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