High-temperature crack-arrest behavior of prototypical and degraded (simulated) reactor pressure vessel steels

Int. J. Pres. Ves. & Piping 39 (1989) 189-208

High-Temperature Crack-Arrest Behavior of Prototypical and Degraded (Simulated) Reactor Pressure Vessel Steels* D. J. N a u s , J. K e e n e y - W a l k e r , B. R. Bass Oak Ridge National Laboratory (ORNL), Oak Ridge, Tennessee, USA R. J. Fields, R. d e W i t & S. R. L o w III National Institute of Standards and Technology (NIST), Gaithersburg, Maryland, USA (Received 9 March 1989; accepted 3 April 1989)

ABSTRACT Sixteen wide-plate crack-arrest tests have been completed, ten utilizing specimens fabricated from A533B Class 1 material and six fabricated from a low-upper-shelf base material. Each test utilized a single-edge notched specimen that was subjected to a linear thermal gradient along the plane o f crack propagation. Test results exhibit an increase in crack-arrest toughness ( Kt~) with temperature, with the rate of increase becoming greater as the temperature increases. When the wide-plate test results are compared with other large-specimen results, the data show a consistent trend in which the Kta data extend above the limit provided in A S M E Section XI.

INTRODUCTION The pressurized-thermal-shock (PTS) issue for pressurized-water reactors (PWRs) involves the broadest range of fracture phenomena. In PTS scenarios, flaws in the inner surface of the reactor pressure vessel (RPV) have * Research sponsored by the Officeof Nuclear Regulatory Research, US Nuclear Regulatory Commission under Interagency Agreement 1886-8011-9B with the US Department of Energy under Contract DE-AC05-840R21400 with Martin Marietta Energy Systems, Inc. 189 © 1989 US Government.

190

D . J . Naus et al.

the greatest propensity to propagate because they are located in the region of highest thermal stress, lowest temperature, and greatest irradiation damage. Although the thermal stresses may decrease with propagation depth, the stress-intensity factor caused by the elevated pressure loading will be increasing. Assessment of the integrity of a RPV under such a postulated crack run-arrest scenario requires prediction of the arrest location, potential reinitiation, stable and unstable ductile crack growth, and structural instability of the remaining vessel wall ligament. The fracture toughness correlations contained in the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME B & PVC) embody the position that one cannot assume a crack-arrest toughness value (K1a) above 220 MPa. x/m for light-water reactor (LWR) pressure-vessel steels. The imposition of this limit is based in part on the fact that no Kta data existed at or above this level and because Charpy tests showed that impact energy levels exhibit an upper-shelf behavior. Therefore, the nature of crackarrest behavior of Kt~ extrapolations to temperatures higher than that at which this limit occurred could not be presumed. The ASME limit does not impose difficulties in making assessments for LWR pressure vessels undergoing thermal shock transients with low accompanying pressure levels. However, PTS scenarios could lead to conditions where the driving force on a propagating crack increases to levels well in excess of the current ASME limit. Thus, safety assessment methods for this type of condition would require an understanding of the following points. (1) If the driving force on a crack exceeds 220 MPa. x//m by a significant margin, can the material exhibit crack-arrest behavior? (2) If the materials do exhibit high K~ values with increasing temperature, what is the relationship between KI~ and temperature? That is, does a temperature limit exist above which cleavage crack propagation cannot continue regardless of how high the driving force? (3) If crack arrest does occur at high temperatures where the material behavior is typically dominated by ductile behavior, then what interactions exist between the various fracture modes, including arrest, stable crack growth, unstable crack growth, and tensile instability? PROGRAM OBJECTIVE AND GOALS The primary objective of the wide-plate crack-arrest studies is to generate data and associated analysis methods for understanding the crack-arrest

High-temperature crack-arrest behaviour

191

behavior of prototypical RPV steels at temperatures near and above the onset of the Charpy upper-shelf region. Program goals include: (I)

extending the existing Ki~ databases to values above those associated with the upper limit in the ASME B & PVC; (2) clearly establishing that crack-arrest occurs prior to fracture-mode conversion; and (3) validating the predictability of crack-arrest, stable tearing, and/or unstable tearing sequences for RPV materials.

MATERIAL PROPERTIES WP-I test series (A533B material) The initial series of wide-plate crack-arrest specimens is taken from the central portion of an 18-73-cm-thick plate ofA533 grade B class 1 steel that is in a quenched and tempered condition. Properties of the plate include Young's modulus ( E ) = 206-9 GPa. Poisson's ratio (v)= 0"3, coefficient of thermal expansion (0t) = 11 x 10-6/°C, and density (p) = 7850 kg/m 3. The ultimate strength of the material, for use in tensile instability calculations, is based on the average stress in the remaining ligament (au) equal to 550 MPa. For tearing instability calculations, the material tearing resistance is represented as a power-law J-resistance curve JR = c(Aa)"

(1)

where c = 0-3539, m = 0-4708, and the units for JR and 6Aa are MJ/m 2 and mm, respectively. Temperature-dependent fracture-toughness relations for initiation and arrest, based on small-specimen data, are given by K~c = 51.28 + 51.90 exp [0.036(TKia = 49.96 + 16.88 exp [0.029(T--

RTNor)] RTNor)]

(2) (3)

with units for K and T being MPa. x/m and °C, respectively. Drop-weight and Charpy V-notch test data indicate that RTNor = -23°C, and Charpy upper-shelf energy is 160J with its onset occurring at 55°C. Analytical studies have used a dynamic fracture-toughness relation in the following form: KID = gla -I- A(T)d 2

(4)

where/(to is given by eqn (3) and

A(T) = [329.7 + 16-25(T- RTsoT)] x 10 -6

(5)

192

D . J . Naus et al.

or

A(T) = [,121"71 + 1"296(T- RTNor)] × 10 -6

(6)

i f ( T - RTNDr)is greater or less than - 13"9°C, respectively. Units for K~o, A, a, and T are megapascals times root meters, megapascals times square second times meters to the power - 3 / 2 , meters per second, and degrees Celcius, respectively.

WP-CE test series (A533B material) The WP-CE specimens were made from a second heat of A 533 grade B class 1 material that was provided to O R N L by Combustion Engineering (CE), Inc. (Windsor, CT, USA). The material was characterized by CE. ~ Pertinent material properties include: ultimate tensile strength ranging from ~ 5 8 0 M P a at 20°C to ~ 5 6 0 M P a at 66°C to ~ 5 2 0 M P a at 120°C, nilductility transition temperature from - 3 4 to - 2 3 ° C , Charpy upper-shelf energy of 180 to 203 J, and minimum temperature for fully ductile behavior occurring at 43-49°C. Temperature-dependent fracture toughness relations are given in eqns (2) and (3) with the RTNor changed to that of the CE material.

WP-2 test series (low-upper-shelf material) The WP-2 series of wide-plate crack-arrest specimens is taken from a 15.88cm thick plate of 2¼Cr-1 Mo steel. The material was supplied by Babcock and Wilcox (Alliance, OH, USA) after being heat treated in an effort to obtain a Charpy upper-shelf energy of 68 J (50 ft-lb), or less. The drop-weight nil-ductility temperature for the material is ,-~60°C, and the Charpy upper-shelf energy is 60-65 J with its onset occurring at about 150°C. The ultimate strength of the material used in tensile instability calculations is 500 MPa. For tearing instability conditions, the values of c and rn in eqn (1) are 0.1114 and 0.3832, respectively. Tentative temperaturedependent fracture-toughness relations for initiation and arrest, which have been used for planning the WP-2 series tests are given by Ktc = 39.53 + 93.47 exp [0.036(T- D WNOT)] K~, = 22"31 + 62"69 exp [-0.0177(T-- DWNDr)]

(7) (8)

with units of K and T being M Pa. x / m and °C, respectively, and the material D WNor = 60°C. The dynamic fracture-toughness relation is presented in eqn (4) with 60°C used as the material RTNDr.

193

High-temperature crack-arrest behaviour

SPECIMEN P R E P A R A T I O N , I N S T R U M E N T A T I O N A N D TESTING PROCEDURE

Specimen preparation The 1 x 1 x 0.1m 3, or 1 x 1 x 0.15m 3, specimens were machined and precracked by ORNL. The precracking was done by hydrogen charging an electron-beam (EB) weld located at the base of a premachined notch in the plate. The initial total crack length, notch depth plus EB weld, for each specimen was nominally 0.2m ( a / W ~ 0.2) and the flaw was orientated perpendicular to the rolling direction. Each side of a specimen was sidegrooved to a depth equal to 12.5% of the plate thickness. Starting with the third specimen in test series WP-1 (WP-1.3), the crack front of each specimen, with the exception of specimens WP-2-3 and WP-2-6, was machined into a truncated chevron configuration to reduce the tensile load required to achieve crack initiation. Upon completion of the machining operations, each specimen was shipped to NIST where it was welded to pull plates nominally having the same cross-section geometry as the specimen to produce the test article shown schematically in Fig. 1. Table 1 presents dimensions for each of the test specimens. CRACK PLANE (SIDE GROOVED)7 / } 9.6

,I \

0,1

ZINITIAL FLAW

~

1-,-1.0

1.0 o

) ./

~

0.0127 RADIUS

0.0127 X 10 .3 IUS

PLAN

~(

,

7

ENLARGED DETAIL

~H~

ELEVATION

DIMENSIONS IN METERS

B = 0.102 OR 0.152

Fig. 1. Schematic of HSST wide-platecrack-arrest specimen.

194

D.J. Naus et al. TABLE 1 Test Specimen Dimensions

Specimen designation

Dimension (mm) Initial crack length ao

Thickness B

Notched thickness ON

Chevron thickness at ao Bc

Width W

Pop-in crack length

Thickness at a'o

a'o

~c

WP-I-I WP-I'2 WP-I'3 WP-1-4 WP-I'5 WP-I'6 WP-I'7 WP-I'8

196"9 199 197 207-5 200 200 202 198

101 101'8 99"5 99"6 101"7 101"8 152'4 152'4

76"3 77"5 75-4 76"9 76-4 75-5 114-3 115'1

NA" NA" 47'5 33"8 41"2 40"0 61"0 56"2

997 998 1000 1000 1000 1000 1000 1000

NA" NA" NA" NA" NA" NA" NA" NAa

NA" NA" NAa NA" NA" NA" NA" NA a

WP-CE-1 WP-CE-2

200 201

101"7 101'8

76"3 76"2

40"0 40"4

1000 999-5

NA" NA ~

NA" NA"

WP-2"I WP-2"2 WP-2"3 WP-2"4 WP-2"5 WP-2'6

199 211 200 203 199 224

152"3 152.4 152"4 101'7 101"6 152"4

113'9 113"9 113"8 76"3 76"2 113'9

61'5 71"9 NA" 40"5 40-7 NA"

1000 1000 1 000 1 000 999 1000

NA~ NA" NA" 251 264 NA~

NA ~ NA" NA~ 75'5 76"2b NA"

" Not applicable. b Crack length after pop-in was past the region of the plate where crack front had been cut into a truncated chevron configuration.

Instrumentation T o o b t a i n pertinent d a t a d u r i n g a test, each wide-plate specimen was i n s t r u m e n t e d with three p r i m a r y types o f devices: (1) t h e r m o c o u p l e s , (2) strain gauges a n d (3) c r a c k - o p e n i n g d i s p l a c e m e n t gauges. U p to 40 t h e r m o c o u p t e s were p o s i t i o n e d o n each specimen with the 20 t h e r m o c o u p l e s a d j a c e n t to the c r a c k plane displayed g r a p h i c a l l y in real time to indicate the relationship between actual a n d desired t h e r m a l gradient across the specimen width. Strain gauges were used to p r o v i d e d y n a m i c strain-field m e a s u r e m e n t s for d e t e r m i n a t i o n o f c r a c k velocity a n d assessing b o u n d a r y conditions. T w o c a p a c i t a n c e - b a s e d c r a c k - o p e n i n g d i s p l a c e m e n t gauges were m o u n t e d o n the plate f r o n t a n d b a c k faces at an a / W t h a t r a n g e d f r o m 0"120 to 0.175 f r o m test to test. Also, an acoustic emission t r a n s d u c e r was

High-temperature crack-arrest behaviour

Fig. 2. Wide-plate crack-arrest specimen under test at NIST.

195

D.J. Naus et al.

196

located on the lower pull tab of each specimen. Reference 2 provides more detailed information on the instrumentation systems.

Testing procedure After instrumenting, the specimen was placed into the 27-MN capacity tensile testing machine and electric-resistance strip heaters attached to the back edge of the plate. A cooling chamber, into which liquid nitrogen (LN 2) was pumped and sprayed directly onto the specimen, was affixed at the notched edge of the plate. The back and front faces of the specimen were then insulated. A temperature gradient was imposed across the plate by TABLE 2 S u m m a r y o f HSST Wide-Plate Crack-Arrest Test C o n d i t i o n s a n d Results for A533 G r a d e B Class 1 Steel: WP-1 a n d W P - C E Series

Test number

Crack location (cm)

Crack temperature

Initiation load (MN)

Arrest location (cm)

(°c)

Arrest temperature

Arrest T-RTNo r (°C)

(oc)

WP-I'I ° WP-I'2A WP-I'2B WP-I'3 WP- l ' 4 A Wpol'4B WP-I'5A WP-I'5B WP-I'6A WP-I'6B WP- l ' 7 A WP-I'7B WP-I'8A WP-I'8B WP-I'8C

20 20 55"5 20 b 20'7 ~'c 44.1 20 b 52"1 20 ~ 49"3 20"2 ~ 52"8 19-8 b 44"9 50"4

-60 -33 62 - 51 - 63 29 - 30 56 - 19 54 - 24 61 -47 40 55

20'! 18'9 18'9 11"25 7"95 9"72 11-03 11"03 14"50 14"50 26"2 26-2 26"5 26"5 26'5

50'2 55"5 64"5 48"5 44" 1 52"7 52" 1 58"0 49-3 59"3 52"8 63"5 44"9 50"4 59"4

51 62 92 54 29 60 56 72 54 80 61 88 40 55 79

74 85 115 77 52 83 79 95 77 103 84 111 63 78 102

WP-CE- 1 WP-CE-2A ~ WP-CE-2B WP-CE-2C

20"0 b 20" 1 b 46"6 50"4

- 34 - 40 42 51

10' 14 14"60 14"60 14-60

42"0 46"6 50"4 52"5

36 42 53 60

70 76 88 95

a Specimen was w a r m prestressed by loading to 10 M N at 70°C. Specimen was also preloaded to 19 M N . b Crack front cut to truncated chevron configuration. c Pillow jack utilized to apply pressure load to specimen's m a c h i n e d notch. d Specimen was w a r m prestressed to 14 M N at 25°C.

High-temperature crack-arrest behaviour

197

spraying LN 2 onto the notched edge while heating the other edge. Liquid nitrogen flow and power to the heaters were continuously adjusted to obtain the desired thermal gradient. Generally, the mid-plate (a/W=0.5) temperature was selected to correspond to that of the onset of Charpy upper-shelf energy for the material being tested, and the crack-tip temperature was varied to provide the desired initiation load. Upon obtaining the desired temperature gradient, tensile load was applied to the specimen at a rate which varied from 11 to 312 kN/s, depending on the test, until fracture occurred. Figure 2 presents a wide-plate crack-arrest specimen under test.

TEST S U M M A R Y Tables 2 and 3 present a summary of the general conditions for the tests utilizing the A533B and low-upper-shelf materials, respectively. A detailed description of each of these tests is provided elsewhere. 3 - 5 Fracture surfaces are presented in Fig. 3 for specimens WP-I.1 to WP-1-6, Fig. 4 for specimens WP-1.7 and WP-1.8, Fig. 5 for specimens WP-CE-1 and WP-CE-2, and Fig. 6 for specimens WP-2.1 to WP-2.6. Fractographic examinations of the fracture surfaces confirm that the crack propagations in the wide-plate tests occurred by a predominantly cleavage mode and that arrest events were not preceded by conversion to ductile tearing. 2

POST-TEST ANALYSES A N D C O M P A R I S O N OF D A T A WITH O T H E R L A R G E - S C A L E TEST RESULTS

Post-test analyses Post-test analyses were conducted for each wide-plate crack-arrest test to investigate the interaction of parameters (plate geometry, material properties, temperature profile and mechanical loading) that affect the crack run-arrest events. Three-dimensional (3-D), static, finite-element analyses were performed to determine the stress-intensity factor at the time of crack initiation using the O R M G E N / O R V I R T 6'7 fracture-analysis system in conjunction with the A D I N A 8 finite-element code. Quasistatic analyses utilized the O R N L computer code WPSTAT 9 to evaluate the static stressintensity factors as a function of crack length and temperature differential across the plate. WPSTAT also categorizes arrested crack lengths in terms of three types of instability limits; i.e. reinitiation, tearing instability, and tensile instability. Elastodynamic analyses were carried out using the

TABLE 3 Summary of HSST Wide-Plate Crack-Arrest Test Conditions and Results for Specially Heat Treated 24!Cr-1 Mo Steel: WP-2 Series Test number

Crack location (cm)

Crack temperature (°C)

Initiation load (MN)

Arrest location (cm)

Arrest temperature (°C)

Arrest T-D WNoT (°C)

WP-2.4A a WP-2.4B WP-2.4C WP-2.4D WP-2'4E WP-2.4F WP-2.4G WP-2"4H

20'3 25-1 b 33-8 39"7 41"3 46.2 48.4 51.5

45 61 86 102 107 121 127 137

7-52 8"85 8"85 8.85 8"85 8-85 8-85 8"85

25.1 33'8 39'7 41 "3 46"2 48.4 51.5 55.5

61 86 102 107 121 127 137 149

1 26 42 47 61 67 77 89

WP-2-1A a WP-2"IB WP-2-1D WP-2.1E WP-2'I F WP-2' 1H WP-2'II WP-2-1J

19"9 27.5 33-5 37'0 40.0 45'0 49.0 52'7

55 80 96 105 112 125 135 145

11.90 11-90 11.90 11"90 11-90 11-90 11-90 11"90

27.5 33'5 37-0 40-0 45"0 49.0 52.7 55-5

80 96 105 112 125 135 145 152

20 36 45 52 65 75 85 92

WP-2.5A ~ WP-2-5B WP-2-5C WP-2'5D WP-2.5E WP-2-5 F

19"9 27.2 b 35'0 43-5 47"8 51'6

66 86 104 124 135 144

7.53 8'90 8"90 8.90 8"90 8"90

27.2 35"0 43.5 47.8 51 '6 56-0

86 104 124 135 144 154

26 44 64 75 84 94

WP-2.3A WP-2.3B WP-2'3D WP-2.3F

20"0 34.0 37.5 39"7

66 97 106 111

15-3 15-3 15"3 ! 5"3

34-0 37"5 39-7 45.7

97 106 111 126

37 46 51 66

WP-2.2A a'c WP-2'2B WP-2'2C WP-2.2D WP-2'2E WP-2.2F WP-2-2G

21.1 43'5 46"5 47.8 49.9 51-0 53-8

58 t20 129 133 139 142 150

17-0 17-0 17.0 17'0 17.0 17.0 17"0

43.5 46.5 47'8 49.9 51.0 53'8 58.2

120 129 133 139 142 150 162

60 69 73 79 82 90 102

WP-2-6A d WP-2.6B WP-2.6C WP-2-6D WP-2.6F WP-2'6G WP-2-6H

22.4 35-7 39.7 41.0 43.0 46-0 48.0

65 104 115 119 125 133 139

19.3 19'3 19"3 19.3 19-3 19.3 19.3

35.7 39'7 41.0 43-0 46-0 48"0 54.0

104 115 119 125 133 139 156

44 55 59 65 73 79 96

a Crack front cut to truncated chevron configuration. b After pop-in event. c Specimen was warm prestressed by loading to 16 MN at 124°C. d Specimen was warm prestressed by loading to 15.6 MN at 110°C.

Fig. 3.

Fracture surfaces of specimens WP-I.I to WP-I'6.

'~

5"

200

D. J. Naus et al.

e-

E

¢D

.a

Fig. 5.

Fracture surfaces of specimens WP-CE-I and WP-CE-2.

Ix2

¢%

:

Fig. 6.

Fracture surfaces o f specimens WP-2.1 to WP-2~6.

203

High-temperature crack-arrest behaviour

A D I N A / V P F 1° d y n a m i c c r a c k a n a l y s i s c o d e . T h e c o d e is c a p a b l e o f p e r f o r m i n g b o t h a p p l i c a t i o n - m o d e ( c r a c k tip is p r o p a g a t e d i n c r e m e n t a l l y w h e n K~, t h e d y n a m i c a l l y c o m p u t e d s t r e s s - i n t e n s i t y f a c t o r , e q u a l s t h e specified d y n a m i c f r a c t u r e - t o u g h n e s s value, K t o ) a n d g e n e r a t i o n - m o d e ( c r a c k tip is p r o p a g a t e d i n c r e m e n t a l l y a c c o r d i n g t o a p r e s c r i b e d c r a c k position versus time relationship with the values of fracture toughness d e t e r m i n e d f r o m t h e d y n a m i c a l l y c o m p u t e d K~) analyses. F o r b o t h m o d e s o f

TABLE 4

Summary of Crack-Arrest Toughness Values a for A533 Grade B Class 1 Steel: WP-1 and WP-CE Series Test number

Crack-arrest toughness values ( M Pa . x/m) Tada static S E N formulas Displ. control b

Load control c

Fedderson alternate secant formula a

Dynamic F E e Generation mode

WP- 1.1 WP- 1.2A WP-I.2B WP-I.3 WP-I.4A WP-I-4B WP-I.5A WP-1-5B WP-I'6A WP- 1-6B WP-1.7A WP-1-7B WP-I-8A WP-1.8B WP-1.8C

391 384 416 215 145 331 217 229 279 306 351 385 325 344 374

8!3 942 1 489 424 248 433 472 616 565 881 793 1 312 576 723 ! 083

340 349 419 185 120 170 191 213 242 290 31 ! 381 273 301 356

NA 424 685 235 NA 387 231 509 275 397 319 555 345 484 563

WP-CE- 1 WP-CE-2A WP-CE-2B WP-CE-2C

180 274 285 291

293 509 597 653

148 232 249 258

170 218 354 576

a Kta values are presently being reassessed to incorporate tunneling effects. Values should therefore not be considered as final. b Assuming a = a: and no further bending occurs due to propagation of the crack (Ref. 11, pp. 2.10-2.11): c Assuming a = a: and full bending according to SEN formula when the final crack depth is used (Ref. 11, pp. 2.10-2.11). a 1(,I = tr{na sec(na/2w)} 1/2 with a = far-field tensile stress, a = a: = final crack length, and w = full plate width.12 e Dynamic finite element analyses (fixed load) using O R N L program ADINA/VPF) °

TABLE 5 Summary of Crack-Arrest Toughness Values a for the WP-2 Rest Series Test number

Crack-arrest toughness values ( M Pa . x / m ) Tada static S E N formulas Displ. control b

Load control c

Fedderson alternate secant formula a

WP-2"4A WP-2.4B WP-2"4C WP-2.4D WP-2-4E WP-2.4F WP-2-4G WP-2.4H

104 155 168 171 181 185 191 198

113 186 234 249 303 332 378 451

79 111 124 128 140 145 153 165

-137 188 281 249 307 381 397

WP-2.1A WP-2.1B WP-2' 1D WP-2'IE WP-2' 1F WP-2'I H WP-2'II WP-2.1J

114 126 133 138 146 153 158 163

132 166 190 213 260 306 359 406

88 100 106 112 123 132 141 149

106 153 158 170 201 293 371 406

WP-2'5A WP-2.5B WP-2'5C WP-2.5D WP-2-5E WP-2.5F

108 165 184 193 200 209

123 196 273 326 382 464

83 114 134 144 155 ! 67

-171 190 268 306 366

WP-2.3A WP-2.3B WP-2.3D WP-2"3F

164 172 177 190

217 249 271 344

129 138 144 160

144 232 255 258

WP-2'2A WP-2.2B WP-2.2C WP-2"2D WP-2.2E WP-2.2F WP-2.2G

210 217 220 225 227 233 242

350 395 416 454 476 538 656

171 180 185 192 195 206 223

201 259 281 299 380 364 446

WP-2-6A WP-2.6B WP-2.6C WP-2-6D WP-2-6F WP-2.6G WP-2.6H

221 233 237 243 251 257 272

293 342 360 390 440 477 617

169 182 189 193 203 211 235

204 259 286 350 328 411 413

a See Table 4 for explanation of footnotes.

Dynamic F E e Generation mode

205

High-temperature crack-arrest behaviour

analysis, the dynamic stress-intensity factor is determined in each time step from the dynamic J-integral containing the appropriate inertial and thermal terms. Tables 4 and 5 summarize crack-arrest toughness values for the A533B and low-upper-shelf materials, respectively, which were computed by both static and dynamic analyses as well as those determined using handbook techniques.l 1,12 The generation-mode (fixed-load point)dynamic analysis crack-arrest toughness results from the wide-plate tests, presented in Fig. 7, extend consistently above the limit provided in section XI of the ASME Code and exhibit a significant increase in toughness with temperature. This increase in arrest toughness with temperature occurs at an accelerating rate suggesting that a temperature limit exists at or below which a cleavage crack propagation will arrest, no matter how high the applied driving force. (It should be noted, however, that the K1a results in Fig. 7 are presently being reassessed to incorporate the influence of tunneling. This may result in a slight revision to the values presented in Tables 4 and 5 and Fig. 7). Comparison

o f d a t a with o t h e r l a r g e - s c a l e test results

The trend for K/a values to extend consistently above the limit provided in ASME section XI is further substantiated in Fig. 7, which also presents data from several large-scale tests.13 - 24 700

t. u) u)

I

I

1

1

4WP-2.2 × WP-2.6 o W P - 2 . 4 u. W P - 2 . 3 e WP-2.1~WP-CE-1 _ ~x W P - 2 . 5 ~ W P - C E - 2 soo • FTSE 4~ESSO C l T S E - 4 ~. W P - 1 . 2 BTSE-5 ¢WP-1.3 vTSE-5AG) WP-1.4 ¢WP-1.5 400 ~-vTSE-6 OPTSE-lm WP-1.6 OPTSE-2A WP-1.7 ~KIR J WP-1.8

..r (3 ::) O 13O0 I-u~ u,I n-

I

r

I ~,1

I

tam, A qD

--

a, 4 ~_e~. o [] oqk4¢ _v • " ~ P m, X

--

oCyO

~ 200 o

100

0 -40

1 -20

1

I

0

20

I

I

1

I

I

40 60 8 0 100 1 2 0 T-RTNo T (oc)

I 140

160

Fig. 7. A comparison of large specimen test results with fixed-load, generation-mode dynamic analysis crack-arrest toughness results for HSST wide-plate tests. Note that HSST wide-plate test results have not been adjusted to account for tunneling effects.

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D.J. Naus et al. CONCLUSIONS

The Heavy-Section Steel Technology (HSST) Program on O R N L under United States Nuclear Regulatory Commission sponsorship has an integrated effort under way to extend the range o f applicability o f current state-of-the-art crack-arrest practices and to develop alternatives where improvements are needed. A consistent trend is formed when the crackarrest data now available from the three types of HSST large-specimen tests are combined on a plot o f K~o versus T - R T N o r. Collectively, these data, along with other large-specimen test results, show that arrest can and does occur at temperatures up to and above that which corresponds to the onset o f Charpy upper-shelf behavior, and the measured gla values extend above the limit included in section XI of the A S M E Code. Further, the data suggest the existence of a limiting temperature above which a cleavage crack cannot propagate. In summary, the data being obtained under an HSST wide-plate crack-arrest program support: (1) the use of fracture-mechanics concepts to analyze cleavage run-arrest events; (2) the treatment of cleavage and ductilefracture modes as separate events; and (3) the fact that cleavage arrest can occur at toughness levels well above the A S M E limit.

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