Article
Engineering, Mechanical
X. X. Zhang, P. -p. Bauer, A. Lutz, C. Wielenberg, F. Palm, W. M. Gan, E. Maawad
Summary: Understanding and controlling the performance of additively manufactured aluminum alloys with scandium and zirconium elements requires knowledge of their microplasticity and macroplasticity behavior, which has received little attention. This study uses in-situ synchrotron X-ray diffraction and full-field crystal plasticity modeling to quantitatively assess the transitions from elasticity to microplasticity and then to macroplasticity, and analyze the development of the initial microstructure. The findings provide deeper insights into controlling the performance of these alloys and pave the way for predicting the behavior of various metallic materials.
INTERNATIONAL JOURNAL OF PLASTICITY
(2023)
Article
Mechanics
Seung Tae Choi, Nghia Trong Mai, Vinh Phu Nguyen
Summary: In this study, the effect of nanoscale roughness of a coating layer on dislocation nucleation and surface microplasticity evolution was investigated. The results show that using a stepped coating can influence the evolution of dislocation nucleation and surface microplasticity, with potential implications for nanoscale thin film engineering.
EUROPEAN JOURNAL OF MECHANICS A-SOLIDS
(2021)
Article
Engineering, Mechanical
Songjiang Lu, Ni Ao, Qianhua Kan, Shengchuan Wu, Guozheng Kang, Xu Zhang
Summary: A three-dimensional discrete dislocation dynamics (DDD) method was used to study the effect of residual stress on the stress-strain response of gradient nano-grained (GNG) metals. The distribution of residual stress was found to have a significant influence on the tensile stress-strain curve. The presence of both compressive and tensile residual stress in GNG samples resulted in a lower initial flow stress but a higher ultimate flow stress compared to samples without residual stress.
INTERNATIONAL JOURNAL OF MECHANICAL SCIENCES
(2023)
Article
Materials Science, Multidisciplinary
Feng Yang, Kun-Mao Li, Xing-Jun Liu, Hong Sun, Cui-Ping Wang
Summary: The vacuum electromagnetic induction nitriding technology was used to prepare a gradient nitrided layer on the surface of a Ti6Al4V alloy. The study found that there were numerous high-density stacking faults and basal stacking faults on the alloy surface, causing lattice distortion. Additionally, the hardness and compressive stress of the nitrided layer also changed.
Article
Materials Science, Multidisciplinary
Q. Rizzardi, P. M. Derlet, R. Maass
Summary: In this study, we demonstrate the gradual transition from scale-free powerlaw scaling to exponential and scale-dependent distribution by introducing various microstructural features in an Al-Cu binary alloy system. The statistics of intermittent microplasticity exhibit fat-tailed contributions as long as the obstacles to dislocation motion can be sheared. The introduction of incoherent precipitates leads to a complete transition in the statistical behavior, suggesting that microstructural length scales and obstacle pinning-strengths are of secondary importance.
PHYSICAL REVIEW MATERIALS
(2022)
Article
Engineering, Mechanical
Songjiang Lu, Jianfeng Zhao, Minsheng Huang, Zhenhuan Li, Guozheng Kang, Xu Zhang
Summary: This paper investigates the mechanical properties and deformation mechanisms of gradient nano-grained (GNG) aluminum using three-dimensional multiscale discrete dislocation dynamics (DDD). The results show that GNG samples exhibit higher yield stress and strain hardening compared to the rule of mixtures, indicating a synergetic strengthening effect. The study also establishes a theoretical model that successfully describes the Bauschinger effect in GNG and uniform nano-grained (UNG) samples based on the evolution of dislocations during unloading.
INTERNATIONAL JOURNAL OF PLASTICITY
(2022)
Article
Chemistry, Multidisciplinary
Ozgur Aslan, Emin Bayraktar
Summary: This work presents analytical solutions for 2D model problems to demonstrate the unique plastic fields generated by the micromorphic approach for gradient plasticity. It also analyzes the constitutive behavior of the material undergoing plastic deformation. Additionally, the matching of analytical solutions with numerical results is demonstrated.
APPLIED SCIENCES-BASEL
(2021)
Article
Chemistry, Physical
Fei Shuang, Katerina E. Aifantis
Summary: This study investigates the interaction mechanisms between graphene nanosheets (GNS) and dislocations using Molecular Dynamics (MD) simulations. The results show that the shear strength of the metal/GNS interface and the bending stiffness of GNS play significant roles in blocking dislocation transmission. The mechanical interface energy is proposed as a unified measure for capturing and tuning the strength of various interfaces.
APPLIED SURFACE SCIENCE
(2021)
Article
Materials Science, Multidisciplinary
Guolong Liu, Decheng Wan, Yunli Feng, Tao Li, Fucheng Zhang
Summary: The optimization of the synergy between the strength and ductility of ordinary medium-carbon steel was studied, and a multiscale lamellar structure was formed through pretreatment and warm rolling. The analysis of subgrain boundaries strengthening revealed the additional strengthening mainly derived from specific subgrain boundaries. The formation of ultrafine shear bands during warm rolling induced a gradient change in the Schmid factor and led to enhanced uniform elongation during plastic deformation.
METALLURGICAL AND MATERIALS TRANSACTIONS B-PROCESS METALLURGY AND MATERIALS PROCESSING SCIENCE
(2023)
Article
Physics, Multidisciplinary
Yang Xiang, Yuying Yu, Yinan Cui, Jianbo Hu
Summary: This study investigates the dynamic yield behavior of single-crystal tungsten using discrete dislocation dynamics (DDD) and finds that the initial dislocation source length and density affect the initial yield and flow stress of tungsten. With increasing dislocation density and length, the plastic yield mechanism shifts from dislocation source activation to dislocation-dislocation interactions, resulting in a decrease in initial yield stress and an increase in flow stress.
Article
Engineering, Mechanical
Xiangru Guo, Chaoyang Sun, Chunhui Wang, Jun Jiang, M. W. Fu
Summary: Deformation twins play a crucial role in the plastic deformation of TWIP steels by affecting dislocation movement. A proposed dislocation-TB interaction model helps understand the strengthening effects of twins on macro deformation behaviors and dislocation reactions in TWIP steel micropillar. This research enhances the knowledge of dislocation-TB interaction mechanisms in plastic deformation of TWIP steels.
INTERNATIONAL JOURNAL OF PLASTICITY
(2021)
Article
Chemistry, Multidisciplinary
Sheng Qian, Yifeng Ni, Yi Gong, Fan Yang, Qi Tong
Summary: This study finds that using a gradient nanograined structure can enhance the damping capacity of metals. The GB orientations in the gradient grains can facilitate GB sliding, thus increasing the damping capacity. This structure can also maintain the level of material strength and achieve a synergy of strength, ductility, and damping.
Article
Materials Science, Multidisciplinary
Xuesong Han
Summary: Nano-polycrystalline materials are difficult to study experimentally due to the difficulty in preparation. However, molecular dynamics has proven to be effective for understanding the mechanical response of these materials. The results show that partial dislocation activity occurs in larger nanocrystalline materials. Transverse deformation perpendicular to the feeding direction leads to side flow. Side flow has a different stress distribution than the substrate, indicating its unique physical properties. Plastic deformation eliminates the different mechanical response caused by crystal orientation at the atomic scale. Discontinuous deformation is a characteristic of polycrystal machining.
APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING
(2022)
Article
Materials Science, Multidisciplinary
Aleksandr Korchuganov, Dmitrij Kryzhevich, Konstantin Zolnikov
Summary: This study investigates the atomic mechanisms of phase transformations, plasticity features, and mechanical properties of two-phase Fe95Ni5 samples with a gradient nanograined structure under uniaxial deformation and shear using molecular dynamics simulations. It is found that uniaxial loading or shear causes the bcc-fcc phase transformation in the lamellae, which is initiated at the junction of lamellae and grain boundaries. Deformation-induced phase transformations occur at the front of bands propagating from grain boundaries. Grains larger than 15 nm exhibit fragmentation due to the collision of different orientated fcc lattices. The study also reveals that the atomic volume increases abruptly during the bcc-fcc phase transformation, and the yield stress of the sample is significantly affected by the volume fraction and spatial distribution of the bcc phase.
Article
Materials Science, Multidisciplinary
Ziqiang Wang, Miaosen Yu, Xuehao Long, Chen Yang, Ning Gao, Zhongwen Yao, Xuelin Wang
Summary: In this study, molecular dynamics simulations were used to investigate the interaction mechanisms between dislocations and radiation defects in irradiated metals. Three new kinetic mechanisms were proposed, and it was found that the specific characteristics of the dislocation loops determine the dominant mechanism for the interaction with dislocation lines. The results also showed that the critical stress for the dislocation to cross the loop varied due to the interactions involved in these new mechanisms.
RESULTS IN PHYSICS
(2022)
Article
Mechanics
Peilin Fu, Jizhong Zhao, Xu Zhang, Guozheng Kang, Ping Wang, Qianhua Kan
Summary: A multi-layered model for thermo-elastic rolling/sliding contact with FG coating was established, showing that adjusting material property gradients can significantly improve the elastic shakedown limit.
COMPOSITE STRUCTURES
(2022)
Article
Engineering, Mechanical
Jianfeng Zhao, Xinlei Pan, Jian Li, Zhiyong Huang, Qianhua Kan, Guozheng Kang, Liucheng Zhou, Xu Zhang
Summary: Systematic characterization of microstructure, mechanical testing and constitutive modeling were conducted to investigate the effects of laser shock peening (LSP) treatment on the tensile properties of Ti-6Al-4 V alloy. The study revealed that LSP treatment resulted in grain refinement and introduction of compressive residual stress, leading to changes in the material's elastic-plastic behavior. The established deformation mechanism-based model showed that surface grain refinement enhanced initial yielding and strain hardening, while residual stress had a weakening effect on initial yielding but little influence on strain hardening behavior.
INTERNATIONAL JOURNAL OF MECHANICAL SCIENCES
(2022)
Article
Materials Science, Multidisciplinary
Dan Wu, Siyao Shuang, Yanxiang Liang, Xiaobao Tian, Guozheng Kang, Xu Zhang
Summary: The interaction mechanisms between dislocations and twin boundaries in high-entropy alloys (HEAs) are studied, and differences between HEAs and pure Ni are observed, possibly related to the statistical fluctuation of chemical ordering.
COMPUTATIONAL MATERIALS SCIENCE
(2022)
Article
Engineering, Mechanical
Qianhua Kan, Jizhong Zhao, Xiang Xu, Ziyi Wang, Xu Zhang, Ping Wang
Summary: The temperature-dependent cyclic plastic deformation of U75VG steel was investigated through experimental studies, revealing the cyclic softening, cyclic hardening, and cyclic softening behavior at different temperatures. The steel also exhibited significant ratcheting behavior, which was influenced by the applied mean stress and stress amplitude. A temperature-dependent cyclic plastic model was constructed to account for the influence of dynamic strain aging on the cyclic plastic deformation.
ENGINEERING FAILURE ANALYSIS
(2022)
Article
Mechanics
Xiaotao Li, Xu Zhang, Wei Feng, Qingyuan Wang
Summary: The effect of micro-defects on fracture toughness and path is predicted using a machine learning method. Neural network models are used to approximate the relationship between micro-defect parameters and fracture parameters. The results show that this method has a strong fitting ability and can be used for toughening design and predicting fracture behaviors of brittle materials.
ENGINEERING FRACTURE MECHANICS
(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
Engineering, Mechanical
Songjiang Lu, Jianfeng Zhao, Minsheng Huang, Zhenhuan Li, Guozheng Kang, Xu Zhang
Summary: This paper investigates the mechanical properties and deformation mechanisms of gradient nano-grained (GNG) aluminum using three-dimensional multiscale discrete dislocation dynamics (DDD). The results show that GNG samples exhibit higher yield stress and strain hardening compared to the rule of mixtures, indicating a synergetic strengthening effect. The study also establishes a theoretical model that successfully describes the Bauschinger effect in GNG and uniform nano-grained (UNG) samples based on the evolution of dislocations during unloading.
INTERNATIONAL JOURNAL OF PLASTICITY
(2022)
Article
Engineering, Aerospace
Yuhang Duan, Bo Zhang, Xu Zhang, Limin Zhang, Huoming Shen
Summary: In this study, the elastic buckling of skew thick microplates under combined in-plane shear and compressive loading is investigated within the framework of modified couple stress theory. A two-variable refined shear deformation theory is used to describe the displacement field of the microplates, resulting in a simple and universal elastic buckling model. An analytical buckling solution is challenging to obtain, so a C1-type four-node 32-DOF differential quadrature finite element is developed. Parametric studies are conducted to analyze the effects of different geometrical dimensions, boundary edges, in-plane loadings, and material length scale parameters. The results show that the buckling modes of skew microplates are influenced by the combination of size effects and skew angle.
AEROSPACE SCIENCE AND TECHNOLOGY
(2023)
Article
Materials Science, Multidisciplinary
Siyao Shuang, Yanxiang Liang, Chao Yu, Qianhua Kan, Guozheng Kang, Xu Zhang
Summary: This study investigates the effect of loading orientation on the plasticity of nano-laminated DP-HEA materials using molecular dynamics simulations. The results show that a switch from strengthening to softening and back to strengthening can be achieved by adjusting the inclination angles of the nanolaminates. Lateral slip, phase transformation, and the formation of shear bands are the main mechanisms for plastic deformation under different inclination angles.
MODELLING AND SIMULATION IN MATERIALS SCIENCE AND ENGINEERING
(2023)
Article
Mechanics
Peilin Fu, Jizhong Zhao, Xu Zhang, Hongchen Miao, Zefeng Wen, Guozheng Kang, Qianhua Kan
Summary: A three-dimensional tractive rolling contact analysis is conducted on functionally graded coating-substrate systems. The surface frictional anisotropy is described by Coulomb's orthotropic friction law, and the discontinuous transmissions of stress and displacement at the coating-substrate interface are modeled by a coupled dislocation-like and force-like interfacial imperfection. A multi-layered model is used to simulate the coating with arbitrarily varying thermo-elastic properties, and numerical methods are employed to obtain the thermo-elastic responses of tractive rolling contact. The results show the effect of friction coefficients and interfacial imperfections on traction and stress distribution.
COMPOSITE STRUCTURES
(2023)
Article
Engineering, Mechanical
Xu Zhang, Yang Gui, Minjie Lai, Xiaochong Lu, Ji Gu, Feng Wang, Tao Yang, Zhangwei Wang, Min Song
Summary: The microstructures, mechanical properties, and deformation substructures of gradient Mo0.3NiCoCr medium-entropy alloys with very coarse grain size created by pre-torsion have been investigated. The strength of these alloys increases with the increase of torsion angle, while the tensile elongation remains the same, suggesting the enhanced strength-ductility synergy. The combination of experimental characterization and theoretical modeling enables to clarify the underlying strengthening and strain hardening mechanisms, providing guidance for optimizing the mechanical performance of structural materials via tuning the design of gradient structure.
INTERNATIONAL JOURNAL OF PLASTICITY
(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
Polymer Science
Jian Li, Zhihong Liang, Kaijuan Chen, Xu Zhang, Guozheng Kang, Qianhua Kan
Summary: Experimental investigations on the mechanical deformations of thermo-induced shape memory polymers at different strain rates reveal the influence of loading history conditions on the glass transition temperature and shape memory effect. Temperature hysteresis is observed in stress freezing and strain recovery stages due to varied temperature rate. A logarithmic rate-based viscoelastic-viscoplastic model is established to simulate the rate-dependent mechanical deformation and shape memory effect, which is validated by comparing with experimental results.
Article
Engineering, Mechanical
Songjiang Lu, Ni Ao, Qianhua Kan, Shengchuan Wu, Guozheng Kang, Xu Zhang
Summary: A three-dimensional discrete dislocation dynamics (DDD) method was used to study the effect of residual stress on the stress-strain response of gradient nano-grained (GNG) metals. The distribution of residual stress was found to have a significant influence on the tensile stress-strain curve. The presence of both compressive and tensile residual stress in GNG samples resulted in a lower initial flow stress but a higher ultimate flow stress compared to samples without residual stress.
INTERNATIONAL JOURNAL OF MECHANICAL SCIENCES
(2023)
Article
Materials Science, Multidisciplinary
Siyao Shuang, Yanxiang Liang, Xie Zhang, Fupin Yuan, Guozheng Kang, Xu Zhang
Summary: High-entropy alloys (HEAs) are considered ideal solid solutions of multi-principal elements, but recent studies have shown that complex interactions among constituents can lead to local chemical ordering at low temperatures. In this study, the impact of chemical ordering on the deformation behaviors of CuNiCoFe HEA was investigated through molecular dynamics simulations. The results reveal that chemical ordering leads to a softening in mechanical properties and a decrease in ultimate strength due to the nucleation of dislocations.
MODELLING AND SIMULATION IN MATERIALS SCIENCE AND ENGINEERING
(2023)