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Search Results (5)

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Keywords = underwater laser cutting

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22 pages, 5568 KB  
Article
Robust 3D Reconstruction in Turbid Water at Low Sampling Rates via Dual-DMD Single-Pixel System
by Wei Feng, Bincheng Wang, Xiaoyuan Pan, Zhenmin Zhu, Shan Lou, Dawei Tang, Feng Gao and Fumin Zhang
Photonics 2026, 13(5), 446; https://doi.org/10.3390/photonics13050446 - 1 May 2026
Viewed by 824
Abstract
Conventional optical imaging struggles to acquire clear images of underwater scenes in turbid water. In this paper, a new dual-DMD single-pixel 3D imaging (DSP3DI) system is designed and constructed to realize the 3D shape reconstruction in highly turbid water conditions. Leveraging the spectral [...] Read more.
Conventional optical imaging struggles to acquire clear images of underwater scenes in turbid water. In this paper, a new dual-DMD single-pixel 3D imaging (DSP3DI) system is designed and constructed to realize the 3D shape reconstruction in highly turbid water conditions. Leveraging the spectral dependence of the scattering coefficient of water on wavelength, the designed system uses a 532 nm laser as the illumination source to minimize scattering and absorption losses during light propagation, and two digital micromirror devices (DMDs) are used to generate phase-shifting fringe patterns and sampling patterns, respectively, and then uses a single-pixel detector to sequentially collect the spatial light field reflected from the surface of the object. A single-pixel imaging (SPI) method based on a cake-cutting strategy for Hadamard encoding reconstructs the deformed fringe images, from which phase information is recovered to calculate the 3D shape of objects. The experimental results show that the system not only achieves millimeter-level measurement accuracy but also successfully reconstructs the 3D shape of complex objects at a sampling rate of 10% and in turbidities as high as 40 NTU. The proposed system, characterized by its compact structure, high measurement accuracy, and strong scattering resistance, offers a novel solution for high-precision 3D imaging in highly turbid water. Full article
(This article belongs to the Special Issue Optical Measurement Systems, 2nd Edition)
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14 pages, 29305 KB  
Article
A Comparative Study on Laser Cutting Performance with Varying Speeds at 10 M Underwater
by Danbi Song, Jungsoo Choi, Sujin Lee, Ryoonhan Kim and Induck Park
Metals 2024, 14(11), 1270; https://doi.org/10.3390/met14111270 - 8 Nov 2024
Cited by 2 | Viewed by 2851
Abstract
Despite the dismantling structures that are submerged to significant depths of water during the decommissioning of nuclear power plants, there is limited research on deep-water laser cutting processes. A self-designed pressurized chamber was used in this study and successfully conducted the world’s first [...] Read more.
Despite the dismantling structures that are submerged to significant depths of water during the decommissioning of nuclear power plants, there is limited research on deep-water laser cutting processes. A self-designed pressurized chamber was used in this study and successfully conducted the world’s first laser cutting experiment in a simulated 10 m water depth environment. laser cutting was performed in a 10 m underwater environment, and the cutting efficiency was compared to that observed in a 1 m underwater environment. Therefore, A 100 mm thickness of 304 stainless steel was successfully cut underwater, and the highest cutting speed of 100 mm/min was achieved. The result indicates that, as the cutting speed increased during underwater laser cutting, both the heat input and the mass flow rate of the assist gas decreased, resulting in a narrower rear kerf width and an ineffective evacuation of the molten metal. Full article
(This article belongs to the Special Issue Advances in Metal Cutting and Machining Processes)
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12 pages, 4008 KB  
Article
A Study on the Characteristics of 304 Stainless Steel According to the Water Temperature Changes in Underwater Laser Beam Machining
by Jun Yeon Lee, Dong-Hyeon Kim, Young Tae Cho and Choon Man Lee
Materials 2023, 16(23), 7463; https://doi.org/10.3390/ma16237463 - 30 Nov 2023
Cited by 2 | Viewed by 1938
Abstract
In underwater laser beam machining (ULBM), water provides a cooling effect by reducing the influence of the laser heat source, which makes ULBM more suitable for marking, cutting, and postprocessing than laser beam machining (LBM). Because the laser heat source not only affects [...] Read more.
In underwater laser beam machining (ULBM), water provides a cooling effect by reducing the influence of the laser heat source, which makes ULBM more suitable for marking, cutting, and postprocessing than laser beam machining (LBM). Because the laser heat source not only affects the substrate temperature, but also heats the water, this study analyzes how the cooling effect occurs when water is heated. In this study, the heat-transformed zones in ULBM and heated underwater laser beam machining (HULBM) were improved by approximately 33% and 24%, respectively, compared to LBM at 400 W. In addition, the heat-affected zones in ULBM and HULBM improved by approximately 15% and 9%, respectively, compared to LBM. The hardness of ULBM and HULBM was higher than that of LBM. Based on these results, it was confirmed that water can reduce the effect of the laser heat source and improve the mechanical properties. Experiments will be conducted on the underwater laser beam machining of various substrates, such as Inconel718 and Ti-6Al-4V, in a future study. In addition, experiments will be conducted on the underwater laser beam machining of various substrates using a cooling system that can lower the temperature of water. Full article
(This article belongs to the Special Issue Innovative Technologies and Materials for High-Performance Components – Volume II)
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11 pages, 6967 KB  
Article
Effect of Process Variables for Reducing Assist Gas Pressure in 50 mm-Thick Stainless Steel Underwater Laser Cutting
by Ryoonhan Kim, Su-Jin Lee, Jungsoo Choi, Dongsig Shin and Jong-Do Kim
Appl. Sci. 2022, 12(19), 9574; https://doi.org/10.3390/app12199574 - 23 Sep 2022
Cited by 7 | Viewed by 3071
Abstract
While dismantling nuclear power plants, the reactor vessel internal is cut underwater using mechanical and thermal cutting. In laser thermal cutting, assist gas must be used to remove melted metal; consequently, a large number of radioactive aerosols can be generated. To reduce the [...] Read more.
While dismantling nuclear power plants, the reactor vessel internal is cut underwater using mechanical and thermal cutting. In laser thermal cutting, assist gas must be used to remove melted metal; consequently, a large number of radioactive aerosols can be generated. To reduce the generation of aerosols, the assist gas pressure should be lowered. However, below the pressure limit, the molten metal is not well-removed from the cut surface and fails to cut. In this study, an assist gas visualization experiment was performed to find a condition for the gas to flow well inside the cut surface, even at low pressures. The top kerf width, nozzle type, distance between nozzle and specimen, and assist gas pressure were selected as process parameters, and in the case of large top kerf width condition, assist gas was able to penetrate deeply. In the actual laser-cutting experiment, the laser beam focus position was set to −20 mm and −30 mm. In the case of −30 mm, the top kerf width was widened due to the characteristics of the laser beam profile, and cutting was successful even though the assist gas pressure was lowered by 20%. Full article
(This article belongs to the Section Mechanical Engineering)
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11 pages, 7088 KB  
Article
Fundamental Study on Underwater Cutting of 50 mm-Thick Stainless Steel Plates Using a Fiber Laser for Nuclear Decommissioning
by Kwan Kim, Moo-Keun Song, Su-Jin Lee, Dongsig Shin, Jeong Suh and Jong-Do Kim
Appl. Sci. 2022, 12(1), 495; https://doi.org/10.3390/app12010495 - 5 Jan 2022
Cited by 19 | Viewed by 5178
Abstract
With nuclear power plants worldwide approaching their design lifespans, plans for decommissioning nuclear power plants are increasing, and interest in decommissioning technology is growing. Laser cutting, which is suitable for high-speed cutting in underwater environments and is amenable to remote control and automation, [...] Read more.
With nuclear power plants worldwide approaching their design lifespans, plans for decommissioning nuclear power plants are increasing, and interest in decommissioning technology is growing. Laser cutting, which is suitable for high-speed cutting in underwater environments and is amenable to remote control and automation, has attracted considerable interest. In this study, the effects of laser cutting were analyzed with respect to relevant parameters to achieve high-quality underwater laser cutting for the decommissioning of nuclear power plants. The kerf width, drag line, and roughness of the specimens during the high-power laser cutting of 50 mm-thick stainless steel in an underwater environment were analyzed based on key parameters (focal position, laser power, and cutting speed) to determine the conditions for satisfactory cutting surface quality. The results indicated that underwater laser cutting with a speed of up to 130 mm/min was possible at a focal position of 30 mm and a laser power of 9 kW; however, the best-quality cutting surface was obtained at a cutting speed of 30 mm/min. Full article
(This article belongs to the Special Issue Advanced Marine Engineering and Technology: Sustainable and Smart Marine Engineering)
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