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- based on a new Technology -. Peter Renzel. History of Krautkramer’s digital Thickness Gauges (from DM 1 to DMS 2 TC) State-of-the-art procedures to determine the Sound Entrance Point State-of-the-art procedures to determine the Sound Velocity New Principles 1: 2 Crystals for AutoV
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- based on a new Technology -Peter RenzelKrautkramer NDT Ultrasonic SystemsHistory of Krautkramer’s digital Thickness Gauges (from DM 1 to DMS 2 TC)
  • State-of-the-art procedures to determine the Sound Entrance Point
  • State-of-the-art procedures to determine the Sound Velocity
  • New Principles 1: 2 Crystals for AutoV
  • New Principles 2: plus 2 Crystals for Thickness Measurement
  • New Principles 3: Through Coat Measuring by DualMulti
  • New Principles 4: 2 Crystals for Coating Measurement (TopCoat)
  • Krautkramer NDT Ultrasonic SystemsHistory of Krautkramer Thickness Measurement (from DM 1 to DMS 2 TC)
  • 1960: TM by superimposing echoes and (sharp) electronic pulses in a USIP
  • 1965: Analog TM with artificial Zeroing, 1 Sound Velocity (internally adjustable only: WSG and CM)
  • 1970: DM 1: artificial Zeroing, 6 Sound Velocities (externally adjustable with quartz stability)
  • 1976: DM 2: artificial Zeroing, 2-Point Calibration available, all Sound Velocities adjustable with quartz stability)
  • 1983: DM 3: automatic Zeroing (on-block), all Sound Velocities adjustable, simple V-Path correction for all DA 3... probes
  • 1992: DM 4: automatic Zeroing (on- and off-block), 2-Point Calibration available, all Sound Velocities adjustable, individual V-Path correction for all DA 4... probes
  • 1995: DM 4: plus DualMulti for Through Coating Measurement
  • 1999: DMS 2 TC: automatic Zeroing (on- and off-block), 2-Point Calibration available, all Sound Velocities adjustable, individual V-Path correction for all DA 4... probes, improved DualMulti, Auto-V, TopCoat
  • Krautkramer NDT Ultrasonic SystemsState-of-the-art procedures to determine the Sound Entrance Point:
  • Presetting of an artificial Zero Signal between SE and 1. RE by hand (i.e by a monostable Flip Flop) in order to compensate the Probe Delay Line:
  • Krautkramer NDT Ultrasonic SystemsState-of-the-art procedures to determine the Sound Entrance Point:
  • Determination of Probe Delay NOT coupled to the Material to be tested (coupled against Air) Off-Block-Zeroing. Best results to be expected in case of:
  • rough, uneven Material Surfaces,
  • Material with low acoustical impedance (Plastics etc.)
  • Material in ambient temperature only(!)
  • Determination of Probe Delay COUPLED to the Material to be tested On-Block-Zeroing. Best results to be expected in case of:
  • Material with higher acoustical impedance
  • Material of all temperatures
  • the need for very stable and reproducible Readings
  • Krautkramer NDT Ultrasonic SystemsBoth Crystals as TransceiversTransmitter CrystalReceiver CrystalMaterialDetermination of Probe Delay COUPLED to the Material to be tested: On-Block-Zeroing.Krautkramer NDT Ultrasonic SystemsState-of-the-art procedures to determine the Sound Velocity:
  • Manual Procedure using two test blocks of different known thickness but same material (2 - Point Method)
  • Manual Procedure using multiple Backwall Echoes of a test block of known thickness
  • Manual Procedure using an artificial Zero Point (from a built-in thickness gauge test block) and the first Backwall Echo of a test block of known thickness (Sound Velocity-Meter (DM V DL))
  • All those Procedures have one disadvantage in common: the determination of the Sound Velocity happens in separated steps!How to simplify that ???Krautkramer NDT Ultrasonic SystemsNew Principles 1: 2 Crystals for AutoVReceiverTransmitterCreeping WaveMaterial
  • Determination of Material‘s Sound Velocity by using a Longitudinal Wave Creeping very closely beneath Material‘s surface
  • Principle: „fastest traveling wave will be registered first“
  • Krautkramer NDT Ultrasonic SystemsTs,SsTe,SeMaterialTmx,SmCalibration of System using 2 Materials with different but known Sound VelocitiesC1 (f.e. Copper) and C2 (f.e. Steel) : Goal: SmTtot1 = Ts + Tm1 + Te Ttot2 = Ts + Tm2 + Te C1 = Sm/Tm1DeltaT = Ttot1 – Ttot2DeltaT = Tm1 – Tm2 C2 = Sm/Tm2DeltaT will be determined by the instrument using Ttot1 and Ttot2 !DeltaT= Sm (1/C1 – 1/C2)Sm = DeltaT / (1/C1 – 1/C2)Krautkramer NDT Ultrasonic SystemsAfter Calibration of the System this Formula is now used to determine the unknown Sound Velocity (AutoV):Sm = DeltaT / (1/C1 – 1/C2)C1 = 1/ (Sm / DeltaT + 1/C2) Depending on the “Distance” of the unknown Sound Velocity Cun to one of the two known Velocities (Cx = C1 or C2) we’ll get a different DeltaTx ( = DeltaT1 or DeltaT2). The instrument selects the bigger difference value of DeltaTx:Formula for AutoV:Cun = 1 / (Sm / DeltaTx + 1/Cx)Krautkramer NDT Ultrasonic SystemsTypical Applications for AutoV:
  • Test of steadily changing Materials between 4000 and 8000 m/s (f.e. for almost all Metals)
  • Testing of Sound Velocity differences within the same lot of parts made from the same Material
  • Testing of Isotropy (dependencies on direction) within the same Material under Test (f.e. rolled Steel)
  • Advantages of AutoV:
  • No further reference blocks needed
  • No mechanical measurements needed
  • Ideal basis for further Measurements “online”
  • Krautkramer NDT Ultrasonic SystemsThe very first practical realization: The AUTO-V SYSTEMKrautkramer NDT Ultrasonic SystemsIs that all we can do with AutoV?No!Imagine our probe has two more Crystals!Krautkramer NDT Ultrasonic SystemsNew Principles 2: plus 2 Crystals for Thickness MeasurementCrystals for Sound VelocityCrystals for Thickness MeasurementMaterialKrautkramer NDT Ultrasonic SystemsBy adding two Crystals we are now able to measure the Thickness without knowing anything about the Sound Velocity of the Material under Test!
  • Sequence of the complete Measurement Procedure:
  • Determination of Sound Velocity using the two Sound Velocity Crystals
  • Determination of the Delay Line Times (DT) (f.e. by On-Block-Zeroing))
  • Measuring the total Transit Time (TT) of a Backwall Or Flaw Echo
  • Reduction of the TT by DT
  • Calculation of the True Thickness using the already known Sound Velocity
  • Indication of Thickness AND Sound Velocity „online“
  • Krautkramer NDT Ultrasonic SystemsWe reached the Goal of our new Method:We are able to perform Thickness Measurement with Ultrasound NOT knowing the Sound Velocity
  • Advantages of this Method:
  • Easy Measurements at most Materials
  • changing Material w/o manually changing the Sound Velocity Value
  • even at corroded Materials (1. Backwall Echo only !)
  • Thickness and Sound Velocity are indicated simultaneously
  • Good visibility of Isotropy during running Tests
  • Krautkramer NDT Ultrasonic SystemsIs that all we can expect from a 4 Crystal Probe?No!Imagine your Material under Test is covered with layers of Painting or Coating...Krautkramer NDT Ultrasonic SystemsNew Principles 3: Through Coat Measuring by DualMultiPaintMetalKrautkramer NDT Ultrasonic SystemsLayers of Paint or Coating influence our Indications:
  • especially thick layers are very inconvenient. If thick enough they produce Echoes with sufficient Amplitude...
  • Thinner layers increase the displayed Values by 2- to 3-times their own thickness!
  • In some Thickness Gauges we therefore know the so called DualMulti – Mode:
  • The Transit time of 2 Backwall Echoes are measured, evaluated by the known Sound Velocity of the base Material (Metal), and displayed.
  • Krautkramer NDT Ultrasonic SystemsThickness Measurement with DualMultiPaintMetal Requirement 1: no or only very little Corrosion Requirement 2: Thickness of Layers not too highKrautkramer NDT Ultrasonic SystemsNon-corroded Sheet Metal (ideal) Corroded Sheet Metal (not useful)Krautkramer NDT Ultrasonic SystemsCrystals for CoatingCrystals for ThicknessPaintMetalNew Principles 4: 2 Crystals for Coating Measurement (TopCoat)Krautkramer NDT Ultrasonic SystemsTs,SsTe,SeDfSm, TmPaintTf,SfTf,Sf, CfBase MaterialTb,Sb, CbDirectly retrievable Transit Times:
  • w/o Paint: Ttoto = Ts + Tm + Te
  • Paint included: Ttotm = Ts + Tf + Tb + Tf + Te
  • DeltaT: DeltaT = Ttotm – Ttoto = 2Tf + Tb - Tm
  • Krautkramer NDT Ultrasonic SystemsProbeDelaySm,TmSf, TfDfaPAINTTbSx, TxBase MaterialDeltaT = 2Tf + Tb - Tm Tm = Tb + 2Tx Cf = Sf/Tf Cb= Sx/TxDeltaT = 2 (Tf – Tx)DeltaT = 2 (Sf/Cf – Sx/Cb)Sin(a) = Sx / Sf Cos(a) = Df / SfDeltaT = 2 Sf (1/Cf – Sin(a)/Cb) DeltaT = (2 Df / Cos(a)) (1/Cf – Sin(a)/Cb)Formula for TopCOAT:Df = DeltaT Cos(a) / (2 (1/Cf – Sin(a)/Cb))Krautkramer NDT Ultrasonic SystemsMeasuring Thickness Through Paint Df:Crystals for CoatingCrystals for ThicknessDfPaintMetalKrautkramer NDT Ultrasonic SystemsRequirements for TopCOAT:
  • Cf, the Sound Velocity of the Coating/Paint has to be known
  • Cb, the Sound Velocity of the Base Material has to be known
  • Delay line Material should not be to different from Cf
  •  a = constAdvantages of the TopCOAT Method:
  • Thickness of Coating/Paint and Base Material are displayed simultaneously
  • Thickness of layer can be as low as 0 mm (no syst. Minimum Value)
  • Rear Surfaces of Base Material may be corroded (1 Echo to be evaluated only!)
  • Top Coat Procedure can simply be combined with AutoV
  • Krautkramer NDT Ultrasonic SystemsThe decribed MethodsAutoV and TopCOATare protected by patents for Agfa NDT GmbH inAmericaEuropeJapan You need more info? Click:www.geinspectiontechnologies.comKrautkramer NDT Ultrasonic Systems
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