Technical Basis for Structural Integrity Performance Criterion for Steam Generator Tubing

Cipolla, Russell C.; Begley, James A.; Keating, Robert F.

doi:10.1115/pvp2006-icpvt-11-93935

Cited by 4 publications

(11 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Figure 7 shows a comparison of the increases of U-bend radii after unloading obtained by FE analyses with a test datum. 8 As shown in this figure, the final U-bend radii increase non-linearly as the radii of the fixed die increase. Analysis results also show that frictions between the tube and the two dies can affect the amount of the elastic spring back.…”

Section: Elastic Spring Backmentioning

confidence: 66%

“…The amount of the elastic spring back can be directly related to the increase of U‐bend radius. Figure 7 shows a comparison of the increases of U‐bend radii after unloading obtained by FE analyses with a test datum 8 . As shown in this figure, the final U‐bend radii increase non‐linearly as the radii of the fixed die increase.…”

Section: Analysis Resultsmentioning

confidence: 95%

“…Figure 6 shows a comparison of the required roller rotation angles obtained by FE analyses for various bend radii with a test datum 8 . As shown in this figure, the required rotation angles for developing 180 degree U‐bends increase non‐linearly as the U‐bend radii increase.…”

Section: Analysis Resultsmentioning

confidence: 98%

“…In other words, once the tube is bent past the point where the two legs are parallel, and then one leg is bent back until it is parallel to the other leg. Therefore, the die rotation angle, which is typically greater than 180 degrees, has to be established through specific tests or numerical simulations for each bending radii 2,8 . Cipolla et al mentioned that it was necessary to bend the tubes to ∼220 degrees in order to achieve the desired U‐bend angle (180 degrees), and that a die with outer radius of about 710 mm resulted in a U‐bend having radius of 915 mm 8 .…”

Section: Bending Processmentioning

confidence: 99%

“…Therefore, the die rotation angle, which is typically greater than 180 degrees, has to be established through specific tests or numerical simulations for each bending radii 2,8 . Cipolla et al mentioned that it was necessary to bend the tubes to ∼220 degrees in order to achieve the desired U‐bend angle (180 degrees), and that a die with outer radius of about 710 mm resulted in a U‐bend having radius of 915 mm 8 . However, detailed information on the die rotation angles and the amounts of elastic spring back for various bend radii are not currently available in the literature.…”

Section: Bending Processmentioning

confidence: 99%

See 4 more Smart Citations

Numerical simulation of rotating bending process for U‐tubes in heat exchangers

Kim¹,

Jin²,

Chang³

et al. 2009

Fatigue Fract Eng Mat Struct

View full text Add to dashboard Cite

A B S T R A C T Heat exchangers comprise thousands of tubes having U-shaped portions. Rotating bending method has been widely utilized to make U-bends. Although this method shows an excellent performance, cracks have been frequently detected in the U-bends due to residual stresses induced by bending. In this paper, the bending process is simulated based on elastic-plastic finite element analyses in order to investigate the magnitude and distribution of the residual stresses including the effects of operating pressure. Analyses results show that the residual stress increases as the radius of U-bend decreases and that operating pressure has a detrimental effect in terms of stress corrosion cracking at the intrados of U-bend. It is thought that these results can be utilized for the estimations of fracture mechanics parameters such as limit load, stress intensity factor and J-integral, prevention of the cracking, and establishment of the optimum inspection strategy for the heat exchanger tubes. E = Young's modulus R B = bend radius of tube R i = inner radius of tube R m = mean radius of tube R o = outer radius of tube t = thickness of tube λ = normalized bend radius (=R B t/R m 2 ) δ = increase of bend radius due to elastic spring back φ = rotation angle of bending die σ Normalized = normalized stress (=σ Residual R m /σ YS t) σ Residual = residual stress σ YS = yield strength σ TS = tensile strength

show abstract

Section: Elastic Spring Backmentioning

confidence: 66%

Section: Analysis Resultsmentioning

confidence: 95%

Section: Analysis Resultsmentioning

confidence: 98%

Section: Bending Processmentioning

confidence: 99%

Section: Bending Processmentioning

confidence: 99%

See 3 more Smart Citations

Numerical simulation of rotating bending process for U‐tubes in heat exchangers

Kim¹,

Jin²,

Chang³

et al. 2009

Fatigue Fract Eng Mat Struct

View full text Add to dashboard Cite

show abstract

Support‐induced restraint effect of thin‐walled tube in a steam generator subjected to combined pressure and bending load

Kim¹,

Jin²,

Chang

et al. 2007

Fatigue Fract Eng Mat Struct

View full text Add to dashboard Cite

A B S T R A C TThe restraint effects of support plates on limit load (LL) are evaluated for thin-walled tubes subjected to combined internal pressure and bending loads. To achieve this goal, three-dimensional (3D) finite element (FE) analyses assuming elastic-perfectly plastic material behaviour are carried out for tubes with various sizes of circumferential cracks. Two crack locations, both the top of the tube sheet (TTS) and transition regions, where circumferential cracks have been found in many steam generators during operation, are considered. FE analysis results show that LLs for the circumferential cracks are significantly affected by the boundary conditions of the tube and that the resulting LL solutions can be simply applied to the practical integrity assessment of steam generator tubes, because the comparison between experimental data and FE analysis results shows a good agreement. E = Young's modulus I = moment of inertia M L = limit bending moment M L FEA = limit bending moment by FE analysis M NL = normalized limit bending moment P L = limit pressure P L FEA = limit pressure by FE analysis P NL = normalized limit pressure R Bend = bend radius of tube R i = inner radius of tube R m = mean radius of tube R o = outer radius of tube S L = limit bending stress t = thickness of tube γ = restraint ratio θ = a half of crack angle λ = normalized bend radius (= R Bend t/R m 2 ) σ f = flow stress σ YS = yield strength σ UTS = tensile strength Correspondence: Y.-J. Kim.

show abstract

Failure Pressure Assessment of the Circumferentially Flawed Heat Exchanger Tubes

Kim¹,

Jin²,

Chang

et al. 2008

JPES

View full text Add to dashboard Cite

Since the structural integrity of thin-walled tubes in the heat exchanger is crucial from the viewpoint of safety and reliability, the integrity evaluation for flawed tubes is quite important. Accurate estimation of the failure pressure is a key element of the structural integrity assessment. With regard to the prediction of the failure pressure, most of preceding researches have been focused on the limit load approach. However, the integrity assessment scheme based on the elastic plastic fracture mechanics concept has not been settled despite of its accuracy and efficiency. In this paper, three-dimensional finite element analyses assuming elastic plastic material behavior are carried out for the thin-walled tubes with various sizes of the circumferential flaws. As for the flaw location, both the top of tube sheet and transition regions are considered. The flaw instability is evaluated by comparing the driving force with the fracture toughness of the tube material. Analysis results show that the elastic plastic fracture mechanics approach accurately predicts the failure pressures compared to the experimental data. Thus, it is thought that the elastic plastic fracture mechanics concept can be applied to the integrity assessment of the heat exchanger tubes with the circumferential through-wall flaws.

show abstract

Technical Basis for Structural Integrity Performance Criterion for Steam Generator Tubing

Cited by 4 publications

References 0 publications

Numerical simulation of rotating bending process for U‐tubes in heat exchangers

Numerical simulation of rotating bending process for U‐tubes in heat exchangers

Support‐induced restraint effect of thin‐walled tube in a steam generator subjected to combined pressure and bending load

Failure Pressure Assessment of the Circumferentially Flawed Heat Exchanger Tubes

Contact Info

Product

Resources

About