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Spatial distribution of backreflecteded laser radiation during laser welding
Horník, Petr ; Mrňa, Libor ; Šebestová, Hana ; Novotný, Jan
Laser sources commonly used in industry are usually equipped with a backscattered detector, which prevents potentially dangerous situations from turning off the laser in the event of too much backscatter. However, the laser radiation is never completely absorbed by the material and to some extent is always reflected in the laser welding. This detector can also be used to monitor the welding process. The output is the intensity value returned by the optical fiber. To better understand which parts of the process contribute most to the backscatter value, an optical assembly with a camera scanning the wavelength of the process laser was designed.
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Measurement of laser welding process by high-speed camera and photodiode
Horník, Petr ; Mrňa, L. ; Šebestová, Hana
Laser welding monitoring system can be realized optically. The solution with photodiode sensing welded area has advantage of simplicity and low cost but faces many challenges. Multi-photodiode measurement show dependency of the measured intensity on the photodiode position. Subsequently, the measured values were compared with high-speed camera images. Using the correlation coefficient, the area providing the same information as photodiode measurement was determined in the images.
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Study of laser wobbling welding process through the radiation of plasma plume
Mrňa, Libor ; Horník, Petr ; Jedlička, Petr ; Pavelka, Jan
During laser welding with wobbling to the vector of the welding speed adds trivial movement of the beam in the shape of a circle or other shapes. Therefore, the laser beam moves with much higher current speeds than during normal welding. The melting of material on the leading edge of the keyhole occurs periodically. This fact is reflected in the character of the radiation of plasma plume over the keyhole. Experiments were conducted in which it was obtained spectrum of plasma plume radiation by using autocorrelation function for different parameters of circular wobbling (circle diameter, frequency) and for different materials. In the spectra are found the higher harmonic frequency of wobbling. The results were also compared with the radiation of the plasma plume during pulsed laser welding where the laser beam also periodically melts the leading edge.
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Possibilities in monitoring of laser welding process
Horník, Petr ; Mrňa, Libor
With increasing demands on the quality of the welds, it is usual to apply automated machine welding with monitoring of the welding process. The resulting quality of the weld is largely affected by the behavior of keyhole. However, its direct observation during the welding process is practically impossible and it is necessary to use indirect methods. At ISI we develop optical methods of monitoring the process based on analysis of radiation of laser-induced plasma using Fourier and autocorrelation analysis. Observation of keyhole inlet opening is partially possible through a coaxial camera mounted on the welding head and the subsequent image processing. A high-speed rear camera to understand the dynamics of the plasma plume. Through optical spectroscopy of the plume, we can study the excitation of elements in a material. Shielding gas flow can be visualized using schlieren method.
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Application of JADE multi-agent environment
ŠTĚPÁNEK, Martin
This work deals with realization of a model of multi-agent system for monitoring and supervising production or work process. System is capable of responding to monitored process events and taking actions leading to solving arised problems. Implementation is performed using Java Agent Development Framework (JADE) and there are demonstrated properties and capabilities of multiagent systems. This work also contains basic introduction of JADE framework.
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