Summary of the Forum discussion of NDT of railroad wheels at the German Bahn AG

Rolf Diederichs

We will comment and summarize 11 of the 33 forum discussions on this topic which were posted from 6.6.1998 to 18.6.1998. That does not mean the other 22 posts are not valuable, please read those on the forum, they may not have been in the scope of our technical review. Thanks to all participants for shearing their ideas on this forum!

Nondestructive testing of railroad wheels at the German Bahn AG
The initial message was posted by: Rolf Diederichs , E-mail: rd@ndt.net, on June 06, 1998 at 20:46:23:
The message looks at two different kind of ultrasonic inspection methods of railroad wheels.

1. Ultrasonic Evaluation of Stresses in the Rims
2. Ultrasonic Evaluation of surface narrow cracks using a surface wave method (Rayleigh waves)

Method 1 is no crack detection method. It measures the residual stress states in the rim of a wheel which can, if stress is high, cause cracking in the rim. This is a prevention method and is usually applied on freight trains at a certain interval without disassembling the wheelset. However, in a publication it is stated that this method could ideally be be applied also for tire wheels of high speed trains, thus the safety needs would be met. It is also mentioned that it could be economically integrated as an add-on in a system.

Method 2 has the benefit that no scanning of the wheel is necessary, thus the surface wave travels around the rim. However it points out that the method did not effectively recognize all possible defects of the wheel. After a relatively short operation time the wheel material characteristics hardened to the extent that sound was already absorbed and no further evaluation was possible. Especially for older wheels, as hardening increased, this method failed. (40% of the wheels according to another message).

For that reason a task force optimized the technique which shows good first results and plans for the necessary modifications are underway for a long term investigation at the service station in Hamburg. Basics of this method have been published in the article of Salzburger FhG 1996 Lindau ('Tiefenbestimmung von Laufflächenfehlen an Eisenbahnrädern unter Nutzung linear polarisierter Transversalwellen'. H.-J. Salzburger, FhG IZFP, Saarbrücken; H. Hintze, Deutsche Bahn AG, Kirchmöser. http://www.ndt.net/article/0698/salzb/salzb.htm (in German only).).

Reply posted by: H. Wuestenberg, BAM - Berlin, E-mail: Hermann.Wuestenberg@bam-berlin.de, on June 07, 1998 at 21:43:48:
This message describes more the weakness of the Rayleigh wave method 2 as well the drawbacks of contactless excitation techniques (EMATs). Other UT methods which scan the surface are suggested.

Reply posted by: C.M. Fortunko, E-mail: fortunko@boulder.nist.gov, on June 08, 1998 at 07:46:20:
"I agree with Dr. Wuestenberg's comments. The subject of wheel inspection should be revisited. However, I think that we must be careful about using magnetostrictive ultrasonic transducers, a version of the EMAT, which operates on Lorentz/Ampere forces. Chris"

(Obituary: Christopher M. Fortunko 1948-1998.
Chris Fortunko passed away on June 27, 1998 due to a heart attack. On his forum subscription, he wrote: "Very useful forum. Hope to be a regular participant." Chris was a leader within the NDE community. He was the U.S. organizer for the "European American Workshop (1997) on Determination of Reliabilitiy and Validation Methods on NDE.") I will miss him.

Reply posted by : Rolf Diederichs on June 06, 1998 at 20:46:23: This message supports Wuestenberg's opinion that a better system is needed, preferably one based on scanning testing methods such as the pulse echo technique in combination with TOFD (time of flight diffraction). Similar systems are working already in refurbishing shops at the DB in Darmstadt and Neumuenster.

Reply posted by: Godfrey Hands, E-mail: Godfrey@hands-ltd.demon.co.uk, on June 08, 1998 at 17:21:50: This message suggests a closer look at a technique called 'WHEEL TAPPING' or hitting the wheel with a hammer and listening to the ring of it. A company in Germany that currently manufactures and markets a high tech version of the WHEEL TAPPING technique is mentioned. A related reference we found with our Database search is "Resonant ultrasound spectroscopy for materials studies and non-destructive testing" Migliori, A.; Darling, T.W. (Los Alamos Nat. Lab., NM, USA) in Ultrasonics v 34 n 2-5 Jun 1996.

Reply posted by: Tom, E-mail: tfmurf@aol.com, on June 09, 1998 at 06:24:51: This message mentioned request for design suggestions on a wheel rim inspection system for rail car wheels in the USA.

Reply Posted by: Ingolf Hertlin , E-mail: ihertlin@rte.de, on June 09, 1998 at 07:52:58:
The message gives more details of the Resonant inspection testing technology. (Thanks also for the comment that this forum is an ideal place for discussions)

Reply posted by: Todd Snyder, E-mail: twsnyder@notes.up.com, on June 24, 1998 at 00:18:06:
Todd Snyder is a metallurgist/mechanical engineer and he work for Union Pacific Railroad R&D Lab. He had spent the last six months analyzing cracks in railroad wheels using ultrasonic,magnetic, acoustic, and destructive metallurgical techniques. In further forum messages we received more details from Todd. His technical note Railroad Wheel Testing of Shattered Rim is published in this issue.

Posted by: Jürgen Rohmann, E-mail: esr-Rohmann@t-online.de, on July 01, 1998 at 13:00:33:
This message highlighted the use of eddy-current technology on railroad wheels. "The company worked between 1993 and 1996 on a project which used the magnetic inductive method to detect deep cracks (more than 4 mm below the running surface) which originated at the running surface, but were not connected to the running surface any more. Finally, with the means available to us, we were able to achieve a depth of penetration (drilled holes with a diameter of 2 mm and filled with ferrous bolts) of up to 20 mm below the running surface." (For more details see [ ])
The sender would like to share experiences of the "magnetic technique" which was used at Union Pacific Railroad (Todd Snyder)

Railroad Wheel Testing Posted by: Hermann Wuestenberg , E-mail: hermann.wuestenberg@bam-berlin.de, on June 11, 1998 at 16:50:33:
This message recommends considering all available methods of the generation and reception of ultrasonic waves and not restricting the solution of this important problem to contactless transducers like the EMAT´s. Some possibilities are briefly described. It was also asked: Is it possible to perform an in situ automatic inspection?

POD of Manual vs. Automatic Testing on Railroad Wheels Posted by: Rolf Diederichs , E-mail: rd@ndt.net, on June 15, 1998 at 08:54:16:
There are concerns that manually applied ultrasonic testing on all wheels of totally 60 of the ICE could not solve the problem. The following article is suggested for further reading. Automated NDT Advantages and Disadvantages, by Godfrey Hands, Vianen, The Netherlands 1.March.1996. This article describes briefly that the probability of detection of manually ultrasonic testing can be 'only' 80% while automated testing reaches 100%. What shall be done with those trains - can they drive with 80% POD? http://www.ndt.net/article/hands/hands.htm Automated NDT Advantages and Disadvantages

Re: broken wheels Posted by: JA Bates , E-mail: trentndt@iinet.net.au, on June 18, 1998 at 13:59:45:
JA Bates in his 60s enjoys looking at some of the articles. He worked for British Rail in NDT for 14 years before coming to Australia. In British Rail they had the same problem in 1976 with wheels with tires. "with modern technology, there must be a solution".