Victor B. Shulyatyev

В данной статье представлено исследование процесса лазерной резки авиационных алюминиево-литиевых сплавов системы Al-Mg-Li с использованием импульсного и непрерывного излучения. Лазерная резка является высокоэффективным методом обработки металлов, обеспечивающим высокую скорость и качество реза. Однако для алюминиевых сплавов процесс осложняется их высокой теплопроводностью и отражательной способностью. В статье сообщается о результатах механических испытаний образцов из алюминий-литиевого сплава системы Al-Mg-Li, полученных лазерной резкой непрерывным и импульсным излучением. Для резки использовался СО2-лазер. Резка импульсным излучением производилась при частоте следования импульсов 40 кГц при одновременном воздействии на материал лазерного излучения и плазмы оптического разряда, создаваемого лазерным излучением в струе технологического газа (аргона). Разрезались листы толщиной 1,5 мм при средней мощности лазерного излучения 1,5 кВт и давлении аргона 0,05 МПа. Определен диапазон скоростей резки, в котором зона термического влияния на кромке реза имеет минимальную величину. По результатам испытаний на малоцикловую усталость образец, вырезанный импульсным излучением, выдержал в 2.6 раза больше циклов нагружения по сравнению с образцом, вырезанным непрерывным излучением при прочих равных условиях. Испытания на растяжение не выявили какого-либо влияния метода резки на прочность. Ключевые слова: алюминий-литиевый сплав, лазерная резка, зона термического влияния, малоцикловая усталость, импульсное излучение, лазерное излучение.

Results of tensile and low-cycle fatigue testing of samples made of an aluminum–lithium alloy of the Al–Mg–Li system obtained by plasma-assisted laser cutting performed by a pulsed CO₂ laser in an argon jet with the laser beam and optical discharge plasma simultaneously affecting the material are reported. Low-cycle fatigue tests show that the number of loading cycles survived by the sample obtained by plasma-assisted laser cutting is more than twice greater than the number of cycles survived by the samples obtained by conventional laser cutting with a continuous beam.

A new method of laser cutting of aluminum alloys is considered, when the material is simultaneously exposed to laser radiation and the optical discharge pl

Characteristics of microcrater structures on a laser-cut surface and their effect on surface roughness were experimentally studied for sheet thicknesses of 3–16 mm. The size and density of craters increased with the sheet thickness. The number of craters had a nonmonotonic dependence on the cutting velocity and peaked at the optimal cutting velocity, which minimized the roughness of the cut surface. A qualitative explanation of the observed phenomena was proposed. It appears that gas flow in the channel removes droplets from the melt mass, which decreases the melt mass in the lower part of the cut and reduces the roughness.

The paper presents the results of experimental investigation of the effect of the beam polarization on the quality of the oxygen-assisted laser cutting of steel by a CO₂-laser. Under consideration is the effect of the laser cutting parameters by the beam with the linear polarization on the cut surface roughness. It is founded that the minimal roughness is reached when the electric field vector is perpendicular to the cutting speed vector. It is concluded that the absorbed power distribution imposes the essential influence on the surface quality, and that the radiation heating of side walls is important to have lower roughness. Obtained results enabled to present probable reasons of the worse surface quality of the metals cut by a fiber laser than the ones cut by a CO₂-laser.

Analysis of the laser cut surface morphology remain topical. It is related with the fact that the surface roughness is the main index of the cut quality. The present paper deals with the experimental study of the relatively unstudied type of defects on the laser cut surface, dimples, or craters. According to the measurement results, amount of craters per unit of the laser cut surface area rises as the sheet thickness rises. The crater diameter rises together with the sheet thickness and distance from the upper sheet edge. The obtained data permit concluding that the defects like craters are observed predominantly in the case of thick sheets. The results agree with the hypothesis of crater formation as impact structures resulting from the melt drops getting on the cut channel walls upon separation from the cut front by the gas flow.

The effect of an optical pulsed discharge created by CO₂-laser with an average power of up to 2.2 kW on the aerodynamic drag of a model in a supersonic air flow is experimentally investigated. Experiments were carried out in a supersonic wind tunnel MAU-M (diameter of the nozzle outlet d_c = 50 mm) on the modes M = 1.36, Re₁ = 1.4– 3.8*10⁷ 1/m. To ensure a stable optical breakdown, a jet of argon gas was introduced into the focusing region of the laser beam. As a result, a decrease in the aerodynamic force acting on the model was obtained. This decrease was 15% when a subsonic flow of argon was introduced into the main flow and another 15% when optical pulsed discharge was organized.