Control of Vib-Shock

7/23/2019 Control of Vib-Shock

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Vibration/ShockControl


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AtomicVibrations:1012 Hz;Disp =108 to106

mm.

Microseismsorminortremorsofearthcrust:

.

. MachineryandBuildingVibrations:10to100

Hz;Disp =0.01to1mm.

.

,

to1000mm


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DefinetheTestingMethodologyfor,and

resultsre uired

for

acce tance

of

ru ed

equipment.

guidelinessetbytheUSDODformilitaryand

commercialequipmentandapplications.


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Todeterminetheabilitytowithstand

mechanicalshocks

from

suddenl

a lied

forcesoranabruptchangeinmotion

,

operation.

RandomMechanicalVibration


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spec ca oncoverss oc es ngrequ remen sforshipboardmachinery,equipment,systems,and

structures,excluding

submarine

pressure

hull

penetrations.

Thepurposeoftheserequirementsistoverifytheabilityofshipboardinstallationstowithstandshockloadingswhichma beincurreddurin wartimeserviceduetotheeffects

ofnuclear

or

conventional

weapons.

Nodegradation;"shockgrade1

u y unc ona u nono sean v ra onrequ remen ;"shockgrade2

Must remain safe "shock rade 3

Acousticsignature;"shockgrade4".


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Testcategories

Lightweight

Me iumweig t

Heavyweight

GradeAGradeAitemsareitemswhichareessentialtothesafetyand

continuedcombatca abilit oftheshi .

GradeBGradeBitemsareitemswhoseoperationIsnotessentialto

the

safety

and

combat

capability

of

the

ship

but

which

could

become

a

azar opersonne , ogra e ems,or o es pasaw o easa

resultofexposuretoshock.


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MIL-901D

High Impact Shock

Testing

LWSM

Light Weight Shock

Machine

MWSM

Medium Weight Shock

Machine

FSP,LFSP and IFSPHeavy Weight Shock Testing

Using the Floating Shock Platforms

Equipment

Class

Class 1

To meet shockreq. without RM

Class 2

Shock req.With RM

Class 3

To meet shock

Req. of both Class 1and 2

Shock Grades Shock test

types

Grade A

e.g. control and

Command

Grade BType A

Principle unit

Type B

Subsidiary

com onent

Type C

subassembly


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ControllingNaturalFrequencies

avoidin

Resonance

PreventingExcessiveResponseat

dissipatingmechanisms

Reducingtransmissionofexciting

forces ReducingResponseofsystem


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Resonance LargeDisplacement Strain

Failure

Masschange FunctionalRequirement

Sti ness


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amp ng s econvers ono mec an ca energy

of

a

structure

into

thermal

energy.

thestructuresdampinglevel.

Welded,Bolted,Rivet

ViscousDamping(ViscosityofFluid)

CoulombDamping.

Changeoffn


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AmplitudeAtResonance 2.6.4

DampingTapes

HighlyNonLinearMaterials

o

D

o


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Passive

Foundationor

Base

Protection

EquipmentProtection

Typeof

Disturbance

Vibration

Harmonic

/Shock

Step


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ReductionoftheForceTransmittedto

Foundation

SS:


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forSmall

value

of

Damping

ratioandr>1


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Forlargevaluesofrandlowvaluesofdamping

thetermbecomesverysmallandcanbe

neglected


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Isolationofsystemswithrotating

unbalance


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ng neer ng ruc ura e emen a

attenuates transmission of vibration in a.

The resilient element includes Rubber and.

Rubber is securely bonded between the two.

Upper Plate is assumed to face the source tov ra on an ower me a sur ace secure ofoundation.


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formofastepvelocityof2m/s.Ifthemaximumallowablevaluesofdeflection(duetoclearancelimit)andaccelerationarespecifiedas

20

mm

and

25

res ectivel

determine

the

s rin

constant

of

anundamped shockisolator.


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Toreducethevibrationof

aprimarydeviceby

addingan

absorber

to

the

system

Eliminateunwanted

Forms2

degree

of

Freedom

Usedinmachineryat

constantspeed

Applications:

ec proca ngmac nes

Buildingexcitedbyanearthquake

Transmissionlinesortelephonelinesexcited


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Undamped DynamicVibration

Absorber


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Vibrationabsorberisoftenusedwithmachines

runatconstantspeedorsystemswithconst.

.,

has

narrow

operating

bandwidth.


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Wires to

MR Fluidap ragm

Bearing &

Seal

SolenoidAccum ul ato r


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IdealizedFormsofShockExcitations&

VelocityChange

Documents

Control of Vib-Shock