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Bekir Sami Yilbas - One of the best experts on this subject based on the ideXlab platform.
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Thermal analysis of the Laser Cutting Process
The Laser Cutting Process, 2018Co-Authors: Bekir Sami YilbasAbstract:The absorption of Laser intensity at any point in a substrate material can be written in terms of Beer-Lambert’s law. Irradiated energy is absorbed in the surface skin of the substrate material. Consideration of surface heat source minimizes this problem. Surface evaporation is the dominant mechanism during key-hole formation. The temporal variation of the Laser-pulse intensity can be considered to decay exponentially with increasing time; therefore, this variation needs to be incorporated in the stress analysis. The liquid surface layer formed during a Laser pulse moves into the metal at a rate determined by the quantity of vapor expelled. The flow field is turbulent; therefore, the Reynolds stress turbulence model (RSM), which is based on the second-moment closure, is used in the analysis. In the Laser gas-assisted Cutting Process, an impinging jet is used to shield the irradiated region from the oxidation reactions.
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Chapter 4 – Laser Cutting Process
Laser Heating Applications, 2012Co-Authors: Bekir Sami YilbasAbstract:Laser Cutting is one of the machining Processes widely used in industry. To optimize Laser Process parameters towards improving end-product quality, an analytical approach for Laser Cutting characteristics becomes important. Although Laser Cutting Process is three dimensional, introducing scale law analysis simplifies the Process and provides useful information on the Process parameters. In the present chapter, an analytical formulation of Laser Cutting Process and analytical solutions for melting and stria formation are introduced. The study is extended to include scale law analysis for the kerf width calculations. In addition, lump parameter analysis is incorporated to formulate the liquid depth and molten flow in the cut sections including the assisting gas jet momentum and heat transfer.
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Three-dimensional consideration of jet impingement onto the kerf in relation to Laser Cutting Process: Effect of jet velocity on heat transfer rates
Optics and Lasers in Engineering, 2011Co-Authors: Omar A. Melhem, Bekir Sami Yilbas, Shahzada Zaman ShujaAbstract:Abstract In Laser Cutting Process, an assisting gas is used to improve the mass removal rate from the Cutting kerf and protect the kerf surfaces from the high temperature exothermic reactions, such as oxidation reactions, during the Cutting Process. Therefore, heat transfer rates from the kerf wall and the skin friction along the kerf surface are important for quality Cutting. In the present study, jet emerging from a conical convergent nozzle and impinging onto the kerf surface is investigated in relation to the Laser Cutting Process. The flow field in the kerf, the heat transfer rates from the kerf wall, and the skin friction along the kerf surface are computed for four average jet velocities at the nozzle exit and two kerf wall wedge angles. The ratio of the stand-off-distance (distance between the nozzle exit and the kerf top surface) to nozzle diameter is selected as H / D =2.2., where H is the stand-off-distance and D is the nozzle exit diameter. The kerf wall temperature is kept at 1500 K to resemble the Laser Cutting Process. It is found that the Nusselt number increases sharply at the kerf inlet and decreases towards the kerf exit for the kerf wall angle of 0°. However, it increases gradually in this region for the kerf wedge angle of 4°. The skin friction decreases along the kerf surface.
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First and second law analyses of Laser Cutting Process in relation to the end product quality
International Journal of Energy Research, 2008Co-Authors: Ahmet Z. Sahin, Tahir Ayar, Bekir Sami YilbasAbstract:Thermal analysis of Laser Cutting Process is carried out, and the first and second law efficiencies of the Cutting Process are formulated. Thermal efficiencies are predicted for various Laser scanning speeds and Laser output power levels. The experiment is conducted to examine the resulting Cutting sections. The F-test is conducted to assess the end product (Cutting section) quality and, later, the thermal efficiencies are related to the end product quality. It is found that increasing Laser output power lowers the first and second law efficiencies of Cutting, which is more pronounced with reducing the Laser scanning speeds. The end product quality improves for low Laser output power levels and high Laser scanning speeds similar to the thermal efficiencies. Copyright © 2007 John Wiley & Sons, Ltd.
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Thermal stress developed during the Laser Cutting Process: consideration of different materials
The International Journal of Advanced Manufacturing Technology, 2008Co-Authors: A. F. M. Arif, Bekir Sami YilbasAbstract:The Laser Cutting of metallic substrates results in the development of thermal stresses around the cut edges. Depending on the Cutting speed, Laser power intensity, and material properties, stress levels reaching and exceeding the yielding limit of the substrate material can result. In the present study, the Laser Cutting situation is simulated and temperature as well as thermal stress fields are computed for steel, Inconel 625, and Ti-6Al-4V alloy. The Cutting speed of the Laser is considered to be constant and a constant temperature heat source with a focused spot diameter is assumed along the kerf surface at the cut edge, resembling the Laser heat source. The equations for energy and thermal stresses are solved numerically using the finite element method (FEM). It is found that the temperature decays sharply in the vicinity of the cut edges and that the equivalent stress attains high values in this region. Inconel 625 results in the highest thermal stress levels in the vicinity of the cut edges and is then followed by steel and titanium alloy.
Ashish K. Nath - One of the best experts on this subject based on the ideXlab platform.
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an investigation of energy loss mechanisms in water jet assisted underwater Laser Cutting Process using an analytical model
International Journal of Machine Tools & Manufacture, 2015Co-Authors: Suvradip Mullick, Yuvraj K. Madhukar, Subhransu Roy, Ashish K. NathAbstract:Abstract The water-jet assisted underwater Laser Cutting Processes has relatively low overall efficiency compared to gas assisted Laser Cutting Process due to high convective loss in water-jet from the hot melt layer and scattering loss of Laser radiation by the water vapour formed at the Laser–workpiece–water interaction region. However, the individual contribution of different losses and their dependency on Process parameters are not fully investigated. Therefore, a lumped parameter analytical model for this Cutting Process has been formulated considering various Laser–material–water interaction phenomena, different loss mechanisms and shear force provided by the water-jet, and has been used to predict various output parameters including the maximum Cutting speed, cut front temperature, cut kerf and the loss of Laser power through different mechanisms as functions of Laser power and water-jet speed. The predictions of Cutting speed, kerf-width and cut front temperature were validated with the experimental results. The modeling revealed that the scattering in water vapour is the dominant loss mechanism, causing ~40–50% of Laser power loss. This also predicted that the percentage losses are lower for higher Laser powers and lower water-jet speeds. In order to minimize the deleterious effect of vapour, dynamics of its formation due to Laser heating and its removal by water-jet was experimentally studied. And, the Cutting was done with modulated power Laser beam of different pulse on- and off-times to determine the pulse on-time sufficiently short to disallow growth of vapour layer, still Cutting be effected and the off-time enough long for water-jet to remove the vapour layer from the interaction zone before next pulse arrives. Compared to CW Laser beam the modulated Laser beam of same average power yielded higher Process efficiency.
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development and parametric study of a water jet assisted underwater Laser Cutting Process
International Journal of Machine Tools & Manufacture, 2013Co-Authors: Suvradip Mullick, Yuvraj K. Madhukar, Subhransu Roy, Shailesh Kumar, Dinesh K Shukla, Ashish K. NathAbstract:Abstract The conventional underwater Laser Cutting Process usually utilizes a high pressure gas jet along with the Laser beam to create a dry condition in the Cutting zone and eject out the molten material. This causes a lot of gas bubbles and turbulence in water, and produces aerosols and waste gas. This may cause contamination in the surrounding atmosphere, while Cutting the radioactive components. In order to minimize this effect, a water-jet assisted underwater Laser Cutting technique has been developed using a high power fiber Laser. A high velocity coaxial water-jet has been employed in place of gas-jet to remove the molten material through the kerf. Some amount of water vapour bubbles is formed at the Laser–metal–water interface; however, they tend to condense as they rise up through the surrounding water. AISI 304 stainless steel sheet of maximum 1.5 mm thickness was cut at 1.4 m/min Cutting speed with the present setup at 1800 W CW Laser power, and the resulting average kerf-width was about 0.75 mm. The heat convection by water jet and the scattering of Laser beam by vapour were found to influence significantly the energy efficiency of the Cutting Process. The effects of various Processing parameters on the Cutting performance were investigated. The energy efficiency improved at higher Cutting speeds. An energy balance model with various loss mechanisms included has been also developed.
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Development of a Water-Jet Assisted Underwater Laser Cutting Process
2013Co-Authors: Suvradip Mullick, Yuvraj K. Madhukar, Subhranshu Roy, Ashish K. NathAbstract:We present the development of a new underwater Laser Cutting Process in which a water-jet has been used along with the Laser beam to remove the molten material through kerf. The conventional underwater Laser Cutting usually utilizes a high pressure gas jet along with Laser beam to create a dry condition in the Cutting zone and also to eject out the molten material. This causes a lot of gas bubbles and turbulence in water, and produces aerosols and waste gas. This may cause contamination in the surrounding atmosphere while Cutting radioactive components like burnt nuclear fuel. The water-jet assisted underwater Laser Cutting Process produces much less turbulence and aerosols in the atmosphere. Some amount of water vapor bubbles is formed at the Laser-metal-water interface; however, they tend to condense as they rise up through the surrounding water. We present the design and development of a water-jet assisted underwater Laser Cutting head and the parametric study of the Cutting of AISI 304 stainless steel sheets with a 2 kW CW fiber Laser. The Cutting performance is similar to that of the gas assist Laser Cutting; however, the Process efficiency is reduced due to heat convection by water-jet and Laser beam scattering by vapor. This Process may be attractive for underwater Cutting of nuclear reactor components
Suvradip Mullick - One of the best experts on this subject based on the ideXlab platform.
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an investigation of energy loss mechanisms in water jet assisted underwater Laser Cutting Process using an analytical model
International Journal of Machine Tools & Manufacture, 2015Co-Authors: Suvradip Mullick, Yuvraj K. Madhukar, Subhransu Roy, Ashish K. NathAbstract:Abstract The water-jet assisted underwater Laser Cutting Processes has relatively low overall efficiency compared to gas assisted Laser Cutting Process due to high convective loss in water-jet from the hot melt layer and scattering loss of Laser radiation by the water vapour formed at the Laser–workpiece–water interaction region. However, the individual contribution of different losses and their dependency on Process parameters are not fully investigated. Therefore, a lumped parameter analytical model for this Cutting Process has been formulated considering various Laser–material–water interaction phenomena, different loss mechanisms and shear force provided by the water-jet, and has been used to predict various output parameters including the maximum Cutting speed, cut front temperature, cut kerf and the loss of Laser power through different mechanisms as functions of Laser power and water-jet speed. The predictions of Cutting speed, kerf-width and cut front temperature were validated with the experimental results. The modeling revealed that the scattering in water vapour is the dominant loss mechanism, causing ~40–50% of Laser power loss. This also predicted that the percentage losses are lower for higher Laser powers and lower water-jet speeds. In order to minimize the deleterious effect of vapour, dynamics of its formation due to Laser heating and its removal by water-jet was experimentally studied. And, the Cutting was done with modulated power Laser beam of different pulse on- and off-times to determine the pulse on-time sufficiently short to disallow growth of vapour layer, still Cutting be effected and the off-time enough long for water-jet to remove the vapour layer from the interaction zone before next pulse arrives. Compared to CW Laser beam the modulated Laser beam of same average power yielded higher Process efficiency.
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development and parametric study of a water jet assisted underwater Laser Cutting Process
International Journal of Machine Tools & Manufacture, 2013Co-Authors: Suvradip Mullick, Yuvraj K. Madhukar, Subhransu Roy, Shailesh Kumar, Dinesh K Shukla, Ashish K. NathAbstract:Abstract The conventional underwater Laser Cutting Process usually utilizes a high pressure gas jet along with the Laser beam to create a dry condition in the Cutting zone and eject out the molten material. This causes a lot of gas bubbles and turbulence in water, and produces aerosols and waste gas. This may cause contamination in the surrounding atmosphere, while Cutting the radioactive components. In order to minimize this effect, a water-jet assisted underwater Laser Cutting technique has been developed using a high power fiber Laser. A high velocity coaxial water-jet has been employed in place of gas-jet to remove the molten material through the kerf. Some amount of water vapour bubbles is formed at the Laser–metal–water interface; however, they tend to condense as they rise up through the surrounding water. AISI 304 stainless steel sheet of maximum 1.5 mm thickness was cut at 1.4 m/min Cutting speed with the present setup at 1800 W CW Laser power, and the resulting average kerf-width was about 0.75 mm. The heat convection by water jet and the scattering of Laser beam by vapour were found to influence significantly the energy efficiency of the Cutting Process. The effects of various Processing parameters on the Cutting performance were investigated. The energy efficiency improved at higher Cutting speeds. An energy balance model with various loss mechanisms included has been also developed.
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Development of a Water-Jet Assisted Underwater Laser Cutting Process
2013Co-Authors: Suvradip Mullick, Yuvraj K. Madhukar, Subhranshu Roy, Ashish K. NathAbstract:We present the development of a new underwater Laser Cutting Process in which a water-jet has been used along with the Laser beam to remove the molten material through kerf. The conventional underwater Laser Cutting usually utilizes a high pressure gas jet along with Laser beam to create a dry condition in the Cutting zone and also to eject out the molten material. This causes a lot of gas bubbles and turbulence in water, and produces aerosols and waste gas. This may cause contamination in the surrounding atmosphere while Cutting radioactive components like burnt nuclear fuel. The water-jet assisted underwater Laser Cutting Process produces much less turbulence and aerosols in the atmosphere. Some amount of water vapor bubbles is formed at the Laser-metal-water interface; however, they tend to condense as they rise up through the surrounding water. We present the design and development of a water-jet assisted underwater Laser Cutting head and the parametric study of the Cutting of AISI 304 stainless steel sheets with a 2 kW CW fiber Laser. The Cutting performance is similar to that of the gas assist Laser Cutting; however, the Process efficiency is reduced due to heat convection by water-jet and Laser beam scattering by vapor. This Process may be attractive for underwater Cutting of nuclear reactor components
Yuvraj K. Madhukar - One of the best experts on this subject based on the ideXlab platform.
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an investigation of energy loss mechanisms in water jet assisted underwater Laser Cutting Process using an analytical model
International Journal of Machine Tools & Manufacture, 2015Co-Authors: Suvradip Mullick, Yuvraj K. Madhukar, Subhransu Roy, Ashish K. NathAbstract:Abstract The water-jet assisted underwater Laser Cutting Processes has relatively low overall efficiency compared to gas assisted Laser Cutting Process due to high convective loss in water-jet from the hot melt layer and scattering loss of Laser radiation by the water vapour formed at the Laser–workpiece–water interaction region. However, the individual contribution of different losses and their dependency on Process parameters are not fully investigated. Therefore, a lumped parameter analytical model for this Cutting Process has been formulated considering various Laser–material–water interaction phenomena, different loss mechanisms and shear force provided by the water-jet, and has been used to predict various output parameters including the maximum Cutting speed, cut front temperature, cut kerf and the loss of Laser power through different mechanisms as functions of Laser power and water-jet speed. The predictions of Cutting speed, kerf-width and cut front temperature were validated with the experimental results. The modeling revealed that the scattering in water vapour is the dominant loss mechanism, causing ~40–50% of Laser power loss. This also predicted that the percentage losses are lower for higher Laser powers and lower water-jet speeds. In order to minimize the deleterious effect of vapour, dynamics of its formation due to Laser heating and its removal by water-jet was experimentally studied. And, the Cutting was done with modulated power Laser beam of different pulse on- and off-times to determine the pulse on-time sufficiently short to disallow growth of vapour layer, still Cutting be effected and the off-time enough long for water-jet to remove the vapour layer from the interaction zone before next pulse arrives. Compared to CW Laser beam the modulated Laser beam of same average power yielded higher Process efficiency.
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development and parametric study of a water jet assisted underwater Laser Cutting Process
International Journal of Machine Tools & Manufacture, 2013Co-Authors: Suvradip Mullick, Yuvraj K. Madhukar, Subhransu Roy, Shailesh Kumar, Dinesh K Shukla, Ashish K. NathAbstract:Abstract The conventional underwater Laser Cutting Process usually utilizes a high pressure gas jet along with the Laser beam to create a dry condition in the Cutting zone and eject out the molten material. This causes a lot of gas bubbles and turbulence in water, and produces aerosols and waste gas. This may cause contamination in the surrounding atmosphere, while Cutting the radioactive components. In order to minimize this effect, a water-jet assisted underwater Laser Cutting technique has been developed using a high power fiber Laser. A high velocity coaxial water-jet has been employed in place of gas-jet to remove the molten material through the kerf. Some amount of water vapour bubbles is formed at the Laser–metal–water interface; however, they tend to condense as they rise up through the surrounding water. AISI 304 stainless steel sheet of maximum 1.5 mm thickness was cut at 1.4 m/min Cutting speed with the present setup at 1800 W CW Laser power, and the resulting average kerf-width was about 0.75 mm. The heat convection by water jet and the scattering of Laser beam by vapour were found to influence significantly the energy efficiency of the Cutting Process. The effects of various Processing parameters on the Cutting performance were investigated. The energy efficiency improved at higher Cutting speeds. An energy balance model with various loss mechanisms included has been also developed.
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Development of a Water-Jet Assisted Underwater Laser Cutting Process
2013Co-Authors: Suvradip Mullick, Yuvraj K. Madhukar, Subhranshu Roy, Ashish K. NathAbstract:We present the development of a new underwater Laser Cutting Process in which a water-jet has been used along with the Laser beam to remove the molten material through kerf. The conventional underwater Laser Cutting usually utilizes a high pressure gas jet along with Laser beam to create a dry condition in the Cutting zone and also to eject out the molten material. This causes a lot of gas bubbles and turbulence in water, and produces aerosols and waste gas. This may cause contamination in the surrounding atmosphere while Cutting radioactive components like burnt nuclear fuel. The water-jet assisted underwater Laser Cutting Process produces much less turbulence and aerosols in the atmosphere. Some amount of water vapor bubbles is formed at the Laser-metal-water interface; however, they tend to condense as they rise up through the surrounding water. We present the design and development of a water-jet assisted underwater Laser Cutting head and the parametric study of the Cutting of AISI 304 stainless steel sheets with a 2 kW CW fiber Laser. The Cutting performance is similar to that of the gas assist Laser Cutting; however, the Process efficiency is reduced due to heat convection by water-jet and Laser beam scattering by vapor. This Process may be attractive for underwater Cutting of nuclear reactor components
Subhransu Roy - One of the best experts on this subject based on the ideXlab platform.
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an investigation of energy loss mechanisms in water jet assisted underwater Laser Cutting Process using an analytical model
International Journal of Machine Tools & Manufacture, 2015Co-Authors: Suvradip Mullick, Yuvraj K. Madhukar, Subhransu Roy, Ashish K. NathAbstract:Abstract The water-jet assisted underwater Laser Cutting Processes has relatively low overall efficiency compared to gas assisted Laser Cutting Process due to high convective loss in water-jet from the hot melt layer and scattering loss of Laser radiation by the water vapour formed at the Laser–workpiece–water interaction region. However, the individual contribution of different losses and their dependency on Process parameters are not fully investigated. Therefore, a lumped parameter analytical model for this Cutting Process has been formulated considering various Laser–material–water interaction phenomena, different loss mechanisms and shear force provided by the water-jet, and has been used to predict various output parameters including the maximum Cutting speed, cut front temperature, cut kerf and the loss of Laser power through different mechanisms as functions of Laser power and water-jet speed. The predictions of Cutting speed, kerf-width and cut front temperature were validated with the experimental results. The modeling revealed that the scattering in water vapour is the dominant loss mechanism, causing ~40–50% of Laser power loss. This also predicted that the percentage losses are lower for higher Laser powers and lower water-jet speeds. In order to minimize the deleterious effect of vapour, dynamics of its formation due to Laser heating and its removal by water-jet was experimentally studied. And, the Cutting was done with modulated power Laser beam of different pulse on- and off-times to determine the pulse on-time sufficiently short to disallow growth of vapour layer, still Cutting be effected and the off-time enough long for water-jet to remove the vapour layer from the interaction zone before next pulse arrives. Compared to CW Laser beam the modulated Laser beam of same average power yielded higher Process efficiency.
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development and parametric study of a water jet assisted underwater Laser Cutting Process
International Journal of Machine Tools & Manufacture, 2013Co-Authors: Suvradip Mullick, Yuvraj K. Madhukar, Subhransu Roy, Shailesh Kumar, Dinesh K Shukla, Ashish K. NathAbstract:Abstract The conventional underwater Laser Cutting Process usually utilizes a high pressure gas jet along with the Laser beam to create a dry condition in the Cutting zone and eject out the molten material. This causes a lot of gas bubbles and turbulence in water, and produces aerosols and waste gas. This may cause contamination in the surrounding atmosphere, while Cutting the radioactive components. In order to minimize this effect, a water-jet assisted underwater Laser Cutting technique has been developed using a high power fiber Laser. A high velocity coaxial water-jet has been employed in place of gas-jet to remove the molten material through the kerf. Some amount of water vapour bubbles is formed at the Laser–metal–water interface; however, they tend to condense as they rise up through the surrounding water. AISI 304 stainless steel sheet of maximum 1.5 mm thickness was cut at 1.4 m/min Cutting speed with the present setup at 1800 W CW Laser power, and the resulting average kerf-width was about 0.75 mm. The heat convection by water jet and the scattering of Laser beam by vapour were found to influence significantly the energy efficiency of the Cutting Process. The effects of various Processing parameters on the Cutting performance were investigated. The energy efficiency improved at higher Cutting speeds. An energy balance model with various loss mechanisms included has been also developed.
