Formulas for Ultrasonic Nondestructive Testing
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Transcript of Formulas for Ultrasonic Nondestructive Testing
Formulas for Ultrasonic Nondestructive Testing
Ultrasonic Key
V = velocity
Sin = sine of angle
Cos = cosine of angle
F = frequency
D = diameter of the transducer
BS = beam spread
= lambda or wavelentgh
p = density of the material
Z = acoustic impedance
dB = decible
NF = near field
Snell's Law:
Sin 1/ Sin 2= V1/ V2or Sin 2= (Sin 1* V2) / V1
Near Field:
NF = D2F / 4V or NF = D2/ 4
Beam's Spread:
BS = K * (V/DF)Note: K = 1.22 for 0 or null point K = 0.7 for 6 dB down
Wave Length:
= V/F
Acoustic Impedance:
Z = pV
Coefficient of Reflection:
((Z1- Z2)2/ (Z1+ Z2)2)1/2
Decibel Ratio:
dB difference = 20 log10(amplitude1/ amplitude2)
Flaw Location Depth:
Depth = cos of the angle X the sound path
Flaw Location from the exit point (surface distance):
Surface = Sound path X Sin of the angle
Formulas for Radiography Nondestructive Testing
Radiography Key
I = intensity
D = distance
Ug = geometric unsharpness
F = focal spot size
D = distance from the source to the source side of the object
T = the thickness of the object plus the distance from the object to the film
SDD = source to the detector (film) distance
Inverse Square Law:
I1/ I2= D22/ D12or I2= I1* D12/ D22
Unsharpness:
Ug = FT / D
Source to Detector Distance:
SDD = (FT / Ug) + T
To figure the strength of a source after a certain amount of time:
If an Ir. 192 source is 120 days old that is 1.6 half lives. So if the source was 100 curies at purchase the strength at 120 days is 39.6 curies.
100 * 0.51.6= 39.6
If you have a 1/2" of lead and the half value layer is 0.2" you have 2.5 have value layers. If you had 60 Roentgens and put the 1/2" of lead at the point of 60 R you would now have 10.6 R on the opposite side of the lead.
60 * 0.52.5= 10.6
Formulas for Magnetic Particle Nondestructive Testing
Magnetic Particle Key
N = number of turns in the coil
I = amperes
R = radius of the coil
L - is the usable length for the examEx. 9" each side of the center coil would allow for a max. length of 18" for ASME Section V; for ASTM E-1444 use coil diameter each side of the coil
All formulas are for American units of measurement.
Testing with part next to the inside wall of the coil:
NI = 45000 / (L / D) or I = (45000 / (L / D)) / N
Testing with part centered in the coil and less than a 10% fill factor:
NI = (35000R) / ((6L / D) - 5)
Effective Diameter of hollow round parts:
(OD2- ID2)1/2
Effective Diameter of hollow rectangular parts:
2(At- Ah/ P)1/2
At= the area of the total cross section of the part and Ah= the area of the hollow cross section of the part