vi[enamjenske vij^ane ma[inemf.unze.ba/wp-content/uploads/2016/10/masinstvo-num1-2004.pdf ·...

Ma{instvo 1(8), 3 – 16, (2004) N.Sto{i}, ...: VI[ENAMJENSKE VIJÂNE MA[INE

VI[ENAMJENSKE VIJÂNE MA[INE Nikola Sto{i}, Ian K. Smith and Ahmed Kova~evi}, Centre for Positive Displacement Compressor Technology, City University, London EC1V OHB, U.K., [email protected] REZIME

Volumetrijske ma{ine se koriste kao kompresori i kao ekspanderi, a vij~ane volumetrijske ma{ine imaju dodatnu prednost nad ostalima zato {to mogu istovremeno komprimirati i ekspandirati na jednom paru rotora. Naime, ako se profil rotora konstrui{e tako da zaptiva na obje strane, onda se isti rotor moè koristiti za obje funkcije, na jednoj strani za kompresiju, a na drugoj za ekspanziju radnog fluida. Takvi se rotori mogu proizvesti istim alatom u jednom prolazu, dok se `lijeb koji razdvaja kompresor i ekspander moè izraditi nakon {to su zubi ve} formirani. [tovi{e, pogodnim postavljanjem ulaznih i izlaznih otvora sile pritiska su na takvom rotoru manje u poredjenju sa silama na rotorima dvije odvojene ma{ine ~ime su mehani~ki gubici kombinovane ma{ine manji. Vi{enamjenske vij~ane ma{ine se mogu koristiti kao zamijena za prigu{ni ventil u rashladnim i klimatizacionim postrojenjima, a mogu se primijeniti i u postrojenjima sa visokim pritiscima radnog fluida, zatim u gorivnim }elijama, ili pri vi{estepenoj kompresiji ili ekspanziji i zaista u svim slu~ajevim gdje se traì istovremena kompresija i ekspanzija radnog medija. Primjer jedne takve neuobi~ajene primjene jeste regulacija protoka kompresora djelomi~nom ekspanzijom vi{ka komprimiranog gasa.

Klju~ne rije~i: Vij~ani kompresor, Vij~ani ekspander, Kompresija i ekspanzijana na jednom paru rotora

MULTIFUNCTIONAL SCREW MACHINES

Nikola Stosic, Ian K. Smith and Ahmed Kovacevic, Centre for Positive Displacement Compressor Technology, City University, London EC1V OHB, U.K., [email protected]

ABSTRACT: Positive displacement machines can be used both as expanders and compressors but those of the twin screw type have a potential advantage over others in that they can act both simultaneously, using only one pair of rotors. A further feature of theirs is that their rotors can be designed to seal on both contacting surfaces so that the same profile may be used for the expander and the compressor sections. By this means, the compressor and expander rotors can be manufactured in a single cutting operation and then separated by machining the parting slot in them on completion of the lobe formation. Moreover, with such an arrangement, by proper location of the machine ports, the pressure loads and therefo e the mechanical friction losses will be less than if the two functions are performed in separate machines. Fields of application for such machines are throttle valve replacement in refrigeration and air conditioning plant, high-pressure compression, fuel cells, multistage compression or expansion and, any other application where simultaneous compression and expansion are required. One unusual example of this is to control compressor capacity by partial expansion of the compressed gas.

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Keywords: Screw Compressor, Screw Expander, Compression and Expansion on one Rotor Pair

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1. UVOD

Vij~ani kompresori su pouzdane i kompaktne volumetrijske ma{ine koje danas ~ine zna~ajan udio u ukupnom broju kompresora na tr`istu i u upotrebi. Osnovni razlozi ovog uspjeha su moderan pristup u razvoju i primjeni novih profila rotora koji zna~ajno smanjuju unutra{enje curenje u ma{ini, kao i napredni postupci i alatne ma{ine kojima se uz prihvatljivu cijenu mogu proizvesti kompleksni oblici rotora vij~anih kompresora sa proizvodnim tolerancijama manjim od 3 µm. Smatra se da je pobolj{anje profila rotora jo{ uvijek najefikasniji na~in za unapredjenje vij~anih kompresora. Danas se velika pa`nja poklanja razvoju metoda kojima se stari oblici profila dobiveni na empirijski na~in zamjenjuju novima ili se mijenjaju proporcije postoje}ih profila kako bi se postigle optimalne performanse kompresora za zahtijevanu primjenu. Osim toga, ta~nije odredjivanje optere}enja i njihovih fluktuacija na rotorima omogu}uje precizniji izbor le`ajeva. Kona~no, ako se deformacije rotora i ku}i{ta usljed povi{ene temperature i pritiska odrede pouzdano, onda se i proizvodni postupci mogu prilagoditi tako da se umanji negativni efekat deformacija na rad kompresora. Vij~ane ma{ine rade sa razli~itim radnim fluidima, koji mogu biti gasovi, pare ili vi{efazne mje{avine te~nosti i pare koje mijenjaju fazu unutar ma{ine. Pri tome se ulje ili neki drugi fluid ubrizgava tokom procesa kompresije ili ekspanzije, ili se process odvija bez njihovog prisustva. Geometrija rotora i cijele ma{ine razli~ita je u zavisnosti od broja zubi na rotorima, od profila rotora i od relativnih proporcija svakog zuba ili njegovih segmenata. Prema tome, ne postoji jedinstvena konfiguracija niti profil rotora koji bi bili jednako dobri za sve namjene vij~anih ma{ina. Zbog toga je detaljna termodinamska analiza procesa kompresije ili ekspanzije potrebna pri odredjivanju uticaja razli~itih konstruktivnih parametara na ukupne performanse vij~ane ma{ine. Dobro definisani kriteriji u okviru pouzdane optimizacione procedure neophodni su preduvjeti za ostvarenje najbolje konstrukcije za svaku posebnu primjenu. Sli~ne smjernice su neophodne za dalje unapredjenje postoje}ih konstrukcija vij~anih ma{ina i za pro{irenje sada{njeg podru~ja njihove primjene. Fleming i drugi 1998, daju dobar prikaz vij~anih kompresora kao i matematskih modela njihovih procesa.

1. INTRODUCTION Screw compressors are reliable and compact machines. Consequently, they comprise a substantial portion of all positive displacement compressors now sold and of those currently in operation. The main reasons for their success are the development of novel rotor profiles, which have drastically reduced internal leakage, and advanced machine tools, which can manufacture the most complex shapes to tolerances of the order of 3 microns at an acceptable cost. Rotor profile enhancement is still the most promising means of further improvement of screw compressors and rational procedures are now being developed both to replace earlier empirically derived shapes and also to vary the proportions of a selected profile to obtain the best result for the application for which the compressor is required. In addition, improved modelling of flow patterns within the machine can lead to better porting design. Also, more accurate determination of bearing loads and how they fluctuate enable better choices of bearings to be made. Finally, if rotor and casing distortion, as a result of temperature and pressure changes within the compressor, can be estimated reliably, machining procedures can be devised to minimise their adverse effects. Screw machines operate on a variety of working fluids, which may be gases, dry vapour or multi-phase mixtures with phase changes taking place within the machine. This may include oil flooding, other fluids injected during the compression or expansion process, or total absence of internal lubrication. Their geometry may vary depending on the number of lobes in each rotor, the basic rotor profile and the relative proportions of each rotor lobe segment. It follows that there is no universal configuration, which would be the best for all applications. Hence, detailed thermodynamic analysis of the compression process and evaluation of the influence of the various design parameters on performance is more important to obtain the best results from these machines than from other types which could be used for the same application. A set of well defined criteria governed by an optimisation procedure is, therefore, a prerequisite for achieving the best design for each application. Such guidelines are also essential for further improvement of the existing screw machine designs and broadening their range of use. Fleming et al, 1998 gives a good review of screw compressor modelling, design and application.

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Jedna od va`nih osobina vij~anog kompresora jeste da on mo`e raditi kao ekspander ako mu se promijeni smijer obrtanja rotora. [tovi{e, ako otvori visokog i niskog pritiska izmjene mjesta na ku}i{tu, ma{ina }e raditi kao ekspander ~ak i ako zadr`i smjer obrtanja kao kompresor.

An important feature of screw machines is that if the direction of rotation of their rotors is reversed, then gas will flow in through the high pressure port and out through the low pressure port and they will act as expanders.

2. ISTOVREMENA KOMPRESIJA I EKSPANZIJA NA JEDNOM PARU ROTORA Vij~ani kompresori su volumetrijske ma{ine koje se sastoje od jednog para spregnutih helikoidalnih rotora smje{tenih unutar ku}ista. Zajedno ku}i{te i rotori formiraju niz radnih prostora kao {to je prikazano na slici 1a, gdje se rotori vide sa gornje zadnje i sa donje prednje strane.

2. SIMULTANEOUS COMPRESSION AND EXPANSION IN ONE PAIR OF ROTORS Screw compressors are positive displacement rotary machines which consist, essentially, of a pair of meshing helical lobed rotors, contained in a casing. Together, these form a series of working chambers, as shown in Fig 1, by means of views from opposite ends and sides of the machine.

1a) Pogled sprijeda i odozgo 1b)Pogled straga i odozdo

Slika 1 Osnovne komponenete vij~ane ma{ine 1a) Front and Top View 1b) Bottom and Rear View

Figure 1 Screw Machine Main Components

Tamnije osjen~eni dijelovi predstavljaju radne prostore zatvorene ku}i{tem u kojima se odvija process kompresije, dok su svijetlo osjen~eni regioni rotora podlo`ni uticaju vanjskog pritiska. Veliki svijetli region pokazan na slici 1a odgovara usisnom otvoru niskog pritiska. Mali svijetli region izmedju dva vratila B i D na slici 1b predstavlja tla~ni otvor visokog pritiska. Gas koji treba komprimirati usisava se u kompresor kroz otvor niskog pritiska koji je postavljen na prednji gornji dio ku}i{ta. Usisavanje se odvija za vrijeme dok je radni prostor izmedju rotora otvoren prema usisnom otvoru.

The dark shaded portions show the enclosed region where the rotors are surrounded by the casing and compression takes place, while the light shaded areas show the regions of the rotors which are exposed to external pressure. The large light shaded area in Fig 1a) corresponds to the low pressure port. The small light shaded region between shaft ends B and D in Fig 1b) corresponds to the high pressure port. Admission of the gas to be compressed occurs through the low pressure port which is formed by opening the casing surrounding the top and front face of the rotors. Exposure of the space between the rotor lobes to the suction port, as their front ends pass across it, allows the gas to fill the passages formed between them and the casing.

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Obrtanjem rotora dolazi do zatvaranja usisnog otvora i dalje do smanjivanja volumena radnog prostora zahva}enog izmadju rotora i ku}i{ta sve dok se prostor izmedju rotora ne otvori prema tla~nom prostoru. Nakon toga gas izlazi kroz tla~ni otvor na pripribli`no konstantnom pritisku. Sa slike 1 se moè zaklju~iti da }e gas, ako se rotori obr}u u smjeru suprotnom od obiljeènog, ulaziti u ma{inu kroz otvor visokog pritiska, ekspandirati u radnom prostoru i kona~no izlaziti kroz otvor niskog pritiska. Pri tom }e ma{ina raditi kao ekspander. Ista }e ma{ina takodjer raditi kao ekspander ako se zadrì smjer obrtanja koji je imao kompresor, ali se usisni i izlazni otvori postave na suprotne strane od onih za kompresor. To je ustvari potpuno isto kao da se rotori obr}u u suprotmom smjeru relativno u odnosu na otvore. Kad radi kao kompresor, vij~anoj ma{ini se mora dovoditi rad. Kad radi kao ekspander, ma{ina }e se vrtjeti samostalno, a rad generisan u njoj }e se vratilom prenijeti van.

Further rotation then leads to cut off of the port and progressive reduction in the trapped volume in each passage, until the rear ends of the passages between the rotors are exposed to the high pressure discharge port. The gas then flows out through this at approximately constant pressure. Examination of Fig 1 shows that if the direction of rotation of the rotors is reversed, then gas will flow into the machine through the high pressure port and out through the low pressure port and it will act as an expander. Moreover, the machine will work as an expander when rotating in the same direction as a compressor provided if the suction and discharge ports are positioned on the opposite sides of the casing to those shown, since this is effectively the same as reversing the direction of rotation relative to the ports. When operating as a compressor, mechanical power must be supplied to shaft A to rotate the machine. When acting as an expander, it will rotate automatically and power generated within it will be supplied externally through a shaft.

Slika 2 Vi{enamjenski rotori na kojima se istovremeno odvija kompresija i ekspanzija Figure 2 View of the multifunctional rotors acting simultaneously as compressor and expander

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Istovremenu kompresiju i ekspanziju mogu}e je izvesti na jednom paru rotora ukoliko rotori zaptivaju na obje strane zuba. Takav princip rada prikazan je na slici 2. Kompresor i ekspander nalaze se unutar jedinstvenog ku}ista i medjusobno su odvojeni pregradom. Na~in na koji radni fluid ulazi u ma{inu i izlazi iz nje kriti~an je pa poloàj otvora odredjuje koliko }e biti optere}enje rotora silama pritiska. Na slici 2 je pokazano da gas visokog pritiska koji treba ekspandirati ulazi u ekspander kroz otvor visokog pritiska odozgo na sredini ma{ine, a izlazi kroz otvor niskog pritiska koji se nalazi na dnu ku}i{ta sa strane. Ekspanzijom se pritisak i temperatura radnog fluida u ma{ini sniàvaju. Pri tom se dobiva rad koji obr}e rotore. Gas za kompresiju ulazi kroz usisini otvor niskog pritiska sa strane na vrhu ku}i{ta, komprimira se izmedju rotora i izlazi kroz tla~ni otvor u sredini na dnu ku}ista. U idealnom slu~aju unutra{nje curenje izmedju posebnih komora kompresora i ekspandera ne postoji. Kako se kompresija i ekspanzija obavljaju u dvije posebne komore, profili rotora kompresora i ekspandera mogli bi biti razli~iti. Medjutim, proizvodnja takvih rotora na jednom vratilu bila bi oteàna zbog malog razmaka izmedju sekcija. Upotrebom istog profila za obje funkcije, rotor se moè glodati ili brusiti u jedinstvenoj operaciji i nakon formiranja zubi razdvojiti na kompresorski i ekspanderski dio prorezivanjem `lijeba izmedju njih. Takvi su rotori predstavljeni na slici 3. Vi{e podataka o ovom konceptu vij~ane ma{ine moè se na}i u ~lanku Sto{i} i drugi 2003

Both expansion and compression can be obtained on one pair of rotors, rotating in the same direction if the rotors form a seal on both contacting surfaces. Fig 2 shows the arrangement of a screw machine that demonstrates this principle. In this case, each set of rotors for compression and expansion is contained in a separate chamber within a single casing. As will be shown, the port layout, for admission and discharge of the fluid in the two sections, was chosen to minimise the machine bearing loads. In the layout shown in Fig 2, high pressure gas enters the expander port at the top of the casing near the centre and is expelled from the low pressure port at the bottom of the casing at one end. The expansion process causes the temperature to drop. However, here the fall in pressure is used to recover power and causes the rotors to turn. Gas enters the low pressure compressor port, at the top of the opposite end of the casing, is compressed within it and expelled from the high pressure discharge port at the bottom of the casing, near the centre, to be delivered to the atmosphere. Ideally, there is no internal transfer of fluid within the machine between the expansion and compression sections. Since the compression and expansion are carried out separately in this case, the compressor and expander profiles could be different. However, this would make manufacture extremely difficult, due to the small clearance space between the two rotor functions. By using the same profile for both, the compressor and expander, the rotors can be milled or ground in a single cutting operation and then separated by machining a parting slot in them on completion of the lobe formation. Such rotors are presented in Fig. 3. More information on this concept can be found in Stosic et al 2003.

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Slika 3. Rotori kompresora-ekspandera Figure 3. Compressor-Expander Rotor Profiles

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3. KONSTRUKTIVNE KARAKTERISTIKE VI[ENAMJENSKIH VIJÂNIH MA[INA Ma{ina sli~na onoj prikazanoj na slici 2 moè se koristiti i kao dvostepeni kompresor tako {to }e otvori niskog i visokog pritiska drugog stepena promijeniti mjesto u odnosu na otvore ekspandera. Otvor nièg pritiska drugog stepena bi}e na vrhu ku}ista u sredini, dok }e tla~ni otvor visokog pritiska biti na dnu ku}ista na kraju rotora. Time se dobiva kompaktna dvostepena ma{ina koja se moè koristiti u suhom re ìmu rada ili kao uljnopodmazivana ma{ina. Sli~na analiza va ì za dvostepeni ekspander. Ako se rotori koriste za vi{estepenu kompresiju ili ekspanziju, oni mogu zadràti oblik karakteristi~an za te ma{ine i ne zahtijeva se njihova obostrana zaptivenost kako je to slu~aj kod simultane kompresije i ekspanzije. Ako se vi{enamjenska vij~ana ma{ina koristi za istovremenu kompresiju i ekspanziju, tad njen ekspanderski dio moè biti opremljen regulatorom protoka u obliku kliù}eg ili podiù}eg ventila ~ime se mijenja zapremina ulaznog fluida za vrijeme djelomi~nog optere}enja ma{ine na sli~an na~in kao kod vij~anih kompresora i time regulisati protok kroz kombinovanu ma{inu. Osnovni problem vij~anih ma{ina je velika razlika pritiska izmedju usisnog i tla~nog otvora koja izaziva veliko optere}enje rotora silama pritiska ~iji su veli~ina, pravac i smjer neovisni o smjeru rotacije. Obi~no se te sile prenose na ku}i{te na obje strane rotora preko leàjeva koji trebaju da izdrè velika radijalna i aksijalna optere}enja usljed razlike pritiska, teìne rotora i vanjskih uticaja, kao {to su sile remenice ili zup~anika. Kao rezultat, jedan dio korisnog rada se tro{i na gubitke usljed trenja u leàjevima. Kori{tenjem kombinovane ma{ine, moè se posti}i gotovo potpuno poni{tavanje aksijalnih sila i djelomi~no balansiranje radijalnih sila, ~ime se pobolj{ava mehani~ko iskori{tenje kombinovane ma{ine u poredjenju sa dvije jedinice koje rade neovisno.

3. DESIGN CHARACTERISTICS OF MULTIFUNCTIONAL SCREW MACHINES The same machine presented in Fig 2 can be used as a two-stage compressor by reversing the positions of the second stage will ports. The low-pressure port of the second stage will then be located on the top of the machine and the high-pressure discharge will be at the machine bottom. This offers a compact two-stage machine, which may be used either in the oil flooded or dry operation mode. A similar layout may also be used for a two-stage expander. If the rotors are used for multistage compression or expansion, they can retain their profile shape common for screw compressors with a small blow-hole on one side and a relatively large one on the opposite side. Additionally, when this layout is used for combined compression and expansion, the expansion section can contain a capacity control such as a slide or lifting valve in the suction region to alter the volume passing through it at part load, in a manner identical to capacity controls normally used in screw compressors. A major problem with screw machines is that the pressure difference between entry and exit creates very large radial and axial forces on the rotors whose magnitude and direction is independent of the direction of rotation. It is normal practice to have bearings on each end of the rotors and these have to withstand both the radial and axial loads induced by the pressure difference. As a result, some of the power transmitted through the rotors is lost in bearing friction. By proper arrangement of the ports in the two working chambers, the axial forces can be fully balanced and the radial forces can be partially balanced. This will make the mechanical friction losses in the combined machine smaller than in two units, operating independently.

4. URAVNOTE@AVANJE SILA NA ROTORIMA KOMPRESORA-EKSPANDERA Kao {to je ranije pokazano, poloàj otvora visokog i niskog pritiska, kod ma{ine u kojoj se kompresija i ekspanzija obavljaju na jednom paru rotora, uti~e na sile na leàjevima. Sa slike 2 vidi se da, ako su otvori visokog pritiska u takvoj ma{ini postavljeni centralno u odnosu na rotore ali na suprotnim stranama ku}i{ta, tad sile pritiska pri kompresiji i ekspanziji djeluju jedna nasuprot druge na relativno malom rastojanju. Time se radijalne komponente sile pritiska jednim dijelom poni{tavaju. Osim toga, kako je na obje strane rotora pritisak gotovo jednak, aksijalne sile se skoro u potpunosti balansiraju.

4. BALANCING FORCES ON COMPRESSOR–EXPANDER ROTORS As indicated in Section 2, when compression and expansion occur in one pair of rotors, the positioning of the ports affects the bearing loads. As shown in Fig 2, because the high pressure ports of such machine are in the centre of the unit and arranged so that they are on opposite sides of the casing, the high pressure forces due to compression and expansion are opposed to each other and, more significantly, only displaced axially from each other by a relatively short distance. The radial forces on the bearings are thereby significantly reduced. In addition, since both ends of the rotors are at more or less equal pressure, the axial forces virtually balance out.

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Razmatrano rashladno postrojenje radi sa 2.75 m3/min CO2 koji u kompresor ulazi kao suho zasi}ena para na usisnom pritisku od 35 bara i komprimira se tako da na ulazu u kondenzator ima pritisak od 100 bara. Primjer kombinovane ma{ine za istovremenu kompresiju i ekspanziju fluida visokog pritiska pokazuje prednosti koje je mogu}e posti}i u ovom aran`manu.

A refrigerator uses 2.75 m3/min CO2 as a working fluid which leaves the evaporator and enters the compressor as dry saturated vapour at a suction pressure of 35 bar to leave the compressor and enter the condenser at a discharge pressure of 100 bar. The following example of a combined compressor and expander in a high-pressure application indicates the extent of the advantages, which are possible from this arrangement.

Slika 4a Konvencionalno rashladno postrojenje Slika 4b Postrojenje sa vi{enamjenskim

kompresorom-ekspanderom Fig 4a Conventional Refrigeration Fig 4b Refrigeration System with Balanced

System Rotor Compressor-Expander

Na slici 4a je prikazano konvencionalno rashladno postrojenje sa kompresorom i prigu{nim ventilom. Zbog velikih sila izazvanih razlikom pritisaka koje vladaju u tom postrojenju prakti~no je nemogu}e konstruisati vij~ani kompresor u tu svrhu. Medjutim, ako bi se klasi~ni kompresor i prigu{ni ventil zamijenili kombinovanim kompressorom-ekspanderom, kao {to je prikazano na slici 4b, optere}enja silama pritiska se reduciraju. U datom primjeru mogla bi se koristiti vij~ana ma{ina sa pre~nikom vode}eg rotora od 102 mm sa relativnom duìnom kompresora u odnosu na pre~nik vode}eg rotora od 1.5. Ekspander koji zamjenjuje prigu{ni ventil ima isti pre~nik rotora, dok je njegova relativna duìna 1.1. Prora~un sila za konvencionalni vij~ani kompresor pokazuje da rotori kompresora i njegovi leàjevi trebaju podnijeti aksijalnu silu na glavnom rotoru od 92.1 kN i radijalnu silu 132.9 kN na strani visokog pritiska, te 45.5 kN na strani niskog pritiska. Sli~an prora~un za ekspander daje aksijalnu silu na glavnom rotoru 91,9 kN dok su odgovaraju}e radijalne sile 85.9 kN na strani visokog pritiska i 34,1 kN na strani niskog pritiska.

As shown in Fig 4a, a conventional system for this involves the use of a compressor and a throttle valve. At this pressure difference, it would be almost impossible to design a screw compressor for this function due to the huge forces which need to be resisted by the bearings. However, if a compressor-expander is used for this, as shown in Fig 4b, the bearing loads can be reduced somewhat. In this case, a screw compressor could be used with a rotor of 102mm in diameter with a length/diameter ratio of 1.5 The expander required to replace a throttle valve in this system would have a male rotor of the same diameter but with a length/diameter ratio of only 1.1. Force calculations on the compressor rotors were made to determine what bearing loads must be resisted if the refrigeration system is designed with a conventional screw compressor drive. On the main rotor alone, there is an axial force of 92 kN and radial bearing forces of 132.9 kN at the high pressure end and 45,5 kN at the suction end. A similar calculation was performed for the expander rotors and their corresponding bearing forces. Here, the axial bearing load on the main rotor is 91,9 kN while the corresponding radial loads are 85.9 kN at the high pressure end and 34,1 kN at the low pressure end.

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Sile u leàjevima, u slu~aju da se kompresija i ekspanzija obavljaju istovremeno na jednom paru rotora sa otvorima visokoga pritiska na sredini rotora, su kako slijedi; aksijalna sila na glavnom rotoru iznosi zanemarivih 0.12 kN, dok su radijalne sile 101 kN na strani kompresora i 117 kN na strani ekspandera. Jo{ povoljnije je, da je sila na pomo}nom rotoru, koji je ina~e slabiji, reducirana sa 146 kN na 119 kN, dakle za oko 19%.

The bearing forces, which would result, if the compressor and expander rotors were machined on the same shafts with the high pressure ports in the middle and the low pressure ports at each end were as following. The male rotor axial load is reduced to 0.12 kN, which is negligible. The radial bearing loads are now 101 kN at the compressor end and 117 kN at the expander end. More significantly, for the female rotor, which is weaker, the maximum bearing load has been reduced from 146 kN to 119 kN, which is 19% less.

Tako je ukupna sila u leàjevima na glavnom rotoru smanjena sa 270.4 kN za kompresor na 218 kN za kombinovani kompresor ekspander. Ako se u obzir uzmu oba rotora, onda se ukupna sila na leàjevima smanjuje sa 556 kN za kompresor na 448 kN za kombinovani kompresor ekspander. Time se ukupno optere}rnje smanjuje za oko 20%. Problemi vezani za konstrukciju visoko optere}enih rotora i leàjeva kod rashladnih kompresora visokog pritiska ovim postaju manje izraèni. Vi{e informacija se moè na}i u ~lanku Sto{i} i drugi, 2003b.

Thus the total bearing load on the male rotor alone has been reduced from 270.4 kN for the compressor to 218 kN for the combined compressor-expander. If both male and female rotors are included, then the total bearing load is reduced from 556 kN for the compressor alone to only 448 kN for the combined balanced rotors. This amounts to a total decrease in bearing load of nearly 20%. Design problems associated with high bearing loads in screw compressors for CO2 systems are thereby reduced. In addition, recovery of power by means of the expander, also improves the COP of the system, significantly. More details of this are given by Stosic et al, 2003

5. PRIMJERI PRIMJENE VI[ENAMJENSKIH VIJÂNIH ROTORA Osim aplikacije ove kombinovane ma{ine za istovremenu kompresiju i ekspanziju CO2 koja je ve} prikazana, u ovom ~lanku dato je jo{ nekoliko primjera primjene vi{enamjenskih rotora. To su: i) ekspresor za simultanu ekspanziju te~nosti

rashladnog fluida i kompresiju oslobodjene pare

ii) kombinovani suhoradni kompresor-ekspander za istovremenu kompresiju zraka i ekspanziju produkata reakcije kod gorivnih }elija

iii) uljnopodmazivani dvostepeni zra~ni kompresor.

5.1 Ekspresor U ~lanku Brasz i drugi, 2000 daje se uvodni izvje{taj o projektu u kojem je prigu{ni ventil u rashladnom kompresionom sistemu zamjenjen jednom kombinovanom ma{inom za simultanu ekspanziju i kompresiju. U njoj se rad dobiven dvofaznom ekspanzijom te~nosti rashladnog fluida direktno koristi za kompresiju dijela pare rashladnog fluida oslobo|enog ekspanzijom. I ekspanzija i rekompresija se obavljaju istovremeno na jednom paru rotora koji nemaju vanjskog pogona. Autori su ovu ma{inu nazvali “ekspresor”. Princip njenog rada prikazan je na slici 5.

5. APPLICATION EXAMPLES OF MULTIFUNCTIONAL SCREW ROTORS In addition to the CO2 Compressor-Expander already cited, other examples of applications suitable for multifunctional rotors are as follows: i) The expressor for simultaneous expansion of

refrigerant liquid and compression of its vapour

ii) A dry fuel cell compressor expander for simultaneous compression of air and expansion of fuel cell reaction products, and

iii) A two stage oil flooded air compressor.

5.1 The Expressor An introductory report on a means of replacing the throttle valve in vapour compression systems was published by Brasz et al, 2000. Power is recovered from the two-phase expansion process and used directly to recompress a portion of the vapour formed during the expansion. Both the expansion and recompression processes are carried out in a self-driven machine with only one pair of rotors and operating in a single working chamber with no external drive shaft. The authors have called such a device an "expressor" and its principle of operation is shown in Fig 5.

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Slika 5 Princip ekspresora

Fig 5: The Expressor Principle Te~nost rashladnog fluida visokog pritiska nakon izlaska iz kondenzatora ekspandira u dvofaznu mje{avinu u ekspanderskom dijelu ma{ine. Gotovo sva te~nost i jedan dio pare generisane pri ekspanziji izlaze na otvor niskog pritiska koji je centralno postavljen na ku}i{tu ma{ine i odlaze u ispariva~. Ostatak pare se komprimira u kompresorskom dijelu ma{ine i izlazi kroz otvor visokog pritiska, obilazi ispariva~ i glavni kompresor i ide direktno u kondenzator. Rotori ove ma{ine, isto kao i rotori na kojima se ekspandira i komprimira radni fluid u dvije odvojene komore, moraju zaptivati na obje strane kako je prikazano na slici 3. Par ekspresorskih rotora prikazan je na slici 6. Ekspresor je konstruisan tako da radi kao tzv. hermeti~ka jedinica bez unutra{njih zaptiva~a i sinhronizacionih zup~anika, u kojoj se za podmazivanje le`ajeva i rotora koristi procesnim fluidom prakti~no bez ulja. Jedna takva ma{ina prije monta`e prikazana je na slici 7. Rezultati mjerenja su pokazali da je ukupna efikasnost ekspresora oko 55%. To odgovara efikasnosti ekspanzije od oko 70% i kompresije 80%. Zbog jednostavne konstrukcije i dobrih radnih karakteristika ekspresor se pokazao kao vrlo ekonomi~na komponenta u velikim rashladnim sistemima.

Here, high pressure liquid leaving the condenser expands into a two-phase mixture. At the intermediate, low pressure port, nearly all the residual liquid is ejected together with a portion of the vapour formed to enter the evaporator. The residual vapour is then recompressed, as a result of further rotation, to be discharged through the other high pressure port to by pass the evaporator and main compressor and be returned directly to the condenser. As in the case of expansion and compression in separate working chambers, the rotors have to seal on both sides, as shown in Fig 3. One pair, as built and tested is shown in Fig 6. In this case, they ran without lubricating oil, using process fluid lubrication without timing gears in a totally sealed unit. The complete unit, disassembled, is shown in Fig 7. Test results on this machine indicate that the overall expansion-compression efficiency of the expressor is of the order of 55%. This corresponds roughly to 70% expansion efficiency and 80% compression efficiency. The simplicity of the expressor design, together with its promising performance, indicate that it should be a highly cost effective component in large commercial chiller systems.

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Dodatne studije trebaju odrediti optimalni ugradjeni odnos volumena i uslove neophodne za bolje odvajanje te~nosti i pare pri izduvavanju mje{avine na niskom pritisku.

Further studies are being performed to determine the best built in volume ratios for the expansion and compression processes and to reduce the carry over of residual liquid into the vapour being recompressed.

Slika 6 Rotori ekspresora zaptiveni na obje strane Fig. 6 Expressor rotors sealed on both sides

Slika 7. Prototip ekspresora prije monta`e Figure 7. The expressor prototype before assembly

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5.2 Kompresor-ekspander za gorivne }elije Poznato je da efikasnost i kapacitet gorivnih }elija raste sa pove}anjem njihovog radnog pritiska. U ve}ini slu~ajeva zahtijeva se pritisak zraka od oko 3 bara koji se se obi~no ostvaruje vij~anim kompresorom za ~iji pogon se tro{i oko 20% ukupne snage gorivne }elije. Ako bi se za ekspanziju produkata reakcije gorivne }elije koristio ekspander, koji je direktno priklju~en na kompresor, oko polovine ove ina~e izgubljene energije moglo bi se iskoristiti, ~ime bi se snaga za pogon kompresora mogla smanjiti na dvije tre}ine njene polazne vrijednosti. Time bi se iskori{tenje gorivne }elije pove}alo za otprilike 8%. Kombinovani kompresor-ekspander na jednom paru rotora sa kompresijom i ekspanzijom u odvojenim komorama kao na slici 2 koristi se za ovu primjenu. Izgled prototipa kompresora-ekspandera za gorivne }elije prije montaè prikazan je na slici 8. Vi{e pojedinosti o ovoj ma{ini moè se na}i u ~lanku Sto{i} i drugi, 2003a.

5.2 Fuel Cell Compressor-Expander It is well known that the efficiency and capacity of a fuel cell is increased if its working pressure is higher. A pressure of 3 bars is usually required and a screw compressor is normally used for this. However, the compressor consumes about 20% of the cell power output. If the compressor is coupled to an expander to recover power from the reaction products leaving the cell, the power required to drive the compressor is cut by approximately 50%. This increases the fuel cell overall efficiency by about 8%. A combined compressor-expander with one pair of rotors but using separate chambers for the compression and expansion processes may be used for this, shown in Figs 2 and 3. A disassembled view of a prototype, designed and built by the authors for this application is shown in Fig 8. Both, the expansion and compression sections are clearly visible being separated by the central plate which contains high pressure ports. More information on this is given in Stosic et al, 2003a.

Slika 8 Kompresor-ekspander za gorivne }elije prije montaè

Figure 8 Expanded View of the Compressor-Expander for Fuel Cell Application

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5.3. Dvostepeni kompresor

Kako je ve} re~eno u poglavlju 3, ako se vij~anoj ma{ini prikazanoj na slici 3 zamijene mjesta otvora na strani ekspandera, ona se moè koristiti kao dvostepeni kompresor kako je to prikazano na slici 9. U tom slu~aju }e se otvor niskog pritiska drugog stepena nalaziti na gornjem dijelu ma{ine u sredini, dok }e tla~ni otvor visokog pritiska biti na donjem dijelu. Na taj je na~in mogu}e dobiti kompaktnu dvostepenu ma{ina koja moè raditi u suhoradnom i u uljnopodmazivanom reìmu. Dvostepeni uljnopodmazivani kompresor je konstruisan i o~ekuje se izrada njegovog prototipa. Sli~an se princip moè prijmijeniti i za dvostepeni ekspander na jednom paru rotora.

5.4. Regulacija dobave kompresora ekspanzijom vi{ka komprimiranog gasa.

Jo{ jedna zanimljiva primjena vi{enamjenskih vij~anih ma{ina jeste za regulaciju dobave kompresora ekspanzijom vi{ka komprimiranog gasa u ekspanderskom dijelu kombinovanog kompresora-ekspandera. Ona se moè pokazati kao dobra alternativa ostalim postupcima regulacije protoka, na primjer, prigu{enju na usisu, promjenljivoj brzini obrtanja kompresora i promjenljivom usisnom volumenu. Prigu{enje je krajnje neefikasno, dok su uredjaji za promjenljivu brzinu kompresora i promjenljivi usisni volumen skupi i komplikovani. Zbog toga predloèni princip, iako optere}en relativno niskom kombinovanom efikasno{}u procesa kompresije i ekspanzije, moè biti prihvatljivo rje{enje.

5.3. Two-Stage Compressor As already mentioned in Section 3, a machine, as shown in Fig. 9, may be used as a two stage compressor, only by exchanging the positions of the second stage ports. The low pressure port of the second stage will be located on the top of the machine and the high pressure discharge will be at the machine bottom. This offers a compact two stage machine which may be used either in the oil flooded or dry operation mode. A similar layout is valid for a two stage expander. 5.4. Capacity Control by Expanding of the Compressed Gas Surplus An interesting possible application of multifunctional rotors is to use them as a means of compressor capacity control by expanding the surplus flow in the expander section of the combined compressor expander. This may prove to be an effective alternative to conventional means of capacity controls such as suction throttling, varying the compressor speed and varying the compressor suction volume. Throttling is inefficient, while variable speed devices and sliding valves are expensive. The proposed principle, although its efficiency is reduced by the product of the losses in the compression and expansion processes, may yet prove to be more cost effective.

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Slika 9 Dvostepeni vij~ani kompresor na jednom paru rotora Figure 9 Two-Stage Oil-Flooded Compressor on one Pair of Rotors

6. ZAKLJUÂK Iako je vij~ani kompresor danas ve} dobro razvijen proizvod, ve}i anga`man inènjerske nauke uz primjenu ra~unarskog modeliranja i matemati~ke analize u fazi njegovog projektovanja i konstruisanja ~ini inovacije jo{ uvijek mogu}im. Upotreba vij~anih ma{ina za istovremenu kompresiju i ekspanziju kombinuje oba ova procesa na jednom paru vij~anih rotora i time pro{iruje podru~je rada vij~anih kompresora. Va`na osobina vij~anog kompresora jeste da on radi kao ekspander ako mu se smjer obrtanja rotora promijeni, ili ako otvori niskog i visokog pritiska zamijene mjesta, {to ima isti efekt kao i promjena smjera obrtanja u odnosu na otvore na ku}istu. Kao rezultat }e rotori i leàjevi biti manje optere}eni silama pritiska. Upotrebom istog profila za oboje, za kompresiju i za ekspanziju, rotori se mogu proizvesti u jedinstvenom prolazu glodanjem ili bru{enjem, a dijelovi za kompersiju i ekspanziju se razdvajaju `lijebom nakon {to su zubi na rotoru ve} formirani. Ovaj princip moè se koristiti u rashladnim sistemima visokog pritiska sa CO2, ali i za konvencionalne rashladne fluide, kao i u drugim prilikama gdje se traì kombinovana kompresija i ekspanzija pa ~ak i u slu~aju kad se ekspanzija uvodi samo zato da se smanji optere}enje rotora usljed djelovanja sila pritiska.

6. CONCLUSION Although the screw compressor is now well developed, greater involvement of engineering science in the form of computer modelling and mathematical analysis at the design stage, makes further innovations possible. The use such machines for expansion as well as compression, leads to possibilities of combining both processes in the same machine and thereby extending their range of application. An important feature of the screw machine is that it will also work as an expander when rotating in the same direction as a compressor provided that the suction and discharge ports are positioned on the opposite sides of the casing. This is effectively the same as reversing the direction of rotation relative to the ports. By using the same profile for both, the compressor and expander rotors can be machined or ground in a single cutting operation and then separated by machining a parting slot in them on completion of the lobe formation. As a result a lower rotor loads will be obtained for the same machine duty. Such a machine may be used wherever there is need for combined expansion and compression processes to improve process efficiencies, as a means of compressor control and, especially in high pressure systems, to reduce the rotor loads.

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7. LITERATURA - REFERENCE [1] Brasz J. J, Shistla V, Stosic N. and Smith, I.

K, 2000: Development of a Twin Screw Expressor as a Throttle Valve Replacement for Water-Cooled Chillers, XV International Compressor Engineering Conference at Purdue, July 2000

[2] Fleming J. S, Tang Y and Cook G, 1998: The

Twin Helical Screw Compressor, Part 1: Development, Applications and Competetive Position, Part 2: A Mathematical Model of the Working process, Proceedings of the IMechEng, Journal of Mechanical Engineering Science, Vol 212, p 369

[3] Stosic N, Smith I. K, and Kovacevic A, 2002:

A Twin Screw Combined Compressor and Expander for CO2 Refrigeration Systems, XVI International Compressor Engineering Conference at Purdue, July 2002

[4] Stosic N, Smith I. K. and Kovacevic A, 2003

Opportunities for Innovation with Screw Compressors, Proceedings of IMechE, Journal of Process Mechanical Engineering, 200, 217, pp 157-170

[5] Stosic N, Smith I. K. and Kovacevic A, 2003a

Combined Screw Compressor-Expander in Fuel Cell Application, International Conference on Compressors and Their Systems, London, September 2003

[6] Stosic N, Smith I. K. and Kovacevic A, 2003b

Multifunctional Screw Compressor Rotors, ICCR International Conference on Compressors and Refrigeration, Xi’an, China, October 2003

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Ma{instvo 1(8), 17 – 32, (2004) I.Hajro, ...: ELEKTRONSKE BAZE PODATAKA...

ELEKTRONSKE BAZE PODATAKA I EKSPERTNI SISTEMI ZA IZBOR MATERIJALA

Ismar Hajro dipl. ma{. ing., Damir Hodì} dipl. ma{. ing., Ma{inski fakultet Sarajevo

REZIME Poznavanje dostupnih kvaliteta materijala i njihovih karakteristika, kao i pra}enje trendova u razvoju novih materijala neophodni su dijelovi dobre inìnjerske prakse. Ovo se prevashodno odnosi na konstruktore i dizajnere novih proizvoda, te za stru~no osoblje zaduèno za pra}enje pona{anja proizvoda, odnosno materijala, u proizvodnji i ekploataciji. Podaci o dostupnim kvalite ima materijala i njihove karakte istike dostupni su u razli~itim formama od kojih je elektronska forma doìvjela najve}i razvoj paralelno sa razvojem kompjuterske tehnike. Upravo stanje razvoja elektronskih baza podataka i pridruèni im ekspertni sistemi za izbor materijala predstavljaja podru~je istraìvanja prezentiranog u ovome radu.

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U radu je data lista dijela dostupnih elektronskih baza podataka materijala (sa kra}im osvrtom na tri karakteristi~ne baze: MatWeb, SteelSelector, Datenbank StahlWissen), na~inu i cijeni pristupa istim, te tipu i strukturi. Dodatno je dat i kra}i osvrt na jedan od ekspertnih sistema za izbor materijala (Cambridge Enginee Selector).

Klju~ne rije~i: Materijal, baza podataka materijala, ekspertni sistem

ELECTRONIC MATERIAL DATABASES AND EXPERT SYSTEMS FOR MATERIAL SELECTION

Ismar Hajro B.Sc. Mech. Eng., Damir Hodì} B.Sc. Mech. Eng., Faculty of Mechanical Engineering Sarajevo

ABSTRACT Cognition of available material qualities and their properties, and following up trends in new materials development are necessary parts of well engineering practice. This is primary related to constructors and designers of new products, and to expert personnel charged for following up product behaviour, apropos materials, through production and exploatation. Data about available material qualities and their characteristics are available in various forms, and electronic form has reached the greatest development together with computer technique development. State of electronic material databases and added expert systems for material selection present researching field in this paper. In the paper, list of the part of available material databases is presented (with short retrospective view on three typical databases: MatWeb, SteelSelector, Datenbank StahlWissen), according to the way and price of access, type and structure. Additionally, short retrospective view of one o the expert system for material selection is presented (Cambridge Enginee Selector).

Key words: Material, material data base, expert system

1. UVOD Izbor materijala u inènjerskoj praksi predstavlja ni malo lak zadatak, i jedan je od rijetkih u procesu konstruisanja (jednog ma{inskog) proizvoda koji je podloàn stalnim izmjenama. S druge strane pogre{an izbor materijala u samom po~etku konstruisanja, moè imati nenadoknadive {tete, kako u procesu proizvodnje, tako i u procesu eksploatacije. Dosada{nja praksa pri razvoju novih proizvoda je bila da se usvajaju provjereni materijali, odnosno materijali primjenjivani u sli~nim proizvodima.

1. PREFACE

Material selection in engineering practice represent noeasy task at all, and it is one rare task of product design process which has permanent changes. Otherwise, wrong material selection in early stage of product design could couse irrecoverable damage in production process, as well as in exploatation process. Up today practice in developing of new products was selection of verified materials in similar products.

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Na osnovu sprovedene analize [6] vidi se da konstruktori naj~es}e koriste pet do {est razli~itih materijala, te su na taj na~in materijali u procesu konstruisanja unaprijed odre|ene konstante, a ne varijable ({to bi zaista trebali i biti). Obzirom da se na svjetskom trì{tu svakodnevno pojavljuju novi materijali, neophodno je pratiti ove trendove i usvajati ih u vlastitoj konstruktivnoj praksi, pri ~emu se ovi trendovi uglavnom odnose na: - pove}anje mehani~kih osobina (u primjeru

~elika prvenstveno ~vrsto}e i ìlavosti), a time izgradnje lak{ih proizvoda (konstrukcija),

- pove}anje obradivosti (plasti~nom deformacijom, rezanjem) i pove}enjem sposobnosti spajanja (zavarivanjem i lijepljenjem),

- pove}enjem korozione otpornost i otpornosti na niske i visoke temperature,

- pove}enje kvaliteta povr{ine u cilju boljeg estetskog izgleda proizvoda,

- primjenu ekolo{ki ~istih materijala (materijala sa mogu}om reciklaòm bez, ili sa minimalnim brojem nerazgradivih nusprodukata).

Informacije o dostupnim tipovima i kvalitetima materijala (od ranije razvijenih i standardizovanih do najnovijih) mogu se na}i u: - {tampanoj formi (priru~nici, katalozi,

enciklopedije, knjige, stru~ni ~asopisi), - elektronskoj formi (On-Line-sa mre`nim

pristupom putem Intraneta ili Interneta, kao softverske aplikacije za pojedina~ne PC korisnike).

By the analysis [6] it could be shown that constructors mostly use from five to six different materials, and in that way material present predetermined constant, while it should be variable. Due to the fact of everyday apperance of new material in the world market, it is neccesary to follow and accept these new trends in own design practice, while these trends are: - increasing of mechanical properties (in

example of steels mostly strength and toughness), with main goal of building lighter construction,

- increasing of treatment ability (plastic deformation, cuting) and increasing joining ability (welding, adhesive joining),

- increasing corosion resistance and resistance on low and high temperatures,

- increasing surface quality for better esthetic product layout,

- use of ecological materials (materials with possible recycling without, or with minimum number of disintegrated by-product).

Information of available material types and qualities (from early to new developed and standardized) could be found as: - printed form (manulas, catalogs, encyclopedies,

books, scientific magazines), - electronic form (On-Line by network access

(Intranet or Internet), as software applications for single PC users).

2. BAZE PODATAKA MATERIJALA Uz veliki napredak kompjuterske tehnike (hardvera i softvera), razvija se i takozvani kompjuterski podràn izbor materijala (CAMS – Computer Aided Material Selection), koji u osnovi nastoji da razvije: - elektronske baze podataka (EBP) razli~itih

materijala (ili grupa materijala), - ekspertne sisteme (ES) za izbor materijala

(tako|e elektronske kao softverske aplikacije). Osnovni problemi sa kojima se susre}u proizvo|a~i ovakih sistema su: - kvalitet i kvantitet baza podataka (detaljnost

podataka o materijalima, i broj upisanih materijala),

- strategija (algoritam) izbora materijala kroz ekspertne sisteme za postoje}e baze podataka.

U svijetu, danas, postoji niz institucija koje se bave razvojem ovakih sistema, pri ~emu se za znatan broj moè saznati putem interneta (web-stranica), {to je i bio jedan od izvora za pisanje ovog rada.

2. MATERIAL DATABASES Together with development of ICT (hardware and software), CAMS – Computer Aided Material Selection is developed, which in basic has intention to develop: - electronic databases (EDB) of different

materials (or groups of materials), - expert systems (ES) for material selection (also

electronic as software applications). The main problems that manufacturers of these systems meet are: - quality and quantity of databases (material data

details, and number of included materials), - strategy (algorythm) of material selection

through expert systems for existing databases. Today, in the world exist number of institutions which are concerned with development of these systems, and for the great number of them it is possible to get informations by using Internet (web-sites). It was one of the sources for the writing of this paper.

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Na osnovu zapaànja strukture, obima, vrste materijala, i na~ina prezentiranja podataka u bazama, mogu}e je izvr{iti sljede}e podjele vrsta baza podataka materijala: 1. Podjela prema tipu institucije koja prezentira

baze podataka materijala: - Proizvo|a~i, odnosno prodava~i materijala (~eli~ane – èljezare, kooperanti): imaju uski dijapazon razli~itih konstrukcionih materijala, obi~no u obliku standardnih profila. Baze sadrè uglavnom osnovne geometrijske karakteristike proizvoda, standardne oznake materijala, te vrlo skromne karakteristike pojedinih materijala. - Nau~no-istraìva~ke institucije (univerziteti (instituti), privatne i dràvne istra ìva~ke ustanove): imaju veliki broj tipova i kvaliteta razli~itih konstrukcionih materijala, sa detaljno prezentiranim velikim brojem podataka o razli~itim osobinama materijala. - Ostale institucije, koje ne spadaju u gornje dvije skupine (razli~ita udruènja, asocijacije, sa {irinom baze u funkciji {irine podru~ja interesovanja za razli~ite konstrukcione materijale).

Neophodno je napomenuti da je samo za manji broj elektronskih baza podataka, pristup podacima uglavnom neometan (slobodan, besplatan), dok je za ve}inu neophodno platiti pristup bazi podataka, obi~no kroz ~lanstvo u istoj (Membe ship charge, mjese~ne ili godi{nje pretplate), kako za online pristup, tako i za kupovinu licence kori{tenja baze podataka u vidu instalacijskog softvera.

r

2. Podjela prema na~inu prezentiranja, odnosno prikaza podataka unutar elektronskih baza podataka [6]:

- Lokalne (instalacijske): - Diskete (alfanumeri~ke), - CD Rom-ovi (alfanumeri~ke i

multimedijalne). - Udaljene (mre`ne):

- On-line (mreè znanja sa neophodnim ~lanstvom za pristup),

- Internet (ve}inom slobodnog, odnosno besplatnog pristupa).

Neophodno je spomenuti i bitnu razliku izme|u elektronskih baza podataka (specijalno onih koje se prikazuju u obliku aplikativnih softvera), ili web-stranica, to jest baze podataka tzv. stati~ke, odnosno dinami~ke strukture. Pod pojmom stati~ke web stranice (baze podataka) smatrale bi se one koje se mogu samo ~itati, dok dinami~ke omogu}uju tzv. komunikaciju sa korisnikom, odnosno posjeduju odre|ene procedure (forme) u procesu pretrage baze podataka [7]. Naravno, podjele EBP-a se ne zavr{avaju na navedene tri, jer mno{tvo je faktora koje razlikuju jednu bazu od druge. U narednoj tabeli dat je spisak 16 dostupnih EBP-a sa njihovim osnovnim karakteristikama.

According to the structure, range, type of material, and way of presenting informations in databases, it is possible to make next divisions of types of material databases: 1. Division according to the type of institution which is presenting material databases: - Manufacturers, apropos material sellers (steel factories, cooperants): have low range of different structural materials, usually in the form of standard profiles. Databases consists mainly basic geometric specifications of product, standard material designations, and very small number of properties for particular materials. - Scientific-researching institutions (universities (institutes), private and state researching centres): have high range of types and qualities of various structural materials, with great number of detailed presented informations about various material properties. - Other institutions, which are not included in the previous groups (various associations, with database range according to the range of interest for various structural materials).

It is necessary to emphasize that access is free only for small number of electronic databases, and for the rest it is necessary to pay access to database, usually through Membership charge, monthly or annualy. This is related with on-line access and buying of licence for using database in form of installed software. 2. Division according to the way of presenting, apropos data preview within electronic databases [6]: - Local (installation):

- Floppy diskettes (alfanumerical), - CD Rom-s (alfanumerical and multimedial).

- Distance (network): - On-line (knowledge networks with

necessary membership for access), - Internet (usually free, apropos access is

free of charge). It is necessary to mention important difference between electronic databases (specially those which are shown in the form of applicative software), or web sites, i.e. databases with so-called statical, apropos dynamical structure. Under the concept of statical web-site (database) we consider one which is read-only, while dynamical enable so-called communication with user, apropos it has some specific procedures in process of database searching [7]. Obviously, EDB divisions are not finished with previous three, becouse there is a lot of factors making differences between databases. Next Table shows list of 16 available EDB with their main characteristics.

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Tabela 1. Dio dostupnih elektronskih baza podataka (EBP)

Br. Naziv baze podataka materijala

Proizvo|a~/ Ponu|a~

Sadràj Na~in pristupa/

Tip (stati~ke, dinami~ke strukture)

1. BH Steel / Proizvodni program

BH Steel Valjani ~eli~ni proizvodi, Standardne oznake.

Dimenzije.

besplatan na: http://www.bhsteel.com.ba stati~ka

2. Compendex Engineering Village 2, Elsevier Engineering Information Inc.

Multidiscliplinarna baza podataka (Material Science,

Mechanical and Metallurgicall Engineering...)

informativno na: http://www.engineeringvillage2.org/controller/servlet/Controller dinami~ka

3. Material Index MEMSnet

MEMS Development Community

Op{te osobine materijala. besplatan na: http://www.memsnet.org/material/ stati~ka

4. MatWeb Automation Creatins Podaci o velikom broju materijala. Mogu}nost

pretraìvanja.

besplatan na: http://www.matls.com http://matweb.com/ dinami~ka

5. Metadex Cambridge Scientific

Abstract Multidiscliplinarna baza

podataka

informativno na: http://www.csa1.co.uk/ dinami~ka

6. NIST Materials Data Program

National Institute of Standards and Technology

- NIST Scientific and Technical Databases

Razli~ite aplikativne baze podataka materijala.

informativno (besplatno) na: http://www.nist.gov/srd/materials.htm stati~ke i dinami~ke

7. Principal Metals

Online Principal Metals

Osnovne karakteristike metalnih legura

besplatan na: http://www.principalmetals.com/ stati~ka

8. Sartid a.d. Proizvodni program

Koncern crne metalurgije Sartid a.d.

êli~ni proizvodi. Osnovne karakteristike. Standardne

oznake, Dimenzije.

besplatan na: http://www.sartid.co.yu stati~ka

9. StahlWissen

Navimat-Online Dr. Sommer

Werkstofftechnik

Instalacijski multimedijalni softver. Karakteristike

~elika.

informativno na: http://www.werkstofftechnik.com/index_ps.htm instalacijski CD-Rom cjena od 99 do 3999 �

10. Steel Selector Metal Ravne

êli~ni proizvodi. Osnovne karakteristike. Standardne

oznake. Dimenzije.

besplatan na: http://www.sz-metal.si dinami~ke

11. StahlSchlussel (Key to Steel)

Verlag Stahlschlüssel Wegst GmbH

Klju~ za ~elik

informativno na: http://www.stahlschluessel.de/IDX_E.HTM instalacijski CD-Rom cjena od 400 � do 3910 �

12. Material Data

Network Granta Design Ltd

Pokriva sve postoje}e materijale obzirom da

objedinjuje 8 velikih baza podataka (pojedine date pod 11, 12, 13, 14).

informativno na (neophodno ~lanstvo): http://matdata.net/index.jsp dinami~ka baza podataka podràna od strane Granta Design Ltd koja objedinjuje: ASM, MIL, NPL MIDAS, UK Steel, TWI, MatWeb, IDES;

13. SteelSpec WEB

Edition UK Steel Association

WEB stranica {tampanog izdanja

Steel Specification

informativno na (neophodno ~lanstvo): http://www.steelspec.org.uk/index.htm dinami~ka

14. Prospector IDES- Integrated Design Engineering Systems

49000 stranica o plasti~nim materijalima od

400 isporu~ilaca

informativno na (neophodno ~lanstvo): http://ides.com/ dinami~ka

15.

ASM Handbook Online

ASM Alloy Center

ASM International 21 ASM zbirke priru~nika + 2 ASM Desk izdanja

informativno na (neophodno ~lanstvo): http://www.asminternational.org/hbk/index.jsp http://www.asminternational.org/alloycenter/index.jsp dinami~ka

16.

MIDAS- Materials

Information, Dissemination, Advice and Services

National Physical Laboratory (UK)

Informacije o polimernim materijalima,

savjeti i servis.

besplatno i informativno na: http://midas.npl.co.uk/midas/index.jsp dinami~ka

- 20 -

http://www.bhsteel.com.ba/http://www.engineeringvillage2.org/controller/servlet/Controllerhttp://www.engineeringvillage2.org/controller/servlet/Controllerhttp://www.memsnet.org/material/http://www.matls.com/http://matweb.com/http://www.csa1.co.uk/http://www.nist.gov/srd/materials.htmhttp://www.principalmetals.com/http://www.sartid.co.yu/http://www.werkstofftechnik.com/index_ps.htmhttp://www.sz-metal.si/http://www.stahlschluessel.de/IDX_E.HTMhttp://matdata.net/index.jsphttp://www.steelspec.org.uk/index.htmhttp://ides.com/http://www.asminternational.org/hbk/index.jsphttp://www.asminternational.org/alloycenter/index.jsphttp://www.asminternational.org/alloycenter/index.jsphttp://midas.npl.co.uk/midas/index.jsp


Table 1. Part of available electronic databases (EDB)

Br. Title of material

data base Manufacturer/

Offer by Content

Access/ Type (static or dynamic structure)

1 BH Steel /

Production program BH Steel

Mill steel products Standard designation.

Dimensions.

Free at: http://www.bhsteel.com.ba static

2 Compendex Engineering Village 2, Elsevier Engineering Information Inc.

Multidisciplinary material database (...Material

Science, Mechanical and Metallurgicall Eng.)

Information at: http://www.engineeringvillage2.org/controller/servlet/Controller dynamic

3 Material Index MEMSnet

MEMS Development Community

Common material properties

Free at: http://www.memsnet.org/material/ static

4 MatWeb Automation Creatins Data baout large number of materials. Possible

search

Free at: www.matls.com; matweb.com/ dynamic

5 Metadex Cambridge Scientific

Abstract Multidisciplinary material

data base

Information at: http://www.csa1.co.uk/ dynamic

6 NIST Materials Data

Program

National Institute of Standards and Technology -

NIST Scientific and Technical Databases

Different applicable material databases

Information (free part) at: http://www.nist.gov/srd/materials.htm static and dynamic

7 Principal Metals

Online Principal Metals

Basic properties of metal alloys

Free at: http://www.principalmetals.com/ static

8 Sartid a.d.

Proizvodni program

Concern of black metallurgy Sartid a.d.

Steel products Basic properties Standard

designation Dimensions

Free at: http://www.sartid.co.yu static

9 StahlWissen

Navimat-Online Dr. Sommer

Werkstofftechnik

Installation software Steel properties

Information at: www.werkstofftechnik.com/index_ps.htm Installation CD-Rom Price: 99 - 3999 �

10 Steel Selector Metal Ravne

Steel products Basic properties

Standard designation Dimensions

Free at: http://www.sz-metal.si dynamic

11 StahlSchlussel (Key

to Steel)

Verlag Stahlschlüssel Wegst GmbH

Key to Steel

Information at: www.stahlschluessel.de/IDX_E.HTM Installation CD-Rom Price: 400 - 3910 �

12 Material Data

Network Granta Design Ltd

Cover all existing materilas due to the fact it join 8 great material databases (some at 11, 12, 13, 14)

Information at (membership): http://matdata.net/index.jsp dynamic material database powered by Granta Design Ltd which join data bases: ASM, MIL, NPL MIDAS, UK Steel, TWI, MatWeb, IDES;

13 SteelSpec WEB

Edition UK Steel Association

WEB page of printed edition of Steel Specification

Information at (membership): http://www.steelspec.org.uk/index.htm dynamic

14 Prospector IDES- Integrated

Design Engineering Systems

49000 pages of plastic materials from 400

deliverer

Information at (membership): http://ides.com/ dynamic

15 ASM Handbook

Online ASM Alloy Center

ASM International 21 ASM handbook

colections + 2 ASM Desk Edition

Information at (membership): www.asminternational.org/hbk/index.jsp www.asminternational.org/alloycenter/index.jsp dynamic

16

MIDAS- Materials Information,

Dissemination, Advice and Services

National Physical Laboratory (UK)

Data about polymers, sugestions and services

Information (free part) at: midas.npl.co.uk/midas/index.jsp dinami~ka

- 21 -

http://www.bhsteel.com.ba/http://www.engineeringvillage2.org/controller/servlet/Controllerhttp://www.engineeringvillage2.org/controller/servlet/Controllerhttp://www.memsnet.org/material/http://www.csa1.co.uk/http://www.nist.gov/srd/materials.htmhttp://www.principalmetals.com/http://www.sartid.co.yu/http://www.sz-metal.si/http://matdata.net/index.jsphttp://www.steelspec.org.uk/index.htmhttp://ides.com/


Slika 1. Rezultat pretrage baze podataka MATWEB prema tipu materijala, za konkretnu vrstu ~elika (~elik poznatog kvaliteta: AISI 1340 normalizovan): hemijski sastav, proizvo|a~i ~elika (snimak web stranice [1] ) Figure 1. Results of search of MATWEB material data base by material type, for exact steel AISI 1340

normalized; chemical composition, steel manufacturers (screenshot of web page [1] ) Pregledi rezultata pretrage baze podataka MATWEB (redni broj 4. u tabeli 1; kombinovano stati~ke i dinami~ke strukture) putem jedne od formi za pretragu dati su na slikama 1, 2 i 3. Rezultat pretrage prema tipu materijala, za konkretnu vrstu ~elika, odnosno ~elika poznatog kvaliteta AISI 1340 (normalizovani ~elik) su: hemijski sastav, proizvo|a~i ~elika (slika 1), mehani~ke, elektri~ne i termi~ke osobine (slika 2), te spisak literature za dodatne informacije.

Reviews of MATWEB database searching results ( No. 4. in Table 1; statical and dynamical structure combined) by using one of the forms for searching are shown in the Pictures 1, 2, and 3. Searching results according to the type of material, for concrete type of steel, apropos known steel quality AISI 1340 (normalized steel) are: chemical composition, steel producers (picture 1), mechanical, electrical and thermical properties (picture 2), and list of references for additional informations.

Dodatno, MatWeb baza sadrì podatke o velikom broju materijala kao {to su: termoplasti~ni polimeri, termoset polimeri, super legure, èljezne (Fe-) legure, neèljezne legure, ~istim elementima (metalima), keramici, te o ostalim inìnjerskim materijalima. Za svaki materijal je mogu}e saznati veliki broj podataka, pri ~emu je potraga za istim mogu}a putem [1]: - sekvencijalne pretrage (potrebna besplatna

registracija putem email-a), - tipu materijal, - karakteristi~nih vrijednosti osobina, - hemijskog sastava, - trgova~kog naziva, - proizvo|a~a materijala (isporu~ilaca).

Additionaly, MatWeb database consists informations for great number of materials like: thermoplastic polymers, thermoset polymers, super alloys, ferous (Fe) alloys, non-ferous alloys, pure elements (metals), ceramics, and other engineering materials. It is possible to find a lot of informations for each material, and searching is enabled by [1]: - sequential searching (free registration by e –

mail is necessary), - type of material, - characteristical values of properties, - chemical composition, - trade name, - material producer (deliverer).

- 22 -


Slika 2. Rezultat pretrage baze podataka MATWEB prema tipu materijala, za konkretnu vrstu ~elika (~elik

poznatog kvaliteta: AISI 1340 normalizovan): mehani~ke, elektri~ne i termi~ke osobine. / snimak web stranice literaturni br. [1] /

Figure 2. Results of search of MATWEB material data base by material type, for exact steel AISI 1340 normalized; mechanical, electrical and thermal characteristics /screenshot of web page reference no. [1] /

Slika 3. Mogu}nost pretrage prema standardnim oznakama ~elika u bazi podataka proizvo|a~a Metal Ravne

d.o.o. (unutar STEEL SELECTOR-a) / snimak web stranice literaturni br. [2] / Figure 3. Possibility of search by standard steel designation inside Metal Ravne d.o.o. material data base

(SteelSelector) / screenshot of web page reference no. [2] / Drugi primjer baze podataka je STEEL SELECTOR On-Line aplikacija (redni broj 10 u tabeli 1; mogu} je i download sa naknadnom instalacijom i pokretanjem direktno sa PC-a), koja nudi mogu}nost pretrage za ~elicima iz proizvodnog programa ~eli~ane Metal Ravne d.o.o.

Next example of database is STEEL SELECTOR On-Line application (No. 10 in Table 1; it is possible to download with later instalation and using directly from PC), which offers possibility of searching for steels from productional program of steel producer Metal Ravne d.o.o.

- 23 -


Slika 4. Dio rezultata pretrage podataka o ~eliku C45E (oznaka prema EN) - pretraga prema standardnim

oznakama ~elika u bazi podataka proizvo|a~a Metal Ravne d.o.o. (unutar STEEL SELECTOR-a) / snimak web stranice literaturni br. [2] /

Figure 4. Part of results of search for data of C45E steel (designation by EN) – search by standard steel designation inside of Metal Ravne d.o.o. steel manufacturer material data base (SteelSelector)

/ screenshot of web page reference no. [2] / U ovom slu~aju mogu}a je pretraga prema [2]: - karakteristi~nim alfanumeri~kim oznaka ~elika

(Steel Search – Java Script-a), - vrsti ~elika, na osnovu hemijskog sastava i

stanja isporuke (Steel Index), - standardnim oznakama: Ravne, Ravne No.,

DIN, Wr. No., BS, UNI, ASTM, SAE, AISI, AFNOR, AIR, UNE, EN, SIS, JIS, GOST, JUS i ^SN (Slika 4),

- proizvodnom programu (profilima standardnih dimenzija, kvaliteta povr{ine i stanja isporuke)

Na osnovu pretrage prema standardnoj EN oznaci ~elika: C45E, mogu} je pregled rezultata kao {to su: hemijske osobine, uporedne standardne oznake (slika 4), mehani~ke osobine, dijagram popu{tanja (tvrdo}a-temperatura) i kona~no podru~je primjene. Prethodna dva primjera predstavljaju na web-u dostupne beplatne (slobodnog pristupa i pretrage) baze podataka. Sljede}i primjer je Datenbank StahlWissen® - NaviMat 2002 baza podataka ~ije pretra`ivanje je mogu}e putem prethodne instalacije na presonalni ra~unar (PC, dostupne na CD-u), a ~ije kori{tenje je mogu}e kao (redni broj 9. u tabeli 1):

In this case searching is possible by [2]: - characteristic alfanumerical steel designation

(Steel Search – Java Script), - type of steel, according to the chemical

composition and delivery condition (Steel Index), - standard designations: Ravne, Ravne No., DIN,

Wr. No., BS, UNI, ASTM, SAE, AISI, AFNOR, AIR, UNE, EN, SIS, JIS, GOST, JUS i ^SN (Picture 4),

- productional program (profiles with standard dimensions, surface quality and delivery conditions)

Related with searching according to the standard EN steel designation: C45E, it is possible to review results like: chemical properties, standard designation comparison (figure 4), mechanical properties, tempering diagram (hardness-temperature) and finally field of application. Previous two examples represent web available free (free access and searching) databases. Next example is Datenbank StahlWissen® - NaviMat 2002 database where searching is possible after installation on personal computer (PC, available on CD), and usage is possible like (No. 9. in Table 1):

- 24 -


- NaviMat-X: Basis und Tabellenversion (osnove i tabelarni podaci: od 99 € za test instalaciju u trajanju od 4 sedmice, do 799 € za 5 mre`nih korisnika),

- NaviMat-XL: Erweiterungs- und Grafikversion (sa mogu}om nadogradnjom i grafi~kom verzijom: od 149 € za test instalaciju u trajanju od 4 sedmice, do 1699 € za 5 mre`nih korisnika),

- NaviMat-XXL: Vollversion Wärmebehandlung (puna verzija uklju~uju}i i termi~ku obradu: od 199 € za test instalaciju u trajanju od 4 sedmice, do 3999 € za 5 mre`nih korisnika).

Osnovne karakteristike Datenbank StahlWissen-a su: - podaci o materijalima sa naznakama o izvorima

podataka, na osnovu 15-godi{njeg iskustva primjene simulacionih tehnologija u Nauci o materijalu,

- osnovni podaci za oko 600 isporu~ilaca, - podaci o internacionalnom sistemu obilljeàvanja, - KH dijagrami, povezani sa jedinstvenom svjetskom

bazom podataka o medijima za razli~ite brzine hla|enja; mogu}nost prora~una brzine hla|enja za razli~ite tipove termi~ke obrade,

- formatirane tabele i dijagrami podataka o ~elicima i neèljeznim metalima i legurama,

- mogu}nost kompleksne pretrage, - mogu}nost eksportovanja svih grafi~kih fajlova

(prikaza tabela i dijagrama) u aplikacije bazirane na operativnom sistemu serije Windows (Win95, 98, NT, 2000, XP).

Na osnovu pregleda dostupnih EBP-a (tabela 1.) mogu se navesti osnovne prednosti kori{tenja elektronskih baza podataka (EBP) u odnosu na {tampane tipove baza podataka materijala: - brza i laka pretraga uz pretpostavku da se

ta~no poznaje bar jedna bitna karakteristika materijala za kojim se traga (standardna oznaka, broj materijala...),

- brz pristup elektronskim bazama podataka i jednostavan na~in pohranjivanja (skladi{tenja baze podataka: On-Line pristup velikog broja korisnika na jedan ra~unar-server),

- mogu}nost integrisanja sa postoje}im bazama podataka materijala unutar CAD sistema (na osnovu kompatibilnosti sa bazama podataka unutar razvijenih softverski aplikacija),

- mogu}nost pro{irenja jedne elektronske baze podataka sa podacima iz drugih baza podataka (elektronskih ili {tampanih), ili na osnovu vlastitih iskustava.

S druge strane osnovni nedostaci su: visoka cijena pristupa, odnosno visoka cijena za ~lanstvo u jednoj od elektronskih baza podataka materijala (zavisno od kvaliteta sadràja {to podrazumjeva broj materijala i njihovih karakteristika; u zavisnosti od broja korisnika, veli~ine baze, vremena kori{tenja: od 100 € do 4000 €),

- NaviMat-X: Basis und Tabellenversion (basics and tabular data: since 99 € for test installation lasting 4 weeks, till 799 € for 5 network users),

- NaviMat-XL: Erweiterungs- und Grafikversion (with upgrade possibility and graphical version: since 149 € for test installation lasting 4 weeks, till 1699 € for 5 network users),

- NaviMat-XXL: Vollversion Wärmebehandlung (full version including heat treatment: since 199 € for test installation lasting 4 weeks, till 3999 € for 5 network users).

Basic performances of Datenbank StahlWissen are: - data about materials with references about

sources of data, on the base of 15-year experience of applying simulation technologies in Materials Science,

- basic data for nearly 600 deliverers, - data about international designation system, - CCT diagrams, connected with unique world

database about mediums for various cooling rates; possibility of cooling rate calculation for various types of heat treatment,

- formated tables and diagrams of data about steels and non-ferous metals and alloys,

- possibility of complex searching, - possibility of all type graphic files exporting

(tables and diagrams) into applications based on Windows operation systems (Win95, 98, NT, 2000, XP).

Considering the review of available EDB-s (table 1.), it is possible to specify main advantages of using electronic databases (EDB), comparing with printed types of material databases: - fast and easy searching with assumption that at

least one substantial characteristic of material is known (standard designation, number of material...),

- fast access to the electronic databases and simple way of storing (database storing: On-Line access of great number of users to one computer-server),

- possibility of integrating with existing material databases within CAD system (on the base of compatibillity with databases within developed software applications),

- possibility of extending one electronic database with data from the other databases (electronic or printed), or on the base of own experiences.

On the other side, main disadvantages are: - high costs of access, apropos high charge for

membership in one of the electronic material databases (depending on content quality related with number of materials and their characteristics; depending on number of users, range of database, period of using: since 100 € untill 4000 €),

- 25 -


- komplikovan i relativno dugotrajan posao kreiranje elektronskih baza podataka (osnovni razlog visoke cijene pristupa) koji zahtjeva angaòvanje vi{e razli~itih specijalista (iz nauke o materijalu, web dizajnera, progamera...).

Nabavka materijala, koji je prona|en u jednom u navedenih tipova baza podataka, moè biti direktna ili indirektna. Materijal (poznatog kvaliteta, oblika i stanja isporuke) se moè dirketno naru~iti u slu~aju baza podataka proizvo|a~a materijala (npr. za ~eli~ne proizvode Metal Ravne, BH Steel, Sartid...) kontaktirjau}i direktno odgovaraju}e odjele za prodaju (Services, Sales Departments...). Indirektna nabavka materijala bi podrazumjevala nabavku materijala putem velikih baza podataka (koje objedinjuju informacije o velikom broju materijala, odnosno velikog broja proizvo|a~a), i koja se vr{i indirektno putem listi dobavlja~a (Suppliers list npr. u slu~aju MatWeb-a), koje se za ve}inu baza podataka date uz same informacije o materijalu. Sa ovih listi se dalje treba kontaktirati odgovaraju}i dobavlja~ ({to se u principu svodi na prvi, direktan na~in nabavke), ili se putem upitnih procedura moè dobiti lista optimalnih dobavlja~a. Tako npr. u slu~aju baze podataka MatWeb prate}i link “Material Suppliers” dolazimo na novu web stranicu Metal Suppliers Online [10], koja sadrì katalog ponude 2800 sjeverno ameri~kih dobavlja~a metalnih proizvoda. Biraju}i link “searchable catalog inventory” pokre}emo upitnu proceduru za pronalaènje odgovaraju}eg dobavlja~a traènog materijala, koja se sastoji iz sljede}ih koraka: - izbor tipa, kvaliteta i oblika materijala (family,

grade and form) - izbor veli}ine, duìne, koli~ine i dodatnih

zahtjeva za materijalom (material size, schedule, length, quantity and supplement requirements),

- izbor èljenih specifi~nosti nabavke, pla~anja i na~ina isporuke (order specifics, payment preferences and shiping preferences),

- predstavljanje li~nih podataka naru~ioca (ime i prezime odgovorne osobe, naziv firme, adresa, kontakt informacije).

Kao rezultat odgovora na navedenu upitnu proceduru {alje se Zahtjev za ponudu sa cjenom ili Zahtjev za kupovinu (Request for quote or Request for purchase) listi potencijalnih dobavlja~a, koji u kratkom vremenskom roku dostavljaju svoju ponude.

- complicated and relatively long lasting process of creating electronic databases (main reason for high access charges) which demands engagement a lot of various specialists (from science of materials, web designers, progamers...).

Supply of material, which is found in one of the mentioned types of databases, can be directly or indirectly. Material (with known quality, form and delivering conditions) is possible to order directly in case of material manufacturer databases (for example, steel products made by Metal Ravne, BH Steel, Sartid...) through direct contact with relevant sales departments (Services, Sales Departments...). Indirect material supplying allude material supplying through large databases (which unify informations about great number of materials, and great number of manufacturers), and it is accomplished indirectly through lists of suppliers (Suppliers list, for example, in case of MatWeb), which are for most of databases available together with material informations. Using this list, it is possible to contact appropriate supplier (in general it is the first, directly, way of supplying), or through questioning procedures to get list of optimal suppliers. For example, in case of MatWeb database by following link “Material Suppliers” we are visiting new web page Metal Suppliers Online [10], which consists catalogue with 2800 North American suppliers of metal products. By selecting link “searchable catalog inventory” we are starting questioning procedure for finding appropriate supplier of material, and procedure has following steps: - selection of type, quality and form of material

(family, grade and form) - selection of material size, length and additional

demands for material (material size, schedule, length, quantity and supplement requirements),

- selection of order specifications, payments and delivering conditions (order specifics, payment preferences and shiping preferences),

- presenting of customer personal data (personal data of responsible person, company name, address, contact informations).

As result of reply on mentioned questioning procedures, Request for quote or Request for purchase has been sent to list of potential suppliers, which send their offering in short term.

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3. EKSPERTNI SISTEMI PRI IZBORU MATERIJALA

U prethodnom poglavlju dat je opis tri karakteristi~na tipa EBP-a, i kao {to se moglo vidjeti svaki nudi mogu}nost potrage za jednim odre|enim materijalom, odnosno odgovor da li baza podataka sadrì traèni materijala. Ako materijal postoji, mogu}e je dalje o istom saznati i niz dodatnih informacija. Razvoj softvera i hardvera omogu}uje da kreatori ovakvih baza podataka materijala idu i korak dalje, tj. da kreiraju specijalne softverske pakete, koji }e ne samo sadràti spomenute baze podataka, ve} nuditi i mogu}nost interaktivnog izbora materijala za razli~ite aplikacije u inìnjerstvu (odnosno sistema sa kompjuterom podrànim izborom materijala - CAMS (Computer Aided Material Selection)). Ciljevi razvoja kompjuterski podrànog sistema za izbor materijala (CAMS) su prije svega [5]: - omogu}ivanje racionalne upotrebe materijala, kojom

se direktno trebaju posti}i u{tede materijala, a indirektno u{tede energije i ekolo{ki efekti,

- pro{irenje fonda znanja koji treba utjecati na smanjenje nastanka glavnih uzroka dotrajavanja tehni~kih proizvoda : lomova, korozije, tro{enja materijala,

- sistematsko i prikladno upravljanje dobivenim informacijama kako bi se one mogle koristiti u konstruisanju, proizvodnji i odràvanju tehni~kih proizvoda izra|enih od metalnih, kerami~kih, polimernih i kompozitnih materijala.

Pojam interaktivni izbor materijala podrazumijeva obostranu komunikaciju, korisnika (inìnjera, konstruktora) i specijalnog softverskog paketa. Shema principa rada ovakvog softverskog paketa je prikazana na slici 5. Primjer jednog ovakog ekspertnog sistema za izbor materijala na osnovu odre|enih zahtjeva inìnjerske aplikacije (kao {to je dato na slici 6.) su i CES (Cambridge Engineering Selector) softverski paketi. Ono {to se isti~e kao bitne karakteristike ovog softvera (od strane proizvo|a~a: Granta Design) su: - organizacija i odràvanje informacija unutar

baze podataka materijala (od strane korisnika), - organizacija i odràvanje informacija vezano za

proizvodne procese, - znatna u{teda novca, - superiorne mogu}nosti dizajniranja, - upravljanje sistemom (mena|ment baze

podataka), - brz protok informacija unutar organizacije. CES softver i moduli baza podataka su me|usobno povezani u prikladno definisane pakete. Svaki paket je izveden tako da omogu}uje potpuno rje{enje za specifi~ne CAD potrebe.

3. MATERIAL SELECTION EXPERT SYSTEMS

In previous chapter three typical EDB types are described, and it is possible to notice that every type offer possibility of searching for some specific material, apropos reply if database consists requested material. If material exists, than it is possible to get other additional informations. Software and hardware development enables that authors of material databases continoue further, i.e. to create special software packages, which will not consist only mentioned databases, but offer possibility of interactive material selection for different applications in engineering (apropos Computer Aided Material Selection – CAMS). Goals of developing Computer Aided Material Selection – CAMS are [5]: - enable rational material usage, directly through

material savings, and indirectly through energy savings and ecology issues.

- increasing knowledge should have influence in decreasing of main reasons for technical products deterioration: fractures, corosion, material waste.

- systematic and appropriate information management for usage in designing, production and maintaining of technical products made by metal, ceramic, polymer and composit materials.

Interactive material selection allude mutual communication, user (engineer, designer) and special software package. Scheme of software package working principle is shown in figure 5. Example of expert system for material selection based on specific engineering application demands (as on the figure 6) are CES (Cambridge Engineering Selector) software packages. Main performances of this software emphasized by producer (Grant Design) are: - information management and maintaining within

material database (by user), - information management and maintaining

related with productional processes, - notable many savings, - superior design possibilities, - database management, - fast information flow within organisation. CES software and database modules are mutually connected into appropriate defined packages. Every package is derived on such way that enable complete solution for specific CAD requirements.

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Slika 5. Principijelna shema rada Ekspertnog sistema za izbor materijala /vlastita shema izra|ena za potrebe rada/ Figure 5. Principal scheme of Expert System for material selection /personal scheme maded for paper purposes/

Slika 6. Shema rada CES Sistema - Moduli CES sistema [3] /snimak web stranice literaturni br. [3]/ Figure 6. Scheme of CES System work – Modules of CES System /screenshot of web page reference no. [3]/ Razvijeni su sljede}i CES paketi: - CES MATERIALS – osnovni paket, inkorporira

module materijala i sadr`i mehani~ke, elektri~ne, termalne osobine materijala, kao i karakteristike otpornosti materijala za razli~ita stanja okoline. Pokriva oko 3000 metala, keramiku, polimere, kompozite i prirodne materijale (drvo). CES Materials u sebi sadr`i aplikativne programe: - CES SELECTOR, - MATERIALS DATABASE, - CES VIEWER, - CES INDEPTH, - CES WEBLINKS.

Following CES packages are developed: - CES MATERIALS – basic package, incorporate

material modules and consists mechanical, electrical, thermal material properties, and material resistance characteristics for various environmental states. It covers about 3000 metals, ceramics, polymers, composits and natural materials (wood). CES Materials consists applicative programs: - CES SELECTOR, - MATERIALS DATABASE, - CES VIEWER, - CES INDEPTH, - CES WEBLINKS.

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- CES ENGINEER – paket pored sadr`aja CES Materials dodatno sadr`i i module o proizvodnim procesima, t.j. njihove opise, te fizi~ke i ekonomske atribute (125 razli~itih procesa).

- CES ENGINEER PRO – unaprije|eni CES Engineer sa dodatkom CES CONSTRUCTOR modula, koji daje mogu}nost vr{enja izmjena (editovanja) u postoje}im bazama podataka materijala, kao i stvaranja novih baza.

CES SELECTOR - CES sistem je sastavljen od niza povezanih modula, kao sto je prikazano na slici 6. Izbor materijala je

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