An experimental method and a theoretical analysis based on continuum damage mechan- ics are applied for the defects tolerance of fixed plate. The defects type studied in this article is scratch, which is considered a ...An experimental method and a theoretical analysis based on continuum damage mechan- ics are applied for the defects tolerance of fixed plate. The defects type studied in this article is scratch, which is considered a typical defect on fixed plate according to the engineering practice. The general approach to the defects tolerance analysis of scratched fixed plate is presented. The method of fatigue life prediction for standard notched specimens has been established on the basis of continuum damage mechanics. For the purpose of obtaining the influence law of fatigue life in consequence of scratches, fatigue experiments of standard notched specimens and scratched specimens have been done. Evalu- ation of the fatigue life of scratched fixed plate has been carried out. And the value of scratch defects permissible to the condition of safety service life has been worked out. According to the results of the- oretical calculations, the fatigue experiment of scratched fixed plate has been performed. The outcome shows that the theoretical prediction tallies with the experimental results.展开更多
Chalcogenide perovskites(CPs) exhibiting lower band gaps than oxide perovskites and higher stability than halide perovskites are promising materials for photovoltaic and optoelectronic applications. For such applicati...Chalcogenide perovskites(CPs) exhibiting lower band gaps than oxide perovskites and higher stability than halide perovskites are promising materials for photovoltaic and optoelectronic applications. For such applications, the absence of deep defect levels serving as recombination centers(dubbed defect tolerance) is a highly desirable property. Here,using density functional theory(DFT) calculations, we study the intrinsic defects in BaZrS_(3), a representative CP material.We compare Hubbard-U and hybrid functional methods, both of which have been widely used in addressing the band gap problem of semi-local functionals in DFT. We find that tuning the U value to obtain experimental bulk band gap and then using the obtained U value for defect calculations may result in over-localization of defect states. In the hybrid functional calculation, the band gap of BaZrS_(3)can be accurately obtained. We observe the formation of small S-atom clusters in both methods, which tend to self-passivate the defects from forming mid-gap levels. Even though in the hybrid functional calculations several relatively deep defects are observed, all of them exhibit too high formation energy to play a significant role if the materials are prepared under thermal equilibrium.BaZrS_(3)is thus expected to exhibit sufficient defect tolerance promising for photovoltaic and optoelectronic applications.展开更多
Carbon and boron have been considered to strengthen grain boundaries that might form during single crystal casting.In this study the effect of boron on solidification behavior and creep properties of the carbon doped ...Carbon and boron have been considered to strengthen grain boundaries that might form during single crystal casting.In this study the effect of boron on solidification behavior and creep properties of the carbon doped single crystal RR 2072 has been investigated.In order to understand solidification behavior with boron addition,the solid/liquid interface morphology and solidification microstructure were examined with solidification rate.The relationship between mi-crostructural evolution and creep properties of the carbon and boron modified single crystal has been also investigated.展开更多
文摘An experimental method and a theoretical analysis based on continuum damage mechan- ics are applied for the defects tolerance of fixed plate. The defects type studied in this article is scratch, which is considered a typical defect on fixed plate according to the engineering practice. The general approach to the defects tolerance analysis of scratched fixed plate is presented. The method of fatigue life prediction for standard notched specimens has been established on the basis of continuum damage mechanics. For the purpose of obtaining the influence law of fatigue life in consequence of scratches, fatigue experiments of standard notched specimens and scratched specimens have been done. Evalu- ation of the fatigue life of scratched fixed plate has been carried out. And the value of scratch defects permissible to the condition of safety service life has been worked out. According to the results of the- oretical calculations, the fatigue experiment of scratched fixed plate has been performed. The outcome shows that the theoretical prediction tallies with the experimental results.
基金supported by the National Natural Science Foundation of China (11774365)the Natural Science Foundation of Shanghai (19ZR1421800)+4 种基金Shanghai International Cooperation Project (20520760900)the Opening Project and Science Foundation for Youth Scholar of State Key Laboratory of High Performance Ceramics and Superfine Microstructures (SKL201804 and SKL201803SIC) support by US National Science Foundation (NSF) (CBET1510121)US Department of Energy (DOE) (DEEE0007364)support by US NSF (CBET-1510948).support by US NSF (DMR-1506669)support by the Fundamental Research Funds for the Central Universities (DUT21RC(3) 033)。
文摘Chalcogenide perovskites(CPs) exhibiting lower band gaps than oxide perovskites and higher stability than halide perovskites are promising materials for photovoltaic and optoelectronic applications. For such applications, the absence of deep defect levels serving as recombination centers(dubbed defect tolerance) is a highly desirable property. Here,using density functional theory(DFT) calculations, we study the intrinsic defects in BaZrS_(3), a representative CP material.We compare Hubbard-U and hybrid functional methods, both of which have been widely used in addressing the band gap problem of semi-local functionals in DFT. We find that tuning the U value to obtain experimental bulk band gap and then using the obtained U value for defect calculations may result in over-localization of defect states. In the hybrid functional calculation, the band gap of BaZrS_(3)can be accurately obtained. We observe the formation of small S-atom clusters in both methods, which tend to self-passivate the defects from forming mid-gap levels. Even though in the hybrid functional calculations several relatively deep defects are observed, all of them exhibit too high formation energy to play a significant role if the materials are prepared under thermal equilibrium.BaZrS_(3)is thus expected to exhibit sufficient defect tolerance promising for photovoltaic and optoelectronic applications.
文摘Carbon and boron have been considered to strengthen grain boundaries that might form during single crystal casting.In this study the effect of boron on solidification behavior and creep properties of the carbon doped single crystal RR 2072 has been investigated.In order to understand solidification behavior with boron addition,the solid/liquid interface morphology and solidification microstructure were examined with solidification rate.The relationship between mi-crostructural evolution and creep properties of the carbon and boron modified single crystal has been also investigated.
