The healing mechanism of hydrogen-attacked cracks in low carbon steel andCr-Mo steel and its influencing factors during the healing process were studied by recovering heattreatment of split specimens in vacuum. The re...The healing mechanism of hydrogen-attacked cracks in low carbon steel andCr-Mo steel and its influencing factors during the healing process were studied by recovering heattreatment of split specimens in vacuum. The result showed that crack pacing turns much smaller underthe condition of pure heating, especially for crack tips. The healing effect is well related to thelength of cracks with the shorter in priority. By the primary mechanism of thermal diffusion, ironand carbon atoms must diffuse at the high speed in steel to realize that plasticity deformationenergy exceeds and overcomes surface tensile force energy. In addition, phase transformation andstress-stain relationship also have positive effects on the process.展开更多
This work aimed at proposing a new combination of technologies to improve military performances and reduce costs of nuclear attack submarines, without overlooking safety constraints. The last generation of nuclear att...This work aimed at proposing a new combination of technologies to improve military performances and reduce costs of nuclear attack submarines, without overlooking safety constraints. The last generation of nuclear attack submarines increased size to meet safety and operational requirements, imposing huge burden on costs side, reducing fleet size. The limitations of current Technologies employed were qualitatively discussed, explaining their limitations. There are new technologies (plate and shell heat exchangers) and architectural choices, like passive safety, and segregation of safety and normal systems, which may lead to reduction of costs and size of submarines. A qualitative analysis was provided on this combination of technologies, stressing their commercial nature and maturity, which reduced risks. The qualitative analysis showed the strong and weak points of this proposal, which adopted the concept of strength in numbers. Concluding, new Technologies enabled the existence of 3800 t nuclear attack submarines with powerful propulsion systems and good acoustic discretion.展开更多
基金This work was financially supported by the National Natural Science Foundation of China (No.59971011) and "973" Science Foundation of China (No. 19990650).
文摘The healing mechanism of hydrogen-attacked cracks in low carbon steel andCr-Mo steel and its influencing factors during the healing process were studied by recovering heattreatment of split specimens in vacuum. The result showed that crack pacing turns much smaller underthe condition of pure heating, especially for crack tips. The healing effect is well related to thelength of cracks with the shorter in priority. By the primary mechanism of thermal diffusion, ironand carbon atoms must diffuse at the high speed in steel to realize that plasticity deformationenergy exceeds and overcomes surface tensile force energy. In addition, phase transformation andstress-stain relationship also have positive effects on the process.
文摘This work aimed at proposing a new combination of technologies to improve military performances and reduce costs of nuclear attack submarines, without overlooking safety constraints. The last generation of nuclear attack submarines increased size to meet safety and operational requirements, imposing huge burden on costs side, reducing fleet size. The limitations of current Technologies employed were qualitatively discussed, explaining their limitations. There are new technologies (plate and shell heat exchangers) and architectural choices, like passive safety, and segregation of safety and normal systems, which may lead to reduction of costs and size of submarines. A qualitative analysis was provided on this combination of technologies, stressing their commercial nature and maturity, which reduced risks. The qualitative analysis showed the strong and weak points of this proposal, which adopted the concept of strength in numbers. Concluding, new Technologies enabled the existence of 3800 t nuclear attack submarines with powerful propulsion systems and good acoustic discretion.
