在一台1.5 L配备有采取阿特金森循环的废气再循环系统(exhaust gas recirculation,EGR)的自然吸气混动汽油机上,使用蝶阀和提升阀对EGR系统进行控制研究,分析其对发动机的影响。结果表明,蝶阀在流量与开度的线性度上要优于提升阀,但气...在一台1.5 L配备有采取阿特金森循环的废气再循环系统(exhaust gas recirculation,EGR)的自然吸气混动汽油机上,使用蝶阀和提升阀对EGR系统进行控制研究,分析其对发动机的影响。结果表明,蝶阀在流量与开度的线性度上要优于提升阀,但气密性差于提升阀,在小负荷工况时会影响发动机的燃烧稳定性。展开更多
Before 1980s,the circular suspension spring in automobile subjected to torsion fatigue load,under the cyclic normal tensile stresses,the majority of fatigue fracture occurred was in normal tensile fracture mode（NTFM...Before 1980s,the circular suspension spring in automobile subjected to torsion fatigue load,under the cyclic normal tensile stresses,the majority of fatigue fracture occurred was in normal tensile fracture mode（NTFM）and the fracture surface was under 45°diagonal.Because there exists the interaction between the residual stresses induced by shot peening and the applied cyclic normal tensile stresses in NTFM,which represents as＂stress strengthening mechanism＂,shot peening technology could be used for improving the fatigue fracture resistance（FFR）of springs.However,since 1990s up to date,in addition to regular NTFM,the fatigue fractures occurred of peened springs from time to time are in longitudinal shear fracture mode（LSFM）or transverse shear fracture mode（TSFM）with the increase of applied cyclic shear stresses,which leads to a remarkable decrease of FFR.However,LSFM/TSFM can be avoided effectively by means of shot peening treatment again on the peened springs.The phenomena have been rarely happened before.At present there are few literatures concerning this problem.Based upon the results of force analysis of a spring,there is no interaction between the residual stresses by shot peening and the applied cyclic shear stresses in shear fracture.This;means that the effect of＂stress strengthening mechanism＂for improving the FFR of LSFM/TSFM is disappeared basically.During shot peening,however,both of residual stress and cyclic plastic deformed microstructure are induced synchronously like＂twins＂in the surface layer of a spring.It has been found for the first time by means of force analysis and experimental results that the modified microstructure in the＂twins＂as a＂structure strengthening mechanism＂can improve the FFR of LSFM/TSFM.At the same time,it is;also shown that the optimum technology of shot peening strengthening must have both＂stress strengthening mechanism＂and＂structure strengthening mechanism＂simultaneously so that the FFR of both NTFM and LSFM/TSFM can be improved by shot peening.展开更多
The electronic structures of wurtzite compounds GaN,AIN and strained-layer super-lattice(SLS)(Ga_(2)N_(2))_(1)(Al_(2)N_(2))_(1)(001) constituted by straining GaN-layer to match the lattice constant of AIN according to...The electronic structures of wurtzite compounds GaN,AIN and strained-layer super-lattice(SLS)(Ga_(2)N_(2))_(1)(Al_(2)N_(2))_(1)(001) constituted by straining GaN-layer to match the lattice constant of AIN according to the elastic theory are studied with the first-principles Linearized-MufRn-Tin-Orbitals band-structure method.The band ofFsets at the SLS are determined by the frozen potential approach.The resutls of the bulk materials are in good agreement with available experimental data.展开更多
Electron structure of silicon nitride β-Si_(3)N_(4) was calculated by LMTO-ASA method cooperated with the use of Lowdin perturbation technique that saved computation time considerably.The results are in good agreemen...Electron structure of silicon nitride β-Si_(3)N_(4) was calculated by LMTO-ASA method cooperated with the use of Lowdin perturbation technique that saved computation time considerably.The results are in good agreement with that of ab initio pseudopo-tential method and indicate that appropriate setting of empty spheres is especially important for a crystal with a widely open structure.展开更多
文摘在一台1.5 L配备有采取阿特金森循环的废气再循环系统(exhaust gas recirculation,EGR)的自然吸气混动汽油机上,使用蝶阀和提升阀对EGR系统进行控制研究,分析其对发动机的影响。结果表明,蝶阀在流量与开度的线性度上要优于提升阀,但气密性差于提升阀,在小负荷工况时会影响发动机的燃烧稳定性。
文摘Before 1980s,the circular suspension spring in automobile subjected to torsion fatigue load,under the cyclic normal tensile stresses,the majority of fatigue fracture occurred was in normal tensile fracture mode（NTFM）and the fracture surface was under 45°diagonal.Because there exists the interaction between the residual stresses induced by shot peening and the applied cyclic normal tensile stresses in NTFM,which represents as＂stress strengthening mechanism＂,shot peening technology could be used for improving the fatigue fracture resistance（FFR）of springs.However,since 1990s up to date,in addition to regular NTFM,the fatigue fractures occurred of peened springs from time to time are in longitudinal shear fracture mode（LSFM）or transverse shear fracture mode（TSFM）with the increase of applied cyclic shear stresses,which leads to a remarkable decrease of FFR.However,LSFM/TSFM can be avoided effectively by means of shot peening treatment again on the peened springs.The phenomena have been rarely happened before.At present there are few literatures concerning this problem.Based upon the results of force analysis of a spring,there is no interaction between the residual stresses by shot peening and the applied cyclic shear stresses in shear fracture.This;means that the effect of＂stress strengthening mechanism＂for improving the FFR of LSFM/TSFM is disappeared basically.During shot peening,however,both of residual stress and cyclic plastic deformed microstructure are induced synchronously like＂twins＂in the surface layer of a spring.It has been found for the first time by means of force analysis and experimental results that the modified microstructure in the＂twins＂as a＂structure strengthening mechanism＂can improve the FFR of LSFM/TSFM.At the same time,it is;also shown that the optimum technology of shot peening strengthening must have both＂stress strengthening mechanism＂and＂structure strengthening mechanism＂simultaneously so that the FFR of both NTFM and LSFM/TSFM can be improved by shot peening.
文摘The electronic structures of wurtzite compounds GaN,AIN and strained-layer super-lattice(SLS)(Ga_(2)N_(2))_(1)(Al_(2)N_(2))_(1)(001) constituted by straining GaN-layer to match the lattice constant of AIN according to the elastic theory are studied with the first-principles Linearized-MufRn-Tin-Orbitals band-structure method.The band ofFsets at the SLS are determined by the frozen potential approach.The resutls of the bulk materials are in good agreement with available experimental data.
基金Supported by the State Key Laboratory of High Performance CeramicsSuperfine Microstructure,Shanghai Institute of Ceramics,Chinese Academy of Science.
文摘Electron structure of silicon nitride β-Si_(3)N_(4) was calculated by LMTO-ASA method cooperated with the use of Lowdin perturbation technique that saved computation time considerably.The results are in good agreement with that of ab initio pseudopo-tential method and indicate that appropriate setting of empty spheres is especially important for a crystal with a widely open structure.
