2008 Int ANSYS Conf Weld Joint Assessment
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Transcript of 2008 Int ANSYS Conf Weld Joint Assessment
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8/11/2019 2008 Int ANSYS Conf Weld Joint Assessment
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2008 ANSYS, Inc. All rights reserved. 1 ANSYS, Inc. Proprietary
2008 International
ANSYS Conference
Fatigue Assessment of Weld JointsUsing ANSYS, BSS & FE-Safe **
Zhichao Wang , Manager Of Analytical Services Aditya Sakhalkar, Engineering Specialist
Emerson Climate Technology** BSS, Battelle Structural Stress Method Proposed by Dr. Dong and
His Colleagues at Battelle
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2008 ANSYS, Inc. All rights reserved. 2 ANSYS, Inc. Proprietary
Fatigue Assessment of Weld Joints UsingANSYS, BSS (Verity) & FE-Safe **
Background
Battelle Structural Stress (BSS) Method & MeshSensitivity
Master S~N Curve? Example Application References
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2008 ANSYS, Inc. All rights reserved. 3 ANSYS, Inc. Proprietary
BackgroundFatigue Assessment Unwelded Structures
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2008 ANSYS, Inc. All rights reserved. 5 ANSYS, Inc. Proprietary
BackgroundFatigue Assessment Welded Structures
Nominal Stress Method (BS,IIW) The nominal stress range is used to develop the
S~N curves using samples with actual weld jointgeometry
The life curves refer to particular weld details,there is no need for the user to attempt to quantifythe local stress concentration effect of the weld
detail itself
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BackgroundFatigue Assessment Welded Structures
Hotspot Stress Approach (structural stress,geometric stress, BS, IIW, CEN,DNV)
This procedure uses hot-spot stress range as aparameter
The SN curves are obtained from tests of actualwelded joints based on the hot-spot stress rangerather than the nominal stress range
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BackgroundFatigue Assessment Welded Structures
Local Notch Stress Method (ASME, BS, IIW). The notch stress approach attempts to include all
sources of stress concentration in the stress usedwith the design S~N curve
Thus a single S~N curve may be sufficient for agiven type of material The problem is that the local geometry of the toe
or root of a weld is highly variable It may be hard to achieve consistent results
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The Fracture Mechanics Approach (For crack propagation life) The parameter widely used is SIF, K The fatigue resistance is represented by fatigue crack growth rate
da/dN Many crack propagation laws are available The simplest one is Paris Law in which the crack growth law
approximates to a linear relationship:
For a flaw size starts from a 0 to a critical fatigue crack size a f , theremaining fatigue life N under stress range S is obtained byintegrating Eq (1):
Verity Equivalent Structural Stress Method (Battelle) Equivalent Structural Stress + Single Master S~N Curve
nda C ( K) (1)dN
=
f
0
a
na
daC N (2)
( K)=
BackgroundFatigue Assessment Welded Structures
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(b) Comparison of SCF predicted by various modelingprocedures and extrapolation based HSS at the weld toe [12] .
(c) Structural Stress Using Verity Method
H o t S p o t N o m i n a
N o m i n a l
l
F E
( H u m a n F a c t o r )
~
0