Search Results (6)

The rectangular spot laser cladding system, due to its large spot size and high efficiency, has been widely applied in laser cladding equipment, significantly improving cladding’s efficiency. However, while enhancing cladding efficiency, the rectangular spot laser cladding system may also affect the stability of the melt pool, thereby impacting the cladding’s quality. To accurately predict the melt pool morphology and size during wide beam laser cladding, this study developed a melt pool monitoring system. Through real-time monitoring of the melt pool morphology, image processing techniques were employed to extract features such as the melt pool width and area. The study used laser power, scanning speed, and the powder feed rate as input variables, and established a prediction model for the melt pool width and area based on Support Vector Regression (SVR). Additionally, an Ant Colony Optimization (ACO) algorithm was applied to optimize the SVR model, resulting in an ACO-SVR-based prediction model for the melt pool. The results show that the relative error in predicting the melt pool width using the ACO-SVR model is less than 2.2%, and the relative error in predicting the melt pool area is less than 9.13%, achieving accurate predictions of the melt pool width and area during rectangular spot laser cladding. Full article

Graded-index fibers have been used in recent years to make high-power fiber lasers and amplifiers. Such fibers exhibit self-imaging, a phenomenon in which any optical beam periodically reproduces its original shape in undoped fibers (no gain). In this work, we employed analytic and numerical techniques to study how self-imaging affects the evolution of a signal beam inside a nonlinear graded-index fiber amplifier, doped with a rare-earth element and pumped optically to provide gain all along its length. We also exploited the variational technique to reduce the computing time and to provide physical insights into the amplification process. We compared the variational and fully numerical results for the two pumping schemes (clad pumping and edge pumping) commonly used for high-power fiber amplifiers and show that the variational results are reliable in most cases of practical interest. The stability of the signal beam undergoing amplification is examined numerically by launching a noisy Gaussian beam at the input end of the amplifier. Our results show that the quality of the amplified beam should improve in the case of edge pumping when a narrower pump beam provides an optical gain that varies considerably in the radial direction of the fiber. Such an improvement does not occur for the clad pumping scheme, for which the use of a relatively wide pump beam results in a nearly uniform gain all along the fiber. Full article

Wide-band laser cladding technology has emerged as a solution to the limitations of traditional cladding techniques, which are small single-path dimensions and low processing efficiency. The existing wide-band cladding technology presents challenges related to the high precision required for the laser–powder coupling and the significant powder-divergence phenomenon. Based on the inside-beam powder-feeding technology, a wide-band powder-feeding nozzle was designed using the multi-channel powder flow shaping method. The size of the powder spot obtained at the processing location can reach 40 mm × 3 mm. A computational fluid dynamics analysis using the FLUENT software was conducted to investigate the impact of the nozzle’s structural parameters on the powder distribution. It was determined that the optimal configuration was achieved when the powder-feeding channel was 8, and the transverse and longitudinal dimensions for the collimating gas outlet were 0.5 mm and 1 mm, respectively. Among the process parameters, an increase in the carrier gas flow rate was found to effectively enhance the stability of powder transportation. However, the powder feed rate had minimal impact on the powder concentration distribution, and the collimating gas flow rate appeared to have a minimal effect on the divergence angle of the powder stream. Wide-band laser cladding experiments were conducted using the designed powder-feeding nozzle, and a single-path cladding with a width of 39.96 mm was finally obtained. Full article

Nowadays, fiber laser has been widely used in industrial processing, especially in welding, cutting and other fields, and the appearance of adjustable ring-mode fiber laser improves effectively the quality of processing. In this paper, a (6 + 1) × 1 adjustable ring-mode fiber signal combiner is developed based on the technology of fiber cladding corrosion. The test results show that under the same injection condition, the beam quality transmitted through the central port of the combiner is degraded by only 8.3% compared with that transmitted through a single 50/250 μm fiber. It is proven to be feasible to maintain the beam quality of the (6 + 1) × 1 combiner by fiber corrosion technology. In order to improve the power of the central port of the (6 + 1) × 1 adjustable ring-mode combiner, a 3 × 1 fiber signal combiner and the central port of (6 + 1) × 1 combiner are cascaded. The output beam quality is M² = 4.45 and the overall transmission efficiency is greater than 95%. This combiner can choose the mode of the output beam according to the actual application requirements, so as to achieve a better application effect. Full article

The results of experimental studies of repair of the supporting structure components made of 316L steel multi-pass laser cladding with filler wire are presented. The influence of the wobbling mode parameters, welding speed, and laser power on the formation of the deposited metal during multi-pass laser cladding with filler wire of 316L steel samples into a narrow slot groove, 6 mm deep and 3 mm wide, are shown. Non-destructive testing, metallographic studies, and mechanical tests of the deposited metal before and after heat treatment (2 h at 450 °C) were carried out. Based on the results of experimental studies, the optimal modes of laser beam wobbling were selected (amplitude—1.3 mm, frequency—100 Hz) at which the formation of a bead of optimal dimensions (height—1672 μm, width—3939 μm, depth of penetration into the substrate—776 μm) was ensured. A laser cladding technology with ESAB OK Autrode 316L filler wire has been developed, which has successfully passed the certification for conformity with the ISO 15614-11 standard. Studies of the chemical elements’ distribution before and after heat treatment showed that, after heat treatment along the grain boundaries, particles with a significantly higher Mo content (5.50%) were found in the sample, presumably precipitated phases. Microstructure studies and microhardness measurements showed that the upper part metal of the third pass, which has a lower microhardness (75% of base metal), higher ferrite content, and differently oriented dendritic austenite, significantly differs from the rest of the cladded metal. Full article

This paper proposes a novel liquid crystal-filled, dual core photonic crystal fiber polarization beam splitter (LC-DC-PCF PBS) based on the coupled mode theory of DC-PCF. The mode birefringence of odd and even modes, coupling lengths (CLs) of the X-polarization (X-pol) and Y-polarization (Y-pol), and the corresponding coupling length ratio (CLR) of the proposed LC-DC-PCF PBS filled without LC E7 and with LC E7 are compared. The change rules of the CLs of the X-pol and Y-pol and CLR of the proposed LC-DC-PCF with wavelengths for different cladding microstructure parameters were investigated. The relationships between the X-pol and Y-pol normalized output powers in core A of the proposed LC-DC-PCF PBS and the propagation length at the wavelength of 1.604 μm are discussed. Finally, by studying the change of extinction ratio (ER) with wavelength, the LC-DC-PCF PBS ER of 60.3 and 72.2 dB at wavelengths 1.386 and 1.619 μm are achieved, respectively. The final splitting length (L_S) is 94 μm, and the splitting bandwidth is 349 nm (1.352~1.701 μm), covering the whole of the E + S + C + L + U communication bands. The proposed LC-DC-PCF PBS has good beam-splitting performance, such as ultra-short L_S and ultra-wide splitting bandwidth, with potential applications in laser, sensing, and communication systems. Full article