Bay Zoltán Foundation for Applied Research
VEIKI Power Research Institute
BAY-LOGI
Fatigue calculations on benchmark
tasks according to ASME code,
experiences, results
Szávai Szabolcs
Pálfi Tamás
Tóth László
1st Hungarian-Ukrainian Joint Conference on
SAFETY-RELIABILITY AND RISK OF ENGINEERING PLANTS AND COMPONENTS”
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Benchmark tasks for the
Paks License Renewal Project
BAY-LOGI
 Created by Mechanical Components Scientific
Committee
 Solution made by different research institutes,
solution methodology accepted by MC-SC
 Conflict the ASME interpretation of different
experts
 Compare the result of different solution methods
and tools
 Develop verification cases for the applied
methodologies of the project
 Create a general solution method which can also
be used for more complicated problems
1st Hungarian-Ukrainian Joint Conference on
SAFETY-RELIABILITY AND RISK OF ENGINEERING PLANTS AND COMPONENTS”
2
Benchmark tasks for the
Paks License Renewal Project
BAY-LOGI
 Analysis of pipeline and its elements
 Evaluation of flange for structural
integrity, stiffness, and leak tightness
 Structural and fatigue analysis of a thick
walled pressure vessel with openings
1st Hungarian-Ukrainian Joint Conference on
SAFETY-RELIABILITY AND RISK OF ENGINEERING PLANTS AND COMPONENTS”
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Applied codes and
regulations
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 ASME BPV CODE SECTION. III. (2001)
 Procedure for actions related to the life
time extension of equipment operating in
nuclear plants
 Directives for structural analysis of
pressure vessels. OAH NBI 3.3
1st Hungarian-Ukrainian Joint Conference on
SAFETY-RELIABILITY AND RISK OF ENGINEERING PLANTS AND COMPONENTS”
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Benchmark tasks for the
Paks License Renewal Project
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 Simple problems require
mainly numerical methods
(e.g. FEM) however
analytical solutions are also
acceptable
 ASME based, PNAE material
properties
 Class I. components
 Design and operational
conditions
 Coupled thermo-mechanical
static and cyclic analysis
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SAFETY-RELIABILITY AND RISK OF ENGINEERING PLANTS AND COMPONENTS”
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Benchmark tasks
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Task
Elements
Analysis of pipeline and Pipes, welds, elbows,
its elements
curved pipes, branch
connections, welded
transitions
Structural and fatigue
analysis of a thick
walled pressure vessel
with openings
Vessel, nozzle,
openings
Evaluation of flange for
structural integrity,
stiffness, and leak
tightness
Flange connection, leak
tightness, bolts.
Type
Structural
Fatigue
Tightness
Load conditions:
Level A
Pressure test
Cyclic loads
1st Hungarian-Ukrainian Joint Conference on
SAFETY-RELIABILITY AND RISK OF ENGINEERING PLANTS AND COMPONENTS”
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Analysis types
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Test problem
Structural analysis
Fatigue
Pipeline and its
elements
Stress indexes
Critical point of the
pipe elements
(branch connections,
welds, etc.)
Vessel
Membrane and
bending stresses
Primary, bending
and peak stresses
Critical FEM elements
Take into
consideration the
FSRF of welds
Flange
Membrane and
bending stresses
Primary, bending
and peak stresses
for bolts
Bolt, thread
leakage
Seals
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SAFETY-RELIABILITY AND RISK OF ENGINEERING PLANTS AND COMPONENTS”
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Loadcases
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 Design Load:
p=13,7 MPa
T=325ºC
Cyclic load:
T [˚C]
T [˚C]
p [MPa]
p [MPa]
130 16
130 19,5
B. Cycle (2x)
A. Cycle (1x)
 Test pressure:
p=16,4 MPa,
T=140ºC
 Load on the nozzle:
N=300kN,
M=200kNm
T=100kNm
60
0,1
1,4
0
T [˚C]
1,65
3,4
300 12
10
40
60
1,65
3,4
2 month
D. Cycle (5x)
t [min]
290 11
t [h]
1,4
p [MPa]
300 12
C. Cycle (5x)
0,1
0
T [˚C]
p [MPa]
0
60
t [h]
60 0,1
0 6
t [h]
1446
1454
1st Hungarian-Ukrainian Joint Conference on
SAFETY-RELIABILITY AND RISK OF ENGINEERING PLANTS AND COMPONENTS”
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Structural and fatigue
analysis of a pressure vessel
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Structural analysis for design
conditions
– Critical points (2. and 3.)
– Nozzle
Fatigue evaluation at 3.
Thermal stress calculation in
the cylindrical wall
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SAFETY-RELIABILITY AND RISK OF ENGINEERING PLANTS AND COMPONENTS”
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Structural analysis
of the nozzle
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Material properties based on PNAE
Analysis of the nozzle based on WRC107
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SAFETY-RELIABILITY AND RISK OF ENGINEERING PLANTS AND COMPONENTS”
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Structural analysis
of pressure vessel
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Axysymmetrical FEM model to get sufficient results
for the critical points.
Derive the primary, secondary and peak stresses
from the calculated stress distribution
Determination of the membrane and
membrane+bending stresses
Fatigue evaluation
–
–
–
–
–
Calculation of the stress intensities
Rainflow analysis for determining the stress cycles
FSRF determination for the analyzed points
CUF calculation
Critical point evaluation
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SAFETY-RELIABILITY AND RISK OF ENGINEERING PLANTS AND COMPONENTS”
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Results, Experiences
BAY-LOGI
Calculations were done by 2 independent research
institutes
– VEIKI Rt., Budapest
– BAY-LOGI and Univ. of Miskolc, Miskolc
Good agreement between the stresses and the
location of critical elements
WRC107: COADE interpolated and „manual” diagram
reading of the parameters caused different results in
the nozzle
1st Hungarian-Ukrainian Joint Conference on
SAFETY-RELIABILITY AND RISK OF ENGINEERING PLANTS AND COMPONENTS”
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Results, Experiences
BAY-LOGI
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Wall temperature distributions
Cycle „A”
Cycle „C”
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Fatigue analysis
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Stress differences were calculated considering
varying principal stress directions:
– At the principal stress calculation the difference of each stress
components in the two time steps was used
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SAFETY-RELIABILITY AND RISK OF ENGINEERING PLANTS AND COMPONENTS”
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Analysis of pipeline and its
elements
BAY-LOGI
Structural analysis
– Design condition
– Level A
– Pressure test
Fatigue analyses
– Primary,
secondary and
thermal stresses
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Required steps for analysis
of pipeline and its elements
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Material properties
– based on PNAE
CAEPIPE model for
– Stiffness calculation
– Determination of the Moments for each element
ASME Class 1 stress indexes
– Pipes, welds, curved pipes, branch connections, welded
transitions
Structural analysis
Fatigue analysis
– Determination of the stress amplitudes
– CUF calculation
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SAFETY-RELIABILITY AND RISK OF ENGINEERING PLANTS AND COMPONENTS”
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Finite element solution
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Stresses were calculated also using shell elements in
Msc Nastran4W
In each cross-section:
– Stress transformations needed to determine stresses in the
local coordinate system
– Parametric calculations needed to calculate the highest
bending stress
1st Hungarian-Ukrainian Joint Conference on
SAFETY-RELIABILITY AND RISK OF ENGINEERING PLANTS AND COMPONENTS”
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Finite element solution
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Results using finite element solution was in good
agreement with the results using CAEPIPE model and
ASME stress indexes
– Large deformation calculation needed, because the pressure
caused deformation at the curved sections essentially affects
stiffness
– Special spring elements had to be
used to model the support
1st Hungarian-Ukrainian Joint Conference on
SAFETY-RELIABILITY AND RISK OF ENGINEERING PLANTS AND COMPONENTS”
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Analysis of flange joint for
structural integrity, stiffness
and leak tightness
BAY-LOGI
Structural analysis for:
– Level A
– Pressure test
Leak tightness evaluation
– seating load
– stiffness
Fatigue analysis of bolts and
threads
1st Hungarian-Ukrainian Joint Conference on
SAFETY-RELIABILITY AND RISK OF ENGINEERING PLANTS AND COMPONENTS”
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Analysis of flange joint for
structural integrity, stiffness and
leak tightness
BAY-LOGI
Material properties:
– based on PNAE
Elastic model including:
– bolts
– sealing
1st Hungarian-Ukrainian Joint Conference on
SAFETY-RELIABILITY AND RISK OF ENGINEERING PLANTS AND COMPONENTS”
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Analysis of flange joint for
structural integrity, stiffness and
leak tightness
BAY-LOGI
Required steps of the evaluation
Required bolt area verification
Analysis of bolts for level A condition
Stiffness calculation of the joint
– Determination of the displacements
– Examination of the leak tightness
1st Hungarian-Ukrainian Joint Conference on
SAFETY-RELIABILITY AND RISK OF ENGINEERING PLANTS AND COMPONENTS”
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Analysis of flange joint for
structural integrity, stiffness and
leak tightness
BAY-LOGI
Required steps of the evaluation:
Analysis of the bolts for test pressure
Calculation of the gasket force
Examination of the thread
Fatigue analysis for bolts and threads
1st Hungarian-Ukrainian Joint Conference on
SAFETY-RELIABILITY AND RISK OF ENGINEERING PLANTS AND COMPONENTS”
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The finite element model
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Spring elements were
used to model the seal
and the bolts
Rigid elements were used
for the washers
The active bolt length=
unconstrained length+2x3
threads
1st Hungarian-Ukrainian Joint Conference on
SAFETY-RELIABILITY AND RISK OF ENGINEERING PLANTS AND COMPONENTS”
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Results
BAY-LOGI
Calculations were done in 2 independent research
institutes
– VEIKI Rt., Budapest:
•
Finite element model including bolts and sealing
– BUTE, Budapest
•
Finite element model for the flanges + semi analytical model for
stiffness calculations
Good agreement between the stiffness values and
the stresses
1st Hungarian-Ukrainian Joint Conference on
SAFETY-RELIABILITY AND RISK OF ENGINEERING PLANTS AND COMPONENTS”
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Results
BAY-LOGI
Some of the stress calculations were done also by
using analytical methods, and got higher stresses
then by FEM calculations, because more complex
analytical model required
1st Hungarian-Ukrainian Joint Conference on
SAFETY-RELIABILITY AND RISK OF ENGINEERING PLANTS AND COMPONENTS”
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Check points for future participants
BAY-LOGI
Task
Check points
Analysis of
pipeline and its
elements
–Stiffness
–Moments at different load cases stress indexes
–Stresses
–Fatigue cycles, CUF
Structural
analysis of a
nozzle of the
pressure vessel
–WRC107 parameters for nozzle analysis, stresses and
categorization
–Stresses for the operational conditions, membrane and
membrane+bending stresses
–Critical points from the fatigue calculation, fatigue cycles, stress
amplitudes, CUF
–Temperature distribution and thermal stresses
Analysis of flange
joint for structural
integrity, stiffness
and leak tightness
–Stress components from the structural analysis, membrane and
membrane+bending stresses
–Stiffness of the flange
–Bolt loads and gasket seating condition.
–Fatigue evaluation, CUF calculation
1st Hungarian-Ukrainian Joint Conference on
SAFETY-RELIABILITY AND RISK OF ENGINEERING PLANTS AND COMPONENTS”
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Summary and conclusions
BAY-LOGI
The developed benchmark tasks are suitable for:
– Demonstrating the ASME methodology in accordance
with the Hungarian directives
– Comparing the result of different solution methods and
tools
– Providing verification points for the applied
methodologies
– Act as a general solution method, can also be used for
more complex problems
1st Hungarian-Ukrainian Joint Conference on
SAFETY-RELIABILITY AND RISK OF ENGINEERING PLANTS AND COMPONENTS”
28