Features of Brass Processing with Powerful Ultraviolet Lasers of Nanosecond Duration

2022 ◽  
Vol 1049 ◽  
pp. 11-17
Author(s):  
Ivan Kaplunov ◽  
Taras Malinskiy ◽  
S.I. Mikolutskiy ◽  
Vladimir Rogalin ◽  
Yuriy Khomich ◽  
...  

We investigated the process of laser heat treatment of polished brass samples (36% zinc, containing a small amount of lead, which does not dissolve in the alloy and is in the form of inclusions, having micron and submicron size) by impacting to a series of 25 - 30 ultraviolet (UV) pulses of a Nd:YAG laser (third harmonic, wavelength λ = 355 nm, duration τ = 10 ns, pulse repetition rate f = 10 Hz, pulse energy density ~ 0.15 - 1.0 J/cm2) in the stationary spot mode. Copper and its alloys absorb up to 90% of the energy of this laser. It is found that the relaxation of the absorbed energy of laser radiation in the metal occurs nonuniformly. Defects in the metal structure such as grain boundaries and lead inclusions are visualized. Traces of crystallographic sliding appear inside some grains. With an increase in the number of impacting impulses, accumulation of damage is observed. A further increase in the radiation energy density leads to an aggravation of the observed phenomena.

2022 ◽  
Vol 92 (2) ◽  
pp. 268
Author(s):  
Т.В. Малинский ◽  
В.Е. Рогалин

The prethreshold processes on the surface of copper and its alloys are investigated. In the absence of obvious traces of melting, while preserving the metal in a condensed state, under a nanosecond ultraviolet laser radiation energy density of 0.1–1.0 J/cm2, manifestations of high-temperature plastic deformation were observed. These are sliding and cracking along grain boundaries, within which crystallographic slipping was observed. A microprotrusion was formed on the surface of the irradiated zone, which was outwardly similar the distribution of laser radiation in the spot. The height of the microprotrusion reached 1 µm, and sometimes even more. An increase in the number of impacting impulses led to the accumulation of damage. The data obtained are in many ways similar to the acoustoplastic, electroplastic, and magnetoplastic effects. By analogy, we consider it possible to call the discovered effect optoplastic.


1988 ◽  
Vol 31 (10) ◽  
pp. 966-967
Author(s):  
V. I. Andreev ◽  
A. P. Palivoda ◽  
S. P. Fetisov ◽  
N. V. Shalomeeva ◽  
V. A. Yakovlev

1981 ◽  
Vol 25 (2) ◽  
pp. 193-213 ◽  
Author(s):  
J. L. Bobin

Gasdynamical equations taking radiation energy density and ponderomotive pressure into account are investigated. Conditions for these quantities to be important are stated: low absorption, reflexion at cut-off. The density ratio in a discontinuity is studied as a function of ponderomotive pressure, absorbed intensity and Mach number in the initial state. Chapman–Jouguet conditions are defined. Compressive (R type) flows and rarefaction (D type) appear. The structure of the latter is discussed including plasma effects.


1972 ◽  
Vol 94 (3) ◽  
pp. 289-294 ◽  
Author(s):  
R. P. Caren

The present paper investigates the impact of one or more small cavity dimensions on the radiation energy density and radiation heat flux in rectangular metallic cavities. The emphasis of the present analysis is the exact treatment of the modal structure of the electromagnetic field in a small cavity in determining the properties of the thermal radiation field in the cavity. The excitation spectrum of the modes is assumed to be given by the Planck distribution function. The Poynting theorem is invoked in order to determine the radiative heat flux absorbed by the walls from the radiation in the cavity. Variation of the dimensions of the rectangular cavity allows the effects of cavity size and shape on the radiant energy density and radiant heat transfer to be assessed, particularly in several interesting limiting cases. It is found that significant deviations from the classical theory occur whenever any of the cavity dimensions satisfy the inequality lT ≤ 1 cm-deg K. It is further found that, when two or more of the cavity dimensions satisfy the above inequality, the radiant energy density and radiant heat transfer are significantly reduced in comparison to the results of classical theory. However, when only one dimension is limited, as in the case of a closely spaced parallel-surface geometry, the radiant energy density and radiant heat transfer are significantly increased compared to the classical theory.


2019 ◽  
Vol 62 (2) ◽  
pp. 232-235
Author(s):  
R. R. Akhmetshin ◽  
E. A. Babichev ◽  
D. N. Grigoriev ◽  
V. R. Groshev ◽  
V. F. Kazanin ◽  
...  

2021 ◽  
Vol 503 (1) ◽  
pp. 1367-1373
Author(s):  
J Fukue

ABSTRACT Two-dimensional funnel flows driven by radiation pressure in the conical funnel formed by the critical accretion disc are examined using the self-similar treatment. The flow is assumed to be steady and axisymmetric, and other forces such as viscosity and magnetic fields are ignored. For various boundary conditions on the funnel wall at the disc surface, the self-similar solutions are found to be classified into three types: funnel-filled solutions, where the flow gas fills the whole region of the funnel; polar-hollow ones, where there appears a cavity around the polar axis, and unphysical ones in a sense that, e.g. the radiation energy density becomes negative. For the physically reasonable solutions, the flow gas generally concentrates to the funnel wall, and the flow density and the radiation energy density monotonically decrease from the funnel wall towards the polar axis, while the radial flux becomes negative near the polar axis. The vertical velocity increases towards the polar axis, while the vertical flux has often the maximum between the polar axis and the funnel wall. As a result, the present self-similar funnel jets are such a flow with a slow dense outer part and a fast rarefied inner part.


2009 ◽  
Vol 24 (20n21) ◽  
pp. 3865-3891 ◽  
Author(s):  
SHE-SHENG XUE

Quantum fluctuation of unstable modes about gravitational instantons causes the instability of flat space at finite temperature, leading to the spontaneous process of nucleating quantum black holes. The energy-density of quantum black holes, depending on the initial temperature, gives the cosmological term, which naturally accounts for the inflationary phase of the early universe. The reheating phase is attributed to the Hawking radiation and annihilation of these quantum black holes. Then, the radiation energy-density dominates over the energy-density of quantum black holes, the universe started the standard cosmology phase. In this phase the energy-density of quantum black holes depends on the reheating temperature. It asymptotically approaches to the cosmological constant in matter domination phase, consistently with current observations.


1992 ◽  
Vol 10 (2) ◽  
pp. 239-251 ◽  
Author(s):  
G. C. Pomraning

We present a diffusion approximation describing the flow of thermal radiation that preserves several important features of the underlying equation of radiative transfer. Specifically, this diffusion description: (1) is flux limited; (2) reduces to the correct transport weak gradient limit; (3) allows correct and simultaneous exponential growth and Decay for a certain class of problems; (4) gives correct transport results for certain contiguous half-space problems; and (5) allows the radiative flux and the gradient of the radiation energy density to point in independent directions. This treatment extends and generalizes earlier flux-limited diffusion approximations that are widely used in radiation–hydrodynamics calculations.


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