Application of the alumo-boron-nitride heat-resistant structural ceramics allows distribution of the thermal and mechanical loads on the metal-ceramic blade elements reasonably rationally from the thermotechnical poin...Application of the alumo-boron-nitride heat-resistant structural ceramics allows distribution of the thermal and mechanical loads on the metal-ceramic blade elements reasonably rationally from the thermotechnical point of view. The ceramic shell, actually free of the mechanical effects, absorbs the heat from the high-temperature gas and serves as a shield for the strength core. The latter, being loaded mechanically, is cooled with air, the flow thereof is mainly the function of the heat supply from the peripheral platform and ceramic shell, additionally separated by a thin- wall metal screen from the core. Calculation of the pattern factors for the basic parts was performed at rating as applied to the nozzle vanes and rotor blades of the 2.5 MW GTE with the gas temperature at the inlet TIT = 1623K. It was demonstrated that an admissible temperature level of the mechanically loaded parts could be achieved at the cooling air flows of 1.5%. Decreasing the power consumption on cooling allowed to get a high efficiency of the designed engine amounting to 42-43% (speed at rating is around 23,000 r/min). During rotation the length of the ceramic shell, installed loosely on the strength core, moves due to the action of the centrifugal forces and is pressed to the platform of the core. At the same time, a relatively lower compressive stresses of around 40 MPa are generated in the shell which ensures a feasibility of a long-term reliable operation of the turbine.展开更多
Complicated changes occur inside the steel parts during quenching process. A three dimensional nonlinear mathematical model for quenching process has been established and the numerical simulation on temperature field,...Complicated changes occur inside the steel parts during quenching process. A three dimensional nonlinear mathematical model for quenching process has been established and the numerical simulation on temperature field, microstructure and stress field has been realized. The alternative technique for the formation of high-strength materials has been developed on the basis of intensification of heat transfer at phase transformations. The technology for the achievement of maximum compressive residual stresses on the hard surface is introduced. It has been shown that there is an optimal depth of hard layer providing the maximum compression stresses on the surface. It has also been established that in the surface hard layer additional strengthening (superstrengthening) of the material is observed. The generalized formula for the determination of the time of reaching maximum compressive stresses on the surface has been proposed.展开更多
Strained Si is recognized as a necessary technology booster for modem integrated circuit technology. However, the thermal oxidation behaviors of strained Si substrates are not well understood yet despite their importa...Strained Si is recognized as a necessary technology booster for modem integrated circuit technology. However, the thermal oxidation behaviors of strained Si substrates are not well understood yet despite their importance. In this study, we for the first time experimentally find that all types of strained Si substrates （uniaxial tensile, uniaxial compressive, biaxial tensile, and biaxial compressive） show smaller thermal oxidation rates than an unstrained Si substrate. The possible mechanisms for these retarded thermal oxidation rates in strained Si substrates are also discussed.展开更多
文摘Application of the alumo-boron-nitride heat-resistant structural ceramics allows distribution of the thermal and mechanical loads on the metal-ceramic blade elements reasonably rationally from the thermotechnical point of view. The ceramic shell, actually free of the mechanical effects, absorbs the heat from the high-temperature gas and serves as a shield for the strength core. The latter, being loaded mechanically, is cooled with air, the flow thereof is mainly the function of the heat supply from the peripheral platform and ceramic shell, additionally separated by a thin- wall metal screen from the core. Calculation of the pattern factors for the basic parts was performed at rating as applied to the nozzle vanes and rotor blades of the 2.5 MW GTE with the gas temperature at the inlet TIT = 1623K. It was demonstrated that an admissible temperature level of the mechanically loaded parts could be achieved at the cooling air flows of 1.5%. Decreasing the power consumption on cooling allowed to get a high efficiency of the designed engine amounting to 42-43% (speed at rating is around 23,000 r/min). During rotation the length of the ceramic shell, installed loosely on the strength core, moves due to the action of the centrifugal forces and is pressed to the platform of the core. At the same time, a relatively lower compressive stresses of around 40 MPa are generated in the shell which ensures a feasibility of a long-term reliable operation of the turbine.
文摘Complicated changes occur inside the steel parts during quenching process. A three dimensional nonlinear mathematical model for quenching process has been established and the numerical simulation on temperature field, microstructure and stress field has been realized. The alternative technique for the formation of high-strength materials has been developed on the basis of intensification of heat transfer at phase transformations. The technology for the achievement of maximum compressive residual stresses on the hard surface is introduced. It has been shown that there is an optimal depth of hard layer providing the maximum compression stresses on the surface. It has also been established that in the surface hard layer additional strengthening (superstrengthening) of the material is observed. The generalized formula for the determination of the time of reaching maximum compressive stresses on the surface has been proposed.
基金supported by the National Key Basic Research Project of China(Grant No.2011CBA00607)the National Natural Science Foundation of China(Grant Nos.61106089 and 61376097)the Program B for Outstanding Ph.D.Candidate of Nanjing University,China(Grant No.201301B005)
文摘Strained Si is recognized as a necessary technology booster for modem integrated circuit technology. However, the thermal oxidation behaviors of strained Si substrates are not well understood yet despite their importance. In this study, we for the first time experimentally find that all types of strained Si substrates （uniaxial tensile, uniaxial compressive, biaxial tensile, and biaxial compressive） show smaller thermal oxidation rates than an unstrained Si substrate. The possible mechanisms for these retarded thermal oxidation rates in strained Si substrates are also discussed.
