US2853775A - Method of preventing shelling in railroad rails - Google Patents

Description

Sept. 30, 1958 i H. c. DRAKE 2,853,775

METHOD OF PREVENTING SHELLING IN RAILROAD RAILS Filed March 51, 1955 p. s. i.

ited States Patent Ofiice 2,853,775 Patented Sept. 30, 1958 METHOD OF PREVENTING SHELLING IN RAILROAD RAILS Harcourt C. Drake,-Hempstead, N. Y.

Application March 31, 1955, Serial No. 498,383

3 Claims. c1. 29-558) This invention relates to method of preventing fatigue failures of the type known as shelling, in railroad rails in track.

Shelling cracks start inside the rail head from about Ms to /8" below the rail tread and from A3" to 1 from the gauge side. Shelling occurs near the upper gage corner of the rail and is the result of cold working of the rail steel by heavy Wheel loads, of the cars operating over the rails in track. At this corner the cold working results in surface compression stresses as high as 20,000

This surface compression stress result in a tension stress of 20,000 p. s. i. at a depth of approximately /8" below the surface, and it is this tensile stress which eventually causes shelling cracks in rails in track.

Shelling cracks frequently develop progressively into transverse defects which may cause breaking of the rail under load, and as a result large numbers of such rails are removed annually. It is the principal object of this invention to prevent the initiation of shelling cracks in rails in track.

The single figure in the accompanying drawing is a cross-section of a railroad rail in track having a typical shelly crack in the upper gauge corner.

Referring to the drawing, the rail 10 is subjected to repeated heavy wheel loads along the tread surface 11 and the gaugeside 12 by cars operating over the track.

These heavy wheel loads cold roll the surface and build up high residual compressive stresses on the order of 20,000 p. s. i. in this outer. skin of the rail. These stresses are distributed relatively uniformly over the large area of tread surface 11, but are applied in more concentrated form to relatively small areas in the region of the upper gauge corner 15 as indicated by the dotted line, resulting in excessively large tensile stresses being set up just below the surface in said region. For this reason, shelling cracks are found almost exclusively in the region of the upper gauge corner, particularly on curved sections of rail. This internal tensile stress, together with the superimposed stresses of the heavy wheel loads when cars operate over them, eventually produces an initial rupture followed by a fatigue growth as at 16 in the drawing. The distance of the dotted line below the surface is shown exaggerated for the purposes of illustration, but is actually only a few thousandths of an inch.

I propose to prevent the initiation of shelly cracks by periodically removing from the rail while in track the outer stressed running surface of the rail in the region of the upper gauge corner, from the point A at which the wheel flange contacts the head, to a point B approximately 1" in from the gauge side of the rail. The distance A to B is referred to here as the region of the upper gauge corner.

The period for removal of outer stressed surface may be determined in several ways to insure that the stressed surface has been removed before the corresponding tensile stresses have caused the initial rupture which forms the shelling crack. One method consists in measuring the hardness of the outer surface in the region of the upper gauge corner, since this hardness is the result of cold rolling and is a function of the total wheel loads which have passed over the rail. Another method is based upon the experience of each individual road with the rate of the formation of shelling cracks under the known operating conditions. In any case, the periodic removal of excessively stressed outer surface from the region of the upper gauge corner would be effected wellrail has effected a rupture of the metal, said stressed.

surface resulting from railroad cars operating over the rails. 1

2. The method of preventing the formation of shellin in railroad rails in track, which consists in removing the stressed outer surface of the rail in the region of the upper gauge corner before the hardness of said surface reaches the predetermined point corresponding to the tensile for e within the rail which causes rupture of the metal, said stressed surface resulting from railroad cars operating over the rails.

3. The method of preventing formation of shelling in railroad rails as specified in claim 1, in which the stressed outer surface of the rail is periodically removed.

References Cited in the file of this patent UNITED STATES PATENTS 1,120,831 Mathias Dec. 15, 1914 2,237,286 Backes Apr. 8, 1941 2,704,396 Lahaye Mar. 22, 1955

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