Lazov, Lyubomir

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Preferred name
Lazov, Lyubomir
Official Name
Lazov, Lyubomir
Alternative Name
Lyubomir Lazov
Lazov, Lyubomir Kostadimov
Main Affiliation
Email
lyubomir.lazov@rta.lv
Scopus Author ID
55384203700
Researcher ID
E-6011-2012

Research Output

Now showing 1 - 10 of 21
  • Publication
    Finite element modeling of laser aluminum marking
    (2021)
    Lazov, Lyubomir 
    ;
    N Angelov
    ;
    Teirumnieks, Edmunds 
    ;
    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
    (2019)
    Lazov, Lyubomir 
    ;
    Nikolay Angelov
    ;
    Teirumnieks, Edmunds 
    ;
    Teirumnieka, Ērika 
    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)
    Teirumnieks, Edmunds 
    ;
    Ivaylo Balchev
    ;
    Risham Singh Ghalot
    ;
    Lazov, Lyubomir 
    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
  • Publication
    COLOR MARKING OF STAINLESS STEEL AND TITANIUM WITH THE LASER OXIDATION METHOD
    (2023)
    Petar Tsvyatkov
    ;
    Emil Yankov
    ;
    Lazov, Lyubomir 
    ;
    Teirumnieks, Edmunds 
    ;
    Teirumnieka, Ērika 
    Marking of metal products is essential in many industrial processes. It is mandatory for the finished products according to regulations of the European and world legislation. Traditional marking usually creates contrasting symbols that can easily be erased and forged.In recent years, a new method for product identification has appeared - color marking. One of the advantages of this method is that it is difficult to counterfeit. This article aims to present the progress of color marking technology on two types of materials. Three groups of factors have been analyzed: the laser source; the technological process; material properties. Their role in obtaining a specific color marking on Ti and AISI 304 is shown. The results are presented in tables. Each color can be repeated only with strict observance of the three groups of factors.
  • Publication
    ON-LINE PROFESSIONAL TRAINING FOR WORKERS WITH THE MOODLE SYSTEM TO IMPROVE PROFESSIONAL SKILLS IN GREEN CONSTRUCTIONS
    (2019)
    Lazov, Lyubomir 
    ;
    Teirumnieka, Ērika 
    ;
    Teirumnieks, Edmunds 
    ;
    Nedka Atanasova
    ;
    Tsanko Karadzhov
    On the global agenda, environmental issues are becoming ever more pressing every moment. At present, it is not enough for individual countries to tackle global climate issues on their own. The time has come for a joint effort to mitigate climate change. The Paris Agreement is an agreement within the United Nations Framework Convention on Climate Change, dealing with greenhouse-gas-emissions mitigation, adaptation, and finance, starting in the year 2020. The Paris Agreement's long-term goal is to keep the increase in global average temperature to well below 2 °C above pre-industrial levels, and to limit the increase to 1.5 °C, since this would substantially reduce the risks and effects of climate change. It is not enough for states to sign this type of act, they need to take active steps to implement them and achieve the set goals. Energy, green construction, resource saving, educating the population, new and advanced teaching methods - all that is required for any global setup to be locally addressed. Now, we are in a situation where the exchange of transnational experience and knowledge is an important stage in solving energy efficiency issues through the education prism. This article will provide an analysis of the experience of four countries in the field of green construction.
  • Publication
    Modification of the roughness of 304 stainless steel by laser surface texturing (LST)
    (2023)
    Lazov, Lyubomir 
    ;
    Teirumnieks, Edmunds 
    ;
    Nikolay Angelov
    ;
    Emil 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.
    Scopus© Citations 3
  • Publication
    LASER TECHNOLOGIES – MASTER’S PROGRAM BETWEEN TWO EUROPEAN UNIVERSITIES OF APPLIED SCIENCES FROM LATVIA AND GERMANY
    (2017)
    Aivars Vilkaste
    ;
    Lazov, Lyubomir 
    ;
    Hristina Deneva
    ;
    Teirumnieka, Ērika 
    ;
    Teirumnieks, Edmunds 
    ;
    Pāvels Narica
    Laser equipment and laser technologies are among the most modern, fastest growing and most promising branches of science and technology in the 21st century. The first laser was created in 1960 and for about 55 years, today there is hardly any area of our lives in which lasers and related technologies are not applied. Laser systems and related innovative technologies ensuring high precision, productivity and quality of production have been developed and proposed worldwide from hundreds of scientific research institutes and companies. The Master's program is accredited in two European universities in Germany and Latvia and allows for the production of double diplomas. The course is based on international experience and reflects the most recent advances in laser techniques and technologies. The program examines the physical fundamentals and technical realization of various types of laser systems and their specific characteristics. First the necessary foundations of the laser physics, optics and the interaction of radiation with matter are presented, followed by more detailed examination of the problems of laser technology in various fields of science, technology and industrial production. Basic physical and technical solutions of the building blocks of lasers are presented in details, such as: optical resonators, active environments, excitation systems, management systems, laser generation. As well as specific issues and practical examples of industrial applications are described.
  • Publication
    INFLUENCE OF THE OVERLAP COEFFICIENT ON THE CONTRAST IN LASER MARKING OF C110W STEEL
    (2021)
    Nikolay Angelov
    ;
    Lazov, Lyubomir 
    ;
    Teirumnieks, Edmunds 
    The laser marking process by melting samples of C110W carbon tool steel was studied. The experiments were performed with a fiber laser and a CuBr laser. A field of squares is marked in a raster method for different values of the overlap coefficient and power density. The contrast of the marking is determined on each marked square. From the obtained experimental data, graphs of the dependence of the contrast on the overlap coefficient for three power densities were drawn. The obtained results for the two lasers are compared and the influence of the wavelength is indirectly analysed. The working intervals of the overlap coefficient for the studied power densities for the two lasers at which the optimal contrast in the processing zone is obtained are determined.
  • Publication
    INVESTIGATION OF THE INFLUENCE OF TECHNOLOGICAL PARAMETERS OF LASER MARKING ON THE DEGREE OF CONTRAST
    (2023)
    Petar Tsvyatkov
    ;
    Emil Yankov
    ;
    Lazov, Lyubomir 
    ;
    Teirumnieks, Edmunds 
    ;
    Pīgožnis, Kārlis 
    In modern production, each finished product entering the market is identified by a special marking. Each mark must meet requirements such as good coding, easy to see, easy to read by certain readers, stable over time, etc. In the present casting, laser marking of the C75 steel was carried out with a fiber laser with an average power of P = 30 W and a wavelength of λ = 1064 nm. For semi-contrast marking, marking speeds from 100 mm/s to 700 mm/s, average power from 10 to 30 W, raster pitch from 20 µm to 60 µm, scanning frequency from 20 kHz to 150 kHz were investigated as constant parameters are the pulse duration τ =100 ns, number of repetitions N = 1 and defocus Δ f = 0 mm. The influence of the changing parameters on the contrast was established, and experimental dependences were constructed. The achieved research results show that to obtain a high contrast mark, the average power should be above 20 W, the scanning speed up to 300 mm/s, the scanning frequency up to 50 kHz and the raster pitch up to 40 µm.
  • Publication
    Numerical modeling and simulation for laser beam welding of ultrafine-grained aluminium
    (2021)
    Lazov, Lyubomir 
    ;
    Teirumnieks, Edmunds 
    ;
    Ivo Draganov
    ;
    Nikolay Angelov
    Laser beam welding of aluminium offers huge potential for a wide variety of welding of different thickness parts with the method of thermal conductivity due to the relatively high difference between melting temperature and evaporation. However, due to the high melting temperature and good thermal conductivity of this light metal, the temperature gradients during the welding process are usually high, causing residual stresses in the weld, which can lead to undesirable deterioration of the weld pool properties and the quality of the process. Physical modelling and simulations of the laser welding process are powerful tools for gaining a fundamental understanding of the technological process. They are also a suitable tool for preliminary assessment of the intervals in which the real preliminary experiments for process optimization should take place. This work is devoted to the numerical modelling of the process of welding ultrafine-grained aluminium using a fibre laser. A three-dimensional model of the welding process was created, using the finite element method implemented in the program ABAQUS. The temperature fields at depth z and on the surface x, y in the welded samples is determined. The temperature change as a function of time for different coordinates of the weld is also analysed. During numerical calculations, the power, machining speed and diameter of the workplace are variable. The obtained results are compared with real experiments conducted in the laboratory by other researchers.
    Scopus© Citations 2