Fracture strain model for hydrogen embrittlement based on hydrogen enhanced localized plasticity mechanism

In this study, the effect of longitudinal distance H between non-aligned twin cracks is investigated using finite element damage analysis. The FE damage analysis based on the stress-modified fracture strain model is used to calculate the failure stress of non-aligned twin cracked pipe. Parametric study on the axial distance H between non-aligned twin cracks with various crack depths and lengths were conducted and compared with predictions using the alignment rules and the net-section collapse load approach for single crack provided in ASME Code. It is shown that the trend of the predicted collapse bending stresses for the non-aligned twin cracked pipes using FE damage analysis are different from the ones using the alignment rule.

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A finite element ductile failure simulation method using stress-modified fracture strain model

Engineering Fracture Mechanics ◽

10.1016/j.engfracmech.2010.10.004 ◽

2011 ◽

Vol 78 (1) ◽

pp. 124-137 ◽

Cited By ~ 112

Author(s):

Chang-Sik Oh ◽

Nak-Hyun Kim ◽

Yun-Jae Kim ◽

Jong-Hyun Baek ◽

Young-Pyo Kim ◽

...

Keyword(s):

Finite Element ◽

Fracture Strain ◽

Ductile Failure ◽

Simulation Method ◽

Failure Simulation ◽

Strain Model

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Ductile Fracture Simulation of CRIEPI STPT 410 Pipe With Circumferential Crack

Volume 6B: Materials and Fabrication ◽

10.1115/pvp2014-28904 ◽

2014 ◽

Author(s):

Hyun-Suk Nam ◽

Young-Ryun Oh ◽

Jae-Jun Han ◽

Chang-Young Oh ◽

Yun-Jae Kim ◽

...

Keyword(s):

Fracture Toughness ◽

Crack Growth ◽

Fracture Strain ◽

Damage Model ◽

Full Scale ◽

Ductile Crack ◽

Size Dependent ◽

Element Size ◽

Ductile Crack Growth ◽

Strain Model

This paper provides simulation of ductile crack growth in full-scale cracked pipe tests using an element-size dependent damage model. This method is based on the stress-modified fracture strain damage model. The stress-modified fracture strain model is determined to be incremental damage in terms of stress triaxiality and fracture strain for dimple fracture from tensile test result with FE analyses technique. To validate the proposed method, this research analyses STPT 410 cracked pipes test at 300°C taken from CRIEPI (Central Research Institute of Electric Power Industry). In order to calibrate the stress-modified fractures strain model, tensile tests and fracture toughness tests were compared with simulated results using element-size dependent damage model. Tensile specimen and fracture toughness specimen were extracted from STPT 410 steel pipe. The calibrated damage model predicts ductile crack growth in 5 type circumferential cracked pipes bending test. And these results were compared with the experimental results. The results show that the proposed method can simulate ductile crack growth in full-scale cracked pipe tests.

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Hydrogen-assisted stress corrosion cracking simulation using the stress-modified fracture strain model

Journal of Mechanical Science and Technology ◽

10.1007/s12206-012-0642-x ◽

2012 ◽

Vol 26 (8) ◽

pp. 2631-2638 ◽

Cited By ~ 7

Author(s):

Nak-Hyun Kim ◽

Chang-Sik Oh ◽

Yun-Jae Kim ◽

Kee-Bong Yoon ◽

Young-Wha Ma

Keyword(s):

Stress Corrosion ◽

Stress Corrosion Cracking ◽

Fracture Strain ◽

Corrosion Cracking ◽

Strain Model

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Applicability of Net-Section Collapse Load Approach to Multiple-Cracked Pipe Assessment: Numerical Study

Journal of Pressure Vessel Technology ◽

10.1115/1.4036656 ◽

2017 ◽

Vol 139 (4) ◽

Author(s):

Myeong-Woo Lee ◽

So-Dam Lee ◽

Yun-Jae Kim

Keyword(s):

Finite Element ◽

Test Data ◽

Parametric Study ◽

Fracture Strain ◽

Numerical Study ◽

Damage Analysis ◽

Collapse Load ◽

Fracture Test ◽

Strain Model

In this paper, applicability of net-section collapse load approach to circumferential multiple-cracked pipe assessment is investigated using finite element (FE) damage analysis. The FE damage analysis based on the stress-modified fracture strain model is validated against limited fracture test data of two circumferential surface-cracked pipes. Then, the systematic parametric study is performed using the FE damage analysis for symmetrical and asymmetrical surface-cracked pipes. It is found that predictions using the net-section collapse load approach tend to be more accurate with increasing the distance between two symmetrical cracks. For asymmetrical cracks, it is found that the deeper crack plays a more important role and that the existing net-section collapse load expression can be potentially nonconservative. Idealization to symmetrical cracks based on the deeper crack is proposed.

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Effects of Side Groove on Fracture Toughness

Volume 6B: Materials and Fabrication ◽

10.1115/pvp2015-45731 ◽

2015 ◽

Author(s):

Ho-Wan Ryu ◽

Hune-Tae Kim ◽

Jae-Jun Han ◽

Yun-Jae Kim ◽

Jong-Sung Kim ◽

...

Keyword(s):

Test Data ◽

Fracture Strain ◽

Failure Criteria ◽

Compact Tension ◽

Damage Analysis ◽

Pipe Material ◽

Ductile Tearing ◽

Different Shapes ◽

Strain Model ◽

Good Agreement

This paper describes ductile tearing simulation for compact tension (C(T)) specimens using FE damage analysis based on the stress-modified fracture strain model. The side groove effect on J-resistance curve was estimated by experimental and analytical ways. In this paper, SA508 Grade 1A low alloy steel pipe material was considered. Tensile and C(T) specimens are simulated to determine the failure criteria with finite element method. Then, different shapes of C(T) specimens are analysed and the results from simulations are compared with test data for verification of proposed method. Overall, the predicted simulation results show good agreement with test data.

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Porosity, Damage Evolution and Fracture in Die-Cast Magnesium Alloy AM60B

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.15-17.455 ◽

2006 ◽

Vol 15-17 ◽

pp. 455-460 ◽

Cited By ~ 1

Author(s):

J.P. Weiler ◽

J.T. Wood ◽

R.J. Klassen ◽

Éric Maire ◽

R. Berkmortel ◽

...

Keyword(s):

Magnesium Alloy ◽

Damage Evolution ◽

Fracture Strain ◽

Predictive Accuracy ◽

Imaging Technique ◽

Local Area ◽

Die Cast ◽

Cast Magnesium Alloy ◽

Cast Magnesium ◽

Strain Model

A series of AM60B, die-cast magnesium alloy specimens have been examined using xray tomography at spatial resolutions from 1 – 20μm and further characterized in uniaxial tension. This paper first reports the utility of a critical strain model to link the local area fraction of porosity and the fracture strain. A discussion of the trade-off between predictive accuracy and the spatial resolution of the imaging technique is also presented in order to address the technological implications of these results. In the second half of the paper, serial tomographic imaging is used to illustrate the evolution of damage with increasing uniaxial strain. The implications are discussed with respect to numerical modeling of the performance of die-cast magnesium components.

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Ductile Fracture Simulation Considering Strain Rate Loading Effect

Volume 6A: Materials and Fabrication ◽

10.1115/pvp2015-45204 ◽

2015 ◽

Author(s):

Hyun-Suk Nam ◽

Ji-Soo Kim ◽

Yun-Jae Kim ◽

Jin-Weon Kim ◽

Chang-Young Oh

Keyword(s):

Finite Element ◽

Strain Rate ◽

Dynamic Loading ◽

Fracture Strain ◽

Fracture Toughness Test ◽

Loading Conditions ◽

Loading Effect ◽

Fracture Simulation ◽

Dynamic Loading Conditions ◽

Strain Model

This paper is based on a ductile failure simulation under dynamic loading conditions using finite element (FE) analyses. Recently a simple finite element method in a quasi-static test has been proposed to implement fracture simulation based on the well-known stress modified fracture strain model. The stress-modified fracture strain model is determined to be incremental damage in terms of stress triaxiality and fracture strain for dimple fracture from tensile test result with FE analyses technique. Since dynamic loading effect is especially important to assess pipe with crack-like defect, this work propose the integrated model which combines quasi-static with dynamic loading effect. In order to validate stress-modified fracture strain model in dynamic loading conditions, this paper compares results of FE analysis using proposed method with strain dependent smooth bar tests and notch tensile tests using Johnson-Cook equation. In conclusion, the stress-modified fracture strain model criterion can be calibrated by FE analyses with strain rate dependent fracture toughness test results.

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A Method to Quantify Thermal Aging Effect on Fracture Toughness of Cast Stainless Steels Using Small Punch Test

Volume 1: Codes and Standards ◽

10.1115/pvp2014-28233 ◽

2014 ◽

Author(s):

Jun-Young Jeon ◽

Dong-Il Ryu ◽

Yun-Jae Kim ◽

Mi-Yeon Lee ◽

Jin-Weon Kim

Keyword(s):

Fracture Toughness ◽

Test Data ◽

Stainless Steels ◽

Fracture Strain ◽

Fracture Toughness Test ◽

Small Punch ◽

Fracture Simulation ◽

Toughness Test ◽

Axial Fracture ◽

Strain Model

In this study, a method to predict fracture toughness of aged cast austenitic stainless steels (CASSs) using small punch (SP) test and finite element (FE) analysis is proposed. Grade CF8M is considered and thermally aged up to 5,000 hours at 400°C. SP tests and fracture toughness test using compact tension (C(T)) specimen are conducted with virgin (unaged) and aged CF8M. FE analyses performed in this study use ductile fracture simulation technique with ‘the multi-axial fracture strain model’. The multi-axial fracture strain model for each aged CF8M are determined from SP test data and FE analyses. Fracture toughness of aged CF8M are predicted by conducting fracture toughness test simulations using FE damage analyses. Predicted fracture toughness results are compared with C(T) data to validate the method suggested in this study. The predicted initiation toughness values are predicted well and fracture toughness values are slightly conservative compared to test data.

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