Journal of Micromechanics and Molecular Physics最新文献_第10页

Fast Fourier transform-based micromechanics of interfacial line defects in crystalline materials 基于快速傅立叶变换的结晶材料界面线缺陷微观力学

Journal of Micromechanics and Molecular Physics Pub Date : 2018-09-01 DOI: 10.1142/S2424913018400076

S. Berbenni, V. Taupin

{"title":"Fast Fourier transform-based micromechanics of interfacial line defects in crystalline materials","authors":"S. Berbenni, V. Taupin","doi":"10.1142/S2424913018400076","DOIUrl":"https://doi.org/10.1142/S2424913018400076","url":null,"abstract":"Spectral methods using Fast Fourier Transform (FFT) algorithms have recently seen a surge in interest in the mechanics community. The present contribution addresses the critical question of determining local mechanical fields using the FFT method in the presence of interfacial defects. Precisely, the present work introduces a numerical approach based on intrinsic discrete Fourier transforms for the simultaneous treatment of material discontinuities arising from the presence of disclinations, i.e., rotational discontinuities, and inhomogeneities. A centered finite difference scheme for differential rules are first used for numerically solving the Poisson-type equations in the Fourier space to get the incompatible elastic fields due to disclinations and dislocations. Second, centered finite differences on a rotated grid are chosen for the computation of the modified Fourier-Green’s operator in the Lippmann–Schwinger–Dyson type equation for heterogeneous media. Elastic fields of disclination dipole distributions interacting with inhomogeneities of varying stiffnesses, grain boundaries seen as DSUM (Disclination Structural Unit Model), grain boundary disconnection defects and phase boundary “terraces” in anisotropic bi-materials are numerically computed as applications of the method.","PeriodicalId":36070,"journal":{"name":"Journal of Micromechanics and Molecular Physics","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1142/S2424913018400076","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49506530","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 5

Author index Volume 3 (2018) 作者索引第3卷（2018）

Journal of Micromechanics and Molecular Physics Pub Date : 2018-09-01 DOI: 10.1142/s2424913018990011

引用次数: 0

Geometric micromechanical modeling of structure changes, fracture and grain boundary layers in polycrystals 多晶体结构变化、断裂和晶界层的几何微观力学建模

Journal of Micromechanics and Molecular Physics Pub Date : 2018-09-01 DOI: 10.1142/S2424913018400015

J. Clayton, J. Knap

{"title":"Geometric micromechanical modeling of structure changes, fracture and grain boundary layers in polycrystals","authors":"J. Clayton, J. Knap","doi":"10.1142/S2424913018400015","DOIUrl":"https://doi.org/10.1142/S2424913018400015","url":null,"abstract":"A constitutive framework based on concepts from phase field theory and pseudo-Finsler geometry is exercised in numerical simulations of deformation and fracture of ceramic polycrystals. The material system of interest is boron carbide, a hard but brittle ceramic. Some microstructures are enabled with thin layers of a secondary amorphous phase of boron nitride between grains of boron carbide. The constitutive theory accounts for physical mechanisms of twinning, crystal-to-glass phase transformations, cleavage fracture within grains and separation and cavitation at grain boundaries (GBs). According to the generalized Finsler approach, geometric quantities such as the metric tensor and connection coefficients can depend on one or more director vectors, also called internal state vectors, that enter the energy potential in a manner similar to order parameters of phase field models. A partially linearized version of the theory is invoked in finite element simulations of polycrystals, with and without GB layers, subjected to pure shear loading. Effects of grain size and layer properties — thickness, shear modulus and surface energy — are studied parametrically. Results demonstrate that twinning and amorphization occur prominently in nanocrystals but less so in aggregates with larger grains that tend to fail earlier by fracture. Structural changes occur readily in the latter at smaller applied strains only in conjunction with elastic shear softening in localized degraded or damaged regions. Hall–Petch scaling of peak shear strength with grain size is observed. Strength is increased via addition of amorphous layers that shift the failure mode from transgranular to intergranular and further by cavity expansion in layers that induces local elastic compression and suppresses crack extension. Stiff layers provide the largest peak strength enhancement, while elastically compliant layers may improve toughness and strength in the softening regime.","PeriodicalId":36070,"journal":{"name":"Journal of Micromechanics and Molecular Physics","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1142/S2424913018400015","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49358839","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 11

Recent developments in dislocation pattern dynamics: Current opinions and perspectives 位错模式动力学的最新进展：当前的观点和展望

Journal of Micromechanics and Molecular Physics Pub Date : 2018-09-01 DOI: 10.1142/S2424913018400027

Dandan Lyu, Shaofan Li

{"title":"Recent developments in dislocation pattern dynamics: Current opinions and perspectives","authors":"Dandan Lyu, Shaofan Li","doi":"10.1142/S2424913018400027","DOIUrl":"https://doi.org/10.1142/S2424913018400027","url":null,"abstract":"The development of crystal plasticity theory based on dislocation patterns dynamics has been an outstanding problem in materials science and condensed matter of physics. Dislocation is the origin of crystal plasticity, and it is both the individual dislocation behavior as well as the aggregated dislocations behaviors that govern the plastic flow. The interactions among dislocations are complex statistical and stochastic events, in which the spontaneous emergence of organized dislocation patterns formations is the most critical and intriguing events. Dislocation patterns consist of quasi-periodic dislocation-rich and dislocation poor regions, e.g. cells, veins, labyrinths, ladders structures, etc. during cyclic loadings. Dislocation patterns have prominent and decisive effects on work hardening and plastic strain localization, and thus these dislocation micro-structures are responsible to material properties at macroscale. This paper reviews the recent developments of experimental observation, physical modeling, and computer modeling on dislocation microstructure. In particular, we focus on examining the mechanism towards plastic deformation. The progress and limitations of different experiments and modeling approaches are discussed and compared. Finally, we share our perspectives on current issues and future challenges in both experimental, analytical modeling, and computational aspects of dislocation pattern dynamics.","PeriodicalId":36070,"journal":{"name":"Journal of Micromechanics and Molecular Physics","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1142/S2424913018400027","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43766521","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 6

Interaction problems between cracks and crystal defects in constrained Cosserat elasticity 约束Cosserat弹性中裂纹与晶体缺陷的相互作用问题

Journal of Micromechanics and Molecular Physics Pub Date : 2018-09-01 DOI: 10.1142/S2424913018400118

K. Baxevanakis, H. Georgiadis

{"title":"Interaction problems between cracks and crystal defects in constrained Cosserat elasticity","authors":"K. Baxevanakis, H. Georgiadis","doi":"10.1142/S2424913018400118","DOIUrl":"https://doi.org/10.1142/S2424913018400118","url":null,"abstract":"In this work, interaction problems between a finite-length crack with plane and antiplane crystal defects in the context of couple-stress elasticity are presented. Two alternative yet equivalent approaches for the formulation of crack problems are discussed based on the distributed dislocation technique. To this aim, the stress fields of climb and screw dislocation dipoles are derived within couple-stress theory and new ‘constrained’ rotational defects are introduced to satisfy the boundary conditions of the opening mode problem. Eventually, all interaction problems are described by single or systems of singular integral equations that are solved numerically using appropriate collocation techniques. The obtained results aim to highlight the deviation from classical elasticity solutions and underline the differences in interactions of cracks with single dislocations and dislocation dipoles. In general, it is concluded that the cracked body behaves in a more rigid way when couple-stresses are considered. Also, the stress level is significantly higher than the classical elasticity prediction. Moreover, the configurational forces acting on the defects are evaluated and their dependence on the characteristic material length of couple-stress theory and the distance between the defect and the crack-tip is discussed. This investigation reveals either a strengthening or a weakening effect in the opening mode problem while in the antiplane mode a strengthening effect is always obtained.","PeriodicalId":36070,"journal":{"name":"Journal of Micromechanics and Molecular Physics","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1142/S2424913018400118","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48571847","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 3

Non-singular solutions of GradEla models for dislocations: An extension to fractional GradEla 位错的GradEla模型的非奇异解:对分数阶GradEla的推广

Journal of Micromechanics and Molecular Physics Pub Date : 2018-09-01 DOI: 10.1142/S2424913018400131

K. Parisis, I. Konstantopoulos, E. Aifantis

引用次数: 5

On Mindlin’s isotropic strain gradient elasticity: Green tensors, regularization, and operator-split 论Mindlin的各向同性应变梯度弹性:格林张量、正则化和算子分裂

Journal of Micromechanics and Molecular Physics Pub Date : 2018-09-01 DOI: 10.1142/S2424913018400088

M. Lazar, G. Po

引用次数: 16

Spatio-temporal plastic instabilities at the nano/micro scale 纳米/微观尺度下的时空塑性不稳定性

Journal of Micromechanics and Molecular Physics Pub Date : 2018-09-01 DOI: 10.1142/S2424913018400064

Yinan Cui, N. Ghoniem

引用次数: 4

Elastic wave propagation in a periodic composite beam structure: A new model for band gaps incorporating surface energy, transverse shear and rotational inertia effects 弹性波在周期复合梁结构中的传播：一个新的带隙模型，包含表面能、横向剪切和转动惯量效应

Journal of Micromechanics and Molecular Physics Pub Date : 2018-09-01 DOI: 10.1142/S2424913018400052

R. Gao, G. Y. Zhang, T. Ioppolo, Xin-Lin Gao

{"title":"Elastic wave propagation in a periodic composite beam structure: A new model for band gaps incorporating surface energy, transverse shear and rotational inertia effects","authors":"R. Gao, G. Y. Zhang, T. Ioppolo, Xin-Lin Gao","doi":"10.1142/S2424913018400052","DOIUrl":"https://doi.org/10.1142/S2424913018400052","url":null,"abstract":"A new model for determining band gaps for elastic wave propagation in a periodic composite beam structure is developed using a non-classical Timoshenko beam model that incorporates the surface energy, transverse shear and rotational inertia effects. The Bloch theorem and transfer matrix method for periodic structures are employed in the formulation. The new model reduces to the classical elasticity-based model when the surface energy effect is not considered. It is shown that the band gaps predicted by the current model depend on the surface elastic constants of each constituent material, beam thickness, unit cell size, and volume fraction. The numerical results reveal that the band gap based on the current non-classical model is always larger than that given by the classical model when the beam thickness is very small, but the difference is diminishing as the thickness becomes large. Also, it is found that the first frequency for producing the band gap and the band gap size decrease with the increase of the unit cell length according to both the current and classical models. In addition, it is observed that the volume fraction has a significant effect on the band gap size, and large band gaps can be obtained by tailoring the volume fraction and material parameters.","PeriodicalId":36070,"journal":{"name":"Journal of Micromechanics and Molecular Physics","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1142/S2424913018400052","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48925292","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 14

Defect nucleation modelling 缺陷成核建模

Journal of Micromechanics and Molecular Physics Pub Date : 2018-09-01 DOI: 10.1142/S2424913018400106

C. Stolz

引用次数: 0