The effect of variable loading onintegrity of a welded joint of high alloy-steel X20

In present paper, experimental investigations have included the effect of exploitation conditions (exploitation time and temperature) on properties of high-cycle fatigue and parameters of fatigue-crack growth of a welded joint of steel X20 CrMoV 12-1 (X20). The effect of exploitation conditions was analysed by testing new pipe and the pipe having been exploited for 116 000 hours. The results obtained by testing and their analysis provide a practical contribution to assessment of quality of a welded joint of steel X20, the aim of which is revitalisation and extension of exploitation life of vital components of thermal power plants manufactured from high-alloy steel for operation at elevated temperatures

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

Effect of variable load on crack initiation microalloyed steel S 690-QL

The accumulation of damage in the form of initiation and growth of micro-cracks is the first stage of destruction that ends when the merger microcracks form macro cracks. Cracks formed in the cycle number N =104 - 105 are the result of low cycle fatigue. From the need to evaluate low cycle fatigue life was carried out to investigate the low cycle fatigue microalloyed high-strength steel S690QL in the heat-treated

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