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 "down-top" cracks under hydro-mechanical loading, while OGFC-graded pavements have the potential to develop both "top-down" and "down-top" 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'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'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
