PRESENTED BY: ALDINO ARYYOGA 4105 100 047 SUPERVISOR: WING HENDROPRASETYO, ST, Me. Surabaya, January 13 th 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 45 O 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
• TO MAKE THE DAC CURVE IS NEEDED A DAC BLOCK AS IMAGINE BELOW DAC BLOCK STANDARD
• DATA ON 100% DAC OF 2.5 mm DIAMETER: Diameter Tebal Posisi Gain SP SOD Depth Amplitudo Diskontinuitas 75 ¼ T 63 26 18.38 18.38 80 % 75 ½ T 63 52 36.76 36.76 50 % 2.5 75 ¾ T 63 79.5 56.25 56.25 35 %
• DATA ON 50% DAC OF 2.5 mm DIAMETER: Diameter Tebal Posisi Gain SP SOD Depth Amplitudo Diskontinuitas 75 ¼ T 57 26 18.38 18.38 40 % 75 ½ T 57 52 36.76 36.76 25 % 2.5 75 ¾ T 57 79.5 56.25 56.25 18 %
• DATA ON 20% DAC OF 2.5 mm DIAMETER: Diameter Tebal Posisi Gain SP SOD Depth Amplitudo Diskontinuitas 75 ¼ T 49 26 18.38 18.38 15 % 75 ½ T 49 52 36.76 36.76 10 % 2.5 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 (SP 0 ), SURFACE OF DISTANCE (SOD 0 ), AND THE DEPTH OF THE HOLE (D 0 ). 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.
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