今日更新:International Journal of Solids and Structures 2 篇,Journal of the Mechanics and Physics of Solids 2 篇,Thin-Walled Structures 3 篇
Vibration characteristics of cylindrical shells with discontinuous connections based on the spectral element method
Kai Chai, Junfeng Liu, Jingjun Lou, Shuyong Liu
doi:10.1016/j.ijsolstr.2024.113148
基于谱元法的非连续连接圆柱壳振动特性研究
Common shell of revolution, such as cylindrical, conical, and spherical shells, are widely used in marine, aerospace, and other engineering fields due to their excellent support and pressure-resistant properties. Research on their vibration characteristics has progressed from single shells to composite shells, from ribbed shells to those with complex internal substructures, and from uniform to discontinuous connections. The discontinuities in wave propagation at the boundaries of discontinuously connected cylindrical shells result in highly complex equation of vibration control, leading to limited studies in this area. This study first models the uniform cylindrical shell and annular plate as spectral elements, using trigonometric and Bessel functions to describe displacement solutions and obtain vibration responses for arbitrary boundary conditions. Then, based on artificial virtual spring theory and the weighted least squares method, the discontinuous connection between the cylindrical shell and annular plate is modeled as a circumferentially varying stiffness distribution, leading to the derivation of dynamic stiffness matrices for both continuous and discontinuous connections. Finite element simulations are conducted using ABAQUS to analyze the vibration characteristics of the discontinuously connected cylindrical shell under free, clamped, and simply supported boundary conditions. Finally, an experimental setup is used to measure the vibration response under harmonic excitation and perform impedance testing with an impact hammer. The results show that the spectral element method accurately calculates the natural frequencies of the stiffened cylindrical shell, with an overall error of less than 2 %, while the maximum error for the experimental shell is 5.8 %.
常见的旋转壳体,如圆柱壳、锥形壳和球形壳,由于其优异的支撑和耐压性能,在船舶、航空航天和其他工程领域得到了广泛的应用。它们的振动特性研究已经从单壳发展到复合壳,从肋壳发展到具有复杂内部子结构的壳,从均匀连接发展到不连续连接。由于波浪在非连续连接圆柱壳边界处的传播不连续,导致振动控制方程非常复杂,导致该领域的研究有限。本研究首先将均匀圆柱壳和环形板建模为谱元,利用三角函数和贝塞尔函数描述位移解,得到任意边界条件下的振动响应。然后,基于人工虚拟弹簧理论和加权最小二乘法,将圆柱壳与环形板之间的不连续连接建模为周向变刚度分布,推导出连续连接和不连续连接的动刚度矩阵;利用ABAQUS软件进行有限元仿真,分析了自由边界、固支边界和简支边界条件下非连续连接圆柱壳的振动特性。最后,利用实验装置测量了谐波激励下的振动响应,并用冲击锤进行了阻抗测试。结果表明,谱元法准确地计算了加筋圆柱壳的固有频率,总体误差小于2 %,而实验壳的最大误差为5.8 %。
An analytical model for the phase transformation front propagation in superelastic SMA under impact tensile loading
Y. Wang, B. Hou, S. Roux, H. Zhao
doi:10.1016/j.ijsolstr.2024.113151
冲击拉伸载荷作用下超弹性SMA相变前沿扩展的解析模型
Shape-memory alloys (SMAs) exhibit superelastic behavior due to reversible phase transformations. Under dynamic (impact) loading, phase transformation is experimentally observed to occur along a band whose front propagates throughout the specimen. However, unlike the static case, the nucleation and propagation of these bands require further understanding. Recently, a Finite Element Method (FEM) simulation based on Thamburaja and Nikabdullah’s constitutive model successfully reproduced the experimental observations. In this study, the model is revisited in the specific case of a one-dimensional dynamic tension test, which allows for the derivation of an analytical closed-form one-dimensional stress–strain relation. When compared to FEM simulations of a single element, this analytical solution shows excellent agreement. From this closed form stress–strain relation, the propagation speed of the phase transformation shock front can be analytically computed. It also highlights that the shock front speed is primarily controlled by the strain reached after the complete transformation from the Austenite to the Martensite phase.
形状记忆合金(sma)由于可逆相变而表现出超弹性行为。在动态(冲击)载荷下,实验观察到相变发生在其前缘沿整个试样传播的条带上。然而,与静态情况不同,这些能带的成核和扩展需要进一步了解。最近,基于Thamburaja和Nikabdullah的本构模型的有限元模拟成功地再现了实验结果。在本研究中,该模型在一维动态张力试验的具体情况下被重新审视,它允许推导一个解析的封闭形式的一维应力-应变关系。与单单元有限元模拟结果比较,该解析解具有较好的一致性。根据这种封闭的应力-应变关系,可以解析计算相变激波前缘的传播速度。研究还表明,冲击前速度主要由奥氏体完全转变为马氏体后达到的应变控制。
Stochastic generalized standard materials and risk-averse effective behavior
Jeremy Bleyer
doi:10.1016/j.jmps.2024.105952
随机广义标准材料与风险规避有效行为
In this work, we develop a theoretical formulation for describing dissipative material behaviors in a stochastic setting, using the framework of Generalized Standard Materials (GSM). Our goal is to capture the variability inherent in the material model while ensuring thermodynamic consistency, by employing the mathematical framework of stochastic programming. We first show how average behaviors can be computed using the expected value of the free energy and dissipation pseudo-potentials. We then introduce the concept of a risk-averse effective measure, which provides both an optimistic and a pessimistic estimate of the uncertain material behavior. To this end, we utilize the Conditional Value-at-Risk, a widely used risk measure in mathematical finance. We also demonstrate how these concepts can be extended to variational problems at the structure scale, allowing us to compute the effective response of a structure composed of a stochastic material.
在这项工作中,我们使用广义标准材料(GSM)的框架,开发了一个理论公式来描述随机设置中的耗散材料行为。我们的目标是通过采用随机规划的数学框架,在确保热力学一致性的同时,捕捉材料模型中固有的可变性。我们首先展示了如何使用自由能和耗散伪势的期望值来计算平均行为。然后,我们引入了风险规避有效度量的概念,它提供了不确定物质行为的乐观和悲观估计。为此,我们利用数学金融中广泛使用的风险度量——条件风险价值。我们还演示了如何将这些概念扩展到结构尺度上的变分问题,使我们能够计算由随机材料组成的结构的有效响应。
Graph neural networks for strut-based architected solids
I. Grega, I. Batatia, P.P. Indurkar, G. Csányi, S. Karlapati, V.S. Deshpande
doi:10.1016/j.jmps.2024.105966
基于结构实体的图神经网络
Machine learning methods for strut-based architected solids are attractive for reducing computational costs in optimisation calculations. However, the space of all realizable strut-based periodic architected solids is vast: not only can the number of nodes, their positions and the radii of the struts be changed but the topological variables such as the connectivity of the nodes brings significant complexity. In this work, we first examine the structure-property relationships of a large dataset of strut-based architected solids (lattices). We enrich the dataset by perturbing nodal positions and observe four classes of mechanical behaviour. A graph neural network (GNN) method is then proposed that directly describes the topology of the strut-based architected solid as a graph. The differentiating feature of our work is that key physical principles are embedded into the GNN architecture. In particular, the GNN model predicts fourth-order tensor with the required major and minor symmetries. The predictions are equivariant to rigid body and self-similar transformations, invariant to the choice of unit cell and constrained to provide a positive semi-definite stiffness tensor. We further demonstrate that augmenting the training dataset with nodal perturbations enables the model to better generalize to unseen lattice topologies.
基于结构实体的机器学习方法对于减少优化计算中的计算成本具有吸引力。然而,所有可实现的基于支柱的周期结构实体的空间是巨大的:不仅节点的数量、位置和支柱的半径可以改变,而且节点的连通性等拓扑变量也带来了极大的复杂性。在这项工作中,我们首先研究了基于结构实体(晶格)的大型数据集的结构-属性关系。我们通过扰动节点位置来丰富数据集,并观察到四类力学行为。然后提出了一种图神经网络(GNN)方法,将基于支柱的体系结构实体的拓扑结构直接描述为图。我们工作的不同之处在于关键的物理原理被嵌入到GNN架构中。特别是,GNN模型预测具有所需的主要和次要对称性的四阶张量。预测对刚体和自相似变换是等变的,对单元格的选择是不变的,并且约束于提供一个正的半定刚度张量。我们进一步证明,用节点扰动增加训练数据集使模型能够更好地推广到看不见的晶格拓扑。
Innovative Auxetic Tubular Reinforced Metamaterial: Design and Mechanical Performance
Yinchuan He, Tingting Wang, Guoxing Lu, Li Wang, Kwong Ming Tse
doi:10.1016/j.tws.2024.112703
创新增强型管状超材料:设计与力学性能
In this study, we present the design, fabrication, and investigation of an innovative auxetic tubular reinforced (ATR) metamaterial. The mechanical properties and deformation characteristics of ATR metamaterials were comprehensively analyzed under quasi-static compression in both axial and radial directions. We conducted a comparative analysis between the ATR metamaterials and the original auxetic tubular (AT) metamaterials, employing both experimental and finite element methods. The findings indicate that the ATR structure surpasses the original AT structure in terms of mechanical properties during quasi-static compression in both directional orientations. Subsequently, a meticulous parametric analysis of the rotation angle of the reinforced straight ribs, a pivotal structural parameter, was conducted. The outcomes revealed that the rotation angle of the reinforced straight ribs, serving as a geometric parameter, can effectively influence the Poisson's ratio of the ATR structure. As the rotation angle of the reinforced straight rib increases, the ATR structure demonstrates superior energy absorption. The optimized ATR structure, in comparison to the original AT structure, showcases notable enhancements, exhibiting a 215% improvement in energy absorption (EA), a 62% increase in specific energy absorption (SEA), and a 46% rise in energy absorption efficiency (EAE) under axial quasi-static compression. Moreover, under radial quasi-static compression, the optimized ATR structure displays a remarkable improvement, featuring a 514% increase in EA, a 230% rise in SEA, and a 52% enhancement in EAE.
在这项研究中,我们提出了一种创新的消声管增强(ATR)超材料的设计、制造和研究。综合分析了ATR超材料在轴向和径向准静态压缩下的力学性能和变形特性。采用实验方法和有限元方法对ATR超材料与原始的AT超材料进行了对比分析。结果表明,在准静态压缩过程中,ATR结构在两个方向上的力学性能都优于原AT结构。随后,对加固直肋的旋转角度进行了细致的参数化分析,这是一个关键的结构参数。结果表明,加筋直肋的旋转角度作为几何参数,对ATR结构的泊松比有显著影响。随着增强直肋旋转角度的增大,ATR结构的吸能性能更好。优化后的ATR结构在轴向准静态压缩下的能量吸收(EA)提高了215%,比能吸收(SEA)提高了62%,能量吸收效率(EAE)提高了46%。此外,在径向准静态压缩下,优化后的ATR结构的EA提高了514%,SEA提高了230%,EAE提高了52%。
Programming morphological and mechanical performance of cyclic ori-kirigami via design-feasible parameter space
Ruoqi He, Yao Chen, Jiayao Shi, Yongtao Bai, Jian Feng
doi:10.1016/j.tws.2024.112706
基于设计可行参数空间的循环织构形态与力学性能规划
Recent advances in origami and kirigami have enabled the creation of unconventional structures that utilize precise folding and strategic cutting to achieve complex functionalities. In this study, we investigate the morphological and mechanical characteristics of one such structure, known as ori-kirigami. We establish the mapping between terminal folding states and parameter space, and analyze topologically feasible solutions for cyclic topology. The sensitivity of multi-stability to geometric parameters is investigated utilizing a nonlinear bar-and-hinge model. To facilitate automated design, analysis, and mechanical prediction, we propose a data-flow framework that supports the development of machine learning models for predicting mechanical responses. Additionally, symbolic regression is applied to derive a quantitative model for stiffness prediction. We anticipate that the findings of this work could open a path to engineering kirigami patterns for the design and fabrication of novel quasi-zero stiffness isolators, mechanical logic gates, and multistable shape-shifting structures.
折纸和基里格米的最新进展使得利用精确的折叠和战略切割来实现复杂功能的非常规结构的创造成为可能。在这项研究中,我们研究了一种被称为ori-kirigami的结构的形态和力学特征。建立了终端折叠态与参数空间的映射关系,分析了循环拓扑的拓扑可行解。利用非线性杆铰模型研究了多稳定性对几何参数的敏感性。为了促进自动化设计,分析和机械预测,我们提出了一个数据流框架,支持用于预测机械响应的机器学习模型的开发。此外,应用符号回归推导了刚度预测的定量模型。我们预计这项工作的发现可以为设计和制造新型准零刚度隔离器、机械逻辑门和多稳态变形结构的工程基里伽米模式开辟一条道路。
Compressive behavior of concrete jacketed in basalt TRM shell: experiments and predictions
Chenglin Wan, Jiyang Wang, Tao Wang, Fan Yang, Pinghuai Zhou
doi:10.1016/j.tws.2024.112709
玄武岩TRM壳套混凝土抗压性能:试验与预测
Numerous studies have investigated the behavior of textile reinforced mortar (TRM)-confined concrete, yielding various stress-strain models predominantly derived from fiber-reinforced polymer (FRP)-confined concrete. Yet, these models frequently overlook the intricate constitutive behavior of TRM materials and inadequately capture how TRM delivers its confinement effects. This often leads to inaccurate representation of the true characteristics of the confinement system, particularly the crucial role of mortar. This paper focuses on the impact of variations in textile layers and mortar matrix strength on the stress-strain behavior of basalt TRM (BTRM)-confined concrete, aiming to enhance our understanding of the confinement mechanism. Additionally, the study critically evaluates the key components of an existing analysis-oriented stress-strain model for FRP-confined concrete and introduces a refined version that more precisely depicts the behavior of confined concrete. This refined model integrates an identified confinement mechanism to provide accurate predictions of BTRM-confined concrete behavior. Our results reveal that low-grade mortar significantly decreases the actual confinement stiffness of BTRM jackets, inducing a steeper decline in the stress-strain curve, while high-strength mortar slightly diminishes the hoop rupture strain. To address the challenges of quantifying the complex confinement effect-compounded by the variable stress state and constitutive behavior of TRM-a novel coefficient, termed km, is introduced to gauge the influence of mortar strength on the confinement stiffness within the confining pressure equation. Predictive outcomes, including stress-strain and axial-to-lateral strain curves, show close alignment with experimental data, particularly in the slope at the plateau stage. This research significantly advances the quantitative understanding of TRM confinement effects and proposes the potential for designing more ductile structures using these materials, which could lead to enhanced resilience against seismic events and other structural challenges.
许多研究调查了纤维增强砂浆(TRM)约束混凝土的行为,得出了各种主要来自纤维增强聚合物(FRP)约束混凝土的应力-应变模型。然而,这些模型往往忽略了TRM材料复杂的本构行为,并没有充分捕捉到TRM如何提供其约束效应。这往往导致对约束系统真实特性的不准确表述,特别是迫击炮的关键作用。本文主要研究了纺织层数和砂浆基体强度的变化对玄武岩TRM (BTRM)约束混凝土应力-应变行为的影响,旨在增强我们对约束机制的理解。此外,该研究批判性地评估了现有frp约束混凝土面向分析的应力-应变模型的关键组成部分,并引入了一个更精确地描述约束混凝土行为的改进版本。这个改进的模型集成了一个确定的约束机制,以提供btrm约束混凝土行为的准确预测。研究结果表明,低等级砂浆显著降低了BTRM导管套的实际约束刚度,导致应力-应变曲线下降幅度更大,而高等级砂浆则略微降低了环向断裂应变。为了解决量化复杂约束效应的挑战-由trm的变应力状态和本构行为加剧-引入了一个新的系数,称为km,以衡量围压方程中砂浆强度对约束刚度的影响。预测结果,包括应力-应变和轴向-侧向应变曲线,显示与实验数据密切一致,特别是在高原阶段的斜坡。这项研究极大地推进了对TRM约束效应的定量理解,并提出了使用这些材料设计更具延展性的结构的潜力,这可能会增强对地震事件和其他结构挑战的弹性。