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【新文速递】2024年7月31日固体力学SCI期刊最新文章

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今日更新:Thin-Walled Structures 4 篇

Thin-Walled Structures

DESIGN OF COLD FORMED C SECTION BEAMS WITH ELONGATED CIRCULAR OPENINGS BASED ON TESTS

R M Lawson, M Stergiopoulos, M Rowell

doi:10.1016/j.tws.2024.112256

基于试验的细长圆孔冷弯c截面梁设计

A design method to determine the shear resistance of elongated web openings in cold formed C sections is presented, that is based on Vierendeel bending in the web-flange Tee sections. The results of 6 tests on pairs of C section beams with stiffened and unstiffened openings of 155mm depth and 220mm length are presented. The tests also included a beam with closely spaced elongated openings and a comparative test on a plain C section. The tests showed that the bending resistance of the beam with stiffened openings was close to that of the plain C section.The design method is based on a derived formula for the normal stresses acting on radial planes around the circular part of the elongated opening. The results are compared to the stresses at an equivalent rectangular opening. It is proposed that in Vierendeel bending, buckling at the unstiffened openings may be represented as an equivalent ‘strut’ with an effective length of 0.3 x opening depth. The post-buckling resistance may take account of the redistribution of moments around the elongated openings. It was also found that for the tested beams, the additional shear and bending deflection due to each elongated opening was approximately 3% of the plain beam deflection.

提出了一种确定冷弯C型钢腹板开孔抗剪能力的设计方法,该方法基于腹板法兰三通截面的纵向弯曲。给出了6组开孔加筋和开孔不加筋的C型钢对梁的试验结果,开孔深度为155mm,开孔长度为220mm。测试还包括一个具有紧密间隔的细长开口的梁和在普通C截面上的比较测试。试验结果表明,加筋开孔梁的抗弯性能与普通C截面接近。设计方法是基于作用在细长开口圆形部分周围径向平面上的法向应力的推导公式。结果与等效矩形开口下的应力进行了比较。有人提出,在Vierendeel弯曲中,未加筋开口处的屈曲可以表示为等效的“支柱”,其有效长度为0.3 x开口深度。后屈曲阻力可以考虑弯矩在细长开口周围的重新分布。还发现,对于测试梁,由于每个拉长开口的额外剪切和弯曲挠度约为普通梁挠度的3%。


Development of a novel full-scaled self-centering brace with notched steel tubes

Guozu Zheng, Jianping Han, Dawei Li, Yan Shi

doi:10.1016/j.tws.2024.112269

新型全尺寸缺口钢管自定心支撑的研制

A novel self-centering brace with a notched steel tube (SCB-NST) was developed and experimentally studied. The proposed SCB-NST consists of a novel notched steel tube (NST) for energy dissipation and disc springs for self-centering, respectively. Three full-scaled specimens were tested to investigate the hysteresis behavior under cyclic loading. These specimens include a brace with NST only, a brace with disc spring only, and an SCB-NST. The first two tests were specifically conducted to obtain the contributions of the NST and disc springs alone, respectively. The test results illustrate that the first proposed NST displays excellent energy dissipation and deformation capabilities. The proposed SCB-NST exhibits a stable flag-shaped hysteresis behavior, distinguished self-centering, and significant energy dissipation capacity without residual displacement. Furthermore, experimental findings reveal that the disc spring functions as a secondary defensive line of the SCB-NST system upon sudden failure of the NST. The cyclic test of the brace with disc spring only shows that the friction between the disc springs should not be neglected, especially when quantities of large-diameter disc springs are stacked. The modular design of the proposed SCB-NST facilitates the replacement of energy-dissipating components, allowing for efficient maintenance and ultimately achieving the design objective of promoting reusability and resource conservation. The SCB-NST equipped with two different ultimate displacements has been confirmed through finite element analysis to have three defense lines, which improves the reliability and redundancy of the SCB-NST system. The parametric finite element analysis results reveal that the thickness of the energy-dissipation ring has the most significant influence on the load-bearing capacity and energy-dissipation capability of the SCB-NST. Concurrently, the pre-pressed force of the disc spring is crucial for eliminating the residual displacement of the SCB-NST.

研制了一种新型缺口钢管自定心支撑,并进行了实验研究。所提出的SCB-NST由一种新型的缺口钢管(NST)和碟形弹簧组成,分别用于耗能和自定心。试验研究了3个试件在循环荷载作用下的滞回特性。这些样品包括仅带NST的支架,仅带碟形弹簧的支架和SCB-NST。前两个测试是专门进行的,分别获得了NST和碟形弹簧单独的贡献。试验结果表明,所提出的NST具有良好的耗能和变形能力。所提出的SCB-NST具有稳定的旗形迟滞行为、显著的自定心和显著的无残余位移的能量耗散能力。此外,实验结果表明,在NST突然失效时,碟形弹簧可作为SCB-NST系统的次级防线。盘形弹簧支撑的循环试验表明,盘形弹簧之间的摩擦不可忽视,特别是当大量大直径盘形弹簧堆叠时。拟议的SCB-NST的模块化设计便于更换耗能组件,从而实现高效维护,最终实现促进可重复使用和节约资源的设计目标。采用两种不同极限位移的SCB-NST,通过有限元分析确定其具有三道防线,提高了SCB-NST系统的可靠性和冗余性。参数化有限元分析结果表明,消能环的厚度对SCB-NST的承载能力和消能能力的影响最为显著。同时,碟形弹簧的预压力对于消除SCB-NST的残余位移至关重要。


Peridynamic formulations for planar arbitrarily curved beams with Euler-Bernoulli beam model

Zwe Yan Aung, Duy Vo, Pana Suttakul, Elena Atroshchenko, Tinh Quoc Bui, Jaroon Rungamornrat

doi:10.1016/j.tws.2024.112278

基于欧拉-伯努利梁模型的平面任意弯曲梁的周动力表达式

This study presents two peridynamic formulations for analysis of planar arbitrarily curved beams using kinematic assumptions of Euler-Bernoulli beam model. Only displacement components of the beam axis are considered as kinematic unknowns. The principle of virtual work is used to derive equilibrium equations and boundary conditions. The equilibrium equations are presented in two forms, i.e., one in terms of cross-sectional stress resultants and one in terms of displacement components of the beam axis. Then, two peridynamic formulations are developed respectively from two forms of equilibrium equations by employing peridynamic functions, which are constructed with the concept of peridynamic differential operators. Several examples are presented to elucidate the performance of the proposed formulations in some regards, i.e., numerical precision, convergence properties, and robustness with respect to the membrane locking effect.

本文利用欧拉-伯努利梁模型的运动学假设,提出了两种平面任意弯曲梁的周动力分析公式。只有梁轴的位移分量被认为是运动学未知数。利用虚功原理推导了平衡方程和边界条件。平衡方程有两种形式,即一种是截面应力结果的形式,另一种是梁轴位移分量的形式。在此基础上,利用周期动力学微分算子的概念构造了周期动力学函数,由两种形式的平衡方程分别推导出两个周期动力学表达式。提出了几个例子来阐明所提出的配方在某些方面的性能,即,数值精度,收敛特性和关于膜锁定效应的鲁棒性。


Global buckling of S35657 austenitic stainless steel welded box- and I-section long columns under axial compression

Shengjie Duan, Yiwen Wu, Shenggang Fan, Ganping Shu, Xianyun Shi, Jingzhong Tong

doi:10.1016/j.tws.2024.112281

S35657奥氏体不锈钢焊接箱式和工字截面长柱在轴压作用下的整体屈曲

Due to its remarkable combination of high yield strength and cost-effectiveness, S35657 austenitic stainless steel has gained increasing attention in the field of construction engineering. This paper delves into the global stability performance of S35657 stainless steel welded long columns. Leveraging test results from 13 welded long columns, consisting of 4 welded box-section columns and 9 welded I-section columns, a numerical simulation analysis was conducted to scrutinize the bearing capacity and failure modes of each specimen. Utilizing validated numerical models, a parametric analysis was undertaken, exploring factors such as cross-sectional classification, slenderness ratio and initial imperfection. Subsequently, the buckling curves for S35657 austenitic stainless steel welded box-section and I-section long columns, both around the major and minor axes, were evaluated using existing test results and numerical outcomes. Through data fitting and reliability analysis, buckling curves tailored to S35657 austenitic stainless steel welded box-section and I-section long columns for global buckling were proposed for the first time, providing guidance for relevant designs based on the European code (prEN 1993-1-4), the American code (SEI/ASCE 8-22) and the Chinese specification (CECS 410: 2015).

由于其高屈服强度和成本效益的显著结合,S35657奥氏体不锈钢在建筑工程领域得到了越来越多的关注。本文研究了S35657不锈钢焊接长柱的整体稳定性能。利用13根焊接长柱(其中4根焊接箱形截面柱和9根焊接工字截面柱)的试验结果,对各试件的承载力和破坏模式进行了数值模拟分析。利用验证的数值模型,对截面分类、长细比和初始缺陷等因素进行了参数化分析。随后,利用已有的试验结果和数值结果,对S35657奥氏体不锈钢焊接的箱形截面和工字截面长柱在主轴和小轴周围的屈曲曲线进行了评估。通过数据拟合和可靠性分析,首次提出了适合S35657奥氏体不锈钢焊接箱形截面和工字截面长柱整体屈曲的屈曲曲线,为基于欧洲规范(prEN 1993-1-4)、美国规范(SEI/ASCE 8-22)和中国规范(CECS 410: 2015)的相关设计提供了指导。



来源:复合材料力学仿真Composites FEM
ACTSystemDeform建筑CONVERGEUG焊接试验
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首次发布时间:2024-11-21
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【新文速递】2024年7月4日固体力学SCI期刊最新文章

今日更新:International Journal of Solids and Structures 5 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 2 篇International Journal of Solids and StructuresError analysis of deformation assumptions for the in-plane torsion test of sheet metalPeter G. Gruber, Jagoba Lekue, Leopold Wagner, Thomas Gross, Stefan Sieberer, Martin Schagerldoi:10.1016/j.ijsolstr.2024.112945板材平面扭转试验变形假设误差分析The in-plane torsion test offers an alternative to common parameter identification tests, needed for material modeling of sheet metal. As compared to common tests during material characterization, higher equivalent plastic strains are achieved, and kinematic hardening laws are calibrated at higher strains. In addition, it also allows to determine fracture strains in pure shear. In this contribution, we focus on a well known approach utilizing optical measurement of a scribed line as indicator for the shear deformation. The underlying mathematical model is studied, and an error analysis is provided regarding the approximation of stress and strain measures. Thereby the assumption of simple shear deformation is found to be accurate for specimen of the assumed geometrical and material properties. The presented approach, however, can be easily adapted to derive error estimates also in cases of differing geometry or material.面内扭转试验为金属板材料建模所需的普通参数识别试验提供了一种替代方法。与材料表征过程中的普通试验相比,可以获得更高的等效塑性应变,并在更高应变下校准运动硬化定律。此外,它还可以确定纯剪切下的断裂应变。在本文中,我们将重点介绍一种众所周知的方法,即利用光学测量刻线作为剪切变形的指标。我们对基本数学模型进行了研究,并对应力和应变测量的近似值进行了误差分析。因此,对于假定几何和材料特性的试样,简单剪切变形的假设是准确的。不过,所提出的方法也可以很容易地适用于不同几何形状或材料情况下的误差估算。Numerical analysis of ductile fracture in stretch bending of AA6061-T6 aluminum alloy sheet using GTN damage modelMaziar Khademi, Mohammad Javad Mirnia, Hassan Moslemi Naeinidoi:10.1016/j.ijsolstr.2024.112947 使用 GTN 损伤模型对 AA6061-T6 铝合金板材拉伸弯曲中的韧性断裂进行数值分析In this paper, the original and shear-modified GTN ductile fracture criteria are utilized to investigate the fracture behavior of the AA6061-T6 aluminum alloy sheet during the stretch bending process. An appropriate calibration strategy is presented to find the unknown coefficients of the fracture models. In this way, different tension tests such as uniaxial tension, plane strain, notched tension, and shear tension specimens are utilized. Results show that the shear-modified GTN model calibrated by the mentioned tension tests is able to predict the onset of fracture of the stretch bending process with a 5% error, while the original GTN model, calibrated by the uniaxial tension is unable to predict the fracture properly. Since the accuracy of fracture prediction depends on the stress state, the effects of the calibration test on onset of fracture were investigated. It is shown that using the original GTN model with a proper calibration test (plane strain tension) can achieve a good accuracy with 3.5% error in the stretch bending process. In addition, results show that any change in the friction coefficient and bending radius in the stretch bending process can lead to different fracture behavior. Several investigations are carried out to examine the evolution of damage and displacement of fractures in the stretch bending process under different forming conditions.本文利用原始和剪切修正的 GTN 延展性断裂准则来研究 AA6061-T6 铝合金板材在拉伸弯曲过程中的断裂行为。本文提出了一种适当的校准策略,以找到断裂模型的未知系数。通过这种方法,利用不同的拉伸试验,如单轴拉、平面应变、缺口拉和剪切拉伸试样。结果表明,通过上述拉伸试验校准的剪切修正 GTN 模型能够预测拉伸弯曲过程中的断裂起始点,误差为 5%,而通过单轴拉伸校准的原始 GTN 模型则无法 正确预测断裂。由于断裂预测的准确性取决于应力状态,因此研究了校准试验对断裂发生的影响。结果表明,在拉伸弯曲过程中,使用原始 GTN 模型并进行适当的校准试验(平面应变拉伸)可获得良好的精度,误差仅为 3.5%。此外,结果表明,在拉伸弯曲过程中,摩擦系数和弯曲半径的任何变化都会导致不同的断裂行为。在不同的成形条件下,对拉伸弯曲过程中断口的损伤和位移演变进行了多项研究。Influence of elastic and toughness anisotropy on crack initiationThomas Duminy, Venkat Ayyalasomayajula, Aurélien Doitrand, Sylvain Meilledoi:10.1016/j.ijsolstr.2024.112950弹性和韧性各向异性对裂纹起始的影响The influence of elastic and toughness anisotropy on crack initiation in V-notched specimens is studied numerically using the coupled criterion and matched asymptotic expansions. A reference isotropic model material is defined with elastic and fracture properties close to nacre-like alumina. The influence of elastic properties, fracture properties, and anisotropy orientation on crack initiation angle and crack initiation force is evaluated. The objective of this work is to determine if nacre-like alumina resistance to crack initiation could be improved by tuning its elastic or fracture properties. Toughness anisotropy significantly affects the crack initiation angle without significantly influencing the crack initiation force, provided that the anisotropy remains low. Conversely, elastic anisotropy can significantly increase the crack initiation force but has a limited effect on the crack initiation angle. Nacre-like alumina already exhibits a near-optimal toughness anisotropy. However, increasing the elastic anisotropy in nacre-like alumina could significantly improve its crack initiation resistance.利用耦合准则和匹配渐近展开,对弹性和韧性各向异性对 V 型缺口试样裂纹萌生的影响进行了数值研究。定义了一种各向同性参考模型材料,其弹性和断裂特性接近于珍珠状氧化铝。评估了弹性特性、断裂特性和各向异性取向对裂纹起始角和裂纹起始力的影响。这项工作的目的是确定是否可以通过调整类珍珠质氧化铝的弹性或断裂特性来提高其抗裂纹起始性。只要各向异性保持在较低水平,韧性各向异性会显著影响裂纹起始角,而不会明显影响裂纹起始力。相反,弹性各向异性可显著增加裂纹萌发力,但对裂纹萌发角的影响有限。珍珠质氧化铝已经表现出接近最佳的韧性各向异性。然而,增加类珍珠质氧化铝的弹性各向异性可显著提高其抗裂纹萌发能力。Mechanisms and micromechanics of intergranular ductile fractureC. Sénacdoi:10.1016/j.ijsolstr.2024.112951晶间韧性断裂的机理和微观力学The process of void nucleation, growth, and coalescence is among the dominant ductile failure modes in metallic alloys and can be transgranular as well as intergranular. In the latter case, the phenomenon of void growth and coalescence happens at grain boundaries due to intense intergranular plastic flow and is associated with fracture surfaces displaying intergranular facets covered in fine dimples. The present review gives a comprehensive summary of intergranular ductile fracture mechanisms based on available experimental evidence, allowing to distinguish precisely this failure mode from other related processes. Moreover, the metallic alloys of industrial significance that can exhibit intergranular ductile fracture are carefully outlined. Then, in order to lay bridges between material science and fracture micromechanics, an overview of the current development of the local approach to fracture applied to grain boundary ductile failure is presented. Emphasis is placed on the accounting of crystallographic effects. Finally, prospects for progress in intergranular ductile fracture modeling and simulation are detailed. In particular, it is foreseen that conflicting trends seen on fracture toughness could be reconciled thanks to physically-based approaches.空洞的成核、生长和凝聚过程是金属合金中最主要的韧性破坏模式之一,可以是跨晶粒破坏,也可以是晶间破坏。在后一种情况下,由于强烈的晶间塑性流动,空洞生长和凝聚现象发生在晶粒边界,并与断裂表面上覆盖着细小凹痕的晶间面有关。本综述根据现有的实验证据,全面总结了晶间韧性断裂机制,从而将这种失效模式与其他相关过程精确区分开来。此外,还仔细概述了可出现晶间韧性断裂的工业用金属合金。然后,为了在材料科学和断裂微观力学之间架起桥梁,介绍了应用于晶界韧性断裂的局部断裂法的当前发展概况。重点是晶体学效应的考虑。最后,详细介绍了晶间韧性断裂建模和模拟的发展前景。特别是,由于采用了基于物理的方法,可以预见在断裂韧性方面出现的相互矛盾的趋势将得到调和。Artificial neural network-based homogenization model for predicting multiscale thermo-mechanical properties of woven compositesMenglei Li, Bing Wang, Jiqiang Hu, Gao Li, Peng Ding, Chunming Ji, Bing Wangdoi:10.1016/j.ijsolstr.2024.112965 基于人工神经网络的均质化模型,用于预测编织复合材料的多尺度热机械特性In this study, we propose an efficient homogenization model based on the fast Fourier transform (FFT) method and artificial neural network (ANN) models to predict the multiscale thermo-mechanical properties of woven composites. We innovatively use the FFT-Plate method to solve the periodic Lippmann–Schwinger equations for thermoelastic problems of heterogeneous plates. We utilize the classical FFT method to determine the homogenized properties of microscale representative volume element (RVE) models and the FFT-Plate method to compute the homogenized properties of mesoscale RVE models for woven composites. In addition, the number of ANN models is determined based on the Pearson correlation coefficient, the Bayesian optimization (BO) algorithm is introduced to optimize the hyperparameters of the ANN models, and the Shapley Additive exPlanations (SHAP) method provides insights into the interpretability of these models. The homogenization model takes into account the material properties of micro constituents, meso-structural parameters, and void defects in woven composites. To evaluate the accuracy of the homogenization model, the predicted uncertainties of unidirectional composites and the stochastic mechanical properties of plain woven composites are compared with experimental results, and the error of the homogenization model is less than 5 %, demonstrating its robustness and reliability.在本研究中,我们提出了一种基于快速傅立叶变换(FFT)方法和人工神经网络(ANN)模型的高效均质化模型,用于预测编织复合材料的多尺度热机械性能。我们创新性地使用 FFT-Plate 方法来求解异质板材热弹性问题的周期性 Lippmann-Schwinger 方程。我们利用经典的 FFT 方法确定微尺度代表体积元素(RVE)模型的均质特性,并利用 FFT-Plate 方法计算编织复合材料中尺度 RVE 模型的均质特性。此外,还根据皮尔逊相关系数确定了 ANN 模型的数量,引入了贝叶斯优化(BO)算法来优化 ANN 模型的超参数,并通过 Shapley Additive exPlanations(SHAP)方法深入了解了这些模型的可解释性。均质化模型考虑了编织复合材料中微观成分的材料特性、中观结构参数和空隙缺陷。为了评估均质化模型的准确性,将单向复合材料的预测不确定性和普通编织复合材料的随机力学性能与实验结果进行了比较,均质化模型的误差小于 5%,证明了其稳健性和可靠性。Journal of the Mechanics and Physics of SolidsMinimal actuation and control of a soft hydrogel swimmer from flutter instabilityAriel Surya Boiardi, Giovanni Nosellidoi:10.1016/j.jmps.2024.105753从扑腾不稳定性中实现对软水凝胶游泳器的最小驱动和控制Micro-organisms propel themselves in viscous environments by the periodic, nonreciprocal beating of slender appendages known as flagella. Active materials have been widely exploited to mimic this form of locomotion. However, the realization of such coordinated beating in biomimetic flagella requires complex actuation modulated in space and time. We prove through experiments on polyelectrolyte hydrogel samples that directed undulatory locomotion of a soft robotic swimmer can be achieved by untethered actuation from a uniform and static electric field. A minimal mathematical model is sufficient to reproduce, and thus explain, the observed behavior. The periodic beating of the swimming hydrogel robot emerges from flutter instability thanks to the interplay between its active and passive reconfigurations in the viscous environment. Interestingly, the flutter-driven soft robot exhibits a form of electrotaxis whereby its swimming trajectory can be controlled by simply reorienting the electric field. Our findings trace the route for the embodiment of mechanical intelligence in soft robotic systems by the exploitation of flutter instability to achieve complex functional responses to simple stimuli. While the experimental study is conducted on millimeter-scale hydrogel swimmers, the design principle we introduce requires simple geometry and is hence amenable for miniaturization via micro-fabrication techniques. We believe it may also be transferred to a wider class of soft active materials.微生物通过被称为鞭毛的细长附肢的周期性、非互惠性跳动,在粘性环境中推动自身前进。活性材料已被广泛用于模仿这种运动形式。然而,要在仿生鞭毛中实现这种协调跳动,需要在空间和时间上进行复杂的驱动调制。我们通过在聚电解质水凝胶样品上的实验证明,软机器人游动器的定向起伏运动可以通过均匀和静态电场的无约束驱动来实现。一个最基本的数学模型就足以再现并解释观察到的行为。由于水凝胶游泳机器人在粘性环境中的主动和被动重新配置之间的相互作用,其周期性跳动产生于扑动不稳定性。有趣的是,扑腾驱动的软机器人表现出一种电共振,只需调整电场方向就能控制其游泳轨迹。我们的发现为在软机器人系统中体现机械智能指明了方向,即利用扑动不稳定性实现对简单刺 激的复杂功能反应。虽然实验研究是在毫米级的水凝胶游泳器上进行的,但我们介绍的设计原理只需要简单的几何形状,因此可以通过微加工技术实现微型化。我们相信,它还可以应用于更广泛的软活性材料。A multiscale mechanics model for elastic properties of densified woodRui Song, Feng Deng, Xu Liang, Jianwei Song, Shengping Shen, Teng Lidoi:10.1016/j.jmps.2024.105761致密木材弹性特性的多尺度力学模型We introduce a multiscale mechanics model for analyzing the elastic properties of super-strong densified wood (DW). Our model incorporates microstructural features such as microfibril angle and densification ratio, along with chemical parameters including degree of polymerization, crystallinity, and density of hydrogen bonds. At the nanoscale and microscale, the elastic properties of cellulose nanofibril and cell wall layers are derived analytically using the mechanics of composite materials. Finite element simulations based on representative volume elements are conducted at the mesoscale to obtain homogenized effective elastic properties at the macroscale. Our quantitative investigations validate that microstructural changes and alterations in chemical components significantly enhance DW's mechanical performance. Densification and chemical changes, especially increased cellulose content and reduced lignin, emerge as vital mechanisms for strengthening DW. The model's insights offer valuable guidance for optimizing the two-step preparation process of DW to achieve superior mechanical performance. Additionally, the versatility of the model allows for exploring the influence of cell dimensions and potential applications in designing bioinspired materials.我们介绍了一种多尺度力学模型,用于分析超强致密化木材(DW)的弹性特性。我们的模型结合了微观结构特征,如微纤维角度和致密化比率,以及化学参数,包括聚合度、结晶度和氢键密度。在纳米和微观尺度上,纤维素纳米纤维和细胞壁层的弹性特性是利用复合材料力学分析得出的。在中观尺度上,基于代表性体积元素进行有限元模拟,以获得宏观尺度上的均质化有效弹性特性。我们的定量研究验证了微观结构的变化和化学成分的改变能显著提高 DW 的机械性能。致密化和化学变化,尤其是纤维素含量的增加和木质素的减少,成为强化 DW 的重要机制。该模型的见解为优化二维纤维素的两步制备过程以实现卓越的机械性能提供了宝贵的指导。此外,该模型的多功能性还有助于探索细胞尺寸的影响以及在设计生物启发材料方面的潜在应用。Mechanics of MaterialsInvestigation, validation and implementation of the p-alpha equation of state for concrete media simulationV.R. Feldgun, D.Z. Yankelevsky, Y.S. Karinskidoi:10.1016/j.mechmat.2024.105083用于混凝土介质模拟的 p-α 状态方程的研究、验证和实施Concrete is the most common material in the construction industry and almost the only material used for building security and protective structures. Such structures are intended to withstand extremely high blast and impact loading. One of the key mechanical properties of materials subjected to such extreme loading is the relationship between the hydrostatic pressure and the volumetric strain, which is known as the equation of state (EOS). In porous materials, this relationship is substantially inelastic due to the closure and collapse of pores. Commonly the EOS is obtained experimentally. Implementation of the experimental EOS curves in analytical and numerical solutions for different applications requires approximate simplified expressions for these curves. One of the most common approximations for describing the nonlinear compression of porous media is the p-alpha EOS. The present paper reviews the p-alpha EOS approximations appearing in the literature and discusses controversial issues concerning the full compaction pressure. New p-alpha EOS approximations are presented for a variety of experimental hydrostatic test results conducted by the authors for different concrete compositions with equal uniaxial compressive strength. An extended investigation is dedicated to the formulation of the p-alpha approximation in the case of limited available data, and a "blind prediction" of the pi-alpha EOS is proposed.To demonstrate the implementation of the derived p-alpha EOS, an extended example is presented, where the quasi-static cavity expansion problem in a concrete medium that is characterized by the p-alpha EOS is worked out.混凝土是建筑业中最常见的材料,也几乎是用于建造安全防护结构的唯一材料。此类结构需要承受极高的爆炸和冲击载荷。承受这种极端荷载的材料的关键机械特性之一是静水压力与体积应变之间的关系,即所谓的状态方程(EOS)。在多孔材料中,由于孔隙的闭合和塌陷,这种关系实质上是非弹性的。EOS 通常是通过实验获得的。要在不同应用的分析和数值解决方案中使用实验 EOS 曲线,需要对这些曲线进行近似简化表达。p-alpha EOS 是描述多孔介质非线性压缩的最常用近似值之一。本文回顾了文献中出现的 p-α EOS 近似值,并讨论了有关全压实压力的争议问题。本文针对作者对具有相同单轴抗压强度的不同混凝土成分进行的各种水压试验结果提出了新α-EOS 近似值。在可用数据有限的情况下,对 p-α 近似值的表述进行了扩展研究,并提出了 pi-α EOS 的 "盲预测 "方法。为了演示推导出的 p-α EOS 的实施,介绍了一个扩展示例,在该示例中研究了以 p-α EOS 为特征的混凝土介质中的准静态空腔膨胀问题。International Journal of PlasticityRevealing mechanism of ductility improvement of titanium thin sheet under normal stress at mesoscale from perspective of microstructure evolutionHaiyang Wang, Gang Chen, Peng Zhang, Chuanjie Wangdoi:10.1016/j.ijplas.2024.104055从微观结构演化的角度揭示钛薄板在中尺度法向应力作用下延展性改善的机理Improving the formability of sheet metal is a constant challenge in microforming. In this study, applying normal stresses to the specimen surface is found to be an effective method for improving the ductility of pure titanium sheets. This case only occurs when the normal stress is higher than a critical value. By characterizing the microstructure, it is found that the normal stress induces a change in the deformation mechanism, which improves the work-hardening rate and the capacity for homogeneous deformation. The plastic deformation mechanism of pure titanium thin sheets undergoes a transformation from exclusively slip-based to a multi-mechanistic mode that couples slip, twinning, and FCC phase transformation. Normal stresses exacerbate the deformation of surface grains and inhibit surface roughening. Moreover, normal stress activates deformation twins and FCC phase transformation by increasing the Schmid factor of the associated twin/slip systems. FCC phases and deformation twins contribute to enhancing the work-hardening rate through mechanisms such as the dynamic Hall-Petch effect, reorientation texture hardening, and dislocation substructure strengthening. Moreover, they enhance the material's ductility by providing additional deformation modes to accommodate strain. By virtue of the coordinated action of various deformation mechanisms, a more uniform distribution of thickness strain is achieved. It delays onset of plastic instability and enhances the formability of thin sheets. Considering the changes in dislocation density induced by different microstructures, a modified model is constructed. Based on the dislocation density and the surface layer model, this model predicts the flow stress size effect, as well as changes in flow stress and work hardening rate induced by normal stress due to microstructure transformation. This work provides a complete understanding of the mechanical property response and microstructure evolution under normal stress. It also gives a feasible solution for improving the formability of titanium thin sheet in microforming.提高金属板材的成形性是微成形领域的一项长期挑战。本研究发现,在试样表面施加法向应力是提高纯钛板延展性的有效方法。只有当法向应力高于临界值时,才会出现这种情况。通过表征微观结构发现,法向应力会引起变形机制的改变,从而提高加工硬化率和均匀变形能力。纯钛薄板的塑性变形机制从完全基于滑移的模式转变为滑移、孪晶和 FCC 相变耦合的多机制模式。法向应力会加剧表面晶粒的变形,抑制表面粗化。此外,法向应力通过增加相关孪晶/滑移系统的施密特因子,激活变形孪晶和催化裂化相变。FCC 相和变形孪晶通过动态霍尔-佩奇效应、重新定向纹理硬化和位错亚结构强化等机制,有助于提高加工硬化率。此外,它们还通过提供额外的变形模式来适应应变,从而增强了材料的延展性。在各种变形机制的协调作用下,厚度应变的分布更加均匀。这可以延迟塑性不稳定性的出现,并提高薄板的成型性。考虑到不同微结构引起的位错密度变化,我们构建了一个修正模型。基于位错密度和表面层模型,该模型预测了流动应力大小效应,以及由于微观结构转变引起的流动应力和法向应力引起的加工硬化率的变化。这项工作使人们对法向应力下的机械性能响应和微观结构演变有了全面的了解。它还为改善钛薄板在微成型中的成型性提供了可行的解决方案。Thin-Walled StructuresA quadruple physics coupling model for vibro-acoustic analysis of heavy fluid-loaded porous FGMEE plates via partition collocation points methodXinxin Wang, Tiangui Ye, Guoyong Jin, Yukun Chen, Zhigang Liudoi:10.1016/j.tws.2024.112181通过分区配位点法建立重流体负载多孔 FGMEE 板振动声学分析的四重物理耦合模型Functionally graded magneto-electro-elastic (FGMEE) materials advance industrial intelligence. Understanding the vibro-acoustic behavior of such structures is crucial for designing and optimizing smart structures. Therefore, considering the pores generated in material manufacturing, this paper establishes a magneto-electro-elastic-acoustic coupling model for underwater vibration and sound radiation of porous FGMEE plates for the first time. Using an improved Voigt formula to characterize the material properties under four pore distributions. Different constraints are quantified as boundary potential energy via virtual springs. The vibrational framework is supported by the first-order shear deformation theory together with MEE constitutive correlations. When taking into account the acoustic pressure loading effect, a partition collocation points method (PCPM) is developed to achieve rapid formulation of the vibro-acoustic coupling problem. The PCPM not only circumvents complicated integrals but also effectively addresses the inherent singularity issues of the Rayleigh integral. Chebyshev polynomials are selected as the spectral functions, and the final characteristic equation is derived by the Rayleigh-Ritz method. Numerical instances validate the feasibility of the solution approach, and the vibro-acoustic analysis of heavy fluid-loaded porous FGMEE plates is conducted comprehensively. It is believed that this study may provide theoretical and data support for subsequent research in this domain.功能分级磁电弹性(FGMEE)材料推动了工业智能化的发展。了解这类结构的振动声学行为对于设计和优化智能结构至关重要。因此,考虑到材料制造过程中产生的孔隙,本文首次建立了多孔 FGMEE 板水下振动和声辐射的磁弹声耦合模型。利用改进的 Voigt 公式表征了四种孔隙分布下的材料特性。不同的约束条件通过虚拟弹簧量化为边界势能。振动框架由一阶剪切变形理论和 MEE 构成相关性提供支持。在考虑声压加载效应时,开发了一种分区配位点法(PCPM),以实现振动-声耦合问题的快速表述。PCPM 不仅规避了复杂的积分,还有效解决了瑞利积分固有的奇异性问题。选择切比雪夫多项式作为谱函数,并通过 Rayleigh-Ritz 方法推导出最终特征方程。数值实例验证了求解方法的可行性,并对重流体负载多孔 FGMEE 板进行了全面的振动声学分析。相信本研究可为该领域的后续研究提供理论和数据支持。Legendre-Ritz solutions for vibration characteristics of three-dimensional double-layer lattice truss sandwich platesShuo Meng, Qingshan Wang, Rui Zhong, Bin Qindoi:10.1016/j.tws.2024.112185三维双层格构桁架夹层板振动特性的 Legendre-Ritz 解决方案In this paper, Legendre-Ritz solutions for vibration characteristics of double-layer lattice truss sandwich plates are proposed based on three-dimensional (3-D) elasticity theory. Double-layer lattice truss sandwich plates consist of three face sheets and two cores. The face sheets are composed of fiber-reinforced composites and the cores are composed of pyramidal lattice trusses made of isotropic materials. The pyramidal lattice core is equated to a homogeneous plate according to equivalence principle. Based on 3-D elasticity theory and pseudo excitation method (PEM), each layer's energy expressions of double-layer lattice truss sandwich plates are constructed. After that, Legendre polynomials are adopted to describe displacement components in length, width and thickness directions. On this basis, the Rayleigh-Ritz method is used to solve energy functions to obtain motion equations of double-layer lattice truss sandwich plates. The accuracy and validity of the present method are corroborated by comparisons with references and finite element method (FEM). Additionally, in order to find out effects of relevant parameters on dynamical characteristics of double-layer lattice truss sandwich plates, parametric studies are carried out by means of some numerical examples.本文基于三维(3-D)弹性理论,提出了双层格构桁架夹层板振动特性的 Legendre-Ritz 解决方案。双层格构桁架夹层板由三块面板和两块芯板组成。面板由纤维增强复合材料组成,芯板由各向同性材料制成的金字塔格构桁架组成。根据等效原理,金字塔晶格核心等同于均质板。基于三维弹性理论和伪激励法(PEM),构建了双层网格桁架夹层板各层的能量表达式。然后,采用 Legendre 多项式来描述长度、宽度和厚度方向上的位移分量。在此基础上,采用雷利-里兹法求解能量函数,从而得到双层格构桁架夹层板的运动方程。通过与参考文献和有限元法(FEM)的比较,证实了本方法的准确性和有效性。此外,为了找出相关参数对双层格构桁架夹层板动力学特性的影响,还通过一些数值实例进行了参数研究。来源:复合材料力学仿真Composites FEM

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