We have calculated the electronic Structures of O-doped and N-doped r-TiAl using the firstprinciples discrete variational method (DVM) with the aim to understand the solution hardening effects of oxygen and nitrogen ...We have calculated the electronic Structures of O-doped and N-doped r-TiAl using the firstprinciples discrete variational method (DVM) with the aim to understand the solution hardening effects of oxygen and nitrogen in r-TiAl. Our combination analysis on the electronic density, density of states (DOS) and the local environment total bond orders (LTBO) will show that, X atom (X is O or N) can strongly bind with its six surrounding atoms via electronic hybridizations of Ti-3d/X-2p and Al-3p/X-2p. As a sequence, there forms a 'hard' cohesive region around the impurity atom. A pinning model based on the calculations is proposed to explain the hardening effects. The consistent results are obtained between the present calculation and formal test experiments.展开更多
Non-linear finite element models accounting for large displacements have been used to investigate the behavior of steel built-up shear links that had previously been tested using large-scale experiments. The links wer...Non-linear finite element models accounting for large displacements have been used to investigate the behavior of steel built-up shear links that had previously been tested using large-scale experiments. The links were designed using steel grades with yield points ranging from high to low strengths. The objectives of the numerical analyses were to further investigate the non-linear behavior and to correlate the numerical results with experimental observations. Elasto-plastic as well as cyclic stress-strain material properties were incorporated to study the influence of material behavior on the overall shear link response. Non-linear monotonie analyses of the shear links incorporating the cyclic stress-strain steel properties resulted in similar trends in the response as the backbone curves recorded from the physical experiments. The numerical models of built-up shear links utilizing structural grade steels closely correlated to the experimentally recorded shear strength. Models utilizing low yield point steels overestimated the shear strength, which was caused by the characteristics of cyclic behavior of those steels. The detailed numerical models also allowed for investigation of the plastic strain demands on the different components of the link. It was shown that finite element models combined with appropriate stress-strain relationship may be used with confidence to check the design of shear links of different steel grades and sectional geometries.展开更多
基金National Pandeng Research Project of China under the giant nUmberof 95-Yu-41 and the National Natural Science FOundationof
文摘We have calculated the electronic Structures of O-doped and N-doped r-TiAl using the firstprinciples discrete variational method (DVM) with the aim to understand the solution hardening effects of oxygen and nitrogen in r-TiAl. Our combination analysis on the electronic density, density of states (DOS) and the local environment total bond orders (LTBO) will show that, X atom (X is O or N) can strongly bind with its six surrounding atoms via electronic hybridizations of Ti-3d/X-2p and Al-3p/X-2p. As a sequence, there forms a 'hard' cohesive region around the impurity atom. A pinning model based on the calculations is proposed to explain the hardening effects. The consistent results are obtained between the present calculation and formal test experiments.
基金the Federal Highway Administration through the Highway Project at the Multidisciplinary Center for Earthquake Engineering Researchthe toll bridge retrofit program of the California Department of Transportation through the University of California,San Diego
文摘Non-linear finite element models accounting for large displacements have been used to investigate the behavior of steel built-up shear links that had previously been tested using large-scale experiments. The links were designed using steel grades with yield points ranging from high to low strengths. The objectives of the numerical analyses were to further investigate the non-linear behavior and to correlate the numerical results with experimental observations. Elasto-plastic as well as cyclic stress-strain material properties were incorporated to study the influence of material behavior on the overall shear link response. Non-linear monotonie analyses of the shear links incorporating the cyclic stress-strain steel properties resulted in similar trends in the response as the backbone curves recorded from the physical experiments. The numerical models of built-up shear links utilizing structural grade steels closely correlated to the experimentally recorded shear strength. Models utilizing low yield point steels overestimated the shear strength, which was caused by the characteristics of cyclic behavior of those steels. The detailed numerical models also allowed for investigation of the plastic strain demands on the different components of the link. It was shown that finite element models combined with appropriate stress-strain relationship may be used with confidence to check the design of shear links of different steel grades and sectional geometries.
