The positioning of paddy field weeding wheels is of great significance for compensating the operation deviation between the weeding wheel and the seedling row in paddy field mechanical weeding. In this paper, a visual positioning method for determining the three-dimensional coordinates of weeding wheels in the camera coordinate system is proposed. By fixing the laser rangefinder with the weeding wheel, the proposed method converts the positioning of weeding wheels into solving the relative pose relationship between the laser rangefinder and the camera. Then, based on the constraints of the laser spots on the AprilTag calibration plane, a nonlinear optimization model is established to obtain the relative pose parameters. In the experiment, two evaluation indicators were proposed to evaluate the calibration accuracy. The experimental results showed that the proposed visual positioning method of the weeding wheel can reach a mean positioning error of 2.766 mm and a mean pixel error of 7.161 pixels.
{"title":"Research on a visual positioning method of paddy field weeding wheels based on laser rangefinder-camera calibration","authors":"Shanshan Wang, Xingsong Wang, Shanshan Yu","doi":"10.2351/7.0001341","DOIUrl":"https://doi.org/10.2351/7.0001341","url":null,"abstract":"The positioning of paddy field weeding wheels is of great significance for compensating the operation deviation between the weeding wheel and the seedling row in paddy field mechanical weeding. In this paper, a visual positioning method for determining the three-dimensional coordinates of weeding wheels in the camera coordinate system is proposed. By fixing the laser rangefinder with the weeding wheel, the proposed method converts the positioning of weeding wheels into solving the relative pose relationship between the laser rangefinder and the camera. Then, based on the constraints of the laser spots on the AprilTag calibration plane, a nonlinear optimization model is established to obtain the relative pose parameters. In the experiment, two evaluation indicators were proposed to evaluate the calibration accuracy. The experimental results showed that the proposed visual positioning method of the weeding wheel can reach a mean positioning error of 2.766 mm and a mean pixel error of 7.161 pixels.","PeriodicalId":50168,"journal":{"name":"Journal of Laser Applications","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2024-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141272682","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Wenyou Zhang, Daniele Pullini, Matteo Alberghini, A. Bertinetti, Alessio Tommasi, Asli Coban, Seán McConnell, H. Naesstroem, Ramesh Padamati Babu, J. Volpp, Rocco Lupoi
Additive manufacturing of AlSi10Mg has obtained increased attention due to its lightweight feature. However, handling of loose powder, efficient usage of feedstock, and powder recycling still remain major open challenges. Herein, a novel additive manufacturing method based on metal additive manufacturing using powder sheet (MAPS) is proposed, which leverages composite flexible films made of the feedstock of metal powder and a polymeric binder, aiming to extend the range of applicability of AlSi10Mg-based additive manufacturing technologies, for example, vehicle components. In situ high-speed imaging is used to explore the underlying manufacturing mechanisms of the proposed MAPS concept and investigate the laser–powder sheet interaction. In addition, a representative computational thermo-mechanical model was used to evaluate the substrate deformation due to the printing process, a critical aspect that must be minimized in order to transfer this technology to larger scale applications.
{"title":"Material incorporation in powder sheet additive manufacturing toward lightweight designs for future mobility","authors":"Wenyou Zhang, Daniele Pullini, Matteo Alberghini, A. Bertinetti, Alessio Tommasi, Asli Coban, Seán McConnell, H. Naesstroem, Ramesh Padamati Babu, J. Volpp, Rocco Lupoi","doi":"10.2351/7.0001348","DOIUrl":"https://doi.org/10.2351/7.0001348","url":null,"abstract":"Additive manufacturing of AlSi10Mg has obtained increased attention due to its lightweight feature. However, handling of loose powder, efficient usage of feedstock, and powder recycling still remain major open challenges. Herein, a novel additive manufacturing method based on metal additive manufacturing using powder sheet (MAPS) is proposed, which leverages composite flexible films made of the feedstock of metal powder and a polymeric binder, aiming to extend the range of applicability of AlSi10Mg-based additive manufacturing technologies, for example, vehicle components. In situ high-speed imaging is used to explore the underlying manufacturing mechanisms of the proposed MAPS concept and investigate the laser–powder sheet interaction. In addition, a representative computational thermo-mechanical model was used to evaluate the substrate deformation due to the printing process, a critical aspect that must be minimized in order to transfer this technology to larger scale applications.","PeriodicalId":50168,"journal":{"name":"Journal of Laser Applications","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2024-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141047092","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Keeping in view the weightage of electric propulsion over chemical propulsion, materials from metals to polymers and liquid (water) have been tested as propellants in ablative laser propulsion. This emerging propulsion technique can be widely used for aerospace applications like debris removal in the range of cm, pointing micro and nano satellites, laser micro thrusters for spacecraft attitude, and orbit control. Laser propulsion can become a less expensive alternative to chemical propulsion. In this review, we compile the work done in ablative laser propulsion and different modes of propulsion along with the efficiency of different propellants. We summarize the optimized propulsive parameters with solid propellants and liquid propellants along with the efficiencies and theories of laser thrusters with optimized specific impulses. The article provides precise developments done in the field of ablative laser propulsion and deep insights into the analysis done between the different propellants used recently in ablative laser propulsion.
{"title":"Ablative laser propulsion, the propellants and measuring parameters: A brief review","authors":"A. Abbas, Syeda Tehreem Iqbal, Yasir Jamil","doi":"10.2351/7.0001342","DOIUrl":"https://doi.org/10.2351/7.0001342","url":null,"abstract":"Keeping in view the weightage of electric propulsion over chemical propulsion, materials from metals to polymers and liquid (water) have been tested as propellants in ablative laser propulsion. This emerging propulsion technique can be widely used for aerospace applications like debris removal in the range of cm, pointing micro and nano satellites, laser micro thrusters for spacecraft attitude, and orbit control. Laser propulsion can become a less expensive alternative to chemical propulsion. In this review, we compile the work done in ablative laser propulsion and different modes of propulsion along with the efficiency of different propellants. We summarize the optimized propulsive parameters with solid propellants and liquid propellants along with the efficiencies and theories of laser thrusters with optimized specific impulses. The article provides precise developments done in the field of ablative laser propulsion and deep insights into the analysis done between the different propellants used recently in ablative laser propulsion.","PeriodicalId":50168,"journal":{"name":"Journal of Laser Applications","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2024-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141044742","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
C. Sánchez-Aké, J. A. Segura-Zavala, O. Depablos-Rivera, M. A. Martínez-Fuentes, T. García-Fernández, S. S. Kanakkillam, Amauri Serrano-Lázaro
We report the fabrication of metal alloy Au–Pd nanoparticles on semiconductor thin film substrates (ZnO) by laser-induced dewetting. Employing a UV excimer laser, a single pulse was directed onto a three-layer film stack on a glass substrate: glass/ZnO/Au/Pd and glass/ZnO/Pd/Au. We simulated the temperature attained by the thin films enabling the prediction of energy thresholds required for melting the metal films but avoiding modifying the ZnO film. A specific range is reported of the pulse energy conducive to nanoparticle formation and the energy threshold required to modify the ZnO film beneath them. Depending on the pulse energy applied, the mean diameter of the nanoparticles varied from approximately 150 to around 70 nm. Notably, higher fluences resulted in smaller particles but also induced surface cracks in the ZnO film. Additionally, we observed a reduction in nanoparticle size with increased Pd content. Our results show that laser-induced dewetting can produce bimetallic alloy nanoparticles and, at the same time, ensure the preservation of the optical properties of the ZnO film. This approach opens avenues for tailoring material characteristics and expanding the range of applications of metal nanoparticles on semiconductor-based systems.
{"title":"Refining laser-induced dewetting for bimetallic Au–Pd nanoparticle synthesis on ZnO thin films: Optimizing fluence for substrate integrity","authors":"C. Sánchez-Aké, J. A. Segura-Zavala, O. Depablos-Rivera, M. A. Martínez-Fuentes, T. García-Fernández, S. S. Kanakkillam, Amauri Serrano-Lázaro","doi":"10.2351/7.0001326","DOIUrl":"https://doi.org/10.2351/7.0001326","url":null,"abstract":"We report the fabrication of metal alloy Au–Pd nanoparticles on semiconductor thin film substrates (ZnO) by laser-induced dewetting. Employing a UV excimer laser, a single pulse was directed onto a three-layer film stack on a glass substrate: glass/ZnO/Au/Pd and glass/ZnO/Pd/Au. We simulated the temperature attained by the thin films enabling the prediction of energy thresholds required for melting the metal films but avoiding modifying the ZnO film. A specific range is reported of the pulse energy conducive to nanoparticle formation and the energy threshold required to modify the ZnO film beneath them. Depending on the pulse energy applied, the mean diameter of the nanoparticles varied from approximately 150 to around 70 nm. Notably, higher fluences resulted in smaller particles but also induced surface cracks in the ZnO film. Additionally, we observed a reduction in nanoparticle size with increased Pd content. Our results show that laser-induced dewetting can produce bimetallic alloy nanoparticles and, at the same time, ensure the preservation of the optical properties of the ZnO film. This approach opens avenues for tailoring material characteristics and expanding the range of applications of metal nanoparticles on semiconductor-based systems.","PeriodicalId":50168,"journal":{"name":"Journal of Laser Applications","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2024-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141131177","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this study, Inconel 713LC superalloy was laser-clad with Amdry 961 powder using a 1 kW fiber laser. Response surface methodology was used to investigate the effect of laser power, duty cycle, and scanning speed on the deposited bead's geometry (width, height, and clad angle) and the dilution ratio. Interestingly, higher laser power and duty cycle increased bead width, clad angle, and dilution ratio but decreased bead height, while the opposite effect was observed for scanning speed. The process optimization was performed by a simultaneous optimization technique. This technique identified the ideal parameters: a laser power of 840 W, a duty cycle of 79.5%, and a scanning speed of 4.38 mm/s. These settings effectively optimized clad properties, with mean absolute errors of 7.96% for clad width, 14.74% for clad height, 16.71% for clad angle, and 5.166% for dilution ratio. These values demonstrate the precision of optimized parameter settings.
{"title":"Statistical modeling and optimization of clad geometry in laser cladding of Amdry 961 on Inconel 713LC superalloy with response surface methodology","authors":"Mahya Hajiahmadi, Ali Khorram, M. Ghoreishi","doi":"10.2351/7.0001364","DOIUrl":"https://doi.org/10.2351/7.0001364","url":null,"abstract":"In this study, Inconel 713LC superalloy was laser-clad with Amdry 961 powder using a 1 kW fiber laser. Response surface methodology was used to investigate the effect of laser power, duty cycle, and scanning speed on the deposited bead's geometry (width, height, and clad angle) and the dilution ratio. Interestingly, higher laser power and duty cycle increased bead width, clad angle, and dilution ratio but decreased bead height, while the opposite effect was observed for scanning speed. The process optimization was performed by a simultaneous optimization technique. This technique identified the ideal parameters: a laser power of 840 W, a duty cycle of 79.5%, and a scanning speed of 4.38 mm/s. These settings effectively optimized clad properties, with mean absolute errors of 7.96% for clad width, 14.74% for clad height, 16.71% for clad angle, and 5.166% for dilution ratio. These values demonstrate the precision of optimized parameter settings.","PeriodicalId":50168,"journal":{"name":"Journal of Laser Applications","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2024-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141025373","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Traditional path planning methods, such as contour and raster methods, suffer from problems like uneven filling, overfilling, and underfilling in the sliced layers, resulting in poor continuity of the lattice melt pool, internal porosity defects, and severe powder adhesion at the contour edges, while research on path planning for three-periodic minimal surfaces lattices is relatively limited. In this study, a scanning path planning method based on lattice equations control is proposed, which differs from traditional contour paths and raster paths. The new paths are controlled by the isosurface parameters of the lattice equation and optimized using the traveling salesman problem, resulting in more uniform scanning paths. The new paths avoid the underfilling issue present in raster path and the sawtooth-shaped borders of raster path. Additionally, they circumvent the nonuniform scanning path problem caused by uneven wall thickness in contour path. Through visualizing the paths and conducting printing experiments on the lattice, it is found that the new path is more uniform compared to contour paths, effectively addressing the issue of overfilling. Compared to raster paths, the new path has smoother boundaries and reduces internal porosity and powder adhesion within the lattice. This research has important value in reducing internal porosity and external powder adhesion issues in three-period minimal surface (TPMS) lattice printing processes, further enhancing the manufacturing quality of TPMS lattices.
{"title":"Novel path planning algorithm for laser powder bed fusion to improve the scan quality of triply periodic minimal surface structures","authors":"Huiliang Tang, Jiangzhao Zhang, Chu Wang, Yu Long","doi":"10.2351/7.0001147","DOIUrl":"https://doi.org/10.2351/7.0001147","url":null,"abstract":"Traditional path planning methods, such as contour and raster methods, suffer from problems like uneven filling, overfilling, and underfilling in the sliced layers, resulting in poor continuity of the lattice melt pool, internal porosity defects, and severe powder adhesion at the contour edges, while research on path planning for three-periodic minimal surfaces lattices is relatively limited. In this study, a scanning path planning method based on lattice equations control is proposed, which differs from traditional contour paths and raster paths. The new paths are controlled by the isosurface parameters of the lattice equation and optimized using the traveling salesman problem, resulting in more uniform scanning paths. The new paths avoid the underfilling issue present in raster path and the sawtooth-shaped borders of raster path. Additionally, they circumvent the nonuniform scanning path problem caused by uneven wall thickness in contour path. Through visualizing the paths and conducting printing experiments on the lattice, it is found that the new path is more uniform compared to contour paths, effectively addressing the issue of overfilling. Compared to raster paths, the new path has smoother boundaries and reduces internal porosity and powder adhesion within the lattice. This research has important value in reducing internal porosity and external powder adhesion issues in three-period minimal surface (TPMS) lattice printing processes, further enhancing the manufacturing quality of TPMS lattices.","PeriodicalId":50168,"journal":{"name":"Journal of Laser Applications","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2024-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141033572","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Laser powder bed fusion is a promising technique that can produce complex-shaped and integrated part. However, distortion and residual stress are two issues that may decrease the precision and performance of built parts. Classical thermal gradient mechanism offers a basic interpretation toward distortion and residual stress. The evolutions of distortion and residual stress in laser powder bed fusion remain unclear. In this study, we used a physical model with an assumption of constraining force to illustrate the evolutions of distortion and residual stress during the additive process. Based on the model, we are able to understand the phenomenon of X-directional shrinkage, Z-directional distortion, and “tensile-compressive-tensile” distribution of X-directional stresses at the same time. It can be concluded that the shrinkage, distortion, and X-directional residual stress all result from the constraint between previously deposited layer and newly deposited layer, which has a strong shrinkage tendency when cooling. The distortion of part increases with deposition height, especially during first several layers. The “tensile-compressive-tensile” distribution of X-directional stresses can be maintained during the additive process. The magnitude of top tensile stress remains stable, while the tensile stress at bottom increases with the deposition height. This work provides a comprehensive understanding toward the evolutions of distortion and residual stress in laser powder bed fusion.
激光粉末床熔融技术是一种很有前途的技术，可以生产形状复杂的集成零件。然而，变形和残余应力这两个问题可能会降低制造零件的精度和性能。经典的热梯度机制为变形和残余应力提供了基本解释。激光粉末床熔融过程中的变形和残余应力的演变仍不清楚。在本研究中，我们使用了一个假定有约束力的物理模型来说明添加过程中变形和残余应力的演变。基于该模型，我们能够同时理解 X 向收缩、Z 向变形以及 X 向应力的 "拉伸-压缩-拉伸 "分布现象。由此可以得出结论，收缩、变形和 X 向残余应力都是由先前沉积层和新沉积层之间的约束造成的，而新沉积层在冷却时有很强的收缩趋势。零件的变形随沉积高度的增加而增大，尤其是在前几层。在添加过程中，X 方向应力的 "拉伸-压缩-拉伸 "分布得以保持。顶部拉伸应力的大小保持稳定，而底部拉伸应力则随着沉积高度的增加而增加。这项研究为全面了解激光粉末床熔化过程中变形和残余应力的演变提供了一个新的视角。
{"title":"Evolutions of distortion and residual stress in laser powder bed fusion based on assumption of constraining force","authors":"Deqiao Xie, Jianfeng Zhao","doi":"10.2351/7.0001336","DOIUrl":"https://doi.org/10.2351/7.0001336","url":null,"abstract":"Laser powder bed fusion is a promising technique that can produce complex-shaped and integrated part. However, distortion and residual stress are two issues that may decrease the precision and performance of built parts. Classical thermal gradient mechanism offers a basic interpretation toward distortion and residual stress. The evolutions of distortion and residual stress in laser powder bed fusion remain unclear. In this study, we used a physical model with an assumption of constraining force to illustrate the evolutions of distortion and residual stress during the additive process. Based on the model, we are able to understand the phenomenon of X-directional shrinkage, Z-directional distortion, and “tensile-compressive-tensile” distribution of X-directional stresses at the same time. It can be concluded that the shrinkage, distortion, and X-directional residual stress all result from the constraint between previously deposited layer and newly deposited layer, which has a strong shrinkage tendency when cooling. The distortion of part increases with deposition height, especially during first several layers. The “tensile-compressive-tensile” distribution of X-directional stresses can be maintained during the additive process. The magnitude of top tensile stress remains stable, while the tensile stress at bottom increases with the deposition height. This work provides a comprehensive understanding toward the evolutions of distortion and residual stress in laser powder bed fusion.","PeriodicalId":50168,"journal":{"name":"Journal of Laser Applications","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2024-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141141302","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Wesley J. Marshall, Robert C. Aldrich, Annette Frederiksen
Since lasers are used in a large variety of applications, new laser products have become more complex. To increase performance, like range or brightness, it is important to consider the maximum optical output that will not exceed laser safety limits. Exposure to an extended source laser results in a larger retinal image and a simplification of treating it as a point source unnecessarily restricts system performance. For laser beams where the location of the apparent source (beam waist) is different in each axis (astigmatic beams), the retinal image is asymmetric and is also a function of eye accommodation. Lasers with astigmatic beams are often evaluated as point sources because accommodation on the source in either beam axis can indicate that the source in that axis is a point source; however, the eye can only focus (accommodate) on one distance at a time. For a single accommodation of the eye, the source may be extended, and extended source lasers are considered less hazardous than point source lasers of the same output power because of the reduction of retinal irradiance (the power is distributed over a larger area). For a line laser with an astigmatic beam, a particular laser hazard class may allow for a higher laser output power than would be allowed if it were a point source laser.
{"title":"Laser hazard classification of a line laser with an astigmatic extended source","authors":"Wesley J. Marshall, Robert C. Aldrich, Annette Frederiksen","doi":"10.2351/7.0001260","DOIUrl":"https://doi.org/10.2351/7.0001260","url":null,"abstract":"Since lasers are used in a large variety of applications, new laser products have become more complex. To increase performance, like range or brightness, it is important to consider the maximum optical output that will not exceed laser safety limits. Exposure to an extended source laser results in a larger retinal image and a simplification of treating it as a point source unnecessarily restricts system performance. For laser beams where the location of the apparent source (beam waist) is different in each axis (astigmatic beams), the retinal image is asymmetric and is also a function of eye accommodation. Lasers with astigmatic beams are often evaluated as point sources because accommodation on the source in either beam axis can indicate that the source in that axis is a point source; however, the eye can only focus (accommodate) on one distance at a time. For a single accommodation of the eye, the source may be extended, and extended source lasers are considered less hazardous than point source lasers of the same output power because of the reduction of retinal irradiance (the power is distributed over a larger area). For a line laser with an astigmatic beam, a particular laser hazard class may allow for a higher laser output power than would be allowed if it were a point source laser.","PeriodicalId":50168,"journal":{"name":"Journal of Laser Applications","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2024-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141039755","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
An accepted approach to computing laser-induced peak surface temperature is to employ the enthalpy formulation of the transient heat conduction equation [Grigoropoulos et al., Adv. Heat Transfer 28, 75–144 (1996); Sawyer et al., J. Laser Appl. 29, 022212 (2017)]. This approach is generally implemented using an explicit numerical scheme to solve the thermal transport equation. While it offers the advantage of modeling the solid-melt phase transition automatically, the approach results in instability-like behavior in the computed surface temperature. When laser-induced ablation becomes significant, the heating rate in the surface cell becomes unrealistically large. This results in spikes in the computed peak surface temperature due to large errors in calculating the heating rate. In this paper, we present a new approach, which we refer to as the Moving Frame Solver, that employs a moving-coordinate frame of reference, located at the receding evaporating surface. We also use an analytical representation for the phase transition region of the enthalpy-temperature relationship. The Moving Frame Solver combined with an implicit scheme leads to a stable solution without surface temperature, pressure, or velocity spikes. In other words, any instability in these computed parameters due to use of an explicit scheme (such as Dufort–Frankel) has been eliminated. Details of the new thermal solver and example calculations are presented. Numerical experiments suggest that the surface cell size needs to be small, ∼0.1 μm, to obtain a highly accurate solution with a typical metal such as aluminum. Using the Moving Frame Solver with a refined grid near the surface, but coarse elsewhere, enables accurate and stable surface temperature computation.
{"title":"New thermal solver for mitigating surface temperature instability in laser-induced heating","authors":"Xun Zhu, Kaushik Iyer, Darren Luke","doi":"10.2351/7.0001201","DOIUrl":"https://doi.org/10.2351/7.0001201","url":null,"abstract":"An accepted approach to computing laser-induced peak surface temperature is to employ the enthalpy formulation of the transient heat conduction equation [Grigoropoulos et al., Adv. Heat Transfer 28, 75–144 (1996); Sawyer et al., J. Laser Appl. 29, 022212 (2017)]. This approach is generally implemented using an explicit numerical scheme to solve the thermal transport equation. While it offers the advantage of modeling the solid-melt phase transition automatically, the approach results in instability-like behavior in the computed surface temperature. When laser-induced ablation becomes significant, the heating rate in the surface cell becomes unrealistically large. This results in spikes in the computed peak surface temperature due to large errors in calculating the heating rate. In this paper, we present a new approach, which we refer to as the Moving Frame Solver, that employs a moving-coordinate frame of reference, located at the receding evaporating surface. We also use an analytical representation for the phase transition region of the enthalpy-temperature relationship. The Moving Frame Solver combined with an implicit scheme leads to a stable solution without surface temperature, pressure, or velocity spikes. In other words, any instability in these computed parameters due to use of an explicit scheme (such as Dufort–Frankel) has been eliminated. Details of the new thermal solver and example calculations are presented. Numerical experiments suggest that the surface cell size needs to be small, ∼0.1 μm, to obtain a highly accurate solution with a typical metal such as aluminum. Using the Moving Frame Solver with a refined grid near the surface, but coarse elsewhere, enables accurate and stable surface temperature computation.","PeriodicalId":50168,"journal":{"name":"Journal of Laser Applications","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2024-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141024500","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
An experiment was conducted on the laser-metal inert gas hybrid welding of 7075 aluminum alloy under alternating magnetic field assistance, in order to investigate the effect of the magnetic field on weld porosity defects in aluminum alloy. The internal porosity of the weld seam under different magnetic field conditions was compared and analyzed through radiographic inspection. The impact of the alternating magnetic field on the arc shape and keyhole dynamic behavior was observed and analyzed by high-speed photography. The results showed that without a magnetic field, the arc shape underwent continuous scaling during the transition of molten droplets, the keyhole root was unstable, and there were a large number of process-induced porosities distributed in the center of the weld. When the magnetic field strength was 10 mT, the keyhole was completely unstable, and the size of the internal porosities in the weld seam significantly increased while the number of porosities decreased. At a magnetic field strength of 20 mT, the arc exhibited a rotating oscillation behavior, the keyhole was in a stable open state, and no porosity was detected in the weld seam. Upon reaching a magnetic field strength of 30 mT, the keyhole was also in a root unstable state, but the collapse and recombination speed of the keyhole were faster than that without a magnetic field, and the size and number of internal porosities in the weld seam significantly decreased.
{"title":"Mechanism of pore suppression in aluminum alloy laser-MIG hybrid welding based on alternating magnetic field","authors":"Benqiang Zhu, Yong Zhao, Fugang Chen, Juan Fu, Feiyun Wang, Guoqiang Chen, Yonghui Qin","doi":"10.2351/7.0001282","DOIUrl":"https://doi.org/10.2351/7.0001282","url":null,"abstract":"An experiment was conducted on the laser-metal inert gas hybrid welding of 7075 aluminum alloy under alternating magnetic field assistance, in order to investigate the effect of the magnetic field on weld porosity defects in aluminum alloy. The internal porosity of the weld seam under different magnetic field conditions was compared and analyzed through radiographic inspection. The impact of the alternating magnetic field on the arc shape and keyhole dynamic behavior was observed and analyzed by high-speed photography. The results showed that without a magnetic field, the arc shape underwent continuous scaling during the transition of molten droplets, the keyhole root was unstable, and there were a large number of process-induced porosities distributed in the center of the weld. When the magnetic field strength was 10 mT, the keyhole was completely unstable, and the size of the internal porosities in the weld seam significantly increased while the number of porosities decreased. At a magnetic field strength of 20 mT, the arc exhibited a rotating oscillation behavior, the keyhole was in a stable open state, and no porosity was detected in the weld seam. Upon reaching a magnetic field strength of 30 mT, the keyhole was also in a root unstable state, but the collapse and recombination speed of the keyhole were faster than that without a magnetic field, and the size and number of internal porosities in the weld seam significantly decreased.","PeriodicalId":50168,"journal":{"name":"Journal of Laser Applications","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2024-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140371271","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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