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USE OF ULTRASOUND İN METROLOGY
Prepared By :
• Mustafa ERARSLAN• Serkan Ahmet ÇAM• Osman KAYA• Ferhat AYDIN• Ahmet KOYUNCU• Kadir YÜZER
SOUND
Sound is a sequence of waves of pressure that propagates through compressible media such as air,water or solids.
During propagation, waves can be reflected, refracted, or attenuated by the medium.
PHYSİCS OF SOUND
The mechanical vibrations that can be interpreted as sound are able to travel through all forms of matter: gases, liquids, solids, and plasmas. The matter that supports the sound is called the medium. Sound cannot travel through a vacuum.
SOUND WAVE PROPERTIES AND CHARACTERISTICS
• Frequency, or its inverse, the period
• Wavelength• Wavenumber• Amplitude• Sound pressure• Sound intensity• Speed of sound• Direction • Polarization (Transverse Waves)
ULTRASOUND
Ultrasound is cyclic sound pressure with a frequency greater than the upper limit of human hearing. Ultrasound is thus not separated from "normal" (audible) sound based on differences in physical properties, only the fact that humans cannot hear it. Although this limit varies from person to person, it is approximately 20 kilohertz (20,000 hertz) in healthy, young adults. The production of ultrasound is used in many different fields, typically to penetrate a medium and measure the reflection signature or supply focused energy. The reflection signature can reveal details about the inner structure of the medium, a property also used by animals such as bats for hunting. The most well known application of ultrasound is its use in sonography to produce pictures of fetuses in the human womb. There are a vast number of other applications as well.
INFRASOUNDInfrasound is sound that is lower in frequency than
20 Hz (Hertz) or cycles per second, the "normal" limit of human hearing. Hearing becomes gradually less sensitive as frequency decreases, so for humans to perceive infrasound, the sound pressure must be sufficiently high. The ear is the primary organ for sensing infrasound, but at higher levels it is possible to feel infrasound vibrations in various parts of the body.
The study of such sound waves is sometimes referred to as infrasonics, covering sounds beneath 20 Hz down to 0.001 Hz. This frequency range is utilized for monitoring earthquakes, charting rock and petroleum formations below the earth, and also in ballistocardiography and seismocardiography to study the mechanics of the heart. Infrasound is characterized by an ability to cover long distances and get around obstacles with little dissipation.
ACOUSTICAcoustics is the interdisciplinary science that deals
with the study of all mechanical waves in gases, liquids, and solids including vibration, sound, ultrasound and infrasound. A scientist who works in the field of acoustics is an acoustician while someone working in the field of acoustics technology may be called an acoustical engineer. The application of acoustics can be seen in almost all aspects of modern society with the most obvious being the audio and noise control industries.
Hearing is one of the most crucial means of survival in the animal world, and speech is one of the most distinctive characteristics of human development and culture. So it is no surprise that the science of acoustics spreads across so many facets of our society—music, medicine, architecture, industrial production, warfare and more. Art, craft, science and technology have provoked one another to advance the whole, as in many other fields of knowledge.
MACH NUMBER
Mach number (Ma or M) is the speed of an object moving through air, or any other fluid substance, divided by the speed of sound as it is in that substance for its particular physical conditions, including those of temperature and pressure. It is commonly used to represent the speed of an object when it is traveling close to or above the speed of sound.
M = Mach NumberV = Relative velocity of the source to the mediuma = Speed of sound in the medium
For Subsonic ;
where:M = is Mach numberqc = is impact pressure (diffrence between total pressure and static pressure)p = is static pressure γ = is the ratio of specific heat of a gas at a constant pressure to heat at a constant volume (1.4 for air).
Regime Subsonic Transonic Sonic Supersonic HypersonicHigh-hypersonic
Mach <1.0 0.8–1.2 1.0 1.2–5.0 5.0–10.0 >10.0
CALCULATİNG MACH NUMBER
CALCULATİNG MACH NUMBER For Supersonic ;
For air Simplified Formula is ;
BASIC PRINCIPLES OF ULTRASONIC TESTING
Spectrum of sound
Frequency range Hz
Description Example
0 - 20 Infrasound Earth quake
20 - 20.000Audible sound
Speech, music
> 20.000 Ultrasound
BASIC PRINCIPLES OF ULTRASONIC TESTING
gas liquid solidAtomic structures
•low density•weak bonding forces
•medium density•medium bonding forces
•high density •strong bonding forces•crystallographic structure
BASIC PRINCIPLES OF ULTRASONIC TESTING
Wave propagation
AirWater
Steel, longSteel, trans
330 m/s
1480 m/s
3250 m/s
5920 m/s
Longitudinal waves propagate in all kind of materials.Transverse waves only propagate in solid bodies.
Due to the different type of oscillation, transverse wavestravel at lower speeds.
Sound velocity mainly depends on the density and E-modulus of the material.
BASIC PRINCIPLES OF ULTRASONIC TESTING
Reflection and Transmission
• As soon as a sound wave comes to a change in material characteristics ,e.g. the surface of a workpiece, or an internal inclusion, wave propagation will change too:
BASIC PRINCIPLES OF ULTRASONIC TESTING
Behaviour at an interface
Medium 1 Medium 2
Incoming wave Transmitted wave
Reflected wave
Interface
BASIC PRINCIPLES OF ULTRASONIC TESTING
Reflection + Transmission: Perspex - Steel
Incoming wave Transmitted wave
Reflected wave
Perspex
Steel
1,87
1,00,87
BASIC PRINCIPLES OF ULTRASONIC TESTING
0,13
1,0
-0,87
Perspex Steel
Incoming wave Transmitted wave
Reflected wave
BASIC PRINCIPLES OF ULTRASONIC TESTING
Amplitude of sound transmissions:
•Strong reflection•Double
transmission
•No reflection•Single
transmission
•Strong reflection with inverted phase•No transmission
Water - Steel Copper - Steel Air - Steel
BASIC PRINCIPLES OF ULTRASONIC TESTING
Piezoelectric Effect
Piezoelectrical Crystal (Quartz)
Battery+
BASIC PRINCIPLES OF ULTRASONIC TESTING
+
The crystal gets thicker, due to a distortion of the crystal lattice
+
The effect inverses with polarity change
BASIC PRINCIPLES OF ULTRASONIC TESTING
BASIC PRINCIPLES OF ULTRASONIC TESTING
U(f)
Sound wave with
frequency f
An alternating voltage generates crystal oscillations at the frequency f
U(f)
BASIC PRINCIPLES OF ULTRASONIC TESTINGReception of ultrasonic waves
A sound wave hitting a piezoelectric crystal, induces crystal vibration which then causes electrical voltages at the crystal surfaces.
Electrical energy
Piezoelectrical crystal
Ultrasonic wave
BLOCK DIAGRAM: ULTRASONIC INSTRUMENT
amplifier
work piece
probe
horizontal sweep
clock
pulser
IP
BE
screen
Sound reflection at a flaw
Probe
Flaw Sound travel path
Work piece
s
Plate testing
delaminationplate 0 2 4 6 8 10
IP
F
BE
IP = Initial pulseF = FlawBE = Backwall echo
0 2 4 6 8 10
s
s
Wall thickness measurement
Corrosion
s
Through transmission testing
0 2 4 6 8 10
Through transmission signal
1
2
1
2
T
T
R
R
Flaw
surface = sound entry
backwall flaw
1 2
water delay
0 2 4 6 8 10 0 2 4 6 8 10
IE IEIP IP
BE BEF
1 2
Immersion testing
Weld inspection
0 20 40 60 80 100
s
aa'
d
x
a = s sinßa = s sinß
a' = a - xa' = a - x
d' = s cosßd' = s cosß
d = 2T - t'd = 2T - t'
s
Lack of fusion
Work piece with welding
F
ß = probe angles = sound patha = surface distancea‘ = reduced surface distanced‘= virtual depthd = actual depthT= material thickness
ß
Straight beam inspection techniques:
Direct contact, single element probe
Direct contact, dual element probe
Fixed delay
Immersion testingThrough transmission
• Sonar stands for sound navigation and ranging.• Sonar uses a beam of sound waves and directs them
downward.• After the sound wave hits the bottom of the ocean
(ocean floor), or an object, it will bounce off and return back causing an echo.
• This is then recorded on a depth recorder on the ship.
• Some marine organisms use Echolocation, which is a form of sonar (dolphins, whales, porpoises).
SONAR (SOUND NAVIGATION AND RANGING)
TYPES OF SONAR SYSTEMSSYSTEMS
Active
• Deploys and receives its own signal
• Two categories echo ranging, and communication
• Allied Submarine Detection Investigation Committee ( ASDICS)
Passive
• Listening device• Detects underwater
sounds• Belongs to the Direct
Listening category
COMPONENTS OF A SONAR SYSTEM
Active
• Transducer (Emitter/Receiver)
• Indicator• Recorder• Computer System
Passive
• Transducer (Only Receiver)
• Indicator• Recorder• Computer System
MEDİCAL ULTRASONOGRAPHY
Diagnostic sonography (ultrasonography) is an ultrasound-based diagnostic imaging technique used for visualizing subcutaneous body structures including tendons, muscles, joints, vessels and internal organs for possible pathology or lesions. Obstetric sonography is commonly used during pregnancy and is widely recognized by the public.
In physics, the term "ultrasound" applies to all sound waves with a frequency above the audible range of human hearing, about 20,000 Hz. The frequencies used in diagnostic ultrasound are typically between 2 and 18 MHz.
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