FZG - Testmethods for Lubricant Related Influences on the Gear Load Capacity

G. SteinbergerTU MünchenB.-R. Höhn

FZG-Test Procedures with the standard FZG back to back test rig

Lubricants Russia 2006, 2nd international conference

Testmethods for Lubricant Related Influences on the Gear Load Capacity

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G. SteinbergerTU MünchenB.-R. Höhn standard FZG back-to-back test rig

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G. SteinbergerTU MünchenB.-R. Höhn

micropitting pitting

scuffing wear

lubricant related gear failure modes2/144.21.36

G. SteinbergerTU MünchenB.-R. Höhn load and speed distribution of test gears type A

test gears type A for scuffing test

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G. SteinbergerTU MünchenB.-R. Höhn load and speed distribution of test gears type C

test gears type C for wear, micro-pitting and pitting test

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G. SteinbergerTU MünchenB.-R. Höhn scuffing

scuffing: local welding of flanks due to breakaway of lubricating film

- no fatigue damage

- scoring/ scuffing already after short-time overload possible

consequences:

- increase of temperature, power loss and abrasion

- increase of additional dynamic forces up to tooth breakage

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G. SteinbergerTU MünchenB.-R. Höhn wear

wear: continuous removal of material from the surface with each mesh

desired:

- smoothing of flanks

- improvement of contact pattern (running-in)

undesired:

- change of tooth form

- removal of hardened layer

cosequences:

- increase of additional dynamic forces

- in advanced stages: tooth breakage

profile deviation removal of hardened layer

minimum thicknessat tooth tip

risk of tooth breakage

Rht

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G. SteinbergerTU MünchenB.-R. Höhn mircro-pitting

increase of dynamical additional forces + gear noiseinfluence on occurrence of pitting

5 µm

5 m

m

new

E

D

C

B

Adedendum flank

consequential damages: - change of involute profile due to profile deviations

load cycles

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G. SteinbergerTU MünchenB.-R. Höhn pitting

fatigue damage, caused by rolling contact stress

increasing of the internal dynamicsprogressive damaging until tooth breakage

result:

shell-shaped spallings on the gear flank surface

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G. SteinbergerTU MünchenB.-R. Höhn FZG scuffing test

Standard FZG scuffing test A/8.3/90 according to ISO 14635

Test parametersGear type APitch line velocity vt = 8.3 m/sDip lubrication with starting oil temperature of 90 °C in each load stage –No coolingDriving pinionLoad stepwise increased until scuffing occurs

Failure criterionVisual method: more than one pinion face width scuffedGravimetric method: wear more than 10 mg above average wear rate

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G. SteinbergerTU MünchenB.-R. Höhn FZG scuffing test procedure

0

400

800

1200

1600

2000

Time

weight loss measurement

Her

tzia

n st

ress

pc

[N/m

m ]

visual inspection

Load stage 1 2 3 4 5 6 7 8 9 10 11 12

Pini

on to

rque

T 1 [N

m]

0

10

50

100

150200

300

400450

550

15min.

2

gear type Av =8,3m/s

=90°Cϑtoil start

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G. SteinbergerTU MünchenB.-R. Höhn FZG scuffing test evaluation

Σ

Δ

0

20

40

60

80

100

mg

5 6 7 8 9 10 11 121-4

load stage

30 60 90 120 150 kWhtransmitted work A

wei

ght c

hang

e m

average wear

beginninghigh wear rate

failure load stage

low wear rate

high wear rate (scuffing) Scuffing line

Scuffing lines

Scuffing

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G. SteinbergerTU MünchenB.-R. Höhn FZG scuffing test results

Test resultsFailure load stage of tested oilCalculation of scuffing temperature according to DIN 3990

Typical scuffing performance

typical scuffing load stage

> 12––150 – 220axle oil> 12––100 – 220transmission oil> 128 – 125 – 7100 – 320industrial gear oil

9 – 116 – 83 – 532 – 68turbine oil9 – 115 – 8 2 – 432 – 46ATFEP oilmild EPnon EP

typicalISO VG

lubricant type

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G. SteinbergerTU MünchenB.-R. Höhn

modifications of the standard FZG scuffing test A/8,3/90 13/144.21.36

G. SteinbergerTU MünchenB.-R. Höhn comparison of different scuffing test methods

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G. SteinbergerTU MünchenB.-R. Höhn results of industrial and transmission gear oils

0

100

200

300

400

500

600

700

800

2

14

13

121110

98764

C1 C2 C3 G1A G3 G4

GL3 GL4 GL4+

A/8.3/90 A10/16.6R/90 S-A10/16.6R/90

G6 G7

GL5

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G. SteinbergerTU MünchenB.-R. Höhn

scuffing integral temperaturefor different test methods

0

100

200

300

400

500

600

700

800

900

1000

3 4 5 6 7 8 9 10 11 12 13 14load stage

scuf

fing

tem

pera

ture

ϑin

t S in

°C

S-A10/16,6R/90

A10/16,6R/90

A/8,3/90

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G. SteinbergerTU MünchenB.-R. Höhn FZG wear test

Standard DGMK slow speed wear test C/0.05/90:120/12

Test parametersGear type CDip lubricationDriving pinion

weight loss of pinion and wheeltest result1 x 40 h2 x 20 h2 x 20 hrunning time

378.2 Nm378.2 Nm378.2 Nmpinion torque(load stage 12)

90 °C120 °C90 °Coil temperature100 rpm8.7 rpm8.7 rpmwheel speed150 rpm13 rpm13 rpmpinion speed0.57 m/s0.05 m/s0.05 m/spitch line velocity

C/0.57/90/12C/0.05/120/12C/0.05/90/12test conditions

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G. SteinbergerTU MünchenB.-R. Höhn modified FZG test rig for wear test

Test gear

Torque measuring coupling

Test wheel

Test pinion

Variable-speed motor

Speed reducer

Slave gear

Temperature sensor Load coupling Load lever with weights

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G. SteinbergerTU MünchenB.-R. Höhn FZG wear test procedure

0

0,1

0,2

0,3

0,4

0,5

0,6

0 20 40 60 80 100 120Time [h]

0

20

40

60

80

100

120

140

160

Pin

ion

spee

d n 1 [r

pm]

weight loss measurement

profile deviation measurement

90°C 90°C120°C

0,05m/s (13rpm)

0,57m/s (150rpm)

Pitc

h lin

e ve

loci

ty v

[m

/s]

t

gear type Cp =1853N/mmT =378.2Nm

C2

Pinion

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G. SteinbergerTU MünchenB.-R. Höhn FZG wear test evaluation

High wear

Medium wear

Low wear

wea

r sum

running time0

100

200

mg

20 40 60 80 h

300

400

500

700= 90 °Cϑoil = 120 °Cϑoil

low wear

120100

= 90 °Cϑoil

medium wear

high wear

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G. SteinbergerTU MünchenB.-R. Höhn FZG wear test results

Test resultsWear category of tested oilSpecific wear rate of tested oilIntroduction of specific wear rate into wear calculationaccording to Plewe

Wear category

> 500 mgvery high< 500 mghigh< 200 mgmedium< 50 mglow

Sum wear per each test periodWear category

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G. SteinbergerTU MünchenB.-R. Höhn FZG micropitting test methods

1 week (2 runs),screening test method

6...8 weekstotal test time

GF-class (GFKT)failure load stage,GF-class (GFT), information on longtime behaviour

test results

KS 7, KS 9KS 5...10 + endurance test

test course

1.5 l in the test gearbox

total amount 25 l, about 2 l/min

amount of lubricant

dip lubricationspray lubricationlubrication

type FZG-C-GF, Ra = 0.5 ± 0.1 µmtest gears

FZG test gear rig, a = 91.5 mmtest rig

short test GFKT(DGMK 575)

standard test GT(FVA 54/I-IV)

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G. SteinbergerTU MünchenB.-R. Höhn FZG micropitting test procedure

running time

load

sta

ge

stage test endurance test

runn

ing-

in, 1

h

3

5

8

6

10

7

10

89

10 10 10 10

running time per load stage16 h

running time per load stage16 h

running time per sequence80 h

running time per sequence80 h

failure criterion: ffm > 7.5 µm

failure criterion: ffm > 20 µm or pitting

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G. SteinbergerTU MünchenB.-R. Höhn FZG micropitting test evaluation and results

failure limit,load stage

test

0

2

4

6

8

10

12

14

16

[µm]20

load stage testrunning time 16 h / load stage check every 80 h

endurance test

5795 945 1094 1245 1395 1547 1245 1547

6 7 8 9 10 8 10 10 10 10 10 load stagepC [N/mm2]

lubricants:ISO VG 32

FZGmicropitting test

C / 8,3 / 90

micropitting load capacity:

mea

npr

ofile

devi

atio

nf fm

test terminatedbecause of pitting GFT - medium

GFT - high

GFT - low

failure limit,endurance

test

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G. SteinbergerTU MünchenB.-R. Höhn FZG-micropitting short test

aim:

• valid for lubricants with different viscosity

optimisedconcerning:

• duration• costs

• lower amount of lubricant

• good correlation to FZG-micropitting test

short test method, screening testto evaluate the GFT of lubricants

FZG-micropitting

short test

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G. SteinbergerTU MünchenB.-R. Höhn FZG-micropitting short test procedure

running time

load

sta

ge9

3 ru

nnin

g-in

, 1h

7

running time per load stage16 h

running time per load stage16 h

failure criterion: ffm > 7.5 µm

max. running time: 33 hmax. running time: 33 h

max. duration: 3 dayswith repetition: 1 week

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G. SteinbergerTU MünchenB.-R. Höhn FZG-micropitting short test evaluation and results

DGMK-FZG Micro-Pitting Short Test

0

2

4

6

8

10

12

14

16

18

20

5 5 6 6 7 7 8 8 9 9 10 10 11 11 12Load stage

ffm

av.

max

. pro

file

devi

atio

n [µ

m]

GFKT-lowGFKT-mediumGFKT-high

Running time 16 h / load stage

Steinberger01.06.2002

7

Test conditions:

GFKT - C / 8.3 / 90

Roughness of thooth flanks in all tests:Ra = approx. 0.50 µm

Candidate lubricants:

Ra = (Ra1+Ra2)/2

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G. SteinbergerTU MünchenB.-R. Höhn FZG-micropitting short test examples

lubricant GFKT-medium

lubricant GFKT-high

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G. SteinbergerTU MünchenB.-R. Höhn pitting test methods

• PT C/9/90

• PT C/10/90

• PTX C/10/90

• PTX C/SNC/90

• PT C/LLS/90

• PT C/HLS/90

• PITS C i80 TS

• PITS C i95 TS

standard pitting test (single stage test)

practice relevant pitting test (single stage orapplication test)

pitting test with load collective

pitting test with oil ageing

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G. SteinbergerTU MünchenB.-R. Höhn comparison of FZG pitting test methods

standard pitting test PT (FVA-information sheet no. 2/IV)

practice relevant pitting test PTX(FVA-information sheet no. 371)

FZG back-to-back test rig, dip lubrication with constant oiltemperature (90 °C), pitch line velocity 8,3 m/s

single stage testload stage MS9 (T1 = 302 Nm) orMS10 (T1 = 372 Nm), depending on viscosity

single stage testload stage MS10 (T1 = 372 Nm), independent from viscosity

extension to application test possibleload stage MS9 (T1 = 302 Nm) orMS11 (T1 = 450 Nm), dependingon result of single stage test

gear type C-PTXpractice relevant flank modificationssuperfinished - Ra = 0.1 ± 0.05 µm

gear type C-PTno flank modificationsgrinded - Ra = 0.3 ± 0.1 µmmicropitting less or no micropitting

failure criterion: 4 % pitting on one pinion flank or 15 µm profile deviationresult: load cycles for 50 % failure probability LC50

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G. SteinbergerTU MünchenB.-R. Höhn FZG pitting test result

NPi

Failu

rePr

obab

ility

in %

80

60

40

20

10

2 442 6 8106 107

LC50

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G. SteinbergerTU MünchenB.-R. Höhn FZG pitting test results

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G. SteinbergerTU MünchenB.-R. Höhn modified SN-curve concerning pitting test result

106 107 108 109

load cycles at pinion

1100

1800

2000

2200

2500

1200

1300

1400

1500

16001700

105

hertz

ian

stre

ss p

C [N

/mm

2 ]

SN curve (straight lubricant)acc. to DIN 3990

ZLp50T = σHP50T,50%

σHPdauer,50%

„new“ SN curve fortested lubricant

MS 9

5•107

σHP50T,50%

σHPdauer,50%

N

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G. SteinbergerTU MünchenB.-R. Höhn Summary

FZG micropitting test

FZG pitting test

FZG scuffing test

FZG wear test

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