PRESENTED BY:

ALDINO ARYYOGA

4105 100 047

SUPERVISOR:

WING HENDROPRASETYO, ST, Me.

Surabaya, January 13th 2010

BACKGROUND

SHIP BUILDING PROCESS ALWAYS NEED WELDING PROCESS

WELD PRODUCT MUST BE INSPECTED

ULTRASONIC TEST IS A KIND OF INSPECTION METHOD IN

NDT

DISTANCE OF DISCONTINUITY FROM THE SURFACE AFFECTS

ACCURACY

PROBLEM FORMULATION

HOW TO KNOW THE INFLUENCE OF THE DISCONTINUITY SIZE

AND DISTANCE ON MATERIAL BASED ON THE DAC CURVE?

WHAT IS THE SIZE OF THE DEVIATION RESULTING FROM THE

USE DAC CURVE?

PURPOSE

TO KNOW THE SIZE OF THE DEVIATION FROM MATERIAL

DISCONTINUITY BASED ON DAC CURVE

BENEFITS

TO KNOW THE SIZE OF THE DEVIATION FROM MATERIAL

DISCONTINUITY BASED ON DAC CURVE SO WE CAN

CALCULATE THE ACTUAL SIZE OF THE DISCONTINUITY

HYPOTHESES

THE FARTHER THE LOCATION OF THE DISCONTINUITY FROM

THE SURFACE, THE SMALLER THE SOUND ENERGY WILL BE

RECEIVED

AMPLITUDE SOUND WAWES SHOULD BE DECREASED A HALF,

IF THE SIZE OF DISCONTINUITY IS A HALF SMALLER AT THE

SAME DISTANCE FROM THE SURFACE.

PROBLEM LIMITATIONS

EXAMINATION PERFORMED ON P-NO.1 CARBON STEEL

EXAMINATION IS USED NORMAL PROBE AND 45O ANGLE

PROBE

ARTIFICIAL DISCONTINUITY IN 2.5 mm AND 5.0 mm

DIAMETER MADE ON SPECIMEN WITH 75 mm THICKNESS

ARTIFICIAL DISCONTINUITY IN 3.0 mm AND 6.0 mm

DIAMETER MADE ON SPECIMEN WITH 38 mm THICKNESS

ARTIFICIAL HOLES ARE LOCATED AT ¼ T, ½ T AND ¾ T FROM

THE SURFACE OF EACH SPECIMEN

SOUND WAVE ENERGY WILL SPREAD DURING TRAVELLING

ON A CERTAIN MEDIA SO THE SOUND INTENSITY AT THE FAR

AWAY FROM THE SOURCE WILL BE DECREASE.

SOUND WAVE IN A CERTAIN MEDIA CAN BE DESCRIBED IN

CONE SHAPE AND DEVIDED INTO 2 (TWO) ZONES, NEAR

(DEAD) FIELD AND FAR FIELD

NEAR (DEAD) FIELD AND FAR FIELD

WHEN THE DISTANCE BETWEEN THE TRANSDUCER AND A

REFLECTOR INCREASES, THE AMOUNT OF ENERGY

REACHING AND RETURNING FROM THE REFLECTOR TO THE

TRANSDUCER

THIS PRINCIPLE IS MADE APPARENT BY OBSERVING THE

AMPLITUDE OF THE REFLECTED SIGNAL FROM A GIVEN SIZE

REFLECTOR PLACED AT DIFFERENT DISTANCES FROM THE

TRANSDUCER.

DAC CURVE

DAC BLOCK STANDARD

• TO MAKE THE DAC CURVE IS NEEDED A DAC BLOCK

AS IMAGINE BELOW

• DATA ON 100% DAC OF 2.5 mm DIAMETER:

Tebal Posisi Gain SP SOD Depth Amplitudo

Diameter

Diskontinuitas

75 ¼ T 63 26 18.38 18.38 80 %

2.575 ½ T 63 52 36.76 36.76 50 %

75 ¾ T 63 79.5 56.25 56.25 35 %

• DATA ON 50% DAC OF 2.5 mm DIAMETER:

Tebal Posisi Gain SP SOD Depth Amplitudo

Diameter

Diskontinuitas

75 ¼ T 57 26 18.38 18.38 40 %

2.575 ½ T 57 52 36.76 36.76 25 %

75 ¾ T 57 79.5 56.25 56.25 18 %

• DATA ON 20% DAC OF 2.5 mm DIAMETER:

Tebal Posisi Gain SP SOD Depth Amplitudo

Diameter

Diskontinuitas

75 ¼ T 49 26 18.38 18.38 15 %

2.575 ½ T 49 52 36.76 36.76 10 %

75 ¾ T 49 79.5 56.25 56.25 5 %

• DEVIATION IS THE STANDARD ERROR OF THE

PREDICTED Y-VALUE FOR EACH X IN THE REGRESSION

• THE STANDARD ERROR IS A MEASURE OF THE AMOUNT

OF ERROR IN THE PREDICTION OF Y FOR AN

INDIVIDUAL X.

• THE DEVIATION CAN BE CALCULATED BY USING

EQUATION BELOW

BASED ON THE EQUATION ABOVE, DEVIATIONS CAN

BE DETERMINED BETWEEN :

100% DAC (2.5 mm) AND 50% DAC (5.0 mm) IS 4.6%

100% DAC (3.0 mm) AND 50% DAC (6.0 mm) IS 5.8%

THE STATEMENT ABOVE SHOW THAT TO DETERMINE

THE ACTUAL SIZE OF INTERNAL DISCONTINUITIES

NEED TO BE ADDED WITH THE VALUE:

± 4.6% FOR MATERIAL WITH 75 mm OF THICKNESS

± 5.8% FOR MATERIAL WITH 38 mm OF THICKNESS

• THE ACCURACY OF TEST RESULTS WITH THE DAC

METHOD IS STRONGLY INFLUENCED BY THE DEPTH

OF INTERNAL DISCONTINUITIES FROM THE

SURFACE. THIS IS CAUSED BY ATTENUATION OF THE

SOUND WAVE ENERGY THAT RETURNED BY THE

REFLECTOR

• THE ACCURACY OF TEST RESULTS WITH THE DAC

METHOD IS ALSO INFLUENCED BY THE

CONSTITUENT GRAINS OF MATERIAL TESTED AS IT

RELATES TO THE AMOUNT OF SCATTERING OF

SOUND WAVES INTO THE MATERIAL

• ADD VARIATION OF SIZE AND THE DEPTH OF

INTERNAL DISCONTINUITIES FROM THE SURFACE IN

ORDER TO THE RESULTS OBTAINED WOULD BE

MORE ACCURATE

• ADDING VARIETY OF DIFFERENT TYPES OF

MATERIAL DENSITY TO BE KNOWN HOW MUCH

INFLUENCE THE MATERIAL DENSITY OF THE

SCATTERING SOUND WAVE ENERGY

• THE PROCEDURE TO GET DATA TO MAKE A DAC

CURVE : CALIBRATE RANGE THE EQUIPMENT FOR 100

PLACE THE PROBE ON THE SURFACE OF THE SPECIMEN

MOVE THE PROBE TO OBTAIN MAXIMUM INDICATION OF THE FIRST HOLE AND SET THE GAIN CONTROL TO GET THE AMPLITUDE OF 80% FSH. AT THE TIME OF MAXIMUM AMPLITUDE RECORDED SOUNDPATH POSITION (SP0), SURFACE OF DISTANCE (SOD0), AND THE DEPTH OF THE HOLE (D0).

DECREASE THE GAIN 6 dB TO OBTAIN THE AMPLITUDE OF 50% FSH AND 14 dB TO OTAIN THE AMPLITUDE OF 20% FSH

DRAW EACH POINT AMPLITUDE INTO THE TRANSPARENT

CONNECT THESE POINT WITH A LINE UP TO FORM A CURVE.