1. Effects of fixture configurations and weld strength mismatch on J-integral calculation procedure for SE(B) specimensPrimož Štefane, Stijn Hertelé, Sameera Naib, Wim de Waele, Nenad Gubeljak, 2022, original scientific article Abstract: This work presents the development of a J-integral estimation procedure for deep and
shallow cracked bend specimens based upon plastic ηpl factors for a butt weld made in an S690 QL
high strength low alloyed steel. Experimental procedures include the characterization of average
material properties by tensile testing and evaluation of base and weld metal resistance to stable tearing
by fracture testing of square SE(B) specimens containing a weld centerline notch. J-integral has been
estimated from plastic work using a single specimen approach and the normalization data reduction
technique. A comprehensive parametric finite element study has been conducted to calibrate plastic
factor ηpl and geometry factor λ for various fixture and weld configurations, while a corresponding
plastic factor γpl was computed on the basis of the former two. The modified ηpl and γpl factors were
then incorporated in the J computation procedure given by the ASTM E1820 standard, for evaluation
of the plastic component of J and its corresponding correction due to crack growth, respectively. Two
kinds of J-R curves were computed on the basis of modified and standard ηpl and γpl factors, where
the latter are given by ASTM E1820. A comparison of produced J-R curves for the base material
revealed that variations in specimen fixtures can lead to ≈10% overestimation of computed fracture
toughness JIc. Furthermore, a comparison of J-R curves for overmatched single-material idealized
welds revealed that the application of standard ηpl and γpl factors can lead to the overestimation of
computed fracture toughness JIc by more than 10%. Similar observations are made for undermatched
single material idealized welds, where fracture toughness JIc is overestimated by ≈5%.
Keywords: metal weld, strength mismatch, fracture, plastic correction factors, fixture rollers, J-R resistance curve
Published in DKUM: 20.03.2025; Views: 0; Downloads: 9
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3. Vloga in nastanek mikrostrukturnih sestavin M-A v zvarnih spojih maloogljičnih visokotrdnostnih konstrukcijskih jekelZdravko Praunseis, Masao Toyoda, Alojz Križman, Mitsuru Ohata, 2001, review article Abstract: The existence of martensite-austenite constituents in the weld metal and heat-affected zone seriously reduces the fracture toughness of the welded joint. Therefore, we have investigated the formation of the martensite-austenite constituents when high-strength low-alloy steel is welded with a high heat input or using multi-pass welding. This paper deals with the effects of martensite-austenite constituents on the fracture toughness, the metallurgical features of the martensite-austenite constituents, and the prevention and elimination of the martensite-austenite constituents in the welded joints.
Keywords: arc welding, high-strength low-alloy steels, microstructure, martensite-austenite constituents, weld metal, heat-affected zone, cooling rate
Published in DKUM: 01.06.2012; Views: 2188; Downloads: 134
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4. Fuzzy logic based quality monitoring in short-circuit gas metal arc weldingMarjan Golob, Arpad Köveš, 2007, original scientific article Abstract: Conventional methods, e.g. destructive and non-destructive testing methods, are expensive and time-consuming; therefore, possibilities of online and automated quality control of a welding process during welding as such are investigated. The paper deals with the possibilities of application of fuzzy logic to the analysis of weld quality, particularly assessment of the weld surface condition by means of measurable electric signals emitted during welding. A simple fuzzy inference system was realised which could relatively efficiently assess the weld quality on the basis of time variations of the welding voltage and short-circuit time in a certain time window.
Keywords: fuzzy systems, fuzzy logic, gas metal arc welding, GMAW, quality monitoring, statistical analysis, quality control, weld quality
Published in DKUM: 31.05.2012; Views: 2504; Downloads: 106
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5. Charpy toughness and microstructure of vibrated weld metalBogdan Pučko, Vladimir Gliha, 2006, original scientific article Abstract: Vibration during welding can be used to obtain certain changes in mechanical properties of weld metal. Research work on the influence of vibration on the secondary microstructure of welds and hence on the Charpy toughness was performed. Vibration during welding exhibits positive effects on the microstructure constituent formation. Multipass welding was simulated with reheating of the original single pass weld in order to obtain similar microstructure to multipass welds. Microstructures were examined with an optical microscope. Additionally, fractographic examination of the rupture of Charpy specimens was performed. Changes in the microstructure according to vibration were observed which affect toughness of the weld metal. Vibration during welding was rated more effective in the case of reheating the weld metal, which is the case in multipass welding.
Keywords: welding, welded joints, mechanical properties of metals, ferrite, vibration, microstructure, toughness, notched bar testing, weld metal
Published in DKUM: 31.05.2012; Views: 2485; Downloads: 109
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