Strain-Hardening Effects on Fracture Toughness and Ductile Crack Growth in Austenitic Stainless Steels

2008 ◽  
pp. 293-293-15 ◽  
Author(s):  
P Balladon ◽  
J Heritier ◽  
C Jarboui
Keyword(s):  
Fracture Toughness ◽  
Strain Hardening ◽  
Crack Growth ◽  
Stainless Steels ◽  
Austenitic Stainless Steels ◽  
Ductile Crack ◽  
Ductile Crack 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.

Ductile Crack Growth Resistance and Rotation Behavior of Miniature C(T) Specimen

2020 ◽  
Author(s):  
Tomoki Shinko ◽  
Masato Yamamoto
Keyword(s):  
Fracture Toughness ◽  
Size Effect ◽  
Crack Growth ◽  
Crack Extension ◽  
Crack Tip ◽  
Crack Growth Resistance ◽  
Specimen Size ◽  
Ductile Crack ◽  
Rotation Center ◽  
Ductile Crack Growth

Abstract A utilization of a miniature compact tension (Mini-C(T)) specimen is expected to enable effective use of limited remaining surveillance specimens for the structural integrity assessment of a Reactor Pressure Vessel (RPV). For developing a direct fracture toughness evaluation method using Mini-C(T) specimen in the upper-shelf temperature range as well as ductile-brittle transition temperature range, this study is aimed to experimentally characterize the Mini-C(T) specimen’s size effect on ductile crack growth resistance and interpolate its mechanism. Mini-C(T) specimen and 0.5T-C(T) specimen were prepared from a Japanese RPV steel SQV2A, and the ductile crack growth tests were conducted on them at room temperature. As a result, the crack growth resistance of Mini-C(T) and 0.5T-C(T) specimens are comparable if the crack extension Δa is less than 0.5 mm. On the other hand, if Δa exceeds 0.5 mm, the crack growth resistance of Mini-C(T) specimen becomes lower than that of 0.5T-C(T) specimen. The measurements of stretch zone width and depth support the fact that the fracture toughness for ductile crack initiation of Mini-C(T) specimen is lower than that of 0.5T-C(T) specimen. From the rotational (crack mouth opening) deformation of Mini-C(T) specimen was measured by simultaneously measuring load-line and front face displacements. The distance between the crack tip and the rotation center of Mini-C(T) specimen is smaller than that of 0.5T-C(T) specimen during the test. Furthermore, The plastic zone in front of the crack tip reaches the rotation center up to the crack extension of Δa = 0.3 mm on Mini-C(T) specimen, indicating that the mechanism of the specimen size effect of Mini-C(T) specimen is likely a plastic constraint due to the influence of the rotation center locating near the crack tip. This suggests that the specimen size effect of Mini-C(T) specimen on ductile crack growth resistance is expected to be corrected by considering an effect of the plastic constraint.

Effect of Constraint on the Initiation of Ductile Fracture in Shear Loading

2004 ◽  
Vol 261-263 ◽  
pp. 183-188 ◽  
Author(s):  
Majid R. Ayatollahi ◽  
David John Smith ◽  
M.J. Pavier
Keyword(s):  
Fracture Toughness ◽  
Ductile Fracture ◽  
Crack Growth ◽  
Void Growth ◽  
Crack Tip ◽  
Shear Loading ◽  
Mode Ii ◽  
Ductile Crack ◽  
Ductile Crack Growth ◽  
Void Growth And Coalescence

Research studies for mode I cracks have shown that fracture toughness or the critical value of J for fracture initiation, Jcrit is not merely a material property but depends also on the geometry and loading configurations. The geometry dependency of fracture toughness can be attributed to the effect of the crack tip constraint. In this paper, the constraint effect is studies for the initiation stage in mode II ductile crack growth. Two major mechanisms of ductile fracture: 'void growth and coalescence' and 'shear band localization and de-cohesion' are considered. A boundary layer model is simulated using the finite element method and the effect of far-filed T-stress on the relevant stress parameters near the crack tip is studied. It is shown that the initiation of the ductile crack growth in mode II is influenced significantly by T for the mechanism of void growth and coalescence and is insensitive to T for the mechanism of shear localisation and de-cohesion.

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