今日更新:International Journal of Solids and Structures 1 篇,Mechanics of Materials 1 篇,International Journal of Plasticity 2 篇,Thin-Walled Structures 2 篇
3D-printed highly stretchable curvy sandwich metamaterials with superior fracture resistance and energy absorption
Hamzehei Ramin, Bodaghi Mahdi, Wu Nan
doi:10.1016/j.ijsolstr.2023.112570
3d打印高拉伸弯曲夹层超材料,具有优异的抗断裂性和能量吸收
This paper focuses on the potential of curvy mechanical metamaterials to show how topological design can significantly enhance fracture toughness along the in-plane and out-of-plane (through-depth) directions. The conventional re-entrant unit cell is first reformulated by introducing local curvy ligaments and then additively manufactured by three-dimensional (3D) printing to form a center/edge-notch lattice metamaterial. The new conceptual design provides multi-stiffness unit cells, helping to control stress distribution within a structure under tensile load, specifically in the vicinity of the notches where stress concentrations occur. In other words, curvy unit cells are capable of arresting and blunting the notch under tensile loads and toughening the metamaterials. The crack tip opening displacement (CTOD) method calculates the fracture toughness. Not only can the fracture of lattice metamaterials be controlled along the in-plane direction by replacing unit cells in the sensitive parts of the metamaterials, but a new assembly method is also proposed. This offers that different thin plates of metamaterials with different layouts can be sandwiched to control out-of-plane fracture propagation (through-depth propagation of opening mode fracture) for the first time in fracture mechanics. This novel sandwiching method offers a multi-step fracture and significantly improves the fracture behavior of the lattice metamaterials from brittle to ductile by taking advantage of multiple through-thickness thin plates instead of considering one thick specimen. A detailed analysis of the effects of the ligament curvature value on the fracture behavior is presented. The results reveal that the more curvature, the more extension (ductility) will be realized, but too large curvature design can provide lower energy absorption capacity.
本文关注弯曲机械超材料的潜力,以展示拓扑设计如何显著提高沿面内和面外(穿过深度)方向的断裂韧性。首先通过引入局部弯曲韧带来重新构造传统的可重入单元格,然后通过三维(3D)打印进行增材制造,形成中心/边缘缺口晶格超材料。新的概念设计提供了多刚度单元,有助于控制拉伸载荷下结构内的应力分布,特别是在应力集中的缺口附近。换句话说,弯曲单元胞能够在拉伸载荷下阻止和钝化缺口,并使超材料增韧。裂纹尖端开度位移(CTOD)法计算断裂韧性。通过替换超材料敏感部位的单元胞,不仅可以沿面内方向控制晶格超材料的断裂,而且还提出了一种新的装配方法。这在断裂力学中首次提出了将不同布局的超材料薄片夹在夹层中,以控制面外断裂扩展(开口模式断裂的纵深扩展)。这种新型的夹夹方法利用多个贯穿厚度的薄板而不是单一的厚试样,提供了多步断裂,显著改善了晶格超材料从脆性到延性的断裂行为。详细分析了韧带曲率值对断裂行为的影响。结果表明,曲率越大,可实现的延展性越大,但曲率过大会降低结构的吸能能力。
An infill-based approach towards stiffer auxetic lattices: Design and study of enhanced in-plane elastic properties
Acharya Antu, Muthkani Vikram, DasGupta Anirvan, Jain Atul
doi:10.1016/j.mechmat.2023.104849
一种基于填充的更硬塑性格的方法:增强面内弹性性能的设计与研究
Mechanical metamaterials have tunable material properties, and the architecture of such materials can be tuned to impart Negative Poisson's Ratio (NPR). However, architected lattices typically have low stiffness. In the current study, the filler-based and infill-based strategies for creating auxetic lattices with enhanced stiffness are proposed and demonstrated. Analytic expressions for different in-plane elastic properties of the sinusoidal re-entrant honeycomb (SRH) lattice are developed. Finite element models are validated using data from published literature and analytic models. Using validated FE modelling, parametric studies involving infill patterns and filler materials in the SRH lattices are undertaken to find combinations leading to enhanced stiffness with minor loss in auxeticity. The possibility of attaining a massive increment in stiffness than that of the empty lattices, while retaining significant auxeticity (Poisson's ratio < −1), is demonstrated, which is a key outcome of this work. Using the proposed approach, high stiffness has been achieved in case of both non-auxetic infill-based (NAIB) and auxetic infill-based (AIB) while retaining NPR is established. Further studies have confirmed that the AIB lattices exhibit much higher stiffness compared to all the other lattices. Finally, the proposed approach is benchmarked against four published approaches towards generating stiff lattices with NPR. When compared with existing approaches, it is found that the strategies proposed in this paper perform better; for the same NPR, the proposed approaches lead to lattices with higher stiffness, and conversely, for the same normalised stiffness higher auxeticity is achieved. Implementation of the proposed approaches can be realized using in-built infill capabilities of prevalent additive manufacturing 3D printing technologies. New opportunities to enhance the capabilities of the existing technology are also indicated.
机械超材料具有可调谐的材料特性,并且这种材料的结构可以调谐以赋予负泊松比(NPR)。然而,结构格通常具有低刚度。在目前的研究中,提出并证明了基于填料和基于填料的策略来创建具有增强刚度的补充晶格。建立了正弦重入蜂窝(SRH)晶格面内弹性特性的解析表达式。有限元模型使用已发表的文献和分析模型的数据进行验证。使用经过验证的有限元模型,对SRH晶格中的填充模式和填充材料进行了参数化研究,以找到既能增强刚度又能减少弹性的组合。证明了在保持显著的弹性(泊松比 < −1)的同时,获得比空晶格大量增加刚度的可能性,这是本工作的关键成果。采用本文提出的方法,在保持非补强填充(NAIB)和补强填充(AIB)的同时,获得了高刚度。进一步的研究证实,与所有其他晶格相比,AIB晶格具有更高的刚度。最后,本文提出的方法与四种已发表的用NPR生成刚性格子的方法进行了基准测试。通过与已有方法的比较,发现本文提出的策略具有更好的效果;对于相同的NPR,所提出的方法导致晶格具有更高的刚度,相反,对于相同的归一化刚度,获得更高的奇异性。所提出的方法可以使用流行的增材制造3D打印技术的内置填充功能来实现。还指出了提高现有技术能力的新机会。
Discrete dislocation dynamics simulations of 〈 a 〉 -type prismatic loops in zirconium
Roig Daniel Hortelano, Kumar Rakesh, Balint Daniel S., Tarleton Edmund
doi:10.1016/j.ijplas.2023.103802
锆中< a >型棱柱环的离散位错动力学模拟
Neutron irradiation of zirconium alloys in light water nuclear reactors generates nano-scale defects in the form of vacancy and interstitial 〈 a 〉 -type prismatic loops which lie in prismatic planes of the sample. The dynamics of idealised conservative rectangular 〈 a 〉 -type prismatic loops have been investigated for a range of loop lengths in the framework of linear isotropic elasticity. Three-dimensional dislocation dynamics (DD) simulations of a dislocation-loop interaction have been performed to investigate the dislocation-loop interaction mechanism. For this purpose, a mobility law developed for hexagonally close-packed materials has been implemented and described in detail. Analytical and numerical calculations have been performed to obtain expressions for the restoring force and angular stability of prismatic loops. These analyses have been used to inform a 2.5D discrete dislocation plasticity (DDP) model in order to emulate realistic prismatic loop physics and improve irradiation hardening simulations. From the 2.5D DDP prismatic loop analyses, it has been observed that the stable angle of smaller sized loops is less sensitive to external stresses compared to that of larger loops, which may have implications for the mechanisms of irradiation hardening. Furthermore, initial 2.5D single-slip simulations predict that prismatic loops cause significantly elevated flow stress that increases with increasing loop density in accord with experimental observations, and that the restraining effect of the out-of-plane loop segments (the restoring force) plays an important role in the strengthening caused by loops.
在轻水核反应堆中中子辐照锆合金会在样品的棱柱面产生空位和间隙< >型棱柱环的纳米级缺陷。在线性各向同性弹性框架下,研究了理想保守矩形< a >型棱柱环在一定长度范围内的动力学。为了研究位错-环相互作用机理,对位错-环相互作用进行了三维位错动力学模拟。为此,对六边形密装材料的迁移率规律进行了实现和详细描述。通过解析和数值计算,得到了棱柱环的恢复力和角稳定性表达式。这些分析已被用于2.5D离散位错塑性(DDP)模型,以模拟真实的棱柱环物理并改进辐照硬化模拟。从2.5D DDP柱形环的分析中可以观察到,与大环相比,小环的稳定角对外部应力的敏感性较低,这可能与辐照硬化的机制有关。此外,初始2.5D单滑移模拟预测,棱柱形环引起的流动应力显著升高,且流动应力随环密度的增加而增加,与实验结果一致,并且面外环段的抑制作用(恢复力)在环引起的强化中起重要作用。
Anisotropic damage and frictional poroplastic modelling of quasi-brittle rocks in a combined homogenization/thermodynamics framework
Zhu Qi-Zhi, Yuan Shuang-Shuang, Shao Jian-Fu
doi:10.1016/j.ijplas.2023.103789
准脆性岩石的各向异性损伤与摩擦孔塑性模型
Hydromechanical coupling is one of the essential theoretical and practical issues in rock mechanics and rock engineering. In geological context, it is critically important to incorporate the effect of pore pressure into the constitutive equations with full account of cracking-induced material anisotropies and friction-related plastic deformation. Focus here is put on poromechanical formulations for quasi-brittle rocks weakened by microcracks and saturated with pore fluid pressure. The linear homogenization method applied to derive the effective properties and system free energy is combined with the irreversible thermodynamics and the problem decomposition. Constitutive derivations include the determination of the system free energy, state equations associated with and evolution laws of the internal variables, closed-form failure criterion, etc.. Inherent coupling between anisotropic unilateral damage, friction-induced plastic deformation and the fluid pressure constitutes one of significant novelties of the work. Continuities required for the total free energy, macroscopic stress and the global porosity are guaranteed at any opening-closure transition of cracks. Through strength and deformation coupling analyses, the effects of fluid pressure on material strength and deformation are elucidated and also validated by experiments we performed upon a sandstone.
流体力学耦合是岩石力学和岩石工程中重要的理论和实践问题之一。在地质环境中,将孔隙压力的影响纳入本构方程并充分考虑材料的各向异性和摩擦相关的塑性变形是至关重要的。本文重点讨论了受微裂纹削弱、孔隙流体压力饱和的准脆性岩石的孔隙力学公式。采用线性均匀化方法推导有效性质和系统自由能,并结合不可逆热力学和问题分解。本构推导包括系统自由能的确定、与内变量相关的状态方程及其演化规律、闭式破坏准则等。各向异性单侧损伤、摩擦引起的塑性变形和流体压力之间的内在耦合是这项工作的重要创新之一。总自由能、宏观应力和整体孔隙率在裂纹的任何开闭过渡段都能保证连续性。通过强度和变形耦合分析,阐明了流体压力对材料强度和变形的影响,并通过砂岩试验进行了验证。
Experimental characterization and modeling of cylindrical CFRP structures under quasi-static multiaxial loading conditions
Duda Szymon, Smolnicki Michał, Stabla Paweł, Zielonka Paweł, Osiecki Tomasz, Gao Chao, Lesiuk Grzegorz
doi:10.1016/j.tws.2023.111364
准静态多轴加载条件下圆柱形CFRP结构的实验表征与建模
An experimental and numerical investigation of the cylindrical carbon fiber reinforced polymer (CFRP) structures under various loads including tension/torsion loading conditions has been conducted. Various boundary conditions and parameters were taken into account to check the impact of the shear component to obtain the result. The nonlinear shear model proposed by Chang has been implemented to take into account the softening effect of the stress-strain curve caused by damage accumulation. The computational model of the thin-walled tubes contains the geometrical architecture of the material, such as interweaving, which are characteristic of the parts made by filament winding technology. The studies were preceded by preliminary tests of the individual components to predict elastic properties based on the Abolin'sh micromechanical approach. The strength parameters were empirically delivered on the basis of the experimental results and used to determine the failure of the structure. The accuracy of the calibrated nonlinear shear model was validated using strain gauges and digital image correlation techniques. The strain distribution obtained from FEA was compared with that of the optical method. The damage distribution provided by FEA is exhibited in a similar manner to the real one captured by DIC. The proposed model provides a precise prediction of the CFRP tubes under quasi-static loading conditions proven by the experiments.
对圆柱形碳纤维增强聚合物(CFRP)结构在不同载荷条件下(包括拉伸/扭转载荷)进行了试验和数值研究。考虑了各种边界条件和参数,对剪切分量的影响进行了校核,得到了结果。采用Chang提出的非线性剪切模型,考虑了损伤累积对应力-应变曲线的软化作用。薄壁管的计算模型包含了材料的几何结构,如交织,这是长丝缠绕技术制造的零件所具有的特征。在研究之前,对各个部件进行了初步测试,以预测基于Abolin'sh微力学方法的弹性性能。在试验结果的基础上,经验地给出了强度参数,并用于确定结构的破坏程度。利用应变片和数字图像相关技术验证了校正后的非线性剪切模型的准确性。将有限元法得到的应变分布与光学法得到的应变分布进行了比较。有限元分析得到的损伤分布与DIC捕捉到的真实损伤分布具有相似的表现方式。该模型对CFRP管在准静态载荷条件下的受力情况进行了较精确的预测,并得到了试验的验证。
Seismic Behaviors of CFT Frame-Four-corner Bolted Connected Buckling-Restrained Steel Plate Shear Walls Using ALC/RAC Panels
Du Yansheng, Mohammed Amer, Chen Zhihua, Al-Haaj Mohammed, Huang Jin
doi:10.1016/j.tws.2023.111365
ALC/RAC板CFT框架-四角螺栓连接抗屈曲钢板剪力墙的抗震性能
A Frame-Buckling Restrained Steel Plate Shear Walls (BRSPSWs) system has been designed, featuring a steel plate connected to frame elements, to withstand lateral loads like seismic or wind forces. This system incorporates recycled aggregate concrete (RAC) to create concrete-filled and concrete panels, promoting eco-friendly and sustainable construction materials. Two single-span, two-floor specimens were tested under cyclic quasi-static load. A four-corner bolted connection was used to connect the steel plate to the square concrete-filled steel tubes (CFTs) column and H-section beam, minimizing the potential deformation of the frame elements produced by the tension field of the steel plate after high-order bucking. The steel plate was sandwiched using either autoclaved lightweight concrete (ALC) or RAC panels. The study analyzed failure modes, load-displacement responses, and characteristic capacities. Test results inferred that BRSPSWs exhibited favorable cyclic behavior, with similar failure modes observed using both ALC and RAC panels. The buckling of steel plates was reduced, and the type of restrained panels had a negligible impact on buckling. Consequently, ALC panels can effectively replace RAC panels. Furthermore, bearing capacities and yield stiffness were primarily determined by the bolted connection forms. A finite element (FE) modeling was developed using ABAQUS software and validated against test results. This FE modeling method successfully simulated failure modes and load-displacement curves. Parametric analyses were conducted and revealed that bearing capacity and yield stiffness positively correlated with steel plate thickness, bolt diameter, and the number of bolts but negatively correlated with the axial compression ratio. In contrast, the panel thickness and span length had a minor impact due to shear deformation in the bolted connection. Based on the test results and parametric studies, an equation for the yield-bearing capacity of BRSPSWs was proposed and verified.
一种框架屈曲约束钢板剪力墙(brspsw)系统已经被设计出来,其特点是钢板连接到框架元件上,可以承受地震或风力等侧向载荷。该系统采用再生骨料混凝土(RAC)来制造混凝土填充和混凝土板,促进生态友好和可持续的建筑材料。两个单跨、两层试件在循环准静力荷载作用下进行了试验。钢板与方钢管混凝土柱和h型梁之间采用四角螺栓连接,最大限度地减少了高阶屈曲后钢板张力场对框架构件产生的潜在变形。钢板夹在蒸压轻质混凝土(ALC)或RAC面板上。研究分析了破坏模式、荷载-位移响应和特征能力。试验结果表明,brspsw具有良好的循环性能,在ALC和RAC面板上观察到相似的破坏模式。钢板屈曲减小,约束板类型对屈曲的影响可以忽略不计。因此,ALC面板可以有效地取代RAC面板。此外,承载能力和屈服刚度主要取决于螺栓连接形式。利用ABAQUS软件建立了有限元模型,并与试验结果进行了对比验证。该有限元建模方法成功地模拟了破坏模式和荷载-位移曲线。参数分析结果表明,承载力和屈服刚度与钢板厚度、螺栓直径和螺栓数量呈正相关,与轴压比呈负相关。相比之下,由于螺栓连接中的剪切变形,面板厚度和跨距长度的影响较小。在试验结果和参数研究的基础上,提出并验证了brspsw的产量承载能力方程。