Nov 29, 2013 - 85. 75. 68. B. 12.5. 20. Section B-B. R40. C. 274. 90. 94. 73. C. 9.4. 13.2. Section C-C r =6 mm. Flat coupon. Curved coupon. Corner coupon ...
Mechanical Properties of Austenitic Stainless Steel after Exposure to Elevated Temperatures Zhong Tao, Tian-Yi Song, Lin-Hai Han 29 November 2013
1
Outline of presentation Introduction
Experimental investigation Test results and discussion Stress-strain models Conclusions
2
3
Introduction 800 Stress σ (MPa)
fy=350 MPa
600 400 Stainless steel (20℃) Stainless steel (600℃)
200 0 0
0.1
0.2
0.3
0.4
Strain ε
models for stainless steel at room temperatures: Rasmussen (2003); Gardner and Nethercot (2004); Quach et al. (2008)
models for stainless steel under elevated temperatures: Chen and Young (2006); Gardner et al. (2010) 4
Research gap models for stainless steel at room temperatures: Rasmussen (2003); Gardner and Nethercot (2004); Quach et al. (2008)
models for stainless steel under elevated temperatures:
models for
12.5 20 Section A-A
B
C
B 274
75
245
75
245
stainless Asteel after fire exposure
R40
R40
R40 A
12.5 20 Section B-B
C
94
85 68
85 68
90 73
Chen and Young (2006); Gardner et al. (2010)
13.2
9.4 r =6 mm Section C-C 5
Outline of presentation Introduction
Experimental investigation Test results and discussion Stress-strain models Conclusions
6
Experimental investigation
85 68
85 68
20 Section A-A
274
12.5 20 Section B-B
Curved coupon
C
94
C
B
75
245
B
12.5
Flat coupon
R40
R40
R40 A
75
245
A
90 73
Tensile tests were done to study the post-fire mechanical properties of austenitic stainless steel of grade 1.4301 (304). Three types of test coupons, including flat, curved and corner coupons, were fabricated
9.4
13.2
r =6 mm Section C-C
Corner coupon
7
Test program Measured data:
Temperature (C)
ts Cooling stage
T Heat soak stage 20
Post-fire full-range stress (σ)– strain (ɛ) curves Modulus of elasticity (E0T)
1 Temperature rising stage
0.2% proof yield strength
Time (min)
Heating and cooling procedures for coupons
(σ0.2T) 0.01% proof yield strength (σ0.01T)
Ultimate strength (σuT) Ultimate strain (ɛuT) corresponding to σuT 8
Outline of presentation Introduction
Experimental investigation Test results and discussion Stress-strain models Conclusions
9
Test results 800 200C 20C 1,000C
400
200
0 0.00
500C
400C
800C (ts=45 min) 700C
A
R40 A
75
20°C 200°C 300°C 400°C 500°C 700°C 800°C 1,000°C
245
Stress (MPa)
600
85 68
300C
12.5 20 Section A-A
0.10
0.20
0.30
Strain
0.40
0.50
0.60
Post-fire stressstrain curves for flat coupons 10
Test results 800
500C
85 68
85 68
700C 300C
0.20
0.30
Strain
0.40
0.50
C
94
20 Section B-B
Section A-A
0.10
274
12.5
20
0 0.00
C
B
75
245
B
20°C 300°C 500°C 700°C 12.5 1,000°C
200
R40
R40
R40 A
75
A 245
Stress (MPa)
600
400
1,000C
90 73
20C
13.2
9.4 r =6 mm Section C-C
0.60
Post-fire stressstrain curves for corner coupons 11
Test results 800 85 68
700C
1,000C
200
R40 B
75
245
B
12.5 20 Section A-A
274
R40 A 20CA
75
20°C 300°C 500°C 700°C 1,000°C
400
245
Stress (MPa)
85 68
500C
600
300C
12.5 20 Section B-B
0 0.00
0.10
0.20
0.30 0.40 Strain
0.50
0.60
Post-fire stressstrain curves for curved coupons 12
Influence of heat-soak time 800
ts=135 min
Stress (MPa)
600 ts=0
ts=90 min
400 ts=45 min
200
Flat coupons, T=800C
0 0.00
0.10
0.20
0.30 0.40 Strain
0.50
0.60
Post-fire stressstrain curves for flat coupons 13
Ratio of fyT/fy as a function of T 800 200C 300C 20C 1,000C 20°C 200°C 300°C 400°C 500°C 700°C 800°C 1,000°C
400
200
0 0.00
0.10
0.20
0.30
Strain
500C
400C 800C (ts=45 min) 700C
1.2 1
0.40
0.50
0.60
fyT/fy
Stress (MPa)
600
Flat coupons
0.8 0.6 Flat coupon
800 300C
Stress (MPa)
600
500C
0.4
Curved coupon Steel bar (Felicetti et al., 2009)
700C
20°C 300°C 500°C 700°C 1,000°C
400
200
1,000C
20C
0.2 0 0
0 0.00
0.10
0.20
0.30 0.40 Strain
0.50
0.60
200
400 600 800 Temperature T (°C)
1000
Curved coupons 14
Influence of fire exposure on corner effect 20C
800
500C
700C 300C
400
fuT fuT,c
20°C 300°C 500°C 700°C 1,000°C
200
0.10
0.20
0.30
Strain
800
0.40
0.50
Corner coupons
0.60
Strength (MPa)
Stress (MPa)
600
0 0.00
1,000C
600 fyT
fyT,c
400 200
Flat coupon Corner coupon
0 0
200
400 600 800 Temperature T (°C)
1000
15
Influence of fire exposure on corner effect 20C
800
500C
700C 300C
400
20°C 300°C 500°C 700°C 1,000°C
200
0.10
0.20
0.30
Strain
0.6 0.40
0.50
Corner coupons
0.60
Ultimate strain
Stress (MPa)
600
0 0.00
1,000C
0.45 0.3 0.15
Flat coupon Corner coupon
0 0
200
400 600 800 Temperature T (°C)
1000
16
Outline of presentation Introduction
Experimental investigation Test results and discussion Stress-strain models Conclusions
17
Rasmussen’s model EsT
Stress σ
1
EyT 1
fuT fyT
εuT
0.002 Strain ε
n 0.002 for f y Es fy m f f f y y y for f y f u 0 . 002 u Es Ey fu fy
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Post-fire model for flat regions n 0.002 f Es yT mT f yT f yT f yT u 0.002 E E f f s yT u yT
for f yT for f yT f u
Es EyT 1 0.002nEs / f yT
mT 1 3.5
f yT fu 19
Ratio of fyT/fy as a function of T f y,c 1.2
fy
1 0.05e
900/ f y
1
fyT/fy
0.8 0.6 Flat coupon
0.4
Curved coupon Steel bar (Felicetti et al., 2009)
0.2 0 0
200
400 600 800 Temperature T (°C)
1000
20
Room temperature - model for corner regions Stress (MPa)
800 600 400 Flat material
200
Corner material
0 0.00
0.10
0.20
0.30
0.40
0.50
Strain
21
Room temperature - model for corner regions 85 test data, 24 full-range curves from 15 references.
nc 0.002 f y,c Es mc f f f y,c y,c y,c 0 . 002 u,c Es Ey,c f u,c f y,c
E y,c
Es 1 0.002nc Es / f y,c
for f y,c for f y,c f u,c
u,c 1
f y,c f u,c
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Room temperature - model for corner regions 2.4
fy,c/fy
1.6 1.2 0.8
Austenitic
0.4
Duplex
f y,c fy
1 0.05e
900/ f y
0
(fu,c/fy,c)/(fu/fy)
2
1.4
f u,c
1.2
f y,c
0.56 f y
0.226
1.4
ff
u y
1 0.8 0.6 0.4
Austenitic
0.2
Duplex
0
250
350
450
550 fy (MPa)
650
750
250
350
450 550 fy (MPa)
650
750
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Post-fire model for corner regions Assumptions: 1) With suitable modifications, Rasmussen's model can still be used. 2) The corner effects due to cold forming disappear when T is 1,000C, but the ultimate strain uT,c of post-fire corner material can be taken as 0.89u, where u is the ultimate strain of flat material without fire exposure. 3) When 20 C
