WO1995035413A1

WO1995035413A1 - Railway rails

Info

Publication number: WO1995035413A1
Application number: PCT/RO1995/000006
Authority: WO
Inventors: Stefan Radulescu
Original assignee: Stefan Radulescu
Priority date: 1994-06-22
Filing date: 1995-06-19
Publication date: 1995-12-28
Also published as: CA2152404A1; EP0703316A2; AU2480695A; EP0703316A3; RO111255B1

Abstract

The disclosure relates to heavy-mass railway rails wherein an increased fatigue resistance is achieved by increasing the moment of inertia of cross section of rail and by increasing the ratio of fatigue loading, a sub-unity ratio given by the specific moments of fatigue of the two halves of cross section of rail defined by the horizontal neutral axis of cross section of rail, or by the squares of normal unity fatigue stresses, which are maximum at the two vertical extremities of cross section of rail.

Description

Railway Rails

BACKGROUND OF THE INVENTION

1. FIELD OF THE INVENTION This invention relates to heavy -type railway rails for rolling stock capable of supporting an increased traffic on the track.

2. PRIOR ART

In the domain of high-speed and heavy-haul railway rails, several types of heavy -masse railway rails are known in which such rails sustain increased loads as the area of cross- section of rail and the moment of inertia of cross-section of rail are increased as well. Among the mostly used rail types are type 54E STAS 9592-74, type 60 STAS 11198-79, type R65 STAS 11201-79, all of Roumania, types S60 and S64 of Germany, types 112 lbs and 155 lbs of United States. These types can be found in an extented list of rail types given in "Schweisstechnisches Taschenbuch", Edition 1968, Elektro-Thermit Corp., Germany. Such rail types achieve increased loads solely by increasing the moment of inertia of cross-section of rail, with the result that the load of fatigue of rail increases at a lower rate compared to the moment of inertia of cross-section of rail, thus increasing the cost of railway. This result is more visible in case of heavier heavy-type rails.

However, no rail type with a masse great than 51 kg/l.m. is known in which the stress applied to the rail head is decreased by increasing the moment of inertia of cross -section of rail and by increasing a height between the rail base and the neutral axis of rail while the moment of fatigue of rail base and the moment of fatigue of rail head are so balanced as to obtain an increase of the endurance of the rail.

SUMMARY OF THE INVENTION

These disadvantages are overcome by the present invention by creating a novel heavy-masse rail type. The present invention comprises a rail composed of at least two rail portions. It is an objective of the present invention to provide a rail having an increased moment of inertia of cross -section and an increased height from the. lower side of rail base to the neutral axis of the rail. It is another objective of the present invention to obtain a balanced stress in the rail base and in the rail head by providing a rail in which the ratio of the moment of fatigue of rail base divided by the moment of fatigue of rail head is between 0.9 and 1.

It is yet another objective of the present invention to provide a heavy-type rail with increased load of fatigue.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be further illustrated by reference to the accompanying drawing, in which:

FIG. 1 is the schematic representation of a method of implementation of railway rails of heavy type with increased fatigue resistance, according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The description is made with reference to heavy -type railway rail.

The present invention introduces new relations related to endurance of materials, and of bars subjected to bending test, respectively. The general equation of bending momentum for a bar simple-standing loaded with a load of fatigue P is given by the relation:

The bending momentum is balanced by the sum of moments given by unitary normal stresses of the bar. It is known that such stresses are null upon the horizontal neutral axis and maximum at vertical extremities of the bar. It is derived that:

where: is the specific moment of fatigue of the

upper side of rail head,

M is the specific moment of fatigue of the

lower side of rail base,

are the unity normal stresses of

fatigue of rail head and rail base, respectively,

H _c is the height of rail head with respect to the horizontal neutral axis of rail,

H_t is the height from the lower side of rail base to the horizontal neutral axis of rail,

ω → 1 mm² is the minimum area element.

The present invention introduces the ratio of fatigue loading of cross -section of rail, defined as:

is a sub-unity ratio given by the ratio of the

two specific moments of fatigue. Alternatively, R_iob is given by the ratio of squares of the heights of rail base and rail head, respectively, with respect to the horizontal neutral axis of cross -section:

From the equality of relations (2) and (3) it is derived that:

With the characteristics of laminated material for rail, which generally is σ_r = 90 kgAmm², it results a maximum unity stress of fatigue equal to for a number of fatigue cycles

N = 10⁷, for rails which do not exceed a certain average height.

Considering in relation (1), it is known

from the curbes of Wohler that as the area of cross- section of rail increases, decreases, and this

is the case of heavy -type railway rails. From relation (1) it is derived that = 2280kgx mm , which is used

for designing.

With these relations, the following conclusions are derived:

1. The ratio of fatigue loading of the two halves of cross-section of a railway rail of heavy type, where the two halves are determined by the horizontal neutral axis of cross- section, the ratio being defined as sub-unity and given by their specific moments of fatigue or by the squares of heights of the two cross -section halves, should be between 0.9 to 1, in order to balance the unity normal fatigue stresses in the two cross -section halves.

2. Any increase of the area of cross -section of railway rails with a masse of at least 51 kg/l.m. should be done in accordance with paragraph 1, having as final result an increase of the lifetime of rails or of the sustained traffic to maximum values.

It is further given an example of implementation of heavy-type rails according to the present invention. Refering to FIG. 1, the left side with respect to vertical axis Y-Y represents the current standard rail, while the right side represents the rail of the present invention. These rails are composed from a rail head 1 at their upper side, a rail web 2 at their center side and a rail base 3 at their lower side. The difference between the two rails is given by the added height h, located at the upper side of rail head.

The standard rail has the moment of inertia

and the height where and represent

the heights of cross -section with respect to its horizontal neutral axis Xo-Xo.

In order to increase the moment of inertia of the cross-section of rail to Ix, the upper side of rail head is increased with a height h, which makes He to slightly increase with respect to Hco. However, Ht increases significantly with respect to Hto, considering the rising of the center of weight, and the new axis X-X, respectively. As it is observed in the right side of FIG. 1, the increase of the moment of inertia Ix is significant by increasing the height of the entire cross- section, while the increase of the ratio of fatigue loading:

is improved by the significant increase of H_t with respect to H_c.

There are further given three examples of calculus and the advantages obtained following the conclusions above.

A. Rail type UIC60

General characteristics:

M = 6034 kg/ L m .; S = 76.86 cm² ; I_X = 3055 cm ⁴ ; = 335.5 cm³ ;

L_t = 150 mm ; H = 172 mm ; H_c - 9 1 mm ; H _t = 81 mm

M

with and N ≃ 10⁷ cycles for the same

characteristics of material. It is obtained:

In the case of a rail simple- standing with an opening of 1 m, the moment of fatigue is:

and the load of fatigue is:

B. Rail type UIC60' (modified)

In order to increase R_iob , the geometry of rail is modified by increasing the height of rail head at the upper side with a height h = 6 mm, such that:

H' = H + h = 178 mm

The width of rail head is increased to 76.2 mm to make possible a comparisson with similar rails.

General characteristics resulted:

M' = 64. 7kg/1. m. ; S ' = 82, 44cm²; I '_x = 3460cm⁴; W'_xc = 381cm³; L_t = 150mm; H' = 178mm; H_c ' = 90. 8mm; H_t ' = 87. 2mm;

The position of the new center of weight, or the height H_c ' of the horizontal neutral axis, respectively, is computed through the method of static moments with respect to the upper side of the new rail head. The moment of inertia I_x ' is computed with respect to the new neutral axis. It results;

C . Rail type R65

General characxteristics :

M = 64.93 kg/1.m, ; S = 82. 65 cm² ; I_x = 3540 cm⁴; W_xc = 358 cm³ L_t = 150 mm; H = 180 mm; H_c = 98. 7 mm; H_t = 81 . 3 mm

It is obtained :

Conclusions:

It is observed that for the rail of type UIC60' (modified) an increase of the moment of inertia of cross - section of rail is obtained at the same time with balancing the unity stresses of fatigue in the two halves of cross-section of rail, reaching a load of fatigue greater with 15.5%, than in the case of rail R65, even for a masse and height of rail smaller than in case of rail R65, assuming the same characteristics of material.

Note:

The data presented as general characteristics for examples A, B, C are taken from oficial national standards and from "Schweisstechnisches Taschenbuch" of Elektro-Thermit Corp.

Claims

CLAIM What is claimed is:

1. A railway rail of heavy type with a masse of at least 51 kg per linear meter, said rail being composed of a rail head (1), a rail web (2) and a rail base (3), characterized in that the sub-unity ratio of fatigue loading (Ri.ob) determined by the specific moments of fatigue at said rail base

(Mob.sp.t.) and at said rail head (Mob.sp.c.) of the two halves of cross-section of said rail defined by the horizontal neutral axis of cross-section of said rail, or determined by the squares of the inferior height (Ht) and superior height (He) with respect to same horizontal neutral axis, is between 0.9 to 1.

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