Eksperimentalno modeliranje i numerička FE analiza procesa izvlačenja sa stanjenjem čeličnih traka

This paper deals with analysis of steel strip ironing using experimental modelling and numerical FE simulation. Since both approaches are complementary to each other, numerous results were obtained that enable complete analysis of the processes within deformation zone. Device for modelling of strip ironing has been developed for experimental testing. Die cone angle, holding force, contact friction conditions on the die and the punch side were varied, due to easily replaceable working elements of the device. Friction coefficient values used in numerical FE simulations were determined based on measured values of forces on die and punch, as well as forming load on machine. Experimentally obtained results were confirmed by FE analysis that provided additional information about physics of the process itself within deformation zone. Presented research results point to coherent influences of process factors on tensile wall stress values, which represents key indicator for efficiency of forming, resulting in recommendations for efficient process management.Rad se bavi analizom procesa izvlačenja sa stanjenjem čelične trake, primjenom eksperimentalnog modeliranja i numeričkih FE simulacija. Kako su oba pristupa komplementarna, dobiveno je mnoštvo rezultata za sveobuhvatnu analizu procesa u deformacijskoj zoni. Za potrebe eksperimentalnog modeliranja razvijen je uređaj za modeliranje procesa izvlačenja sa stanjenjem trake. Zahvaljujući lako izmjenjivim radnim elementima uređaja, varirane su vrijednosti kuta matrice, sile držanja, uvjeti kontaktnog trenja na strani izvlakača i matrice. Vrijednosti faktora trenja, korištenih u numeričkim FE simulacijama su određene na osnovu izmjerenih vrijednosti sila na matrici i izvlakaču, kao i ukupne sile na stroju. Eksperimentalno dobiveni rezultati potvrđeni su numeričkom FE analizom, pri čemu je ona dala dodatne informacije o samoj fizici procesa u deformacijskoj zoni. Prikazani rezultati istraživanja ukazuju na spregnute utjecaje analiziranih faktora procesa na iznos rasteznog naprezanja u stijenki matrice, koji predstavlja ključni pokazatelj uspješnosti obrade, iz kojih proizlaze preporuke za uspješno upravljanje procesom

ARTIFICAL NEURAL NETWORKS IN RF MEMS SWITCH MODELING

The increased growth of the applications of RF MEMS switches in modern communication systems has created an increased need for their accurate and efficient models. Artificial neural networks have appeared as a fast and efficient modeling tool providing similar accuracy as the standard commercial simulation packages. This paper gives an overview of the applications of artificial neural networks in modeling of RF MEMS switches, in particular of the capacitive shunt switches, proposed by the authors of the paper. Models for the most important switch characteristics in electrical and mechanical domains are considered, as well as the inverse models aimed to determine the switch bridge dimensions for given requirements for the switch characteristics

Efekat prelaska sa konvencionalne na konzervacijsku obradu i setvu pšenice, soje, stočnog graška i pasulja

These paper presents and analyzes the results achieved in assays of production wheat, soybean, bean, which is set to determine exploitation, energy and environmental effects of land use conservation tillage and direct seeding. The work will be displayed along side conventional and conservation planting these cultures of working hours,fuel, yield, comparative two different conceptions of cultivation and sowing.U radu se prezentuje i analizira ostvareni rezultati na ogledima pšenice, soje, pasulja koji je postavljen radi utvrđivanja eksploatacionih, energetskih i ekoloških efekata u primeni konzervacijske obrade zemljišta direktne setve. U radu će se prikazati uporedo konvencionalna i konzervacijska setva navedenih kultura i analiza utroška radnih sati, goriva, prinosa, uporedne radne operacije dve različite koncepcije obrade zemljišta i setve

Experimental study of physical parameters significant in fullerene synthesis

In this work, the effect of physical parameters on the yield of fullerene, synthesized in a hollow cathode plasma reactor is investigated. The experimental investigations done previously have shown that the fullerene yield depended on tehcnical parameters - the current intensity, inert gas pressure, type of gas and interelectrode gap. The aim of this work was to show that the fullerene yield depends on physical parameters - carbon concentration, carbon flow rate from the interelectrode gap, axial temperature and temperature gradient between the. arc channel and the chamber walls as,well. It was found that fullerene synthesis occurs in an inert heat bath with dimensions determined by die temperature gradient. The lower temperature limit is around 2000 K and the value of the upper limit is die value of the axis temperature which depends on the discharge conditions. The synthesis of fullerenes is more effective if the carbon concentration in the heat bath is large and the carbon flow rate from that zone to colder parts of chamber is small

Artificial Neural Network based Design of RF MEMS Capacitive ShuntSwitches

Artificial neural networks (ANNs) have appeared as a very efficient alternative to time consuming full-wave simulations of electrical characteristics of RF MEMS. In this paper, a new ANN based method to be used in the design of RF MEMS devices is proposed. ANNs are trained to model dependence of the scattering parameters and the resonant frequency of an RF MEMS switch on the switch geometrical parameters, as well as to perform the opposite procedure, i.e., to determine values of the geometrical parameters to achieve the desired electrical resonant frequency. The developed models can be used for fast simulation and optimization of the switch characteristics replacing time consuming procedures in full-wave simulators, which leads to a significant reduction of time needed for the device design.9 halama