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【新文速递】2024年9月22日固体力学SCI期刊最新文章

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今日更新:International Journal of Solids and Structures 1 篇,Journal of the Mechanics and Physics of Solids 3 篇,Mechanics of Materials 2 篇,Thin-Walled Structures 4 篇

International Journal of Solids and Structures

Effective toughness based on Eshelby transformation theory for heterogeneous composites

Yun Xu, Yao Long, Hengbing An, Jun Chen

doi:10.1016/j.ijsolstr.2024.113074

基于Eshelby相变理论的非均质复合材料有效韧性研究

Predicting fracture toughness of heterogeneous composites is an important and challenging problem in physics and mechanics. The dependence of effective toughness on elastic properties of phases remains unclear. Considering that energy plays an essential role in crack propagation, an energy approach is proposed to obtain effective toughness in this study. We built the relationship between effective toughness and the homogenized local surface energy. The energy is constructed by generalizing Eshelby’s equivalent inclusion formulation to heterogeneous case, which couples physical features with elastic properties. An analytical formula of effective toughness can be derived for heterogeneous composites. Based on this formula, effects of toughness and elastic properties of the phases are discussed in depth, which reveals that how elastic heterogeneity can influence the effective toughness fundamentally. It is demonstrated that the predictions of concretes and metal toughening glasses agree well with experimental evidences.

预测非均相复合材料的断裂韧性是物理力学领域的一个重要而富有挑战性的问题。有效韧性与相弹性性能的关系尚不清楚。考虑到能量在裂纹扩展过程中起着至关重要的作用,本研究提出了一种获取有效韧性的能量法。建立了有效韧性与均质局部表面能之间的关系。将Eshelby等效包合公式推广到物理特征与弹性特性耦合的非均质情况,构造了能量。推导出非均相复合材料有效韧性的解析公式。在此基础上,深入讨论了相的韧性和弹性性能的影响,揭示了弹性非均质性对有效韧性的根本影响。结果表明,混凝土和金属增韧玻璃的预测结果与实验结果吻合较好。


Journal of the Mechanics and Physics of Solids

On the experimental identification of equilibrium relations and the separation of inelastic effects in soft biological tissues

Francesca Bogoni, Maximilian P. Wollner, Gerhard A. Holzapfel

doi:10.1016/j.jmps.2024.105868

软体生物组织中平衡关系的实验鉴定及非弹性效应的分离

The mechanical characterization of vascular tissues has been mainly focused on the measurement of elastic properties, while the investigation of inelastic effects has received comparatively little attention. Even the relatively simple, purely elastic description of the material behavior requires an appropriate set of experimental data that cannot be easily isolated using standard testing procedures. The presence of viscous and damage-related phenomena poses some challenges in the definition of appropriate testing protocols capable of identifying an equilibrium response, which in general does not solely represent the elastic material behavior. The primary goal of the present study is therefore to devise an experimental procedure that can distinguish and evaluate the different constitutive phenomena separately. To this end, we apply methodologies widely used in the mechanical testing of rubber-like materials and transfer them to the field of biomechanics. We performed two types of experiments in equibiaxial extensions on porcine thoracic aorta: a continuous cyclic test followed by a single-step relaxation test and a cyclic multi-step relaxation test, each at varying stretch rates. We demonstrate that the approximation of quasi-stationarity through continuous testing at slow rates is inadequate for the identification of an equilibrium relation. Alternatively, a step-wise protocol allows for the separation of equilibrium and viscous effects. This motivates a thermodynamic discussion of the experimental results in terms of energy dissipation and a closer look at the interplay of inelastic phenomena.

维管组织的力学表征主要集中在弹性特性的测量上,而对非弹性效应的研究相对较少。即使是相对简单的,对材料行为的纯弹性描述也需要一组适当的实验数据,而这些数据不能用标准测试程序轻易地分离出来。黏性和损伤相关现象的存在对确定平衡响应的适当测试方案提出了一些挑战,平衡响应通常并不仅仅代表弹性材料的行为。因此,本研究的主要目标是设计一个实验程序,可以分别区分和评估不同的本构现象。为此,我们将广泛应用于类橡胶材料力学测试的方法转移到生物力学领域。我们在猪胸主动脉上进行了两种类型的等双轴伸展实验:连续循环测试,然后是单步放松测试和循环多步放松测试,每一种测试都以不同的拉伸速率进行。我们证明,通过缓慢速率连续测试的准平稳近似不足以识别平衡关系。或者,一步一步的协议允许分离平衡和粘性效应。这激发了从能量耗散角度对实验结果进行热力学讨论,并更仔细地观察非弹性现象的相互作用。


Exponential time propagators for elastodynamics

Paavai Pari, Bikash Kanungo, Vikram Gavini

doi:10.1016/j.jmps.2024.105871

弹性动力学的指数时间传播算子

We propose a computationally efficient and systematically convergent approach for elastodynamics simulations. We recast the second-order dynamical equation of elastodynamics into an equivalent first-order system of coupled equations, so as to express the solution in the form of a Magnus expansion. With any spatial discretization, it entails computing the exponential of a matrix acting upon a vector. We employ an adaptive Krylov subspace approach to inexpensively and accurately evaluate the action of the exponential matrix on a vector. In particular, we use an apriori error estimate to predict the optimal Kyrlov subspace size required for each time-step size. We show that the Magnus expansion truncated after its first term provides quadratic and superquadratic convergence in the time-step for nonlinear and linear elastodynamics, respectively. We demonstrate the accuracy and efficiency of the proposed method for one linear (linear cantilever beam) and three nonlinear (nonlinear cantilever beam, soft tissue elastomer, and hyperelastic rubber) benchmark systems. For a desired accuracy in energy, displacement, and velocity, our method allows for 10−100× larger time-steps than conventional time-marching schemes such as Newmark-β method. Computationally, it translates to a  ∼1000× and ∼10−100× speed-up over conventional time-marching schemes for linear and nonlinear elastodynamics, respectively.

我们提出了一种计算高效、系统收敛的弹性动力学模拟方法。我们将弹性动力学的二阶动力学方程重构为一个等效的一阶耦合方程系统,从而以马格努斯展开的形式表达解。在任何空间离散化的情况下,都需要计算作用于矢量的矩阵的指数。我们采用自适应克雷洛夫子空间方法,以低成本准确评估指数矩阵对矢量的作用。特别是,我们使用先验误差估计来预测每个时间步长所需的最佳克雷洛夫子空间大小。我们证明,在第一项之后截断的马格努斯展开分别为非线性和线性弹性力学提供了二次收敛和超二次收敛的时间步长。我们对一个线性(线性悬臂梁)和三个非线性(非线性悬臂梁、软组织弹性体和超弹性橡胶)基准系统演示了所提方法的准确性和效率。对于所需的能量、位移和速度精度,我们的方法允许的时间步长比 Newmark-β 方法等传统时间行进方案大 10-100 倍。在计算方面,与线性和非线性弹性动力学的传统时间行进方案相比,我们的方法分别提高了 1000 倍和 10-100 倍的速度。


Modeling of textile composite using analytical network-averaging and gradient damage approach

Vu Ngoc Khiêm, Mahmood Jabareen, Rabin Poudel, Xuefeng Tang, Mikhail Itskov

doi:10.1016/j.jmps.2024.105874

基于分析网络平均和梯度损伤方法的纺织复合材料建模

In this contribution, we present a gradient damage model for anisotropic textile reinforcements including fiber inextensibility and fiber sliding. In contrast to previous works, the gradient damage formulation stems not from a numerical regularization basis but from the thermodynamics of internal variables. It results in a nonlocal term as the internal energy of fiber bending with measurable nonlocal parameter. Furthermore, to guarantee a priori that rotations and reflections determined by orthogonal tensors among the symmetry group do not affect the response function of the anisotropic constitutive law, a novel mesoscopic kinematic measure for the representative volume element of the fabric is defined on the basis of the analytical network-averaging concept. Such kinematic measure is of crucial importance for material modeling of damage-elastoplasticity in anisotropic textile reinforcements, and allows for analytical descriptions of inter- and intra-ply sliding of fibers. A mixed finite element formulation is then presented for textile reinforcements taking into account fiber inextensibility. The predictive capability of the computational model is demonstrated by comparing with multiple experimental datasets of dry textile fabrics.

在这篇文章中,我们提出了一个梯度损伤模型的各向异性纺织增强包括纤维的不延伸性和纤维滑动。与以往的工作不同,梯度损伤公式不是基于数值正则化基础,而是基于内变量的热力学。得到非局部项作为光纤弯曲内能,具有可测量的非局部参数。此外,为了保证对称群中正交张量所决定的旋转和反射不会先验地影响各向异性本构律的响应函数,基于解析网络平均的概念,定义了一种新的具有代表性的织物体元的细观运动学测度。这种运动学测量对于各向异性纺织增强材料的损伤弹塑性建模具有重要意义,并允许对纤维的层间和层内滑动进行分析描述。然后提出了考虑纤维不可扩展性的纺织增强材料的混合有限元公式。通过与多个实验数据集的比较,验证了计算模型的预测能力。


Mechanics of Materials

Damage ratio strength criterion for asphalt mixtures and its application in rutting prediction

Xia Wu, Faxing Ding, Jiaqi Chen, Leixin Nie, Zhiwu Yu

doi:10.1016/j.mechmat.2024.105165

沥青混合料损伤比强度判据及其在车辙预测中的应用

The current damage ratio strength theory is employed to predict the multiaxial strength of asphalt mixtures at various temperatures. Based on the dimensionless triaxial strength of asphalt mixtures, the values of six empirical parameters are recommended to establish the corresponding dimensionless strength criterion. The multiaxial strength data of diverse asphalt mixtures, including OGFC-13, AC-13, AC-20, AC-25, SMA-13, and SUP12.5 at different temperatures, are employed to validate the proposed criterion, which is then compared with other criteria. The results indicate that the suggested dimensionless strength criterion with uniform parameter values can accurately predict the true triaxial, confining triaxial, and biaxial strength values of asphalt mixtures across various temperatures. Furthermore, the proposed criterion is employed to elucidate the mechanical mechanism of rutting, offering a valuable insight for predicting flow rutting of pavement under loads.

采用当前损伤比强度理论对沥青混合料在不同温度下的多轴强度进行了预测。根据沥青混合料的无量纲三轴强度,推荐6个经验参数的取值,建立相应的无量纲强度准则。采用OGFC-13、AC-13、AC-20、AC-25、SMA-13、SUP12.5等不同沥青混合料在不同温度下的多轴强度数据对所提出的准则进行验证,并与其他准则进行比较。结果表明,所提出的参数值统一的无量纲强度准则能够准确预测沥青混合料在不同温度下的真三轴、围三轴和双轴强度值。此外,该准则还阐明了车辙的力学机理,为荷载作用下路面流动车辙的预测提供了有价值的见解。


Integrating MIL and Mori–Tanaka methods for microstructural analysis and mechanical behaviour prediction in heterogeneous materials

Lívia M. Nogueira, Lavinia A. Borges, Daniel A. Castello

doi:10.1016/j.mechmat.2024.105167

整合MIL和Mori-Tanaka方法在非均质材料的微观结构分析和力学行为预测

This paper explores heterogeneous materials, investigating their intricate nature characterized by structural and property variations across length scales. These variations, stemming from a variety of phases and structural constituents, lead to orientation-dependent properties, and challenge material isotropy assumptions. The present work focuses on unraveling mechanical behaviour for material selection and predictive modeling. More specifically, this paper proposes a strategy for micromechanical analyses integrating the Mori–Tanaka (M-T) homogenization model and the Mean Intercept Length (MIL) morphology-based method. The initial analysis examines the impact of both pore shape and distribution on microstructural characterization, replicating isotropic and anisotropic conditions for certain scenarios. MIL proves effective for microstructure orientation analysis, regardless of porosity. Subsequently, the M-T method is applied to estimate Young’s modulus, and its relationship with pore shape, orientation, and volume fraction is investigated. This investigation into Young’s modulus provides valuable insights into the proposed framework’s capability to uncover the intricate relationship between microstructural features and macroscopic properties within heterogeneous materials. The overall framework presented in this paper holds promise for practical applications in predicting properties in real materials using micro-CT images, contributing to a deeper understanding of these complex materials and their behaviour.

本文探讨了非均质材料,研究了其复杂的性质,其特征是结构和性质在长度尺度上的变化。这些变化源于各种相和结构成分,导致取向依赖的性质,并挑战材料的各向同性假设。目前的工作重点是揭示材料选择和预测建模的机械行为。更具体地说,本文提出了一种将Mori-Tanaka (M-T)均匀化模型和基于平均截距长度(MIL)形态学的方法相结合的微力学分析策略。初步分析考察了孔隙形状和分布对微观结构表征的影响,在某些情况下复 制了各向同性和各向异性条件。事实证明,无论孔隙度如何,MIL对微观结构取向分析都是有效的。随后,采用M-T方法估算杨氏模量,并研究其与孔隙形状、取向和体积分数的关系。这项对杨氏模量的调查提供了宝贵的见解,以揭示非均质材料中微观结构特征和宏观特性之间的复杂关系。本文提出的总体框架有望在实际应用中使用微ct图像预测真实材料的性能,有助于更深入地了解这些复杂材料及其行为。


Thin-Walled Structures

New 3D Petal-like Structures with Lightweight, High Strength, High Energy Absorption, and Auxetic Characteristics

Zhen-Yu Li, Wei-Ming Zhang, Wei-Jing Wang, Mabel Mei Po Ho, Jian Xiong, Jin-Shui Yang, Xin-Tao Wang, Minglonghai Zhang, Hong Hu

doi:10.1016/j.tws.2024.112483

新型3D花瓣状结构,具有轻量化、高强度、高能量吸收和增减特性

A novel type of petal-like structure that exhibits superior mechanical properties, was proposed and fabricated by integrating advantages of metamaterial, multi-stage deformation, and high strength of fiber-reinforced composites. Compression testing and finite element analysis were first conducted on three petal-like structures formed with different angles and made from fiber-reinforced composites. The findings indicated that these composite-based multi-cell structures can also exhibit a satisfactory stress plateau stage through judicious structural design. After ensuring the structures' performance under quasi-static compression load, the impact resistance of the new structures was further examined. It was found that the structure's auxetic characteristics diminished under low-speed impact load. However, under a 20J impact load, the structures exhibited energy absorption characteristics (SEA) that surpassed those of both conventional and other new auxetic structures by 8-40 times. These promising results demonstrate that the newly designed petal-like structures have high potential applications in various fields such as construction and automotive industries.

结合纤维增强复合材料的超材料、多阶段变形和高强度等优点,提出并制备了一种具有优异力学性能的新型花瓣状结构。首先对三种不同角度的纤维增强复合材料花瓣状结构进行了压缩试验和有限元分析。研究结果表明,通过合理的结构设计,这些复合材料基多胞结构也可以表现出令人满意的应力平台阶段。在保证结构在准静态压缩载荷下的性能后,进一步研究了新结构的抗冲击性能。结果表明,在低速冲击载荷作用下,结构的消声特性有所降低。在20J冲击荷载作用下,结构的能量吸收特性(SEA)是传统结构和其他新型减震结构的8 ~ 40倍。这些有希望的结果表明,新设计的花瓣状结构在建筑和汽车工业等各个领域具有很高的应用潜力。


Design and demonstration of a roll-out membrane antenna based on thin-walled deployable composite booms

Chao Xie, Zhiyi Wang, Yu Liu, Feng Gao, Li Qin, Jinping Yang, Fujun Peng, Wujun Chen

doi:10.1016/j.tws.2024.112486

基于薄壁可展开复合臂的展开膜天线设计与论证

The thin-walled deployable composite boom (DCB) features the advantages of high deployment-to-package envelope ratio and elastic self-development, which is an enduring topic of interest in the field of lightweight aerospace structures. The structural design and performance demonstration was proposed herein for a roll-out membrane antenna (ROMA) based on DCBs. Firstly, a simplified analytical algorithm was formulated for approximate fundamental frequencies of the ROMA frame structure, and the two types of first-order torsional modal shapes of the frame structure was investigated with respect to configurational design parameters. In sequentially, the bending, swing and the two distinct torsional fundamental frequencies of the ROMA frame were estimated comparatively. Furthermore, the effects of the equilibrated tension from the membrane array on the bending fundamental frequency of the ROMA structure was investigated by assuming a simplified mass distribution model for the thin-film structures. Finally, The simplified analytical algorithm was used for structural design of an AIS/VDE (automatic identification system/VHF data exchange system) ROMA and its performance was validated through numerical simulations and ground tests. The successful deployment and operation of the AIS/VDE ROMA on the Pujiang-2 satellite further demonstrated the practical aerospace application significance of thin-walled DCBs.

薄壁可展开复合材料臂架(DCB)具有高展开包封比和弹性自发展等优点,是航空轻量化结构领域的研究热点。提出了一种基于dcb的滚动膜天线(ROMA)的结构设计和性能论证。首先,建立了ROMA框架结构近似基频的简化解析算法,并根据构型设计参数研究了两类框架结构的一阶扭转模态振型。然后,比较估计了ROMA框架的弯曲、摆动和两种不同的扭转基频。此外,通过假设薄膜结构的简化质量分布模型,研究了薄膜阵列的平衡张力对ROMA结构弯曲基频的影响。最后,将简化的解析算法应用于AIS/VDE(自动识别系统/甚高频数据交换系统)ROMA的结构设计,并通过数值模拟和地面试验验证了其性能。AIS/VDE ROMA在浦江二号卫星上的成功部署和运行,进一步证明了薄壁dcb在航天领域的实际应用意义。


BPNN-based prediction for the shapes of a petal hole induced by hydrodynamic ram

Kerong Ren, Wenwen Wang, Hua Qing, Yong Peng, Wentao Xu, Zongkai He, Xiangyu Li, Fangyun Lu

doi:10.1016/j.tws.2024.112488

基于bpnn的水动力撞击器花瓣孔洞形状预测

The attitude angles of a projectile moving through a liquid are important factors that influence the dynamic failure of liquid-filled structures induced by hydrodynamic ram (HRAM). In this study, the effect of the attitude angles of a cylindrical projectile on the shapes of the petal hole in the rear plate of a kerosene-filled tank was investigated through ballistic impact experiments using three-dimensional digital image correlation, finite element simulations, and a back propagation neural network (BPNN). The inclination angle λ characterizing the shapes of the petal hole was related to the projection shapes of the projectile when impacting on the rear plate. The formation of petal-hole shapes was also accompanied by the formation of plastic hinge lines in the rear plate. Additionally, a method combining a BPNN and physical equations that accurately predict the drag coefficient and motion of a projectile moving through a liquid was proposed. A function describing the shapes of the petal hole was provided in the 2D space of the two initial attitude angles. The results provide offer insights into trajectory stability during liquid entry and aid in predicting the dynamic failure mode of a liquid-filled tank induced by HRAM.

弹丸在液体中运动时的姿态角是影响充液结构在水动力撞击下发生动力破坏的重要因素。采用三维数字图像相关、有限元仿真和反向传播神经网络(BPNN)技术,研究了圆柱弹丸姿态角对煤油罐后板花瓣孔形状的影响。表征花瓣孔形状的倾角λ与弹丸撞击后板时的投影形状有关。花瓣孔形状的形成还伴随着后板塑性铰线的形成。此外,提出了一种结合bp神经网络和物理方程的方法,可以准确地预测弹丸在液体中的阻力系数和运动。在两个初始姿态角的二维空间中,给出了描述花瓣孔形状的函数。研究结果有助于了解液体进入过程中的轨迹稳定性,并有助于预测由HRAM引起的充液罐的动态失效模式。


The effect of cold forming residual stresses in local fatigue approaches: A numerical perspective

Carlos Souto, Marco Parente, José Correia, Abílio de Jesus

doi:10.1016/j.tws.2024.112476

局部疲劳方法中冷成形残余应力的影响:数值视角

Thin-walled structures generally rely on cold-formed mild steel profiles. Due to cold forming, a significant formation of residual stresses impacts their overall fatigue behaviour. In this work, a state-of-the-art framework for fatigue life prediction is proposed and applied to both roll-formed and press-braked full-scale profiles. In summary, the profile’s manufacturing process is numerically simulated to obtain a representative residual stress field. These results are then used as the initial state during a subsequent structural and fatigue analysis. A clear detrimental residual stress effect is verified. Importantly, however, is to note that prediction accuracy increases significantly when these effects are considered.

薄壁结构通常依靠冷弯低碳钢型材。由于冷成形,残余应力的显著形成影响其整体疲劳行为。在这项工作中,提出了一个最先进的疲劳寿命预测框架,并将其应用于滚动成形和冲压制动的全尺寸型材。最后,对型材的加工过程进行了数值模拟,得到了具有代表性的残余应力场。这些结果随后被用作后续结构和疲劳分析的初始状态。验证了明显的有害残余应力效应。然而,重要的是要注意,当考虑到这些影响时,预测的准确性会显著提高。




来源:复合材料力学仿真Composites FEM
ACTMechanicalSystemMarcDeform疲劳断裂复合材料非线性航空航天汽车建筑裂纹理论材料试验纺织模具
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【新文速递】2024年9月25日固体力学SCI期刊最新文章

今日更新:International Journal of Solids and Structures 2 篇,Journal of the Mechanics and Physics of Solids 2 篇,Mechanics of Materials 1 篇,International Journal of Plasticity 1 篇,Thin-Walled Structures 1 篇International Journal of Solids and StructuresA rheological constitutive model to predict the anisotropic biaxial bending behavior of spiral strands subjected to variable axial forceMohammad Ali Saadat, Damien Durvilledoi:10.1016/j.ijsolstr.2024.113082用流变本构模型预测螺旋股在变轴力作用下的各向异性双轴弯曲行为Spiral strands exhibit dissipative bending behavior when subjected to external axial force. To the best of the authors’ knowledge, only the uniaxial bending behavior of spiral strands subjected to constant axial force has been studied in the literature so far. Thanks to a recently developed mixed stress–strain driven computational homogenization for spiral strands, this paper is the first to study the biaxial bending behavior of spiral strands subjected to variable tensile force. Based on the observed anisotropic behavior, a rheological constitutive model equivalent to multilayer spiral strands is proposed to predict their behavior under such loading. For an N l -layer strand, the proposed model consists of several angularly distributed uniaxial spring systems, referred to as a multiaxial spring system, where each uniaxial spring system consists of a spring and N l slider-springs. In a uniaxial spring system, the spring represents the slip contribution of all wires to the bending stiffness of the strand, while each slider-spring represents the stick contribution of each layer. A major advantage of the proposed scheme is its straightforward parameter identification, requiring only several monotonic uniaxial bendings under constant axial force. The proposed rheological model has been verified against the responses obtained from the mixed stress–strain driven computational homogenization through several numerical examples. These examples consist of complex uniaxial and biaxial load cases with variable tensile force. It has been shown that the proposed scheme not only predicts the response of the strand, but also provides helpful insight into the complex underlying mechanism of spiral strands. Furthermore, the low computational cost of the proposed models makes them perfect candidates for implementation as a constitutive law in a beam model. Using a single beam with the proposed constitutive law, spiral strand simulations can be performed in a few seconds on a laptop instead of a few hours or days on a supercomputer.当受到外部轴向力时,螺旋股表现出耗散弯曲行为。据作者所知,迄今为止,文献中只研究了螺旋股在恒定轴向力作用下的单轴弯曲行为。由于最近发展了螺旋股的混合应力-应变驱动的计算均匀化,本文首次研究了螺旋股在变拉力作用下的双轴弯曲行为。基于观察到的各向异性行为,提出了一种相当于多层螺旋股的流变本构模型来预测其在这种载荷下的行为。对于N - 1层钢绞线,所提出的模型由几个角度分布的单轴弹簧系统组成,称为多轴弹簧系统,其中每个单轴弹簧系统由弹簧和N - 1滑动弹簧组成。在单轴弹簧系统中,弹簧代表所有钢丝对钢绞线弯曲刚度的滑移贡献,而每个滑动弹簧代表每层的粘滞贡献。该方案的一个主要优点是参数识别简单,只需要在恒定轴向力下进行几次单调单轴弯曲。通过数值算例验证了所提出的流变模型与混合应力-应变驱动计算均质化的响应。这些例子包括复杂的单轴和双轴载荷情况下的可变拉伸力。研究表明,所提出的方案不仅预测了螺旋链的响应,而且为了解螺旋链的复杂潜在机制提供了有益的见解。此外,所提出的模型的低计算成本使其成为梁模型中本构律的完美候选。使用单束和提出的本构律,螺旋链模拟可以在笔记本电脑上几秒钟完成,而不是在超级计算机上几个小时或几天。Unravelling electromechanical mechanism of mechanoreceptor inspired capacitive pressure sensor considering size effectWenxuan Ding, Yonglin Chen, Wenbin Kang, Zhuangjian Liu, Peng Wang, Weidong Yangdoi:10.1016/j.ijsolstr.2024.113083 考虑尺寸效应的机械感受器启发电容式压力传感器的解耦机电机理The rapid development of intelligent sensing technologies, including electronic skins, wearable devices and robots, has put forward an urgent demand for various tactile biomimetic sensors. However, the design of tactile sensors is mostly based on independent experimental research and lack theoretical guidance at present. In this work, drawing inspiration from human skin microstructure mechanoreceptors responsible for tactile sensation, we proposed a capacitive pressure sensor model featuring a biomimetic conformal microstructured electrode with a round-crown shape. Moreover, at the micrometer scale, size effect profoundly influences the mechanical behavior of sensing materials and microstructured devices. Firstly, we conducted in-depth research on the electromechanical behavior of conformal microstructured electrode pressure sensor, considering the size effect based on couple stress elasticity and Hertz contact theory. We validated the effectiveness of the model by comparing it with experimental and simulation results of human skin. Through numerical simulation, we further verified that the theoretical model of a single microstructured electrode can be utilized for calculating microstructured electrode arrays. Furthermore, our analysis reveals that the geometric morphology and material properties of the dielectric layer, the arrangement density of the microstructured electrode arrays, along with the radius of the round-crown shaped microstructured electrode are the dominant parameters influencing the electromechanical sensitivity through parameter analysis. Finally, we devised a high-k (high dielectric permittivity) polymer composites dielectric layer with a tunable Poisson’s ratio structure, offering feasible approach to achieving highly sensitive capacitive microstructure sensors. This theoretical model that takes into account the size effect in microstructured electrode contact problem provides theoretical insights that can guide the optimization design of high-performance tactile sensors.电子皮肤、可穿戴设备、机器人等智能传感技术的快速发展,对各种触觉仿生传感器提出了迫切的需求。然而,目前触觉传感器的设计多基于独立的实验研究,缺乏理论指导。在这项工作中,我们从负责触觉的人体皮肤微观结构机械感受器中获得灵感,提出了一种具有圆形冠状仿生共形微结构电极的电容式压力传感器模型。此外,在微米尺度上,尺寸效应深刻地影响着传感材料和微结构器件的力学行为。首先,基于耦合应力弹性和赫兹接触理论,考虑尺寸效应,对共形微结构电极压力传感器机电性能进行了深入研究。通过与人体皮肤实验和仿真结果的对比,验证了该模型的有效性。通过数值模拟,我们进一步验证了单个微结构电极的理论模型可以用于计算微结构电极阵列。此外,通过参数分析,我们的分析表明介电层的几何形态和材料特性,微结构电极阵列的排列密度以及圆冠状微结构电极的半径是影响机电灵敏度的主要参数。最后,我们设计了一种具有可调泊松比结构的高k(高介电常数)聚合物复合材料介电层,为实现高灵敏度电容性微结构传感器提供了可行的途径。该理论模型考虑了微结构电极接触问题中的尺寸效应,为高性能触觉传感器的优化设计提供了理论指导。Journal of the Mechanics and Physics of SolidsAn analytic traction-displacement model for a reinforcing ligament bridging a crack at an arbitrary angle, including elastic, frictional, snubbing, yielding, creep, and fatigue phenomena.B.N. Cox, N. Sridhar, Q.D. Yangdoi:10.1016/j.jmps.2024.105879以任意角度桥接裂缝的加固韧带的牵拉-位移解析模型,包括弹性、摩擦、弯曲、屈服、蠕变和疲劳现象。A micromechanical model is developed that generates analytic expressions for the crack displacement vector u given an arbitrary far-field stress state σa for a crack that is bridged by an array of ligaments oriented at an arbitrary angle with respect to the crack plane. The model is applicable to various materials, e.g., fibrous ceramic composites, or polymer composites reinforced by stitches or z-pins or woven tows, and deals with interfacial friction, enhanced friction due to increased contact pressure (“snubbing”), and the possibility of ligament deflection enabled by yield or damage. The model also conveniently incorporates ligament failure and rate dependent phenomena (fatigue or creep). Adaptability of the model is enabled by the definition of a standard Reference Model, which generates analytic expressions for the crack displacement for given possible yield, ligament deflection, and friction and snubbing effects and is invariant for all geometrical and material choices. The switching on or off and the strengths of all phenomena are governed by assigning values to a handful of material parameters. The material parameters will generally be calibrated against data in a top-down strategy, the model thereby mapping material selection onto engineering fracture via the predicted bridging relationship u[σa]. The relationship u[σa] can depend strongly on bi-angular ligament orientation. Yield and deflection can change u[σa] qualitatively, e.g., by creating fracture surface contact even when σa includes substantial opening tension. Snubbing has significant effects, including possible stabilization of the pullout of a finite ligament. Since model output is computed via analytic expressions, its speed will support the model's use in large-scale material simulations or as constraining physical information in machine learning algorithms.本研究开发了一种微观力学模型,在给定任意远场应力状态 σa 的情况下,可生成裂纹位移矢量 u 的解析表达式,该裂纹由相对于裂纹平面以任意角度定向的韧带阵列桥接。该模型适用于各种材料,例如纤维状陶瓷复合材料,或通过缝合线、Z 形针或编织丝束加固的聚合物复合材料,并可处理界面摩擦、因接触压力增大(“挤压”)而增强的摩擦,以及因屈服或损坏而导致韧带变形的可能性。该模型还可方便地纳入韧带失效和速率相关现象(疲劳或蠕变)。标准参考模型可生成给定屈服、韧带挠度、摩擦和挤压效应下裂纹位移的解析表达式,并在所有几何和材料选择下保持不变。所有现象的开启或关闭以及强度都受一些材料参数值的制约。材料参数一般采用自上而下的策略根据数据进行校准,模型通过预测的桥接关系 u[σa] 将材料选择映射到工程断裂上。u[σa]关系在很大程度上取决于双角韧带的走向。屈服和挠曲可以从本质上改变 u[σa],例如,即使 σa 包括很大的张开张力,也会产生断裂面接触。挤压会产生重大影响,包括可能稳定有限韧带的拉伸。由于模型输出是通过解析表达式计算的,其速度将支持模型用于大规模材料模拟或作为机器学习算法中的约束物理信息。A multiscale Bayesian method to quantify uncertainties in constitutive and microstructural parameters of 3D-printed compositesXiang Hong, Peng Wang, Weidong Yang, Junming Zhang, Yonglin Chen, Yan Lidoi:10.1016/j.jmps.2024.105881 三维打印复合材料本构和微观结构参数不确定性的多尺度贝叶斯量化方法3D-printed continuous carbon fiber reinforced composites (CCFRCs) are promising for various engineering applications due to high strength-to-weight ratios and design flexibility. However, the large variations in their mechanical properties pose a considerable challenge to their widespread applications. Here we develop a multiscale Bayesian method to quantify uncertainties in the constitutive parameters and microstructural parameters of 3D-printed CCFRCs. Based on the characterized microstructure of CCFRCs, a multiscale micromechanical model is developed to reveal the relationship between the properties of constituent materials, the microstructural parameters, and the macroscopic constitutive parameters. Furthermore, the joint posterior probability distribution of these parameters is formulated, and the Markov Chain Monte Carlo method (MCMC) is used to compute the posterior distributions of constitutive and microstructural parameters, enabling assessment of parameter uncertainty, correlation, and model calibration error. The inferred microstructural parameters are consistent with those measured by experiments. The posterior predictive distributions of the constitutive response are further computed to validate the probability model. Our method quantifies uncertainties in the constitutive parameters of 3D-printed CCFRCs and identifies their origins, which can optimize constituent material properties and microstructural parameters to achieve more robust composites.3d打印连续碳纤维增强复合材料(CCFRCs)由于其高强度重量比和设计灵活性,在各种工程应用中都很有前景。然而,其机械性能的巨大变化对其广泛应用构成了相当大的挑战。本文提出了一种多尺度贝叶斯方法来量化3d打印CCFRCs的本构参数和微观结构参数的不确定性。基于CCFRCs的微观结构特征,建立了CCFRCs的多尺度细观力学模型,揭示了组成材料性能、微观结构参数和宏观本构参数之间的关系。在此基础上,建立了这些参数的联合后验概率分布,并利用马尔可夫链蒙特卡罗方法(MCMC)计算了本构参数和微观结构参数的后验分布,从而评估了参数的不确定性、相关性和模型校准误差。推断出的微观结构参数与实验测量结果一致。进一步计算了本构响应的后验预测分布,验证了概率模型。我们的方法量化了3d打印CCFRCs本构参数中的不确定性,并确定了它们的来源,从而可以优化组成材料的性能和微观结构参数,以获得更坚固的复合材料。Mechanics of MaterialsAtomistic investigation on the anisotropic elastic and plastic responses of nanotwinned metalsLigang Sun, Lianyu Jiao, Zhijia Qin, Linli Zhu, Bin Gan, Dongfeng Lidoi:10.1016/j.mechmat.2024.105164 纳米孪晶金属各向异性弹塑性响应的原子性研究Introducing nanotwins into materials is one of the important strengthening methods to achieve the synergistic improvement of strength and ductility. The anisotropic mechanical behaviors of nanotwinned materials have been widely studied by experimental and computational methods. The dominant deformation mechanisms about dislocation slippages can be effectively switched among three modes, and controlled by twin spacing and the angle between twin boundaries (TBs) orientation and loading direction. Particularly, most of previous researches mainly focused on the deformation mechanisms during the plastic flow stage and researchers paid little attention on the anisotropic characteristics of TBs at the elastic stage which are also essential to manufacture the high-performance materials. Therefore, this study is aiming to systemically investigate the anisotropic effect of TBs both on the elastic and plastic stages within the single crystalline or polycrystalline by molecular dynamics (MD) simulations. It is revealed that, when the loading direction is parallel to twin planes, the introduction of TBs in single crystalline models will significantly affect the characteristics of atomic bond rotation and elongation dominated elastic deformation, which can alter the Poisson’s ratio of materials, generate elastic-softening behavior and inhomogeneous elastic deformation. At the plastic flow stage, the deformation mechanism transforms from trans-twin dislocation slippage into the coexistence of Hard Mode I and threading dislocation slippage (Hard Mode II) when the loading direction changes from parallel to perpendicular direction with respect to TBs. However, both the elastic and plastic behaviors are less sensitive to TBs in vertical direction. Moreover, the dislocation segments at the conjunction of trans-twin dislocation play a momentous role in enhancing material strength. The results for polycrystalline models are consistent with that of single crystalline ones. These findings are expected to be beneficial for the development of high-performance nanostructured materials for structural and functional applications by strain engineering and defect regulation.在材料中引入纳米孪晶是实现材料强度和塑性协同提高的重要强化方法之一。纳米孪晶材料的各向异性力学行为已经通过实验和计算方法得到了广泛的研究。位错滑移的主导变形机制可以在三种模式之间有效切换,并受孪晶间距和孪晶边界取向与加载方向夹角的控制。特别是,以往的研究大多集中在塑性流动阶段的变形机理上,而对弹性阶段的各向异性特性研究较少,而弹性阶段的各向异性特性对高性能材料的制造至关重要。因此,本研究旨在通过分子动力学(MD)模拟系统地研究TBs在单晶或多晶中弹性和塑性阶段的各向异性效应。结果表明,当加载方向平行于双平面时,TBs的引入将显著影响单晶模型中原子键旋转和伸长主导的弹性变形特性,从而改变材料的泊松比,产生弹性软化行为和非均匀弹性变形。在塑性流动阶段,当加载方向相对于TBs由平行方向变为垂直方向时,变形机制由跨孪位错滑移转变为硬模式I和螺纹位错滑移(硬模式II)并存。然而,在垂直方向上,弹性和塑性行为对TBs都不太敏感。跨孪位错结合处的位错段对提高材料强度有重要作用。多晶模型的结果与单晶模型的结果一致。这些发现将有助于通过应变工程和缺陷调节来开发用于结构和功能应用的高性能纳米结构材料。International Journal of PlasticityTailoring thickness debit for high-temperature fatigue resistance of Inconel 718 superalloy fabricated by laser powder bed fusionTao Ma, Bin Zhang, Li-Ming Lei, Yuan-Chen Wang, Zhu-Man Song, Guang-Ping Zhangdoi:10.1016/j.ijplas.2024.104137 激光粉末床熔合法制备因康乃尔718高温合金的耐高温疲劳性能The thickness debit often leads to uncertainty regarding the fatigue performance of laser powder bed fusion (LPBF)-fabricated Inconel 718 thin-walled components and restricts the structural design of these components. Aiming to address this issue, fatigue properties of LPBF-fabricated Inconel 718 homogenized at various temperatures were investigated at 650°C using specimens with different thicknesses. The results reveal a pronounced influence of both the thickness debit and the intricate interplay between the microstructural and geometrical scales of the thin-walled specimens on their fatigue life at 650°C. The fatigue life of the thin-wall specimens with the same microstructural scale reduces with decreasing the ratio (t/d) of the specimen thickness (t) to the grain length (d). The coupling effect is described by a mechanism model correlated with the geometrical and microstructural scales of the specimens, in which continuous damage mechanics (CDM) and calculation of the yield strength have been considered. Based on the model, a criterion of t/d > 6.2 for the LPBF-fabricated Inconel 718 specimens homogenized at 1100°C, and t/d > 8.8 for those homogenized at 1065°C are proven to be satisfied to ensure a longer and more stable fatigue life of the thin-walled specimens serving at 650°C. Elevating the homogenization temperature from 1065°C to 1100°C results in an extension of the fatigue life for specimens of the same thickness. This enhancement is attributed to the improved ability of grains to coordinate local deformation, as well as the reduced prevalence of elongated Laves and other phases, which typically serve as preferential sites for crack initiation and propagation. The finding suggests that the thickness debit in high-temperature fatigue resistance of LPBF-fabricated components can be minimized by tailoring the heat treatment strategy.厚度偏差经常导致激光粉末床熔合(LPBF)制造的Inconel 718薄壁部件疲劳性能的不确定性,并限制了这些部件的结构设计。为了解决这一问题,在650℃下,使用不同厚度的试样,研究了lpbf制备的Inconel 718在不同温度下均质化的疲劳性能。结果表明,薄壁试样在650℃下的疲劳寿命受到厚度偏差和微观组织与几何尺度之间复杂的相互作用的显著影响。相同显微组织尺度下薄壁试样的疲劳寿命随着试样厚度与晶粒长度之比(t/d)的减小而减小。本文建立了考虑连续损伤力学和屈服强度计算的与试样几何和显微组织尺度相关的力学模型来描述这种耦合效应。基于该模型,在1100℃下均质化lpbf制备的Inconel 718薄壁试样满足t/d > 6.2准则,在1065℃下均质化的Inconel 718薄壁试样满足t/d > 8.8准则,可保证650℃下薄壁试样具有更长的稳定疲劳寿命。将均匀化温度从1065℃提高到1100℃,可以延长相同厚度试样的疲劳寿命。这种增强是由于晶粒协调局部变形的能力提高,以及拉长的Laves和其他相的流行减少,而这些相通常是裂纹萌生和扩展的首选部位。这一发现表明,通过调整热处理策略可以最大限度地减少lpbf制造的部件的高温疲劳抗力的厚度损失。Thin-Walled StructuresTheoretical prediction and experimental validation of flexural behaviour and failure modes of 3D-woven honeycomb sandwich panelsPrabhjot Singh, Sameer K Behera, Omender Singh, Javed Sheikh, B K Beheradoi:10.1016/j.tws.2024.112481三维编织蜂窝夹层板抗弯性能及破坏模式的理论预测与试验验证This study presents a novel approach to enhance the flexural performance of sandwich composite panels by introducing 3D-woven honeycomb (HC) composites as core material. The flexural performance and failure modes of these novel structures are compared with traditional aluminium honeycombs across various facesheet materials. Experimental findings are complemented by numerical analyses, while observed failure modes are compared with theoretical flexural failure modes. The results reveal that 3D-woven Kevlar HC cores demonstrate superior flexural stiffness and strength due to its integrated structure, while enhanced energy absorption is attributed to unique deformation mechanisms within the 3D-woven core. Failure modes observed in the experiments closely aligned with theoretical predictions, further validating the approach. Overall, the findings validate the potential of novel 3D-woven Kevlar HC cores as promising alternatives for lightweight, high-performance sandwich composite panels.本文提出了一种采用三维编织蜂窝复合材料作为芯材来提高夹层复合板抗弯性能的新方法。这些新型结构的弯曲性能和破坏模式与传统的铝蜂窝在不同的面板材料进行了比较。数值分析补充了实验结果,并将观察到的破坏模式与理论的弯曲破坏模式进行了比较。结果表明,3d编织的凯夫拉纤维HC芯由于其整体结构而具有优越的抗弯刚度和强度,而增强的能量吸收归因于3d编织芯内部独特的变形机制。实验中观察到的失效模式与理论预测密切相关,进一步验证了该方法。总的来说,研究结果验证了新型3d编织Kevlar HC芯作为轻质高性能夹层复合板的有希望的替代品的潜力。来源:复合材料力学仿真Composites FEM

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