今日更新:International Journal of Solids and Structures 1 篇,Journal of the Mechanics and Physics of Solids 1 篇,Mechanics of Materials 1 篇,International Journal of Plasticity 1 篇,Thin-Walled Structures 10 篇
Competing behavior of interface delamination and wafer cracking during peeling film from ultra-thin wafer
Wei Jian, Hanbin Yin, Ying Chen, Xue Feng
doi:10.1016/j.ijsolstr.2024.113058
超薄硅片剥离过程中界面分层与晶圆开裂的竞争行为
Peeling the front-side film from the flexible and ultra-thin wafer is a critical procedure for the fabrication of ultra-thin chips. For a successful peeling process, the following conditions are required simultaneously: the interface between the film and the wafer is debonded, the interface between the wafer and the substrate remains undelaminated, and the wafer stays intact. However, there are relatively few studies focusing on the underlying mechanism in this peeling process. Here, a theoretical model is developed to investigate the competing behavior of interface delamination and wafer cracking for the bilayer film-substrate system. Based on the constant-stress (Dugdale) cohesive law and Euler-Bernoulli beam theory, both the competing interface delamination criterion and the wafer cracking criterion are determined. The corresponding competing maps of interface delamination and wafer cracking are obtained, in which the interface delamination path and the wafer safety status can be predicted. The effect of several dimensionless parameters on the competing behavior of interface delamination and wafer cracking is examined systematically, including the property of the geometry, the material, and the interface of the bilayer film-substrate system. The theoretical model is validated by both finite element analysis (FEA) and experimental results. This research aims to provide some guidance for optimizing the peeling parameters and contribute to a higher success rate of peeling process.
从柔性超薄晶圆上剥离正面薄膜是制造超薄芯片的关键工序。对于一个成功的剥离过程,同时需要以下条件:薄膜和晶圆之间的界面是脱粘的,晶圆和衬底之间的界面保持不分层,晶圆保持完整。然而,对这一剥落过程的潜在机制的研究相对较少。本文建立了一个理论模型来研究双层薄膜-衬底体系中界面分层和晶圆开裂的竞争行为。基于恒应力(Dugdale)内聚规律和欧拉-伯努利梁理论,确定了竞争界面分层判据和晶圆开裂判据。得到了相应的界面分层和晶圆开裂竞争图,可以预测界面分层路径和晶圆安全状态。系统地研究了几种无量纲参数对界面分层和晶圆开裂竞争行为的影响,包括双层膜-衬底系统的几何特性、材料特性和界面特性。通过有限元分析和实验验证了理论模型的正确性。本研究旨在为优化脱皮工艺参数,提高脱皮工艺的成功率提供一定的指导。
Intrinsic Interlayer Shear Strength of Graphite
Yelingyi Wang, Shizhe Feng, Deli Peng, Tengfei Li, Cheng Zheng, Zubo Cai, Zhanghui Wu, Quanshui Zheng, Zhiping Xu
doi:10.1016/j.jmps.2024.105853
石墨的层间固有剪切强度
Graphite holds significant values in the energy and electronics industries due to its unique properties. As a quintessential example of highly anisotropic materials, the shear strength measures one of its most fundamental mechanical properties. However, the lack of ideal materials and testing methods has led to a wide dispersion in the reported values. To address this issue, we utilized epitaxially grown single-crystal graphite and developed a high-throughput sample preparation method, along with a novel loading technique in this work. The intrinsic shear strength of AB-stacked graphite was determined to be τs = 62 MPa, by excluding the size effect in measurements. The results are further compared to highly oriented pyrolytic graphite specimens processed down to nanoscale thickness, highlighting the adverse impact of twisted single-crystalline interfaces between the graphitic layers. Additionally, we observed a distinctive failure mechanism with continuous and uniform cascade plastic slips across the thickness of graphite samples, which corresponds to an interlayer shear strength approaching τs. The intrinsic shear strength characterized in our work sets an upper limit for the interlayer shear resistance of graphite. The experimental procedure for measuring shear strength can be applied to other van der Waals materials.
石墨由于其独特的性能,在能源和电子工业中具有重要的价值。作为高度各向异性材料的典型例子,抗剪强度是其最基本的力学性能之一。然而,由于缺乏理想的材料和测试方法,导致了报道值的广泛分散。为了解决这个问题,我们利用外延生长单晶石墨,开发了一种高通量样品制备方法,以及一种新的负载技术。测定了ab堆积石墨的固有抗剪强度为τs = 62 MPa,排除测量中的尺寸效应。结果进一步与高度取向的热解石墨样品加工至纳米级厚度进行了比较,突出了石墨层之间扭曲单晶界面的不利影响。此外,我们观察到一种独特的破坏机制,即在石墨样品的厚度上连续而均匀的级联塑性滑移,这对应于层间剪切强度接近τ5 .本文所描述的固有抗剪强度为石墨的层间抗剪能力设定了一个上限。测定抗剪强度的实验方法可应用于其它范德华材料。
Exact solutions for functionally graded flexoelectric micro-cylinders
Jinchen Xie, Christian Linder
doi:10.1016/j.mechmat.2024.105148
功能梯度柔性电微缸的精确解决方案
The flexoelectric effect implies a wide application potential in micro- and nanoscale electromechanical systems, where cylinders are widely used due to their wide range of applications. At the same time, functionally graded materials combine the advantages of different materials to achieve optimized material properties. Motivated by these considerations, we use the generalized power series method for the first time to derive exact solutions to functionally graded flexoelectric cylinder problems, including pressure and shear scenarios. This research systematically investigates the effects of material gradation, characteristic length parameters, and flexoelectric coefficients on the intricate electromechanical coupling behavior of functionally graded flexoelectric micro-cylinders. In addition, a comparative analysis between the exact and mixed finite element solutions demonstrates remarkable agreement. In particular, this investigation pioneers the extension of the Lamé problem, a cornerstone of classical elasticity, into the advanced realm of higher-order electroelasticity in inhomogeneous materials. This advance holds great promise for the design and optimization of micro- and nanoscale electromechanical systems based on the principles of flexoelectricity.
挠性电效应在微纳米机电系统中具有广泛的应用潜力,其中气缸由于其广泛的应用范围而被广泛使用。同时,功能梯度材料结合不同材料的优点,实现材料性能的优化。出于这些考虑,我们首次使用广义幂级数方法来推导功能梯度柔性电动缸问题的精确解,包括压力和剪切情况。本研究系统地研究了材料级配、特征长度参数和挠曲电系数对功能梯度挠曲电微缸复杂机电耦合行为的影响。此外,对精确有限元解和混合有限元解进行了比较分析,结果表明两者具有显著的一致性。特别是,这项研究将经典弹性的基石lam<s:1>问题扩展到非均匀材料的高阶电弹性的高级领域。这一进展为基于柔性电原理的微纳米机电系统的设计和优化提供了巨大的希望。
A new yield criterion for strength modeling from biaxial compression to biaxial tension
Lihuang Zheng, Jeong Whan Yoon
doi:10.1016/j.ijplas.2024.104113
从双轴压缩到双轴拉伸强度建模的屈服准则
Accurate strength modeling from equi-biaxial tension (EBT) to equi-biaxial compression (EBC) is critical for the plastic behavior prediction covering the wide-range of stress triaxiality encountered in sheet metal forming. To date, however, few yield criteria are available that can precisely model the initial yield and hardening behavior under six typical stress states between EBC and EBT, simultaneously. Furthermore, there is still a lack of a unified yield criterion for accurate strength modeling across various stress state ranges. To address the issues, a theoretical framework for constructing yield criteria dependent on stress states is provided and a new analytically described isotropic yield criterion is presented in this study. The flexibility in terms of the yield locus and application range is thoroughly explored to make the new yield criterion general. Subsequently, the isotropic yield criterion is extended into an analytically described anisotropic-asymmetric yield criterion. Furthermore, the extended yield criterion is applied to capture the initial yield behavior of DP980, AA5754-O, and AZ31 sheets, and the strain hardening behavior of QP1180 sheets at various stress states ranging from EBC to EBT along different loading directions. The predicted results from the extended criterion agree well with the corresponding experimental findings. The applications demonstrate that the proposed anisotropic-asymmetric yield criterion can effectively model the initial yield and hardening behavior of HCP, BCC, and FCC metal sheets under EBT, EBC, uniaxial tension (UT), plane strain tension (PST), shear (SH), and uniaxial compression (UC) in an analytical way.
从等双轴拉伸到等双轴压缩的精确强度建模,对于覆盖板料成形过程中所遇到的大范围应力三轴性的塑性行为预测至关重要。然而,迄今为止,很少有屈服准则能够同时精确模拟EBC和EBT之间六种典型应力状态下的初始屈服和硬化行为。此外,还缺乏统一的屈服准则来精确模拟各种应力状态范围内的强度。为了解决这一问题,本文提出了基于应力状态的屈服准则的理论框架,并提出了一种新的解析描述的各向同性屈服准则。深入探讨了屈服轨迹和适用范围的灵活性,使新屈服准则具有通用性。随后,将各向同性屈服准则推广为解析描述的各向异性-非对称屈服准则。应用扩展屈服准则捕捉了DP980、AA5754-O和AZ31板材在EBC ~ EBT不同应力状态下沿不同加载方向的初始屈服行为,以及QP1180板材的应变硬化行为。推广准则的预测结果与相应的实验结果吻合较好。应用结果表明,所提出的各向异性-非对称屈服准则可以有效地模拟HCP、BCC和FCC金属板在EBT、EBC、单轴拉伸(UT)、平面应变拉伸(PST)、剪切(SH)和单轴压缩(UC)作用下的初始屈服和硬化行为。
Predicting Maximum Deflection of N-Edged Thin-Shelled Hyperbolic-Paraboloid Umbrella Using Machine Learning Techniques
Hamid ElDarwich, Iman Mansouri, Maria Garlock, Shengzhe Wang
doi:10.1016/j.tws.2024.112412
利用机器学习技术预测n边薄壳双曲抛物面伞的最大挠度
Many thin-shelled hyperbolic paraboloid (hypar) umbrella forms have been built in the last 60 years as roof coverings. While the stresses in these forms remain relatively low, the deflections are a critical design parameter, and one that must be considered by architects and engineers in the conceptual design phase, meaning the design stage when the scale and form is given to the structure. To-date, there is no closed-form solution that can predict the maximum deflection of umbrellas due to their highly varying and complex geometry. The best option for predicting deflection is via finite element analysis, which is time-consuming for conceptual (preliminary) design purposes. In response, this paper uses machine learning via genetic programming (GP) and gene expression programming (GEP) to develop closed-form equations that predict the maximum corner deflection of N-edged hypar umbrellas – where N = 3, 4, 5, 6, 7, and 8. For a given a boundary condition and material, geometry is the most significant parameter influencing a shell's stiffness; thus, elastic finite element (FE) models use geometric properties as input variables (N, projected area, normalized rise, and shell thickness). The maximum corner deflection is recorded as an output and the FE analyses generate a large dataset of 53,754 results. It is observed that both GP and GEP can effectively parameterize the maximum deflection of N-edged hypar umbrellas, with GEP producing more concise, but relatively less accurate, equations than GP. While the formulations are trained using concrete material, a material factor multiplier transforms the results to other material properties within the assumption of elastic limits. The results of the study can be used to assist with conceptual design of hypar umbrellas and to validate complex FE models of hypar umbrellas. This research also illustrates the use of machine learning techniques as applied to the conceptual design of structures with highly varying geometries.
在过去的60年里,许多薄壳双曲抛物面伞形建筑被用作屋顶覆盖物。虽然这些形式的应力仍然相对较低,但挠度是一个关键的设计参数,建筑师和工程师在概念设计阶段必须考虑到这一点,这意味着在设计阶段,结构的规模和形式是给定的。迄今为止,由于雨伞高度变化和复杂的几何形状,没有封闭形式的解决方案可以预测雨伞的最大挠度。预测挠度的最佳选择是通过有限元分析,这对于概念(初步)设计目的是耗时的。作为回应,本文通过遗传编程(GP)和基因表达编程(GEP)使用机器学习来开发封闭形式方程,预测N边超伞的最大转角挠度-其中N = 3,4,5,6,7和8。对于给定的边界条件和材料,几何形状是影响壳刚度最显著的参数;因此,弹性有限元(FE)模型使用几何属性作为输入变量(N、投影面积、归一化高度和外壳厚度)。最大转角挠度被记录为输出,FE分析生成53,754个结果的大型数据集。观察到GP和GEP都能有效地参数化n边超伞的最大挠度,其中GEP生成的方程比GP更简洁,但精度相对较低。当公式使用混凝土材料进行训练时,材料因子乘数将结果转换为弹性极限假设内的其他材料属性。研究结果可用于辅助超超伞的概念设计和验证超超伞的复杂有限元模型。这项研究还说明了机器学习技术在高度变化几何结构概念设计中的应用。
Nonlinear dynamics and chaos of functionally graded graphene origami-enabled auxetic metamaterials doubly curved shells with bi-directionally stepped thickness in thermal environment
Qi Li, Vu Ngoc Viet Hoang, Peng Shi, Jian Yang, Ferruh Turan
doi:10.1016/j.tws.2024.112420
热环境下功能梯度石墨烯折纸辅助超材料双向阶梯厚度双弯曲壳的非线性动力学与混沌
This paper presents the dynamic and chaotic responses of functionally graded graphene origami (GOri)-enabled auxetic metamaterials (GOEAMs) doubly curved shells featuring stepped thickness profiles in thermal environment. A novel analytical framework is introduced to investigate geometric variations and material distributions, highlighting their crucial roles. Specifically, the investigation delves into structural variations in shell thickness, characterized by abrupt changes in uni- or bi-directional orientations, encompassing both single and double stepped thickness profiles. The five geometric configurations of the stepped structures encompass plates, cylindrical shells, spherical shells, hyperbolic paraboloid shells, and elliptical paraboloid shells. The FG-GOEAM structures, comprising multiple layers with varied GOri distributions across their thickness, are scrutinized using genetic programming-assisted micromechanical models. Central to the present approach is the formulation of nonlinear kinematic relationships using Reddy’s third-order shear deformation theory alongside von Kármán’s nonlinear geometric assumptions, with equations of motion being solved utilizing Galerkin’s technique. Notably, the enhanced model is developed to address non-continuous thickness variation through integral calculus operations, enhancing computational efficiency and obviating the need for complex algorithms. To verify the accuracy of the proposed method, the obtained results are compared with those from published literature. The study thoroughly investigates the influence of material properties, thermal conditions, and geometric parameters on the free vibration and nonlinear behaviors of the structures. Key findings include: The shell stiffness of the functionally graded (FG) shell (X−WGr) surpasses that of the homogeneous shell (U−WGr). The transitions from periodic to chaotic states of the stepped structures are discerned through the analysis of the time history response, the phase plane illustrating the deflection-velocity relationship, and the Poincaré map. Increasing the thickness ratios and GOri content while reducing the folding degree of GOri results in a significant increase in the fundamental frequency and critical load, along with a simultaneous decrease in vibrational amplitudes.
本文介绍了具有阶梯厚度轮廓的功能分级石墨烯折纸(GOri)辅助超材料(GOEAMs)双曲面外壳在热环境中的动态和混沌响应。该研究引入了一个新颖的分析框架来研究几何变化和材料分布,突出了它们的关键作用。具体而言,该研究深入探讨了外壳厚度的结构变化,其特点是单向或双向方向的突然变化,包括单阶梯和双阶梯厚度剖面。阶梯结构的五种几何构造包括板、圆柱形壳、球形壳、双曲抛物面壳和椭圆抛物面壳。FG-GOEAM 结构由多层组成,各层厚度上的 GOri 分布各不相同,我们使用遗传编程辅助微机械模型对其进行了仔细研究。本研究方法的核心是利用 Reddy 的三阶剪切变形理论和 von Kármán 的非线性几何假设来建立非线性运动关系,并利用 Galerkin 技术求解运动方程。值得注意的是,增强型模型是通过积分微积分运算来解决非连续厚度变化问题的,从而提高了计算效率,并避免了对复杂算法的需求。为了验证所提方法的准确性,将获得的结果与已发表的文献进行了比较。研究深入探讨了材料特性、热条件和几何参数对结构自由振动和非线性行为的影响。主要发现包括 功能分级(FG)壳体(X-WGr)的壳体刚度超过了均质壳体(U-WGr)。通过分析时间历程响应、说明挠度-速度关系的相位平面以及波恩卡雷图,可以发现阶梯结构从周期状态到混沌状态的过渡。提高厚度比和 GOri 含量,同时降低 GOri 的折叠度,可显著提高基频和临界载荷,同时降低振幅。
Stochastic response of FGM slantingly coupled plates in aero-thermal environment using meshfree method
Xuanzhi Shi, Rui Zhong, Qingshan Wang, Bin Qin, Hailiang Xu
doi:10.1016/j.tws.2024.112395
气动-热环境下FGM斜耦合板随机响应的无网格分析
The paper investigates the dynamic characteristics of functionally graded slantingly coupled plate structures in an aerospace thermal environment using meshfree methods. The displacement and energy equations of sub-rectangular plates are derived based on the first-order shear deformation theory (FSDT) and Hamilton's principle. The functionally graded material (FGM) model in thermal environments is defined by the Voigt mixing rule, incorporating thermal elasticity theory and supersonic piston theory to characterize the effects of thermal and aerodynamic loads on structural dynamic properties. The pseudo-excitation method (PEM) is employed to analyze stochastic response vibrations. Finally, meshfree methods are utilized to solve the system's vibration properties as well as stationary/non-stationary stochastic response characteristics. The proposed approach aligns closely with both existing literature and finite element simulation outcomes. Furthermore, the paper elucidates the influence patterns of load types, excitation types, and boundary conditions on the free and stochastic vibration characteristics of FG slantingly coupled plate structures. This study contributes to a deeper understanding of the dynamic properties of functionally graded coupled structures for researchers in the aerospace field.
本文采用无网格法研究了航天热环境下功能梯度斜耦合板结构的动态特性。基于一阶剪切变形理论(FSDT)和Hamilton原理,推导了亚矩形板的位移和能量方程。采用Voigt混合规则定义热环境下的功能梯度材料(FGM)模型,结合热弹性理论和超音速活塞理论来表征热载荷和气动载荷对结构动力性能的影响。采用伪激励法(PEM)分析随机响应振动。最后,利用无网格法求解系统的振动特性以及平稳/非平稳随机响应特性。所提出的方法与现有文献和有限元模拟结果密切相关。进一步阐明了载荷类型、激励类型和边界条件对FG倾斜耦合板结构自由和随机振动特性的影响规律。本研究有助于航空航天领域的研究人员对功能梯度耦合结构的动力特性有更深入的了解。
Compression after impact behavior of asymmetrically tapered laminates: Experimental and numerical studies
Xiaonan Yu, Xiwu Xu, Luofeng Huang, Qing Qin, Chao Zhang
doi:10.1016/j.tws.2024.112403
非对称锥形层压板的冲击后压缩性能:实验与数值研究
This paper presents experimental and numerical studies on the compression after impact (CAI) behavior of composite tapered laminates. It introduces newly designed impact platforms and compression fixtures specifically tailored for the specimens. Drop-weight impacts are applied to the center of the specimens, and the resulting damage is briefly described. Compression tests are then conducted on both non-impacted and impacted specimens, with strain gauges used to monitor the strain distribution. Internal damage is detected using CT scanning and ultrasonic C-scan techniques. The numerical simulations are performed using ABAQUS/Explicit finite element analysis (FEA), incorporating an intra-laminar progressive damage model and an inter-laminar cohesive model, while additionally modeling resin pockets as elastomers. The simulation and experimental results indicate that before compression failure, impact damage in the thin section minimally affects the out-of-plane displacement, which is predominantly influenced by structural asymmetry. Stress concentration is observed at the junction between the thin and tapered sections in the compression test, while in the CAI test, stress concentration appears in the impact zone. The impact induces a notable shift in failure location and damage modes, resulting in decreased compressive strength, although the impact on stiffness remains minimal.
本文对复合材料锥形层合板的冲击后压缩(CAI)性能进行了实验和数值研究。它引入了新设计的冲击平台和压缩夹具,专门为试样量身定制。落重冲击作用于试件的中心,并简要描述了由此产生的损伤。然后在非冲击和冲击试样上进行压缩试验,用应变片监测应变分布。使用CT扫描和超声c扫描技术检测内部损伤。数值模拟使用ABAQUS/显式有限元分析(FEA)进行,结合层流内渐进损伤模型和层流间黏结模型,同时将树脂袋建模为弹性体。仿真和实验结果表明,在压缩破坏前,薄截面的冲击损伤对面外位移的影响最小,面外位移主要受结构不对称的影响。在压缩试验中,在细截面和锥形截面交界处观察到应力集中,而在CAI试验中,应力集中出现在冲击区。冲击引起破坏位置和损伤模式的显著变化,导致抗压强度下降,但对刚度的影响仍然很小。
A novel self-centring jacket-type offshore wind turbine structure: A proof-of-concept study and seismic fragility analysis
Ke Ke, Wuhua Xie, Xuhong Zhou, Yuhang Wang, Xiuzhang He
doi:10.1016/j.tws.2024.112407
一种新型自定心导管式海上风力涡轮机结构:概念验证研究和地震易损性分析
Recent installations of jacket-type offshore wind turbines (JOWTs) in seismically active regions have drawn increasing concerns regarding the seismic safety of JOWTs. To enhance the seismic performance of JOWTs, a novel self-centring jacket-type offshore wind turbine (SCJOWT) design is proposed in this study by replacing the traditional transition piece (TP) connecting the tower and jacket with a novel TP system equipped with the self-centring energy dissipation bearing (SCEDB). The SCJOWT is designed with three states of seismic behaviour: initial, controlled rocking, and post-earthquake restoring, and exhibits good ductility, self-centring capacity, and flexibility in adjusting hysteretic behaviours. The benefits of the SCJOWT in seismic mitigation over the traditional JOWT are evaluated by a comparative study. First, the finite element models of a 5-MW JOWT prototype structure and nine SCJOWT structures equipped with the SCEDBs of various flag-shaped hysteretic behaviours are developed, and the rationality of the modelling techniques is verified by test data. Then, the seismic dynamic responses of the structures are carefully examined. Finally, seismic fragility analyses are performed based on a suite of design-spectrum-compliant ground motions. The results show that the SCJOWT can mitigate the fragility of collapse and serviceability compared to the JOWT. Moreover, the hysteretic behaviour of SCEDBs has a significant influence on the seismic fragility of SCJOWTs, and hence the seismic performance of SCJOWTs can be optimised by modulating the structural hysteretic parameters.
最近在地震活跃地区安装的导管式海上风力涡轮机(JOWTs)引起了人们对JOWTs地震安全性的日益关注。为了提高海上风电机组的抗震性能,本文提出了一种新型的自定心导管套式海上风电机组(SCJOWT)设计方案,将连接塔架和导管套的传统过渡件(TP)替换为带有自定心耗能轴承(SCEDB)的新型导管套系统。SCJOWT设计具有三种地震行为状态:初始状态、可控摇摆状态和震后恢复状态,并具有良好的延展性、自中心能力和调节迟滞行为的灵活性。通过对比研究,评估了SCJOWT与传统JOWT相比在抗震方面的优势。首先,建立了一个5mw JOWT原型结构和9个具有不同旗形滞回行为的scedb的SCJOWT结构的有限元模型,并通过试验数据验证了建模技术的合理性。然后,仔细检查了结构的地震动力响应。最后,基于一套符合设计谱的地面运动进行了地震易损性分析。结果表明,与JOWT相比,SCJOWT可以减轻坍塌的易碎性和可维护性。此外,scedb的滞回特性对scjots的地震易损性有显著影响,因此可以通过调节结构滞回参数来优化scjots的抗震性能。
Design Method for Axially Compressed H-sectional Aluminium Alloy Slender Column Based on CSM
Guohan Chen, Pengcheng Li, Han Bao, Yunchang Huang, Chenglin Liu, Tianhao Zhang, Gang Xiong
doi:10.1016/j.tws.2024.112417
基于CSM的轴向压缩h型钢铝合金细长柱设计方法
In this study, a section-limiting stress that considers the influence of cross-section slenderness on the load-carrying capacity proposed by the continuous strength method (CSM) is introduced for the first time in the design of axially compressed H-section aluminium alloy slender columns. Experimental and numerical simulation tests are conducted on these columns to understand their axial compression performance and failure modes, with subsequent validation of the numerical simulation methods. Using the CSM limiting stress, imperfection factor, and stability calculation factor, this study proposes a design method for the overall stability load-carrying capacity of axially compressed H-section aluminium alloy slender columns. The load-carrying capacity predictions of the proposed design method are compared with those of the European, American, Australian/New Zealand, and Chinese design standards using axial compression tests and numerical simulations. An evaluation of these design methods and standards is also presented. In addition, reliability analyses are conducted following the approaches proposed by the American Institute of Steel Construction and the European design standard to assess the reliability levels of the aforementioned design methods and standards. Finally, the study presents a calculation example of an aluminium alloy slender column using the proposed design method.
本文首次将连续强度法(CSM)中考虑截面长细比对承载力影响的截面极限应力引入轴压h型铝合金细长柱的设计中。对这些柱进行了试验和数值模拟试验,了解了它们的轴压性能和破坏模式,并对数值模拟方法进行了验证。利用CSM极限应力、缺陷因子和稳定计算因子,提出了轴压h型钢铝合金细长柱整体稳定承载能力的设计方法。通过轴压试验和数值模拟,将提出的设计方法的承载能力预测与欧洲、美国、澳大利亚/新西兰和中国的设计标准进行了比较。对这些设计方法和标准进行了评价。此外,根据美国钢结构协会和欧洲设计标准提出的方法进行可靠性分析,对上述设计方法和标准的可靠性水平进行评估。最后,以某铝合金细长柱为例,给出了采用本文提出的设计方法的计算实例。
Experimental and numerical study on ballistic response of stitched aramid woven fabrics under normal and oblique dynamic impact
Xiaoyuan Zheng, Hao Wu, Xing Li, Qianran Hu, Ke Yan, Shaobo Qi, Mengqi Yuan
doi:10.1016/j.tws.2024.112424
缝式芳纶机织物在正、斜动力冲击下的弹道响应试验与数值研究
The objective of this study was to examine the influence of impact angle and stitching method on the ballistic properties of fabrics. Multi-layer stitched fabrics and multi-layer unstitched fabrics were designed and manufactured. Subsequent pull-out tests, as well as positive and oblique impact ballistic tests, were conducted. A validated yarn-level ballistic impact finite element model was established to analyze the effects of impact angle and stitching methods on ballistic properties, including stress distribution, back deformation, and energy absorption. The results of experiments and simulations demonstrate that impact angle and stitching methods significantly affect the impact resistance and response mechanism of the fabric. The suture treatment significantly enhanced the energy absorption capacity of PW4, with an average energy absorption ratio of 16.72% at various angles. This treatment facilitates stress propagation within the yarn, resulting in a maximum reduction of 576.00 mm2 in the low-stress area, thereby maximizing the yarn's load-bearing potential. The peak value of back deformation is decreased. In comparison to PW4-0, the peak value of out-of-plane deformation displacement of PWS4-0 is reduced by 17.89%. Additionally, the energy absorption mechanism of the fabric varied with the incident angle, showing a "falling-rising-falling" trend in total energy absorbed.
本研究的目的是研究冲击角度和缝合方式对织物弹道性能的影响。设计并制造了多层有缝织物和多层无缝织物。随后进行了拉出试验,以及正冲击和斜冲击弹道试验。建立了经过验证的纱线级弹道冲击有限元模型,分析了冲击角度和缝合方式对弹道性能的影响,包括应力分布、背变形和能量吸收。实验和仿真结果表明,冲击角度和拼接方式对织物的抗冲击性能和响应机理有显著影响。缝线处理显著增强了PW4的能量吸收能力,各角度的平均能量吸收比为16.72%。这种处理有利于纱线内部的应力传播,导致低应力区域最大减少576.00 mm2,从而最大化纱线的承载潜力。背变形峰值减小。与PW4-0相比,PWS4-0的面外变形位移峰值减小了17.89%。织物的吸能机制随入射角的变化而变化,总吸能呈现“下降-上升-下降”的趋势。
Compressive chord sidewall failure of equal-width RHS X joints with brace inclination
Sihyeong Park, Seon-Hu Kim, Cheol-Ho Lee
doi:10.1016/j.tws.2024.112425
带支撑倾斜的等宽RHS X节点受压弦边破坏
The compressive chord sidewall failure in equal-width RHS (rectangular hollow section) X joints has been extensively investigated in recent years, primarily due to the awareness of the excessive conservatism implied in the resistance formula of current design codes. However, most previous studies on chord sidewall failure have covered only the case of orthogonal joints where chord and brace members are joined at right angle. Consequently, non-orthogonal joints, involving brace inclination, have been rarely studied to date, despite their frequent use in the field application. This study investigates the effect of brace inclination on the chord sidewall strength, both analytically and numerically, with the aim of critically evaluating related design provisions and proposing necessary modifications. This study starts with noting that the design resistance calculation in current codes for chord sidewall failure typically consists of two steps, computing the strength of orthogonal joints first and then extending the orthogonal joint strength to that of the inclined joint. The rule for extending buckling-related parameters from orthogonal to inclined joints, as adopted in current design codes, is shown not to well reflect the actual load-transfer mechanism in the chord sidewall. A modified rule is proposed for inclined joints, with paying special attention to the significant coupled effects between brace inclination and chord stresses. Test-validated FE analysis is used to demonstrate that the proposed modification results in improved accuracy in predicting the chord sidewall failure strength of inclined joints.
近年来,等宽RHS(矩形空心截面)X节点的受压弦侧壁破坏得到了广泛的研究,这主要是由于人们意识到现行设计规范中阻力公式中隐含的过度保守性。然而,以往关于弦杆侧壁破坏的研究大多只涵盖了弦杆和支撑构件以直角连接的正交节点的情况。因此,尽管在现场应用中经常使用,但涉及支撑倾角的非正交节点迄今为止很少进行研究。本研究从分析和数值两方面探讨了支撑倾角对弦侧壁强度的影响,目的是批判性地评估相关设计规定并提出必要的修改。本文首先注意到,现行规范中斜拉索侧壁破坏的设计抗力计算一般分为两个步骤,首先计算正交节点的强度,然后将正交节点的强度扩展到斜节点的强度。结果表明,现行设计规范中有关屈曲参数由正交节点扩展到斜节点的规则并不能很好地反映弦侧壁的实际荷载传递机制。提出了一种适用于倾斜节点的修正规则,特别注意了支撑倾角和 弦应力之间的显著耦合效应。试验验证的有限元分析结果表明,修正后的方法提高了斜节理弦边破坏强度预测的准确性。
Numerical modeling and simulation prediction of the forming process of 3D-tubular braided composite reinforcements
Jinlei Li, Nahiène Hamila, Eduardo Guzman-Maldonado, Gildas L'Hostis, Peng Wang
doi:10.1016/j.tws.2024.112426
三维管状编织复合材料增强材料成形过程的数值模拟与仿真预测
Tubular braids with a hollow structure are considered to be ideal reinforcements for manufacturing composite pipes and cylindrical structures. The mechanical properties of the fabric are critical in the forming process. A new simulation approach based on the non-orthogonal hyperelastic constitutive model for predicting the mechanical behavior of tubular braided reinforcements during forming was proposed. The validity and accuracy of this approach were certified by the uniaxial tensile test of tubular braided fabrics and the maximum errors are less than 15%. In addition, preforming of fabrics on the tetrahedrons and cylinders has been investigated. The predicted shear angle and elongation of a single yarn of the tubular fabric after forming showed good agreement with experimental results. The maximum errors of shear angle and elongation of a single yarn are 10.4% and 9.8%, respectively. Furthermore, the formability of the fabric was also predicted to achieve damage-free preforms. This work thus gives a novelty perspective to further guide tubular braided fabric processing during the forming process.
具有中空结构的管状编织带被认为是制造复合管道和圆柱结构的理想增强材料。织物的机械性能在成型过程中是至关重要的。提出了一种基于非正交超弹性本构模型的管状编织增强件成形力学行为模拟方法。通过管状编织织物的单轴拉伸试验,验证了该方法的有效性和准确性,最大误差小于15%。此外,还对织物在四面体和圆柱体上的预成形进行了研究。预测的管状织物成型后单根纱线的剪切角和伸长率与实验结果吻合较好。单根纱线的剪切角和伸长最大误差分别为10.4%和9.8%。此外,还预测了织物的可成形性,以实现无损伤预成型。从而为进一步指导管状编织织物成形过程中的加工提供了一个新颖的视角。
Nonlinear Guided Wave Mixing in Weld Joints for Detection of Material Nonlinearity
Mohammed Aslam, Jaesun Lee
doi:10.1016/j.tws.2024.112428
焊接接头非线性导波混频检测材料非线性
The remarkable sensitivity of ultrasonic waves to detect the early stages of material degradation stems from their inherent nonlinear nature. However, distinguishing the nonlinearity induced by the measurement system from that of the weak materials remains a persistent challenge in second harmonic generation methods. Ultrasonic wave mixing has emerged as a feasible solution for isolating nonlinearities originating from the measurement system. While bulk waves, surface waves, and guided waves have undergone extensive study in wave mixing, the potential of feature-guided wave (FGW) mixing remains largely unexplored. This paper investigates the mutual interaction of FGWs to generate second-order mixed harmonic waves, focusing specifically on weld joints. Acoustic energy trapped along structural features such as weld joints exhibits reduced decay compared to uniform plates, making them ideal for nonlinear characterization. We investigate the effectiveness of FGW mixing for characterizing material nonlinearities in welded joints, utilizing phase velocity matching and resonance criteria to enhance the generation of mixed harmonic components. Through three-dimensional numerical simulations and experimental tests, we showcase the generation of mixed harmonics induced by the mixing of FGWs. Our findings underscore the potential of FGW mixing as a novel approach for enhancing nonlinear-based damage detection techniques in welded joints.
超声波在检测材料降解早期阶段的显著灵敏度源于其固有的非线性性质。然而,如何区分测量系统引起的非线性与弱材料引起的非线性仍然是二次谐波产生方法的一个长期挑战。超声波混频已成为隔离测量系统非线性的一种可行方法。虽然体波、面波和导波在波混频方面已经得到了广泛的研究,但特征导波(FGW)混频的潜力仍未得到充分的开发。本文以焊缝为研究对象,研究了fgw相互作用产生二阶混合谐波的过程。与均匀板相比,沿着结构特征(如焊接接头)捕获的声能表现出更少的衰减,使其成为非线性表征的理想选择。我们研究了FGW混合在表征焊接接头材料非线性方面的有效性,利用相速度匹配和共振准则来增强混合谐波分量的产生。通过三维数值模拟和实验测试,我们展示了FGWs混合引起的混合谐波的产生。我们的研究结果强调了FGW混合作为一种新方法的潜力,可以增强基于非线性的焊接接头损伤检测技术。