Lyubomir Si Bao Peydzyu Van

Mr. Lyubomir Si Bao Peydzyu Van


Research Focus & Metrics

Academic Career Length

4Years (2023-Present)

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

Representative Publications

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21 June 2023 in Sensors
Verified
Journal Article
Open access
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SSStoyan Dimitrov Slavov
Stoyan Dimitrov Slavov
LVLyubomir Si Bao Peydzyu Van
Lyubomir Si Bao Peydzyu Van
DDDiyan Dimitrov
Diyan Dimitrov
BNBoris Nikolov
Boris Nikolov
Advanced in the present paper is an innovative approach for three-dimensional modeling of the regular relief topography formed via a ball burnishing process. The proposed methodology involves capturing a greyscale image of and profile measuring the surface topography in two perpendicular directions using a stylus method. A specially developed algorithm further identifies the best match between the measured profile segment and a row or column from the captured topography image by carrying out a signal correlation assessment based on an appropriate similarity metric. To ensure accurate scaling, the image pixel grey levels are scaled with a factor calculated as being the larger ratio between the ultimate heights of the measured profilograms and the more perfectly matched image row/column. Nine different similarity metrics were tested to determine the best performing model. The developed approach was evaluated for eight distinct types of fully and partially regular reliefs, and the results reveal that the best-scaled 3D topography models are produced for the fully regular reliefs with much greater heights. Following a thorough analysis of the results obtained, at the end of the paper, we draw some conclusions and discuss potential future work.

11 May 2023 in Materials
Verified
Journal Article
Open access
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SSStoyan Dimitrov Slavov
Stoyan Dimitrov Slavov
DDDiyan Dimitrov
Diyan Dimitrov
MKMariya Konsulova-Bakalova
Mariya Konsulova-Bakalova
LVLyubomir Si Bao Peydzyu Van
Lyubomir Si Bao Peydzyu Van
The present work focusses on the research of the plastic deformation accumulated effect obtained after two different plastic deformation treatments, over the fatigue life of AISI 304 austenitic stainless steel. The research is focused on ball burnishing as a finishing process to form specific, so-called “regular micro-reliefs” (RMRs) on a pre-rolled stainless-steel sheet. RMRs are formed using a CNC (Computerized Numerically Controlled) milling machine and toolpaths with the shortest unfolded length, generated by an improved algorithm, based on the Euclidean Distance calculation. The effect of the predominant tool trajectory direction during the ball burnishing process (which can be coinciding or transverse with the rolling direction), the magnitude of applied deforming force, and feed-rate is subjected to evaluation using Bayesian rule analyses of experimentally obtained results for the fatigue life of AISI 304 steel. The obtained results give us reason to conclude that the fatigue life of researched steel is increased when directions of pre-rolled plastic deformation and the tool movement during ball burnishing are coincident. It also been found that the magnitude of deforming force has a stronger impact over the fatigue life, than the feed-rate of the ball tool.

10 December 2024 in Materials Research Proceedings
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Conference Paper
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DDDiyan Dimitrov
Diyan Dimitrov
SSStoyan Slavov
Stoyan Slavov
LVLyubomir Si Bao Peydzyu Van
Lyubomir Si Bao Peydzyu Van
In this paper, a digital model of the ball burnishing process, developed using data from tests on bronze and aluminum alloys, to create regular micro-reliefs on a cylindrical surface." is presented. The experiments were carried out on a CNC lathe using a cylindrical stock. The input features were burnishing force, feedrate, machine condition and material type, while the results were surface roughness and hardness. A Bayesian approach was used to infer the parameters of the digital model, enabling the creation of distributions that directly account for uncertainty caused to regression coefficients and by random factors incorporated in machine condition feature. The proposed digital model was subsequently used to run simulations and check various optimization algorithms. Additionally, a large language model NexusRaven-V2 that were fine tunned for function calling is combined with the functions from the digital model.

15 July 2025 in Symmetry
Verified
Journal Article
Open access
PDF file
SSStoyan Dimitrov Slavov
Stoyan Dimitrov Slavov
LVLyubomir Si Bao Peydzyu Van
Lyubomir Si Bao Peydzyu Van
MVMarek Vozar
Marek Vozar
PGPeter Gogola
Peter Gogola
DDDiyan Dimitrov
Diyan Dimitrov
The present research is related to the application of artificial intelligence (AI) approaches for classifying surface textures, specifically regular reliefs patterns formed by ball burnishing operations. A two-stage methodology is employed, starting with the creation of regular reliefs (RRs) on test parts by ball burnishing, followed by 3D topography scanning with Alicona device and data preprocessing with Gwyddion, and Blender software, where the acquired 3D topographies are converted into a set of 2D images, using various virtual camera movements and lighting to simulate the symmetrical fluctuations around the tool-path of the real camera. Four pre-trained convolutional neural networks (DenseNet121, EfficientNetB0, MobileNetV2, and VGG16) are used as a base for transfer learning and tested for their generalization performance on different combinations of synthetic and real image datasets. The models were evaluated by using confusion matrices and four additional metrics. The results show that the pretrained VGG16 model generalizes the best regular reliefs textures (96%), in comparison with the other models, if it is subjected to transfer learning via feature extraction, using mixed dataset, which consist of 34,037 images in following proportions: non-textured synthetic (87%), textured synthetic (8%), and real captured (5%) images of such a regular relief.