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Comparison of different optimization and process control procedures
Marko Reibenschuh, Franc Čuš, Uroš Župerl, 2010, pregledni znanstveni članek

Opis: This paper includes a comparison of different optimization methods, used for optimizing the cutting conditions during milling. It includes also a part of using soft computer techniques in process control procedures. Milling is a cutting procedure dependent of a number of variables. These variables are dependent from each other in consequence, if we change one variable, the others change too. PSO and GA algorithm are applied to the CNC milling program to improve cutting conditions, improve end finishing, reduce tool wear and reduce the stress on the tool, the machine and the machined part. At the end a summary will be given of pasted and future researches.
Ključne besede: optimization, milling, cutting parameters, LENS
Objavljeno: 04.08.2017; Ogledov: 113; Prenosov: 22
.pdf Celotno besedilo (481,24 KB)

Fatigue crack initiation and propagation in lotus-type porous material
Srečko Glodež, Sašo Dervarič, Janez Kramberger, Matjaž Šraml, 2016, izvirni znanstveni članek

Opis: The investigation of fatigue strength of lotus-type structure with nodular cast iron as a base material using computational model is analysed in present study. The irregular pores distribution in transversal and longitudinal direction, regarding the external loading, is considered in the computational models. The complete fatigue process of analyzed porous structure is then divided into the crack initiation (Ni) and crack propagation (Np) period where the total fatigue life (N) is defined as: N = Ni + Np. The crack initiation period is determined using strain life approach where elastic-plastic numerical analysis is performed to obtain the total strain amplitude in the critical stress fields around the pores. The simplified universal slope method is then used to determine the number of stress cycles, Ni, required for formation of initial cracks. The number of stress cycles, Np, required for crack propagation from initial to the critical crack length is also numerically determined using finite element (FE) models, in the frame of Abaqus computation FEM code. The maximum tensile stress (MTS) criterion is considered when analyzing the crack path inside the porous structure. The performed computational analyses show that stress concentrations around individual pores are higher when external loading is acting in transversal direction in respect to the pore distribution. Therefore, further computational analyses regarding crack initiation and crack propagation period have been done only for pores distribution in transversal direction.
Ključne besede: lotus-type porous structures, fatigue crack initiation, fatigue crack propagation, numerical analysis
Objavljeno: 02.08.2017; Ogledov: 197; Prenosov: 36
.pdf Celotno besedilo (4,75 MB)

Damage and failure modeling of lotus-type porous material subjected to low-cycle fatigue
Janez Kramberger, Klemen Sterkuš, Srečko Glodež, 2016, izvirni znanstveni članek

Opis: The investigation of low-cycle fatigue behaviour of lotus-type porous material is presented in this paper. Porous materials exhibit some unique features which are useful for a number of various applications. This paper evaluates a numerical approach for determining of damage initiation and evolution of lotus-type porous material with computational simulations, where the considered computational models have different pore topology patterns. The low-cycle fatigue analysis was performed by using a damage evolution law. The damage state was calculated and updated based on the inelastic hysteresis energy for stabilized cycle. Degradation of the elastic stiffness was modelled using scalar damage variable. In order to examine crack propagation path finite elements with severe damage were deleted and removed from the mesh during simulation. The direct cyclic analysis capability in Abaqus/Standard was used for low-cycle fatigue analysis to obtain the stabilized response of a model subjected to the periodic loading. The computational results show a qualitative understanding of pores topology influence on low-cycle fatigue under transversal loading conditions in relation to pore orientation.
Ključne besede: porous materials, low-cycle fatigue, damage, finite element analysis
Objavljeno: 02.08.2017; Ogledov: 130; Prenosov: 44
.pdf Celotno besedilo (2,32 MB)

Computational simulation of biaxial fatigue behaviour of lotus-type porous material
Janez Kramberger, Marko Šori, Matjaž Šraml, Srečko Glodež, 2016, izvirni znanstveni članek

Opis: A computational simulation of low-cycle fatigue behaviour of lotus-type porous material, subjected to biaxial in-phase loading cycles is presented in this paper. Fatigue properties of porous materials are less frequently published in the literature. This paper evaluates computational analyses, where different pore distribution and biaxial loading conditions in relation to the pore orientations is considered in each simulation. The fatigue analysis is performed by using a damage initiation and evolution law based on the inelastic strain energy. The computational results are subjected to the appropriate statistical analysis, because of different pore topology a different fatigue lives are obtained on the same loading level. Results of computational simulations show also a qualitative understanding of porosity influence on low-cycle fatigue failures of lotus-type porous material under biaxial loading conditions.
Ključne besede: Lotus-type porous material, low-cycle fatigue, damage, finite element analysis
Objavljeno: 02.08.2017; Ogledov: 144; Prenosov: 35
.pdf Celotno besedilo (1,08 MB)

Influence of the temperature on the efficiency of cellulose treatment using copolymer chitosan-eugenol
Olivera Šauperl, Jasna Tompa, Julija Volmajer Valh, 2014, izvirni znanstveni članek

Opis: In order to achieve effective antimicrobial protection of textile materials against microorganisms, a natural compound called chitosan has become very interesting. In regard to the antimicrobial protection of textile materials, functionalization with chitosan does not affect some other properties, such as anti-oxidative or any other action. For this reason, it seems appropriate for chitosan to be combined with any natural antimicrobial active compound, such as eugenol, an extract of clove oil. During this research viscose as a representative of cellulose fibers was used, because it can be functionalized relatively easily. In terms of functionalization, the drying temperature of viscose, after antimicrobial compound application onto substrate, as well as the successful synthesis of copolymer chitosan/eugenol is also important. FTIR spectroscopy was used to evaluate the efficiency of synthesizing a chitosan/eugenol graft copolymer. The spectrophotometric method Acid Orange 7 was chosen as a means for determining the proportion of available antimicrobial active amino groups. In addition, microbiological testing of selected pathogenic micro-organisms was also performed. The results were compared with the results for viscose functionalized by a 1% solution of chitosan.
Ključne besede: chitosan, eugenol, functionalization, viscose, FTIR spectroscopy, Acid orange 7, antimicrobial
Objavljeno: 02.08.2017; Ogledov: 160; Prenosov: 29
.pdf Celotno besedilo (233,00 KB)

Chemical binding of chitosan and chitosan nanoparticles onto oxidized cellulose
Olivera Šauperl, Mirjana Kostić, Jovana Milanovic, Lidija Fras, 2015, izvirni znanstveni članek

Opis: The aim of this study was to analyze binding of chitosan and chitosan nanoparticles onto cellulose via oxidized cellulose. The ability of chitosan and chitosan nanoparticles to be adsorbed onto surfaces was determined by the use of the XPS spectroscopy which provided information about chemical composition of the fiber surface. On the other hand, the gravimetric method was also used by which the amount of chitosan and chitosan nanoparticles bounded onto surface was calculated based on the difference in masses before and after functionalization. The most important was to study the influence of aldehyde groups on the stability of chitosan binding onto cellulose. Thus, desorption of chitosan/chitosan nanoparticles from the fiber surfaces was evaluated by the presence of total nitrogen (TN) in desorption bath as well as by polyelectrolyte titrations. Together with these two methods, desorption was evaluated also by gravimetric method, where the extent of desorption was evaluated on the basis of the differences in the masses of fibers before and after desorption. It is concluded that the chitosan and chitosan nanoparticles are more efficiently bounded onto oxidized cellulose in comparison with the non-oxidized (reference) ones. Despite the binding of the positively-charged amino groups with the negative groups of cellulose and consequently smaller amount of available/residual protonated amino groups that are responsible for bioactivity, such functionalized fibers are still specifically antimicrobial.
Ključne besede: cellulose, oxidized cellulose, oxidation, chitosan, chitosan nanoparticles, FTIR, XPS, antimicrobial functionalization
Objavljeno: 02.08.2017; Ogledov: 223; Prenosov: 61
.pdf Celotno besedilo (144,32 KB)

Experimental testing of single APM spheres
Matej Vesenjak, Lovre Krstulović-Opara, 2010, objavljeni znanstveni prispevek na konferenci

Opis: Advanced pore morphology (APM) foam, consisting of sphere-like metallic foam elements, proves to have advantageous mechanical properties and unique application adjustability. Since the APM foam manufacturing procedure has been developed recently, the mechanical characterization of these materials is still very limited. Therefore, the purpose of this research was to determine the behaviour of APM spheres and its composites when subjected to quasi-staticand dynamic compressive loading. The results of the performed research have shown valuable mechanical properties of the composite APM foam structures, offering new possibilities for their use in general engineering applications.
Ključne besede: advanced pore morphology, foam, composite APM foam structures
Objavljeno: 26.07.2017; Ogledov: 252; Prenosov: 27
.pdf Celotno besedilo (1,61 MB)

Effect of low-density static magnetic field on the oxidation of ammonium by Nitrosomonas europaea and by activated sludge in municipal wastewater
Jasmina Filipič, Ines Mandić-Mulec, Brigita Tepuš, Vanja Kokol, Barbara Kraigher, 2015, izvirni znanstveni članek

Opis: Ammonium removal is a key step in biological wastewater treatment and novel approaches that improve this process are in great demand. The aim of this study is to test the hypothesis that ammonium removal from wastewater can be stimulated by static magnetic fields. This was achieved by analysis of the effects of static magnetic field (SMF) on the growth and activity of Nitrosomonas europaea, a key ammonia-oxidising bacterium, where increased growth and increased ammonia oxidation rate were detected when bacteria were exposed to SMF at 17 mT. Additionally, the effect of SMF on mixed cultures of ammonia oxidisers in activated sludge, incubated in sequencing batch bioreactors simulating wastewater treatment process, was assessed. SMFs of 30 and 50 mT, but not of 10 mT, increased ammonium oxidation rate in municipal wastewater by up to 77 % and stimulated ammonia oxidiser growth. The results demonstrate the potential for use of static magnetic fields in increasing ammonium removal rates in biological wastewater treatment plants.
Ključne besede: odpadne vode, bakterije, Nitrosomonas europaea, statično magnetno polje, biološke čistilne naprave, nitrifikacija
Objavljeno: 24.07.2017; Ogledov: 162; Prenosov: 16
.pdf Celotno besedilo (323,02 KB)

Advances in production and industrial engineering
2017, znanstvena monografija

Opis: This publication, scientific monograph, offers comprehensive chapter series from scientific researchers conducted by regional authors, authorities in the fields and summarizes the principal scientific contributions. The chapters deal with range topics from optimization techniques in production development, quality in production processes, product and process development, technologies for business development and factors of social and economic development. Edited by two editors with contributions from chapters’ authors, this scientific monograph presents advanced topics for students, educators and practitioners. The editors would like to thank all chapters’ authors for devoting of the research results and expertise with the great enthusiasm. We encourage all of them to continue successful highly valuable cooperation, between Faculty of Mechanical Engineering at the University of Maribor and Faculty of Mechanical Engineering at the Ss. Cyril and Methodius University in Skopje.
Ključne besede: mechanical engineering, production management, manufacturing, artificial intelligence, process development, economic development
Objavljeno: 19.07.2017; Ogledov: 286; Prenosov: 15
.pdf Celotno besedilo (8,32 MB)

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