Angle Beam Inspection Calculations
When performing an angle beam inspection, it is important to know where the sound beam is
encountering an interface and reflecting. The reflection points are sometimes referred to as nodes.
The location of the nodes can be obtained by using the trigonometric functions or by using the trigbased formulas which are given below.
Nodes - surface points where sound waves reflect.
Skip Distance - surface distance of two successive nodes.
Leg 1 (L1) - sound path in material to 1st node.
Leg 2 (L2) - sound path in material from 1st to 2nd node.
qR - refracted sound wave angle.
Skip Distance Formulas
Surface Distance Formulas
Leg 1 and Leg 2 Formulas
Flaw Depth (1st Leg)
Flaw Depth (2nd Leg)
Longitudinal Wave
Velocity
Where:
Shear Wave Velocity
Where:
VL
=
E
=
ρ
μ
=
=
Longitudinal Wave
Velocity
Modulus of
Elasticity
Density
Poisson’s Ratio
Refraction
(Snellʼs Law)
Where:
θΙ
=
θR
=
V1
=
V2
=
Angle of the Incident
Wave
Angle of the Reflected Wave
Velocity of Incident
Wave
Velocity of Reflected
Wave
Vs
E
ρ
μ
G
=
=
=
=
=
Wavelength
Where:
Shear Wave Velocity
Modulus of Elasticity
Density
Poisson’s Ratio
Shear Modulus
=
=
=
λ
V
F
Wavelength
Velocity
Frequency
Acoustic Impedance
Reflection Coefficient
Where:
Where:
Z
ρ
V
=
=
=
Acoustic Impedance
Density
Velocity
R
Z1
=
=
Z2
=
Reflection Coefficient
Acoustic Impedance of
Medium 1
Acoustic Impedance of
Medium 2
Beam Spread
Half Angle
Near Field
Where:
N
D
λ
V
=
=
=
=
Where:
Near Field
Transducer Diameter
Wavelength
Velocity
λ
D
V
F
=
=
=
=
Decibel (dB)
Gain or Loss
Where:
Wavelength
Transducer Diameter
Velocity
Frequency
dB
A1
A2
=
=
=
Decibel
Amplitude 1
Amplitude 2