Keyhole Formation by Laser Drilling in Laser Powder Bed Fusion of Ti6Al4V Biomedical Alloy: Mesoscopic Computational Fluid Dynamics Simulation versus Mathematical Modelling Using Empirical Validation
In the laser powder bed fusion (LPBF) process, the operating conditions are essential in determining laser-induced keyhole regimes based on the thermal distribution. These regimes, classified into shallow and deep keyholes, control the probability and defects formation intensity in the LPBF process....
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| Format: | Article |
| Language: | English |
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MDPI AG
2021-12-01
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| Series: | Nanomaterials |
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| Online Access: | https://www.mdpi.com/2079-4991/11/12/3284 |
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| author | Asif Ur Rehman Muhammad Arif Mahmood Fatih Pitir Metin Uymaz Salamci Andrei C. Popescu Ion N. Mihailescu |
| author_facet | Asif Ur Rehman Muhammad Arif Mahmood Fatih Pitir Metin Uymaz Salamci Andrei C. Popescu Ion N. Mihailescu |
| author_sort | Asif Ur Rehman |
| collection | DOAJ |
| description | In the laser powder bed fusion (LPBF) process, the operating conditions are essential in determining laser-induced keyhole regimes based on the thermal distribution. These regimes, classified into shallow and deep keyholes, control the probability and defects formation intensity in the LPBF process. To study and control the keyhole in the LPBF process, mathematical and computational fluid dynamics (CFD) models are presented. For CFD, the volume of fluid method with the discrete element modeling technique was used, while a mathematical model was developed by including the laser beam absorption by the powder bed voids and surface. The dynamic melt pool behavior is explored in detail. Quantitative comparisons are made among experimental, CFD simulation and analytical computing results leading to a good correspondence. In LPBF, the temperature around the laser irradiation zone rises rapidly compared to the surroundings in the powder layer due to the high thermal resistance and the air between the powder particles, resulting in a slow travel of laser transverse heat waves. In LPBF, the keyhole can be classified into shallow and deep keyhole mode, controlled by the energy density. Increasing the energy density, the shallow keyhole mode transforms into the deep keyhole mode. The energy density in a deep keyhole is higher due to the multiple reflections and concentrations of secondary reflected beams within the keyhole, causing the material to vaporize quickly. Due to an elevated temperature distribution in deep keyhole mode, the probability of pores forming is much higher than in a shallow keyhole as the liquid material is close to the vaporization temperature. When the temperature increases rapidly, the material density drops quickly, thus, raising the fluid volume due to the specific heat and fusion latent heat. In return, this lowers the surface tension and affects the melt pool uniformity. |
| first_indexed | 2024-03-10T03:26:08Z |
| format | Article |
| id | doaj.art-344be33337db4a70bb3a8bfbcaadd55e |
| institution | Directory Open Access Journal |
| issn | 2079-4991 |
| language | English |
| last_indexed | 2024-03-10T03:26:08Z |
| publishDate | 2021-12-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Nanomaterials |
| spelling | doaj.art-344be33337db4a70bb3a8bfbcaadd55e2023-11-23T09:50:29ZengMDPI AGNanomaterials2079-49912021-12-011112328410.3390/nano11123284Keyhole Formation by Laser Drilling in Laser Powder Bed Fusion of Ti6Al4V Biomedical Alloy: Mesoscopic Computational Fluid Dynamics Simulation versus Mathematical Modelling Using Empirical ValidationAsif Ur Rehman0Muhammad Arif Mahmood1Fatih Pitir2Metin Uymaz Salamci3Andrei C. Popescu4Ion N. Mihailescu5ERMAKSAN, Bursa 16065, TurkeyNational Institute for Laser, Plasma and Radiation Physics (INFLPR), Magurele, 077125 Ilfov, RomaniaERMAKSAN, Bursa 16065, TurkeyDepartment of Mechanical Engineering, Gazi University, Ankara 06570, TurkeyNational Institute for Laser, Plasma and Radiation Physics (INFLPR), Magurele, 077125 Ilfov, RomaniaNational Institute for Laser, Plasma and Radiation Physics (INFLPR), Magurele, 077125 Ilfov, RomaniaIn the laser powder bed fusion (LPBF) process, the operating conditions are essential in determining laser-induced keyhole regimes based on the thermal distribution. These regimes, classified into shallow and deep keyholes, control the probability and defects formation intensity in the LPBF process. To study and control the keyhole in the LPBF process, mathematical and computational fluid dynamics (CFD) models are presented. For CFD, the volume of fluid method with the discrete element modeling technique was used, while a mathematical model was developed by including the laser beam absorption by the powder bed voids and surface. The dynamic melt pool behavior is explored in detail. Quantitative comparisons are made among experimental, CFD simulation and analytical computing results leading to a good correspondence. In LPBF, the temperature around the laser irradiation zone rises rapidly compared to the surroundings in the powder layer due to the high thermal resistance and the air between the powder particles, resulting in a slow travel of laser transverse heat waves. In LPBF, the keyhole can be classified into shallow and deep keyhole mode, controlled by the energy density. Increasing the energy density, the shallow keyhole mode transforms into the deep keyhole mode. The energy density in a deep keyhole is higher due to the multiple reflections and concentrations of secondary reflected beams within the keyhole, causing the material to vaporize quickly. Due to an elevated temperature distribution in deep keyhole mode, the probability of pores forming is much higher than in a shallow keyhole as the liquid material is close to the vaporization temperature. When the temperature increases rapidly, the material density drops quickly, thus, raising the fluid volume due to the specific heat and fusion latent heat. In return, this lowers the surface tension and affects the melt pool uniformity.https://www.mdpi.com/2079-4991/11/12/3284laser powder bed fusioncomputational fluid dynamicsanalytical modellingshallow and deep keyhole modesexperimental correlation |
| spellingShingle | Asif Ur Rehman Muhammad Arif Mahmood Fatih Pitir Metin Uymaz Salamci Andrei C. Popescu Ion N. Mihailescu Keyhole Formation by Laser Drilling in Laser Powder Bed Fusion of Ti6Al4V Biomedical Alloy: Mesoscopic Computational Fluid Dynamics Simulation versus Mathematical Modelling Using Empirical Validation Nanomaterials laser powder bed fusion computational fluid dynamics analytical modelling shallow and deep keyhole modes experimental correlation |
| title | Keyhole Formation by Laser Drilling in Laser Powder Bed Fusion of Ti6Al4V Biomedical Alloy: Mesoscopic Computational Fluid Dynamics Simulation versus Mathematical Modelling Using Empirical Validation |
| title_full | Keyhole Formation by Laser Drilling in Laser Powder Bed Fusion of Ti6Al4V Biomedical Alloy: Mesoscopic Computational Fluid Dynamics Simulation versus Mathematical Modelling Using Empirical Validation |
| title_fullStr | Keyhole Formation by Laser Drilling in Laser Powder Bed Fusion of Ti6Al4V Biomedical Alloy: Mesoscopic Computational Fluid Dynamics Simulation versus Mathematical Modelling Using Empirical Validation |
| title_full_unstemmed | Keyhole Formation by Laser Drilling in Laser Powder Bed Fusion of Ti6Al4V Biomedical Alloy: Mesoscopic Computational Fluid Dynamics Simulation versus Mathematical Modelling Using Empirical Validation |
| title_short | Keyhole Formation by Laser Drilling in Laser Powder Bed Fusion of Ti6Al4V Biomedical Alloy: Mesoscopic Computational Fluid Dynamics Simulation versus Mathematical Modelling Using Empirical Validation |
| title_sort | keyhole formation by laser drilling in laser powder bed fusion of ti6al4v biomedical alloy mesoscopic computational fluid dynamics simulation versus mathematical modelling using empirical validation |
| topic | laser powder bed fusion computational fluid dynamics analytical modelling shallow and deep keyhole modes experimental correlation |
| url | https://www.mdpi.com/2079-4991/11/12/3284 |
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