Powder mixture of pure A1 and oxidized SiC was consolidated into 10% （mass fraction） SiCp/AI composites at 523 K by equal channel angular pressing and torsion （ECAP-T）. The interfacial bonding of the composites wa...Powder mixture of pure A1 and oxidized SiC was consolidated into 10% （mass fraction） SiCp/AI composites at 523 K by equal channel angular pressing and torsion （ECAP-T）. The interfacial bonding of the composites was characterized by transmission electron microscopy （TEM） and high resolution transmission electron microscopy （HRTEM）. The selected area electron diffraction （SAED） for the interface was investigated. The elements at the interface were scanned by energy dispersive spectroscopy （EDS） and the EDS mapping was also obtained. X-ray diffraction （XRD） analysis was carried out for the composites fabricated by 1 pass, 2 passes and 4 passes ECAP-T. According to the XRD analysis, the influences of ECAP-T pass on the Bragg angle and interplanar spacing for AI crystalline planes were studied. The results show that after ECAP-T, the interface between A1 and SiC within the composites is a belt of amorphous SiO2 containing a trace of A1, Si and C which diffused from the matrix and the reinforcement. With the growing ECAP-T pass, the Bragg angle decreases and interplanar spacing increases for A1 crystalline planes, due to the accumulated lattice strain. The increasing lattice strain of A1 grains also boosts the density of the dislocation within A1 grains.展开更多
This work was undertaken to evaluate the applicability of the Ashby grain-boundary hardening model for a high strain range.To this end,Al Mg alloy with distinctly different grain sizes(~100μm vs^1μm)was cold-rolled ...This work was undertaken to evaluate the applicability of the Ashby grain-boundary hardening model for a high strain range.To this end,Al Mg alloy with distinctly different grain sizes(~100μm vs^1μm)was cold-rolled to a true strain of^1.6 and the resulting dislocation densities were compared by using transmission electron microscopy.A minor difference revealed by the measurements suggested a violation of the Ashby’s model.This effect was attributed to a partial relaxation of strain constraints due to significant change of grain shape,development of texture and formation of pronounced substructure.展开更多
Study on the dynamic response, and especially the nonlinear dynamic response of stiffened plates is complicated by their discontinuity and inhomogeneity. The finite element method (FEM) and the finite strip method are...Study on the dynamic response, and especially the nonlinear dynamic response of stiffened plates is complicated by their discontinuity and inhomogeneity. The finite element method (FEM) and the finite strip method are usually adopted in their analysis. Although many useful conclusions have been obtained, the computational cost is enormous. Based on some assumptions, the dynamic plastic response of clamped stiffened plates with large deflections was theoretically investigated herein by a singly symmetric beam model. Firstly, the deflection conditions that a plastic string must satisfy were obtained by the linearized moment-axial force interaction curve for singly symmetric cross sections and the associated plastic flow rule. Secondly, the possible motion mechanisms of the beam under different load intensity were analysed in detail. For structures with plastic deformations, a simplified method was then given that the arbitrary impact load can be replaced equivalently by a rectangular pulse. Finally, to confirm the validity of the proposed method, the dynamic plastic response of a one-way stiffened plate with four fully clamped edges was calculated. The theoretical results were in good agreement with those of FEM. It indicates that the present calculation model is easy and feasible, and the equivalent substitution of load almost has no influence on the final deflection.展开更多
基金Project(51175138) supported by the National Natural Science Foundation of ChinaProjects(2012HGZX0030,2013HGCH0011) supported by the Fundamental Research Funds for the Central Universities,China
文摘Powder mixture of pure A1 and oxidized SiC was consolidated into 10% （mass fraction） SiCp/AI composites at 523 K by equal channel angular pressing and torsion （ECAP-T）. The interfacial bonding of the composites was characterized by transmission electron microscopy （TEM） and high resolution transmission electron microscopy （HRTEM）. The selected area electron diffraction （SAED） for the interface was investigated. The elements at the interface were scanned by energy dispersive spectroscopy （EDS） and the EDS mapping was also obtained. X-ray diffraction （XRD） analysis was carried out for the composites fabricated by 1 pass, 2 passes and 4 passes ECAP-T. According to the XRD analysis, the influences of ECAP-T pass on the Bragg angle and interplanar spacing for AI crystalline planes were studied. The results show that after ECAP-T, the interface between A1 and SiC within the composites is a belt of amorphous SiO2 containing a trace of A1, Si and C which diffused from the matrix and the reinforcement. With the growing ECAP-T pass, the Bragg angle decreases and interplanar spacing increases for A1 crystalline planes, due to the accumulated lattice strain. The increasing lattice strain of A1 grains also boosts the density of the dislocation within A1 grains.
基金financially supported by the Russian Science Foundation, grant No.18-79-10174
文摘This work was undertaken to evaluate the applicability of the Ashby grain-boundary hardening model for a high strain range.To this end,Al Mg alloy with distinctly different grain sizes(~100μm vs^1μm)was cold-rolled to a true strain of^1.6 and the resulting dislocation densities were compared by using transmission electron microscopy.A minor difference revealed by the measurements suggested a violation of the Ashby’s model.This effect was attributed to a partial relaxation of strain constraints due to significant change of grain shape,development of texture and formation of pronounced substructure.
文摘Study on the dynamic response, and especially the nonlinear dynamic response of stiffened plates is complicated by their discontinuity and inhomogeneity. The finite element method (FEM) and the finite strip method are usually adopted in their analysis. Although many useful conclusions have been obtained, the computational cost is enormous. Based on some assumptions, the dynamic plastic response of clamped stiffened plates with large deflections was theoretically investigated herein by a singly symmetric beam model. Firstly, the deflection conditions that a plastic string must satisfy were obtained by the linearized moment-axial force interaction curve for singly symmetric cross sections and the associated plastic flow rule. Secondly, the possible motion mechanisms of the beam under different load intensity were analysed in detail. For structures with plastic deformations, a simplified method was then given that the arbitrary impact load can be replaced equivalently by a rectangular pulse. Finally, to confirm the validity of the proposed method, the dynamic plastic response of a one-way stiffened plate with four fully clamped edges was calculated. The theoretical results were in good agreement with those of FEM. It indicates that the present calculation model is easy and feasible, and the equivalent substitution of load almost has no influence on the final deflection.
