In laser ＋ P-GMA hybrid welding, laser-wire distance is an important parameter to describe the distance from laser spot to the center of the pulsed gas metal arc. The experiments results show that the optimal laser-w...In laser ＋ P-GMA hybrid welding, laser-wire distance is an important parameter to describe the distance from laser spot to the center of the pulsed gas metal arc. The experiments results show that the optimal laser-wire distance with the deepest weld penetration increases with welding current and laser power being increased and decreases with welding speed being increased. Welding current, laser power and welding speed determine the hybrid welding heat input in laser ＋ arc hybrid welding process, so there is a correlation between the optimal laser-wire distanee and the hybrid heat input welding parameters for the deepest weld penetration： the optimal laser-wire distance increases with the heat input being increased. The positive correlation between the optimal laser-wire distance and the hybrid welding heat input is induced by the characteristics of the limited influence of P-GMA welding process on laser transmission and the dependence of weld penetration of hybrid welding on laser power.展开更多
Three-beam laser internal coaxial wire feeding cladding is regarded as a promising additive manufacturing technique because it is highly efficient and controllable.In this study,the effects of the defocus distance on ...Three-beam laser internal coaxial wire feeding cladding is regarded as a promising additive manufacturing technique because it is highly efficient and controllable.In this study,the effects of the defocus distance on cladding using a three-beam laser with internal wire feeding are experimentally and numerically studied.A process map indicating the surface characteristics at different defocus distances with various parameter combinations was developed.The transmission characteristics including laser intensity,beam size,and laser spot distance of the three-beam laser at different defocus distances were analyzed using TracePro software.Based on the TracePro results as heat source,a three-dimensional transient finite element(FE)thermal model was formulated to predict the thermal field,temperature history and molten pool shape at different defocus distances.A molten pool with a flat bottom and low melting depth is generated when the defocus distance is−2.5 mm,whereas when this distance is−1.5 mm,a pool with a valley-shaped bond and high melting depth is formed.The simulated results of the temperature cycle and clad geometry are both validated and found to well agree with experimental measurements.The influence of the defocus distance on the microstructure and microhardness are discussed based on the temperature history and cooling rate.With the increase in the absolute defocus distance,the height and dilution of the clad decreased,whereas the width increased.In addition,the effects of defocus distance with various parameter combinations on clad geometry were explored using the formulated FE model.展开更多
The temperature fields in laser ＋ GMAW-P hybrid welding for different laser-wire distances in quasi-steady state were calculated using an developed combined heat source model, and the influence of laser-wire distance...The temperature fields in laser ＋ GMAW-P hybrid welding for different laser-wire distances in quasi-steady state were calculated using an developed combined heat source model, and the influence of laser-wire distance on them was analyzed. The results show tbat, at a low level of arc power, the temperature profiles caused by laser and arc energy respecively cannot couple well when the laser-wire distance reaches 4 mm, a trend of separation between them beginning to take place. In the case of high arc power, both the critical laser-wire distance and HAZ width increase.展开更多
The present study is concerned with laser beam welding and its effect on size and microstructure of fusion zone then, on mechanical and corrosion properties of duplex stainless steel welded joints. In this regard, inf...The present study is concerned with laser beam welding and its effect on size and microstructure of fusion zone then, on mechanical and corrosion properties of duplex stainless steel welded joints. In this regard, influence of different laser welding parameters was clarified. Both bead-on-plate and autogenously butt welded joints were made using carbon dioxide laser with a maximum output of 9 kW in the continuous wave mode. Welded joints were subjected to visual, dye penetrant and radiography tests before sectioning it for different destructive tests. Accelerated corrosion test was carried out based on tafel plot technique. The results achieved in this investigation disclosed that welding parameters play an important role in obtaining satisfactory properties of welded joint. High laser power and/or high welding speed together with adjusting laser focused spot at specimen surface have produced welded joints with a remarkable decrease in fusion zone size and an acceptable weld profile with higher weld depth/width ratio. Besides, acceptable mechanical and corrosion properties were obtained. Using nitrogen as a shielding gas has resulted in improving mechanical and corrosion properties of welded joints in comparison with argon shielding. This is related to maintaining proper ferrite/austenite balance in both weld metal and HAZ in case of nitrogen shielding. As a conclusion, laser power, welding speed, defocusing distance and type of shielding gas combination have to be optimized for obtaining welded joints with acceptable profile as well as mechanical and corrosion properties.展开更多
The laser wire （LW） method has been demonstrated to be an effective non-interceptive technique for measuring transverse profile and emittance of electron beams in colliders, storage rings and dumping rings. In this ...The laser wire （LW） method has been demonstrated to be an effective non-interceptive technique for measuring transverse profile and emittance of electron beams in colliders, storage rings and dumping rings. In this paper, we present an improved design of high repetition LW system for high average power free electron lasers （HAP FELs） and energy recovery linacs （ERLs）. This improved LW utilizes the excess power of the photocathode drive laser, thus making itself much cheaper and simpler. The system main parameters are optimized with numerical calculations and Monte Carlo simulations, indicating that resolutions would be better than 100 ~m and scanning time less than 1 minute. Status of the experiment preparation is also presented.展开更多
为了解决激光驾束制导中发动机烟雾对制导激光场信号的衰减问题,采用van de Hulst近似计算方法,模拟研究了烟雾对1.06μm,1.55μm,10.6μm波长的激光在不同复折射率参量下的吸收、散射、衰减效应。结果表明,复折射率不变时,烟雾对长波...为了解决激光驾束制导中发动机烟雾对制导激光场信号的衰减问题,采用van de Hulst近似计算方法,模拟研究了烟雾对1.06μm,1.55μm,10.6μm波长的激光在不同复折射率参量下的吸收、散射、衰减效应。结果表明,复折射率不变时,烟雾对长波长激光的吸收衰减较小;烟雾对激光的衰减峰值随着折射率虚部的增大而变小;峰值的位置随着激光波长的增加向粒子半径增大的方向移动。该研究结果对激光驾束制导武器的研制具有较大的参考价值。展开更多
基金Supported by the key project of Natural Science Foundation of Heilongjiang Province （ZJG0601 and the National Key Technologies Research and Development Program of China during the 11^th Five-Year Plan Period （2006BAFO4B10）.
文摘In laser ＋ P-GMA hybrid welding, laser-wire distance is an important parameter to describe the distance from laser spot to the center of the pulsed gas metal arc. The experiments results show that the optimal laser-wire distance with the deepest weld penetration increases with welding current and laser power being increased and decreases with welding speed being increased. Welding current, laser power and welding speed determine the hybrid welding heat input in laser ＋ arc hybrid welding process, so there is a correlation between the optimal laser-wire distanee and the hybrid heat input welding parameters for the deepest weld penetration： the optimal laser-wire distance increases with the heat input being increased. The positive correlation between the optimal laser-wire distance and the hybrid welding heat input is induced by the characteristics of the limited influence of P-GMA welding process on laser transmission and the dependence of weld penetration of hybrid welding on laser power.
基金Supported by National Natural Science Foundation of China(Grant No.61903268)Jiangsu Provincial Natural Science Foundation of China(Grant No.BK20190823)China Postdoctoral Science Foundation Grant(Grant No.2019M661921).
文摘Three-beam laser internal coaxial wire feeding cladding is regarded as a promising additive manufacturing technique because it is highly efficient and controllable.In this study,the effects of the defocus distance on cladding using a three-beam laser with internal wire feeding are experimentally and numerically studied.A process map indicating the surface characteristics at different defocus distances with various parameter combinations was developed.The transmission characteristics including laser intensity,beam size,and laser spot distance of the three-beam laser at different defocus distances were analyzed using TracePro software.Based on the TracePro results as heat source,a three-dimensional transient finite element(FE)thermal model was formulated to predict the thermal field,temperature history and molten pool shape at different defocus distances.A molten pool with a flat bottom and low melting depth is generated when the defocus distance is−2.5 mm,whereas when this distance is−1.5 mm,a pool with a valley-shaped bond and high melting depth is formed.The simulated results of the temperature cycle and clad geometry are both validated and found to well agree with experimental measurements.The influence of the defocus distance on the microstructure and microhardness are discussed based on the temperature history and cooling rate.With the increase in the absolute defocus distance,the height and dilution of the clad decreased,whereas the width increased.In addition,the effects of defocus distance with various parameter combinations on clad geometry were explored using the formulated FE model.
文摘The temperature fields in laser ＋ GMAW-P hybrid welding for different laser-wire distances in quasi-steady state were calculated using an developed combined heat source model, and the influence of laser-wire distance on them was analyzed. The results show tbat, at a low level of arc power, the temperature profiles caused by laser and arc energy respecively cannot couple well when the laser-wire distance reaches 4 mm, a trend of separation between them beginning to take place. In the case of high arc power, both the critical laser-wire distance and HAZ width increase.
文摘The present study is concerned with laser beam welding and its effect on size and microstructure of fusion zone then, on mechanical and corrosion properties of duplex stainless steel welded joints. In this regard, influence of different laser welding parameters was clarified. Both bead-on-plate and autogenously butt welded joints were made using carbon dioxide laser with a maximum output of 9 kW in the continuous wave mode. Welded joints were subjected to visual, dye penetrant and radiography tests before sectioning it for different destructive tests. Accelerated corrosion test was carried out based on tafel plot technique. The results achieved in this investigation disclosed that welding parameters play an important role in obtaining satisfactory properties of welded joint. High laser power and/or high welding speed together with adjusting laser focused spot at specimen surface have produced welded joints with a remarkable decrease in fusion zone size and an acceptable weld profile with higher weld depth/width ratio. Besides, acceptable mechanical and corrosion properties were obtained. Using nitrogen as a shielding gas has resulted in improving mechanical and corrosion properties of welded joints in comparison with argon shielding. This is related to maintaining proper ferrite/austenite balance in both weld metal and HAZ in case of nitrogen shielding. As a conclusion, laser power, welding speed, defocusing distance and type of shielding gas combination have to be optimized for obtaining welded joints with acceptable profile as well as mechanical and corrosion properties.
文摘The laser wire （LW） method has been demonstrated to be an effective non-interceptive technique for measuring transverse profile and emittance of electron beams in colliders, storage rings and dumping rings. In this paper, we present an improved design of high repetition LW system for high average power free electron lasers （HAP FELs） and energy recovery linacs （ERLs）. This improved LW utilizes the excess power of the photocathode drive laser, thus making itself much cheaper and simpler. The system main parameters are optimized with numerical calculations and Monte Carlo simulations, indicating that resolutions would be better than 100 ~m and scanning time less than 1 minute. Status of the experiment preparation is also presented.
文摘为了解决激光驾束制导中发动机烟雾对制导激光场信号的衰减问题,采用van de Hulst近似计算方法,模拟研究了烟雾对1.06μm,1.55μm,10.6μm波长的激光在不同复折射率参量下的吸收、散射、衰减效应。结果表明,复折射率不变时,烟雾对长波长激光的吸收衰减较小;烟雾对激光的衰减峰值随着折射率虚部的增大而变小;峰值的位置随着激光波长的增加向粒子半径增大的方向移动。该研究结果对激光驾束制导武器的研制具有较大的参考价值。
