US2717739A - Head bearing rail joint - Google Patents

Description

Sept. 13, 1 G. R. BURKHARDT ET AL 2,717,739

HEAD BEARING RAIL JOINT Filed May 51, 1951 mf 3 m d T r W. w P MVIM mm F m r0 MW 5 ur ..M m BB c m m R m 1 m H F F 1? i m I- GE w S O P w.

m o 0 O 5 O moGE zoEEzwuzoQwWwEm ATTO RNEYS of rail shows that the contact must be confined to the aforesaid sector above the line joining the center of the radius of the fillet and the intersection of the underside of the head with the vertical center line of the section of the rail.

In Figure l, the available head bearing area extends from the juncture of the head-web fillet with the web throughout said head-web fillet and including a short tangent connecting this fillet with the fillet determining the under outer portion of the rail head. In Figure 2, the available head area is similar to Figure 1, except that the tangent is longer. Thus, if the head of the bar is provided with a short tangent at the upper and outer terminus of the arc defining the major bearing portion 5, the application of the invention is not altered as indicated by dotted line 5a in Figure 2.

The wear produced by the conventional head-free bar extends throughout the hatched area of Figure 1, but the horizontal hatching on the left hand side of Figure 1 shows the zone of heaviest wear of the web produced by the head-free bar B while the vertical hatching shows the location of wear that will occur in the preferred area with the present improved head bearing bar A.

The point of maximum stress in the rail is substantially at the location of the point of tangency of the head-web fillets with the web, and progressively diminishes towards the intersection of the head-web fillet with the head substantially at the point indicated by the radius line RA. The range of bearing between 4 and 5 is indicated by line 9 and radius line RA. The centroid of the preferred are of bearing support is indicated by line 13 which is above the region of maximum stress.

Figure 1 shows a 1l2-lb. T. R. rail with bar A having its upper inner head portion shaped so that the position of centroid of the curved bearing is in the area of low stress under the head. This is the result of confining the bearing between head and bar above the line 9 joining the center of the radius of fillet and the intersection of the vertical center line of the rail and the lines 11 defining the underside of the head of the rail.

The bar B is the usual type of head-free bar in which a substantial portion of the bearing area is below the line 9 drawn from the center of the radius of the fillet to the intersection of the vertical center line and the underside of the head of rail. In this case, the centroid of bearing is in an area of high stress so that the bearing stresses are additive to the compressive stresses resulting from the strain of the fillet under eccentric load on the head of the rail.

The force diagrams in Figure 1 indicate that the vertical component of the force through the centroid of bearing is much greater with bar A than with bar B so that more support for the head results with bar A than bar B and the horizontal component is lower so that less wear is to be expected in a horizontal direction. The scale in Figure 1 provides ready reference to the position of the centroid of the bearing.

Studies have been made of rails and joint bars to determine the effect of controlling the centroid of the curved bearing surfaces under the head of the rail so the wear of the web would be reduced and so that the centroid of the bearing would be changed from an area of maximum stress to an area where tests of steel rails and plastic models used with polarized light have shown the stress to be low.

The maximum stress a max. occurring in the fillets at the junction of the head and the web may be expressed as a multiple of the nominal stress at juncture of fillet and web, a nom.=P/ U. Accordingly, a max.:k a nom. where k is the stress concentration factor.

k stress concentration factor 4 Uh =width of web at juncture with fillets Z=length of rail affected Figures 1 and 2 illustrate the force triangles above described. In these diagrams the resultant of the force through the centroid of the bearing is indicated as 2. Since this is constant in magnitude the length of the hypotenuse in each of the triangles is the same. The resultant is resolved into vertical and horizontal components to show graphically the relative magnitude of the force applied to the rail vertically and horizontally. The letter V or H indicates direction. The subscript A, B, C, or D has reference to the joint bar with corresponding letter. Referring to Figure 1, it is noted by use of dividers or by marking a piece of paper that VA is about five divisions on the scale in Figure l, and HA is three so that with improved bar A, the vertical force is 1.6 times the horizontal force. VB is three divisions on the scale, and HE is five divisions so that in the old type bar B, the vertical force applied to the rail is only 73 of the horizontal force applied so wear of the web results instead of wear of the metal under the head. Similarly in bar C, V0 is four divisions of the scale in Figure 2, and He is three, whereas in the A. R. E. A. type bar D, VD is 3 /2 divisions and HD is slightly more than four.

Our observation of photoelastic exhibits and strain of models indicates that there are five principal factors which contribute to the reduction of k, namely:

(1) Distribution of metal in the rail so that the width of the web at the juncture is substantially equal to the radii of the fillet joining head and web or within the range of not less than 0.8 times or more than 1.6 times the width of the web at the juncture of the web and fillets, as covered in Burkhardt Patent No. 2,577,601.

(2) Control of bearing between rail and joint bar so that the centroid of the curved bearing is in an area of low stress under the head of the rail.

(3) The proximity of the centroid to the juncture of web and fillet.

h (:11) The proximity of the centroid to the edge of the (5) The bending of the flanges of the head as covered by Burkhardt application Serial No. 568,309 which shows that stress concentration in the fillets is a minimum when the depth of the head is four times the width of the web at the juncture with the head-web fillets and that the stress concentration increases as the depth of the head is reduced.

Figure 2 shows the A.R.E.A. 115 joint bar C with the improved curved surface head-free bar, while the head portion of the bar D shown in dotted lines is the old standard bar for this rail. The application of the invention in this view is the same as that described in connection with Figure 1, and is presented to show that the invention is of such range and scope as to be applied to all rail sections.

The effect of the proximity to the juncture of web and head-web fillets is seen in Figure 3 which shows that the stress concentration factor k increases rapidly as the centroid approaches the juncture of web and fillets. The value of k is 76% of the maximum when the centroid of the bearing is in the position occurring in bar B and only 58% with bars A and C. The stress concentration is 68% with bar D.

We claim:

1. The combination, comprising, a vignoles rail including a head, a web, a base, curved fillets joining the head and web, and joint bars having head portions engaging the major portions of the curved fillets, said head portions formed on an arc having the same center as the radii of the fillets and in initial and permanent bearing engagement therewith in the zone of lowest stress in the head fillets of the rail, said zone lying between the underside of the head of the rail and the line drawn from the center of the head web fillets to the point of intersection of the vertical center line of the rail head and the underside of the head of the rail.

2. The combination, comprising, a vignoles rail including a head, a web, a base, curved fillets joining the head and web and joint bars having head portions engaging the major portions of the curved fillets, said head portion formed on an arc having same center as the radii of the fillets and in initial and permanent engagement above a line drawn through the center of the radius describing the headweb fillets and the intersection of the underside of the head and the vertical center of the rail section to locate the centroid of the bearing above the region of maximum stress.

3. The combination, comprising, a vignoles rail including a head, a web, a base, curved fillets joining the head and web, the radii of said fillets being not less than 0.8 times and not more than 1.6 times the width of said web at the point of juncture of the web and fillets, and joint bars having head portions engaging the major portions of the curved fillets, said head portions formed on a an are having the same center as the radii of the fillets and in initial and permanent bearing engagement therewith in the zone of lowest stress in the head fillets of the rail.

4. The combination, comprising, a vignoles rail in- 1 cluding a head, a web, a base, fillets joining the head and web, the radii of said fillets being not less than 0.8 times and not more than 1.6 times the width of said web at the juncture of the web and the fillets, and joint bars having the major portion of their hearing area formed on an arc whose radius is equal to the radii of the fillets joining the head and web, said bearing area engaging and supporting the head-web fillets and rail head above a line drawn from the center of the radius of the fillet joining the head and web of the rail to the intersection of the vertical center line of the web with the junction of the intersecting lines defining the lower limit of the underside of the head of the rail.

5. The combination, comprising, a vignoles rail including a head, a web, a base, fillets joining the head and web, and joint bars having the major portion of their bearing area formed on an arc whose radius is equal to the radii of the fillets joining the head and web, said bearing area engaging and supporting the head-web fillets and rail head above a line drawn from the center of the radius of the fillet joining the head and web of the rail to the intersection of the vertical center line of the web with the junction of the intersecting lines defining the lower limit of the underside of the head of the rail.

6. An improved head bearing rail joint bar for use with vignoles rails having a head bearing area extending from the juncture of the head-web fillet with the web to juncture with the outer under head fillet and the underside of the head of the rail, said joint bar having a head which engages the portion of the head-web fillet in the zone of lowest stress of the fillet lying above a line drawn head-web fillet above a line drawn from the center of the radius of the said fillet to the intersection of the vertical center line of the rail with the junction of the intersecting lines defining the lower limit of the underside of the head of the rail.

8. The combination, comprising, a vignoles rail including a head, a web, a base, curved fillets joining the head and web, and joint bars having head portions engaging the portions of the curved fillets of the rail head lying in the zone of lowest stress of the rail head, said zone comprising the sector of the fillets lying between the point of tangency of the fillets with the under side of the head of the rail and the line drawn between the extremity of the radius of the fillet and the intersection of the plane of the under side of the head of the rail with the intersection with the vertical center line of the rail, said head portions of the bars being formed on an arc having the same center as the radii of the rail fillets and in initial and permanent bearing engagement therewith.

9. The combination, comprising, a vignoles rail including a head, a web, a base, curved fillets joining the head and web, and joint bars having head portions engaging the portions of the curved fillets of the rail head lying in the zone of lowest stress of the rail head, said zone comprising the sector of the fillets lying between the point of tangency of the fillets with the under side of the head of the rail and the line drawn between the extremity of the radius of the fillet and the intersection of the plane of the under side of the head of the rail with the intersection with the vertical center line of the rail, the radii of the fillets coincident with said line drawn to said intersection being not less than 0.8 and not more than 1.6 times the thickness of the Web at the juncture with said head web fillet, said head portions of the bars being formed on an arc having the same center as the radii of the rail fillets and in initial and permanent hearing engagement therewith.

References Cited in the file of this patent UNITED STATES PATENTS 1,791,390 Thompson Feb. 3, 1931 1,831,227 Clark Nov. 10, 1931 1,967,509 Jackson July 24, 1934 OTHER REFERENCES Seely and Ensign: Analytic Mechanics for Engineers, John Wiley and Sons,. 1921, copy of which is in the Patent Ofiice Scientific Library.

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