今日更新:Journal of the Mechanics and Physics of Solids 2 篇,Mechanics of Materials 1 篇,Thin-Walled Structures 2 篇
A Theoretical Model of Enhanced Adhesion of Bioinspired Micropillar Arrayed Surfaces
Yonggui Cheng, Zhilong Peng, Shaohua Chen
doi:10.1016/j.jmps.2024.105592
生物启发微柱阵列表面附着力增强的理论模型
To achieve better adhesion, micropillar arrayed surfaces inspired by the gecko adhesion system have gained significant attention. However, debate continues on whether micropillar arrayed surfaces actually enhance interfacial adhesion compared to smooth surfaces. To clearly understand the factors influencing the adhesion force of micropillar arrayed surfaces and provide a criterion for achieving enhanced adhesion of such the surfaces, a theoretical model of a micropillar arrayed surface containing an elastic backing layer is established. Under a vertically uniform displacement load, the micropillars will detach from the rigid substrate. The adhesion behavior of each micropillar and the variation pattern of the entire adhesion force influenced by the geometry of the micropillars, materials of the micropillars and backing layer during the detaching process are analyzed. A load sharing efficiency is defined, and is found to increase with an increase in the micropillar aspect ratio, Young's modulus ratio of the backing layer to the micropillars, and separation distance between neighboring micropillars, but decrease with an increase in sample size. The entire adhesion force of a micropillar arrayed surface can be quantified, which is larger than that of a smooth surface if the micropillar aspect ratio, Young's modulus ratio of the backing layer to the micropillars and separation distance between neighboring micropillars are appropriate. Detailed diagrams are respectively provided for the load sharing efficiency of all the micropillars and the comparison of the adhesion forces between micropillar arrayed and smooth surfaces with different geometric and material parameters, from which the design strategies of approaching equal load sharing regime and stronger adhesion force of the micropillar arrayed surface than that of the smooth one can be clearly found. The obtained results can not only deepen the understanding of the adhesion behavior of fibrillar surfaces but also provide theoretical guidance for achieving robust adhesion of the micropillar arrayed surfaces.
为了获得更好的附着力,受壁虎附着系统启发的微柱阵列表面受到了广泛关注。然而,与光滑表面相比,微柱阵列表面是否真的能增强界面粘附力的争论仍在继续。为了清楚地了解微柱阵列表面粘附力的影响因素,并为增强这种表面的粘附力提供一个标准,本文建立了一个包含弹性背层的微柱阵列表面的理论模型。在垂直均匀位移载荷作用下,微柱将从刚性基底上脱离。分析了分离过程中每个微柱的粘附行为以及整个粘附力受微柱几何形状、微柱材料和背衬层影响的变化规律。结果发现,随着微柱长宽比、背衬层与微柱的杨氏模量比以及相邻微柱之间的分离距离的增加,负载分担效率会增加,但随着样品尺寸的增加,负载分担效率会降低。如果微柱的长宽比、背衬层与微柱的杨氏模量比以及相邻微柱之间的间距合适,则可以量化微柱阵列表面的整个附着力,其大于光滑表面的附着力。详细的图表分别显示了所有微柱的负载分担效率,以及不同几何和材料参数下微柱阵列表面与光滑表面的附着力对比,从中可以清楚地发现接近等负载分担机制的设计策略,以及微柱阵列表面比光滑表面更强的附着力。所得结果不仅能加深对纤维素表面粘附行为的理解,还能为实现微柱阵列表面的稳健粘附提供理论指导。
High-efficient and reusable impact mitigation metamaterial based on compression-torsion coupling mechanism
Haifeng Ou, Lingling Hu, Yanbin Wang, Chang Liu
doi:10.1016/j.jmps.2024.105594
基于压缩-扭转耦合机制的高效、可重复使用的冲击减缓超材料
Lightweight and reusable materials are desired in engineering for mitigating repetitive impacts. However, the limitation of mitigation efficiency is always a problem in spite of various materials have been studied. And other issues need to be improved, such as bulky and poor load-bearing. There still exists challenge to design a reusable impact mitigation material with high efficient, lightweight and high stiffness. Here, a lightweight syndiotactic chiral metamaterial (SCM) with compression-torsion coupling effect (CTCE) is proposed and fabricated for repetitive impact mitigation. Impact experiments indicate that the proposed metamaterials exhibit significant superiorities in impact mitigation efficiency, lightweight, higher stiffness and less cells over the previously reported ones. In order to reveal the deeper mechanism of the superior properties, the band gaps of SCM with CTCE and isometric chiral metamaterial (ICM) without CTCE are analyzed and compared by transmissibility tests and numerical simulations. It is found that the extra energy dissipated by torsion caused by CTCE is the key factor for excellent mitigation performance, which enlarges the band gap to low-frequencies and prevents more waves pass through. To balance the mitigation performance and load carrying capacity, the gradient design strategy is proposed to cope with large impact loads with maintaining high mitigation efficiency, which is achieved by overlapping the band gaps of different cells to widen the band gap range. The mechanism of improving impact mitigation performance by CTCE revealed in the present work enlightens a new avenue to develop effective, reusable and lightweight buffer materials.
轻质和可重复使用的材料是减轻重复撞击的理想工程材料。然而,尽管已经对各种材料进行了研究,但缓解效率的限制始终是一个问题。还有一些问题需要改进,如体积庞大、承重能力差等。如何设计一种可重复使用的高效、轻质、高刚度的冲击缓解材料仍然是一个挑战。本文提出并制造了一种具有压缩-扭转耦合效应(CTCE)的轻质辛迪加手性超材料(SCM),用于重复冲击缓解。冲击实验表明,与之前报道的超材料相比,所提出的超材料在冲击缓解效率、轻量化、高刚度和少细胞等方面具有显著优势。为了揭示其卓越性能的深层机理,我们通过透射率测试和数值模拟,分析并比较了带 CTCE 的 SCM 和不带 CTCE 的等轴手性超材料(ICM)的带隙。结果发现,CTCE 产生的扭转所耗散的额外能量是实现出色缓和性能的关键因素,它扩大了低频带隙,阻止了更多的波通过。为了平衡缓和性能和承载能力,提出了梯度设计策略,通过重叠不同单元的带隙来扩大带隙范围,从而在保持高缓和效率的同时应对大的冲击载荷。本研究揭示的 CTCE 提高冲击缓解性能的机制为开发有效、可重复使用和轻质的缓冲材料提供了新的途径。
Preserving non-negative porosity values in a bi-phase elasto-plastic material under Terzaghi’s effective stress principle
Giuliano Pretti, William M. Coombs, Charles E. Augarde, Marc Marchena Puigvert, José Antonio Reyna Gutiérrez
doi:10.1016/j.mechmat.2024.104958
在特尔扎吉有效应力原理下保持双相弹塑性材料中的非负孔隙率值
Poromechanics is a well-established field of continuum mechanics which seeks to model materials with multiple phases, usually a stiff solid phase and fluid phases of liquids or gases. Applications are widespread particularly in geomechanics where Terzaghi’s effective stress is widely used to solve engineering soil mechanics problems. This approach assumes that the solid phase is incompressible, an assumption that leads to many advantages and simplifications without major loss of fidelity to the real world. Under the assumption of finite (as opposed to infinitesimal) strains, the poromechanics of two- or bi-phase materials gains complexity and while the compressible solid phase case has received attention from researchers, the incompressible case has received less. For the finite strain - incompressible solid phase case there is a fundamental issue with standard material models, in that for some loadings solid skeleton mass conservation is violated and negative Eulerian porosities are predicted. While, to the authors’ best knowledge, acknowledgement of this essential problem has been disregarded in the literature, an elegant solution is presented here, where the constraint on Eulerian porosity can be incorporated into the free energy function for a material. The formulation is explained in detail, soundly grounded in the laws of thermodynamics and validated on a number of illustrative examples.
孔隙力学是连续介质力学的一个成熟领域,旨在为具有多相(通常是坚硬的固相和液体或气体的流体相)的材料建模。其应用非常广泛,尤其是在地质力学中,特尔扎吉有效应力法被广泛用于解决工程土壤力学问题。这种方法假定固相是不可压缩的,这一假定带来了许多优点和简化,但并没有严重丧失对现实世界的忠实性。在有限应变(而非无穷小应变)的假设下,两相或双相材料的孔隙力学变得更加复杂,虽然可压缩固相情况受到了研究人员的关注,但不可压缩情况受到的关注较少。对于有限应变-不可压缩固相情况,标准材料模型存在一个基本问题,即在某些载荷下,固体骨架的质量守恒被违反,欧拉孔隙率被预测为负值。据作者所知,文献中一直忽略了这一基本问题,而本文提出了一个优雅的解决方案,即可以将对欧拉孔隙率的约束纳入材料的自由能函数中。本文详细解释了这一公式,以热力学定律为坚实基础,并通过大量示例进行了验证。
EQUIVALENT LAYER-WISE THEORY FOR THE HYGRO-THERMO-MAGNETO-ELECTRO-ELASTIC ANALYSIS OF LAMINATED CURVED SHELLS
Francesco Tornabene, Matteo Viscoti, Rossana Dimitri
doi:10.1016/j.tws.2024.111751
层状曲面壳体的湿热磁电弹性分析等效分层理论
The paper presents a multifield formulation involving five different physical problems under the equilibrium thermodynamic conditions for laminated doubly-curved shell structures. More specifically, the study focuses on the coupling between the mechanical elasticity and the thermo-hygrometric problem, while also considering the magneto-electricity of the solid. The configuration variables are described with a generalized formulation based on the Equivalent Layer Wise (ELW) approach, taking into account higher order polynomial interpolations along the thickness direction. The fundamental relations are derived from the Master Balance principle and solved using the Navier's method. Furthermore, the three-dimensional response of the doubly-curved shell solid in terms of primary and secondary variables is recovered from the two-dimensional solution with a methodology based on the three-dimensional multifield balance equations and the Generalized Differential Quadrature (GDQ) numerical technique. Some examples are then presented in which panels of different curvatures and lamination schemes are investigated. The results are compared with success to those coming from three-dimensional numerical models developed with a commercial software. It is shown that the present analytical solution is a valid tool for modelling multifield problems for the evaluation of the response of doubly-curved shells under generalized external actions and pre-determined values of the configuration variables.
本文提出了一种多场公式,涉及层叠双曲壳结构平衡热力学条件下的五个不同物理问题。更具体地说,研究重点是机械弹性和热-偏振问题之间的耦合,同时还考虑了固体的磁电性。配置变量采用基于等效层智(ELW)方法的通用公式进行描述,并考虑了沿厚度方向的高阶多项式插值。基本关系由主平衡原理导出,并使用纳维法求解。此外,通过基于三维多场平衡方程和广义微分正交(GDQ)数值技术的方法,从二维解法中还原了双曲面壳体实体在主变量和次变量方面的三维响应。随后介绍了一些实例,研究了不同曲率和层压方案的面板。研究结果与使用商业软件开发的三维数值模型得出的结果进行了比较。结果表明,本分析解决方案是一种有效的工具,可用于多场问题建模,以评估双曲面壳体在广义外部作用和预定配置变量值下的响应。
Thermo-mechanical buckling and sound radiation characteristics of 3D graphene porous core curved sandwich panels with composite facings
R. Kiran Kumar Reddy, A.R. Veerappan, Nivish George, Vinod Bhagat
doi:10.1016/j.tws.2024.111753
带复合面层的三维石墨烯多孔芯曲面夹层板的热机械屈曲和声辐射特性
Buckling and sound radiation characteristics of curved sandwich panels subjected to combined thermo-mechanical loads are presented in the paper. The panel comprises a 3-D functionally graded graphene porous core sandwiched between FG-VΛ CNT reinforced composite face sheets (3DGrF-CF). The governing differential equations of 3DGrF-CF sandwich panels are derived using the parabolic shear deformation theory (PSDT), and the vibration responses are predicted using Navier’s approach. The vibration response thus obtained is fed into the Rayleigh integral to capture the acoustic pressure. The buckling and sound radiation characteristics were found to vary significantly with the core’s porosity coefficient and porosity grading pattern. However, the impact of this influence also depends on the magnitude of thermal & mechanical loading. This implies that selecting a core for acoustic comfort depends on the dominance of loading conditions and is illustrated using octave band analysis.
本文介绍了曲面夹层板在承受热机械综合载荷时的屈曲和声辐射特性。该夹芯板由三维功能分级石墨烯多孔夹芯和 FG-VΛ CNT 增强复合材料面片(3DGrF-CF)组成。利用抛物线剪切变形理论(PSDT)推导出了 3DGrF-CF 夹层板的控制微分方程,并利用纳维方法预测了振动响应。由此获得的振动响应被送入瑞利积分,以捕捉声压。研究发现,屈曲和声辐射特性随岩心的孔隙度系数和孔隙度分级模式的变化而显著不同。然而,这种影响也取决于热负荷和机械负荷的大小。这就意味着,要选择声学舒适度高的芯材,取决于加载条件的主导地位,并通过倍频程带分析加以说明。