Laser-induced deformation modes in thin metal targets

O’Keefe, J. D.; Skeen, C. H.; York, C. M.

doi:10.1063/1.1662012

Cited by 68 publications

(19 citation statements)

References 15 publications

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“…For the same laser fluence, the use of the femtosecond laser pulse results in a higher power density (~ 10 15 W/cm 2 ), which is appoximately five orders of magnitude higher than the nanosecond laser (~10 9 -10 10 W/cm 2 ). It is known that higher laser power density increases the mechanical load placed on materials due to high ablation and plasma pressures [26,27]. In the present study of the single crystal superalloy, a layer of plastically deformed material ~5 m in extent was observed.…”

Section: Discussionmentioning

confidence: 52%

Femtosecond Laser Micromachining of Single-Crystal Superalloys

Feng

Picard

Liu

et al. 2004

Superalloys 2004 (Tenth International Symposium)

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Investigations on femtosecond laser micromachining of single crystal superalloys with and without plasma-sprayed thermal barrier coatings were conducted under laser fluences ranging from 0.1 J/cm 2 up to 160 J/cm 2 . Micromachining was carried out in air using a titanium:sapphire laser system ( = 780 nm) operating at a repetition rate of 1 kHz and delivering individual pulses of ~150 fs duration. The ablation threshold of the single crystal superalloy was determined as 203 ± 20 mJ/cm 2 . Laser-induced damage was examined by means of scanning electron microscopy and transmission electron microscopy. These studies indicate a complete absence of any melting, recast layers, heat-affected zones or microcracks in the vicinity of the machining area. The only form of damage observed in the single crystal superalloy machined near or above the ablation threshold was a laser-induced plastically deformed layer with a maximum extent of ~5 m. Machining through ceramic thermal barrier coatings on a superalloy produced no delamination along the superalloy/coating interfaces or cracks within the TBC or bond coat. The residual roughness of the machined surface was in the sub-micron range. The present study suggests that femtosecond laser micromachining is a very promising technique for production of finescale features in multi-layer material systems for aerospace and power generation components.

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Section: Discussionmentioning

confidence: 52%

Femtosecond Laser Micromachining of Single-Crystal Superalloys

Feng

Picard

Liu

et al. 2004

Superalloys 2004 (Tenth International Symposium)

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“…In addition to usual regime of free-expanding plasma from the irradiated front surface of the film, some experiments were performed when a transparent fused silica window was set adjacent to the film. It confined plasma expansion towards the laser beam in the same manner as the water layer did in early experiments [7][8][9][10][11][12][13][14][15][16][17][18][19] . This increased the SW velocity in the confinement regime by the factor 1.3 − 1.4.…”

Section: Acceleration Of Thin Films and Generation Of Forward Swmentioning

confidence: 95%

High-energy GARPUN KrF laser interaction with solid and thin-foil targets in ambient air

Зворыкин

Bakaev

Batani

et al. 2004

High-Power Laser Ablation V

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Hydrodynamic regimes of KrF laser interaction with solid and thin-film targets in atmospheric and reduced pressure air were investigated at high-energy GARPUN installation. These experiments were performed with 100-J, 100-ns laser pulses in planar focusing geometry and compared with numerical simulations with ATLANT code to verify the concept of laser-driven shock tube (LST), which could accelerate a gas to hypersonic velocity and produce strong shock waves (SW). Laser beam was focused by a prism raster optical system that provided very uniform intensity distribution at moderate laser intensities q ≤ 1 GW/cm 2 over a square spot of ~ 1-cm size. Dynamics of laser-produced plasma and SW in a surrounding gas were investigated by means of high-speed photo-chronograph and streak camera in combination with shadow or schlieren techniques, time and space resolved spectroscopy in a visible spectral range. Both experiments and simulations confirmed that target evaporation and blow-up of expanding plasma are the main mechanisms of UV laser-target interaction in a surrounding gas. Planar shock waves with velocities up to 7 km/s towards the laser beam were observed in a normal density air and up to 30 km/s in a rarefied air. Acceleration of thin CH films of 1 to 50-µm thickness was investigated both in a free-expansion and plasma-confined regimes with the highest achieved velocities up to 4 km/s. The SW damping law in a free space independently on laser intensity and air pressure could be approximated by a power law x ~ t n with a power indexes n 1 = 0.85 -0.95 at the initial stage and n 2 = 0.5 -0.6 later, when a distance of the SW front from a target became comparable with a size of the irradiated spot. Instability growth at contact interfaces between ablative plasma and accelerated film, as well as between plasma and compressed air were observed and compared for various initial irradiation non-uniformities. They were introduced by a grid, which was set in front of the film target.

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“…al. investigated the laser shock-induced deformation modes in thin 6061-T6 aluminum and stainless steel targets using a Nd-glass laser and fused quartz or Plexiglass for confining the plasma [23]. They attributed the time sequence of events during bulging and puncturing the thin targets to the interplay of the dilatational and shear waves generated by the pressure pulse.…”

Section: The Phenomenological Origins Of Laser Processingmentioning

confidence: 99%

Laser Shock Peening, the Path to Production

Clauer

2019

Metals

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This article describes the path to commercialization for laser shock peening beginning with the discovery of the basic phenomenology of the process through to its implementation as a commercial process. It describes the circumstances leading to its invention, the years spent on exploring and defining characteristics of the process, and the journey to commercialization. Like many budding technologies displaying unique characteristics, but no immediately evident application, i.e., “a solution looking for a problem”, there were several instances where its development may have been delayed or ended except for an unanticipated event that enabled it to move forward. An important contributor to the success of laser peening, is that nearly 15 years after its invention, universities world-wide began extensive research into the process, dramatically broadening the knowledge base and increasing confidence in, and understanding of its potential. Finally, a critical problem in need of a solution, laser peening, appeared, culminating in its first industrial application on aircraft turbine engine fan blades.

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Laser-induced deformation modes in thin metal targets

Cited by 68 publications

References 15 publications

Femtosecond Laser Micromachining of Single-Crystal Superalloys

Femtosecond Laser Micromachining of Single-Crystal Superalloys

High-energy GARPUN KrF laser interaction with solid and thin-foil targets in ambient air

Laser Shock Peening, the Path to Production

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