PWSCC Assessment by Using Extended Finite Element Method

2015 ◽  
Vol 06 (03) ◽  
pp. 1550007
Author(s):  
Sung-Jun Lee ◽  
Sang-Hwan Lee ◽  
Yoon-Suk Chang
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Extended Finite Element Method ◽  
Structural Integrity ◽  
Displacement Function ◽  
Driving Mechanism ◽  
Extended Finite Element ◽  
Control Rod ◽  
Head Penetration ◽  
Element Method

The head penetration nozzle of control rod driving mechanism (CRDM) is known to be susceptible to primary water stress corrosion cracking (PWSCC) due to the welding-induced residual stress. Especially, the J-groove dissimilar metal weld regions have received many attentions in the previous studies. However, even though several advanced techniques such as weight function and finite element alternating methods have been introduced to predict the occurrence of PWSCC, there are still difficulties in respect of applicability and efficiency. In this study, the extended finite element method (XFEM), which allows convenient crack element modeling by enriching degree of freedom (DOF) with special displacement function, was employed to evaluate structural integrity of the CRDM head penetration nozzle. The resulting stress intensity factors of surface cracks were verified for the reliability of proposed method through the comparison with those suggested in the American Society of Mechanical Engineering (ASME) code. The detailed results from the FE analyses are fully discussed in the manuscript.

A Benchmark Study on Applying Extended Finite Element Method to the Structural Integrity Assessment of Subsea Pipelines at HPHT Service Conditions

2018 ◽  
Author(s):  
Ankang Cheng ◽  
Nian-Zhong Chen
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Extended Finite Element Method ◽  
Structural Integrity ◽  
Future Application ◽  
Extended Finite Element ◽  
Integrity Assessment ◽  
Service Conditions ◽  
Subsea Pipelines ◽  
Element Method

Structural integrity assessment for subsea pipelines at high pressure high temperature (HPHT) service conditions is one of the most challenging research topics in offshore engineering sector. This paper is to introduce an extended finite element method (XFEM) based numerical approach for structural integrity assessment for subsea pipelines serving HPHT reservoir. A 3D model of a quarter of subsea pipe section with an external semi-elliptical surface crack located at the weld toe is built and the crack propagation under fatigue load is simulated using the XFEM. Results are presented and investigated from both geometric and mechanical aspects. Theoretical basis and limitation for this technique are discussed. Suggestions are given for future application of the XFEM technique based on fracture mechanics when assessing the structural integrity of subsea pipelines at HPHT service conditions.

Crack Initiation and Growth Simulation for CRDM Nozzles by eXtended Finite Element Method

2015 ◽  
Author(s):  
Sung-Jun Lee ◽  
Yoon-Suk Chang
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Crack Initiation ◽  
Power Plants ◽  
Extended Finite Element Method ◽  
Zone Model ◽  
Extended Finite Element ◽  
Integrity Assessment ◽  
Head Penetration ◽  
Element Method

The head penetration nozzles of control rod driving mechanisms (CRDMs) are susceptible components on primary water stress corrosion cracking (PWSCC) due to the dissimilar metal welds. The accurate integrity assessment of the CRDM head penetration nozzles is important for the safe operation of nuclear power plants. To resolve the integrity issue, conventional finite element methods, a cohesive zone model, and a virtual crack closure technique have been employed; however, there are still many uncertainties in accuracy and efficiency. In the present study, a specific Strain Rate Damage Model (SRDM) with stress and thermal dependent parameters was adopted to calculate crack initiation time. Also, a level set method, which defines the crack location based on the crack surface and vertical surface of crack tip, was considered to simulate arbitrary crack growth. By taking into account these two features, the eXtended Finite Element Method (XFEM) was implemented to simulate the PWSCC initiation and growth with a user subroutine code. Finally, the validity of the proposed method was evaluated by comparing the reference cracks that occurred in the CRDM head penetration nozzles.

scholarly journals A mesh-independent framework for crack tracking in elastodamaging materials through the regularized extended finite element method

2021 ◽  
Author(s):  
Elena Benvenuti ◽  
Nicola Orlando
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Damage Evolution ◽  
Extended Finite Element Method ◽  
Mesh Adaptivity ◽  
Extended Finite Element ◽  
Evolution Law ◽  
Crack Paths ◽  
Original Crack ◽  
Element Method

AbstractWe propose a formulation for tracking general crack paths in elastodamaging materials without mesh adaptivity and broadening of the damage band. The idea is to treat in a unified way both the damaging process and the development of displacement discontinuities by means of the regularized finite element method. With respect to previous authors’ contributions, a novel damage evolution law and an original crack tracking framework are proposed. We face the issue of mesh objectivity through several two-dimensional tests, obtaining smooth crack paths and reliable structural results.

scholarly journals An Extended Finite Element Method (XFEM) Study on the Elastic T-Stress Evaluations for a Notch in a Pipe Steel Exposed to Internal Pressure

Mathematics ◽  
2021 ◽  
Vol 9 (5) ◽  
pp. 507
Author(s):  
K. Yakoubi ◽  
S. Montassir ◽  
Hassane Moustabchir ◽  
A. Elkhalfi ◽  
Catalin Iulian Pruncu ◽  
...  
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Internal Pressure ◽  
Extended Finite Element Method ◽  
Research Study ◽  
Extended Finite Element ◽  
T Stress ◽  
Cracked Structures ◽  
Element Method

The work investigates the importance of the K-T approach in the modelling of pressure cracked structures. T-stress is the constant in the second term of the Williams expression; it is often negligible, but recent literature has shown that there are cases where T-stress plays the role of opening the crack, also T-stress improves elastic modeling at the point of crack. In this research study, the most important effects of the T-stress are collected and analyzed. A numerical analysis was carried out by the extended finite element method (X-FEM) to analyze T-stress in an arc with external notch under internal pressure. The different stress method (SDM) is employed to calculate T-stress. Moreover, the influence of the geometry of the notch on the biaxiality is also examined. The biaxiality gave us a view on the initiation of the crack. The results are extended with a comparison to previous literature to validate the promising investigations.

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