Dry Friction Clutch Research Articles

Finite Element Simulation of Thermal Behavior of Dry Friction Clutch System during the Slipping Period

Finite Element Simulation of Thermal Behavior of Dry Friction Clutch System during the Slipping Period

Micromechanical model of dry friction hybrid polymer composite clutch facings

Modelling the complex coupled thermomechanical and tribological contact of a dry friction clutch system between cast iron flywheel and scatter-wound hybrid composite clutch facing requires a thought through investigation of the friction material properties and behaviour. Challenges of the creation of a mechanical stiffness matrix for such a complex material are described in this paper along with simplification ideas and solutions.

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.

Design, analysis, and experimental validation of a novel seamless automatic transmission for electric vehicle

The transmission system has an important influence on the dynamic performance, endurance mileage, and energy saving in an all-electric vehicle. This article proposes an innovative two-speed seamless dry-friction automatic transmission system to improve the dynamic performance and endurance mileage of an all-electric vehicle with the existing battery technology. The proposed system consists of two-stage epicyclical gear sets without outer ring gears, a dry-friction clutch, and a brake band, realizes a seamless shifting between any two speeds in an electric vehicle. Based on the working principle and dynamic modeling of the proposed seamless dry-friction automatic transmission system, the ratio optimization was carried out to improve the dynamic performance and the power consumption at the same time, and the combination of the weight ratio method and the multi-island genetic algorithm method was introduced to solve the optimization problem. It is shown both theoretically and experimentally that the proposed seamless dry-friction automatic transmission method demonstrates a better dynamic performance and shifting comfort when compared to the automated manual transmission with same transmission ratio.

Experimental investigation of the permeability of a tribo-contact in dry friction clutches

Abstract The effect of the first order phase transition from solid organic material to gas on fading in dry clutches has been discussed recently. In the present paper the permeability of the contact layer being one of the key parameters determining if the sufficient gas cushion can occur, is measured for friction linings commonly used in the automotive industry. It is shown that the permeability at 20 °C is too high. Chemical analysis shows that fluid compounds with high viscosity occur while heating the lining material alongside with gas. Further experiments indicate that the gas permeability of the contact decreases rapidly in presence of a viscous fluid. This result points out a promising direction for the further investigations of the fading phenomenon.

Influence of Dry Clutch and ICE Transmission Integration on the Thermal Load of a PM-Based Integrated Starter-Generator

Aiming to increase vehicle performance, the thermal influence of the vehicle integration on the thermal load on an integrated starter-generator (ISG) is discussed. In the investigated case, the vehicle integration concerns a dry clutch module and an internal combustion engine (ICE) attached. An experimentally validated numerical thermal model is developed as a tool for the analysis. This model includes the additional heat sources given by the ICE and the dry friction clutch. The influence on three temperatures considered most critical, those of the bearings, the permanent magnets, and the stator winding, is studied.

Design for reliability of automotive systems; case study of dry friction clutch

Design and production of highly reliable and safer automotive systems with longer life has been a challenge. The pressure is outcome of high competitive market and recent safety issues of reputable car manufacturers. In this paper, an integrated methodology is proposed based on design for reliability of automotive systems and considering its reliability/safety critical sub-systems. In the proposed approach, the FMEA results are used in the process of failure mode/mechanism identification. The basic failure data, mostly obtained from generic databases, are adjusted by multiplicative corrective factors to account for the design and environment impacts on system failure characteristics. The system is modeled by reliability block diagram method, simulated by Monte Carlo technique. The results of FMEA and reliability evaluation are used for system improvement by reducing the components’ failure rates and potential change of system configuration. The components’ reliability is improved by increasing the quality of components by utilization of high quality materials and modern manufacturing techniques. Modification of system configuration, e.g., adding redundancy, is an alternative for system reliability improvement in some cases. The results show that the friction lining component is the most critical elements in terms of reliability importance. After completion of this phase, an assessment is done for system reliability by comparing the system reliability targets. As a case study, dry friction clutch is studied for assessment of the proposed method. In this study, the life test requirement is researched for each component using a reliability testing techniques. Finally, the uncertainties are computed associated with the failure data and final reliability estimations and the results were presented with a confidence interval.

Dry Friction Clutch Disc of an Automobile under Transient Thermal Load: A Comparison of Friction Lining Materials

This paper shows the comparison of temperatures produced in a dry friction clutch disc with different materials during a single engagement to assist in clutch plate design and analysis. A study of usage of different materials for friction lining of clutch disc is required, which will provide improved performance and enhanced life. This investigation is modelled mathematically and solved numerically using finite element method. ANSYS ® 15.0 is a dedicated finite element package used for determining the temperature distribution across a clutch disc. In the present work, an investigation of a conventionally used harmful friction lining material asbestos is compared with carbon-carbon composite, S2-glass fibre and aluminium metal matrix composite. The transient thermal analysis of a clutch disc with different materials is performed and the temperature distribution on the clutch system is compared. Simulation results indicate that all the values of the temperature obtained from the analysis of aluminium metal matrix are less than those of asbestos based lining material, therefore clutch disc made up of aluminium metal matrix composite will assure the extended service life and the longer stability due to the fact that the temperature responsible for the wear and tear has been reduced. Furthermore, the slipping time is also considered in this investigation.

ENGAGEMENT SLIP CONTROLLER DEVELOPMENT BASED ON ACTUATOR DISPLACEMENT FOR AN ELECTRO-MECHANICAL FRICTION CLUTCH SYSTEM

This paper describes a controller development for an electro-mechanical friction clutch (EMFC) system for automotive applications and especially for vehicles that use continuously variable transmission. The work focuses on developing an EMFC engagement controller based on experimental work using a Proportional Derivative (PID) controller algorithm to engage the dry friction clutch. The EMFC is electromechanically actuated using a DC motor system, such that a smooth engagement process can be performed satisfactorily. To develop the controller, the dynamic behaviors of the EMFC system are investigated by performing tests on the EMFC bench-test. Results from this experiment show that the percentage of slip between the input and output shaft of the EMFC system depends on the input speed and output torque. Therefore, by applying slip control, engagement of the EMFC can be controlled and achieved for any input speed and torque during the standing start of a vehicle.

Identification of Characteristics For Wet and Dry Friction Clutches

Identification of Characteristics For Wet and Dry Friction Clutches

Engagement Model of Dry Friction Clutch with Diaphragm Spring

The duration of engagement of automotive clutch plays an important role in the driving comfort and smooth launching of the vehicle. It is a transient phenomenon controlled by many variables like dynamics of release bearing and linkage, relation between release bearing travel and pressure plate lift, the clamp load developed with respect to cushion deflection and inertia of driver and driven shafts. Modern automobiles employ diaphragm spring clutch, which is advantageous in terms of less overall height and weight, number of components, low release load and increased service life. The non-linear characteristics of the diaphragm spring can be exploited favorably in achieving smooth engagement process. In this paper a mathematical model of transient engagement dynamics is developed correlating the parameters like spring characteristics, clamp load characteristics, pressure plate lift and release bearing travel characteristics, clutch pedal kinematics during engagement, vehicle driveline dynamics during startup, etc. The engagement duration of the clutch can be simulated along with the clamp load build up and torque transmission to the driveline using this model. Results of simulation are also included here which were verified through actual tests. This analysis should be useful in design of release mechanism for achieving smooth clutch engagement and to compare various clutches on the duration of slippage.

Computation of surface temperatures and energy dissipation in dry friction clutches for varying torque with time

This paper describes an investigation of the energy dissipated and the surface temperature at any instant of dry friction clutch assuming torque being a function of time during the slipping. The equations of the thermal loads, total energy dissipated and relative velocity between contact surfaces are presented. Two-dimensional axisymmetric heat conduction problem of dry friction clutch is modeled mathematically and solved numerically using the finite element method to determine the temperature distribution during a single engagement assuming uniform wear between the contact surfaces. The comparison is made between temperature field assuming the torque varying with time and when it’s constant with time. Moreover, the effects of slipping time and dimensionless thickness of the pressure plate λ are to be investigated as well.

An Investigation Into the Thermal Behavior of the Grooved Dry Friction Clutch

The heat generated during the sliding period at the initiation of engagement in friction clutches is considered to be one of the main reasons for the failure of the friction material. One way to reduce the risk of this problem is to increase the rate of heat transfer by convection or, in other words, reduce the heat content of the friction material (internal energy) and thereby increase the lifecycle of the friction clutch. In this paper, the finite element technique has been used to study the effect of radial circumferential grooves on the temperature distribution and the amount of energy transferred by convection for a dry friction clutch disk during a single engagement, assuming a uniform distribution for the thermal load between the contact surfaces (i.e., uniform wear on clutch surfaces). Three-dimensional transient simulations are conducted to study the thermoelastic coupling of the problem. The effect of the groove area ratio (GR, defined as the groove area divided by the nominal contact area) is investigated. Furthermore, this paper presents the equations for energy considerations and energy balance at any time for the friction clutch system. The numerical results show that the amount of energy transferred by convection from the friction material can be controlled (within a limitation) by adjusting the value of the groove area ratio. Commercial ANSYS13 software has been used to perform the numerical computations in this paper.

Contact Analysis of a Dry Friction Clutch System

The numerical simulation of the friction clutch system (pressure plate, clutch disc, and flywheel) during the full engagement period (assuming no slipping between contact surfaces) is carried out using finite element method. Two types of load condition considered affect on the clutch elements during the full engagement period are the contact pressure of diaphragm spring and the centrifugal force. The study of the pressure distribution between the contact surfaces and the factors affecting it is one of the fundamentals in the process of designing the friction clutch to obtain accurate estimation of the temperature distribution during the slipping period and the contact stresses during the full engagement period. The investigation covers the effect of the contact stiffness factor FKN on the pressure distribution between contact surfaces, stresses, and penetration. The penalty and augmented Lagrange algorithms have been used to obtain the pressure distribution between contact surfaces. ANSYS13 software has been used to perform the numerical calculation in this paper.

A Theoretical and Numerical Study of an Additional Viscosity Term in a Modified Elasto-Plastic Friction Model for Wet Friction Clutch Simulations

This paper deals with a theoretical and numerical study of various viscosity terms in the modified elasto-plastic friction model and their influence on the resulting friction force-torque, transmitted through the contact of the friction clutch. Various simple viscous definitions for fluids considering shear rate dependent viscosity were investigated. The Carreau fluid model was chosen as a basis for the research, since it can describe Newtonian, dilatant, and pseudo plastic fluids. In addition to theoretical investigations, numerical simulations under realistic friction clutch operation conditions were carried out. The results were compared to the results of a validation case for a dry friction clutch simulation using the modified elasto-plastic friction model. This research showed significant differences between various viscosity definitions and revealed the drawbacks of such approach, were simple viscous models were used. In addition to viscosity, calculating the heat generated due to friction and its influence on the contact temperatures are discussed briefly. The basic theory and equations are given along with the directions for future work. The requirements for an accurate temperature calculation in the friction contact are outlined.

Tribological Properties of PM Cu-Based Dry Friction Clutch

Sintered Cu-based frictional materials were developed by using powder metallurgy (PM) method. The materials are aimed for application in a passenger car as a dry friction clutch. Effects of sintering temperature and composition on mechanical and tribological properties were determined. It was found that improper frictional material formulations caused inferior properties, particularly when the sintering temperatures were increased. Admixing of high Sn content (8 wt. %) resulted in decreases of sintered density and hardness with increasing sintering temperature. High Sn contents caused swelling of the sintered materials. Tribological properties (friction coefficient and wear rate) of the sintered specimens of the investigated materials were insensitive to sintering temperatures in the range of 800-950 °C but they were strongly influenced by chemical compositions. Addition of 3 wt. % graphite lowered the friction coefficient, which subsequently lowered the wear rate of the sintered material. To increase friction coefficient, one of the crucial properties of the dry friction clutch, of the sintered Cu-based frictional materials, two approaches were employed. In the first approach, substitution of graphite by SiO2 powders could improve the material friction coefficient. In the second approach, decreases of graphite content from 3 to 1 wt. % and of Sn content from 8 to 2 wt. % were conducted. The latter approach not only improved friction coefficient but also improved sintered density and hardness of the Cu-based frictional materials.

Effect of Band Contact on the Temperature Distribution for Dry Friction Clutch

Effect of Band Contact on the Temperature Distribution for Dry Friction Clutch

Nonlinear dynamic effects in automotive clutches

AbstractDynamic effects appearing in the dry friction clutches are very complex. The reason for this is the usual design of the clutches including complex two dimensional friction, unilateral contacts and nonlinear springs. The final quality of the clutch system for a customer depends among other criteria on the awareness of dynamic effects, which can affect functioning and comfort negatively.One of the usual nonlinear dynamic effects in the friction clutch is presented in this work. That is the problem of dynamic disengagement which can cause significant safety problems. First of all the global nonlinear dynamic behavior is considered roughly by means of an analytical approach. Secondly a MBS‐model, which includes not only the nominal design of the clutch system but also dispersion of several parameters, is used in order to identify the influence of the asymmetry on the dynamic behavior. Analytical and numerical results are compared with measurements. Finally a possible solution of the considered problem is presented. (© 2011 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)

The Study on Fuzzy Control of Automotive Clutch

Due to the complexity of the car running condition, the differences of the subjective intention of the driver, and Continuously Variable Transmission control system itself existed nonlinear, time delay, interference, variable parameter factors, the traditional control arithmetic based on scale model is hard to meet the clutch control requirements. This article through to design the drive mechanism of the dry friction clutch on a new, without hydraulic pump, pure electronic control car continuously variable transmission, and analyze its mechanical properties and control target, the clutch control model was established, according to the fuzzy control theory, driving experience and developers’ technical experience, the corresponding fuzzy language rules were formed, and intelligent control of the clutch on the single-chip control system was realized. At present, the pure electronic control continuously variable transmission has been tested on the experimental bench and car operation, and has passed the inspection by the national vehicle quality supervision and inspection center (Chongqing) and the identification by China Machinery Industry Federation .