Determination of Residual Fatigue Life of Welded Structures at Bucket-Wheel Excavators through the Use of Fracture Mechanics

This paper presents a methodological approach for the assessment of service life of vital welded structures of a bucket-wheel excavator Sch Rs 650/5x24 ('Thyssen Krupp', Germany) boom, subjected to cyclic loading with a variable amplitude through the use of experimental tests carried out in order to determine operational strength and growth of a fatigue crack. Realized researches and results presented in this paper offer great possibilities for the analyses of behaviour of vital welded structures of the bucket-wheel boom. By the application of the measurement device with 8 channels for registration and processing of electric signals HBM Spider 8 and measurement tapes HBM 6/350xXY31 deformations were measured at vital welded structures of the boom in the area of the bucket-wheel, made of steels St 37.2 and St 52.3 in accordance with standard DIN 17100, or steels S235J2G3 and S355J2G3 in accordance with standard EN 10025-2. The objective of the test is to determine if there is a possibility of occurrence of plastic deformations or initial cracks due to fatigue at vital welded structures. Tests that refer to the growth of the fatigue crack located at the welded joint have been carried out by bending at three points with asymmetric load R = 0.5 (R = sigma(min) / sigma(max)) at the specimen with a single edge notch. Tests were performed through the use of controlled force, ranging between F-max and F-min at the high frequency pulsator 'Cracktronic', while obtainment of data regarding the crack growth was carried out through the use of measurement gauge ARM A-10

Primena dvoparametarskog pristupa mehanike loma na ocenu integriteta konstrukcija

U radu je analizirana primena dvoparametarske mehanike loma na procenu integriteta zavarenih konstrukcija sa centralnom prolaznom prslinom. Izrađeni su fortranski programi za izračunavanje dijagrama za procenu loma (FAD). U linearno-elastičnoj oblasti izračunavaju se faktori intenziteta napona, a za elasto-plastičnu oblast izračunava se J integral prema EPN pristupu. Dat je diiagram za analizu integriteta ravnog konstrukcionog eiementa u obliku ploče. Analiziran je uticaj dužine prsline na stabilnost konstrukcije

Ispitivanje oscilacija noseće konstrukcije rotornog bagera

U toku eksploatacije, većina sklopova i elemenata bagera su izloženi složenim dinamičkim opterećenjima, koja zavise od uslova eksploatacije i sopstvenih oscilacija. Oscilatorna kretanja elemenata noseće konstrukcije bagera pojavljuju se u oba slučaja: stacionarnom i nestacionarnom režimu rada sistema pogona bagera i mogu biti veoma složena i širokog frekventnog spektra. U radu su prikazani rezultati teoretske i eksperimentalne analize sopstvenih i prinudnih oscilacija noseće konstrukcije bagera klase SRs 470 za različite eksploatacione usIove

Proces optimizacije noseće strukture kontejnera

U radu je na primerima teretnog kontejnera i kontejnera za sme taj telekomunikacione opreme dat pregled procesa optimizacije nose ih struktura tih konstrukcija upotrebom ra unarskih programa za projektovanje, konstruisanje i prora un vode i ra una o va e im propisima i standardima za tu vrstu opreme

Modeliranje i metodološki pristup proračunu čvrstoće noseće strukture nestandardnog izotermičkog kontejnera

U radu je vodeći računa o važecim propisima i standardima dat metodološki pristup modeliranja i proračuna čvrstoće noseće strukture nestandardnog izotermičkog kontejnera metodom konačnih elemenata. Na osnovu analize dobijenih rezultata proverena je stabilnost elemenata strukture, ocenjena je nosivost i dat je predlog poboljšanja nosivosti i optimizacije date strukture

Proračun čvrstoće noseće strukture nestandardnog izotermičkog kontejnera metodom konačnih elemenata

U radu je vodeći računa o važećim propisima i standardima dat metodološki pristup modeliranja i proračuna čvrstoće noseće strukture nestandardnog izotermičkog kontejnera metodom konačnih elemenata. Na osnovtu analize dobijenih rezultata proverena je stabilnost elemenata strukture, ocenjena je nosivost, a dati su i predlozi u cilju poboljšanja nosivosti i optimizacije date strukture

Primena parametara mehanike loma na procenu integriteta zavarenih konstrukcija

U radu ie analizirana primena parametara mehanike loma na procenu integriteta zavarenih konstrukciia sa površinskom ili unutrašnjom prslinom, sa posebnim naglaskom na određivanje sile rasta prsline Kingovim modelom. Imajuci u vidu heterogenost zavarenih spojeva, odnosno pojavu mismečinga (različite čvrstoće metala šava i osnovnog metala), analiza obuhvata elasto-plastične parametre mehanike loma, kao što su otvaranje vrha prsline i J integral. Takode, analiza u ovom radu obuhvata i probleme kao što su zaostali naponi i geometrijske nepravilnosti, koji mogu značajno da utiču na integritet zavarenih konstrukcija

Selecting the low alloy-tempered steel for manufacturing the highly loaded responsible parts

The selecting procedure of the optimal material for manufacturing the highly loaded responsible parts for military applications is presented in this paper. The considered part is in exploitation subjected to complex compressive-impact loading and cyclically to high temperatures, as well. The proper selection of material can be done exclusively based on the theoretical and experimental analysis of properties of the steel in question. The theoretical and experimental selecting of adequate steel for manufacturing such parts is done based on requirements arising from their working conditions. Based on the available data for various steels, chemical composition, mechanical and technological properties, available CCT diagram, the optimal steel was selected for the given working conditions. After the selection of the material, experimental investigations on specially prepared material samples were conducted. The real chemical composition of material was established, its most important mechanical properties were determined, the hardness was measured and the microstructure was determined, as well. After the conducted theoretical and experimental investigations, the responsible machine part was manufactured from the selected material by forging. Then, the mechanical and heat processing was executed, after which the part was tested in the real working conditions. Based on investigations of part's behavior in the real working conditions, it was concluded that the selection of the material was adequate.This research was partially financially supported by the European regional development fund and Slovak state budget by the project “Research Centre of the University of Zilina” – ITMS 26220220183 and by the Ministry of Education, Science and Technological Development of Republic of Serbia through grants: ON174004 and TR35024.Publishe

Prediction of service life of components and structures of hydro power plants during the design, prototyping and service period

During the rehabilitation of turbine and hydromechanical equipment at hydro power plant 'Djerdap 1' results of tests and researches carried out in order to analyze the condition of vital components and structures during service led to the conclusion that the components and structures could be made only if parameters of fracture mechanics were applied during the design and prototyping phase, because by doing so the occurrence of fatigue fracture and/or degradation of parent material and welded joints due to variable loading, corrosion, erosion and cavitation would be prevented, therefore the integrity of material would be maintained. Experimental determination of the fatigue crack propagation rate as an important property of development of the fatigue process during the action of the variable load, from the initial to the critical length, enables the prediction of the stable crack propagation period, or in other words of the service life of vital components and structures of turbine and hydromechanical equipment. Taking into account the fact that cracks are most severe of all defects, the results obtained for cracks could safely be applied for other types of defects which often occur in welded joints. This paper contains the methodological approaches for the assessment of integrity and evaluation of service life of components and structures of turbine and hydromechanical equipment during the design, prototyping and service period based on history of fatigue loading and application of fracture mechanics parameters

Procedure for selecting the low alloy-tempered steel for manufacturing the responsible highly loaded parts

The procedure for selecting the optimal material for manufacturing the highly loaded responsible parts is presented in this paper. The proper selection of material can be done exclusively based on the theoretical and experimental analysis of properties of steel in question. The theoretical and experimental selecting of adequate steel for manufacturing the machine parts is done based on requirements arising from their working conditions. Based on the available data for various steels, chemical composition, mechanical and technological properties, available CCT diagram, the optimal steel was selected for the given working conditions. After the selection of the material, experimental investigations were conducted on specially prepared material samples. The real chemical composition of material was established, its most important mechanical properties were determined, the hardness was measured and the microstructure was determined, as well. After the conducted theoretical and experimental investigations, the responsible machine part was manufactured by forging. Then, the mechanical and heat processing was executed, after which the part was tested in the real working conditions. Based on investigations of part's behavior in the real working conditions it was concluded that the selection of the material was adequate.Publishe