Self-healing of engineered cementitious composites(ECC) subjected to a cyclic drying and wetting regime simulated summer outdoor environment was investigated in this paper.Uniaxial tension tests were used to generate ...Self-healing of engineered cementitious composites(ECC) subjected to a cyclic drying and wetting regime simulated summer outdoor environment was investigated in this paper.Uniaxial tension tests were used to generate multiple cracks in ECC specimens deformed to varying tensile strains.To quantify self-healing,resonant frequency measurements were conducted throughout drying-wetting cycles followed by tensile testing of self-healing ECC specimens.It was found that through self-healing the resonant frequency of ECC can recover 81% to 90% of initial values while showing a distinct rebound in stiffness of cracked ECC after self-healing.For specimens pre-loaded to high levels of strain between 2% and 3%,the tensile strain after self-healing can recover from 1.8% to 2.2%.Also,the effects of temperature during cyclic regime can lead to an increase in the ultimate strength of the material while slightly decreasing the strain-hardening capacity of ECC due to further hydration of unreacted cement and fly ash.展开更多
Tensile-strained epitaxial La0.67Ba0.33MnO3(LBMO)film has been prepared by magnetron sputtering technique on(001)oriented spinel MgAl2O4substrate.The transport and magnetic measurements give an insulator-metal transit...Tensile-strained epitaxial La0.67Ba0.33MnO3(LBMO)film has been prepared by magnetron sputtering technique on(001)oriented spinel MgAl2O4substrate.The transport and magnetic measurements give an insulator-metal transition and paramagnetic-ferromagnetic transition occurring at^150 K and 250 K respectively,which implies the phase separation in such a tensile-strained film.By analyzing the angular and temperature dependences of the ferromagnetic resonance(FMR),we determine the magnetocrystalline anisotropy of the film.It is found that the tensile-strained film is dominated by an easy-axis corresponding to the compressive out-of-plane direction,though the magnitudes of anisotropy constants are relatively small and their temperature dependences are some complex.Furthermore,the FMR spectra show additional spin wave resonance(SWR),and the field positions can be indexed to follow a linear dependence on the square of index n.The scaling gives a spin-wave exchange stiffness D of 20.7 meV 2at low temperature,which is less than half of that in strain-free LBMO films,implying that the double exchange interaction is remarkably suppressed in the tensile-strained LBMO films.展开更多
文摘Self-healing of engineered cementitious composites(ECC) subjected to a cyclic drying and wetting regime simulated summer outdoor environment was investigated in this paper.Uniaxial tension tests were used to generate multiple cracks in ECC specimens deformed to varying tensile strains.To quantify self-healing,resonant frequency measurements were conducted throughout drying-wetting cycles followed by tensile testing of self-healing ECC specimens.It was found that through self-healing the resonant frequency of ECC can recover 81% to 90% of initial values while showing a distinct rebound in stiffness of cracked ECC after self-healing.For specimens pre-loaded to high levels of strain between 2% and 3%,the tensile strain after self-healing can recover from 1.8% to 2.2%.Also,the effects of temperature during cyclic regime can lead to an increase in the ultimate strength of the material while slightly decreasing the strain-hardening capacity of ECC due to further hydration of unreacted cement and fly ash.
基金supported by the National Natural Science Foundation of China (11174261)
文摘Tensile-strained epitaxial La0.67Ba0.33MnO3(LBMO)film has been prepared by magnetron sputtering technique on(001)oriented spinel MgAl2O4substrate.The transport and magnetic measurements give an insulator-metal transition and paramagnetic-ferromagnetic transition occurring at^150 K and 250 K respectively,which implies the phase separation in such a tensile-strained film.By analyzing the angular and temperature dependences of the ferromagnetic resonance(FMR),we determine the magnetocrystalline anisotropy of the film.It is found that the tensile-strained film is dominated by an easy-axis corresponding to the compressive out-of-plane direction,though the magnitudes of anisotropy constants are relatively small and their temperature dependences are some complex.Furthermore,the FMR spectra show additional spin wave resonance(SWR),and the field positions can be indexed to follow a linear dependence on the square of index n.The scaling gives a spin-wave exchange stiffness D of 20.7 meV 2at low temperature,which is less than half of that in strain-free LBMO films,implying that the double exchange interaction is remarkably suppressed in the tensile-strained LBMO films.
