TechnicalNotes
TableTable2
AcousticPropertiesofMaterialsNearFieldDistanceofFlatTransducersinWater
LongitudinalShearAcoustic
ElementFocalLength(PTF)
Material
FrequencyN
VelocityVelocityImpedance
Diameter
MinMax
26
(in/ms)(m/s)(in/ms)(m/s)(Kg/msx10)
(MHz)(inches)(inches)(inches)(inches)
?
Acrylicresin(Perspex)0.1072,7300.0561,4303.22
1.504.7572.153.80
Aluminum0.2496,3200.1233,13017.06
1.1252.6611.502.10
0.5
Beryllium0.50812,9000.3508,88023.5
1.002.0951.251.65
Brass,naval0.1744,4300.0832,12037.30
0.751.1640.780.93
Cadmium0.1092,7800.0591,50024.02
1.509.5592.507.65
Columbium0.1944,9200.0832,10042.16
1.1255.3661.904.30
Copper0.1834,6600.0892,26041.61
1.01.004.2351.6253.38
Glycerine0.0761,920——2.42
0.752.3721.001.90
Gold0.1283,2400.0471,20062.60
0.501.0430.600.80
?
Inconel0.295,8200.1193,02049.47
1.5021.5342.7014.50
Iron0.2325,9000.1273,23045.43
1.12512.0992.159.50
Iron,cast
1.009.5541.8757.60
(slow)0.1383,5000.0872,20025.00
2.250.755.3641.004.30
(fast)0.2205,6000.1263,22040.00
0.502.3740.801.90
Lead0.0852,1600.02870024.49
0.3751.3290.501.06
Manganese0.1834,6600.0932,35034.44
0.250.5840.350.45
Mercury0.0571,450——19.66
1.0014.8681.9511.5
Molybdenum0.2466,2500.1323,35063.75
0.758.3501.006.65
MotorOil(SAE20or30)0.0691,740——1.51
3.50.503.6990.832.95
Nickel,pure0.2225,6300.1172,96049.99
0.3752.0730.601.65
Platinum0.1563,9600.0661,67084.74
0.250.9140.3850.70
?
Polyamide,(nylon,Perlon)
1.0021.2431.9514.40?
(slow)0.0872,2000.0431,100.40
0.7511.9321.009.50
(fast)0.1022,6000.0471,2003.10
5.00.505.2870.754.20
Polystyrene0.0922,340——2.47
0.3752.9650.602.35
Polyvinylchloride,PVC,hard0.0942,3950.0421,0603.35
0.251.3090.431.00
Silver0.1423,6000.0631,59037.76
0.7517.9001.0012.75?
7.5
Steel,10200.2325,8900.1283,24045.63
0.507.9330.756.30?
Steel,43400.2305,8500.1283,24045.63
1.0042.4902.0020.00?
Steel,3020.2235,6600.1233,12045.45
0.7523.8681.0015.375?
austeniticstainlessSteel,3470.2265,7400.1223,09045.40
100.5010.5790.758.40?
austeniticstainlessTin0.1313,3200.0661,67024.20
0.3755.9340.604.75?
Titanium,Ti150A0.2406,1000.1233,12027.69
0.252.6220.462.10
Tungsten0.2045,1800.1132,87099.72
0.5015.8700.7511.75?
Uranium0.1333,3700.0781,98063.02
150.3758.9020.607.10?
Water(20°C)0.0581,480——1.48
0.253.9350.503.15?
Zinc0.1644,1700.0952,41029.61
0.255.2470.504.20?
20
Zirconium0.1834,6500.0892,25030.13
0.1251.2900.251.00?
-5
250.256.5590.505.25?
ConversionFactor:1m/s=3.937x10in/μS
Source:NondestructiveTestingHandbook2ndEditionVolume7
Panametrics’StandardCaseStyle,LargeDiameterCaseStyle,SlimLineCaseStyle,andPencil
UltrasonicTestingASNT1991edPaulMcIntire
CaseStyleImmersionTransducerswithstraightconnectors(seepages20-24)canbefocusedbetween
theMinimumandMaximumPointTargetFocal(PTF)distancelimitslistedinTable2.Pleaseconsult
Panametricsbeforeorderingatransducerfocusedoutsidetheselimits.
NearFieldDistancesofFlatTransducersinWater
Thenearfieldvaluesinthistablehavebeendeterminedusingthefollowing
?Considerationshouldbegiventoattenuationeffectswhichincreaselinearityandwiththesquare
equation:
offrequencyandthesquareofbandwidth.Inapplicationswherelongwaterpathsarerequiredthe
effectsoffrequencydependentattenuationshouldbecheckedperASTME1065AnnexA7.Itis
advisabletoconsidertheeffectsoffrequencydependentattenuationifthefocaldistanceequalsor
exceedsthefollowingvalues:
FrequencyFocalLength
Notethatequations8and8aonpage42werederivedfromthis
MHzinches
expression.Thecalculationswerecarriedoutassuminganultrasonic
5
velocityinwaterof0.586x10in/secat22°Candusingtheactual
5.013
transducerelementdiameters.Itshouldbenotedthattheactualtransducer
7.56
elementdiametersareslightlysmallerthanthenominalelementdiameters
103.5
listedinthetablesinthecatalog.
151.5
Theminimumandmaximumpracticalfocallengthshavebeencalculatedby
200.8
consideringtheacousticandmechanicallimitationsofeachconfiguration.
250.5
Theselimitationsareafunctionoftransducerfrequency,elementdiameter,
300.4
andcasedimensions.Theremaybeexceptionstothelimitslistedinthe
table.
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