E L S E V I E R Wear215 ( 19981 18-24

WEAR

Wheel flange/rail head wear simulation

Sergey Zakharov *, Igor Komarovsky, Ilya Zharov AII.Rux*ia, Ruihray Rc.~eurch I,.l'tilute, 103-d ~lvli.~hin.~'ktmya. 129851 Mosc~lr. Ru~.~ian ~,dentli~m

Received 18 July 19t)7: accepted I1 Pecember tt)97

Abstract

The diftict:lties and expenses involved in field experiments on wheel-rail system wear forced researchers to use. whenever possible. lal'~r.qory texts. The major problem in laboratory tests is how to transfer the results obtained to the real wheel-rail system. Modeling of the wear process between wheel flange and side face of a rail head is studied and discussed. It is noted that the laboratory tests with rolling-lateral ~liding better simulates wheel flange and rail head wear. Four wear modes, refi:rred to as mild. severe, heavy and catastrophic, have been identified in the lal~ratory tests. The heavy wear mode has not been identified beft~re. The catastrophic wear mode has been observed at the lateral creepage of 5%. The wear mtvdes that occur in worn wheel flanges and in side-worn rails have been found to correlate with those tkmnd on the rollers during lalx~ratoD" tests. The boundaries of wear modes in terms of product of maximum contact pressure and creep value were defined. The hypt~thesis of wear mechanisms responsible for wear processes wa~ suggested. © 1998 Elsevier Science S.A.

Kcywt,rd~: Wear traMe~.: Rolling-r, liding: Wheel: Rail

!. Introduction

It is known that in the process of wheel- ra i l interaction. particularly in curves, the wheel flange and gauge lace o f rails are the subject o f intensive wear. Although ra i l /wheel lubri- cation considerably decreases the wear rate o f b o l h elements. still wear may be comparat ively great especially under heavy haul railroad conditions, in steep curves and when the lubri- cant lilm is worn out. Wheel flange and rail gauge face wear is a major factor in railroad maintenance cost. To compete with other mtxles o f transport, railroads have to maintain an optimal maintenance technology that is a result o f balancing between rail lubrication, rail grinding and wheel flange turn- ing scheduled practices.

Over the years, wheel- ra i l wear has been extensively stud- ied. A review of experimental research in this field has been given by Clayton I I I. Some of these studies were laboratory tests 12-81. and some were simulated field experiments t 9 I. The difficulties and expenses involved in field experiments fierce researchers to use, whenever possibi¢, the laboratory tests.

The major problem of the laboratory tests is how to transfi:r the results to the real wheel- ra i l syslem. The considerable dif l icuhies involved in this problem and criteria to be satisfied have been described in Refs. I 1.2.61. The present work is

- Corre)l~mding author. Tel.: + 7-W95-2~7-733{~: Ihx: * 7-0t)5-287-723~.

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another attempt to use laboratory simulated tests for the pre- diction of wheel-ra i l wear.

The simulation of wear process between the wheel flange and side Ihce o f a rail head is understood as the transfer to the real wheel- ra i l system: the wear rate as a function o f maxinmm contact pressure and average creep, and wear rate as a function of their surface hardness.

When perft~rming simulation tests using the roller model. it is assumed that: ( i ) wheel slip due to braking is not con- sidered: ( ii ) the wear rate depends on creep, but not on the absolute velocity, and thermal effects are neglected: ( iii ) the dependence of the friction coefficient from creep components at simulation tests is considered similar to that of the real wheel- ra i l system: and ( iv ) although the wear process of the real wheel-rai l system is not in steady-state, in simulation tests, wear is considered as steady-state after the running-in period.

Therelbre. it is difficult to justify the successful correlation between the laboratory results and those in the lield, based only on load and kinematics simulation.

Another approach I I 01 for the justi l ication of transt~rring the results obtained from the laboratory tests requires simi- larity of wear mechanisms that are characterized by ( I ) the wear rate. (21 surface layer thickness and microhardness distribution along layer 's depth. (3) worn surface features, particularly its roughness, and (4) size. morphology and color of wear debris.

s. i~tkharov et aL / tV¢itr 2 1 5 1 1 0 9 ~ 1~-24 19

Thus. laboratory wheel-rail wear simulation requirescom- parison of wear parameters at the similar wear modes, thus providing correct utilization of the laboratory test resulls.

The main objectives of the present study are: ( i ) to design criteria for laboratory accelerated wear simulation testsallow- ing the reproduction of the desired type of wear: (it) to elaborate more realistic dependence of the wear rate on the contact parameters since many authors gave different and sometimes contradictory ones: and ( iii ) to make ,a classifi- cation of surfaces and to lind the relation between the surface class and the wear rate.

2. E x p e r i m e n t a l m e t h o d

Laboratory experiments were carried out on the rolling- lateral sliding wear testing machine in unlubricated condi- lions. The lateral creep was achieved by setting rollers axes under defined angle in relation to each other. The rollers. 4() mm in diameter. 6 and 10 mm wide. were mounted on two horizontal shafts. The shaft axes were skewed in relation to each other on a changeable angle allowing to simulate lateral creep 2.5.5 and I 0 ~ . The load was applied to the upper a, ller by lever with weights producing the contact pressure from 300 to 1100 MPa. The rollers" speed was 500 rpm. All rollers were machined from rail heads, and wheels which were man- ufactured from the standard rail and wheel steels (Table I 1. The rollers" surlhces were g n , u n d . The average rollers" sur- face hardness was 2(h0 H B.

This scheme of testing better simulates wheel-rail inter- action conditions than that in the Amsler tests, it is known that in a process of wheel flange/rail head interaction, lateral creep is generally comparable with the longitudinal creep, in sharp curves, the contribution of the lateral creep become predominant because of the increase of the angle of attack. A selected scheme of testing allows the avoidance of the wear debris's accumulating efl~ct and the roller's surfaceoxidation process, considerably affecting the test results. Besides, dur- ing tests, the surfaces of the upper and the lower rollers are similar, thus avoiding the necessity to select the right roller ft,r the study. All this gives more confidence in the test results. since during these tests, both interacting materials, but not their oxides or "third body" objects are tested.

The rollers" surfaces were subjected to primary examina- tion primary after every 50iX) revolutions of n,tlers up to 20 (X}(} revolutions and further afterevery 10 000revolutions. Examination of rollers comprised its weighing to find volume wear. surface photography attd the wear debris analyses.

The rollers" surface li:atures were studied using the Quantimet 520 image analyzer. The evaluation of freight cars' wheel set displacements has shown that the maximum range of creep is 2-10c~. The estimated average pressure in the contact zone depending on the axle load and curve nego- tiation conditions ranged from 500 to more than 2(XH) MPa.

The wear rates were calculated in milligrams of rollers" weight loss per meter rolled by a rol]er, per the narrowest

Table I Chemical compo~ilion of rail and ~,,heel ~,tceb,

Steel Chemical coml'x~sition ! " ; I

C Mg Si F S

Rail n.75 I .n5 41.22 t1.1127 0.023 Wheel n.62 0.63 0,29 0.023 U.02 !

2.5

¢1l 2

1

05

W e a

r

(a)

• -B...-2.5%. 119kg i --~--5%. 97 kg [ --'e-- 10%, 42 kg [ - ~ - m % . g k g [

20 40 60 80 I00 T lmtmands o f ro l lm~" revo lu t i ons

2 3

(b)

j j ~ f J

R o l l e r s ' r e v o l u t i o n s |-ig. 1. Dependence t,t' total ~ear on the number of roilerr." revtflutil,n,,: I a J .u r experiment.,. I h) .general ~xear cur,.e.I. 2. 3 and 4 wear ,.t;,ger.•

roller width, e.g../.tg m z mm 1. To evaluate an intluence of additional running-in after the samples" weighing, wear loss of two pair of rollers was measured after 50(X). IO (XX). 20(X~. 3()(XX). 40(XX) revolutions and after IO{XX) and 40 ()IX) revolutions, correspondingly. The difference in the results was not significant.

Four wear stages can be distinguished from the wear rate vs. the rolMrs" number of revolutions curve ( Fig. I }: ( I ) wear of surface It[ms. (2) running-in period. (3) minimum wear rate. and ( 4 } quasi-steady wear rate stagc.s. As it is clear fnnn Fig. I a. wear rates vary from one .stage to another. More than that. it was found that for different contact pressure. creep and surface hardness, the duration of the wear •sta,,es= may vary considerably.

if the base of testing N is wrongly selected, one may fall into a mistake, as at the small load. it may be the first stage. at the medium load. one may pass the first and the second stage, at the high load-- three sta,,es~ .. and at the maximum load--all hmr stages.

it was decided to determine the wear rates in the inflection point of medium part of the third stage t Fig. Ibm. This choice was justified by the lbllowing: (i) the wear rates at the firs| and second sta,,es are not steady-state, highly dependent on

20 S. Zakharov el aLI Wear 21511998~ 18-24

the initial ,sample settings; ( i i) to determine the wear rate at the fourth stage requires long tests and is influenced by changes of rollers" diameters due to wear; ( iii ) a wear curve in the mean part of the third stage is close to a straight line in an interval of several thousands of revolutions, thus providing sufficiently acute wear rate measurements; ( iv ) most of the results of other authors were obtained at the third wear stage, thus making it possible to compare them.

It ~ e m s that these reasons were not always fully consid- ered when performing the wheel-rail laboratory simulating tests I i i .

3. Experimental results

In Refs. 12.3 ], the wear rate was studied as a function of the TA/A parameter, where T is tangential force, A is the slide-to-roll ratio (creep), and A is the Hertzian contact area. It was found that pA, wherep is the contact pressure and A is the creep, is a more suitable parameter for the description of the wear modes and the wear mechanisms when the friction coefficient is stable. Parameter TA/A differs from that o fpA only by -a"f/4 factor, w h e r e f i s the coefficient of friction, It was also found that the total wear rate of both rollers is a more convenient parameter for study and analyses than that of a separate roller. This is because the total wear is more stable to the variation of external conditions: its change dur- ing the wear process is much less than that of a separate roller: thus. reproduction of the test results is much better. Besides. the total wear is a criterion for the optimization of wheel-rail as a system, especially when the wear resistance of both malerials are close to each other.

The results of the tests are shown in Table 2. Fig. 2 shows how the wear ra'e varies with the parameter

pA. For comparison. Table 3 gives the data obtained by Danks and Clayton 161 on an Amsler test machine with rollers 5 mm in width and about 35 mm in diameter under roll ing- longitudinal sliding test conditions. Surface hardness of rollers was 247 HB.

Fig. 3 shows the corresponding wear rate vs. the parameter pA. Ascan be seen from Figs. 2 and 3a, the wear rate increases with the increase of the pA parameter, but then the wear rate decreases. Corresponding changes occur on the surfaces of rollers even at the steady-state stage of wear I Fig. 4) .

Three regimes (modes) of wear has been identilied in Re lg. [ 1-31, which were referred to as Type i (mi ld) . Type II (severe) . and Type I!1 (catastrophic). Examination of roll- ers" surfaces, measuring the wear rate. analyses of the wear mechanisms indicated that between severe (Type II) and catastrophic (Type I11). there is the heavy wear mode. The present study allowed to verily approximate pA transition values and the wear rates corresponding to the wear modes (Table 4) . It is important to note that these values are valid for the particular rail /wheel steels used in the experiments and possibly the test rig. Therelbre. the transition values of

Table 2 Variation of the total wear rate ( g.g m - ~ ram- i ) of rollers made of wheel and rail steel with the contact pressure (p) and the laueral creep ( A )

C~cpl ~ ) Conlaclp~sstt~ (MPa)

311 3~5 450 498 688 837 963 l l~3

2.5 13 t7 24 5.0 13 29 40 31 25 10.n 36 60 93 82 44 29 16

E °,oo[ , o 6o ,o

o 0

o 50 tO0 150

p 2 MPa Fig. 2. "l'otat wcar rate versus the pA parameter obtained for lateral creep tests.

Table 3 Variatitm of the totul ",,,'car rate (/.t.g m ~ mm ~ ) of roller made of wheel and rail steel with the contact pressure and the kmgimdina[ creep ohtaincd on the Amsler texts [ ¢01

Creep ( c/, ) Contac! pressure ( MPa )

5IX) 6(XI 700 800 9(XI liMI) 1080 1140 1280

3 4 13 29 33 5 21 4[ 53 05 7 33 O0 76 51 65 77 54 60

I() 72 77 93 55 63 53 3[ 25 S48 2531 5710 8854 35 2058 6783 13 3(R) 16621

l= = t0o

~ 60 -~ 40 E 2o

o 50 100

9,,l MPa

E 20UO0

E t5UO0

::L IO000

5000

0

7% I + I0% I

150

/ 20O 4O0

p,~ MPa Fig. 3. Tot;,[ wear rate vcr~;us the pA paramch:r obtained for longitudinal ,:ro:p te..,e, I h I: ( a I creepage 3-if)Y;. ( h ) creepagu 10-35'~);.

S. Zakharm, et ~L / Wear 215 ( If~Xj IB-2d 21

Fig. 4. Weur surfaces of 6 mm wide miler made from wheel steel. -'teepage 59: p~ = 48,

Table 4 Wear modu ranges and rates

Wear modes pA ( MPa } Total wear rate

mmrev-~×l(~' p.gm 'mm '

Mild < 20 O. I-!.6 0.8-12.5 Severe 20 ..... ( 40-60 ) 1.7- I 1.9 13.3-92.9 Heavy (4n-60) ..... 120 I 1.9-2.O 92.9-15.9 Cata.,q rophic > 120 109-2130 848--t f~ )

the parameler pA from the severe to the heavy wear modes turned out to be in a range from 40 to 60 (Table 4) .

3. I. W e a r m o d e a n a l y s e s

Mild wear is characterized by the bright surface of rollers and by the large thin metallic flakes that were tormed at the surface of the rollers ! 2 I. Severe wear is characterized by the surface shown on Fig. 4a, The wear rate grew intensively with increase of the p,~ parameter. Wear debris are bright flakes up to 50 # m in size and 3 lain in thickness [ 2 ]- Mean size of worn particles is growing with an increase in p,t.

The heavy wear mode is characterized by the following features. The maximal and the minimal ratio o f wear to the number of rollers" revolulions or time differed one order during the test run. The wear rate is decreasing with the growth of the pA parameter. Wear particles are becoming darker to compare with the previous wear mode. Wear debris are of the following dimensions: dark particles are up to 200 p,m in size and l0/.tin in thickness; bright particles are up to 1000 p.m. The surf:ace is becoming less ordered. It often changes during the experintents. Fig. 4b shows the photo- graph of a roller surface, characteristic lot the heavy wear mode.

Under the catastrophic wear mode. both worn s u r f a c e s are very rough and showed prominent score marks. Wear debris are of different size. The greater particles are up to 300/~m in size [2] and 50 p.m in thickness 16]. Smaller spherical particles are up to l0/ . t in in size [2] . in Refs. [2,6]. tara-

(a) load 800 N. 70000 cycles, pA =34; (b) krad 1570 N. 60000 cycles.

s t rophic ( T y p e I i l ) wea r mode was ob .~ r ved at the contact

pressure less than 1300 M P a . and the creepage more lhan

15c/~. I t has not been evident how th is wea r mode may appear in the real wheel-rai l system, since the creepage in that system ~ l d o m exceeds IOC,~. An assumption was made that the cat- a, strophic wear mode may be at much lower crcepagc and much higher contact pressure than that in mentioned labora- tory tests | 2,6 ]. Since it is known that the maximum co, tac t pressure in the real wheel-rai l system often exceeds 2000 MPa [ I I,! 21. additional tests were run to test this a s s u m p lion. A special pair of 30-ram rol le~ was u~d : one roller was narrow. 3 mm in width and made of rail steel of 310 HB. another roller was I0 mm in width, made of wheel steel of 280 HB. Tests were run at the contact pressure 1800 MPa and the lateral creepage 5e,~. During this tests due to plastic deformation, a width of a narrow roller has increased up to 4 ram. Rollers were weighed after every 500 rollers" revolu- lions. The total wear rate under this condition was 0.001 mm rev ~ or 3500/.tg m ~ ram- '. Based on this wear rate and on the rollers" surface analy.~s (Fig. 5) . a conclusion was made that this is predominantly catastrophic but adjacent to the heavy wear mode.

Fig. 5. Wear surl~:es of (.aJ IO mm wide roller made from wheel slecl and ( h ) 3 mm wid~ ,:oonlar-rollar m',~le from rail steel; creep'age 5~. Io',al 2100 N. 2<HM} cyck:~, pA = ~.kq.

2 2 S . Zokharov et a L / Wear215 (1~tt81 18-24

4. Examinat ion o f worn wheel -ra i l surfaces

In this study, an examination of the wheel flanges and the gauge lace of rail surfaces has been ca~ied out. Depending on the objective of this study, the level of this examination may vary from general surface observation to a detailed examination.

The main sources of wheel-rail surface observation were two experiments. The first source was examination and meas- urements of wheel flanges o f eight-axle cistern-car trains on the way from lrkutsk in Siberia to port Nakhodka in the Pacific Ocean coast. The second source was simulated field tests under non-lubricated conditions that have been per- formed with 14 four-axle 21.4-ton axle load freight cars at the Institute's Test Center (Scherbinka). During these tests. the following examinations were done: (i) photography of the .~lected wheel flanges and rail gauge lace of the running surfaces under magnification from 1.5 to 2.2 times: ( ii ) fixing wear debris along the wheel flange height with the help of adhesive paper; and (iii) measurement of the wheel flange thickness at fixed distance from the flange top.

Four types of surfaces corresponding to wear modes were found at the wheel flanges and the rail gauge laces. The

similarities in the nature of wear process are reflected in the wear surface features. Very often, several types of the wear modes exist simultaneously.

Most of the studied surfaces correspond to the severe and the heavy wear modes ( Fig. 6) . The surfaces under the severe wear mode have many small gouges and have no clear direc- tion of motion marks (Fig, 6a). This type is usually met at the wheel flange and rail gauge faces.

The heavy wear mode is characterized by deep gouges and grooves 2-3 mm in size with clearly seen arcs of motions of the wheel flange ( Fig. 6a). Wear debris are I -2 mm in size. Since the severe and the heavy wear modes have similar wear rates, they may exist on the wheel flange and the rail ~oauge lace surfaces simultaneously.

The mild wear mode is usually accounted on the rail and the wheel rolling surfaces, and on the wheel flange and the rail gauge laces. It is characterized by the shiny surfaces and flake type of debris ( Fig. 7a ).

Under the catastrophic wear mode, all or almosl all wheel flange and side rail head surfaces are worn out. Because o f high wear rate, this wear mechanism substitute others ( Fig. 7b). Another feature of the surfaces subjected to the cata- strophic wear mode is multiple small surface gouges "dam-

(b)

(1)

Fig. 6, Whee l f lange surface secl ion I -" ) a n d a . ' ,keleh o f its or ig im.I pt~.,,iliol] ( b } ; ( I ) and ! 2 i. p~lrt:, o f die surf'ac¢ section corresponding to lhe severe and the hea r } wear m~Ie~., re..,p.-clively.

i ~ A2

.... ii I

1

(a) ( I)

~ ' ~ - ~ {2)

(b)

lq~. 7. R~il head ~.idc f',,~:e ~;urfm.'e t a ) i l l uu~'c ( N ~ 21 () ii1 ) and a ,,,kek'il o f il~ origin;d posilion ( h I: I I ) all.d ( --. ), parl~, dt Ihe sur|'~ice ,:orr,:~,pondhlg h~ the mi ld and the ~:ata,.trophk- ~c~ r smiles, r¢sp:cl iv¢l.~.

S. 7~tlkharm" rt aL / Wear 215 ¢ 199~) 18-24 23

aged" by the wheel flange motion arcs. A considerable loss of material evidenced by the great volume of wear debris. usually observed in steep curves, resulted from this wear mode.

5. Discussion

5. I. Test schemes

Most of the experiments on laboratory wheel-rail wear simulation have been performed on Amsler test machines modeling rolling-longitudinal sliding conditions 12,6,81. Very few works have been done to simulate rolling-lateral sliding conditions [ 4.7 I. Work 17 ! has been pertbrmed on the test machine simulating lateral creep from 2 to 10% at the contact pressure 650 MPa. Rollers were made from the rail steel that had surface hardness 350 HB and wheel steel with hardness 250 HB. It was found that the total wear rate was intensively, growing at 2% creep and slowed down its growth at about 6% creep. This corresponds 1o ph change from 13 to 40 MPa. which is within pA range Ibund in our experiments ¢~Table 4) for the severe wear mode.

It was considered essential to compare the results of wear tests performed on machines simulating lateral and longitu- dinal sliding. The comparison tests perlormed on the same rollers, loads and creep up to 10% had shown that the depend- encies of wear rate from TA/A or pA parameters are qualita- lively similar. However. when performing the.~e tests on an Amsler machine simulating longitudinal creep, measures are required to remove wear debris from the contact area. and to prevent oxide layer formatio: -m the surface of lower roller.

Thus, for more appropriate simulation of wheel flange/rail head side wear, it is better to use rolling-lateral sliding scheme of testing because: ( i ) at the angle of wheel attack more than 0.01 radian, which is expected in sharp curves, the lateral creep component became larger than that of the lon- gitudinal component: ( ii ) during tests on a machine simulat- ing lateral sliding conditions, surfaces of upper and lower rollers are similar, thus avoiding the necessity to deline the roller in modeling the wear process; ( i i i ) real wheel flange and rail head surfaces at the corresponding wear modes were fimnd to correlate with those found in rollers during labora~ tory tests: ( iv) no special measures are required to remove wear debris from the contact area. and to prevent lbrmation of oxide layer on the lower roller: and ( v ) the lateral creepage does not depend on a roller 's diameter, thus it does not oh:rage due to wear especially during tests at the catastrophic wear mode.

5.2. Scah" ¢l.'fect

The similarities in the wear mechanisms of rolling-lateral sliding laba~ratory tests and wheel-rail service conditions are reflected in the wear surface features. The most obvious dif- ference is the size of score marks, gouges and wear debris

produced under each wear mode. This fact has been noted in relation to the Amsler tests in Ref. 12 I. Our study has shown about five times difference in sizes of the surface character features t ~ o r e marks, gouges, etc. ) for the given wear mode ( Figs. ( 1 ) - ( 3 ) ). This is an indication of the necessity to consider scale factors when using the results of labora- tory tests to predict wheel and rail wear rate. and to design the relation between wear rate and wheel-rai l contact param- eters.

An attempt has been made to consider ~ a l e f~ to r s using the following approach. Two causes of scale effects are con- sidered. The first is the difference in sizes of interacting bod- ies. the second is the diffe,'ence in the contact zone geometry. The present study allowed the preliminary conclusion that wear debris sizes and surface character features for the given wear mode are proportional to the size of contact zone in the sliding direction.

5.3, Wear mechanism

Another subject of discussion is an assumption of wear mechanisms. Knowing the total wear rates and wear debris thickness, it is possible to estimate the average number of revolutions required to wear the rollers' surface layer corre- sponding to the maximum particles" thickness. For mild wear. 6000 revolutions arc required: for severe, 4000, for heavy. 2(h'X): and for catastrophic. 50-100 rollers" revolutions.

Estimation of a number of cycles necessary for the sepa- ration of wear particles in all wear modes allows to assume that low-cycle fatigue with maximum 6000 cycles is the mechanism responsible for the wear process.

6. C o ~ l m k m s

( I ) Four wear modes, referred to as mild. severe, heavy and catastrophic, have been identified in laboratory rol l ing- lateral sliding unlubricated wear tests. The heavy wear mode has not been identified before. The catastrophic wear mode was discovered at 5c/r of crcepage.

(2) The wear modes that occur on worn wheel flange surfaces and on the surfaces of side worn rails have been found to correlate with those found on the rollers" surfaces during laboratory tests. The similarities in the nature of the wear prt~ess are reflected in the wear surface features. This allows us to work out a meth~,'d o f transferring the results obtained in the laboratory test to the real wheel-rai l system.

(3) There is a good correlation between the results of described tests and known resu|ts obtained on Am:Jcr wear testing machines with the longitudinal creep. It is. however. noted that lal'mratory tests with riffling-lateral sliding better simulate wheel flange and rail head side wear.

(4) It has been Ikmnd that pA is the effective parameter that enables to develop relations between the wear rates and

24 S. Zttkharm" e / ,L I Wear 215 (I 9PR) 18-24

test contact parameters, and to locate the wear modes' limi- ting values. The boundaries of the wear modes for the con- ventional rail and wheel steels used for the Russian Railways have been defined.

(5) Estimation of a number of cycles necessary for the separation of wear particles allows the assumption that the low-cycle fatigue is the mechanism responsible for the wear process.

References

[ I I P- Clayton. Tril~logical aspecls o f wheel-rail contacl: A review of recent experimental research. Wear It)] ~ 1996 ) 170-183,

121 P J- Bohon, P. Clayton. Rolling-sliding wear damage in rail and lyre ~,teels. Wear 93 I ) 984 ) ] 45-165.

131 H. Krau.,,e, G. Ptdl. Wear of wheel-rail surfaces. Wear 113 I 19861 1113-122.

141 J. Katousek. G. Ro.~,val, H. Gh(mcr'n, Latend creep and its effc¢! on wear in rail whce! interface. Contact Mechanics and Wear of Rail/ Wheel Systems, Univ. of Waterlt~ Press, Watcrhm, 1983.

151 S. Kumar, .i.S. Kim, B. Rajkumar, A lal'K~ratt)ry study of the dynamic nature of wheel-rail contact, Contact Mechanics and Wear of Wheel Rail System, Univ. o t Wate r [~ Press. 1983.

161 D. Danks . P. Clayton, Comparison of the ~eur process for eutect~id rail steeb.: Field and lalm)ralory IcM~. Wear 121') ( 1987 ) 233-250.

171 E.A. Shur. N.Y. By,,:hkova. D.P. Markov. N.N. Ku~,~nin. Wear resi.,,- lance of rail and wheel steels. Fricli~m and Wear 17 I I ) ( t995 ) 81~ 91. Ge,~l. Inli~lril',o,

181 1"). Marko~,. Lal~rato~' lest.,, for wear of rail and wheel s l e e k Wear 181-183 ( 11~.151 678-686.

I 91 R .K Sleel. R. Reif. Rail: hr, behavior and relationship to I~lal ~,yr, lem wear~ Proc. 2rid Inl. Heaxy Haul Conf.. Colorad~ Spring~, 19F,2, pp. 227-276.

t I1[)1 V.N. Vint~gradov. G.M. Stwokin. Mcchanicalwcartd',,leelsandalloy,, I in Ru~,ian I. Nedra. Moscow. I t K~. 364 pp.

I I l I H. Krau.~. G. Poll. Plastic defi~nnation~, of wheel-rail surl'acer,. Wear 113 (198b) 123-1311.

1121 VH, Bogdam~v. A.P. (k;D'aehe~. I,G, G~Dacheva. M.N. D~h.~cltin. S,M. Zakharo~,. V.G~ Krktmogov. I.A. Soldatenkov. O,G. Chekina. A ~.ludy of ~ heel-rail ctmtacl prt~e.,,~,, wear and cumulali~e danlage. Fric|itm and Wear I t995 ) 12-26, Gt~ll:Jel. Inl'*~lriho.

Biographies

Sergey M. Zakharov graduated from the Moscow Institute (Technical University) of Railway Engineers in 1959. He also graduated from a mathematical faculty of the Moscow State University in 1967, In 1967, he was a candidate of the technical science degree (equivalent to a PhD degree) and in 1984, he was a doctor of the technical science degree in tribology, in 1989, he became a professor at the Moscow Automechanical Technical University. His previous research concentrated on the performance characteristics ofcrankshaft bearings, including hydrodynamic and mixed lubrication conditions and wear. In 1980, he became the head of labo- ratory and tribology group at the material testing department of the All-Russian Railway Research Institute, (Moscow) and concentrated on the designing of complex tribology sys- tems, including the wheel-rail system. He is the head of a section in the Russian National Tribolog2~ Committee, a member of the Russian Association of Tribology Engineers. a member of SAE. and a member of the Technical Committee ISO (TC 1231.

Igor A. Komarovsky graduated from the Moscow Institute of Steel and Alloys (MIS&A). Physical Chemical Faculty in 1986. In 1986--1989 he was a postgraduate student of MIS&A, He was a candidate of physics and mathematics degree in 1990. From 1993 to present, he is a senior researcher of the All-Russian Railway Research institute. His field of scientific interests: ion beam modification of surfaces, SEM, X-ray microanalysis, image analysis, rail and wheel steels' wear resistance testing.

llya A, Zharov graduated from the Moscow Institute (Tech- nical University) of Railway Engineers in 1985. He has his postgraduate study in the All-Russian Railway Research Institute. In 1996. he was a candidate of the technical science degree (equivalent to a PhD degree). His previous research aimed at studying the performance characteristics of crank- shaft bearings, including hydrodynamic and mixed lubrica- tion conditions and wear. Lately he became involved in wheel-rail wear research.