今日更新：International Journal of Solids and Structures 1 篇，Mechanics of Materials 2 篇，International Journal of Plasticity 1 篇，Thin-Walled Structures 4 篇
International Journal of Solids and Structures
Legendre-based node-dependent kinematics shell models for the global-local analysis of homogeneous and layered structures
E. Carrera, A. Pagani, D. Scano
doi:10.1016/j.ijsolstr.2023.112630
基于 Legendre 的节点运动学壳模型，用于均质结构和层状结构的全局-局部分析
The present work demonstrates the use of the node-dependent kinematics method to derive and compare several two-dimensional shell theories. The three dimensional displacement field is expressed in terms of generalized coordinates, which are subsequently expanded along the shell thickness using arbitrary functions. The in-plane unknowns, are then discretized through classical finite element approximation. Based on the Carrera Unified Formulation, the proposed method combines in a unique manner the theory of structures and the finite element method; thickness interpolation functions are defined node-wise. As a consequence, the resulting finite element model represents diverse approximation theories at each single node. In this work Taylor-based kinematics (including the Murakami Zig-Zag function) and Legendre-type nodal kinematics are incorporated at the element level without adopting mathematical artifices leading to the global-local strategy, where refined theories are selectively employed in specific areas, while maintaining acceptable computational costs. Numerical cases from the existing literature are employed to establish the effectiveness of node-dependent models in bridging a locally refined theories to global kinematics when local effects need to be considered. The analyses focus on localized loads for both homogeneous and multi-layered structures.
In recent years, van der Waals (vdW) heterostructures and homostructures, which consist of stacks of two-dimensional (2D) materials, have risen to prominence due to their association with exotic quantum phenomena originating from correlated electronic states harbored by them. Atomistic scale relaxation effects play an extremely important role in the electronic scale quantum physics of these systems, providing means of manipulation of these materials and allowing them to be tailored for emergent technologies. We investigate such structural relaxation effects in this work using atomistic and mesoscale models, within the context of twisted bilayer graphene — a well-known heterostructure system that features moiré patterns arising from the lattices of the two graphene layers. For small twist angles, atomic relaxation effects in this system are associated with the natural emergence of interface dislocations or strain solitons, which result from the cyclic nature of the generalized stacking fault energy (GSFE), that measures the interface energy based on the relative movement of the two layers. In this work, we first demonstrate using atomistic simulations that atomic reconstruction in bilayer graphene under a large twist also results from interface dislocations, although the Burgers vectors of such dislocations are considerably smaller than those observed in small-twist systems. To reveal the translational invariance of the heterointerface responsible for the formation of such dislocations, we derive the translational symmetry of the GSFE of a 2D heterostructure using the notions of coincident site lattices (CSLs) and displacement shift complete lattices (DSCLs). The workhorse for this exercise is a recently developed Smith normal form bicrystallography framework. Next, we construct a bicrystallography-informed and frame-invariant Frenkel—Kontorova model, which can predict the formation of strain solitons in arbitrary 2D heterostructures, and apply it to study a heterostrained, large-twist bilayer graphene system. Our mesoscale model is found to produce results consistent with atomistic simulations. We anticipate that the model will be invaluable in predicting structural relaxation and for providing insights into various heterostructure systems, especially in cases where the fundamental unit cell is large and therefore, atomistic simulations are computationally expensive.
Torsional waves in hyperelastic shells: Appearing shock waves and energy dissipation
Sergey V. Kuznetsov
doi:10.1016/j.mechmat.2023.104905
超弹性壳中的扭转波：冲击波的出现和能量耗散
Nonlinear torsional waves propagating in cylindrical shells made of hyperelastic material obeying Ogden model, are studied by a combined approach comprising theoretical and finite element analysis. It was found, apparently for the first time, that delta-like pulses of torsional waves attenuate with distance due to the appearance of shock wave fronts. Moreover, both strain and kinetic mechanical energy dissipate due to the release of thermal energy.
Yield criterion for intergranular void coalescence under combined tension and shear
C. Sénac, J. Hure, B. Tanguy
doi:10.1016/j.ijplas.2023.103864
拉伸和剪切联合作用下晶粒间空隙凝聚的屈服准则
Intergranular ductile fracture is a failure mode that may arise in many metallic alloys used in industrial applications. It manifests as the successive nucleation, growth, and coalescence of cavities at grain boundaries. Thus, simulation of intergranular ductile fracture in polycrystals requires modeling those three different stages at the scale of grain boundaries, i.e. at the interface between two different crystals. In this study, a yield criterion for the coalescence of cavities at the interface between two isotropic materials obeying Mises plasticity is first developed by limit analysis in order to provide some insights into that phenomenon. This criterion is checked against numerical limit analysis under combined tension and shear and is found to agree with unit-cell simulations quantitatively. The model is then extended to crystals so as to account for the complex coupling between loading state, crystallographic orientations, and void microstructure in intergranular coalescence. This second criterion is also assessed through comparisons to numerical limit analysis for an FCC crystal lattice. The agreement is very good in the case of coalescence by internal necking and the trends displayed by coalescence under combined tension and shear are captured correctly. Some implications of the model on the competition between transgranular and intergranular ductile fracture are discussed. Finally, by combining this model with an existing criterion for void growth at grain boundaries, a multi-surface yield function relevant to intergranular ductile fracture is obtained and compared to unit-cell simulations.
Thermal conductivity and nonreciprocity in wrinkled monolayer graphene ring
Bohan Li, Qingxiang Ji, Jinliang Wang, Changguo Wang, Muamer Kadic
doi:10.1016/j.tws.2023.111523
皱褶单层石墨烯环的导热性和非互易性
We explore an external tunable approach to produce thermal nonreciprocity, by means of controlling wrinkle characteristics in graphene rings. The wrinkling formation and evolution law of graphene rings under torsional deformation is studied. Results show that wrinkle patterns of monolayer graphene can be flexibly tuned by controlling mechanical torsion. We further study the dependence of graphene rings’ thermal conductivity on sizes, temperatures and torsional angles, and reveal the influential mechanism by phonon density of states. Specifically, the thermal conductivity is reduced by 20.4% when the torsional angle increases from θ=0° to θ=10.3°. Finally, nonreciprocal conductive heat transfer is demonstrated in torsion-wrinkled graphene rings. It is found that thermal nonreciprocity effect is dependent on both torsional angles and temperature differences, i.e., the thermal nonreciprocity factor increase from 1.9% to 4.5% as temperature difference varies from 100K to 400K under torsional angle θ=6.9°. Our work paves new avenues for the design and implementation of thermal metadevices by mechanical tuning approach.
AXIAL COMPRESSIVE BEHAVIOR OF THE CHORD IN HYBRID FRP-CONCRETE-STEEL DOUBLE-SKIN TUBULAR MEMBER T-JOINTS
Guan Lin, Junjie Zeng, Jiaxing Li, G.M. Chen
doi:10.1016/j.tws.2023.111535
钢-混凝土混合结构双层管状构件 T 型接头弦杆的轴向受压行为
Hybrid fiber reinforced polymer (FRP)-concrete-steel double-skin tubular members (DSTMs) are a promising form of structural members with superior mechanical performance and durability, which have great potential for application in ocean structures. Such hybrid DSTMs consist of three components: an inner steel tube, an outer FRP tube, and concrete filled between the two tubes. Despite a significant number of studies demonstrating the excellent performance of hybrid DSTMs, no studies have been concerned with the joints of these members. The lack of a reliable design method for DSTM joints is certainly a huge obstacle to their wide application in practice. Against the above background, a research project has been proposed to understand the static behavior of circular DSTM T-joints through a combined experimental, modeling, and theoretical study. This paper presents the results of an experimental program on the axial compressive behavior of the chord in DSTM T-joints. The effects of various important factors, such as FRP tube thickness, steel tube thickness, brace-to-chord diameter ratio, void ratio, and concrete strength, on the performance of the DSTM T-joints were examined in detail. The test results demonstrated that the DSTM T-joints exhibited a ductile behavior provided that the joint region was appropriately strengthened and the presence of a brace did not significantly affect the compressive behavior of the chord in the joints with a brace-to-chord diameter ratio of 0.5. Finally, a simple method was proposed to predict the axial load-axial strain behavior of the DSTM T-joints.
混合纤维增强聚合物（FRP）-混凝土-钢双层管状构件（DSTM）是一种很有前途的结构构件形式，具有优异的机械性能和耐久性，在海洋结构中的应用潜力巨大。这种混合 DSTM 由三部分组成：内钢管、外玻璃钢管和填充在两根钢管之间的混凝土。尽管有大量研究表明混合 DSTM 性能卓越，但还没有研究涉及这些构件的连接问题。缺乏可靠的 DSTM 接头设计方法无疑是 DSTM 在实践中广泛应用的巨大障碍。在上述背景下，我们提出了一个研究项目，通过实验、建模和理论相结合的研究来了解圆形 DSTM T 型接头的静态行为。本文介绍了 DSTM T 型接头中弦杆轴向受压行为的实验结果。详细研究了玻璃钢管厚度、钢管厚度、支撑与弦直径比、空隙率和混凝土强度等各种重要因素对 DSTM T 型连接性能的影响。试验结果表明，DSTM T 型接头表现出延展性，前提是接头区域得到了适当的加固，并且在支撑与弦直径比为 0.5 的接头中，支撑的存在不会对弦杆的抗压性能产生显著影响。最后，提出了一种简单的方法来预测 DSTM T 型接头的轴向载荷-轴向应变行为。
Tailored twisted CNT bundle with improved inter-tube slipping performances
Danyang Zhao, Xing Quan Wang, Lik-ho Tam, Cheuk Lun Chow, Denvid Lau
doi:10.1016/j.tws.2023.111536
改进了管间滑移性能的定制扭曲碳纳米管束
The exceptional mechanical properties of carbon nanotubes (CNTs) have encouraged the development of high-performance synthetic fibers in composite materials. To understand the effect of twisting on the mechanical and slipping performances of CNT bundles, molecular dynamics simulation is applied to investigate the tensile performances, failure mode, and pull-out responses of twisted CNT bundles. A molecular model comprising nineteen parallel aligned single-walled carbon nanotubes (SWCNTs) is twisted into bundles at angles of 0°, 10°, and 20°, and further tensile and pull-out simulations are performed. The tensile simulation indicates that compared with the non-twisted CNT bundle showing a tensile strength of about 82 GPa with obvious inter-tube slipping, the 10°-twisted bundle exhibits a tensile strength of approximately 70 GPa with SWCNTs fracture as the main failure mode, which indicates that twisting improves the inter-tube slipping performance without causing excessive strength reduction. Comparatively, when the twisting angle is 20°, no inter-tube slipping is observed and the tensile strength of the CNT bundle is measured to be 55 GPa, which decreases by approximately 32.9 %. The pull-out simulations further reveal that the pull-out forces increase as the twisting angle increases and the weakened bundle strength of twisted bundle is attributed to the repulsive van der Waals forces caused by the reduced distances between inter-tubes. Essentially, twisting is unfavorable for the overall mechanical strength while torsional densification mitigates the inter-tube slipping, which indicates that a trade-off need to be achieved. This paper provides insights into the tensile and slipping performances of twisted CNT bundles and forms a basis for enhancing the assembled CNTs bundle as the next-generation reinforcing phase in composite materials.
This paper presents a study on the characterization of low-velocity and low-energy impact responses of elastic-plastic plate struck by elastic-plastic spherical impactor. The applicability of the existing impact characterization diagram is examined firstly by intensive finite element (FE) simulations for a wide range of complicated impact situations including all three types of contact: indentation, flattening and combined flattening and indentation. The limitations of the existing diagram are found in identifying the type of impact response and predicting the maximum impact force for complicated impact situations. The effects of elastic and plastic deformations of impactor on the identification and prediction by the existing diagram are analyzed. A new linear contact law is presented according to the piecewise linear characteristics of contact stiffness observed from the intensive FE results. An extended impact characterization diagram is then proposed to characterize low-velocity and low-energy impact responses of plate under complicated impact situations with arbitrary three contact types. The extended diagram is validated by the intensive FE simulations and experimental results. It is concluded that the extended impact characterization diagram can identify correctly the plate response type to complicated impacts and predict accurately the maximum impact force in a fast and simple way without the aid of FE models and experimental tests.
本文研究了弹性塑料板在受到弹性塑料球形冲击器撞击时的低速和低能冲击响应特征。首先通过密集的有限元（FE）模拟，考察了现有撞击表征图的适用性，模拟了各种复杂的撞击情况，包括所有三种接触类型：压痕、压扁以及压扁和压痕组合。现有图表在确定冲击响应类型和预测复杂冲击情况下的最大冲击力方面存在局限性。分析了冲击器的弹性和塑性变形对现有图表识别和预测的影响。根据从强化 FE 结果中观察到的接触刚度的片状线性特征，提出了一种新的线性接触定律。然后提出了一个扩展的撞击特征图，以描述板材在任意三种接触类型的复杂撞击情况下的低速和低能撞击响应。强化 FE 仿真和实验结果对扩展图进行了验证。结论是，扩展的撞击特征图可以正确识别板材对复杂撞击的响应类型，并以快速、简单的方式准确预测最大撞击力，而无需借助有限元模型和实验测试。
