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Independent dislocation space model for synchronous improvement of strength and plasticity in fcc metals 认领 引用 被引量：2
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作者 Rui Liu Keqiang Li +3 位作者 Zhenjun Zhang Zhan Qu Peng Zhang Zhefeng Zhang 《Journal of Materials Science & Technology》 SCIE EI CAS CSCD 2025年第21期239-244,共6页
Strength and plasticity of metallic structural materials are the fundamental indicators of the service reliability[1].However,as is well known,a general trade-offrelationship exists between strength and plasticity of ... Strength and plasticity of metallic structural materials are the fundamental indicators of the service reliability[1].However,as is well known,a general trade-offrelationship exists between strength and plasticity of metallic materials,making it difficult to improve both of them synchronously[2].At present,only few of the successful cases[3-8],achieved via nano-particles[7],heterogeneous microstructures[8],etc.are mostly limited to some specific materials or processes. 展开更多
关键词 metallic materialsmaking nanoparticles strength heterogeneous microstructures trade off strength plasticity plasticity metallic structural materials
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Micro-bending of metallic crystalline foils by non-local dislocation density based crystal plasticity finite element model 认领 引用 被引量：7
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作者 章海明 董湘怀 +1 位作者 王倩 李河宗 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2013年第11期3362-3371,共10页
A non-local dislocation density based crystal plasticity model, which takes account of the microstrncture inhomogeneity, was used to investigate the micro-bending of metallic crystalline foils. In this model, both sta... A non-local dislocation density based crystal plasticity model, which takes account of the microstrncture inhomogeneity, was used to investigate the micro-bending of metallic crystalline foils. In this model, both statistically stored dislocations （SSDs） and geometrically necessary dislocations （GNDs） are taken as the internal state variables. The strain gradient hardening in micro-bending of single-grained metal foils was predicted by evolution of GNDs. The predicted results were compared with the micro-hardness distribution of the previous micro-bending experiments of CuZn37 a-brass foils with coarse grains and fine grains. Comparison of the simulated dislocation densities distribution of SSDs and GNDs with the experimental results shows that different micro-hardness distribution patterns of the coarse and fine grain foils can be attributed to the corresponding SSDs and GNDs distributions. The present model provides a physical insight into the deformation mechanism and dislocation densities evolution of the micro-bending process. 展开更多
关键词 crystal plasticity micro-bending statistically stored dislocations geometrically necessary dislocations
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Investigation of non-Schmid effects in dual-phase steels using a dislocation density-based crystal plasticity model 认领 引用 被引量：1
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作者 Jianchang Zhu Mohamed Ben Bettaieb +2 位作者 Zhenhuan Li Farid Abed-Meraim Minsheng Huang 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 2025年第11期101-120,共20页
Non-Schmid(NS)effects in body-centered cubic(BCC)single-phase metals have received special attention in recent years.However,a deep understanding of these effects in the BCC phase of dual-phase(DP)steels has not yet b... Non-Schmid(NS)effects in body-centered cubic(BCC)single-phase metals have received special attention in recent years.However,a deep understanding of these effects in the BCC phase of dual-phase(DP)steels has not yet been reached.This study explores the NS effects in ferrite-martensite DP steels,where the ferrite phase has a BCC crystallographic structure and exhibits NS effects.The influences of NS stress components on the mechanical response of DP steels are studied,including stress/strain partitioning,plastic flow,and yield surface.To this end,the mechanical behavior of the two phases is described by dislocation density-based crystal plasticity constitutive models,with the NS effect only incorporated into the ferrite phase modeling.The NS stress contribution is revealed for two types of microstructures commonly observed in DP steels:equiaxed phases with random grain orientations,and elongated phases with preferred grain orientations.Our results show that,in the case of a microstructure with equiaxed phases,the normal NS stress components play significant roles in tension-compression asymmetry.By contrast,in microstructures with elongated phases,a combined influence of crystallographic texture and NS effect is evident.These findings advance our knowledge of the intricate interplay between microstructural features and NS effects and help to elucidate the mechanisms underlying anisotropic-asymmetric plastic behavior of DP steels. 展开更多
关键词 DP steels Non-Schmid effects Crystal plasticity modeling Tension-compression asymmetry
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CONSTRUCTION OF QUANTUM FIELD THEORY OF DISLOCATIONS BASED ON THE NON-RIEMANNIANPLASTICITY 认领 引用
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作者 T.Hasebe Y.Imaida 《Acta Metallurgica Sinica(English Letters)》 EI CAS 1998年第6期405-411,共7页
A new microscopic approach was proposed, which bridges the order gap between the dislocation theory and the crystalline plasticity based on the quantum field theory of dislocations. The Ginzburg-Landau equation was de... A new microscopic approach was proposed, which bridges the order gap between the dislocation theory and the crystalline plasticity based on the quantum field theory of dislocations. The Ginzburg-Landau equation was derived rigorously from the quantized Hamiltonian for a crystal body containing a large number of dislocations, which gives the reaction-diffusion (RD) type differential equations. The RD equation describes periodic patterning shown in PSBs, etc.. relationship between the proposed theory and the concepts appeared in the non-Riemannian plasticity was extensively discussed by introducing the gauge field of dislocations. (Edited author abstract) 15 Refs. 展开更多
关键词 crystalline plasticity field theory Non-Riemannian plasticity,dislocation theory gauge field
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Shedding new light on the dislocation-mediated plasticity in wurtzite ZnO single crystals by photoindentation 认领 引用
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作者 Yan Li Xufei Fang +8 位作者 Eita Tochigi Yu Oshima Sena Hoshino Takazumi Tanaka Hiroto Oguri Shigenobu Ogata Yuichi Ikuhara Katsuyuki Matsunaga Atsutomo Nakamura 《Journal of Materials Science & Technology》 SCIE EI CAS CSCD 2023年第25期206-216,共11页
Dislocation-mediated plasticity in inorganic semiconductors and oxides has attracted increasing research interest because of the promising mechanical and functional properties tuned by dislocations.In this study,we in... Dislocation-mediated plasticity in inorganic semiconductors and oxides has attracted increasing research interest because of the promising mechanical and functional properties tuned by dislocations.In this study,we investigated the effects of light illumination on the dislocation-mediated plasticity in hexagonal wurtzite ZnO,a representative third-generation semiconductor material.A(0001)45o off sample was specially designed to preferentially activate the basal slip on(0001)plane.Three types of nanoindentation tests were performed under four different light conditions(550 nm,334 nm,405 nm,and darkness),including low-load(60μN)pop-in tests,high-load(500μN)nanoindentation tests,and nanoindentation creep tests.The maximum shear stresses at pop-in were found to approximate the theoretical shear strength regardless of the light conditions.The activation volume at pop-ins was calculated to be larger in light than in darkness.Cross-sectional transmission electron microscope images taken from beneath the indentation imprints showed that all indentation-induced dislocations were located beneath the indentation imprint in a thin-plate shape along one basal slip plane.These indentation-induced dislocations could spread much deeper in darkness than in light,revealing the suppressive effect of light on dislocation behavior.An analytical model was adopted to estimate the elastoplastic stress field beneath the indenter.It was found that dislocation glide ceased at a higher stress level in light,indicating the increase in the Peierls barrier under light illumination.Furthermore,nanoindentation creep tests showed the suppression of both indentation depth and creep rate by light.Nanoindentation creep also yielded a larger activation volume in light than in darkness. 展开更多
关键词 Photoindentation Compound semiconductors Oxides Crystal plasticity Dislocations
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Plasticity and Interfacial Dislocation Mechanisms in Epitaxial and Polycrystalline Al Films Constrained by Substrates 认领 引用
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作者 G.Dehm B.J.Inkson 《Journal of Materials Science & Technology》 SCIE EI CAS 2002年第2期113-117,共5页
Stresses in epitaxial and textured Al films were determined by substrate-curvature measurements. It was found that in both cases the flow stresses increase with decreasing film thickness. The flow stresses in the epit... Stresses in epitaxial and textured Al films were determined by substrate-curvature measurements. It was found that in both cases the flow stresses increase with decreasing film thickness. The flow stresses in the epitaxial Al films are in agreement with a dislocation-based model, while the same model strongly underestimates the flow stresses of textured Al films. In-situ transmission electron microscopy studies indicate that dislocations channeling through epitaxial Al films on single-crystalline (0001) α-AI2O3 substrates frequently deposit dislocation segments adjacent to the interface. Furthermore, the AI/α-AI2O3 interface acted as a dislocation source. In this case, the interface is between two crystalline lattices. In contrast, the interface of textured Al films on oxidized silicon substrates is between the crystalline Al and the amorphous SiOx interlayer. It is speculated that the different nature of the interfaces changes dislocation mechanisms and thus influences the flow stresses. 展开更多
关键词 Thin film Plasticity Dislocation Interface
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A CONSTITUTIVE MODEL FOR CREEP-PLASTICITY INTERACTION BASED ON DISLOCATION DYNAMICS 认领 引用
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作者 钱正芳 段祝平 范镜泓 《Acta Mechanica Sinica》 SCIE EI CAS 1993年第3期261-268,共8页
A glide-plus-climb micromechanism of dislocation evolution with the formation of subgrains is pro- posed for modelling of the creep-plasticity interaction (CPI). The long-range internal stress can be divided into the ... A glide-plus-climb micromechanism of dislocation evolution with the formation of subgrains is pro- posed for modelling of the creep-plasticity interaction (CPI). The long-range internal stress can be divided into the resistance for dislocation climb in subgrain boundaries and that for dislocation glide within grains or subgrains. Their evolution equations are then derived based on dislocation dynamics. Furthermore, a unified constitutive model for CPI is developed from Orowan's formula. Theoretical calculations on the basis of this model show a very good agreement between the model prediction and experimental results of benchmark tests for 2 1/4 Cr -1 Mo steel at 600℃. 展开更多
关键词 creep-plasticity interaction constitutive model dislocation dynamics
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A Crystal-Plasticity Cyclic Constitutive Model for the Ratchetting of Polycrystalline Material Considering Dislocation Substructures 认领 引用 被引量：2
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作者 Xuehong Ren Shaopu Yang +1 位作者 Guilin Wen Wenjie Zhao 《Acta Mechanica Solida Sinica》 SCIE EI CSCD 2020年第2期268-280,共13页
A crystal-plasticity cyclic constitutive model of polycrystalline material considering intra-granular heterogeneous dislocation substructures,in terms of three dislocation categories:mobile dislocations,immobile dislo... A crystal-plasticity cyclic constitutive model of polycrystalline material considering intra-granular heterogeneous dislocation substructures,in terms of three dislocation categories:mobile dislocations,immobile dislocations in the cell interiors and in the cell walls,is proposed based on the existing microscopic and macroscopic experimental results.The multiplication,annihilation,rearrangement and immobilization of dislocations on each slip system are taken as the basic evolutionary mechanism of the three dislocation categories,and the cross-slip of screw dislocations is viewed as the dynamic recovery mechanism at room temperature.The slip resistance associated with the isotropic hardening rule results from the interactions of dislocations on the slip systems.Meanwhile,a modified nonlinear kinematic hardening rule and a rate-dependent flow rule at the slip system level are employed to improve the predictive capability of the model for ratchetting deformation.The predictive ability of the developed model to uniaxial and mul-tiaxial ratchetting in macroscopic scale is verified by comparing with the experimental results of polycrystalline 316L stainless steel.The ratchetting in intra-granular scale which is obviously dependent on the crystallographic orientation and stress levels can be reasonably predicted by the proposed model. 展开更多
关键词 Ratchetting Dislocation substructures Crystal plasticity Polycrystalline materials Constitutive model
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Geometrically-Compatible Dislocation Pattern and Modeling of Crystal Plasticity in Body-Centered Cubic(BCC)Crystal at Micron Scale Dedicated to Professor Karl Stark Pister for his 95th birthday 认领 引用 被引量：1
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作者 Yuxi Xie Shaofan Li 《Computer Modeling in Engineering & Sciences》 SCIE EI 2021年第12期1419-1440,共22页
The microstructure of crystal defects,e.g.,dislocation patterns,are not arbitrary,and it is possible that some of them may be related to the microstructure of crystals itself,i.e.,the lattice structure.We call those d... The microstructure of crystal defects,e.g.,dislocation patterns,are not arbitrary,and it is possible that some of them may be related to the microstructure of crystals itself,i.e.,the lattice structure.We call those dislocation patterns or substructures that are related to the corresponding crystal microstructure as the Geometrically Compatible Dislocation Patterns(GCDP).Based on this notion,we have developed a Multiscale Crystal Defect Dynamics(MCDD)to model crystal plasticity without or with minimum empiricism.In this work,we employ the multiscale dislocation pattern dynamics,i.e.,MCDD,to simulate crystal plasticity in body-centered cubic(BCC)single crystals,mainlyα-phase Tantalum(α-Ta)single crystals.The main novelties of the work are:(1)We have successfully simulated crystal plasticity at micron scale without any empirical parameter inputs;(2)We have successfully employed MCDD to perform direct numerical simulation of inelastic hysteresis of the BCC crystal;(3)We have used MCDD crystal plasticity model to demonstrate the size-effect of crystal plasticity and(4)We have captured cross-slip which may lead to size-effect. 展开更多
关键词 α-phase tantalum BCC crystal crystal plasticity dislocation pattern dynamics multiscale simulation size effect
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Dislocation Source and Pile-up in a Twinning-induced Plasticity Steel at High-Cycle Fatigue 认领 引用 被引量：3
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作者 Rendong Liu Zhiyuan Liang +1 位作者 Li Lin Mingxin Huang 《Acta Metallurgica Sinica(English Letters)》 SCIE EI CAS CSCD 2021年第2期169-173,共5页
Dislocation behaviour of a twinning-induced plasticity(TWIP)steel subjected to high-cycle fatigue tests is investigated in the present study.Grain boundaries are the important sources of dislocation generation during ... Dislocation behaviour of a twinning-induced plasticity(TWIP)steel subjected to high-cycle fatigue tests is investigated in the present study.Grain boundaries are the important sources of dislocation generation during fatigue tests,contributing to the increase in dislocation density.Continuous emission of dislocations from grain boundaries is observed in many grains.Inclusions can sustain large dislocation pile-ups at the inclusion interfaces,leading to a high stress concentration and therefore acting as potential sites of microcrack nucleation.In contrast,annealing twin boundaries are relatively weak boundaries for dislocation pile-ups.When the number of dislocations in a pile-up is large,dislocations can crossover twin boundaries and glide inside the annealing twins.The stress concentration at the twin boundary is relatively low so that twin boundaries could not act as the sites for microcrack initiation. 展开更多
关键词 Dislocation source Grain boundary Twin boundary Fatigue Inclusion
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Bauschinger and size effects in thin-film plasticity due to defect-energy of geometrical necessary dislocations 认领 引用 被引量：3
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作者 Zhan-Li Liu Zhuo Zhuang +2 位作者 Xiao-Ming Liu Xue-Chuan Zhao Yuan Gao 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 2011年第2期266-276,共11页
The Bauschinger and size effects in the thinfilm plasticity theory arising from the defect-energy of geometrically necessary dislocations(GNDs)are analytically investigated in this paper.Firstly,this defect-energy is ... The Bauschinger and size effects in the thinfilm plasticity theory arising from the defect-energy of geometrically necessary dislocations(GNDs)are analytically investigated in this paper.Firstly,this defect-energy is deduced based on the elastic interactions of coupling dislocations(or pile-ups)moving on the closed neighboring slip plane.This energy is a quadratic function of the GNDs density,and includes an elastic interaction coefficient and an energetic length scale L.By incorporating it into the work-conjugate strain gradient plasticity theory of Gurtin,an energetic stress associated with this defect energy is obtained,which just plays the role of back stress in the kinematic hardening model.Then this back-stress hardening model is used to investigate the Bauschinger and size effects in the tension problem of single crystal Al films with passivation layers.The tension stress in the film shows a reverse dependence on the film thickness h.By comparing it with discrete-dislocation simulation results,the length scale L is determined,which is just several slip plane spacing,and accords well with our physical interpretation for the defect-energy.The Bauschinger effect after unloading is analyzed by combining this back-stress hardening model with a friction model.The effects of film thickness and pre-strain on the reversed plastic strain after unloading are quantified and qualitatively compared with experiment results. 展开更多
关键词 Thin film Crystal plasticity Defect energy Back stress Size effect
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Interstitial concentration effects on incipient plasticity and dislocation behaviors of face-centered cubic FeNiCr multicomponent alloys based on nanoindentation 认领 引用
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作者 Quanqing Zeng Kefu Gan +2 位作者 Fei Chen Dongyao Wang Songsheng Zeng 《Journal of Materials Science & Technology》 SCIE EI CAS CSCD 2022年第17期212-221,共10页
Interstitial atoms that commonly occupy the octahedral or tetrahedral interstices of face-centered cubic(FCC)lattice,can significantly affect the dislocation behaviors on deformation.Recently,interstitial doping has b... Interstitial atoms that commonly occupy the octahedral or tetrahedral interstices of face-centered cubic(FCC)lattice,can significantly affect the dislocation behaviors on deformation.Recently,interstitial doping has been applied to tune the mechanical properties of the emerging multicomponent,often termed high-entropy alloys(HEAs)or medium-entropy alloys(MEAs).However,the fundamental mechanisms of the dislocation nucleation and the onset of plasticity of interstitial multicomponent alloys governed by the concentration of interstitial atoms are still unclear.Therefore,in the present work,an instrumented nanoindentation was employed to investigate the interstitial concentration effects of carbon atoms on single FCC-phase equiatomic FeNiCr MEAs during loading.The results show that the pop-in events that denote the onset of incipient plasticity are triggered by the sudden heterogeneous dislocation nucleation via the primary atoms-vacancy exchange with the instant stress field,regardless of the interstitial concentration.Moreover,the measured activation volumes for dislocation nucleation of the FeNiCr MEAs are determined to be increased with the interstitial concentration,which definitely suggests the participation of interstitial atoms in the nucleation process.Besides,it is also found that the average value measured in statistics of the maximum shear stress corresponding to the first pop-in is enhanced with the interstitial concentration.Such scenario can be attributed to the improved local change transfer and lattice cohesion caused by the interstitial atoms with higher concentrations.Furthermore,the significant drag effect of interstitial carbon atoms hinders the mobile dislocations before exhaustion,which severely suppresses the subsequent occurrence of pop-in events in the carbon-doped specimens.The work gives a microscale view of interstitial effects on the mechanical properties of multicomponent alloys,which can further help to develop new interstitial strengthening strategies for structural materials with remarkable performance. 展开更多
关键词 Multicomponent alloy Interstitial atoms Dislocation Nanoindentation pop-in Incipient plasticity
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Unveiling the grain boundary-related effects on the incipient plasticity and dislocation behavior in nanocrystalline CrCoNi medium-entropy alloy 认领 引用 被引量：1
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作者 Shuo Sun Yang Yang +8 位作者 Chenxu Han Guixun Sun Yan Chen Hongxiang Zong Jiangjiang Hu Shuang Han Xiaozhou Liao Xiangdong Ding Jianshe Lian 《Journal of Materials Science & Technology》 SCIE EI CAS CSCD 2022年第32期98-107,共10页
The incipient plasticity and dislocation behavior in a nanocrystalline(NC)CrCoNi medium-entropy alloy were systematically investigated in terms of pop-in events during instrumental nano-indentation tests.Quantitative ... The incipient plasticity and dislocation behavior in a nanocrystalline(NC)CrCoNi medium-entropy alloy were systematically investigated in terms of pop-in events during instrumental nano-indentation tests.Quantitative statistical analysis and molecular dynamic simulations were performed to reveal the effects of grain boundaries(GBs)on initial stages of plastic deformation.Multiple pop-in events appeared during loading on the NC CrCoNi.The first pop-in that represents the initial yielding was identified to be controlled by dislocation nucleation,which is in sharp contrast to the continuous elastic-plastic transition mediated by GB mechanisms in NC pure metals.This can be attributed to the sluggish kinetics of the chemically complex GBs(CCGBs)in the NC CrCoNi that hinders diffusive GB activities but facilitates dislocation nucleation.Subsequent pop-ins were also found to be closely related to the extra dragging effects imposed by the CCGBs on dislocation propagation in the NC alloy.Moreover,the extremely small grain sizes and the consequent high-volume fraction of GBs in the NC alloy severely restrict the lengths of dislocation source and the radii of dislocation loop,giving rise to a higher critical stress,smaller activation volume and lower pop-in width as compared with its coarse-grained counterpart.These results provide new insights into the onset of nano-plasticity in concentrated multi-principal element alloys. 展开更多
关键词 Medium-entropy alloy Nanocrystalline Nanoindentation Incipient plasticity Grain boundary
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Incipient plasticity and activation volume of dislocation nucleation for TiZrNbTaMo high-entropy alloys characterized by nanoindentation 认领 引用 被引量：2
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作者 Shao-Ping Wang Jian Xu 《Journal of Materials Science & Technology》 SCIE EI CAS CSCD 2019年第5期812-816,共5页
With instrumented nanoindentation, incipient plasticity of two as-cast BCC TiZrNbTa and TiZrNbTaMo high-entropy alloys(HEAs) are investigated in terms of pop-in events during loading, to characterize the dislocation b... With instrumented nanoindentation, incipient plasticity of two as-cast BCC TiZrNbTa and TiZrNbTaMo high-entropy alloys(HEAs) are investigated in terms of pop-in events during loading, to characterize the dislocation behavior in these solid-solution alloys. It is shown that the maximum shear stress (max)required for dislocation nucleation is determined to be 1/16-1/12 and 1/18-1/14 of shear modulus for the TiZrNbTa and TiZrNbTaMo HEAs, respectively, which is nearly comparative to the theoretical shear stress of these alloys. The activation volumes of dislocation nucleation the TiZrNbTa and TiZrNbTaMo HEAs are determined to be 1.2 b^3 for and 1.3 b^3, respectively, which is substantially irrespective of alloying with Mo. Furthermore, activation volumes of these two HEAs are on the order of cubic burger’s vector and only one-third of the value for TiZrHfNb HEA, suggesting that a heterogeneous nucleation of dislocation took place in a way of direct atom-vacancy exchange, rather than of the cooperative motion of several atoms. These findings reveal the unique feature in deformation of BCC solid-solution complex alloys. 展开更多
关键词 High-entropy alloys Nanoindentation Refractory metals BCC phase Incipient plasticity
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Discrete dislocation plasticity analysis of dispersion strengthening in oxide dispersion strengthened(ODS) steels 认领 引用 被引量：1
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作者 Akiyuki Takahashi Shota Sato 《Journal of Central South University》 SCIE EI CAS 2014年第4期1249-1255,共7页
A discrete dislocation plasticity analysis of dispersion strengthening in oxide dispersion strengthened(ODS) steels was described. Parametric dislocation dynamics(PDD) simulation of the interaction between an edge dis... A discrete dislocation plasticity analysis of dispersion strengthening in oxide dispersion strengthened(ODS) steels was described. Parametric dislocation dynamics(PDD) simulation of the interaction between an edge dislocation and randomly distributed spherical dispersoids(Y2O3) in bcc iron was performed for measuring the influence of the dispersoid distribution on the critical resolved shear stress(CRSS). The dispersoid distribution was made using a method mimicking the Ostwald growth mechanism. Then, an edge dislocation was introduced, and was moved under a constant shear stress condition. The CRSS was extracted from the result of dislocation velocity under constant shear stress using the mobility(linear) relationship between the shear stress and the dislocation velocity. The results suggest that the dispersoid distribution gives a significant influence to the CRSS, and the influence of dislocation dipole, which forms just before finishing up the Orowan looping mechanism, is substantial in determining the CRSS, especially for the interaction with small dispersoids. Therefore, the well-known Orowan equation for determining the CRSS cannot give an accurate estimation, because the influence of the dislocation dipole in the process of the Orowan looping mechanism is not accounted for in the equation. 展开更多
关键词 parametric dislocation dynamics oxide dispersion strengthened steel Orowan mechanism critical resolved shear stress dislocation dipole
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MULTISCALE SIMULATION OF INCIPIENT PLASTICITY AND DISLOCATION NUCLEATION ON NICKEL FILM DURING TILTED FLAT-ENDED NANOINDENTATION 认领 引用 被引量：1
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作者 Fanlin Zeng Bing Zhao Yi Sun 《Acta Mechanica Solida Sinica》 SCIE EI CSCD 2015年第5期484-496,共13页
Multiscale simulations of the tilted flat-ended nanoindentation with different tilted angles （from 5° ～ 30°） on the （-1 1 0） surface of nickel crystal were studied using the QC method. The model of the ... Multiscale simulations of the tilted flat-ended nanoindentation with different tilted angles （from 5° ～ 30°） on the （-1 1 0） surface of nickel crystal were studied using the QC method. The model of the indentation is a flat-end indenter inclined by an angle ε driven into a half- plane vertically. Load-displacement responses, initiM stages of the plasticity deformations and dislocation emissions for nickel film at different inclined angles were obtained and analyzed as well. An energy criterion was successfully proposed to analyze the critical load for the first dislocation emission beneath the edge of the indenter. Simulation results agree well with analytical ones. An elastic model based on the contact theory and the Peierls-Nabarro dislocation model were combined to analyze when and where the dislocation will be emitted beneath the lower surface of an inclined indenter. Results indicate that the key parameter is the ratio of the contact half- width to the position of the slip plane. This parameter shows the range in which a dislocation will probably be emitted. This mechanism explains the simulation results well. This work is of value for understanding the mechanism of dislocation emissions of FCC crystals under tilted flat- ended nanoindentation while providing approaches to predicting when the first dislocation will be emitted and where subsequent dislocations will probably be emitted. 展开更多
关键词 multiscale simulations tilted flat-ended nanoindentation dislocations mechanism
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Neuronal plasticity and its role in Alzheimer's disease and Parkinson's disease 认领 引用 被引量：4
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作者 Israt Jahan Mohammad Harun-Ur-Rashid +4 位作者 MdAminul Islam Farhana Sharmin Soad K.Al Jaouni Abdullah M.Kaki Samy Selim 《Neural Regeneration Research》 SCIE CAS CSCD 2026年第1期107-125,共19页
Neuronal plasticity,the brain's ability to adapt structurally and functionally,is essential for learning,memory,and recovery from injuries.In neurodegenerative diseases such as Alzheimer's disease and Parkinso... Neuronal plasticity,the brain's ability to adapt structurally and functionally,is essential for learning,memory,and recovery from injuries.In neurodegenerative diseases such as Alzheimer's disease and Parkinson's disease,this plasticity is disrupted,leading to cognitive and motor deficits.This review explores the mechanisms of neuronal plasticity and its effect on Alzheimer's disease and Parkinson's disease.Alzheimer's disease features amyloid-beta plaques and tau tangles that impair synaptic function,while Parkinson's disease involves the loss of dopaminergic neurons affecting motor control.Enhancing neuronal plasticity offers therapeutic potential for these diseases.A systematic literature review was conducted using databases such as PubMed,Scopus,and Google Scholar,focusing on studies of neuronal plasticity in Alzheimer's disease and Parkinson's disease.Data synthesis identified key themes such as synaptic mechanisms,neurogenesis,and therapeutic strategies,linking molecular insights to clinical applications.Results highlight that targeting synaptic plasticity mechanisms,such as long-term potentiation and long-term depression,shows promise.Neurotrophic factors,advanced imaging techniques,and molecular tools(e.g.,clustered regularly interspaced short palindromic repeats and optogenetics)are crucial in understanding and enhancing plasticity.Current therapies,including dopamine replacement,deep brain stimulation,and lifestyle interventions,demonstrate the potential to alleviate symptoms and improve outcomes.In conclusion,enhancing neuronal plasticity through targeted therapies holds significant promise for treating neurodegenerative diseases.Future research should integrate multidisciplinary approaches to fully harness the therapeutic potential of neuronal plasticity in Alzheimer's disease and Parkinson's disease. 展开更多
关键词 Alzheimer's disease long-term depression long-term potentiation neuroinflammation neuronal plasticity Parkinson's disease synaptic plasticity
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Cold dwell behaviour of Ti6Al alloy:Understanding load shedding using digital image correlation and dislocation based crystal plasticity simulations 认领 引用 被引量：1
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作者 Yi Xiong NicolòGrilli +3 位作者 Phani S.Karamched Bo-Shiuan Li Edmund Tarleton Angus J.Wilkinson 《Journal of Materials Science & Technology》 SCIE EI CAS CSCD 2022年第33期254-272,共19页
Digital image correlation(DIC)and dislocation based crystal plasticity simulation were utilised to study cold dwell behaviour in a coarse grain Ti-6Al alloy at 3 different temperatures up to 230℃.Strains extracted fr... Digital image correlation(DIC)and dislocation based crystal plasticity simulation were utilised to study cold dwell behaviour in a coarse grain Ti-6Al alloy at 3 different temperatures up to 230℃.Strains extracted from large volume grains were measured during creep by DIC and were used to calibrate the crystal plasticity model.The values of critical resolved shear stresses(CRSS)of the two main slip systems(basal and prismatic)were determined as a function of temperature.Stress along paths across the boundaries of four grain pairs,three“rogue”grain pairs and one“non-rogue”grain pair,were determined at different temperatures.Large load shedding was observed in one of the“rogue”grain pairs,where a stress increment during the creep period was found in the“hard”grain.A minor load shedding mechanism was observed in two non-typical“rogue”grain pairs,in which the plastic deformation is nonuniform inside the grains and geometrically necessary dislocations accumulate in the centre of the grains.At elevated temperatures,120℃was found to be the worst case scenario as the stress difference at the grain boundaries of these four grain pairs was found to be the largest among the three temperatures analysed.The origin of this critical temperature is debated in the literature and it is investigated for the first time in the present work by analysing the simultaneous effects of the geometrically necessary dislocations(GND)and the strain rate sensitivity(SRS)of the slip systems.The analysis shows that the combined effects of the peak SRS of both prismatic and basal slip systems at 80℃and of the increase of the spread of the GND distribution around the grain boundary at higher temperatures are the origin of the observed worst case scenario. 展开更多
关键词 Cold dwell fatigue Digital image correlation Crystal plasticity Load shedding Titanium alloy
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A mesoscale numerical study on the geometrically necessary dislocations at grain boundaries and the back stress in polycrystalline grains 认领 引用
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作者 Tao Zhang Shuang Xu +2 位作者 Xin Lai Lisheng Liu Maoyuan Jiang 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 2026年第3期258-273,共16页
Elucidating the relationship between geometrically necessary dislocations(GNDs)and back stress is essential for modeling the strain hardening behavior of polycrystalline materials.This study employs dislocation dynami... Elucidating the relationship between geometrically necessary dislocations(GNDs)and back stress is essential for modeling the strain hardening behavior of polycrystalline materials.This study employs dislocation dynamics simulations to quantitatively assess the impact of GND distributions on the associated back stress at the mesoscale.In a simple cubic lattice,the stress fields generated by elementary GND boundaries,including variations in boundary sizes,dislocation types,and distribution patterns,are systematically analyzed.By taking into account the fluctuation of surface GND density,the calculation of back stress is established using the elasticity theory of dislocations combined with scaling functions.It has been demonstrated that the surface GND density is a critical parameter that controls the amplitude of back stress.Subsequently,the prediction of back stress in face-centered cubic crystalline grains is validated with more realistic GND distributions.Considering identical initial Frank-Read sources,dislocation pile-ups are predominantly formed in coarse grains,yet the resulting surface GND density remains comparable to that observed in smaller grains.This phenomenon is responsible for the similar back stress values in grains of varying sizes.Finally,the activation of cross-slip inhibits the formation of dislocation pile-ups,leading to a linear decrease in back stress with increasing plastic strain. 展开更多
关键词 Geometrically necessary dislocations Back stress Dislocation dynamics simulations Elasticity theory of dislocations
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An Electro-thermo-mechanically Coupled Crystal Plasticity Model for Electroplasticity 认领 引用
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作者 Xinghai Zheng Min Yi 《Acta Mechanica Solida Sinica》 SCIE EI CSCD 2026年第3期279-290,共12页
This study establishes an electro-thermo-mechanically coupled crystal plasticity framework incorporating electroplastic effect to elucidate the fundamental mechanisms of current-assisted deformation in pure copper.In ... This study establishes an electro-thermo-mechanically coupled crystal plasticity framework incorporating electroplastic effect to elucidate the fundamental mechanisms of current-assisted deformation in pure copper.In this framework,the thermal and athermal effects of electric current are independently described by the crystal plasticity constitutive model in terms of temperature and current density,respectively.The temperature field and current density distribution are obtained by solving the coupled heat conduction equation and current continuity equation.The model parameters are calibrated using experimental stress-strain responses of polycrystalline copper at different temperatures and current densities.Numerical simulations reveal that the thermal effects of electric current primarily manifest as shear modulus softening and enhanced thermal activation of dislocations,which have a relatively minor impact on flow stress.In contrast,the athermal effect significantly reduces both yield stress and hardening modulus by weakening the short-range and long-range resistances,leading to notable differences in fow stress during the work-hardening stage.Microstructural analysis shows that electric current alleviates stress concentrations caused by grain orientation differences and promotes more uniform distributions of dislocation density and slip deformation during plastic deformation.The proposed framework bridges the mesoscale dislocation slip and evolution with macroscale mechanical responses,providing critical insights for optimizing electrically-assisted forming processes through controlled electroplastic deformation. 展开更多
关键词 Electroplasticity Crystal plasticity Dislocation evolution Electric current Electro-thermo-mechanical coupling
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