今日更新：International Journal of Solids and Structures 4 篇，Journal of the Mechanics and Physics of Solids 1 篇，International Journal of Plasticity 1 篇，Thin-Walled Structures 2 篇International Journal of Solids and StructuresDependence of stiffness on water content in hydrogels: A statistical mechanics-based frameworkRoberto Brighenti, Matteo Montanari, Silvia Monchetti, Tamara Hanuhov, Andrea Spagnoli, Noy Cohendoi:10.1016/j.ijsolstr.2024.112920水凝胶中含水量对刚度的依赖性:基于统计力学的框架Hydrogels are polymers that can uptake large amounts of water within their molecular network. Thanks to their physical, chemical, and mechanical properties, which are close to those of biological materials, hydrogels can be conveniently employed in a variety of fields, ranging from soft robots to biomedical applications. The microstructure of dry hydrogels comprises chains that are chemically cross-linked and interact with one another through intermolecular hydrogen bonds. In the present paper, we derive a model that describes the influence of water content on the overall stiffness of hydrogels. Broadly, water uptake in a hydrogel has three main consequences: (1) the presence of (compliant) liquid softens the gel, (2) the stretching of the chains to accommodate water molecules leads to entropic stiffening, and (3) water molecules dissociate intermolecular bonds, resulting in entropic gain and significant softening. In this work, we derive a microscopically motivated model that accounts for these three effects and captures the influence of water molecules on the stiffness of hydrogels. To validate the model, we perform compression tests on superabsorbent polymers that swell to >100 times in volume and employ Hertzian contact theory to determine the stiffness. The model is in agreement with the experimental findings. To enable one to control the mechanical properties, we employ the model to investigate the role of pertinent microscopic quantities such as chain length and the number of intermolecular hydrogen bonds on the overall stiffness. The findings from this work pave the way to the microstructural design of hydrogels with tunable water content dependent stiffness.水凝胶是一种聚合物，可以在其分子网络中吸收大量水分。由于水凝胶具有接近生物材料的物理、化学和机械特性，因此可以方便地应用于从软机器人到生物医学应用等多个领域。干水凝胶的微观结构由化学交联的链组成，这些链通过分子间氢键相互作用。在本文中，我们推导出一个模型，用于描述水含量对水凝胶整体刚度的影响。概括地说，水凝胶中的水分吸收会产生三个主要后果： (1）（顺从的）液体的存在会使凝胶软化；（2）为容纳水分子而拉伸链条会导致熵变硬；（3）水分子解离分子间的键，导致熵增和显著软化。在这项工作中，我们推导出一个微观模型，该模型考虑了这三种效应，并捕捉到了水分子对水凝胶硬度的影响。为了验证该模型，我们对体积膨胀 >100 倍的超吸收聚合物进行了压缩试验，并采用赫兹接触理论确定了刚度。模型与实验结果一致。为了能够控制机械性能，我们利用该模型研究了链长和分子间氢键数量等相关微观量对整体刚度的作用。这项研究成果为设计出具有可调水含量刚度的水凝胶微结构铺平了道路。The use of Cauchy-type singular integrals over neighboring intervals to compute induced slip in displaced faultsBernard Meulenbroek, Jan Dirk Jansendoi:10.1016/j.ijsolstr.2024.112922利用相邻区间上的柯西型奇异积分计算位移断层的诱发滑动We present expressions to compute the inverse of a Cauchy-type singular integral equation representing the relation between a double-peaked Coulomb stress in a fault or fracture and the resulting slip gradient in two distinct collinear slip patches. In particular we consider a situation where the patches are close enough to account for the influence of the slip gradient in one patch on the slip-induced shear stress in the other patch and vice versa. This situation can occur during depletion-induced or injection-induced fault slip in subsurface reservoirs for, e.g., natural gas production, hydrogen or CO 2 storage, or geothermal operations. The theory for a single slip patch is well-developed but the situation is less clear for a configuration with two patches although the monographs of Muskhelishvili (1953) and Weertman (1996) provide earlier results. We show that the general inverse solution for the coupled two-patch problem requires six auxiliary conditions to ensure six physical requirements: boundedness of the slip gradient at the four end points of the slip patches and vanishing of the integrals of the slip gradient over the patches. Mathematically, the presence of two additional conditions, as compared to earlier formulations, corresponds to two undetermined coefficients in the general solution of the governing integral equation. Numerical simulation confirms that at least one of these is always non-zero in the coupled situation. For a coupled double-patch case with a symmetric pre-slip Coulomb stress pattern, the general inverse solution requires three auxiliary conditions. Moreover the conditions for the asymmetric case may be reduced to a set of four again, but these are different from the sets of four obtained earlier by Muskhelishvili (1953) and Weertman (1996). We illustrate the theory with a numerical example in which the evaluation of the Cauchy integrals is performed with a modified version of augmented Gauss–Chebyshev quadrature that relies on analytical inversion.我们给出了一个柯西型奇异积分方程的逆表达式，该方程表示断层或裂缝中的双峰库仑应力与两个不同共线滑动斑块中产生的滑动梯度之间的关系。我们特别考虑了这样一种情况，即斑块足够接近，以解释一个斑块中的滑移梯度对另一个斑块中滑移引起的剪切应力的影响，反之亦然。这种情况可能发生在天然气生产、氢气或二氧化碳储存或地热作业等地下储层的枯竭或注入诱发断层滑动期间。虽然Muskhelishvili(1953)和Weertman(1996)的专著提供了更早的结果，但单滑移斑块的理论已经发展得很好，但对于具有两个斑块的构型，情况就不太清楚了。我们证明了耦合两斑块问题的一般逆解需要六个辅助条件来保证六个物理要求:滑移梯度在滑移斑块的四个端点处的有界性和滑移梯度在斑块上的积分的消失。在数学上，与先前的公式相比，两个附加条件的存在对应于控制积分方程通解中的两个待定系数。数值模拟证实，在耦合情况下，这两个参数至少有一个不为零。对于具有对称预滑移库仑应力图的耦合双片情况，一般反解需要三个辅助条件。此外，非对称情况的条件可以再次简化为四个集 合，但这些条件不同于Muskhelishvili(1953)和Weertman(1996)早先得到的四个集 合。我们用一个数值例子来说明这个理论，在这个数值例子中，柯西积分的计算是用依赖于解析反演的增广高斯-切比雪夫正交的改进版本来进行的。Modeling a triclinic lattice elastic body based on the linear couple stress theoryRyunosuke Suzuki, Yoshitaka Kameo, Taiji Adachidoi:10.1016/j.ijsolstr.2024.112923基于线性耦合应力理论的三斜点阵弹性体建模Triclinic lattice structures with generalized parallelepiped unit cells are crucial targets in understanding the influence of lattice structure on the mechanical behaviors of lattice elastic bodies. This study models a three-dimensional elastic body with a triclinic lattice microstructure comprising three uniform elastic members rigidly joined at a single point. Based on the linear couple stress theory, a specialized case of the Cosserat theory, this study derives elasticity tensors in the constitutive equations of the triclinic lattice elastic body that depend on the crossing angles between the members. To derive the angular-dependent elasticity tensors, coordinate transformations between oblique and orthogonal coordinate systems are effectively employed in formulating the substitution of deformation and force fields in the continuum for the fields in the lattice structure. Evaluating the elasticity tensors reveals the influences of the crossing angles on the anisotropic tensile and torsional properties, the existence of the angle-covariant lattice number manipulation that cancels out the size effect, and several types of geometrical shape dependence. This study could contribute to the theoretical evaluation of elastic behaviors of both artificially engineered and naturally formed materials with lattice microstructures.具有广义平行六面体的三斜点阵结构是研究点阵结构对点阵弹性体力学行为影响的重要对象。本研究模拟了一个三维弹性体，其具有三斜晶格微结构，由三个均匀弹性构件刚性连接在一个单点上。本文基于线偶应力理论(Cosserat理论的一个特例)，导出了三斜点阵弹性体本构方程中依赖于构件间交叉角的弹性张量。为了推导出与角相关的弹性张量，利用斜坐标系和正交坐标系之间的坐标变换，有效地表达了连续体中的变形场和力场对晶格结构中的场的替代。评估弹性张量揭示了交叉角对各向异性拉伸和扭转性能的影响，角协变晶格数操作的存在抵消了尺寸效应，以及几种类型的几何形状依赖。该研究有助于从理论上评价人工工程和自然形成的晶格微结构材料的弹性行为。Crystal plasticity-based finite element simulations of load reversals and hat-shaped draw-bending for predicting the springback behavior of dual-phase steel sheetsMarko Knezevicdoi:10.1016/j.ijsolstr.2024.112924基于晶体塑性的有限元模拟载荷逆转和帽形拉伸弯曲，预测双相钢板的回弹行为This work is concerned with predicting geometrical shape changes in sheet metal forming using a multi-level simulation framework that considers the directionality of deformation mechanisms acting at the single-crystal level and microstructural evolution. The multi-level model is an elasto-plastic self-consistent (EPSC) homogenization of single-crystal behavior giving the constitutive response at each finite element (FE) material point. Numerical solution of a boundary value problem over geometry is then obtained using continuum finite elements at the macro-level. First, a set of model parameters for the evolution of slip resistance of ferrite and martensite and backstress are established by fitting a comprehensive set of mechanical data for dual-phase (DP) steels 590, 780, and 1180 using one-element model. Next, the potential of the FE-EPSC modeling framework is illustrated by carrying out a set of hat-shaped draw-bending simulations of the steel sheets. The evolution of geometry after hat-shaped draw-bending and springback is predicted and verified with experimental measurements for as-received DP 780. In doing so, the role of accounting for backstress is revealed as critical for the accurate prediction of the part geometry. The same process simulation involving a pre-strained sheet of DP 780 is compared with a corresponding experiment to reveal the role of strain hardening and residual stress on the subsequent part shape changes after the hat-shaped draw-bending test and springback. Finally, the same process simulations involving DP 590 and DP 1180 are performed to confirm the effect of strength on the geometrical shape changes of the sheets after springback.这项工作涉及使用多级模拟框架来预测金属板成形中的几何形状变化，该框架考虑了在单晶水平和微观结构演变上作用的变形机制的方向性。多层模型是单晶行为的弹塑性自洽(EPSC)均匀化，给出了每个有限元(FE)材料点的本构响应。然后在宏观层面上用连续体有限元得到了几何边值问题的数值解。首先，采用单单元模型拟合了590,780和1180双相(DP)钢的综合力学数据，建立了铁素体、马氏体和背应力的抗滑演化模型参数。接下来，通过对钢板进行一组帽形拉伸弯曲模拟，说明了FE-EPSC建模框架的潜力。对帽形拉伸弯曲回弹后的几何演化进行了预测，并用实测数据进行了验证。在这样做的过程中，计算背应力的作用被揭示为准确预测零件几何形状的关键。通过对DP 780预应变板料的工艺模拟与实验对比，揭示了应变硬化和残余应力对帽形拉伸弯曲试验和回弹后零件形状变化的影响。最后，对DP 590和DP 1180进行了相同的工艺模拟，以确定强度对回弹后板件几何形状变化的影响。Journal of the Mechanics and Physics of SolidsCharacterization of the interface fracture energy dependency on mixed mode fracture between rigid fiber and soft matrixP.-Y. Corbel, J. Jumeldoi:10.1016/j.jmps.2024.105745硬纤维与软基体混合模式断裂界面断裂能依赖性表征An enhanced version of the Rubber Cord Adhesion Inflation Test (RCAIT) has been designed to experimentally assess the internal pressure and cable tension applied to the specimen needed to propagate a crack along the matrix/reinforcement interface. To calculate the critical strain energy release rate, we develop a semi-analytical model describing the deformation of a hyperelastic tube under loading conditions that reflect the ones applied experimentally. A more comprehensive numerical model of the test is also proposed to investigate the influence of loading conditions on rubber deformation near the crack tip. Comparison of different experimental data sets with the theoretical/numerical data demonstrates that the new experimental setup allows for a reliable determination of the rubber/cord interface failure envelope under combined loading conditions.一种增强版的橡胶索黏附膨胀测试(RCAIT)被设计出来，通过实验来评估施加在试样上的内部压力和电缆张力，这些压力和电缆张力需要沿着基体/增强界面扩展裂缝。为了计算临界应变能释放率，我们建立了一个半解析模型来描述超弹性管在加载条件下的变形，该模型反映了实验应用的变形。本文还提出了一种更全面的试验数值模型，以研究加载条件对裂纹尖端附近橡胶变形的影响。不同实验数据集与理论/数值数据的比较表明，新的实验装置可以可靠地确定复合加载条件下橡胶/索界面的破坏包络线。International Journal of PlasticityMicrostructural causes and mechanisms of crack growth rate transition and fluctuation of additively manufactured titanium alloyXinyan Wang, Mengyu Cao, Yang Zhao, Jingjing He, Xuefei Guandoi:10.1016/j.ijplas.2024.104034 增材钛合金裂纹扩展速率转变和波动的显微组织原因及机理Wire and arc additive manufacturing (WAAM) enables rapid near-net-shape fabrications of large-size parts and in-situ remanufacturing in many industry sectors. A comprehensive understanding of the fatigue failure mechanism of WAAM titanium alloys is a prerequisite for their widespread use in critical structural components subject to fatigue load. Here, the fatigue crack growth behavior of WAAM TA15 material is investigated. Fatigue crack growth tests are performed using compact tension specimens sampled from different locations and with different crack orientations of the WAAM TA15 block. The fatigue crack growth rate (FCGR) data exhibit two governing rates separated by a transition stress intensity factor value, ΔKn, and the degrees of fluctuation of the FCGR data in the two regimes are notably different. A piecewise log-linear model is first proposed by incorporating the Heaviside step function and ΔKn into the classical Paris’ model, allowing for the transition ΔKn to be determined by the data. The potential causes of the transition ΔKn are phenomenologically inferred via fractography and surface roughness profiling results. The critical microstructure affecting the value of ΔKn is identified by relating the crack tip cyclic plastic zone size at ΔKn to the sizes of main microstructures. The cause of different degrees of fluctuations in the two regimes separated by ΔKn is inferred by examining the microstructures within the plastic zone. The microstructural mechanisms of the local FCGR reduction and fluctuation are further identified and explained.线弧增材制造（WAAM）可在许多工业领域实现大尺寸零件的快速近净成形制造和就地再制造。全面了解 WAAM 钛合金的疲劳失效机理是将其广泛用于承受疲劳载荷的关键结构部件的先决条件。本文研究了 WAAM TA15 材料的疲劳裂纹生长行为。疲劳裂纹生长测试使用从 WAAM TA15 块体的不同位置和不同裂纹方向取样的紧凑拉伸试样进行。疲劳裂纹生长速率（FCGR）数据显示出两种支配速率，以过渡应力强度因子值 ΔKn 为分界线，并且 FCGR 数据在两种状态下的波动程度明显不同。通过将 Heaviside 阶跃函数和 ΔKn 纳入经典的帕里斯模型，首先提出了一个片断对数线性模型，允许过渡 ΔKn 由数据决定。过渡 ΔKn 的潜在原因可通过断裂图和表面粗糙度剖面测量结果进行现象推断。通过将 ΔKn 处的裂纹尖端循环塑性区尺寸与主要微观结构尺寸联系起来，确定了影响 ΔKn 值的临界微观结构。通过研究塑性区内的微观结构，可以推断出以 ΔKn 为分界的两种状态下不同波动程度的原因。进一步确定并解释了 FCGR 局部降低和波动的微观结构机制。Thin-Walled StructuresEnergy absorption performance of woven metallic lattices with orthogonal spiral wires under quasi-static compressionFang Wu, Congcong Lin, Shaoxiang Ge, Xin Xuedoi:10.1016/j.tws.2024.112121 准静态压缩下正交螺旋丝编织金属晶格的吸能性能Woven metallic lattice (WML) structures are gaining attention for their beneficial mechanical properties, such as low weight and special energy absorption capability. They hold potential for diverse applications, including energy absorption components in aerospace. Drawing inspiration from the traditional double-arrow lattice, this study proposes a novel WML design featuring multi-plateau stresses. The deformation behavior of this structure under compression was investigated using finite element analysis and experimental methods. Three gradient structures defined by the different layer arrangements along load direction associated with specific structure variables, namely positive gradient (PG), negative gradient (NG), and hybrid gradient (HG), were introduced, along with an examination of their mechanical properties. The study explored the influence of key parameters of the cell structure on compression characteristics. Findings suggest that enhancing cell vertex angle and wire diameter can improve energy absorption, while the opposite holds true for cell base angle. Among the gradient structures analyzed, the PG WML structure demonstrates optimal energy absorption due to its dual-plateau stress characteristics. The NG WML structure is noteworthy for its uniform lattice deformation during initial compression stages, which is crucial for precision engineering with subtle deformation control strategies. Lastly, the deformation pattern of the HG WML structure during compression progresses from low to high strength.编织金属晶格(WML)结构以其较轻的重量和特殊的吸能能力等良好的力学性能而受到人们的关注。它们具有多种应用潜力，包括航空航天中的能量吸收组件。从传统的双箭头晶格中汲取灵感，本研究提出了一种具有多平台应力的新型WML设计。采用有限元分析和试验相结合的方法研究了该结构在压缩作用下的变形行为。介绍了三种梯度结构，即正梯度(PG)、负梯度(NG)和混合梯度(HG)，并对它们的力学性能进行了测试。研究了胞体结构关键参数对压缩特性的影响。研究结果表明，增加细胞顶角和丝径可以提高能量吸收，而增加细胞底角则相反。在所分析的梯度结构中，PG - WML结构由于其双平台应力特征而具有最佳的能量吸收。NG WML结构在初始压缩阶段具有均匀的晶格变形，这对于具有精细变形控制策略的精密工程至关重要。最后，HG - WML结构在压缩过程中的变形模式由低强度向高强度发展。Chaotic vibration of a curved CNT conveying magnetic fluid in the thermo-magnetic field considering the surface effectsQiyu Wang, Zilin Zhangdoi:10.1016/j.tws.2024.112047考虑表面效应的弯曲碳纳米管输送磁流体在热磁场中的混沌振动The nonlinear chaotic vibration of curved single-walled carbon nanotube (CSWCNT) conveying magnetic fluid is studied based on the nonlocal Euler-Bernoulli beam model. The governing equation of CSWCNT is presented considering the axial thermo-magnetic load and the surface effect. By employing the Galerkin decomposition approximation method along with the admissible beam shape function satisfying the cantilevered beam boundary conditions, the nonlinear partial differential equation of the system is reduced to a nonlinear ordinary differential equation and numeric integration procedures are used to solve it. By considering the non-dimensional damping, cubic and quadratic terms, and amplitude of external force as controlling parameters, the bifurcation diagram and the largest Lyapunov exponent are employed to distinguish the chaotic, periodic, and quasi-periodic critical parameters of the curved CNT dynamics and validate the predicted results. Also, the phase plane and Poincare map for these critical parameters are provided. The results show that decreasing values of damping coefficient and quadratic term leads to quasi-periodic or chaotic motion, while system has periodic behaviour for smaller values of the external force and nonlinear cubic term. Also, magnetic field intensity and length of the CSWCNT help preventing the chaotic motion. Furthermore, adverse effects of higher values of temperature change, flow velocity and its correction factor are seen based on the obtained results.基于非局部欧拉-伯努利梁模型，研究了弯曲单壁碳纳米管输送磁性流体的非线性混沌振动。提出了考虑轴向热磁载荷和表面效应的碳纳米管控制方程。采用伽辽金分解近似法，结合满足悬臂梁边界条件的容许梁形函数，将系统的非线性偏微分方程化为非线性常微分方程，并采用数值积分方法进行求解。通过考虑无量纲阻尼、三次项和二次项以及外力幅值作为控制参数，利用分岔图和最大Lyapunov指数区分了弯曲碳纳米管动力学的混沌、周期和准周期临界参数，并验证了预测结果。并给出了这些关键参数的相平面和庞加莱图。结果表明，阻尼系数和二次项的减小会导致系统的准周期或混沌运动，而外力和非线性三次项的减小则会导致系统的周期运动。此外，cswcnts的磁场强度和长度有助于防止混沌运动。此外，根据所得结果，还可以看出温度变化、流速及其校正因子的较大值所产生的不利影响。来源：复合材料力学仿真Composites FEM
