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Paper XI (vii) Monitoring of Wear of Large Machinery With use of Oil Sampling
Wear Particles - D. Dowson et al. (Editors)
0 1992 Elsevier Science Publishers B. V. All rights reserved.
483
Paper Xi (vii)
Monitoring of Wear of Large Machinery with Use of Oil Sampling 1. Mazdrek and P. DobeS
The evaluationprocedure of the course of the mechanical System wear (the automotive gearbox) based on oü sampling is described. Further, the using of this procedure, changed to the Computer program, is described on example of comparathre test oi automdive gearboxes.
1. iNTRODUCTlON
2.2 EVALUATiON OF WEAR
The research of w a r during the deveiopment of new cars (and other products) becomes more and more important. Many types of tests are used for this purpose, from the simplest instrumentaltests to long term operational testing d the compieted machine. Our general target was to fulfil the gap between the test on test gearbox FiG and the full scaie test on the Prototype of a new car with the stand wear test of a fuii scaie gearbox. From this arised the need of a new testing procedure, especialiy the elaboration of an algorithm for Computer evaluation of a long term wear monitoring test.
To obtain the maximum speed up of the test and dimination of negative influences on representative resuits, it was decMed to use the particies in ol without monitoring of wear dismantling.After each load Hock was completed, the sampling of oii was carried out. The analysis of wear particies was performed using more methods, and as a dominant method AAS analysis of Fe concentration was found.
h
2
2. TESTMETHOD
p
64 48
12
4O 2O 3O
16
2.1 MODELLlNG OF REAL LOAD
At first, the problem of the real Operation conditions modelling was solved. The gearbox is loaded on the test stand at constant speed by ioad biocks, whkh are repeated in cycles, and their effect is equivaient to the operational loading spectrum.
Constantinputved: Total Of the bleck: Corresponding ran track: o, running:
Generation of a ioad biock was made with a high care, as it is vety important'for outstanding Of this test -Pared with the test @-'p Operation. For each gear degree, the Mock was designed as a two levei biock, one level for possitive and the othor for negative sign of torque (Fig.1).
Fig. 1
Magram for two level loading block Fiesta 4' gearbox
3900 RPM 1.9 GJ 2500 km 164 kmih
- Ford
484
3. ALGORITHM OF TEST RESULTS EVALUATION At the end of the test procedure, not only operational
data (timetable of loading and sampling, vdume of sample) but also these wear data of oil are received: 0
0
0
0
concentration of impurities in oii M o r e the test fi, Concentration of impurities in d after the test 6l, amount of washed out particles after the test N, wear partides concentration in each sample N,
lmportantfor correct evaluation of tribologicai state in the gearbox is the procedure of analysis of resuits. The sirnplest modei is the computatbn of the difference between beginning and final concentration of wear partides. Nevertheiess, by this procedure we neglect at least the particles sedimented on gearbox Walls. So we need to solve the question of sedimentation and separation of wear partides. The maln reasons of separation of wear particles from oii are adhesive and squeezing procedures resulting in squeezing of partides especially to nonmoving parts. Simiiarly as In [2] the separation coefficient to calculationwas introduced,whkh describesefficiency of separation of wear particles. With regard to evaluation of the amount of separated wear partides, we receive oveiview informatlon on total production of w a r particles during the test. If we know the tlmetaMe of loading and sampling, we can enumerate the separation coefficient which is described as a ratio of separated to total amount of wear partides in a given time period. Duringthe experiments it was confirmed, that in intensive test operation of the gearbox the stratification of particies in oii occurs. Because the sample is always withdrawn from the same place, we do need to know the dependence betwwn the concentration of partides in this place and the mean concentrationin all the filiing. Taking into account the value of the last sample concentration and mean filling concentration after drainage, we can include the stratification coefficient b, which describes this effect quantitativeiy, to the caicuiation. Nevertheless, in this case we are not aMe to take into account the different intensity of generation ot wear particies x in diiferent test perlods. In case of failure of the gearbox in the end of the experiment, all the results of expensive test are
deteriorated. Thus we need to indude the concentration of each sample to evaluation and establish the coefficients of wear production between individual samples. Completing all these calculatlorrswe are able to modei the Course of the apparent concentratlond wear partides in ideal conditlons, when: 0
0
0
0
no Separation of particles exists no stratificath d partides In the fiiling exists the process is not affected by =mpling the loading of the gearbox tS COnStant
The result Os this procedure gives us the intensity d wear In each period of the test (Fig.2). Based on the Course 04 the apparent concentration d wear partides, we are able to separate individual atypical Stages of the experiment (running-in, failure) and for a selected part of the test we can make regrescion analysis (designed by a straight iine). The algorithm gives the possibüiiyto get back the Course of the real concentration of w a r particlesend verify how tight the simulation is (Fig.3).
8
100
200
Mo
400
Rrotlon [h]
Fig. 2 Example oi the Course oi the apparent Concentration oi
wear partichs in oil during the tesi
These above mentioned physicai modeis created the basis for mathematical models, whkh were saived, with respect to their nonlinearlty, by an iteratlon method. The computationai procedure 1s described in detail in [l], here only the flow chart 1s given (Fig.4). When the algoriihm is started, ii is branched with the dependence to sufficiency of given values. The left branch of the chart describes ths soiution d complete enter data. In the central part Os the chart the Situation is sdved, when for some reasons the amount of sedimented wear particles is not known
485
(the casing was not washed). In this case the value of the Separation coefficient a, found during simlar experiment, 1s needed. The rlght branch of the chart
4 0
100
200
300
The comparative measurement of gear Oys in a Prototype gearbox S781 (Skoda Favorit) gives the overview on tribological properties of these oils. Espechlly the second Version of SAE 75W/80 semisynthetic oii shows bad results.
D
400
Dumiirn [h]
Fig. 3 Exunpie oi moddling oi the w a r partide concmtration courso in piatx oi wnt (2) and the mran war particir concmtration in the sump (1). The pointa show the valur8 mrawred during the uiaIy808.
is reiated to the Situation, when no data on oii filling are avaUable (eg.after the fahre of the gearbox) and therefore we can not receive the mean concentration of wear partides after the test. In this case the program asks for the value of the stratification coefficient b. Iterationfunctions are tuned up for the fastest convergency and stability d the procedure in a wide range of input data. Using these relations the program TRIBOX for PC compatible Computers was generated. This program, using above mentioned enter data and parameters, can simulate the course d the apparent concentrationunder ideal conditions, and the Operator can decide, Wich period of the test wUI be regressionanalysed. The regression vilue of the coetficient of wear production is the final information describing the intensity of gearbox wear (or another machine). The results of computation are arranged into the Wear test evaluation sheet (Fig.5).
Fig. 4 flow chart of the computetionai p r d u r r
Because between the first (with PP 80 oii) and the last (with EP 80 oil) tests the gearbox ran the track equivalent to 94 OOO km, we should accept, that tribologicai conditions were not the same. For this reason the resuits of PP 80 oil are probaMy exaggerated, and so further Special comparative test of PP 80 oii and the last Version of SAE 75W/80/ED semisynthetic oil were carried out in the seriai gearbox S781 with better resuits of the new 03.
4. EXPERIMENTAL VERlFlCATlON
With respect to the fact that a test of a gearbox is expensive and time consuming procedure (400 h for one comparative test), not too many experiments were carried out. The results of tests of Skoda Favorit and Ford Fiesta gearboxes run in different lubricants are shown in Taue 1. Together with the values d the mean production of wear partides, the Separation CoefFicient and the stratification coefficient, the total production of wear partlcies and number of censored Mocks are also given here.
REFERENCES 1. Maztirek, 1.: Metodika hodnocenl zkouSek opotiebenl automobilo@ch pFevodo9ch skFfnf, Kand. diseitaCnl pdce, VUT-FS Brno, 1990 (Method Os evaluation d wear test of automotive gearboxes; PhD Thesis, Technical University of Brno, 1990) 2. Anderson, D.P.: Wear Particle Atlas, Telus Inc., 1982
486
ibcord:
Woer tost waiuation sh-t Gearboxtypo: Oil designatlon:
samp.
LMdinQdak Nx589 sampiinQdata NX5w
S781 72 -
No.
5159i21.04.1990
Sirmple concentr. [PPml
1 2 3 4 5 6
2.5 51.O 80.0 87.0 105.0 115.0
Not sampl. time [hl 0.00 39.00 77.00 106.00 144.00 180.00
Hlbar prod.
aw.
[ma/GJI 0.00 26.52 20.91 15.12 18.26 16.29
Note
cenrored
REGRESSION ANALYSIS Corrected wear production [ma/GJI: Correlaüon codiidont: Flg. 5 Tho evaiuatlon shmt
Tabie 1
17.11 0.-
0 1992 Elsevier Science Publishers B. V. All rights reserved.
483
Paper Xi (vii)
Monitoring of Wear of Large Machinery with Use of Oil Sampling 1. Mazdrek and P. DobeS
The evaluationprocedure of the course of the mechanical System wear (the automotive gearbox) based on oü sampling is described. Further, the using of this procedure, changed to the Computer program, is described on example of comparathre test oi automdive gearboxes.
1. iNTRODUCTlON
2.2 EVALUATiON OF WEAR
The research of w a r during the deveiopment of new cars (and other products) becomes more and more important. Many types of tests are used for this purpose, from the simplest instrumentaltests to long term operational testing d the compieted machine. Our general target was to fulfil the gap between the test on test gearbox FiG and the full scaie test on the Prototype of a new car with the stand wear test of a fuii scaie gearbox. From this arised the need of a new testing procedure, especialiy the elaboration of an algorithm for Computer evaluation of a long term wear monitoring test.
To obtain the maximum speed up of the test and dimination of negative influences on representative resuits, it was decMed to use the particies in ol without monitoring of wear dismantling.After each load Hock was completed, the sampling of oii was carried out. The analysis of wear particies was performed using more methods, and as a dominant method AAS analysis of Fe concentration was found.
h
2
2. TESTMETHOD
p
64 48
12
4O 2O 3O
16
2.1 MODELLlNG OF REAL LOAD
At first, the problem of the real Operation conditions modelling was solved. The gearbox is loaded on the test stand at constant speed by ioad biocks, whkh are repeated in cycles, and their effect is equivaient to the operational loading spectrum.
Constantinputved: Total Of the bleck: Corresponding ran track: o, running:
Generation of a ioad biock was made with a high care, as it is vety important'for outstanding Of this test -Pared with the test @-'p Operation. For each gear degree, the Mock was designed as a two levei biock, one level for possitive and the othor for negative sign of torque (Fig.1).
Fig. 1
Magram for two level loading block Fiesta 4' gearbox
3900 RPM 1.9 GJ 2500 km 164 kmih
- Ford
484
3. ALGORITHM OF TEST RESULTS EVALUATION At the end of the test procedure, not only operational
data (timetable of loading and sampling, vdume of sample) but also these wear data of oil are received: 0
0
0
0
concentration of impurities in oii M o r e the test fi, Concentration of impurities in d after the test 6l, amount of washed out particles after the test N, wear partides concentration in each sample N,
lmportantfor correct evaluation of tribologicai state in the gearbox is the procedure of analysis of resuits. The sirnplest modei is the computatbn of the difference between beginning and final concentration of wear partides. Nevertheiess, by this procedure we neglect at least the particles sedimented on gearbox Walls. So we need to solve the question of sedimentation and separation of wear partides. The maln reasons of separation of wear particles from oii are adhesive and squeezing procedures resulting in squeezing of partides especially to nonmoving parts. Simiiarly as In [2] the separation coefficient to calculationwas introduced,whkh describesefficiency of separation of wear particles. With regard to evaluation of the amount of separated wear partides, we receive oveiview informatlon on total production of w a r particles during the test. If we know the tlmetaMe of loading and sampling, we can enumerate the separation coefficient which is described as a ratio of separated to total amount of wear partides in a given time period. Duringthe experiments it was confirmed, that in intensive test operation of the gearbox the stratification of particies in oii occurs. Because the sample is always withdrawn from the same place, we do need to know the dependence betwwn the concentration of partides in this place and the mean concentrationin all the filiing. Taking into account the value of the last sample concentration and mean filling concentration after drainage, we can include the stratification coefficient b, which describes this effect quantitativeiy, to the caicuiation. Nevertheless, in this case we are not aMe to take into account the different intensity of generation ot wear particies x in diiferent test perlods. In case of failure of the gearbox in the end of the experiment, all the results of expensive test are
deteriorated. Thus we need to indude the concentration of each sample to evaluation and establish the coefficients of wear production between individual samples. Completing all these calculatlorrswe are able to modei the Course of the apparent concentratlond wear partides in ideal conditlons, when: 0
0
0
0
no Separation of particles exists no stratificath d partides In the fiiling exists the process is not affected by =mpling the loading of the gearbox tS COnStant
The result Os this procedure gives us the intensity d wear In each period of the test (Fig.2). Based on the Course 04 the apparent concentration d wear partides, we are able to separate individual atypical Stages of the experiment (running-in, failure) and for a selected part of the test we can make regrescion analysis (designed by a straight iine). The algorithm gives the possibüiiyto get back the Course of the real concentration of w a r particlesend verify how tight the simulation is (Fig.3).
8
100
200
Mo
400
Rrotlon [h]
Fig. 2 Example oi the Course oi the apparent Concentration oi
wear partichs in oil during the tesi
These above mentioned physicai modeis created the basis for mathematical models, whkh were saived, with respect to their nonlinearlty, by an iteratlon method. The computationai procedure 1s described in detail in [l], here only the flow chart 1s given (Fig.4). When the algoriihm is started, ii is branched with the dependence to sufficiency of given values. The left branch of the chart describes ths soiution d complete enter data. In the central part Os the chart the Situation is sdved, when for some reasons the amount of sedimented wear particles is not known
485
(the casing was not washed). In this case the value of the Separation coefficient a, found during simlar experiment, 1s needed. The rlght branch of the chart
4 0
100
200
300
The comparative measurement of gear Oys in a Prototype gearbox S781 (Skoda Favorit) gives the overview on tribological properties of these oils. Espechlly the second Version of SAE 75W/80 semisynthetic oii shows bad results.
D
400
Dumiirn [h]
Fig. 3 Exunpie oi moddling oi the w a r partide concmtration courso in piatx oi wnt (2) and the mran war particir concmtration in the sump (1). The pointa show the valur8 mrawred during the uiaIy808.
is reiated to the Situation, when no data on oii filling are avaUable (eg.after the fahre of the gearbox) and therefore we can not receive the mean concentration of wear partides after the test. In this case the program asks for the value of the stratification coefficient b. Iterationfunctions are tuned up for the fastest convergency and stability d the procedure in a wide range of input data. Using these relations the program TRIBOX for PC compatible Computers was generated. This program, using above mentioned enter data and parameters, can simulate the course d the apparent concentrationunder ideal conditions, and the Operator can decide, Wich period of the test wUI be regressionanalysed. The regression vilue of the coetficient of wear production is the final information describing the intensity of gearbox wear (or another machine). The results of computation are arranged into the Wear test evaluation sheet (Fig.5).
Fig. 4 flow chart of the computetionai p r d u r r
Because between the first (with PP 80 oii) and the last (with EP 80 oil) tests the gearbox ran the track equivalent to 94 OOO km, we should accept, that tribologicai conditions were not the same. For this reason the resuits of PP 80 oil are probaMy exaggerated, and so further Special comparative test of PP 80 oii and the last Version of SAE 75W/80/ED semisynthetic oil were carried out in the seriai gearbox S781 with better resuits of the new 03.
4. EXPERIMENTAL VERlFlCATlON
With respect to the fact that a test of a gearbox is expensive and time consuming procedure (400 h for one comparative test), not too many experiments were carried out. The results of tests of Skoda Favorit and Ford Fiesta gearboxes run in different lubricants are shown in Taue 1. Together with the values d the mean production of wear partides, the Separation CoefFicient and the stratification coefficient, the total production of wear partlcies and number of censored Mocks are also given here.
REFERENCES 1. Maztirek, 1.: Metodika hodnocenl zkouSek opotiebenl automobilo@ch pFevodo9ch skFfnf, Kand. diseitaCnl pdce, VUT-FS Brno, 1990 (Method Os evaluation d wear test of automotive gearboxes; PhD Thesis, Technical University of Brno, 1990) 2. Anderson, D.P.: Wear Particle Atlas, Telus Inc., 1982
486
ibcord:
Woer tost waiuation sh-t Gearboxtypo: Oil designatlon:
samp.
LMdinQdak Nx589 sampiinQdata NX5w
S781 72 -
No.
5159i21.04.1990
Sirmple concentr. [PPml
1 2 3 4 5 6
2.5 51.O 80.0 87.0 105.0 115.0
Not sampl. time [hl 0.00 39.00 77.00 106.00 144.00 180.00
Hlbar prod.
aw.
[ma/GJI 0.00 26.52 20.91 15.12 18.26 16.29
Note
cenrored
REGRESSION ANALYSIS Corrected wear production [ma/GJI: Correlaüon codiidont: Flg. 5 Tho evaiuatlon shmt
Tabie 1
17.11 0.-