Experimental measurement and analytical calculation of preheating, i. e. interpass temperature during multi-pass repair welding has been presented. Analytical calculation is based on heat transfer analysis, whereas measurements have been performed by thermovision camera. Repair welding was performed on crane wheels in the Steelworks Smederevo. Comparison of results indicated that analytical calculation is good enough as the first approximation, but it needs further elaboration, e. g. taking into account the radiation component of heat dissipation and/or temperature dependence of material thermomechanical properties.
Original scientific paper Shown in this paper are the results of microstructure testing of crane wheels, along with the repair welding procedure performed by hard-surfacing. Repair welding involved the application of a welded layer to the crane wheel, due to the damage that was caused by wear. Detailed analyses, based on the mechanical and chemical properties of the materials used for crane wheels, as well as for repair welding, were performed for the contact between the rail and wheel in real exploitation conditions, as well as by using numerical simulations. Numerical simulations were performed by using the finite element method. For the purpose of the analysis, contact stresses between the wheel and rail were calculated according to Hertz theory. Each of the numerical models was used to perform stress analysis with or without a crack in order to determine crack influence on the crane wheel integrity, and to compare the results with the values obtained theoretically. In addition, the symmetry of the contact area between the wheel and rail was taken into account, i.e. both symmetric and asymmetric contact models were made. : crack; FEM; hard-surfacing; integrity; microstructure; rail; wear; wheel Keywords Utjecaj pukotina na stanje naprezanja u navarenom sloju kotača dizalice pri kontaktnom opterećenjuIzvorni znanstveni članak U ovom su radu prikazani rezultati ispitivanja mikrostrukture kotača dizalice, kao i procedura navarivanja koja je uporabljena za popravak. Reparaturno navarivanje se sastojalo iz dodavanja navarenog sloja na kotač dizalice, koji je prethodno pretrpio oštećenja uslijed habanja. Detaljna analiza kontakta između tračnice i kotača provedena je za realne uvjete opterećenja, kao i pomoću numeričke simulacije, a na osnovu mehaničkih i kemjskih karakteristika materijala uporabljenih za izradu kotača, kao i za reparaturno navarivanje. Numeričke su simulacije provedene primjenom metode konačnih elemenata. Za potrebe analize, vrijednosti kontaktnih naprezanja između kotača dizalice i tračnice određene su prema Hertz-ovoj teoriji. Svi numerički modeli su rabljeni za analizu naprezanja za slučajeve s i bez pukotine u cilju određivanja utjecaja pukotine na integritet kotača dizalice, a dobiveni rezultati su upoređeni s teorijskim vrijednostima. Također, u obzir je uzeta i simetrija kontaktnog područka između kotača i tračnice, tj. napravljeni su numerički modeli sa simetričnom i asimetričnom pozicijom kontakta.
The goal of this study was to determine the reasons for failure of slab carrying clamps which had occurred in one of the clamp support levers. Detailed fractography analysis revealed that there was a welded joint at the location where failure occurred, which was not expected, since the second lever was not welded. Once the presence of the welded joint was confirmed by hardness measuring and the analysis of chemical composition, attempts were made to determine which materials were used for the welding, in order to obtain a more detailed insight into the nature of the failure. The first step of this extensive analysis involved the development of a simple, approximated numerical model, with the goal of determining the location of stress concentration in the support lever, so that it could be compared to the real failure location. Further investigations will involve more complex models, including the ones that will simulate crack growth, once its location is numerically verified.
Comparative analysis of a repaired and a new crane wheel, was performed in Steelworks Smederevo, including an economic analysis and technological procedures. The repair procedure for a crane wheel is presented, along with the selection of filler materials, as well as testing of mechanical properties performed on samples taken from hard faced welds. The advantages of repair techniques compared to the manufacturing of a new wheel are shown, but also the flaws that may affect the worklife and integrity of wear-damaged elements and components.
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