Dry Clutches Research Articles

Advancing automobile dry clutch fault diagnosis through innovative imaging techniques and Vision transformer integration

The study investigates the significance of clutch condition monitoring in automotive transmissions to preempt mechanical failures, enhance efficiency, and mitigate risks to human safety and maintenance costs. It explores the integration of Vision Transformer (ViT) with imaging techniques, such as scalograms, spectrograms, polar plots, radar plots, and Hilbert-Huang transforms, to diagnose faults in dry friction clutches. By transforming vibration signals into image representations and utilizing ViT for fault classification, the study aims to identify the most effective imaging technique and optimal hyperparameters for accurate fault diagnosis. Experimental studies on a test rig with varying fault conditions demonstrate the effectiveness of ViT in diagnosing clutch faults when coupled with different image conversion techniques. The results highlight the potential of integrating spectrogram image processing with ViT, achieving a 100% accuracy in fault diagnosis for clutch systems, thus advancing the analysis of faults in clutch systems.

Finite element analysis of the thermal and thermo-mechanical coupling problems in the dry friction clutches using functionally graded material

Abstract The friction clutch is an important machine part in the torque transmission system, where it is responsible for gently transmitting the power from the engine to the gearbox and damping the tensional vibration. At the beginning of the engagement between the clutch’s elements, a large amount of heat is released due to frictional sliding between the elements of the clutch system, generating very high temperatures. In this work, the two- and three-dimensional finite element models were developed from scratch to explore the clutch disk’s temperature and contact pressure behaviors using an alternative frictional material such as functionally graded material (FGM). The two assumptions for the thermal loads were considered: uniform wear and uniform pressure assumptions. The thermal–structural problem for the new frictional material was solved numerically and then presented as the temperature distributions and the contact pressure at any instant of sliding time. Also, a comparison was made between the clutch system behaviors when using FGM with different frictional materials. The results showed that the FGM has superior results to the other available frictional materials.

A Study on Power Transmission Control for Applying MR Fluid Multi-Plate Clutch to Automobile Power Distribution Device

The aim of this study is to design and manufacture a multi-plate clutch system that uses magnetorheological (MR) fluid control to allow for a variable power transmission ratio in power distribution systems. MR fluid is a smart material that enables presenting a solution to the shocks and power loss that occur due to mechanical problems in power distribution systems. As such, the longitudinal and lateral dynamic properties of 4WD (four-wheel drive) vehicles were examined and analyzed to develop an algorithm to control the front/rear power distribution according to the road surface state and driving conditions. To verify the algorithm, the CarSim vehicle dynamics simulation program was adopted to perform experiments to understand the vehicle’s dynamic performance improvements and turning stability via a HILS (Hardware in the Loop) system. In this study, an MR fluid, multi-plate clutch was used that combines a dry clutch and a wet clutch using the characteristics of the MR fluid. Such a clutch was designed to enable continuous and smooth torque transmission by utilizing the strengths of each of the dry and wet clutches. The CarSim vehicle dynamics program was used to conduct the experiments, which were conducted by linking to the manufactured MR fluid clutch experimental device. The experiments investigated the dynamic performance based on the power distribution ratio by performing longitudinal flat, inclined driving and lateral DLC (double lane change) driving. In summary, this study found that it is possible to perform power transmission by applying a current to an MR fluid and forming a magnetic field to change the flow properties of the fluid to control the torque transmission ratio that occurs in an MR fluid clutch.

Ultrafine particle emissions from dry clutches: number concentration, size distribution and chemical composition

Clutches in automobiles are shown to produce ultrafine particles, consisting of several metallic elements, which become airborne.

Airborne Wear Particles from Dry Clutches

A significant part of non-exhaust particle emissions in cities comes from the wear of vehicle components. Several studies on airborne particles from the wear of disc brakes and tires have been completed. However, few publications can be found in the scientific literature regarding airborne emissions from dry clutches used in road vehicles. With this in mind, this preliminary study designs a clutch tribometer for the generation of airborne wear particles in a controlled environment. The number concentration and the size distribution of airborne wear particles generated from a typical dry clutch used in passenger cars are investigated. The tests are run at a constant rotational speed, and normal load. The results show that the particle number concentration from dry clutches exhibits a running-in period and a steady state, similar to the particle emissions from disc brake contact. A significant number of nanoparticles (aerodynamic diameter < 100 nm) are emitted from the dry clutch contact.

Thermal behavior of friction discs in dry clutches based on a non-uniform pressure model

To investigate the thermal behavior of friction discs in dry clutches during long-term slipping, a two-dimensional transient thermal model was established using the finite element method. Because the pressure distribution on the friction interface is important, a dimensionless non-uniform pressure model was proposed based on measured data using Fuji Prescale pressure-sensitive films arranged on the friction disc. Subsequently, the frictional heat flux, which varied nonlinearly with the radius, was determined. The heat conduction processes of the friction pairs were analyzed in detail. The results of the temperature distribution calculated using the non-uniform pressure model agree well with those obtained from dynamometer experiments. The results reveal that high temperatures exist near the high-pressure region on the friction interface. Compared to the results of two conventional models, those of the non-uniform pressure model are closer to the experimental data. The maximum temperature error is reduced by 23.23% and 34.03% relative to the uniform pressure and uniform wear models, respectively, after a 15 s slipping period. Therefore, by using the non-uniform pressure model, the thermal analysis can be more effective in avoiding excessive wear and prolonging the service life of dry clutches.

Breeding Behaviour of Black-Winged Stilt, Himantopus himantopus (Linnaeus, 1758) in Agricultural Landscape of Punjab, India

During the breeding seasons (2017-2019), the hitherto little known aspects of breeding behavior of Black-winged Stilt, Himantopus himantopus were studied in the ploughed agricultural fields, village ponds and adjacent shallow pools located in rural outskirts in district Ludhiana, Punjab, India. Observations on nest structure, egg laying, incubation, hatching and other behavioural aspects of the parents/chicks were inferred from videorecords, photographs and direct field observations made on 19 clutches containing 59 eggs. In the study area the breeding season extended from April to July. The mean clutch size was 3.29±0.77 (range 1-4, n=19) that differed between the dry ploughed field clutches (3.4±0.70, range: 2-4, n=10) and wet pool/pond sites (2.78±1.09, range: 1-4, n=9). In the dry ploughed fields, the nest scrapes were lined mainly with the wheat rootlets/ straw pieces only. However, the nest material used in/around ponds and pools included predominantly dry twigs, decaying leaves and some thermocol chips. The egg length, breadth, weight, egg shape index and volume (n=54) measured 42.22±2.50 mm, 30.71±1.13 mm, 19.77±2.34 gm, 72.88±3.19 and 20.39±2.36 cm3, respectively. The eggs hatched mostly synchronously after biparental incubation period of 25 or 26 days (n=4). As per traditional method, only 20.34% (12 out of 59 eggs) of the eggs hatched successfully and the hatching success calculated as per the Mayfield Method showed that it was only 2.07% in post-harvest field sites and 36.26% in non-agricultural sites (shallow water pools and edge waters of village ponds). The use of polluted sites as nesting grounds has been opined as a habitat shift and an adaptation in process

Modeling and Experimental Study for Automotive Dry Clutch Sliding Noise

Automotive dry clutches have been found to produce a low frequency sliding noise in many applications, which challenges the ride comfort of vehicles. In order to study this clutch sliding noise, a detailed finite element model including both a pressure plate assembly and a driven plate assembly was developed. Based on this model, a complex eigenvalue analysis is performed in this research. The effect of several major factors on the clutch sliding noise, such as the coefficient of friction, the clamping force, the geometric imperfection of the friction plate, and the thermal deformation of the pressure plate, were investigated numerically. A vehicle road test with clutch sliding noise was conducted for several different conditions. The leading frequencies of the clutch sliding noise in the testing were obtained and compared with the frequencies predicted by the numerical model. The simulation results show the same tendency as the road test. It is found that the clutch sliding noise can be reduced by decreasing the coefficient of friction. With the presence of the surface bumping of the friction plate, the propensity of the clutch sliding noise greatly increases and the corresponding squeal frequencies fall into the range lower than 1 kHz. With the consideration of the thermally introduced deformation of the clutch pressure plate, the possibility of clutch sliding noise is significantly reduced. It is concluded that the model with the incorporation of the thermal deformation of the pressure plate is more effective for the frequency prediction of clutch sliding noise.

Analysis of the parameters of the double clutch drive with reduced control energy consumption

The global trend of improving vehicle and traction transmissions is associated with the use of robotic preselector gearboxes, an important component of which is the friction clutch. The review of existing designs and analysis of clutch development concepts allows determining the directions of their improvement, in particular, the improvement of dry double clutches, which is the subject of research in this paper. A significant disadvantage of existing dual-clutch designs is the use of additional special (mostly hydraulic or combined) systems for on-off friction pairs, so the structural cost and energy costs for control are increased, and the design, maintenance, and repair are complicated. The proposed design of the drive to control the original dry dual-clutch involves a lever mechanism with the use of rotary stops, which are made in the form of mobile carriages with rollers, this provides switching clutches in a short time and actually without interruption of power flow, so the acceleration dynamics of vehicles will be improved, the clutch design will be simplified and energy consumption for its control during the start and gear shifting will be reduced. The mathematical model of the proposed clutch drive on the basis of which the control mechanism operation is simulated and influence of its design parameters on operational indicators of the clutch drive, in particular, on kinematic characteristics of the drive, ranges of kinematic and power gear ratios, the power interaction of the mechanism links, the power of the actuator when each clutch is turning on. It is established that the switching of clutches requires less energy, the movement of the mechanism elements is different, and the compression force of the friction pairs when starting the first and second clutches is different. The simulation results confirm that the proposed original lever design of the clutch control mechanism is effective. The obtained results allow us to reasonably determine the parameters of a clutch, but the choice of optimal-rational parameters of its control mechanism requires further research, for which appropriate methods, search algorithms, and their software implementation have been developed.

Three-Dimensional Finite Element Analysis of Contact Problem in Dry Friction Clutches

We present an investigation through numerical analysis (FEM) of the solution of the contact problem in friction clutch systems during engagement manoeuver. The case of high contact pressure between the sliding elements of a clutch system (flywheel, friction clutch and pressure plate) has been also considered. A finite element model of a dry friction clutch system (single disc) to estimate the distributions of the contact pressure between the contact elements of the clutch system under different working conditions has been developed and the main findings are discussed. Furthermore, the effect of modules of elasticity (contact stiffness) on the distribution of contact pressure of the mating surfaces was investigated. Also, the results encompass the deformations of the contacting surfaces for different cases. This work could provide a fundamental intermediate step to obtain a partial solution to the thermos-elastic problem in order to compute the thermal-driven deformations and stresses in the automotive clutches and brakes under different working conditions.

Algorithm for adapting the clutch of robotic transmissions of commercial vehicles in the light commercial vehicles and light-duty trucks class

In the modern world, the main efforts of developers of commercial vehicles are aimed at increasing the economic efficiency of using cars, reducing the negative impact on the environment and increasing the level of safety, both passive and active. The use of automatic transmissions allows the engine to work in the most optimal modes, and the driver to concentrate on monitoring the traffic situation and not be distracted by gear shifting. In commercial vehicles, robotic mechanical transmissions have become widespread. In such a transmission, the clutch and gear selection are controlled by actuators controlled by an electronic unit. Dry clutches are common in commercial vehicle transmissions. For adequate control of the clutch, it is necessary to have its high-quality model, which takes into account the coefficient of friction, touch point, the effect of temperature and many other factors. Therefore, the actual problem in the control of such transmissions is to determine the touch point of the clutch, which can serve as the main source of uncertainty in the clutch model along with the coefficient of friction. This article proposes an adaptation method for assessing the clutch touch point in real time. This approach has been applied to dry clutch control in transmissions of LCV and LDT vehicles, and the results are experimentally validated on robotic transmissions in production vehicles.

Thermal and thermoelastic problems in dry friction clutch: A comprehensive review

AbstractThe friction clutch is considered a very important element of machines, as it plays a major role in transferring power from the driving part to the driven part. A common application of the friction clutch is in vehicles to connect between the gearbox and the engine. Fast wear occurs as a result of frictional heating that is generated when the clutch is starting to engage. This wear, in addition to the high thermal stresses, will lead to premature failure in the contacting surfaces. The present review highlights the most important studies of the thermal and thermoelastic problems of friction clutches during the last 10 years to show the challenges that were overcome and also the other challenges that needed to find solutions. The present paper will discuss in detail the influence of the frictional heat generated between contact surfaces during slipping and the main factors affecting the thermal behavior of dry friction clutches, such as sliding speed, friction materials, applied pressure, and so on. Furthermore, significant conclusions and remarks based on the available solutions to the thermal problem of the clutch are presented.

Judder Suppression of Friction Transmission Device with <i>H</i><sub>∞</sub> Control

Judder is well known as a vibration that occurs in a dry clutch. In order to maintain the ride quality and quietness of dry clutches, research on judder analysis and mechanical design to suppress judder is actively pursued. This paper describes the design and implementation of robust control techniques as an approach to suppressing judder during gear shifting in traction-controlled transmissions. This paper is concerned with transmissions that exhibit strongly nonlinear frictional characteristics that can only be approximated by higher order polynomials. Specifically, the coefficient of friction varies significantly nonlinearly with the rotational speed during gear shifting. In this paper, the controller is designed by expressing this nonlinear property as the uncertainty of the frequency. Simulation and bench test results are presented to validate the validity of such an approach. The results show that judder-free shifting is possible with the proposed approach. Furthermore, the requirements of three controllers are presented by analyzing the robust controllers.

The Effect of Applied Pressure Function on Thermo-elastic Problem in the Dry Friction Clutches

The main purpose of this paper is to investigate deeply the effect the contact pressure function on the thermo-mechanical behavior of the friction clutch system during the slipping time (heating stage). The other purpose is to explore theoretically the complex interaction among the contact pressure, sliding speed and frictional characteristics of frictional facings to specify the magnitude and distribution of the frictional heating generation on the contact surfaces of the dry friction clutch under different applied pressure. It was developed a numerical code based on finite element method (ANSYS/APDL 2019) to determine accurately the contact pressure, temperature and frictional heat generated on contact surfaces of the friction clutch disc that has two effective frictional faces at any instant during the slipping period. It was found a significant effect of the magnitude and variation of applied pressure during the heating phase on the surface temperatures, contact pressure and frictional heat generated. Where, the hot spot can be appeared when the applied pressure is constant. Under such circumstances, high amount of temperature and contact pressure focused on a small zone of the nominal contact area. This phenomenon is considered one of the main reasons for the early failure of the contacting surfaces of friction clutch.

Numerical analysis of thermal problem in dry friction clutches based on the interactive design approach

During the engagement, the thermo-elastic behavior of the friction clutches over specific sliding periods was taken into consideration as an essential factor to obtain a successful design based on interactive approach for automotive engineers that voided premature failure. It is worth mentioning that the finite element technique was adopted in the current study to investigate and analyze the angular sliding speed influence on the generated heat due to friction among the elements of friction clutch at the initial period of engagement. The distributions of the heat generated during the complete sliding periods were achieved via coupling between the thermal and the elastic models analyses to obtain the solution that required by automotive designers. Results in the form of the distributions of generated heat due to friction, temperatures of surface, and contact pressure are presented for different values of sliding speed. Obviously, the results showed that the frictional heat generated was increased dramatically when the sliding speed increased too. Also, it was proved that the proposed interactive design approach succeeded to detect the status of the friction clutch system if it’s stable or not.

Development of Empirical Asperity Contact Model for Wet Friction Material

<div class="section abstract"><div class="htmlview paragraph">A wet clutch couples or decouples gear elements to alter torque paths in an automatic transmission system. During the gear shifting event, the clutch torque is directly transmitted to the output shaft. Hence, clutch torque heavily influences the dynamics of the transmission. In order to evaluate the behavior of the transmission early and efficiently, the development process increasingly relies on high-fidelity transmission system simulations with added complexity. However, a wet clutch continues to be modeled using Coulomb’s friction in a typical shift simulation. Its linear framework does not physically represent non-linear hydrodynamic effects due to the presence of oil layer during clutch engagement. To make up the lack of physics, Coulomb’s clutch model often requires extensive tuning to match actual shift behaviors. Alternatively, a squeeze film based clutch model, coupled with an asperity contact model, can be employed to represent hydrodynamic behaviors and enable the broader use of dynamic simulation models in transmission development. However, while the squeeze film model has been extensively studied over the years, the asperity contact model remains largely unexamined. In this research, the contact behaviors of the asperities are empirically characterized for a wet clutch friction material. The results are compared against the base theory of Greenwood-Williamson asperity contact model (GW model) which is commonly accepted in wet clutch modeling. The analysis shows that the key assumptions of GW model, specifically the elastic deformation of spherical asperity tip and Gaussian distribution of their heights, do not hold for clutch friction materials. A new empirical asperity contact model is developed for wet friction material based on asperity roughness characterization and microscopic contact area measurements. The empirical model provides an accurate representation of asperity behaviors in wet clutch modeling, as an alternative to the conventional GW model, for high-fidelity transmission system simulations. The modeling framework is also applicable to a broad range of friction materials used in dry clutches, brakes and other applications that are characterized with hard constituents embedded in an elastic matrix.</div></div>

Adaptive torque tracking control during slip engagement of a dry clutch in vehicle powertrain

Dry clutches have been gaining its popularity for use in the transmission systems of small and medium-sized vehicles as well as the engine clutch systems of parallel hybrid vehicles. With this trend, the ability to appropriately control the amount of torque transferred through the dry clutch becomes important. This paper addresses a feedforward control method of clutch torque during slip engagement of a dry clutch utilizing a clutch friction model. In many studies, the clutch friction coefficient is considered as the only uncertain parameter in the clutch friction model. However, the clutch touch point can also serve as a major source of uncertainty in the clutch friction model. Thus, this paper proposes a simultaneous adaptation method to estimate the clutch friction coefficient and the clutch touch point in real time and a feedforward control method of clutch torque during slip engagement of a dry clutch based on the proposed adaptation algorithm. This control approach is applied to the slip engagement control of a dry engine clutch in a parallel hybrid vehicle and its effect is experimentally verified using a production vehicle.

Effects of Frictional Facing Thickness on the Heat Generated in Dry Friction Clutches

The accurate calculation of the frictional heat generated between the contacting surfaces of friction clutch elements during the slipping period due to the relative motion between the driving and driven parts is considered to be an essential factor for automotive designers. A numerical model of a single-disc clutch was built using the finite element method to investigate the effect of frictional facing thickness on the heat generation and distribution between the contacting surfaces of the flywheel, friction clutch disc and pressure plate. A sequentially coupled thermal-mechanical approach was used to simulate the thermal-elastic coupling that occurs in dry friction clutches during the slipping period. An axisymmetric finite element model was used to represent the single-disc clutch system at the start of the engagement. The results approved that frictional facing thickness has a significant effect on the distribution of the frictional heat generated and the actual contact area of friction clutches.

Thermal stress analysis of dry friction clutches

Purpose The purpose of this paper is to present an approach to compute accurately the distributions of the frictional heat generated, contact pressure and thermal stresses at any instant during the sliding period (heating phase) of the single-disc friction clutch system works in the dry condition and the complex interaction among them. Design/methodology/approach Numerical work was achieved using the developed elastic and thermal finite element models (axisymmetric models) to simulate the engagement of the single-disc friction clutch system. Findings The change of distribution of contact pressure during the sliding period (heating phase) affects significantly the magnitude and distribution of the produced thermal stress. The high local heat generated appeared in the contacting surfaces because of the non-uniformity of the distribution of contact pressure during the heating phase (sliding time) and this will dramatically increase the thermal stresses. Originality/value Sequentially coupled thermal-mechanical approach was developed to investigate the thermal stresses problem in automotive clutches under dry conditions. This approach is considered a promising approach to investigate the effect of material, sliding time, torque function, etc., on the thermal stresses of different types of friction clutch.

Stability Analysis of a Force-Aided Lever Actuation System for Dry Clutches with Negative Stiffness Element

A force-aided lever with a preload spring is not only force-saving but also energy-saving. Therefore, it has great potential to be applied to dry clutch actuations. However, the negative stiffness of the clutch diaphragm spring introduces unstable dynamics which becomes more intensive due to the preload spring. In order to explore the intensified unstability, this paper builds dynamic models for the rotating lever coupling a negative stiffness diaphragm spring and a preload spring. The stability analysis using the Routh-Huiwitz criterion shows that the open-loop system can never be stable due to the negative stiffness. Even if the diaphragm spring stiffness is positive, the system is still unstable when the preload of the spring exceeds an upper limit. A proportionalintegral- derivative (PID) closed-loop scheme addressing this problem is designed to stabilize the system. The stability analysis for the closed-loop system shows that stable region emerges in spite of the negative stiffness; the more the negative stiffness is, the less the allowed preload is. Further, the influences of the dimensions and PID parameters on the stability condition are investigated. Finally, the transient dynamic responses of the system subjected to disturbance are compared between the unstable open-loop and stabilized closed-loop systems.