今日更新:International Journal of Solids and Structures 1 篇,Mechanics of Materials 1 篇,International Journal of Plasticity 1 篇,Thin-Walled Structures 6 篇
Elliptic crack problem under shear mode in one-dimensional hexagonal quasicrystals with crack surface parallel to the quasiperiodic axis
Ruifeng Zheng, Haining Liu, Peidong Li, Zichen Deng
doi:10.1016/j.ijsolstr.2023.112601
裂纹面平行于准周期轴的一维六方准晶体剪切模式下的椭圆裂纹问题
In this work we are concerned with a special elliptic crack problem in one-dimensional hexagonal quasicrystals. The crack surface is assumed to be parallel to the quasiperiodic axis. A couple of anti-symmetrical uniform shear loadings is applied on the crack surfaces. Taking advantage of the potential theory method, we develop the governing integral equation and obtain the phonon-phason field in terms of simple integrals. The crack slip displacement and the stress intensity factor are derived explicitly. Based on the analytical solution, we investigate the effects of phason filed, crack orientation and the eccentricity of elliptic crack on the important fracture parameters. The solutions obtained in this work are helpful to understand the fracture behavior of one-dimensional hexagonal quasicrystals, especially for the situations in which the cracks are not located on the isotropic planes.
在这项研究中,我们关注的是一维六边形准晶体中的特殊椭圆裂纹问题。假设裂纹表面平行于准周期轴。在裂纹表面施加一对反对称均匀剪切载荷。利用势理论方法,我们建立了控制积分方程,并通过简单积分得到了声子声场。裂纹滑移位移和应力强度因子都是明确推导出来的。在分析解的基础上,我们研究了声子滤波、裂纹取向和椭圆裂纹偏心率对重要断裂参数的影响。本研究获得的解有助于理解一维六方准晶体的断裂行为,尤其是裂纹不位于各向同性平面上的情况。
Computational homogenization of linear elastic properties in porous non-woven fibrous materials
Mikhail Kuts, James Walker, Pania Newell
doi:10.1016/j.mechmat.2023.104868
多孔无纺纤维材料线性弹性特性的计算同质化
Porous non-woven fibrous media are widely used in various industrial applications such as filtration, insulation, and medical textiles due to their unique structural and functional properties. However, predicting the mechanical behavior of these materials is challenging due to their complex microstructure and anisotropic nature. In this study, a computational model is developed to simulate the mechanical response of porous non-woven fibrous media under external loading. The model is based on the finite element method and takes into account the geometric and material properties of the fibers and the void spaces between them. The effects of various factors such as fiber size, porosity, and fibers’ intersection ratio on the mechanical behavior of the material are investigated. The results reveal that the material’s porosity and fibers’ intersection ratio are the most significant factors influencing its mechanical properties. Additionally, the increase in fiber diameter has a relatively minor effect on the material’s elastic properties. However, such changes in elastic properties are primarily attributed to the increase in randomness within the fibrous network, which is directly related to the fiber diameter for the investigated structure. The proposed computational model predicts the mechanical properties of porous non-woven fibrous media and can provide invaluable insights into the design and optimization of porous non-woven fibrous media for various scientific and engineering applications.
多孔非织造纤维介质因其独特的结构和功能特性,被广泛应用于过滤、绝缘和医用纺织品等各种工业领域。然而,由于其复杂的微观结构和各向异性,预测这些材料的机械行为具有挑战性。本研究开发了一个计算模型,用于模拟多孔无纺纤维介质在外部负载下的机械响应。该模型基于有限元法,考虑了纤维的几何和材料特性以及纤维之间的空隙。研究了纤维尺寸、孔隙率和纤维交叉比等各种因素对材料力学行为的影响。研究结果表明,材料的孔隙率和纤维交叉比是影响其机械性能的最重要因素。此外,纤维直径的增加对材料弹性性能的影响相对较小。不过,弹性性能的这种变化主要归因于纤维网内部随机性的增加,而随机性的增加与所研究结构的纤维直径直接相关。所提出的计算模型可以预测多孔非织造纤维介质的力学性能,并为设计和优化多孔非织造纤维介质的各种科学和工程应用提供宝贵的见解。
Heterostructure Manipulation of Ti2AlNb Alloy through Directional Induction Heating: Investigation of Multi-Scale Deformation Mechanisms in the O Phase
Zedong Liu, Jieren Yang, Xiaoliang Zhao, Ruirun Chen
doi:10.1016/j.ijplas.2023.103830
通过定向感应加热操纵 Ti2AlNb 合金的异质结构:研究 O 相的多尺度变形机制
In this study, a heterostructure of Ti2AlNb alloy (Ti-22Al-26Nb) was fabricated using directional heating treatment (DHT) technology. The microstructure of the alloy was examined before and after DHT treatment using scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). The primary objective of the study is to investigate the deformation mode and strain hardening mechanism in the multi-scale O phase. The results indicate that DHT treatment leads to a significant refinement in the grain size of the alloy, resulting in a 14.2% increase in ultimate tensile strength (UTS) and a 29.2% increase in elongation. However, the treatment also causes a decrease in yield strength. The soft phase region, characterized by the microstructure with micron-sized O phase precipitates, and the hard phase region, characterized by the microstructure with submicron-sized O phase precipitates, exhibit different modes of strain adjustment. To mitigate the internal stress arising from the deformation mismatch between the soft and hard phases, the micron-sized O phase activates slip on the {110} and {010} planes during the tensile process at room temperature. Additionally, twinning behavior was observed on the {110} plane. On the other hand, the submicron O-phase activates slip on the {041} plane and occurs a crystal rotation of approximately 90 degrees along the 〈012〉and 〈100〉orientations. These high-angle grain boundaries (HAGBs), which form continuously during deformation, effectively store dislocations and contribute to a continuous strain hardening effect in the alloy. Additionally, the alloy exhibits a high strain hardening ability due to the accumulation of geometrically necessary dislocations caused by the strain gradient resulting from the uneven plastic deformation of the soft and hard phase components, as well as the potential hetero deformation-induced (HDI) hardening. Ultimately, a Ti2AlNb alloy with a favorable balance of UTS and elongation was achieved.
本研究采用定向加热处理(DHT)技术制造了一种 Ti2AlNb 合金(Ti-22Al-26Nb)异质结构。使用扫描电子显微镜(SEM)和电子反向散射衍射(EBSD)检查了定向加热处理前后合金的微观结构。研究的主要目的是探究多尺度 O 相的变形模式和应变硬化机制。结果表明,DHT 处理可显著细化合金的晶粒尺寸,使极限拉伸强度 (UTS) 提高 14.2%,伸长率提高 29.2%。不过,这种处理也会导致屈服强度下降。以微米级 O 相析出物微观结构为特征的软相区和以亚微米级 O 相析出物微观结构为特征的硬相区呈现出不同的应变调整模式。在室温拉伸过程中,为了缓解软硬相之间的变形不匹配所产生的内应力,微米级的 O 相在{110}和{010}平面上产生滑移。此外,在{110}面上还观察到了孪晶行为。另一方面,亚微米级的 O 相会激活{041}面上的滑移,并沿 〈012〉和 〈100〉方向发生约 90 度的晶体旋转。这些在变形过程中不断形成的高角度晶界(HAGBs)有效地储存了位错,并在合金中产生了持续的应变硬化效应。此外,由于软硬相成分的不均匀塑性变形所产生的应变梯度以及潜在的异质变形诱导硬化(HDI)所导致的几何必要位错的积累,该合金表现出很高的应变硬化能力。最终,Ti2AlNb 合金实现了 UTS 和伸长率的良好平衡。
Flexural capacity and local buckling half-wavelength of high strength steel tubular beams under moment gradients: an experimental study
Zichang Yang, Xin Meng, Fiona Walport, Leroy Gardner
doi:10.1016/j.tws.2023.111420
弯矩梯度下高强度钢管梁的抗弯能力和局部屈曲半波长:实验研究
An experimental investigation into the effect of moment gradients on the flexural behaviour of hot-rolled high strength steel square hollow section (SHS) beams is presented in this paper. In total, 20 beam specimens in steel grades S690 and S770, and with cross-sections spanning from Class 2 to Class 4 based on the Eurocode 3 slenderness limits, were tested under three- and four-point bending. In the three-point bending tests, the beam spans were varied to achieve a range of moment gradients; the influence of different stiffening arrangements at the loading point was also considered. Local geometric imperfections were measured by means of 3D laser-scanning prior to testing and digital image correlation (DIC) was adopted to monitor the displacement and strain fields at critical regions and to assess the local buckling half-wavelengths of the test specimens for which a consistent measurement approach was proposed. The measured local buckling half-wavelengths were compared against the elastic local buckling half-wavelengths calculated using the finite strip method. It was observed that while the measured local buckling half-wavelengths remained approximately constant up to first yield, a significant reduction in half-wavelength was observed with increasing moment due to the non-uniform spread of plasticity. The comparisons also revealed that the local buckling half-wavelengths reduced with both the presence of moment gradients and intermediate stiffeners, with a new parameter proposed to quantify the local moment gradient. It was shown from the tests that the specimens subjected to moment gradients, despite the presence of shear, exhibited higher ultimate moment capacities (up to 10.5% for stiffened specimens and 3.4% for unstiffened specimens) than those subjected to uniform moments. This is attributed to the delay in the local buckling of the critical cross-section of beams under moment gradients due to the restraint provided by the less heavily stressed adjacent cross-sections.
本文介绍了力矩梯度对热轧高强度方形空心型钢(SHS)梁弯曲性能影响的实验研究。在三点和四点弯曲试验中,共测试了 20 个钢级为 S690 和 S770 的横截面试样,其横截面跨度从 2 级到 4 级(基于欧洲规范 3 的纤度限值)。在三点弯曲试验中,改变了梁的跨度,以实现一系列力矩梯度;还考虑了加载点处不同加劲安排的影响。测试前通过三维激光扫描测量了局部几何缺陷,并采用数字图像相关技术(DIC)监测了关键区域的位移和应变场,评估了测试样本的局部屈曲半波长,并提出了一致的测量方法。将测得的局部屈曲半长与使用有限条带法计算的弹性局部屈曲半长进行了比较。结果表明,虽然测得的局部屈曲半波长在首次屈曲前大致保持不变,但由于塑性扩散不均匀,随着力矩的增加,半波长显著减少。比较结果还显示,局部屈曲半长随力矩梯度和中间加强筋的存在而减小,并提出了一个新参数来量化局部力矩梯度。试验结果表明,尽管存在剪力,但受力矩梯度作用的试样比受均一力矩作用的试样具有更高的极限力矩承载能力(加劲试样高达 10.5%,非加劲试样为 3.4%)。这是因为在弯矩梯度作用下,由于受力较小的相邻截面提供了约束,梁的临界截面局部屈曲发生了延迟。
Fluid-Solid Coupling for Microscale Transport of Nanoparticles in Ultralong Carbon Nanotubes
Jiantao Leng, Tienchong Chang
doi:10.1016/j.tws.2023.111431
超长碳纳米管中纳米粒子微尺度传输的流固耦合
Achieving microscale motion of nanoparticles is crucial for the development of various nanodevices. Here we propose a novel fluid-solid coupling device that leverages a thermally-induced water flow to enable long-range nanoparticle transport within carbon nanotubes (CNTs). Our device comprises an ultralong CNT filled with water, composed of repeated units. Each unit experiences an asymmetrical thermal gradient induced by intentionally incorporating asymmetrical configurations of atomic vacancies on the CNT surface. Through molecular dynamics (MD) simulations, we demonstrate that these repeated units with periodic thermal fields effectively induce a steady water flow, enabling continuous transportation of a nanoparticle (e.g., a C60 fullerene) within the ultralong CNT over microscale distances. Moreover, we reveal that the device can be also designed with various alternative options (e.g., Stone-Wales defects or carbon/boron-nitride heterojunctions). Our proposed device holds promising potential for microscale nanoparticle transport applications.
实现纳米粒子的微尺度运动对于各种纳米器件的开发至关重要。在此,我们提出了一种新型流固耦合装置,利用热诱导水流实现纳米粒子在碳纳米管(CNT)内的长程传输。我们的装置包括一个充满水的超长 CNT,由重复单元组成。通过有意在 CNT 表面加入非对称配置的原子空位,每个单元都会经历非对称的热梯度。通过分子动力学(MD)模拟,我们证明了这些具有周期性热场的重复单元能有效地诱导稳定的水流,从而使纳米粒子(如 C60 富勒烯)在超长 CNT 内的微观距离上持续传输。此外,我们还发现该装置还可以设计成各种替代方案(如石-威尔士缺陷或碳/氮化硼异质结)。我们提出的装置在微尺度纳米粒子传输应用方面具有广阔的前景。
Mechanical properties prediction and design of curved beams by neural network
Junhua Zhang, Xiao Xue
doi:10.1016/j.tws.2023.111434
利用神经网络预测和设计曲线梁的力学性能
It is known that curved beams are used widely in vibration isolation and noise reduction. The curved beam can show bistable, negative stiffness and other mechanical characteristics in the compression process through design. The preflex beam absorbs energy during the multi-state jump process and can recover its initial configuration after undergoing loading and unloading, so it is an ideal energy absorb component. In this paper, preflex beams are designed and the mechanical properties are studied and predicted by neural network. Firstly, a large number of finite element models for sinusoidal preflex beams are built by using Python randomly selected the parameters of beams. Secondly, the dataset corresponding to the parameters of the beams and mechanical properties is established. The variation trend of mechanical properties such as initial stiffness, force threshold, negative stiffness and total absorbed energy with the change of structural parameters and the sensitivity of structural parameters to the above mechanical indexes are obtained. Thirdly, by substituting the data set into the artificial neural network, the trained neural network can predict the mechanical properties of the beams within the allowable error range. At last, a new type of preflex beam with porous section is proposed in order to optimize the specific absorbed energy of the preflex beam. After data screening and optimization, the specific absorbed energy of the porous preflex beam is increased by 15.56% compared with the beam whose section without porous. The results obtained show that the data-driven method can greatly shorten the structural design time and expand the design space. This study will provide a theoretical basis for the wider application of preflex beams in engineering field.
众所周知,曲线梁在隔振和降噪方面应用广泛。通过设计,曲线梁在压缩过程中可表现出双稳态、负刚度等力学特性。预弯梁在多态跃变过程中吸收能量,并能在加载和卸载后恢复初始构型,是一种理想的吸能部件。本文设计了预弯梁,并利用神经网络对其力学性能进行了研究和预测。首先,通过 Python 随机选择梁的参数,建立了大量正弦波预弯梁的有限元模型。其次,建立与梁参数和力学性能相对应的数据集。得出初始刚度、力阈值、负刚度和总吸收能量等力学性能随结构参数变化的变化趋势,以及结构参数对上述力学指标的敏感性。第三,将数据集代入人工神经网络,经过训练的神经网络可以在允许误差范围内预测梁的力学性能。最后,为了优化预弯梁的比吸收能量,提出了一种新型多孔预弯梁。经过数据筛选和优化,多孔预制梁的比吸收能比无孔预制梁提高了 15.56%。结果表明,数据驱动法可以大大缩短结构设计时间,拓展设计空间。这项研究将为预弯梁在工程领域的广泛应用提供理论依据。
Hysteretic performance of thin-walled Q690 high-strength steel H-section beam-columns bent about the weak-axis
Zhongqi Chen, Mark A. Bradford, Guo-Qiang Li, Yan-Bo Wang, Guotao Yang
doi:10.1016/j.tws.2023.111436
围绕弱轴弯曲的薄壁 Q690 高强度钢 H 型钢梁柱的滞回性能
High-strength steel has broad application prospects in steel structures as its weight to strength ratio is low, but the reduced ductility limits its application in seismic design. In order to evaluate the application potential of high-strength steel in light steel structures, four Q690 high-strength steel beam-columns with large width to thickness ratios were tested under cyclic loading about the weak axis. The failure mode, ultimate strength, hysteretic curve, stiffness degradation, ductility and energy dissipation capacity of the tested specimens are discussed. Subsequently, a finite element analysis model is established, and an extensive parametric study is carried out using the verified finite element model. The test results show that the failure mode is the local buckling of column base. The hysteretic behavior of the specimens is mainly affected by the axial load ratio and the flange width to thickness ratio. The results of the parametric study show that the extent of development of plasticity in the cross-section is related to the axial load ratio. The calculated ultimate strength of the beam-column shows that Eurocode 3 is conservative for the classification of the beam-column as having a Class 4 cross-section, members with Class 4 cross-sections should in fact be classified as having Class 3 cross-sections. Accordingly, a section classification for a high-strength steel beam-column subjected to weak axis bending is discussed.
高强度钢的重量强度比低,在钢结构中具有广阔的应用前景,但其延性较差,限制了其在抗震设计中的应用。为了评估高强度钢在轻钢结构中的应用潜力,我们对四根宽厚比较大的 Q690 高强度钢梁柱进行了绕弱轴循环加载试验。讨论了试验试件的破坏模式、极限强度、滞回曲线、刚度退化、延性和耗能能力。随后,建立了有限元分析模型,并利用验证后的有限元模型进行了广泛的参数研究。试验结果表明,破坏模式是柱基的局部屈曲。试件的滞回行为主要受轴向载荷比和翼板宽厚比的影响。参数研究结果表明,横截面塑性的发展程度与轴向荷载比有关。计算得出的梁柱极限强度表明,《欧洲规范 3》将梁柱划分为 4 级截面是保守的,具有 4 级截面的构件实际上应划分为 3 级截面。因此,本文讨论了承受弱轴弯曲的高强度钢梁柱的截面分类。
Impact dynamic response of large aperture space deployable antenna supporting structures based on a dual-scale model
Lu Jin, Boheng Li, Dake Tian, Qinghe Wang, Yinyin Hou
doi:10.1016/j.tws.2023.111432
基于双尺度模型的大孔径空间可部署天线支撑结构的冲击动态响应
This study investigates the joint damage patterns and changes in shape accuracy of large aperture space deployable antenna supporting structures subject to hypervelocity impacts from micro space debris. Based on the dual-scale method, a joint scale model is constructed for a hexagonal prismatic space deployable truss antenna supporting structure with an aperture of six meters and 37 modules. ANSYS/AUTODYN is used for the impact damage analysis, with an equivalent model of impact force integrating the structure's actual damage characteristics in the structure scale model. The dynamic response and deformation performance of the antenna supporting structure under impact velocities from 2.5 to 15.0 km/s, with spherical space debris of 2.5 mm and 5.0 mm diameters, impacting modular central points in both positive and negative directions, are analyzed. The results show that the primary damage to the joint scale model after impact includes cratering, perforation, punch failure, and joint failure. The debris diameter significantly influences joint damage and deformation of the bolt hole diameter. Additionally, the debris cloud post-impact significantly affects the vertical bar's inner wall, spalling the wall and reducing the rod's strength. As the impact point moves towards the structure's centroid, the antenna's overall response increases. With higher impact velocities, the antenna supporting structure's overall deformation first increases, then decreases. At an impact velocity of 12.5 km/s, the impact area of the structure gradually reduces post-impact. Our proposed joint damage forms and three-case damage classification (no effect, repairable, and joint failure) may serve as a valuable reference for designing structural protection and impact identification for space deployable antennas.
本研究探讨了大孔径空间可部署天线支撑结构在受到微型空间碎片超高速撞击时的联合损伤模式和形状精度变化。基于双尺度法,为一个孔径为 6 米、有 37 个模块的六角棱柱形空间可展开桁架天线支撑结构构建了一个联合尺度模型。ANSYS/AUTODYN 用于冲击损伤分析,冲击力等效模型将结构的实际损伤特征整合到结构比例模型中。分析了天线支撑结构在 2.5 至 15.0 千米/秒的撞击速度下的动态响应和变形性能,直径分别为 2.5 毫米和 5.0 毫米的球形空间碎片从正反两个方向撞击模块中心点。结果表明,撞击后关节比例模型的主要损伤包括缩孔、穿孔、冲孔失效和关节失效。碎片直径对接头损坏和螺栓孔直径变形有很大影响。此外,撞击后的碎片云对垂直杆的内壁有很大影响,使内壁剥落并降低杆的强度。随着撞击点向结构中心移动,天线的整体响应也随之增加。随着撞击速度的增加,天线支撑结构的整体变形先增大后减小。在 12.5 km/s 的撞击速度下,结构的撞击面积在撞击后逐渐减小。我们提出的关节损坏形式和三种损坏情况分类(无影响、可修复和关节损坏)可为空间可部署天线的结构保护设计和撞击识别提供有价值的参考。
Numerical study and design of ultra-high-strength steel plate girders subjected to patch loading after elevated temperature
Zeqiao Luo, Yu Shi, Xuanyi Xue, Yunpeng Xu, Lei Xu
doi:10.1016/j.tws.2023.111433
高温后承受贴片荷载的超高强度钢板梁的数值研究与设计
When a steel structure does not collapse after a fire, it is meaningful to study its residual resistance after exposure to elevated temperatures to evaluate its post-fire service capacity. The elevated temperatures of a fire change the residual mechanical properties of structural steel, which influences the patch-loading resistance performance of steel plate girders. However, the effects of temperature on the residual resistance performance of Q960 ultra-high-strength steel (UHSS) plate girders subjected to patch loading remain unclear. This study aims to determine the variation trends of the post-fire bearing performance of Q960 UHSS plate girders subjected to patch loading based on their mechanical properties after exposure to elevated temperature and natural cooling. The effects of the web width-to-height ratio, web height-to-thickness ratio, load length, and exposure temperature were considered in the parametric study; a total of 400 numerical models were included. Additionally, the influence of the exposure temperature on the serviceability limit state of Q960 UHSS plate girders was considered. The applicability of EN 1993-1-5 was verified based on the finite element analysis results, which showed that the design methods in EN 1993-1-5 significantly underestimated the ultimate resistance of Q960 UHSS plate girders exposed to elevated temperatures. Thus, the strength reduction function in EN 1993-1-5 was revised to improve the accuracy of the statistical analysis.
当钢结构在火灾后没有倒塌时,研究其暴露于高温后的残余阻力以评估其火灾后的使用能力是非常有意义的。火灾中的高温会改变钢结构的残余力学性能,从而影响钢板梁的抗补载性能。然而,温度对 Q960 超高强度钢(UHSS)钢板梁承受贴片加载的残余抗压性能的影响仍不清楚。本研究旨在根据 Q960 超高强度钢板梁在暴露于高温和自然冷却后的力学性能,确定承受补丁加载的 Q960 超高强度钢板梁火灾后承载性能的变化趋势。参数研究考虑了腹板宽高比、腹板高厚比、荷载长度和暴露温度的影响,共包括 400 个数值模型。此外,还考虑了暴露温度对 Q960 超高强度钢板梁适用性极限状态的影响。有限元分析结果表明,EN 1993-1-5 中的设计方法大大低估了暴露在高温下的 Q960 超高强度聚苯乙烯板梁的极限抗力。因此,对 EN 1993-1-5 中的强度降低函数进行了修订,以提高统计分析的准确性。