CASS Fracture Tests Using Flat Plate Specimens With a Surface Flaw

2015 ◽  
Author(s):  
Kiminobu Hojo ◽  
Wataru Nishi ◽  
Shotaro Hayashi
Keyword(s):  
Stainless Steel ◽  
Flat Plate ◽  
Thermal Aging ◽  
Limit Load ◽  
Surface Flaw ◽  
Tensile Fracture ◽  
Ferrite Number ◽  
Fracture Tests ◽  
Depth Curve ◽  
Two Parameter

JSME rules for fitness for service have flaw acceptance rules for cast austenitic stainless steel (CASS) pipes. They allow applying two-parameter and elastic-plastic fracture mechanics methods using Z-factor. However they do not clearly describe whether limit load method is applicable for the case of no or low thermal aging condition. The authors performed tensile fracture tests using flat plate specimens with a surface flaw and confirmed that limit load method is applicable in the conditions of no thermal aging and even fully saturated thermal aging with high ferrite number. Also the plate with a shallow flaw ruptured at the critical stress defined by nominal stress at rupture-flaw depth curve in the code case which was determined by the similar flat plate tests of stainless steel or nickel alloy specimens. These results will be reflected to the revision of the code.

Introduction of CASS Pipe Flaw Evaluation of JSME Rules on Fitness for Service

2019 ◽  
Author(s):  
Kiminobu Hojo
Keyword(s):  
Stainless Steel ◽  
Evaluation Method ◽  
Limit Load ◽  
Evaluation Procedure ◽  
Screening Criteria ◽  
Steel Pipes ◽  
Evaluation Procedures ◽  
Degradation Models ◽  
Fracture Tests ◽  
Cast Stainless Steel

Abstract This paper summarizes the revised flaw evaluation procedures for cast austenitic stainless steel (CASS) pipe of the Japan Society of Mechanical Engineers (JSME) rules on fitness for service (FFS) in 2018 addenda. The revision includes the introduction of thermal aging degradation models for stressstrain curve and fracture resistance (J-R) curve, application of a screening criteria for the fracture evaluation procedure of cast stainless steel pipes, and introduction of a new critical stress parameter for the limit load evaluation method of a shallow flaw with a flaw depth to thickness ratio of less than or equal to 0.5. These revisions are based on a large database of specimen tests and several fracture tests of flat plate and large pipe models using thermally aged material, which have already been published.

Introduction of JSME Rules on Fitness for Service for CASS Piping and Proposal for Improvements

2013 ◽  
Author(s):  
Kiminobu Hojo ◽  
Masayuki Kamaya
Keyword(s):  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Brittle Fracture ◽  
Nuclear Power ◽  
Power Plants ◽  
Failure Modes ◽  
Limit Load ◽  
Evaluation Procedure ◽  
Japan Society ◽  
Two Parameter

The Japan Society of Mechanical Engineers (JSME) Code Rules on Fitness for Service (FFS) for Nuclear Power Plants describe a flaw evaluation procedure for stainless steel piping including cast austenitic stainless steel (CASS) piping. It consists of three methods; limit load, elastic plastic fracture mechanics (EPFM) and two-parameter (covering failure modes from brittle fracture to limit load) methods. This paper describes a brief introduction of the flaw evaluation procedure for CASS piping in the JSME rules. Some improvements for the current rules are also proposed.

Ductile Fracture Strength of Ni-Based Alloy With an Inch Thickness

2010 ◽  
Author(s):  
Katsumasa Miyazaki ◽  
Koichi Saito
Keyword(s):  
Flat Plate ◽  
Limit Load ◽  
Maximum Load ◽  
Assessment Procedure ◽  
Element Analysis ◽  
Butt Weld ◽  
Metal Plates ◽  
Failure Assessment ◽  
Fracture Tests ◽  
The Difference

To develop the failure assessment procedure of Ni-based alloy, the fracture tests of flat plate specimens with a rectangular flaw were conducted at 302°C in temperature. The flat plate specimens were base metal plates, NCF600 and butt weld joints, whose weld metal was Alloy 182 with an inch (25 mm) in thickness. The maximum load at 302°C could be estimated by the limit load analysis (LLA) and twice elastic slope (TES) method with finite element analysis. In addition, the difference between maximum load obtained by the fracture tests and estimations by LLA and TES method became smaller with increasing the flaw area. The net stress at the maximum load depends on the flaw depth and this tendency in Ni-based alloy at 302°C is almost the same as the Hasegawa’s experimental proposal obtained by the fracture tests of austenitic stainless steel.

Experimental Investigation on the Limit Load Estimation Method for Pipes Containing a Circumferential Surface Flaw With Complicated Shape

2011 ◽  
Author(s):  
Yinsheng Li ◽  
Kunio Hasegawa ◽  
Naoki Miura ◽  
Katsuaki Hoshino
Keyword(s):  
Stainless Steel ◽  
Nuclear Power ◽  
Power Plants ◽  
Estimation Method ◽  
Limit Load ◽  
Surface Flaw ◽  
Experimental Results ◽  
Load Estimation ◽  
Bending Moments ◽  
Steel Pipes

When a flaw is detected in the stainless steel pipes at nuclear power plants during in-service inspections, the limit load estimation method provided in the codes such as JSME Rules on Fitness-for-Service for Nuclear Power Plants or ASME Boiler and Pressure Vessel Code Section XI can be applied to evaluate the integrity of the flawed pipe. However, in these current codes, the limit load estimation method is only derived for pipes containing a flaw with uniform depth, although many flaws with complicated shapes, such as stress corrosion cracks, have actually been detected in pipes. In order to evaluate the integrity of the flawed pipes in a more rational way, a limit load estimation method has been proposed by authors considering the complicated circumferential surface flaw in its shape. In this study, failure bending experiments are performed for stainless steel pipes containing a circumferential surface flaw with a complicated asymmetrical shape. The proposed method is verified by comparing with experimental results of failure bending moments obtained in this study and in previous experiments. It is observed that the predicted failure bending moments by the proposed method are consistent with the experimental results, and the proposed method is applicable to estimate the realistic load-carrying capacity of flawed pipes.

Effect of Flaw Dimensions on Ductile Fracture Behavior of Non-Aligned Multiple Flaws in a Plate

2011 ◽  
Author(s):  
Katsumasa Miyazaki ◽  
Kunio Hasegawa ◽  
Koichi Saito
Keyword(s):  
Ductile Fracture ◽  
Flat Plate ◽  
Fracture Behavior ◽  
Maximum Load ◽  
Surface Flaws ◽  
Fracture Tests ◽  
The Difference ◽  
Almost All ◽  
Maximum Minimum

The fitness-for-service codes require the characterization of non-aligned multiple flaws for flaw evaluation, which is performed using a flaw proximity rule. Worldwide, almost all such codes provide their own proximity rule, often with unclear technical bases of the application of proximity rule to ductile or fully plastic fracture. In particular, the effect of flaw dimensions of multiple surface flaws on fully plastic fracture of non-aligned multiple flaws had not been clear. To clarify the effect of the difference of part through-wall and through-wall flaws on the behavior of fully plastic fracture, the fracture tests of flat plate specimens with non-aligned multiple part through-wall flaws were conducted. When the flaw depth a was shallow with 0.4 in ratio of a to thickness t, the maximum load Pmax occurred at penetration of multiple flaws and the effect of vertical distance of non-aligned multiple flaws H on Pmax was not so significant. However, when flaw depth was deep with 0.8 in a/t, Pmax occurred after penetration of flaws and the effect of H on Pmax could be seen clearly. It was judged that the through-wall flaw tests were appropriate for discussion of the effect of H on Pmax and the alignment rule of multiple flaws. In addition, in order to clarify the appropriate length parameter to estimate Pmax of test specimens with dissimilar non-aligned through-wall multiple flaws, the fracture tests of plate specimens were also conducted. The effect of different flaw length on Pmax was discussed with maximum, minimum and averages of dissimilar non-aligned multiple flaw lengths. Experimental results showed that the maximum length lmax would be an appropriate length parameter to estimate Pmax, when the non-aligned multiple through-wall flaws were dissimilar.

Effect of recrystallization on degree of sensitization in nickel free austenitic stainless steel

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Sourabh Shukla ◽  
Awanikumar P. Patil ◽  
Ashlesha Kawale ◽  
Anand Babu Kotta ◽  
Inayat Ullah
Keyword(s):  
Stainless Steel ◽  
Thermal Aging ◽  
Thermomechanical Processing ◽  
Cold Work ◽  
Austenitic Stainless Steels ◽  
Content Type ◽  
High Deformation ◽  
Strain Induced Martensite ◽  
Degree Of Sensitization ◽  
Cold Worked

Purpose Effect of grain size on degree of sensitization (DOS) was been evaluated in Nickel free steel. Manganese and nitrogen contained alloy is a Ni-free austenitic stainless steels (ASS) having type 202 grade. The main purpose of this investigation is to find the effect of recrystallization on the DOS of stainless steel after the thermo-mechanical processing (cold work and thermal aging). Design/methodology/approach In the present investigation, the deformation of 202 grade analyzed using X-ray diffraction (XRD) and microstructural testing. Optical microstructure of Ni-free ASS has been done for cold worked samples with thermally aged at 900°C_6 h. Double loop electrochemical potentiodynamic reactivation test used for findings of degree of sensitization. Findings Ni-free ASS appears to be deformed more rapidly due to its higher stacking fault energy which gave results in rapid transformation from strain induced martensite to austenite in form of recrystallized grains, i.e. it concluded that as cold work percentage increases more rapidly recrystallization occurs. XRD results also indicate that more fraction of martensite formed as percentage of CW increases but as thermal aging reverted those all martensite to austenite. So investigation gives the conclusion which suggests that with high deformation at higher temperature and duration gives very less DOS. Originality/value Various literatures available for 300 series steel related to the effect of cold work on mechanical properties and sensitization mechanism. However, no one has investigated the effect of recrystallization through thermomechanical processing on the sensitization of nickel-free steel.

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