One of the major problems in experimental vibration analysis is to determine location of transducers. It is important to place the transducers on locations with largest vibration amplitude and to avoid locations with zero-movement (nodal lines). These locations are best seen from vibration mode shapes. Finite element analysis (FEA) provides numerical values for natural frequencies, which are sorted by size and not by mode shapes. Computer visualization can be used to recognize mode shapes and to perform proper classification of FEA results.

Validation is the subjective process that determines the accuracy with which the mathematical model describes the actual physical phenomenon. This research was conducted in order to validate the use of finite element analysis for springback compensation in 3D scanning of sheet metal objects. The measurement uncertainty analysis was used to compare the digitized 3D model of deformed sheet metal product with the 3D model obtained by simulated deformation. The influence factors onto 3D scanning and numerical simulation processes are identified and analysed. It is shown that major contribution to measurement uncertainty comes from scanning method and deviations of parts due to manufacturing technology. The analysis results showed that numerical methods, such as finite element method, can successfully be used in computeraided quality control and automated inspection of manufactured parts.

REZIME Kućanski aparati i uredska oprema troše više od četvrtine ukupne potrošnje električne energije i nakon vrijednosti utrošene energije za prijevoz je najbrže rastući sektor potrošnje energije. U razvijenim zemljama, energetska učinkovitost se promovira standardnim oznakama, kojima se potiče upotreba učinkovitijih uređaja. Usvajanje zakona koji tretiraju oblast energetske učinkovitosti dio je postupka ispunjavanja uvjeta koje zahtijeva proces europske integracije i uspostavljanja mjeriteljske infrastrukture u Bosni i Hercegovini. Zakoni koji tretiraju ovu oblast u BiH nisu usvojeni i moraju se usvojiti što prije. Svrha izvršenog istraživanja je bila provjera karakteristika uređaja deklariranih od strane proizvođača, posebno sa metrološkog aspekta i problematike vezane na mjerenja i uvjete zahtijevane standardom EN50304:2001. Provjera energetske učinkovitosti je izvršena u lokalnoj laboratoriji, čime je pokazano da se uz mala ulaganja u mjernu opremu ova ispitivanja mogu izvršiti u Bosni i Hercegovini.

The idea of using buckling analysis to predict wrinkling of sheet metal products manufactured by incremental forming is presented in this paper. We start from assumption that buckling analysis can be used to obtain geometry of product after first forming operation. That shape and critical buckling force are calculated using finite element method in elastic domain. The analysis was performed for various values of tool diameter. Results were tested through measurement of product geometry after first forming operation. The analysis showed that upper tool diameter can be reduced without change in product quality expressed through number of wrinkles.

Truss structures are widely used in construction of large-scale buildings. Design of steel structures is standardised in detail through set of European standards called EUROCODE. One of these standards, ENV 1993-1-8 deals with design of joints, but it does not cover the design of conical element for reduction of circular hollow section to the joint. Finite element method was used in this paper to analyse this conical element with complex shape. The chosen design parameters were varied in order to obtain smooth stress distribution. Results showed that existing design can be modified, reducing the mass while keeping stress levels within acceptable limits.

Truss structures are widely used in construction of large-scale buildings. Design of steel structures is standardised in detail through set of European standards called EUROCODE. One of these standards, ENV 1993-1-8 deals with design of joints, but it does not cover the design of conical element for reduction of circular hollow section to the joint. Finite element method was used in this paper to analyse this conical element with complex shape. The chosen design parameters were varied in order to obtain smooth stress distribution. Results showed that existing design can be modified, reducing the mass while keeping stress levels within acceptable limits.

A common technology for manufacturing of large-scale vessel-ends is incremental forming. The first step in forming process is based on buckling phenomena. The buckling mode shapes of circular plate influence wrinkling and surface quality of final product. Increased number of wrinkles in the first forming step lengthens the manufacturing process and increases the number of forming steps needed. To obtain the desired buckling mode shape, an analysis was performed by varying tool parameters. The analysis resulted in defined relationship between tool parameters and buckling mode shapes, and guidelines for the tool design in terms of minimum wrinkling.

A experiences show that on vessel head quality the most effect make pressure force, radius of tool and number and order of operations. This paper present results of tool radius effect on pressure vessel heads quality made by numerical and experimental researches. Numerical analysis is performed by calculating critical buckling force. Presumption is, that wrinkling of circular plate after first deformation make the greatest effect on number of operations, and it directly instance on residual stress magnitude and distribution in finally product.

The quality of 3D scanned data is influenced by many factors, such as scanned surface colour, glossiness, geometry, ambient light, scanner resolution, proper selection of scanned segments, etc. Ambient light is important source of errors, especially for scanners that are based on projected patterns and structured lighting. The laser 3D scanners are also influenced by ambient light, and this paper studies the effects of ambient light on a specific commercial scanner. Preparatory phase of digitising process includes selecting proper combination of scanner’s sensor aperture and shutter time, depending on the characteristics of scanned surface. This paper investigates a relationship between the ambient light intensity, the colour of scanned surface, and the laser scanning quality.

Nermina Zaimović-Uzunović, Samir Lemeš , Fuad Hadžikadunić, Nedeljko Vukojević 1 University of Sarajevo, Faculty of Mechanical Engineering in Zenica., nzaimovic@mf-ze. unsa. ba 2 University of Sarajevo, Faculty of Mechanical Engineering in Zenica., slemes@mf-ze. unsa. ba 3 University of Sarajevo, Faculty of Mechanical Engineering in Zenica., hfuad@mf-ze. unsa. ba 4 University of Sarajevo, Faculty of Mechanical Engineering in Zenica., nvukojevic@mf-ze. unsa. ba

This paper gives research results about commercial examination of aluminum alloy-based products according to industrial standards. Results of metallographic tests of extruded aluminum microstructure shown in this paper indice that irregular deformation of material leads to microstructure variations through certain zones of the product. That influences mechanical properties, and it can even be the main cause of indications obtained by penetrants.

Plastic products nowdays are used more and more, previously as a substitution for expencive products made of other materials. Parts of machines like gears can be made of plastics by injection moulding process. Quality of the tools in the injection moulding process and quality of the material are main factors for a good product. In this paper trends and criterions in selection of thermoplastic material for injection moulding are presented. The characteristics of different kinds of plastics are also described, specially for the materials for mechanical parts production. 1. UVOD 1.1. Osobine plastike Šira primjena plastičnih materijala faktički je započela tek u drugoj polovini 20. vijeka. Jedan od razloga za to je i smanjenje izvora prirodnih materijala uz porast broja ljudi na Zemlji. Plastika i u pogledu zaštite čovjekove okoline ima svijetlu budućnost u smislu recikliranja, kao i biorazgradivih plastika. To je jedan od razloga sve veće primjene termoplasta. Tako naprimjer, prema članku “Potrošnja plastike u ekonomiji USA” [1], napravljenog od strane Probe Economics iz 1997. godine, potrošnja plastike se drastično povećava, pa npr. u 1996. godini je u USA potrošeno 95,6 mild. kubnih metara plastike. Najčešće korišćeni tipovi plastike su Polypropylene, Polystyrene i PVC. Od 1994. do 1996. godine porast potrošnje se kreće oko 6% godišnje, za razliku od perioda od 1989. do 1996. godine kada je rast proizvodnje bio 5,3% godišnje. Vrijednost ukupne isporuke plastike u 1996. godini je u USA bila 274,5 mild. US$ i porasla je za 5,5% u odnosu na 1991. godinu. Broj zaposlenih radnika u industriji plastike je bio oko 1.400.000 u 1996. godini. Ovi podaci dovoljno govore o razvijenosti industrije plastike i daljim razvojnim tendencijama u najrazvijenijoj zemlji svijeta. Na Slici 1. prikazana je generalna podjela svih materijala i unutar te podjele i mjesto plastike u odnosu na ostale materijale. Slika 1. Podjela materijala [2] Na osnovu prethodne podjele, plastike uključuju sve polimere koji se ne javljaju u prirodi, sve sintetske elastomere i sve visoko modifikovane polimere. Sama riječ polimer potiče kao složenica iz grčkih riječi poly i meros i predstavlja takvu tvar koja se sastoji od mnogo čestica sastavljenih na specifičan način. Polimeri su posebna grupa materijala koji su uglavnom sastavljeni od elemenata: ugljik, vodik i kisik a ponekad sadržavaju i hlor, fluor ili azot. Prema tehničkom ponašanju, polimerni materijali se mogu podijeliti na: ― termoplaste (plastomere, termoplastike), ― duromere (duroplaste), ― elastomere. Ako se termoplastika zagrijava, ona doživljava promjenu stanja, postaje mekana ili rastopljena, dok ne postane fluid. Kada se termoplastika hladi, ona se ponovo stvrdnjava. Ovaj proces se može više puta ponavljati. Ovo je razlog što je, kada se radi sa termoplastikom, dio za plastifikaciju mašine za injekciono presovanje zagrijan a kalup hladan. Obično je razlika temperatura između dijela za plastifikaciju i kalupa viša od 100 C. Zato kalup mora brzo i stabilno odvesti toplotu tečne plastike, tj. neophodno je kvalitetno dizajnirati sistem za hlađenje. Sredstvo za hlađenje je obično voda, i ona teče kroz kanale kalupa sve dok je temperatura kalupa ispod 100 C. Sredstvo za hlađenje cirkuliše ili se ugrađuje izmjenjivač toplote koji omogućuje hlađenje. Zato što je rastopljena termoplastika više ili manje fluid (u zavisnosti od tipa termoplastičnog materijala), vrh vretena za plastifikaciju treba biti opremljen sa nepovratnim ventilom. 1.2. Karakteristike, prednosti i nedostaci plastike 1.2.1. Prednosti plastike Masa: Gustoća plastičnog materijala je približno 10% od gustoće čelika. Kod transporta redukcija mase ima mnoge prednosti. Smanjenje mase vozila ili aviona utiče na ekonomičnost potrošnje goriva i performance. Smanjenje mase proizvoda koji se treba transportovati može biti takođe bitno. Ovo ima uticaj kako na ekonomičnost tako i na zaštitu čovjekove okoline. Smanjenje mase komada može takođe olakšati rukovanje (alati, obrada, itd.). Ovo može uticati i na ličnu sigurnost kod transporta proizvoda u pogledu samopovređivanja. Tabela 1. Količina energije potrebna za dobijanje proizvoda [3] Materijal Cp (J/kg K) Tm(C) Q (J/kg) Al 895 700 611,331 Fe 45

Summary: Steam boiler is a large industrial agregate which is very sensitive to temperature variations. In the period of work the steam production and high temperatures cause displacements of the construction. The consequences are various: construction is flexibile and suspended on the springs, while large displacements lead to the cracks at the weak parts of the steam boiler. In transient startup period, which can be extended on a whole day, steam boiler changes its dimensions. Extremely high elongations occur in the vertical direction, where there are no constrains. Measurements of the displacements of the steam boiler were performed using telemetric equipment and displacement sensors. The measured values discussed in this paper, are result of one-year study of the steam boiler behaviour in thermo power plant. Results are important and were used to manage working parameters of the steam boiler.