- Email: [email protected]
Metrologie et aptitudes fonctionelles des etats de surface microgeometriques
bearings. Kurtosis is a statistical interpretation of the amplitude/repetition rate of frequency data which represents 'spikiness'. A plot of kurtosis, /3, in different frequency bands indicates the condition of the bearing. For a 'healthy' bearing,/3 = 3; an increase in/3 in one band indicates initial damage, and more advanced damage is signalled by increasing values of/3 in more than one frequency band. The main advantage of kurtosis is that, unlike the basic vibration data, it is independent of rotational speed and bearing size. Also, there is no need for a 'signature' taken from the bearing when new. The technique was developed under BSC sponsorship at the University of Southampton Institute of Sound and Vibration Research. The Corporation are currently evaluating the technique in a number of works, and are building 'kurtosis meters'.
Applications A number of cases where condition monitoring has enabled, or offers prospects of, substantial savings were des-
cribed. For example, vibration monitoring of work-roll bearings on hot mills could save BSC £40-50000 per year. The importance of matching monitoring equipment to the application was illustrated by a heated debate over the value of Shock Pulse Monitoring. Frank Ibbott of Esso described their experience in refineries as "disastrous". Geoff Knight, Head of Rotary Testing for the National Coal Board, suggested that they had "about 70% success rate"; he knew of only two cases where SPM had given no warning of failure. Robin Monk of AVT Ltd stated that in his experience SPM "was no better than a wide-band spectrum analysis" and added that the system " . . . misses other defects such as alignment". Paul English, however, reported that shock pulse analysis using portable equipment is widely used throughout BSC. It seems that the Corporation use the pulse signals as early warning and the signal level to predict advanced wear and catastrophic failure.
March 14-15, 1977, Paris, France
Metrologie et Aptitudes Fonctionelles des Etats de Surface Microgeometriques The two day meeting which was organised by the Groupement pour L'Avancement de la Mechaniqtte Industrielle concerned the application of surface analysis methods to metal forming, metal cutting, lubrication, adhesive bonding, painting, and the study of road surfaces. The meeting attracted approximately 70 delegates, mostly industrialists, from many parts of France. Speakers drawn from industry and universities presented a wide range of topics related to the characterisation and statistical consideration of surfaces. The conference was divided into four sessions at which over twenty papers were presented.
Surface characterisation Session 1 was devoted to specification of standards and modern methods of surface eharaeterisation by electro-
190
mechanical profilometry methods. The introductory paper ~ reviewed the statistical techniques employed for surface analysis and demonstrated the composite elements which combine to form the total surface prof'fle. The speaker classified the roughness into six classes. The higher classes referred to the material's crystalline structure, the lower ones referred to waviness and form errors, caused for example by undulations present in machine tool slideways. Various statistical concepts were introduced, and the delegates were given an introduction to f'dtering techniques. A number of national standards were briefly reviewed. A lecture by Thomas 2 was devoted to applications of statistical surface measurement to engineering problems and he reviewed some of his earlier work. The paper by Prebet 3 introduced
TRIBOLOGY international June 1977
Overall, delegates were given the impression that various vibration monitoring techniques find the widest application. Other, perhaps more expensive, techniques such as spectroscopic oil analysis, ferrography, and thermography, are being developed and may find wider application in the future.
Papers presented* Westlake F. and Oxlade R. Why condition-
based maintenance? English P. and Rush A. From senses to sensors - a review of the broad spectrum of condition monitoring Monk R. The role of vibration techniques (;add, P. The role of fluid-based techniques. Green L. The roJe of thermography. Elliott M. The role of visual inspection. Matthews O. The role of data gathering and automatic test equipement. Neale MJ. and Woodley B.J. Selecting a system which pays off. * Preprints may be obtained from Conference Communication, Monks Hill, Tilford, Farnham, Surrey GUI O 2A J, UK
the concepts of three dimensional microgeometry, and a measurement technique developed by CETIM was described. The specimen is mounted on a table which can be moved in XY co-ordinates under the control of stepping motors, giving an automatic process. The measuring head incorporates a rectilinear reference, and a XY plotter enables a three dimensional perspective diagram to be produced. Lucas4 presented an interesting and unusual paper relating to the analysis of the profile of roadways. The speaker described an experimental apparatus which could be towed behind a vehicle without disturbing normal traffic flow. A method of analysis was described which enabled the power spectral density of the road surface to be obtained for wavelengths up to 40 metres in length. Results were presented which indicated that this method of roadway assessment is useful for the assessment of the acceptability of road construction methods and surfacing materials. A further paper by Thomas s demonstrated m a n y other ways in which stylus instruments could be employed, and he cited applications such as ship hulls and articular cartilages.
Contact The second session was concerned with the contact o f surfaces and included m a n y interesting and relevant fields including adhesive bonding, metal forming and metal cutting. An interesting paper by Gillberd 7 considered the effect of surfaces on glued joints and demonstrated a test procedure b y intermittent traction for determining the joint strength. This was followed by an interesting exposition b y Jezeguel s who discussed the rote o f surface topography in the wetting of surfaces by adhesives. The author explained the importance o f obtaining good wetting properties, pointing out that poor wetting resulted in weak bonds. It was thus recoguised that surface tension played an important part in adhesive bonding and an analysis based on a triangular asperity model was developed to relate surface microgeometry to surface tension. Hisakado 9 described the deformation mechanism at solid interfaces. A theoretical model was derived for an elastic displacement due to contact asperities occurring at a flat solid interface subjected to tangential forces, assuming that the asperities on the solids are conical with a random distribution o f slopes. Experimental evidence suggests that the model is valid, and that microslip and the elastic displacement for a given tangential force are smaller for two sand blasted surfaces than for a ground on sand blasted surface. A further interesting paper in the session was concerned with rolling of sheet steel and the effects of roll roughness on the processed steel 10 .
Surface analysis Session three was concerned with both optical and pneumatic methods for surface analysis. The papers included descriptions o f interference microscopy examinations of finely polished surfaces and the application o f lasers, including scanning laser beams. An interesting device was described b y Wartelle 19 who presented details of a pneumatic instrument for measuring surface irregularities. The principles of this instrument, which had only become available this year, were described and it was claimed to have advantages o f lightness, accuracy and rapidity of
c a t i o n , and four papers were presented in this area. A very informative discussion concerning the role o f roughness in the attainment o f hydrodynamic separation was presented by de Gee 2° . He showed that the region o f minimum friction depends upon a parameter defined as a contact parameter which takes into account surface roughness, force on the bearing, bearing length and Young's Modulus o f the bearing material. Other papers in this session were concerned with effects o f microgeometry on the behaviour of gears, and topography o f running-in o f marginally lubricated plain bearings.
Bielle J. Typologie des surfaces traces d6jet~es. Probldme du choix de la longueur "1" dans le calcul du crit~re R (1) des prof'fls mesur~s des surfaces ~ftraces dejet~es.
7
Gflibert Y and Collot C. Influence de la rugosit~ des subjectiles, de la microstructure et du module d'eqasticit~ des plaques m~talliques sur la r6sistance au cisaillement d'assemblages coil,s.
8
Jezequei M. and Pochard M. Influence de la microg~om~trie des surfaces dans les ph6nom~nes de moullage. Application au collage.
9
Hisakado T. Deformation mechanism at solid interfaces subjected to tangential loads. Felder E. D6termination du frottement et de l'6volution de l'~tat de surface du m~tal lors de sa d~formation plastique par le test de la barre. Moes A. Recherche de critdres fonctionnels en ~tat de surface. Application ~ l'emboutissage et ~ la peinture des carrosseries. Sayles R.S. and Thomas T.R. A stochastic explanation of some structural properties of a ground surface. Pasaskevas D. Nouvelles m6thodes optiques de caract6risation des ~tats de surface. Nomarski G. Application ~ila microscopie interf~rentielle ~i l'6tude des d~fauts r6siduels de surfaces finement polies utilis6es en optique et en m~trologie. Roblin and Menu M. Mesure de rugosit~ par speckle.
10
Information for industry
A refreshing feature o f this conference was the emphasis on presenting information to industrialists, rather than the self glorification of academics. There is obviously a need for conferences where academics gather to further their own knowledge, but in contrast there is a greater need for conferences to be held specifically for the benefit of industry. The conference organised b y GAMI appeared to meet the requirements o f the industrial delegates by providing a number o f basic papers which briefly introduced the fundamentals of the analysis methods. This was followed by a wide range o f applications papers and descriptions of specialised analysis methods. GAMI are to be congratulated for organising such a useful programme, and it would be wise for many British universities and polytechnics to follow their example by providing similar style meetings in this country. The interest o f the delegates was shown b y lively, and occasionally hostile discussions, which resulted in every session overrunning its allotted time by some considerable margin.
7". G. King and If. J. Stout
11
12
13 14
15 16 17 18
19 20
21
Papers presented 1
Perrat J. Crit~res usuels de caracterisation et appareillages de mesures.
2
Thomas T.R. and Sayles R.S. Some applications of statistical surface measurements to engineering problems.
23
3
Prebet M. ReprEsentation tridimensionnelle de la microgdom6trie des surfaces.
24
4
Lucas L Analyse moderne du profil des chauss~es; appareil, m~thodes d'analyse, r~sultats obtenus.
5
Thomas T.R. Some examples of the versatility of stylus instruments.
use.
The final session concerned applications of analysis techniques to lubri-
6
22
Jonathan J.M. and Clair J.J. Contr61e d'objects p6riodiques. Olivie M. Mesure de position de surface et d'~paisseur par balayage laser. Beranger M. Proc6d~s physico-chimiques d'examen des surfaces microg~om6triques. WartelleC. Nouvelles possibilit~s de la mesure pneumatique de la rugosit6. de Gee A.WJ. The rote of surface roughness in the attainment of separation of the running surfaces of hydrodynamically lubricated journal bearings. Georges J.M., Mathia T., and Szuder A. Remarques sur les correlations entre les critdres statistiques des ~tats de surface, les conditions de lubrification limite et les modes d'usinage al~atoires. Berthe M. Influence de la microg6om6trie sur la formation de film d' huile. Application aux engrenages. Stout K.J., King T.G., and Watson W. Topography of "running-in" of plain bearings. Courtel M.R. Synth6ses des journ~es.
GAMI, 3 Rue Fernand Hainault, 93 Saint Ouen, Paris, France
TRIBOLOGY international June 1977
191
Applications A number of cases where condition monitoring has enabled, or offers prospects of, substantial savings were des-
cribed. For example, vibration monitoring of work-roll bearings on hot mills could save BSC £40-50000 per year. The importance of matching monitoring equipment to the application was illustrated by a heated debate over the value of Shock Pulse Monitoring. Frank Ibbott of Esso described their experience in refineries as "disastrous". Geoff Knight, Head of Rotary Testing for the National Coal Board, suggested that they had "about 70% success rate"; he knew of only two cases where SPM had given no warning of failure. Robin Monk of AVT Ltd stated that in his experience SPM "was no better than a wide-band spectrum analysis" and added that the system " . . . misses other defects such as alignment". Paul English, however, reported that shock pulse analysis using portable equipment is widely used throughout BSC. It seems that the Corporation use the pulse signals as early warning and the signal level to predict advanced wear and catastrophic failure.
March 14-15, 1977, Paris, France
Metrologie et Aptitudes Fonctionelles des Etats de Surface Microgeometriques The two day meeting which was organised by the Groupement pour L'Avancement de la Mechaniqtte Industrielle concerned the application of surface analysis methods to metal forming, metal cutting, lubrication, adhesive bonding, painting, and the study of road surfaces. The meeting attracted approximately 70 delegates, mostly industrialists, from many parts of France. Speakers drawn from industry and universities presented a wide range of topics related to the characterisation and statistical consideration of surfaces. The conference was divided into four sessions at which over twenty papers were presented.
Surface characterisation Session 1 was devoted to specification of standards and modern methods of surface eharaeterisation by electro-
190
mechanical profilometry methods. The introductory paper ~ reviewed the statistical techniques employed for surface analysis and demonstrated the composite elements which combine to form the total surface prof'fle. The speaker classified the roughness into six classes. The higher classes referred to the material's crystalline structure, the lower ones referred to waviness and form errors, caused for example by undulations present in machine tool slideways. Various statistical concepts were introduced, and the delegates were given an introduction to f'dtering techniques. A number of national standards were briefly reviewed. A lecture by Thomas 2 was devoted to applications of statistical surface measurement to engineering problems and he reviewed some of his earlier work. The paper by Prebet 3 introduced
TRIBOLOGY international June 1977
Overall, delegates were given the impression that various vibration monitoring techniques find the widest application. Other, perhaps more expensive, techniques such as spectroscopic oil analysis, ferrography, and thermography, are being developed and may find wider application in the future.
Papers presented* Westlake F. and Oxlade R. Why condition-
based maintenance? English P. and Rush A. From senses to sensors - a review of the broad spectrum of condition monitoring Monk R. The role of vibration techniques (;add, P. The role of fluid-based techniques. Green L. The roJe of thermography. Elliott M. The role of visual inspection. Matthews O. The role of data gathering and automatic test equipement. Neale MJ. and Woodley B.J. Selecting a system which pays off. * Preprints may be obtained from Conference Communication, Monks Hill, Tilford, Farnham, Surrey GUI O 2A J, UK
the concepts of three dimensional microgeometry, and a measurement technique developed by CETIM was described. The specimen is mounted on a table which can be moved in XY co-ordinates under the control of stepping motors, giving an automatic process. The measuring head incorporates a rectilinear reference, and a XY plotter enables a three dimensional perspective diagram to be produced. Lucas4 presented an interesting and unusual paper relating to the analysis of the profile of roadways. The speaker described an experimental apparatus which could be towed behind a vehicle without disturbing normal traffic flow. A method of analysis was described which enabled the power spectral density of the road surface to be obtained for wavelengths up to 40 metres in length. Results were presented which indicated that this method of roadway assessment is useful for the assessment of the acceptability of road construction methods and surfacing materials. A further paper by Thomas s demonstrated m a n y other ways in which stylus instruments could be employed, and he cited applications such as ship hulls and articular cartilages.
Contact The second session was concerned with the contact o f surfaces and included m a n y interesting and relevant fields including adhesive bonding, metal forming and metal cutting. An interesting paper by Gillberd 7 considered the effect of surfaces on glued joints and demonstrated a test procedure b y intermittent traction for determining the joint strength. This was followed by an interesting exposition b y Jezeguel s who discussed the rote o f surface topography in the wetting of surfaces by adhesives. The author explained the importance o f obtaining good wetting properties, pointing out that poor wetting resulted in weak bonds. It was thus recoguised that surface tension played an important part in adhesive bonding and an analysis based on a triangular asperity model was developed to relate surface microgeometry to surface tension. Hisakado 9 described the deformation mechanism at solid interfaces. A theoretical model was derived for an elastic displacement due to contact asperities occurring at a flat solid interface subjected to tangential forces, assuming that the asperities on the solids are conical with a random distribution o f slopes. Experimental evidence suggests that the model is valid, and that microslip and the elastic displacement for a given tangential force are smaller for two sand blasted surfaces than for a ground on sand blasted surface. A further interesting paper in the session was concerned with rolling of sheet steel and the effects of roll roughness on the processed steel 10 .
Surface analysis Session three was concerned with both optical and pneumatic methods for surface analysis. The papers included descriptions o f interference microscopy examinations of finely polished surfaces and the application o f lasers, including scanning laser beams. An interesting device was described b y Wartelle 19 who presented details of a pneumatic instrument for measuring surface irregularities. The principles of this instrument, which had only become available this year, were described and it was claimed to have advantages o f lightness, accuracy and rapidity of
c a t i o n , and four papers were presented in this area. A very informative discussion concerning the role o f roughness in the attainment o f hydrodynamic separation was presented by de Gee 2° . He showed that the region o f minimum friction depends upon a parameter defined as a contact parameter which takes into account surface roughness, force on the bearing, bearing length and Young's Modulus o f the bearing material. Other papers in this session were concerned with effects o f microgeometry on the behaviour of gears, and topography o f running-in o f marginally lubricated plain bearings.
Bielle J. Typologie des surfaces traces d6jet~es. Probldme du choix de la longueur "1" dans le calcul du crit~re R (1) des prof'fls mesur~s des surfaces ~ftraces dejet~es.
7
Gflibert Y and Collot C. Influence de la rugosit~ des subjectiles, de la microstructure et du module d'eqasticit~ des plaques m~talliques sur la r6sistance au cisaillement d'assemblages coil,s.
8
Jezequei M. and Pochard M. Influence de la microg~om~trie des surfaces dans les ph6nom~nes de moullage. Application au collage.
9
Hisakado T. Deformation mechanism at solid interfaces subjected to tangential loads. Felder E. D6termination du frottement et de l'6volution de l'~tat de surface du m~tal lors de sa d~formation plastique par le test de la barre. Moes A. Recherche de critdres fonctionnels en ~tat de surface. Application ~ l'emboutissage et ~ la peinture des carrosseries. Sayles R.S. and Thomas T.R. A stochastic explanation of some structural properties of a ground surface. Pasaskevas D. Nouvelles m6thodes optiques de caract6risation des ~tats de surface. Nomarski G. Application ~ila microscopie interf~rentielle ~i l'6tude des d~fauts r6siduels de surfaces finement polies utilis6es en optique et en m~trologie. Roblin and Menu M. Mesure de rugosit~ par speckle.
10
Information for industry
A refreshing feature o f this conference was the emphasis on presenting information to industrialists, rather than the self glorification of academics. There is obviously a need for conferences where academics gather to further their own knowledge, but in contrast there is a greater need for conferences to be held specifically for the benefit of industry. The conference organised b y GAMI appeared to meet the requirements o f the industrial delegates by providing a number o f basic papers which briefly introduced the fundamentals of the analysis methods. This was followed by a wide range o f applications papers and descriptions of specialised analysis methods. GAMI are to be congratulated for organising such a useful programme, and it would be wise for many British universities and polytechnics to follow their example by providing similar style meetings in this country. The interest o f the delegates was shown b y lively, and occasionally hostile discussions, which resulted in every session overrunning its allotted time by some considerable margin.
7". G. King and If. J. Stout
11
12
13 14
15 16 17 18
19 20
21
Papers presented 1
Perrat J. Crit~res usuels de caracterisation et appareillages de mesures.
2
Thomas T.R. and Sayles R.S. Some applications of statistical surface measurements to engineering problems.
23
3
Prebet M. ReprEsentation tridimensionnelle de la microgdom6trie des surfaces.
24
4
Lucas L Analyse moderne du profil des chauss~es; appareil, m~thodes d'analyse, r~sultats obtenus.
5
Thomas T.R. Some examples of the versatility of stylus instruments.
use.
The final session concerned applications of analysis techniques to lubri-
6
22
Jonathan J.M. and Clair J.J. Contr61e d'objects p6riodiques. Olivie M. Mesure de position de surface et d'~paisseur par balayage laser. Beranger M. Proc6d~s physico-chimiques d'examen des surfaces microg~om6triques. WartelleC. Nouvelles possibilit~s de la mesure pneumatique de la rugosit6. de Gee A.WJ. The rote of surface roughness in the attainment of separation of the running surfaces of hydrodynamically lubricated journal bearings. Georges J.M., Mathia T., and Szuder A. Remarques sur les correlations entre les critdres statistiques des ~tats de surface, les conditions de lubrification limite et les modes d'usinage al~atoires. Berthe M. Influence de la microg6om6trie sur la formation de film d' huile. Application aux engrenages. Stout K.J., King T.G., and Watson W. Topography of "running-in" of plain bearings. Courtel M.R. Synth6ses des journ~es.
GAMI, 3 Rue Fernand Hainault, 93 Saint Ouen, Paris, France
TRIBOLOGY international June 1977
191