今日更新:International Journal of Solids and Structures 1 篇,Journal of the Mechanics and Physics of Solids 1 篇,Thin-Walled Structures 4 篇
Effect of polydispersity on the transport and sound absorbing properties of three-dimensional random fibrous structures
Quang Vu Tran, Camille Perrot, Raymond Panneton, Minh Tan Hoang, Ludovic Dejaeger, Valérie Marcel, Mathieu Jouve
doi:10.1016/j.ijsolstr.2024.112840
多分散性对三维随机纤维结构输运和吸声性能的影响
A technique is proposed that uses a multi-scale approach to calculate transport properties of compressed felts using only image analysis and numerical calculations. From the image analysis fiber diameter distribution and fiber orientation are determined. From a known porosity and the latter two characteristics, two representative elementary volumes (REV) are constructed: one based on the volume-weighted average diameter and one on an inverse volume-weighted average diameter. Numerical calculations on the former showed that it correctly estimates viscous and thermal permeabilities, while the latter correctly estimates tortuosity and viscous and thermal characteristic lengths. From these calculations, micro-macro analytical expressions are developed to estimate the transport properties of polydisperse composite felts based solely on open porosity, fiber diameter polydiversity, and fiber orientation. Good agreements are obtained between analytical predictions and measurements of transport properties. The predicted transport properties are also used in the Johnson-Champoux-Allard-Lafarge (JCAL) equivalent fluid model to predict the sound absorption coefficient of the felts. Excellent agreements are obtained with impedance tube measurements.
提出了一种基于图像分析和数值计算的多尺度压缩毛毡传输特性计算方法。通过图像分析,确定了光纤的直径分布和方向。根据已知孔隙度和后两个特征,构建了两个代表性的基本体积(REV):一个基于体积加权平均直径,另一个基于逆体积加权平均直径。数值计算表明,前者能正确估计黏性和热渗透性,后者能正确估计弯曲度和黏性和热特性长度。根据这些计算,建立了微宏观分析表达式,仅根据开孔率、纤维直径多样性和纤维取向来估计多分散复合毡的输运特性。在输运性质的分析预测和测量之间得到了很好的一致性。预测的输运特性也被用于Johnson-Champoux-Allard-Lafarge (JCAL)等效流体模型来预测毡的吸声系数。阻抗管测量结果非常吻合。
Continuum Strain of Point Defects
G. Gengor, O.K. Celebi, A.S.K. Mohammed, H. Sehitoglu
doi:10.1016/j.jmps.2024.105653
点缺陷的连续应变
We propose a new Regularized Green's Function Method (RGFM) derived from electron densities and captures the disturbance due to point defects, successfully extending the elastic strain determination to the lattice scales. The RGFM circumvents the use of concentrated point forces, which results in unrealistic singular fields. The objective is to determine the force variations at the atomic scales from Ab-initio calculations as Quantum Mechanical Force Density (QMFD). QMFD encodes the information regarding the electronic structure of the defect since it is related to the gradients of electron wavefunctions generated from the Density Functional Theory (DFT) calculations. Once the QMFD is calculated, RGFM solves the force equilibrium equation via Fourier transforms to compute elastic fields. Therefore, the present treatment reflects the electronic structure of the atomic positions, hence the complex elastic deformations and interactions at short range, which represents a significant advancement compared to previous studies. The RGFM can also capture the long-range fields since it calculates the decay of the force fields away from the nuclei. Previous theories, such as the elastic dipole method, face two main shortcomings: they can only handle the long-range elastic fields and contain an unphysical singularity at the center of the point defect. Our novel derivation of distributed forces addresses both challenges, i.e., it renders non-singular displacement and strain fields at the nuclei and can also describe the elastic response accurately far from the nuclei center. The application of the method to the NV (nitrogen-vacancy) center in SiC is demonstrated in comparison with the elastic dipole theory, showing the advantages of the present methodology.
我们提出了一种基于电子密度的正则化格林函数方法(RGFM),并捕获了点缺陷引起的扰动,成功地将弹性应变的测定扩展到晶格尺度。RGFM避免了集中点力的使用,这会导致不切实际的奇异场。目的是确定力在原子尺度上的变化从从头算作为量子力学力密度(QMFD)。QMFD编码了有关缺陷电子结构的信息,因为它与密度泛函理论(DFT)计算产生的电子波函数的梯度有关。一旦计算出QMFD, RGFM通过傅里叶变换求解力平衡方程来计算弹性场。因此,目前的处理方法反映了原子位置的电子结构,因此在近距离内复杂的弹性变形和相互作用,与以往的研究相比,这是一个重大的进步。RGFM还可以捕获远程场,因为它计算了远离原子核的力场的衰减。以前的理论,如弹性偶极子方法,面临两个主要缺点:它们只能处理远程弹性场,并且在点缺陷的中心包含非物理奇点。我们的分布式力的新推导解决了这两个挑战,即,它可以呈现原子核处的非奇异位移和应变场,也可以准确地描述远离原子核中心的弹性响应。将该方法应用于碳化硅中氮空位中心,并与弹性偶极子理论进行了比较,表明了该方法的优越性。
Experimental research on H-section beam-square steel column joints connected by self-tapping screws
Jiahang Xu, Ting Zhou, Zhihua Chen, Xueshan Liu, Wentao Qiao
doi:10.1016/j.tws.2024.111923
自攻螺钉连接h型钢-方钢柱节点的试验研究
This paper proposes a novel thin-walled steel beam-column joint entirely using self-tapping screws. Compared to bolted and welded connections, its advantages of easy construction, low precision requirements, and fast construction are suitable for low-rise steel structures. Four full-scale H-section beam-square steel column joints connected by self-tapping screws were tested and the force transfer mechanism was investigated. Three of the specimens were loaded monotonically at the beam ends. The effects of the L-shaped connecting plate thickness and the arrangement of stiffening ribs on the bending performance of the joints are analyzed. Monotonic loading tests have demonstrated that the increased thickness and the arrangement of stiffening ribs enhance the common forces in the clusters of self-tapping screws, thereby increasing the bending stiffness of the joints. One of the specimens was tested with cyclic loads. The cyclic loading test revealed that the hysteretic curve of the self-tapping screws connection is relatively full, with high energy dissipation capacity and low degradation of strength and stiffness. Finally, the improved component method proposed the calculation method of bending resistance of self-tapping connection joints. The calculation accuracy is within 10%, which can be used as a reference for the design of bending resistance.
本文提出了一种全自攻螺钉连接的薄壁钢梁-柱节点。与螺栓连接和焊接连接相比,其施工方便、精度要求低、施工快捷等优点适用于低层钢结构。对采用自攻螺钉连接的4个全尺寸h型钢-方钢柱节点进行了试验,并对其传力机理进行了研究。其中3个试件在梁端进行单调加载。分析了l型连接板厚度和加筋肋布置对节点抗弯性能的影响。单调加载试验表明,增加厚度和加劲肋的布置增加了自攻螺钉簇中的共同力,从而增加了节点的抗弯刚度。其中一个试件进行了循环荷载试验。循环加载试验表明,自攻螺钉连接的滞回曲线较为饱满,具有较高的耗能能力和较低的强度刚度退化。最后,采用改进的构件法提出了自攻连接节点抗弯性能的计算方法。计算精度在10%以内,可为抗弯设计提供参考。
Lateral load behavior of shear connections between steel storage racks and the spine bracing with posts
Zhaoqi Huang, Xianzhong Zhao, Ken S. Sivakumaran
doi:10.1016/j.tws.2024.111924
钢储物架与带柱支撑梁剪力连接的横向荷载特性
High-rise steel storage racks are cold-formed thin-walled steel frames, which achieve their lateral strength and stiffness by the use of a spine bracing system in the down-aisle direction commonly located at a short horizontal distance away from the main rack frames. The shear connections between the main rack frame and the spine bracing system play a dominant role in the effectiveness of the spine bracing system. This paper experimentally investigates the behavior of the shear connections used in industrial practice between a steel storage rack and the spine bracing system with posts using four groups of three nominally identical connection specimens. By employing a digital image correlation (DIC) system, the tests generate comprehensive data and establish the real-time deformation fields of individual components of such shear connections. Based on the component-based approach, a linear-elastic analytical model is developed for the type of shear connections under consideration. The proposed analytical model explicitly captures the behavior of the individual connection components, including the three-dimensional flexural bending of endplates, as well as the distortions of the open sections of the upright and the bracing post. Based on the proposed model, this paper quantifies the contribution of each component towards the total deformation of the shear connections. The investigation establishes that the cross-sectional distortion of the bracing post and the out-of-plane bending of the upright web are the most flexible components of such shear connections. Recommendations associated with the shear connections under consideration are proposed for the rack designers and manufacturers.
高层钢货架是冷弯薄壁钢框架,其横向强度和刚度是通过在通道下方向使用脊柱支撑系统来实现的,通常位于距离主货架框架较短的水平距离处。主机架与脊柱支撑系统之间的剪切连接对脊柱支撑系统的有效性起着主导作用。本文试验研究了工业实践中使用的钢存储架和带有柱子的脊柱支撑系统之间的剪切连接的行为,使用四组三个名义上相同的连接试件。试验采用数字图像相关(DIC)系统,生成了全面的数据,建立了此类剪切连接各构件的实时变形场。基于基于构件的方法,建立了考虑剪切连接类型的线弹性分析模型。所提出的分析模型明确地捕捉了各个连接部件的行为,包括端板的三维弯曲,以及直立和支撑柱的开口部分的变形。基于所提出的模型,本文量化了各构件对剪切连接总变形的贡献。研究表明,支撑柱的截面变形和直立腹板的面外弯曲是这种剪切连接中最灵活的构件。对机架设计人员和制造商提出了与考虑中的剪切连接相关的建议。
Comparative Experimental Analysis of Local Buckling in Mild and High-Strength Steel (HSS) CHS Subjected to Various Galvanization Techniques
Drilon Gubetini, Martin Mensinger, Tohid Ghanbari-Ghazijahani
doi:10.1016/j.tws.2024.111925
不同镀锌工艺下低碳钢和高强钢(HSS) CHS局部屈曲的对比试验分析
This article reports on an extensive experimental study on galvanized and ungalvanized cold-formed circular hollow sections (CFCHS). All samples were produced by cold-forming thermomechanically rolled steels (TM-steels) in S355, S550, S600, S700, and S960 with high-frequency induction welding (HFI). The test specimens were examined without galvanization, with a pre-galvanization and a post-galvanization. Hardness measurements and microstructural analysis were conducted on seven samples, while the mechanical behavior was examined through 82 tensile and 78 stub-column tests with corresponding imperfection measurements. Despite being classified as prone to local elastic buckling according to international standards, the S960 samples in this study did not exhibit such failure. This suggests that the classification by the codes was conservative. The effects of pre-galvanization on CHS have not been investigated so far, and current findings from literature regarding the impact of post-galvanization on load-bearing behavior suggest a severe capacity decrease for CFCHS in high steel grades. Contrary to previous findings, the current study reveals capacity-enhancing effects resulting from galvanization. Both galvanization types enhanced the stiffness and the cross-section capacity under compression. Galvanization induces changes in material properties, including yield and tensile strength, ductility, and the characteristics of the stress-strain curve. This study serves as a validation base for less conservative yet reliable approaches for the cross-section design of high-strength steel CHS and the utilization of beneficial effects due to galvanization.
本文报道了镀锌和未镀锌冷弯圆空心型钢(CFCHS)的广泛实验研究。所有样品均由S355, S550, S600, S700和S960冷成形热机械轧制钢(tm钢)采用高频感应焊接(HFI)生产。试验样品在没有镀锌的情况下进行了检查,有预镀锌和后镀锌。对7个试样进行了硬度测量和显微组织分析,并通过82次拉伸试验和78次短柱试验进行了力学性能测试,并进行了相应的缺陷测量。尽管按照国际标准,S960样品容易发生局部弹性屈曲,但本研究中S960样品并未出现这种破坏。这表明,由代码分类是保守的。到目前为止,预镀锌对CFCHS的影响还没有被研究过,目前文献中关于后镀锌对承载行为影响的研究结果表明,在高钢等级中,CFCHS的产能严重下降。与以往的研究结果相反,目前的研究揭示了镀锌带来的能力增强效应。两种镀锌方式都提高了刚度和抗压截面能力。镀锌引起材料性能的变化,包括屈服和抗拉强度、延展性以及应力-应变曲线的特征。本研究为高强度钢CHS截面设计和利用镀锌带来的有利效应提供了不那么保守但可靠的方法验证基础。
Experimental study on the axial compression behavior of circular steel tube short columns under coastal environmental corrosion
Wanpeng Zhang, Siying Chen, Yao Zhu, ShuPing Liu, Wei Chen, Yu Chen
doi:10.1016/j.tws.2024.111929
海岸环境腐蚀下圆钢管短柱轴压性能试验研究
This study adopts experimental, numerical, and algorithmic methods to investigate the compressive behavior and failure mode of corroded circular steel tube short columns. The study establishes an equivalent relationship between electrochemical accelerated corrosion and natural coastal corrosion environments. The effects of current intensity, sodium chloride concentration, and energizing time on corrosion equivalent duration and mechanical properties of specimens are analyzed. The results demonstrate that the ultimate bearing capacity and energy absorption capacity of the specimens are significantly reduced with increasing current intensity and energized time. However, the NaCl concentration has minimal effect on the mechanical properties of the specimens. After natural corrosion in a coastal area with medium salinity for 19.2 years, the ultimate bearing capacity, ductility, initial stiffness, and energy absorption capacity of circular steel tube short columns decreased by 49.5%, 63.1%, 48.9%, and 85.6%, respectively. A novel corrosion pit generation algorithm is suggested to accurately simulate the distribution of corrosion pits and determine the ultimate bearing capacity of circular steel tube short columns. This algorithm demonstrates improved accuracy and stability compared to traditional simplified methods. Subsequently, a corrosion pit random generation model is developed using this method, and the accuracy of the finite element model is validated against experimental results. Furthermore, the impact of the diameter thickness ratio on the ultimate bearing capacity of corrosion specimens is thoroughly analyzed.
本文采用试验、数值和算法等方法对腐蚀圆钢短柱的压缩性能和破坏模式进行了研究。该研究建立了电化学加速腐蚀与自然海岸腐蚀环境的等效关系。分析了电流强度、氯化钠浓度和通电时间对试样腐蚀等效时间和力学性能的影响。结果表明:随着电流强度和通电时间的增加,试件的极限承载力和能量吸收能力显著降低;而NaCl浓度对试样力学性能的影响较小。在沿海中等盐度地区,经19.2年自然腐蚀后,圆钢管短柱的极限承载力、延性、初始刚度和吸能能力分别下降49.5%、63.1%、48.9%和85.6%。提出了一种新的腐蚀坑生成算法,以准确模拟腐蚀坑的分布,确定圆钢管短柱的极限承载力。与传统的简化方法相比,该算法具有更高的精度和稳定性。利用该方法建立了腐蚀坑随机生成模型,并与实验结果对比验证了有限元模型的准确性。进一步分析了直径厚度比对腐蚀试件极限承载力的影响。