Cranfield Institute of Technology. A Study of The Charpy v-notch Impact Test

Transcription

1 CRANFIELD REPORT MAT. NO OKT T LI TEc::r;::c. -^ir^itj T VLlEGTUi3:^:,UW;'.:UXC K!uyverv,C3 1 - DELFT Cranfield Institute f Technlgy A Study f The Charpy v-ntch Impact Test By E. SMITH

2 Cranfield Reprt Mat. N. 10 May 1973 A STUDY OF THE CHARPY V-NOTCH IMPACT TEST by E. Smith, Ph.D., B.Sc, A.I.M. SUMMARY Dimensinal changes and the develpment f cracking in the Charpy V-ntch impact test have been studied using a lw energy blw technique. Ntch pening, angle f bend, ntch rt cntractin and lateral expansin are shwn t be prprtinal t the energy f the lw blw which des nt cause cmplete fracture and t be relatively independent f temperature ver the range -10 C t -70 C but dependent n material. When cmplete fracture ccurs the same lateral expansin/energy relatinship still hlds fr brittle fractures but gradually breaks dwn as the plasticity f the specimen increases. This is due t an appreciable energy increment invlved in frming the shear lips n the sides f the specimen withut crrespnding increase in lateral expansin. The lateral expansin after cmplete fracture is shwn t be independent f the number and magnitude f blws taken t fracture. The develpment f cracking at the ntch rt has been studied by direct examinatin f the surface with a lw pwered bincular micrscpe after successive lw energy blws and by sectining specimens after varius amunts f defrmatin. Tw main stages f crack initiatin were identified which were relatively independent f temperature. In cntrast the prpagatin f these initiating cracks was markedly temperature dependent.

3 CONTENTS 1. INTRODUCTION 2. MATERIALS 3. PROCEDURE 3-1 Single lw blw tests 3-2 Multiple lw blw tests 3-3 Full blw tests 3-4 Supplementary tests 4. RESULTS 4.1 Single lw blw tests 4.2 Multiple lw blw tests 4.3 Full blw and supplementary tests 5. DISCUSSION 6. CONCLUSIONS 7. ACKNOWLEDGEMENT 8. REFERENCES

4 INTRODUCTION The behaviur f specimens during the Charpy V-ntch impact test is difficult t assess because f the instantaneus nature f the test. Techniques must rely, therefre, n rapid respnse instrumentatin r n mdifying the test prcedure in such a way that time is available fr bservatins t be made withut affecting specimen behaviur. Three techniques have been used:- 1. The slw bend test. Evidence suggests, hwever, that the ductile - brittle transitin f structural steels is displaced t lwer temperatures when the slw bend test is used as ppsed t the impact test, (1). 2. The instrumented Charpy test which enables the lad-time diagram t be measured. The velcity f crack prpagatin can als be determined using a high speed camera, (2). This technique, hwever, requires the use f sphisticated and cstly equipment and des nt permit the develpment f cracking at the ntch rt t be bserved. 3. The lw blw Charpy test. This permits defrmatin and fracture t be studied withut the use f additinal equipment. The validity f the technique depends upn specimen behaviur being unaffected by variatins in impact velcity. HARTBOWER (3) has demnstrated the general validity f the technique and has shwn that variatins in impact velcity in the range m/sec. have n effect n test perfrmance. The aim f the present wrk was t study the behaviur f Charpy V-ntch specimens using the lw energy blw technique. This invlved measuring changes in ntch pening, angle f bend, ntch rt cntractin and lateral expansin after bth single and multiple lw energy blws and relating these t the develpment f cracking at the ntch rt as bserved by direct examinatin f the surface with a lw pwered bincular micrscpe and by sectining specimens after varius amunts f defrmatin. 2. MATERIALS The materials used were tw mild steel weld metals which will be designated A and B and QT35 steel in the fllwing cnditins:- (a) (b) as received water quenched frm 1025 C, tempered 1 hur at 550OC

5 - 'j - (c) water quenched frm 1025 C, tempered 1 hur at 650 C (d) water quenched frm 1025 C. table 1. The cmpsitin f the QT35 steel is shwn in N analysis was made n the weld metals. c Mn P S Si Ni Cr M V Cu Table 1: Cmpsitin f QT35 Steel 3. PROCEDURE All tests were carried ut n standard 10mm square Charpy V-ntch specimens. 3.1 Single lw blw tests Specimens f weld metal A and QT35 parent material were given single blws in the range 7-81J (ne blw per specimen) in a Lsenhausen impact testing machine with the additinal weights remved. This was achieved by raising the pendulum t the required height and releasing it by hand. The ntch pening, ntch rt cntractin, and lateral expansin were then measured by means f a linear traverse using a micrscpe with micrmeter attachments. Angles f bend were measured by drawing the utline f the specimens n a piece f paper and measuring the angle with a prtractr. This methd was expeditius and enabled angles t be measured t within 0.5. Weld metal A was tested at ^0, QT35 at -looc and -7OOC. The minimum blw required t prduce a crack visible, t the naked eye was nted. 3.2 Multiple lw blw tests Specimens f QT35 in cnditins (a), (b) and (c) described abve were given a successin f lw impact blws f abut 7J nminal capacity (with the additinal weights remved) in the temperature range OC t -100^0. After each blw the lateral expansin was measured and the surface f the ntch rt was was examined fr cracks using a lw pwered bincular micrscpe at a magnificatin f 50. Althugh cracking culd prbably be detected earlier at higher magnificatins this was nt pssible because f the difficulty in fcusing at the bttm f a deep ntch. Hwever, it iriight be expected that the bservable crack length wuld be a functin f the ttal

6 - 6 actual length. The lateral expansin crrespnding t varius stages f cracking was nted. The lw blws were repeated until the cmplete length f the ntch rt was cracked. 3.3 Full blw tests After the single and multiple lw blw tests described abve were cmpleted the defrmed specimens were fractured at the same temperature at which the lw blws were carried ut using the full capacity blw (294J) and the energy absrbed was recrded and the lateral expansin measured. Standard tests n undefrmed specimens were carried ut fr cmparisn. In rder t get accurate and cnsistent measurements f lateral expansin it was necessary t fit the brken specimen tgether in a vice and measure the maximum lateral expansin by traversing frm ne side f the specimen t the ther using a micrscpe with micrmeter attachments. This need arises because the final fracture des nt, in general, pass thrugh the pints f maximum lateral expansin n each side f the specimen and, mrever, the maximum lateral expansin n each side f the specimen may be lcated n different halves f the brken specimen. This finding agrees with that f ORNER and HARTBOWER (4). 3.4 Supplementar^y tests Additinal tests were carried ut n weld metal B and n QT35 in the water quenched cnditin using the fllwing sequence f blws:- 1. single lw blw plus full capacity blw. 2. multiple lw blws plus full capacity blw. 3. full capacity blw. In each case the lateral expansin at fracture was measured in rder t prvide further cmparisn n the effect f the number and magnitude f blws taken t fracture n lateral expansin. A limited number f specimens were sectined after varius lw blws in rder t relate the stages f cracking bserved at the surface with the develpment f cracking thrugh the depth f the specimen. 4. RESULTS 4.1 Single lw blw tests Fig. 1 shws that ntch pening, angle f bend, ntch rt cntractin and lateral expansin increase linearly with energy absrptin in the single lw blw tests n weld I.-,.

7 - 7 - metal A and QT35 parent material. The minimum blws required t prduce visible cracking at the ntch rt, table 2, shw that these relatinships are nt affected by the nset f cracking at the ntch rt. Material Weld metal A QT35 (-10 C) QT35 (-70OC) Minimum blw fr visible cracking (J) Table 2: Minimum lw blws required t prduce visible cracks at the ntch rt. The energy values in fig. 1 have nt been crrected fr lsses which arse mainly frm rebund f the pendulum after impact. These lsses varied between 1.4 and 2.7J regardless f the magnitude f the lw blw and wuld, therefre, nt affect the linearity f the relatinships shwn in fig. 1. The relatinships fr QT35 were different frm thse f weld metal A indicating a dependence n structure but the relatinships were essentially the same at -10 C and -70OC indicating a relative independence n temperature ver this range. ^ 2 Multiple lw blw tests In the multiple lw blw tests cracking at the surface f the ntch rt ccurred in a number f stages. After the first blw shrt fine cracks lying parallel t the length f the ntch were frmed. These were difficult t identify because f the.pr surface appearance f the ntch rt. Occasinally mre well-develped cracks lying perpendicular t the length f the ntch appeared at this stage but these were ignred since they did nt appear t influence the subsequent develpment f cracking alng the ntch rt. In the secnd stage shrt well-develped cracks frmed alng the ntch rt, the sides f which culd be clearly reslved under the micrscpe. With increasing defrmatin the cracks grew laterally t frm a mre r less cntinuus crack extending ver the greater part f the ntch rt. The end f the third stage was taken arbitrarily t cincide with the frmatin f a crack extending ver half f the length f the ntch rt. In the furth stage lateral extensin cntinued until the crack reached the sides f the specimen. The distinctin between the third and furth stages was cnsidered necessary since crack extensin became mre difficult after the central length f the ntch had cracked. This is prbably due t a change frm plane strain cnditins at the centre f the ntch length t plane stress cnditins near the sides. In the fifth stage the crack

8 - 8 - prpagated thrugh the depth f the specimen causing cmplete fracture. The extent f cracking bserved n central lngitudinal sectins after stages 1-4 f cracking at the surface is shwn in figs. 2 and 3 respectively fr a ductile and a brittle fracture. In bth cases there was n evidence f cracking after stage 1 as shwn in figs. 2(a) and 3(a) althugh sme surface indentatins can be bserved which are presumably the fine cracks described after the surface examinatin. The ductile fracture exhibited a fine shear crack at apprximately 45 t the principal stress after stage 2, fig. 2(b), which crrespnds t the initiating shear cracks described by HARTBOWER (3)- This crack pened up during stage 3 and initiated a crack nrmal t the principal stress, fig. 2(c). This crrespnds t the secnd stage f crack initiatin described by HARTBOWER (3). During stage 4 the crack pened up cnsiderably and limited prpagatin nrmal t the principal stress ccurred, fig. 2(d). The brittle fracture exhibited a number f different features frm the ductile fracture. After stage 2 the initiating crack, which was quite extensive, was mainly nrmal t the principal stress althugh a shrt initiating shear crack can be bserved at the surface in fig. 3(b). During stage 3 the crack pened up and prpagated a cnsiderable distance nrmal t the principal stress, fig. 3(c). This prcess cntinued during stage 4 as shwn in fig. 3(d). The ductile fracture exhibited much mre "crack pening" than the brittle fracture. The results f multiple lw blw tests n QT35 L^tecL in three heat treatment cnditins are shwn in fig. 4. Here lateral expansin crrespnding t stages 2-5 f cracking are pltted against temperature. Stage 1 was mitted because f the uncertainties invlved in crack detectin. Stages 2 and 3 are relatively independent f temperature, while stages 4 and 5 are markedly temperature dependent. 4.3 Full blw and supplementary tests The lateral expansin f specimens fractured using nly the full capacity blw and thse fractured with the full capacity blw after previus single and multiple lw blws are cmpared in table 3. The small variatins between the three grups are randm and generally less than 10^ and are cnsidered t reflect the nrmal scatter assciated with ntchimpact tests. It seems reasnable t cnclude, therefre, that specimen behaviur is nt influenced by the number and magnitude f blws taken t fracture and wuld thus appear t vindicate the prcedure. The relatinship between lateral expansin and energy absrptin after fracture was similar t the relatinship prir t fracture fr relatively brittle materials as shwn in fig. 5 fr QT35 in the the water quenched cnditin. With mre ductile materials, hwever, energy absrptin during the final

9 - 9 - stages f the test increased at a greater rate than lateral expansin as shwn in fig. 6 fr QT35 parent material. This can be attributed t an appreciable energy increment invlveer in frming the shear lips and separating the final ligament withut a crrespnding increment in lateral expansin. The increasing deviatin frm the lateral expansin-energy relatinship prir t fracture with increasing energy absrptin is a manifestatin f this. Material Test Temp. ( C) Type f blw N. f Tests Average lateral expansin (mm) Deviatin frm standard test Weld metal A 11 Standard Duble Multiple % Weld metal B It " Standard Duble Multiple ^ + 5? QT35,as received II It Standard Duble Multiple I.70 QT35,as received 1 " 1 " Standard Duble Multiple % -10;. 1 QT35 WQ 1025 C! Temp. 65OOC Standard Duble Multiple % + 9^ 1 QT35 WQ 1025 C Temp. 55OOC Standard Duble Multiple % QT35 WQ 1025 C Standard Duble Multiple i % -e% Table 3: Cmparisn f lateral expansin at failure between standard and lw blw tests.

10 DISCUSSION The validity f the lw energy blw apprach fr studying defrmatin and fracture in the cnventinal Charpy test depends upn specimen behaviur being unaffected by the differences in impact velcity between the tw prcedures. HARTBOWER (3) demnstrated that variatins in impact velcity within the range m/sec. des nt affect impact perfrmance and this is apprximately the range f impact velcities used in the present wrk. Table 3 shws that, within the nrmal scatter assciated with ntch impact tests, the lateral expansin after cmplete fracture is independent f the number and magnitude f the blws used, i.e. is independent f impact velcity. This being s, it is reasnable t assume that the intermediate stages invlved in fracture will be als independent f impact velcity. The lw energy blw prcedure, therefre, ffers a unique pprtunity fr studying behaviur in the Charpy test withut the need fr additinal equipment apart frm that required fr ptical examinatin and measurement f lateral expansin. Tw variatins in the prcedure are available. Either the test can be carried ut using a single specimen fr each temperature by impacting it with successive lw energy blws r a series f specimens can be used fr each temperature with each specimen receiving a different lw energy blw. In bth cases a cntinuus recrd f specimen behaviur is nt btained but the steps between each pint in the test can be kept small by using small increments in energy, preferably arund 7J (5ft. lbs.). The single lw blw tests are less time cnsuming and the effective energy absrbed by the specimen can be estimated by nting the distance f rebund f the pendulum which is cnsidered t be the main surce f energy lss. Hwever, this prcedure is mre expensive in terms f the number f specimens required. The multiple lw blw prcedure, n the ther hand, is mre ecnmical in terms f the number f specimens required, but can be mre time cnsuming especially with tests nt carried ut at rm temperature since the specimen has t be examined and taken back t test temperature between successive blws. It was als fund that ther surces f energy lss arse in the multiple lw blw tests as was apparent frm the bservatin that the increments in lateral expansin decreased with successive blws f the same nminal energy. The linear relatinship between lateral expansin and energy absrptin in the single lw blw tests (fig. 1(d)) indicates that if all the energy f the pendulum, after allwance has been made fr rebund, is absrbed by the specimen then the successive increments in lateral expansin shuld als be similar. This extra surce f energy lss may be due t the fact that the specimen, which has been bent by preceding blws, has a much reduced cntact with the machine anvil r else wrk hardening has increased the energy required t cause further plastic defrmatin. Whatever the explanatin the successive energy blws are nt additive and in rder t cnvert lateral expansin values int energy values it is necessary t

11 establish the crrelatin between the tw parameters using a series f single lw blw tests. Hwever, it has been well established that lateral expansin and energy values in the Charpy test are apprximately equivalent (5, 6) s that fr purpses f studying specimen behaviur the cnversin t energy values is nt really necessary. The results shwn in fig. 1 indicate that ntch pening, angle f bend, and n tch rt cntractin are alternative parameters by whic h prgress f the test can be measured. Hwever, ntch pe ning and angle f bend becme indeterminate when the specime n breaks inj tw and s d nt permit the test t be studied t the end.^ Ntch rt cntracure accurately and reprducibly tin is mre difficult t meas than lateral expansin as can be seen frm the greater degree f scatter in fig. 1(c) cmpar ed with fi^. 1(d). Cnsequently lateral expansin measurements are the mst satisfactry fr fllwing prgress f the test up t and including the final stage f fracture. Tw main stages f fracture initiatin can be identified. The initiatin f shear cracks at apprximately 45 t the principal stress fllwed by the initiatin f cracks nrmal t the principal stress. These cracks frm in the central part f the ntch length whert'e the stress system is mst severe and crrespnd t the tw stages f initiatin described by HARTBOWER (3). Prpagatin can als be described as a tw stage prcess. In the first stage the initiating crack extends laterally t the sides f the specimen and at the same time limited prpagatin thrugh the depth f the specimen ccurs. This is fllwed by the final prcess f fracture thrugh the full depth f the specimen. The tw stages f initiatin are relatively independent f temperature but the prpagatin stages are markedly temperature dependent and reflect mst f the temperature dependence displayed by the standard Charpy test. Previus attempts t measure the energy fr initiatin have shwn this t'be independent f temperature ver a wide range (3, 7)- RARING (8) using slw bend tests n Charpy V-ntch specim ens has bserved that the start f crack prpagatin thrug h the depth f the specimen cincides with the maximum lad i n the lad-deflectin diagram and at this pint a crack extend ing ver the entire length f the ntch rt was bserv ed. The present results indicate^that fr impact ratec f la ding at least sme prpagatin thrugh the depth f the specim en ccurs befre cracking has extended ver the entire length f the ntch rt. The single lw blw tests (fig:. 1) have shwn that defrmatin in the Charpy test, as measujred by ntch pening, angle f bend, ntch rt cntractin, and lateral expansin ccurs unifrmly during mst f the test, even after cracks have initiated and extended alng the entire length f the

12 ntch rt. A cmparisn between these results and values f lateral expansin and energy at fracture explains the limited success achieved in the past in attempting t relate lateral expansin at fracture with energy absrptin (1, 5, 6, 8, 9, 10). Such relatinships, althugh generally linear, have been characterised by a gd deal f scatter. This scatter, which was als bserved in the present tests after the specimens had been cmpletely fractured can be explained by the fact that during the final stages f fracture when the sides and final ligament break there is an energy increment withut a crrespnding increase in lateral expansin. The bservatin that the final fracture des nt pass thrugh the pints f maximum lateral expansin n either side f the specimen indicates that the lateral expansin is nt affected at this stage. A number f features bserved in the present wrk suggests a clse similarity in behaviur between 10mm square Charpy and crack pening displacement (COD) specimens. The linear relatinship between ntch pening and ntch rt cntractin bserved in the present tests is analgus t the linear relatinship between COD and ntch rt cntractin reprted fr the COD test (11, 12). In; fact the COD f a test specimen has been shwn t be directly prprtinal t the ntch pening as measured at the surface by means f clip ganges (11). The present results suggest, therefre, that the linearity between COD and ntch rt cntractin in the COD test culd be extended t include angle f bend, lateral expansin, and energy absrptin. The chice f parameter wuld appear t be relatively unimprtant in thery and t be dictated by the practical cnsideratins f ease and accuracy f measurement. The essential difference between Charpy and the COD tests, apart frm the bvius nes f strain rate and ntch prfile wuld thus appear t be in the pint during the test at which fracture behaviur is assessed. In the COD test this is dne at the pint f instability whereas in the Charpy test the assessment includes the unstable part f fracture. The relative ineffectiveness f small cracks prduced in the early stages f the Charpy test indicates that fatigue cracking shuld have little influence n test perfrmance. This has been substantiated by the wrk f ZENO and LOW (13). BURDEKIN (11) has als shwn that fatigue cracking f 10mm square COD specimens has nly a marginal effect n test perfrmance. In additin it wuld seem likely that the prductin f a unifrm fatigue crack at the ntch rt wuld be difficult t achieve since cracking wuld be expected t ccur first in the mre severely stressed regin at the centre f the ntch length. 6. CONCLUSIONS The lw energy blw technique is a valid methd fr studying behaviur in the Charpy test. Using this technique the fllwing bservatins were made:-

13 Prir t fracture, ntch pening, angle f bend,ntch rt cntractin, and lateral expansin increase linearly with energy absrptin. In the brittle regime the lateral expansinin crdinates after fracture energy absrpt fllw clsely the relatinship prir t fracture. Wi th increasing p^lasticity the lateral expans in-energy absrptin crdinates af ter fracture deviate mre frm the relatinsh ip prir t fracture due t an increasing ene rgy increment used in frming the shear lips and separating the final ligament with ut a crrespnding increase in lateral expans in. The final fracture des nt, in general, pass thrugh the pints f maximum lateral expansin n either side f the specimen indicating that lateral expansin ceases befre fracture is cmplete. The lateral expansin at fracture is independent f the number and magnitude f blws 1,aken t fracture. Cracking at the ntch rt deurs very early in the test and prgresses in a series f stages. Tw main stages f initiatin can be identified viz. the frmatin f shear cracks at apprximately 45^0 t the principal stress fllwed by the frmatin f cracks nrmal t the principal stress. These initiating cracks frm in the central length f the ntch rt where the stress system is mst severe. Tw main stages f prpagatin can als be identified viz. the extensin f the initiating cracks t the'sides f the specimen cupled with limited prpagatin thrugh the depth f the specfimen fllwed by prpagatin thrugh the full depth f the specimen The initiating stages f fracture are relatively independent f temperature. The prpagatin stages f fracture are markedly temperature dependent and reflect mst f the temperature dependence displayed by the standard test.

14 ACKNOWLEDGEMENT The authr wishes t express his appreciatin t the Ministry f Defence (Navy Department) fr the supprt f this study and t Prfessr P. Hancck and Dr. R. L. Apps fr helpful discussins. 8. REFERENCES 1. Hartbwer, C. E., Weld. Jnl., 1957, I63 (9), 40]-s. 2. Cleman, C. E., Hardie, D., and Wraith, A. E., Trans. Met. Sc. AIME, I966, 236, (5), Hartbwer, C. E., Weld. Jnl., 1957, 36, (11), 494-s. 4. Orner, G. H., and Hartbwer, C. E., Weld. Jnl., 1957, 36, (12), 521-s. 5. Grss, J. H., and Stut, R. D., Weld. Jnl., 1958, y(_, (4), I5I-S. 6. Hartbwer, C. E., ASTM Prc., 1954, 54.^ Harris, W. J., Rineblt, J. A., and Raring, R., Weld. Jnl., 1951, 30, (9), 417-s. 8. Raring, R., ASTM Prc, 1952, 52, Kellck, G. T. B., M.Sc. Thesis, Cranfield Institute f Technlgy, I Grtke, G. E., Weld. Jnl., 1964, 43, (6), 265-s. 11. Burdekin, F. M., Weld. Inst. Rep. E/11/66, Dec, I Dlby, R. E., Weld. Jnl., C1/10/68, June, I Zen, R. S., and Lw, J. R., Weld. Jnl., 1948, 27, (3), 145-s.

15 - cr ]b c 'c K (a) Weid metal A / OT35 parent material (b) Weld metal A I+OT35 parent [xot 35 parent at mat 2 0 C at erial materia at -10 = 'C -70 C ) OT35 parent 'weld metal A material 40 dj Ol 0; 30 3 c il XI -^ 10 en c < V6 - (c) -1-6 E ^ 1-2 c g ^H~Ö8 Weld metal A Ö t 35 parent material' OT 35 parent E Weld metal A- i.2 "g material if) c Q. D8_L O " 0-^ OA AO ^ 30 Nminal energy f blw (ft.lbf) AG FIG. 1. RELATIONSHIP BETWEEN NOMINAL ENERGY ABSORPTION AND (a) NOTCH OPENING (b) ANGLE OF BEND (c) NOTCH ROOT CONTRACTION AND (d) LATERAL EXPANSION FOR SINGLE LOW ENERGY BLOW TESTS.

16 (a) Stage 1 -.3J(15 ft.lb.) blw (b) Stage J(25 ft.lb.) blw (c) Stage J(30 ft.lb.) blw (d) Stage J(50 ft,lb.) blw FIG. 2. EXTENT OF CRACKING OBSERVED ON CENTRAL LONGITUDINAL SECTIONS OF A DUCTILE FRACTURE AFTER VARIOUS SINGLE LOW ENERGY BLOWS, x

17 (a) (b) (c) L 1 ' m w 1 «- (d) ' r- < "? ',.. -v» "'.I'i» f < ' -M. -. (a) (c) Stage J(10 ft.lb.) blw Stage J(2ü ft. lb.) blw (b) (d) Stage 2-2ü.3J(15 ft.lb.) blw Stage J(25 ft. lb.) blw FIG 3 EXTENT OF CRACKING OBSERVED ON CENTRAL LONGITUDINAL SECTIONS OF A BRITTLE FRACTURE AFTER VARIOUS SINGLE LOW ENERGY BLOWS, x

18 A n X A D X shrt cracks at ntch rt - stage 2 crack extending ver half length f ntch-stage 3 crack extending t sides f specimen -stage 4 ttal fracture using multiple lw blws stage 5 ttal fracture using standard full capacity blw QT 35 as received QT 35 water quenched frm 1025^0 QT 35 water quenched frm 1025*>C and tempered I hr. at 550 C and tempered 1 hr at 650'C FIG. 4. LATERAL EXPANSION TRANSITION CURVES FOR VARIOUS STAGES OF CRACKING AND TOTAL FRACTURE

19 2 0- X full single l multiple blw tests OW blw blws & & tuil blw full blw tests tests E E tn c Q. X 0; 06 2 experimerital relatinship extraplatin f experimental relatinship >\tf ^v'.'^v,^.0! \ ^^ c' S^'l a O^A * AO Energy absrptin (ft Ibf) FIG. 5. LATERAL EXPAIMSION - ENERGY VALUES AT FRACTURE FOR QT35 WATER QUENCHED FROM 1025 C

20 X full blw tests» single lw blw & full blw tests multiple lw blw & full blw tests experimental relatinship extraplatin f experimental relatinship ^^l \ ^^ ' K^'i.^^><.sf^: x% X Ü Energy absrptin (ft.ibf) FIG. 6. LATERAL EXPANSION OF ENERGY VALUES AT FRACTURE FOR QT35 PARENT MATERIAL