Fatigue Analysis Using ANSYS Fatigue Module and ANSYS

45 Pages·2012·2.51 MB·English

Fatigue Analysis
Using
ANSYS® Fatigue Module and
ANSYS® nCode DesignLife™
Confidence by Design
ANSYS, Inc.
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OUTLINE
• Importance and Motivation
• What is Fatigue?
• ANSYS Fatigue Module
• ANSYS nCode Design Life
• Conclusions
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PRODUCT DURABILITY

Manufacturing Costs
Product
Time to Market
Durability Legal Exposure
Warranty Costs
Skilled Labor
Uncertainty Complexity
Margin for Error
Failure of components
Down time Competition
Product Lifecycle
Product Innovation
Customer Expectations
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FATIGUE FAILURE
• “...Between 80 - 90% of all
structural failures occur
through a fatigue
mechanism…” NBS report
– Estimated cost > $600B/year
• The cost of failure is high:
– Legal Liability
– Maintenance costs
Gear failure from fatigue
– Redesign Costs
– Repair Costs
– Damaged PR and Brand
– Loss of future business

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DE HAVILLAND COMET

• de Havilland Comet, 1954
• Cracks initiated at sharp corners caused failure of fuselage
Fatigue failure due to cyclic pressurization, major damage
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ICE TRAIN DERAILED
• Train derailed, 1998 Eschede, Germany
– Failure: crack in a wheel
– Wheel vibration (original design)
– Redesign based on streetcar wheel
– Dynamic, repetitive forces not considered
– Design lacked an adequate margin of safety
Inexpensive, part, major damage
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FATIGUE DAMAGE OF PIPELINES
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FATIGUE SIMULATION

• Facilitates Product Integrity for an “expected life”
• Informed design decision about parameters used
– Conservative designs: too expensive
– Not conservative enough: exposure to high costs
• Optimize with simulation instead of product revisions
• Redesign ,if needed, is expedited with simulation
• Provides informed choices to ensure product
durability

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FATIGUE ?
Material response under loading
Failure under repeated or
s Plastic
s
e
otherwise varying load r
t Failure
S
which never reaches a level
sufficient to cause failure in Elastic
a single application.

Strain

s
s
e
r
t
S
Time
Simple loading history Complex loading history
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Factors that influence fatigue failure
• Material • Material
Geometry Loading

Manu-
Material
facturing

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