A generalized thermal modeling for laser drilling process—I. Mathematical modeling and numerical methodology

Ganesh, Ram K.; Faghri, Amir; Hahn, Yukap

doi:10.1016/s0017-9310(96)00368-7

Cited by 101 publications

(50 citation statements)

References 19 publications

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“…The speed of sound in aluminium vapour is included to show that the compressed air speed or the speed of aluminium vapour is subsonic for the intensities of interest. This is in contrast to the assumptions in [6,7]. The magnitude of these velocities with the typical length-scale ('" 1mm) allows us to determine the time-scale for the gas dynamics ('" 1O-6 s).…”

Section: P4 P3mentioning

confidence: 94%

“…The solidification model then becomes (and without ambiguity the hats on the n~n-dimensionalvariables can be omitted) for 1/(X, t) < y < h(:r, t), (6) 1 8¢ 8h 8¢8h (9) T -+ T a as y -+ -00.…”

Section: Solidification Modelmentioning

confidence: 99%

“…The convection terms in the energy equation for the fluid are unusual in this context. The weak formulation is far more amenable to numerical methods than the model in [6,7] and is the first stage towards nunH~rical calculations with the enthalpy method. …”

Section: Suffilnarymentioning

confidence: 99%

“…The subject of laser percussion drilling has been studied by several authors (see [6] and references therein). The models take the form of incompressible Navier-Stokes equations including gravity.…”

Section: Introductionmentioning

confidence: 99%

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Models for Solidification and Splashing in Laser Percussion Drilling

Smith¹

2002

SIAM J. Appl. Math.

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Abstract. This paper studies systems of partial differential equations modelling laser percussion drilling. The particular phenomenon considered in detail is the ejection of the thin layer of molten material. This thin layer is modelled as an inviscid flow between the fluid surface and fluid/solid interface, both of which are unknown moving boundaries. Through a regular asymptotic expansion, the governing equations are reduced to a combination of the shallow water equations and a two-phase Stefan problem; the key small parameter being the square of the aspect ratio. These leading-order problems exhibit shocks which represents a possible mechanism for the previously unexplained fluid clumping. Approximate formulas and a parameter gronping are derived to predict the rate of melt solidification during ejection. Finally, weak formulations of thp convection-diffusion equation for energy conservation are presented. These weak formulations are novel becanse the energy equation in the fluid contains convection terms. An appropriate extension to the enthalpy method is suggest{~d as a first stage towards numerical calculations.

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Section: P4 P3mentioning

confidence: 94%

Section: Solidification Modelmentioning

confidence: 99%

Section: Suffilnarymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Models for Solidification and Splashing in Laser Percussion Drilling

Smith¹

2002

SIAM J. Appl. Math.

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“…Their simulations predicted the formation of broad-spectrum surface pressure fluctuations due to both the turbulent nature of the gas jet and the blunt shock oscillation on the surface. On the other hand, in order to understand the thermal phenomena and temperature fields, several models for the laser drilling process have been reported in the literature [21][22][23][24][25][26][27]. For example, Chan and Mazumder [21,22] used multiphase model with the heat equation to analytically analyze the evaporation and melt expulsion and discuss the material removal rates.…”

Section: Introductionmentioning

confidence: 99%

Continuous-wave laser drilling assisted by intermittent gas jets

Hsu

Lin

Chang

et al. 2015

Int J Adv Manuf Technol

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We describe a study of the laser drilling of stainless steel (SUS304) using a fiber laser with a wavelength of 1090 nm, assisted by intermittent gas jets. By comparing with the results obtained with the conventional continuous gas jets used in assisted laser drilling, we demonstrate that the use of the intermittent gas jets can effectively increase the material removal rate and reduce the consumption of assist gas. The intermittent gas jets can be modulated according to the frequency to effectively reduce the overcooling effect of the assist gas. Experimental results show that both the drilling depth and machining quality can be greatly and simultaneously improved. Two types of intermittent gas jets, namely, straight and swirling jets, are considered, and the effects of the intermittent frequencies and gas pressures on the laser drilling are investigated and discussed. We conclude that the intermittent gas jet method greatly reduces heat loss and slag formation around the hole exit in the laser drilling process. Compared with the results obtained when using a continuous straight gas jet, laser drilling with a 20-Hz intermittent straight gas jet reduces the drilled hole entrance diameter and increases the drilled hole depth by a factor of up to 1.7. The intermittent gas jet method can reduce the quantity of assist gas being used, and therefore the cost, especially when expensive gases such as helium and argon are being used.

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Lasers in Aerospace Industry Manufacturing

Mazumder

2010

Encyclopedia of Aerospace Engineering

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The Aerospace Industry has adopted laser technology from its early days and several laser‐aided manufacturing processes have become routine. Lasers can deliver energy from zero to a trillion watts in a small spot in an instant. That generated a wide portfolio. For example, laser peening needs more than 10 9 W cm −2 , whereas laser welding can be accomplished with 10 6 W cm −2 ; laser drilling requires 10 8 W cm −2 compared to 10 5 W cm −2 or more for laser cladding and solid free form formation. The mechanism for different processes is different although the energy source is common. Interaction time for each process is different, too. Laser shock peening utilizes nanosecond pulses compared to millisecond pulses for drilling. Welding and cladding are generally carried out with continuous wave. The role they play is also varied. Drilling generates cooling holes for turbine blades to enhance the operating temperature whereas shot peening produces residual compressive stress on the blades to improve fatigue properties and reduce crack propagation. Welding is mostly used to join structural components whereas cladding repair of reconfigured aerospace components is used to increase their service life. This chapter will discuss the four most common uses of lasers in Aerospace Industry Manufacturing.

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A generalized thermal modeling for laser drilling process—I. Mathematical modeling and numerical methodology

Cited by 101 publications

References 19 publications

Models for Solidification and Splashing in Laser Percussion Drilling

Models for Solidification and Splashing in Laser Percussion Drilling

Continuous-wave laser drilling assisted by intermittent gas jets

Lasers in Aerospace Industry Manufacturing

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