【新文速递】2023年11月24日固体力学SCI期刊最新文章

今日更新：International Journal of Solids and Structures 1 篇，Mechanics of Materials 2 篇，International Journal of Plasticity 3 篇，Thin-Walled Structures 3 篇

International Journal of Solids and Structures

The fracture failure modelling of three-dimensional structures composed of quasi-brittle materials subjected to different loading velocities rates by the dipole-based BEM approach

Luís Philipe Ribeiro Almeida, Edson Denner Leonel

doi:10.1016/j.ijsolstr.2023.112595

通过基于偶极子的 BEM 方法，建立准脆性材料组成的三维结构在不同加载速度下的断裂破坏模型

This study presents a numerical formulation for representing the fracture-failure of three dimensional structures composed of quasi-brittle materials. In addition to the nonlinear nature of quasi-brittle fracture, the formulation accounts the mechanical effects of different loading velocities rates. Therefore, these developments enable the modelling of viscous-cohesive fracture processes. The Boundary Element Method (BEM) describes the mechanical fields by the dipole-based approach, which has been extended to the three dimensional problems herein. This BEM approach is effective in crack growth modelling because only one crack surface requires discretisation. The classical cohesive crack approach models the material resistance at the energy dissipation zone surrounding the crack front. Besides, a time dependent function updates the cohesive crack approach and incorporates the viscous behaviour by modifying the tensile material strength and the material fracture energy as a function of the loading velocity rate. Three applications demonstrate the adequate performance of the proposed formulation, in which the results obtained the BEM have been compared against analytical and experimental responses available in the literature.

本研究提出了一种表示由准脆性材料组成的三维结构断裂-失效的数值公式。除了准脆性断裂的非线性性质外，该公式还考虑了不同加载速度的机械效应。因此，这些发展使得粘聚断裂过程的建模成为可能。边界元素法（BEM）通过基于偶极子的方法来描述机械场，该方法已扩展到此处的三维问题。这种 BEM 方法在裂纹生长建模中非常有效，因为只需要对一个裂纹表面进行离散化处理。经典的内聚裂缝方法对裂缝前沿周围能量耗散区的材料阻力进行建模。此外，随时间变化的函数更新了内聚裂纹方法，并通过修改拉伸材料强度和材料断裂能作为加载速度的函数，将粘性行为纳入其中。三个应用案例证明了所建议的计算方法性能良好，其中 BEM 得出的结果与文献中的分析和实验结果进行了比较。

Mechanics of Materials

Isolated disclination in an orthotropic von Kármán elastic plate

Saptarshi Paul, Anurag Gupta

doi:10.1016/j.mechmat.2023.104869

正交冯卡尔曼弹性板中的孤立偏析

We investigate geometry and mechanics of the buckled orthotropic von Kármán elastic plate, with free boundary condition, in the presence of an isolated positive, or negative, disclination. The buckled shape of an isotropic elastic plate is cone-like for a positive disclination or saddle-like for a negative disclination. In either case, with increasing orthotropy, the shape of the buckled plate becomes more tent-like. The Gaussian curvature accordingly spreads along the ridge of the tent. The stress fields too remain focused in the neighbourhood of the defect point and the ridge, indicating that most of the stretching energy is accommodated in these singular regions.

我们研究了具有自由边界条件的正交各向同性 von Kármán 弹性板在孤立的正或负倾角存在下的屈曲几何和力学。各向同性弹性板的屈曲形状在正离散时为锥形，在负离散时为鞍形。无论哪种情况，随着各向同性的增加，屈曲板的形状会变得更像帐篷。高斯曲率相应地沿着帐篷的脊扩展。应力场也仍然集中在缺陷点和脊的附近，这表明大部分拉伸能量都集中在这些奇异区域。

Viscoelastic-damage constitutive model and mechanical characterizations of Aluminium/polytetrafluoroethylene under impact loading

Huilan Ren, Han Zhao, Jianguo Ning

doi:10.1016/j.mechmat.2023.104871

铝/聚四氟乙烯在冲击荷载下的粘弹性-损伤构成模型和机械特性分析

As a typical structural energy-containing material, aluminium/polytetrafluoroethylene (Al/PTFE) exhibits excellent mechanical properties under conventional conditions and releases large amounts of energy through chemical reactions under impact loading. In this research, a viscoelastic-damage constitutive model suitable for polymer-based reactive materials was developed, which consisted of an elastic element, two Maxwell elements, and a SCRAM damage element. The effect of damage on the stress–strain relationship was obtained by analysing the crack evolution process and deformation field. A modified Split Hopkinson pressure bar experiment investigated the mechanical characteristics of aluminium/polytetrafluoroethylene under uniaxial/multiaxial impact loading. The results indicated that the viscoelastic-damage constitutive model could describe the effects of the initial crack size and initial crack density on the mechanical properties of aluminium/polytetrafluoroethylene. With the decrease in initial crack length and density, the damage to the aluminium/polytetrafluoroethylene under impact loading was limited, which caused the dynamic mechanical properties to increase. When the pre-stress increases from 0 MPa to 10 MPa, the dynamic ultimate compressive stress of aluminium/polytetrafluoroethylene increases from 77.2 MPa to 89.8 MPa at 2910 s−1 strain rate. A comparison of the experimental and calculated strain-stress curves shows that the established constitutive model is feasible to predicting the mechanical behaviour of aluminium/polytetrafluoroethylene.

作为一种典型的含能结构材料，铝/聚四氟乙烯（Al/PTFE）在常规条件下具有优异的机械性能，而在冲击载荷下则会通过化学反应释放出大量能量。本研究建立了一个适合聚合物基反应材料的粘弹性-损伤构成模型，该模型由一个弹性元件、两个麦克斯韦元件和一个 SCRAM 损伤元件组成。通过分析裂纹演变过程和变形场，得出了损伤对应力应变关系的影响。改进的斯普利特-霍普金森压力棒实验研究了铝/聚四氟乙烯在单轴/多轴冲击载荷下的机械特性。结果表明，粘弹性-损伤构成模型可以描述初始裂纹尺寸和初始裂纹密度对铝/聚四氟乙烯力学性能的影响。随着初始裂纹长度和密度的减小，铝/聚四氟乙烯在冲击荷载作用下的损伤受到限制，从而导致其动态力学性能增加。当预应力从 0 兆帕增加到 10 兆帕时，在应变速率为 2910 s-1 时，铝/聚四氟乙烯的动态极限压缩应力从 77.2 兆帕增加到 89.8 兆帕。实验和计算应变-应力曲线的比较表明，所建立的构成模型可用于预测铝/聚四氟乙烯的机械性能。

International Journal of Plasticity

Kinetic nature of electrochemical plasticization

Jianyun Yan, Tijun Chen, Emmanuel M. Gutman, Yakov B. Unigovski

doi:10.1016/j.ijplas.2023.103820

电化学塑化的动力学性质

The electrochemical plasticization (EP) of metallic materials has been known for decades, but the underlying mechanisms, especially the kinetic mechanisms, remain unclear. Herein, the kinetic nature of EP has been investigated by employing the electrochemical cold drawing of single-crystal copper (in a 0.35 mol L−1 dilute sulfuric acid aqueous electrolyte and with a current density of 0.67 × 10−2 A cm−2) through microstructural characterizations and reactive force field molecular dynamic simulations. The results intuitively reveal that the surface-loosened atoms, due to the selective corrosion dissolution, acts as the sources of dislocations to accelerate the formation of dislocations in a multi-slip manner, which then rapidly move toward the inside, and react with the internal early-formed dislocations to undergo abnormal slip of Lomer-Cottrell locks, cross-slip, and annihilation, leading the dislocation entanglements to reconfigure into the movable short-range wavy dislocations and their density to reduce, thus resulting in the softening and the weakening of work-hardening. These findings provide in-depth insights into the kinetic mechanism of EP, which will inevitably accelerate the development and engineering applications of new metal processing technologies based on EP as well as get a deeper understanding of stress corrosion cracking.

金属材料的电化学塑化（EP）已有几十年的历史，但其基本机制，尤其是动力学机制仍不清楚。本文采用单晶铜（在 0.35 mol L-1 稀硫酸水溶液电解液中，电流密度为 0.67 × 10-2 A cm-2）的电化学冷拔，通过微结构表征和反应力场分子动力学模拟研究了 EP 的动力学性质。结果直观地显示，由于选择性腐蚀溶解，表面松动的原子成为位错的来源，以多滑移的方式加速位错的形成，然后位错迅速向内部移动、并与内部早期形成的位错发生反应，发生 Lomer-Cottrell 锁的异常滑移、交叉滑移和湮灭，导致位错纠缠重构为可移动的短程波浪形位错，其密度降低，从而导致软化和加工硬化减弱。这些发现深入揭示了 EP 的动力学机制，必将加速基于 EP 的新型金属加工技术的开发和工程应用，并加深对应力腐蚀开裂的理解。

Improving ductility by coherent nanoprecipitates in medium entropy alloy

Zihan Zhang, Yan Ma, Muxin Yang, Ping Jiang, Hangqi Feng, Yuntian Zhu, Xiaolei Wu, Fuping Yuan

doi:10.1016/j.ijplas.2023.103821

通过相干纳米沉淀物提高中熵合金的延展性

Controlling precipitates in spatial density and size distribution is essential for tailoring the microstructure and mechanical properties through precipitation hardening. We herein obtained heterogeneous grain structures with coherent L12 nanoprecipitates in (CrCoNi)94Al4Ti2 medium entropy alloy (MEA) by annealing and aging. Additional pre-aging leads to a high spatial density and more random distribution nucleation sites of the coherent L12 nanoprecipitates. The pre-aging doubled the ductility without apparently sacrificing the strength. Transmission electron microscopy (TEM) revealed that, in pre-aged MEA, finely dispersed L12 nanoprecipitates with higher spatial density were sheared by dislocation, promoting planar slips, which favors geometrically necessary dislocations (GNDs) piling up to increased hetero-deformation-induced (HDI) stress and work-hardening. Stacking faults, Lomer-Cottrell locks, and 9R structures were formed in aged and pre-aged MEA after tensile deformation. The formation of these defects enormously enhanced strain hardening by blocking dislocation movements and accumulating dislocations. Moreover, a higher frequency of interactions between defects and coherent L12 nanoprecipitates can be observed in the pre-aged MEA due to the more randomly distributed L12 nanoprecipitates, substantially increasing ductility. This work demonstrates a new route to achieving a super strength-ductility combination of single-phase FCC high entropy alloys by nanoscale coherent precipitation strengthening.

控制沉淀物的空间密度和尺寸分布对于通过沉淀硬化定制微观结构和机械性能至关重要。在此，我们通过退火和时效处理，在 (CrCoNi)94Al4Ti2 中熵合金 (MEA) 中获得了具有相干 L12 纳米析出物的异质晶粒结构。额外的预时效会导致相干 L12 纳米沉淀的空间密度更高，成核点分布更随机。预时效增加了一倍的延展性，但显然没有牺牲强度。透射电子显微镜（TEM）显示，在预时效 MEA 中，空间密度较高的细小分散 L12 纳米沉淀被位错剪切，促进了平面滑移，这有利于几何必要位错（GNDs）堆积，增加异变形诱导应力（HDI）和加工硬化。拉伸变形后，在老化和预老化 MEA 中形成了堆积断层、Lomer-Cottrell 锁和 9R 结构。这些缺陷的形成通过阻止位错运动和位错累积，极大地增强了应变硬化。此外，在预老化 MEA 中，由于 L12 纳米沉淀物的分布更加随机，可以观察到缺陷与相干 L12 纳米沉淀物之间更高频率的相互作用，从而大大提高了延展性。这项研究为通过纳米级相干沉淀强化实现单相 FCC 高熵合金的超强度-延展性组合提供了一条新途径。

Understanding extra strengthening in gradient nanotwinned Cu using crystal plasticity model considering dislocation types and strain gradient effect

Xiangru Guo, Jian Zhang, Tieqiang Kong, Ningdong Mao, Chaoyang Sun, Yinan Cui, Zhiping Xiong

doi:10.1016/j.ijplas.2023.103822

利用考虑了位错类型和应变梯度效应的晶体塑性模型理解梯度纳米缠绕铜的额外强化

Gradient nanotwinned (GNT) Cu, composed of various homogeneous nanotwinned (HNT) components, successfully achieves the synergistic enhancement of strength and ductility due to the combined advantages of gradient and nanotwinned structures. However, the complicated dislocation-twin boundary (TB) interactions in each HNT component and extra strengthening mechanism in GNT Cu remain elusive. In this study, a crystal plasticity model, which takes into account the reaction characteristics of various dislocation types at the TB and the extra size dependent geometrically necessary dislocations (GNDs) induced by plastic strain gradients, is developed for understanding both HNT and GNT Cu. The developed model successfully captures the mechanical behavior and microstructure evolution of HNT Cu with different TB orientations and grain sizes (and twin thicknesses). The simulation results emphasize the importance of incorporating dislocation types when describing dislocation-TB interactions. Furthermore, the intrinsic mechanism for the extra strengthening in the GNT Cu is revealed through the analysis of deformation contours and microstructural evolutions. The results show that the HNT components with the lower original strength have the higher extra back stress increment with the increase of structural gradient. This study provides valuable insights into predicting and further optimizing the strength of the GNT Cu through manipulating the gradient microstructure.

梯度纳米孪晶（GNT）铜由多种均质纳米孪晶（HNT）成分组成，由于梯度结构和纳米孪晶结构的综合优势，它成功地实现了强度和延展性的协同增强。然而，各 HNT 成分中复杂的位错-孪晶边界（TB）相互作用以及 GNT Cu 中的额外强化机制仍未得到阐明。本研究建立了一个晶体塑性模型，该模型考虑了 TB 上各种位错类型的反应特性以及塑性应变梯度诱发的与尺寸相关的额外几何必要位错（GND），用于理解 HNT 和 GNT 铜。所开发的模型成功捕捉到了具有不同 TB 取向和晶粒大小（以及孪晶厚度）的 HNT 铜的机械行为和微观结构演变。模拟结果强调了在描述位错-TB 相互作用时纳入位错类型的重要性。此外，通过对变形轮廓和微结构演变的分析，还揭示了 GNT 铜额外强化的内在机制。结果表明，随着结构梯度的增加，原始强度较低的 HNT 成分具有较高的额外背应力增量。这项研究为通过操纵梯度微结构预测和进一步优化 GNT 铜的强度提供了有价值的见解。

Thin-Walled Structures

Effects of CNT microstructural characteristics on the interfacial enhancement mechanism of carbon fiber reinforced epoxy composites via molecular dynamics simulations

Muhan Zhang, Yalin Yu, Yihao Luan, Helezi Zhou, Xiongqi Peng, Luyang Gong, Huamin Zhou

doi:10.1016/j.tws.2023.111413

通过分子动力学模拟研究碳纳米管微结构特性对碳纤维增强环氧树脂复合材料界面增强机制的影响

Numerous studies have concentrated on improving the mechanical properties of carbon fiber reinforced polymer composite (CFRP) through the modification of carbon fiber (CF) with carbon nanotubes (CNTs). However, most of them were confined to describing experimental phenomena. In this study, molecular dynamics (MD) simulation was used to systematically reveal the effect of CNT nanostructures on the interfacial reinforcement of CF/epoxy. An all-atom modelling method was used to provide a quantitative description of the CF-CNT/polymer interface characteristic structure. Computational results indicate that nanotubes can protect the intra- and intermolecular interactions of epoxy segments from being destroyed, thereby preventing the initiation and propagation of micro-defects during interfacial deterioration. The mechanical competition between the interface and polymer bulk leads to different failure mechanisms, and the strengthened interface region has fewer atoms leaving the equilibrium state during tensile deformation. The insertion of CNTs on the fiber surface, specifically increasing their length, diameter, distribution density, and orientation, can improve interfacial tensile strength (up to +62.11%) and delay the detachment of epoxy molecules from the CF. Additionally, MD outcomes were verified by synthesizing CNTs onto CF using an electric field-assisted flame synthesis approach, leading to improvement in IFSS (+62.67 %) and ILSS (+27.78 %).

通过对碳纤维（CF）进行碳纳米管（CNTs）改性来提高碳纤维增强聚合物复合材料（CFRP）的机械性能是众多研究的重点。然而，这些研究大多局限于描述实验现象。本研究采用分子动力学（MD）模拟系统揭示了碳纳米管纳米结构对 CF/ 环氧树脂界面加固的影响。采用全原子建模方法对 CF-CNT/ 聚合物界面特征结构进行了定量描述。计算结果表明，纳米管可以保护环氧片段的分子内和分子间相互作用不被破坏，从而防止界面劣化过程中微缺陷的产生和传播。界面和聚合物体之间的机械竞争导致了不同的破坏机制，而强化后的界面区域在拉伸变形过程中离开平衡态的原子数量更少。在纤维表面插入碳纳米管，特别是增加其长度、直径、分布密度和取向，可以提高界面拉伸强度（最高可达 +62.11%），并延缓环氧分子从 CF 上脱离。此外，利用电场辅助火焰合成法在 CF 上合成 CNT 也验证了 MD 的结果，从而提高了 IFSS（+62.67 %）和 ILSS（+27.78 %）。

Cold-formed steel strength predictions for torsion and bending-torsion interaction

Yu Xia, Robert S. Glauz, Benjamin W. Schafer, Michael Seek, Hannah B. Blum

doi:10.1016/j.tws.2023.111367

扭转和弯曲扭转相互作用下的冷弯型钢强度预测

Locally slender cross-section members, such as cold-formed steel open sections, are susceptible to significant twisting and high warping torsion stresses. Torsion considerations are complicated by whether it is derived as a first-order effect from loading or a second-order effect from instability. Previous direct torsion experiments on lipped Cee sections have shown significant inelastic reserve. Furthermore, the current design for combined bending-torsion interaction has limitations, including only considering the first yield and ignoring the cross-section slenderness in torsion. Two parametric studies were conducted to predict both the torsion capacity and the combined bending-torsion interaction in locally slender cross-sections. Shell finite element analysis of lipped Cee and Zee sections for both the torsion only and the combined bending-torsion cases were created using a validated model. For the torsion-only study, various cross-section geometries, steel grades, and member lengths covering the range of practically expected torsional slenderness were investigated. A set of bimoment parameters, including yield, buckling, and plastic bimoments, were calculated and the ultimate bimoment was determined by shell finite element collapse analyses. A simple uniform equation predicting the bimoment capacity was adopted and two bimoment strength curves are proposed for local and distortional buckling-controlled cases respectively. For the combined bending-torsion case, various practical cross-sections and bracing conditions were investigated with various ratios of applied torsion and bending. Shell finite element buckling and collapse analyses were performed to determine the critical and ultimate moments and bimoments. It was found that the current AISI standard is conservative under most scenarios. Updated torsion-bending interaction equations incorporating bimoment and bending moments are proposed. The interaction equations are dependent on the cross-section, the direction of the applied torsion, and the bracing condition.

局部细长截面的构件，例如冷弯型钢开口型钢，很容易受到明显扭曲和高翘曲扭转应力的影响。由于扭转是由加载产生的一阶效应还是由不稳定性产生的二阶效应，因此扭转的考虑变得复杂。以前对有唇 Cee 截面进行的直接扭转实验显示，非弹性储备量很大。此外，目前的弯曲-扭转联合作用设计也有局限性，包括只考虑第一次屈服和忽略扭转时的横截面细长度。我们进行了两项参数研究，以预测局部细长横截面的抗扭能力和组合弯曲-扭转相互作用。利用一个经过验证的模型，对仅有扭转和弯曲-扭转组合情况下的有边 Cee 和 Zee 截面进行了壳体有限元分析。在纯扭转研究中，研究了各种截面几何形状、钢材等级和构件长度，涵盖了实际预期的扭转纤度范围。计算了一组双弯矩参数，包括屈服双弯矩、屈曲双弯矩和塑性双弯矩，并通过壳体有限元坍塌分析确定了极限双弯矩。采用一个简单的统一方程预测双弯矩能力，并分别针对局部和扭曲屈曲控制情况提出了两条双弯矩强度曲线。对于弯曲-扭转组合情况，研究了各种实用截面和支撑条件，以及不同的扭转和弯曲应用比例。进行了壳体有限元屈曲和坍塌分析，以确定临界力矩和极限力矩以及双矩。结果发现，现行的 AISI 标准在大多数情况下都是保守的。提出了包含双弯矩和弯矩的最新扭转-弯曲相互作用方程。相互作用方程取决于横截面、施加扭力的方向和支撑条件。

Experimentally validated numerical analyses on the seismic responses of extra-large LNG storage structures

Ding-Yuan Zhang, Jian-Ying Wu

doi:10.1016/j.tws.2023.111407

经实验验证的超大型液化天然气储存结构地震响应数值分析

Extra-large liquefied natural gas (LNG) storage tanks are comprised by a steel inner tank and an outer protective tank of prestressed reinforced concrete (PRC), both being very thin. These important lifeline infrastructures are prone to damage and even failure under earthquake during their service life. Convincing numerical simulation, verified by shake table tests, is a feasible tool to quantify the seismic responses and to mitigate the potential damage/failure of LNG storage structures. This work addresses systematically the three-dimensional finite element (FE) modeling, experimental validation and numerical simulations of such structures, with the soil–pile interaction of the foundation, the fluid–structure interaction of the inner tank and damage of the outer tank all properly accounted for. For the sake of computational efficiency with no loss of too much precision, the soil–pile interaction is described by the mass-damper-spring model, and the fluid–structure interaction by the mass–spring model with both the convective and impulsive components accounted for. Moreover, the nonlinear mechanical behavior of concrete is considered by the damaged-plasticity model regularized with the fracture energy. The concrete–steel interaction in PRC is practically dealt with by modifying the constitutive relations of concrete and steel rebars/tendons properly with the equilibrium and compatibility conditions accounted for. The FE modeling strategy is validated against the recently conducted benchmark shaking table test of a scaled extra-large LNG storage structure. The capability in capturing the overall dynamic responses, e.g., the hydrodynamic pressure and structural vibrations under seismic actions, etc., is sufficiently verified. Finally, the dynamic responses and structural reliability of an extra-large LNG storage tank under deterministic and stochastic seismic actions are numerically studied in details.

特大型液化天然气（LNG）储罐由钢制内罐和预应力钢筋混凝土（PRC）外保护罐组成，两者都非常薄。这些重要的生命线基础设施在使用期间很容易在地震中受损甚至失效。通过振动台试验验证的令人信服的数值模拟是量化地震响应和减轻液化天然气储存结构潜在损坏/失效的可行工具。本研究系统地探讨了此类结构的三维有限元（FE）建模、实验验证和数值模拟，地基的土-桩相互作用、内罐的流-结构相互作用以及外罐的损坏都得到了适当的考虑。为了提高计算效率，同时又不损失过多精度，土-桩相互作用采用质量-阻尼-弹簧模型，流-结构相互作用采用质量-弹簧模型，并考虑了对流和冲力成分。此外，混凝土的非线性力学行为是通过断裂能正则化的损伤塑性模型来考虑的。通过适当修改混凝土和钢筋/肌腱的构成关系，并考虑平衡和相容性条件，实际处理了 PRC 中混凝土与钢筋的相互作用。最近对一个超大型液化天然气储存结构进行了基准振动台试验，对有限元建模策略进行了验证。充分验证了模型捕捉整体动态响应的能力，如地震作用下的水动力压力和结构振动等。最后，对超大型 LNG 储罐在确定性和随机地震作用下的动态响应和结构可靠性进行了详细的数值研究。