Fracture Toughness of A516 Gr70

KSME International Journal, VoL 14, No. J, pp. lJ-J8.2000 Effect of Temperature on the Fracture Toughness of A516 Gr70 Steel Chang-Sung Seok* (Sungkyunkwan University) Fracture toughness HC and KIC tests were performed on ASI6 Or70 carbon steel plate at the temperature ranging from -160'C to 600'C, and test results were analyzed according to ASTM E 813 and ASTM E 399. Unloading compliance J-integral tests were performed on ITCT specimens. The relation between the J Ie value and the test temperature was obtained. It was concluded that the temperature ranging from -IS'C to 600'C is the upper shelf region of ductile-brittle transition temperature, and in this temperature range, fracture toughness J re values decreased with increasing temperature. The ductile brittle transition temperature of the material may be around -30·C. In the region near -30'C, the tendency of J Ie to decrease with decreasing temperature was significant. Key Words: J-Integral, Fracture Toughness, Temperature Effect, DBTT 11 1. Introduction Elastic-plastic fracture toughness, J Ie can be used as an effective design criterion in nuclear and thermal steam rising systems. Most of these systems are operated at high temperature and J re values are affected by temperature. (Mills, 1987 ; Jung and Murty, 1988) Therefore, the J re values at high temperature must be determined for the use of integrity evaluation and designing of such systems. The ductile brittle transinon temperature (DBTT) has long been used in the design of steel construction. The material must be chosen so that its transition temperature is low enough in com- parison with the minimum service temperature, the difference being a function of the degree of safety which is tolerated. Therefore, the DBTT must be determined for designing of mechanical constructions. (Francois, 1986) With the advance- • Corresponding Author, E-mail: [email protected] TEL: +82-331-290-7477; FAX: +82-331-290-7482 Dept. of Mechanical Engineering, Sungkyunkwan University, 300 Chunchun-dong, Jangan-gu, Suwon Kyonggi-do 440-746, Korea. (Manuscript Received February 27, 1999; Revised October 7, 1999) ment of the J-integral(Rice, 1968) elastic plastic fracture mechanics, it has become possible to develop transition temperature data in terms of the J IC fracture toughness parameter which defines the upper shelf toughness as well as the lower shelf and transitional toughness values. (Joyce and Hasson, 1980) The objective of this paper is to investigate the effect of temperature on the elastic-plastic frac- ture toughness J re and K le in ASI6 Or70 steel. The fracture tests were performed at temperature ranging from - 160'C to 600'C according to ASTM E 399(1996) and ASTM E 813(1996). 2. Fracture Toughness Test 2.1 Specimens The ASI6 Or70 carbon steel plate supplied in the normalized condition has been used extensive- ly in nuclear vessel applications. The chemical composition and mechanical properties are shown in Table I and Table 2, respectively. Figures I and 2 show the dimensions and orientation of the test specimens. All specimens configurations were ASTM standard compact tension (CT) type, with the pin hole of 0.2S W and 0.187S W where 'W' is the specimen width. 12 Chang-Sung Seok Table 1 Chemical composition of A516 Or70 (wt %) C Si Mn P S Mo AI Ni V 0.21 0.24 1.07 0.013 0.004 0.06 0.035 0.20 0.38 Table 2 Mechanical prperties of A516 Or70 In ~ _._f- SO.8 U'l ~ _._. Fig. 2 Orientation of specimen 2.2 Test procedure Fracture toughness tests were performed fol- lowing ASTM E813 test procedure at tempera- tures ranging from -160·C to 600·C which covers the ductile-to-brittle transition as well as upper shelf regimes. Load line displacements were measured by a COD gage (Instron Ltd. Catalog No. 2670-116) for a temperature range of - 160·C ~ T ~ lOO·C and by a high temperature extensometer (Instron Ltd. Catalog No. 2632- 001) for 20·C~ T ~ 6 0 0 · C . Usually, the load line displacement is measured by a high temperature COD gage in an environmental chamber for high temperature llc test. In this paper, high tempera- ture llc tests were performed with a high tempera- ture extensometer in a split furnace. Temperature control was achieved by enclosing the specimen in an electrically heated split furnace and mount- ing a thermocouple nearby the crack tip of the specimen. In all cases, temperatures were controlled to better than ± I·C with self-adaptive temperature controllers. A high temperature extensometer was mounted on the crack mouth at the load line of the speci- men as shown in Fig. 3, and held in position by a set of springs. Tests were also performed with the COD gage at 20·C and lOO·C. Figure 4 shows the schematic diagram of the high temperature HC testing system. To observe the ductile brittle transition temper- ature behavior, fracture toughness llc and K lc tests were performed at the temperature range of -160·C to 20·C. The specimen temperature was controlled by liquid nitrogen below the room temperature in an environmental chamber. Figure 5 shows the schematic diagram of the low temper- ature fracture toughness testing system. After fatigue precracking at room temperature, unit:mm unit:mm 63 (a) Specimen for COD gage (b) Specimen for high temperature extensometer Fig. 1 Dimension of CT specimen Temperature Tensile Strength Yield Strength Elongation(%) rc: (MPa) (MPa) -30 628 451 18 -15 618 422 20 0 618 412 19 10 598 402 20 20 569 383 22 100 559 373 26 200 549 373 29 300 540 363 31 400 579 363 27 500 520 304 34 600 441 265 37 Specimens were notched to an initial ajW ratio of 0.5 and precracked to a crack length of approxi- mately ajW=0.6 where 'a' is the crack length. Effect of Temperature on the Fracture Toughness of A516 Gr70 Steel 13 all tests were performed in stroke control on dynamic universal testing machine at test tempera- ture. The test loading was regularly interrupted by 10% unloadings(Smith and Doig, 1986; Neal and Priest, 1986) and autographic records ofload versus load-line displacement were obtained. At the end of each test, specimens were completely unloaded, heat-tinted at about 300'C for 10 minutes and broken open. The fatigue crack length and final crack extension were measured directly from the fractured surface. All procedures HIGH dWPERATlm oj ENSG'1ETER K " SPECIMEN I' Il. 01 Fig. 3 Measurement of load-line displacement with high temperature extensometer Fig. 4 Schematic diagram of high temperature J,e testing system of tests and reductions were carried out in accor- dance with the ASTM E 813 and ASTM E 399. 2.3 Test results Test results with the high temperature exten- someter at temperatures ranging from 20'C to 600'C are as shown in Figs. 6-12. Results with the COD gage at -15'C, O'C, 20'C and IOO'C are as shown in Fig. 13-16. Table 3 shows J le values and constants C, and C 2 of R-curves [J= C,(t.a) C2] obtained from the test. At temperature ranging from -160'C to -30'C, all specimens fractured in a brittle man- ners during loading without stable crack exten- sion. In these cases, the areas (A) under the P-o curves were determined from which the J Q was calculated (ASTM E 813), (I) where b is the remaining ligament. 500 <400 i' 380 zoo -\ Te.p. : 10'C 1110 J,< : 114 kN/. o I Z 3 CRACKEXTENSIONI_I Fig. 6 J-,1a curve for A516Gr70 steel with high temperature extensometer at 20'C Fig. 5 Schematic diagram of low temperature testing system 500 408 I 380 1110 -\ 100 • Fig. 7 o Temp. : 100'C J,< : 103 kN/m o 1 1 CRACKEXTENSIONI_I J-,1a curve for A516 Gr70 steel with high temperature extensometer at lOO'C 14 Chang-Sung Seok 580 500 400 40Q I 300 I 300 ~ 0 ~ 1:1 1:1 ~ 100 101 100 ~ T••p. , 108·C .:, 100 100 J,e , 91 tNt. a 0 0 1 1 3 CRACKItXTINSIONl-l o T••p. : 500·C J,e: 85 kNt.. 1 1 3 CRACKItXTINSION<-l Fig. 8 J - ~ a curve for A516 Or70 steel with high temperature extensometer at 200·C Fig. 11 J - ~ a curve for A5l6 Or70 Steel with high temperature extensometer at 500·C 5OOr----r--n--------,----, 400 I 34MI ~ ~ 0 .:, Te..p. : 600·C J ,e , 80 tNt. 0 0 1 1 3 CRACKEXTENSION (....l Fig. 12 J - ~ a curve for A516 Or70 steel with high temperature extensometer at 600·C o T••p.: 300·C J,e: 9. tNt.. 400 o I 300 I ~ 100 o 1 1 3 CRACKItXTINSIONl-l Fig. 9 J - ~ a curve for A516 Or70 steel with high temperature extensometer at 300·C 580 r----r""TT"------.,----.... 5OOr----r-rr------,------, 1 1 CRACKEXTENSIONl-l 8 500 400 I 300 ~ ~ 100 Te..p. : -15·C 180 J,c: 113 tNt.. Fig. 13 J - ~ a curve for A5l6 Or70 steel with COD gage at -15·C tion at maximum load. J (K Q ) values were then calculated from K Q values using the following conversion equation. (Rice, 1968) 3 o o T••p. : 400·C J,e: ,. tNt. 400 1 1 CRACKEX'1'I'.NSIONl-l Fig. 10 J - ~ a curve for A516 Or70 steel with high temperature extensometer at 400·C Results of the fracture toughness parameter J IC versus the temperature are summarized in Table 4. For the tests at temperatures ranging from -IOO·C to -30·C, the specimens were broken after some ductile deformation. However, for the -130·C, -140·C, -150·C and -160·C tests, brittle fracture occurred without ductile deforma- Effect of Temperature on the Fracture Toughness of A516 Gr70 Steel 15 500 4811 I 380 I 100 Te.p. : O'C 108 J,c: 118 kN/. I 1 1 3 CRACKEXTENSIONe.m) Fig. 14 J-l!.a curve for A516 Gr70 steel with COD gage at O'C 150 119 ~ l i l a I e e 90 0 0 o ~ 60 ElWIlH COD GAGE .. 30 (;)WITH HIGH TEMPERATURE EXTENSOMETER 9 9 100 ZOO 300 400 500 600 TEMPERATURE ("C) Fig. 17 The effect of temperature on the lIe of the upper shelf region of DBTT (3) flc=-O.06T+ 115 where T is the temperature ['C], and J rc is the elastic-plastic fracture toughness[kN/m]. It may be recognized in this study that the temperature ranging from - IS'C to 600'C was the upper shelf region of ductile-brittle transition temperature. The constants C\ and C z of R-curve [j = C, ( L ~ a ) C,] are shown in Table 3, and J rc values might be affected by the C\ and Cz(Ross and Eisele, 1988). It is noted that C\ decreases with the test tem- perature very similar to J IC while C, slightly increases initially reaching essentially a constant 3. Discussion Experimental results show that the load-line displacement can be measured successfully by the high temperature extensometer. Figs. 6, 15, and also Figs. 7, 16 are the Jrc test results for the same temperature of 20'C and lOO'C, respectively, but the different load line displacement sensor. That is Figs. 5 and 6 are obtained with the high temper- ature extensometer while Figs. 15 and 16 with the COD gage. The J,c values and R-curves deter- mined by the high temperature extensometer well agreed with those determined by the COD gage at that temperatures. Figure 17 shows that the elastic plastic fracture toughness, J rc values at the upper shelf region of ductile-brittle transition temperature (DBTT) de- creased with increasing temperature. The J IC value and the test temperature can be correlated as follows: 3 (2) Te.p. : 100'C J. c : 103 kN/. 1 Z CRACKEXTENSION <mm> o 4811 I 308 ~ ~ ! 100 Te.p. : lO'C 101 J,c : 118 kN/m 400 o 500..---.....,....,.,...-------,------, 5OO,..---r-rr--------,-----, 1 1 CRACKEXTENSION emm> I ~ 300 ~ ZOO 100 Fig. 16 J-l!.a curve for A516 Gr70 steel with COD gage at loo'C Fig. 15 J-l!.a curve for A5l6 Gr70 steel with COD gage at 20'C The K,c test results versus temperatures are as summarized in Table 4. 16 Chang-Sung Seok Table 3 The effect of temperature on J IC Test Method Temperature R-Curve [j= CdLla) C,] rc: 11C<kN/m) CI C 2 -15 123 185 0.34 0 118 199 0.44 With COD 10 121 192 0.40 gage 20 118 197 0.56 100 1103 187 0.50 20 114 224 0.59 100 103 188 0.51 With high 200 98 178 0.50 temperature 300 98 178 0.50 extensometer 400 90 160 0.47 500 85 153 0.49 600 80 135 0.45 Table 4 Test results of J IC and K lc Temperature ]IC Test Results K,c Test Results «» ]IC or JQ(kN/m) Validity KQ(kN/m 312 ) J ( ~ ) (kN/m) 20 118 0 58800 15 10 121 0 60400 16 0 118 0 57600 15 -15 123 x 59800 16 -30 63 x 62300 17 -50 51 x 68600 20 -100 40 x 74000 24 -130 18 x 63900 18 -140 18 x 64200 18 -150 12 x 52800 12 -160 12 x 52500 12 value. None of the three parameters reveals any discernible effect of DSA. However, the load- displacement curves seem to reveal DSA effects. At temperatures of 200'C and 300'C, the maxi- mum load attained on the reloading of the speci- men after the small unloading to determine the crack length is higher than that just prior to the unloading as shown in Fig. 18. The phenomenon exhibits serrations in load - displacement curves, and the temperature might be influencing the magnitude of this effect and the J IC values. The strain aging may be suspected, (Miglin et a\., 1986) however, no dips in the DSA range were -rrrrrr.: TlTTI{soo"C -nT!t400"C Q. ~ 9 7 7 7 I I 7~ O O " C 7 7 77 / T 2O"C LOAD UNE DISPLACEMENT. c5 Fig. 18 P-8 curve for A516 Or70 steel at several test temperature noted contrary to the earlier researcher's observa- tions in A533B steel and pure iron. (lung and Murty, 1988 ; Murty, 1999 ; Murry and Mah- mood, 1990) For O°C and 20'C tests, stable crack extension was observed as shown in Fig. 14 and Fig. 15, and the J IC values were valid by ASTM standard. For the J IC test result at -IS'C as shown in Fig. 13, stable crack extension was not large enough to be valid by ASTM E 813. At low temperatures below -30'C stable crack extension was not long enough to evaluate J IC based on ASTM standard, and J Q calculated from maximum load revealed transition from brittle to ductile fracture. In order to meet the ASTM validity require- ment for the thickness of K lc specimen, specimen thickness B should be greater than 2.5 (K Q / O'Y) 2. But in this study, the requirement was not satis- fied. The variation of the elastic-plastic fracture toughness parameter J IC and K IC versus tempera- ture at the range below room temperature is presented in Fig. 19. At temperature range below - IYC, the J Q values are invalid because the stable crack extension of the specimen was not sufficient, but it is obvious that the values are critical values of J at onset of fracture. So the value may be used as a reference fracture tough- ness value. The K 1C values at the temperature range of -130'C to - 160°C are useful in spite of Effect of Temperature on the Fracture Toughness of A516 Gr70 Steel 17 The following conclusions were obtained from 4. Conclusions where T is the test temperaturej't: J, and the J Q is the elastic-plastic fracture toughness val- ue[kNjmJ. The author is grateful for the support provided by a grant from the Korea Science & Engineering Foundation (KOSEF) and Safety and Structural Integrity Research Center at the Sungkyunkwan University. References Acknowledgements Francois, D., 1986, "Relation between Various Fracture Transition Temperature and the K 1c Fracture Toughness Transition Curve," Engineer- ing Fracture Mechanics, Vol. 23, No.2, pp. 455 -465. Joyce J. A. and Hasson, D. F., 1980, "Charac- terization of Transition Temperature Behavior of HY 130 steel by the J IC Fracture Toughness Parameter," Engineering Fracture Mechanics, Vol. 13, pp. 417-430. Jung Y. H. and Murty, K. L., 1988, "Effect of Temperature and Strain Rate on Upper Shelf Fracture Behavior of A533B Class I Pressure Vessel Steel," ASTM STP969, pp. 392-401. Miglin, M. T., Van Der Sluys, W. A., Futato, R. J. and Domian, H. A., 1986, "Effect of Strain Aging in the Unloading Compliance J Test," ASTM STP 856, pp. 150-165. the study. (I) It may be recognized that the temperature ranging from -15·C to 600"C is the upper shelf region of ductile-brittle transition temperature (DBTT). In this temperature range, the elastic plastic fracture toughness J le values decreased with increasing temperature, however, it was in- significant. (2) The DBTT of A516 Or70 steel may be -30·C. In the transition region near -30·C, the tendency of J{C decrease with decreasing tempera- ture was significant. (3) The load-displacement results during the J-tests show some evidence of strain aging phe- nomenon at temperatures 2oo·C and 300·C. How- ever, no dips in the DSA range were noted con- trary to the earlier researcher's observations in A533B steel and pure iron. (4) • •••• • 10 4000 (T-15) 30 ISO 120 o :J IC 000 0: J Q 'i 90 • : JlI<oI ! !> 60 .. o -ISl -45ll -120 -00 -60 -30 0 30 TEMPERATURE ("C) Fig. 19 The effect of temperature on the Jle at the range below room temperature. the thickness requirement not being satisfied. In this region, brittle fracture occurred without duc- tile deformation and J Q values calculated from Eq. (I) agreed well with J (K Q ) values calculated from Eq. (2). However, the ~ values determined in the other temperature regions cannot be taken as a fracture toughness of the material. In this study, the J le fracture toughness parameter was used for evaluation of temperature effect. The ductile brittle transition temperature (DBTT) of A516 Or70 steel is about -30·C. The ductile-to-brittle transition temperature of -30"C was determined as the temperature corre- sponding to the average of the upper shelf tough- ness and the fracture toughness at the tempera- tures below -130·C. In the transition region near - 30·C, the tendency of J le to decrease with decreasing temperature was significant. The ten- dency of transition temperature behavior of frac- ture toughness was similar to the results of others. (Joyce and Hasson, 1980; Watainabe et ai, 1987) At temperatures ranging from - 160·C to -IYC, the J Q value and the test temperature can be correlated as follows: 18 Chang-Sung Seok Mills, W. J. 1987, "Fracture Toughness of Two Ni-Fe-Cr Alloys," Engineering Fracture Mechanics, Vol. 26, No.2, pp. 223-228. Murty, K. L. and Mahmood, S. T., 1990, "Ser- rated Flow in Irradiated and Partially Denitrided Mild Steel," ASTM STP 1046, pp. 422-430. Murty, K. L., 1999, "Role and Significance of Source Hardening in Radiation Embrittlement of Iron and Ferritic Steels," Journal of Nuclear Materials 270, pp. 115-128. Neal, B. K. and Priest, R. H., 1986, "The Unloading Compliance Method for Crack Length Measurement Using Compact Tension and Pre- cracked Charpy Specimens," ASTM STP 856, pp. 375- 393. Rice, J. R., 1968, "A Path Independent Integral and the Approximate Analysis of Strain Concen- tration by Notches and Cracks," Journal of Applied Mechanics, Vol. 35, pp. 379-386. Ross, E. and Eisele, V. 1988, "Determination of Material Characteristic Values in Elastic-Plas- tic Fracture Mechanics by Means of J-Integral Crack Resistance Curve," Journal of Testing and Evaluation, Vol. 16, No. I, pp. I-II. Smith, R. F., and Doig, P., 1986, "Crack Length Measurement by Compliance in Fracture Toughness Testing," Experimental Mechanics, pp. 122-127. Watanabe, J., Iwadate, T., Tanaka, Y., and Yokobori, T., 1987, "Fracture Toughness in the Transition Region," Engineering Fracture Mechanics, Vol. 28, No. 516, pp. 589-600. 1996, "Standard Test Method for J le , A Mea- sure of Fracture Toughness," Annual Book of ASTM Standards, ASTM E 813-89. 1996, "Standard Method of Test for Plane- Strain Fracture Toughness of Metallic Materials," Annual Book of ASTM Standards, ASTM E 399-90. 21 0. 2670-116) for a temperature range of .24 1. 2. Load line displacements were measured by a COD gage (Instron Ltd. Figure 4 shows the schematic diagram of the high temperature HC testing system. Catalog No. .2 Test procedure Fracture toughness tests were performed following ASTM E813 test procedure at temperatures ranging from -160·C to 600·C which covers the ductile-to-brittle transition as well as upper shelf regimes. 2 Orientation of specimen -30 -15 0 628 618 618 598 569 559 549 540 579 520 441 451 422 412 402 383 373 373 363 363 304 265 18 20 19 20 22 26 29 31 27 34 37 10 20 100 200 300 400 500 600 63 ~ In _. In this paper. A high temperature extensometer was mounted on the crack mouth at the load line of the specimen as shown in Fig.20 0._f- unit:mm (a) Specimen for COD gage ~ U'l _. high temperature llc tests were performed with a high temperature extensometer in a split furnace.5 and precracked to a crack length of approximately ajW =0.8 (b) Specimen for high temperature extenso meter Fig. 2632001) for 20·C ~T~600·C. After fatigue precracking at room temperature. 1 Dimension of CT specimen Specimens were notched to an initial ajW ratio of 0.06 0. 3. In all cases. The specimen temperature was controlled by liquid nitrogen below the room temperature in an environmental chamber. and held in position by a set of springs. Tests were also performed with the COD gage at 20·C and lOO·C. unit:mm SO.013 0. To observe the ductile brittle transition temperature behavior. Catalog No.035 0. Temperature control was achieved by enclosing the specimen in an electrically heated split furnace and mounting a thermocouple nearby the crack tip of the specimen. the load line displacement is measured by a high temperature COD gage in an environmental chamber for high temperature llc test.07 0. Figure 5 shows the schematic diagram of the low temperature fracture toughness testing system.6 where 'a' is the crack length.38 Table 2 Mechanical prperties of A516 Or70 Temperature Tensile Strength Yield Strength Elongation(%) (MPa) (MPa) rc: Fig.004 0._. temperatures were controlled to better than ± I·C with self-adaptive temperature controllers. Usually.160·C ~ T ~ lOO·C and by a high temperature extensometer (Instron Ltd. fracture toughness llc and K lc tests were performed at the temperature range of -160·C to 20·C.12 Chang-Sung Seok Table 1 Chemical composition of A516 Or70 (wt %) C Si Mn P S Mo AI Ni V 0. 1986.522~) where b is the remaining ligament. 13-16.p. the areas (A) under the P-o curves were determined from which the J Q was calculated (ASTM E 813). 20'C and IOO'C are as shown in Fig. 500 <400 380 (I) Fig.1a curve for A516Gr70 steel with high temperature extensometer at 20'C 500 I ~ -\ 408 380 o ~ 1110 Temp. The fatigue crack length and final crack extension were measured directly from the fractured surface.Effect of Temperature on the Fracture Toughness of A516 Gr70 Steel 13 all tests were performed in stroke control on dynamic universal testing machine at test temperature. and C 2 of R-curves [J= C. all specimens fractured in a brittle manners during loading without stable crack extension. o I Z 3 CRACKEXTENSION I_I Fig. At temperature ranging from -160'C to -30'C. 5 Schematic diagram of low temperature testing system 1 1 CRACKEXTENSION I_I Fig. JQ=~(2+0. In these cases.< : 114 kN/. Neal and Priest. O'C. heat-tinted at about 300'C for 10 minutes and broken open. : 10'C 1110 J. All procedures HIGH of tests and reductions were carried out in accordance with the ASTM E 813 and ASTM E 399.3 Test results Test results with the high temperature extensometer at temperatures ranging from 20'C to 600'C are as shown in Figs. " 2. 1986) and autographic records ofload versus load-line displacement were obtained. The test loading was regularly interrupted by 10% unloadings(Smith and Doig. : 100'C 100 J. Results with the COD gage at -15'C.e testing system Fig. At the end of each test. 4 Schematic diagram of high temperature J. specimens were completely unloaded. 6 J-. oj K SPECIMEN dWPERATlm ENSG'1ETER 01 I' Il.1a curve for A516 Gr70 steel with high temperature extensometer at lOO'C .a) C2] obtained from the test.(t. Table 3 shows J le values and constants C. 3 Measurement of load-line displacement with high temperature extensometer i' ~ -\ ~ ~ zoo Te. 6-12. 7 J-.< : 103 kN/m •o Fig. -150·C and -160·C tests.----.:.:.l CRACKEXTENSION (.: 300·C 100 ~ Te. (Rice.14 500 Chang-Sung Seok 580 40Q I ~ ~ 1:1 400 300 100 0 I ~ 1:1 101 300 o 100 100 T•• p.c: 113 tNt. : -15·C J.----.e: 85 kNt. .. 400 I I~ o o I ~ . 8 J-~a curve for A516 Or70 steel with high temperature extensometer at 200·C Fig. 108·C 100 ~ . p. CRACKEX'1'I'. 1968) . 11 J-~a curve for A5l6 Or70 Steel with high temperature extensometer at 500·C 580 r----r""TT"------.e . 10 curve for A516 Or70 steel with high temperature extenso meter at 400·C Fig. : 400·C J. J (K Q ) values were then calculated from KQ values using the following conversion equation. 91 tNt.l Fig. J. tNt. : 600·C J.NSION l .l Fig.. brittle fracture occurred without ductile deforma- J-~a curve for A5l6 Or70 steel with COD gage at -15·C tion at maximum load. a 0 1 0 1 3 1 1 3 CRACKItXTINSIONl .. : 500·C T•• p.. the specimens were broken after some ductile deformation. 500 400 400 o o I T••p. 1 1 ~ 3 ~ 300 100 180 8 Te. J.e: .l Results of the fracture toughness parameter J IC versus the temperature are summarized in Table 4.e .. 80 tNt. tNt... p.. for the -130·C.. 0 0 1 1 o 1 1 3 CRACKItXTINSIONl . 400 300 5OOr----r--n--------. For the tests at temperatures ranging from -IOO·C to -30·C.------. 34MI 0 T•• p.. 3 J . -140·C... 13 J-~a 1 1 CRACKEXTENSION l . 12 J-~a curve for A516 Or70 steel with high temperature extenso meter at 600·C 5OOr----r-rr------. However.l CRACKItXTINSION<-l Fig. 9 J-~a curve for A516 Or70 steel with high temperature extensometer at 300·C Fig..e: 9. Effect of Temperature on the Fracture Toughness of A516 Gr70 Steel 500 15 150 119 I I ~ ~ I 4811 380 100 I .p. 1988). : lO'C J. 16 J-l!. and Jrc values might be affected by the C\ and Cz(Ross and Eisele..06T+ 115 3 (3) o o Z CRACKEXTENSION <mm> Fig....------..-------. That is Figs. 7...p. 17 The effect of temperature on the lIe of the upper shelf region of DBTT 5OO. and also Figs. respectively.c : 118 kN/m 1 1 CRACK EXTENSION emm> Fig. 14 J-l!..] are shown in Table 3. The J.p.c: 118 kN/. slightly increases initially reaching essentially a constant ...a curve for A516 Gr70 steel with COD gage at loo'C (2) The K. : O'C J.. J rc values at the upper shelf region of ductile-brittle transition temperature (DBTT) decreased with increasing temperature.c values and R-curves determined by the high temperature extenso meter well agreed with those determined by the COD gage at that temperatures. 400 I ~ 300 ~ ZOO Te. It may be recognized in this study that the temperature ranging from . where T is the temperature ['C].... ~ 90 60 ~lila El WIlH e e 0 0 o 108 Te.. 15 and 16 with the COD gage. 4811 3.---r-rr--------. It is noted that C\ decreases with the test temperature very similar to J IC while C. : 100'C 100 J. 30 9 3 COD GAGE (. but the different load line displacement sensor. The constants C\ and C z of R-curve [j = C.. 16 are the Jrc test results for the same temperature of 20'C and lOO'C.-----.IS'C to 600'C was the upper shelf region of ductile-brittle transition temperature. Figure 17 shows that the elastic plastic fracture toughness. 6.a curve for A516 Gr70 steel with COD gage at O'C Fig. and J rc is the elastic-plastic fracture toughness[kN/m]. Figs. Discussion Experimental results show that the load-line displacement can be measured successfully by the high temperature extenso meter.---. 1 flc=-O.a curve for A5l6 Gr70 steel with COD gage at 20'C 500. c : 103 kN/.. 15..c test results versus temperatures are as summarized in Table 4. (L~a) C. 15 J-l!.m) Fig. The J IC value and the test temperature can be correlated as follows: 308 ! 100 101 Te. 5 and 6 are obtained with the high temperature extensometer while Figs.)WITH HIGH TEMPERATURE EXTENSOMETER 9 100 I 1 1 500 ZOO 300 400 TEMPERATURE ("C) 600 CRACK EXTENSION e. Murry and Mahmood. and the JIC values were valid by ASTM standard. The phenomenon exhibits serrations in load . specimen thickness B should be greater than 2. stable crack extension was not large enough to be valid by ASTM E 813. 1999 . 15. At temperatures of 200'C and 300'C. But in this study. 1986) however.59 0. None of the three parameters reveals any discernible effect of DSA. no dips in the DSA range were noted contrary to the earlier researcher's observations in A533B steel and pure iron. (lung and Murty..50 0.34 -15 123 rc: 0 10 20 -rrrrrr. stable crack extension was observed as shown in Fig.displacement curves.] 11C<kN/m) C I C2 185 0.47 0. the JQ values are invalid because the stable crack extension of the specimen was not sufficient.56 0. For the J IC test result at -IS'C as shown in Fig. 18 P-8 curve for A516 Or70 steel at several test temperature Table 4 Test results of J IC and Klc Temperature ]IC Test Results K. c5 500 600 Fig. (Miglin et a\. 14 and Fig.: TlTTI{soo"C -nT!t400"C Q.IYC. However. 1988 .c Test Results J(~) «» 20 10 0 -15 -30 -50 -100 -130 -140 -150 -160 ]IC or JQ(kN/m) Validity KQ(kN/m312) 118 121 118 123 63 51 40 18 18 12 12 (kN/m) 15 16 15 16 17 20 24 18 18 12 12 0 0 0 x x x x x x x x 58800 60400 57600 59800 62300 68600 74000 63900 64200 52800 52500 value.160°C are useful in spite of .50 0. The variation of the elastic-plastic fracture toughness parameter J IC and K IC versus temperature at the range below room temperature is presented in Fig. the maximum load attained on the reloading of the specimen after the small unloading to determine the crack length is higher than that just prior to the unloading as shown in Fig. So the value may be used as a reference fracture toughness value. 1990) For O°C and 20'C tests.49 0. The K1C values at the temperature range of -130'C to .5 (KQ/ O'Y) 2.16 Chang-Sung Seok Table 3 The effect of temperature on J IC Test Method Temperature R-Curve [j= CdLla) C. but it is obvious that the values are critical values of J at onset of fracture. the requirement was not satisfied.50 0. and the temperature might be influencing the magnitude of this effect and the J IC values. At temperature range below . At low temperatures below -30'C stable crack extension was not long enough to evaluate J IC based on ASTM standard. 13.44 0. 19. the loaddisplacement curves seem to reveal DSA effects.45 ~ With COD gage 9 100 20 100 With high temperature extensometer 200 300 400 7 7 7 I I 7~OO"C 7 7 77 / T 2O"C LOAD U NE DISPLACEMENT. 118 121 118 1103 114 103 98 98 90 85 80 199 192 197 187 224 188 178 178 160 153 135 0. The strain aging may be suspected. Murty. 18.40 0.51 0. and J Q calculated from maximum load revealed transition from brittle to ductile fracture. In order to meet the ASTM validity requirement for the thickness of K lc specimen. 1986. 13. (2). L. D.160·C to -IYC. the tendency of J{C decrease with decreasing temperature was significant. The ductile-to-brittle transition temperature of -30"C was determined as the temperature corresponding to the average of the upper shelf toughness and the fracture toughness at the temperatures below -130·C. the ~ values determined in the other temperature regions cannot be taken as a fracture toughness of the material.2. A." Engineering Fracture Mechanics. it was insignificant. Vol. Futato. 30 o Fig. In this region. K. D. however. pp. H. (3) The load-displacement results during the J-tests show some evidence of strain aging phenomenon at temperatures 2oo·C and 300·C. "Characterization of Transition Temperature Behavior of HY 130 steel by the J IC Fracture Toughness Parameter. The tendency of transition temperature behavior of fracture toughness was similar to the results of others. Miglin. pp. Joyce J. (I) It may be recognized that the temperature ranging from -15·C to 600"C is the upper shelf region of ductile-brittle transition temperature (DBTT). "Effect of Strain Aging in the Unloading Compliance J Test. (Joyce and Hasson. no dips in the DSA range were noted contrary to the earlier researcher's observations in A533B steel and pure iron.Effect of Temperature on the Fracture Toughness of A516 Gr70 Steel ISO 120 17 o :JIC 0: JQ • : JlI<oI 000 ! 'i !> 90 60 . F. "Effect of Temperature and Strain Rate on Upper Shelf Fracture Behavior of A533B Class I Pressure Vessel Steel. pp. In the transition region near -30·C. In this temperature range. A. 1987) At temperatures ranging from . However. and Hasson." ASTM STP 856. 23. Vol. the thickness requirement not being satisfied. "Relation between Various Fracture Transition Temperature and the K1c Fracture Toughness Transition Curve. and Murty. Jung Y. W. The ductile brittle transition temperature (DBTT) of A516 Or70 steel is about -30·C. References Francois. A. T. the JQ value and the test temperature can be correlated as follows: 4000 (T-15) the study. 150-165. 417-430. No. the J le fracture toughness parameter was used for evaluation of temperature effect. (I) agreed well with J (KQ) values calculated from Eq. and the JQ is the elastic-plastic fracture toughness value[kNjmJ.. 1980.. 392-401. In the transition region near . Van Der Sluys.30·C.. brittle fracture occurred without ductile deformation and JQ values calculated from Eq. the elastic plastic fracture toughness J le values decreased with increasing temperature. Conclusions The following conclusions were obtained from . pp. and Domian. R. 1988." Engineering Fracture Mechanics. 455 -465. In this study.. 1980. 4." ASTM STP969. the tendency of J le to decrease with decreasing temperature was significant. 1986. Acknowledgements The author is grateful for the support provided by a grant from the Korea Science & Engineering Foundation (KOSEF) and Safety and Structural Integrity Research Center at the Sungkyunkwan University. J. Watainabe et ai.. 19 • • •••• -45ll -ISl -120 -00 -60 -30 0 30 TEMPERATURE ("C) The effect of temperature on the Jle at the range below room temperature.. However. (2) The DBTT of A516 Or70 steel may be -30·C. M. H. 10 (4) where T is the test temperaturej't: J. 1968." ASTM STP 856.. "Role and Significance of Source Hardening in Radiation Embrittlement of Iron and Ferritic Steels. Vol. H.. and Doig. K.. 16. 28.. K.. No." Experimental Mechanics. 122-127." Engineering Fracture Mechanics." Journal of Nuclear Materials 270. I-II. J.. B. R." Engineering Fracture Mechanics.. Ross. and Eisele. pp. pp. 1990. 379-386. 26. "Determination . J. J. 1987. W. 1996. I. "Crack Length Measurement by Compliance in Fracture Toughness Testing. T. L. No. 375. Smith. pp. No. Watanabe. ASTM E 399-90. Y. Rice. Vol.. pp.. Tanaka. pp. pp. pp. "A Path Independent Integral and the Approximate Analysis of Strain Concentration by Notches and Cracks.18 Chang-Sung Seok of Material Characteristic Values in Elastic-Plastic Fracture Mechanics by Means of J-Integral Crack Resistance Curve. "Standard Method of Test for PlaneStrain Fracture Toughness of Metallic Materials." Journal of Applied Mechanics.393." Annual Book of ASTM Standards. P. and Mahmood. 115-128. pp. 223-228. Vol. "Fracture Toughness in the Transition Region. 1999. T. 589-600. E. Mills. "Serrated Flow in Irradiated and Partially Denitrided Mild Steel. R. 516. Murty." Annual Book of ASTM Standards. A Measure of Fracture Toughness. "Fracture Toughness of Two Ni-Fe-Cr Alloys." ASTM STP 1046. 1987. Iwadate.2. Murty. and Priest." Journal of Testing and Evaluation. 1986. 422-430. F. "Standard Test Method for J le . and Yokobori. 1988. Neal. T. ASTM E 813-89. V. 35. K. S. R. 1996. 1986. Vol.. "The Unloading Compliance Method for Crack Length Measurement Using Compact Tension and Precracked Charpy Specimens. L. 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