Article
Engineering, Multidisciplinary
WaiLam Chan, Hailong Chen
Summary: This paper presents a study on modeling material length-scale effect using peridynamics via the second-order material correspondence formulation. The connections of the second-order model with all three types of Mindlin first gradient theory are established. An implicit solution scheme based on the automatic differentiation technique for the construction of the stiffness matrix for linear elastic problems is developed. Numerical examples are used to examine the material stability of the model and verify its capability in modeling material length-scale effect for different length-scale parameters. The wave dispersion analysis shows that the second-order model is stable as long as the material has a nonzero length-scale parameter. In the linear elastic deformation study, great agreements between the model predictions and the analytical solutions for nonzero length-scale parameters are observed.
INTERNATIONAL JOURNAL OF ENGINEERING SCIENCE
(2023)
Article
Chemistry, Physical
Shubiao Guo, Chenchen Tian, Haitao Pan, Xuefeng Tang, Lu Han, Jilai Wang
Summary: Hydrogen fuel cells, known for their high energy density and zero emissions, are widely used worldwide. The metallic bipolar plate, a crucial component of the fuel cell, significantly affects its efficiency. However, the springback behavior of the metallic bipolar plate has a great impact on the forming accuracy in micro-scale sheet metal forming.
Article
Mechanics
Luca Placidi, Dmitry Timofeev, Valerii Maksimov, Emilio Barchiesi, Alessandro Ciallella, Anil Misra, Francesco Dell'Isola
Summary: In this study, a granular micromechanics approach is generalized by introducing an intrinsic 2nd gradient energy storage mechanism and a pantographic connection. Through homogenization, the mechanical behavior of the macro-scale continuum is determined. The inclusion of the pantographic term successfully models and finely tunes the desired thickness of the localization zone, and predicts the complex mechanics of load-path dependency.
INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES
(2022)
Article
Engineering, Mechanical
Jianfeng Zhao, Bo Zhang, Dabiao Liu, Avraam A. Konstantinidis, Guozheng Kang, Xu Zhang
Summary: This study has reformulated Aifantis' SGP model by incorporating a power-law relation for strain-dependent ILS and considering the grain size effect. The results show that the ILS depends on both the sample size and grain size and can be described by the strain hardening exponent.
ACTA MECHANICA SINICA
(2022)
Article
Nanoscience & Nanotechnology
Jin-Xi Chen, Yan Chen, Jun-Peng Liu, Tian-Wei Liu, Lan-Hong Dai
Summary: Micron-sized CoCrNi medium-entropy alloy wires were fabricated for the first time using the Taylor-Ulitovsky method, showing excellent mechanical properties. An anomalous size effect was observed, with the 40 micron-wire exhibiting higher tensile strength and ductility compared to the 100 micron-wire, attributed to the higher density of geometrically necessary dislocation and the formation of multiple deformation twins in the 40 micron-wire.
SCRIPTA MATERIALIA
(2021)
Article
Materials Science, Multidisciplinary
Karthik S., T. Yamashita, Rajagopal A.
Summary: An approach for modeling damage in materials under geometrically nonlinear settings is studied, with a focus on a gradient-enhanced damage method. The proposed method considers the damage variable as an independent variable and computes the fluxes related to the damage gradient. The global Kuhn-Tucker conditions are derived based on the concept of maximum dissipation. The regularization capabilities, accuracy, and efficiency of the proposed damage models are demonstrated through benchmark examples.
MECHANICS OF ADVANCED MATERIALS AND STRUCTURES
(2023)
Article
Engineering, Multidisciplinary
Haidong Lin, Shujuan Hou
Summary: Recently developed cross-scale optimization methods based on traditional homogenization method realize macro equivalent calculation of performances. However, the traditional homogenization method is limited to Cauchy-Boltzmann continuum and cannot explain the size dependence of the optimum result. Therefore, a new cross-scale optimization method is proposed based on Wei-Hutchinson strain gradient theory and non-local homogenization model to consider the size dependence during the optimization process, especially when micro structures are involved. The topological optimization procedure achieves coupled computing using subdomain parameterized coarse meshes, and the entire model can be solved in one iteration, eliminating mesh dependencies and greatly reducing computation time. The results show that the final stiffness of the optimized periodic structure can be significantly increased by considering the strain gradient theory compared to the classic homogenization scheme in the cross-scale optimization process.
COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING
(2023)
Article
Materials Science, Multidisciplinary
Jianfeng Zhao, Baoxi Liu, Yanfei Wang, Yanxiang Liang, Jicheng Li, Xu Zhang
Summary: Gradient nano-grained (GNG) metals exhibit superior strength-ductility synergy compared to homogeneous counterparts. This study develops a dislocation density-based strain gradient plasticity model coupled with a damage model to describe the strain hardening and softening behavior of GNG material. The results predict the tensile response of GNG nickel with varying degrees of grain size gradient, revealing that dispersed strain bands stabilize in the nano-grained surface layer and improve ductility. The method developed in this study enhances the understanding of strength-ductility synergy and optimization of microstructure gradient in GNG materials.
MECHANICS OF MATERIALS
(2023)
Article
Mechanics
Alok Negi, Umed Singh, Sachin Kumar
Summary: The study focuses on the size effect phenomenon in quasi-brittle structures using a micromorphic stress-based localizing gradient damage model. By incorporating evolving anisotropic nonlocal interactions, the model successfully reproduces experimental results with localized damage profiles.
ENGINEERING FRACTURE MECHANICS
(2021)
Article
Mechanics
Y. Xiao, K. L. Nielsen, C. F. Niordson
Summary: Void interaction leading to coalescence is the mechanism for ductile failure under intense shearing. Micro-mechanisms like void collapse, elongation, and rotation in the material have been studied using unit cell simulations, showing that gradient strengthening within the matrix delays loss of load-carrying capacity. The results also indicate that the void mechanism is sensitive to changes in applied load, hardening, and initial void volume fraction at small scales.
EUROPEAN JOURNAL OF MECHANICS A-SOLIDS
(2021)
Article
Engineering, Multidisciplinary
Mohammed Al-Bahrani, Alistair Cree
Summary: Self-sensing nanocomposites based on MWCNTs demonstrate improved electrical and mechanical properties, with increasing concentrations of MWCNTs resulting in enhanced hardness and electrical conductivity. Structural damage at the micro-scale level can lead to changes in electrical resistance and permanent electric damage. A micro-scale model is suggested to predict resistance changes caused by micro-indentation damage.
COMPOSITES PART B-ENGINEERING
(2021)
Article
Engineering, Mechanical
Jun Jin, Ningdong Hu, Hongping Hu
Summary: In this study, the size-dependent band structure of a phononic crystal (PnC) was investigated using nonlocal strain gradient theory (NSGT). Numerical simulations showed that as the lattice constant approached the nano-scale, the size effect became more significant and resulted in a narrower band gap. It was also found that the strength of the size effect was mainly influenced by the thickness of the minimum connector.
INTERNATIONAL JOURNAL OF MECHANICAL SCIENCES
(2022)
Article
Engineering, Mechanical
Li Ding, Chao Yu, Xu Zhang, Zefeng Wen, Qianhua Kan, Guozheng Kang
Summary: Experimental observations indicate that the torsional deformation of copper micro-wires is influenced by sample and grain size. In this study, a higher-order strain gradient constitutive model is developed based on the cyclic plastic J2 flow rule to explain the size effect in torsional deformation of copper micro-wires. A new kinematic hardening evolution rule is proposed considering the coupling effect of sample and grain sizes. Numerical implementation is accomplished using a finite element iterative algorithm, and the proposed model is validated using the finite element software ABAQUS. Simulation results show that the proposed model effectively captures the size-dependent torsional deformation of copper micro-wires. This research lays a solid foundation for the combination of strain gradient plasticity theory and cyclic plasticity constitutive model.
INTERNATIONAL JOURNAL OF MECHANICAL SCIENCES
(2023)
Article
Materials Science, Multidisciplinary
Amer Darvishvand, Asghar Zajkani
Summary: This study investigates a comparative study of lower and higher-order strain gradient plasticity theories regarding size-dependent micromechanically flexural behaviors of crystalline thin plates. The analysis shows a significant dependence of deflections on length scale, plastic work hardening, and other parameters.
METALS AND MATERIALS INTERNATIONAL
(2021)
Article
Chemistry, Analytical
Jishou Piao, Lu Liu, Long Cai, Hyok Chol Ri, Xiangzi Jin, Huaze Sun, Xiangfan Piao, Hai-bo Shang, Xuejun Jin, Qiaosheng Pu, Yong Cai, Zhongping Yao, Donatella Nardiello, Maurizio Quinto, Donghao Li
Summary: This paper introduces a highly accurate size-based microparticle separation technique, in which magnetic nanoparticles are manipulated by an external magnetic field to collide with microparticles for high-accuracy separation. The method has achieved good results in the analysis of cancer cells.
ANALYTICAL CHEMISTRY
(2022)