ENVIRONMENTAL EFFECTS ON FATIGUE LIFE · PDF fileenvironmental effects on fatigue life ... 2016 3 0.1 1 10 10 103 105 107 109 304lt 304mt 304ht 316lt ... (nureg report and asme code)

Central Research Institute of Electric Power Industry

ENVIRONMENTAL EFFECTS ON FATIGUE LIFE

（outline of chapter 5）

Materials Science Laboratory

2016

Technical Meeting on Fatigue Assessment in LWR

July 8,2016

Yukio Takahashi

1

Contents of Section

OUTLINE OF PHENOMENA

METHODS FOR ESTIMATING ENVIRONMENTAL EFFECTS

APPLICATION TO GENERAL LOADING CONDITIONS

REFLECTION TO DESIGN CODES AND REGULATION

ENVIRONMENTAL EFFECTS IN FATIGUE CRACK GROWTH

SUMMARY

REFERENCES

2016 2

OUTLINE OF PHENOMENA

2016 3

0.1

1

10

10 103 105 107 109

304LT

304MT

304HT

316LT

316HT

US304LT

US304HT

US316LT

US316HT

Best-fit curve

Strain a

mpli

tude (

%)

Number of cycles to failure

LT：Room Temp.

MT:100-200℃HT:260-350℃

0.1

1

10

10 103 105 107 109

304LT

304MT

304HT

316LT

316HT

US304LT

US304HT

US316LT

US316HT

Best-fit curve

Strain a

mpli

tude (

%)


LT：Room Temp.

MT:100-200℃HT:260-350℃

0.1

1

10

10 102 103 104 105 106 107 108

Carbon steelLow-alloy steel

Best-fit curve

Strain amplitude (%)


0.1

1

10 102

103

104

105

106

107

108

SUS316

SUS304SCS14ASUS316 (WM)SUS304 (WM)best-fit equation for in-air databest-fit equation for in-water data (0.01%/s)best-fit equation for in-water data (0.0004%/s)

Str

ain

am

plit

ud

e (

%)

Number of cycles to fa ilure

0.1

1

10

10 102 103 104 105 106 107 108

STS410Best-fit curve for in-air dataBest-fit curve divided by maximum Fen (288C)

Strain amplitude (%)


Stainless steel in-air data Ferritic steel in-air data

Stainless steel in-HT water data Ferritic steel in-HT water data

METHODS FOR ESTIMATING ENVIRONMENTAL EFFECTS

Basic principles (use of Fen=Nf,air/Nf, water)

Reference in-air fatigue curves

Influence of strain rate

Influence of temperature

Influence of material composition and water chemistry

Effect of strain amplitude

Existing formulae for Fen

2016 4


2016 5


2016 6

0.1

1

10

101

102

103

104

105

106

107

108

Carbon steel (JSME)

Carbon steel (NUREG)

Low-alloy steel (JSME)

Low-alloy steel (NUREG)

Str

ain

am

plit

ude

(%

)


0.1

1

10

101

102

103

104

105

106

107

108

NUREG (stainless steel &Ni-Cr-Fe alloys)JSME (type 304&316 stainless steels)JSME (Ni-Cr-Fe alloys))KTA (type 321&347, T<80C)KTA (type 321&347, T>80C)

Str

ain

am

plit

ud

e (

%)


(a) Ferritic steels (b) Stainless steels and Ni-Cr-Fe alloys

Influence of strain rate on Fen

2016 7

Ferritic steels in high DO water Stainless steels in PWR water

Stainless steels in BWR water Ni-Cr-Fe alloys

Influence of temperature on Fen

2016 8

Ferritic steels in high DO water Stainless steels in BWR and PWR water

Ni-Cr-Fe alloys in BWR and PWR water

Influence of material composition and water chemistry on Fen for ferritic steels

2016 9

Sulfur content dependency Dissolved oxygen dependency

Existing formulae for Fen

2016 10

JSME S NF1-2009 NUREG/CR-6909

ln(Fen)=0.00822(0.772ὲ*)S*T*O* ln(Fen)=0.5540.101S*T*O*ὲ* (CS)

ὲ*=ln(2.16) (ὲ>2.16%/s) ln(Fen)=0.8980.101S*T*O*ὲ* (LAS)

ὲ*=ln(ὲ)(DO≤0.7ppm, 0.0004≤ὲ≤2.16%/s) ὲ*=0 (ὲ>1%/s)

ὲ*=ln(ὲ)(DO≤0.7ppm, 0.0001≤ὲ≤2.16%/s) ὲ*=ln(ὲ) (0.001≤ὲ≤1&/s)

ὲ*=ln(0.0004) (DO≤0.7ppm, ὲ<0.0004%/s) ὲ*=ln(0.001) (ὲ<0.001%/s)

ὲ*=ln(0.0001) (DO>0.7ppm, ὲ<0.0001%/s) T*=0 (T≤150ºC)

S*=ln(12.32)+97.92XS T*=T150 (150<T≤350ºC)

T*=0.0358XT (T<50ºC) O*=0 (DO<0.04ppm)

T*=ln(6) (50≤T≤160ºC) O*=ln(DO/0.04) (0.04≤DO≤0.5ppm)

T*=ln(0.398)+0.0170XT(T>160ºC) O*=ln(12.5) (DO>0.5ppm)

O*=ln(3.28) (DO<0.02 ppm) S*=0.015 (DO>1.0ppm)

O*=ln(70.79)+0.7853Xln(DO) S*=0.001 (DO≤1.0ppm & S≤0.001%)

(0.02≤DO≤0.7

ppm)

S*=S(DO≤1.0ppm & 0.001<S≤0.015%)

O*=ln(53.5) (DO>0.7 ppm) S*=0.015 (≤1.0ppm & S>0.015%)

Fen=1.0 (a≤0.042% or in the case of an earthquake) Fen=1.0 (a≤0.07%)

JSME S NF1-2009 NUREG/CR-6909

ln(Fen)=(Cὲ*)T* ln(Fen)=0.734T*O*ὲ*

(BWR)

C=0.992 ὲ*=0 (ὲ>0.4%/s)

ὲ*=ln(2.69) (ὲ>2.69%/s) ὲ*=ln(ὲ) (0.0004≤ὲ≤0.4%/s)

ὲ*=ln(ὲ) (0.00004≤ὲ≤2.69%/s) ὲ*=ln(0.0004) (ὲ<0.0004%/s)

ὲ*=ln(0.00004)(ὲ<0.00004%/s) T*=0 (T≤150ºC)

T*=0.000969T T*=(T-150)/175 (150≤T≤325ºC)

(PWR) T*=1.0 (T≥325ºC)

C=3.910 O*=0.281 (all DO levels)

ὲ*=ln(49.9) (ὲ>49.9%/s) Fen=1.0 (a≤0.10%)

ὲ*=ln(ὲ) (0.0004≤ὲ≤49.9%/s, wrought)

ὲ*=ln(ὲ)(0.00004≤ὲ≤49.9%/s, cast)

ὲ*=ln(0.0004)(ὲ<0.0004%/s, wrought)

ὲ*=ln(0.00004)(ὲ<0.00004%/s, cast)

T*=0.000782T (T≤325ºC)

T*=0.254 (T>325ºC)

Fen=1.0 (a≤0.11% or in the case of

earthquake)

Ferritic steels Stainless steels

APPLICATION TO GENERAL LOADING CONDITIONS

2016 11

( / )en k k k

ien

F t

F

( / )en enF F t

Average Fen approach Integrated Fen approach

Remaining issues to be solved

Application to general multiaxial loading including rotating principal stress case

Differentiation of tensile- and compressive- going process

Some principal stress components

Mean (hydrostatic) stress

No test data available to compare or justify the approaches under multiaxial stress

2016 12

REFLECTION TO DESIGN CODES AND REGULATION

Development in Japan (TENPES/JSME guidelines)

Development in US (NUREG report and ASME code)

Development in France

Development in Germany

Development in Finland

Summary

2016 13

Development in US

2016 14

10

100

1000

10000

101

102

103

104

105

106

107

108

109

1010

1011

ASME design curve (before 2009)

NUREG/CR-6909 (ASME design

curve after 2009 revision)

Str

ess a

mplit

ude, S

a (

MP

a)

Number of cycles

10

100

1000

10000

101

102

103

104

105

106

107

108

109

1010

1011

ASME design curve

NUREG/CR-6909 (low-alloy steel)

NUREG/CR-6909 (carbon steel)

Str

ess a

mplit

ude, S

a (

MP

a)

Number of cycles

(a) Stainless steels (b) Ferritic steels

(a) Stainless steels (b) Ferritic steels

Design fatigue curves

including environmental

effect in ASME code case

N-792

Updated design fatigue

curves in NUREG report

and ASME code

Development in France (AREVA NP)

2016 15

,( / ,1)en en en allowbleF Max F F

,,

,5

f testen test

en allowble

design

NFF

N

Reduction of Fen in

consideration of the

interaction of surface finish

and environmental effect

ENVIRONMENTAL EFFECTS IN FATIGUE CRACK GROWTH

Outline

Ferritic steels

Austenitic stainless steels

Ni-Cr-Fe alloys

Comparison of crack growth equations for different materials

Comparison with Fen values

2016 16

Crack growth curves for Ferritic Steels

2016 17

Comparison of crack growth data with

curves given in ASME Section XI Comparison of codified crack growth curves

in code case N-643 and Section XI

Crack growth curves for Stainless Steels

2016 18

10-9

10-7

10-5

10-3

10-1

1 10 100

In air (RT)

In air (325C)

PWR water (tr=1s)

PWR water (tr=100s)

PWR water (tr=1000s)

Cra

ck g

row

th r

ate

, da

/dN

(m

m/c

ycle

)

Stress intensity factor range, K (MPa√m)

10-9

10-7

10-5

10-3

10-1

1 10 100

In air (RT)

In air (289C)

BWR water (tr=1s)

BWR water (tr=100s)

BWR water (tr=1000s)

Cra

ck g

row

th r

ate

, da

/dN

(m

m/c

ycle

)


JSME code (PWR water) JSME code (BWR water)

Comparison of JSME code

curves and ASME code case

under development

Crack growth curves for Ni-Cr-Fe alloys

2016 19

10-11

10-9

10-7

10-5

10-3

10-1

1 10 100

ASME (air, 325C)

Nomura et al (air, 325C)

ASME (in HT water, tr=1s)

ASME (in HT water, tr=10s)

ASME (in HT water, tr>30s)

Nomura et al (in HT water,tr=1s)




Cra

ck g

row

th r

ate

, da

/dN

(m

m/c

ycle

)

0.1

1

10

100

1000

1 10 100

ASME (R=0, tr=1s)

ASME (R=0, tr=10s)

ASME (R=0, tr>30s)

ASME (R=0.9, tr=1s)

ASME (R=0.9, tr=10s)

ASME (R=0.9, tr>30s)

Nomura (R=0, tr=1s)

Nomura (R=0, tr=100s)

Nomura (R=0, tr=1000s)

Nomura (R=0.9, tr=1s)



Strtess intensity factor range (MPa m0.5

)

Cra

ck g

row

th r

ate

in

HT

wate

r

/ C

rack g

row

th r

ate

in

air

Comparison of JSME curves and

ASME code case

Comparison of amplification

factors as a function of ΔK

Comparison of crack growth curves for different materials

2016 20

10-10

10-8

10-6

10-4

10-2

100

1 10 100

Ferritic steels (R=0)Ferritic steels (R=0.9)Austenitic steels (R=0)Austenitic steels (R=0.9)Ni-Cr-Fe Allys (R=0)Ni-Cr-Fe Allys (R=0.9)

Cra

ck

gro

wth

ra

te d

a/d

N (

mm

/cycle

)

Stress intensity factor range K (MPa m0.5

)

10-8

10-6

10-4

10-2

100

1 10 100


Cra

ck

gro

wth

ra

te d

a/d

N (

mm

/cycle

)


)

(a) In-air at Room Temperature (b) In HT water at 300℃ (tr=1000sec)

difference is relatively small.

Acceleration rate in HT water

2016 21

1

10

100

1000

1 10 100


Ra

tio

of

cra

ck g

row

th r

ate

d

a/d

Ni n

Wate

r/a/d

Nin

Airr


)

1

10

100

1000

1 10 100


Ra

tio

of

cra

ck g

row

th r

ate

d

a/d

Ni n

Wate

r/a/d

Nin

Airr


)

At the same rise time (tr=1000s) At the same dK/dt (=0.1MPam0.5/s)

According to JSME code

Comparison of Fen and the acceleration ratio in CT test performed in PSI (H. Seifert and S. Ritter)

2016 22

Notation: i,PSI

env

SCG ,PSI

env

i,A N L

env

F : Life reduction in crack initiation (CT test in PSI)

F : Life reduction in sm all crack growth (CT test in PSI)

F : Life reduction in fatigue life (A N L report)

About 1.0 About 1.0

Much larger than 1.0

Much larger than 1.0

Comparison of acceleration in crack growth rate and Fen (Kamaya)

2016 23

Normalized crack growth rate as a

Function of rising time

Predictability of fatigue life based

on crack growth property

Fen from JSME code

Comparison of loading rate effects on fatigue life and crack growth

2016 24

1

10

100

10-5

0.0001 0.001 0.01 0.1 1

100C (JSME)

150C

200C

250C

300C

350C

Fen

ddt (%//s)

1

10

100

10-5

0.0001 0.001 0.01 0.1 1

100C (JSME)

150C

200C

250C

300C

350C

100C (ASME)

150C

200C

250C

300C

350C

da

/dt

(wa

ter)

/d

a/d

t (a

ir)

dK/dt (MPa m0.5

/s)

K=1MPam0.5

, R=0

Fatigue life Fatigue crack growth rate

4.1/

exp 2516 / ( 273.15) for150 C 343 C

T R ENV

T

da dN CS S S K

S T T

ln(Fen)=(Cὲ*)T*

T*=0.000969T

Summary Practices for taking the environmental effects on fatigue lives as

well as fatigue crack growth into account have been.

Extensive works have been done in relation with this crucial issue in fatigue assessment for light water reactor plants for recent two decades.

As a whole, much progress has been made in understanding the material behaviours and developing procedures to deal with them.

However there are still active discussions as well as on-going studies on this topic and more time would be required in order to reach some kind of consensus regarding the procedure to be applied for plant assessment.

2016 25

Future works Way of transformation from the mean material curves to design

fatigue curves in air as well as in high-temperature water

Incorporation of fatigue crack growth properties into fatigue damage assessment, to reconsider one or both of them or obtain a stronger confidence for both of them

Establishment of flaw tolerance-type approach as an alternative or complementary tool to the conventional fatigue damage approach

Performance of welded joints under environmental effect

Influence of stress multiaxiality in terms of environmental effect.

Higher stress triaxiality or mean stress may bring about a larger environmental effect than uniaxial push-pull condition, because of a larger involvement of tensile stresses.

2016 26

Documents

ENVIRONMENTAL EFFECTS ON FATIGUE LIFE · PDF fileenvironmental effects on fatigue life ... 2016 3 0.1 1 10 10 103 105 107 109 304lt 304mt 304ht 316lt ... (nureg report and asme code)