Igor Emri - Academia.edu (original) (raw)

Papers by Igor Emri

Flow of granular material during processing, handling and transportation strongly influences the ... more Flow of granular material during processing, handling and transportation strongly influences the quality of the final product and its cost, that is why it is important to measure flow properties of granular materials. Flowability of granular materials depends on the characteristics of the material and on the conditions at which flow is occurring. In this paper a new methodology is introduced to measure friction between granular materials under pressure induced with uniaxial compression. Apparatus also allows analysis of conditions at which granular material starts to flow when exposed to uniaxial compressive load, i.e., zero-rate flowability. We call the apparatus the Granular Friction Analyzer (GFA).

Kovine zlitine tehnologije, 1997

Materials Today: Proceedings, 2016

Long-term behavior of polymers and their composites is related mainly to their time-dependent mec... more Long-term behavior of polymers and their composites is related mainly to their time-dependent mechanical properties, i.e. material functions or master curves, usually obtained by time-temperature superposition (tTS) principle. The “weakest” point utilizing tTS lies in “manual or hand” shifting procedure, which can lead to over- or under-estimated life span of polymeric materials. This problem was solved by using closed form mathematical solution called Closed-Form-Shifting (CFS) algorithm which completely removes issues of “manual or hand” shifting procedure. However, it is important to acknowledge that tTS is well established only within the realm of linear viscoelastic theory. Results have shown that utilizing tTS in non-linear domain, where time-dependent properties become dependent on magnitude of external load, my lead to construction of misleading master curves, i.e. overestimated long-term behavior of polymers that could consequently cause premature failure of polymeric products.

Materials Today: Proceedings

Journal of Membrane Science, 2018

Mechanical properties and drug permeability of the PA6 membranes prepared by immersion precipitat... more Mechanical properties and drug permeability of the PA6 membranes prepared by immersion precipitation from PA6-formic acid-water system,

Construction and Building Materials, 2017

h i g h l i g h t s Creep compliance of bitumen impregnated fiberglass mat (BIFM) is investigated... more h i g h l i g h t s Creep compliance of bitumen impregnated fiberglass mat (BIFM) is investigated. Creep response of BIFM is compared with polymer modified bitumen (PMB) sample. Results show significant improvement in the performance of BIFM at higher temperatures. Retardation spectra obtained are capable of accurately reconstructing creep response.

Applied Mechanics and Materials, 2016

Polymers always show time-dependent mechanical properties. In order to use polymers in engineerin... more Polymers always show time-dependent mechanical properties. In order to use polymers in engineering applications, long-term mechanical propertes should be characterized. Free volume theroy is the mostly used theory to predict and model the mechanical properties of polymers. The effect of temperature is modelled thorugh William-Landel-Ferry (WLF) equation, whereas, the combined effect of temperature and pressure is modelled by Filler-Moonan-Tschoegl (FMT) equation. Both of the models are based on free volume theory. A set of expermentations were performed to investigate the validity of free volume concpet for one of the most important engineering polymer; i.e. Polyamide-6.

Rheologica Acta, 2016

The closed-form shifting (CFS) algorithm is a simple mathematical methodology which determines th... more The closed-form shifting (CFS) algorithm is a simple mathematical methodology which determines the unique solution in the process of constructing master curves at selected reference temperature and pressure conditions. In a previous paper, the CFS algorithm has been fully described for monotonically increasing or monotonically decreasing functions only. This paper presents detailed steps of the generalized CFS methodology for non-monotonic functions, like the loss tangent. Performing shifting on the loss tangent, which does not require vertical shifting, is particularly important for materials which require vertical adjustment of dynamic viscoelastic functions, i.e., loss and storage moduli. Thus, based on horizontal shifting of the loss tangent, the CFS-based procedure of consecutive Marina Gergesova

Journal of Cereal Science, 2007

The effect of hydrostatic pressure (0.1–800MPa) in combination with various temperatures (30–80°C... more The effect of hydrostatic pressure (0.1–800MPa) in combination with various temperatures (30–80°C) on the chemical and physical properties of wheat gluten, gliadin and glutenin was studied. Chemical changes of proteins were determined by extraction, reversed-phase high-performance liquid chromatography (HPLC), sodium dodecylsulphate (SDS) polyacrylamide gel electrophoresis (PAGE), circular dichroism (CD) spectroscopy, thiol measurement and studies on disulphide bonds. Rheological changes were measured by extension tests and dynamic stress rheometry. Treatment of gluten with low pressure (200MPa) and temperature (30°C) increased the proportion of the ethanol-soluble fraction (ESF) and decreased gluten strength. The enhancement of both pressure and temperature provoked a strong reduction of the ESF and the thiol content of gluten. Within gliadin types, cysteine containing α- and γ-gliadins, but not cysteine-free ω-gliadins were sensitive to pressure and were transferred to the ethanol-insoluble fraction. Disulphide peptides isolated from treated gluten confirmed that cleavage and rearrangement of disulphide bonds were involved in pressure-induced reactions. Increased pressure and temperature induced a significant strengthening of gluten, and under extreme conditions (e.g. 800MPa, 60°C), gluten cohesivity was lost. Isolated gliadin and glutenin reacted differently: solubility, HPLC and SDS-PAGE patterns of gliadin having a very low thiol content were not influenced by pressure and heat treatment; only conformational changes were detected by CD spectroscopy. In contrast, the properties of isolated glutenin having a relatively high thiol content were strongly affected by high pressure and temperature, similar to the effects on total gluten.

Anali PAZU

Članek obravnava znanje izuma, ki temelji na patentirani disipativni zrnati visokotlačni tehnolog... more Članek obravnava znanje izuma, ki temelji na patentirani disipativni zrnati visokotlačni tehnologiji. Ugotovljeno je bilo, da je z ustrezno izbiro dušilnega materiala in hidrostatičnim tlakom, ki mu je material izpostavljen med nakladanjem, mogoče ujemati največje lastnosti dušenja materiala s pogostostjo ali hitrostjo uporabljene obremenitve. Na ta način lahko v celoti izkoristimo lastnosti dušenja izbranega materiala in povečamo absorpcijske lastnosti lopute. Z uporabo tega edinstvenega potenciala disipativne zrnate visokotlačne tehnologije je mogoče zgraditi vrhunske dušilne elemente, ki za nekaj vrst presegajo obstoječe dušilne elemente. Uporaba takšnih blažilnih elementov vključuje na primer nosilce za industrijske stroje za dušenje vibracij, temelje v gradbenih konstrukcijah za zmanjšanje dovzetnosti za potresne poškodbe in resonanco, pa tudi vlake in železniške tire za zmanjšanje vibracij med potovanjem in za izboljšanje pasivne varnosti avtomobilov na cestah prevoz. Ta člane...

Polymers

Granular materials promise opportunities for the development of high-performance, lightweight vib... more Granular materials promise opportunities for the development of high-performance, lightweight vibration-damping elements that provide a high level of safety and comfort. Presented here is an investigation of the vibration-damping properties of prestressed granular material. The material studied is thermoplastic polyurethane (TPU) in Shore 90A and 75A hardness grades. A method for preparing and testing the vibration-damping properties of tubular specimens filled with TPU granules was developed. A new combined energy parameter was introduced to evaluate the damping performance and weight-to-stiffness ratio. Experimental results show that the material in granular form provides up to 400% better vibration-damping performance as compared to the bulk material. Such improvement is possible by combining both the effect of the pressure–frequency superposition principle at the molecular scale and the effect of the physical interactions between the granules (force-chain network) at the macro s...

Springer eBooks, 2018

Effect of pressure on material properties of polymers Definitions Polymer is a substance consisti... more Effect of pressure on material properties of polymers Definitions Polymer is a substance consisting of macromolecules of different lengths, which have a long sequence of one or more groups of monomeric units (shorter molecules) linked together with a primary or covalent chemical bond. Time-dependent mechanical property is the characteristic of a polymer (or any other viscoelastic material) that interrelates the cause in the form of stress or strain and the timedependent response (in the form of increasing strain or decaying stress). Time-pressure superposition principle claims that material function can be generated by shifting isobaric segments of time-dependent mechanical properties measured at different pressures along the logarithmic time scale in respect to the segment selected at reference pressure. Compressibility is a measure of relative change of the volume of polymer exposed to the pressure change.

Mechanics of Time-Dependent Materials, 2016

Health monitoring systems for plastic based structures require capability of real time tracking c... more Health monitoring systems for plastic based structures require capability of real time tracking changes in response of polymer based structures, related to their time-dependent behavior. The paper proposes artificial neural networks as a tool of solving inverse problem appearing within time-dependent material characterization, since the conventional methods are computationally demanding and cannot operate in a real time mode. Abilities of a Multilayer Perceptron (MLP) and a Radial Basis Function Neural Network (RBFN) to solve ill-posed inverse problems on an example of determination of a time-dependent relaxation modulus curve segment from constant strain rate tensile test data are investigated. The required modelling data composed of strain rate, tensile and related relaxation modulus were generated using existing closed-form solution. Several neural networks topologies were tested with respect to the structure of input data and their performance was compared to an exponential fitting technique. Selected optimal topologies of MLP and RBFN were tested for generalization and robustness on noisy data; performance of all the modeling methods with respect to the number of data points in the input vector was analyzed as well. It was shown that MLP and RBFN are capable of solving inverse problems related to the determination of time dependent relaxation modulus curve segment. Particular topologies demonstrate good generalization and robustness capabilities, where the topology of RBFN with data provided in parallel proved to be superior compared to other methods.

Polymers, Mar 4, 2023

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Experimental Techniques, Jul 1, 1999

Experimental Techniques, May 1, 2000