NOLTR 70-25

CALIBRATION OF THE NOL LARGE SCALEGAP TEST WITH A PENTOLITE DONOR II

ByDonna Price

DDC

III ~ MARC H 1970 91UNITED STATES NAVAL ORDNANCE LABORATORY, WHITE OAK, MARYLAND

ATTENTION0Z This do•cment has been approved for

public release and sale, Its distribution

is tunlirlted.

NOLME 70-25

CALIBRATION OF TIM NOL LARGE SCALE O T WIIT A PEETOUTE DONOR II

Prepared by:Donna Price

ABSTRACW: HIenceforth the standard donor in the NOL large scale gap test villbe 50/50 pentolite pellets pressed to a density of 1.56 g/cc instead of thetetryl pellets previously used. The pentolite donors will be supplied byMAD, Crsne, Indiana. This report gives the current calibration curve forthe large scale gap test with the pentolite donors.

Approved by: Carl Boy- s, ChiefAdvanced Chetr4try Division

CMU4STR RIULOCH DEPAEHTMU. S. NAVAL ORDVW\E LABORATORY

White, Oek, Silver Spring, garyland

NOLTR 70-25 17 March 1970

CALIBRATION OF THE NOL LARGE SCALE GAPTEST WITH A PENTOLITE DONOR II

The work described in this report was carried out under TaskORD 331-002/092-1/UF19-332-302 (Propellant and Ingredient Sen-sitivity). It presents the calibration data (pressure vs gapthickness) for the NOL large scale gap test with a standardpentolite donor. This information is of importance to the studyof shock sensitivity of explosives and propellants.

GEORGE G. BALLCaptain, USNCommander

ALBERT LIGI•BODYBy direction

4i4

ijAii i'I

SC01MMPagei+°°TO .... ... .. .. .. .. .. .. ... .

2-D OCHPMTATOM . . . 2

CHOICE OF CAMBRATIO J ..RVE . ......... 2

. . . . . . . . .. . . . . . . . . 5

. . . . . . . . . . . . . . . . . . .. . . 6

Figure T-itle Page

1 Compariso ofIU ýw X Cu•rves for Tetryl - Pentolite Donors 7Pe

2 CImparisca of Cali%-rtion Curves for Tetryl and PentoliteDonors . . . . . . . . . . . . . . . . . . . . .. . .. ..

Table Title ae

•- i Spread in Velocity -Data for Three Nethods of Differentiation 9

i•2 Comparison of Average Shock Velocities in PWIA for Pentolite

Sand Tetryl Dm~ors .. .. .. .. .. .. .. .. .. . .. 10

S3 Calibration Data Chosen for LSEGT with Pentol.Lte Dcaor . . .. 11

4 LSM•G Results vitt the Two Different Donors .. .. .. . .. 12

SVMI

WOLM 70-`5

C.I --X• TION OF '70 NOL IAME SCAlE GAP TEST WITH A TOLIhM E DONOR 11

INTRUION

Because NOS, Macon, Georgia, nas been closed, there ic so longer a catisfac-tory source of tetryl pellets for use as a standard donor in the large scale gaptevx- (LZOT). Henceforth, the standard donor will be 50/50 pentolite pressed toa density of 1 56 g/cc; pellets will be supplied by WAD, Cran, Indiana, (FederalStock No. 1375-991-8891). It is the purpose of this report to present the cali-bration cw'ee, pressure vs thickness of polysnthylmethacrylate (PM ) attenuator,

* most in accord with our present knowledge of the pentolite/P.MM system in the" LSGT.

The MSGT is fully described in Reference (I). It consists of a donor, aPMHRA gap, a moderately confined test charge (acceptor), and a mild steel vitaeesplate. The gap length is varied until the 50% value is found; it is that lengthof attenuator at which a hole is punched in the witness plate in 50% of thetrials. The 50% gap is, in fact, that length of attenuator which permits trans-olssion of the critical pressure required to iritiate the acceptor explosive todetonation. Because the amplitude of the shock transmitted from the donor toVie PMKA is complexly related to the gap thickness, the test must be rAlibratedoSWe are ccncerned here with the calibration carve obtained with a 5.08 cm dis~mx 5.0cm long donor of 50/50 pentolite at 1.56 g/cc used to shock load a 5.08 cmdiu cIylnder of FWAA,

Tn-' 1."rst lot of pentolite pellets was made at NL?- and a calibration ofthe pent-..Uit!z/T1A system was carried out with then. Our usual proc.dure is tolollow tht ahock front in the PW9A with a streak camera. The reordis giveposititu, (x3) vj 'me (t) dsta which mast be differentiated to obtain the desiredshock. velocity •UT vs X data. Once the U vs X da+,a arte btained, tqey can becmverted tv preasure (P) vs X data through the M'tk sbock Hugoniot . UMcogthe problems involved axe (a) obtaining accurate X vs t deta, and (b) differen-tiating them pVzperly. Of these, the latter is by far the more diffieult probleemIn the first work, an . a3ytiral procedure and a graphica2procedure gave valies

of U which differed by 3 .wuch as 0. 3 mm/w*ec at X 5 20 maV,

Subsequent calibratio workn led to a revision of the U vi X curve (obtainedfrom, the same X vs t data). 1+ also shajed the advantage of working with U vs Xrather than P vs X, inasucn vs conversion of U to P magwiflvd differences by aftctor of 3 or 4. Finally, it di-mcwtrated, eith Record 11 44A, trAt three graphl-cal methods of differentiating týe same. X vs t data (considered equivalent) gav'edifferences in 'he U vs t data shcwn in Vdble I; the mximuw spread is 0.25mm/psec. A later numerical treatment cf the same X vs t data by use of a splinef5mction gave a U vs X curvie belov thoee obtained by the three graphical methodsan6L increased the miaimm difference betieen methods to about 0.4 mm/woec for

4-

IXOLTR 70-25-

X < 50 mm. These different U vs X frcv the same X vst data are desc~ibed toe~ihacize the difficalty of choosing a mathod of differentiation~. It Is not aproblem that we can expect to solve,, cuiy to minimize. It is one tbat vill beurder continuing study because there is -no physical basis for choosinfg a "correcU vs X curve.

The se-cond lot of peutolit~e paall~ts was obtained from Crane. They, too,have been used in a callibration atudy,, and from the four shots aiFde, X vsdUta were read at much closer intervals than in the first 3tuety. The X vs t-data of the first study fit into the X vs t data of the second for X:5 50 my,i .e.,# thure soems no experimentall.y significant difference betvn~en the two sets

c~ psiio -time data. The more recent set of data has bendfeetateflwaerlcally5. It is nom su~rprising that the U vs X curve diiffers from the bestgraphical 'Creatment~ by 0. to 0.05 mrn/Ufitc ovrer the range of 5, to0 m nXUnfo't.noately, &a vs indicated above, there Is as yet n-, method of selecting[the more accurate curve. Hence, at the present time,, and pending the resultsof continuirgetudies,, the tdo U vs X curves will be averaged X5 5 0 mm; themoze Xecent va-lues (numerict.1 differentiation) viii be used at X > 50 mm.Usi choice te also based in part, on tlae results of 2-]) flow cnuain

described balow,

K 2-D) CCtJTATIONS

Wehave long needetl a riydrodiynanic 2-dimerisioeal cm'AtxtW.on of tate cmplexfLowr in the shiocked PZWA to assist in interpreting the gap test results. Tivc

atteptsbav no ben rdeeach with variants of the MW~ code. The first 6used 14+ zones per inch of PH*(A, which priduced a P vs X curve ahowing a number

inte acton :of sheek corsio rarefaction. vaves or both. The second7ue20zones per inch ai hwda nwoth U s coarseTe zoning dor s co at

setobe sufficiently fine to account for the result; some smoothing of thedat msthave been & part of deriving the U vs X curve.) Neither computation

shmasharp dip in14U for X Ž;ý T0 mm shown in the best graphically derived curve-rpentolite., Lot 1 . It was cn this basis as well as a signifiý-ant .differenceinthe X vs t data (X > 50 m) of Lot 1 froi -the X vs t data of Lot 25 'that the

f~rhave been discarded.

It' nzais evien t<10 nete ofA the cosderedynowicalcuDataiors sem Ž 10mplaetextisaptolate back to leat the are 0o corr~elpondington 4the peachr enther.ingthl

In4 feat.eicetpesuei theiCs pressurefd pentolite. a hsnbcumo t sflihait boundary

p.esxtrapshatld backtu ally be tat indce by torespondig' theun (notsure entrin thessr

PXA f heicien pesue s h CJ resrefa pnolte /Tisbon21

-!- -1.frfn ~

ItNOLTE 70-25

of the donor. However, we are not yet able to make good pressure measurementsat small values of X in the gap teat. The electromagnetic method, which measurespaezKcle velocity (u) directly,,has been used to verify the tetryl calibrationcurve at X - 10, 20, and 25 mm. The P values obtained from the measured uivere well within the expected accuracy (tI0%) of the tetryl calibration; theydiffered from the current calibration values by -4%, 0% and 1% for X's of10, 20, and 25 mm, respectively.j

Comutations of detonation parameters at se've.l densities of both TIT andPEM' by a Ruby-iike code are given in Reference (9). If these are combinedaccording to the method Sor mixtures given in Reference (10) and interpolatedto the proper density, C-J values for 50/50 pentolite at 1.56 g/cc are:

D 7.2 mm/jsec,

U 19 mm/wsec,

and P 216 kbar

L The isentrope from thii; point was taken approximately parallel to that for castpentolite (Walker-Sternberg curvesII) and intersected the PM4A Huge3iot at

U = 6.24 mm/pec,

u = 2.28 mm!psec,

and P = 168 kbar

Hence cx~r nominal values at X - 0 are Uo - 6.24 mm//.ec and Po = 168 kbar, as

P shown in Tables 2 and 3.

Table 2 contains the two sets of U vs X data for the rentolite donor andtheir average for the range X < 50 mm. It also gives the Reference (5) dataselected for X > 50 mm and the corresponding calibration data for the tetryldonor. These data are plctted in Figure 1 which shows the U vs X curve (pentolite

donor) slightly above that for the tetryl donor as vvald be expected from therespective computed C-J pressures. The two curves appear to becowe coincidentat X - 35 mm (possibly as early as X - 25 mm). For X > 35 m., the a&erage differ-ence in the velocities for the two curves i1 0.02 mm/Lec; the naximum is 0.05

hmm/psec or less than 2% U. The maximum value is less than the average difference

S(0.07 mm/tsec) found in differentiating the same X ve t data by different methods(Table I). Hence it cannot be considered significant, and the t-c calibrationcurves will be treated as coincident for X >_35 mm.

For X < 35 am, only oue additiomal smoothing adjustment was made. The valueof U at X 5 mm was increased by about 1% to make the present curve more similarin shape to the caliSbration cuave for the tetryl donor. This is in the region ofnominal v•uhes (ieX < i0 rm) loere we now know, fro electrcmagntic Vie-asure.

meats of particle velocity in PWA, that both mlibration curves mast eventuallybe revised.

M

30

--- . .,• • •• - ••' LI ! o J

NOLTR r0O-25

Table 3 coutains the data selected for the present calibration curve of theLSOT with a 50/50 pressed pentolite donor, P. - 1.56 g/cc. The P vs X data*are plotted in Figure 2 where the calibration for the tetryl donor is also shownfor comparison. In both cases, for X 10 to 100 mm, the accuracy is believedto be t2.5% in U and ±10% in P or better. Largest errors would be expected atthe two extremes of the range.

The revised calibratiom for the pentolite donor can now be used for compari-son of P measured in the gap test with the two different domors. Table 4 containsthe resuats for such a comparison obtained about five years ago with pentolitepellets from Lot 1. With the present calibration, the value of U at the 50% pointis the same for the two donors to ±0.5% and the value of Pg is the same to ±2%.The previous calibration gave differences larger by a factor of five.

The only material that has so far been tested with both pentolite pellets,Lot 2, and tetryl is DA7B. The results were:

DAMB Acceptor 50% Value• i D~mor

p.(g/cc) % T4D Gap(cards) Gap(nm-) Pg (kbar)

P 1,667 90.75 139 35.3 35.1

T 1. 67T4 91.13 138 35.0 34.7**

B** ecomes 34.9 when corrected to .= 1.66T g/cc.

For x 35 mm both the 50% gap value and P. were the same to within less than 1%an•d this fact lends support to the coincidence of the two calibration curves ofFigure 2 at X >_ 35 m. So too does the result for Com B-3 oZ Table 4.

The gap test results for both lots of pentolite pellets indicate that the50% pressure P is the same as that measured with the tetryl donor. Inasmuchas the pentolife vas chosen to have the same detonation velocity and approximatelythe same detomtion pressure as the standard tetryl donor, it is reasonable toexpect that the pressure pulse it produces in the PM4A will be of approximtelythe s#am shape ar duration as that produced by the tetryl. If so, the measuredP8 should be the sam in each case, as it appears to be.

4

As mentiowed earlier, the PMA Hugoniot was used to convert U vu X datato P vs X.

4!

NOLER 70-25

SUNKWff

The calibration c.urve for the I= with 50/50 pentolite as the donor hasbeen revised in the light of additional data for the pentolite/lXKA system anda better knowledge of the P4A Miuoniot. Work will be continued and the presentcurve will be revised when new data indicates that a revision should be made.

I

U 5

-~~~~F F1 I IN P-0W1IITJ2

NOLTh 7C-25

REYERENCES

1. I. Jaffe, G. E. Roberson, A. R. Clairmcnt and D. Price, NOLTR 65-177

(15 Nov 1965). Co0TD)DMIAL

2. I. Jaffe, G. Roberson and J. Toscano, NOLTR 63-19 (29 jan 1963).

.3. D. Price ard T. P. Liddiae,, NOLTh 66-87 (7 July 1966), Table A-i.

4. T. P. Lidd!ard and Donna Price, NOLTR 65-43 (20 Aug 1965), particularlythe appendices.

5. J. 0. Xrkman,"3eha'*-1or of PMMA under Stjock Loading by a Pentolite Donor I,"in preparation.

6. 1. E. Fisber, R. G. Johnson, and R. F. Paulson, "Simulation of tre DynamicalLoading of PMWA in the NOL Regular Card Gap Test," Honeywell document12135- MI(Nov 1968).

7. N. Kamegai, Numerical Analysis of a Diverging Wave in Lucite," InternalReport, University of California, UL, (Oct 1969).

8. D. J. Ewards, et &l, "The Electromagnetic Velocity Gage and Applicationsto the Measurement of Particle Velocity in PNKA," in preparation.

9. C. L. Mader, University of California, Los Alamoe, Report 2900 (1963).

* 10. D. Price and H. Hurwitz, NOLJTR 63-216 (1963).

11. H. X. Sternberg and W. A. Walker, ROL, Worksheets compiled from data

&avilable in 19,60.

I i

12. D. Price, •Om, 64-148 (28 Au 1964).

6

NOLTR 70-25

z z0 0

0 0LU

0 n0z

a-

t f.- .-

o UJ

> LU

ca

I 4

-n Ucs>LLJ-Iiww~

7V

NOLTR 70-25

-• 200

150'

S100-

a. PENTOLITE

TETRYL

50

a

20 40 60 80

j X (MM1

t FIG. 2 COMPARISON OF CALIBRAV'ION CURVES FOP. TETRYL AND PENTOLITE DONORS

1 8

F.- --VP-M-

NOLTH TO-25

Table 1*

SPREAD IN VELOCMTY DATA FOIR I q M0DS 0F DII• ONAA•0N

X Mean Value Spread In U values from threo(i) U mmhWec methos 0/~e

0 5.62 0.255 5.28 0.24

10 4.97 0.2215 lg.66 o.1420 4.40 0.09-25 4,20 O.0230 '1.05 0.0435 3.86 0.0740 3.66 0o09145 3.47 0.0650 3.36 0.05-5 3.29 0.0460 3.23 0.0565 3.19 0.0870 3.15 0.0975 3.14 0.0880 3.12 0.06

* Data for tetryl/IMfA system. Taken frcm Table B1of Reference (4).

ii9

CWMARSOF OF AVMWAE SHlOC VLCITIES INPWA FOR PEOIJTE ANDTETFL DONORS

S~~Lm! (No. Qr.s) ,I,•.....

S5 19.7 5.34 5.71 5.52 5.391o 39. 4.93 5.25 5.09 4.9415 59.0 4.68 4.84, 4.76 4.63S:1 2.___g 78.7 _ .43 _ _.__ _ 9 4_.__ ,6 _.3925 98.4. 4.25 4..20 4.22 4.1930 118.1 .. I 3.96 4.04 .. ol35 137.8 3.90 3.74 3.82 3.8440 157,5 3.7. 3.58 3.65 3.66

15 177.2 3.58 3.44 3.51 3.5050 1.9 .3,3 3.38 3.4054-.-61- 215 3.32 3.32 3.34,59.69 235 3.27 3.27 3.286.T77 255 3.26 3.2669.85 2T5 3.25 3.25 3.20

34.193 295 3.1 3.218"80.0o 31r 3.16 3.16 3.1585.09 335 3.16 3.1690.17 355 3.15 3.15 3.1295.-25 375 3.14 3.14

100.33 395 3.06 3.06 3.10

* Tble A4 data at X > 50 U discarded. See text.

r1iII•

Table 3

CALI3RATI-ON DATA CHOSEN FOR LSM WITL PEMLITE DONOR*

XJ.M Pg(kbar) U(imm/.ac) u(imn/ilMec)

0 (168).... ....5 (123)55ý18

10 93.7 5.09 1.5615 76.3 1..6 1.3620 051. 6 4. 46 I.r1

-55.7L 4.22 1.0230 .03.5 0•. 0.91335 35.7 3.84 0.7884o 28.& 3.66 o.651-.45 2. 0 3.50 0.53350 18.o 3.41o o.449

1q 3.3 0.3712. 3.2U 0.32070 9.2 3.20 o.24480 7.4 3.15 0..9990 6.2 3.12 o.168

100 5.3 3.10 0.145

N PEI/TIT, 50/50, 0, - 1.56 g/ee. Values sbown in parentbeses are omly nouinal.

i

11I

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3 REPORT TITLE

CALBArL-ON Ow ToR ?KL Lulwk sCaI GA? =5 WrA A PM~TOLITh DO=O 37

4 DESCRIPTIVE NOTES (Type ,>JIpor end Inclusive dteso)

5 AUTHOR(S) (Led. neme, first reneie Initial)Price, Dcna

e vrVo-R-To 1ATE TOTAL wo or PAGri b N OF RERS

17 March 19(0 21,S,B& CONTRACT OR GRANT NO 94. OAIa1NAr1tCR4 REPORT 10,8I

ORD 331 002/ 092-1/UPI9--332-302 ________ __

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13 ABSTRACT

"Renceforth tbe standard donior in the SOL large scale gap test w-ill. be 50/50pentolite pellets pressed to a density of 1.56 g/cc inste-ad of the tetry'lpellets previously used. The pentolite dcanors will, be supplied by MAD,Crane,, Indiana. This report gives" the current calibration curve for thelarge sea!,- gap test with the pentolite decors.

RIDD '11473__ _ __ _

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ITArge Scale Gap !SestPt'ntolite Donor Ire,

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