Papers by Keyword: Laser

Abstract: The influence of thermal post-treatment by means of flame and laser energy on the mechanical properties of NiCrBSi coating was studied. The evaluation was done in terms of microstructure, surface hardness, microhardness and instrumented indentation. The microstructure evaluation showed an increase of coatings inner cohesion, together with the creation of metallurgical bond between the coating and the substrate material. In the the case of laser remelted coating, the creation of thick transition layer responsible for lower measured microhardness and hardness value was proved.

Abstract: Now the ejection lifesaving equipment in aircraft depends on the mechanical transmission device to transmit the initial detonation energy,but the device is with many transmission links, high energy consumption, quick wear, high failure rate, and difficult to be detected, to improve the ejection lifesaving equipment performance, laser technology was used successfully to ejection lifesaving equipment, a new type of laser initiating system was designed, its structure ,detector and test method of the system are introduced. The laser energy of the system was transmitted conveniently, fficiently and the system is easy to be checked and maintained, thus which greatly improves safety and reliability of the ejection lifesaving equipment.

Abstract: A novel hybrid process (2D scanner + LASER + CNC machining) was used to join transparent and opaque polymers. A 30W diode laser and a 3-axis CNC machining center were combined to accommodate a 2D scanning system for high flexibility and productivity. The scanning speed, the number of repetitions and the laser power were selected as parameters for the weld test. By combining CNC and laser, the productivity and accuracy were improved and manufacturing cost decreased accordingly. The maximum speed of 1130 mm/min was achieved with minimum power of 2Watt. The developed system demonstrated the joining of transparent PC and opaque ABS polymers by using 2 dimensional laser beam motion. The air gap could be minimized by using constant force on the upper holding plate, and preheating by the first run of the laser system. The weld bead decreased at the lower laser power and the higher laser scanning speed.

Abstract: Laser-Arc Hybrid welding technology was first introduced by English scholar W.M.Steen in 20th century 70s, developed very rapidly. In order to study the effect mechanism of laser and arc,This paper presents a control strategy,the strategy can collect welding electric information, high speed photos and spectral information synchronously. By using the Labview software, industrial computer, data acquisition card, a high speed camera, spectrometer, synchronous multi-information acquisition system of welding has been established.the system has been used for the hybrid welding experiment, the peak value, base value and platform value of the laser-arc hybrid welding has been collected. Laid the foundation for further diagnosis of laser-arc in a variety of state.

Abstract: We consider in the present work the fusion laser cutting of stainless steel sheets under a nitrogen laminar gas jet. The molten metal is treated as a laminar and steady viscous incompressible fluid. The mathematical model describing our problem is set in terms of Navier-Stokes equations, solved numerically using the finite differences method, where the effect of the gas jet velocity on the molten boundary layer is considered. The generated shear stress occurring on the gas-liquid interface and its contribution in the momentum is carried out, and it is found that when the skin friction and the shear stress decrease, the thickness and the velocity at the edge of the molten boundary layer increase along the kerf surface. The layer thickness reduces when the assisting gas velocity is increased.

Abstract: In view of the cutting speed reduced and cutting quality became poor because cutting front changes to flat and amount of lag changes to large, light-gas eccentrically cutting method was proposed. Through the experiment and analysis of the results, the conclusion can be obtained that when laser beam is before gas jet, cutting speed can be improved. While offset distance have impacts to cutting result. If the offset distance is too small, it has no difference with light - gas coaxial cutting; if the offset distance is too large, it weakens the gas jet at the cutting surface, which is not conducive to cutting. It can achieve the best results when the offset distance is 0.3mm.The cutting quality with 1.5mm diameter nozzle is better than that of 2mm. Therefore within the allowable range in the offset distance the nozzle aperture should be reduced.

Abstract: The simple model to estimate the depth of the keyhole during laser welding is presented. The model is based on the energy balance between the radiation absorbed by the kehole walls and the heat conducted in the horizontal direction. The calculations conducted for the solid and liquid phase give lower and upper estimate of the depth of the keyhole.

Abstract: In this paper, feasibility of laser percussion drilling on highly reflective materials i.e., Al5052 using an assisting magnetic field was explored. During the laser percussion drilling, the Lorentz force generated by the assisting magnetic field affects the laser-induced plasma and results in significant influence of the laser percussion drilling. The magnetic field simulation was performed to investigate the field strength of the circular hollow permanent magnet. The influences of magnetic field and the laser radiation energy on the penetration depth and inlet diameter were examined.

Abstract: In this project, laser induced breakdown spectroscopy (LIBS) has been utilized to determine the heavy element (Copper) in soil sample. LIBS was used in this work to measure the detection limit of Cu in soil sample, on the basis of spectral features, many parameters to improve the sensitivity of LIBS detection of copper are proposed. Q-switch Nd:YAG laser pulse was carried out at 90 mJ and wavelength of 1064 nm to excite the soil samples in purpose of produce a fluorescence emission (plasma), which were analyzed via spectrum analyzer. The important experimental conditions such as the energy of laser source, integration time, the distance and angle of optical fiber from the sparks were optimized for obtain a best LIBS signal. Calibration curve of the Cu peak found to be 236.81 nm as the best peak to calculate the limit of detection (LOD) and found in this study about 2 ppm. From the results the concentrations of Cu is realized to be lower than the allowance limits of 1500 ppm according to the United States Environmental Protection Agency USEPA.

Abstract: In this work, the effect of the laser shock-wave treatment on the surface morphology and regularities in failure of nanotitanium is investigated. Based on the data of fractodiagnostics it is established that the shock-wave treatment changes the mechanism of failure from the brittle chipping to the mixed ductile-brittle one by the shear + separation scheme.