Textile tribology

Textile tribology

European countries. When introducing the SI system, a few units will have to be replaced, for example, the metric horsepower, the calorie and the kilo...

293KB Sizes 0 Downloads 49 Views

European countries. When introducing the SI system, a few units will have to be replaced, for example, the metric horsepower, the calorie and the kilopond. In some branches of industry the unit inch is still used. At Norwegian schools and universities SI units have been introduced and are being used to an increasing degree. The Norwegian council for secondary education emphasised recently that SI units must be used in science instruction. This will undoubtedly accelerate the introduction of the SI system in Norway. During the last two years the Norwegian Standards Association has issued new standards that conform with the IS0 recommendations for quantities and units. A complete changeover to SI units in Norway depends largely on what is done in other countries and by international organisations like IS0 and IEC. Poland (J. Wodzicki, President, Polish Standards Committee) In March 1968 the Polish Committee for Standardisation prepared ‘Directives for the application of SI units to standards and standards publications’. The general regulations contained in these directives are as follows: 1 The values of the parameters specified in Polish standards, sectional standards and company standards must normally be expressed either in SI units or in their decimal multiples, or in other units agreed upon the application concerned. 2

The introduction of SI units into the standards carried out in two stages.

Conference papers Simonsgaard, V. (Danish Standards 1 agreed SI units’

Sweden (Technical Board of the Swedish Standards Institution) Nearly all Swedish standards have included both SI units and the previously used units. These units have been presented with the previously used units quoted first and the SI units in parentheses. In recent standards SI units have preceded the previously used units which then appear in parentheses. At present, however, this practice is limited. The next step will be to express quantities in SI units only. France (J. Clerc, Director of Technical Co-ordination, The French Standards Association) It would be inaccurate to state that only SI units are now employed everywhere. But it is correct to emphasise that the adoption of SI has been in constant progress for the last eight years and that the use of SI is spreading to all fields, due to the efforts of specialists and teachers, of the Service of Instruments of Measurement, and of the French Standards Association. United Kingdom (G. B. R. Fielden, Deputy Director General, British Standards Institution) The United Kingdom has decided to change from the imperial system of units to the metric system. National plans are

Nottingham. 1 July 1969 TEXTILE TRIBOLOGY of Mechanical and Production Engineering, Regional College of Technology

Intricate machines for making lace and hosiery pose some very interesting tribological problems. P. Wilson has done some research on wear in the Leavers Lace machine. His programme involved a search for new materials and re-

Association)

‘The

2

Hens, A. T. (NV Philips Gloeilampenfabrieken, Eindhoven, Holland) ‘The practical application of SI units in the field of mechanical engineering’

3

Ede, A. J. (The University of Aston in Birmingham) ‘Design calculations in SI units’

4

Ludwig, N. (German Standards Association) ‘Problems in introducing SI units in the field of materials testing’ Weibull, I. (Alfa-Laval AB, Tumba, Sweden) ‘SI units in Swedish metal standards’ Jacobs, P. (Mons Polytechnic Faculty, Belgium) ‘Electrical engineers and the international system of units’

5 6

must be

The first requires that SI units are quoted for values of parameters whenever non-SI units are used. The second eliminates non-SI units. The directives are to be put into practice (1) in the preparation of projects of standsrdisation as from July, 1969 and (2) in the preparation of standards publications as from January, 1970.

Department Nottingham

that by 1975 a substantial proportion of British industry will have changed to the metric system; progrsmmes published by the British Standards Institution (BSI) in co-operation with major industries, such as general engineering, building and construction, ship-building and marine engineering, and electrical engineering show that by 1975 about 75 per cent of production should be in metric measure. The UK has decided that its only reasonable action is to move in one step to the International System of Units. Bound conference proceedings are available from PERA.

7

Tinbergen, D. (International Gas Union, Holland) introduction of SI in the gas industry’

8

Glass, H. M. (British Standards Institution) Wynn, A. H. A. (Ministry of Technology, United Kingdom) ‘Energy units and the consumer’

9

Aroutunov, V. O., Oleinik, B. N., Chirokov, K. P. (Committee for Standards, Measures and Measuring Instruments under the Council of Ministers of the USSR) ‘Principles of standardization of units for physical quantities in the USSR. Bager, 0. (Telefon AB L. M. Ericsson, Stockholm, Sweden) ‘Recommendations to Swedish power industry on the use of units’ Noren, A. (Royal Institute of Technology, Stockholm, Sweden) ‘Energy terms for hydraulic machinery’

10

11

‘The

12

Professor Leyniers, Brussels)

13

Clarke, M.D. (British Standards Institution) ‘The use of SI units in the UK construction industry’ Nergard, L. (Danish Standards Association) ‘The application of SI units in the construction and building industry in Denmark’ Lyng, 0. (Norwegian Council for Building Standardization) ‘The application of SI units to the construction and building industry’

14

15

16

Thomas, (Belgian Institute of Standardization) M. (Centre of the Royal Military School, ‘The use of SI units in vacuum technology’

Gigou, A. (French Association for Standardization) ‘Application of SI units to civil engineering and the building industry’

design, development of compounds for in situ repairs of worn parts, and durable self-lubricating coatings. Among the materials used were ptfe with various fibres and an interesting American surface coating technique was mentioned which could deposit tungsten carbide &, millionth of an inch thick capable of withstanding 35O,OOOlbf/inz. Skilbeck from Glacier said that operating speeds of textile machinery have doubled in the last five years. High speeds and a hostile environment due to airbone fly (dust from yarn, Tribology

November

1969

243

especially prevelsnt in carpet mills) make dry or pre-lubricated bearings a favourable solution for spindles in textile machinery. Yarn lubricants must be able to withstand high sliding speeds and must not stain the yarn. F. Hurt described various yarn lubricant principles.

2

Only thirty delegates interesting problems solve.

4

were present but this field has some that will require a lot of research to

5

Conference papers 1 Holdsworth, S. (Lace Research Association, ‘The history of the lace machine lubrication

Silsoe, Bedford. ABRASIVE Materials

6 Nottingham) and wear’

16,17 July 1969

WEAR OF MATERIALS Science Club *

There are probably few technical or scientific conferences which fully satisfy the expectations of their organizers and participants, but this meeting on abrasive wear must come close to qualifying for inclusion into this select group. A considerable part of the credit is undoubtedly due to Dr R. C. D. Richardson and his colleagues at the National Institute of Agricultural Engineering who took particular care in selecting both a well-balanced range of topics and the individual speakers for each. The resulting blend of academic and practical work was one which organizers of conferences in other areas of tribology have long tried to achieve. The first part of the meeting was devoted to fundamentals and reviews of the current state of knowledge on the abrasive wear of different types of materials-metals, polymers, rubbers and brittle solids. The differing deformation processes in these materials lead to different mechanisms of wear and considerable effort has been expended in trying to relate wear to material properties. With metals, the major part of the wear process usually results from cutting on a localised scale, and the angle of attack of the abrading particles or asperities is an important factor. The controlling material parameter is hardness,but there is still some difficulty in explaining the well-established linear relationship between wear resistance and the hardness of the annealed metals, in view of the fact that abrasion produces extreme work-hardening of the surface layers. For both polymers and rubbers the controlling material parameter appears to be the energy to break, as typified by the area under the stress-strain curve. Fatigue wear processes become increasingly important as the elastic modulus of the material &creases and when the contacting hard asperities are rounded rather than sharp. In brittle solids crack formation and propagation govern the damage obtained and there are significant differences between crystalline materials, such as MgO and ‘amorphous’ ones, such as glass. When a hard slider moves over a flat plate, abrasion can arise as a result of fractures in three areas. Tensile stresses behind the slider cause characteristic ring cracks, dislocation reactions cause cracks on particular crystallographic planes in front of the slider, and finally, cracks may be produced parallel to the surface as a consequence of plled-up edge dislocations. As a general summary of this first session, whilst no really major advances were reported, it was abundantly clear that steady progress is being made in elucidating.detail. An essential part in this is the use of sophisticated ‘techniques for surface examination and the session was concluded with a review by Dr Wilman of the uses of electron diffraction for studying abraded surfaces. Following this background survey, the second, and major, part of the conference was devoted to specific problem areas in abrasive wear. Transport was well to the fore here and 244

Tribology

November

3

1969

Wilson, P. (Lace Research Association, Nottingham) ‘Current tribological research on the Leavers lace machine’ Askwith, T. C. (Tribology Unit, Leeds University) ‘Factors involving choice of solid lubricant in lace machinery’ Skilbeck, J.. (Glacier Metal Co, Wembley) ‘Dry and prelubricated bearings’ Hurt, F. N. (Hosiery and Allied Trades Research Association, Nottingham) ‘Lubrication of yarns for lolitting Jarvis, R.N. (Research Department, Courtaulds, Spondon) ‘Frictional properties of fabrics in terms of other mechanical properties’

the papers ranged over such diverse topics as sand and rain erosion of engine components, wear of rubber tyres, cast iron brake blocks, carbon brushes on copper slip rings and even the wear of shoe-leather soles. Some surprisingly abstruse information came to light, such as the fact that raindrops will bounce on pea leaves but not on broad-bean leaves, that English children are much more erratic in wearing out their shoes than Dutch adults, and that alcohol is much less harmful to teeth than certain, unspecified, soft drinks. Rather more significant from an economic standpoint, however, were descriptions of the enormous rates of wear which are sometimes observed in practice. Dr Shallamach re-emphasized that tyre wear varies as the fourth power of the speed during cornering, and Dr Tilley reported that the life of hovercraft turbines operating in desert conditions can be as short as 35 minutes. In many examples of abrasive wear in practice there is a growing realisation of the importance of fatigue wear processes. Multiple impacts are usually required to initiate sand or rain-erosion damage, and in a very different field, Mr Bale showed that the wear of dffferent grades of carbon brushes on copper correlates well with the ratio flow stress/fatigue endurance limit. It is perhaps in these areas where fatigue becomes the dominant failure process-low modulus materials, rounded asperities and elastic deformation-that more research is required. Abrasive wear is usually considered to be a particularly serious problem in comminution and it was pleasing to learn from Mr Dodd that considerable progress has been made over recent years in extending the life of components involved in such processes. Replacement of manganese steel liners (by alloy cast irons) in ball mills for reducing cement clinker has increased lives from several months to several years. In this type of problem it is a relatively straightforward affair, albeit expensive and time-consuming, to test different materials in the practical situation. When the human element enters into a problem, however, testing inevitably increases in complexity. This point was wellillustrated by Dr Mitton’s paper on testing of shoe leathers, where different individuals performing identical functions may exhibit enormous differences in the rates of wear of their shoe-soles. Laboratory simulation is difficult and the seventeen or so different types of apparatus which have been used do not always rate materials in the same order. The problem is aggravated even further by the fact that-the raw material-leather-is not an entirely consistent and reproducible product. Similar considerations apply when studying the abrasion of teeth by dentifrice. Dr Wright has spent a great deal of time and effort in developing a standard laboratory test method for assessing the abrasiveness of toothpaste and using radioactive tracer techniques has examined the wear of both enamel and dentine. There issome evidence that with many types of toothpaste the wear ofthe dentine is now close to the tolerable limit. The discussion.following this paper suggested that the manufacturers are well aware of all the.complicati’ons involved in abrasion by toothpastes; it may possibly be significant, however, that Dr Wright still prefers to use hfs own personal formulation.