首页/文章/ 详情

【新文速递】2024年6月8日固体力学SCI期刊最新文章

1天前浏览31

 

今日更新:Journal of the Mechanics and Physics of Solids 1 篇,Mechanics of Materials 1 篇,Thin-Walled Structures 3 篇

Journal of the Mechanics and Physics of Solids

Realization of planar and surface conformal mappings through stress-free growth of hyperelastic plates: Analytical formulas and numerical calculations

Jiong Wang, Zili Jin, Zhanfeng Li

doi:10.1016/j.jmps.2024.105727

通过超弹性板的无应力生长实现平面和表面共形映射:解析公式和数值计算

Conformal mapping is a well-known concept and has a long research history in mathematics. Accompanying the developments of computational science and 3D digital scanning technology, conformal mapping has also found wide applications in geometric modeling, computer graphics, medical imaging and other fields. In the virtual image or animation world, conformal mapping offers a convenient approach to achieve various shape changes of planar regions and 3D surfaces. In this work, we propose a promising approach, i.e., through the stress-free growth of hyperelastic plates, to realize arbitrary planar and surface conformal mappings in the physical world. The growth field in a hyperelastic plate can be represented by a symmetric tensor field. For any given planar or surface conformal mappings with explicit analytical expressions, the formulas of growth functions in the growth tensor are derived. In the case that the target surfaces of conformal mappings have no explicit analytical expressions, we further propose a numerical scheme to determine the growth data in the hyperelastic plates. The efficiency of the approach proposed in the current work is validated through several typical examples, where the 3D finite element simulations are conducted. The results demonstrate that, by incorporating the obtained growth functions or growth data, the target surfaces can be generated accurately through growth deformations of hyperelastic plates. As an application of the current work, we further propose an approach of shape-control for double-layer grid structures with plate forms. According to any given target shapes, the values of elongation or contraction of the bar elements are determined, then the desired deformations of the grid structures can be realized.

保角映射是一个众所周知的概念,在数学中有着悠久的研究历史。随着计算科学和三维数字扫描技术的发展,保角映射在几何建模、计算机图形学、医学成像等领域也得到了广泛的应用。在虚拟图像或动画世界中,保角映射为实现平面区域和三维曲面的各种形状变化提供了一种方便的方法。在这项工作中,我们提出了一种很有前途的方法,即通过超弹性板的无应力生长,实现物理世界中的任意平面和表面共形映射。超弹性板的生长场可以用对称张量场表示。对于任意给定平面或曲面的保角映射,导出了生长张量中生长函数的表达式。在保形映射的目标表面没有明确的解析表达式的情况下,我们进一步提出了一种确定超弹性板中生长数据的数值格式。通过几个典型实例进行了三维有限元仿真,验证了本文方法的有效性。结果表明,结合得到的生长函数或生长数据,可以通过超弹性板的生长变形精确地生成目标曲面。作为现有工作的应用,我们进一步提出了一种板型双层网架结构的形状控制方法。根据给定的目标形状,确定杆单元的伸长或收缩值,从而实现所需的网格结构变形。


Mechanics of Materials

Modeling the heterogeneous and anisotropic plastic deformation of lath martensite

J. Wijnen, S.A.O. Dreessen, V. Rezazadeh, R.H.J. Peerlings

doi:10.1016/j.mechmat.2024.105056

模拟板条马氏体的非均质和各向异性塑性变形

The plastic behavior of microscale lath martensite samples is highly anisotropic. Depending on the orientation, the deformation of such samples may be heterogeneous, with only a few localized slip traces while the remainder of the sample remains largely elastic. Although several continuum plasticity models that account for the anisotropy exist, they cannot reproduce the heterogeneous response observed in experiments. In this study, a model for lath martensite at the microscale is proposed which captures the orientation-dependent heterogeneous behavior observed in experiments. Before formulating the model we first study in detail two idealized cases, in which two different deformation mechanisms are activated. In both cases, the lath martensite is modeled using a discrete slip plane model. In the model, the activation stress of the individual slip systems varies randomly in space according to a distribution based on the underlying dislocation motion. The two configurations differ only in the orientation of the applied tensile load relative to that of the laths – either perpendicular or at 45 ° . In the latter case, slip along the so-called habit plane results in localized plastic deformation, while the former results in a more diffuse activation of plasticity. Insights obtained based on the idealized cases are used to formulate a three-dimensional constitutive model, which captures both deformation mechanisms. The model is applied to microtensile tests of single-packet lath martensite samples. It is shown that the orientation-dependent heterogeneity is accurately captured by the two deformation mechanisms accounted for by the model.

微尺度板条马氏体试样的塑性行为具有高度的各向异性。根据取向的不同,这些样品的变形可能是不均匀的,只有少数局部滑移痕迹,而样品的其余部分仍然具有很大的弹性。虽然存在几种解释各向异性的连续介质塑性模型,但它们不能再现实验中观察到的非均质响应。本文提出了板条马氏体的微观模型,该模型捕捉了实验中观察到的与取向相关的非均相行为。在建立模型之前,我们首先详细研究了两种理想情况,其中两种不同的变形机制被激活。在这两种情况下,板条马氏体采用离散滑移面模型建模。在该模型中,单个滑移系统的激活应力在空间上随机变化,其分布基于位错运动。这两种结构的不同之处在于施加的拉伸载荷相对于板条的方向——垂直或45°。在后一种情况下,沿着所谓的习惯面滑动导致局部塑性变形,而前者导致更广泛的塑性激活。根据理想情况获得的见解用于制定三维本构模型,该模型捕获了两种变形机制。将该模型应用于单包板条马氏体试样的微拉伸试验。结果表明,该模型所考虑的两种变形机制准确地反映了取向相关的非均质性。


Thin-Walled Structures

Dynamic analysis with point-masses of perforated pallet rack structural members by means of the Generalized Beam Theory

Ignasi López, Jordi Bonada, Oriol Bové, Miquel Casafont

doi:10.1016/j.tws.2024.112090

基于广义梁理论的开孔托盘架结构点质量动力分析

This paper presents two different formulations for introducing point-masses into a dynamic problem using the Generalized Beam Theory (GBT) method. The first one implies placing a point-mass at a beam-node (with or without eccentricities) while the other implies placing a point-mass at a cross-section node. In order to evaluate the accuracy of such formulations, different modal analyses of members have been performed using GBT beam elements, shell elements and classical beam elements. The values of natural modal frequencies obtained through different models have been successfully compared. The results of various harmonic analyses are also presented. Some of the studied structural members include perforations. Finally, the influence of GBT modes and perforations when using point-masses is discussed.

本文用广义梁理论(GBT)方法给出了两种不同的将点质量引入动力问题的公式。第一种方法意味着在光束节点(有或没有偏心)放置一个点质量,而另一种方法意味着在截面节点放置一个点质量。为了评估这些公式的准确性,分别用GBT梁单元、壳单元和经典梁单元对构件进行了不同的模态分析。对不同模型得到的固有模态频率进行了比较。文中还介绍了各种谐波分析的结果。研究的一些结构构件包括孔洞。最后,讨论了采用点质量时GBT模式和穿孔的影响。


Low-Cycle Fatigue Behaviour of Stainless-Clad Bimetallic Steel Welded Connections

Xiaofeng Yang, Huiyong Ban, Yongjiu Shi, Kwok-Fai Chung, Yi-Fei Hu

doi:10.1016/j.tws.2024.112104

不锈钢包层双金属钢焊接接头的低周疲劳行为

The stainless-clad (SC) bimetallic steel is the most widely used laminated high-performance steel in construction, which often offers a variety of prominent structural performance and competitive advantages. Welding with electrodes of suitable mechanical properties and corrosion resistance is vital for SC bimetallic steel structures to ensure a complete corrosion-resistant surface. However, the research on welded connections under cyclic actions is very limited. Many recommendation designs and current standards for SC bimetallic steel are primarily developed for precision equipment, and they are not suitable for structural engineering. To this end, this paper aims to investigate the low-cycle fatigue behaviour of butt welded connections with different welding configurations for the SC bimetallic steel. Failure modes, cyclic characteristics and Masing behaviour of typical welded connections were analysed, and the low-cyclic fatigue behaviour was validated using the Basquin-Coffin-Manson model. A new proposed strain energy-based model was also proposed to describe. Differences in the low-cycle fatigue behaviour between the welded connections and the base bimetal were demonstrated, as well as that for various welding configurations. It was found that the low-cycle fatigue life of the welded connections with a transition weld zone is similar to that of these welded connections without a transition weld zone, both being about 60% to 80% of the base bimetal's fatigue life. However, the fatigue life of the welded connection with a single filler material is much shorter than that of the previous two, being only 15% to 30% of that of the base bimetal. It should be noted that both the adapted Basquin-Coffin-Manson model and the newly proposed strain energy-based model may predict well the low-cycle fatigue life of the three welded connections. Finally, the transition weld zone in these welded connections is recommended to be eliminated in order to simplify the welding procedures, and hence to improve welding efficiency.

不锈钢包层(SC)双金属钢是建筑中应用最广泛的层压高性能钢,通常具有多种突出的结构性能和竞争优势。焊接具有合适的机械性能和耐腐蚀性的电极是确保SC双金属钢结构具有完全耐腐蚀表面的关键。然而,对循环作用下焊接连接的研究非常有限。SC双金属钢的许多推荐设计和现行标准主要是为精密设备而制定的,并不适用于结构工程。为此,本文旨在研究SC双金属钢不同焊接形式对接焊接连接的低周疲劳行为。分析了典型焊接接头的破坏模式、循环特性和振动行为,并采用Basquin-Coffin-Manson模型验证了接头的低周疲劳行为。提出了一种新的基于应变能的模型来描述。结果表明,焊接接头和基体双金属之间的低周疲劳性能存在差异,不同的焊接结构也存在差异。结果表明,带过渡焊区的焊接接头的低周疲劳寿命与不带过渡焊区的焊接接头相似,均为母材疲劳寿命的60% ~ 80%。但单填料焊接接头的疲劳寿命比前两种材料短得多,仅为母材双金属的15% ~ 30%。值得注意的是,无论是修正后的Basquin-Coffin-Manson模型,还是新提出的基于应变能的模型,都能较好地预测三种焊接接头的低周疲劳寿命。最后,建议消除这些焊接连接中的过渡焊区,以简化焊接程序,从而提高焊接效率。


Exact Solutions for the Elastic-plastic Response of Functionally Graded Pipe under External Pressure

Shitang Cui, Jingsong Cheng, Yongliang Zhang

doi:10.1016/j.tws.2024.112106

外压作用下功能梯度管弹塑性响应的精确解

This study investigates the influence of material gradient on the elastoplastic response of functionally graded (FG) thick-walled pipes subjected to external pressure. Closed-form solutions are derived for radial and circumferential stresses across various stages: purely elastic, partially plastic, and post-unloading from plastic regimes. Both the elastic modulus and yield stress exhibit radial variation defined by power-law functions, while Poisson's ratio remains constant. The stress distribution within the pipe depends not only on the external pressure but also on the material gradient index and the geometric dimensions of the pipe. A method is presented to accurately determine the first yielding position in a thin-walled tube based on the material gradient index by employing Tresca's yield criterion. Plastic zones nucleate at one or both surfaces as external pressure increases. The propagation of elastoplastic interfaces and stress distributions within each zone are examined in detail. Notably, following plastic deformation and complete unloading, FG thick-walled pipes may exhibit re-emergence of plastic deformation, depending on the pre-unloading stress state and the gradient of the elastic modulus. The conclusions of this work expected to aid in the design of FG pressure vessels and improve their load-carrying capacity and safety.

研究了材料梯度对功能梯度厚壁管外压弹塑性响应的影响。推导了不同阶段径向和周向应力的封闭解:纯弹性、部分塑性和从塑性状态卸载后。弹性模量和屈服应力均呈现幂律函数定义的径向变化,泊松比保持不变。管道内的应力分布不仅与外部压力有关,还与材料梯度指数和管道的几何尺寸有关。提出了一种基于材料梯度指数,利用Tresca屈服准则精确确定薄壁管首屈服位置的方法。当外部压力增加时,在一个或两个表面形成塑性区。详细研究了弹塑性界面的传播和各区域内的应力分布。值得注意的是,在塑性变形和完全卸载后,FG厚壁管可能会再次出现塑性变形,这取决于卸载前的应力状态和弹性模量的梯度。本研究的结论将有助于FG压力容器的设计,提高其承载能力和安全性。



来源:复合材料力学仿真Composites FEM
ACTMechanicalSystemDeform振动疲劳建筑UG焊接BIM理论材料控制试验曲面
著作权归作者所有,欢迎分享,未经许可,不得转载
首次发布时间:2024-11-20
最近编辑:1天前
Tansu
签名征集中
获赞 3粉丝 0文章 690课程 0
点赞
收藏
作者推荐

【新文速递】2024年6月10日固体力学SCI期刊最新文章

今日更新:International Journal of Solids and Structures 1 篇,Journal of the Mechanics and Physics of Solids 3 篇,International Journal of Plasticity 1 篇,Thin-Walled Structures 3 篇International Journal of Solids and StructuresCorrugation parameters and mechanical performance of corrugated shells under the same weight and volumeJianliang Sun, Cunyao Shan, Zhang Xu, Li Kundoi:10.1016/j.ijsolstr.2024.112918相同重量和体积下波纹壳的波纹参数和力学性能Cylindrical shells are easy to buckle under external pressure and need to be strengthened before they can be used in engineering. At present, the cylindrical shells are mainly enhanced by welding stiffeners inside them. However, for underwater pressure vessels, it is important to reduce the welding area. Some scholars have proposed various forms of corrugated shells, such as longitudinally corrugated shells, and studied the buckling behavior of corrugated shells under hydrostatic pressure. However, few studies have been conducted on such shells under the same weight conditions. Because an increase in the height of the corrugation necessarily leads to an increase in weight. So this reduces the comparability between the corrugated shells. The mechanism of non-uniform wall thickness on the improvement of shell material utilization is not explained. It is worth exploring how to achieve the best buckling performance under the limited weight. In this paper, the shape parameters of corrugations are explored, including the number, height and width of corrugations, and the coupling between them. The mechanical behavior of corrugated shell is studied from theory, FEA and experiment. In addition to hydrostatic pressure, the collapse of corrugated shells under concentrated pressure is also studied and comparative tests are carried out. The whole process of the collapse of the corrugated shell under concentrated pressure can be directly observed, and this is also an important performance index. In order to ensure the dimensional accuracy of the test samples, 3D printing technology was used for processing. In this paper, higher corrugations are not always better for the same weight. Because corrugation troughs tend to crack before buckling. This is like the short board effect, which requires collaborative optimization of peak and trough thickness.圆柱壳在外力作用下容易发生屈曲,在工程应用前需要进行加固。目前,圆柱壳的增强主要是通过焊接加强筋来实现的。然而,对于水下压力容器,减小焊接面积是很重要的。一些学者提出了各种形式的波纹壳,如纵向波纹壳,并研究了波纹壳在静水压力下的屈曲行为。然而,在相同重量条件下对这种壳进行的研究很少。因为波纹高度的增加必然导致重量的增加。这就降低了波纹壳之间的可比性。不均匀壁厚对提高壳体材料利用率的作用机理未作解释。如何在有限重量下获得最佳屈曲性能值得探讨。本文探讨了波纹的形状参数,包括波纹的数量、高度和宽度以及它们之间的耦合。从理论、有限元和试验三个方面对波纹壳的力学性能进行了研究。除静水压力外,还对波纹壳在集中压力下的破坏进行了研究,并进行了对比试验。可以直接观察到波纹壳在集中压力下坍塌的全过程,这也是一个重要的性能指标。为了保证测试样品的尺寸精度,采用3D打印技术进行加工。在本文中,对于相同的重量,更高的波纹并不总是更好。因为波纹槽在屈曲前容易开裂。这就像短板效应,需要峰谷厚度协同优化。Journal of the Mechanics and Physics of SolidsBridging scales with Machine Learning: From first principles statistical mechanics to continuum phase field computations to study order–disorder transitions in LixCoO2M. Faghih Shojaei, J. Holber, S. Das, G.H. Teichert, T. Mueller, L. Hung, V. Gavini, K. Garikipatidoi:10.1016/j.jmps.2024.105726用机器学习连接尺度: 从第一原理统计力学到连续相场计算,研究 LixCoO2 的有序-无序转变LixTMO2 (TM=Ni, Co, Mn) forms an important family of cathode materials for Li-ion batteries, whose performance is strongly governed by Li composition-dependent crystal structure and phase stability. Here, we use LixCoO2 (LCO) as a model system to benchmark a machine learning-enabled framework for bridging scales in materials physics. We focus on two scales: (a) assemblies of thousands of atoms described by density functional theory-informed statistical mechanics, and (b) continuum phase field models to study the dynamics of order–disorder transitions in LCO. Central to the scale bridging is the rigorous, quantitatively accurate, representation of the free energy density and chemical potentials of this material system by coarse-graining formation energies for specific atomic configurations. We develop active learning workflows to train recently developed integrable deep neural networks for such high-dimensional free energy density and chemical potential functions. The resulting, first principles-informed, machine learning-enabled, phase-field computations allow us to study LCO cathodes’ order–disorder transitions in terms of temperature, microstructure, and charge cycling. We highlight several insights gained to the dynamics of the phase transitions, and that have been made possible by the quantitatively rigorous scale bridging. To the best of our knowledge, such a scale bridging framework has not been previously demonstrated for LCO, or for materials systems of comparable technological interest. This approach can be expanded to other materials systems and can incorporate additional physics to that studied here.LixTMO2(TM=Ni、Co、Mn)是锂离子电池的重要正极材料系列,其性能主要受锂离子成分相关晶体结构和相稳定性的影响。在此,我们以 LixCoO2(LCO)为模型系统,对一个用于连接材料物理学尺度的机器学习框架进行基准测试。我们将重点放在两个尺度上:(a)由密度泛函理论为基础的统计力学描述的成千上万原子的集 合体,以及(b)研究 LCO 中有序-无序转变动力学的连续相场模型。尺度桥接的核心是通过粗粒化特定原子构型的形成能,对这种材料系统的自由能密度和化学势进行严格、精确的定量表示。我们开发了主动学习工作流程,针对此类高维自由能密度和化学势函数训练最近开发的可积分深度神经网络。由此产生的、基于第一性原理的、支持机器学习的相场计算使我们能够研究 LCO 阴极在温度、微观结构和电荷循环方面的有序-无序转变。我们重点介绍了通过严格的定量尺度桥接获得的对相变动力学的若干见解。据我们所知,这种尺度桥接框架以前从未用于 LCO 或具有类似技术意义的材料系统。这种方法可以扩展到其他材料系统,并可以在本文研究的基础上加入更多的物理学内容。Model-guided Navigation of Magnetic Soft Guidewire for Safe Endovascular SurgeryJiyu Li, Han Chen, Liu Wangdoi:10.1016/j.jmps.2024.105731磁软导丝模型导航在血管内手术中的应用The emergent magnetic soft guidewires (MSGs) that can be remotely navigated by magnetic fields hold great promise in minimally invasive endovascular surgery. However, existing models of MSGs have been limited in practical applications, largely due to insufficient consideration of contacts within actual endovascular settings. In this work, we present a theoretical model incorporating the magneto-mechanical behavior of MSGs with these critical contacts, allowing for a detailed evaluation of their navigation capability in various vascular configurations. Specifically, we categorize blood vessels into two main types: curved vessels and bifurcated vessels and identify a critical contact angle between the MSG tip and the vessel wall, beyond which the vascular damage may occur. By applying the principles of hard-magnetic elastica to account for the large deflection of MSGs, we develop a numerical framework that employs polynomial approximations and an energy minimization strategy. Through parametric analysis of different vessel types, we propose a method for adjusting magnetic fields for the safe navigation of MSGs through them. Our theoretical predictions have been substantiated by finite element modeling and experimental validation. The results of this paper offer a solid foundation for establishing practical guidelines for remote MSG navigation with minimal risk of vascular damage.紧急磁软导丝(MSGs)可以通过磁场远程导航,在微创血管内手术中具有很大的应用前景。然而,现有的msg模型在实际应用中受到限制,主要是由于没有充分考虑实际血管内环境中的接触。在这项工作中,我们提出了一个理论模型,该模型结合了msg与这些关键接触的磁力学行为,从而可以详细评估其在各种血管结构中的导航能力。具体来说,我们将血管分为两种主要类型:弯曲血管和分叉血管,并确定味精尖端与血管壁之间的临界接触角,超过该接触角可能会发生血管损伤。通过应用硬磁弹性原理来解释msg的大挠度,我们开发了一个采用多项式近似和能量最小化策略的数值框架。通过对不同船型的参数分析,提出了一种调整磁场的方法,以保证井下矿物船通过它们的安全航行。我们的理论预测已被有限元模型和实验验证所证实。本文的结果为建立具有最小血管损伤风险的远程味精导航实用指南提供了坚实的基础。Strain-Engineered Particle Diffusion in Uniaxially Deformed Polymer NetworksJiabin Liu, Shaoting Lindoi:10.1016/j.jmps.2024.105732应变工程粒子在单轴变形聚合物网络中的扩散Precise control of particle diffusion is highly valuable in diverse modern technologies. Traditional methods for regulating particle diffusion are often limited by the inherent properties of liquid medium. This study explores mechanical deformation as a new design space to engineer particle diffusion in stretchable soft materials. Combining experimental and theoretical analyses, we discover that particle diffusivity in a uniaxially deformed polymer network is governed by two dimensionless parameters: the ratio of particle size to the polymer network's mesh size and the stretch ratio applied to the polymer network. We further demonstrate a transition in the relationship between particle diffusivity and stretch ratio, characterized by a monotonic decrease for small particles and a non-monotonic trend for large particles. This transition is attributed to the synergistic effects involving geometric transformation in the deformed polymer network and energy modulation of the stretched polymer chains. This work introduces a new mechanism for controlling particle diffusivity in polymeric materials and establishes a theoretical foundation for developing previously inaccessible transport-based technologies.粒子扩散的精确控制在各种现代技术中具有很高的价值。传统的调节颗粒扩散的方法往往受到液体介质固有特性的限制。本研究探索了机械变形作为一种新的设计空间来设计可拉伸软材料中的颗粒扩散。结合实验和理论分析,我们发现单轴变形聚合物网络中的颗粒扩散率由两个无量纲参数控制:颗粒尺寸与聚合物网络网目尺寸的比例和应用于聚合物网络的拉伸比。我们进一步证明了粒子扩散率和拉伸比之间的关系的转变,其特征是小颗粒呈单调下降趋势,而大颗粒呈非单调趋势。这种转变归因于包括变形聚合物网络的几何变换和拉伸聚合物链的能量调制在内的协同效应。这项工作介绍了一种控制聚合物材料中颗粒扩散的新机制,并为开发以前无法实现的基于传输的技术奠定了理论基础。International Journal of PlasticityAtomistic investigation of the interaction between an edge dislocation and 1/2<111> interstitial dislocation loops in irradiated tungstenPing Yu, Guisen Liu, Yao Shendoi:10.1016/j.ijplas.2024.104030辐照钨中边缘位错与1/2<111>间隙位错环相互作用的原子性研究By impeding dislocation motion, the irradiation-induced dislocation loops cause irradiation hardening and further embrittlement of plasma-facing tungsten in fusion reactors, leading to its performance degradation. But fundamental questions regarding the mechanisms remain to be clarified and predictive model for loop hardening remains to be built. In this paper, interactions between gliding edge dislocations and interstitial dislocation loops (with Burger vector bL = ½<111>) are studied using atomistic simulations. The influences of bL orientations, dislocation-loop intersection positions, loop sizes, and loading conditions (temperature and strain rate) on the interactions are systematically calculated and analyzed. Results show a large variety of interaction mechanisms, depending mainly on the relative orientations of bL to dislocation slip plane, while slightly affected by loading conditions. Although loops with bL parallel to the plane can be easily swept away by gliding dislocations, loops with bL inclined to dislocation slip plane can strongly pin the gliding dislocation by forming a sessile <100> segment, which would bend the dislocation line into a screw dipole. Thus, high stress is required for the dislocation line to break away from the inclined loops by cross-slip of each individual arm of the screw dipole coupled with glide of the <100> segment. On the other hand, increasing temperature and/or decreasing strain rate hardly change the above mechanisms, but monotonically reduce the obstruction by these loops. Simplifying the complex motion of the edge dislocation pinned by the inclined loops as a thermally-activated process of a 1/2[111] edge dislocation overcoming barriers, a hardening model for the inclined loops is proposed. This model well describes the dependence of loop strength on loop sizes, temperatures and strain rates. The model is then applied to predict irradiation hardening at experimental strain rates, and it shows reasonable agreement with experimental results.通过阻碍位错运动,辐照诱发的位错环会导致辐照硬化,并使聚变反应堆中面向等离子体的钨进一步脆化,从而导致其性能下降。但有关机制的基本问题仍有待澄清,环状硬化的预测模型仍有待建立。本文利用原子模拟研究了滑行边缘位错与间隙位错环(布尔矢量 bL = ½<111>)之间的相互作用。系统地计算和分析了 bL 方向、差排-环交叉位置、环尺寸和加载条件(温度和应变速率)对相互作用的影响。结果表明,相互作用机制多种多样,主要取决于 bL 与差排滑移面的相对方向,同时受加载条件的影响较小。虽然bL平行于平面的环很容易被滑动位错扫除,但bL倾斜于位错滑移面的环却能通过形成无梗<100>段来强力钉住滑动位错,从而使位错线弯曲成螺钉偶极子。因此,位错线需要很高的应力,才能通过螺旋偶极的每个单臂的交叉滑动和<100>段的滑行脱离斜环。另一方面,温度升高和/或应变率降低几乎不会改变上述机制,但会单调地减少这些环的阻碍。将边缘位错被斜环钉住的复杂运动简化为 1/2[111]边缘位错克服障碍的热激活过程,提出了斜环的硬化模型。该模型很好地描述了斜环强度与斜环尺寸、温度和应变率的关系。然后将该模型用于预测实验应变速率下的辐照硬化,结果显示与实验结果相当吻合。Thin-Walled StructuresInvestigation on Special-Shaped Concrete-Filled Steel Tubular Column under combined compression and torsionYuanlong Yang, Qipeng Zhou, Xinchen Han, Yohchia Frank Chendoi:10.1016/j.tws.2024.112109压扭联合作用下异形钢管混凝土柱的研究This paper discussed the combined compressive and torsional performance of special-shaped concrete-filled steel tubes (SCFST) columns. A pseudo-static test research of eight specimens including two kinds of stiffening forms was carried out under compression and torsion. The investigated factors include section shape, stiffening form, stiffening position and axial compression ratio. From the test, specimens presented the characteristics of compression-torsion failure. The steel tube experienced buckling deformation and separated from the concrete at the middle and bottom of the column. The welds of some specimens cracked from the top to the bottom at the concave corner during the stage of decreasing load capacity. This resulted in localized crushing and the generation of torsional oblique cracks in the concrete. The hysteresis curves of the SCFST columns were relatively full in spindle shape without obvious pinching phenomenon, representing a good energy dissipation capacity. The ductility of the multi-cell CFST (MCFST) column is slightly better than that of the tensile-bar stiffened CFST (BCFST) column. There is a positive correlation between the torsion bearing capacity and parameters, such as the column limb width-thickness ratio, steel tube thickness and yield strength. When the axial compression ratio is less than 0.5, the axial compression can improve the torsion bearing capacity; when the axial compression ratio exceeds 0.5, the existence of axial compression will weaken the torsional capacity. The finite element model was established for parameters analysis, and calculation method for the T/Tu-N/Nu bearing capacity correlation curve was proposed, and the calculation results are more conservative and have certain safety reserve.本文讨论了异型混凝土填充钢管(SCFST)柱的抗压和抗扭组合性能。对包括两种加劲形式在内的八个试件进行了抗压和抗扭的伪静力试验研究。研究因素包括截面形状、加劲形式、加劲位置和轴向压缩比。试验结果表明,试样呈现出压缩-扭转破坏的特征。钢管发生了屈曲变形,并在支柱的中部和底部与混凝土分离。在承载能力下降阶段,一些试样凹角处的焊缝自上而下开裂。这导致了混凝土的局部挤压和扭转斜裂缝的产生。SCFST 柱的滞后曲线呈相对饱满的纺锤形,没有明显的挤压现象,代表了良好的消能能力。多孔 CFST(MCFST)柱的延性略好于拉杆加劲 CFST(BCFST)柱。扭转承载能力与柱肢宽厚比、钢管厚度和屈服强度等参数之间存在正相关。当轴向压缩比小于 0.5 时,轴向压缩可以提高抗扭承载力;当轴向压缩比大于 0.5 时,轴向压缩的存在会削弱抗扭承载力。建立了参数分析的有限元模型,提出了 T/Tu-N/Nu 轴承能力相关曲线的计算方法,计算结果较为保守,并有一定的安全储备。Vibration Analysis of Sandwich Functionally Graded Material Plate with Cut-outs using Artificial Neural Network TechniqueDheer Singh, Sourabh Rai, Ankit Guptadoi:10.1016/j.tws.2024.112072基于人工神经网络技术的夹层带切口功能梯度材料板振动分析In the present article, the effect of geometric discontinuities on the vibrational response of porous sandwich functionally graded material (SFGM) plates with double FGM factsheets has been investigated using the artificial neural network (ANN) technique. Generalized governing equations for the SFGM plate have been derived based on nonpolynomial based higher-order shear deformation theory (HSDT). Geometric discontinuities have been incorporated in terms of cut-outs in the SFGM plates. The FGM layers integrate a porosity model, while the core layer is considered a ceramic layer within the SFGM plate structure. Further, a C° continuous isoparametric finite element formulation with a four-noded, isoparametric quadrilateral element with seven degrees of freedom (DOFs) per node has been employed to accomplish the results. The accuracy of the present results has been demonstrated through convergence and validation studies. A comprehensive study has been carried out to investigate the influence of volume fraction index, even and uneven porosity distribution and cut-outs on the frequency parameter of SFGM plates. However, the finite element method (FEM) is computationally challenging. Therefore, the motivation behind adopting ANN technique to develop a predictive model for reasonable accuracy with less computational time. The ANN technique is proposed to predict the NDFP of the SFGM plate using cut-outs under various conditions using numerical simulation datasets. An optimised ANN model has been developed with an architecture of (6-5-10-5-1), exhibits best performance based on mean error value, which accurately predicts the Non-Dimensional Frequency Parameter (NDFP) of the SFGM plate.本文利用人工神经网络(ANN)技术研究了几何不连续对多孔夹层功能梯度材料(SFGM)板的振动响应的影响。基于非多项式高阶剪切变形理论(HSDT),导出了SFGM板的广义控制方程。几何不连续被纳入到SFGM板块的切割中。FGM层集成了孔隙率模型,而核心层被认为是SFGM板结构中的陶瓷层。此外,采用C°连续等参有限元公式,每个节点具有7个自由度(dof)的四节点等参四边形单元来完成结果。目前结果的准确性已通过收敛和验证研究证明。本文研究了体积分数指数、均匀和不均匀孔隙率分布以及切割对SFGM板频率参数的影响。然而,有限元法(FEM)在计算上具有挑战性。因此,采用人工神经网络技术开发一种以更少的计算时间实现合理精度的预测模型的动机。利用数值模拟数据集,提出了利用人工神经网络技术预测不同条件下SFGM板的NDFP。基于平均误差值的优化模型(6-5-10-5-1)能准确预测SFGM板的无因次频率参数(NDFP)。Behavior of Hybrid FRP-Concrete-Steel Double-Skin Tubular Member T-Joints Subjected to Brace Axial CompressionGuan Lin, Junjie Zeng, Jiaxing Li, G.M. Chen, J.K. Zhoudoi:10.1016/j.tws.2024.112081frp -混凝土-钢复合管形构件t形节点在支撑轴压作用下的性能Hybrid fiber reinforced polymer (FRP)-concrete-steel double-skin tubular members (DSTMs) are a novel form of structural members comprised of an outer FRP tube, an inner steel tube, and an annular concrete sandwiched between the two tubes. By leveraging the advantageous properties of each constituent material, DSTMs possess superior mechanical performance and exceptional durability, making them highly promising for applications in ocean structures. Despite extensive research highlighting the excellent performance of individual DSTMs such as beams and columns since their inception, investigations into the behavior of DSTM joints have been scarce. This critical knowledge gap presents a significant obstacle to the widespread practical application of DSTMs. To address this gap, the present study was proposed to investigate the behavior of circular DSTM T-joints subjected to brace axial compression. An experimental program was conducted to systematically examine the influence of key factors such as FRP/steel tube thickness, brace-to-chord diameter ratio, void ratio, and concrete strength on the performance of DSTM T-joints. The experimental results demonstrated that the DSTM T-joints exhibited a ductile behavior; FRP confinement was demonstrably effective in enhancing the joint bearing capacity; the brace-to-chord diameter ratio and void ratio were identified as two crucial factors influencing the joint bearing capacity. Finally, simple design equations capable of providing reasonably accurate and slightly conservative predictions for the bearing capacities of the test DSTM T-joint specimens were proposed.混合纤维增强聚合物(FRP)-混凝土-钢双皮管构件(DSTMs)是一种由外FRP管、内钢管和夹在两管之间的环形混凝土组成的新型结构构件。通过利用每种组成材料的优势特性,dstm具有卓越的机械性能和卓越的耐久性,使其在海洋结构中的应用前景非常广阔。尽管广泛的研究强调了单个DSTM(如梁和柱)自成立以来的优异性能,但对DSTM节点行为的研究却很少。这一关键的知识差距对DSTMs的广泛实际应用构成了重大障碍。为了解决这一差距,本研究提出了研究圆形DSTM t形接头受支撑轴向压缩的行为。采用试验程序,系统考察了FRP/钢管厚度、托弦直径比、孔洞比、混凝土强度等关键因素对DSTM t形节点性能的影响。试验结果表明:DSTM t形接头具有良好的延性;FRP约束对提高节点承载力有明显效果;确定了支撑弦径比和空隙比是影响节点承载力的两个关键因素。最后,提出了简单的设计方程,能够对试验DSTM t形节点试件的承载力提供合理准确且略保守的预测。来源:复合材料力学仿真Composites FEM

未登录
还没有评论
课程
培训
服务
行家
VIP会员 学习 福利任务 兑换礼品
下载APP
联系我们
帮助与反馈