Toward Incorporating Cold Dwell Fatigue Lifetime ...•DARWIN has been integrated with DEFORM to...
Transcript of Toward Incorporating Cold Dwell Fatigue Lifetime ...•DARWIN has been integrated with DEFORM to...
Toward Incorporating Cold Dwell Fatigue
Lifetime Predictions into DARWIN®
Kwai S. Chan, Michael P. Enright, and R. Craig McClung
Southwest Research Institute®
San Antonio, TX 78238
Cold Dwell Fatigue Workshop
Dayton, Ohio
April 18-19, 2016
Outline
• Status of SwRI cold dwell fatigue modeling
NAVAIR Phase II Program, Ray Pickering TPOC
• Status of ICME modeling in DARWIN
AFRL Phase II & IIE Programs, Pat Golden TPOC
• Future needs for incorporating cold dwell
fatigue life prediction into DARWIN
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Characteristics of Cold Dwell Fatigue
• Beta-transformed
microstructures with
large prior beta grains
• Micro-textured region
(MTR) with hard
alpha grains (basal
planes aligned
normal to stress axis)
• Time-dependent
crack formation and
growth mechanisms
3
Time-Dependent
Degradation
Mechanisms
o Creep
o Hydrogen
Microtexture
o Orientation
o Size
Processing
o Beta
o Alpha + Beta
Highlights of SwRI CDF Modeling
• Treated fracture mechanisms identified in the paper by
Pilchak and Williams (Metall. Mater. Trans. A, Vol. 42A,
2011, 1000-1027)
• Developed a decohesion model for treating hydrogen-
induced time-dependent crack growth
• Applied model to analyze cold dwell fatigue life data of
Ti-6-4 and IMI 685 from the literature
• Delineated various hydrogen degradation modes as a
function of hydrogen content
Chan and Moody, “A Hydrogen-Induced Decohesion Model for Treating Cold Dwell
Fatigue in Ti-based Alloys,” Metall. Mater. Trans. A, published online, 2016
4
SwRI CDF Modeling: Hydrogen-Induced Decohesion Model
Strain
0.00 0.02 0.04 0.06 0.08 0.10 0.12
Str
ess, M
Pa
0
1000
2000
3000
4000
5000
CH = 0 ppm
10 ppm
20 ppm
40 ppm
100 ppm
1 = CH
C-Axis
(0001) Slip Plane
Slip
Plane
Dislo
cation P
ileup
Slip
: Hydrogen Atom
5
C-Axis
(0001) Plane
Slip
Plane
Dislo
cation P
ileup
Slip
: Hydride Habit Plane
: Hydrogen Atom
SwRI CDF Modeling: Hydrogen-Induced Failure Modes
• Slipband
decohesion: strain-
dominated failure
• Facet decohesion
• S-Nf data from Hack
and Leverant (x)
and Evans (y)
Cycles To Failure
100 101 102 103 104 105
Str
ess, M
Pa
1000
2000
500
Ti AlloysRT
1Hz, 300s Dwell
Model Calculation
Strain-dominated Faiure
Facet-dominated Faiure
IMI 685 [y]
Strain-Dominated Failure
Facet-Dominated Fracture
Ti-6-4 [x] IMI 685 [x]
IMI 685 [y]Ti-6-4 [y]
x: MMTA, Vol. 13A, 1982, 1729-1738; y: Scripta Metallurgica, Vol. 21(4), 1987, 469-474.
6
mm
fcr fN
RT
Q
c
E H
o
exp2
Highlights of SwRI CDF Modeling (2)
• Developed a methodology for treating combined cycle-
dependent and time-dependent crack growth in Ti-6-4
• Applied methodology to treat cold dwell fatigue crack
growth in Ti-6-4
• Performed a demonstration probabilistic analysis on a
Ti-6-4 ring disk by hacking into DARWIN
• Identified microtexture most susceptible to cold dwell
fatigue and quantified the conditional risk
7
SwRI CDF Modeling: da/dt Response vs Grain Orientation
• Extracted da/dt data from dwell
fatigue data of textured Ti-6Al-
4V (basal transverse texture)
from Stubbington and Pearson
(z)
K, MPa(m)1/2
1 10 100
da/d
t, m
/s
10-13
10-12
10-11
10-10
10-9
10-8
10-7
10-6
Ti-6Al-4V
20oC
TL Orientation
30 ded from TL
70 deg from TL
90 deg from TL
C-Axis
Angle From C-Axis (), Deg
0 20 40 60 80 100
No
rmali
zed
Rate
(N
R)
10-3
10-2
10-1
100
101
log (NR) = - 0.01945
C-Axis
Ti-6Al-4VRT
Basal Transverse Texture
z: Eng. Frac. Mech., Vol. 10, 1978, 723-756
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mBKFdt
da
SwRI CDF Modeling: da/dN Response vs Frequency
• Strong
dependence on
alpha grain
orientation
• da/dN data from
Stubbington and
Pearson
• Basal
Transverse
Texture
Effective Frequency, Hz
10-4 10-3 10-2 10-1 100 101 102
da/d
N, m
/cycle
10-7
10-6
10-5
10-4
10-3
Ti-6Al-4V
R=0.1, 20oC
K = 20 MPa(m)1/2
Experiment
TL Orientation
30 deg from TL
70 deg from TL
90 deg from TL
Model
C-Axis
9
dt
dat
fdN
da
dN
dad
Ftotal
1
SwRI CDF Modeling: Kth and Kc Properties
• Kc (fracture
toughness) depends
on alpha grain
orientation
• Kth (static threshold)
is assumed to be
independent of grain
orientation
10
o
H
m
thC
CRTtK ln
12
32/1
HV
RT
Q
bC
H
mo
exp
Orientation Angle ( ), Deg
0 20 40 60 80 100
Kth
or
KC
, M
Pa(m
)1/2
0
20
40
60
80
100
120
Ti-6Al-4VRT
Basal Transverse Texture
KC
Kth
C-Axis
Stubbington and Pearson
Model
DARWIN® Overview
Design Assessment of Reliability With INspection
11
Demonstration DARWIN Analysis
• Ti-6Al-4V ring disk in FAA
AC33.14-1 test case
modified with a cold dwell
loading cycle
• The dwell time is two hours
per flight cycle
Time
Sp
eed
6800 rpm
Room Temperature Test Cycle
Basal-Transverse
Basal-Longitudinal
12
Demonstration DARWIN Analysis: Deterministic Life Calculation
• Disk life under
cold dwell
fatigue loading
is strongly
influenced by
orientation of
the alpha
grains
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Flight Cycles
101 102 103 104
Defe
ct
Are
a,
mm
2
10-2
10-1
100
101
102
103
104
Ti-6Al-4V, RTTL Orientation
Basal Transverse Texture
0oC-Axis
Angle ( ) from C-Axis
30o
45o
70o
90o
Demonstration DARWIN Analysis: Risk of Disk Fracture
• Strong dependence
on microtexture
• Basal transverse is
most susceptible to
cold dwell fatigue
Flight Cycles
0 5000 10000 15000
Ris
k o
f F
ractu
re
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
Ti-6Al-4V, RT
Basal Transverse Random Texture
Basal Longitudinal
14
Key Takeaways from
SwRI CDF Modeling
• Cold dwell fatigue occurs in hard alpha grains with c-axis
parallel to the stress axis and is enhanced by hydrogen-
induced decohesion
• Materials with the basal transverse microtexture are
most susceptible to cold dwell fatigue
• Time-dependent fracture response equations for
quantifying the effects of microtexture on cold dwell
fatigue and fracture risk have been developed
• Cold dwell fatigue can be mitigated or even eliminated
by controlling the microtexture to reduce clustering of
hard alpha grains
15
Integrating Life Management with
Manufacturing Process Simulation
Link DEFORM output with DARWIN input
Finite element geometry (nodes and elements)
Finite element stress, temperature, and strain results
Residual stresses at the end of processing / spin test
Location specific microstructure / property data
Tracked location and orientation of material anomalies
16 Copyright 2016 Southwest Research Institute
Status of ICME Modeling in DARWIN: Location-Specific Microstructure
• DARWIN has been integrated with DEFORM to accept
(deterministic or probabilistic) DEFORM calculations of
average grain size, ALA grain size, and volume fractions of
ALA grains at specific locations of a Ni-base superalloy disk.
17
Visualization of DARWIN random
grain size results based on
average grain size training data
from DEFORM:
(a) grain size mean, and
(b) grain size standard deviation.
(a) (b)
Status of ICME Modeling in DARWIN: Supergrain Identification
• DARWIN was enhanced to
import additional microstructure
information (Euler angles, major
and minor axes of grains) from
DEFORM
• Identified supergrains at
selected locations within a
component by computing the
grain mis-orientation angles
between grain neighbors in a
cluster of grains (currently for
Ni-base alloys)
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Supergrain
Status of ICME Modeling in DARWIN: Location-Specific Crack Growth Properties
19
• da/dt and da/dN prediction based on grain size or
precipitate size scaling for Ni-base superalloys
Visualization of DARWIN da/dt scaling
factor results based on average grain
size training data from DEFORM:
(a) da/dN and da/dt scaling factor
means, and
(b) da/dN and da/dt scaling factor
standard deviations.
(a) (b)
O
m
O
DdN
da
D
DD
dN
da2/
o
p
o
dt
da
dt
da
Vision: DEFORM-DARWIN ICME Platform for
Designing Robust CDF-Resistant Ti Disks
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◆ Stress
◆ Strain
◆ Temperature
◆ residual stress
◆ anomaly orientat ion
◆ average grain size
Key◆ Current DARWIN
◆ Completed in Phase I
◆ Proposed Phase II
◆ Other DARWIN Funding
Cycle-&Time-basedResults
◆ Fracture risk
◆ Risk contribut ion–Location–Anomalytype–Failuremode–Microstructure–Environment
Forma onModule◆ Mult iple Anomaly Types
◆ Multiple Failure Modes
Propaga onModule◆ Single Failure Mode
◆ Mult iple Failure Modes
◆ Microstructure
◆ Environment
Compe ngFailureModeAnalysis
Fa gue&ReliabilityAnalysis
DARWIN®
◆ Cycle- based life/ risk
◆ Time- based life/ risk
ANSYS
ABAQUS
MARC
FEAnalysis
ManufacturingProcessModeling
DEFORMMicrocode
RawMaterialProduc on
FormingOpera ons
HeatTreatment
MachiningOpera ons
Stochas cParameters
◆ Anomaly size
◆ Anomaly orientat ion
◆ Stress scatter
◆ Life scatter
◆ Residual stress scatter
◆ Grain size scatter
Orientation Distribution Function (ODF), Volume
Fraction, and Size of Alpha Grains
Probabilistic
Life-Prediction,
Fracture Risk
Certification
Improve Design
Glavicic and Venkatesh, JOM, V.66, 2014, pp 1310-1320
DEFORM
New Capabilities Needed From DEFORM
• Orientation and size of alpha grains for the entire disk (not
just at selected locations)
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• Option 1
• Upgrade DEFORM to provide alpha grain
size and orientation information for the entire
disk
Potential Approaches
• Option 2
• Consider a threshold stress approach for CDF and develop a technique
to use the alpha grain size and orientation information for critical
locations identified by the threshold stress
• Use autozoning to identify and reduce the number of microtexture
regions where grain orientation data are needed
New Capabilities Needed for DARWIN
• New interface to read and visualize alpha grain
orientation and size data from DEFORM
• Enhanced capability for treating microtexture region in
DARWIN
• Need to treat orientation as well as the size of the
microtexture region for the entire disk
• Probability distribution function of alpha grains needs to
include both grain size and grain orientation
• Need to expand da/dt response equation to include both
grain size and grain orientation effects
• Need robust Kth and Kc models for various microtextures
and sizes
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Demonstration of New Capabilities
• Implement cold dwell fatigue modeling
methodology including hydrogen-
induced time-dependent crack growth
and microtextured regions into
DARWIN
• Perform deterministic analyses on a Ti
engine component using a realistic
mission profile with cold dwell fatigue
loads and actual microtextural data
generated by EBSD measurements
• Perform probabilistic analyses on a
demonstration problem
23
Alpha Grain Orientation
Alpha Grain Size
Multilevel V&V of CDF Design Platform
Individual Models
• V&V of microtextural
predictions from DEFORM
compared with EBSD
measurements
• V&V of da/dt, Kth, and Kc
models compared against
experimental data and
texture measurements by
EBSD or other techniques
• Performed on small number
of laboratory specimens
Combined DEFORM-DARWIN
• V&V of DEFORM-DARWIN
predictions of alpha grain
size and orientation
distributions compared
against experimental data
from multiple disks (from a
previous MAI program)
• V&V of DARWIN predictions
of disk fracture risk under
cold dwell fatigue with
assistance from OEM
partners
24
Summary
• Cold dwell fatigue involves both cycle-dependent and
time-dependent crack growth mechanisms
• Developed da/dt framework for treating microtexture
effects on cold dwell fatigue
• Current DEFORM-DARWIN platform may be extended
to treat cold dwell fatigue in Ti rotors
• Vision of a DEFORM-DARWIN ICME platform for design
of CDF-resistant Ti disks was presented
• New capabilities needed for the DEFORM-DARWIN
ICME Ti disk design platform were identified
25
26
Thank You
Hydrogen Degradation Maps
Hydrogen Content, wt. ppm
10 100 1000
E(C
H)/
E(r
ef)
, c
r(C
H)/
cr(
ref)
or
cr(
CH)/
cr(
ref)
0.01
0.1
1
E(CH)/E(ref) >
cr(C
H)/
cr(ref)
Dislocation Core Effects Dominate
cr(C
H)/
cr(ref) >
E(CH)/E(ref)
DecohesionEffects Dominate
Hydrogen Effects
Hydride Fracture
cr(C
H)/
cr(ref)
E(CH)/E(ref)
cr(C
H)/
cr(ref)
Region I
Region II
Region III
Fracture Mechanism Maps
• Hydrogen-related time-
dependent crack
growth is operative at
temperatures below Td
• Creep and oxidation-
related crack growth is
operative at
temperatures above Td
28
Temperature, K
0 200 400 600 800 1000
da/d
t, m
/s
10-11
10-10
10-9
10-8
10-7
10-6
10-5
10-4
10-3
Creep + OxidationHydride Embrittment
K = 50 MPa(m)1/2 K = 20 MPa(m)1/2
Ti-6246
Ti-6-4240 wppm H
Ti-6-460 wppm H
Ti-6Al100 wppm H
Ti-6Al-6V-2Sn38 wppm H
Ti-5Al-2.5Sn0.9 atm H
2
Td
Hydrogen in Solid Solution
Fracture Mechanism Map
Demonstration DARWIN Analysis: Orientation Distributions of Alpha Grains
• Three textures are
analyzed
Basal Transverse
Basal Longitudinal
Random Texture
Orientation Angle ( ), Deg
0 20 40 60 80 100
PD
F
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
Ti-6Al-4V
C-Axis
Basal Transverse
Random Texture
Basal Logitudinal
29
Potential Benefits
• Mitigate or reduce the risk of fracture of Ti disks due to
cold dwell fatigue in traditional near-alpha Ti alloys
• Provide a new ICME platform for designing robust Ti
disks for current and future Ti alloys
• Accelerate the certification process for Ti disks made
from new Ti alloys
• Improve the reliability and safety of current and future Ti
disks used in military and commercial aircrafts
30