Estimation of the energy of crack propagation in different zones of a welded joint by the local technique

P91 steel is a typical steel used in the manufacture of boilers in ultra-supercritical power plants and heat exchangers in nuclear power plants. For the long-term serviced P91 steel pressurized structures, the main failure mode is the welded joint failure, especially the heat affected zone (HAZ) failure. Repair welding technique is an effective method for repairing such local defects. However, the thermal shock composed of high temperature and thermal stress in the repair welding process will pose a critical loading condition for the existing defects near the heat source which cannot be detected by conventional means. So, the evaluation of structural integrity for the welded joint in the thermal-mechanical coupling field is necessary. In this work, the crack propagation law in the HAZ for the P91 steel welded joint was investigated under repair welding thermal loads. The weld repair model of the P91 steel welded joint was established by ABAQUS. The transient temperature field and stress field in repair welding process were calculated by relevant user subroutines and sequential coupling simulation method. The residual stress was determined by the impact indentation strain method to verify the feasibility of the finite element (FE) model and simulation method. In order to obtain the crack propagation path, the elastoplastic fracture analysis of the welded joint with initial crack was performed based on the extended finite element method (XFEM). The influence of different welding linear energy on the crack propagation was analyzed. The results show that the cracks in the HAZ propagate perpendicular to the surface and tend to deflect to the welding seam under repair welding thermal loads. The crack propagation occurs in the early stage of cooling. Higher welding linear energy leads to larger HAZ and higher overall temperature. With the increase of welding linear energy, the length and critical distance of the crack propagation increase. Therefore, low welding linear energy can effectively inhibit the crack propagation in the HAZ. The above calculation and analysis provide a reference for the thermal shock damage analysis of repair welding process, which is of great significance to improving the safety and reliability of weld repaired components.

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Study on crack propagation simulation of surface crack in welded joint structure

Marine Structures ◽

10.1016/j.marstruc.2014.08.001 ◽

2014 ◽

Vol 39 ◽

pp. 315-334 ◽

Cited By ~ 21

Author(s):

Satoyuki Tanaka ◽

Takahiro Kawahara ◽

Hiroshi Okada

Keyword(s):

Crack Propagation ◽

Surface Crack ◽

Welded Joint ◽

Joint Structure

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Influence of Cooling Time t8/5 on Impact Toughness of P460NL1 Steel Welded Joints

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1157.154 ◽

2020 ◽

Vol 1157 ◽

pp. 154-160

Author(s):

Simon A. Sedmak ◽

Mihajlo Aranđelović ◽

Radomir Jovicic ◽

Dorin Radu ◽

Ivica Čamagić

Keyword(s):

Crack Initiation ◽

Crack Propagation ◽

Impact Energy ◽

Welded Joint ◽

Welding Process ◽

Impact Testing ◽

Cooling Time ◽

Initiation And Propagation ◽

Higher Temperature ◽

Total Impact

The results of impact testing of welded joint specimens taken from a welded plate made of P460NL1 steel are presented in this paper, and analysed with regards to the cooling time t8/5, that was previously calculated. The aim was to determine how the cooling times that were measured, some of which were below the minimum required values, affected the toughness, in terms of total impact energy and its components, crack initiation and crack propagation energy. In addition, this analysis included the effects of temperatures measured at the opposite ends of the plate during the welding process, since this had also affected the cooling times for each welding pass. After observing the differences in total, crack initiation and propagation energy between the tested specimens taken from different parts of the welded plate, it was determined that the specimens from the part where the higher temperatures were measured had shown better, more uniform results, whereas the average total impact energy for specimens from both groups were very similar. It was also noticed that the ratio of crack propagation to crack initiation was more favourable (greater) in the case of specimens from the second group (with higher temperature), as the values of crack initiation energy decreased slightly and the crack propagation energy increased.

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