NON DESTRUCTIVE TESTING

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NON DESTRUCTIVE TESTING Flaw Detection Flaw Localization Type of Flaw Determination Flaw Dimension Estimation

description

NON DESTRUCTIVE TESTING. Flaw Detection Flaw Localization Type of Flaw Determination Flaw Dimension Estimation. Flaw Detection. CRT Display. Flaw Localization. The transducer is scanning until the maximum echo is obtained - The flaw is exactly below the transducer. - PowerPoint PPT Presentation

Transcript of NON DESTRUCTIVE TESTING

Page 1: NON DESTRUCTIVE TESTING

NON DESTRUCTIVE TESTING

Flaw Detection Flaw Localization Type of Flaw Determination Flaw Dimension Estimation

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Flaw Detection

Face AV = Front wall echo (FWE)

Face AR = Back wall echo (BWE)

d1 = Dimension of first flaw

d2 = Dimension of second flaw

CRT Display

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Flaw Localization

•The transducer is scanning until the maximum echo is obtained

- The flaw is exactly below the transducer

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• 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

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• The transducer position must be changed for obtaining an echo

• If the flaw is perpendicular to the object surface

- Use two transducers

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Type of Flaw Determination

• Planar flaw (cracks) more dangerous

• Volume flaw (voids, inclusions) less dangerous

• Change transducer orientation 10o and observe the echo

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Flaw Dimension Estimation

• Amplitude Analysis

- 6 db Drop Method

- Comparison Method

- DGS Method

• Time Analysis

- TOFD Method

• Frequency Analysis

- Ultrasonic Spectroscopy

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6 dB Drop Method

- Flaw dimension > transducer diameter

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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

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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

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DGS graphic for near field

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Time of Flight Diffraction (TOFD) Method

- Measure the time propagation of

diffraction waves from the crack tips

221

2 42

1StVd

dStVa 222

2 42

12

V = Wave velocity

d = Crack depth

2S = Transducer distance

2a = Crack dimension

t1, t2 = Time propagation of diffracted waves

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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

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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 (R1 and R2) as receiving transducer. These transducer are transversal transducers with wave velocity of VT. The distances between them are a, b and c as shown at figure below. The time propagation from T to R1 is t1 whereas the time propagation from T to R2 is t2.

a). Express the crack dimension and orientation as function of the wave velocity VT

the distances (a, b and c) and the time propagation (t1 and t2).

b). Calculate h and , if VT = 3230 m/s, a = 40 mm, b = 60 mm, c = 110 mm,

t1 = 32.275 s and t2 = 47.554 s.

Steel

T R1

a b

h

c

R2

x yz

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Steel

T R1

a b

h

c

R2

x yz

(*)GFqqDh)aE(q)a2DE2(qDh

EDEq2qDaq2ahEDqf2

q)b2a2(bafaq2ah

aq2ahf2aq2ahfbq2bh

aq2ahfbq2bhbq2bhaq2ahf

qcoshcosbh2bhcosah2ahftVyx

cosch2chzcosbh2bhycosah2ahx

22222222

22222222

22

2222222

22222222

22221T

222222

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(*)GFqqDh)aE(q)a2DE2(qDh

EDEq2qDaq2ahEDqf2

q)b2a2(bafaq2ah

aq2ahf2aq2ahfbq2bh

aq2ahfbq2bhbq2bhaq2ahf

qcoshcosbh2bhcosah2ahftVyx

cosch2chzcosbh2bhycosah2ahx

22222222

22222222

22

2222222

22222222

22221T

222222

(**)KJqqHh)aI(q)a2HI2(qHh

IHIq2qHaq2ahIHqg2

q)c2a2(cafaq2ah

aq2ahf2aq2ahgcq2ch

aq2ahgcq2chcq2chaq2ahg

qcoshcosch2chcosah2ahgtVzx

cosch2chzcosbh2bhycosah2ahx

22222222

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22

2222222

22222222

22222T

222222

h

qKJqqHh

A

ACBBqCBqAq

KGqJFqHDKJqqHGFqqD

1222

2

2222222

cos2

40

0)()()(

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Steel

T R1

a b

h

c

R2

x yz

(**)KJqqHh)aI(q)a2HI2(qHh

IHIq2qHaq2ahIHqg2

q)c2a2(cafaq2ah

aq2ahf2aq2ahgcq2ch

aq2ahgcq2chcq2chaq2ahg

qcoshcosch2chcosah2ahgtVzx

cosch2chzcosbh2bhycosah2ahx

22222222

22222222

22

2222222

22222222

22222T

222222

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h

qcosKJqqHh

A2

AC4BBq0CBqAq

0)KG(q)JF(q)HD(KJqqHGFqqD

(**)KJqqHh)aI(q)a2HI2(qHh

IHIq2qHaq2ahIHqg2

q)c2a2(cafaq2ah

(*)GFqqDh)aE(q)a2DE2(qDh

EDEq2qDaq2ahEDqf2

q)b2a2(bafaq2ah

122

22

2222222

22222222

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22

22222222

22222222

22

h

qKJqqHh

A

ACBBqCBqAq

KGqJFqHDKJqqHGFqqD

122

22

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cos

2

40

0)()()(

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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 :

t1(T-R1) = 20.9 S, t2(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.