Topology optimization stands as a pivotal technique in realizing periodic microstructure design.A novel approach is proposed,integrating the energy-based homogenization method with the Floating Projection Topology Opt...Topology optimization stands as a pivotal technique in realizing periodic microstructure design.A novel approach is proposed,integrating the energy-based homogenization method with the Floating Projection Topology Optimization(FPTO)method to achieve smooth topology design.The objective is to optimize the periodic microstructure to maximize the properties of specific materials,such as bulk modulus and shear modulus,or to achieve negative Poisson's ratio.Linear material interpolation is used to eliminate the nonlinear challenges and design dependence caused by material penalty.Furthermore,the three-field density representation technique is applied to augment length scales and solid/void characteristics.Through systematic analysis and numerical simulations,the impacts of various initial designs and optimization parameters on the optimization outcomes are investigated.The results demonstrate that the optimized periodic microstructures exhibit extreme performance with clear boundaries.The identification of appropriate optimization parameters is crucial for enhancing the extreme mechanical properties of material microstructures.It can provide valuable guidance for aerospace component design involving material microstructures and metamaterials.展开更多
Mechanical exfoliation is a widely used method to isolate high quality graphene layers from bulk graphite. In our recent experiments, some ordered microstructures, consisting of a periodic alternation of kinks and str...Mechanical exfoliation is a widely used method to isolate high quality graphene layers from bulk graphite. In our recent experiments, some ordered microstructures, consisting of a periodic alternation of kinks and stripes, were observed in thin graphite flakes that were mechanically peeled from highly oriented pyrolytic graphite. In this paper, a theoretical model is presented to attribute the formation of such ordered structures to the alternation of two mechanical processes during the exfoliation： （1） peeling of a graphite flake and （2） mechanical buckling of the flake being sub- jected to bending. In this model, the width of the stripes L is determined by thickness h of the flakes, surface energy Y, and critical buckling strain ecr. Using some appropriate values of y and ecr that are within the ranges determined by other inde- pendent experiments and simulations, the predicted relations between the stripe width and the flake thickness agree reason- ably well with our experimental measurements. Conversely, measuring the L-h relations of the periodic microstructures in thin graphite flakes could help determine the critical mechan- ical buckling strain εcr and the interface energy γ.展开更多
The microstructure evolutions and mechanical properties of a heterogeneous Mg88Y8Zn4（in at.%） alloy during multi-pass equal channel angular pressing（ECAP） were systematically investigated in this work.The results ...The microstructure evolutions and mechanical properties of a heterogeneous Mg88Y8Zn4（in at.%） alloy during multi-pass equal channel angular pressing（ECAP） were systematically investigated in this work.The results show that four phases,i.e.α-Mg,18 R long period stacking ordered（LPSO） phase,Mg24Y5 and Y-rich phase,are present in cast alloy.During ECAP,dynamic recrystallization（DRX） occurs and the diameter of DRXedα-Mg grains decreases to 0.8 μm.Moreover,precipitation of lamellar 14 H LPSO structure is developed withinα-Mg phase.Both the refinement of α-Mg grains and precipitation of 14 H LPSO contribute to the increase in micro-hardness from 98 HV to 135 HV for α-Mg.In addition,a simplified model describing the evolution of 18 R LPSO phase is established,which illustrates that 18 R undergoes a four-step morphological evolution with increasing strains during ECAP,i.e.original lath → bent lath → cracked lath → smaller particles.Compression test results indicate that the alloy has been markedly strengthened after multi-pass ECAP,and the main reason for the significantly enhanced mechanical properties could be ascribed to the DRXed α-Mg grains,newly precipitated 14 H lamellas,18 R kinking and refined 18 R particles.展开更多
基金supported by the financial support from the National Natural Science Foundation of China(No.52172356)Hunan Provincial Natural Science Foundation of China(No.2022JJ10012)。
文摘Topology optimization stands as a pivotal technique in realizing periodic microstructure design.A novel approach is proposed,integrating the energy-based homogenization method with the Floating Projection Topology Optimization(FPTO)method to achieve smooth topology design.The objective is to optimize the periodic microstructure to maximize the properties of specific materials,such as bulk modulus and shear modulus,or to achieve negative Poisson's ratio.Linear material interpolation is used to eliminate the nonlinear challenges and design dependence caused by material penalty.Furthermore,the three-field density representation technique is applied to augment length scales and solid/void characteristics.Through systematic analysis and numerical simulations,the impacts of various initial designs and optimization parameters on the optimization outcomes are investigated.The results demonstrate that the optimized periodic microstructures exhibit extreme performance with clear boundaries.The identification of appropriate optimization parameters is crucial for enhancing the extreme mechanical properties of material microstructures.It can provide valuable guidance for aerospace component design involving material microstructures and metamaterials.
基金financia support from NSFC(Grant 10832005)the National Basic Research Program of China(Grant 2007CB936803)+1 种基金the National 863 Project(Grant2008AA03Z302)the support from the engineering faculty of Monash University through seed grant 2014
文摘Mechanical exfoliation is a widely used method to isolate high quality graphene layers from bulk graphite. In our recent experiments, some ordered microstructures, consisting of a periodic alternation of kinks and stripes, were observed in thin graphite flakes that were mechanically peeled from highly oriented pyrolytic graphite. In this paper, a theoretical model is presented to attribute the formation of such ordered structures to the alternation of two mechanical processes during the exfoliation： （1） peeling of a graphite flake and （2） mechanical buckling of the flake being sub- jected to bending. In this model, the width of the stripes L is determined by thickness h of the flakes, surface energy Y, and critical buckling strain ecr. Using some appropriate values of y and ecr that are within the ranges determined by other inde- pendent experiments and simulations, the predicted relations between the stripe width and the flake thickness agree reason- ably well with our experimental measurements. Conversely, measuring the L-h relations of the periodic microstructures in thin graphite flakes could help determine the critical mechan- ical buckling strain εcr and the interface energy γ.
基金the financial support from the Natural Science Foundation of Jiangsu Province(No.BK20160869)the Nantong Science and Technology Project(No.GY12015009)+1 种基金the Fundamental Research Funds for the Central Universities(No.2015B01314)the National Natural Science Foundation of China(No.51501039)
文摘The microstructure evolutions and mechanical properties of a heterogeneous Mg88Y8Zn4（in at.%） alloy during multi-pass equal channel angular pressing（ECAP） were systematically investigated in this work.The results show that four phases,i.e.α-Mg,18 R long period stacking ordered（LPSO） phase,Mg24Y5 and Y-rich phase,are present in cast alloy.During ECAP,dynamic recrystallization（DRX） occurs and the diameter of DRXedα-Mg grains decreases to 0.8 μm.Moreover,precipitation of lamellar 14 H LPSO structure is developed withinα-Mg phase.Both the refinement of α-Mg grains and precipitation of 14 H LPSO contribute to the increase in micro-hardness from 98 HV to 135 HV for α-Mg.In addition,a simplified model describing the evolution of 18 R LPSO phase is established,which illustrates that 18 R undergoes a four-step morphological evolution with increasing strains during ECAP,i.e.original lath → bent lath → cracked lath → smaller particles.Compression test results indicate that the alloy has been markedly strengthened after multi-pass ECAP,and the main reason for the significantly enhanced mechanical properties could be ascribed to the DRXed α-Mg grains,newly precipitated 14 H lamellas,18 R kinking and refined 18 R particles.
