# Ultrasonic Testing Formula

Topics: Sound, Ultrasound, Hertz Pages: 7 (544 words) Published: December 4, 2012
ULTRASONIC TESTING (UT) USEFUL FORMULAE
1. Velocity of Ultrasonic Waves in a medium (V) = f x l
OR

W here
f = Number of cycles per second is called frequency. Measured in ‘Hertz’. Abbreviated as ‘Hz’. One Hertz is equivalent to One cycle per second l = Distance covered in one cycle is wavelength
V= Velocity of Ultrasonic wave inside the medium in ‘mm/s’ 2. A coustic Impedance (Z) = V x r
W here:
Z=

Acoustic Impedance

r=

D ensity

V=

Velocity

3. R eflection Coefficient

W here:
R = Reflection Coefficient
Z1 = A coustic Impedance of Medium 1
Z2 = A coustic Impedance of Medium 2

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2011-12

For refererence only. ‘TINT’ is not responsible for errors and omissions in the data if any.

4. Transmission coefficient
T = 4 Z1Z2/ (Z1+Z2)2
W here:
R = Reflection Coefficient
Z1 = Acoustic Impedance of Medium 1
Z2 = Acoustic Impedance of Medium 2
5. Longitudinal Wave Velocity

W here:
VL =
E=
r=
m=

Longitudinal Wave Velocity
Modulus of Elasticity
Density
Poisson's Ratio

6. Shear Wave Velocity

W here:
Vs =
E=
r=
m=
G=

Shear Wave Velocity
Modulus of Elasticity
Density
Poisson's Ratio
Shear Modulus

7. Refraction - Snell's Law: That is the ratio of sine of the angle to the respective wave velocities are proportional.

Where:
qI =
qR =
V1 =
V2 =

Angle of the Incident Wave
Angle of the Reflected Wave
Velocity of Incident Wave
Velocity of Reflected Wave

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2011-12

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8. Near Field

Where:
N
D
l
V

=
=
=
=

Near Field
Transducer Diameter
W avelength
Velocity

Where:
l
D
V
F

=
=
=
=

Wavelength
Transducer Diameter
Velocity
Frequency

10. Decibel (dB) Gain or Loss

Where:
dB = Decibel
P1 = Pressure Amplitude 1
P2 = Pressure Amplitude 2
11. Angle Beam testing of Pipe
t=

d(1- Sin Ø)
2

S in Ø = 1-

2t
d
d = O.D. of Pipe

t = Maximum wall thickness

Ø = Probe angle

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2011-12

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12. Formulae for Angle Beam Calculations
β = Sound beam refracted angle in the test material
T = Thickness of the test material

Skip Distance
S = 2T x tan β

V-Path Length
2T
cosβ

V-Path =

Leg Length
T
cosβ

Leg =

Surface Distnace
SD = sinβ x Soundpath Length

Depth in First Leg
Depth (1st L eg) = cosβ x Sound path Length

Depth in Second Leg
D epth (2nd Leg) = 2T – (cosβ x S ound path Length)

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2011-12

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For refererence only. ‘TINT’ is not responsible for errors and omissions in the data if any.