今日更新:International Journal of Solids and Structures 1 篇,Journal of the Mechanics and Physics of Solids 2 篇,International Journal of Plasticity 1 篇,Thin-Walled Structures 2 篇
Frequency domain Green’s function and boundary integral equations for multifield materials and quasicrystals
Pasternak Viktoriya, Sulym Heorhiy, Pasternak Iaroslav M.
doi:10.1016/j.ijsolstr.2023.112562
多场材料和准晶体的频域格林函数和边界积分方程
Present paper considers anisotropic elastic, magnetoelectroelastic and quasicrystal solids. It is shown that the equations of time-harmonic motion and constitutive relations for considered materials can be presented in the compact and unified form. The matrix approach is proposed for derivation of 3D time-harmonic Green’s functions for considered materials. The cases of each material type are studied separately. Two models of phason field dynamics in quasicrystals are considered in details. It is shown that in the case of phason field models based on the use of hydrodynamic formulations, phonon oscillations have an elastic nature, while the phason field leads to their decay due to phonon-phason interaction. The strict proof is given to the statement that the eigenvalues of the time-harmonic magnetoelectroelaticity problem are all positive. The paper also shows the application of the obtained time-harmonic Green’s functions in obtaining the boundary integral equations for the considered classes of problems. For this purpose, the novel approach is proposed, which utilizes only the symmetry of the unified material property tensor and the inertia matrix. Derived boundary integral equations can be used in the solution of boundary value problems for considered classes of materials.
本文研究了各向异性弹性、磁电弹性和准晶体固体。研究表明,所考虑材料的时谐运动方程和构成关系可以以紧凑统一的形式呈现。为推导所考虑材料的三维时谐格林函数,提出了矩阵方法。对每种材料的情况分别进行了研究。详细考虑了准晶体中的两种相声场动力学模型。结果表明,在基于流体力学公式的声子场模型中,声子振荡具有弹性性质,而声子场则由于声子-声子相互作用而导致其衰减。本文对时谐磁电静问题的特征值均为正值这一说法给出了严格的证明。论文还展示了所获得的时谐格林函数在获得所考虑问题类别的边界积分方程中的应用。为此,论文提出了一种新方法,即只利用统一材料属性张量和惯性矩阵的对称性。推导出的边界积分方程可用于求解所考虑材料类别的边界值问题。
Pinning cracks by microstructure design in brittle materials
Xiong Xun, Zeng Qinglei, Wang Yonghuan, Li Ying
doi:10.1016/j.jmps.2023.105497
脆性材料微观结构设计中的针状裂纹
In this work, we explore the possibility of controlling toughening mechanisms in brittle materials through microstructure design to enhance their resistance to crack growth. First, a computational framework is established using the distinct element method (DEM) with J integral implemented to simulate complex crack propagation and characterize the effective fracture energy of brittle materials. The fracture behavior of a soda-lime glass plate containing pre-existing voids under tensile loading is simulated, and toughening mechanisms associated with the existence of voids, including blunting-induced pinning and deflection-induced pinning, are identified in brittle materials. Then we seek to modulate the fracture toughness of brittle materials by introducing either randomly distributed voids or sinusoidally distributed voids and controlling the pinning events. Our findings reveal that randomly distributed voids with different volume fractions induce only modest toughening in brittle materials. Sinusoidally distributed voids with specific amplitude and wavelength trigger both crack blunting and deflection in the vicinity of voids, increasing the probability of crack pinning and leading to a significant increase in crack growth resistance. Moreover, we identify the critical conditions for the "embrittlement-toughening transition" and "maximized toughening". Finally, we discuss the difference between void toughening for brittle materials and ductile materials due to distinct toughening mechanisms activated, and also extend the toughening strategy to nacre-like materials. The stairwise herringbone structure is demonstrated to be a promising candidate for structure optimization due to unique stiffness, strength, and toughness.
在这项研究中,我们探讨了通过微结构设计控制脆性材料增韧机制的可能性,以增强其抗裂纹生长的能力。首先,我们利用独特的元素法(DEM)建立了一个计算框架,并将该框架与 J 积分来模拟复杂的裂纹扩展,并描述脆性材料的有效断裂能。我们模拟了含有预先存在空隙的钠钙玻璃板在拉伸载荷下的断裂行为,并确定了脆性材料中与空隙存在相关的增韧机制,包括钝化诱导针 刺和挠曲诱导针 刺。然后,我们试图通过引入随机分布的空隙或正弦曲线分布的空隙并控制针 刺事件来调节脆性材料的断裂韧性。我们的研究结果表明,不同体积分数的随机分布空隙只能对脆性材料产生适度的增韧作用。具有特定振幅和波长的正弦分布空隙会在空隙附近引发裂纹钝化和挠曲,增加裂纹针销的概率,从而显著提高裂纹生长阻力。此外,我们还确定了 "脆化-韧化转变 "和 "最大化韧化 "的临界条件。最后,我们讨论了脆性材料和韧性材料由于激活了不同的增韧机制而产生的空隙增韧差异,并将增韧策略扩展到了珍珠质材料。由于具有独特的刚度、强度和韧性,阶梯状人字形结构被证明是结构优化的理想候选材料。
Angle-dependent protrusion of cell membranes
Tang Huayuan, Ye Hongfei, Zhang Hongwu, Yi Xin, Zheng Yonggang
doi:10.1016/j.jmps.2023.105500
细胞膜的角度突起
Protrusion induced by cylindrical tubes against cell membranes plays essential roles in numerous biological processes, including filopodia growth, cellular packing or entry of one-dimensional nanomaterials, and indentation of cells by needle-like probes. Though the mechanical interaction between the cell membrane and a perpendicular tube has been widely investigated, little is known about how an inclined protruding tube interacts with the cell membrane. Here, we theoretically investigate the angle-dependent protrusion of cylindrical tubes against cell membranes. It is found that perpendicular protrusion is stabilized by the elastic deformation of cell membranes. Increasing the angle between the protrusion direction and perpendicular direction or increasing membrane tension leads to an increasing peak force for the membrane tubulation and increasing plateau resistive force for the maintenance of membrane tubules. Moreover, two fundamental protruding modes leading to the tip-roof and finial-roof system configurations are identified. Inclined protrusion retards the configurational transition from the tip-roof to the finial-roof configuration, and causes possible bending and buckling of protruding tubes due to a large membrane resistive force. Our results offer fundamental insights into the interaction between cell membranes and one-dimensional nanomaterials, and contribute to the understanding and control of membrane protrusion in biological systems.
圆柱管对细胞膜的突起在许多生物过程中发挥着重要作用,包括丝状体的生长、细胞的包装或一维纳米材料的进入,以及针状探针对细胞的压入。虽然细胞膜与垂直管之间的机械相互作用已被广泛研究,但人们对倾斜的突出管如何与细胞膜相互作用却知之甚少。在此,我们从理论上研究了圆柱形管与细胞膜之间随角度变化的突起。研究发现,细胞膜的弹性变形稳定了垂直突起。增大突出方向与垂直方向之间的角度或增加膜张力会导致膜管化的峰值力增加,而维持膜管化的高原阻力增加。此外,还确定了两种基本的突出模式,分别导致尖端-屋顶和顶端-屋顶系统配置。倾斜突起延缓了从顶端-屋顶构型到顶盖-屋顶构型的构型转变,并由于较大的膜阻力可能导致突起管弯曲和屈曲。我们的研究结果从根本上揭示了细胞膜与一维纳米材料之间的相互作用,有助于理解和控制生物系统中的膜突起。
Ductile ultrastrong China low activation martensitic steel with lamellar grain structure
Zhou J.H., Wang J., Ritchie Robert O., Wu Y.C., Cheng J.W., Wang L., Yin X.W., Jiang Y.F., Ren J.G.
doi:10.1016/j.ijplas.2023.103813
具有片状晶粒结构的韧性超强中国低活化马氏体钢
The low high-temperature mechanical properties of reduced activated ferrite martensitic (RAFM) heat-resistant steels limit the maximum operating temperature of nuclear fusion reactors. However, it is difficult to improve the strength of the material without reducing its plasticity. In this study we prepared a China low activation martensitic (CLAM) steel with a layered structure through hot rolling followed by low-temperature tempering, which successfully improved its strength and ductility. In addition, we elucidate the ductility mechanisms in such lamellar structural materials. When the strength of the grain boundaries exceeds that of the grains, cracks will continuously extend along the layered grain boundaries, eventually resulting in a delamination fracture mechanism. When the grains strength exceeds that of the grain boundaries, cracks will continuously form through the relative sliding of the grain boundaries, and a large number of small cracks will initiate and propagate longitudinally along the layered boundaries. Both forms of crack propagation cause longitudinal expansion along the layered grain boundaries. The resulting longitudinal extension of cracks markedly diminishes local stress concentration to promote plastic deformation, thereby significantly increasing the ductility of the material. Employing the combination of this delamination ductility mechanism with interface strengthening and precipitation strengthening, the strength of the CLAM steel for nuclear applications is shown to be enhanced by ∼30% without loss of elongation. The current delamination ductility strategy provides a unique pathway to develop materials with ultrahigh strength and superior ductility at economical material costs.
还原活化铁素体马氏体(RAFM)耐热钢的高温机械性能较低,限制了核聚变反应堆的最高工作温度。然而,要在不降低材料塑性的情况下提高其强度却很困难。在这项研究中,我们通过热轧和低温回火制备了具有层状结构的中国低活化马氏体(CLAM)钢,成功提高了其强度和延展性。此外,我们还阐明了这种层状结构材料的延性机理。当晶界强度超过晶粒强度时,裂纹会沿着层状晶界不断延伸,最终形成分层断裂机制。当晶粒强度超过晶界强度时,裂纹会通过晶界的相对滑动不断形成,大量细小裂纹会沿着层状晶界纵向扩展。这两种形式的裂纹扩展都会导致沿层状晶界的纵向扩展。由此产生的裂纹纵向扩展明显减少了局部应力集中,促进了塑性变形,从而显著提高了材料的延展性。将这种分层延展机制与界面强化和析出强化相结合,用于核应用的 CLAM 钢的强度可提高 30%,而伸长率不会降低。当前的分层延展性策略为以经济的材料成本开发具有超高强度和卓越延展性的材料提供了一条独特的途径。
Coupled vibration analysis of a rotating pre-twist blade-hub assembly with a setting angle reinforced by graphene nanoplatelets
Yan Kai, Zhao Tian Yu, Ma Hui
doi:10.1016/j.tws.2023.111287
用石墨烯纳米片强化带设定角的旋转预扭叶片-轮毂组件的耦合振动分析
Due to its light weight and great mechanical performance, the spinning blade-hub assembly are widely used in modern rotary machines, such as the aero-engine, gas turbine, and so on. This paper conducted theoretical modeling and vibration analysis of a functionally graded (FG) pre-twist blade-hub rotor structure with a setting angle reinforced by graphene nanoplatelets (GPLs), where the hub and blade are modeled by elastic cylindrical shell and plate, respectively. To improve the structural stiffness, the blade-hub (plate-cylindrical shell) assembly is prepared from graphene nanoplatelet (GPL) reinforcement and polymer matrix. Both uniform and nonuniform GPL distributions are considered in the plate and cylindrical shell, which leads to a FG assembly. Determined via the Halpin-Tsai model and the rule of the mixture, the effective material properties vary continuously along the thickness direction of the plate and cylindrical shell. According to the Kirchhoff plate theory and the Donnell shell theory, the coupled equations of motion of the FG rotating blade-hub assembly are derived by using the Lagrange's equation. Moreover, the component mode synthesis (CMS) and assumed mode method are applied to obtain the free vibration results of the blade-hub rotor. By employing the finite element method, the theoretical model and analysis is verified. Finally, special attention is given to the influence of the material parameters (GPL distribution pattern, GPL weight fraction, GPL length-to-thickness ratio and GPL length-to-width ratio) and structural parameters (blade pre-twist angle and blade setting angle) on the free vibration frequency of the composite blade-hub rotor system.
由于重量轻、机械性能好,旋转叶片-轮毂组件被广泛应用于航空发动机、燃气轮机等现代旋转机械中。本文对石墨烯纳米片(GPL)增强的带设定角的功能分级(FG)预扭转叶片-轮毂转子结构进行了理论建模和振动分析,其中轮毂和叶片分别以弹性圆柱壳和板为模型。为了提高结构刚度,叶片-轮毂(板-圆柱壳)组件由石墨烯纳米片(GPL)增强材料和聚合物基质制备而成。在板和圆柱形外壳中考虑了均匀和不均匀的 GPL 分布,从而得到了 FG 组件。通过 Halpin-Tsai 模型和混合物规则确定,有效材料特性沿板和圆柱形外壳的厚度方向连续变化。根据基尔霍夫板理论和唐奈壳理论,利用拉格朗日方程推导出 FG 旋转叶片-轮毂组件的耦合运动方程。此外,还应用了组件模态综合法(CMS)和假定模态法来获得叶片-轮毂转子的自由振动结果。通过采用有限元方法,对理论模型和分析进行了验证。最后,特别关注了材料参数(GPL 分布模式、GPL 重量分数、GPL 长厚比和 GPL 长宽比)和结构参数(叶片预扭角和叶片设置角)对复合材料叶片-轮毂转子系统自由振动频率的影响。
Free vibration of thin, creased elastic plates: Optimization and scaling laws
Vijayachandran Avinkrishnan A., Oudghiri-Idrissi Othman, Danawe Hrishikesh, Mao Xiaoming, Arruda Ellen, Tol Serife, Waas Anthony M.
doi:10.1016/j.tws.2023.111393
皱褶弹性薄板的自由振动:优化和缩放定律
Creasing, crumpling, and folding help to increase the flexural rigidity of thin elastic plates. In this study, the fundamental frequency is used as a measure of improvement in flexural stiffness. Firstly, an analysis of an orderly, creased, thin elastic plate with nine separate pyramidal crumples is presented. Such a plate shows an increase of 124% in the fundamental frequency with only a 0.5% increase in the total mass/ surface area when compared to that of a flat configuration. Further, scaling laws are introduced for such ordered creased structures for three separate cases- scaling based on (i) the total surface area of the structure, (ii) the amplitude/ height of the ordered pyramidal crumples, and (iii) the number of unit cells within a given edge length of the plate. Further, an optimization problem is posed to achieve maximum flexural stiffness under given constraints for an additively manufactured thin, elastic plate supported on all four edges. The objective is posed as a constrained optimization problem maximizing the fundamental frequency of the structure compared to that of a flat sheet. The results are promising, with a 176% increase in stiffness with only a 0.84% increase in the total mass/ surface area.
压痕、皱褶和折叠有助于提高弹性薄板的抗弯刚度。在本研究中,基频被用来衡量抗弯刚度的改善程度。首先,我们分析了一个有序折皱、带有九个独立金字塔形皱褶的弹性薄板。与平面结构相比,这种板的基频提高了 124%,而总质量/表面积仅增加了 0.5%。此外,还针对三种不同的情况为这种有序皱褶结构引入了缩放定律--缩放基于 (i) 结构的总表面积,(ii) 有序金字塔皱褶的振幅/高度,以及 (iii) 板给定边长内的单元格数量。此外,还提出了一个优化问题,即在给定约束条件下,使加成法制造的四边都有支撑的弹性薄板达到最大挠曲刚度。与平板相比,该问题的目标是使结构的基频最大化。结果很有希望,在总质量/表面积仅增加 0.84% 的情况下,刚度增加了 176%。