【新文速递】2024年1月29日固体力学SCI期刊最新文章

 

今日更新：International Journal of Solids and Structures 3 篇，Mechanics of Materials 1 篇，International Journal of Plasticity 1 篇，Thin-Walled Structures 1 篇

International Journal of Solids and Structures

Crushing of a closed-cell polymeric foam under triaxial loading

Joe W. Skeens, Stelios Kyriakides

doi:10.1016/j.ijsolstr.2024.112686

闭孔聚合物泡沫在三轴载荷下的破碎

The crushing behavior of a polymeric closed-cell foam with a relative density of 0.077 under combined axial compression and external pressure is investigated experimentally. The foam has a nearly monodisperse polyhedral microstructure with mean cell size and wall thickness of 0.50 mm and 0.0348 mm respectively. A custom triaxial apparatus is used to compress cylindrical specimens at different levels of external pressure. A typical axial stress-displacement response exhibits a stiff elastic branch that terminates into a maximum beyond which deformation localizes into a horizontal axisymmetric band of crushed cells. The band then propagates axially with the stress remaining essentially constant. Both the initial stress maximum and the plateau stress decrease linearly as the pressure increases. Micro-computed tomography imaging of the microstructure of a specimen crushed axially at zero pressure confirmed that during the stress plateau, a highly crushed zone of cells with an average strain of about 50 % coexists with zones of essentially undeformed cells. Above a critical pressure, the mode of instability switches to predominantly lateral contraction that evolves into a neck. This is also the mechanism of failure under pure pressure. The localized crushing behavior observed is similar to that of low-density open-cell foams and the results should inform and guide further development of homogenized models for this class of materials.

实验研究了相对密度为0.077的聚合物闭孔泡沫塑料在轴压和外压联合作用下的破碎行为。泡沫具有接近单分散的多面体微观结构，平均孔大小和壁厚分别为0.50 mm和0.0348 mm。一个定制的三轴装置被用来压缩圆柱形试样在不同水平的外部压力。典型的轴向应力-位移响应表现为一个刚性弹性分支，该分支终止于一个最大值，超过该最大值，变形局部定位为破碎细胞的水平轴对称带。然后带沿轴向传播，应力基本保持恒定。初始应力最大值和平台应力均随压力的增加而线性减小。在零压力下轴向破碎的试样微观结构的显微计算机断层成像证实，在应力平台期间，平均应变约为50% %的细胞高度破碎区与基本未变形的细胞区共存。超过临界压力，不稳定模式切换为主要的侧缩，演变成颈部。这也是纯压力下的失效机制。观察到的局部破碎行为与低密度开孔泡沫相似，结果应该为这类材料的均匀化模型的进一步发展提供信息和指导。

Indentation responses of piezoelectric semiconductors

Shijing Gao, Zeran Zhang, Guoquan Nie, Jinxi Liu, Weiqiu Chen

doi:10.1016/j.ijsolstr.2024.112682

压电半导体的压痕响应

In this paper, the indentation responses of a piezoelectric semiconductor (PSC) half-space by an insulating and rigid spherical indenter are investigated. It is assumed that the contact area between the indenter and the PSC is frictionless. Based on the Hankel integral transformation, the considered indentation problem is reduced to a pair of dual integral equations. Due to the complexity of the coupled governing differential equations, the explicit closed-form expressions for the PSC indentation responses cannot be derived like the piezoelectric counterparts. Therefore, the dual integral equations are converted into the Fredholm integral equation of the second kind, which is numerically solved to determine the concerned responses. These responses include the relationships of the indentation force, the electric potential and the change of carrier concentration with the indentation depth. The numerical results show that the semiconducting property has a significant influence on the indentation characteristics. In addition, the three-dimensional finite element simulations are carried out to validate the theoretical results computed by the singular integral equation method. It turns out that the two results are well consistent. The distributions of the stress and electric potential near the contact area are simulated by finite element method to reveal the effect of the steady carrier concentration. The obtained findings are useful for understanding the interaction between piezoelectricity and semiconducting property.

研究了绝缘刚性球形压头对压电半导体半空间的压痕响应。假设压头和PSC之间的接触区域是无摩擦的。基于汉克尔积分变换，将所考虑的压痕问题简化为一对对偶积分方程。由于耦合控制微分方程的复杂性，PSC压痕响应的显式封闭表达式不能像压电压痕响应那样导出。因此，将对偶积分方程转化为第二类Fredholm积分方程，并对其进行数值求解，以确定相关响应。这些响应包括压痕力、电势和载流子浓度随压痕深度的变化关系。数值结果表明，半导体特性对压痕特性有显著影响。此外，还进行了三维有限元仿真，验证了奇异积分方程法计算的理论结果。结果表明，这两个结果是一致的。利用有限元方法模拟了接触区附近的应力和电势分布，揭示了稳定载流子浓度的影响。所得结果有助于理解压电性和半导体性之间的相互作用。

Micro-mechanical modeling of semi-crystalline polymers: A review

Mohsen Mirkhalaf, Rahele Vadizadeh

doi:10.1016/j.ijsolstr.2024.112691

半结晶聚合物的微观力学建模:综述

Highly heterogeneous and complex micro-structure of semi-crystalline polymers challenges accurate prediction of their macroscopic behavior. Micro-mechanical models establish a relationship between the micro-structure and macroscopic properties (structure–property relationship), and are able of predicting not only the macro-scale behavior, but also the evolution of the micro-structure. Therefore, micro-mechanical modeling can be used as a virtual experiment to predict the overall behavior of semi-crystalline polymers, where the effect of any single micro-structural parameter can be investigated. These parameters include morphological information about distribution of amorphous and crystalline phases, and constitutive properties of both phases. In this review paper, two main categories of micro-mechanical models, including mean-field and full-field models, are reviewed in detail. Three different groups of mean-field models, namely single-phase, two-phase, and three-phase models are discussed. Besides, the morphology of semi-crystalline polymers together with different deformation mechanisms, involved in different deformation regimes, are illustrated.

半晶聚合物的高度非均相和复杂的微观结构对其宏观行为的准确预测提出了挑战。微观力学模型建立了微观结构和宏观性能之间的关系(结构-性能关系)，不仅可以预测宏观尺度的行为，而且可以预测微观结构的演变。因此，微力学建模可以作为一种虚拟实验来预测半结晶聚合物的整体行为，其中可以研究任何单一微观结构参数的影响。这些参数包括有关非晶相和结晶相分布的形态学信息，以及两相的本构性质。本文详细介绍了两类主要的微力学模型，即平均场模型和全场模型。讨论了三组不同的平均场模型，即单相、两相和三相模型。此外，还说明了半晶聚合物的形态以及不同变形机制，涉及不同的变形制度。

Mechanics of Materials

A numerical investigation of slip evolution of shear crack faces oriented arbitrarily under non-steady contact

Qingbing Dong, Xingsheng Zhou, Zhuang Chen, Zurong Wu, Qing Luo

doi:10.1016/j.mechmat.2024.104936

非稳态接触下任意取向剪切裂纹面滑移演化的数值研究

Shear loading is induced on the surfaces of a crack that is aligned at an arbitrary angle in relation to the direction of compressive loading. Contact faces may experience relative slip if the tangential stress along the crack surpasses the friction threshold determined by the product of normal stress and coefficient of friction. In contrast, other regions remain in stick contact with a lower level of shear stress than the friction limit. The resulting slip motion generates additional stress, potentially driving already slipped points further. The overall motion of crack faces is constrained by the bonding tip. Therefore, the stick-slip conditions can not possibly be determined in advance, and the slip evolution should be investigated further for the analysis of friction fracture, especially in cases of non-steady contact, such as rolling or loading-unloading contact. This study explores the loading history effect on stick-slip contact of arbitrarily oriented shear cracks. The crack is assumed as distributed glide dislocations based on the discrete dislocation technique. The loading is incrementally applied until the targeted amplitude with the slip displacement gradually accumulating during the contact cycle. The initial contact position is successively changed during a rolling contact process, while the loading amplitude is decreased when followed by an unloading process. The factors that influence the stick-slip patterns of crack faces, including loading history, crack orientation and coefficient of friction, are investigated. The developed methods are expected to provide insight into the study of contact mechanics, and the conclusions can be used to predict the frictional fracture under rolling or loading-unloading contact.

剪切荷载是在与压缩荷载方向成任意角度排列的裂缝表面上产生的。如果沿裂纹方向的切向应力超过由正应力和摩擦系数乘积确定的摩擦阈值，接触面就会发生相对滑移。相反，其他区域保持粘接触，剪应力水平低于摩擦极限。由此产生的滑动运动产生额外的应力，可能会进一步推动已经滑动的点。裂纹面的整体运动受到键合尖端的约束。因此，不可能提前确定粘滑条件，在分析摩擦断裂时，特别是在滚动或加载-卸载接触等非稳态接触情况下，需要进一步研究滑移演化。研究了加载历史对任意取向剪切裂纹粘滑接触的影响。基于离散位错技术，假定裂纹为分布滑动位错。在接触周期中，加载是递增的，直到滑动位移逐渐累积到目标振幅为止。在滚动接触过程中，初始接触位置是连续变化的，而在随后的卸载过程中，加载幅度减小。研究了影响裂纹面粘滑形态的因素，包括加载历史、裂纹方向和摩擦系数。所开发的方法有望为接触力学研究提供新的见解，所得结论可用于预测滚动或加载-卸载接触下的摩擦断裂。

International Journal of Plasticity

Multi-scale defects activation in Gd18.33Tb18.33Dy18.34Co17.5Al27.5 high-entropy metallic glasses revealed by nanoindentation

W. Li, X.F. Zuo, R. Liu, C.M. Pang, F. Jin, W.W. Zhu, C.C. Yuan

doi:10.1016/j.ijplas.2024.103893

基于纳米压痕的Gd18.33Tb18.33Dy18.34Co17.5Al27.5高熵金属玻璃多尺度缺陷激活研究

Defect activation is of fundamental importance for plastic deformation. However, its mechanism is not yet fully disclosed in metallic glasses (MGs), especially for those with high configurational entropy that demonstrate outstanding physical or chemical properties, more particularly, mechanical characteristics. In this work, multi-scale defects activation of three rare-earth-based MGs with low-, medium-, and high-entropy (LE, ME, and HE) were systematically investigated by tracing their room-temperature nanoindentation behaviors. Among the three alloys, the Gd18.33Tb18.33Dy18.34Co17.5Al27.5 HE MG exhibits the highest hardness and elastic modulus. Unlike the poor deformability of the LE MG, the pronounced nanoindentation displacements under a constant load were observed in HE and ME MGs, especially at high loading rates. To reveal the plastic origin of HE MGs, a generalized physical model (so-called Maxwell-Voigt) was utilized to describe the nanoindentation deformation on the mesoscale. The characteristic relaxation spectra show that the activated defects with longer relaxation time are mainly responsible for the large nanoindentation displacement at high strain rates. Based on the cooperative shearing model, the shear transformation zone (STZ) volume is determined to be around 0.45-2.98 nm3. The statistics of the short-range order indicate that the HE MG possesses a highly ordered configuration, which results in the difficulty of STZ activation for requiring overcoming a high energy barrier, and a high elastic modulus of the HE MG. Our work might provide insight into the underlying plastic deformation mechanism of HE MGs from the characteristics of activated defects as well as their entropy effect.

缺陷激活是塑性变形的基础。然而，其机制在金属玻璃(mg)中尚未完全揭示，特别是对于那些具有高构型熵的金属玻璃，它们表现出突出的物理或化学性质，特别是机械特性。在这项工作中，通过跟踪其室温纳米压痕行为，系统地研究了三种具有低、中、高熵(LE、ME和HE)的稀土基mg的多尺度缺陷激活。三种合金中，Gd18.33Tb18.33Dy18.34Co17.5Al27.5 HE MG的硬度和弹性模量最高。与LE MG的变形能力差不同，HE和ME MG在恒定载荷下观察到明显的纳米压痕位移，特别是在高加载速率下。为了揭示高能微球的塑性成因，利用广义物理模型(Maxwell-Voigt)在中尺度上描述了纳米压痕变形。特征弛豫谱表明，在高应变速率下，具有较长弛豫时间的激活缺陷是造成较大纳米压痕位移的主要原因。根据协同剪切模型，确定剪切转变区(STZ)体积约为0.45-2.98 nm3。近程阶数统计结果表明，HE MG具有高度有序的结构，这导致了需要克服高能量势垒而难以激活STZ，并且HE MG具有较高的弹性模量。我们的工作可能会从激活缺陷的特征及其熵效应中深入了解HE mg的潜在塑性变形机制。

Thin-Walled Structures

A strain gradient quadrature element for geometrically exact beam with torsion warping

Jiahao Cheng, Run Zhang, Xiang Ou, Xiaohu Yao

doi:10.1016/j.tws.2024.111635

具有扭转翘曲的几何精确梁的应变梯度正交单元

Based on the weak form quadrature element method, this paper proposes a geometrically exact strain gradient beam formulation incorporating torsion warping effects. This formulation provides a computationally efficient numerical scheme for analyzing size dependent arbitrarily cross-sectional beams undergoing large displacements and rotations. By accommodating all high order strain and strain gradient terms in the formulation, the Wagner effects that crucial to the model's accuracy are taken into account. The warping functions determined by cross-sectional governing equations involving strain gradients are obtained using a C1 quadrilateral quadrature element procedure. Five numerical tests are presented to demonstrate the validity and accuracy of the proposed formulation, while investigating the influences of size effects and Wagner effects on nonlinear behaviors of beam structures.

基于弱形式正交单元法，提出了一种考虑扭转翘曲效应的几何精确应变梯度梁公式。该公式为分析受大位移和大旋转作用的任意截面梁的尺寸相关问题提供了一种计算效率高的数值格式。通过在公式中容纳所有高阶应变和应变梯度项，考虑到对模型精度至关重要的瓦格纳效应。采用C1四边形正交单元法得到了包含应变梯度的截面控制方程所确定的变形函数。通过五个数值试验验证了所提公式的有效性和准确性，同时研究了尺寸效应和Wagner效应对梁结构非线性行为的影响。