10/20/2015Copyright © 2008 Ballios, Dow, Vogtmann, Zofchak.

Overview Introduction to Ultrasound

Applications

Physics

Waveforms

Data Example

Summary


Introduction to Ultrasonic Transducers


• An ultrasonic transducer converts electrical energy to mechanical energy, in the form of sound, and vice versa. The main components are the active element, backing, and wear plate.

Transducer Components Active element: piezo or ferroelectric material,

converts electrical energy such as an excitation pulse from a flaw detector into ultrasonic energy. The materials are polarized ceramics which can be cut in a variety of manners to produce different wave modes.

Wear plate: is to protect the transducer element from the testing environment.

Backing: highly attenuative, high density material that is used to control the vibration of the transducer by absorbing the energy radiating from the back face of the active element.


Ultrasound

Ultrasound is used in many different applications, typically to penetrate a medium and measure the reflection signature.

The ultrasound is generated and received by piezoelectric transducers using a variety of techniques.

Ultrasound consists of acoustic waves; the same type of wave as detected by the human ear except the frequency is higher.

Ultrasonic imaging uses frequencies in the range from 1 to 20 MHz at powers from 0.01 to 200 mW/cm2


www.wikipedia.com

Basic Theory of Ultrasound

A sound wave can be transmitted by means of longitudinal waves.

These waves can be scattered, reflected, refracted, and absorbed.

Noise from external surroundings can possibly distort the sound wave being measured.

The velocity of sound is dependent on the type of medium it is passing through.

Velocity (v) Bulk Modulus (K)

Substance's resistance to uniform compression

Density (ρ)


v K

Medical Ultrasound


Cardiology

Interventional Biopsy

Gastroenterology

Obstetrics

Urology

Kidney

Fetal Cranial Volume

www.medscape.com

www.wikipedia.com

Industrial UltrasoundCommonly used as a non-destructive test to

locate flaws in materials.

Frequencies commonly used range between 2 to 10 MHz. This varies depending on the material being tested.

Recently there has beeninterest in lower frequency highenergy ultrasound as anintensification technology. Fluid degasification. Improvement of surface defects.


www.wikipedia.com

Liquid Level Measurement

L = Liquid level v = Sound velocity in the liquid t = Round-trip transit time

http://www.olympus-ims.com/en/ndt-application/183-id.209715246.html


Lvt

2

Internal Liquid Measurement


External Liquid Level Measurement


Physics of Ultrasound


Ultrasound VelocityMaterial

Velocity (m/sec)

Fat 1450

Water 1480

Soft tissue 1540

Bone 4100

Steel 5890

Reflection Coefficient

Transmission Coefficient

999.

642.

4

),(

),(

221

21

waterfat

watersteel

T

T

ZZ

ZZT


001.

385.

),(

),(

212

212

waterfat

watersteel

R

R

ZZ

ZZR

ReflectionMaterial

Coefficient (dB/cm MHz)

Water 0.002

Fat 0.66

Soft tissue (average) 0.9

Muscle (average) 2

Air 12

Bone 20

lung 40


Spectra

Time

Fre

quency

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.450

0.5

1

1.5

2

x 104


Spectra Mesh


Ultrasound Waveform


Data ExampleSolid in Liquid

Measurement

Fast Fourier Transform Amplitude

measurements

Attenuation Coefficient Gradient calculations


www.kakinan.com

W

K

I

I10log20

2maxmin ff

f c

fC – Fix Center frequency

µ – Attenuation CoefficientIK – FFT of Solid mixtureIW – FFT of Control

Data Example (cont.)Variables

Time-of-Flight (TOF) Attenuation

Gradient calculation vs.Amplitude measurement FFT simpler to

calculate Gradient tolerable to

inconsistent center freq.


www.kakinan.com

Data Example (cont.)


www.kakinan.com

Summary Ultrasonic Theory

Applications Medical Industrial

Waveforms

Data Interpretation Methods Gradient Attenuation FFT


Questions


10/20/2015Copyright © 2008 Ballios, Dow, Vogtmann, Zofchak.

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