Modified J Estimation by GE/EPRI Method for Circumferential Surface Cracked Pipes Under Bending or Combined Bending and Pressure Loads

2011 ◽  
Author(s):  
Jing Zhang ◽  
Chang-Jun Liu ◽  
Fu-Zhen Xuan ◽  
Pei-Ning Li
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Structural Integrity ◽  
Estimation Method ◽  
J Integral ◽  
Element Analysis ◽  
Shape Factors ◽  
Failure Assessment ◽  
Integral Estimation ◽  
J Estimation

In order to assess the structural integrity of the components in nuclear power plants, it is necessary to accurately evaluate the J-integral. EPRI J-integral estimation method has been widely used. However for the pipes with circumferential surface cracks, since the solutions of fully plastic factors H1 were few under the combined pressure and bending loading condition. In such a case, EPRI J-integral might be non-conservative in elastic-plastic transition zone. Considering the problems, detailed finite element analysis (FEA) were conducted in this work, and H1, shape factors F were provided for the pure pressure, pure bending, and combined pressure and bending conditions. The reasons for non-conservatism of EPRI method were discussed, and a modified J estimation method was developed. For validation, failure assessment curves (FACs) were employed to compare the proposed J-integral estimation, EPRI J-integral and FEA method. The results showed that FAC based on the proposed J-integral method agreed well with FEA result, which provided good confidence in the use of this method.

Determination of J-Integral Using the Load-COD Record for Circumferential Through-Wall Cracked Pipes

2008 ◽  
Vol 130 (4) ◽  
Author(s):  
Nam-Su Huh ◽  
Yun-Jae Kim
Keyword(s):  
Crack Opening ◽  
Estimation Method ◽  
J Integral ◽  
Opening Displacement ◽  
Element Analysis ◽  
Load Line ◽  
Load Line Displacement ◽  
Η Factor ◽  
J Estimation

The present paper provides experimental J estimation equation based on the load-crack opening displacement (COD) record for testing the circumferential through-wall cracked pipe under combined tension and bending. Based on the limit analysis and the kinematically admissible rigid-body rotation field, the plastic η-factor for the load-COD record is derived and is compared with that for the load-load line displacement record. Comparison with the J results from detailed elastic-plastic finite element analysis shows that the proposed method based on the load-COD record provides reliable J estimates even for shallow cracks (small crack angle), whereas the conventional approach based on the load-load line displacement record gives erroneous results for shallow cracks. Thus, the proposed J estimation method could be recommended for testing the circumferential through-wall cracked pipe, particularly with shallow cracks.

Experimental Investigation on Failure Estimation Method for Circumferentially Cracked Pipes Subjected to Combined Bending and Torsion Loads

2013 ◽  
Author(s):  
Yinsheng Li ◽  
Kunio Hasegawa ◽  
Michiya Sakai ◽  
Shinichi Matsuura ◽  
Naoki Miura
Keyword(s):  
Experimental Investigation ◽  
Pressure Vessel ◽  
Nuclear Power ◽  
Power Plants ◽  
Structural Integrity ◽  
Estimation Method ◽  
Bending Moment ◽  
Limit Load ◽  
Piping System ◽  
Torsion Moment

When a crack is detected in a nuclear piping system during in-service inspections, the failure estimation method provided in codes such as the ASME Boiler and Pressure Vessel Code Section XI or JSME Rules on Fitness-for-Service for Nuclear Power Plants can be applied to evaluate the structural integrity of the cracked pipe. In the current codes, the failure estimation method for circumferentially cracked pipes includes bending moment and axial force due to pressure. Torsion moment is not considered. The Working Group on Pipe Flaw Evaluation for the ASME Boiler and Pressure Vessel Code Section XI is developing guidance for combining torsion load within the existing solutions provided in Appendix C for bending and pressure loadings on a pipe. A failure estimation method for circumferentially cracked pipes subjected to general loading conditions including bending moment, internal pressure and torsion moment with general magnitude has been proposed based on analytical investigations on the limit load for cracked pipes. In this study, experimental investigation was conducted to confirm the applicability of the proposed failure estimation method. Experiments were carried out on 8-inch diameter Schedule 80 stainless steel pipes containing a circumferential surface crack. Based on the experimental results, the proposed failure estimation method was confirmed to be applicable to cracked pipes subjected to combined bending and torsion moments.

Experimental Investigation of Failure Estimation Method for Cylinders With a Circumferential Crack Subjected to Combined Tensile and Torsion Loads

2012 ◽  
Author(s):  
Yinsheng Li ◽  
Kunio Hasegawa ◽  
Naoki Miura ◽  
Katsuaki Hoshino
Keyword(s):  
Stainless Steel ◽  
Nuclear Power ◽  
Power Plants ◽  
Structural Integrity ◽  
Estimation Method ◽  
Bending Moment ◽  
Failure Behavior ◽  
Axial Loads ◽  
Circumferential Crack ◽  
Torsion Moment

When a crack is detected in a stainless steel pipe during in-service inspections, the failure estimation method given in codes such as the ASME Boiler and Pressure Vessel Code Section XI or JSME Rules on Fitness-for-Service for Nuclear Power Plants can be applied to evaluate the structural integrity of the cracked pipe. In the current codes, the failure estimation method includes the bending moment and axial force due to pressure. The torsion moment is assumed to be relatively small and is not considered. Recently, analytical investigations considering multi-axial loads including torsion were conducted in several previous studies by examining the limit load for pipes with a circumferential crack. A failure estimation method for the combined bending moment, torsion moment and internal pressure was proposed. In this study, the failure behavior of pipes with a circumferential crack subjected to multi-axial loads including the torsion is investigated to provide experimental support for the failure estimation method. Experiments were carried out on small size stainless steel cylinders containing a circumferential surface or through-wall crack, subjected to the combined tensile and torsion loads. Based on the experimental results, the proposed failure estimation method was confirmed to be applicable to cracked pipes subjected to combined tensile and torsion loads.

Development of Stress Intensity Factors for Surface Cracks With Large Aspect Ratio in Plates

2015 ◽  
Vol 137 (5) ◽  
Author(s):  
Yinsheng Li ◽  
Kunio Hasegawa ◽  
Genshichiro Katsumata ◽  
Kazuya Osakabe ◽  
Hiroshi Okada
Keyword(s):  
Stress Intensity ◽  
Aspect Ratio ◽  
Nuclear Power ◽  
Power Plants ◽  
Structural Integrity ◽  
Crack Depth ◽  
Surface Cracks ◽  
Large Aspect Ratio ◽  
Element Analysis ◽  
Integrity Assessment

A number of surface cracks with large aspect ratio have been detected in components of nuclear power plants (NPPs) in recent years. The depths of these cracks are even larger than the half of crack lengths. When a crack is detected during in-service inspections, methods provided in ASME Boiler and Pressure Vessel Code Section XI or JSME Rules on fitness-for-service for NPPs can be used to assess the structural integrity of cracked components. The solution of the stress intensity factor (SIF) is very important in the structural integrity assessment. However, in the current codes, the solutions of the SIF are provided for semi-elliptical surface cracks with a limitation of a/ℓ ≤ 0.5, where a is the crack depth, and ℓ is the crack length. In this study, the solutions of the SIF were calculated using finite element analysis (FEA) with quadratic hexahedron elements for semi-elliptical surface cracks with large aspect ratio in plates. The crack dimensions were focused on the range of a/ℓ = 0.5–4.0 and a/t = 0.0–0.8, where t is the wall thickness. Solutions were provided at both the deepest and the surface points of the surface cracks. Furthermore, some of solutions were compared with the available existing results as well as with solutions obtained using FEA with quadratic tetrahedral elements and the virtual crack closure-integral method (VCCM). Finally, it was concluded that the solutions proposed in this paper are applicable in engineering applications.

Experimental Study on Failure Estimation Method for Circumferentially Cracked Pipes Subjected to Multi-Axial Loads

2015 ◽  
Author(s):  
Yinsheng Li ◽  
Kunio Hasegawa ◽  
Naoki Miura ◽  
Katsuaki Hoshino
Keyword(s):  
Axial Force ◽  
Nuclear Power ◽  
Power Plants ◽  
Structural Integrity ◽  
Estimation Method ◽  
Bending Moment ◽  
Estimation Methods ◽  
Failure Behavior ◽  
Axial Loads ◽  
Torsion Moment

When a crack is detected in a piping line during in-service inspections, failure estimation method provided in ASME Boiler and Pressure Vessel Code Section XI or JSME Rules on Fitness-for-Service for Nuclear Power Plants can be applied to evaluate the structural integrity of the cracked pipe. The failure estimation method in the current codes accounts for the bending moment and axial force due to pressure. The torsion moment is not considered. Recently, analytical investigations have been carried out by several authors on the limit load of cracked pipes considering multi-axial loads including torsion and two failure estimation methods for multi-axial loads including torsion moment with different ranges of values have been proposed. In this study, to investigate the failure behavior of cracked pipes subjected to multi-axial loads including the torsion moment and to provide experimental support for the failure estimation methods, failure experiments were performed on 20 mm diameter stainless steel pipes with a circumferential surface crack or a through-wall crack under combined axial force and bending and torsion moments. Based on the experimental results, the proposed failure estimation methods were confirmed to be applicable to cracked pipes subjected to multi-axial loads.

Experimental Study on Failure Estimation Method for Circumferentially Cracked Pipes Subjected to Multi-Axial Loads

2016 ◽  
Vol 139 (1) ◽  
Author(s):  
Yinsheng Li ◽  
Kunio Hasegawa ◽  
Naoki Miura ◽  
Katsuaki Hoshino
Keyword(s):  
Axial Force ◽  
Nuclear Power ◽  
Power Plants ◽  
Structural Integrity ◽  
Estimation Method ◽  
Bending Moment ◽  
Estimation Methods ◽  
Failure Behavior ◽  
Axial Loads ◽  
Torsion Moment

When a crack is detected in a piping line during in-service inspections, failure estimation method provided in ASME Boiler and Pressure Vessel Code Section XI (ASME Code Section XI) or JSME Rules on Fitness-for-Service for Nuclear Power Plants (JSME FFS Code) can be applied to evaluate the structural integrity of the cracked pipe. The failure estimation method in the current codes accounts for the bending moment and axial force due to pressure. The torsion moment is not considered. Recently, analytical investigation was carried out by the authors on the limit load of cracked pipes considering multi-axial loads including torsion. Two failure estimation methods for multi-axial loads including torsion moment with different ranges were proposed. In this study, to investigate the failure behavior of cracked pipes subjected to multi-axial loads including the torsion moment and to provide experimental support for the failure estimation methods, failure experiments were performed on 20 mm diameter stainless steel pipes with a circumferential surface crack or a through-wall crack under combined axial force, bending moment, and torsion moment. Based on the experimental results, the proposed failure estimation methods were confirmed to be applicable to cracked pipes subjected to multi-axial loads.

Experimental Investigation of Failure Estimation Method for Circumferentially Cracked Pipes Subjected to Combined Bending and Torsion Moments

2014 ◽  
Vol 137 (2) ◽  
Author(s):  
Yinsheng Li ◽  
Kunio Hasegawa ◽  
Michiya Sakai ◽  
Shinichi Matsuura ◽  
Naoki Miura
Keyword(s):  
Experimental Investigation ◽  
Nuclear Power ◽  
Power Plants ◽  
Structural Integrity ◽  
Estimation Method ◽  
Bending Moment ◽  
Limit Load ◽  
Estimation Methods ◽  
Piping System ◽  
Steel Pipes

When a crack is detected in a nuclear piping system during in-service inspections, failure estimation method provided in codes such as ASME Boiler and Pressure Vessel Code Section XI or JSME Rules on Fitness-for-Service for Nuclear Power Plants can be applied to evaluate the structural integrity of the cracked pipe. In the current codes, the failure estimation method for circumferentially cracked pipes is applicable for both bending moment and axial force due to pressure. Torsion moment is not considered. Recently, two failure estimation methods for circumferentially cracked pipes subjected to combined bending and torsion moments were proposed based on analytical investigations on the limit load for cracked pipes. In this study, experimental investigation was conducted to confirm the applicability of the failure estimation method for cracked pipes subjected to bending and torsion moments. Experiments were carried out on 8-in. diameter Schedule 80 stainless steel pipes containing a circumferential surface crack. Based on the experimental results, the proposed failure estimation methods were confirmed to be applicable to cracked pipes subjected to combined bending and torsion moments.

Development of Stress Intensity Factors for Deep Surface Cracks in Plates and Cylinders

2012 ◽  
Author(s):  
Yinsheng Li ◽  
Hiroto Itoh ◽  
Kunio Hasegawa ◽  
Kazuya Osakabe ◽  
Hiroshi Okada
Keyword(s):  
Finite Element Analysis ◽  
Stress Intensity Factor ◽  
Finite Element ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Nuclear Power ◽  
Power Plants ◽  
Structural Integrity ◽  
Surface Cracks ◽  
Element Analysis

A number of deep surface cracks have been detected in components of nuclear power plants in recent years. The depths of these cracks are even greater than the half of crack lengths. When a crack is detected during in-service inspections, methods provided in the ASME Boiler and Pressure Vessel Code Section XI or JSME Rules on Fitness-for-Service for Nuclear Power Plants can be used to assess the structural integrity of cracked components. The solution of the stress intensity factor is very important in the assessment of structural integrity. However, in the current codes, the solutions of the stress intensity factor are provided for semi-elliptical surface cracks with a limitation of a/l ≤ 0.5, where a is the crack depth, and l is the crack length. In this study, in order to assess the structural integrity in a more rational manner, the solutions of the stress intensity factor were calculated using finite element analysis with quadratic hexahedron elements for deep semi-elliptical surface cracks in plates, and for axial and circumferential semi-elliptical surface cracks in cylinders. The crack dimensions were focused on the range of a/l = 0.5 to 4.0. Solutions were provided at both the deepest and the surface points of the cracks. Furthermore, some of solutions were compared with the available existing studies and with solutions obtained using finite element analysis with quadratic tetrahedral elements and the virtual crack closure-integral method. As the conclusion, it is concluded that the solutions proposed in this paper are applicable in engineering applications.

Development of 1500-r/min 75-Inch Ultra-Long Last Stage Blades for Nuclear Steam Turbine

2017 ◽  
Author(s):  
Deqi Yu ◽  
Jiandao Yang ◽  
Wei Lu ◽  
Daiwei Zhou ◽  
Kai Cheng ◽  
...  
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Large Scale ◽  
Vibration Monitoring ◽  
Steam Turbines ◽  
Element Analysis ◽  
Rotating Blade ◽  
Lifetime Analysis ◽  
Computational Fluid Dynamics Cfd ◽  
Last Stage

The 1500-r/min 1905mm (75inch) ultra-long last three stage blades for half-speed large-scale nuclear steam turbines of 3rd generation nuclear power plants have been developed with the application of new design features and Computer-Aided-Engineering (CAE) technologies. The last stage rotating blade was designed with an integral shroud, snubber and fir-tree root. During operation, the adjacent blades are continuously coupled by the centrifugal force. It is designed that the adjacent shrouds and snubbers of each blade can provide additional structural damping to minimize the dynamic stress of the blade. In order to meet the blade development requirements, the quasi-3D aerodynamic method was used to obtain the preliminary flow path design for the last three stages in LP (Low-pressure) casing and the airfoil of last stage rotating blade was optimized as well to minimize its centrifugal stress. The latest CAE technologies and approaches of Computational Fluid Dynamics (CFD), Finite Element Analysis (FEA) and Fatigue Lifetime Analysis (FLA) were applied to analyze and optimize the aerodynamic performance and reliability behavior of the blade structure. The blade was well tuned to avoid any possible excitation and resonant vibration. The blades and test rotor have been manufactured and the rotating vibration test with the vibration monitoring had been carried out in the verification tests.

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