今日更新：International Journal of Solids and Structures 2 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 StructuresPhase-field modeling of anisotropic crack propagation based on higher-order nonlocal operator theoryNhon Nguyen-Thanh, Timon Rabczukdoi:10.1016/j.ijsolstr.2023.112632基于高阶非局部算子理论的各向异性裂纹扩展相场建模This paper presents a novel higher-order nonlocal operator theory for the phase-field modeling of brittle fracture in anisotropic materials. Incorporating higher order nonlocal operators can enhance the accuracy of the phase-field model by effectively capturing long-range interactions that hold significance in numerous materials. The reproducing kernel particle method is employed to derive a nonlocal differential operator to enhance computational stability and accuracy. Moreover, the proposed method eliminates the need for direct computation of derivatives of the modified kernel function, which avoids the calculation of moment matrix derivatives and improves computational efficiency. The phase-field modeling of polycrystalline materials, considering the anisotropic fracture resistance of each grain, is implemented using this numerical framework. The present method is able to capture different scenarios intergranular and transgranular crack propagation patterns in polycrystalline materials. The proposed method involves a detailed representation of the complex process of crack initiation and propagation in 2D and 3D models of polycrystalline materials.提出了一种新的高阶非局部算子理论，用于各向异性材料脆性断裂相场建模。结合高阶非局部算符可以通过有效地捕获在许多材料中具有重要意义的远程相互作用来提高相场模型的准确性。采用再现核粒子法推导非局部微分算子，提高了计算的稳定性和精度。此外，该方法不需要直接计算修正核函数的导数，避免了矩矩阵导数的计算，提高了计算效率。采用该数值框架对多晶材料进行了相场建模，考虑了各晶粒的抗断裂性能各向异性。该方法能够捕获多晶材料中不同情况下的晶间和穿晶裂纹扩展模式。该方法在二维和三维多晶材料模型中详细描述了裂纹萌生和扩展的复杂过程。Fracture resistance enhanced by both nonlocal interaction and damping of locally resonant structureXuan Zhang, Yi-Ze Wangdoi:10.1016/j.ijsolstr.2023.112635非局部相互作用和局部共振结构的阻尼增强了抗断裂能力In this study, the arrest behavior of locally resonant structure with nonlocal interaction and damping are analyzed. Based on the Wiener-Hopf method, the energy release ratio G0/G which denotes the arrest property is derived. The effects of nonlocal interaction and damping parameters on the oscillation and stability regions during the crack growth are discussed. The arrest characteristics of three locally resonant structures are compared. In order to support the theoretical calculation, both the finite element simulation and fracture experiment are performed. Results show that the locally resonant structure with nonlocal interaction and damping has smaller energy release ratio G0/G. It indicates that the coupling of both nonlocal interaction and damping can significantly enhance the propagation resistance of crack propagation.本研究分析了具有非局部相互作用和阻尼的局部谐振结构的阻滞行为。基于 Wiener-Hopf 方法，推导出了表示停滞特性的能量释放比 G0/G。讨论了非局部相互作用和阻尼参数对裂纹生长过程中振荡区和稳定区的影响。比较了三种局部共振结构的抑制特性。为了支持理论计算，进行了有限元模拟和断裂实验。结果表明，具有非局部相互作用和阻尼的局部共振结构的能量释放比 G0/G 较小。这表明，非局部相互作用和阻尼的耦合可以显著增强裂纹的抗扩展能力。Journal of the Mechanics and Physics of SolidsRate Induced Thermomechanical Interactions in NiTi Tensile Tests on StripsSolon Tsimpoukis, Stelios Kyriakidesdoi:10.1016/j.jmps.2023.105530带材镍钛拉伸试验中速率诱导的热-机械相互作用The paper uses tensile experiments on NiTi strips at different displacement rates to establish and simulate the thermomechanical interactions caused by the latent heat of the reversible transformation between the austenitic and martensitic phases. The evolution of deformation in the specimen is synchronously monitored with digital image correlation, and the temperature field through infrared imaging, essential for structural modelling. Transformation leads to localized deformation that propagates through the specimen, while the latent heat released/absorbed at the propagating fronts locally heats/cools the specimen. The sensitivity of the transformation stress to temperature results in a complex interaction between the heat transfer conditions and the nucleation and evolution of transformation in the specimen. At low rates of loading, the alternate phase propagates nearly isothermally with a small number of fronts producing relatively flat stress plateaus. Higher rates lead to significant heating/cooling that results in progressive nucleation of multiple fronts and apparent "hardening" responses. The experiments are simulated in a three-dimensional static displacement transient temperature finite element analysis, using a new fully coupled thermomechanical constitutive model. Transformation strain and entropy are its internal variables whose evolution is governed by the motion in the stress-temperature space of a single transformation surface governing both transformations. The prevailing localization is captured by the introduction of softening over the unstable branches of the recorded isothermal material response. The results demonstrate how the important role of the thermal interaction between the specimen and the environment can be addressed. This, together with appropriate calibration of the constitutive and structural model, enable the analysis to reproduce the effect of rate on the recorded response, the evolution of localization patterns, and the associated thermal fields. The results can guide the development of constitutive and structural models of phase transforming materials with strong thermomechanical interactions.本文采用不同位移速率下NiTi带材的拉伸实验，建立并模拟了奥氏体与马氏体可逆相变潜热引起的热力相互作用。通过数字图像相关同步监测试样的变形演变，并通过红外成像同步监测温度场，这对结构建模至关重要。相变导致局部变形在试样中传播，而在传播前沿释放/吸收的潜热局部加热/冷却试样。相变应力对温度的敏感性导致传热条件与试样的形核和相变演化之间存在复杂的相互作用。在低加载速率下，交替相几乎等温传播，少数锋面产生相对平坦的应力高原。较高的速率导致显著的加热/冷却，导致多个锋面逐渐成核和明显的“硬化”反应。采用一种新的全耦合热-力本构模型，对实验进行了三维静位移瞬态温度有限元模拟。相变应变和熵是其内部变量，其演化由控制两种相变的单一相变表面在应力-温度空间中的运动决定。通过在记录的等温材料响应的不稳定分支上引入软化，捕获了普遍的局部化。结果表明，如何在试样和环境之间的热相互作用的重要作用可以解决。这与本构和结构模型的适当校准一起，使分析能够重现速率对记录响应的影响，定位模式的演变以及相关的热场。研究结果对具有强热力相互作用的相变材料的本构模型和结构模型的建立具有指导意义。International Journal of PlasticityRevealing the effects of martensitic transformation and dislocation slip in austenite on the micromechanical behaviors of a 9Ni steel using crystal plasticity finite element methodW.X. Zhang, Y.B. Cong, J. Wang, C. Li, J. Wan, Y.Z. Chendoi:10.1016/j.ijplas.2023.103869 利用晶体塑性有限元法揭示了马氏体相变和奥氏体 位错滑移对9Ni钢微观力学行为的影响Austenite is an extremely important phase that significantly influence the mechanical properties of (austenite + martensite) duplex steels. Two different deformation mechanisms, i.e., dislocation slip and martensitic transformation, can be activated in the austenite upon plastic deformation. However, these two deformation mechanisms make different contributions to the work hardening and flow stress of the austenite which are hardly separated by experimental methods, making it difficult to clarify the effect of austenite on the micromechanical behavior of (austenite + martensite) duplex steels. In this work, the influence of martensitic transformation and dislocation slip in austenite on the micromechanical behaviors is investigated in a model 9Ni steel consisting of austenite and tempered martensite (TM) using the crystal plasticity finite element method (CPFEM). The austenite and fresh martensite (FM) formed within the austenite grain upon deformation process are regarded as a whole named as FM/A island in the CPFEM. To accurately model the rate of martensitic transformation, the martensitic transformation kinetics law used in the CPFEM is developed by relating the number of possible nucleation sites for fresh martensite to the mechanical driving force originating from the resolved shear stress on each transformation system. The material parameters for the TM were determined by micropillar compression tests. Besides, the method for separating and determining the material parameters accounting for dislocation slip in austenite and martensitic transformation by a combination of neutron diffraction and measurements of stress-strain curves and austenite volume fractions is developed and exemplified. The CPFEM simulation results show that the local concentration of equivalent plastic strain and stress triaxiality in the FM/A island can be enhanced by the dislocation slip in austenite but suppressed by the martensitic transformation. In addition, the martensitic transformation has a remarkable effect on strengthening the local concentration of maximum principal stress in the FM/A island.奥氏体是影响(奥氏体 + 马氏体)双相钢力学性能的重要相。塑性变形时，奥氏体可激活两种不同的变形机制，即位错滑移和马氏体相变。然而，这两种变形机制对奥氏体的加工硬化和流动应力的贡献各不相同，且难以通过实验方法加以区分，因此很难阐明奥氏体对(奥氏体 + 马氏体)双相钢微观力学行为的影响。本文采用晶体塑性有限元法(CPFEM)研究了奥氏体和回火马氏体(TM)组成的9Ni钢中马氏体相变和位错滑移对微观力学行为的影响。在CPFEM中，将形变过程中在奥氏体晶粒内形成的奥氏体和新马氏体(FM)视为一个整体，称为FM/ a岛。为了准确地模拟马氏体转变的速率，CPFEM中使用的马氏体转变动力学定律是通过将新马氏体可能成核的位置的数量与每个转变系统上由分解的剪切应力产生的机械驱动力相关联而建立的。通过微柱压缩试验确定了TM的材料参数。此外，还提出了利用中子衍射、应力-应变曲线和奥氏体体积分数测量相结合的方法来分离和确定奥氏体和马氏体相变中位错滑移的材料参数。CPFEM模拟结果表明，奥氏体 位错滑移增强了FM/A岛的局部等效塑性应变集中和应力三轴性，但马氏体相变抑制了等效塑性应变的集中。此外，马氏体相变对强化FM/ a岛局部最大主应力集中有显著作用。Thin-Walled StructuresExperimental and numerical study on the lightweight design of load-bearing energy absorption structure for subway trainJialin Li, Guangjun Gao, Yao Yu, Tianyu Zhuo, Jian Lidoi:10.1016/j.tws.2023.111542地铁列车承载吸能结构轻量化设计的试验与数值研究The load-bearing underframe is widely utilized on the crashworthiness design of subway trains. However, studies on load-bearing underframes mainly focused on conceptual design and structural optimization, and didn't consider the combination of bearing loads during the normal operation and absorbing impact kinetic energy under collisions. In addition, the traditional load-bearing underframe for subway trains is mainly made of stainless steel, which has a relatively large weight and cannot meet the requirement of lightweight design. To address these limitations, this paper presents a novel lightweight aluminum alloy load-bearing underframe with the alternative thin-walled energy absorption component, which can both satisfy the function of bearing loads and energy absorption. Firstly, the impact tests and numerical simulations are conducted to compare the crashworthiness of the energy absorption component, i.e., the thin-walled square tube made of S304 (abbreviated as S3N4) and aluminum alloy 5083P-O (abbreviated as A3N4). The result shows that S3N4 has higher energy absorption and mean crushing force, and A3N4 is 56.94 % lower than S3N4 in initial peak crushing force and 53.79 % higher in special energy absorption. Then, the aluminum alloy thin-walled tube is adopted on the novel load-bearing underframe and the parameter study on the wall thickness and number of diaphragms for the energy absorption component is conducted. The result reveals that the 5083P-O thin-walled tube with 5 mm wall thickness and 4 diaphragms can provide the stable and ordered deformation mode and high energy absorption. Finally, a real vehicle impact test is conducted to verify the crashworthiness of the optimized load-bearing underframe, which shows that the deformation modes and mechanical responses are consistent with the numerical simulation. The proposed aluminum alloy load-bearing underframe energy absorption structure can be adopted on subway trains.在地铁列车的耐撞性设计中，承重型车架得到了广泛的应用。然而，对承重型车架的研究主要集中在概念设计和结构优化上，没有考虑车架正常运行时承受载荷与碰撞时吸收冲击动能的结合。此外，传统的地铁列车承重底架以不锈钢为主，自重较大，不能满足轻量化设计的要求。针对这些局限性，本文提出了一种新型的轻质铝合金承载底架，并采用替代薄壁吸能组件，既能满足承载载荷又能满足吸能功能。首先，对S304薄壁方管(简称S3N4)和5083P-O铝合金(简称A3N4)两种吸能构件的耐撞性进行了冲击试验和数值模拟比较。结果表明，S3N4具有更高的能量吸收和平均破碎力，A3N4初始峰值破碎力比S3N4低56.94%，特殊能量吸收比S3N4高53.79%。然后，在新型承力底架上采用铝合金薄壁管，对吸能构件的壁厚和隔板数进行了参数研究。结果表明:5083P-O薄壁管的壁厚为5mm，隔板为4个，可以提供稳定有序的变形模式和较高的能量吸收。最后，进行了实车碰撞试验，验证了优化后的承载底架的耐撞性，结果表明，其变形模式和力学响应与数值模拟结果一致。本文提出的铝合金承力底架吸能结构可用于地铁列车。An all-composite sandwich structure with PMI foam-filled for adjustable vibration suppression and improved mechanical propertiesJiaming Sun, Leilei Yan, Keyu Zhu, Pengfei Jiang, Yanlong Xu, Xitao Zhengdoi:10.1016/j.tws.2023.111544采用PMI泡沫填充的全复合夹层结构，可调抑制振动，提高力学性能A novel all-composite double-layer sandwich structure with tubular cores (DSST) is designed and fabricated to achieve the both of vibration suppression and enhancement of mechanical properties. The suppression effect of the proposed sandwich structure on the structural vibration is verified numerically and experimentally, and the mechanism of bandgap generation as well the structural wave propagation modes are revealed and analyzed. The anisotropy of the carbon fiber reinforced polymer (CFRP) is utilized to enables the intermediate resonant layer to exist a wide frequency adjustment range of vibration suppression without altering its geometrical parameters. Then, the improvement of structural vibration characteristics (i.e., natural frequencies and mode shapes) by filling the polymethacrylimide (PMI) foam in the DSST is discussed. And PMI foam-filling also leads to improved mechanical properties, out-of-plane compression tests are conducted to reveal the mechanism of mechanical enhancement, and it is found that the interaction effect of the foam filled in DSST in the axial direction enhances the compressive strength and the specific energy absorption (SEA) compared to the one without foam by 35.7% and 26.2%, respectively. In addition, the core configuration and the composite material preparation enable the proposed structure to outperform competing ones in terms of load-bearing capacity and bandgap characteristics.设计并制造了一种新型的双层管状芯夹芯全复合材料结构(DSST)，以达到抑制振动和提高力学性能的目的。通过数值和实验验证了夹层结构对结构振动的抑制作用，揭示和分析了带隙产生的机理以及结构波的传播模式。利用碳纤维增强聚合物(CFRP)的各向异性，使中间谐振层在不改变其几何参数的情况下存在较宽的频率调节范围来抑制振动。然后讨论了在DSST中填充聚甲基丙烯酰亚胺(PMI)泡沫对结构振动特性(即固有频率和振型)的改善。PMI泡沫填充也能改善材料的力学性能，通过面外压缩试验揭示了力学增强的机理，结果发现，在轴向填充泡沫后，材料的抗压强度和比能吸收(SEA)比未填充泡沫时分别提高了35.7%和26.2%。此外，核心配置和复合材料制备使所提出的结构在承载能力和带隙特性方面优于竞争结构。来源：复合材料力学仿真Composites FEM
