Abstract

Periodic singular stress fields and K-dominant regions arise adjacent to sharp 90° indenter edges if an elastic substrate is subject to indentation with rigid, flat-ended and periodic indenters. The concept of indentation stress intensity factor Kind is convenient to describe such a singular indentation stress field, which is mathematically similar to that of a Mode-I crack. The singular indentation stress field is sufficient to induce surface cracking even if the substrate surface is free of any micro-cracks. This surface cracking mechanism generated from the flat-ended indentation potentially can play a significant role in damage analysis of rock cutting. During the rock-cutting processing, those periodic singular-stress fields will move along the rock surface, leading to continuous rock surface fracture. In this study, a fracture mechanics model is proposed for rock breakage by using an energy-based approach. The indentation stress intensity factor Kind and indentation cracking equation for rock-cutting/breakage have thus been formulated analytically.

Highlights

  • A rock-cutting tool schematically illustrated in Fig.1 can be modeled by periodic rigid and flat-tipped indenters

  • When an half-space elastic substrate is subject to indentation with rigid, flat-ended and periodic indenters, a periodic singular stress fields and K-dominant regions should arise adjacent to the indenter edges

  • The singular indentation stress field is sufficient to induce cracking from a smooth crack-free surface, which can potentially play a significant role in damage analysis of rock cutting

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Summary

Introduction

A rock-cutting tool schematically illustrated in Fig. can be modeled by periodic rigid and flat-tipped indenters. It is noted from the work [1-4] that a mixed-mode singular stress field exists in an incompressible substrate at the sliding contact edge of a rigid flat-ended indenter pressing down onto the substrate. The damage in a form of the micro-crack initiation on the contact surface will be induced by such a singular stress field, which can contribute substantially to rock cutting. A fracture-based method similar to the classical fracture mechanics is proposed to formularize the cracking or indentation damage induced by the singular indentation stress field next to the corners of the periodic indenters

Periodic indentation configurations
Boundary Condition
Singular stress fields due to the normal and tangential loads
Characters of the stress fields
Conservation integral
An indirect technique on the periodic indentation
Energy release rate for boundary cracking
Conclusions

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