2008 int ansys conf weld joint assessment

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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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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BackgroundFatigue Assessment Unwelded Structures


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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


6/27 2008 ANSYS, Inc. All rights reserved. 6 ANSYS, Inc. Proprietary


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




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



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)=




(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

2008 int ansys conf weld joint assessment

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