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Frontiers of Mechanical Engineering

Front Mech Eng    2013, Vol. 8 Issue (3) : 283-290     https://doi.org/10.1007/s11465-013-0250-1
RESEARCH ARTICLE
Local fracture properties and dissimilar weld integrity in nuclear power plants
Guozhen WANG(), Haitao WANG, Fuzhen XUAN, Shantung TU, Changjun LIU
Key Laboratory of Pressure Systems and Safety (Ministry of Education), East China University of Science and Technology, Shanghai 200237, China
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Abstract

In this paper, the local fracture properties in a Alloy52M dissimilar metal welded joint (DMWJ) between A508 ferritic steel and 316 L stainless steel in nuclear power plants were investigated by using the single-edge notched bend (SENB) specimens, and their use in integrity assessment of DMWJ structures was analyzed. The results show that the local fracture resistance in the DMWJ is determined by local fracture mechanism, and which is mainly related to the microstructures and local strength mismatches of materials at the crack locations. The initial cracks always grow towards the materials with lower strength, and the crack path deviation is mainly controlled by the local strength mismatch. If the local fracture properties could not be used for cracks in the heat affected zones (HAZs), interface and near interface zones, the use of the fracture properties (J-resistance curves) of base metals or weld metals following present codes will unavoidably produce non-conservative (unsafe) or excessive conservative assessment results. In most cases, the assessment results will be potentially unsafe. Therefore, it is recommended to obtain and use local mechanical and fracture properties in the integrity assessment of DMWJs.

Keywords local fracture properties      dissimilar metal welded joint      integrity assessment      strength mismatch      crack growth path     
Corresponding Author(s): WANG Guozhen,Email:gzwang@ecust.edu.cn   
Issue Date: 05 September 2013
 Cite this article:   
Guozhen WANG,Haitao WANG,Fuzhen XUAN, et al. Local fracture properties and dissimilar weld integrity in nuclear power plants[J]. Front Mech Eng, 2013, 8(3): 283-290.
 URL:  
http://journal.hep.com.cn/fme/EN/10.1007/s11465-013-0250-1
http://journal.hep.com.cn/fme/EN/Y2013/V8/I3/283
Fig.1  The DMWJ structure for connecting the pipe-nozzle of a reactor pressure vessel to safe-end pipe
Fig.2  Schematic diagram showing initial crack positions and SENB specimen orientation in the DMWJ (C: circumferential; R: radial direction; A: axial direction)
Fig.3  The SENB specimen geometry, size and loading method typically shown by the crack 4 specimen
Fig.4  -resistance curves for the 13 cracks in the DMWJ
Fig.5  SEM images show fracture mechanism of the A508 HAZ crack 2: (a) overview of fracture surface; (b) higher magnification of area A in (a); (c) higher magnification of area B in (a); (d) crack growth path
Fig.6  The strength distributions []and crack positions across the DMWJ
Fig.7  (a) Crack growth path (b) and fracture surface of A508/52Mb interface crack 3
Fig.8  Typical damage patterns ahead of crack tips for the cracks in (a) Alloy52Mb and (b) Alloy52Mw
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