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

Effect of structural heterogeneity on the fracture mechanics parameters of welded joints of A.387 steel

Radi potpunijeg razumevanja uzroka i načina pojave i rasta prslina u zavarenim spojevima čelika A-387 Gr.11 predviđenog za rad u uslovima povišene temperature i pritiska, potrebno je da se utvrdi kako heterogenost strukture i mehaničkih svojstava zavarenog spoja, utiče na žilavost loma i pojavu i rast zamorne prsline. Ispitivanjem CT i Šarpi epruveta sa iniciranom zamornom prslinom data je ocena kako heterogenost strukture i mehaničkih svojstava zavarenog spoja utiču na parametre žilavosti loma i brzinu rasta zamorne prsline.For better understanding of the phenomenon of crack initiation and propagation in welded joints of A-387 Gr. 11 steel designed for high-temperature and high-pressure applications, it is necessary to determine the effect of the heterogeneity of microstructural and mechanical properties on fracture toughness and fatigue crack initiation and propagation. Based on the tests conducted with pre-cracked CT and Charpy size specimens, the effect of the heterogeneity of the microstructural and mechanical properties of welded joints on fracture toughness and fatigue-crack growth parameters was determined

Effect of structural heterogeneity on the fracture mechanics parameters of welded joints of A.387 steel

Radi potpunijeg razumevanja uzroka i načina pojave i rasta prslina u zavarenim spojevima čelika A-387 Gr.11 predviđenog za rad u uslovima povišene temperature i pritiska, potrebno je da se utvrdi kako heterogenost strukture i mehaničkih svojstava zavarenog spoja, utiče na žilavost loma i pojavu i rast zamorne prsline. Ispitivanjem CT i Šarpi epruveta sa iniciranom zamornom prslinom data je ocena kako heterogenost strukture i mehaničkih svojstava zavarenog spoja utiču na parametre žilavosti loma i brzinu rasta zamorne prsline.For better understanding of the phenomenon of crack initiation and propagation in welded joints of A-387 Gr. 11 steel designed for high-temperature and high-pressure applications, it is necessary to determine the effect of the heterogeneity of microstructural and mechanical properties on fracture toughness and fatigue crack initiation and propagation. Based on the tests conducted with pre-cracked CT and Charpy size specimens, the effect of the heterogeneity of the microstructural and mechanical properties of welded joints on fracture toughness and fatigue-crack growth parameters was determined

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

Influence of temperature on fracture toughness values in different regions of A-387 Gr. B welded joint

The influence of temperature on fracture toughness values in different regions of a welded joint is analysed low-alloyed Cr-Mo steel A-387 Gr. B, designed for high temperature applications. Heterogeneity of microstructure and properties of welded joint is evaluated by testing standard 3BP specimens with crack tip located at different regions of a joint, including the base metal (BM), weld metal (WM) and heat-affected-zone (HAZ). Experiments were performed both at the room temperature and at design working temperature, 5400C. Based on these results, temperature effect on crack resistance is established for all different regions in a welded joint. 2019 The Authors. Published by Elsevier B.V

Structural integrity assessment from the aspect of fracture mechanics

An increasing diversity of operations and different materials, as well as different working conditions lead to various construction solutions. Structural design is the preparation of structures that shall be efficient in fulfilling anticipated exploitation conditions, both economically and safely, i.e. there will be no damage resulting in the loss of structural functionality in service. In practice, however, there are fractures that can occur during construction, assembly, and exploitation. Fracture may be caused by overloads, by static fracture, or by dynamic loads, and by fatigue. Upon calculation of static structural durability, normal and tangential stresses are taken into account, while the dynamic durability calculation defines structural resistance to crack formation and its propagation under dynamic loading. The aim of this paper is to demonstrate the possibility of applying fracture mechanics to structural integrity assessment. To this end, the basic concepts of linear elastic fracture mechanics will be explained

Structural integrity assessment from the aspect of fracture mechanics

An increasing diversity of operations and different materials, as well as different working conditions lead to various construction solutions. Structural design is the preparation of structures that shall be efficient in fulfilling anticipated exploitation conditions, both economically and safely, i.e. there will be no damage resulting in the loss of structural functionality in service. In practice, however, there are fractures that can occur during construction, assembly, and exploitation. Fracture may be caused by overloads, by static fracture, or by dynamic loads, and by fatigue. Upon calculation of static structural durability, normal and tangential stresses are taken into account, while the dynamic durability calculation defines structural resistance to crack formation and its propagation under dynamic loading. The aim of this paper is to demonstrate the possibility of applying fracture mechanics to structural integrity assessment. To this end, the basic concepts of linear elastic fracture mechanics will be explained

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

Influence of temperature and exploitation time on hardness and micro-structure of a welded joint in a reactor mantle

This paper presents the analysis of the influence of temperature and exploitation time on the cross-sectional hardness and microstructure changes of characteristic zones of a welded joint made of low-alloyed Cr-Mo steel A-387 Gr. B. Exploited parent metal is a part of a reactor mantle which was working for over 40 years and is in the damage repair stage, i.e. part of its mantle is being replaced with new material. Cross-sectional hardness of a butt-welded joint was measured and macroscopic investigation of the welded joint and microstructural analysis of the parent material, weld metal and the heat affected zone were performed. The comparison of parameters obtained for characteristic zones of a welded joint provides a way to meausre the justifiability of the selected welding technology

Relation between impact and fracture toughness of A-387 Gr. B welded joint

The influence of temperature on impact and fracture toughness values in different regions of a welded joint is analysed for low-alloyed Cr-Mo steel A-387 Gr. B, designed for high temperature applications. Standard Charpy specimens were tested on instrumented pendulum to separate total impact energy into energy for initiation and propagation energy for base metal (BM), weld metal (WM) and heat-affected-zone (HAZ). Standard three point bending (3BP) specimens with crack tip located at different regions of a joint (BM, WM, HAZ), were used for fracture toughness testing. Experiments were performed both at the room temperature and at design working temperature, 540 degrees C, which is the focus of this paper, to evaluate temperature effect on both notch and crack resistance for all different regions in a welded joint. Moreover, the relation between crack initiation energy and fracture toughness is established, purely on empirical base