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1.
HAZ toughness of Ti-microalloyed ofshore steel in as-welded and simulated condition
Inoslav Rak, Mustafa Koçak, Blagoj Petrovski, Vladimir Gliha, 1995, izvirni znanstveni članek

Opis: The CTOD values measured on 34 mm thick SENB specimen taken from multipass 1/2K joints were compared with the values obtained from 8 mm thick SENB specimens with simulated microstructures of CGHAZ (a/W=0.5). Single and double thermal cycles were used to simulate various thermal treatment which HAZ at the weld bond may xperience during the welding.
Ključne besede: varjenje, Ti-ofshore jekla
Objavljeno: 10.07.2015; Ogledov: 639; Prenosov: 15
URL Povezava na celotno besedilo

2.
Lomno-žilavostne lastnosti toplotno vplivanega področja mikrolegiranega jekla tipa StE 355Ti za zahtevne konstrukcije
Inoslav Rak, 1994, izvirni znanstveni članek

Opis: Lomno-žilavostne lastnosti toplotno vplivanega področja mikrolegiranega jekla tipa StE 355Ti za zhtevne konstrukcije
Objavljeno: 10.07.2015; Ogledov: 568; Prenosov: 16
URL Povezava na celotno besedilo

3.
4.
Vpliv mehkega korena na vedenje zvarnega spoja pri lomu
Vladimir Gliha, Nenad Gubeljak, Inoslav Rak, 1997, izvirni znanstveni članek

Opis: Primerjali smo lomno žilavost treh različnih zvarnih spojev, katerih meja plastičnosti je presegala mejo plastičnosti osnovnega materiala. Dva zvara smo v korenskem delu zvarili z mehkejšim dodajanim materialom, da smo lahko opustili predgrevanje. Mehki koren vpliva na znižanje lomne žilavosti spoja. Rezultati merjenja lomne žilavosti so na zvaru, kjer je bil koren izdelan dvovarkovno, višji od štirivarkovnega.
Ključne besede: varenje, zvarni spoji, koren zvara, krhki lom, lomna žilavost, dodajani material
Objavljeno: 10.07.2015; Ogledov: 649; Prenosov: 27
URL Povezava na celotno besedilo

5.
Flaw acceptability assessment detected in HSLA steel weld joints
Inoslav Rak, 1999, izvirni znanstveni članek

Opis: The flow size in weld joint can be determined by non destructive examination (NDE). Because of different mateials, and loading as well as because of the possible effect of corrosive environment the question arises how to assess reliably the allowable falw size in different weld joint parts. The presence of flaws is obvious but the possibilities of their revealing are limited and not always posssible. The flaw size and distribution are the essential parameters for the structure capacity of bearing under high loading the weld joint. The larger is the allowable flaw size anticipated, the safer is the welded structure, and the easiest is the detection of the flaw size by NDE methods. Thus for assessing the safety of complex loaded welded structure, machine parts or equipment life time, it is obligatory to consider the requirements of different "Fitness for Purpose" systems. The article presents the possibility of assessing the detected flaw by means of NDE if the material fracture toughness of the area where the fatigue crack tip located is known. The fatigue crack represents the severest discontinuity that can occur in a welded joint. The principles of IIW Guidance on Assessment of The Fitness for Purpose of Welded Structures - IIW/IIS-SST-1157-90 and BS PD 6493 and separately ETM that treats mis-matched weld joints are shown and used.
Ključne besede: zvarni spoji, dopustna velikost napake, lomna žilavost, trdnostna heterogenost, primernost za uporabo, weld joint, allowable flaw size, fracture toughness, strength mis-match, fitness for purpose
Objavljeno: 10.07.2015; Ogledov: 923; Prenosov: 12
URL Povezava na celotno besedilo

6.
Modificirano numerično modeliranje lomnega vedenja zvarnega spoja v prehodnem področju iz duktilnega h krhkemu lomu
Dražan Kozak, Nenad Gubeljak, Inoslav Rak, 1998, izvirni znanstveni članek

Opis: Varno obratovanje varjene konstrukcije je odvisno od lomno mehanskih lastnosti zvarnih spojev. Največje spremembe teh lastnosti nastopajo v prehodnem področju iz duktilnega v krhki lom. Namen tega raziskovalnega dela je z metodo končnih elementov definirati primeren numerični postopek za izračun napetostno-deformacijskega stanja v trenutku nestabilnega loma. Uporabljen modificirani postopek numeričnega modeliranja mora omogočiti vedenje materiala zvara na konici razpoke v sksladu s teorijo nastanka in širjenja duktilne oziroma cepilne razpoke ter zagotoviti verifikacijo z eksperimentalnimi rezultati. Uporaba ravninskega deformacijskega stanja na konici razpoke ob ravninsko napetostnem stanju preostalega preizkušanca med sukcesivnim obremenjevanjem omogoča dobro korelacijo med eksperimentalnimi in numeričnimi rezultati. Na osnovi tega je možno definirati pogoje sprožanja nestabilnega loma v poljubno oblikovanem modelu, kakor tudi določiti prag za varno obratovanje dejanske varjene konstrukcije v prehodnem področju iz duktilnega v krhki lom.
Ključne besede: zvarni spoj, metoda končnih elementov, lomna žilavost CTOD, krhki cepilni lom, omejitev
Objavljeno: 10.07.2015; Ogledov: 748; Prenosov: 47
URL Povezava na celotno besedilo

7.
Weld joint fracture behaviour of HSLA steels dissimilar in strength
Inoslav Rak, Arpad Treiber, 1998, izvirni znanstveni članek

Opis: The effect of strength differences (mismatch) between weld metal and two base metals as well as local variations of strength within weld metal/HAZ zones on the toughness properties were discussed. The significance of local fracture toughness measurement technique was also discussed by comparing the CTOD results of [delta]5 and British Standard [delta]BS. Some differences between the two techniqes were discussed in particular for CGHAZ toughness of similar and dissimilar joints.
Ključne besede: welding, welded joints, fracture mechanics, HSLA steels, fracture toughness
Objavljeno: 10.07.2015; Ogledov: 887; Prenosov: 25
URL Povezava na celotno besedilo

8.
Role of residual stresses on fracture properties of under-matched butt weld
Inoslav Rak, Vladimir Gliha, 1999, izvirni znanstveni članek

Opis: Under-matched weld joints were adopted for producing a penstock of 47 mm wall thickness and 4200 mm diameter, to improve the weldability. The isothermal Robertson wide plate test on the under-matched weld joints, were the allowable stress level was 0.6 of the yield stress, proved that the longitudinal stresses caused the crack propagation alog the weld joint to deviate into tough base material where it was arrested. The arrest temperature was between -10 and -20°C. The behaviour of the crack propagation was the reason to omit the thermal stress relieving of the pipe section and on circumferential weld joints executed on this side. One can always take into consideration the role of axial residual stresses when assessing whether to use, or not, under-matched weld joints in severer loaded structures.
Ključne besede: strjeni zvar z nižjo mejo tečenja, zaostale napetosti, potek loma, lastnosti ujetja, lomna žilavost, under-matched weld joint, residual stresses, fracture path, arrest properties, fracture toughness
Objavljeno: 10.07.2015; Ogledov: 963; Prenosov: 27
URL Povezava na celotno besedilo

9.
Ocenitev občutljivosti na razpokljivost v hladnem pri varjenju visokotrdnostnega jekla Niomol 490 K
Zdravko Praunseis, Vladimir Gliha, Inoslav Rak, 2000, izvirni znanstveni članek

Opis: V članku je predstavljena analitična (z empiričnimi enačbami) in eksperimentalna (z Y-preizkusom) določitev temperature predgrevanja visokotrdnostnega jekla Niomol 490 K debeline 19 mm, pri kateri ne bo prišlo do pojava razpok v hladnem v zvarnem spoju. Ugotovljeno je, da je pri varjenju jekla Niomol 490 K z oplaščeno elektrodo EVB NiMo nastanku razpok v hladnem bolj podvržen var kot osnovni material. Z izračuni lahko dovolj natančno napovemo temperaturo predgrevanja jekla, vendar je treba dokazati temperaturo predgrevanja tudi z Y-preizkusom.
Ključne besede: visokotrdnostno jeklo, razpokljivost v hladnem, Y-preizkus, temperatura predgrevanja
Objavljeno: 01.06.2012; Ogledov: 1519; Prenosov: 83
.pdf Celotno besedilo (756,66 KB)
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10.
The fracture behaviour of global/local mis-matched weld joints provided on HSLA steels
Inoslav Rak, Nenad Gubeljak, Zdravko Praunseis, 2001, izvirni znanstveni članek

Opis: The fracture behaviour of thick section high strength steel weldments, that contain soft root passes, has been studied. Two different weld consumables with different strength mismatch (1>M>1) and fracture toughness properties in the WM have significantly increased the complexity of the mis-match effect and failure behaviour of weld joints, depending on the crack location and the thickness of the soft root layer. The aim was to explain the effect of strength heterogeneity between BM and WM and between different regions in WM (global/local mismatching). R-curves of WM and HAZ regions were also discussed. The conclusion is that the application of a welding procedure with a two-pass soft root layer, introduced for the purpose of reducing or even omitting preheating, can be recommended in mis-matched weld joints on steel grade HT80. Nevertheless, the alloying from BM, and the tempering effect of subsequent weld passes, have to be taken into account. They can cause reduction of the root region ductility and affect the local mismatch in WM and HAZ. The deterioration by providing a soft root layer can probably be reduced by a selected consumable and proper welding procedure. The final conclusion is that the application of a mismatched weld joint with a soft root layer can be recommended only if high root toughness can be provided.
Ključne besede: welding, welded joints, strength mismatching, fracture toughness, CTOD, hardness, impact toughness, HSLA steels
Objavljeno: 01.06.2012; Ogledov: 1505; Prenosov: 104
.pdf Celotno besedilo (441,77 KB)
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