A coding and decoding process of argon plasma images using digital holography is proposed. The digital Fourier holography is applied to two images of matrix dimensions 512 × 512 pixels. The decoded images are imp...A coding and decoding process of argon plasma images using digital holography is proposed. The digital Fourier holography is applied to two images of matrix dimensions 512 × 512 pixels. The decoded images are improved using wiener filtering techniques. We have constructed three basic color images of the original image which is useful to extract the thermal distribution of the plasma image. Also, the profiles of the reconstructed images are checked showing better smooth profiles using wiener filter. The Mat-lab code is applied in the operation of image processing using Fourier techniques.展开更多
High-speed photography was used to obtain the dynamic changes in the surface plasma during a high-power disk laser welding process. A color space clustering algorithm to extract the edge information of the surface pla...High-speed photography was used to obtain the dynamic changes in the surface plasma during a high-power disk laser welding process. A color space clustering algorithm to extract the edge information of the surface plasma region was developed in order to improve the accuracy of image processing. With a comparative analysis of the plasma features, i.e., area and height, and the characteristics of the welded seam, the relationship between the surface plasma and the stability of the laser welding process was characterized, which provides a basic understanding for the real-time monitoring of laser welding.展开更多
In-flight particle velocity and flux distribution were measured using CCD thermal spray monitor system during supersonic plasma spray processing with nano-structured Al_2O_3-TiO_2 feed stocks. According to the results...In-flight particle velocity and flux distribution were measured using CCD thermal spray monitor system during supersonic plasma spray processing with nano-structured Al_2O_3-TiO_2 feed stocks. According to the results of particle flux measurement, the largest radian of the divergent particle stream is about 0.2. Within the measuring range, top speed of in-flight particles reached 800m/s. Particle acceleration was accomplished within 4cm down stream of the nozzle. Average particle velocity (about 450m/s) exceeded local sound speed (340m/s) even at a mean standoff distance of 17cm. With increasing mean standoff distance, average velocity of in-flight particle decreased according to a parabolic rule approximately. Image diagnosis showed that the result of in-flight particle velocity measurement is credible.展开更多
This paper is devoted to experimentally investigating the influence of magnetic field intensity and gas temperature on the plasma jet deflection controlled by magneto hydrodynamics. The catalytic ionization seed CS_2C...This paper is devoted to experimentally investigating the influence of magnetic field intensity and gas temperature on the plasma jet deflection controlled by magneto hydrodynamics. The catalytic ionization seed CS_2CO_3 is injected into combustion gas by artificial forced ionization to obtain plasma fluid on a high-temperature magnetic fluid experimental platform. The plasma jet was deflected under the effect of an external magnetic field, forming a thrust-vector effect.Magnesium oxide was selected as a tracer particle, and a two-dimensional image of the jet flow field was collected using the particle image velocimetry(PIV) measurement method. Through image processing and velocity vector analysis of the flow field, the value of the jet deflection angle was obtained quantitatively to evaluate the thrust-vector effect. The variation of the jet deflection angle with the magnetic field intensity and gas temperature was studied under different experimental conditions. Experimental results show that the jet deflection angle increased gradually with a rise in gas temperature and then increased substantially when the gas temperature exceeded 2300 K. The jet deflection angle also increased with an increase in magnetic induction intensity. Experiments demonstrate it is feasible to use PIV test technology to study the thrust vector under magnetic control conditions.展开更多
Manual monitoring and seam tracking through watching weld pool images in real-time, by naked eyes or by industrial TV, are experience-depended, subjective, labor intensive, and sometimes biased. So it is necessary to ...Manual monitoring and seam tracking through watching weld pool images in real-time, by naked eyes or by industrial TV, are experience-depended, subjective, labor intensive, and sometimes biased. So it is necessary to realize the automation of computer-aided seam tracking. A PAW (plasma arc welding) seam tracking system was developed, which senses the molten pool and the seam in one frame by a vision sensor, and then detects the seam deviation to adjust the work piece motion adaptively to the seam position sensed by vision sensor. A novel molten pool area image-processing algorithm based on machine vision was proposed. The algorithm processes each image at the speed of 20 frames/second in real-time to extract three feature variables to get the seam deviation. It is proved experimentally that the algorithm is very fast and effective. Issues related to the algorithm are also discussed.展开更多
Plasma spraying is an important enabling technology i n near-net-shaped process as well as many high-performance coating applicatio ns. Recently, it is being applied to rapid mould manufacturing to reduce develop ment...Plasma spraying is an important enabling technology i n near-net-shaped process as well as many high-performance coating applicatio ns. Recently, it is being applied to rapid mould manufacturing to reduce develop ment time and manufacturing cost. In this process, inputted powders are heated a nd accelerated by plasma jet, and impinge on master pattern or prototype to form ing a thick coating. Mould will be fabricated after backed-up with consolidated material and other post-treatments. Amongst numerous factors that affect the l ife and properties of mould made by this novel method, quality of coating is the most important one. However, the complex nature of the spray process results in a large number of processing parameters that must be controlled in order to obt ain optimum coatings. Traditional "trial and error" method is too time and cost consuming for the optimal processing parameters. Maybe modeling and diagnostics of process is the best way to ravel out the problems. It has been proved that pl asma-gas flowrate, power level and spray distance are the most critical variabl es. So flow visualization and diagnostics for plasma jet quality has become an i mportant task to obtain a repeatable and reliable plasma processing technology. Using enthalpy probe diagnostics, spectrometry and optical measurement, we can o btain the distribution of temperature field of plasma jet. These results can hel p us to design gun configuration and optimize processing parameters for high dep osition efficiency and good qualities of rapid mould manufacturing. Nevertheless , it is still very difficult to realize real-time diagnoses because of restrict of diagnosis condition and drawback of measurement approach. In our researches, a real-time data collection and image processing system for plasma jet with high temperature, velocity and compressed energy has been realiz ed by CCD sensor. In this paper, we firstly focus our attention on collection pr inciple and methods, and an effective method for collecting data in high tempera ture area is presented. Then a system of real-time data collection by CCD camer a is developed. Finally, fake color image processing is given to analyze the law of temperature field distribution under different conditions. The results are i mportant to realize the visualization of plasma spraying, and especially to furt her study on closed-loop feedback control of forming quality for plasma rapid m anufacturing process.展开更多
文摘A coding and decoding process of argon plasma images using digital holography is proposed. The digital Fourier holography is applied to two images of matrix dimensions 512 × 512 pixels. The decoded images are improved using wiener filtering techniques. We have constructed three basic color images of the original image which is useful to extract the thermal distribution of the plasma image. Also, the profiles of the reconstructed images are checked showing better smooth profiles using wiener filter. The Mat-lab code is applied in the operation of image processing using Fourier techniques.
基金supported in part by National Natural Science Foundation of China (No.51175095)the Guangdong Provincial Natural Science Foundation of China (10251009001000001, 9151009001000020, 07001764)the Specialized Research Fund for the Doctoral Program of Higher Education of China (20104420110001)
文摘High-speed photography was used to obtain the dynamic changes in the surface plasma during a high-power disk laser welding process. A color space clustering algorithm to extract the edge information of the surface plasma region was developed in order to improve the accuracy of image processing. With a comparative analysis of the plasma features, i.e., area and height, and the characteristics of the welded seam, the relationship between the surface plasma and the stability of the laser welding process was characterized, which provides a basic understanding for the real-time monitoring of laser welding.
文摘In-flight particle velocity and flux distribution were measured using CCD thermal spray monitor system during supersonic plasma spray processing with nano-structured Al_2O_3-TiO_2 feed stocks. According to the results of particle flux measurement, the largest radian of the divergent particle stream is about 0.2. Within the measuring range, top speed of in-flight particles reached 800m/s. Particle acceleration was accomplished within 4cm down stream of the nozzle. Average particle velocity (about 450m/s) exceeded local sound speed (340m/s) even at a mean standoff distance of 17cm. With increasing mean standoff distance, average velocity of in-flight particle decreased according to a parabolic rule approximately. Image diagnosis showed that the result of in-flight particle velocity measurement is credible.
基金supported by National Natural Science Foundation of China (No. 90716025)
文摘This paper is devoted to experimentally investigating the influence of magnetic field intensity and gas temperature on the plasma jet deflection controlled by magneto hydrodynamics. The catalytic ionization seed CS_2CO_3 is injected into combustion gas by artificial forced ionization to obtain plasma fluid on a high-temperature magnetic fluid experimental platform. The plasma jet was deflected under the effect of an external magnetic field, forming a thrust-vector effect.Magnesium oxide was selected as a tracer particle, and a two-dimensional image of the jet flow field was collected using the particle image velocimetry(PIV) measurement method. Through image processing and velocity vector analysis of the flow field, the value of the jet deflection angle was obtained quantitatively to evaluate the thrust-vector effect. The variation of the jet deflection angle with the magnetic field intensity and gas temperature was studied under different experimental conditions. Experimental results show that the jet deflection angle increased gradually with a rise in gas temperature and then increased substantially when the gas temperature exceeded 2300 K. The jet deflection angle also increased with an increase in magnetic induction intensity. Experiments demonstrate it is feasible to use PIV test technology to study the thrust vector under magnetic control conditions.
文摘Manual monitoring and seam tracking through watching weld pool images in real-time, by naked eyes or by industrial TV, are experience-depended, subjective, labor intensive, and sometimes biased. So it is necessary to realize the automation of computer-aided seam tracking. A PAW (plasma arc welding) seam tracking system was developed, which senses the molten pool and the seam in one frame by a vision sensor, and then detects the seam deviation to adjust the work piece motion adaptively to the seam position sensed by vision sensor. A novel molten pool area image-processing algorithm based on machine vision was proposed. The algorithm processes each image at the speed of 20 frames/second in real-time to extract three feature variables to get the seam deviation. It is proved experimentally that the algorithm is very fast and effective. Issues related to the algorithm are also discussed.
文摘Plasma spraying is an important enabling technology i n near-net-shaped process as well as many high-performance coating applicatio ns. Recently, it is being applied to rapid mould manufacturing to reduce develop ment time and manufacturing cost. In this process, inputted powders are heated a nd accelerated by plasma jet, and impinge on master pattern or prototype to form ing a thick coating. Mould will be fabricated after backed-up with consolidated material and other post-treatments. Amongst numerous factors that affect the l ife and properties of mould made by this novel method, quality of coating is the most important one. However, the complex nature of the spray process results in a large number of processing parameters that must be controlled in order to obt ain optimum coatings. Traditional "trial and error" method is too time and cost consuming for the optimal processing parameters. Maybe modeling and diagnostics of process is the best way to ravel out the problems. It has been proved that pl asma-gas flowrate, power level and spray distance are the most critical variabl es. So flow visualization and diagnostics for plasma jet quality has become an i mportant task to obtain a repeatable and reliable plasma processing technology. Using enthalpy probe diagnostics, spectrometry and optical measurement, we can o btain the distribution of temperature field of plasma jet. These results can hel p us to design gun configuration and optimize processing parameters for high dep osition efficiency and good qualities of rapid mould manufacturing. Nevertheless , it is still very difficult to realize real-time diagnoses because of restrict of diagnosis condition and drawback of measurement approach. In our researches, a real-time data collection and image processing system for plasma jet with high temperature, velocity and compressed energy has been realiz ed by CCD sensor. In this paper, we firstly focus our attention on collection pr inciple and methods, and an effective method for collecting data in high tempera ture area is presented. Then a system of real-time data collection by CCD camer a is developed. Finally, fake color image processing is given to analyze the law of temperature field distribution under different conditions. The results are i mportant to realize the visualization of plasma spraying, and especially to furt her study on closed-loop feedback control of forming quality for plasma rapid m anufacturing process.
