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|NDT.net Issue - 2011-06 - NEWS |
|Significantly Reduce the Chances of Flaw Oversizing
Huerth, Germany, March 8, 2011 - Patent-pending trueDGS technology from GEs Inspection Technologies business has allowed the company to develop and introduce a range of ultrasonic trueDGS angle beam probes, which offer increased accuracy in sizing of flaws using the DGS method. The DGS (Distance, Gain and equivalent reflector Size) method is specified throughout Europe (e.g. EN 583-2), and in many other countries worldwide, as a sentencing technique for detecting discontinuities above specific equivalent reflector sizes. The new angle beam probes now offer the same DGS accuracy as circular straight beam probes and are available as single element and phased array transducers for applications in all industrial sectors where accurate, compliant, ultrasonic inspection is required.
Currently, angle beam probes which are to be used for detecting and sizing material flaws using the DGS technique are supplied with an accompanying DGS diagram. The ultrasonic inspector will read a flaw indication on his flaw detector and by fitting this to the DGS curve, the equivalent reflector size of the flaw can be determined. Generally, this is used for sentencing, where any workpiece with flaws greater than a given equivalent reflector size is rejected. However, the DGS method was developed originally for straight beam probes, using flat circular transducers. Todays single element angle beam probes and ultrasonic phased arrays have different ultrasonic characteristics to straight beam probes due to the refraction, which means that there can be deviations in DGS evaluation. This has now been acknowledged with the development of the new range of trueDGS probes.
As Wolf Kleinert, one of the inventors of the new probes at GE, explains, The new transducer shape is calculated using a given circular straight beam probe transferring the properties of all sound beams of this probe to an angle beam probe with a given angle of incidence and a given delay line length. The resulting point cloud defines the transducer shape of the trueDGS angle beam probe.
Subsequent CAD modeling has allowed the manufacture of trueDGS angle beam probes which provide significantly improved match to the respective DGS diagram. The same philosophy can also be extended to phased array probes. As a result, ultrasonics inspections using the DGS method are now significantly more accurate. This means there is less scrap or rework, as current DGS angle beam probes tend to oversize flaws. Successors of most prevalent MWB-series probes will be available with trueDGS-technology and the associated software will be incorporated in all relevant GE flaw detectors.
trueDGS Ultrasonic Angle Beam Transducer Overview
trueDGS Ultrasonic Transducer Tutorial 1 of 2
trueDGS Ultrasonic Transducer Tutorial 2 of 2
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