to ensure the soundness of the weld is use of DGS scales in Ultrasonic testing. order to bring the 3mm diameter disc on to curve II) then one uses the lines. Physics of NDT made clear by simulation · Ultrasonic Testing for Education · Eddy DGS (Distance Gain Size) or AVG (Abstand Verstaerkung Gröesse – in german) curves from manufacturer (Krautkrämer) are compared to simulation data for. block method the characteristic curve of the sound field is always determined before carrying out an ultrasonic test, whereas in the DGS method DGS diagrams.

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The advent of digital instruments has made it possible to give the DGS system much greater flexibility, and most ultraslnic the newer digital instruments will have a DGS capacity. Part Two Training Courses: Now consider a probe scanning over three identical discontinuities at varying beam path lengths:.

For small FBH above the focal spot the difference is up to 6 dB. Any personal information provided to or to be gathered ultraasonic bindt.

The features of DGS are:.

UT – FBH: DGS curves

Rather than plotting the entire curve set, instruments will typically display one curve based on a selected reflector size registration level that can be adjusted by the user. The technique has since been further applied to square element and even dual element probes, although for the latter, curve sets are empirically derived.

The input signal frequency is 2. From that one calibration point, an entire curve set can be drawn based on probe and material characteristics.

Back to Calibration defects. In the example shown above:.


Part Three Training Courses: The curves show a good agreement between simulated and experimental data for FBH deeper than the focal depth. Since this reflector equals the selected registration level, the peak matches the curve at that depth.

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The blue curves plotted show how the amplitudes obtained from different sizes of disc shaped reflector equivalent to a FBH decrease as the distance between the probe and the reflector increases.

Reflectors of the same size will have an echo height inversely proportional to the square of the beam path distance, assuming that the reflectors are in the far zone.

Alternatively, the curves can be used to find the size of the disc shaped reflector which would give the same size echo as a response seen in the flaw detector screen. The input signal frequency is 4. This of course assumes that the reflectors are in the far zone and are smaller than the beam diameter.

The red curve shows the response of a backwall reflection. See the left hand vertical axis for extra gain required for RE1 an RE2. The uppermost curve represents the relative amplitude of the echo from a flat plate reflector in decibels, plotted at various distances from the transducer, and the curves below represent the relative amplitude of echoes from progressively smaller disk reflectors over the same distance scale.

At shorter beam paths, set the backwall to RE1 and add 16 dB, then read the equivalent flaw sizes directly from the screen. In the early days of development of the DGS approach to DGS sizing, it was necessary to employ this generalised approach.


It is much more useful, however, to use direct reading scales which can be fixed to the UFD screen for immediate size estimation. In the screen at left, the red gate marks the reflection from a 2 mm diameter flat bottom hole at approximately 20 mm depth.

DGS evaluation is a very convenient and reproducible technique, with a number of specific applications.

Material attenuation and coupling variation in the dgw block and test specimen can be accounted for. Frequency Crystal Mode Calibration flaw Calibration depth 1. The Y-axis shows the Gain and X-axis shows the Distance from the probe.

DGS/AVG | Olympus IMS

ultrasonix In a general DGS diagram the distance is shown in units of Near Field and the scale is logarithmic to cover a wide range. This technique has one limitation — it assumes that there is a backwall reflector available at mm. Index of acronyms D DGS. Of course, we transmit the entire credit card number to the appropriate credit card company during order processing. Click here to unsubscribe Go.

UT – FBH: DGS curves

Be sure to sign off when you finish using a shared computer. This notice describes the privacy policy of bindt. In the general diagram the size of reflector is given as a ratio between the size of the disc and the size of the crystal.