Re: railroad wheel testing

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Re: railroad wheel testing
Posted by: Hassan Rahimi , E-mail: hassan_rahimi@hotmail.com, on June 19, 2000 at 10:20 :
In Reply to: railroad wheel testing posted by : Hermann Wuestenberg on June 11, 1998 at 16:50:33:
: Railroad wheel rim testing:
: The ultrasonic inspection for possible cracks at the railroad wheel rim must take into account the
: multitude of crack positions, orientations and depth´s as described by Mr. Hintze´s contribution.
: A reliable detection of those cracks with a low false call rate requires a multitude of ultrasonic
: beam directions and different physical interactions. We should therefore consider all available methods of the generation and reception of ultrasonic waves and not restrict the solution of this important problem
: to contactless transducers like the EMAT´s. It could be possible that the standard probe techniques with
: liquid couplants are offering much better adaptability to some of the problems than the EMAT´s.
: Beam focussing, small beam divergence, frequency bandwith and high near surface resolution, multimode probes are some of the aspects to be considered. If at an in situ rim testing one has to choose a multiprobe concept for a future automatic UT-inspection system - eg. 2 x 64 probes imbedded into two 4 to 6 m long test rails - there are certainly some severe advantages on the side of the traditional contact probes. The real advantages of the EMAT´s - to be contactless and to enable the use of shear horizontally polarized shear waves - must be compared with the restrictions concerning e.g. the frequency, the sound field structuration and the cost, if a multiprobe concept has to be considered.
: Another aspect is the separate evaluation of the basic potential of a NDT method for the given task and the problems in connection with it´s application under practical circumstances. Both aspects are of course influencing the decision for the one or the other approach. E.g. the eddy current technique with a strong magnetization has apparently some attractivity. But is there also a possibility to modify it´s applicability to a degree that it complies with the requirements of an in situ automatic inspection?

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: : Railroad wheel rim testing: : : The ultrasonic inspection for possible cracks at the railroad wheel rim must take into account the : : multitude of crack positions, orientations and depth´s as described by Mr. Hintze´s contribution. : : A reliable detection of those cracks with a low false call rate requires a multitude of ultrasonic : : beam directions and different physical interactions. We should therefore consider all available methods of the generation and reception of ultrasonic waves and not restrict the solution of this important problem : : to contactless transducers like the EMAT´s. It could be possible that the standard probe techniques with : : liquid couplants are offering much better adaptability to some of the problems than the EMAT´s. : : Beam focussing, small beam divergence, frequency bandwith and high near surface resolution, multimode probes are some of the aspects to be considered. If at an in situ rim testing one has to choose a multiprobe concept for a future automatic UT-inspection system - eg. 2 x 64 probes imbedded into two 4 to 6 m long test rails - there are certainly some severe advantages on the side of the traditional contact probes. The real advantages of the EMAT´s - to be contactless and to enable the use of shear horizontally polarized shear waves - must be compared with the restrictions concerning e.g. the frequency, the sound field structuration and the cost, if a multiprobe concept has to be considered. : : Another aspect is the separate evaluation of the basic potential of a NDT method for the given task and the problems in connection with it´s application under practical circumstances. Both aspects are of course influencing the decision for the one or the other approach. E.g. the eddy current technique with a strong magnetization has apparently some attractivity. But is there also a possibility to modify it´s applicability to a degree that it complies with the requirements of an in situ automatic inspection?

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