Stefan Bostina

Mr. Stefan Bostina


Research Focus & Metrics

Academic Career Length

2Years (2025-Present)

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

Representative Publications

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7 February 2025 in Agriengineering
Verified
Journal Article
Open access
PDF file
Oncescu Teofil AlinOncescu Teofil Alin
Oncescu Teofil Alin
SBSorin Ștefan Biriș
Sorin Ștefan Biriș
SBStefan Bostina
Stefan Bostina
Sorin Ștefan BirișSorin Ștefan Biriș
Sorin Ștefan Biriș
VVValentin Marius Vilceleanu
Valentin Marius Vilceleanu
Daniela TarnitaDaniela Tarnita
Daniela Tarnita
The present paper investigates the comparative impact of vibrations on operator safety for two diesel and electric agricultural tractors under real operating conditions. Vibrations were measured using four triaxial accelerometers installed at critical points, including the seat base, backrest, floor, and operator’s head. Tests were conducted on two comparable tractor models, a diesel New Holland TCE 50 and an electric prototype TE-0, across four types of terrains (concrete, grass, uneven agricultural road, and plowed land) and at two working speeds (5 km/h and 10 km/h). The root mean square (RMS) accelerations, seat-to-head transmissibility, and isolation efficiency were calculated in compliance with ISO 2631 standards to evaluate the effects on operator health and comfort. The results showed superior vibration isolation efficiency for the electric tractor, particularly within the critical frequency range of 4–12 Hz, where human health risks are most significant and a better isolation efficiency of 98%, significantly reducing operator exposure to harmful vibrations. These findings highlight the potential of electric tractors to improve operator comfort, safety, and long-term health in agricultural applications.

1 November 2025 in Agriengineering
Verified
Journal Article
Open access
PDF file
Oncescu Teofil AlinOncescu Teofil Alin
Oncescu Teofil Alin
Sorin Ștefan BirișSorin Ștefan Biriș
Sorin Ștefan Biriș
IGIuliana Gageanu
Iuliana Gageanu
Valentin Nicolae VLADUTValentin Nicolae VLADUT
Valentin Nicolae VLADUT
CPCătălin Persu
Cătălin Persu
Daniela TarnitaDaniela Tarnita
Daniela Tarnita
The central purpose of this study is to develop and validate an advanced numerical model capable of simulating the vibrational behavior of the operator’s seat in a tractor-type agricultural vehicle designed for operation in protected horticultural environments, such as vegetable greenhouses. The three-dimensional (3D) model of the seat was created using SolidWorks 2023, while its dynamic response was investigated through Finite Element Analysis (FEA) in Altair SimSolid, enabling a detailed evaluation of the natural vibration modes within the 0–80 Hz frequency range. Within this interval, eight significant natural frequencies were identified and correlated with the real structural behavior of the seat assembly. For experimental validation, direct time-domain measurements were performed at a constant speed of 5 km/h on an uneven, grass-covered dirt track within the research infrastructure of INMA Bucharest, using the TE-0 self-propelled electric tractor prototype. At the operator’s seat level, vibration data were collected considering the average anthropometric characteristics of a homogeneous group of subjects representative of typical tractor operators. The sample of participating operators, consisting exclusively of males aged between 27 and 50 years, was selected to ensure representative anthropometric characteristics and ergonomic consistency for typical agricultural tractor operators. Triaxial accelerometer sensors (NexGen Ergonomics, Pointe-Claire, Canada, and Biometrics Ltd., Gwent, UK) were strategically positioned on the seat cushion and backrest to record accelerations along the X, Y, and Z spatial axes. The recorded acceleration data were processed and converted into the frequency domain using Fast Fourier Transform (FFT), allowing the assessment of vibration transmissibility and resonance amplification between the floor and seat. The combined numerical–experimental approach provided high-fidelity validation of the seat’s dynamic model, confirming the structural modes most responsible for vibration transmission in the 4–8 Hz range—a critical sensitivity band for human comfort and health as established in previous studies on whole-body vibration exposure. Beyond validating the model, this integrated methodology offers a predictive framework for assessing different seat suspension configurations under controlled conditions, reducing experimental costs and enabling optimization of ergonomic design before physical prototyping. The correlation between FEA-based modal results and field measurements allows a deeper understanding of vibration propagation mechanisms within the operator–seat system, supporting efforts to mitigate whole-body vibration exposure and improve long-term operator safety in horticultural mechanization.

17 April 2026 in Agriengineering
Verified
Journal Article
Open access
PDF file
Oncescu Teofil AlinOncescu Teofil Alin
Oncescu Teofil Alin
Sorin Ștefan BirișSorin Ștefan Biriș
Sorin Ștefan Biriș
IGIuliana Gageanu
Iuliana Gageanu
Valentin Nicolae VLADUTValentin Nicolae VLADUT
Valentin Nicolae VLADUT
CPCătălin Persu
Cătălin Persu
TATeodor Anița
Teodor Anița
The aim of this study is to evaluate the biomechanical response of a seated operator subjected to whole-body vibrations generated by two agricultural tractors with different propulsion systems: a diesel model (TD80D) and an electric prototype (TE-0). An integrated experimental–numerical approach was employed, combining triaxial accelerometer measurements under real operating conditions (constant speed of 5 km/h on unprepared terrain) with random vibration response simulations performed in Altair SimSolid. The excitation input for the numerical model was defined using frequency-dependent power spectral density (PSD) functions derived from experimentally measured acceleration signals and scaled to a representative global RMS value. The analysis focused on the distribution of mechanical stress in key anatomical regions of a virtual human dummy in a seated posture, including the foot sole, knee, lumbar region, and head. The results indicate that, under the analysed conditions, the electric tractor (TE-0) exhibits improved vibration attenuation, leading to significant reductions in mechanical stress across all analysed regions, with decreases of up to 56.3% at the foot sole, 50.0% at the knee, 53.3% in the lumbar region, and 91.1% at the head compared to the diesel tractor (TD80D). These findings highlight the relevance of integrating experimental measurements with numerical simulation for assessing operator exposure to vibrations and suggest that electric tractor configurations may provide improved biomechanical comfort under the analysed operating conditions.