Uticaj višestrukih grešaka u zavarenom spoju na integritet zavarene konstrukcije

Abstract

Glavni cilj ovog istraživanja je utvrđivanje kombinacije realnih grešaka koji predstavljaju potencijalno najveću opasnost po integritet zavarenih spojeva i konstrukcija. Analiziran je uticaj prisustva više različitih grešaka u zavarenom spoju čelika S275JR na integritet zavarene konstrukcije. Sa tim ciljem formirani su numerički proračunski modeli i fizički modeli epruveta, koji su bili ispitivani jednoosnim zatezanjem, a deformacije zona zavarenog spoja su merene beskontaktnom optičkom metodom. Osnovna ideja je bila da se predvidi ponašanje zavarenih spojeva u radnim uslovima u prisustvu višestrukih površinskih grešaka numeričkoeskperimentralnim pristupom. Određeni su naponi pri kojima dolazi do pojave prsline u zavarenim spojevima za sve merodavne kombinacije grešaka, pri čemu je takođe utvrđeno koja greška inicara početnu prsline za sve slučajeve kombinacije grešaka. Kao rezultat ovog ispitivanja određene su karakteristike materijala svih zona zavarenog spoja. Razvijeni su početni modeli koji su potom unapređvani. Polja deformacija dobijena ekperimentalnim istraživanjima, pre svega digitalnom korelacijom slika, su korišćena u ovoj studiji. Na taj način su iterativno razvijeni novi realni numerički modeli, koji su omogućili određivanje napona pri kojem dolazi do pojave prsline, kao i naponskog i deformacijskog stanja u zoni uticaja toplote. Kombinacije grešaka u zavarenom spoju sa smaknućem ploča su se pokazale kao najkritičnije u pogledu integriteta zavarene konstrukcije, kao i sama priroda kombinacije pomenutih grešaka. Usled primetnog “overmatching” efekta, ova studija je pokazala da lomovi “kreću” iz grešaka smeštenih u zoni uticaja toplote (pre svega na ili blizu linije stapanja).

The main goal of this research was to determine the combination of real defects that potentially represent the greatest danger to the integrity of welded joints and structures. The influence of multiple defects in the welded joint of S275JR steel on the integrity of the welded structure was investigated. For this purpose, numerical calculation models and physical models of specimens were formed, which were tested by uniaxial tension, and the deformations of the welded joint zones were measured by the non-contact optical method. The basic idea was to predict the behavior of welded joints in working conditions with presence of multiple surface defects by numerical-experimental approach. The stress at which a crack occurs in welded joints with a combination of defects has been determined, as well as which defect inititates the crack propagation for all defets combinaction. As a consequence of this test, the material characteristics of all zones of the welded joint were determined. Initial models were developed and then improved. The deformation field obtained by experimental research was included. Thus, a new real numerical models were iteratively developed, which enabled both the determination of the stress at which the crack occurs as well as the stress in the heat affected zone. Combinations of defets in welded joints with vertical misalignment were recocnized as the most critical one concerning welded construction integrity, as well as the nature of these defects combinations. Due to the noticeable "overmatching" effect of the welded joint, this study shown that the fractures originated from defects located in the heat affected zone (primarily at or near the fusion line).