Conclusions of Part B: Rock properties influencing cutting and wear
This part conclusion presents some closing thoughts on the key concepts discussed in the preceding chapters. The part examines the influence of rock properties on cutting and wear of tools. It has been pointed out that the nature of the rock mass influences excavation. The rock material properties relevant during cutting have been established mainly by tests carried out in the laboratory. The scraper test of Jan Reinout Deketh has shown that during the penetration of the cutting tool into the rock, the tool at first scrapes over the rock surface and experiences a transition towards real cutting. If adhesive wear occurs, the tool surface is weakened due to temperature dependent phase transformations in the tool material. At temperatures below the tool material weakening threshold, wear will be mainly by abrasion. Abrasive wear is mainly due to the contrast in hardness between the mineral grains and the tool material.