ESTIMATION OF FRACTURE TOUGHNESS ANDCRITICAL CRACK LENGTH OF ZrRCALOY PRESSURE TUBE

FROM RING TENSION TESTby

S. Chatterjee, S. Anantharaman, K.. S. Batakrislman and H. K. SriharshaRadiometallurgy Division

1999

BARC/1999/E/025

$ GOVERNMENT OF INDIA£ ATOMIC ENERGY COMMISSION

I

ESTIMATION OF FRACTURE TOUGHNESS AND

CRITICAL CRACK LENGTH OF ZERCALOY PRESSURE TUBE

FROM RING TENSION TEST

by

S. Chatterjee, S. Anantharaman, K.S. Balakrishnan and H.K. Sriharsha

Radiometallurgy Division

BHABHA ATOMIC RESEARCH CENTREMUMBAI, INDIA

1999

BARC/1999/E/025

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BARC External

Technical Report

BARC/1999/E/025

Estimation of fracture toughness and critical crack length of zircalo)pressure tube from ring tension test

21 p., 2 figs., 8 tabs.

S. Chatterjee; S. Anantharaman; K.S. Balakrishnan;H.K. Sriharsha

Radiometallurgy Division, Bhabha Atomic Research Centre,Mumbai

Bhabha Atomic Research Centre, Mumbai • 400 085

Radiometallurgy Division,BARC, Mumbai

Department of Atomic Energy

Government

Contd... (ii)-l-

30 Date of submission: August 1999

31 Publication/Issue date: September 1999

40 Publisher/Distributor: Head, Library and Information Services Division,

Bhabha Atomic Research Centre, Mumbai

42 Form of distribution: Hard copy

50 Language of text: English

51 Language of summary: English

52 No. of references: 5 refs.

53 Gives data on :

Abstract: Transverse fracture toughness data of zircaloy pressure tubes are needed for assuring leak-before-break, if any, during their in-reactor residence. These data are conventionally computed fromburst tests and/or using compact tension specimens. A study was undertaken to derive fracturetoughness of zircaloy in the temperature range ambient to 300 °C, from the transverse tensile properties.The fracture toughness properties so derived were used to estimate the values of critical crack lengthof zircaloy pressure tubes in the above temperature range.

70 Keywords/Descriptors: PHWRTYPE REACTORS; ZIRCALOY 2; PRESSURE TUBES;

FRACTURE PROPERTIES; CRACKS; TENSILE PROPERTIES; TEMPERATURE RANGE

0400-1000 K; LEAKS; TESTING

71 INIS Subject Category: E3400; B223O

99 Supplementary elements :

-it-

Estimation of Fracture Toughness and Critical Crack Length of ZircaloyPressure Tube from Ring Tension Test

S.Chatteijee, S.Anantharaman, K.S.Balakrishnan and H.K.SriharshaRadiometallurgy Division

Bhabha Atomic Research Centre, Mumbai - 400085

ABSTRACT

Transverse fracture toughness data of zircaloy pressure tubes are needed for assuringleak-before-break, if any, during their in-reactor residence. These data areconventionally computed from burst tests and/or using compact tension specimens. Astudy was undertaken to derive fracture toughness of zircaloy in the temperature rangeambient to 300 °Cy from the transverse tensile properties. The fracture toughnessproperties so derived were used to estimate the values of critical crack length of zircaloypressure tubes in the above temperature range.

KEYWORDS

ring tension test, transverse tensile properties, fracture toughness, critical crack length,Zircaloy-2, curved compact tension test specimen.

NOMENCLATURE

2aCCTbESv

s fSH

P

n

Kic

Jic

Kjicexpt

Kjjcest

Jic,est

Jmax3T,est

Jmax

critical crack lengthcurved compact tensionremaining ligament length of CCT specimenYoung's modulusyield strengthfracture stresshoop stresscorrelation coefficientj3 from intercomparison of CCT specimen and ring tension test results onZirconium alloysstrain hardening exponenttrue fracture strainfracture toughnessinitiation fracture toughness from CCT specimensK value derived using JicK value estimated from ring tension testJiC derived from Kjic>estJmax estimated from burst testmaximum load fracture toughness

Jmax,ccT maximum load fracture toughness from J-R curve of CCT specimensmaximum load fracture toughness from burst testingestimated value of maximum load fracture toughness for burst test

M Folias factor

1.0 INTRODUCTION :

During late sixties and mid-seventies, when fracture toughness was determinedusing Kic specimens, a number of attempts had been made to calculate K[C values frommore easily measurable mechanical properties. Among the various such methods, the onedeveloped by Hahn and Rosenfield[1] is very much worthy of consideration. It wasestablished mostly at ambient temperature, on materials having widely varying mechanicalproperties and fracture toughness values. The materials studied were aluminium alloysand steels (which are isotropic), and Titanium alloys (which are anisotropic). The Kicvalues of these materials were estimated from their corresponding tensile properties:elastic modulus, yield strength, strain hardening exponent and fracture ductility. Theestimated Kic values were found to be within ± 30% of the corresponding values obtainedfrom the Kic tests done with standard specimens following the procedures of ASTMdesignation E399. The following correlation was used for the estimation of fracturetoughness :

—(1)where,

Kic = Fracture toughness in ksWinE = Young's modulus in ksiSy = Yield strength in ksiGf = True fracture strainn = Strain hardening exponentfj = Correlation coefficient = ^2/^3 (=0.82)

The above correlation did not include the effect of test temperatures and was notapplied to Zirconium alloys. However, the study had included Titanium alloys havingcrystal structure identical to that of Zirconium. Hence, it was envisaged that a similarapproach could be attempted for Zirconium alloys also. With this view in mind, a studywas undertaken to evaluate the applicability of the above correlation with regard toderiving fracture toughness of Zirconium alloys like Zircaloy-2 and Zr-2.5 Nb, at suitabletest temperatures ranging from ambient to 300"C.

2.0 APPROACH :

2.1 Evaluation of the correlation coefficient((3gr):

Transverse tensile properties were obtained from tension testing of rings attemperatures from ambient to 300°C. Curved Compact Tension (CCT) specimens were

also tested at ambient temperature and at 300°C. Stressing in the circumferential directionwas adopted so as to bring about crack propagation in the longitudinal direction, similar tothe direction of crack propagation in CCT specimens. J-R curves were obtained usingmultispecimen test method as per ASTM E-813-81 standard. The pressure tube materialswere Zircaloy-2 and Zr-2.5% Nb in unirradiated condition. Fig. 1 gives the relevant details'of the procedure followed. As KJic (KjiC>expt) obtained from J-R curves at ambienttemperature tests and 30G°C tests was same, it was also used as the KjjC value at alltemperatures upto 300°C. The Pzr values were obtained from the intercomparison of thetransverse tensile properties obtained from ring tension test, and the correspondingfracture toughness, KJiCiCXpt obtained from testing of CCT specimens.

The Pzr values established for Zircaloy-2 at these temperatures could be used forthe estimation of fracture toughness (Kjic>cst), from ring tension tests, of Zirconium alloycomponents at these temperatures using equation (1).

2.2 Estimation of fracture toughness of pressure tubes:

Zirconium alloys with nominal hydrogen content, and toughness in the region ofupper shelf, are capable of accommodating a large amount of slow stable crack growthunder increasing loads. Hence, JJC gives extremely conservative values for evaluating themaximum pressure the pressure tube is able to sustain. Therefore J value at somedesignated amount of stable crack growth will be a more realistic measure of fracturetoughness, rather than Jic itself.

The maximum load carrying capacity is best derived from imax^i (value of J at themaximum load as obtained from burst test). It has been reported'21 that J ^ obtained fromfracture toughness test using CCT specimens (Jmax,ccT) would always be a conservativeestimate of Jmax r- It has also been reported12' that in such cases, Jma ccr can be scaled upto Jmax T by using the scaling factor (-/2rm / b), where rro is the mean radius of the

pressure tube and b is the remaining ligament length of the CCT specimen. As Jmax,cciwould always be greater than or equal to the corresponding Jic, maximum load fracturetoughness can be expressed as:

"-(2)

where fc = Jic obtained using CCT specimens~ JicRT.est estimated from ring tension tests and

- estimated value of Jmax for burst test

2.3 Estimation of Critical Crack LengtMCCL):

The axial CCL for the pressure tube was estimated by finding the value of thesemi-crack length, a, which satisfies Eq.(3), recommended by Keifher et.al.,f3] withJ-Jmax3T,est at the hoop stress corresponding to the reactor operating pressure.

SaS 2

j _ ——In7tE

SecnMSH

2Sf

where,2a = axial CCLSf = flow stress from ring tension test = (Sy + Strrs)/2M - Folias factor =V [l+(a2/t.r)jSH = Pd/2t, the applied Hoop stressP = the reactor operating pressured = 2r = the diameter of the pressure tubet = the wall thickness of the pressure tube

3.0 RESULTS :

3.1 Fracture Toughness Evaluated from CCT Specimens:

3.1.1 Ambient Temperature:Tables 1 and 2 give the ambient temperature fracture toughness J^a^ of unirradiated

Zircaloy-2 and Zr-2.5%Nb evaluated experimentally from CCT specimens fabricated from fullthickness (4 mm for Zircaioy-2 and 3.5 mm for Zr-2.5%Nb) pressure tube sections. The respectiveKKC values were calculated using the correlation Knc

2 = Jic E.

3.1.2 Elevated Temperature:Tables 3 and 4 give the fracture toughness Jic.expt evaluated at 300 °C using CCT specimen

fabricated from the same Zircaloy and Zr-2.5%Nb pressure tubes.

3.2 Fracture Toughness Estimated from Transverse Tensile Properties.

3.2.1 Evaluation of correlation coefficient constant (fi/r):

Table 5 gives the P& values obtained on Zirconium alloys tested between ambienttemperature and 300°C. The experimentally obtained tensile properties (Sy, £f and n) andKJic values calculated (in Tables 1-4) are also depicted in Table 2. These values are usedfor computing P&. It can be seen that over the temperature range of the tests, P& valuesshowed a distinct trend and were nearly same for the two alloys at identical temperatures.In the temperature range from ambient to 175°C, it varied between 0.75 and 1.21 with0.95 as the mean value, and it can be said with 97.5% confidence that the P value wasabove 0.87. However the mean value of Pzr at ambient temperature was 0.86, which wasvery close to those reported [1J for aluminum and titanium alloys and steels. Similarly,between 200°C to 300°C, the value of pzr varied between 1.83 and 2.48, with 2.1 as themean value, and it can be said with 97.5% confidence that P& value was above 1.93.

These p& values of 0.87 and 1.93 in the temperature ranges of ambient to 175°C,and 200°C to 300°C respectively, have been used to evaluate Kjjc for Zircaloy pressuretube using Eq.(l).

3.2.2 Estimation of fracture toughness ambient temperature:

Table 6 gives the estimated ambient temperature Kjicest of these alloys from ringtension test using Eq.(l). The estimated values of KjiC were within ±15% for Zircaloy-2and within ±18% for Zr-2.5%Nb, of the experimentally obtained values on CCTspecimens. As compared to the average of experimental KjiC values obtained from CCTspecimens, the average value of Kjic,est was within 3% for Zircaloy-2. Similar results wereobtained in the case of Zr-2.5%Nb alloy.

3.2.3 Estimation of fracture toughness at elevated temperature:

The fracture toughness estimated from ring tension tests carried out at 300°C forZircaloy-2 and Zr-2.5%Nb are given in Table 7. The estimated values of average K^cstwere within ±15% of the experimental value for both these alloys.

4.0 DISCUSSION :

4.1 Fracture toughness:

The origin of the equation (1) evolves from the following equation in fracturemechanicsfl]:

K2 oc ( e f E L S y ) — ( 4 )

where L is the calculated plastic zone width. L has been substituted by n2 on the basis ofexperimental evidence established on aluminium alloys, titanium alloys and steels.

The region ahead of the crack tip can be considered to be made up of gaugelengths of a series of small tension test specimens. The crack extends under monotonicloading by fracturing these specimens. Hence, it is possible to say that the local strain atthe crack tip at the initiation of crack growth is proportional to the strain at fracture in anormal tension test specimen. Hence the utilization of a correlation coefficient (5 inequation (1) which relates the material fracture toughness to the parameters obtained in anormal tension test, is justified.

The thermomechanical treatmentsfl] that result in an increase in yield strength(Sy) bring about corresponding decrease in fracture ductility (ef) and strain hardeningexponent (n). Such treatments bring about decrease in the fracture toughness KK. Thesechanges in fracture toughness could be predicted for heat treated 4340 steels usingequation (1) with (5 as 0.82. However, at the higher test temperature of 300°C, forZirconium alloys the lower Sy is associated with a decrease in n and an increase in€f,(Tables 6 and 7). For such cases equation (1) can still be expected to hold good, as it is

based on the more basic equation (4) which can be related to the deformation zone in thevicinity of the crack tip. For such cases, the proportionality constant p will change. Thisjustifies the increase of the mean value of P from 0.87 to 1.93 with an for the increase oftest temperature from ambient to 300°C for Zirconium alloys.

Comparison of fracture toughness estimated from the ring tension test results andthose obtained from the tests on CCT specimens at 300°C on unirradiated Zircaloy-2 andZr-2.5%Nb confirms that Eq. (1) is applicable with 0=1.93. This is inspite of the feet thatbetween Zircaloy-2 and Zr-2.5%Nb, the variations in S,, n and ef are by factors of 1.5,1.75 and 1.5 respectively, and Knc^t varying by a factor of 1.8 (Table 7).

However, as has been illustrated already, analysis of p values over a wider testtemperature range from ambient to 300°C, has yielded values of 0.87 and 1.93 forestimating Kj;c in the temperature ranges from ambient to 175°C, and from 200°C to300°C respectively. Fracture toughness valuesCKjicest) of Zircaloy pressure tube soestimated are depicted in Fig.2(a).

It may be mentioned that the CCT specimens used in the tests had in-planedimensions proportional to standard compact tension specimens,. However the specimenthickness being only wall thickness of the pressure tube, it violated the requirements ofplane strain. Even then, in these specimens the plastic zone size ahead of the crack tip wassmall with respect to the remaining ligament length (W-a,,). The (J,Aa) data depicted inTables 1-4 were evaluated with respect to criteria Aa < 0.07 (W-a,,) and J < (W-a)dJ ofHutchinson et.al.,14' and 10 da

J < (Smg + Sy). (W-a) of ASTM E-l 152 standard {5l Only (J,Aa) points which did not2 20

exceed limits on Aa, and satisfied either of the two limits on J were considered forevaluating fracture toughness Jjc, representative of the wall thickness of the tube.

4.2 Critical Crack Length:

The fracture toughness Kic does not correspond to unstable failure for ductilespecimens. It is evaluated by the R-Curve approach to give credit for the ability of thematerial to toughen during the stable crack growth. Thus ideally the CCL for the ductileconditions is to be evaluated by finding the point of tangency between the JR curvegenerated by conducting burst test, and the crack driving force (CDF) curve as defined bythe equation (3) for the pressure tube for different crack lengths at the reactor operatingpressure. Fig. 2(b) depicts CCL estimated. However, the value of the semi-crack length a,satisfying the above equation with J equal to Jmax would also give sufficientlyrepresentative CCL values.

The fracture process is said to be J-controlled when it is independent of size,geometry and initial crack length of the specimen. Thus the JR curves of CCT specimensand the burst test specimens would give similar results only in the J-controlled regime

which include JjC values. Beyond the J controlled regime, the results obtained on the CCTspecimens tend to be conservative121. The Jmax (the value of J on the JR curvecorresponding to the maximum load on the load versus load line displacement record forthe burst specimen) being beyond J-controlled regime, the J-R curve obtained from CCTspecimens needs to be scaled up by a factor {^2rm I b). For Indian 220 MWe pressurisedheavy water reactors(PHWR), using Zircaloy-2 pressure tubes, the scaling factor works

out typically as 2.8 j =

The CCL values as depicted in Fig.2(b) used scaled up values of Jic, obtained fromCCT specimens instead of the corresponding 1 ,^ to obtain Jmax.BT,**, the estimate of Jmaxof burst test. Table 8 gives the input data utilised for the estimation of CCL. As illustratedin Tables 6 and 7, J,c values could have been overpredicted typically upto 8%. Theoverpredicted values however would be unlikely to approach the corresponding J ^values. Therefore, since values of Jmaxj3T,est are likely to be conservative, the CCL values inFig.2 are also likely to be conservative.

4.3 Estimation of Fracture Toughness(Kjig) of reactor operated pressure tubes:

The variations in tensile properties in 4340 steel as mentioned earlier, follow thedistinct pattern i.e. increase in Sy is associated with decreases in €f and n, and isaccompanied by reduction in KiC. During in-reactor residence, the Zircaloy-2 pressuretubes experience fast neutron flux and deuterium pick-up causing hydriding of the tubes.As neutron irradiation and hydriding of the tubes bring about exactly similar variations intensile properties and KiC, as in 4340 steel, the value of (5 for the irradiated and hydridedmaterial is expected to be same as that for the unirradiated and unhydrided material. Thusit is expected that Eq. 1 would be able to predict KjiC of the reactor operated pressure tubesin the temperature range ambient to 300°C.

S.0 CONCLUSIONS:

The ring tension test method is a simple method which is proposed for the estimation ofthe transverse fracture toughness and hence the critical crack length of Zircaloy-2 pressuretubes, in situations where a similar estimation using curved compact tension specimensand burst tests are difficult.

6.0 REFERENCES :

1. Hahn, G.T. and Rosenfield, A.R., "Sources of Fracture Toughness: The Relationbetween KJC and the Ordinary Tensile Properties of Metals," ASTM STP 432,1968.

2. Davies, P.H. and Shewfelt, R.S.W., "Link Between the Results of Small-and-Large-Scale Toughness Tests on Irradiated Zr-2.5%Nb Pressure Tube Material", ASTMSTP 1196, 1996.

3. Keifher, IF . , Maxey, W.A., Eiber, RJ., and Duffy, A.R., "Progress in Flaw Growth aFracture Toughness Testing", ASTM STP 536,1973.

4. Hutchinson, J.W., and Paris, P.C., "Stability Analysis of J-Controlled crack Growth",ASTM STP 668, 1979.

5. Anon, "Standard Test Method for Determining J-R Curves", ASTM Designation E1152-87.

8

SLNo.1.2.3.4.5.6.7.8.9.10.

mm14.8715.3615.5216.1114.6414.8315.9913.9416.0414.65

W-aomm11.0510.4310.429.8310.9811.159.9811.989.9711.29

Bmm

4

a/W

0.570.600.600.620.570.570.620.540.620.56

UkN-mm

2.762.523.574.022.962.803.502.121.131.16

JkJ/m2

1391341892251501401931007257

Aamm1.210.970.820.790.530.500.450.230.110.10

Sp. No.

02121101060405080310

Linear regression equation : J = 184 Aa + 56r = 0.89

Blunting line equation: J = 1400 AaJic = 65 kJ/m2

= 80 MPaVm (74 ksWia)

Table 1 J (Aa) data points Evaluation of JJC and iusing curved compact tension specimens

of Zircaloy-2 at ambient temperature

SI.No.1.2.3.4.5.6.

a0

mm15.2114.9515.5914.4414.9314.69

W-aomm10.7410.9710.3211.5510.9911.31

Bmm

3.5

a/W

0.590.580.600.560.580.57

UkN-mm

6.335.874.834.853.503.33

JkJ/m2

374340296268202188

Aamm0.770.700.520.490.350.33

Sp. No.

ZN-1ZN-11ZN-2ZN-13ZN-12ZN-14

Linear regression equation : J = 412 Aa + 62

r = 0.99

Blunting line equation : J = 1493 Aa

Jic = 86 kJ/m2

Kjice.pt = 91 MPaVm (KksiVin)

Table 2 J (Aa) data points. Evaluation of Jic and KjiCjOXpt of Zr-2.5%Nb at ambient temperatureusing curved compact tension specimens

10

SLNo.

1.2.3.4.5.6.7.8.

. 9.

a0mm14.4314.8014.1914.7914.9014.4214.8514.3514.64

W-a0

mm11.7311.3011.7711.6011.4311.7211.3411.8511.72

Bmm

4

a/W

0.550.570.550.560.570.550.570.550.56

UkN-mm

4.095.105.493.943.933.153.012.371.78

Jkj/m2

19525226119019215114811285

Aamm0.760.690.600.540.510.480.300.290.13

Sp, No.

B4BIOB2

B12B9B8BllB6B5

Linear regression equation : J = 246 Aa + 58

r = 0.85

Blunting line equation : J = 800 Aa

Jic=84kJ/m2

Kjsce.pt = 81 MPaVm (75 ksiVin)

Table 3 J ( Aa) data points. Evaluation of JiC and KjiC(expt of Zircaloy-2 at 300°C using curvedcompact tension specimens

11

SI.No.1.2.3.4.5.6.7.

aomm14.1314.8715.0416.4815.1015.4415.65

W-aomm10.9210.8911.229.5110.7810.5610.50

Bmm

3.5

a/W

0.560.580.570.630.580.590.60

UkN-mm

6.986.897.254.745.704.913.61

JkJ/m2

408402411313336295217

Aamm0.560.430.400.350.330.280.15

Sp. No.

ZN-3ZN-7ZN-8ZN-5ZN-10ZN-6ZN-4

Linear regression equation :J = 517Aa+158r = 0.91

Blunting line equation : J = 1140 Aa

Jic = 289 kJ/m2

Kiice^ = 151 MPaVm (139 ksWin)

Table 4 J ( Aa) data points. Evaluation of Jic and KJic,cxp» of Zr-2.5% Nb at 300°C usingcurved compact tension specimens

12

SI.No.

l.

2.

3.

4.

5.

6.

7.

Temp.°C

Ambient

100

150

175

200

250

300

Eksi

14000

13000

12800

12500

12000

11800

11500

SY

ksi

90878186656462656360624242657261636859565859

IS

Zircaloy-2

0.670.560.710.640.930.950.940.961.041.031.051.021.030.850.780.870.840.961.071.030.980.97

0.090.110.110.090.070.050.080.070.080.080.090.120.100.050.050.040.050.040.040.050.040.05

Kjic,exptksiVin

74

75

75

75

75

75

75

P &

0.890.800.750.931.211.691.081.191.021.050.910.851.021.851.832.341.902.142.171.882.271.97

Sp. No.

l2343130323341424335346713141559316

Zr-2.5%Nb

8.

9.

Ambient

300

14000

11500

96109113103827882

0.530.790.760.871.331.451.17

0.130.080.100.070.050.060.07

83

139

0.760.950.761.062.482.031.89

ZN-2ZN-5ZN-6ZN-7ZN-1ZN-3ZN-4

Table 5 Evaluation of correlation coefficient constant Pzr of Zirconium Alloy

13

SLNo.

1.

Eksi

14000

SY

ksi*

Zircaloy-2

90878186

0.670.560.710.64

0.87

ksiVin

74

Average

ksiVin

72 (-3)80 (+8)85 (+15)69 (-7)76 (+3)

Sp.No.

1234

Zr-2.5%Nb

2. 1400096109113103

0.530.790.760.87

0.87 83

Average

94 (+14)76 (-8)

95 (+15)68 (-18)83(0)

ZN-2ZN-5ZN-6ZN-7

Note:= 0.87(ESyefn

2)2vl/2

100

: Kjic derived from JiC obtained from curved CT specimenK/ic estimated from transverse tensile properties

Table 6 Estimation of Kjic>cst of Zircaloy-2 and Zr-2.5%Nb at ambient temperature from thering tension test results using (}& =0.87

14

SI.No.

1.

2.

Eksi

11500

11500

SYksi

55565859

827882

i

n

ZircaIoy-2

0.981.030.980.97

0.091.030.040.05

1.93

Average

Zr-2.5%Nb

1.331.451.17

0.050.060.07

1.93

\verage

KjJcexpt

ksiVin

75

139

Kjic,««(A%)ksiVin

131 (+75)77 (+3)64 (-15)73 (-3)86(15)

104 (-25)129 (-7)146 (+5)

, 126(-9)

Sp.No.

159316

ZN-1ZN-3ZN-4

Note:

. Kjjc estimated from transverse tensile properties

• K|jC estimated from Jic obtained from curved CT specimen

= 1.93(ESy£fn2)

= (Klicrest - Kjjc. exnt)

2 ) 1 / 2

Estimation of K,ic of Zircaloy-2 and Zr-2.5%Nb at 300°C from ringtension test results using fa, =1.93

15

SI.No.

1.

2.

3.

4.

5.

6.

7.

Temp.°C

Ambient

100

150

175

200

250

300

Eksi

14000

13000

12800

12500

12000

11800

11500

s fksi

Kjjc>est

ksWin

Zircaloy-2

102102102101716868706966685047657261636859586061

72798669543961556462717664797962766867796278

JniMjBT.est

kJ/m2

18221925916611057139114156147196229161252257155242191185264166262

CCLmm

79848876634967636967746861

777966757168746675

Sp. No.

1234

3130323341424335346713141559316

Table 8 Estimation of critical crack length for Zircaloy-2 pressure tube of4mm thickness and 82.5mm ID under hoop stress of 110 MPausing Kjic>est obtained from ring tensile test results and suitably scaledValues Of Jmax,BT,est

16

EVALUATION OF FRACTURE TOUGHNESS OF PHWR PRESSURETUBES AT RMD, BARC

PRESSURE TUBEBLANK Wall thtcB;

Curved CT(mu!tispecfmen){ASTM E-813)

d ^ J Milling n^

31.2

IN mm)

•+•

,,32,5 ,

rj<-FPC

8 0.55—0.65

Testing

.J - A./(ao/w)Btw-ao)

Heat Tinting

crack

'ic J-R Curvo

Ring Tension Test

(8Nmu)

p

M M )

>

r

when KjC is in ksi V. fTY and E in ksi

Hahneta! ASTM-STP-432(1968) 5-32

Fiy. 1

-17-

00

oTEMPERATURE C

ss

CC

L r

8 0 -

6 0 -

4 0 -

2 0 --

0 -

o

o8

(b)

O0

O

9 1

o8 o

o

8

o

1

o 8

o

CCL = 50mm

• i " i •0 50 100 150 200 250 300 350

TEMPERATURE °C

Fig. 2 Variation of (a) KJicest and (b) CCL with temperature

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Published by: Dr. Vijai Kumar, Head Library & Information Services DivisionBhabha Atomic Research Centre, Mumbai - 400 085, India.