【新文速递】2023年12月29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，International Journal of Plasticity 1 篇，Thin-Walled Structures 1 篇

International Journal of Solids and Structures

A limit analysis-based CASS approach for the in-plane seismic capacity of masonry façades

Antonino Iannuzzo, Andrea Montanino

doi:10.1016/j.ijsolstr.2023.112633

基于极限分析的砌体外墙平面抗震能力 CASS 方法

The present paper proposes a new methodology for the load-bearing capacity analysis of 2D masonry constructions by extending and reformulating the Continuous Airy-based for Stress Singularities (CASS) method, with a particular focus on the incorporation of volume forces, crucial to solve mechanical problems involving masonry constructions accurately. The masonry material is modelled using a Normal, Rigid, No-Tension (NRNT) model, largely adopted by the scientific community as material parameters, often unknowable, are not needed. The load-bearing capacity problem is derived from an energy-based formulation and framed as a classic limit analysis approach, allowing for the direct determination of the maximum incremental load that a masonry structure can withstand, along with the corresponding internal stress pattern. The structural domain is discretised with a simple finite element mesh, and the Airy stress potential is adopted to enforce the internal equilibrium directly. The boundary value problem is then solved as second-order cone programming (SOCP). The CASS method is shown to offer modelling and computational advantages. Indeed, it accurately describes the mechanical response, including the ability to capture singular stress fields typically exhibited by masonry structures, particularly where cracks appear. The adoption of the Airy potential allows for a reduction in the number of explicit constraints from the problem. Moreover, the formulation of the boundary value problem as a SOCP ensures the existence of a unique load multiplier while offering computationally fast solutions even for large problems. Several numerical examples are presented to demonstrate the CASS potential. Specifically, the ability to capture singular stress patterns diagonally crossing the finite elements showcases the CASS mesh independence, providing a straightforward approach to modelling complex geometries and loading conditions.

本文通过扩展和重新制定应力奇异性连续空气法（CASS），提出了一种用于二维砌体结构承载力分析的新方法，尤其侧重于纳入体积力，这对于准确解决涉及砌体结构的力学问题至关重要。砌体材料使用法向、刚性、无张力（NRNT）模型建模，该模型已被科学界广泛采用，因为不需要通常不可知的材料参数。承载能力问题源自基于能量的表述，采用经典的极限分析方法，可直接确定砌体结构可承受的最大增量荷载以及相应的内应力模式。结构域采用简单的有限元网格离散化，并采用艾里应力势能直接强制实现内部平衡。然后以二阶锥体编程（SOCP）的方式求解边界值问题。CASS 方法具有建模和计算优势。事实上，它能准确描述机械响应，包括捕捉砌体结构通常表现出的奇异应力场的能力，尤其是在出现裂缝的地方。采用 Airy 势能可以减少问题中显式约束的数量。此外，将边界值问题表述为 SOCP 可确保存在唯一的荷载乘数，同时即使对于大型问题也能提供计算速度极快的解决方案。本文列举了几个数值示例来证明 CASS 的潜力。具体来说，CASS 能够捕捉对角线穿过有限元的奇异应力模式，从而展示了 CASS 的网格独立性，为复杂几何形状和加载条件的建模提供了一种直接的方法。

International Journal of Plasticity

Contributions of multimodal microstructure in the deformation behavior of extruded Mg alloys containing LPSO phase

Koji Hagihara, Tsuyoshi Mayama, Michiaki Yamasaki, Stefanus Harjo, Toko Tokunaga, Kazuki Yamamoto, Mika Sugita, Kairi Aoyama, Wu Gong, Soya Nishimoto

doi:10.1016/j.ijplas.2023.103865

多模态微观结构对含有 LPSO 相的挤压镁合金变形行为的影响

The unique control mechanisms of the plastic deformation of two-phase extruded alloy composed of Mg and long-period stacking ordered (LPSO) phase were clarified by comparison with those of other Mg solid-solution alloys, focusing on the question “why do the Mg/LPSO two-phase alloys exhibit both large elongation and high strength?”. The stress-strain curves for each grain in the alloys could be imaginary estimated using neutron diffraction analysis during the tensile test. The results demonstrate that the deformation behaviors of the worked and recrystallized grains are significantly different in all the Mg-extruded alloys owing to the strong plastic anisotropy in Mg with hexagonal close-packed (hcp) structure. Therefore, the deformation behavior is controlled by a composite-like deformation mechanism, even in single-phase Mg solid-solution alloys. In Mg-Y-Zn ternary alloys, the recrystallized Mg grains exhibited significant lattice softening at the initial stage of yielding owing to the escape of basal dislocations from the Y/Zn dragging atmosphere. However, the worked grains acted as strengthening components. In the Mg/LPSO two-phase alloy, the composite-like deformation behavior was enhanced, and the LPSO phase significantly contributed to the strengthening of the alloy. Moreover, it was hypothesized that the LPSO phase contributes not only to the alloy's strength but also to its elongation by increasing the work-hardening rate. We proposed the new concept “Anisotropic Mechanical property-Induced Ductilization (AMID)” by multimodal microstructure, to explain this phenomenon. As the physical origin for inducing AMID, kink-band strengthening in the LPSO phase is believed to be one of the reasons for the increase in the work-hardening rate of the extruded LPSO-phase grains in the Mg/LPSO two-phase alloy, resulting in an improved ductility.

通过与其他镁固溶合金的比较，阐明了由镁和长周期堆积有序相（LPSO）组成的两相挤压合金塑性变形的独特控制机制，重点研究了 "为什么镁/LPSO 两相合金同时表现出大伸长率和高强度？合金中每个晶粒的应力-应变曲线可在拉伸试验过程中通过中子衍射分析进行假想估算。结果表明，由于具有六方紧密堆积（hcp）结构的镁具有很强的塑性各向异性，所有镁挤压合金的加工晶粒和再结晶晶粒的变形行为都有很大不同。因此，即使在单相镁固溶合金中，变形行为也受复合变形机制的控制。在 Mg-Y-Zn 三元合金中，由于基底位错从 Y/Zn 拖曳气氛中逃逸，再结晶的镁晶粒在屈服初期表现出明显的晶格软化。然而，加工过的晶粒起到了强化作用。在 Mg/LPSO 两相合金中，复合变形行为得到了增强，LPSO 相对合金的强化做出了显著贡献。此外，我们还假设 LPSO 相不仅提高了合金的强度，还通过增加加工硬化率提高了合金的伸长率。我们通过多模态微结构提出了 "各向异性机械性能诱导延展（AMID）"这一新概念来解释这一现象。作为诱导 AMID 的物理根源，LPSO 相中的扭结带强化被认为是 Mg/LPSO 两相合金中挤压 LPSO 相晶粒做功硬化率增加并导致延展性提高的原因之一。

Thin-Walled Structures

Review of sandwich structures under impact loadings: experimental, numerical and theoretical analysis

Haoyuan Guo, Hui Yuan, Jianxun Zhang, Dong Ruan

doi:10.1016/j.tws.2023.111541

冲击载荷下的夹层结构回顾：实验、数值和理论分析

With the swift advancement of aerospace, shipbuilding and engineering, the significance of sandwich structures with cellular cores is becoming increasingly prominent due to their multi-functional and lightweight attributes. In addition, impact loadings are very common in the engineering practice and may potentially cause significant adverse impact on products and equipment. Emerging manufacturing technologies facilitate the fabrication of high quality sandwich plates with improved stiffness and strength to withstand impact loadings. Therefore, extensive investigations have been conducted on sandwich structures under various impact loadings. This paper provides a comprehensive review of the valuable experimental, analytical, and numerical investigations conducted on the dynamic response of sandwich structures spanning several decades. The paper aims to reveal the underlying deformation mechanisms governing the response of sandwich structures subject to impact loadings. The focus is primarily on popular sandwich structures, such as beams, plates, and curved plates, under low-velocity impact, blast loading, and ballistic impact. Various core configurations of sandwich structures are explored, including metal and polymer foams, uniform and graded honeycombs, auxetic honeycombs, foam inserted honeycombs, corrugated core and foam inserted corrugated core, truss core, undrilled and drilled I-core, chiral core, star-shaped core and Y-shaped core. Current challenges and recommendations for future work have also been articulated.

随着航空航天、造船和工程技术的飞速发展，带蜂窝芯材的夹层结构因其多功能和轻质的特性而变得越来越重要。此外，冲击载荷在工程实践中非常常见，有可能对产品和设备造成重大不利影响。新出现的制造技术有助于制造刚度和强度更高的高质量夹层板，以承受冲击载荷。因此，人们对各种冲击载荷下的夹层结构进行了广泛的研究。本文全面回顾了数十年来针对夹层结构动态响应所进行的宝贵实验、分析和数值研究。本文旨在揭示支配夹层结构在冲击载荷下响应的基本变形机制。重点主要放在低速冲击、爆炸荷载和弹道冲击下的常用夹层结构，如梁、板和曲面板。研究探讨了夹层结构的各种芯材配置，包括金属和聚合物泡沫、均匀和分级蜂窝、辅助蜂窝、泡沫插入蜂窝、波纹芯材和泡沫插入波纹芯材、桁架芯材、未钻孔和钻孔工字芯材、手性芯材、星形芯材和 Y 形芯材。此外，还阐述了当前面临的挑战和对未来工作的建议。

来源：复合材料力学仿真Composites FEM

【新文速递】2024年1月1日固体力学SCI期刊最新文章

今日更新：Mechanics of Materials 1 篇，International Journal of Plasticity 2 篇，Thin-Walled Structures 1 篇Mechanics of MaterialsEffect of the sonic shock wave on void evolution in materials under irradiationNing Zhou, YinBo Zhu, HengAn Wudoi:10.1016/j.mechmat.2023.104907 声波冲击波对辐照下材料空隙演变的影响Understanding the void-cascade interaction is of great importance for clarifying the irradiation damage as a major challenge in nuclear industry, since it typically causes void annihilation or shrinkage, which greatly affects the swelling of irradiated materials. But the current understanding of it is extremely limited due to the neglect of the sonic shock wave. Herein, we take γ-U as the representative model due to the emergence of a violent sonic shock wave there. Molecular dynamics simulations are performed to explore the underlying mechanism of the sonic shock wave interacting with voids. It is firstly revealed that the sonic shock wave is essentially focusons along <111> crystal orientation family, attributed to the highest energy transfer efficiency along <111> in γ-U. These focusons can cause void annihilation or shrinkage via sliding, while thermal spikes only cause annihilation by covering voids. Combining these two factors, we propose a model to qualitatively epitomize the void-cascade interaction, in which the influence scope exhibits an intriguing anisotropic feature, overturning a long-accepted view that the void-cascade interaction is isotropic. This model is further generalized to other nuclear materials owing to the similar mechanism of the sonic shock wave. Moreover, we find distinct size effect of voids on void-cascade interaction. Thermal spikes hardly affect voids that are too large to be covered, while the sonic shock wave also causes visible shrinkage in large voids. The present work proves that the sonic shock wave has a non-negligible effect on void evolution, improving the fundamental understanding of void-cascade interaction in irradiated materials.空隙-级联相互作用通常会导致空隙湮灭或收缩，从而极大地影响辐照材料的膨胀，因此了解空隙-级联相互作用对于澄清辐照损伤这一核工业领域的重大挑战具有重要意义。但由于忽视了声波冲击波，目前对它的认识极为有限。在此，我们以γ-U 为代表模型，因为那里出现了剧烈的声波冲击波。通过分子动力学模拟来探索声波冲击波与空隙相互作用的内在机理。研究首先揭示了声波冲击波本质上是沿 <111> 晶向系列的焦子，这归因于在 γ-U 中沿 <111> 晶向的能量传递效率最高。这些聚焦子可以通过滑动造成空隙湮灭或收缩，而热尖峰只能通过覆盖空隙造成湮灭。结合这两个因素，我们提出了一个模型来定性地表征空隙-级联相互作用，其中的影响范围呈现出令人感兴趣的各向异性特征，推翻了长期以来公认的空隙-级联相互作用各向同性的观点。由于音速冲击波的机制类似，这一模型还可进一步推广到其他核材料。此外，我们还发现空隙的大小对空隙-级联相互作用有明显的影响。热尖峰几乎不会影响大到无法覆盖的空隙，而声波冲击波也会导致大空隙的明显收缩。本研究证明了声波冲击波对空隙演变具有不可忽视的影响，从而提高了对辐照材料中空隙-级联相互作用的基本认识。International Journal of PlasticityAchieving exceptional work-hardening capability of additively-manufactured multiphase Fe-Mn alloys via multiple deformation mechanismsPeifeng Liu, Qinyuan Huang, Quan Shan, Zengbao Jiao, Qingge Wang, Yang Ma, Runhua Zhou, Ian Baker, Hong Wudoi:10.1016/j.ijplas.2023.103871 通过多种变形机制实现快速成型多相铁-锰合金的超强加工硬化能力Laser-powder-bed-fusion (LPBF) fabricated Fe-Mn biodegradable alloys provide an attractive prospect for orthopedic applications due to their good tensile strength and high degradation rate. Nevertheless, the ε-martensite and heterogeneous microstructures produced by the LPBF processing often lead to premature failure of alloys. Herein, we report a LPBFed multiphase Fe-18Mn alloy (γ-austenite, ε-martensite, and α-ferrite) fabricated from pre-alloyed powders. After annealing at 650 °C, the alloy with a uniform microstructure displays a high 1 GPa tensile strength, a good fracture elongation of 16 %, and an extremely high work-hardening rate of 8500 MPa. The work-hardening rate is higher than that reported in most Fe-Mn steels and Fe-based high entropy alloys. The grain size of a few hundred nanometers provided the excess Gibbs free energy, resulting in an increase in the stacking fault energy (SFE) to 23.9 mJ/m2. The multiple deformation mechanisms, i.e., SFs, the martensitic transformation (γ → ε → α') and nano-deformation twins (DTs), were sequentially activated. We elucidate such unique work-hardening capability, originating from the interaction between the DTs, SFs and transformed martensite. Besides a high-density of dislocations were accumulated between parallel planar defects, the cooperative deformation of the soft and hard phases provided continuous hardening. Our findings highlight the exceptional work-hardening capability of additively-manufactured Fe-Mn alloys achieved by a multiphase material exhibiting multiple deformation mechanisms. The work also provides a straightforward approach for the development of stable-implanted Fe-based bone substitutes.激光粉末床熔融（LPBF）制造的铁锰生物可降解合金具有良好的抗拉强度和较高的降解率，为矫形外科应用提供了诱人的前景。然而，LPBF加工过程中产生的ε-马氏体和异质微结构往往会导致合金过早失效。在此，我们报告了一种由预合金化粉末制成的 LPBFed 多相铁-18Mn 合金（γ-奥氏体、ε-马氏体和 α-铁素体）。在 650 °C 退火后，具有均匀微观结构的合金显示出较高的 1 GPa 抗拉强度、16 % 的良好断裂伸长率和 8500 MPa 的极高加工硬化率。该加工硬化率高于大多数铁锰钢和铁基高熵合金的加工硬化率。几百纳米的晶粒尺寸提供了过剩的吉布斯自由能，导致堆叠断层能（SFE）增加到 23.9 mJ/m2。多种变形机制，即 SFs、马氏体转变（γ → ε → α'）和纳米变形孪晶（DTs）依次被激活。我们阐明了这种独特的加工硬化能力，它源于 DTs、SFs 和转化马氏体之间的相互作用。除了在平行平面缺陷之间积累了高密度位错之外，软硬相的协同变形还提供了持续硬化。我们的研究结果凸显了加成法制造的铁锰合金通过表现出多种变形机制的多相材料实现的卓越加工硬化能力。这项研究还为开发稳定的植入式铁基骨替代物提供了一种直接的方法。Distinct avalanche dynamics detected in metallic glasses with high energy state revealing the crack-like shear banding mechanismKai Tao, Fucheng Li, Yanhui Liu, Eloi Pineda, Kaikai Song, Jichao Qiaodoi:10.1016/j.ijplas.2023.103873在金属玻璃中探测到的高能态雪崩动力学揭示了类似裂纹的剪切带机制When a sufficiently high stress is applied to a metallic glass, causing plastic deformation, the material undergoes structural reconfiguration through dissipative slip avalanche events that release local stresses. By utilizing isothermal annealing and cold rolling techniques to tune the energy levels of metallic glasses, it has been observed that structural rejuvenation is accompanied by structural relaxation, as evidenced by distinct changes in avalanche dynamics. We present detailed statistics of the avalanche dynamics during shear band formation in energy-tuned metallic glasses, ranging from structurally relaxed to rejuvenated states. By analyzing shear band characteristics and examining scaling exponents, avalanche durations, and stress relaxation rates, we can establish a connection between the local activation of shear transformation zones and the formation of macroscopic shear bands. The statistics of avalanche duration indicate that an increase in soft zones within metallic glasses can alleviate stress release and stabilize plastic flow, as evidenced by the characteristics of shear bands. We attribute the significant transition of serrated flow, observed at different energy levels (i.e., as-cast, relaxed, and rejuvenated states) to the variations in nucleation and multiplication of shear bands that originate from local weak spots. Analysis of the distinct avalanche dynamics suggests that in lower energy level metallic glasses, the nucleation and propagation of shear bands exhibit localized crack-like behavior, while in higher energy level metallic glasses, they display diffused crack-like characteristics. Indeed, our results strongly support that the decreased avalanches observed in the high energy level metallic glasses originate from the nucleation of numerous small shear bands, which directly compete with the propagation of the main local shear band. These findings deepen our fundamental understanding of the relationship between the microscopic mechanism of slip avalanche dynamics and shear banding, providing a pathway to control the plasticity of metallic glasses.当对金属玻璃施加足够大的应力导致塑性变形时，材料会通过释放局部应力的耗散滑移雪崩事件进行结构重构。通过利用等温退火和冷轧技术调节金属玻璃的能级，我们观察到结构年轻化伴随着结构松弛，雪崩动力学的明显变化就是证明。我们介绍了能量调谐金属玻璃剪切带形成过程中雪崩动力学的详细统计数据，包括从结构松弛状态到年轻化状态。通过分析剪切带特征并研究缩放指数、雪崩持续时间和应力松弛率，我们可以建立剪切转换区局部激活与宏观剪切带形成之间的联系。雪崩持续时间的统计结果表明，金属玻璃内部软区的增加可以缓解应力释放并稳定塑性流动，剪切带的特征也证明了这一点。我们认为，在不同能级（即铸造态、松弛态和恢复态）下观察到的锯齿流的显著转变是由于局部薄弱点产生的剪切带的成核和增殖变化造成的。对不同雪崩动力学的分析表明，在低能级金属玻璃中，剪切带的成核和传播表现出局部裂纹状行为，而在高能级金属玻璃中，则表现出扩散裂纹状特征。事实上，我们的研究结果有力地证明，在高能级金属玻璃中观察到的雪崩现象的减少源于无数小剪切带的成核，这些剪切带与主要局部剪切带的传播直接竞争。这些发现加深了我们对滑动雪崩动力学微观机制与剪切带之间关系的基本理解，为控制金属玻璃的塑性提供了一条途径。Thin-Walled StructuresWave propagation in beams with functionally graded porosity distribution under highly transient axial and transverse impactsM. Heshmati, S.K. Jalali, N.M. Pugnodoi:10.1016/j.tws.2023.111548在高瞬态轴向和横向冲击下，具有功能分级孔隙分布的梁中的波传播Recent advances in the manufacturing process provide a possibility of fabricating a new generation of porous materials denoted by functionally graded porous materials (FGPM). This paper aims to present a time domain analysis of wave propagation through the porous structures with functionally graded porosity distribution, which has not been completely studied before. For this purpose, the beams with different functionally graded porosity distributions subjected to both axial and transverse tip impact loads with a high-frequency content are investigated. The shear deformable cantilevered functionally graded porous beams with various porosity distributions through the beam thickness are studied. The governing differential equations are derived using the Hamiltonian principle based on the Timoshenko beam theory. A locking-free first-order shear deformable beam element is used to derive the finite element formulation of the equations. The Newmark time integration method is used to perform a time domain analysis of the equations of motion and to investigate the transient response of the beams. The axial and transverse wave propagation characteristics through functionally graded (FG) porous beams are found using time domain analysis of the results. Deflection and velocity time histories of the tip and each point of the beam, reflection time, and variation of support reactions are obtained. The influences of the porosity magnitude and porosity distribution on the wave propagation characteristics and overall time responses are investigated. The results reveal that porosity distribution has a significant effect on the wave amplitude, wave speed, and reflection from the boundary. Also, this study can help in a better understanding of porous structures' behavior subjected to high-transient impact loads in different engineering applications.制造工艺的最新进展为制造新一代多孔材料提供了可能，这种材料被称为功能分级多孔材料（FGPM）。本文旨在对波在具有功能分级孔隙率分布的多孔结构中的传播进行时域分析，而这在以前还没有过完整的研究。为此，本文研究了具有不同功能分级孔隙率分布的横梁，这些横梁同时承受轴向和横向尖端高频冲击载荷。研究了在梁厚度上具有不同孔隙率分布的可剪切变形悬臂功能分级多孔梁。基于季莫申科梁理论，利用哈密顿原理推导出了控制微分方程。无锁定一阶剪切变形梁元素用于推导方程的有限元公式。采用纽马克时间积分法对运动方程进行时域分析，并研究梁的瞬态响应。通过对结果进行时域分析，发现了穿过功能分级（FG）多孔梁的轴向和横向波传播特性。得出了梁顶端和各点的挠度和速度时间历程、反射时间以及支撑反作用力的变化。研究了孔隙率大小和孔隙率分布对波传播特性和整体时间响应的影响。结果表明，孔隙率分布对波幅、波速和边界反射有显著影响。此外，这项研究还有助于更好地理解多孔结构在不同工程应用中承受高瞬态冲击载荷时的行为。来源：复合材料力学仿真Composites FEM