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
International Journal of Solids and Structures
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.
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.
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.
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.
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.