Nikolay Angelov Petrov

Dr. Nikolay Angelov Petrov

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Research Focus & Metrics

Academic Career Length

17Years (2010-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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2 March 2023 in Laser Physics
Verified
Journal Article
Closed access
Lyubomir LazovLyubomir Lazov
Lyubomir Lazov
ETEdmunds Teirumnieks
Edmunds Teirumnieks
NPNikolay Angelov Petrov
Nikolay Angelov Petrov
Emil Hristov YankovEmil Hristov Yankov
Emil Hristov Yankov
Surface texturing is one of the most effective approaches to modifying the surface to improve many properties: tribological, corrosion resistance, microhardness and others characteristics of a number of engineering materials. Among the surface texturing techniques developed in recent years, the most widely used method is the laser surface texturing method (LST) due to its high flexibility, superior texturing accuracy and good process controllability and reproducibility. With its rapid development, LST has attracted considerable attention in various industries such as automotive, biomedical and aerospace. The present study considers the changes in roughness in different modes of laser texturing of stainless steel specimens 304. The effects and role of individual laser parameters on the change in roughness are analyzed as a main characteristic of the surface properties of the processed material. Heating and its surface melting is one of the studied effects and its role in changing the roughness. The focus of the study is on the process of laser–material interaction as a function of absorbed energy density, pulse frequency, scan rate, and overlap coefficients leading to different effects of LST parameters. It has been found that increasing the energy density, accompanied by a decrease in the frequency and speed of scanning, can increase the surface roughness.

25 February 2021 in Laser Physics
Verified
Journal Article
Closed access
NPNikolay Angelov Petrov
Nikolay Angelov Petrov
ETEdmunds Teirumnieks
Edmunds Teirumnieks
Lyubomir LazovLyubomir Lazov
Lyubomir Lazov
Depending on the processing of a particular material, the laser marking process must meet certain requirements. A certain laser peak intensity or fluency must be reached on the treatment surface above which the laser ablation process starts. Some experimental studies have shown that this particular marking threshold is related to many other parameters characterizing the laser source. This requires the realization of an appropriate combination of peak power or pulse energy and the radius of the beam in focus, the frequency of the laser pulses as well as the pulse duration. Achieving high resolution in the marking process requires optimal focusing, and this in turn is associated with the presence of high quality generated and propagated laser radiation. The study concerns the process of laser marking of CT80 carbon tool steel products with wide application in industry. Numerical experiments are performed with specialized software TEMPERATURFELD3D to obtain two-dimensional and three-dimensional temperature fields in the laser impact zone. The influence of the duration of the pulses of fibre laser on the process is investigated. Graphs of the dependence of normalized temperature on time and depth for pulse duration on 10 ns, 100 ns and 1 μ s are discussed.

20 November 2023 in Coatings
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Journal Article
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Risham Singh GhalotRisham Singh Ghalot
Risham Singh Ghalot
Lyubomir LazovLyubomir Lazov
Lyubomir Lazov
Emil Hristov YankovEmil Hristov Yankov
Emil Hristov Yankov
NPNikolay Angelov Petrov
Nikolay Angelov Petrov
The aim of this research is to achieve a high-quality and long-lasting laser marking of ammunition, which is of interest to the defense industry. The study is about the effects of speed, raster pitch and power on the roughness and microhardness of the marked areas of copper samples. The experiments were carried out with a fiber laser and a copper bromide laser—modern lasers widely used in industrial production. Laser power, scan speed and raster step were varied to determine their effects on the resulting microhardness and surface roughness. The lasers operate in different wavelength ranges, with the optical laser operating at 1064 nm in the near-infrared region and the copper bromide laser at 511 nm and 578 nm in the visible region, allowing the influence of wavelengths on the process to be investigated. The roughness and microhardness velocity dependence for three powers and two pulse durations for the fiber laser were obtained from the experimental data. The dependence of roughness and microhardness on the raster step for both types of lasers was also demonstrated.

3 July 2010 in Contemporary Materials
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Journal Article
Closed access
Lyubomir LazovLyubomir Lazov
Lyubomir Lazov
NPNikolay Angelov Petrov
Nikolay Angelov Petrov
Савремени материјали, међународна научна конференција - Contemporary materials, International scientific conference

5 November 2025 in Materials
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Lyubomir LazovLyubomir Lazov
Lyubomir Lazov
NPNikolay Angelov Petrov
Nikolay Angelov Petrov
Emil Hristov YankovEmil Hristov Yankov
Emil Hristov Yankov
TKTsanko Karadzhov
Tsanko Karadzhov
DPDimcho Pulov
Dimcho Pulov
DDDimitar Dichev
Dimitar Dichev
This study investigates the influence of laser processing parameters on the surface roughness and color formation of AISI 304 stainless steel. Experiments were conducted to explore how raster step, scanning speed, frequency, linear energy density, and overlap coefficient affect the surface characteristics of laser-marked zones. It was found that increasing the raster step from 20 µm to 80 µm led to a consistent increase in surface roughness (from 1.23 µm to 1.47 µm at 20 kHz and 25 mm/s), accompanied by a shift in color from dark brown to lighter yellow hues. In contrast, increasing scanning speed (from 25 mm/s to 125 mm/s) caused a nonlinear reduction in roughness (e.g., from 1.23 µm to 0.76 µm at 20 kHz and Δx = 20 µm), resulting in a lighter surface color. Frequency was identified as a critical factor; increasing it from 20 kHz to 100 kHz resulted in a threefold decrease in roughness (from 1.23 µm to 0.25 µm at 20 µm raster step and 125 mm/s), which correlated with a shift to brighter yellow tones. Higher linear energy density values (1.60–8.00 J/cm) increased roughness and darkened the surface color, while higher overlap coefficients produced the opposite trend. The study highlights the relationship between surface nanostructuring and the formation of stable interference colors, providing quantitative parameters for achieving desired chromatic effects. These findings establish a basis for the industrial application of laser color marking, where both aesthetic differentiation and functional enhancements—such as corrosion resistance, hydrophobicity, and antibacterial properties—are essential. Future research will focus on quantitatively evaluating the functional properties, including corrosion resistance, hydrophobicity, and durability, of the colored surfaces produced under optimized parameters. This research aims to further develop laser marking as a foundational tool for both aesthetic and functional surface engineering.

22 June 2024 in ENVIRONMENT. TECHNOLOGIES. RESOURCES. Proceedings of the International Scientific and Practical Conference
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Journal Article
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VJVitālijs Jurčs
Vitālijs Jurčs
Emil Hristov YankovEmil Hristov Yankov
Emil Hristov Yankov
NPNikolay Angelov Petrov
Nikolay Angelov Petrov
APAntons Pacejs
Antons Pacejs
IAImants Adijans
Imants Adijans
Laser marking technology today is a key part of the production of many products and devices used in our daily lives. At the same time, for specific types of products, the process must be optimized depending on the material used, laser system and marking method. Copper is such a metal that has a number of applications in the military industry, electrical engineering, electronics, household, etc. The scientific report investigates the influence of the technological parameters speed, raster step and number of repetitions on the contrast and roughness of marking for copper samples. A fiber laser technology system was used to perform the experiments, and the roughness measurements were performed with an OLS 5000 laser microscope. A wide range of marking speeds from 10 mm/s to 1500 mm/s was selected, where the contrast and roughness behavior of the marking is tracked for different raster steps in both single marking and double marking. It was found that as the speed increased, the contrast and roughness decreased. Also, with double marking, the contrast and roughness values are higher than with single marking. The velocity intervals in which the contrast has positive values and those in which it has negative values are established. The regularity was obtained that increasing the step of the raster leads to a decrease in contrast and an increase in roughness.