vibration

DR.EBADI.A –FACULTY OF AEROSPACE & DIVING MEDICIN ARMY UNIVERSITY OF MEDICAL SCIENCE

AVIATION MEDICIN SERIES

IN THE NAME OF GOD

ERNSTING´S AVIATION MEDICINFOURTH EDITION-2006

DR.EBADI.A –FACULTY OF AEROSPACE & DIVING MEDICIN

AVIATION MEDICIN SERIESERNSTING´S AVIATION MEDICIN

VIBRATION-SECTION14

FOURTH EDITION-2006

ARMY UNIVERSITY OF MEDICAL SCIENCE

VIBRATION

SECTION-14



VIBRATION-SECTION14

FOURTH EDITION-2006

ARMY UNIVERSITY OF MEDICAL SCIENCEF22 fighter



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INTRUDUCTION

Definition:Motion repeatedly alternates in direction

Examples:Tides & Ocean waves-Earthquakes-Pistons-Turbulent air-Travelling High speed sea-craft-uneven terrain-Helicopters-Low level flight(fixed-wing)

Transmission:Direct contact-Air-Water-Soil conduction

Significance:Impair visual acuity-Lead to fatigue-Interfere with neuromascular control&speech-



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INTRUDUCTION



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PRINCIPLES OF VIBRATION

1-Natural vibration-Mass hanging by a spring(Normal mass spring system)

-Repeated interchange of energy(mass: Gravitational& spring:In Extention)

-Air resistance for mass & Heat production for spring

-Sinusoidal graph:Mass Frequency(C/S-Hz)&Spring Amplitude(Meter)

Forced Vibration))-Damping:Spring heat production-Damper:Piston in an oil-filled cylinder



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1-Natural vibration

Representation of the Measures of Vibration Exposure



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2 -Forced vibration

Mass spring damper system



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MECANICAL PROPERTIES OF BIOLOGICAL TISSUES

-Spring:Springiness-Uniform stiffness-Non biological effect

Tendon& Muscle:Elasticity_Non-uniform stiffness-Biological effect)Muscle tension & contraction (



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VIBRATION SOURCES

1 -Engine

2-Environment:Land travelling-Flying-Sailing

3600rpm(60Hz)



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VIBRATION SOURCES

-Low frequency& High amplitude vibration(number of rotor blades&speed-<100Hz)

-Three axes motion(vertical-lateral-backward&forward)



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Comparison:VIBRATION SOURCES6000 rpm-100Hz:-Propeller-driven aircraft

-Fixed-wing jet aircraft:8000 rpm-130Hz

-High-pressure(Dual –stage)turbine:13000rpm-230Hz



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VIBRATION SOURCES:Remarkable

1-Atmospheric turbulence

2-Storm-cloud penetration

3-High-speed low level flight



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Modified:VIBRATION SOURCES

1-Pilot control

2-aerodynamic charactristics



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MEASURMENT AND ANALYSIS OF VIBRATION

-Accelerometer: High acceleration impact or below the threshold of human perception



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Vibration wave form:

1-Periodic wave:Machinery

2 -aperiodic wave:Atmospheric turbulence

3-Vibration spectrum:Amplitude–frequance plot



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BIOMECANICAL EFFECTS OF VIBRATION

1-Mecanical impedance of the body

2-Body resonances



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1-Mecanical impedance of the body

Definition:Force-Vibration Response(Peak oscillatory force/Peak velocity of vibration)



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Body resonances




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Body resonances

Effects:

4-5Hz:Shoulder vibration

14-15Hz:Head vibration

5-8Hz:Difficulty in controlling tasks

15-20Hz:Facial tissues vibration

20-40Hz:Visual Acuity impairment



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EFFECTS OF VIBRATION ON VISION

1 -Focus in image formation

2 -Directed on the fovea without motion (Vestibulo-ocular-R+Pursuit-R)

3-VOR Decreased:Angular velocity >40 degrees/S(outside inviornment)

4 -Pursuit-R Decreased:Oscillation>1Hz/S(pilot&instruments>1-2Hz/S)

5-Other factors :Size-Line width-Colour-Brightness-Contrast



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)HMDS (made by Vision Systems International, LLC (VSI) recently flew for the first time on an F-35 Joint Strike Fighter aircraft. The HMDS provides the pilot video with imagery in day or night conditions combined with precision symbology to give the pilot situational awareness and tactical capability. The HMDS has been in development for five years and recently completed all required safety of flight tests toward full certification.

Helmet-Mounted Display Systems



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CARDIOVASCULAR EFFECTS OF VIBRATION

1-An increase in PR at the start of vibration

2-An increase in BP 1-2h afterward vibration

3-Pripheral vasoconstriction

4-Transient arrhythmia

5 -Fatal dysrhythmias



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RESPIRATORY EFFECTS OF VIBRATION

1-An increase in RR

2-Oscillatory airflow in 3-4Hz-Gz vibration(effects on gas exchange)

3-Hyperventilation&Hypocapnia

http://upload.wikimedia.org/wikipedia/commons/5/5e/Respiratory_system_complete_en.svg



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RESPIRATORY EFFECTS OF VIBRATION



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NEUROMASCULAR EFFECTS OF VIBRATION

1 -Reflex contraction(20-100Hz-in directly vibration)2 -Reflex inhibition(in whole body vibration)

3-Neck muscle vibration :Illusion of forward flexion4 -Rectus abdominis vibration :Illusion of extension of the upper trunk 5-Stop vibration :Transient illusion of motion in the opposite direction

http://www.baileybio.com/plogger/images/anatomy___physiology/08._powerpoint_-_peripheral_nervous_system/somatic_reflex.jpg

http://www.baileybio.com/plogger/images/anatomy___physiology/05._powerpoint_-_muscular_system/skeletal_muscle_structure.jpg



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VIBRATION AND MOTION SICKNESS

-Whole body vibration:0.2-0.7Hz in seated subjects(Gx>Gz)

-Prevention:Supine posture



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INFRASONIC VIBRATION

-F<25Hz(if High intensity)

-Feeling of ear fullness or pressure-nausea-imbalance-Chest tightness-Tiredness-

-Vascular injection-Vertical nystagmus-low concentration

-Psychological stressor effects



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HUMAN TOLERANCE TO VIBRATION

-15 well-motivated volunteers

-Tolerance:4-8 Hz vibration

-Main symptoms :Precordial & central abdominal pain

-Difficulty in breathing:1-3 Hz

-Nodal tachycardia



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HUMAN TOLERANCE TO VIBRATION



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PROTECTION AGAINST VIBRATION

1 -Attention to the source of vibration(engine design)2-Modification of the transmission pathway(dynamic vibration absorbers-

Connecting the seat-pan and backrest to the body - seat-Active vibration absorption )

3 -Alteration of the dynamic properties of the body



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OCCUPATIONAL HAZARDS OF VIBRATION-VIBRATION WHITE FINGER:

-Hand-held vibrating tools-20-200Hz-after months or years

-Tingling or numbness in the finger-Attacks of finger blanching(cold)-Touch & temprethre sensation impaired-Dusky cyanosis-Finger pulps atrophy(skin necrosis)



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OCCUPATIONAL HAZARDS OF VIBRATION-WHOLE-BODY VIBRATION

-4Hz(vertical-fore-aft-rotational)-Disorders of the lumbar spine-stomach-related disorders

-Drivers of tractors-earth-moving vehicles and trucks



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ARMY UNIVERSITY OF MEDICAL SCIENCE F35 fighter

vibration

Business

start of vibration

gravitational spring

spring heat productiondamper

springsinusoidal graph

mass heat production

principles of vibration1

vision systems international

neuromascular controlspeechdr