Influence of crack on welded joint characteristics in different types of loads

Primena čelika visoke čvrstoće kod projektovanja zavarenih konstrukcija zahteva podatke o svojstvima istih pri različitim uslovima opterećenja. Zahvaljujući visokom naponu tečenja debljina zida može se smanjiti u poređenju sa opštim konstrukcijskim čelicima, a shodno tome, dimenzije zavarenog spoja, potrošnja dodatnog materijala za zavarivanje i vreme za izradu zavarenih spojeva će biti minimizirani. Ovo je od značaja za opremu pod pritiskom, ali i za druge industrijske grane (kranove, bagere). Kompletna karakterizacija zavarenog spoja mora uključiti podatke za osnovni metal, ali takođe su neophodne osobine metala šava i zone uticaja toplote (ZUT), bar da bi ih uporedili sa svojstvima osnovnog metala. Ovo je od posebnog značaja zbog heterogenosti strukture u ZUT-u. .The application of high strength steels in design of heavy duty welded structures requires data about properties in different loading conditions. Thanks to high yield stress the wall thickness can be reduced compared to mild structural steels, and accordingly welded joint cross-sections, welding consumables consumption and time for welded joints manufacturing will be minimized. This is of importance for pressurized equipment, but also for other industrial branches (cranes, excavator). Complete characterization of welded joint has to include data for parent metal, but also the properties for weld metal and the heat-affected-zone (HAZ) are necessary, at least in order to compare them with parent metal properties. This is of special importance because of heterogeneity structure in HAZ

Influence of Corrosion on Parameters of Fracture Mechanics of Aluminium Alloys 2024-T351 and 7075-T651

This paper presents the results of determining the fatigue crack growth parameters in aluminium alloy specimens 2024-T351 and 7075-T651, with different levels of previous corrosion, in the laboratory environment. Tests were performed, under the same load conditions, for each case of corrosion (without corrosion, 7 days of exposure in a corrosive environment and 30 days of exposure in a corrosive environment). All the tests were performed at room temperature. The analysis of the results includes changes in the basic parameters of fatigue crack growth, depending on the time of exposure to the action of controlled moisture. In addition, this paper gives a brief overview of modern design processes in the environment of computer mechanics and presents the results of the crack growth simulation, using the software package ANSYS

Surface modification of laser welded nimonic 263 sheets

Laser surface treatment is both a thermomechanical and mechanical process, based on the ability of a high energy laser pulse to generate shock waves and plastic deformation in metallic materials. Laser welding is a high energy density process with many advantages such as narrow heat affected zone, lower heat input and lower heat/energy distortion compared to conventional welding processes. In this paper, Nimonic 263 alloy sheets are laser welded by Nd:YAG laser using different laser processing parameters. The microstructure, surface roughness and mechanical properties are investigated. Welded joints are mechanically treated by laser in order to improve the surface and mechanical characteristics. Mechanical characteristics are determined by tensile test, and fractures and laser treated weld surfaces are observed by scanning and optical microscopy. Surface topography is analysed by optical profilometry and micro hardness is measured by Vickers method

Crack initiation and growth in welded joint of steel for operation at elevated temperature

U radu su prikazana eksperimentalna istraživanja koja uključuju analizu stvaranja i rasta prsline u zavarenom spoju čelika za rad na povišenim temperaturama. Za bolje razumevanje fenomena stvaranja i rasta prsline u zavarenim spojevima čelika A-204 Gr. A, namenjenog za rad na visokim temperaturama i pritiscima, potrebno je utvrditi uticaj heterogenosti mikrostrukturnih i mehaničkih svojstava na žilavost loma i stvaranje i rast zamorne prsline u komponentama zavarenog spoja. Na osnovu ispitivanja provedenih na CT i Charpy epruvetama na kojima su prethodno inicirane prsline utvrđen je uticaj heterogenosti mikrostrukturnih i mehaničkih svojstava zavarenog spojeva na žilavost loma i parametre rasta zamorne prsline.In a paper given, experimental investigations have included the analysis of crack initiation and growth in welded joint of steel for operation at elevated temperatures. For better understanding of the phenomenon of crack initiation and propagation in welded joints of A-204 Gr. A steel, designed for high-temperature and high-pressure application, it is necessary to determine the effect of heterogeneity of microstructural and mechanical properties on fracture toughness and fatigue crack initiation and propagation in welded components. Based on the tests conducted with pre-cracked CT and Charpy size specimens, the effect of heterogeneity of microstructural and mechanical properties of welded joints on fracture toughness and fatigue-crack growth parameters was determined

Corrosion effect on mechanical properties of aluminium alloys 2024-t351 and 7075-t651

Results of static tensile testing of aluminium alloys 2024T351 and 7075-T651 are presented with different levels of corrosion exposure in the laboratory environment. Specimens from two different rolling directions are tested (parallel and transverse rolling direction) after 7 and 30 days of corrosion exposure, respectively, using SCHENCK TREBEL Prufmaschinen 4030 Ratingen, type RM100 testing machine. The obtained results indicate the change in the tensile properties depending on the time of corrosion exposure and moisture content

Corrosion effect on mechanical properties of aluminium alloys 2024-t351 and 7075-t651

Results of static tensile testing of aluminium alloys 2024T351 and 7075-T651 are presented with different levels of corrosion exposure in the laboratory environment. Specimens from two different rolling directions are tested (parallel and transverse rolling direction) after 7 and 30 days of corrosion exposure, respectively, using SCHENCK TREBEL Prufmaschinen 4030 Ratingen, type RM100 testing machine. The obtained results indicate the change in the tensile properties depending on the time of corrosion exposure and moisture content

Surface modification of laser welded nimonic 263 sheets

Laser surface treatment is both a thermomechanical and mechanical process, based on the ability of a high energy laser pulse to generate shock waves and plastic deformation in metallic materials. Laser welding is a high energy density process with many advantages such as narrow heat affected zone, lower heat input and lower heat/energy distortion compared to conventional welding processes. In this paper, Nimonic 263 alloy sheets are laser welded by Nd:YAG laser using different laser processing parameters. The microstructure, surface roughness and mechanical properties are investigated. Welded joints are mechanically treated by laser in order to improve the surface and mechanical characteristics. Mechanical characteristics are determined by tensile test, and fractures and laser treated weld surfaces are observed by scanning and optical microscopy. Surface topography is analysed by optical profilometry and micro hardness is measured by Vickers method

Experimental determining of fracture behaviour of P460NL1 steel welded joint specimens

This paper is focused on the experimental measuring of impact energy as a part of the doctoral dissertation involving the fatigue behaviour of welded joints, made of fine grain normalised micro-alloyed low carbon high strength steel P460NL1 [1,2], typically used for pressure vessels working at subzero temperatures. VAC 65 [3] was used as filler material, and two plates were welded using the MAG welding procedure (with 82% Ar + 18% CO2 shielding gas). The specimens were taken from two opposite ends of the welded plate, taking into account the measured values of groove edge temperature in these locations, wherein the temperatures in Location 2 (near the end of the weld) were higher than those in Location 1 (near the weld's beginning). Based on their specific position, in terms of temperature and notch position (weld root or face), the specimens were divided into four groups of three. This testing was performed using a SCHENCK-TREBEL instrumented Charpy pendulum. The total impact energy was determined, along with its components, crack initiation and crack propagation energy. The obtained results have confirmed that the test specimens were of high toughness, with total impact energy ranging from 165200 J, at room temperature. The crack propagation energy was the dominant component, being several times greater than the crack initiation energy, as was expected

Experimental determining of fracture behaviour of P460NL1 steel welded joint specimens

This paper is focused on the experimental measuring of impact energy as a part of the doctoral dissertation involving the fatigue behaviour of welded joints, made of fine grain normalised micro-alloyed low carbon high strength steel P460NL1 [1,2], typically used for pressure vessels working at subzero temperatures. VAC 65 [3] was used as filler material, and two plates were welded using the MAG welding procedure (with 82% Ar + 18% CO2 shielding gas). The specimens were taken from two opposite ends of the welded plate, taking into account the measured values of groove edge temperature in these locations, wherein the temperatures in Location 2 (near the end of the weld) were higher than those in Location 1 (near the weld's beginning). Based on their specific position, in terms of temperature and notch position (weld root or face), the specimens were divided into four groups of three. This testing was performed using a SCHENCK-TREBEL instrumented Charpy pendulum. The total impact energy was determined, along with its components, crack initiation and crack propagation energy. The obtained results have confirmed that the test specimens were of high toughness, with total impact energy ranging from 165200 J, at room temperature. The crack propagation energy was the dominant component, being several times greater than the crack initiation energy, as was expected

Numerical and Experimental Investigations of Fracture Behaviour of Welded Joints with Multiple Defects

Current standards related to welded joint defects (EN ISO 5817) only consider individual cases (i.e., single defect in a welded joint). The question remains about the behaviour of a welded joint in the simultaneous presence of several different types of defects, so-called multiple defects, which is the topic of this research. The main focus is on defects most commonly encountered in practice, such as linear misalignments, undercuts, incomplete root penetration, and excess weld metal. The welding procedure used in this case was metal active gas welding, a common technique when it comes to welding low-alloy low-carbon steels, including those used for pressure equipment. Different combinations of these defects were deliberately made in welded plates and tested in a standard way on a tensile machine, along with numerical simulations using the finite element method (FEM), based on real geometries. The goal was to predict the behaviour in terms of stress concentrations caused by geometry and affected by multiple defects and material heterogeneity. Numerical and experimental results were in good agreement, but only after some modifications of numerical models. The obtained stress values in the models ranged from noticeably lower than the yield stress of the used materials to slightly higher than it, suggesting that some defect combinations resulted in plastic strain, whereas other models remained in the elastic area. The stress-strain diagram obtained for the first group (misalignment, undercut, and excess root penetration) shows significantly less plasticity. Its yield stress is very close to its ultimate tensile strength, which in turn is noticeably lower compared with the other three groups. This suggests that welded joints with misalignment and incomplete root penetration are indeed the weakest of the four groups either due to the combination of the present defects or perhaps because of an additional unseen internal defect. From the other three diagrams, it can be concluded that the test specimens show very similar behaviour with nearly identical ultimate tensile strengths and considerable plasticity. The diagrams shows the most prominent yielding, with an easily distinguishable difference between the elastic and plastic regions. The diagrams are the most similar, having the same strain of around 9% and with a less obvious yield stress limit