Strojniski Vestnik-Journal of Mechanical Engineering最新文献

{"title":"Nonlinear Dynamic Force Balance Mass-spring-damper Modelof Laser Droplet Generation from a Metal Wire","authors":"A. Jeromen, E. Govekar","doi":"10.5545/SV-JME.2019.6062","DOIUrl":"https://doi.org/10.5545/SV-JME.2019.6062","url":null,"abstract":"Direct laser metal deposition is one of the established metal-based additive manufacturing processes [1]. It usually employs input material in shape of wire [2] or powder [3]. In contrast to the wire or powder deposition process, where the laser is used to generate melt pool on the workpiece surface, the process of metal droplet deposition significantly reduces the workpiece heat load, since the laser beam is used only for droplet generation. In consequence, metal droplets have been employed in various innovative technologies, including the droplet joining of electrical contacts, and of dissimilar and temperaturesensitive materials [4], as well as 3D printing [5]. A necessary basis for droplet-based technologies is a reliable method for the generation of metal droplets. To achieve this, a number of metal-droplet generation methods based on melt ejection from a nozzle have been developed, employing different techniques to generate the ejection pulse: piezoelectric [6], pneumatic [7], solenoid [8], and electromagnetic [9]. The above methods employ a heated crucible to maintain a reservoir of molten metal. Metals with relatively low melting temperatures are used, such as solder [9], indium, lead, zinc [7], and aluminum [10]. To avoid an energy-inefficient crucible and simplify the system, a method employing induction melting of the wire tip in the pressurized tube leading to the nozzle was proposed [11]. Common to all of the above methods is the nozzle, the diameter of which should be well below the diameter of the generated droplets and is subject to wear. To avoid melt oxidation, leading to nozzle clogging, a low-oxygen-content atmosphere should be provided [7]. Besides the methods based on melt ejection, several laser-based methods have been developed that take advantage of the high level of spatial and temporal control of the laser’s energy delivery. They differ in terms of the shape of the input metal material, which can be either a foil [12], a spherical preform [13], or a wire [14]. Although it achieves lower dropletgeneration frequencies compared to melt-ejection methods, the laser droplet generation from a wire using an annular laser beam [15] shows strong application potential, since it can employ metals with a high melting point, such as nickel [14], is not very sensitive to oxygen content, and the related system includes no wearable parts. In annular laser beam droplet generation (ALDG), a metal wire is fed axially into the center of the annular laser beam, which is focused on the circumference of the wire-end. ALDG can be performed either as drop-on-demand ALDG [14], where the pendant-droplet formation and detachment Nonlinear Dynamic Force Balance Mass-spring-damper Model of Laser Droplet Generation from a Metal Wire Jeromen, A. – Govekar, E. Andrej Jeromen* – Edvard Govekar University of Ljubljana, Faculty of Mechanical Engineering, Slovenia","PeriodicalId":49472,"journal":{"name":"Strojniski Vestnik-Journal of Mechanical Engineering","volume":"68 1","pages":"201-211"},"PeriodicalIF":1.7,"publicationDate":"2018-04-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90760842","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Application of LCS and Information Entropy as a Novel Fusion Algorithm for Degradation Feature Extraction","authors":"Haotian Wang, Jian Sun, Xiusheng Duan, Ganlin Shan, Wen Yang","doi":"10.5545/sv-jme.2017.4671","DOIUrl":"https://doi.org/10.5545/sv-jme.2017.4671","url":null,"abstract":"Feature extraction is significant for the prognostics and health management (PHM) of hydraulic pumps. In this paper, a novel fusion algorithm is proposed based on local characteristic-scale decomposition (LCD), composite spectrum (LCS). and information entropy. To make full use of feature information, the LCS is proposed based on the modification of traditional composite spectral algorithm. LCS high-order power entropy and high-order singular entropy, which are relatively defined in Shannon entropy (SE) and Tsallis entropy (TE), are extracted as initial features. Furthermore, the method of feature fusion is presented to modify the features’ conciseness and to improve the performance. Results of the analysis in the experiment indicate that the proposed method is available, and the fused feature is effective in evaluating the pump degradation process.","PeriodicalId":49472,"journal":{"name":"Strojniski Vestnik-Journal of Mechanical Engineering","volume":"27 1","pages":"17-25"},"PeriodicalIF":1.7,"publicationDate":"2018-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86517078","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Numerical Study of Heat Transfer Enhancement for Low-Pressure Flows in a Square Cavity with Two Fins Attached to the Hot Wall Using Al2O3-Air Nanofluid","authors":"W. Al-Kouz, S. Kiwan, Ammar Alkhalidi, M. Sari, Aiman Alshare","doi":"10.5545/sv-jme.2017.4989","DOIUrl":"https://doi.org/10.5545/sv-jme.2017.4989","url":null,"abstract":"The gaseous low-pressure nanofluid flow of a steady-state two-dimensional laminar natural convection heat transfer in a square cavity of length L with two attached solid fins to the hot wall is numerically investigated. Such flows are found in many engineering applications, such as nuclear reactors and electronic cooling equipment. Physical parameter ranges in this study are as follows: 0 ≤ Kn ≤ 0.1, 103 ≤ Ra ≤106, 0 ≤ ϕ ≤ 0.2, LF/L takes the value of 0.5, HF takes the values of 0.25 to 0.75. Simulation results show that Nusselt number depends directly on the Rayleigh number and inversely on the Knudsen number. In addition, it is found that heat transfer will be enhanced by dispersing the nanoparticles of Al2O3 in the base low-pressure gaseous flow. Moreover, it is found that the Nusselt number of such flows increases as the nano-particle volume fraction increases for the investigated range of volume fractions considered in this study. In addition, a correlation of the Nusselt number among all the investigated parameters in this study is proposed as Nu = 0.2196 Ra0.0829 Kn–0.511 ϕ0.104.","PeriodicalId":49472,"journal":{"name":"Strojniski Vestnik-Journal of Mechanical Engineering","volume":"11 1","pages":"26-36"},"PeriodicalIF":1.7,"publicationDate":"2018-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89553280","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Nonlinear Control of a Flexible Joint Robotic Manipulator with Experimental Validation","authors":"Waqar Alam, A. Mehmood, Khurram Ali, U. Javaid, S. Alharbi, J. Iqbal","doi":"10.5545/SV-JME.2017.4786","DOIUrl":"https://doi.org/10.5545/SV-JME.2017.4786","url":null,"abstract":"This article addresses the design and implementation of robust nonlinear control approaches to obtain the desired trajectory tracking of a flexible joint manipulator driven with a direct-current (DC) geared motor. The nonlinear control schemes have been designed and implemented such that they locally stabilize the closed loop system considering all the states as bounded. The system model has been derived using Euler-Lagrange approach. Two different approaches based on sliding mode control (SMC), i.e. the traditional SMC and integral SMC, have been considered in the present study. To experimentally validate the proposed control laws, an electrically-driven single-link flexible manipulator has been designed and fabricated. The designed control algorithms have been developed and experimentally validated on the custom-developed platform. The results obtained both from MATLAB/Simulink and the experimental platform verify the performance of the proposed control algorithms.","PeriodicalId":49472,"journal":{"name":"Strojniski Vestnik-Journal of Mechanical Engineering","volume":"39 1","pages":"47-55"},"PeriodicalIF":1.7,"publicationDate":"2018-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85044550","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Studying the Fatigue Life of a Non-pneumatic Wheel by Using Finite-Life Design for Life Prediction","authors":"Zhen Xiao, Qun Zhao, Fen Lin, Mingmin Zhu, Jinlian Deng","doi":"10.5545/sv-jme.2017.4695","DOIUrl":"https://doi.org/10.5545/sv-jme.2017.4695","url":null,"abstract":"To avoid pneumatic tire puncture, blow-out and other problems, a new type of non-pneumatic safety wheel called the mechanical elastic wheel (ME-Wheel) has been developed and investigated. The durability of the ME-Wheel is studied to improve its life; at the same time, the best preventive maintenance period can also be provided for the users, to ensure the safety and reliability of the ME-Wheel in operating conditions. The finite-life design method is proposed to predict the ME-Wheel life; the weakest component of ME-Wheel is ascertained by analysing its structure static strength, and the predicted model of pin for lifetime theory is established by using finite-life design method. Furthermore, the ME-Wheel durability is simulated using the finite element method (FEM) on the basis of the established virtual proving ground, and the enhancement coefficient is combined to calculate ME-Wheel lifespan. Finally, the results of theoretical calculation and simulation are verified using endurable road testing. The results show that the methods of theoretical calculation and simulation, which are applied in our paper to predict the lifespan of ME-Wheel, are highly congruent with the experimental results. Therefore, the proposed method is also entirely suitable for other mechanical structures in the durability research field.","PeriodicalId":49472,"journal":{"name":"Strojniski Vestnik-Journal of Mechanical Engineering","volume":"10 1","pages":"56-67"},"PeriodicalIF":1.7,"publicationDate":"2018-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79653596","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Analysis of the Bulk Coal Transport State of a Scraper Conveyor Using the Discrete Element Method","authors":"Xuewen Wang, Bo Li, Zhaojian Yang","doi":"10.5545/sv-jme.2017.4790","DOIUrl":"https://doi.org/10.5545/sv-jme.2017.4790","url":null,"abstract":"A scraper conveyor is the main transport equipment in a coal mine, and its condition considerably influences the production capacity and profitability of the enterprise. In this study, the discrete element method (DEM) was used to study the interaction between the scraper conveyor and bulk coal. The particle size and velocity distributions of bulk coal were analysed at different transport velocities, transport angles, feed velocities and mining heights by changing the transport conditions of the conveyor. The influence of the transport velocity, coefficient of static friction between particles and mass flow rate were also studied. The results showed that the particle size distribution of bulk coal is mostly unrelated to the transport state parameters in the stable transport stage. Large particles gather at higher positions, whereas small particles gather at lower positions. The speed of bulk coal in the front area of the scraper was equal to the velocity of the scraper, whereas the coal in other locations had a lower speed. The mass flow rate of the bulk coal increased with increasing transport velocity and reached its peak when the coefficient of static friction between particles was 0.4.","PeriodicalId":49472,"journal":{"name":"Strojniski Vestnik-Journal of Mechanical Engineering","volume":"198 1","pages":"37-46"},"PeriodicalIF":1.7,"publicationDate":"2018-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73670359","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Fabrication of High Chromium White Iron Surface Layers on Ductile Cast Iron Substrate by Laser Surface Alloying","authors":"D. Janicki","doi":"10.5545/SV-JME.2017.4379","DOIUrl":"https://doi.org/10.5545/SV-JME.2017.4379","url":null,"abstract":"High chromium white iron surface layers (HWSLs) have been produced on a ductile cast iron EN-GJS-700-2 substrate by diode laser surface alloying with a direct injection of a pure chromium powder into the molten pool. The main objective of this study was to investigate the effect of laser alloying parameters on the microstructural evolution in the HWSLs. The composition of the uniformly alloyed HWSLs contained up to 14.4 wt.% Cr. Both hypoeutectic and eutectic high chromium white iron microstructures were obtained. The type and morphology of eutectic carbides are affected by both the chromium concentration in the molten pool and the solidification conditions. With increasing chromium content, the fraction of eutectic regions in the hypoeutectic HWSLs increases and the eutectic carbides become progressively smaller. The rodtype morphology of the M7C3 eutectic carbides was dominant in the eutectic HWSLs. An average hardness of the HWSLs was influenced by the size of carbide precipitations, and was 675 HV and 650 HV for hypoeutectic and eutectic compositions, respectively.","PeriodicalId":49472,"journal":{"name":"Strojniski Vestnik-Journal of Mechanical Engineering","volume":"117 1","pages":"705-714"},"PeriodicalIF":1.7,"publicationDate":"2017-11-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73046876","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Rapid and Automatic Zero-Offset Calibration of a 2-DOF Parallel Robot Based on a New Measuring Mechanism","authors":"J. Mei, Jiawei Zang, Yabin Ding, Shenglong Xie, Xu Zhang","doi":"10.5545/SV-JME.2017.4529","DOIUrl":"https://doi.org/10.5545/SV-JME.2017.4529","url":null,"abstract":"This paper deals with the rapid and automatic zero-offset calibration of a 2-DOF parallel robot using distance measurements. The calibration system is introduced with emphasis on the design of a new measuring mechanism. A simplified error model of the robot is proposed after the sensitivity analyses of source errors, based on which a zero-offset identification model is developed using the truncated singular value decomposition (TSVD) method, and then it is modified with the manufacturing and assembly errors of the measuring mechanism (MAEMM). Furthermore, an optimization approach for selecting measurement positions is proposed by considering the condition number of the identification matrix. Finally, simulations and experiments are carried out to verify the effectiveness of the zero-offset calibration method. The results show that the identification model has good identifiability and robustness, and the position accuracy after calibration can be significantly improved.","PeriodicalId":49472,"journal":{"name":"Strojniski Vestnik-Journal of Mechanical Engineering","volume":"70 1","pages":"715-724"},"PeriodicalIF":1.7,"publicationDate":"2017-11-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86339261","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"An Analysis of Continuous Sandwich Panels with Profiled Faces","authors":"M. Čuk, F. Kosel, Nenad Đ. Zrnić, B. Jerman","doi":"10.5545/SV-JME.2017.4844","DOIUrl":"https://doi.org/10.5545/SV-JME.2017.4844","url":null,"abstract":"Structural sandwich panels made of two thin steel facings that are bonded to a thick mineral wool core are often used as roofing material. This paper explores an application of numerical simulations in the investigation of structural behaviour of long span, continuous roof sandwich panels with profiled faces. Because of the required higher load-bearing capacity and strict deflection limitations, roof sandwich panels usually have one of the cover faces strongly profiled. A finite element analysis and an experimental study of a long span sandwich panel (with an inner strongly profiled and a flat outer face) in two-span configuration with transverse loading were conducted with a special attention given to the failure modes and bearing capacity prediction. The results obtained from the experiment confirmed the finite element analysis results.","PeriodicalId":49472,"journal":{"name":"Strojniski Vestnik-Journal of Mechanical Engineering","volume":"277 1","pages":"746-753"},"PeriodicalIF":1.7,"publicationDate":"2017-11-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82358672","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Classification of Malignancy in Suspicious Lesions Using Autofluorescence Bronchoscopy","authors":"Tomaž Finkšt, J. Tasic, M. Terčelj, M. Meza","doi":"10.5545/SV-JME.2016.4019","DOIUrl":"https://doi.org/10.5545/SV-JME.2016.4019","url":null,"abstract":"This paper presents a novel approach to the classification of bronchial tissue as either malignant or precancerous based on autofluorescence bronchoscopy (AFB) images. The study consisted of 44 images, of which 22 were confirmed as malignant and 22 as nonmalignant precancerous cases. Our approach starts with the detection of a region of interest (ROI). This is followed by an analysis of semi-normal intensity distributions in gray-scale images of red and green components of the previously identified ROI. Based on the results of this analysis, features are computed, which are then used to build an image-classification model. This model classifies the tissue images into malignant/nonmalignant classes. We utilized several classification algorithms, i.e., naive Bayes, K-nearest-neighbor (K-NN), and support vector machine (SVM) with dot kernel. The criteria used when testing their performance were accuracy, sensitivity, specificity, and the area under the curve. Wilcoxon’s signed-rank test was used to confirm the accuracy of the classification method. The proposed method was compared to a similar approach reported by Buountris et al., who analyzed the texture features in a gray-level co-occurrence matrix (GLCM). Using the bestperforming classification algorithm (SVM with dot kernel), the accuracy of the proposed approach (95.8 %) was better than that reported by Bountris et al. (92.1 %).","PeriodicalId":49472,"journal":{"name":"Strojniski Vestnik-Journal of Mechanical Engineering","volume":"474 1","pages":"685-695"},"PeriodicalIF":1.7,"publicationDate":"2017-11-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84046212","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}