NDTnet 1998 Aug, Vol.3 No.8

Full-Text -Abstract

The stress states in railroad wheels are strongly influenced by the heating and cooling process during and after the brakings using brake shoes. Different ultrasonic set-ups to evaluate the stress states in the rims of monoblock railroad wheels are already in use. Although developed by different institutions, the technique used by the set-ups is the same. By measurements of the times-of-flight of an ultrasonic shear wave polarized along the radial and along the circumferential direction, the difference of the principal stresses acting in the circumferential and in the radial directions (_circum. - _radial ) is calculated. The application of this ultrasonic technique presumes that there is no other reason for the times-of-flight differences of the shear wave polarized along the two directions than the stress state. But in numerous older wheels, which are still in use, the manufacturing process caused a texture in the rim. The texture also influences the times-of-flight of the shear wave polarized along the two principal axis. Hence, the stresses evaluated for textured wheels are not reliable.

Texture is often going along with a significant direction dependence of the grain dimensions resulting in direction dependent ultrasonic attenuation. The direction dependences of the ultrasonic attenuation and of the shear wave time-of-flight have been measured using more than 60 wheels of the older types. It is found that both quantities change significantly if there is a texture in the wheel and small changes are observed for wheels without texture or with a slightly developed texture. A threshold value is defined to separate wheels with a strong texture from those with no or with a slightly developed texture. The stress analysis for wheels with a strongly developed texture is only possible if the texture is homogeneous along the circumference of each wheel. The characterization of the stress state in wheels with a slightly developed texture is possible as first results show.

Abstract Source:
Book of Abstracts, 7th European Conference on Non-Destructive Testing, 26-29 May 1998, ISBN: 87-986898-0-00

Full-Text Source:
Proceedings of the 7th European Conference on Non-Destructive Testing, 26-29 May 1998, ISBN:

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