The Experts below are selected from a list of 324 Experts worldwide ranked by ideXlab platform
J A Piper - One of the best experts on this subject based on the ideXlab platform.
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study of the interplay of vaporisation Melt displacement and Melt Ejection mechanisms under multiple pulse irradiation of metals
Applied Surface Science, 2006Co-Authors: J M Fishburn, Michael J Withford, David W Coutts, J A PiperAbstract:Abstract A threefold study combining profilometry, high speed imaging and recoil momentum measurements is used to deconvolve the relative contributions to material removal attributable to vaporisation, Melt displacement and explosive Melt Ejection. The interplay of these three mechanisms is studied as a function of the number of laser pulses incident on an aluminium target and pulse repetition frequency. This study shows cumulative heating affects matter removed as both vapour and liquid Melt, and highlights the influence of the vapour plume and ablation crater morphology on the proportions of material removed as Melt displacement and Melt Ejection.
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study of the fluence dependent interplay between laser induced material removal mechanisms in metals vaporization Melt displacement and Melt Ejection
Applied Surface Science, 2006Co-Authors: J M Fishburn, Michael J Withford, David W Coutts, J A PiperAbstract:Abstract Three quantitative methods, namely profilometry, high speed imaging and recoil momentum measurements using a ballistic pendulum, are used to determine the interplay of vaporization, Melt displacement and Melt Ejection on nanosecond laser induced material removal. At low to moderate fluences ( −2 ) material removal occurs via vaporization and Melt displacement in aluminium. At high fluences (>7 J cm −2 ), material removal occurs predominantly via the explosive Ejection of liquid droplets from the Melt pool.
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study of the interplay of vaporisation Melt displacement and Melt Ejection mechanisms under single and multiple pulse irradiation
PICALO 2006 - 2nd Pacific International Conference on Applications of Laser and Optics, 2006Co-Authors: J M Fishburn, Michael J Withford, David W Coutts, J A PiperAbstract:We report the use of a combination of profilometry, high speed imaging and recoil measurements using a ballistic pendulum to calculate the amount of material removed due to mechanisms of vaporisation, Melt displacement and Melt Ejection when ablating aluminium with a visible nanosecond laser. Single laser pulses are shown to induce material removal predominantly by the mechanism of Melt displacement at fluences 7 J.cm-2. Studies of the effects of multiple laser pulses, as a function of spot size and pulse rate demonstrate the additional influence of the geometric constraints of the ablation crater and cumulative heating on laser ablation.We report the use of a combination of profilometry, high speed imaging and recoil measurements using a ballistic pendulum to calculate the amount of material removed due to mechanisms of vaporisation, Melt displacement and Melt Ejection when ablating aluminium with a visible nanosecond laser. Single laser pulses are shown to induce material removal predominantly by the mechanism of Melt displacement at fluences 7 J.cm-2. Studies of the effects of multiple laser pulses, as a function of spot size and pulse rate demonstrate the additional influence of the geometric constraints of the ablation crater and cumulative heating on laser ablation.
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Quantitative study of laser induced material removal mechanisms in aluminium: contributions due to vaporization, Melt displacement and Ejection
2005 Pacific Rim Conference on Lasers & Electro-Optics, 2005Co-Authors: Michael J Withford, J M Fishburn, David W Coutts, J A PiperAbstract:We report the results of a threefold investigation of nanosecond laser ablation of aluminium that permits us to isolate the relative contributions to material removal associated with vaporization, Melt displacement and Melt Ejection. The analytical methods employed and results will be discussed.
David W Coutts - One of the best experts on this subject based on the ideXlab platform.
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study of the interplay of vaporisation Melt displacement and Melt Ejection mechanisms under multiple pulse irradiation of metals
Applied Surface Science, 2006Co-Authors: J M Fishburn, Michael J Withford, David W Coutts, J A PiperAbstract:Abstract A threefold study combining profilometry, high speed imaging and recoil momentum measurements is used to deconvolve the relative contributions to material removal attributable to vaporisation, Melt displacement and explosive Melt Ejection. The interplay of these three mechanisms is studied as a function of the number of laser pulses incident on an aluminium target and pulse repetition frequency. This study shows cumulative heating affects matter removed as both vapour and liquid Melt, and highlights the influence of the vapour plume and ablation crater morphology on the proportions of material removed as Melt displacement and Melt Ejection.
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study of the fluence dependent interplay between laser induced material removal mechanisms in metals vaporization Melt displacement and Melt Ejection
Applied Surface Science, 2006Co-Authors: J M Fishburn, Michael J Withford, David W Coutts, J A PiperAbstract:Abstract Three quantitative methods, namely profilometry, high speed imaging and recoil momentum measurements using a ballistic pendulum, are used to determine the interplay of vaporization, Melt displacement and Melt Ejection on nanosecond laser induced material removal. At low to moderate fluences ( −2 ) material removal occurs via vaporization and Melt displacement in aluminium. At high fluences (>7 J cm −2 ), material removal occurs predominantly via the explosive Ejection of liquid droplets from the Melt pool.
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study of the interplay of vaporisation Melt displacement and Melt Ejection mechanisms under single and multiple pulse irradiation
PICALO 2006 - 2nd Pacific International Conference on Applications of Laser and Optics, 2006Co-Authors: J M Fishburn, Michael J Withford, David W Coutts, J A PiperAbstract:We report the use of a combination of profilometry, high speed imaging and recoil measurements using a ballistic pendulum to calculate the amount of material removed due to mechanisms of vaporisation, Melt displacement and Melt Ejection when ablating aluminium with a visible nanosecond laser. Single laser pulses are shown to induce material removal predominantly by the mechanism of Melt displacement at fluences 7 J.cm-2. Studies of the effects of multiple laser pulses, as a function of spot size and pulse rate demonstrate the additional influence of the geometric constraints of the ablation crater and cumulative heating on laser ablation.We report the use of a combination of profilometry, high speed imaging and recoil measurements using a ballistic pendulum to calculate the amount of material removed due to mechanisms of vaporisation, Melt displacement and Melt Ejection when ablating aluminium with a visible nanosecond laser. Single laser pulses are shown to induce material removal predominantly by the mechanism of Melt displacement at fluences 7 J.cm-2. Studies of the effects of multiple laser pulses, as a function of spot size and pulse rate demonstrate the additional influence of the geometric constraints of the ablation crater and cumulative heating on laser ablation.
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Quantitative study of laser induced material removal mechanisms in aluminium: contributions due to vaporization, Melt displacement and Ejection
2005 Pacific Rim Conference on Lasers & Electro-Optics, 2005Co-Authors: Michael J Withford, J M Fishburn, David W Coutts, J A PiperAbstract:We report the results of a threefold investigation of nanosecond laser ablation of aluminium that permits us to isolate the relative contributions to material removal associated with vaporization, Melt displacement and Melt Ejection. The analytical methods employed and results will be discussed.
J M Fishburn - One of the best experts on this subject based on the ideXlab platform.
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study of the interplay of vaporisation Melt displacement and Melt Ejection mechanisms under multiple pulse irradiation of metals
Applied Surface Science, 2006Co-Authors: J M Fishburn, Michael J Withford, David W Coutts, J A PiperAbstract:Abstract A threefold study combining profilometry, high speed imaging and recoil momentum measurements is used to deconvolve the relative contributions to material removal attributable to vaporisation, Melt displacement and explosive Melt Ejection. The interplay of these three mechanisms is studied as a function of the number of laser pulses incident on an aluminium target and pulse repetition frequency. This study shows cumulative heating affects matter removed as both vapour and liquid Melt, and highlights the influence of the vapour plume and ablation crater morphology on the proportions of material removed as Melt displacement and Melt Ejection.
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study of the fluence dependent interplay between laser induced material removal mechanisms in metals vaporization Melt displacement and Melt Ejection
Applied Surface Science, 2006Co-Authors: J M Fishburn, Michael J Withford, David W Coutts, J A PiperAbstract:Abstract Three quantitative methods, namely profilometry, high speed imaging and recoil momentum measurements using a ballistic pendulum, are used to determine the interplay of vaporization, Melt displacement and Melt Ejection on nanosecond laser induced material removal. At low to moderate fluences ( −2 ) material removal occurs via vaporization and Melt displacement in aluminium. At high fluences (>7 J cm −2 ), material removal occurs predominantly via the explosive Ejection of liquid droplets from the Melt pool.
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study of the interplay of vaporisation Melt displacement and Melt Ejection mechanisms under single and multiple pulse irradiation
PICALO 2006 - 2nd Pacific International Conference on Applications of Laser and Optics, 2006Co-Authors: J M Fishburn, Michael J Withford, David W Coutts, J A PiperAbstract:We report the use of a combination of profilometry, high speed imaging and recoil measurements using a ballistic pendulum to calculate the amount of material removed due to mechanisms of vaporisation, Melt displacement and Melt Ejection when ablating aluminium with a visible nanosecond laser. Single laser pulses are shown to induce material removal predominantly by the mechanism of Melt displacement at fluences 7 J.cm-2. Studies of the effects of multiple laser pulses, as a function of spot size and pulse rate demonstrate the additional influence of the geometric constraints of the ablation crater and cumulative heating on laser ablation.We report the use of a combination of profilometry, high speed imaging and recoil measurements using a ballistic pendulum to calculate the amount of material removed due to mechanisms of vaporisation, Melt displacement and Melt Ejection when ablating aluminium with a visible nanosecond laser. Single laser pulses are shown to induce material removal predominantly by the mechanism of Melt displacement at fluences 7 J.cm-2. Studies of the effects of multiple laser pulses, as a function of spot size and pulse rate demonstrate the additional influence of the geometric constraints of the ablation crater and cumulative heating on laser ablation.
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Quantitative study of laser induced material removal mechanisms in aluminium: contributions due to vaporization, Melt displacement and Ejection
2005 Pacific Rim Conference on Lasers & Electro-Optics, 2005Co-Authors: Michael J Withford, J M Fishburn, David W Coutts, J A PiperAbstract:We report the results of a threefold investigation of nanosecond laser ablation of aluminium that permits us to isolate the relative contributions to material removal associated with vaporization, Melt displacement and Melt Ejection. The analytical methods employed and results will be discussed.
Lin Li - One of the best experts on this subject based on the ideXlab platform.
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Repeatability characteristics of laser percussion drilling of stainless-steel sheets
Optics and Lasers in Engineering, 2020Co-Authors: Gary K L Ng, Lin LiAbstract:An analysis on the repeatability of a laser percussion drilling process is conducted using a flash lamp pumped Nd:YAG laser on 2 mm thick stainless-steel sheets. Laser drilling process is finding increasingly widespread application in the industry and has continually attracted new interests to the industry in recent years. However, the inherent problem of hole geometry repeatability associated with laser percussion drilling is likely to limit the extent of industrial applications of the process. The characteristic of Melt Ejection is found to be dependent on the parameter setting and is shown to have a significant influence on entrance hole geometry and hence repeatability. The relationship between the percentage standard deviation of entrance hole diameter and the operating parameters is established, and varies between 1.8% and 5.6% in the operating range under this study.
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Three-phase 3D modelling of a laser cutting process using Smoothed Particle Hydrodynamics (SPH)
International Congress on Applications of Lasers & Electro-Optics, 2020Co-Authors: N. Muhammad, Benedict D. Rogers, Lin LiAbstract:Smoothed Particle Hydrodynamics (SPH) is used to develop a numerical model to simulate the three-phase laser cutting process for medical coronary stent manufacture. The open-source code SPHysics is used to model the interaction between the laser beam and workpiece. This enables the Melt flow behaviour in the non-linear pulsed fibre laser cutting process to be modelled. The developed model considers the conversion of laser energy into heat within a very thin surface layer, heat conduction into the parent material and the phase transition between solid, liquid and vapour. Promising agreement with experimental data is obtained for predicting the penetration depth and Melt Ejection velocity is in acceptable agreement with the published data. Water is also incorporated in this model to help explain the wet cutting mechanism in laser cutting. It is demonstrated that the meshless characteristics of SPH are able to model the droplets ejected from kerf where it is difficult for conventional modelling. A static beam was used throughout the model development.Smoothed Particle Hydrodynamics (SPH) is used to develop a numerical model to simulate the three-phase laser cutting process for medical coronary stent manufacture. The open-source code SPHysics is used to model the interaction between the laser beam and workpiece. This enables the Melt flow behaviour in the non-linear pulsed fibre laser cutting process to be modelled. The developed model considers the conversion of laser energy into heat within a very thin surface layer, heat conduction into the parent material and the phase transition between solid, liquid and vapour. Promising agreement with experimental data is obtained for predicting the penetration depth and Melt Ejection velocity is in acceptable agreement with the published data. Water is also incorporated in this model to help explain the wet cutting mechanism in laser cutting. It is demonstrated that the meshless characteristics of SPH are able to model the droplets ejected from kerf where it is difficult for conventional modelling. A static bea...
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Mechanisms of Acute Angle Laser Drilling Induced Thermal Barrier Coating Delamination
Journal of Manufacturing Science and Engineering-transactions of The Asme, 2009Co-Authors: H. K. Sezer, Lin LiAbstract:Laser fabrication of cooling holes in certain parts of the aero-engine components involves percussion or trepan drilling at acute angles (e.g., 16―30 deg) to the surface. These parts are often covered with plasma sprayed ceramic thermal barrier coatings (TBCs) to protect them from reaching excessive temperatures in hot engine environments. Delamination of the TBC is the main problem of laser drilling acute angled holes in the coated components. The present study investigates the mechanisms involved in the development of the delamination cracks. A significant role qf Melt Ejection in the formation of cracks and the delamination at the coating/coating interface of the leading edge of a laser-drilled inclined hole was identified. It is shown that the delamination mechanisms at the TBC coating/bond coating and the bond coating/substrate interfaces are different. Melt Ejection induced stresses were identified as the key mechanisms for the former type, while the thermal effects dominates the latter type.
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An analytical model for laser drilling incorporating effects of exothermic reaction, pulse width and hole geometry
International Journal of Heat and Mass Transfer, 2006Co-Authors: Gk Ng, Philip Crouse, Lin LiAbstract:Abstract An analytical model is presented which incorporates the effects of using O2 as assist gas. The contribution of the enthalpy of oxidation used in the model was determined experimentally by capturing the ejected Melt and measuring the volume percentage of oxidation. The formulation of recoil pressure used in the model takes into account hole diameter and depth, and the associated pressure variation. The model presented also considers pulse width which is shown to affect the drilling velocity. The model enables the prediction of the velocity of Melt Ejection, and the drilling rate, as well as the contributions of Melt Ejection and vapourisation to the overall drilling rate. The calculated drilling rates are in close agreement with the experimental results.
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An investigation into delamination mechanisms in inclined laser drilling of thermal barrier coated aerospace superalloys
Journal of Laser Applications, 2005Co-Authors: H. K. Sezer, Lin Li, Andrew J. Pinkerton, P.j ByrdAbstract:Thermal barrier coatings are widely used in aircraft engine hot-end components to protect the component materials from direct exposure to the damaging high temperatures. Effusion cooling techniques are widely used in these situations and laser drilling is normally employed to produce holes of less than 1.5 mm diameter in tough aerospace alloys coated with heat-resistant ceramics. In order to provide the essential cooling effects, a large proportion of these holes must be drilled at acute angles to the surface. During this low-angle laser drilling, microstructural damage of the thermal barrier coating may occur; this is highly undesirable as propagation of the delamination may occur in service, leading to premature failure of the coating. In this article, the role of Melt Ejection and the coaxial assist gas jet in low angle laser drilling of a thermal barrier coated substrate is studied using a finite volume method. The work identifies the significant role of Melt Ejection in the formation of cracks and delamination at the coating/substrate interface on the leading edge of a laser-drilled cooling hole. The numerical model shows that the Melt particles are accelerated towards the leading edge by the coaxial assist gas jet, and as a result of molten metal flowing across the edge the damage through mechanical stresses and subsequent erosion is found to be more serious here than at the trailing edge. The higher shear stress found at the leading edge also implies higher viscous forces acting parallel to the free stream direction to overcome the bonding strength of the coating interface.Thermal barrier coatings are widely used in aircraft engine hot-end components to protect the component materials from direct exposure to the damaging high temperatures. Effusion cooling techniques are widely used in these situations and laser drilling is normally employed to produce holes of less than 1.5 mm diameter in tough aerospace alloys coated with heat-resistant ceramics. In order to provide the essential cooling effects, a large proportion of these holes must be drilled at acute angles to the surface. During this low-angle laser drilling, microstructural damage of the thermal barrier coating may occur; this is highly undesirable as propagation of the delamination may occur in service, leading to premature failure of the coating. In this article, the role of Melt Ejection and the coaxial assist gas jet in low angle laser drilling of a thermal barrier coated substrate is studied using a finite volume method. The work identifies the significant role of Melt Ejection in the formation of cracks and de...
Michael J Withford - One of the best experts on this subject based on the ideXlab platform.
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study of the interplay of vaporisation Melt displacement and Melt Ejection mechanisms under multiple pulse irradiation of metals
Applied Surface Science, 2006Co-Authors: J M Fishburn, Michael J Withford, David W Coutts, J A PiperAbstract:Abstract A threefold study combining profilometry, high speed imaging and recoil momentum measurements is used to deconvolve the relative contributions to material removal attributable to vaporisation, Melt displacement and explosive Melt Ejection. The interplay of these three mechanisms is studied as a function of the number of laser pulses incident on an aluminium target and pulse repetition frequency. This study shows cumulative heating affects matter removed as both vapour and liquid Melt, and highlights the influence of the vapour plume and ablation crater morphology on the proportions of material removed as Melt displacement and Melt Ejection.
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study of the fluence dependent interplay between laser induced material removal mechanisms in metals vaporization Melt displacement and Melt Ejection
Applied Surface Science, 2006Co-Authors: J M Fishburn, Michael J Withford, David W Coutts, J A PiperAbstract:Abstract Three quantitative methods, namely profilometry, high speed imaging and recoil momentum measurements using a ballistic pendulum, are used to determine the interplay of vaporization, Melt displacement and Melt Ejection on nanosecond laser induced material removal. At low to moderate fluences ( −2 ) material removal occurs via vaporization and Melt displacement in aluminium. At high fluences (>7 J cm −2 ), material removal occurs predominantly via the explosive Ejection of liquid droplets from the Melt pool.
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study of the interplay of vaporisation Melt displacement and Melt Ejection mechanisms under single and multiple pulse irradiation
PICALO 2006 - 2nd Pacific International Conference on Applications of Laser and Optics, 2006Co-Authors: J M Fishburn, Michael J Withford, David W Coutts, J A PiperAbstract:We report the use of a combination of profilometry, high speed imaging and recoil measurements using a ballistic pendulum to calculate the amount of material removed due to mechanisms of vaporisation, Melt displacement and Melt Ejection when ablating aluminium with a visible nanosecond laser. Single laser pulses are shown to induce material removal predominantly by the mechanism of Melt displacement at fluences 7 J.cm-2. Studies of the effects of multiple laser pulses, as a function of spot size and pulse rate demonstrate the additional influence of the geometric constraints of the ablation crater and cumulative heating on laser ablation.We report the use of a combination of profilometry, high speed imaging and recoil measurements using a ballistic pendulum to calculate the amount of material removed due to mechanisms of vaporisation, Melt displacement and Melt Ejection when ablating aluminium with a visible nanosecond laser. Single laser pulses are shown to induce material removal predominantly by the mechanism of Melt displacement at fluences 7 J.cm-2. Studies of the effects of multiple laser pulses, as a function of spot size and pulse rate demonstrate the additional influence of the geometric constraints of the ablation crater and cumulative heating on laser ablation.
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Quantitative study of laser induced material removal mechanisms in aluminium: contributions due to vaporization, Melt displacement and Ejection
2005 Pacific Rim Conference on Lasers & Electro-Optics, 2005Co-Authors: Michael J Withford, J M Fishburn, David W Coutts, J A PiperAbstract:We report the results of a threefold investigation of nanosecond laser ablation of aluminium that permits us to isolate the relative contributions to material removal associated with vaporization, Melt displacement and Melt Ejection. The analytical methods employed and results will be discussed.