Ústav automobilního a dopravního inženýrství

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    An Initial Case Study of the Computational Modeling of Cord-Rubber Segments
    (MDPI, 2024-01-29) Láštic, Daniel; Řehák, Kamil; Prokop, Aleš; Krpalek, David; Šplíchal, Jan; Žlábek, Pavel
    This paper presents an initial study of the computational modeling for determining the stress-strain behavior of the cord-rubber segment, tailored to be used as a flexible member in the construction of torque transfer coupling in railway vehicles. The presented computational models use the multibody simulation approach for the assessment of segment deformation under diverse loading characteristics. The results are then used in the finite element computational models of the cord-rubber segment. The computational model is validated through tension tests of cord-rubber segments. The homogenized and microstructural models show their ability to simulate the overall stiffness of the segment relatively accurately in tension, but they are limited in not being able to include the influence of the segment's manufacturing technology. The micro-scale computational model then incorporates realistic representations of cord bundles, considering various cross-sectional shapes, whereas a very important factor significantly influencing the correlation of the results of the technical experiment and simulation is the consideration of the manufacturing technology in the process of building the computational model. The results show that the computational modeling approach in this work can be used for the determination of the optimal manufacturing technology conditions with regard to the stress-strain behavior of the given segment.
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    Methodology for Measuring Forces in Motorcycle Suspension Using a System Based on Analogue Potentiometers
    (Slovak University of Technology in Bratislava, 2024-06-01) Míša, Jiří; Tobiáš, Martin; Repka, Martin; Straka, Tomáš; Gregor, Lukáš
    This study explores the quest for a more cost-effective and practical method of measuring forces in motorcycle suspension systems by utilizing simple potentiometers as an alternative to sophisticated strain gauges. The research delves into the feasibility of potentiometers to provide accurate and reliable force measurements, offering potential advantages in terms of affordability, accessibility, and ease of implementation. Through empirical testing and verification, this investigation aims to establish potentiometers as a viable and economical solution for enhancing motorcycle suspension performance monitoring and tuning.
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    Comparative study of engine dynamics for rolling and selective cylinder deactivation
    (PERGAMON-ELSEVIER SCIENCE LTD, 2024-09-15) Fridrichová, Kateřina; Drápal, Lubomír; Raffai, Peter; Böhm, Michael
    Strict emission limits have forced the automotive industry to reduce the carbon dioxide emissions produced by internal combustion engines. Emissions can also be reduced by increasing the efficiency of internal combustion engines by implementing technologies such as cylinder deactivation, the main benefit of which is a reduction in fuel consumption. However, there are some negative effects associated with this technology. There are two approaches to cylinder deactivation - selective and rolling. This paper focuses on the constraints of the technology and compares the two methods of cylinder deactivation in terms of torsional vibration, friction losses and load on the main bearings. The results for the selective and rolling cylinder deactivation are obtained from a verified multibody simulation of a four-cylinder engine.
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    Experimental Investigation of Microcontroller-Based Acoustic Temperature Transducer Systems
    (MDPI, 2023-01-12) Al-Rawashdeh, Ayman Y.; Younes, Tariq M.; Dalabeeh, Ali; Al_Issa, Huthaifa; Qawaqzeh, Mohamed; Miroshnyk, Oleksandr; Kondratiev, Andrii; Kučera, Pavel; Píštěk, Václav; Stepenko, Serhii
    Temperature transducers are commonly used to monitor process parameters that are controlled by various types of industrial controllers. The purpose of this study is to design and model a simple microcontroller-based acoustic temperature transducer based on the variations of resonance conditions in a cylindrical resonance tube. The transducer’s operation is based on the generation of an acoustic standing wave in the free resonance mode of generation within a cylindrical resonance tube which is converted into a train of pulses using Schmitt trigger circuit. The frequency of the generated standing wave (i.e., the train of pulses) is measured by the Arduino Uno microcontroller, where a digital pin is used to acquire pulses that are counted using a build-in software function in an Arduino IDE environment. Experimental results are performed for three sizes of diameters to investigate the effect of the diameter of resonance tube on the obtained results. The maximum nonlinearity error according to Full-Scale Deflection (FSD) is about 2.3 percent, and the relative error of the transducer is evaluated using experimental findings and the regression model. The circuit simplicity and design of the suggested transducer, as well as the linearity of its measurements, are notable.
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    Methodological Approach in the Simulation of the Robustness Boundaries of Tribosystems under the Conditions of Boundary Lubrication
    (MDPI, 2023-01-04) Al-Quraan, Tareq M. A.; Alfaqs, Fadi; Alrefo, Ibrahim F. S.; Vojtov, Viktor; Voitov, Anton; Kravtsov, Andrey; Miroshnyk, Oleksandr; Kondratiev, Andrii; Kučera, Pavel; Píštěk, Václav
    In the presented work, a methodical approach was developed for determining rational operation modes of tribosystems, taking into account their design. This approach makes it possible in the designing stage, according to the predicted operating modes, to calculate the limits and margins of stable work in operation. The definition of the robustness of the tribosystem and the criteria for assessing the robustness are formulated based on the theory of stability of technical systems. It is shown that such a methodical approach allows for determining the modes of the rational operation of the designed structures without damaging the friction surfaces. Experimental studies have proven that not all designs of tribosystems lose stability due to the appearance of friction surface burrs. There are designs where the loss of stability occurs upon the appearance of accelerated wear. The developed criteria take into account two options for the loss of stability. An experimental verification of the modes of loss of stability of tribosystems was performed by the appearance of a burr or the beginning of accelerated wear with the calculated values of the robustness criteria. The obtained results allow us to conclude that the modeling error is within 8.3–18.7%, which is a satisfactory result in the study of friction and wear processes. Robustness criteria is based on the coefficient of friction RRf and wear rate RRI, and must be used when designing new constructions of tribosystems. Theoretical calculations of such criteria and the dependence of their change on changing the predicted operating modes will allow for justifying rational operating modes within their stability.