Analysis of Impact Rock-Breaking Characteristics and Temperature Field of PDC Cutter

Abstract

Polycrystalline diamond compact (PDC) bits often experience localized heating during impact rock breaking in complex formations, resulting in reduced service life and lower drilling efficiency. An optimized structural design of PDC cutters can significantly enhance bit performance, mitigate thermal concentration, and extend operational longevity. Inspired by previous work on PDC cutter surface topography, five saw-type tooth-shaped cutter designs—featuring one to five saw-type teeth were developed. To evaluate their rock-breaking effectiveness and identify the optimum design, the impact-induced rock fragmentation processes of these cutters were compared using the finite element method. Key indicators, including cutting force, mechanical specific energy (MSE), and cutter surface temperature, were analyzed to determine the superior tooth configuration. Among the five designs, the four-saw-tooth cutter induced the most pronounced stress concentration in the rock. Its optimized number of saw-type teeth ensured full participation of all teeth in rock cutting, enabling efficient rock removal and maximizing breakage performance. Compared with other designs, this cutter exhibited the smallest fluctuations and mean cutting force. The specific mechanical energy decreased initially and then increased with the number of saw-type teeth, reaching a minimum for the four saw-type tooth design. Moreover, it showed the lowest surface temperature and the mildest temperature variation, which helps alleviate localized heating and improve wear resistance. The cutting performance of the four saw-type tooth was further influenced by cutting depth and back rake angle, with optimal values identified as 1.5 mm and 20°, respectively. Compared with a conventional cutter, the four saw-type tooth design reduced the overall surface temperature by approximately 10.69%, with temperature rise confined mainly to the grooves between adjacent saw-type teeth and no widespread thermal concentration observed, confirming its design superiority. Full-scale rock-breaking simulations demonstrated that the bit equipped with four saw-type tooth achieved greater penetration depth and required lower torque than the conventional design, indicating enhanced rock-breaking ability and higher drilling efficiency. In conclusion, the four saw-type tooth PDC cutter design offers a promising approach for developing high-performance drill bits and reducing drilling costs.

1. Introduction

With the rapid growth of oil and gas exploration and development projects, deep strata have become a crucial focus for improving oil and gas extraction efficiency. However, deep strata pose several challenges, including high rock hardness, strong wear resistance, and difficulties in drilling [1]. Therefore, accelerating the pace of domestic oil and gas resource exploration and development is crucial not only to the national economy and people’s well-being but also to the security of the national energy strategy. Increasing drilling speed is an essential technical approach to ensure the efficient, rapid development of oil and gas resources. As PDC bits become the dominant bit type, both domestic and international researchers have conducted extensive studies on the impact of drilling technology involving PDC bits, impactors, and the mechanisms of impact rock breaking. A new impact rock-breaking technology has emerged, significantly enhancing drilling efficiency [2,3]. However, while focusing on rock-breaking efficiency, the wear of the cutting teeth must also be considered [4]. The temperature fluctuations of the cutting teeth on PDC drill bits substantially impact drilling performance and the cutting tool’s service life [5]. As drilling continues, the cutting teeth tend to generate concentrated, high temperatures under impact, which accelerate their wear. Relevant studies have shown that the temperature increase in worn teeth during rock cutting is much higher than in unworn teeth [6]. Optimizing design parameters for the cutting structure is the primary focus of PDC drill bit design, and it directly affects the service life of the cutting teeth [7]. In response to this situation, this paper analyzes the impact of rock breaking by cutting teeth on the temperature field. To address the issue of temperature concentration on the cutting teeth, the surface shape of the teeth is modified to improve their temperature distribution, reduce wear, and thereby extend their service life and increase rock breaking efficiency.

Studies have shown that the rock-breaking process and mode can influence the temperature changes in the cutting teeth. The structure and parameters of the cutting teeth are essential throughout the rock-breaking process. In recent years, many scholars have conducted related research. Zhang et al. conducted a thermal–mechanical coupling simulation analysis of PDC three-angled teeth. They concluded that the inclination angle of the ridge surface of the three-angled teeth affects the wear of PDC cutting teeth [8]. Chen et al. conducted an indoor test on the rock-breaking performance of a single PDC cutting tooth. They performed an in-depth analysis of the cutting force, rock-breaking process, and cutting-temperature field of rock samples at different temperatures [9]. Zhang et al. established a two-dimensional numerical model of the interaction between the cutting tooth and the rock. They found that the thermal-affected zone of the diamond layer is larger than that of the tungsten carbide matrix [10]. Deng et al. used a three-dimensional curved-surface rock model for simulation, which more closely approximates real working conditions. They concluded that the temperature in the cutting area near the drill bit axis is lower than farther from it [11]. Li et al. studied the temperature distribution of PDC drill bit cutting teeth based on orthogonal cutting theory. They found that optimal cutting parameters can reduce the wear on the cutting tool’s teeth [12]. Zhang et al. also examined how the cutting depth of PDC cutting teeth affects their temperature and found that depth plays a key role [13]. Yang et al. studied the wear of PDC cutting teeth caused by high temperatures during cutting and concluded that the wear of the cutting teeth increases when cutting granite [14]. Xin et al. conducted a thermal analysis of PDC drill bits and optimized the cutting speed and cutting depth. Tooth inclination angle using the response surface method, providing the best parameter combination [15]. Cao et al. conducted a fluid-solid-thermal coupling field analysis of PDC drill bits. They found that the high-temperature region of PDC drill bits is primarily located on the surface of the cutting teeth at the bottom of the drill bit [16]. Can et al. studied the changes in rock fracture and natural wear temperature of PDC teeth under different rock hardness conditions, and concluded that when the cutting teeth cut complex rock layers, the friction coefficient (CFO) decreases as the cutting temperature and MSE value increase [17]. Yao et al. conducted a study on the dynamic wear rate of PDC cutting teeth under thermal–mechanical coupling. The results showed that the temperature and wear rate of PDC cutting teeth increase linearly with rising environmental temperature conditions [18].

Although many studies have examined the rock-breaking properties and temperature field analysis of PDC cutting teeth, research on impact rock-breaking technology remains limited. Specifically, little attention has been given to the characteristics and temperature distribution of PDC teeth during impact rock-breaking, and even less to improving their surface shape to enhance temperature distribution. In response to this, based on elastoplastic mechanics and the Drucker–Prager rock failure criterion, an interaction model between PDC cutting teeth and rocks was developed using the ABAQUS/Explicit module. This study analyzed the impact of rock-breaking characteristics and the temperature distribution of PDC teeth. It examined temperature patterns during the rock-breaking process, optimized the tooth profile, and aimed to improve surface-temperature distribution to extend service life. The findings provide valuable insights for enhancing drill bit durability and optimizing PDC cutting tooth design.

2. Theoretical Analysis

2.1. Theoretical Analysis of Heat Generation in the PDC Cutting Tooth Rock Crushing Process

During the process of PDC bits cutting rocks, the heat mainly results from the friction between the cutting teeth and the rock, and most of the mechanical energy is converted into frictional heat. This heat is the primary cause of the temperature increase in the PDC cutting teeth, and the rise in temperature directly causes thermal wear of the teeth. In severe cases, it can lead to their failure. Existing studies have shown that the rock cutting process is very similar to metal cutting. Therefore, the theory of metal-cutting temperature can be used to analyze the temperature distribution during rock-cutting [19].

As in metal cutting, rock cutting also involves three deformation zones. The temperature changes in PDC cutting teeth during cutting mainly result from these three heat-generating zones [20]: The first heat-generating zone is the shear heat generated by the shear deformation of the rock when the cutting teeth cut the rock. The second heat-generation zone is the frictional heat generated by the cutting teeth and the rock cuttings. The third heat generation zone is the heat generated by the friction between the bottom of the cutting teeth and the rock, as shown in Figure 1.

If other energy losses during the rock cutting process are ignored and it is assumed that all the energy used by the PDC cutting teeth to break rock converts into heat energy, then the total heat generated can be expressed as [21]:

$$Q=F_q{v}_1+q$$

(1)

In the equation, $Q$ represents the cutting heat, measured in $\mathrm{J}$; $F_q$ represents the cutting force, measured in $\mathrm{N}$; $v_1$ represents the cutting speed, measured in $\mathrm{m}/\mathrm{s}$; $q$ represents the frictional heat, measured in $\mathrm{J}$.

When analyzing heat transfer, it is essential to combine the heat transfer equation with the heat conduction equation and to consider factors such as rock type, rock cuttings, and environmental conditions that influence the drill bit’s temperature. This approach helps accurately determine its temperature field. Based on the law of conservation of energy and Fourier’s law of heat conduction, the differential equation for thermal conductivity can be derived.

$${\displaystyle \frac{\partial }{{\partial }_x}}\left(E_x{\displaystyle \frac{\partial T}{\partial x}}\right)+{\displaystyle \frac{\partial }{{\partial }_y}}\left(E_y{\displaystyle \frac{\partial T}{\partial y}}\right)+{\displaystyle \frac{\partial }{{\partial }_z}}\left(E_z{\displaystyle \frac{\partial T}{\partial z}}\right)+Q=\rho c_T{\displaystyle \frac{\partial T}{\partial t}}$$

(2)

In the equation, $\rho$ represents the density of the material; $c_T$ represents the specific heat capacity: $E_x$, $E_{\mathrm{y}}$, $E_z$ respectively represents the thermal conductivity coefficient in the direction of $x,y,z$; $Q$ represents the intensity of the heat source; $T$ represents the flow meter temperature reading, measured in °C.

Based on Fourier’s Law, the relationship between the heat flux density and temperature generated by the frictional contact between PDC cutting teeth and rocks or cuttings can be expressed as:

$$E_x{\displaystyle \frac{\partial T}{\partial x}}{n}_x+E_y{\displaystyle \frac{\partial T}{\partial y}}{n}_y+E_z{\displaystyle \frac{\partial T}{\partial z}}{n}_z=\overline{q_f}\left(t\right)$$

(3)

In the equation, $n_x$, $n_y$, $n_z$ respectively represent the cosine of the direction of the normal outside the boundary; $\overline{q_f}\left(t\right)$ represents the given heat flux density on the boundary, measured in $\mathrm{J}/({\mathrm{m}}^2\cdot \mathrm{s})$.

During the rock-breaking process, if it is assumed that the friction between the PDC cutting teeth and the rock is completely converted into heat energy, it can be expressed as:

$$\overline{q_f}\left(t\right)=\lambda F{v}_2$$

(4)

In the equation, $\lambda$ represents the frictional factors; $F$ represents the normal force on the contact surface, measured in $\mathrm{N}$; $v_2$ represents the speed of sliding friction, measured in $\mathrm{m}/\mathrm{s}$.

In real drilling conditions, the circulation of drilling fluid cools the PDC cutting teeth, thereby reducing frictional heat. Due to limitations in research time and experimental setup, the effect of drilling fluid heat exchange on the temperature field of the cutting teeth has not been considered in this paper for now. This will be a key focus for future research. Therefore, in the temperature field simulation analysis below, the heat carried away by the drilling fluid is ignored.

This paper aims to analyze the distribution pattern of the temperature field around PDC cutting teeth during the rock-breaking process. To effectively construct the physical model of PDC cutting teeth and rocks while focusing on key influencing factors, the numerical simulation adopts simplified thermal boundary conditions, with a uniform 27 °C temperature field as the initial condition. This initial temperature represents the surface conditions and does not take into account the geothermal gradient encountered in deep drilling. This approach helps to isolate the thermal effects caused by changes in cutting parameters, thus avoiding interference from fluctuations in cooling conditions or ground temperature gradients in real-world operations on the analysis results. Although the absolute temperature obtained from the simulation may differ from the on-site measured values, the trends in temperature variation and the comparative conclusions among parameters remain scientifically significant. The following simplified assumptions were made for the simulation process:

(1)

Assuming that both the PDC cutting teeth and the rock material are homogeneous and continuous, the influence of the internal microstructure differences in the materials on the temperature field is ignored.

(2)

It is assumed that the density and thermal physical performance parameters (such as specific heat capacity, thermal conductivity, etc.) of the PDC cutting teeth do not change with temperature, that is, they are regarded as constant values during the analysis process.

The above assumptions help reduce the model’s complexity, thereby revealing more clearly the main formation mechanism and distribution characteristics of the temperature field in PDC cutting teeth.

2.2. Rock Constitutive Model and Rock Failure Evaluation Index

Rock is a non-linear, anisotropic structure, so selecting an appropriate rock constitutive model is essential for developing a rock-breaking model. The constitutive model is a mathematical framework that describes the material’s stress–strain relationship. Using experimental data and theoretical assumptions, it can predict and simulate yield failure behavior under multi-axial stress. The traditional Mohr–Coulomb (C-M) criterion employs a linear function. However, it is widely used in two-dimensional stress analysis; it does not account for the effects of the intermediate principal stress, which can lead to deviations in the prediction of initial strength under high confining pressure. The Drucker–Prager (D-P) criterion defines a nonlinear yield function by incorporating the static water-pressure correction term ($I_1$) and the deviatoric invariant ($J_2$). It not only maintains the shear failure mechanism of C-M but also provides a more detailed description of the three-dimensional stress state via the σ-sensitivity parameter. The improvement of the D-P criterion over C-M and Mises includes the following [22]:

$$\rho I_1+\sqrt{J_2}-K=0$$

(5)

$$I_1={\sigma }_1+{\sigma }_2+{\sigma }_3$$

(6)

$$J_2={\displaystyle \frac{1}{6}}\left[{\left({\sigma }_1+{\sigma }_2\right)}^2+{\left({\sigma }_2-{\sigma }_3\right)}^2+{\left({\sigma }_3-{\sigma }_1\right)}^2\right]$$

(7)

$$\rho ={\displaystyle \frac{2\sin \alpha }{\sqrt{3}\left(3-\sin \alpha \right)}}$$

(8)

$$K={\displaystyle \frac{6e\cos \alpha }{\sqrt{3}\left(3-\sin \alpha \right)}}$$

(9)

In the equation, $I_1$ represents the first invariant of stress, measured in MPa; $J_2$ represents the second invariant of stress components, measured in MPa²; $\rho$ and $K$ are experimental constants; $\alpha$ is the friction angle of the rock, measured in (°); $e$ is the cohesion, measured in MPa; ${\sigma }_1$, ${\sigma }_2$, and ${\sigma }_3$ represent the first, second, and third principal stresses, respectively, measured in MPa.

The PDC teeth mainly break rocks through shear. When the rock’s plastic stress exceeds its critical value, damage begins to occur. Ignoring the influence of the already damaged units on the rock, the plastic strain criterion of the rock is:

$${\epsilon }^{\mathrm{r}}\le {\epsilon }_f^{rl}$$

(10)

In the equation, ${\epsilon }^r$ represents the equivalent plastic strain of the rock, measured in %; ${\epsilon }_f^{rl}$ is the equivalent plastic strain when the rock undergoes failure, measured in %.

Mechanical specific energy (MSE) is an important factor in evaluating drilling efficiency. The lower the MSE, the higher the cutting tool’s energy utilization rate; thus, MSE is defined as the energy required to break a unit volume of rock. Its formula is as follows [23]:

$$MSE={\displaystyle \frac{W}{V}}$$

(11)

In the equation, $W$ represents the total energy consumed when crushing rocks, measured in $\mathrm{J}$; $V$ represents the volume of crushed rocks, measured in m³.

To quantitatively analyze the fragmentation efficiency during PDC cutting teeth rock breaking, it is necessary to accurately count the amount of rock fragmentation. This paper uses the ABAQUS 2022 finite element software to establish a rock-cutting model and to simulate rock fragmentation using the element-damage failure criterion. In ABAQUS/Explicit, the element failure state is characterized by the damage variable SDEG (Stiffness Degradation, stiffness degradation coefficient): when SDEG reaches 1, the element is considered completely damaged, and the deletion mechanism is triggered. The rock material represented by this element is removed from the model, and the corresponding rock debris is shed during the actual rock-breaking process. Based on this characteristic, this paper uses the Python 2025 script interface in ABAQUS to automatically extract element-damage information from the calculation result database (.odb) after the numerical simulation is completed. By traversing all elements and screening the failed elements with an SDEG value of 1, the original geometric volume of each failed element is extracted, and the total rock fragmentation volume under the specified cutting path is accumulated. This automated method avoids the cumbersome, error-prone manual statistics and provides accurate data support for subsequent analysis of the relationship between cutting parameters and fragmentation efficiency.

2.3. Experimental Analysis

To clarify that PDC cutting teeth will undergo thermal wear at high temperatures, thereby decreasing their service life, this paper cites the experimental results from another reference [24]. This experimental data is not our own experimental data. It is used to illustrate the high-temperature thermal wear process of PDC cutting teeth. As shown in Figure 2a, when PDC cutting teeth perform rock-breaking operations under high-temperature conditions, cracks as shown in the figure will occur on their surfaces, thereby reducing the service life of PDC cutting teeth. Figure 2b shows the infrared temperature image of the PDC cutting teeth during the rock-breaking process. The picture shows that the high temperature is mainly concentrated on the surface of the PDC cutting teeth. Based on this experiment, PDC cutting teeth do indeed wear out due to high temperatures during rock breaking, which significantly reduces their service life. Under impact load conditions, wear will be even more severe. Therefore, it is crucial to design a new type of PDC cutting teeth to disperse the high temperature concentration of the PDC cutting teeth.

2.4. Rock Theory Model

Other researchers [25] conducted X-ray diffraction (XRD) experiments on granite samples and systematically tested their basic physical and mechanical properties, including density, elastic modulus, and Poisson’s ratio. This paper cites the above experimental results, combines literature research and numerical inversion analysis, and comprehensively calibrates the key parameters of the Drucker–Prager model, thereby ensuring the rationality and reliability of the model parameter selection.

To further verify the computational accuracy of the Drucker–Prager (D-P) model for rocks, uniaxial compression and Brazilian splitting numerical simulations were conducted on granites, and the simulation results were compared and analyzed with the experimental data reported in the literature.

In this uniaxial compression simulation, the granite sample is 50 mm in diameter and 100 mm in height. The boundary conditions are set with the lower end fixed and a 5 mm compressive displacement applied to the upper end [26]. The relevant results are shown in Figure 3a. The comparison curve between the simulation results and the experimental results is shown in the reference. The trends of the two are highly consistent. This comparison effectively confirms the accuracy of the established rock D-P model.

In the Brazilian splitting simulation, the granite sample had a diameter of 50 mm, an aspect ratio of 0.5, and end-face and circumference unevenness of less than 0.02 mm [27]. The parameters were selected based on SHPB experiments reported in the literature, and the granite specimens were subjected to impact compression. The simulation results and experimental data are shown in Figure 3b. The two are in good agreement.

3. Establishment of the Finite Element Model

A three-dimensional model of PDC cutting teeth and rocks was built. The overall structure and mesh division of the model are shown in Figure 4. In this model, the diameter of the PDC cutting teeth is 13.44 mm, the diamond layer is 3 mm thick, the alloy layer is 5 mm high, the back rake angle is 15°, and the rock sample is a rectangular prism measuring 100 mm in length, 50 mm in width, and 25 mm in height. To balance calculation accuracy and efficiency, a 1 mm refined grid is used for the contact area between the two, while the grid size for the remaining regions is set at 1.6 mm. Additionally, C3D8T units are selected for both the cutting tools and the rocks.

In the simulation, the PDC cutting teeth moved at the set speed. Fixed constraints were applied to the rock except for the upper surface and both sides of the cutting path. At the same time, the cutting speed was set to 500 mm/s, and the simulation time to 0.2 s.

In the ABAQUS/Interaction module, the contact behavior between the PDC cutting teeth and the rock is defined. Specifically, the contact property between the PDC cutting teeth and the rock is set to surface-to-surface. Considering that the hardness of the PDC cutting teeth is much higher than that of the rock stratum, in the definition of the contact pair, the surface of the PDC cutting teeth is set as the master surface, while the surface of the rock is set as the slave surface. The master and slave surfaces are set according to the general principle of finite element contact analysis: the surface with greater stiffness and a coarser mesh is designated as the master surface to ensure accurate contact detection and stable convergence.

For mechanical constraint algorithms, the Penalty contact method is used to approximately enforce normal contact constraints. This method allows for a small amount of penetration between contact surfaces, thereby improving convergence efficiency and computational stability while ensuring calculation accuracy. Tangential friction behavior is also described based on the Penalty friction formulation. The coefficient of friction was set at 0.3 based on the relevant literature in rock mechanics and previous experimental data. This value can reasonably characterize the sliding friction at the interface between PDC cutting teeth and granite-like rock under dry conditions. To simplify the model and focus on the relative influence of cutting parameters on the temperature field, this paper assumes the coefficient of friction is constant and does not vary with temperature, contact pressure, or sliding speed.

In addition, in the definition of contact attributes, the default contact behavior is “Hard contact”; that is, separation is allowed when the contact pressure crosses zero, and the contact pressure can be transmitted arbitrarily after the contact surface is closed. Meanwhile, to enhance convergence, no additional parameters, such as viscous or contact damping, were introduced, maintaining the simplicity and physical clarity of the contact definition.

Other researchers [28] used mechanical parameter testing equipment and reported that the thermal conductivity of granite at 27 °C was 3.15 W/(m·°C). During its finite element modeling, the corresponding thermal–physical performance parameters, such as thermal conductivity, specific heat capacity, and thermal expansion coefficient, were assigned to the PDC cutting gear and the cemented carbide layer. This study, based on the above material parameters, carried out a numerical simulation of the impact rock-breaking process of PDC cutting teeth. The initial temperature was set at 27 °C to ensure the rationality and comparability of the materials’ thermodynamic properties. The specific material parameters are shown in

Table 1. Material parameter.

Name	Elastic Modulus/GPa	Density/(kg·m−3)	Thermal Conductivity/(W·m−1 °C)	Specific Heat/(J·kg−1 °C−1)	Coefficient of Thermal Expansion/°C−1	Poisson’s Ratio
PDC	890	3500	543.0	790	2.5 × 10−6	0.07
Hard alloy layer	579	15,000	100.0	230	5.2 × 10−6	0.22
Granite	40	2650	3.5	800	52.0 × 10−6	0.25

.

Some people [29] conducted an indoor rotary impact drilling experiment using an 89 mm four-wing PDC bit at 50 r/min. The experimental setup is shown in Figure 5. The results show that when the static load is 7 kN, the peak dynamic load is 2 kN, and the impact frequency is 5 Hz, the drilling rate under the rectangular wave impact load is 0.0217 mm/s, while that under the sinusoidal wave impact load is 0.01684 mm/s, and the difference between the two is relatively small. From the test results, it can be known that the peak dynamic load is approximately 28.57% of the static load, meaning that effective rock breaking can be achieved when the dynamic load is slightly higher than the static load. Based on this, this article selects the shock peak of 1.2 mm/s, corresponding to a 6 Hz sine wave, as the impact load, as shown in Figure 6. Although there are certain differences between this setting and the actual drilling conditions, this study aims to reveal the fragmentation mechanism and the law governing the temperature field distribution of PDC cutting teeth during the impact rock-breaking process. Therefore, the above simplification does not affect the main conclusions and analysis of this paper.

The impact load is applied to the PDC cutting teeth in the form of a sine wave:

$$v(t)=A\sin (2\pi ft)$$

(12)

where A = 1.2 mm/s is the velocity amplitude, f = 6 Hz is the frequency, and t is time. This velocity is applied to the reference point to simulate the impact action of a downhole impactor.

4. Finite Element Model Verification

4.1. Verification of the Energy Conservation Hypothesis

To further verify the accuracy of the thermodynamic coupling model established in this paper, it is necessary to verify the energy conservation assumption outlined below. According to the law of conservation of energy, if the total mechanical energy input during the cutting process is equal to the sum of the portion converted into thermal energy (including plastic heat dissipation and frictional heat dissipation) and other forms of energy (such as strain energy, kinetic energy, etc.), it can be proved that the model is reasonable and consistent at the energy conversion level.

In ABAQUS/Explicit, the heat flux rate generated by plastic dissipation is characterized by the history output variable ALLPD, while the heat flux rate resulting from frictional dissipation is represented by the variable ALLFD. The simulation results are shown in Figure 7. The input total mechanical power is calculated as the product of the cutting force and the cutting speed. The specific values of the above-mentioned energies are shown in

Table 2. Verification of conservation of energy.

Energy	Numerical Value (mJ)	Proportion (%)	Illustrate
Input the total mechanical energy	42,030	100%	_
Plastic dissipation energy (ALLPD)	40,452	96.3%	Stabilize the cumulative value of the cutting section
Frictional dissipation energy (ALLFD)	1505	3.6%	Stabilize the cumulative value of the cutting section
Other energy	73	0.1%	Residual term (Input-plasticity-friction)
Energy closure error	0.2%	_	It indicates that the conservation of energy is good

. By comparing and analyzing the sum of the input energy and the output heat flux, the validity of the energy conservation assumption can be quantitatively evaluated.

4.2. Sensitivity Analysis

To evaluate the impact of the heat-source distribution assumption on the temperature field, we conducted a parameter sensitivity analysis of the frictional heat distribution coefficient. The changes in the temperature distribution of the cutting tools were compared by setting different distribution ratios (0.4, 0.5, and 0.6). As shown in Figure 8, although there are minor fluctuations in the peak temperature, the overall distribution pattern of the temperature field and the relative comparison relationship among different cutting parameters remain stable. This verifies that the paper’s conclusion is robust to uncertainty in the frictional heat distribution coefficient.

4.3. Grid Convergence Verification

In finite element analysis, the selection of mesh size directly affects the accuracy and reliability of the simulation results. If it does not converge, the calculation results lose their validity. For this purpose, this paper verified the model’s mesh convergence by setting the mesh sizes to 1.5 mm, 1 mm, and 0.5 mm, respectively, for comparative analysis, as shown in Figure 9. The relevant results of the grid convergence verification are summarized in

Table 3. Convergence test under different grid sizes.

Size of Mesh Opening (mm)	Peak Temperature (°C)	Rate of Temperature Change (%)	Peak Cutting Force (N)	Rate of Change in Cutting Force (%)
1.5	55.60	—	4432	—
1.0	53.40	−3.96%	4322	−2.48%
0.5	56.27	+5.38%	4557	+5.44%

. From the table data, when the grid size is 1 mm, the simulation result has approached convergence. Although further encryption to 0.5 mm can improve the calculation accuracy to a certain extent, the corresponding calculation cost also increases significantly. Considering both computational efficiency and simulation accuracy, a 1 mm grid can effectively capture the main physical trends and meet the simulation requirements for the temperature field distribution law in this study. Therefore, all subsequent analyses were conducted using a 1 mm grid for modeling and calculation.

During the meshing process, the cell type is set to C3D8T. This unit is an eight-node hexahedral thermodynamic coupling unit. Each node has both temperature and displacement degrees of freedom, enabling the simultaneous solution of stress fields and temperature fields. It is suitable for direct thermo-force coupling analysis. Compared with other unit types, the C3D8T unit offers higher calculation accuracy and better convergence when handling thermodynamic coupling problems such as contact heat transfer, frictional heat generation, and plastic heat dissipation, and can effectively capture the temperature evolution and stress distribution of PDC cutting teeth during rock breaking. Therefore, in this paper, the C3D8T element is adopted to discretize the model, ensuring the accuracy and reliability of the thermodynamic coupling analysis.

4.4. Time-Step Stability Test

The stability of the explicit solution algorithm requires that the actual time increment does not exceed the above-mentioned critical value; otherwise, the numerical calculation will diverge. To enhance computational efficiency, the mass scaling technique is often used to artificially increase the stabilization time increment. This method alters wave velocity by adjusting the material’s density, thereby enabling a larger time step. However, mass scaling can affect the accuracy of simulation results: if the scaling ratio is too large, it may introduce non-physical inertial effects, distorting the dynamic response. Therefore, when applying mass scaling, it is necessary to balance computational efficiency and solution accuracy to ensure that the dynamic characteristics of the physical process of concern are not significantly disturbed.

In ABAQUS/Explicit dynamic analysis, the stabilization time increment is jointly determined by the minimum element size and the material wave velocity, and their relationship can be expressed as:

$$\Delta t\approx {\displaystyle \frac{L_{\min }}{c_d}}$$

(13)

In the equation, $L_{\min }$ is the smallest unit feature size in the model, which $c_d$ is the material’s expansion wave velocity. The material wave velocity can be estimated based on the elastic modulus $E$ and density $\rho$, and the expression is:

$$c_d=\sqrt{E/\rho }$$

(14)

To explore the influence of the mass scaling coefficient on calculation accuracy and efficiency, this paper designs three sets of time-step stability test schemes under different working conditions: turning off the mass scaling, setting the mass scaling coefficient to 100, and setting it to 1000. By comparing the differences in key physical responses (such as temperature field distribution, temperature peak, and cutting force peak, etc.) among the simulation results of each group, the influence degree of mass scaling on the reliability of the simulation is evaluated, thereby determining the optimal time step setting that takes into account both computational efficiency and solution accuracy. This inspection process provides a basis for the reasonable selection of time steps in the subsequent thermodynamic coupling analysis.

The relevant results are shown in

Table 4. Stable time increment step test data.

Working Condition	Quality Scaling Coefficient	Stable Time Step Increment (s)	Peak Cutting Force (N)	Rate of Change in Temperature (%)	Peak Temperature (°C)	Rate of Change in Cutting Force (%)
1	0	1.48304 × 10−7	4159	—	51.57	—
2	100	1.48384 × 10−6	4322	+3.92	52.39	+1.59
3	1000	4.33697 × 10−6	4940	+18.8	54.26	+5.22

. The results indicate that when the quality scaling coefficient is not set, the calculation results are the most accurate, the incremental step is stable, but the calculation time is the longest. When the coefficient is 100, the results maintain high accuracy, the incremental step remains stable, and the calculation time is significantly reduced. When the coefficient increases to 1000, although the calculation efficiency improves significantly, the results’ accuracy drops and can no longer accurately reflect the physical process. Based on this, considering both calculation accuracy and solution cost, this paper selects a mass scaling coefficient of 100 as the optimal setting for subsequent analysis.

4.5. Comparative Analysis of Thermal Properties Between the PDC Layer and the Cemented Carbide Layer

The geometric model of the PDC cutting teeth was established in SolidWorks 2022, and the uncertainty analysis of the material thermophysical parameters for the PDC and cemented carbide layers was performed using a thermodynamic-coupling numerical method. This analysis simulates the temperature response of PDC cutting teeth under different material property allocation schemes by systematically varying the combinations of thermal conductivity and specific heat capacity parameters for the two layers, and then examines the influence of each parameter change on the tooth surface temperature distribution. The specific parameter settings are shown in

Table 5. Parameter settings for PDC layer and cemented carbide layer.

Working Condition	The Thermal Conductivity of the PDC Layer (W/(m·K))	The Specific Heat Capacity of the PDC Layer (J/(kg·K))	The Thermal Conductivity of Cemented Carbide (W/(m·K))	Specific Heat Capacity of Cemented Carbide (J/(kg·K))
Standard	543	790	100	230
Lower limit	443	710	50	170
Upper limit	643	870	150	280

.

Simulation verification was carried out based on the above parameter settings, and the results are shown in Figure 10. As shown in the figure, although the thermal conductivity and specific heat capacity of the PDC and cemented carbide layers have changed, the overall temperature distribution of the PDC cutting teeth remains essentially unchanged. Further analysis of the data in

Table 6. Data of the PDC layer and the cemented carbide layer.

Working Condition	Maximum Temperature of the Cutting Tool (°C)	Rate of Change (%)	Temperature Field Morphology
Standard	52.39	—	Standard
Lower limit	51.88	−0.97%	Basically consistent
Upper limit	53.97	+3.02%	Basically consistent

reveals that the maximum temperature change rates of the PDC cutting teeth are −0.97% and +3.02% respectively. This indicates that the temperature of PDC cutting teeth is sensitive to changes in thermal conductivity, and fluctuations in the material’s thermal physical parameters can cause a quantitative change in temperature. However, from the perspective of the overall distribution pattern of the temperature field, its basic laws are less affected by parameter changes, and its spatial distribution characteristics remain relatively stable.

5. Interpretation of Result

5.1. Temperature Comparison of PDC Cutting Teeth Under Two Operating Conditions

As shown in Figure 11, during the initial stage, the surface temperature of the PDC cutting teeth rises rapidly under both working conditions. The surface temperature under impact working conditions is slightly higher than under conventional conditions. When the stable cutting stage is reached, the surface temperature of PDC cutting teeth under impact conditions is generally higher than under traditional conditions. Additionally, in the final stage, due to the effect of shock waves under impact conditions, the PDC cutting teeth will complete the cutting task earlier. Compared to the conventional condition, the surface temperature drops earlier. Under both working conditions, the overall average temperature difference is 1.33 °C. As shown in Figure 12, for the PDC cutter, the start and end times under both conditions are shown in Figure 12a and Figure 12c, respectively. Initially, the surface temperature distribution of the PDC cutter is roughly identical under both conditions, but the peak temperature under impact conditions is 3 °C higher than under normal conditions. Figure 12b,d shows that at the final moment, after the PDC cutting teeth undergo impact cutting, their temperature spreads upward across a wide area. In contrast, under normal operating conditions, the temperature distribution of the PDC cutting teeth mainly concentrates in the middle and lower parts of the teeth. In conclusion, PDC cutter rock fragmentation under impact shows a wider regional temperature distribution. For PDC cutters, higher temperatures increase wear rates. To address this, the paper proposes optimizing the PDC cutter surface by altering its shape to improve surface temperature dispersion. This further reduces the wear rate of the PDC cutting teeth.

5.2. Optimization of PDC Cutting Tooth Profile

High temperatures will accelerate the wear of PDC cutting teeth, reducing their lifespan. Therefore, it is necessary to optimize the tooth profile. In this paper, five types of polycrystalline diamond surface shapes are designed, as shown in Figure 13: one saw-type tooth shape (Scheme 1), two saw-type tooth shapes (Scheme 2), three saw-type tooth shapes (Scheme 3), four saw-type tooth shapes (Scheme 4), and five saw-type tooth shapes (Scheme 5).

In the PDC cutting tooth and rock interaction model, the cutting depth is set to 1.5 mm, the back rake angle is 15°, the cutting speed is 500 mm/s, and the impact load mentioned is applied. A rock-breaking simulation of five different tooth-shaped PDC cutting teeth is conducted to compare and analyze their rock-breaking effects.

5.3. Rock-Breaking Characteristics and Temperature Analysis Under Different Design Schemes

To maximize the benefits of saw-tooth-shaped PDC cutting teeth, the rock-breaking characteristics of these teeth were studied under five different design schemes. The study focused on two-dimensional cross-sectional stress cloud maps, three-dimensional stress cloud maps, cutting force, and mechanical specific energy. The goal was to compare and analyze the rock-breaking performance of PDC cutting teeth across different designs and identify the tooth profile with optimal rock-breaking capability.

Figure 14 and Figure 15, respectively, show the two-dimensional cross-sectional and three-dimensional stress contours of the saw-type tooth-shaped PDC cutting teeth during rock breaking under different schemes. From the stress contours, for Scheme 1, the stress is mainly concentrated at the leading edges of the cutting teeth and at the rock contact area, with a “half-moon” and “wedge” distribution, and the stress gradient is relatively small. From Schemes 2 and 3, it is evident that the stress concentration is quite apparent. However, as the number of serrations on the surface of the PDC cutting teeth increases, the stress concentration phenomenon becomes more prominent in Schemes 4 and 5. This is because there are more saw structures on the surface. During the rock-breaking process, the saw cutting edge cuts into the rock in the form of point loading, causing the maximum stress of the rock to be concentrated in the contact area between the saw cutting edge and the rock. In addition, the concave–convex structure formed between the adjacent saw-tooth edge surfaces of the saw-type teeth effectively reduces the contact area with the rock. Meanwhile, the concave area in the middle of the teeth can also exert an extrusion effect on the rock, further assisting in the rock-breaking process. Therefore, the stress concentration area is closer to the tooth tip, with higher stress values, further indicating that the rock is more prone to multiple failures.

The variations in cutting force and mechanical specific energy of PDC cutting teeth under different design schemes are shown in Figure 16. Figure 16a shows the variation curves of the cutting force produced by the PDC cutting teeth during the rock-breaking process under different designs. In contrast, Figure 16b displays the average cutting force and the calculated mechanical specific energy values. As evident in Figure 16a, the peak values of the cutting force curves generated by the PDC cutting teeth during rock breaking under different design schemes vary greatly. By comparing different design schemes, it can be seen that the overall cutting force levels of Schemes 3 and 4 are relatively low, while those of Schemes 1 and 2 are relatively high. As shown in Figure 16b, the average cutting force and MSE across the five design schemes follow a consistent trend. They first decrease and then increase as the saw-tooth shape on the PDC cutting tooth surface becomes larger. Under the design of Scheme 4, the overall average cutting force and mechanical specific energy are the lowest. The design of Scheme 4 reduces the resistance encountered by the PDC cutting teeth during rock breaking, increasing their penetration and enhancing their wear resistance. This shows that, under the same conditions, their rock-breaking efficiency has improved significantly, confirming the analysis in Figure 14 and Figure 15.

Figure 17 shows the temperature distribution of PDC cutting teeth during rock fragmentation under various surface tooth configurations. The box plot shows that as the number of surface teeth increases, the tooth body’s temperature distribution changes noticeably. From Scheme 1 to Scheme 5, the average temperature initially drops and then rises as the number of teeth increases. Scheme 1 displays a single tooth structure, with the highest overall temperature peaking at 37–39 °C. This is because the tooth surface lacks a recessed structure for auxiliary heat dissipation, resulting in heat buildup. As the number of saw types increases, the number of adjacent recesses also grows, boosting heat dissipation capacity. When there are four saw-type tooth (Scheme 4), the temperature drops to the lowest range (29–31 °C), indicating that this configuration has the ideal spacing between teeth and recess layout, working together to enhance heat dissipation. However, when the number of teeth reaches 5, the tooth spacing becomes too tight, reducing heat dissipation from the recesses and causing the temperature to rise again. In conclusion, Scheme 4, with a well-designed layout of tooth-recess spaces, significantly lowers the surface temperature of the cutting teeth, enhances heat dissipation efficiency, and effectively prevents temperature increase during the cutting process.

Figure 18 shows the temperature contours of the PDC cutting teeth at a given moment during rock breaking under different design schemes. From the five cloud maps, it can be seen that the surface temperature of the PDC cutting teeth generally decreases, then rises, as the number of surface saw-type teeth increases. As can be seen from Figure 18a, Figure 18b and Figure 18c, under the designs of Scheme 1, Scheme 2, and Scheme 3, respectively, the temperature of the PDC cutting teeth is mainly concentrated in the middle and lower parts, and it will expand upwards and to both sides along the edge line as the number of surface serrations increases. The more serration on the surface, the more pronounced the temperature concentration in the groove. From Figure 18d,e, it can be seen that under the designs of Schemes 4 and 5, the surface temperature distribution range of the PDC during cutting is significantly reduced, with the majority concentrated at the lower part of the PDC cutting teeth. Compared with the PDC cutting teeth under Scheme 5, the surface temperature of the PDC cutting teeth under Scheme 4 reaches the lowest. This is mainly because when the number of saw-type teeth on the surface is 4, each protruding saw can participate in rock breaking, thereby contributing to temperature diffusion. When the number of saw teeth on the surface of the PDC cutting teeth is 5, since the most edge positions on both sides are far from the rock-breaking center, they cannot participate in rock breaking, thus failing to achieve the effect of temperature diffusion. As shown in Figure 19, the cutting edges of the five-toothed saw-tooth PDC cutting teeth are numbered from 1 to 5 in sequence. The figure clearly shows that the tooth edges 1, 2, and 3 all bear significant contact forces, whereas the contact forces between tooth edges 4 and 5 are zero. This contact force distribution feature directly validates the aforementioned assertion that only some of the tooth edges actually participate in effective cutting; that is, tooth edges 4 and 5 do not have substantial contact with the rock under the current cutting conditions.

From this, it can be concluded that when the number of saw shapes on the PDC cutting teeth is 4, the overall temperature benefit is most significant.

In summary, the PDC cutting tooth design under Scheme 4 exhibits excellent rock-breaking characteristics, as evidenced by a reasonable stress distribution, low cutting force and MSE, and outstanding temperature dispersion, demonstrating the best comprehensive performance and application potential. Based on this conclusion, the following text mainly analyzes the optimal cutting depth and optimal cutting angle of the four saw-type PDC cutting teeth, as well as the differences in rock-breaking characteristics and temperature distribution between the four saw-type PDC cutting teeth and the ordinary PDC cutting teeth under impact loads. The intention is to illustrate that the tooth profile design of the four saw-type PDC cutting teeth not only outperforms the ordinary PDC cutting teeth in rock-breaking characteristics, but also outperforms the ordinary PDC cutting teeth in temperature field analysis, thereby improving the excessive wear of the ordinary PDC cutting teeth due to temperature concentration.

6. Analysis of Rock-Breaking Characteristics and the Temperature Field of Four Saw-Type PDC Cutting Teeth

6.1. Rock-Breaking Characteristics at Different Cutting Depths

To find the best cutting depth of the four saw-type PDC teeth within the interaction model between the teeth and the rock, the simulation will be run with a cutting speed of 500 mm/s, a back rake angle of 15°, and cutting depths at 0.5 mm, 1 mm, 1.5 mm, 2 mm, 2.5 mm, and 3 mm.

Among them, Figure 20 displays the variation curves of the cutting force for the four saw-type PDC cutting teeth at the specified different cutting depths. Figure 21a shows the average cutting force and mechanical specific energy data for this cutting tooth at the corresponding cutting depth. Figure 21b shows the peak-temperature line graphs for this cutting tooth at various cutting depths. Analyzing data from Figure 20 and Figure 21a, it is clear that cutting depth significantly influences the cutting force characteristics of PDC cutting teeth, which display distinct phase features. When the cutting depth ranges from 0.5 mm to 1.5 mm, the peak and average cutting force values for this PDC cutting tooth fluctuate slightly, showing only a weak upward trend. However, when the cutting depth exceeds 1.5 mm, the peak and average force values increase sharply. The reason for this is that the type of rock failure at this stage has fundamentally changed from small, block-shaped, plastic failure to large, block-shaped, brittle detachment. Removing large block-shaped rocks requires multiple cutting actions with cutting teeth, thereby significantly increasing cutting force.

Furthermore, analysis of the data in Figure 21a, along with the data in the exact figure, shows that when the cutting depth is 1.5 mm, the overall MSE of the PDC cutting teeth reaches a minimum, indicating that the overall rock-breaking efficiency under this cutting condition has peaked. When the cutting depth exceeds 1.5 mm, the mechanical specific energy of the PDC cutting tooth increases sharply, leading to a significant decrease in rock-breaking efficiency. The main reason is that the large rock chips produced during cutting at this stage require more energy from the cutting teeth to process, and the block-shaped rocks that fall off must undergo repeated crushing. The combined effect of these two factors results in a significant increase in energy loss, ultimately leading to higher MSE and lower rock-breaking efficiency. As shown in Figure 21b, the surface temperature of the PDC cutting tooth reaches its peak only at a cutting depth of 1 mm. At other cutting depths, the surface temperature of the cutting tooth remains relatively low. In conclusion, the optimal cutting depth for the four saw-type PDC cutting teeth is 1.5 mm.

6.2. Rock-Breaking Characteristics with Different Back Rake Angles

The back rake angle inclination is crucial for the cutting teeth to maximize their benefits. As mentioned earlier, the optimal cutting depth for a four saw-type tooth is 1.5 mm. Therefore, with a cutting speed of 500 mm/s and a cutting depth of 1.5 mm as the boundary conditions, the rock-breaking process of the four saw-type tooth at different back rake angles (5°, 10°, 15°, 20°, and 25°) was simulated and analyzed to determine the optimal cutting angle of the four saw-type tooth.

Figure 22 shows a schematic diagram of rock breaking by cutting teeth at different back rake angles. It is clear that the back rake angle mainly influences the flow of cuttings, thereby affecting rock-breaking performance.

Figure 23a shows the average cutting force and MSE at different back rake angles. Figure 23b displays the temperature peak curves of the cutting teeth under various back rake angles. From Figure 23a, it is clear that when the cutting depth remains constant, and the back rake angle is between 5° and 10°, the saw surface increases the contact area between the four-tooth saw-type PDC cutting teeth and the rock. This directly causes a significant rise in the cutting reaction force they experience. This reaction force hampers the smooth progress of the rock-breaking process. Due to the influence of the reaction force and contact conditions, the plowing effect of the cutting teeth is weak, and the chips produced during rock breaking cannot be discharged in time. The remaining chips are then repeatedly cut. This phenomenon greatly increases the cutting force of the four saw-type tooth. Also, it raises their mechanical specific energy, ultimately leading to a notable reduction in overall rock-breaking efficiency. When the cutting depth remains constant, and the back rake angle is between 15° and 20°, the cutting teeth are at the optimal rock-breaking angle, allowing the rock to be discharged promptly. When the back rake angle exceeds 20°, the increased projected area of the cutting teeth’ top surfaces in the vertical direction makes them more susceptible to secondary contact with rock debris, leading to repeated cutting. This raises the resistance encountered, thereby increasing the average cutting force and mechanical specific energy, while decreasing efficiency. Only at a back rake angle of 20°, the average cutting force and mechanical specific energy decrease.

Figure 23b illustrates the surface-temperature pattern of the PDC cutting teeth as the back rake angle increases: the temperature initially rises and then falls. When the angle is slight, the contact area between the cutting teeth and the rock is larger, and the continuous cutting and repeated crushing processes generate significant frictional heat, raising the temperature. When the back rake angle reaches 20°, the cutting efficiency improves, rock debris is expelled quickly, and repeated crushing is minimized. Frictional heat declines accordingly, resulting in an overall temperature drop. In conclusion, under this simulation condition, a 20° back rake angle effectively controls temperature increase while ensuring optimal fracture performance of the cutting teeth.

6.3. Analysis of the Impact of Rock-Breaking Temperature Between Conventional Cutting Teeth and Four Saw-Type Tooth

Based on the above conclusions, this section compares the temperature distributions of four saw-type PDC cutting teeth and ordinary PDC cutting teeth under impact rock-breaking conditions. The main goal is to verify the superiority of the four saw-tooth profile designs. Compared to ordinary cutting teeth, it can not only optimize rock-breaking performance but also further improve wear resistance by enhancing temperature distribution and reducing high-temperature concentration. This provides technical support for extending the service life of PDC cutting teeth.

The same settings were used for both tooth profiles. The cutting depth was 1.5 mm, the back rake angle was 15°, and the cutting speed was 500 mm/s. A sinusoidal shock wave, as mentioned above, was applied. The results of the temperature field data comparison and analysis are provided below.

As shown in Figure 24, Figure 24a displays the temperature contours for the four-saw PDC cutting teeth. As depicted, under impact conditions, the temperature distribution on both sides of the saw-type tooth grooves spreads upward along the grooves during cutting, reaching a maximum of 34.99 °C. Figure 24b shows the temperature contours of a standard PDC cutting tooth under impact conditions. As shown in the figure, the temperature distribution under impact conditions spreads across a wide area to the upper left and upper right during the cutting process, reaching a maximum temperature of 46.95 °C. Compared to the typical PDC cutting teeth, the surface temperature distribution range of the four saw-type PDC cutting teeth is notably smaller than that of standard PDC cutting teeth. Moreover, compared to common PDC cutting teeth, its maximum temperature has decreased by approximately 10.69% overall. This reduction results from the heat-dissipation effect of the saw-type tooth structure, which effectively reduces wear caused by high-temperature concentration. Figure 25 shows the two types of PDC cutters under impact conditions, along with the temperature curve for broken rock displayed in the diagram. The two temperature curves exhibit a significant difference in gradient. The design of the four saw-type PDC cutting teeth keeps overall temperature relatively low and maintains a stable temperature fluctuation range. This shows that the PDC cutting teeth under this design, due to their unique saw-type tooth structure and groove design, can effectively dissipate heat during rock breaking, thereby reducing overall temperature fluctuations. The temperature of typical PDC cutting teeth is relatively high and varies sharply. This indicates that during rock breaking, friction between the PDC cutting teeth and the rock generates heat that is not readily dissipated, leading to significant temperature changes. Based on this, it can be concluded that the tooth profile design of the four saw-type PDC cutting teeth can effectively lower their temperature, and this result also confirms the previous hypothesis.

7. Comparative Analysis of Full-Size Conventional PDC Bits and Full-Size Saw Tooth PDC Bits

7.1. 3D Modeling of PDC Bits

To evaluate the overall rock-breaking performance of the 4 saw-type tooth, two three-dimensional models of PDC drill bits were created using SOLIDWORKS-2022 software, as shown in Figure 26. One of the drill bits features 4 saw-type tooth, while the other has conventional cutting tooth. The drill bit has a diameter of 215.9 mm and five blades. Aside from the different shapes of the saw-type tooth surfaces, the two models share the same structural parameters.

7.2. Finite Element Modeling

The three-dimensional models of the two types of PDC drill bits described above were imported into the commercial software ABAQUS 2022, and a finite element model was created, as shown in Figure 27. In this finite element model, the rock’s diameter was 500 mm, and its height was 300 mm. During the simulation, the degrees of freedom of all surfaces except the rock surface were constrained. The drill bit was treated as a rigid body, and wear on its cutting structure was ignored. A drilling pressure of 30 kN and a constant rotational speed of 60 r/min were applied to the drill bit. And to improve the accuracy and efficiency of the results, the impact sine wave mentioned above was applied, and the meshing of the contact area between the drill bit and the rock was refined to 4 mm, while the rest of the model was meshed at 12 mm. The rock mesh type was set to C3D8T, and the drill bit mesh type was set to C3D10M. The simulation duration was set to 10 s.

7.3. Temperature Field Analysis of Full-Size PDC Bits

Based on the above model, a simulation analysis was conducted to examine the temperature distribution characteristics of PDC bits under different cutting tooth configurations. To more clearly reveal the temperature evolution law of PDC bit cutting teeth during drilling, the inner-circle teeth of the bit were taken as the analysis object, as shown in Figure 28. The simulation results show that during the rock-breaking process of the conventional PDC cutting teeth, the temperature field is mainly concentrated in the local high-temperature area on the tooth surface (as shown in the area numbered 1 in the figure), presenting a distinct feature of high-temperature concentration; while the temperature distribution of the four-saw-tooth-shaped tooth shows an upward diffusion trend, and the affected thermal area is relatively wider. Further, as shown in the temperature change curve in Figure 29, the temperature rise rate of the conventional PDC cutting teeth is significantly faster than that of the four-saw-tooth-shaped teeth, and the maximum temperature reached is also higher. This conclusion is in good agreement with the previous single-tooth simulation results, further verifying the effectiveness of the saw-tooth structure in improving the thermal distribution of PDC cutting teeth and suppressing local temperature rise.

7.4. Analysis of the Simulation Result

Figure 30 shows a comparison of stress contours at the bottom of the well after simulation for PDC drill bits with conventional and four saw-type tooth. Based on the fragmentation pattern and location, the failure area at the bottom of the well can be divided into two parts: the central failure zone near the inner row of teeth on the drill bit (Zone A), and the well wall failure zone near the outer row of teeth (Zone B).

The comparative analysis shows that the rock fragmentation patterns caused by the two types of cutting teeth differ significantly. Compared to traditional cutting teeth, the four saw-type cutting teeth produced a finer and more uniform rock fragmentation network in both Area A and Area B. Their unique tooth surface structure allows each tooth to effectively penetrate the rock, thereby evenly distributing the fragmentation effect across the contact surface and preventing the formation of large areas of inadequately fragmented regions at the bottom of the well. This fragmentation characteristic helps reduce repeated cutting and, in theory, improves the overall rock-breaking efficiency of the drill bit.

Figure 31 compares the drilling processes of the two drill bits throughout the entire operation. The analysis shows that the four saw-type PDC bits exhibit more intense dynamic rock-breaking behavior across all drilling stages. Its unique tooth design penetrates the rock through a multi-point, discrete-loading method, which is more likely to cause local stress concentration and effectively initiate cracks. Compared to conventional cutting teeth, the stress distribution at the bottom of the well and the well wall area under this drill bit’s action is more continuous and uniform. This dynamic behavior aligns with the static stress contours of the well bottom shown in Figure 31, which jointly illustrates the internal mechanism by which the four saw-type cutting teeth promote the formation of a fine, uniform fracture network in the rock, thereby achieving higher rock-breaking efficiency.

Figure 32 compares drilling data for two types of drill bits. Figure 32a shows the drilling depths, and Figure 32b displays the torque required for the drill bits to break the rocks. From the chart, it is evident that at the beginning of drilling, there was no significant difference in drilling depth between the two bits. However, as drilling continued, the depth difference steadily increased. Lower torque indicates less resistance as the cutting teeth break the rock. It is clear from Figure 32b that the torque fluctuation of the four-toothed cutting teeth assembly is considerably smaller than that of the conventional drill bit, indicating it has better rock-breaking ability.

As shown in the simulation results in

Table 7. Drilling data.

Type	Drilling Depth/mm	Cumulative Time/s	ROP/(mm·s−1)
Conventional PDC bit	120.209	10	12.02
Saw-tooth PDC bit	129.515	10	12.95

, for the same drilling duration (10 s), the drill bit with four saw-type cutting teeth increases the penetration rate by 7.74% compared to a conventional cutting-tooth drill bit. This result further demonstrates that the four saw-type tooth significantly outperform the conventional tooth type in drilling performance, confirming the effectiveness of their structural design.

8. Conclusions

This study started by examining the temperature distribution patterns of traditional tooth profiles under impact and normal operating conditions. First, five structural designs for the PDC cutting tooth surface were developed. Then, using the finite element method, the rock-breaking performance of each tooth profile was systematically simulated and analyzed. To ensure simulation accuracy, the best tooth profile was selected under identical conditions, and the optimal cutting depth and camber angle for that profile were identified. By comparing the temperature fields of the optimized tooth profile with those of the conventional profile, the temperature distribution characteristics were revealed. Lastly, a full-scale drill bit model with different tooth profiles was created, and the rock-breaking process was compared and analyzed. The following conclusions were drawn:

(1)

Under impact loading, conventional PDC cutters exhibit a global temperature increase with broad spatial distribution, which accelerates thermal wear and reduces service life. In contrast, the optimized four-saw-tooth design significantly mitigates this effect—achieving a 10.69% reduction in maximum temperature compared to conventional cutters. This thermal advantage suggests that the saw-tooth geometry enhances heat dissipation and reduces frictional heat accumulation, which is critical for extending cutter durability in high-frequency impact drilling applications.

(2)

The four-saw-tooth cutter consistently generated lower peak and average cutting forces, along with reduced mechanical specific energy (MSE), indicating improved rock-breaking efficiency. Parametric analysis further revealed an optimal cutting depth of 1.5 mm, where MSE is minimized and efficiency is maximized; exceeding this depth results in a sharp increase in cutting forces, suggesting a threshold for the ductile-to-brittle transition or chip-formation mechanisms. Additionally, a 20° back rake angle was identified as optimal, balancing effective cutting with reduced frictional heating—smaller angles increase contact area and heat generation, while larger angles may compromise cutting stability. These findings provide quantitative guidance for selecting operating parameters to balance efficiency and tool life.

(3)

When integrated into a full drill bit, the four-saw-tooth configuration increased the mechanical rate of penetration (ROP) by 7.74% compared to conventional designs. This performance enhancement, validated through both simulation and experimental comparisons, demonstrates that the geometric optimization of individual cutters effectively translates into bit-level drilling efficiency.

(4)

The results support the feasibility of implementing saw-tooth PDC cutters in field operations where impact rock-breaking is prevalent, such as hard rock drilling, percussion drilling, or hybrid rotary-percussive systems. The design is scalable: the optimized tooth geometry can be adapted to various bit diameters and cutter layouts without fundamental redesign. Furthermore, the identified sensitivity to cutting depth and back rake angle offers operators a reference for adjusting drilling parameters to match specific rock formations.

(5)

While this study provides validated insights into cutter optimization, several limitations should be acknowledged. First, the thermal analysis assumed simplified downhole conditions, neglecting geothermal gradients and drilling fluid convection, which may affect absolute temperature predictions in deep-well applications. Second, although the Drucker–Prager constitutive model was validated against uniaxial compression tests, the simulated cutting forces and cutter temperatures lack direct experimental verification because no dedicated single-cutter tests under controlled conditions have been conducted. Consequently, the quantitative results (e.g., the 10.69% temperature reduction) should be interpreted as comparative trends rather than absolute values. Future work should focus on conducting single-cutter experiments to measure cutting forces and temperatures, and on incorporating more realistic downhole thermal environments to further validate the long-term benefits of the saw-tooth design.

The innovation of this research lies in proposing a surface-structure optimization design to address increased wear caused by temperature concentration in conventional cutting teeth under impact conditions. This design effectively alleviates high-temperature buildup and associated wear by guiding heat away from the tooth surface. The proposed tooth shape is currently in the preliminary design stage and has not yet been implemented in practice. However, its design concept can serve as a theoretical foundation for optimizing the performance of PDC cutting teeth and enhancing drill head efficiency. Future research will focus on a parametric study of full-scale PDC drill bits, evaluating the rock-breaking performance of this tooth shape across different rock formations and further validating its engineering practicality through laboratory tests and field trials, ultimately supporting the optimization of PDC tooth design and improving drilling efficiency.