今日更新:Journal of the Mechanics and Physics of Solids 2 篇,International Journal of Plasticity 1 篇
A generalized geometric mechanics theory for multi-curve-fold origami: Vertex constrained universal configurations
Zhixuan Wen, Pengyu Lv, Fan Feng, Huiling Duan
doi:10.1016/j.jmps.2024.105829
多曲线折纸的广义几何力学理论:顶点约束的通用构型
Folding paper along curves leads to spatial structures that have curved surfaces meeting at spatial creases, defined as curve-fold origami. In this work, we provide an Eulerian framework focusing on the mechanics of arbitrary curve-fold origami, especially for multi-curve-fold origami with vertices. We start with single-curve-fold origami that has wide panels. Wide panel leads to different domains of mechanical responses induced by various generator distributions of the curved surface. The theories are then extended to multi-curve-fold origami, involving additional geometric correlations between creases. As an illustrative example, the deformation and equilibrium configuration of origami with annular creases are studied both theoretically and numerically. Afterward, single-vertex curved origami theory is studied as a special type of multi-curve-fold origami. We find that the extra periodicity at the vertex strongly constrains the configuration space, leading to a region near the vertex that has a striking universal equilibrium configuration regardless of the mechanical properties. Both theories and numerics confirm the existence of the universality in the near-field region. In addition, the far-field deformation is obtained via energy minimization and validated by finite element analysis. Our generalized multi-curve-fold origami theory, including the vertex-contained universality, is anticipated to provide a new understanding and framework for the shape programming of the curve-fold origami system.
沿着曲线折纸会产生曲面在空间折痕处相交的空间结构,定义为曲线折纸。在这项工作中,我们提供了一个欧拉框架,专注于任意曲线折纸的力学,特别是具有顶点的多曲线折纸。我们从具有宽面板的单曲线折纸开始。宽面板导致不同的曲面发生器分布导致不同的力学响应域。然后将理论扩展到多曲线折纸,涉及折痕之间的额外几何关联。以环形折纸为例,从理论上和数值上研究了环形折纸的变形和平衡构型。然后,将单顶点曲线折纸理论作为一种特殊类型的多曲线折纸进行了研究。我们发现顶点处的额外周期性强烈地约束了构型空间,导致顶点附近的区域具有引人注目的普遍平衡构型,而不管力学性能如何。理论和数值都证实了在近场区域存在普适性。此外,通过能量最小化计算得到远场变形,并通过有限元分析进行验证。我们的广义多曲线折纸理论,包括包含顶点的普适性,有望为曲线折纸系统的形状规划提供新的理解和框架。
A Photo-Chemo-Mechanical Coupling Constitutive Model for Photopolymerization-based 3D Printing Hydrogels
Heng Zhu, Yujun Guo, Zhe Chen, Shaoxing Qu
doi:10.1016/j.jmps.2024.105830
基于光聚合的3D打印水凝胶的光化学-力学耦合本构模型
Photopolymerization-based 3D printing has emerged as a key technology in hydrogel manufacturing, broadening the attributes of hydrogels and extending their applications into diverse engineering fields. However, the mechanical properties of hydrogels dramatically impact the functionality and quality in practice. It is necessary to develop an appropriate theoretical model to predict the evolution of the mechanical properties of hydrogels during the photopolymerization process. In this work, systematical experiments were performed to investigate mechanical properties of PAAm hydrogel under different photopolymerization condition. The results reveal a noticeable increasement in both elastic and viscous behavior of hydrogel with the advancement of polymerization. To fully capture the experimental observations, we developed a coupled photo-chemo-mechanical theoretical framework that integrates reaction kinetics with a physically-based viscoelastic constitutive model. Within this model, the degree of conversion serves as an internal variable, which related to microscopic structures such as correlation length, and tube diameter. The developed model exhibits remarkable prediction ability for hydrogels with various degree of polymerization. The current work paves a potentially new avenue for understanding the evolution of mechanical properties in photopolymerized hydrogels, providing theoretical guidance for the manufacturing of hydrogels through photopolymerization-based 3D printing.
基于光聚合的3D打印技术已经成为水凝胶制造的一项关键技术,拓宽了水凝胶的属性,并将其应用扩展到各种工程领域。然而,在实际应用中,水凝胶的力学性能极大地影响了水凝胶的功能和质量。有必要建立一个合适的理论模型来预测光聚合过程中水凝胶力学性能的演变。本文通过系统的实验研究了PAAm水凝胶在不同光聚合条件下的力学性能。结果表明,随着聚合的进展,水凝胶的弹性和粘性行为都显著增加。为了充分捕捉实验观察结果,我们开发了一个耦合的光化学-力学理论框架,将反应动力学与基于物理的粘弹性本构模型相结合。在该模型中,转换程度作为一个内部变量,与相关长度、管径等微观结构有关。所建立的模型对不同聚合程度的水凝胶具有较好的预测能力。目前的工作为理解光聚合水凝胶力学性能的演变铺平了一条潜在的新途径,为通过基于光聚合的3D打印制造水凝胶提供了理论指导。
The influence of mineral inclusion on the effective strength of rock-like geomaterials
W.Q. Shen, Y.J. Cao, J.L. Chen, S.Y. Liu, B. Han
doi:10.1016/j.ijplas.2024.104104
矿物包裹体对类岩岩土材料有效强度的影响
The influences of microstructure on the macroscopic mechanical behavior of a composite with a porous matrix reinforced by mineral inclusions are investigated in the present work by both numerical and theoretical methods. The mineral inclusions are embedded at the mesoscopic scale and much bigger than the pores which are located at the microscopic scale. In order to consider the properties of the studied rock-like geomaterials, such as the dissymmetry between tension and compression, the soild phase at the microscopic scale is assumed to obey to a Drucker–Prager criterion. Based on the studied microstructure, the Fast Fourier Transform (FFT) based numerical method is firstly adopted to investigate the macroscopic plastic yield stress of the studied composite. Different microstructure having different volume fraction of inclusion, micro-porosity and frictional coefficient of the solid phase are considered. Based on these numerical results, the existing theoretical yield criterion is estimated. One finds that it should be improved for the case of a microstructure having a high inclusion content. Then, a new macroscopic yield criterion is constructed in the present work by using the modified secant method. This criterion ameliorates fundamentally the one proposed in Shen et al. (2013), specially for the case of a deviatoric loading. It is then estimated and validated by comparing with the FFT based numerical results which were carried out in this work with different volume fractions of heterogeneous phase.
本文采用数值和理论两种方法研究了微观结构对矿物包裹体增强多孔基体复合材料宏观力学行为的影响。矿物包裹体包裹在细观尺度上,比位于微观尺度上的孔隙大得多。为了考虑所研究的类岩石岩土材料的特性,如拉伸和压缩之间的不对称性,假设微观尺度下的固体相服从Drucker-Prager准则。在研究复合材料微观结构的基础上,首次采用基于快速傅立叶变换(FFT)的数值方法对复合材料宏观塑性屈服应力进行了研究。考虑了不同夹杂物体积分数、微孔隙率和固相摩擦系数的微观组织。根据这些数值结果,估计了现有的理论屈服准则。发现对于夹杂物含量高的微观结构,应加以改进。然后,利用改进的割线法构造了一个新的宏观屈服准则。该准则从根本上改进了Shen等人(2013)提出的标准,特别是对于偏差加载的情况。然后,通过与基于FFT的数值结果进行比较,对不同体积分数的非均相进行估计和验证。