Engineering Mechanics

Road accidents and collisions are negative effects of automotive development. Should there be no possibility of identifying the offender at the scene, experts are appointed to perform the investigation. To reconstruct a collision, the experts use simulation programs and the expertise developed when applying the programs affects the outcome of court proceedings. Currently the analytical calculations have been replaced with computer programs the results of which the experts usually consider valid. The article investigates a problem of the simulation program generating different results for the same incident. The results can be used by researchers modelling the collisions of vehicles, vehicles with elements of road infrastructure and with pedestrians; the results are also used in applications.

A significant amount of attention has been devoted to rapid bridge testing in recent years at the Institute of Theoretical and Applied Mechanics. New methods, such as the Vehicle Scanning Method and Moving Impulse Load Testing, have been developed and/or tested on a scaled laboratory bridge model. This article summarizes all conducted tests, discusses the evaluation methods used, presents the results obtained, and explores possibilities for their improvement. Among the tested methods, the application of Moving Impulse Load (MIL) moving at slow speed, with an excitation frequency around the first natural frequency of the tested bridge, appears to be the most promising. Two passages of the MIL allow for an approximate estimation of the dominant natural frequencies, while repeated passages at small velocity increments provide an excellent means of detecting changes in structural stiffness.

This paper briefly presents the investigation results of the dynamic response of the flume RC structure due to turbulent water flow (case study). The purpose of the dynamic diagnosis of the reinforced concrete structure (RCS) of the OORS (COSS) channel (Danube Gabčíkovo - Nagymaros Waterworks) was to verify the flume structure dynamic resistance due to turbulent water flow with a rate from 30 m3/s to 90 m3/s and 120 m3/s (COSS – collection object shoulder system).

This paper discusses the recent accomplishments in the testing of the W-WING whirl flutter demonstrator. First, the paper gives a theoretical background on the whirl flutter phenomenon and outlines information about the demonstrator itself, past design and development activities and preparatory experiments including mass and stiffness measurements, modal tests and engine tests. The main focus is paid on the wind tunnel measurements. The wind tunnel test description includes the test equipment and methodology as well as the test result assessment methodology and examples of the results. Finally, the outcome and future activities are outlined.

This paper investigates various approaches for approximating the stationary aeroelastic response characteristics under near-resonance conditions, with a focus on the lock-in regime. A reduced form of the Fokker–Planck equation—derived via stochastic averaging—is used to represent the long-term behavior. Comparative analysis is performed between traditional finite element solutions and refined semi-analytical techniques based on a Galerkin-type expansion of an analytical solution available for exact resonance conditions. Although full verification via Monte Carlo simulations is constrained due to the elusive nature of the generalized partial amplitudes inherent in the reduced FPE framework, indicative comparisons reveal an unexpectedly analogy across methods. These results highlight both the practical value and the limitations of different modeling strategies in the probabilistic assessment of nonlinear systems.

Laser shock peening (LSP) is a modern but already established approach to improve the strength and fatigue resistance of components by hardening their surface. LSP is based on the use of a high-energy laser to generate mechanical loading of the component surface. Compared to standard peening techniques, e.g., shot peening, LSP allows for precision surface treatment since the individual laser spots can be positioned with an accuracy of the order of 0.1 mm. Furthermore, the laser energy (∼ 1 J) as well as the spot size (∼ 1 mm) are tunable parameters. This process tunability allows for component- and material-based optimization that can be accelerated through simulations. However, simulations of LSP treatment of real-life components are time consuming in such a way that it disallows their direct usage in process optimization. In this contribution, we present an approach to mitigate the computational costs of simulation-based LSP process optimization. The approach is based on sampling the optimization parameter space by computing several simulations while varying the optimized parameters. Next, the precomputed solutions are used to construct a reduced order model (ROM) usable in optimization. ROM in question leverages proper orthogonal decomposition (POD) and artificial neural networks (ANNs). Compared to the original full order model (FOM), ROM evaluation is by orders of magnitude faster. Furthermore, the loss of information between FOM and ROM can be controlled during the ROM construction.

This study analyzes the noise emission of the Inogen One G2 oxygen concentrator under operational conditions. The focus is on measuring sound pressure levels in different environmental settings and user positions. Measurements were conducted according to PN-EN ISO 11200 – 11204 standards, considering both direct and reflected acoustic waves. The main noise sources were identified, and the impact of the surrounding environment on sound propagation was examined. Based on the conducted research, recommendations were developed to optimize device usage while ensuring acoustic comfort. This study provides essential insights into the noise emission characteristics of the oxygen concentrator and its impact on the user under various operational conditions.

This study investigates the influence of uncertainties in materials on nonlinear crack detection, particularly in cases where responses exhibit slight nonlinearity. A stochastic sensitivity analysis approach is conducted on a novel indicator for nonlinear crack detection, known as the quadratic Teager-Kaiser energy, and its performance is compared with the harmonic indicator derived from the frequency spectrum. The method considers each input parameter as a random variable individually, as well as all input parameters collectively as random variables, by incorporating the partial sensitivity factor of each input and the coefficient of variation of all inputs. The findings indicate that, among all material parameters discussed, quadratic Teager-Kaiser energy exhibits relatively greater sensitivity than frequency spectrum responses, with elastic modulus being the most influential parameter in both cases. These results suggest that considering the uncertainties in input parameters is crucial when utilizing harmonic indicators for crack detection, especially for slight cracks.

Stochastic resonance is a phenomenon observed in nonlinear dynamical systems with bistable behavior under combined deterministic and stochastic excitation. In its classical form, it is modeled using a Duffing-type oscillator subjected to harmonic forcing and additive white noise, resulting in noise-assisted transitions between stable states. This study investigates numerical methods for capturing transient effects related to stochastic resonance in the context of aeroelastic post-critical behavior, with a focus on a prismatic beam exposed to cross air flow. Motivated by wind tunnel observations, stochastic resonance is explored as a theoretical framework for modeling complex aeroelastic responses in bridge decks. Two computational approaches are employed: direct stochastic simulation using Monte Carlo methods, and numerical solution of the associated Fokker–Planck equation using the method of lines. The results highlight the capability of these methods to reproduce resonance-driven switching and demonstrate their potential for predicting transient aeroelastic responses relevant to the stability of slender structures under aerodynamic loading.

This paper presents the development and validation of an aircraft performance model for regional turboprop aircraft, with a focus on integrating hybrid propulsion systems. Hybrid propulsion technologies, combining traditional gas turbines with hydrogen fuel cells, offer a promising solution to reduce aviation's carbon footprint, addressing the sector’s impact to global CO2 emissions. The model, programmed in MATLAB, incorporates key flight phases (take-off, climb, cruise, descent, approach) and accounts for altitudedependent variations in air density, weight, and thrust requirements. Validation of the model was conducted using reference data from standard turboprop aircraft, demonstrating accurate fuel consumption and performance predictions across missions of 200 NM and 300 NM. The results confirm the model’s reliability in supporting hybrid propulsion optimization while meeting mission operational requirements.

A new industrial building was constructed for processing rough mining material, with sieves used for rock sorting. However, these sieves induced intense dynamic effects, resulting in significant vibrations. The building’s design did not incorporate dynamic assessments, leading to unbearable vibrations that severely restricted its operation. To address this issue, dynamic measurements were conducted to determine the building's parameters and its resulting dynamic response. As a solution, a tuned mass damper (TMD) was designed for the building's critical parts. The TMD parameters were optimized, and its performance was validated through extensive dynamic numerical analyses. Samples of these dampers were fabricated in the laboratory and subsequently installed in the building. The effectiveness of the dampers was evaluated through both numerical analysis and in-situ tests. These procedures demonstrated that the numerical model, developed using the Finite Element Method, accurately represents the system as a digital twin, including the building, dynamic drivers, and tuned mass dampers.

The indexing gearbox is used in dynamic applications. To improve its dynamic performance, the hybrid indexing gearbox turret follower disc consisting of a composite body with the steel inserts for pins and a steel shaft flange has been introduced. Such a hybrid disc composite body is made of long-fiber epoxy composite using fiber in place (FIP) technology. That allows integration of inserts into the part during the lamination process. Newly designed hybrid discs have undergone modal analysis in this work to determine their natural frequencies and assess their dependency on composite fiber volume ratio. Results of modal analysis show that 35 % of fiber volume ratio is the limiting value under which natural frequencies of FIP hybrid disc are lower than frequencies of steel disc. The first two modes have similar frequencies which can lead to their superposition. Typical values of 50 % of fiber volume ratio FIP composite shows 11 % increase of frequencies in comparison with steel disc and these frequency values are out of operating frequency range. FIP technology is suitable for hybrid “steel-composite” disc in turret follower application as it contributes to improvement of dynamic performance of the mechanism or its individual parts.