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【新文速递】2024年9月18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 1 篇,International Journal of Plasticity 1 篇,Thin-Walled Structures 5 篇

International Journal of Solids and Structures

Post-Necking full-field FEMU identification of anisotropic plasticity from flat notched tension experiments

Emmanouil Sakaridis, Christian C. Roth, Benoit Jordan, Dirk Mohr

doi:10.1016/j.ijsolstr.2024.113076

基于平缺口拉伸实验的后颈场FEMU各向异性塑性识别

This work introduces a finite element model updating (FEMU) identification scheme to determine the material parameters of an anisotropic metal plasticity model. Surround digital image correlation (DIC) data is collected from tensile tests on mildly notched flat specimens and it is used to minimize specimen alignment errors when comparing simulations and experiments. The front surface displacement fields and resultant force history are leveraged to calibrate a Whip-Bezier based material model in a computationally-efficient procedure, which treats the pre- and post-necking regimes separately. Experimental data from specimens with a larger notch radius (NT20) serve as the training set, while data from specimens with a smaller notch radius (NT6) are used for validation. Analysis of identification methods using datasets from virtual experiments highlights the improved generalization ability of the full-field approach compared to solely using force–displacement curves. However, this work also demonstrates that through-thickness necking in real notched tensile experiments is asymmetric. This can hinder the identification of the large strain segment of hardening laws, especially when a FEMU approach incorporates full-field information from one specimen surface only. Consequently, it is recommended to use advanced finite element models that capture asymmetric localized strain fields or to base the identification of large strain hardening responses on experiments that achieve large strains without asymmetric through-thickness strain localization, such as in-plane torsion tests.

本文介绍了一种有限元模型更新(FEMU)识别方案,用于确定各向异性金属塑性模型的材料参数。环绕数字图像相关(DIC)数据是从轻度缺口平面试样的拉伸试验中收集的,并用于在比较模拟和实验时最小化试样对准误差。利用前表面位移场和合力历史,在计算效率高的程序中校准基于Whip-Bezier的材料模型,该程序分别处理颈缩前和颈缩后状态。缺口半径较大的标本(NT20)的实验数据作为训练集,缺口半径较小的标本(NT6)的数据用于验证。利用虚拟实验数据集的识别方法分析表明,与仅使用力-位移曲线相比,全场方法具有更好的泛化能力。然而,这项工作也表明,在实际缺口拉伸实验中,全厚度颈缩是不对称的。这可能会阻碍对硬化规律的大应变段的识别,特别是当FEMU方法仅包含来自一个试样表面的全场信息时。因此,建议使用捕捉非对称局部应变场的先进有限元模型,或者基于在没有非对称全厚度应变局部化的情况下获得大应变的实验(如面内扭转试验)来识别大应变硬化响应。


Journal of the Mechanics and Physics of Solids

Intrinsic tensile brittleness of tilted grain boundaries and its shear toughening

Jia Meng, Shenyou Peng, Qihong Fang, Jia Li, Yujie Wei

doi:10.1016/j.jmps.2024.105869

倾斜晶界的内在拉伸脆性及其剪切增韧

In the endeavors of working with microstructures in polycrystalline metals for better strength and ductility, grain boundaries (GBs) are placed at the front burner for their pivotal roles in plastic deformation. Often the mechanical properties of polycrystalline metals are governed by mutual interactions among GBs and dislocations. A thorough comprehension of GB deformation is therefore critical for the design of metals of superb performance. In this research, we investigated the mechanical behavior of symmetric tilt grain boundaries in face-centred cubic (F.C.C.) nickel, which may be subject to tension, shearing, and mixing-mode load using molecular dynamics simulations. We observed that (1) there exist four types of micro deformation mechanisms in GBs, and illustrate at the atomistic scale their distinctions and their dependence on the activation of lattice slip in the crystal; (2) GBs are intrinsically brittle under tension but exhibit ductile behavior during shearing. Shifting from pure tension with increasing shear component during mixing-mode load leads to GB toughening; and (3) there lacks conceivable dependence of GB tensile strength on tilted GBs, in contrast to a relatively rough trend of greater shear strength in GBs of large misorientation. GB energy shows no direct connection with GB strength, as broadly reported in existing literature. This research enhances our mechanistic understanding of GB plasticity in crystalline metals, and points to a potential way of making strong-yet-tough polycrystalline metals through GB engineering: in addition to GB structure manipulation, tuning the loading mode of GBs may open another avenue for their better performance.

在研究多晶金属的显微组织以获得更好的强度和延展性的过程中,晶界(GBs)因其在塑性变形中的关键作用而受到重视。多晶金属的力学性能通常是由位错和gb之间的相互作用决定的。因此,对GB变形的透彻理解对于设计具有卓越性能的金属至关重要。在这项研究中,我们利用分子动力学模拟研究了面心立方镍中对称倾斜晶界的力学行为,这种晶界可能受到张力、剪切和混合模式载荷的影响。结果表明:(1)晶体中存在四种微变形机制,并在原子尺度上说明了四种微变形机制的区别及其对晶格滑移激活的依赖;(2) GBs在拉伸作用下具有脆性,但在剪切作用下具有延性。混合模式下,随着剪切分量的增加,由纯拉伸转变为GB增韧;(3)相对于取向偏差较大的GB, GB抗拉强度对倾斜GB的依赖程度较低,而相对粗糙的趋势是GB的抗剪强度增大。如现有文献广泛报道的那样,国标能量与国标强度没有直接关系。本研究增强了我们对结晶金属中GB塑性的机理理解,并指出了通过GB工程制造强韧多晶金属的潜在途径:除了对GB结构进行操纵外,调整GB的加载模式可能为其更好的性能开辟另一条途径。


International Journal of Plasticity

Crack-tip cleavage/dislocation emission competition behaviors/mechanisms in magnesium:ALEFM prediction and atomic simulation

Jia-ping Ma, Lin Yuan, Ying-ying Zong, Ming-yi Zheng, De-bin Shan, Bin Guo

doi:10.1016/j.ijplas.2024.104134

镁中裂纹尖端解理/位错发射竞争行为/机制:ALEFM预测和原子模拟

Structural properties and reliability of materials can be improved by increasing fracture toughness. At the atomic scale, the fracture is a material separation process, and the fracture toughness of materials is associated with the atomic-scale crack-tip behaviors/mechanisms. The crack-tip behaviors are relevant to the energy state of atoms in the system. Atomic thermal oscillation increases with increasing temperature, which may affect/alter the crack tip behaviors. This work is the first to investigate the temperature-dependent crack-tip cleavage/dislocation emitting competition in magnesium (Mg) using anisotropic linear elastic fracture mechanics theory, Density Functional Theory (DFT), and atomic simulation. Crack-tip behaviors are examined using a specially designed ‘K-field’ loads model. DFT calculations show that a single crystal system with lower entropy and higher Gibbs free energy implies stronger interatomic bonding that favors a higher KIc. Changes in the stress distribution initiate a brittle-ductile transition in crack-tip behavior. The ductile crack tip can be blunted by continuous crack-tip dislocations nucleation/slip, and the evolution of the ductile crack-tip geometry from sharp to semicircular structure significantly decreases the stress concentration at the crack tip. A new criterion of the crack-tip force vector is established, which reasonably explains the geometrical evolution of ductile crack tip where the angle θ between the crack plane and the slip plane is 0°<θ<90° and θ=90°. This work expands the atomic-scale brittle/ductile crack-tip behaviors/mechanisms of Mg, which provides a reference for crack-tip behavior analysis in engineering research.

通过提高断裂韧性可以改善材料的结构特性和可靠性。在原子尺度上,断裂是一种材料分离过程,材料的断裂韧性与原子尺度的裂纹尖端行为/机制有关。裂纹尖端行为与系统中原子的能量状态有关。原子热振荡随温度升高而增加,这可能会影响/改变裂纹尖端行为。本研究首次使用各向异性线性弹性断裂力学理论、密度泛函理论(DFT)和原子模拟研究了镁 (Mg) 中与温度相关的裂纹尖端裂解/位错发射竞争。利用专门设计的 “K-场 ”载荷模型对裂纹尖端行为进行了研究。密度泛函理论计算表明,单晶体系统具有较低的熵和较高的吉布斯自由能,这意味着较强的原子间键合有利于较高的 KIc。应力分布的变化引发了裂纹尖端行为的脆性-韧性转变。韧性裂纹尖端可通过连续的裂纹尖端位错成核/滑移而变钝,韧性裂纹尖端的几何形状从尖锐结构演变为半圆形结构可显著降低裂纹尖端的应力集中。建立了一个新的裂纹尖端力矢量准则,该准则合理地解释了裂纹平面与滑移平面之间的夹角θ为0°<θ<90°和θ=90°时韧性裂纹尖端的几何演变。这项工作拓展了镁的原子尺度脆性/韧性裂纹尖端行为/机理,为工程研究中的裂纹尖端行为分析提供了参考。


Thin-Walled Structures

A Meshfree Formulation for Size-dependent Thermal Buckling and Post-Buckling Behaviour of Porous Microplates on Elastic Foundation Subjected to Localized Heating

Varun Jain, Rajesh Kumar, Tanish Dey, S.N. Patel, Gaurav Watts

doi:10.1016/j.tws.2024.112451

局部加热作用下弹性地基上多孔微板尺寸相关热屈曲和后屈曲行为的无网格计算公式

The semi-analytical framework is developed for in-plane thermal stresses within the microplates under localized heating. Localized heating is modelled using Fourier Series expansions over the complete domain of the plate. These stresses within the plate are estimated after solving the in-plane thermoelasticity problem using Airy's stress approach. Utilizing these stresses, present work also studies the buckling and post-buckling behaviour of a porous metal foam microplate resting on Winkler and Pasternak elastic foundations. The plate is modelled using Reddy's third-order shear deformation theory (TSDT) and von Kármán geometric nonlinearity, and the size-dependent effects are included using the modified strain gradient theory (MSGT). Galerkin's weighted residual method converts the partial differential equations (PDEs) into algebraic equations. The post-buckling equilibrium path is obtained using the modified Newton-Raphson method. The mode shapes of the microplate for the various configurations of the plate with different boundary conditions due to localized thermal loading are plotted. Also, these mode shapes are compared with the mode shapes of the microplate due to in-plane mechanical loading. The parametric effect of porosity, elastic foundation parameters, thickness of plate, size of plate, boundary conditions and loading concentrations on the buckling and post-buckling behaviour of the plate is studied.

建立了微板局部加热条件下面内热应力的半解析框架。局部加热是用傅立叶级数在整个板域上展开来模拟的。在用艾里应力法求解面内热弹性问题后,对板内应力进行了估计。利用这些应力,本工作还研究了基于温克勒和帕斯捷尔纳克弹性地基的多孔金属泡沫微板的屈曲和后屈曲行为。采用Reddy的三阶剪切变形理论(TSDT)和von Kármán几何非线性对板进行了建模,并采用修正应变梯度理论(MSGT)考虑了尺寸相关效应。伽辽金加权残差法将偏微分方程转化为代数方程。采用改进的牛顿-拉夫逊法得到了后屈曲平衡路径。绘制了微孔板在不同边界条件下的模态振型图。同时,将这些模态振型与微孔板在平面内机械载荷作用下的模态振型进行了比较。研究了孔隙率、弹性基础参数、板厚、板尺寸、边界条件和加载浓度等参数对板屈曲和后屈曲行为的影响。


A quasi-3D SinZZ model-driven multi-field Chebyshev FEM for nonlinear vibration control in multilayer multiferroic composite plates

Duy-Khuong Ly, Bao-Anh Hoang Tran, Trung-Hau Dang, Chanachai Thongchom, Trung Nguyen-Thoi

doi:10.1016/j.tws.2024.112457

准三维SinZZ模型驱动的多场Chebyshev有限元法用于多层多铁复合材料板的非线性振动控制

This paper presents an advanced numerical method for modeling and mitigating nonlinear vibrations in thin multilayered fiber-reinforced multiferroic composite plates, addressing complex multi-physical interactions. The proposed methodology leverages a multi-physical coupling Chebyshev finite element formulation, utilizing high-order shape functions derived from Chebyshev polynomials. By integrating the strengths of spectral element methods and Legendre spectral finite element methods, this approach effectively overcomes challenges such as shear locking and spurious zero energy modes while ensuring high convergence rates in multi-physical problems. A quasi-3D refined model, incorporating the Murakami zig-zag model and sinusoidal shear deformation theory, is employed to accurately capture the nonlinear Von Kármán strain–displacement relationship and the magneto-electro-elastic coupling in multilayer structures with thickness-dependent material properties. To suppress nonlinear vibrations, the study utilizes a closed-loop multiphysical Chebyshev finite element model for time-domain analysis of viscoelastically damped systems, employing the Golla-Hughes-McTavish model. The results underscore the significant influence of multiferroic properties and the strategic distribution of ferroelectric fibers within the substrate on the dynamic behavior of the plate. The numerical validation, supported by rigorous verification, demonstrates the robustness of the proposed method in effectively simulating and controlling multilayer fiber-reinforced multiferroic composite plates. Additionally, this research highlights the potential for significant vibration reduction through semi-active damping mechanisms, offering valuable insights for practical applications in industries where precision and stability are critical.

本文提出了一种先进的数值方法来模拟和减轻薄多层纤维增强多铁复合材料板的非线性振动,处理复杂的多物理相互作用。提出的方法利用多物理耦合切比雪夫有限元公式,利用由切比雪夫多项式衍生的高阶形状函数。该方法结合了谱元方法和勒让德谱有限元方法的优点,在保证多物理问题的高收敛速度的同时,有效克服了剪切锁定和伪零能模式等难题。结合村上之锯齿模型和正弦剪切变形理论,建立准三维精细模型,精确捕捉材料厚度相关多层结构中的非线性Von Kármán应变-位移关系和磁-电弹性耦合。为了抑制非线性振动,该研究利用闭环多物理Chebyshev有限元模型对粘弹性阻尼系统进行时域分析,采用了Golla-Hughes-McTavish模型。结果强调了多铁性和铁电纤维在衬底内的策略性分布对板的动态行为的显著影响。数值验证得到了严格的验证,证明了该方法对多层纤维增强多铁复合材料板的有效模拟和控制具有鲁棒性。此外,这项研究强调了通过半主动阻尼机制显著减少振动的潜力,为精度和稳定性至关重要的行业的实际应用提供了有价值的见解。


Superior strength and energy absorption capability of LPBF metallic functionally graded lattice structures

Saad Waqar, Sajjad Hussain, Chuanxi Ren, Meng Wang, Aamer Nazir, Xingdong Dan, Chunjin Wang, Zibin Chen

doi:10.1016/j.tws.2024.112471

LPBF金属功能梯度晶格结构具有优异的强度和吸能性能

Lightweight structures exhibiting superior mechanical response are highly desirable and find widespread applications in aerospace, biomedical, and automotive industries. Lattice structures are among the promising lightweight mechanical metamaterials with excellent specific strength and energy absorption capabilities. To further enhance the behavior of stretching dominant lattice structures for high-strength applications without compromising their lightweight nature, volume fraction-based functional gradience has been proposed and evaluated in detail in this study. Laser powder bed fusion fabricated Ti6Al4V octet lattice structures with uniform volume fractions and functionally graded lattice structures were fabricated and investigated. Experimental and numerical investigations focused on various functional gradient lattice structures, including Uni-Graded, Bi-Graded Horizontal, and Bi-Graded Vertical, encompassing a wide range of volume fraction variations. The incorporation of functional gradience resulted in a substantial enhancement in both strength and energy absorption capabilities. Uni-Graded and Bi-Graded Vertical functionally graded lattice structures with significant volume fraction variations (referred to as UG3 & BGV3) exhibited an approximate 25% enhancement in compressive strength, rising from 160 MPa for uniform lattice structure to 200 MPa. Furthermore, these functionally graded lattice structures also demonstrated a remarkable enhancement in energy absorption capacity per unit volume (91% for UG3 and 101% for BGV3), underscoring the significant role of functional grading patterns and volume fraction variations in shaping the behavior of lattice structures.

具有优异机械响应的轻质结构是非常可取的,并在航空航天,生物医学和汽车工业中得到广泛应用。晶格结构具有优异的比强度和能量吸收能力,是一种很有前途的轻型机械超材料。为了进一步增强在高强度应用中拉伸主导晶格结构而不影响其轻量化特性的行为,本研究提出了基于体积分数的功能梯度,并对其进行了详细评估。制备并研究了均匀体积分数的Ti6Al4V八元晶格结构和功能梯度晶格结构。实验和数值研究集中于各种功能梯度晶格结构,包括单梯度、双梯度水平和双梯度垂直,涵盖了广泛的体积分数变化。功能梯度的结合导致了强度和能量吸收能力的实质性增强。体积分数变化较大的单梯度和双梯度垂直功能梯度晶格结构(称为UG3和BGV3)的抗压强度提高了约25%,从均匀晶格结构的160 MPa提高到200 MPa。此外,这些功能梯度晶格结构也显示出单位体积能量吸收能力的显著增强(UG3为91%,BGV3为101%),强调了功能梯度模式和体积分数变化在塑造晶格结构行为方面的重要作用。


Vibration of composite open shell of hydrogen-electric fuselage with rectangular cutout in hygrothermal circumstances: theoretical and experimental research

Xu-Yuan Song, Hao-Ran Li, Zhen Zhang, Jian Zang, Ye-Wei Zhang, Li-Qun Chen

doi:10.1016/j.tws.2024.112473

热湿环境下矩形开壳复合材料氢电机身振动的理论与实验研究

An effective formulation is performed to approximate calculate the vibration of the typical composite fuselage battery compartment structures of the hydrogen-electric aircraft, which are highly sensitive to hygrothermal circumstances. The strain energy, kinetic energy and hygrothermal potential energy of CLOCSRC are deduced in frame of Donnell's shell assumption and a series of hypothetical elastic springs operating on the edges of divided components are introduced to simulate coupling connection and the elastic supports of the open shell, which contribute to total system energy in the form of elastic spring potential energy. The equations of motion for CLOCSRC subjected to distinct hygrothermal circumstances and arbitrary boundaries are eventually obtained in frame of the Rayleigh-Ritz method by means of the modified orthogonal polynomial as the displacement admissible function. After confirming the convergence and accuracy of the presented formulation by experiment and finite element method, several numerical examples are presented to investigative the effects of geometric parameters, elastic boundaries and hygrothermal circumstances on the vibration of CLOCSRC. Differ from traditional investigation, the present paper offers an effective approach to insight the hygrothermal mechanism of open shell with rectangular cutouts creatively. The relevant investigation demonstrated that the current strategy is beneficial for further research on the vibration characteristics of CLOCSRC.

对典型的对湿热环境高度敏感的氢动力飞机复合材料机身电池舱结构的振动进行了有效的近似计算。在Donnell壳体假设框架下推导了CLOCSRC的应变能、动能和湿热势能,并引入一系列假设的弹性弹簧作用于分离构件的边缘,模拟了耦合连接和开壳的弹性支撑,以弹性弹簧势能的形式贡献了系统总能量。最后以修正正交多项式作为位移容许函数,在Rayleigh-Ritz法的框架下得到了不同热湿环境和任意边界下CLOCSRC的运动方程。在通过实验和有限元方法验证了该公式的收敛性和准确性的基础上,通过数值算例研究了几何参数、弹性边界和湿热环境对CLOCSRC振动的影响。与传统的研究不同,本文创造性地提供了一种有效的方法来了解矩形开壳的热湿机理。相关研究表明,目前的策略有利于进一步研究CLOCSRC的振动特性。


Experimental study on seismic performance of assembled buckling-restrained brace with low yield point steel

Meng Wang, Yunshan Tong

doi:10.1016/j.tws.2024.112474

低屈服点钢组合抗屈曲支撑抗震性能试验研究

Based on the design concept of seismic resilience, which aims to achieve controllable damage during earthquakes and rapid post-earthquake functional recovery within the structure, an assembled buckling-restrained brace with low yield point steel (ALYBRB) was proposed. To evaluate its seismic performance, quasi-static cyclic loading tests were conducted on five ALYBRB specimens. The influence of core steel material, bolt spacing of the external restraint system, and the gap between the core and the external restraint system on the seismic performance of ALYBRBs were investigated. The results indicated that the ALYBRBs exhibited superior plastic deformation capacity, stable energy dissipation capacity, and exceptional fatigue performance, as well as significant cyclic hardening characteristics and hysteretic properties with good symmetry. The cumulative plastic deformation coefficient (CPD) of ALYBRBs with LYP100 and LYP160 steel were 2.33 times and 1.51 times greater than that with Q235 steel, respectively. The maximum equivalent viscous damping coefficients of all specimens can achieve a range of 73.0% to 86.2% of the theoretically maximum value. The strain hardening adjustment factors of all specimens ranged between 1.34 and 1.90. The average compression strength adjustment factor for the properly designed ALYBRB specimens was 1.12. Reducing the bolt spacing can effectively inhibit the multi-wave buckling of the core, which is conducive to the improvement of energy dissipation efficiency in ALYBRBs. ALYBRB specimen with excessive gap exhibited decreased ductility, energy dissipation efficiency, and fatigue performance, and its out-of-plane deformation mode was a combination of bending deformation in the constrained yield segment and the transition segment deformation.

基于抗震弹性设计理念,提出了一种低屈服点钢组合抗屈曲支撑(ALYBRB),旨在实现地震时结构损伤可控和震后结构功能快速恢复。为评价其抗震性能,对5个ALYBRB试件进行了准静力循环加载试验。研究了芯钢材料、外约束系统螺栓间距、芯与外约束系统间距对alybrb抗震性能的影响。结果表明:alybrb具有优异的塑性变形能力、稳定的耗能能力和优异的疲劳性能,具有显著的循环硬化特性和良好的对称性滞回性能。使用LYP100和LYP160的alybrb的累积塑性变形系数(CPD)分别是使用Q235的2.33倍和1.51倍。各试件的最大等效粘性阻尼系数可达到理论最大值的73.0% ~ 86.2%。各试样应变硬化调整系数在1.34 ~ 1.90之间。合理设计的ALYBRB试件的平均抗压强度调整系数为1.12。减小锚杆间距可以有效抑制锚杆芯的多波屈曲,有利于提高alybrb的耗能效率。间隙过大的ALYBRB试件延性、耗能效率和疲劳性能下降,其面外变形模式为约束屈服段弯曲变形和过渡段变形的结合。



来源:复合材料力学仿真Composites FEM
ACTMechanicalSystemMAGNETDeform振动疲劳断裂复合材料非线性航空航天汽车裂纹理论电机材料分子动力学
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首次发布时间:2024-11-27
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【新文速递】2024年8月16日固体力学SCI期刊最新文章

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 3 篇International Journal of Solids and StructuresThe stick-slip bending behavior of the multilevel helical structures: A 3D thin rod model with frictional contactYuchen Han, Jingshan Hao, Huadong Yong, Youhe Zhoudoi:10.1016/j.ijsolstr.2024.113005多层螺旋结构粘滑弯曲行为:含摩擦接触的三维细杆模型The multilevel helical structures in various engineering and natural fields offer excellent deformation flexibility and load bearing capabilities. Understanding the interplay between the local frictional contact and the geometric characteristics of the helical structure under complex external loads has attracted considerable interest. In this work, the effect of local frictional contact behaviors on the bending in multilevel helical structures is investigated by using a combination of theoretical modeling, finite element (FE) simulations, and experiments. In the case of pure bending, the kinematic parameters of the bent multi-stage helix are derived concisely by the idea of the kinematic analogy. The bending stiffness of the multi-stage helix is further obtained. In the case of the combined tension/torsion and bending, the 3D thin rod model incorporating Coulomb’s friction is established to describe the mechanical responses. It is found that the relationship between equivalent bending stiffness and the laying angle exhibits nonlinearity. A comparison with the classical Papailiou model reveals that, for helical structures at large laying angles, the influence of friction is primarily determined by the internal force in the tangential direction, which is the core assumption of the Papailiou model. However, in the case of small laying angles, the helical twisting characteristics and the contribution of the internal forces and moments in the other two directions (normal and binormal directions) to the friction cannot be ignored. Subsequently, a multilevel frictional contact transmission formulation is proposed according to the force action–reaction principle. Based on the above formulation, the non-simplified thin rod equations with Coulomb’s friction are extended to describe the multilevel stick-slip bending behaviors of the second stage cable (3*3). The dissipation capacity of helical structures is evaluated quantitatively under the hysteretic bending. Finally, the theoretical model is verified by FE simulations and experimental results. This work provides insights for unveiling the intrinsic relationship between the nonlinear bending and local frictional contact behaviors in the multilevel helical structures.多层螺旋结构在各种工程和自然领域中具有优异的变形灵活性和承载能力。复杂外载荷作用下螺旋结构的局部摩擦接触与几何特性之间的相互作用引起了人们的广泛关注。本文采用理论建模、有限元模拟和实验相结合的方法,研究了局部摩擦接触行为对多层螺旋结构弯曲的影响。在纯弯曲情况下,利用运动学类比的思想,简明地导出了弯曲多级螺旋的运动学参数。进一步得到了多级螺旋的弯曲刚度。在拉伸/扭转和弯曲复合作用下,建立了考虑库仑摩擦的细杆三维力学响应模型。结果表明,等效抗弯刚度与铺设角呈非线性关系。与经典Papailiou模型的对比表明,对于大铺放角的螺旋结构,摩擦的影响主要由切向内力决定,这是Papailiou模型的核心假设。然而,在铺设角较小的情况下,螺旋扭转特性以及其他两个方向(法向和法向)的内力和弯矩对摩擦的贡献是不可忽视的。随后,根据力-反作用原理,提出了多级摩擦接触传动公式。在此基础上,将含库仑摩擦的非简化细杆方程推广到描述二级索(3*3)的多级粘滑弯曲行为。对螺旋结构在滞回弯曲作用下的耗散能力进行了定量评价。最后,通过有限元仿真和实验结果对理论模型进行了验证。这项工作为揭示多层螺旋结构中非线性弯曲和局部摩擦接触行为之间的内在关系提供了见解。Journal of the Mechanics and Physics of SolidsEnhancement of adhesion strength in viscoelastic unsteady contactsC. Mandriota, N. Menga, G. Carbonedoi:10.1016/j.jmps.2024.105826粘弹性非定常接触中粘接强度的增强We present a general energy approach to study the unsteady adhesive contact of viscoelastic materials. Under the assumption of infinitely short-range adhesive interactions, we exploit the principle of virtual work to generalize Griffith’s local energy balance at contact edges to the case of a non-conservative (viscoelastic) material, subjected to a generic contact time–history. We apply the proposed energy balance criterion to study the approach-retraction motion of a rigid sphere in contact with a viscoelastic half-space. A strong interplay between adhesion and viscoelastic hysteretic losses is reported as the adhesion strength can strongly increase, depending on the loading history. Two different mechanisms govern the pull-off force increase during either approach-retraction cycles and approach – full relaxation – retraction tests. In the former case, hysteretic losses occurring close to the circular perimeter of the contact play the major role, significantly enhancing the energy release rate required change the contact size. In the latter case, instead, the pull-off enhancement depends on the glassy response of the whole material which, triggered by the fast retraction after relaxation, leads to a sort of ‘frozen’ state and flat-punch-like detachment mechanism (i.e., constant contact area). In this case, the JKR theory of adhesive contact cannot be invoked to relate the observed pull-off force to the effective adhesion energy, i.e. the energy release rate G , and strongly overestimates it. Therefore, a rigorous mathematical procedure is also proposed to correctly calculate the energy release rate in viscoelastic dissipative contacts.提出了一种研究粘弹性材料非定常粘接接触的通用能量方法。在无限短距离粘接相互作用的假设下,我们利用虚功原理将Griffith在接触边缘的局部能量平衡推广到非保守(粘弹性)材料的情况下,受到一般接触时程的影响。应用所提出的能量平衡准则,研究了刚性球体与粘弹性半空间接触时的接近-收缩运动。粘连和粘弹性滞回损失之间有很强的相互作用,据报道,粘连强度会随着加载历史的变化而显著增加。在接近-收放循环和接近-完全放松-收放测试中,有两种不同的机制控制着拉离力的增加。在前一种情况下,发生在接触圆周附近的滞回损耗起主要作用,显著提高了改变接触尺寸所需的能量释放率。在后一种情况下,拉脱增强取决于整个材料的玻璃响应,这种响应是由弛豫后的快速缩回触发的,导致一种“冻结”状态和平冲孔式分离机制(即恒定的接触面积)。在这种情况下,不能援引JKR黏着接触理论将观察到的拉脱力与有效黏着能即能量释放率G联系起来,并且严重高估了它。因此,还提出了一种严格的数学方法来正确计算粘弹性耗散接触的能量释放率。Mechanics of MaterialsMulti-scale FE analysis of coupled load-moisture mechanical behavior of saturated asphalt pavements considering transversely isotropic permeabilityMingyang Gong, Xin Sui, Zhen Leng, Binbin Yindoi:10.1016/j.mechmat.2024.105116考虑横向各向同性渗透率的饱和沥青路面荷载-水分耦合力学特性多尺度有限元分析Assessing the collective impacts of external loading and void pressure on the mechanical behavior of porous media presents a significant challenge due to its inherent heterogeneity and complex multi-physical field coupling mechanisms. This study addresses this challenge by developing a novel multiscale hydraulic-mechanical modeling framework to investigate the structural response of water-saturated asphalt pavement under sequential coupling hydro-mechanical loading. The framework comprises three key components. Firstly, incorporating an upscaling homogenization approach to establish the linkage of material properties between different scales; secondly, developing a downscaling transfer procedure to transfer the structural response across scales for insight into its multiphysics mechanisms; and finally, proposing a new sequential coupling algorithm in multiscale simulations for comprehensive multi-field coupling calculations. The primary outcomes of this study demonstrate that AC-graded pavements are susceptible to &quot;down-top&quot; cracks under hydro-mechanical loading, while OGFC-graded pavements have the potential to develop both &quot;top-down&quot; and &quot;down-top&quot; cracks. In AC-graded pavements, increasing the hydraulic head reduces stress concentrations, while in OGFC-graded pavements, changes in the permeability coefficient have a lesser impact on mechanical response. At the mesoscopic level, tensile stress concentrations in the asphalt mortar decrease significantly at higher temperatures. Furthermore, the OGFC-graded RVE model exhibits higher tensile stresses in the asphalt mortar compared to the AC-graded RVE model.由于多孔介质固有的非均质性和复杂的多物理场耦合机制,评估外部载荷和空隙压力对多孔介质力学行为的集体影响是一项重大挑战。本研究通过开发一种新颖的多尺度水力力学建模框架来研究水饱和沥青路面在顺序耦合水力力学载荷下的结构响应,从而解决了这一挑战。该框架包括三个关键部分。首先,采用上尺度均质化方法,建立不同尺度间材料性能的联系;其次,开发一个降尺度转移程序,以跨尺度转移结构响应,以深入了解其多物理场机制;最后,提出了一种新的多尺度模拟序列耦合算法,用于综合多场耦合计算。本研究的主要结果表明,在水-机械荷载作用下,ac级配路面容易出现“自上而下”裂缝,而ogfc级配路面则可能同时出现“自上而下”和“自上而下”裂缝。在ac级配路面中,增加水头可以降低应力集中,而在ogfc级配路面中,渗透系数的变化对力学响应的影响较小。在细观水平上,高温下沥青砂浆中的拉应力浓度显著降低。此外,与ac -分级RVE模型相比,ogfc分级RVE模型在沥青砂浆中表现出更高的拉应力。International Journal of PlasticityHigh-temperature creep mechanism of Ti-Ta-Nb-Mo-Zr refractory high-entropy alloys prepared by laser powder bed fusion technologyJunyi Feng, Binghao Wang, Yintao Zhang, Peilei Zhang, Changxi Liu, Xiaoli Ma, Kuaishe Wang, Lechun Xie, Ning Li, Liqiang Wangdoi:10.1016/j.ijplas.2024.104080 激光粉末床熔合Ti-Ta-Nb-Mo-Zr难熔高熵合金高温蠕变机理Creep resistance, which is one of the most important deformation modes, is rarely reported for refractory high entropy alloys (RHEAs). The experiment investigated the high-temperature creep mechanism of Ti-Ta-Nb-Mo-Zr RHEA prepared by laser powder bed fusion (LPBF) technology. The high cooling rate of LPBF suppresses most of the elemental segregation, but there are still over-solidified precipitates and a few continuous precipitates (CP). In the range of 923-1023 K, the stress exponent and activation energy were determined to be 3.2-3.4 and 261.5 ± 19.5 kJ/mol, respectively. Compared with other conventional alloys and HEAs, a large reduction of the minimum creep rate is found in the LPBF-built Ti1.5Ta0.5NbZrMo0.5 RHEA, indicating a significant improvement in high-temperature properties. The dislocation tangles at the interface is formed during the creep process and new Zr-rich CP phases are generated in the dislocation tangles region. The interfacial dislocation tangles is the result of the interaction between dislocations and two-phase mismatch stresses. The dislocation tangles prevents dislocations from further cutting the matrix phase, which is very favorable to the high-temperature creep performance. At the same time, the formation of this dislocation tangles greatly accelerates the nucleation process and growth rate of the new CP phase. The present work provides a pathway to design novel HEAs with improved high-temperature creep resistance.高温高熵合金的蠕变抗力是其最重要的变形模式之一,但目前对高温高熵合金的蠕变抗力研究较少。实验研究了激光粉末床熔融(LPBF)技术制备Ti-Ta-Nb-Mo-Zr RHEA的高温蠕变机理。高冷却速率抑制了大部分元素偏析,但仍存在过凝固析出相和少量连续析出相(CP)。在923 ~ 1023 K范围内,应力指数为3.2 ~ 3.4,活化能为261.5±19.5 kJ/mol。与其他传统合金和HEAs相比,lpbf构建的Ti1.5Ta0.5NbZrMo0.5 RHEA的最小蠕变速率大幅降低,表明其高温性能得到了显著改善。蠕变过程中在界面处形成位错缠结,在位错缠结区生成新的富zr CP相。界面位错缠结是位错与两相失配应力相互作用的结果。位错缠结阻止了位错进一步切削基体相,有利于提高材料的高温蠕变性能。同时,这种位错缠结的形成大大加快了新CP相的成核过程和生长速度。本工作为设计具有更好的高温蠕变性能的新型HEAs提供了途径。Thin-Walled StructuresRandom thermal-vibration mechanisms of sandwich ventral fin-type plate-shell systems with porous functionally graded coreShuangwei Hu, Qingshan Wang, Rui Zhong, Bin Qindoi:10.1016/j.tws.2024.112333多孔功能梯度岩心夹层腹鳍型板壳系统的随机热振动机理The stochastic thermal-vibration mechanisms within a sandwich ventral fin-type plate-shell system, featuring a porous functionally graded (FG) core, are exhaustively analyzed under various random loading conditions employing an innovative node-based, meshless computational approach. The studied structure is decoupled into several plates and open cylindrical panel according to the geometric characteristics, and the mechanical relationships at the structural boundaries or connection interfaces are equivalently simulated by using penalty parameters. Following the general Hamilton&#39;s principle, the meshless approach combined with the first-order shear deformation theory (FSDT) incorporating thermal effects is employed to derive the vibration equations of the sandwich ventral fin-type plate-shell systems. Also, the pseudo excitation method (PEM) is introduced to calculate stationary and nonstationary random responses. In order to verify the accuracy of the meshless algorithm in this study, the convergence and correctness are studied comprehensively. And then, the effects of some parameters such as temperature variation, porosity parameters, power-law index and random excitations on the thermal vibration characteristics of the sandwich ventral fin-type plate-shell systems with porous FG core are presented. The results show that the power-law index and temperature can increase the frequency parameter of the structure. The smooth power spectral density (PSD) excitation only affects the amplitude of the response curve, and does not affect the frequency corresponding to the peak. In the analysis of non-stationary random vibration, the influence of modulation parameters on response is very significant.采用创新的基于节点的无网格计算方法,对具有多孔功能梯度(FG)核心的夹层腹鳍型板壳系统在各种随机载荷条件下的随机热振动机制进行了详尽分析。将所研究的结构根据几何特性解耦为若干板和开式圆柱板,采用罚参数等效模拟结构边界或连接界面处的力学关系。根据Hamilton原理,采用无网格法结合考虑热效应的一阶剪切变形理论(FSDT),推导了夹层腹鳍型板壳系统的振动方程。同时,引入了伪激励法(PEM)来计算平稳和非平稳随机响应。为了验证本文无网格算法的准确性,对其收敛性和正确性进行了全面的研究。然后,研究了温度变化、孔隙率参数、幂律指数和随机激励等参数对多孔FG芯夹层腹鳍型板壳系统热振动特性的影响。结果表明,幂律指数和温度可以提高结构的频率参数。平滑功率谱密度(PSD)激励只影响响应曲线的幅值,而不影响峰值对应的频率。在非平稳随机振动分析中,调制参数对响应的影响是非常显著的。Nonlinear thermo-mechanical static stability analysis of FG-TPMS shallow spherical shellsDang Thuy Dong, Tran Quang Minh, Bui Tien Tu, Kim Q. Tran, H. Nguyen-Xuandoi:10.1016/j.tws.2024.112343FG-TPMS浅球壳的非线性热-机械静稳定性分析An analytical solution for the nonlinear static stability problem of functionally graded triply periodic minimal surface (FG-TPMS) shallow spherical shells is studied in the current research for the first time. Three common TPMS structures including Primitive (P), Gyroid (G), and I-graph and Wrapped Package-graph (IWP) with three models of functionally graded porosity distribution along the thickness are considered. The shallow spherical shells (shallow SSs) are subjected to combined thermo-mechanical loadings and rested on a nonlinear elastic foundation. The fundamental formulas are expressed based on the higher-order shear deformation theory (HSDT) and von Kármán&#39;s geometrical nonlinearities. Employing the Ritz energy minimization method, the explicit relationship between load and deflection is derived. Subsequently, the static stability behavior of FG-TPMS shallow SSs is investigated. Numerical illustrations are investigated to show the superior thermo-mechanical load-carrying performance of the FG-TPMS SSs compared to corresponding isotropic structures of the same weight. The significant effects of geometric parameters, nonlinear elastic foundation parameters, and the type of FG-TPMS structures on the nonlinear static stability behavior of shallow SSs are further considered.本文首次研究了功能梯度三周期最小表面(FG-TPMS)浅球壳非线性静稳定性问题的解析解。考虑了三种常见的TPMS结构,包括Primitive (P), Gyroid (G), I-graph和Wrapped Package-graph (IWP),以及沿厚度的三种功能梯度孔隙度分布模型。浅球壳在非线性弹性基础上承受热-力复合载荷。基本公式是基于高阶剪切变形理论(HSDT)和von Kármán的几何非线性来表达的。采用里兹能量最小化方法,推导了载荷与挠度之间的显式关系。随后,研究了FG-TPMS浅层SSs的静稳定性行为。数值计算表明,与同等重量的各向同性结构相比,FG-TPMS SSs具有优越的热机械承载性能。进一步考虑了几何参数、非线性弹性基础参数和FG-TPMS结构类型对浅层SSs非线性静力稳定行为的显著影响。Integrating parametric HFGMC and isogeometric RZT^{3,2} for multiscale damage modeling of composite structures: A numerical and experimental studyAryan Kheyabani, Adnan Kefaldoi:10.1016/j.tws.2024.112344将参数 HFGMC 和等几何 RZT^{3,2} 整合用于复合材料结构的多尺度损伤建模: 数值和实验研究In this research effort, a novel multiscale analysis scheme is proposed for damage modeling of composite laminates, sandwich structures, and stiffened plates relying on capabilities of the parametric HFGMC and isogeometric RZT^{3,2} formulations. The Ramberg Osgood (RO) model is incorporated into the micromechanics model to reflect polymer matrix material nonlinearities on the overall homogenized composite behavior. Carbon fibers are assumed to behave in a linear transversely isotropic manner. The higher order RZT^{3,2} theory employed at the macro level facilitates efficient applicability of the model to thick composite laminates and soft core sandwiches. On the other hand, it generates all three-dimensional stress components and thus ensures dimensional consistency between micro and macro levels. Numerical discretization and prediction of RZT^{3,2} kinematic variables are enabled by performing NURBS based isogeometric analysis (IGA) thereby enhancing modeling efficacy to a significant degree. Soft core plasticity and failure in the composite are evaluated at the macro level through the RO model and Hashin criteria, respectively. Applicability of the method is presented for thin and thick flat composite and sandwich laminates; and further extended to stiffened plates via developing a multipatch formulation. A comprehensive validation of our analysis is conducted by comparing the results with established benchmarks from the literature, experimental data, and three-dimensional finite element method (3D-FEM) simulations. Initially, a moderately thick, simply supported square laminate under transverse loading is examined, a common verification benchmark. Then, results from standard mechanical tests, including tensile, shear, and four-point bending tests on thin laminates, followed by experiments on moderately thick sandwich structures subjected to four-point bending, are presented. Finally, the analysis is extended to a stiffened plate under uniform pressure, demonstrating the method’s accuracy and applicability across diverse structural configurations.在这项研究工作中,利用参数 HFGMC 和等几何 RZT^{3,2} 公式的能力,为复合材料层压板、夹层结构和加劲板的损伤建模提出了一种新的多尺度分析方案。微观力学模型中加入了 Ramberg Osgood(RO)模型,以反映聚合物基体材料对整体均质复合材料行为的非线性影响。碳纤维被假定为线性横向各向同性材料。在宏观层面上采用的高阶 RZT^{3,2} 理论有助于将模型有效地应用于厚复合材料层压板和软芯三明治。另一方面,它生成了所有三维应力分量,从而确保了微观和宏观层面的尺寸一致性。通过执行基于 NURBS 的等几何分析 (IGA),实现了 RZT^{3,2} 运动变量的数值离散化和预测,从而在很大程度上提高了建模效率。通过 RO 模型和 Hashin 标准,分别对复合材料的软芯塑性和失效进行了宏观评估。该方法适用于薄、厚平板复合材料和三明治夹芯层压板,并通过开发多补丁配方进一步扩展到加劲板。通过将分析结果与文献、实验数据和三维有限元法(3D-FEM)模拟的既定基准进行比较,对我们的分析进行了全面验证。首先,对横向载荷作用下的中等厚度简支撑方形层压板进行了研究,这是一种常见的验证基准。然后,介绍标准机械测试的结果,包括薄层板的拉伸、剪切和四点弯曲测试,接着是中等厚度夹层结构承受四点弯曲的实验。最后,将分析扩展到均匀压力下的加劲板,证明了该方法在不同结构配置中的准确性和适用性。来源:复合材料力学仿真Composites FEM

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