CARS measurement of vibrational and rotational temperature with high power laser and high speed visualization of total radiation behind hypervelocity shock waves of 5-7km/s

2010 ◽  
Author(s):  
Kotaro Sakurai ◽  
Venigalla Hima Bindu ◽  
Shota Niinomi ◽  
Masanori Ota ◽  
Kazuo Maeno
Keyword(s):  
Shock Waves ◽  
High Power ◽  
High Speed ◽  
Rotational Temperature ◽  
Total Radiation ◽  
High Power Laser ◽  
Power Laser

Characteristics of High Power Laser Shock Waves and Their Cleaning Performance

2019 ◽  
Vol 11 (2) ◽  
pp. 41-46 ◽  
Author(s):  
Tae-Gon Kim ◽  
Young-Sam Yoo ◽  
Il-Ryong Son ◽  
Deoksuk Jang ◽  
Dongsik Kim ◽  
...  
Keyword(s):  
Shock Waves ◽  
High Power ◽  
Laser Shock ◽  
High Power Laser ◽  
Power Laser ◽  
Cleaning Performance

Laser-Induced Bubble Formation on a Micro Gold Particle Levitated Under Ultrasound

2016 ◽  
Author(s):  
Jaekyoon Oh ◽  
Yungpil Yoo ◽  
Samsun Seung ◽  
Ho-Young Kwak
Keyword(s):  
Resonance Frequency ◽  
Gold Particle ◽  
High Power ◽  
High Speed ◽  
Bubble Formation ◽  
Scattering Data ◽  
High Speed Camera ◽  
Scattered Intensity ◽  
High Power Laser ◽  
Power Laser

It is well known that a high-power laser could breakdown liquid [1, 2]. Laser-induced breakdown of liquids is characterized by fast plasma formation after evaporation of liquid and subsequent vapor expansion accompanied by shock wave emission [2]. The bubble wall velocity after the shock departure has been found to be sufficiently high to produce emission of light at the collapse point [3]. Recently, bubble formation on the surface of gold nanoparticles irradiated by a high-power laser in water [4, 5] has been studied for medical applications such as cancer diagnosis and possible therapy [5]. However, it is very hard to perform these experiments and to obtain good data from the bubble formation on the surface of laser-irradiated nano-particles because the nanoparticles dispersed in liquid cannot be controlled properly. In this study, laser-induced bubble formation on a micro gold particle levitated at the center of a spherical flask under ultrasound was investigated experimentally. The obtained results are compared with the results for laser cavitation without the gold particle, i.e., typical laser-induced cavitation. Figure 1 shows a schematic of the experimental setup used to investigate the laser-induced bubble formation on a micro gold particle. Two disk-type lead zirconate titanate (PZT) transducers (Channel Industries Inc.; 15 mm in diameter and 5.0 mm in thickness) attached to the side of the wall of the cell produced a velocity stagnation point near the center of the flask. The driving frequency of the PZT transducers was approximately 27.0 kHz which was close to the resonance frequency of the LRC circuit (Its capacitor unis is PZT.) and the acoustic resonance frequency of the water-filled flask. A drop of water containing gold particles with an average diameter of 10 μm are dispersed was injected into a 100-ml pyrex spherical flask filled with degassed water. When the body force of a gold particle in liquid is slightly lower than the Bjerknes force [6] induced by ultrasound, the particle will stay near the pressure antinode, i.e., the center of the flask. A Q-switched Nd:Yag laser delivered a single pulse of 0.5 ns in width with an energy of 7.5 mJ at a wavelength of 1064 nm to the gold particle or liquid at the center of the cell. The laser light was focused at the center of the flask using a lens with an effective focal length of 36.3 mm. Bubble formation and subsequent growth and collapse were visuallized by a high-speed camera (V2511, Phantom, USA) with 0.45 Mfps (million frames per second). The time-dependent radius was also obtained by the light scattering method. The scattering angle chosen was 80 degree where one-to-one relationship exists between the scattered intensity and the bubble radius [7]. The scattered intensity from a bubble illuminated by a 5-mW He-Ne laser was received by a photomultiplier tube (PMT: Hamamatsu, R2027) and was recorded in an oscilloscope. The scattering data were calibrated using the maximum radius for different bubble, which was obtained by high-speed camera. The shock strength during the expansion stage of bubbles was measured by a calibrated needle hydrophone (HPM1, Precision Acoustics, UK) at various distances from the center of the cell for different bubbles. The hydrophone can measure acoustic signals ranging from 1 kPa to 20 MPa. The hydrophone was attached to a three-dimensional micro stage so that fine control of the positioning of the hydrophone was possible.

Filaments in high-speed counter-streaming plasma interactions driven by high-power laser pulses

2013 ◽  
Vol 56 (12) ◽  
pp. 2381-2385 ◽  
Author(s):  
DaWei Yuan ◽  
YuTong Li ◽  
LuNing Su ◽  
GuoQian Liao ◽  
ChuanLei Yin ◽  
...  
Keyword(s):  
High Power ◽  
High Speed ◽  
Laser Pulses ◽  
High Power Laser ◽  
Power Laser ◽  
Plasma Interactions

scholarly journals The bulging effect and its relevance in high power laser beam welding

2021 ◽  
Vol 1135 (1) ◽  
pp. 012003
Author(s):  
Antoni Artinov ◽  
Xiangmeng Meng ◽  
Nasim Bakir ◽  
Ömer Üstündağ ◽  
Marcel Bachmann ◽  
...  
Keyword(s):  
Laser Beam ◽  
Penetration Depth ◽  
Weld Pool ◽  
High Power ◽  
High Speed ◽  
Laser Beam Welding ◽  
Hot Cracking ◽  
Alloying Elements ◽  
High Power Laser ◽  
Power Laser

Abstract The present work deals with the recently confirmed widening of the weld pool interface, known as a bulging effect, and its relevance in high power laser beam welding. A combined experimental and numerical approach is utilized to study the influence of the bulge on the hot cracking formation and the transport of alloying elements in the molten pool. A technique using a quartz glass, a direct-diode laser illumination, a high-speed camera, and an infrared camera is applied to visualize the weld pool geometry in the longitudinal section. The study examines the relevance of the bulging effect on both, partial and complete penetration, as well as for different sheet thicknesses ranging from 8 mm to 25 mm. The numerical analysis shows that the formation of a bulge region is highly dependent on the penetration depth and occurs more frequently during partial penetration above 6 mm and complete penetration above 8 mm penetration depth, respectively. The location of the bulge correlates strongly with the cracking location. The obtained experimental and numerical results reveal that the bulging effect increases the hot cracking susceptibility and limits the transfer of alloying elements from the top of the weld pool to the weld root.

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