Now showing 1 - 10 of 36
  • Publication
    Investigation of the influence of the processing speed and the linear pulse density of the laser surface texturing process
    (2023) ; ;
    Ilieva, Mariana
    ;
    Plamenova Nikolova, Maria
    Fine-tuning laser parameters is necessary to achieve the desired quality of the process of laser surface texturing. This requires a set of experiments to assess the influence of the main process parameters on the quality of the surface of a treated alloy. By varying the laser parameters, different laser-material interactions, such as heating, melting, or evaporation can be observed. This study analyzes the influence of two interrelated processing parameters in laser surface texturing – the speed of beam motion on the surface on the one hand, and, on the other, the linear pulse density. They ultimately have a direct impact on the resulting microstructure, hydrophilicity, and electrochemical properties of austenitic steel (AISI 304). By adjusting the pulse repetition rate of a 1064-nm fiber laser from 500 kHz to 1000 kHz at a constant speed of 100 mm/s, the surface wettability changes from hydrophobicity to hydrophilicity. All surfaces treated with laser scanning speeds varying from 20 mm/s to 200 mm/s at a constant rate of 500 kHz are hydrophobic. As a result, the changed ability to repel liquids alters the corrosion properties of the steel in a 0.5 M H2SO4 solution. The results allow one to distinguish ranges of laser-beam parameters that could be useful in selecting certain properties of the stainless-steel surface layer.
  • Publication
    Investigation of the change in wettability properties and corrosion behavior of AISI 304 after laser surface texturing
    (2023) ; ;
    Ilieva, Mariana
    ;
    Plamenova Nikolova, Maria
    Stainless steel is a widely used material in industry, architecture, and medical instruments. However, after various thermal processing of stainless steels, chromium carbides can be formed, which locally depletes the chromium available to form a passive film and reduces the corrosion performance. Laser surface treatment can change the surface chemistry of the steel and improve some electrochemical characteristics. However, these characteristics are influenced by the laser power, pulse width, distance between the lines, scanning speed, etc., which all change the surface chemistry and characteristics of laser surface texturing. Simultaneously, the ability to repel liquids that cause corrosion actions could combine to enhance corrosion performance. Since the wettability of a solid surface depends both on its topography and chemical nature, the micro structuring of an austenitic steel surface is an effective way of fabricating hydrophobic or super hydrophobic corrosion-resistant surfaces. For this reason, this study discusses the effect of laser power in the impact zone and the distance between raster lines on the microstructure, wettability, and corrosion resistance of austenitic steel (AISI 304) when exposed to nanosecond fiber laser radiation. The results indicate that parameter-controlled micro structuring can be used to form both hydrophilic and hydrophobic surfaces with different electrochemical performances.
  • Publication
    Evaluation of laser cutting process with auxiliary gas pressure by soft computing approach
    (2018) ;
    Vlastimir Nikolić
    ;
    Srdjan Jovic
    ;
    Miloš Milovančević
    ;
    Heristina Deneva
    ;
    ;
    Nebojsa Arsic
    Evaluation of the optimal laser cutting parameters is very important for the high cut quality. This is highly nonlinear process with different parameters which is the main challenge in the optimization process. Data mining methodology is one of most versatile method which can be used laser cutting process optimization. Support vector regression (SVR) procedure is implemented since it is a versatile and robust technique for very nonlinear data regression. The goal in this study was to determine the optimal laser cutting parameters to ensure robust condition for minimization of average surface roughness. Three cutting parameters, the cutting speed, the laser power, and the assist gas pressure, were used in the investigation. As a laser type TruLaser 1030 technological system was used. Nitrogen as an assisted gas was used in the laser cutting process. As the data mining method, support vector regression procedure was used. Data mining prediction accuracy was very high according the coefficient (R2) of determination and root mean square error (RMSE): R2 = 0.9975 and RMSE = 0.0337. Therefore the data mining approach could be used effectively for determination of the optimal conditions of the laser cutting process.
  • Publication
    RESEARCH OF POSSIBILITIES OF LASER POLISHING OF THE SURFACE OF ALUMINUM
    (2021)
    Bulavskis, Kevins
    ;
    ;
    The report considers the possibility of reducing the roughness after laser polishing of Aluminum plates. A CHANXAN CX-20G fiber laser with a wavelength of 1064 nm is used for the research. As a result of the experiment, 4 matrices were marked with a fiber laser on 3 samples for each series of the experiment. Then, using a multifunctional microscope, the roughness of the treated and untreated aluminum surface was measured. At the end of the research, conclusions were made about the changes in roughness in the course of this experiment.
  • Publication
    INVESTIGATING THE IMPACT OF LASER POWER AND SCAN SPEED ON ENGRAVING ASPEN THERMOWOOD
    (2023)
    Rāviņš, Dzintars
    ;
    Yankov, Emil
    ;
    ; ;
    Rāviņš, Daivis
    This study examines the effect of pre-heat treatment on laser engraving of aspen thermowood. We used an infrared CO2 laser with a wavelength of 10640 nm to engrave aspen thermowood samples with different pre-treatment temperatures, including one non-treated sample (base). The samples had a similar moisture content of about 6 - 8%, but exhibited different shades of brown depending on the pre-treatment temperature. The engraving depth and width were measured for each sample, and 8 graphs were constructed to analyze the results. Our findings show that pre-treatment temperature has a significant effect on the efficiency of laser engraving, with higher pre-treatment temperatures resulting in deeper engraving lines. The study provides valuable insights into the optimization of laser engraving parameters for aspen thermowood, and demonstrates the potential of pre-heat treatment to improve the quality of laser-engraved wooden products.
  • Publication
    LASER AS A DEVICE FOR MEASUREMENT OF THIN THREADS - A SCHOOL LABORATORY EXPERIMENT IN PHYSICS
    (2017)
    Hristina Deneva
    ;
    ;
    The physics of the last century is included in all EU curricula and emphasis in education is shifted from content to the forms, methods and means of teaching and learning. Different kinds of lessons (including laboratory classes) and their didactic structure are subject to the understanding, adoption and creating conditions to build motivation to learn physics and astronomy, active utilization of physical knowledge and building cognitive and practical skills. Performance of demonstration and laboratory classes using a laser device is a type of teaching strategy to good education in physics. Properties of laser light as observation, classification, communication, drawing conclusions, planning, interpretation and forecasting, are particularly suitable when monitoring and studying the phenomena of interference and diffraction. Through both qualitative and quantitate ways, in this paper is presented a physical experiment for measurement of thin threads in a High school from students. Experimental skills will enhance interest in physics and especially to modern applications of laser devices, as well as career guidance of students.
  • Publication
    RESEARCH OF LASER MARKING AND ENGRAVING ON BRASS ALLOY 260
    Brass Alloy 260 is widely used in mechanical engineering (odometer contacts, radiator cores), electrical engineering (electrical connectors, screw shells), plumbing (bathroom fixtures), consumers (watch parts, buttons, lamps) etc. The paper presents an analysis of the laser marking and engraving process. The ability Rofin powerline f20 laser system to engrave on Brass Alloy 260 is described. Recommendations are given on choosing the right parameters for laser marking and engraving of Brass Alloy 260 products.
    Scopus© Citations 1
  • Publication
    Finite element modeling of laser aluminum marking
    (2021) ;
    N Angelov
    ;
    ;
    I Draganov
    ;
    A Lengerov
    ;
    A Atanasov
    ;
    I Balchev
    This work makes use of the finite element model, whose results are validated by experiments. The effect is discussed of the speed on the laser marking process. Numerical experiments are performed to determine the temperature fields produced by laser pulses on samples of aluminum, a material with wide industrial uses. The numerical calculations are performed for the cases of a fiber laser and a CuBr laser. Plots are drawn of the temperature dependence on the speed for two power densities for both lasers. Preliminary working speed intervals are determined for the power densities used.
    Scopus© Citations 1
  • Publication
    PRELIMINARY NUMERICAL ANALYSIS FOR THE ROLE OF SPEED ONTO LASER TECHNOLOGICAL PROCESSES
    Studying the impact of speed on a number of laser processes such as marking, engraving, cutting, welding and others is crucial for the optimization of these technological processes. The processing speed, along with the frequency of laser pulses and their duration, also determines the time of action in the processing area and hence the absorbed quantity of electromagnetic energy. Based on numerical experiments with specialized software TEMPERATURFELD3D, the report analyzes the temperature variation in the processing area as a function of speed. The researches were analyzed for processing with two types of lasers emitting in the visible and infrared areas of the electromagnetic spectrum and two types of steels (tool and structural). From the course of the obtained temperature fields the dependence of temperature on the speed at two power densities was obtained. The obtained results help to make a preliminary assessment the speed work intervals for the processes as laser marking, laser engraving, laser cutting, laser welding and others. In this way, it is assisted in building an optimal concept for the passing of a particular technological process in function of the laser source, the material and the type of the technological operation.
    Scopus© Citations 13
  • Publication
    Antibacterial and anti-viral effects of silver nanoparticles in medicine against COVID-19—a review
    (2020) ;
    Ivaylo Balchev
    ;
    Risham Singh Ghalot
    ;
    The article reviews the research on disinfecting the air through air filters and ventilation systems using silver nanoparticles (Ag NPs) (encouraged from the present situation of COVID-19) focusing on stopping the spreading of deadly viruses. The primary goal of the research is to demonstrate possible antiviral Ag NP formulations to be delivered by inhalation, to minimize the worsening of respiratory system infections. The basic design of the study includes a bibliometric analysis of the study of the effect of Ag NPs on the disinfection of viral infections. The research will discuss the idea of the use of laser ablation with Ag NPs for antiviral and antibacterial effects. The research article results in compelling evidence for the use of Ag NPs for medicinal purposes for infectious diseases/viruses and will contribute to the progress of medical science to protect healthcare workers from dangerous viruses at medical institutions. Practically, the research will generate a sterile system, which might be employed by every public or private institution economically with Ag NPs (because of their antimicrobial properties).
    Scopus© Citations 25