Background Elements of Investigation Numerical Simulations Results Investigation of the Fatigue Cracking and Leakage Rate potential of U-Bend Tube Bundles subjected to Flow-Induced Vibrations University of Guelph Fluid-Structure Interaction Laboratory Canadian Nuclear Safety Commission Marwan Hassan, Jovica Riznic and Salim Elbouzidi Marwan Hassan, Jovica Riznic and Salim Elbouzidi — Investigation of the Fatigue Cracking and Leakage Rate potential of U-Bend T 1/80
Background Elements of Investigation Numerical Simulations Results Outline 1 Background 2 Elements of Investigation 3 Numerical Simulations 4 Results Marwan Hassan, Jovica Riznic and Salim Elbouzidi — Investigation of the Fatigue Cracking and Leakage Rate potential of U-Bend T 2/80
Background Elements of Investigation Numerical Simulations Results SG Mechanical Problems SG Problems Many failures due to corrosion FIV related failures Fretting Wear at Supports Cracking Tube-to-Tube Impact SG Support Functional architecture Hydraulically invisible Ensure stability Clearance A ff ects fretting wear Should be kept small Marwan Hassan, Jovica Riznic and Salim Elbouzidi — Investigation of the Fatigue Cracking and Leakage Rate potential of U-Bend T 3/80
Background Elements of Investigation Numerical Simulations Results Clearance Enlargement Cause: Tube Degradation Fretting wear damage Should be accounted for at the design stage Support Degradation Support S2A, probability of exceeding t w % 100 Tube support plate corrosion 90 40% Loss of support e ff ectiveness 80 < Percentage of wall loss [t w %] 70 50% May a ff ect stability 60 60% 50 May accelerate wear at other 40 70% supports 80% 30 90% 20 10 0 0 5 10 15 20 25 30 Time [y] Marwan Hassan, Jovica Riznic and Salim Elbouzidi — Investigation of the Fatigue Cracking and Leakage Rate potential of U-Bend T 4/80
Background Elements of Investigation Numerical Simulations Results Background Tube/support Example : Bruce Boilers 7 Tube support plates (TSPs) 3 U-bend supports. TSPs are 25.4 mm thick carbon steel plates. Marwan Hassan, Jovica Riznic and Salim Elbouzidi — Investigation of the Fatigue Cracking and Leakage Rate potential of U-Bend T 5/80
Background Elements of Investigation Numerical Simulations Results Bruce Unit 8 FAC damage to the tube support plate Minor to complete loss of ligaments (H07) Loss of tube support = ⇒ risk of instability Counter measures: 2 pairs of flat bars in the U-bend 1 Comb support at H07 Marwan Hassan, Jovica Riznic and Salim Elbouzidi — Investigation of the Fatigue Cracking and Leakage Rate potential of U-Bend T 6/80
Background Elements of Investigation Numerical Simulations Results Objectives The main objective is to independently evaluate the integrity of steam generator tubes as plants age and degradation proceeds. Special attention will be paid to the consequence of support loss in the straight portion of the tube in terms of fatigue cracking rate of the tube bundle. Marwan Hassan, Jovica Riznic and Salim Elbouzidi — Investigation of the Fatigue Cracking and Leakage Rate potential of U-Bend T 7/80
Background Elements of Investigation Numerical Simulations Results Outline 1 Background 2 Elements of Investigation 3 Numerical Simulations 4 Results Marwan Hassan, Jovica Riznic and Salim Elbouzidi — Investigation of the Fatigue Cracking and Leakage Rate potential of U-Bend T 8/80
Background Elements of Investigation Numerical Simulations Results Elements of Investigation Structural Modelling (FEA) Tube Loose supports (impact+friction) Fluid Excitation Modelling Turbulence Fluidelastic Tube Cracking and Leakage Marwan Hassan, Jovica Riznic and Salim Elbouzidi — Investigation of the Fatigue Cracking and Leakage Rate potential of U-Bend T 9/80
Background Elements of Investigation Numerical Simulations Results Structural Modelling (FEA) n ·· n · o o [ M ] + [ C ] + [ K ] { w } = { f T } + { f a } + { f fei } + { f c ) } w w { f c ) } Contact Forces { f a } Add Mass E ff ect { f T } Turbulence Forces { f fei } Fluidelastic Forces Marwan Hassan, Jovica Riznic and Salim Elbouzidi — Investigation of the Fatigue Cracking and Leakage Rate potential of U-Bend T 10/80
Background Elements of Investigation Numerical Simulations Results Support Types Support Types Drilled-Hole Support Scallop-Bar Support Broached-Hole Support Lattice-Bar Support Marwan Hassan, Jovica Riznic and Salim Elbouzidi — Investigation of the Fatigue Cracking and Leakage Rate potential of U-Bend T 11/80
Background Elements of Investigation Numerical Simulations Results Forces due to support contact Tube support contact by adding massless bars attached to: Contact Sti ff ness δ ni = y ni − C ri Contact damper F ci = F si + F di F si = − ( K ci δ ni ) ˆ e ni F di = ⇣ ⌘ ˙ (1 . 5 α | F si | ) ˆ − sign δ ni e ni Marwan Hassan, Jovica Riznic and Salim Elbouzidi — Investigation of the Fatigue Cracking and Leakage Rate potential of U-Bend T 12/80
Background Elements of Investigation Numerical Simulations Results Fluid Excitation Turbulence Random excitation Small amplitude response ( < 2% tube diameter) Determines the long-term wear Turbulence Bounding Spectrum = ⇒ Equivalent Random Distributed force Fluidelastic Forces (FEI) FEI under the spotlight for the last 40 years. Extensive research provided a progressive understanding: Empirical Models. Semi-Analytical. Marwan Hassan, Jovica Riznic and Salim Elbouzidi — Investigation of the Fatigue Cracking and Leakage Rate potential of U-Bend T 13/80
Background Elements of Investigation Numerical Simulations Results Fluidelastic Instability (FEI) Self exciting mechanism Critical flow velocity Reduced critical velocity U cr = U c fd Mass-damping parameter MDP = m δ ρ d 2 U c = Critical flow velocity f = Tube frequency m =Tube mass per unit length δ = Logarithmic decrement ρ = Flow density Marwan Hassan, Jovica Riznic and Salim Elbouzidi — Investigation of the Fatigue Cracking and Leakage Rate potential of U-Bend T 14/80
Background Elements of Investigation Numerical Simulations Results Fluidelastic Instability Force Model Based on the original model of Weaver et al. Flow-cell 1-D flow Flow perturbation A ( s , t ) = A 0 + a ( s , t ) U ( s , t ) = U 0 + u ( s , t ) P ( s , t ) = P 0 + p ( s , t ) Time Lag R s s F L ( t ) = s a [ P i 1 − P i 2 ] cos β∂ s R s s F D ( t ) = s a [ P i 1 − P i 2 ] sin β∂ s Marwan Hassan, Jovica Riznic and Salim Elbouzidi — Investigation of the Fatigue Cracking and Leakage Rate potential of U-Bend T 15/80
Background Elements of Investigation Numerical Simulations Results U-bend Fluid Force Model Flow is divided into a number of layers Each layer is associated with a tube finite element. Layer = two flow channels. For layer i we have U oi and ρ oi . The flow is defined by u Li Lift ˆ u Di Drag ˆ Marwan Hassan, Jovica Riznic and Salim Elbouzidi — Investigation of the Fatigue Cracking and Leakage Rate potential of U-Bend T 16/80
Background Elements of Investigation Numerical Simulations Results Tube Cracking and Leakage Marwan Hassan, Jovica Riznic and Salim Elbouzidi — Investigation of the Fatigue Cracking and Leakage Rate potential of U-Bend T 17/80
Background Elements of Investigation Numerical Simulations Results Marwan Hassan, Jovica Riznic and Salim Elbouzidi — Investigation of the Fatigue Cracking and Leakage Rate potential of U-Bend T 18/80
Background Elements of Investigation Numerical Simulations Results Fatigue Crack Growth Inconel 600 Crack Growth Model (Kozluk 1989) 2 . 39 da e � 0 . 66 R �⇤ 2 25 . 9 × 10 � 6 E ⇥ � � � dN = E 2 √ ∆ K − × 1 − R Calculate Crack Growth Rate Determine Stress Cycles Rainflow counting Determine Crack Length vs. Time Block Method Marwan Hassan, Jovica Riznic and Salim Elbouzidi — Investigation of the Fatigue Cracking and Leakage Rate potential of U-Bend T 19/80
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