Машински факултет [Научни радови] / Faculty of Mechanical Engineering [Scientific papers]
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- СтавкаReliability Evaluation of Transmission Planetary Gears “bottom-up” approach(Polish Maintanace Society, 2023) Živković, Predrag; Milutinović, Miroslav; Tica, Milan; Trifković, Spasoje; Čamagić, IvicaThe reliability study is the most important part of the engineering design process, as it is the basis of analysis and assessment of future product performance in exploitation. Since performance cannot be predicted with absolute certainty, the application of reliability theory includes probability theory and unreliability modeling. The proposed approach has been applied to assess the reliability of gear planetary power transmissions. The assessment of system reliability was determined on the basis of the block diagram method, as a function of the reliability of individual components, calculated by statistical analysis. Using the Weibull model, the reliability of the planetary gear was defined on the basis of the probability of failure of the gear teeth and the results were interpreted to assess the reliability of the component and the entire planetary train. For a more precise assessment of reliability and to avoid modeling every failure and mode of occurrence, a competitive risk model was developed. The reliability assessment study was conducted with a “bottom-up” approach. Reliability has been assessed, for instantaneous, estimated and assigned failures rate of planetary train and component.
- СтавкаOPTIMIZATION OF ENERGY MIX AND POSSIBILITIES OF ITS APPLICATION IN ENERGY TRANSITION USING MULTI-CRITERIA DECISION MAKING APPROACH(Vinca Inst Nuclear Sci, Serbia, 2023) MRKIĆ-BOSANČIĆ, Maja; VASKOVIĆ, Srdjan; GVERO, PetarThe process of optimizing energy production is becoming increasingly important with the development and use of RES and energy efficiency measures. Given that these are optimization processes that require taking into account several indicators according to which the set of optimal technologies for energy production will be ranked, and take their percentage share in the total percentage of energy supply. Indicators describing the process of energy production and utilization include technological, environmental, economic, energy, and limiting domains of their application. From that aspect, when the energy supply process is optimized from several possible alternatives according to the optimization factors defined in this way and the percentage of participation from each is calculated, a very realistic picture of the optimal energy mix of a state or local community is obtained. In this paper, a comparison of the energy mix for Copenhagen, Denmark and Banja Luka, Bosnia and Herzegovina is made. The process of comparing energy mixes was made possible by a previously developed mathematical model for optimizing and searching for an optimal energy mix based on the compromise ranking method, also known as the VIKOR, as well as entropy and analytic hierarchy process methods for defining weight values of criteria describing energy mix. Since we know that the introduction of new RES and the replacement of fossil fuels with them is a process of transition of existing energy sectors, the approach presented in this paper would greatly facilitate the transition process itself.
- СтавкаNext-Gen Manufacturing: Machine Learning for Surface Roughness Prediction in Ti-6Al-4V Biocompatible Alloy Machining(MDPI, 2023) Kosarac, Aleksandar; Tabakovic, Slobodan; Mladjenovic, Cvijetin; Zeljkovic, Milan; Orasanin, GoranMechanical engineering plays an important role in the design and manufacture of medical devices, implants, prostheses, and other medical equipment, where the machining of bio-compatible materials have a special place. There are a lot of different conventional and non-conventional types of machining of biocompatible materials. One of the most frequently used methods is milling. The first part of this research explores the machining parameters optimization minimizing surface roughness in milling titanium alloy Ti-6Al-4V. A full factorial design involving four factors (cutting speed, feed rate, depth of cut, and the cooling/lubricating method), each having three levels, implies the 81 experimental runs. Using the Taguchi method, the number of experimental runs was reduced from 81 to 27 through an orthogonal design. According to the analysis of variance (ANOVA), the most significant parameter for surface roughness is feed rate. The second part explores the possibilities of using different ML techniques to create a predictive model for average surface roughness using the previously created small datasets. The paper presents a comparative analysis of several commonly used techniques for handling small datasets and regression problems. The best results indicate that the widely used machine learning algorithm Random Forest excels in handling regression problems and small datasets.
- СтавкаAnalysis of Power Losses in Constrained Cycloid Drive(Strojarski Facultet, Sveucilist Joseph Jurj Strossmayer in Osijeka, 2023) MAČKIĆ, Tihomir; MARJANOVIĆ, Nenad; TICA, Milan; TROHA, Sanjin; MILUTINOVIĆ, Miroslav; RAŠOVIĆ, NebojšaThe aim of this paper is to present a theoretical model for efficiency evaluation of a simple cycloid drive train with one degree of freedom (DOF) or constrained cycloid drive. In order to evaluate the efficiency, it is necessary to find the losses generated in the simple cycloid drive, where only losses depending on the load were considered. Expressions for determining speed ratios, efficiency, velocities and forces acting inside the cycloid drive are presented. These expressions are implemented in the theoretical model, where the places where the losses occur are defined. A computer program was created to facilitate analysis and obtain loss values based on different input data. Only load-dependent losses were considered in the theoretical model and computer program. In order to verify the theoretical model, experimental measurements were performed. A physical model of the simple cycloid drive train was created and analyzed on the test bench. The results for "S1" operating mode, i.e. when shaft 2 is stopped, show a mean value of the efficiency of 63.49%, for experimental measurements, while the mean value for theoretical analysis is 65.25%. For the operating mode "S2", i.e. with shaft 1 stopped, the mean value of the experimental measurements of the efficiency is 60.9%, while the theoretical mean value is 62.82%.
- СтавкаInfluence of Surface Preparation of Aluminum Alloy AW-5754 and Stainless Steel X5CRNI18-10 on the Properties of Bonded Joints(MDPI, 2024) Zdravković, Nataša; Klobčar, Damjan; Milčić, Dragan; Zupančić, Matevž; Žužek, Borut; Milčić, Miodrag; Ðurić, AleksijaAdhesive bonding has proven to be a reliable method of joining materials, and the development of new adhesives has made it possible to use bonding in a variety of applications. This article addresses the challenges of bonding metals such as the aluminum alloy EN AW-5754 and the stainless steel X5CrNi18-10. In this study, the effects of laser cleaning and texturing on the surface properties and strength of two bonded joints were investigated and compared with mechanical preparation (hand sanding with Scotch-Brite and P180 sandpaper). The bonded joints were tested with three different epoxy adhesives. During the tests, the adhesion properties of the bonded surface were determined by measuring the contact angle and assessing the wettability, the surface roughness parameters for the different surface preparations, and the mechanical properties (tensile lap-shear strength). Based on the strength test results, it was found that bonded joints made of stainless steel had 16% to 40% higher strength than aluminum alloys when using the same adhesive and surface preparation. Laser cleaning resulted in maximum shear strength of the aluminum alloy bond, while the most suitable surface preparation for both materials was preparation with P180 sandpaper for all adhesives.