xiuxia Geng, Mingzhi Wang, Yinzhu Wang, Weidong Wang
doi:10.1016/j.tws.2024.112241
甲虫鞘翅启发晶格结构的实验和数值研究:增强的力学性能和可定制的响应
The elytra of the ironclad beetles possess very strong and toughness performance, to protect the body from catastrophic physical damage, owing to its unique curved geometry and layered microstructure. In this paper, inspired by the elytra of ironclad beetles, a novel configuration of lattice structure (IBCC) was developed. The digital light processing (DLP) with hard-tough resin was used to fabricate the lattice structures. The compression experiment and simulation were performed to investigate the mechanical response and deformation mechanism. The response surface model (RSM) was adopted to build a forward relationship between structure parameters and mechanical properties. A numerical method was developed to inversely design structure parameters of IBCC with “target” mechanical properties using genetic algorithm. The novel lattice structure exhibits superior stiffness and energy absorption than conventional BCC (body-centered cubic) and OCT (Octet) structures, under the same relative density. For example, IBCC shows a maximum 59% improvement (at ρ¯=9.60%) of stiffness, and a maximum 25% improvement (at ρ¯=7.40%) of SEA, with respect to OCT. Besides, the stress plateau of IBCC is more stable than OCT, even at relatively large compression strain. The superior mechanical response of the IBCC lattice structure is mainly ascribed to bio-inspired topological design and interaction effects of curved rods in the “V-shaped” region. Besides, the effectiveness of the proposed inverse design method is verified by three numerical cases. The proposed bio-inspired design strategy, mechanical enhancement mechanism, and customizable method will be helpful in expanding the prospects of lattice structures in future multifunctional application fields.
铁甲虫的甲壳具有独特的弯曲几何形状和分层微结构,因此具有非常强的韧性,可保护身体免受灾难性的物理损伤。本文受铁甲虫鳞甲的启发,开发了一种新颖的晶格结构(IBCC)。采用数字光处理技术(DLP)和硬韧树脂制造了晶格结构。通过压缩实验和模拟研究了机械响应和变形机理。采用响应面模型(RSM)建立了结构参数与力学性能之间的正向关系。利用遗传算法开发了一种数值方法来反向设计具有 “目标 ”力学性能的 IBCC 结构参数。在相同的相对密度下,新型晶格结构比传统的 BCC(体心立方)和 OCT(八面体)结构具有更高的刚度和能量吸收能力。例如,与 OCT 相比,IBCC 的刚度最大提高了 59%(ρ¯=9.60% 时),SEA 最大提高了 25%(ρ¯=7.40% 时)。此外,IBCC 的应力平台比 OCT 更稳定,即使在相对较大的压缩应变下也是如此。IBCC 晶格结构优越的机械响应主要归因于生物启发的拓扑设计和 “V 形 ”区域弯曲杆的相互作用效应。此外,还通过三个数值案例验证了所提出的逆向设计方法的有效性。所提出的生物启发设计策略、力学增强机制和可定制方法将有助于拓展晶格结构在未来多功能应用领域的前景。
Nonlinear Resonant Analyses of Graphene Oxide Powder Reinforced Hyperelastic Cylindrical Shells Containing Flowing-Fluid
J. Zhang, W. Zhang, Y.F. Zhang
doi:10.1016/j.tws.2024.112248
含流动流体的氧化石墨烯粉末增强超弹性圆柱壳的非线性共振分析
The resonant responses are investigated for the graphene oxide powder reinforced hyperelastic cylindrical (GOPRHC) shells containing flowing-fluid, and the shells are subjected to the radial harmonic excitations. Employing the improved Donnell's nonlinear shell theory, Halpin-Tsai model, hyperelastic constitution relation, velocity potential theory and Lagrange equation, the governing equation of motions are obtained for the GOPRHC shells containing flowing fluid. The amplitude frequency and force amplitude curves are presented by using the harmonic balance method and the pseudo-arc length continuation method. The effects of three distributions of the GOP, weight fraction of the GOP and fluid velocity on the natural frequency for the GOPRHC shells are discussed. The influences of different parameters on the dynamical responses for the GOPRHC shells containing flowing-fluid are conducted, including the external excitation, weight fraction of the GOP, fluid velocity and structural parameters. The results show that the GOPRHC shells with Hypere-X distribution containing flowing-fluid have the largest frequency. The super-harmonic resonance responses appear and present the synchronization effects with the primary resonant responses in the GOPRHC shells containing flowing-fluid. The increases of external excitations, fluid velocity, weight fraction of the GOP and structural parameters enrich the resonant responses for the GOPRHC shells. Compared to the fluid-filled hyperelastic cylindrical shells, the existence of the flowing-fluid makes the GOPRHC shells more prone to the chaotic vibrations. The hysteresis phenomena of chaotic vibrations occur in the GOPRHC shells containing flowing-fluid.
研究了含流动流体的氧化石墨烯粉末增强超弹性圆柱(GOPRHC)壳在径向谐波激励下的共振响应。利用改进的Donnell非线性壳理论、Halpin-Tsai模型、超弹性本构关系、速度势理论和拉格朗日方程,得到了含流动流体的GOPRHC壳的运动控制方程。采用谐波平衡法和伪弧长延延法得到了幅值、频率和力幅值曲线。讨论了GOP的三种分布、GOP的质量分数和流体速度对GOPRHC壳固有频率的影响。研究了外部激励、GOP质量分数、流体速度和结构参数等参数对含流动流体的GOPRHC壳动力响应的影响。结果表明:含流动流体的Hypere-X分布的GOPRHC壳层频率最大;在含流动流体的GOPRHC壳层中出现了超谐波共振响应,并与主共振响应呈现同步效应。外部激励、流体速度、GOP质量分数和结构参数的增加丰富了GOPRHC壳层的共振响应。与充满流体的超弹性圆柱壳相比,流动流体的存在使GOPRHC壳更容易产生混沌振动。含流动流体的GOPRHC壳体中存在混沌振动的滞回现象。
Static/fatigue response and degradation behaviors of CFRP/Ti bolted joints under salt-fog and ultraviolet synergistic marine environment
Haoyuan Suo, Kelin Deng, Kaifu Zhang, Hui Cheng, Biao Liang, Hailin Li, Bin Luo
doi:10.1016/j.tws.2024.112251
盐雾和紫外线协同海洋环境下CFRP/Ti螺栓连接静力/疲劳响应及退化行为
The complexity and uncertainty of the mechanical response behaviors of the bolted joints formed by carbon fiber reinforced polymer composites (CFRP) and titanium alloy (Ti) under complicated marine environment are serious challenges for their continuous and reliable service. This paper conducted comprehensive experimental research to characterize the static/fatigue response and degradation behaviors of CFRP/Ti bolted joints after salt-fog & ultraviolet synergistic environment aging. The load-displacement and strain properties during loading process, and the failure mechanisms were analyzed to identify the mechanical performances evolution of the joints. The results show that the structural damage and instability mechanisms are significantly influenced by the evolution of the contact state around the overlapping area and the composite materials degradation. More serious composites delamination occurs during loading process after aging, and the effect of friction energy dissipation to offset applied load decreases, leading to the failure mode evolves from bolt fracture to hole crushing. In addition, the fatigue life data were analyzed mathematically to reveal the evolution law of fatigue life with aging time and loading level, and two-parameter Weibull distribution was employed to study the fatigue life under different reliability levels.
复杂海洋环境下碳纤维增强聚合物复合材料(CFRP)与钛合金(Ti)螺栓连接力学响应行为的复杂性和不确定性对其持续可靠使用提出了严峻挑战。本文对CFRP/Ti螺栓连接在盐雾和紫外线协同环境老化后的静力/疲劳响应和退化行为进行了综合试验研究。分析了节点在加载过程中的荷载-位移和应变特性,以及破坏机制,识别了节点的力学性能演变过程。结果表明,复合材料的降解和重叠区域周围接触状态的演变对结构损伤和失稳机制有显著影响。时效后加载过程中复合材料分层现象更为严重,摩擦耗能抵消外加载荷的作用减弱,破坏模式由螺栓断裂演变为孔压破碎。此外,对疲劳寿命数据进行数学分析,揭示疲劳寿命随老化时间和载荷水平的演化规律,并采用双参数威布尔分布研究不同可靠性水平下的疲劳寿命。