stress and fatigue analysis of asme pressure vessels using ... · 15/6/2014 · stress and fatigue...
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Unrestricted © Siemens AG 2014
FEMAP SYMPOSIUM 2014
Discover New Insights Femap Symposium 2014
May 14-16, Atlanta, GA, USA
Stress and Fatigue Analysis of ASME Pressure
Vessels using Femap API and Fatigue Essentials
Adrian Jensen, Predictive Engineering | Brian Reiling, Endeavor Analysis
2014-05-15
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Stress and Fatigue Analysis of ASME Pressure
Vessels using Femap API and Fatigue Essentials
Abstract
The application of the ASME Section VIII, Division 2 pressure vessel code is
becoming increasingly more popular since it facilitates the optimization of
pressure vessels via detailed stress and fatigue analysis.
The basis of this analysis is the creation of a high quality plate and/or solid mesh
followed by accurate load application and then the extraction and classification of
stresses per code.
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Stress and Fatigue Analysis of ASME Pressure
Vessels using Femap API and Fatigue Essentials
Abstract
Much of this work is algebraic in nature
and is well suited for automation.
Through the use of Femap’s Application
Programing Interface (API) and
customized spreadsheets, the analysis
of ASME-type pressure vessels can be
accelerated from days to minutes.
In many cases, once the vessel has
passed its baseline load requirements, a
fatigue analysis is required to address
cyclic mechanical and thermal loads.
2014-05-15
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Stress and Fatigue Analysis of ASME Pressure
Vessels using Femap API and Fatigue Essentials
Abstract
To simplify this calculation, the software program Fatigue Essentials is used and
a brief example is presented on how this program automates the fatigue
calculation.
Although fatigue analysis can be
quite basic and almost an
accounting exercise, the more
stringent ASME requirements of
specialized fatigue curves and
stress output as stress intensity
complicates the procedure.
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ASME VIII Pressure Vessels
Modeling, Analysis and Post Processing
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ASME Section VIII Pressure Vessels
• What happened in Massachusetts?
• Pressure Loads (>15 psig)
• Nozzle Loads
• Fluid Dead Weight
• Thermal Loads
• Seismic Loads
• Highly Ductile Stainless Steel
• Stress Analysis Method
• Specialized Post Processing
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ASME Section VIII Pressure Vessels
What happened in Massachusetts?
On March 10, 1905, a catastrophic boiler explosion occurred in a shoe factory in
Brockton, Massachusetts, that killed 58 and injured 150 people. At about 8:00
AM there were around 400 employees at the R. B. Grover & Company shoe
factory in Campello, when the boiler exploded, shot through the roof, and caused
the building to collapse.
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ASME Section VIII Pressure Vessels
What happened in Massachusetts?
The boiler traveled several hundred feet, damaging a number of buildings and
coming to rest in the wall of a house. Thirty-six of the victims were never
identified and were buried in a common grave, where a monument to the victims
was later erected by the city.
Balmer, Robert T (2010). Modern Engineering Thermodynamics. 13.10 Modern Steam Power Plants: Academic Press.
This and similar explosions brought
about the development of the ASME
Boiler and Pressure Vessel Code in
1915.
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ASME Section VIII Pressure Vessels
Stress Analysis Method
• Surface Stress
• Membrane Stress
• Localized Stress
• Thermal Stress
Post Processing
• Stress Intensity Calculator
• Membrane Stress Calculator
• Stress Linearization Tool
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ASME Section VIII Pressure Vessels
Loading Conditions
• Pressure loads (external or internal) in excess of 15 psig
• Fluid dead weight loads (hydrostatic pressure)
• Thermal loads (hot/cold fluid, cooling jackets, local/general)
• Seismic Loads (requires analysis even if the vessel is Div. 1)
Materials
• Highly ductile stainless steel
• Excellent fatigue properties
• “Allowable Stress” based on σy
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Transient Thermal Analysis
Development and Load Application
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Transient Thermal Analysis
• Transient Temperature Profile
• Transient Boundary Conditions
• Heat Transfer Coefficients
• Modeling Considerations
• Femap API
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Transient Thermal Analysis
• Transient Temperature Profile
• The thick wall vessel has a significant thermal gradient
though wall thickness and along the length of the vessel
• Transient Boundary Conditions
• The vessel is filling throughout the analysis
• Gas, Boiling Liquid and Non-boiling Liquid have different
temperature deltas and heat transfer coefficients
• The inside surface was meshed with membrane elements
• This allows for easy thermal load application
• Also provides better stress recovery
Low ΔT, High h
High ΔT, Low h
Negligible ΔT,
Negligible h
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Fatigue Essentials
Stress Life Made Easy
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Fatigue Analysis Using Fatigue Essentials
Fatigue Essentials is intended to provide a user friendly tool for conducting
Stress-Life analysis either using classical stress calculations or linked with
FEMAP and using the finite element generated stresses.
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More advanced techniques to account for high strain – low cycle (Strain-Life) are
available as well as more advanced models of crack initiation and multi-axial
stress situations but in most cases these are not necessary for the design of
durable structure.
Fatigue Analysis Using Fatigue Essentials
Fatigue Essentials is intended to
provide a user friendly tool for
conducting Stress-Life analysis
either using classical stress
calculations or linked with FEMAP
and using the finite element
generated stresses.
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Fatigue Analysis Using Fatigue Essentials
Fatigue Essentials is set up to guide the
user through the analysis by following a
tree structure.
General analysis options are selected
following loads, materials, and spectrum
branches. Within each branch are
options for analysis variations or input
methods.
When the model solves there are
multiple options for selecting output to
the screen. For large models (usually
FEA based) it is usually best to push a
damage plot back to FEMAP to view.
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Fatigue Analysis Using Fatigue Essentials
• Analysis Options
• Load Cases
• Material Definition
• Mean Stress Correction
• Spectrum Definition
• Fatigue Damage Calculation
• Material Plot
• Report Generation
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Fatigue Analysis Using Fatigue Essentials
Analysis Options
• Scatter Factor
o Easy way to add reliability
• Stress Units
• Rainflow per ASTM E1049
o Rainflow
o Peak Counting
• Stress Modification
o Stress Multipliers
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Fatigue Analysis Using Fatigue Essentials
Load Cases (Details)
• Enter inter-actively within
GUI
`
• Load from CSV file
• Load from FEMAP
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Fatigue Analysis Using Fatigue Essentials
Material Definition
• Choose from existing library
or create new material curve
• Flexible input allows user to
input any curve and account
for confidence and reliability
vs using a mean curve.
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Fatigue Analysis Using Fatigue Essentials
Material Definition
• Curve can be created three
different ways
• Tabulated
o Log-Log interpolation
• Estimated
o Based on percentages of
material ultimate strength
• Walker Equation (MMPDS)
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Mean Stress Correction
Four methods of correcting for mean stress (stress ratio)
Fatigue Analysis Using Fatigue Essentials
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Fatigue Analysis Using Fatigue Essentials
Material Assignment
• Once material is created
and/or selected it is
assigned to the analysis
detail(s)
• Can have multiple details
and multiple materials in
the same analysis if desired
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Fatigue Analysis Using Fatigue Essentials
Spectrum Definition
• Spectrum can either be
entered in using the GUI or
can be read in from CSV
file.
• The number of spectrum
repeats is entered here
• Multiple spectrums can be
used and the damages for
each spectrum are added
together
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Fatigue Analysis Using Fatigue Essentials
Fatigue Damage
• Options for report
generation are entered
here
• For large models it is best
to have minimal reporting
• Small models it can be
useful to view additional
data
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Fatigue Analysis Using Fatigue Essentials
Material Plot
• The material curve is
plotted for reference at
three stress ratios:
o R = -1
o R = 0
o R = 0.5
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Fatigue Analysis Using Fatigue Essentials
Report Generation
• The report can generate
plots and tables of:
o Details and stresses
o Spectra plot
o Spectra table
o Rainflow pairs
o Damage summary
o Margin of safety
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Fatigue Analysis Using Fatigue Essentials
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Contact Information
Adrian Jensen
Sr. Staff Engineer
Predictive Engineering, Inc.
Phone: (503) 206-5571
E-mail: [email protected]
Brian Reiling
Partner / Principal Engineer
Endeavor Analysis, LLC
Phone: (206) 805-9030
E-mail: [email protected]