Damage Model for Predicting the Effect of Steel Properties on Ductile Crack Growth Resistance

2009 ◽  
Vol 19 (4) ◽  
pp. 441-459 ◽  
Author(s):  
Mitsuru Ohata ◽  
Takuya Fukahori ◽  
Fumiyoshi Minami
Keyword(s):  
Crack Growth ◽  
Damage Model ◽  
Crack Growth Resistance ◽  
Ductile Crack ◽  
Ductile Crack Growth ◽  
Steel Properties

Ductile Damage Model Based On Void Growth Analysis for Application to Ductile Crack Growth Simulation

2021 ◽  
Author(s):  
Takehisa Yamada ◽  
Mitsuru Ohata
Keyword(s):  
Crack Growth ◽  
Void Growth ◽  
Damage Evolution ◽  
Damage Model ◽  
Crack Growth Resistance ◽  
Growth Behavior ◽  
Ductile Crack ◽  
Growth Simulation ◽  
Crack Growth Simulation ◽  
Ductile Crack Growth

Abstract The aim of this study is to propose damage model on the basis of the mechanism for ductile fracture related to void growth and to confirm the applicability of the proposed model to ductile crack growth simulation for steel. To figure out void growth behavior, elasto-plastic finite element analyses using unit cell model with an initial void were methodically performed. From the results of those analyses, it was evident that the relationships between normalized void volume fraction and normalized strain by each critical value corresponding to crack initiation were independent of stress-strain relationship of material and stress triaxiality state. Based on this characteristic associated with void growth, damage evolution law was derived. Then, using the damage evolution law, simple and phenomenological ductile damage model reflecting void growth behavior and ductility of material was proposed. To confirm the validation and application of proposed damage model, the damage model was implemented in finite element models and ductile crack growth resistance was simulated for cracked components were performed. Then, the simulated results were compared with experimental ones and it was found that the proposed damage model could accurately predict ductile crack growth resistance and was applicable to ductile crack growth simulation.

scholarly journals Damage Model for Simulating the Effect of Material Properties on Ductile Crack Growth Resistance-Simulation of Ductile Crack Growth-

2008 ◽  
Vol 94 (6) ◽  
pp. 222-230 ◽  
Author(s):  
Takuya Fukahori ◽  
Mitsuru Ohata ◽  
Fumiyoshi Minami ◽  
Yoichi Kayamori ◽  
Takehiro Inoue
Keyword(s):  
Crack Growth ◽  
Material Properties ◽  
Damage Model ◽  
Crack Growth Resistance ◽  
Ductile Crack ◽  
Ductile Crack Growth

Ductile Crack Extension Analysis for X80 Bending Deformation Using Damage-Based Model

2014 ◽  
Author(s):  
Satoshi Igi ◽  
Mitsuru Ohata ◽  
Takahiro Sakimoto ◽  
Kenji Oi ◽  
Joe Kondo
Keyword(s):  
Plastic Strain ◽  
Simulation Model ◽  
Crack Growth ◽  
Crack Extension ◽  
Damage Model ◽  
Stress Triaxiality ◽  
Crack Growth Behavior ◽  
Ductile Crack ◽  
Ductile Crack Growth ◽  
Notch Tip

This paper presents experimental and analytical results focusing on the strain limit of X80 linepipe. Ductile crack growth behavior from a girth weld notch is simulated by FE analysis based on a proposed damage model and is compared with the experimental results. The simulation model for ductile crack growth accompanied by penetration through the wall thickness consists of two criteria. One is a criterion for ductile crack initiation from the notch-tip, which is described by the plastic strain at the notch tip, because the onset of ductile cracking can be expressed by constant plastic strain independent of the shape and size of the components and the loading mode. The other is a damage-based criterion for simulating ductile crack extension associated with damage evolution influenced by plastic strain in accordance with the stress triaxiality ahead of the extending crack tip. The proposed simulation model is applicable to prediction of ductile crack growth behaviors from a circumferentially-notched girth welded pipe with high internal pressure, which is subjected to tensile loading or bending (post-buckling) deformation.

Prediction of Ductile Crack Growth from Ductility of Steel

2007 ◽  
Vol 539-543 ◽  
pp. 2186-2191 ◽  
Author(s):  
Mitsuru Ohata ◽  
Takuya Fukahori ◽  
Fumiyoshi Minami
Keyword(s):  
Mechanical Properties ◽  
Crack Initiation ◽  
Crack Growth ◽  
Damage Model ◽  
Stress Triaxiality ◽  
Local Strain ◽  
Strength Properties ◽  
Ductile Crack ◽  
Ductile Crack Growth ◽  
Point Bend

This study pays attention to reveal the material properties that control resistance curve for ductile crack growth (CTOD-R curve) on the basis of the mechanism for ductile crack growth, so that the R-curve could be numerically predicted only from those properties. The crack growth tests using 3-point bend specimens with fatigue pre-crack were conducted for two steels that have different ductile crack growth resistance with almost the same CTOD level for crack initiation, whereas both steels have the same “Mechanical properties” in terms of strength and work hardenability. The observation of crack growth behaviors provided that different mechanisms between ductile crack initiations from fatigue pre-crack and subsequent growth process could be applied. It was found that two “Mechanical properties” associated with ductile damage of steel could mainly influence CTOD-R curve; one is a resistance of ductile crack initiation estimated with critical local strain for ductile cracking from the surface of notched specimen, and the other one is a dependence of stress triaxiality on ductility obtained with circumferentially notched round-bar specimens. The damage model for numerically simulating the R-curve was proposed taking the two “ductile properties” into account, where ductile crack initiation from crack-tip was in accordance with critical local strain based criterion, and subsequent crack growth GTN (Gurson-Tvergaard-Needleman) based triaxiality dependent damage criterion. The proposed model accurately predicted the measured R-curve for the two steels used with the same “strength properties” through ductile crack initiation to growth.

Ductile Fracture Simulation of CRIEPI STPT 410 Pipe With Circumferential Crack

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.

Finite Element Ductile Crack Growth Simulations of Specimens Under Combined Mechanical and Residual Stresses

2013 ◽  
Author(s):  
Chang-Young Oh ◽  
Jong-Hyun Kim ◽  
Yun-Jae Kim ◽  
P. J. Budden
Keyword(s):  
Residual Stress ◽  
Crack Growth ◽  
Stress Reduction ◽  
Growth Response ◽  
Damage Model ◽  
Stress Distributions ◽  
Ductile Crack ◽  
Size Dependent ◽  
Element Size ◽  
Ductile Crack Growth

This paper provides simulations of ductile crack growth in test specimens using an element-size dependent damage model. The present method used in this paper is based on a stress modified fracture strain damage model with a stress reduction technique. The calibrated damage model is used to predict the load versus ductile crack growth response of test specimens. These tests included some samples that contained self-balancing residual stress distributions. The influence of a residual stress on the load versus crack growth relationship is accurately simulated using the element-size dependent damage model.

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