Ductile Failure Simulation to Predict Burst Pressures of Steam Generator Tubes With Multiple Axial Cracks

2013 ◽  
Author(s):  
Han-Sang Lee ◽  
Nak Hyun Kim ◽  
Yun-jae Kim ◽  
Jong Sung Kim ◽  
Jin Weon Kim
Keyword(s):  
Steam Generator ◽  
Stress Reduction ◽  
Damage Model ◽  
Ductile Failure ◽  
Thin Plates ◽  
Alloy 600 ◽  
Surface Cracks ◽  
Failure Simulation ◽  
Steam Generator Tubes ◽  
Axial Surface

This paper a new simple numerical method to predict burst pressures of Alloy 600 steam generator tubes with multiple through-wall cracks, based on the stress-modified fracture strain damage model with stress reduction technique. To validate the new method, simulated results using the proposed method are compared with thirty-on published test data of Alloy 600 thin plates and tubes with single or multiple through-wall cracks. Simulated results showing that predicted loads are within 10% of experimentally-measured ones for all cases considered. Moreover, a parametric study is performed to investigate the interaction effect of two axial surface cracks in Alloy 600 steam generator tubes under internal pressure.

Ductile Failure Simulation of Bending Pipes With Multiple Circumferential Surface Cracks Using an Element-Size Dependent Damage Model

2012 ◽  
Author(s):  
Jong-Hyun Kim ◽  
Nak-Hyun Kim ◽  
Yun-Jae Kim ◽  
Kunio Hasegawa ◽  
Katsumasa Miyazaki
Keyword(s):  
Stress Reduction ◽  
Damage Model ◽  
Ductile Failure ◽  
Bending Moment ◽  
Failure Behavior ◽  
Surface Cracks ◽  
Size Dependent ◽  
Element Size ◽  
Crack Penetration ◽  
Failure Simulation

The purpose of this study is to simulate ductile failure of bending pipes with multiple circumferential surface cracks using an element-size dependent damage model. This method is based on the stress-modified fracture strain damage model with stress reduction technique proposed previously by the authors [9,10]. For validation, simulated results using the proposed method are compared with experimental data of Type 304SS pipes performed by Japanese researchers [19]. To calibrate the proposed method, pipe test data with a single surface crack were compared with simulated results using the damage model. Based on the calibrated damage model, the pipe tests with multiple circumferential surface cracks were simulated. The bending moment at both crack penetration and coalescence were calculated from the FE damage analysis. These results were compared with the experimental results. In spite of its simplicity, the results show that proposed method can simulate ductile failure behavior of bending pipes with multiple circumferential surface cracks.

Development of Burst Pressure Estimation Equations for Steam Generator Tubes With Multiple Axial Surface Crack

2018 ◽  
Author(s):  
Ji-Seok Kim ◽  
Myeong-Woo Lee ◽  
Jin-Weon Kim ◽  
Yun-Jae Kim
Keyword(s):  
Steam Generator ◽  
Surface Crack ◽  
Burst Pressure ◽  
Damage Analysis ◽  
Surface Cracks ◽  
Test Results ◽  
Estimation Equations ◽  
Pressure Estimation ◽  
Steam Generator Tubes ◽  
Axial Surface

In this paper, the burst pressure estimation equations for steam generator tubes with multiple axial surface cracks are proposed based on the local collapse load approach concept. The proposed equations are for a single axial surface crack, two collinear axial surface cracks and two non-aligned axial surface cracks. The proposed equations are validated against experimental tube burst test results and finite element damage analysis for twin cracks. Predicted burst pressures agree well with the experimental results and FE analysis results, suggesting validity of the proposed equations to estimate burst pressures for twin axial surface cracks.

Evaluation of the Creep Rupture Behavior of Alloy 690 Steam Generator Tubes Considering the Pressure Ramp Rate

2021 ◽  
Author(s):  
Jongmin Kim ◽  
Min-Chul Kim ◽  
Joonyeop Kwon
Keyword(s):  
Steam Generator ◽  
Creep Rupture ◽  
Parameter Method ◽  
Alloy 600 ◽  
Steam Generator Tube ◽  
Failure Pressure ◽  
Alloy 690 ◽  
Rupture Model ◽  
Temperature And Pressure ◽  
Steam Generator Tubes

Abstract The materials used previously for steam generator tubes around the world have been replaced and will be replaced by Alloy 690 given its improved corrosion resistance relative to that of Alloy 600. However, studies of the high- temperature creep and creep-rupture characteristics of steam generator tubes made of Alloy 690 are insufficient compared to those focusing on Alloy 600. In this study, several creep tests were conducted using half tube shape specimens of the Alloy 690 material at temperatures ranging from 650 to 850C and stresses in the range of 30 to 350 MPa, with failure times to creep rupture ranging from 3 to 870 hours. Based on the creep test results, creep life predictions were then made using the well-known Larson Miller Parameter method. Steam generator tube rupture tests were also conducted under the conditions of a constant temperature and pressure ramp using steam generator tube specimens. The rupture test equipment was designed and manufactured to simulate the transient state (rapid temperature and pressure changes) in the event of a severe accident condition. After the rupture test, the damage to the steam generator tubes was predicted using a creep rupture model and a flow stress model. A modified creep rupture model for Alloy 690 steam generator tube material is proposed based on the experimental results. A correction factor of 1.7 in the modified creep rupture model was derived for the Alloy 690 material. The predicted failure pressure was in good agreement with the experimental failure pressure.

Characterization of Notched Ductile Failure With Continuum Damage Mechanics

1990 ◽  
Vol 112 (4) ◽  
pp. 412-421 ◽  
Author(s):  
C. L. Chow ◽  
K. Y. Sze
Keyword(s):  
Ductile Fracture ◽  
Circular Hole ◽  
Damage Mechanics ◽  
Damage Model ◽  
Ductile Failure ◽  
Continuum Damage Mechanics ◽  
Thin Plates ◽  
Continuum Damage ◽  
Anisotropic Model ◽  
Aluminum Alloy 2024

A recently developed anisotropic model of continuum damage mechanics has been applied successfully to characterize ductile fracture of cracked plates under mode I and mixed mode failures. The damage model is further extended in this investigation to examine its applicability to include notch ductile fracture of thin plates containing a circular hole. Two hole sizes of 16 mm and 24 mm diameters are chosen and the specimen material is aluminum alloy 2024-T3. Fracture loads of the plates are predicted by the damage model and compared satisfactorily with those determined experimentally. This investigation provides an important confirmation that not only the anisotropic model of continuum damage mechanics but also the same failure criterion developed can be effectively employed to characterize both ductile fracture for plates containing an isolated macro-crack or circular hole which would otherwise not be possible using the conventional theory of fracture mechanics. The successful development of the unified approach to characterize ductile failure provides a vital impetus for design engineers in the general application of the theory of continuum damage mechanics to solve practical engineering problems.

Plastic Limit Load Solutions for Surface Crack in the Steam Generator Tubes

2005 ◽  
Vol 297-300 ◽  
pp. 1704-1712
Author(s):  
Ouk Sub Lee ◽  
Hyun Su Kim ◽  
Jong Sung Kim ◽  
Tae Eun Jin ◽  
Hong Deok Kim ◽  
...  
Keyword(s):  
Steam Generator ◽  
Safety Margin ◽  
Local Limit ◽  
Limit Load ◽  
Material Behavior ◽  
Surface Cracks ◽  
Steam Generators ◽  
Integrity Assessment ◽  
Global And Local ◽  
Steam Generator Tubes

Operating experience of steam generators has shown that cracks of various morphologies frequently occur in the steam generator tubes. These cracked tubes can stay in service if it is proved that the tubes have sufficient safety margin to preclude the risk of burst and leak. Therefore, integrity assessment using exact limit load solutions is very important for safe operation of the steam generators. This paper provides global and local limit load solutions for surface cracks in the steam generator tubes. Such solutions are developed based on three-dimensional (3-D) finite element analyses assuming elastic-perfectly plastic material behavior. For the crack location, both axial and circumferential surface cracks, and for each case, both external and internal cracks are considered. The resulting global and local limit load solutions are given in polynomial forms, and thus can be simply used in practical integrity assessment of the steam generator tubes, because the comparison between experimental data and FE solutions shows good agreement.

An Investigation on Multiple Axial Surface PWSCC Growth Behaviors in Primary Alloy 600 Components Using the PWSCC Initiation Model and Damage Mechanics Approach

2014 ◽  
Author(s):  
Jong-Sung Kim ◽  
Eun-Ju Heo ◽  
Jun-Young Jeon ◽  
Yun-Jae Kim
Keyword(s):  
Damage Mechanics ◽  
Assessment Method ◽  
Alloy 600 ◽  
Surface Cracks ◽  
Collinear Crack ◽  
Parallel Cracks ◽  
Element Size ◽  
Study Results ◽  
Axial Surface ◽  
Penetration Time

The paper proposes a new numerical method to predict the growth behavior of the multiple PWSCCs in the primary alloy 600 components. The method based on the PWSCC initiation model and macroscopic phenomenological damage mechanics approach can induce same results irrespective of the element size. The assessment method was verified comparing with the previous study results. The verified method was applied to collinear and parallel axial surface cracks. As a result, for the collinear crack, the penetration times of the collinear cracks are earlier than those of the single cracks, and the penetration time increases with increasing the space between two cracks. For the parallel crack, the penetration times of the parallel cracks are later than those of the single cracks, and the penetration time increases with decreasing the space between two cracks.

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