NDT Lesson 1 - 8. PDF

Portions of this manual have been taken from the General DynamicsCorporation’s Classroom Training Handbook CT 6-4, Ultrasonic Testing. AndProgrammed Instruction Handbooks PI-4-1, Introduction and PI-4-4, UltrasonicTesting. These portions are subject to General Dynamics Cooperation’s copyright1967.

Printed in the United State of America

PREPARED BY: George L. PherigoDirector of EducationAmerican Society for Nondestructive Testing. Inc.

REVIEWED AND EDITED BY THE FOLLOWING MEMBERS OF THEEDUCATIONALCOUNCILOFASNT:

Boyd W. BrownArgonne National Laboratory

Kinney C. McKeelGeneral Electric Co.

W. C. MorreyEbasco Services

PhillipA. OlkleYankeeAtomic Electric Co.

Allen ReynoldsStone & Webster Corp.

Ward d. RummelMartin Marietta Corp.

A. J. SchwarberLawrence Livermore Laboratories

Albert L. SmithWestinghouse Hanford Co.

John L. SummersRockwell Int ernational

Paul H. ToddMartin Marietta Corp.

Published by TheAmerican Society for Nondestructive Testing4153Arlington Caller # 28518 Columbus. Ohio 43228

Copyright© by The American Society for Nondestructive Testing. Inc. Allrights reserved.

-1- External training services : PT. Diametral Dharma PersadaNon Destructive Testing (NDT)

STUDENT’S GUIDE

NDT TRAINING PROGRAM

ULTRASONIC METHOD

I INTRODUCTION TO THE ULTRASONIC TRAINING PACKAGEThe training materials in this package are designed to provide a basic knowledge of the

fundamentals of ultrasonic testing. The training program that you are participating in will

contain the following classroom hours of instruction to present the information as

suggested in the ASNT publication SNT-IC-IA. Recommended Practice, June 1980

Edition.

Level 1 Training will include lectures on all 14 lesson with approximately 2.9 hours per

lesson. The student should assume the responsibility for reading all assignments,

attending lectures, and participating in class discussions. Short exams will be

administrated after each lesson to provide the student with a measure of progress and to

stimulate study.

II CONTENTS OF TRAINING PACKAGEYour training package contains the following materials with specific instructions and

assignments to be given by the course instructor.

1. STUDENT PACKAGEA. Students’ Guide which outline the purpose, content and use of the training

materials.B. 1 Classroom Training Handbook (CT-6.4) which serves as the major text for the

training course.C. 1 set of individual lecture guide packets on the fundamentals of ultrasonic

testing the lecture guide materials are provided with each lesson and are

identical to the transparencies used by the instructor during the lecture. During

the lecture, the student should use the guide to make additional notes. and the

guide will then become valuable for future study .D. 1 packet of exams. The instructor may elect to remove the exams from your

packet poor to starting the course and administer them as each lesson is

completed. An exam will be furnished for each of the 14 lesson in the training

course.

2. INSTRUCTOR PACKAGEA. The instructor’s package contains all of the information that you have with the

addition of lecture guide transparencies and exam keys.B. At the option of the instructor a set of filmstrips may be used to provide additional

depth and clanty .C. At the option of the instructor, the programmable instruction handbook may be

used for additional assignments.D. Several types of certificates are available from ASNT and may be issued at the

option of the instructor.

III OUTLINE OF LESSONSAND RELATED READINGASSIGNMENTSThe reading assignments will be made by the instructor and will correlate with the lectures

the Classroom Training Handbook (CT-6-4) and programmed instruction Handbooks (PI-

4-4) follow the lesson in this training course in the following order.


Lesson 1 Applications, Training, and CertificationCT-6-4, Chapter 1 allSNT-TC-1A all

Lesson 2 Ultrasonic, PrinciplesCT-6-4, Chapter 2 2-5 to 2-8PI-4-4, Volume 1, Chapter 1 allPI-4-4, Volume 1, Chapter 2 2-1 to 2-6

Lesson 3 Equipment ControlsCT-6-4, Chapter 2 2-8 to 2-16PI-4-4, Volume 1, Chapter 5 allPI-4-4, Volume 2, Chapter 4 4-1 to 4- 60

Lesson 4 Wave Propagation, Reflection, and RefractionCT 6-4, Chapter 2 2-16 to 2-31PI-4-4, Volume 1, Chapter 3 all

Lesson 5 Couplants, Material Characteristics, Beam SpreadCT-6-4, Chapter 2 2-26 to 2-36PI-4-4, Volume 1, Chapter 6 allPI-4-4, Volume 2, Chapter 2 all

Lesson 6 Attenuation, Impedance, and ResonanceCT-6-4, Chapter 2 2-23 to endPI-4-4, Volume 1, Chapters 2 & 4 allPI-4-4, Volume 2, Chapter 4 4-61 to end

Lesson 7 Screen Presentations, Angle Beam Inspection WithUT CalculatorCT-6-4, Chapter 3 3-3 to 3-12PI-4-4, Volume 1, Chapter 5 allPI-4-4, Volume 2, Chapter 5 allPI-4-4, Volume 3, Chapter 3 3-60 to end

Lesson 8 Transducers, Standard Reference BlocksCT-6-4, Chapter 3 3-3 to 3-12PI-4-4, Volume 2, Chapters 1 & 3 all

Lesson 9 Immersion InspectionCT-6-4, Chapter 4 4-1 to 4-18PI-4-4, Volume 3, Chapters 4 & 5 all

Lesson 10 Contact Testing, Longitudinal & Shear Waves, Shell’s LawCT-6-4, Chapter 4 4-19 to 4-28PI-4-4, Volume 3, Chapters 1 & 2 all

Lesson 11 Applications of Angle Beam Contact TestingCT-6-4, Chapter 4, 4-19 to 4-31PI-4-4, Volume 3, Chapter 3 all

Lesson 12 Nonrelevant Ultrasonic IndicationsCT-6-4, Chapter 4 4-32 to endPI-4-4, Volume 3, Chapter 6 all

Lesson 13 Classification of Discontinuities in UTCT-6-4, Chapter 7 7-1 to 7-7PI-4-4, Chapters 1 through 7 all

Lesson 14 Identification and Compensation of DiscontinuitiesCT-6-4, Chapter 7 7-8 to end


BASICAPPLICATIONS OF ULTRASONICS

ULTRASONICS ISAVERSATILE INSPECTION TECHNIQUE, IT IS USED TO TEST

A VARIETY OF BOTH METALLIC AND NON METALLIC PRODUCTS SUCH AS

WELDS FORGINGS, CASTINGS, SHEET, TUBING, PLASTICSAND CERAMICS.

ULTRASONICS HAS AN ADVANTAGE OF DETECTING SUBSURFACE

DISCONTINUITIES WITHACCESS TO ONLY ONE SIDE OF THE SPECIMEN.

THE OBJECTIVE OF ULTRASONIC TESTING IS TO ENSURE PRODUCT

RELIABILITY BY MEASNS OF:

1. OBTAINING INFORMATION RELATED TO DISCONTINUITIES2. DISCLOSING THE NATURE OF THE DISCONTINUITY IMPAIRING THE

USEFULNESS OF THE PART.3. SEPARATING ACCEPTABLE AND UNACCEPTABLE MATERIALS IN

ACORDANCE WITH PREDETERMINED STANDARDS

TRAININGAND CERTIFICATION

IT IS IMPORTANT THAT THE TECHNICIAN AND SUPERVISOR BE QUALIFIED IN

THE ULTRASONIC METHOD BEFORE THE TECHNIQUE IS USED AND TEST

RESULTS EVALUATED

THE AMERICAN SOCIETY FOR NON DESTRUCTIVE TESTING RECOMMENDS

THE USE OF THEIR DOCUMENT “RECOMMENDED PRACTICE NO. SNT-TC-1A.”

THIS DOCUMENT PROVIDES THE EMPLOYER WITH THE NECESSARY GUIDE

LINES TO PROPERLY QUALIFY AND CERTIFY THE NDT TECHNICIAN IN ALL

METHODS.

TO COMPLY WITH THIS DOCUMENT THE EMPLOYER MUST ESTABLISH A

“WRIT TEN PRACTICE” WHICH DESCRIBES IN DETAIL HOW THE TECHNICIAN

WILLBE TRAINED, EXAMINEDAND CERTIFIED.

THE STUDENT IS ADVISED TO STUDY THE CURRENT EDITION OF SNT-TC-1A

TO DETERMINE THE RECOMMENDED INITIAL NUMBER OF HOURS OF

CLASSROOM INSTRUCTION AND MONTHS OF EXPERIENCE NECESSARY TO

BE CERTIFIEDASAN ULTRASONIC TESTING TECHNICIAN

Lesson 1


External training services : PT. Diametral Dharma PersadaNon Destructive Testing (NDT)

CERTIFICATION OF NDT PERSONNEL IS THE RESPONSIBILITY OF THE

EMPLOYERAND IS USUALLYATTHREE LEVELS

LEVELI PERFORM SPECIFIC CALIBRATIONS, SPECIFIC TESTS, AND

SPECIFIC EVALUATIONS ACCORDING TO WRITTEN

INSTRUCTIONS.

LEVELII SET UP AND CALIBRATE EQUIPMENT AND INTERPRET AND

EVALUATE RESULTS WITH RESPECT TO CODES, STANDARDS

AND SPECIFICATIONS. MUST BE ABLE TO PREPARE WRITTEN

INSTRUCTIONSAND REPORTTEST RESULTS

LEVELIII RESPONSIBLE FOR ESTABLISHING TECHNIQUES,

INTERPRETING CODES, AND DESIGNATING THE TEST METHOD

AND TECHNIQUE TO BE USED. MUST HAVE A PRACTICAL

BACKGROUND IN THE TECHNOLOGY AND BE FAMILIAR WITH

OTHER COMMONLY USED METHODS OF NDT.

THE SNT. TC. 1A DOCUMENT RECOMMENDS THAT LEVEL I AND II NDT

TECHNICIANS BE EXAMINED IN THE FOLLOWINGAREAS

A. GENERALEXAMINATIONB. SPECIFIC EXAMINATIONC. PRACTICALEXAMINATION

Lesson 1

UT Lecture Guide

-5-


ASNT PROVIDES A SERVICE TO THE INDUSTRY BY PROVIDING LEVEL III

EXAMINATIONS IN THE BASIC AND METHOD AREAS, BECAUSE OF THE

INDIVIDUAL REQUIREMENTS OF THE MANY INDUSTRIES USING NDT, THE

SPECIFIC EXAMINATION IS STILL THE RESPONSIBILITY OF THE EMPLOYER.

THE FOLLOWING FLOW CHART INDICATES THE PATHS THAT CAN BE TAKEN

TO CERTIFIED ACCORDING TO THE SNT-TC-1A DOCUMENT.

ASNT CERTIFICATION WITHOUT EXAMINATION

Basic, Method, Specific15 years Education/ Experience

ASNT CERTIFICATION BY EXAMINATION

Basic, Method

LEVEL III

CERTIFICATION

PER

RECOMMENDED

PRACTICE

SNT TC-1A

June 1980 EDITION

QUALIFICATIONS

FERIFIED AND

DOCUMENTED

PER THE

EMPLOYERS

WRITTEN

PRACTICE

LEVEL III

CERTIFICATION

ISSUED BY THE

EMPLOYER

CU

ST

OM

ER

AC

CE

PTA

NC

EEXAMINATION BY THE EMPLOYER

EXAMINATION BY OUTSIDE AGENCY

EMPLOYER WAIVES EXAMINATION

Lesson 1

UT Lecture Guide

-6-

Notes :

Certificate issued to individual

This documentation as recommended

in paragraph 5, 6-3.3, 6.3.4 and

9 of the SNT-TC- 1A 1980 edition


UT LESSON 1QUIZ

1. The selection of one test method over another is usually the decision

of the Level I technician performing the test.2. ASNT provides a service for examining Level I, II and III personnel in

the General and specific areas.3. The responsibility of issuing a certificate to the NDT technician is

always retained by the employer in compliance with the SNT-TC-1A

document.4. If the SNT-TC-1A document is to be used as recommended guideline,

the “written Practice” must be submitted toASNT for approval.5. If the SNT-TC-1A guidelines are followed, the Level III technician

should have a knowledge of other commonly used methods of NDT

even though certification is needed only in the ultrasonic area.6. ALevel I technician performing an ultrasonic test is permitted to accept

or reject the part provided that written instructions or procedures are

given to him by a Level II or Level III. (in accordance with SNT-TC-1A)7. To comply with the guidelines of SNT-TC-1A all three levels of

technicians must take a “General”, “Practical” and “Specific” test it

examinations are used to determine certification.8. The June 1980 Edition of SNT-TC-1A permits the employer to waive

an examination for Level III personnel provided that documentation is

on file showing the technician’s qualifications.9. It is essential that every employer that uses the SNT-TC-1A document

establish a “written Practice”10. If an employer does not have a Level III in his company the services of

an outside agency may be retained to perform these functions11. An advantage of ultrasonics is that it reveals internal discontinuities

with access to only one side of the part being inspected.12. Ultrasonic inspection techniques can be used without impairing the

future usefulness of the material

Name

-7-


Lesson 2

ULTRASONIC PRINCIPLESIN ULTRASONIC TESTING WE USE SOMETHING CALLED “ULTRASONIC

VIBRATIONS.” WE MUST KNOW TWO FACTSABOUTAVIBRATION

1. AVIBRATION ISABACKAND FORTH MOVEMENT.2. AVIBRATION IS ENERGY IN MOTION

A DEPRESSION OF A SURFACE FROM ITS NORMAL POSITION IS CALLED A

DISPLACEMENT.

RUBER BALL

VIBRATIONS PASS THROUGHASOLID MATERIALASASUCCESSION OF PART ICLE DISPLACEMENTS. THIS CAN BE VISUALIZEDAS SHOWN BELOW:

THE STRUCTURE OF A MATERIAL IS ACTUALLY MANY SMALL PARTICLES OR

GROUPS OFATOMS.

THESE PARTICLES HAVE NORMAL OR REST POSITIONS, AND CAN BE

DISPLACED FROM THESE POSITIONS BY SOME FORCE WHEN THE FORCE IS

REMOVED, THE PARTICLES WILL TEND TO RETURN TO THEIR ORIGINAL

POSITIONS.

1 2 3 4 5

-8-


ENERGY IS TRANSMITTED THROUGH A SOLID MATERIAL BY A SERIES OF

SMALLMATERIALDISPLACEMENTS WITHIN THE MATERIAL.

THE TRANSMISSION OF ULTRASONIC VIBRATIONS THROUGH A MATERIAL IS

RELATED TO THE ELASTIC PROPERTIES OF THE MATERIAL.

IF YOU TAP A METAL SURFACE, THE SURFACE MOVES INWARD, CAUSING A

DISPLACEMENT.

SINCE THE METAL IS ELASTIC THE SURFACE WILL TEND TO MOVE BACK TO

ITS ORIGINAL (REST) POSITION. THE SURFACE WILL ALSO MOVE THROUGH

THE ORIGINAL POSITION AND MOVE TO A MAXIMUM DISTANCE IN THE

OPPOSITE DIRECTIONTHIS COMPLETE SEQUENCE OF MOVEMENTS IS DEFINED AS A CYCLE.

THE TIME REQUIRED FOR SOMETHING TO MOVE THROUGH ONE COMPLETE

CYCLE IS CALLED THE PERIODEXAMPLE : IF THE SWINGING BALL ABOVE MOVES OVER PATH ABCDE IN

ONE SECOND, THEN THE PERIOD OF THE CYCLE IS ONE SECOND.

PLATE STRUCKWITH HAMMERTHIN PLATE

SUPPORTVIEW A

STRING

BALL

PENCIL

DIRECTION OFBALL SWING

A

B

C

D

E

DIRECTION OFSTRING TRAVEL

A

B

CD

E

CYCLE

STRING

BALL

PENCIL

Lesson 2

UT Lecture Guide

-9-

ONE


THE NUMBER OF CYCLES IN A GIVEN PERIOD OF TIME IS CALLED THE

FREQUENCY.EXAMPLE: IF THE BALL SWINGS THROUGH THREE COMPLETE CYCLES IN

ONE SECOND, THEN THE FREQUENCY IS 3 CPS (CYCLES PER

SECOND).IF YOU STRIKE A DRUM, IT HAS A FREQUENCY THAT IS LOW,

APPROXIMATELY 50 CPS.THE TOP NOTE ON THE PIANO HAS A HIGHER FREQUENCY, APPROXIMATELY

4100 CPS.THE UNIT OF FREQUENCY USED TO DENOTE ONE CYCLE PER SECOND IS

HERTZ (ABBREVIATED Hz). ONE CYCLE PER SECOND (CPS) IS EQUAL TO

ONE HERTZ (Hz), 2 CPS = 2 Hz, ETC.SOUND TRAVELS IN METAL AS WELL AS IN AIR SOUND IS A VIBRATION AND

HASARANGE OF FREQUENCIESMAN CAN ONLY HEAR VIBRATIONS (SOUND) UPTOABOUT 20.000 Hz.HOWEVER. SOUND FROMAN ULTRASONIC TESTING UNIT ISABOUT 5,000.000

Hz. (5 MEGAHERTZ)VIBRATIONS ABOVE THE HUMAN HEARING RANGE ARE CALLED

ULTRASONIC VIBRATIONS.THE TWO TERMS. SOUND AND VIBRATIONS, AS WE WILL USE THEM WILL

MEAN THE SAME THING.THE BEST WAY TO DEFINE SOUND IS TO SAY THAT IT IS A VIBRATION THAT

TRANSMITS ENERGY BYASERIES OF SMALLMATERIALDISPLACEMENTS

JACK HAMMER

Lesson 2

UT Lecture Guide

-10-


ULTRASONIC TESTING IS THE PROCESS OF APPLYING ULTRASONIC SOUND

TOASPECIMENAND DETERMINING ITS SOUNDNESS, THICKNESS, OR SOME

PHYSICALPROPERTY.

THE ENERGY IS ORIGINATED IN SOMETHING CALLED A “TRANSDUCER”WHICH CAUSES MATERIALDISPLACEMENT WITHIN THE SPECIMEN.

ATRANSDUCER IS A DEVICE THAT CONVERTS ENERGY FROM ONE FROM TO

ANOTHER.

EXAMPLE : ELECTRICAL ENERGY TO MECHANICAL, OR MECHANICAL TO

ELECTRICALA SPEAKER IN A RADIO CONVERTS ELECTRICAL ENERGY TO A

BACKAND FORTH MECHANICALMOVEMENTVIEW “A” BELOW ILLUSTRATES THE “PIEZOELECTRIC EFFECT” ELECTRICAL

ENERGY IS APPLIED THROUGH TWO WIRES CONNECTED TO A CRYSTAL,

CAUSING THE CRYSTALTO VIBRATE.THE TERMS CRYSTAL AND TRANSDUCER ARE USED INTERCHANGEABLY IN

THIS LESSON.

ELECTRICAL ENERGY CAUSES A PIEZOELECTRIC CRYSTAL TO EXPAND AND

CONTRACT, FORMING MECHANICAL VIBRATIONS. A PIEZOELECTRIC

TRANSDUCER CAN ALSO CONVERT MECHANICAL ENERGY TO ELECTRICAL

ENERGY. THEREFOR, A TRANSDUCER CAN BOTH SEND AND RECEIVE

ENERGY.

TRANSDUCER

SPECIMEN

VIEW B

NOTE:SOUND IS REFLECTEDWITHIN SPECIMEN ANDRETURN TO TRANSDUCER

WIRE

CRYSTALTRANSDUCER

VIBRATION

SOUND

WIRE

VIEW A VIEW B

ELECTRICAL ENERGY

Lesson 2

UT Lecture Guide

-11-


ENERGY TRANSMITTED BY A TRANSDUCER CAN BE EITHER PULSED OR

CONTINUOUS.PULSED ULTRASOUND IS DEFINED AS SHORT GROUPS OF TRANSMITTED

VIBRATIONS BEFORE AND AFTER WHICH THE TRANSDUCER CAN ACT AS A

RECEIVER.STEEL, WATER AND OIL WILL TRANSMIT ULTRASOUND VERY WELL, BUT AIR

PRESENTSAPROBLEM.

TRANSDUCER

OIL

STEELSPECIMEN

AIR IS A POOR TRANSMITTER OF ULTRASOUND BECAUSE THE PARTICLE

DENSITY IS SO LOW THAT IT IS DIFFICULT TO TRANSMIT SOUND ENERGY

FROM PARTICLE TO PARTICLE THAT IS WHY WE PUT OIL OR GREASE

BETWEEN THE TRANSDUCERAND THE SPECIMEN.THE PARTICLE DENSITY OF A MATERIAL HELPS DETERMINE THE VELOCITY

OF SOUND. THE VELOCITY OF SOUND WILL CHANGE AS IT MOVES FROM

ONE MEDIUM TO ANOTHER AS SHOWN BELOW. THE ELASTICITY OF THE

MATERIAL ISALSOA FACTOR.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

AIR WATER STEEL

0.33 KM/SEC 1.48 KM/SEC 5.9 KM/SEC

VISUALIZE THAT THE BALLS SHOWN ABOVE REPRESENT THE INTERNAL

STRUCTURE OFAIR, WATERAND STEEL.THE IMPULSE MOVING THROUGH THE ROW OF BALLS CAN BE COMPARED

TOAPULSE OF ULTRASONIC SOUND

Lesson 2

UT Lecture Guide

-12-


A PRACTICAL EXAMPLE OF THE VELOCITY OF SOUND IN DIFFERENT

MATERIALS IS SHOWN BELOW.

TRANSDUCER

PISTON

WATER

STEELSPECIMEN

IT WILL TAKE LONGER FOR THE SOUND TO TRAVEL THROUGH THE WATER

THAN THROUGH THE STEEL. THE SOUND VELOCITY IN STEEL IS

APPROXIMATELY FOUR TIMES GREATER THAN IN WATER.A WAVELENGTH IS CONSIDERED TO BE THE DISTANCE BETWEEN TWO

SUCCESSIVE DISPLACEMENTS.

TRANSDUCERWAVELENGTH

ABA A A

THE WAVELENGTH CAN ALSO BE DEFINED AS THE DISTANCE A WAVE

TRAVELS DURING ONE COMPLETE CYCLE.

TRANSDUCER

VELOCITY

VIEW B

1234

V

1

PISTON

SOUND WAVE

VIEW A

A B

THE SYMBOL IS USED TO REPRESENT A WAVELENGTH AND IS CALLED

“LAMBDA”

Lesson 2

UT Lecture Guide

-13-


THE ILLUSTRATION BELOW SHOWS A TRANSDUCER VIBRATING AT A FIXED

FREQUENCY (f)AND TRANSMITTING SOUND WAVES INTO THE SPECIMEN.

TRANSDUCERVELOCITY

SOUND WAVES

THESE SOUND WAVES MOVE AT A FIXED VELOCITY (v) THROUGH THE

SPECIMEN.THE WAVELENGTH CAN BE CHANGED IF THE FREQUENCY OF THE

TRANSDUCER VIBRATION CHANGES.

WAVELENGTHVELOCITY

FREQUENCY=

v

f

=

EXAMPLE: YOU CAN SHORTEN THE WAVELENGTH BY INCREASING THE

FREQUENCYWAVELENGTH IS A RATIO OF A FIXED VALUE (VELOCITY) DIVIDED BY A

VARIABLE (FREQUENCY).IN PRACTICAL SITUATIONS, THE SMALLEST DISCONTINUITY YOU CAN FIND

WITH ULTRASONIC TESTING IS ABOUT ½ LAMBDA(WAVELENGTH)THEREFORE . TO DETECT SMALLER DEFECTS, YOU WILL NEED

TRANSDUCERS THAT PRODUCE HIGHER FREQUENCIES.

EXAMPLE: WHAT WOULD BE THE SMALLEST DISCONTINUITY THAT YOU

COULD FIND IN A STEEL SPECIMEN WITH A VELOCITY OF

6KM/SEC USING A TRANSDUCER WITH A FREQUENCY OF 3

MEGAHERTZ (MHz).

6 X 10 CM/SEC5

3 Mhz= 2 MILLIMETERS=

IF THE SMALLEST DEFECT DETECTABLE IS ½ LAMBDA. THEN

THEANSWER IS 1 MILLIMETER OR 0.040 INCHES.

Lesson 2

UT Lecture Guide

-14-


A The distance between two displacements is called the WAVELENGTH. This is

the distance a wave advances white a particle makes one complete cycle.B The symbol used to represent a wavelength “ ” is called LAMBDA.C The wavelength is a ratio of a fixed value (VELOCITY) divided by a variable

(FREQUENCY).

WAVELENGTH = ------------------- or = ----------

UT LESSON 2WORKSHEET

VELOCITY

FREQUENCY

v

f

D For the purpose of this exercise, consider that the smallest discontinuity

detectable using pulse echo testing is one half lambda.1. What is the smallest defect you can detect with a 2 Mhz probe inspecting a

steel specimen with a velocity of 60 x 10 cm/sec? = (answer in inches)

(1 mm equals . 040 )

5

-

2. What is the smallest detect could detect if you increased the probe

frequency to 5 Mhz? (Answer in inches)

3. What probe below would detect the smallest detect if you were inspecting a

steel specimen with a velocity of 5.9 x 10 cm/sec?What is the smallest each of the below would detect? (Answer in inches)______ 2.5 Mhz______ 5.0 Mhz______ 10.0 Mhz

5

4. With everything else equal. Would a wavelength be longer in water or steel?

-15-

1. Relative to ultrasonic testing, air is considered a good conductor and for

ths reason ultrasound will carry long distances in air.2. Particle density of a material has a direct relationship to the velocity of

sound in that material.3. The symbol used to represent a wavelength is called “Shepda.”4. With everything else equal, the wavelength in water would be shorter than

a wavelength in steel.5. To understand our definition of ultrasonics, a steel ball is considered to be

more elastic than a lead ball6. Man can hear sound up to approximately 5.000.000 Hz.7. Vibration pass through a solid material as a series of particle

displacements.8. The velocity of sound is slower in steel than in water.9. The number of cycles in a given period of time is called the frequency.10. For the purposes of this lesson, ½ the wavelength is considered to be the

smallest discontinuity that can be detected with ultrasonics.

11. If the longitudinal velocity in aluminum is 6.5 x 10 cm/sec and you are

using a 2.5 MHz probe, what is the smallest discontinuity you can detect?

(3 pts)

12. The ability of a transducer to convert mechanical energy to electrical and

electrical energy to mechanical is due to the _______________ effect.13. The distance that an ultrasonic pulse travels while a particle makes one

complete cycle is called ______________

5

UT LESSON 2QUIZ



ULTRASONIC EQUIPMENT

LESSON 3

MARKERCIRCUIT

TIMER(RATE

GENERATION)

SWEEPCIRCUIT

TRANSDUCER

(TO EACH CIRCUIT)

TESTSPECIMEN

DISCONTINUITY

BACK REFLECTION

POWERSUPPLY

PULSERCIRCUIT

RECEIVERAMPLIFIER

CIRCUIT

CRT

THE ULTRASONIC PULSE ECHO INSTRUMENT GENERATES HIGH VOLTAGE

ELETRICALPULSES OF SHORT DURATION. THESE PUYLSESAREAPPLIED TO

THE TRANSDUCER WHICH CONVERTS THEM INTO MECHANICAL

VIBRATIONS THATAREAPPLIED TO THE MATERIALBEING INSPECTED.

A LARGE PERCENTAGE OF THE SOUND IS REFLECTED FROM THE FRONT

SURFACE OF THE TEST PART BACK TO THE TRANSDUCER. THE

REMAINDER IS REFLECTED BY THE BACK SURFACE OR

DISCONTINUITIES.THE SOUND REFLECTED BACK TO THE TRANSDUCER IS CONVERTED

BACK TO ELECTRICAL PULSES. WHICH ARE AMPLIPIED AND DISPLAYED

ON THE CATHODE RAYTUBE (CRT)AS VERTICALPULSES.

THE AMPLITUDE IS A RELATIVE MEASURE OF THE AMOUNT OF

REFLECTED ENERGY.

THE A-SCAN DISPAY INDICATES THE DEPTH AND THE AMPLITUDE OF THE

SOUND REFLECTIONS FROMADISCONTINUITY.

-17-


THEREARE TWO BASIC ULTRASONIC TEST SYSTEMS:

PULSE-ECHO

COUPLANT

SPECIMEN

DISCONTINUITY

GENERATOR/INDICATORINSTRUMENT COAXIAL CABLE

TRANSDUCERTRANSMITTING

CATHODE-RAY TUBE

THROUGH TRANSMISSIONRECEIVINGTRANSDUCER

COUPLANT

THROUGH TRANSMISSION SYSTEM

CATHODE-RAY TUBE

TRANSDUCER

COAXIAL CABLEGENERATOR/INDICATORINSTRUMENT

PULSE-ECHO SYSTEM

COUPLANT

SPECIMEN

DISCONTINUITY

Lesson 3

UT Lecture Guide

-18-


PULSE-ECHO IS THE MOST WIDELY USED ULTRASONIC SYSTEM.SHORT EVENLY TIMED PULSES OF ULTRASONIC WAVES ARE

TRANSMITTED INTO THE MATERIALS BEING TESTED.THESE PULSES REFLECT FROM DISCONTINUITIES IN THEIR PATH, OR

FROMANY BOUNDARYTHATTHEY STRIKE.THE RECEIVED REFLECTIONSARE THEN DISPLAYED ONACATHODE RAY

TUBE (CRT)THE SAME TRANSDUCER CAN BE USED TO TRANSMITAND RECEIVE.

THROUGH TRANSMISSION REQUIRES THE USED OF TWO TRANSDUCERS,

ONE FOR SENDINGAND THE OTHER FOR RECEIVING.EITHER SHORT PULSES OR CONTINUOS WAVES ARE TRANSMITTED INTO

THE MATERIAL.THE QUALITY OF THE MATERIAL BEING TESTED IS MEASURED IN TERMS OF

ENERGY LOST BYASOUND BEAMAS ITTRAVELS THROUGH THE MATERIAL

WHERE THE TRANSDUCER IS COUPLED TO THE

MATERIALTHROUGH THIN LAYER OF COUPLANT.BOTH THE MATERIAL AND THE TRANSDUCER ARE

IMMERSED INATANK OF COUPLANT (USUALLY WATER).

THEREARE TWO TEST METHODS NORMALLY USED IN ULTRASONIC TESTING

"CONTACT TESTING"

" IMMERSION TESTING ".

Lesson 3

UT Lecture Guide

-19-


TO DETERMINE THE LOCATION OF DISCONTINUITIES WITHIN A TEST PART,

THE CRT HORIZONTAL DISPAY IS DEVIDED INTO CONVENIENT INCREMENTS

SUCHAS CENTIMETERS, INCHES, ETC.

AT A GIVEN SESNSITIVITY THE AMPLITUDE OF THE PIP IS

DETERMINED BY THE STRENGTH OF THE SIGNAL GENERATED BY THE

REFLECTED SOUND WAVE.THUS,1.2.

FOCUS AND ASTIGMATISM COTROLS. ADJUST THE SHARPNESS OF THE

DISPLAYED SIGNALS

SENSITIVITY OR GAIN CONTROLS. DETERMINE THE AMOUNT OF

AMPLIFICATION THE SIGNALS FROM THE DISCONTINUITY RECIEVED.INCREASING THE SENSITIVITY (GAIN) INCREASES THE AMPLITUDE OF THE

PIPS ON THE CRT SCREEN.

(GAIN) SETTING.

THE CRT DISPLAYS TWO TYPES OF INFORMATION:DISTANCE (TIME) OF THE DISCONTINUITY FROM THE TRANSDUCERRELATIVE MAGNITUDE OF THE REFLECTED ENERGY

1 2 3 41 2 3 4

A B

4"

Lesson 3

UT Lecture Guide

-20-


TWO CONTROLS, THE "SWEEP LENGTH" AND "SWEEP DELAY" REGULATE

HOW MUCH OF THE TEST PART IS DISPLAYED AT ONE TIME ON THE CRT, AND

WHAT PORTION OF THE PART IS DISPLAYED.THE SWEEP LENGTH (MATERIAL CONTROL) EXPANDS OR COMPRESSES

THE DISPLAY ON THE CRTAS SHOWN BELOW:

THE SWEEP DELAY CONTROLALLOWS ONE TO MOVE THE VIEWING SCREEN

ALONG THE DEPTH OF THE TEST PART.IN IMMERSION TESTING, THE SWEEP DELAY CAN BE USED TO REMOVE THE

INITIALPULSE FROM THE CRT.

1 IN. 4 0 F T

EXPANDED SWEEP

VIEW A

COMPRESSED SWEEP

VIEW B

A - INITIAL PULSEB - FRONT SURFACE PIPC - 1 BACK SURFACE REFLECTION PIP

ST

A

BC

VIEW A VIEW B

A A BC

B

C

Lesson 3

UT Lecture Guide

-21-


"PULSE REPETITION RATE" CONTROL REGULATES HOW OFTEN THE PULSE

IS APPLIED. PULSE RATES VARY FROM 50 TO 1200 PULSES PER SECOND OR

MORE.

WHEN THE SWEEP IS LONG, THE PULSE RATE MUST BE LOWER TOALLOW

ENOUGH TIME FOR THE SWEEP TO BE DISPLAYED BEFORE ANOTHER

PULSE IS TRANSMITTED.

IN SOME INSTRUMENTS THE PULSE RATE IS ADJUSTED AUTOMATICALLY.

INCREASING THE PULSE LENGTH INCREASES THE AMOUNT OF SOUND

ENERGY APPLIED TO THE TEST PART. BUT DECREASES THE RESOLVING

POWER OF THE EQUIPMENT.THE "PULSE ENERGY" MUST BE INCREASED TO OBTAIN DEEP

PENETRATION OR TO PENETRATE COARSEGRAINED MATERIALS.THE "REJECT CONTROL" OR "SUPPRESSION CONTROL" IS USED TO

ELIMINATE OR REDUCE "GRASS" OR VERY LOW AMPLITUDE PIPS ALONG

THE BASE OF THE SWEEP LINE. THIS CONTROL MAY AFFECT THE

VERTICALLINEARITY OF THE PRESENTATION.

A "FLAW ALARM" OR "GATING CIRCUIT" IS USED TO ESTABLISH ZONES

ALONG THE SWEEP LINE WITHIN WHICH PIPS OF PREDETERMINED

AMPLITUDE WILLACTIVATE EITHERANALARM ORARECORDING SYSTEM.

AB

CA

B C

ALARM AMPLITUDE

END OF GATESTART OF GATE

VIEW A VIEW B

Lesson 3

UT Lecture Guide

-22-


“DISTANCE AMPLITUDE CONTROL” . ULTRASONIC TESTING THEAMPLITUDE OF THE PIP FROM A DISCONTINUITY OF A GIVEN SIZEDECREASES AS THE DEPTH INCREASES. TO COMPENSATE FOR THIS“ATTENUATION,” AN ELECTRONIC CONTROL HAS BEEN ADDED TO MANYULTRASONIC UNITS.

SOME OF THE COMMON NAMES FOR THIS CONTROL ARE:DAC - DISTANCE AMPLITUDE CORECTIONTCD - TIME CORRECTED GAINSTC - SENSITIVITY TIME CONTROL

THIS CONTROL IS VERY USEFUL WHEN USED IN CONDUCTION WITHTHE FLAW ALARM AND WITH RECORDING SYSTEMS.

WITHOUT DAC

WITH DACWITH DAC

Lesson 3

UT Lecture Guide

-23-


A. As shown below, many ultrasonic units have 50 divisions along the base line of

the CRT screen. By using the simple formula below, we can make the distance

across the screen represent any distance we wish from about 5 inches to over

100 inches.The formula used to find the value of each division on the screen below is:

UT LESSON 3WORKSHEET #1

Increment/Division =Range x 2

100

0 1 2 4 53

0 1 2 3 4 5 6 7 8 9 10

-2-10-1-2

-2-10-1-2

EXAMPLE: If you wanted the entire screen to represent 10, we would find that by

using the formula that, each division on the base line represents 0.2

Inc/Div =10 x 2 20

100 100= 02”=

B. After you have selected a suitable screen range it is than possible to use the

sweep controls and match the pulses on the CRT to a know thickness calibration

block. This will be discussed in later lessons.C. Many Ultrasonic units have 100 divisions across the base line instead of 50 in

this case simply divide the range by 100 to find the increment per division.D. On the next page rill in the CRT screens as instructed.

-24-


On the CRT screens below, draw in the left edge of the first back reflection and at least

one multiple the back echo as if would appear using a normal beam transducer on a

properly calibrated unit

UT LESSON 3WORKSHEET #1

A

0 1 2 4 53

0 1 2 3 4 5 6 7 8 9 10

-2-10-1-2

-2-10-1-2

0 1 2 4 53

0 1 2 3 4 5 6 7 8 9 10

-2-10-1-2

-2-10-1-2

0 1 2 4 53

0 1 2 3 4 5 6 7 8 9 10

-2-10-1-2

-2-10-1-2

0 1 2 4 53

0 1 2 3 4 5 6 7 8 9 10

-2-10-1-2

-2-10-1-2

0 1 2 4 53

0 1 2 3 4 5 6 7 8 9 10

-2-10-1-2

-2-10-1-2

0 1 2 4 53

0 1 2 3 4 5 6 7 8 9 10

-2-10-1-2

-2-10-1-2

B

D

C

E

F

SCREEN RANGE - 1 inchPART THICKNESS - 0.49”

SCREEN RANGE - 25”PART THICKNESS -

SCREEN RANGE - 1”PART THICKNESS - 3/16”

SCREEN RANGE - 20”PART THICKNESS - 6

SCREEN RANGE - 2.5”PART THICKNESS - .6B”

SCREEN RANGE - 50”PART THICKNESS - 10

-25-


Name _______________________________

UT LESSON 3

WORKSHEET #2

Calculate the depth to each pulse on the CRT screens below. Consider that a normal

beam transducer was used on a properly calibrated unit.

A

0 1 2 4 53

0 1 2 3 4 5 6 7 8 9 10

-2-10-1-2

-2-10-1-2

If The above CRT is calibrated toa 25° range, what is the distanceto the pulse? ____________

B

0 1 2 4 53

0 1 2 3 4 5 6 7 8 9 10

-2-10-1-2

-2-10-1-2

If The above CRT is calibrated to a25° range, what is the distance tothe pulse? ____________

C

0 1 2 4 53

0 1 2 3 4 5 6 7 8 9 10

-2-10-1-2

-2-10-1-2

If The above CRT is calibrated toa 2.5° range, what is the distanceto the pulse? ____________

D

0 1 2 4 53

0 1 2 3 4 5 6 7 8 9 10

-2-10-1-2

-2-10-1-2

If The above CRT is calibrated toa 2.5° range, what is the distanceto the pulse? ____________

E

0 1 2 4 53

0 1 2 3 4 5 6 7 8 9 10

-2-10-1-2

-2-10-1-2

If The above CRT is calibrated to a2.5° range, where would the pips fora two discontinuities and backcohoes shear as shown is Fig. 1?

EACH SQUARE REPRESENTS 1/4°Fig. 1

F

-26-


________ 1. With “Through Transmission”, an increase in amplitude indicates the presence of

a possible discontinuity.________ 2. The “Pulse Echo” system uses a continuous wave and a separate transducer

receives the echo.________ 3. Both contact testing and immersion testing require the use of a coupling medium.________ 4. Typically, the “gain” control will determine the amount of amplification for a

suspected discontinuity indication.________ 5. Sweep length and sweep delay are two names for the same control.________ 6. The sweep length control is often used to sweep the initial pulse off the CRT in

immersion testing.________ 7. In the a-scan presentation used in contact testing, the height of the vertical

deflection (pip) on the CRT represents:A. VelocityB. Elapsed timeC. DistanceD. Signal amplitude

________ 8. The “distance amplitude correction” control has the ability to automatically

increase the screen range when a thicker part is inspected.________ 9. On the CRT “A” below, draw in the pulse if a normal beam transducer were used

to show a 9° deep continuity using a 15° screen range. How many division from

the left?___________ (3 pts)

________ 10. On the CRT “B” below, what is the distance to the pulse if a 2.5° screen range

were being used for the inspection? ___________ (3 pts)

Name _______________________________

UT LESSON 3

QUIZ

-2-10-1-2

-2-10-1-2

0 1 2 3 4 5

0 1 2 3 4 5 6 7 8 9 10

-2-10-1-2

-2-10-1-2

0 1 2 3 4 5

0 1 2 3 4 5 6 7 8 9 10

A B

-27-


MODES OF ULTRASONIC WAVELTRAVEL

VELOCITY CAN BE DEFINED AS THE DISTANCE A WAVE WILL PROPOGATETHROUGHAMEDIUM INAGIVEN UNIT OF TIME, USUALLYASECOND.THE WAVE SPEED REMAINS CONSTANTTHROUGHAGIVEN MEDIUM.

LISTED BELOW IS A TABLE OF IMPEDANCE, VELOCITY AND DENSITYVALUES.THIS INFORMATION WILL BE USEFUL LATER IN THIS LESSON FORPERFORMING BASIC ULTRASONIC CALCULATIONS.

ULTRASONIC WAVES ARE REFLECTED WHEN THEY ENCOUNTER A MEDIUMOF A DIFFERENT ACOUSTICAL IMPEDANCE. THE “SURFACE” AT WHICH THISREFLECTION OCCURS IS CALLEDAN “INTERFACE”.AN INTERFACE IS THE COMMON BOUNDARY BETWEEN TWO MATERIALS ORPHASES, SUCH AS ALUMINUM-TO-STEELOR WATER-TO STELL.

POINT B

POINT A

STEEL

TRANSOUCER

OIL COUPLANT

PULSES

ACOUSTIC SOUND

MATERIAL

AIR

WATER

ALUMINUM

STEEL

IMPEDANCE

(GRAM)CM - SEC2

VELOCITY

(CM /SEC)2

DENSITY

(GRAM/CM )3

0.000033 X 10

0.149 X 10

1.72 X 10

4.56 X 10

6

6

6

6

0.001

1.00

2.71

7.8

Lesson 4

-28-

0.33 X 10

1.49 X 10

6.35 X 10

5.85 X 10

5

5

5

5


A BEAM OF ENERGY APPROACHING AN INTERFACE IS REFERRED TO ASAN “INCIDENT WAVE”.

THE ANGLE AT WHICH THE WAVE STRIKES THE INTERFACE IS KNOW ASTHE “ANGLE OF INCIDENT” AS SHOWN BELOW

THE INCIDENT WAVE IS SAID TO HAVE NORMAL INCIDENCE WHEN ITSDIRECTION OF PROPAGATION IS PERPENDICULAR TO AN INTERFACE.

AS SHAWM BELOW THE ANGLE OF INCIDENCE IS ZERO.

SOME OF THE WAVE ENERGY STRIKING AN INTERFACE WILL BETRANSMITTED THROUGH THE INTERFACE, AND SOME WILL BEREFLECTED AT THE ANGLE OF INCIDENCE.

THE AMOUNT OF REFLECTION DEPENDS ON THE ACOUSTIC IMPEDANCERATIO BETWEEN THE TWO MEDIA INVOLVED THIS REFLECTANCE WILLFACTOR WILL BE DISCUSSED IN DETAIL IN THE NEXT LESSON.

INCIDENT WAVE

IMAGINARYPERPENDICULARLINE

INTERFACE

INCIDENT WAVE

INTERFACE

NORMAL INCIDENCE

Lesson 4

UT Lecture Guide

-29-


THE ANGLE OF REFLECTION AT AN INTERFACE OR BOUNDARYALWAYS EQUALS THE ANGLE OF INCIDENCE ANGLE = ANGLE “B”

ULTRASONIC VIBRATIONS TRAVEL IN MANY MODES. AND THEMOST COMMON ARE:

1. LONGITUDINAL (COMPRESSION)2. SHEAR (TRANSVERSE)3. SURFACE (RAYLEIGH)4. PLATE (LAMB)

EACH WAVE MODE HAS A SPECIFIC FUNCTION IN ULTRASONICINSPECTION AND IT IS IMPORTANT THAT EACH BE UNDERSTOODCOMPLETELY

INCIDENT WAVE

NORMALINCIDENCE

ANGLE OF REFLECTION

REFLECTED WAVE

INTERFACE

INTERFACE OR BOUNDARY

A

B

TRANSDUCER

COUPLANT

INCIDENT WAVE

REFLECTED WAVE

IMAGINARY LINE

Lesson 4

UT Lecture Guide

-30-

A B


LONGITUDINAL (COMPRESSIONAL) WAVES HAVE PARTICLE VIBRATIONS IN ABACKAND FORTH MOTION IN THE DIRECTION OF WAVE PROPAGATION.

CONSIDER THAT ALL MATERIALS ARE MADE UP OF ATOMS LINED UP INSTRAIGHT LINES TO FORM A LATTICE STRUCTURE. WHEN STRIKING THESIDE OF THE LATTICE, A CHAIN REACTION OF PARTICLE MOVEMENT ISSTARTED CAUSING THE LONGITUDINALWAVE

MEDIUM

(SHEAR WAVES)(SHEAR WAVES)

DIRECTION OF PROPAGATIONDIRECTION OF PROPAGATION

PARTICLE MOTIONPARTICLE MOTION

DIRECTION OF PROPAGATIONDIRECTION OF PROPAGATION

LONGITUDINAL WAVES

MEDIUM

PARTICLE MOTIONPARTICLE MOTION

SHEAR (TRANSVERSE) WAVES HAVE PARTICLE VIBRATIONSPERPENDICULAR TO THE DIRECTION OF WAVE MOTION.

SHEAR WAVES WILLNOTTRAVELTHROUGH LIQUIDS OR GASSES.IN SOME MATERIALS, VELOCITY OF A SHEAR WAVE IS ABOUT ½ THAT OF

LONGITUDINAL WAVES. THEREFORE, THE WAVELENGTH IS SHORTER(ABOUT ½)PERMTTING SMALLER DISCONTINUITIES TO BE LOCATED.

Lesson 4

UT Lecture Guide

-31-


THE ULTRASONIC ANGLE BEAM TRANSDUCER USES THE FOLLOWINGEXAMPLE THE “REFRACTED” SHEAR WAVES ARE USEFUL IN MANYINSPECTION TECHNIQUES.

THE “ANGLE OF REFRACTION” IS THE ANGLE FORMED BETWEEN AREFRACTED BEAM AS IT ENTERS THE SECOND MEDIUM AND A KLINEDRAWN PERPENDICULAR TO THE INTERFACE.

MODE CONVERSION TAKES PLACE WHENASOUND BEAM HITSAN INTEFACEBETWEEN TWO DIFFERENT MEDIAATANANGLE OTHER THAN 90 DEGREES.MODE CONVERSION IN THE CASE PRESENTED BELOW PRODUCES TWOREFLECTED BEAM:ONE BEAM CONSISTS OF LONGITUDINAL WAVES. THE OTHER BEAMCONSISTS OF SHEAR WAVES.

TRANSDUCER

GREASE COUPLANT

STEEL BLOCKINCIDENT BEAM(LONGITUDINAL WAVES)

AIR

REFLECTED BEAM (LONGITUDINAL WAVES) REFLECTED BEAM (SHEAR WAVES)

NORMALINCIDENCE

INCIDENT BEAM(LONGITUDINAL) ANGLE

OF

INCIDENCE

INTERFACE

ANGLE OF REFLECTION (LONGITUDINAL)

REFLECTED BEAM(LONGITUDINAL WAVES)

REFRECTED BEAM (SHEAR WAVES)

ANGLE OF REFRECTION (SHEAR)

PLASTIC

STEEL

Lesson 4

UT Lecture Guide

-32-

SNELL’S LAW CAN BE USED TO DETERMINE ANGULAR RELATIONSHIPSBETWEEN MEDIAFOR BOTH LONGITUDINALAND SHEAR WAVES.

V

V

SIN

SIN 2

1

2

1

=

= ANGLE OF INCIDENCE= VELOCITY IN FIRST MEDIUM= ANGLE OF REFRACTION= VELOCITY IN SECOND MEDIUM

1

V1

V2

2

THE FOLLOWING EXAMPLE CALCULATES THEANGLE OF REFRACTIONALONGITUDINALWAVE PASSING THROUGHAWATER TO-STEELINTERFACE.

10 DEGREES =ANGLE OF INCIDENCE1.49 KM/SEC = LONGITUDINALVELOCITY IN WATER (V )

5.85 KM/SEC = LONGITUDINALVELOCITY IN STEEL(V )

FOR

1

2

2

2

FIRST MEDIUM (WATER)

SECOND MEDIUM (STEEL)

V1

V2

2

1

V1

V2

sin

sin2

1

V2

=

=V1

(sin )sin

sin

sin

2

2

2

2

1

=

=

=

1 . 49

1 . 012

0 . 6791

42 46'o

Lesson 4

UT Lecture Guide



AS THE ANGLE OF INCIDENCE INCREASES, THE ANGLE OF REFRACTIONINCREASES.

WHEN THE REFRACTION ANGLE OF A LONGITUDINAL WAVE REACHES 90DEGREES, THE WAVE EMERGES FROM THE SECOND MEDIUM ANDTRAVELS PARALLELTO THE INTERFACE OR SURFACE.THIS IS CALLED ITS FIRST OR LOWER "CRITICAL ANGLE" ABOVEAPPROXIMATELY 28 DEGREES WITH A PLASTIC-TO-STEEL INTERFACE,ONLY SHEAR WAVESARE GENERATED IN THE PART.

ANGLEOF INCIDENCE

PLASTIC

STEEL

REFRACTEDLONGITUDINALWAVE

REFRACTED SHEARWAVE

IF THE ANGLE OF INCIDENCE IS INCREASED PAST THE FIRST CRITICALANGLE, ONLYASHEAR WAVE IS GENERATED IN THE PART. WHEN THEANGLEOF REFRACTION FOR THE SHEAR WAVE IS 90 DEGREES, THEN WE HAVEREACHED THE UPPER OR SECOND CRITICAL ANGLE WHICH PRODUCESSURFACE WAVES,

AS SHOWN BELOW, THERE IS THEN TOTAL REFLECTION FOR BOTHLONGITUDINALAND SHEAR WAVES.WITH A PLASTIC-TO-STEEL INTERFACE. THIS HAPPENS ATAPPROXIMATELY 58 DEGREES

9 0O

ANGLEOF INCIDENCE

PLASTIC

STEELREFRACTED SHEARWAVE

9 0O

28O

28O

(SURFACE WAVE)

REFLECTED LONGITUDINALWAVE

Lesson 4

UT Lecture Guide

-34-


WHEN THE INCIDENT BEAM IS AT ITS SECOND CRTITICAL ANGLE, A THIRDTYPE OF WAVE IS DEVELOPED, CALLEDARAYLEIGH OR SURFACE WAVE.

AS SHOWN BELOW, THE WAVE TRAVELS WITH AN ELLIPTICAL PARTICELMOTION.SURFACE WAVES ARE USEFUL IN DETECTING SURFACE CRACKS, BUTONLY PENETRATEABOUT ONE WAVELENGTH.

PARTICLEMEDIUM'S SURFACE

PARTICLE MOTION

SURFACE WAVES

DIRECTION OF PROPAGATION

AS SHOWN, SURFACE WAVES HAVE THE ABILITY TO FOLLOW THE SURFACECONTOUR AS LONG AS THE CONTOUR DOES NOT SHARPLY CHANGE.HOWEVER, THE SURFACE WAVE CAN BE ALMOST COMPLETELY ABSORBEDBY EXCESS COUPLANT OR BY TOUCHING YOUR FINGER TO THE SURFACEOF THE PARTAHEAD OF THE TRANSDUCER.

TRANSDUCER

TEST SPECIMEN

DISCONTINUITY

WEDGE

Lesson 4

UT Lecture Guide

-35-


PLATE WAVES OR LAMB WAVES HAVE THE ABILITY TO PROPAGATETHROUGH THIN PLATES IN A VARIETY OF WAVE MODES DEPENDING ONPLATE THICKNESS, TRANSDUCER. FREQUENCYAND INCIDENTANGLE.

PLATE WAVESARE GENERATED BY USING LONGITUDINALWAVES WHICHDEVELOP EITHER SYMMETRICAL ORASYMMETRICAL WAVESAS SHOWNBELOW.PLATE WAVES OCCUPY THE ENTIRE THICKNESS OF THE PART. WITHOUT"SATURATING" THE PART, THE WAVE CANNOT EXIST.

TO GENERATED PLATE WAVES, YOU ADJUST THE INCIDENT ANGLE TO THEPOINT THAT MAXIMUM REFLECTIONS ARE OBSERVED ON THE CRT SCREENFROMAKNOWN REFLECTOR.IT IS NOT POSSIBLE TO GENERATE SHEAR OR SURFACE WAVES ONMATERIALS THINNER THAN ONE-HALF WAVELENGTH. THEREFORE, PLATEWAVEARE USEFULAS SHOWN BELOW.

TRANSDUCER

HOLLOW EXTRUSION

THIN SHEET OR PLATE

PARTICLE MOTION


PARTICLE MOTION

THIN SHEET OR PLATE

SYMMETRICAL

PLATE WAVES

ASYMMETRICAL

Lesson 4

UT Lecture Guide

-36-



A. Using snell’s Law and the attached Sine table, calculate the following refractionproblems, using the information in the sketch below.

Name _______________________________

UT LESSON 4

WORKSHEET #1

1

2

LUCITE

(long. Velocity 2.73 x 10 cm/sec)5

STEEL ( long. Velocity 5.9 x 10 cm/sec)( shear velocity 3.23 x 10 cm/sec)

5

5

________ 1. Find the refracted longitudinal wave if the incident angle Ø is 25 degrees.

(SHOW WORK) (2 pts)

________ 2. Find the refracted shear wave angle if the incidence angle is 45 degrees.

(SHOW WORK) (2 pts)

________ 3. If you wanted a shear wave to travel into the steel at 70 degrees, what would the

incident angle through the lucite be? (SHOW WORK) (2 pts)

________ 4. If Ø = 18º, is it possible to have a refracted longitudinal wave?

If yes, what is it? (SHOW WORK) (2 pts)If no, why not?

________ 5. If Ø = 36°, is it possible to have a refracted longitudinal wave?

If yes. what is it?If no. Why not?

1

1

1

-37-


UT LESSON 4

WORKSHEET #1

Angle Cos Tan Angle Sin Cos Tan

1*

2*

3*

4*

5*

6*

7*

8*

9*

10*

11*

12*

13*

14*

15*

16*

17*

18*

19*

20*

21*

22*

23*

24*

25*

26*

27*

28*

29*

30*

31*

32*

33*

34*

35*

36*

37*

38*

39*

40*

41*

42*

43*

45*

.0175

.0349

.0523

.0698

.0872

.1045

.1219

.1392

.1564

.1736

.1908

.2079

.2250

.2419

.2588

.2756

.2924

.3090

.3256

.3420

.3584

.3746

.3907

.4067

.4226

.4384

.4540

.4695

.4848

.5000

.5150

.5299

.5446

.5592

.5736

.5878

.6018

.6157

.6293

.6428

.8561

.6691

.6820

6947

.7071

.9998

.9994

.9986

.9976

.9962

.9945

.9925

.9903

.9877

.9848

.9816

.9781

.9744

.9703

.9659

.9613

.9563

.9511

.9455

.9397

.9336

.9272

.9205

.9135

.9063

.8988

.8910

.8829

.8746

.8660

.8572

.8480

.8387

.8290

.8192

.8090

.7986

.7880

.7771

.7660

.7547

.7231

.7314

7193

.7071

.0175

.0349

.0524

.0699

.0875

.1051

.1228

.1405

.1584

.1763

.1944

.2126

.2309

.2493

.2679

.2867

.3057

.3249

.3443

.3640

.3839

.4040

.4245

.4452

.4663

.4877

.5095

.5317

.5543

.5774

.6009

.6249

.6494

.6745

.7002

.7265

.7536

.7813

.8098

.8391

.8893

.9004

.9325

.9657

1.0000

46*

47*

48*

49*

50*

51*

52

53

54

55*

56*

57*

58*

59*

60*

61*

62*

63*

64*

65*

66*

67*

68*

69*

70*

71*

72*

73*

74*

75*

76*

77*

78*

79*

80*

81*

82*

83*

84*

85*

86*

87*

88*

89*

90*

*

*

*

.7193

.7314

.7431

.7547

.7660

.7771

.7880

.7986

.8090

.8192

.8290

.8387

.8480

.8572

.8660

.8740

.8829

.8910

.8988

.9063

.9135

.9205

.9272

.9336

.9397

.9455

.9511

.9563

.9613

.9659

.9703

.9744

.9788

.9816

.9848

.9877

.9900

.9925

.9945

.9962

.9976

.9986

.9994

.9898

1.0000

.6947

.6820

.6691

.6561

.6428

.6293

.6157

.6018

.5878

.5736

.5992

.5446

.5299

.5150

.5000

.4848

.4695

.4540

.4384

.4226

.4067

.3907

.3746

.3584

.3420

.3256

.3090

.2924

.2757

.2588

.2419

.2250

.2079

.1908

.1736

.1564

.1392

.1219

.1045

.0872

.0698

.0523

.0349

.0175

.0000

1.0355

1.0724

1.1108

1.1504

1.1918

1.2349

1.2799

1.3270

1.3764

1.4281

1.4826

1.5399

1.6013

1.6643

1.7321

1.8040

1.8807

1.9626

2.0503

2.1445

2.2460

2.3559

2.4751

2.6051

2.7475

2.9042

3.0777

3.2709

3.4874

3.7321

4.0108

4.3315

4.7046

5.1446

5.6713

6.3138

7.1154

8.1443

9.5144

11.4301

14.3007

19.0811

28.6363

57.2900

-38-


________ 1. An “ultrasonic beam” travels trough a medium as waves of sound energy.________ 2. Normal incidence is when the incident beam is parallel to the interface.________ 3. The reflection of an incident beam at an interface is equal to its angle of reflection.________ 4. Particle vibration in a longitudinal wave is in the direction of wave propagation.________ 5. Shear wave velocity is approximately twice the velocity of longitudinal waves.________ 6. Mode conversion occurs when a sound beam strikes an interface between two

media of different velocities at an angle.________ 7. The bending of an incident beam as it passes through an interface is called

refraction.________ 8. Longitudinal waves will propagate through both solids and liquids.________ 9. Both plate waves and surface waves can follow the part contour.

Shear velocity in steel = 3.23 x 10 cm/secLong. Velocity in steel = 5.85 x 10 cm/sec.Long. Velocity in water = 1.49 x 10 cm/secLong. Velocity in lucite = 2.73 x 10 cm/sec

USING THEABOVE INFORMATION, SOLVE THE FOLLOWING PROBLEMS.INDICATE THE APPROXIMATE ANGLES ON THE SKETCH AND LABEL

EACH.

________ 10. If you wanted a shear wave to travel into steel at 60 degrees, what would be the

incident angle on the lucite wedge? (SHOW WORK) (3 pts)

________ 11. What would be the refracted longitudinal wave if the angle of incidence through a

water to steel interface is 12 degrees? (SHOW WORK) (3 pts)

5

5

5

5

Name _______________________________

UT LESSON 4

QUIZ

Sin O1

2V

=

Sin O

1

2

V

60

120

-39-


UT LESSON 4

QUIZ


1*

2*

3*

4*

5*

6*

7*

8*

9*

10*

11*

12*

13*

14*

15*

16*

17*

18*

19*

20*

21*

22*

23*

24*

25*

26*

27*

28*

29*

30*

31*

32*

33*

34*

35*

36*

37*

38*

39*

40*

41*

42*

43*

45*

.0175

.0349

.0523

.0698

.0872

.1045

.1219

.1392

.1564

.1736

.1908

.2079

.2250

.2419

.2588

.2756

.2924

.3090

.3256

.3420

.3584

.3746

.3907

.4067

.4226

.4384

.4540

.4695

.4848

.5000

.5150

.5299

.5446

.5592

.5736

.5878

.6018

.6157

.6293

.6428

.8561

.6691

.6820

6947

.7071

.9998

.9994

.9986

.9976

.9962

.9945

.9925

.9903

.9877

.9848

.9816

.9781

.9744

.9703

.9659

.9613

.9563

.9511

.9455

.9397

.9336

.9272

.9205

.9135

.9063

.8988

.8910

.8829

.8746

.8660

.8572

.8480

.8387

.8290

.8192

.8090

.7986

.7880

.7771

.7660

.7547

.7231

.7314

7193

.7071

.0175

.0349

.0524

.0699

.0875

.1051

.1228

.1405

.1584

.1763

.1944

.2126

.2309

.2493

.2679

.2867

.3057

.3249

.3443

.3640

.3839

.4040

.4245

.4452

.4663

.4877

.5095

.5317

.5543

.5774

.6009

.6249

.6494

.6745

.7002

.7265

.7536

.7813

.8098

.8391

.8893

.9004

.9325

.9657

1.0000

46*

47*

48*

49*

50*

51*

52

53

54

55*

56*

57*

58*

59*

60*

61*

62*

63*

64*

65*

66*

67*

68*

69*

70*

71*

72*

73*

74*

75*

76*

77*

78*

79*

80*

81*

82*

83*

84*

85*

86*

87*

88*

89*

90*

*

*

*

.7193

.7314

.7431

.7547

.7660

.7771

.7880

.7986

.8090

.8192

.8290

.8387

.8480

.8572

.8660

.8740

.8829

.8910

.8988

.9063

.9135

.9205

.9272

.9336

.9397

.9455

.9511

.9563

.9613

.9659

.9703

.9744

.9788

.9816

.9848

.9877

.9900

.9925

.9945

.9962

.9976

.9986

.9994

.9898

1.0000

.6947

.6820

.6691

.6561

.6428

.6293

.6157

.6018

.5878

.5736

.5992

.5446

.5299

.5150

.5000

.4848

.4695

.4540

.4384

.4226

.4067

.3907

.3746

.3584

.3420

.3256

.3090

.2924

.2757

.2588

.2419

.2250

.2079

.1908

.1736

.1564

.1392

.1219

.1045

.0872

.0698

.0523

.0349

.0175

.0000

1.0355

1.0724

1.1108

1.1504

1.1918

1.2349

1.2799

1.3270

1.3764

1.4281

1.4826

1.5399

1.6013

1.6643

1.7321

1.8040

1.8807

1.9626

2.0503

2.1445

2.2460

2.3559

2.4751

2.6051

2.7475

2.9042

3.0777

3.2709

3.4874

3.7321

4.0108

4.3315

4.7046

5.1446

5.6713

6.3138

7.1154

8.1443

9.5144

11.4301

14.3007

19.0811

28.6363

57.2900

-40-


COUPLANTSAND ULTRASONIC SOUND ENERGY

THE PRIMARY PURPOSE OFACOUPLANT IS TO PROVIDEASUITABLE SOUNDPATH BETWEEN THE TRANSDUCERAND THE TEST SURFACE.

A COUPLANT MUST EFFECTIVELY WET OR TOTALLY CONTACT BOTHSURFACES OF THE TRANSDUCERAND TEST PART.

1. THE COUPLANT MUST EXCLUDE ALL AIR FROM BETWEEN THESURFACESASAIR ISAVERY POOR CONDUCTOR OF SOUND.

2. THE COUPLANT FILLS IN AND SMOOTHS OUT IRREGULARITIES ONTHE SURFACE OF THE TEST PART.

3. THE COUPLANT AIDS IN THE MOVEMENT OF THE TRANSDUCEROVER THE SURFACE IN CONTACTTESTING.

4. A PRACTICAL COUPLANT MUST BE AESY TO APPLY AND EASY TOREMOVE IT MUSTALSO BE HARMLESS TO THE PART SURFACE.

OIL OR WATER MIXED WITH GLYCERINE (2 PARTS WATER AND 1 PARTGLYCERINE) ARE COMMONLY USED COUPLANTS. EVEN WALLPAPER PASTEHASADVANTAGESASACOUPLANT.

HEAVER COUPLANTS, SUCH S GREASE OR HEAVY OIL CAN BE USED ONROUGH OR VERTICALSURFACES.SPECIALLY FORMULATED LIQUID AND PASTE COUPLANTS ARE ALSOAVAILABLE FROM ULTRASONIC EQUIPMENT MANUFACTURERS.

IN CIRCUMSTANCES WHERE THE USE OF LIQUIDS OR PASTE ISUNDESIRABLE, THIN RUBBER OR RUBBER-LIKE MATERIALS MAY BE USED.

IN ALL CASES THE COUPLANT SHOULD BE AS THIN AS POSSIBLE IF THECOUPLANT IS EXCESSIVE, IT MAY ACT AS A WEDGE AND ALTER THEDIRECTION OF THE SOUND BEAM.

TRANSDUCER

COUPLANT

TEST MATERIAL

Lesson 5

-41-


THE SURFACE OF A TEST SPECIMEN CAN GREATLY AFFECT ULTRASONICWAVE PROPAGATION.ROUGH SURFACE CAN CAUSE UNDESIRABLE EFFECTS SUCH ASREDUCTION OF DISCONTINUITY AND BACK SURFACE AMPLITUDES DUE TODISTORTION OF WAVE DIRECTIVITY.

COUPLANT

UNEVEN BUT CONSISTANT

SURFACEFLAT SMOOTH SURFACE ROUGH AND IRREGULAR

SURFACE

COUPLANT

FAIR TEST POOR

FRONT SURFACE

(INITIAL PULSE)

WIDE

FRONT SURFACE

BACK SURFACE

DISCONTINUITY REDUCED

AMPLITUDE

MARKERS

FLAT SMOOTH SURFACE - GOOD RESPONSE

CRT INDICATIONS

A-SCAN PRESENTATION

(PULSE-ECHO)

ROUGH AND IRREGULAR SURFACE-POOR RESPONSE

Lesson 5

UT Lecture Guide

-42-


A GOOD BACK SURFACE REFLECTION INDICATES A GOOD RESPONSE FROMTHE MATERIAL BEING TESTED. IT IS REFLECTED BACK TO ITS SOURCESSIMILAR TO LIGHT STRIKINGAMIRROR.

IF THE SURFACESARE NOT PARALLEL, THE REFLECTED ENERGY WILL BEDIRECTEDAWAY FROM THE TRANSDUCER SIMILAR TO LIGHT FALLING ONAMIRRORATANANGLE.

FRONT SURFACE

(INITIAL PULSE)

TRANSDUCER

FRONT SURFACE

SPECIMEN

CROSS-SECTION

REFLECTION

BACK SURFACE CRT INDICATIONS

REDUCEDBACK SURFACE

INDICATION

THE PHYSICAL SHAPE OR CONTOUR OF A PART MUST BE CONSIDEREDWHENATTEMPTING TO DISCERN WHETHERADISCONTINUITY INDICATION ISREALOR FALSE.

EXAMPLES OF SOUND PATHS LEADING TO SPURIOUS INDICATIONS

IN TESTING LONG SPECIMENS, REFLECTION F A SPREADING BEAM CANPRODUCE FALSE INDICATIONS ON THE CRTAS SHOWN BELOW

A SHEAR WAVE MAY BE GENERATED WHICH IS REFLECTED AT A STEEPANGLE TO THE OPPOSITE SIDE, WHERE MODE CONVERSION TAKESPLACE. MODE CONVERSION WILL BE DISCUSSED IN A LATER LESSON.HOWEVER, THIS TYPE OF FALSE SIGNAL WILL APPEAR ON THE RIGHTSIDE OF THE FIRST BACK ECHO.

LONGITUDINAL WAVE

TRANSDUCER

SHEAR WAVE

SPECIMEN

DIAMETER

FIRST BACKLONGITUDINAL WAVE

Lesson 5

UT Lecture Guide

-43-


GRAIN STRUCTURE HAS A GREAT INFLUENCE ON THE ACOUSTICALPROPERTIES OFAMATERIAL

A STEEL FORGING GENERALLY HAS A FINE GRAIN STRUCTURE AND HASALOW DAMPING EFFECT ON THE SOUND BEM.HOWEVER, A CASTING GENERALLY HAS A COARSER GRAIN STRUCTUREWHICH IS MOE DIFFICULTTO GET SOUND THROUGH.

FRONT SURFACEDISCONTINUITY

FINE GRAIN

BACK SURFACE

REFLECTION

COARSE GRAIN

BACK SURFCEREFLECTIONLOST OR REDUCED

FRONT SURFACE

WHENADISCONTINUITY IS NOT NORMAL (AT 90 DEGREES) TO THE INCIDENTWAVE THE REFLECTED WAVE WILLBEATANANGLE.

AS SHOWN BELOW, THE RESULT IS A REDUCTION IN THE AMPLITUDE OFTHE DISCONTINUITY INDICATION DISPLAYED ON THE CRT.

POSITION C

POSITION B

POSITION A

CRACK

CYLINDRICAL SPECIMEN

POSITION A POSITION B POSITION C

AT POSITION “A”ABOVE, THERE ISASHARP DISCONTINUITY INDICATIONANDLITTLE BACK SURFACE INDICATION. AT POSITION “C” THE DISCONTINUITY SAT MINIMUM, OR MAY NOT BE SEENATALL.

Lesson 5

UT Lecture Guide

-44-

TWO BASIC TECHNIQUES ARE USED IN LOCATING AND EVALUATING ANGULARFLAWS.

1. CONTACTTESTING UTILIZESAN “ANGLE BEAM” TRANSDUCER WITHA PLASTIC WEDGE TO CHANGES THE DIRECTION OF WAVEPROPAGATION.

2. IMMERSION TESTING USES WATER AS A COUPLANT, TILTING THETRANSDUCER TOACHIEVE THE NECESSARY DIRECTIONALITY.

THE SHAPE OR SURFACE CONDITION OF A DISCONTINUITY INFLUENCES THEINDICATION ON THE CRT.A DISCONTINUITY HAVING A ROUGH SURFACE WILL TEND TO SCATTER THEREFLECTIONAS COMPARED TOASMOOTH FLAW.NONMETALLIC INCLUSIONS ARE TYPICAL ROUGH AND WOULD SCATTER THESOUND MORE THANACRACK-LIKE DISCONTINUITY.

Lesson 5

UT Lecture Guide

ANGLE BEAMTRANSDUCER

PLASTIC WEDGE

SPECIMEN

CONTACT TESTING

SPECIMEN

PROBE TRANSDUCER

IMMERSION TESTING

WATERTANK



AIR IS A POOR MEDIUM FOR TRANSFERRING ULTRASONIC VIBRATIONSINTO LIQUIDS OR SOLIDS. THEREFORE, A COUPLANT MUST BE USED TOTRANSFER ENERGY FROM HE TRANSDUCER TO THE TEST MATERIAL.

WATER ISACOMMONLY USED COPLANTAS SHOWN BELOW:

WATER

TRANSDUCERPRINCIPAL DIRECTIONOF SOUND BEAM

SECODARY LOBER

SECODARY LOBER

MOST OF THE ULTRASONIC ENERGY IS CONCENTRATED ALONG THECENTERLINE OF THE BEAM.THE SECONDARY OR SIDE LOBES FROM AT THE TRANSDUCER FACE ANDRADIATEAWAY FROM THE PRINCIPLE DIRECTION OF SOUND TRAVEL.

THESE SECONDARY LOBES REPRESENT AREAS OF HIGH AND LOWINTENSITIESATTHE EDGE OF THE BEAM.BECAUSE OF THE SECONDARY LOBES, THE USEFUL WIDTH OF ATRANSDUCER BEAM IS-LESS THAN THE TRANSDUCER’S PHYSICALWIDTH.

TRANSDUCER DIAMETER HASADEFINITE INFLUENCE ON THE SOUND BEAMTRANSMITTED THROUGHAMEDIUM.FOR A GIVEN FREQUENCY, A SMALLER TRANSDUCER HAS A GREATER BEAMSPREAD ANGLE THAN A LARGER DIAMETER TRANSDUCER AS SHOWNBELOW:

SMALL DIAMETER

TRANSDUCERMEDIUM

BEAM DIVERGES

LARGE DIAMETERTRANSDUCER

MEDIUM

BEAM CONSTANT

Lesson 5

UT Lecture Guide

-46-


CHANGING THE TRANSDUCER’S VIBRATING FREQUENCY WILL ALSOCHANGE THE BEAM SPREAD.

DIVERGENCE IS INVERSELY PROPORTIONALTO FREQUENCY.THEREFORE, A HIGH FREQUENCY TRANSDUCER HAS A MORECONSTANT DIAMETER SOUND BEAM THAN A LOW FREQUENCYTRANSDUCER.FREQUENCY OR BY USINGALARGER DIAMETER TRANSDUCER.

THE AMOUNT OF BEAM SPREAD IS DETERMINED BY THE FOLLOWINGEQUATION:

HALF

POWER

POINT (. 707 OF INTENSITY)

= WAVELENGTH

= DIAMETER

= HALF-ANGLE OF

= BEAM SPREAD TO

= HALF-POWER POINT

DSIN O = 1.22

WHERE

D

O

THE BEAM SPREAD OF A ½ INCHDIAMETER, 1 Mhz TRANSDUCER ISSHOWN TO BE 34 DEGREES.REMEMBER THAT WAVELENGTH ( ) ISDETERMINED BY DIVIDING THEVELOCITY BY THE FREQUENCY.TO CHANGE INCHES TO CENTIMETERS.MULTIPLY BY 2.54.

0 = 34O

0O

SECONDARY

LOBES

Lesson 5

UT Lecture Guide

-47-


Name _______________________________

UT LESSON 5

WORKSHEET #1

Understanding “Beam Spread” will help point out importance of selecting the properfrequency and size transducer. The length of the ultrasonic wave and the diameter of thetransducer are often critical in the determination of flaw size and location.Using the information given below, determine the “Beam Spread” for the conditions listed.

(a) Velocity in steel = .585 x 10º cm/sec(b) Velocity in aluminum = .625 x 10º cm/sec(c) One inch = 2.54 centimeters

(D) Wavelength ( ) =

(E) Sin O = 1.22

y Velocity

Frequency

D

y

________ 1. What would be the beam spread using a 1” diameter, 2.25 MHz transducer on an

aluminum test part? (SHOW WORK) (3 pts)

________ 2. What would be the beam spread using a 1” diameter, one MHZ transducer on an

aluminum test part? (SHOW WORK) (3 pts)

________ 3. What would be the beam spread using a one half inch diameter, 2.25 MHz

transducer on a steel test part? (SHOW WORK) (3 pts)

-48-


UT LESSON 5

WORKSHEET #1


1*

2*

3*

4*

5*

6*

7*

8*

9*

10*

11*

12*

13*

14*

15*

16*

17*

18*

19*

20*

21*

22*

23*

24*

25*

26*

27*

28*

29*

30*

31*

32*

33*

34*

35*

36*

37*

38*

39*

40*

41*

42*

43*

45*

.0175

.0349

.0523

.0698

.0872

.1045

.1219

.1392

.1564

.1736

.1908

.2079

.2250

.2419

.2588

.2756

.2924

.3090

.3256

.3420

.3584

.3746

.3907

.4067

.4226

.4384

.4540

.4695

.4848

.5000

.5150

.5299

.5446

.5592

.5736

.5878

.6018

.6157

.6293

.6428

.8561

.6691

.6820

6947

.7071

.9998

.9994

.9986

.9976

.9962

.9945

.9925

.9903

.9877

.9848

.9816

.9781

.9744

.9703

.9659

.9613

.9563

.9511

.9455

.9397

.9336

.9272

.9205

.9135

.9063

.8988

.8910

.8829

.8746

.8660

.8572

.8480

.8387

.8290

.8192

.8090

.7986

.7880

.7771

.7660

.7547

.7231

.7314

7193

.7071

.0175

.0349

.0524

.0699

.0875

.1051

.1228

.1405

.1584

.1763

.1944

.2126

.2309

.2493

.2679

.2867

.3057

.3249

.3443

.3640

.3839

.4040

.4245

.4452

.4663

.4877

.5095

.5317

.5543

.5774

.6009

.6249

.6494

.6745

.7002

.7265

.7536

.7813

.8098

.8391

.8893

.9004

.9325

.9657

1.0000

46*

47*

48*

49*

50*

51*

52

53

54

55*

56*

57*

58*

59*

60*

61*

62*

63*

64*

65*

66*

67*

68*

69*

70*

71*

72*

73*

74*

75*

76*

77*

78*

79*

80*

81*

82*

83*

84*

85*

86*

87*

88*

89*

90*

*

*

*

.7193

.7314

.7431

.7547

.7660

.7771

.7880

.7986

.8090

.8192

.8290

.8387

.8480

.8572

.8660

.8740

.8829

.8910

.8988

.9063

.9135

.9205

.9272

.9336

.9397

.9455

.9511

.9563

.9613

.9659

.9703

.9744

.9788

.9816

.9848

.9877

.9900

.9925

.9945

.9962

.9976

.9986

.9994

.9898

1.0000

.6947

.6820

.6691

.6561

.6428

.6293

.6157

.6018

.5878

.5736

.5992

.5446

.5299

.5150

.5000

.4848

.4695

.4540

.4384

.4226

.4067

.3907

.3746

.3584

.3420

.3256

.3090

.2924

.2757

.2588

.2419

.2250

.2079

.1908

.1736

.1564

.1392

.1219

.1045

.0872

.0698

.0523

.0349

.0175

.0000

1.0355

1.0724

1.1108

1.1504

1.1918

1.2349

1.2799

1.3270

1.3764

1.4281

1.4826

1.5399

1.6013

1.6643

1.7321

1.8040

1.8807

1.9626

2.0503

2.1445

2.2460

2.3559

2.4751

2.6051

2.7475

2.9042

3.0777

3.2709

3.4874

3.7321

4.0108

4.3315

4.7046

5.1446

5.6713

6.3138

7.1154

8.1443

9.5144

11.4301

14.3007

19.0811

28.6363

57.2900

-49-


________ 1. Higher frequency transducer have less beam spread than low frequency

transducers.________ 2. Lower frequency transducers are usually used to find the smaller defects.________ 3. The longer the wavelength ( ). The greater the beam spread and better ability to

locate small discontinuities.________ 4. When comparing two transducer of the same frequency, the larger transducer

will have the greatest beam spread.________ 5. A rough surface on the test specimen may cause a loss in amplitude on the CRT

screen.________ 6. If the front and back surface of a test part are not parallel, there will be a greatly

reduced signal amplitude from any discontinuity in the part.________ 7. Long or thin specimens may cause false indications due to mode conversion of

the longitudinal beam.________ 8. A smooth discontinuity (crack) will reflect more energy than a discontinuity will a

rough surface (inclusion)________ 9. Both contact and immersion testing techniques can be used for performing an

“angle beam” examination of a part.________ 10. The couplant used in ultrasonic inspection should be as thick as possible to

properly direct the sound beam.________ 11. Where a liquid or paste couplant cannot be used, a rubber sheet may sometimes

be used by placing it between the transducer and test part.________ 12. What would be the “Beam Spread” if the following conditions existed?

A. 1” Diameter, 5 MHz transducer.B. Velocity in steel = .585 x 10 cm/sec

C. Sin O = 1.22

D. Wavelength ( ) =

E. One inch

Name _______________________________

UT LESSON 5

QUIZ

y

y

D

YVelocity

frequency

-50-


UT LESSON 5

QUIZ

Angl Tan Angl Cos Tan

1*

2*

3*

4*

5*

6*

7*

8*

9*

10*

11*

12*

13*

14*

15*

16*

17*

18*

19*

20*

21*

22*

23*

24*

25*

26*

27*

28*

29*

30*

31*

32*

33*

34*

35*

36*

37*

38*

39*

40*

41*

42*

43*

45*

.0175

.0349

.0523

.0698

.0872

.1045

.1219

.1392

.1564

.1736

.1908

.2079

.2250

.2419

.2588

.2756

.2924

.3090

.3256

.3420

.3584

.3746

.3907

.4067

.4226

.4384

.4540

.4695

.4848

.5000

.5150

.5299

.5446

.5592

.5736

.5878

.6018

.6157

.6293

.6428

.8561

.6691

.6820

6947

.7071

.9998

.9994

.9986

.9976

.9962

.9945

.9925

.9903

.9877

.9848

.9816

.9781

.9744

.9703

.9659

.9613

.9563

.9511

.9455

.9397

.9336

.9272

.9205

.9135

.9063

.8988

.8910

.8829

.8746

.8660

.8572

.8480

.8387

.8290

.8192

.8090

.7986

.7880

.7771

.7660

.7547

.7231

.7314

7193

.7071

.0175

.0349

.0524

.0699

.0875

.1051

.1228

.1405

.1584

.1763

.1944

.2126

.2309

.2493

.2679

.2867

.3057

.3249

.3443

.3640

.3839

.4040

.4245

.4452

.4663

.4877

.5095

.5317

.5543

.5774

.6009

.6249

.6494

.6745

.7002

.7265

.7536

.7813

.8098

.8391

.8893

.9004

.9325

.9657

1.0000

46*

47*

48*

49*

50*

51*

52

53

54

55*

56*

57*

58*

59*

60*

61*

62*

63*

64*

65*

66*

67*

68*

69*

70*

71*

72*

73*

74*

75*

76*

77*

78*

79*

80*

81*

82*

83*

84*

85*

86*

87*

88*

89*

90*

*

*

*

.7193

.7314

.7431

.7547

.7660

.7771

.7880

.7986

.8090

.8192

.8290

.8387

.8480

.8572

.8660

.8740

.8829

.8910

.8988

.9063

.9135

.9205

.9272

.9336

.9397

.9455

.9511

.9563

.9613

.9659

.9703

.9744

.9788

.9816

.9848

.9877

.9900

.9925

.9945

.9962

.9976

.9986

.9994

.9898

1.0000

.6947

.6820

.6691

.6561

.6428

.6293

.6157

.6018

.5878

.5736

.5992

.5446

.5299

.5150

.5000

.4848

.4695

.4540

.4384

.4226

.4067

.3907

.3746

.3584

.3420

.3256

.3090

.2924

.2757

.2588

.2419

.2250

.2079

.1908

.1736

.1564

.1392

.1219

.1045

.0872

.0698

.0523

.0349

.0175

.0000

1.0355

1.0724

1.1108

1.1504

1.1918

1.2349

1.2799

1.3270

1.3764

1.4281

1.4826

1.5399

1.6013

1.6643

1.7321

1.8040

1.8807

1.9626

2.0503

2.1445

2.2460

2.3559

2.4751

2.6051

2.7475

2.9042

3.0777

3.2709

3.4874

3.7321

4.0108

4.3315

4.7046

5.1446

5.6713

6.3138

7.1154

8.1443

9.5144

11.4301

14.3007

19.0811

28.6363

57.2900

-51-


ATTENUATION,ACOUSTIC IMPEDANCE,AND RESONANCEAS SHOWN BELOW, A BEAM OF SOUND ENERGY WILL SPREADS OUT(DIVERGE) AS IT MOVES THROUGH THE SPECIMEN, AND THE INTENSITY(ENERGY) DECREASES WITH DISTANCEAWAY FROM THE TRANSDUCERANDAWAY FROM THE CENTER OF THE BEAM.

FORAGIVEN SIZE TRANSDUCERHIGH FREQUENCY TRANSDUCERS PRODUCE NARROWER SOUND BEAMSTHAN LOW FREQUENCYTRANSDUCERS.FOR THE PURPOSE OF ILLUSTRATION, ULTRASONIC SOUND CAN BEVIEWED AS A NARROW CONE-SHAPED BEAM WHICH IS DIVIDED INTO TWOZONES.THE INTENSITY IN THE NEAR ZONE VARIES IRREGULARLY DUE TO SOUNDWAVE INTERACTION CLOSE TO THE TRANSDUCER. THIS PREVENTSRELIABLE DETECTION OF DISCONTINUITIES CLOSE TO THE SURFACE.IN THE FAR ZONE, THE INTENSITY (ENERGY) DECREASES STEADILY DUE TOBOTHATTENUATIONAND BEAM SPREAD

THE INTENSITY AT POINT “Y” ABOVE IS LESS THAN AT POINT “X”.ATTENUATION IS THE TERM USED TO DESCRIBE THIS CONDITION OFENERGY LOSS. ATTENUATION MEANS THE PROCESS OF LESSENING THEAMOUNT.THE PRIMARY REASONS FOR ATTENUATION ARE ABSORPTION ANDSCATTERING OF THE ULTRASONIC ENERGY.

TRANSDUCER(TRANSMITTER)

NEARZONE

FAR ZONE

SPECIMEN (MATERIAL)

TRANSDUCER

(RECEIVER)YX

Lesson 6

-52-

TRANSDUCER

NEAR ZONESPECIMENT

4O

12O


ATTENUATION IS DIFFERENT IN DIFFERENT MATERIALS, DEPENDING ONTHE ABSORPTION AND SCATTERING OF THE SOUND ENERGY, ANOTHERPHENOMENON WHICH PERTAINS TO THE INTERRELATIONSHIP OF THESOUNDAND MATERIAL PROPERTIES (S “ACOUSTIC IMPEDANCE.” THIS TERMSHOULD NOT BE CONFUSED WITH “ATTENUATION.”“ACOUSTICAL IMPEDANCE” (Z) IS DEFINED AS THE PRODUCT OF THEDENSITY ( )AND SOUND VELOCITY (V) WITHINAGIVEN MATERIALIMPEDANCE = DENSITY X VELOCITY, OR Z = VIMPEDANCE VALUES FOR TYPICALMATERIALSARE SHOWN BELOW:

MATERIAL

IMPEDANCE

(GRAM/CM - SEC)2

VELOCITY

(CM/SEC)

DENSITY

(GRAM/CM )3

AIR

WATER

ALUMINUM

STEEL

0.000033 X 106

0.149 X 106

1.72 X 106

4.56 X 106

0.33 X 105

1. 49 X 105

6.35 X 105

5.85 X 105

0.001

1.00

2.71

7.8

ATTENUATION IS DEFINED AS THE LOSS OF ENERGY (ACOUSTIC) PER UNITOF DISTANCE. FOR ULTRASONIC WAVE PROPAGATION, THE ATTENUATIONCONSTANT IS GIVEN BY:

I2

I1

= e-2

WHERE =ATTENUATION CONSTANT

I2

I1

= RATIO OF INTENSITIESATTWO POINTS A UNIT DISTANCEAPART

I > I1 2

Lesson 6

UT Lecture Guide

-53-


IF ACOUSTIC ENERGY IS TRANSMITTED INTO TWO PICES OF PERFECTLYBONDED INDENTICAL STEEL, WE FIND THE SOUND HAS THE SAMEVELOCITYTHROUGH BOTH, WITHAN IMPEDANCE RATIO OF 1 TO 1.

TRANSDUCER

STEEL

SOUND BEAM

VELOCITY REMAINS CONSTANT

STEEL

AN IMPEDANCE RATIO OFANYTHING LESS OR GREATER THAN 1 TO 1 IS LESSTHAN IDEAL.AS SHOWN BELOW A LARGE PORTION OF THE SOUND BEAM FROM A WATERTO STEEK INTERFACE WILL REFLECT BACK TOWARDS THE TRANSDUCERAND NEVER ENTER THE PART.

TRANSDUCER

SOUND BEAM

STEEL

WATER

TO DETERMINE HOW MUCH OF THE ENERGY IS REFLECTED YOU CAN USETHE FOLLOWING FORMULA:

REFLECTION FACTOR (R) =

Z =ACOUSTICALIMPEDANCE

IN THE ILLUSTRATION ABOVE , HOW MUCH OF THE SOUND ENERGY ISREFLECTED FROM THE WATER TO STEELINTERFAACE?

Z1 2

Z2

Z2

Z1

-

+

4. 56 - .149

4. 56 + .149

2

R =

24.411

4.709= = 88 PERCENT REFLECTED

Lesson 6

UT Lecture Guide

-54-


RESONANCE CAN BE DEFINED AS THE CHARACTERISTIC OF A VIBRATINGBODYTO RESONATE OR VIBRATE IN SYMPATHY WITHAVIBRATION SOURCE.

AS SHOWN BELOW, A RESONANT CONDITION WILL EXIST ANY TIME ACONTINOUS LONGITUDINAL WAVE IS INTRODUCED INTO A SPECIMEN ANDREFLECTED "IN PHASE" WITH THE INCOMING WAVE.

COUPLANT

TRANSDUCERSTANDING WAVE

RESONANCE WILL OCUR ONLY WHEN THE THICKNESS OF A SPECIMEN ISEQUAL TO A HALF-WAVELENGTH OR AN EXACT MULTIPLE OF A HALF-WAVELENGTH. SHOWN BELOW IS A "FUNDAMENTAL FREQUENCY" ANDMULTIPLES CALLED "HARMONICS"

TRANSDUCER

TEST SPECIMEN REFLECTED WAVE

INCIDENT WAVE

THICKNESS = 1/2 WAVELENGTH

THICKNESS = 1 WAVELENGTH

THICKNESS = 1-1/2 WAVELENGTH

1

(FUNDAMENTAL FREQUENCY)MHz

2

(2ND HARMONIC)MHz

3

(3RD HARMONIC)MHz

Lesson 6

UT Lecture Guide

-55-


ULTRASONIC UNITS USING THE PRINCIPLE OF RESONANCE WERECOMMONLY USED FOR THICKNESS MEASUREMENT AND BOND ORLAMINATION INSPECTION.

HOWEVER, PULSE-ECHO UNITS HAVE BEEN REFINED TO PERFORM MOSTOF THESE FUNCTIONSAND RESONANT INSTRUMENTSARE RARELY USED.

RESONANCE OCCURS WHEN THE MATERIAL THICKNESS IS EQUAL TO AHALF-WAVENGTH OR EXACT MULTIPLES.

THE WAVELENGTH CAN BE CHANGED BY VARYING THE FREQUENCY

THE FUNDAMENTAL RESONANT FREQUENCY IS THE FREQUENCY AT WHICHASPECIMEN WILLRESONATE.

HARMONICS ARE EXACT MULTIPLES OF THE FUNDAMENTAL (MINIMUM)RESONANT FREQUENCY.

THE FUNDAMENTALRESONANT FREQUENCY CAN BE FOUND BY:

F =V

2T F = FUNDAMENTAL RESONANT FREQUENCYV = VELOCITY OF LONGITUDINAL WAVET = THICKNESS OF MATERIAL

"A" "B"MATERIAL TRANSDUCER

STANDING WAVE

DISCONTINUITY

AS SHOWWN ABOVE IN "A" THE FREQUENCY HAS BEEN ADJUSTED UNTIL ASTANDING WAVE "RESONANCE" HAS BEEN ESTABLISHED.

IF THE TRANSDUCER IS MOVED TO POSITION "B" THE MATERIAL WILL STOPRESONATING UNTIL THE FREQUENCY (WAVELENGTH) IS ADJUSTED TOAGAIN ESTABLISH RESONANCEAS SHOWN.

Lesson 6

UT Lecture Guide

-56-


Name _______________________________

UT LESSON 6

WORKSHEET #1

A. Using the information given below, solve the problems relating to “reflection factors”.B. The chart below lists the common impedance values.

(IMPEDANCE = VELOCITY X DENSITY)

MATERIALDENSITY(GRAM / CM )

3

IMPEDANCE(GRAM/CM - SEC)

2

VELOCITY(CM / SEC)

0.000033 X 106AIR

WATER

ALUMINUM

STEEL

1.72 X 106

0.149 X 106

4.56 X 106

0.33 X 105

1.49 X 105

6.35 X 105

5.85 X 105

0.001

1.00

2.71

7.8

C. Reflection factor =Z1

2-

+

Z Z

Z

1

2

2

Z. = Acoustic Impedance

Water

Aluminum

1Z

Z2

________ 1. What percentage of the original sound energy will be reflected back to the probe

at the water to aluminum interface? (SHOW WORK) (3 pts)

________ 2. What percentage of the original sound energy will finally enter the water on its

way back to the transducer from the back surface of the aluminum part? (SHOW

WORK) (3 pts).Only consider the reflection factors, do not consider the normal attenuation that

would occur in the material it self.

-57-


________ 3. A clad material is to be tested for bond defects. One material has a thickness of

0.3 inches and an acoustic impedance of 5.0 x 10 gram/cm - second and the

other material is 4.0 inches thick and has an acoustic impedance of 4.

________ 4. Would you inspect the bonded material through the thick side or through the thin

side? Why? (2 pts)

________ 5. On the CRT screen below, using a 5 inch screen range, sketch the approximate

location and amplitude of the pips from an acceptable bond condition. (2 pts)

• As a general rule, “R” should be less than 20% for adequate bond inspection.

2 2

5 x 10

gram/cm - second.If the bond is perfect and acceptable, what percentage of sound would you

expect to be reflected from the interface? (SHOW WORK) (3 pts)

2

2

Name _______________________________

UT LESSON 6

WORKSHEET #1 (continued)

-2-10-1-2

-2-10-1-2

0 1 2 3 4 5

0 1 2 3 4 5 6 7 8 9 10

-58-


________ 1. The gradual loss of energy as a sound beam travels through a material is called

attenuation.________ 2. Whenever possible, the UT inspection should be done in the “near zone” before

the sound can spread out and attenuated.________ 3. “Acoustic Impedance” refers to resistance of sound propagation through a part.________ 4. Compared to steel, air has a very high acoustic impedance value.________ 5. The original ultrasonic velocity remains the same regardless of the media it is

passing through.________ 6. A sound beam with a given energy will travel farther in aluminum than in steel

before it is attenuated by the same amount.________ 7. A fine grained material will usually caused less attenuation than a coarse grained

material.________ 8. The terms “Intensity” and Impendence” mean the same thing.________ 9. In immersion testing, it is typical that less than 1% of the original sound energy is

returned to the transducer.________ 10. Using the information given below, what would be the reflection Factor at the

interface shown between the water (Z ) and steel (Z )? (SHOW WORK) (3 pts)1 2

Name _______________________________

UT LESSON 6

QUIZ

Reflection Facto (R) =Z - Z1 2

Z + Z1 2

2

=

Z = Acoustic Impedence

STEEL Z2TRANSDUCER WATERZ 1

CRACK BEAM

MATERIALDENSITY(GRAM / CM )

3

IMPEDANCE(GRAM/CM - SEC)

2

VELOCITY(CM / SEC)

0.000033 X 106AIR

WATER

ALUMINUM

STEEL

1.72 X 106

0.149 X 106

4.56 X 106

0.33 X 105

1.49 X 105

6.35 X 105

5.85 X 105

0.001

1.00

2.71

7.8

-59-


DISPLAYING ULTRASONIC INDICATIONS

THERE ARE THERE BASIC TYPES OF VISUAL DISPLAYS WHICH ARE

COMMONLY USED TO EVALUATE THE SOUNDNESS OR QUALITY OF A

MATERIALBEING TESTED;A-SCAN, B-SCANAND C-SCAN.

A-SCAN IS A "TIME VERSUS AMPLITUDE" DISPLAY WHICH REVEALS A

DISCONTINUITY USINGA"PIP" ONACATHODE-RAYTUBE (CRT).

AMPLITUDE

INITIALPULSE

BACK SURFACEREFLECTION

DISCONTINUITY

HORIZONTAL SWEEP

TIME

THEA-SCAN PRESENTATION,AS HAS BEEN DISCUSSED, IS READ FROM LEFT

TO RIGHT. THE HEIHT OF A PIP CAN BE COMPARED TO THE HEIHT OF A PIP

FROM A KNOWN REFERENCE REFLECTOR TO GIVE AN INDICATION OF

RELATIVE DISCONTINUITY SIZE.

AMPLITUDE

TRANSDUCER

DISCONTINUITY

MATERIAL

INITIAL PULSE DISCONTINUITYINDICATION

BACK SURFACEREFLECTION

A-SCAN PRESENTATION

HORIZONTAL SWEEP

Lesson 7

-60-


B-SCAN PRESENTATION, AS SHOWN BELOW, TYPICALLY USES AN

OSCILLOSCOPE SCREEN TO DISPLAY A CROSS-SECTIONAL VIEW OF THE

MATERIALBEING TESTED.

THE IMAGE IS RETAINED ON THE CRT LONG ENOUGH TO EVALUATE THE

SAMPLE AND TO PHOTOGRAPH THE SCREEN FOR A A PERMANENT

RECORD.

C-SCAN ISA"PLAN VIEW" PRESENTATION SIMILAR TOAN X-RAY PICTURE.

AS SHOWN BELOW, THE C-SCAN SHOWNS THE SHAPE AND LOCATION OF

THE DISCONTINUITY, BUT DOES NOT SHOW THE DEPTH.

DISCONTINUITIES

B-SCAN PRESENTATION

THICKNESS OF

TEST MATERIAL

FRONT SURFACE

BACK SURFACE

DISCONTINUITIES

C-SCAN PRESENTATION

Lesson 7

UT Lecture Guide

-61-


HIGH SPEED ULTRASONIC SCANNING GENERALLY UTILIZES THE C-SCAN

PRESENTATION.

AS SHOWN BELOW, SOME RECORDERS USE A CHEMICALLY TREATED

PAPER. THE PAPER MOVEMENT IS SYNCHRONIZED WITH THE MOVEMENT

OF THE TRANSDUCERACROSS THE TEST SURFACE.

THE ADNANTAGE OF THE C-SCAN IS ITS SPEED AND ABILITY TO PRODUCE A

PERMANENT RECORD. HOWEVER, THE SCAN SHOWS ONLY LENGTH AND

WIDTH, BUT NOT DEPTH.

PRINT BAR

SCAN LINES

DISCONTINUITY

RECORDING PAPER FEED

HELIX DRUM

MOTION OFTRANSDUCER

DISCONTINUITY

Lesson 7

UT Lecture Guide

-62-


A TYPICAL BRIDGE/MANIPULATOR IS SHOWN FOR A BASIC ULTRASONIC

IMMERSION TEST.

WHEN A C-SCAN IS TO BE MADE, ELECTRIC MOTORS ARE UTILIZED TO

ACTIVATE THE TRAVELING MECHANISMS AND THE UP AND DOWN

MOVEMENT OF THE SEARCH TUBE.

A TYPICAL A-SCAN PRESENTATION IS SHOWN BELOW USING CONTACT

TESTING WITHANANGLE BEAM TRANSDUCER

THE PROCEDURE USED TO CALIBRATE THE UT UNIT IS SIMILAR TO NORMAL

BEAM TESTING AND REQUIRES A CALIBRATION BLOCK WITH A KNOWN SIZE

REFLECTION SURFACEATAKNOWN METALTRAVEL

TANK WITH MOTORIZED BRIDGE

CARRIACE ORBRIDGE

TEST SPECIMEN

SCANNER TURBE

MANIPULATOR

TRANSDUCER

SUPPORT FOR TEST SPECIMEN

CRT

DISCONTINIUTY

SHEARWAVES

ANGLE BEAM TRANSDUCER

A

B

Lesson 7

UT Lecture Guide

-63-

A B


ACALIBRATION BLOCK (IIW TEST BLOCK FURTHER DISCUSSED IN LESSON 8)

IS SHOWN BELOW WITH A KNOW DISTANCE OF A INCHES TO THE CURVED

SURFACE.

USING THE SWEEP AND DELAY CONTROLS, THE PIPS ARE ADJUSTED TO

SHOWN MULTIPLES OF 4 INCHES ON THE CRT.

IF THE MINATURE ANGLE BEAM CALIBRATION BLOCK SHOWN BELOW WERE

USED TO CALIBRATE THE ABOVE CRT SCREEN, WHERE WOULD THE PIPS

APPEAR?

DEPENDING ON THE DIRECTION OF THE ANGLE BEAM PROBE, THE PIPS

WOULD EITHER APPEAR AT ONE, FOUR, AND SEVEN INCHES OR TWO, FIVE,

AND EIGHT INCHES.

1” 2”

MINIATURE ANGLE BEAM

0 2 4 6 8 10

NOTCH4 “

Lesson 7

UT Lecture Guide

-64-


THE ANGLE BEAM TECHNIQUE IS OFTEN USED FOR WELD INSPECTION AS

SHOWN BELOW.

2nd 4th

3rd1st

LEGLEG

LEG LEG

1 st skip distance(”V” PATH)

2 nd skip distance(”V” PATH)

TYPICALLY, THE WELD SHOULD BE INSPECTED IN THE 1 ST OR 2 ND LEG

WHENEVER POSSIBLEAS SHOWN BELOW.

SKIPDISTANCE

VIEW A VIEW B VIEW C

TO ASSIST IN EVALUATING THE RESULTS OF ANGLE BEAM INSPECTION, A

DIRECT READING ULTRASONIC CALCULATOR IS COMMONLY USED.

THE HORIZONTAL SCALEACROSS THE TOP OF THE CARD REPRESENTS THE

NUMBER OF INCHES BETWEEN THE TRANSDUCERAND THE CENTER OF THE

WELD.THE VERTICAL SCALE REPRESENTS SPECIMEN THICKNESS AND THE ARC

SHOWN THEANGLE OF THE SOUND BEAM.

40

50

60

70

80

1

2 3 4 5 6 7 8 9 101

2

1

2

0

Lesson 7

UT Lecture Guide

-65-


THE FOLLOWING IS AN EXAMPLE OF A TYPICAL ANGLE BEAM INSPECTION

USING THE ULTRASONIC CALCULATOR.ADOUBLE VEE WELD WITHAN OPENING OF 30 DEGREES INA2” STEELPLATE

USINGA60 DEGREE SHEAR WAVE IN THE SPECIMEN.

DISCONTINUITY

DASHED LINEPOINT OF INCIDENCE B

A

1 2 3 4 5 6 7 8 9 100

1

2

3 4

5

6

7

2

11

2

4050

60

70

80

THE FOLLOWING PROCEDURE SHOULD BE USED IN SETTING UP THE

CALCULATOR:1. DRAW A LINE REPRESENTING THE SOUND PATH FROM THE UPPER

LEFT CORNER THROUGH THE 60 DEGREE MARK ON THE ARC,

EXTENDING TO THE 2 - POINT REPRESENTING THE PLATE

THICKNESS. CALIBRATE THE HORIZONTAL SWEEP OF THE CRT TO

REPRESENT BEAM TRAVEL DISTANCE IN THE MATERIAL BEING

TESTED.2. TO SHOW THE FULL SKIP DISTANCE OF THE SOUND BEAM, YOU

THEN DOUBLE THE 3 7/16” AND MARK THAT POINT AT

APPROXIMATELY 6 7/8” (POINT “B”ABOVE)3. NEXT, DRAW THE 30 DEGREE FEE WELD ON THE PLASTIC SLIDE OR

TRANSPARENT PAPER THAT SLIDES BACK AND FORTH OVER THE

CALCULATOR.4. AS SHOWN ABOVE, A DISCONTINUITY IS DISPLAYED ON THE CRT

SCREEN AT 5.5”.THE OPERATOR THEN MEASURES THE DISTANCE

BETWEEN THE CENTER OF THE TRANSDUCER (EXIT POINT) AND

THE CENTER OF THE WELDMENT (4 5/8”) AND SLIDES THE

TRANSPARENT PAPER TO THE SAME DISTANCE.5. THE POSITION OF THE DISCONTINUITY IS INDICATED AND CAN BE

EVALUATED.

Lesson 7

UT Lecture Guide

-66-


Name _______________________________

LESSON 7

WORKSHEET #1

Angle beam inspection requires that the operator understand how the sound beam is

reflected within the specimen. On the CRT screen provided, indicate the location of each

pip based on the sound path distances shown. (3 pts each)

3”

3”

2”

8”

2”

8”

-2-10-1-2

-2-10-1-2

0 1 2 3 4 5

15 INCH SCREEN RANGEA

0 1 2 3 4 5 6 7 8 9 10

-2-10-1-2

-2-10-1-2

0 1 2 3 4 520 INCH SCREEN RANGEB

0 1 2 3 4 5 6 7 8 9 10

-2-10-1-2

-2-10-1-2

0 1 2 3 4 512 INCH SCREEN RANGEC

0 1 2 3 4 5 6 7 8 9 10

-67-


________ 1. On a typical B-Scan, the horizontal sweep represents time and the vertical

deflection represents amplitude.________ 2. The B-Scan can display how deep the discontinuity is below surface of the

specimen.________ 3. The typical A-Scan is the display commonly used for recording a permanent

record with the immersion inspection technique.________ 4. The vertical pip on an A-Scan can be used to compare the relative size of a

discontinuity.________ 5. The C-Scan display will indicate length and width of a discontinuity, but it cannot

show death.________ 6. To obtain an A-Scan display with ultrasonic immersion testing, it is necessary to

auto mate the bridge/manipulator with electric motors.________ 7. The “Ultrasonic Calculator” can be used in weld inspection to indicate the

location of a discontinuity in the weldment.________ 8. Whenever possible, the weld should be inspected in the “2nd Skip Distance.”________ 9. The calibration of a UT instrument for sound path distance can be performed

using the curved surface of the “IIW Block”________ 10. To accurately utilize the “Ultrasonic Calculator” it is necessary to accurately

measure the distance from center line of the weld to the exist point of the

transducer.________ 11. Using an E-Screen range on the CRT below, indicate where the “pips” should

appear if the instrument is to be properly calibrated for sound path distance in the

block shown (SHOW WORK) (3 pts).

Name _______________________________

UT LESSON 7

QUIZ

MINIATURE ANGLE BEAM-2-10-1-2

-2-10-1-2

0 1 2 3 4 5

0 1 2 3 4 5 6 7 8 9 10

-68-

1”2”


ULTRASONIC TRANSDUCERSAND STANDARD REFERENCE BLOCKS THE

ULTRASONIC TRANSDUCER IS THE HEART OF THE UTTEST SYSTEM.

THE CRYSTAL MATERIAL IN AN ULTRASONIC TRANSDUCER IS MADE OF

PIEZOELECTRIC MATERIAL SUCH AS QUARTZ, LITHIUM SULFATE AND

POLARIZED CERAMICS.1. QUARTZ WAS THE FIRST MATERIAL USED.

CHARACTERISTICS. HOWEVER, QUARTZ IS A POOR

GENERATOR OF ACOUSTIC ENERGY AND HAS GENERALLY BEEN

REPLACED BY MORE EFFICIENT MATERIALS.2. LITHIUM SULFATE IS A VERY EFFICIENT RECEIVER OF ACOUSTIC

ENERGY, BUT IS FRAGILE, SOLUBLE IN WATER AND LIMITED TO USE

ATTEMPERATURES BELOW 165 F.3. POLARIZED CERAMICS PRODUCE THE MOST EFFICIENT

GENERATORS OF ACOUSTICS ENERGY BUT THEY DO HAVE A

TENDENCY TO WEAR. COMMON POLARIZED CERAMICS INCLUDE

B A R I U M T I TA N AT E , L E A D M E TA N I O B AT E , A N D L E A D

ZIRCONATE/TITANATE.THE CAPABILITY OFATRANSDUCER IS DESCRIBED BYTHREE TERMS:

1. SENSITIVITY. THEABILITYTO DETECT SMALLDISCONTINUITIES.2. RESOLUTION. THE ABILITY TO SEPARATE THE SOUND REFLECTIONS

FROM TWO DISCONTINUITIES CLOSE TOGETHER IN DEPTH OR TIME.3. EFFICIENCY. ENERGY CONVERSION EFFECTIVENESS.

IT HAS VERY STABLE

FREQUENCY

O

SEALED CASE

SIGNALCONNECTOR

BACKING

ELECTRODES

GROUNDCONNECTOR

CRYSTAL

Lesson 8

-69-


SENSITIVITY OF A TRANSDUCER IS RATED BY ITS ABILITY TO DETECT A

CERTAIN SIZE FLAT-BOTTOM HOLE, AT A SPECIFIED DEPTH, IN A STANDARD

REFERENCE BLOCK.

THE SMALLER THE DETECTABLE HOLE, THE GREATER THE SENSITIVITY.

TRANSDUCER SENSITIVITY IS MEASURED BY THE AMPLITUDE OF ITS

RESPONSE FROM AN ARTIFICIAL DISCONTINUITY IN A STANDARD

REFERENCE BLOCK

THE REFERENCE BLOCK IS NECESSARY, BECAUSE EVEN TRANSDUCERS

OF THE SAME SIZE, FREQUENCY AND MATERIAL DO NOT ALWAYS PRODUCE

THE SAME AMPLITUDE SIGNAL FROM A GIVEN REFLECTOR.

TRANSDUCER

REFERENCE

BLOCK

FLAT BOTTOMED HOLE

RESOLUTION IS THE ABILITY TO SEPARATE (DISTINGUISH BETWEEN) THE

SOUND REFLECTIONS FROM A DISCONTINUITY CLOSE TO A BOUNDARY OR

TWO DISCONTINUITIES CLOSE TOGETHER IN DEPTH OR TIME.

INITIALPULSE

BACK SURFACE

REFLECTION

DISCONTINUITY

TIME

POOR RESOLUTION

INITIALPULSE

BACK SURFACE

REFLECTION

DISCONTINUITY

TIME

GOOD RESOLUTION

Lesson 8

UT Lecture Guide

-70-


TRANSDUCER MATERIALARE USUALLY CUT IN TWO WAYS:

1. CRYSTALS CUT PERPENDICULAR TO THE X-AXIS PRODUCE

LONGITUDINALWAVES.2. CRYSTALS CUT PERPENDICULAR TO THE Y-AXIS PRODUCE SHEAR

WAVES.

AS SHOWN BELOW, MOST CRYSTALS USED FOR UT ARE CUT

PERPENDICULAR TO THE X-AXIS.

CRYSTAL DEFORMATIONAXIS X-AXIS

Y-AXIS

Z-AXIS

SIZE ISACONTRIBUTING FACTOR IN PERFORMANCE OFATRANSDUCER.1. THE LARGER DIAMETER THE TRANSDUCER, THE LESS THE SOUND

BEAM WILLSPREAD FORAGIVEN FREQUENCY.2. HOWEVER, THE SMALL, HIGH FREQUENCY TRANSDUCER ARE

BETTERABLE TO DETECT VERY SMALLDISCONTINUITIES.3. THE LARGER THE TRANSDUCER, THE MORE SOUND ENERGY IT

TRANSMITS INTO THE TEST PART. LARGE LOW FREQUENCY

TRANSDUCERSARE OFTEN USED TO GET MORE PENETRATION.4. LARGE SINGLE CRYSTAL TRANSDUCERS ARE GENERALLY LIMITED

TO THE LOWER FREQUENCIES. HIGH FREQUENCY CRYSTALS ARE

SUSCEPTIBLE TO DAMAGE BECAUSE THEYARE VERYTHIN.

Lesson 8

UT Lecture Guide

-71-


THE FREQUENCY OF A TRANSDUCER IS AN IMPORTANT FACTOR IN ITS

APPLICATION.

1. THE HIGHER THE FREQUENCY OF A TRANSDUCER, THE LESS THE

SOUND BEAM WILL SPREAD AND THE GREATER THE SENSITIVITY

AND RESOLUTION.WHEN THE SOUND BEAM IS SPREAD AS SHOWN BELOW, LESS

SOUND IS LIKELY TO BE REFLECTED FROM A SMALL

DISCONTINUITY

DISCONTINUITY

HIGH FREQUENCY TRANSDUCER

FIG. 1A

LOW FREQUENCY TRANSDUCER

FIG. 1B

2. THE LOWER THE FREQUENCY, THE DEEPER THE SOUND

PENETRATION AND THE LESS SCATTER. THE GREATER BEAM

SPREAD AIDS IN DETECTING REFLECTORS WHICH ARE NOT

PERPENDICULAR TO THEAXIS OF THE SOUND BEAM.3. CRYSTALS THICKNESS IS ALSO RELATED TO TRANSDUCER

FREQUENCY. THE HIGHER THE FREQUENCY OF THE

TRANSDUCER, THE THINNER THE CRYSTALWILLBE.MOST ULTRASONIC TESTING IS DONE BETWEEN 0.2 MHz AND 25

Mhz AND CRYSTALS CUT FOR USEABOVE 10 MHzARE TO THINAND

FRAGILE FOR CONTACTTESTING.THEREFORE, TRANSDUCERS WITH OPERATING FREQUENCIES

ABOVE 10 MHzARE USED PRIMARILY FOR IMMERSION TESTING.

Lesson 8

UT Lecture Guide

-72-


TRANSDUCERS FOR CONTACT TESTING AND IMMERSION TESTING ARE

ESSENTIALLYTHE SAME BUT USUALLYARE NOT INTERCHANGEABLE.

MOST CONTACT TESTING TRANSDUCERS HAVE WEAR PLATES IN FRONT OF

THE PIEZOELECTRIC ELEMENTTO PROTECT IT. THE EXCEPTION TO THIS ISA

QUARTZ TRANSDUCER.

AS SHOWN BELOW, CONTACT TRANSDUCERS CAN BE EITHER “STRAIGHT

BEAM” OR “ANGLE BEAM.”

TRANSDUCER A TRANSDUCER BLUCITE

CERAMIC

STRAIGHT BEAM TRANSDUCERS USUALLY HAVE A LUCITE, CERAMIC, OR

QUARTZ WEAR PLATE IN FRONT OF THE CRYSTAL.

ANGLE BEAM TRANSDUCERS HAVE THE WEAR PLATE WEDGE-SHAPED TO

PRODUCE THE DESIRED REFRACTEDANGLE.

AS SHOWN ABOVE, THE LUCITE WEDGE PROTECTS THE FACE OF THE

CRYSTAL AND DETERMINES THE ANGLE OF INCIDENCE OF THE SOUND

BEAM ON THE TEST PART.

AS HAS BEEN DISCUSSED, WHEN SOUND WAVES ARE DIRECTED INTO THE

TEST PART AT AN ANGLE, THEY ARE DIVIDED INTO LONGITUDINAL AND

SHEAR WAVES BY REFRACTION.MOSTANGLE BEAM TESTING IS DONE WITH SHEAR WAVES.

STRAIGHT BEAM TRANSDUCER ANGLE BEAM TRANSDUCER

LONGITUDINALWAVES

SHEARWAVES

DISCONTINUITY

Lesson 8

UT Lecture Guide

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THE ANGLE BEAM PROBE CAN ALSO BE USED TO GENERATE SURFACE

WAVES.

AS WE HAVE DISCUSSED, SURFACE WAVES ARE GENERATED WHEN THE

INCIDENT ANGLE OF THE SOUND BEAM REACHES THE SECOND OR UPPER

CRITICALANGLE.

MOST ANGLE BEAM CONTACT TRANSDUCERS ARE IDENTIFIED. BY THE

REFRACTED SHEAR WAVE PRODUCED (70 , 60 , ETC.), IN A SPECIFIC

MATERIAL, USUALLY STEELANDALUMINUM.

SPHERICALLY GROUND AND CYLINDRICALLY GROUND ACOUSTICAL

LENSES ARE COMMONLY ADDED TO IMMERSION TYPE TRANSDUCERS.

THEYARE USED TO:

1. IMPROVE SENSITIVITYAND RESOLUTION.2. COMPENSATE FOR TEST PART CONTOURS.3. EXAMINEAGIVEN DEPTH OF THE TEST PART MORE CAREFULLY.

AS SHOWN BELOW, CYLINDRICALLY GROUND LENSES FOCUS THE SOUND

ENERGY TO A LINE. SPHERICALLY GROUND LENSES FOCUS THE SOUND

ENERGYTOAPOINT.

O O

WATER

BEAM

METAL

TRANSDUCER

ACOUSTICALLENS

Lesson 8

UT Lecture Guide

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CYLINDRICALLENSESARE USED IN TWO WAYS:

1. TO INCREASE THE SENSITIVITYAND RESOLUTION OF EQUIPMENT.2. FOR CONTOUR CORRECTION AS SHOWN BELOW. THE LENS CAN BE

GROUND SPECIALLY TO DIRECT THE SOUND ENERGY NORMAL

(PERPENDICULAR) TOACURVED SURFACEATALLPOINTS.

SPHERICAL LENSES CONCENTRATE THE SOUND ENERGY INTO A CONE

SHAPED BEAM.

1. THE FOCUSING INCREASES ITS INTENSITY, BUT SHORTENS ITS

USEFULRANGE.2. WHILE THE CYLINDERICAL LENS ABOVE HAS A GREATER WIDTH, THE

SPHERICALLENS HAS THE GREATEST SENSITIVITY.3. THE SPHERICAL LENS IS OFTEN USED WHEN IMMERSION TESTING

PARTS HAVINGAROUGH SURFACE.

FOCUSED TRANSDUCERSARE DESCRIBED BYTHEIR FOCALLENGTH.

THE SHORT FOCAL LENGTHS ARE FOR EXAMINING AREAS OF THE

SPECIMEN CLOSE TO THE SURFACE. LONGER FOCAL LENGTHS ARE FOR

INCREASINGLY DEEPER AREAS.

CONTOURCORRECTIONLENS

TUBING

VIEW B

CRT SCREEN DISPLAY

TUBING

VIEW A

FLAT SHOE

Lesson 8

UT Lecture Guide

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TRANSDUCERS COME IN MANY SHAPES, SIZES AND PHYSICAL

CHARACTERISTICS.

SOME COMMON TYPES INCLUDE PAINT-BRUSH, DUAL ELEMENT, SINGLE

ELEMENT,ANGLE BEAM, FOCUSED, MOSAIC, CONTACT,AND IMMERSION.

SINGLE ELEMENT TRANSDUCERS MAY BE TRANSMITTERS ONLY,

RECEIVERS ONLY, OR BUTTRANSMITTERAND RECEIVER.

DOUBLE ELEMENT TRANSDUCERS (AS SHOWN BELOW) MAY BE EITHER

SINGLE TRANSDUCERS MOUNTED SIDE BY SIDE OR STAKED.

IN A DOUBLE ELEMENT TRANSDUCER, ONE IS A TRANSMITTER AND THE

OTHERARECEIVER.

SIDE BY SIDE

TRANSMITTER RECEIVER

SOUND BARRIER

STACKED

TRANSMITTERRECEIVER

SOUND BARRIER

DOUBLE ELEMENT TRANSDUCERS HAVE BETTER NEAR SURFACE

RESOLUTION BECAUSE THE RECEIVER CAN RECEIVER DISCONTINUITY

SIGNALS BEFORE THE TRANSMITTER COMPLETES ITS TRANSMISSION.

DISCONTINUITY OBSCUREDBY INITIAL PULSE

SWEEP

MARKER

TRANSDUCER

DISCONTINUITY

TESTSPECIMEN

COAXIAL CABLE

Lesson 8

UT Lecture Guide

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STANDARD REFERENCE BLOCKS

IN ULTRASONIC TESTING, DISCONTINUITIES ARE USUALLY COMPARED TO A

REFERENCE STANDARD.

THE STANDARD MY BE ONE OF MANY REFERENCE BLOCKS OR SETS OF

BLOCKS SPECIFIED FORAGIVEN TEST.

REFERENCE BLOCKS COME IN MANY DIFFERENT SHAPES AND SIZES AND

THIS LESSON WILL DISCUSS ONLY A FEW OF THOSE COMMONLY USED. A

TYPICALBLOCKS IS SHOWN BELOW

MOST REFERENCE BLOCKS HAVE THE FOLLOWING IN COMMON:1. THEYARE MADE FROM CAREFULLY SELECTED MATERIAL2. THE MATERIAL MUST HAVE THE PROPERATTENUATION, GRAIN SIZE,

HEATTREATMENTAND BE FREE OF DISCONTINUITIES.3.ALLDIMENSIONS MUST BE PRECISELY MACHINED.4. ALL HOLES MUST BE FLAT-BOTTOMED AND HAVE A SPECIFIED

DIAMETER TO BEAN IDEALREFLECTOR.5. SIDE DRILLED HOLE DIAMETER MUST BE CAREFULLY CONTROLLED.

THREE COMMONLY USED SETS OF STANDARD REFERENCE BLOCKSARE:1.AREAMPLITUDE BLOCKS2. DISTANCEAMPLITUDE BLOCKS3.ASTM BASIC SET OFAREAND DISTANCEAMPLITUDE BLOCKS.

AREAAMPLITUDE BLOCKS PROVIDE STANDARDS FOR DISCONTINUITIES OF

DIFFERENT SIZES,ATTHE SAME DEPTH.

DISTANCE AMPLITUDE BLOCKS PROVIDE STANDARDS FOR

DISCONTINUITIES OF THE SAME SIZEAT DIFFERENT DEPTHS.

A = DIAMETER OF FBHB = METAL DISTANCE

FROM TESTSURFACE TO FBH

C = METAL DISTANCEFROM TESTSURFACE TOBOTTOM OF BLOCK

FLAT-BOTTOM HOLE

TEST SURFACE

B

C

A

Lesson 8

UT Lecture Guide

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THE ASTM BASIC SET OF AREA/DISTANCE AMPLITUDE BLOCKS CONSISTS

OF TEN, TWO INCH DIAMETER BLOCKSAS SHOWN BELOW:

TEST

SURFACE

TARGET

FLAT-BOTTOMHOLE (FB) DIA(SEE TABLE)

METAL DISTANCE(SEE TABLE) 3/4 INCH

METAL DISTANCE, INCHES

FBH DIA IN 64 THS INCH

1/8 1/4 3/4 1-1/2 3 3 3 6 6

5 5 5 5 5 3 5 8 5 8

1 / 2

ANOTHER TYPE OF CALIBRATION BLOCK IS THE IIW BLOCK

(INTERNATIONALINSTITUTE OF WELDING). IT PROVIDES THE FOLLOWING:

VERIFICATION OF DISTANCE KNOWN DISTANCES & ANGULAR

RELATIONSHIPS, VERIFIES TRANSDUCERANGLEAND BEAM EXIT POINTAND

CHECKS TRANSDUCER RESOLUTION.

8” 0.125”

0.25”

3.64”

0.06” HOLE

2” DIAMETER HOLE4”

40” 50” 60”

75”70”60”

FOCAL POINT

12”

4”

PLASTIC INSERT

1”

Lesson 8

UT Lecture Guide

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IN CONTACT ANGLE BEAM TESTING, THE BEAM EXIT POINT OF THE

TRANSDUCER MUST BE KNOWN TO ACCURATELY DETERMINE THE

LOCATION OF THE DISCONTINUITY.

AS SHOWN BELOW, THE TRANSDUCER IS MOVED BACK AND FORTH UNTIL

THE PIP ON THE CRT REACHES MAXIMUMAMPLITUDE.

THE FOCAL POINT ON THE IIW BLOCK THEN CORRESPONDS WITH THE BEAM

EXIT POINT OF THE TRANSDUCER.

40”50”60”

75” 70” 60”

ANGLE BEAMTRANSDUCER

BEAM EXIT POINT

FOCAL POINT

SPECIALCALIBRATION STANDARDSSPECIAL STANDARDS ARE OFTEN USED FOR ITEMS SUCH AS WELDMENT,

CASTINGS, AND PIPING. THE STANDARDS ARE NORMALLY OF THE SAME

MATERIAL AND PRODUCT FROM TO BE TESTED. REFERENCE REFLECTORS

SUCHAS NOTCHES OR HOLESAREARTIFICIALLYADDED TO THE STANDARD.

Lesson 8

UT Lecture Guide

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VERIFICATION OF THE TRANSDUCER ANGLE IS ACCOMPLISHED AS SHOWN

BELOW:

THE PLASTIC WEDGE OF THE ANGLE BEAM TRANSDUCER IS SUBJECT TO

WEAR IN NORMAL USE. THIS WEAR CAN CHANGE THE BEAM EXIT POINTAND

THEANGLE OF THE SOUND BEAM.

40” 50” 60”

75”70”60”

60 DEGREE TRANSDUCER

BEAM EXIT POINT

2” DIAMETER HOLE

FROM THE POSITION SHOWN ABOVE, THE TRANSDUCER IS MOVED BACK

AND FORTH UNTIL THE REFLECTION FROM THE 2 INCH HOLE SHOWS

MAXIMUMAMPLITUDE ON THE CRT.

THE ANGLE OF SOUND BEAM CAN THEN BE READ FROM WHERE THE EXIT

POINT ON THE TRANSDUCER MATCHES THE DEGREES STAMPED ON THE

SIDE OF THE BLOCK.

THE TRANSDUCER SOUND BEAM EXIT POINT SHOULDALWAYS BE CHECKED

FIRST. IF THE EXIT POINT MARKING IS NOT CORRECT, THEN THE ANGLE

CHEXK WILLNOT BEACCURATE.

Lesson 8

UT Lecture Guide

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THE FAR FIELD RESOLVING POWER OF THE TEST EQUIPMENT CAN BE

ESTIMATED BY PLACING A NORMAL BEAM TRANSDUCER ON THE IIW BLOCK

AS SHOWN.

GOOD RESOLUTION WILL BE INDICATED IF THE INSTRUMENT CAN

SATISFACTORILY SEPARATE THE PIPS FROMALLTHREE REFLECTORS

TRANSDUCER

IIW BLOCKCOOD BAD

CRT DISPLAY

THE MINIATUREANGLE BEAM BLOCK CANALSO BE USED TO CALIBRATE THE

INSTRUMENT FORANGLE BEAM INSPECTION.

THE MINIATURE BLOCK IS INTENDED FOR FIELD WORK AND IS NOT AS

COMPREHENSIVEAS THE LARGER IIW BLOCK.

FOCAL POINT

MINIATURE ANGLE BEAM BLOCK

70o

45o

60o

1”

3”

2”

0. 750”

1.75”

0.060” HOLE

0. 750”

Lesson 8

UT Lecture Guide

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________ 1. The term “resolution” refers to the ability of a transducer to detect a very small

discontinuity.________ 2. Quartz is the only transducer material commonly used that is not a piezoelectric

material.________ 3. If the frequency of a transducer is raised then the beam spread is reduced.________ 4. The polarized ceramic transducer is considered to be a very good generator of

ultrasonic energy.________ 5. Quartz is a type of polarized ceramic transducer material.________ 6. A transducer that can defect a discontinuity close to the surface is saint to have a

good resolving power.________ 7. Larger transducer usually have a higher frequency because they are more

fragile.________ 8. The higher the frequency of a transducer, the smaller the sound cone (i.a. Less

beam spread).________ 9. Immersion testing is always done with transducer that have a frequency between

2.5 and 5.0 MHz.________ 10. Angle beam testing is usually done with longitudinal waves.________ 11. Angle beam probes may be used to generate surface waves.________ 12. A spherical focusing lens will usually have the ability to provide better sensitivity

as compared to a cylinderical lens.________ 13. Focused transducers are often used for shear wave inspection of welded plate

due to the increased penetration.________ 14. A double or dual element transducer can only be used in the longitudinal wave

mode.________ 15. With a double element transducer, the sensitivity is increased because both

elements are receiving and sending sound energy.________ 16. Acoustical tenses increases transducer sensitivity and resolution, but decreases

their useful range.________ 17. Areference block should be made from the same basic material as the part being

tested.________ 18. Blocks which provide a size reference and are used to check the systems

linearity are known as area amplitude blocks.________ 19. The exist point of an angle beam transducer should always be determined before

the angle of the transducer is checked.________ 20. Both the iiw block and miniature block will check the test system resolution.

Name _______________________________

UT LESSON 8

QUIZ

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