Development of GTN Model Parameters for Simulating Ductile Fracture Behavior of X 70 Carbon Steel SENT Specimens

2019 ◽  
Author(s):  
Sung Ho Yoon ◽  
Tae-Young Ryu ◽  
Moon Ki Kim ◽  
Jae-Boong Choi ◽  
Ik-Joong Kim
Keyword(s):  
Carbon Steel ◽  
Ductile Fracture ◽  
Fracture Behavior ◽  
Boundary Effect ◽  
Test Method ◽  
Pipe Material ◽  
Single Edge ◽  
Fracture Characteristics ◽  
Gtn Model ◽  
Senb Specimen

Abstract Single-Edge-Notched-Bending (SENB) specimen is mainly used for fracture characteristics test of pipe material. However, there is also a disadvantage in that it does not sufficiently simulate the fracture characteristics of thin pipes due to the difference in boundary effect between the SENB specimen and the actual pipe. The Single-Edge-Notched-Tensile (SENT) specimen can be used as complementary test method due to its less boundary effect compared to the SENB specimen. In this study, the SENT specimen which are fabricated with API X 70 carbon steel was simulated ductile fracture behavior by using finite-element-analysis (FEA). To simulate ductile fracture behavior, Gurson-Tvergaard-Needleman (GTN) model was applied. GTN model is a kind of damage model that describes the behavior of ductile fracture through three steps of void changes : nucleation, growth, and coalescence. And GTN model is composed of three constitutive equations and nine parameters. In order to develop the GTN ductile fracture model for API X 70 carbon steel, five kinds of tensile specimen tests were simulated by FEA. In addition, we analyzed the influence of parameters of GTN model through analysis and developed optimal material parameters for API X 70 carbon steel. Finally, the ductile fracture behavior of the SENT specimen was simulated and the FEA results of SENT specimen was compared with actual SENT specimen test.

Evaluations of Ductile and Cleavage Fracture Using Coupled GTN and Beremin Model in API X70 Pipelines Steel

2019 ◽  
Author(s):  
Youn-Young Jang ◽  
Ji-Hee Moon ◽  
Nam-Su Huh ◽  
Ki-Seok Kim ◽  
Woo-Yeon Cho ◽  
...  
Keyword(s):  
Ductile Fracture ◽  
Cleavage Fracture ◽  
Fracture Behavior ◽  
Pipeline Steel ◽  
Model Parameters ◽  
Experiment Data ◽  
Local Approach ◽  
Gtn Model ◽  
Weibull Parameters ◽  
X70 Pipeline Steel

Abstract This paper is aimed to characterize ductile and cleavage fracture behavior of API X70 pipeline steel and investigate applicability of a micro-damage mechanics model to simulate static and dynamic crack propagation of single-edge notched tension (SENT) and drop-weight tear test (DWTT) specimens, as well as a local approach to describe cleavage fracture behavior. Gurson-Tvergaard-Needleman (GTN) model was applied to simulate ductile fracture behavior of SENT and DWTT specimens, where GTN model has been widely known for well-established model to characterize micro-damage process of void nucleation, growth and coalescence. As for a local approach, Beremin model was considered to estimate probability of cleavage fracture. In this regard, this study was especially focused on abnormal fracture appearance of DWTT specimen. In the present study, firstly, experiment data from tensile specimen test was used to obtain plastic flow curve (i.e. stress and strain curve). And load-CMOD and J-integral/CTOD resistance curves obtained from SENT test were used to characterize static ductile fracture and calibrate GTN model parameters for X70 pipeline steel. And the calibrated GTN model parameters were verified by comparing experiment data from DWTT test such as load-displacement and crack length-time curves with those from FE analysis. To accommodate dynamic effect on material properties, rate-dependent stress-strain curves were considered in FE analyses. To describe cleavage fracture, the Weibull stress was calculated from FE analyses of DWTT and Weibull parameters were calibrated by comparing with probability distribution of cleavage fracture from experiment data of DWTT specimen. Using Weibull parameters, the whole of cleavage fracture probability can be estimated as ductile shear area of DWTT specimen increases.

Ductile Tearing Prediction of Ferritic Pipe Material by GTN Model for ATLAS+ European Project

2020 ◽  
Author(s):  
Kiminobu Hojo ◽  
Takatoshi Hirota ◽  
Naoki Ogawa ◽  
Satoshi Kumagai
Keyword(s):  
Fracture Behavior ◽  
Structural Integrity ◽  
Assessment Tools ◽  
Pipe Material ◽  
Work Package ◽  
Gtn Model ◽  
Term Operation ◽  
Integrity Assessment ◽  
European Project

Abstract The main objective and mission of the European project ATLAS+ (Advanced Structural Integrity Assessment Tools for Safe Long Term Operation) are to address the remaining technology gaps for the safe and long term operation of nuclear reactor pressure coolant boundary systems. This project includes the development and validation of advanced simulation tools based on fracture mechanics methods using physically based mechanistic models. In the Work Package 3 (WP3), benchmark calculations using different available models are conducted to investigate the accuracy and the capability of the different models for ductile crack growth of different constraint condition, such as laboratory specimens and piping structure, which were tested in the Work Package 1 (WP 1). The authors joined the WP3 activity and investigated the effect of the parameters of the GTN (Gurson-Tvergaard-Needleman) model on the fracture behavior of the specimens. In this paper, the parameters of the GTN model were calibrated to simulate the fracture behavior of CT specimens, notched tensile (NT) specimens and single edge notched tensile (SENT) specimens of ferritic pipe material and the applicability of the GTN model. The adjusted parameters by the CT specimen predicted the fracture behavior of the SENT specimens, but did not those of the NT specimens. The adjusted parameters by the CT specimens were applied to the piping structure mock-up and they predicted the maximum load in high accuracy.

Numerical Prediction of Fracture Behavior for Austenitic and Martensitic Stainless Steels

2017 ◽  
Vol 09 (04) ◽  
pp. 1750052 ◽  
Author(s):  
Goran Vukelic ◽  
Josip Brnic
Keyword(s):  
Fracture Toughness ◽  
Stainless Steels ◽  
Fracture Behavior ◽  
Fe Analysis ◽  
Fe Model ◽  
Single Edge ◽  
Type Specimens ◽  
Martensitic Stainless Steels ◽  
Standardized Formula ◽  
Senb Specimen

Two types of stainless steels are compared in this paper, austenitic X15CrNiSi25-20 and martensitic X20Cr13, based on their numerically predicted fracture behavior. There are engineering applications where both of the steels can be considered for use and where these materials can be exposed to crack occurrence and growth, so proper distinction between them is desirable. Comparison is made on the basis of [Formula: see text]-integral values that are numerically determined using finite element (FE) stress analysis results. FE analysis is performed on compact tensile (CT) and single-edge notched bend (SENB) type specimens that are usually used in standardized [Formula: see text]-integral experimental procedures. Calculated [Formula: see text]-integral values are plotted versus crack growth lengths for mentioned specimens. Results show somewhat higher values of [Formula: see text]-integral for steel X20Cr13 than X15CrNiSi25-20. Further, when comparing [Formula: see text]-integral values obtained through FE model of CT and SENB specimen, it is noticed that CT specimens give somewhat conservative results. Results obtained by this analysis can be used in predicting fracture toughness assessment during design process.

Evaluation of Ductile Fracture Behavior Using GTN Model

2014 ◽  
Author(s):  
Hidekazu Takazawa ◽  
Fuminori Iwamatsu ◽  
Katsumasa Miyazaki
Keyword(s):  
Tensile Test ◽  
Ductile Fracture ◽  
Flat Plate ◽  
Material Properties ◽  
Fracture Behavior ◽  
Monotonic Loading ◽  
Gtn Model ◽  
Plate Specimen ◽  
Safe Side ◽  
Load Displacement

Ductile fracture behavior using GTN (Gurson-Tvergaard-Needleman) model in commercial FEA code was evaluated. The material properties of the GTN model for Type 304 SS were experimentally identified. Smooth-bar and notched-bar specimens were subjected to monotonic loading by tensile test, and load-displacement curves were measured. Then, the tensile test was simulated. Material properties of the GTN model were calculated from measured and simulated load-displacement curves with inverse analysis based on Bayes’ theorem. Simulated load-displacement curves using the GTN model of different curvature notched-specimens agreed well with the measured results. To verify the evaluation of ductile fracture behavior using the GTN model, flat-plate specimen with a single surface flaw and specimen with multiple through flaws were subjected to monotonic loading. Ductile fracture of the flat-plate specimen was simulated by FEA using the GTN model using the calculated material properties. The simulated load was less than the measured load at the same displacement. The analysis using the GTN model can estimate the load on the safe side and the GTN model can conservatively simulate ductile fracture behavior.

Ductile Fracture Behavior of Carbon Steel Cracked Pipes With Moderate-Toughness

2002 ◽  
Author(s):  
Naoki Miura ◽  
Koichi Kashima ◽  
Katsumasa Miyazaki ◽  
Masakazu Hisatsune ◽  
Kunio Hasegawa
Keyword(s):  
Carbon Steel ◽  
Fracture Mechanics ◽  
Ductile Fracture ◽  
Fracture Behavior ◽  
Evaluation Criteria ◽  
Four Point Bending ◽  
Maintenance Program ◽  
Mechanics Analysis ◽  
Piping Systems ◽  
Class 1

To achieve a rational maintenance program for aged light water reactor components, it is important to establish and to improve the flaw evaluation criteria. The current flaw evaluation criteria such as ASME Boiler and Pressure Vessel Code Section XI are focused on Class 1 piping, which usually shows relatively higher toughness. On the other hand, flaw evaluation criteria suitable for Class 2 and Class 3 piping with moderate-toughness are also required because some Class 2 and Class 3 piping systems are as important to plant risk analysis as Class 1 piping. In this study, fracture experiments by four-point bending were conducted for circumferentially cracked pipes. Tested pipes were made of moderate-toughness carbon steel, STPT410 carbon steel. Ductile fracture behavior and load-carrying capacity were compared with those from elastic-plastic fracture mechanics analysis. As a result, it was ascertained that ductile fracture behavior could be well predicted by fracture mechanics analysis using J-integrals. A Z-factor approach applicable to moderate-toughness pipes was also discussed.

Low cycle fatigue and ductile fracture for Japanese carbon steel piping under dynamic loadings

1994 ◽  
Vol 153 (1) ◽  
pp. 57-69 ◽  
Author(s):  
Naoki Miura ◽  
Terutaka Fujioka ◽  
Koichi Kashima ◽  
Satoshi Kanno ◽  
Makoto Hayashi ◽  
...  
Keyword(s):  
Carbon Steel ◽  
Ductile Fracture ◽  
Low Cycle Fatigue ◽  
Cycle Fatigue ◽  
Dynamic Loadings ◽  
Steel Piping
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