Single Polycrystalline Diamond Compact Cutter Research Articles

Mechanism Analysis and Mathematical Modeling of Brittle Failure in Rock Cutting with a Single Sharp Cylinder-Shaped PDC Cutter

Summary The drilling efficiency of a polycrystalline diamond compact (PDC) bit plays a vital role in oil and gas exploration, which is greatly affected by the rock-cutting performance of a single PDC cutter. Although many research efforts have been put in, the rock-cutting mechanism of a single PDC cutter is still indistinct. In this work, the rock-cutting process of a single sharp cylinder-shaped PDC cutter was captured using a high-speed camera. The brittle failure mode mechanism in the rock cutting of the PDC cutter was thus revealed by this real-time observation combined with the findings in previous publications. The brittle rock-cutting failure zones in front of the cutter were separated into three different zones: crushing zone, plastic flow zone, and rock chipping zone. The crushing zone grew while the cutter cut forward and generated a plastic flow zone. When the crushing zone was large enough, a tensile crack would tear apart the rock, forming the rock chip. Based on this rock-cutting mechanism, a new mathematical model of brittle failure in rock cutting of PDC cutter was developed, considering the rock properties and cutting parameters. The boundary geometry of the crushing zone was calculated using elastoplastic theory and the Mohr-Coulomb criterion. All forces on the boundaries of these three failure zones were calculated and combined into the tangential and normal forces in the 3D mathematical model. Furthermore, a new parameter, named as crescent area, was proposed in the mathematical model. When compared to previous publications, the newly developed mathematical model had no variables that needed to be calibrated with experimental data fitting. Moreover, a series of single PDC cutter cutting tests were carried out at various depths of cut (DOCs) and backrake angles to validate the mathematical model. The results showed that the model-predicted forces basically matched the experimental data. The modeling and experimental results shared the same trend for both tangential and normal cutting forces. The experimental phenomena could be well explained by the developed mathematical model. For example, the cutting forces increase with increasing DOC and backrake angle, which is caused by the changing of the crescent area of the rock-cutter interaction. All resultant forces have almost the same inclination angle to the horizontal plane because of the almost constant boundary shape of the crushing zone. The differences between modeling and experimental results could be attributed to several reasons, one of which was the oversimplified plastic flow zone. This work presents a mathematical model that can guide the PDC bit design at different formation properties.

A novel perspective to study rock failure characteristics during single PDC cutter tests: Based on the combined cutting and penetration

Polycrystalline diamond compact (PDC) cutter tests have been extensively conducted to shed light on the rock failure mechanism, thus further enhancing the performance of PDC bits. However, most of these studies primarily focus on the cutting process. Specifically, the cutting depth is pre-set rather than calculated based on rock penetration process. In the present paper, a physical model is developed to examine the combined effects of cutting and penetration on rock breaking. Experimental and theoretical analyses are also performed to study the individual impact of cutting and penetration. Based on rock failure characteristics under varying back rake angles and penetration forces, cutting parameters are recommended. The findings indicate that the back rake angle should not exceed 40° to prevent cutter breakage. Increasing the back rake angle simultaneously improves penetration efficiency and limit cutting efficiency. For rocks with high strength and it is challenge to load the weight on bit (WOB), a back rake angle of 20–30° is advised for efficient cutter penetration. However, the smaller the back rake angles, the more obvious the enhancement in penetration depth and rock-breaking volume with the further increase of penetration forces. At an equivalent cutting depth, larger back rake angles yield higher rates of penetration (ROP), while smaller angles enhance drilling efficiency. The determination of drilling parameters should further depend on field requirements. The present study provides an in-depth understanding of the rock failure process and the arrangement of PDC bits.

Experimental and theoretical analysis of rock failure characteristics by a single PDC cutter under downhole pressurized conditions

The development of high-efficiency polycrystalline diamond compact (PDC) bits plays a major role in developing unconventional oil and gas. Thereby, a series of single cutter tests have been conducted in the past few years. However, most of them were performed under atmosphere conditions due to the limitation of the experimental setup. In the present study, a series of single cutter experiments were performed under pressurized conditions, in which both principal stress and hydrostatic pressures were loaded with a self-developed facility. The cutting force, topography of cutting grooves, and mechanical specific energy (MSE) were analyzed to evaluate rock failure efficiency. Furthermore, a theoretical model was developed to study stress evolution. Combined with experimental results, the rock failure mechanism and the effects of bottom hole pressures on rock breaking characteristics were revealed. The results indicate that the increase in principal stress and hydrostatic pressures cause larger cutting forces and reduced rock cutting efficiency. Additionally, a larger hydrostatic pressure will promote the propagation of subsurface cracks, leading to larger roughness of cutting grooves and facilitating the subsequent rock cutting process. In this study, the hydrostatic pressure has the greatest impact on rock failure process, followed by the principal stress when parallel to the cutting direction. Comparing the experimental and simulation results, we can find that only a fraction of cutting force is directly utilized in breaking rocks, while the remaining force is applied to overcome the friction induced by the flow of cuttings along the cutter surface. Consequently, measures should be taken to prevent bit balling and decrease the friction force, thus weakening the effects of hydrostatic pressures and improving the efficiency of PDC bits.

Experimental studies on rock failure mechanisms under impact load by single polycrystalline diamond compact cutter

Percussive drilling shows excellent potential for promoting the rate of penetration (ROP) in drilling hard formations. Polycrystalline diamond compact (PDC) bits account for most of the footage drilled in the oil and gas fields. To reveal the rock failure mechanisms under the impact load by PDC bits, a series of drop tests with a single PDC cutter were conducted to four kinds of rocks at different back rake angles, drop heights, drop mass, and drop times. Then the morphology characteristics of the craters were obtained and quantified by using a three-dimensional profilometer. The fracture micrographs can be observed by using scanning electron microscope (SEM). The distribution and propagation process of subsurface cracks were captured in rock-like silica glass by a high-speed photography system. The results can indicate that percussive drilling has a higher efficiency and ROP when the rock fractures in brittle mode. The failure mode of rock is related with the type of rock, the impact speed, and the back rake angle of the cutter. Both the penetration depth and fragmentation volume get the maximum values at a back rake angle of about 45°. Increasing the weight and speed of falling hammer is beneficial to improving the rock breaking effects and efficiency. The subsurface cracks under the impact load by a single PDC cutter is shaped like a clamshell, and its size is much larger than the crater volume. These findings can help to shed light on the rock failure mechanisms under the impact of load by a single PDC cutter and provide a theoretical explanation for better field application of percussive drilling.

Numerical studies on rock breaking of single axe-shaped PDC cutter

For a drill bit, the cutter is the most important part to break the rock. In oilwell drilling, polycrystalline diamond compact (PDC) bit is widely used to shear the rock formation. In this paper, a finite element model with including the axe-shaped PDC cutter and rock formation is developed to study the rock breaking behaviours. Results show that the effect of axe-shaped PDC cutter on rock breaking is better than that of the planar PDC cutter. The front rake angle and face angel play significant role on the axial force but have little influence on the tangential force. In addition, both the tangential force and axial force increase rapidly with increasing the depth of cut.

Simulation and experimental investigations of ultrasonic-assisted drilling with Micro-PDC bit

Ultrasonic-assisted drilling (UAD) technology is a new drilling technology, which combines polycrystalline diamond compact (PDC) bits and performs better than conventional PDC drilling in improving the rock-breaking efficiency during deep hard formations. In this study, a series of simulations and laboratory tests were conducted to explore the dynamic rock-breaking mechanism of UAD with a PDC bit and the influence of different input parameters on the force and energy distribution. First, the UAD process was analyzed using a simplified drilling system model, and the relationship between the axial and tangential forces was investigated using a single PDC cutter cutting model. Then, a finite element analysis model that considers rock heterogeneity was used for the analysis. The drilling process, element damage situation, and broken form of the borehole bottom of conventional drilling (CD) and UAD were compared, and the impact of amplitude, frequency, and rotary speed on the weight on bit (WOB), torque, cutting force, and energy consumption were evaluated. Finally, laboratory experiments on PDC micro-drilling for different drilling conditions were conducted to verify the effectiveness of UAD. The results indicate that during rock-breaking using UAD, the PDC cutter periodically penetrated and broke away from the rock with ultra-high frequency, causing a large amount of damage to the rock. The frequency and amplitude significantly influenced the UAD: when the vibration frequency was between 25 and 35 kHz, the force state of the PDC cutter greatly improved compared with that of CD, and the effect of ultrasonic load reached the maximum at 33 kHz; when the amplitude was between 10 and 50 μm, WOB and torque decreased significantly and the effect of ultrasonic load improved with increase in amplitude, but the rotary speed had little effect on the torque and WOB of UAD. During the laboratory experiments, the drilling efficiency and rate of penetration (ROP) improved on using UAD. When the WOB was 100–200 N and the rotary speed was 300–400 rpm, the efficiency of ultrasonic rotary drilling to improve the ROP increased by 14.7–23.4%.

Numerical simulation of rock-breaking and influence laws of dynamic load parameters during axial-torsional coupled impact drilling with a single PDC cutter

Axial and torsional impact drilling technology is used to improve the drilling efficiency of hard rock formation in the deep underground. Still, the corresponding theory is not mature, and there are few correlative research reports on the rock-breaking mechanism of axial and torsional coupled impact drilling tools. Considering the influence of the impact hammer geometry and movement on the dynamic load parameters (i.e., wavelength, amplitude, frequency, and phase difference), a numerical model that includes a hard formation and single polycrystalline diamond compact cutter was established. The Riedel-Hiermaier-Thoma model, which considers the dynamic damage and strength behavior of rocks, was adopted to analyze the rock damage under axial and torsional impact loads. The numerical simulation results were verified by the experimental results. It was found that compared with conventional drilling, the penetration depths of axial, torsional, and axial-torsional coupled impact drilling increased by 31.3%, 5.6%, and 34.7%, respectively. Increasing the wavelength and amplitude of the axial impact stress wave improved the penetration depth. When the bit rotation speed remained unchanged, increasing the frequency in the axial and circumferential directions had little effect on the penetration depth. However, as the frequency increased, the cutting surface became increasingly smooth, which reduced the occurrence of bit vibration. When the phase difference between the axial and circumferential stress waves was 25%, the penetration depth significantly increased. In addition, the bit vibration problem can be effectively reduced. Finally, the adjustment of engineering and tool structure parameters is proposed to optimize the efficiency of the axial-torsional coupled impact drilling tool.

Experimental investigation on the cuttings formation process and its relationship with cutting force in single PDC cutter tests

The single polycrystalline diamond compact (PDC) cutter test is widely used to investigate the mechanism of rock-breaking. The generated cuttings and cutting force are important indexes reflecting the rock failure process. However, they were treated as two separate parameters in previous publications. In this study, through a series of rock block cutting tests, the relationship between them was investigated to obtain an in-depth understanding of the formation of cuttings. In addition, to validate the standpoints obtained in the aforementioned experiments, rock sheet cutting tests were conducted and the rock failure process was monitored by a high-speed camera frame by frame. The cutting force was recorded with the same sampling rate as the camera. By this design, every sampled point of cutting force can match a picture captured by the camera, which reflects the interaction between the rock and the cutter. The results indicate that the increase in cutting depth results in a transition of rock failure modes. At shallow cutting depth, ductile failure dominates and all the cuttings are produced by the compression of the cutter. The corresponding cutting force fluctuates slightly. However, beyond the critical depth, brittle failure occurs and chunk-like cuttings appear, which leads to a sharp decrease in cutting force. After that, the generation of new surface results in a significant decrease in actual cutting depth, a parameter proposed to reflect the interaction between the rock and the cutter. Consequently, ductile failure dominates again and a slight fluctuation of cutting force can be detected. As the cutter moves to the rock, the actual cutting depth gradually increases, which results in the subsequent generation of chunk-like cuttings. It is accompanied by an obvious cutting force drop. That is, ductile failure and brittle failure, one following another, present at large cutting depth. The transition of rock failure mode can be correlated with the variation of cutting force. Based on the results of this paper, the real-time monitoring of torque may be helpful to determine the efficiency of PDC bits in the downhole.

Novel PDC cutter for reinforced concrete based on linear and rotational cutting tests

In tunnel mechanical excavation, when constructing in densely populated areas, it is challenging to cut through some obstacles, such as piles, tunnel segments, and diaphragm walls, using traditional tools. To address this, herein, a new type of polycrystalline diamond compact (PDC) cutter, which is based on cutters widely used in oil drilling, is used to cut reinforced concrete (RC). A linear cutting platform improved from a shaping machine is used, and the orthogonal test method is employed to investigate the sensitivities of different construction parameters on cutting performance when using a single PDC cutter. Rotational cutting tests with a pipe jacking machine are performed with multiple PDC cutters and their modified forms for RC cutting. The most significant factor is concrete strength, and it is not a changeable factor in practical engineering applications. Thus, the cutting depth should be finely controlled and the cutter taper should be optimized. Furthermore, a new form of PDC cutter with triple teeth is proposed for cutting RC in a pipe jacking machine with circular cutting trajectory. The results show that the conical cutterhead is more suitable for cutting segments than the plane cutterhead owing to its smoother torque and small-scale concrete chips that are formed during the final cutting stages. To avoid damage and wear to the cutter holder, a staggered arrangement of two PDC tools is designed for RC cutting. The optimal advancing speed is determined to be < 1 mm/min because it is most suitable for removing formed steel chips (length < 5 cm) and causes less damage on PDC tools. To adapt to the central turn of an “8″-like trajectory in a planetary oval pipe jacking machine, a cutter holder rotated 30° left and right is used. These results can provide important technical insights for efficient and safe RC cutting using PDC tools with more flexible structures in practical engineering applications.

Investigation of the cutting force response to a PDC cutter in rock using the discrete element method

In the drilling industry, Polycrystalline Diamond Compact (PDC) bits with multiple fixed PDC cutters are widely applied to cut rock under high bottom hole pressure and high temperature. The bit-rock interaction is the main excitation source of drill string vibrations and needs to be understood and controlled better to improve the performance of the drilling process. Rock cutting mechanisms can be examined best for a single PDC cutter: Limitations of dynamic control and available sensors in experimental setups are eliminated in numerical simulations. Using the Discrete Element Method (DEM), deformation and strength of rock can be modeled through its full degradation in the PDC cutting process under typical environmental conditions. Stresses and strains in the rock material and on the cutter faces become available for examination.In this paper, numerical simulations of the cutting process are conducted using a modified bonded-particle model (specialized DEM), which is calibrated to a pressure series of high-strain triaxial laboratory tests. The simulation results are interpreted from the perspective of continuum mechanics providing stress and strain rate fields within the rock. These serve to identify two primary deformation modes predominant in two distinct zones moving with the PDC cutter: A crush zone below the chamfer and a shear zone ahead of the cutter face. The influences of two cutter design parameters, the back rake angle and the chamfer size, on these zones and the cutting force, are investigated. The shear angle is found to decrease with increasing back rake angle, resulting in a wider shear band. Moreover, the back rake angle has a considerable influence on the cutting forces both in the normal and tangential direction, whereas the chamfer size affects the normal cutting force predominantly. These results are in good accordance with experimental observations in the literature. Furthermore, the relationship between the cutting force and underlying rock failure mechanisms is clarified.This study enhances the understanding of the rock cutting process and gives first indications for dynamic cutting force control through cutter design.

Numerical Study on Fragmentation Characteristics of Granite Under a Single Polycrystalline Diamond Compact Cutter in Rotary-Percussive Drilling

Abstract Fragmentation characteristics of granite in rotary-percussive drilling (RPD) are studied using the distinct element method. We developed a model to investigate the interaction between the rock and a polycrystalline diamond compact (PDC) 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 to 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 deg and impact frequency of 30 Hz 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.

Experimental and numerical investigations on rock-breaking mechanism of rotary percussion drilling with a single PDC cutter

To achieve high-efficiency drilling in hard formations, the rotary percussive drilling tool was designed to improve rock-breaking efficiency. Currently, few studies are conducted to analyze the relationship between the percussion parameters and rock breaking efficiency, considering the dynamic characteristics of rock during rock breaking. According to this situation, to quantify the influence of different percussion parameters on the rock-breaking efficiency, a series of dynamic experiments on hard rock and numerical simulations were carried out. Orthogonal experiments of split Hopkinson pressure bar (SHPB) device were conducted to analyze 13 parameters of the Riedel Hiermaier Thoma (RHT) material model. A polycrystalline diamond compact (PDC) cutter was selected as the research object, and a corresponding numerical model was established, considering the actual size of the drilling teeth and the load transmitted to the formation. Subsequently, the numerical simulation results of the SHPB test and cutting experiment were verified using the physical model. A sensitivity analysis was carried out to analyze the effect of different factors, including dynamic amplitude, frequency, and waveform, on the penetration depth and eroded volume fraction of formation. The results proved that rotary percussion drilling increased the penetration depth and eroded volume fraction of hard rock. The rock-breaking efficiency of the square wave was more obvious than that of the triangular and sine waves. Increasing the dynamic to static load ratio was beneficial for increasing the penetration depth and eroded volume fraction of formation. When the frequency increased, the cutting section became smoother, and the cuttings were finer, which was beneficial in cleaning the borehole. • Orthogonal experiments were used to obtain RHT material model parameters. • The physical model verified the rock failure of numerical simulation. • The rock-breaking efficiency of the square wave was most apparent.

DEM numerical investigation on the effect of back rake angle of PDC bit in drilling hard rock strata

Polycrystalline diamond compact (PDC) drill bits used in the Deep Borehole Placement (DBP) approach for nuclear waste disposal are subjected to highly competent, low-porosity, and low-permeability rock mass that cause severe wear and damage. To augment the penetration rate and minimize the wear-induced cost, a novel interaction rock cutting model with breakable granite and unbreakable cutter was established using two-dimensional discrete element method (2D-DEM). The particle element was used to simulate the granite sample, and the micro parameters of the contact elements between them were calibrated based on the uniaxial compression and Brazilian tests. While the rigid block element was used to reproduce the single PDC cutter including its elastic properties and geometric structure (i.e., back rake angle). The cutting process was simulated by applying normal force and tangential velocity on the single cutter to explore the effect of the back rake angle (5, 10, 15, 20 and 25°) on the stress condition of the cutter and penetration rate. The simulation results show that with the increase of the back rake angle, the maximum shear stress magnitude and stress concentration area decrease simultaneously, in according with the decrease of material removal rate, which do good help to decrease the wear and unexpected damage of bit cutter. In addition, the cutting process can be divided into the effective cutting stage when the elastic energy continuously stores and the fragmentation initiation stage when the stored energy suddenly releases and numerous cracks generate. In long term, the established DEM model can be used to optimize the structure of the PDC bit.

Numerical study on optimal impact angle of a single PDC cutter in impact rock cutting

In previous work (Liu et al., 2020), we studied the differences between conventional rock cutting and cutting with compound vertical and horizontal impact force. In this work, we investigated the relationship between the impact force direction and cutting efficiency, which is the key to the impactor design. We established an impact rock cutting model with a single sharp polycrystalline diamond compact (PDC) cutter, and the direction of the impact force was described by an impact angle (β), which ranged from 0 to 90°. Simulations with different β were conducted, and the fragmentation process, forces, and mechanical specific energy (MSE) were analyzed. We also investigated the effects of the amplitude and duration of the impact forces on the MSE. The results showed that there is an optimal β, for which the MSE is the lowest and cutting efficiency is the highest. The effects of the vertical and horizontal impact forces on the rock cutting process were different, and excessive vertical or horizontal impact forces were not conducive to improving the cutting efficiency. The optimal β decreased with an increase in the impact amplitude, and a similar relationship was found between the optimal β and the duration of the impact force. In practice, designers are suggested to set the β of the impactor between 30° and 60°, and a lower β may be necessary to adapt to a higher impact amplitude and lower frequency.

Effects of the chamfer and materials on performance of PDC cutters

Polycrystalline diamond compact (PDC) cutters play a key role in the performance of PDC bits in the oil & gas drilling. The study of single cutter on the rock-breaking mechanism is very important for PDC bits to deal with challenging formations, especially when the wells become increasingly longer and complex. Both cutting efficiency and durability are always the focuses of attention for the researches on single PDC cutter. Of all the factors influencing the cutting efficiency, the chamfer is always ignored in theoretical and experimental studies. In this work, the rock-cutter interaction model was modified with considering the effect of the chamfer, which could be used to predict the cutting forces and cutting efficiency of PDC cutters while shearing the rocks. All cutters have been tested on a vertical turret lathe to verify the modified theoretical model. The accuracy of the theoretical prediction agreed well with the experimental results. It was found that the cutting efficiency could be greatly enhanced by reducing the chamfer size for the cylinder-shaped PDC cutters. Unfortunately, the small chamfer size made PDC cutters vulnerable to the premature failure. In order to improve the durability of small-chamfered PDC cutters while retaining their cutting efficiency, an optimized mix of diamond grains was developed and experimentally studied. The results illustrated that the cutter with optimized diamond mix exhibited much better wear resistance. On the other hand, the chamfer size has relatively weak effect on the wear resistance of PDC cutters. The increased chamfer size contributes to protect the cutter edge from chipping but will cause more cumulative friction heat and impair the cutter's durability. The findings in this work will provide a valuable guideline for the manufacturers of PDC bits. • A theoretical prediction model is modified by considering chamfer. • Obtain a relationship between MSE and chamfer size. • Explored the relationship between the diamond grains and wear resistance. • Both wear resistance and thermal durability of PDC cutters are more influenced by material composition than chamfer size.

Fragmentation Characteristics of Rocks Under Indentation by a Single Polycrystalline Diamond Compact Cutter

Abstract Polycrystalline diamond compact (PDC) bit accounts for the most drilling footage in the development of deep and geothermal resources. The goal of this paper is to investigate the PDC cutter-rock interaction and reveal the rock fragmentation mechanism. A series of loading and unloading tests are conducted to obtain the curves of contact force versus penetration displacement. A single practical PDC cutter is fixed on the designed clamping devices that are mounted on the servo experiment system TAW-1000 in the tests. The craters morphology and quantified data were obtained by scanning the fragmented rock specimen using a three-dimensional morphology scanner. Finally, a numerical model is established to get the stress and deformation fields of the rock under a single PDC cutter. The results show that there are two kinds of failure modes, i.e., brittle failure and plastic failure, in the loading process. Marble is more prone to brittle fracture and has the lowest specific energy, followed by shale and granite. The brittle failure in marble mainly occurs behind the cutter while that happens ahead of the cutter for shale. Curves of contact force versus penetration displacement illustrate that a cutter with a back rake angle of 40 deg has a better penetration result than that with a back rake angle of 30 deg. Enhancing loading speed has a positive effect on brittle fragmentation. The distribution of von Mises stress indicates the initiation point and direction, which has a good agreement with the experiment. The research is of great significance for optimizing the PDC bit design and increasing the rate of penetration.

A novel experimental apparatus for single polycrystalline diamond compact cutter tests.

Polycrystalline diamond compact (PDC) bits are increasingly favored in the drilling field due to their high efficiency in rock breaking together with their longevity. To investigate the rock failure mechanism and further improve the performance of PDC bits, innovative experimental equipment is proposed in this paper. With its assistance, we can study the characteristics of rock-breaking using a PDC cutter under different conditions, e.g., high pressure and high temperature (HPHT), confining pressure, and jet impingement. The setup can be grouped into three parts: a rock cutting system, high-pressure jet generation system, and controlling system. A series of experiments was conducted to demonstrate the reliability of the setup. The results demonstrate the improvement in performance of PDC bits in the exploration of HPHT formations.

Interaction Effect of Depth of Cut, Back Rake Angle and Rock Properties on Temperature of Single Polycrystalline Diamond Compact Cutter

The single polycrystalline diamond compact (PDC) cutter’s performance is affected by temperature during rock cutting process. The study towards understanding the factors and its interaction affecting the cutter’s temperature is essential prior to cutting process optimization. Thus, this study aims to investigate the effect of various cutting parameters and its interaction on the temperature of a single PDC cutter. A series of test was conducted in a lathe machine which utilized facing operation to cut the rock samples at 0.5 to 1.5 mm depth of cut and back rake angle of 5° to 15°. Two types of rock being tested in this study were Indiana limestone and Carthage marble. The analysis of variance (ANOVA) output indicated that cutting parameters and rock properties and its interaction have a significant effect on cutter’s temperature except for interaction between back rake angle and rock properties. Increasing the depth of cut and decreasing back rake angle has resulted in increasing temperature. The temperature of the single PDC cutter is higher when cutting Carthage marble than Indiana limestone. Combination of low back rake angle and high depth of cut producing maximum temperature. It is also validated that the data developed from the mathematical model having a difference of 5% as compared to the experimental data obtained using similar parameters which indicates that the results are reliable and can be forwarded in the future study.

Three-dimensional numerical simulation of the straight shale cutting process of single polycrystalline diamond cutter

The finite element method offers a cost-effective way to test the performance of polycrystalline diamond compact (PDC) cutters, which is much cheaper than lab experiments. However, the finite element simulation often fails to output accurate results, owing to improper model selection and parameter setting. To solve the problem, this paper carries out a three-dimensional (3D) simulation of the straight shale cutting process of a single PDC cutter on finite element software Abaqus. The model size, material model, damage, and failure criterion were determined through triaxial tests on the shale. The adaptive meshing method and mass scaling were adopted to improve the calculation stability and reduce the simulation cost. The simulation reveals the residual stress field in the shale, the reaction force to the PDC cutter, and the relationship between the three components of the reaction force. Based on the simulation results, the authors explored the effects of back rake angle, side rake angle, cutting depth, cutter diameter, and confining pressure on the cutting force and vertical force. Our results were found consistent with those of the previous theoretical analyses and experiments. The numerical simulation of cutter-rock interaction provides an effective way for the design of new PDC cutters.

EFFECT OF CUTTING PARAMETERS ON TEMPERATURE OF A SINGLE POLYCRYSTALLINE DIAMOND COMPACT (PDC) CUTTER

The usage of polycrystalline diamond compact (PDC) drill bit has significantly increased in the petroleum industry due to its high rate of penetration and long life. However, it is becoming increasingly difficult to ignore the temperature effect to PDC bit, specifically its cutter during the drilling operation. Temperature causes the degradation of the PDC cutter by reducing its lifespan. A thorough understanding of factors that affect the temperature of the PDC cutter is crucial in predicting the optimum cutting parameters. Hence, it is the objective of this study to evaluate the effect of cutting parameters on the temperature of the single PDC cutter in rock cutting. In this study, a rock cutting experiment was conducted by using a lathe machine tested on single PDC cutter. The parameters involve were rotational speed and depth of cut. The temperature was captured using an infrared thermographic camera, FLIR T640 and the spot measurement was used to pinpoint the temperature readings at the tooltip of PDC cutter. It was found that the depth of cut had the greater influence on temperature when measured over a range of 16 levels as the temperature increase in linear trend with increasing depth of cut as well as the high correlation of the plot (R2=0.98). However, tests for rotational speed showed less significant influence on temperature when measured over a range of four levels where the percentage error of the temperature for each rotational speed was less than 10%. It can be concluded that only the depth of cut has a significant effect on the temperature of a single PDC cutter.&#x0D; Keywords: Rock cutting, temperature, Polycrystalline Diamond Compact (PDC), rotational speed, depth of cut