scholarly journals Reduction of speckle noise in laser energy distribution on the target by means of modified Fourier hologram and incoherent averaging technique

2018 ◽  
Vol 21 (4) ◽  
pp. 429-433
Author(s):  
A.G. Derzhypolskyi ◽  
Keyword(s):  
Energy Distribution ◽  
Laser Energy ◽  
Speckle Noise ◽  
Averaging Technique ◽  
Fourier Hologram ◽  
Incoherent Averaging

Activation of the Si(100)/Cl2 Etching Reaction at High Cl2 Translational Energies

1991 ◽  
Vol 236 ◽  
Author(s):  
Francis X. Campos ◽  
Gabriela C. Weaver ◽  
Curtis J. Waltman ◽  
Stephen R. Leone
Keyword(s):  
Kinetic Energy ◽  
Film Thickness ◽  
Energy Distribution ◽  
Rate Increase ◽  
Laser Energy ◽  
Etching Rate ◽  
Laser Vaporization ◽  
Translational Energy ◽  
Break Surface ◽  
Broad Energy

AbstractExposing a Si(100) surface to a pulsed beam of neutral Cl2 with high translational energy results in etching at a rate faster than that seen with chlorine at thermal energies. The Cl2 beam used in these experiments is produced by laser vaporization of cryogenic films. It has a broad energy distribution which can be varied by changing laser energy and film thickness. Beams with mean energies as low as 0.4 eV result in etching =10 times faster than etching by thermal Cl2. When Cl2 beams are used which have considerable flux above 3 eV, the etching rate increases by a further factor of 3.6 ± 0.6. This rate increase, which occurs at energies just above the Si-Si bond energy, suggests that kinetic energy can be efficiently utilized to break surface bonds.

Porosity Formation Mechanisms and Controlling Technique for Laser Penetration Welding

2011 ◽  
Vol 287-290 ◽  
pp. 2191-2194 ◽  
Author(s):  
Wei Yao ◽  
Shui Li Gong
Keyword(s):  
Aluminum Alloy ◽  
Energy Distribution ◽  
Weld Pool ◽  
Laser Energy ◽  
Formation Mechanisms ◽  
Porosity Formation

The distribution and appearance characteristics of porosities in laser penetrated weld of aluminum alloy were observed, and the formation mechanisms of porosities were analyzed in detail, and the influences of twin spot laser energy distribution on porosities were investigated. It showed that there are two kinds of porosities, metallurgical and technologic porosities, in laser penetrated weld of aluminum alloy. The formation of metallurgical porosities is related to the separation, congregation and incorporation of hydrogen in the weld pool, while instantaneous instability of the keyhole is an essential reason for the occurrence of technologic porosities. Twin spot laser energy distribution can enlarge diameters of the opening and the root of the keyhole, improve fluctuating conditions of the wall of the keyhole, increase stability of the keyhole, and consequently decrease technologic porosities in number, but it has no obvious influence on metallurgical porosities.

Nd-YAG laser energy distribution in an artificial obstruction: Influence of lasing parameters in a model of laser angioplasty

1988 ◽  
Vol 8 (1) ◽  
pp. 90-94 ◽  
Author(s):  
Rienk Rienks ◽  
Ruud M. Verdaasdonk ◽  
Cornelius Borst ◽  
Peter C. Smits ◽  
George Jambroes ◽  
...  
Keyword(s):  
Energy Distribution ◽  
Laser Energy ◽  
Laser Angioplasty ◽  
Yag Laser

scholarly journals Grain refinement and laser energy distribution during laser oscillating welding of Invar alloy

2020 ◽  
Vol 186 ◽  
pp. 108195 ◽  
Author(s):  
Zhenguo Jiang ◽  
Xi Chen ◽  
Hao Li ◽  
Zhenglong Lei ◽  
Yanbin Chen ◽  
...  
Keyword(s):  
Energy Distribution ◽  
Grain Refinement ◽  
Laser Energy ◽  
Invar Alloy

scholarly journals Simulation and Experimental Study on Residual Stress Distribution in Titanium Alloy Treated by Laser Shock Peening with Flat-Top and Gaussian Laser Beams

Materials ◽  
2019 ◽  
Vol 12 (8) ◽  
pp. 1343 ◽  
Author(s):  
Xiang Li ◽  
Weifeng He ◽  
Sihai Luo ◽  
Xiangfan Nie ◽  
Le Tian ◽  
...  
Keyword(s):  
Residual Stress ◽  
Titanium Alloy ◽  
Stress Distribution ◽  
Energy Distribution ◽  
Laser Energy ◽  
Residual Stress Distribution ◽  
Laser Shock Peening ◽  
Laser Beams ◽  
Laser Shock ◽  
Shock Peening

The residual stress introduced by laser shock peening (LSP) is one of the most important factors in improving metallic fatigue life. The shock wave pressure has considerable influence on residual stress distribution, which is affected by the distribution of laser energy. In this work, a titanium alloy is treated by LSP with flat-top and Gaussian laser beams, and the effects of spatial energy distribution on residual stress are investigated. Firstly, a 3D finite element model (FEM) is developed to predict residual stress with different spatial energy distribution, and the predicted residual stress is validated by experimental data. Secondly, three kinds of pulse energies, 3 J, 4 J and 5 J, are chosen to study the difference of residual stress introduced by flat-top and Gaussian laser beams. Lastly, the effect mechanism of spatial energy distribution on residual stress is revealed.

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