pin on disc test results

7/27/2019 Pin on disc test results

1/9

Tribology International Vol. 29. No. 5, pp. 415-423, 1996Copyright 0 1996 Elsevier Scienc e Ltd

Printed in Great Britain. All rights reserved0301-679X/96/$15.00 +O.OO0301-679X( 95)00097-6

Characteristics of wear resultsy pin-on-disc atte to high speedsH. SoThe use of a pin-on-disc configuration for investigating the wearmechanism or behaviour of solid materials is examined carefullysince the results of such configurations differ from published dataand some existing theories cannot be applied to such aconfiguration directly. The obvious contradictions include thefollowing. The results between the arrangements of the rotatingpin and the stationary pin under the same load and speed aredifferent. The bulk temperatures of the rubbing specimens increasewith the duration of testing, which may eventually arrive at asteady state. However, before the wear condition reaches a steadystate, it will have continuously varied. Moreover, the frictioncoefficient increases with sliding speed when the applied load onthe rubbing specimens is over certain levels. All thesecontradictions can be reasonably explained with the accurateprediction of bulk and flash temperatures at the contact area. Tothis end, this paper provides a more reasonable method for thecalculation of temperatures and the real and apparent contactareas. Copyright 0 1996 Elsevier Science LtdKeywords: characteristics, pin-on-disc, rotating (stationary) pin, wear,friction

IntroductionThe pin-on-disc configuration is commonly used forwear tests in laboratories because of its simple arrange-ment. However, some phenomena which affect thetest results markedly are always overlooked. Theseinclude the fact that the bulk temperature of the pinis higher than that of the disc and that the temperatureas well as the wear rate of a stationary pin forced ona rotating disc is higher than that of a rotating pinsliding on a stationary disc when the normal load isover some level. If the test is not limited to a singlepass of rubbing, the pin and the disc will accumulatethe rubbing heat and cause their bulk temperature to

Department of Mechanical Engineering, National Taiwan University.Taipei, Taiwan, 10617Received 2 November 1994; revised 13 April 1995; accepted 6 June1995

rise correspondingly, until they reach a thermal steadystate. Therefore, the theoretical results for computingthe flash temperature presented by Blok*,2, Jaeger3,Barbe? and Archard and for computing the meansurface temperature presented by Ashby and co-worker@ cannot be directly applied to the pin-on-discconfiguration for a long time test unless the bulktemperatures of the rubbing specimens are knownsimultaneously. A high bulk temperature at highrubbing speeds will decrease the yield strength of thematerial and lead to changes in the wear mechanismand the real contact configuration. Lim and Ashbynoticed the rise of temperature in the pin and disc,but neglected the influence of the bulk temperatureon the yield strength of the rubbing materials. There-fore, their predicted results fo r wear rate at higherspeeds may deviate from the real wear mechanism.Based on the theory for predicting the flash temperatureat contact surfaces, some investigator& presented

Tribology International Volume 29 Number 5 1996 415


2/9

Characteristics of wear results by pin-on-disc: H. So

NotationA4COc 1.2FHFK&okPQd.pTEiTCTOVWPflf

apparent contact area or cross-sectional area of the pin (m)real contact area (m*)circumference of the pin (m)constants (IS)normal load (N)hardness (Pa)Vickers hardness numberconvection heat-transfer coefficient(W/m* K)thermal conductivity (J/msK)length of the pin (m)asperity height or thickness of oxidefilm (m)apparent contact pressure (Pa)heat flow to disc and pin,respectively (W)room temperature (K)flash temperaturemean surface temperature atapparent contact areasliding speed (m/s)wear rate (m3/m)friction coefficientflow stress (Pa)

theoretical results for the friction coefficient of slidingcontact at very high speed, but it can be shown thatthose formulae cannot be applied to the pin-on-discconfiguration if the disc is made from metals of muchlower melting point than that of the pin, because thewhole disc is softened by frictional heat and deformsplastically over the whole contact area. Finally, thefriction coefficient will increase with increasing slidingspeed.Quinn pointed out that if the pin and the disc weremade from any kind of steel, an oxide film mightform on the rubbed area in accordance with the slidingspeed. In such a condition both the wear rate and thefriction coefficient would decrease correspondingly. Infact, this is not always true in many conditions.According to intensive test results conducted with apin-on-disc configuration, this paper indicates somemechanisms of friction and wear, which are differentfrom most published results. The present results canhelp to distinguish the applicability of the pin-on-discconfiguration on wear tests.Experimental detailsWear test rigA Falex multi-specimen friction test machine was usedas the wear test rig. Two arrangements of the pin anddisc can be established as shown in Fig 1 in which, ifthe disc is mounted on the upper rotating shaft, thepin will be fixed to the lower stationary rod, and viceversu. The load is applied by means of dead weightsor by an air cylinder through the stationary rod against

Fig 1 Schematic diagram of pin-on-disc configuration.Left: rotating pin; right: stationary pin

the rotating specimen. The frictional torque is measuredwith a load cell fastened on the stationary rod. Therotating shaft is controlled by a dc servo motor toprovide the sliding speeds ranging from 0.1 m/s to10 m/s in the present tests. The load varied from 5 Nto 400 N. The temperature of the pin that is mounted onthe stationary rod can be measured with thermocoupleswelded on the pin. In the present tests two thermo-couples were welded on the pin at distances of 2 mmand 6 mm from the top of the pin, respectively. Thetwo thermo-couples give two readings for temperature,TI and T2 of the pin. In such an arrangement, thedistances from the welded thermocouples to the contactsurface may change at every moment as the pin isworn by rubbing action. The amount of wear ismeasured with a linear varied differential transformer(LVDT) and a data acquisition system. The averagetemperature of the rotating disc can only be measuredapproximately with an infrared microscope. If the discis fixed to the stationary rod, its bulk temperaturecan be measured with thermocouples, while thetemperature of the rotating pin can only be estimatedby its colour if it is made of steel. The latter methodis based on the fact that when a steel is heated to aspecified high temperature and cooled in air, thesurface of the steel will result in a specific colour.Comparing the colour between the pin and the sampledsteel of the same type, the temperatures along thepin axis can be estimated. However, the error intemperature prediction by such a method will bewithin 30C.SpecimensThe pin specimens were made from several alloysincluding medium and high carbon steels, AISI 4140Cr-Mo steel, 410 stainless steel and forging die steel.The disc specimens were made from medium and high

416 Tribology International Volume 29 Number 5 1996


3/9

carbon steels, AISI 4340 Ni-Cr-Mo steel, 410 stainlesssteel and 6061 aluminium alloy. The dimensions ofthe pins were 4.75 mm diameter and 15 mm length,and those of the disc were 55.5 mm or 31.78 mmdiameter and 10.88 mm thick. The distance betweenthe centres of the pin and the shaft was 23.4 mm or11.85 mm.The hardness numbers of the specimens used in presenttests are listed in Table 1.Test proceduresThe experiments were carried out at nominal slidingspeeds ranging from 0.2 m/s to 8 m/s. The loadsranged from 9.8 to 392 N to yield an apparent contactpressure ranging from 0.55 to 22 MPa. The durationof each test depended upon the rubbing materials, thespeed and the load. Each test was conducted as longas the thermal condition or the wear rate reached asteady state condition, unless the wear rate was toohigh either causing the pin to be shortened too fastor to making the rubbed track on the disc wear toodeep; in such situations, the test was terminated.Temperature calculationAccording to Archard, the greater part of frictionalheat is supplied to the moving specimen at high slidingspeeds. This is not true in the pin-on-disc configurationwhile the pin is rotating, because the bulk temperatureof the disc is much lower than that of the pin, andmost of the frictional heat will be supplied to thestationary disc. On the other hand, by measurementof temperatures at the stationary pin and the rotatingdisc, both temperatures increase with increasing rub-bing time (Fig 2), where To is the temperature at theapparent contact surface of the pin computed with themethod described later. The temperature of thestationary pin is always higher than that of the rotatingdisc. Moreover, the mean temperature at the apparentcontact surface is found to be different from thatpredicted by Ashby et al. 6,7. The discrepancy is causedby the different bulk temperatures of the pin and thedisc, which Ashby et al. did not take into consideration.A modified calculation of the mean surface temperatureat the apparent contact area is proposed as follows.If a natural convection condition is assumed for thestationary pin, the heat conducted away from theclamped end of the pin dominates that convected by

Characteristics of wear results by pin-on-disc: H. so

150- To

0 10 20 30 40 50 60Timefmin)

Fig 2 Variation in temperature of the specimens withrubbing time for a 6061 alumin ium alloy disc slidingon a die steel pin at 1 mls and 2.2 MPa. T,,: temperatureat apparent contact area of the pin; Td: mean surfacetemperature of disc; T,, T2: measured temperature onthe pinthe air. Moreover, the diameter of the pin is less thanits length. Therefore, one-dimensional heat conductionis assumed. From heat conduction in a one-dimensionalcondition, the energy balance between any two cross-sections of area A separated by a small axial distancedx of a cylinder is given as:

$ KA ; - h&(T - T,) = 0i i (1)where K is the thermal conductivity of the pin material,h the convection heat-transfer coefficient, C, is thecircumference of the pin, and T, is room temperature.If the thermal conductivity and convection heat-transfer coefficient are assumed to be constant andequal to the average values, respectively, the generalsolution for Eq. (1) is

T = T, + C, exp(mx) + Cz exp( -mx)where

(2)

(3)If the temperatures at any two positions of the pin,T, and T,, are measured, the constants C, and C2 can

Table 1 Hardness of the alloys used in the present testsMedium High carbon 410 4140 4340 Die steel 6061carbon steel steel stainless steel steel alumin iumsteel

Vickershardnessnumber(4)

160annealed560quenched

210annealed800quenched

160 970 750 600 100



4/9


be obtained and the temperature at any point on thepin can be determined as well.The convection heat-transfer coefficient is approxi-mated as:

(4)if the pin is stationary.The mean temperature at the apparent contact area,TO is found to be:

T,, = T, + C1 + C, (5)The heat flow Q,, transferred to the pin is:

Q,, = K AmC2 - K AmC, (6)The flash temperature T, at the real contact area A,can be obtained by the energy balance in the contactzone of the pin and is:

T, = To + !@EKOA, (7)where KO is the thermal conductivity of the materialin the contact area or of the oxide film; Ii is theaverage height of surface asperities or the thicknessof the oxide film. If oxide film can hardly be foundon the contact surface of the pin, I, is given by themean peak-to-valley height, R,(DIN), measured witha profiling type proficorder. The real contact area isdifficult to determine12, but the usual calculation canbe employed as follows.

A, = -FH (8)where F is the normal load, and H is the smaller ofthe hardness numbers of the two contacting specimensat the flash temperature. H can be replaced by thevalue of 3~7r,,where af is the flow stress of the specimenat the flash temperature. Therefore:

Tc = To + F K. I%Q pTo determine T,, one should assume a value for T,at first, then, obtain H at the assumed T, from thepublished data elsewhere13*14, and compute the resulton the right-hand-side of Eq. (9). If the computedresult is equal to the assumed T,, then T, is therequired flash temperature. Although the shear strainrate on the real contact asperities may be very high,it has little effect on the flow stress of the material undercompression because of the anisotropic behaviour inplastic deformation. This is because the planes thatsuffer frictional shearing are different from the planesthat are subjected to maximum shear stress due tonormal compression. However, for more accuratecalculation, the normal load F can be replaced by theresultant load obtained from the normal and frictionalforces.

The bulk temperature of the disc is always neglectedby many investigators, but this temperature does affectthe rate and mechanism of wear of the rubbing bodies.Figure 4a indicates the wear loss of the discs made of410 stainless steel sliding on a stationary pin made ofdie steel. One of the discs was cooled by a waterjacket, while the other experienced natural heattransfer, and all other conditions were the same inthe tests. As the temperature rose to a certain levelin the latter condition (Fig 4b), the wear rate of thedisc increased suddenly. Although the wear rate inthe cooled condition was quite steady, the wear losswas heavier. This was caused by the lower contacttemperature in the water-jacket-cooled condition,which inhibited the pin from forming oxides. In thenatural heat-transfer case, as the temperature of thedisc rose the disc was softened, allowing heavier wearloss.Because of sharing the same interface, the flashtemperature of the rubbing bodies should be the same,while the mean surface temperature at the apparentcontact area of the two contacting bodies may bedifferent from each other and should be computedseparately. The temperature at any position on therubbing track but outside the current apparent contactarea of the disc will be much lower than the meantemperature inside the current contact zone. The meansurface temperature at the current apparent contactarea is:

Figure 3 indicates typical results for the flash tempera-ture computed with Eq. (9). The flash temperaturesbased on the hardness at room temperature are alsoshown for comparison.

Qci=Hv-Qp-Q (10)where Qd is the heat flow supplied to the disc, Q isthe rate of energy for creating new surfaces and foraccelerating the debris. But Q is difficult to determineand is therefore neglected. Neglecting Q causes thecomputed result for the flash and mean surface

PI8 Triboloav International Volume 29 Number 5 1996

I0 015 I 1.k 1P (MW

Fig 3 Computed results for temperature of rubbingpairs made from medium carbon steel at a constantsliding speed of 4 mls against different apparent contactpressure p, MPa. T,: flash temperature based onthe hardness of the rubbed material at the requiredtemperature T,; TL: flash temperature based on hardnessat room temperature

Temperature of the disc


5/9

1000Slide Distance (m)600

F -J1000Slide Distance (m) 2000Fig 4 (a) Comparison of wear loss between disc speci-mens in the conditions of water-jacket-cooled disc (+)and the natural heat-transfer (*); (b) variation of meansurface temperature at the apparent contact area of pinspecimens with time in the conditions of water-jacket-cooled disc (+) and natural heat-transfer (*)temperatures to be slightly overestimated. ReplacingQr, by Qd and substituting the appropriate values forK,, I, and I-I for the disc in Eq. (9) gives the meansurface temperature To at the current apparent contactarea on the disc.It is found that the temperature at any cross-sectionof the disc parallel to the rubbing surface onlydepends on the distance from the rubbing plane. Thetemperature is almost the same at the same cross-section.Effect of moving specimenBased on the dimensions of the pin used in the presentexperiments and the comparison of the convectioncoefficients between natural and forced convection,


when the speed of the pin is higher than 0.2 m/s, theheat convected to the atmosphere increases withincreasing speed. Consequently, the temperature ofthe pin and the disc is lower in the arrangement witha rotating pin than for a stationary pin. This affectsthe wear behaviour of the pin remarkably as shownin Fig 5, which indicates the wear appearance of arotating pin and a stationary pin subjected to anapparent contact pressure of 5.5 MPa and at a slidingspeed of 4 m/s. The stationary pin has a mushroomshape at the rubbing end. This implies that thetemperature of the stationary pin was much higherthan that of the rotating pin subjected to the sameload and speed. The high temperature softened thestationary pin. By comparing the colours o f the pinsurface, the temperature distribution of a rotating pinat the end of a test can be estimated. The meansurface temperatures at the apparent contact area ofsome tested pins are listed in Table 2 in which theaverage temperatures on the rubbing track of themating discs are also shown.Wear rateEffect of moving specimen

Same material for the rubbing pairIf the pin and the disc are made of the same material,the amount of wear will be dominated by the pin,whichever is rotating (Fig 6). The wear of the disc isnegligible.Different materials for the rubbing pairHardness of the same order. If the hardness numbersof the two rubbing materials at room temperature areof the same order, the wear rate of the pin specimenwill dominate that of the disc specimen, although thehardness of the pin is higher than that of the disc atroom temperaature. In Fig 7 the pin and the disc weremade from AISI 4140 and 4340 alloy steels and heat-treated to Vickers hardness numbers of 970 and 750,respectively. It was found that the wear loss of thedisc was less than one tenth that of the pin. Figure 8shows a comparison of the wear loss of the fourarrangements for the high and medium carbon steelscorresponding to Table 2. In whichever arrangementall the wear loss is contributed by the pin specimen,while that of the discs is negligible. Such results aremainly caused by the much higher bulk temperatureof the pins near the contact surface. High temperaturescan markedly decrease the hardness of steels. There-fore, the pin specimen having a softer sub-surfaceresults in heavier wear loss.The hardness of one specimen is much higher than thatof the other. In such a condition the wear is dominatedby the soft material, whether the soft material ismachined to be the pin or the disc. Figures 4 and 9indicate the wear loss of a stainless steel rubbed witha die steel whose wear loss is negligible. In Fig 9, thecritical load (or the apparent pressure) for the transitionfrom mild oxidational to severe wear is shown.



6/9


Fig 5 Comparison of wear appearance between the rubbed surfaces of pin specimens in different arrangements.Left: stationary pin; right: rotating pin made of high carbon steel (Hv = 210) rubbed with medium carbon steeldiscs (Hv = 160) at 4 mls and 5.5 MPa

Table 2 Mean surface temperature fC) at apparent contact area measured at a sliding distance of1200 m, sliding speed 2 m/s and contact pressure 5.5 MPaRotating pin Stationary disc Stationary pin Rotating disc

HC pin on MC disc 430 260 750 340MC pin on HC disc 348 250 500 270

Effects of sliding speed and normal loadThe individual effect of sliding speed on wear rate ofthe rubbing pair is ambiguous in experiments subjectedto a wide range of combinations of speeds and loads.It is found that when the applied load is over somelevel but the sliding speed keeps increasing at thatconstant load, the wear rate of the pin specimen will

30

25 -msE 20-$I

brise suddenly at some speed. Higher than such a speedthe wear rate increases with increasing sliding speed. 5 15-Figure 10 indicates the typical results. 222On the other hand, if the sliding speed is kept constant 3 lobut the load varies, there is a critical load over which sthe wear rate of the stationary pin increases to a much 5-higher value (Fig 11). The rapid increase in wear ratein Fig 11 is caused by the massive volume in the pinundergoing plastic deformation as shown in Fig 5. The 0 I I I Iplastic deformation is caused by a decrease in flow 0.00 1.00 2.00 3.00stress at high bulk temperatures. It is found that inmany tests, if the mean temperature at the apparent Pressure (MPa)contact area is higher than 400C and the apparent Fig 6 Comparison of wear rates between rubbing pairscontact pressure is higher than 5 MPa, the wear of made of medium carbon steel in different arrangementsthe pin specimens will turn to a severe condition for at a constant sliding speed of 2 mls: (+), stationarymost steels. pin; (*), rotating pin420 Tribology International Volume 29 Number 5 1996


7/9

i i 6 10Sliding distance(103m)

Fig 7 Wear loss, W of a 4140 steel pin (Hv = 970)rubbing against a 4340 steel disc (H, = 750) at 2 mls


00 50 100Slide Distance m) 150and 2.5 M-Pa

Fig 9 Wear loss of stainless steel pins rubbing againstdie steel discs at a sliding speed of 0.8 mls and undera contact pressure of 8.3 MPa (*) and 7.74 MPa (H)

0 300 600 900 1200 1500Slide Distance (m)Fig 8 Comparison of wear loss between the pin speci-mens in four arrangements indicated in Table 2 at 2mls and 5.5 MPa. (*), HC disc sliding on stationaryMC pin; (@), MC disc sliding on stationary HC pin;(El), rotating MC pin sliding on a HC disc; (O),rotating HC pin sliding on a MC disc. MC: mediumcarbon steel (Hv = 160); HC: high carbon steel(H, = 210)

Oxidational effectThe ranges of sliding speeds and normal loads employedin the present tests fall into the condition of oxidationalwear1r,15. Therefore, in most cases the friction as wellas the wear rate is controlled by the formation of anoxide film on the rubbing surfaces, especially whenthe speed is high enough. However, it should bepointed out that even in a severe wear condition thereare oxide films created on the rubbing surfaces, andin such a case the wear rate is not affected by theformation of oxides.

1000

z;E 100T 0

a,E 10

E

1

II I I I1 2 3 4 5

Speed (m/s)Fig 10 Variation in wear rate with rubbing speed or aHC pin (H, = 800) under a pressure of 4.43 MPa (A)and for a stellite pin (H, = 650) under 8.85 MPa (0)

Friction coefficientTwo important results for the coefficient of friction ofthe rubbing pair in the pin-on-disc configuration areobtained. First, the friction coefficient in a rotatingpin arrangement is lower than that for a stationarypin, when the applied load is raised to certain levels(Fig 12). Secondly, when one of the rubbing bodieshas a much lower melting point than the other, thefriction coefficient increases with increasing speed (Fig13). The variation in temperature of the stationarydisc with rubbing time is also shown in Fig 13. Theseresults are different from most published results andare caused by an increase in plastic zone size near thecontact area subjected to the high bulk temperaturewhich softens the lower melting point material. Thereal contact area therefore increases with increasing



8/9


OC 2 4 6 0P (MW

Fig 11 Variation in wear rate with apparent pressure pfor different materials rubbed with AISI 4340 disc. HC,high carbon steel pin (Hv = 800) at 4 m/s; DS, diesteel pin, (Hv = 600) at 2 mls; ST, MC pin lasercladded with stellite (H., = 650) at 4 m/s

0.8

0.2

0.00 300 600 900 1200 1500Slide Distance (m)

Fig 12 Comparison offriction coefficients between rotat-ing pin and stationary pin corresponding to Fig 8 andTable 2: (O), stationary HC pin; (*), stationary MCpin; (O), rotating HC pin; (El), rotating MC pinplastic zone size. The increases in plastic zone sizeand real contact area hinder the rubbing motion.Consequently, the friction coefficient increases withincreasing sliding speed.ConclusionsSome important conclusions can be drawn in accord-ance with the wear tests conducted with a pin-on-discconfiguration.(1) The wear mechanism, friction coefficient andbulk temperature of the rubbing bodies aredifferent between the arrangements with rotating

1.75

1

3mls

1.50f0 I / ,2mls

0 5 10 15 20 25 30 35Time (min)400350- 3mls

300-9; 250-

52 200-ta& 150- 1 mls

kloo-

0 I 1 1 , I 6 I0 5 10 15 20 25 30 35Time(min)Fig 13 (a) Variation in friction coefficient with rubbingspeed of die steel pin sliding on stationary discs madeof 6061 aluminium alloy under a contact pressure of2.2 MPa; (b) variation in bulk temperature of alu-minium discs with the speed of die steel pin correspond-ing to Fig 13(a)

and stationary pins. This is caused by differentheat-transfer conditions occurring in the twoarrangements.(2) A more accurate prediction of flash temperatureand mean surface temperature at the apparentcontact area can be achieved with the calculationproposed in the paper in accordance with themeasurement of temperature on the stationarypin.(3) The increase in bulk temperatures of the rubbingbodies decreases the flow stresses of the rubbingmaterials to a certain extent, which results in anincrease in the plastic zone size in the sub-surfaces of the rubbing bodies. Consequently,the friction coefficient as well as wear rateincreases with increasing sliding speed when thenormal load is over certain levels.

422 Tribology International Volume 29 Number 5 1996


9/9


(4) In order to avoid ambiguity in the presentedresults from the pin-on-disc configuration, it issensible to point out the arrangement for the pinand the disc, and whether a steady state conditionis reached, and if not, how long the slidingdistance is. Moreover, the use of a dimensionlesswear rate is preferable.

AcknowledgementsThe author wishes to thank H. M. Chen, Y. A. Chen,W. S. Jean, C. T. Chen, and C. H. Chen for theirassistance in the experiments.References

1. Blok H. Surface temperature under extreme pressure lubricatingconditions. Proc. Seco nd World Petr. Cong. 1937, 3, 471-4842. Block H. Measurement of temperature flashes on gear teethunder extreme pressure conditions. Proc. Instn. Mech. Engrs.

1937, 2, 14-203. Jaeger, J.C. Moving sources of heat and the temperatures atsliding contacts. Proc. Roy. Sot. N.S.W. 1942, 26, 203-2244. Barber, J.R. Distribution of heat between sliding surfaces. J.

Mech. Eng. Sci. 1967. 9, 351-354

5.6.

7.8.9.

10.11.12.13.

14.15.

Archard, J.F. The temperature of rubbing surfaces. Wear 1958159, 2, 438-455Ashby M.F., Abulawi J. and Kong H.S. Temperature maps forfrictional heating in dry sliding. STLE Tribol. Trans. 1991, 34,577-587Lim, S.C. and Ashby M.F. Wear-mechanism maps. Acta MetaN.1987, 35, l-24Ettles, C.M.McC. The thermal control of friction at high slidingspeeds. ASME Trans. J. Tribol. 1986, 108, 98-104Marscher W.D. A critical evaluation of the flash-temperatureconcept. ASLE Trans. 1982, 25, 157-174Lingard S. Estimation of flash temperature in dry sliding. Proc.Instn. Mech. Engrs. 1984, 198C, 8. 91-97Quinn T.F.J. Review o f oxidational wear, Part I: The originsof oxidational wear. Tribol. lnt. 1983, 16, 257-271So H. and Liu D.C. An elastic-plastic model fo r the contact ofanisotropic rough surfaces. Wear 1991, 146, 201-218Baragar D.L. The high temperature and high strain ratebehaviours of a plain carbon and an HSLA steel. J. Mech.Work. Technol. 1987, 14, 295-307Lange, K. Handbook of Metal Forming, McGraw-Hill, 1985,4.1-4.18So H. The mechanism of oxidational wear. Wear 1995. 184,161-167


pin on disc test results

Documents