coe & oD — fe= GES t' [= buted ain ™ canal abel ae a WSS OG Vio. (S0( LOE! LYOdau / TIN QUALIFIED REQUESTERS MAY OBTAIN COPIES OF THIS REPORT FROM DDC. STOCK AVAILABLE AT: CLEARINGHOUSE FOR FEDERAL SCIENTIFIC AND TECHNICAL INFORMATION, CFSTI SILLS BUILDING 5285 PORT ROVAL ROAD SPRINGFIELD, VIRGINIA 22151 WN PROBLEM Design, develop, and construct a pressure vessel that will encapsulate a sonar transducer under test and permit calibration under pressure. RESULTS 1. A pressure vessel with favorable acoustical proper- ties was built under contract. 2. It was designed to house only the test transducer. 3. Maximum operating pressure is 800 psig for long- term cycling. 4. Maximum operating frequency is 500 kc/s. 5. The mounting mechanism holds the transducer on the regular calibration column either inside or outside the vessel. RECOMMENDATIONS 1. Consider the use of acoustically transparent pres- sure vessels for evaluating sonar transducers. 2. Consider a mounting mechanism that holds the vessel on the regular calibration column with the test transducer inside the vessel. 3. Consider the vessel as part of the rotating system to obtain polar patterns of the transducer. THUMM 0040504 0 ADMINISTRATIVE INFORMATION Work was accomplished under SF 101 03 18, Task 8049 (NEL L30151). The report covers work from October 1964 to March 1965 and was approved for publication 26 July 1965. CONTENTS INTRO DU CMON a Degems MECHANICAL DESIGN... 5 ACOUSTICAL DESIGN... @ EVALUATION OF THE VESSEL... 9 Capsule Walls Uniform... 9 Directivity Unaffected by Pressure... 9 Attenuation Uniform to 100 kc/s... 9 Beam Patterns Unaffected by Vessel...11 PRESSURE VESSEL SPECIFICATIONS... 13 TESTS OF THE B24FA TRANSDUCER. ..14 CONCEUSIONSS ee ILLUSTRATIONS Pressure vessel, with fiber glass capsule and steel end cap assembled. Photograph...p2ge § End cap, with transducer bolted in place prior to assembly of pressure vessel. Photograph... 6 Pressure vessel. Sectional... 7 Pneumatic-hydraulic pump on calibration column in shed. Photograph. ..& Attenuation as a function of frequency... 10 Directivity patterns of transducer inside and outside the capsule, 100 kc/s... 71 Directivity patterns of transducer inside and outside the Capsules 50) key/isee le Directivity patterns of transducer at 0 and 500 psig, 24 kc/s...14 Directivity patterns of transducer at 0 and 500 psig, 34 IG //Sia 9 6 da Complex impedance of B24FA transducer at 0 and 500 OSHSS 5 > 220 Transmitting response of B24FA transducer at 0 and 500 psig...17 REVERSE SIDE BLANK , i Dy SAGE Se 0S pe eriahs ite Tue be Pel o 59 ~it HT S 74.90 { fies wha mare acted hee i ¢ ait : 4 oy a tf “ante leacer’ ¥ Ph. - d a = 4 oy ¥ tC i i it ] . : , / < f INTRODUCTION Requests for calibration of sonar transducers at depths beyond normal station capability are becoming more frequent. The NEL solution to the problem is a system for applying pressure to a transducer within an acoustically transparent vessel. The acoustical transparency permits other transducers involved in the tests to be located out- side the vessel in their normal environment. MECHANICAL DESIGN The pressure vessel is cylindrical with elliptical end sections. Fiber glass-consolidated resin providing both acceptable wall thickness and acoustical transparency is used for the walls of the capsule. A geodesic winding pattern minimizes the amount of fiber glass required. The radial strength of the vessel is increased by a cylindrically- wound additional layer. The wall has a breaking strength of several thousand psig. The consolidated windings were vacuum-cured to reduce air entrapment. Hnd cap, with transducer bolted in place prior to assembly of pressure vessel. Mounting plate (top of photo- graph) couples directly to CONGO FOGBOD COLMUR tin LPCRSS ducer Hvaluation Center (HPOPSOGCC) FOCBIGCYC Pressure vessél, with fiber glass capsule and steel end cap assembled. TRANSDUCER MOUNT ‘AN 30 IN. VERTICAL SECTION WABBRBBBBBBaaaaawa SSE ESS SSS S S $ ? YL Secor FILL AND DRAIN VALVE Pressure vessel accommodates transducers up to 22 inches in diameter and 36 inches long. Hlectrical leads are coupled to watertight connectors and ex- tended to calibration equipment. High-pressure solenoid valve permits filling or draining of ves- SEGil GS Go BS HOMGTEE Or PEOUSECEHOS Pressure relief is provided by bolts of high tensile strength and nuts which strip on pressure increase to failure limit (three times operating pressure of 800 psig)$ when threads strips cap rises slightly and water escapes past O-ring seal. Pneumatic-~hydraulic pump on calibration column in shed supplies water to vessel at pressure 10 times that of supply air. ACOUSTICAL DESIGN Maximum operating pressure was set at 800 psig by the demand for calibration at the depth it represents. Acoustic attenuation is acceptable with the wall thickness required by this pressure. The steel cap was considered to be located far enough from the transducer under test to be of no acoustical con- sequence. If it had become a source of significant reflec - tions, it would have been coated with Goodrich absorbent rubber SOAB. EVALUATION OF THE VESSEL In the evaluation of the vessel it was necessary to determine acoustically (1) the circular uniformity of the capsule walls, (2) the reflective and absorptive behavior due to pressure alone, (3) the effect of the vessel on fre- quency response, and (4) the effect of the vessel on direc- tivity patterns. Capsule Walls Uniform Uniform wall thickness of the capsule permits trans- ducers to be mounted in random orientation with respect to the walls. Thickness is more important acoustically at high frequency, where the behavior of materials is more critical. Specifically, a high-frequency test checks the uniformity of the consolidation of the fiber windings and the thickness of the epoxy. The high-frequency measurement was performed by comparing cylindrical free-field polar patterns made by a probe mounted on the cap with and with- out the capsule attached. No measurable difference in pat- terns was observed. Several checks of this type indicated that the walls are uniform enough for this application. Directivity Unaffected by Pressure The vessel was tested for change in acoustical be- havior due to pressure alone with a selection of nonpressure- sensitive transducers with directivity indexes varying from very low to very high. Patterns plotted at 0 psig and at in- crements of 100 psig to 800 psig show no change, and it is presumed that vessel behavior is independent of pressure. Attenuation Uniform to 100 kc/s Change in acoustical behavior as a function of fre- quency was expected, since the frequency spectrum of interest encompasses the range from a fraction of a cycle to several 10 cycles within the thickness of the plastic. A number of transducers of various sizes were calibrated inside and outside the capsule at 0 psig. Very little capsule effect on signal strength was revealed below 8 kc/s. As shown in the chart, the transmitted signal is reduced smoothly and uni- formly up to 100 kc/s, and fluctuates above that frequency. These results seem quite predictable. Results of tests on unknown transducers can be checked against duplicate mea- surements made without the capsule, if necessary. KC/S Attenuation as a function of frequency. Since for frequencies below 8 kc/s the walls of the capsule have little effect on the signal, measurements can be steady state or pulse. At higher frequencies reflections from the walls add to or subtract from the signal, and pulse measurements are required. The vessel is large enough compared to the transducer to provide adequate time delay in the reflected signal for true evaluation of the incident sound only. Beam Patterns Unaffected by Vessel 100 KC/S OUT OF VESSEL IN VESSEL (0 PSIG) Close correspondence of directivity patterns of transducer within and without the capsule indicates that transmission properties of the plastic are lineare Beam patterns are unaffected by the pres-— sure of the vessel. al 12 750 KC/S OUT OF VESSEL 0° al NIVESSELO}P SIG) Lobes do not correspond so closely at higher fre- quencies. The divergence revealed by tests at OSC 72 UBSOrul UR URECTOPECCUAG PESUIGS OF CeSES under pressure. PRESSURE VESSEL SPECIFICATIONS (Complete specifications are provided by drawing 153-SSK- 1001, Rohr Corporation, Riverside, California. ) OPERATING PRESSURE METAL COMPONENTS FIBER GLASS RESIN VESSEL INNER SURFACE VESSEL OUTER SURFACE DRAIN VALVE ELECTRICAL CONNECTIONS WATER PUMP LIFE SPAN 800 psig, max 4340 steel $99-4, with tensile strength of 600, 000 psi Union Carbide ERL-2772, cured with 22L-0820 hardener Rubber Compliant plastic, Furane Plastics Company, 100 parts Epocast 202 to 150 parts 9615 hardener Atkomatic Dymo Company, solenoid model EWPCV, with watertight case Marsh Marine XSK3PML 3- terminal pressure panel mount Sprague air-actuated piston pump model $216C; hydraulic pressure is 10 times air pres- sure (50-psig air pressure provides 500-psig water pressure) 1000 cycles over 10 years 13 TESTS OF THE B24FA TRANSDUCER The B24FA transducer was designed for use on sub- marines at varying depths. A test transducer was cali- brated at shallow depth at Transdec, repeatedly pressurized 24 KC/S ————— 0. PSIG 0° —_——— 500 PSIG B24FA Directivity patcerns for 0 and 500 psig are very similar at 24 and 32 kc/s. to prove mechanical soundness, and calibrated again at shallow depth. No deterioration was revealed by this cy- cling. Transmitting response and impedance at 0 psig were the same before and after pressurization. However, test results demonstrate that transducer performance differs profoundly from surface to deep-sea operation. 32 KC/S 0 PSIG B24FA 0° 500 PSIG 15 B24FA 0 PSIG eeeeccccce 500 PSIG 600 400 200 -200 -400 Complex impedance is sufficiently changed by pres-— suTization tio! detune the transiducem and theme by change driver requirements. B24FA ——— 0 OF VESSEL ----- IN VESSEL (0 PSIG) ecoceceooe|N VESSEL (500 PSIG) DB RE 1 AMPERE AT 1 METER Fransmitting nmesponse therefore ius markedly dif ferent at 500 psig. CONCLUSIONS The acoustic pressure vessel can be used on the regular calibration column for testing frequency response, directivity, and impedance of transducers. Water pressure can be controlled to any value up to 800 psig. The effect of the presence of the vessel is negligible for frequencies below 8 kc/s and predictable for frequencies up to 1 Mc/s. Calibration can be accomplished by cw or pulse at lower frequencies; however, pulse technique must be used above 8 kc/s for accurate readings. 17 od 5 ae Saale OUR TE oe Aa i (3) ASSIFIED Security Classification DOCUMENT CONTROL DATA - R&D (Security classification of title, body of abstract and indexing annotation must be entered when the overall report is classified) 1. ORIGINATIN G ACTIVITY (Corporate author) ¢ : UNCLASSIFIED Navy Electronics Laboratory, San Diego, Calif. 26. GROUP 92152 None 3. REPORT TITLE PRESSURE VESSEL FOR CALIBRATING SONAR TRANSDUCERS 4. DESCRIPTIVE NOTES (Type of report and inclusive dates) Research and development report, October 1964 to March 1965 5. AUTHOR(S) (Last name, first name, initial) Green, C. E. 6. REPORT DATE 7a. TOTAL NO. OF PAGES 76. NO. OF REFS 26 July 1965 17 None 8a. CONTRACT OR GRANT NO. 9a. ORIGINATOR'’S REPORT NUMBER(S) SF 101 03 18, Task 8049 b. PROJECT NO. (NEL L30151) 1301 9b. OTHER REPORT NO(S) (Any other numbers that may be assigned this report) 10. AVAILABILITY/LIMITATION TI Ss «ps . ° . y 4 PUNO SE Qualified requesters may obtain copies of this report from DDC. Also available from Clearinghouse for Federal Scientific & Technical Information. 11. SUPPLEMENTARY NOTES 12. SPONSORING MILITARY ACTIVITY Bureau of Ships, Department of the Navy, Washington, D. C. 20360 13. ABSTRACT Acoustically transparent vessel houses a single transducer for testing under pressure to 800 psig. Tests of B24FA transducer indicate marked difference in transmitting response at depth. 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Jaonp -SUBJ} W4pzd JO S}Sa1 “Bisd QOg 0} ainssaid apun Bunjsa} 404 Jaonpsued} ajbuls e sasnoy jassan juatedsuedy AljeNSNody GaldISSVIONN "69 INf 92 ‘"d JT ‘uaasg °3 °9 Aq ‘SUIONGSNVUL YVNOS ONILWYITVD NOI 13SS3A JUNSSAYd TO€T Hoday "ye9 ‘obaiq ues ‘*ge] s91U04}9917 Aven “yydap je asuodsas Huljiwsues} Ul aduaiajJIp paysew ayedipul Jaonp SUP} V4pZg JO $}Sa, “bisd 00g 0} aunssaid 4apuN Bulysa} 404 Jaonpsuedj ajbuls e sasnoy jassaa juasedsues) Ajjeasnooy daldISSVIONA "69 INf 92 ‘“d JT ‘uaatg °3 °9 Aq SYJINGSNVUL YVNOS ONILVYSITVD YOd T3SS3A JUNSSIYd TO€T }4oday “yye9 ‘obaig ues ‘ qe] s91u04}9913 AneN GAldISSWIONN S! p4ed siyy (IST0€1 13N) 6108 ¥S21 ‘81 €0 TOT 4S "3 °9 ‘ua019 +] s}|nsaJ }S9] - Suaonpsued ‘2 juawidinby - suaonpsued "LT GAIdISSWIONN S! p4eo sty (IST0€1 TAN) 608 ASEL ‘ST €0 IOI 4S "9 ‘uaal9 * s}nsad }S9] - Sdaonpsued| °Z juawdinby - suaonpsues, °T “uydap ye asuodsas Bulyiwsues} Ul aduasayjip paysew ayeoipul 4a9np -SUBI} W4pZg JO S}sa, ‘Bisd 00g 0} aunssasd uapunN Hulse} Joy Jaonpsued} ajbuis e sasnoy jassan juasedsued} Ajjedsnooy dald!SSVIONN "69 INf 9% ‘"d JT ‘uaedg °3 “9 Aq ‘SUJONGSNVUL YVNOS ONILWYSITVD YOI T9SS3A JNNSSId TOET }4oday "y42Q ‘obaig ues ‘*qe7 s91U04199/3 Aven “yydap ye asuodsas bulyjiwsued} Ul aduadasjIp payjew a}edipul Jaonp -SUPJ} W4pZg JO S}Sa, “isd 00g 0} aunssasd Japun buljsa} 40} daonpsued} ajbuls e sasnoy jassan udsedsued} Ajjennsnooy ddldISSWIONN "¢9 Inf 92 ‘“d JT ‘uaasg °3 °9 Aq ‘SUJONGSNVUL YVNOS ONILVYGITVO YO4 TaSSIA JUNSSIud TOET j4oday "yyeQ ‘obaiq ues ‘°qe] s91u04}99}9 AneN CODE 1610 CODE 1620 CODE 1631 (2) CODE 210L CODE 320 CODE 360 CODE 452E CODE 670 (2) CHIEF» BUREAU OF NAVAL WEAPONS DLI=3 DLI=31 R-56 RUDC=2 CHIEF OF NAVAL PERSONNEL PERS 118 CHIEF OF NAVAL OPERATIONS OP-07T OP-701E1 OP-71 OP-03EG OP-09B5 CHIEF OF NAVAL RESEARCH CODE 455 CODE 461 CODE 466 CODE 468 COMMANDER IN CHIEF US PACIFIC FLEET COMMANDER IN CHIEF US ATLANTIC FLEET COMMANDER OPERATIONAL TEST AND EVALUATION FORCE DEPUTY COMMANDER OPERATIONAL TEST = EVALUATION FORCE» PACIFIC COMMANDER CRUISER=DESTROYER FORCEs US ATLANTIC FLEET US PACIFIC FLEET COMMANDER SUBMARINE FORCE US PACIFIC FLEET US ATLANTIC FLEET DEPUTY COMMANDER SUBMARINE FORCE» US ATLANTIC FLEET COMMANDER ANTISUBMARINE WARFARE FOR US PACIFIC FLEET COMMANDER TRAINING COMMAND US PACIFIC FLEET OCEANOGRAPHIC SYSTEM PACIFIC (2) COMMANDER SUBMARINE DEVELOPMENT GROUP TWO COMMANDER SERVICE FORCE US ATLANTIC FLEET COMMANDER KEY WEST TEST - 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