USRE23745E - burkhardt - Google Patents

Description

Reissued Dec. 1, 1953 RAILWAY RAILHN Geor'gfe Ri Burkhardt, Qhica'gmilllc-u orig ating,lzszac'o datedecember 19's SerialiNo, 568309} December {151 1921 i cation 'forl reissuc January -.10-,- --1a52*,="sm1 9 Claimant: (Cl. 213M125) Matter enclosed inheavy brackets appears in the: original pateht' but forms no part of this reissue specification; matterprinted in italics indicates the additions;madeby reissue. I

This case is a continuation part of my pending application?Serial" *N6f"*438,31l, now abandoned, Alled April. .9, 1942, and relates to railway railshf'tne' vignclestype, i. e.,' railswhich are of substantially T-shape in cross-section, and has particular reference to an improved distribution of metal in suchrailsji for the purpose of reducing stress :concentrations therein, particularly'iinllan'd.aboutiithe head-web and base 'we'b fillts itliereoiiwhre;"according to" prior rail 'de' signs,"undesirablehighand' dangerous stress con: centrations have occurred.

Stress concentration .in.. and-about the headweb and the bases-web 'fill'etsof T-raiis causes fatigueioftmetaltin theselocationsand. are conducivetousplit heads; crackedtwebs, and-other types of rail failures. In this connection, the A. R. E. A. formulae forstresses in railway rails (page 886, A. R. E. A.,- volume 19) are based on the assumption that the stress is distributed acq cordingi to" the law that. it "increasesuirectly as the" distance'from the neutral axis? However the abrupt ""ch'angesoccurring in T-iail sections results in discontinuity in the distribution of stress. Accordingly, thsaid A. R. E. A. formulae for calculating stress in rails is, in many cases, not'everra roughiapproxi-matiomofcthermaximumszstress concentrated in the head-web and the. base welri filletstzof fa fidyriamically'aloaded? sraila' In ethr wordsj rail design practi'cesit heretofore no in rogue -do not take -'into considerationz tall 'ofc. f thei-factors esserrtial tor-reduction in stress 56011-1115 cent/ration in andab out-the" mau aw eb :andx:thex. base web' fill 'tsof T-iail ln thair theyi do not sufilclentl y 'consi'dei the relationship of the' di trihiiti'on ofmetal in the web at its junction: wi 1 the head and' th baise of the rail as well as the relation' of th v width an'd depthof the: head tom the'wwidth of the --web-: These facts tea'ch I-tlie'; necessity of a -more fundamental 'study Poi the' Je; 0 stress conditions in th unctu'resof.=head and webs-and web'with basei- Toi'thisien'd', extensivec; studies have been. '::made kWhiCl-T would establish the effect of -proportions". off the head; web and o fillets *of tlfe =rai1-*section 'on the resultingxstress:5 concentrations. The study ofthefiect of 'these proportions was made from the measurements ofstrains in the rail as shown by two 'dimensional photoelastic and strain gage tests on rails and from membrane analogy-n Tests were made on 5 models with vertical loads applied accentrically to the heads 'Ihe ibasecofethetrail wasiuniformly supporteddnisome cases. and in other; cases-the .l, base't was supported-xonly zatathe s edges to simulate the conditions resultingairclmzthe 11S'11a1fCOI16a7l/e'r5 tiecplatera Investigatic'mwas made of :the stress-o in modtels- -imwhich thei-rat-iofidepth offlange to: widtlik ofwwebawas-ikeptrcconstant and 'the ratios of width of 'i head towidth :offweb; and ratio= of- "radiuszof zfillet toawidth of Web varied;-1.Investi-.

gationwasalsmmadewo-f theeffect of 'de'ep flanges;

Therefore,-i.-tlre1-:primary ,objectof the" presentsinventionis to iprovideia :T-rail having an ecor1om-ica'han d-eiiicientmetalidistriloution:involvingcf a novel ratio..ofvwidtlr-iof web at the j-unctiomofw thefheadawebz-and theibase'eweb fillets therewith to the radii fzs'aid.lhead-.-web: andsbaser-web fillets, i: combinedwith:v a widtlfiand depth of -zthe -he'ad-,..- suchzthatihiglr and "dangerous stress-concentrate; tions inland? about-.sthehead-web andthe -:base#- wetx==fillets-;.andr throughout: the -rai1v are avoided-.2, That is iato say,:.- whilethe stressv concentration t; factor. s the ratioibetween-the stress in the fillet smiths-stress'iin'sitlie =web, ithis: factor :in a shape such as a rail, where the change in shape from iwebito h'adiand web :toibasei's rapid; -is -a simul taneous function; of 'th'erratio width and depth of i head =ton width' ofrwveb combined with "a novel radius lofi fillet to W'i'dthi-Of webvratio;tandthesem ratiosli are'" criticali'im mutually -producing a safe and emcientnraih:

According :totethei present -invention; the -radiic of 'the' head-webifilletsz are "substantially. equ'a1;-:t0= theiwidth ofithe webi-rattheljuncture oftthe headwand thel-webzlii Imother words; the headoven-fillets of a railxprodu'cedrih accordance with the present inventionvhaveiconsiderably longer-radii thant-he head'eweblfill'ets of'lra'ils producedin accordance with prior practice. As a consequence, wide bearaing'ar-eas are afforded to be engaged =by :the heads wide bearing areas-are conducive toii'oiigerclife' and" mOresatisfaEtOr-y"performance generally J of v, He'adfre-j oints if the latter areemployedtozconuf. .nectthepresentrails. Tlius; rails produce'd inaccorda'nce'with-"the"- presentinvention are specially adapted for advantageous connection-by- Hea'dfr'e'e' joints:

With the foregoingandother objectsin view?"- .wh'lch will more 'readily'appear-to those familiar withth'e art; as the-"intention "is better under stood',."the same consists in-the novel metal dis tributioii" and proportion of" parts herei'naftr more fully described; "illustrated-in the -ac'com*-=- panyingdrawings, and defined in the appended claims.

In the accompanyingdrawings: Figure 1 is an end elevation of a rail, in full lines-,5: having tits. -metal distributed. inaccord-.. ance' with the present'mventionwhile the-.- bro--- ken lines show the distortion resulting from loading the rail in the manner described.

Figure 2 is a chart showing a series of graphs indicating the results of studies of different rail sections, and teaches the ideal ratios between radius of fillets and the width of web and ratios of width of head to width of web at the juncture with the fillets.

Referring to the drawings in detail, it will be observed from Figure 1 that the present rail is of the Vignoles or T-type and comprises, as usual, a head I, web 2, base 3 and head-web and baseweb fillets 4 and 5, respectively, at the junctures of the head and the base with the web. Also, dimension lines with reference letters are shown to describe the ideal proportionof the metal distribution of the present invention.

Generally the letter C has been used to designate the width of flanges, treating the head I as well as the base 3 as such, and likewise R and U are used in the equations to designate the radii of the fillets and width of web at the juncture of the fillets therewith respectively, so that the graphs of Fig. 2 will apply equally to the head or the base and M generally designates the depth of the flanges. However, as will be seen from the drawing, an appropriate subscript is used in each case to designate the specific flange, radius or web thickness. For example, CH designates the width of the head and CB designates the width of the base, while the radii of the head fillets 4 and base fillets 5 are respectively designated as RH and RB, and the width of the web 2 at the junction of said fillets with the web is also respectively designated as UH and UB. The depth of the head I is indicated as Mn and the depth of the base is shown by the reference MB. Also the width of the head along the top line of the fishing is designated as CF.

The outer sides of the web 2 are each of a substantially flat concave curvature as conventional in rails of the Vignoles type and the point of minimum thickness of the web is between the head fillets and base fillets along a horizontal line passing through the center of curvature of the arcs. of greatest radii of the web on opposite sides of the vertical center line of the cross section of the rail. For example, in Fig. '1, the dimension T represents the minimum, width of the web, andthe dimensions UH and U represent the maximum width of the web. The

ratio of T to overall rail heights is empirically determined.

As previously indicated, the present invention relates to a new distribution of metal in the web, head and base of the rail where the factors to be considered arethe relationship of the width and depth of the head to the. width of the web and the radii of the fillets to width of web. The graphs-show that these ratios simultaneously 'affeet the stress concentration factor.

Referring first to the feature 'of'the radii of the fillets 4 and 5 joining the web 2 to the head I and the web 2 to the base 3 of therail and assuming, for example, that RH and R13 are the radii of the fillets, andUH and Us are respectively the thickness of the web at the junction with the head and base fillets, it has been found that stress concentration in said fillets increases with decrease of the ratio below one or unity and also increases again with increase of said ratio above one or. unity. In.

other words, it has been found that stress concentration in said fillets decreases rapidly to a minimum when and that R R fi-0.8 and I are the desirable limits to be placed on this ratio. The ratio of is made because the stress concentration factor is lowest'at this point. The graphs show a substantial equality in the stress concentration factor between the ratio R R R fi-(LS, and It is to be noted that there is a sharp increase in the stress concentration factor for the ratio In other words, 0.8 is just below the knee of the curve which is substantially horizontal between 0.8 and 1.6. At the point where the ratio of the curves again turn upward at an increasedrate.

Referring now to the width CH of thehead I I and the width of the base Ca in relation to the Width UH or Us of the web and the radii RH and RB of the fillets, my studies of rail stress by membrane analogy show that stress concentration increases rapidly when the ratio of width of head C to width U of web exceeds four, and likewise stress concentration increases again when thewidth C of the head is less than two and one-half times the width U of the web tion which is not less than twice the width C of the head section I.

In Figure 2 The line-marked.

contains points obtained by investigating? the old type rails, for example, the A. R. E. A. 112.1b. sections and modifications thereof such as ducing the width of the head.

5 v 'Ilie-dottd -linE- marked :11

-2.4 and- OJ shows thei efieet of 'sincreasingzthe ratio of radius of head-web fillet to width ofrwehxandemain q taming-the sameiratio iof .depthfuof hadctowidth of-web foundzixrthe firstrlines.

The line marked and 2-:-

P vREL. V

wasldr-awn throughv points obtained front-measurements tofu. rails strained as; shown -in=--Fig. v 1 a The.=.line marked -Mand l -1.0..

shows that: lowest stress -:.concentration= factors result Arom equality i-betweem the thickness. lof:

The lline :marked; a

. 1; ,-4.0 and 1.0.

15 substantially horizontalsbecause the bending J30 ofithe fianges is negligiblewhen Myianalysisof stressin 'railwayrail with curved webs shoWsthatthe shearing 'stressin'theweb increases" in'verse1y'"as the: radius of the curves.

Alsoj'when a fillet"'ra'diusiis'employed equal to. the width of webat the" point bf .1 compounding; stress concentration is a minimum? Furthermore," my' analysis demonstrates thatthe transition of the stress from web to head is'lesscritical when the radius of the filletiequals thewidth'of the web.

My experience with failed rails, particularly failureinth'e base, shows that concave tieplates and "convex rail bases cause'xthe type of bend-t." in'g'in the baseshowninF'lgure' l. Accr'dingly', g itis important" that the'radiusof the" fillet as; is inot'less'than 0.8 times 'thedepthof the. baseat the juncture or point of .tang'ency with the fillet Also "the radius ofIfilletshould not be more than 1.6 times the" depth ofxbase. The. idealratio is of course"'1.0 so"that* ati'the point of ta'ngency'with' fillet the Width of web should 5 equal the depth of base;

Thus, the graphs of Figure'2 teachth'e ideal ratios between radius of filletsand' the width of'web and ratio of. width'of head tonwidth 'of web of'the juncture with the fillet. Therseveral J illustrations" given definitely show that thesev ratios simultaneouslvafiect the stress concentrationfactor; The maximum. stress; a max, occurring'in the fillet joininghead and web and web and base "can be expressed as" a multiple") of thenominal stress; a nom, in the web; Thus. a maxzkv' nom' where'k isthe stress concentration factor.

The studies" undertaken showed that the following ,factors contribute to an increase in the max stress, .1 max.

With respect to the relation. ofithe point of load tofllletsyi. e.,'the ratio of widthof flange to-width'of web, as shown "in the graphs, the straight edge'of' the'cross section opposite the 6 t filletr 'esul-ts-"in a slight ihcre'ase-imth stressseem-kw centration factor, when The ratio the web -at the juncture ofthehead-webnllets V therewith as illustrated byVU Hf Thusyaccordin'g to'th'e drawingpthelowest limit of the .ratio":

this bending-canbe :disreg'arded.= The'zstress con-a centration, then; increases asthratio M1; U decreasesfassumings that:

iskeptconstant. v

The solid line's' in the graph were drawnwhene; three :1011 imore .pointswwere lo'bt'ainedwfrom test-i data. The-dotted. lines-were drawn when only:;; 011E501 tWOnpQiIltS could. be obtained-:from testa data; 4. The rSOlidvdOliS indicate: points confirmed 1* by; photoelastiou exhibits. :v The =:open- .;dots=. indie;

cate; r/points obtained: from test 'ameasurments-s The numerals assigned to thel'points are: the ;-test or: :exhibitrnumbers-at Points RA H 5: is. the: cr sulti'ofs tests on::a railthaving'tthe following pro-1 portionsi 1 as V. ca

Tests have [been] shown that theshapesof-the-- 'curvesor'graphs are similar when" the stress I concentration factor is platted as a function of the ratios coupled with C H C B UH and E; The most economical and satisfactory metal distribution results from making not less than 0.8 nor more than 1.6 and at the same time making and not more than 4.0

As to the feature of providing increased bearing area between the underside of a Headfree rail at the location of the fillets 4 and the top bearing surface of a Headfree joint bar, it may be pointed out that in the Headfree type rail, the width of the head at the top of the fishing may be defined in terms of the width of the web at the juncture with the head-web fillets. If R=U then the width Cr' of the head along the top line of the fishing equals ture, the point of minimum width of said web lying between the point of tangency of the headweb and base-web fillets with the web and being along a horizontal line passing through the center of curvature of the arcs of greatest radii of the web on opposite sides of the vertical center line of the cross section of the rail, the width of the web at the juncture with the head-web and base-web fillets being not less than said minimum width, the radius of each of said fillets being not more than 1.6 and not less than 0.8 times the width of the web at its juncture with the fillets, said head section at its thickest point having a depth of not more than 4 and not less than 2.4 times the width of the web at the juncture of web and head-web fillets, the maximum width of said head being not more than 4 times and not less than 2.5 times the width of the web at the juncture of the web and head-web fillets, the overall height of the rail being not more than 13 times the minimum width of web, not more than 1%, times and not less than the width of the base to provide against overturning by the resultant of vertical and lateral loads and being greater than the width of the base section which is not less than twice the width of the head section.

2. A Vignoles type rail according to claim 1 wherein the radii of the fillets are equal to the width of the web at the point of tangency of said fillets with said web.

3. A Vignoles type rail construction according to claim 1 wherein the depth of the base section at the point of tangency of the base-web fillets therewith is not less than 0.8 or more than 1.6 times the radius of the base-web fillets.

4. A Vignoles type rail construction according to claim 1 wherein the depth of the base at the point of tangency of the base-web fillets therewith is equal to the radius of the base-web fillets.

5. A Vignoles type rail having a head section, a base section, a web section, head-web fillets and base-web fillets, the sides of said web section being of a substantially flat concave curvature, the point of minimum width of said web lying between the point of tangency of the head-web and base-web fillets with the web and being along a horizontal line passing through the center of curvature of the arcs of greatest radii of the web on opposite sides of the vertical center line of the cross section of the rail, the width of the web at the juncture with the head-web and base-web fillets being not less than said minimum width, the radius of each of said fillets being not more than 1.6 and not less than 0.8 times the width of the web at its juncture with the fillets, said head section at its thickest point having a depth of not more than 4 and not less than 2.0 times the width of the web at the juncture of web and head-web fillets, the maximum width of said head being not more than 4 times and not less than 2.5 times the width of the web at the juncture of the web and headweb fillets.

6. A Vignoles type rail having a head section, a base section, a web section, head-web fillets and base-web fillets, the sides of said web section being of a substantially flat concave curvature, the point of minimum width of said web lying between the point of tangency of the headweb and base-web fillets with the web and being along a horizontal line passing through the center of curvature of the arcs of greatest radii of the web on opposite sides of the vertical center line of the cross section of the rail, the width of the web at the juncture with the head-web and base-web fillets being not less than said minimum width, the radius (of each) of said head-web fillets being not more than 1.6 and not less than 0.8 times the width of the web at its juncture with the head-web fillets, the depth of the base section at the point of tangency of the base-web fillets therewith being not less than 0.8 or more than 1.6 times the radius of the base-web fillets, and said head section at its thickest point having a depth of not more than 4 and not less than 2.0 times t e width of the web at the juncture of web and head-web fillets, the maximum width of said head being not more than 4 times and not less than 2.5 times the width of the web at the juncture of the web and head-web fillets.

7. A Vignoles type rail having a head section, a base section, a web section, head-web fillets and base-web fillets, the sides of said web section being of a substantially flat concave curvature, the point of minimum width of said web lying between the point of tangency of the headweb and base-web fillets with the web and being along a horizontal line passing through the center' of curvature of the arcs of greatest radii of the web on opposite sides of the vertical center line of the cross section of the rail, the width of the web at the juncture with the head-web (and base-web) fillets being not less than said minimum width, the radius (of each) of said fillets being not more than 1.6 and not less than 0.8 times the width of the web at its juncture with the fillets, said head section at its thickest point having a depth of not more than 4 and not less than 2.0 times the width of the web at the juncture of web and head-web fillets, the maximum width of said head being not more than 4 times and not less than 2.5 times the width of the web at the juncture of the web and headweb fillets, the width of the web at the juncture with the base-web fillets being not less than said minimum width, the of the base-web fillets being not more than 0.3 and not less than 0.5 times the width of the web at the juncture with said base-web fillets.

8. A Vignoles type rail having a head section, a base section, a web section, head-web fillets and base-web fillets, the sides of said web section being of a substantially flat concave curvature, the point of minimum width of said web lying between the point of tangency of the headweb and base-web fillets with the web and being along a horizontal line passing through the center of curvature of the arcs of greatest radii of the web on opposite sides of the vertical center line of the cross section of the rail, the width of the web at the juncture with the head-web and base-web fillets being not less than said than 4 and not less than 2.0 times the width of the web at the juncture of web and head-web fillets, the maximum width of said head being not more than 4 times and not less than 2.5 times the width of the web at the juncture of the web and head-web fillets, the width of the web at the juncture with the base-web fillets being not less than said minimum width, the radii of the base-web fillets being not more than 0.8 and not less than 0.5 times the width of the web at the juncture with said base-web fillets.

9. A Vignoles type rail having a head section, a base section, a web section, head-web fillets and base-web fillets, the sides of said web section being of a substantially fiat concave curvature, the point of minimum width of said web lying between the point of tangency of the headweb and base-web fillets with the web and being along a horizontal line passing through the center of curvature of the arcs of greatest radii of the web on omiosite sides of the vertical center line of the cross section of the rail, the width of the web at the juncture with the head-web (and base-web) fillets being not less than said minimum width, the radius (of each) of said fillets being substantially equal to the width of the web at its juncture with the fillets, said head section at its thickest point having a depth of not more than 4 and not less than 2.0 times the width of the web at the juncture of web and head-web fillets, the maximum width of said head being not more than 4 times and not less than 2.5 times the width of the web at the juncture of the web and head-webfillets, the width of the web of the juncture with the baseweb fillets being not less than said minimum width, the radii of the base-web fillets being not more than 0.8 and not less than 0.5 times the width 0 the web at the juncture with. said base-web fillets.

GEORGE R. BURKHARDT.

References Cited in the file of this patent or the original patent UNITED STATES PATENTS Number Name Date 2,260,211 Burkhardt Oct. 21, 1941 FOREIGN PATENTS N umber Country Date 1,856 Great Britain May 29, 1875 ()TI-IER REFERENCES Stress Concentration Produced by Holes and Fillets, by S. Timoshenko and W. Dietz, American Society Mechanical Engineers, Transactions 1925, page 212, section et seq.

Torsion in Structural Beams, by F. L. Ehasz, Lawrence Calvin Brink, Research Fellow in Civil Engineering, Lehigh University.

Railway Age, December 12, 1942, pp. 953-967, vol. 113, No. 24.

Steel Rails, by William Sellew. Plate No. XVII, deposited in the U. S. Patent Ofiice Library June 26, 1941, printed in 1913 by Van Nostrang Co. of New York.

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