Symmetry

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18 pages, 3312 KiB

Open AccessArticle

Statistical Assessment of Low-Cycle Fatigue Durability

by Žilvinas Bazaras and Vaidas Lukoševičius

Symmetry 2022, 14(6), 1205; https://doi.org/10.3390/sym14061205 - 10 Jun 2022

Cited by 5 | Viewed by 1980

This article presents an experimental–analytical statistical study of low-cycle fatigue to crack initiation and complete failure. The application of statistical and probability methods provides for the possibility of improving the characteristics related to the structural life and the justification for the respective values [...] Read more.

This article presents an experimental–analytical statistical study of low-cycle fatigue to crack initiation and complete failure. The application of statistical and probability methods provides for the possibility of improving the characteristics related to the structural life and the justification for the respective values of cyclic loads in the design stage. Most studies investigating statistical descriptions of crack initiation or complete failure do not analyse the distribution of the characteristics, correlation relationships, and statistical parameters of low-cycle fatigue. Low-cycle failure may be quasistatic or (due to the fatigue) transient. Materials with contrasting cyclic properties were selected for the investigation: cyclically softening alloyed steel 15Cr2MoVA; cyclically stable structural steel C45; cyclically hardening aluminium alloy D16T1. All samples were produced in a single batch of each respective material to reduce the distribution of data. The lowest values of the variation coefficient of one of the key statistical indicators were obtained using the log-normal distribution, which is superior to the normal or Weibull distribution. Statistical analysis of the durability parameters showed that the distribution was smaller than the parameters of the distribution of the deformation diagram. The results obtained in the study enable the verification of durability and life of the structural elements of in-service facilities subjected to elastoplastic loading by assessing the distribution of characteristics of crack initiation and failure and low-cycle strain parameters as well as the permissible distribution limits. Full article

(This article belongs to the Special Issue Symmetry and Asymmetry Principles in Latest Advances and Prospects of the Materials Science and Engineering)

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16 pages, 6733 KiB

Open AccessArticle

Assessment of Dynamics of a Rail Vehicle in Terms of Running Properties While Moving on a Real Track Model

by Ján Dižo, Miroslav Blatnický, Jozef Harušinec and Andrej Suchánek

Symmetry 2022, 14(3), 536; https://doi.org/10.3390/sym14030536 - 6 Mar 2022

Cited by 13 | Viewed by 2812

Abstract

Simulation computations represent a very effective tool for investigating operational characteristics and behaviours of vehicles without having a real product. The rail vehicles sector is typical, in that simulation computations including multibody modelling of individual vehicles (i.e., wagons) as well as entire trainsets [...] Read more.

Simulation computations represent a very effective tool for investigating operational characteristics and behaviours of vehicles without having a real product. The rail vehicles sector is typical, in that simulation computations including multibody modelling of individual vehicles (i.e., wagons) as well as entire trainsets are widely used. In the case of designing rail vehicles, running safety and ride comfort are two of the most important assessment areas. The presented work is focused on the research of the dynamical effects of a rail vehicle while running on a railway track created in a commercial multibody model. There is a lot of research focused on the investigation of dynamic performances while a rail vehicle is running on a flexible railway track. The real operation of a rail vehicle meets problems on track, where the stiffness-damping parameters of a railway track vary in transient sections (e.g., the exit of a tunnel). This work brings a contribution to research related to the assessment of the dynamic response of a rail vehicle on a chosen track section. A passenger railway vehicle is chosen as a reference multibody model. Simulation computations were performed for three different railway track models, i.e., for a rigid track model and for a flexible track model defined in two different manners. The stiffness-damping parameters of the rail vehicle are defined symmetrically in relation to the longitudinal axis of the vehicle, e.g., they are the same values for the left and right side. The centre of gravity is not located symmetrically, but it is partially shifted in the lateral direction. This can be observed in the results of wheel forces and their waveforms. There are evaluated values and waveforms of the vertical wheel forces, the lateral wheel forces and the derailment quotient. The obtained results have revealed the influence of the railway track formulation in the model on the output parameters. Full article

(This article belongs to the Special Issue Symmetry and Asymmetry Principles in Latest Advances and Prospects of the Materials Science and Engineering)

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17 pages, 1593 KiB

Open AccessArticle

Negative-Inertia Converters: Devices Manifesting Negative Mass and Negative Moment of Inertia

by Josip Lončar, Bojan Igrec and Dubravko Babić

Symmetry 2022, 14(3), 529; https://doi.org/10.3390/sym14030529 - 4 Mar 2022

Cited by 9 | Viewed by 5134

Abstract

Negative inertia is an unusual and counter-intuitive property of matter, extensively investigated in some of the most exotic branches of physics and engineering at both macroscopic and microscopic levels. Such an exotic property promises a wide range of applications, from Alcubierre drive to [...] Read more.

Negative inertia is an unusual and counter-intuitive property of matter, extensively investigated in some of the most exotic branches of physics and engineering at both macroscopic and microscopic levels. Such an exotic property promises a wide range of applications, from Alcubierre drive to acoustic wave manipulation. Here, a novel approach to the realization of negative inertia and the concept of negative-inertia converters are introduced for both translational and rotational motion. The proposed devices, capable of exhibiting negative mass and negative moment of inertia, base their operational principle on actuating the loading inertia, concealed within the housing of the device, synchronously with the displacement of the housing itself. Negative-inertia converters share many similarities with negative-impedance converters, including their proneness to instability. Thus, an equivalent circuit model of the proposed devices is developed and simulated in lossless and lossy environments. Friction, unavoidable in every practical system, is found to be the main cause of instability. The derived closed-form stability condition suggests that the effective inertia of a system containing a negative-inertia converter must remain positive to ensure the stability. Despite this limitation, negative-inertia converters may become the key elements in applications requiring reduction of an object’s inertia. Full article

(This article belongs to the Special Issue Symmetry and Asymmetry Principles in Latest Advances and Prospects of the Materials Science and Engineering)

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28 pages, 6438 KiB

Open AccessArticle

Analysis of Symmetrical/Asymmetrical Loading Influence of the Full-Suspension Downhill Bicycle’s Frame on the Crack Failure Formation at a Critical Point during Different Driving Scenarios and Design Improvement

by Vladimír Bulej, Ivan Kuric, Milan Sága, Milan Vaško, Zuzana Ságová, Michal Bartoš and Stanislaw Legutko

Symmetry 2022, 14(2), 255; https://doi.org/10.3390/sym14020255 - 28 Jan 2022

Cited by 4 | Viewed by 11050

Abstract

The article deals with the analysis of the existing full-suspension downhill bicycle’s frame damaged while using and the subsequent conceptual improved design of the critical point. The origin of symmetrical and asymmetrical bicycle loads in individual riding modes is investigated. Subsequently, their impact [...] Read more.

The article deals with the analysis of the existing full-suspension downhill bicycle’s frame damaged while using and the subsequent conceptual improved design of the critical point. The origin of symmetrical and asymmetrical bicycle loads in individual riding modes is investigated. Subsequently, their impact on the overall load of the frame and especially the identified critical point are assessed. An overview of different full-suspension bicycle frames, complemented by a literature overview of research related to cycling engineering and sport application is introduced. The first phase began with a kinematic analysis of the bicycle suspension system and an effect assessment of the symmetrical or asymmetrical distribution of forces, respectively, in the individual components. Furthermore, a strength analysis of the main frame was performed, taking into account the static and dynamic forces. Based on the results of the analyses performed in the ANSYS/Workbench, a critical frame point, as well as the role of individual driving regimes, were identified. The structural detail of the pocket under the saddle tube together with the asymmetrical combined load generated while out of saddle pedalling proved to be crucial for frame crack initiation and formation. Different design variants with improved stiffness were proposed for the given place. The chosen variant can be successfully implemented due to the final reduction of the maximum stress level approximately two times compared to the original pocket (only 50.4% of the original maximum stress) as well as a simple design and repair of the damaged area in terms of technology. Full article

(This article belongs to the Special Issue Symmetry and Asymmetry Principles in Latest Advances and Prospects of the Materials Science and Engineering)

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18 pages, 4090 KiB

Open AccessArticle

Analysis of Control Methods for the Traction Drive of an Alternating Current Electric Locomotive

by Sergey Goolak, Viktor Tkachenko, Pavol Šťastniak, Svitlana Sapronova and Borys Liubarskyi

Symmetry 2022, 14(1), 150; https://doi.org/10.3390/sym14010150 - 13 Jan 2022

Cited by 22 | Viewed by 2846

Abstract

The analysis of operating conditions of traction drives of electric locomotives with asynchronous traction motors has been carried out. It was found that during operation in the output converter of an asynchronous motor, defects may occur, which leads to asymmetric modes of its [...] Read more.

The analysis of operating conditions of traction drives of electric locomotives with asynchronous traction motors has been carried out. It was found that during operation in the output converter of an asynchronous motor, defects may occur, which leads to asymmetric modes of its operation. Models of a traction drive of an electric locomotive with asynchronous motors with scalar and vector control of the output converter are proposed, taking into account asymmetric operating modes. As a result of the simulation, the starting characteristics of the traction drive were obtained for various control methods both in normal and emergency modes of the drive. For the drive-in emergency mode, the following cases were investigated: the balance of the converter output voltages and the turn-to-turn circuit of 10% of phase A winding of the motor stator; imbalance of the output voltages of the inverter and an intact motor; imbalance of the output voltages of the converter and interturn short circuit of 10% of phase A winding of the motor stator. Comparison of the simulation results have shown that in emergency modes in the traction drive, the torque ripple on the motor shaft in the drive with vector control is 13% less, and in scalar control, the phase current unbalance coefficient is 22% less. The results of this work can be used to study the influence of the output converter control methods on the energy efficiency indicators of the traction drive of an AC electric locomotive. Full article

(This article belongs to the Special Issue Symmetry and Asymmetry Principles in Latest Advances and Prospects of the Materials Science and Engineering)

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15 pages, 2061 KiB

Open AccessArticle

Optimization of the Motion Algorithm and Reduction of the External Dynamic Load of the Machinery Actuator in Translational and Rotational Modes

by Volodymyr Musiiko, Pavol Šťastniak, Mykhailo Honchar, Volodymyr Nikolaienko, Jurii Lazaruk, Anatolii Korpach and Andrej Suchánek

Symmetry 2022, 14(1), 51; https://doi.org/10.3390/sym14010051 - 1 Jan 2022

Cited by 2 | Viewed by 1417

Abstract

This article deals with the theoretical preconditions for creating a high-performance, universal earthmoving vehicle with continuous motion that can create long grooves of different depths and widths in the soil using a single actuator. For this purpose, a new symmetrical rotor actuator was [...] Read more.

This article deals with the theoretical preconditions for creating a high-performance, universal earthmoving vehicle with continuous motion that can create long grooves of different depths and widths in the soil using a single actuator. For this purpose, a new symmetrical rotor actuator was developed, which operates in translational and rotational modes due to the two-level actuator with a double-swivel mounting on the base chassis, instead of the traditional single-swivel mounting. Its use eliminates the possibility of leveling the thickness of the shavings when digging the soil. The rotor-actuator-movement algorithm at the front part was developed from a combination of vehicle movement and cyclic-lateral-actuator movement. In real practice, this means digging up the soil with even shavings. The implementation of the developed algorithm in the physical model of the symmetrical actuator confirmed the possibility of balancing the thickness of the shavings, which are cut by the rotor buckets with up to 10% accuracy. The difference between the results in determining the thickness of the shavings analytically and experimentally is 12% with a confidence interval of 0.95. Full article

(This article belongs to the Special Issue Symmetry and Asymmetry Principles in Latest Advances and Prospects of the Materials Science and Engineering)

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13 pages, 2530 KiB

Open AccessArticle

Development of a Method for Evaluating the Technical Condition of a Car’s Hybrid Powertrain

by Oleksiy Bazhinov, Juraj Gerlici, Oleksandr Kravchenko, Yevhen Haiek, Tetiana Bazhynova, Ruslan Zaverukha and Kateryna Kravchenko

Symmetry 2021, 13(12), 2356; https://doi.org/10.3390/sym13122356 - 7 Dec 2021

Cited by 10 | Viewed by 2193

Abstract

The article presents the results of a study performed and substantiated based on the principles of a new method of diagnostics of technical conditions of a hybrid powertrain regardless of the structural diagram and design features of a hybrid vehicle. The presented new [...] Read more.

The article presents the results of a study performed and substantiated based on the principles of a new method of diagnostics of technical conditions of a hybrid powertrain regardless of the structural diagram and design features of a hybrid vehicle. The presented new technology of the diagnostics of hybrid powertrains allows an objective complex assessment of their technical condition by diagnostic parameters in contrast to existing diagnostic methods. In the proposed method, a mechanism for the general standardization of diagnostic parameters has been developed as well as for determining the numerical values of the parameters of the powertrain. The control subset was used to control the learning error. As a result of debugging the system, the scatter of experimental and calculated points has decreased, which confirms the quality of debugging the tested fuzzy model. As a result of training the artificial neural network, the standard deviation of the error in the control sample was 0.012·P_k. A symmetry method of diagnostics of the technical state of a hybrid propulsion system was developed based on the concept of a neural network together with a neuro-fuzzy control with an adaptive criteria based on the method of training a neural network with reinforcement. The components of the vector functional include the criteria for control accuracy, the use of traction battery energy, and the degree of toxicity of exhaust gases. It is proposed to use the principle of symmetry of the guaranteed result and the linear inversion of the vector criterion into a supercriterion to determine the technical state of a hybrid powertrain on a set of Pareto-optimal controls under unequal conditions of optimality. Full article

(This article belongs to the Special Issue Symmetry and Asymmetry Principles in Latest Advances and Prospects of the Materials Science and Engineering)

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20 pages, 9872 KiB

Open AccessArticle

The Dynamic and Strength Analysis of an Articulated Covered Wagon with the Circular Pipe Design

by Oleksij Fomin, Alyona Lovska, Juraj Gerlici, Yuliia Fomina, Ján Dižo and Miroslav Blatnický

Symmetry 2021, 13(8), 1398; https://doi.org/10.3390/sym13081398 - 1 Aug 2021

Cited by 1 | Viewed by 2105

Abstract

An articulated covered wagon design was developed. The wagon feature is that the body-bearing elements are made of circular pipes. This technical solution made it possible to reduce the tare weight of the wagon while ensuring the strength conditions. Mathematical simulation of the [...] Read more.

An articulated covered wagon design was developed. The wagon feature is that the body-bearing elements are made of circular pipes. This technical solution made it possible to reduce the tare weight of the wagon while ensuring the strength conditions. Mathematical simulation of the dynamic loading of the developed articulated covered wagon design was carried out under the main operating conditions. In the calculations of the observed quantities, an application of symmetry with regard to the longitudinal axis of the wagon was used. The accelerations, as the components of the dynamic load acting on the wagon, were determined. The dynamic loading computer simulation results of the developed wagon design are also presented. The strength analysis of the articulated covered wagon supporting structure made it possible to conclude that the strength indexes were within the allowed limits. The wagon bearing structure was analyzed for fatigue strength. The weld strength analysis results of the most loaded part of the wagon-bearing structure are presented. The results obtained for the desired quantities revealed their symmetrical distribution in the wagon structure. This research will contribute to improving the efficiency of railway transport operation. Full article

(This article belongs to the Special Issue Symmetry and Asymmetry Principles in Latest Advances and Prospects of the Materials Science and Engineering)

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