今日更新：International Journal of Solids and Structures 1 篇，Journal of the Mechanics and Physics of Solids 2 篇，International Journal of Plasticity 1 篇，Thin-Walled Structures 3 篇
International Journal of Solids and Structures
Atomic simulations of crack propagation in Ni-Al binary single crystal superalloy with a central crack
Liu Yang, Huicong Dong, Dayong Wu, Haikun Ma, Zhihao Feng, Peng He, Balaji Narayanaswamy, Baocai You, Qian Wang, Ru Su
doi:10.1016/j.ijsolstr.2024.113006
含中心裂纹Ni-Al二元单晶高温合金裂纹扩展的原子模拟
Nickel (Ni)-based single-crystal superalloys are of great importance in the aircraft industry due to their excellent mechanical properties, and cracks as unavoidable defects may affect the mechanical performances of materials dramatically. In this paper, large scale molecular dynamics (MD) simulations are carried out to understand the deformation mechanisms of Ni-based single crystal with a central crack under tension. Here, the effects of matrixes (γ, γ′ and γ/γ′), strain rates (1 × 109 s−1 ∼ 3 × 109 s−1) and temperatures (300 K∼900 K) on the role of crack propagation are considered. It is observed that dislocations and slip systems in the γ′ model are concentrated near the crack, resulting in the rapid expansion of dislocation, which leads to the fastest crack growth speed and early fracture. While the crack propagation rate of γ and γ/γ′ models are relatively slow, due to the combined action of the Lomer-Cottrell lock and stacking fault tetrahedron structure and Stair-rod dislocation, which hinders crack propagation. In addition, deformation at increased strain rates and/or reduced temperatures, lead to superior yield stress and Young′s modulus for models with a central crack at γ/γ′ interface. On the other hand, high temperature and high strain rate will promote crack propagation in the γ phase, and the higher the strain rate and/or temperature, the faster the crack propagation speed will be. These results will enrich our understanding on the crack propagation and evolution mechanisms in Ni-based single crystal superalloy.
Reconstruction of the local contractility of the cardiac muscle from deficient apparent kinematics
G. Pozzi, D. Ambrosi, S. Pezzuto
doi:10.1016/j.jmps.2024.105793
从表观运动学缺陷重建心肌局部收缩力
Active solids are a large class of materials, including both living soft tissues and artificial matter, that share the ability to undergo strain even in absence of external loads. While in engineered materials the actuation is typically designed a priori, in natural materials it is an unknown of the problem. In such a framework, the identification of inactive regions in active materials is of particular interest. An example of paramount relevance is cardiac mechanics and the assessment of regions of the cardiac muscle with impaired contractility. The impossibility to measure the local active forces directly suggests us to develop a novel methodology exploiting kinematic data from clinical images by a variational approach to reconstruct the local contractility of the cardiac muscle. By finding the stationary points of a suitable cost functional we recover the contractility map of the muscle. Numerical experiments, including severe conditions with added noise to model uncertainties, and data knowledge limited to the boundary, demonstrate the effectiveness of our approach. Unlike other methods, we provide a spatially continuous recovery of the contractility map without compromising the computational efficiency.
Unravelling the relation between free volume gradient and shear band deflection induced extra plasticity in metallic glasses
Haiming Lu, Zhenghao Zhang, Yao Tang, Haofei Zhou
doi:10.1016/j.jmps.2024.105806
揭示了金属玻璃中自由体积梯度与剪切带挠度之间的关系
Previous experiments have revealed that the controllable introduction of structural gradients in metallic glasses (MGs) can endow the materials with extra plasticity due to the gradient-induced deflection of shear bands. However, the relation between the spatial structural gradient and the initiation of shear band deflection remains unclear. The current study has been focused on investigating the relationship between the improved mechanical properties of MGs and structural gradients specified by the distribution of the intrinsic free volume. Molecular dynamics (MD) simulations are firstly performed on homogeneous MG models containing various initial free volume values, showing that the shear band angle increases with decreasing free volume under uniaxial compression, whereas higher shear band angle is observed under uniaxial tension with increasing free volume. Based on the asymmetric behaviors of MGs under compression and tension, a theoretical model is developed to quantitatively characterize the influence of free volume on the mechanical response of MGs, which incorporates a failure criterion based on free volume generation during external loadings. The model can be further utilized to interpret and predict the fracture strain, shear band angle, maximum stress, and fracture surface morphology of gradient structured MGs in both simulations and experiments. The relationship between free volume gradient and shear band deflection induced extra plasticity established in this study provides valuable guidance for the structural design of MGs with enhanced mechanical properties.
Achieving excellent uniform tensile ductility and strength in dislocation-cell-structured high-entropy alloys
Rui Huang, Lingkun Zhang, Abdukadir Amar, Peter K. Liaw, Tongmin Wang, Tingju Li, Yiping Lu
doi:10.1016/j.ijplas.2024.104079
在位错细胞结构高熵合金中实现了优异的均匀拉伸延展性和强度
Body-centered-cubic (BCC) high-entropy alloys (HEAs) encounter significant challenges in obtaining a high uniform tensile ductility (UTD). A dense dislocation-cell (DC) structure is produced in a heterogeneously grained HEA under tensile deformation, resulting from the anchored dislocation motion by grain interior elemental segregation. This fluctuation in elemental concentration is facilitated by thermomechanical processing. The activation of multiple-slip mechanisms, prompted by strain incompatibility among grains of varying sizes, significantly propels this process forward. This novel DC structure simultaneously increased the UTD (by 349.1%) and yield strength (σ0.2, by 29.0%) for a stable BCC HEA. Specifically, the single-phase alloy achieved a record-high UTD of 7.5% and an σ0.2 of > 1,200 MPa, outperforming the counterparts of all the single-phase BCC HEAs. We employed a combination of transmission electron microscopy, in-situ scanning electron microscopy tensile testing coupled with an electron backscatter diffraction technology to investigate underlying strengthening mechanisms and identified that the serious stress concentration as a result of prevalent planar slip caused premature failure and localized strain of common BCC HEAs. At the initial stage of deformation, the DC structure promoted the activation of multiple slip systems and facilitated the extension of a plastic flow across the sample volume, effectively weakening stress concentration and premature failure. The extended plasticity zone and intensified dislocation interactions contributed to the increased UTD and σ0.2. These findings offer valuable inspiration for tailoring alloy properties via microstructure strategies and promoting their adoption in advanced manufacturing.
体心立方（BCC）高熵合金（HEAs）在获得高均匀拉伸延展性（UTD）方面遇到了重大挑战。在拉伸变形条件下，异质晶粒 HEA 中会产生密集的位错胞（DC）结构，这是晶粒内部元素偏析导致的锚定位错运动造成的。热机械加工促进了元素浓度的波动。不同尺寸晶粒之间的应变不相容性导致的多重滑移机制的启动，极大地推动了这一过程。这种新型直流结构同时提高了稳定 BCC HEA 的UTD（349.1%）和屈服强度（σ0.2，29.0%）。具体而言，单相合金的UTD达到了创纪录的7.5%，σ0.2大于1,200兆帕，优于所有单相BCC HEA。我们采用透射电子显微镜、原位扫描电子显微镜拉伸测试和电子反向散射衍射技术相结合的方法来研究其潜在的强化机制，发现由于普遍存在的平面滑移导致严重的应力集中，从而造成普通 BCC HEA 的过早失效和局部应变。在变形的初始阶段，直流结构促进了多重滑移系统的激活，促进了塑性流动在样品体积上的扩展，有效削弱了应力集中和过早失效。塑性区的扩展和位错相互作用的加强导致了UTD和σ0.2的增加。这些发现为通过微结构策略定制合金特性以及促进其在先进制造业中的应用提供了宝贵的启示。
Thin-Walled Structures
Free Vibration analysis of C/SiC blisk based on modified global mode method
Qian Xu, Lei Hou, Lixian Hou, Zhonggang Li, Shuangxing Ren, Mohamed K. Aboudaif, Emad Mahrous Awwad, Nasser A. Saeed
doi:10.1016/j.tws.2024.112285
基于改进全局模态法的C/SiC圆盘自由振动分析
The bladed disk is the core component which is under load in aero-engine, rocket engine and gas turbine. In recent years, the bladed disk has developed towards the direction of integrated bladed disk (blisk) and being applied with ceramic matrix composites. However, there is no accurate semi-analytical dynamic model to describe the dynamic characteristic of ceramic matrix composite blisk. In this paper, a new semi-analytical method, modified global mode method (MGMM) is proposed to model the 2D C/SiC laminated blisk. In proposed method, Chebyshev polynomials series are used to expand the displacements of the blades and disk, constraints between blades and disk is strictly satisfied by multi-modal transformation and integrated into governing equation, and high-order shear deformation theory is combined to establish the dynamic model of the blisk of 2D C/SiC laminated composite material. The proposed method avoids the matrix singular problem appearing in traditional global mode method when modeling of combined structure and makes the system perform dynamic analysis and mode prediction without mode extraction and reconstruction. Then, amplitude frequency response and modal experiment are carried out to verify the correctness and convergence of the proposed method. Finally, under the framework of proposed method, the effects of material parameters and geometric parameters on the modal characteristics of the blisk are analyzed. The results show that compared with the geometric parameters, the material parameters have less influence on the modal characteristics of blisk, additionally, a series of modal steering is observed. The work in this paper can provide theoretical guidance for the dynamic design of composite blisk.
The development of modern aeronautical and aerospace industries has greatly been accelerated by the upgradation of advanced lightweight architecture materials. As a recognized and promising kind, lightweight composite structures amalgamate the benefits of advanced fiber-reinforced composite materials and innovative design concepts for weight reduction and thus have attracted substantial attention from structural engineers and scholars over the past few decades. The primary objective of the present article is to provide an extensive review and analysis of the recent achievement of a pivotal component in modern aeronautical and aerospace architectures: lightweight composite shells. This review delves into various composite grid, grid-stiffened, and sandwich shells with diverse constructions, elucidating their structural design concepts and applicable conditions. The academic discourse focuses on the three relevant key component technologies for developing lightweight composite shells, including manufacturing techniques, mechanical characterization and optimum design methods. Additionally, this article presents a comprehensive review of their applications and potentials in aeronautical and aerospace systems. The existing research gap and contemplates on future directions are discussed. The encountered challenges and possible opportunities for lightweight composite shells are also illuminated.
Compressive properties of aperiodic but ordered cellular materials inspired by Penrose tilings
Ge Qi, Ji-jing Tian, Chen-xi Liu, Yun-long Chen, Song Jiang, Zhi-jie He, Meng Han, Kai-Uwe Schröder, Li Ma
doi:10.1016/j.tws.2024.112287
受彭罗斯瓷砖启发的非周期性有序细胞材料的压缩特性
Various cellular materials have been emerging in the past decades, whose design strategy focuses on the periodic arrangements of a representative unit cell. Recent studies indicate that aperiodic tessellations possess the ability to eliminate the risk of catastrophic global failure. However, extracting the exact relation between each localized microstructural features and macroscopic material properties of stochastic structures is not applicable due to the intrinsic randomness and disorderliness. In an effort to break through this challenge, this paper develops a class of aperiodic but ordered cellular materials (AOCMs) inspired by three types of Penrose tilings. Both finite element simulations and quasi-static compressive experiments are carried out to address the macroscopic mechanical performance and the microscopic mechanisms. The results show that the distinct deformation and failure mechanisms are induced by their different topological configurations, including the architectural shapes and tessellating orientations. The proposed AOCMs possess excellent potentials as load carrying structures and energy absorbers, and the outcomes reported here serve to provide a new perspective on the development of advanced cellular materials.
