The efficiency of ablation of metals by scanning beam of pulsed irradiation with nanosecond-range fiber Yb:YAG laser

2021 ◽  
Vol 3 ◽  
pp. 5-23
Author(s):  
S. B. Mikhailov ◽  
◽  
S. G. Gorny ◽  
N. V. Zhukov ◽  
◽  
...  
Keyword(s):  
Target Surface ◽  
Ablation Depth ◽  
Radiation Shielding ◽  
Scanning Beam ◽  
Nanosecond Pulses ◽  
Increase With Increase ◽  
Internal Shock ◽  
The Impact ◽  
Impact Zones ◽  
Pulsed Irradiation

The results of experiments on ablation of targets made of stainless steel and aluminum by a scanning beam of nanosecond pulses at intensity up to 109 W/cm2 are presented. It was found that the overlap of the impact zones during irradiating leads to an increase in the ablation depth in proportion to the area of overlap of the irradiation spots. This is due to increase in overlap irradiation spots degree, zones with a large number of pulse effects are formed on surface, which increases the depth of the melt bath and leads to the ejection of larger particles. An increase in ablation depth of aluminum increase with increase of the interval between pulses up to 10 ms and overlapping of the irradiation spots. The shape of the ejected particles changes from spherical, when formed from a melt, to an irregular shape, when the target is mechanically destroyed by an internal shock wave. The size and velocity distribution of the ejected particles was determined, and on the basis of these data, the laser radiation shielding coefficients were calculated depending on the degree of overlapping of the irradiation spots. It was found that the main mechanism for the decrease in the efficiency of ablation by a scanning beam of radiation is the backflow of microparticles deposited on the target surface. The analysis of the energy balance of the aluminum ablation process is carried out.

Numerical Modeling of Laser Ablation of Polymers and Metals by Nanosecond Pulses of Infrared Radiation

2010 ◽  
Vol 5 (1) ◽  
pp. 37-47
Author(s):  
Lev A. Zakharov ◽  
Nadezhda M. Bulgakova
Keyword(s):  
Numerical Modeling ◽  
Laser Ablation ◽  
Initial Temperature ◽  
Pulsed Laser ◽  
Target Surface ◽  
Laser Pulses ◽  
Ablation Depth ◽  
Metallic Materials ◽  
Nanosecond Pulses ◽  
Vaporization Process

In the paper a comparative analysis has been carried out of pulsed laser ablation of polymers and metals. On the basis of a thermal model with the mobile boundary «vapor – target surface», numerical modeling of laser ablation of poly(methyl methacrylate) and copper by nanosecond CO2 laser pulses (at wavelength of 10.6 nm) has been performed for different initial temperatures of the irradiated samples. Conclusions are drawn on differences in heating and ablation dynamics of polymer and metallic materials, values of subsurface superheating, and initial temperature effects on the vaporization process and ablation depth.

The Impact of TeO2 on Physical, structural, optical and radiation shielding features for borate glass samples

Optik ◽  
2021 ◽  
pp. 167924
Author(s):  
M.H.A. Mhareb ◽  
Ragad Alsharhan ◽  
M.I. Sayyed ◽  
Y.S.M. Alajerami ◽  
Muna Alqahtani ◽  
...  
Keyword(s):  
Borate Glass ◽  
Radiation Shielding ◽  
The Impact

scholarly journals A Method for Evaluating the Impact Wear Behavior of Multilayer TiN/Ti Coating

Coatings ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 132 ◽  
Author(s):  
Xin Cao ◽  
Weisheng Xu ◽  
Weifeng He
Keyword(s):  
Wear Behavior ◽  
Failure Mechanisms ◽  
High Stress ◽  
Impact Wear ◽  
Maximum Value ◽  
Impact Peak ◽  
Energy Dissipated ◽  
The Impact ◽  
Impact Zones ◽  
Circular Cracks

An energy-controlled cycling impact test was applied to evaluate the impact wear behavior of hard coating. A multilayer TiN/Ti coating with a total thickness of ~10 μm, containing two TiN layers and two Ti layers, with the thickness ratio of these two kinds of the layers being 9:1, was chosen as the research object. The impact velocities were 60, 120, and 180 mm/s, and the impact cycles were 10, 102, 103, and 104, respectively. Damage morphology observation and numerical simulation were used to analyze the failure mechanisms. The results show that the contact time keeps almost constant under different impact velocities and cycles. Impact peak forces remain unchanged with increasing cycles at the same velocity, but they increase linearly with impact velocities, reaching a maximum value of 262.26 N at 180 mm/s. The energy dissipated rate (EDR) increases from 31.58% at 60 mm/s to 35.59% at 180 mm/s, indicating the degenerative toughness. Two impact-wear failure mechanisms are found in impact zones of the coating; these are peeling and circular cracks. Peelings are induced by cycling high-stress gradients in hard layers and interfaces. Circular cracks are caused by cycling tensile stresses in the form of fatigue at the edge of impacted pits.

scholarly journals 42. Solar cosmic radiation and the interstellar magnetic field

1958 ◽  
Vol 6 ◽  
pp. 404-419 ◽  
Author(s):  
A. Ehmert
Keyword(s):  
Magnetic Field ◽  
Solar Radiation ◽  
Cosmic Radiation ◽  
The Sun ◽  
High Latitudes ◽  
Narrow Angle ◽  
The Earth ◽  
Order Of Magnitude ◽  
The Impact ◽  
Impact Zones

The increase of cosmic radiation on 23 February 1956 by solar radiation exhibited in the first minutes a high peak at European stations that were lying in direct impact zones for particles coming from a narrow angle near the sun, whilst other stations received no radiation for a further time of 10 minutes and more. An hour later all stations in intermediate and high latitudes recorded solar radiation in a distribution as would be expected if this radiation fell into the geomagnetic field in a fairly isotropic distribution. The intensity of the solar component decreased at this time at all stations according to the same hyperbolic law (~t–2).It is shown, that this decreasing law, as well as the increase of the impact zones on the earth, can be understood as the consequence of an interstellar magnetic field in which the particles were running and bent after their ejection from the sun.Considering the bending in the earth's magnetic field, one can estimate the direction of this field from the times of the very beginning of the increase in Japan and at high latitudes. The lines of magnetic force come to the earth from a point with astronomical co-ordinates near 12·00, 30° N. This implies that within the low accuracy they have the direction of the galactic spiral arm in which we live. The field strength comes out to be about 0·7 × 10–6gauss. There is a close agreement with the field, that Fermi and Chandrasekhar have derived from Hiltner's measurements of the polarization of starlight and the strength of which they had estimated to the same order of magnitude.

scholarly journals Modeling of pulsed laser ablation of aluminum under the action of infrared nanosecond laser pulses

2019 ◽  
Vol 196 ◽  
pp. 00020
Author(s):  
Nikolay Rubtsov ◽  
Victor Bessmeltsev ◽  
Maksim Grishin
Keyword(s):  
Pulsed Laser ◽  
Pulsed Laser Ablation ◽  
Laser Pulses ◽  
Ablation Depth ◽  
Aluminum Surface ◽  
Nanosecond Laser ◽  
Ablation Process ◽  
Nanosecond Pulses ◽  
Nanosecond Laser Pulses ◽  
Plasma Shielding

The paper presents the results of numerical simulation of aluminum ablation process that is caused by a series of incident nanosecond pulses on a wavelength λ=1064 nm. The mechanism of normal evaporation and the effect of plasma shielding were taken into account. As a result of mathematical modeling the ablation depth was obtained. It is shown that plasma shielding reduces the effectiveness of ablation process much more than cooling of the aluminum surface between pulses.

scholarly journals A New Method for Predicting Erosion Damage of Suddenly Contracted Pipe Impacted by Particle Cluster via CFD-DEM

Materials ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 1858 ◽  
Author(s):  
Jiarui Cheng ◽  
Yihua Dou ◽  
Ningsheng Zhang ◽  
Zhen Li ◽  
Zhiguo Wang
Keyword(s):  
Erosion Rate ◽  
Numerical Study ◽  
Target Surface ◽  
Impact Angle ◽  
Particle Collision ◽  
Particle Cluster ◽  
Interparticle Collision ◽  
Velocity Decay ◽  
Discrete Element Methods ◽  
The Impact

A numerical study on the erosion of particle clusters in an abrupt pipe was conducted by means of the combined computational fluid dynamics (CFD) and discrete element methods (DEM). Furthermore, a particle-wall extrusion model and a criterion for judging particle collision interference were developed to classify and calculate the erosion rate caused by different interparticle collision mechanisms in a cluster. Meanwhile, a full-scale pipe flow experiment was conducted to confirm the effect of a particle cluster on the erosion rate and to verify the calculated results. The reducing wall was made of super 13Cr stainless steel materials and the round ceramsite as an impact particle was 0.65 mm in diameter and 1850 kg/m3 in density. The results included an erosion depth, particle-wall contact parameters, and a velocity decay rate of colliding particles along the radial direction at the target surface. Subsequently, the effect of interparticle collision mechanisms on particle cluster erosion was discussed. The calculated results demonstrate that collision interference between particles during one cluster impact was more likely to appear on the surface with large particle impact angles. This collision process between the rebounded particles and the following particles not only consumed the kinetic energy but also changed the impact angle of the following particles.

Impact of Sweeping Jet on Area-Averaged Impingement Heat Transfer

2019 ◽  
Author(s):  
Andrea Osorio ◽  
Justin Hodges ◽  
Husam Zawati ◽  
Erik J. Fernandez ◽  
Jayanta S. Kapat ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heated Surface ◽  
Thermal Inertia ◽  
Jet Impingement ◽  
Target Surface ◽  
Bottom Surface ◽  
Fluidic Oscillator ◽  
Surface Temperatures ◽  
Sweeping Motion ◽  
The Impact

Abstract A series of sweeping jet-impingement experiments are conducted over a circular heated surface, with a main objective of understanding the impact of the unique flow field on the resulting heat transfer. The sweeping motion of the fluidic oscillator is influenced by the sweeping frequency and sweeping angle where each is directly dependent on the geometric design (i.e. internal feedback loops, mixing chamber, etc.). The target surface consists of a heated copper disk, where heater power is supplied to the bottom surface of the disk and adjusted until a differential of 30°C is obtained between the jet and target surface temperatures. An energy balance over the target surface temperatures provides a means for calculating area-averaged heat transfer rate, hence Nusselt number. An increase in the sweeping jet’s thermal inertia initiates an augmentation in heat transfer due to sweeping motion of the jet across the target surface. PIV data was acquired for two jet configurations, confined and unconfined, so that the recirculation behavior can be determined. The fluidic oscillator is found to improve only at a low z/d. At large z/d (greater than 4 in this study), the fluidic oscillator adversely affects the heat transfer.

On the Indicators of the Radioecological Situation at the Mid-Botuobin Oil and Gas Condensate Field with Underground Nuclear Explosions

2020 ◽  
Vol 24 (1) ◽  
pp. 56-61 ◽  
Author(s):  
V.E. Stepanov ◽  
V.D. Yakovleva ◽  
E.V. Sleptsova
Keyword(s):  
Industrial Development ◽  
Oil And Gas ◽  
Nuclear Explosion ◽  
Underground Nuclear Explosion ◽  
Laboratory Studies ◽  
Underground Nuclear Explosions ◽  
Nuclear Explosions ◽  
Radionuclide Composition ◽  
The Impact ◽  
Impact Zones

The results of expeditionary and laboratory studies of the radiation situation of 2001–2002 and dosimetry measurements of 2017 are presented. there are small radioactive spots. The radionuclide composition in the soil-vegetation cover of the impact zones of the underground nuclear explosion has been studied. Data obtained prior to the industrial development of the field are reperator for further radioecological research and can be used by subsoil users in the development of the area.

A New Look into the Loose Particle Impact Process for Ductile Materials

2016 ◽  
Vol 874 ◽  
pp. 213-218 ◽  
Author(s):  
Jun Wang ◽  
Wei Yi Li
Keyword(s):  
Material Removal ◽  
Computational Study ◽  
Target Surface ◽  
Abrasive Waterjet ◽  
Surface Phenomenon ◽  
Ductile Materials ◽  
Micro Particles ◽  
Abrasive Waterjet Machining ◽  
Erosion Mechanisms ◽  
The Impact

Abrasive waterjet machining involves the impact of micro-particles at high or ultrahigh velocities. The material removal mechanism for ductile materials has been popularly accepted for over a half century as cutting wear and deformation wear caused by the component of impact force parallel and perpendicular to the target surface respectively. However, this definition of erosion mechanisms does not give an insight into the erosion process, but describes a surface phenomenon of the event. A computational study has been undertaken to reveal the underlying mechanisms of the material removal process. Based on the findings, the impact erosion mechanisms are re-defined as material destruction through (a) failures induced by inertia, (b) failure induced by elongation, and (c) failure induced by adiabatic shear bending. This new definition appears to better represent the physical process of material deformation and removal by loose micro-particle impacts at high and ultrahigh velocities.

THE SUN AS A SOURCE OF COSMIC RAYS OF INTERMEDIATE ENERGIES

1959 ◽  
Vol 37 (11) ◽  
pp. 1207-1215
Author(s):  
J. Katzman
Keyword(s):  
Cosmic Rays ◽  
Cosmic Ray ◽  
The Sun ◽  
Relative Importance ◽  
Cosmic Ray Intensity ◽  
Intermediate Energies ◽  
Narrow Angle ◽  
The Impact ◽  
Impact Zones

The cosmic ray intensity as measured with an extremely narrow-angle telescope, 1.2 × 10−3 steradians, and with 96 inches of lead as absorber for the period 1 January 1955 to 31 December 1958 shows an increase of 20%. This increase is attributed to particles coming from the sun. It is shown that the change in hour of maximum of the first and second harmonics can be explained by a change in the relative importance of the impact zones. This phenomenon is attributed to a change in the number and polarity of sunspots.

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