Laser processing of granular structures — method of analysis of distribution of a thermal field in an object

The unique properties of laser radiation, such as monochromaticity, coherence, small spatial beam divergence, and the ability to receive a very high energy density during fo­cusing, provide a solid basis for the use of laser heaters, in particular short-acting impul­ses, to control the distribution of the thermal field both inside the object and in its sur­face layers.

The laser radiation is concentrated near one wavelength and coherent. Typically, the initial radiation is also focused on a narrow collimated beam. This collimated, coherent and monochromatic light source can be used as an extremely accurate source of heat in a wide range of applications, in particular to detect hidden surface defects of the object and to create a fairly accurate thermographic picture based on the distribution of thermal field with a clear temperature distribution.

When the laser radiation enters the object, part of its energy is absorbed, thereby leading to local heating. Objects can be partially or completely non-transparent for ra­diation at laser wavelengths. Accordingly, different approaches can be applied to simulate a laser source of heat. In addition, all scales should be compared with the wavelength of radiation. Different approaches are needed to describe the focused radiation and for a relatively broad beam. If in a material interacting with the incident beam there are geometric peculiarities that can be compared with the wavelength, one must additionally consider how the beam interacts with these small structures. If in a material interacting with an incident laser beam there are geometric features that can be compared with the wavelength, then one can obtain a very accurate thermodynamic simulative estimation of the parameters of the distribution of narrow-band surface perturbations.

Keywords: Gaussian profile, Gaussian impulse functions, thermal load, radiating ability (Albedo effect), laser heating.