Environmental Engineering Grade A Shock Tests

Transcription

1 Environmntal Enginring Grad A Shok Tsts Juanito Dl Rosario and Stvn Murphy, SSC San Digo SPAWAR Systms Cntr San Digo Hull Strt San Digo, California, , USA Dl.Dlrosario@navy.mil Stvn.Murphy@navy.mil Abstrat- This papr an hlp provid bttr insight to th rational bhind on of th important and ritial dstrutiv tsts: th Environmntal Shok Tst. On may ask, why build a highly funtional working modl or systm and thn subjt it to svr harsh blows? Today's Navy and othr military branhs ar rlying mor havily on Commrial-Off-Th- Shlf (COTS) hardwar. It has bn a hallng to all managrs, nginrs and administrators to oprat undr limitd budgt and rdud rsours. In som ass, on may vn tak th option of dangrous stps of short uts and ost utting thniqu suh as unjustifid xmptions. This papr an srv as a hallng to managrs, dvloprs, and systms intgrators not only in th govrnmnt but also in th industry. It may provid som insight and undrstanding of th ways w do businss in th nvironmntal nginring aras in ordr to provid and dlivr a systm that an withstand harsh nvironmnt as wll as maintain fighting apability during ombat. I. INTRODUCTION Limitd budgt, rdud rsour alloations, and ost utting hav posd signifiant hallngs to projt managrs and program administrators. In th past, basi dsign nginrs, systm nginrs, systm intgrators, managrs, and projt ladrs hav followd solly th military spifiations and standards to build quipmnt for th military nvironmnt. With th availability of th vast lading dg thnologis in th ommrial world oupld with rdud rsours, th military systms hav adoptd and xpandd usag of Commrial Off-Th-Shlf (COTS) omponnts. Dspit ths hallngs, prsrvation of th fundamntal and ssntial safty of military prsonnl and th ombat apability of th Navy s fighting ships ar still ruial. Combat survivability of instrumntation is signifiant on th battlfild. Fighting ships hav to arry out thir mission in xtrm onditions, whih oftn inlud xposur to suh hazards as fir, ltromagnti intrfrn and shok. Ths ar th rasons why stablishd poliis, guidlins and ssntial rquirmnts play signifiant rols in ship, quipmnt, systms dsign and aquisition. Widsprad us of COTS poss hallngs to survivability. Th only way w an nsur that th us of latst thnology and nw produts offrd by industry supports th ombat apability and survivability of our fighting ships is to maintain th Grad A shok tsting. This is th only way w an rdu vulnrability and prvnt atastrophi loss of ritial funtions. II. SHOCK TEST REQUIREMENT BASIC TUTORIAL Survivability is th apaity of th ship to absorb damag and maintain mission intgrity. Warships ar xptd to prform offnsiv missions, to sustain battl damag and to surviv. As suh, ships prsonnl on board must b suffiintly traind and ships quipmnt must b suffiintly hardnd to withstand various thrat lvls. To attain this minimum baslin of survivability, installd quipmnt hardnd to appropriat standards must b implmntd through appropriat ship and quipmnt spifiations. A shok tsting rquirmnt vrifis th ability of installations to withstand shok loadings, whih may b inurrd during wartim srvi du to th ffts of nular or onvntional wapons [1]. Spifiation rquirmnts ar drivn by th quipmnt appliation. Th sltion of a suitabl standard or spifiation for a spifi dsign appliation is th rsponsibility of th prouring ativity. Thr ar rquird lvls of shok rsistan of shipboard quipmnt and systms and ar lassifid into two grads, Grad A and Grad B. Ths Grads ar dfind as follows [1,2]: Grad A: Grad A systms, subsystms, or itms ar thos whih ar onsidrd by Naval Sa Systms Command (NAVSEA) to b ssntial for th safty and ontinud ombat apability of th ship. Ths quipmnt and systms ar propulsion, ship ontrol, navigation, ommand, ontrol and ommuniation, surfa, air and undrwatr survillan, ountrmasurs, fir ontrol, firing or launhing, guidan of wapons, intrior ommuniation and data prossing systms ndd to support th ssntial mission. Ship has to rtain ths gnral apabilitis during and aftr attak without signifiant impairmnt of th systms. In th prvious wars, th loss of HMS Shffild in 1982 and th rippling of USS Stark in 1987 highlightd th vulnrabilitis of surfa warships not adquatly quippd or prpard to ountr th modrn Anti-Ship Cruis Missils (ASCMs) approahing undr th radar horizon [3]

2 Rport Doumntation Pag Form Approvd OMB No Publi rporting burdn for th olltion of information is stimatd to avrag 1 hour pr rspons, inluding th tim for rviwing instrutions, sarhing xisting data sours, gathring and maintaining th data ndd, and omplting and rviwing th olltion of information. Snd ommnts rgarding this burdn stimat or any othr aspt of this olltion of information, inluding suggstions for rduing this burdn, to Washington Hadquartrs Srvis, Dirtorat for Information Oprations and Rports, 1215 Jffrson Davis Highway, Suit 1204, Arlington VA Rspondnts should b awar that notwithstanding any othr provision of law, no prson shall b subjt to a pnalty for failing to omply with a olltion of information if it dos not display a urrntly valid OMB ontrol numbr. 1. REPORT DATE 01 SEP REPORT TYPE N/A 3. DATES COVERED - 4. TITLE AND SUBTITLE Environmntal Enginring Grad A Shok Tsts 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d. PROJECT NUMBER 5. TASK NUMBER 5f. WORK UNIT NUMBER 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) SPAWAR Systms Cntr San Digo Hull Strt San Digo, California, , USA 8. PERFORMING ORGANIZATION REPORT NUMBER 9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR S ACRONYM(S) 12. DISTRIBUTION/AVAILABILITY STATEMENT Approvd for publi rlas, distribution unlimitd 11. SPONSOR/MONITOR S REPORT NUMBER(S) 13. SUPPLEMENTARY NOTES S also ADM Oans 2003 MTS/IEEE Confrn, hld in San Digo, California on Sptmbr 22-26, U.S. Govrnmnt or Fdral Purpos Rights Lins, Th original doumnt ontains olor imags. 14. ABSTRACT 15. SUBJECT TERMS 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT UU a. REPORT unlassifid b. ABSTRACT unlassifid. THIS PAGE unlassifid 18. NUMBER OF PAGES 7 19a. NAME OF RESPONSIBLE PERSON Standard Form 298 (Rv. 8-98) Prsribd by ANSI Std Z39-18

3 Part of th problms was also attributd to shok and Eltromagnti Intrfrn (EMI). Grad B: Grad B systms ar itms whos opration is not ssntial to th safty and ombat apability of th ship but whih ould bom a hazard to prsonnl, to Grad A quipmnt, or to th ship as a whol as a rsult of xposur to shok. Shok tsting validats shok rsistan of missionssntial itms, and validation of total ship hardnss inluding onboard mission-ssntial itms (installd and /or stowd onfigurations). This is aomplishd by ship shok trials [4]. Itms to b tstd ar also lassifid into thr lasss: Class I, Class II, and Class III. Class I quipmnt is dfind as that whih is rquird to mt ths shok rquirmnts without th us of rsilint mountings installd btwn th quipmnt and th ship strutur or foundation. Class II quipmnt is dfind as that whih is rquird to mt ths shok rquirmnts with th us of rsilint mountings installd btwn th quipmnt and th ship strutur or shipboard foundation. Class III quipmnt is dfind as that whih has shipboard appliation both with and without th us of rsilint mountings and is thrfor rquird to mt both Class I and Class II rquirmnts. III. GRADE A SHOCK BASIC THEORY, METHOD AND PRACTICE As on may rall in his or hr arly yars of nginring lasss, th law of physis holds tru to ithr ltrial or mhanial world. Th rspons of th basi Rsistiv-Indutiv-Capaitiv (RLC) ltrial iruit and a simpl mass-spring-visous dampr, as shown in Fig. 1, to a foring funtion may b xprssd in a similar mathmatial modl. Eah modl dos xhibit th dampd natural frquny of th systm. Fig. 1. is a singl dgr-of-frdom systm with visous damping and subjtd to a varying xitation for F= F(t). Th diffrntial quation of motion for this systm is Equation (1.1) [5,6]: whr: md 2 x/dt 2 + dx/dt + kx = F(t) (1.1) or d 2 x/dt 2 + (/m)dx/dt + (k/m)x = F(t)/m (1.2) x = displamnt oordinat; displamnt of th systm as a funtion of tim dx/dt = vloity of th mass d 2 x/dt 2 = alration ()dx/dt = damping for = damping offiint m = mass k = spring onstant F(t) = Extrnal foring funtion As w may rogniz, (1.2) rprsnts a sond-ordr, ordinary diffrntial quation of th typ most ommonly nountrd in lmntary vibration or in shok analysis. To obtain th omplt solution of th diffrntial quation, w must dtrmin both a partiular solution (Xp) whih satisfis (1.2) and th homognous solution (Xh), whih also satisfis (1.2.), i.. d 2 /dt 2 (Xp) + (/m)d/dt (Xp) + (k/m)xp = F(t)/m (1.3) d 2 /dt 2 (Xh) + (/m)d/dt (Xh) + (k/m)xh = 0 (1.4) Th omplt solution to th diffrntial quation is th sum of (1.3) and (1.4): d 2 /dt 2 (Xp) + (/m)d/dt (Xp) + (k/m)xp + d 2 /dt 2 (Xh) + (/m)d/dt (Xh) + (k/m)xh = F(t)/m + 0 (1.5) or by ollting trms in th quation, w gt d 2 /dt 2 (Xp + Xh) + (/m)d/dt(xp + Xh) + (k/m)(xp + Xh) = F(t)/m (1.6) k M X Eq. 1.1 is th typial quation of motion for th mass m of th passiv ontrol systm. If a stp funtion is hosn as th foring funtion F(t) with a magnitud F = Fo whn t > 0 and F = 0 whn t < 0, w an find th typial tim solution by taking th Lapla transform of th quation: FORCE, F L [x(t)] = X(s) = (Fo/ms){1/[s 2 +(/m)s+k/m]} (1.7) Fig. 1. A singl-dgr-of-frdom systm with visous damping and xitation for, F Whr X(s) is th Lapla transform of x, a funtion of tim. Th initial ondition x(0 + )=0 and d/dt[x(0 + )]=

4 For a onvntional ontrol systm, th transmissibility T of a systm at th ondition of rsonan is [5]: T = (1/)(km) 1/2 = 1/[2(/ )] (1.8) Whr: = damping offiint = ritial damping offiint / = damping ratio< 0.2 m = mass k = spring onstant Similarly, th rsonan frquny Wr is approximatly qual to th undampd natural frquny w n [5]: w n = (k/m) 1/2 (1.9) or (w n ) 2 = k/m (1.10) From (1.8) and (1.10), w an driv th rlationship: 2 (/ )w n = /m (1.11) Using (1.10) and (1.11), quation (1.7) may b writtn as: X(s) = (Fo/ms){1/ [s 2 + 2(/ )w n s + w n 2 ] } (1.12) Th typial tim solution of (1.12) is a dampd sinusoid. Exampl of th wavform is shown in Fig t os( 300t) t 80 Fig. 2. Dampd sinusoid wavform. Exampl of a typial tim solution for a systm with stp funtion as th foring funtion W an thn apply th final valu thorm to dtrmin th movmnt of th isolator oil rprsntd by k and in Fig. 1. lim sx(s) = lim x(t) s 0 t lim s (F 0 /ms) {1/[s 2 + 2(/ )w n s + (w n ) 2 } = (F 0 /m)(1/w n 2 ) (1.13) Th disussion abov is a dsription of a basi mthod of finding solution for a simpl systm. Th solution in (1.6) givs th displamnt x of th mass from th rfrn position as a funtion of tim. Th magnitud of that displamnt is th atual rspons of th systm to th shok, whih an b xprssd as th tim-history of a paramtr that dsribs th motion of th systm. For this systm, th magnituds of th rspons paks an b summarizd as a funtion of th natural priod of th rsponding systm (natural frquny), at various valus of th fration of ritial damping [5]. Foring funtions ar shok motions that may b sltd for analysis and an b apturd for data rdution. Exampls of shok motions ar th dlta (impuls) funtion, unit stp funtion, half-sin alration, daying funtions and omplx shok motion. All of ths an b dfind mathmatially xpt for th omplx shok motion. In rality, foring funtions may b a omplx shok motion with an unknown funtional form and annot b dfind by analyti funtion. Thrfor it is dtrmind by atual masurmnt. Typial xampl of a omplx shok motion is shown in Fig. 3. A l r a t i o n ( g ' s ) Shot 4B JO-1427A Fil A01S4B.txt Gag ACC-1 : 250Hz Lowpass -40. ACC-1 Vrtial on DSF Blastsid Cntrlin Tim (sonds) Fig.3. Typial xampl of a omplx shok motion. This sampl is th rsult of atual masurmnt It is a ommon prati to prov th dsign of quipmnt by atual shok tsts that simulat th antiipatd oprational shok ondition. This is a ralisti approah and an altrnativ option to th diffiultis of using analytial mthods in th dsign of quipmnt to withstand svr shok. An atual systm may onsist of hundrds or thousands of vital omponnts that nd to b qualifid as Grad A. Going through th analytial pross for ah on of ths omponnts may b a tdious pross spially if th systm has multipl dgrs-of -frdom. Fig.4 is th typial onfiguration and ommonly usd strutural modl of th havywight shok tst. It onsists of two basi struturs, primary and sondary strutur. Th Floating Shok Platform (FSP) supports th primary and sondary struturs and th Dk Simulator Fixtur 1006

5 (DSF) supports th sondary strutur. Th sondary mass m is muh smallr than th primary mass M. Th rspons of th primary mass to an input shok motion is th input shok motion to th sondary strutur. SECONDARY STRUCTURE PRIMARY STRUCTURE EQUIPMENT UNDER TEST (mass = m) DSF (mass = M) FSP m << M MEASURED RESPONSE OF SECONDARY STRUCTURE MEASURED SHOCK MOTION A. Tst Pross and Prparation All tst fixturs should dynamially simulat th most svr mounting ondition likly to b nountrd onboard ship. Standard fixturs ar to b usd whnvr possibl and all spial fixturs must b approvd by NAVSEA 05P3 or NSWCCD od 623 as pr NAVSEAINST A. Havywight shok tsts rquir a tst produr and tst fixtur drawing whih must also b approvd by th NAVSEA 05P3/NSWCCD Cod 623. Fig. 6 shows th pitur of th quipmnt rak undr tst installd on th DSF and th DSF was mountd on a FSP whos innr bottom provids ovrall support to th primary and sondary struturs. Alromtrs wr installd on th DSF and FSP to vrify propr tst gomtris and to monitor shok input paramtrs and rspons frqunis. Th rak systm dsign alls for using bas shok isolators and rar stabilizing isolators. Fig. 4. Normal onfiguration and strutural modl of a primary and a sondary strutur usd in barg tsting. IV. A CASE OF GRADE A SHOCK REAL SHOCK AND LESSONS LEARNED Fig. 5. shows th modl of th stup of th Havywight High Impat Shok Tsting (Barg Tst) of th Navigation Snsor Systm Intrfa (NAVSSI) Display Control Subsystm (DCS) systm. NAVSSI RACK UNDER TEST DSF FSP FORCE, F Fig. 5. Strutural modl and stup of th Havywight High Impat Shok Tsting of th Navigation Snsor Systm Intrfa (NAVSSI) systm Fig. 6. Pitorial viw of th NAVSSI rak undr tst. Th rak was installd in a Floating Shok Platform (FSP) on Dk Simulator fixtur Extnsiv prparations ar nssary prior to shok tsting. S Fig. 7. A thorough visual xamination of th tst itm has to b prformd to loat any of th following: Brokn, loos or dformd parts Crakd wlds Othr vidn of physial damag Any ondition that ould ndangr quipmnt or prsonnl during subsqunt tsting Physial insptions, built in tsts, and funtional tsts hav to b ondutd to nsur that no disrpanis wr obsrvd prior to shots. This prati also applis following ah shot to assss th rsults. 1007

6 Grad A itms had to b tstd whil in thir normal oprating mods, positions, and onditions. Oprational tsts wr ondutd on th NAVSSI DCS to insur that th rquirmnts for opration wr bing mt bfor, during, and aftr ah shot of th tst sris. Using th installd instrumntation insid th rak, th prforman of th systm was monitord to insur normal opration bfor, during and aftr ah shot. For this shok tst sris, th dk fixtur frquny was dfind as th frquny assoiatd with th pak magnitud valu of th Fast Fourir Transform (FFT) of th raw data from alromtr installd in th DSF ntrlin [7]. Fig. 7. NAVSSI DCS installd on th Barg for Grad A Shok Tst Shot No. Two tst squns wr ondutd against th NAVSSI DCS rak. On th first four shots, th DSF, with th quipmnt installd, was tund to provid a fundamntal vrtial rspons frquny of 14 +/-2 Hz. Ths ar th qualifiation shots for th gnral lass ships suh as CG, DDG and LPD. On th last two shots, th DSF was tund to 10 +/-1 Hz. Ths ar th qualifiation shots for th arrir typ dks (CVs / CVNs). A pitur of on of th tst shots is shown in Fig 8. Th six tst shots usd th standard sixty-pound Navy xplosiv hargs that wr suspndd twnty-four ft bnath th watr surfa at horizontal standoff of 30,25 and 20 ft from th nar sid of th FSP. Shots wr ondutd in th ordr listd in Tabl 1. Tabl 1. Tst Gomtris for NAVSSI DCS shok tst Charg Dpth (ft) TEST GEOMETRIES FOR NAVSSI DCS SHOCK TEST (14 +/-2 HZ AND 10 +/- 1 HZ DSF ) Horizontal Standoff (ft) Loation of Charg with Rspt to th FSP Orintation of Tst Itm Frontto-Bak Axis with Rspt to For/Aft Axis of FSP Athwartship Paralll Athwartship Paralll Athwartship Paralll 4R Athwartship Prpndiular 4RA Athwartship Paralll 4RB Athwartship Prpndiular Fig. 8. A Barg Tst shot at HI-TEST Laboratoris, In. B. Tst Rsults Th NAVSSI DCS rak ontinud to oprat normally and no damag was obsrvd following ah of four shots of th first tst squn. This qualifid it for th 14 Hz platforms, CGs, DDGs, and LPDs. Th sond tst squn was ondutd with th rak installd on a 10 +/- 1 Hz DSF (for Carrir installation). This tst squn onsistd of two 20 ft standoff athwartship shots, dsignatd shots 4RA and 4RB, with th front of th rak faing athwartship. Tsting was trminatd following shot 4RB du to th following failurs whih violatd Grad A and Grad B shok tst aptan ritria: Th hard disk driv and th RAID driv assmbly had ompltly jtd and wr found on th dk. This is shown in Fig. 9. Th kyboard am out and impatd th Flat Panl display, -raking th front and bak glass in th display. This is shown in Fig

7 Invstigations wr mad and a losr xamination and omparison of th shok input frquny at th DSF and th shok rspons frquny of th NAVSSI DCS hav indiatd that th mhanial onfiguration of th systm has rahd th rsonan frquny. Eah loation has th sam frquny rading of 9.77 Hz. A l r a t i o n Hz Shot 4B JO-1427A Fil A01S4B.txt Gag ACC-1 ( g ' s ) Frquny (Hz) Fig. 11. Frquny rspons of Dk Simulator Fixtur (DSF) 2.0 Shot 4R JO-1427A Fil A05S4R.txt Gag ACC-5 Fig. 9 DCS RAID Driv assmbly missing and out of th rak. Pis of th raid drivs wr found on th FSP dk. A l r a t i o n Hz ( g ' s ) Frquny (Hz) Fig. 12. Frquny rspons of NAVSSI DCS Du to th damag and failur of th NAVSSI DCS, rpairs and modifiations to th systm had to b don bfor th rpat of th 10 Hz shok qualifiation tst. Fig. 10. Kyboard hanging from th brokn slidr. Fig. 11 and Fig. 12 show th pak magnitud valus of th Fast Fourir Transform (FFT) of th alromtrs installd insid th NAVSSI DCS and at th DSF. Ths figurs hav larly rvald that our systm as dsignd rsonats on a 10-Hrtz dk. This dangrous situation would not hav bn disovrd without shok tsting. Carful analysis was don to dtrmin th root aus of th problm and to find th solution to this rsonan ondition. W lookd at th isolation systm and an ffort was don to dvlop an isolator oil that would provid adquat isolation for our NAVSSI rak on th 10 Hz FSP. Du to th omplx natur of th problm, th sltion of th propr oil would involv itration pross in ordr to dtrmin th bst possibl solution. Fators suh as quipmnt rigidity, oil stiffnss, drop onditions, oupling, fator of safty and hight rstritions wr onsidrd to minimiz th bottoming out of th systm during shok tsting. Prditions wr mad using modls dvlopd in a systms dynamis simulation nvironmnt of Finit Elmnt Analysis (FEA) softwar. Prototyps wr built and load-dfltion tstd. Th rsult was a biggr oil with a natural frquny of 5 to 6 Hrtz. A rpat of th tst was don at HI-TEST Laboratoris, In. with ths nw isolator oils. Th 1009

8 NAVSSI DCS systm wnt through th rquird Grad A shok tst with no physial or oprational disrpanis. Shok tsts fall undr on of th following atgoris: lightwight, mdiumwight and havywight tsts. Th lightwight tst is a tst prformd on th lightwight shok mahin. In this tst, th total wight supportd by th lightwight shok mahin anvil plat annot xd 550 pounds. Th mdiumwight tst is a tst prformd on th mdium wight shok mahin. Th total wight supportd by th mdium wight shok mahin anvil tabl annot xd 7,400 pounds. Th havywight tst, disussd in this papr, is a tst prformd on a standard or larg floating shok platform. Shok qualifiation rquirs on or mor of th following: shok analysis, shok tst, and shok xtnsion. A shok qualifiation analysis rquirs th quipmnt to b analyzd in aordan with NAVSEA 0908-LP (DDAM). A shok qualifiation by tst rquirs th quipmnt to b tstd as dtaild in MIL-S-901D and a shok qualifiation by xtnsion rquirs th quipmnt to b xtndd from a prviously shok qualifid quipmnt in aordan with MIL-S-901D or NAVSEA 0908-LP (DDAM) [8]. High Impat Shok Tsting may b don on a lightwight shok mahin, mdiumwight shok mahin and havywight barg tsting using th floating shok platforms, submarin Shok Tst Vhil (SSTV), Full Sal Stions (FSS) and Paddlwhl Tst Vhil (PWTV) [8]. Submarin Shok Tsts and Surfa Ship Shok Trials ar ship trials prformd on th lad ship of a nw lass of submarins or surfa ships. Th purpos of ship trial is to provid Navy plannrs and administrators an insight into platform vulnrabilitis to undrwatr bursts. This tst may provid signifiant dision-making data for orrtiv ations. In a shok tst trial, th vhil is subjtd to a sris of undrwatr xplosion (UNDEX) shoks gnratd by larg xplosiv hargs at a standoff distans off th bram of a ship. This blast simulats undrwatr xplosions. Ship Shok Trials ar prformd with a rw on board, and ar not intndd to damag quipmnt. A photograph of a surfa ship shok trial is shown in Fig. 13. Fig. 13. USS Winston Churhill (DDG-81) Shok Trial V. CONCLUSIONS Th abundan and th radily availabl thnologis, nw produts and srvis from th ommrial industry, ombind with limitd budgt hav alratd th intgration of COTS itms into shipboard nvironmnts. This ation inrass our unrtaintis in th systms that w ar dsigning for our ombat ships. On of th options w nd to tak is to subjt our nwly dsignd systm to th propr validation tsts. Thr will always b inhrnt limitations on vrything w do. In th world of nvironmntal tsting, disionmaking data ar usually gnratd through som ombination of tsting and omputr simulation. Systms an b dsignd in a way that will allow thm to oprat in a harsh nvironmnt. This may b ahivd by arful dsign followd by xtnsiv analysis and validation tsting to provid th right onfidn lvl that our war fightrs will sud and win. REFERENCES [1] MIL-S-901D (NAVY) 17 Marh 1989, Shok Tsts High Impat Shipboard Mahinry, Equipmnt, and Systms, Rquirmnts [2] Stion 072a2, Shok Grad Critria, DDG 52 and Follow Ship Sp, datd 1 July 1986 [3] Sott, Rihard, JDW Naval Editor, JANE S DEFENCE WEEKLY, January 23, 2002 [4] OPNAVINST , January 12, 1987 [5] Cyril M. Harris, Allan G. Pirsol, HARRIS Shok and Vibration Handbook, 5 th Ed [6] David V. Hutton, Applid Mhanial Vibrations, MGraw-Hill, Nw York, 1981 [7] HI-TEST REPORT NO. 1056, Havywight High Impat Shok Tsting of th OJ-751 (V)4/SSN-6(V) NAVIGATION SENSOR SYSTEM INTERFACE (NAVSSI) DISPLAY CONTROL SUBSYSTEM (DCS) and th NAVSSI BRIDGE WORKSTATION FLAT PANEL DISPLAY POWER SUPPLY WITH ENCLOSURE [8] NSWCCD PHILADELPHIA, Th Navy Shok Qualifiation Pross, 73 rd Shok & Vibration Symposium, Novmbr 18,