scholarly journals A new approach to evaluate rock drillability of polycrystalline diamond compact bits using scratch test data

2020 ◽  
Vol 38 (4) ◽  
pp. 884-904 ◽  
Author(s):  
Yannong Han ◽  
Xiaorong Li ◽  
Yongcun Feng
Keyword(s):  
Specific Energy ◽  
Polycrystalline Diamond ◽  
New Method ◽  
New Model ◽  
The Core ◽  
Mechanical Specific Energy ◽  
Rock Drillability ◽  
Micro Drilling ◽  
Scratch Tests ◽  
Polycrystalline Diamond Compact

Rock drillability is a comprehensive index that indicates the ease of drilling a hole in the rock mass, which is a main basis for the design of drilling bits, the optimization of drilling operational parameters, and the prediction of rate of penetration. This paper established a conversion relationship between mechanical specific energy measured from micro-drilling tests and mechanical specific energy measured from scratch tests, based on the consistency of rock breaking mechanism between these two types of tests. By incorporating the methodology of calculating rock drillability grade of polycrystalline diamond compact bits, a new mathematical model for predicting rock drillability of polycrystalline diamond compact bits is developed. Subsequently, a new method for acquiring continuous rock drillability profile by scratching the core surface is developed. A wide range of rocks with different hardness were tested by the proposed scratch method. The results show that the new model has high consistency with the results of laboratory micro-drilling tests. For example, the average errors of sandstone, shale, and carbonate test results are only 7.41%, 8.18%, and 4%, respectively. The new method can fully characterize the effect of mineral composition, cementation strength, and microstructure of rock on drillability. Besides, the new model has high utilization efficiency of expensive core samples because the core usually remains nondestructive after scratch tests.

Relative Significance of Multiple Parameters on the Mechanical Specific Energy and Frictional Responses of Polycrystalline Diamond Compact Cutters

2016 ◽  
Vol 139 (2) ◽  
Author(s):  
Babak Akbari ◽  
Stefan Z. Miska
Keyword(s):  
Specific Energy ◽  
Polycrystalline Diamond ◽  
Friction Angle ◽  
Rake Angle ◽  
Fractional Factorial ◽  
Depth Of Cut ◽  
Relative Significance ◽  
Mechanical Specific Energy ◽  
Wellbore Pressure ◽  
Polycrystalline Diamond Compact

A high pressure single polycrystalline diamond compact (PDC) cutter testing facility was used to investigate the effect of five factors on PDC cutter performance on Alabama marble. The factors include: depth of cut (DOC), rotary speed, back rake angle, side rake angle, and confining (wellbore) pressure. The performance is quantified by two parameters: mechanical specific energy (MSE) and friction angle. Fractional factorial design of experiments methodology was used to design the experiments, enabling detection of potential interactions between factors. Results show that, in the range tested, the only statistically significant factor affecting the MSE is DOC. In other words, DOC's influence is predominant and it can mask the effect of all the other factors. These results could have applications in real time pore pressure detection. Further, the results show that back rake angle is the most statistically significant factor in friction angle. Side rake angle and depth of cut also affect the friction angle, but in a relatively unimportant manner. The MSE–DOC behavior is explained and modeled by cutter edge–groove friction and the circular cutter shape. It is speculated that high cutter edge friction overwhelms the actual cutting process. A comparison of five currently present models in the literature with these results is presented and the conclusion is that the future PDC cutter models should digress from the traditional shear failure plane models.

The Effect on Cutting Tool Forces of Pre-Weakening a Rock Surface by Waterjet Kerfing

1989 ◽  
Vol 111 (1) ◽  
pp. 1-6
Author(s):  
J. E. Geier ◽  
M. Hood
Keyword(s):  
Unit Volume ◽  
Cutting Tool ◽  
Normal Force ◽  
Mechanical Energy ◽  
Polycrystalline Diamond ◽  
Empirical Models ◽  
Depth Of Cut ◽  
Rock Surface ◽  
Mechanical Specific Energy ◽  
Polycrystalline Diamond Compact

Empirical models are developed to describe the influence on the cutting process of preweakening a rock, by cutting a series of parallel kerfs in the surface with high pressure waterjets, prior to excavating the rock with a polycrystalline diamond compact (PDC) drag bit. These models show that both the bit cutting force and the bit normal force are reduced substantially (by as much as a factor of four) when the spacing and the depth of the kerfs is appropriate to the depth of cut taken by the bit. The mechanical specific energy, or the mechanical energy applied to the bit to excavate a unit volume of rock, is also reduced dramatically when the rock is prekerfed.

scholarly journals Effects of Structural Parameters on Seismic Behaviour of Historical Masonry Minaret

2017 ◽  
Author(s):  
Barış Erdil ◽  
Mücip Tapan ◽  
İsmail Akkaya ◽  
Fuat Korkut
Keyword(s):  
Modal Analysis ◽  
Structural Parameters ◽  
Masonry Structure ◽  
Operational Modal Analysis ◽  
Shear Cracks ◽  
Seismic Behaviour ◽  
New Model ◽  
The Core ◽  
Historical Masonry ◽  
Stiffness Distribution

The October 23, 2011 (Mw = 7.2) and November 9, 2011 (Mw = 5.6) earthquakes increased the damage in the minaret of Van Ulu Mosque, an important historical masonry structure built with solid bricks in Eastern Turkey, resulting in significant shear cracks. It was found that since the door and window openings are not symmetrically placed, they result in unsymmetrical stiffness distribution. The contribution of staircase and the core on stiffness is ignorable but its effect on the mass is significant. The pulpit with chamfered corner results in unsymmetrical transverse displacements. Brace wall improves the stiffness however contributes to the unsymmetrical behaviour considerably. The reason for the diagonal cracks can be attributed to the unsymmetrical brace wall and the chamfered pulpit but the effect of brace wall is more pronounced. After introducing the cracks, a new model was created and calibrated according to the results of Operational Modal Analysis. Diagonal cracks were found to be likely to develop under earthquake loading. Drifts are observed to increase significantly upon the introduction of the cracks.

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