Thermal shock assisted percussive drilling: A numerical study on the single-bit axisymmetric case

Abstract Fragmentation characteristics of granite in rotary-percussive drilling are studied using the distinct element method. We developed a model to investigate the interaction between the rock and a Polycrystalline Diamond Compact cutter. The micro contact parameters in the model are calibrated by conducting a series of simulated mechanical tests of the rock. Sensitivity analyses are then conducted according the drilling performances which are quantified as the penetration displacement, the fragmentation volume and the specific energy, as well as the lateral force and the particle size distribution. Results show that the model can well represent the typical fracture system under indentation of the cutter, the torque fluctuation phenomenon in drilling and the formation of lateral chips, which verify the reliability of the model. The cutter with a back rake angle of 55°and impact frequency of 30Hz has the best penetration performance in evaluated parameters. Increasing the frequency has a great effect on the rock breaking speed under the coupling effect of impact and cutting in the low frequency range. Considering crushing efficiency, 50 Hz is the recommended impact frequency. This paper provides a useful tool to represent the fragmentation performance of rotary-percussive drilling and sensitivity analyses shed light on the potential ways to improve the performance.

Download Full-text

Experimental and Numerical Study of a New Percussive Drilling Model With a Drift

Volume 5: 19th Biennial Conference on Mechanical Vibration and Noise, Parts A, B, and C ◽

10.1115/detc2003/vib-48624 ◽

2003 ◽

Cited By ~ 2

Author(s):

Luiz Fernando P. Franca ◽

Hans Ingo Weber

Keyword(s):

Numerical Analysis ◽

Chaotic Motion ◽

Hard Rock ◽

Penetration Rate ◽

Numerical Study ◽

Experimental Investigations ◽

Harmonic Load ◽

Percussive Drilling ◽

Forward Motion ◽

Stick Slip

New drilling techniques have been studied to increase the penetration in hard rock. These techniques use harmonic load and, in some cases, also impacts to generate a greater penetration rate. Analyzing only a percussive penetration phenomenon, the new model presented in this paper allows the forward motion (with a drift) in stick-slip condition without impact. Numerical and experimental investigations are presented and are qualitatively compared. Expanding the numerical analysis it is shown that the behavior may vary from periodic to chaotic motion.

Download Full-text

Thermal fracture of zirconia–mullite composite thermal barrier coatings under thermal shock: A numerical study

Surface and Coatings Technology ◽

10.1016/j.surfcoat.2008.08.003 ◽

2008 ◽

Vol 203 (1-2) ◽

pp. 91-98 ◽

Cited By ~ 23

Author(s):

Anna Gilbert ◽

Klod Kokini ◽

Santosh Sankarasubramanian

Keyword(s):

Thermal Shock ◽

Thermal Barrier Coatings ◽

Numerical Study ◽

Thermal Barrier ◽

Thermal Fracture ◽

Barrier Coatings

Download Full-text

3D numerical modelling of thermal shock assisted percussive drilling

Computers and Geotechnics ◽

10.1016/j.compgeo.2020.103849 ◽

2020 ◽

Vol 128 ◽

pp. 103849

Author(s):

Timo Saksala

Keyword(s):

Numerical Modelling ◽

Thermal Shock ◽

Percussive Drilling ◽

3D Numerical Modelling

Download Full-text

A controller for safe, convenient operation of LaB6 emitters on electron-beam instruments

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100075798 ◽

1983 ◽

Vol 41 ◽

pp. 408-409

Author(s):

W. J. Abramson ◽

H. W. Estry ◽

L. F. Allard

Keyword(s):

Electron Beam ◽

Control System ◽

Thermal Shock ◽

Appropriate Care ◽

Electron Guns ◽

Tungsten Filaments ◽

Order Of Magnitude ◽

Main Components

LaB6 emitters are becoming increasingly popular as direct replacements for tungsten filaments in the electron guns of modern electron-beam instruments. These emitters offer order of magnitude increases in beam brightness, and, with appropriate care in operation, a corresponding increase in source lifetime. They are, however, an order of magnitude more expensive, and may be easily damaged (by improper vacuum conditions and thermal shock) during saturation/desaturation operations. These operations typically require several minutes of an operator's attention, which becomes tedious and subject to error, particularly since the emitter must be cooled during sample exchanges to minimize damage from random vacuum excursions. We have designed a control system for LaBg emitters which relieves the operator of the necessity for manually controlling the emitter power, minimizes the danger of accidental improper operation, and makes the use of these emitters routine on multi-user instruments.Figure 1 is a block schematic of the main components of the control system, and Figure 2 shows the control box.

Download Full-text