Razvan Oprea

Dr. Razvan Oprea

orcid

Research Focus & Metrics

Academic Career Length

15Years (2012-Present)

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

Representative Publications

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1 March 2013 in Vehicle System Dynamics
Verified
Journal Article
Closed access
RORazvan Oprea
Razvan Oprea
CCCatalin Cruceanu
Catalin Cruceanu
MSMarius-Adrian Spiroiu
Marius-Adrian Spiroiu
Braking dynamics plays an essential role in ensuring the comfort and running safety of trains. Due to the complexity of the phenomena involved and the presence of dry friction, studies have been carried out by numerical methods using smoothening. Based on the non-smooth dynamics framework, in the present paper, an efficient and comprehensive alternative model is defined. Set-valued friction of Coulomb's law type is accounted for and motion equations are formulated as a differential inclusion. Some of the fundamental issues of contact dynamics are briefly reviewed. Static friction forces which arise in buffers are computed in a very intuitive and efficient manner, using an original method involving generalised inverses of matrices. The corresponding algorithm is described. Numerical integration is done by an event-driven algorithm. Indeterminate system configurations can be appropriately handled. The number of vehicles on which tests have been carried out ranged from 5 to 50. Comparison with the smoothening method reveals significant differences. Computational efficiency is dramatically improved. Computation speed can rise by a few orders of magnitude. Specific phenomena such as stick–slip or persistent longitudinal forces can be evidenced. Computed values of the system states differ substantially. In addition to this, any wagon connection model can be embedded.

12 July 2012 in Nonlinear Dynamics
Verified
Journal Article
Closed access
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RORazvan Oprea
Razvan Oprea

20 April 2013 in Multibody System Dynamics
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Journal Article
Closed access
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RORazvan Oprea
Razvan Oprea

19 August 2025 in Technologies
Verified
Journal Article
Open access
PDF file
GPGabriel Popa
Gabriel Popa
RORazvan Oprea
Razvan Oprea
Emil TUDOREmil TUDOR
Emil TUDOR
MGMarius Alin Gheți
Marius Alin Gheți
Iulian Sorin MunteanuIulian Sorin Munteanu
Iulian Sorin Munteanu
The main purpose of this paper is to present a comprehensive and systematically organized overview of the current state of vibration monitoring and measurement techniques used in railway stock. It aims to raise awareness of significant technological developments in recent years and their practical applications. The scope of the analysis is strongly informed by established European norms, fundamental research efforts across the continent, and the practical needs of the railway sector. Last but not least, we hope this paper serves as a valuable reference point for engineers, researchers, and decision-makers working within the complex context of railway system design, maintenance, and evolving regulations. For effective monitoring of railway vehicle vibrations, a combination of specialized measurement methods and system architectures is recommended. These approaches are carefully developed to capture the dynamic responses of critical components of the railway vehicle, thereby providing invaluable data. This information is essential for thorough condition monitoring, improved ride comfort, and a deeper structural understanding of vehicle quality throughout its lifecycle.

2 February 2026 in Technologies
Verified
Journal Article
Open access
PDF file
CSCornelia Stan
Cornelia Stan
RORazvan Oprea
Razvan Oprea
Whole-body vibration (WBV) remains a critical factor influencing ride comfort, driver performance and occupational health in vehicle applications. Despite the widespread use of standardized indicators, assessing WBV exposure and its perceptual implications remains challenging due to the complex interaction between road excitation, vehicle dynamics, seat transmissibility and human biodynamic response. This review provides a comprehensive synthesis of contemporary methods for WBV assessment, emphasizing their theoretical foundations, practical implementation and inherent limitations. The paper examines classical evaluation metrics, including frequency-weighted root mean square acceleration and vibration dose value, alongside complementary approaches such as overall vibration total value, absorbed power and motion sickness indicators. Biodynamic modeling strategies for the human–seat–vehicle system are critically reviewed, highlighting trade-offs between model simplicity and physiological realism. Particular attention is given to road surface representation and excitation modeling, discussing the implications of ISO 8608-based stochastic profiles versus measured, time-domain inputs on WBV assessment outcomes. Simulation frameworks, experimental platforms and driving simulators are reviewed as complementary tools for evaluating vibration exposure and validating predictive models. Emerging methods, including time–frequency analysis and data-driven approaches, are discussed with a focus on interpretability, validation and integration with established standards such as ISO 2631. The review consolidates recent advances in integrated evaluation approaches, including the role of driving simulators and simulation-, hardware- and driver-in-the-loop (SiL/HiL/DiL) frameworks as enabling tools for repeatable testing, objective–subjective comfort correlation and early-stage vibration-control development. By critically examining both established and emerging methodologies, this review aims to support informed selection and interpretation of WBV assessment tools in vehicle design and evaluation. The findings underscore the need for integrated, transparent and application-oriented approaches to advance vibration comfort assessment and guide future research and standardization efforts.

4 May 2018 in Australian Journal of Mechanical Engineering
Verified
Journal Article
Closed access
RORazvan Oprea
Razvan Oprea
Start-up dynamics plays an essential role in ensuring the comfort and running safety and structural integrity of trains. Based on the discontinuous dynamics framework, in the present work, an efficient innovative model is proposed. The model is derived from previous train braking studies and in order to highlight the possibility of a non-smooth approach to train start longitudinal dynamics. Set-valued friction of Coulomb’s law type is accounted for and motion equations are formulated as a differential inclusion. Static friction forces which arise in buffers are computed in a very intuitive and efficient manner, using involving generalised inverses of matrices. The corresponding algorithm is described. Numerical integration is done by an event-driven algorithm. Indeterminate system configurations can be appropriately handled. The number of train vehicles may be easily adjusted, and any wagon connection model can be embedded. Specific phenomena like stick–slip or persistent longitudinal forces can be evidenced. Any feature or situation regarding train collisions may be modelled. A demonstrative application is presented.