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1130 Large Scale Fatigue Test in Japan
	ML18267A089
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Issue date:	09/24/2018
From:	Robert Tregoning; NRC/RES/DE
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ML18267A083	List: ML18267A084; ML18267A085; ML18267A086; ML18267A087; ML18267A088; ML18267A089; ML18267A090; ML18267A091; ML18267A092; ML18267A093; ML18267A094; ML18267A095; ML18267A096; ML18267A097; ML18267A098; ML18267A099; ML18284A002; ST-HL-AE-1611, Use of Increased Cumulative Usage Factor for Pipe Rupture Postulation, with Rodabaugh Attachment;
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0

Seiji Asada Yun Wang Mitsubishi Heavy Industries, Ltd.

Hitachi, Ltd.

Masahiro Takanashi Kentaro Hayashi IHI Corporation The Kansai Electric Power Co., Inc.

Development of New Design Fatigue Curves in Japan

- Discussion of Best Fit Curves based on Fatigue Test Data -

Environmentally Assisted Fatigue (EAF) Research and Related ASME Activities, NRC Public Meeting, September 25, 2018

1

1 Outlines

Introduction

Fatigue Tests Using Small Specimens [*1]

Large-Scale Fatigue Tests Using Carbon and Low-Alloy Steel Plates [*2]

Large-Scale Fatigue Tests Using Stainless Steel Piping [*3]

Conclusions (Notes)

The details of the above fatigue experimental tests are shown in the following 2018 PVP papers.

[*1] Wang, Yun, et al., Development of New Design Fatigue Curves in Japan -

Discussion of Best-Fit Curves Based on Fatigue Test Data With Small-Scale Test Specimen -, PVP2018-84052, ASME, 2018.

[*2] Takanashi, M., et al., Development of New Design Fatigue Curves in Japan

-Discussion of Best-Fit Curves Based on Large-Scale Fatigue Tests of Carbon and Low-Alloy Steel Plates -, PVP2018-84456, ASME, 2018.

[*3] Bodai, M., Development of New Design Fatigue Curves in Japan -

Discussion of Best-Fit Curves Based on Fatigue Test Data with Large-Scale Piping -, PVP2018-84436, ASME, 2018.

2

2 Introduction

The DFC1/DFC2 subcommittee has not only developed a new fatigue evaluation method but also produced beneficial outcomes. To support this study, a Japanese utility project performed not only large scale fatigue tests using carbon & low-alloy steel flat plates and austenitic stainless steel piping but also fatigue tests using small specimens to obtain not only basic data but also fatigue data of mean stress effect.

Fatigue life of a small specimen is generally defined as the number of cycles by 25% load drop, and this is considered to correspond to 3mm-deep crack in the test specimen.

Hence, the fatigue lives of the large-scale fatigue tests are compared with the best-fit curve developed by the DFC1 subcommittee and the fatigue lives obtained by the small specimen fatigue tests.

In this presentation, the fatigue tests using small specimens and large scale fatigue tests using carbon & low-alloy steel flat plates and austenitic stainless steel piping are summarized.

3

3 Fatigue Tests Using Small Specimens [*1]

Materials Material C

Si Mn P

S Ni Cr Mo Cu Fe SUS316LTP 0.012 0.44 1.76 0.024 0.000 14.47 17.38 2.62

Bal.

STPT370 0.200 0.25 0.82 0.014 0.001

Bal.

SQV2A 0.18 0.24 1.43 0.005 0.002 0.66 0.11 0.520 0.001 Bal.

SCM435H 0.37 0.28 0.76 0.014 0.011 0.08 0.91 0.15

Bal.

Material su (MPa) s0.2 (MPa)

Elongation

(%)

Reduction of Area (%)

SUS316LTP 556 (480) 238 (175) 53 (35) 86 STPT370 493 (370) 272 (215) 32 (30) 68 SQV2A 597 (550-690) 450 (345) 26 (18) 77 SCM435H 1074 (930) 991 (785) 17 (15) 58

[Notes]

- SUS316LTP (SA312 TP316L) was taken from the large-scale piping.

- STPT370 (SA106) is a carbon steel piping.

- SQV2A (SA533 Gr.B Cl.1) was taken from the large-scale Low-Alloy Steel (LAS) plate.

- SCM435H is a Cr-Mo steel with high tensile strength.

[wt%]

4

4 Fatigue Tests Using Small Specimens [*1] (continued)

Fully Reversed Axial Fatigue Tests SUS316LTP STPT370 BFC of DFC Subcommittee (u = 556 MPa)

BFC of DFC Subcommittee (u = 493 MPa)

=. x

.+. +

=. x

.+.

[Best-Fit Curve of DFC Subcommittee]

For Stainless Steels

[Best-Fit Curve of DFC Subcommittee]

For CS&LAS Steels

5

5 Fatigue Tests Using Small Specimens [*1] (continued)

Fully Reversed Axial Fatigue Tests (continued)

SQV2A SCM435H BFC of DFC Subcommittee (u = 597 MPa)

BFC of DFC Subcommittee (u = 1074 MPa)

=. x

.+. +

[Best-Fit Curve of DFC Subcommittee]

For CS&LAS Steels

6

6 Fatigue Tests Using Small Specimens [*1] (continued)

Fully Reversed Axial Fatigue Tests (continued)

SUS316LTP (ta=0.15%, Nf=1.06x106 cycles)

STPT370 (ta=0.135%, Nf=5.40x105 cycles)

SQV2A (ta=0.15%, Nf=1.89x107 cycles)

SCM435H (ta=0.3%, Nf=1.01x105 cycles)

7

7 Fatigue Tests Using Small Specimens [*1] (continued)

Mean Stress Correction Modified Goodman Approach

=

1

Gerber Approach

=

1

Peterson Approach

=

7 8 1 +

Smith-Watson-Topper Approach

=

+

Stress Amplitude, : Equivalent Stress Amplitude,

Mean Stress,

Maximum Stress Amplitude, : Tensile Strength Mean Stress (MPa) 0 200 400 600 800 1000 1200 0

200 400 600 800 u =1000 MPa y =0.72 u w0 =0.45 u Gerber Peterson S-W-T Mod. Goodman y y Fatigue Endurance Limit (MPa)

8

8 Fatigue Tests Using Small Specimens [*1] (continued)

Mean Stress Correction SUS316LTP STPT370 SCM435H SQV2A Conservative

9

9 Large-Scale Fatigue Tests Using CS&LAS Plates [*2]

Test Specimen and Test Machine Stress Concentration Factor = 1.27

10

10 Large-Scale Fatigue Tests Using CS&LAS Plates [*2]

(continued)

Test Results ID Mat.

Aim Upper strain

(%)

Strain amp.

(%)

Mean strain

(%)

CS1 CS Size effect 0.24 0.24 0

CS2 CS Mean stress 0.3 0.24 0.06 LAS1 LAS Size effect 0.22 0.22 0

LAS2 LAS Size effect 0.18 0.18 0

LAS3 LAS Mean stress 0.3 0.22 0.08 LAS4 LAS Mean stress 0.3 0.18 0.12

[*] Fatigue Life: Crack penetrated the plate width or the load decreased

11

11 Large-Scale Fatigue Tests Using Stainless Steel Piping[*3]

Test Specimen and Test Machine Notched Portion 3,000 170.3 216.3 216.3 23 3

40.5 50.6 Point A (Center)

Point B (Edge)

X Load

[Load Cell]

Strain Gages Displacement, a

[Actuator]

u1 u2 u4 u5 d1 d2 d4 d5 d3 Thermocouple L

u8 u10 - u14 u9 u6 u7 Stress Concentration Factor = 1.39

12

12 Large-Scale Fatigue Tests Using SS Piping[*3]

(continued)

Test Specimen and Test Machine Strain Amplitude Mean Strain TP-A

+/-0.44%

No TP-B

+/-0.44%

No TP-C

+/-0.25%

No TP-D

+/-0.25%

+2.25%

TP-E

+/-0.5%

+2.0%

TP-F

+/-0.2%

+2.3%

13

13 Large-Scale Fatigue Tests Using SS Piping[*3]

(continued)

The fatigue lives of pipes for 3 mm crack and through-wall crack (TWC) are compared with the fatigue lives of the small specimens and the estimated best fit curve developed by the DFC subcommittee.

0.1 1.0 10.0 1.E+02 1.E+03 1.E+04 1.E+05 1.E+06 1.E+07 1/2N or 1/2 N25 Ncycle SUS316L

3 20 3

20 N25 TS542MPa F

20 AE20 3

0.868 A

0.981.00 Number of Cycles Strain, Range at 1/2N or 1/2N25, (%)

SUS316LTP (in air)

Pipe [No Mean Stress, 3mm crack]

Pipe [No Mean Stress, TWC]

Pipe [Mean Stress, 3mm crack]

Pipe [Mean Stress, TWC]

Small Specimens (N25)

--- : Estimated Best Fit Curve (TS=542MPa)

TP-A (, )

0.98%, 1.00%

TP-F of Through Wall Crack( ):

[estimated from the average of ratio between 3mm crack and TWC for TP-A to TP-E]

14

14 Large-Scale Fatigue Tests Using SS Piping[*3]

(continued)

[Fatigue Test] Target strain amplitude = +/-0.44%

Observation on Notched Portion by replica printing Number of Cycles: 10,000 Number of Cycles: 11,450 Number of Cycles: 8,000 Number of Cycles: 9,000 Cracks

15

15 Large-Scale Fatigue Tests Using SS Piping[*3]

(continued)

[Fatigue Test] Target strain amplitude = +/-0.44% (continued)

Observation of Fracture Surface (beach marking) 1 3

2 3

3 4

5 6

7 8

16

16 Large-Scale Fatigue Tests Using SS Piping[*3]

(continued)

The data of the tested pipes are plotted for nominal strain amplitude and nominal mean stress calculated from the loads at 3 mm crack depth with mean stress correction.

The S-W-T approach is more appropriate than the Modified Goodman approach

TP-A (0%)

TP-B (0%)

TP-C (0%)

TP-D (2.25%)

TP-E (2%)

TP-F (2.3%)

[Note] ( )= Mean Strain

S-W-T

Modified Goodman Nominal Mean Stress Nominal Stress Amplitude, a (MPa)

17

17 Conclusions

To support the new fatigue evaluation method by DFC1/DFC2 subcommittee, a Japanese utility project performed not only large scale fatigue tests using carbon & low-alloy steel flat plates and austenitic stainless steel piping but also fatigue tests using small specimens to obtain not only basic data but also fatigue data of mean stress effect.

The fatigue lives of not only the small specimens but also the CS & LAS plates and the stainless steel pipes are close to the best-fit curve developed by the DFC1 subcommittee, and the size effect can be considered as negligible.

The mean stress effect is remarkable in materials with higher tensile strength. The correction of mean stress effect with the S-W-T approach shows good agreement with the BFCs.

18

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