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,Thin-Walled Structures 3 篇
Shape-retaining beam-like morphing structures via localized snap through
Asifur Rahman, Samuele Ferracin, Sujata Tank, Chris Zhang, Paolo Celli
doi:10.1016/j.ijsolstr.2024.112917
保持形状的梁状变形结构通过局部snap通过
In this study, we present a concept of morphing structure – featuring an arch mounted on a compliant base – that can be reconfigured via snap-through buckling and leverages bistability to retain its morphed shape. We show that one-dimensional arrays of such units yield beam-like structures that, upon localized snapping, can attain multiple, morphologically distinct stable shapes. Units are modeled using discrete elastic rods, a reduced-order formulation for beams and beam structures, and the results are validated via experiments. We leverage our model to understand the influence of the geometrical design parameters on the response and final shape of a unit. We then show that the morphed shapes of arrays of units can be predicted by concatenating results of simulations on single units, and leverage this idea to inverse-design structures that can be snapped into target stable shapes. Ultimately, our work suggests an up-scalable way to create shape-retaining morphing structures with target stable shapes.
在这项研究中,我们提出了一种变形结构的概念-具有安装在柔性基座上的拱门-可以通过卡扣 扣重新配置,并利用双稳定性来保持其变形形状。我们展示了这种单元的一维阵列产生的梁状结构,在局部捕获后,可以获得多个,形态上不同的稳定形状。单元使用离散弹性杆建模,这是梁和梁结构的降阶公式,并通过实验验证了结果。我们利用我们的模型来理解几何设计参数对单元响应和最终形状的影响。然后,我们展示了单元阵列的变形形状可以通过连接单个单元的模拟结果来预测,并利用这一想法来逆向设计可以快速进入目标稳定形状的结构。最终,我们的工作提出了一种可扩展的方法来创建具有目标稳定形状的保持形状的变形结构。
Effective boundary conditions for second-order homogenization
Manon Thbaut, Basile Audoly, Claire Lestringant
doi:10.1016/j.jmps.2024.105707
二阶均匀化的有效边界条件
Using matched asymptotic expansions, we derive an equivalent bar model for a periodic, one-dimensional lattice made up of linear elastic springs connecting both nearest and next-nearest neighbors. We obtain a strain-gradient model with effective boundary conditions capturing the boundary layers forming at the endpoints. It is accurate to second order in the scale separation parameter ɛ≪1, as shown by a comparison with the solution to the discrete lattice problem. The homogenized modulus associated with the gradient effect (gradient stiffness) is found negative, as is often the case in second-order homogenization. Negative gradient stiffnesses are widely viewed as paradoxical as they can induce short-wavelength oscillations in the homogenized solution. In the one-dimensional lattice, the asymptotically correct boundary conditions are shown to suppress the oscillations, thereby restoring consistency. By contrast, most of the existing work on second-order homogenization makes use of postulated boundary conditions which, we argue, not only ruin the order of the approximation but are also the root cause of the undesirable oscillations.
利用匹配渐近展开法,我们推导出了由连接最近和次近邻的线性弹性弹簧组成的周期性一维晶格的等效棒模型。我们得到了一个应变梯度模型,其有效边界条件捕捉到了端点处形成的边界层。通过与离散晶格问题的解进行比较,可以看出该模型的精确度达到了尺度分离参数ɛ≪1 的二阶。与梯度效应相关的均质化模量(梯度刚度)为负值,这在二阶均质化中很常见。人们普遍认为负梯度刚度是自相矛盾的,因为它会在均质化解中引起短波长振荡。在一维晶格中,渐近正确的边界条件可以抑制振荡,从而恢复一致性。相比之下,大多数现有的二阶均质化研究都使用了假定的边界条件,我们认为这些条件不仅破坏了近似的阶次,而且是产生不良振荡的根本原因。
Statistical description of fracture toughness revisited: Implications for evaluation of the reference temperature, T0, and characteristic fracture toughness
Claudio Ruggieri, Luís G.T.S. Leite, Daniel C.F. Ferreira
doi:10.1016/j.mechmat.2024.105055
重新审视断裂韧性的统计描述: 对参考温度 T0 和特征断裂韧性评估的影响
The present study focuses on further extensions of the more general three-parameter Weibull distribution to describe the statistical scatter of fracture toughness values and to evaluate the characteristic toughness of structural steels using a statistical description of toughness data in comparison with the minimum of three equivalent (MOTE) method. Fracture toughness tests conducted on several types of structural steels, including an ultra high strength steel and pressure vessel steels, provide the experimental data upon which the Weibull statistical analyses are conducted. These analyses compare descriptions of fracture toughness values based on a standard three-parameter Weibull function with fixed values for parameters α and Kmin, and a general three-parameter Weibull distribution with unknown parameters (α,K0, Kmin) in connection with a goodness-of-fit method to assess how well the experimental data fits the assumed distribution. Further, the study also shows that use of a fixed percentile of the distribution describing the toughness data set provides more consistent values of characteristic toughness compared to the MOTE procedure.
本研究的重点是进一步扩展更一般的三参数威布尔分布,以描述断裂韧性值的统计散布,并使用韧性数据的统计描述与最小三当量法(MOTE)进行比较,评估结构钢的特征韧性。对几种结构钢(包括一种超高强度钢和压力容器钢)进行的断裂韧性测试提供了进行 Weibull 统计分析所依据的实验数据。这些分析比较了基于参数 α 和 Kmin 固定值的标准三参数 Weibull 函数和未知参数(α、K0、Kmin)的一般三参数 Weibull 分布对断裂韧性值的描述,并结合拟合优度法评估实验数据与假定分布的拟合程度。此外,研究还表明,与 MOTE 程序相比,使用描述韧性数据集的分布的固定百分位数可提供更一致的特性韧性值。
Prediction of machining deformation for circular metallic plates under residual stress and clamping force in turning
Kang Ju, Chunzheng Duan, Yuwen Sun, Jiahao Shi, Abdolhamid Akbarzadeh
doi:10.1016/j.tws.2024.112049
车削过程中残余应力和夹紧力作用下圆形金属板加工变形预测
Workpiece deformation under the coupling effect of clamping force, initial residual stress (IRS), and machining residual stress (MRS) is an essential concern in the manufacturing of thin-walled metallic parts. Prediction of machining deformations is critical for ensuring machining quality and has significant guiding implications for producing thin-walled parts. However, most research has been focused on calculating machining deformation caused by a single factor. Based on the energy principle, the effect of clamping deformation on the material removal amount and the effect of the cyclic material removal process on both IRS and MRS are analyzed. To predict the machining deformation of circular metallic plates, energy functions under the three-dimensional non-uniform residual stress field consider the coupling effect of multiple factors, which is established and solved by the Raleigh-Ritz method. This analysis elucidates the formation mechanism of machining deformation under the single-factor effects of IRS and MRS as well as the coupling effect of clamping force and residual stress. In this article, an analytical prediction model with a prediction error of around 8.5% is established for machining deformation under the coupling effect. Additionally, leveraging the quantitative results of the proposed model, the impacts of cutting parameters and strategies on machining deformation, as well as the evolution of machining deformation throughout the entire material removal process are elicited.
夹紧力、初始残余应力(IRS)和加工残余应力(MRS)耦合作用下的工件变形是薄壁金属零件制造中的一个重要问题。加工变形预测是保证加工质量的关键,对薄壁件的生产具有重要的指导意义。然而,大多数研究都集中在计算由单一因素引起的加工变形上。基于能量原理,分析了夹紧变形对材料去除量的影响以及循环去除过程对IRS和MRS的影响。为预测圆形金属板的加工变形,建立了三维非均匀残余应力场下考虑多因素耦合效应的能量函数,并采用罗利-里兹法求解。分析了IRS和MRS单因素作用下加工变形的形成机理以及夹紧力和残余应力的耦合作用。本文建立了耦合作用下加工变形的解析预测模型,预测误差在8.5%左右。此外,利用所提出的模型的定量结果,得出切削参数和策略对加工变形的影响,以及在整个材料去除过程中加工变形的演变。
Inter-layer failure and toughening mechanisms of carbon/aramid hybrid fiber composites interleaved with micro/nano pulps under low-velocity impact load
Hangyan Wang, Yang Lin, Hongyong Jiang, Zhihui Liu
doi:10.1016/j.tws.2024.112086
微纳浆与碳/芳纶混杂纤维复合材料在低速冲击载荷下的层间破坏及增韧机理
Hybrid fiber-reinforced polymer (HFRP) composites are widely used in aerospace structures because of their excellent overall performance. However, it is still challenging to address the issue of high sensitivity to delamination between dissimilar material interlayers in HFRP composites. This study combines experimental and numerical simulation to analyze the low-velocity impact behavior and interlaminar damage of two types of HFRP. Based on a micromechanical model, an equivalent aramid pulp (eAP) toughening laminate model is developed. The impact behavior of the HFRP toughen by eAP only in dissimilar material interlayers is simulated based on the model. The effect of eAP areal density on the impact behavior and evolution of interlaminar damage is analyzed. Results show that the maximum force and impact stiffness of eAP-toughened HFRP increase initially with the increase in eAP areal density, and then decrease slowly. The area and extent of damage of dissimilar material interlayers in eAP toughened laminates is significantly reduced. Finally, the interlaminar toughening and failure mechanisms by eAP-toughening only in dissimilar material interlayers of the HFRP composites are systematically revealed from fiber bridging and damage transfer perspectives.
混杂纤维增强聚合物(HFRP)复合材料以其优异的综合性能在航空航天结构中得到广泛应用。然而,解决HFRP复合材料中不同材料夹层间分层的高敏感性问题仍然具有挑战性。本研究采用实验与数值模拟相结合的方法,对两种HFRP材料的低速冲击行为和层间损伤进行了分析。在微观力学模型的基础上,建立了等效芳纶浆料增韧层压模型。基于该模型,模拟了eAP增韧HFRP在不同材料层间的冲击行为。分析了eAP面密度对冲击行为和层间损伤演化的影响。结果表明:eAP增韧HFRP的最大受力和冲击刚度随eAP面密度的增加先增大后缓慢减小;eAP增韧层合板中异种材料间层的损伤面积和程度明显减小。最后,从纤维桥接和损伤传递的角度系统揭示了eap增韧在HFRP复合材料不同材料层间的层间增韧和破坏机制。
Dynamic response analysis of monopile CFDST wind turbine tower system under wind-wave-seismic coupling action
Li-Xin Duan, Wen-Da Wang, Long Zheng, Yan-Li Shi
doi:10.1016/j.tws.2024.112089
风波-地震耦合作用下单桩CFDST风塔系统动力响应分析
The dynamic response of monopile-supported offshore wind turbine tower (OWT) structures under seismic action in undrained conditions is analyzed using ABAQUS. A typical example is established by using the NREL5MW OC3 Monopile wind turbine tower as a prototype. The aim is to compare the seismic performance of concrete-filled double-skin steel tubes (CFDST) and steel structural wind turbine tower systems. The impact of seismic incidence angles on the dynamic response of both types of wind turbine towers is investigated. Combining OpenFAST, a sophisticated numerical model for the multi-hazard coupling is also established for both CFDST and steel structural offshore monopile wind turbine tower systems. The influence of various loads on the tower top acceleration, tower top displacement, base shear, and base moment for the aforementioned two types of wind turbine tower systems is studied. The results indicate that under the coupling effects of wind, waves, and seismic forces, the monopile CFDST wind turbine tower system exhibits superior seismic performance, operational stability, and safety compared to traditional steel wind turbine tower systems, and has better development prospects.
采用ABAQUS软件,分析了不排水条件下单桩支撑海上风电塔架结构在地震作用下的动力响应。以NREL5MW OC3单桩风力机塔架为原型,建立了典型实例。目的是比较双皮钢管混凝土(CFDST)和钢结构风塔系统的抗震性能。研究了地震入射角对两种风塔动力响应的影响。结合OpenFAST,建立了CFDST和钢结构海上单桩风电塔架系统多危害耦合的复杂数值模型。研究了不同荷载对上述两种风力机塔架系统塔顶加速度、塔顶位移、基础剪力和基础弯矩的影响。结果表明,在风、波、地震力的耦合作用下,单桩CFDST风塔体系比传统钢结构风塔体系具有更优越的抗震性能、运行稳定性和安全性,具有更好的发展前景。