ABSTRACT:

Tool's wear is a problem of the greatest importance in various field of the civil and mining engineering. In this paper the problem of rock abrasivity is discussed, some tests for the measurement of the abrasivity are proposed and some correlations between the wear of tools and the results of the tests are presented. Finally an original approach which considers the interaction of rock-metal pair is introduced.

RESUME:

L'usure des outils des machines d'abattage des roches et d'excavation joue un role economique très important dans l'ingenierie civile et minière. Dans cet article des essais de mesure de l'abrasivite des roches dans des differentes echelles et des correlations entre I'usure des outils et les resultats des essais sont presentes. Enfin une approche nouvelle est proposee, qui prend en consideration l'interaction de la couple roche-metal de l'outil.

ZUSAMENFASSUNG:

Der Werkzeugenverschleiss der Abbaumaschinen, die im Bergbau und in den Baustellen angetrieben werden, verursachen hohe Geldkosten fuer die Unternehmungen. Im Beitrag werden Versuchsproben fuer die Bestimmung der Schleifeigenschaften in der verschidenen Masstaben eingeleitet; dann werden einige Wechselbeziehungen zwischen erkzeugenverschleiss und Versuchsergebnissen dargestellt. Zum Scluss wird ein eigenes Verfahren, hinsichtlich des Wechselwirkung zwischen Hartmetall und Gesteine, ausfuehrlich erklart.

1 FOREWORD

The tool's wear is a problem of the greatest importance in various fields of the civil and mining engineering, specially for the economical implications. In the tunnel excavation with Tunnel boring Machines (TBM), for example, the wear of discs can involve up to 8–10% of the total cost of the excavation work. The attention may be directed on the various and different technical applications in the civil and mining fields: rock drilling, rock excavation by machines (TBM's, road headers), cutting and ploughing of the weak rocks in mines and quarries, the comminution of rock by crushers, and so on. Frequently to a certain application corresponds a typical art of operation of the tool or of the machine, so the parameters involved in the phenomena may be different from a case to another. From this fact it follows that each problem has been studied from its particular point of view and then, a difficulty arises to unify a field of researches and experiences so various and scattered, From the other part, in rock mechanics the subject of the mutual interaction between the rock and the metal tool, though being from long time studied, had not, specially in recent times, the attention that such important field requires. The aim of this paper is to add, in any case, a little stone to the building of the knowledge of the phenomena considered, that is slowly progressing.

2 GENERAL

In rock excavation, in drilling, in comminution, the rock-metal interaction gives rise to two effects, the desired one, rock destruction, and the unwanted one, metal destruction. The latter can take different forms, schematically classed as wear and breakages, whose cumulated effect is accounted as metal loss, or referring to unit production, specific metal consumption (metal mass or number of tools, lost per cubic meter of rock). We deal here mainly with the wear subject, tough being wear and breakages somehow interconnected. Wear is the cumulated effect of micro-breakages (scratches and pits) occurring in the metal at the metal-rock contact points; in the fields considered, wear is essentially a mechanical phenomenon, though being chemical metal destruction (corrosion) a sizeable component of metal loss in special cases. Rocks are mechanically characterised in many ways, and at different size scales, mainly with the aim of solving stability problems.

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