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

Overview Introduction to Ultrasound Applications Physics Waveforms Data Example Summary 10/20/2015Copyright © 2008 Ballios, Dow, Vogtmann, Zofchak

Introduction to Ultrasonic Transducers 10/20/2015Copyright © 2008 Ballios, Dow, Vogtmann, Zofchak 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. 10/20/2015Copyright © 2008 Ballios, Dow, Vogtmann, Zofchak

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

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

Medical Ultrasound 10/20/2015Copyright © 2008 Ballios, Dow, Vogtmann, Zofchak Cardiology Interventional Biopsy Gastroenterology Obstetrics Urology Kidney Fetal Cranial Volume

Industrial Ultrasound Commonly 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 been interest in lower frequency high energy ultrasound as an intensification technology. Fluid degasification. Improvement of surface defects. 10/20/2015Copyright © 2008 Ballios, Dow, Vogtmann, Zofchak

Liquid Level Measurement L = Liquid level v = Sound velocity in the liquid t = Round-trip transit time 10/20/2015Copyright © 2008 Ballios, Dow, Vogtmann, Zofchak

Internal Liquid Measurement 10/20/2015Copyright © 2008 Ballios, Dow, Vogtmann, Zofchak

External Liquid Level Measurement 10/20/2015Copyright © 2008 Ballios, Dow, Vogtmann, Zofchak

Physics of Ultrasound 10/20/2015Copyright © 2008 Ballios, Dow, Vogtmann, Zofchak

Ultrasound Velocity MaterialVelocity (m/sec) Fat1450 Water1480 Soft tissue1540 Bone4100 Steel5890 Reflection Coefficient Transmission Coefficient 10/20/2015Copyright © 2008 Ballios, Dow, Vogtmann, Zofchak

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

Reflection Material Coefficient (dB/cm MHz) Water0.002 Fat0.66 Soft tissue (average)0.9 Muscle (average)2 Air12 Bone20 lung40 10/20/2015Copyright © 2008 Ballios, Dow, Vogtmann, Zofchak

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

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

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

Data Example Solid in Liquid Measurement Fast Fourier Transform Amplitude measurements Attenuation Coefficient Gradient calculations 10/20/2015Copyright © 2008 Ballios, Dow, Vogtmann, Zofchak f C – Fix Center frequency µ – Attenuation Coefficient I K – FFT of Solid mixture I W – 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. 10/20/2015Copyright © 2008 Ballios, Dow, Vogtmann, Zofchak

Data Example (cont.) 10/20/2015Copyright © 2008 Ballios, Dow, Vogtmann, Zofchak

Summary Ultrasonic Theory Applications Medical Industrial Waveforms Data Interpretation Methods Gradient Attenuation FFT 10/20/2015Copyright © 2008 Ballios, Dow, Vogtmann, Zofchak

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