A submerged cavitation water jet(SCWJ)is an effective method to recycle solid propellant from obsolete solid engines by the breaking method.Solid propellant's breaking modes and mechanical process under SCWJ impac...A submerged cavitation water jet(SCWJ)is an effective method to recycle solid propellant from obsolete solid engines by the breaking method.Solid propellant's breaking modes and mechanical process under SCWJ impact are unclear.This study aims to understand those impact breaking mechanisms.The hydroxyl-terminated polybutadiene(HTPB)propellant was chosen as the research material,and a self-designed test system was used to conduct impact tests at four different working pressures.The high-speed camera characterized crack propagation,and the DIC method calculated strain change during the impact process.Besides,micro and macro fracture morphologies were characterized by scanning electron microscope(SEM)and computed tomography(CT)scanning.The results reveal that the compressive strain concentration region locates right below the nozzle,and the shear strain region distributes symmetrically with the jet axis,which increases to 4% at first 16th ms,the compressive strain rises to 2% and 6% in the axial and transverse direction,respectively.The two tensile cracks formed first at the compression strain concentrate region,and there generate many shear cracks around the tensile cracks,and those shear cracks that develop and aggregate cause the cracks to become wider and cut through the tensile cracks,forming the tensile-shear cracks and the impact parts eventually fail.The HTPB propellant forms a breaking hole shaped conical after impact 10 s.The mass loss increases by 17 times at maximum,with the working pressure increasing by three times.Meanwhile,the damage value of the breaking hole remaining on the surface increases by 7.8 times while 2.9 times in the depth of the breaking hole.The breaking efficiency is closely affected by working pressures.The failure modes of HTPB impacted by SCWJ are classified as tensile crack-dominated and tensile-shear crack-dominated damage mechanisms.展开更多
An adaptive heat source mode is proposed to account for the keyhole effect and the characteristics of volumetric distribution along the direction of the workpiece thickness. Finite element analysis of the temperature ...An adaptive heat source mode is proposed to account for the keyhole effect and the characteristics of volumetric distribution along the direction of the workpiece thickness. Finite element analysis of the temperature field in keyhole plasma arc welding is conducted and the weld geometry is obtained. The predicted results are in agreement with the measured ones.展开更多
Using Xenon lamp lights to overcome the strong interference from the welding arc,a computer-based system is developed to sense and visualize the metal transfer in GMAW.This system combines through-the-arc sensing of t...Using Xenon lamp lights to overcome the strong interference from the welding arc,a computer-based system is developed to sense and visualize the metal transfer in GMAW.This system combines through-the-arc sensing of the welding current and arc voltage with high speed imaging of the metal transfer.It can simultaneously display the metal transfer processes and waveforms of electrical welding parameters in real-time The metal transfer videos and waveforms of electrical welding parameters can be recorded.Metal transfers under various welding conditions have been investigated with the system developed.展开更多
Dilution of a pad weld must be limited to a certain critical level to improve its wear and/or corrosion properties.To do that,a novel single wire indirect arc metal inert gas welding process operated in streaming mode...Dilution of a pad weld must be limited to a certain critical level to improve its wear and/or corrosion properties.To do that,a novel single wire indirect arc metal inert gas welding process operated in streaming mode was realized.A metal inert gas welding torch,arranged perpendicular to a substrate in vertical position,is fixed with an auxiliary tungsten electrode horizontally.The arc is ignited between a wire through the torch and the auxiliary electrode.The substrate is not electrically connected.The welding current is set in the range of streaming mode.304 stainless steel was pad welded on Q235 substrates in vertical position by this process.Microstructures were analyzed with optical microscope.Dilution ratios were measured with stereo light microscope and calculated.The results show that,after eliminating interference of the massive torch setup,the dilution ratio of the pad weld with optimized parameters is 5.07%,much less than that with a metal inert gas welding process,which is 26.46%.The pad weld is bonded to the substrate without defects.Microstructures of the pad weld consist of columnar austenite and ferrite between the columns.The dilution ratio increases with increasing welding current or welding velocity,and decreases with increasing distance to the substrate.展开更多
The influence of an arc current on the discharge development and the arc modes ofa single coil type axial magnetic field(AMF)electrode were investigated by a high-speed chargecouple device(CCD)video camera in a long g...The influence of an arc current on the discharge development and the arc modes ofa single coil type axial magnetic field(AMF)electrode were investigated by a high-speed chargecouple device(CCD)video camera in a long gap distance of 40 ram.The distribution of the axialmagnetic field of the single coil type AMF electrode was computed.By computational results,thesingle coil type AMF electrode could generate higher axial magnetic flux density than the slot typeAMF electrode.It was found that the single coil type AMF electrode could perform better thanthe slot type AMF electrode with the same designing parameters.And the development of the arcmodes experienced diffuse mode,constricted but unstable mode,and constricted and stable modewith the amplitude of the arc current increasing.The correlation between the vacuum arc andthe noise components of arc voltage was investigated too.The interruption capability could beknown in a practical commercial vacuum interrupter by the test results in a demountable vacuuminterrupter(DVC)with a electrode diameter of 50mm and a gap distance of 40mm.The testresults could provide reference to design the high voltage vacuum interrupter adopting the singlecoil type AMF electrode.展开更多
基金supported by the Program for National Defense Science and Technology Foundation Strengtheningthe Youth Foundation of Rocket Force University of Engineering(Grant No.2021QN-B014)。
文摘A submerged cavitation water jet(SCWJ)is an effective method to recycle solid propellant from obsolete solid engines by the breaking method.Solid propellant's breaking modes and mechanical process under SCWJ impact are unclear.This study aims to understand those impact breaking mechanisms.The hydroxyl-terminated polybutadiene(HTPB)propellant was chosen as the research material,and a self-designed test system was used to conduct impact tests at four different working pressures.The high-speed camera characterized crack propagation,and the DIC method calculated strain change during the impact process.Besides,micro and macro fracture morphologies were characterized by scanning electron microscope(SEM)and computed tomography(CT)scanning.The results reveal that the compressive strain concentration region locates right below the nozzle,and the shear strain region distributes symmetrically with the jet axis,which increases to 4% at first 16th ms,the compressive strain rises to 2% and 6% in the axial and transverse direction,respectively.The two tensile cracks formed first at the compression strain concentrate region,and there generate many shear cracks around the tensile cracks,and those shear cracks that develop and aggregate cause the cracks to become wider and cut through the tensile cracks,forming the tensile-shear cracks and the impact parts eventually fail.The HTPB propellant forms a breaking hole shaped conical after impact 10 s.The mass loss increases by 17 times at maximum,with the working pressure increasing by three times.Meanwhile,the damage value of the breaking hole remaining on the surface increases by 7.8 times while 2.9 times in the depth of the breaking hole.The breaking efficiency is closely affected by working pressures.The failure modes of HTPB impacted by SCWJ are classified as tensile crack-dominated and tensile-shear crack-dominated damage mechanisms.
文摘An adaptive heat source mode is proposed to account for the keyhole effect and the characteristics of volumetric distribution along the direction of the workpiece thickness. Finite element analysis of the temperature field in keyhole plasma arc welding is conducted and the weld geometry is obtained. The predicted results are in agreement with the measured ones.
基金supported by the Opening Project Foundation of MOE Key Laboratory of Liquid Structure and Heredity of Materials and Natural Science foundation of Shandong Province(Grant NO.Y20002F24).
文摘Using Xenon lamp lights to overcome the strong interference from the welding arc,a computer-based system is developed to sense and visualize the metal transfer in GMAW.This system combines through-the-arc sensing of the welding current and arc voltage with high speed imaging of the metal transfer.It can simultaneously display the metal transfer processes and waveforms of electrical welding parameters in real-time The metal transfer videos and waveforms of electrical welding parameters can be recorded.Metal transfers under various welding conditions have been investigated with the system developed.
文摘Dilution of a pad weld must be limited to a certain critical level to improve its wear and/or corrosion properties.To do that,a novel single wire indirect arc metal inert gas welding process operated in streaming mode was realized.A metal inert gas welding torch,arranged perpendicular to a substrate in vertical position,is fixed with an auxiliary tungsten electrode horizontally.The arc is ignited between a wire through the torch and the auxiliary electrode.The substrate is not electrically connected.The welding current is set in the range of streaming mode.304 stainless steel was pad welded on Q235 substrates in vertical position by this process.Microstructures were analyzed with optical microscope.Dilution ratios were measured with stereo light microscope and calculated.The results show that,after eliminating interference of the massive torch setup,the dilution ratio of the pad weld with optimized parameters is 5.07%,much less than that with a metal inert gas welding process,which is 26.46%.The pad weld is bonded to the substrate without defects.Microstructures of the pad weld consist of columnar austenite and ferrite between the columns.The dilution ratio increases with increasing welding current or welding velocity,and decreases with increasing distance to the substrate.
基金National Nature Science Foundation of China(No.50477024)
文摘The influence of an arc current on the discharge development and the arc modes ofa single coil type axial magnetic field(AMF)electrode were investigated by a high-speed chargecouple device(CCD)video camera in a long gap distance of 40 ram.The distribution of the axialmagnetic field of the single coil type AMF electrode was computed.By computational results,thesingle coil type AMF electrode could generate higher axial magnetic flux density than the slot typeAMF electrode.It was found that the single coil type AMF electrode could perform better thanthe slot type AMF electrode with the same designing parameters.And the development of the arcmodes experienced diffuse mode,constricted but unstable mode,and constricted and stable modewith the amplitude of the arc current increasing.The correlation between the vacuum arc andthe noise components of arc voltage was investigated too.The interruption capability could beknown in a practical commercial vacuum interrupter by the test results in a demountable vacuuminterrupter(DVC)with a electrode diameter of 50mm and a gap distance of 40mm.The testresults could provide reference to design the high voltage vacuum interrupter adopting the singlecoil type AMF electrode.
