The electrode structures in ignition devices for Electrically Controlled Solid Propellants(ECSP)can be classified into fixed and movable types.In movable electrode structures,springs are typically used to push the ele...The electrode structures in ignition devices for Electrically Controlled Solid Propellants(ECSP)can be classified into fixed and movable types.In movable electrode structures,springs are typically used to push the electrodes and the propellant.The effects of spring pressure on the ignition and combustion of propellants have not yet been studied.In this paper,a universal testing machine and an electrochemical workstation were firstly utilized to investigate the compressive mechanical property and conductivity of Hydroxylamine Nitrate(HAN)-ECSP.The maximum pressure at which the propellant undergoes elastic deformation is 65 kPa.When the spring pressure increased from 5.1 kPa to 20.4 kPa,the propellant resistance decreased from 56.8 X to 36.8 X.Various observation methods were employed to study the process of electrical energy injection and the ignition and combustion characteristics under constant voltage.Appropriately increasing the spring pressure can accelerate the injection of electrical energy into the propellant,increase the electrification current,and thus reduce the initial ignition delay time of the propellant.When the spring pressure is 20.4 kPa,the squeezing speed of the propellant is too fast,making it difficult for the propellant to be adequately heated at the electrode interface,which is unfavorable for ignition.Excessive spring pressure also leads to the accumulation of a large amount of combustion residue on the electrode plate,hindering the mixing and diffusion of hot gases during the second ignition process,preventing the gaseous flame of the propellant.When the spring pressure is 5.1 kPa,improving the working voltage can enhance the repeated ignition characteristics of the propellant.展开更多
Self-Centering Piston-Based Braced Frames(SC-PBBFs)are designed to curtail structural damage under severe ground motions.The self-centering mechanism in this bracing mitigates structural damage during an earthquake,th...Self-Centering Piston-Based Braced Frames(SC-PBBFs)are designed to curtail structural damage under severe ground motions.The self-centering mechanism in this bracing mitigates structural damage during an earthquake,thereby reducing post-earthquake repair costs and contributing to seismic resilience.However,non-structural components,particularly those sensitive to floor acceleration,remain vulnerable,resulting in prolonged func-tional recovery times.This paper aims to address this limitation by introducing a novel structural archetype,the Self-Centering Viscous-Based Braced Frame(SC-VBBF),which integrates superelastic shape memory alloy(SMA)bars,viscous dampers(VDs),and friction springs(FSs).A streamlined analytical approach relies on the strength decoupling of VD from other components using aλfactor to design SC-VBBFs.To evaluate the effectiveness of the hybrid brace,a set of 4-,8-,and 12-story archetypes equipped with SC-PBBs and SC-VBBFs are simulated in OpenSees and analyzed under various earthquake types,including crustal,subcrustal,and subduction events.The results demonstrate the superior performance of the SC-VBBF withλ≤0.5 system compared to SC-PBBFs in mitigating floor accelerations under design-level earthquakes and improving seismic resilience.展开更多
The Ti（C,N）precipitation and texture evolution in ultra-low carbon Ti-bearing enamel steel were studied to discover their correlation.Two different cooling paths of simulative coiling were adopted to gain different ...The Ti（C,N）precipitation and texture evolution in ultra-low carbon Ti-bearing enamel steel were studied to discover their correlation.Two different cooling paths of simulative coiling were adopted to gain different morphologies of Ti（C,N）precipitate in hot strips.It is found that the Ti（C,N）precipitate in hot strip using Path 2（put into asbestos box and air cooled）are finer and much more in quantity than that in hot strip using Path 1（held at 730℃ for 30min and furnace cooled）.The morphology of Ti（C,N）precipitate in hot strip has great effect on recrystallization texture in the subsequent cold-rolled annealed sheet.γ-fiber texture of strong recrystallization is gained in coldrolled and annealed sheet came from Path 1.On the contrary,in the one came from Path 2,theγ-fiber texture is weak.This may be due to the pinning force of numerous fine Ti（C,N）precipitate which retard the growth of preferential nucleated{111}orientated grains.Annealed steel sheets in the test came from both paths have excellent fishscale resistance.展开更多
基金supported by the National Natural Science Foundation of China(Nos.T222100,22205258,52302485 and 2024JJ5404).
文摘The electrode structures in ignition devices for Electrically Controlled Solid Propellants(ECSP)can be classified into fixed and movable types.In movable electrode structures,springs are typically used to push the electrodes and the propellant.The effects of spring pressure on the ignition and combustion of propellants have not yet been studied.In this paper,a universal testing machine and an electrochemical workstation were firstly utilized to investigate the compressive mechanical property and conductivity of Hydroxylamine Nitrate(HAN)-ECSP.The maximum pressure at which the propellant undergoes elastic deformation is 65 kPa.When the spring pressure increased from 5.1 kPa to 20.4 kPa,the propellant resistance decreased from 56.8 X to 36.8 X.Various observation methods were employed to study the process of electrical energy injection and the ignition and combustion characteristics under constant voltage.Appropriately increasing the spring pressure can accelerate the injection of electrical energy into the propellant,increase the electrification current,and thus reduce the initial ignition delay time of the propellant.When the spring pressure is 20.4 kPa,the squeezing speed of the propellant is too fast,making it difficult for the propellant to be adequately heated at the electrode interface,which is unfavorable for ignition.Excessive spring pressure also leads to the accumulation of a large amount of combustion residue on the electrode plate,hindering the mixing and diffusion of hot gases during the second ignition process,preventing the gaseous flame of the propellant.When the spring pressure is 5.1 kPa,improving the working voltage can enhance the repeated ignition characteristics of the propellant.
文摘Self-Centering Piston-Based Braced Frames(SC-PBBFs)are designed to curtail structural damage under severe ground motions.The self-centering mechanism in this bracing mitigates structural damage during an earthquake,thereby reducing post-earthquake repair costs and contributing to seismic resilience.However,non-structural components,particularly those sensitive to floor acceleration,remain vulnerable,resulting in prolonged func-tional recovery times.This paper aims to address this limitation by introducing a novel structural archetype,the Self-Centering Viscous-Based Braced Frame(SC-VBBF),which integrates superelastic shape memory alloy(SMA)bars,viscous dampers(VDs),and friction springs(FSs).A streamlined analytical approach relies on the strength decoupling of VD from other components using aλfactor to design SC-VBBFs.To evaluate the effectiveness of the hybrid brace,a set of 4-,8-,and 12-story archetypes equipped with SC-PBBs and SC-VBBFs are simulated in OpenSees and analyzed under various earthquake types,including crustal,subcrustal,and subduction events.The results demonstrate the superior performance of the SC-VBBF withλ≤0.5 system compared to SC-PBBFs in mitigating floor accelerations under design-level earthquakes and improving seismic resilience.
基金Sponsored by National Natural Science Foundation of China(50527402)National Basic Research Program(973Program)of China(2011CB606306-2)
文摘The Ti（C,N）precipitation and texture evolution in ultra-low carbon Ti-bearing enamel steel were studied to discover their correlation.Two different cooling paths of simulative coiling were adopted to gain different morphologies of Ti（C,N）precipitate in hot strips.It is found that the Ti（C,N）precipitate in hot strip using Path 2（put into asbestos box and air cooled）are finer and much more in quantity than that in hot strip using Path 1（held at 730℃ for 30min and furnace cooled）.The morphology of Ti（C,N）precipitate in hot strip has great effect on recrystallization texture in the subsequent cold-rolled annealed sheet.γ-fiber texture of strong recrystallization is gained in coldrolled and annealed sheet came from Path 1.On the contrary,in the one came from Path 2,theγ-fiber texture is weak.This may be due to the pinning force of numerous fine Ti（C,N）precipitate which retard the growth of preferential nucleated{111}orientated grains.Annealed steel sheets in the test came from both paths have excellent fishscale resistance.
