Presentation on theme: " NON DESTRUCTIVE TESTING Flaw Detection Flaw Localization Type of Flaw Determination Flaw Dimension Estimation."— Presentation transcript:
NON DESTRUCTIVE TESTING Flaw Detection Flaw Localization Type of Flaw Determination Flaw Dimension Estimation
Flaw Detection Face AV=Front wall echo (FWE) Face AR=Back wall echo (BWE) d1d1 =Dimension of first flaw d2d2 =Dimension of second flaw CRT Display
Flaw Localization The transducer is scanning until the maximum echo is obtained - The flaw is exactly below the transducer
If the flaw is not perpendicular to beam wave direction : - The flaw can not be detected by using straight beam probe - The flaw can only be detected by using angle beam probe
The transducer position must be changed for obtaining an echo If the flaw is perpendicular to the object surface - Use two transducers
Type of Flaw Determination Planar flaw (cracks) more dangerous Volume flaw (voids, inclusions) less dangerous Change transducer orientation 10 o and observe the echo
Flaw Dimension Estimation Amplitude Analysis - 6 db Drop Method - Comparison Method - DGS Method Time Analysis - TOFD Method Frequency Analysis - Ultrasonic Spectroscopy
6 dB Drop Method - Flaw dimension > transducer diameter
Comparison Method - Flaw dimension < transducer diameter - Using block references with flat bottom hole (FBH) - Flaw dimension is estimated by amplitude comparison - If the amplitude of flaw echo equal to the amplitude of FBH Flaw dimension diameter of FBH
Distance Gain Scale (DGS) Method - D is distance of the flaw - A is amplitude of the echo - G is the ratio between flaw dimension and transducer diameter DGS graphic for far field
Time of Flight Diffraction (TOFD) Method - Measure the time propagation of diffraction waves from the crack tips V=Wave velocity d=Crack depth 2S=Transducer distance 2a=Crack dimension t 1, t 2 =Time propagation of diffracted waves
TOFD method for oblique crack Using tandem transducer Measure time propagation for two positions of transducer Calculate the position of the crack tips Estimate the crack depth and orientation
Problem No. 1 A surface crack is detected in a steel material. For estimating its dimension (h) and orientation ( ), a tandem system is used which consists of one transducer as transmitting transducer (T) and two transducers (R 1 and R 2 ) as receiving transducer. These transducer are transversal transducers with wave velocity of V T. The distances between them are a, b and c as shown at figure below. The time propagation from T to R 1 is t 1 whereas the time propagation from T to R 2 is t 2. a). Express the crack dimension and orientation as function of the wave velocity V T the distances (a, b and c) and the time propagation (t 1 and t 2 ). b). Calculate h and , if V T = 3230 m/s, a = 40 mm, b = 60 mm, c = 110 mm, t 1 = 32.275 s and t 2 = 47.554 s. Steel T R 1 a b h c R 2 x y z
T(0,50)R1(80,50)R2(100,50) O(0,0) Assignment No. 1 An oblique crack is detected inside an aluminum material. For estimating its dimension (h) and orientation ( ), three transversal transducer with wave velocity of 3100 m/s are used. When these transducers are located at (0, 50), (80,50) and (100, 50) the time propagation measured are : t 1(T-R1) = 20.9 S, t 2(T-R1) = 24.6 S t 1(T-R2) = 21.8 S, t 2(T-R2) = 26.1 S. a). Design a computer program using MatLab for estimating the crack dimension and orientation. b). Calculate h and using the computer program.
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