scholarly journals Fracture Toughness Evaluation of S355 Steel Using Circumferentially Notched Round Bars

2018 ◽  
Vol 47 (2) ◽  
pp. 91-95 ◽  
Author(s):  
Fatih Bozkurt ◽  
Eva Schmidová
Keyword(s):  
Fracture Toughness ◽  
Fracture Mechanics ◽  
Compact Tension ◽  
Compact Tension Specimen ◽  
Fracture Load ◽  
Alternative Methods ◽  
Test Procedures ◽  
Toughness Evaluation ◽  
Fracture Toughness Evaluation

In engineering applications, steels are commonly used in various areas. The mechanical members are exposed to different loading conditions and this subject can be investigated in fracture mechanics. Fracture toughness (KIC) is the important material property for fracture mechanics. Determination of this properties is possible using a compact tension specimen, a single edge notched bend or three-point loaded bend specimen, which are standardized by different institutions. Researchers underline that these standardized methods are complex, the manufacturing process is difficult, they require special fixtures for loading during the experiment and the test procedures are time consuming. Alternative methods are always being sought by researchers. In this work, two different approaches are investigated for S355 steels. In the first method, a circumferentially cracked round bar was loaded in tensile mode and pulled till failure. Using suitable equations, fracture toughness can be calculated. In the second method, a circumferentially notched bar specimen without fatigue pre-cracking was loaded in a tensile machine. By means of fracture load values, fracture toughness was determined by the proposed equations. It can be stated that these two different approaches for calculating fracture toughness are simple, fast and economical.

Embedded Crack Treatments and Fracture Toughness Evaluation Methods in Probabilistic Fracture Mechanics Analysis Code for the PTS Analysis of RPV

2004 ◽  
Author(s):  
Kunio Onizawa ◽  
Katsuyuki Shibata ◽  
Masahide Suzuki ◽  
Daisuke Kato ◽  
Yinsheng Li
Keyword(s):  
Fracture Toughness ◽  
Fracture Mechanics ◽  
Crack Growth ◽  
Treatment Method ◽  
Evaluation Methods ◽  
Probabilistic Fracture Mechanics ◽  
Mechanics Analysis ◽  
Toughness Evaluation ◽  
Embedded Crack ◽  
Fracture Toughness Evaluation

Using the probabilistic fracture mechanics analysis code PASCAL, we studied the treatment method of an embedded crack and the fracture toughness evaluation methods on the probability of crack initiation and fracture of a reactor pressure vessel (RPV). For calculating the stress intensity factor (SIF) of an embedded crack, the ASME and CRIEPI procedures were introduced into the PASCAL code. The CRIEPI method enables us to calculate the SIF values at three points on the crack tip. Under a severe pressurized thermal shock (PTS) condition, the crack growth analysis methods with different SIF calculation points and crack growth directions are compared. To evaluate precisely the fracture toughness after neutron irradiation, the new fracture toughness curves based on the Weibull distribution were incorporated into the PASCAL code. The calculated results with these new curves showed little difference in the conditional probabilities of RPV fracture as compared to the curve currently used in the U.S.

Fracture Toughness Evaluation of Reactor Pressure Vessel Steels by Master Curve Method Using Miniature Compact Tension Specimens

2015 ◽  
Vol 137 (5) ◽  
Author(s):  
Tohru Tobita ◽  
Yutaka Nishiyama ◽  
Takuyo Ohtsu ◽  
Makoto Udagawa ◽  
Jinya Katsuyama ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Pressure Vessel ◽  
Master Curve ◽  
Loading Rate ◽  
Compact Tension ◽  
Master Curve Method ◽  
Toughness Evaluation ◽  
Curve Method ◽  
Fracture Toughness Evaluation ◽  
Reactor Pressure

We conducted fracture toughness testing on five types of commercially manufactured steel with different ductile-to-brittle transition temperatures. This was performed using specimens of different sizes and shapes, including the precracked Charpy-type (PCCv), 0.4T-CT, 1T-CT, and miniature compact tension specimens (0.16T-CT). Our objective was to investigate the applicability of 0.16T-CT specimens to fracture toughness evaluation by the master curve method for reactor pressure vessel (RPV) steels. The reference temperature (To) values determined from the 0.16T-CT specimens were overall in good agreement with those determined from the 1T-CT specimens. The scatter of the 1T-equivalent fracture toughness values obtained from the 0.16T-CT specimens was equivalent to that obtained from the other larger specimens. Furthermore, we examined the loading rate effect on To for the 0.16T-CT specimens within the quasi-static loading range prescribed by ASTM E1921. The higher loading rate gave rise to a slightly higher To, and this dependency was almost the same for the larger specimens. We suggested an optimum test temperature on the basis of the Charpy transition temperature for determining To using the 0.16T-CT specimens.

Acoustic Emission Entropy for Evaluation of Fracture Toughness of HSLA Steel Welded Joint

2017 ◽  
Author(s):  
Mengyu Chai ◽  
Weijie Wu ◽  
Zaoxiao Zhang ◽  
Guangxu Cheng ◽  
Quan Duan
Keyword(s):  
Fracture Toughness ◽  
Acoustic Emission ◽  
Welded Joint ◽  
Hsla Steel ◽  
Amplitude Distribution ◽  
Compact Tension ◽  
Compact Tension Specimen ◽  
New Approach ◽  
Astm Standard

In this investigation, fracture toughness behavior of high strength low alloy (HSLA) steel welded joint was studied using acoustic emission (AE) monitoring. For the design of new structures and for the safety and reliability analyses of operating components, fracture toughness (KIC) values of materials play an essential role. Acoustic emission technique (AET) has been used for determination of fracture toughness based on some observable changes of AE evolutions. However, the occurrence of appreciable plasticity in materials, the friction between the crack surfaces and mechanical noise could generate high emission and may result in some difficulties in precise determination of fracture toughness. Thus, the objective of this study is to propose a new approach to evaluate fracture toughness values and to characterize the fracture process based on AE entropy. Specimens were selected from 2.25Cr-1Mo-0.25V steel welded joint which were thermally aged at 978 K for 8 h. The AE signals generated during fracture processes were recorded and the corresponding AE entropy was calculated based on the probability amplitude distribution from each original AE waveform. The point of crack initiation was identified by the occurrence of sudden rise of AE entropy and the corresponding critical load was used to estimate fracture toughness value. The estimated values obtained from the proposed new approach were compared with those determined by the methodology proposed by compact tension specimen testing according to ASTM standard E399. The results showed that the estimated values were in close agreement with those gained from ASTM standard. It was concluded that AE entropy was an effective parameter to estimate fracture characteristics and fracture toughness values.

Finite Element Analysis on the Application of Mini-C(T) Test Specimens for Fracture Toughness Evaluation

2015 ◽  
Author(s):  
Hisashi Takamizawa ◽  
Tohru Tobita ◽  
Takuyo Ohtsu ◽  
Jinya Katsuyama ◽  
Yutaka Nishiyama ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Finite Element Analysis ◽  
Finite Element ◽  
Plastic Zone ◽  
Compact Tension ◽  
Distribution Analysis ◽  
Constraint Effect ◽  
Element Analysis ◽  
Toughness Evaluation ◽  
Fracture Toughness Evaluation

Fracture toughness evaluation by the Master Curve method using 4-mm-thick miniature compact tension (mini-C(T)) specimens taken from the broken halves of surveillance Charpy specimens has been proposed. In the present study, we performed finite element analysis (FEA) to examine the difference in the constraint effect of the crack tip for differently sized C(T) and precracked Charpy v-notch specimens. The constraint effect of the mini-C(T) specimens in terms of the T-stress and Q-parameter was similar to that of the larger C(T) specimens. In addition, to optimize the fatigue precracking conditions for the mini-C(T) specimen, plastic zone distribution analysis was performed by FEA. Using plastic zone distribution analysis, we demonstrated that a wider machined notch and shorter fatigue precrack length than that in conventional configurations can be applied for narrow and straight notches. We also obtained the fracture toughness data for two kinds of SA533B-1 steels and one weld metal with different sizes in addition to the data obtained in our previous study. It was shown that the reference temperature To obtained from the mini-C(T) specimens was in good agreement with those from other specimens. We compared the fracture toughness data, including the plane strain fracture toughness value obtained by 4T-C(T) specimens, with T41J-based fracture toughness curves proposed in a recent study. Most of the data, including the 4T-C(T) and irradiated specimens, were enveloped by the proposed lower-bound curve.

Applicability of Miniature Compact Tension Specimens for Fracture Toughness Evaluation of Highly Neutron Irradiated Reactor Pressure Vessel Steels

2018 ◽  
Vol 140 (5) ◽  
Author(s):  
Yoosung Ha ◽  
Tohru Tobita ◽  
Takuyo Ohtsu ◽  
Hisashi Takamizawa ◽  
Yutaka Nishiyama
Keyword(s):  
Fracture Toughness ◽  
Pressure Vessel ◽  
Compact Tension ◽  
Specimen Size ◽  
Reactor Pressure Vessel ◽  
Margin Of Error ◽  
Toughness Evaluation ◽  
Fracture Toughness Evaluation ◽  
Reactor Pressure ◽  
Selection Of

The applicability of miniature compact tension (Mini-C(T)) specimens to fracture toughness evaluation of neutron-irradiated reactor pressure vessel (RPV) steels was investigated. Three types of RPV steels neutron-irradiated to a high-fluence region were prepared and manufactured as Mini-C(T) specimens according to Japan Electric Association Code (JEAC) 4216-2015. Through careful selection of the test temperature by considering previously obtained mechanical properties data, valid fracture toughness, and reference temperature (To) was obtained with a relatively small number of specimens. Comparing the fracture toughness and To values determined using other larger specimens with those determined using the Mini-C(T) specimens, To values of both unirradiated and irradiated Mini-C(T) specimens were found to be the acceptable margin of error. The scatter of 1T-equivalent fracture toughness values of both unirradiated and irradiated materials obtained using Mini-C(T) specimens did not differ significantly from the values obtained using larger specimens. The correlation between the Charpy 41 J transition temperature (T41J) and the To values agreed very well with that of the data in the literature, regardless of specimen size and fracture toughness of the materials before irradiation. Based on these findings, it was concluded that Mini-C(T) specimens can be applied to fracture toughness evaluation of neutron-irradiated materials without significant specimen size dependence.

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