Short-arc pulsed gas metal arc welding(P-GMAW)was used to solve the dificulties of molten pool spreading and droplet transfer of Ni-based welding wire.Suppression of short-circuit current was used to reduce spatter.Ar...Short-arc pulsed gas metal arc welding(P-GMAW)was used to solve the dificulties of molten pool spreading and droplet transfer of Ni-based welding wire.Suppression of short-circuit current was used to reduce spatter.Arc length stabilizer was used to acquire a proper and stable arc length maintained at the critical position where short circuit starts to occur.Short-arc P-GMAW with or without arc length stabilizer was compared.The droplet transfer,arc behaviors and weld bead profiles were investigated and compared based on the high-speed photography and observation of weld cross-section.When the arc length stabilizer was deactivated,the arc length was unstable and too short.The droplet transfer mode was mainly short circuit partial transfer,with only a small part of the droplet transferred into the molten pool,with the characteristics of no obvious necking,a few spatters,small droplet impact,long short circuit duration and high short-circuit current.There was also a small proportion of short circuit complete transfer with obvious necking,larger droplet impact,shorter short-circuit duration and lower short-circuit current.With arc length stabilizer,droplet transfer modes were short circuit complete transfer and spray transfer.The spray transfer had the largest droplet impact,no short circuit and no spatter.With the arc length stabilizer activated,a deep penetration,a high penetration ratio,a small reinforcement and a large reinforcement factor were acquired.This provides an innovative method to solve the difficulties of droplet transfer and molten pool spreading and eliminate the incomplete fusion in the GMAW of 9%Ni steel with nickel-based alloy welding wire.展开更多
The shockwave induced by surface direct-current （DC） arc discharge is investigated both experimentally and numer- ically. In the experiment, the shockwave generated by rapid gas heating is clearly observed from Schl...The shockwave induced by surface direct-current （DC） arc discharge is investigated both experimentally and numer- ically. In the experiment, the shockwave generated by rapid gas heating is clearly observed from Schlieren images. The peak velocity of the shockwave is measured to be over 410 m/s; during its upright movement, it gradually falls to about 340 m/s; no remarkable difference is seen after changing the discharge voltage and the pulse frequency. In the modeling of the arc plasma, the arc domain is not simulated as a boundary condition with fixed temperature or pressure, but a source term with a time-varying input power density, which could better reflect the influence of the heating process. It is found that with a reference power density of 2.8× 1012 W/m2, the calculated peak velocity is higher than the measured one, but they quickly （in 30 Its） become agreed with each other. The peak velocity also rises while increasing the power density, the maximum velocity acquired in the simulation is over 468 m/s, which is expected to be effective for high speed flow control.展开更多
Ti Ni形状记忆合金是目前唯一用作生物医学材料的形状记忆合金。它的主要缺点是不具有生物活性,会对机体造成不利影响。DLC膜以其优异的生物相容性、抗腐蚀性及化学稳定性倍受关注。利用脉冲真空电弧离子镀技术镀制DLC膜改善Ti Ni合... Ti Ni形状记忆合金是目前唯一用作生物医学材料的形状记忆合金。它的主要缺点是不具有生物活性,会对机体造成不利影响。DLC膜以其优异的生物相容性、抗腐蚀性及化学稳定性倍受关注。利用脉冲真空电弧离子镀技术镀制DLC膜改善Ti Ni合金的表面性能。对DLC膜的表面形貌、显微硬度、摩擦系数、耐磨性能及耐腐蚀性能进行了测试。结果表明:用脉冲真空电弧离子镀技术制备的DLC膜膜层表面形貌较好、硬度高、摩擦系数小、耐磨及耐腐蚀性能良好。展开更多
An empirical relationship to predict tensile strength of pulsed current gas tungsten arc welded AZ31B magnesium alloy was developed. Incorporating process parameters such as peak current, base current, pulse frequency...An empirical relationship to predict tensile strength of pulsed current gas tungsten arc welded AZ31B magnesium alloy was developed. Incorporating process parameters such as peak current, base current, pulse frequency and pulse on time were studied. The experiments were conducted based on a four-factor, five-level, central composite design matrix. The developed empirical relationship can be effectively used to predict the tensile strength of pulsed current gas tungsten arc welded AZ31B magnesium alloy joints at 95% confidence level. The results indicate that pulse frequency has the greatest influence on tensile strength, followed by peak current, pulse on time and base current.展开更多
This study conducted experiments on producing inhaled medical nitric oxide （iNO） by pulsed arc discharge in dry and clean air under different discharge current. The concentration of NO and NO2 produced by air discha...This study conducted experiments on producing inhaled medical nitric oxide （iNO） by pulsed arc discharge in dry and clean air under different discharge current. The concentration of NO and NO2 produced by air discharge, as well as the change of the ratio of NO2/NO under different discharge current were investigated. Through the analysis of plasma emission spectrum, the relationship between discharge current and arc plasma temperature was studied. The results indicate that, as discharge current increases, the arc plasma temperature increases, which then leads to the increase of NO concentration, the decrease of NO2 concentration, and the rapid decrease of the ratio of NO2/NO. When the plasma temperature is 9000 K, the ratio of NO2/NO is approximately 60%, while when the plasma temperature varies between 10550 K and 11300 K, the NO2/NO ratio is within the range of 4.2% to 4.6%.展开更多
Arc deposition, a widely used surface coating technique, has disadvantages such as large droplet size and high deposition temperature. Recent trend in its renovation is the introduction of pulsed bias at the. substrat...Arc deposition, a widely used surface coating technique, has disadvantages such as large droplet size and high deposition temperature. Recent trend in its renovation is the introduction of pulsed bias at the. substrate. The present paper attempts to describe the deposition process of TiN films using this technique with emphasis laid on the understanding of the basic problems such as discharge plasma properties, temperature calculation, and droplet size reduction. We show that this technique improves the film micro structure and quality, lowers deposition temperature, and allows coatings on insulating substrates. After analyzing load current oscillation behaviors, we have determined that the plasma load is of capacitance nature due to plasma sheath and that it is equivalent to a circuit element consisting of parallel capacitance and resistance. At last, we point out the remaining problems and future development of the pulsed-bias arc deposition technique.展开更多
A novel synergetic arc control method was used to control twin-electrode alternating current （ AC） to direct current （DC） pulsed arc welding and the mechanism of poor sidewall fusion in narrow gap welding was inve...A novel synergetic arc control method was used to control twin-electrode alternating current （ AC） to direct current （DC） pulsed arc welding and the mechanism of poor sidewall fusion in narrow gap welding was investigated. The synergetic arc control method easured that the arc voltage of DC welding source could switch in phase with the AC welding source. To test the reliability and operability of this method, a twin-electrode AC to DC pulsed arc welding system was set up and data was acquired through high-speed photography and electrical signal measurement system. The results show that the interactions between the two arcs can be controlled effectively and the control method is a sensitive and efficient control method.展开更多
基金the MARK III Materials Research Project of Ministry of Industry and Information Technology of China。
文摘Short-arc pulsed gas metal arc welding(P-GMAW)was used to solve the dificulties of molten pool spreading and droplet transfer of Ni-based welding wire.Suppression of short-circuit current was used to reduce spatter.Arc length stabilizer was used to acquire a proper and stable arc length maintained at the critical position where short circuit starts to occur.Short-arc P-GMAW with or without arc length stabilizer was compared.The droplet transfer,arc behaviors and weld bead profiles were investigated and compared based on the high-speed photography and observation of weld cross-section.When the arc length stabilizer was deactivated,the arc length was unstable and too short.The droplet transfer mode was mainly short circuit partial transfer,with only a small part of the droplet transferred into the molten pool,with the characteristics of no obvious necking,a few spatters,small droplet impact,long short circuit duration and high short-circuit current.There was also a small proportion of short circuit complete transfer with obvious necking,larger droplet impact,shorter short-circuit duration and lower short-circuit current.With arc length stabilizer,droplet transfer modes were short circuit complete transfer and spray transfer.The spray transfer had the largest droplet impact,no short circuit and no spatter.With the arc length stabilizer activated,a deep penetration,a high penetration ratio,a small reinforcement and a large reinforcement factor were acquired.This provides an innovative method to solve the difficulties of droplet transfer and molten pool spreading and eliminate the incomplete fusion in the GMAW of 9%Ni steel with nickel-based alloy welding wire.
基金Project supported by the Key Program of the National Natural Science Foundation of China(Grant No.51336011)the National Natural Science Foundation of China(Grant Nos.51207169 and 51276197)
文摘The shockwave induced by surface direct-current （DC） arc discharge is investigated both experimentally and numer- ically. In the experiment, the shockwave generated by rapid gas heating is clearly observed from Schlieren images. The peak velocity of the shockwave is measured to be over 410 m/s; during its upright movement, it gradually falls to about 340 m/s; no remarkable difference is seen after changing the discharge voltage and the pulse frequency. In the modeling of the arc plasma, the arc domain is not simulated as a boundary condition with fixed temperature or pressure, but a source term with a time-varying input power density, which could better reflect the influence of the heating process. It is found that with a reference power density of 2.8× 1012 W/m2, the calculated peak velocity is higher than the measured one, but they quickly （in 30 Its） become agreed with each other. The peak velocity also rises while increasing the power density, the maximum velocity acquired in the simulation is over 468 m/s, which is expected to be effective for high speed flow control.
文摘 Ti Ni形状记忆合金是目前唯一用作生物医学材料的形状记忆合金。它的主要缺点是不具有生物活性,会对机体造成不利影响。DLC膜以其优异的生物相容性、抗腐蚀性及化学稳定性倍受关注。利用脉冲真空电弧离子镀技术镀制DLC膜改善Ti Ni合金的表面性能。对DLC膜的表面形貌、显微硬度、摩擦系数、耐磨性能及耐腐蚀性能进行了测试。结果表明:用脉冲真空电弧离子镀技术制备的DLC膜膜层表面形貌较好、硬度高、摩擦系数小、耐磨及耐腐蚀性能良好。
文摘An empirical relationship to predict tensile strength of pulsed current gas tungsten arc welded AZ31B magnesium alloy was developed. Incorporating process parameters such as peak current, base current, pulse frequency and pulse on time were studied. The experiments were conducted based on a four-factor, five-level, central composite design matrix. The developed empirical relationship can be effectively used to predict the tensile strength of pulsed current gas tungsten arc welded AZ31B magnesium alloy joints at 95% confidence level. The results indicate that pulse frequency has the greatest influence on tensile strength, followed by peak current, pulse on time and base current.
基金supported by National Natural Science Foundation of China (No.50677026)the Graduates' Innovation Foundation of Huazhong University of Science and Technology of China (HF-08-11-2011-261)
文摘This study conducted experiments on producing inhaled medical nitric oxide （iNO） by pulsed arc discharge in dry and clean air under different discharge current. The concentration of NO and NO2 produced by air discharge, as well as the change of the ratio of NO2/NO under different discharge current were investigated. Through the analysis of plasma emission spectrum, the relationship between discharge current and arc plasma temperature was studied. The results indicate that, as discharge current increases, the arc plasma temperature increases, which then leads to the increase of NO concentration, the decrease of NO2 concentration, and the rapid decrease of the ratio of NO2/NO. When the plasma temperature is 9000 K, the ratio of NO2/NO is approximately 60%, while when the plasma temperature varies between 10550 K and 11300 K, the NO2/NO ratio is within the range of 4.2% to 4.6%.
基金This work was supported by the National Natural Science Foundation of China (Grant No.50071017).
文摘Arc deposition, a widely used surface coating technique, has disadvantages such as large droplet size and high deposition temperature. Recent trend in its renovation is the introduction of pulsed bias at the. substrate. The present paper attempts to describe the deposition process of TiN films using this technique with emphasis laid on the understanding of the basic problems such as discharge plasma properties, temperature calculation, and droplet size reduction. We show that this technique improves the film micro structure and quality, lowers deposition temperature, and allows coatings on insulating substrates. After analyzing load current oscillation behaviors, we have determined that the plasma load is of capacitance nature due to plasma sheath and that it is equivalent to a circuit element consisting of parallel capacitance and resistance. At last, we point out the remaining problems and future development of the pulsed-bias arc deposition technique.
基金Supported by National Natural Science Foundation of China （Grant No. 51175374）, the Application of Basic ＆ Frontier Technology Program of Tianjin （Grant No. 09JCYBJC05000） and the Science ＆ Technology Pillar Program of Tianjin（ Grant No. 10ZCKFSF00200）.
文摘A novel synergetic arc control method was used to control twin-electrode alternating current （ AC） to direct current （DC） pulsed arc welding and the mechanism of poor sidewall fusion in narrow gap welding was investigated. The synergetic arc control method easured that the arc voltage of DC welding source could switch in phase with the AC welding source. To test the reliability and operability of this method, a twin-electrode AC to DC pulsed arc welding system was set up and data was acquired through high-speed photography and electrical signal measurement system. The results show that the interactions between the two arcs can be controlled effectively and the control method is a sensitive and efficient control method.
