Laser cladding monitoring is one of the cladding layer quality controlling methods. At present, cladding monitoring
usually monitor the temperature or the shape of melting pool. The height deviation between melted and unmelted point is
also considered. In this paper, optical signal of plasma which is one of the characteristic signal of plasma has been
detected by phototube in cladding. The relationship between blue-violet light intensity and laser power scan velocity has
been discussed, and the relevance between quality of layer and intensity has been analysed as well. The results indicate
that while laser power growed the intensity increased just at a low rate, and the intensity decreased as scan velocity
increased when the power is lower than a definite value. But when the power is greater than this value the intensity will
rise as velocity increase. The quality of layer is improved greatly when the intensity value rang from 1.7 μW/cm2 to
2.5μW/cm2 with a slight fluctuation.
Most of the temperature and stress fields simulations in laser cladding were based on flat surface, while actually cladding
may occur on any curved surface. The difference between cladding on flat surface and curved surface is that the latter
will result in uneven distribution of laser power. Experiments of laser cladding have been done on different material
gears under various technical conditions, and crackles have been observed by SEM. Some factors that affect laser power
actually, such as laser shielding, the incident angle of laser and curved surface of gear are all considered. Based the
analysis of the shape of layer after cladding and the phase transformaion during cladding, temperature and stress fields of
gear surface laser cladding have been simulated by ANSYS in this article. The results indicate that appropriate material
matching and base preheating can decrease the likelihood of crackles, even eliminate it.
It is easy to produce molten dross by using traditional laser cutting technology in laser cutting silicon steel sheet. The
main reason is that oxidizing reaction will take place inevitably by using oxygen as aided gas, so high pressure and
high purity N2 or inert gases is used as aided cutting gas in laser cutting process. Although the cut quality is improved,
the cutting efficiency is dropped because of the lack of energy resulting from an exothermic oxidation reaction. A fire
new laser cutting technology by using an additional nozzle put under the workpiece that will form lateral gas flow to
control the direction of the flowing dross gas is raised. In this technology oxygen is still used as aided gas, the laser
power is reduced and the cut is fine. The experiments prove that by controlling the technical parameter reasonably,
glossy and dross-free cutting kerfs are obtained. The gas flow acting under the workpiece is simulated by Finite
Element Method (FEM). The varieties of pneumatic fields when the additional nozzle is in different degree and flow
velocity are analyzed, which provides academic basis for controlling the flowing direction of the dross gas more
reasonably. This laser cutting technology is practical and feasible.
The new idea of the optimum controlling of laser processing technique and parameters with multi-objectives and
multi-variables was put forth. With the comprehensive discussion about the quality index of laser transformation
hardening (LTH), a hierarchical structure of the LTH quality index system and a decision-making framework model of
the quality control were set up. Then, based on the conclusions of the sensitivities of LTH parameters' influences on
the case indexes, the principle of LTH's parameters optimization was discussed by means of fuzzy decision method.
With the combination of the principle and the sectionlly changing scanning velocity technique, which can effectively
the uniformity of longitudinal case-distribution, a decision-making framework for optimal controlling on the laser
scanning technique and the parameters with multi-objectives were put forward. An optimization model was developed
and the validity of the model was verified both by theoretical computation and experimental results.
In order to meet the special demands for laser materials processing, after the analysis and design of the resonator parameters and pulse parameters, a mechanical chopper Q-switched CO2 pulse laser unit is developed. At last, a Q-switched CO2 laser pulse with high peak power of more than 10kW and the maximum beam power of 800W (at this time the pulse repetition rate is 20kHz) and TEM00 mode is obtained. The width of the pulse duration is adjustable and in order of μs.
Laser welding of A5083 aluminum alloys with high power CO2 laser is experimental studied in this paper. The study shows that under determinated welding condition, an additional plasma control tube would achieve good plasma suppression, which results in good welding quality. The shielded gas flow acting on the keyhole in CO2 laser welding of A5083 aluminum alloy is numerical simulated by finite element method. From the ANSYS numerical simulation diagrams of the keyhole’s gas flow field, it can be seen that the additional plasma control tube would achieve good plasma suppression to maintain the keyhole.
The interactive effects of aided cutting gases on CO2 TEMOO CW laser cutting of silicon steel sheet are studied. The qualitative analysis of the formation and elimination of the sinter is discussed.
Folded quasi-sealed-off CO2 laser units of both 1000W continuous wave and 500W mechanically Q-switched are presented. Their characteristics are high beam quality, high reliability, economy, easy to operate and maintain, and acceptable workshop floor area required. The CW laser is used for cutting and welding of thin metal sheets. The Q- switched laser is mainly used for crack-free cutting of hard and brittle material such as engineering ceramics.
A mechanical chopper Q-switched CO2 pulse laser with high peak power, short pulse duration, high pulse repetition rate and moderate average power is developed. Using this laser, a cutting process of high cutting speed and multi-pass is proposed for cutting hard and brittle materials such as engineering ceramics. Crack-free and fine cut is obtained in cutting Si3N4 ceramics.
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