
今日更新:International Journal of Solids and Structures 1 篇,Mechanics of Materials 2 篇,International Journal of Plasticity 2 篇,Thin-Walled Structures 3 篇
Building a monostable tetrahedron
Gergő Almádi, Robert J. MacG. Dawson, Gábor Domokos
doi:10.1016/j.ijsolstr.2026.114068
构造单稳定四面体
In this paper we describe what we believe to be the first working model of a monostable tetrahedron, which, if supported on a horizontal plane, would only rest in a stable position on one of its faces. If positioned on any other face, it would tip over its edges to arrive at the stable face. The sequence in which faces are visited is called the tipping sequence of the monostable tetrahedron. We prove that for any convex body K and any desired center of mass O in the interior of K , the ratio of the maximum and minimum density associated with any density distribution producing O as the center of mass of K will achieve its minimum if K is binary, i.e. it is composed by two homogeneous parts, separated by a plane passing through O . If O is not the center of mass of the homogeneous body then this plane is unique. We define 6 combinatorial classes of binary monostable tetrahedra based on their geometry and on their respective tipping sequences. Combining this theory with results on monostable tetrahedra from an earlier paper and with a numerical search algorithm we identify local minima for the ratio of maximal and minimal density in 5 out of the 6 combinatorial classes and we design a binary tetrahedron belonging to the lowest minimum out of these 5. Here, the ratio of densities of the heavy and light parts is approximately 907, and we believe the structure to be close to the global optimum in a degenerate combinatorial class, belonging simultaneously to two combinatorial classes. We also demonstrate a working physical model of this tetrahedron which we dubbed Bille.
在本文中,我们描述了我们认为是单稳定四面体的第一个工作模型,如果支撑在一个水平面上,它只会在它的一个面上处于稳定的位置。如果它被放置在其他面上,它就会越过它的边缘到达稳定的面。面被访问的序列称为单稳定四面体的倾斜序列。我们证明了对于任何凸体K和K内部的任何期望质心O,如果K是二进制的,即它由两个均匀的部分组成,由一个经过O的平面分开,那么与产生O作为K质心的任何密度分布相关的最大和最小密度之比将达到最小值。如果0不是均匀物体的质心,那么这个平面是唯一的。根据二元单稳定四面体的几何形状及其各自的倾转序列,定义了6个组合类。将此理论与前人关于单稳定四面体的研究结果相结合,并结合数值搜索算法,确定了6个组合类中5个类的最大与最小密度之比的局部极小值,并设计了一个属于这5个类中最小值的二元四面体。在这里,重、轻部件的密度比约为907,我们认为该结构在一个退化组合类中接近全局最优,同时属于两个组合类。我们还演示了这个四面体的工作物理模型,我们称之为Bille。
Compaction of porous materials under dynamic loading: A comparison of the p − α and ɛ − α model for concrete and concrete-like materials
Christoph Grunwald, Luis Brunnabend, Werner Riedel, Johann Maltan
doi:10.1016/j.mechmat.2026.105708
动荷载作用下多孔材料的压实:混凝土和类混凝土材料的p−α和α模型的比较
This work investigates the compaction behavior of concrete and adobe considering its porosity under dynamic loading. Two evolution equations for the porosity, the p − α and the ɛ − α model, are detailed and compared. The p − α model is well established in conjunction with the RHT model for concrete and parameter for different concrete grades are available. Unfortunately, the model describes the porosity as a function of the pressure, rendering the formulation implicit with accompanying high computational costs in explicit time integration schemes. In contrast, the ɛ − α model offers a simplified approach by linking porosity to the volumetric strain, a measure which is known at the beginning of an integration cycle. This model has found wide spread in the geological community where astronomical problems are of interest, but has not yet been applied to construction materials. We compare standard single element compaction paths as well as high dynamic planar plate impact tests for concrete and derive parameter sets for the ɛ − α model, which yield almost identical results as the p − α model. Computational efforts are reduced, however, limitations in the choice of the parameters make the model in rare cases less flexible compared to the p − α description.
本文研究了混凝土和土坯在动荷载作用下的压实特性。详细比较了两种孔隙度演化方程p−α模型和ε−α模型。结合混凝土的RHT模型建立了p−α模型,并给出了不同混凝土等级的参数。不幸的是,该模型将孔隙度描述为压力的函数,使得公式隐式化,同时在显式时间积分方案中伴随着高昂的计算成本。相比之下,ε−α模型通过将孔隙度与体积应变联系起来提供了一种简化的方法,体积应变是在积分周期开始时已知的一种度量。这个模型在对天文问题感兴趣的地质学界得到了广泛的应用,但尚未应用于建筑材料。我们比较了混凝土的标准单单元压实路径和高动态平面板冲击试验,并推导了模型的参数集,其结果与p - α模型几乎相同。计算量减少了,然而,参数选择的限制使模型在极少数情况下比p−α描述更不灵活。
Role of fiber dispersion in the torsion-induced Poynting effect of biological tissues
Jayant Kumar, Deepak Kumar
doi:10.1016/j.mechmat.2026.105728
纤维分散在生物组织扭转诱导的坡印亭效应中的作用
Collagen and/or elastin fibers are key load-bearing constituents of biological tissues. To realistically model the Poynting effect in biological tissues, which refers to the expansion or contraction of a material in directions perpendicular to an applied twist or shear, fiber dispersion cannot be neglected. The purpose of this work is to examine the often-ignored mechanics of fiber dispersion in accurately predicting the torque and axial stress responses of soft tissues under torsion, with particular emphasis on the Poynting effect. To model the critical role of fiber dispersion, a well-established generalized structural tensor framework is employed. Unlike the conventional quadratic term ( I 4 ∗ − 1 ) 2 , which causes unphysical instabilities associated with negative instantaneous stiffness under specific deformation regions of tissues, an amended form of strain energy density with a nonlinear term I 4 ∗ − m − 1 , m > 0 , is formulated. The impact of fiber dispersion on torque and axial stress is illustrated for white rabbit papillary muscle samples by comparing anisotropic modes to isotropic modes, with and without fiber-dispersion effects.
胶原蛋白和/或弹性蛋白纤维是生物组织的关键承重成分。为了真实地模拟生物组织中的坡印亭效应,即材料在垂直于施加扭转或剪切的方向上的膨胀或收缩,纤维色散不能被忽视。这项工作的目的是研究经常被忽视的纤维分散力学,以准确预测扭转下软组织的扭矩和轴向应力响应,特别强调坡印亭效应。为了模拟光纤色散的关键作用,采用了一个完善的广义结构张量框架。与传统的二次项(I 4∗−1)2不同,它在组织的特定变形区域下导致与负瞬时刚度相关的非物理不稳定性,一个非线性项I 4∗−m−1,m > 0的应变能密度的修正形式被表述出来。通过比较具有和不具有纤维分散效应的各向异性和各向同性模式,说明了纤维分散对白兔乳 头肌样品的扭矩和轴向应力的影响。
Breaking the strength-ductility trade-off in copper alloy laminates by heterostructure homogenization
Haitao Gao, Kun Qiao, Zhide Li, Lingling Song, Alexander Pesin, Charlie Kong, M.W. Fu, Hailiang Yu
doi:10.1016/j.ijplas.2026.104726
利用异质组织均质化技术打破铜合金层合板的强度-塑性平衡
The development of high-strength metallic materials is typically restricted by the strength-ductility trade-off, and conventional alloying techniques often result in higher production costs. To address these challenges, a “heterostructure-homogenization” strategy is posited. A complete and fully homogenized transition zone was achieved in a 200-layer heterostructure-homogenized laminate (HHL) comprising T2 Cu/QBe2.0 beryllium copper by deliberately setting the single-layer thickness to be s maller than the interdiffusion width. This design enables sufficient interelement diffusion, thereby forming a monocrystalline layer structure embedded with nanoprecipitates. Atomic diffusion facilitated the refinement of γ precipitates in the beryllium copper layer into 110 nm angular γ phases, whereas 12 nm-scale nanoprecipitates were nucleated on the T2-Cu side. Notably, with a 50% reduction in alloying elements, the HHL sample exhibited a tensile strength (651±5 MPa) comparable to that of QBe2.0 beryllium copper (729±9 MPa), whereas the elongation to fracture was increased by 307% (from 4.8±0.3% to 19.7±0.8%) and the electrical conductivity was improved by 110% (from 23.6 %IACS to 49.1 %IACS). Microstructural an alyses demonstrate that the synergistic effect of monocrystalline texture and homogeneous nanoprecipitates suppresses crack nucleation, while the interfacial transition zone promotes uniform dislocation distribution. Therefore, this strategy overcomes the performance limitations of conventional heterogeneous structures, offering a novel paradigm for developing low-cost copper alloys with integrated high strength and ductility.
高强度金属材料的发展通常受到强度与延性权衡的限制,而传统的合金化技术往往导致较高的生产成本。为了应对这些挑战,提出了“异质结构-均质化”策略。在由T2 Cu/QBe2.0铍铜组成的200层异质结构均质层压板(HHL)中,通过设置单层厚度小于互扩散宽度,实现了完全均匀化的过渡区。这种设计使元素间充分扩散,从而形成嵌入纳米沉淀物的单晶层结构。原子扩散使铍铜层中的γ析出相细化为110 nm角γ相,而T2-Cu侧则形成12 nm尺度的纳米析出相成核。值得注意的是,当合金元素减少50%时,HHL样品的抗拉强度(651±5 MPa)与QBe2.0铍铜(729±9 MPa)相当,而断裂伸长率提高了307%(从4.8±0.3%提高到19.7±0.8%),电导率提高了110%(从23.6% IACS提高到49.1% IACS)。微观组织分析表明,单晶织构和均匀的纳米沉淀物的协同作用抑制了裂纹的形核,而界面过渡区促进了位错的均匀分布。因此,该策略克服了传统非均质结构的性能限制,为开发低成本、高强度和高延展性的铜合金提供了新的范例。
Machine learning based constitutive modelling for thermal-elasto-plasto amorphous polymers
Keyi Jiang, Jici Wen, Yongmao Pei, Yujie Wei
doi:10.1016/j.ijplas.2026.104725
基于机器学习的热弹塑性非晶聚合物本构建模
For its superior recyclability, abundance in resources, and easiness in shape-forming, the application of amorphous thermoplastic polymers as structural materials is ever-growing. The intertwining mechanical, thermal, rate-dependence at both elastic and plastic stages, pressure-sensitivity characteristics, in combination with large deformation, have attracted the attention of the plasticity community. Here we design a physics-driven machine learning (PD-ML) constitutive framework to reconstruct the temperature, stress and rate-dependent deformation in amorphous polymers. We have applied the framework to three exemplary amorphous polymers, poly(methyl methacrylate), polycarbonate, and Zeonex. A finite element (FE) procedure based on the PD-ML constitutive framework is developed. The integration of PD-ML with FE procedure inherits the power of FE an alysis and the accuracy originated from PD-ML in describing temperature, stress and rate-dependent mechanical response of amorphous polymer. We demonstrate that the PD-ML model, fed with limited experimental results, can predict the mechanical response of amorphous polymers in a wide span of temperature and deformation rate and for a broad suit of experiments including uni-axial deformation, embossing, indentation and shear localization under plane strain compression. The constitutive framework could be readily generalized to a broad range of materials exhibiting perplexing temporal, spatial and multi-field coupling.
无定形热塑性聚合物具有可回收性好、资源丰富、易成型等优点,作为结构材料的应用日益广泛。其力学、热学、弹塑性阶段速率依赖、压敏特性以及大变形等相互交织的特点,引起了塑性界的广泛关注。在这里,我们设计了一个物理驱动的机器学习(PD-ML)本构框架来重建非晶聚合物的温度、应力和速率相关变形。我们已经将该框架应用于三种典型的非晶聚合物,聚(甲基丙烯酸甲酯),聚碳酸酯和Zeonex。开发了一种基于PD-ML本构框架的有限元程序。PD-ML与有限元程序的集成继承了有限元分析的强大功能和PD-ML在描述非晶聚合物的温度、应力和速率相关力学响应方面的准确性。我们证明了PD-ML模型,在有限的实验结果的支持下,可以预测非晶聚合物在大范围的温度和变形速率下的力学响应,以及在平面应变压缩下的单轴变形、压纹、压痕和剪切局部化等广泛的实验。本构框架可以很容易地推广到广泛的材料表现出复杂的时间,空间和多场耦合。
Post-Fire Simulated Mechanical Properties of Plas ma Arc Welded Dissimilar DP590-DP780 Steels
A. Rajesh Kannan, Hafiz Muhammad Rehan Tariq, Taemin Jeon, N. Siva Shanmugam, Minki Kim, Tea-Sung Jun
doi:10.1016/j.tws.2026.115104
不同DP590-DP780钢等离子弧焊后的模拟力学性能
The post-fire mechanical performance of dissimilar dual-phase (DP) steel welded joints is critical for the structural integrity of automotive components exposed to elevated temperatures. This study systematically investigates the post-fire behavior of plas ma arc-welded (PAW) DP590-DP780 steel joints heated to 300, 600, and 900°C and then air-cooled. Microstructural evolution, hardness distribution, and tensile properties were evaluated to elucidate the temperature-dependent response. The fusion zone (FZ) in the as-welded condition primarily consisted of martensite, whereas post-fire exposure induced significant phase transformations. At 300°C, partial martensite tempering caused moderate softening with limited strength loss. Exposure at 600°C resulted in extensive tempering and the formation of ferrite-tempered martensite, which enhanced ductility while maintaining adequate strength. In contrast, exposure at 900°C resulted in recrystallization and heterogeneous phase re-transformation, producing irregular lath martensite, bainite, tempered martensite, and grain-boundary ferrite. This microstructural heterogeneity increased FZ hardness but caused pronounced softening in adjacent regions, leading to a mechanical mis match and a substantial reduction in ductility. A predictive model for post-fire mechanical properties of dissimilar DP steel weldments, adapted from prior research, was applied using a simplified three-parameter formulation. The results demonstrate that post-fire exposure temperature critically governs the microstructure-property relationship, providing a balance between strength and ductility. These findings provide guidance for evaluating the residual performance and structural reliability of dissimilar DP steel weldments in automotive applications.
不同双相钢(DP)焊接接头的火灾后力学性能对高温下汽车零部件的结构完整性至关重要。本研究系统地研究了等离子弧焊(PAW) DP590-DP780钢接头加热到300、600和900℃,然后风冷后的火灾行为。显微组织演变,硬度分布和拉伸性能进行了评估,以阐明温度依赖的响应。在焊接状态下,熔合区(FZ)主要由马氏体组成,而在火灾后,熔合区发生了明显的相变。在300℃时,部分马氏体回火导致适度软化,强度损失有限。在600℃下暴露导致大量回火并形成铁素体回火马氏体,在保持足够强度的同时增强了延展性。而在900℃下暴露则导致再结晶和非均相再转变,形成不规则板条马氏体、贝氏体、回火马氏体和晶界铁素体。这种微观组织的不均匀性增加了FZ硬度,但在邻近区域造成明显的软化,导致机械失配和延展性的大幅降低。采用简化的三参数公式,建立了不同DP钢焊接件火灾后力学性能的预测模型。结果表明,火灾后的暴露温度对微观组织-性能关系起着关键的控制作用,在强度和延性之间提供了平衡。这些发现为评价不同DP钢焊接件在汽车应用中的残余性能和结构可靠性提供了指导。
Morphing characteristics of series-connected composite laminates under mechanical and piezoelectric actuation with clamped boundary conditions
P.R. Manu, P.M. Anilkumar, A. Haldar, B.N. Rao
doi:10.1016/j.tws.2026.115059
夹紧边界条件下机械和压电驱动下串联复合材料层合板的变形特性
Unsymmetrical composite laminates exhibit significant potential due to their inherent bistable behavior, which arises from thermally induced residual stresses developed during curing. This unique characteristic offers a distinct advantage in morphing applications, where continuous shape-change capabilities are desired. By connecting multiple bistable composite shells in series, it is possible to achieve a surface with a high degree of multistability. However, imposed boundary constraints critically affect the morphing capability through their influence on the structural stability landscape. Most of the existing modeling and design studies employ idealized center-fixed boundary conditions, which often do not represent realistic application scenarios. For instance, clamped edge boundary conditions can have a detrimental effect on multistability, sometimes even reducing it to monostability. This study aims to design series-connected multistable laminates with one edge clamped, investigating how such constraints affect the multistable behavior. An efficient strategy utilizing a transition region with a different unsymmetrical layup, connecting to the unsymmetrical connected multistable laminates, has been explored to mitigate the adverse effects of clamping and thereby preserve multistability. A dedicated nonlinear FE modeling has been adopted for the an alysis. Once a viable baseline design is established, the laminate configuration is manufactured, and the displacement profiles predicted by the FE model are validated experimentally. The snap-through process is initially investigated under mechanical loading. Subsequently, piezoelectric macro fiber composite actuators are incorporated to actively induce snap-through transitions between the stable equilibrium configurations. Ultimately, the study addresses two key aspects: (1) the effect of clamped boundary conditions on multistability, and (2) the additional influence of piezoelectric actuation on shape transitions. In all these studies, the out-of-plane displacements of the modeled laminates are an alyzed, along with the corresponding snap-through requirements. These results provide new perspectives on the application of multistable composite laminates in morphing structures by expanding the feasible design space under realistic boundary constraints.
非对称复合层压板由于其固有的双稳态行为而表现出显著的潜力,这是由固化过程中产生的热诱导残余应力引起的。这种独特的特性在需要连续形状变化功能的变形应用中提供了明显的优势。通过串联多个双稳态复合壳,可以实现具有高度多稳定性的表面。然而,施加的边界约束通过对结构稳定性景观的影响而严重影响变形能力。现有的建模和设计研究大多采用理想化的中心固定边界条件,往往不能代表实际应用场景。例如,箝位边缘边界条件会对多稳定性产生不利影响,有时甚至会使其降为单稳定性。本研究旨在设计单边箝位的串联多稳定层压板,研究这些约束如何影响多稳定性能。研究了一种有效的策略,利用具有不同不对称层合的过渡区域,连接到不对称连接的多稳定层压板,以减轻夹紧的不利影响,从而保持多稳定性。采用了专门的非线性有限元模型进行分析。一旦确定了可行的基线设计,就可以制造层压板结构,并通过实验验证有限元模型预测的位移曲线。在机械载荷下初步研究了断裂过程。随后,采用压电宏观纤维复合促动器来主动诱导稳定平衡构型之间的过断转变。最后,该研究解决了两个关键方面:(1)箝位边界条件对多稳定性的影响,以及(2)压电驱动对形状转变的附加影响。在所有这些研究中,分析了模型层压板的面外位移,以及相应的snap-through要求。这些结果扩大了在现实边界约束下的可行设计空间,为多稳定复合材料层合板在变形结构中的应用提供了新的视角。
Fatigue creep characteristics and performance prediction of PTFE gaskets undergone cryogenic liquid oxygen immersion aging
Zhan Liu, Wenlong Xue, Jin Bai, Jibin Shen, Zhongzhu Zhang
doi:10.1016/j.tws.2026.115106
低温液氧浸渍老化PTFE垫片的疲劳蠕变特性及性能预测
Due to excellent advantages, Polytetrafluoroethylene PTFE material is widely used in extreme environments, such as extremely low temperature and ultra-high pressure. Until now, there is still a lack of fatigue creep performance investigations of PTFE materials at cryogenic condition, especially at liquid oxygen temperature. In this study, the PTFE sealing gaskets used in an aerospace cryogenic liquid oxygen filling system were adopted as research object. The selected PTFE samples were immersed in liquid oxygen for several aging treatments, and the related mechanical performance of liquid oxygen aged samples were experimentally tested. The static compression mechanical performance and fatigue creep characteristics of cryogenic aged PTFE samples were systematically investigated. The quantitative an alysis was conducted on influences of three factors, namely loading stress level, cryogenic aging cycle number, and load holding duration, on the strain response of PTFE samples. Based on experimental data, a multi factor statistical model was established using partial least squares regression (PLSR) method, and the material life was reasonably predicted through fitting S-N curve. Some key findings were achieved. This research is significant to depth understanding the evolution of fatigue creep behavior of PTFE gaskets undergone cryogenic immersion aging treatments.
聚四氟乙烯PTFE材料由于具有优异的优点,被广泛应用于极低温、超高压等极端环境中。迄今为止,对聚四氟乙烯材料在低温条件下,特别是在液氧温度下的疲劳蠕变性能的研究仍然缺乏。本研究以航天低温液氧填充系统中使用的聚四氟乙烯密封垫片为研究对象。将选定的PTFE试样浸泡在液氧中进行多次时效处理,并对其相关力学性能进行了实验测试。系统地研究了低温老化PTFE试样的静态压缩力学性能和疲劳蠕变特性。定量分析了加载应力水平、低温老化循环次数、载荷保持时间三个因素对PTFE试样应变响应的影响。基于实验数据,采用偏最小二乘回归(PLSR)方法建立了多因素统计模型,并通过拟合S-N曲线对材料寿命进行了合理预测。取得了一些重要发现。本研究对深入了解低温浸渍时效处理后聚四氟乙烯垫片疲劳蠕变行为的演变具有重要意义。