Effects of Automotive Test Parameters on Dry Friction Fiber-Reinforced Clutch Facing Surface Microgeometry and Wear

Abstract

Wear and surface microgeometry aspects of fiber-reinforced hybrid composite dry friction clutch facings are revealed in a novel way: after different, real life automotive tests during their lifetime. This study examines and reveals the tribological response of friction material surfaces to real life application conditions with two different facing diameters and in two directions. Along the increasing activation energy scale, wear values increased according to two different trends, sorting tests into two main groups, namely ‘clutch killer’ and ‘moderate’. Wear results also highlighted the influence of mileage and test conditions, with clutch killer tests also creating considerable wear-more than 0.1 mm-at inner diameters: 1% higher wear was generated by 90% higher mileage; another 1% increment could be caused by insufficient cooling time or test bench-specific conditions. Surface roughness values trends varied accordingly with exceptions revealing effects of facing size, friction diameter and directions and test conditions: small (S) facings produced significantly decreased Rmax roughness, while large (L) and medium (M) size facings had increased roughness values; Rmax results showed the highest deviations among roughness values in radial direction; tests run with trailer and among city conditions resulted in more than 2% thickness loss and a 40–50% roughness decrease.

Retracted: Allocation of Hybrid Composite Materials in Friction Disc Clutches

“…Mileage and test conditions caused clutch killer tests to wear more than 0.1 mm at inner diameters. With some exceptions, facing size, friction diameter, and directions affected surface roughness trends [4]. Naemah et al [5] examine the wear characteristics of an aluminum-based composite material.…”

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

“…The main reason for this assumption is the effective management of large contact area and complexes geometries. There are many investigations that proved the accuracy of the selection of this contact type, e.g., [11][12][13][14].…”

Average and Local Effect of Thermal Fatigue on the Coefficients of the Thermal Expansion of a Complex Continuous Composite Fibre Used for Car Clutch Facing: A Multi-Technique Study

“…When dry clutch engages, there is a sliding contact between the clutch facing and mating surfaces, dissipating kinetic energy and generating heat. The temperature variation of the clutch facing can be divided into two stages [1][2][3]: a very fast rise in temperature, which can reach 250 or 300 • C in the case of repeated engagements for less than a second (Figure 1b), followed by cooling. A clutch facing is therefore subjected to different types of loads: tribological and thermomechanical stresses during clutch engagement (slipping with a temperature rise), followed by mechanical stresses (contact pressure and a centrifugal effect due to the speed of rotation at the engine output).…”

“…The choice of materials that make up the composite largely depends on the application (car, truck, racing, etc. ), but in all cases, the matrix and the reinforcements play a role in the thermal, mechanical and tribological properties [3,[5][6][7]. The orientation of the reinforcements must enable them to withstand stresses in all directions, and, due to the manufacturing process, the tracing is three-dimensional with variable angles of intersection [7,8] (Figure 2).…”

“…Experimental studies focus mainly on the tribological behaviour of new friction materials [35][36][37][38][39] such as non-woven fabrics [40] or environmentally friendly friction materials [41], which have interesting properties. The tests are carried out on standard laboratory devices [6] or real tests in the automotive industry [3] and show, for example, the influence of the sliding speed on the coefficient of friction [42]. The mechanical or thermomechanical properties depend on the manufacturing process [43] and are generally obtained by measurements during tests performed on samples cut from clutch facings and on as-received A clutch facing therefore needs to have a number of different properties to work effectively, including a high coefficient of friction, a good wear resistance, a high thermal stability, a low density and good mechanical properties.…”