AMMRC TR 76-20 (j ) AD

ULTRASONIC INSPECTION OF

"BRAZED AND WELDED OVERLAYo ROTATING BAND ATTACHMENT

o ON ARTILLERY SHELLS

FREDERICK S. HANNON, ROBERT H. BROCKELMAN,JAMES M. QUIGLEY, and DANIEL J. RODERICKMATERIALS TESTING TECHNOLOGY DIVISION

July 1976 D D -

OCT 14 1976

Approved for public relem; distribution unlimited.

ARMY MATERIALS AND MECHANICS RESEARCH CENTERWatertown, Massachusetts 02172

' It 0- " .... ..i

4r -

The findings in this report are not to be comtrusd as an officialDepartment of the Army position, unless so deulted by otherauthorized documents.

Mention of any trade nams or mamufacturrs In this rpormtshall not be construed as dertjng nor s an officialM aindorsement or approval of such products or companies bythe United States Goverrnent.

Ot MT" 1ITmcImOw

Oegae " son Isu " i i o w *M.o ". sehin Is a dw iloma.

UNCLASSIFIEDSECURITY CLASSIFICATION OF THIS PAGE (USta, Dae Entered)

REPOR DOCMENTTIONPAGEREAD INSTRUCTIONS________________________________PAGE_ BEFORECOMPLETNGFORM

I. REORT NMI aGOVT ACCESSION NO S. RECIPIENT'S CATALOG NUMBER

14. TITL-9-andLitoes)S. TYPE OF REPORT A PERIOD COVERED

'OVERLAY ROTATING BAND ATTACHMENT ON -ARTILLERY 6PR01tIGO6-EOTNME

-SHELLS.,_____________

---- --- ---. CONTRACT ON GRANT NUMBER(s)

Frederick S..1lannon, Robert H,/B ockelman,James M./'Quigley,.. Daniel J/'Roderick______________

S. ERO.iNOORANZATION NAME AND ADDRESS 10. PROGRAM ELEMENT. PROJECT. TASK

Army Materials and Mechanics Research Center ARE Aroject: IT

Watertown, Massachusetts 02172 kC Code: 685801.49.11100DRXMR-M ____________

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U. S. Army Materiel Development and Readiness " u 11Command, Alexandria, Virginia 22333IT USRO 2S

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SCHEDULE

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19. KEY WORDS (Continue en ravors* side it necessary and Identify by block number)

Ultrasonic testsBrazed jointsProjectilesRotating bands

SO. ABSTRACT (Continue on retreree side It necoeeetrv and Identify by btock number)

(SEE REVERSE SIDE)

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ABSTRACT

This report describes an effort to generate the correlation datanecessary to establish ultrasonic standards and specifications for theinspection of brazed and weld overlay joints of artillery shell rotat-ing bands. Ultrasonic pulse-echo C-scan tests were made of the brazedand weld overlay areas of projectile motor bodies. Mechanical testplugs were machined from selected areas of these bands. The shear bondstrengths of the plugs were measured and correlated with C-scan results.Artificial and actual unbond areas of bond joints were destructivelyexamined and correlated with C-scans.

" OCT 14 190u

D

UNCLASSIFIED i.S.Cu3I? CLAIS...AO. O. ... .A... 0.. I .. E)

Yi WE OC 14 IN l i~ III

CONTENTS

Page

INTRODUCTION .............. ............................. 1

TEST PREPARATION AND PROCEDURE

Brazed Motor Bodies ........... ....................... 1

Weld Overlay Bodies ........... ....................... 2

Ultrasonic C-Scan Tests .......... ..................... 2

Test Plug Specimens .......... ........................ 4

Destructive Tests ......... ........................ ... 12

RESULTS AND DISCUSSION

Visual Correlation of C-Scans with Unbonds ... ........... ... 14

X-Ray and Dye Penetrant Examination of Mechanical Test Plugs 14

Correlation of Mechanical Shear Strength and C-Scan Results. 15

CONCLUSIONS ........... ............................. .... 18

AAIM

INTRODUCTION

The application of improved techniques for attaching artillery shell rotatingbands over the conventional mechanically hot-swaged method has been the subject ofconsiderable attention since it was recognized that their use could result insignificant savings in cost and critical materials. Two completely distincthanding techniques, the ,eld overlay and foil interlayer braze, have been demon-stratcd to possess the above advantages and they are applicable to both conven-tional and nuclear shell. Further exploitation and application of these methodsis contingent upon implementation of industrial testing techniques that assure themaintenance of required mechanical properties. In the case of the weld overlaybanding technique, problems exist in inspecting not only for bond defects betweenthe rotating band and projectile body, but also for discontinuities (cracks andcraters) in the steel under the rotating band. Inspection of brazed joints isconcerned only with the detection of unbonds because the process has no adverseeffects on the steel body.

Ultrasonic C-scan techniques were initially employed during the developmentalstages of braze banding in order to provide a fast, reliable means of bond eval-uation. Ultrasonic testing was found to be more sensitive to changes in the con-dition of the brazed joint than radiography. Although conventional black andwhite or go-no-go ultras3nic C-scan techniques have been successfully applied todetect unbonds at the braze interface surface, very little correlation data areavailable for establishing complete nondestructive testing (NDT) standards andspecifications for production inspection of these components. This MaterialsTesting Technology Program study was undertaken to perform a destructive analysisand to correlate the physical condition and mechanical properties of silver andnickel brazed joints and weld overlay joints with ultrasonic test results. Thisreport addresses the problem of unbonded detection. A preliminary study involvingthe inspection of weld overlay motor bodies for cracks and craters was the subjectof a previous report. 1 A more comprehensive crack investigation study is cur-rently being conducted at AMMRC.

TEST PREPARATION AND PROCEDURE

Brazed Motor Bodies

Eight forged motor bodies for the XM650 RAP (rocket-assisted projectile)were available for brazing. For purposes of this report the motor bodies werearbitrarily identified as forged bodies 1 through 8. Forged body 4 was found tobe defective prior to brazing and removed from the test sampling. The brazingmaterials employed were Palcusil and Cusil, silver base alloys, and Nicrobraz 10,a nickel base alloy, all of which have been successfully used in previous applica-tions. All brazing was done in an inert atmosphere except for forged body 5,which was brazed in air. Forged body 1 was used as the C-scan standard.

I. BROCKELMAN, R. H., MULDOON, R. A., and RODERICK, D. ,velimnarj Development of Vltreaonk C-Seen Test Methodsand Standards to Determine PoVectile-Rotatbn Band Intearty. Army Materials and Mechanics Research Center, AMMRC TR 76-1,January 1976.

- - - - - -*. .,

Forged bodies 1, 2, and 3 were brazed with Palcusil 15 foil. To produceunbonds of known dimensions, six 0.005-inch-thick Grafoil disks, two each of 1/16-,1/8-, and 1/4-inch diameter, were positioned at the interface of bodies I and 2.(These disks prevent wetting of the mating surfaces during the brazing cycle; ifbonding takes place adjacent to the disks, unbonds of known dimensions will beproduced.) Forged bodies 5 and 8 were brazed with Nicrobraz 10 paste, body 6with electroless nickel, and body 7 with Cusil foil. Prior to brazing forgedbody 6, both the forging and rotating band were plated with 2 to 5 mils nickel.On forged body 8, too much pressure at temperature was applied and the rotatingband was deformed. Figure 1 shows a typical brazing operation.

Six of the brazed motor bodies were heat treated to obtain the propertyrequirements for a 4340 steel, i.e., austenitized for 1 hour at 1500 F in a vacuum,oil quenched, then tempered for 1 hour at 800 F and air cooled to room temperature.The bodies were processed in two lots - 2, 6, and 8, and 3, 5, and 7 - due tofurnace size limitations.

Weld Overlay Bodies

Two finish machined XM650 plasma-arc weld overlay RAP motor bodies were madeavailable by Picatinny Arsenal for correlation of ultrasonic and destructive testresults.

Ultrasonic C-Scan Tests

The seven brazed motor bodies and two weld over.'ay bodies were C-scannedin accordance with the test procedure for unbonds. 1 A pulse-echo immersion

Figure 1. Typical brazing operation

19-066-511/AMC-75

2

fl~EEE

a

ADJUSTMENT LOCK

A DJUSTMENT

WATER

TANK

LOCATOR

TRANSDUCER

b1 9

4W66/AMC.74 Figure 2. Ultrasonic C-scan test equipment (a) and schematic of test setup 1b)

100

90a

70

> 60W-J 500

40Figure 3. Screen picture of ultrasonicpulse echo signals

20

I0

ttFRONT SURFACE BOND JOINT BACK SURFACE

REFLECTION REFLECTION REFLECTION

system using the longitudinal wave technique was employed. Figure 2 shows theinspection equipment and a schematic of the test setup. Figure 3 is a typicalA-scan presentation.

The acoustic energy generated by the transducer is reflected sequentiallyat the inside diameter of the steel shell (front surface reflection), the inter-face between the outside diameter of the steel shell and the inside diameter ofthe copper rotating band (bond joint reflection), and the outside diameter of thecopper rotating band (back surface reflection). The reflected signal from theinterface of the steel shell and copper rotating band is separated for C-scanrecording purposes by means of a time gate. Negative black and white C-scan re-cordings were made of the test motor bodies. With this method of recording, thereflected signal has to exceed a preset threshold level to interrupt mark:ng ofthe recording paper. Each body was scanned at three arbitrary threshold levels(30%, 50%, and 70% of full-scale screen height) to provide the range of amplitudedata necessary for subsequent correlation with destructive testing. After align-ment, the sensitivity of the test is set by moving the transducer above the rotat--ing band and then adjusting the reflection from the outside steel body diameter andwater interface to 100% screen height. Fine adjustment of the sensitivity is thenmade to duplicate a standard scan of a motor body containing both artificial andactual unbonded areas.

C-scan recordings of the test motor bodies are shown in Figures 4a through g.The figures do not present the entire C-scans but only the sections that are ofinterest to this program.

Test Plug Specimens

Mechanical test plugs (Figure 5) were machined from selected areas in therotating bands of seven of the test motor bodies to fit a destructive shear testfixture. The locations selected are noted as circles in Figure 4. Only two testplugs were taken from weld overlay motor body 110. Each brazed plug was markedfor complete identification, e.g., 2-7. The first number represents the forgedbody and the second number locates the test plug on the C-scan.

4

70% o

50%

If

30%0

1 2 345 67Figure 4a. C-scan recording of forged body 2

--...----70%

L

50%3.4

30%O~

1 2 3 4 5 6

Figure 4b. C-scan recording of forged body 3

6

i~i 41,

50%

30%

24 3

Figure 4c, C-scan recording or Torged body 5

70% M

30%

1-Figure~ ~ ~ ~ 4d -cnreodn ffogdbd

10%

AT

50%

12 3 4 56Figure 4e. C scan recording of forged body 7

...........

70%

Ipi N

ts '

2, 3 4

50%10

ti4i

0%0]0

-1 -2Figure 4g. C-scan recording of weld overlay motor body 110

z a

•I flL 19-066-1213/AMC-75~Test Plugs;' a.Bonded Ts

I .!b. Unbonded Test Plugs

19-066-1210/AMC-75 Figure 5. Mechanical test plugsThe atualtestplug are0o50 +000

The actual test plugs are 0.500 -:005 inch in diameter by 0.30 ±0.01 inchthick, with the interface at mid-thickness. A minimum of six test plugs weretaken from six of the brazed motor bodies. Two were taken from an area that re-mained predominantly dark throughout the three threshold levels, signifying goodbonding; two were taken from an area that remained predominantly light, signifyingpoor bonding; and two were taken from an area that contained both light and darkpatches throughout the three levels

A number of test plugs did not have sufficient bond strength to withstand themachining operations (Figure Sb). Those which had sufficient bond strength wereX-ray tested at one time and dye-penetrant inspected for open porosity at theinterface.

Destructive Tests

The shear test fixture (Figure 6) is comprised of five basic components: amovable center slide, two stationary guide blocks, a tapered wedge, and a retainingbox. The test plug is inserted into the appropriate diameter hole of the moveableslide (Figure 7). The test plug braze or weld overlay interface is positioned atthe shear surface by an adjusting screw. The second guide block is positioned toaccept the other half of the test plug and pin aligned with the first guide block.These three components are placed into the retaining box along with the taperedwedge. The actual test setup utilizes a compression machine which records theload in pounds (Figure 8).

12

,-AMA

t Figure 6. Complete shear testfixture, disassembled

19-066-1212/AMC-75

Figure 7. Movable slide with test

194066.1211 /AMC-75

Figure 8. Shear test setup incompression machine

19.066-1214/AMC-75

13

me eWO64

RESULTS AND DISCUSSION

Visual Correlation of C-Scans with Unbonds

A C-scan section of the standard, brazed motor body 1 with its six foildisks, is shown in Figure 9. The unbonded areas produced by these disks arereadily detected by C-scanning, and by adjustment of transducer size and waterpath, a one-to-one correspondence between artificial unbond size and C-scan pre-sentation was attainable.

While inspecting other weld overlay bodies for Picatinny Arsenal (PA), asignificant unbond area was observed on body 41105. Accordingly, permission wasobtained from PA to remove the weld overlay material and correlate the C-scanfindings with the unbond area. The bulk of the copper rotating band was quicklyremoved in a lathe to just shy of the interface. The remaining copper materialwas removed in 0.001-inch increments until the unbond areas were visible. Thethin copper layer over the unbond was easily peeled off. Figure 10 illustratesthe success with which the C-scan technique details actual unbonded areas.

X-Ray and Dye Penetrant Examination of Mechanical Test Plugs

X-radiographic inspection of the mechanical test plugs did not reveal anyof the unbonds but did disclose gross copper voids in brazed test plugs 8-2 and8-5 and in weld overlay test plug 110-1 (Figure 11). The void in test plug 8-5

,'- • --. -

-1/16 DIA -1/8 DIA 1- /4 DIA

19-066-1533/AMC-75 Figure 9. C-scans of motor body standard

14

Vol,

'25 7

2W3 6

6 66

110 TEST NU, X RAY

Figure 10. Ultrasonic C-scan and corresponding Figure 11. Test plug X-rayunbonded area of copper weld overlay rotating band

was so far removed from the shear area that it had no effect on the shear load(see Table 1). While not discernible in the figure the actual X-ray negative doesshow the presence of the 1/8-inch-diameter Grafoil disk in test plug 2-7.

In general there was fairly good agreement between the extent of dye pene-tration and the C-scans (see Table 2 and Figure 4 for actual comparison). Testplugs 2-6, 3-5, and 6-6 were exceptions in that the C-scans indicated a greaterdye penetration than was actually observed. Visual examination of the shearedtest plugs generally showed that even when the dye did penetrate it did not pene-trate deeply, indicating that the unbonds were not gross. Correspondingly, visualexamination of the test plugs that came apart during machining indicated acomplete unbond.

Correlation of Mechanical Shear Strength and C-Scan Results

The C-scan predictions of Table 3 are based on a visual examination of theC-scans of Figure 4, i,e., an area that remains completely white throughout thethree threshold levels is assumed to be unbonded; an area that remains completelydark throughout the three levels is assumed to be bonded; and an area that ispartially white and which contracts over the three levels is assumed to be par-tially bonded. The latter case is a prime area of interest for it represents the

15

-A_

Table I. MAXIMUM SHEAR LOAD ON TEST PLUGS*

Load LoadTest Plug (Ib) Test Plug (Ib)

2-1 8400 6-3 73002-2 8750 6-4 74502-5 8050 6-5 70002-6 3900 6-6 43002-7 5800 7-2 3350

3-2 1350 7-3 68503-3 6900 7-4 35203-4 6525 7-5 68503-5 5800 7-6 62003-6 6700 8-1 7100

5-1 4600 8-2 25005-3 7850 8-3 74505-4 6700 8-4 68005-6 7600 8-5 7225

110-1 3150 8-6 6700110-2 6900 8-7 7100

*Unreported plugs parted at theinterface during machining.

Table 2. FRACTION OF OPEN POROSITY AT THE INTERFACE

CIRCUMFERENCE AS DETERMINED BY DYE PENETRANT INSPECTION

(Fraction Percent)

7/8 3/4 5/8 1/2 3/8 1/4 1/8 0

#3-2 #3-6 #5-1 #5-6 #5-3 #2-5 #2-7 Remainder7-2 6-5 110-1 5-4 7-58-1 8-2 7-6

Table 3. C-SCAN PREDICTION VERSUS PERCENT RATING

Completely Completely PartiallyUnbonded Rating Bonded Rating Bonded Rating

Test Plugs (%) Test Plugs (%) Test Plugs (%)

2-3 0 2-1 96 2-5 922-4 0 2-2 100 2-6 45

2-7 66

3-1 0 3-3 100 3-5 843-2 20 3-4 95 3-6 97

5-2 0 - - 5-1 595-3 0 - - 5-3 100

5-4 855-6 97

6-1 0 6-3 98 6-5 946-2 0 6-4 100 6-6 587-1 0 7-3 100 7-5 1007-2 49 7-4 51 7-6 91

8-1 95 8-3 100 8-2 348-4 91 8-5 978-6 908-7 95

16

-7,

transition from bonded to unbonded. The percent rating is an arbitrary numberarrived at by taking the shear load for each test plug and dividing it by thehighest shear load developed within each forged body category (see Table 1 forshear loads). From Table 3 it is readily observable that of the eleven test plugscategorized as completely unbonded, eight failed during the machining operation,17 ' had significantly lower percent ratings, and only 1 had a high percent rating.Of the eleven predictions for unbonds, ten proved to be accurate. It is equallyas observable that of the twelve test plugs categorized as completely bonded,eleven had percent rating over 90 and only one was low. The partial bonds are notso easily described nor interpreted. Attempts to correlate the C-scans made atth. three threshold levels with a visual examination of the sheared surfaces wereimpossible as the unbonds were indistinguishable, although gross copper voids andthe Grafoil disk are clearly visible (see Figure 12). Comparisons made on theratio of dark areas throughout the three threshold levels to shear load were in-conclusive in determining which more accurately predicts bond strength (althoughtht, test plug C-scans at the 70% level appeared more accurate than those at 30%and 50%).

While examination of a specific level C-scan was useful in predicting therelative bond strengths, the best approach was to examine the three C-scan levelstogether (see Figure 4). Starting with the 30% C-scan, note the white areas(indicating unbonds) and observe how the white areas contract as a function ofincreased threshold level. The quicker and more extensive the contraction (whitearea), the greater the relative bond strength. While admittedly the samplepopulation is small it may be observed from Table 3 that the average percent ratingfor the partially bonded test plugs was about 80. Considering that the completelybonded test plug categories averaged about 93% and the unbonded about 15%, it wouldappear that partially bonded areas cannot automatically be relegated to therejection box.

Brazed with Electroless Nickel Brazed with Nicrobraz 10

L 3 L- Gratoil Disk

Brazed with Palcusil 15 Weld Overlay

Figure 12. Typical trepanned test specimens after shear "sting

19-066-1239/AMC-75

17

AI-'-.

CONCLUSIONS

1. The size and shape of unbond areas can be accurately depicted by non-destructive ultrasonic C-scan tests.

2. The dark areas on a C-scan taken at the 30% threshold level are repre-sentative of the bonded areas of the shell and will be characterized by fullybonded strength levels.

3. The white areas on a C-scan taken at the 70% threshold level are repre-sentative of the unbonded areas of the shell and will be characterized by lowstrength levels.

4. White areas on a C-scan that contract (or dark areas that expand) as thethreshold level decreases from 30% to 70% are partially bonded and their bondstrength is directly related to how fast and to what extent this contraction (orexpansion) occurs.

S. Gray scale ultrasonic C-scan recordings should be applied for testingbrazed rotating band joints to eliminate the necessity of generating more thanone C-scan per component and the uncertainty involved in interpretation of blackand white ultrasonic C-scans.

6. Strength requirements of rotating bands are needed before NDT specifica-tions can be formalized.

18

- -1!Now

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