M. Pástor, P. Frankovský, M. Hagara, P. Lengvarský
Abstract Anchoring parts of technical systems are often damaged due to the heavy forces acting on these systems during their operation. For that reason, various modifications are suggested and created on the anchoring screws, which should help to reduce the mechanical stress values in a place of the first load-bearing thread of a female screw. For the determination of stress fields on the surface of a plane model of a threaded joint, two non-contact optical methods were used – conventional transmission photoelasticimetry and modern digital image correlation.
{"title":"The Use of Optical Methods in the Analysis of the Areas with Stress Concentration","authors":"M. Pástor, P. Frankovský, M. Hagara, P. Lengvarský","doi":"10.2478/scjme-2018-0018","DOIUrl":"https://doi.org/10.2478/scjme-2018-0018","url":null,"abstract":"Abstract Anchoring parts of technical systems are often damaged due to the heavy forces acting on these systems during their operation. For that reason, various modifications are suggested and created on the anchoring screws, which should help to reduce the mechanical stress values in a place of the first load-bearing thread of a female screw. For the determination of stress fields on the surface of a plane model of a threaded joint, two non-contact optical methods were used – conventional transmission photoelasticimetry and modern digital image correlation.","PeriodicalId":35968,"journal":{"name":"Strojnicky Casopis","volume":"68 1","pages":"61 - 76"},"PeriodicalIF":0.0,"publicationDate":"2018-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49177304","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract During the gas turbine exploitation the presence of small defects can cause very high vibration amplifications, localized on the components of this rotating machine. For this, a diagnostic process is necessary for decision-making during the monitoring of failures caused by vibration phenomena, which consists in observing the system by comparing its current data with the data coming from a normal operation. These indicators help engineer to determine the symptoms for the failing components of the system. This work deals with problems related to these vibrations, with the aim of developing a system of detection of failures using dynamic neural networks approach. The originality of this contribution is to calculate the various alarms based on this system which used the determined vibration models in order to ensure a reliable and safe operation of the gas compression installation using the examined gas turbine.
{"title":"Detection and Modeling Vibrational Behavior of a Gas Turbine Based on Dynamic Neural Networks Approach","authors":"Mohamed Benrahmoune, Hafaifa Ahmed, Guemana Mouloud, Chen Xiaoqi","doi":"10.2478/scjme-2018-0032","DOIUrl":"https://doi.org/10.2478/scjme-2018-0032","url":null,"abstract":"Abstract During the gas turbine exploitation the presence of small defects can cause very high vibration amplifications, localized on the components of this rotating machine. For this, a diagnostic process is necessary for decision-making during the monitoring of failures caused by vibration phenomena, which consists in observing the system by comparing its current data with the data coming from a normal operation. These indicators help engineer to determine the symptoms for the failing components of the system. This work deals with problems related to these vibrations, with the aim of developing a system of detection of failures using dynamic neural networks approach. The originality of this contribution is to calculate the various alarms based on this system which used the determined vibration models in order to ensure a reliable and safe operation of the gas compression installation using the examined gas turbine.","PeriodicalId":35968,"journal":{"name":"Strojnicky Casopis","volume":"68 1","pages":"143 - 166"},"PeriodicalIF":0.0,"publicationDate":"2018-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48195508","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract In the paper the locomotion of snake robot is introduced considering locomotion in straight and curved pipe. For the straight pipe locomotion was designed traveling wave locomotion pattern with sine-like wave which expands from rear of the robot to its front. For the locomotion in curved pipe was designed approach which is based on inverse kinematic model including besides primary task also secondary tasks, namely kinematic singularities avoidance task, obstacle avoidance task and joint limit avoidance task. For final inverse kinematic model was used approach of weight matrices by which can be stated the priorities of particular tasks. Both case studies were tested by experimental snake robot in order to verify introduced methodology for locomotion in the straight and curved pipe.
{"title":"Snake Robot Locomotion Patterns for Straight and Curved Pipe","authors":"Ivan Virgala, T. Lipták, Ľ. Miková","doi":"10.2478/scjme-2018-0020","DOIUrl":"https://doi.org/10.2478/scjme-2018-0020","url":null,"abstract":"Abstract In the paper the locomotion of snake robot is introduced considering locomotion in straight and curved pipe. For the straight pipe locomotion was designed traveling wave locomotion pattern with sine-like wave which expands from rear of the robot to its front. For the locomotion in curved pipe was designed approach which is based on inverse kinematic model including besides primary task also secondary tasks, namely kinematic singularities avoidance task, obstacle avoidance task and joint limit avoidance task. For final inverse kinematic model was used approach of weight matrices by which can be stated the priorities of particular tasks. Both case studies were tested by experimental snake robot in order to verify introduced methodology for locomotion in the straight and curved pipe.","PeriodicalId":35968,"journal":{"name":"Strojnicky Casopis","volume":"68 1","pages":"104 - 91"},"PeriodicalIF":0.0,"publicationDate":"2018-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44515709","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract The paper describes role of non-proportional damping in flutter type instability, demonstrated on simplified disc brake model. The discrete two degrees of freedom system is considered to imply damping induced instability through a system eigenvalues evaluation. The Frequency Response Function (FRF) is further calculated from measurements on the physical disc brake model. From FRF, damping properties are estimated and discussed. Several different loading states of the pad versus disc are considered to show loading impact on FRF and thus damping of the system.
{"title":"Frequency Response Function Measurement on Simplified Disc Brake Model","authors":"Úradníček Juraj, M. Musil, M. Bachratý","doi":"10.2478/scjme-2018-0036","DOIUrl":"https://doi.org/10.2478/scjme-2018-0036","url":null,"abstract":"Abstract The paper describes role of non-proportional damping in flutter type instability, demonstrated on simplified disc brake model. The discrete two degrees of freedom system is considered to imply damping induced instability through a system eigenvalues evaluation. The Frequency Response Function (FRF) is further calculated from measurements on the physical disc brake model. From FRF, damping properties are estimated and discussed. Several different loading states of the pad versus disc are considered to show loading impact on FRF and thus damping of the system.","PeriodicalId":35968,"journal":{"name":"Strojnicky Casopis","volume":"68 1","pages":"225 - 230"},"PeriodicalIF":0.0,"publicationDate":"2018-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47801753","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract The article deals with the contribution of Dr.h.c. mult. prof. Ing. František Trebuňa, CSc to the field of engineering. Born in 1947, he studied and subsequently remained at the Faculty of Mechanical Engineering, Technical University of Košice since 1965. Under his leadership 25 dissertation theses were defended in the study programs Applied mechanics, Mechatronics and Forensic engineering. He is author to 14 monographs, 16 textbooks, 5 other books, 12 university textbooks and more than 350 original scientific papers published in domestic and foreign journals and conference proceedings. Professor Trebuňa is currently the dean at the faculty and is known as a gifted educator.
{"title":"Dedicated to Dr. H. C. Mult. Prof. Ing. František Trebuňa, CSC. on the Occasion of his 70th Birthday","authors":"J. Bocko, R. Janco, B. Hucko","doi":"10.2478/SCJME-2018-0012","DOIUrl":"https://doi.org/10.2478/SCJME-2018-0012","url":null,"abstract":"Abstract The article deals with the contribution of Dr.h.c. mult. prof. Ing. František Trebuňa, CSc to the field of engineering. Born in 1947, he studied and subsequently remained at the Faculty of Mechanical Engineering, Technical University of Košice since 1965. Under his leadership 25 dissertation theses were defended in the study programs Applied mechanics, Mechatronics and Forensic engineering. He is author to 14 monographs, 16 textbooks, 5 other books, 12 university textbooks and more than 350 original scientific papers published in domestic and foreign journals and conference proceedings. Professor Trebuňa is currently the dean at the faculty and is known as a gifted educator.","PeriodicalId":35968,"journal":{"name":"Strojnicky Casopis","volume":"68 1","pages":"5 - 8"},"PeriodicalIF":0.0,"publicationDate":"2018-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41545143","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Saha Sabhasachi, R. Koushik, Roy Souvik, Rahman Md. Asfakur, Hasan Md. Zahid
Abstract In the present world, nuclear energy is a must need for various purposes. The main cause of nuclear energy is because of the increasing energy demand, which is not possible to provide by using convenient energy generation. Bangladesh is a lower income country and the energy sector is not so developed here though there is a very high demand for energy. Rooppur Nuclear Power Plant is the only one nuclear generation plant which can provide this kind of huge energy within a very short time. This paper mainly depicts the ins and outs of this plant and discusses it’s feasibility in Bangladesh. It also focuses on the worlds various power generation methods and comprises it with nuclear energy generation. A detailed technical brief is presented in this paper along with advantages, location selection, financial and environmental impacts. This will help researchers to do further researches about nuclear energy in Bangladesh.
{"title":"Rooppur Nuclear Power Plant: Current Status & Feasibility","authors":"Saha Sabhasachi, R. Koushik, Roy Souvik, Rahman Md. Asfakur, Hasan Md. Zahid","doi":"10.2478/scjme-2018-0033","DOIUrl":"https://doi.org/10.2478/scjme-2018-0033","url":null,"abstract":"Abstract In the present world, nuclear energy is a must need for various purposes. The main cause of nuclear energy is because of the increasing energy demand, which is not possible to provide by using convenient energy generation. Bangladesh is a lower income country and the energy sector is not so developed here though there is a very high demand for energy. Rooppur Nuclear Power Plant is the only one nuclear generation plant which can provide this kind of huge energy within a very short time. This paper mainly depicts the ins and outs of this plant and discusses it’s feasibility in Bangladesh. It also focuses on the worlds various power generation methods and comprises it with nuclear energy generation. A detailed technical brief is presented in this paper along with advantages, location selection, financial and environmental impacts. This will help researchers to do further researches about nuclear energy in Bangladesh.","PeriodicalId":35968,"journal":{"name":"Strojnicky Casopis","volume":"68 1","pages":"167 - 182"},"PeriodicalIF":0.0,"publicationDate":"2018-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.2478/scjme-2018-0033","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42907343","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract As a continuation of the author’s previous studies on the buckling analysis of helical springs, a closed-form formula having been obtained with the help of the artificial neural network (ANN) is proposed and discussed in detail for the first time for a cylindrical close/open-coiled helical spring with fixed ends and having a solid circular section. As far as the author knows there is no such a formula in the open-literature to consider the effects of all stress resultants (torsional and bending moments, axial and shearing forces), large helix pitch angles together with the axial and shear deformations on the buckled state. The present formula may be used in a wide range of the total number of active turns, the ratio of the free axial length to the mean helix diameter, and the spring index. It is yet again revealed that it is not appropriate to use the elementary theory to determine the critical buckling loads for open-coiled springs. The present formula may allow the deeper understanding of spring buckling mechanism and to be used directly and safely in the design processes of such closely/open-coiled springs.
{"title":"A Closed-Form Buckling Formula for Open-Coiled and Properly Supported Circular-Bar Helical Springs","authors":"Yildirim Vebil","doi":"10.2478/scjme-2018-0025","DOIUrl":"https://doi.org/10.2478/scjme-2018-0025","url":null,"abstract":"Abstract As a continuation of the author’s previous studies on the buckling analysis of helical springs, a closed-form formula having been obtained with the help of the artificial neural network (ANN) is proposed and discussed in detail for the first time for a cylindrical close/open-coiled helical spring with fixed ends and having a solid circular section. As far as the author knows there is no such a formula in the open-literature to consider the effects of all stress resultants (torsional and bending moments, axial and shearing forces), large helix pitch angles together with the axial and shear deformations on the buckled state. The present formula may be used in a wide range of the total number of active turns, the ratio of the free axial length to the mean helix diameter, and the spring index. It is yet again revealed that it is not appropriate to use the elementary theory to determine the critical buckling loads for open-coiled springs. The present formula may allow the deeper understanding of spring buckling mechanism and to be used directly and safely in the design processes of such closely/open-coiled springs.","PeriodicalId":35968,"journal":{"name":"Strojnicky Casopis","volume":"68 1","pages":"33 - 48"},"PeriodicalIF":0.0,"publicationDate":"2018-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.2478/scjme-2018-0025","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47184153","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract In the article we show the possibility of distorting the results of the experiment by photoelasticity path, in case the isochromatic fringe patterns are recorded by the camera. The recording of the color spectrum may be distorted by inappropriate selection of the recording medium, which is reflected by different types of aberrations. Transferring a record to a computer allows you to automate the experiment process, thus saving time to work with isochromatic fringes. As an example, we present the experimental determination of the stresses of the rotor with a symmetrical arm. The analysis was performed using software developed by the authors. This software enables full automation of the experiment process. The rotor is investigated by the method of reflection photoelasticity. The experimental solution is realized as a case of periodically repeating dynamic effects, in which a stroboscopic source of white light is needed. The results of the experiment are compared with the numerical solution and their dependence is represented by diagram.
{"title":"Distorsion of Isochromatic Fringes in the Process of Stress Measurement in Structural Part by Photoelasticimetry","authors":"P. Frankovský, O. Ostertag, I. Delyová","doi":"10.2478/scjme-2018-0017","DOIUrl":"https://doi.org/10.2478/scjme-2018-0017","url":null,"abstract":"Abstract In the article we show the possibility of distorting the results of the experiment by photoelasticity path, in case the isochromatic fringe patterns are recorded by the camera. The recording of the color spectrum may be distorted by inappropriate selection of the recording medium, which is reflected by different types of aberrations. Transferring a record to a computer allows you to automate the experiment process, thus saving time to work with isochromatic fringes. As an example, we present the experimental determination of the stresses of the rotor with a symmetrical arm. The analysis was performed using software developed by the authors. This software enables full automation of the experiment process. The rotor is investigated by the method of reflection photoelasticity. The experimental solution is realized as a case of periodically repeating dynamic effects, in which a stroboscopic source of white light is needed. The results of the experiment are compared with the numerical solution and their dependence is represented by diagram.","PeriodicalId":35968,"journal":{"name":"Strojnicky Casopis","volume":"68 1","pages":"53 - 60"},"PeriodicalIF":0.0,"publicationDate":"2018-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42905284","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract The buckling analysis of carbon nanotubes without and with hetero-junctions is described in this paper. The buckling behaviour was investigated by the finite element method and the carbon nanotubes were modelled as space frame structures. The results showed that the critical buckling force depends on the dimensions of carbon nanotubes. The critical buckling forces of hetero-junction carbon nanotubes are in range between critical buckling forces of carbon nanotubes of both used diameters with the same chiralities without hetero-junction.
{"title":"Buckling Analysis of Hetero-Junction Carbon Nanotubes","authors":"J. Bocko, P. Lengvarský, Juraj Šarloši","doi":"10.2478/scjme-2018-0013","DOIUrl":"https://doi.org/10.2478/scjme-2018-0013","url":null,"abstract":"Abstract The buckling analysis of carbon nanotubes without and with hetero-junctions is described in this paper. The buckling behaviour was investigated by the finite element method and the carbon nanotubes were modelled as space frame structures. The results showed that the critical buckling force depends on the dimensions of carbon nanotubes. The critical buckling forces of hetero-junction carbon nanotubes are in range between critical buckling forces of carbon nanotubes of both used diameters with the same chiralities without hetero-junction.","PeriodicalId":35968,"journal":{"name":"Strojnicky Casopis","volume":"68 1","pages":"16 - 9"},"PeriodicalIF":0.0,"publicationDate":"2018-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44282286","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract This paper treats influencing factors in the determination of vehicles speed on the pedestrian crash moment according to pedestrian throw distance and formulates a mathematical model for vehicle speed determination. Vehicle speed is one of the highest causes of accidents. The mathematical model formulation (as the target of this paper) for velocity calculation, in the case of pedestrian accidents, presents great help and guidance to experts of this field when dealing with accident analysis that through accurate determination of this parameter to find other circumstances as close as possible to the technical process of pedestrian accidents. The target of this paper is to define a mathematical model formulation for vehicle velocity calculation in pedestrian crash moment depending on relevant parameters. For the purpose of model formulating, we have selected three cases of real accidents that involved vehicles (“Peugeot 307”, “VW Golf ” and “Mercedes E 220”) with different geometrical parameters of the front profile and pedestrians with different heights and weights. For regression analysis we used “R” and “SPSS” software, which enables the statistical analysis of the data and mathematical model formulation. Also, for analysis of impact of relevant factors, model formulation and model testing have used “Virtual Crash” and “PC Crash” software, which enables pedestrian-vehicle crash simulation using vehicles with real technical characteristics and various pedestrian characteristics. Inductive, comparative, and deductive methods are part of the research methods in this paper.
{"title":"Mathematical Model for Velocity Calculation of Three Types of Vehicles in the Case of Pedestrian Crash","authors":"Hoxha Gëzim, Shala Ahmet, Likaj Ramë, Bajrami Xhevahir","doi":"10.2478/scjme-2018-0029","DOIUrl":"https://doi.org/10.2478/scjme-2018-0029","url":null,"abstract":"Abstract This paper treats influencing factors in the determination of vehicles speed on the pedestrian crash moment according to pedestrian throw distance and formulates a mathematical model for vehicle speed determination. Vehicle speed is one of the highest causes of accidents. The mathematical model formulation (as the target of this paper) for velocity calculation, in the case of pedestrian accidents, presents great help and guidance to experts of this field when dealing with accident analysis that through accurate determination of this parameter to find other circumstances as close as possible to the technical process of pedestrian accidents. The target of this paper is to define a mathematical model formulation for vehicle velocity calculation in pedestrian crash moment depending on relevant parameters. For the purpose of model formulating, we have selected three cases of real accidents that involved vehicles (“Peugeot 307”, “VW Golf ” and “Mercedes E 220”) with different geometrical parameters of the front profile and pedestrians with different heights and weights. For regression analysis we used “R” and “SPSS” software, which enables the statistical analysis of the data and mathematical model formulation. Also, for analysis of impact of relevant factors, model formulation and model testing have used “Virtual Crash” and “PC Crash” software, which enables pedestrian-vehicle crash simulation using vehicles with real technical characteristics and various pedestrian characteristics. Inductive, comparative, and deductive methods are part of the research methods in this paper.","PeriodicalId":35968,"journal":{"name":"Strojnicky Casopis","volume":"68 1","pages":"110 - 95"},"PeriodicalIF":0.0,"publicationDate":"2018-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45810386","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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