Friction Reduction Research Articles

Establishment and analysis of a piezoelectric actuator dynamic model with temperature-dependent damping, stiffness, and piezoelectric constant

The characteristics of the piezo-stack and the flexible mechanism are both influenced by temperature, which induces the performance change of piezoelectric actuators in low-temperature. This study investigates how temperature affects the dynamics model's stiffness, damping, driving force, and friction. An axial heat conduction model based on Fourier's heat conduction law was established, and finite element analysis was carried out to study the temperature distribution of the piezo-stack. Moreover, finite element analysis was carried out at various temperatures to investigate the impact of temperature on the flexible mechanism's deformation. Based on the aforementioned study, a dynamics model with variable stiffness and damping is proposed in this paper, and the simulation results are verified. In the experiment, the effects of temperature, voltage, and frequency on the output performance of the piezoelectric actuator were investigated separately using impedance and amplitude-frequency characteristic curves to determine the resonant frequency and damping ratio of the flexible mechanism at low temperatures. Theory and experiment show that high stiffness and low piezoelectric constants at low temperatures reduce the piezoelectric actuator's output displacement, friction reduction will enhance the driving displacement of the piezoelectric actuator, and the effect of damping on output displacement is insignificant. This study offers significant theoretical value and guidance for the use of piezoelectric actuators in low-temperature situations.

High power pulsed magnetron sputtering tailored low temperature CrAlN + MoWS coatings for dry tribological contacts

Gears are used in a variety of applications, for example, in automotive and aerospace industries. In these applications, gears are exposed to harsh conditions such as high Hertzian pressures. In many cases, lubricants are used to achieve a reduction in the coefficient of friction and, thus, in the wear of the components. Nevertheless, in some applications, the use of a lubricant is difficult, for example, in vacuum environments. One promising approach is the application of solid lubricants by using triboactive elements. The present study shows the potential of a process combining high power pulsed magnetron sputtering (HPPMS) and direct current magnetron sputtering (dcMS) for the deposition of CrAlN + MoWS coatings. In HPPMS/dcMS processes, especially, the share of HPPMS leads to higher ionization of the coating plasma and, therefore, to higher coating thicknesses on the teeth of gears. One major challenge in coating processes is the adjustment of the deposition temperature, since steels used for gear applications are temperature sensitive. Therefore, starting from an established coating process with a high coating temperature, the coating process was adjusted by reducing the number of used cathodes. By reducing the count of used dcMS cathodes, the share of HPPMS cathodes within the coating process was increased. Furthermore, segments of gears were coated in order to determine the coating thickness at different distances from the head of the gear tooth. A sufficient coating thickness distribution on the flank of the gear tooth is crucial for friction reduction and wear protection when used in gearboxes. The reduction of used cathodes led to a decrease in the coating temperature from a maximum coating temperature of Tmax = 281 °C to Tmax = 214 and 197 °C. It was shown by nanoindentation measurements that the effect of soft annealing was eliminated by reducing the coating temperature. At the same time, coatings deposited with increased HPPMS fraction led to a reduced coefficient of friction as well as lower wear volumes for pin-on-disk measurements in a dry tribological contact with an uncoated 100Cr6 counterpart. Moreover, these processes exhibited a good coatability of the gear tooth with a relatively high coating thickness even near the gear tooth root. The present study shows the potential of increasing the share of HPPMS during the deposition of coatings for dry-running applications. By increasing the HPPMS content, the tribological behavior as well as the coating thickness distribution on gears can be significantly improved.

Synergistic lubrication mechanism of nanodiamonds with organic friction modifier

Nanoparticles and organic friction modifiers (OFMs) as lubricant additives have shown great potential in friction and wear reduction by forming tribofilms which prevent direct contact at the sliding interface. Potential mechanisms for the formation of these tribofilms remain poorly understood, limiting the ability to optimise the performance of the entire tribosystem. Incorporation of nanoparticles and OFM together in a lubricant could provide a unique solution to enhance frictional and wear properties. In this study, Nanodiamonds (NDs) and Glycerol Monooleate (GMO) have been added to a PAO base oil containing low concentration of Zinc dialkyl dithio-phosphate (ZDDP) to produce a novel lubricant combination that significantly reduces coefficient of friction (COF) and wear. Experimental studies showed that NDs reacted with additives present in the lubricant combination to expedite tribofilm formation. Friction reduction performance can be attributed to the encapsulation of carboxylated NDs due to tribochemical interaction with GMO, their mechanical interlocking in the tribofilm and polishing effect of NDs. The visible presence of NDs in tribofilms and the formation of a thicker tribofilm layer with NDs have been corroborated for the first time in this study. Synergy achieved among NDs, GMO, and low concentration ZDDP to formulate a novel environmentally friendly lubricant with advanced tribological performance has been shown, providing a great potential to develop sustainable tribological solutions for a wide variety of engineering applications.

ZnFe2O4@C/graphene oxide nanocomposites designed for enhancing the friction reduction property of lubricants

Improving the friction reduction property of lubricant to ensure the efficient operation of advanced heavy-duty machinery has been taken seriously. Herein, as a novel additive with a distinctive sphere-on-sheet structure, ZnFe2O4@C/graphene oxide (ZnFe2O4@C/GO) nanocomposites were designed via the response surface method to drastically enhance the friction reduction property of the polyalphaolefin oil. The particular lubrication mechanism of the ZnFe2O4@C/GO nanocomposites was simultaneously revealed. Results showed that the friction coefficient could be reduced by an order of magnitude (less than 0.05) at several frictional moments under the contact stress of 1.20 GPa when the ZnFe2O4@C/GO nanocomposites were added to polyalphaolefin oil. Specifically, the largest decrease in friction coefficient during the friction process was from 0.24 to 0.025 (approximately 90 %). According to the molecular dynamics simulations, the outstanding friction reduction property of the ZnFe2O4@C/GO nanocomposites was determined by the sliding structures with low shear force between the bent graphite in the ZnFe2O4@C microspheres and the graphene tribofilms at the friction interface. These findings reveal the application prospects of the ZnFe2O4@C/GO nanocomposites as a superior lubricant additive for advanced heavy-duty machinery in the future.

Experimental study of viscous oil-water core-annular flow in horizontal pipe

Transporting viscous oils through pipelines is usually challenging due to their very high viscosity. Significant friction reduction in the transportation of viscous oils through pipelines using an ecologically friendly way is the most appealing feature of the core annular Flow (CAF) technique. An experimental study has been conducted to investigate the flow patterns and pressure gradient of viscous oil-water two-phase flow in a horizontal acrylic pipe with a 50 mm inner diameter. The test section was equipped with a fluid lubrication injector element to artificially provide CAF. The pressure gradient measurements were focused on the CAF pattern. The prediction models of the CAF pressure gradient were reviewed and evaluated. An empirical prediction model of CAF pressure gradient was developed, relying on both the present and previously published experimental results. The flow patterns were classified into five patterns. It was observed that the CAF occupied a large region in the constructed flow pattern map and its frictional pressure gradient closely resembles that of water flowing alone. It was found that the developed empirical model provided quite good predictions of the experimental pressure gradients and significantly outperformed the original model. The reviewed prediction models in this area for CAF either overpredicted or underpredicted the experimental pressure gradients. Some of these models considered the extensive effect of viscous oil adhered to the inner wall of the pipe, while others neglected the effect entirely.

Tribological Synergism of Anodic Aluminum Oxide Surface Containing Micro-Holes and Nanopores under Lubricated Reciprocation

Micro-drilled aluminum surfaces containing micro-holes were anodized to produce nanopores over the machined and lapped surfaces. The anodized nanopores had an approximate diameter of 30–40 nm and a depth distribution of 20–30 μm from the surface. The diameter and depth of the machined micro-holes were 125 μm and 300 μm, respectively. Anodization itself did not change the surface roughness because the nanopores were very small. Ball-on-disk reciprocating tests were performed under lubricated conditions for 2 h using a frequency of 2 Hz, a load of 2 N, and a travel distance of 5 mm. The results showed that both the micro-drilled and anodized surfaces greatly reduced the coefficient of friction compared with the lapped bare surface; however, the coefficient of friction of the hole-textured specimen was not maintained till the end. Contrary to expectations, the lubricant retention capability of the textured structure declined because of hole failure that occurred during oscillation. This gradually increased friction until the end of the reciprocating test. When the micro-drilled surface was anodized, the coefficient of friction decreased again, implying that non-anodized micro-holes alone were ineffective for reducing friction. The surface hardness of Al increased owing to anodization, and thus the micro-holes remained intact. Therefore, it is concluded in this study that a prerequisite for friction reduction in Al is to increase the hardness to minimize the failure of micro-holes, which can be achieved by anodization. The synergistic lubricant retention capability can be maintained by the presence of both nanopores and micro-holes.

Considerations on an embedded pile’s effective length in an analytical calculation according to the commentary on the STN 73 1002 standard

The analytical model for calculating the bearing capacity of a pile, presented in the commentary to STN 73 1002 – Pile Foundations, gives a recommendation to reduce the pile’s length in the calculation of the shaft resistance. The recommendation is based on Caquot-Kérisel’s theory. Especially in the case of embedded piles, reducing a pile’s length in the calculation can cause the shaft friction of the embedded pile to be neglected, and the calculated resistance of the pile is thus significantly lower. The results of instrumented static load tests of embedded piles were analysed. The main aim of the study was to verify the validity of reducing the pile’s length in the analytical calculation of the shaft resistance. The results of the static load tests analysed did not show any reduction in the shaft friction on the embedded part of the pile. In the form of a parametric study, the effect of reducing the pile’s length in the calculation of shaft friction was analysed for different dimensions of embedded piles.

Effects of Erucamide and N-phenyl-α-naphthylamine on the Friction and Torque Behaviors of Grease on Roller Bearings

To evaluate the impact of various proportions of erucamide and N-phenyl-α-naphthylamine on grease’s tribological performance for roller bearings, lithium complex grease (LCG) and polyurea grease (PG) were prepared with erucamide and N-phenyl-α-naphthylamine proportions of (0,0), (0,3), (1,2), (2,1), and (3,0). An investigation was conducted into the microscopic structures of the ten greases and their effects on the friction coefficients and wear scars of GCr15 steel. These findings were validated through bearing friction torque tests. The results indicate that the addition of 2 wt. % erucamide and 1 wt. % N-phenyl-α-naphthylamine to PG/LCG significantly enhances their tribological properties and reduces friction torque, with PG exhibiting superior performance. This enhancement was attributed to the synergistic interaction of erucamide and N-phenyl-α-naphthylamine with the lamellar thickener within PG. Erucamide contributed to friction reduction, while N acted as an antioxidant.

Study on the Superlubricity Behavior of Ions under External Electric Fields at Steel Interfaces.

Realizing macroscopic superlubricity in the presence of external electric fields (EEFs) at the steel interfaces is still challenging. In this work, macroscopic superlubricity with a coefficient of friction value of approximately 0.008 was realized under EEFs with the lubrication of LiPF6-based ionic liquids at steel interfaces. The roles of cations and anions in the superlubricity realization under EEFs were studied. Based on the experimental results, the macroscopic superlubricity behavior of Li(PEG)PF6 under EEFs at steel interfaces is attributed to the strong hydration effect of Li+ cations and the complete reactions of anions that contributed to the formation of a boundary film on the appropriate surface. Moreover, the reduction in the number of iron oxides in the boundary film on the disc was beneficial for friction reduction. We also provide a calculation model to describe the relationship between the hydration effect and the optimal voltage position, at which the lowest friction might occur. Ultimately, this work proves that macroscopic superlubricity can be realized under EEFs at steel interfaces and provides a foundation for engineering applications of superlubricity in an electrical environment.

Lubricant-infused anodic aluminum oxide surface (AAO-LIS) for durable slipperiness under harsh conditions

The wettability of surfaces plays a crucial role in determining their applications, and slippery surfaces have been utilized in various fields. Especially, lubricant-infused surface (LIS) has been undergone extensive research over the past decade. However, LIS tends to lose its infused lubricant and consequently lose its slippery properties when exposed to harsh conditions. Therefore, there is a strong need to enhance the durability of the infused lubricant. Herein, two strategies are adopted to improve the durability of slippery properties against centrifugal forces and high-speed shear flows. One strategy is using re-entrant shaped nanocavities, and the other is grafting PDMS brush onto the surface. Anodic aluminum oxide (AAO) is employed to fabricate the re-entrant shaped nanocavities, and the durability of the infused lubricant is improved when the cavities have a smaller diameter. Furthermore, the re-entrant shape of nanocavity significantly improves the durability compared to nanocavity with a constant diameter. The grafting of PDMS brush is essential for enhancing the durability, and an increase in the length of the PDMS brush also improves the durability. The fabricated AAO-based LIS (AAO-LIS) maintains the slippery properties for 50 min under a high-speed water flow of 12 m/s. In addition, it maintains its superior slipperiness for more than a few days when exposed to actual seawater. Furthermore, the frictional drag reduction performance of the fabricated AAO-LIS is assessed. The proposed AAO-LIS maintains a certain drag reduction performance durably even after losing its superior slipperiness, demonstrating its strong potential for practical applications across various industrial fields.

MoS2 Nanomaterials as Lubricant Additives: A Review

Improving the lubricating properties of base oils through additives is a crucial objective of tribological research, as it helps to reduce friction and wear of materials. Molybdenum disulfide (MoS2) is a 2D nanomaterial with excellent tribological properties that is often used as a lubricant additive. Several studies have been conducted on the preparation and utilization of MoS2 and its nanocomposites as lubricant additives. This paper reviews the research progress on MoS2 nanomaterials as lubricant additives. It firstly introduces various synthesis methods of MoS2 nanomaterials while focusing on the preparation of nano-MoS2 as lubricant additives. It then summarizes the dispersion stability of nano-MoS2 in lubricating oils which has been paid extensive attention. Moreover, this paper reviews and discusses the tribological properties of nano-MoS2 and its various composites as lubricant additives. The possible anti-wear and friction reduction mechanisms of nano-MoS2 and its composites are also discussed. Finally, this paper presents the challenges faced by nano-MoS2 additives in the field of lubrication and the prospects for future research in view of previous studies.

Mechanism for friction reduction of aluminum alloy at high-pressure and ultra-low temperature

Temperature and pressure have a significant impact on friction in aluminum alloy ultra-low temperature forming. In this paper, cryogenic strip drawing test (CSDT), morphologies analysis and microstructure characterization were used for friction mechanism investigation of aluminum alloy under different temperatures and pressures. The findings indicated that the coefficient of friction (COF) first increased and then decreased as pressure increased. From 2 to 10 MPa, the lowest COF was observed at −190 °C. The formation of fine deformation microstructure enhanced surface material plasticity and resistance to deformation leading to reduced adhesive friction or plowing friction, resulting in low COF at high-pressure and ultra-low temperature. Furthermore, higher temperatures and pressures increased the adhesion, which was detrimental to prolonging the service life of die.

Transforming water-soluble carbon dots with high particle size regularity as the high-performance oil-based lubricant additives by one-step surface modification

Developing high-performance carbon dot (CD)-based lubricant additives towards non-polar base oils is always challenging because it is an arduous task to gain hydrophobic CDs with high quality. In this work, with the aid of the chemical reaction between hydroxyl groups and lauroyl chloride molecules, the water-soluble CDs-OH derived from the solvothermal method with particularly high particle size regularity were transformed as the oil-soluble CDs-LA by the one-step surface modification process. As expected, the CDs-LA capped by abundant long alkyl chain groups exhibited excellent long-term dispersion stability in non-polar base oil of polyalphaolefin (PAO4) and hence could be served as the additives of PAO4 directly. Under the same test conditions, the tribological performance of CDs-LA was obviously superior to the hydrophobic CDs obtained by the pyrolysis method, implying that the high particle size regularity was beneficial for making full use of the lubrication functions of CDs. Loading 1.7 wt% of CDs-LA made the friction and wear of PAO4 reduced by 32.2 % and 76.4 %, respectively. When the duration prolonged from 20 min to 200 min, the friction reduction of base oil triggered by CDs-LA further enlarged to 46.9 %. The friction-reducing and anti-wear performance of CDs-LA under high loads was also satisfactory. The worn surface analysis results demonstrated that the robust and homogenous boundary lubrication films composed of FexOy and CDs have generated on the rubbing surfaces lubricated by CDs-LA/PAO4 dispersion, well accounting for the outstanding friction reduction and wear resistance functions of CDs-LA.

Effect of the high temperature phase transition on the tribological behavior of atmospheric plasma sprayed AlCoCrFeNi-Bi2O3 coating

Owing to the brittleness of the body-centered cubic (BCC) structure and lack of self-lubrication, plasma-sprayed AlCoCrFeNi high-entropy alloy (HEA) coatings undergo severe abrasive wear, resulting in high friction and wear. In this study, the substrate surface temperature was increased (800 °C) to promote the phase transition from BCC to ductile FCC during spraying. As a result, the prepared AlCoCrFeNi HEA coating contained BCC and FCC phases, exhibiting a higher adhesive strength, lower friction coefficient and wear rate at room temperature (RT)–800 °C. In addition, the elevated substrate surface temperature enabled the transition of the low-temperature stable phase α-Bi2O3 to the high-temperature stable phase δ-Bi2O3. δ-Bi2O3 promoted the formation of low shear strength planes owing to its low interaction parameter and defect-fluorite structure with 25 % anionic vacancies similar to that of the Magnéli phase, which facilitated friction reduction in a wide temperature range. This study confirms that δ-Bi2O3 can effectively improve the anti-wear performance of the AlCoCrFeNi-Bi2O3 coating at RT, 200, 600 and 800 °C. However, at 400 °C, the low melting point and soft nature of the Bi2O3 weakened the mechanical strength of the coating and inhibited the construction of a solid and tough tribo-layer, resulting in a relatively high wear rate for AlCoCrFeNi-Bi2O3 coating. At 800 °C specifically, under the thermal coupling effect, δ-Bi2O3 migrated and aggregated on the worn surface with the oxidation product Al2O3 of the AlCoCrFeNi HEA matrix, and jointly promoted the formation of a compact and smooth tribo-layer with lubricating capability, which not only effectively reduced friction but also inhibited wear.

Tribological considerations of threaded fastener friction and the importance of lubrication

The torque-tension relationship of threaded fasteners affects almost all engineering disciplines. Tribological processes at fastener interfaces manifest as the system's friction coefficient. Lubrication-related influences are usually described empirically using K or μ. The drive towards lightweight fastener materials in engineering systems and lubricants with reduced environmental impact is challenging existing knowledge and industrial practice in a range of applications, many safety critical. More comprehensive understanding is needed to achieve repeatable friction during assembly and re-assembly, resistance to loosening and fretting during operation, and effective anti-seize for disassembly with a growing range of materials and lubricants. The lubricants considered showed three predominant lubrication mechanisms: plastic deformation of metal powders; burnishing/alignment of molybdenum disulphide, MoS2; and adhering/embedding of non-metal particles. Multivariate analysis identified key sensitivities for these mechanisms. Assembly generated changes at fastener surfaces and in the lubricating materials. Re-assembly exhibited significant reductions in friction.

Vibration-induced friction modulation for a general frequency of excitation

Applying an oscillatory load is one of the most efficient ways to alter friction forces. Several theoretical and experimental studies on the influence of oscillatory loads on friction have been conducted, investigating the effect of both in-plane and out-of-plane oscillations for different tribological pairings. However, in the literature, the effect of an oscillatory load on the friction force has been studied with an emphasis on dynamic loads characterized by a high-frequency content, while a clear statement as to what is considered “high-frequency” is missing. Moreover, the effect of a combination of load directions on the friction reduction is not accounted for. Therefore, this study aims to determine the vibration-induced effect on friction regardless of the frequency range and direction of harmonic force for a single and multi-degree-of-freedom system. Analytical methods are used to obtain the friction modulation due to harmonic loads, considering a classical mass–spring–dashpot system on a moving belt and the Amontons–Coulomb law. It is found that, in the case of continuous slip, a general relation for the vibration-induced friction modulation is obtained utilizing the velocity response function of the investigated system. The latter is used to highlight a threshold from which the high-frequency regime starts and to determine the stick–slip boundaries. Moreover, through the velocity response function, the influence of different external harmonic forces is investigated and discussed. This includes considerations of phase, excitation frequency, system characteristics, and the choice of the normal contact force expression.

Laser surface texturing for superhydrophobic, icephobic and friction reduction functionalization

Nanometre and/or micrometer scale periodic features naturally present decorating the skin of many insects, fishes or plants have been found to give them extraordinary aesthetic, adhesion, antifouling, wear resistance, superhydrophobic or drag reduction properties. With the aim of artificially conveying the same properties to products and tools, researchers have tried to reproduce such bionic topography on the surface of a huge variety of materials using different manufacturing methods. Among the different manufacturing technologies, surface texturing based on direct laser writing using ultrashort pulses offers great flexibility in terms of geometry and size of the feature to be created. This work will focus on two specific types of functionalization of metallic as well as rubber surfaces through laser surface texturing, i.e., icephobicity and friction reduction. In the first case, different texture patterns were laser written on sheet samples of Aluminum Alloy of interest for aerospace applications. Their wettability and anti-icing properties were investigated through water contact angle experiments in different environmental conditions and steam-freezing experiments were conducted in a climate chamber. The role of the laser textured pattern geometry on the frictional performances of a rubber surface under lubricated non-conformal as well as conformal point contact has been also widely investigated. In the first case, no improvements were obtained in terms of frictional performances, ascribable to the reduced number of dimples involved in the contact area. Conversely, remarkable friction reduction was achieved in mixed and in the transition between the mixed and the elasto-hydrodinamic lubrication regime, thanks to the concurrence of several effects as micro-cavitation, wear debris trapping, and lubricant entrapping within the texture.

Effect of height waviness on the friction behavior of 100Cr6 steel under mixed or hydrodynamic lubrication

Friction can indeed have a significant impact on energy consumption and CO2 emissions. Height waviness changes depending on the fabrication, mounting or deformation due to high load. This can be an important factor in determining the friction performance of many engineering systems that involve contact and sliding between two surfaces. However, the relation between height waviness and friction remains for a further investigation. In this work, a pin-on-disk setup was used to investigate the effect of height waviness on friction between surfaces in conformal contact. The tribological system was lubricated with FVA2 oil with the contact load of 150 N. Friction was measured at different speed steps ranging from 0.04 to 2 m/s for acquiring the Stribeck curve. Screws on the back of the disk were used to control the height waviness of the disk surface. The results show up to 60 % friction reduction for high waviness surface. The findings of this study suggest a potential that the reduction in friction for high waviness surfaces could be exploited to enhance the performance of engineering systems.

Laser Surface Texturing: Characteristics and Applications

Abstract Laser surface texturing (LST) has emerged as a versatile and efficient technique for modifying surface properties across various materials. This paper provides an analysis of the characteristics and diverse applications of laser surface texturing. The paper begins by explaining the fundamental principles underlying LST, highlighting the mechanisms involved in material interaction and the resultant surface modifications. It explores the influence of laser parameters such as pulse duration, energy density, and wavelength on the texturing process, emphasizes their impact on surface morphology, roughness, and topographical features. Furthermore, this paper delves into the wideranging applications of LST across different industries and fields. It examines how LST enhances surface functionalities, including improvements in tribological properties, wettability, friction reduction, and biocompatibility. Additionally, the utilization of LST for creating microstructures enabling advanced functionalities in optics, electronics, biomedical devices, and energy harvesting systems is discussed. Moreover, the challenges and future directions in LST technology are highlighted, which encompass advances in precision, scalability, and integration of LST with other manufacturing processes. The potential environmental implications and economic feasibility of LST are also discussed. In summary, this paper examines the characteristics, applications, challenges, and future prospects of laser surface texturing, showcasing its significance as a promising technology for tailoring surface properties across diverse materials and industries.

Sliding behaviors of the trapezoidal roof rock block under a lateral dynamic disturbance

The surrounding rock of underground space is always affected by external dynamic disturbance from the side position, such as blasting vibration from a stope at the same level or seismic waves from adjacent strata. A series of laboratory tests, numerical simulations and theoretical analyses were carried out in this study to disclose the sliding mechanism of roof rock blocks under lateral disturbance. Firstly, the experiments on trapezoidal key block under various clamping loads and disturbance were conducted, followed by numerical simulations using the fast Lagrangian analysis of continua (FLAC3D). Then, based on the conventional wave propagation model and the classical shear-slip constitutive model, a theoretical model was proposed to capture the relative displacement between blocks and the sliding displacement of the key block. The results indicate that the sliding displacement of the key block increased linearly with the disturbance energy and decreased exponentially with the clamping load when the key block was disturbed to slide (without instability). Meanwhile, when the key block was disturbed to fall, two types of instability process may appear as immediate type or delayed type. In addition, the propagation of stress waves in the block system exhibited obvious low-velocity and low-frequency characteristics, resulting in the friction reduction effect appearing at the contact interface, which is the essential reason for the sliding of rock blocks. The results can be applied to practical underground engineering and provide valuable guidance for the early detection and prevention of rock-falling disasters.