Abstract
A heat treatment is effective for reducing the residual stress of the welded structures. A post-weld heat treatment (PWHT) requires a large heating apparatus (furnace). It requires a high energy, a long time, and a high cost. For examining the possibility of cost and energy saving in PWHT work, an economical and mechanical investigation of the local PWHT to stiffened plate members in steel bridges was conducted. The expense of apparatus for the furnace PWHT was 1.5 times higher than that of local PWHT by sheet-type ceramic heaters. When the number of heater units was reduced and were repeatedly used, the expense for the apparatus became lower. However, it took longer to complete the heat treatment than with the furnace PWHT or the local PWHT with full heater units. The thermal elastic-plastic finite element (FE) analysis examined the effect of local PWHT. The tendency of the stress distribution after the local PWHT differed from the welding residual stress or the stress after the furnace PWHT because of the temperature difference between the heated and the non-heated parts of the local PWHT. However, the effect of residual stress relief by the local PWHT could be almost the same as that of the furnace PWHT.
Highlights
Stiffened steel plates are generally used in steel bridge structural members, such as box girders, piers, and decks [1,2,3]
This study investigates the primary applicability of the local post-weld heat treatment (PWHT) to steel bridge members from economical and mechanical viewpoints
(1) The costs required for the furnace PWHT and the local PWHT on the stiffened plate were estimated and compared
Summary
Stiffened steel plates are generally used in steel bridge structural members, such as box girders, piers, and decks [1,2,3]. It is well known that the compressive stress applied by the peening enhances the fatigue strength of the weld toe These countermeasures are useful and reasonable, the treatment area is limited to the area locally around the welded part. Paradowska et al applied PWHT to welded tubular joints in order to improve the fatigue life by reducing hardness and residual stress [13]. Aung et al investigated the effectiveness of PWHT for improving the fatigue strength of patch-plate welded joints by mild steel [14]. It has been shown that, by using sheet-type ceramic heaters, local PWHT could reduce the residual welding stress and improve the fatigue strength and the load-carrying capacity of welded members [16,17]. Numerical simulation by finite element (FE) analysis for comparing the effects of residual stress relief by the furnace PWHT and the local PWHT was carried out
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