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1.
Fracture toughness of HSLA welds made on penstock material
Zdravko Praunseis, 2019, izvirni znanstveni članek

Opis: The presence of different microstructures along the pre-crack fatigue front has a significant effect on the critical crack tip opening displacement (CTOD). This value is the relevant parameter for the safe servicing of welded structures (penstocks). In the case of specimens with the through-thickness notch partly in the weld metal, partly in the heat-affected zone, and partly in the base material, i.e., using the composite notched specimen, the fracture behaviour significantly depends on the portion of the ductile base material, the size, and the distribution of mismatching factor along the vicinity of the crack front.
Ključne besede: High Strength low Alloyed Steel, CTOD Fracture Toughness Testing, CTOD-R resistance Curve, Welded joints
Objavljeno v DKUM: 22.12.2023; Ogledov: 548; Prenosov: 6
.pdf Celotno besedilo (2,41 MB)
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2.
The influence of delta ferrite on the quality assessment of austenitic stainless steel welds for the production of ovens
Zdravko Praunseis, 2020, izvirni znanstveni članek

Opis: Rust-resistant metals, such as the popular stainless steel, often contain some quantities of delta ferrite that lower the mechanical properties of welded joints. The results of the study show that the amount of ferrite influences the quality assessment of austenitic stainless steel welds for the production of ovens using the resistance seam welding process. In this article, the basic device of resistance seam welding for the production of stainless steel welds is described. The device itself will have a significant role in the operation of the line; therefore, it was very precisely constructed and designed.
Ključne besede: austenitic stainless steel, delta ferrite, quality assessment, welded joints, production of ovenss
Objavljeno v DKUM: 15.11.2023; Ogledov: 381; Prenosov: 8
.pdf Celotno besedilo (1,80 MB)
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3.
Quality assessment of single-pass corner steel welded joints
Zdravko Praunseis, Bojan Stergar, Iztok Brinovar, 2021, izvirni znanstveni članek

Opis: The aim of this paper is to analyse the quality assessment of single-pass corner steel welded joints. The testing revealed the most burdened welded joints, which were cut out of the workpiece and prepared for metallographic macroscopic and microscopic analysis. Thus, for all examinations of single-pass corner steel welded joints, the standard test procedures were used to determine the weldability and quality assessment of base materials and welded joints. Additionally, the effects of various welded defects of single-pass weld material on the bearing strength of corner welded joints will be analysed.
Ključne besede: welded joints, microstructure, cracks, undercut, main frame
Objavljeno v DKUM: 13.11.2023; Ogledov: 351; Prenosov: 7
.pdf Celotno besedilo (3,61 MB)
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4.
The influence of simulated thermal cycle on the formation of microstructures of multi-pass weld metal
Danilo Rojko, Vladimir Gliha, 2005, izvirni znanstveni članek

Opis: The influence of weld thermal cycle on the micrstructural changes in weld metal by use of the simulated microstructures. We examined the kinetics of the formation of austenite from the starting microstructure. The simulated microstructures were prepared by the application of simulated thermal cycles with different peak temperatures on a sample of real single-pass weld metal. The reproduction of thermal cycles were carried out by the SMITWELD simulator. Special attention was dedicated to the influence of thermal cycle on the formation of microstructures, which can be potential triggers of brittle fracture (local brittle zones).
Ključne besede: welding, welded joints, multi-pass weld metal, simulated microstructure, impact toughness
Objavljeno v DKUM: 03.07.2017; Ogledov: 2320; Prenosov: 131
.pdf Celotno besedilo (223,13 KB)
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5.
Fatigue crack initiation from microstructurally small Vickers indentations
Tomaž Vuherer, Andrej Godina, Zijah Burzić, Vladimir Gliha, 2007, izvirni znanstveni članek

Opis: The resistivity of coarse grain steel against crack initiation in the presence of micro defects is discussed. Samples of material with martensitic microstructure were prepared by adequate thermal treatment. Microstructurally small Vickers indentations were used as an artificial micro defect. The compressive residual stresses are due to the irreversibility of plastic deformation. The moment of indenting enables to prepare samples with and without effects of residual stresses. The stress level for crack initiation depends on the actual indentation size. The location of initiated cracks is affected by the presence and character of residual stresses.
Ključne besede: welded joints, micro defect, coarse grain HAZ, crack initiation, crack growth, stress concentration, fatigue limit, Vickers, residual stresses
Objavljeno v DKUM: 03.07.2017; Ogledov: 1671; Prenosov: 114
.pdf Celotno besedilo (1,02 MB)
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6.
Charpy toughness of vibrated microstructures
Bogdan Pučko, Vladimir Gliha, 2005, izvirni znanstveni članek

Opis: The aim of this study was to investigate the influence of vibration on impact toughness of weld metal. Studies were carried out on two welds, of which one had been welded with applying vibration during welding. From test plates samples were made to simulate heat affect in combination with or without vibration after solidification. In this way conditions at multi-pass welding were simulated. According to different conditions Charpy toughness on non standard specimens and fracture appearance were observed. Vibration during welding benefits impact energy of weld metal, especially if weld metal undergoes further heatb treatment.
Ključne besede: welded joints, impact toughness, vibration, Charpy toughness, SAW
Objavljeno v DKUM: 03.07.2017; Ogledov: 1062; Prenosov: 109
.pdf Celotno besedilo (118,79 KB)
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7.
Factors influencing the yielding constraint by cracked welded components
Dražan Kozak, Jelena Vojvodič-Tuma, Nenad Gubeljak, Damir Semenski, 2005, izvirni znanstveni članek

Opis: The effect of strength mismatch for welded joints performed with different geometries on the yielding constraint has been investigated in the context of single-edged fracture-toughness specimens subjected to bending SE(B) using the finite-element method. The crack was located in the centre of the weld. Two geometri cal parameters have been identified as being the most important: the crack-Iength ratio a/W and the sIenderness of the welded joint (W-a)/H. They were systematically varied as follows: a/W = 0.1; 0.2; 0.3; 0.4; 0.5 and W = 2H, 4H, 8H, 16H, 24H. Basic equations and plane-strain finite-element solutions for the overmatched SE(B) specimen with all configuration combinations are given. The results are in good agreement with those in literature. This paper aims to establish yield-Ioad solutions for the same weldment configurations, but with materials dissimilarity present within the weld. This situation is usually encountered during repair welding. For this purpose, a practical combination of filler materials, with the same portion of overmatched part with M = 1.19 and undermatched part with M = 0.86, has been selected. Plane-strain solutions for the heterogeneous weld with the cracklocated in the overmatched half were obtained. The influence of the yielding-constraint key parameters has al so been evaluated. Yield-Ioad results for the specimens performed with different weld widths have the greatest scattering for the a/W = 0.5. The transition from the overmatched to the undermatched solution with increasing H is evident. On the other hand, the behaviour of the specimen with a shallow crack is dictated by the overmatch region ahead of the crack tip and depends very little on the weld slenderness. An approximated 3-D area of the yield-Ioad solutions depending ona/W and (W-a)lH has been proposed. Furthermore, the stress triaxility parameter h has been calculated using 2-D and 3-D finite-element analysis, and given as a field in the spec imen to get an insight into yielding-constraint regions. It was found that the 3-D yield-Ioad solutions are very close to the plane-strain solutions. Also, the effect of a/W on the yielding constraint is more significant than the effect of Mand (W-a)/H.
Ključne besede: welded structures, welded joints, fracture mechanics, cracks, SE(B) specimens, yielding load, yielding constraint parameters
Objavljeno v DKUM: 06.04.2017; Ogledov: 1450; Prenosov: 116
.pdf Celotno besedilo (793,79 KB)
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8.
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 v DKUM: 10.07.2015; Ogledov: 1461; Prenosov: 42
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9.
Microstructural investigation of the heat-affected zone of simulated welded joint of P91 steel
Tomaž Vuherer, Marko Dunđer, Ljubica Milović, Milorad Zrilić, Ivan Samardžić, 2013, izvirni znanstveni članek

Opis: In the process of testing real components exposed to elevated temperature, it is not possible to neglect cracks. The most significant cracks can be induced by welding, which is applied for joining of structural components. Pressure equipment in service is also exposed to high pressure and high stresses. Materials for their manufacturing are designed to resist high stressat elevated temperature, and to meet requirements regarding creep resistance. The objective of this study is to investigate microstructure of different regions of the heat affected zone in T/P91 steels by using thermal simulation instead of welding.
Ključne besede: welded joints, microstructures, P91 steel, heat-affected zone, heat treatment
Objavljeno v DKUM: 10.07.2015; Ogledov: 1262; Prenosov: 171
.pdf Celotno besedilo (921,38 KB)
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10.
The transferability of fracture-mechanics parameters to fracture performance evaluation of welds with mismatching
Masao Toyoda, Zdravko Praunseis, 2000, izvirni znanstveni članek

Opis: The differences in the mechanical properties between different weld-metal regions obviously affect the strain distribution around the crack tip during a fracture test and hence influence the fracture toughness value. The variation in plastic constraint during fracture mechanics testing has an additional effect on the ductile and brittle fracture initiation behaviour of any weld joint. This paper deals with the transferability of fracture toughness results to the fracture performance evaluation of the strenght of mismatch welded joints based on the two-parameter criterion and the local approach. It was found that the numerical simulations based on the transferrable fracture concept are effective in practice.
Ključne besede: welding, welded joints, strength mismatching, plastic constraint, transferability concept
Objavljeno v DKUM: 01.06.2012; Ogledov: 3099; Prenosov: 451
.pdf Celotno besedilo (802,24 KB)
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