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TRANSPORTATION|1

A SURVEYOF SHOCK AND VIBRATION ENVIRONMENTS

IN THEFOUR MAJOR MODES OF TRANSPORTATION*

R. W. Schock

Marshall Space Flight Center, NASAand

W. E. Paulson

Brown Engineering CompanyHunt sville,AL'tbam a

An investigationhas been conducted, the purpose of which was a review iof all availableinformation and test data describing shock and vibrationenvironments in the four r_ajor modes of transportation. This infor-

_i mation has been collated,analyzed, and combined, to provide a unified

._ J z'eference source of transportation environments for use by the packag-"_ ing and/or design engineer. A portion of the results of this investiga-

tion are presented in this paper.

INTRODUCTION , 3. Many studies have been conducted Onmilitary vehicles operating under the most se- ,

Over three hundred reportswere reviewed vere conditions,which, althoughsettingan up-and contacts were made with fifty-five agencies per limit, are not representative of normal , _.and organizations active in the transportation commercial carrier environments.field. Based on the data collected; a_'celerationversus frequency envelopes were constructed 4. Many programs, although providingfor each of the four major transportation modes, meaningful information for the purpose forThes_ envelopes facilitate the comparison of which they were conducted, have no generaltransportation environments in the different application.modes. Where applicable, the information anddata are _lso presented to show th_ effect of 5. Measurements were made on vehiclesvarious operating parameters on the transpor- that are obsolete or of limited interest.tation environment.

'-: 6. Measurements were made over unknown

Although mat_y programs have been con- or restricted frequency ranges, or other factorsducted to collect transportation shock and vi- of,importxunce to general criteria were not re=bration data, only a portion of the collected data corded.is applicable for use in a general _ansportationcriteria. The lack of applicability is summa- 7. The original data existed in a variety ofrlzed as foUows: form.

I. Few programs dealt solely with cargo In order to correlate the data, a require-environments, ment of the review was_o edit all reports and

Include only response measurements of the......... 2. The data are not segregated and include cargo floor (i.e., input to the cargo). No at-

measurements from locations such as vehicle tempt has been made to define transfer functions

i appendages, aircraft wing tips, etc. or cargo response relationships. In addition to

e

*Conducted by the MRD Division of General American Transportation Corpor&Li_u under MSFC Con-tract NAS8-11451.

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1968068792-002

https://ntrs.nasa.gov/search.jsp?R=19680068792 2020-04-13T20:35:59+00:00Z

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the constraint that data be included which are lack of significant levels may occur in certaindescriptive only of the cargo floor, unless frequency bands.otherwise noted, the data have been further re-

I commercial vehicles trav-stricted to staJtdaxd

, eling normal routes. Data obtained from (a) Aircraftmilitary vehicles, (b) cross-country terrainoperations, (c) spectal road course operations, Extensive shock and vibration measure-and (d) special transporters, have been omitted ments on aircraft have been performed by thefrom the study. Excep_as to the above are Wright Air Development Division (WADD). .(a) data for ships which describe the environ- Their most recent test programs cover themerit at the aft perpendicui_r (the area of se- following aircraft:verest vibrational environment), and (b) resultsof tests with the 377PG (Pregnant Guppy Air- 1. (C-123), Medium assauli cargo airplane,craft), a special transporter, h_gh wing.._, jn engine (reciprocating), three-

bladed, pr_,;: _l_rs.In the subsequent figures defining the en-

vironments, instrumentation and/or interest 2. (C-130), Medium range cargo airplane,limits define the frequency ranges from which high wing, four engine (turboprop), three-the data were taken. A lack of definition in bladed propellers. 'some frequency ranges should not be construedas a lack of environment, but merely a lack of 3. (C-133), I._ng range cargo airplane,available data to define that environment, high wing, four engine (turboprop), three-

bladed propellers.s

DATA PRESENTATION _. (H-37), Cargo helicopter, single mainrotor plus torque compensating taft rotor, twin

The data used to develop the graphs sum- engine (reciprocating), five main rotor bladesmarizing the shock and vibration environments a_! four tail rotor blades.were extracted from numerous reports. The =original data existed in a variety of forms. The mea_urer.ents were taken during allSome data were in the form of peak accelera* of the normal service conditions, suchas taxi,tion versus frequency, other data were given in ground run-up, take-off, straight and level

: ;: peak acceleration versus duration. For the flight (at various altitudes and speeds, andlatter, unless otherwise specified, a half sinus- power settings), turns, descents, landing, andotdal shape was assumed and a frequency corn- landing roll. The effects of cargo load, speedputed. , , brakes, and other control Surfaces were also

investigated on some of the aircraft.An acceleration versus frequency format

was chosen for the graph to utilize as much of These aircraft were instrumented with /the available data as possible. The selection of velocity pickups, and the vibration data werethe format was based on two principa_ factors: recorded on magnetic tape. Data reduction was(a) it is the only one which wi_Aaccept all use- performed with a Davies Automatic Analyzerful data, and (b) it permits data originally pre- employing a variable-frequer, cy, narrow-band

sented in terms of power spectral density _o be (I0 cps) filter. , //transformed to its original form by merelynoUng thebandwidthusedintheoriginalar_ly- . Vibrationdatafrom thePregnantGuppysis. G (rms) versus frequency iS used for the (377PG), a low wing, four-engine (reciprocat-format when the original data were reduced by ing), four-bladed propeller cargo airpla,ie,a Spectrum Analyzer. G zero-to-peak versus were also _-_viewed. This aircraft is used infrequency is used for the format when original transporting space rockets and their allieddata were recorded with oscillographs and vis- equipment. A considerable number of vibrationually analyzed, measurements have been taken on the cargo

floor during transportation of this specialVibrations which occur in the cargo area cargo.

have dominant frequencies for particular vehi- /_cles, loads, locations, and speeds. Even thotkgh The environment in these tests was moni-conditions and circumstances vary, the graphs tored with accelerometers, and the data wereshow that the vibration levels are fairly con- recorded on magnetic tape. A variable fre-stant over wide frequency ranges. In some in- quency, one-half cycle, bandwidth filter wasstances, li_cularly with aircraft, a noticeable used in the analysis of the data. Frequency

#

1968068792-003

,' bandshavingrelativelyb@h vibrationlevels Railroad _were analyzedfurther.A distributionofthe _:

i accelerations was determined at these frequen- Data descriptive of the railroad shock andcies. Data are available for a numberof loca- vibration environment have been cattworizedtions, for a number of flight conditions, _nd for into two major classifications: (a) over-the- _various loads. These data represent one uf the road operation, and (b) coupling. The over-

i most complete deL_criptions of the shock and the-road environment includes all data except

vibration environment for any transport vehicle, the shock motions associated with coupling or"_ humping operations.

Vibration data for the KC-135, a military \ _ i

P_ version of the Boeing 707 jet aircraft, has been :_ Acceleration versus frequency envelopes •obtained from tests by Boeing.The data cover "of the shock and vibration envi'-'onment of rail-groundrun-up,laxi_take-offand cruisecondi- roadcarshavebeen compiledfrom manytions. The o,_iginal report presents the vibra- sources. Because of the high ampiihlde tran- *I

i, tion data in power spectral density (g2/cps sient vibrations which occur durin_ starts, stops, |versusfrequency).The datawere convertedto slack_mn-outs,and run-ins,thesedatahaveg (rms) versus frequency for presentation in been segregated, when specified, from the vi- _ithispaper. The vibrationswere monitoredwith brationd_tadescribingnormal runningcondi- _ _

i accelerometers and recorded on magnetic tape. tions. These high amplitude vibrations in Fig. 3{ Analyseswere performedwitha Daviesana- are labeled'_ransienL"whereasthenormal _ ,: lyzerwiththefollowingfiltersbeingused for runningcondi._ionsare labeled"continuous." z

differentfrequencyranges: BothoftheseI_.lotshave beenconstructedby I.... _ enveloping all reliable data for all types of

trucks, rail contritions, directions, and speeds.

Frequency Range Filter Bandwidth Therefore, the transient and continuous plots _(cps) (cps) in Fig. 3 represent the highest vibration levels .:_ _!

.... which would be en,:ountered duris_g over-the-0-30 0.80 road operations.

30-53 1.33 The two plots _ppearing in the lower half :150-100 2.64 of Fig. 3 show the effect that soft ride equip-

me_ has on the oW,_r_the-road vibration envi-100-200 5.41 ronment. These plots were formed by _envelop-200-400 10.1 lug the imaximumaccelerations recorded on the

floor _df a Minuteman transporter railroad car400-800 18.7 durllg cross-country operation. The data were800-1000 35.3 reduced by averaging the 4-6 maximum accel-

eration values within each frequency bandwidth.1000-2000 43.5 The _xuck suspensiov, system for this missile '

.... car c_nsisted of a combination air and coilSpring system in the _vertical direction, and a

'_ Figure 1 is composed of acceleration enve- pendulum system with snubbers in the lateral ;lopes depicting the environment for propeller, direction. Damping is provided in both direc,helicopter, and jet aircraft. These envelopes tions of motion. In the longitudinal directionwere obtained by encompassing the maximum isolation is provided by a sliding center sillvibrztion levels for the respective classification, and &_hydraulic cushioni_ 4evice.

_ , Dat.t for the C-123, C-130, C-133, and 377PG _ iwere used in developing the plot for 1 :opeller The effect of tral_ speed on vibration lee- 'aircraft, while the H-37 and KC-135 were used els is _hev.._ in Fig. 4 for a number of train

.... j_ to describe the environment for the helicopter speeds (20, 40, 73, 80 mph). The curvesde=and je'., respectively. The plots show that the plct'_g the environment at 40, _, and 80 mphvibration levels are highest for the helicopter, are a result of tests conducted _y the U.S. Armyand lowest for the jet. Signal Corps. The data were taken #ith differ-

ent types of trucks. The vibrations on the cargoFigure 2 shows the maximum acceleration floor were monitored with barium-titanate ac-

envelopes for several individual aircraft. '' celerometers and recorded on magnetic tape.These plots were constructed by encompassing The frequency range r,f interest in these teststhe highest recorded vibration levels for all was 20-10,000 cps. The recorded data wereflight conditions. The plots are presented in analyzed by passing them througk i series ofterms of g (rms) versus frequency, octal band pass filters. The results o_ the

g

1968068792-004

._.?.

I

( 't10.0 :

%- im

,/- ,,__ _ -

_,.o =- A:, I" _ - "I " d

Z _ °

. .,,/ / , .,,, _ - ,_ Propeller

r_iproaU_}_

.o,. I Im. m Helfcop_r

m

" FREQUENCY (CPB).00| I _lllIIl I I IIallIl I i iiJiiil I _lllaia l i iliIiI

,. 0.1 1.0 10 100 1000 10004)

Fig. 1. Aircraft acceleration envelopes (overall composites)

iO.O

. ,o /,,,,,t_,,..V_,,,;i: _1,1

.,-,_.. /r..) - C-i33< _ ..... 37_P0

C-130.01 " !: ........ C-123

I. ....- ..._ H-OY....... KC-135

FREQUr-NCY(CPS).001 I I II ilia a i ilJiiiI i i ilJillI i i iIilii I I I IiIII

,. O. 1,,0 10 100 1000 10000

Fig. 2. Aircraft acceleration envelopes (indivsdual composites)

/,

.},,

1968068792-005

_Itl,

+ I

10.0 ....

i

.01 . 1 1Flt_UZee=y (CPs) "

++ ,0051 I j ililll J i llllllJ i I llllill I l ill'ill I i iillll

+O. t i. 0 tO tO0 tO00 tO000

r L) + Fi I. 4. Ratlroatd acceler&tion euvelopes lover-the-road) ....

,>q

/ •

1968068792-006

\' _ analysis are presented in terms of average excitation. This method of data presentation" i!_ acceleration versus frequency (cps). has been chosen because it provides A_/orma-

tion on all frequency components.The data presented for 20 mph speed may

be. misleading because of the different frequency Data are presented for both standard-,_ range. These data are a result of a separate shock-absorbing draft gears. These shockprogram in which frequencies greater than 25 spectra were constructed by enveloping thecpswere not of interest. The data were aria- peaks of shock spectra given in the original re-

" _ lyzed with a frequency analyzer having a con- port. Figures 6-14 show shock spectra fortinuous band-scan device, with a frequency standard draft gear at coupling speeds of 3.4,resolution less than one-hal/cycle. These data 6.0, 8.0_ and I0 mph. The data used in Figs.were also presented in terms of average accel- 6-14 were obtained from tests conducted by :

,_ erationversus frequency. SandiaCorporation. The testswere conducted :!_"

by impactir_ a lightly loaded test car with aFigure 5 consists of plots that show the hammer car. X

effect of orientation (direction). These plots '_'are restricted to include only the data descrip- Figures 15-18 present additional shock _

\,

• tive of the continuous vibration environment spectra for a Miner draft gear at various ira-

(i.e., data for transient vibration have been pact speeds. The Miner draft gear is a highomitted). The plot shows that the vertical is capacity shock absorbil_g dr_t gear. /the most severe environment over wide fre-quency ranges.

, Railroad Distribution of Coupling1 Spe ede =

Railroad Coupling ",'_ Figure 19 shows the distributionof cou-

Curves describingfizeshock and vibration plingspeeds based on 3369 measured impacts.environment for railroadcouplingand/or hump- This plothas been constructedby averaginging operationsare presented as shock spectra, the resultsof a number of independentinvesti-A shock spectrum isdefinedas the maximum gRtions. Data are presented interms of per-

accelerationof a seriesof singledegree-of- centof totalimpacts versus couplingspeedfreedom systems resulting from a specific shock (mph).

,°.°II.o II "

_ " ._\ v " .&-_• ......% ,'_ "%°°.

, ',...... .........,,j

<.Ol "

" . VerU_I II

- _ Lateral" Fore/AR.le*oeeoo

,I " FREQUENCY (CPS).00| I I tiltt| I I ttttttt I t ilt*lll t t ttttat t t tttttt' O.i:_' t.O 10 tO0 tO00 10000

- Fig. 5. Railroad acceleration envelopes(directional composites)

6

*" 1968068792-007

t

i/ i g_

Im i I

r_

I

ii/..." I .j =_ o.5,C/Ce5% c/c¢FREQUENCY (CPS}

_" Oo f I I llilll: | | lilJ|_J l l ttllllJ [ I lilllJ I l I IlllJ

O. 1 1,0 10 tO0 tO00 10000 '

.. Fig. 8. IL_ilroad coupling shock spectrum (3,4 mph, ,.

latera/) standard draft gear

$0_ : •

D

" r

, , ioo!

..o M@' "_ ,L ' ' '

IL,q

: .,.)- .---- o_,_:/cc_ . ...... O" 5 % C/C c • ' "i " r

- ------- 5 % ClCc

FRI_UEN_Y (Cl:_)O. i l liilil I • l,_llllJ 1 I lltlilJ i i llllli i i llllil

O. l 1.0 10 100 1000 10000 ,,

Fig. 9. _Iroad coupling shock spectrum (6.0 mph.fore/a/t) 8t6J_i_rd draft gear ,,

4

1968068792-009

I000 = •D ,

,4..," "V

•"\ r_, --

. _ //Z

10 _

,-1 -

' ' "_ 1.q_ I

• 1" _: _ 0 %c/ce

., - ......o.s% c/ce_-5 % c/ce

z ' - _ FREQUENCY (CPS) I" ' __0o| I I I Illl I I iIIllll I I llllllI I I IIIlll I i 1 illl]O. 1 1.0 10 100 1000 10000

Fig. 12. Railroad coupling shock spectrum (10.0 mph,

... vertical) standard draft gear?

1000 =

, _. .o

100 -=- .i_._.." ,,-_- ..I

•f._ - t_sssS

_ le, -2 "

0 _0 '

'_ 1.0 =,

: _ 0 %c/c_' : = ..... 0.5% ClCc

- _--- 57oclccFREQUENCY ,(CPS)

-0._ I ! IlllJi I I It,llil " I I ililill I I I|*ttl I I lillllO. 1.0 10 100 10_0 tO000

-" Fig. 13. Railroad coupling shock spectrum (10.0 mph,: fore/aft) standa,rd draft gear

.,

:'; ':" . 10_j

, J

1968068792-011

I

lOOO _-

-loo ,: ,"_/':l

Z " i"

£ to _- i

0 - :

I 1. ; l

I_ " I -- °% C/Co

....... o.5% clc c5 %C/Ce

raEQurNcy('cps) tF 0.1 I I JJJll| J | IIIIl|l -_ 1 lit|U| I I IAIIII[ J I I IllllJ

i "O. 1 1.0 10 100 1000 ' 10000

Fig. 14. R.a.ilroad coupling shock spectrum (10o0 mph,lateral) standard draft ge&r

,\

1000

o'_ .,| ,/

I0

1.0_1 [ -- 0% c/cc .,

- [ ...... o.5 % c/c c- --_:5 % c/c c" FREQUENCY (CPS) ] ,-.

0._.-0 I I _ I | Jill1.0 I I II_ill|4_O 1 i llJlU|_IO0 I i I I |111111000 I I i 1111|10000 "'_, "

Fig. 15. Railroad coupling _hock spectrum (3_ mph, J ",,fore/aft) cushioned draft gear \

r,

Q

U

/!1 ........

o •

b,: ,ooo-..= /Jl : :

i, ?,I00 .

00

1.0=: -- o % C/Cc ._.

..... o. s % C/C e ¢_-- s %C/Cc

FREQUENCY (CPS) I "0._ J | |JlllJ i I liillJi | i lllJlll I i IJllli I t i lilll

O. 1 1.0 10 100 JO00 10000 ff

Fig. 16. Railroad coupling shock spectrum (6.8 mph,

fore/aft) cushioned draft gear •

: L,,

100 =

I

Z

,,-1f.,.1r,.,)

_l r..)

1,0

I: ------0% C/Cod . ......0.5,/. clCe

' .>" " -.----- S,% C/C c_ ' " FIa_QUENCY (CPS)

0. I I I illlll i I Illll|. I 1 Illilli I I IIIIII J I I Illil

O. 1 1.0 10 100 1000 10000

• _ "'." Fig. 17. Railroad coupling shock spectrum (9.8 mph,\ "'- fore/aft) cushioned draft gear

\

9"\"\ ,

12

...... >. ,

fj x

• 1 1000 :• , =

1i '_ 100 :

" = _ o%c/Ce __. - . ..... u.5%C/Cc

- ------ 5 %ClCc

_.: ; - FREQUENCY (Cl:_) I '_

0._ I I IlJlll I I IIIIllJ I 1 tJlllil I I Illlli I J I iJJil : J

: O. 1.0 10 100 1000 10000 ;"

Fig. 18. Railroad coupling shock spectrum (12.0 mph,fore/aft) cushioned draft gear

!!

_,.;_. 100

8O

/ d

,-1

_ j

0

z "

40 / I,I :I

20 i ?"

j: .I :I

0 | 4 6 8 10 12 , _

COUPtJlqGSPICEDMPH ._

! Fig. 19. Kailroad distribution of coupllag speeds _

t

!' 13 l

1968068792-014

•_ Ship envelopeincludesdata recorded under extremelyrough sea conditions.

' The dataused inplotting the overallcorn- !

positecurves for ships have been separated The thirdand lowestplotin Fig.20 is con-•_ I intocontinuousand transientvibrations.Tran-

! sient vibraUons are defined as those which oc- stx ucted from data taken on a 572-ft, singlecur during emergency maneuvers and slam- screw ship. Measurements were taken with

. ruing(theimpactingofthe shipwithwater after velocitypic_-ups mounted atthe main thrustbearing four_tion and to an angle welded to thethe bow has left the water). This separation of deck over the main transverse member at the

data is made because transient vibrations can aft perpendicular. The data were recorded onusually be eliminated from the environment, straight runs and maneuvers during operationsSlamming, for example, can be avoided if the in calm seas, and at various propeller speeds.ship avoids storm areas. Continuous vibrationsare defined as those which occur during normaloperations, including operations in rough seas. Figure 21 shows the effect of orie_ltation

(i.e., the effect of direction). The data usod to

Most of the data for the shipboard shock construct this figure were obtained from theand vibration environment were collected by tests conducted on the 572-ft single screw shipthe David Taylor Model Basin. The major por- mentioned above. The curves show that thetion of their data, however, have been recorded vertical vibration _nvironment is the highest,near the aft perpendicular (a line perpendicular followed by the lateral and fore-and-aft direc-to the water line at the stern). This area ex- tions.periencesthe highestvibrationallevelson a •'

ship. The levelsofvibrationfor the cargo Figures 22 and 23 show the effectof seaarea willalways be lower. However, since statefor two differentship lengths(L = 820 ftmeager informationis availablefor the cargo and L -380 R). The curves show thatthe ac_area, dataforthe sternlocationcan serve as celerationlevelsincrease withincreasingire-

an upper bound ofthe environment, quency from 4 to 10 cps, and are constantathigherfrequencies.The accelerationsfor the

The upper two curves in Fig.20 have been small ship(L = 380 it)are almost twice as

constructedby envelopingalldataapplyingto largeas those forthe largership(L ---820 ft).continuousvibrationon one diagram, and all For each shipclass,the accelerationincreasesdata referringto slamming and emergency by a factorof two,whvn the shipoperates inaon another. The continuousvibrationcomposite rough ratherthan ina smooth sea.

/

10.0• " Slam&__ Emergency -,

Maneuvers - /

- Normal Maneuvers

.01 ." ]FREQUENCY (CPS)

.00] t I I "lllll I i Iliil|l | l IIIlUi i i liiiil i i Iliill

O. ! t. 0 10 100 1000 tO000

Fig. 20. Ship acceleration envelopes

14,./

1968068792-015

10.0 :-m.

t.o.- : .

[ " " I/

_, 0.1 _

ro - _

i. < .oi ._. .__ _ .._._ VerUcal _.

- _ I.,_t_rAli' - _ ......Fore/Aft _:,

- V IFREQUENCY (CPS) - -

; 0.1 , 1.0 10 100/ 1000 10000 /:_ , ! |Fig. 21. Ship acceleration envelopes (straight runs) /

!_ 10.0

!i Definition of Sea.S_.tes [

"_ i I. LW<- t L 3.,Lw_< 11.5 L,

H w-- _'_ L s Hw,< _ L sI. o • /•_s_nz Seas_,te i • '

: _ _i ,.L_<_L_L_<,.A

.o 0.1%--- _oL, ._< :._ I_.

•OL i

: Ls = Leq_h_fSS_o ....

" FREQUENCY (CPS)i I I llil I I I I lill

\ ..00_ i I lllill I I IIIIII| I I llUlil i

"' O.1 1.0 10 100 I000 10000

Fig. Z_. Ship acceleration envelopes (L. = 8ZO ft)

±

15/

'_ L,,

1968068792-016

'li

!

:, i

¢ .

1 '°° 1 w l i '_ ;

Definition of Sea States

I Slammi_ _.<I i

._ • O) Sea State t. Lw _ Ls 3. Lw<_ 1."_ L• iii S

• O._. i.0 Hw < 12-"_Ls Hw < _" L' S

!1

._ Z 2. L - _" L 4. L < L_. W S W-- S

-< H <--34 Ft.0•I Hw "_ Ls w

'_ L " LvngU*of WaveW \

%,

• 01 H .. Height of Wavef '_, W

/

L - LePz'_Laof Ship

t i-_"_" FREQUENCY (CPS)

.001 ,• _ , 0.1 1.0 10 100 1000 10000 " '

Fig. 23. 'Shipaccelerationenvelopes(Ls = 380 ft)

- ?, _ ,, The higher vibration frequencies (> 10cps) vibration environment occurring during opera-,• _, . _ are due to machinery vibration, and are less a Lion on paved roads.

.function of sea state than the lower frequency

_" rigid body motions. Figure 25 shows the effects of cargo loadon the vibration environment. These curves

axe the result of a single measurement pro-Truck gram. The tests were conducted with three,

standard commercial semitrailers, each havingFigure 24 shows the effect of road condition/_ one of three basic types of suspension (air-

on the vibrationenvironment, iI .Jr_de tandem suspension,siable-ridesingle•, , suspensionand single-axlespringsuspension).

The upper curve in Fig.24 has been ob- _ _\_ Tests were run attwo loadconditions,emptytainedby envelopingdata h_om a number of in-_', } and full,over a first-classasphaltroad• Ver-dividualtestprograms. This curve includes ticalaccelerationswere monitored at three

peak valuesrepresentingthe environment ex- " locationson the cargo floor(overthe fifthperiencedintraversingrough roads,ditches, wheel,the centerof the van floor,and over thepotholes,raikoad crossings,and bridges. Data rear axle). These curves show thatthe vibra-

reductionprocedures vary from one reportto tionlevelsare practicallyunaffectedby loadinanother,but inmost cases t_,emethod used was the lower frequencyranges. Higher frequency

. torecord thedata oscillogr_phically,and visu- components, however, are reduced on loadedallydetermine thepeak (zer,)-to-peak)acceler- trucks.

ationand predominant freqmmcy. This methodhas been used extensivelyintransportation

studies,sinceitrequireslit!']eauxiliaryequip- CONCLUSIONS ANDment, and sincethe magnitude of the significant RECOMMENDATIONS

" predominant frequenciesca_be conveniently

and immediately determined! The most severe transientenvironment

• _, associatedwith transportvehiclesoccurs dur-

The lower curve in Fig,_24 has been ob- ing railroadcar couplingor humping operations,tainedby envelopingpaved toad data. The whereas the most severe steady-stateenviron-combinationof these two curves showthe dif- ment occurs duringphases ofaircrafttrans-

ferences in vibration Ievels'between _'!brations 'portation. Railroad, truck, and ship followwhich occur while traversDg potholes,, ditches, .aircraR in order of decre_sing levels of

railroad crossings, etc., _ the maximum environment.I ,J / ' . / , ,"r

t / 16

,' / ,I/

1968068792-017

1968068792-018

The levels of vibration presented in this Future studies of interest that would greatlypaper are considered reliable, even though they enhance and supplement this investigation couldare derived from data analyzed by diverse re- include (a) correlation of fantail to cargo hold i

I duction methods. This conclusion is based on shipboard environments, (b) a more extensive._. the relatively close correlation between data breakdown of transportation modes, (c) a sta-j. from various reports (for similar test vehicles ti_tical processing of accumulated data, (d) a• s and conditions), continuing effort of environmental definition, !

particularly in the truck mode, and (e)an in, t

- i Data are sufficient at the present time to vestigation of terminal handling environments.define adequately the transportation environment

' in terms of maximum acceleration versus ire- Due to the increased nationwide interest tn "

quency; however, the term maximum should be transportation environments, many programs Iemphasized. For example, because of the pau- are currently being conducted in the previouslycity of data describing the environment in the outlined areas, and should go far to supplement "cargo area of ships, data from the extensively the basic criteria contained herein.monitored fa_tail area were utilized. Since '_ ,

/

this is the highest encountered shipboard envi- ....ronment, it does not represent the cargo hold, ACKNOWLEDGMENTbut doesset an upper bound on the expectedcargo hold environment. The philosophy of en- The assistance and contributions of theveloping all data lends itself to a conservative survey's principal investigator, Mr. Fred E .....environmental definition with a very high (99 Ostrem of General American Transportationpercent) statistical confidence level. Corporation, are acknowledged and appreciated.

DISCUSSIONi

Mr. Markson (E.R.A. Inc.l: The set of Mr. Schock: Yes, over 300 reports wereship acceleration curves appears to be a corn- reviewed. .,bination of vibration accelerations and shockaccelerations. Is that correct ? _ Mr. Fitzgibbon (Mechanics Research):

Why did you not present your vibration data inMr. Schock: Yes, the impact vibrations terms of the power spectral densities r_ther

are transient in nature although they are of than g's rms ? In this manner you could showrather long duration. It could be termed a an envelope of all of the power spectral densi-shock vibration. It is a response, but over a ties from the various environments which wouldlonger duration than one would normally con- be a criterion for all environments. _'sider a shock response.

Mr. Schock: We had spectral analyses inMr. Markson: What kind of instruments some cases during the course of the study, '

did you use to pick up the two different types of while others presented only data from peakaccelerations ? _ detection meters or oscillograph records.

• \_ _;/Most of_th_ data on aircraft were in spectral,_,' Mr. S_hock: We used accelerometers, analyses'and given in psd. We reduced these

mounted in the fantail area. to g-rms/to get them in a form comparable-,_ ::_' • _ ..... _, with the;other data.

J' _ _ Mr. Markson: Did you use the same ac- /celerometers for reading vibration at 100 cps kJr. Fitz_ibbon: Are you suggesting that

_ Onthe ship as you did for reading the low ire- the rms g's be taken from your curves and- _quency shock i_npact ? converted to ped to arrive at specifications for

:' shock and design ?,Mr. Schock: No, there were two different

_ ,, studies. On_-was for vibration, and the other Mr. Schock: No, I would not use these• ...... was specifically to pick up the slam mr,des, curves, in specifications. The paper itself

.... _ Different'accelerometers were used in each breaks these curves down in much more detail•__: ,_ ,, study, with more detailed parameters, such as the

_1 direction of measurements, and individual air-". Mr. Markson: This is a summary o_ sev- craft measurements. This will greatly facill*

eral different reports? .... tate the definitiOn of a better specification.t _.

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1968068792-019

't I would not try to envelope curves such as Mr. Krachman (TRW Systems): That truckt these for use in a specification. It gives the data seems to be a little lo_v. Was this on any1 designer a feel for what the maximum levels special type of truck?

will be and what to design for.

i Mr. Schock: The maxim_m environment 1

Voice: Could you classify _e helicopter was on trucks ti.st had stargiard truck gear.and thep-"--repellerexcitationas beingone ofthe •Some ofthem didhave_ir-rideand some had_ most severely characterized as steady state ? only coil springs and single axles. Th__data in

the lower environment were taken over verygood first class asphalt roads, whereas the data

Mr. Schock:Yes,thehelicopterdatawas intheupperenvironmentswere takenon a typ-characterizedas steadystate.Itiscausedby icalroughroadwhichhadpotholes,railway

" theresponseofthestructuretothesteadystate crossings,and bumps. Itwas uot_s roughprop wash. the Munson course. _ ',

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