A theory based on the superposition principle is developed to uncover the basic physics of wave behavior in a finite grating of N unit cells.The theory reveals that bound states in the continuum(BICs)of infinite quali...A theory based on the superposition principle is developed to uncover the basic physics of wave behavior in a finite grating of N unit cells.The theory reveals that bound states in the continuum(BICs)of infinite quality factor(Q-factor)can be supported by such a grating when perfect reflection is introduced at its boundaries.If geometrical perturbations are introduced into the structure,the dark BICs transform into bright quasi-BICs with finite Q-factor,maintaining spectral characteristics nearly identical to those of quasi-BICs supported by infinite gratings.When the boundaries are replaced with high-reflectivity metallic mirrors,the Q-factor of the resonant mode is reduced to be finite;however,it can be much larger than that in the corresponding nanostructure with open boundaries and can be tuned over a large range by varying the number of unit cells or boundary conditions.展开更多
Repeated Unit Cell（RUC）is a useful tool in micromechanical analysis of composites using Displacement-based Finite Element（DFE）method,and merely applying Periodic Displacement Boundary Conditions（PDBCs）to RUC is ...Repeated Unit Cell（RUC）is a useful tool in micromechanical analysis of composites using Displacement-based Finite Element（DFE）method,and merely applying Periodic Displacement Boundary Conditions（PDBCs）to RUC is almost a standard practice to conduct such analysis.Two basic questions arising from this practice are whether Periodic Traction Boundary Conditions（PTBCs,also known as traction continuity conditions）are guaranteed and whether the solution is independent of selection of RUCs.This paper presents the theoretical aspects to tackle these questions,which unify the strong form,weak form and DFE method of the micromechanical problem together.Specifically,the solution’s independence of selection of RUCs is dealt with on the strong form side,PTBCs are derived from the weak form as natural boundary conditions,and the validity of merely applying PDBCs in micromechanical Finite Element（FE）analysis is proved by referring to its intrinsic connection to the strong form and weak form.Key points in the theoretical aspects are demonstrated by illustrative examples,and the merits of setting micromechanical FE analysis under the background of a clear theoretical framework are highlighted in the efficient selection of RUCs for Uni Directional（UD）fiber-reinforced composites.展开更多
A three-dimensional contact model of 1×7 steel strand was established. Contact point was searched by Splitting-pinball algorithm, and Augmented-Lagrangian algorithm was applied for analysis of contact loads. The ...A three-dimensional contact model of 1×7 steel strand was established. Contact point was searched by Splitting-pinball algorithm, and Augmented-Lagrangian algorithm was applied for analysis of contact loads. The exerted tensile loads to the model were analyzed using finite element method. After analyzing calculation results, the laws of steel wire stress distribution in axis direction and in its cross-section were found. Friction coefficients were set as 0.10, 0.11, and 0.12, respec- tively, to obtain the influence law of friction coefficient to steel wire stresses. Research result shows that friction coefficient has significant influence on the shear stress of steel wire. Analyzed the calculation results of steel strand with five different lay pitch multiples and got the influence law of lay pitch multiple to the stresses of steel wire in steel strand. The Von Misses stress of steel wire increases following with the increasing of lay pitches nmltiples, but the increment value is not very prominent. The shear stress of steel wire decreases following the increase of lay pitch multiple, and the changing amplitude is large when lay pitch multiple is small. Finally, carried out a steel strand tensile deformation test and the consistency of test results with the calculation results shows that the selected model is reasonable.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.11874270 and 12174228)the Shenzhen Basic Research Special Project(Grant No.JCYJ20240813141606009)。
文摘A theory based on the superposition principle is developed to uncover the basic physics of wave behavior in a finite grating of N unit cells.The theory reveals that bound states in the continuum(BICs)of infinite quality factor(Q-factor)can be supported by such a grating when perfect reflection is introduced at its boundaries.If geometrical perturbations are introduced into the structure,the dark BICs transform into bright quasi-BICs with finite Q-factor,maintaining spectral characteristics nearly identical to those of quasi-BICs supported by infinite gratings.When the boundaries are replaced with high-reflectivity metallic mirrors,the Q-factor of the resonant mode is reduced to be finite;however,it can be much larger than that in the corresponding nanostructure with open boundaries and can be tuned over a large range by varying the number of unit cells or boundary conditions.
文摘Repeated Unit Cell（RUC）is a useful tool in micromechanical analysis of composites using Displacement-based Finite Element（DFE）method,and merely applying Periodic Displacement Boundary Conditions（PDBCs）to RUC is almost a standard practice to conduct such analysis.Two basic questions arising from this practice are whether Periodic Traction Boundary Conditions（PTBCs,also known as traction continuity conditions）are guaranteed and whether the solution is independent of selection of RUCs.This paper presents the theoretical aspects to tackle these questions,which unify the strong form,weak form and DFE method of the micromechanical problem together.Specifically,the solution’s independence of selection of RUCs is dealt with on the strong form side,PTBCs are derived from the weak form as natural boundary conditions,and the validity of merely applying PDBCs in micromechanical Finite Element（FE）analysis is proved by referring to its intrinsic connection to the strong form and weak form.Key points in the theoretical aspects are demonstrated by illustrative examples,and the merits of setting micromechanical FE analysis under the background of a clear theoretical framework are highlighted in the efficient selection of RUCs for Uni Directional（UD）fiber-reinforced composites.
文摘A three-dimensional contact model of 1×7 steel strand was established. Contact point was searched by Splitting-pinball algorithm, and Augmented-Lagrangian algorithm was applied for analysis of contact loads. The exerted tensile loads to the model were analyzed using finite element method. After analyzing calculation results, the laws of steel wire stress distribution in axis direction and in its cross-section were found. Friction coefficients were set as 0.10, 0.11, and 0.12, respec- tively, to obtain the influence law of friction coefficient to steel wire stresses. Research result shows that friction coefficient has significant influence on the shear stress of steel wire. Analyzed the calculation results of steel strand with five different lay pitch multiples and got the influence law of lay pitch multiple to the stresses of steel wire in steel strand. The Von Misses stress of steel wire increases following with the increasing of lay pitches nmltiples, but the increment value is not very prominent. The shear stress of steel wire decreases following the increase of lay pitch multiple, and the changing amplitude is large when lay pitch multiple is small. Finally, carried out a steel strand tensile deformation test and the consistency of test results with the calculation results shows that the selected model is reasonable.
