今日更新：Journal of the Mechanics and Physics of Solids 3 篇，International Journal of Plasticity 1 篇，Thin-Walled Structures 2 篇
Journal of the Mechanics and Physics of Solids
A finite geometry, inertia assisted coarsening-to-complexity transition in homogeneous frictional systems
Thibault Roch, Efim A. Brener, Jean-François Molinari, Eran Bouchbinder
doi:10.1016/j.jmps.2024.105706
有限几何，惯性辅助粗糙到复杂的过渡均质摩擦系统
The emergence of statistical complexity in frictional systems (where nonlinearity and dissipation are confined to an interface), manifested in broad distributions of various observables, is not yet understood. We study this problem in velocity-driven, homogeneous (no quenched disorder) unstable frictional systems of height H. The latter are described at the continuum scale within a realistic rate-and-state friction interfacial constitutive framework, where elasto-frictional instabilities emerge from rate-weakening friction. For large H, such frictional systems were recently shown to undergo continuous coarsening until settling into a spatially periodic traveling solution. We show that when the system’s height-to-length ratio becomes small — characteristic of various engineering and geophysical systems —, coarsening is less effective and the periodic solution is dynamically avoided. Instead, and consistently with previous reports, the system settles into a stochastic, statistically stationary state. The latter features slip bursts, whose slip rate is larger than the driving velocity, which are non-trivially distributed. The slip bursts are classified into two types: predominantly non-propagating, accompanied by small total slip and propagating, accompanied by large total slip. The statistical distributions emerge from dynamically self-generated heterogeneity, where both the non-equilibrium history of the interface and wave reflections from finite boundaries, mediated by material inertia, play central roles. Specifically, the dynamics and statistics of large bursts reveal a timescale ∼H/cs, where cs is the shear wave-speed. We discuss the robustness of our findings against variations of the frictional parameters, most notably affecting the magnitude of frictional rate-weakening, as well as against different interfacial state evolution laws. Finally, we demonstrate a reverse transition in which statistical complexity disappears in favor of the spatially periodic traveling solution. Overall, our results elucidate how relatively simple physical ingredients can give rise to the emergence of slip complexity.
Configuration space of helical chiral self-assembly of micro/nano-fibers
Juntao Chen, Langquan Shui, Tao Ding, Ze Liu
doi:10.1016/j.jmps.2024.105708
微/纳米纤维螺旋手性自组装的构型空间
As undertaking various key functions, helical chiral structures are widely presented in nature. Herein, we develop a general theoretical framework to guide the formation of helical chiral structures through self-assembly of micro/nano-fibers driven by adhesion. By analyzing the spiral contact geometric characteristics of multiple fibers and extending the JKR theory, an analytical model for adhesive contact between helical interfaces is proposed. Further, the complete configuration space of self-assembled fibers depending on the adhesion work, elastic modulus, aspect ratio, and initial helix angle is theoretically analyzed. A diversity of helical configurations that far beyond existing experimental findings are predicted, which stems from the existence of multiple energy minimum points on the configuration-energy map. This work reveals the mechanism of adhesion-driven helical chiral structures, and provides theoretical foundation for guiding high-efficient fabrication of helical chiral structures through self-assembly method, which could promote the wide application of chiral structures in fields such as optics, catalysis and drug screening.
Mechanical characterization and constitutive modeling of additively-manufactured polymeric materials and lattice structures
Xiao Guo, Erdong Wang, Hang Yang, Wei Zhai
doi:10.1016/j.jmps.2024.105711
增材制造高分子材料和晶格结构的力学表征和本构建模
Additively manufactured polymeric lattice structures are being extensively studied, primarily because their mechanical properties can be tailored by controlling the unit cell geometry, giving them higher designability than stochastic materials. However, the inherent layer-wise additive manufacturing process affects the base material properties related to the printing direction, which in turn affects the macroscopic responses of the entire lattice materials. A robust understanding and modeling of lattice structures' elastic and plastic yield behavior in a homogenized approach are essential to enhance their design and analysis efficiency in engineering applications. In pursuit of this goal, a unified printing angle-dependent constitutive model of base materials is proposed in line with the tensile experimental data. The elastic material properties (elastic modulus, shear modulus, and Poisson's ratio), obtained through numerical simulations of one unit-cell with periodic boundary conditions, exhibit anisotropic properties, with the degree of anisotropy determined by the angle of the constituent members and base materials. Furthermore, both experimental and numerical results of lattices demonstrate anisotropic mechanical response under horizontal and vertical compression. Virtual multiaxial experiments are conducted through multi-cell numerical simulations, enabling the determination of initial yielding points of two different lattice structures (Kelvin and Simple cubic and body-centered cubic hybrid structures) under various loading conditions using a dissipation energy-based criterion. Overall, the multiaxial yield surface of the investigated lattices under various stress states, except for the isotropic principal stress plane, can be properly depicted by the Extended-Hill anisotropic yield criterion.
Tri-functional co-nanoprecipitates enhanced cryogenic ductility by inducing structural heterogeneity and refining nano-twins in a low-stacking-fault-energy 17Mn steel
Xiaoli Chu, Yu Li, Chun Xu, Wei Li, Bin Fu, Xiaoshuai Jia
doi:10.1016/j.ijplas.2024.104014
三官能团共纳米沉淀物通过诱导组织非均质性和细化纳米孪晶来增强低叠错能17Mn钢的低温延展性
In this study, an innovative tri-functional co-nanoprecipitation strategy was employed to enhance the mechanical properties of a low stacking-fault energy (SFE) 17Mn steel for cryogenic applications. By combining severe cold deformation and subsequent annealing, a hierarchical structure emerged, featuring (Ti, Nb)C carbide (∼10 nm) and Cu-rich intermetallic (∼2 nm) in the austenitic matrix with heterogeneous grain size distributions. The co-precipitation (CP) sample exhibited superior performance compared to single-precipitation (SP) steel, with a yield strength of ∼1150 MPa, tensile elongation of ∼44.8%, and an impact toughness of ∼110 J at liquid nitrogen temperature (LNT), even surpassing the base-17Mn steel. The CP-17Mn samples displayed a higher density and thinner nano-twins at larger strains, leading to a rapid increase in geometrically necessary dislocations (GNDs). The detrimental martensitic transformation was effectively suppressed during both tensile and impact tests. The observed inverse strength-ductility and strength-toughness trade-off can be attributed to the tri-functional co-precipitates’ roles: they provide disperse strengthening, induce structural heterogeneity, and act as effective barriers for twin thickening. The large-sized (Ti, Nb)C carbides facilitate grain refinement and pin boundary migration, while the smaller Cu-rich intermetallic inhibits the growth and thickening of nano-twins, preventing further dislocation movement due to their strong stress fields at the twin-precipitate interactions. This novel mechanism paves the way for developing higher-performance steels with fine and dense nano-twins at cryogenic conditions.
Exact three-dimensional elasticity analysis for buckling of composite laminated plates resting on viscoelastic foundation
Meisam Kheradpisheh, Mehdi Hojjati
doi:10.1016/j.tws.2024.112060
粘弹性基础上复合材料层合板屈曲的精确三维弹性分析
This paper aims to present novel exact solutions for the buckling of a laminated plate resting on the viscoelastic foundation with both normal and shear viscoelastic layers. The governing equations of plate buckling are derived using three-dimensional elasticity theory and state-space formulation. The normal and shear layers of the viscoelastic foundations are modeled using the generalized Maxwell model to represent both the elastic and viscose properties of the foundation. To couple the viscoelastic foundation equation with the buckling equation, Boltzmann’s superposition principle along with the Laplace transform is utilized. Then, the effects of geometry, relaxation modulus of normal and shear layers, viscosity, and time are investigated on the buckling load. The results reveal that the higher viscosity coefficient leads to a slower rate of change in the buckling loads. In addition, the viscoelastic properties have a significant impact on the buckling behavior of the plate. In this regard, the results show that instead of the expected second mode at a constant aspect ratio, the plate experiences the first mode as time passes. The computed results also show that there is a critical threshold. When the foundation stiffness exceeds this threshold, the conventional method of reducing the aspect ratio to prevent buckling not only proves ineffective in reducing the probability of buckling but also, in fact, leads to an increase in buckling occurrences. In addition to the analytical investigation, a finite element (FE) analysis is carried out to study the buckling response of the composite plate. The finite element results also show a reasonably good agreement with those of the analytical method.
Eccentric compression behavior of L-shaped column fabricated by thin-walled square steel tubes based on self-drilling screw connections
Xiaodun Wang, Jincheng Jiang, Yang Liu, Zhihua Chen
doi:10.1016/j.tws.2024.112063
基于自钻螺纹连接的薄壁方钢管l形柱偏心受压特性
In this study, a new L-shaped column fabricated by thin-walled square steel tubes (LFTST columns) based on self-drilling screw connections is proposed. The LFTST columns consisted of square steel tubes, U-shaped parts, angle parts, gusset plates, and self-drilling screw connections. LFTST columns possess several advantages including easy transportation, rapid assembly, and eco-friendliness. Consequently, they are suitable for low-rise buildings, such as village-building, low-rise dormitories, and low-rise office buildings. However, the compression behavior of LFTST columns remains silent. Five full-scale LFTST column specimens were subjected to eccentric compression tests. The variables under consideration included eccentricity (with values of 0mm, 40mm, and 80mm), thickness (2mm and 4mm), and the number of gusset plates (0, 1, and 3). The failure modes, bearing capacity, load-displacement response, and strain development of the LFTST specimens were obtained. Subsequently, finite element (FE) models of LFTST columns were established and used to analyze the eccentric compression behavior of LFTST columns. The FE modeling results agreed well with the experimental results. A detailed parameter analysis was conducted to evaluate the effects of various factors. These factors included the thickness of the plates (2mm, 3mm, and 4mm), the width of the gusset plates (100mm, 150mm, and 200mm), limb spacing values (0mm, 150mm, and 300mm), and eccentricity (0mm, 20mm, 40mm, 60mm, and 80mm). In addition, the calculation formula for estimating the ultimate bearing capacity of the LFTST columns was derived employing the double coefficient product method. The proposed formula was validated by experimental and FE results.
