Gear Friction Research Articles

Predictive Model for Scuffing Temperature Field Rise of Spiral Bevel Gears under Different Machining Conditions

Spiral bevel gears are extensively employed in mechanical transmissions; however, they are prone to adhesive wear when operating under high-speed and heavy-load conditions. Research indicates that the tooth surface roughness of gears significantly influences the friction and wear of the meshing gears. The present study delves into the origins of tooth surface roughness through the integration of the W-M function and fractal theory. Utilizing an involute helical gear with surface roughness for tooth cutting, a three-dimensional model is established with roughened tooth surfaces. This paper introduces an approach to developing three-dimensional gear models with roughness and applies the finite element method to perform thermodynamic analysis on gears exhibiting diverse levels of surface roughness. The thermal analysis of gears with varying degrees of roughness was conducted using the finite element method. Comparative analysis of the results under specific operating conditions elucidated the impact of roughness on tooth surface temperature rise. In order to validate the simulation model, an experimental test platform for spiral bevel gears of identical size was established. This model integrates tooth surface roughness with thermodynamic analysis, allowing for the rapid assessment of tooth surface temperature rise under different machining conditions, and reducing the cost of validating predicted tooth surface load-carrying capacity.

The friction behavior and wear mechanism of RV reducer gear steel (20CrMo) subjected to three different heat treatment processes from −20 °C to 100 °C

The gear friction pairs in RV reducer always withstand a broad range of temperature, sliding velocity and heavy load. In the research, three types of heat treatment methods (carburizing + quenching, nitrocarburizing and high concentration nitrocarburizing) are applied on the 20CrMo (cycloidal gear material) disc to study the tribological behavior and wear mechanism. The friction coefficient, wear depth and wear rate of the three types of friction pairs under various temperature (−20 °C, 25 °C, 50 °C, 100 °C) are measured and the microstructure characteristics are analyzed by SEM and EDS. The results reveal that high temperature can dramatically decrease the wear scar dimensions and wear rate due to the more active lubricant. Although the lubricant lost its activity at −20 °C, the friction coefficient and maximum wear depth for GCr15/20CrMo (carburizing + quenching) and GCr15/20CrMo (high concentration nitrocarburizing) are relatively less than 0.1 and 4 μm. The wear rate of GCr15/20CrMo (carburizing + quenching) and GCr15/20CrMo (high concentration nitrocarburizing) are 14.49 μm3/N·m and 17.20 μm3/N·m, which are only 28.7% and 34.1% of GCr15/20CrMo (nitrocarburizing). With the temperature increases to 25 °C, tribofilm is more likely to form on the 20CrMo specimen after nitrocarburizing, leading to better wear resistance. At high temperature (50 °C and 100 °C), GCr15/20CrMo (high concentration nitrocarburizing) system presents excellent tribological behavior by the combination of good lubricant activity, formation of tribofilm and refined nitrides. The wear rate even reaches 0.45 μm3/N·m and 0.43 μm3/N·m at the sliding velocity of 300 mm/s and 562 mm/s under 100 °C. Overall, specimen with high concentration nitrocarburizing process exhibits exceptional wear performance under full operating conditions of RV reducer.

Failure analysis and structural improvement of helicopter landing gear seals based on experiments and three-dimensional numerical simulation

The utilization of O-ring seal structures in landing gears has historically been associated with high rates of failure. Therefore, this study analyzes helicopter landing gear friction failures based on experimental and numerical simulations. The model is designed to replicate the failure phenomena including “seal extrusion”, “seal leakage”, “seal wear”, and “seal distortion”, and to further investigate causes of failure. Corresponding failure criteria are also presented. Addressing the deficiencies inherent in the original O-ring structure, three composite seal structures—namely, the VL seal, double triangle seal, and T-seal—are introduced to enhance the respective seal structure of the buffer pillar. The findings exhibit that, following the transition to the composite seal structure, the strain peaks are optimized. Finally, this paper offers optimal contact pressure ranges for the optimized seals.

Diagnosis-based design of electric power steering system considering multiple degradations: role of designable generative adversarial network anomaly detection

Abstract Recently, interest in functional safety has surged because vehicle technology increasingly relies on electronics and automation. Failure of certain system components can endanger driver safety and is costly to address. The detection of abnormal data is crucial for enhancing the reliability, safety, and efficiency. This study introduces a novel anomaly-detection method of designable generative adversarial network anomaly detection (DGANomaly). DGANomaly combines the data augmentation method of a designable generative adversarial network (DGAN) with a generative adversarial network anomaly-detection data classification technique. DGANomaly not only generates virtual data that are challenging to obtain or simulate but also produces a range of statistical design variables for normal and abnormal data. This approach enables the specific identification of normal and abnormal design variables. To demonstrate its effectiveness, the DGANomaly method was applied to an electric power steering (EPS) model when multiple degradations of gear stiffness, gear friction, and rack displacement were considered. An EPS model was constructed and validated using simulation programs such as Prescan, Amesim, and Simulink. Consequently, DGANomaly exhibited a higher classification accuracy than the other methods, allowing for more accurate detection of abnormal data. Additionally, a clearer range of statistical designs can be obtained for normal data. These results indicate that the statistical design variables that are less likely to fail can be obtained using minimal data.

Metal 3D-Printed Bioinspired Lattice Elevator Braking Pads for Enhanced Dynamic Friction Performance.

The elevator industry is constantly expanding creating an increased demand for the integration of high technological tools to increase elevator efficiency and safety. Towards this direction, Additive Manufacturing (AM), and especially metal AM, is one of the technologies that could offer numerous competitive advantages in the production of industrial parts, such as integration of complex geometry, high manufacturability of high-strength metal alloys, etc. In this context, the present study has 3D designed, 3D printing manufactured, and evaluated novel bioinspired structures for elevator safety gear friction pads with the aim of enhancing their dynamic friction performance and eliminating the undesired behavior properties observed in conventional pads. Four different friction pads with embedded bioinspired surface lattice structures were formed on the template of the friction surface of the conventional pads and 3D printed by the Selective Laser Melting (SLM) process utilizing tool steel H13 powder as feedstock material. Each safety gear friction pad underwent tribological tests to evaluate its dynamic coefficient of friction (CoF). The results indicated that pads with a high contact surface area, such as those with car-tire-like and extended honeycomb structures, exhibit high CoF of 0.549 and 0.459, respectively. Based on the acquired CoFs, Finite Element Models (FEM) were developed to access the performance of braking pads under realistic operation conditions, highlighting the lower stress concentration for the aforementioned designs. The 3D-printed safety gear friction pads were assembled in an existing emergency progressive safety gear system of KLEEMANN Group, providing sufficient functionality.

Data driven modeling of heavy-duty joint system for DEMO manipulators: An initial study from MPD joint simulation

This study investigates the subspace modeling method in developing surrogate model of a heavy-duty joint system in a muti-purpose deployer. The joint system is constructed in the Matlab SIMULINK Simscape environment, which includes the multibody dynamics with friction models, meshing loss models and viscous models. The input and output data generated in simulation are used to develop the subspace model. The result shows the subspace modeling method can accurately identify the system order and linear part of dynamics in this joint system. The nonlinearity contributed by the gear friction, meshing and viscosity can't be neglected in the surrogate model. Further model augmentation technics are needed to improve the capability of subspace modeling method applying in nonlinear system.

Fatigue life and transmission efficiency prediction of marine timing gears under 3D mixed lubrication state

The timing gears are the core transmission components of marine diesel engine, whose working conditions are complex and harsh, transient and coupled with the microscopic lubrication state, meshing in the mixed lubrication environment with lubrication-contact coexistence, local asperity contact brings stress concentration, further affects the fatigue life and friction loss. In this study, based on a three-dimensional (3D) line-contact mixed lubrication model, dynamic subsurface stress calculation, fatigue life prediction, and friction loss power study were carried out on timing gears, taking into account transient operating conditions and actual surface roughness. For the established simulation model, an equivalent simulation test of line-contact friction of timing gears was carried out, which can realize the measurement of friction coefficient under the condition of different slip-roll ratios, and make up for the deficiency that the traditional test equipment can only carry out the test under the fixed slip-roll ratio. Although the gear meshing process can only be simulated by the disc specimen due to the limitation of the specimen form, this limitation is similar to the simplified form of the simulation model, which can meet the needs of the verification test. The influence of structure and material on the lubrication state, fatigue life and friction power consumption are studied, which provide theoretical guidance for the tribological optimization design and reliability analysis for the marine timing gears.

Validation of Gear Friction Equation Using Directional Parameter

Abstract In our previous study, the Matsumoto equation was modified by introducing the directivity of machining marks on the tooth surfaces (directional parameter), and it was adapted to estimate the gear friction coefficient with various finishing processes. However, this new estimation equation has been applied only to gear pairs with the same finishing process and under manual transmission fluid (MTF) lubricated conditions. Thus, this study extends its application to a gear pair with different finishing processes and the case under automatic transmission fluid (ATF) lubricated conditions. Herein, efficiency tests were performed using gears with four different finishing processes (grinding, barreling, honing, and small-angle honing), and friction values obtained experimentally were compared with the values estimated from the unmodified and modified Matsumoto equations. Consequently, the correlations between the experimental and estimated friction values were significantly improved.

ALTERNATE SLIDING FRICTION FORMULATIONS OF ELASTO - HYDRODYNAMIC OF SPUR GEARS

In this paper, several sliding friction formulations used in spur gear dynamics are examined and compared in terms of the predictions of interfacial friction forces and off-line-of-action. Computing friction formulations include Coulomb models with time-varying friction coefficients and empirical expressions based on elasto - hydrodynamic and/or boundary lubrication regime principles. Predicted results compare well with friction force measurements and appeared completely conformed with specific objectives of this paper are established as follows: (1) propose an improved MDOF spur gear pair model with time-varying coefficient of' friction, µ(t), given realistic mesh stiffness profiles.(2) comparatively evaluate alternate sliding friction models and predict the interfacial friction forces and motions in the off-line-of-action (OLOA) direction: and (3) validate one particular model (III) by comparing predictions to the benchmark gear friction force measurements

Utilizing design of experiments techniques to determine the optimal coefficient of friction in spur gears

The friction occurring between the teeth of gears is a significant contributor to energy loss in gear drives. Factors like the load, speed, and coefficient of friction (µ) play a crucial role in determining the extent of frictional losses in gears. The coefficient of friction (µ) is a complex function influenced by various tribological parameters, including rolling, and sliding velocities, normal load at the tooth contact zone, oil temperature, and contact surface roughness. To analyze the impact of design and operating parameters on the coefficient of friction, a comprehensive statistical parametric approach was employed, combining numerical and statistical methods. The study employed a design of experiments methodology to numerically examine the impact of various tribological factors on the coefficient of friction. This methodology facilitated the identification of primary effects and crucial factors that have a significant impact on the variable µ. The findings derived from the computational models were subsequently compared with the discoveries of pre-existing investigations that includes both experimental and theoretical approaches. The proposed method represents a powerful tool for understanding the relationship and correlation between major tribological factors and the coefficient of friction. By employing this approach, it becomes possible to identify optimized tribological parameters. This information is valuable in improving the design and operation of gear systems, with the aim of reducing energy loss due to friction and enhancing overall efficiency.

Control of a worm-wheel gear driven rescue robot with friction compensation and its experimental verification

This paper presents the control of a rescue robot driven by the worm-wheel gear transmission. In the modeling process, the load-dependent friction of the worm-wheel gear is considered, and the governing equations for static and dynamic analyses are formulated. Especially we examine the dependency of break-in joint torques on the loading torque and directionality of motion. The friction parameters of the worm-wheel gear of a physical rescue robot are identified through experimental investigation. A friction compensation controller is then designed based on the modeling results and experimental operating conditions. And the designed controller is applied to a dual-arm rescue robot to validate its effectiveness.

Influence of single phase NiS nanoparticles as lubricant additive in microscale deformation of copper gear

ABSTRACT Demand for miniature gears is increasing daily due to huge development in MEMS and microdevices. As a result of this drive towards miniaturisation, microsystem technologies are becoming increasingly important. In this concern, researchers are interested in developing a micro forming process to manufacture highly accurate micro gears, improved operational and functional characteristics, capacity to perform in hazardous environmental conditions, and longer service life. Single-phase NiS nanospheres were developed using a high-temperature wet chemical method and were dispersed in engine oil (SAE 20 W-40) for further forming process. During plastic deformation (micro-scale), the combined grain size effects and NiS nanoparticle added lubricant on formability and interfacial friction of the micro gear are investigated. The grain size effect significantly impacts the micro gear’s formability during micro forming. The grain size and orientation significantly influence the microscale deformation process. Due to the size effect, the microhardness value at the centre and the tooth varies considerably. Due to the existence of NiS nano additive lubricant, the surface quality of micro gear improved significantly. The findings of this work help to comprehend the properties of nano additive lubricant and how it behaves tribologically throughout the micro-forming process.

Design of an adjustable constant-force mechanism using a geared Sarrus linkage and spring

This paper presents the design of a novel adjustable constant-force mechanism (CFM) using a geared Sarrus linkage and a linear spring. The uniqueness of this design is that it provides a constant force over a wide range of displacement and the constant-force level can be adjusted energy-freely by varying the spring position without a preload. In this work, the construction, geometric constraints, and constant-force design of the CFM are expressed. The desired parameters of the mechanism, with consideration of gear friction, are also determined. A numerical example is then given to illustrate the constant-force performance and the effect of gear friction. This paper also shows a prototype of a CFM and experimental studies on it. It was found that the CFM delivered a constant force of up to 20 N within a stroke of 140 mm, and the force error was less than 6%. Moreover, the CFM compensated for masses of 1 and 2 kg with a torque reduction of more than 90%.

Influence of Nonlinear Characteristics of Planetary Flywheel Inerter Actuator on Vehicle Active Suspension Performance

The planetary flywheel can significantly reduce the weight of the flywheel, allowing the inerter to be lightweight. When a planetary flywheel ball screw inerter-based active actuator is used in a vehicle suspension system, the nonlinear features of the actuator affect vehicle performance. The planetary flywheel inerter actuator’s nonlinear dynamic model is constructed in this study based on the dynamic features of the planetary flywheel ball screw inerter and the electromagnetic torque generating mechanism of the permanent magnet synchronous motor. The impact of ball screw–nut friction, transmission clearance, planetary gear friction, and gear backlash on the performance of an active tuned inerter damper suspension is then investigated. As a result, the impact and sensitivity of numerous nonlinear parameters on suspension performance are shown, providing a theoretical foundation for the design of planetary flywheel inerter actuator and active inerter suspension.

Kalorimetrische Messung der Ver- zahnungsverlustleistung im Bereich hoher Umfangsgeschwindigkeiten

Gear damage, e.g. scuffing, reacts sensitively to the local dissipation of frictional heat during a full gear mesh. Several empirical friction models have been established in relevant literature. These can be used to calculate the gear friction locally or averaged over a mesh. For calibration purpose, experimental data from twin disc machines with stationary contact conditions are mostly used. However, the assignment of the model as well as the consideration of topographical, rheological and geometrical effects is often subject to uncertainties. In this paper, a method is presented to measure the power losses of high-speed spur gears up to vt = 100 m/s. The measurement principle uses the calorimetric properties of the circulating lubricant. The implementation of the measurement setup in a highspeed gear test rig reduces thermal interferences from sealings and bearings. Analysis regarding the measurement quality show that the measurement method delivers reproducible results with a high measurement resolution over a wide range of operating conditions.

Study on gear meshing power loss calculation considering the coupling effect of friction and dynamic characteristics

Gear transmission system is widely used in many mechanical equipment to achieve power transmission and rotational speed changes. Meshing power loss is one key index to assess the performance of a gear system, which directly influences heat generation and lubrication, etc. Over the past decades, many computational models of gear meshing power loss have been proposed to support gear design and optimization. However, the coupling effect between the gear friction and dynamic characteristics are usually ignored, including time-varying meshing stiffness (TVMS) and dynamic meshing force (DMF), which are not conducive to accurate calculation and improvement of meshing power loss. Therefore, an improved gear meshing power loss calculation method is proposed to settle this problem in this paper. With the proposed method, the friction calculation model is established considering the effect of DMF and surface roughness based on mixed elastohydrodynamic lubrication (EHL). Then the TVMS is obtained with the friction force along the meshing line and DMF was taken into consideration. On the basis of modelling of friction and TVMS, a six degrees-of-freedom (DOF) gear dynamic model, as well as a power loss iteration calculation process are established and studied. The effects of gear surface manufacturing quality and loads on power loss are analyzed. Furthermore, a gear meshing power loss experimental setup is constructed to verify the effectiveness of the proposed method. The results show that this method is in better agreement with the experimental results than the traditional method which does not consider the coupling effects.

Modeling and control analysis of electric driving system considering gear friction based on dual-inertia system

In the electric driving system, the measurement of the motor speed error becomes more and more important, which has an impact on the system vibration suppression. In this paper, based on the single-neuron adaptive PID control method, the dual-inertia system considering gear friction torque is modeled and studied. Firstly, the dual-inertia system with gear friction is established, and dynamic differential equations of it are derived; Then, the comprehensive meshing stiffness and the time-varying friction torque of the gear system are deduced; Next, the Ziegler-Nichlos frequency domain response method is adopted to obtain the parameters of the PID controller. The control methods including the PID, Fuzzy-PID with DOB and single-neuron adaptive PID are utilized to adjust the motor speed of the system; Finally, the effects of gear friction, the moment of inertia of load and control methods on motor speed and system error are analyzed.

Overview of EHL Helical Gear Friction Based on Point Contact

Helical gears have the advantages of smooth transmission,large bearing capacity and small axial force,and are widely used in reducers of aviation gas turbines,large crane structures and core drive components of marine power system.This paper summarizes the development of elastohydrodynamic lubrication theory at home and abroad,elaborates the application and calculation method of elastohydrodynamic lubrication theory in gear transmission system,discusses the research status of Point Contact Elastohydrodynamic Lubrication of helical gears,and points out the research focus and development direction in the future.

Analysis of Engine and Powertrain Losses of a Passenger Type 4-Stroke Gasoline Vehicle in 4 Different Driving Cycles with GT-Suite Vehicle Simulation Program

Vehicle simulations have a very important place in the automotive R&D process. These simulations provide automotive companies with the benefits of saving money on model creation and the user changing many parameters throughout the vehicles as soon as possible. In this study, the engine and powertrain energy losses of a 4-stroke gasoline passenger car were investigated in FTP75 (Federal Test Procedure), HFET (Highway Fuel Economy Test), US06 and WLTP (Worldwide Harmonized Light Vehicles Test Cycles) cycles, in urban and extra-urban conditions. examined physically and by testing with the help of GT-Suite vehicle simulation program. Ac-cording to the analysis results, the lowest CO2 emission (127.58 g/km) and average fuel consumption (5.29 l/100km) were obtained in the HFET driving cycle. While the transmission and gear friction values were close to each other between the driving cy-cles, the lowest loss in terms of torque converter losses was obtained in the HFET driving cycle (0.2%).

A two-dimensional buffer valve for heavy-duty vehicles: Design, dynamic modeling, and experimental verification

Focusing on the problems of weak anti-pollution capability and large lateral sliding friction of gears in traditional vehicle cushion valves, this study combined two-dimensional (2D) technology and the concept of pressure torsion transmission and proposed a 2D buffer valve with a fast response, high precision, and strong anti-pollution capability. The structure and working principle of the 2D buffer valve were introduced, and a dynamic model was developed for the 2D buffer valve. The model was jointly solved by Simulink and AMESim, and simulation analyses and experimental research were performed. The research results show that the step response time of the 2D pressure torque transmission buffer valve was approximately 0.024 s, and the maximum overshoot was approximately 7.4%. During the shift buffering process, the maximum deviation was 0.077 MPa, and the steady-state error was 0.018 MPa. The buffer valve proposed in this paper could achieve good control of the clutch oil pressure of the vehicle transmission, thereby improving the buffering performance and shifting quality in heavy-duty vehicles.