The thermo-elastic.plastic finite element method(FEM)is used to simulate the thermo-mechanical behavior of Al/steel tungsten inert gas(TIG)arc-assisted laser welding-brazing(A-LWB)butt joint.The influence of material ...The thermo-elastic.plastic finite element method(FEM)is used to simulate the thermo-mechanical behavior of Al/steel tungsten inert gas(TIG)arc-assisted laser welding-brazing(A-LWB)butt joint.The influence of material nonlinearity,geometrical nonlinearity and work hardening on the welding process is studied,and the differences in the welding temperature field,residual stress and welding distortion by A-LWB and by single laser welding-brazing(SLWB)are analyzed.The results show that the thermal cycle,residual stress distribution and welding distortion by the numerical simulation are in good agreement with the measured data by experiments,which verifies the effectiveness of FEM.Compared with the SLWB,A-LWB can make the high-temperature distribution zone of weld in width direction wider,decrease the transverse tensile stress in the weld and reduce the distribution range of longitudinal tensile stress.And the welding deformation also decreases to some extent.展开更多
Tungsten inert gas(TIG) arc-assisted laser welding–brazing was used for the butt joining of 5A06 aluminum alloy to the galvanized steel by preset filler powder without groove. The spreading behavior of liquid metal o...Tungsten inert gas(TIG) arc-assisted laser welding–brazing was used for the butt joining of 5A06 aluminum alloy to the galvanized steel by preset filler powder without groove. The spreading behavior of liquid metal on the back of the galvanized steel at different assisted welding currents was also investigated. The results show that the assisted TIG arc optimizes the interface reaction temperature, enhances the wettability of liquid metal on the steel side, and forms a sound butt joint at an appropriate welding current. A non-uniform intermetallic compound is formed at the interfacial layer, which is composed of Fe2Al5 close to the steel substrate and Fe4Al13 close to the solidified aluminum. The superior tensile strength of joint is indicated when the welding current ranges from 13 to 16 A. The average tensile strength can reach 151 MPa at the welding current of 16 A, and the corresponding fracture belongs to the ductile and brittle hybrid mode.展开更多
Wire arc additive manufacturing(WAAM)has been investigated to deposit large-scale metal parts due to its high deposition efficiency and low material cost.However,in the process of automatically manufacturing the high-...Wire arc additive manufacturing(WAAM)has been investigated to deposit large-scale metal parts due to its high deposition efficiency and low material cost.However,in the process of automatically manufacturing the high-quality metal parts by WAAM,several problems about the heat build-up,the deposit-path optimization,and the stability of the process parameters need to be well addressed.To overcome these issues,a new WAAM method based on the double electrode micro plasma arc welding(DE-MPAW)was designed.The circuit principles of different metal-transfer models in the DE-MPAW deposition process were analyzed theoretically.The effects between the parameters,wire feed rate and torch stand-off distance,in the process of WAAM were investigated experimentally.In addition,a real-time DE-MPAW control system was developed to optimize and stabilize the deposition process by self-adaptively changing the wire feed rate and torch stand-off distance.Finally,a series of tests were performed to evaluate the control system’s performance.The results show that the capability against interferences in the process of WAAM has been enhanced by this self-adaptive adjustment system.Further,the deposition paths about the metal part’s layer heights in WAAM are simplified.Finally,the appearance of the WAAM-deposited metal layers is also improved with the use of the control system.展开更多
Researchers have recently attempted to monitor pool oscillations using the three-dimensional laser vision method.However,the deficiency of simulation software will result in significant capital expenditure.Both simula...Researchers have recently attempted to monitor pool oscillations using the three-dimensional laser vision method.However,the deficiency of simulation software will result in significant capital expenditure.Both simulations and experiments are performed in this study,and the Bessel equation is used to analyze the oscillation mode of a weld pool.The laser dot matrix images of(0,1),(1,1),(2,1),and(0,2)oscillation modes at different times are obtained via structured laser optical measurement simulation.The oscillation mode of a stationary gas tungsten arc weld pool is analyzed based on laser dot matrix images obtained from a structure laser experiment.Results show that the simulated laser dot matrix images are consistent with the experiment results.The oscillation mode of the weld pool can be recognized based on the laser dot matrix image.This study not only provides conditions for assessing the penetrating state of a weld pool,but also enable a further understanding of the oscillation mode of a weld pool and the development of more effective observation methods and measurement tools to effectively control and improve welding quality.展开更多
The automatic forming device of the cladding layer of the solid rocket engine is a kind of equipment that can automatically complete the coating process of the coating layer.It is mainly composed of the feeding system...The automatic forming device of the cladding layer of the solid rocket engine is a kind of equipment that can automatically complete the coating process of the coating layer.It is mainly composed of the feeding system,the detection system and the automatic control system.The feeding system plays the role of providing the slurry in the coating process.In order to ensure the uniformity and stability of the feeding device,the automatic forming and feeding system of the coating is studied in this paper.The dynamic analysis of the slurry transportation process in the automatic coating system is carried out.In this paper,the feed cylinder is designed in theory.The feeding mode of the servo electric cylinder is adopted.Through the analysis of the hydrodynamic equations,the mixture model is chosen as the basis for the numerical simulation analysis.We use the SolidWorks software to create the geometric model of the feed cylinder.The dynamic analysis of the feed cylinder is carried out by Fluent software,and the convergent residual diagram and the fluid cloud chart are obtained.Fluent software is used for simulation analysis.The simulation results show that the distribution device has stable flow velocity and uniform slurry flow in the feeding process.The effect of scraping and coating process can be guaranteed by the feeding device,which provides a theoretical basis for actual production.展开更多
The transformation and governance of urban villages with historic culture is faced with difficulties such as lack of attention and large-scale demolition and construction,which is not conducive to the continuation of ...The transformation and governance of urban villages with historic culture is faced with difficulties such as lack of attention and large-scale demolition and construction,which is not conducive to the continuation of urban characteristic culture.Taking Xiaxifang,Yongfeng County,Ji'an City,Jiangxi Province for example,this study explored the transformation and governance of urban villages with historic culture from the perspectives of spatial structure,urban function,infrastructure,ecological environment,and community governance,so as to provide a reference for the research and practice of urban villages with historic culture.展开更多
基金Project(51465031)supported by the National Natural Science Foundation of ChinaProject(17JR5RA126)supported by the Natural Science Foundation of Gansu Province,China
文摘The thermo-elastic.plastic finite element method(FEM)is used to simulate the thermo-mechanical behavior of Al/steel tungsten inert gas(TIG)arc-assisted laser welding-brazing(A-LWB)butt joint.The influence of material nonlinearity,geometrical nonlinearity and work hardening on the welding process is studied,and the differences in the welding temperature field,residual stress and welding distortion by A-LWB and by single laser welding-brazing(SLWB)are analyzed.The results show that the thermal cycle,residual stress distribution and welding distortion by the numerical simulation are in good agreement with the measured data by experiments,which verifies the effectiveness of FEM.Compared with the SLWB,A-LWB can make the high-temperature distribution zone of weld in width direction wider,decrease the transverse tensile stress in the weld and reduce the distribution range of longitudinal tensile stress.And the welding deformation also decreases to some extent.
基金financially supported by the National Natural Science Foundation of China (No. 51465031)the Natural Science Foundation of Gansu Province (No. 145RJYA305)the Science and Technology Project of Lanzhou City (No. 2014-2-12)
文摘Tungsten inert gas(TIG) arc-assisted laser welding–brazing was used for the butt joining of 5A06 aluminum alloy to the galvanized steel by preset filler powder without groove. The spreading behavior of liquid metal on the back of the galvanized steel at different assisted welding currents was also investigated. The results show that the assisted TIG arc optimizes the interface reaction temperature, enhances the wettability of liquid metal on the steel side, and forms a sound butt joint at an appropriate welding current. A non-uniform intermetallic compound is formed at the interfacial layer, which is composed of Fe2Al5 close to the steel substrate and Fe4Al13 close to the solidified aluminum. The superior tensile strength of joint is indicated when the welding current ranges from 13 to 16 A. The average tensile strength can reach 151 MPa at the welding current of 16 A, and the corresponding fracture belongs to the ductile and brittle hybrid mode.
基金Supported by National Natural Science Foundation of China(Grant No.51665034).
文摘Wire arc additive manufacturing(WAAM)has been investigated to deposit large-scale metal parts due to its high deposition efficiency and low material cost.However,in the process of automatically manufacturing the high-quality metal parts by WAAM,several problems about the heat build-up,the deposit-path optimization,and the stability of the process parameters need to be well addressed.To overcome these issues,a new WAAM method based on the double electrode micro plasma arc welding(DE-MPAW)was designed.The circuit principles of different metal-transfer models in the DE-MPAW deposition process were analyzed theoretically.The effects between the parameters,wire feed rate and torch stand-off distance,in the process of WAAM were investigated experimentally.In addition,a real-time DE-MPAW control system was developed to optimize and stabilize the deposition process by self-adaptively changing the wire feed rate and torch stand-off distance.Finally,a series of tests were performed to evaluate the control system’s performance.The results show that the capability against interferences in the process of WAAM has been enhanced by this self-adaptive adjustment system.Further,the deposition paths about the metal part’s layer heights in WAAM are simplified.Finally,the appearance of the WAAM-deposited metal layers is also improved with the use of the control system.
基金Supported by National Natural Science Foundation of China(Grant No.51205197).
文摘Researchers have recently attempted to monitor pool oscillations using the three-dimensional laser vision method.However,the deficiency of simulation software will result in significant capital expenditure.Both simulations and experiments are performed in this study,and the Bessel equation is used to analyze the oscillation mode of a weld pool.The laser dot matrix images of(0,1),(1,1),(2,1),and(0,2)oscillation modes at different times are obtained via structured laser optical measurement simulation.The oscillation mode of a stationary gas tungsten arc weld pool is analyzed based on laser dot matrix images obtained from a structure laser experiment.Results show that the simulated laser dot matrix images are consistent with the experiment results.The oscillation mode of the weld pool can be recognized based on the laser dot matrix image.This study not only provides conditions for assessing the penetrating state of a weld pool,but also enable a further understanding of the oscillation mode of a weld pool and the development of more effective observation methods and measurement tools to effectively control and improve welding quality.
基金Research Projects of Science Foundation of Institutions of Higher Learning in Inner Mongolia Autonomous Region,China(No.NJZY13117)
文摘The automatic forming device of the cladding layer of the solid rocket engine is a kind of equipment that can automatically complete the coating process of the coating layer.It is mainly composed of the feeding system,the detection system and the automatic control system.The feeding system plays the role of providing the slurry in the coating process.In order to ensure the uniformity and stability of the feeding device,the automatic forming and feeding system of the coating is studied in this paper.The dynamic analysis of the slurry transportation process in the automatic coating system is carried out.In this paper,the feed cylinder is designed in theory.The feeding mode of the servo electric cylinder is adopted.Through the analysis of the hydrodynamic equations,the mixture model is chosen as the basis for the numerical simulation analysis.We use the SolidWorks software to create the geometric model of the feed cylinder.The dynamic analysis of the feed cylinder is carried out by Fluent software,and the convergent residual diagram and the fluid cloud chart are obtained.Fluent software is used for simulation analysis.The simulation results show that the distribution device has stable flow velocity and uniform slurry flow in the feeding process.The effect of scraping and coating process can be guaranteed by the feeding device,which provides a theoretical basis for actual production.
文摘The transformation and governance of urban villages with historic culture is faced with difficulties such as lack of attention and large-scale demolition and construction,which is not conducive to the continuation of urban characteristic culture.Taking Xiaxifang,Yongfeng County,Ji'an City,Jiangxi Province for example,this study explored the transformation and governance of urban villages with historic culture from the perspectives of spatial structure,urban function,infrastructure,ecological environment,and community governance,so as to provide a reference for the research and practice of urban villages with historic culture.
