Development of Engineering Formulae for Stress Concentration Factors of Local Wall Thinning in CANDU Feeder Pipe Under Pressure

2011 ◽  
Author(s):  
Jong Sung Kim ◽  
Jae Seok Seo
Keyword(s):  
Stress Concentration ◽  
Power Plants ◽  
Degradation Mechanism ◽  
Peak Stress ◽  
Design Stage ◽  
Fatigue Assessment ◽  
Wall Thinning ◽  
Concentration Factors ◽  
Stress Concentration Factors ◽  
Local Wall Thinning

Feeder pipes that connect the inlet and outlet headers with the in-reactor fuel channels in CANDU nuclear power plants are considered as safety Class 1 piping items. Therefore, fatigue of the feeder pipes should be assessed at design stage in order to verify structural integrity during design lifetime. In accordance with the fatigue assessment result, cumulative usage factors of some feeder pipes have significant values. An active degradation mechanism for the outlet feeder piping made of SA-106 Grade B carbon steel is local wall thinning due to flow-accelerated corrosion. This local wall thinning can cause increase of peak stress due to stress concentration by notch effect. The increase of peak stress results in increase of the cumulative usage factor. However, present fatigue assessment doesn’t consider the stress concentration due to the local wall thinning. Therefore, it is necessary to assess the effect of local wall thinning on the stress concentration. This study developed the engineering formulae for stress concentration factors of the local wall thinning in the CANDU feeder pipe under internal pressure by using the engineering procedure of Kinectrics Co.. Finally, the developed formulae were applied to the elbow feeder pipes and compared with the finite element analysis results. As a result of comparison, it is identified that the engineering formulae is valid.

An Investigation on Stress Concentration of Local Wall Thinning in Feeder Elbow Pipe

2010 ◽  
Author(s):  
Jong Sung Kim ◽  
Jae Seok Seo
Keyword(s):  
Stress Concentration ◽  
Carbon Steel ◽  
Power Plants ◽  
Structural Integrity ◽  
Degradation Mechanism ◽  
Peak Stress ◽  
Design Stage ◽  
Fatigue Assessment ◽  
Wall Thinning ◽  
Local Wall Thinning

Feeder pipes that connect the inlet and outlet headers with the in-reactor fuel channels in CANDU nuclear power plants are considered as safety Class 1 piping items. Therefore, fatigue of feeder pipes should be assessed at design stage in order to verify structural integrity during design lifetime. In accordance with the fatigue assessment result, cumulative usage factors of some feeder pipes have significant values. The feeder pipes made of SA-106 Grade B carbon steel have some elbows and bends. An active degradation mechanism for the carbon steel outlet feeder piping is local wall thinning due to flow-accelerated corrosion. Inspection results from plants and metallurgical examinations of removed feeders indicated the presence of localized thinning. This local wall thinning can cause increase of peak stress due to stress concentration by notch effect. The increase of peak stress results in increase of cumulative usage factor. However, present fatigue assessment doesn’t consider the stress concentration due to local wall thinning. Therefore, it is necessary to assess the effect of local wall thinning on stress concentration. This study investigates the effect of local wall thinning geometry on stress concentration by performing finite element elastic stress analysis.

scholarly journals Stress Concentration Factors for Welded Plate T-Joints Subjected to Tensile, Bending and Shearing Loads

Materials ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 546
Author(s):  
Krzysztof L. Molski ◽  
Piotr Tarasiuk
Keyword(s):  
Stress Concentration ◽  
Plate Thickness ◽  
Percentage Error ◽  
Geometrical Parameters ◽  
T Joints ◽  
Loading Mode ◽  
Weld Toe ◽  
Concentration Factors ◽  
Parametric Expression ◽  
Stress Concentration Factors

The paper deals with the problem of stress concentration at the weld toe of a plate T-joint subjected to axial, bending, and shearing loading modes. Theoretical stress concentration factors were obtained from numerical simulations using the finite element method for several thousand geometrical cases, where five of the most important geometrical parameters of the joint were considered to be independent variables. For each loading mode—axial, bending, and shearing—highly accurate closed form parametric expression has been derived with a maximum percentage error lower than 2% with respect to the numerical values. Validity of each approximating formula covers the range of dimensional proportions of welded plate T-joints used in engineering applications. Two limiting cases are also included in the solutions—when the weld toe radius tends to zero and the main plate thickness becomes infinite.

Effect of Torsion on Collapse Bending Moment for 24-Inch Diameter Schedule 80 Pipes With Wall Thinning

2012 ◽  
Author(s):  
Kunio Hasegawa ◽  
Yinsheng Li ◽  
Bostjan Bezensek ◽  
Phuong Hoang
Keyword(s):  
Power Plants ◽  
Bending Moment ◽  
Combined Loading ◽  
Bending Moments ◽  
Compressive Stresses ◽  
Wall Thinning ◽  
Nominal Thickness ◽  
Calculation Results ◽  
Loading Modes ◽  
Local Wall Thinning

Piping items in power plants may experience combined bending and torsion moments during operation. Currently, there is a lack of guidance in the ASME B&PV Code Section XI for combined loading modes including pressure, torsion and bending. Finite element analyses were conducted for 24-inch diameter Schedule 80 pipes with local wall thinning subjected to tensile and compressive stresses. Plastic collapse bending moments were calculated under constant torsion moments. From the calculation results, it can be seen that collapse bending moment for pipes with local thinning subjected to tensile stress is smaller than that subjected to compressive stress. In addition, equivalent moment is defined as the root the sum of the squares of the torsion and bending moments. It is found that the equivalent moments can be approximated with the pure bending moments, when the wall thinning length is equal or less than 7.73R·t for the wall thinning depth of 75% of the nominal thickness, where R is the mean radius and t is the wall thickness of the pipe.

Stress Analysis of Holes in Thick Plates

2004 ◽  
Vol 1-2 ◽  
pp. 153-158 ◽  
Author(s):  
S. Quinn ◽  
Janice M. Dulieu-Barton
Keyword(s):  
Stress Concentration ◽  
Stress Analysis ◽  
Uniaxial Tension ◽  
Plane Stress ◽  
Plate Surface ◽  
Flat Plates ◽  
Thick Plates ◽  
Concentration Factors ◽  
Stress Concentration Factors

A review of the Stress Concentration Factors (SCFs) obtained from normal and oblique holes in thick flat plates loaded in uniaxial tension has been conducted. The review focuses on values from the plate surface and discusses the ramifications of making a plane stress assumption.

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