- TITLE: VIBRATION-BASED TOOL CONDITION MONITORING AND AUTOMATIC FEED RATE CONTROL IN CNC MILLING MACHINES
- AUTHOR(S): F. Dalmis, E. Ucar
- ABSTRACT: This study presents the design and implementation of a mechatronic system aimed at improving the efficiency of machining operations in Computer Numerical Control (CNC) machines. This developed system automatically adjusts the feed rate of the CNC milling machine based on the wear condition of the cutting tools by monitoring their status via sensors during the milling operation. This system, integrating mechanical, computer, and electronic engineering disciplines, adopts an interdisciplinary approach to minimize errors and production losses arising from operators’ lack of experience. Data acquired through a vibration sensor is utilized to optimize machining parameters (cutting speed and feed rate), with the goals of extending tool life, improving the surface quality of the workpiece, and reducing overall production costs. While existing systems in the literature primarily focus on tool condition monitoring, this study proposes a universal solution that can be adapted to various brands and models of CNC machines, capable of adjusting the feed rate automatically without altering the original structure of the machine.
- DOI:
- PAGES:
- DOWNLOAD: Vol72-2026.pdf
- HOW TO CITE THIS ARTICLE: F. Dalmis, E. Ucar, VIBRATION-BASED TOOL CONDITION MONITORING AND AUTOMATIC FEED RATE CONTROL IN CNC MILLING MACHINES. Journal of the Technical University of Gabrovo. 72 (2026).
- TITLE: A COMPREHENSIVE OVERVIEW OF THE MECHANICS AND APPLICATIONS OF DOUBLE-BEAM SYSTEMS
- AUTHOR(S): F. Karacam, Y. E. Altinok
- ABSTRACT: Double-beam systems have attracted significant attention due to their unique mechanical behavior and wide range of engineering applications. This study offers an extensive review of the mechanics and applications of double-beam systems, addressing both theoretical progress and practical uses. Initially, the theoretical foundations, including Euler-Bernoulli and Timoshenko beam theories, higher-order shear deformation models, and advanced non-local elasticity and strain gradient theories for micro- and nano-scale applications are reviewed. In addition, the role of elastic and viscoelastic interlayers-modeled by Kelvin-Voigt, Maxwell, Burgers, and Zener approaches is discussed, as well as the influence of different foundation models such as Winkler, Pasternak, and Kerr. The literature survey traces the historical evolution of double-beam research, from early vibration and stability studies in the 1970s to recent advances involving functionally graded materials, cracked beam analyses, and moving load problems. Future research directions include the development of smart material-based double-beam systems, broader adoption of computational methods, and coupling theoretical models with experimental approaches. These perspectives underline the importance of double-beam systems not only in structural mechanics but also in advanced engineering applications.
- DOI:
- PAGES:
- DOWNLOAD: Vol72-2026.pdf
- HOW TO CITE THIS ARTICLE: F. Karacam, Y. E. Altinok, A COMPREHENSIVE OVERVIEW OF THE MECHANICS AND APPLICATIONS OF DOUBLE-BEAM SYSTEMS, Journal of the Technical University of Gabrovo. 72 (2026).
- TITLE: THE DESIGN AND THERMAL ANALYSIS OF A HIGH-SPEED TRAIN BRAKE DISC
- AUTHOR(S): F. Karacam, Y. Cakar
- ABSTRACT: Brake discs used in high-speed trains are one of the most critical components of these systems. They convert a significant amount of kinetic energy into heat through friction. The high temperatures generated during the process cause thermal stresses, microstructural changes, and surface wear in the disc material, directly affecting its performance and lifespan. Therefore, investigating the tribological and thermomechanical behavior of brake discs is crucial in the optimization of safety, durability, and maintenance costs. In this study, the thermomechanical behavior of brake discs used in high-speed trains will be investigated by use of a computer-aided engineering approach. After modeling the brake disc that satisfies the specific operating conditions, thermal analysis will be performed to obtain values for temperature and heat flux. The variation of these parameters will be presented graphically, and the performance of the brake disc will be analyzed.
- DOI:
- PAGES:
- DOWNLOAD: Vol72-2026.pdf
- HOW TO CITE THIS ARTICLE: F. Karacam, Y. Cakar, THE DESIGN AND THERMAL ANALYSIS OF A HIGH-SPEED TRAIN BRAKE DISC, Journal of the Technical University of Gabrovo. 72 (2026).
- TITLE: CFD MODELING OF HYDRODYNAMIC CAVITATION IN A VARIABLE THROTTLE
- AUTHOR(S): I. Nochnichenko, D. Kostiuk, O. Haletskyi, S. Serhiy
- ABSTRACT: This study presents a computational fluid dynamics (CFD) investigation of hydrodynamic cavitation in a variable throttle. The primary objective is to analyze the onset, growth, and suppression of cavitation phenomena under different throttle openings and flow conditions, including variations in inlet pressure, velocity, and temperature.
The simulations were conducted using the turbulence model combined with a cavitation model accounting for liquid - vapor phase change. Several throttle configurations were examined to evaluate local pressure distribution, vapor volume fraction, cavitation zone development, and associated hydraulic losses.
The results indicate that at small throttle openings cavitation remains weak and localized near the vena contracta, while increasing the degree of throttling significantly expands the cavitation region and can lead to local pressure drops below the vaporization threshold. This causes the formation of extended vapor pockets with potential for material erosion. Additionally, fluid temperature and liquid properties (viscosity, vapor pressure) strongly influence the critical conditions for cavitation onset.
Overall, the findings highlight that proper throttle design - aimed at reducing regions of critical pressure - and optimized control of throttling degree and flow parameters can mitigate cavitation intensity and its detrimental effects. These results provide useful insights for the design and operation of hydraulic systems, pumps, injectors, and turbines where variable throttling is commonly employed.
- DOI:
- PAGES:
- DOWNLOAD: Vol72-2026.pdf
- HOW TO CITE THIS ARTICLE: I. Nochnichenko, D. Kostiuk, O. Haletskyi, S. Serhiy, CFD MODELING OF HYDRODYNAMIC CAVITATION IN A VARIABLE THROTTLE, Journal of the Technical University of Gabrovo. 72 (2026).
- TITLE: BEND RADIUS (R/T) EFFECTS ON STRESS IN S355 SHEET BENDING: ELASTIC VS. ELASTOPLASTIC FINITE ELEMENT ANALYSIS
- AUTHOR(S): G. Irsel
- ABSTRACT: In this study, the effects of bend radius on stress concentration and permanent deformation in sheet metal geometries were numerically investigated using both elastic and elastoplastic material models. Static analyses were conducted in ANSYS for ST52 (S355) steel plates with a constant thickness of 4 mm and various inner bend radii (R = 2, 4, 6, 8 mm). The material behavior was defined by a Multilinear Isotropic Hardening (MISO) model calibrated from tensile test data. Results showed that as the bend radius increased, the maximum equivalent stress decreased almost linearly. The mean stress was 390 MPa, with a standard deviation of 6.98 MPa and a strong negative correlation between R and stress (r = −0.994). The regression equation σ = −2.73R + 403.3 (MPa) indicates a stress drop of approximately 2–3 MPa per mm radius increase. Elastic models produced unrealistic stresses exceeding the material’s ultimate strength (≈ 670 MPa), while the MISO-based elastoplastic model realistically captured post-yield strain hardening and stiffness reduction. The activation of Large Deflection significantly improved deformation prediction under geometric nonlinearity, and Force Convergence evaluation confirmed stable and accurate nonlinear solutions. These results demonstrate that reliable FE analysis of sheet bending requires both plasticity modeling and geometric nonlinearity for physically meaningful stress prediction.
- DOI:
- PAGES:
- DOWNLOAD: Vol72-2026.pdf
- HOW TO CITE THIS ARTICLE: G. Irsel. BEND RADIUS (R/T) EFFECTS ON STRESS IN S355 SHEET BENDING: ELASTIC VS. ELASTOPLASTIC FINITE ELEMENT ANALYSIS. Journal of the Technical University of Gabrovo. 72 (2026).
